1 \input texinfo @c -*-texinfo-*-
2 @c Copyright 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,
3 @c 1999, 2000, 2001, 2002, 2003, 2004
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 Free Software Foundation, Inc.
57 Permission is granted to copy, distribute and/or modify this document
58 under the terms of the GNU Free Documentation License, Version 1.1 or
59 any later version published by the Free Software Foundation; with the
60 Invariant Sections being ``Free Software'' and ``Free Software Needs
61 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
62 and with the Back-Cover Texts as in (a) below.
64 (a) The Free Software Foundation's Back-Cover Text is: ``You have
65 freedom to copy and modify this GNU Manual, like GNU software. Copies
66 published by the Free Software Foundation raise funds for GNU
71 @title Debugging with @value{GDBN}
72 @subtitle The @sc{gnu} Source-Level Debugger
74 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
75 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
79 \hfill (Send bugs and comments on @value{GDBN} to bug-gdb\@gnu.org.)\par
80 \hfill {\it Debugging with @value{GDBN}}\par
81 \hfill \TeX{}info \texinfoversion\par
85 @vskip 0pt plus 1filll
86 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,
87 1996, 1998, 1999, 2000, 2001, 2002, 2003, 2004 Free Software Foundation, Inc.
89 Published by the Free Software Foundation @*
90 59 Temple Place - Suite 330, @*
91 Boston, MA 02111-1307 USA @*
94 Permission is granted to copy, distribute and/or modify this document
95 under the terms of the GNU Free Documentation License, Version 1.1 or
96 any later version published by the Free Software Foundation; with the
97 Invariant Sections being ``Free Software'' and ``Free Software Needs
98 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
99 and with the Back-Cover Texts as in (a) below.
101 (a) The Free Software Foundation's Back-Cover Text is: ``You have
102 freedom to copy and modify this GNU Manual, like GNU software. Copies
103 published by the Free Software Foundation raise funds for GNU
109 @node Top, Summary, (dir), (dir)
111 @top Debugging with @value{GDBN}
113 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
115 This is the @value{EDITION} Edition, for @value{GDBN} Version
118 Copyright (C) 1988-2004 Free Software Foundation, Inc.
121 * Summary:: Summary of @value{GDBN}
122 * Sample Session:: A sample @value{GDBN} session
124 * Invocation:: Getting in and out of @value{GDBN}
125 * Commands:: @value{GDBN} commands
126 * Running:: Running programs under @value{GDBN}
127 * Stopping:: Stopping and continuing
128 * Stack:: Examining the stack
129 * Source:: Examining source files
130 * Data:: Examining data
131 * Macros:: Preprocessor Macros
132 * Tracepoints:: Debugging remote targets non-intrusively
133 * Overlays:: Debugging programs that use overlays
135 * Languages:: Using @value{GDBN} with different languages
137 * Symbols:: Examining the symbol table
138 * Altering:: Altering execution
139 * GDB Files:: @value{GDBN} files
140 * Targets:: Specifying a debugging target
141 * Remote Debugging:: Debugging remote programs
142 * Configurations:: Configuration-specific information
143 * Controlling GDB:: Controlling @value{GDBN}
144 * Sequences:: Canned sequences of commands
145 * TUI:: @value{GDBN} Text User Interface
146 * Interpreters:: Command Interpreters
147 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
148 * Annotations:: @value{GDBN}'s annotation interface.
149 * GDB/MI:: @value{GDBN}'s Machine Interface.
151 * GDB Bugs:: Reporting bugs in @value{GDBN}
152 * Formatting Documentation:: How to format and print @value{GDBN} documentation
154 * Command Line Editing:: Command Line Editing
155 * Using History Interactively:: Using History Interactively
156 * Installing GDB:: Installing GDB
157 * Maintenance Commands:: Maintenance Commands
158 * Remote Protocol:: GDB Remote Serial Protocol
159 * Agent Expressions:: The GDB Agent Expression Mechanism
160 * Copying:: GNU General Public License says
161 how you can copy and share GDB
162 * GNU Free Documentation License:: The license for this documentation
171 @unnumbered Summary of @value{GDBN}
173 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
174 going on ``inside'' another program while it executes---or what another
175 program was doing at the moment it crashed.
177 @value{GDBN} can do four main kinds of things (plus other things in support of
178 these) to help you catch bugs in the act:
182 Start your program, specifying anything that might affect its behavior.
185 Make your program stop on specified conditions.
188 Examine what has happened, when your program has stopped.
191 Change things in your program, so you can experiment with correcting the
192 effects of one bug and go on to learn about another.
195 You can use @value{GDBN} to debug programs written in C and C@t{++}.
196 For more information, see @ref{Support,,Supported languages}.
197 For more information, see @ref{C,,C and C++}.
200 Support for Modula-2 is partial. For information on Modula-2, see
201 @ref{Modula-2,,Modula-2}.
204 Debugging Pascal programs which use sets, subranges, file variables, or
205 nested functions does not currently work. @value{GDBN} does not support
206 entering expressions, printing values, or similar features using Pascal
210 @value{GDBN} can be used to debug programs written in Fortran, although
211 it may be necessary to refer to some variables with a trailing
214 @value{GDBN} can be used to debug programs written in Objective-C,
215 using either the Apple/NeXT or the GNU Objective-C runtime.
218 * Free Software:: Freely redistributable software
219 * Contributors:: Contributors to GDB
223 @unnumberedsec Free software
225 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
226 General Public License
227 (GPL). The GPL gives you the freedom to copy or adapt a licensed
228 program---but every person getting a copy also gets with it the
229 freedom to modify that copy (which means that they must get access to
230 the source code), and the freedom to distribute further copies.
231 Typical software companies use copyrights to limit your freedoms; the
232 Free Software Foundation uses the GPL to preserve these freedoms.
234 Fundamentally, the General Public License is a license which says that
235 you have these freedoms and that you cannot take these freedoms away
238 @unnumberedsec Free Software Needs Free Documentation
240 The biggest deficiency in the free software community today is not in
241 the software---it is the lack of good free documentation that we can
242 include with the free software. Many of our most important
243 programs do not come with free reference manuals and free introductory
244 texts. Documentation is an essential part of any software package;
245 when an important free software package does not come with a free
246 manual and a free tutorial, that is a major gap. We have many such
249 Consider Perl, for instance. The tutorial manuals that people
250 normally use are non-free. How did this come about? Because the
251 authors of those manuals published them with restrictive terms---no
252 copying, no modification, source files not available---which exclude
253 them from the free software world.
255 That wasn't the first time this sort of thing happened, and it was far
256 from the last. Many times we have heard a GNU user eagerly describe a
257 manual that he is writing, his intended contribution to the community,
258 only to learn that he had ruined everything by signing a publication
259 contract to make it non-free.
261 Free documentation, like free software, is a matter of freedom, not
262 price. The problem with the non-free manual is not that publishers
263 charge a price for printed copies---that in itself is fine. (The Free
264 Software Foundation sells printed copies of manuals, too.) The
265 problem is the restrictions on the use of the manual. Free manuals
266 are available in source code form, and give you permission to copy and
267 modify. Non-free manuals do not allow this.
269 The criteria of freedom for a free manual are roughly the same as for
270 free software. Redistribution (including the normal kinds of
271 commercial redistribution) must be permitted, so that the manual can
272 accompany every copy of the program, both on-line and on paper.
274 Permission for modification of the technical content is crucial too.
275 When people modify the software, adding or changing features, if they
276 are conscientious they will change the manual too---so they can
277 provide accurate and clear documentation for the modified program. A
278 manual that leaves you no choice but to write a new manual to document
279 a changed version of the program is not really available to our
282 Some kinds of limits on the way modification is handled are
283 acceptable. For example, requirements to preserve the original
284 author's copyright notice, the distribution terms, or the list of
285 authors, are ok. It is also no problem to require modified versions
286 to include notice that they were modified. Even entire sections that
287 may not be deleted or changed are acceptable, as long as they deal
288 with nontechnical topics (like this one). These kinds of restrictions
289 are acceptable because they don't obstruct the community's normal use
292 However, it must be possible to modify all the @emph{technical}
293 content of the manual, and then distribute the result in all the usual
294 media, through all the usual channels. Otherwise, the restrictions
295 obstruct the use of the manual, it is not free, and we need another
296 manual to replace it.
298 Please spread the word about this issue. Our community continues to
299 lose manuals to proprietary publishing. If we spread the word that
300 free software needs free reference manuals and free tutorials, perhaps
301 the next person who wants to contribute by writing documentation will
302 realize, before it is too late, that only free manuals contribute to
303 the free software community.
305 If you are writing documentation, please insist on publishing it under
306 the GNU Free Documentation License or another free documentation
307 license. Remember that this decision requires your approval---you
308 don't have to let the publisher decide. Some commercial publishers
309 will use a free license if you insist, but they will not propose the
310 option; it is up to you to raise the issue and say firmly that this is
311 what you want. If the publisher you are dealing with refuses, please
312 try other publishers. If you're not sure whether a proposed license
313 is free, write to @email{licensing@@gnu.org}.
315 You can encourage commercial publishers to sell more free, copylefted
316 manuals and tutorials by buying them, and particularly by buying
317 copies from the publishers that paid for their writing or for major
318 improvements. Meanwhile, try to avoid buying non-free documentation
319 at all. Check the distribution terms of a manual before you buy it,
320 and insist that whoever seeks your business must respect your freedom.
321 Check the history of the book, and try to reward the publishers that
322 have paid or pay the authors to work on it.
324 The Free Software Foundation maintains a list of free documentation
325 published by other publishers, at
326 @url{http://www.fsf.org/doc/other-free-books.html}.
329 @unnumberedsec Contributors to @value{GDBN}
331 Richard Stallman was the original author of @value{GDBN}, and of many
332 other @sc{gnu} programs. Many others have contributed to its
333 development. This section attempts to credit major contributors. One
334 of the virtues of free software is that everyone is free to contribute
335 to it; with regret, we cannot actually acknowledge everyone here. The
336 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
337 blow-by-blow account.
339 Changes much prior to version 2.0 are lost in the mists of time.
342 @emph{Plea:} Additions to this section are particularly welcome. If you
343 or your friends (or enemies, to be evenhanded) have been unfairly
344 omitted from this list, we would like to add your names!
347 So that they may not regard their many labors as thankless, we
348 particularly thank those who shepherded @value{GDBN} through major
350 Andrew Cagney (releases 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
351 Jim Blandy (release 4.18);
352 Jason Molenda (release 4.17);
353 Stan Shebs (release 4.14);
354 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
355 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
356 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
357 Jim Kingdon (releases 3.5, 3.4, and 3.3);
358 and Randy Smith (releases 3.2, 3.1, and 3.0).
360 Richard Stallman, assisted at various times by Peter TerMaat, Chris
361 Hanson, and Richard Mlynarik, handled releases through 2.8.
363 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
364 in @value{GDBN}, with significant additional contributions from Per
365 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
366 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
367 much general update work leading to release 3.0).
369 @value{GDBN} uses the BFD subroutine library to examine multiple
370 object-file formats; BFD was a joint project of David V.
371 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
373 David Johnson wrote the original COFF support; Pace Willison did
374 the original support for encapsulated COFF.
376 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
378 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
379 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
381 Jean-Daniel Fekete contributed Sun 386i support.
382 Chris Hanson improved the HP9000 support.
383 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
384 David Johnson contributed Encore Umax support.
385 Jyrki Kuoppala contributed Altos 3068 support.
386 Jeff Law contributed HP PA and SOM support.
387 Keith Packard contributed NS32K support.
388 Doug Rabson contributed Acorn Risc Machine support.
389 Bob Rusk contributed Harris Nighthawk CX-UX support.
390 Chris Smith contributed Convex support (and Fortran debugging).
391 Jonathan Stone contributed Pyramid support.
392 Michael Tiemann contributed SPARC support.
393 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
394 Pace Willison contributed Intel 386 support.
395 Jay Vosburgh contributed Symmetry support.
396 Marko Mlinar contributed OpenRISC 1000 support.
398 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
400 Rich Schaefer and Peter Schauer helped with support of SunOS shared
403 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
404 about several machine instruction sets.
406 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
407 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
408 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
409 and RDI targets, respectively.
411 Brian Fox is the author of the readline libraries providing
412 command-line editing and command history.
414 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
415 Modula-2 support, and contributed the Languages chapter of this manual.
417 Fred Fish wrote most of the support for Unix System Vr4.
418 He also enhanced the command-completion support to cover C@t{++} overloaded
421 Hitachi America (now Renesas America), Ltd. sponsored the support for
422 H8/300, H8/500, and Super-H processors.
424 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
426 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
429 Toshiba sponsored the support for the TX39 Mips processor.
431 Matsushita sponsored the support for the MN10200 and MN10300 processors.
433 Fujitsu sponsored the support for SPARClite and FR30 processors.
435 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
438 Michael Snyder added support for tracepoints.
440 Stu Grossman wrote gdbserver.
442 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
443 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
445 The following people at the Hewlett-Packard Company contributed
446 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
447 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
448 compiler, and the Text User Interface (nee Terminal User Interface):
449 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
450 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
451 provided HP-specific information in this manual.
453 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
454 Robert Hoehne made significant contributions to the DJGPP port.
456 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
457 development since 1991. Cygnus engineers who have worked on @value{GDBN}
458 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
459 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
460 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
461 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
462 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
463 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
464 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
465 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
466 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
467 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
468 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
469 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
470 Zuhn have made contributions both large and small.
472 Jim Blandy added support for preprocessor macros, while working for Red
476 @chapter A Sample @value{GDBN} Session
478 You can use this manual at your leisure to read all about @value{GDBN}.
479 However, a handful of commands are enough to get started using the
480 debugger. This chapter illustrates those commands.
483 In this sample session, we emphasize user input like this: @b{input},
484 to make it easier to pick out from the surrounding output.
487 @c FIXME: this example may not be appropriate for some configs, where
488 @c FIXME...primary interest is in remote use.
490 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
491 processor) exhibits the following bug: sometimes, when we change its
492 quote strings from the default, the commands used to capture one macro
493 definition within another stop working. In the following short @code{m4}
494 session, we define a macro @code{foo} which expands to @code{0000}; we
495 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
496 same thing. However, when we change the open quote string to
497 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
498 procedure fails to define a new synonym @code{baz}:
507 @b{define(bar,defn(`foo'))}
511 @b{changequote(<QUOTE>,<UNQUOTE>)}
513 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
516 m4: End of input: 0: fatal error: EOF in string
520 Let us use @value{GDBN} to try to see what is going on.
523 $ @b{@value{GDBP} m4}
524 @c FIXME: this falsifies the exact text played out, to permit smallbook
525 @c FIXME... format to come out better.
526 @value{GDBN} is free software and you are welcome to distribute copies
527 of it under certain conditions; type "show copying" to see
529 There is absolutely no warranty for @value{GDBN}; type "show warranty"
532 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
537 @value{GDBN} reads only enough symbol data to know where to find the
538 rest when needed; as a result, the first prompt comes up very quickly.
539 We now tell @value{GDBN} to use a narrower display width than usual, so
540 that examples fit in this manual.
543 (@value{GDBP}) @b{set width 70}
547 We need to see how the @code{m4} built-in @code{changequote} works.
548 Having looked at the source, we know the relevant subroutine is
549 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
550 @code{break} command.
553 (@value{GDBP}) @b{break m4_changequote}
554 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
558 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
559 control; as long as control does not reach the @code{m4_changequote}
560 subroutine, the program runs as usual:
563 (@value{GDBP}) @b{run}
564 Starting program: /work/Editorial/gdb/gnu/m4/m4
572 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
573 suspends execution of @code{m4}, displaying information about the
574 context where it stops.
577 @b{changequote(<QUOTE>,<UNQUOTE>)}
579 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
581 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
585 Now we use the command @code{n} (@code{next}) to advance execution to
586 the next line of the current function.
590 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
595 @code{set_quotes} looks like a promising subroutine. We can go into it
596 by using the command @code{s} (@code{step}) instead of @code{next}.
597 @code{step} goes to the next line to be executed in @emph{any}
598 subroutine, so it steps into @code{set_quotes}.
602 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
604 530 if (lquote != def_lquote)
608 The display that shows the subroutine where @code{m4} is now
609 suspended (and its arguments) is called a stack frame display. It
610 shows a summary of the stack. We can use the @code{backtrace}
611 command (which can also be spelled @code{bt}), to see where we are
612 in the stack as a whole: the @code{backtrace} command displays a
613 stack frame for each active subroutine.
616 (@value{GDBP}) @b{bt}
617 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
619 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
621 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
622 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
624 #4 0x79dc in expand_input () at macro.c:40
625 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
629 We step through a few more lines to see what happens. The first two
630 times, we can use @samp{s}; the next two times we use @code{n} to avoid
631 falling into the @code{xstrdup} subroutine.
635 0x3b5c 532 if (rquote != def_rquote)
637 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
638 def_lquote : xstrdup(lq);
640 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
643 538 len_lquote = strlen(rquote);
647 The last line displayed looks a little odd; we can examine the variables
648 @code{lquote} and @code{rquote} to see if they are in fact the new left
649 and right quotes we specified. We use the command @code{p}
650 (@code{print}) to see their values.
653 (@value{GDBP}) @b{p lquote}
654 $1 = 0x35d40 "<QUOTE>"
655 (@value{GDBP}) @b{p rquote}
656 $2 = 0x35d50 "<UNQUOTE>"
660 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
661 To look at some context, we can display ten lines of source
662 surrounding the current line with the @code{l} (@code{list}) command.
668 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
670 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
673 538 len_lquote = strlen(rquote);
674 539 len_rquote = strlen(lquote);
681 Let us step past the two lines that set @code{len_lquote} and
682 @code{len_rquote}, and then examine the values of those variables.
686 539 len_rquote = strlen(lquote);
689 (@value{GDBP}) @b{p len_lquote}
691 (@value{GDBP}) @b{p len_rquote}
696 That certainly looks wrong, assuming @code{len_lquote} and
697 @code{len_rquote} are meant to be the lengths of @code{lquote} and
698 @code{rquote} respectively. We can set them to better values using
699 the @code{p} command, since it can print the value of
700 any expression---and that expression can include subroutine calls and
704 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
706 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
711 Is that enough to fix the problem of using the new quotes with the
712 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
713 executing with the @code{c} (@code{continue}) command, and then try the
714 example that caused trouble initially:
720 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
727 Success! The new quotes now work just as well as the default ones. The
728 problem seems to have been just the two typos defining the wrong
729 lengths. We allow @code{m4} exit by giving it an EOF as input:
733 Program exited normally.
737 The message @samp{Program exited normally.} is from @value{GDBN}; it
738 indicates @code{m4} has finished executing. We can end our @value{GDBN}
739 session with the @value{GDBN} @code{quit} command.
742 (@value{GDBP}) @b{quit}
746 @chapter Getting In and Out of @value{GDBN}
748 This chapter discusses how to start @value{GDBN}, and how to get out of it.
752 type @samp{@value{GDBP}} to start @value{GDBN}.
754 type @kbd{quit} or @kbd{C-d} to exit.
758 * Invoking GDB:: How to start @value{GDBN}
759 * Quitting GDB:: How to quit @value{GDBN}
760 * Shell Commands:: How to use shell commands inside @value{GDBN}
761 * Logging output:: How to log @value{GDBN}'s output to a file
765 @section Invoking @value{GDBN}
767 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
768 @value{GDBN} reads commands from the terminal until you tell it to exit.
770 You can also run @code{@value{GDBP}} with a variety of arguments and options,
771 to specify more of your debugging environment at the outset.
773 The command-line options described here are designed
774 to cover a variety of situations; in some environments, some of these
775 options may effectively be unavailable.
777 The most usual way to start @value{GDBN} is with one argument,
778 specifying an executable program:
781 @value{GDBP} @var{program}
785 You can also start with both an executable program and a core file
789 @value{GDBP} @var{program} @var{core}
792 You can, instead, specify a process ID as a second argument, if you want
793 to debug a running process:
796 @value{GDBP} @var{program} 1234
800 would attach @value{GDBN} to process @code{1234} (unless you also have a file
801 named @file{1234}; @value{GDBN} does check for a core file first).
803 Taking advantage of the second command-line argument requires a fairly
804 complete operating system; when you use @value{GDBN} as a remote
805 debugger attached to a bare board, there may not be any notion of
806 ``process'', and there is often no way to get a core dump. @value{GDBN}
807 will warn you if it is unable to attach or to read core dumps.
809 You can optionally have @code{@value{GDBP}} pass any arguments after the
810 executable file to the inferior using @code{--args}. This option stops
813 gdb --args gcc -O2 -c foo.c
815 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
816 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
818 You can run @code{@value{GDBP}} without printing the front material, which describes
819 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
826 You can further control how @value{GDBN} starts up by using command-line
827 options. @value{GDBN} itself can remind you of the options available.
837 to display all available options and briefly describe their use
838 (@samp{@value{GDBP} -h} is a shorter equivalent).
840 All options and command line arguments you give are processed
841 in sequential order. The order makes a difference when the
842 @samp{-x} option is used.
846 * File Options:: Choosing files
847 * Mode Options:: Choosing modes
851 @subsection Choosing files
853 When @value{GDBN} starts, it reads any arguments other than options as
854 specifying an executable file and core file (or process ID). This is
855 the same as if the arguments were specified by the @samp{-se} and
856 @samp{-c} (or @samp{-p} options respectively. (@value{GDBN} reads the
857 first argument that does not have an associated option flag as
858 equivalent to the @samp{-se} option followed by that argument; and the
859 second argument that does not have an associated option flag, if any, as
860 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
861 If the second argument begins with a decimal digit, @value{GDBN} will
862 first attempt to attach to it as a process, and if that fails, attempt
863 to open it as a corefile. If you have a corefile whose name begins with
864 a digit, you can prevent @value{GDBN} from treating it as a pid by
865 prefixing it with @file{./}, eg. @file{./12345}.
867 If @value{GDBN} has not been configured to included core file support,
868 such as for most embedded targets, then it will complain about a second
869 argument and ignore it.
871 Many options have both long and short forms; both are shown in the
872 following list. @value{GDBN} also recognizes the long forms if you truncate
873 them, so long as enough of the option is present to be unambiguous.
874 (If you prefer, you can flag option arguments with @samp{--} rather
875 than @samp{-}, though we illustrate the more usual convention.)
877 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
878 @c way, both those who look for -foo and --foo in the index, will find
882 @item -symbols @var{file}
884 @cindex @code{--symbols}
886 Read symbol table from file @var{file}.
888 @item -exec @var{file}
890 @cindex @code{--exec}
892 Use file @var{file} as the executable file to execute when appropriate,
893 and for examining pure data in conjunction with a core dump.
897 Read symbol table from file @var{file} and use it as the executable
900 @item -core @var{file}
902 @cindex @code{--core}
904 Use file @var{file} as a core dump to examine.
906 @item -c @var{number}
907 @item -pid @var{number}
908 @itemx -p @var{number}
911 Connect to process ID @var{number}, as with the @code{attach} command.
912 If there is no such process, @value{GDBN} will attempt to open a core
913 file named @var{number}.
915 @item -command @var{file}
917 @cindex @code{--command}
919 Execute @value{GDBN} commands from file @var{file}. @xref{Command
920 Files,, Command files}.
922 @item -directory @var{directory}
923 @itemx -d @var{directory}
924 @cindex @code{--directory}
926 Add @var{directory} to the path to search for source files.
930 @cindex @code{--mapped}
932 @emph{Warning: this option depends on operating system facilities that are not
933 supported on all systems.}@*
934 If memory-mapped files are available on your system through the @code{mmap}
935 system call, you can use this option
936 to have @value{GDBN} write the symbols from your
937 program into a reusable file in the current directory. If the program you are debugging is
938 called @file{/tmp/fred}, the mapped symbol file is @file{/tmp/fred.syms}.
939 Future @value{GDBN} debugging sessions notice the presence of this file,
940 and can quickly map in symbol information from it, rather than reading
941 the symbol table from the executable program.
943 The @file{.syms} file is specific to the host machine where @value{GDBN}
944 is run. It holds an exact image of the internal @value{GDBN} symbol
945 table. It cannot be shared across multiple host platforms.
949 @cindex @code{--readnow}
951 Read each symbol file's entire symbol table immediately, rather than
952 the default, which is to read it incrementally as it is needed.
953 This makes startup slower, but makes future operations faster.
957 You typically combine the @code{-mapped} and @code{-readnow} options in
958 order to build a @file{.syms} file that contains complete symbol
959 information. (@xref{Files,,Commands to specify files}, for information
960 on @file{.syms} files.) A simple @value{GDBN} invocation to do nothing
961 but build a @file{.syms} file for future use is:
964 gdb -batch -nx -mapped -readnow programname
968 @subsection Choosing modes
970 You can run @value{GDBN} in various alternative modes---for example, in
971 batch mode or quiet mode.
978 Do not execute commands found in any initialization files. Normally,
979 @value{GDBN} executes the commands in these files after all the command
980 options and arguments have been processed. @xref{Command Files,,Command
986 @cindex @code{--quiet}
987 @cindex @code{--silent}
989 ``Quiet''. Do not print the introductory and copyright messages. These
990 messages are also suppressed in batch mode.
993 @cindex @code{--batch}
994 Run in batch mode. Exit with status @code{0} after processing all the
995 command files specified with @samp{-x} (and all commands from
996 initialization files, if not inhibited with @samp{-n}). Exit with
997 nonzero status if an error occurs in executing the @value{GDBN} commands
998 in the command files.
1000 Batch mode may be useful for running @value{GDBN} as a filter, for
1001 example to download and run a program on another computer; in order to
1002 make this more useful, the message
1005 Program exited normally.
1009 (which is ordinarily issued whenever a program running under
1010 @value{GDBN} control terminates) is not issued when running in batch
1015 @cindex @code{--nowindows}
1017 ``No windows''. If @value{GDBN} comes with a graphical user interface
1018 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1019 interface. If no GUI is available, this option has no effect.
1023 @cindex @code{--windows}
1025 If @value{GDBN} includes a GUI, then this option requires it to be
1028 @item -cd @var{directory}
1030 Run @value{GDBN} using @var{directory} as its working directory,
1031 instead of the current directory.
1035 @cindex @code{--fullname}
1037 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1038 subprocess. It tells @value{GDBN} to output the full file name and line
1039 number in a standard, recognizable fashion each time a stack frame is
1040 displayed (which includes each time your program stops). This
1041 recognizable format looks like two @samp{\032} characters, followed by
1042 the file name, line number and character position separated by colons,
1043 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1044 @samp{\032} characters as a signal to display the source code for the
1048 @cindex @code{--epoch}
1049 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1050 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1051 routines so as to allow Epoch to display values of expressions in a
1054 @item -annotate @var{level}
1055 @cindex @code{--annotate}
1056 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1057 effect is identical to using @samp{set annotate @var{level}}
1058 (@pxref{Annotations}). The annotation @var{level} controls how much
1059 information @value{GDBN} prints together with its prompt, values of
1060 expressions, source lines, and other types of output. Level 0 is the
1061 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1062 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1063 that control @value{GDBN}, and level 2 has been deprecated.
1065 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
1069 @cindex @code{--args}
1070 Change interpretation of command line so that arguments following the
1071 executable file are passed as command line arguments to the inferior.
1072 This option stops option processing.
1074 @item -baud @var{bps}
1076 @cindex @code{--baud}
1078 Set the line speed (baud rate or bits per second) of any serial
1079 interface used by @value{GDBN} for remote debugging.
1081 @item -tty @var{device}
1082 @itemx -t @var{device}
1083 @cindex @code{--tty}
1085 Run using @var{device} for your program's standard input and output.
1086 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1088 @c resolve the situation of these eventually
1090 @cindex @code{--tui}
1091 Activate the @dfn{Text User Interface} when starting. The Text User
1092 Interface manages several text windows on the terminal, showing
1093 source, assembly, registers and @value{GDBN} command outputs
1094 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1095 Text User Interface can be enabled by invoking the program
1096 @samp{gdbtui}. Do not use this option if you run @value{GDBN} from
1097 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1100 @c @cindex @code{--xdb}
1101 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1102 @c For information, see the file @file{xdb_trans.html}, which is usually
1103 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1106 @item -interpreter @var{interp}
1107 @cindex @code{--interpreter}
1108 Use the interpreter @var{interp} for interface with the controlling
1109 program or device. This option is meant to be set by programs which
1110 communicate with @value{GDBN} using it as a back end.
1111 @xref{Interpreters, , Command Interpreters}.
1113 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1114 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1115 The @sc{gdb/mi} Interface}) included since @var{GDBN} version 6.0. The
1116 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1117 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1118 @sc{gdb/mi} interfaces are no longer supported.
1121 @cindex @code{--write}
1122 Open the executable and core files for both reading and writing. This
1123 is equivalent to the @samp{set write on} command inside @value{GDBN}
1127 @cindex @code{--statistics}
1128 This option causes @value{GDBN} to print statistics about time and
1129 memory usage after it completes each command and returns to the prompt.
1132 @cindex @code{--version}
1133 This option causes @value{GDBN} to print its version number and
1134 no-warranty blurb, and exit.
1139 @section Quitting @value{GDBN}
1140 @cindex exiting @value{GDBN}
1141 @cindex leaving @value{GDBN}
1144 @kindex quit @r{[}@var{expression}@r{]}
1145 @kindex q @r{(@code{quit})}
1146 @item quit @r{[}@var{expression}@r{]}
1148 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1149 @code{q}), or type an end-of-file character (usually @kbd{C-d}). If you
1150 do not supply @var{expression}, @value{GDBN} will terminate normally;
1151 otherwise it will terminate using the result of @var{expression} as the
1156 An interrupt (often @kbd{C-c}) does not exit from @value{GDBN}, but rather
1157 terminates the action of any @value{GDBN} command that is in progress and
1158 returns to @value{GDBN} command level. It is safe to type the interrupt
1159 character at any time because @value{GDBN} does not allow it to take effect
1160 until a time when it is safe.
1162 If you have been using @value{GDBN} to control an attached process or
1163 device, you can release it with the @code{detach} command
1164 (@pxref{Attach, ,Debugging an already-running process}).
1166 @node Shell Commands
1167 @section Shell commands
1169 If you need to execute occasional shell commands during your
1170 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1171 just use the @code{shell} command.
1175 @cindex shell escape
1176 @item shell @var{command string}
1177 Invoke a standard shell to execute @var{command string}.
1178 If it exists, the environment variable @code{SHELL} determines which
1179 shell to run. Otherwise @value{GDBN} uses the default shell
1180 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1183 The utility @code{make} is often needed in development environments.
1184 You do not have to use the @code{shell} command for this purpose in
1189 @cindex calling make
1190 @item make @var{make-args}
1191 Execute the @code{make} program with the specified
1192 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1195 @node Logging output
1196 @section Logging output
1197 @cindex logging @value{GDBN} output
1199 You may want to save the output of @value{GDBN} commands to a file.
1200 There are several commands to control @value{GDBN}'s logging.
1204 @item set logging on
1206 @item set logging off
1208 @item set logging file @var{file}
1209 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1210 @item set logging overwrite [on|off]
1211 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1212 you want @code{set logging on} to overwrite the logfile instead.
1213 @item set logging redirect [on|off]
1214 By default, @value{GDBN} output will go to both the terminal and the logfile.
1215 Set @code{redirect} if you want output to go only to the log file.
1216 @kindex show logging
1218 Show the current values of the logging settings.
1222 @chapter @value{GDBN} Commands
1224 You can abbreviate a @value{GDBN} command to the first few letters of the command
1225 name, if that abbreviation is unambiguous; and you can repeat certain
1226 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1227 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1228 show you the alternatives available, if there is more than one possibility).
1231 * Command Syntax:: How to give commands to @value{GDBN}
1232 * Completion:: Command completion
1233 * Help:: How to ask @value{GDBN} for help
1236 @node Command Syntax
1237 @section Command syntax
1239 A @value{GDBN} command is a single line of input. There is no limit on
1240 how long it can be. It starts with a command name, which is followed by
1241 arguments whose meaning depends on the command name. For example, the
1242 command @code{step} accepts an argument which is the number of times to
1243 step, as in @samp{step 5}. You can also use the @code{step} command
1244 with no arguments. Some commands do not allow any arguments.
1246 @cindex abbreviation
1247 @value{GDBN} command names may always be truncated if that abbreviation is
1248 unambiguous. Other possible command abbreviations are listed in the
1249 documentation for individual commands. In some cases, even ambiguous
1250 abbreviations are allowed; for example, @code{s} is specially defined as
1251 equivalent to @code{step} even though there are other commands whose
1252 names start with @code{s}. You can test abbreviations by using them as
1253 arguments to the @code{help} command.
1255 @cindex repeating commands
1256 @kindex RET @r{(repeat last command)}
1257 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1258 repeat the previous command. Certain commands (for example, @code{run})
1259 will not repeat this way; these are commands whose unintentional
1260 repetition might cause trouble and which you are unlikely to want to
1263 The @code{list} and @code{x} commands, when you repeat them with
1264 @key{RET}, construct new arguments rather than repeating
1265 exactly as typed. This permits easy scanning of source or memory.
1267 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1268 output, in a way similar to the common utility @code{more}
1269 (@pxref{Screen Size,,Screen size}). Since it is easy to press one
1270 @key{RET} too many in this situation, @value{GDBN} disables command
1271 repetition after any command that generates this sort of display.
1273 @kindex # @r{(a comment)}
1275 Any text from a @kbd{#} to the end of the line is a comment; it does
1276 nothing. This is useful mainly in command files (@pxref{Command
1277 Files,,Command files}).
1279 @cindex repeating command sequences
1280 @kindex C-o @r{(operate-and-get-next)}
1281 The @kbd{C-o} binding is useful for repeating a complex sequence of
1282 commands. This command accepts the current line, like @kbd{RET}, and
1283 then fetches the next line relative to the current line from the history
1287 @section Command completion
1290 @cindex word completion
1291 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1292 only one possibility; it can also show you what the valid possibilities
1293 are for the next word in a command, at any time. This works for @value{GDBN}
1294 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1296 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1297 of a word. If there is only one possibility, @value{GDBN} fills in the
1298 word, and waits for you to finish the command (or press @key{RET} to
1299 enter it). For example, if you type
1301 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1302 @c complete accuracy in these examples; space introduced for clarity.
1303 @c If texinfo enhancements make it unnecessary, it would be nice to
1304 @c replace " @key" by "@key" in the following...
1306 (@value{GDBP}) info bre @key{TAB}
1310 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1311 the only @code{info} subcommand beginning with @samp{bre}:
1314 (@value{GDBP}) info breakpoints
1318 You can either press @key{RET} at this point, to run the @code{info
1319 breakpoints} command, or backspace and enter something else, if
1320 @samp{breakpoints} does not look like the command you expected. (If you
1321 were sure you wanted @code{info breakpoints} in the first place, you
1322 might as well just type @key{RET} immediately after @samp{info bre},
1323 to exploit command abbreviations rather than command completion).
1325 If there is more than one possibility for the next word when you press
1326 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1327 characters and try again, or just press @key{TAB} a second time;
1328 @value{GDBN} displays all the possible completions for that word. For
1329 example, you might want to set a breakpoint on a subroutine whose name
1330 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1331 just sounds the bell. Typing @key{TAB} again displays all the
1332 function names in your program that begin with those characters, for
1336 (@value{GDBP}) b make_ @key{TAB}
1337 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1338 make_a_section_from_file make_environ
1339 make_abs_section make_function_type
1340 make_blockvector make_pointer_type
1341 make_cleanup make_reference_type
1342 make_command make_symbol_completion_list
1343 (@value{GDBP}) b make_
1347 After displaying the available possibilities, @value{GDBN} copies your
1348 partial input (@samp{b make_} in the example) so you can finish the
1351 If you just want to see the list of alternatives in the first place, you
1352 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1353 means @kbd{@key{META} ?}. You can type this either by holding down a
1354 key designated as the @key{META} shift on your keyboard (if there is
1355 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1357 @cindex quotes in commands
1358 @cindex completion of quoted strings
1359 Sometimes the string you need, while logically a ``word'', may contain
1360 parentheses or other characters that @value{GDBN} normally excludes from
1361 its notion of a word. To permit word completion to work in this
1362 situation, you may enclose words in @code{'} (single quote marks) in
1363 @value{GDBN} commands.
1365 The most likely situation where you might need this is in typing the
1366 name of a C@t{++} function. This is because C@t{++} allows function
1367 overloading (multiple definitions of the same function, distinguished
1368 by argument type). For example, when you want to set a breakpoint you
1369 may need to distinguish whether you mean the version of @code{name}
1370 that takes an @code{int} parameter, @code{name(int)}, or the version
1371 that takes a @code{float} parameter, @code{name(float)}. To use the
1372 word-completion facilities in this situation, type a single quote
1373 @code{'} at the beginning of the function name. This alerts
1374 @value{GDBN} that it may need to consider more information than usual
1375 when you press @key{TAB} or @kbd{M-?} to request word completion:
1378 (@value{GDBP}) b 'bubble( @kbd{M-?}
1379 bubble(double,double) bubble(int,int)
1380 (@value{GDBP}) b 'bubble(
1383 In some cases, @value{GDBN} can tell that completing a name requires using
1384 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1385 completing as much as it can) if you do not type the quote in the first
1389 (@value{GDBP}) b bub @key{TAB}
1390 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1391 (@value{GDBP}) b 'bubble(
1395 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1396 you have not yet started typing the argument list when you ask for
1397 completion on an overloaded symbol.
1399 For more information about overloaded functions, see @ref{C plus plus
1400 expressions, ,C@t{++} expressions}. You can use the command @code{set
1401 overload-resolution off} to disable overload resolution;
1402 see @ref{Debugging C plus plus, ,@value{GDBN} features for C@t{++}}.
1406 @section Getting help
1407 @cindex online documentation
1410 You can always ask @value{GDBN} itself for information on its commands,
1411 using the command @code{help}.
1414 @kindex h @r{(@code{help})}
1417 You can use @code{help} (abbreviated @code{h}) with no arguments to
1418 display a short list of named classes of commands:
1422 List of classes of commands:
1424 aliases -- Aliases of other commands
1425 breakpoints -- Making program stop at certain points
1426 data -- Examining data
1427 files -- Specifying and examining files
1428 internals -- Maintenance commands
1429 obscure -- Obscure features
1430 running -- Running the program
1431 stack -- Examining the stack
1432 status -- Status inquiries
1433 support -- Support facilities
1434 tracepoints -- Tracing of program execution without@*
1435 stopping the program
1436 user-defined -- User-defined commands
1438 Type "help" followed by a class name for a list of
1439 commands in that class.
1440 Type "help" followed by command name for full
1442 Command name abbreviations are allowed if unambiguous.
1445 @c the above line break eliminates huge line overfull...
1447 @item help @var{class}
1448 Using one of the general help classes as an argument, you can get a
1449 list of the individual commands in that class. For example, here is the
1450 help display for the class @code{status}:
1453 (@value{GDBP}) help status
1458 @c Line break in "show" line falsifies real output, but needed
1459 @c to fit in smallbook page size.
1460 info -- Generic command for showing things
1461 about the program being debugged
1462 show -- Generic command for showing things
1465 Type "help" followed by command name for full
1467 Command name abbreviations are allowed if unambiguous.
1471 @item help @var{command}
1472 With a command name as @code{help} argument, @value{GDBN} displays a
1473 short paragraph on how to use that command.
1476 @item apropos @var{args}
1477 The @code{apropos @var{args}} command searches through all of the @value{GDBN}
1478 commands, and their documentation, for the regular expression specified in
1479 @var{args}. It prints out all matches found. For example:
1490 set symbol-reloading -- Set dynamic symbol table reloading
1491 multiple times in one run
1492 show symbol-reloading -- Show dynamic symbol table reloading
1493 multiple times in one run
1498 @item complete @var{args}
1499 The @code{complete @var{args}} command lists all the possible completions
1500 for the beginning of a command. Use @var{args} to specify the beginning of the
1501 command you want completed. For example:
1507 @noindent results in:
1518 @noindent This is intended for use by @sc{gnu} Emacs.
1521 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1522 and @code{show} to inquire about the state of your program, or the state
1523 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1524 manual introduces each of them in the appropriate context. The listings
1525 under @code{info} and under @code{show} in the Index point to
1526 all the sub-commands. @xref{Index}.
1531 @kindex i @r{(@code{info})}
1533 This command (abbreviated @code{i}) is for describing the state of your
1534 program. For example, you can list the arguments given to your program
1535 with @code{info args}, list the registers currently in use with @code{info
1536 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1537 You can get a complete list of the @code{info} sub-commands with
1538 @w{@code{help info}}.
1542 You can assign the result of an expression to an environment variable with
1543 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1544 @code{set prompt $}.
1548 In contrast to @code{info}, @code{show} is for describing the state of
1549 @value{GDBN} itself.
1550 You can change most of the things you can @code{show}, by using the
1551 related command @code{set}; for example, you can control what number
1552 system is used for displays with @code{set radix}, or simply inquire
1553 which is currently in use with @code{show radix}.
1556 To display all the settable parameters and their current
1557 values, you can use @code{show} with no arguments; you may also use
1558 @code{info set}. Both commands produce the same display.
1559 @c FIXME: "info set" violates the rule that "info" is for state of
1560 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1561 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1565 Here are three miscellaneous @code{show} subcommands, all of which are
1566 exceptional in lacking corresponding @code{set} commands:
1569 @kindex show version
1570 @cindex version number
1572 Show what version of @value{GDBN} is running. You should include this
1573 information in @value{GDBN} bug-reports. If multiple versions of
1574 @value{GDBN} are in use at your site, you may need to determine which
1575 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1576 commands are introduced, and old ones may wither away. Also, many
1577 system vendors ship variant versions of @value{GDBN}, and there are
1578 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1579 The version number is the same as the one announced when you start
1582 @kindex show copying
1584 Display information about permission for copying @value{GDBN}.
1586 @kindex show warranty
1588 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1589 if your version of @value{GDBN} comes with one.
1594 @chapter Running Programs Under @value{GDBN}
1596 When you run a program under @value{GDBN}, you must first generate
1597 debugging information when you compile it.
1599 You may start @value{GDBN} with its arguments, if any, in an environment
1600 of your choice. If you are doing native debugging, you may redirect
1601 your program's input and output, debug an already running process, or
1602 kill a child process.
1605 * Compilation:: Compiling for debugging
1606 * Starting:: Starting your program
1607 * Arguments:: Your program's arguments
1608 * Environment:: Your program's environment
1610 * Working Directory:: Your program's working directory
1611 * Input/Output:: Your program's input and output
1612 * Attach:: Debugging an already-running process
1613 * Kill Process:: Killing the child process
1615 * Threads:: Debugging programs with multiple threads
1616 * Processes:: Debugging programs with multiple processes
1620 @section Compiling for debugging
1622 In order to debug a program effectively, you need to generate
1623 debugging information when you compile it. This debugging information
1624 is stored in the object file; it describes the data type of each
1625 variable or function and the correspondence between source line numbers
1626 and addresses in the executable code.
1628 To request debugging information, specify the @samp{-g} option when you run
1631 Most compilers do not include information about preprocessor macros in
1632 the debugging information if you specify the @option{-g} flag alone,
1633 because this information is rather large. Version 3.1 of @value{NGCC},
1634 the @sc{gnu} C compiler, provides macro information if you specify the
1635 options @option{-gdwarf-2} and @option{-g3}; the former option requests
1636 debugging information in the Dwarf 2 format, and the latter requests
1637 ``extra information''. In the future, we hope to find more compact ways
1638 to represent macro information, so that it can be included with
1641 Many C compilers are unable to handle the @samp{-g} and @samp{-O}
1642 options together. Using those compilers, you cannot generate optimized
1643 executables containing debugging information.
1645 @value{NGCC}, the @sc{gnu} C compiler, supports @samp{-g} with or
1646 without @samp{-O}, making it possible to debug optimized code. We
1647 recommend that you @emph{always} use @samp{-g} whenever you compile a
1648 program. You may think your program is correct, but there is no sense
1649 in pushing your luck.
1651 @cindex optimized code, debugging
1652 @cindex debugging optimized code
1653 When you debug a program compiled with @samp{-g -O}, remember that the
1654 optimizer is rearranging your code; the debugger shows you what is
1655 really there. Do not be too surprised when the execution path does not
1656 exactly match your source file! An extreme example: if you define a
1657 variable, but never use it, @value{GDBN} never sees that
1658 variable---because the compiler optimizes it out of existence.
1660 Some things do not work as well with @samp{-g -O} as with just
1661 @samp{-g}, particularly on machines with instruction scheduling. If in
1662 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1663 please report it to us as a bug (including a test case!).
1664 @xref{Variables}, for more information about debugging optimized code.
1666 Older versions of the @sc{gnu} C compiler permitted a variant option
1667 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1668 format; if your @sc{gnu} C compiler has this option, do not use it.
1672 @section Starting your program
1678 @kindex r @r{(@code{run})}
1681 Use the @code{run} command to start your program under @value{GDBN}.
1682 You must first specify the program name (except on VxWorks) with an
1683 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1684 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1685 (@pxref{Files, ,Commands to specify files}).
1689 If you are running your program in an execution environment that
1690 supports processes, @code{run} creates an inferior process and makes
1691 that process run your program. (In environments without processes,
1692 @code{run} jumps to the start of your program.)
1694 The execution of a program is affected by certain information it
1695 receives from its superior. @value{GDBN} provides ways to specify this
1696 information, which you must do @emph{before} starting your program. (You
1697 can change it after starting your program, but such changes only affect
1698 your program the next time you start it.) This information may be
1699 divided into four categories:
1702 @item The @emph{arguments.}
1703 Specify the arguments to give your program as the arguments of the
1704 @code{run} command. If a shell is available on your target, the shell
1705 is used to pass the arguments, so that you may use normal conventions
1706 (such as wildcard expansion or variable substitution) in describing
1708 In Unix systems, you can control which shell is used with the
1709 @code{SHELL} environment variable.
1710 @xref{Arguments, ,Your program's arguments}.
1712 @item The @emph{environment.}
1713 Your program normally inherits its environment from @value{GDBN}, but you can
1714 use the @value{GDBN} commands @code{set environment} and @code{unset
1715 environment} to change parts of the environment that affect
1716 your program. @xref{Environment, ,Your program's environment}.
1718 @item The @emph{working directory.}
1719 Your program inherits its working directory from @value{GDBN}. You can set
1720 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1721 @xref{Working Directory, ,Your program's working directory}.
1723 @item The @emph{standard input and output.}
1724 Your program normally uses the same device for standard input and
1725 standard output as @value{GDBN} is using. You can redirect input and output
1726 in the @code{run} command line, or you can use the @code{tty} command to
1727 set a different device for your program.
1728 @xref{Input/Output, ,Your program's input and output}.
1731 @emph{Warning:} While input and output redirection work, you cannot use
1732 pipes to pass the output of the program you are debugging to another
1733 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1737 When you issue the @code{run} command, your program begins to execute
1738 immediately. @xref{Stopping, ,Stopping and continuing}, for discussion
1739 of how to arrange for your program to stop. Once your program has
1740 stopped, you may call functions in your program, using the @code{print}
1741 or @code{call} commands. @xref{Data, ,Examining Data}.
1743 If the modification time of your symbol file has changed since the last
1744 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1745 table, and reads it again. When it does this, @value{GDBN} tries to retain
1746 your current breakpoints.
1751 @cindex run to main procedure
1752 The name of the main procedure can vary from language to language.
1753 With C or C@t{++}, the main procedure name is always @code{main}, but
1754 other languages such as Ada do not require a specific name for their
1755 main procedure. The debugger provides a convenient way to start the
1756 execution of the program and to stop at the beginning of the main
1757 procedure, depending on the language used.
1759 The @samp{start} command does the equivalent of setting a temporary
1760 breakpoint at the beginning of the main procedure and then invoking
1761 the @samp{run} command.
1763 @cindex elaboration phase
1764 Some programs contain an @dfn{elaboration} phase where some startup code is
1765 executed before the main procedure is called. This depends on the
1766 languages used to write your program. In C@t{++}, for instance,
1767 constructors for static and global objects are executed before
1768 @code{main} is called. It is therefore possible that the debugger stops
1769 before reaching the main procedure. However, the temporary breakpoint
1770 will remain to halt execution.
1772 Specify the arguments to give to your program as arguments to the
1773 @samp{start} command. These arguments will be given verbatim to the
1774 underlying @samp{run} command. Note that the same arguments will be
1775 reused if no argument is provided during subsequent calls to
1776 @samp{start} or @samp{run}.
1778 It is sometimes necessary to debug the program during elaboration. In
1779 these cases, using the @code{start} command would stop the execution of
1780 your program too late, as the program would have already completed the
1781 elaboration phase. Under these circumstances, insert breakpoints in your
1782 elaboration code before running your program.
1786 @section Your program's arguments
1788 @cindex arguments (to your program)
1789 The arguments to your program can be specified by the arguments of the
1791 They are passed to a shell, which expands wildcard characters and
1792 performs redirection of I/O, and thence to your program. Your
1793 @code{SHELL} environment variable (if it exists) specifies what shell
1794 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1795 the default shell (@file{/bin/sh} on Unix).
1797 On non-Unix systems, the program is usually invoked directly by
1798 @value{GDBN}, which emulates I/O redirection via the appropriate system
1799 calls, and the wildcard characters are expanded by the startup code of
1800 the program, not by the shell.
1802 @code{run} with no arguments uses the same arguments used by the previous
1803 @code{run}, or those set by the @code{set args} command.
1808 Specify the arguments to be used the next time your program is run. If
1809 @code{set args} has no arguments, @code{run} executes your program
1810 with no arguments. Once you have run your program with arguments,
1811 using @code{set args} before the next @code{run} is the only way to run
1812 it again without arguments.
1816 Show the arguments to give your program when it is started.
1820 @section Your program's environment
1822 @cindex environment (of your program)
1823 The @dfn{environment} consists of a set of environment variables and
1824 their values. Environment variables conventionally record such things as
1825 your user name, your home directory, your terminal type, and your search
1826 path for programs to run. Usually you set up environment variables with
1827 the shell and they are inherited by all the other programs you run. When
1828 debugging, it can be useful to try running your program with a modified
1829 environment without having to start @value{GDBN} over again.
1833 @item path @var{directory}
1834 Add @var{directory} to the front of the @code{PATH} environment variable
1835 (the search path for executables) that will be passed to your program.
1836 The value of @code{PATH} used by @value{GDBN} does not change.
1837 You may specify several directory names, separated by whitespace or by a
1838 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1839 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1840 is moved to the front, so it is searched sooner.
1842 You can use the string @samp{$cwd} to refer to whatever is the current
1843 working directory at the time @value{GDBN} searches the path. If you
1844 use @samp{.} instead, it refers to the directory where you executed the
1845 @code{path} command. @value{GDBN} replaces @samp{.} in the
1846 @var{directory} argument (with the current path) before adding
1847 @var{directory} to the search path.
1848 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1849 @c document that, since repeating it would be a no-op.
1853 Display the list of search paths for executables (the @code{PATH}
1854 environment variable).
1856 @kindex show environment
1857 @item show environment @r{[}@var{varname}@r{]}
1858 Print the value of environment variable @var{varname} to be given to
1859 your program when it starts. If you do not supply @var{varname},
1860 print the names and values of all environment variables to be given to
1861 your program. You can abbreviate @code{environment} as @code{env}.
1863 @kindex set environment
1864 @item set environment @var{varname} @r{[}=@var{value}@r{]}
1865 Set environment variable @var{varname} to @var{value}. The value
1866 changes for your program only, not for @value{GDBN} itself. @var{value} may
1867 be any string; the values of environment variables are just strings, and
1868 any interpretation is supplied by your program itself. The @var{value}
1869 parameter is optional; if it is eliminated, the variable is set to a
1871 @c "any string" here does not include leading, trailing
1872 @c blanks. Gnu asks: does anyone care?
1874 For example, this command:
1881 tells the debugged program, when subsequently run, that its user is named
1882 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
1883 are not actually required.)
1885 @kindex unset environment
1886 @item unset environment @var{varname}
1887 Remove variable @var{varname} from the environment to be passed to your
1888 program. This is different from @samp{set env @var{varname} =};
1889 @code{unset environment} removes the variable from the environment,
1890 rather than assigning it an empty value.
1893 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
1895 by your @code{SHELL} environment variable if it exists (or
1896 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
1897 that runs an initialization file---such as @file{.cshrc} for C-shell, or
1898 @file{.bashrc} for BASH---any variables you set in that file affect
1899 your program. You may wish to move setting of environment variables to
1900 files that are only run when you sign on, such as @file{.login} or
1903 @node Working Directory
1904 @section Your program's working directory
1906 @cindex working directory (of your program)
1907 Each time you start your program with @code{run}, it inherits its
1908 working directory from the current working directory of @value{GDBN}.
1909 The @value{GDBN} working directory is initially whatever it inherited
1910 from its parent process (typically the shell), but you can specify a new
1911 working directory in @value{GDBN} with the @code{cd} command.
1913 The @value{GDBN} working directory also serves as a default for the commands
1914 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
1919 @item cd @var{directory}
1920 Set the @value{GDBN} working directory to @var{directory}.
1924 Print the @value{GDBN} working directory.
1927 It is generally impossible to find the current working directory of
1928 the process being debugged (since a program can change its directory
1929 during its run). If you work on a system where @value{GDBN} is
1930 configured with the @file{/proc} support, you can use the @code{info
1931 proc} command (@pxref{SVR4 Process Information}) to find out the
1932 current working directory of the debuggee.
1935 @section Your program's input and output
1940 By default, the program you run under @value{GDBN} does input and output to
1941 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
1942 to its own terminal modes to interact with you, but it records the terminal
1943 modes your program was using and switches back to them when you continue
1944 running your program.
1947 @kindex info terminal
1949 Displays information recorded by @value{GDBN} about the terminal modes your
1953 You can redirect your program's input and/or output using shell
1954 redirection with the @code{run} command. For example,
1961 starts your program, diverting its output to the file @file{outfile}.
1964 @cindex controlling terminal
1965 Another way to specify where your program should do input and output is
1966 with the @code{tty} command. This command accepts a file name as
1967 argument, and causes this file to be the default for future @code{run}
1968 commands. It also resets the controlling terminal for the child
1969 process, for future @code{run} commands. For example,
1976 directs that processes started with subsequent @code{run} commands
1977 default to do input and output on the terminal @file{/dev/ttyb} and have
1978 that as their controlling terminal.
1980 An explicit redirection in @code{run} overrides the @code{tty} command's
1981 effect on the input/output device, but not its effect on the controlling
1984 When you use the @code{tty} command or redirect input in the @code{run}
1985 command, only the input @emph{for your program} is affected. The input
1986 for @value{GDBN} still comes from your terminal.
1989 @section Debugging an already-running process
1994 @item attach @var{process-id}
1995 This command attaches to a running process---one that was started
1996 outside @value{GDBN}. (@code{info files} shows your active
1997 targets.) The command takes as argument a process ID. The usual way to
1998 find out the process-id of a Unix process is with the @code{ps} utility,
1999 or with the @samp{jobs -l} shell command.
2001 @code{attach} does not repeat if you press @key{RET} a second time after
2002 executing the command.
2005 To use @code{attach}, your program must be running in an environment
2006 which supports processes; for example, @code{attach} does not work for
2007 programs on bare-board targets that lack an operating system. You must
2008 also have permission to send the process a signal.
2010 When you use @code{attach}, the debugger finds the program running in
2011 the process first by looking in the current working directory, then (if
2012 the program is not found) by using the source file search path
2013 (@pxref{Source Path, ,Specifying source directories}). You can also use
2014 the @code{file} command to load the program. @xref{Files, ,Commands to
2017 The first thing @value{GDBN} does after arranging to debug the specified
2018 process is to stop it. You can examine and modify an attached process
2019 with all the @value{GDBN} commands that are ordinarily available when
2020 you start processes with @code{run}. You can insert breakpoints; you
2021 can step and continue; you can modify storage. If you would rather the
2022 process continue running, you may use the @code{continue} command after
2023 attaching @value{GDBN} to the process.
2028 When you have finished debugging the attached process, you can use the
2029 @code{detach} command to release it from @value{GDBN} control. Detaching
2030 the process continues its execution. After the @code{detach} command,
2031 that process and @value{GDBN} become completely independent once more, and you
2032 are ready to @code{attach} another process or start one with @code{run}.
2033 @code{detach} does not repeat if you press @key{RET} again after
2034 executing the command.
2037 If you exit @value{GDBN} or use the @code{run} command while you have an
2038 attached process, you kill that process. By default, @value{GDBN} asks
2039 for confirmation if you try to do either of these things; you can
2040 control whether or not you need to confirm by using the @code{set
2041 confirm} command (@pxref{Messages/Warnings, ,Optional warnings and
2045 @section Killing the child process
2050 Kill the child process in which your program is running under @value{GDBN}.
2053 This command is useful if you wish to debug a core dump instead of a
2054 running process. @value{GDBN} ignores any core dump file while your program
2057 On some operating systems, a program cannot be executed outside @value{GDBN}
2058 while you have breakpoints set on it inside @value{GDBN}. You can use the
2059 @code{kill} command in this situation to permit running your program
2060 outside the debugger.
2062 The @code{kill} command is also useful if you wish to recompile and
2063 relink your program, since on many systems it is impossible to modify an
2064 executable file while it is running in a process. In this case, when you
2065 next type @code{run}, @value{GDBN} notices that the file has changed, and
2066 reads the symbol table again (while trying to preserve your current
2067 breakpoint settings).
2070 @section Debugging programs with multiple threads
2072 @cindex threads of execution
2073 @cindex multiple threads
2074 @cindex switching threads
2075 In some operating systems, such as HP-UX and Solaris, a single program
2076 may have more than one @dfn{thread} of execution. The precise semantics
2077 of threads differ from one operating system to another, but in general
2078 the threads of a single program are akin to multiple processes---except
2079 that they share one address space (that is, they can all examine and
2080 modify the same variables). On the other hand, each thread has its own
2081 registers and execution stack, and perhaps private memory.
2083 @value{GDBN} provides these facilities for debugging multi-thread
2087 @item automatic notification of new threads
2088 @item @samp{thread @var{threadno}}, a command to switch among threads
2089 @item @samp{info threads}, a command to inquire about existing threads
2090 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2091 a command to apply a command to a list of threads
2092 @item thread-specific breakpoints
2096 @emph{Warning:} These facilities are not yet available on every
2097 @value{GDBN} configuration where the operating system supports threads.
2098 If your @value{GDBN} does not support threads, these commands have no
2099 effect. For example, a system without thread support shows no output
2100 from @samp{info threads}, and always rejects the @code{thread} command,
2104 (@value{GDBP}) info threads
2105 (@value{GDBP}) thread 1
2106 Thread ID 1 not known. Use the "info threads" command to
2107 see the IDs of currently known threads.
2109 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2110 @c doesn't support threads"?
2113 @cindex focus of debugging
2114 @cindex current thread
2115 The @value{GDBN} thread debugging facility allows you to observe all
2116 threads while your program runs---but whenever @value{GDBN} takes
2117 control, one thread in particular is always the focus of debugging.
2118 This thread is called the @dfn{current thread}. Debugging commands show
2119 program information from the perspective of the current thread.
2121 @cindex @code{New} @var{systag} message
2122 @cindex thread identifier (system)
2123 @c FIXME-implementors!! It would be more helpful if the [New...] message
2124 @c included GDB's numeric thread handle, so you could just go to that
2125 @c thread without first checking `info threads'.
2126 Whenever @value{GDBN} detects a new thread in your program, it displays
2127 the target system's identification for the thread with a message in the
2128 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2129 whose form varies depending on the particular system. For example, on
2130 LynxOS, you might see
2133 [New process 35 thread 27]
2137 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2138 the @var{systag} is simply something like @samp{process 368}, with no
2141 @c FIXME!! (1) Does the [New...] message appear even for the very first
2142 @c thread of a program, or does it only appear for the
2143 @c second---i.e.@: when it becomes obvious we have a multithread
2145 @c (2) *Is* there necessarily a first thread always? Or do some
2146 @c multithread systems permit starting a program with multiple
2147 @c threads ab initio?
2149 @cindex thread number
2150 @cindex thread identifier (GDB)
2151 For debugging purposes, @value{GDBN} associates its own thread
2152 number---always a single integer---with each thread in your program.
2155 @kindex info threads
2157 Display a summary of all threads currently in your
2158 program. @value{GDBN} displays for each thread (in this order):
2161 @item the thread number assigned by @value{GDBN}
2163 @item the target system's thread identifier (@var{systag})
2165 @item the current stack frame summary for that thread
2169 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2170 indicates the current thread.
2174 @c end table here to get a little more width for example
2177 (@value{GDBP}) info threads
2178 3 process 35 thread 27 0x34e5 in sigpause ()
2179 2 process 35 thread 23 0x34e5 in sigpause ()
2180 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2186 @cindex debugging multithreaded programs (on HP-UX)
2187 @cindex thread identifier (GDB), on HP-UX
2188 For debugging purposes, @value{GDBN} associates its own thread
2189 number---a small integer assigned in thread-creation order---with each
2190 thread in your program.
2192 @cindex @code{New} @var{systag} message, on HP-UX
2193 @cindex thread identifier (system), on HP-UX
2194 @c FIXME-implementors!! It would be more helpful if the [New...] message
2195 @c included GDB's numeric thread handle, so you could just go to that
2196 @c thread without first checking `info threads'.
2197 Whenever @value{GDBN} detects a new thread in your program, it displays
2198 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2199 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2200 whose form varies depending on the particular system. For example, on
2204 [New thread 2 (system thread 26594)]
2208 when @value{GDBN} notices a new thread.
2211 @kindex info threads (HP-UX)
2213 Display a summary of all threads currently in your
2214 program. @value{GDBN} displays for each thread (in this order):
2217 @item the thread number assigned by @value{GDBN}
2219 @item the target system's thread identifier (@var{systag})
2221 @item the current stack frame summary for that thread
2225 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2226 indicates the current thread.
2230 @c end table here to get a little more width for example
2233 (@value{GDBP}) info threads
2234 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2236 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2237 from /usr/lib/libc.2
2238 1 system thread 27905 0x7b003498 in _brk () \@*
2239 from /usr/lib/libc.2
2243 @kindex thread @var{threadno}
2244 @item thread @var{threadno}
2245 Make thread number @var{threadno} the current thread. The command
2246 argument @var{threadno} is the internal @value{GDBN} thread number, as
2247 shown in the first field of the @samp{info threads} display.
2248 @value{GDBN} responds by displaying the system identifier of the thread
2249 you selected, and its current stack frame summary:
2252 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2253 (@value{GDBP}) thread 2
2254 [Switching to process 35 thread 23]
2255 0x34e5 in sigpause ()
2259 As with the @samp{[New @dots{}]} message, the form of the text after
2260 @samp{Switching to} depends on your system's conventions for identifying
2263 @item thread apply [@var{threadno}] [@var{all}] @var{args}
2264 The @code{thread apply} command allows you to apply a command to one or
2265 more threads. Specify the numbers of the threads that you want affected
2266 with the command argument @var{threadno}. @var{threadno} is the internal
2267 @value{GDBN} thread number, as shown in the first field of the @samp{info
2268 threads} display. To apply a command to all threads, use
2269 @code{thread apply all} @var{args}.
2272 @cindex automatic thread selection
2273 @cindex switching threads automatically
2274 @cindex threads, automatic switching
2275 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2276 signal, it automatically selects the thread where that breakpoint or
2277 signal happened. @value{GDBN} alerts you to the context switch with a
2278 message of the form @samp{[Switching to @var{systag}]} to identify the
2281 @xref{Thread Stops,,Stopping and starting multi-thread programs}, for
2282 more information about how @value{GDBN} behaves when you stop and start
2283 programs with multiple threads.
2285 @xref{Set Watchpoints,,Setting watchpoints}, for information about
2286 watchpoints in programs with multiple threads.
2289 @section Debugging programs with multiple processes
2291 @cindex fork, debugging programs which call
2292 @cindex multiple processes
2293 @cindex processes, multiple
2294 On most systems, @value{GDBN} has no special support for debugging
2295 programs which create additional processes using the @code{fork}
2296 function. When a program forks, @value{GDBN} will continue to debug the
2297 parent process and the child process will run unimpeded. If you have
2298 set a breakpoint in any code which the child then executes, the child
2299 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2300 will cause it to terminate.
2302 However, if you want to debug the child process there is a workaround
2303 which isn't too painful. Put a call to @code{sleep} in the code which
2304 the child process executes after the fork. It may be useful to sleep
2305 only if a certain environment variable is set, or a certain file exists,
2306 so that the delay need not occur when you don't want to run @value{GDBN}
2307 on the child. While the child is sleeping, use the @code{ps} program to
2308 get its process ID. Then tell @value{GDBN} (a new invocation of
2309 @value{GDBN} if you are also debugging the parent process) to attach to
2310 the child process (@pxref{Attach}). From that point on you can debug
2311 the child process just like any other process which you attached to.
2313 On some systems, @value{GDBN} provides support for debugging programs that
2314 create additional processes using the @code{fork} or @code{vfork} functions.
2315 Currently, the only platforms with this feature are HP-UX (11.x and later
2316 only?) and GNU/Linux (kernel version 2.5.60 and later).
2318 By default, when a program forks, @value{GDBN} will continue to debug
2319 the parent process and the child process will run unimpeded.
2321 If you want to follow the child process instead of the parent process,
2322 use the command @w{@code{set follow-fork-mode}}.
2325 @kindex set follow-fork-mode
2326 @item set follow-fork-mode @var{mode}
2327 Set the debugger response to a program call of @code{fork} or
2328 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2329 process. The @var{mode} can be:
2333 The original process is debugged after a fork. The child process runs
2334 unimpeded. This is the default.
2337 The new process is debugged after a fork. The parent process runs
2342 @item show follow-fork-mode
2343 Display the current debugger response to a @code{fork} or @code{vfork} call.
2346 If you ask to debug a child process and a @code{vfork} is followed by an
2347 @code{exec}, @value{GDBN} executes the new target up to the first
2348 breakpoint in the new target. If you have a breakpoint set on
2349 @code{main} in your original program, the breakpoint will also be set on
2350 the child process's @code{main}.
2352 When a child process is spawned by @code{vfork}, you cannot debug the
2353 child or parent until an @code{exec} call completes.
2355 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2356 call executes, the new target restarts. To restart the parent process,
2357 use the @code{file} command with the parent executable name as its
2360 You can use the @code{catch} command to make @value{GDBN} stop whenever
2361 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2362 Catchpoints, ,Setting catchpoints}.
2365 @chapter Stopping and Continuing
2367 The principal purposes of using a debugger are so that you can stop your
2368 program before it terminates; or so that, if your program runs into
2369 trouble, you can investigate and find out why.
2371 Inside @value{GDBN}, your program may stop for any of several reasons,
2372 such as a signal, a breakpoint, or reaching a new line after a
2373 @value{GDBN} command such as @code{step}. You may then examine and
2374 change variables, set new breakpoints or remove old ones, and then
2375 continue execution. Usually, the messages shown by @value{GDBN} provide
2376 ample explanation of the status of your program---but you can also
2377 explicitly request this information at any time.
2380 @kindex info program
2382 Display information about the status of your program: whether it is
2383 running or not, what process it is, and why it stopped.
2387 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2388 * Continuing and Stepping:: Resuming execution
2390 * Thread Stops:: Stopping and starting multi-thread programs
2394 @section Breakpoints, watchpoints, and catchpoints
2397 A @dfn{breakpoint} makes your program stop whenever a certain point in
2398 the program is reached. For each breakpoint, you can add conditions to
2399 control in finer detail whether your program stops. You can set
2400 breakpoints with the @code{break} command and its variants (@pxref{Set
2401 Breaks, ,Setting breakpoints}), to specify the place where your program
2402 should stop by line number, function name or exact address in the
2405 In HP-UX, SunOS 4.x, SVR4, and Alpha OSF/1 configurations, you can set
2406 breakpoints in shared libraries before the executable is run. There is
2407 a minor limitation on HP-UX systems: you must wait until the executable
2408 is run in order to set breakpoints in shared library routines that are
2409 not called directly by the program (for example, routines that are
2410 arguments in a @code{pthread_create} call).
2413 @cindex memory tracing
2414 @cindex breakpoint on memory address
2415 @cindex breakpoint on variable modification
2416 A @dfn{watchpoint} is a special breakpoint that stops your program
2417 when the value of an expression changes. You must use a different
2418 command to set watchpoints (@pxref{Set Watchpoints, ,Setting
2419 watchpoints}), but aside from that, you can manage a watchpoint like
2420 any other breakpoint: you enable, disable, and delete both breakpoints
2421 and watchpoints using the same commands.
2423 You can arrange to have values from your program displayed automatically
2424 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2428 @cindex breakpoint on events
2429 A @dfn{catchpoint} is another special breakpoint that stops your program
2430 when a certain kind of event occurs, such as the throwing of a C@t{++}
2431 exception or the loading of a library. As with watchpoints, you use a
2432 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2433 catchpoints}), but aside from that, you can manage a catchpoint like any
2434 other breakpoint. (To stop when your program receives a signal, use the
2435 @code{handle} command; see @ref{Signals, ,Signals}.)
2437 @cindex breakpoint numbers
2438 @cindex numbers for breakpoints
2439 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2440 catchpoint when you create it; these numbers are successive integers
2441 starting with one. In many of the commands for controlling various
2442 features of breakpoints you use the breakpoint number to say which
2443 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2444 @dfn{disabled}; if disabled, it has no effect on your program until you
2447 @cindex breakpoint ranges
2448 @cindex ranges of breakpoints
2449 Some @value{GDBN} commands accept a range of breakpoints on which to
2450 operate. A breakpoint range is either a single breakpoint number, like
2451 @samp{5}, or two such numbers, in increasing order, separated by a
2452 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2453 all breakpoint in that range are operated on.
2456 * Set Breaks:: Setting breakpoints
2457 * Set Watchpoints:: Setting watchpoints
2458 * Set Catchpoints:: Setting catchpoints
2459 * Delete Breaks:: Deleting breakpoints
2460 * Disabling:: Disabling breakpoints
2461 * Conditions:: Break conditions
2462 * Break Commands:: Breakpoint command lists
2463 * Breakpoint Menus:: Breakpoint menus
2464 * Error in Breakpoints:: ``Cannot insert breakpoints''
2465 * Breakpoint related warnings:: ``Breakpoint address adjusted...''
2469 @subsection Setting breakpoints
2471 @c FIXME LMB what does GDB do if no code on line of breakpt?
2472 @c consider in particular declaration with/without initialization.
2474 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2477 @kindex b @r{(@code{break})}
2478 @vindex $bpnum@r{, convenience variable}
2479 @cindex latest breakpoint
2480 Breakpoints are set with the @code{break} command (abbreviated
2481 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2482 number of the breakpoint you've set most recently; see @ref{Convenience
2483 Vars,, Convenience variables}, for a discussion of what you can do with
2484 convenience variables.
2486 You have several ways to say where the breakpoint should go.
2489 @item break @var{function}
2490 Set a breakpoint at entry to function @var{function}.
2491 When using source languages that permit overloading of symbols, such as
2492 C@t{++}, @var{function} may refer to more than one possible place to break.
2493 @xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
2495 @item break +@var{offset}
2496 @itemx break -@var{offset}
2497 Set a breakpoint some number of lines forward or back from the position
2498 at which execution stopped in the currently selected @dfn{stack frame}.
2499 (@xref{Frames, ,Frames}, for a description of stack frames.)
2501 @item break @var{linenum}
2502 Set a breakpoint at line @var{linenum} in the current source file.
2503 The current source file is the last file whose source text was printed.
2504 The breakpoint will stop your program just before it executes any of the
2507 @item break @var{filename}:@var{linenum}
2508 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2510 @item break @var{filename}:@var{function}
2511 Set a breakpoint at entry to function @var{function} found in file
2512 @var{filename}. Specifying a file name as well as a function name is
2513 superfluous except when multiple files contain similarly named
2516 @item break *@var{address}
2517 Set a breakpoint at address @var{address}. You can use this to set
2518 breakpoints in parts of your program which do not have debugging
2519 information or source files.
2522 When called without any arguments, @code{break} sets a breakpoint at
2523 the next instruction to be executed in the selected stack frame
2524 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2525 innermost, this makes your program stop as soon as control
2526 returns to that frame. This is similar to the effect of a
2527 @code{finish} command in the frame inside the selected frame---except
2528 that @code{finish} does not leave an active breakpoint. If you use
2529 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2530 the next time it reaches the current location; this may be useful
2533 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2534 least one instruction has been executed. If it did not do this, you
2535 would be unable to proceed past a breakpoint without first disabling the
2536 breakpoint. This rule applies whether or not the breakpoint already
2537 existed when your program stopped.
2539 @item break @dots{} if @var{cond}
2540 Set a breakpoint with condition @var{cond}; evaluate the expression
2541 @var{cond} each time the breakpoint is reached, and stop only if the
2542 value is nonzero---that is, if @var{cond} evaluates as true.
2543 @samp{@dots{}} stands for one of the possible arguments described
2544 above (or no argument) specifying where to break. @xref{Conditions,
2545 ,Break conditions}, for more information on breakpoint conditions.
2548 @item tbreak @var{args}
2549 Set a breakpoint enabled only for one stop. @var{args} are the
2550 same as for the @code{break} command, and the breakpoint is set in the same
2551 way, but the breakpoint is automatically deleted after the first time your
2552 program stops there. @xref{Disabling, ,Disabling breakpoints}.
2555 @item hbreak @var{args}
2556 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2557 @code{break} command and the breakpoint is set in the same way, but the
2558 breakpoint requires hardware support and some target hardware may not
2559 have this support. The main purpose of this is EPROM/ROM code
2560 debugging, so you can set a breakpoint at an instruction without
2561 changing the instruction. This can be used with the new trap-generation
2562 provided by SPARClite DSU and some x86-based targets. These targets
2563 will generate traps when a program accesses some data or instruction
2564 address that is assigned to the debug registers. However the hardware
2565 breakpoint registers can take a limited number of breakpoints. For
2566 example, on the DSU, only two data breakpoints can be set at a time, and
2567 @value{GDBN} will reject this command if more than two are used. Delete
2568 or disable unused hardware breakpoints before setting new ones
2569 (@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}.
2570 @xref{set remote hardware-breakpoint-limit}.
2574 @item thbreak @var{args}
2575 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2576 are the same as for the @code{hbreak} command and the breakpoint is set in
2577 the same way. However, like the @code{tbreak} command,
2578 the breakpoint is automatically deleted after the
2579 first time your program stops there. Also, like the @code{hbreak}
2580 command, the breakpoint requires hardware support and some target hardware
2581 may not have this support. @xref{Disabling, ,Disabling breakpoints}.
2582 See also @ref{Conditions, ,Break conditions}.
2585 @cindex regular expression
2586 @item rbreak @var{regex}
2587 Set breakpoints on all functions matching the regular expression
2588 @var{regex}. This command sets an unconditional breakpoint on all
2589 matches, printing a list of all breakpoints it set. Once these
2590 breakpoints are set, they are treated just like the breakpoints set with
2591 the @code{break} command. You can delete them, disable them, or make
2592 them conditional the same way as any other breakpoint.
2594 The syntax of the regular expression is the standard one used with tools
2595 like @file{grep}. Note that this is different from the syntax used by
2596 shells, so for instance @code{foo*} matches all functions that include
2597 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2598 @code{.*} leading and trailing the regular expression you supply, so to
2599 match only functions that begin with @code{foo}, use @code{^foo}.
2601 @cindex non-member C@t{++} functions, set breakpoint in
2602 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2603 breakpoints on overloaded functions that are not members of any special
2606 @cindex set breakpoints on all functions
2607 The @code{rbreak} command can be used to set breakpoints in
2608 @strong{all} the functions in a program, like this:
2611 (@value{GDBP}) rbreak .
2614 @kindex info breakpoints
2615 @cindex @code{$_} and @code{info breakpoints}
2616 @item info breakpoints @r{[}@var{n}@r{]}
2617 @itemx info break @r{[}@var{n}@r{]}
2618 @itemx info watchpoints @r{[}@var{n}@r{]}
2619 Print a table of all breakpoints, watchpoints, and catchpoints set and
2620 not deleted, with the following columns for each breakpoint:
2623 @item Breakpoint Numbers
2625 Breakpoint, watchpoint, or catchpoint.
2627 Whether the breakpoint is marked to be disabled or deleted when hit.
2628 @item Enabled or Disabled
2629 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2630 that are not enabled.
2632 Where the breakpoint is in your program, as a memory address. If the
2633 breakpoint is pending (see below for details) on a future load of a shared library, the address
2634 will be listed as @samp{<PENDING>}.
2636 Where the breakpoint is in the source for your program, as a file and
2637 line number. For a pending breakpoint, the original string passed to
2638 the breakpoint command will be listed as it cannot be resolved until
2639 the appropriate shared library is loaded in the future.
2643 If a breakpoint is conditional, @code{info break} shows the condition on
2644 the line following the affected breakpoint; breakpoint commands, if any,
2645 are listed after that. A pending breakpoint is allowed to have a condition
2646 specified for it. The condition is not parsed for validity until a shared
2647 library is loaded that allows the pending breakpoint to resolve to a
2651 @code{info break} with a breakpoint
2652 number @var{n} as argument lists only that breakpoint. The
2653 convenience variable @code{$_} and the default examining-address for
2654 the @code{x} command are set to the address of the last breakpoint
2655 listed (@pxref{Memory, ,Examining memory}).
2658 @code{info break} displays a count of the number of times the breakpoint
2659 has been hit. This is especially useful in conjunction with the
2660 @code{ignore} command. You can ignore a large number of breakpoint
2661 hits, look at the breakpoint info to see how many times the breakpoint
2662 was hit, and then run again, ignoring one less than that number. This
2663 will get you quickly to the last hit of that breakpoint.
2666 @value{GDBN} allows you to set any number of breakpoints at the same place in
2667 your program. There is nothing silly or meaningless about this. When
2668 the breakpoints are conditional, this is even useful
2669 (@pxref{Conditions, ,Break conditions}).
2671 @cindex pending breakpoints
2672 If a specified breakpoint location cannot be found, it may be due to the fact
2673 that the location is in a shared library that is yet to be loaded. In such
2674 a case, you may want @value{GDBN} to create a special breakpoint (known as
2675 a @dfn{pending breakpoint}) that
2676 attempts to resolve itself in the future when an appropriate shared library
2679 Pending breakpoints are useful to set at the start of your
2680 @value{GDBN} session for locations that you know will be dynamically loaded
2681 later by the program being debugged. When shared libraries are loaded,
2682 a check is made to see if the load resolves any pending breakpoint locations.
2683 If a pending breakpoint location gets resolved,
2684 a regular breakpoint is created and the original pending breakpoint is removed.
2686 @value{GDBN} provides some additional commands for controlling pending
2689 @kindex set breakpoint pending
2690 @kindex show breakpoint pending
2692 @item set breakpoint pending auto
2693 This is the default behavior. When @value{GDBN} cannot find the breakpoint
2694 location, it queries you whether a pending breakpoint should be created.
2696 @item set breakpoint pending on
2697 This indicates that an unrecognized breakpoint location should automatically
2698 result in a pending breakpoint being created.
2700 @item set breakpoint pending off
2701 This indicates that pending breakpoints are not to be created. Any
2702 unrecognized breakpoint location results in an error. This setting does
2703 not affect any pending breakpoints previously created.
2705 @item show breakpoint pending
2706 Show the current behavior setting for creating pending breakpoints.
2709 @cindex operations allowed on pending breakpoints
2710 Normal breakpoint operations apply to pending breakpoints as well. You may
2711 specify a condition for a pending breakpoint and/or commands to run when the
2712 breakpoint is reached. You can also enable or disable
2713 the pending breakpoint. When you specify a condition for a pending breakpoint,
2714 the parsing of the condition will be deferred until the point where the
2715 pending breakpoint location is resolved. Disabling a pending breakpoint
2716 tells @value{GDBN} to not attempt to resolve the breakpoint on any subsequent
2717 shared library load. When a pending breakpoint is re-enabled,
2718 @value{GDBN} checks to see if the location is already resolved.
2719 This is done because any number of shared library loads could have
2720 occurred since the time the breakpoint was disabled and one or more
2721 of these loads could resolve the location.
2723 @cindex negative breakpoint numbers
2724 @cindex internal @value{GDBN} breakpoints
2725 @value{GDBN} itself sometimes sets breakpoints in your program for
2726 special purposes, such as proper handling of @code{longjmp} (in C
2727 programs). These internal breakpoints are assigned negative numbers,
2728 starting with @code{-1}; @samp{info breakpoints} does not display them.
2729 You can see these breakpoints with the @value{GDBN} maintenance command
2730 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
2733 @node Set Watchpoints
2734 @subsection Setting watchpoints
2736 @cindex setting watchpoints
2737 @cindex software watchpoints
2738 @cindex hardware watchpoints
2739 You can use a watchpoint to stop execution whenever the value of an
2740 expression changes, without having to predict a particular place where
2743 Depending on your system, watchpoints may be implemented in software or
2744 hardware. @value{GDBN} does software watchpointing by single-stepping your
2745 program and testing the variable's value each time, which is hundreds of
2746 times slower than normal execution. (But this may still be worth it, to
2747 catch errors where you have no clue what part of your program is the
2750 On some systems, such as HP-UX, @sc{gnu}/Linux and some other x86-based targets,
2751 @value{GDBN} includes support for
2752 hardware watchpoints, which do not slow down the running of your
2757 @item watch @var{expr}
2758 Set a watchpoint for an expression. @value{GDBN} will break when @var{expr}
2759 is written into by the program and its value changes.
2762 @item rwatch @var{expr}
2763 Set a watchpoint that will break when watch @var{expr} is read by the program.
2766 @item awatch @var{expr}
2767 Set a watchpoint that will break when @var{expr} is either read or written into
2770 @kindex info watchpoints
2771 @item info watchpoints
2772 This command prints a list of watchpoints, breakpoints, and catchpoints;
2773 it is the same as @code{info break}.
2776 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
2777 watchpoints execute very quickly, and the debugger reports a change in
2778 value at the exact instruction where the change occurs. If @value{GDBN}
2779 cannot set a hardware watchpoint, it sets a software watchpoint, which
2780 executes more slowly and reports the change in value at the next
2781 statement, not the instruction, after the change occurs.
2783 When you issue the @code{watch} command, @value{GDBN} reports
2786 Hardware watchpoint @var{num}: @var{expr}
2790 if it was able to set a hardware watchpoint.
2792 Currently, the @code{awatch} and @code{rwatch} commands can only set
2793 hardware watchpoints, because accesses to data that don't change the
2794 value of the watched expression cannot be detected without examining
2795 every instruction as it is being executed, and @value{GDBN} does not do
2796 that currently. If @value{GDBN} finds that it is unable to set a
2797 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
2798 will print a message like this:
2801 Expression cannot be implemented with read/access watchpoint.
2804 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
2805 data type of the watched expression is wider than what a hardware
2806 watchpoint on the target machine can handle. For example, some systems
2807 can only watch regions that are up to 4 bytes wide; on such systems you
2808 cannot set hardware watchpoints for an expression that yields a
2809 double-precision floating-point number (which is typically 8 bytes
2810 wide). As a work-around, it might be possible to break the large region
2811 into a series of smaller ones and watch them with separate watchpoints.
2813 If you set too many hardware watchpoints, @value{GDBN} might be unable
2814 to insert all of them when you resume the execution of your program.
2815 Since the precise number of active watchpoints is unknown until such
2816 time as the program is about to be resumed, @value{GDBN} might not be
2817 able to warn you about this when you set the watchpoints, and the
2818 warning will be printed only when the program is resumed:
2821 Hardware watchpoint @var{num}: Could not insert watchpoint
2825 If this happens, delete or disable some of the watchpoints.
2827 The SPARClite DSU will generate traps when a program accesses some data
2828 or instruction address that is assigned to the debug registers. For the
2829 data addresses, DSU facilitates the @code{watch} command. However the
2830 hardware breakpoint registers can only take two data watchpoints, and
2831 both watchpoints must be the same kind. For example, you can set two
2832 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
2833 @strong{or} two with @code{awatch} commands, but you cannot set one
2834 watchpoint with one command and the other with a different command.
2835 @value{GDBN} will reject the command if you try to mix watchpoints.
2836 Delete or disable unused watchpoint commands before setting new ones.
2838 If you call a function interactively using @code{print} or @code{call},
2839 any watchpoints you have set will be inactive until @value{GDBN} reaches another
2840 kind of breakpoint or the call completes.
2842 @value{GDBN} automatically deletes watchpoints that watch local
2843 (automatic) variables, or expressions that involve such variables, when
2844 they go out of scope, that is, when the execution leaves the block in
2845 which these variables were defined. In particular, when the program
2846 being debugged terminates, @emph{all} local variables go out of scope,
2847 and so only watchpoints that watch global variables remain set. If you
2848 rerun the program, you will need to set all such watchpoints again. One
2849 way of doing that would be to set a code breakpoint at the entry to the
2850 @code{main} function and when it breaks, set all the watchpoints.
2853 @cindex watchpoints and threads
2854 @cindex threads and watchpoints
2855 @emph{Warning:} In multi-thread programs, watchpoints have only limited
2856 usefulness. With the current watchpoint implementation, @value{GDBN}
2857 can only watch the value of an expression @emph{in a single thread}. If
2858 you are confident that the expression can only change due to the current
2859 thread's activity (and if you are also confident that no other thread
2860 can become current), then you can use watchpoints as usual. However,
2861 @value{GDBN} may not notice when a non-current thread's activity changes
2864 @c FIXME: this is almost identical to the previous paragraph.
2865 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
2866 have only limited usefulness. If @value{GDBN} creates a software
2867 watchpoint, it can only watch the value of an expression @emph{in a
2868 single thread}. If you are confident that the expression can only
2869 change due to the current thread's activity (and if you are also
2870 confident that no other thread can become current), then you can use
2871 software watchpoints as usual. However, @value{GDBN} may not notice
2872 when a non-current thread's activity changes the expression. (Hardware
2873 watchpoints, in contrast, watch an expression in all threads.)
2876 @xref{set remote hardware-watchpoint-limit}.
2878 @node Set Catchpoints
2879 @subsection Setting catchpoints
2880 @cindex catchpoints, setting
2881 @cindex exception handlers
2882 @cindex event handling
2884 You can use @dfn{catchpoints} to cause the debugger to stop for certain
2885 kinds of program events, such as C@t{++} exceptions or the loading of a
2886 shared library. Use the @code{catch} command to set a catchpoint.
2890 @item catch @var{event}
2891 Stop when @var{event} occurs. @var{event} can be any of the following:
2894 @cindex stop on C@t{++} exceptions
2895 The throwing of a C@t{++} exception.
2898 The catching of a C@t{++} exception.
2901 @cindex break on fork/exec
2902 A call to @code{exec}. This is currently only available for HP-UX.
2905 A call to @code{fork}. This is currently only available for HP-UX.
2908 A call to @code{vfork}. This is currently only available for HP-UX.
2911 @itemx load @var{libname}
2912 @cindex break on load/unload of shared library
2913 The dynamic loading of any shared library, or the loading of the library
2914 @var{libname}. This is currently only available for HP-UX.
2917 @itemx unload @var{libname}
2918 The unloading of any dynamically loaded shared library, or the unloading
2919 of the library @var{libname}. This is currently only available for HP-UX.
2922 @item tcatch @var{event}
2923 Set a catchpoint that is enabled only for one stop. The catchpoint is
2924 automatically deleted after the first time the event is caught.
2928 Use the @code{info break} command to list the current catchpoints.
2930 There are currently some limitations to C@t{++} exception handling
2931 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
2935 If you call a function interactively, @value{GDBN} normally returns
2936 control to you when the function has finished executing. If the call
2937 raises an exception, however, the call may bypass the mechanism that
2938 returns control to you and cause your program either to abort or to
2939 simply continue running until it hits a breakpoint, catches a signal
2940 that @value{GDBN} is listening for, or exits. This is the case even if
2941 you set a catchpoint for the exception; catchpoints on exceptions are
2942 disabled within interactive calls.
2945 You cannot raise an exception interactively.
2948 You cannot install an exception handler interactively.
2951 @cindex raise exceptions
2952 Sometimes @code{catch} is not the best way to debug exception handling:
2953 if you need to know exactly where an exception is raised, it is better to
2954 stop @emph{before} the exception handler is called, since that way you
2955 can see the stack before any unwinding takes place. If you set a
2956 breakpoint in an exception handler instead, it may not be easy to find
2957 out where the exception was raised.
2959 To stop just before an exception handler is called, you need some
2960 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
2961 raised by calling a library function named @code{__raise_exception}
2962 which has the following ANSI C interface:
2965 /* @var{addr} is where the exception identifier is stored.
2966 @var{id} is the exception identifier. */
2967 void __raise_exception (void **addr, void *id);
2971 To make the debugger catch all exceptions before any stack
2972 unwinding takes place, set a breakpoint on @code{__raise_exception}
2973 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
2975 With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
2976 that depends on the value of @var{id}, you can stop your program when
2977 a specific exception is raised. You can use multiple conditional
2978 breakpoints to stop your program when any of a number of exceptions are
2983 @subsection Deleting breakpoints
2985 @cindex clearing breakpoints, watchpoints, catchpoints
2986 @cindex deleting breakpoints, watchpoints, catchpoints
2987 It is often necessary to eliminate a breakpoint, watchpoint, or
2988 catchpoint once it has done its job and you no longer want your program
2989 to stop there. This is called @dfn{deleting} the breakpoint. A
2990 breakpoint that has been deleted no longer exists; it is forgotten.
2992 With the @code{clear} command you can delete breakpoints according to
2993 where they are in your program. With the @code{delete} command you can
2994 delete individual breakpoints, watchpoints, or catchpoints by specifying
2995 their breakpoint numbers.
2997 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
2998 automatically ignores breakpoints on the first instruction to be executed
2999 when you continue execution without changing the execution address.
3004 Delete any breakpoints at the next instruction to be executed in the
3005 selected stack frame (@pxref{Selection, ,Selecting a frame}). When
3006 the innermost frame is selected, this is a good way to delete a
3007 breakpoint where your program just stopped.
3009 @item clear @var{function}
3010 @itemx clear @var{filename}:@var{function}
3011 Delete any breakpoints set at entry to the function @var{function}.
3013 @item clear @var{linenum}
3014 @itemx clear @var{filename}:@var{linenum}
3015 Delete any breakpoints set at or within the code of the specified line.
3017 @cindex delete breakpoints
3019 @kindex d @r{(@code{delete})}
3020 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3021 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3022 ranges specified as arguments. If no argument is specified, delete all
3023 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3024 confirm off}). You can abbreviate this command as @code{d}.
3028 @subsection Disabling breakpoints
3030 @cindex enable/disable a breakpoint
3031 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3032 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3033 it had been deleted, but remembers the information on the breakpoint so
3034 that you can @dfn{enable} it again later.
3036 You disable and enable breakpoints, watchpoints, and catchpoints with
3037 the @code{enable} and @code{disable} commands, optionally specifying one
3038 or more breakpoint numbers as arguments. Use @code{info break} or
3039 @code{info watch} to print a list of breakpoints, watchpoints, and
3040 catchpoints if you do not know which numbers to use.
3042 A breakpoint, watchpoint, or catchpoint can have any of four different
3043 states of enablement:
3047 Enabled. The breakpoint stops your program. A breakpoint set
3048 with the @code{break} command starts out in this state.
3050 Disabled. The breakpoint has no effect on your program.
3052 Enabled once. The breakpoint stops your program, but then becomes
3055 Enabled for deletion. The breakpoint stops your program, but
3056 immediately after it does so it is deleted permanently. A breakpoint
3057 set with the @code{tbreak} command starts out in this state.
3060 You can use the following commands to enable or disable breakpoints,
3061 watchpoints, and catchpoints:
3065 @kindex dis @r{(@code{disable})}
3066 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3067 Disable the specified breakpoints---or all breakpoints, if none are
3068 listed. A disabled breakpoint has no effect but is not forgotten. All
3069 options such as ignore-counts, conditions and commands are remembered in
3070 case the breakpoint is enabled again later. You may abbreviate
3071 @code{disable} as @code{dis}.
3074 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3075 Enable the specified breakpoints (or all defined breakpoints). They
3076 become effective once again in stopping your program.
3078 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3079 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3080 of these breakpoints immediately after stopping your program.
3082 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3083 Enable the specified breakpoints to work once, then die. @value{GDBN}
3084 deletes any of these breakpoints as soon as your program stops there.
3087 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3088 @c confusing: tbreak is also initially enabled.
3089 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3090 ,Setting breakpoints}), breakpoints that you set are initially enabled;
3091 subsequently, they become disabled or enabled only when you use one of
3092 the commands above. (The command @code{until} can set and delete a
3093 breakpoint of its own, but it does not change the state of your other
3094 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3098 @subsection Break conditions
3099 @cindex conditional breakpoints
3100 @cindex breakpoint conditions
3102 @c FIXME what is scope of break condition expr? Context where wanted?
3103 @c in particular for a watchpoint?
3104 The simplest sort of breakpoint breaks every time your program reaches a
3105 specified place. You can also specify a @dfn{condition} for a
3106 breakpoint. A condition is just a Boolean expression in your
3107 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3108 a condition evaluates the expression each time your program reaches it,
3109 and your program stops only if the condition is @emph{true}.
3111 This is the converse of using assertions for program validation; in that
3112 situation, you want to stop when the assertion is violated---that is,
3113 when the condition is false. In C, if you want to test an assertion expressed
3114 by the condition @var{assert}, you should set the condition
3115 @samp{! @var{assert}} on the appropriate breakpoint.
3117 Conditions are also accepted for watchpoints; you may not need them,
3118 since a watchpoint is inspecting the value of an expression anyhow---but
3119 it might be simpler, say, to just set a watchpoint on a variable name,
3120 and specify a condition that tests whether the new value is an interesting
3123 Break conditions can have side effects, and may even call functions in
3124 your program. This can be useful, for example, to activate functions
3125 that log program progress, or to use your own print functions to
3126 format special data structures. The effects are completely predictable
3127 unless there is another enabled breakpoint at the same address. (In
3128 that case, @value{GDBN} might see the other breakpoint first and stop your
3129 program without checking the condition of this one.) Note that
3130 breakpoint commands are usually more convenient and flexible than break
3132 purpose of performing side effects when a breakpoint is reached
3133 (@pxref{Break Commands, ,Breakpoint command lists}).
3135 Break conditions can be specified when a breakpoint is set, by using
3136 @samp{if} in the arguments to the @code{break} command. @xref{Set
3137 Breaks, ,Setting breakpoints}. They can also be changed at any time
3138 with the @code{condition} command.
3140 You can also use the @code{if} keyword with the @code{watch} command.
3141 The @code{catch} command does not recognize the @code{if} keyword;
3142 @code{condition} is the only way to impose a further condition on a
3147 @item condition @var{bnum} @var{expression}
3148 Specify @var{expression} as the break condition for breakpoint,
3149 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3150 breakpoint @var{bnum} stops your program only if the value of
3151 @var{expression} is true (nonzero, in C). When you use
3152 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3153 syntactic correctness, and to determine whether symbols in it have
3154 referents in the context of your breakpoint. If @var{expression} uses
3155 symbols not referenced in the context of the breakpoint, @value{GDBN}
3156 prints an error message:
3159 No symbol "foo" in current context.
3164 not actually evaluate @var{expression} at the time the @code{condition}
3165 command (or a command that sets a breakpoint with a condition, like
3166 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3168 @item condition @var{bnum}
3169 Remove the condition from breakpoint number @var{bnum}. It becomes
3170 an ordinary unconditional breakpoint.
3173 @cindex ignore count (of breakpoint)
3174 A special case of a breakpoint condition is to stop only when the
3175 breakpoint has been reached a certain number of times. This is so
3176 useful that there is a special way to do it, using the @dfn{ignore
3177 count} of the breakpoint. Every breakpoint has an ignore count, which
3178 is an integer. Most of the time, the ignore count is zero, and
3179 therefore has no effect. But if your program reaches a breakpoint whose
3180 ignore count is positive, then instead of stopping, it just decrements
3181 the ignore count by one and continues. As a result, if the ignore count
3182 value is @var{n}, the breakpoint does not stop the next @var{n} times
3183 your program reaches it.
3187 @item ignore @var{bnum} @var{count}
3188 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3189 The next @var{count} times the breakpoint is reached, your program's
3190 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3193 To make the breakpoint stop the next time it is reached, specify
3196 When you use @code{continue} to resume execution of your program from a
3197 breakpoint, you can specify an ignore count directly as an argument to
3198 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3199 Stepping,,Continuing and stepping}.
3201 If a breakpoint has a positive ignore count and a condition, the
3202 condition is not checked. Once the ignore count reaches zero,
3203 @value{GDBN} resumes checking the condition.
3205 You could achieve the effect of the ignore count with a condition such
3206 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3207 is decremented each time. @xref{Convenience Vars, ,Convenience
3211 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3214 @node Break Commands
3215 @subsection Breakpoint command lists
3217 @cindex breakpoint commands
3218 You can give any breakpoint (or watchpoint or catchpoint) a series of
3219 commands to execute when your program stops due to that breakpoint. For
3220 example, you might want to print the values of certain expressions, or
3221 enable other breakpoints.
3226 @item commands @r{[}@var{bnum}@r{]}
3227 @itemx @dots{} @var{command-list} @dots{}
3229 Specify a list of commands for breakpoint number @var{bnum}. The commands
3230 themselves appear on the following lines. Type a line containing just
3231 @code{end} to terminate the commands.
3233 To remove all commands from a breakpoint, type @code{commands} and
3234 follow it immediately with @code{end}; that is, give no commands.
3236 With no @var{bnum} argument, @code{commands} refers to the last
3237 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3238 recently encountered).
3241 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3242 disabled within a @var{command-list}.
3244 You can use breakpoint commands to start your program up again. Simply
3245 use the @code{continue} command, or @code{step}, or any other command
3246 that resumes execution.
3248 Any other commands in the command list, after a command that resumes
3249 execution, are ignored. This is because any time you resume execution
3250 (even with a simple @code{next} or @code{step}), you may encounter
3251 another breakpoint---which could have its own command list, leading to
3252 ambiguities about which list to execute.
3255 If the first command you specify in a command list is @code{silent}, the
3256 usual message about stopping at a breakpoint is not printed. This may
3257 be desirable for breakpoints that are to print a specific message and
3258 then continue. If none of the remaining commands print anything, you
3259 see no sign that the breakpoint was reached. @code{silent} is
3260 meaningful only at the beginning of a breakpoint command list.
3262 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3263 print precisely controlled output, and are often useful in silent
3264 breakpoints. @xref{Output, ,Commands for controlled output}.
3266 For example, here is how you could use breakpoint commands to print the
3267 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3273 printf "x is %d\n",x
3278 One application for breakpoint commands is to compensate for one bug so
3279 you can test for another. Put a breakpoint just after the erroneous line
3280 of code, give it a condition to detect the case in which something
3281 erroneous has been done, and give it commands to assign correct values
3282 to any variables that need them. End with the @code{continue} command
3283 so that your program does not stop, and start with the @code{silent}
3284 command so that no output is produced. Here is an example:
3295 @node Breakpoint Menus
3296 @subsection Breakpoint menus
3298 @cindex symbol overloading
3300 Some programming languages (notably C@t{++} and Objective-C) permit a
3301 single function name
3302 to be defined several times, for application in different contexts.
3303 This is called @dfn{overloading}. When a function name is overloaded,
3304 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3305 a breakpoint. If you realize this is a problem, you can use
3306 something like @samp{break @var{function}(@var{types})} to specify which
3307 particular version of the function you want. Otherwise, @value{GDBN} offers
3308 you a menu of numbered choices for different possible breakpoints, and
3309 waits for your selection with the prompt @samp{>}. The first two
3310 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3311 sets a breakpoint at each definition of @var{function}, and typing
3312 @kbd{0} aborts the @code{break} command without setting any new
3315 For example, the following session excerpt shows an attempt to set a
3316 breakpoint at the overloaded symbol @code{String::after}.
3317 We choose three particular definitions of that function name:
3319 @c FIXME! This is likely to change to show arg type lists, at least
3322 (@value{GDBP}) b String::after
3325 [2] file:String.cc; line number:867
3326 [3] file:String.cc; line number:860
3327 [4] file:String.cc; line number:875
3328 [5] file:String.cc; line number:853
3329 [6] file:String.cc; line number:846
3330 [7] file:String.cc; line number:735
3332 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3333 Breakpoint 2 at 0xb344: file String.cc, line 875.
3334 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3335 Multiple breakpoints were set.
3336 Use the "delete" command to delete unwanted
3342 @c @ifclear BARETARGET
3343 @node Error in Breakpoints
3344 @subsection ``Cannot insert breakpoints''
3346 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3348 Under some operating systems, breakpoints cannot be used in a program if
3349 any other process is running that program. In this situation,
3350 attempting to run or continue a program with a breakpoint causes
3351 @value{GDBN} to print an error message:
3354 Cannot insert breakpoints.
3355 The same program may be running in another process.
3358 When this happens, you have three ways to proceed:
3362 Remove or disable the breakpoints, then continue.
3365 Suspend @value{GDBN}, and copy the file containing your program to a new
3366 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3367 that @value{GDBN} should run your program under that name.
3368 Then start your program again.
3371 Relink your program so that the text segment is nonsharable, using the
3372 linker option @samp{-N}. The operating system limitation may not apply
3373 to nonsharable executables.
3377 A similar message can be printed if you request too many active
3378 hardware-assisted breakpoints and watchpoints:
3380 @c FIXME: the precise wording of this message may change; the relevant
3381 @c source change is not committed yet (Sep 3, 1999).
3383 Stopped; cannot insert breakpoints.
3384 You may have requested too many hardware breakpoints and watchpoints.
3388 This message is printed when you attempt to resume the program, since
3389 only then @value{GDBN} knows exactly how many hardware breakpoints and
3390 watchpoints it needs to insert.
3392 When this message is printed, you need to disable or remove some of the
3393 hardware-assisted breakpoints and watchpoints, and then continue.
3395 @node Breakpoint related warnings
3396 @subsection ``Breakpoint address adjusted...''
3397 @cindex breakpoint address adjusted
3399 Some processor architectures place constraints on the addresses at
3400 which breakpoints may be placed. For architectures thus constrained,
3401 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3402 with the constraints dictated by the architecture.
3404 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3405 a VLIW architecture in which a number of RISC-like instructions may be
3406 bundled together for parallel execution. The FR-V architecture
3407 constrains the location of a breakpoint instruction within such a
3408 bundle to the instruction with the lowest address. @value{GDBN}
3409 honors this constraint by adjusting a breakpoint's address to the
3410 first in the bundle.
3412 It is not uncommon for optimized code to have bundles which contain
3413 instructions from different source statements, thus it may happen that
3414 a breakpoint's address will be adjusted from one source statement to
3415 another. Since this adjustment may significantly alter @value{GDBN}'s
3416 breakpoint related behavior from what the user expects, a warning is
3417 printed when the breakpoint is first set and also when the breakpoint
3420 A warning like the one below is printed when setting a breakpoint
3421 that's been subject to address adjustment:
3424 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3427 Such warnings are printed both for user settable and @value{GDBN}'s
3428 internal breakpoints. If you see one of these warnings, you should
3429 verify that a breakpoint set at the adjusted address will have the
3430 desired affect. If not, the breakpoint in question may be removed and
3431 other breakpoints may be set which will have the desired behavior.
3432 E.g., it may be sufficient to place the breakpoint at a later
3433 instruction. A conditional breakpoint may also be useful in some
3434 cases to prevent the breakpoint from triggering too often.
3436 @value{GDBN} will also issue a warning when stopping at one of these
3437 adjusted breakpoints:
3440 warning: Breakpoint 1 address previously adjusted from 0x00010414
3444 When this warning is encountered, it may be too late to take remedial
3445 action except in cases where the breakpoint is hit earlier or more
3446 frequently than expected.
3448 @node Continuing and Stepping
3449 @section Continuing and stepping
3453 @cindex resuming execution
3454 @dfn{Continuing} means resuming program execution until your program
3455 completes normally. In contrast, @dfn{stepping} means executing just
3456 one more ``step'' of your program, where ``step'' may mean either one
3457 line of source code, or one machine instruction (depending on what
3458 particular command you use). Either when continuing or when stepping,
3459 your program may stop even sooner, due to a breakpoint or a signal. (If
3460 it stops due to a signal, you may want to use @code{handle}, or use
3461 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3465 @kindex c @r{(@code{continue})}
3466 @kindex fg @r{(resume foreground execution)}
3467 @item continue @r{[}@var{ignore-count}@r{]}
3468 @itemx c @r{[}@var{ignore-count}@r{]}
3469 @itemx fg @r{[}@var{ignore-count}@r{]}
3470 Resume program execution, at the address where your program last stopped;
3471 any breakpoints set at that address are bypassed. The optional argument
3472 @var{ignore-count} allows you to specify a further number of times to
3473 ignore a breakpoint at this location; its effect is like that of
3474 @code{ignore} (@pxref{Conditions, ,Break conditions}).
3476 The argument @var{ignore-count} is meaningful only when your program
3477 stopped due to a breakpoint. At other times, the argument to
3478 @code{continue} is ignored.
3480 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3481 debugged program is deemed to be the foreground program) are provided
3482 purely for convenience, and have exactly the same behavior as
3486 To resume execution at a different place, you can use @code{return}
3487 (@pxref{Returning, ,Returning from a function}) to go back to the
3488 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3489 different address}) to go to an arbitrary location in your program.
3491 A typical technique for using stepping is to set a breakpoint
3492 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the
3493 beginning of the function or the section of your program where a problem
3494 is believed to lie, run your program until it stops at that breakpoint,
3495 and then step through the suspect area, examining the variables that are
3496 interesting, until you see the problem happen.
3500 @kindex s @r{(@code{step})}
3502 Continue running your program until control reaches a different source
3503 line, then stop it and return control to @value{GDBN}. This command is
3504 abbreviated @code{s}.
3507 @c "without debugging information" is imprecise; actually "without line
3508 @c numbers in the debugging information". (gcc -g1 has debugging info but
3509 @c not line numbers). But it seems complex to try to make that
3510 @c distinction here.
3511 @emph{Warning:} If you use the @code{step} command while control is
3512 within a function that was compiled without debugging information,
3513 execution proceeds until control reaches a function that does have
3514 debugging information. Likewise, it will not step into a function which
3515 is compiled without debugging information. To step through functions
3516 without debugging information, use the @code{stepi} command, described
3520 The @code{step} command only stops at the first instruction of a source
3521 line. This prevents the multiple stops that could otherwise occur in
3522 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3523 to stop if a function that has debugging information is called within
3524 the line. In other words, @code{step} @emph{steps inside} any functions
3525 called within the line.
3527 Also, the @code{step} command only enters a function if there is line
3528 number information for the function. Otherwise it acts like the
3529 @code{next} command. This avoids problems when using @code{cc -gl}
3530 on MIPS machines. Previously, @code{step} entered subroutines if there
3531 was any debugging information about the routine.
3533 @item step @var{count}
3534 Continue running as in @code{step}, but do so @var{count} times. If a
3535 breakpoint is reached, or a signal not related to stepping occurs before
3536 @var{count} steps, stepping stops right away.
3539 @kindex n @r{(@code{next})}
3540 @item next @r{[}@var{count}@r{]}
3541 Continue to the next source line in the current (innermost) stack frame.
3542 This is similar to @code{step}, but function calls that appear within
3543 the line of code are executed without stopping. Execution stops when
3544 control reaches a different line of code at the original stack level
3545 that was executing when you gave the @code{next} command. This command
3546 is abbreviated @code{n}.
3548 An argument @var{count} is a repeat count, as for @code{step}.
3551 @c FIX ME!! Do we delete this, or is there a way it fits in with
3552 @c the following paragraph? --- Vctoria
3554 @c @code{next} within a function that lacks debugging information acts like
3555 @c @code{step}, but any function calls appearing within the code of the
3556 @c function are executed without stopping.
3558 The @code{next} command only stops at the first instruction of a
3559 source line. This prevents multiple stops that could otherwise occur in
3560 @code{switch} statements, @code{for} loops, etc.
3562 @kindex set step-mode
3564 @cindex functions without line info, and stepping
3565 @cindex stepping into functions with no line info
3566 @itemx set step-mode on
3567 The @code{set step-mode on} command causes the @code{step} command to
3568 stop at the first instruction of a function which contains no debug line
3569 information rather than stepping over it.
3571 This is useful in cases where you may be interested in inspecting the
3572 machine instructions of a function which has no symbolic info and do not
3573 want @value{GDBN} to automatically skip over this function.
3575 @item set step-mode off
3576 Causes the @code{step} command to step over any functions which contains no
3577 debug information. This is the default.
3581 Continue running until just after function in the selected stack frame
3582 returns. Print the returned value (if any).
3584 Contrast this with the @code{return} command (@pxref{Returning,
3585 ,Returning from a function}).
3588 @kindex u @r{(@code{until})}
3591 Continue running until a source line past the current line, in the
3592 current stack frame, is reached. This command is used to avoid single
3593 stepping through a loop more than once. It is like the @code{next}
3594 command, except that when @code{until} encounters a jump, it
3595 automatically continues execution until the program counter is greater
3596 than the address of the jump.
3598 This means that when you reach the end of a loop after single stepping
3599 though it, @code{until} makes your program continue execution until it
3600 exits the loop. In contrast, a @code{next} command at the end of a loop
3601 simply steps back to the beginning of the loop, which forces you to step
3602 through the next iteration.
3604 @code{until} always stops your program if it attempts to exit the current
3607 @code{until} may produce somewhat counterintuitive results if the order
3608 of machine code does not match the order of the source lines. For
3609 example, in the following excerpt from a debugging session, the @code{f}
3610 (@code{frame}) command shows that execution is stopped at line
3611 @code{206}; yet when we use @code{until}, we get to line @code{195}:
3615 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
3617 (@value{GDBP}) until
3618 195 for ( ; argc > 0; NEXTARG) @{
3621 This happened because, for execution efficiency, the compiler had
3622 generated code for the loop closure test at the end, rather than the
3623 start, of the loop---even though the test in a C @code{for}-loop is
3624 written before the body of the loop. The @code{until} command appeared
3625 to step back to the beginning of the loop when it advanced to this
3626 expression; however, it has not really gone to an earlier
3627 statement---not in terms of the actual machine code.
3629 @code{until} with no argument works by means of single
3630 instruction stepping, and hence is slower than @code{until} with an
3633 @item until @var{location}
3634 @itemx u @var{location}
3635 Continue running your program until either the specified location is
3636 reached, or the current stack frame returns. @var{location} is any of
3637 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
3638 ,Setting breakpoints}). This form of the command uses breakpoints, and
3639 hence is quicker than @code{until} without an argument. The specified
3640 location is actually reached only if it is in the current frame. This
3641 implies that @code{until} can be used to skip over recursive function
3642 invocations. For instance in the code below, if the current location is
3643 line @code{96}, issuing @code{until 99} will execute the program up to
3644 line @code{99} in the same invocation of factorial, i.e. after the inner
3645 invocations have returned.
3648 94 int factorial (int value)
3650 96 if (value > 1) @{
3651 97 value *= factorial (value - 1);
3658 @kindex advance @var{location}
3659 @itemx advance @var{location}
3660 Continue running the program up to the given location. An argument is
3661 required, anything of the same form as arguments for the @code{break}
3662 command. Execution will also stop upon exit from the current stack
3663 frame. This command is similar to @code{until}, but @code{advance} will
3664 not skip over recursive function calls, and the target location doesn't
3665 have to be in the same frame as the current one.
3669 @kindex si @r{(@code{stepi})}
3671 @itemx stepi @var{arg}
3673 Execute one machine instruction, then stop and return to the debugger.
3675 It is often useful to do @samp{display/i $pc} when stepping by machine
3676 instructions. This makes @value{GDBN} automatically display the next
3677 instruction to be executed, each time your program stops. @xref{Auto
3678 Display,, Automatic display}.
3680 An argument is a repeat count, as in @code{step}.
3684 @kindex ni @r{(@code{nexti})}
3686 @itemx nexti @var{arg}
3688 Execute one machine instruction, but if it is a function call,
3689 proceed until the function returns.
3691 An argument is a repeat count, as in @code{next}.
3698 A signal is an asynchronous event that can happen in a program. The
3699 operating system defines the possible kinds of signals, and gives each
3700 kind a name and a number. For example, in Unix @code{SIGINT} is the
3701 signal a program gets when you type an interrupt character (often @kbd{C-c});
3702 @code{SIGSEGV} is the signal a program gets from referencing a place in
3703 memory far away from all the areas in use; @code{SIGALRM} occurs when
3704 the alarm clock timer goes off (which happens only if your program has
3705 requested an alarm).
3707 @cindex fatal signals
3708 Some signals, including @code{SIGALRM}, are a normal part of the
3709 functioning of your program. Others, such as @code{SIGSEGV}, indicate
3710 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
3711 program has not specified in advance some other way to handle the signal.
3712 @code{SIGINT} does not indicate an error in your program, but it is normally
3713 fatal so it can carry out the purpose of the interrupt: to kill the program.
3715 @value{GDBN} has the ability to detect any occurrence of a signal in your
3716 program. You can tell @value{GDBN} in advance what to do for each kind of
3719 @cindex handling signals
3720 Normally, @value{GDBN} is set up to let the non-erroneous signals like
3721 @code{SIGALRM} be silently passed to your program
3722 (so as not to interfere with their role in the program's functioning)
3723 but to stop your program immediately whenever an error signal happens.
3724 You can change these settings with the @code{handle} command.
3727 @kindex info signals
3730 Print a table of all the kinds of signals and how @value{GDBN} has been told to
3731 handle each one. You can use this to see the signal numbers of all
3732 the defined types of signals.
3734 @code{info handle} is an alias for @code{info signals}.
3737 @item handle @var{signal} @var{keywords}@dots{}
3738 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
3739 can be the number of a signal or its name (with or without the
3740 @samp{SIG} at the beginning); a list of signal numbers of the form
3741 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
3742 known signals. The @var{keywords} say what change to make.
3746 The keywords allowed by the @code{handle} command can be abbreviated.
3747 Their full names are:
3751 @value{GDBN} should not stop your program when this signal happens. It may
3752 still print a message telling you that the signal has come in.
3755 @value{GDBN} should stop your program when this signal happens. This implies
3756 the @code{print} keyword as well.
3759 @value{GDBN} should print a message when this signal happens.
3762 @value{GDBN} should not mention the occurrence of the signal at all. This
3763 implies the @code{nostop} keyword as well.
3767 @value{GDBN} should allow your program to see this signal; your program
3768 can handle the signal, or else it may terminate if the signal is fatal
3769 and not handled. @code{pass} and @code{noignore} are synonyms.
3773 @value{GDBN} should not allow your program to see this signal.
3774 @code{nopass} and @code{ignore} are synonyms.
3778 When a signal stops your program, the signal is not visible to the
3780 continue. Your program sees the signal then, if @code{pass} is in
3781 effect for the signal in question @emph{at that time}. In other words,
3782 after @value{GDBN} reports a signal, you can use the @code{handle}
3783 command with @code{pass} or @code{nopass} to control whether your
3784 program sees that signal when you continue.
3786 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
3787 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
3788 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
3791 You can also use the @code{signal} command to prevent your program from
3792 seeing a signal, or cause it to see a signal it normally would not see,
3793 or to give it any signal at any time. For example, if your program stopped
3794 due to some sort of memory reference error, you might store correct
3795 values into the erroneous variables and continue, hoping to see more
3796 execution; but your program would probably terminate immediately as
3797 a result of the fatal signal once it saw the signal. To prevent this,
3798 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
3802 @section Stopping and starting multi-thread programs
3804 When your program has multiple threads (@pxref{Threads,, Debugging
3805 programs with multiple threads}), you can choose whether to set
3806 breakpoints on all threads, or on a particular thread.
3809 @cindex breakpoints and threads
3810 @cindex thread breakpoints
3811 @kindex break @dots{} thread @var{threadno}
3812 @item break @var{linespec} thread @var{threadno}
3813 @itemx break @var{linespec} thread @var{threadno} if @dots{}
3814 @var{linespec} specifies source lines; there are several ways of
3815 writing them, but the effect is always to specify some source line.
3817 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
3818 to specify that you only want @value{GDBN} to stop the program when a
3819 particular thread reaches this breakpoint. @var{threadno} is one of the
3820 numeric thread identifiers assigned by @value{GDBN}, shown in the first
3821 column of the @samp{info threads} display.
3823 If you do not specify @samp{thread @var{threadno}} when you set a
3824 breakpoint, the breakpoint applies to @emph{all} threads of your
3827 You can use the @code{thread} qualifier on conditional breakpoints as
3828 well; in this case, place @samp{thread @var{threadno}} before the
3829 breakpoint condition, like this:
3832 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
3837 @cindex stopped threads
3838 @cindex threads, stopped
3839 Whenever your program stops under @value{GDBN} for any reason,
3840 @emph{all} threads of execution stop, not just the current thread. This
3841 allows you to examine the overall state of the program, including
3842 switching between threads, without worrying that things may change
3845 @cindex thread breakpoints and system calls
3846 @cindex system calls and thread breakpoints
3847 @cindex premature return from system calls
3848 There is an unfortunate side effect. If one thread stops for a
3849 breakpoint, or for some other reason, and another thread is blocked in a
3850 system call, then the system call may return prematurely. This is a
3851 consequence of the interaction between multiple threads and the signals
3852 that @value{GDBN} uses to implement breakpoints and other events that
3855 To handle this problem, your program should check the return value of
3856 each system call and react appropriately. This is good programming
3859 For example, do not write code like this:
3865 The call to @code{sleep} will return early if a different thread stops
3866 at a breakpoint or for some other reason.
3868 Instead, write this:
3873 unslept = sleep (unslept);
3876 A system call is allowed to return early, so the system is still
3877 conforming to its specification. But @value{GDBN} does cause your
3878 multi-threaded program to behave differently than it would without
3881 Also, @value{GDBN} uses internal breakpoints in the thread library to
3882 monitor certain events such as thread creation and thread destruction.
3883 When such an event happens, a system call in another thread may return
3884 prematurely, even though your program does not appear to stop.
3886 @cindex continuing threads
3887 @cindex threads, continuing
3888 Conversely, whenever you restart the program, @emph{all} threads start
3889 executing. @emph{This is true even when single-stepping} with commands
3890 like @code{step} or @code{next}.
3892 In particular, @value{GDBN} cannot single-step all threads in lockstep.
3893 Since thread scheduling is up to your debugging target's operating
3894 system (not controlled by @value{GDBN}), other threads may
3895 execute more than one statement while the current thread completes a
3896 single step. Moreover, in general other threads stop in the middle of a
3897 statement, rather than at a clean statement boundary, when the program
3900 You might even find your program stopped in another thread after
3901 continuing or even single-stepping. This happens whenever some other
3902 thread runs into a breakpoint, a signal, or an exception before the
3903 first thread completes whatever you requested.
3905 On some OSes, you can lock the OS scheduler and thus allow only a single
3909 @item set scheduler-locking @var{mode}
3910 Set the scheduler locking mode. If it is @code{off}, then there is no
3911 locking and any thread may run at any time. If @code{on}, then only the
3912 current thread may run when the inferior is resumed. The @code{step}
3913 mode optimizes for single-stepping. It stops other threads from
3914 ``seizing the prompt'' by preempting the current thread while you are
3915 stepping. Other threads will only rarely (or never) get a chance to run
3916 when you step. They are more likely to run when you @samp{next} over a
3917 function call, and they are completely free to run when you use commands
3918 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
3919 thread hits a breakpoint during its timeslice, they will never steal the
3920 @value{GDBN} prompt away from the thread that you are debugging.
3922 @item show scheduler-locking
3923 Display the current scheduler locking mode.
3928 @chapter Examining the Stack
3930 When your program has stopped, the first thing you need to know is where it
3931 stopped and how it got there.
3934 Each time your program performs a function call, information about the call
3936 That information includes the location of the call in your program,
3937 the arguments of the call,
3938 and the local variables of the function being called.
3939 The information is saved in a block of data called a @dfn{stack frame}.
3940 The stack frames are allocated in a region of memory called the @dfn{call
3943 When your program stops, the @value{GDBN} commands for examining the
3944 stack allow you to see all of this information.
3946 @cindex selected frame
3947 One of the stack frames is @dfn{selected} by @value{GDBN} and many
3948 @value{GDBN} commands refer implicitly to the selected frame. In
3949 particular, whenever you ask @value{GDBN} for the value of a variable in
3950 your program, the value is found in the selected frame. There are
3951 special @value{GDBN} commands to select whichever frame you are
3952 interested in. @xref{Selection, ,Selecting a frame}.
3954 When your program stops, @value{GDBN} automatically selects the
3955 currently executing frame and describes it briefly, similar to the
3956 @code{frame} command (@pxref{Frame Info, ,Information about a frame}).
3959 * Frames:: Stack frames
3960 * Backtrace:: Backtraces
3961 * Selection:: Selecting a frame
3962 * Frame Info:: Information on a frame
3967 @section Stack frames
3969 @cindex frame, definition
3971 The call stack is divided up into contiguous pieces called @dfn{stack
3972 frames}, or @dfn{frames} for short; each frame is the data associated
3973 with one call to one function. The frame contains the arguments given
3974 to the function, the function's local variables, and the address at
3975 which the function is executing.
3977 @cindex initial frame
3978 @cindex outermost frame
3979 @cindex innermost frame
3980 When your program is started, the stack has only one frame, that of the
3981 function @code{main}. This is called the @dfn{initial} frame or the
3982 @dfn{outermost} frame. Each time a function is called, a new frame is
3983 made. Each time a function returns, the frame for that function invocation
3984 is eliminated. If a function is recursive, there can be many frames for
3985 the same function. The frame for the function in which execution is
3986 actually occurring is called the @dfn{innermost} frame. This is the most
3987 recently created of all the stack frames that still exist.
3989 @cindex frame pointer
3990 Inside your program, stack frames are identified by their addresses. A
3991 stack frame consists of many bytes, each of which has its own address; each
3992 kind of computer has a convention for choosing one byte whose
3993 address serves as the address of the frame. Usually this address is kept
3994 in a register called the @dfn{frame pointer register} while execution is
3995 going on in that frame.
3997 @cindex frame number
3998 @value{GDBN} assigns numbers to all existing stack frames, starting with
3999 zero for the innermost frame, one for the frame that called it,
4000 and so on upward. These numbers do not really exist in your program;
4001 they are assigned by @value{GDBN} to give you a way of designating stack
4002 frames in @value{GDBN} commands.
4004 @c The -fomit-frame-pointer below perennially causes hbox overflow
4005 @c underflow problems.
4006 @cindex frameless execution
4007 Some compilers provide a way to compile functions so that they operate
4008 without stack frames. (For example, the @value{GCC} option
4010 @samp{-fomit-frame-pointer}
4012 generates functions without a frame.)
4013 This is occasionally done with heavily used library functions to save
4014 the frame setup time. @value{GDBN} has limited facilities for dealing
4015 with these function invocations. If the innermost function invocation
4016 has no stack frame, @value{GDBN} nevertheless regards it as though
4017 it had a separate frame, which is numbered zero as usual, allowing
4018 correct tracing of the function call chain. However, @value{GDBN} has
4019 no provision for frameless functions elsewhere in the stack.
4022 @kindex frame@r{, command}
4023 @cindex current stack frame
4024 @item frame @var{args}
4025 The @code{frame} command allows you to move from one stack frame to another,
4026 and to print the stack frame you select. @var{args} may be either the
4027 address of the frame or the stack frame number. Without an argument,
4028 @code{frame} prints the current stack frame.
4030 @kindex select-frame
4031 @cindex selecting frame silently
4033 The @code{select-frame} command allows you to move from one stack frame
4034 to another without printing the frame. This is the silent version of
4043 @cindex stack traces
4044 A backtrace is a summary of how your program got where it is. It shows one
4045 line per frame, for many frames, starting with the currently executing
4046 frame (frame zero), followed by its caller (frame one), and on up the
4051 @kindex bt @r{(@code{backtrace})}
4054 Print a backtrace of the entire stack: one line per frame for all
4055 frames in the stack.
4057 You can stop the backtrace at any time by typing the system interrupt
4058 character, normally @kbd{C-c}.
4060 @item backtrace @var{n}
4062 Similar, but print only the innermost @var{n} frames.
4064 @item backtrace -@var{n}
4066 Similar, but print only the outermost @var{n} frames.
4071 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4072 are additional aliases for @code{backtrace}.
4074 Each line in the backtrace shows the frame number and the function name.
4075 The program counter value is also shown---unless you use @code{set
4076 print address off}. The backtrace also shows the source file name and
4077 line number, as well as the arguments to the function. The program
4078 counter value is omitted if it is at the beginning of the code for that
4081 Here is an example of a backtrace. It was made with the command
4082 @samp{bt 3}, so it shows the innermost three frames.
4086 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4088 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4089 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4091 (More stack frames follow...)
4096 The display for frame zero does not begin with a program counter
4097 value, indicating that your program has stopped at the beginning of the
4098 code for line @code{993} of @code{builtin.c}.
4100 Most programs have a standard user entry point---a place where system
4101 libraries and startup code transition into user code. For C this is
4102 @code{main}. When @value{GDBN} finds the entry function in a backtrace
4103 it will terminate the backtrace, to avoid tracing into highly
4104 system-specific (and generally uninteresting) code.
4106 If you need to examine the startup code, or limit the number of levels
4107 in a backtrace, you can change this behavior:
4110 @item set backtrace past-main
4111 @itemx set backtrace past-main on
4112 @kindex set backtrace
4113 Backtraces will continue past the user entry point.
4115 @item set backtrace past-main off
4116 Backtraces will stop when they encounter the user entry point. This is the
4119 @item show backtrace past-main
4120 @kindex show backtrace
4121 Display the current user entry point backtrace policy.
4123 @item set backtrace limit @var{n}
4124 @itemx set backtrace limit 0
4125 @cindex backtrace limit
4126 Limit the backtrace to @var{n} levels. A value of zero means
4129 @item show backtrace limit
4130 Display the current limit on backtrace levels.
4134 @section Selecting a frame
4136 Most commands for examining the stack and other data in your program work on
4137 whichever stack frame is selected at the moment. Here are the commands for
4138 selecting a stack frame; all of them finish by printing a brief description
4139 of the stack frame just selected.
4142 @kindex frame@r{, selecting}
4143 @kindex f @r{(@code{frame})}
4146 Select frame number @var{n}. Recall that frame zero is the innermost
4147 (currently executing) frame, frame one is the frame that called the
4148 innermost one, and so on. The highest-numbered frame is the one for
4151 @item frame @var{addr}
4153 Select the frame at address @var{addr}. This is useful mainly if the
4154 chaining of stack frames has been damaged by a bug, making it
4155 impossible for @value{GDBN} to assign numbers properly to all frames. In
4156 addition, this can be useful when your program has multiple stacks and
4157 switches between them.
4159 On the SPARC architecture, @code{frame} needs two addresses to
4160 select an arbitrary frame: a frame pointer and a stack pointer.
4162 On the MIPS and Alpha architecture, it needs two addresses: a stack
4163 pointer and a program counter.
4165 On the 29k architecture, it needs three addresses: a register stack
4166 pointer, a program counter, and a memory stack pointer.
4167 @c note to future updaters: this is conditioned on a flag
4168 @c SETUP_ARBITRARY_FRAME in the tm-*.h files. The above is up to date
4169 @c as of 27 Jan 1994.
4173 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4174 advances toward the outermost frame, to higher frame numbers, to frames
4175 that have existed longer. @var{n} defaults to one.
4178 @kindex do @r{(@code{down})}
4180 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4181 advances toward the innermost frame, to lower frame numbers, to frames
4182 that were created more recently. @var{n} defaults to one. You may
4183 abbreviate @code{down} as @code{do}.
4186 All of these commands end by printing two lines of output describing the
4187 frame. The first line shows the frame number, the function name, the
4188 arguments, and the source file and line number of execution in that
4189 frame. The second line shows the text of that source line.
4197 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4199 10 read_input_file (argv[i]);
4203 After such a printout, the @code{list} command with no arguments
4204 prints ten lines centered on the point of execution in the frame.
4205 You can also edit the program at the point of execution with your favorite
4206 editing program by typing @code{edit}.
4207 @xref{List, ,Printing source lines},
4211 @kindex down-silently
4213 @item up-silently @var{n}
4214 @itemx down-silently @var{n}
4215 These two commands are variants of @code{up} and @code{down},
4216 respectively; they differ in that they do their work silently, without
4217 causing display of the new frame. They are intended primarily for use
4218 in @value{GDBN} command scripts, where the output might be unnecessary and
4223 @section Information about a frame
4225 There are several other commands to print information about the selected
4231 When used without any argument, this command does not change which
4232 frame is selected, but prints a brief description of the currently
4233 selected stack frame. It can be abbreviated @code{f}. With an
4234 argument, this command is used to select a stack frame.
4235 @xref{Selection, ,Selecting a frame}.
4238 @kindex info f @r{(@code{info frame})}
4241 This command prints a verbose description of the selected stack frame,
4246 the address of the frame
4248 the address of the next frame down (called by this frame)
4250 the address of the next frame up (caller of this frame)
4252 the language in which the source code corresponding to this frame is written
4254 the address of the frame's arguments
4256 the address of the frame's local variables
4258 the program counter saved in it (the address of execution in the caller frame)
4260 which registers were saved in the frame
4263 @noindent The verbose description is useful when
4264 something has gone wrong that has made the stack format fail to fit
4265 the usual conventions.
4267 @item info frame @var{addr}
4268 @itemx info f @var{addr}
4269 Print a verbose description of the frame at address @var{addr}, without
4270 selecting that frame. The selected frame remains unchanged by this
4271 command. This requires the same kind of address (more than one for some
4272 architectures) that you specify in the @code{frame} command.
4273 @xref{Selection, ,Selecting a frame}.
4277 Print the arguments of the selected frame, each on a separate line.
4281 Print the local variables of the selected frame, each on a separate
4282 line. These are all variables (declared either static or automatic)
4283 accessible at the point of execution of the selected frame.
4286 @cindex catch exceptions, list active handlers
4287 @cindex exception handlers, how to list
4289 Print a list of all the exception handlers that are active in the
4290 current stack frame at the current point of execution. To see other
4291 exception handlers, visit the associated frame (using the @code{up},
4292 @code{down}, or @code{frame} commands); then type @code{info catch}.
4293 @xref{Set Catchpoints, , Setting catchpoints}.
4299 @chapter Examining Source Files
4301 @value{GDBN} can print parts of your program's source, since the debugging
4302 information recorded in the program tells @value{GDBN} what source files were
4303 used to build it. When your program stops, @value{GDBN} spontaneously prints
4304 the line where it stopped. Likewise, when you select a stack frame
4305 (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
4306 execution in that frame has stopped. You can print other portions of
4307 source files by explicit command.
4309 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4310 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4311 @value{GDBN} under @sc{gnu} Emacs}.
4314 * List:: Printing source lines
4315 * Edit:: Editing source files
4316 * Search:: Searching source files
4317 * Source Path:: Specifying source directories
4318 * Machine Code:: Source and machine code
4322 @section Printing source lines
4325 @kindex l @r{(@code{list})}
4326 To print lines from a source file, use the @code{list} command
4327 (abbreviated @code{l}). By default, ten lines are printed.
4328 There are several ways to specify what part of the file you want to print.
4330 Here are the forms of the @code{list} command most commonly used:
4333 @item list @var{linenum}
4334 Print lines centered around line number @var{linenum} in the
4335 current source file.
4337 @item list @var{function}
4338 Print lines centered around the beginning of function
4342 Print more lines. If the last lines printed were printed with a
4343 @code{list} command, this prints lines following the last lines
4344 printed; however, if the last line printed was a solitary line printed
4345 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4346 Stack}), this prints lines centered around that line.
4349 Print lines just before the lines last printed.
4352 By default, @value{GDBN} prints ten source lines with any of these forms of
4353 the @code{list} command. You can change this using @code{set listsize}:
4356 @kindex set listsize
4357 @item set listsize @var{count}
4358 Make the @code{list} command display @var{count} source lines (unless
4359 the @code{list} argument explicitly specifies some other number).
4361 @kindex show listsize
4363 Display the number of lines that @code{list} prints.
4366 Repeating a @code{list} command with @key{RET} discards the argument,
4367 so it is equivalent to typing just @code{list}. This is more useful
4368 than listing the same lines again. An exception is made for an
4369 argument of @samp{-}; that argument is preserved in repetition so that
4370 each repetition moves up in the source file.
4373 In general, the @code{list} command expects you to supply zero, one or two
4374 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4375 of writing them, but the effect is always to specify some source line.
4376 Here is a complete description of the possible arguments for @code{list}:
4379 @item list @var{linespec}
4380 Print lines centered around the line specified by @var{linespec}.
4382 @item list @var{first},@var{last}
4383 Print lines from @var{first} to @var{last}. Both arguments are
4386 @item list ,@var{last}
4387 Print lines ending with @var{last}.
4389 @item list @var{first},
4390 Print lines starting with @var{first}.
4393 Print lines just after the lines last printed.
4396 Print lines just before the lines last printed.
4399 As described in the preceding table.
4402 Here are the ways of specifying a single source line---all the
4407 Specifies line @var{number} of the current source file.
4408 When a @code{list} command has two linespecs, this refers to
4409 the same source file as the first linespec.
4412 Specifies the line @var{offset} lines after the last line printed.
4413 When used as the second linespec in a @code{list} command that has
4414 two, this specifies the line @var{offset} lines down from the
4418 Specifies the line @var{offset} lines before the last line printed.
4420 @item @var{filename}:@var{number}
4421 Specifies line @var{number} in the source file @var{filename}.
4423 @item @var{function}
4424 Specifies the line that begins the body of the function @var{function}.
4425 For example: in C, this is the line with the open brace.
4427 @item @var{filename}:@var{function}
4428 Specifies the line of the open-brace that begins the body of the
4429 function @var{function} in the file @var{filename}. You only need the
4430 file name with a function name to avoid ambiguity when there are
4431 identically named functions in different source files.
4433 @item *@var{address}
4434 Specifies the line containing the program address @var{address}.
4435 @var{address} may be any expression.
4439 @section Editing source files
4440 @cindex editing source files
4443 @kindex e @r{(@code{edit})}
4444 To edit the lines in a source file, use the @code{edit} command.
4445 The editing program of your choice
4446 is invoked with the current line set to
4447 the active line in the program.
4448 Alternatively, there are several ways to specify what part of the file you
4449 want to print if you want to see other parts of the program.
4451 Here are the forms of the @code{edit} command most commonly used:
4455 Edit the current source file at the active line number in the program.
4457 @item edit @var{number}
4458 Edit the current source file with @var{number} as the active line number.
4460 @item edit @var{function}
4461 Edit the file containing @var{function} at the beginning of its definition.
4463 @item edit @var{filename}:@var{number}
4464 Specifies line @var{number} in the source file @var{filename}.
4466 @item edit @var{filename}:@var{function}
4467 Specifies the line that begins the body of the
4468 function @var{function} in the file @var{filename}. You only need the
4469 file name with a function name to avoid ambiguity when there are
4470 identically named functions in different source files.
4472 @item edit *@var{address}
4473 Specifies the line containing the program address @var{address}.
4474 @var{address} may be any expression.
4477 @subsection Choosing your editor
4478 You can customize @value{GDBN} to use any editor you want
4480 The only restriction is that your editor (say @code{ex}), recognizes the
4481 following command-line syntax:
4483 ex +@var{number} file
4485 The optional numeric value +@var{number} specifies the number of the line in
4486 the file where to start editing.}.
4487 By default, it is @file{@value{EDITOR}}, but you can change this
4488 by setting the environment variable @code{EDITOR} before using
4489 @value{GDBN}. For example, to configure @value{GDBN} to use the
4490 @code{vi} editor, you could use these commands with the @code{sh} shell:
4496 or in the @code{csh} shell,
4498 setenv EDITOR /usr/bin/vi
4503 @section Searching source files
4504 @cindex searching source files
4505 @kindex reverse-search
4507 There are two commands for searching through the current source file for a
4512 @kindex forward-search
4513 @item forward-search @var{regexp}
4514 @itemx search @var{regexp}
4515 The command @samp{forward-search @var{regexp}} checks each line,
4516 starting with the one following the last line listed, for a match for
4517 @var{regexp}. It lists the line that is found. You can use the
4518 synonym @samp{search @var{regexp}} or abbreviate the command name as
4521 @item reverse-search @var{regexp}
4522 The command @samp{reverse-search @var{regexp}} checks each line, starting
4523 with the one before the last line listed and going backward, for a match
4524 for @var{regexp}. It lists the line that is found. You can abbreviate
4525 this command as @code{rev}.
4529 @section Specifying source directories
4532 @cindex directories for source files
4533 Executable programs sometimes do not record the directories of the source
4534 files from which they were compiled, just the names. Even when they do,
4535 the directories could be moved between the compilation and your debugging
4536 session. @value{GDBN} has a list of directories to search for source files;
4537 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
4538 it tries all the directories in the list, in the order they are present
4539 in the list, until it finds a file with the desired name.
4541 For example, suppose an executable references the file
4542 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
4543 @file{/mnt/cross}. The file is first looked up literally; if this
4544 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
4545 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
4546 message is printed. @value{GDBN} does not look up the parts of the
4547 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
4548 Likewise, the subdirectories of the source path are not searched: if
4549 the source path is @file{/mnt/cross}, and the binary refers to
4550 @file{foo.c}, @value{GDBN} would not find it under
4551 @file{/mnt/cross/usr/src/foo-1.0/lib}.
4553 Plain file names, relative file names with leading directories, file
4554 names containing dots, etc.@: are all treated as described above; for
4555 instance, if the source path is @file{/mnt/cross}, and the source file
4556 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
4557 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
4558 that---@file{/mnt/cross/foo.c}.
4560 Note that the executable search path is @emph{not} used to locate the
4561 source files. Neither is the current working directory, unless it
4562 happens to be in the source path.
4564 Whenever you reset or rearrange the source path, @value{GDBN} clears out
4565 any information it has cached about where source files are found and where
4566 each line is in the file.
4570 When you start @value{GDBN}, its source path includes only @samp{cdir}
4571 and @samp{cwd}, in that order.
4572 To add other directories, use the @code{directory} command.
4575 @item directory @var{dirname} @dots{}
4576 @item dir @var{dirname} @dots{}
4577 Add directory @var{dirname} to the front of the source path. Several
4578 directory names may be given to this command, separated by @samp{:}
4579 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
4580 part of absolute file names) or
4581 whitespace. You may specify a directory that is already in the source
4582 path; this moves it forward, so @value{GDBN} searches it sooner.
4586 @vindex $cdir@r{, convenience variable}
4587 @vindex $cwdr@r{, convenience variable}
4588 @cindex compilation directory
4589 @cindex current directory
4590 @cindex working directory
4591 @cindex directory, current
4592 @cindex directory, compilation
4593 You can use the string @samp{$cdir} to refer to the compilation
4594 directory (if one is recorded), and @samp{$cwd} to refer to the current
4595 working directory. @samp{$cwd} is not the same as @samp{.}---the former
4596 tracks the current working directory as it changes during your @value{GDBN}
4597 session, while the latter is immediately expanded to the current
4598 directory at the time you add an entry to the source path.
4601 Reset the source path to empty again. This requires confirmation.
4603 @c RET-repeat for @code{directory} is explicitly disabled, but since
4604 @c repeating it would be a no-op we do not say that. (thanks to RMS)
4606 @item show directories
4607 @kindex show directories
4608 Print the source path: show which directories it contains.
4611 If your source path is cluttered with directories that are no longer of
4612 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
4613 versions of source. You can correct the situation as follows:
4617 Use @code{directory} with no argument to reset the source path to empty.
4620 Use @code{directory} with suitable arguments to reinstall the
4621 directories you want in the source path. You can add all the
4622 directories in one command.
4626 @section Source and machine code
4627 @cindex source line and its code address
4629 You can use the command @code{info line} to map source lines to program
4630 addresses (and vice versa), and the command @code{disassemble} to display
4631 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
4632 mode, the @code{info line} command causes the arrow to point to the
4633 line specified. Also, @code{info line} prints addresses in symbolic form as
4638 @item info line @var{linespec}
4639 Print the starting and ending addresses of the compiled code for
4640 source line @var{linespec}. You can specify source lines in any of
4641 the ways understood by the @code{list} command (@pxref{List, ,Printing
4645 For example, we can use @code{info line} to discover the location of
4646 the object code for the first line of function
4647 @code{m4_changequote}:
4649 @c FIXME: I think this example should also show the addresses in
4650 @c symbolic form, as they usually would be displayed.
4652 (@value{GDBP}) info line m4_changequote
4653 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
4657 @cindex code address and its source line
4658 We can also inquire (using @code{*@var{addr}} as the form for
4659 @var{linespec}) what source line covers a particular address:
4661 (@value{GDBP}) info line *0x63ff
4662 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
4665 @cindex @code{$_} and @code{info line}
4666 @cindex @code{x} command, default address
4667 @kindex x@r{(examine), and} info line
4668 After @code{info line}, the default address for the @code{x} command
4669 is changed to the starting address of the line, so that @samp{x/i} is
4670 sufficient to begin examining the machine code (@pxref{Memory,
4671 ,Examining memory}). Also, this address is saved as the value of the
4672 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
4677 @cindex assembly instructions
4678 @cindex instructions, assembly
4679 @cindex machine instructions
4680 @cindex listing machine instructions
4682 This specialized command dumps a range of memory as machine
4683 instructions. The default memory range is the function surrounding the
4684 program counter of the selected frame. A single argument to this
4685 command is a program counter value; @value{GDBN} dumps the function
4686 surrounding this value. Two arguments specify a range of addresses
4687 (first inclusive, second exclusive) to dump.
4690 The following example shows the disassembly of a range of addresses of
4691 HP PA-RISC 2.0 code:
4694 (@value{GDBP}) disas 0x32c4 0x32e4
4695 Dump of assembler code from 0x32c4 to 0x32e4:
4696 0x32c4 <main+204>: addil 0,dp
4697 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
4698 0x32cc <main+212>: ldil 0x3000,r31
4699 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
4700 0x32d4 <main+220>: ldo 0(r31),rp
4701 0x32d8 <main+224>: addil -0x800,dp
4702 0x32dc <main+228>: ldo 0x588(r1),r26
4703 0x32e0 <main+232>: ldil 0x3000,r31
4704 End of assembler dump.
4707 Some architectures have more than one commonly-used set of instruction
4708 mnemonics or other syntax.
4711 @kindex set disassembly-flavor
4712 @cindex Intel disassembly flavor
4713 @cindex AT&T disassembly flavor
4714 @item set disassembly-flavor @var{instruction-set}
4715 Select the instruction set to use when disassembling the
4716 program via the @code{disassemble} or @code{x/i} commands.
4718 Currently this command is only defined for the Intel x86 family. You
4719 can set @var{instruction-set} to either @code{intel} or @code{att}.
4720 The default is @code{att}, the AT&T flavor used by default by Unix
4721 assemblers for x86-based targets.
4726 @chapter Examining Data
4728 @cindex printing data
4729 @cindex examining data
4732 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
4733 @c document because it is nonstandard... Under Epoch it displays in a
4734 @c different window or something like that.
4735 The usual way to examine data in your program is with the @code{print}
4736 command (abbreviated @code{p}), or its synonym @code{inspect}. It
4737 evaluates and prints the value of an expression of the language your
4738 program is written in (@pxref{Languages, ,Using @value{GDBN} with
4739 Different Languages}).
4742 @item print @var{expr}
4743 @itemx print /@var{f} @var{expr}
4744 @var{expr} is an expression (in the source language). By default the
4745 value of @var{expr} is printed in a format appropriate to its data type;
4746 you can choose a different format by specifying @samp{/@var{f}}, where
4747 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
4751 @itemx print /@var{f}
4752 @cindex reprint the last value
4753 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
4754 @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
4755 conveniently inspect the same value in an alternative format.
4758 A more low-level way of examining data is with the @code{x} command.
4759 It examines data in memory at a specified address and prints it in a
4760 specified format. @xref{Memory, ,Examining memory}.
4762 If you are interested in information about types, or about how the
4763 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
4764 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
4768 * Expressions:: Expressions
4769 * Variables:: Program variables
4770 * Arrays:: Artificial arrays
4771 * Output Formats:: Output formats
4772 * Memory:: Examining memory
4773 * Auto Display:: Automatic display
4774 * Print Settings:: Print settings
4775 * Value History:: Value history
4776 * Convenience Vars:: Convenience variables
4777 * Registers:: Registers
4778 * Floating Point Hardware:: Floating point hardware
4779 * Vector Unit:: Vector Unit
4780 * Auxiliary Vector:: Auxiliary data provided by operating system
4781 * Memory Region Attributes:: Memory region attributes
4782 * Dump/Restore Files:: Copy between memory and a file
4783 * Character Sets:: Debugging programs that use a different
4784 character set than GDB does
4788 @section Expressions
4791 @code{print} and many other @value{GDBN} commands accept an expression and
4792 compute its value. Any kind of constant, variable or operator defined
4793 by the programming language you are using is valid in an expression in
4794 @value{GDBN}. This includes conditional expressions, function calls,
4795 casts, and string constants. It also includes preprocessor macros, if
4796 you compiled your program to include this information; see
4799 @cindex arrays in expressions
4800 @value{GDBN} supports array constants in expressions input by
4801 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
4802 you can use the command @code{print @{1, 2, 3@}} to build up an array in
4803 memory that is @code{malloc}ed in the target program.
4805 Because C is so widespread, most of the expressions shown in examples in
4806 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
4807 Languages}, for information on how to use expressions in other
4810 In this section, we discuss operators that you can use in @value{GDBN}
4811 expressions regardless of your programming language.
4813 @cindex casts, in expressions
4814 Casts are supported in all languages, not just in C, because it is so
4815 useful to cast a number into a pointer in order to examine a structure
4816 at that address in memory.
4817 @c FIXME: casts supported---Mod2 true?
4819 @value{GDBN} supports these operators, in addition to those common
4820 to programming languages:
4824 @samp{@@} is a binary operator for treating parts of memory as arrays.
4825 @xref{Arrays, ,Artificial arrays}, for more information.
4828 @samp{::} allows you to specify a variable in terms of the file or
4829 function where it is defined. @xref{Variables, ,Program variables}.
4831 @cindex @{@var{type}@}
4832 @cindex type casting memory
4833 @cindex memory, viewing as typed object
4834 @cindex casts, to view memory
4835 @item @{@var{type}@} @var{addr}
4836 Refers to an object of type @var{type} stored at address @var{addr} in
4837 memory. @var{addr} may be any expression whose value is an integer or
4838 pointer (but parentheses are required around binary operators, just as in
4839 a cast). This construct is allowed regardless of what kind of data is
4840 normally supposed to reside at @var{addr}.
4844 @section Program variables
4846 The most common kind of expression to use is the name of a variable
4849 Variables in expressions are understood in the selected stack frame
4850 (@pxref{Selection, ,Selecting a frame}); they must be either:
4854 global (or file-static)
4861 visible according to the scope rules of the
4862 programming language from the point of execution in that frame
4865 @noindent This means that in the function
4880 you can examine and use the variable @code{a} whenever your program is
4881 executing within the function @code{foo}, but you can only use or
4882 examine the variable @code{b} while your program is executing inside
4883 the block where @code{b} is declared.
4885 @cindex variable name conflict
4886 There is an exception: you can refer to a variable or function whose
4887 scope is a single source file even if the current execution point is not
4888 in this file. But it is possible to have more than one such variable or
4889 function with the same name (in different source files). If that
4890 happens, referring to that name has unpredictable effects. If you wish,
4891 you can specify a static variable in a particular function or file,
4892 using the colon-colon (@code{::}) notation:
4894 @cindex colon-colon, context for variables/functions
4896 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
4897 @cindex @code{::}, context for variables/functions
4900 @var{file}::@var{variable}
4901 @var{function}::@var{variable}
4905 Here @var{file} or @var{function} is the name of the context for the
4906 static @var{variable}. In the case of file names, you can use quotes to
4907 make sure @value{GDBN} parses the file name as a single word---for example,
4908 to print a global value of @code{x} defined in @file{f2.c}:
4911 (@value{GDBP}) p 'f2.c'::x
4914 @cindex C@t{++} scope resolution
4915 This use of @samp{::} is very rarely in conflict with the very similar
4916 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
4917 scope resolution operator in @value{GDBN} expressions.
4918 @c FIXME: Um, so what happens in one of those rare cases where it's in
4921 @cindex wrong values
4922 @cindex variable values, wrong
4923 @cindex function entry/exit, wrong values of variables
4924 @cindex optimized code, wrong values of variables
4926 @emph{Warning:} Occasionally, a local variable may appear to have the
4927 wrong value at certain points in a function---just after entry to a new
4928 scope, and just before exit.
4930 You may see this problem when you are stepping by machine instructions.
4931 This is because, on most machines, it takes more than one instruction to
4932 set up a stack frame (including local variable definitions); if you are
4933 stepping by machine instructions, variables may appear to have the wrong
4934 values until the stack frame is completely built. On exit, it usually
4935 also takes more than one machine instruction to destroy a stack frame;
4936 after you begin stepping through that group of instructions, local
4937 variable definitions may be gone.
4939 This may also happen when the compiler does significant optimizations.
4940 To be sure of always seeing accurate values, turn off all optimization
4943 @cindex ``No symbol "foo" in current context''
4944 Another possible effect of compiler optimizations is to optimize
4945 unused variables out of existence, or assign variables to registers (as
4946 opposed to memory addresses). Depending on the support for such cases
4947 offered by the debug info format used by the compiler, @value{GDBN}
4948 might not be able to display values for such local variables. If that
4949 happens, @value{GDBN} will print a message like this:
4952 No symbol "foo" in current context.
4955 To solve such problems, either recompile without optimizations, or use a
4956 different debug info format, if the compiler supports several such
4957 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
4958 usually supports the @option{-gstabs+} option. @option{-gstabs+}
4959 produces debug info in a format that is superior to formats such as
4960 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
4961 an effective form for debug info. @xref{Debugging Options,,Options
4962 for Debugging Your Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}.
4963 @xref{C, , Debugging C++}, for more info about debug info formats
4964 that are best suited to C@t{++} programs.
4967 @section Artificial arrays
4969 @cindex artificial array
4971 @kindex @@@r{, referencing memory as an array}
4972 It is often useful to print out several successive objects of the
4973 same type in memory; a section of an array, or an array of
4974 dynamically determined size for which only a pointer exists in the
4977 You can do this by referring to a contiguous span of memory as an
4978 @dfn{artificial array}, using the binary operator @samp{@@}. The left
4979 operand of @samp{@@} should be the first element of the desired array
4980 and be an individual object. The right operand should be the desired length
4981 of the array. The result is an array value whose elements are all of
4982 the type of the left argument. The first element is actually the left
4983 argument; the second element comes from bytes of memory immediately
4984 following those that hold the first element, and so on. Here is an
4985 example. If a program says
4988 int *array = (int *) malloc (len * sizeof (int));
4992 you can print the contents of @code{array} with
4998 The left operand of @samp{@@} must reside in memory. Array values made
4999 with @samp{@@} in this way behave just like other arrays in terms of
5000 subscripting, and are coerced to pointers when used in expressions.
5001 Artificial arrays most often appear in expressions via the value history
5002 (@pxref{Value History, ,Value history}), after printing one out.
5004 Another way to create an artificial array is to use a cast.
5005 This re-interprets a value as if it were an array.
5006 The value need not be in memory:
5008 (@value{GDBP}) p/x (short[2])0x12345678
5009 $1 = @{0x1234, 0x5678@}
5012 As a convenience, if you leave the array length out (as in
5013 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5014 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5016 (@value{GDBP}) p/x (short[])0x12345678
5017 $2 = @{0x1234, 0x5678@}
5020 Sometimes the artificial array mechanism is not quite enough; in
5021 moderately complex data structures, the elements of interest may not
5022 actually be adjacent---for example, if you are interested in the values
5023 of pointers in an array. One useful work-around in this situation is
5024 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5025 variables}) as a counter in an expression that prints the first
5026 interesting value, and then repeat that expression via @key{RET}. For
5027 instance, suppose you have an array @code{dtab} of pointers to
5028 structures, and you are interested in the values of a field @code{fv}
5029 in each structure. Here is an example of what you might type:
5039 @node Output Formats
5040 @section Output formats
5042 @cindex formatted output
5043 @cindex output formats
5044 By default, @value{GDBN} prints a value according to its data type. Sometimes
5045 this is not what you want. For example, you might want to print a number
5046 in hex, or a pointer in decimal. Or you might want to view data in memory
5047 at a certain address as a character string or as an instruction. To do
5048 these things, specify an @dfn{output format} when you print a value.
5050 The simplest use of output formats is to say how to print a value
5051 already computed. This is done by starting the arguments of the
5052 @code{print} command with a slash and a format letter. The format
5053 letters supported are:
5057 Regard the bits of the value as an integer, and print the integer in
5061 Print as integer in signed decimal.
5064 Print as integer in unsigned decimal.
5067 Print as integer in octal.
5070 Print as integer in binary. The letter @samp{t} stands for ``two''.
5071 @footnote{@samp{b} cannot be used because these format letters are also
5072 used with the @code{x} command, where @samp{b} stands for ``byte'';
5073 see @ref{Memory,,Examining memory}.}
5076 @cindex unknown address, locating
5077 @cindex locate address
5078 Print as an address, both absolute in hexadecimal and as an offset from
5079 the nearest preceding symbol. You can use this format used to discover
5080 where (in what function) an unknown address is located:
5083 (@value{GDBP}) p/a 0x54320
5084 $3 = 0x54320 <_initialize_vx+396>
5088 The command @code{info symbol 0x54320} yields similar results.
5089 @xref{Symbols, info symbol}.
5092 Regard as an integer and print it as a character constant.
5095 Regard the bits of the value as a floating point number and print
5096 using typical floating point syntax.
5099 For example, to print the program counter in hex (@pxref{Registers}), type
5106 Note that no space is required before the slash; this is because command
5107 names in @value{GDBN} cannot contain a slash.
5109 To reprint the last value in the value history with a different format,
5110 you can use the @code{print} command with just a format and no
5111 expression. For example, @samp{p/x} reprints the last value in hex.
5114 @section Examining memory
5116 You can use the command @code{x} (for ``examine'') to examine memory in
5117 any of several formats, independently of your program's data types.
5119 @cindex examining memory
5121 @kindex x @r{(examine memory)}
5122 @item x/@var{nfu} @var{addr}
5125 Use the @code{x} command to examine memory.
5128 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5129 much memory to display and how to format it; @var{addr} is an
5130 expression giving the address where you want to start displaying memory.
5131 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5132 Several commands set convenient defaults for @var{addr}.
5135 @item @var{n}, the repeat count
5136 The repeat count is a decimal integer; the default is 1. It specifies
5137 how much memory (counting by units @var{u}) to display.
5138 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5141 @item @var{f}, the display format
5142 The display format is one of the formats used by @code{print},
5143 @samp{s} (null-terminated string), or @samp{i} (machine instruction).
5144 The default is @samp{x} (hexadecimal) initially.
5145 The default changes each time you use either @code{x} or @code{print}.
5147 @item @var{u}, the unit size
5148 The unit size is any of
5154 Halfwords (two bytes).
5156 Words (four bytes). This is the initial default.
5158 Giant words (eight bytes).
5161 Each time you specify a unit size with @code{x}, that size becomes the
5162 default unit the next time you use @code{x}. (For the @samp{s} and
5163 @samp{i} formats, the unit size is ignored and is normally not written.)
5165 @item @var{addr}, starting display address
5166 @var{addr} is the address where you want @value{GDBN} to begin displaying
5167 memory. The expression need not have a pointer value (though it may);
5168 it is always interpreted as an integer address of a byte of memory.
5169 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5170 @var{addr} is usually just after the last address examined---but several
5171 other commands also set the default address: @code{info breakpoints} (to
5172 the address of the last breakpoint listed), @code{info line} (to the
5173 starting address of a line), and @code{print} (if you use it to display
5174 a value from memory).
5177 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5178 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5179 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5180 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5181 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5183 Since the letters indicating unit sizes are all distinct from the
5184 letters specifying output formats, you do not have to remember whether
5185 unit size or format comes first; either order works. The output
5186 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5187 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5189 Even though the unit size @var{u} is ignored for the formats @samp{s}
5190 and @samp{i}, you might still want to use a count @var{n}; for example,
5191 @samp{3i} specifies that you want to see three machine instructions,
5192 including any operands. The command @code{disassemble} gives an
5193 alternative way of inspecting machine instructions; see @ref{Machine
5194 Code,,Source and machine code}.
5196 All the defaults for the arguments to @code{x} are designed to make it
5197 easy to continue scanning memory with minimal specifications each time
5198 you use @code{x}. For example, after you have inspected three machine
5199 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5200 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5201 the repeat count @var{n} is used again; the other arguments default as
5202 for successive uses of @code{x}.
5204 @cindex @code{$_}, @code{$__}, and value history
5205 The addresses and contents printed by the @code{x} command are not saved
5206 in the value history because there is often too much of them and they
5207 would get in the way. Instead, @value{GDBN} makes these values available for
5208 subsequent use in expressions as values of the convenience variables
5209 @code{$_} and @code{$__}. After an @code{x} command, the last address
5210 examined is available for use in expressions in the convenience variable
5211 @code{$_}. The contents of that address, as examined, are available in
5212 the convenience variable @code{$__}.
5214 If the @code{x} command has a repeat count, the address and contents saved
5215 are from the last memory unit printed; this is not the same as the last
5216 address printed if several units were printed on the last line of output.
5219 @section Automatic display
5220 @cindex automatic display
5221 @cindex display of expressions
5223 If you find that you want to print the value of an expression frequently
5224 (to see how it changes), you might want to add it to the @dfn{automatic
5225 display list} so that @value{GDBN} prints its value each time your program stops.
5226 Each expression added to the list is given a number to identify it;
5227 to remove an expression from the list, you specify that number.
5228 The automatic display looks like this:
5232 3: bar[5] = (struct hack *) 0x3804
5236 This display shows item numbers, expressions and their current values. As with
5237 displays you request manually using @code{x} or @code{print}, you can
5238 specify the output format you prefer; in fact, @code{display} decides
5239 whether to use @code{print} or @code{x} depending on how elaborate your
5240 format specification is---it uses @code{x} if you specify a unit size,
5241 or one of the two formats (@samp{i} and @samp{s}) that are only
5242 supported by @code{x}; otherwise it uses @code{print}.
5246 @item display @var{expr}
5247 Add the expression @var{expr} to the list of expressions to display
5248 each time your program stops. @xref{Expressions, ,Expressions}.
5250 @code{display} does not repeat if you press @key{RET} again after using it.
5252 @item display/@var{fmt} @var{expr}
5253 For @var{fmt} specifying only a display format and not a size or
5254 count, add the expression @var{expr} to the auto-display list but
5255 arrange to display it each time in the specified format @var{fmt}.
5256 @xref{Output Formats,,Output formats}.
5258 @item display/@var{fmt} @var{addr}
5259 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
5260 number of units, add the expression @var{addr} as a memory address to
5261 be examined each time your program stops. Examining means in effect
5262 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
5265 For example, @samp{display/i $pc} can be helpful, to see the machine
5266 instruction about to be executed each time execution stops (@samp{$pc}
5267 is a common name for the program counter; @pxref{Registers, ,Registers}).
5270 @kindex delete display
5272 @item undisplay @var{dnums}@dots{}
5273 @itemx delete display @var{dnums}@dots{}
5274 Remove item numbers @var{dnums} from the list of expressions to display.
5276 @code{undisplay} does not repeat if you press @key{RET} after using it.
5277 (Otherwise you would just get the error @samp{No display number @dots{}}.)
5279 @kindex disable display
5280 @item disable display @var{dnums}@dots{}
5281 Disable the display of item numbers @var{dnums}. A disabled display
5282 item is not printed automatically, but is not forgotten. It may be
5283 enabled again later.
5285 @kindex enable display
5286 @item enable display @var{dnums}@dots{}
5287 Enable display of item numbers @var{dnums}. It becomes effective once
5288 again in auto display of its expression, until you specify otherwise.
5291 Display the current values of the expressions on the list, just as is
5292 done when your program stops.
5294 @kindex info display
5296 Print the list of expressions previously set up to display
5297 automatically, each one with its item number, but without showing the
5298 values. This includes disabled expressions, which are marked as such.
5299 It also includes expressions which would not be displayed right now
5300 because they refer to automatic variables not currently available.
5303 @cindex display disabled out of scope
5304 If a display expression refers to local variables, then it does not make
5305 sense outside the lexical context for which it was set up. Such an
5306 expression is disabled when execution enters a context where one of its
5307 variables is not defined. For example, if you give the command
5308 @code{display last_char} while inside a function with an argument
5309 @code{last_char}, @value{GDBN} displays this argument while your program
5310 continues to stop inside that function. When it stops elsewhere---where
5311 there is no variable @code{last_char}---the display is disabled
5312 automatically. The next time your program stops where @code{last_char}
5313 is meaningful, you can enable the display expression once again.
5315 @node Print Settings
5316 @section Print settings
5318 @cindex format options
5319 @cindex print settings
5320 @value{GDBN} provides the following ways to control how arrays, structures,
5321 and symbols are printed.
5324 These settings are useful for debugging programs in any language:
5328 @item set print address
5329 @itemx set print address on
5330 @cindex print/don't print memory addresses
5331 @value{GDBN} prints memory addresses showing the location of stack
5332 traces, structure values, pointer values, breakpoints, and so forth,
5333 even when it also displays the contents of those addresses. The default
5334 is @code{on}. For example, this is what a stack frame display looks like with
5335 @code{set print address on}:
5340 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
5342 530 if (lquote != def_lquote)
5346 @item set print address off
5347 Do not print addresses when displaying their contents. For example,
5348 this is the same stack frame displayed with @code{set print address off}:
5352 (@value{GDBP}) set print addr off
5354 #0 set_quotes (lq="<<", rq=">>") at input.c:530
5355 530 if (lquote != def_lquote)
5359 You can use @samp{set print address off} to eliminate all machine
5360 dependent displays from the @value{GDBN} interface. For example, with
5361 @code{print address off}, you should get the same text for backtraces on
5362 all machines---whether or not they involve pointer arguments.
5365 @item show print address
5366 Show whether or not addresses are to be printed.
5369 When @value{GDBN} prints a symbolic address, it normally prints the
5370 closest earlier symbol plus an offset. If that symbol does not uniquely
5371 identify the address (for example, it is a name whose scope is a single
5372 source file), you may need to clarify. One way to do this is with
5373 @code{info line}, for example @samp{info line *0x4537}. Alternately,
5374 you can set @value{GDBN} to print the source file and line number when
5375 it prints a symbolic address:
5378 @item set print symbol-filename on
5379 @cindex closest symbol and offset for an address
5380 Tell @value{GDBN} to print the source file name and line number of a
5381 symbol in the symbolic form of an address.
5383 @item set print symbol-filename off
5384 Do not print source file name and line number of a symbol. This is the
5387 @item show print symbol-filename
5388 Show whether or not @value{GDBN} will print the source file name and
5389 line number of a symbol in the symbolic form of an address.
5392 Another situation where it is helpful to show symbol filenames and line
5393 numbers is when disassembling code; @value{GDBN} shows you the line
5394 number and source file that corresponds to each instruction.
5396 Also, you may wish to see the symbolic form only if the address being
5397 printed is reasonably close to the closest earlier symbol:
5400 @item set print max-symbolic-offset @var{max-offset}
5401 @cindex maximum value for offset of closest symbol
5402 Tell @value{GDBN} to only display the symbolic form of an address if the
5403 offset between the closest earlier symbol and the address is less than
5404 @var{max-offset}. The default is 0, which tells @value{GDBN}
5405 to always print the symbolic form of an address if any symbol precedes it.
5407 @item show print max-symbolic-offset
5408 Ask how large the maximum offset is that @value{GDBN} prints in a
5412 @cindex wild pointer, interpreting
5413 @cindex pointer, finding referent
5414 If you have a pointer and you are not sure where it points, try
5415 @samp{set print symbol-filename on}. Then you can determine the name
5416 and source file location of the variable where it points, using
5417 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
5418 For example, here @value{GDBN} shows that a variable @code{ptt} points
5419 at another variable @code{t}, defined in @file{hi2.c}:
5422 (@value{GDBP}) set print symbol-filename on
5423 (@value{GDBP}) p/a ptt
5424 $4 = 0xe008 <t in hi2.c>
5428 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
5429 does not show the symbol name and filename of the referent, even with
5430 the appropriate @code{set print} options turned on.
5433 Other settings control how different kinds of objects are printed:
5436 @item set print array
5437 @itemx set print array on
5438 @cindex pretty print arrays
5439 Pretty print arrays. This format is more convenient to read,
5440 but uses more space. The default is off.
5442 @item set print array off
5443 Return to compressed format for arrays.
5445 @item show print array
5446 Show whether compressed or pretty format is selected for displaying
5449 @item set print elements @var{number-of-elements}
5450 @cindex number of array elements to print
5451 Set a limit on how many elements of an array @value{GDBN} will print.
5452 If @value{GDBN} is printing a large array, it stops printing after it has
5453 printed the number of elements set by the @code{set print elements} command.
5454 This limit also applies to the display of strings.
5455 When @value{GDBN} starts, this limit is set to 200.
5456 Setting @var{number-of-elements} to zero means that the printing is unlimited.
5458 @item show print elements
5459 Display the number of elements of a large array that @value{GDBN} will print.
5460 If the number is 0, then the printing is unlimited.
5462 @item set print null-stop
5463 @cindex @sc{null} elements in arrays
5464 Cause @value{GDBN} to stop printing the characters of an array when the first
5465 @sc{null} is encountered. This is useful when large arrays actually
5466 contain only short strings.
5469 @item set print pretty on
5470 Cause @value{GDBN} to print structures in an indented format with one member
5471 per line, like this:
5486 @item set print pretty off
5487 Cause @value{GDBN} to print structures in a compact format, like this:
5491 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
5492 meat = 0x54 "Pork"@}
5497 This is the default format.
5499 @item show print pretty
5500 Show which format @value{GDBN} is using to print structures.
5502 @item set print sevenbit-strings on
5503 @cindex eight-bit characters in strings
5504 @cindex octal escapes in strings
5505 Print using only seven-bit characters; if this option is set,
5506 @value{GDBN} displays any eight-bit characters (in strings or
5507 character values) using the notation @code{\}@var{nnn}. This setting is
5508 best if you are working in English (@sc{ascii}) and you use the
5509 high-order bit of characters as a marker or ``meta'' bit.
5511 @item set print sevenbit-strings off
5512 Print full eight-bit characters. This allows the use of more
5513 international character sets, and is the default.
5515 @item show print sevenbit-strings
5516 Show whether or not @value{GDBN} is printing only seven-bit characters.
5518 @item set print union on
5519 @cindex unions in structures, printing
5520 Tell @value{GDBN} to print unions which are contained in structures. This
5521 is the default setting.
5523 @item set print union off
5524 Tell @value{GDBN} not to print unions which are contained in structures.
5526 @item show print union
5527 Ask @value{GDBN} whether or not it will print unions which are contained in
5530 For example, given the declarations
5533 typedef enum @{Tree, Bug@} Species;
5534 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
5535 typedef enum @{Caterpillar, Cocoon, Butterfly@}
5546 struct thing foo = @{Tree, @{Acorn@}@};
5550 with @code{set print union on} in effect @samp{p foo} would print
5553 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
5557 and with @code{set print union off} in effect it would print
5560 $1 = @{it = Tree, form = @{...@}@}
5566 These settings are of interest when debugging C@t{++} programs:
5569 @cindex demangling C@t{++} names
5570 @item set print demangle
5571 @itemx set print demangle on
5572 Print C@t{++} names in their source form rather than in the encoded
5573 (``mangled'') form passed to the assembler and linker for type-safe
5574 linkage. The default is on.
5576 @item show print demangle
5577 Show whether C@t{++} names are printed in mangled or demangled form.
5579 @item set print asm-demangle
5580 @itemx set print asm-demangle on
5581 Print C@t{++} names in their source form rather than their mangled form, even
5582 in assembler code printouts such as instruction disassemblies.
5585 @item show print asm-demangle
5586 Show whether C@t{++} names in assembly listings are printed in mangled
5589 @cindex C@t{++} symbol decoding style
5590 @cindex symbol decoding style, C@t{++}
5591 @item set demangle-style @var{style}
5592 Choose among several encoding schemes used by different compilers to
5593 represent C@t{++} names. The choices for @var{style} are currently:
5597 Allow @value{GDBN} to choose a decoding style by inspecting your program.
5600 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
5601 This is the default.
5604 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
5607 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
5610 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
5611 @strong{Warning:} this setting alone is not sufficient to allow
5612 debugging @code{cfront}-generated executables. @value{GDBN} would
5613 require further enhancement to permit that.
5616 If you omit @var{style}, you will see a list of possible formats.
5618 @item show demangle-style
5619 Display the encoding style currently in use for decoding C@t{++} symbols.
5621 @item set print object
5622 @itemx set print object on
5623 @cindex derived type of an object, printing
5624 When displaying a pointer to an object, identify the @emph{actual}
5625 (derived) type of the object rather than the @emph{declared} type, using
5626 the virtual function table.
5628 @item set print object off
5629 Display only the declared type of objects, without reference to the
5630 virtual function table. This is the default setting.
5632 @item show print object
5633 Show whether actual, or declared, object types are displayed.
5635 @item set print static-members
5636 @itemx set print static-members on
5637 @cindex static members of C@t{++} objects
5638 Print static members when displaying a C@t{++} object. The default is on.
5640 @item set print static-members off
5641 Do not print static members when displaying a C@t{++} object.
5643 @item show print static-members
5644 Show whether C@t{++} static members are printed, or not.
5646 @c These don't work with HP ANSI C++ yet.
5647 @item set print vtbl
5648 @itemx set print vtbl on
5649 @cindex pretty print C@t{++} virtual function tables
5650 Pretty print C@t{++} virtual function tables. The default is off.
5651 (The @code{vtbl} commands do not work on programs compiled with the HP
5652 ANSI C@t{++} compiler (@code{aCC}).)
5654 @item set print vtbl off
5655 Do not pretty print C@t{++} virtual function tables.
5657 @item show print vtbl
5658 Show whether C@t{++} virtual function tables are pretty printed, or not.
5662 @section Value history
5664 @cindex value history
5665 Values printed by the @code{print} command are saved in the @value{GDBN}
5666 @dfn{value history}. This allows you to refer to them in other expressions.
5667 Values are kept until the symbol table is re-read or discarded
5668 (for example with the @code{file} or @code{symbol-file} commands).
5669 When the symbol table changes, the value history is discarded,
5670 since the values may contain pointers back to the types defined in the
5675 @cindex history number
5676 The values printed are given @dfn{history numbers} by which you can
5677 refer to them. These are successive integers starting with one.
5678 @code{print} shows you the history number assigned to a value by
5679 printing @samp{$@var{num} = } before the value; here @var{num} is the
5682 To refer to any previous value, use @samp{$} followed by the value's
5683 history number. The way @code{print} labels its output is designed to
5684 remind you of this. Just @code{$} refers to the most recent value in
5685 the history, and @code{$$} refers to the value before that.
5686 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
5687 is the value just prior to @code{$$}, @code{$$1} is equivalent to
5688 @code{$$}, and @code{$$0} is equivalent to @code{$}.
5690 For example, suppose you have just printed a pointer to a structure and
5691 want to see the contents of the structure. It suffices to type
5697 If you have a chain of structures where the component @code{next} points
5698 to the next one, you can print the contents of the next one with this:
5705 You can print successive links in the chain by repeating this
5706 command---which you can do by just typing @key{RET}.
5708 Note that the history records values, not expressions. If the value of
5709 @code{x} is 4 and you type these commands:
5717 then the value recorded in the value history by the @code{print} command
5718 remains 4 even though the value of @code{x} has changed.
5723 Print the last ten values in the value history, with their item numbers.
5724 This is like @samp{p@ $$9} repeated ten times, except that @code{show
5725 values} does not change the history.
5727 @item show values @var{n}
5728 Print ten history values centered on history item number @var{n}.
5731 Print ten history values just after the values last printed. If no more
5732 values are available, @code{show values +} produces no display.
5735 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
5736 same effect as @samp{show values +}.
5738 @node Convenience Vars
5739 @section Convenience variables
5741 @cindex convenience variables
5742 @value{GDBN} provides @dfn{convenience variables} that you can use within
5743 @value{GDBN} to hold on to a value and refer to it later. These variables
5744 exist entirely within @value{GDBN}; they are not part of your program, and
5745 setting a convenience variable has no direct effect on further execution
5746 of your program. That is why you can use them freely.
5748 Convenience variables are prefixed with @samp{$}. Any name preceded by
5749 @samp{$} can be used for a convenience variable, unless it is one of
5750 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
5751 (Value history references, in contrast, are @emph{numbers} preceded
5752 by @samp{$}. @xref{Value History, ,Value history}.)
5754 You can save a value in a convenience variable with an assignment
5755 expression, just as you would set a variable in your program.
5759 set $foo = *object_ptr
5763 would save in @code{$foo} the value contained in the object pointed to by
5766 Using a convenience variable for the first time creates it, but its
5767 value is @code{void} until you assign a new value. You can alter the
5768 value with another assignment at any time.
5770 Convenience variables have no fixed types. You can assign a convenience
5771 variable any type of value, including structures and arrays, even if
5772 that variable already has a value of a different type. The convenience
5773 variable, when used as an expression, has the type of its current value.
5776 @kindex show convenience
5777 @item show convenience
5778 Print a list of convenience variables used so far, and their values.
5779 Abbreviated @code{show conv}.
5782 One of the ways to use a convenience variable is as a counter to be
5783 incremented or a pointer to be advanced. For example, to print
5784 a field from successive elements of an array of structures:
5788 print bar[$i++]->contents
5792 Repeat that command by typing @key{RET}.
5794 Some convenience variables are created automatically by @value{GDBN} and given
5795 values likely to be useful.
5798 @vindex $_@r{, convenience variable}
5800 The variable @code{$_} is automatically set by the @code{x} command to
5801 the last address examined (@pxref{Memory, ,Examining memory}). Other
5802 commands which provide a default address for @code{x} to examine also
5803 set @code{$_} to that address; these commands include @code{info line}
5804 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
5805 except when set by the @code{x} command, in which case it is a pointer
5806 to the type of @code{$__}.
5808 @vindex $__@r{, convenience variable}
5810 The variable @code{$__} is automatically set by the @code{x} command
5811 to the value found in the last address examined. Its type is chosen
5812 to match the format in which the data was printed.
5815 @vindex $_exitcode@r{, convenience variable}
5816 The variable @code{$_exitcode} is automatically set to the exit code when
5817 the program being debugged terminates.
5820 On HP-UX systems, if you refer to a function or variable name that
5821 begins with a dollar sign, @value{GDBN} searches for a user or system
5822 name first, before it searches for a convenience variable.
5828 You can refer to machine register contents, in expressions, as variables
5829 with names starting with @samp{$}. The names of registers are different
5830 for each machine; use @code{info registers} to see the names used on
5834 @kindex info registers
5835 @item info registers
5836 Print the names and values of all registers except floating-point
5837 and vector registers (in the selected stack frame).
5839 @kindex info all-registers
5840 @cindex floating point registers
5841 @item info all-registers
5842 Print the names and values of all registers, including floating-point
5843 and vector registers (in the selected stack frame).
5845 @item info registers @var{regname} @dots{}
5846 Print the @dfn{relativized} value of each specified register @var{regname}.
5847 As discussed in detail below, register values are normally relative to
5848 the selected stack frame. @var{regname} may be any register name valid on
5849 the machine you are using, with or without the initial @samp{$}.
5852 @value{GDBN} has four ``standard'' register names that are available (in
5853 expressions) on most machines---whenever they do not conflict with an
5854 architecture's canonical mnemonics for registers. The register names
5855 @code{$pc} and @code{$sp} are used for the program counter register and
5856 the stack pointer. @code{$fp} is used for a register that contains a
5857 pointer to the current stack frame, and @code{$ps} is used for a
5858 register that contains the processor status. For example,
5859 you could print the program counter in hex with
5866 or print the instruction to be executed next with
5873 or add four to the stack pointer@footnote{This is a way of removing
5874 one word from the stack, on machines where stacks grow downward in
5875 memory (most machines, nowadays). This assumes that the innermost
5876 stack frame is selected; setting @code{$sp} is not allowed when other
5877 stack frames are selected. To pop entire frames off the stack,
5878 regardless of machine architecture, use @code{return};
5879 see @ref{Returning, ,Returning from a function}.} with
5885 Whenever possible, these four standard register names are available on
5886 your machine even though the machine has different canonical mnemonics,
5887 so long as there is no conflict. The @code{info registers} command
5888 shows the canonical names. For example, on the SPARC, @code{info
5889 registers} displays the processor status register as @code{$psr} but you
5890 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
5891 is an alias for the @sc{eflags} register.
5893 @value{GDBN} always considers the contents of an ordinary register as an
5894 integer when the register is examined in this way. Some machines have
5895 special registers which can hold nothing but floating point; these
5896 registers are considered to have floating point values. There is no way
5897 to refer to the contents of an ordinary register as floating point value
5898 (although you can @emph{print} it as a floating point value with
5899 @samp{print/f $@var{regname}}).
5901 Some registers have distinct ``raw'' and ``virtual'' data formats. This
5902 means that the data format in which the register contents are saved by
5903 the operating system is not the same one that your program normally
5904 sees. For example, the registers of the 68881 floating point
5905 coprocessor are always saved in ``extended'' (raw) format, but all C
5906 programs expect to work with ``double'' (virtual) format. In such
5907 cases, @value{GDBN} normally works with the virtual format only (the format
5908 that makes sense for your program), but the @code{info registers} command
5909 prints the data in both formats.
5911 Normally, register values are relative to the selected stack frame
5912 (@pxref{Selection, ,Selecting a frame}). This means that you get the
5913 value that the register would contain if all stack frames farther in
5914 were exited and their saved registers restored. In order to see the
5915 true contents of hardware registers, you must select the innermost
5916 frame (with @samp{frame 0}).
5918 However, @value{GDBN} must deduce where registers are saved, from the machine
5919 code generated by your compiler. If some registers are not saved, or if
5920 @value{GDBN} is unable to locate the saved registers, the selected stack
5921 frame makes no difference.
5923 @node Floating Point Hardware
5924 @section Floating point hardware
5925 @cindex floating point
5927 Depending on the configuration, @value{GDBN} may be able to give
5928 you more information about the status of the floating point hardware.
5933 Display hardware-dependent information about the floating
5934 point unit. The exact contents and layout vary depending on the
5935 floating point chip. Currently, @samp{info float} is supported on
5936 the ARM and x86 machines.
5940 @section Vector Unit
5943 Depending on the configuration, @value{GDBN} may be able to give you
5944 more information about the status of the vector unit.
5949 Display information about the vector unit. The exact contents and
5950 layout vary depending on the hardware.
5953 @node Auxiliary Vector
5954 @section Operating system auxiliary vector
5955 @cindex auxiliary vector
5956 @cindex vector, auxiliary
5958 Some operating systems supply an @dfn{auxiliary vector} to programs at
5959 startup. This is akin to the arguments and environment that you
5960 specify for a program, but contains a system-dependent variety of
5961 binary values that tell system libraries important details about the
5962 hardware, operating system, and process. Each value's purpose is
5963 identified by an integer tag; the meanings are well-known but system-specific.
5964 Depending on the configuration and operating system facilities,
5965 @value{GDBN} may be able to show you this information.
5970 Display the auxiliary vector of the inferior, which can be either a
5971 live process or a core dump file. @value{GDBN} prints each tag value
5972 numerically, and also shows names and text descriptions for recognized
5973 tags. Some values in the vector are numbers, some bit masks, and some
5974 pointers to strings or other data. @value{GDBN} displays each value in the
5975 most appropriate form for a recognized tag, and in hexadecimal for
5976 an unrecognized tag.
5979 @node Memory Region Attributes
5980 @section Memory region attributes
5981 @cindex memory region attributes
5983 @dfn{Memory region attributes} allow you to describe special handling
5984 required by regions of your target's memory. @value{GDBN} uses attributes
5985 to determine whether to allow certain types of memory accesses; whether to
5986 use specific width accesses; and whether to cache target memory.
5988 Defined memory regions can be individually enabled and disabled. When a
5989 memory region is disabled, @value{GDBN} uses the default attributes when
5990 accessing memory in that region. Similarly, if no memory regions have
5991 been defined, @value{GDBN} uses the default attributes when accessing
5994 When a memory region is defined, it is given a number to identify it;
5995 to enable, disable, or remove a memory region, you specify that number.
5999 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
6000 Define memory region bounded by @var{lower} and @var{upper} with
6001 attributes @var{attributes}@dots{}. Note that @var{upper} == 0 is a
6002 special case: it is treated as the the target's maximum memory address.
6003 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
6006 @item delete mem @var{nums}@dots{}
6007 Remove memory regions @var{nums}@dots{}.
6010 @item disable mem @var{nums}@dots{}
6011 Disable memory regions @var{nums}@dots{}.
6012 A disabled memory region is not forgotten.
6013 It may be enabled again later.
6016 @item enable mem @var{nums}@dots{}
6017 Enable memory regions @var{nums}@dots{}.
6021 Print a table of all defined memory regions, with the following columns
6025 @item Memory Region Number
6026 @item Enabled or Disabled.
6027 Enabled memory regions are marked with @samp{y}.
6028 Disabled memory regions are marked with @samp{n}.
6031 The address defining the inclusive lower bound of the memory region.
6034 The address defining the exclusive upper bound of the memory region.
6037 The list of attributes set for this memory region.
6042 @subsection Attributes
6044 @subsubsection Memory Access Mode
6045 The access mode attributes set whether @value{GDBN} may make read or
6046 write accesses to a memory region.
6048 While these attributes prevent @value{GDBN} from performing invalid
6049 memory accesses, they do nothing to prevent the target system, I/O DMA,
6050 etc. from accessing memory.
6054 Memory is read only.
6056 Memory is write only.
6058 Memory is read/write. This is the default.
6061 @subsubsection Memory Access Size
6062 The acccess size attributes tells @value{GDBN} to use specific sized
6063 accesses in the memory region. Often memory mapped device registers
6064 require specific sized accesses. If no access size attribute is
6065 specified, @value{GDBN} may use accesses of any size.
6069 Use 8 bit memory accesses.
6071 Use 16 bit memory accesses.
6073 Use 32 bit memory accesses.
6075 Use 64 bit memory accesses.
6078 @c @subsubsection Hardware/Software Breakpoints
6079 @c The hardware/software breakpoint attributes set whether @value{GDBN}
6080 @c will use hardware or software breakpoints for the internal breakpoints
6081 @c used by the step, next, finish, until, etc. commands.
6085 @c Always use hardware breakpoints
6086 @c @item swbreak (default)
6089 @subsubsection Data Cache
6090 The data cache attributes set whether @value{GDBN} will cache target
6091 memory. While this generally improves performance by reducing debug
6092 protocol overhead, it can lead to incorrect results because @value{GDBN}
6093 does not know about volatile variables or memory mapped device
6098 Enable @value{GDBN} to cache target memory.
6100 Disable @value{GDBN} from caching target memory. This is the default.
6103 @c @subsubsection Memory Write Verification
6104 @c The memory write verification attributes set whether @value{GDBN}
6105 @c will re-reads data after each write to verify the write was successful.
6109 @c @item noverify (default)
6112 @node Dump/Restore Files
6113 @section Copy between memory and a file
6114 @cindex dump/restore files
6115 @cindex append data to a file
6116 @cindex dump data to a file
6117 @cindex restore data from a file
6119 You can use the commands @code{dump}, @code{append}, and
6120 @code{restore} to copy data between target memory and a file. The
6121 @code{dump} and @code{append} commands write data to a file, and the
6122 @code{restore} command reads data from a file back into the inferior's
6123 memory. Files may be in binary, Motorola S-record, Intel hex, or
6124 Tektronix Hex format; however, @value{GDBN} can only append to binary
6130 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6131 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
6132 Dump the contents of memory from @var{start_addr} to @var{end_addr},
6133 or the value of @var{expr}, to @var{filename} in the given format.
6135 The @var{format} parameter may be any one of:
6142 Motorola S-record format.
6144 Tektronix Hex format.
6147 @value{GDBN} uses the same definitions of these formats as the
6148 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
6149 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
6153 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6154 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
6155 Append the contents of memory from @var{start_addr} to @var{end_addr},
6156 or the value of @var{expr}, to @var{filename}, in raw binary form.
6157 (@value{GDBN} can only append data to files in raw binary form.)
6160 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
6161 Restore the contents of file @var{filename} into memory. The
6162 @code{restore} command can automatically recognize any known @sc{bfd}
6163 file format, except for raw binary. To restore a raw binary file you
6164 must specify the optional keyword @code{binary} after the filename.
6166 If @var{bias} is non-zero, its value will be added to the addresses
6167 contained in the file. Binary files always start at address zero, so
6168 they will be restored at address @var{bias}. Other bfd files have
6169 a built-in location; they will be restored at offset @var{bias}
6172 If @var{start} and/or @var{end} are non-zero, then only data between
6173 file offset @var{start} and file offset @var{end} will be restored.
6174 These offsets are relative to the addresses in the file, before
6175 the @var{bias} argument is applied.
6179 @node Character Sets
6180 @section Character Sets
6181 @cindex character sets
6183 @cindex translating between character sets
6184 @cindex host character set
6185 @cindex target character set
6187 If the program you are debugging uses a different character set to
6188 represent characters and strings than the one @value{GDBN} uses itself,
6189 @value{GDBN} can automatically translate between the character sets for
6190 you. The character set @value{GDBN} uses we call the @dfn{host
6191 character set}; the one the inferior program uses we call the
6192 @dfn{target character set}.
6194 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
6195 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
6196 remote protocol (@pxref{Remote,Remote Debugging}) to debug a program
6197 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
6198 then the host character set is Latin-1, and the target character set is
6199 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
6200 target-charset EBCDIC-US}, then @value{GDBN} translates between
6201 @sc{ebcdic} and Latin 1 as you print character or string values, or use
6202 character and string literals in expressions.
6204 @value{GDBN} has no way to automatically recognize which character set
6205 the inferior program uses; you must tell it, using the @code{set
6206 target-charset} command, described below.
6208 Here are the commands for controlling @value{GDBN}'s character set
6212 @item set target-charset @var{charset}
6213 @kindex set target-charset
6214 Set the current target character set to @var{charset}. We list the
6215 character set names @value{GDBN} recognizes below, but if you type
6216 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6217 list the target character sets it supports.
6221 @item set host-charset @var{charset}
6222 @kindex set host-charset
6223 Set the current host character set to @var{charset}.
6225 By default, @value{GDBN} uses a host character set appropriate to the
6226 system it is running on; you can override that default using the
6227 @code{set host-charset} command.
6229 @value{GDBN} can only use certain character sets as its host character
6230 set. We list the character set names @value{GDBN} recognizes below, and
6231 indicate which can be host character sets, but if you type
6232 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6233 list the host character sets it supports.
6235 @item set charset @var{charset}
6237 Set the current host and target character sets to @var{charset}. As
6238 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
6239 @value{GDBN} will list the name of the character sets that can be used
6240 for both host and target.
6244 @kindex show charset
6245 Show the names of the current host and target charsets.
6247 @itemx show host-charset
6248 @kindex show host-charset
6249 Show the name of the current host charset.
6251 @itemx show target-charset
6252 @kindex show target-charset
6253 Show the name of the current target charset.
6257 @value{GDBN} currently includes support for the following character
6263 @cindex ASCII character set
6264 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
6268 @cindex ISO 8859-1 character set
6269 @cindex ISO Latin 1 character set
6270 The ISO Latin 1 character set. This extends @sc{ascii} with accented
6271 characters needed for French, German, and Spanish. @value{GDBN} can use
6272 this as its host character set.
6276 @cindex EBCDIC character set
6277 @cindex IBM1047 character set
6278 Variants of the @sc{ebcdic} character set, used on some of IBM's
6279 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
6280 @value{GDBN} cannot use these as its host character set.
6284 Note that these are all single-byte character sets. More work inside
6285 GDB is needed to support multi-byte or variable-width character
6286 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
6288 Here is an example of @value{GDBN}'s character set support in action.
6289 Assume that the following source code has been placed in the file
6290 @file{charset-test.c}:
6296 = @{72, 101, 108, 108, 111, 44, 32, 119,
6297 111, 114, 108, 100, 33, 10, 0@};
6298 char ibm1047_hello[]
6299 = @{200, 133, 147, 147, 150, 107, 64, 166,
6300 150, 153, 147, 132, 90, 37, 0@};
6304 printf ("Hello, world!\n");
6308 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
6309 containing the string @samp{Hello, world!} followed by a newline,
6310 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
6312 We compile the program, and invoke the debugger on it:
6315 $ gcc -g charset-test.c -o charset-test
6316 $ gdb -nw charset-test
6317 GNU gdb 2001-12-19-cvs
6318 Copyright 2001 Free Software Foundation, Inc.
6323 We can use the @code{show charset} command to see what character sets
6324 @value{GDBN} is currently using to interpret and display characters and
6328 (@value{GDBP}) show charset
6329 The current host and target character set is `ISO-8859-1'.
6333 For the sake of printing this manual, let's use @sc{ascii} as our
6334 initial character set:
6336 (@value{GDBP}) set charset ASCII
6337 (@value{GDBP}) show charset
6338 The current host and target character set is `ASCII'.
6342 Let's assume that @sc{ascii} is indeed the correct character set for our
6343 host system --- in other words, let's assume that if @value{GDBN} prints
6344 characters using the @sc{ascii} character set, our terminal will display
6345 them properly. Since our current target character set is also
6346 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
6349 (@value{GDBP}) print ascii_hello
6350 $1 = 0x401698 "Hello, world!\n"
6351 (@value{GDBP}) print ascii_hello[0]
6356 @value{GDBN} uses the target character set for character and string
6357 literals you use in expressions:
6360 (@value{GDBP}) print '+'
6365 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
6368 @value{GDBN} relies on the user to tell it which character set the
6369 target program uses. If we print @code{ibm1047_hello} while our target
6370 character set is still @sc{ascii}, we get jibberish:
6373 (@value{GDBP}) print ibm1047_hello
6374 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
6375 (@value{GDBP}) print ibm1047_hello[0]
6380 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
6381 @value{GDBN} tells us the character sets it supports:
6384 (@value{GDBP}) set target-charset
6385 ASCII EBCDIC-US IBM1047 ISO-8859-1
6386 (@value{GDBP}) set target-charset
6389 We can select @sc{ibm1047} as our target character set, and examine the
6390 program's strings again. Now the @sc{ascii} string is wrong, but
6391 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
6392 target character set, @sc{ibm1047}, to the host character set,
6393 @sc{ascii}, and they display correctly:
6396 (@value{GDBP}) set target-charset IBM1047
6397 (@value{GDBP}) show charset
6398 The current host character set is `ASCII'.
6399 The current target character set is `IBM1047'.
6400 (@value{GDBP}) print ascii_hello
6401 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
6402 (@value{GDBP}) print ascii_hello[0]
6404 (@value{GDBP}) print ibm1047_hello
6405 $8 = 0x4016a8 "Hello, world!\n"
6406 (@value{GDBP}) print ibm1047_hello[0]
6411 As above, @value{GDBN} uses the target character set for character and
6412 string literals you use in expressions:
6415 (@value{GDBP}) print '+'
6420 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
6425 @chapter C Preprocessor Macros
6427 Some languages, such as C and C@t{++}, provide a way to define and invoke
6428 ``preprocessor macros'' which expand into strings of tokens.
6429 @value{GDBN} can evaluate expressions containing macro invocations, show
6430 the result of macro expansion, and show a macro's definition, including
6431 where it was defined.
6433 You may need to compile your program specially to provide @value{GDBN}
6434 with information about preprocessor macros. Most compilers do not
6435 include macros in their debugging information, even when you compile
6436 with the @option{-g} flag. @xref{Compilation}.
6438 A program may define a macro at one point, remove that definition later,
6439 and then provide a different definition after that. Thus, at different
6440 points in the program, a macro may have different definitions, or have
6441 no definition at all. If there is a current stack frame, @value{GDBN}
6442 uses the macros in scope at that frame's source code line. Otherwise,
6443 @value{GDBN} uses the macros in scope at the current listing location;
6446 At the moment, @value{GDBN} does not support the @code{##}
6447 token-splicing operator, the @code{#} stringification operator, or
6448 variable-arity macros.
6450 Whenever @value{GDBN} evaluates an expression, it always expands any
6451 macro invocations present in the expression. @value{GDBN} also provides
6452 the following commands for working with macros explicitly.
6456 @kindex macro expand
6457 @cindex macro expansion, showing the results of preprocessor
6458 @cindex preprocessor macro expansion, showing the results of
6459 @cindex expanding preprocessor macros
6460 @item macro expand @var{expression}
6461 @itemx macro exp @var{expression}
6462 Show the results of expanding all preprocessor macro invocations in
6463 @var{expression}. Since @value{GDBN} simply expands macros, but does
6464 not parse the result, @var{expression} need not be a valid expression;
6465 it can be any string of tokens.
6467 @item macro expand-once @var{expression}
6468 @itemx macro exp1 @var{expression}
6469 @cindex expand macro once
6470 @i{(This command is not yet implemented.)} Show the results of
6471 expanding those preprocessor macro invocations that appear explicitly in
6472 @var{expression}. Macro invocations appearing in that expansion are
6473 left unchanged. This command allows you to see the effect of a
6474 particular macro more clearly, without being confused by further
6475 expansions. Since @value{GDBN} simply expands macros, but does not
6476 parse the result, @var{expression} need not be a valid expression; it
6477 can be any string of tokens.
6480 @cindex macro definition, showing
6481 @cindex definition, showing a macro's
6482 @item info macro @var{macro}
6483 Show the definition of the macro named @var{macro}, and describe the
6484 source location where that definition was established.
6486 @kindex macro define
6487 @cindex user-defined macros
6488 @cindex defining macros interactively
6489 @cindex macros, user-defined
6490 @item macro define @var{macro} @var{replacement-list}
6491 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
6492 @i{(This command is not yet implemented.)} Introduce a definition for a
6493 preprocessor macro named @var{macro}, invocations of which are replaced
6494 by the tokens given in @var{replacement-list}. The first form of this
6495 command defines an ``object-like'' macro, which takes no arguments; the
6496 second form defines a ``function-like'' macro, which takes the arguments
6497 given in @var{arglist}.
6499 A definition introduced by this command is in scope in every expression
6500 evaluated in @value{GDBN}, until it is removed with the @command{macro
6501 undef} command, described below. The definition overrides all
6502 definitions for @var{macro} present in the program being debugged, as
6503 well as any previous user-supplied definition.
6506 @item macro undef @var{macro}
6507 @i{(This command is not yet implemented.)} Remove any user-supplied
6508 definition for the macro named @var{macro}. This command only affects
6509 definitions provided with the @command{macro define} command, described
6510 above; it cannot remove definitions present in the program being
6515 @cindex macros, example of debugging with
6516 Here is a transcript showing the above commands in action. First, we
6517 show our source files:
6525 #define ADD(x) (M + x)
6530 printf ("Hello, world!\n");
6532 printf ("We're so creative.\n");
6534 printf ("Goodbye, world!\n");
6541 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
6542 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
6543 compiler includes information about preprocessor macros in the debugging
6547 $ gcc -gdwarf-2 -g3 sample.c -o sample
6551 Now, we start @value{GDBN} on our sample program:
6555 GNU gdb 2002-05-06-cvs
6556 Copyright 2002 Free Software Foundation, Inc.
6557 GDB is free software, @dots{}
6561 We can expand macros and examine their definitions, even when the
6562 program is not running. @value{GDBN} uses the current listing position
6563 to decide which macro definitions are in scope:
6566 (@value{GDBP}) list main
6569 5 #define ADD(x) (M + x)
6574 10 printf ("Hello, world!\n");
6576 12 printf ("We're so creative.\n");
6577 (@value{GDBP}) info macro ADD
6578 Defined at /home/jimb/gdb/macros/play/sample.c:5
6579 #define ADD(x) (M + x)
6580 (@value{GDBP}) info macro Q
6581 Defined at /home/jimb/gdb/macros/play/sample.h:1
6582 included at /home/jimb/gdb/macros/play/sample.c:2
6584 (@value{GDBP}) macro expand ADD(1)
6585 expands to: (42 + 1)
6586 (@value{GDBP}) macro expand-once ADD(1)
6587 expands to: once (M + 1)
6591 In the example above, note that @command{macro expand-once} expands only
6592 the macro invocation explicit in the original text --- the invocation of
6593 @code{ADD} --- but does not expand the invocation of the macro @code{M},
6594 which was introduced by @code{ADD}.
6596 Once the program is running, GDB uses the macro definitions in force at
6597 the source line of the current stack frame:
6600 (@value{GDBP}) break main
6601 Breakpoint 1 at 0x8048370: file sample.c, line 10.
6603 Starting program: /home/jimb/gdb/macros/play/sample
6605 Breakpoint 1, main () at sample.c:10
6606 10 printf ("Hello, world!\n");
6610 At line 10, the definition of the macro @code{N} at line 9 is in force:
6613 (@value{GDBP}) info macro N
6614 Defined at /home/jimb/gdb/macros/play/sample.c:9
6616 (@value{GDBP}) macro expand N Q M
6618 (@value{GDBP}) print N Q M
6623 As we step over directives that remove @code{N}'s definition, and then
6624 give it a new definition, @value{GDBN} finds the definition (or lack
6625 thereof) in force at each point:
6630 12 printf ("We're so creative.\n");
6631 (@value{GDBP}) info macro N
6632 The symbol `N' has no definition as a C/C++ preprocessor macro
6633 at /home/jimb/gdb/macros/play/sample.c:12
6636 14 printf ("Goodbye, world!\n");
6637 (@value{GDBP}) info macro N
6638 Defined at /home/jimb/gdb/macros/play/sample.c:13
6640 (@value{GDBP}) macro expand N Q M
6641 expands to: 1729 < 42
6642 (@value{GDBP}) print N Q M
6649 @chapter Tracepoints
6650 @c This chapter is based on the documentation written by Michael
6651 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
6654 In some applications, it is not feasible for the debugger to interrupt
6655 the program's execution long enough for the developer to learn
6656 anything helpful about its behavior. If the program's correctness
6657 depends on its real-time behavior, delays introduced by a debugger
6658 might cause the program to change its behavior drastically, or perhaps
6659 fail, even when the code itself is correct. It is useful to be able
6660 to observe the program's behavior without interrupting it.
6662 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
6663 specify locations in the program, called @dfn{tracepoints}, and
6664 arbitrary expressions to evaluate when those tracepoints are reached.
6665 Later, using the @code{tfind} command, you can examine the values
6666 those expressions had when the program hit the tracepoints. The
6667 expressions may also denote objects in memory---structures or arrays,
6668 for example---whose values @value{GDBN} should record; while visiting
6669 a particular tracepoint, you may inspect those objects as if they were
6670 in memory at that moment. However, because @value{GDBN} records these
6671 values without interacting with you, it can do so quickly and
6672 unobtrusively, hopefully not disturbing the program's behavior.
6674 The tracepoint facility is currently available only for remote
6675 targets. @xref{Targets}. In addition, your remote target must know how
6676 to collect trace data. This functionality is implemented in the remote
6677 stub; however, none of the stubs distributed with @value{GDBN} support
6678 tracepoints as of this writing.
6680 This chapter describes the tracepoint commands and features.
6684 * Analyze Collected Data::
6685 * Tracepoint Variables::
6688 @node Set Tracepoints
6689 @section Commands to Set Tracepoints
6691 Before running such a @dfn{trace experiment}, an arbitrary number of
6692 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
6693 tracepoint has a number assigned to it by @value{GDBN}. Like with
6694 breakpoints, tracepoint numbers are successive integers starting from
6695 one. Many of the commands associated with tracepoints take the
6696 tracepoint number as their argument, to identify which tracepoint to
6699 For each tracepoint, you can specify, in advance, some arbitrary set
6700 of data that you want the target to collect in the trace buffer when
6701 it hits that tracepoint. The collected data can include registers,
6702 local variables, or global data. Later, you can use @value{GDBN}
6703 commands to examine the values these data had at the time the
6706 This section describes commands to set tracepoints and associated
6707 conditions and actions.
6710 * Create and Delete Tracepoints::
6711 * Enable and Disable Tracepoints::
6712 * Tracepoint Passcounts::
6713 * Tracepoint Actions::
6714 * Listing Tracepoints::
6715 * Starting and Stopping Trace Experiment::
6718 @node Create and Delete Tracepoints
6719 @subsection Create and Delete Tracepoints
6722 @cindex set tracepoint
6725 The @code{trace} command is very similar to the @code{break} command.
6726 Its argument can be a source line, a function name, or an address in
6727 the target program. @xref{Set Breaks}. The @code{trace} command
6728 defines a tracepoint, which is a point in the target program where the
6729 debugger will briefly stop, collect some data, and then allow the
6730 program to continue. Setting a tracepoint or changing its commands
6731 doesn't take effect until the next @code{tstart} command; thus, you
6732 cannot change the tracepoint attributes once a trace experiment is
6735 Here are some examples of using the @code{trace} command:
6738 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
6740 (@value{GDBP}) @b{trace +2} // 2 lines forward
6742 (@value{GDBP}) @b{trace my_function} // first source line of function
6744 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
6746 (@value{GDBP}) @b{trace *0x2117c4} // an address
6750 You can abbreviate @code{trace} as @code{tr}.
6753 @cindex last tracepoint number
6754 @cindex recent tracepoint number
6755 @cindex tracepoint number
6756 The convenience variable @code{$tpnum} records the tracepoint number
6757 of the most recently set tracepoint.
6759 @kindex delete tracepoint
6760 @cindex tracepoint deletion
6761 @item delete tracepoint @r{[}@var{num}@r{]}
6762 Permanently delete one or more tracepoints. With no argument, the
6763 default is to delete all tracepoints.
6768 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
6770 (@value{GDBP}) @b{delete trace} // remove all tracepoints
6774 You can abbreviate this command as @code{del tr}.
6777 @node Enable and Disable Tracepoints
6778 @subsection Enable and Disable Tracepoints
6781 @kindex disable tracepoint
6782 @item disable tracepoint @r{[}@var{num}@r{]}
6783 Disable tracepoint @var{num}, or all tracepoints if no argument
6784 @var{num} is given. A disabled tracepoint will have no effect during
6785 the next trace experiment, but it is not forgotten. You can re-enable
6786 a disabled tracepoint using the @code{enable tracepoint} command.
6788 @kindex enable tracepoint
6789 @item enable tracepoint @r{[}@var{num}@r{]}
6790 Enable tracepoint @var{num}, or all tracepoints. The enabled
6791 tracepoints will become effective the next time a trace experiment is
6795 @node Tracepoint Passcounts
6796 @subsection Tracepoint Passcounts
6800 @cindex tracepoint pass count
6801 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
6802 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
6803 automatically stop a trace experiment. If a tracepoint's passcount is
6804 @var{n}, then the trace experiment will be automatically stopped on
6805 the @var{n}'th time that tracepoint is hit. If the tracepoint number
6806 @var{num} is not specified, the @code{passcount} command sets the
6807 passcount of the most recently defined tracepoint. If no passcount is
6808 given, the trace experiment will run until stopped explicitly by the
6814 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
6815 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
6817 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
6818 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
6819 (@value{GDBP}) @b{trace foo}
6820 (@value{GDBP}) @b{pass 3}
6821 (@value{GDBP}) @b{trace bar}
6822 (@value{GDBP}) @b{pass 2}
6823 (@value{GDBP}) @b{trace baz}
6824 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
6825 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
6826 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
6827 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
6831 @node Tracepoint Actions
6832 @subsection Tracepoint Action Lists
6836 @cindex tracepoint actions
6837 @item actions @r{[}@var{num}@r{]}
6838 This command will prompt for a list of actions to be taken when the
6839 tracepoint is hit. If the tracepoint number @var{num} is not
6840 specified, this command sets the actions for the one that was most
6841 recently defined (so that you can define a tracepoint and then say
6842 @code{actions} without bothering about its number). You specify the
6843 actions themselves on the following lines, one action at a time, and
6844 terminate the actions list with a line containing just @code{end}. So
6845 far, the only defined actions are @code{collect} and
6846 @code{while-stepping}.
6848 @cindex remove actions from a tracepoint
6849 To remove all actions from a tracepoint, type @samp{actions @var{num}}
6850 and follow it immediately with @samp{end}.
6853 (@value{GDBP}) @b{collect @var{data}} // collect some data
6855 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
6857 (@value{GDBP}) @b{end} // signals the end of actions.
6860 In the following example, the action list begins with @code{collect}
6861 commands indicating the things to be collected when the tracepoint is
6862 hit. Then, in order to single-step and collect additional data
6863 following the tracepoint, a @code{while-stepping} command is used,
6864 followed by the list of things to be collected while stepping. The
6865 @code{while-stepping} command is terminated by its own separate
6866 @code{end} command. Lastly, the action list is terminated by an
6870 (@value{GDBP}) @b{trace foo}
6871 (@value{GDBP}) @b{actions}
6872 Enter actions for tracepoint 1, one per line:
6881 @kindex collect @r{(tracepoints)}
6882 @item collect @var{expr1}, @var{expr2}, @dots{}
6883 Collect values of the given expressions when the tracepoint is hit.
6884 This command accepts a comma-separated list of any valid expressions.
6885 In addition to global, static, or local variables, the following
6886 special arguments are supported:
6890 collect all registers
6893 collect all function arguments
6896 collect all local variables.
6899 You can give several consecutive @code{collect} commands, each one
6900 with a single argument, or one @code{collect} command with several
6901 arguments separated by commas: the effect is the same.
6903 The command @code{info scope} (@pxref{Symbols, info scope}) is
6904 particularly useful for figuring out what data to collect.
6906 @kindex while-stepping @r{(tracepoints)}
6907 @item while-stepping @var{n}
6908 Perform @var{n} single-step traces after the tracepoint, collecting
6909 new data at each step. The @code{while-stepping} command is
6910 followed by the list of what to collect while stepping (followed by
6911 its own @code{end} command):
6915 > collect $regs, myglobal
6921 You may abbreviate @code{while-stepping} as @code{ws} or
6925 @node Listing Tracepoints
6926 @subsection Listing Tracepoints
6929 @kindex info tracepoints
6930 @cindex information about tracepoints
6931 @item info tracepoints @r{[}@var{num}@r{]}
6932 Display information about the tracepoint @var{num}. If you don't specify
6933 a tracepoint number, displays information about all the tracepoints
6934 defined so far. For each tracepoint, the following information is
6941 whether it is enabled or disabled
6945 its passcount as given by the @code{passcount @var{n}} command
6947 its step count as given by the @code{while-stepping @var{n}} command
6949 where in the source files is the tracepoint set
6951 its action list as given by the @code{actions} command
6955 (@value{GDBP}) @b{info trace}
6956 Num Enb Address PassC StepC What
6957 1 y 0x002117c4 0 0 <gdb_asm>
6958 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
6959 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
6964 This command can be abbreviated @code{info tp}.
6967 @node Starting and Stopping Trace Experiment
6968 @subsection Starting and Stopping Trace Experiment
6972 @cindex start a new trace experiment
6973 @cindex collected data discarded
6975 This command takes no arguments. It starts the trace experiment, and
6976 begins collecting data. This has the side effect of discarding all
6977 the data collected in the trace buffer during the previous trace
6981 @cindex stop a running trace experiment
6983 This command takes no arguments. It ends the trace experiment, and
6984 stops collecting data.
6986 @strong{Note:} a trace experiment and data collection may stop
6987 automatically if any tracepoint's passcount is reached
6988 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
6991 @cindex status of trace data collection
6992 @cindex trace experiment, status of
6994 This command displays the status of the current trace data
6998 Here is an example of the commands we described so far:
7001 (@value{GDBP}) @b{trace gdb_c_test}
7002 (@value{GDBP}) @b{actions}
7003 Enter actions for tracepoint #1, one per line.
7004 > collect $regs,$locals,$args
7009 (@value{GDBP}) @b{tstart}
7010 [time passes @dots{}]
7011 (@value{GDBP}) @b{tstop}
7015 @node Analyze Collected Data
7016 @section Using the collected data
7018 After the tracepoint experiment ends, you use @value{GDBN} commands
7019 for examining the trace data. The basic idea is that each tracepoint
7020 collects a trace @dfn{snapshot} every time it is hit and another
7021 snapshot every time it single-steps. All these snapshots are
7022 consecutively numbered from zero and go into a buffer, and you can
7023 examine them later. The way you examine them is to @dfn{focus} on a
7024 specific trace snapshot. When the remote stub is focused on a trace
7025 snapshot, it will respond to all @value{GDBN} requests for memory and
7026 registers by reading from the buffer which belongs to that snapshot,
7027 rather than from @emph{real} memory or registers of the program being
7028 debugged. This means that @strong{all} @value{GDBN} commands
7029 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
7030 behave as if we were currently debugging the program state as it was
7031 when the tracepoint occurred. Any requests for data that are not in
7032 the buffer will fail.
7035 * tfind:: How to select a trace snapshot
7036 * tdump:: How to display all data for a snapshot
7037 * save-tracepoints:: How to save tracepoints for a future run
7041 @subsection @code{tfind @var{n}}
7044 @cindex select trace snapshot
7045 @cindex find trace snapshot
7046 The basic command for selecting a trace snapshot from the buffer is
7047 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
7048 counting from zero. If no argument @var{n} is given, the next
7049 snapshot is selected.
7051 Here are the various forms of using the @code{tfind} command.
7055 Find the first snapshot in the buffer. This is a synonym for
7056 @code{tfind 0} (since 0 is the number of the first snapshot).
7059 Stop debugging trace snapshots, resume @emph{live} debugging.
7062 Same as @samp{tfind none}.
7065 No argument means find the next trace snapshot.
7068 Find the previous trace snapshot before the current one. This permits
7069 retracing earlier steps.
7071 @item tfind tracepoint @var{num}
7072 Find the next snapshot associated with tracepoint @var{num}. Search
7073 proceeds forward from the last examined trace snapshot. If no
7074 argument @var{num} is given, it means find the next snapshot collected
7075 for the same tracepoint as the current snapshot.
7077 @item tfind pc @var{addr}
7078 Find the next snapshot associated with the value @var{addr} of the
7079 program counter. Search proceeds forward from the last examined trace
7080 snapshot. If no argument @var{addr} is given, it means find the next
7081 snapshot with the same value of PC as the current snapshot.
7083 @item tfind outside @var{addr1}, @var{addr2}
7084 Find the next snapshot whose PC is outside the given range of
7087 @item tfind range @var{addr1}, @var{addr2}
7088 Find the next snapshot whose PC is between @var{addr1} and
7089 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
7091 @item tfind line @r{[}@var{file}:@r{]}@var{n}
7092 Find the next snapshot associated with the source line @var{n}. If
7093 the optional argument @var{file} is given, refer to line @var{n} in
7094 that source file. Search proceeds forward from the last examined
7095 trace snapshot. If no argument @var{n} is given, it means find the
7096 next line other than the one currently being examined; thus saying
7097 @code{tfind line} repeatedly can appear to have the same effect as
7098 stepping from line to line in a @emph{live} debugging session.
7101 The default arguments for the @code{tfind} commands are specifically
7102 designed to make it easy to scan through the trace buffer. For
7103 instance, @code{tfind} with no argument selects the next trace
7104 snapshot, and @code{tfind -} with no argument selects the previous
7105 trace snapshot. So, by giving one @code{tfind} command, and then
7106 simply hitting @key{RET} repeatedly you can examine all the trace
7107 snapshots in order. Or, by saying @code{tfind -} and then hitting
7108 @key{RET} repeatedly you can examine the snapshots in reverse order.
7109 The @code{tfind line} command with no argument selects the snapshot
7110 for the next source line executed. The @code{tfind pc} command with
7111 no argument selects the next snapshot with the same program counter
7112 (PC) as the current frame. The @code{tfind tracepoint} command with
7113 no argument selects the next trace snapshot collected by the same
7114 tracepoint as the current one.
7116 In addition to letting you scan through the trace buffer manually,
7117 these commands make it easy to construct @value{GDBN} scripts that
7118 scan through the trace buffer and print out whatever collected data
7119 you are interested in. Thus, if we want to examine the PC, FP, and SP
7120 registers from each trace frame in the buffer, we can say this:
7123 (@value{GDBP}) @b{tfind start}
7124 (@value{GDBP}) @b{while ($trace_frame != -1)}
7125 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
7126 $trace_frame, $pc, $sp, $fp
7130 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
7131 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
7132 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
7133 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
7134 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
7135 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
7136 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
7137 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
7138 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
7139 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
7140 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
7143 Or, if we want to examine the variable @code{X} at each source line in
7147 (@value{GDBP}) @b{tfind start}
7148 (@value{GDBP}) @b{while ($trace_frame != -1)}
7149 > printf "Frame %d, X == %d\n", $trace_frame, X
7159 @subsection @code{tdump}
7161 @cindex dump all data collected at tracepoint
7162 @cindex tracepoint data, display
7164 This command takes no arguments. It prints all the data collected at
7165 the current trace snapshot.
7168 (@value{GDBP}) @b{trace 444}
7169 (@value{GDBP}) @b{actions}
7170 Enter actions for tracepoint #2, one per line:
7171 > collect $regs, $locals, $args, gdb_long_test
7174 (@value{GDBP}) @b{tstart}
7176 (@value{GDBP}) @b{tfind line 444}
7177 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
7179 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
7181 (@value{GDBP}) @b{tdump}
7182 Data collected at tracepoint 2, trace frame 1:
7183 d0 0xc4aa0085 -995491707
7187 d4 0x71aea3d 119204413
7192 a1 0x3000668 50333288
7195 a4 0x3000698 50333336
7197 fp 0x30bf3c 0x30bf3c
7198 sp 0x30bf34 0x30bf34
7200 pc 0x20b2c8 0x20b2c8
7204 p = 0x20e5b4 "gdb-test"
7211 gdb_long_test = 17 '\021'
7216 @node save-tracepoints
7217 @subsection @code{save-tracepoints @var{filename}}
7218 @kindex save-tracepoints
7219 @cindex save tracepoints for future sessions
7221 This command saves all current tracepoint definitions together with
7222 their actions and passcounts, into a file @file{@var{filename}}
7223 suitable for use in a later debugging session. To read the saved
7224 tracepoint definitions, use the @code{source} command (@pxref{Command
7227 @node Tracepoint Variables
7228 @section Convenience Variables for Tracepoints
7229 @cindex tracepoint variables
7230 @cindex convenience variables for tracepoints
7233 @vindex $trace_frame
7234 @item (int) $trace_frame
7235 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
7236 snapshot is selected.
7239 @item (int) $tracepoint
7240 The tracepoint for the current trace snapshot.
7243 @item (int) $trace_line
7244 The line number for the current trace snapshot.
7247 @item (char []) $trace_file
7248 The source file for the current trace snapshot.
7251 @item (char []) $trace_func
7252 The name of the function containing @code{$tracepoint}.
7255 Note: @code{$trace_file} is not suitable for use in @code{printf},
7256 use @code{output} instead.
7258 Here's a simple example of using these convenience variables for
7259 stepping through all the trace snapshots and printing some of their
7263 (@value{GDBP}) @b{tfind start}
7265 (@value{GDBP}) @b{while $trace_frame != -1}
7266 > output $trace_file
7267 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
7273 @chapter Debugging Programs That Use Overlays
7276 If your program is too large to fit completely in your target system's
7277 memory, you can sometimes use @dfn{overlays} to work around this
7278 problem. @value{GDBN} provides some support for debugging programs that
7282 * How Overlays Work:: A general explanation of overlays.
7283 * Overlay Commands:: Managing overlays in @value{GDBN}.
7284 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
7285 mapped by asking the inferior.
7286 * Overlay Sample Program:: A sample program using overlays.
7289 @node How Overlays Work
7290 @section How Overlays Work
7291 @cindex mapped overlays
7292 @cindex unmapped overlays
7293 @cindex load address, overlay's
7294 @cindex mapped address
7295 @cindex overlay area
7297 Suppose you have a computer whose instruction address space is only 64
7298 kilobytes long, but which has much more memory which can be accessed by
7299 other means: special instructions, segment registers, or memory
7300 management hardware, for example. Suppose further that you want to
7301 adapt a program which is larger than 64 kilobytes to run on this system.
7303 One solution is to identify modules of your program which are relatively
7304 independent, and need not call each other directly; call these modules
7305 @dfn{overlays}. Separate the overlays from the main program, and place
7306 their machine code in the larger memory. Place your main program in
7307 instruction memory, but leave at least enough space there to hold the
7308 largest overlay as well.
7310 Now, to call a function located in an overlay, you must first copy that
7311 overlay's machine code from the large memory into the space set aside
7312 for it in the instruction memory, and then jump to its entry point
7315 @c NB: In the below the mapped area's size is greater or equal to the
7316 @c size of all overlays. This is intentional to remind the developer
7317 @c that overlays don't necessarily need to be the same size.
7321 Data Instruction Larger
7322 Address Space Address Space Address Space
7323 +-----------+ +-----------+ +-----------+
7325 +-----------+ +-----------+ +-----------+<-- overlay 1
7326 | program | | main | .----| overlay 1 | load address
7327 | variables | | program | | +-----------+
7328 | and heap | | | | | |
7329 +-----------+ | | | +-----------+<-- overlay 2
7330 | | +-----------+ | | | load address
7331 +-----------+ | | | .-| overlay 2 |
7333 mapped --->+-----------+ | | +-----------+
7335 | overlay | <-' | | |
7336 | area | <---' +-----------+<-- overlay 3
7337 | | <---. | | load address
7338 +-----------+ `--| overlay 3 |
7345 @anchor{A code overlay}A code overlay
7349 The diagram (@pxref{A code overlay}) shows a system with separate data
7350 and instruction address spaces. To map an overlay, the program copies
7351 its code from the larger address space to the instruction address space.
7352 Since the overlays shown here all use the same mapped address, only one
7353 may be mapped at a time. For a system with a single address space for
7354 data and instructions, the diagram would be similar, except that the
7355 program variables and heap would share an address space with the main
7356 program and the overlay area.
7358 An overlay loaded into instruction memory and ready for use is called a
7359 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
7360 instruction memory. An overlay not present (or only partially present)
7361 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
7362 is its address in the larger memory. The mapped address is also called
7363 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
7364 called the @dfn{load memory address}, or @dfn{LMA}.
7366 Unfortunately, overlays are not a completely transparent way to adapt a
7367 program to limited instruction memory. They introduce a new set of
7368 global constraints you must keep in mind as you design your program:
7373 Before calling or returning to a function in an overlay, your program
7374 must make sure that overlay is actually mapped. Otherwise, the call or
7375 return will transfer control to the right address, but in the wrong
7376 overlay, and your program will probably crash.
7379 If the process of mapping an overlay is expensive on your system, you
7380 will need to choose your overlays carefully to minimize their effect on
7381 your program's performance.
7384 The executable file you load onto your system must contain each
7385 overlay's instructions, appearing at the overlay's load address, not its
7386 mapped address. However, each overlay's instructions must be relocated
7387 and its symbols defined as if the overlay were at its mapped address.
7388 You can use GNU linker scripts to specify different load and relocation
7389 addresses for pieces of your program; see @ref{Overlay Description,,,
7390 ld.info, Using ld: the GNU linker}.
7393 The procedure for loading executable files onto your system must be able
7394 to load their contents into the larger address space as well as the
7395 instruction and data spaces.
7399 The overlay system described above is rather simple, and could be
7400 improved in many ways:
7405 If your system has suitable bank switch registers or memory management
7406 hardware, you could use those facilities to make an overlay's load area
7407 contents simply appear at their mapped address in instruction space.
7408 This would probably be faster than copying the overlay to its mapped
7409 area in the usual way.
7412 If your overlays are small enough, you could set aside more than one
7413 overlay area, and have more than one overlay mapped at a time.
7416 You can use overlays to manage data, as well as instructions. In
7417 general, data overlays are even less transparent to your design than
7418 code overlays: whereas code overlays only require care when you call or
7419 return to functions, data overlays require care every time you access
7420 the data. Also, if you change the contents of a data overlay, you
7421 must copy its contents back out to its load address before you can copy a
7422 different data overlay into the same mapped area.
7427 @node Overlay Commands
7428 @section Overlay Commands
7430 To use @value{GDBN}'s overlay support, each overlay in your program must
7431 correspond to a separate section of the executable file. The section's
7432 virtual memory address and load memory address must be the overlay's
7433 mapped and load addresses. Identifying overlays with sections allows
7434 @value{GDBN} to determine the appropriate address of a function or
7435 variable, depending on whether the overlay is mapped or not.
7437 @value{GDBN}'s overlay commands all start with the word @code{overlay};
7438 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
7443 Disable @value{GDBN}'s overlay support. When overlay support is
7444 disabled, @value{GDBN} assumes that all functions and variables are
7445 always present at their mapped addresses. By default, @value{GDBN}'s
7446 overlay support is disabled.
7448 @item overlay manual
7449 @cindex manual overlay debugging
7450 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
7451 relies on you to tell it which overlays are mapped, and which are not,
7452 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
7453 commands described below.
7455 @item overlay map-overlay @var{overlay}
7456 @itemx overlay map @var{overlay}
7457 @cindex map an overlay
7458 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
7459 be the name of the object file section containing the overlay. When an
7460 overlay is mapped, @value{GDBN} assumes it can find the overlay's
7461 functions and variables at their mapped addresses. @value{GDBN} assumes
7462 that any other overlays whose mapped ranges overlap that of
7463 @var{overlay} are now unmapped.
7465 @item overlay unmap-overlay @var{overlay}
7466 @itemx overlay unmap @var{overlay}
7467 @cindex unmap an overlay
7468 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
7469 must be the name of the object file section containing the overlay.
7470 When an overlay is unmapped, @value{GDBN} assumes it can find the
7471 overlay's functions and variables at their load addresses.
7474 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
7475 consults a data structure the overlay manager maintains in the inferior
7476 to see which overlays are mapped. For details, see @ref{Automatic
7479 @item overlay load-target
7481 @cindex reloading the overlay table
7482 Re-read the overlay table from the inferior. Normally, @value{GDBN}
7483 re-reads the table @value{GDBN} automatically each time the inferior
7484 stops, so this command should only be necessary if you have changed the
7485 overlay mapping yourself using @value{GDBN}. This command is only
7486 useful when using automatic overlay debugging.
7488 @item overlay list-overlays
7490 @cindex listing mapped overlays
7491 Display a list of the overlays currently mapped, along with their mapped
7492 addresses, load addresses, and sizes.
7496 Normally, when @value{GDBN} prints a code address, it includes the name
7497 of the function the address falls in:
7500 (@value{GDBP}) print main
7501 $3 = @{int ()@} 0x11a0 <main>
7504 When overlay debugging is enabled, @value{GDBN} recognizes code in
7505 unmapped overlays, and prints the names of unmapped functions with
7506 asterisks around them. For example, if @code{foo} is a function in an
7507 unmapped overlay, @value{GDBN} prints it this way:
7510 (@value{GDBP}) overlay list
7511 No sections are mapped.
7512 (@value{GDBP}) print foo
7513 $5 = @{int (int)@} 0x100000 <*foo*>
7516 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
7520 (@value{GDBP}) overlay list
7521 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
7522 mapped at 0x1016 - 0x104a
7523 (@value{GDBP}) print foo
7524 $6 = @{int (int)@} 0x1016 <foo>
7527 When overlay debugging is enabled, @value{GDBN} can find the correct
7528 address for functions and variables in an overlay, whether or not the
7529 overlay is mapped. This allows most @value{GDBN} commands, like
7530 @code{break} and @code{disassemble}, to work normally, even on unmapped
7531 code. However, @value{GDBN}'s breakpoint support has some limitations:
7535 @cindex breakpoints in overlays
7536 @cindex overlays, setting breakpoints in
7537 You can set breakpoints in functions in unmapped overlays, as long as
7538 @value{GDBN} can write to the overlay at its load address.
7540 @value{GDBN} can not set hardware or simulator-based breakpoints in
7541 unmapped overlays. However, if you set a breakpoint at the end of your
7542 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
7543 you are using manual overlay management), @value{GDBN} will re-set its
7544 breakpoints properly.
7548 @node Automatic Overlay Debugging
7549 @section Automatic Overlay Debugging
7550 @cindex automatic overlay debugging
7552 @value{GDBN} can automatically track which overlays are mapped and which
7553 are not, given some simple co-operation from the overlay manager in the
7554 inferior. If you enable automatic overlay debugging with the
7555 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
7556 looks in the inferior's memory for certain variables describing the
7557 current state of the overlays.
7559 Here are the variables your overlay manager must define to support
7560 @value{GDBN}'s automatic overlay debugging:
7564 @item @code{_ovly_table}:
7565 This variable must be an array of the following structures:
7570 /* The overlay's mapped address. */
7573 /* The size of the overlay, in bytes. */
7576 /* The overlay's load address. */
7579 /* Non-zero if the overlay is currently mapped;
7581 unsigned long mapped;
7585 @item @code{_novlys}:
7586 This variable must be a four-byte signed integer, holding the total
7587 number of elements in @code{_ovly_table}.
7591 To decide whether a particular overlay is mapped or not, @value{GDBN}
7592 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
7593 @code{lma} members equal the VMA and LMA of the overlay's section in the
7594 executable file. When @value{GDBN} finds a matching entry, it consults
7595 the entry's @code{mapped} member to determine whether the overlay is
7598 In addition, your overlay manager may define a function called
7599 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
7600 will silently set a breakpoint there. If the overlay manager then
7601 calls this function whenever it has changed the overlay table, this
7602 will enable @value{GDBN} to accurately keep track of which overlays
7603 are in program memory, and update any breakpoints that may be set
7604 in overlays. This will allow breakpoints to work even if the
7605 overlays are kept in ROM or other non-writable memory while they
7606 are not being executed.
7608 @node Overlay Sample Program
7609 @section Overlay Sample Program
7610 @cindex overlay example program
7612 When linking a program which uses overlays, you must place the overlays
7613 at their load addresses, while relocating them to run at their mapped
7614 addresses. To do this, you must write a linker script (@pxref{Overlay
7615 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
7616 since linker scripts are specific to a particular host system, target
7617 architecture, and target memory layout, this manual cannot provide
7618 portable sample code demonstrating @value{GDBN}'s overlay support.
7620 However, the @value{GDBN} source distribution does contain an overlaid
7621 program, with linker scripts for a few systems, as part of its test
7622 suite. The program consists of the following files from
7623 @file{gdb/testsuite/gdb.base}:
7627 The main program file.
7629 A simple overlay manager, used by @file{overlays.c}.
7634 Overlay modules, loaded and used by @file{overlays.c}.
7637 Linker scripts for linking the test program on the @code{d10v-elf}
7638 and @code{m32r-elf} targets.
7641 You can build the test program using the @code{d10v-elf} GCC
7642 cross-compiler like this:
7645 $ d10v-elf-gcc -g -c overlays.c
7646 $ d10v-elf-gcc -g -c ovlymgr.c
7647 $ d10v-elf-gcc -g -c foo.c
7648 $ d10v-elf-gcc -g -c bar.c
7649 $ d10v-elf-gcc -g -c baz.c
7650 $ d10v-elf-gcc -g -c grbx.c
7651 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
7652 baz.o grbx.o -Wl,-Td10v.ld -o overlays
7655 The build process is identical for any other architecture, except that
7656 you must substitute the appropriate compiler and linker script for the
7657 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
7661 @chapter Using @value{GDBN} with Different Languages
7664 Although programming languages generally have common aspects, they are
7665 rarely expressed in the same manner. For instance, in ANSI C,
7666 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
7667 Modula-2, it is accomplished by @code{p^}. Values can also be
7668 represented (and displayed) differently. Hex numbers in C appear as
7669 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
7671 @cindex working language
7672 Language-specific information is built into @value{GDBN} for some languages,
7673 allowing you to express operations like the above in your program's
7674 native language, and allowing @value{GDBN} to output values in a manner
7675 consistent with the syntax of your program's native language. The
7676 language you use to build expressions is called the @dfn{working
7680 * Setting:: Switching between source languages
7681 * Show:: Displaying the language
7682 * Checks:: Type and range checks
7683 * Support:: Supported languages
7684 * Unsupported languages:: Unsupported languages
7688 @section Switching between source languages
7690 There are two ways to control the working language---either have @value{GDBN}
7691 set it automatically, or select it manually yourself. You can use the
7692 @code{set language} command for either purpose. On startup, @value{GDBN}
7693 defaults to setting the language automatically. The working language is
7694 used to determine how expressions you type are interpreted, how values
7697 In addition to the working language, every source file that
7698 @value{GDBN} knows about has its own working language. For some object
7699 file formats, the compiler might indicate which language a particular
7700 source file is in. However, most of the time @value{GDBN} infers the
7701 language from the name of the file. The language of a source file
7702 controls whether C@t{++} names are demangled---this way @code{backtrace} can
7703 show each frame appropriately for its own language. There is no way to
7704 set the language of a source file from within @value{GDBN}, but you can
7705 set the language associated with a filename extension. @xref{Show, ,
7706 Displaying the language}.
7708 This is most commonly a problem when you use a program, such
7709 as @code{cfront} or @code{f2c}, that generates C but is written in
7710 another language. In that case, make the
7711 program use @code{#line} directives in its C output; that way
7712 @value{GDBN} will know the correct language of the source code of the original
7713 program, and will display that source code, not the generated C code.
7716 * Filenames:: Filename extensions and languages.
7717 * Manually:: Setting the working language manually
7718 * Automatically:: Having @value{GDBN} infer the source language
7722 @subsection List of filename extensions and languages
7724 If a source file name ends in one of the following extensions, then
7725 @value{GDBN} infers that its language is the one indicated.
7746 Objective-C source file
7753 Modula-2 source file
7757 Assembler source file. This actually behaves almost like C, but
7758 @value{GDBN} does not skip over function prologues when stepping.
7761 In addition, you may set the language associated with a filename
7762 extension. @xref{Show, , Displaying the language}.
7765 @subsection Setting the working language
7767 If you allow @value{GDBN} to set the language automatically,
7768 expressions are interpreted the same way in your debugging session and
7771 @kindex set language
7772 If you wish, you may set the language manually. To do this, issue the
7773 command @samp{set language @var{lang}}, where @var{lang} is the name of
7775 @code{c} or @code{modula-2}.
7776 For a list of the supported languages, type @samp{set language}.
7778 Setting the language manually prevents @value{GDBN} from updating the working
7779 language automatically. This can lead to confusion if you try
7780 to debug a program when the working language is not the same as the
7781 source language, when an expression is acceptable to both
7782 languages---but means different things. For instance, if the current
7783 source file were written in C, and @value{GDBN} was parsing Modula-2, a
7791 might not have the effect you intended. In C, this means to add
7792 @code{b} and @code{c} and place the result in @code{a}. The result
7793 printed would be the value of @code{a}. In Modula-2, this means to compare
7794 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
7797 @subsection Having @value{GDBN} infer the source language
7799 To have @value{GDBN} set the working language automatically, use
7800 @samp{set language local} or @samp{set language auto}. @value{GDBN}
7801 then infers the working language. That is, when your program stops in a
7802 frame (usually by encountering a breakpoint), @value{GDBN} sets the
7803 working language to the language recorded for the function in that
7804 frame. If the language for a frame is unknown (that is, if the function
7805 or block corresponding to the frame was defined in a source file that
7806 does not have a recognized extension), the current working language is
7807 not changed, and @value{GDBN} issues a warning.
7809 This may not seem necessary for most programs, which are written
7810 entirely in one source language. However, program modules and libraries
7811 written in one source language can be used by a main program written in
7812 a different source language. Using @samp{set language auto} in this
7813 case frees you from having to set the working language manually.
7816 @section Displaying the language
7818 The following commands help you find out which language is the
7819 working language, and also what language source files were written in.
7821 @kindex show language
7824 Display the current working language. This is the
7825 language you can use with commands such as @code{print} to
7826 build and compute expressions that may involve variables in your program.
7829 @kindex info frame@r{, show the source language}
7830 Display the source language for this frame. This language becomes the
7831 working language if you use an identifier from this frame.
7832 @xref{Frame Info, ,Information about a frame}, to identify the other
7833 information listed here.
7836 @kindex info source@r{, show the source language}
7837 Display the source language of this source file.
7838 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
7839 information listed here.
7842 In unusual circumstances, you may have source files with extensions
7843 not in the standard list. You can then set the extension associated
7844 with a language explicitly:
7846 @kindex set extension-language
7847 @kindex info extensions
7849 @item set extension-language @var{.ext} @var{language}
7850 Set source files with extension @var{.ext} to be assumed to be in
7851 the source language @var{language}.
7853 @item info extensions
7854 List all the filename extensions and the associated languages.
7858 @section Type and range checking
7861 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
7862 checking are included, but they do not yet have any effect. This
7863 section documents the intended facilities.
7865 @c FIXME remove warning when type/range code added
7867 Some languages are designed to guard you against making seemingly common
7868 errors through a series of compile- and run-time checks. These include
7869 checking the type of arguments to functions and operators, and making
7870 sure mathematical overflows are caught at run time. Checks such as
7871 these help to ensure a program's correctness once it has been compiled
7872 by eliminating type mismatches, and providing active checks for range
7873 errors when your program is running.
7875 @value{GDBN} can check for conditions like the above if you wish.
7876 Although @value{GDBN} does not check the statements in your program, it
7877 can check expressions entered directly into @value{GDBN} for evaluation via
7878 the @code{print} command, for example. As with the working language,
7879 @value{GDBN} can also decide whether or not to check automatically based on
7880 your program's source language. @xref{Support, ,Supported languages},
7881 for the default settings of supported languages.
7884 * Type Checking:: An overview of type checking
7885 * Range Checking:: An overview of range checking
7888 @cindex type checking
7889 @cindex checks, type
7891 @subsection An overview of type checking
7893 Some languages, such as Modula-2, are strongly typed, meaning that the
7894 arguments to operators and functions have to be of the correct type,
7895 otherwise an error occurs. These checks prevent type mismatch
7896 errors from ever causing any run-time problems. For example,
7904 The second example fails because the @code{CARDINAL} 1 is not
7905 type-compatible with the @code{REAL} 2.3.
7907 For the expressions you use in @value{GDBN} commands, you can tell the
7908 @value{GDBN} type checker to skip checking;
7909 to treat any mismatches as errors and abandon the expression;
7910 or to only issue warnings when type mismatches occur,
7911 but evaluate the expression anyway. When you choose the last of
7912 these, @value{GDBN} evaluates expressions like the second example above, but
7913 also issues a warning.
7915 Even if you turn type checking off, there may be other reasons
7916 related to type that prevent @value{GDBN} from evaluating an expression.
7917 For instance, @value{GDBN} does not know how to add an @code{int} and
7918 a @code{struct foo}. These particular type errors have nothing to do
7919 with the language in use, and usually arise from expressions, such as
7920 the one described above, which make little sense to evaluate anyway.
7922 Each language defines to what degree it is strict about type. For
7923 instance, both Modula-2 and C require the arguments to arithmetical
7924 operators to be numbers. In C, enumerated types and pointers can be
7925 represented as numbers, so that they are valid arguments to mathematical
7926 operators. @xref{Support, ,Supported languages}, for further
7927 details on specific languages.
7929 @value{GDBN} provides some additional commands for controlling the type checker:
7931 @kindex set check type
7932 @kindex show check type
7934 @item set check type auto
7935 Set type checking on or off based on the current working language.
7936 @xref{Support, ,Supported languages}, for the default settings for
7939 @item set check type on
7940 @itemx set check type off
7941 Set type checking on or off, overriding the default setting for the
7942 current working language. Issue a warning if the setting does not
7943 match the language default. If any type mismatches occur in
7944 evaluating an expression while type checking is on, @value{GDBN} prints a
7945 message and aborts evaluation of the expression.
7947 @item set check type warn
7948 Cause the type checker to issue warnings, but to always attempt to
7949 evaluate the expression. Evaluating the expression may still
7950 be impossible for other reasons. For example, @value{GDBN} cannot add
7951 numbers and structures.
7954 Show the current setting of the type checker, and whether or not @value{GDBN}
7955 is setting it automatically.
7958 @cindex range checking
7959 @cindex checks, range
7960 @node Range Checking
7961 @subsection An overview of range checking
7963 In some languages (such as Modula-2), it is an error to exceed the
7964 bounds of a type; this is enforced with run-time checks. Such range
7965 checking is meant to ensure program correctness by making sure
7966 computations do not overflow, or indices on an array element access do
7967 not exceed the bounds of the array.
7969 For expressions you use in @value{GDBN} commands, you can tell
7970 @value{GDBN} to treat range errors in one of three ways: ignore them,
7971 always treat them as errors and abandon the expression, or issue
7972 warnings but evaluate the expression anyway.
7974 A range error can result from numerical overflow, from exceeding an
7975 array index bound, or when you type a constant that is not a member
7976 of any type. Some languages, however, do not treat overflows as an
7977 error. In many implementations of C, mathematical overflow causes the
7978 result to ``wrap around'' to lower values---for example, if @var{m} is
7979 the largest integer value, and @var{s} is the smallest, then
7982 @var{m} + 1 @result{} @var{s}
7985 This, too, is specific to individual languages, and in some cases
7986 specific to individual compilers or machines. @xref{Support, ,
7987 Supported languages}, for further details on specific languages.
7989 @value{GDBN} provides some additional commands for controlling the range checker:
7991 @kindex set check range
7992 @kindex show check range
7994 @item set check range auto
7995 Set range checking on or off based on the current working language.
7996 @xref{Support, ,Supported languages}, for the default settings for
7999 @item set check range on
8000 @itemx set check range off
8001 Set range checking on or off, overriding the default setting for the
8002 current working language. A warning is issued if the setting does not
8003 match the language default. If a range error occurs and range checking is on,
8004 then a message is printed and evaluation of the expression is aborted.
8006 @item set check range warn
8007 Output messages when the @value{GDBN} range checker detects a range error,
8008 but attempt to evaluate the expression anyway. Evaluating the
8009 expression may still be impossible for other reasons, such as accessing
8010 memory that the process does not own (a typical example from many Unix
8014 Show the current setting of the range checker, and whether or not it is
8015 being set automatically by @value{GDBN}.
8019 @section Supported languages
8021 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, assembly, Modula-2, and Ada.
8022 @c This is false ...
8023 Some @value{GDBN} features may be used in expressions regardless of the
8024 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
8025 and the @samp{@{type@}addr} construct (@pxref{Expressions,
8026 ,Expressions}) can be used with the constructs of any supported
8029 The following sections detail to what degree each source language is
8030 supported by @value{GDBN}. These sections are not meant to be language
8031 tutorials or references, but serve only as a reference guide to what the
8032 @value{GDBN} expression parser accepts, and what input and output
8033 formats should look like for different languages. There are many good
8034 books written on each of these languages; please look to these for a
8035 language reference or tutorial.
8039 * Objective-C:: Objective-C
8040 * Modula-2:: Modula-2
8045 @subsection C and C@t{++}
8047 @cindex C and C@t{++}
8048 @cindex expressions in C or C@t{++}
8050 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
8051 to both languages. Whenever this is the case, we discuss those languages
8055 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
8056 @cindex @sc{gnu} C@t{++}
8057 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
8058 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
8059 effectively, you must compile your C@t{++} programs with a supported
8060 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
8061 compiler (@code{aCC}).
8063 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
8064 format; if it doesn't work on your system, try the stabs+ debugging
8065 format. You can select those formats explicitly with the @code{g++}
8066 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
8067 @xref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
8068 CC, gcc.info, Using @sc{gnu} CC}.
8071 * C Operators:: C and C@t{++} operators
8072 * C Constants:: C and C@t{++} constants
8073 * C plus plus expressions:: C@t{++} expressions
8074 * C Defaults:: Default settings for C and C@t{++}
8075 * C Checks:: C and C@t{++} type and range checks
8076 * Debugging C:: @value{GDBN} and C
8077 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
8081 @subsubsection C and C@t{++} operators
8083 @cindex C and C@t{++} operators
8085 Operators must be defined on values of specific types. For instance,
8086 @code{+} is defined on numbers, but not on structures. Operators are
8087 often defined on groups of types.
8089 For the purposes of C and C@t{++}, the following definitions hold:
8094 @emph{Integral types} include @code{int} with any of its storage-class
8095 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
8098 @emph{Floating-point types} include @code{float}, @code{double}, and
8099 @code{long double} (if supported by the target platform).
8102 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
8105 @emph{Scalar types} include all of the above.
8110 The following operators are supported. They are listed here
8111 in order of increasing precedence:
8115 The comma or sequencing operator. Expressions in a comma-separated list
8116 are evaluated from left to right, with the result of the entire
8117 expression being the last expression evaluated.
8120 Assignment. The value of an assignment expression is the value
8121 assigned. Defined on scalar types.
8124 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
8125 and translated to @w{@code{@var{a} = @var{a op b}}}.
8126 @w{@code{@var{op}=}} and @code{=} have the same precedence.
8127 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
8128 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
8131 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
8132 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
8136 Logical @sc{or}. Defined on integral types.
8139 Logical @sc{and}. Defined on integral types.
8142 Bitwise @sc{or}. Defined on integral types.
8145 Bitwise exclusive-@sc{or}. Defined on integral types.
8148 Bitwise @sc{and}. Defined on integral types.
8151 Equality and inequality. Defined on scalar types. The value of these
8152 expressions is 0 for false and non-zero for true.
8154 @item <@r{, }>@r{, }<=@r{, }>=
8155 Less than, greater than, less than or equal, greater than or equal.
8156 Defined on scalar types. The value of these expressions is 0 for false
8157 and non-zero for true.
8160 left shift, and right shift. Defined on integral types.
8163 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8166 Addition and subtraction. Defined on integral types, floating-point types and
8169 @item *@r{, }/@r{, }%
8170 Multiplication, division, and modulus. Multiplication and division are
8171 defined on integral and floating-point types. Modulus is defined on
8175 Increment and decrement. When appearing before a variable, the
8176 operation is performed before the variable is used in an expression;
8177 when appearing after it, the variable's value is used before the
8178 operation takes place.
8181 Pointer dereferencing. Defined on pointer types. Same precedence as
8185 Address operator. Defined on variables. Same precedence as @code{++}.
8187 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
8188 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
8189 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
8190 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
8194 Negative. Defined on integral and floating-point types. Same
8195 precedence as @code{++}.
8198 Logical negation. Defined on integral types. Same precedence as
8202 Bitwise complement operator. Defined on integral types. Same precedence as
8207 Structure member, and pointer-to-structure member. For convenience,
8208 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
8209 pointer based on the stored type information.
8210 Defined on @code{struct} and @code{union} data.
8213 Dereferences of pointers to members.
8216 Array indexing. @code{@var{a}[@var{i}]} is defined as
8217 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
8220 Function parameter list. Same precedence as @code{->}.
8223 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
8224 and @code{class} types.
8227 Doubled colons also represent the @value{GDBN} scope operator
8228 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
8232 If an operator is redefined in the user code, @value{GDBN} usually
8233 attempts to invoke the redefined version instead of using the operator's
8241 @subsubsection C and C@t{++} constants
8243 @cindex C and C@t{++} constants
8245 @value{GDBN} allows you to express the constants of C and C@t{++} in the
8250 Integer constants are a sequence of digits. Octal constants are
8251 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
8252 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
8253 @samp{l}, specifying that the constant should be treated as a
8257 Floating point constants are a sequence of digits, followed by a decimal
8258 point, followed by a sequence of digits, and optionally followed by an
8259 exponent. An exponent is of the form:
8260 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
8261 sequence of digits. The @samp{+} is optional for positive exponents.
8262 A floating-point constant may also end with a letter @samp{f} or
8263 @samp{F}, specifying that the constant should be treated as being of
8264 the @code{float} (as opposed to the default @code{double}) type; or with
8265 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
8269 Enumerated constants consist of enumerated identifiers, or their
8270 integral equivalents.
8273 Character constants are a single character surrounded by single quotes
8274 (@code{'}), or a number---the ordinal value of the corresponding character
8275 (usually its @sc{ascii} value). Within quotes, the single character may
8276 be represented by a letter or by @dfn{escape sequences}, which are of
8277 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
8278 of the character's ordinal value; or of the form @samp{\@var{x}}, where
8279 @samp{@var{x}} is a predefined special character---for example,
8280 @samp{\n} for newline.
8283 String constants are a sequence of character constants surrounded by
8284 double quotes (@code{"}). Any valid character constant (as described
8285 above) may appear. Double quotes within the string must be preceded by
8286 a backslash, so for instance @samp{"a\"b'c"} is a string of five
8290 Pointer constants are an integral value. You can also write pointers
8291 to constants using the C operator @samp{&}.
8294 Array constants are comma-separated lists surrounded by braces @samp{@{}
8295 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
8296 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
8297 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
8301 * C plus plus expressions::
8308 @node C plus plus expressions
8309 @subsubsection C@t{++} expressions
8311 @cindex expressions in C@t{++}
8312 @value{GDBN} expression handling can interpret most C@t{++} expressions.
8314 @cindex debugging C@t{++} programs
8315 @cindex C@t{++} compilers
8316 @cindex debug formats and C@t{++}
8317 @cindex @value{NGCC} and C@t{++}
8319 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
8320 proper compiler and the proper debug format. Currently, @value{GDBN}
8321 works best when debugging C@t{++} code that is compiled with
8322 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
8323 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
8324 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
8325 stabs+ as their default debug format, so you usually don't need to
8326 specify a debug format explicitly. Other compilers and/or debug formats
8327 are likely to work badly or not at all when using @value{GDBN} to debug
8333 @cindex member functions
8335 Member function calls are allowed; you can use expressions like
8338 count = aml->GetOriginal(x, y)
8341 @vindex this@r{, inside C@t{++} member functions}
8342 @cindex namespace in C@t{++}
8344 While a member function is active (in the selected stack frame), your
8345 expressions have the same namespace available as the member function;
8346 that is, @value{GDBN} allows implicit references to the class instance
8347 pointer @code{this} following the same rules as C@t{++}.
8349 @cindex call overloaded functions
8350 @cindex overloaded functions, calling
8351 @cindex type conversions in C@t{++}
8353 You can call overloaded functions; @value{GDBN} resolves the function
8354 call to the right definition, with some restrictions. @value{GDBN} does not
8355 perform overload resolution involving user-defined type conversions,
8356 calls to constructors, or instantiations of templates that do not exist
8357 in the program. It also cannot handle ellipsis argument lists or
8360 It does perform integral conversions and promotions, floating-point
8361 promotions, arithmetic conversions, pointer conversions, conversions of
8362 class objects to base classes, and standard conversions such as those of
8363 functions or arrays to pointers; it requires an exact match on the
8364 number of function arguments.
8366 Overload resolution is always performed, unless you have specified
8367 @code{set overload-resolution off}. @xref{Debugging C plus plus,
8368 ,@value{GDBN} features for C@t{++}}.
8370 You must specify @code{set overload-resolution off} in order to use an
8371 explicit function signature to call an overloaded function, as in
8373 p 'foo(char,int)'('x', 13)
8376 The @value{GDBN} command-completion facility can simplify this;
8377 see @ref{Completion, ,Command completion}.
8379 @cindex reference declarations
8381 @value{GDBN} understands variables declared as C@t{++} references; you can use
8382 them in expressions just as you do in C@t{++} source---they are automatically
8385 In the parameter list shown when @value{GDBN} displays a frame, the values of
8386 reference variables are not displayed (unlike other variables); this
8387 avoids clutter, since references are often used for large structures.
8388 The @emph{address} of a reference variable is always shown, unless
8389 you have specified @samp{set print address off}.
8392 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
8393 expressions can use it just as expressions in your program do. Since
8394 one scope may be defined in another, you can use @code{::} repeatedly if
8395 necessary, for example in an expression like
8396 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
8397 resolving name scope by reference to source files, in both C and C@t{++}
8398 debugging (@pxref{Variables, ,Program variables}).
8401 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
8402 calling virtual functions correctly, printing out virtual bases of
8403 objects, calling functions in a base subobject, casting objects, and
8404 invoking user-defined operators.
8407 @subsubsection C and C@t{++} defaults
8409 @cindex C and C@t{++} defaults
8411 If you allow @value{GDBN} to set type and range checking automatically, they
8412 both default to @code{off} whenever the working language changes to
8413 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
8414 selects the working language.
8416 If you allow @value{GDBN} to set the language automatically, it
8417 recognizes source files whose names end with @file{.c}, @file{.C}, or
8418 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
8419 these files, it sets the working language to C or C@t{++}.
8420 @xref{Automatically, ,Having @value{GDBN} infer the source language},
8421 for further details.
8423 @c Type checking is (a) primarily motivated by Modula-2, and (b)
8424 @c unimplemented. If (b) changes, it might make sense to let this node
8425 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
8428 @subsubsection C and C@t{++} type and range checks
8430 @cindex C and C@t{++} checks
8432 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
8433 is not used. However, if you turn type checking on, @value{GDBN}
8434 considers two variables type equivalent if:
8438 The two variables are structured and have the same structure, union, or
8442 The two variables have the same type name, or types that have been
8443 declared equivalent through @code{typedef}.
8446 @c leaving this out because neither J Gilmore nor R Pesch understand it.
8449 The two @code{struct}, @code{union}, or @code{enum} variables are
8450 declared in the same declaration. (Note: this may not be true for all C
8455 Range checking, if turned on, is done on mathematical operations. Array
8456 indices are not checked, since they are often used to index a pointer
8457 that is not itself an array.
8460 @subsubsection @value{GDBN} and C
8462 The @code{set print union} and @code{show print union} commands apply to
8463 the @code{union} type. When set to @samp{on}, any @code{union} that is
8464 inside a @code{struct} or @code{class} is also printed. Otherwise, it
8465 appears as @samp{@{...@}}.
8467 The @code{@@} operator aids in the debugging of dynamic arrays, formed
8468 with pointers and a memory allocation function. @xref{Expressions,
8472 * Debugging C plus plus::
8475 @node Debugging C plus plus
8476 @subsubsection @value{GDBN} features for C@t{++}
8478 @cindex commands for C@t{++}
8480 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
8481 designed specifically for use with C@t{++}. Here is a summary:
8484 @cindex break in overloaded functions
8485 @item @r{breakpoint menus}
8486 When you want a breakpoint in a function whose name is overloaded,
8487 @value{GDBN} breakpoint menus help you specify which function definition
8488 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
8490 @cindex overloading in C@t{++}
8491 @item rbreak @var{regex}
8492 Setting breakpoints using regular expressions is helpful for setting
8493 breakpoints on overloaded functions that are not members of any special
8495 @xref{Set Breaks, ,Setting breakpoints}.
8497 @cindex C@t{++} exception handling
8500 Debug C@t{++} exception handling using these commands. @xref{Set
8501 Catchpoints, , Setting catchpoints}.
8504 @item ptype @var{typename}
8505 Print inheritance relationships as well as other information for type
8507 @xref{Symbols, ,Examining the Symbol Table}.
8509 @cindex C@t{++} symbol display
8510 @item set print demangle
8511 @itemx show print demangle
8512 @itemx set print asm-demangle
8513 @itemx show print asm-demangle
8514 Control whether C@t{++} symbols display in their source form, both when
8515 displaying code as C@t{++} source and when displaying disassemblies.
8516 @xref{Print Settings, ,Print settings}.
8518 @item set print object
8519 @itemx show print object
8520 Choose whether to print derived (actual) or declared types of objects.
8521 @xref{Print Settings, ,Print settings}.
8523 @item set print vtbl
8524 @itemx show print vtbl
8525 Control the format for printing virtual function tables.
8526 @xref{Print Settings, ,Print settings}.
8527 (The @code{vtbl} commands do not work on programs compiled with the HP
8528 ANSI C@t{++} compiler (@code{aCC}).)
8530 @kindex set overload-resolution
8531 @cindex overloaded functions, overload resolution
8532 @item set overload-resolution on
8533 Enable overload resolution for C@t{++} expression evaluation. The default
8534 is on. For overloaded functions, @value{GDBN} evaluates the arguments
8535 and searches for a function whose signature matches the argument types,
8536 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
8537 expressions}, for details). If it cannot find a match, it emits a
8540 @item set overload-resolution off
8541 Disable overload resolution for C@t{++} expression evaluation. For
8542 overloaded functions that are not class member functions, @value{GDBN}
8543 chooses the first function of the specified name that it finds in the
8544 symbol table, whether or not its arguments are of the correct type. For
8545 overloaded functions that are class member functions, @value{GDBN}
8546 searches for a function whose signature @emph{exactly} matches the
8549 @item @r{Overloaded symbol names}
8550 You can specify a particular definition of an overloaded symbol, using
8551 the same notation that is used to declare such symbols in C@t{++}: type
8552 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
8553 also use the @value{GDBN} command-line word completion facilities to list the
8554 available choices, or to finish the type list for you.
8555 @xref{Completion,, Command completion}, for details on how to do this.
8559 @subsection Objective-C
8562 This section provides information about some commands and command
8563 options that are useful for debugging Objective-C code.
8566 * Method Names in Commands::
8567 * The Print Command with Objective-C::
8570 @node Method Names in Commands, The Print Command with Objective-C, Objective-C, Objective-C
8571 @subsubsection Method Names in Commands
8573 The following commands have been extended to accept Objective-C method
8574 names as line specifications:
8576 @kindex clear@r{, and Objective-C}
8577 @kindex break@r{, and Objective-C}
8578 @kindex info line@r{, and Objective-C}
8579 @kindex jump@r{, and Objective-C}
8580 @kindex list@r{, and Objective-C}
8584 @item @code{info line}
8589 A fully qualified Objective-C method name is specified as
8592 -[@var{Class} @var{methodName}]
8595 where the minus sign is used to indicate an instance method and a
8596 plus sign (not shown) is used to indicate a class method. The class
8597 name @var{Class} and method name @var{methodName} are enclosed in
8598 brackets, similar to the way messages are specified in Objective-C
8599 source code. For example, to set a breakpoint at the @code{create}
8600 instance method of class @code{Fruit} in the program currently being
8604 break -[Fruit create]
8607 To list ten program lines around the @code{initialize} class method,
8611 list +[NSText initialize]
8614 In the current version of @value{GDBN}, the plus or minus sign is
8615 required. In future versions of @value{GDBN}, the plus or minus
8616 sign will be optional, but you can use it to narrow the search. It
8617 is also possible to specify just a method name:
8623 You must specify the complete method name, including any colons. If
8624 your program's source files contain more than one @code{create} method,
8625 you'll be presented with a numbered list of classes that implement that
8626 method. Indicate your choice by number, or type @samp{0} to exit if
8629 As another example, to clear a breakpoint established at the
8630 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
8633 clear -[NSWindow makeKeyAndOrderFront:]
8636 @node The Print Command with Objective-C
8637 @subsubsection The Print Command With Objective-C
8638 @kindex print-object
8639 @kindex po @r{(@code{print-object})}
8641 The print command has also been extended to accept methods. For example:
8644 print -[@var{object} hash]
8647 @cindex print an Objective-C object description
8648 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
8650 will tell @value{GDBN} to send the @code{hash} message to @var{object}
8651 and print the result. Also, an additional command has been added,
8652 @code{print-object} or @code{po} for short, which is meant to print
8653 the description of an object. However, this command may only work
8654 with certain Objective-C libraries that have a particular hook
8655 function, @code{_NSPrintForDebugger}, defined.
8657 @node Modula-2, Ada, Objective-C, Support
8658 @subsection Modula-2
8660 @cindex Modula-2, @value{GDBN} support
8662 The extensions made to @value{GDBN} to support Modula-2 only support
8663 output from the @sc{gnu} Modula-2 compiler (which is currently being
8664 developed). Other Modula-2 compilers are not currently supported, and
8665 attempting to debug executables produced by them is most likely
8666 to give an error as @value{GDBN} reads in the executable's symbol
8669 @cindex expressions in Modula-2
8671 * M2 Operators:: Built-in operators
8672 * Built-In Func/Proc:: Built-in functions and procedures
8673 * M2 Constants:: Modula-2 constants
8674 * M2 Defaults:: Default settings for Modula-2
8675 * Deviations:: Deviations from standard Modula-2
8676 * M2 Checks:: Modula-2 type and range checks
8677 * M2 Scope:: The scope operators @code{::} and @code{.}
8678 * GDB/M2:: @value{GDBN} and Modula-2
8682 @subsubsection Operators
8683 @cindex Modula-2 operators
8685 Operators must be defined on values of specific types. For instance,
8686 @code{+} is defined on numbers, but not on structures. Operators are
8687 often defined on groups of types. For the purposes of Modula-2, the
8688 following definitions hold:
8693 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
8697 @emph{Character types} consist of @code{CHAR} and its subranges.
8700 @emph{Floating-point types} consist of @code{REAL}.
8703 @emph{Pointer types} consist of anything declared as @code{POINTER TO
8707 @emph{Scalar types} consist of all of the above.
8710 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
8713 @emph{Boolean types} consist of @code{BOOLEAN}.
8717 The following operators are supported, and appear in order of
8718 increasing precedence:
8722 Function argument or array index separator.
8725 Assignment. The value of @var{var} @code{:=} @var{value} is
8729 Less than, greater than on integral, floating-point, or enumerated
8733 Less than or equal to, greater than or equal to
8734 on integral, floating-point and enumerated types, or set inclusion on
8735 set types. Same precedence as @code{<}.
8737 @item =@r{, }<>@r{, }#
8738 Equality and two ways of expressing inequality, valid on scalar types.
8739 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
8740 available for inequality, since @code{#} conflicts with the script
8744 Set membership. Defined on set types and the types of their members.
8745 Same precedence as @code{<}.
8748 Boolean disjunction. Defined on boolean types.
8751 Boolean conjunction. Defined on boolean types.
8754 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8757 Addition and subtraction on integral and floating-point types, or union
8758 and difference on set types.
8761 Multiplication on integral and floating-point types, or set intersection
8765 Division on floating-point types, or symmetric set difference on set
8766 types. Same precedence as @code{*}.
8769 Integer division and remainder. Defined on integral types. Same
8770 precedence as @code{*}.
8773 Negative. Defined on @code{INTEGER} and @code{REAL} data.
8776 Pointer dereferencing. Defined on pointer types.
8779 Boolean negation. Defined on boolean types. Same precedence as
8783 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
8784 precedence as @code{^}.
8787 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
8790 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
8794 @value{GDBN} and Modula-2 scope operators.
8798 @emph{Warning:} Sets and their operations are not yet supported, so @value{GDBN}
8799 treats the use of the operator @code{IN}, or the use of operators
8800 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
8801 @code{<=}, and @code{>=} on sets as an error.
8805 @node Built-In Func/Proc
8806 @subsubsection Built-in functions and procedures
8807 @cindex Modula-2 built-ins
8809 Modula-2 also makes available several built-in procedures and functions.
8810 In describing these, the following metavariables are used:
8815 represents an @code{ARRAY} variable.
8818 represents a @code{CHAR} constant or variable.
8821 represents a variable or constant of integral type.
8824 represents an identifier that belongs to a set. Generally used in the
8825 same function with the metavariable @var{s}. The type of @var{s} should
8826 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
8829 represents a variable or constant of integral or floating-point type.
8832 represents a variable or constant of floating-point type.
8838 represents a variable.
8841 represents a variable or constant of one of many types. See the
8842 explanation of the function for details.
8845 All Modula-2 built-in procedures also return a result, described below.
8849 Returns the absolute value of @var{n}.
8852 If @var{c} is a lower case letter, it returns its upper case
8853 equivalent, otherwise it returns its argument.
8856 Returns the character whose ordinal value is @var{i}.
8859 Decrements the value in the variable @var{v} by one. Returns the new value.
8861 @item DEC(@var{v},@var{i})
8862 Decrements the value in the variable @var{v} by @var{i}. Returns the
8865 @item EXCL(@var{m},@var{s})
8866 Removes the element @var{m} from the set @var{s}. Returns the new
8869 @item FLOAT(@var{i})
8870 Returns the floating point equivalent of the integer @var{i}.
8873 Returns the index of the last member of @var{a}.
8876 Increments the value in the variable @var{v} by one. Returns the new value.
8878 @item INC(@var{v},@var{i})
8879 Increments the value in the variable @var{v} by @var{i}. Returns the
8882 @item INCL(@var{m},@var{s})
8883 Adds the element @var{m} to the set @var{s} if it is not already
8884 there. Returns the new set.
8887 Returns the maximum value of the type @var{t}.
8890 Returns the minimum value of the type @var{t}.
8893 Returns boolean TRUE if @var{i} is an odd number.
8896 Returns the ordinal value of its argument. For example, the ordinal
8897 value of a character is its @sc{ascii} value (on machines supporting the
8898 @sc{ascii} character set). @var{x} must be of an ordered type, which include
8899 integral, character and enumerated types.
8902 Returns the size of its argument. @var{x} can be a variable or a type.
8904 @item TRUNC(@var{r})
8905 Returns the integral part of @var{r}.
8907 @item VAL(@var{t},@var{i})
8908 Returns the member of the type @var{t} whose ordinal value is @var{i}.
8912 @emph{Warning:} Sets and their operations are not yet supported, so
8913 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
8917 @cindex Modula-2 constants
8919 @subsubsection Constants
8921 @value{GDBN} allows you to express the constants of Modula-2 in the following
8927 Integer constants are simply a sequence of digits. When used in an
8928 expression, a constant is interpreted to be type-compatible with the
8929 rest of the expression. Hexadecimal integers are specified by a
8930 trailing @samp{H}, and octal integers by a trailing @samp{B}.
8933 Floating point constants appear as a sequence of digits, followed by a
8934 decimal point and another sequence of digits. An optional exponent can
8935 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
8936 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
8937 digits of the floating point constant must be valid decimal (base 10)
8941 Character constants consist of a single character enclosed by a pair of
8942 like quotes, either single (@code{'}) or double (@code{"}). They may
8943 also be expressed by their ordinal value (their @sc{ascii} value, usually)
8944 followed by a @samp{C}.
8947 String constants consist of a sequence of characters enclosed by a
8948 pair of like quotes, either single (@code{'}) or double (@code{"}).
8949 Escape sequences in the style of C are also allowed. @xref{C
8950 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
8954 Enumerated constants consist of an enumerated identifier.
8957 Boolean constants consist of the identifiers @code{TRUE} and
8961 Pointer constants consist of integral values only.
8964 Set constants are not yet supported.
8968 @subsubsection Modula-2 defaults
8969 @cindex Modula-2 defaults
8971 If type and range checking are set automatically by @value{GDBN}, they
8972 both default to @code{on} whenever the working language changes to
8973 Modula-2. This happens regardless of whether you or @value{GDBN}
8974 selected the working language.
8976 If you allow @value{GDBN} to set the language automatically, then entering
8977 code compiled from a file whose name ends with @file{.mod} sets the
8978 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
8979 the language automatically}, for further details.
8982 @subsubsection Deviations from standard Modula-2
8983 @cindex Modula-2, deviations from
8985 A few changes have been made to make Modula-2 programs easier to debug.
8986 This is done primarily via loosening its type strictness:
8990 Unlike in standard Modula-2, pointer constants can be formed by
8991 integers. This allows you to modify pointer variables during
8992 debugging. (In standard Modula-2, the actual address contained in a
8993 pointer variable is hidden from you; it can only be modified
8994 through direct assignment to another pointer variable or expression that
8995 returned a pointer.)
8998 C escape sequences can be used in strings and characters to represent
8999 non-printable characters. @value{GDBN} prints out strings with these
9000 escape sequences embedded. Single non-printable characters are
9001 printed using the @samp{CHR(@var{nnn})} format.
9004 The assignment operator (@code{:=}) returns the value of its right-hand
9008 All built-in procedures both modify @emph{and} return their argument.
9012 @subsubsection Modula-2 type and range checks
9013 @cindex Modula-2 checks
9016 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
9019 @c FIXME remove warning when type/range checks added
9021 @value{GDBN} considers two Modula-2 variables type equivalent if:
9025 They are of types that have been declared equivalent via a @code{TYPE
9026 @var{t1} = @var{t2}} statement
9029 They have been declared on the same line. (Note: This is true of the
9030 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
9033 As long as type checking is enabled, any attempt to combine variables
9034 whose types are not equivalent is an error.
9036 Range checking is done on all mathematical operations, assignment, array
9037 index bounds, and all built-in functions and procedures.
9040 @subsubsection The scope operators @code{::} and @code{.}
9042 @cindex @code{.}, Modula-2 scope operator
9043 @cindex colon, doubled as scope operator
9045 @vindex colon-colon@r{, in Modula-2}
9046 @c Info cannot handle :: but TeX can.
9049 @vindex ::@r{, in Modula-2}
9052 There are a few subtle differences between the Modula-2 scope operator
9053 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
9058 @var{module} . @var{id}
9059 @var{scope} :: @var{id}
9063 where @var{scope} is the name of a module or a procedure,
9064 @var{module} the name of a module, and @var{id} is any declared
9065 identifier within your program, except another module.
9067 Using the @code{::} operator makes @value{GDBN} search the scope
9068 specified by @var{scope} for the identifier @var{id}. If it is not
9069 found in the specified scope, then @value{GDBN} searches all scopes
9070 enclosing the one specified by @var{scope}.
9072 Using the @code{.} operator makes @value{GDBN} search the current scope for
9073 the identifier specified by @var{id} that was imported from the
9074 definition module specified by @var{module}. With this operator, it is
9075 an error if the identifier @var{id} was not imported from definition
9076 module @var{module}, or if @var{id} is not an identifier in
9080 @subsubsection @value{GDBN} and Modula-2
9082 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
9083 Five subcommands of @code{set print} and @code{show print} apply
9084 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
9085 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
9086 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
9087 analogue in Modula-2.
9089 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
9090 with any language, is not useful with Modula-2. Its
9091 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
9092 created in Modula-2 as they can in C or C@t{++}. However, because an
9093 address can be specified by an integral constant, the construct
9094 @samp{@{@var{type}@}@var{adrexp}} is still useful.
9096 @cindex @code{#} in Modula-2
9097 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
9098 interpreted as the beginning of a comment. Use @code{<>} instead.
9104 The extensions made to @value{GDBN} for Ada only support
9105 output from the @sc{gnu} Ada (GNAT) compiler.
9106 Other Ada compilers are not currently supported, and
9107 attempting to debug executables produced by them is most likely
9111 @cindex expressions in Ada
9113 * Ada Mode Intro:: General remarks on the Ada syntax
9114 and semantics supported by Ada mode
9116 * Omissions from Ada:: Restrictions on the Ada expression syntax.
9117 * Additions to Ada:: Extensions of the Ada expression syntax.
9118 * Stopping Before Main Program:: Debugging the program during elaboration.
9119 * Ada Glitches:: Known peculiarities of Ada mode.
9122 @node Ada Mode Intro
9123 @subsubsection Introduction
9124 @cindex Ada mode, general
9126 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
9127 syntax, with some extensions.
9128 The philosophy behind the design of this subset is
9132 That @value{GDBN} should provide basic literals and access to operations for
9133 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
9134 leaving more sophisticated computations to subprograms written into the
9135 program (which therefore may be called from @value{GDBN}).
9138 That type safety and strict adherence to Ada language restrictions
9139 are not particularly important to the @value{GDBN} user.
9142 That brevity is important to the @value{GDBN} user.
9145 Thus, for brevity, the debugger acts as if there were
9146 implicit @code{with} and @code{use} clauses in effect for all user-written
9147 packages, making it unnecessary to fully qualify most names with
9148 their packages, regardless of context. Where this causes ambiguity,
9149 @value{GDBN} asks the user's intent.
9151 The debugger will start in Ada mode if it detects an Ada main program.
9152 As for other languages, it will enter Ada mode when stopped in a program that
9153 was translated from an Ada source file.
9155 While in Ada mode, you may use `@t{--}' for comments. This is useful
9156 mostly for documenting command files. The standard @value{GDBN} comment
9157 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
9158 middle (to allow based literals).
9160 The debugger supports limited overloading. Given a subprogram call in which
9161 the function symbol has multiple definitions, it will use the number of
9162 actual parameters and some information about their types to attempt to narrow
9163 the set of definitions. It also makes very limited use of context, preferring
9164 procedures to functions in the context of the @code{call} command, and
9165 functions to procedures elsewhere.
9167 @node Omissions from Ada
9168 @subsubsection Omissions from Ada
9169 @cindex Ada, omissions from
9171 Here are the notable omissions from the subset:
9175 Only a subset of the attributes are supported:
9179 @t{'First}, @t{'Last}, and @t{'Length}
9180 on array objects (not on types and subtypes).
9183 @t{'Min} and @t{'Max}.
9186 @t{'Pos} and @t{'Val}.
9192 @t{'Range} on array objects (not subtypes), but only as the right
9193 operand of the membership (@code{in}) operator.
9196 @t{'Access}, @t{'Unchecked_Access}, and
9197 @t{'Unrestricted_Access} (a GNAT extension).
9205 @code{Characters.Latin_1} are not available and
9206 concatenation is not implemented. Thus, escape characters in strings are
9207 not currently available.
9210 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
9211 equality of representations. They will generally work correctly
9212 for strings and arrays whose elements have integer or enumeration types.
9213 They may not work correctly for arrays whose element
9214 types have user-defined equality, for arrays of real values
9215 (in particular, IEEE-conformant floating point, because of negative
9216 zeroes and NaNs), and for arrays whose elements contain unused bits with
9217 indeterminate values.
9220 The other component-by-component array operations (@code{and}, @code{or},
9221 @code{xor}, @code{not}, and relational tests other than equality)
9222 are not implemented.
9225 There are no record or array aggregates.
9228 Calls to dispatching subprograms are not implemented.
9231 The overloading algorithm is much more limited (i.e., less selective)
9232 than that of real Ada. It makes only limited use of the context in which a subexpression
9233 appears to resolve its meaning, and it is much looser in its rules for allowing
9234 type matches. As a result, some function calls will be ambiguous, and the user
9235 will be asked to choose the proper resolution.
9238 The @code{new} operator is not implemented.
9241 Entry calls are not implemented.
9244 Aside from printing, arithmetic operations on the native VAX floating-point
9245 formats are not supported.
9248 It is not possible to slice a packed array.
9251 @node Additions to Ada
9252 @subsubsection Additions to Ada
9253 @cindex Ada, deviations from
9255 As it does for other languages, @value{GDBN} makes certain generic
9256 extensions to Ada (@pxref{Expressions}):
9260 If the expression @var{E} is a variable residing in memory
9261 (typically a local variable or array element) and @var{N} is
9262 a positive integer, then @code{@var{E}@@@var{N}} displays the values of
9263 @var{E} and the @var{N}-1 adjacent variables following it in memory as an array.
9264 In Ada, this operator is generally not necessary, since its prime use
9265 is in displaying parts of an array, and slicing will usually do this in Ada.
9266 However, there are occasional uses when debugging programs
9267 in which certain debugging information has been optimized away.
9270 @code{@var{B}::@var{var}} means ``the variable named @var{var} that appears
9271 in function or file @var{B}.'' When @var{B} is a file name, you must typically
9272 surround it in single quotes.
9275 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
9276 @var{type} that appears at address @var{addr}.''
9279 A name starting with @samp{$} is a convenience variable
9280 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
9283 In addition, @value{GDBN} provides a few other shortcuts and outright additions specific
9288 The assignment statement is allowed as an expression, returning
9289 its right-hand operand as its value. Thus, you may enter
9293 print A(tmp := y + 1)
9297 The semicolon is allowed as an ``operator,'' returning as its value
9298 the value of its right-hand operand.
9299 This allows, for example,
9300 complex conditional breaks:
9304 condition 1 (report(i); k += 1; A(k) > 100)
9308 Rather than use catenation and symbolic character names to introduce special
9309 characters into strings, one may instead use a special bracket notation,
9310 which is also used to print strings. A sequence of characters of the form
9311 @samp{["@var{XX}"]} within a string or character literal denotes the
9312 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
9313 sequence of characters @samp{["""]} also denotes a single quotation mark
9314 in strings. For example,
9316 "One line.["0a"]Next line.["0a"]"
9319 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF}) after each
9323 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
9324 @t{'Max} is optional (and is ignored in any case). For example, it is valid
9332 When printing arrays, @value{GDBN} uses positional notation when the
9333 array has a lower bound of 1, and uses a modified named notation otherwise.
9334 For example, a one-dimensional array of three integers with a lower bound of 3 might print as
9341 That is, in contrast to valid Ada, only the first component has a @code{=>}
9345 You may abbreviate attributes in expressions with any unique,
9346 multi-character subsequence of
9347 their names (an exact match gets preference).
9348 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
9349 in place of @t{a'length}.
9352 @cindex quoting Ada internal identifiers
9353 Since Ada is case-insensitive, the debugger normally maps identifiers you type
9354 to lower case. The GNAT compiler uses upper-case characters for
9355 some of its internal identifiers, which are normally of no interest to users.
9356 For the rare occasions when you actually have to look at them,
9357 enclose them in angle brackets to avoid the lower-case mapping.
9360 @value{GDBP} print <JMPBUF_SAVE>[0]
9364 Printing an object of class-wide type or dereferencing an
9365 access-to-class-wide value will display all the components of the object's
9366 specific type (as indicated by its run-time tag). Likewise, component
9367 selection on such a value will operate on the specific type of the
9372 @node Stopping Before Main Program
9373 @subsubsection Stopping at the Very Beginning
9375 @cindex breakpointing Ada elaboration code
9376 It is sometimes necessary to debug the program during elaboration, and
9377 before reaching the main procedure.
9378 As defined in the Ada Reference
9379 Manual, the elaboration code is invoked from a procedure called
9380 @code{adainit}. To run your program up to the beginning of
9381 elaboration, simply use the following two commands:
9382 @code{tbreak adainit} and @code{run}.
9385 @subsubsection Known Peculiarities of Ada Mode
9386 @cindex Ada, problems
9388 Besides the omissions listed previously (@pxref{Omissions from Ada}),
9389 we know of several problems with and limitations of Ada mode in
9391 some of which will be fixed with planned future releases of the debugger
9392 and the GNU Ada compiler.
9396 Currently, the debugger
9397 has insufficient information to determine whether certain pointers represent
9398 pointers to objects or the objects themselves.
9399 Thus, the user may have to tack an extra @code{.all} after an expression
9400 to get it printed properly.
9403 Static constants that the compiler chooses not to materialize as objects in
9404 storage are invisible to the debugger.
9407 Named parameter associations in function argument lists are ignored (the
9408 argument lists are treated as positional).
9411 Many useful library packages are currently invisible to the debugger.
9414 Fixed-point arithmetic, conversions, input, and output is carried out using
9415 floating-point arithmetic, and may give results that only approximate those on
9419 The type of the @t{'Address} attribute may not be @code{System.Address}.
9422 The GNAT compiler never generates the prefix @code{Standard} for any of
9423 the standard symbols defined by the Ada language. @value{GDBN} knows about
9424 this: it will strip the prefix from names when you use it, and will never
9425 look for a name you have so qualified among local symbols, nor match against
9426 symbols in other packages or subprograms. If you have
9427 defined entities anywhere in your program other than parameters and
9428 local variables whose simple names match names in @code{Standard},
9429 GNAT's lack of qualification here can cause confusion. When this happens,
9430 you can usually resolve the confusion
9431 by qualifying the problematic names with package
9432 @code{Standard} explicitly.
9435 @node Unsupported languages
9436 @section Unsupported languages
9438 @cindex unsupported languages
9439 @cindex minimal language
9440 In addition to the other fully-supported programming languages,
9441 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
9442 It does not represent a real programming language, but provides a set
9443 of capabilities close to what the C or assembly languages provide.
9444 This should allow most simple operations to be performed while debugging
9445 an application that uses a language currently not supported by @value{GDBN}.
9447 If the language is set to @code{auto}, @value{GDBN} will automatically
9448 select this language if the current frame corresponds to an unsupported
9452 @chapter Examining the Symbol Table
9454 The commands described in this chapter allow you to inquire about the
9455 symbols (names of variables, functions and types) defined in your
9456 program. This information is inherent in the text of your program and
9457 does not change as your program executes. @value{GDBN} finds it in your
9458 program's symbol table, in the file indicated when you started @value{GDBN}
9459 (@pxref{File Options, ,Choosing files}), or by one of the
9460 file-management commands (@pxref{Files, ,Commands to specify files}).
9462 @cindex symbol names
9463 @cindex names of symbols
9464 @cindex quoting names
9465 Occasionally, you may need to refer to symbols that contain unusual
9466 characters, which @value{GDBN} ordinarily treats as word delimiters. The
9467 most frequent case is in referring to static variables in other
9468 source files (@pxref{Variables,,Program variables}). File names
9469 are recorded in object files as debugging symbols, but @value{GDBN} would
9470 ordinarily parse a typical file name, like @file{foo.c}, as the three words
9471 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
9472 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
9479 looks up the value of @code{x} in the scope of the file @file{foo.c}.
9482 @kindex info address
9483 @cindex address of a symbol
9484 @item info address @var{symbol}
9485 Describe where the data for @var{symbol} is stored. For a register
9486 variable, this says which register it is kept in. For a non-register
9487 local variable, this prints the stack-frame offset at which the variable
9490 Note the contrast with @samp{print &@var{symbol}}, which does not work
9491 at all for a register variable, and for a stack local variable prints
9492 the exact address of the current instantiation of the variable.
9495 @cindex symbol from address
9496 @item info symbol @var{addr}
9497 Print the name of a symbol which is stored at the address @var{addr}.
9498 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
9499 nearest symbol and an offset from it:
9502 (@value{GDBP}) info symbol 0x54320
9503 _initialize_vx + 396 in section .text
9507 This is the opposite of the @code{info address} command. You can use
9508 it to find out the name of a variable or a function given its address.
9511 @item whatis @var{expr}
9512 Print the data type of expression @var{expr}. @var{expr} is not
9513 actually evaluated, and any side-effecting operations (such as
9514 assignments or function calls) inside it do not take place.
9515 @xref{Expressions, ,Expressions}.
9518 Print the data type of @code{$}, the last value in the value history.
9521 @item ptype @var{typename}
9522 Print a description of data type @var{typename}. @var{typename} may be
9523 the name of a type, or for C code it may have the form @samp{class
9524 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
9525 @var{union-tag}} or @samp{enum @var{enum-tag}}.
9527 @item ptype @var{expr}
9529 Print a description of the type of expression @var{expr}. @code{ptype}
9530 differs from @code{whatis} by printing a detailed description, instead
9531 of just the name of the type.
9533 For example, for this variable declaration:
9536 struct complex @{double real; double imag;@} v;
9540 the two commands give this output:
9544 (@value{GDBP}) whatis v
9545 type = struct complex
9546 (@value{GDBP}) ptype v
9547 type = struct complex @{
9555 As with @code{whatis}, using @code{ptype} without an argument refers to
9556 the type of @code{$}, the last value in the value history.
9559 @item info types @var{regexp}
9561 Print a brief description of all types whose names match @var{regexp}
9562 (or all types in your program, if you supply no argument). Each
9563 complete typename is matched as though it were a complete line; thus,
9564 @samp{i type value} gives information on all types in your program whose
9565 names include the string @code{value}, but @samp{i type ^value$} gives
9566 information only on types whose complete name is @code{value}.
9568 This command differs from @code{ptype} in two ways: first, like
9569 @code{whatis}, it does not print a detailed description; second, it
9570 lists all source files where a type is defined.
9573 @cindex local variables
9574 @item info scope @var{addr}
9575 List all the variables local to a particular scope. This command
9576 accepts a location---a function name, a source line, or an address
9577 preceded by a @samp{*}, and prints all the variables local to the
9578 scope defined by that location. For example:
9581 (@value{GDBP}) @b{info scope command_line_handler}
9582 Scope for command_line_handler:
9583 Symbol rl is an argument at stack/frame offset 8, length 4.
9584 Symbol linebuffer is in static storage at address 0x150a18, length 4.
9585 Symbol linelength is in static storage at address 0x150a1c, length 4.
9586 Symbol p is a local variable in register $esi, length 4.
9587 Symbol p1 is a local variable in register $ebx, length 4.
9588 Symbol nline is a local variable in register $edx, length 4.
9589 Symbol repeat is a local variable at frame offset -8, length 4.
9593 This command is especially useful for determining what data to collect
9594 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
9599 Show information about the current source file---that is, the source file for
9600 the function containing the current point of execution:
9603 the name of the source file, and the directory containing it,
9605 the directory it was compiled in,
9607 its length, in lines,
9609 which programming language it is written in,
9611 whether the executable includes debugging information for that file, and
9612 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
9614 whether the debugging information includes information about
9615 preprocessor macros.
9619 @kindex info sources
9621 Print the names of all source files in your program for which there is
9622 debugging information, organized into two lists: files whose symbols
9623 have already been read, and files whose symbols will be read when needed.
9625 @kindex info functions
9626 @item info functions
9627 Print the names and data types of all defined functions.
9629 @item info functions @var{regexp}
9630 Print the names and data types of all defined functions
9631 whose names contain a match for regular expression @var{regexp}.
9632 Thus, @samp{info fun step} finds all functions whose names
9633 include @code{step}; @samp{info fun ^step} finds those whose names
9634 start with @code{step}. If a function name contains characters
9635 that conflict with the regular expression language (eg.
9636 @samp{operator*()}), they may be quoted with a backslash.
9638 @kindex info variables
9639 @item info variables
9640 Print the names and data types of all variables that are declared
9641 outside of functions (i.e.@: excluding local variables).
9643 @item info variables @var{regexp}
9644 Print the names and data types of all variables (except for local
9645 variables) whose names contain a match for regular expression
9648 @kindex info classes
9650 @itemx info classes @var{regexp}
9651 Display all Objective-C classes in your program, or
9652 (with the @var{regexp} argument) all those matching a particular regular
9655 @kindex info selectors
9656 @item info selectors
9657 @itemx info selectors @var{regexp}
9658 Display all Objective-C selectors in your program, or
9659 (with the @var{regexp} argument) all those matching a particular regular
9663 This was never implemented.
9664 @kindex info methods
9666 @itemx info methods @var{regexp}
9667 The @code{info methods} command permits the user to examine all defined
9668 methods within C@t{++} program, or (with the @var{regexp} argument) a
9669 specific set of methods found in the various C@t{++} classes. Many
9670 C@t{++} classes provide a large number of methods. Thus, the output
9671 from the @code{ptype} command can be overwhelming and hard to use. The
9672 @code{info-methods} command filters the methods, printing only those
9673 which match the regular-expression @var{regexp}.
9676 @cindex reloading symbols
9677 Some systems allow individual object files that make up your program to
9678 be replaced without stopping and restarting your program. For example,
9679 in VxWorks you can simply recompile a defective object file and keep on
9680 running. If you are running on one of these systems, you can allow
9681 @value{GDBN} to reload the symbols for automatically relinked modules:
9684 @kindex set symbol-reloading
9685 @item set symbol-reloading on
9686 Replace symbol definitions for the corresponding source file when an
9687 object file with a particular name is seen again.
9689 @item set symbol-reloading off
9690 Do not replace symbol definitions when encountering object files of the
9691 same name more than once. This is the default state; if you are not
9692 running on a system that permits automatic relinking of modules, you
9693 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
9694 may discard symbols when linking large programs, that may contain
9695 several modules (from different directories or libraries) with the same
9698 @kindex show symbol-reloading
9699 @item show symbol-reloading
9700 Show the current @code{on} or @code{off} setting.
9703 @kindex set opaque-type-resolution
9704 @item set opaque-type-resolution on
9705 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
9706 declared as a pointer to a @code{struct}, @code{class}, or
9707 @code{union}---for example, @code{struct MyType *}---that is used in one
9708 source file although the full declaration of @code{struct MyType} is in
9709 another source file. The default is on.
9711 A change in the setting of this subcommand will not take effect until
9712 the next time symbols for a file are loaded.
9714 @item set opaque-type-resolution off
9715 Tell @value{GDBN} not to resolve opaque types. In this case, the type
9716 is printed as follows:
9718 @{<no data fields>@}
9721 @kindex show opaque-type-resolution
9722 @item show opaque-type-resolution
9723 Show whether opaque types are resolved or not.
9725 @kindex maint print symbols
9727 @kindex maint print psymbols
9728 @cindex partial symbol dump
9729 @item maint print symbols @var{filename}
9730 @itemx maint print psymbols @var{filename}
9731 @itemx maint print msymbols @var{filename}
9732 Write a dump of debugging symbol data into the file @var{filename}.
9733 These commands are used to debug the @value{GDBN} symbol-reading code. Only
9734 symbols with debugging data are included. If you use @samp{maint print
9735 symbols}, @value{GDBN} includes all the symbols for which it has already
9736 collected full details: that is, @var{filename} reflects symbols for
9737 only those files whose symbols @value{GDBN} has read. You can use the
9738 command @code{info sources} to find out which files these are. If you
9739 use @samp{maint print psymbols} instead, the dump shows information about
9740 symbols that @value{GDBN} only knows partially---that is, symbols defined in
9741 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
9742 @samp{maint print msymbols} dumps just the minimal symbol information
9743 required for each object file from which @value{GDBN} has read some symbols.
9744 @xref{Files, ,Commands to specify files}, for a discussion of how
9745 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
9747 @kindex maint info symtabs
9748 @kindex maint info psymtabs
9749 @cindex listing @value{GDBN}'s internal symbol tables
9750 @cindex symbol tables, listing @value{GDBN}'s internal
9751 @cindex full symbol tables, listing @value{GDBN}'s internal
9752 @cindex partial symbol tables, listing @value{GDBN}'s internal
9753 @item maint info symtabs @r{[} @var{regexp} @r{]}
9754 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
9756 List the @code{struct symtab} or @code{struct partial_symtab}
9757 structures whose names match @var{regexp}. If @var{regexp} is not
9758 given, list them all. The output includes expressions which you can
9759 copy into a @value{GDBN} debugging this one to examine a particular
9760 structure in more detail. For example:
9763 (@value{GDBP}) maint info psymtabs dwarf2read
9764 @{ objfile /home/gnu/build/gdb/gdb
9765 ((struct objfile *) 0x82e69d0)
9766 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
9767 ((struct partial_symtab *) 0x8474b10)
9770 text addresses 0x814d3c8 -- 0x8158074
9771 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
9772 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
9776 (@value{GDBP}) maint info symtabs
9780 We see that there is one partial symbol table whose filename contains
9781 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
9782 and we see that @value{GDBN} has not read in any symtabs yet at all.
9783 If we set a breakpoint on a function, that will cause @value{GDBN} to
9784 read the symtab for the compilation unit containing that function:
9787 (@value{GDBP}) break dwarf2_psymtab_to_symtab
9788 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
9790 (@value{GDBP}) maint info symtabs
9791 @{ objfile /home/gnu/build/gdb/gdb
9792 ((struct objfile *) 0x82e69d0)
9793 @{ symtab /home/gnu/src/gdb/dwarf2read.c
9794 ((struct symtab *) 0x86c1f38)
9797 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
9807 @chapter Altering Execution
9809 Once you think you have found an error in your program, you might want to
9810 find out for certain whether correcting the apparent error would lead to
9811 correct results in the rest of the run. You can find the answer by
9812 experiment, using the @value{GDBN} features for altering execution of the
9815 For example, you can store new values into variables or memory
9816 locations, give your program a signal, restart it at a different
9817 address, or even return prematurely from a function.
9820 * Assignment:: Assignment to variables
9821 * Jumping:: Continuing at a different address
9822 * Signaling:: Giving your program a signal
9823 * Returning:: Returning from a function
9824 * Calling:: Calling your program's functions
9825 * Patching:: Patching your program
9829 @section Assignment to variables
9832 @cindex setting variables
9833 To alter the value of a variable, evaluate an assignment expression.
9834 @xref{Expressions, ,Expressions}. For example,
9841 stores the value 4 into the variable @code{x}, and then prints the
9842 value of the assignment expression (which is 4).
9843 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
9844 information on operators in supported languages.
9846 @kindex set variable
9847 @cindex variables, setting
9848 If you are not interested in seeing the value of the assignment, use the
9849 @code{set} command instead of the @code{print} command. @code{set} is
9850 really the same as @code{print} except that the expression's value is
9851 not printed and is not put in the value history (@pxref{Value History,
9852 ,Value history}). The expression is evaluated only for its effects.
9854 If the beginning of the argument string of the @code{set} command
9855 appears identical to a @code{set} subcommand, use the @code{set
9856 variable} command instead of just @code{set}. This command is identical
9857 to @code{set} except for its lack of subcommands. For example, if your
9858 program has a variable @code{width}, you get an error if you try to set
9859 a new value with just @samp{set width=13}, because @value{GDBN} has the
9860 command @code{set width}:
9863 (@value{GDBP}) whatis width
9865 (@value{GDBP}) p width
9867 (@value{GDBP}) set width=47
9868 Invalid syntax in expression.
9872 The invalid expression, of course, is @samp{=47}. In
9873 order to actually set the program's variable @code{width}, use
9876 (@value{GDBP}) set var width=47
9879 Because the @code{set} command has many subcommands that can conflict
9880 with the names of program variables, it is a good idea to use the
9881 @code{set variable} command instead of just @code{set}. For example, if
9882 your program has a variable @code{g}, you run into problems if you try
9883 to set a new value with just @samp{set g=4}, because @value{GDBN} has
9884 the command @code{set gnutarget}, abbreviated @code{set g}:
9888 (@value{GDBP}) whatis g
9892 (@value{GDBP}) set g=4
9896 The program being debugged has been started already.
9897 Start it from the beginning? (y or n) y
9898 Starting program: /home/smith/cc_progs/a.out
9899 "/home/smith/cc_progs/a.out": can't open to read symbols:
9901 (@value{GDBP}) show g
9902 The current BFD target is "=4".
9907 The program variable @code{g} did not change, and you silently set the
9908 @code{gnutarget} to an invalid value. In order to set the variable
9912 (@value{GDBP}) set var g=4
9915 @value{GDBN} allows more implicit conversions in assignments than C; you can
9916 freely store an integer value into a pointer variable or vice versa,
9917 and you can convert any structure to any other structure that is the
9918 same length or shorter.
9919 @comment FIXME: how do structs align/pad in these conversions?
9920 @comment /doc@cygnus.com 18dec1990
9922 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
9923 construct to generate a value of specified type at a specified address
9924 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
9925 to memory location @code{0x83040} as an integer (which implies a certain size
9926 and representation in memory), and
9929 set @{int@}0x83040 = 4
9933 stores the value 4 into that memory location.
9936 @section Continuing at a different address
9938 Ordinarily, when you continue your program, you do so at the place where
9939 it stopped, with the @code{continue} command. You can instead continue at
9940 an address of your own choosing, with the following commands:
9944 @item jump @var{linespec}
9945 Resume execution at line @var{linespec}. Execution stops again
9946 immediately if there is a breakpoint there. @xref{List, ,Printing
9947 source lines}, for a description of the different forms of
9948 @var{linespec}. It is common practice to use the @code{tbreak} command
9949 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
9952 The @code{jump} command does not change the current stack frame, or
9953 the stack pointer, or the contents of any memory location or any
9954 register other than the program counter. If line @var{linespec} is in
9955 a different function from the one currently executing, the results may
9956 be bizarre if the two functions expect different patterns of arguments or
9957 of local variables. For this reason, the @code{jump} command requests
9958 confirmation if the specified line is not in the function currently
9959 executing. However, even bizarre results are predictable if you are
9960 well acquainted with the machine-language code of your program.
9962 @item jump *@var{address}
9963 Resume execution at the instruction at address @var{address}.
9966 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
9967 On many systems, you can get much the same effect as the @code{jump}
9968 command by storing a new value into the register @code{$pc}. The
9969 difference is that this does not start your program running; it only
9970 changes the address of where it @emph{will} run when you continue. For
9978 makes the next @code{continue} command or stepping command execute at
9979 address @code{0x485}, rather than at the address where your program stopped.
9980 @xref{Continuing and Stepping, ,Continuing and stepping}.
9982 The most common occasion to use the @code{jump} command is to back
9983 up---perhaps with more breakpoints set---over a portion of a program
9984 that has already executed, in order to examine its execution in more
9989 @section Giving your program a signal
9993 @item signal @var{signal}
9994 Resume execution where your program stopped, but immediately give it the
9995 signal @var{signal}. @var{signal} can be the name or the number of a
9996 signal. For example, on many systems @code{signal 2} and @code{signal
9997 SIGINT} are both ways of sending an interrupt signal.
9999 Alternatively, if @var{signal} is zero, continue execution without
10000 giving a signal. This is useful when your program stopped on account of
10001 a signal and would ordinary see the signal when resumed with the
10002 @code{continue} command; @samp{signal 0} causes it to resume without a
10005 @code{signal} does not repeat when you press @key{RET} a second time
10006 after executing the command.
10010 Invoking the @code{signal} command is not the same as invoking the
10011 @code{kill} utility from the shell. Sending a signal with @code{kill}
10012 causes @value{GDBN} to decide what to do with the signal depending on
10013 the signal handling tables (@pxref{Signals}). The @code{signal} command
10014 passes the signal directly to your program.
10018 @section Returning from a function
10021 @cindex returning from a function
10024 @itemx return @var{expression}
10025 You can cancel execution of a function call with the @code{return}
10026 command. If you give an
10027 @var{expression} argument, its value is used as the function's return
10031 When you use @code{return}, @value{GDBN} discards the selected stack frame
10032 (and all frames within it). You can think of this as making the
10033 discarded frame return prematurely. If you wish to specify a value to
10034 be returned, give that value as the argument to @code{return}.
10036 This pops the selected stack frame (@pxref{Selection, ,Selecting a
10037 frame}), and any other frames inside of it, leaving its caller as the
10038 innermost remaining frame. That frame becomes selected. The
10039 specified value is stored in the registers used for returning values
10042 The @code{return} command does not resume execution; it leaves the
10043 program stopped in the state that would exist if the function had just
10044 returned. In contrast, the @code{finish} command (@pxref{Continuing
10045 and Stepping, ,Continuing and stepping}) resumes execution until the
10046 selected stack frame returns naturally.
10049 @section Calling program functions
10052 @cindex calling functions
10053 @cindex inferior functions, calling
10054 @item print @var{expr}
10055 Evaluate the expression @var{expr} and displaying the resuling value.
10056 @var{expr} may include calls to functions in the program being
10060 @item call @var{expr}
10061 Evaluate the expression @var{expr} without displaying @code{void}
10064 You can use this variant of the @code{print} command if you want to
10065 execute a function from your program that does not return anything
10066 (a.k.a.@: @dfn{a void function}), but without cluttering the output
10067 with @code{void} returned values that @value{GDBN} will otherwise
10068 print. If the result is not void, it is printed and saved in the
10072 @cindex weak alias functions
10073 Sometimes, a function you wish to call is actually a @dfn{weak alias}
10074 for another function. In such case, @value{GDBN} might not pick up
10075 the type information, including the types of the function arguments,
10076 which causes @value{GDBN} to call the inferior function incorrectly.
10077 As a result, the called function will function erroneously and may
10078 even crash. A solution to that is to use the name of the aliased
10082 @section Patching programs
10084 @cindex patching binaries
10085 @cindex writing into executables
10086 @cindex writing into corefiles
10088 By default, @value{GDBN} opens the file containing your program's
10089 executable code (or the corefile) read-only. This prevents accidental
10090 alterations to machine code; but it also prevents you from intentionally
10091 patching your program's binary.
10093 If you'd like to be able to patch the binary, you can specify that
10094 explicitly with the @code{set write} command. For example, you might
10095 want to turn on internal debugging flags, or even to make emergency
10101 @itemx set write off
10102 If you specify @samp{set write on}, @value{GDBN} opens executable and
10103 core files for both reading and writing; if you specify @samp{set write
10104 off} (the default), @value{GDBN} opens them read-only.
10106 If you have already loaded a file, you must load it again (using the
10107 @code{exec-file} or @code{core-file} command) after changing @code{set
10108 write}, for your new setting to take effect.
10112 Display whether executable files and core files are opened for writing
10113 as well as reading.
10117 @chapter @value{GDBN} Files
10119 @value{GDBN} needs to know the file name of the program to be debugged,
10120 both in order to read its symbol table and in order to start your
10121 program. To debug a core dump of a previous run, you must also tell
10122 @value{GDBN} the name of the core dump file.
10125 * Files:: Commands to specify files
10126 * Separate Debug Files:: Debugging information in separate files
10127 * Symbol Errors:: Errors reading symbol files
10131 @section Commands to specify files
10133 @cindex symbol table
10134 @cindex core dump file
10136 You may want to specify executable and core dump file names. The usual
10137 way to do this is at start-up time, using the arguments to
10138 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
10139 Out of @value{GDBN}}).
10141 Occasionally it is necessary to change to a different file during a
10142 @value{GDBN} session. Or you may run @value{GDBN} and forget to specify
10143 a file you want to use. In these situations the @value{GDBN} commands
10144 to specify new files are useful.
10147 @cindex executable file
10149 @item file @var{filename}
10150 Use @var{filename} as the program to be debugged. It is read for its
10151 symbols and for the contents of pure memory. It is also the program
10152 executed when you use the @code{run} command. If you do not specify a
10153 directory and the file is not found in the @value{GDBN} working directory,
10154 @value{GDBN} uses the environment variable @code{PATH} as a list of
10155 directories to search, just as the shell does when looking for a program
10156 to run. You can change the value of this variable, for both @value{GDBN}
10157 and your program, using the @code{path} command.
10159 On systems with memory-mapped files, an auxiliary file named
10160 @file{@var{filename}.syms} may hold symbol table information for
10161 @var{filename}. If so, @value{GDBN} maps in the symbol table from
10162 @file{@var{filename}.syms}, starting up more quickly. See the
10163 descriptions of the file options @samp{-mapped} and @samp{-readnow}
10164 (available on the command line, and with the commands @code{file},
10165 @code{symbol-file}, or @code{add-symbol-file}, described below),
10166 for more information.
10169 @code{file} with no argument makes @value{GDBN} discard any information it
10170 has on both executable file and the symbol table.
10173 @item exec-file @r{[} @var{filename} @r{]}
10174 Specify that the program to be run (but not the symbol table) is found
10175 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
10176 if necessary to locate your program. Omitting @var{filename} means to
10177 discard information on the executable file.
10179 @kindex symbol-file
10180 @item symbol-file @r{[} @var{filename} @r{]}
10181 Read symbol table information from file @var{filename}. @code{PATH} is
10182 searched when necessary. Use the @code{file} command to get both symbol
10183 table and program to run from the same file.
10185 @code{symbol-file} with no argument clears out @value{GDBN} information on your
10186 program's symbol table.
10188 The @code{symbol-file} command causes @value{GDBN} to forget the contents
10189 of its convenience variables, the value history, and all breakpoints and
10190 auto-display expressions. This is because they may contain pointers to
10191 the internal data recording symbols and data types, which are part of
10192 the old symbol table data being discarded inside @value{GDBN}.
10194 @code{symbol-file} does not repeat if you press @key{RET} again after
10197 When @value{GDBN} is configured for a particular environment, it
10198 understands debugging information in whatever format is the standard
10199 generated for that environment; you may use either a @sc{gnu} compiler, or
10200 other compilers that adhere to the local conventions.
10201 Best results are usually obtained from @sc{gnu} compilers; for example,
10202 using @code{@value{GCC}} you can generate debugging information for
10205 For most kinds of object files, with the exception of old SVR3 systems
10206 using COFF, the @code{symbol-file} command does not normally read the
10207 symbol table in full right away. Instead, it scans the symbol table
10208 quickly to find which source files and which symbols are present. The
10209 details are read later, one source file at a time, as they are needed.
10211 The purpose of this two-stage reading strategy is to make @value{GDBN}
10212 start up faster. For the most part, it is invisible except for
10213 occasional pauses while the symbol table details for a particular source
10214 file are being read. (The @code{set verbose} command can turn these
10215 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
10216 warnings and messages}.)
10218 We have not implemented the two-stage strategy for COFF yet. When the
10219 symbol table is stored in COFF format, @code{symbol-file} reads the
10220 symbol table data in full right away. Note that ``stabs-in-COFF''
10221 still does the two-stage strategy, since the debug info is actually
10225 @cindex reading symbols immediately
10226 @cindex symbols, reading immediately
10228 @cindex memory-mapped symbol file
10229 @cindex saving symbol table
10230 @item symbol-file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10231 @itemx file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10232 You can override the @value{GDBN} two-stage strategy for reading symbol
10233 tables by using the @samp{-readnow} option with any of the commands that
10234 load symbol table information, if you want to be sure @value{GDBN} has the
10235 entire symbol table available.
10237 If memory-mapped files are available on your system through the
10238 @code{mmap} system call, you can use another option, @samp{-mapped}, to
10239 cause @value{GDBN} to write the symbols for your program into a reusable
10240 file. Future @value{GDBN} debugging sessions map in symbol information
10241 from this auxiliary symbol file (if the program has not changed), rather
10242 than spending time reading the symbol table from the executable
10243 program. Using the @samp{-mapped} option has the same effect as
10244 starting @value{GDBN} with the @samp{-mapped} command-line option.
10246 You can use both options together, to make sure the auxiliary symbol
10247 file has all the symbol information for your program.
10249 The auxiliary symbol file for a program called @var{myprog} is called
10250 @samp{@var{myprog}.syms}. Once this file exists (so long as it is newer
10251 than the corresponding executable), @value{GDBN} always attempts to use
10252 it when you debug @var{myprog}; no special options or commands are
10255 The @file{.syms} file is specific to the host machine where you run
10256 @value{GDBN}. It holds an exact image of the internal @value{GDBN}
10257 symbol table. It cannot be shared across multiple host platforms.
10259 @c FIXME: for now no mention of directories, since this seems to be in
10260 @c flux. 13mar1992 status is that in theory GDB would look either in
10261 @c current dir or in same dir as myprog; but issues like competing
10262 @c GDB's, or clutter in system dirs, mean that in practice right now
10263 @c only current dir is used. FFish says maybe a special GDB hierarchy
10264 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
10268 @item core-file @r{[} @var{filename} @r{]}
10270 Specify the whereabouts of a core dump file to be used as the ``contents
10271 of memory''. Traditionally, core files contain only some parts of the
10272 address space of the process that generated them; @value{GDBN} can access the
10273 executable file itself for other parts.
10275 @code{core-file} with no argument specifies that no core file is
10278 Note that the core file is ignored when your program is actually running
10279 under @value{GDBN}. So, if you have been running your program and you
10280 wish to debug a core file instead, you must kill the subprocess in which
10281 the program is running. To do this, use the @code{kill} command
10282 (@pxref{Kill Process, ,Killing the child process}).
10284 @kindex add-symbol-file
10285 @cindex dynamic linking
10286 @item add-symbol-file @var{filename} @var{address}
10287 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10288 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
10289 The @code{add-symbol-file} command reads additional symbol table
10290 information from the file @var{filename}. You would use this command
10291 when @var{filename} has been dynamically loaded (by some other means)
10292 into the program that is running. @var{address} should be the memory
10293 address at which the file has been loaded; @value{GDBN} cannot figure
10294 this out for itself. You can additionally specify an arbitrary number
10295 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
10296 section name and base address for that section. You can specify any
10297 @var{address} as an expression.
10299 The symbol table of the file @var{filename} is added to the symbol table
10300 originally read with the @code{symbol-file} command. You can use the
10301 @code{add-symbol-file} command any number of times; the new symbol data
10302 thus read keeps adding to the old. To discard all old symbol data
10303 instead, use the @code{symbol-file} command without any arguments.
10305 @cindex relocatable object files, reading symbols from
10306 @cindex object files, relocatable, reading symbols from
10307 @cindex reading symbols from relocatable object files
10308 @cindex symbols, reading from relocatable object files
10309 @cindex @file{.o} files, reading symbols from
10310 Although @var{filename} is typically a shared library file, an
10311 executable file, or some other object file which has been fully
10312 relocated for loading into a process, you can also load symbolic
10313 information from relocatable @file{.o} files, as long as:
10317 the file's symbolic information refers only to linker symbols defined in
10318 that file, not to symbols defined by other object files,
10320 every section the file's symbolic information refers to has actually
10321 been loaded into the inferior, as it appears in the file, and
10323 you can determine the address at which every section was loaded, and
10324 provide these to the @code{add-symbol-file} command.
10328 Some embedded operating systems, like Sun Chorus and VxWorks, can load
10329 relocatable files into an already running program; such systems
10330 typically make the requirements above easy to meet. However, it's
10331 important to recognize that many native systems use complex link
10332 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
10333 assembly, for example) that make the requirements difficult to meet. In
10334 general, one cannot assume that using @code{add-symbol-file} to read a
10335 relocatable object file's symbolic information will have the same effect
10336 as linking the relocatable object file into the program in the normal
10339 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
10341 You can use the @samp{-mapped} and @samp{-readnow} options just as with
10342 the @code{symbol-file} command, to change how @value{GDBN} manages the symbol
10343 table information for @var{filename}.
10345 @kindex add-shared-symbol-file
10346 @item add-shared-symbol-file
10347 The @code{add-shared-symbol-file} command can be used only under Harris' CXUX
10348 operating system for the Motorola 88k. @value{GDBN} automatically looks for
10349 shared libraries, however if @value{GDBN} does not find yours, you can run
10350 @code{add-shared-symbol-file}. It takes no arguments.
10354 The @code{section} command changes the base address of section SECTION of
10355 the exec file to ADDR. This can be used if the exec file does not contain
10356 section addresses, (such as in the a.out format), or when the addresses
10357 specified in the file itself are wrong. Each section must be changed
10358 separately. The @code{info files} command, described below, lists all
10359 the sections and their addresses.
10362 @kindex info target
10365 @code{info files} and @code{info target} are synonymous; both print the
10366 current target (@pxref{Targets, ,Specifying a Debugging Target}),
10367 including the names of the executable and core dump files currently in
10368 use by @value{GDBN}, and the files from which symbols were loaded. The
10369 command @code{help target} lists all possible targets rather than
10372 @kindex maint info sections
10373 @item maint info sections
10374 Another command that can give you extra information about program sections
10375 is @code{maint info sections}. In addition to the section information
10376 displayed by @code{info files}, this command displays the flags and file
10377 offset of each section in the executable and core dump files. In addition,
10378 @code{maint info sections} provides the following command options (which
10379 may be arbitrarily combined):
10383 Display sections for all loaded object files, including shared libraries.
10384 @item @var{sections}
10385 Display info only for named @var{sections}.
10386 @item @var{section-flags}
10387 Display info only for sections for which @var{section-flags} are true.
10388 The section flags that @value{GDBN} currently knows about are:
10391 Section will have space allocated in the process when loaded.
10392 Set for all sections except those containing debug information.
10394 Section will be loaded from the file into the child process memory.
10395 Set for pre-initialized code and data, clear for @code{.bss} sections.
10397 Section needs to be relocated before loading.
10399 Section cannot be modified by the child process.
10401 Section contains executable code only.
10403 Section contains data only (no executable code).
10405 Section will reside in ROM.
10407 Section contains data for constructor/destructor lists.
10409 Section is not empty.
10411 An instruction to the linker to not output the section.
10412 @item COFF_SHARED_LIBRARY
10413 A notification to the linker that the section contains
10414 COFF shared library information.
10416 Section contains common symbols.
10419 @kindex set trust-readonly-sections
10420 @item set trust-readonly-sections on
10421 Tell @value{GDBN} that readonly sections in your object file
10422 really are read-only (i.e.@: that their contents will not change).
10423 In that case, @value{GDBN} can fetch values from these sections
10424 out of the object file, rather than from the target program.
10425 For some targets (notably embedded ones), this can be a significant
10426 enhancement to debugging performance.
10428 The default is off.
10430 @item set trust-readonly-sections off
10431 Tell @value{GDBN} not to trust readonly sections. This means that
10432 the contents of the section might change while the program is running,
10433 and must therefore be fetched from the target when needed.
10436 All file-specifying commands allow both absolute and relative file names
10437 as arguments. @value{GDBN} always converts the file name to an absolute file
10438 name and remembers it that way.
10440 @cindex shared libraries
10441 @value{GDBN} supports HP-UX, SunOS, SVr4, Irix 5, and IBM RS/6000 shared
10444 @value{GDBN} automatically loads symbol definitions from shared libraries
10445 when you use the @code{run} command, or when you examine a core file.
10446 (Before you issue the @code{run} command, @value{GDBN} does not understand
10447 references to a function in a shared library, however---unless you are
10448 debugging a core file).
10450 On HP-UX, if the program loads a library explicitly, @value{GDBN}
10451 automatically loads the symbols at the time of the @code{shl_load} call.
10453 @c FIXME: some @value{GDBN} release may permit some refs to undef
10454 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
10455 @c FIXME...lib; check this from time to time when updating manual
10457 There are times, however, when you may wish to not automatically load
10458 symbol definitions from shared libraries, such as when they are
10459 particularly large or there are many of them.
10461 To control the automatic loading of shared library symbols, use the
10465 @kindex set auto-solib-add
10466 @item set auto-solib-add @var{mode}
10467 If @var{mode} is @code{on}, symbols from all shared object libraries
10468 will be loaded automatically when the inferior begins execution, you
10469 attach to an independently started inferior, or when the dynamic linker
10470 informs @value{GDBN} that a new library has been loaded. If @var{mode}
10471 is @code{off}, symbols must be loaded manually, using the
10472 @code{sharedlibrary} command. The default value is @code{on}.
10474 @cindex memory used for symbol tables
10475 If your program uses lots of shared libraries with debug info that
10476 takes large amounts of memory, you can decrease the @value{GDBN}
10477 memory footprint by preventing it from automatically loading the
10478 symbols from shared libraries. To that end, type @kbd{set
10479 auto-solib-add off} before running the inferior, then load each
10480 library whose debug symbols you do need with @kbd{sharedlibrary
10481 @var{regexp}}, where @var{regexp} is a regular expresion that matches
10482 the libraries whose symbols you want to be loaded.
10484 @kindex show auto-solib-add
10485 @item show auto-solib-add
10486 Display the current autoloading mode.
10489 To explicitly load shared library symbols, use the @code{sharedlibrary}
10493 @kindex info sharedlibrary
10496 @itemx info sharedlibrary
10497 Print the names of the shared libraries which are currently loaded.
10499 @kindex sharedlibrary
10501 @item sharedlibrary @var{regex}
10502 @itemx share @var{regex}
10503 Load shared object library symbols for files matching a
10504 Unix regular expression.
10505 As with files loaded automatically, it only loads shared libraries
10506 required by your program for a core file or after typing @code{run}. If
10507 @var{regex} is omitted all shared libraries required by your program are
10511 On some systems, such as HP-UX systems, @value{GDBN} supports
10512 autoloading shared library symbols until a limiting threshold size is
10513 reached. This provides the benefit of allowing autoloading to remain on
10514 by default, but avoids autoloading excessively large shared libraries,
10515 up to a threshold that is initially set, but which you can modify if you
10518 Beyond that threshold, symbols from shared libraries must be explicitly
10519 loaded. To load these symbols, use the command @code{sharedlibrary
10520 @var{filename}}. The base address of the shared library is determined
10521 automatically by @value{GDBN} and need not be specified.
10523 To display or set the threshold, use the commands:
10526 @kindex set auto-solib-limit
10527 @item set auto-solib-limit @var{threshold}
10528 Set the autoloading size threshold, in an integral number of megabytes.
10529 If @var{threshold} is nonzero and shared library autoloading is enabled,
10530 symbols from all shared object libraries will be loaded until the total
10531 size of the loaded shared library symbols exceeds this threshold.
10532 Otherwise, symbols must be loaded manually, using the
10533 @code{sharedlibrary} command. The default threshold is 100 (i.e.@: 100
10536 @kindex show auto-solib-limit
10537 @item show auto-solib-limit
10538 Display the current autoloading size threshold, in megabytes.
10541 Shared libraries are also supported in many cross or remote debugging
10542 configurations. A copy of the target's libraries need to be present on the
10543 host system; they need to be the same as the target libraries, although the
10544 copies on the target can be stripped as long as the copies on the host are
10547 You need to tell @value{GDBN} where the target libraries are, so that it can
10548 load the correct copies---otherwise, it may try to load the host's libraries.
10549 @value{GDBN} has two variables to specify the search directories for target
10553 @kindex set solib-absolute-prefix
10554 @item set solib-absolute-prefix @var{path}
10555 If this variable is set, @var{path} will be used as a prefix for any
10556 absolute shared library paths; many runtime loaders store the absolute
10557 paths to the shared library in the target program's memory. If you use
10558 @samp{solib-absolute-prefix} to find shared libraries, they need to be laid
10559 out in the same way that they are on the target, with e.g.@: a
10560 @file{/usr/lib} hierarchy under @var{path}.
10562 You can set the default value of @samp{solib-absolute-prefix} by using the
10563 configure-time @samp{--with-sysroot} option.
10565 @kindex show solib-absolute-prefix
10566 @item show solib-absolute-prefix
10567 Display the current shared library prefix.
10569 @kindex set solib-search-path
10570 @item set solib-search-path @var{path}
10571 If this variable is set, @var{path} is a colon-separated list of directories
10572 to search for shared libraries. @samp{solib-search-path} is used after
10573 @samp{solib-absolute-prefix} fails to locate the library, or if the path to
10574 the library is relative instead of absolute. If you want to use
10575 @samp{solib-search-path} instead of @samp{solib-absolute-prefix}, be sure to
10576 set @samp{solib-absolute-prefix} to a nonexistant directory to prevent
10577 @value{GDBN} from finding your host's libraries.
10579 @kindex show solib-search-path
10580 @item show solib-search-path
10581 Display the current shared library search path.
10585 @node Separate Debug Files
10586 @section Debugging Information in Separate Files
10587 @cindex separate debugging information files
10588 @cindex debugging information in separate files
10589 @cindex @file{.debug} subdirectories
10590 @cindex debugging information directory, global
10591 @cindex global debugging information directory
10593 @value{GDBN} allows you to put a program's debugging information in a
10594 file separate from the executable itself, in a way that allows
10595 @value{GDBN} to find and load the debugging information automatically.
10596 Since debugging information can be very large --- sometimes larger
10597 than the executable code itself --- some systems distribute debugging
10598 information for their executables in separate files, which users can
10599 install only when they need to debug a problem.
10601 If an executable's debugging information has been extracted to a
10602 separate file, the executable should contain a @dfn{debug link} giving
10603 the name of the debugging information file (with no directory
10604 components), and a checksum of its contents. (The exact form of a
10605 debug link is described below.) If the full name of the directory
10606 containing the executable is @var{execdir}, and the executable has a
10607 debug link that specifies the name @var{debugfile}, then @value{GDBN}
10608 will automatically search for the debugging information file in three
10613 the directory containing the executable file (that is, it will look
10614 for a file named @file{@var{execdir}/@var{debugfile}},
10616 a subdirectory of that directory named @file{.debug} (that is, the
10617 file @file{@var{execdir}/.debug/@var{debugfile}}, and
10619 a subdirectory of the global debug file directory that includes the
10620 executable's full path, and the name from the link (that is, the file
10621 @file{@var{globaldebugdir}/@var{execdir}/@var{debugfile}}, where
10622 @var{globaldebugdir} is the global debug file directory, and
10623 @var{execdir} has been turned into a relative path).
10626 @value{GDBN} checks under each of these names for a debugging
10627 information file whose checksum matches that given in the link, and
10628 reads the debugging information from the first one it finds.
10630 So, for example, if you ask @value{GDBN} to debug @file{/usr/bin/ls},
10631 which has a link containing the name @file{ls.debug}, and the global
10632 debug directory is @file{/usr/lib/debug}, then @value{GDBN} will look
10633 for debug information in @file{/usr/bin/ls.debug},
10634 @file{/usr/bin/.debug/ls.debug}, and
10635 @file{/usr/lib/debug/usr/bin/ls.debug}.
10637 You can set the global debugging info directory's name, and view the
10638 name @value{GDBN} is currently using.
10642 @kindex set debug-file-directory
10643 @item set debug-file-directory @var{directory}
10644 Set the directory which @value{GDBN} searches for separate debugging
10645 information files to @var{directory}.
10647 @kindex show debug-file-directory
10648 @item show debug-file-directory
10649 Show the directory @value{GDBN} searches for separate debugging
10654 @cindex @code{.gnu_debuglink} sections
10655 @cindex debug links
10656 A debug link is a special section of the executable file named
10657 @code{.gnu_debuglink}. The section must contain:
10661 A filename, with any leading directory components removed, followed by
10664 zero to three bytes of padding, as needed to reach the next four-byte
10665 boundary within the section, and
10667 a four-byte CRC checksum, stored in the same endianness used for the
10668 executable file itself. The checksum is computed on the debugging
10669 information file's full contents by the function given below, passing
10670 zero as the @var{crc} argument.
10673 Any executable file format can carry a debug link, as long as it can
10674 contain a section named @code{.gnu_debuglink} with the contents
10677 The debugging information file itself should be an ordinary
10678 executable, containing a full set of linker symbols, sections, and
10679 debugging information. The sections of the debugging information file
10680 should have the same names, addresses and sizes as the original file,
10681 but they need not contain any data --- much like a @code{.bss} section
10682 in an ordinary executable.
10684 As of December 2002, there is no standard GNU utility to produce
10685 separated executable / debugging information file pairs. Ulrich
10686 Drepper's @file{elfutils} package, starting with version 0.53,
10687 contains a version of the @code{strip} command such that the command
10688 @kbd{strip foo -f foo.debug} removes the debugging information from
10689 the executable file @file{foo}, places it in the file
10690 @file{foo.debug}, and leaves behind a debug link in @file{foo}.
10692 Since there are many different ways to compute CRC's (different
10693 polynomials, reversals, byte ordering, etc.), the simplest way to
10694 describe the CRC used in @code{.gnu_debuglink} sections is to give the
10695 complete code for a function that computes it:
10697 @kindex gnu_debuglink_crc32
10700 gnu_debuglink_crc32 (unsigned long crc,
10701 unsigned char *buf, size_t len)
10703 static const unsigned long crc32_table[256] =
10705 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
10706 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
10707 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
10708 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
10709 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
10710 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
10711 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
10712 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
10713 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
10714 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
10715 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
10716 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
10717 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
10718 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
10719 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
10720 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
10721 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
10722 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
10723 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
10724 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
10725 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
10726 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
10727 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
10728 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
10729 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
10730 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
10731 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
10732 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
10733 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
10734 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
10735 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
10736 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
10737 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
10738 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
10739 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
10740 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
10741 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
10742 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
10743 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
10744 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
10745 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
10746 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
10747 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
10748 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
10749 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
10750 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
10751 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
10752 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
10753 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
10754 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
10755 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
10758 unsigned char *end;
10760 crc = ~crc & 0xffffffff;
10761 for (end = buf + len; buf < end; ++buf)
10762 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
10763 return ~crc & 0xffffffff;
10768 @node Symbol Errors
10769 @section Errors reading symbol files
10771 While reading a symbol file, @value{GDBN} occasionally encounters problems,
10772 such as symbol types it does not recognize, or known bugs in compiler
10773 output. By default, @value{GDBN} does not notify you of such problems, since
10774 they are relatively common and primarily of interest to people
10775 debugging compilers. If you are interested in seeing information
10776 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
10777 only one message about each such type of problem, no matter how many
10778 times the problem occurs; or you can ask @value{GDBN} to print more messages,
10779 to see how many times the problems occur, with the @code{set
10780 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
10783 The messages currently printed, and their meanings, include:
10786 @item inner block not inside outer block in @var{symbol}
10788 The symbol information shows where symbol scopes begin and end
10789 (such as at the start of a function or a block of statements). This
10790 error indicates that an inner scope block is not fully contained
10791 in its outer scope blocks.
10793 @value{GDBN} circumvents the problem by treating the inner block as if it had
10794 the same scope as the outer block. In the error message, @var{symbol}
10795 may be shown as ``@code{(don't know)}'' if the outer block is not a
10798 @item block at @var{address} out of order
10800 The symbol information for symbol scope blocks should occur in
10801 order of increasing addresses. This error indicates that it does not
10804 @value{GDBN} does not circumvent this problem, and has trouble
10805 locating symbols in the source file whose symbols it is reading. (You
10806 can often determine what source file is affected by specifying
10807 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
10810 @item bad block start address patched
10812 The symbol information for a symbol scope block has a start address
10813 smaller than the address of the preceding source line. This is known
10814 to occur in the SunOS 4.1.1 (and earlier) C compiler.
10816 @value{GDBN} circumvents the problem by treating the symbol scope block as
10817 starting on the previous source line.
10819 @item bad string table offset in symbol @var{n}
10822 Symbol number @var{n} contains a pointer into the string table which is
10823 larger than the size of the string table.
10825 @value{GDBN} circumvents the problem by considering the symbol to have the
10826 name @code{foo}, which may cause other problems if many symbols end up
10829 @item unknown symbol type @code{0x@var{nn}}
10831 The symbol information contains new data types that @value{GDBN} does
10832 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
10833 uncomprehended information, in hexadecimal.
10835 @value{GDBN} circumvents the error by ignoring this symbol information.
10836 This usually allows you to debug your program, though certain symbols
10837 are not accessible. If you encounter such a problem and feel like
10838 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
10839 on @code{complain}, then go up to the function @code{read_dbx_symtab}
10840 and examine @code{*bufp} to see the symbol.
10842 @item stub type has NULL name
10844 @value{GDBN} could not find the full definition for a struct or class.
10846 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
10847 The symbol information for a C@t{++} member function is missing some
10848 information that recent versions of the compiler should have output for
10851 @item info mismatch between compiler and debugger
10853 @value{GDBN} could not parse a type specification output by the compiler.
10858 @chapter Specifying a Debugging Target
10860 @cindex debugging target
10863 A @dfn{target} is the execution environment occupied by your program.
10865 Often, @value{GDBN} runs in the same host environment as your program;
10866 in that case, the debugging target is specified as a side effect when
10867 you use the @code{file} or @code{core} commands. When you need more
10868 flexibility---for example, running @value{GDBN} on a physically separate
10869 host, or controlling a standalone system over a serial port or a
10870 realtime system over a TCP/IP connection---you can use the @code{target}
10871 command to specify one of the target types configured for @value{GDBN}
10872 (@pxref{Target Commands, ,Commands for managing targets}).
10875 * Active Targets:: Active targets
10876 * Target Commands:: Commands for managing targets
10877 * Byte Order:: Choosing target byte order
10878 * Remote:: Remote debugging
10879 * KOD:: Kernel Object Display
10883 @node Active Targets
10884 @section Active targets
10886 @cindex stacking targets
10887 @cindex active targets
10888 @cindex multiple targets
10890 There are three classes of targets: processes, core files, and
10891 executable files. @value{GDBN} can work concurrently on up to three
10892 active targets, one in each class. This allows you to (for example)
10893 start a process and inspect its activity without abandoning your work on
10896 For example, if you execute @samp{gdb a.out}, then the executable file
10897 @code{a.out} is the only active target. If you designate a core file as
10898 well---presumably from a prior run that crashed and coredumped---then
10899 @value{GDBN} has two active targets and uses them in tandem, looking
10900 first in the corefile target, then in the executable file, to satisfy
10901 requests for memory addresses. (Typically, these two classes of target
10902 are complementary, since core files contain only a program's
10903 read-write memory---variables and so on---plus machine status, while
10904 executable files contain only the program text and initialized data.)
10906 When you type @code{run}, your executable file becomes an active process
10907 target as well. When a process target is active, all @value{GDBN}
10908 commands requesting memory addresses refer to that target; addresses in
10909 an active core file or executable file target are obscured while the
10910 process target is active.
10912 Use the @code{core-file} and @code{exec-file} commands to select a new
10913 core file or executable target (@pxref{Files, ,Commands to specify
10914 files}). To specify as a target a process that is already running, use
10915 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
10918 @node Target Commands
10919 @section Commands for managing targets
10922 @item target @var{type} @var{parameters}
10923 Connects the @value{GDBN} host environment to a target machine or
10924 process. A target is typically a protocol for talking to debugging
10925 facilities. You use the argument @var{type} to specify the type or
10926 protocol of the target machine.
10928 Further @var{parameters} are interpreted by the target protocol, but
10929 typically include things like device names or host names to connect
10930 with, process numbers, and baud rates.
10932 The @code{target} command does not repeat if you press @key{RET} again
10933 after executing the command.
10935 @kindex help target
10937 Displays the names of all targets available. To display targets
10938 currently selected, use either @code{info target} or @code{info files}
10939 (@pxref{Files, ,Commands to specify files}).
10941 @item help target @var{name}
10942 Describe a particular target, including any parameters necessary to
10945 @kindex set gnutarget
10946 @item set gnutarget @var{args}
10947 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
10948 knows whether it is reading an @dfn{executable},
10949 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
10950 with the @code{set gnutarget} command. Unlike most @code{target} commands,
10951 with @code{gnutarget} the @code{target} refers to a program, not a machine.
10954 @emph{Warning:} To specify a file format with @code{set gnutarget},
10955 you must know the actual BFD name.
10959 @xref{Files, , Commands to specify files}.
10961 @kindex show gnutarget
10962 @item show gnutarget
10963 Use the @code{show gnutarget} command to display what file format
10964 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
10965 @value{GDBN} will determine the file format for each file automatically,
10966 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
10969 @cindex common targets
10970 Here are some common targets (available, or not, depending on the GDB
10975 @item target exec @var{program}
10976 @cindex executable file target
10977 An executable file. @samp{target exec @var{program}} is the same as
10978 @samp{exec-file @var{program}}.
10980 @item target core @var{filename}
10981 @cindex core dump file target
10982 A core dump file. @samp{target core @var{filename}} is the same as
10983 @samp{core-file @var{filename}}.
10985 @item target remote @var{dev}
10986 @cindex remote target
10987 Remote serial target in GDB-specific protocol. The argument @var{dev}
10988 specifies what serial device to use for the connection (e.g.
10989 @file{/dev/ttya}). @xref{Remote, ,Remote debugging}. @code{target remote}
10990 supports the @code{load} command. This is only useful if you have
10991 some other way of getting the stub to the target system, and you can put
10992 it somewhere in memory where it won't get clobbered by the download.
10995 @cindex built-in simulator target
10996 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
11004 works; however, you cannot assume that a specific memory map, device
11005 drivers, or even basic I/O is available, although some simulators do
11006 provide these. For info about any processor-specific simulator details,
11007 see the appropriate section in @ref{Embedded Processors, ,Embedded
11012 Some configurations may include these targets as well:
11016 @item target nrom @var{dev}
11017 @cindex NetROM ROM emulator target
11018 NetROM ROM emulator. This target only supports downloading.
11022 Different targets are available on different configurations of @value{GDBN};
11023 your configuration may have more or fewer targets.
11025 Many remote targets require you to download the executable's code
11026 once you've successfully established a connection.
11030 @kindex load @var{filename}
11031 @item load @var{filename}
11032 Depending on what remote debugging facilities are configured into
11033 @value{GDBN}, the @code{load} command may be available. Where it exists, it
11034 is meant to make @var{filename} (an executable) available for debugging
11035 on the remote system---by downloading, or dynamic linking, for example.
11036 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
11037 the @code{add-symbol-file} command.
11039 If your @value{GDBN} does not have a @code{load} command, attempting to
11040 execute it gets the error message ``@code{You can't do that when your
11041 target is @dots{}}''
11043 The file is loaded at whatever address is specified in the executable.
11044 For some object file formats, you can specify the load address when you
11045 link the program; for other formats, like a.out, the object file format
11046 specifies a fixed address.
11047 @c FIXME! This would be a good place for an xref to the GNU linker doc.
11049 @code{load} does not repeat if you press @key{RET} again after using it.
11053 @section Choosing target byte order
11055 @cindex choosing target byte order
11056 @cindex target byte order
11058 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
11059 offer the ability to run either big-endian or little-endian byte
11060 orders. Usually the executable or symbol will include a bit to
11061 designate the endian-ness, and you will not need to worry about
11062 which to use. However, you may still find it useful to adjust
11063 @value{GDBN}'s idea of processor endian-ness manually.
11067 @item set endian big
11068 Instruct @value{GDBN} to assume the target is big-endian.
11070 @item set endian little
11071 Instruct @value{GDBN} to assume the target is little-endian.
11073 @item set endian auto
11074 Instruct @value{GDBN} to use the byte order associated with the
11078 Display @value{GDBN}'s current idea of the target byte order.
11082 Note that these commands merely adjust interpretation of symbolic
11083 data on the host, and that they have absolutely no effect on the
11087 @section Remote debugging
11088 @cindex remote debugging
11090 If you are trying to debug a program running on a machine that cannot run
11091 @value{GDBN} in the usual way, it is often useful to use remote debugging.
11092 For example, you might use remote debugging on an operating system kernel,
11093 or on a small system which does not have a general purpose operating system
11094 powerful enough to run a full-featured debugger.
11096 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
11097 to make this work with particular debugging targets. In addition,
11098 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
11099 but not specific to any particular target system) which you can use if you
11100 write the remote stubs---the code that runs on the remote system to
11101 communicate with @value{GDBN}.
11103 Other remote targets may be available in your
11104 configuration of @value{GDBN}; use @code{help target} to list them.
11107 @section Kernel Object Display
11108 @cindex kernel object display
11111 Some targets support kernel object display. Using this facility,
11112 @value{GDBN} communicates specially with the underlying operating system
11113 and can display information about operating system-level objects such as
11114 mutexes and other synchronization objects. Exactly which objects can be
11115 displayed is determined on a per-OS basis.
11118 Use the @code{set os} command to set the operating system. This tells
11119 @value{GDBN} which kernel object display module to initialize:
11122 (@value{GDBP}) set os cisco
11126 The associated command @code{show os} displays the operating system
11127 set with the @code{set os} command; if no operating system has been
11128 set, @code{show os} will display an empty string @samp{""}.
11130 If @code{set os} succeeds, @value{GDBN} will display some information
11131 about the operating system, and will create a new @code{info} command
11132 which can be used to query the target. The @code{info} command is named
11133 after the operating system:
11137 (@value{GDBP}) info cisco
11138 List of Cisco Kernel Objects
11140 any Any and all objects
11143 Further subcommands can be used to query about particular objects known
11146 There is currently no way to determine whether a given operating
11147 system is supported other than to try setting it with @kbd{set os
11148 @var{name}}, where @var{name} is the name of the operating system you
11152 @node Remote Debugging
11153 @chapter Debugging remote programs
11156 * Connecting:: Connecting to a remote target
11157 * Server:: Using the gdbserver program
11158 * NetWare:: Using the gdbserve.nlm program
11159 * Remote configuration:: Remote configuration
11160 * remote stub:: Implementing a remote stub
11164 @section Connecting to a remote target
11166 On the @value{GDBN} host machine, you will need an unstripped copy of
11167 your program, since @value{GDBN} needs symobl and debugging information.
11168 Start up @value{GDBN} as usual, using the name of the local copy of your
11169 program as the first argument.
11171 @cindex serial line, @code{target remote}
11172 If you're using a serial line, you may want to give @value{GDBN} the
11173 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
11174 before the @code{target} command.
11176 After that, use @code{target remote} to establish communications with
11177 the target machine. Its argument specifies how to communicate---either
11178 via a devicename attached to a direct serial line, or a TCP or UDP port
11179 (possibly to a terminal server which in turn has a serial line to the
11180 target). For example, to use a serial line connected to the device
11181 named @file{/dev/ttyb}:
11184 target remote /dev/ttyb
11187 @cindex TCP port, @code{target remote}
11188 To use a TCP connection, use an argument of the form
11189 @code{@var{host}:@var{port}} or @code{tcp:@var{host}:@var{port}}.
11190 For example, to connect to port 2828 on a
11191 terminal server named @code{manyfarms}:
11194 target remote manyfarms:2828
11197 If your remote target is actually running on the same machine as
11198 your debugger session (e.g.@: a simulator of your target running on
11199 the same host), you can omit the hostname. For example, to connect
11200 to port 1234 on your local machine:
11203 target remote :1234
11207 Note that the colon is still required here.
11209 @cindex UDP port, @code{target remote}
11210 To use a UDP connection, use an argument of the form
11211 @code{udp:@var{host}:@var{port}}. For example, to connect to UDP port 2828
11212 on a terminal server named @code{manyfarms}:
11215 target remote udp:manyfarms:2828
11218 When using a UDP connection for remote debugging, you should keep in mind
11219 that the `U' stands for ``Unreliable''. UDP can silently drop packets on
11220 busy or unreliable networks, which will cause havoc with your debugging
11223 Now you can use all the usual commands to examine and change data and to
11224 step and continue the remote program.
11226 @cindex interrupting remote programs
11227 @cindex remote programs, interrupting
11228 Whenever @value{GDBN} is waiting for the remote program, if you type the
11229 interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the
11230 program. This may or may not succeed, depending in part on the hardware
11231 and the serial drivers the remote system uses. If you type the
11232 interrupt character once again, @value{GDBN} displays this prompt:
11235 Interrupted while waiting for the program.
11236 Give up (and stop debugging it)? (y or n)
11239 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
11240 (If you decide you want to try again later, you can use @samp{target
11241 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
11242 goes back to waiting.
11245 @kindex detach (remote)
11247 When you have finished debugging the remote program, you can use the
11248 @code{detach} command to release it from @value{GDBN} control.
11249 Detaching from the target normally resumes its execution, but the results
11250 will depend on your particular remote stub. After the @code{detach}
11251 command, @value{GDBN} is free to connect to another target.
11255 The @code{disconnect} command behaves like @code{detach}, except that
11256 the target is generally not resumed. It will wait for @value{GDBN}
11257 (this instance or another one) to connect and continue debugging. After
11258 the @code{disconnect} command, @value{GDBN} is again free to connect to
11263 @section Using the @code{gdbserver} program
11266 @cindex remote connection without stubs
11267 @code{gdbserver} is a control program for Unix-like systems, which
11268 allows you to connect your program with a remote @value{GDBN} via
11269 @code{target remote}---but without linking in the usual debugging stub.
11271 @code{gdbserver} is not a complete replacement for the debugging stubs,
11272 because it requires essentially the same operating-system facilities
11273 that @value{GDBN} itself does. In fact, a system that can run
11274 @code{gdbserver} to connect to a remote @value{GDBN} could also run
11275 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
11276 because it is a much smaller program than @value{GDBN} itself. It is
11277 also easier to port than all of @value{GDBN}, so you may be able to get
11278 started more quickly on a new system by using @code{gdbserver}.
11279 Finally, if you develop code for real-time systems, you may find that
11280 the tradeoffs involved in real-time operation make it more convenient to
11281 do as much development work as possible on another system, for example
11282 by cross-compiling. You can use @code{gdbserver} to make a similar
11283 choice for debugging.
11285 @value{GDBN} and @code{gdbserver} communicate via either a serial line
11286 or a TCP connection, using the standard @value{GDBN} remote serial
11290 @item On the target machine,
11291 you need to have a copy of the program you want to debug.
11292 @code{gdbserver} does not need your program's symbol table, so you can
11293 strip the program if necessary to save space. @value{GDBN} on the host
11294 system does all the symbol handling.
11296 To use the server, you must tell it how to communicate with @value{GDBN};
11297 the name of your program; and the arguments for your program. The usual
11301 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
11304 @var{comm} is either a device name (to use a serial line) or a TCP
11305 hostname and portnumber. For example, to debug Emacs with the argument
11306 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
11310 target> gdbserver /dev/com1 emacs foo.txt
11313 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
11316 To use a TCP connection instead of a serial line:
11319 target> gdbserver host:2345 emacs foo.txt
11322 The only difference from the previous example is the first argument,
11323 specifying that you are communicating with the host @value{GDBN} via
11324 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
11325 expect a TCP connection from machine @samp{host} to local TCP port 2345.
11326 (Currently, the @samp{host} part is ignored.) You can choose any number
11327 you want for the port number as long as it does not conflict with any
11328 TCP ports already in use on the target system (for example, @code{23} is
11329 reserved for @code{telnet}).@footnote{If you choose a port number that
11330 conflicts with another service, @code{gdbserver} prints an error message
11331 and exits.} You must use the same port number with the host @value{GDBN}
11332 @code{target remote} command.
11334 On some targets, @code{gdbserver} can also attach to running programs.
11335 This is accomplished via the @code{--attach} argument. The syntax is:
11338 target> gdbserver @var{comm} --attach @var{pid}
11341 @var{pid} is the process ID of a currently running process. It isn't necessary
11342 to point @code{gdbserver} at a binary for the running process.
11345 @cindex attach to a program by name
11346 You can debug processes by name instead of process ID if your target has the
11347 @code{pidof} utility:
11350 target> gdbserver @var{comm} --attach `pidof @var{PROGRAM}`
11353 In case more than one copy of @var{PROGRAM} is running, or @var{PROGRAM}
11354 has multiple threads, most versions of @code{pidof} support the
11355 @code{-s} option to only return the first process ID.
11357 @item On the host machine,
11358 connect to your target (@pxref{Connecting,,Connecting to a remote target}).
11359 For TCP connections, you must start up @code{gdbserver} prior to using
11360 the @code{target remote} command. Otherwise you may get an error whose
11361 text depends on the host system, but which usually looks something like
11362 @samp{Connection refused}. You don't need to use the @code{load}
11363 command in @value{GDBN} when using gdbserver, since the program is
11364 already on the target.
11369 @section Using the @code{gdbserve.nlm} program
11371 @kindex gdbserve.nlm
11372 @code{gdbserve.nlm} is a control program for NetWare systems, which
11373 allows you to connect your program with a remote @value{GDBN} via
11374 @code{target remote}.
11376 @value{GDBN} and @code{gdbserve.nlm} communicate via a serial line,
11377 using the standard @value{GDBN} remote serial protocol.
11380 @item On the target machine,
11381 you need to have a copy of the program you want to debug.
11382 @code{gdbserve.nlm} does not need your program's symbol table, so you
11383 can strip the program if necessary to save space. @value{GDBN} on the
11384 host system does all the symbol handling.
11386 To use the server, you must tell it how to communicate with
11387 @value{GDBN}; the name of your program; and the arguments for your
11388 program. The syntax is:
11391 load gdbserve [ BOARD=@var{board} ] [ PORT=@var{port} ]
11392 [ BAUD=@var{baud} ] @var{program} [ @var{args} @dots{} ]
11395 @var{board} and @var{port} specify the serial line; @var{baud} specifies
11396 the baud rate used by the connection. @var{port} and @var{node} default
11397 to 0, @var{baud} defaults to 9600@dmn{bps}.
11399 For example, to debug Emacs with the argument @samp{foo.txt}and
11400 communicate with @value{GDBN} over serial port number 2 or board 1
11401 using a 19200@dmn{bps} connection:
11404 load gdbserve BOARD=1 PORT=2 BAUD=19200 emacs foo.txt
11408 On the @value{GDBN} host machine, connect to your target (@pxref{Connecting,,
11409 Connecting to a remote target}).
11413 @node Remote configuration
11414 @section Remote configuration
11416 The following configuration options are available when debugging remote
11420 @kindex set remote hardware-watchpoint-limit
11421 @kindex set remote hardware-breakpoint-limit
11422 @anchor{set remote hardware-watchpoint-limit}
11423 @anchor{set remote hardware-breakpoint-limit}
11424 @item set remote hardware-watchpoint-limit @var{limit}
11425 @itemx set remote hardware-breakpoint-limit @var{limit}
11426 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
11427 watchpoints. A limit of -1, the default, is treated as unlimited.
11431 @section Implementing a remote stub
11433 @cindex debugging stub, example
11434 @cindex remote stub, example
11435 @cindex stub example, remote debugging
11436 The stub files provided with @value{GDBN} implement the target side of the
11437 communication protocol, and the @value{GDBN} side is implemented in the
11438 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
11439 these subroutines to communicate, and ignore the details. (If you're
11440 implementing your own stub file, you can still ignore the details: start
11441 with one of the existing stub files. @file{sparc-stub.c} is the best
11442 organized, and therefore the easiest to read.)
11444 @cindex remote serial debugging, overview
11445 To debug a program running on another machine (the debugging
11446 @dfn{target} machine), you must first arrange for all the usual
11447 prerequisites for the program to run by itself. For example, for a C
11452 A startup routine to set up the C runtime environment; these usually
11453 have a name like @file{crt0}. The startup routine may be supplied by
11454 your hardware supplier, or you may have to write your own.
11457 A C subroutine library to support your program's
11458 subroutine calls, notably managing input and output.
11461 A way of getting your program to the other machine---for example, a
11462 download program. These are often supplied by the hardware
11463 manufacturer, but you may have to write your own from hardware
11467 The next step is to arrange for your program to use a serial port to
11468 communicate with the machine where @value{GDBN} is running (the @dfn{host}
11469 machine). In general terms, the scheme looks like this:
11473 @value{GDBN} already understands how to use this protocol; when everything
11474 else is set up, you can simply use the @samp{target remote} command
11475 (@pxref{Targets,,Specifying a Debugging Target}).
11477 @item On the target,
11478 you must link with your program a few special-purpose subroutines that
11479 implement the @value{GDBN} remote serial protocol. The file containing these
11480 subroutines is called a @dfn{debugging stub}.
11482 On certain remote targets, you can use an auxiliary program
11483 @code{gdbserver} instead of linking a stub into your program.
11484 @xref{Server,,Using the @code{gdbserver} program}, for details.
11487 The debugging stub is specific to the architecture of the remote
11488 machine; for example, use @file{sparc-stub.c} to debug programs on
11491 @cindex remote serial stub list
11492 These working remote stubs are distributed with @value{GDBN}:
11497 @cindex @file{i386-stub.c}
11500 For Intel 386 and compatible architectures.
11503 @cindex @file{m68k-stub.c}
11504 @cindex Motorola 680x0
11506 For Motorola 680x0 architectures.
11509 @cindex @file{sh-stub.c}
11512 For Renesas SH architectures.
11515 @cindex @file{sparc-stub.c}
11517 For @sc{sparc} architectures.
11519 @item sparcl-stub.c
11520 @cindex @file{sparcl-stub.c}
11523 For Fujitsu @sc{sparclite} architectures.
11527 The @file{README} file in the @value{GDBN} distribution may list other
11528 recently added stubs.
11531 * Stub Contents:: What the stub can do for you
11532 * Bootstrapping:: What you must do for the stub
11533 * Debug Session:: Putting it all together
11536 @node Stub Contents
11537 @subsection What the stub can do for you
11539 @cindex remote serial stub
11540 The debugging stub for your architecture supplies these three
11544 @item set_debug_traps
11545 @findex set_debug_traps
11546 @cindex remote serial stub, initialization
11547 This routine arranges for @code{handle_exception} to run when your
11548 program stops. You must call this subroutine explicitly near the
11549 beginning of your program.
11551 @item handle_exception
11552 @findex handle_exception
11553 @cindex remote serial stub, main routine
11554 This is the central workhorse, but your program never calls it
11555 explicitly---the setup code arranges for @code{handle_exception} to
11556 run when a trap is triggered.
11558 @code{handle_exception} takes control when your program stops during
11559 execution (for example, on a breakpoint), and mediates communications
11560 with @value{GDBN} on the host machine. This is where the communications
11561 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
11562 representative on the target machine. It begins by sending summary
11563 information on the state of your program, then continues to execute,
11564 retrieving and transmitting any information @value{GDBN} needs, until you
11565 execute a @value{GDBN} command that makes your program resume; at that point,
11566 @code{handle_exception} returns control to your own code on the target
11570 @cindex @code{breakpoint} subroutine, remote
11571 Use this auxiliary subroutine to make your program contain a
11572 breakpoint. Depending on the particular situation, this may be the only
11573 way for @value{GDBN} to get control. For instance, if your target
11574 machine has some sort of interrupt button, you won't need to call this;
11575 pressing the interrupt button transfers control to
11576 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
11577 simply receiving characters on the serial port may also trigger a trap;
11578 again, in that situation, you don't need to call @code{breakpoint} from
11579 your own program---simply running @samp{target remote} from the host
11580 @value{GDBN} session gets control.
11582 Call @code{breakpoint} if none of these is true, or if you simply want
11583 to make certain your program stops at a predetermined point for the
11584 start of your debugging session.
11587 @node Bootstrapping
11588 @subsection What you must do for the stub
11590 @cindex remote stub, support routines
11591 The debugging stubs that come with @value{GDBN} are set up for a particular
11592 chip architecture, but they have no information about the rest of your
11593 debugging target machine.
11595 First of all you need to tell the stub how to communicate with the
11599 @item int getDebugChar()
11600 @findex getDebugChar
11601 Write this subroutine to read a single character from the serial port.
11602 It may be identical to @code{getchar} for your target system; a
11603 different name is used to allow you to distinguish the two if you wish.
11605 @item void putDebugChar(int)
11606 @findex putDebugChar
11607 Write this subroutine to write a single character to the serial port.
11608 It may be identical to @code{putchar} for your target system; a
11609 different name is used to allow you to distinguish the two if you wish.
11612 @cindex control C, and remote debugging
11613 @cindex interrupting remote targets
11614 If you want @value{GDBN} to be able to stop your program while it is
11615 running, you need to use an interrupt-driven serial driver, and arrange
11616 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
11617 character). That is the character which @value{GDBN} uses to tell the
11618 remote system to stop.
11620 Getting the debugging target to return the proper status to @value{GDBN}
11621 probably requires changes to the standard stub; one quick and dirty way
11622 is to just execute a breakpoint instruction (the ``dirty'' part is that
11623 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
11625 Other routines you need to supply are:
11628 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
11629 @findex exceptionHandler
11630 Write this function to install @var{exception_address} in the exception
11631 handling tables. You need to do this because the stub does not have any
11632 way of knowing what the exception handling tables on your target system
11633 are like (for example, the processor's table might be in @sc{rom},
11634 containing entries which point to a table in @sc{ram}).
11635 @var{exception_number} is the exception number which should be changed;
11636 its meaning is architecture-dependent (for example, different numbers
11637 might represent divide by zero, misaligned access, etc). When this
11638 exception occurs, control should be transferred directly to
11639 @var{exception_address}, and the processor state (stack, registers,
11640 and so on) should be just as it is when a processor exception occurs. So if
11641 you want to use a jump instruction to reach @var{exception_address}, it
11642 should be a simple jump, not a jump to subroutine.
11644 For the 386, @var{exception_address} should be installed as an interrupt
11645 gate so that interrupts are masked while the handler runs. The gate
11646 should be at privilege level 0 (the most privileged level). The
11647 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
11648 help from @code{exceptionHandler}.
11650 @item void flush_i_cache()
11651 @findex flush_i_cache
11652 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
11653 instruction cache, if any, on your target machine. If there is no
11654 instruction cache, this subroutine may be a no-op.
11656 On target machines that have instruction caches, @value{GDBN} requires this
11657 function to make certain that the state of your program is stable.
11661 You must also make sure this library routine is available:
11664 @item void *memset(void *, int, int)
11666 This is the standard library function @code{memset} that sets an area of
11667 memory to a known value. If you have one of the free versions of
11668 @code{libc.a}, @code{memset} can be found there; otherwise, you must
11669 either obtain it from your hardware manufacturer, or write your own.
11672 If you do not use the GNU C compiler, you may need other standard
11673 library subroutines as well; this varies from one stub to another,
11674 but in general the stubs are likely to use any of the common library
11675 subroutines which @code{@value{GCC}} generates as inline code.
11678 @node Debug Session
11679 @subsection Putting it all together
11681 @cindex remote serial debugging summary
11682 In summary, when your program is ready to debug, you must follow these
11687 Make sure you have defined the supporting low-level routines
11688 (@pxref{Bootstrapping,,What you must do for the stub}):
11690 @code{getDebugChar}, @code{putDebugChar},
11691 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
11695 Insert these lines near the top of your program:
11703 For the 680x0 stub only, you need to provide a variable called
11704 @code{exceptionHook}. Normally you just use:
11707 void (*exceptionHook)() = 0;
11711 but if before calling @code{set_debug_traps}, you set it to point to a
11712 function in your program, that function is called when
11713 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
11714 error). The function indicated by @code{exceptionHook} is called with
11715 one parameter: an @code{int} which is the exception number.
11718 Compile and link together: your program, the @value{GDBN} debugging stub for
11719 your target architecture, and the supporting subroutines.
11722 Make sure you have a serial connection between your target machine and
11723 the @value{GDBN} host, and identify the serial port on the host.
11726 @c The "remote" target now provides a `load' command, so we should
11727 @c document that. FIXME.
11728 Download your program to your target machine (or get it there by
11729 whatever means the manufacturer provides), and start it.
11732 Start @value{GDBN} on the host, and connect to the target
11733 (@pxref{Connecting,,Connecting to a remote target}).
11737 @node Configurations
11738 @chapter Configuration-Specific Information
11740 While nearly all @value{GDBN} commands are available for all native and
11741 cross versions of the debugger, there are some exceptions. This chapter
11742 describes things that are only available in certain configurations.
11744 There are three major categories of configurations: native
11745 configurations, where the host and target are the same, embedded
11746 operating system configurations, which are usually the same for several
11747 different processor architectures, and bare embedded processors, which
11748 are quite different from each other.
11753 * Embedded Processors::
11760 This section describes details specific to particular native
11765 * BSD libkvm Interface:: Debugging BSD kernel memory images
11766 * SVR4 Process Information:: SVR4 process information
11767 * DJGPP Native:: Features specific to the DJGPP port
11768 * Cygwin Native:: Features specific to the Cygwin port
11774 On HP-UX systems, if you refer to a function or variable name that
11775 begins with a dollar sign, @value{GDBN} searches for a user or system
11776 name first, before it searches for a convenience variable.
11778 @node BSD libkvm Interface
11779 @subsection BSD libkvm Interface
11782 @cindex kernel memory image
11783 @cindex kernel crash dump
11785 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
11786 interface that provides a uniform interface for accessing kernel virtual
11787 memory images, including live systems and crash dumps. @value{GDBN}
11788 uses this interface to allow you to debug live kernels and kernel crash
11789 dumps on many native BSD configurations. This is implemented as a
11790 special @code{kvm} debugging target. For debugging a live system, load
11791 the currently running kernel into @value{GDBN} and connect to the
11795 (@value{GDBP}) @b{target kvm}
11798 For debugging crash dumps, provide the file name of the crash dump as an
11802 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
11805 Once connected to the @code{kvm} target, the following commands are
11811 Set current context from pcb address.
11814 Set current context from proc address. This command isn't available on
11815 modern FreeBSD systems.
11818 @node SVR4 Process Information
11819 @subsection SVR4 process information
11821 @cindex examine process image
11822 @cindex process info via @file{/proc}
11824 Many versions of SVR4 and compatible systems provide a facility called
11825 @samp{/proc} that can be used to examine the image of a running
11826 process using file-system subroutines. If @value{GDBN} is configured
11827 for an operating system with this facility, the command @code{info
11828 proc} is available to report information about the process running
11829 your program, or about any process running on your system. @code{info
11830 proc} works only on SVR4 systems that include the @code{procfs} code.
11831 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
11832 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
11838 @itemx info proc @var{process-id}
11839 Summarize available information about any running process. If a
11840 process ID is specified by @var{process-id}, display information about
11841 that process; otherwise display information about the program being
11842 debugged. The summary includes the debugged process ID, the command
11843 line used to invoke it, its current working directory, and its
11844 executable file's absolute file name.
11846 On some systems, @var{process-id} can be of the form
11847 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
11848 within a process. If the optional @var{pid} part is missing, it means
11849 a thread from the process being debugged (the leading @samp{/} still
11850 needs to be present, or else @value{GDBN} will interpret the number as
11851 a process ID rather than a thread ID).
11853 @item info proc mappings
11854 @cindex memory address space mappings
11855 Report the memory address space ranges accessible in the program, with
11856 information on whether the process has read, write, or execute access
11857 rights to each range. On @sc{gnu}/Linux systems, each memory range
11858 includes the object file which is mapped to that range, instead of the
11859 memory access rights to that range.
11861 @item info proc stat
11862 @itemx info proc status
11863 @cindex process detailed status information
11864 These subcommands are specific to @sc{gnu}/Linux systems. They show
11865 the process-related information, including the user ID and group ID;
11866 how many threads are there in the process; its virtual memory usage;
11867 the signals that are pending, blocked, and ignored; its TTY; its
11868 consumption of system and user time; its stack size; its @samp{nice}
11869 value; etc. For more information, see the @samp{proc(5)} man page
11870 (type @kbd{man 5 proc} from your shell prompt).
11872 @item info proc all
11873 Show all the information about the process described under all of the
11874 above @code{info proc} subcommands.
11877 @comment These sub-options of 'info proc' were not included when
11878 @comment procfs.c was re-written. Keep their descriptions around
11879 @comment against the day when someone finds the time to put them back in.
11880 @kindex info proc times
11881 @item info proc times
11882 Starting time, user CPU time, and system CPU time for your program and
11885 @kindex info proc id
11887 Report on the process IDs related to your program: its own process ID,
11888 the ID of its parent, the process group ID, and the session ID.
11893 @subsection Features for Debugging @sc{djgpp} Programs
11894 @cindex @sc{djgpp} debugging
11895 @cindex native @sc{djgpp} debugging
11896 @cindex MS-DOS-specific commands
11898 @sc{djgpp} is the port of @sc{gnu} development tools to MS-DOS and
11899 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
11900 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
11901 top of real-mode DOS systems and their emulations.
11903 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
11904 defines a few commands specific to the @sc{djgpp} port. This
11905 subsection describes those commands.
11910 This is a prefix of @sc{djgpp}-specific commands which print
11911 information about the target system and important OS structures.
11914 @cindex MS-DOS system info
11915 @cindex free memory information (MS-DOS)
11916 @item info dos sysinfo
11917 This command displays assorted information about the underlying
11918 platform: the CPU type and features, the OS version and flavor, the
11919 DPMI version, and the available conventional and DPMI memory.
11924 @cindex segment descriptor tables
11925 @cindex descriptor tables display
11927 @itemx info dos ldt
11928 @itemx info dos idt
11929 These 3 commands display entries from, respectively, Global, Local,
11930 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
11931 tables are data structures which store a descriptor for each segment
11932 that is currently in use. The segment's selector is an index into a
11933 descriptor table; the table entry for that index holds the
11934 descriptor's base address and limit, and its attributes and access
11937 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
11938 segment (used for both data and the stack), and a DOS segment (which
11939 allows access to DOS/BIOS data structures and absolute addresses in
11940 conventional memory). However, the DPMI host will usually define
11941 additional segments in order to support the DPMI environment.
11943 @cindex garbled pointers
11944 These commands allow to display entries from the descriptor tables.
11945 Without an argument, all entries from the specified table are
11946 displayed. An argument, which should be an integer expression, means
11947 display a single entry whose index is given by the argument. For
11948 example, here's a convenient way to display information about the
11949 debugged program's data segment:
11952 @exdent @code{(@value{GDBP}) info dos ldt $ds}
11953 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
11957 This comes in handy when you want to see whether a pointer is outside
11958 the data segment's limit (i.e.@: @dfn{garbled}).
11960 @cindex page tables display (MS-DOS)
11962 @itemx info dos pte
11963 These two commands display entries from, respectively, the Page
11964 Directory and the Page Tables. Page Directories and Page Tables are
11965 data structures which control how virtual memory addresses are mapped
11966 into physical addresses. A Page Table includes an entry for every
11967 page of memory that is mapped into the program's address space; there
11968 may be several Page Tables, each one holding up to 4096 entries. A
11969 Page Directory has up to 4096 entries, one each for every Page Table
11970 that is currently in use.
11972 Without an argument, @kbd{info dos pde} displays the entire Page
11973 Directory, and @kbd{info dos pte} displays all the entries in all of
11974 the Page Tables. An argument, an integer expression, given to the
11975 @kbd{info dos pde} command means display only that entry from the Page
11976 Directory table. An argument given to the @kbd{info dos pte} command
11977 means display entries from a single Page Table, the one pointed to by
11978 the specified entry in the Page Directory.
11980 @cindex direct memory access (DMA) on MS-DOS
11981 These commands are useful when your program uses @dfn{DMA} (Direct
11982 Memory Access), which needs physical addresses to program the DMA
11985 These commands are supported only with some DPMI servers.
11987 @cindex physical address from linear address
11988 @item info dos address-pte @var{addr}
11989 This command displays the Page Table entry for a specified linear
11990 address. The argument linear address @var{addr} should already have the
11991 appropriate segment's base address added to it, because this command
11992 accepts addresses which may belong to @emph{any} segment. For
11993 example, here's how to display the Page Table entry for the page where
11994 the variable @code{i} is stored:
11997 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
11998 @exdent @code{Page Table entry for address 0x11a00d30:}
11999 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
12003 This says that @code{i} is stored at offset @code{0xd30} from the page
12004 whose physical base address is @code{0x02698000}, and prints all the
12005 attributes of that page.
12007 Note that you must cast the addresses of variables to a @code{char *},
12008 since otherwise the value of @code{__djgpp_base_address}, the base
12009 address of all variables and functions in a @sc{djgpp} program, will
12010 be added using the rules of C pointer arithmetics: if @code{i} is
12011 declared an @code{int}, @value{GDBN} will add 4 times the value of
12012 @code{__djgpp_base_address} to the address of @code{i}.
12014 Here's another example, it displays the Page Table entry for the
12018 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
12019 @exdent @code{Page Table entry for address 0x29110:}
12020 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
12024 (The @code{+ 3} offset is because the transfer buffer's address is the
12025 3rd member of the @code{_go32_info_block} structure.) The output of
12026 this command clearly shows that addresses in conventional memory are
12027 mapped 1:1, i.e.@: the physical and linear addresses are identical.
12029 This command is supported only with some DPMI servers.
12032 @node Cygwin Native
12033 @subsection Features for Debugging MS Windows PE executables
12034 @cindex MS Windows debugging
12035 @cindex native Cygwin debugging
12036 @cindex Cygwin-specific commands
12038 @value{GDBN} supports native debugging of MS Windows programs, including
12039 DLLs with and without symbolic debugging information. There are various
12040 additional Cygwin-specific commands, described in this subsection. The
12041 subsubsection @pxref{Non-debug DLL symbols} describes working with DLLs
12042 that have no debugging symbols.
12048 This is a prefix of MS Windows specific commands which print
12049 information about the target system and important OS structures.
12051 @item info w32 selector
12052 This command displays information returned by
12053 the Win32 API @code{GetThreadSelectorEntry} function.
12054 It takes an optional argument that is evaluated to
12055 a long value to give the information about this given selector.
12056 Without argument, this command displays information
12057 about the the six segment registers.
12061 This is a Cygwin specific alias of info shared.
12063 @kindex dll-symbols
12065 This command loads symbols from a dll similarly to
12066 add-sym command but without the need to specify a base address.
12068 @kindex set new-console
12069 @item set new-console @var{mode}
12070 If @var{mode} is @code{on} the debuggee will
12071 be started in a new console on next start.
12072 If @var{mode} is @code{off}i, the debuggee will
12073 be started in the same console as the debugger.
12075 @kindex show new-console
12076 @item show new-console
12077 Displays whether a new console is used
12078 when the debuggee is started.
12080 @kindex set new-group
12081 @item set new-group @var{mode}
12082 This boolean value controls whether the debuggee should
12083 start a new group or stay in the same group as the debugger.
12084 This affects the way the Windows OS handles
12087 @kindex show new-group
12088 @item show new-group
12089 Displays current value of new-group boolean.
12091 @kindex set debugevents
12092 @item set debugevents
12093 This boolean value adds debug output concerning events seen by the debugger.
12095 @kindex set debugexec
12096 @item set debugexec
12097 This boolean value adds debug output concerning execute events
12098 seen by the debugger.
12100 @kindex set debugexceptions
12101 @item set debugexceptions
12102 This boolean value adds debug ouptut concerning exception events
12103 seen by the debugger.
12105 @kindex set debugmemory
12106 @item set debugmemory
12107 This boolean value adds debug ouptut concerning memory events
12108 seen by the debugger.
12112 This boolean values specifies whether the debuggee is called
12113 via a shell or directly (default value is on).
12117 Displays if the debuggee will be started with a shell.
12122 * Non-debug DLL symbols:: Support for DLLs without debugging symbols
12125 @node Non-debug DLL symbols
12126 @subsubsection Support for DLLs without debugging symbols
12127 @cindex DLLs with no debugging symbols
12128 @cindex Minimal symbols and DLLs
12130 Very often on windows, some of the DLLs that your program relies on do
12131 not include symbolic debugging information (for example,
12132 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
12133 symbols in a DLL, it relies on the minimal amount of symbolic
12134 information contained in the DLL's export table. This subsubsection
12135 describes working with such symbols, known internally to @value{GDBN} as
12136 ``minimal symbols''.
12138 Note that before the debugged program has started execution, no DLLs
12139 will have been loaded. The easiest way around this problem is simply to
12140 start the program --- either by setting a breakpoint or letting the
12141 program run once to completion. It is also possible to force
12142 @value{GDBN} to load a particular DLL before starting the executable ---
12143 see the shared library information in @pxref{Files} or the
12144 @code{dll-symbols} command in @pxref{Cygwin Native}. Currently,
12145 explicitly loading symbols from a DLL with no debugging information will
12146 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
12147 which may adversely affect symbol lookup performance.
12149 @subsubsection DLL name prefixes
12151 In keeping with the naming conventions used by the Microsoft debugging
12152 tools, DLL export symbols are made available with a prefix based on the
12153 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
12154 also entered into the symbol table, so @code{CreateFileA} is often
12155 sufficient. In some cases there will be name clashes within a program
12156 (particularly if the executable itself includes full debugging symbols)
12157 necessitating the use of the fully qualified name when referring to the
12158 contents of the DLL. Use single-quotes around the name to avoid the
12159 exclamation mark (``!'') being interpreted as a language operator.
12161 Note that the internal name of the DLL may be all upper-case, even
12162 though the file name of the DLL is lower-case, or vice-versa. Since
12163 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
12164 some confusion. If in doubt, try the @code{info functions} and
12165 @code{info variables} commands or even @code{maint print msymbols} (see
12166 @pxref{Symbols}). Here's an example:
12169 (@value{GDBP}) info function CreateFileA
12170 All functions matching regular expression "CreateFileA":
12172 Non-debugging symbols:
12173 0x77e885f4 CreateFileA
12174 0x77e885f4 KERNEL32!CreateFileA
12178 (@value{GDBP}) info function !
12179 All functions matching regular expression "!":
12181 Non-debugging symbols:
12182 0x6100114c cygwin1!__assert
12183 0x61004034 cygwin1!_dll_crt0@@0
12184 0x61004240 cygwin1!dll_crt0(per_process *)
12188 @subsubsection Working with minimal symbols
12190 Symbols extracted from a DLL's export table do not contain very much
12191 type information. All that @value{GDBN} can do is guess whether a symbol
12192 refers to a function or variable depending on the linker section that
12193 contains the symbol. Also note that the actual contents of the memory
12194 contained in a DLL are not available unless the program is running. This
12195 means that you cannot examine the contents of a variable or disassemble
12196 a function within a DLL without a running program.
12198 Variables are generally treated as pointers and dereferenced
12199 automatically. For this reason, it is often necessary to prefix a
12200 variable name with the address-of operator (``&'') and provide explicit
12201 type information in the command. Here's an example of the type of
12205 (@value{GDBP}) print 'cygwin1!__argv'
12210 (@value{GDBP}) x 'cygwin1!__argv'
12211 0x10021610: "\230y\""
12214 And two possible solutions:
12217 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
12218 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
12222 (@value{GDBP}) x/2x &'cygwin1!__argv'
12223 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
12224 (@value{GDBP}) x/x 0x10021608
12225 0x10021608: 0x0022fd98
12226 (@value{GDBP}) x/s 0x0022fd98
12227 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
12230 Setting a break point within a DLL is possible even before the program
12231 starts execution. However, under these circumstances, @value{GDBN} can't
12232 examine the initial instructions of the function in order to skip the
12233 function's frame set-up code. You can work around this by using ``*&''
12234 to set the breakpoint at a raw memory address:
12237 (@value{GDBP}) break *&'python22!PyOS_Readline'
12238 Breakpoint 1 at 0x1e04eff0
12241 The author of these extensions is not entirely convinced that setting a
12242 break point within a shared DLL like @file{kernel32.dll} is completely
12246 @section Embedded Operating Systems
12248 This section describes configurations involving the debugging of
12249 embedded operating systems that are available for several different
12253 * VxWorks:: Using @value{GDBN} with VxWorks
12256 @value{GDBN} includes the ability to debug programs running on
12257 various real-time operating systems.
12260 @subsection Using @value{GDBN} with VxWorks
12266 @kindex target vxworks
12267 @item target vxworks @var{machinename}
12268 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
12269 is the target system's machine name or IP address.
12273 On VxWorks, @code{load} links @var{filename} dynamically on the
12274 current target system as well as adding its symbols in @value{GDBN}.
12276 @value{GDBN} enables developers to spawn and debug tasks running on networked
12277 VxWorks targets from a Unix host. Already-running tasks spawned from
12278 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
12279 both the Unix host and on the VxWorks target. The program
12280 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
12281 installed with the name @code{vxgdb}, to distinguish it from a
12282 @value{GDBN} for debugging programs on the host itself.)
12285 @item VxWorks-timeout @var{args}
12286 @kindex vxworks-timeout
12287 All VxWorks-based targets now support the option @code{vxworks-timeout}.
12288 This option is set by the user, and @var{args} represents the number of
12289 seconds @value{GDBN} waits for responses to rpc's. You might use this if
12290 your VxWorks target is a slow software simulator or is on the far side
12291 of a thin network line.
12294 The following information on connecting to VxWorks was current when
12295 this manual was produced; newer releases of VxWorks may use revised
12298 @findex INCLUDE_RDB
12299 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
12300 to include the remote debugging interface routines in the VxWorks
12301 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
12302 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
12303 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
12304 source debugging task @code{tRdbTask} when VxWorks is booted. For more
12305 information on configuring and remaking VxWorks, see the manufacturer's
12307 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
12309 Once you have included @file{rdb.a} in your VxWorks system image and set
12310 your Unix execution search path to find @value{GDBN}, you are ready to
12311 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
12312 @code{vxgdb}, depending on your installation).
12314 @value{GDBN} comes up showing the prompt:
12321 * VxWorks Connection:: Connecting to VxWorks
12322 * VxWorks Download:: VxWorks download
12323 * VxWorks Attach:: Running tasks
12326 @node VxWorks Connection
12327 @subsubsection Connecting to VxWorks
12329 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
12330 network. To connect to a target whose host name is ``@code{tt}'', type:
12333 (vxgdb) target vxworks tt
12337 @value{GDBN} displays messages like these:
12340 Attaching remote machine across net...
12345 @value{GDBN} then attempts to read the symbol tables of any object modules
12346 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
12347 these files by searching the directories listed in the command search
12348 path (@pxref{Environment, ,Your program's environment}); if it fails
12349 to find an object file, it displays a message such as:
12352 prog.o: No such file or directory.
12355 When this happens, add the appropriate directory to the search path with
12356 the @value{GDBN} command @code{path}, and execute the @code{target}
12359 @node VxWorks Download
12360 @subsubsection VxWorks download
12362 @cindex download to VxWorks
12363 If you have connected to the VxWorks target and you want to debug an
12364 object that has not yet been loaded, you can use the @value{GDBN}
12365 @code{load} command to download a file from Unix to VxWorks
12366 incrementally. The object file given as an argument to the @code{load}
12367 command is actually opened twice: first by the VxWorks target in order
12368 to download the code, then by @value{GDBN} in order to read the symbol
12369 table. This can lead to problems if the current working directories on
12370 the two systems differ. If both systems have NFS mounted the same
12371 filesystems, you can avoid these problems by using absolute paths.
12372 Otherwise, it is simplest to set the working directory on both systems
12373 to the directory in which the object file resides, and then to reference
12374 the file by its name, without any path. For instance, a program
12375 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
12376 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
12377 program, type this on VxWorks:
12380 -> cd "@var{vxpath}/vw/demo/rdb"
12384 Then, in @value{GDBN}, type:
12387 (vxgdb) cd @var{hostpath}/vw/demo/rdb
12388 (vxgdb) load prog.o
12391 @value{GDBN} displays a response similar to this:
12394 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
12397 You can also use the @code{load} command to reload an object module
12398 after editing and recompiling the corresponding source file. Note that
12399 this makes @value{GDBN} delete all currently-defined breakpoints,
12400 auto-displays, and convenience variables, and to clear the value
12401 history. (This is necessary in order to preserve the integrity of
12402 debugger's data structures that reference the target system's symbol
12405 @node VxWorks Attach
12406 @subsubsection Running tasks
12408 @cindex running VxWorks tasks
12409 You can also attach to an existing task using the @code{attach} command as
12413 (vxgdb) attach @var{task}
12417 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
12418 or suspended when you attach to it. Running tasks are suspended at
12419 the time of attachment.
12421 @node Embedded Processors
12422 @section Embedded Processors
12424 This section goes into details specific to particular embedded
12430 * H8/300:: Renesas H8/300
12431 * H8/500:: Renesas H8/500
12432 * M32R/D:: Renesas M32R/D
12433 * M68K:: Motorola M68K
12434 * MIPS Embedded:: MIPS Embedded
12435 * OpenRISC 1000:: OpenRisc 1000
12436 * PA:: HP PA Embedded
12439 * Sparclet:: Tsqware Sparclet
12440 * Sparclite:: Fujitsu Sparclite
12441 * ST2000:: Tandem ST2000
12442 * Z8000:: Zilog Z8000
12451 @item target rdi @var{dev}
12452 ARM Angel monitor, via RDI library interface to ADP protocol. You may
12453 use this target to communicate with both boards running the Angel
12454 monitor, or with the EmbeddedICE JTAG debug device.
12457 @item target rdp @var{dev}
12463 @subsection Renesas H8/300
12467 @kindex target hms@r{, with H8/300}
12468 @item target hms @var{dev}
12469 A Renesas SH, H8/300, or H8/500 board, attached via serial line to your host.
12470 Use special commands @code{device} and @code{speed} to control the serial
12471 line and the communications speed used.
12473 @kindex target e7000@r{, with H8/300}
12474 @item target e7000 @var{dev}
12475 E7000 emulator for Renesas H8 and SH.
12477 @kindex target sh3@r{, with H8/300}
12478 @kindex target sh3e@r{, with H8/300}
12479 @item target sh3 @var{dev}
12480 @itemx target sh3e @var{dev}
12481 Renesas SH-3 and SH-3E target systems.
12485 @cindex download to H8/300 or H8/500
12486 @cindex H8/300 or H8/500 download
12487 @cindex download to Renesas SH
12488 @cindex Renesas SH download
12489 When you select remote debugging to a Renesas SH, H8/300, or H8/500
12490 board, the @code{load} command downloads your program to the Renesas
12491 board and also opens it as the current executable target for
12492 @value{GDBN} on your host (like the @code{file} command).
12494 @value{GDBN} needs to know these things to talk to your
12495 Renesas SH, H8/300, or H8/500:
12499 that you want to use @samp{target hms}, the remote debugging interface
12500 for Renesas microprocessors, or @samp{target e7000}, the in-circuit
12501 emulator for the Renesas SH and the Renesas 300H. (@samp{target hms} is
12502 the default when @value{GDBN} is configured specifically for the Renesas SH,
12503 H8/300, or H8/500.)
12506 what serial device connects your host to your Renesas board (the first
12507 serial device available on your host is the default).
12510 what speed to use over the serial device.
12514 * Renesas Boards:: Connecting to Renesas boards.
12515 * Renesas ICE:: Using the E7000 In-Circuit Emulator.
12516 * Renesas Special:: Special @value{GDBN} commands for Renesas micros.
12519 @node Renesas Boards
12520 @subsubsection Connecting to Renesas boards
12522 @c only for Unix hosts
12524 @cindex serial device, Renesas micros
12525 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
12526 need to explicitly set the serial device. The default @var{port} is the
12527 first available port on your host. This is only necessary on Unix
12528 hosts, where it is typically something like @file{/dev/ttya}.
12531 @cindex serial line speed, Renesas micros
12532 @code{@value{GDBN}} has another special command to set the communications
12533 speed: @samp{speed @var{bps}}. This command also is only used from Unix
12534 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
12535 the DOS @code{mode} command (for instance,
12536 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
12538 The @samp{device} and @samp{speed} commands are available only when you
12539 use a Unix host to debug your Renesas microprocessor programs. If you
12541 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
12542 called @code{asynctsr} to communicate with the development board
12543 through a PC serial port. You must also use the DOS @code{mode} command
12544 to set up the serial port on the DOS side.
12546 The following sample session illustrates the steps needed to start a
12547 program under @value{GDBN} control on an H8/300. The example uses a
12548 sample H8/300 program called @file{t.x}. The procedure is the same for
12549 the Renesas SH and the H8/500.
12551 First hook up your development board. In this example, we use a
12552 board attached to serial port @code{COM2}; if you use a different serial
12553 port, substitute its name in the argument of the @code{mode} command.
12554 When you call @code{asynctsr}, the auxiliary comms program used by the
12555 debugger, you give it just the numeric part of the serial port's name;
12556 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
12560 C:\H8300\TEST> asynctsr 2
12561 C:\H8300\TEST> mode com2:9600,n,8,1,p
12563 Resident portion of MODE loaded
12565 COM2: 9600, n, 8, 1, p
12570 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
12571 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
12572 disable it, or even boot without it, to use @code{asynctsr} to control
12573 your development board.
12576 @kindex target hms@r{, and serial protocol}
12577 Now that serial communications are set up, and the development board is
12578 connected, you can start up @value{GDBN}. Call @code{@value{GDBP}} with
12579 the name of your program as the argument. @code{@value{GDBN}} prompts
12580 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
12581 commands to begin your debugging session: @samp{target hms} to specify
12582 cross-debugging to the Renesas board, and the @code{load} command to
12583 download your program to the board. @code{load} displays the names of
12584 the program's sections, and a @samp{*} for each 2K of data downloaded.
12585 (If you want to refresh @value{GDBN} data on symbols or on the
12586 executable file without downloading, use the @value{GDBN} commands
12587 @code{file} or @code{symbol-file}. These commands, and @code{load}
12588 itself, are described in @ref{Files,,Commands to specify files}.)
12591 (eg-C:\H8300\TEST) @value{GDBP} t.x
12592 @value{GDBN} is free software and you are welcome to distribute copies
12593 of it under certain conditions; type "show copying" to see
12595 There is absolutely no warranty for @value{GDBN}; type "show warranty"
12597 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
12598 (@value{GDBP}) target hms
12599 Connected to remote H8/300 HMS system.
12600 (@value{GDBP}) load t.x
12601 .text : 0x8000 .. 0xabde ***********
12602 .data : 0xabde .. 0xad30 *
12603 .stack : 0xf000 .. 0xf014 *
12606 At this point, you're ready to run or debug your program. From here on,
12607 you can use all the usual @value{GDBN} commands. The @code{break} command
12608 sets breakpoints; the @code{run} command starts your program;
12609 @code{print} or @code{x} display data; the @code{continue} command
12610 resumes execution after stopping at a breakpoint. You can use the
12611 @code{help} command at any time to find out more about @value{GDBN} commands.
12613 Remember, however, that @emph{operating system} facilities aren't
12614 available on your development board; for example, if your program hangs,
12615 you can't send an interrupt---but you can press the @sc{reset} switch!
12617 Use the @sc{reset} button on the development board
12620 to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has
12621 no way to pass an interrupt signal to the development board); and
12624 to return to the @value{GDBN} command prompt after your program finishes
12625 normally. The communications protocol provides no other way for @value{GDBN}
12626 to detect program completion.
12629 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
12630 development board as a ``normal exit'' of your program.
12633 @subsubsection Using the E7000 in-circuit emulator
12635 @kindex target e7000@r{, with Renesas ICE}
12636 You can use the E7000 in-circuit emulator to develop code for either the
12637 Renesas SH or the H8/300H. Use one of these forms of the @samp{target
12638 e7000} command to connect @value{GDBN} to your E7000:
12641 @item target e7000 @var{port} @var{speed}
12642 Use this form if your E7000 is connected to a serial port. The
12643 @var{port} argument identifies what serial port to use (for example,
12644 @samp{com2}). The third argument is the line speed in bits per second
12645 (for example, @samp{9600}).
12647 @item target e7000 @var{hostname}
12648 If your E7000 is installed as a host on a TCP/IP network, you can just
12649 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
12652 @node Renesas Special
12653 @subsubsection Special @value{GDBN} commands for Renesas micros
12655 Some @value{GDBN} commands are available only for the H8/300:
12659 @kindex set machine
12660 @kindex show machine
12661 @item set machine h8300
12662 @itemx set machine h8300h
12663 Condition @value{GDBN} for one of the two variants of the H8/300
12664 architecture with @samp{set machine}. You can use @samp{show machine}
12665 to check which variant is currently in effect.
12674 @kindex set memory @var{mod}
12675 @cindex memory models, H8/500
12676 @item set memory @var{mod}
12678 Specify which H8/500 memory model (@var{mod}) you are using with
12679 @samp{set memory}; check which memory model is in effect with @samp{show
12680 memory}. The accepted values for @var{mod} are @code{small},
12681 @code{big}, @code{medium}, and @code{compact}.
12686 @subsection Renesas M32R/D
12690 @kindex target m32r
12691 @item target m32r @var{dev}
12692 Renesas M32R/D ROM monitor.
12694 @kindex target m32rsdi
12695 @item target m32rsdi @var{dev}
12696 Renesas M32R SDI server, connected via parallel port to the board.
12703 The Motorola m68k configuration includes ColdFire support, and
12704 target command for the following ROM monitors.
12708 @kindex target abug
12709 @item target abug @var{dev}
12710 ABug ROM monitor for M68K.
12712 @kindex target cpu32bug
12713 @item target cpu32bug @var{dev}
12714 CPU32BUG monitor, running on a CPU32 (M68K) board.
12716 @kindex target dbug
12717 @item target dbug @var{dev}
12718 dBUG ROM monitor for Motorola ColdFire.
12721 @item target est @var{dev}
12722 EST-300 ICE monitor, running on a CPU32 (M68K) board.
12724 @kindex target rom68k
12725 @item target rom68k @var{dev}
12726 ROM 68K monitor, running on an M68K IDP board.
12732 @kindex target rombug
12733 @item target rombug @var{dev}
12734 ROMBUG ROM monitor for OS/9000.
12738 @node MIPS Embedded
12739 @subsection MIPS Embedded
12741 @cindex MIPS boards
12742 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
12743 MIPS board attached to a serial line. This is available when
12744 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
12747 Use these @value{GDBN} commands to specify the connection to your target board:
12750 @item target mips @var{port}
12751 @kindex target mips @var{port}
12752 To run a program on the board, start up @code{@value{GDBP}} with the
12753 name of your program as the argument. To connect to the board, use the
12754 command @samp{target mips @var{port}}, where @var{port} is the name of
12755 the serial port connected to the board. If the program has not already
12756 been downloaded to the board, you may use the @code{load} command to
12757 download it. You can then use all the usual @value{GDBN} commands.
12759 For example, this sequence connects to the target board through a serial
12760 port, and loads and runs a program called @var{prog} through the
12764 host$ @value{GDBP} @var{prog}
12765 @value{GDBN} is free software and @dots{}
12766 (@value{GDBP}) target mips /dev/ttyb
12767 (@value{GDBP}) load @var{prog}
12771 @item target mips @var{hostname}:@var{portnumber}
12772 On some @value{GDBN} host configurations, you can specify a TCP
12773 connection (for instance, to a serial line managed by a terminal
12774 concentrator) instead of a serial port, using the syntax
12775 @samp{@var{hostname}:@var{portnumber}}.
12777 @item target pmon @var{port}
12778 @kindex target pmon @var{port}
12781 @item target ddb @var{port}
12782 @kindex target ddb @var{port}
12783 NEC's DDB variant of PMON for Vr4300.
12785 @item target lsi @var{port}
12786 @kindex target lsi @var{port}
12787 LSI variant of PMON.
12789 @kindex target r3900
12790 @item target r3900 @var{dev}
12791 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
12793 @kindex target array
12794 @item target array @var{dev}
12795 Array Tech LSI33K RAID controller board.
12801 @value{GDBN} also supports these special commands for MIPS targets:
12804 @item set processor @var{args}
12805 @itemx show processor
12806 @kindex set processor @var{args}
12807 @kindex show processor
12808 Use the @code{set processor} command to set the type of MIPS
12809 processor when you want to access processor-type-specific registers.
12810 For example, @code{set processor @var{r3041}} tells @value{GDBN}
12811 to use the CPU registers appropriate for the 3041 chip.
12812 Use the @code{show processor} command to see what MIPS processor @value{GDBN}
12813 is using. Use the @code{info reg} command to see what registers
12814 @value{GDBN} is using.
12816 @item set mipsfpu double
12817 @itemx set mipsfpu single
12818 @itemx set mipsfpu none
12819 @itemx show mipsfpu
12820 @kindex set mipsfpu
12821 @kindex show mipsfpu
12822 @cindex MIPS remote floating point
12823 @cindex floating point, MIPS remote
12824 If your target board does not support the MIPS floating point
12825 coprocessor, you should use the command @samp{set mipsfpu none} (if you
12826 need this, you may wish to put the command in your @value{GDBN} init
12827 file). This tells @value{GDBN} how to find the return value of
12828 functions which return floating point values. It also allows
12829 @value{GDBN} to avoid saving the floating point registers when calling
12830 functions on the board. If you are using a floating point coprocessor
12831 with only single precision floating point support, as on the @sc{r4650}
12832 processor, use the command @samp{set mipsfpu single}. The default
12833 double precision floating point coprocessor may be selected using
12834 @samp{set mipsfpu double}.
12836 In previous versions the only choices were double precision or no
12837 floating point, so @samp{set mipsfpu on} will select double precision
12838 and @samp{set mipsfpu off} will select no floating point.
12840 As usual, you can inquire about the @code{mipsfpu} variable with
12841 @samp{show mipsfpu}.
12843 @item set remotedebug @var{n}
12844 @itemx show remotedebug
12845 @kindex set remotedebug@r{, MIPS protocol}
12846 @kindex show remotedebug@r{, MIPS protocol}
12847 @cindex @code{remotedebug}, MIPS protocol
12848 @cindex MIPS @code{remotedebug} protocol
12849 @c FIXME! For this to be useful, you must know something about the MIPS
12850 @c FIXME...protocol. Where is it described?
12851 You can see some debugging information about communications with the board
12852 by setting the @code{remotedebug} variable. If you set it to @code{1} using
12853 @samp{set remotedebug 1}, every packet is displayed. If you set it
12854 to @code{2}, every character is displayed. You can check the current value
12855 at any time with the command @samp{show remotedebug}.
12857 @item set timeout @var{seconds}
12858 @itemx set retransmit-timeout @var{seconds}
12859 @itemx show timeout
12860 @itemx show retransmit-timeout
12861 @cindex @code{timeout}, MIPS protocol
12862 @cindex @code{retransmit-timeout}, MIPS protocol
12863 @kindex set timeout
12864 @kindex show timeout
12865 @kindex set retransmit-timeout
12866 @kindex show retransmit-timeout
12867 You can control the timeout used while waiting for a packet, in the MIPS
12868 remote protocol, with the @code{set timeout @var{seconds}} command. The
12869 default is 5 seconds. Similarly, you can control the timeout used while
12870 waiting for an acknowledgement of a packet with the @code{set
12871 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
12872 You can inspect both values with @code{show timeout} and @code{show
12873 retransmit-timeout}. (These commands are @emph{only} available when
12874 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
12876 The timeout set by @code{set timeout} does not apply when @value{GDBN}
12877 is waiting for your program to stop. In that case, @value{GDBN} waits
12878 forever because it has no way of knowing how long the program is going
12879 to run before stopping.
12882 @node OpenRISC 1000
12883 @subsection OpenRISC 1000
12884 @cindex OpenRISC 1000
12886 @cindex or1k boards
12887 See OR1k Architecture document (@uref{www.opencores.org}) for more information
12888 about platform and commands.
12892 @kindex target jtag
12893 @item target jtag jtag://@var{host}:@var{port}
12895 Connects to remote JTAG server.
12896 JTAG remote server can be either an or1ksim or JTAG server,
12897 connected via parallel port to the board.
12899 Example: @code{target jtag jtag://localhost:9999}
12902 @item or1ksim @var{command}
12903 If connected to @code{or1ksim} OpenRISC 1000 Architectural
12904 Simulator, proprietary commands can be executed.
12906 @kindex info or1k spr
12907 @item info or1k spr
12908 Displays spr groups.
12910 @item info or1k spr @var{group}
12911 @itemx info or1k spr @var{groupno}
12912 Displays register names in selected group.
12914 @item info or1k spr @var{group} @var{register}
12915 @itemx info or1k spr @var{register}
12916 @itemx info or1k spr @var{groupno} @var{registerno}
12917 @itemx info or1k spr @var{registerno}
12918 Shows information about specified spr register.
12921 @item spr @var{group} @var{register} @var{value}
12922 @itemx spr @var{register @var{value}}
12923 @itemx spr @var{groupno} @var{registerno @var{value}}
12924 @itemx spr @var{registerno @var{value}}
12925 Writes @var{value} to specified spr register.
12928 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
12929 It is very similar to @value{GDBN} trace, except it does not interfere with normal
12930 program execution and is thus much faster. Hardware breakpoints/watchpoint
12931 triggers can be set using:
12934 Load effective address/data
12936 Store effective address/data
12938 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
12943 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
12944 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
12946 @code{htrace} commands:
12947 @cindex OpenRISC 1000 htrace
12950 @item hwatch @var{conditional}
12951 Set hardware watchpoint on combination of Load/Store Effecive Address(es)
12952 or Data. For example:
12954 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
12956 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
12960 Display information about current HW trace configuration.
12962 @item htrace trigger @var{conditional}
12963 Set starting criteria for HW trace.
12965 @item htrace qualifier @var{conditional}
12966 Set acquisition qualifier for HW trace.
12968 @item htrace stop @var{conditional}
12969 Set HW trace stopping criteria.
12971 @item htrace record [@var{data}]*
12972 Selects the data to be recorded, when qualifier is met and HW trace was
12975 @item htrace enable
12976 @itemx htrace disable
12977 Enables/disables the HW trace.
12979 @item htrace rewind [@var{filename}]
12980 Clears currently recorded trace data.
12982 If filename is specified, new trace file is made and any newly collected data
12983 will be written there.
12985 @item htrace print [@var{start} [@var{len}]]
12986 Prints trace buffer, using current record configuration.
12988 @item htrace mode continuous
12989 Set continuous trace mode.
12991 @item htrace mode suspend
12992 Set suspend trace mode.
12997 @subsection PowerPC
13001 @kindex target dink32
13002 @item target dink32 @var{dev}
13003 DINK32 ROM monitor.
13005 @kindex target ppcbug
13006 @item target ppcbug @var{dev}
13007 @kindex target ppcbug1
13008 @item target ppcbug1 @var{dev}
13009 PPCBUG ROM monitor for PowerPC.
13012 @item target sds @var{dev}
13013 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
13018 @subsection HP PA Embedded
13022 @kindex target op50n
13023 @item target op50n @var{dev}
13024 OP50N monitor, running on an OKI HPPA board.
13026 @kindex target w89k
13027 @item target w89k @var{dev}
13028 W89K monitor, running on a Winbond HPPA board.
13033 @subsection Renesas SH
13037 @kindex target hms@r{, with Renesas SH}
13038 @item target hms @var{dev}
13039 A Renesas SH board attached via serial line to your host. Use special
13040 commands @code{device} and @code{speed} to control the serial line and
13041 the communications speed used.
13043 @kindex target e7000@r{, with Renesas SH}
13044 @item target e7000 @var{dev}
13045 E7000 emulator for Renesas SH.
13047 @kindex target sh3@r{, with SH}
13048 @kindex target sh3e@r{, with SH}
13049 @item target sh3 @var{dev}
13050 @item target sh3e @var{dev}
13051 Renesas SH-3 and SH-3E target systems.
13056 @subsection Tsqware Sparclet
13060 @value{GDBN} enables developers to debug tasks running on
13061 Sparclet targets from a Unix host.
13062 @value{GDBN} uses code that runs on
13063 both the Unix host and on the Sparclet target. The program
13064 @code{@value{GDBP}} is installed and executed on the Unix host.
13067 @item remotetimeout @var{args}
13068 @kindex remotetimeout
13069 @value{GDBN} supports the option @code{remotetimeout}.
13070 This option is set by the user, and @var{args} represents the number of
13071 seconds @value{GDBN} waits for responses.
13074 @cindex compiling, on Sparclet
13075 When compiling for debugging, include the options @samp{-g} to get debug
13076 information and @samp{-Ttext} to relocate the program to where you wish to
13077 load it on the target. You may also want to add the options @samp{-n} or
13078 @samp{-N} in order to reduce the size of the sections. Example:
13081 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
13084 You can use @code{objdump} to verify that the addresses are what you intended:
13087 sparclet-aout-objdump --headers --syms prog
13090 @cindex running, on Sparclet
13092 your Unix execution search path to find @value{GDBN}, you are ready to
13093 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
13094 (or @code{sparclet-aout-gdb}, depending on your installation).
13096 @value{GDBN} comes up showing the prompt:
13103 * Sparclet File:: Setting the file to debug
13104 * Sparclet Connection:: Connecting to Sparclet
13105 * Sparclet Download:: Sparclet download
13106 * Sparclet Execution:: Running and debugging
13109 @node Sparclet File
13110 @subsubsection Setting file to debug
13112 The @value{GDBN} command @code{file} lets you choose with program to debug.
13115 (gdbslet) file prog
13119 @value{GDBN} then attempts to read the symbol table of @file{prog}.
13120 @value{GDBN} locates
13121 the file by searching the directories listed in the command search
13123 If the file was compiled with debug information (option "-g"), source
13124 files will be searched as well.
13125 @value{GDBN} locates
13126 the source files by searching the directories listed in the directory search
13127 path (@pxref{Environment, ,Your program's environment}).
13129 to find a file, it displays a message such as:
13132 prog: No such file or directory.
13135 When this happens, add the appropriate directories to the search paths with
13136 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
13137 @code{target} command again.
13139 @node Sparclet Connection
13140 @subsubsection Connecting to Sparclet
13142 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
13143 To connect to a target on serial port ``@code{ttya}'', type:
13146 (gdbslet) target sparclet /dev/ttya
13147 Remote target sparclet connected to /dev/ttya
13148 main () at ../prog.c:3
13152 @value{GDBN} displays messages like these:
13158 @node Sparclet Download
13159 @subsubsection Sparclet download
13161 @cindex download to Sparclet
13162 Once connected to the Sparclet target,
13163 you can use the @value{GDBN}
13164 @code{load} command to download the file from the host to the target.
13165 The file name and load offset should be given as arguments to the @code{load}
13167 Since the file format is aout, the program must be loaded to the starting
13168 address. You can use @code{objdump} to find out what this value is. The load
13169 offset is an offset which is added to the VMA (virtual memory address)
13170 of each of the file's sections.
13171 For instance, if the program
13172 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
13173 and bss at 0x12010170, in @value{GDBN}, type:
13176 (gdbslet) load prog 0x12010000
13177 Loading section .text, size 0xdb0 vma 0x12010000
13180 If the code is loaded at a different address then what the program was linked
13181 to, you may need to use the @code{section} and @code{add-symbol-file} commands
13182 to tell @value{GDBN} where to map the symbol table.
13184 @node Sparclet Execution
13185 @subsubsection Running and debugging
13187 @cindex running and debugging Sparclet programs
13188 You can now begin debugging the task using @value{GDBN}'s execution control
13189 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
13190 manual for the list of commands.
13194 Breakpoint 1 at 0x12010000: file prog.c, line 3.
13196 Starting program: prog
13197 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
13198 3 char *symarg = 0;
13200 4 char *execarg = "hello!";
13205 @subsection Fujitsu Sparclite
13209 @kindex target sparclite
13210 @item target sparclite @var{dev}
13211 Fujitsu sparclite boards, used only for the purpose of loading.
13212 You must use an additional command to debug the program.
13213 For example: target remote @var{dev} using @value{GDBN} standard
13219 @subsection Tandem ST2000
13221 @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
13224 To connect your ST2000 to the host system, see the manufacturer's
13225 manual. Once the ST2000 is physically attached, you can run:
13228 target st2000 @var{dev} @var{speed}
13232 to establish it as your debugging environment. @var{dev} is normally
13233 the name of a serial device, such as @file{/dev/ttya}, connected to the
13234 ST2000 via a serial line. You can instead specify @var{dev} as a TCP
13235 connection (for example, to a serial line attached via a terminal
13236 concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
13238 The @code{load} and @code{attach} commands are @emph{not} defined for
13239 this target; you must load your program into the ST2000 as you normally
13240 would for standalone operation. @value{GDBN} reads debugging information
13241 (such as symbols) from a separate, debugging version of the program
13242 available on your host computer.
13243 @c FIXME!! This is terribly vague; what little content is here is
13244 @c basically hearsay.
13246 @cindex ST2000 auxiliary commands
13247 These auxiliary @value{GDBN} commands are available to help you with the ST2000
13251 @item st2000 @var{command}
13252 @kindex st2000 @var{cmd}
13253 @cindex STDBUG commands (ST2000)
13254 @cindex commands to STDBUG (ST2000)
13255 Send a @var{command} to the STDBUG monitor. See the manufacturer's
13256 manual for available commands.
13259 @cindex connect (to STDBUG)
13260 Connect the controlling terminal to the STDBUG command monitor. When
13261 you are done interacting with STDBUG, typing either of two character
13262 sequences gets you back to the @value{GDBN} command prompt:
13263 @kbd{@key{RET}~.} (Return, followed by tilde and period) or
13264 @kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D).
13268 @subsection Zilog Z8000
13271 @cindex simulator, Z8000
13272 @cindex Zilog Z8000 simulator
13274 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
13277 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
13278 unsegmented variant of the Z8000 architecture) or the Z8001 (the
13279 segmented variant). The simulator recognizes which architecture is
13280 appropriate by inspecting the object code.
13283 @item target sim @var{args}
13285 @kindex target sim@r{, with Z8000}
13286 Debug programs on a simulated CPU. If the simulator supports setup
13287 options, specify them via @var{args}.
13291 After specifying this target, you can debug programs for the simulated
13292 CPU in the same style as programs for your host computer; use the
13293 @code{file} command to load a new program image, the @code{run} command
13294 to run your program, and so on.
13296 As well as making available all the usual machine registers
13297 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
13298 additional items of information as specially named registers:
13303 Counts clock-ticks in the simulator.
13306 Counts instructions run in the simulator.
13309 Execution time in 60ths of a second.
13313 You can refer to these values in @value{GDBN} expressions with the usual
13314 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
13315 conditional breakpoint that suspends only after at least 5000
13316 simulated clock ticks.
13318 @node Architectures
13319 @section Architectures
13321 This section describes characteristics of architectures that affect
13322 all uses of @value{GDBN} with the architecture, both native and cross.
13335 @kindex set rstack_high_address
13336 @cindex AMD 29K register stack
13337 @cindex register stack, AMD29K
13338 @item set rstack_high_address @var{address}
13339 On AMD 29000 family processors, registers are saved in a separate
13340 @dfn{register stack}. There is no way for @value{GDBN} to determine the
13341 extent of this stack. Normally, @value{GDBN} just assumes that the
13342 stack is ``large enough''. This may result in @value{GDBN} referencing
13343 memory locations that do not exist. If necessary, you can get around
13344 this problem by specifying the ending address of the register stack with
13345 the @code{set rstack_high_address} command. The argument should be an
13346 address, which you probably want to precede with @samp{0x} to specify in
13349 @kindex show rstack_high_address
13350 @item show rstack_high_address
13351 Display the current limit of the register stack, on AMD 29000 family
13359 See the following section.
13364 @cindex stack on Alpha
13365 @cindex stack on MIPS
13366 @cindex Alpha stack
13368 Alpha- and MIPS-based computers use an unusual stack frame, which
13369 sometimes requires @value{GDBN} to search backward in the object code to
13370 find the beginning of a function.
13372 @cindex response time, MIPS debugging
13373 To improve response time (especially for embedded applications, where
13374 @value{GDBN} may be restricted to a slow serial line for this search)
13375 you may want to limit the size of this search, using one of these
13379 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
13380 @item set heuristic-fence-post @var{limit}
13381 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
13382 search for the beginning of a function. A value of @var{0} (the
13383 default) means there is no limit. However, except for @var{0}, the
13384 larger the limit the more bytes @code{heuristic-fence-post} must search
13385 and therefore the longer it takes to run.
13387 @item show heuristic-fence-post
13388 Display the current limit.
13392 These commands are available @emph{only} when @value{GDBN} is configured
13393 for debugging programs on Alpha or MIPS processors.
13396 @node Controlling GDB
13397 @chapter Controlling @value{GDBN}
13399 You can alter the way @value{GDBN} interacts with you by using the
13400 @code{set} command. For commands controlling how @value{GDBN} displays
13401 data, see @ref{Print Settings, ,Print settings}. Other settings are
13406 * Editing:: Command editing
13407 * History:: Command history
13408 * Screen Size:: Screen size
13409 * Numbers:: Numbers
13410 * ABI:: Configuring the current ABI
13411 * Messages/Warnings:: Optional warnings and messages
13412 * Debugging Output:: Optional messages about internal happenings
13420 @value{GDBN} indicates its readiness to read a command by printing a string
13421 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
13422 can change the prompt string with the @code{set prompt} command. For
13423 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
13424 the prompt in one of the @value{GDBN} sessions so that you can always tell
13425 which one you are talking to.
13427 @emph{Note:} @code{set prompt} does not add a space for you after the
13428 prompt you set. This allows you to set a prompt which ends in a space
13429 or a prompt that does not.
13433 @item set prompt @var{newprompt}
13434 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
13436 @kindex show prompt
13438 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
13442 @section Command editing
13444 @cindex command line editing
13446 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
13447 @sc{gnu} library provides consistent behavior for programs which provide a
13448 command line interface to the user. Advantages are @sc{gnu} Emacs-style
13449 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
13450 substitution, and a storage and recall of command history across
13451 debugging sessions.
13453 You may control the behavior of command line editing in @value{GDBN} with the
13454 command @code{set}.
13457 @kindex set editing
13460 @itemx set editing on
13461 Enable command line editing (enabled by default).
13463 @item set editing off
13464 Disable command line editing.
13466 @kindex show editing
13468 Show whether command line editing is enabled.
13471 @xref{Command Line Editing}, for more details about the Readline
13472 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
13473 encouraged to read that chapter.
13476 @section Command history
13477 @cindex command history
13479 @value{GDBN} can keep track of the commands you type during your
13480 debugging sessions, so that you can be certain of precisely what
13481 happened. Use these commands to manage the @value{GDBN} command
13484 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
13485 package, to provide the history facility. @xref{Using History
13486 Interactively}, for the detailed description of the History library.
13488 Here is the description of @value{GDBN} commands related to command
13492 @cindex history substitution
13493 @cindex history file
13494 @kindex set history filename
13495 @cindex @env{GDBHISTFILE}, environment variable
13496 @item set history filename @var{fname}
13497 Set the name of the @value{GDBN} command history file to @var{fname}.
13498 This is the file where @value{GDBN} reads an initial command history
13499 list, and where it writes the command history from this session when it
13500 exits. You can access this list through history expansion or through
13501 the history command editing characters listed below. This file defaults
13502 to the value of the environment variable @code{GDBHISTFILE}, or to
13503 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
13506 @cindex history save
13507 @kindex set history
13508 @item set history save
13509 @itemx set history save on
13510 Record command history in a file, whose name may be specified with the
13511 @code{set history filename} command. By default, this option is disabled.
13513 @item set history save off
13514 Stop recording command history in a file.
13516 @cindex history size
13517 @item set history size @var{size}
13518 Set the number of commands which @value{GDBN} keeps in its history list.
13519 This defaults to the value of the environment variable
13520 @code{HISTSIZE}, or to 256 if this variable is not set.
13523 History expansion assigns special meaning to the character @kbd{!}.
13524 @xref{Event Designators}, for more details.
13526 @cindex history expansion, turn on/off
13527 Since @kbd{!} is also the logical not operator in C, history expansion
13528 is off by default. If you decide to enable history expansion with the
13529 @code{set history expansion on} command, you may sometimes need to
13530 follow @kbd{!} (when it is used as logical not, in an expression) with
13531 a space or a tab to prevent it from being expanded. The readline
13532 history facilities do not attempt substitution on the strings
13533 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
13535 The commands to control history expansion are:
13538 @item set history expansion on
13539 @itemx set history expansion
13540 @kindex set history expansion
13541 Enable history expansion. History expansion is off by default.
13543 @item set history expansion off
13544 Disable history expansion.
13547 @kindex show history
13549 @itemx show history filename
13550 @itemx show history save
13551 @itemx show history size
13552 @itemx show history expansion
13553 These commands display the state of the @value{GDBN} history parameters.
13554 @code{show history} by itself displays all four states.
13560 @item show commands
13561 Display the last ten commands in the command history.
13563 @item show commands @var{n}
13564 Print ten commands centered on command number @var{n}.
13566 @item show commands +
13567 Print ten commands just after the commands last printed.
13571 @section Screen size
13572 @cindex size of screen
13573 @cindex pauses in output
13575 Certain commands to @value{GDBN} may produce large amounts of
13576 information output to the screen. To help you read all of it,
13577 @value{GDBN} pauses and asks you for input at the end of each page of
13578 output. Type @key{RET} when you want to continue the output, or @kbd{q}
13579 to discard the remaining output. Also, the screen width setting
13580 determines when to wrap lines of output. Depending on what is being
13581 printed, @value{GDBN} tries to break the line at a readable place,
13582 rather than simply letting it overflow onto the following line.
13584 Normally @value{GDBN} knows the size of the screen from the terminal
13585 driver software. For example, on Unix @value{GDBN} uses the termcap data base
13586 together with the value of the @code{TERM} environment variable and the
13587 @code{stty rows} and @code{stty cols} settings. If this is not correct,
13588 you can override it with the @code{set height} and @code{set
13595 @kindex show height
13596 @item set height @var{lpp}
13598 @itemx set width @var{cpl}
13600 These @code{set} commands specify a screen height of @var{lpp} lines and
13601 a screen width of @var{cpl} characters. The associated @code{show}
13602 commands display the current settings.
13604 If you specify a height of zero lines, @value{GDBN} does not pause during
13605 output no matter how long the output is. This is useful if output is to a
13606 file or to an editor buffer.
13608 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
13609 from wrapping its output.
13614 @cindex number representation
13615 @cindex entering numbers
13617 You can always enter numbers in octal, decimal, or hexadecimal in
13618 @value{GDBN} by the usual conventions: octal numbers begin with
13619 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
13620 begin with @samp{0x}. Numbers that begin with none of these are, by
13621 default, entered in base 10; likewise, the default display for
13622 numbers---when no particular format is specified---is base 10. You can
13623 change the default base for both input and output with the @code{set
13627 @kindex set input-radix
13628 @item set input-radix @var{base}
13629 Set the default base for numeric input. Supported choices
13630 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
13631 specified either unambiguously or using the current default radix; for
13641 sets the base to decimal. On the other hand, @samp{set radix 10}
13642 leaves the radix unchanged no matter what it was.
13644 @kindex set output-radix
13645 @item set output-radix @var{base}
13646 Set the default base for numeric display. Supported choices
13647 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
13648 specified either unambiguously or using the current default radix.
13650 @kindex show input-radix
13651 @item show input-radix
13652 Display the current default base for numeric input.
13654 @kindex show output-radix
13655 @item show output-radix
13656 Display the current default base for numeric display.
13660 @section Configuring the current ABI
13662 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
13663 application automatically. However, sometimes you need to override its
13664 conclusions. Use these commands to manage @value{GDBN}'s view of the
13671 One @value{GDBN} configuration can debug binaries for multiple operating
13672 system targets, either via remote debugging or native emulation.
13673 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
13674 but you can override its conclusion using the @code{set osabi} command.
13675 One example where this is useful is in debugging of binaries which use
13676 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
13677 not have the same identifying marks that the standard C library for your
13682 Show the OS ABI currently in use.
13685 With no argument, show the list of registered available OS ABI's.
13687 @item set osabi @var{abi}
13688 Set the current OS ABI to @var{abi}.
13691 @cindex float promotion
13692 @kindex set coerce-float-to-double
13694 Generally, the way that an argument of type @code{float} is passed to a
13695 function depends on whether the function is prototyped. For a prototyped
13696 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
13697 according to the architecture's convention for @code{float}. For unprototyped
13698 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
13699 @code{double} and then passed.
13701 Unfortunately, some forms of debug information do not reliably indicate whether
13702 a function is prototyped. If @value{GDBN} calls a function that is not marked
13703 as prototyped, it consults @kbd{set coerce-float-to-double}.
13706 @item set coerce-float-to-double
13707 @itemx set coerce-float-to-double on
13708 Arguments of type @code{float} will be promoted to @code{double} when passed
13709 to an unprototyped function. This is the default setting.
13711 @item set coerce-float-to-double off
13712 Arguments of type @code{float} will be passed directly to unprototyped
13717 @kindex show cp-abi
13718 @value{GDBN} needs to know the ABI used for your program's C@t{++}
13719 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
13720 used to build your application. @value{GDBN} only fully supports
13721 programs with a single C@t{++} ABI; if your program contains code using
13722 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
13723 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
13724 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
13725 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
13726 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
13727 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
13732 Show the C@t{++} ABI currently in use.
13735 With no argument, show the list of supported C@t{++} ABI's.
13737 @item set cp-abi @var{abi}
13738 @itemx set cp-abi auto
13739 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
13742 @node Messages/Warnings
13743 @section Optional warnings and messages
13745 By default, @value{GDBN} is silent about its inner workings. If you are
13746 running on a slow machine, you may want to use the @code{set verbose}
13747 command. This makes @value{GDBN} tell you when it does a lengthy
13748 internal operation, so you will not think it has crashed.
13750 Currently, the messages controlled by @code{set verbose} are those
13751 which announce that the symbol table for a source file is being read;
13752 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
13755 @kindex set verbose
13756 @item set verbose on
13757 Enables @value{GDBN} output of certain informational messages.
13759 @item set verbose off
13760 Disables @value{GDBN} output of certain informational messages.
13762 @kindex show verbose
13764 Displays whether @code{set verbose} is on or off.
13767 By default, if @value{GDBN} encounters bugs in the symbol table of an
13768 object file, it is silent; but if you are debugging a compiler, you may
13769 find this information useful (@pxref{Symbol Errors, ,Errors reading
13774 @kindex set complaints
13775 @item set complaints @var{limit}
13776 Permits @value{GDBN} to output @var{limit} complaints about each type of
13777 unusual symbols before becoming silent about the problem. Set
13778 @var{limit} to zero to suppress all complaints; set it to a large number
13779 to prevent complaints from being suppressed.
13781 @kindex show complaints
13782 @item show complaints
13783 Displays how many symbol complaints @value{GDBN} is permitted to produce.
13787 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
13788 lot of stupid questions to confirm certain commands. For example, if
13789 you try to run a program which is already running:
13793 The program being debugged has been started already.
13794 Start it from the beginning? (y or n)
13797 If you are willing to unflinchingly face the consequences of your own
13798 commands, you can disable this ``feature'':
13802 @kindex set confirm
13804 @cindex confirmation
13805 @cindex stupid questions
13806 @item set confirm off
13807 Disables confirmation requests.
13809 @item set confirm on
13810 Enables confirmation requests (the default).
13812 @kindex show confirm
13814 Displays state of confirmation requests.
13818 @node Debugging Output
13819 @section Optional messages about internal happenings
13820 @cindex optional debugging messages
13824 @cindex gdbarch debugging info
13825 @item set debug arch
13826 Turns on or off display of gdbarch debugging info. The default is off
13828 @item show debug arch
13829 Displays the current state of displaying gdbarch debugging info.
13830 @item set debug event
13831 @cindex event debugging info
13832 Turns on or off display of @value{GDBN} event debugging info. The
13834 @item show debug event
13835 Displays the current state of displaying @value{GDBN} event debugging
13837 @item set debug expression
13838 @cindex expression debugging info
13839 Turns on or off display of @value{GDBN} expression debugging info. The
13841 @item show debug expression
13842 Displays the current state of displaying @value{GDBN} expression
13844 @item set debug frame
13845 @cindex frame debugging info
13846 Turns on or off display of @value{GDBN} frame debugging info. The
13848 @item show debug frame
13849 Displays the current state of displaying @value{GDBN} frame debugging
13851 @item set debug observer
13852 @cindex observer debugging info
13853 Turns on or off display of @value{GDBN} observer debugging. This
13854 includes info such as the notification of observable events.
13855 @item show debug observer
13856 Displays the current state of observer debugging.
13857 @item set debug overload
13858 @cindex C@t{++} overload debugging info
13859 Turns on or off display of @value{GDBN} C@t{++} overload debugging
13860 info. This includes info such as ranking of functions, etc. The default
13862 @item show debug overload
13863 Displays the current state of displaying @value{GDBN} C@t{++} overload
13865 @cindex packets, reporting on stdout
13866 @cindex serial connections, debugging
13867 @item set debug remote
13868 Turns on or off display of reports on all packets sent back and forth across
13869 the serial line to the remote machine. The info is printed on the
13870 @value{GDBN} standard output stream. The default is off.
13871 @item show debug remote
13872 Displays the state of display of remote packets.
13873 @item set debug serial
13874 Turns on or off display of @value{GDBN} serial debugging info. The
13876 @item show debug serial
13877 Displays the current state of displaying @value{GDBN} serial debugging
13879 @item set debug target
13880 @cindex target debugging info
13881 Turns on or off display of @value{GDBN} target debugging info. This info
13882 includes what is going on at the target level of GDB, as it happens. The
13883 default is 0. Set it to 1 to track events, and to 2 to also track the
13884 value of large memory transfers. Changes to this flag do not take effect
13885 until the next time you connect to a target or use the @code{run} command.
13886 @item show debug target
13887 Displays the current state of displaying @value{GDBN} target debugging
13889 @item set debug varobj
13890 @cindex variable object debugging info
13891 Turns on or off display of @value{GDBN} variable object debugging
13892 info. The default is off.
13893 @item show debug varobj
13894 Displays the current state of displaying @value{GDBN} variable object
13899 @chapter Canned Sequences of Commands
13901 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
13902 command lists}), @value{GDBN} provides two ways to store sequences of
13903 commands for execution as a unit: user-defined commands and command
13907 * Define:: User-defined commands
13908 * Hooks:: User-defined command hooks
13909 * Command Files:: Command files
13910 * Output:: Commands for controlled output
13914 @section User-defined commands
13916 @cindex user-defined command
13917 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
13918 which you assign a new name as a command. This is done with the
13919 @code{define} command. User commands may accept up to 10 arguments
13920 separated by whitespace. Arguments are accessed within the user command
13921 via @var{$arg0@dots{}$arg9}. A trivial example:
13925 print $arg0 + $arg1 + $arg2
13929 To execute the command use:
13936 This defines the command @code{adder}, which prints the sum of
13937 its three arguments. Note the arguments are text substitutions, so they may
13938 reference variables, use complex expressions, or even perform inferior
13944 @item define @var{commandname}
13945 Define a command named @var{commandname}. If there is already a command
13946 by that name, you are asked to confirm that you want to redefine it.
13948 The definition of the command is made up of other @value{GDBN} command lines,
13949 which are given following the @code{define} command. The end of these
13950 commands is marked by a line containing @code{end}.
13955 Takes a single argument, which is an expression to evaluate.
13956 It is followed by a series of commands that are executed
13957 only if the expression is true (nonzero).
13958 There can then optionally be a line @code{else}, followed
13959 by a series of commands that are only executed if the expression
13960 was false. The end of the list is marked by a line containing @code{end}.
13964 The syntax is similar to @code{if}: the command takes a single argument,
13965 which is an expression to evaluate, and must be followed by the commands to
13966 execute, one per line, terminated by an @code{end}.
13967 The commands are executed repeatedly as long as the expression
13971 @item document @var{commandname}
13972 Document the user-defined command @var{commandname}, so that it can be
13973 accessed by @code{help}. The command @var{commandname} must already be
13974 defined. This command reads lines of documentation just as @code{define}
13975 reads the lines of the command definition, ending with @code{end}.
13976 After the @code{document} command is finished, @code{help} on command
13977 @var{commandname} displays the documentation you have written.
13979 You may use the @code{document} command again to change the
13980 documentation of a command. Redefining the command with @code{define}
13981 does not change the documentation.
13983 @kindex help user-defined
13984 @item help user-defined
13985 List all user-defined commands, with the first line of the documentation
13990 @itemx show user @var{commandname}
13991 Display the @value{GDBN} commands used to define @var{commandname} (but
13992 not its documentation). If no @var{commandname} is given, display the
13993 definitions for all user-defined commands.
13995 @kindex show max-user-call-depth
13996 @kindex set max-user-call-depth
13997 @item show max-user-call-depth
13998 @itemx set max-user-call-depth
13999 The value of @code{max-user-call-depth} controls how many recursion
14000 levels are allowed in user-defined commands before GDB suspects an
14001 infinite recursion and aborts the command.
14005 When user-defined commands are executed, the
14006 commands of the definition are not printed. An error in any command
14007 stops execution of the user-defined command.
14009 If used interactively, commands that would ask for confirmation proceed
14010 without asking when used inside a user-defined command. Many @value{GDBN}
14011 commands that normally print messages to say what they are doing omit the
14012 messages when used in a user-defined command.
14015 @section User-defined command hooks
14016 @cindex command hooks
14017 @cindex hooks, for commands
14018 @cindex hooks, pre-command
14021 You may define @dfn{hooks}, which are a special kind of user-defined
14022 command. Whenever you run the command @samp{foo}, if the user-defined
14023 command @samp{hook-foo} exists, it is executed (with no arguments)
14024 before that command.
14026 @cindex hooks, post-command
14028 A hook may also be defined which is run after the command you executed.
14029 Whenever you run the command @samp{foo}, if the user-defined command
14030 @samp{hookpost-foo} exists, it is executed (with no arguments) after
14031 that command. Post-execution hooks may exist simultaneously with
14032 pre-execution hooks, for the same command.
14034 It is valid for a hook to call the command which it hooks. If this
14035 occurs, the hook is not re-executed, thereby avoiding infinte recursion.
14037 @c It would be nice if hookpost could be passed a parameter indicating
14038 @c if the command it hooks executed properly or not. FIXME!
14040 @kindex stop@r{, a pseudo-command}
14041 In addition, a pseudo-command, @samp{stop} exists. Defining
14042 (@samp{hook-stop}) makes the associated commands execute every time
14043 execution stops in your program: before breakpoint commands are run,
14044 displays are printed, or the stack frame is printed.
14046 For example, to ignore @code{SIGALRM} signals while
14047 single-stepping, but treat them normally during normal execution,
14052 handle SIGALRM nopass
14056 handle SIGALRM pass
14059 define hook-continue
14060 handle SIGLARM pass
14064 As a further example, to hook at the begining and end of the @code{echo}
14065 command, and to add extra text to the beginning and end of the message,
14073 define hookpost-echo
14077 (@value{GDBP}) echo Hello World
14078 <<<---Hello World--->>>
14083 You can define a hook for any single-word command in @value{GDBN}, but
14084 not for command aliases; you should define a hook for the basic command
14085 name, e.g. @code{backtrace} rather than @code{bt}.
14086 @c FIXME! So how does Joe User discover whether a command is an alias
14088 If an error occurs during the execution of your hook, execution of
14089 @value{GDBN} commands stops and @value{GDBN} issues a prompt
14090 (before the command that you actually typed had a chance to run).
14092 If you try to define a hook which does not match any known command, you
14093 get a warning from the @code{define} command.
14095 @node Command Files
14096 @section Command files
14098 @cindex command files
14099 A command file for @value{GDBN} is a file of lines that are @value{GDBN}
14100 commands. Comments (lines starting with @kbd{#}) may also be included.
14101 An empty line in a command file does nothing; it does not mean to repeat
14102 the last command, as it would from the terminal.
14105 @cindex @file{.gdbinit}
14106 @cindex @file{gdb.ini}
14107 When you start @value{GDBN}, it automatically executes commands from its
14108 @dfn{init files}, normally called @file{.gdbinit}@footnote{The DJGPP
14109 port of @value{GDBN} uses the name @file{gdb.ini} instead, due to the
14110 limitations of file names imposed by DOS filesystems.}.
14111 During startup, @value{GDBN} does the following:
14115 Reads the init file (if any) in your home directory@footnote{On
14116 DOS/Windows systems, the home directory is the one pointed to by the
14117 @code{HOME} environment variable.}.
14120 Processes command line options and operands.
14123 Reads the init file (if any) in the current working directory.
14126 Reads command files specified by the @samp{-x} option.
14129 The init file in your home directory can set options (such as @samp{set
14130 complaints}) that affect subsequent processing of command line options
14131 and operands. Init files are not executed if you use the @samp{-nx}
14132 option (@pxref{Mode Options, ,Choosing modes}).
14134 @cindex init file name
14135 On some configurations of @value{GDBN}, the init file is known by a
14136 different name (these are typically environments where a specialized
14137 form of @value{GDBN} may need to coexist with other forms, hence a
14138 different name for the specialized version's init file). These are the
14139 environments with special init file names:
14141 @cindex @file{.vxgdbinit}
14144 VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit}
14146 @cindex @file{.os68gdbinit}
14148 OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit}
14150 @cindex @file{.esgdbinit}
14152 ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit}
14155 You can also request the execution of a command file with the
14156 @code{source} command:
14160 @item source @var{filename}
14161 Execute the command file @var{filename}.
14164 The lines in a command file are executed sequentially. They are not
14165 printed as they are executed. An error in any command terminates
14166 execution of the command file and control is returned to the console.
14168 Commands that would ask for confirmation if used interactively proceed
14169 without asking when used in a command file. Many @value{GDBN} commands that
14170 normally print messages to say what they are doing omit the messages
14171 when called from command files.
14173 @value{GDBN} also accepts command input from standard input. In this
14174 mode, normal output goes to standard output and error output goes to
14175 standard error. Errors in a command file supplied on standard input do
14176 not terminate execution of the command file --- execution continues with
14180 gdb < cmds > log 2>&1
14183 (The syntax above will vary depending on the shell used.) This example
14184 will execute commands from the file @file{cmds}. All output and errors
14185 would be directed to @file{log}.
14188 @section Commands for controlled output
14190 During the execution of a command file or a user-defined command, normal
14191 @value{GDBN} output is suppressed; the only output that appears is what is
14192 explicitly printed by the commands in the definition. This section
14193 describes three commands useful for generating exactly the output you
14198 @item echo @var{text}
14199 @c I do not consider backslash-space a standard C escape sequence
14200 @c because it is not in ANSI.
14201 Print @var{text}. Nonprinting characters can be included in
14202 @var{text} using C escape sequences, such as @samp{\n} to print a
14203 newline. @strong{No newline is printed unless you specify one.}
14204 In addition to the standard C escape sequences, a backslash followed
14205 by a space stands for a space. This is useful for displaying a
14206 string with spaces at the beginning or the end, since leading and
14207 trailing spaces are otherwise trimmed from all arguments.
14208 To print @samp{@w{ }and foo =@w{ }}, use the command
14209 @samp{echo \@w{ }and foo = \@w{ }}.
14211 A backslash at the end of @var{text} can be used, as in C, to continue
14212 the command onto subsequent lines. For example,
14215 echo This is some text\n\
14216 which is continued\n\
14217 onto several lines.\n
14220 produces the same output as
14223 echo This is some text\n
14224 echo which is continued\n
14225 echo onto several lines.\n
14229 @item output @var{expression}
14230 Print the value of @var{expression} and nothing but that value: no
14231 newlines, no @samp{$@var{nn} = }. The value is not entered in the
14232 value history either. @xref{Expressions, ,Expressions}, for more information
14235 @item output/@var{fmt} @var{expression}
14236 Print the value of @var{expression} in format @var{fmt}. You can use
14237 the same formats as for @code{print}. @xref{Output Formats,,Output
14238 formats}, for more information.
14241 @item printf @var{string}, @var{expressions}@dots{}
14242 Print the values of the @var{expressions} under the control of
14243 @var{string}. The @var{expressions} are separated by commas and may be
14244 either numbers or pointers. Their values are printed as specified by
14245 @var{string}, exactly as if your program were to execute the C
14247 @c FIXME: the above implies that at least all ANSI C formats are
14248 @c supported, but it isn't true: %E and %G don't work (or so it seems).
14249 @c Either this is a bug, or the manual should document what formats are
14253 printf (@var{string}, @var{expressions}@dots{});
14256 For example, you can print two values in hex like this:
14259 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
14262 The only backslash-escape sequences that you can use in the format
14263 string are the simple ones that consist of backslash followed by a
14268 @chapter Command Interpreters
14269 @cindex command interpreters
14271 @value{GDBN} supports multiple command interpreters, and some command
14272 infrastructure to allow users or user interface writers to switch
14273 between interpreters or run commands in other interpreters.
14275 @value{GDBN} currently supports two command interpreters, the console
14276 interpreter (sometimes called the command-line interpreter or @sc{cli})
14277 and the machine interface interpreter (or @sc{gdb/mi}). This manual
14278 describes both of these interfaces in great detail.
14280 By default, @value{GDBN} will start with the console interpreter.
14281 However, the user may choose to start @value{GDBN} with another
14282 interpreter by specifying the @option{-i} or @option{--interpreter}
14283 startup options. Defined interpreters include:
14287 @cindex console interpreter
14288 The traditional console or command-line interpreter. This is the most often
14289 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
14290 @value{GDBN} will use this interpreter.
14293 @cindex mi interpreter
14294 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
14295 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
14296 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
14300 @cindex mi2 interpreter
14301 The current @sc{gdb/mi} interface.
14304 @cindex mi1 interpreter
14305 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
14309 @cindex invoke another interpreter
14310 The interpreter being used by @value{GDBN} may not be dynamically
14311 switched at runtime. Although possible, this could lead to a very
14312 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
14313 enters the command "interpreter-set console" in a console view,
14314 @value{GDBN} would switch to using the console interpreter, rendering
14315 the IDE inoperable!
14317 @kindex interpreter-exec
14318 Although you may only choose a single interpreter at startup, you may execute
14319 commands in any interpreter from the current interpreter using the appropriate
14320 command. If you are running the console interpreter, simply use the
14321 @code{interpreter-exec} command:
14324 interpreter-exec mi "-data-list-register-names"
14327 @sc{gdb/mi} has a similar command, although it is only available in versions of
14328 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
14331 @chapter @value{GDBN} Text User Interface
14333 @cindex Text User Interface
14336 * TUI Overview:: TUI overview
14337 * TUI Keys:: TUI key bindings
14338 * TUI Single Key Mode:: TUI single key mode
14339 * TUI Commands:: TUI specific commands
14340 * TUI Configuration:: TUI configuration variables
14343 The @value{GDBN} Text User Interface, TUI in short, is a terminal
14344 interface which uses the @code{curses} library to show the source
14345 file, the assembly output, the program registers and @value{GDBN}
14346 commands in separate text windows.
14348 The TUI is enabled by invoking @value{GDBN} using either
14350 @samp{gdbtui} or @samp{gdb -tui}.
14353 @section TUI overview
14355 The TUI has two display modes that can be switched while
14360 A curses (or TUI) mode in which it displays several text
14361 windows on the terminal.
14364 A standard mode which corresponds to the @value{GDBN} configured without
14368 In the TUI mode, @value{GDBN} can display several text window
14373 This window is the @value{GDBN} command window with the @value{GDBN}
14374 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
14375 managed using readline but through the TUI. The @emph{command}
14376 window is always visible.
14379 The source window shows the source file of the program. The current
14380 line as well as active breakpoints are displayed in this window.
14383 The assembly window shows the disassembly output of the program.
14386 This window shows the processor registers. It detects when
14387 a register is changed and when this is the case, registers that have
14388 changed are highlighted.
14392 The source and assembly windows show the current program position
14393 by highlighting the current line and marking them with the @samp{>} marker.
14394 Breakpoints are also indicated with two markers. A first one
14395 indicates the breakpoint type:
14399 Breakpoint which was hit at least once.
14402 Breakpoint which was never hit.
14405 Hardware breakpoint which was hit at least once.
14408 Hardware breakpoint which was never hit.
14412 The second marker indicates whether the breakpoint is enabled or not:
14416 Breakpoint is enabled.
14419 Breakpoint is disabled.
14423 The source, assembly and register windows are attached to the thread
14424 and the frame position. They are updated when the current thread
14425 changes, when the frame changes or when the program counter changes.
14426 These three windows are arranged by the TUI according to several
14427 layouts. The layout defines which of these three windows are visible.
14428 The following layouts are available:
14438 source and assembly
14441 source and registers
14444 assembly and registers
14448 On top of the command window a status line gives various information
14449 concerning the current process begin debugged. The status line is
14450 updated when the information it shows changes. The following fields
14455 Indicates the current gdb target
14456 (@pxref{Targets, ,Specifying a Debugging Target}).
14459 Gives information about the current process or thread number.
14460 When no process is being debugged, this field is set to @code{No process}.
14463 Gives the current function name for the selected frame.
14464 The name is demangled if demangling is turned on (@pxref{Print Settings}).
14465 When there is no symbol corresponding to the current program counter
14466 the string @code{??} is displayed.
14469 Indicates the current line number for the selected frame.
14470 When the current line number is not known the string @code{??} is displayed.
14473 Indicates the current program counter address.
14478 @section TUI Key Bindings
14479 @cindex TUI key bindings
14481 The TUI installs several key bindings in the readline keymaps
14482 (@pxref{Command Line Editing}).
14483 They allow to leave or enter in the TUI mode or they operate
14484 directly on the TUI layout and windows. The TUI also provides
14485 a @emph{SingleKey} keymap which binds several keys directly to
14486 @value{GDBN} commands. The following key bindings
14487 are installed for both TUI mode and the @value{GDBN} standard mode.
14496 Enter or leave the TUI mode. When the TUI mode is left,
14497 the curses window management is left and @value{GDBN} operates using
14498 its standard mode writing on the terminal directly. When the TUI
14499 mode is entered, the control is given back to the curses windows.
14500 The screen is then refreshed.
14504 Use a TUI layout with only one window. The layout will
14505 either be @samp{source} or @samp{assembly}. When the TUI mode
14506 is not active, it will switch to the TUI mode.
14508 Think of this key binding as the Emacs @kbd{C-x 1} binding.
14512 Use a TUI layout with at least two windows. When the current
14513 layout shows already two windows, a next layout with two windows is used.
14514 When a new layout is chosen, one window will always be common to the
14515 previous layout and the new one.
14517 Think of it as the Emacs @kbd{C-x 2} binding.
14521 Change the active window. The TUI associates several key bindings
14522 (like scrolling and arrow keys) to the active window. This command
14523 gives the focus to the next TUI window.
14525 Think of it as the Emacs @kbd{C-x o} binding.
14529 Use the TUI @emph{SingleKey} keymap that binds single key to gdb commands
14530 (@pxref{TUI Single Key Mode}).
14534 The following key bindings are handled only by the TUI mode:
14539 Scroll the active window one page up.
14543 Scroll the active window one page down.
14547 Scroll the active window one line up.
14551 Scroll the active window one line down.
14555 Scroll the active window one column left.
14559 Scroll the active window one column right.
14563 Refresh the screen.
14567 In the TUI mode, the arrow keys are used by the active window
14568 for scrolling. This means they are available for readline when the
14569 active window is the command window. When the command window
14570 does not have the focus, it is necessary to use other readline
14571 key bindings such as @key{C-p}, @key{C-n}, @key{C-b} and @key{C-f}.
14573 @node TUI Single Key Mode
14574 @section TUI Single Key Mode
14575 @cindex TUI single key mode
14577 The TUI provides a @emph{SingleKey} mode in which it installs a particular
14578 key binding in the readline keymaps to connect single keys to
14582 @kindex c @r{(SingleKey TUI key)}
14586 @kindex d @r{(SingleKey TUI key)}
14590 @kindex f @r{(SingleKey TUI key)}
14594 @kindex n @r{(SingleKey TUI key)}
14598 @kindex q @r{(SingleKey TUI key)}
14600 exit the @emph{SingleKey} mode.
14602 @kindex r @r{(SingleKey TUI key)}
14606 @kindex s @r{(SingleKey TUI key)}
14610 @kindex u @r{(SingleKey TUI key)}
14614 @kindex v @r{(SingleKey TUI key)}
14618 @kindex w @r{(SingleKey TUI key)}
14624 Other keys temporarily switch to the @value{GDBN} command prompt.
14625 The key that was pressed is inserted in the editing buffer so that
14626 it is possible to type most @value{GDBN} commands without interaction
14627 with the TUI @emph{SingleKey} mode. Once the command is entered the TUI
14628 @emph{SingleKey} mode is restored. The only way to permanently leave
14629 this mode is by hitting @key{q} or @samp{@key{C-x} @key{s}}.
14633 @section TUI specific commands
14634 @cindex TUI commands
14636 The TUI has specific commands to control the text windows.
14637 These commands are always available, that is they do not depend on
14638 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
14639 is in the standard mode, using these commands will automatically switch
14645 List and give the size of all displayed windows.
14649 Display the next layout.
14652 Display the previous layout.
14655 Display the source window only.
14658 Display the assembly window only.
14661 Display the source and assembly window.
14664 Display the register window together with the source or assembly window.
14666 @item focus next | prev | src | asm | regs | split
14668 Set the focus to the named window.
14669 This command allows to change the active window so that scrolling keys
14670 can be affected to another window.
14674 Refresh the screen. This is similar to using @key{C-L} key.
14676 @item tui reg float
14678 Show the floating point registers in the register window.
14680 @item tui reg general
14681 Show the general registers in the register window.
14684 Show the next register group. The list of register groups as well as
14685 their order is target specific. The predefined register groups are the
14686 following: @code{general}, @code{float}, @code{system}, @code{vector},
14687 @code{all}, @code{save}, @code{restore}.
14689 @item tui reg system
14690 Show the system registers in the register window.
14694 Update the source window and the current execution point.
14696 @item winheight @var{name} +@var{count}
14697 @itemx winheight @var{name} -@var{count}
14699 Change the height of the window @var{name} by @var{count}
14700 lines. Positive counts increase the height, while negative counts
14705 @node TUI Configuration
14706 @section TUI configuration variables
14707 @cindex TUI configuration variables
14709 The TUI has several configuration variables that control the
14710 appearance of windows on the terminal.
14713 @item set tui border-kind @var{kind}
14714 @kindex set tui border-kind
14715 Select the border appearance for the source, assembly and register windows.
14716 The possible values are the following:
14719 Use a space character to draw the border.
14722 Use ascii characters + - and | to draw the border.
14725 Use the Alternate Character Set to draw the border. The border is
14726 drawn using character line graphics if the terminal supports them.
14730 @item set tui active-border-mode @var{mode}
14731 @kindex set tui active-border-mode
14732 Select the attributes to display the border of the active window.
14733 The possible values are @code{normal}, @code{standout}, @code{reverse},
14734 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
14736 @item set tui border-mode @var{mode}
14737 @kindex set tui border-mode
14738 Select the attributes to display the border of other windows.
14739 The @var{mode} can be one of the following:
14742 Use normal attributes to display the border.
14748 Use reverse video mode.
14751 Use half bright mode.
14753 @item half-standout
14754 Use half bright and standout mode.
14757 Use extra bright or bold mode.
14759 @item bold-standout
14760 Use extra bright or bold and standout mode.
14767 @chapter Using @value{GDBN} under @sc{gnu} Emacs
14770 @cindex @sc{gnu} Emacs
14771 A special interface allows you to use @sc{gnu} Emacs to view (and
14772 edit) the source files for the program you are debugging with
14775 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
14776 executable file you want to debug as an argument. This command starts
14777 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
14778 created Emacs buffer.
14779 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
14781 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
14786 All ``terminal'' input and output goes through the Emacs buffer.
14789 This applies both to @value{GDBN} commands and their output, and to the input
14790 and output done by the program you are debugging.
14792 This is useful because it means that you can copy the text of previous
14793 commands and input them again; you can even use parts of the output
14796 All the facilities of Emacs' Shell mode are available for interacting
14797 with your program. In particular, you can send signals the usual
14798 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
14803 @value{GDBN} displays source code through Emacs.
14806 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
14807 source file for that frame and puts an arrow (@samp{=>}) at the
14808 left margin of the current line. Emacs uses a separate buffer for
14809 source display, and splits the screen to show both your @value{GDBN} session
14812 Explicit @value{GDBN} @code{list} or search commands still produce output as
14813 usual, but you probably have no reason to use them from Emacs.
14815 If you specify an absolute file name when prompted for the @kbd{M-x
14816 gdb} argument, then Emacs sets your current working directory to where
14817 your program resides. If you only specify the file name, then Emacs
14818 sets your current working directory to to the directory associated
14819 with the previous buffer. In this case, @value{GDBN} may find your
14820 program by searching your environment's @code{PATH} variable, but on
14821 some operating systems it might not find the source. So, although the
14822 @value{GDBN} input and output session proceeds normally, the auxiliary
14823 buffer does not display the current source and line of execution.
14825 The initial working directory of @value{GDBN} is printed on the top
14826 line of the @value{GDBN} I/O buffer and this serves as a default for
14827 the commands that specify files for @value{GDBN} to operate
14828 on. @xref{Files, ,Commands to specify files}.
14830 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
14831 need to call @value{GDBN} by a different name (for example, if you
14832 keep several configurations around, with different names) you can
14833 customize the Emacs variable @code{gud-gdb-command-name} to run the
14836 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
14837 addition to the standard Shell mode commands:
14841 Describe the features of Emacs' @value{GDBN} Mode.
14844 Execute to another source line, like the @value{GDBN} @code{step} command; also
14845 update the display window to show the current file and location.
14848 Execute to next source line in this function, skipping all function
14849 calls, like the @value{GDBN} @code{next} command. Then update the display window
14850 to show the current file and location.
14853 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
14854 display window accordingly.
14857 Execute until exit from the selected stack frame, like the @value{GDBN}
14858 @code{finish} command.
14861 Continue execution of your program, like the @value{GDBN} @code{continue}
14865 Go up the number of frames indicated by the numeric argument
14866 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
14867 like the @value{GDBN} @code{up} command.
14870 Go down the number of frames indicated by the numeric argument, like the
14871 @value{GDBN} @code{down} command.
14874 In any source file, the Emacs command @kbd{C-x SPC} (@code{gud-break})
14875 tells @value{GDBN} to set a breakpoint on the source line point is on.
14877 If you type @kbd{M-x speedbar}, then Emacs displays a separate frame which
14878 shows a backtrace when the @value{GDBN} I/O buffer is current. Move
14879 point to any frame in the stack and type @key{RET} to make it become the
14880 current frame and display the associated source in the source buffer.
14881 Alternatively, click @kbd{Mouse-2} to make the selected frame become the
14884 If you accidentally delete the source-display buffer, an easy way to get
14885 it back is to type the command @code{f} in the @value{GDBN} buffer, to
14886 request a frame display; when you run under Emacs, this recreates
14887 the source buffer if necessary to show you the context of the current
14890 The source files displayed in Emacs are in ordinary Emacs buffers
14891 which are visiting the source files in the usual way. You can edit
14892 the files with these buffers if you wish; but keep in mind that @value{GDBN}
14893 communicates with Emacs in terms of line numbers. If you add or
14894 delete lines from the text, the line numbers that @value{GDBN} knows cease
14895 to correspond properly with the code.
14897 The description given here is for GNU Emacs version 21.3 and a more
14898 detailed description of its interaction with @value{GDBN} is given in
14899 the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu} Emacs Manual}).
14901 @c The following dropped because Epoch is nonstandard. Reactivate
14902 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
14904 @kindex Emacs Epoch environment
14908 Version 18 of @sc{gnu} Emacs has a built-in window system
14909 called the @code{epoch}
14910 environment. Users of this environment can use a new command,
14911 @code{inspect} which performs identically to @code{print} except that
14912 each value is printed in its own window.
14917 @chapter The @sc{gdb/mi} Interface
14919 @unnumberedsec Function and Purpose
14921 @cindex @sc{gdb/mi}, its purpose
14922 @sc{gdb/mi} is a line based machine oriented text interface to @value{GDBN}. It is
14923 specifically intended to support the development of systems which use
14924 the debugger as just one small component of a larger system.
14926 This chapter is a specification of the @sc{gdb/mi} interface. It is written
14927 in the form of a reference manual.
14929 Note that @sc{gdb/mi} is still under construction, so some of the
14930 features described below are incomplete and subject to change.
14932 @unnumberedsec Notation and Terminology
14934 @cindex notational conventions, for @sc{gdb/mi}
14935 This chapter uses the following notation:
14939 @code{|} separates two alternatives.
14942 @code{[ @var{something} ]} indicates that @var{something} is optional:
14943 it may or may not be given.
14946 @code{( @var{group} )*} means that @var{group} inside the parentheses
14947 may repeat zero or more times.
14950 @code{( @var{group} )+} means that @var{group} inside the parentheses
14951 may repeat one or more times.
14954 @code{"@var{string}"} means a literal @var{string}.
14958 @heading Dependencies
14961 @heading Acknowledgments
14963 In alphabetic order: Andrew Cagney, Fernando Nasser, Stan Shebs and
14967 * GDB/MI Command Syntax::
14968 * GDB/MI Compatibility with CLI::
14969 * GDB/MI Output Records::
14970 * GDB/MI Command Description Format::
14971 * GDB/MI Breakpoint Table Commands::
14972 * GDB/MI Data Manipulation::
14973 * GDB/MI Program Control::
14974 * GDB/MI Miscellaneous Commands::
14976 * GDB/MI Kod Commands::
14977 * GDB/MI Memory Overlay Commands::
14978 * GDB/MI Signal Handling Commands::
14980 * GDB/MI Stack Manipulation::
14981 * GDB/MI Symbol Query::
14982 * GDB/MI Target Manipulation::
14983 * GDB/MI Thread Commands::
14984 * GDB/MI Tracepoint Commands::
14985 * GDB/MI Variable Objects::
14988 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14989 @node GDB/MI Command Syntax
14990 @section @sc{gdb/mi} Command Syntax
14993 * GDB/MI Input Syntax::
14994 * GDB/MI Output Syntax::
14995 * GDB/MI Simple Examples::
14998 @node GDB/MI Input Syntax
14999 @subsection @sc{gdb/mi} Input Syntax
15001 @cindex input syntax for @sc{gdb/mi}
15002 @cindex @sc{gdb/mi}, input syntax
15004 @item @var{command} @expansion{}
15005 @code{@var{cli-command} | @var{mi-command}}
15007 @item @var{cli-command} @expansion{}
15008 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
15009 @var{cli-command} is any existing @value{GDBN} CLI command.
15011 @item @var{mi-command} @expansion{}
15012 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
15013 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
15015 @item @var{token} @expansion{}
15016 "any sequence of digits"
15018 @item @var{option} @expansion{}
15019 @code{"-" @var{parameter} [ " " @var{parameter} ]}
15021 @item @var{parameter} @expansion{}
15022 @code{@var{non-blank-sequence} | @var{c-string}}
15024 @item @var{operation} @expansion{}
15025 @emph{any of the operations described in this chapter}
15027 @item @var{non-blank-sequence} @expansion{}
15028 @emph{anything, provided it doesn't contain special characters such as
15029 "-", @var{nl}, """ and of course " "}
15031 @item @var{c-string} @expansion{}
15032 @code{""" @var{seven-bit-iso-c-string-content} """}
15034 @item @var{nl} @expansion{}
15043 The CLI commands are still handled by the @sc{mi} interpreter; their
15044 output is described below.
15047 The @code{@var{token}}, when present, is passed back when the command
15051 Some @sc{mi} commands accept optional arguments as part of the parameter
15052 list. Each option is identified by a leading @samp{-} (dash) and may be
15053 followed by an optional argument parameter. Options occur first in the
15054 parameter list and can be delimited from normal parameters using
15055 @samp{--} (this is useful when some parameters begin with a dash).
15062 We want easy access to the existing CLI syntax (for debugging).
15065 We want it to be easy to spot a @sc{mi} operation.
15068 @node GDB/MI Output Syntax
15069 @subsection @sc{gdb/mi} Output Syntax
15071 @cindex output syntax of @sc{gdb/mi}
15072 @cindex @sc{gdb/mi}, output syntax
15073 The output from @sc{gdb/mi} consists of zero or more out-of-band records
15074 followed, optionally, by a single result record. This result record
15075 is for the most recent command. The sequence of output records is
15076 terminated by @samp{(@value{GDBP})}.
15078 If an input command was prefixed with a @code{@var{token}} then the
15079 corresponding output for that command will also be prefixed by that same
15083 @item @var{output} @expansion{}
15084 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(@value{GDBP})" @var{nl}}
15086 @item @var{result-record} @expansion{}
15087 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
15089 @item @var{out-of-band-record} @expansion{}
15090 @code{@var{async-record} | @var{stream-record}}
15092 @item @var{async-record} @expansion{}
15093 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
15095 @item @var{exec-async-output} @expansion{}
15096 @code{[ @var{token} ] "*" @var{async-output}}
15098 @item @var{status-async-output} @expansion{}
15099 @code{[ @var{token} ] "+" @var{async-output}}
15101 @item @var{notify-async-output} @expansion{}
15102 @code{[ @var{token} ] "=" @var{async-output}}
15104 @item @var{async-output} @expansion{}
15105 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
15107 @item @var{result-class} @expansion{}
15108 @code{"done" | "running" | "connected" | "error" | "exit"}
15110 @item @var{async-class} @expansion{}
15111 @code{"stopped" | @var{others}} (where @var{others} will be added
15112 depending on the needs---this is still in development).
15114 @item @var{result} @expansion{}
15115 @code{ @var{variable} "=" @var{value}}
15117 @item @var{variable} @expansion{}
15118 @code{ @var{string} }
15120 @item @var{value} @expansion{}
15121 @code{ @var{const} | @var{tuple} | @var{list} }
15123 @item @var{const} @expansion{}
15124 @code{@var{c-string}}
15126 @item @var{tuple} @expansion{}
15127 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
15129 @item @var{list} @expansion{}
15130 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
15131 @var{result} ( "," @var{result} )* "]" }
15133 @item @var{stream-record} @expansion{}
15134 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
15136 @item @var{console-stream-output} @expansion{}
15137 @code{"~" @var{c-string}}
15139 @item @var{target-stream-output} @expansion{}
15140 @code{"@@" @var{c-string}}
15142 @item @var{log-stream-output} @expansion{}
15143 @code{"&" @var{c-string}}
15145 @item @var{nl} @expansion{}
15148 @item @var{token} @expansion{}
15149 @emph{any sequence of digits}.
15157 All output sequences end in a single line containing a period.
15160 The @code{@var{token}} is from the corresponding request. If an execution
15161 command is interrupted by the @samp{-exec-interrupt} command, the
15162 @var{token} associated with the @samp{*stopped} message is the one of the
15163 original execution command, not the one of the interrupt command.
15166 @cindex status output in @sc{gdb/mi}
15167 @var{status-async-output} contains on-going status information about the
15168 progress of a slow operation. It can be discarded. All status output is
15169 prefixed by @samp{+}.
15172 @cindex async output in @sc{gdb/mi}
15173 @var{exec-async-output} contains asynchronous state change on the target
15174 (stopped, started, disappeared). All async output is prefixed by
15178 @cindex notify output in @sc{gdb/mi}
15179 @var{notify-async-output} contains supplementary information that the
15180 client should handle (e.g., a new breakpoint information). All notify
15181 output is prefixed by @samp{=}.
15184 @cindex console output in @sc{gdb/mi}
15185 @var{console-stream-output} is output that should be displayed as is in the
15186 console. It is the textual response to a CLI command. All the console
15187 output is prefixed by @samp{~}.
15190 @cindex target output in @sc{gdb/mi}
15191 @var{target-stream-output} is the output produced by the target program.
15192 All the target output is prefixed by @samp{@@}.
15195 @cindex log output in @sc{gdb/mi}
15196 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
15197 instance messages that should be displayed as part of an error log. All
15198 the log output is prefixed by @samp{&}.
15201 @cindex list output in @sc{gdb/mi}
15202 New @sc{gdb/mi} commands should only output @var{lists} containing
15208 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
15209 details about the various output records.
15211 @node GDB/MI Simple Examples
15212 @subsection Simple Examples of @sc{gdb/mi} Interaction
15213 @cindex @sc{gdb/mi}, simple examples
15215 This subsection presents several simple examples of interaction using
15216 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
15217 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
15218 the output received from @sc{gdb/mi}.
15220 @subsubheading Target Stop
15221 @c Ummm... There is no "-stop" command. This assumes async, no?
15222 Here's an example of stopping the inferior process:
15233 <- *stop,reason="stop",address="0x123",source="a.c:123"
15237 @subsubheading Simple CLI Command
15239 Here's an example of a simple CLI command being passed through
15240 @sc{gdb/mi} and on to the CLI.
15250 @subsubheading Command With Side Effects
15253 -> -symbol-file xyz.exe
15254 <- *breakpoint,nr="3",address="0x123",source="a.c:123"
15258 @subsubheading A Bad Command
15260 Here's what happens if you pass a non-existent command:
15264 <- ^error,msg="Undefined MI command: rubbish"
15268 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15269 @node GDB/MI Compatibility with CLI
15270 @section @sc{gdb/mi} Compatibility with CLI
15272 @cindex compatibility, @sc{gdb/mi} and CLI
15273 @cindex @sc{gdb/mi}, compatibility with CLI
15274 To help users familiar with @value{GDBN}'s existing CLI interface, @sc{gdb/mi}
15275 accepts existing CLI commands. As specified by the syntax, such
15276 commands can be directly entered into the @sc{gdb/mi} interface and @value{GDBN} will
15279 This mechanism is provided as an aid to developers of @sc{gdb/mi}
15280 clients and not as a reliable interface into the CLI. Since the command
15281 is being interpreteted in an environment that assumes @sc{gdb/mi}
15282 behaviour, the exact output of such commands is likely to end up being
15283 an un-supported hybrid of @sc{gdb/mi} and CLI output.
15285 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15286 @node GDB/MI Output Records
15287 @section @sc{gdb/mi} Output Records
15290 * GDB/MI Result Records::
15291 * GDB/MI Stream Records::
15292 * GDB/MI Out-of-band Records::
15295 @node GDB/MI Result Records
15296 @subsection @sc{gdb/mi} Result Records
15298 @cindex result records in @sc{gdb/mi}
15299 @cindex @sc{gdb/mi}, result records
15300 In addition to a number of out-of-band notifications, the response to a
15301 @sc{gdb/mi} command includes one of the following result indications:
15305 @item "^done" [ "," @var{results} ]
15306 The synchronous operation was successful, @code{@var{results}} are the return
15311 @c Is this one correct? Should it be an out-of-band notification?
15312 The asynchronous operation was successfully started. The target is
15315 @item "^error" "," @var{c-string}
15317 The operation failed. The @code{@var{c-string}} contains the corresponding
15321 @node GDB/MI Stream Records
15322 @subsection @sc{gdb/mi} Stream Records
15324 @cindex @sc{gdb/mi}, stream records
15325 @cindex stream records in @sc{gdb/mi}
15326 @value{GDBN} internally maintains a number of output streams: the console, the
15327 target, and the log. The output intended for each of these streams is
15328 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
15330 Each stream record begins with a unique @dfn{prefix character} which
15331 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
15332 Syntax}). In addition to the prefix, each stream record contains a
15333 @code{@var{string-output}}. This is either raw text (with an implicit new
15334 line) or a quoted C string (which does not contain an implicit newline).
15337 @item "~" @var{string-output}
15338 The console output stream contains text that should be displayed in the
15339 CLI console window. It contains the textual responses to CLI commands.
15341 @item "@@" @var{string-output}
15342 The target output stream contains any textual output from the running
15345 @item "&" @var{string-output}
15346 The log stream contains debugging messages being produced by @value{GDBN}'s
15350 @node GDB/MI Out-of-band Records
15351 @subsection @sc{gdb/mi} Out-of-band Records
15353 @cindex out-of-band records in @sc{gdb/mi}
15354 @cindex @sc{gdb/mi}, out-of-band records
15355 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
15356 additional changes that have occurred. Those changes can either be a
15357 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
15358 target activity (e.g., target stopped).
15360 The following is a preliminary list of possible out-of-band records.
15367 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15368 @node GDB/MI Command Description Format
15369 @section @sc{gdb/mi} Command Description Format
15371 The remaining sections describe blocks of commands. Each block of
15372 commands is laid out in a fashion similar to this section.
15374 Note the the line breaks shown in the examples are here only for
15375 readability. They don't appear in the real output.
15376 Also note that the commands with a non-available example (N.A.@:) are
15377 not yet implemented.
15379 @subheading Motivation
15381 The motivation for this collection of commands.
15383 @subheading Introduction
15385 A brief introduction to this collection of commands as a whole.
15387 @subheading Commands
15389 For each command in the block, the following is described:
15391 @subsubheading Synopsis
15394 -command @var{args}@dots{}
15397 @subsubheading @value{GDBN} Command
15399 The corresponding @value{GDBN} CLI command.
15401 @subsubheading Result
15403 @subsubheading Out-of-band
15405 @subsubheading Notes
15407 @subsubheading Example
15410 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15411 @node GDB/MI Breakpoint Table Commands
15412 @section @sc{gdb/mi} Breakpoint table commands
15414 @cindex breakpoint commands for @sc{gdb/mi}
15415 @cindex @sc{gdb/mi}, breakpoint commands
15416 This section documents @sc{gdb/mi} commands for manipulating
15419 @subheading The @code{-break-after} Command
15420 @findex -break-after
15422 @subsubheading Synopsis
15425 -break-after @var{number} @var{count}
15428 The breakpoint number @var{number} is not in effect until it has been
15429 hit @var{count} times. To see how this is reflected in the output of
15430 the @samp{-break-list} command, see the description of the
15431 @samp{-break-list} command below.
15433 @subsubheading @value{GDBN} Command
15435 The corresponding @value{GDBN} command is @samp{ignore}.
15437 @subsubheading Example
15442 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",line="5"@}
15449 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15450 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15451 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15452 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15453 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15454 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15455 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15456 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15457 addr="0x000100d0",func="main",file="hello.c",line="5",times="0",
15463 @subheading The @code{-break-catch} Command
15464 @findex -break-catch
15466 @subheading The @code{-break-commands} Command
15467 @findex -break-commands
15471 @subheading The @code{-break-condition} Command
15472 @findex -break-condition
15474 @subsubheading Synopsis
15477 -break-condition @var{number} @var{expr}
15480 Breakpoint @var{number} will stop the program only if the condition in
15481 @var{expr} is true. The condition becomes part of the
15482 @samp{-break-list} output (see the description of the @samp{-break-list}
15485 @subsubheading @value{GDBN} Command
15487 The corresponding @value{GDBN} command is @samp{condition}.
15489 @subsubheading Example
15493 -break-condition 1 1
15497 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15498 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15499 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15500 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15501 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15502 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15503 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15504 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15505 addr="0x000100d0",func="main",file="hello.c",line="5",cond="1",
15506 times="0",ignore="3"@}]@}
15510 @subheading The @code{-break-delete} Command
15511 @findex -break-delete
15513 @subsubheading Synopsis
15516 -break-delete ( @var{breakpoint} )+
15519 Delete the breakpoint(s) whose number(s) are specified in the argument
15520 list. This is obviously reflected in the breakpoint list.
15522 @subsubheading @value{GDBN} command
15524 The corresponding @value{GDBN} command is @samp{delete}.
15526 @subsubheading Example
15534 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
15535 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15536 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15537 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15538 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15539 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15540 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15545 @subheading The @code{-break-disable} Command
15546 @findex -break-disable
15548 @subsubheading Synopsis
15551 -break-disable ( @var{breakpoint} )+
15554 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
15555 break list is now set to @samp{n} for the named @var{breakpoint}(s).
15557 @subsubheading @value{GDBN} Command
15559 The corresponding @value{GDBN} command is @samp{disable}.
15561 @subsubheading Example
15569 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15570 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15571 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15572 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15573 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15574 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15575 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15576 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
15577 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
15581 @subheading The @code{-break-enable} Command
15582 @findex -break-enable
15584 @subsubheading Synopsis
15587 -break-enable ( @var{breakpoint} )+
15590 Enable (previously disabled) @var{breakpoint}(s).
15592 @subsubheading @value{GDBN} Command
15594 The corresponding @value{GDBN} command is @samp{enable}.
15596 @subsubheading Example
15604 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15605 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15606 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15607 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15608 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15609 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15610 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15611 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
15612 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
15616 @subheading The @code{-break-info} Command
15617 @findex -break-info
15619 @subsubheading Synopsis
15622 -break-info @var{breakpoint}
15626 Get information about a single breakpoint.
15628 @subsubheading @value{GDBN} command
15630 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
15632 @subsubheading Example
15635 @subheading The @code{-break-insert} Command
15636 @findex -break-insert
15638 @subsubheading Synopsis
15641 -break-insert [ -t ] [ -h ] [ -r ]
15642 [ -c @var{condition} ] [ -i @var{ignore-count} ]
15643 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
15647 If specified, @var{line}, can be one of:
15654 @item filename:linenum
15655 @item filename:function
15659 The possible optional parameters of this command are:
15663 Insert a tempoary breakpoint.
15665 Insert a hardware breakpoint.
15666 @item -c @var{condition}
15667 Make the breakpoint conditional on @var{condition}.
15668 @item -i @var{ignore-count}
15669 Initialize the @var{ignore-count}.
15671 Insert a regular breakpoint in all the functions whose names match the
15672 given regular expression. Other flags are not applicable to regular
15676 @subsubheading Result
15678 The result is in the form:
15681 ^done,bkptno="@var{number}",func="@var{funcname}",
15682 file="@var{filename}",line="@var{lineno}"
15686 where @var{number} is the @value{GDBN} number for this breakpoint, @var{funcname}
15687 is the name of the function where the breakpoint was inserted,
15688 @var{filename} is the name of the source file which contains this
15689 function, and @var{lineno} is the source line number within that file.
15691 Note: this format is open to change.
15692 @c An out-of-band breakpoint instead of part of the result?
15694 @subsubheading @value{GDBN} Command
15696 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
15697 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
15699 @subsubheading Example
15704 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
15706 -break-insert -t foo
15707 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",line="11"@}
15710 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15711 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15712 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15713 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15714 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15715 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15716 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15717 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15718 addr="0x0001072c", func="main",file="recursive2.c",line="4",times="0"@},
15719 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
15720 addr="0x00010774",func="foo",file="recursive2.c",line="11",times="0"@}]@}
15722 -break-insert -r foo.*
15723 ~int foo(int, int);
15724 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c",line="11"@}
15728 @subheading The @code{-break-list} Command
15729 @findex -break-list
15731 @subsubheading Synopsis
15737 Displays the list of inserted breakpoints, showing the following fields:
15741 number of the breakpoint
15743 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
15745 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
15748 is the breakpoint enabled or no: @samp{y} or @samp{n}
15750 memory location at which the breakpoint is set
15752 logical location of the breakpoint, expressed by function name, file
15755 number of times the breakpoint has been hit
15758 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
15759 @code{body} field is an empty list.
15761 @subsubheading @value{GDBN} Command
15763 The corresponding @value{GDBN} command is @samp{info break}.
15765 @subsubheading Example
15770 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15771 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15772 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15773 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15774 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15775 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15776 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15777 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15778 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
15779 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
15780 addr="0x00010114",func="foo",file="hello.c",line="13",times="0"@}]@}
15784 Here's an example of the result when there are no breakpoints:
15789 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
15790 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15791 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15792 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15793 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15794 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15795 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15800 @subheading The @code{-break-watch} Command
15801 @findex -break-watch
15803 @subsubheading Synopsis
15806 -break-watch [ -a | -r ]
15809 Create a watchpoint. With the @samp{-a} option it will create an
15810 @dfn{access} watchpoint, i.e. a watchpoint that triggers either on a
15811 read from or on a write to the memory location. With the @samp{-r}
15812 option, the watchpoint created is a @dfn{read} watchpoint, i.e. it will
15813 trigger only when the memory location is accessed for reading. Without
15814 either of the options, the watchpoint created is a regular watchpoint,
15815 i.e. it will trigger when the memory location is accessed for writing.
15816 @xref{Set Watchpoints, , Setting watchpoints}.
15818 Note that @samp{-break-list} will report a single list of watchpoints and
15819 breakpoints inserted.
15821 @subsubheading @value{GDBN} Command
15823 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
15826 @subsubheading Example
15828 Setting a watchpoint on a variable in the @code{main} function:
15833 ^done,wpt=@{number="2",exp="x"@}
15837 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
15838 value=@{old="-268439212",new="55"@},
15839 frame=@{func="main",args=[],file="recursive2.c",line="5"@}
15843 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
15844 the program execution twice: first for the variable changing value, then
15845 for the watchpoint going out of scope.
15850 ^done,wpt=@{number="5",exp="C"@}
15854 ^done,reason="watchpoint-trigger",
15855 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
15856 frame=@{func="callee4",args=[],
15857 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
15861 ^done,reason="watchpoint-scope",wpnum="5",
15862 frame=@{func="callee3",args=[@{name="strarg",
15863 value="0x11940 \"A string argument.\""@}],
15864 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
15868 Listing breakpoints and watchpoints, at different points in the program
15869 execution. Note that once the watchpoint goes out of scope, it is
15875 ^done,wpt=@{number="2",exp="C"@}
15878 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15879 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15880 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15881 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15882 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15883 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15884 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15885 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15886 addr="0x00010734",func="callee4",
15887 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
15888 bkpt=@{number="2",type="watchpoint",disp="keep",
15889 enabled="y",addr="",what="C",times="0"@}]@}
15893 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
15894 value=@{old="-276895068",new="3"@},
15895 frame=@{func="callee4",args=[],
15896 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
15899 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15900 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15901 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15902 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15903 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15904 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15905 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15906 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15907 addr="0x00010734",func="callee4",
15908 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
15909 bkpt=@{number="2",type="watchpoint",disp="keep",
15910 enabled="y",addr="",what="C",times="-5"@}]@}
15914 ^done,reason="watchpoint-scope",wpnum="2",
15915 frame=@{func="callee3",args=[@{name="strarg",
15916 value="0x11940 \"A string argument.\""@}],
15917 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
15920 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15921 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15922 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15923 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15924 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15925 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15926 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15927 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15928 addr="0x00010734",func="callee4",
15929 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@}]@}
15933 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15934 @node GDB/MI Data Manipulation
15935 @section @sc{gdb/mi} Data Manipulation
15937 @cindex data manipulation, in @sc{gdb/mi}
15938 @cindex @sc{gdb/mi}, data manipulation
15939 This section describes the @sc{gdb/mi} commands that manipulate data:
15940 examine memory and registers, evaluate expressions, etc.
15942 @c REMOVED FROM THE INTERFACE.
15943 @c @subheading -data-assign
15944 @c Change the value of a program variable. Plenty of side effects.
15945 @c @subsubheading GDB command
15947 @c @subsubheading Example
15950 @subheading The @code{-data-disassemble} Command
15951 @findex -data-disassemble
15953 @subsubheading Synopsis
15957 [ -s @var{start-addr} -e @var{end-addr} ]
15958 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
15966 @item @var{start-addr}
15967 is the beginning address (or @code{$pc})
15968 @item @var{end-addr}
15970 @item @var{filename}
15971 is the name of the file to disassemble
15972 @item @var{linenum}
15973 is the line number to disassemble around
15975 is the the number of disassembly lines to be produced. If it is -1,
15976 the whole function will be disassembled, in case no @var{end-addr} is
15977 specified. If @var{end-addr} is specified as a non-zero value, and
15978 @var{lines} is lower than the number of disassembly lines between
15979 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
15980 displayed; if @var{lines} is higher than the number of lines between
15981 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
15984 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
15988 @subsubheading Result
15990 The output for each instruction is composed of four fields:
15999 Note that whatever included in the instruction field, is not manipulated
16000 directely by @sc{gdb/mi}, i.e. it is not possible to adjust its format.
16002 @subsubheading @value{GDBN} Command
16004 There's no direct mapping from this command to the CLI.
16006 @subsubheading Example
16008 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
16012 -data-disassemble -s $pc -e "$pc + 20" -- 0
16015 @{address="0x000107c0",func-name="main",offset="4",
16016 inst="mov 2, %o0"@},
16017 @{address="0x000107c4",func-name="main",offset="8",
16018 inst="sethi %hi(0x11800), %o2"@},
16019 @{address="0x000107c8",func-name="main",offset="12",
16020 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
16021 @{address="0x000107cc",func-name="main",offset="16",
16022 inst="sethi %hi(0x11800), %o2"@},
16023 @{address="0x000107d0",func-name="main",offset="20",
16024 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
16028 Disassemble the whole @code{main} function. Line 32 is part of
16032 -data-disassemble -f basics.c -l 32 -- 0
16034 @{address="0x000107bc",func-name="main",offset="0",
16035 inst="save %sp, -112, %sp"@},
16036 @{address="0x000107c0",func-name="main",offset="4",
16037 inst="mov 2, %o0"@},
16038 @{address="0x000107c4",func-name="main",offset="8",
16039 inst="sethi %hi(0x11800), %o2"@},
16041 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
16042 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
16046 Disassemble 3 instructions from the start of @code{main}:
16050 -data-disassemble -f basics.c -l 32 -n 3 -- 0
16052 @{address="0x000107bc",func-name="main",offset="0",
16053 inst="save %sp, -112, %sp"@},
16054 @{address="0x000107c0",func-name="main",offset="4",
16055 inst="mov 2, %o0"@},
16056 @{address="0x000107c4",func-name="main",offset="8",
16057 inst="sethi %hi(0x11800), %o2"@}]
16061 Disassemble 3 instructions from the start of @code{main} in mixed mode:
16065 -data-disassemble -f basics.c -l 32 -n 3 -- 1
16067 src_and_asm_line=@{line="31",
16068 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
16069 testsuite/gdb.mi/basics.c",line_asm_insn=[
16070 @{address="0x000107bc",func-name="main",offset="0",
16071 inst="save %sp, -112, %sp"@}]@},
16072 src_and_asm_line=@{line="32",
16073 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
16074 testsuite/gdb.mi/basics.c",line_asm_insn=[
16075 @{address="0x000107c0",func-name="main",offset="4",
16076 inst="mov 2, %o0"@},
16077 @{address="0x000107c4",func-name="main",offset="8",
16078 inst="sethi %hi(0x11800), %o2"@}]@}]
16083 @subheading The @code{-data-evaluate-expression} Command
16084 @findex -data-evaluate-expression
16086 @subsubheading Synopsis
16089 -data-evaluate-expression @var{expr}
16092 Evaluate @var{expr} as an expression. The expression could contain an
16093 inferior function call. The function call will execute synchronously.
16094 If the expression contains spaces, it must be enclosed in double quotes.
16096 @subsubheading @value{GDBN} Command
16098 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
16099 @samp{call}. In @code{gdbtk} only, there's a corresponding
16100 @samp{gdb_eval} command.
16102 @subsubheading Example
16104 In the following example, the numbers that precede the commands are the
16105 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
16106 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
16110 211-data-evaluate-expression A
16113 311-data-evaluate-expression &A
16114 311^done,value="0xefffeb7c"
16116 411-data-evaluate-expression A+3
16119 511-data-evaluate-expression "A + 3"
16125 @subheading The @code{-data-list-changed-registers} Command
16126 @findex -data-list-changed-registers
16128 @subsubheading Synopsis
16131 -data-list-changed-registers
16134 Display a list of the registers that have changed.
16136 @subsubheading @value{GDBN} Command
16138 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
16139 has the corresponding command @samp{gdb_changed_register_list}.
16141 @subsubheading Example
16143 On a PPC MBX board:
16151 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
16152 args=[],file="try.c",line="5"@}
16154 -data-list-changed-registers
16155 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
16156 "10","11","13","14","15","16","17","18","19","20","21","22","23",
16157 "24","25","26","27","28","30","31","64","65","66","67","69"]
16162 @subheading The @code{-data-list-register-names} Command
16163 @findex -data-list-register-names
16165 @subsubheading Synopsis
16168 -data-list-register-names [ ( @var{regno} )+ ]
16171 Show a list of register names for the current target. If no arguments
16172 are given, it shows a list of the names of all the registers. If
16173 integer numbers are given as arguments, it will print a list of the
16174 names of the registers corresponding to the arguments. To ensure
16175 consistency between a register name and its number, the output list may
16176 include empty register names.
16178 @subsubheading @value{GDBN} Command
16180 @value{GDBN} does not have a command which corresponds to
16181 @samp{-data-list-register-names}. In @code{gdbtk} there is a
16182 corresponding command @samp{gdb_regnames}.
16184 @subsubheading Example
16186 For the PPC MBX board:
16189 -data-list-register-names
16190 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
16191 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
16192 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
16193 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
16194 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
16195 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
16196 "", "pc","ps","cr","lr","ctr","xer"]
16198 -data-list-register-names 1 2 3
16199 ^done,register-names=["r1","r2","r3"]
16203 @subheading The @code{-data-list-register-values} Command
16204 @findex -data-list-register-values
16206 @subsubheading Synopsis
16209 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
16212 Display the registers' contents. @var{fmt} is the format according to
16213 which the registers' contents are to be returned, followed by an optional
16214 list of numbers specifying the registers to display. A missing list of
16215 numbers indicates that the contents of all the registers must be returned.
16217 Allowed formats for @var{fmt} are:
16234 @subsubheading @value{GDBN} Command
16236 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
16237 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
16239 @subsubheading Example
16241 For a PPC MBX board (note: line breaks are for readability only, they
16242 don't appear in the actual output):
16246 -data-list-register-values r 64 65
16247 ^done,register-values=[@{number="64",value="0xfe00a300"@},
16248 @{number="65",value="0x00029002"@}]
16250 -data-list-register-values x
16251 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
16252 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
16253 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
16254 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
16255 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
16256 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
16257 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
16258 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
16259 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
16260 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
16261 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
16262 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
16263 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
16264 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
16265 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
16266 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
16267 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
16268 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
16269 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
16270 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
16271 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
16272 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
16273 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
16274 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
16275 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
16276 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
16277 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
16278 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
16279 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
16280 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
16281 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
16282 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
16283 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
16284 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
16285 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
16286 @{number="69",value="0x20002b03"@}]
16291 @subheading The @code{-data-read-memory} Command
16292 @findex -data-read-memory
16294 @subsubheading Synopsis
16297 -data-read-memory [ -o @var{byte-offset} ]
16298 @var{address} @var{word-format} @var{word-size}
16299 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
16306 @item @var{address}
16307 An expression specifying the address of the first memory word to be
16308 read. Complex expressions containing embedded white space should be
16309 quoted using the C convention.
16311 @item @var{word-format}
16312 The format to be used to print the memory words. The notation is the
16313 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
16316 @item @var{word-size}
16317 The size of each memory word in bytes.
16319 @item @var{nr-rows}
16320 The number of rows in the output table.
16322 @item @var{nr-cols}
16323 The number of columns in the output table.
16326 If present, indicates that each row should include an @sc{ascii} dump. The
16327 value of @var{aschar} is used as a padding character when a byte is not a
16328 member of the printable @sc{ascii} character set (printable @sc{ascii}
16329 characters are those whose code is between 32 and 126, inclusively).
16331 @item @var{byte-offset}
16332 An offset to add to the @var{address} before fetching memory.
16335 This command displays memory contents as a table of @var{nr-rows} by
16336 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
16337 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
16338 (returned as @samp{total-bytes}). Should less than the requested number
16339 of bytes be returned by the target, the missing words are identified
16340 using @samp{N/A}. The number of bytes read from the target is returned
16341 in @samp{nr-bytes} and the starting address used to read memory in
16344 The address of the next/previous row or page is available in
16345 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
16348 @subsubheading @value{GDBN} Command
16350 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
16351 @samp{gdb_get_mem} memory read command.
16353 @subsubheading Example
16355 Read six bytes of memory starting at @code{bytes+6} but then offset by
16356 @code{-6} bytes. Format as three rows of two columns. One byte per
16357 word. Display each word in hex.
16361 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
16362 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
16363 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
16364 prev-page="0x0000138a",memory=[
16365 @{addr="0x00001390",data=["0x00","0x01"]@},
16366 @{addr="0x00001392",data=["0x02","0x03"]@},
16367 @{addr="0x00001394",data=["0x04","0x05"]@}]
16371 Read two bytes of memory starting at address @code{shorts + 64} and
16372 display as a single word formatted in decimal.
16376 5-data-read-memory shorts+64 d 2 1 1
16377 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
16378 next-row="0x00001512",prev-row="0x0000150e",
16379 next-page="0x00001512",prev-page="0x0000150e",memory=[
16380 @{addr="0x00001510",data=["128"]@}]
16384 Read thirty two bytes of memory starting at @code{bytes+16} and format
16385 as eight rows of four columns. Include a string encoding with @samp{x}
16386 used as the non-printable character.
16390 4-data-read-memory bytes+16 x 1 8 4 x
16391 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
16392 next-row="0x000013c0",prev-row="0x0000139c",
16393 next-page="0x000013c0",prev-page="0x00001380",memory=[
16394 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
16395 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
16396 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
16397 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
16398 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
16399 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
16400 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
16401 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
16405 @subheading The @code{-display-delete} Command
16406 @findex -display-delete
16408 @subsubheading Synopsis
16411 -display-delete @var{number}
16414 Delete the display @var{number}.
16416 @subsubheading @value{GDBN} Command
16418 The corresponding @value{GDBN} command is @samp{delete display}.
16420 @subsubheading Example
16424 @subheading The @code{-display-disable} Command
16425 @findex -display-disable
16427 @subsubheading Synopsis
16430 -display-disable @var{number}
16433 Disable display @var{number}.
16435 @subsubheading @value{GDBN} Command
16437 The corresponding @value{GDBN} command is @samp{disable display}.
16439 @subsubheading Example
16443 @subheading The @code{-display-enable} Command
16444 @findex -display-enable
16446 @subsubheading Synopsis
16449 -display-enable @var{number}
16452 Enable display @var{number}.
16454 @subsubheading @value{GDBN} Command
16456 The corresponding @value{GDBN} command is @samp{enable display}.
16458 @subsubheading Example
16462 @subheading The @code{-display-insert} Command
16463 @findex -display-insert
16465 @subsubheading Synopsis
16468 -display-insert @var{expression}
16471 Display @var{expression} every time the program stops.
16473 @subsubheading @value{GDBN} Command
16475 The corresponding @value{GDBN} command is @samp{display}.
16477 @subsubheading Example
16481 @subheading The @code{-display-list} Command
16482 @findex -display-list
16484 @subsubheading Synopsis
16490 List the displays. Do not show the current values.
16492 @subsubheading @value{GDBN} Command
16494 The corresponding @value{GDBN} command is @samp{info display}.
16496 @subsubheading Example
16500 @subheading The @code{-environment-cd} Command
16501 @findex -environment-cd
16503 @subsubheading Synopsis
16506 -environment-cd @var{pathdir}
16509 Set @value{GDBN}'s working directory.
16511 @subsubheading @value{GDBN} Command
16513 The corresponding @value{GDBN} command is @samp{cd}.
16515 @subsubheading Example
16519 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
16525 @subheading The @code{-environment-directory} Command
16526 @findex -environment-directory
16528 @subsubheading Synopsis
16531 -environment-directory [ -r ] [ @var{pathdir} ]+
16534 Add directories @var{pathdir} to beginning of search path for source files.
16535 If the @samp{-r} option is used, the search path is reset to the default
16536 search path. If directories @var{pathdir} are supplied in addition to the
16537 @samp{-r} option, the search path is first reset and then addition
16539 Multiple directories may be specified, separated by blanks. Specifying
16540 multiple directories in a single command
16541 results in the directories added to the beginning of the
16542 search path in the same order they were presented in the command.
16543 If blanks are needed as
16544 part of a directory name, double-quotes should be used around
16545 the name. In the command output, the path will show up separated
16546 by the system directory-separator character. The directory-seperator
16547 character must not be used
16548 in any directory name.
16549 If no directories are specified, the current search path is displayed.
16551 @subsubheading @value{GDBN} Command
16553 The corresponding @value{GDBN} command is @samp{dir}.
16555 @subsubheading Example
16559 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
16560 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
16562 -environment-directory ""
16563 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
16565 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
16566 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
16568 -environment-directory -r
16569 ^done,source-path="$cdir:$cwd"
16574 @subheading The @code{-environment-path} Command
16575 @findex -environment-path
16577 @subsubheading Synopsis
16580 -environment-path [ -r ] [ @var{pathdir} ]+
16583 Add directories @var{pathdir} to beginning of search path for object files.
16584 If the @samp{-r} option is used, the search path is reset to the original
16585 search path that existed at gdb start-up. If directories @var{pathdir} are
16586 supplied in addition to the
16587 @samp{-r} option, the search path is first reset and then addition
16589 Multiple directories may be specified, separated by blanks. Specifying
16590 multiple directories in a single command
16591 results in the directories added to the beginning of the
16592 search path in the same order they were presented in the command.
16593 If blanks are needed as
16594 part of a directory name, double-quotes should be used around
16595 the name. In the command output, the path will show up separated
16596 by the system directory-separator character. The directory-seperator
16597 character must not be used
16598 in any directory name.
16599 If no directories are specified, the current path is displayed.
16602 @subsubheading @value{GDBN} Command
16604 The corresponding @value{GDBN} command is @samp{path}.
16606 @subsubheading Example
16611 ^done,path="/usr/bin"
16613 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
16614 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
16616 -environment-path -r /usr/local/bin
16617 ^done,path="/usr/local/bin:/usr/bin"
16622 @subheading The @code{-environment-pwd} Command
16623 @findex -environment-pwd
16625 @subsubheading Synopsis
16631 Show the current working directory.
16633 @subsubheading @value{GDBN} command
16635 The corresponding @value{GDBN} command is @samp{pwd}.
16637 @subsubheading Example
16642 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
16646 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16647 @node GDB/MI Program Control
16648 @section @sc{gdb/mi} Program control
16650 @subsubheading Program termination
16652 As a result of execution, the inferior program can run to completion, if
16653 it doesn't encounter any breakpoints. In this case the output will
16654 include an exit code, if the program has exited exceptionally.
16656 @subsubheading Examples
16659 Program exited normally:
16667 *stopped,reason="exited-normally"
16672 Program exited exceptionally:
16680 *stopped,reason="exited",exit-code="01"
16684 Another way the program can terminate is if it receives a signal such as
16685 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
16689 *stopped,reason="exited-signalled",signal-name="SIGINT",
16690 signal-meaning="Interrupt"
16694 @subheading The @code{-exec-abort} Command
16695 @findex -exec-abort
16697 @subsubheading Synopsis
16703 Kill the inferior running program.
16705 @subsubheading @value{GDBN} Command
16707 The corresponding @value{GDBN} command is @samp{kill}.
16709 @subsubheading Example
16713 @subheading The @code{-exec-arguments} Command
16714 @findex -exec-arguments
16716 @subsubheading Synopsis
16719 -exec-arguments @var{args}
16722 Set the inferior program arguments, to be used in the next
16725 @subsubheading @value{GDBN} Command
16727 The corresponding @value{GDBN} command is @samp{set args}.
16729 @subsubheading Example
16732 Don't have one around.
16735 @subheading The @code{-exec-continue} Command
16736 @findex -exec-continue
16738 @subsubheading Synopsis
16744 Asynchronous command. Resumes the execution of the inferior program
16745 until a breakpoint is encountered, or until the inferior exits.
16747 @subsubheading @value{GDBN} Command
16749 The corresponding @value{GDBN} corresponding is @samp{continue}.
16751 @subsubheading Example
16758 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
16759 file="hello.c",line="13"@}
16764 @subheading The @code{-exec-finish} Command
16765 @findex -exec-finish
16767 @subsubheading Synopsis
16773 Asynchronous command. Resumes the execution of the inferior program
16774 until the current function is exited. Displays the results returned by
16777 @subsubheading @value{GDBN} Command
16779 The corresponding @value{GDBN} command is @samp{finish}.
16781 @subsubheading Example
16783 Function returning @code{void}.
16790 *stopped,reason="function-finished",frame=@{func="main",args=[],
16791 file="hello.c",line="7"@}
16795 Function returning other than @code{void}. The name of the internal
16796 @value{GDBN} variable storing the result is printed, together with the
16803 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
16804 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
16805 file="recursive2.c",line="14"@},
16806 gdb-result-var="$1",return-value="0"
16811 @subheading The @code{-exec-interrupt} Command
16812 @findex -exec-interrupt
16814 @subsubheading Synopsis
16820 Asynchronous command. Interrupts the background execution of the target.
16821 Note how the token associated with the stop message is the one for the
16822 execution command that has been interrupted. The token for the interrupt
16823 itself only appears in the @samp{^done} output. If the user is trying to
16824 interrupt a non-running program, an error message will be printed.
16826 @subsubheading @value{GDBN} Command
16828 The corresponding @value{GDBN} command is @samp{interrupt}.
16830 @subsubheading Example
16841 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
16842 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",line="13"@}
16847 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
16852 @subheading The @code{-exec-next} Command
16855 @subsubheading Synopsis
16861 Asynchronous command. Resumes execution of the inferior program, stopping
16862 when the beginning of the next source line is reached.
16864 @subsubheading @value{GDBN} Command
16866 The corresponding @value{GDBN} command is @samp{next}.
16868 @subsubheading Example
16874 *stopped,reason="end-stepping-range",line="8",file="hello.c"
16879 @subheading The @code{-exec-next-instruction} Command
16880 @findex -exec-next-instruction
16882 @subsubheading Synopsis
16885 -exec-next-instruction
16888 Asynchronous command. Executes one machine instruction. If the
16889 instruction is a function call continues until the function returns. If
16890 the program stops at an instruction in the middle of a source line, the
16891 address will be printed as well.
16893 @subsubheading @value{GDBN} Command
16895 The corresponding @value{GDBN} command is @samp{nexti}.
16897 @subsubheading Example
16901 -exec-next-instruction
16905 *stopped,reason="end-stepping-range",
16906 addr="0x000100d4",line="5",file="hello.c"
16911 @subheading The @code{-exec-return} Command
16912 @findex -exec-return
16914 @subsubheading Synopsis
16920 Makes current function return immediately. Doesn't execute the inferior.
16921 Displays the new current frame.
16923 @subsubheading @value{GDBN} Command
16925 The corresponding @value{GDBN} command is @samp{return}.
16927 @subsubheading Example
16931 200-break-insert callee4
16932 200^done,bkpt=@{number="1",addr="0x00010734",
16933 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
16938 000*stopped,reason="breakpoint-hit",bkptno="1",
16939 frame=@{func="callee4",args=[],
16940 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
16946 111^done,frame=@{level="0",func="callee3",
16947 args=[@{name="strarg",
16948 value="0x11940 \"A string argument.\""@}],
16949 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
16954 @subheading The @code{-exec-run} Command
16957 @subsubheading Synopsis
16963 Asynchronous command. Starts execution of the inferior from the
16964 beginning. The inferior executes until either a breakpoint is
16965 encountered or the program exits.
16967 @subsubheading @value{GDBN} Command
16969 The corresponding @value{GDBN} command is @samp{run}.
16971 @subsubheading Example
16976 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
16981 *stopped,reason="breakpoint-hit",bkptno="1",
16982 frame=@{func="main",args=[],file="recursive2.c",line="4"@}
16987 @subheading The @code{-exec-show-arguments} Command
16988 @findex -exec-show-arguments
16990 @subsubheading Synopsis
16993 -exec-show-arguments
16996 Print the arguments of the program.
16998 @subsubheading @value{GDBN} Command
17000 The corresponding @value{GDBN} command is @samp{show args}.
17002 @subsubheading Example
17005 @c @subheading -exec-signal
17007 @subheading The @code{-exec-step} Command
17010 @subsubheading Synopsis
17016 Asynchronous command. Resumes execution of the inferior program, stopping
17017 when the beginning of the next source line is reached, if the next
17018 source line is not a function call. If it is, stop at the first
17019 instruction of the called function.
17021 @subsubheading @value{GDBN} Command
17023 The corresponding @value{GDBN} command is @samp{step}.
17025 @subsubheading Example
17027 Stepping into a function:
17033 *stopped,reason="end-stepping-range",
17034 frame=@{func="foo",args=[@{name="a",value="10"@},
17035 @{name="b",value="0"@}],file="recursive2.c",line="11"@}
17045 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
17050 @subheading The @code{-exec-step-instruction} Command
17051 @findex -exec-step-instruction
17053 @subsubheading Synopsis
17056 -exec-step-instruction
17059 Asynchronous command. Resumes the inferior which executes one machine
17060 instruction. The output, once @value{GDBN} has stopped, will vary depending on
17061 whether we have stopped in the middle of a source line or not. In the
17062 former case, the address at which the program stopped will be printed as
17065 @subsubheading @value{GDBN} Command
17067 The corresponding @value{GDBN} command is @samp{stepi}.
17069 @subsubheading Example
17073 -exec-step-instruction
17077 *stopped,reason="end-stepping-range",
17078 frame=@{func="foo",args=[],file="try.c",line="10"@}
17080 -exec-step-instruction
17084 *stopped,reason="end-stepping-range",
17085 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",line="10"@}
17090 @subheading The @code{-exec-until} Command
17091 @findex -exec-until
17093 @subsubheading Synopsis
17096 -exec-until [ @var{location} ]
17099 Asynchronous command. Executes the inferior until the @var{location}
17100 specified in the argument is reached. If there is no argument, the inferior
17101 executes until a source line greater than the current one is reached.
17102 The reason for stopping in this case will be @samp{location-reached}.
17104 @subsubheading @value{GDBN} Command
17106 The corresponding @value{GDBN} command is @samp{until}.
17108 @subsubheading Example
17112 -exec-until recursive2.c:6
17116 *stopped,reason="location-reached",frame=@{func="main",args=[],
17117 file="recursive2.c",line="6"@}
17122 @subheading -file-clear
17123 Is this going away????
17127 @subheading The @code{-file-exec-and-symbols} Command
17128 @findex -file-exec-and-symbols
17130 @subsubheading Synopsis
17133 -file-exec-and-symbols @var{file}
17136 Specify the executable file to be debugged. This file is the one from
17137 which the symbol table is also read. If no file is specified, the
17138 command clears the executable and symbol information. If breakpoints
17139 are set when using this command with no arguments, @value{GDBN} will produce
17140 error messages. Otherwise, no output is produced, except a completion
17143 @subsubheading @value{GDBN} Command
17145 The corresponding @value{GDBN} command is @samp{file}.
17147 @subsubheading Example
17151 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
17157 @subheading The @code{-file-exec-file} Command
17158 @findex -file-exec-file
17160 @subsubheading Synopsis
17163 -file-exec-file @var{file}
17166 Specify the executable file to be debugged. Unlike
17167 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
17168 from this file. If used without argument, @value{GDBN} clears the information
17169 about the executable file. No output is produced, except a completion
17172 @subsubheading @value{GDBN} Command
17174 The corresponding @value{GDBN} command is @samp{exec-file}.
17176 @subsubheading Example
17180 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
17186 @subheading The @code{-file-list-exec-sections} Command
17187 @findex -file-list-exec-sections
17189 @subsubheading Synopsis
17192 -file-list-exec-sections
17195 List the sections of the current executable file.
17197 @subsubheading @value{GDBN} Command
17199 The @value{GDBN} command @samp{info file} shows, among the rest, the same
17200 information as this command. @code{gdbtk} has a corresponding command
17201 @samp{gdb_load_info}.
17203 @subsubheading Example
17207 @subheading The @code{-file-list-exec-source-file} Command
17208 @findex -file-list-exec-source-file
17210 @subsubheading Synopsis
17213 -file-list-exec-source-file
17216 List the line number, the current source file, and the absolute path
17217 to the current source file for the current executable.
17219 @subsubheading @value{GDBN} Command
17221 There's no @value{GDBN} command which directly corresponds to this one.
17223 @subsubheading Example
17227 123-file-list-exec-source-file
17228 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
17233 @subheading The @code{-file-list-exec-source-files} Command
17234 @findex -file-list-exec-source-files
17236 @subsubheading Synopsis
17239 -file-list-exec-source-files
17242 List the source files for the current executable.
17244 It will always output the filename, but only when GDB can find the absolute
17245 file name of a source file, will it output the fullname.
17247 @subsubheading @value{GDBN} Command
17249 There's no @value{GDBN} command which directly corresponds to this one.
17250 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
17252 @subsubheading Example
17255 -file-list-exec-source-files
17257 @{file=foo.c,fullname=/home/foo.c@},
17258 @{file=/home/bar.c,fullname=/home/bar.c@},
17259 @{file=gdb_could_not_find_fullpath.c@}]
17263 @subheading The @code{-file-list-shared-libraries} Command
17264 @findex -file-list-shared-libraries
17266 @subsubheading Synopsis
17269 -file-list-shared-libraries
17272 List the shared libraries in the program.
17274 @subsubheading @value{GDBN} Command
17276 The corresponding @value{GDBN} command is @samp{info shared}.
17278 @subsubheading Example
17282 @subheading The @code{-file-list-symbol-files} Command
17283 @findex -file-list-symbol-files
17285 @subsubheading Synopsis
17288 -file-list-symbol-files
17293 @subsubheading @value{GDBN} Command
17295 The corresponding @value{GDBN} command is @samp{info file} (part of it).
17297 @subsubheading Example
17301 @subheading The @code{-file-symbol-file} Command
17302 @findex -file-symbol-file
17304 @subsubheading Synopsis
17307 -file-symbol-file @var{file}
17310 Read symbol table info from the specified @var{file} argument. When
17311 used without arguments, clears @value{GDBN}'s symbol table info. No output is
17312 produced, except for a completion notification.
17314 @subsubheading @value{GDBN} Command
17316 The corresponding @value{GDBN} command is @samp{symbol-file}.
17318 @subsubheading Example
17322 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
17327 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17328 @node GDB/MI Miscellaneous Commands
17329 @section Miscellaneous @value{GDBN} commands in @sc{gdb/mi}
17331 @c @subheading -gdb-complete
17333 @subheading The @code{-gdb-exit} Command
17336 @subsubheading Synopsis
17342 Exit @value{GDBN} immediately.
17344 @subsubheading @value{GDBN} Command
17346 Approximately corresponds to @samp{quit}.
17348 @subsubheading Example
17355 @subheading The @code{-gdb-set} Command
17358 @subsubheading Synopsis
17364 Set an internal @value{GDBN} variable.
17365 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
17367 @subsubheading @value{GDBN} Command
17369 The corresponding @value{GDBN} command is @samp{set}.
17371 @subsubheading Example
17381 @subheading The @code{-gdb-show} Command
17384 @subsubheading Synopsis
17390 Show the current value of a @value{GDBN} variable.
17392 @subsubheading @value{GDBN} command
17394 The corresponding @value{GDBN} command is @samp{show}.
17396 @subsubheading Example
17405 @c @subheading -gdb-source
17408 @subheading The @code{-gdb-version} Command
17409 @findex -gdb-version
17411 @subsubheading Synopsis
17417 Show version information for @value{GDBN}. Used mostly in testing.
17419 @subsubheading @value{GDBN} Command
17421 There's no equivalent @value{GDBN} command. @value{GDBN} by default shows this
17422 information when you start an interactive session.
17424 @subsubheading Example
17426 @c This example modifies the actual output from GDB to avoid overfull
17432 ~Copyright 2000 Free Software Foundation, Inc.
17433 ~GDB is free software, covered by the GNU General Public License, and
17434 ~you are welcome to change it and/or distribute copies of it under
17435 ~ certain conditions.
17436 ~Type "show copying" to see the conditions.
17437 ~There is absolutely no warranty for GDB. Type "show warranty" for
17439 ~This GDB was configured as
17440 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
17445 @subheading The @code{-interpreter-exec} Command
17446 @findex -interpreter-exec
17448 @subheading Synopsis
17451 -interpreter-exec @var{interpreter} @var{command}
17454 Execute the specified @var{command} in the given @var{interpreter}.
17456 @subheading @value{GDBN} Command
17458 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
17460 @subheading Example
17464 -interpreter-exec console "break main"
17465 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
17466 &"During symbol reading, bad structure-type format.\n"
17467 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
17473 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17474 @node GDB/MI Kod Commands
17475 @section @sc{gdb/mi} Kod Commands
17477 The Kod commands are not implemented.
17479 @c @subheading -kod-info
17481 @c @subheading -kod-list
17483 @c @subheading -kod-list-object-types
17485 @c @subheading -kod-show
17487 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17488 @node GDB/MI Memory Overlay Commands
17489 @section @sc{gdb/mi} Memory Overlay Commands
17491 The memory overlay commands are not implemented.
17493 @c @subheading -overlay-auto
17495 @c @subheading -overlay-list-mapping-state
17497 @c @subheading -overlay-list-overlays
17499 @c @subheading -overlay-map
17501 @c @subheading -overlay-off
17503 @c @subheading -overlay-on
17505 @c @subheading -overlay-unmap
17507 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17508 @node GDB/MI Signal Handling Commands
17509 @section @sc{gdb/mi} Signal Handling Commands
17511 Signal handling commands are not implemented.
17513 @c @subheading -signal-handle
17515 @c @subheading -signal-list-handle-actions
17517 @c @subheading -signal-list-signal-types
17521 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17522 @node GDB/MI Stack Manipulation
17523 @section @sc{gdb/mi} Stack Manipulation Commands
17526 @subheading The @code{-stack-info-frame} Command
17527 @findex -stack-info-frame
17529 @subsubheading Synopsis
17535 Get info on the current frame.
17537 @subsubheading @value{GDBN} Command
17539 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
17540 (without arguments).
17542 @subsubheading Example
17545 @subheading The @code{-stack-info-depth} Command
17546 @findex -stack-info-depth
17548 @subsubheading Synopsis
17551 -stack-info-depth [ @var{max-depth} ]
17554 Return the depth of the stack. If the integer argument @var{max-depth}
17555 is specified, do not count beyond @var{max-depth} frames.
17557 @subsubheading @value{GDBN} Command
17559 There's no equivalent @value{GDBN} command.
17561 @subsubheading Example
17563 For a stack with frame levels 0 through 11:
17570 -stack-info-depth 4
17573 -stack-info-depth 12
17576 -stack-info-depth 11
17579 -stack-info-depth 13
17584 @subheading The @code{-stack-list-arguments} Command
17585 @findex -stack-list-arguments
17587 @subsubheading Synopsis
17590 -stack-list-arguments @var{show-values}
17591 [ @var{low-frame} @var{high-frame} ]
17594 Display a list of the arguments for the frames between @var{low-frame}
17595 and @var{high-frame} (inclusive). If @var{low-frame} and
17596 @var{high-frame} are not provided, list the arguments for the whole call
17599 The @var{show-values} argument must have a value of 0 or 1. A value of
17600 0 means that only the names of the arguments are listed, a value of 1
17601 means that both names and values of the arguments are printed.
17603 @subsubheading @value{GDBN} Command
17605 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
17606 @samp{gdb_get_args} command which partially overlaps with the
17607 functionality of @samp{-stack-list-arguments}.
17609 @subsubheading Example
17616 frame=@{level="0",addr="0x00010734",func="callee4",
17617 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
17618 frame=@{level="1",addr="0x0001076c",func="callee3",
17619 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
17620 frame=@{level="2",addr="0x0001078c",func="callee2",
17621 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
17622 frame=@{level="3",addr="0x000107b4",func="callee1",
17623 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
17624 frame=@{level="4",addr="0x000107e0",func="main",
17625 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
17627 -stack-list-arguments 0
17630 frame=@{level="0",args=[]@},
17631 frame=@{level="1",args=[name="strarg"]@},
17632 frame=@{level="2",args=[name="intarg",name="strarg"]@},
17633 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
17634 frame=@{level="4",args=[]@}]
17636 -stack-list-arguments 1
17639 frame=@{level="0",args=[]@},
17641 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
17642 frame=@{level="2",args=[
17643 @{name="intarg",value="2"@},
17644 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
17645 @{frame=@{level="3",args=[
17646 @{name="intarg",value="2"@},
17647 @{name="strarg",value="0x11940 \"A string argument.\""@},
17648 @{name="fltarg",value="3.5"@}]@},
17649 frame=@{level="4",args=[]@}]
17651 -stack-list-arguments 0 2 2
17652 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
17654 -stack-list-arguments 1 2 2
17655 ^done,stack-args=[frame=@{level="2",
17656 args=[@{name="intarg",value="2"@},
17657 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
17661 @c @subheading -stack-list-exception-handlers
17664 @subheading The @code{-stack-list-frames} Command
17665 @findex -stack-list-frames
17667 @subsubheading Synopsis
17670 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
17673 List the frames currently on the stack. For each frame it displays the
17678 The frame number, 0 being the topmost frame, i.e. the innermost function.
17680 The @code{$pc} value for that frame.
17684 File name of the source file where the function lives.
17686 Line number corresponding to the @code{$pc}.
17689 If invoked without arguments, this command prints a backtrace for the
17690 whole stack. If given two integer arguments, it shows the frames whose
17691 levels are between the two arguments (inclusive). If the two arguments
17692 are equal, it shows the single frame at the corresponding level.
17694 @subsubheading @value{GDBN} Command
17696 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
17698 @subsubheading Example
17700 Full stack backtrace:
17706 [frame=@{level="0",addr="0x0001076c",func="foo",
17707 file="recursive2.c",line="11"@},
17708 frame=@{level="1",addr="0x000107a4",func="foo",
17709 file="recursive2.c",line="14"@},
17710 frame=@{level="2",addr="0x000107a4",func="foo",
17711 file="recursive2.c",line="14"@},
17712 frame=@{level="3",addr="0x000107a4",func="foo",
17713 file="recursive2.c",line="14"@},
17714 frame=@{level="4",addr="0x000107a4",func="foo",
17715 file="recursive2.c",line="14"@},
17716 frame=@{level="5",addr="0x000107a4",func="foo",
17717 file="recursive2.c",line="14"@},
17718 frame=@{level="6",addr="0x000107a4",func="foo",
17719 file="recursive2.c",line="14"@},
17720 frame=@{level="7",addr="0x000107a4",func="foo",
17721 file="recursive2.c",line="14"@},
17722 frame=@{level="8",addr="0x000107a4",func="foo",
17723 file="recursive2.c",line="14"@},
17724 frame=@{level="9",addr="0x000107a4",func="foo",
17725 file="recursive2.c",line="14"@},
17726 frame=@{level="10",addr="0x000107a4",func="foo",
17727 file="recursive2.c",line="14"@},
17728 frame=@{level="11",addr="0x00010738",func="main",
17729 file="recursive2.c",line="4"@}]
17733 Show frames between @var{low_frame} and @var{high_frame}:
17737 -stack-list-frames 3 5
17739 [frame=@{level="3",addr="0x000107a4",func="foo",
17740 file="recursive2.c",line="14"@},
17741 frame=@{level="4",addr="0x000107a4",func="foo",
17742 file="recursive2.c",line="14"@},
17743 frame=@{level="5",addr="0x000107a4",func="foo",
17744 file="recursive2.c",line="14"@}]
17748 Show a single frame:
17752 -stack-list-frames 3 3
17754 [frame=@{level="3",addr="0x000107a4",func="foo",
17755 file="recursive2.c",line="14"@}]
17760 @subheading The @code{-stack-list-locals} Command
17761 @findex -stack-list-locals
17763 @subsubheading Synopsis
17766 -stack-list-locals @var{print-values}
17769 Display the local variable names for the current frame. With an
17770 argument of 0 or @code{--no-values}, prints only the names of the variables.
17771 With argument of 1 or @code{--all-values}, prints also their values. With
17772 argument of 2 or @code{--simple-values}, prints the name, type and value for
17773 simple data types and the name and type for arrays, structures and
17774 unions. In this last case, the idea is that the user can see the
17775 value of simple data types immediately and he can create variable
17776 objects for other data types if he wishes to explore their values in
17779 @subsubheading @value{GDBN} Command
17781 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
17783 @subsubheading Example
17787 -stack-list-locals 0
17788 ^done,locals=[name="A",name="B",name="C"]
17790 -stack-list-locals --all-values
17791 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
17792 @{name="C",value="@{1, 2, 3@}"@}]
17793 -stack-list-locals --simple-values
17794 ^done,locals=[@{name="A",type="int",value="1"@},
17795 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
17800 @subheading The @code{-stack-select-frame} Command
17801 @findex -stack-select-frame
17803 @subsubheading Synopsis
17806 -stack-select-frame @var{framenum}
17809 Change the current frame. Select a different frame @var{framenum} on
17812 @subsubheading @value{GDBN} Command
17814 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
17815 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
17817 @subsubheading Example
17821 -stack-select-frame 2
17826 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17827 @node GDB/MI Symbol Query
17828 @section @sc{gdb/mi} Symbol Query Commands
17831 @subheading The @code{-symbol-info-address} Command
17832 @findex -symbol-info-address
17834 @subsubheading Synopsis
17837 -symbol-info-address @var{symbol}
17840 Describe where @var{symbol} is stored.
17842 @subsubheading @value{GDBN} Command
17844 The corresponding @value{GDBN} command is @samp{info address}.
17846 @subsubheading Example
17850 @subheading The @code{-symbol-info-file} Command
17851 @findex -symbol-info-file
17853 @subsubheading Synopsis
17859 Show the file for the symbol.
17861 @subsubheading @value{GDBN} Command
17863 There's no equivalent @value{GDBN} command. @code{gdbtk} has
17864 @samp{gdb_find_file}.
17866 @subsubheading Example
17870 @subheading The @code{-symbol-info-function} Command
17871 @findex -symbol-info-function
17873 @subsubheading Synopsis
17876 -symbol-info-function
17879 Show which function the symbol lives in.
17881 @subsubheading @value{GDBN} Command
17883 @samp{gdb_get_function} in @code{gdbtk}.
17885 @subsubheading Example
17889 @subheading The @code{-symbol-info-line} Command
17890 @findex -symbol-info-line
17892 @subsubheading Synopsis
17898 Show the core addresses of the code for a source line.
17900 @subsubheading @value{GDBN} Command
17902 The corresponding @value{GDBN} command is @samp{info line}.
17903 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
17905 @subsubheading Example
17909 @subheading The @code{-symbol-info-symbol} Command
17910 @findex -symbol-info-symbol
17912 @subsubheading Synopsis
17915 -symbol-info-symbol @var{addr}
17918 Describe what symbol is at location @var{addr}.
17920 @subsubheading @value{GDBN} Command
17922 The corresponding @value{GDBN} command is @samp{info symbol}.
17924 @subsubheading Example
17928 @subheading The @code{-symbol-list-functions} Command
17929 @findex -symbol-list-functions
17931 @subsubheading Synopsis
17934 -symbol-list-functions
17937 List the functions in the executable.
17939 @subsubheading @value{GDBN} Command
17941 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
17942 @samp{gdb_search} in @code{gdbtk}.
17944 @subsubheading Example
17948 @subheading The @code{-symbol-list-lines} Command
17949 @findex -symbol-list-lines
17951 @subsubheading Synopsis
17954 -symbol-list-lines @var{filename}
17957 Print the list of lines that contain code and their associated program
17958 addresses for the given source filename. The entries are sorted in
17959 ascending PC order.
17961 @subsubheading @value{GDBN} Command
17963 There is no corresponding @value{GDBN} command.
17965 @subsubheading Example
17968 -symbol-list-lines basics.c
17969 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
17974 @subheading The @code{-symbol-list-types} Command
17975 @findex -symbol-list-types
17977 @subsubheading Synopsis
17983 List all the type names.
17985 @subsubheading @value{GDBN} Command
17987 The corresponding commands are @samp{info types} in @value{GDBN},
17988 @samp{gdb_search} in @code{gdbtk}.
17990 @subsubheading Example
17994 @subheading The @code{-symbol-list-variables} Command
17995 @findex -symbol-list-variables
17997 @subsubheading Synopsis
18000 -symbol-list-variables
18003 List all the global and static variable names.
18005 @subsubheading @value{GDBN} Command
18007 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
18009 @subsubheading Example
18013 @subheading The @code{-symbol-locate} Command
18014 @findex -symbol-locate
18016 @subsubheading Synopsis
18022 @subsubheading @value{GDBN} Command
18024 @samp{gdb_loc} in @code{gdbtk}.
18026 @subsubheading Example
18030 @subheading The @code{-symbol-type} Command
18031 @findex -symbol-type
18033 @subsubheading Synopsis
18036 -symbol-type @var{variable}
18039 Show type of @var{variable}.
18041 @subsubheading @value{GDBN} Command
18043 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
18044 @samp{gdb_obj_variable}.
18046 @subsubheading Example
18050 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18051 @node GDB/MI Target Manipulation
18052 @section @sc{gdb/mi} Target Manipulation Commands
18055 @subheading The @code{-target-attach} Command
18056 @findex -target-attach
18058 @subsubheading Synopsis
18061 -target-attach @var{pid} | @var{file}
18064 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
18066 @subsubheading @value{GDBN} command
18068 The corresponding @value{GDBN} command is @samp{attach}.
18070 @subsubheading Example
18074 @subheading The @code{-target-compare-sections} Command
18075 @findex -target-compare-sections
18077 @subsubheading Synopsis
18080 -target-compare-sections [ @var{section} ]
18083 Compare data of section @var{section} on target to the exec file.
18084 Without the argument, all sections are compared.
18086 @subsubheading @value{GDBN} Command
18088 The @value{GDBN} equivalent is @samp{compare-sections}.
18090 @subsubheading Example
18094 @subheading The @code{-target-detach} Command
18095 @findex -target-detach
18097 @subsubheading Synopsis
18103 Disconnect from the remote target. There's no output.
18105 @subsubheading @value{GDBN} command
18107 The corresponding @value{GDBN} command is @samp{detach}.
18109 @subsubheading Example
18119 @subheading The @code{-target-disconnect} Command
18120 @findex -target-disconnect
18122 @subsubheading Synopsis
18128 Disconnect from the remote target. There's no output.
18130 @subsubheading @value{GDBN} command
18132 The corresponding @value{GDBN} command is @samp{disconnect}.
18134 @subsubheading Example
18144 @subheading The @code{-target-download} Command
18145 @findex -target-download
18147 @subsubheading Synopsis
18153 Loads the executable onto the remote target.
18154 It prints out an update message every half second, which includes the fields:
18158 The name of the section.
18160 The size of what has been sent so far for that section.
18162 The size of the section.
18164 The total size of what was sent so far (the current and the previous sections).
18166 The size of the overall executable to download.
18170 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
18171 @sc{gdb/mi} Output Syntax}).
18173 In addition, it prints the name and size of the sections, as they are
18174 downloaded. These messages include the following fields:
18178 The name of the section.
18180 The size of the section.
18182 The size of the overall executable to download.
18186 At the end, a summary is printed.
18188 @subsubheading @value{GDBN} Command
18190 The corresponding @value{GDBN} command is @samp{load}.
18192 @subsubheading Example
18194 Note: each status message appears on a single line. Here the messages
18195 have been broken down so that they can fit onto a page.
18200 +download,@{section=".text",section-size="6668",total-size="9880"@}
18201 +download,@{section=".text",section-sent="512",section-size="6668",
18202 total-sent="512",total-size="9880"@}
18203 +download,@{section=".text",section-sent="1024",section-size="6668",
18204 total-sent="1024",total-size="9880"@}
18205 +download,@{section=".text",section-sent="1536",section-size="6668",
18206 total-sent="1536",total-size="9880"@}
18207 +download,@{section=".text",section-sent="2048",section-size="6668",
18208 total-sent="2048",total-size="9880"@}
18209 +download,@{section=".text",section-sent="2560",section-size="6668",
18210 total-sent="2560",total-size="9880"@}
18211 +download,@{section=".text",section-sent="3072",section-size="6668",
18212 total-sent="3072",total-size="9880"@}
18213 +download,@{section=".text",section-sent="3584",section-size="6668",
18214 total-sent="3584",total-size="9880"@}
18215 +download,@{section=".text",section-sent="4096",section-size="6668",
18216 total-sent="4096",total-size="9880"@}
18217 +download,@{section=".text",section-sent="4608",section-size="6668",
18218 total-sent="4608",total-size="9880"@}
18219 +download,@{section=".text",section-sent="5120",section-size="6668",
18220 total-sent="5120",total-size="9880"@}
18221 +download,@{section=".text",section-sent="5632",section-size="6668",
18222 total-sent="5632",total-size="9880"@}
18223 +download,@{section=".text",section-sent="6144",section-size="6668",
18224 total-sent="6144",total-size="9880"@}
18225 +download,@{section=".text",section-sent="6656",section-size="6668",
18226 total-sent="6656",total-size="9880"@}
18227 +download,@{section=".init",section-size="28",total-size="9880"@}
18228 +download,@{section=".fini",section-size="28",total-size="9880"@}
18229 +download,@{section=".data",section-size="3156",total-size="9880"@}
18230 +download,@{section=".data",section-sent="512",section-size="3156",
18231 total-sent="7236",total-size="9880"@}
18232 +download,@{section=".data",section-sent="1024",section-size="3156",
18233 total-sent="7748",total-size="9880"@}
18234 +download,@{section=".data",section-sent="1536",section-size="3156",
18235 total-sent="8260",total-size="9880"@}
18236 +download,@{section=".data",section-sent="2048",section-size="3156",
18237 total-sent="8772",total-size="9880"@}
18238 +download,@{section=".data",section-sent="2560",section-size="3156",
18239 total-sent="9284",total-size="9880"@}
18240 +download,@{section=".data",section-sent="3072",section-size="3156",
18241 total-sent="9796",total-size="9880"@}
18242 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
18248 @subheading The @code{-target-exec-status} Command
18249 @findex -target-exec-status
18251 @subsubheading Synopsis
18254 -target-exec-status
18257 Provide information on the state of the target (whether it is running or
18258 not, for instance).
18260 @subsubheading @value{GDBN} Command
18262 There's no equivalent @value{GDBN} command.
18264 @subsubheading Example
18268 @subheading The @code{-target-list-available-targets} Command
18269 @findex -target-list-available-targets
18271 @subsubheading Synopsis
18274 -target-list-available-targets
18277 List the possible targets to connect to.
18279 @subsubheading @value{GDBN} Command
18281 The corresponding @value{GDBN} command is @samp{help target}.
18283 @subsubheading Example
18287 @subheading The @code{-target-list-current-targets} Command
18288 @findex -target-list-current-targets
18290 @subsubheading Synopsis
18293 -target-list-current-targets
18296 Describe the current target.
18298 @subsubheading @value{GDBN} Command
18300 The corresponding information is printed by @samp{info file} (among
18303 @subsubheading Example
18307 @subheading The @code{-target-list-parameters} Command
18308 @findex -target-list-parameters
18310 @subsubheading Synopsis
18313 -target-list-parameters
18318 @subsubheading @value{GDBN} Command
18322 @subsubheading Example
18326 @subheading The @code{-target-select} Command
18327 @findex -target-select
18329 @subsubheading Synopsis
18332 -target-select @var{type} @var{parameters @dots{}}
18335 Connect @value{GDBN} to the remote target. This command takes two args:
18339 The type of target, for instance @samp{async}, @samp{remote}, etc.
18340 @item @var{parameters}
18341 Device names, host names and the like. @xref{Target Commands, ,
18342 Commands for managing targets}, for more details.
18345 The output is a connection notification, followed by the address at
18346 which the target program is, in the following form:
18349 ^connected,addr="@var{address}",func="@var{function name}",
18350 args=[@var{arg list}]
18353 @subsubheading @value{GDBN} Command
18355 The corresponding @value{GDBN} command is @samp{target}.
18357 @subsubheading Example
18361 -target-select async /dev/ttya
18362 ^connected,addr="0xfe00a300",func="??",args=[]
18366 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18367 @node GDB/MI Thread Commands
18368 @section @sc{gdb/mi} Thread Commands
18371 @subheading The @code{-thread-info} Command
18372 @findex -thread-info
18374 @subsubheading Synopsis
18380 @subsubheading @value{GDBN} command
18384 @subsubheading Example
18388 @subheading The @code{-thread-list-all-threads} Command
18389 @findex -thread-list-all-threads
18391 @subsubheading Synopsis
18394 -thread-list-all-threads
18397 @subsubheading @value{GDBN} Command
18399 The equivalent @value{GDBN} command is @samp{info threads}.
18401 @subsubheading Example
18405 @subheading The @code{-thread-list-ids} Command
18406 @findex -thread-list-ids
18408 @subsubheading Synopsis
18414 Produces a list of the currently known @value{GDBN} thread ids. At the
18415 end of the list it also prints the total number of such threads.
18417 @subsubheading @value{GDBN} Command
18419 Part of @samp{info threads} supplies the same information.
18421 @subsubheading Example
18423 No threads present, besides the main process:
18428 ^done,thread-ids=@{@},number-of-threads="0"
18438 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18439 number-of-threads="3"
18444 @subheading The @code{-thread-select} Command
18445 @findex -thread-select
18447 @subsubheading Synopsis
18450 -thread-select @var{threadnum}
18453 Make @var{threadnum} the current thread. It prints the number of the new
18454 current thread, and the topmost frame for that thread.
18456 @subsubheading @value{GDBN} Command
18458 The corresponding @value{GDBN} command is @samp{thread}.
18460 @subsubheading Example
18467 *stopped,reason="end-stepping-range",thread-id="2",line="187",
18468 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
18472 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18473 number-of-threads="3"
18476 ^done,new-thread-id="3",
18477 frame=@{level="0",func="vprintf",
18478 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
18479 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
18483 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18484 @node GDB/MI Tracepoint Commands
18485 @section @sc{gdb/mi} Tracepoint Commands
18487 The tracepoint commands are not yet implemented.
18489 @c @subheading -trace-actions
18491 @c @subheading -trace-delete
18493 @c @subheading -trace-disable
18495 @c @subheading -trace-dump
18497 @c @subheading -trace-enable
18499 @c @subheading -trace-exists
18501 @c @subheading -trace-find
18503 @c @subheading -trace-frame-number
18505 @c @subheading -trace-info
18507 @c @subheading -trace-insert
18509 @c @subheading -trace-list
18511 @c @subheading -trace-pass-count
18513 @c @subheading -trace-save
18515 @c @subheading -trace-start
18517 @c @subheading -trace-stop
18520 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18521 @node GDB/MI Variable Objects
18522 @section @sc{gdb/mi} Variable Objects
18525 @subheading Motivation for Variable Objects in @sc{gdb/mi}
18527 For the implementation of a variable debugger window (locals, watched
18528 expressions, etc.), we are proposing the adaptation of the existing code
18529 used by @code{Insight}.
18531 The two main reasons for that are:
18535 It has been proven in practice (it is already on its second generation).
18538 It will shorten development time (needless to say how important it is
18542 The original interface was designed to be used by Tcl code, so it was
18543 slightly changed so it could be used through @sc{gdb/mi}. This section
18544 describes the @sc{gdb/mi} operations that will be available and gives some
18545 hints about their use.
18547 @emph{Note}: In addition to the set of operations described here, we
18548 expect the @sc{gui} implementation of a variable window to require, at
18549 least, the following operations:
18552 @item @code{-gdb-show} @code{output-radix}
18553 @item @code{-stack-list-arguments}
18554 @item @code{-stack-list-locals}
18555 @item @code{-stack-select-frame}
18558 @subheading Introduction to Variable Objects in @sc{gdb/mi}
18560 @cindex variable objects in @sc{gdb/mi}
18561 The basic idea behind variable objects is the creation of a named object
18562 to represent a variable, an expression, a memory location or even a CPU
18563 register. For each object created, a set of operations is available for
18564 examining or changing its properties.
18566 Furthermore, complex data types, such as C structures, are represented
18567 in a tree format. For instance, the @code{struct} type variable is the
18568 root and the children will represent the struct members. If a child
18569 is itself of a complex type, it will also have children of its own.
18570 Appropriate language differences are handled for C, C@t{++} and Java.
18572 When returning the actual values of the objects, this facility allows
18573 for the individual selection of the display format used in the result
18574 creation. It can be chosen among: binary, decimal, hexadecimal, octal
18575 and natural. Natural refers to a default format automatically
18576 chosen based on the variable type (like decimal for an @code{int}, hex
18577 for pointers, etc.).
18579 The following is the complete set of @sc{gdb/mi} operations defined to
18580 access this functionality:
18582 @multitable @columnfractions .4 .6
18583 @item @strong{Operation}
18584 @tab @strong{Description}
18586 @item @code{-var-create}
18587 @tab create a variable object
18588 @item @code{-var-delete}
18589 @tab delete the variable object and its children
18590 @item @code{-var-set-format}
18591 @tab set the display format of this variable
18592 @item @code{-var-show-format}
18593 @tab show the display format of this variable
18594 @item @code{-var-info-num-children}
18595 @tab tells how many children this object has
18596 @item @code{-var-list-children}
18597 @tab return a list of the object's children
18598 @item @code{-var-info-type}
18599 @tab show the type of this variable object
18600 @item @code{-var-info-expression}
18601 @tab print what this variable object represents
18602 @item @code{-var-show-attributes}
18603 @tab is this variable editable? does it exist here?
18604 @item @code{-var-evaluate-expression}
18605 @tab get the value of this variable
18606 @item @code{-var-assign}
18607 @tab set the value of this variable
18608 @item @code{-var-update}
18609 @tab update the variable and its children
18612 In the next subsection we describe each operation in detail and suggest
18613 how it can be used.
18615 @subheading Description And Use of Operations on Variable Objects
18617 @subheading The @code{-var-create} Command
18618 @findex -var-create
18620 @subsubheading Synopsis
18623 -var-create @{@var{name} | "-"@}
18624 @{@var{frame-addr} | "*"@} @var{expression}
18627 This operation creates a variable object, which allows the monitoring of
18628 a variable, the result of an expression, a memory cell or a CPU
18631 The @var{name} parameter is the string by which the object can be
18632 referenced. It must be unique. If @samp{-} is specified, the varobj
18633 system will generate a string ``varNNNNNN'' automatically. It will be
18634 unique provided that one does not specify @var{name} on that format.
18635 The command fails if a duplicate name is found.
18637 The frame under which the expression should be evaluated can be
18638 specified by @var{frame-addr}. A @samp{*} indicates that the current
18639 frame should be used.
18641 @var{expression} is any expression valid on the current language set (must not
18642 begin with a @samp{*}), or one of the following:
18646 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
18649 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
18652 @samp{$@var{regname}} --- a CPU register name
18655 @subsubheading Result
18657 This operation returns the name, number of children and the type of the
18658 object created. Type is returned as a string as the ones generated by
18659 the @value{GDBN} CLI:
18662 name="@var{name}",numchild="N",type="@var{type}"
18666 @subheading The @code{-var-delete} Command
18667 @findex -var-delete
18669 @subsubheading Synopsis
18672 -var-delete @var{name}
18675 Deletes a previously created variable object and all of its children.
18677 Returns an error if the object @var{name} is not found.
18680 @subheading The @code{-var-set-format} Command
18681 @findex -var-set-format
18683 @subsubheading Synopsis
18686 -var-set-format @var{name} @var{format-spec}
18689 Sets the output format for the value of the object @var{name} to be
18692 The syntax for the @var{format-spec} is as follows:
18695 @var{format-spec} @expansion{}
18696 @{binary | decimal | hexadecimal | octal | natural@}
18700 @subheading The @code{-var-show-format} Command
18701 @findex -var-show-format
18703 @subsubheading Synopsis
18706 -var-show-format @var{name}
18709 Returns the format used to display the value of the object @var{name}.
18712 @var{format} @expansion{}
18717 @subheading The @code{-var-info-num-children} Command
18718 @findex -var-info-num-children
18720 @subsubheading Synopsis
18723 -var-info-num-children @var{name}
18726 Returns the number of children of a variable object @var{name}:
18733 @subheading The @code{-var-list-children} Command
18734 @findex -var-list-children
18736 @subsubheading Synopsis
18739 -var-list-children [@var{print-values}] @var{name}
18742 Returns a list of the children of the specified variable object. With
18743 just the variable object name as an argument or with an optional
18744 preceding argument of 0 or @code{--no-values}, prints only the names of the
18745 variables. With an optional preceding argument of 1 or @code{--all-values},
18746 also prints their values.
18748 @subsubheading Example
18752 -var-list-children n
18753 numchild=@var{n},children=[@{name=@var{name},
18754 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
18756 -var-list-children --all-values n
18757 numchild=@var{n},children=[@{name=@var{name},
18758 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
18762 @subheading The @code{-var-info-type} Command
18763 @findex -var-info-type
18765 @subsubheading Synopsis
18768 -var-info-type @var{name}
18771 Returns the type of the specified variable @var{name}. The type is
18772 returned as a string in the same format as it is output by the
18776 type=@var{typename}
18780 @subheading The @code{-var-info-expression} Command
18781 @findex -var-info-expression
18783 @subsubheading Synopsis
18786 -var-info-expression @var{name}
18789 Returns what is represented by the variable object @var{name}:
18792 lang=@var{lang-spec},exp=@var{expression}
18796 where @var{lang-spec} is @code{@{"C" | "C++" | "Java"@}}.
18798 @subheading The @code{-var-show-attributes} Command
18799 @findex -var-show-attributes
18801 @subsubheading Synopsis
18804 -var-show-attributes @var{name}
18807 List attributes of the specified variable object @var{name}:
18810 status=@var{attr} [ ( ,@var{attr} )* ]
18814 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
18816 @subheading The @code{-var-evaluate-expression} Command
18817 @findex -var-evaluate-expression
18819 @subsubheading Synopsis
18822 -var-evaluate-expression @var{name}
18825 Evaluates the expression that is represented by the specified variable
18826 object and returns its value as a string in the current format specified
18833 Note that one must invoke @code{-var-list-children} for a variable
18834 before the value of a child variable can be evaluated.
18836 @subheading The @code{-var-assign} Command
18837 @findex -var-assign
18839 @subsubheading Synopsis
18842 -var-assign @var{name} @var{expression}
18845 Assigns the value of @var{expression} to the variable object specified
18846 by @var{name}. The object must be @samp{editable}. If the variable's
18847 value is altered by the assign, the variable will show up in any
18848 subsequent @code{-var-update} list.
18850 @subsubheading Example
18858 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
18862 @subheading The @code{-var-update} Command
18863 @findex -var-update
18865 @subsubheading Synopsis
18868 -var-update @{@var{name} | "*"@}
18871 Update the value of the variable object @var{name} by evaluating its
18872 expression after fetching all the new values from memory or registers.
18873 A @samp{*} causes all existing variable objects to be updated.
18877 @chapter @value{GDBN} Annotations
18879 This chapter describes annotations in @value{GDBN}. Annotations were
18880 designed to interface @value{GDBN} to graphical user interfaces or other
18881 similar programs which want to interact with @value{GDBN} at a
18882 relatively high level.
18884 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
18888 This is Edition @value{EDITION}, @value{DATE}.
18892 * Annotations Overview:: What annotations are; the general syntax.
18893 * Server Prefix:: Issuing a command without affecting user state.
18894 * Prompting:: Annotations marking @value{GDBN}'s need for input.
18895 * Errors:: Annotations for error messages.
18896 * Invalidation:: Some annotations describe things now invalid.
18897 * Annotations for Running::
18898 Whether the program is running, how it stopped, etc.
18899 * Source Annotations:: Annotations describing source code.
18902 @node Annotations Overview
18903 @section What is an Annotation?
18904 @cindex annotations
18906 Annotations start with a newline character, two @samp{control-z}
18907 characters, and the name of the annotation. If there is no additional
18908 information associated with this annotation, the name of the annotation
18909 is followed immediately by a newline. If there is additional
18910 information, the name of the annotation is followed by a space, the
18911 additional information, and a newline. The additional information
18912 cannot contain newline characters.
18914 Any output not beginning with a newline and two @samp{control-z}
18915 characters denotes literal output from @value{GDBN}. Currently there is
18916 no need for @value{GDBN} to output a newline followed by two
18917 @samp{control-z} characters, but if there was such a need, the
18918 annotations could be extended with an @samp{escape} annotation which
18919 means those three characters as output.
18921 The annotation @var{level}, which is specified using the
18922 @option{--annotate} command line option (@pxref{Mode Options}), controls
18923 how much information @value{GDBN} prints together with its prompt,
18924 values of expressions, source lines, and other types of output. Level 0
18925 is for no anntations, level 1 is for use when @value{GDBN} is run as a
18926 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
18927 for programs that control @value{GDBN}, and level 2 annotations have
18928 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
18929 Interface, annotate, GDB's Obsolete Annotations}). This chapter
18930 describes level 3 annotations.
18932 A simple example of starting up @value{GDBN} with annotations is:
18935 $ @kbd{gdb --annotate=3}
18937 Copyright 2003 Free Software Foundation, Inc.
18938 GDB is free software, covered by the GNU General Public License,
18939 and you are welcome to change it and/or distribute copies of it
18940 under certain conditions.
18941 Type "show copying" to see the conditions.
18942 There is absolutely no warranty for GDB. Type "show warranty"
18944 This GDB was configured as "i386-pc-linux-gnu"
18955 Here @samp{quit} is input to @value{GDBN}; the rest is output from
18956 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
18957 denotes a @samp{control-z} character) are annotations; the rest is
18958 output from @value{GDBN}.
18960 @node Server Prefix
18961 @section The Server Prefix
18962 @cindex server prefix for annotations
18964 To issue a command to @value{GDBN} without affecting certain aspects of
18965 the state which is seen by users, prefix it with @samp{server }. This
18966 means that this command will not affect the command history, nor will it
18967 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
18968 pressed on a line by itself.
18970 The server prefix does not affect the recording of values into the value
18971 history; to print a value without recording it into the value history,
18972 use the @code{output} command instead of the @code{print} command.
18975 @section Annotation for @value{GDBN} Input
18977 @cindex annotations for prompts
18978 When @value{GDBN} prompts for input, it annotates this fact so it is possible
18979 to know when to send output, when the output from a given command is
18982 Different kinds of input each have a different @dfn{input type}. Each
18983 input type has three annotations: a @code{pre-} annotation, which
18984 denotes the beginning of any prompt which is being output, a plain
18985 annotation, which denotes the end of the prompt, and then a @code{post-}
18986 annotation which denotes the end of any echo which may (or may not) be
18987 associated with the input. For example, the @code{prompt} input type
18988 features the following annotations:
18996 The input types are
19001 @findex post-prompt
19003 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
19005 @findex pre-commands
19007 @findex post-commands
19009 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
19010 command. The annotations are repeated for each command which is input.
19012 @findex pre-overload-choice
19013 @findex overload-choice
19014 @findex post-overload-choice
19015 @item overload-choice
19016 When @value{GDBN} wants the user to select between various overloaded functions.
19022 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
19024 @findex pre-prompt-for-continue
19025 @findex prompt-for-continue
19026 @findex post-prompt-for-continue
19027 @item prompt-for-continue
19028 When @value{GDBN} is asking the user to press return to continue. Note: Don't
19029 expect this to work well; instead use @code{set height 0} to disable
19030 prompting. This is because the counting of lines is buggy in the
19031 presence of annotations.
19036 @cindex annotations for errors, warnings and interrupts
19043 This annotation occurs right before @value{GDBN} responds to an interrupt.
19050 This annotation occurs right before @value{GDBN} responds to an error.
19052 Quit and error annotations indicate that any annotations which @value{GDBN} was
19053 in the middle of may end abruptly. For example, if a
19054 @code{value-history-begin} annotation is followed by a @code{error}, one
19055 cannot expect to receive the matching @code{value-history-end}. One
19056 cannot expect not to receive it either, however; an error annotation
19057 does not necessarily mean that @value{GDBN} is immediately returning all the way
19060 @findex error-begin
19061 A quit or error annotation may be preceded by
19067 Any output between that and the quit or error annotation is the error
19070 Warning messages are not yet annotated.
19071 @c If we want to change that, need to fix warning(), type_error(),
19072 @c range_error(), and possibly other places.
19075 @section Invalidation Notices
19077 @cindex annotations for invalidation messages
19078 The following annotations say that certain pieces of state may have
19082 @findex frames-invalid
19083 @item ^Z^Zframes-invalid
19085 The frames (for example, output from the @code{backtrace} command) may
19088 @findex breakpoints-invalid
19089 @item ^Z^Zbreakpoints-invalid
19091 The breakpoints may have changed. For example, the user just added or
19092 deleted a breakpoint.
19095 @node Annotations for Running
19096 @section Running the Program
19097 @cindex annotations for running programs
19101 When the program starts executing due to a @value{GDBN} command such as
19102 @code{step} or @code{continue},
19108 is output. When the program stops,
19114 is output. Before the @code{stopped} annotation, a variety of
19115 annotations describe how the program stopped.
19119 @item ^Z^Zexited @var{exit-status}
19120 The program exited, and @var{exit-status} is the exit status (zero for
19121 successful exit, otherwise nonzero).
19124 @findex signal-name
19125 @findex signal-name-end
19126 @findex signal-string
19127 @findex signal-string-end
19128 @item ^Z^Zsignalled
19129 The program exited with a signal. After the @code{^Z^Zsignalled}, the
19130 annotation continues:
19136 ^Z^Zsignal-name-end
19140 ^Z^Zsignal-string-end
19145 where @var{name} is the name of the signal, such as @code{SIGILL} or
19146 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
19147 as @code{Illegal Instruction} or @code{Segmentation fault}.
19148 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
19149 user's benefit and have no particular format.
19153 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
19154 just saying that the program received the signal, not that it was
19155 terminated with it.
19158 @item ^Z^Zbreakpoint @var{number}
19159 The program hit breakpoint number @var{number}.
19162 @item ^Z^Zwatchpoint @var{number}
19163 The program hit watchpoint number @var{number}.
19166 @node Source Annotations
19167 @section Displaying Source
19168 @cindex annotations for source display
19171 The following annotation is used instead of displaying source code:
19174 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
19177 where @var{filename} is an absolute file name indicating which source
19178 file, @var{line} is the line number within that file (where 1 is the
19179 first line in the file), @var{character} is the character position
19180 within the file (where 0 is the first character in the file) (for most
19181 debug formats this will necessarily point to the beginning of a line),
19182 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
19183 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
19184 @var{addr} is the address in the target program associated with the
19185 source which is being displayed. @var{addr} is in the form @samp{0x}
19186 followed by one or more lowercase hex digits (note that this does not
19187 depend on the language).
19190 @chapter Reporting Bugs in @value{GDBN}
19191 @cindex bugs in @value{GDBN}
19192 @cindex reporting bugs in @value{GDBN}
19194 Your bug reports play an essential role in making @value{GDBN} reliable.
19196 Reporting a bug may help you by bringing a solution to your problem, or it
19197 may not. But in any case the principal function of a bug report is to help
19198 the entire community by making the next version of @value{GDBN} work better. Bug
19199 reports are your contribution to the maintenance of @value{GDBN}.
19201 In order for a bug report to serve its purpose, you must include the
19202 information that enables us to fix the bug.
19205 * Bug Criteria:: Have you found a bug?
19206 * Bug Reporting:: How to report bugs
19210 @section Have you found a bug?
19211 @cindex bug criteria
19213 If you are not sure whether you have found a bug, here are some guidelines:
19216 @cindex fatal signal
19217 @cindex debugger crash
19218 @cindex crash of debugger
19220 If the debugger gets a fatal signal, for any input whatever, that is a
19221 @value{GDBN} bug. Reliable debuggers never crash.
19223 @cindex error on valid input
19225 If @value{GDBN} produces an error message for valid input, that is a
19226 bug. (Note that if you're cross debugging, the problem may also be
19227 somewhere in the connection to the target.)
19229 @cindex invalid input
19231 If @value{GDBN} does not produce an error message for invalid input,
19232 that is a bug. However, you should note that your idea of
19233 ``invalid input'' might be our idea of ``an extension'' or ``support
19234 for traditional practice''.
19237 If you are an experienced user of debugging tools, your suggestions
19238 for improvement of @value{GDBN} are welcome in any case.
19241 @node Bug Reporting
19242 @section How to report bugs
19243 @cindex bug reports
19244 @cindex @value{GDBN} bugs, reporting
19246 A number of companies and individuals offer support for @sc{gnu} products.
19247 If you obtained @value{GDBN} from a support organization, we recommend you
19248 contact that organization first.
19250 You can find contact information for many support companies and
19251 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
19253 @c should add a web page ref...
19255 In any event, we also recommend that you submit bug reports for
19256 @value{GDBN}. The prefered method is to submit them directly using
19257 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
19258 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
19261 @strong{Do not send bug reports to @samp{info-gdb}, or to
19262 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
19263 not want to receive bug reports. Those that do have arranged to receive
19266 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
19267 serves as a repeater. The mailing list and the newsgroup carry exactly
19268 the same messages. Often people think of posting bug reports to the
19269 newsgroup instead of mailing them. This appears to work, but it has one
19270 problem which can be crucial: a newsgroup posting often lacks a mail
19271 path back to the sender. Thus, if we need to ask for more information,
19272 we may be unable to reach you. For this reason, it is better to send
19273 bug reports to the mailing list.
19275 The fundamental principle of reporting bugs usefully is this:
19276 @strong{report all the facts}. If you are not sure whether to state a
19277 fact or leave it out, state it!
19279 Often people omit facts because they think they know what causes the
19280 problem and assume that some details do not matter. Thus, you might
19281 assume that the name of the variable you use in an example does not matter.
19282 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
19283 stray memory reference which happens to fetch from the location where that
19284 name is stored in memory; perhaps, if the name were different, the contents
19285 of that location would fool the debugger into doing the right thing despite
19286 the bug. Play it safe and give a specific, complete example. That is the
19287 easiest thing for you to do, and the most helpful.
19289 Keep in mind that the purpose of a bug report is to enable us to fix the
19290 bug. It may be that the bug has been reported previously, but neither
19291 you nor we can know that unless your bug report is complete and
19294 Sometimes people give a few sketchy facts and ask, ``Does this ring a
19295 bell?'' Those bug reports are useless, and we urge everyone to
19296 @emph{refuse to respond to them} except to chide the sender to report
19299 To enable us to fix the bug, you should include all these things:
19303 The version of @value{GDBN}. @value{GDBN} announces it if you start
19304 with no arguments; you can also print it at any time using @code{show
19307 Without this, we will not know whether there is any point in looking for
19308 the bug in the current version of @value{GDBN}.
19311 The type of machine you are using, and the operating system name and
19315 What compiler (and its version) was used to compile @value{GDBN}---e.g.
19316 ``@value{GCC}--2.8.1''.
19319 What compiler (and its version) was used to compile the program you are
19320 debugging---e.g. ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
19321 C Compiler''. For GCC, you can say @code{gcc --version} to get this
19322 information; for other compilers, see the documentation for those
19326 The command arguments you gave the compiler to compile your example and
19327 observe the bug. For example, did you use @samp{-O}? To guarantee
19328 you will not omit something important, list them all. A copy of the
19329 Makefile (or the output from make) is sufficient.
19331 If we were to try to guess the arguments, we would probably guess wrong
19332 and then we might not encounter the bug.
19335 A complete input script, and all necessary source files, that will
19339 A description of what behavior you observe that you believe is
19340 incorrect. For example, ``It gets a fatal signal.''
19342 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
19343 will certainly notice it. But if the bug is incorrect output, we might
19344 not notice unless it is glaringly wrong. You might as well not give us
19345 a chance to make a mistake.
19347 Even if the problem you experience is a fatal signal, you should still
19348 say so explicitly. Suppose something strange is going on, such as, your
19349 copy of @value{GDBN} is out of synch, or you have encountered a bug in
19350 the C library on your system. (This has happened!) Your copy might
19351 crash and ours would not. If you told us to expect a crash, then when
19352 ours fails to crash, we would know that the bug was not happening for
19353 us. If you had not told us to expect a crash, then we would not be able
19354 to draw any conclusion from our observations.
19357 @cindex recording a session script
19358 To collect all this information, you can use a session recording program
19359 such as @command{script}, which is available on many Unix systems.
19360 Just run your @value{GDBN} session inside @command{script} and then
19361 include the @file{typescript} file with your bug report.
19363 Another way to record a @value{GDBN} session is to run @value{GDBN}
19364 inside Emacs and then save the entire buffer to a file.
19367 If you wish to suggest changes to the @value{GDBN} source, send us context
19368 diffs. If you even discuss something in the @value{GDBN} source, refer to
19369 it by context, not by line number.
19371 The line numbers in our development sources will not match those in your
19372 sources. Your line numbers would convey no useful information to us.
19376 Here are some things that are not necessary:
19380 A description of the envelope of the bug.
19382 Often people who encounter a bug spend a lot of time investigating
19383 which changes to the input file will make the bug go away and which
19384 changes will not affect it.
19386 This is often time consuming and not very useful, because the way we
19387 will find the bug is by running a single example under the debugger
19388 with breakpoints, not by pure deduction from a series of examples.
19389 We recommend that you save your time for something else.
19391 Of course, if you can find a simpler example to report @emph{instead}
19392 of the original one, that is a convenience for us. Errors in the
19393 output will be easier to spot, running under the debugger will take
19394 less time, and so on.
19396 However, simplification is not vital; if you do not want to do this,
19397 report the bug anyway and send us the entire test case you used.
19400 A patch for the bug.
19402 A patch for the bug does help us if it is a good one. But do not omit
19403 the necessary information, such as the test case, on the assumption that
19404 a patch is all we need. We might see problems with your patch and decide
19405 to fix the problem another way, or we might not understand it at all.
19407 Sometimes with a program as complicated as @value{GDBN} it is very hard to
19408 construct an example that will make the program follow a certain path
19409 through the code. If you do not send us the example, we will not be able
19410 to construct one, so we will not be able to verify that the bug is fixed.
19412 And if we cannot understand what bug you are trying to fix, or why your
19413 patch should be an improvement, we will not install it. A test case will
19414 help us to understand.
19417 A guess about what the bug is or what it depends on.
19419 Such guesses are usually wrong. Even we cannot guess right about such
19420 things without first using the debugger to find the facts.
19423 @c The readline documentation is distributed with the readline code
19424 @c and consists of the two following files:
19426 @c inc-hist.texinfo
19427 @c Use -I with makeinfo to point to the appropriate directory,
19428 @c environment var TEXINPUTS with TeX.
19429 @include rluser.texinfo
19430 @include inc-hist.texinfo
19433 @node Formatting Documentation
19434 @appendix Formatting Documentation
19436 @cindex @value{GDBN} reference card
19437 @cindex reference card
19438 The @value{GDBN} 4 release includes an already-formatted reference card, ready
19439 for printing with PostScript or Ghostscript, in the @file{gdb}
19440 subdirectory of the main source directory@footnote{In
19441 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
19442 release.}. If you can use PostScript or Ghostscript with your printer,
19443 you can print the reference card immediately with @file{refcard.ps}.
19445 The release also includes the source for the reference card. You
19446 can format it, using @TeX{}, by typing:
19452 The @value{GDBN} reference card is designed to print in @dfn{landscape}
19453 mode on US ``letter'' size paper;
19454 that is, on a sheet 11 inches wide by 8.5 inches
19455 high. You will need to specify this form of printing as an option to
19456 your @sc{dvi} output program.
19458 @cindex documentation
19460 All the documentation for @value{GDBN} comes as part of the machine-readable
19461 distribution. The documentation is written in Texinfo format, which is
19462 a documentation system that uses a single source file to produce both
19463 on-line information and a printed manual. You can use one of the Info
19464 formatting commands to create the on-line version of the documentation
19465 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
19467 @value{GDBN} includes an already formatted copy of the on-line Info
19468 version of this manual in the @file{gdb} subdirectory. The main Info
19469 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
19470 subordinate files matching @samp{gdb.info*} in the same directory. If
19471 necessary, you can print out these files, or read them with any editor;
19472 but they are easier to read using the @code{info} subsystem in @sc{gnu}
19473 Emacs or the standalone @code{info} program, available as part of the
19474 @sc{gnu} Texinfo distribution.
19476 If you want to format these Info files yourself, you need one of the
19477 Info formatting programs, such as @code{texinfo-format-buffer} or
19480 If you have @code{makeinfo} installed, and are in the top level
19481 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
19482 version @value{GDBVN}), you can make the Info file by typing:
19489 If you want to typeset and print copies of this manual, you need @TeX{},
19490 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
19491 Texinfo definitions file.
19493 @TeX{} is a typesetting program; it does not print files directly, but
19494 produces output files called @sc{dvi} files. To print a typeset
19495 document, you need a program to print @sc{dvi} files. If your system
19496 has @TeX{} installed, chances are it has such a program. The precise
19497 command to use depends on your system; @kbd{lpr -d} is common; another
19498 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
19499 require a file name without any extension or a @samp{.dvi} extension.
19501 @TeX{} also requires a macro definitions file called
19502 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
19503 written in Texinfo format. On its own, @TeX{} cannot either read or
19504 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
19505 and is located in the @file{gdb-@var{version-number}/texinfo}
19508 If you have @TeX{} and a @sc{dvi} printer program installed, you can
19509 typeset and print this manual. First switch to the the @file{gdb}
19510 subdirectory of the main source directory (for example, to
19511 @file{gdb-@value{GDBVN}/gdb}) and type:
19517 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
19519 @node Installing GDB
19520 @appendix Installing @value{GDBN}
19521 @cindex configuring @value{GDBN}
19522 @cindex installation
19523 @cindex configuring @value{GDBN}, and source tree subdirectories
19525 @value{GDBN} comes with a @code{configure} script that automates the process
19526 of preparing @value{GDBN} for installation; you can then use @code{make} to
19527 build the @code{gdb} program.
19529 @c irrelevant in info file; it's as current as the code it lives with.
19530 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
19531 look at the @file{README} file in the sources; we may have improved the
19532 installation procedures since publishing this manual.}
19535 The @value{GDBN} distribution includes all the source code you need for
19536 @value{GDBN} in a single directory, whose name is usually composed by
19537 appending the version number to @samp{gdb}.
19539 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
19540 @file{gdb-@value{GDBVN}} directory. That directory contains:
19543 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
19544 script for configuring @value{GDBN} and all its supporting libraries
19546 @item gdb-@value{GDBVN}/gdb
19547 the source specific to @value{GDBN} itself
19549 @item gdb-@value{GDBVN}/bfd
19550 source for the Binary File Descriptor library
19552 @item gdb-@value{GDBVN}/include
19553 @sc{gnu} include files
19555 @item gdb-@value{GDBVN}/libiberty
19556 source for the @samp{-liberty} free software library
19558 @item gdb-@value{GDBVN}/opcodes
19559 source for the library of opcode tables and disassemblers
19561 @item gdb-@value{GDBVN}/readline
19562 source for the @sc{gnu} command-line interface
19564 @item gdb-@value{GDBVN}/glob
19565 source for the @sc{gnu} filename pattern-matching subroutine
19567 @item gdb-@value{GDBVN}/mmalloc
19568 source for the @sc{gnu} memory-mapped malloc package
19571 The simplest way to configure and build @value{GDBN} is to run @code{configure}
19572 from the @file{gdb-@var{version-number}} source directory, which in
19573 this example is the @file{gdb-@value{GDBVN}} directory.
19575 First switch to the @file{gdb-@var{version-number}} source directory
19576 if you are not already in it; then run @code{configure}. Pass the
19577 identifier for the platform on which @value{GDBN} will run as an
19583 cd gdb-@value{GDBVN}
19584 ./configure @var{host}
19589 where @var{host} is an identifier such as @samp{sun4} or
19590 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
19591 (You can often leave off @var{host}; @code{configure} tries to guess the
19592 correct value by examining your system.)
19594 Running @samp{configure @var{host}} and then running @code{make} builds the
19595 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
19596 libraries, then @code{gdb} itself. The configured source files, and the
19597 binaries, are left in the corresponding source directories.
19600 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
19601 system does not recognize this automatically when you run a different
19602 shell, you may need to run @code{sh} on it explicitly:
19605 sh configure @var{host}
19608 If you run @code{configure} from a directory that contains source
19609 directories for multiple libraries or programs, such as the
19610 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
19611 creates configuration files for every directory level underneath (unless
19612 you tell it not to, with the @samp{--norecursion} option).
19614 You should run the @code{configure} script from the top directory in the
19615 source tree, the @file{gdb-@var{version-number}} directory. If you run
19616 @code{configure} from one of the subdirectories, you will configure only
19617 that subdirectory. That is usually not what you want. In particular,
19618 if you run the first @code{configure} from the @file{gdb} subdirectory
19619 of the @file{gdb-@var{version-number}} directory, you will omit the
19620 configuration of @file{bfd}, @file{readline}, and other sibling
19621 directories of the @file{gdb} subdirectory. This leads to build errors
19622 about missing include files such as @file{bfd/bfd.h}.
19624 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
19625 However, you should make sure that the shell on your path (named by
19626 the @samp{SHELL} environment variable) is publicly readable. Remember
19627 that @value{GDBN} uses the shell to start your program---some systems refuse to
19628 let @value{GDBN} debug child processes whose programs are not readable.
19631 * Separate Objdir:: Compiling @value{GDBN} in another directory
19632 * Config Names:: Specifying names for hosts and targets
19633 * Configure Options:: Summary of options for configure
19636 @node Separate Objdir
19637 @section Compiling @value{GDBN} in another directory
19639 If you want to run @value{GDBN} versions for several host or target machines,
19640 you need a different @code{gdb} compiled for each combination of
19641 host and target. @code{configure} is designed to make this easy by
19642 allowing you to generate each configuration in a separate subdirectory,
19643 rather than in the source directory. If your @code{make} program
19644 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
19645 @code{make} in each of these directories builds the @code{gdb}
19646 program specified there.
19648 To build @code{gdb} in a separate directory, run @code{configure}
19649 with the @samp{--srcdir} option to specify where to find the source.
19650 (You also need to specify a path to find @code{configure}
19651 itself from your working directory. If the path to @code{configure}
19652 would be the same as the argument to @samp{--srcdir}, you can leave out
19653 the @samp{--srcdir} option; it is assumed.)
19655 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
19656 separate directory for a Sun 4 like this:
19660 cd gdb-@value{GDBVN}
19663 ../gdb-@value{GDBVN}/configure sun4
19668 When @code{configure} builds a configuration using a remote source
19669 directory, it creates a tree for the binaries with the same structure
19670 (and using the same names) as the tree under the source directory. In
19671 the example, you'd find the Sun 4 library @file{libiberty.a} in the
19672 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
19673 @file{gdb-sun4/gdb}.
19675 Make sure that your path to the @file{configure} script has just one
19676 instance of @file{gdb} in it. If your path to @file{configure} looks
19677 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
19678 one subdirectory of @value{GDBN}, not the whole package. This leads to
19679 build errors about missing include files such as @file{bfd/bfd.h}.
19681 One popular reason to build several @value{GDBN} configurations in separate
19682 directories is to configure @value{GDBN} for cross-compiling (where
19683 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
19684 programs that run on another machine---the @dfn{target}).
19685 You specify a cross-debugging target by
19686 giving the @samp{--target=@var{target}} option to @code{configure}.
19688 When you run @code{make} to build a program or library, you must run
19689 it in a configured directory---whatever directory you were in when you
19690 called @code{configure} (or one of its subdirectories).
19692 The @code{Makefile} that @code{configure} generates in each source
19693 directory also runs recursively. If you type @code{make} in a source
19694 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
19695 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
19696 will build all the required libraries, and then build GDB.
19698 When you have multiple hosts or targets configured in separate
19699 directories, you can run @code{make} on them in parallel (for example,
19700 if they are NFS-mounted on each of the hosts); they will not interfere
19704 @section Specifying names for hosts and targets
19706 The specifications used for hosts and targets in the @code{configure}
19707 script are based on a three-part naming scheme, but some short predefined
19708 aliases are also supported. The full naming scheme encodes three pieces
19709 of information in the following pattern:
19712 @var{architecture}-@var{vendor}-@var{os}
19715 For example, you can use the alias @code{sun4} as a @var{host} argument,
19716 or as the value for @var{target} in a @code{--target=@var{target}}
19717 option. The equivalent full name is @samp{sparc-sun-sunos4}.
19719 The @code{configure} script accompanying @value{GDBN} does not provide
19720 any query facility to list all supported host and target names or
19721 aliases. @code{configure} calls the Bourne shell script
19722 @code{config.sub} to map abbreviations to full names; you can read the
19723 script, if you wish, or you can use it to test your guesses on
19724 abbreviations---for example:
19727 % sh config.sub i386-linux
19729 % sh config.sub alpha-linux
19730 alpha-unknown-linux-gnu
19731 % sh config.sub hp9k700
19733 % sh config.sub sun4
19734 sparc-sun-sunos4.1.1
19735 % sh config.sub sun3
19736 m68k-sun-sunos4.1.1
19737 % sh config.sub i986v
19738 Invalid configuration `i986v': machine `i986v' not recognized
19742 @code{config.sub} is also distributed in the @value{GDBN} source
19743 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
19745 @node Configure Options
19746 @section @code{configure} options
19748 Here is a summary of the @code{configure} options and arguments that
19749 are most often useful for building @value{GDBN}. @code{configure} also has
19750 several other options not listed here. @inforef{What Configure
19751 Does,,configure.info}, for a full explanation of @code{configure}.
19754 configure @r{[}--help@r{]}
19755 @r{[}--prefix=@var{dir}@r{]}
19756 @r{[}--exec-prefix=@var{dir}@r{]}
19757 @r{[}--srcdir=@var{dirname}@r{]}
19758 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
19759 @r{[}--target=@var{target}@r{]}
19764 You may introduce options with a single @samp{-} rather than
19765 @samp{--} if you prefer; but you may abbreviate option names if you use
19770 Display a quick summary of how to invoke @code{configure}.
19772 @item --prefix=@var{dir}
19773 Configure the source to install programs and files under directory
19776 @item --exec-prefix=@var{dir}
19777 Configure the source to install programs under directory
19780 @c avoid splitting the warning from the explanation:
19782 @item --srcdir=@var{dirname}
19783 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
19784 @code{make} that implements the @code{VPATH} feature.}@*
19785 Use this option to make configurations in directories separate from the
19786 @value{GDBN} source directories. Among other things, you can use this to
19787 build (or maintain) several configurations simultaneously, in separate
19788 directories. @code{configure} writes configuration specific files in
19789 the current directory, but arranges for them to use the source in the
19790 directory @var{dirname}. @code{configure} creates directories under
19791 the working directory in parallel to the source directories below
19794 @item --norecursion
19795 Configure only the directory level where @code{configure} is executed; do not
19796 propagate configuration to subdirectories.
19798 @item --target=@var{target}
19799 Configure @value{GDBN} for cross-debugging programs running on the specified
19800 @var{target}. Without this option, @value{GDBN} is configured to debug
19801 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
19803 There is no convenient way to generate a list of all available targets.
19805 @item @var{host} @dots{}
19806 Configure @value{GDBN} to run on the specified @var{host}.
19808 There is no convenient way to generate a list of all available hosts.
19811 There are many other options available as well, but they are generally
19812 needed for special purposes only.
19814 @node Maintenance Commands
19815 @appendix Maintenance Commands
19816 @cindex maintenance commands
19817 @cindex internal commands
19819 In addition to commands intended for @value{GDBN} users, @value{GDBN}
19820 includes a number of commands intended for @value{GDBN} developers.
19821 These commands are provided here for reference.
19824 @kindex maint info breakpoints
19825 @item @anchor{maint info breakpoints}maint info breakpoints
19826 Using the same format as @samp{info breakpoints}, display both the
19827 breakpoints you've set explicitly, and those @value{GDBN} is using for
19828 internal purposes. Internal breakpoints are shown with negative
19829 breakpoint numbers. The type column identifies what kind of breakpoint
19834 Normal, explicitly set breakpoint.
19837 Normal, explicitly set watchpoint.
19840 Internal breakpoint, used to handle correctly stepping through
19841 @code{longjmp} calls.
19843 @item longjmp resume
19844 Internal breakpoint at the target of a @code{longjmp}.
19847 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
19850 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
19853 Shared library events.
19857 @kindex maint internal-error
19858 @kindex maint internal-warning
19859 @item maint internal-error
19860 @itemx maint internal-warning
19861 Cause @value{GDBN} to call the internal function @code{internal_error}
19862 or @code{internal_warning} and hence behave as though an internal error
19863 or internal warning has been detected. In addition to reporting the
19864 internal problem, these functions give the user the opportunity to
19865 either quit @value{GDBN} or create a core file of the current
19866 @value{GDBN} session.
19869 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
19870 @dots{}/maint.c:121: internal-error: testing, 1, 2
19871 A problem internal to GDB has been detected. Further
19872 debugging may prove unreliable.
19873 Quit this debugging session? (y or n) @kbd{n}
19874 Create a core file? (y or n) @kbd{n}
19878 Takes an optional parameter that is used as the text of the error or
19881 @kindex maint print dummy-frames
19882 @item maint print dummy-frames
19884 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
19887 (@value{GDBP}) @kbd{b add}
19889 (@value{GDBP}) @kbd{print add(2,3)}
19890 Breakpoint 2, add (a=2, b=3) at @dots{}
19892 The program being debugged stopped while in a function called from GDB.
19894 (@value{GDBP}) @kbd{maint print dummy-frames}
19895 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
19896 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
19897 call_lo=0x01014000 call_hi=0x01014001
19901 Takes an optional file parameter.
19903 @kindex maint print registers
19904 @kindex maint print raw-registers
19905 @kindex maint print cooked-registers
19906 @kindex maint print register-groups
19907 @item maint print registers
19908 @itemx maint print raw-registers
19909 @itemx maint print cooked-registers
19910 @itemx maint print register-groups
19911 Print @value{GDBN}'s internal register data structures.
19913 The command @code{maint print raw-registers} includes the contents of
19914 the raw register cache; the command @code{maint print cooked-registers}
19915 includes the (cooked) value of all registers; and the command
19916 @code{maint print register-groups} includes the groups that each
19917 register is a member of. @xref{Registers,, Registers, gdbint,
19918 @value{GDBN} Internals}.
19920 Takes an optional file parameter.
19922 @kindex maint print reggroups
19923 @item maint print reggroups
19924 Print @value{GDBN}'s internal register group data structures.
19926 Takes an optional file parameter.
19929 (@value{GDBP}) @kbd{maint print reggroups}
19940 @kindex maint set profile
19941 @kindex maint show profile
19942 @cindex profiling GDB
19943 @item maint set profile
19944 @itemx maint show profile
19945 Control profiling of @value{GDBN}.
19947 Profiling will be disabled until you use the @samp{maint set profile}
19948 command to enable it. When you enable profiling, the system will begin
19949 collecting timing and execution count data; when you disable profiling or
19950 exit @value{GDBN}, the results will be written to a log file. Remember that
19951 if you use profiling, @value{GDBN} will overwrite the profiling log file
19952 (often called @file{gmon.out}). If you have a record of important profiling
19953 data in a @file{gmon.out} file, be sure to move it to a safe location.
19955 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
19956 compiled with the @samp{-pg} compiler option.
19958 @kindex maint set dwarf2 max-cache-age
19959 @kindex maint show dwarf2 max-cache-age
19960 @item maint set dwarf2 max-cache-age
19961 @itemx maint show dwarf2 max-cache-age
19962 Control the DWARF 2 compilation unit cache.
19964 In object files with inter-compilation-unit references, such as those
19965 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
19966 reader needs to frequently refer to previously read compilation units.
19967 This setting controls how long a compilation unit will remain in the cache
19968 if it is not referenced. Setting it to zero disables caching, which will
19969 slow down @value{GDBN} startup but reduce memory consumption.
19974 @node Remote Protocol
19975 @appendix @value{GDBN} Remote Serial Protocol
19980 * Stop Reply Packets::
19981 * General Query Packets::
19982 * Register Packet Format::
19984 * File-I/O remote protocol extension::
19990 There may be occasions when you need to know something about the
19991 protocol---for example, if there is only one serial port to your target
19992 machine, you might want your program to do something special if it
19993 recognizes a packet meant for @value{GDBN}.
19995 In the examples below, @samp{->} and @samp{<-} are used to indicate
19996 transmitted and received data respectfully.
19998 @cindex protocol, @value{GDBN} remote serial
19999 @cindex serial protocol, @value{GDBN} remote
20000 @cindex remote serial protocol
20001 All @value{GDBN} commands and responses (other than acknowledgments) are
20002 sent as a @var{packet}. A @var{packet} is introduced with the character
20003 @samp{$}, the actual @var{packet-data}, and the terminating character
20004 @samp{#} followed by a two-digit @var{checksum}:
20007 @code{$}@var{packet-data}@code{#}@var{checksum}
20011 @cindex checksum, for @value{GDBN} remote
20013 The two-digit @var{checksum} is computed as the modulo 256 sum of all
20014 characters between the leading @samp{$} and the trailing @samp{#} (an
20015 eight bit unsigned checksum).
20017 Implementors should note that prior to @value{GDBN} 5.0 the protocol
20018 specification also included an optional two-digit @var{sequence-id}:
20021 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
20024 @cindex sequence-id, for @value{GDBN} remote
20026 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
20027 has never output @var{sequence-id}s. Stubs that handle packets added
20028 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
20030 @cindex acknowledgment, for @value{GDBN} remote
20031 When either the host or the target machine receives a packet, the first
20032 response expected is an acknowledgment: either @samp{+} (to indicate
20033 the package was received correctly) or @samp{-} (to request
20037 -> @code{$}@var{packet-data}@code{#}@var{checksum}
20042 The host (@value{GDBN}) sends @var{command}s, and the target (the
20043 debugging stub incorporated in your program) sends a @var{response}. In
20044 the case of step and continue @var{command}s, the response is only sent
20045 when the operation has completed (the target has again stopped).
20047 @var{packet-data} consists of a sequence of characters with the
20048 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
20051 Fields within the packet should be separated using @samp{,} @samp{;} or
20052 @cindex remote protocol, field separator
20053 @samp{:}. Except where otherwise noted all numbers are represented in
20054 @sc{hex} with leading zeros suppressed.
20056 Implementors should note that prior to @value{GDBN} 5.0, the character
20057 @samp{:} could not appear as the third character in a packet (as it
20058 would potentially conflict with the @var{sequence-id}).
20060 Response @var{data} can be run-length encoded to save space. A @samp{*}
20061 means that the next character is an @sc{ascii} encoding giving a repeat count
20062 which stands for that many repetitions of the character preceding the
20063 @samp{*}. The encoding is @code{n+29}, yielding a printable character
20064 where @code{n >=3} (which is where rle starts to win). The printable
20065 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
20066 value greater than 126 should not be used.
20073 means the same as "0000".
20075 The error response returned for some packets includes a two character
20076 error number. That number is not well defined.
20078 For any @var{command} not supported by the stub, an empty response
20079 (@samp{$#00}) should be returned. That way it is possible to extend the
20080 protocol. A newer @value{GDBN} can tell if a packet is supported based
20083 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
20084 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
20090 The following table provides a complete list of all currently defined
20091 @var{command}s and their corresponding response @var{data}.
20095 @item @code{!} --- extended mode
20096 @cindex @code{!} packet
20098 Enable extended mode. In extended mode, the remote server is made
20099 persistent. The @samp{R} packet is used to restart the program being
20105 The remote target both supports and has enabled extended mode.
20108 @item @code{?} --- last signal
20109 @cindex @code{?} packet
20111 Indicate the reason the target halted. The reply is the same as for
20115 @xref{Stop Reply Packets}, for the reply specifications.
20117 @item @code{a} --- reserved
20119 Reserved for future use.
20121 @item @code{A}@var{arglen}@code{,}@var{argnum}@code{,}@var{arg}@code{,@dots{}} --- set program arguments @strong{(reserved)}
20122 @cindex @code{A} packet
20124 Initialized @samp{argv[]} array passed into program. @var{arglen}
20125 specifies the number of bytes in the hex encoded byte stream @var{arg}.
20126 See @code{gdbserver} for more details.
20134 @item @code{b}@var{baud} --- set baud @strong{(deprecated)}
20135 @cindex @code{b} packet
20137 Change the serial line speed to @var{baud}.
20139 JTC: @emph{When does the transport layer state change? When it's
20140 received, or after the ACK is transmitted. In either case, there are
20141 problems if the command or the acknowledgment packet is dropped.}
20143 Stan: @emph{If people really wanted to add something like this, and get
20144 it working for the first time, they ought to modify ser-unix.c to send
20145 some kind of out-of-band message to a specially-setup stub and have the
20146 switch happen "in between" packets, so that from remote protocol's point
20147 of view, nothing actually happened.}
20149 @item @code{B}@var{addr},@var{mode} --- set breakpoint @strong{(deprecated)}
20150 @cindex @code{B} packet
20152 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
20153 breakpoint at @var{addr}.
20155 This packet has been replaced by the @samp{Z} and @samp{z} packets
20156 (@pxref{insert breakpoint or watchpoint packet}).
20158 @item @code{c}@var{addr} --- continue
20159 @cindex @code{c} packet
20161 @var{addr} is address to resume. If @var{addr} is omitted, resume at
20165 @xref{Stop Reply Packets}, for the reply specifications.
20167 @item @code{C}@var{sig}@code{;}@var{addr} --- continue with signal
20168 @cindex @code{C} packet
20170 Continue with signal @var{sig} (hex signal number). If
20171 @code{;}@var{addr} is omitted, resume at same address.
20174 @xref{Stop Reply Packets}, for the reply specifications.
20176 @item @code{d} --- toggle debug @strong{(deprecated)}
20177 @cindex @code{d} packet
20181 @item @code{D} --- detach
20182 @cindex @code{D} packet
20184 Detach @value{GDBN} from the remote system. Sent to the remote target
20185 before @value{GDBN} disconnects via the @code{detach} command.
20189 @item @emph{no response}
20190 @value{GDBN} does not check for any response after sending this packet.
20193 @item @code{e} --- reserved
20195 Reserved for future use.
20197 @item @code{E} --- reserved
20199 Reserved for future use.
20201 @item @code{f} --- reserved
20203 Reserved for future use.
20205 @item @code{F}@var{RC}@code{,}@var{EE}@code{,}@var{CF}@code{;}@var{XX} --- Reply to target's F packet.
20206 @cindex @code{F} packet
20208 This packet is send by @value{GDBN} as reply to a @code{F} request packet
20209 sent by the target. This is part of the File-I/O protocol extension.
20210 @xref{File-I/O remote protocol extension}, for the specification.
20212 @item @code{g} --- read registers
20213 @anchor{read registers packet}
20214 @cindex @code{g} packet
20216 Read general registers.
20220 @item @var{XX@dots{}}
20221 Each byte of register data is described by two hex digits. The bytes
20222 with the register are transmitted in target byte order. The size of
20223 each register and their position within the @samp{g} @var{packet} are
20224 determined by the @value{GDBN} internal macros
20225 @var{DEPRECATED_REGISTER_RAW_SIZE} and @var{REGISTER_NAME} macros. The
20226 specification of several standard @code{g} packets is specified below.
20231 @item @code{G}@var{XX@dots{}} --- write regs
20232 @cindex @code{G} packet
20234 @xref{read registers packet}, for a description of the @var{XX@dots{}}
20245 @item @code{h} --- reserved
20247 Reserved for future use.
20249 @item @code{H}@var{c}@var{t@dots{}} --- set thread
20250 @cindex @code{H} packet
20252 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
20253 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
20254 should be @samp{c} for step and continue operations, @samp{g} for other
20255 operations. The thread designator @var{t@dots{}} may be -1, meaning all
20256 the threads, a thread number, or zero which means pick any thread.
20267 @c 'H': How restrictive (or permissive) is the thread model. If a
20268 @c thread is selected and stopped, are other threads allowed
20269 @c to continue to execute? As I mentioned above, I think the
20270 @c semantics of each command when a thread is selected must be
20271 @c described. For example:
20273 @c 'g': If the stub supports threads and a specific thread is
20274 @c selected, returns the register block from that thread;
20275 @c otherwise returns current registers.
20277 @c 'G' If the stub supports threads and a specific thread is
20278 @c selected, sets the registers of the register block of
20279 @c that thread; otherwise sets current registers.
20281 @item @code{i}@var{addr}@code{,}@var{nnn} --- cycle step @strong{(draft)}
20282 @anchor{cycle step packet}
20283 @cindex @code{i} packet
20285 Step the remote target by a single clock cycle. If @code{,}@var{nnn} is
20286 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
20287 step starting at that address.
20289 @item @code{I} --- signal then cycle step @strong{(reserved)}
20290 @cindex @code{I} packet
20292 @xref{step with signal packet}. @xref{cycle step packet}.
20294 @item @code{j} --- reserved
20296 Reserved for future use.
20298 @item @code{J} --- reserved
20300 Reserved for future use.
20302 @item @code{k} --- kill request
20303 @cindex @code{k} packet
20305 FIXME: @emph{There is no description of how to operate when a specific
20306 thread context has been selected (i.e.@: does 'k' kill only that
20309 @item @code{K} --- reserved
20311 Reserved for future use.
20313 @item @code{l} --- reserved
20315 Reserved for future use.
20317 @item @code{L} --- reserved
20319 Reserved for future use.
20321 @item @code{m}@var{addr}@code{,}@var{length} --- read memory
20322 @cindex @code{m} packet
20324 Read @var{length} bytes of memory starting at address @var{addr}.
20325 Neither @value{GDBN} nor the stub assume that sized memory transfers are
20326 assumed using word aligned accesses. FIXME: @emph{A word aligned memory
20327 transfer mechanism is needed.}
20331 @item @var{XX@dots{}}
20332 @var{XX@dots{}} is mem contents. Can be fewer bytes than requested if able
20333 to read only part of the data. Neither @value{GDBN} nor the stub assume
20334 that sized memory transfers are assumed using word aligned
20335 accesses. FIXME: @emph{A word aligned memory transfer mechanism is
20341 @item @code{M}@var{addr},@var{length}@code{:}@var{XX@dots{}} --- write mem
20342 @cindex @code{M} packet
20344 Write @var{length} bytes of memory starting at address @var{addr}.
20345 @var{XX@dots{}} is the data.
20352 for an error (this includes the case where only part of the data was
20356 @item @code{n} --- reserved
20358 Reserved for future use.
20360 @item @code{N} --- reserved
20362 Reserved for future use.
20364 @item @code{o} --- reserved
20366 Reserved for future use.
20368 @item @code{O} --- reserved
20370 @item @code{p}@var{hex number of register} --- read register packet
20371 @cindex @code{p} packet
20373 @xref{read registers packet}, for a description of how the returned
20374 register value is encoded.
20378 @item @var{XX@dots{}}
20379 the register's value
20383 Indicating an unrecognized @var{query}.
20386 @item @code{P}@var{n@dots{}}@code{=}@var{r@dots{}} --- write register
20387 @anchor{write register packet}
20388 @cindex @code{P} packet
20390 Write register @var{n@dots{}} with value @var{r@dots{}}, which contains two hex
20391 digits for each byte in the register (target byte order).
20401 @item @code{q}@var{query} --- general query
20402 @anchor{general query packet}
20403 @cindex @code{q} packet
20405 Request info about @var{query}. In general @value{GDBN} queries have a
20406 leading upper case letter. Custom vendor queries should use a company
20407 prefix (in lower case) ex: @samp{qfsf.var}. @var{query} may optionally
20408 be followed by a @samp{,} or @samp{;} separated list. Stubs must ensure
20409 that they match the full @var{query} name.
20413 @item @var{XX@dots{}}
20414 Hex encoded data from query. The reply can not be empty.
20418 Indicating an unrecognized @var{query}.
20421 @item @code{Q}@var{var}@code{=}@var{val} --- general set
20422 @cindex @code{Q} packet
20424 Set value of @var{var} to @var{val}.
20426 @xref{general query packet}, for a discussion of naming conventions.
20428 @item @code{r} --- reset @strong{(deprecated)}
20429 @cindex @code{r} packet
20431 Reset the entire system.
20433 @item @code{R}@var{XX} --- remote restart
20434 @cindex @code{R} packet
20436 Restart the program being debugged. @var{XX}, while needed, is ignored.
20437 This packet is only available in extended mode.
20441 @item @emph{no reply}
20442 The @samp{R} packet has no reply.
20445 @item @code{s}@var{addr} --- step
20446 @cindex @code{s} packet
20448 @var{addr} is address to resume. If @var{addr} is omitted, resume at
20452 @xref{Stop Reply Packets}, for the reply specifications.
20454 @item @code{S}@var{sig}@code{;}@var{addr} --- step with signal
20455 @anchor{step with signal packet}
20456 @cindex @code{S} packet
20458 Like @samp{C} but step not continue.
20461 @xref{Stop Reply Packets}, for the reply specifications.
20463 @item @code{t}@var{addr}@code{:}@var{PP}@code{,}@var{MM} --- search
20464 @cindex @code{t} packet
20466 Search backwards starting at address @var{addr} for a match with pattern
20467 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
20468 @var{addr} must be at least 3 digits.
20470 @item @code{T}@var{XX} --- thread alive
20471 @cindex @code{T} packet
20473 Find out if the thread XX is alive.
20478 thread is still alive
20483 @item @code{u} --- reserved
20485 Reserved for future use.
20487 @item @code{U} --- reserved
20489 Reserved for future use.
20491 @item @code{v} --- verbose packet prefix
20493 Packets starting with @code{v} are identified by a multi-letter name,
20494 up to the first @code{;} or @code{?} (or the end of the packet).
20496 @item @code{vCont}[;@var{action}[@code{:}@var{tid}]]... --- extended resume
20497 @cindex @code{vCont} packet
20499 Resume the inferior. Different actions may be specified for each thread.
20500 If an action is specified with no @var{tid}, then it is applied to any
20501 threads that don't have a specific action specified; if no default action is
20502 specified then other threads should remain stopped. Specifying multiple
20503 default actions is an error; specifying no actions is also an error.
20504 Thread IDs are specified in hexadecimal. Currently supported actions are:
20510 Continue with signal @var{sig}. @var{sig} should be two hex digits.
20514 Step with signal @var{sig}. @var{sig} should be two hex digits.
20517 The optional @var{addr} argument normally associated with these packets is
20518 not supported in @code{vCont}.
20521 @xref{Stop Reply Packets}, for the reply specifications.
20523 @item @code{vCont?} --- extended resume query
20524 @cindex @code{vCont?} packet
20526 Query support for the @code{vCont} packet.
20530 @item @code{vCont}[;@var{action}]...
20531 The @code{vCont} packet is supported. Each @var{action} is a supported
20532 command in the @code{vCont} packet.
20534 The @code{vCont} packet is not supported.
20537 @item @code{V} --- reserved
20539 Reserved for future use.
20541 @item @code{w} --- reserved
20543 Reserved for future use.
20545 @item @code{W} --- reserved
20547 Reserved for future use.
20549 @item @code{x} --- reserved
20551 Reserved for future use.
20553 @item @code{X}@var{addr}@code{,}@var{length}@var{:}@var{XX@dots{}} --- write mem (binary)
20554 @cindex @code{X} packet
20556 @var{addr} is address, @var{length} is number of bytes, @var{XX@dots{}}
20557 is binary data. The characters @code{$}, @code{#}, and @code{0x7d} are
20558 escaped using @code{0x7d}.
20568 @item @code{y} --- reserved
20570 Reserved for future use.
20572 @item @code{Y} reserved
20574 Reserved for future use.
20576 @item @code{z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- remove breakpoint or watchpoint @strong{(draft)}
20577 @itemx @code{Z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- insert breakpoint or watchpoint @strong{(draft)}
20578 @anchor{insert breakpoint or watchpoint packet}
20579 @cindex @code{z} packet
20580 @cindex @code{Z} packets
20582 Insert (@code{Z}) or remove (@code{z}) a @var{type} breakpoint or
20583 watchpoint starting at address @var{address} and covering the next
20584 @var{length} bytes.
20586 Each breakpoint and watchpoint packet @var{type} is documented
20589 @emph{Implementation notes: A remote target shall return an empty string
20590 for an unrecognized breakpoint or watchpoint packet @var{type}. A
20591 remote target shall support either both or neither of a given
20592 @code{Z}@var{type}@dots{} and @code{z}@var{type}@dots{} packet pair. To
20593 avoid potential problems with duplicate packets, the operations should
20594 be implemented in an idempotent way.}
20596 @item @code{z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- remove memory breakpoint @strong{(draft)}
20597 @item @code{Z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- insert memory breakpoint @strong{(draft)}
20598 @cindex @code{z0} packet
20599 @cindex @code{Z0} packet
20601 Insert (@code{Z0}) or remove (@code{z0}) a memory breakpoint at address
20602 @code{addr} of size @code{length}.
20604 A memory breakpoint is implemented by replacing the instruction at
20605 @var{addr} with a software breakpoint or trap instruction. The
20606 @code{length} is used by targets that indicates the size of the
20607 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
20608 @sc{mips} can insert either a 2 or 4 byte breakpoint).
20610 @emph{Implementation note: It is possible for a target to copy or move
20611 code that contains memory breakpoints (e.g., when implementing
20612 overlays). The behavior of this packet, in the presence of such a
20613 target, is not defined.}
20625 @item @code{z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- remove hardware breakpoint @strong{(draft)}
20626 @item @code{Z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- insert hardware breakpoint @strong{(draft)}
20627 @cindex @code{z1} packet
20628 @cindex @code{Z1} packet
20630 Insert (@code{Z1}) or remove (@code{z1}) a hardware breakpoint at
20631 address @code{addr} of size @code{length}.
20633 A hardware breakpoint is implemented using a mechanism that is not
20634 dependant on being able to modify the target's memory.
20636 @emph{Implementation note: A hardware breakpoint is not affected by code
20649 @item @code{z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- remove write watchpoint @strong{(draft)}
20650 @item @code{Z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- insert write watchpoint @strong{(draft)}
20651 @cindex @code{z2} packet
20652 @cindex @code{Z2} packet
20654 Insert (@code{Z2}) or remove (@code{z2}) a write watchpoint.
20666 @item @code{z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- remove read watchpoint @strong{(draft)}
20667 @item @code{Z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- insert read watchpoint @strong{(draft)}
20668 @cindex @code{z3} packet
20669 @cindex @code{Z3} packet
20671 Insert (@code{Z3}) or remove (@code{z3}) a read watchpoint.
20683 @item @code{z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- remove access watchpoint @strong{(draft)}
20684 @item @code{Z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- insert access watchpoint @strong{(draft)}
20685 @cindex @code{z4} packet
20686 @cindex @code{Z4} packet
20688 Insert (@code{Z4}) or remove (@code{z4}) an access watchpoint.
20702 @node Stop Reply Packets
20703 @section Stop Reply Packets
20704 @cindex stop reply packets
20706 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
20707 receive any of the below as a reply. In the case of the @samp{C},
20708 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
20709 when the target halts. In the below the exact meaning of @samp{signal
20710 number} is poorly defined. In general one of the UNIX signal numbering
20711 conventions is used.
20716 @var{AA} is the signal number
20718 @item @code{T}@var{AA}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}
20719 @cindex @code{T} packet reply
20721 @var{AA} = two hex digit signal number; @var{n...} = register number
20722 (hex), @var{r...} = target byte ordered register contents, size defined
20723 by @code{DEPRECATED_REGISTER_RAW_SIZE}; @var{n...} = @samp{thread},
20724 @var{r...} = thread process ID, this is a hex integer; @var{n...} =
20725 (@samp{watch} | @samp{rwatch} | @samp{awatch}, @var{r...} = data
20726 address, this is a hex integer; @var{n...} = other string not starting
20727 with valid hex digit. @value{GDBN} should ignore this @var{n...},
20728 @var{r...} pair and go on to the next. This way we can extend the
20733 The process exited, and @var{AA} is the exit status. This is only
20734 applicable to certain targets.
20738 The process terminated with signal @var{AA}.
20740 @item O@var{XX@dots{}}
20742 @var{XX@dots{}} is hex encoding of @sc{ascii} data. This can happen at
20743 any time while the program is running and the debugger should continue
20744 to wait for @samp{W}, @samp{T}, etc.
20746 @item F@var{call-id}@code{,}@var{parameter@dots{}}
20748 @var{call-id} is the identifier which says which host system call should
20749 be called. This is just the name of the function. Translation into the
20750 correct system call is only applicable as it's defined in @value{GDBN}.
20751 @xref{File-I/O remote protocol extension}, for a list of implemented
20754 @var{parameter@dots{}} is a list of parameters as defined for this very
20757 The target replies with this packet when it expects @value{GDBN} to call
20758 a host system call on behalf of the target. @value{GDBN} replies with
20759 an appropriate @code{F} packet and keeps up waiting for the next reply
20760 packet from the target. The latest @samp{C}, @samp{c}, @samp{S} or
20761 @samp{s} action is expected to be continued.
20762 @xref{File-I/O remote protocol extension}, for more details.
20766 @node General Query Packets
20767 @section General Query Packets
20769 The following set and query packets have already been defined.
20773 @item @code{q}@code{C} --- current thread
20775 Return the current thread id.
20779 @item @code{QC}@var{pid}
20780 Where @var{pid} is a HEX encoded 16 bit process id.
20782 Any other reply implies the old pid.
20785 @item @code{q}@code{fThreadInfo} -- all thread ids
20787 @code{q}@code{sThreadInfo}
20789 Obtain a list of active thread ids from the target (OS). Since there
20790 may be too many active threads to fit into one reply packet, this query
20791 works iteratively: it may require more than one query/reply sequence to
20792 obtain the entire list of threads. The first query of the sequence will
20793 be the @code{qf}@code{ThreadInfo} query; subsequent queries in the
20794 sequence will be the @code{qs}@code{ThreadInfo} query.
20796 NOTE: replaces the @code{qL} query (see below).
20800 @item @code{m}@var{id}
20802 @item @code{m}@var{id},@var{id}@dots{}
20803 a comma-separated list of thread ids
20805 (lower case 'el') denotes end of list.
20808 In response to each query, the target will reply with a list of one or
20809 more thread ids, in big-endian hex, separated by commas. @value{GDBN}
20810 will respond to each reply with a request for more thread ids (using the
20811 @code{qs} form of the query), until the target responds with @code{l}
20812 (lower-case el, for @code{'last'}).
20814 @item @code{q}@code{ThreadExtraInfo}@code{,}@var{id} --- extra thread info
20816 Where @var{id} is a thread-id in big-endian hex. Obtain a printable
20817 string description of a thread's attributes from the target OS. This
20818 string may contain anything that the target OS thinks is interesting for
20819 @value{GDBN} to tell the user about the thread. The string is displayed
20820 in @value{GDBN}'s @samp{info threads} display. Some examples of
20821 possible thread extra info strings are ``Runnable'', or ``Blocked on
20826 @item @var{XX@dots{}}
20827 Where @var{XX@dots{}} is a hex encoding of @sc{ascii} data, comprising
20828 the printable string containing the extra information about the thread's
20832 @item @code{q}@code{L}@var{startflag}@var{threadcount}@var{nextthread} --- query @var{LIST} or @var{threadLIST} @strong{(deprecated)}
20834 Obtain thread information from RTOS. Where: @var{startflag} (one hex
20835 digit) is one to indicate the first query and zero to indicate a
20836 subsequent query; @var{threadcount} (two hex digits) is the maximum
20837 number of threads the response packet can contain; and @var{nextthread}
20838 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
20839 returned in the response as @var{argthread}.
20841 NOTE: this query is replaced by the @code{q}@code{fThreadInfo} query
20846 @item @code{q}@code{M}@var{count}@var{done}@var{argthread}@var{thread@dots{}}
20847 Where: @var{count} (two hex digits) is the number of threads being
20848 returned; @var{done} (one hex digit) is zero to indicate more threads
20849 and one indicates no further threads; @var{argthreadid} (eight hex
20850 digits) is @var{nextthread} from the request packet; @var{thread@dots{}}
20851 is a sequence of thread IDs from the target. @var{threadid} (eight hex
20852 digits). See @code{remote.c:parse_threadlist_response()}.
20855 @item @code{q}@code{CRC:}@var{addr}@code{,}@var{length} --- compute CRC of memory block
20859 @item @code{E}@var{NN}
20860 An error (such as memory fault)
20861 @item @code{C}@var{CRC32}
20862 A 32 bit cyclic redundancy check of the specified memory region.
20865 @item @code{q}@code{Offsets} --- query sect offs
20867 Get section offsets that the target used when re-locating the downloaded
20868 image. @emph{Note: while a @code{Bss} offset is included in the
20869 response, @value{GDBN} ignores this and instead applies the @code{Data}
20870 offset to the @code{Bss} section.}
20874 @item @code{Text=}@var{xxx}@code{;Data=}@var{yyy}@code{;Bss=}@var{zzz}
20877 @item @code{q}@code{P}@var{mode}@var{threadid} --- thread info request
20879 Returns information on @var{threadid}. Where: @var{mode} is a hex
20880 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
20887 See @code{remote.c:remote_unpack_thread_info_response()}.
20889 @item @code{q}@code{Rcmd,}@var{command} --- remote command
20891 @var{command} (hex encoded) is passed to the local interpreter for
20892 execution. Invalid commands should be reported using the output string.
20893 Before the final result packet, the target may also respond with a
20894 number of intermediate @code{O}@var{output} console output packets.
20895 @emph{Implementors should note that providing access to a stubs's
20896 interpreter may have security implications}.
20901 A command response with no output.
20903 A command response with the hex encoded output string @var{OUTPUT}.
20904 @item @code{E}@var{NN}
20905 Indicate a badly formed request.
20907 When @samp{q}@samp{Rcmd} is not recognized.
20910 @item @code{qSymbol::} --- symbol lookup
20912 Notify the target that @value{GDBN} is prepared to serve symbol lookup
20913 requests. Accept requests from the target for the values of symbols.
20918 The target does not need to look up any (more) symbols.
20919 @item @code{qSymbol:}@var{sym_name}
20920 The target requests the value of symbol @var{sym_name} (hex encoded).
20921 @value{GDBN} may provide the value by using the
20922 @code{qSymbol:}@var{sym_value}:@var{sym_name} message, described below.
20925 @item @code{qSymbol:}@var{sym_value}:@var{sym_name} --- symbol value
20927 Set the value of @var{sym_name} to @var{sym_value}.
20929 @var{sym_name} (hex encoded) is the name of a symbol whose value the
20930 target has previously requested.
20932 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
20933 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
20939 The target does not need to look up any (more) symbols.
20940 @item @code{qSymbol:}@var{sym_name}
20941 The target requests the value of a new symbol @var{sym_name} (hex
20942 encoded). @value{GDBN} will continue to supply the values of symbols
20943 (if available), until the target ceases to request them.
20946 @item @code{qPart}:@var{object}:@code{read}:@var{annex}:@var{offset},@var{length} --- read special data
20948 Read uninterpreted bytes from the target's special data area
20949 identified by the keyword @code{object}.
20950 Request @var{length} bytes starting at @var{offset} bytes into the data.
20951 The content and encoding of @var{annex} is specific to the object;
20952 it can supply additional details about what data to access.
20954 Here are the specific requests of this form defined so far.
20955 All @samp{@code{qPart}:@var{object}:@code{read}:@dots{}}
20956 requests use the same reply formats, listed below.
20959 @item @code{qPart}:@code{auxv}:@code{read}::@var{offset},@var{length}
20960 Access the target's @dfn{auxiliary vector}. @xref{Auxiliary Vector}.
20961 Note @var{annex} must be empty.
20967 The @var{offset} in the request is at the end of the data.
20968 There is no more data to be read.
20970 @item @var{XX@dots{}}
20971 Hex encoded data bytes read.
20972 This may be fewer bytes than the @var{length} in the request.
20975 The request was malformed, or @var{annex} was invalid.
20977 @item @code{E}@var{nn}
20978 The offset was invalid, or there was an error encountered reading the data.
20979 @var{nn} is a hex-encoded @code{errno} value.
20981 @item @code{""} (empty)
20982 An empty reply indicates the @var{object} or @var{annex} string was not
20983 recognized by the stub.
20986 @item @code{qPart}:@var{object}:@code{write}:@var{annex}:@var{offset}:@var{data@dots{}}
20988 Write uninterpreted bytes into the target's special data area
20989 identified by the keyword @code{object},
20990 starting at @var{offset} bytes into the data.
20991 @var{data@dots{}} is the hex-encoded data to be written.
20992 The content and encoding of @var{annex} is specific to the object;
20993 it can supply additional details about what data to access.
20995 No requests of this form are presently in use. This specification
20996 serves as a placeholder to document the common format that new
20997 specific request specifications ought to use.
21002 @var{nn} (hex encoded) is the number of bytes written.
21003 This may be fewer bytes than supplied in the request.
21006 The request was malformed, or @var{annex} was invalid.
21008 @item @code{E}@var{nn}
21009 The offset was invalid, or there was an error encountered writing the data.
21010 @var{nn} is a hex-encoded @code{errno} value.
21012 @item @code{""} (empty)
21013 An empty reply indicates the @var{object} or @var{annex} string was not
21014 recognized by the stub, or that the object does not support writing.
21017 @item @code{qPart}:@var{object}:@var{operation}:@dots{}
21018 Requests of this form may be added in the future. When a stub does
21019 not recognize the @var{object} keyword, or its support for
21020 @var{object} does not recognize the @var{operation} keyword,
21021 the stub must respond with an empty packet.
21024 @node Register Packet Format
21025 @section Register Packet Format
21027 The following @samp{g}/@samp{G} packets have previously been defined.
21028 In the below, some thirty-two bit registers are transferred as
21029 sixty-four bits. Those registers should be zero/sign extended (which?)
21030 to fill the space allocated. Register bytes are transfered in target
21031 byte order. The two nibbles within a register byte are transfered
21032 most-significant - least-significant.
21038 All registers are transfered as thirty-two bit quantities in the order:
21039 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
21040 registers; fsr; fir; fp.
21044 All registers are transfered as sixty-four bit quantities (including
21045 thirty-two bit registers such as @code{sr}). The ordering is the same
21053 Example sequence of a target being re-started. Notice how the restart
21054 does not get any direct output:
21059 @emph{target restarts}
21062 <- @code{T001:1234123412341234}
21066 Example sequence of a target being stepped by a single instruction:
21069 -> @code{G1445@dots{}}
21074 <- @code{T001:1234123412341234}
21078 <- @code{1455@dots{}}
21082 @node File-I/O remote protocol extension
21083 @section File-I/O remote protocol extension
21084 @cindex File-I/O remote protocol extension
21087 * File-I/O Overview::
21088 * Protocol basics::
21089 * The F request packet::
21090 * The F reply packet::
21091 * Memory transfer::
21092 * The Ctrl-C message::
21094 * The isatty call::
21095 * The system call::
21096 * List of supported calls::
21097 * Protocol specific representation of datatypes::
21099 * File-I/O Examples::
21102 @node File-I/O Overview
21103 @subsection File-I/O Overview
21104 @cindex file-i/o overview
21106 The File I/O remote protocol extension (short: File-I/O) allows the
21107 target to use the hosts file system and console I/O when calling various
21108 system calls. System calls on the target system are translated into a
21109 remote protocol packet to the host system which then performs the needed
21110 actions and returns with an adequate response packet to the target system.
21111 This simulates file system operations even on targets that lack file systems.
21113 The protocol is defined host- and target-system independent. It uses
21114 it's own independent representation of datatypes and values. Both,
21115 @value{GDBN} and the target's @value{GDBN} stub are responsible for
21116 translating the system dependent values into the unified protocol values
21117 when data is transmitted.
21119 The communication is synchronous. A system call is possible only
21120 when GDB is waiting for the @samp{C}, @samp{c}, @samp{S} or @samp{s}
21121 packets. While @value{GDBN} handles the request for a system call,
21122 the target is stopped to allow deterministic access to the target's
21123 memory. Therefore File-I/O is not interuptible by target signals. It
21124 is possible to interrupt File-I/O by a user interrupt (Ctrl-C), though.
21126 The target's request to perform a host system call does not finish
21127 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
21128 after finishing the system call, the target returns to continuing the
21129 previous activity (continue, step). No additional continue or step
21130 request from @value{GDBN} is required.
21133 (@value{GDBP}) continue
21134 <- target requests 'system call X'
21135 target is stopped, @value{GDBN} executes system call
21136 -> GDB returns result
21137 ... target continues, GDB returns to wait for the target
21138 <- target hits breakpoint and sends a Txx packet
21141 The protocol is only used for files on the host file system and
21142 for I/O on the console. Character or block special devices, pipes,
21143 named pipes or sockets or any other communication method on the host
21144 system are not supported by this protocol.
21146 @node Protocol basics
21147 @subsection Protocol basics
21148 @cindex protocol basics, file-i/o
21150 The File-I/O protocol uses the @code{F} packet, as request as well
21151 as as reply packet. Since a File-I/O system call can only occur when
21152 @value{GDBN} is waiting for the continuing or stepping target, the
21153 File-I/O request is a reply that @value{GDBN} has to expect as a result
21154 of a former @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
21155 This @code{F} packet contains all information needed to allow @value{GDBN}
21156 to call the appropriate host system call:
21160 A unique identifier for the requested system call.
21163 All parameters to the system call. Pointers are given as addresses
21164 in the target memory address space. Pointers to strings are given as
21165 pointer/length pair. Numerical values are given as they are.
21166 Numerical control values are given in a protocol specific representation.
21170 At that point @value{GDBN} has to perform the following actions.
21174 If parameter pointer values are given, which point to data needed as input
21175 to a system call, @value{GDBN} requests this data from the target with a
21176 standard @code{m} packet request. This additional communication has to be
21177 expected by the target implementation and is handled as any other @code{m}
21181 @value{GDBN} translates all value from protocol representation to host
21182 representation as needed. Datatypes are coerced into the host types.
21185 @value{GDBN} calls the system call
21188 It then coerces datatypes back to protocol representation.
21191 If pointer parameters in the request packet point to buffer space in which
21192 a system call is expected to copy data to, the data is transmitted to the
21193 target using a @code{M} or @code{X} packet. This packet has to be expected
21194 by the target implementation and is handled as any other @code{M} or @code{X}
21199 Eventually @value{GDBN} replies with another @code{F} packet which contains all
21200 necessary information for the target to continue. This at least contains
21207 @code{errno}, if has been changed by the system call.
21214 After having done the needed type and value coercion, the target continues
21215 the latest continue or step action.
21217 @node The F request packet
21218 @subsection The @code{F} request packet
21219 @cindex file-i/o request packet
21220 @cindex @code{F} request packet
21222 The @code{F} request packet has the following format:
21227 @code{F}@var{call-id}@code{,}@var{parameter@dots{}}
21230 @var{call-id} is the identifier to indicate the host system call to be called.
21231 This is just the name of the function.
21233 @var{parameter@dots{}} are the parameters to the system call.
21237 Parameters are hexadecimal integer values, either the real values in case
21238 of scalar datatypes, as pointers to target buffer space in case of compound
21239 datatypes and unspecified memory areas or as pointer/length pairs in case
21240 of string parameters. These are appended to the call-id, each separated
21241 from its predecessor by a comma. All values are transmitted in ASCII
21242 string representation, pointer/length pairs separated by a slash.
21244 @node The F reply packet
21245 @subsection The @code{F} reply packet
21246 @cindex file-i/o reply packet
21247 @cindex @code{F} reply packet
21249 The @code{F} reply packet has the following format:
21254 @code{F}@var{retcode}@code{,}@var{errno}@code{,}@var{Ctrl-C flag}@code{;}@var{call specific attachment}
21257 @var{retcode} is the return code of the system call as hexadecimal value.
21259 @var{errno} is the errno set by the call, in protocol specific representation.
21260 This parameter can be omitted if the call was successful.
21262 @var{Ctrl-C flag} is only send if the user requested a break. In this
21263 case, @var{errno} must be send as well, even if the call was successful.
21264 The @var{Ctrl-C flag} itself consists of the character 'C':
21271 or, if the call was interupted before the host call has been performed:
21278 assuming 4 is the protocol specific representation of @code{EINTR}.
21282 @node Memory transfer
21283 @subsection Memory transfer
21284 @cindex memory transfer, in file-i/o protocol
21286 Structured data which is transferred using a memory read or write as e.g.@:
21287 a @code{struct stat} is expected to be in a protocol specific format with
21288 all scalar multibyte datatypes being big endian. This should be done by
21289 the target before the @code{F} packet is sent resp.@: by @value{GDBN} before
21290 it transfers memory to the target. Transferred pointers to structured
21291 data should point to the already coerced data at any time.
21293 @node The Ctrl-C message
21294 @subsection The Ctrl-C message
21295 @cindex ctrl-c message, in file-i/o protocol
21297 A special case is, if the @var{Ctrl-C flag} is set in the @value{GDBN}
21298 reply packet. In this case the target should behave, as if it had
21299 gotten a break message. The meaning for the target is ``system call
21300 interupted by @code{SIGINT}''. Consequentially, the target should actually stop
21301 (as with a break message) and return to @value{GDBN} with a @code{T02}
21302 packet. In this case, it's important for the target to know, in which
21303 state the system call was interrupted. Since this action is by design
21304 not an atomic operation, we have to differ between two cases:
21308 The system call hasn't been performed on the host yet.
21311 The system call on the host has been finished.
21315 These two states can be distinguished by the target by the value of the
21316 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
21317 call hasn't been performed. This is equivalent to the @code{EINTR} handling
21318 on POSIX systems. In any other case, the target may presume that the
21319 system call has been finished --- successful or not --- and should behave
21320 as if the break message arrived right after the system call.
21322 @value{GDBN} must behave reliable. If the system call has not been called
21323 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
21324 @code{errno} in the packet. If the system call on the host has been finished
21325 before the user requests a break, the full action must be finshed by
21326 @value{GDBN}. This requires sending @code{M} or @code{X} packets as they fit.
21327 The @code{F} packet may only be send when either nothing has happened
21328 or the full action has been completed.
21331 @subsection Console I/O
21332 @cindex console i/o as part of file-i/o
21334 By default and if not explicitely closed by the target system, the file
21335 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
21336 on the @value{GDBN} console is handled as any other file output operation
21337 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
21338 by @value{GDBN} so that after the target read request from file descriptor
21339 0 all following typing is buffered until either one of the following
21344 The user presses @kbd{Ctrl-C}. The behaviour is as explained above, the
21346 system call is treated as finished.
21349 The user presses @kbd{Enter}. This is treated as end of input with a trailing
21353 The user presses @kbd{Ctrl-D}. This is treated as end of input. No trailing
21354 character, especially no Ctrl-D is appended to the input.
21358 If the user has typed more characters as fit in the buffer given to
21359 the read call, the trailing characters are buffered in @value{GDBN} until
21360 either another @code{read(0, @dots{})} is requested by the target or debugging
21361 is stopped on users request.
21363 @node The isatty call
21364 @subsection The isatty(3) call
21365 @cindex isatty call, file-i/o protocol
21367 A special case in this protocol is the library call @code{isatty} which
21368 is implemented as it's own call inside of this protocol. It returns
21369 1 to the target if the file descriptor given as parameter is attached
21370 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
21371 would require implementing @code{ioctl} and would be more complex than
21374 @node The system call
21375 @subsection The system(3) call
21376 @cindex system call, file-i/o protocol
21378 The other special case in this protocol is the @code{system} call which
21379 is implemented as it's own call, too. @value{GDBN} is taking over the full
21380 task of calling the necessary host calls to perform the @code{system}
21381 call. The return value of @code{system} is simplified before it's returned
21382 to the target. Basically, the only signal transmitted back is @code{EINTR}
21383 in case the user pressed @kbd{Ctrl-C}. Otherwise the return value consists
21384 entirely of the exit status of the called command.
21386 Due to security concerns, the @code{system} call is refused to be called
21387 by @value{GDBN} by default. The user has to allow this call explicitly by
21391 @kindex set remote system-call-allowed 1
21392 @item @code{set remote system-call-allowed 1}
21395 Disabling the @code{system} call is done by
21398 @kindex set remote system-call-allowed 0
21399 @item @code{set remote system-call-allowed 0}
21402 The current setting is shown by typing
21405 @kindex show remote system-call-allowed
21406 @item @code{show remote system-call-allowed}
21409 @node List of supported calls
21410 @subsection List of supported calls
21411 @cindex list of supported file-i/o calls
21428 @unnumberedsubsubsec open
21429 @cindex open, file-i/o system call
21433 int open(const char *pathname, int flags);
21434 int open(const char *pathname, int flags, mode_t mode);
21437 Fopen,pathptr/len,flags,mode
21441 @code{flags} is the bitwise or of the following values:
21445 If the file does not exist it will be created. The host
21446 rules apply as far as file ownership and time stamps
21450 When used with O_CREAT, if the file already exists it is
21451 an error and open() fails.
21454 If the file already exists and the open mode allows
21455 writing (O_RDWR or O_WRONLY is given) it will be
21456 truncated to length 0.
21459 The file is opened in append mode.
21462 The file is opened for reading only.
21465 The file is opened for writing only.
21468 The file is opened for reading and writing.
21471 Each other bit is silently ignored.
21476 @code{mode} is the bitwise or of the following values:
21480 User has read permission.
21483 User has write permission.
21486 Group has read permission.
21489 Group has write permission.
21492 Others have read permission.
21495 Others have write permission.
21498 Each other bit is silently ignored.
21503 @exdent Return value:
21504 open returns the new file descriptor or -1 if an error
21512 pathname already exists and O_CREAT and O_EXCL were used.
21515 pathname refers to a directory.
21518 The requested access is not allowed.
21521 pathname was too long.
21524 A directory component in pathname does not exist.
21527 pathname refers to a device, pipe, named pipe or socket.
21530 pathname refers to a file on a read-only filesystem and
21531 write access was requested.
21534 pathname is an invalid pointer value.
21537 No space on device to create the file.
21540 The process already has the maximum number of files open.
21543 The limit on the total number of files open on the system
21547 The call was interrupted by the user.
21551 @unnumberedsubsubsec close
21552 @cindex close, file-i/o system call
21561 @exdent Return value:
21562 close returns zero on success, or -1 if an error occurred.
21569 fd isn't a valid open file descriptor.
21572 The call was interrupted by the user.
21576 @unnumberedsubsubsec read
21577 @cindex read, file-i/o system call
21581 int read(int fd, void *buf, unsigned int count);
21584 Fread,fd,bufptr,count
21586 @exdent Return value:
21587 On success, the number of bytes read is returned.
21588 Zero indicates end of file. If count is zero, read
21589 returns zero as well. On error, -1 is returned.
21596 fd is not a valid file descriptor or is not open for
21600 buf is an invalid pointer value.
21603 The call was interrupted by the user.
21607 @unnumberedsubsubsec write
21608 @cindex write, file-i/o system call
21612 int write(int fd, const void *buf, unsigned int count);
21615 Fwrite,fd,bufptr,count
21617 @exdent Return value:
21618 On success, the number of bytes written are returned.
21619 Zero indicates nothing was written. On error, -1
21627 fd is not a valid file descriptor or is not open for
21631 buf is an invalid pointer value.
21634 An attempt was made to write a file that exceeds the
21635 host specific maximum file size allowed.
21638 No space on device to write the data.
21641 The call was interrupted by the user.
21645 @unnumberedsubsubsec lseek
21646 @cindex lseek, file-i/o system call
21650 long lseek (int fd, long offset, int flag);
21653 Flseek,fd,offset,flag
21656 @code{flag} is one of:
21660 The offset is set to offset bytes.
21663 The offset is set to its current location plus offset
21667 The offset is set to the size of the file plus offset
21672 @exdent Return value:
21673 On success, the resulting unsigned offset in bytes from
21674 the beginning of the file is returned. Otherwise, a
21675 value of -1 is returned.
21682 fd is not a valid open file descriptor.
21685 fd is associated with the @value{GDBN} console.
21688 flag is not a proper value.
21691 The call was interrupted by the user.
21695 @unnumberedsubsubsec rename
21696 @cindex rename, file-i/o system call
21700 int rename(const char *oldpath, const char *newpath);
21703 Frename,oldpathptr/len,newpathptr/len
21705 @exdent Return value:
21706 On success, zero is returned. On error, -1 is returned.
21713 newpath is an existing directory, but oldpath is not a
21717 newpath is a non-empty directory.
21720 oldpath or newpath is a directory that is in use by some
21724 An attempt was made to make a directory a subdirectory
21728 A component used as a directory in oldpath or new
21729 path is not a directory. Or oldpath is a directory
21730 and newpath exists but is not a directory.
21733 oldpathptr or newpathptr are invalid pointer values.
21736 No access to the file or the path of the file.
21740 oldpath or newpath was too long.
21743 A directory component in oldpath or newpath does not exist.
21746 The file is on a read-only filesystem.
21749 The device containing the file has no room for the new
21753 The call was interrupted by the user.
21757 @unnumberedsubsubsec unlink
21758 @cindex unlink, file-i/o system call
21762 int unlink(const char *pathname);
21765 Funlink,pathnameptr/len
21767 @exdent Return value:
21768 On success, zero is returned. On error, -1 is returned.
21775 No access to the file or the path of the file.
21778 The system does not allow unlinking of directories.
21781 The file pathname cannot be unlinked because it's
21782 being used by another process.
21785 pathnameptr is an invalid pointer value.
21788 pathname was too long.
21791 A directory component in pathname does not exist.
21794 A component of the path is not a directory.
21797 The file is on a read-only filesystem.
21800 The call was interrupted by the user.
21804 @unnumberedsubsubsec stat/fstat
21805 @cindex fstat, file-i/o system call
21806 @cindex stat, file-i/o system call
21810 int stat(const char *pathname, struct stat *buf);
21811 int fstat(int fd, struct stat *buf);
21814 Fstat,pathnameptr/len,bufptr
21817 @exdent Return value:
21818 On success, zero is returned. On error, -1 is returned.
21825 fd is not a valid open file.
21828 A directory component in pathname does not exist or the
21829 path is an empty string.
21832 A component of the path is not a directory.
21835 pathnameptr is an invalid pointer value.
21838 No access to the file or the path of the file.
21841 pathname was too long.
21844 The call was interrupted by the user.
21848 @unnumberedsubsubsec gettimeofday
21849 @cindex gettimeofday, file-i/o system call
21853 int gettimeofday(struct timeval *tv, void *tz);
21856 Fgettimeofday,tvptr,tzptr
21858 @exdent Return value:
21859 On success, 0 is returned, -1 otherwise.
21866 tz is a non-NULL pointer.
21869 tvptr and/or tzptr is an invalid pointer value.
21873 @unnumberedsubsubsec isatty
21874 @cindex isatty, file-i/o system call
21878 int isatty(int fd);
21883 @exdent Return value:
21884 Returns 1 if fd refers to the @value{GDBN} console, 0 otherwise.
21891 The call was interrupted by the user.
21895 @unnumberedsubsubsec system
21896 @cindex system, file-i/o system call
21900 int system(const char *command);
21903 Fsystem,commandptr/len
21905 @exdent Return value:
21906 The value returned is -1 on error and the return status
21907 of the command otherwise. Only the exit status of the
21908 command is returned, which is extracted from the hosts
21909 system return value by calling WEXITSTATUS(retval).
21910 In case /bin/sh could not be executed, 127 is returned.
21917 The call was interrupted by the user.
21920 @node Protocol specific representation of datatypes
21921 @subsection Protocol specific representation of datatypes
21922 @cindex protocol specific representation of datatypes, in file-i/o protocol
21925 * Integral datatypes::
21931 @node Integral datatypes
21932 @unnumberedsubsubsec Integral datatypes
21933 @cindex integral datatypes, in file-i/o protocol
21935 The integral datatypes used in the system calls are
21938 int@r{,} unsigned int@r{,} long@r{,} unsigned long@r{,} mode_t @r{and} time_t
21941 @code{Int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
21942 implemented as 32 bit values in this protocol.
21944 @code{Long} and @code{unsigned long} are implemented as 64 bit types.
21946 @xref{Limits}, for corresponding MIN and MAX values (similar to those
21947 in @file{limits.h}) to allow range checking on host and target.
21949 @code{time_t} datatypes are defined as seconds since the Epoch.
21951 All integral datatypes transferred as part of a memory read or write of a
21952 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
21955 @node Pointer values
21956 @unnumberedsubsubsec Pointer values
21957 @cindex pointer values, in file-i/o protocol
21959 Pointers to target data are transmitted as they are. An exception
21960 is made for pointers to buffers for which the length isn't
21961 transmitted as part of the function call, namely strings. Strings
21962 are transmitted as a pointer/length pair, both as hex values, e.g.@:
21969 which is a pointer to data of length 18 bytes at position 0x1aaf.
21970 The length is defined as the full string length in bytes, including
21971 the trailing null byte. Example:
21974 ``hello, world'' at address 0x123456
21985 @unnumberedsubsubsec struct stat
21986 @cindex struct stat, in file-i/o protocol
21988 The buffer of type struct stat used by the target and @value{GDBN} is defined
21993 unsigned int st_dev; /* device */
21994 unsigned int st_ino; /* inode */
21995 mode_t st_mode; /* protection */
21996 unsigned int st_nlink; /* number of hard links */
21997 unsigned int st_uid; /* user ID of owner */
21998 unsigned int st_gid; /* group ID of owner */
21999 unsigned int st_rdev; /* device type (if inode device) */
22000 unsigned long st_size; /* total size, in bytes */
22001 unsigned long st_blksize; /* blocksize for filesystem I/O */
22002 unsigned long st_blocks; /* number of blocks allocated */
22003 time_t st_atime; /* time of last access */
22004 time_t st_mtime; /* time of last modification */
22005 time_t st_ctime; /* time of last change */
22009 The integral datatypes are conforming to the definitions given in the
22010 approriate section (see @ref{Integral datatypes}, for details) so this
22011 structure is of size 64 bytes.
22013 The values of several fields have a restricted meaning and/or
22020 st_ino: No valid meaning for the target. Transmitted unchanged.
22022 st_mode: Valid mode bits are described in Appendix C. Any other
22023 bits have currently no meaning for the target.
22025 st_uid: No valid meaning for the target. Transmitted unchanged.
22027 st_gid: No valid meaning for the target. Transmitted unchanged.
22029 st_rdev: No valid meaning for the target. Transmitted unchanged.
22031 st_atime, st_mtime, st_ctime:
22032 These values have a host and file system dependent
22033 accuracy. Especially on Windows hosts the file systems
22034 don't support exact timing values.
22037 The target gets a struct stat of the above representation and is
22038 responsible to coerce it to the target representation before
22041 Note that due to size differences between the host and target
22042 representation of stat members, these members could eventually
22043 get truncated on the target.
22045 @node struct timeval
22046 @unnumberedsubsubsec struct timeval
22047 @cindex struct timeval, in file-i/o protocol
22049 The buffer of type struct timeval used by the target and @value{GDBN}
22050 is defined as follows:
22054 time_t tv_sec; /* second */
22055 long tv_usec; /* microsecond */
22059 The integral datatypes are conforming to the definitions given in the
22060 approriate section (see @ref{Integral datatypes}, for details) so this
22061 structure is of size 8 bytes.
22064 @subsection Constants
22065 @cindex constants, in file-i/o protocol
22067 The following values are used for the constants inside of the
22068 protocol. @value{GDBN} and target are resposible to translate these
22069 values before and after the call as needed.
22080 @unnumberedsubsubsec Open flags
22081 @cindex open flags, in file-i/o protocol
22083 All values are given in hexadecimal representation.
22095 @node mode_t values
22096 @unnumberedsubsubsec mode_t values
22097 @cindex mode_t values, in file-i/o protocol
22099 All values are given in octal representation.
22116 @unnumberedsubsubsec Errno values
22117 @cindex errno values, in file-i/o protocol
22119 All values are given in decimal representation.
22144 EUNKNOWN is used as a fallback error value if a host system returns
22145 any error value not in the list of supported error numbers.
22148 @unnumberedsubsubsec Lseek flags
22149 @cindex lseek flags, in file-i/o protocol
22158 @unnumberedsubsubsec Limits
22159 @cindex limits, in file-i/o protocol
22161 All values are given in decimal representation.
22164 INT_MIN -2147483648
22166 UINT_MAX 4294967295
22167 LONG_MIN -9223372036854775808
22168 LONG_MAX 9223372036854775807
22169 ULONG_MAX 18446744073709551615
22172 @node File-I/O Examples
22173 @subsection File-I/O Examples
22174 @cindex file-i/o examples
22176 Example sequence of a write call, file descriptor 3, buffer is at target
22177 address 0x1234, 6 bytes should be written:
22180 <- @code{Fwrite,3,1234,6}
22181 @emph{request memory read from target}
22184 @emph{return "6 bytes written"}
22188 Example sequence of a read call, file descriptor 3, buffer is at target
22189 address 0x1234, 6 bytes should be read:
22192 <- @code{Fread,3,1234,6}
22193 @emph{request memory write to target}
22194 -> @code{X1234,6:XXXXXX}
22195 @emph{return "6 bytes read"}
22199 Example sequence of a read call, call fails on the host due to invalid
22200 file descriptor (EBADF):
22203 <- @code{Fread,3,1234,6}
22207 Example sequence of a read call, user presses Ctrl-C before syscall on
22211 <- @code{Fread,3,1234,6}
22216 Example sequence of a read call, user presses Ctrl-C after syscall on
22220 <- @code{Fread,3,1234,6}
22221 -> @code{X1234,6:XXXXXX}
22225 @include agentexpr.texi
22239 % I think something like @colophon should be in texinfo. In the
22241 \long\def\colophon{\hbox to0pt{}\vfill
22242 \centerline{The body of this manual is set in}
22243 \centerline{\fontname\tenrm,}
22244 \centerline{with headings in {\bf\fontname\tenbf}}
22245 \centerline{and examples in {\tt\fontname\tentt}.}
22246 \centerline{{\it\fontname\tenit\/},}
22247 \centerline{{\bf\fontname\tenbf}, and}
22248 \centerline{{\sl\fontname\tensl\/}}
22249 \centerline{are used for emphasis.}\vfill}
22251 % Blame: doc@cygnus.com, 1991.