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 Some programs contain an elaboration phase where some startup code is
1764 executed before the main program is called. This depends on the
1765 languages used to write your program. In C@t{++} for instance,
1766 constructors for static and global objects are executed before
1767 @code{main} is called. It is therefore possible that the debugger stops
1768 before reaching the main procedure. However, the temporary breakpoint
1769 will remain to halt execution.
1771 Specify the arguments to give to your program as arguments to the
1772 @samp{start} command. These arguments will be given verbatim to the
1773 underlying @samp{run} command. Note that the same arguments will be
1774 reused if no argument is provided during subsequent calls to
1775 @samp{start} or @samp{run}.
1777 It is sometimes necessary to debug the program during elaboration. In
1778 these cases, using the @code{start} command would stop the execution of
1779 your program too late, as the program would have already completed the
1780 elaboration phase. Under these circumstances, insert breakpoints in your
1781 elaboration code before running your program.
1785 @section Your program's arguments
1787 @cindex arguments (to your program)
1788 The arguments to your program can be specified by the arguments of the
1790 They are passed to a shell, which expands wildcard characters and
1791 performs redirection of I/O, and thence to your program. Your
1792 @code{SHELL} environment variable (if it exists) specifies what shell
1793 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1794 the default shell (@file{/bin/sh} on Unix).
1796 On non-Unix systems, the program is usually invoked directly by
1797 @value{GDBN}, which emulates I/O redirection via the appropriate system
1798 calls, and the wildcard characters are expanded by the startup code of
1799 the program, not by the shell.
1801 @code{run} with no arguments uses the same arguments used by the previous
1802 @code{run}, or those set by the @code{set args} command.
1807 Specify the arguments to be used the next time your program is run. If
1808 @code{set args} has no arguments, @code{run} executes your program
1809 with no arguments. Once you have run your program with arguments,
1810 using @code{set args} before the next @code{run} is the only way to run
1811 it again without arguments.
1815 Show the arguments to give your program when it is started.
1819 @section Your program's environment
1821 @cindex environment (of your program)
1822 The @dfn{environment} consists of a set of environment variables and
1823 their values. Environment variables conventionally record such things as
1824 your user name, your home directory, your terminal type, and your search
1825 path for programs to run. Usually you set up environment variables with
1826 the shell and they are inherited by all the other programs you run. When
1827 debugging, it can be useful to try running your program with a modified
1828 environment without having to start @value{GDBN} over again.
1832 @item path @var{directory}
1833 Add @var{directory} to the front of the @code{PATH} environment variable
1834 (the search path for executables) that will be passed to your program.
1835 The value of @code{PATH} used by @value{GDBN} does not change.
1836 You may specify several directory names, separated by whitespace or by a
1837 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1838 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1839 is moved to the front, so it is searched sooner.
1841 You can use the string @samp{$cwd} to refer to whatever is the current
1842 working directory at the time @value{GDBN} searches the path. If you
1843 use @samp{.} instead, it refers to the directory where you executed the
1844 @code{path} command. @value{GDBN} replaces @samp{.} in the
1845 @var{directory} argument (with the current path) before adding
1846 @var{directory} to the search path.
1847 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1848 @c document that, since repeating it would be a no-op.
1852 Display the list of search paths for executables (the @code{PATH}
1853 environment variable).
1855 @kindex show environment
1856 @item show environment @r{[}@var{varname}@r{]}
1857 Print the value of environment variable @var{varname} to be given to
1858 your program when it starts. If you do not supply @var{varname},
1859 print the names and values of all environment variables to be given to
1860 your program. You can abbreviate @code{environment} as @code{env}.
1862 @kindex set environment
1863 @item set environment @var{varname} @r{[}=@var{value}@r{]}
1864 Set environment variable @var{varname} to @var{value}. The value
1865 changes for your program only, not for @value{GDBN} itself. @var{value} may
1866 be any string; the values of environment variables are just strings, and
1867 any interpretation is supplied by your program itself. The @var{value}
1868 parameter is optional; if it is eliminated, the variable is set to a
1870 @c "any string" here does not include leading, trailing
1871 @c blanks. Gnu asks: does anyone care?
1873 For example, this command:
1880 tells the debugged program, when subsequently run, that its user is named
1881 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
1882 are not actually required.)
1884 @kindex unset environment
1885 @item unset environment @var{varname}
1886 Remove variable @var{varname} from the environment to be passed to your
1887 program. This is different from @samp{set env @var{varname} =};
1888 @code{unset environment} removes the variable from the environment,
1889 rather than assigning it an empty value.
1892 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
1894 by your @code{SHELL} environment variable if it exists (or
1895 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
1896 that runs an initialization file---such as @file{.cshrc} for C-shell, or
1897 @file{.bashrc} for BASH---any variables you set in that file affect
1898 your program. You may wish to move setting of environment variables to
1899 files that are only run when you sign on, such as @file{.login} or
1902 @node Working Directory
1903 @section Your program's working directory
1905 @cindex working directory (of your program)
1906 Each time you start your program with @code{run}, it inherits its
1907 working directory from the current working directory of @value{GDBN}.
1908 The @value{GDBN} working directory is initially whatever it inherited
1909 from its parent process (typically the shell), but you can specify a new
1910 working directory in @value{GDBN} with the @code{cd} command.
1912 The @value{GDBN} working directory also serves as a default for the commands
1913 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
1918 @item cd @var{directory}
1919 Set the @value{GDBN} working directory to @var{directory}.
1923 Print the @value{GDBN} working directory.
1927 @section Your program's input and output
1932 By default, the program you run under @value{GDBN} does input and output to
1933 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
1934 to its own terminal modes to interact with you, but it records the terminal
1935 modes your program was using and switches back to them when you continue
1936 running your program.
1939 @kindex info terminal
1941 Displays information recorded by @value{GDBN} about the terminal modes your
1945 You can redirect your program's input and/or output using shell
1946 redirection with the @code{run} command. For example,
1953 starts your program, diverting its output to the file @file{outfile}.
1956 @cindex controlling terminal
1957 Another way to specify where your program should do input and output is
1958 with the @code{tty} command. This command accepts a file name as
1959 argument, and causes this file to be the default for future @code{run}
1960 commands. It also resets the controlling terminal for the child
1961 process, for future @code{run} commands. For example,
1968 directs that processes started with subsequent @code{run} commands
1969 default to do input and output on the terminal @file{/dev/ttyb} and have
1970 that as their controlling terminal.
1972 An explicit redirection in @code{run} overrides the @code{tty} command's
1973 effect on the input/output device, but not its effect on the controlling
1976 When you use the @code{tty} command or redirect input in the @code{run}
1977 command, only the input @emph{for your program} is affected. The input
1978 for @value{GDBN} still comes from your terminal.
1981 @section Debugging an already-running process
1986 @item attach @var{process-id}
1987 This command attaches to a running process---one that was started
1988 outside @value{GDBN}. (@code{info files} shows your active
1989 targets.) The command takes as argument a process ID. The usual way to
1990 find out the process-id of a Unix process is with the @code{ps} utility,
1991 or with the @samp{jobs -l} shell command.
1993 @code{attach} does not repeat if you press @key{RET} a second time after
1994 executing the command.
1997 To use @code{attach}, your program must be running in an environment
1998 which supports processes; for example, @code{attach} does not work for
1999 programs on bare-board targets that lack an operating system. You must
2000 also have permission to send the process a signal.
2002 When you use @code{attach}, the debugger finds the program running in
2003 the process first by looking in the current working directory, then (if
2004 the program is not found) by using the source file search path
2005 (@pxref{Source Path, ,Specifying source directories}). You can also use
2006 the @code{file} command to load the program. @xref{Files, ,Commands to
2009 The first thing @value{GDBN} does after arranging to debug the specified
2010 process is to stop it. You can examine and modify an attached process
2011 with all the @value{GDBN} commands that are ordinarily available when
2012 you start processes with @code{run}. You can insert breakpoints; you
2013 can step and continue; you can modify storage. If you would rather the
2014 process continue running, you may use the @code{continue} command after
2015 attaching @value{GDBN} to the process.
2020 When you have finished debugging the attached process, you can use the
2021 @code{detach} command to release it from @value{GDBN} control. Detaching
2022 the process continues its execution. After the @code{detach} command,
2023 that process and @value{GDBN} become completely independent once more, and you
2024 are ready to @code{attach} another process or start one with @code{run}.
2025 @code{detach} does not repeat if you press @key{RET} again after
2026 executing the command.
2029 If you exit @value{GDBN} or use the @code{run} command while you have an
2030 attached process, you kill that process. By default, @value{GDBN} asks
2031 for confirmation if you try to do either of these things; you can
2032 control whether or not you need to confirm by using the @code{set
2033 confirm} command (@pxref{Messages/Warnings, ,Optional warnings and
2037 @section Killing the child process
2042 Kill the child process in which your program is running under @value{GDBN}.
2045 This command is useful if you wish to debug a core dump instead of a
2046 running process. @value{GDBN} ignores any core dump file while your program
2049 On some operating systems, a program cannot be executed outside @value{GDBN}
2050 while you have breakpoints set on it inside @value{GDBN}. You can use the
2051 @code{kill} command in this situation to permit running your program
2052 outside the debugger.
2054 The @code{kill} command is also useful if you wish to recompile and
2055 relink your program, since on many systems it is impossible to modify an
2056 executable file while it is running in a process. In this case, when you
2057 next type @code{run}, @value{GDBN} notices that the file has changed, and
2058 reads the symbol table again (while trying to preserve your current
2059 breakpoint settings).
2062 @section Debugging programs with multiple threads
2064 @cindex threads of execution
2065 @cindex multiple threads
2066 @cindex switching threads
2067 In some operating systems, such as HP-UX and Solaris, a single program
2068 may have more than one @dfn{thread} of execution. The precise semantics
2069 of threads differ from one operating system to another, but in general
2070 the threads of a single program are akin to multiple processes---except
2071 that they share one address space (that is, they can all examine and
2072 modify the same variables). On the other hand, each thread has its own
2073 registers and execution stack, and perhaps private memory.
2075 @value{GDBN} provides these facilities for debugging multi-thread
2079 @item automatic notification of new threads
2080 @item @samp{thread @var{threadno}}, a command to switch among threads
2081 @item @samp{info threads}, a command to inquire about existing threads
2082 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2083 a command to apply a command to a list of threads
2084 @item thread-specific breakpoints
2088 @emph{Warning:} These facilities are not yet available on every
2089 @value{GDBN} configuration where the operating system supports threads.
2090 If your @value{GDBN} does not support threads, these commands have no
2091 effect. For example, a system without thread support shows no output
2092 from @samp{info threads}, and always rejects the @code{thread} command,
2096 (@value{GDBP}) info threads
2097 (@value{GDBP}) thread 1
2098 Thread ID 1 not known. Use the "info threads" command to
2099 see the IDs of currently known threads.
2101 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2102 @c doesn't support threads"?
2105 @cindex focus of debugging
2106 @cindex current thread
2107 The @value{GDBN} thread debugging facility allows you to observe all
2108 threads while your program runs---but whenever @value{GDBN} takes
2109 control, one thread in particular is always the focus of debugging.
2110 This thread is called the @dfn{current thread}. Debugging commands show
2111 program information from the perspective of the current thread.
2113 @cindex @code{New} @var{systag} message
2114 @cindex thread identifier (system)
2115 @c FIXME-implementors!! It would be more helpful if the [New...] message
2116 @c included GDB's numeric thread handle, so you could just go to that
2117 @c thread without first checking `info threads'.
2118 Whenever @value{GDBN} detects a new thread in your program, it displays
2119 the target system's identification for the thread with a message in the
2120 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2121 whose form varies depending on the particular system. For example, on
2122 LynxOS, you might see
2125 [New process 35 thread 27]
2129 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2130 the @var{systag} is simply something like @samp{process 368}, with no
2133 @c FIXME!! (1) Does the [New...] message appear even for the very first
2134 @c thread of a program, or does it only appear for the
2135 @c second---i.e.@: when it becomes obvious we have a multithread
2137 @c (2) *Is* there necessarily a first thread always? Or do some
2138 @c multithread systems permit starting a program with multiple
2139 @c threads ab initio?
2141 @cindex thread number
2142 @cindex thread identifier (GDB)
2143 For debugging purposes, @value{GDBN} associates its own thread
2144 number---always a single integer---with each thread in your program.
2147 @kindex info threads
2149 Display a summary of all threads currently in your
2150 program. @value{GDBN} displays for each thread (in this order):
2153 @item the thread number assigned by @value{GDBN}
2155 @item the target system's thread identifier (@var{systag})
2157 @item the current stack frame summary for that thread
2161 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2162 indicates the current thread.
2166 @c end table here to get a little more width for example
2169 (@value{GDBP}) info threads
2170 3 process 35 thread 27 0x34e5 in sigpause ()
2171 2 process 35 thread 23 0x34e5 in sigpause ()
2172 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2178 @cindex debugging multithreaded programs (on HP-UX)
2179 @cindex thread identifier (GDB), on HP-UX
2180 For debugging purposes, @value{GDBN} associates its own thread
2181 number---a small integer assigned in thread-creation order---with each
2182 thread in your program.
2184 @cindex @code{New} @var{systag} message, on HP-UX
2185 @cindex thread identifier (system), on HP-UX
2186 @c FIXME-implementors!! It would be more helpful if the [New...] message
2187 @c included GDB's numeric thread handle, so you could just go to that
2188 @c thread without first checking `info threads'.
2189 Whenever @value{GDBN} detects a new thread in your program, it displays
2190 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2191 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2192 whose form varies depending on the particular system. For example, on
2196 [New thread 2 (system thread 26594)]
2200 when @value{GDBN} notices a new thread.
2203 @kindex info threads (HP-UX)
2205 Display a summary of all threads currently in your
2206 program. @value{GDBN} displays for each thread (in this order):
2209 @item the thread number assigned by @value{GDBN}
2211 @item the target system's thread identifier (@var{systag})
2213 @item the current stack frame summary for that thread
2217 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2218 indicates the current thread.
2222 @c end table here to get a little more width for example
2225 (@value{GDBP}) info threads
2226 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2228 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2229 from /usr/lib/libc.2
2230 1 system thread 27905 0x7b003498 in _brk () \@*
2231 from /usr/lib/libc.2
2235 @kindex thread @var{threadno}
2236 @item thread @var{threadno}
2237 Make thread number @var{threadno} the current thread. The command
2238 argument @var{threadno} is the internal @value{GDBN} thread number, as
2239 shown in the first field of the @samp{info threads} display.
2240 @value{GDBN} responds by displaying the system identifier of the thread
2241 you selected, and its current stack frame summary:
2244 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2245 (@value{GDBP}) thread 2
2246 [Switching to process 35 thread 23]
2247 0x34e5 in sigpause ()
2251 As with the @samp{[New @dots{}]} message, the form of the text after
2252 @samp{Switching to} depends on your system's conventions for identifying
2255 @item thread apply [@var{threadno}] [@var{all}] @var{args}
2256 The @code{thread apply} command allows you to apply a command to one or
2257 more threads. Specify the numbers of the threads that you want affected
2258 with the command argument @var{threadno}. @var{threadno} is the internal
2259 @value{GDBN} thread number, as shown in the first field of the @samp{info
2260 threads} display. To apply a command to all threads, use
2261 @code{thread apply all} @var{args}.
2264 @cindex automatic thread selection
2265 @cindex switching threads automatically
2266 @cindex threads, automatic switching
2267 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2268 signal, it automatically selects the thread where that breakpoint or
2269 signal happened. @value{GDBN} alerts you to the context switch with a
2270 message of the form @samp{[Switching to @var{systag}]} to identify the
2273 @xref{Thread Stops,,Stopping and starting multi-thread programs}, for
2274 more information about how @value{GDBN} behaves when you stop and start
2275 programs with multiple threads.
2277 @xref{Set Watchpoints,,Setting watchpoints}, for information about
2278 watchpoints in programs with multiple threads.
2281 @section Debugging programs with multiple processes
2283 @cindex fork, debugging programs which call
2284 @cindex multiple processes
2285 @cindex processes, multiple
2286 On most systems, @value{GDBN} has no special support for debugging
2287 programs which create additional processes using the @code{fork}
2288 function. When a program forks, @value{GDBN} will continue to debug the
2289 parent process and the child process will run unimpeded. If you have
2290 set a breakpoint in any code which the child then executes, the child
2291 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2292 will cause it to terminate.
2294 However, if you want to debug the child process there is a workaround
2295 which isn't too painful. Put a call to @code{sleep} in the code which
2296 the child process executes after the fork. It may be useful to sleep
2297 only if a certain environment variable is set, or a certain file exists,
2298 so that the delay need not occur when you don't want to run @value{GDBN}
2299 on the child. While the child is sleeping, use the @code{ps} program to
2300 get its process ID. Then tell @value{GDBN} (a new invocation of
2301 @value{GDBN} if you are also debugging the parent process) to attach to
2302 the child process (@pxref{Attach}). From that point on you can debug
2303 the child process just like any other process which you attached to.
2305 On some systems, @value{GDBN} provides support for debugging programs that
2306 create additional processes using the @code{fork} or @code{vfork} functions.
2307 Currently, the only platforms with this feature are HP-UX (11.x and later
2308 only?) and GNU/Linux (kernel version 2.5.60 and later).
2310 By default, when a program forks, @value{GDBN} will continue to debug
2311 the parent process and the child process will run unimpeded.
2313 If you want to follow the child process instead of the parent process,
2314 use the command @w{@code{set follow-fork-mode}}.
2317 @kindex set follow-fork-mode
2318 @item set follow-fork-mode @var{mode}
2319 Set the debugger response to a program call of @code{fork} or
2320 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2321 process. The @var{mode} can be:
2325 The original process is debugged after a fork. The child process runs
2326 unimpeded. This is the default.
2329 The new process is debugged after a fork. The parent process runs
2334 @item show follow-fork-mode
2335 Display the current debugger response to a @code{fork} or @code{vfork} call.
2338 If you ask to debug a child process and a @code{vfork} is followed by an
2339 @code{exec}, @value{GDBN} executes the new target up to the first
2340 breakpoint in the new target. If you have a breakpoint set on
2341 @code{main} in your original program, the breakpoint will also be set on
2342 the child process's @code{main}.
2344 When a child process is spawned by @code{vfork}, you cannot debug the
2345 child or parent until an @code{exec} call completes.
2347 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2348 call executes, the new target restarts. To restart the parent process,
2349 use the @code{file} command with the parent executable name as its
2352 You can use the @code{catch} command to make @value{GDBN} stop whenever
2353 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2354 Catchpoints, ,Setting catchpoints}.
2357 @chapter Stopping and Continuing
2359 The principal purposes of using a debugger are so that you can stop your
2360 program before it terminates; or so that, if your program runs into
2361 trouble, you can investigate and find out why.
2363 Inside @value{GDBN}, your program may stop for any of several reasons,
2364 such as a signal, a breakpoint, or reaching a new line after a
2365 @value{GDBN} command such as @code{step}. You may then examine and
2366 change variables, set new breakpoints or remove old ones, and then
2367 continue execution. Usually, the messages shown by @value{GDBN} provide
2368 ample explanation of the status of your program---but you can also
2369 explicitly request this information at any time.
2372 @kindex info program
2374 Display information about the status of your program: whether it is
2375 running or not, what process it is, and why it stopped.
2379 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2380 * Continuing and Stepping:: Resuming execution
2382 * Thread Stops:: Stopping and starting multi-thread programs
2386 @section Breakpoints, watchpoints, and catchpoints
2389 A @dfn{breakpoint} makes your program stop whenever a certain point in
2390 the program is reached. For each breakpoint, you can add conditions to
2391 control in finer detail whether your program stops. You can set
2392 breakpoints with the @code{break} command and its variants (@pxref{Set
2393 Breaks, ,Setting breakpoints}), to specify the place where your program
2394 should stop by line number, function name or exact address in the
2397 In HP-UX, SunOS 4.x, SVR4, and Alpha OSF/1 configurations, you can set
2398 breakpoints in shared libraries before the executable is run. There is
2399 a minor limitation on HP-UX systems: you must wait until the executable
2400 is run in order to set breakpoints in shared library routines that are
2401 not called directly by the program (for example, routines that are
2402 arguments in a @code{pthread_create} call).
2405 @cindex memory tracing
2406 @cindex breakpoint on memory address
2407 @cindex breakpoint on variable modification
2408 A @dfn{watchpoint} is a special breakpoint that stops your program
2409 when the value of an expression changes. You must use a different
2410 command to set watchpoints (@pxref{Set Watchpoints, ,Setting
2411 watchpoints}), but aside from that, you can manage a watchpoint like
2412 any other breakpoint: you enable, disable, and delete both breakpoints
2413 and watchpoints using the same commands.
2415 You can arrange to have values from your program displayed automatically
2416 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2420 @cindex breakpoint on events
2421 A @dfn{catchpoint} is another special breakpoint that stops your program
2422 when a certain kind of event occurs, such as the throwing of a C@t{++}
2423 exception or the loading of a library. As with watchpoints, you use a
2424 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2425 catchpoints}), but aside from that, you can manage a catchpoint like any
2426 other breakpoint. (To stop when your program receives a signal, use the
2427 @code{handle} command; see @ref{Signals, ,Signals}.)
2429 @cindex breakpoint numbers
2430 @cindex numbers for breakpoints
2431 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2432 catchpoint when you create it; these numbers are successive integers
2433 starting with one. In many of the commands for controlling various
2434 features of breakpoints you use the breakpoint number to say which
2435 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2436 @dfn{disabled}; if disabled, it has no effect on your program until you
2439 @cindex breakpoint ranges
2440 @cindex ranges of breakpoints
2441 Some @value{GDBN} commands accept a range of breakpoints on which to
2442 operate. A breakpoint range is either a single breakpoint number, like
2443 @samp{5}, or two such numbers, in increasing order, separated by a
2444 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2445 all breakpoint in that range are operated on.
2448 * Set Breaks:: Setting breakpoints
2449 * Set Watchpoints:: Setting watchpoints
2450 * Set Catchpoints:: Setting catchpoints
2451 * Delete Breaks:: Deleting breakpoints
2452 * Disabling:: Disabling breakpoints
2453 * Conditions:: Break conditions
2454 * Break Commands:: Breakpoint command lists
2455 * Breakpoint Menus:: Breakpoint menus
2456 * Error in Breakpoints:: ``Cannot insert breakpoints''
2457 * Breakpoint related warnings:: ``Breakpoint address adjusted...''
2461 @subsection Setting breakpoints
2463 @c FIXME LMB what does GDB do if no code on line of breakpt?
2464 @c consider in particular declaration with/without initialization.
2466 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2469 @kindex b @r{(@code{break})}
2470 @vindex $bpnum@r{, convenience variable}
2471 @cindex latest breakpoint
2472 Breakpoints are set with the @code{break} command (abbreviated
2473 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2474 number of the breakpoint you've set most recently; see @ref{Convenience
2475 Vars,, Convenience variables}, for a discussion of what you can do with
2476 convenience variables.
2478 You have several ways to say where the breakpoint should go.
2481 @item break @var{function}
2482 Set a breakpoint at entry to function @var{function}.
2483 When using source languages that permit overloading of symbols, such as
2484 C@t{++}, @var{function} may refer to more than one possible place to break.
2485 @xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
2487 @item break +@var{offset}
2488 @itemx break -@var{offset}
2489 Set a breakpoint some number of lines forward or back from the position
2490 at which execution stopped in the currently selected @dfn{stack frame}.
2491 (@xref{Frames, ,Frames}, for a description of stack frames.)
2493 @item break @var{linenum}
2494 Set a breakpoint at line @var{linenum} in the current source file.
2495 The current source file is the last file whose source text was printed.
2496 The breakpoint will stop your program just before it executes any of the
2499 @item break @var{filename}:@var{linenum}
2500 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2502 @item break @var{filename}:@var{function}
2503 Set a breakpoint at entry to function @var{function} found in file
2504 @var{filename}. Specifying a file name as well as a function name is
2505 superfluous except when multiple files contain similarly named
2508 @item break *@var{address}
2509 Set a breakpoint at address @var{address}. You can use this to set
2510 breakpoints in parts of your program which do not have debugging
2511 information or source files.
2514 When called without any arguments, @code{break} sets a breakpoint at
2515 the next instruction to be executed in the selected stack frame
2516 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2517 innermost, this makes your program stop as soon as control
2518 returns to that frame. This is similar to the effect of a
2519 @code{finish} command in the frame inside the selected frame---except
2520 that @code{finish} does not leave an active breakpoint. If you use
2521 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2522 the next time it reaches the current location; this may be useful
2525 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2526 least one instruction has been executed. If it did not do this, you
2527 would be unable to proceed past a breakpoint without first disabling the
2528 breakpoint. This rule applies whether or not the breakpoint already
2529 existed when your program stopped.
2531 @item break @dots{} if @var{cond}
2532 Set a breakpoint with condition @var{cond}; evaluate the expression
2533 @var{cond} each time the breakpoint is reached, and stop only if the
2534 value is nonzero---that is, if @var{cond} evaluates as true.
2535 @samp{@dots{}} stands for one of the possible arguments described
2536 above (or no argument) specifying where to break. @xref{Conditions,
2537 ,Break conditions}, for more information on breakpoint conditions.
2540 @item tbreak @var{args}
2541 Set a breakpoint enabled only for one stop. @var{args} are the
2542 same as for the @code{break} command, and the breakpoint is set in the same
2543 way, but the breakpoint is automatically deleted after the first time your
2544 program stops there. @xref{Disabling, ,Disabling breakpoints}.
2547 @item hbreak @var{args}
2548 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2549 @code{break} command and the breakpoint is set in the same way, but the
2550 breakpoint requires hardware support and some target hardware may not
2551 have this support. The main purpose of this is EPROM/ROM code
2552 debugging, so you can set a breakpoint at an instruction without
2553 changing the instruction. This can be used with the new trap-generation
2554 provided by SPARClite DSU and some x86-based targets. These targets
2555 will generate traps when a program accesses some data or instruction
2556 address that is assigned to the debug registers. However the hardware
2557 breakpoint registers can take a limited number of breakpoints. For
2558 example, on the DSU, only two data breakpoints can be set at a time, and
2559 @value{GDBN} will reject this command if more than two are used. Delete
2560 or disable unused hardware breakpoints before setting new ones
2561 (@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}.
2562 @xref{set remote hardware-breakpoint-limit}.
2566 @item thbreak @var{args}
2567 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2568 are the same as for the @code{hbreak} command and the breakpoint is set in
2569 the same way. However, like the @code{tbreak} command,
2570 the breakpoint is automatically deleted after the
2571 first time your program stops there. Also, like the @code{hbreak}
2572 command, the breakpoint requires hardware support and some target hardware
2573 may not have this support. @xref{Disabling, ,Disabling breakpoints}.
2574 See also @ref{Conditions, ,Break conditions}.
2577 @cindex regular expression
2578 @item rbreak @var{regex}
2579 Set breakpoints on all functions matching the regular expression
2580 @var{regex}. This command sets an unconditional breakpoint on all
2581 matches, printing a list of all breakpoints it set. Once these
2582 breakpoints are set, they are treated just like the breakpoints set with
2583 the @code{break} command. You can delete them, disable them, or make
2584 them conditional the same way as any other breakpoint.
2586 The syntax of the regular expression is the standard one used with tools
2587 like @file{grep}. Note that this is different from the syntax used by
2588 shells, so for instance @code{foo*} matches all functions that include
2589 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2590 @code{.*} leading and trailing the regular expression you supply, so to
2591 match only functions that begin with @code{foo}, use @code{^foo}.
2593 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2594 breakpoints on overloaded functions that are not members of any special
2597 @kindex info breakpoints
2598 @cindex @code{$_} and @code{info breakpoints}
2599 @item info breakpoints @r{[}@var{n}@r{]}
2600 @itemx info break @r{[}@var{n}@r{]}
2601 @itemx info watchpoints @r{[}@var{n}@r{]}
2602 Print a table of all breakpoints, watchpoints, and catchpoints set and
2603 not deleted, with the following columns for each breakpoint:
2606 @item Breakpoint Numbers
2608 Breakpoint, watchpoint, or catchpoint.
2610 Whether the breakpoint is marked to be disabled or deleted when hit.
2611 @item Enabled or Disabled
2612 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2613 that are not enabled.
2615 Where the breakpoint is in your program, as a memory address. If the
2616 breakpoint is pending (see below for details) on a future load of a shared library, the address
2617 will be listed as @samp{<PENDING>}.
2619 Where the breakpoint is in the source for your program, as a file and
2620 line number. For a pending breakpoint, the original string passed to
2621 the breakpoint command will be listed as it cannot be resolved until
2622 the appropriate shared library is loaded in the future.
2626 If a breakpoint is conditional, @code{info break} shows the condition on
2627 the line following the affected breakpoint; breakpoint commands, if any,
2628 are listed after that. A pending breakpoint is allowed to have a condition
2629 specified for it. The condition is not parsed for validity until a shared
2630 library is loaded that allows the pending breakpoint to resolve to a
2634 @code{info break} with a breakpoint
2635 number @var{n} as argument lists only that breakpoint. The
2636 convenience variable @code{$_} and the default examining-address for
2637 the @code{x} command are set to the address of the last breakpoint
2638 listed (@pxref{Memory, ,Examining memory}).
2641 @code{info break} displays a count of the number of times the breakpoint
2642 has been hit. This is especially useful in conjunction with the
2643 @code{ignore} command. You can ignore a large number of breakpoint
2644 hits, look at the breakpoint info to see how many times the breakpoint
2645 was hit, and then run again, ignoring one less than that number. This
2646 will get you quickly to the last hit of that breakpoint.
2649 @value{GDBN} allows you to set any number of breakpoints at the same place in
2650 your program. There is nothing silly or meaningless about this. When
2651 the breakpoints are conditional, this is even useful
2652 (@pxref{Conditions, ,Break conditions}).
2654 @cindex pending breakpoints
2655 If a specified breakpoint location cannot be found, it may be due to the fact
2656 that the location is in a shared library that is yet to be loaded. In such
2657 a case, you may want @value{GDBN} to create a special breakpoint (known as
2658 a @dfn{pending breakpoint}) that
2659 attempts to resolve itself in the future when an appropriate shared library
2662 Pending breakpoints are useful to set at the start of your
2663 @value{GDBN} session for locations that you know will be dynamically loaded
2664 later by the program being debugged. When shared libraries are loaded,
2665 a check is made to see if the load resolves any pending breakpoint locations.
2666 If a pending breakpoint location gets resolved,
2667 a regular breakpoint is created and the original pending breakpoint is removed.
2669 @value{GDBN} provides some additional commands for controlling pending
2672 @kindex set breakpoint pending
2673 @kindex show breakpoint pending
2675 @item set breakpoint pending auto
2676 This is the default behavior. When @value{GDBN} cannot find the breakpoint
2677 location, it queries you whether a pending breakpoint should be created.
2679 @item set breakpoint pending on
2680 This indicates that an unrecognized breakpoint location should automatically
2681 result in a pending breakpoint being created.
2683 @item set breakpoint pending off
2684 This indicates that pending breakpoints are not to be created. Any
2685 unrecognized breakpoint location results in an error. This setting does
2686 not affect any pending breakpoints previously created.
2688 @item show breakpoint pending
2689 Show the current behavior setting for creating pending breakpoints.
2692 @cindex operations allowed on pending breakpoints
2693 Normal breakpoint operations apply to pending breakpoints as well. You may
2694 specify a condition for a pending breakpoint and/or commands to run when the
2695 breakpoint is reached. You can also enable or disable
2696 the pending breakpoint. When you specify a condition for a pending breakpoint,
2697 the parsing of the condition will be deferred until the point where the
2698 pending breakpoint location is resolved. Disabling a pending breakpoint
2699 tells @value{GDBN} to not attempt to resolve the breakpoint on any subsequent
2700 shared library load. When a pending breakpoint is re-enabled,
2701 @value{GDBN} checks to see if the location is already resolved.
2702 This is done because any number of shared library loads could have
2703 occurred since the time the breakpoint was disabled and one or more
2704 of these loads could resolve the location.
2706 @cindex negative breakpoint numbers
2707 @cindex internal @value{GDBN} breakpoints
2708 @value{GDBN} itself sometimes sets breakpoints in your program for
2709 special purposes, such as proper handling of @code{longjmp} (in C
2710 programs). These internal breakpoints are assigned negative numbers,
2711 starting with @code{-1}; @samp{info breakpoints} does not display them.
2712 You can see these breakpoints with the @value{GDBN} maintenance command
2713 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
2716 @node Set Watchpoints
2717 @subsection Setting watchpoints
2719 @cindex setting watchpoints
2720 @cindex software watchpoints
2721 @cindex hardware watchpoints
2722 You can use a watchpoint to stop execution whenever the value of an
2723 expression changes, without having to predict a particular place where
2726 Depending on your system, watchpoints may be implemented in software or
2727 hardware. @value{GDBN} does software watchpointing by single-stepping your
2728 program and testing the variable's value each time, which is hundreds of
2729 times slower than normal execution. (But this may still be worth it, to
2730 catch errors where you have no clue what part of your program is the
2733 On some systems, such as HP-UX, @sc{gnu}/Linux and some other x86-based targets,
2734 @value{GDBN} includes support for
2735 hardware watchpoints, which do not slow down the running of your
2740 @item watch @var{expr}
2741 Set a watchpoint for an expression. @value{GDBN} will break when @var{expr}
2742 is written into by the program and its value changes.
2745 @item rwatch @var{expr}
2746 Set a watchpoint that will break when watch @var{expr} is read by the program.
2749 @item awatch @var{expr}
2750 Set a watchpoint that will break when @var{expr} is either read or written into
2753 @kindex info watchpoints
2754 @item info watchpoints
2755 This command prints a list of watchpoints, breakpoints, and catchpoints;
2756 it is the same as @code{info break}.
2759 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
2760 watchpoints execute very quickly, and the debugger reports a change in
2761 value at the exact instruction where the change occurs. If @value{GDBN}
2762 cannot set a hardware watchpoint, it sets a software watchpoint, which
2763 executes more slowly and reports the change in value at the next
2764 statement, not the instruction, after the change occurs.
2766 When you issue the @code{watch} command, @value{GDBN} reports
2769 Hardware watchpoint @var{num}: @var{expr}
2773 if it was able to set a hardware watchpoint.
2775 Currently, the @code{awatch} and @code{rwatch} commands can only set
2776 hardware watchpoints, because accesses to data that don't change the
2777 value of the watched expression cannot be detected without examining
2778 every instruction as it is being executed, and @value{GDBN} does not do
2779 that currently. If @value{GDBN} finds that it is unable to set a
2780 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
2781 will print a message like this:
2784 Expression cannot be implemented with read/access watchpoint.
2787 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
2788 data type of the watched expression is wider than what a hardware
2789 watchpoint on the target machine can handle. For example, some systems
2790 can only watch regions that are up to 4 bytes wide; on such systems you
2791 cannot set hardware watchpoints for an expression that yields a
2792 double-precision floating-point number (which is typically 8 bytes
2793 wide). As a work-around, it might be possible to break the large region
2794 into a series of smaller ones and watch them with separate watchpoints.
2796 If you set too many hardware watchpoints, @value{GDBN} might be unable
2797 to insert all of them when you resume the execution of your program.
2798 Since the precise number of active watchpoints is unknown until such
2799 time as the program is about to be resumed, @value{GDBN} might not be
2800 able to warn you about this when you set the watchpoints, and the
2801 warning will be printed only when the program is resumed:
2804 Hardware watchpoint @var{num}: Could not insert watchpoint
2808 If this happens, delete or disable some of the watchpoints.
2810 The SPARClite DSU will generate traps when a program accesses some data
2811 or instruction address that is assigned to the debug registers. For the
2812 data addresses, DSU facilitates the @code{watch} command. However the
2813 hardware breakpoint registers can only take two data watchpoints, and
2814 both watchpoints must be the same kind. For example, you can set two
2815 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
2816 @strong{or} two with @code{awatch} commands, but you cannot set one
2817 watchpoint with one command and the other with a different command.
2818 @value{GDBN} will reject the command if you try to mix watchpoints.
2819 Delete or disable unused watchpoint commands before setting new ones.
2821 If you call a function interactively using @code{print} or @code{call},
2822 any watchpoints you have set will be inactive until @value{GDBN} reaches another
2823 kind of breakpoint or the call completes.
2825 @value{GDBN} automatically deletes watchpoints that watch local
2826 (automatic) variables, or expressions that involve such variables, when
2827 they go out of scope, that is, when the execution leaves the block in
2828 which these variables were defined. In particular, when the program
2829 being debugged terminates, @emph{all} local variables go out of scope,
2830 and so only watchpoints that watch global variables remain set. If you
2831 rerun the program, you will need to set all such watchpoints again. One
2832 way of doing that would be to set a code breakpoint at the entry to the
2833 @code{main} function and when it breaks, set all the watchpoints.
2836 @cindex watchpoints and threads
2837 @cindex threads and watchpoints
2838 @emph{Warning:} In multi-thread programs, watchpoints have only limited
2839 usefulness. With the current watchpoint implementation, @value{GDBN}
2840 can only watch the value of an expression @emph{in a single thread}. If
2841 you are confident that the expression can only change due to the current
2842 thread's activity (and if you are also confident that no other thread
2843 can become current), then you can use watchpoints as usual. However,
2844 @value{GDBN} may not notice when a non-current thread's activity changes
2847 @c FIXME: this is almost identical to the previous paragraph.
2848 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
2849 have only limited usefulness. If @value{GDBN} creates a software
2850 watchpoint, it can only watch the value of an expression @emph{in a
2851 single thread}. If you are confident that the expression can only
2852 change due to the current thread's activity (and if you are also
2853 confident that no other thread can become current), then you can use
2854 software watchpoints as usual. However, @value{GDBN} may not notice
2855 when a non-current thread's activity changes the expression. (Hardware
2856 watchpoints, in contrast, watch an expression in all threads.)
2859 @xref{set remote hardware-watchpoint-limit}.
2861 @node Set Catchpoints
2862 @subsection Setting catchpoints
2863 @cindex catchpoints, setting
2864 @cindex exception handlers
2865 @cindex event handling
2867 You can use @dfn{catchpoints} to cause the debugger to stop for certain
2868 kinds of program events, such as C@t{++} exceptions or the loading of a
2869 shared library. Use the @code{catch} command to set a catchpoint.
2873 @item catch @var{event}
2874 Stop when @var{event} occurs. @var{event} can be any of the following:
2877 @cindex stop on C@t{++} exceptions
2878 The throwing of a C@t{++} exception.
2881 The catching of a C@t{++} exception.
2884 @cindex break on fork/exec
2885 A call to @code{exec}. This is currently only available for HP-UX.
2888 A call to @code{fork}. This is currently only available for HP-UX.
2891 A call to @code{vfork}. This is currently only available for HP-UX.
2894 @itemx load @var{libname}
2895 @cindex break on load/unload of shared library
2896 The dynamic loading of any shared library, or the loading of the library
2897 @var{libname}. This is currently only available for HP-UX.
2900 @itemx unload @var{libname}
2901 The unloading of any dynamically loaded shared library, or the unloading
2902 of the library @var{libname}. This is currently only available for HP-UX.
2905 @item tcatch @var{event}
2906 Set a catchpoint that is enabled only for one stop. The catchpoint is
2907 automatically deleted after the first time the event is caught.
2911 Use the @code{info break} command to list the current catchpoints.
2913 There are currently some limitations to C@t{++} exception handling
2914 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
2918 If you call a function interactively, @value{GDBN} normally returns
2919 control to you when the function has finished executing. If the call
2920 raises an exception, however, the call may bypass the mechanism that
2921 returns control to you and cause your program either to abort or to
2922 simply continue running until it hits a breakpoint, catches a signal
2923 that @value{GDBN} is listening for, or exits. This is the case even if
2924 you set a catchpoint for the exception; catchpoints on exceptions are
2925 disabled within interactive calls.
2928 You cannot raise an exception interactively.
2931 You cannot install an exception handler interactively.
2934 @cindex raise exceptions
2935 Sometimes @code{catch} is not the best way to debug exception handling:
2936 if you need to know exactly where an exception is raised, it is better to
2937 stop @emph{before} the exception handler is called, since that way you
2938 can see the stack before any unwinding takes place. If you set a
2939 breakpoint in an exception handler instead, it may not be easy to find
2940 out where the exception was raised.
2942 To stop just before an exception handler is called, you need some
2943 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
2944 raised by calling a library function named @code{__raise_exception}
2945 which has the following ANSI C interface:
2948 /* @var{addr} is where the exception identifier is stored.
2949 @var{id} is the exception identifier. */
2950 void __raise_exception (void **addr, void *id);
2954 To make the debugger catch all exceptions before any stack
2955 unwinding takes place, set a breakpoint on @code{__raise_exception}
2956 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
2958 With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
2959 that depends on the value of @var{id}, you can stop your program when
2960 a specific exception is raised. You can use multiple conditional
2961 breakpoints to stop your program when any of a number of exceptions are
2966 @subsection Deleting breakpoints
2968 @cindex clearing breakpoints, watchpoints, catchpoints
2969 @cindex deleting breakpoints, watchpoints, catchpoints
2970 It is often necessary to eliminate a breakpoint, watchpoint, or
2971 catchpoint once it has done its job and you no longer want your program
2972 to stop there. This is called @dfn{deleting} the breakpoint. A
2973 breakpoint that has been deleted no longer exists; it is forgotten.
2975 With the @code{clear} command you can delete breakpoints according to
2976 where they are in your program. With the @code{delete} command you can
2977 delete individual breakpoints, watchpoints, or catchpoints by specifying
2978 their breakpoint numbers.
2980 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
2981 automatically ignores breakpoints on the first instruction to be executed
2982 when you continue execution without changing the execution address.
2987 Delete any breakpoints at the next instruction to be executed in the
2988 selected stack frame (@pxref{Selection, ,Selecting a frame}). When
2989 the innermost frame is selected, this is a good way to delete a
2990 breakpoint where your program just stopped.
2992 @item clear @var{function}
2993 @itemx clear @var{filename}:@var{function}
2994 Delete any breakpoints set at entry to the function @var{function}.
2996 @item clear @var{linenum}
2997 @itemx clear @var{filename}:@var{linenum}
2998 Delete any breakpoints set at or within the code of the specified line.
3000 @cindex delete breakpoints
3002 @kindex d @r{(@code{delete})}
3003 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3004 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3005 ranges specified as arguments. If no argument is specified, delete all
3006 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3007 confirm off}). You can abbreviate this command as @code{d}.
3011 @subsection Disabling breakpoints
3013 @cindex enable/disable a breakpoint
3014 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3015 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3016 it had been deleted, but remembers the information on the breakpoint so
3017 that you can @dfn{enable} it again later.
3019 You disable and enable breakpoints, watchpoints, and catchpoints with
3020 the @code{enable} and @code{disable} commands, optionally specifying one
3021 or more breakpoint numbers as arguments. Use @code{info break} or
3022 @code{info watch} to print a list of breakpoints, watchpoints, and
3023 catchpoints if you do not know which numbers to use.
3025 A breakpoint, watchpoint, or catchpoint can have any of four different
3026 states of enablement:
3030 Enabled. The breakpoint stops your program. A breakpoint set
3031 with the @code{break} command starts out in this state.
3033 Disabled. The breakpoint has no effect on your program.
3035 Enabled once. The breakpoint stops your program, but then becomes
3038 Enabled for deletion. The breakpoint stops your program, but
3039 immediately after it does so it is deleted permanently. A breakpoint
3040 set with the @code{tbreak} command starts out in this state.
3043 You can use the following commands to enable or disable breakpoints,
3044 watchpoints, and catchpoints:
3048 @kindex dis @r{(@code{disable})}
3049 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3050 Disable the specified breakpoints---or all breakpoints, if none are
3051 listed. A disabled breakpoint has no effect but is not forgotten. All
3052 options such as ignore-counts, conditions and commands are remembered in
3053 case the breakpoint is enabled again later. You may abbreviate
3054 @code{disable} as @code{dis}.
3057 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3058 Enable the specified breakpoints (or all defined breakpoints). They
3059 become effective once again in stopping your program.
3061 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3062 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3063 of these breakpoints immediately after stopping your program.
3065 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3066 Enable the specified breakpoints to work once, then die. @value{GDBN}
3067 deletes any of these breakpoints as soon as your program stops there.
3070 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3071 @c confusing: tbreak is also initially enabled.
3072 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3073 ,Setting breakpoints}), breakpoints that you set are initially enabled;
3074 subsequently, they become disabled or enabled only when you use one of
3075 the commands above. (The command @code{until} can set and delete a
3076 breakpoint of its own, but it does not change the state of your other
3077 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3081 @subsection Break conditions
3082 @cindex conditional breakpoints
3083 @cindex breakpoint conditions
3085 @c FIXME what is scope of break condition expr? Context where wanted?
3086 @c in particular for a watchpoint?
3087 The simplest sort of breakpoint breaks every time your program reaches a
3088 specified place. You can also specify a @dfn{condition} for a
3089 breakpoint. A condition is just a Boolean expression in your
3090 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3091 a condition evaluates the expression each time your program reaches it,
3092 and your program stops only if the condition is @emph{true}.
3094 This is the converse of using assertions for program validation; in that
3095 situation, you want to stop when the assertion is violated---that is,
3096 when the condition is false. In C, if you want to test an assertion expressed
3097 by the condition @var{assert}, you should set the condition
3098 @samp{! @var{assert}} on the appropriate breakpoint.
3100 Conditions are also accepted for watchpoints; you may not need them,
3101 since a watchpoint is inspecting the value of an expression anyhow---but
3102 it might be simpler, say, to just set a watchpoint on a variable name,
3103 and specify a condition that tests whether the new value is an interesting
3106 Break conditions can have side effects, and may even call functions in
3107 your program. This can be useful, for example, to activate functions
3108 that log program progress, or to use your own print functions to
3109 format special data structures. The effects are completely predictable
3110 unless there is another enabled breakpoint at the same address. (In
3111 that case, @value{GDBN} might see the other breakpoint first and stop your
3112 program without checking the condition of this one.) Note that
3113 breakpoint commands are usually more convenient and flexible than break
3115 purpose of performing side effects when a breakpoint is reached
3116 (@pxref{Break Commands, ,Breakpoint command lists}).
3118 Break conditions can be specified when a breakpoint is set, by using
3119 @samp{if} in the arguments to the @code{break} command. @xref{Set
3120 Breaks, ,Setting breakpoints}. They can also be changed at any time
3121 with the @code{condition} command.
3123 You can also use the @code{if} keyword with the @code{watch} command.
3124 The @code{catch} command does not recognize the @code{if} keyword;
3125 @code{condition} is the only way to impose a further condition on a
3130 @item condition @var{bnum} @var{expression}
3131 Specify @var{expression} as the break condition for breakpoint,
3132 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3133 breakpoint @var{bnum} stops your program only if the value of
3134 @var{expression} is true (nonzero, in C). When you use
3135 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3136 syntactic correctness, and to determine whether symbols in it have
3137 referents in the context of your breakpoint. If @var{expression} uses
3138 symbols not referenced in the context of the breakpoint, @value{GDBN}
3139 prints an error message:
3142 No symbol "foo" in current context.
3147 not actually evaluate @var{expression} at the time the @code{condition}
3148 command (or a command that sets a breakpoint with a condition, like
3149 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3151 @item condition @var{bnum}
3152 Remove the condition from breakpoint number @var{bnum}. It becomes
3153 an ordinary unconditional breakpoint.
3156 @cindex ignore count (of breakpoint)
3157 A special case of a breakpoint condition is to stop only when the
3158 breakpoint has been reached a certain number of times. This is so
3159 useful that there is a special way to do it, using the @dfn{ignore
3160 count} of the breakpoint. Every breakpoint has an ignore count, which
3161 is an integer. Most of the time, the ignore count is zero, and
3162 therefore has no effect. But if your program reaches a breakpoint whose
3163 ignore count is positive, then instead of stopping, it just decrements
3164 the ignore count by one and continues. As a result, if the ignore count
3165 value is @var{n}, the breakpoint does not stop the next @var{n} times
3166 your program reaches it.
3170 @item ignore @var{bnum} @var{count}
3171 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3172 The next @var{count} times the breakpoint is reached, your program's
3173 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3176 To make the breakpoint stop the next time it is reached, specify
3179 When you use @code{continue} to resume execution of your program from a
3180 breakpoint, you can specify an ignore count directly as an argument to
3181 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3182 Stepping,,Continuing and stepping}.
3184 If a breakpoint has a positive ignore count and a condition, the
3185 condition is not checked. Once the ignore count reaches zero,
3186 @value{GDBN} resumes checking the condition.
3188 You could achieve the effect of the ignore count with a condition such
3189 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3190 is decremented each time. @xref{Convenience Vars, ,Convenience
3194 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3197 @node Break Commands
3198 @subsection Breakpoint command lists
3200 @cindex breakpoint commands
3201 You can give any breakpoint (or watchpoint or catchpoint) a series of
3202 commands to execute when your program stops due to that breakpoint. For
3203 example, you might want to print the values of certain expressions, or
3204 enable other breakpoints.
3209 @item commands @r{[}@var{bnum}@r{]}
3210 @itemx @dots{} @var{command-list} @dots{}
3212 Specify a list of commands for breakpoint number @var{bnum}. The commands
3213 themselves appear on the following lines. Type a line containing just
3214 @code{end} to terminate the commands.
3216 To remove all commands from a breakpoint, type @code{commands} and
3217 follow it immediately with @code{end}; that is, give no commands.
3219 With no @var{bnum} argument, @code{commands} refers to the last
3220 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3221 recently encountered).
3224 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3225 disabled within a @var{command-list}.
3227 You can use breakpoint commands to start your program up again. Simply
3228 use the @code{continue} command, or @code{step}, or any other command
3229 that resumes execution.
3231 Any other commands in the command list, after a command that resumes
3232 execution, are ignored. This is because any time you resume execution
3233 (even with a simple @code{next} or @code{step}), you may encounter
3234 another breakpoint---which could have its own command list, leading to
3235 ambiguities about which list to execute.
3238 If the first command you specify in a command list is @code{silent}, the
3239 usual message about stopping at a breakpoint is not printed. This may
3240 be desirable for breakpoints that are to print a specific message and
3241 then continue. If none of the remaining commands print anything, you
3242 see no sign that the breakpoint was reached. @code{silent} is
3243 meaningful only at the beginning of a breakpoint command list.
3245 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3246 print precisely controlled output, and are often useful in silent
3247 breakpoints. @xref{Output, ,Commands for controlled output}.
3249 For example, here is how you could use breakpoint commands to print the
3250 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3256 printf "x is %d\n",x
3261 One application for breakpoint commands is to compensate for one bug so
3262 you can test for another. Put a breakpoint just after the erroneous line
3263 of code, give it a condition to detect the case in which something
3264 erroneous has been done, and give it commands to assign correct values
3265 to any variables that need them. End with the @code{continue} command
3266 so that your program does not stop, and start with the @code{silent}
3267 command so that no output is produced. Here is an example:
3278 @node Breakpoint Menus
3279 @subsection Breakpoint menus
3281 @cindex symbol overloading
3283 Some programming languages (notably C@t{++} and Objective-C) permit a
3284 single function name
3285 to be defined several times, for application in different contexts.
3286 This is called @dfn{overloading}. When a function name is overloaded,
3287 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3288 a breakpoint. If you realize this is a problem, you can use
3289 something like @samp{break @var{function}(@var{types})} to specify which
3290 particular version of the function you want. Otherwise, @value{GDBN} offers
3291 you a menu of numbered choices for different possible breakpoints, and
3292 waits for your selection with the prompt @samp{>}. The first two
3293 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3294 sets a breakpoint at each definition of @var{function}, and typing
3295 @kbd{0} aborts the @code{break} command without setting any new
3298 For example, the following session excerpt shows an attempt to set a
3299 breakpoint at the overloaded symbol @code{String::after}.
3300 We choose three particular definitions of that function name:
3302 @c FIXME! This is likely to change to show arg type lists, at least
3305 (@value{GDBP}) b String::after
3308 [2] file:String.cc; line number:867
3309 [3] file:String.cc; line number:860
3310 [4] file:String.cc; line number:875
3311 [5] file:String.cc; line number:853
3312 [6] file:String.cc; line number:846
3313 [7] file:String.cc; line number:735
3315 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3316 Breakpoint 2 at 0xb344: file String.cc, line 875.
3317 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3318 Multiple breakpoints were set.
3319 Use the "delete" command to delete unwanted
3325 @c @ifclear BARETARGET
3326 @node Error in Breakpoints
3327 @subsection ``Cannot insert breakpoints''
3329 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3331 Under some operating systems, breakpoints cannot be used in a program if
3332 any other process is running that program. In this situation,
3333 attempting to run or continue a program with a breakpoint causes
3334 @value{GDBN} to print an error message:
3337 Cannot insert breakpoints.
3338 The same program may be running in another process.
3341 When this happens, you have three ways to proceed:
3345 Remove or disable the breakpoints, then continue.
3348 Suspend @value{GDBN}, and copy the file containing your program to a new
3349 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3350 that @value{GDBN} should run your program under that name.
3351 Then start your program again.
3354 Relink your program so that the text segment is nonsharable, using the
3355 linker option @samp{-N}. The operating system limitation may not apply
3356 to nonsharable executables.
3360 A similar message can be printed if you request too many active
3361 hardware-assisted breakpoints and watchpoints:
3363 @c FIXME: the precise wording of this message may change; the relevant
3364 @c source change is not committed yet (Sep 3, 1999).
3366 Stopped; cannot insert breakpoints.
3367 You may have requested too many hardware breakpoints and watchpoints.
3371 This message is printed when you attempt to resume the program, since
3372 only then @value{GDBN} knows exactly how many hardware breakpoints and
3373 watchpoints it needs to insert.
3375 When this message is printed, you need to disable or remove some of the
3376 hardware-assisted breakpoints and watchpoints, and then continue.
3378 @node Breakpoint related warnings
3379 @subsection ``Breakpoint address adjusted...''
3380 @cindex breakpoint address adjusted
3382 Some processor architectures place constraints on the addresses at
3383 which breakpoints may be placed. For architectures thus constrained,
3384 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3385 with the constraints dictated by the architecture.
3387 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3388 a VLIW architecture in which a number of RISC-like instructions may be
3389 bundled together for parallel execution. The FR-V architecture
3390 constrains the location of a breakpoint instruction within such a
3391 bundle to the instruction with the lowest address. @value{GDBN}
3392 honors this constraint by adjusting a breakpoint's address to the
3393 first in the bundle.
3395 It is not uncommon for optimized code to have bundles which contain
3396 instructions from different source statements, thus it may happen that
3397 a breakpoint's address will be adjusted from one source statement to
3398 another. Since this adjustment may significantly alter @value{GDBN}'s
3399 breakpoint related behavior from what the user expects, a warning is
3400 printed when the breakpoint is first set and also when the breakpoint
3403 A warning like the one below is printed when setting a breakpoint
3404 that's been subject to address adjustment:
3407 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3410 Such warnings are printed both for user settable and @value{GDBN}'s
3411 internal breakpoints. If you see one of these warnings, you should
3412 verify that a breakpoint set at the adjusted address will have the
3413 desired affect. If not, the breakpoint in question may be removed and
3414 other breakpoints may be set which will have the desired behavior.
3415 E.g., it may be sufficient to place the breakpoint at a later
3416 instruction. A conditional breakpoint may also be useful in some
3417 cases to prevent the breakpoint from triggering too often.
3419 @value{GDBN} will also issue a warning when stopping at one of these
3420 adjusted breakpoints:
3423 warning: Breakpoint 1 address previously adjusted from 0x00010414
3427 When this warning is encountered, it may be too late to take remedial
3428 action except in cases where the breakpoint is hit earlier or more
3429 frequently than expected.
3431 @node Continuing and Stepping
3432 @section Continuing and stepping
3436 @cindex resuming execution
3437 @dfn{Continuing} means resuming program execution until your program
3438 completes normally. In contrast, @dfn{stepping} means executing just
3439 one more ``step'' of your program, where ``step'' may mean either one
3440 line of source code, or one machine instruction (depending on what
3441 particular command you use). Either when continuing or when stepping,
3442 your program may stop even sooner, due to a breakpoint or a signal. (If
3443 it stops due to a signal, you may want to use @code{handle}, or use
3444 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3448 @kindex c @r{(@code{continue})}
3449 @kindex fg @r{(resume foreground execution)}
3450 @item continue @r{[}@var{ignore-count}@r{]}
3451 @itemx c @r{[}@var{ignore-count}@r{]}
3452 @itemx fg @r{[}@var{ignore-count}@r{]}
3453 Resume program execution, at the address where your program last stopped;
3454 any breakpoints set at that address are bypassed. The optional argument
3455 @var{ignore-count} allows you to specify a further number of times to
3456 ignore a breakpoint at this location; its effect is like that of
3457 @code{ignore} (@pxref{Conditions, ,Break conditions}).
3459 The argument @var{ignore-count} is meaningful only when your program
3460 stopped due to a breakpoint. At other times, the argument to
3461 @code{continue} is ignored.
3463 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3464 debugged program is deemed to be the foreground program) are provided
3465 purely for convenience, and have exactly the same behavior as
3469 To resume execution at a different place, you can use @code{return}
3470 (@pxref{Returning, ,Returning from a function}) to go back to the
3471 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3472 different address}) to go to an arbitrary location in your program.
3474 A typical technique for using stepping is to set a breakpoint
3475 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the
3476 beginning of the function or the section of your program where a problem
3477 is believed to lie, run your program until it stops at that breakpoint,
3478 and then step through the suspect area, examining the variables that are
3479 interesting, until you see the problem happen.
3483 @kindex s @r{(@code{step})}
3485 Continue running your program until control reaches a different source
3486 line, then stop it and return control to @value{GDBN}. This command is
3487 abbreviated @code{s}.
3490 @c "without debugging information" is imprecise; actually "without line
3491 @c numbers in the debugging information". (gcc -g1 has debugging info but
3492 @c not line numbers). But it seems complex to try to make that
3493 @c distinction here.
3494 @emph{Warning:} If you use the @code{step} command while control is
3495 within a function that was compiled without debugging information,
3496 execution proceeds until control reaches a function that does have
3497 debugging information. Likewise, it will not step into a function which
3498 is compiled without debugging information. To step through functions
3499 without debugging information, use the @code{stepi} command, described
3503 The @code{step} command only stops at the first instruction of a source
3504 line. This prevents the multiple stops that could otherwise occur in
3505 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3506 to stop if a function that has debugging information is called within
3507 the line. In other words, @code{step} @emph{steps inside} any functions
3508 called within the line.
3510 Also, the @code{step} command only enters a function if there is line
3511 number information for the function. Otherwise it acts like the
3512 @code{next} command. This avoids problems when using @code{cc -gl}
3513 on MIPS machines. Previously, @code{step} entered subroutines if there
3514 was any debugging information about the routine.
3516 @item step @var{count}
3517 Continue running as in @code{step}, but do so @var{count} times. If a
3518 breakpoint is reached, or a signal not related to stepping occurs before
3519 @var{count} steps, stepping stops right away.
3522 @kindex n @r{(@code{next})}
3523 @item next @r{[}@var{count}@r{]}
3524 Continue to the next source line in the current (innermost) stack frame.
3525 This is similar to @code{step}, but function calls that appear within
3526 the line of code are executed without stopping. Execution stops when
3527 control reaches a different line of code at the original stack level
3528 that was executing when you gave the @code{next} command. This command
3529 is abbreviated @code{n}.
3531 An argument @var{count} is a repeat count, as for @code{step}.
3534 @c FIX ME!! Do we delete this, or is there a way it fits in with
3535 @c the following paragraph? --- Vctoria
3537 @c @code{next} within a function that lacks debugging information acts like
3538 @c @code{step}, but any function calls appearing within the code of the
3539 @c function are executed without stopping.
3541 The @code{next} command only stops at the first instruction of a
3542 source line. This prevents multiple stops that could otherwise occur in
3543 @code{switch} statements, @code{for} loops, etc.
3545 @kindex set step-mode
3547 @cindex functions without line info, and stepping
3548 @cindex stepping into functions with no line info
3549 @itemx set step-mode on
3550 The @code{set step-mode on} command causes the @code{step} command to
3551 stop at the first instruction of a function which contains no debug line
3552 information rather than stepping over it.
3554 This is useful in cases where you may be interested in inspecting the
3555 machine instructions of a function which has no symbolic info and do not
3556 want @value{GDBN} to automatically skip over this function.
3558 @item set step-mode off
3559 Causes the @code{step} command to step over any functions which contains no
3560 debug information. This is the default.
3564 Continue running until just after function in the selected stack frame
3565 returns. Print the returned value (if any).
3567 Contrast this with the @code{return} command (@pxref{Returning,
3568 ,Returning from a function}).
3571 @kindex u @r{(@code{until})}
3574 Continue running until a source line past the current line, in the
3575 current stack frame, is reached. This command is used to avoid single
3576 stepping through a loop more than once. It is like the @code{next}
3577 command, except that when @code{until} encounters a jump, it
3578 automatically continues execution until the program counter is greater
3579 than the address of the jump.
3581 This means that when you reach the end of a loop after single stepping
3582 though it, @code{until} makes your program continue execution until it
3583 exits the loop. In contrast, a @code{next} command at the end of a loop
3584 simply steps back to the beginning of the loop, which forces you to step
3585 through the next iteration.
3587 @code{until} always stops your program if it attempts to exit the current
3590 @code{until} may produce somewhat counterintuitive results if the order
3591 of machine code does not match the order of the source lines. For
3592 example, in the following excerpt from a debugging session, the @code{f}
3593 (@code{frame}) command shows that execution is stopped at line
3594 @code{206}; yet when we use @code{until}, we get to line @code{195}:
3598 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
3600 (@value{GDBP}) until
3601 195 for ( ; argc > 0; NEXTARG) @{
3604 This happened because, for execution efficiency, the compiler had
3605 generated code for the loop closure test at the end, rather than the
3606 start, of the loop---even though the test in a C @code{for}-loop is
3607 written before the body of the loop. The @code{until} command appeared
3608 to step back to the beginning of the loop when it advanced to this
3609 expression; however, it has not really gone to an earlier
3610 statement---not in terms of the actual machine code.
3612 @code{until} with no argument works by means of single
3613 instruction stepping, and hence is slower than @code{until} with an
3616 @item until @var{location}
3617 @itemx u @var{location}
3618 Continue running your program until either the specified location is
3619 reached, or the current stack frame returns. @var{location} is any of
3620 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
3621 ,Setting breakpoints}). This form of the command uses breakpoints, and
3622 hence is quicker than @code{until} without an argument. The specified
3623 location is actually reached only if it is in the current frame. This
3624 implies that @code{until} can be used to skip over recursive function
3625 invocations. For instance in the code below, if the current location is
3626 line @code{96}, issuing @code{until 99} will execute the program up to
3627 line @code{99} in the same invocation of factorial, i.e. after the inner
3628 invocations have returned.
3631 94 int factorial (int value)
3633 96 if (value > 1) @{
3634 97 value *= factorial (value - 1);
3641 @kindex advance @var{location}
3642 @itemx advance @var{location}
3643 Continue running the program up to the given location. An argument is
3644 required, anything of the same form as arguments for the @code{break}
3645 command. Execution will also stop upon exit from the current stack
3646 frame. This command is similar to @code{until}, but @code{advance} will
3647 not skip over recursive function calls, and the target location doesn't
3648 have to be in the same frame as the current one.
3652 @kindex si @r{(@code{stepi})}
3654 @itemx stepi @var{arg}
3656 Execute one machine instruction, then stop and return to the debugger.
3658 It is often useful to do @samp{display/i $pc} when stepping by machine
3659 instructions. This makes @value{GDBN} automatically display the next
3660 instruction to be executed, each time your program stops. @xref{Auto
3661 Display,, Automatic display}.
3663 An argument is a repeat count, as in @code{step}.
3667 @kindex ni @r{(@code{nexti})}
3669 @itemx nexti @var{arg}
3671 Execute one machine instruction, but if it is a function call,
3672 proceed until the function returns.
3674 An argument is a repeat count, as in @code{next}.
3681 A signal is an asynchronous event that can happen in a program. The
3682 operating system defines the possible kinds of signals, and gives each
3683 kind a name and a number. For example, in Unix @code{SIGINT} is the
3684 signal a program gets when you type an interrupt character (often @kbd{C-c});
3685 @code{SIGSEGV} is the signal a program gets from referencing a place in
3686 memory far away from all the areas in use; @code{SIGALRM} occurs when
3687 the alarm clock timer goes off (which happens only if your program has
3688 requested an alarm).
3690 @cindex fatal signals
3691 Some signals, including @code{SIGALRM}, are a normal part of the
3692 functioning of your program. Others, such as @code{SIGSEGV}, indicate
3693 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
3694 program has not specified in advance some other way to handle the signal.
3695 @code{SIGINT} does not indicate an error in your program, but it is normally
3696 fatal so it can carry out the purpose of the interrupt: to kill the program.
3698 @value{GDBN} has the ability to detect any occurrence of a signal in your
3699 program. You can tell @value{GDBN} in advance what to do for each kind of
3702 @cindex handling signals
3703 Normally, @value{GDBN} is set up to let the non-erroneous signals like
3704 @code{SIGALRM} be silently passed to your program
3705 (so as not to interfere with their role in the program's functioning)
3706 but to stop your program immediately whenever an error signal happens.
3707 You can change these settings with the @code{handle} command.
3710 @kindex info signals
3713 Print a table of all the kinds of signals and how @value{GDBN} has been told to
3714 handle each one. You can use this to see the signal numbers of all
3715 the defined types of signals.
3717 @code{info handle} is an alias for @code{info signals}.
3720 @item handle @var{signal} @var{keywords}@dots{}
3721 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
3722 can be the number of a signal or its name (with or without the
3723 @samp{SIG} at the beginning); a list of signal numbers of the form
3724 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
3725 known signals. The @var{keywords} say what change to make.
3729 The keywords allowed by the @code{handle} command can be abbreviated.
3730 Their full names are:
3734 @value{GDBN} should not stop your program when this signal happens. It may
3735 still print a message telling you that the signal has come in.
3738 @value{GDBN} should stop your program when this signal happens. This implies
3739 the @code{print} keyword as well.
3742 @value{GDBN} should print a message when this signal happens.
3745 @value{GDBN} should not mention the occurrence of the signal at all. This
3746 implies the @code{nostop} keyword as well.
3750 @value{GDBN} should allow your program to see this signal; your program
3751 can handle the signal, or else it may terminate if the signal is fatal
3752 and not handled. @code{pass} and @code{noignore} are synonyms.
3756 @value{GDBN} should not allow your program to see this signal.
3757 @code{nopass} and @code{ignore} are synonyms.
3761 When a signal stops your program, the signal is not visible to the
3763 continue. Your program sees the signal then, if @code{pass} is in
3764 effect for the signal in question @emph{at that time}. In other words,
3765 after @value{GDBN} reports a signal, you can use the @code{handle}
3766 command with @code{pass} or @code{nopass} to control whether your
3767 program sees that signal when you continue.
3769 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
3770 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
3771 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
3774 You can also use the @code{signal} command to prevent your program from
3775 seeing a signal, or cause it to see a signal it normally would not see,
3776 or to give it any signal at any time. For example, if your program stopped
3777 due to some sort of memory reference error, you might store correct
3778 values into the erroneous variables and continue, hoping to see more
3779 execution; but your program would probably terminate immediately as
3780 a result of the fatal signal once it saw the signal. To prevent this,
3781 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
3785 @section Stopping and starting multi-thread programs
3787 When your program has multiple threads (@pxref{Threads,, Debugging
3788 programs with multiple threads}), you can choose whether to set
3789 breakpoints on all threads, or on a particular thread.
3792 @cindex breakpoints and threads
3793 @cindex thread breakpoints
3794 @kindex break @dots{} thread @var{threadno}
3795 @item break @var{linespec} thread @var{threadno}
3796 @itemx break @var{linespec} thread @var{threadno} if @dots{}
3797 @var{linespec} specifies source lines; there are several ways of
3798 writing them, but the effect is always to specify some source line.
3800 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
3801 to specify that you only want @value{GDBN} to stop the program when a
3802 particular thread reaches this breakpoint. @var{threadno} is one of the
3803 numeric thread identifiers assigned by @value{GDBN}, shown in the first
3804 column of the @samp{info threads} display.
3806 If you do not specify @samp{thread @var{threadno}} when you set a
3807 breakpoint, the breakpoint applies to @emph{all} threads of your
3810 You can use the @code{thread} qualifier on conditional breakpoints as
3811 well; in this case, place @samp{thread @var{threadno}} before the
3812 breakpoint condition, like this:
3815 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
3820 @cindex stopped threads
3821 @cindex threads, stopped
3822 Whenever your program stops under @value{GDBN} for any reason,
3823 @emph{all} threads of execution stop, not just the current thread. This
3824 allows you to examine the overall state of the program, including
3825 switching between threads, without worrying that things may change
3828 @cindex thread breakpoints and system calls
3829 @cindex system calls and thread breakpoints
3830 @cindex premature return from system calls
3831 There is an unfortunate side effect. If one thread stops for a
3832 breakpoint, or for some other reason, and another thread is blocked in a
3833 system call, then the system call may return prematurely. This is a
3834 consequence of the interaction between multiple threads and the signals
3835 that @value{GDBN} uses to implement breakpoints and other events that
3838 To handle this problem, your program should check the return value of
3839 each system call and react appropriately. This is good programming
3842 For example, do not write code like this:
3848 The call to @code{sleep} will return early if a different thread stops
3849 at a breakpoint or for some other reason.
3851 Instead, write this:
3856 unslept = sleep (unslept);
3859 A system call is allowed to return early, so the system is still
3860 conforming to its specification. But @value{GDBN} does cause your
3861 multi-threaded program to behave differently than it would without
3864 Also, @value{GDBN} uses internal breakpoints in the thread library to
3865 monitor certain events such as thread creation and thread destruction.
3866 When such an event happens, a system call in another thread may return
3867 prematurely, even though your program does not appear to stop.
3869 @cindex continuing threads
3870 @cindex threads, continuing
3871 Conversely, whenever you restart the program, @emph{all} threads start
3872 executing. @emph{This is true even when single-stepping} with commands
3873 like @code{step} or @code{next}.
3875 In particular, @value{GDBN} cannot single-step all threads in lockstep.
3876 Since thread scheduling is up to your debugging target's operating
3877 system (not controlled by @value{GDBN}), other threads may
3878 execute more than one statement while the current thread completes a
3879 single step. Moreover, in general other threads stop in the middle of a
3880 statement, rather than at a clean statement boundary, when the program
3883 You might even find your program stopped in another thread after
3884 continuing or even single-stepping. This happens whenever some other
3885 thread runs into a breakpoint, a signal, or an exception before the
3886 first thread completes whatever you requested.
3888 On some OSes, you can lock the OS scheduler and thus allow only a single
3892 @item set scheduler-locking @var{mode}
3893 Set the scheduler locking mode. If it is @code{off}, then there is no
3894 locking and any thread may run at any time. If @code{on}, then only the
3895 current thread may run when the inferior is resumed. The @code{step}
3896 mode optimizes for single-stepping. It stops other threads from
3897 ``seizing the prompt'' by preempting the current thread while you are
3898 stepping. Other threads will only rarely (or never) get a chance to run
3899 when you step. They are more likely to run when you @samp{next} over a
3900 function call, and they are completely free to run when you use commands
3901 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
3902 thread hits a breakpoint during its timeslice, they will never steal the
3903 @value{GDBN} prompt away from the thread that you are debugging.
3905 @item show scheduler-locking
3906 Display the current scheduler locking mode.
3911 @chapter Examining the Stack
3913 When your program has stopped, the first thing you need to know is where it
3914 stopped and how it got there.
3917 Each time your program performs a function call, information about the call
3919 That information includes the location of the call in your program,
3920 the arguments of the call,
3921 and the local variables of the function being called.
3922 The information is saved in a block of data called a @dfn{stack frame}.
3923 The stack frames are allocated in a region of memory called the @dfn{call
3926 When your program stops, the @value{GDBN} commands for examining the
3927 stack allow you to see all of this information.
3929 @cindex selected frame
3930 One of the stack frames is @dfn{selected} by @value{GDBN} and many
3931 @value{GDBN} commands refer implicitly to the selected frame. In
3932 particular, whenever you ask @value{GDBN} for the value of a variable in
3933 your program, the value is found in the selected frame. There are
3934 special @value{GDBN} commands to select whichever frame you are
3935 interested in. @xref{Selection, ,Selecting a frame}.
3937 When your program stops, @value{GDBN} automatically selects the
3938 currently executing frame and describes it briefly, similar to the
3939 @code{frame} command (@pxref{Frame Info, ,Information about a frame}).
3942 * Frames:: Stack frames
3943 * Backtrace:: Backtraces
3944 * Selection:: Selecting a frame
3945 * Frame Info:: Information on a frame
3950 @section Stack frames
3952 @cindex frame, definition
3954 The call stack is divided up into contiguous pieces called @dfn{stack
3955 frames}, or @dfn{frames} for short; each frame is the data associated
3956 with one call to one function. The frame contains the arguments given
3957 to the function, the function's local variables, and the address at
3958 which the function is executing.
3960 @cindex initial frame
3961 @cindex outermost frame
3962 @cindex innermost frame
3963 When your program is started, the stack has only one frame, that of the
3964 function @code{main}. This is called the @dfn{initial} frame or the
3965 @dfn{outermost} frame. Each time a function is called, a new frame is
3966 made. Each time a function returns, the frame for that function invocation
3967 is eliminated. If a function is recursive, there can be many frames for
3968 the same function. The frame for the function in which execution is
3969 actually occurring is called the @dfn{innermost} frame. This is the most
3970 recently created of all the stack frames that still exist.
3972 @cindex frame pointer
3973 Inside your program, stack frames are identified by their addresses. A
3974 stack frame consists of many bytes, each of which has its own address; each
3975 kind of computer has a convention for choosing one byte whose
3976 address serves as the address of the frame. Usually this address is kept
3977 in a register called the @dfn{frame pointer register} while execution is
3978 going on in that frame.
3980 @cindex frame number
3981 @value{GDBN} assigns numbers to all existing stack frames, starting with
3982 zero for the innermost frame, one for the frame that called it,
3983 and so on upward. These numbers do not really exist in your program;
3984 they are assigned by @value{GDBN} to give you a way of designating stack
3985 frames in @value{GDBN} commands.
3987 @c The -fomit-frame-pointer below perennially causes hbox overflow
3988 @c underflow problems.
3989 @cindex frameless execution
3990 Some compilers provide a way to compile functions so that they operate
3991 without stack frames. (For example, the @value{GCC} option
3993 @samp{-fomit-frame-pointer}
3995 generates functions without a frame.)
3996 This is occasionally done with heavily used library functions to save
3997 the frame setup time. @value{GDBN} has limited facilities for dealing
3998 with these function invocations. If the innermost function invocation
3999 has no stack frame, @value{GDBN} nevertheless regards it as though
4000 it had a separate frame, which is numbered zero as usual, allowing
4001 correct tracing of the function call chain. However, @value{GDBN} has
4002 no provision for frameless functions elsewhere in the stack.
4005 @kindex frame@r{, command}
4006 @cindex current stack frame
4007 @item frame @var{args}
4008 The @code{frame} command allows you to move from one stack frame to another,
4009 and to print the stack frame you select. @var{args} may be either the
4010 address of the frame or the stack frame number. Without an argument,
4011 @code{frame} prints the current stack frame.
4013 @kindex select-frame
4014 @cindex selecting frame silently
4016 The @code{select-frame} command allows you to move from one stack frame
4017 to another without printing the frame. This is the silent version of
4026 @cindex stack traces
4027 A backtrace is a summary of how your program got where it is. It shows one
4028 line per frame, for many frames, starting with the currently executing
4029 frame (frame zero), followed by its caller (frame one), and on up the
4034 @kindex bt @r{(@code{backtrace})}
4037 Print a backtrace of the entire stack: one line per frame for all
4038 frames in the stack.
4040 You can stop the backtrace at any time by typing the system interrupt
4041 character, normally @kbd{C-c}.
4043 @item backtrace @var{n}
4045 Similar, but print only the innermost @var{n} frames.
4047 @item backtrace -@var{n}
4049 Similar, but print only the outermost @var{n} frames.
4054 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4055 are additional aliases for @code{backtrace}.
4057 Each line in the backtrace shows the frame number and the function name.
4058 The program counter value is also shown---unless you use @code{set
4059 print address off}. The backtrace also shows the source file name and
4060 line number, as well as the arguments to the function. The program
4061 counter value is omitted if it is at the beginning of the code for that
4064 Here is an example of a backtrace. It was made with the command
4065 @samp{bt 3}, so it shows the innermost three frames.
4069 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4071 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4072 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4074 (More stack frames follow...)
4079 The display for frame zero does not begin with a program counter
4080 value, indicating that your program has stopped at the beginning of the
4081 code for line @code{993} of @code{builtin.c}.
4083 Most programs have a standard user entry point---a place where system
4084 libraries and startup code transition into user code. For C this is
4085 @code{main}. When @value{GDBN} finds the entry function in a backtrace
4086 it will terminate the backtrace, to avoid tracing into highly
4087 system-specific (and generally uninteresting) code.
4089 If you need to examine the startup code, or limit the number of levels
4090 in a backtrace, you can change this behavior:
4093 @item set backtrace past-main
4094 @itemx set backtrace past-main on
4095 @kindex set backtrace
4096 Backtraces will continue past the user entry point.
4098 @item set backtrace past-main off
4099 Backtraces will stop when they encounter the user entry point. This is the
4102 @item show backtrace past-main
4103 @kindex show backtrace
4104 Display the current user entry point backtrace policy.
4106 @item set backtrace limit @var{n}
4107 @itemx set backtrace limit 0
4108 @cindex backtrace limit
4109 Limit the backtrace to @var{n} levels. A value of zero means
4112 @item show backtrace limit
4113 Display the current limit on backtrace levels.
4117 @section Selecting a frame
4119 Most commands for examining the stack and other data in your program work on
4120 whichever stack frame is selected at the moment. Here are the commands for
4121 selecting a stack frame; all of them finish by printing a brief description
4122 of the stack frame just selected.
4125 @kindex frame@r{, selecting}
4126 @kindex f @r{(@code{frame})}
4129 Select frame number @var{n}. Recall that frame zero is the innermost
4130 (currently executing) frame, frame one is the frame that called the
4131 innermost one, and so on. The highest-numbered frame is the one for
4134 @item frame @var{addr}
4136 Select the frame at address @var{addr}. This is useful mainly if the
4137 chaining of stack frames has been damaged by a bug, making it
4138 impossible for @value{GDBN} to assign numbers properly to all frames. In
4139 addition, this can be useful when your program has multiple stacks and
4140 switches between them.
4142 On the SPARC architecture, @code{frame} needs two addresses to
4143 select an arbitrary frame: a frame pointer and a stack pointer.
4145 On the MIPS and Alpha architecture, it needs two addresses: a stack
4146 pointer and a program counter.
4148 On the 29k architecture, it needs three addresses: a register stack
4149 pointer, a program counter, and a memory stack pointer.
4150 @c note to future updaters: this is conditioned on a flag
4151 @c SETUP_ARBITRARY_FRAME in the tm-*.h files. The above is up to date
4152 @c as of 27 Jan 1994.
4156 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4157 advances toward the outermost frame, to higher frame numbers, to frames
4158 that have existed longer. @var{n} defaults to one.
4161 @kindex do @r{(@code{down})}
4163 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4164 advances toward the innermost frame, to lower frame numbers, to frames
4165 that were created more recently. @var{n} defaults to one. You may
4166 abbreviate @code{down} as @code{do}.
4169 All of these commands end by printing two lines of output describing the
4170 frame. The first line shows the frame number, the function name, the
4171 arguments, and the source file and line number of execution in that
4172 frame. The second line shows the text of that source line.
4180 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4182 10 read_input_file (argv[i]);
4186 After such a printout, the @code{list} command with no arguments
4187 prints ten lines centered on the point of execution in the frame.
4188 You can also edit the program at the point of execution with your favorite
4189 editing program by typing @code{edit}.
4190 @xref{List, ,Printing source lines},
4194 @kindex down-silently
4196 @item up-silently @var{n}
4197 @itemx down-silently @var{n}
4198 These two commands are variants of @code{up} and @code{down},
4199 respectively; they differ in that they do their work silently, without
4200 causing display of the new frame. They are intended primarily for use
4201 in @value{GDBN} command scripts, where the output might be unnecessary and
4206 @section Information about a frame
4208 There are several other commands to print information about the selected
4214 When used without any argument, this command does not change which
4215 frame is selected, but prints a brief description of the currently
4216 selected stack frame. It can be abbreviated @code{f}. With an
4217 argument, this command is used to select a stack frame.
4218 @xref{Selection, ,Selecting a frame}.
4221 @kindex info f @r{(@code{info frame})}
4224 This command prints a verbose description of the selected stack frame,
4229 the address of the frame
4231 the address of the next frame down (called by this frame)
4233 the address of the next frame up (caller of this frame)
4235 the language in which the source code corresponding to this frame is written
4237 the address of the frame's arguments
4239 the address of the frame's local variables
4241 the program counter saved in it (the address of execution in the caller frame)
4243 which registers were saved in the frame
4246 @noindent The verbose description is useful when
4247 something has gone wrong that has made the stack format fail to fit
4248 the usual conventions.
4250 @item info frame @var{addr}
4251 @itemx info f @var{addr}
4252 Print a verbose description of the frame at address @var{addr}, without
4253 selecting that frame. The selected frame remains unchanged by this
4254 command. This requires the same kind of address (more than one for some
4255 architectures) that you specify in the @code{frame} command.
4256 @xref{Selection, ,Selecting a frame}.
4260 Print the arguments of the selected frame, each on a separate line.
4264 Print the local variables of the selected frame, each on a separate
4265 line. These are all variables (declared either static or automatic)
4266 accessible at the point of execution of the selected frame.
4269 @cindex catch exceptions, list active handlers
4270 @cindex exception handlers, how to list
4272 Print a list of all the exception handlers that are active in the
4273 current stack frame at the current point of execution. To see other
4274 exception handlers, visit the associated frame (using the @code{up},
4275 @code{down}, or @code{frame} commands); then type @code{info catch}.
4276 @xref{Set Catchpoints, , Setting catchpoints}.
4282 @chapter Examining Source Files
4284 @value{GDBN} can print parts of your program's source, since the debugging
4285 information recorded in the program tells @value{GDBN} what source files were
4286 used to build it. When your program stops, @value{GDBN} spontaneously prints
4287 the line where it stopped. Likewise, when you select a stack frame
4288 (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
4289 execution in that frame has stopped. You can print other portions of
4290 source files by explicit command.
4292 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4293 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4294 @value{GDBN} under @sc{gnu} Emacs}.
4297 * List:: Printing source lines
4298 * Edit:: Editing source files
4299 * Search:: Searching source files
4300 * Source Path:: Specifying source directories
4301 * Machine Code:: Source and machine code
4305 @section Printing source lines
4308 @kindex l @r{(@code{list})}
4309 To print lines from a source file, use the @code{list} command
4310 (abbreviated @code{l}). By default, ten lines are printed.
4311 There are several ways to specify what part of the file you want to print.
4313 Here are the forms of the @code{list} command most commonly used:
4316 @item list @var{linenum}
4317 Print lines centered around line number @var{linenum} in the
4318 current source file.
4320 @item list @var{function}
4321 Print lines centered around the beginning of function
4325 Print more lines. If the last lines printed were printed with a
4326 @code{list} command, this prints lines following the last lines
4327 printed; however, if the last line printed was a solitary line printed
4328 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4329 Stack}), this prints lines centered around that line.
4332 Print lines just before the lines last printed.
4335 By default, @value{GDBN} prints ten source lines with any of these forms of
4336 the @code{list} command. You can change this using @code{set listsize}:
4339 @kindex set listsize
4340 @item set listsize @var{count}
4341 Make the @code{list} command display @var{count} source lines (unless
4342 the @code{list} argument explicitly specifies some other number).
4344 @kindex show listsize
4346 Display the number of lines that @code{list} prints.
4349 Repeating a @code{list} command with @key{RET} discards the argument,
4350 so it is equivalent to typing just @code{list}. This is more useful
4351 than listing the same lines again. An exception is made for an
4352 argument of @samp{-}; that argument is preserved in repetition so that
4353 each repetition moves up in the source file.
4356 In general, the @code{list} command expects you to supply zero, one or two
4357 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4358 of writing them, but the effect is always to specify some source line.
4359 Here is a complete description of the possible arguments for @code{list}:
4362 @item list @var{linespec}
4363 Print lines centered around the line specified by @var{linespec}.
4365 @item list @var{first},@var{last}
4366 Print lines from @var{first} to @var{last}. Both arguments are
4369 @item list ,@var{last}
4370 Print lines ending with @var{last}.
4372 @item list @var{first},
4373 Print lines starting with @var{first}.
4376 Print lines just after the lines last printed.
4379 Print lines just before the lines last printed.
4382 As described in the preceding table.
4385 Here are the ways of specifying a single source line---all the
4390 Specifies line @var{number} of the current source file.
4391 When a @code{list} command has two linespecs, this refers to
4392 the same source file as the first linespec.
4395 Specifies the line @var{offset} lines after the last line printed.
4396 When used as the second linespec in a @code{list} command that has
4397 two, this specifies the line @var{offset} lines down from the
4401 Specifies the line @var{offset} lines before the last line printed.
4403 @item @var{filename}:@var{number}
4404 Specifies line @var{number} in the source file @var{filename}.
4406 @item @var{function}
4407 Specifies the line that begins the body of the function @var{function}.
4408 For example: in C, this is the line with the open brace.
4410 @item @var{filename}:@var{function}
4411 Specifies the line of the open-brace that begins the body of the
4412 function @var{function} in the file @var{filename}. You only need the
4413 file name with a function name to avoid ambiguity when there are
4414 identically named functions in different source files.
4416 @item *@var{address}
4417 Specifies the line containing the program address @var{address}.
4418 @var{address} may be any expression.
4422 @section Editing source files
4423 @cindex editing source files
4426 @kindex e @r{(@code{edit})}
4427 To edit the lines in a source file, use the @code{edit} command.
4428 The editing program of your choice
4429 is invoked with the current line set to
4430 the active line in the program.
4431 Alternatively, there are several ways to specify what part of the file you
4432 want to print if you want to see other parts of the program.
4434 Here are the forms of the @code{edit} command most commonly used:
4438 Edit the current source file at the active line number in the program.
4440 @item edit @var{number}
4441 Edit the current source file with @var{number} as the active line number.
4443 @item edit @var{function}
4444 Edit the file containing @var{function} at the beginning of its definition.
4446 @item edit @var{filename}:@var{number}
4447 Specifies line @var{number} in the source file @var{filename}.
4449 @item edit @var{filename}:@var{function}
4450 Specifies the line that begins the body of the
4451 function @var{function} in the file @var{filename}. You only need the
4452 file name with a function name to avoid ambiguity when there are
4453 identically named functions in different source files.
4455 @item edit *@var{address}
4456 Specifies the line containing the program address @var{address}.
4457 @var{address} may be any expression.
4460 @subsection Choosing your editor
4461 You can customize @value{GDBN} to use any editor you want
4463 The only restriction is that your editor (say @code{ex}), recognizes the
4464 following command-line syntax:
4466 ex +@var{number} file
4468 The optional numeric value +@var{number} specifies the number of the line in
4469 the file where to start editing.}.
4470 By default, it is @file{@value{EDITOR}}, but you can change this
4471 by setting the environment variable @code{EDITOR} before using
4472 @value{GDBN}. For example, to configure @value{GDBN} to use the
4473 @code{vi} editor, you could use these commands with the @code{sh} shell:
4479 or in the @code{csh} shell,
4481 setenv EDITOR /usr/bin/vi
4486 @section Searching source files
4487 @cindex searching source files
4488 @kindex reverse-search
4490 There are two commands for searching through the current source file for a
4495 @kindex forward-search
4496 @item forward-search @var{regexp}
4497 @itemx search @var{regexp}
4498 The command @samp{forward-search @var{regexp}} checks each line,
4499 starting with the one following the last line listed, for a match for
4500 @var{regexp}. It lists the line that is found. You can use the
4501 synonym @samp{search @var{regexp}} or abbreviate the command name as
4504 @item reverse-search @var{regexp}
4505 The command @samp{reverse-search @var{regexp}} checks each line, starting
4506 with the one before the last line listed and going backward, for a match
4507 for @var{regexp}. It lists the line that is found. You can abbreviate
4508 this command as @code{rev}.
4512 @section Specifying source directories
4515 @cindex directories for source files
4516 Executable programs sometimes do not record the directories of the source
4517 files from which they were compiled, just the names. Even when they do,
4518 the directories could be moved between the compilation and your debugging
4519 session. @value{GDBN} has a list of directories to search for source files;
4520 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
4521 it tries all the directories in the list, in the order they are present
4522 in the list, until it finds a file with the desired name. Note that
4523 the executable search path is @emph{not} used for this purpose. Neither is
4524 the current working directory, unless it happens to be in the source
4527 If @value{GDBN} cannot find a source file in the source path, and the
4528 object program records a directory, @value{GDBN} tries that directory
4529 too. If the source path is empty, and there is no record of the
4530 compilation directory, @value{GDBN} looks in the current directory as a
4533 Whenever you reset or rearrange the source path, @value{GDBN} clears out
4534 any information it has cached about where source files are found and where
4535 each line is in the file.
4539 When you start @value{GDBN}, its source path includes only @samp{cdir}
4540 and @samp{cwd}, in that order.
4541 To add other directories, use the @code{directory} command.
4544 @item directory @var{dirname} @dots{}
4545 @item dir @var{dirname} @dots{}
4546 Add directory @var{dirname} to the front of the source path. Several
4547 directory names may be given to this command, separated by @samp{:}
4548 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
4549 part of absolute file names) or
4550 whitespace. You may specify a directory that is already in the source
4551 path; this moves it forward, so @value{GDBN} searches it sooner.
4555 @vindex $cdir@r{, convenience variable}
4556 @vindex $cwdr@r{, convenience variable}
4557 @cindex compilation directory
4558 @cindex current directory
4559 @cindex working directory
4560 @cindex directory, current
4561 @cindex directory, compilation
4562 You can use the string @samp{$cdir} to refer to the compilation
4563 directory (if one is recorded), and @samp{$cwd} to refer to the current
4564 working directory. @samp{$cwd} is not the same as @samp{.}---the former
4565 tracks the current working directory as it changes during your @value{GDBN}
4566 session, while the latter is immediately expanded to the current
4567 directory at the time you add an entry to the source path.
4570 Reset the source path to empty again. This requires confirmation.
4572 @c RET-repeat for @code{directory} is explicitly disabled, but since
4573 @c repeating it would be a no-op we do not say that. (thanks to RMS)
4575 @item show directories
4576 @kindex show directories
4577 Print the source path: show which directories it contains.
4580 If your source path is cluttered with directories that are no longer of
4581 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
4582 versions of source. You can correct the situation as follows:
4586 Use @code{directory} with no argument to reset the source path to empty.
4589 Use @code{directory} with suitable arguments to reinstall the
4590 directories you want in the source path. You can add all the
4591 directories in one command.
4595 @section Source and machine code
4596 @cindex source line and its code address
4598 You can use the command @code{info line} to map source lines to program
4599 addresses (and vice versa), and the command @code{disassemble} to display
4600 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
4601 mode, the @code{info line} command causes the arrow to point to the
4602 line specified. Also, @code{info line} prints addresses in symbolic form as
4607 @item info line @var{linespec}
4608 Print the starting and ending addresses of the compiled code for
4609 source line @var{linespec}. You can specify source lines in any of
4610 the ways understood by the @code{list} command (@pxref{List, ,Printing
4614 For example, we can use @code{info line} to discover the location of
4615 the object code for the first line of function
4616 @code{m4_changequote}:
4618 @c FIXME: I think this example should also show the addresses in
4619 @c symbolic form, as they usually would be displayed.
4621 (@value{GDBP}) info line m4_changequote
4622 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
4626 @cindex code address and its source line
4627 We can also inquire (using @code{*@var{addr}} as the form for
4628 @var{linespec}) what source line covers a particular address:
4630 (@value{GDBP}) info line *0x63ff
4631 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
4634 @cindex @code{$_} and @code{info line}
4635 @cindex @code{x} command, default address
4636 @kindex x@r{(examine), and} info line
4637 After @code{info line}, the default address for the @code{x} command
4638 is changed to the starting address of the line, so that @samp{x/i} is
4639 sufficient to begin examining the machine code (@pxref{Memory,
4640 ,Examining memory}). Also, this address is saved as the value of the
4641 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
4646 @cindex assembly instructions
4647 @cindex instructions, assembly
4648 @cindex machine instructions
4649 @cindex listing machine instructions
4651 This specialized command dumps a range of memory as machine
4652 instructions. The default memory range is the function surrounding the
4653 program counter of the selected frame. A single argument to this
4654 command is a program counter value; @value{GDBN} dumps the function
4655 surrounding this value. Two arguments specify a range of addresses
4656 (first inclusive, second exclusive) to dump.
4659 The following example shows the disassembly of a range of addresses of
4660 HP PA-RISC 2.0 code:
4663 (@value{GDBP}) disas 0x32c4 0x32e4
4664 Dump of assembler code from 0x32c4 to 0x32e4:
4665 0x32c4 <main+204>: addil 0,dp
4666 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
4667 0x32cc <main+212>: ldil 0x3000,r31
4668 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
4669 0x32d4 <main+220>: ldo 0(r31),rp
4670 0x32d8 <main+224>: addil -0x800,dp
4671 0x32dc <main+228>: ldo 0x588(r1),r26
4672 0x32e0 <main+232>: ldil 0x3000,r31
4673 End of assembler dump.
4676 Some architectures have more than one commonly-used set of instruction
4677 mnemonics or other syntax.
4680 @kindex set disassembly-flavor
4681 @cindex Intel disassembly flavor
4682 @cindex AT&T disassembly flavor
4683 @item set disassembly-flavor @var{instruction-set}
4684 Select the instruction set to use when disassembling the
4685 program via the @code{disassemble} or @code{x/i} commands.
4687 Currently this command is only defined for the Intel x86 family. You
4688 can set @var{instruction-set} to either @code{intel} or @code{att}.
4689 The default is @code{att}, the AT&T flavor used by default by Unix
4690 assemblers for x86-based targets.
4695 @chapter Examining Data
4697 @cindex printing data
4698 @cindex examining data
4701 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
4702 @c document because it is nonstandard... Under Epoch it displays in a
4703 @c different window or something like that.
4704 The usual way to examine data in your program is with the @code{print}
4705 command (abbreviated @code{p}), or its synonym @code{inspect}. It
4706 evaluates and prints the value of an expression of the language your
4707 program is written in (@pxref{Languages, ,Using @value{GDBN} with
4708 Different Languages}).
4711 @item print @var{expr}
4712 @itemx print /@var{f} @var{expr}
4713 @var{expr} is an expression (in the source language). By default the
4714 value of @var{expr} is printed in a format appropriate to its data type;
4715 you can choose a different format by specifying @samp{/@var{f}}, where
4716 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
4720 @itemx print /@var{f}
4721 @cindex reprint the last value
4722 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
4723 @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
4724 conveniently inspect the same value in an alternative format.
4727 A more low-level way of examining data is with the @code{x} command.
4728 It examines data in memory at a specified address and prints it in a
4729 specified format. @xref{Memory, ,Examining memory}.
4731 If you are interested in information about types, or about how the
4732 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
4733 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
4737 * Expressions:: Expressions
4738 * Variables:: Program variables
4739 * Arrays:: Artificial arrays
4740 * Output Formats:: Output formats
4741 * Memory:: Examining memory
4742 * Auto Display:: Automatic display
4743 * Print Settings:: Print settings
4744 * Value History:: Value history
4745 * Convenience Vars:: Convenience variables
4746 * Registers:: Registers
4747 * Floating Point Hardware:: Floating point hardware
4748 * Vector Unit:: Vector Unit
4749 * Auxiliary Vector:: Auxiliary data provided by operating system
4750 * Memory Region Attributes:: Memory region attributes
4751 * Dump/Restore Files:: Copy between memory and a file
4752 * Character Sets:: Debugging programs that use a different
4753 character set than GDB does
4757 @section Expressions
4760 @code{print} and many other @value{GDBN} commands accept an expression and
4761 compute its value. Any kind of constant, variable or operator defined
4762 by the programming language you are using is valid in an expression in
4763 @value{GDBN}. This includes conditional expressions, function calls,
4764 casts, and string constants. It also includes preprocessor macros, if
4765 you compiled your program to include this information; see
4768 @cindex arrays in expressions
4769 @value{GDBN} supports array constants in expressions input by
4770 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
4771 you can use the command @code{print @{1, 2, 3@}} to build up an array in
4772 memory that is @code{malloc}ed in the target program.
4774 Because C is so widespread, most of the expressions shown in examples in
4775 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
4776 Languages}, for information on how to use expressions in other
4779 In this section, we discuss operators that you can use in @value{GDBN}
4780 expressions regardless of your programming language.
4782 @cindex casts, in expressions
4783 Casts are supported in all languages, not just in C, because it is so
4784 useful to cast a number into a pointer in order to examine a structure
4785 at that address in memory.
4786 @c FIXME: casts supported---Mod2 true?
4788 @value{GDBN} supports these operators, in addition to those common
4789 to programming languages:
4793 @samp{@@} is a binary operator for treating parts of memory as arrays.
4794 @xref{Arrays, ,Artificial arrays}, for more information.
4797 @samp{::} allows you to specify a variable in terms of the file or
4798 function where it is defined. @xref{Variables, ,Program variables}.
4800 @cindex @{@var{type}@}
4801 @cindex type casting memory
4802 @cindex memory, viewing as typed object
4803 @cindex casts, to view memory
4804 @item @{@var{type}@} @var{addr}
4805 Refers to an object of type @var{type} stored at address @var{addr} in
4806 memory. @var{addr} may be any expression whose value is an integer or
4807 pointer (but parentheses are required around binary operators, just as in
4808 a cast). This construct is allowed regardless of what kind of data is
4809 normally supposed to reside at @var{addr}.
4813 @section Program variables
4815 The most common kind of expression to use is the name of a variable
4818 Variables in expressions are understood in the selected stack frame
4819 (@pxref{Selection, ,Selecting a frame}); they must be either:
4823 global (or file-static)
4830 visible according to the scope rules of the
4831 programming language from the point of execution in that frame
4834 @noindent This means that in the function
4849 you can examine and use the variable @code{a} whenever your program is
4850 executing within the function @code{foo}, but you can only use or
4851 examine the variable @code{b} while your program is executing inside
4852 the block where @code{b} is declared.
4854 @cindex variable name conflict
4855 There is an exception: you can refer to a variable or function whose
4856 scope is a single source file even if the current execution point is not
4857 in this file. But it is possible to have more than one such variable or
4858 function with the same name (in different source files). If that
4859 happens, referring to that name has unpredictable effects. If you wish,
4860 you can specify a static variable in a particular function or file,
4861 using the colon-colon (@code{::}) notation:
4863 @cindex colon-colon, context for variables/functions
4865 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
4866 @cindex @code{::}, context for variables/functions
4869 @var{file}::@var{variable}
4870 @var{function}::@var{variable}
4874 Here @var{file} or @var{function} is the name of the context for the
4875 static @var{variable}. In the case of file names, you can use quotes to
4876 make sure @value{GDBN} parses the file name as a single word---for example,
4877 to print a global value of @code{x} defined in @file{f2.c}:
4880 (@value{GDBP}) p 'f2.c'::x
4883 @cindex C@t{++} scope resolution
4884 This use of @samp{::} is very rarely in conflict with the very similar
4885 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
4886 scope resolution operator in @value{GDBN} expressions.
4887 @c FIXME: Um, so what happens in one of those rare cases where it's in
4890 @cindex wrong values
4891 @cindex variable values, wrong
4892 @cindex function entry/exit, wrong values of variables
4893 @cindex optimized code, wrong values of variables
4895 @emph{Warning:} Occasionally, a local variable may appear to have the
4896 wrong value at certain points in a function---just after entry to a new
4897 scope, and just before exit.
4899 You may see this problem when you are stepping by machine instructions.
4900 This is because, on most machines, it takes more than one instruction to
4901 set up a stack frame (including local variable definitions); if you are
4902 stepping by machine instructions, variables may appear to have the wrong
4903 values until the stack frame is completely built. On exit, it usually
4904 also takes more than one machine instruction to destroy a stack frame;
4905 after you begin stepping through that group of instructions, local
4906 variable definitions may be gone.
4908 This may also happen when the compiler does significant optimizations.
4909 To be sure of always seeing accurate values, turn off all optimization
4912 @cindex ``No symbol "foo" in current context''
4913 Another possible effect of compiler optimizations is to optimize
4914 unused variables out of existence, or assign variables to registers (as
4915 opposed to memory addresses). Depending on the support for such cases
4916 offered by the debug info format used by the compiler, @value{GDBN}
4917 might not be able to display values for such local variables. If that
4918 happens, @value{GDBN} will print a message like this:
4921 No symbol "foo" in current context.
4924 To solve such problems, either recompile without optimizations, or use a
4925 different debug info format, if the compiler supports several such
4926 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
4927 usually supports the @option{-gstabs+} option. @option{-gstabs+}
4928 produces debug info in a format that is superior to formats such as
4929 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
4930 an effective form for debug info. @xref{Debugging Options,,Options
4931 for Debugging Your Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}.
4932 @xref{C, , Debugging C++}, for more info about debug info formats
4933 that are best suited to C@t{++} programs.
4936 @section Artificial arrays
4938 @cindex artificial array
4940 @kindex @@@r{, referencing memory as an array}
4941 It is often useful to print out several successive objects of the
4942 same type in memory; a section of an array, or an array of
4943 dynamically determined size for which only a pointer exists in the
4946 You can do this by referring to a contiguous span of memory as an
4947 @dfn{artificial array}, using the binary operator @samp{@@}. The left
4948 operand of @samp{@@} should be the first element of the desired array
4949 and be an individual object. The right operand should be the desired length
4950 of the array. The result is an array value whose elements are all of
4951 the type of the left argument. The first element is actually the left
4952 argument; the second element comes from bytes of memory immediately
4953 following those that hold the first element, and so on. Here is an
4954 example. If a program says
4957 int *array = (int *) malloc (len * sizeof (int));
4961 you can print the contents of @code{array} with
4967 The left operand of @samp{@@} must reside in memory. Array values made
4968 with @samp{@@} in this way behave just like other arrays in terms of
4969 subscripting, and are coerced to pointers when used in expressions.
4970 Artificial arrays most often appear in expressions via the value history
4971 (@pxref{Value History, ,Value history}), after printing one out.
4973 Another way to create an artificial array is to use a cast.
4974 This re-interprets a value as if it were an array.
4975 The value need not be in memory:
4977 (@value{GDBP}) p/x (short[2])0x12345678
4978 $1 = @{0x1234, 0x5678@}
4981 As a convenience, if you leave the array length out (as in
4982 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
4983 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
4985 (@value{GDBP}) p/x (short[])0x12345678
4986 $2 = @{0x1234, 0x5678@}
4989 Sometimes the artificial array mechanism is not quite enough; in
4990 moderately complex data structures, the elements of interest may not
4991 actually be adjacent---for example, if you are interested in the values
4992 of pointers in an array. One useful work-around in this situation is
4993 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
4994 variables}) as a counter in an expression that prints the first
4995 interesting value, and then repeat that expression via @key{RET}. For
4996 instance, suppose you have an array @code{dtab} of pointers to
4997 structures, and you are interested in the values of a field @code{fv}
4998 in each structure. Here is an example of what you might type:
5008 @node Output Formats
5009 @section Output formats
5011 @cindex formatted output
5012 @cindex output formats
5013 By default, @value{GDBN} prints a value according to its data type. Sometimes
5014 this is not what you want. For example, you might want to print a number
5015 in hex, or a pointer in decimal. Or you might want to view data in memory
5016 at a certain address as a character string or as an instruction. To do
5017 these things, specify an @dfn{output format} when you print a value.
5019 The simplest use of output formats is to say how to print a value
5020 already computed. This is done by starting the arguments of the
5021 @code{print} command with a slash and a format letter. The format
5022 letters supported are:
5026 Regard the bits of the value as an integer, and print the integer in
5030 Print as integer in signed decimal.
5033 Print as integer in unsigned decimal.
5036 Print as integer in octal.
5039 Print as integer in binary. The letter @samp{t} stands for ``two''.
5040 @footnote{@samp{b} cannot be used because these format letters are also
5041 used with the @code{x} command, where @samp{b} stands for ``byte'';
5042 see @ref{Memory,,Examining memory}.}
5045 @cindex unknown address, locating
5046 @cindex locate address
5047 Print as an address, both absolute in hexadecimal and as an offset from
5048 the nearest preceding symbol. You can use this format used to discover
5049 where (in what function) an unknown address is located:
5052 (@value{GDBP}) p/a 0x54320
5053 $3 = 0x54320 <_initialize_vx+396>
5057 The command @code{info symbol 0x54320} yields similar results.
5058 @xref{Symbols, info symbol}.
5061 Regard as an integer and print it as a character constant.
5064 Regard the bits of the value as a floating point number and print
5065 using typical floating point syntax.
5068 For example, to print the program counter in hex (@pxref{Registers}), type
5075 Note that no space is required before the slash; this is because command
5076 names in @value{GDBN} cannot contain a slash.
5078 To reprint the last value in the value history with a different format,
5079 you can use the @code{print} command with just a format and no
5080 expression. For example, @samp{p/x} reprints the last value in hex.
5083 @section Examining memory
5085 You can use the command @code{x} (for ``examine'') to examine memory in
5086 any of several formats, independently of your program's data types.
5088 @cindex examining memory
5090 @kindex x @r{(examine memory)}
5091 @item x/@var{nfu} @var{addr}
5094 Use the @code{x} command to examine memory.
5097 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5098 much memory to display and how to format it; @var{addr} is an
5099 expression giving the address where you want to start displaying memory.
5100 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5101 Several commands set convenient defaults for @var{addr}.
5104 @item @var{n}, the repeat count
5105 The repeat count is a decimal integer; the default is 1. It specifies
5106 how much memory (counting by units @var{u}) to display.
5107 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5110 @item @var{f}, the display format
5111 The display format is one of the formats used by @code{print},
5112 @samp{s} (null-terminated string), or @samp{i} (machine instruction).
5113 The default is @samp{x} (hexadecimal) initially.
5114 The default changes each time you use either @code{x} or @code{print}.
5116 @item @var{u}, the unit size
5117 The unit size is any of
5123 Halfwords (two bytes).
5125 Words (four bytes). This is the initial default.
5127 Giant words (eight bytes).
5130 Each time you specify a unit size with @code{x}, that size becomes the
5131 default unit the next time you use @code{x}. (For the @samp{s} and
5132 @samp{i} formats, the unit size is ignored and is normally not written.)
5134 @item @var{addr}, starting display address
5135 @var{addr} is the address where you want @value{GDBN} to begin displaying
5136 memory. The expression need not have a pointer value (though it may);
5137 it is always interpreted as an integer address of a byte of memory.
5138 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5139 @var{addr} is usually just after the last address examined---but several
5140 other commands also set the default address: @code{info breakpoints} (to
5141 the address of the last breakpoint listed), @code{info line} (to the
5142 starting address of a line), and @code{print} (if you use it to display
5143 a value from memory).
5146 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5147 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5148 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5149 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5150 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5152 Since the letters indicating unit sizes are all distinct from the
5153 letters specifying output formats, you do not have to remember whether
5154 unit size or format comes first; either order works. The output
5155 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5156 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5158 Even though the unit size @var{u} is ignored for the formats @samp{s}
5159 and @samp{i}, you might still want to use a count @var{n}; for example,
5160 @samp{3i} specifies that you want to see three machine instructions,
5161 including any operands. The command @code{disassemble} gives an
5162 alternative way of inspecting machine instructions; see @ref{Machine
5163 Code,,Source and machine code}.
5165 All the defaults for the arguments to @code{x} are designed to make it
5166 easy to continue scanning memory with minimal specifications each time
5167 you use @code{x}. For example, after you have inspected three machine
5168 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5169 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5170 the repeat count @var{n} is used again; the other arguments default as
5171 for successive uses of @code{x}.
5173 @cindex @code{$_}, @code{$__}, and value history
5174 The addresses and contents printed by the @code{x} command are not saved
5175 in the value history because there is often too much of them and they
5176 would get in the way. Instead, @value{GDBN} makes these values available for
5177 subsequent use in expressions as values of the convenience variables
5178 @code{$_} and @code{$__}. After an @code{x} command, the last address
5179 examined is available for use in expressions in the convenience variable
5180 @code{$_}. The contents of that address, as examined, are available in
5181 the convenience variable @code{$__}.
5183 If the @code{x} command has a repeat count, the address and contents saved
5184 are from the last memory unit printed; this is not the same as the last
5185 address printed if several units were printed on the last line of output.
5188 @section Automatic display
5189 @cindex automatic display
5190 @cindex display of expressions
5192 If you find that you want to print the value of an expression frequently
5193 (to see how it changes), you might want to add it to the @dfn{automatic
5194 display list} so that @value{GDBN} prints its value each time your program stops.
5195 Each expression added to the list is given a number to identify it;
5196 to remove an expression from the list, you specify that number.
5197 The automatic display looks like this:
5201 3: bar[5] = (struct hack *) 0x3804
5205 This display shows item numbers, expressions and their current values. As with
5206 displays you request manually using @code{x} or @code{print}, you can
5207 specify the output format you prefer; in fact, @code{display} decides
5208 whether to use @code{print} or @code{x} depending on how elaborate your
5209 format specification is---it uses @code{x} if you specify a unit size,
5210 or one of the two formats (@samp{i} and @samp{s}) that are only
5211 supported by @code{x}; otherwise it uses @code{print}.
5215 @item display @var{expr}
5216 Add the expression @var{expr} to the list of expressions to display
5217 each time your program stops. @xref{Expressions, ,Expressions}.
5219 @code{display} does not repeat if you press @key{RET} again after using it.
5221 @item display/@var{fmt} @var{expr}
5222 For @var{fmt} specifying only a display format and not a size or
5223 count, add the expression @var{expr} to the auto-display list but
5224 arrange to display it each time in the specified format @var{fmt}.
5225 @xref{Output Formats,,Output formats}.
5227 @item display/@var{fmt} @var{addr}
5228 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
5229 number of units, add the expression @var{addr} as a memory address to
5230 be examined each time your program stops. Examining means in effect
5231 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
5234 For example, @samp{display/i $pc} can be helpful, to see the machine
5235 instruction about to be executed each time execution stops (@samp{$pc}
5236 is a common name for the program counter; @pxref{Registers, ,Registers}).
5239 @kindex delete display
5241 @item undisplay @var{dnums}@dots{}
5242 @itemx delete display @var{dnums}@dots{}
5243 Remove item numbers @var{dnums} from the list of expressions to display.
5245 @code{undisplay} does not repeat if you press @key{RET} after using it.
5246 (Otherwise you would just get the error @samp{No display number @dots{}}.)
5248 @kindex disable display
5249 @item disable display @var{dnums}@dots{}
5250 Disable the display of item numbers @var{dnums}. A disabled display
5251 item is not printed automatically, but is not forgotten. It may be
5252 enabled again later.
5254 @kindex enable display
5255 @item enable display @var{dnums}@dots{}
5256 Enable display of item numbers @var{dnums}. It becomes effective once
5257 again in auto display of its expression, until you specify otherwise.
5260 Display the current values of the expressions on the list, just as is
5261 done when your program stops.
5263 @kindex info display
5265 Print the list of expressions previously set up to display
5266 automatically, each one with its item number, but without showing the
5267 values. This includes disabled expressions, which are marked as such.
5268 It also includes expressions which would not be displayed right now
5269 because they refer to automatic variables not currently available.
5272 @cindex display disabled out of scope
5273 If a display expression refers to local variables, then it does not make
5274 sense outside the lexical context for which it was set up. Such an
5275 expression is disabled when execution enters a context where one of its
5276 variables is not defined. For example, if you give the command
5277 @code{display last_char} while inside a function with an argument
5278 @code{last_char}, @value{GDBN} displays this argument while your program
5279 continues to stop inside that function. When it stops elsewhere---where
5280 there is no variable @code{last_char}---the display is disabled
5281 automatically. The next time your program stops where @code{last_char}
5282 is meaningful, you can enable the display expression once again.
5284 @node Print Settings
5285 @section Print settings
5287 @cindex format options
5288 @cindex print settings
5289 @value{GDBN} provides the following ways to control how arrays, structures,
5290 and symbols are printed.
5293 These settings are useful for debugging programs in any language:
5297 @item set print address
5298 @itemx set print address on
5299 @cindex print/don't print memory addresses
5300 @value{GDBN} prints memory addresses showing the location of stack
5301 traces, structure values, pointer values, breakpoints, and so forth,
5302 even when it also displays the contents of those addresses. The default
5303 is @code{on}. For example, this is what a stack frame display looks like with
5304 @code{set print address on}:
5309 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
5311 530 if (lquote != def_lquote)
5315 @item set print address off
5316 Do not print addresses when displaying their contents. For example,
5317 this is the same stack frame displayed with @code{set print address off}:
5321 (@value{GDBP}) set print addr off
5323 #0 set_quotes (lq="<<", rq=">>") at input.c:530
5324 530 if (lquote != def_lquote)
5328 You can use @samp{set print address off} to eliminate all machine
5329 dependent displays from the @value{GDBN} interface. For example, with
5330 @code{print address off}, you should get the same text for backtraces on
5331 all machines---whether or not they involve pointer arguments.
5334 @item show print address
5335 Show whether or not addresses are to be printed.
5338 When @value{GDBN} prints a symbolic address, it normally prints the
5339 closest earlier symbol plus an offset. If that symbol does not uniquely
5340 identify the address (for example, it is a name whose scope is a single
5341 source file), you may need to clarify. One way to do this is with
5342 @code{info line}, for example @samp{info line *0x4537}. Alternately,
5343 you can set @value{GDBN} to print the source file and line number when
5344 it prints a symbolic address:
5347 @item set print symbol-filename on
5348 @cindex closest symbol and offset for an address
5349 Tell @value{GDBN} to print the source file name and line number of a
5350 symbol in the symbolic form of an address.
5352 @item set print symbol-filename off
5353 Do not print source file name and line number of a symbol. This is the
5356 @item show print symbol-filename
5357 Show whether or not @value{GDBN} will print the source file name and
5358 line number of a symbol in the symbolic form of an address.
5361 Another situation where it is helpful to show symbol filenames and line
5362 numbers is when disassembling code; @value{GDBN} shows you the line
5363 number and source file that corresponds to each instruction.
5365 Also, you may wish to see the symbolic form only if the address being
5366 printed is reasonably close to the closest earlier symbol:
5369 @item set print max-symbolic-offset @var{max-offset}
5370 @cindex maximum value for offset of closest symbol
5371 Tell @value{GDBN} to only display the symbolic form of an address if the
5372 offset between the closest earlier symbol and the address is less than
5373 @var{max-offset}. The default is 0, which tells @value{GDBN}
5374 to always print the symbolic form of an address if any symbol precedes it.
5376 @item show print max-symbolic-offset
5377 Ask how large the maximum offset is that @value{GDBN} prints in a
5381 @cindex wild pointer, interpreting
5382 @cindex pointer, finding referent
5383 If you have a pointer and you are not sure where it points, try
5384 @samp{set print symbol-filename on}. Then you can determine the name
5385 and source file location of the variable where it points, using
5386 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
5387 For example, here @value{GDBN} shows that a variable @code{ptt} points
5388 at another variable @code{t}, defined in @file{hi2.c}:
5391 (@value{GDBP}) set print symbol-filename on
5392 (@value{GDBP}) p/a ptt
5393 $4 = 0xe008 <t in hi2.c>
5397 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
5398 does not show the symbol name and filename of the referent, even with
5399 the appropriate @code{set print} options turned on.
5402 Other settings control how different kinds of objects are printed:
5405 @item set print array
5406 @itemx set print array on
5407 @cindex pretty print arrays
5408 Pretty print arrays. This format is more convenient to read,
5409 but uses more space. The default is off.
5411 @item set print array off
5412 Return to compressed format for arrays.
5414 @item show print array
5415 Show whether compressed or pretty format is selected for displaying
5418 @item set print elements @var{number-of-elements}
5419 @cindex number of array elements to print
5420 Set a limit on how many elements of an array @value{GDBN} will print.
5421 If @value{GDBN} is printing a large array, it stops printing after it has
5422 printed the number of elements set by the @code{set print elements} command.
5423 This limit also applies to the display of strings.
5424 When @value{GDBN} starts, this limit is set to 200.
5425 Setting @var{number-of-elements} to zero means that the printing is unlimited.
5427 @item show print elements
5428 Display the number of elements of a large array that @value{GDBN} will print.
5429 If the number is 0, then the printing is unlimited.
5431 @item set print null-stop
5432 @cindex @sc{null} elements in arrays
5433 Cause @value{GDBN} to stop printing the characters of an array when the first
5434 @sc{null} is encountered. This is useful when large arrays actually
5435 contain only short strings.
5438 @item set print pretty on
5439 Cause @value{GDBN} to print structures in an indented format with one member
5440 per line, like this:
5455 @item set print pretty off
5456 Cause @value{GDBN} to print structures in a compact format, like this:
5460 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
5461 meat = 0x54 "Pork"@}
5466 This is the default format.
5468 @item show print pretty
5469 Show which format @value{GDBN} is using to print structures.
5471 @item set print sevenbit-strings on
5472 @cindex eight-bit characters in strings
5473 @cindex octal escapes in strings
5474 Print using only seven-bit characters; if this option is set,
5475 @value{GDBN} displays any eight-bit characters (in strings or
5476 character values) using the notation @code{\}@var{nnn}. This setting is
5477 best if you are working in English (@sc{ascii}) and you use the
5478 high-order bit of characters as a marker or ``meta'' bit.
5480 @item set print sevenbit-strings off
5481 Print full eight-bit characters. This allows the use of more
5482 international character sets, and is the default.
5484 @item show print sevenbit-strings
5485 Show whether or not @value{GDBN} is printing only seven-bit characters.
5487 @item set print union on
5488 @cindex unions in structures, printing
5489 Tell @value{GDBN} to print unions which are contained in structures. This
5490 is the default setting.
5492 @item set print union off
5493 Tell @value{GDBN} not to print unions which are contained in structures.
5495 @item show print union
5496 Ask @value{GDBN} whether or not it will print unions which are contained in
5499 For example, given the declarations
5502 typedef enum @{Tree, Bug@} Species;
5503 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
5504 typedef enum @{Caterpillar, Cocoon, Butterfly@}
5515 struct thing foo = @{Tree, @{Acorn@}@};
5519 with @code{set print union on} in effect @samp{p foo} would print
5522 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
5526 and with @code{set print union off} in effect it would print
5529 $1 = @{it = Tree, form = @{...@}@}
5535 These settings are of interest when debugging C@t{++} programs:
5538 @cindex demangling C@t{++} names
5539 @item set print demangle
5540 @itemx set print demangle on
5541 Print C@t{++} names in their source form rather than in the encoded
5542 (``mangled'') form passed to the assembler and linker for type-safe
5543 linkage. The default is on.
5545 @item show print demangle
5546 Show whether C@t{++} names are printed in mangled or demangled form.
5548 @item set print asm-demangle
5549 @itemx set print asm-demangle on
5550 Print C@t{++} names in their source form rather than their mangled form, even
5551 in assembler code printouts such as instruction disassemblies.
5554 @item show print asm-demangle
5555 Show whether C@t{++} names in assembly listings are printed in mangled
5558 @cindex C@t{++} symbol decoding style
5559 @cindex symbol decoding style, C@t{++}
5560 @item set demangle-style @var{style}
5561 Choose among several encoding schemes used by different compilers to
5562 represent C@t{++} names. The choices for @var{style} are currently:
5566 Allow @value{GDBN} to choose a decoding style by inspecting your program.
5569 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
5570 This is the default.
5573 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
5576 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
5579 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
5580 @strong{Warning:} this setting alone is not sufficient to allow
5581 debugging @code{cfront}-generated executables. @value{GDBN} would
5582 require further enhancement to permit that.
5585 If you omit @var{style}, you will see a list of possible formats.
5587 @item show demangle-style
5588 Display the encoding style currently in use for decoding C@t{++} symbols.
5590 @item set print object
5591 @itemx set print object on
5592 @cindex derived type of an object, printing
5593 When displaying a pointer to an object, identify the @emph{actual}
5594 (derived) type of the object rather than the @emph{declared} type, using
5595 the virtual function table.
5597 @item set print object off
5598 Display only the declared type of objects, without reference to the
5599 virtual function table. This is the default setting.
5601 @item show print object
5602 Show whether actual, or declared, object types are displayed.
5604 @item set print static-members
5605 @itemx set print static-members on
5606 @cindex static members of C@t{++} objects
5607 Print static members when displaying a C@t{++} object. The default is on.
5609 @item set print static-members off
5610 Do not print static members when displaying a C@t{++} object.
5612 @item show print static-members
5613 Show whether C@t{++} static members are printed, or not.
5615 @c These don't work with HP ANSI C++ yet.
5616 @item set print vtbl
5617 @itemx set print vtbl on
5618 @cindex pretty print C@t{++} virtual function tables
5619 Pretty print C@t{++} virtual function tables. The default is off.
5620 (The @code{vtbl} commands do not work on programs compiled with the HP
5621 ANSI C@t{++} compiler (@code{aCC}).)
5623 @item set print vtbl off
5624 Do not pretty print C@t{++} virtual function tables.
5626 @item show print vtbl
5627 Show whether C@t{++} virtual function tables are pretty printed, or not.
5631 @section Value history
5633 @cindex value history
5634 Values printed by the @code{print} command are saved in the @value{GDBN}
5635 @dfn{value history}. This allows you to refer to them in other expressions.
5636 Values are kept until the symbol table is re-read or discarded
5637 (for example with the @code{file} or @code{symbol-file} commands).
5638 When the symbol table changes, the value history is discarded,
5639 since the values may contain pointers back to the types defined in the
5644 @cindex history number
5645 The values printed are given @dfn{history numbers} by which you can
5646 refer to them. These are successive integers starting with one.
5647 @code{print} shows you the history number assigned to a value by
5648 printing @samp{$@var{num} = } before the value; here @var{num} is the
5651 To refer to any previous value, use @samp{$} followed by the value's
5652 history number. The way @code{print} labels its output is designed to
5653 remind you of this. Just @code{$} refers to the most recent value in
5654 the history, and @code{$$} refers to the value before that.
5655 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
5656 is the value just prior to @code{$$}, @code{$$1} is equivalent to
5657 @code{$$}, and @code{$$0} is equivalent to @code{$}.
5659 For example, suppose you have just printed a pointer to a structure and
5660 want to see the contents of the structure. It suffices to type
5666 If you have a chain of structures where the component @code{next} points
5667 to the next one, you can print the contents of the next one with this:
5674 You can print successive links in the chain by repeating this
5675 command---which you can do by just typing @key{RET}.
5677 Note that the history records values, not expressions. If the value of
5678 @code{x} is 4 and you type these commands:
5686 then the value recorded in the value history by the @code{print} command
5687 remains 4 even though the value of @code{x} has changed.
5692 Print the last ten values in the value history, with their item numbers.
5693 This is like @samp{p@ $$9} repeated ten times, except that @code{show
5694 values} does not change the history.
5696 @item show values @var{n}
5697 Print ten history values centered on history item number @var{n}.
5700 Print ten history values just after the values last printed. If no more
5701 values are available, @code{show values +} produces no display.
5704 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
5705 same effect as @samp{show values +}.
5707 @node Convenience Vars
5708 @section Convenience variables
5710 @cindex convenience variables
5711 @value{GDBN} provides @dfn{convenience variables} that you can use within
5712 @value{GDBN} to hold on to a value and refer to it later. These variables
5713 exist entirely within @value{GDBN}; they are not part of your program, and
5714 setting a convenience variable has no direct effect on further execution
5715 of your program. That is why you can use them freely.
5717 Convenience variables are prefixed with @samp{$}. Any name preceded by
5718 @samp{$} can be used for a convenience variable, unless it is one of
5719 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
5720 (Value history references, in contrast, are @emph{numbers} preceded
5721 by @samp{$}. @xref{Value History, ,Value history}.)
5723 You can save a value in a convenience variable with an assignment
5724 expression, just as you would set a variable in your program.
5728 set $foo = *object_ptr
5732 would save in @code{$foo} the value contained in the object pointed to by
5735 Using a convenience variable for the first time creates it, but its
5736 value is @code{void} until you assign a new value. You can alter the
5737 value with another assignment at any time.
5739 Convenience variables have no fixed types. You can assign a convenience
5740 variable any type of value, including structures and arrays, even if
5741 that variable already has a value of a different type. The convenience
5742 variable, when used as an expression, has the type of its current value.
5745 @kindex show convenience
5746 @item show convenience
5747 Print a list of convenience variables used so far, and their values.
5748 Abbreviated @code{show conv}.
5751 One of the ways to use a convenience variable is as a counter to be
5752 incremented or a pointer to be advanced. For example, to print
5753 a field from successive elements of an array of structures:
5757 print bar[$i++]->contents
5761 Repeat that command by typing @key{RET}.
5763 Some convenience variables are created automatically by @value{GDBN} and given
5764 values likely to be useful.
5767 @vindex $_@r{, convenience variable}
5769 The variable @code{$_} is automatically set by the @code{x} command to
5770 the last address examined (@pxref{Memory, ,Examining memory}). Other
5771 commands which provide a default address for @code{x} to examine also
5772 set @code{$_} to that address; these commands include @code{info line}
5773 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
5774 except when set by the @code{x} command, in which case it is a pointer
5775 to the type of @code{$__}.
5777 @vindex $__@r{, convenience variable}
5779 The variable @code{$__} is automatically set by the @code{x} command
5780 to the value found in the last address examined. Its type is chosen
5781 to match the format in which the data was printed.
5784 @vindex $_exitcode@r{, convenience variable}
5785 The variable @code{$_exitcode} is automatically set to the exit code when
5786 the program being debugged terminates.
5789 On HP-UX systems, if you refer to a function or variable name that
5790 begins with a dollar sign, @value{GDBN} searches for a user or system
5791 name first, before it searches for a convenience variable.
5797 You can refer to machine register contents, in expressions, as variables
5798 with names starting with @samp{$}. The names of registers are different
5799 for each machine; use @code{info registers} to see the names used on
5803 @kindex info registers
5804 @item info registers
5805 Print the names and values of all registers except floating-point
5806 and vector registers (in the selected stack frame).
5808 @kindex info all-registers
5809 @cindex floating point registers
5810 @item info all-registers
5811 Print the names and values of all registers, including floating-point
5812 and vector registers (in the selected stack frame).
5814 @item info registers @var{regname} @dots{}
5815 Print the @dfn{relativized} value of each specified register @var{regname}.
5816 As discussed in detail below, register values are normally relative to
5817 the selected stack frame. @var{regname} may be any register name valid on
5818 the machine you are using, with or without the initial @samp{$}.
5821 @value{GDBN} has four ``standard'' register names that are available (in
5822 expressions) on most machines---whenever they do not conflict with an
5823 architecture's canonical mnemonics for registers. The register names
5824 @code{$pc} and @code{$sp} are used for the program counter register and
5825 the stack pointer. @code{$fp} is used for a register that contains a
5826 pointer to the current stack frame, and @code{$ps} is used for a
5827 register that contains the processor status. For example,
5828 you could print the program counter in hex with
5835 or print the instruction to be executed next with
5842 or add four to the stack pointer@footnote{This is a way of removing
5843 one word from the stack, on machines where stacks grow downward in
5844 memory (most machines, nowadays). This assumes that the innermost
5845 stack frame is selected; setting @code{$sp} is not allowed when other
5846 stack frames are selected. To pop entire frames off the stack,
5847 regardless of machine architecture, use @code{return};
5848 see @ref{Returning, ,Returning from a function}.} with
5854 Whenever possible, these four standard register names are available on
5855 your machine even though the machine has different canonical mnemonics,
5856 so long as there is no conflict. The @code{info registers} command
5857 shows the canonical names. For example, on the SPARC, @code{info
5858 registers} displays the processor status register as @code{$psr} but you
5859 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
5860 is an alias for the @sc{eflags} register.
5862 @value{GDBN} always considers the contents of an ordinary register as an
5863 integer when the register is examined in this way. Some machines have
5864 special registers which can hold nothing but floating point; these
5865 registers are considered to have floating point values. There is no way
5866 to refer to the contents of an ordinary register as floating point value
5867 (although you can @emph{print} it as a floating point value with
5868 @samp{print/f $@var{regname}}).
5870 Some registers have distinct ``raw'' and ``virtual'' data formats. This
5871 means that the data format in which the register contents are saved by
5872 the operating system is not the same one that your program normally
5873 sees. For example, the registers of the 68881 floating point
5874 coprocessor are always saved in ``extended'' (raw) format, but all C
5875 programs expect to work with ``double'' (virtual) format. In such
5876 cases, @value{GDBN} normally works with the virtual format only (the format
5877 that makes sense for your program), but the @code{info registers} command
5878 prints the data in both formats.
5880 Normally, register values are relative to the selected stack frame
5881 (@pxref{Selection, ,Selecting a frame}). This means that you get the
5882 value that the register would contain if all stack frames farther in
5883 were exited and their saved registers restored. In order to see the
5884 true contents of hardware registers, you must select the innermost
5885 frame (with @samp{frame 0}).
5887 However, @value{GDBN} must deduce where registers are saved, from the machine
5888 code generated by your compiler. If some registers are not saved, or if
5889 @value{GDBN} is unable to locate the saved registers, the selected stack
5890 frame makes no difference.
5892 @node Floating Point Hardware
5893 @section Floating point hardware
5894 @cindex floating point
5896 Depending on the configuration, @value{GDBN} may be able to give
5897 you more information about the status of the floating point hardware.
5902 Display hardware-dependent information about the floating
5903 point unit. The exact contents and layout vary depending on the
5904 floating point chip. Currently, @samp{info float} is supported on
5905 the ARM and x86 machines.
5909 @section Vector Unit
5912 Depending on the configuration, @value{GDBN} may be able to give you
5913 more information about the status of the vector unit.
5918 Display information about the vector unit. The exact contents and
5919 layout vary depending on the hardware.
5922 @node Auxiliary Vector
5923 @section Operating system auxiliary vector
5924 @cindex auxiliary vector
5925 @cindex vector, auxiliary
5927 Some operating systems supply an @dfn{auxiliary vector} to programs at
5928 startup. This is akin to the arguments and environment that you
5929 specify for a program, but contains a system-dependent variety of
5930 binary values that tell system libraries important details about the
5931 hardware, operating system, and process. Each value's purpose is
5932 identified by an integer tag; the meanings are well-known but system-specific.
5933 Depending on the configuration and operating system facilities,
5934 @value{GDBN} may be able to show you this information.
5939 Display the auxiliary vector of the inferior, which can be either a
5940 live process or a core dump file. @value{GDBN} prints each tag value
5941 numerically, and also shows names and text descriptions for recognized
5942 tags. Some values in the vector are numbers, some bit masks, and some
5943 pointers to strings or other data. @value{GDBN} displays each value in the
5944 most appropriate form for a recognized tag, and in hexadecimal for
5945 an unrecognized tag.
5948 @node Memory Region Attributes
5949 @section Memory region attributes
5950 @cindex memory region attributes
5952 @dfn{Memory region attributes} allow you to describe special handling
5953 required by regions of your target's memory. @value{GDBN} uses attributes
5954 to determine whether to allow certain types of memory accesses; whether to
5955 use specific width accesses; and whether to cache target memory.
5957 Defined memory regions can be individually enabled and disabled. When a
5958 memory region is disabled, @value{GDBN} uses the default attributes when
5959 accessing memory in that region. Similarly, if no memory regions have
5960 been defined, @value{GDBN} uses the default attributes when accessing
5963 When a memory region is defined, it is given a number to identify it;
5964 to enable, disable, or remove a memory region, you specify that number.
5968 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
5969 Define memory region bounded by @var{lower} and @var{upper} with
5970 attributes @var{attributes}@dots{}. Note that @var{upper} == 0 is a
5971 special case: it is treated as the the target's maximum memory address.
5972 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
5975 @item delete mem @var{nums}@dots{}
5976 Remove memory regions @var{nums}@dots{}.
5979 @item disable mem @var{nums}@dots{}
5980 Disable memory regions @var{nums}@dots{}.
5981 A disabled memory region is not forgotten.
5982 It may be enabled again later.
5985 @item enable mem @var{nums}@dots{}
5986 Enable memory regions @var{nums}@dots{}.
5990 Print a table of all defined memory regions, with the following columns
5994 @item Memory Region Number
5995 @item Enabled or Disabled.
5996 Enabled memory regions are marked with @samp{y}.
5997 Disabled memory regions are marked with @samp{n}.
6000 The address defining the inclusive lower bound of the memory region.
6003 The address defining the exclusive upper bound of the memory region.
6006 The list of attributes set for this memory region.
6011 @subsection Attributes
6013 @subsubsection Memory Access Mode
6014 The access mode attributes set whether @value{GDBN} may make read or
6015 write accesses to a memory region.
6017 While these attributes prevent @value{GDBN} from performing invalid
6018 memory accesses, they do nothing to prevent the target system, I/O DMA,
6019 etc. from accessing memory.
6023 Memory is read only.
6025 Memory is write only.
6027 Memory is read/write. This is the default.
6030 @subsubsection Memory Access Size
6031 The acccess size attributes tells @value{GDBN} to use specific sized
6032 accesses in the memory region. Often memory mapped device registers
6033 require specific sized accesses. If no access size attribute is
6034 specified, @value{GDBN} may use accesses of any size.
6038 Use 8 bit memory accesses.
6040 Use 16 bit memory accesses.
6042 Use 32 bit memory accesses.
6044 Use 64 bit memory accesses.
6047 @c @subsubsection Hardware/Software Breakpoints
6048 @c The hardware/software breakpoint attributes set whether @value{GDBN}
6049 @c will use hardware or software breakpoints for the internal breakpoints
6050 @c used by the step, next, finish, until, etc. commands.
6054 @c Always use hardware breakpoints
6055 @c @item swbreak (default)
6058 @subsubsection Data Cache
6059 The data cache attributes set whether @value{GDBN} will cache target
6060 memory. While this generally improves performance by reducing debug
6061 protocol overhead, it can lead to incorrect results because @value{GDBN}
6062 does not know about volatile variables or memory mapped device
6067 Enable @value{GDBN} to cache target memory.
6069 Disable @value{GDBN} from caching target memory. This is the default.
6072 @c @subsubsection Memory Write Verification
6073 @c The memory write verification attributes set whether @value{GDBN}
6074 @c will re-reads data after each write to verify the write was successful.
6078 @c @item noverify (default)
6081 @node Dump/Restore Files
6082 @section Copy between memory and a file
6083 @cindex dump/restore files
6084 @cindex append data to a file
6085 @cindex dump data to a file
6086 @cindex restore data from a file
6088 You can use the commands @code{dump}, @code{append}, and
6089 @code{restore} to copy data between target memory and a file. The
6090 @code{dump} and @code{append} commands write data to a file, and the
6091 @code{restore} command reads data from a file back into the inferior's
6092 memory. Files may be in binary, Motorola S-record, Intel hex, or
6093 Tektronix Hex format; however, @value{GDBN} can only append to binary
6099 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6100 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
6101 Dump the contents of memory from @var{start_addr} to @var{end_addr},
6102 or the value of @var{expr}, to @var{filename} in the given format.
6104 The @var{format} parameter may be any one of:
6111 Motorola S-record format.
6113 Tektronix Hex format.
6116 @value{GDBN} uses the same definitions of these formats as the
6117 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
6118 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
6122 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6123 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
6124 Append the contents of memory from @var{start_addr} to @var{end_addr},
6125 or the value of @var{expr}, to @var{filename}, in raw binary form.
6126 (@value{GDBN} can only append data to files in raw binary form.)
6129 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
6130 Restore the contents of file @var{filename} into memory. The
6131 @code{restore} command can automatically recognize any known @sc{bfd}
6132 file format, except for raw binary. To restore a raw binary file you
6133 must specify the optional keyword @code{binary} after the filename.
6135 If @var{bias} is non-zero, its value will be added to the addresses
6136 contained in the file. Binary files always start at address zero, so
6137 they will be restored at address @var{bias}. Other bfd files have
6138 a built-in location; they will be restored at offset @var{bias}
6141 If @var{start} and/or @var{end} are non-zero, then only data between
6142 file offset @var{start} and file offset @var{end} will be restored.
6143 These offsets are relative to the addresses in the file, before
6144 the @var{bias} argument is applied.
6148 @node Character Sets
6149 @section Character Sets
6150 @cindex character sets
6152 @cindex translating between character sets
6153 @cindex host character set
6154 @cindex target character set
6156 If the program you are debugging uses a different character set to
6157 represent characters and strings than the one @value{GDBN} uses itself,
6158 @value{GDBN} can automatically translate between the character sets for
6159 you. The character set @value{GDBN} uses we call the @dfn{host
6160 character set}; the one the inferior program uses we call the
6161 @dfn{target character set}.
6163 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
6164 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
6165 remote protocol (@pxref{Remote,Remote Debugging}) to debug a program
6166 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
6167 then the host character set is Latin-1, and the target character set is
6168 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
6169 target-charset EBCDIC-US}, then @value{GDBN} translates between
6170 @sc{ebcdic} and Latin 1 as you print character or string values, or use
6171 character and string literals in expressions.
6173 @value{GDBN} has no way to automatically recognize which character set
6174 the inferior program uses; you must tell it, using the @code{set
6175 target-charset} command, described below.
6177 Here are the commands for controlling @value{GDBN}'s character set
6181 @item set target-charset @var{charset}
6182 @kindex set target-charset
6183 Set the current target character set to @var{charset}. We list the
6184 character set names @value{GDBN} recognizes below, but if you type
6185 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6186 list the target character sets it supports.
6190 @item set host-charset @var{charset}
6191 @kindex set host-charset
6192 Set the current host character set to @var{charset}.
6194 By default, @value{GDBN} uses a host character set appropriate to the
6195 system it is running on; you can override that default using the
6196 @code{set host-charset} command.
6198 @value{GDBN} can only use certain character sets as its host character
6199 set. We list the character set names @value{GDBN} recognizes below, and
6200 indicate which can be host character sets, but if you type
6201 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6202 list the host character sets it supports.
6204 @item set charset @var{charset}
6206 Set the current host and target character sets to @var{charset}. As
6207 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
6208 @value{GDBN} will list the name of the character sets that can be used
6209 for both host and target.
6213 @kindex show charset
6214 Show the names of the current host and target charsets.
6216 @itemx show host-charset
6217 @kindex show host-charset
6218 Show the name of the current host charset.
6220 @itemx show target-charset
6221 @kindex show target-charset
6222 Show the name of the current target charset.
6226 @value{GDBN} currently includes support for the following character
6232 @cindex ASCII character set
6233 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
6237 @cindex ISO 8859-1 character set
6238 @cindex ISO Latin 1 character set
6239 The ISO Latin 1 character set. This extends @sc{ascii} with accented
6240 characters needed for French, German, and Spanish. @value{GDBN} can use
6241 this as its host character set.
6245 @cindex EBCDIC character set
6246 @cindex IBM1047 character set
6247 Variants of the @sc{ebcdic} character set, used on some of IBM's
6248 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
6249 @value{GDBN} cannot use these as its host character set.
6253 Note that these are all single-byte character sets. More work inside
6254 GDB is needed to support multi-byte or variable-width character
6255 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
6257 Here is an example of @value{GDBN}'s character set support in action.
6258 Assume that the following source code has been placed in the file
6259 @file{charset-test.c}:
6265 = @{72, 101, 108, 108, 111, 44, 32, 119,
6266 111, 114, 108, 100, 33, 10, 0@};
6267 char ibm1047_hello[]
6268 = @{200, 133, 147, 147, 150, 107, 64, 166,
6269 150, 153, 147, 132, 90, 37, 0@};
6273 printf ("Hello, world!\n");
6277 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
6278 containing the string @samp{Hello, world!} followed by a newline,
6279 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
6281 We compile the program, and invoke the debugger on it:
6284 $ gcc -g charset-test.c -o charset-test
6285 $ gdb -nw charset-test
6286 GNU gdb 2001-12-19-cvs
6287 Copyright 2001 Free Software Foundation, Inc.
6292 We can use the @code{show charset} command to see what character sets
6293 @value{GDBN} is currently using to interpret and display characters and
6298 The current host and target character set is `ISO-8859-1'.
6302 For the sake of printing this manual, let's use @sc{ascii} as our
6303 initial character set:
6305 (gdb) set charset ASCII
6307 The current host and target character set is `ASCII'.
6311 Let's assume that @sc{ascii} is indeed the correct character set for our
6312 host system --- in other words, let's assume that if @value{GDBN} prints
6313 characters using the @sc{ascii} character set, our terminal will display
6314 them properly. Since our current target character set is also
6315 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
6318 (gdb) print ascii_hello
6319 $1 = 0x401698 "Hello, world!\n"
6320 (gdb) print ascii_hello[0]
6325 @value{GDBN} uses the target character set for character and string
6326 literals you use in expressions:
6334 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
6337 @value{GDBN} relies on the user to tell it which character set the
6338 target program uses. If we print @code{ibm1047_hello} while our target
6339 character set is still @sc{ascii}, we get jibberish:
6342 (gdb) print ibm1047_hello
6343 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
6344 (gdb) print ibm1047_hello[0]
6349 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
6350 @value{GDBN} tells us the character sets it supports:
6353 (gdb) set target-charset
6354 ASCII EBCDIC-US IBM1047 ISO-8859-1
6355 (gdb) set target-charset
6358 We can select @sc{ibm1047} as our target character set, and examine the
6359 program's strings again. Now the @sc{ascii} string is wrong, but
6360 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
6361 target character set, @sc{ibm1047}, to the host character set,
6362 @sc{ascii}, and they display correctly:
6365 (gdb) set target-charset IBM1047
6367 The current host character set is `ASCII'.
6368 The current target character set is `IBM1047'.
6369 (gdb) print ascii_hello
6370 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
6371 (gdb) print ascii_hello[0]
6373 (gdb) print ibm1047_hello
6374 $8 = 0x4016a8 "Hello, world!\n"
6375 (gdb) print ibm1047_hello[0]
6380 As above, @value{GDBN} uses the target character set for character and
6381 string literals you use in expressions:
6389 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
6394 @chapter C Preprocessor Macros
6396 Some languages, such as C and C@t{++}, provide a way to define and invoke
6397 ``preprocessor macros'' which expand into strings of tokens.
6398 @value{GDBN} can evaluate expressions containing macro invocations, show
6399 the result of macro expansion, and show a macro's definition, including
6400 where it was defined.
6402 You may need to compile your program specially to provide @value{GDBN}
6403 with information about preprocessor macros. Most compilers do not
6404 include macros in their debugging information, even when you compile
6405 with the @option{-g} flag. @xref{Compilation}.
6407 A program may define a macro at one point, remove that definition later,
6408 and then provide a different definition after that. Thus, at different
6409 points in the program, a macro may have different definitions, or have
6410 no definition at all. If there is a current stack frame, @value{GDBN}
6411 uses the macros in scope at that frame's source code line. Otherwise,
6412 @value{GDBN} uses the macros in scope at the current listing location;
6415 At the moment, @value{GDBN} does not support the @code{##}
6416 token-splicing operator, the @code{#} stringification operator, or
6417 variable-arity macros.
6419 Whenever @value{GDBN} evaluates an expression, it always expands any
6420 macro invocations present in the expression. @value{GDBN} also provides
6421 the following commands for working with macros explicitly.
6425 @kindex macro expand
6426 @cindex macro expansion, showing the results of preprocessor
6427 @cindex preprocessor macro expansion, showing the results of
6428 @cindex expanding preprocessor macros
6429 @item macro expand @var{expression}
6430 @itemx macro exp @var{expression}
6431 Show the results of expanding all preprocessor macro invocations in
6432 @var{expression}. Since @value{GDBN} simply expands macros, but does
6433 not parse the result, @var{expression} need not be a valid expression;
6434 it can be any string of tokens.
6436 @item macro expand-once @var{expression}
6437 @itemx macro exp1 @var{expression}
6438 @cindex expand macro once
6439 @i{(This command is not yet implemented.)} Show the results of
6440 expanding those preprocessor macro invocations that appear explicitly in
6441 @var{expression}. Macro invocations appearing in that expansion are
6442 left unchanged. This command allows you to see the effect of a
6443 particular macro more clearly, without being confused by further
6444 expansions. Since @value{GDBN} simply expands macros, but does not
6445 parse the result, @var{expression} need not be a valid expression; it
6446 can be any string of tokens.
6449 @cindex macro definition, showing
6450 @cindex definition, showing a macro's
6451 @item info macro @var{macro}
6452 Show the definition of the macro named @var{macro}, and describe the
6453 source location where that definition was established.
6455 @kindex macro define
6456 @cindex user-defined macros
6457 @cindex defining macros interactively
6458 @cindex macros, user-defined
6459 @item macro define @var{macro} @var{replacement-list}
6460 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
6461 @i{(This command is not yet implemented.)} Introduce a definition for a
6462 preprocessor macro named @var{macro}, invocations of which are replaced
6463 by the tokens given in @var{replacement-list}. The first form of this
6464 command defines an ``object-like'' macro, which takes no arguments; the
6465 second form defines a ``function-like'' macro, which takes the arguments
6466 given in @var{arglist}.
6468 A definition introduced by this command is in scope in every expression
6469 evaluated in @value{GDBN}, until it is removed with the @command{macro
6470 undef} command, described below. The definition overrides all
6471 definitions for @var{macro} present in the program being debugged, as
6472 well as any previous user-supplied definition.
6475 @item macro undef @var{macro}
6476 @i{(This command is not yet implemented.)} Remove any user-supplied
6477 definition for the macro named @var{macro}. This command only affects
6478 definitions provided with the @command{macro define} command, described
6479 above; it cannot remove definitions present in the program being
6484 @cindex macros, example of debugging with
6485 Here is a transcript showing the above commands in action. First, we
6486 show our source files:
6494 #define ADD(x) (M + x)
6499 printf ("Hello, world!\n");
6501 printf ("We're so creative.\n");
6503 printf ("Goodbye, world!\n");
6510 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
6511 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
6512 compiler includes information about preprocessor macros in the debugging
6516 $ gcc -gdwarf-2 -g3 sample.c -o sample
6520 Now, we start @value{GDBN} on our sample program:
6524 GNU gdb 2002-05-06-cvs
6525 Copyright 2002 Free Software Foundation, Inc.
6526 GDB is free software, @dots{}
6530 We can expand macros and examine their definitions, even when the
6531 program is not running. @value{GDBN} uses the current listing position
6532 to decide which macro definitions are in scope:
6538 5 #define ADD(x) (M + x)
6543 10 printf ("Hello, world!\n");
6545 12 printf ("We're so creative.\n");
6546 (gdb) info macro ADD
6547 Defined at /home/jimb/gdb/macros/play/sample.c:5
6548 #define ADD(x) (M + x)
6550 Defined at /home/jimb/gdb/macros/play/sample.h:1
6551 included at /home/jimb/gdb/macros/play/sample.c:2
6553 (gdb) macro expand ADD(1)
6554 expands to: (42 + 1)
6555 (gdb) macro expand-once ADD(1)
6556 expands to: once (M + 1)
6560 In the example above, note that @command{macro expand-once} expands only
6561 the macro invocation explicit in the original text --- the invocation of
6562 @code{ADD} --- but does not expand the invocation of the macro @code{M},
6563 which was introduced by @code{ADD}.
6565 Once the program is running, GDB uses the macro definitions in force at
6566 the source line of the current stack frame:
6570 Breakpoint 1 at 0x8048370: file sample.c, line 10.
6572 Starting program: /home/jimb/gdb/macros/play/sample
6574 Breakpoint 1, main () at sample.c:10
6575 10 printf ("Hello, world!\n");
6579 At line 10, the definition of the macro @code{N} at line 9 is in force:
6583 Defined at /home/jimb/gdb/macros/play/sample.c:9
6585 (gdb) macro expand N Q M
6592 As we step over directives that remove @code{N}'s definition, and then
6593 give it a new definition, @value{GDBN} finds the definition (or lack
6594 thereof) in force at each point:
6599 12 printf ("We're so creative.\n");
6601 The symbol `N' has no definition as a C/C++ preprocessor macro
6602 at /home/jimb/gdb/macros/play/sample.c:12
6605 14 printf ("Goodbye, world!\n");
6607 Defined at /home/jimb/gdb/macros/play/sample.c:13
6609 (gdb) macro expand N Q M
6610 expands to: 1729 < 42
6618 @chapter Tracepoints
6619 @c This chapter is based on the documentation written by Michael
6620 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
6623 In some applications, it is not feasible for the debugger to interrupt
6624 the program's execution long enough for the developer to learn
6625 anything helpful about its behavior. If the program's correctness
6626 depends on its real-time behavior, delays introduced by a debugger
6627 might cause the program to change its behavior drastically, or perhaps
6628 fail, even when the code itself is correct. It is useful to be able
6629 to observe the program's behavior without interrupting it.
6631 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
6632 specify locations in the program, called @dfn{tracepoints}, and
6633 arbitrary expressions to evaluate when those tracepoints are reached.
6634 Later, using the @code{tfind} command, you can examine the values
6635 those expressions had when the program hit the tracepoints. The
6636 expressions may also denote objects in memory---structures or arrays,
6637 for example---whose values @value{GDBN} should record; while visiting
6638 a particular tracepoint, you may inspect those objects as if they were
6639 in memory at that moment. However, because @value{GDBN} records these
6640 values without interacting with you, it can do so quickly and
6641 unobtrusively, hopefully not disturbing the program's behavior.
6643 The tracepoint facility is currently available only for remote
6644 targets. @xref{Targets}. In addition, your remote target must know how
6645 to collect trace data. This functionality is implemented in the remote
6646 stub; however, none of the stubs distributed with @value{GDBN} support
6647 tracepoints as of this writing.
6649 This chapter describes the tracepoint commands and features.
6653 * Analyze Collected Data::
6654 * Tracepoint Variables::
6657 @node Set Tracepoints
6658 @section Commands to Set Tracepoints
6660 Before running such a @dfn{trace experiment}, an arbitrary number of
6661 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
6662 tracepoint has a number assigned to it by @value{GDBN}. Like with
6663 breakpoints, tracepoint numbers are successive integers starting from
6664 one. Many of the commands associated with tracepoints take the
6665 tracepoint number as their argument, to identify which tracepoint to
6668 For each tracepoint, you can specify, in advance, some arbitrary set
6669 of data that you want the target to collect in the trace buffer when
6670 it hits that tracepoint. The collected data can include registers,
6671 local variables, or global data. Later, you can use @value{GDBN}
6672 commands to examine the values these data had at the time the
6675 This section describes commands to set tracepoints and associated
6676 conditions and actions.
6679 * Create and Delete Tracepoints::
6680 * Enable and Disable Tracepoints::
6681 * Tracepoint Passcounts::
6682 * Tracepoint Actions::
6683 * Listing Tracepoints::
6684 * Starting and Stopping Trace Experiment::
6687 @node Create and Delete Tracepoints
6688 @subsection Create and Delete Tracepoints
6691 @cindex set tracepoint
6694 The @code{trace} command is very similar to the @code{break} command.
6695 Its argument can be a source line, a function name, or an address in
6696 the target program. @xref{Set Breaks}. The @code{trace} command
6697 defines a tracepoint, which is a point in the target program where the
6698 debugger will briefly stop, collect some data, and then allow the
6699 program to continue. Setting a tracepoint or changing its commands
6700 doesn't take effect until the next @code{tstart} command; thus, you
6701 cannot change the tracepoint attributes once a trace experiment is
6704 Here are some examples of using the @code{trace} command:
6707 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
6709 (@value{GDBP}) @b{trace +2} // 2 lines forward
6711 (@value{GDBP}) @b{trace my_function} // first source line of function
6713 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
6715 (@value{GDBP}) @b{trace *0x2117c4} // an address
6719 You can abbreviate @code{trace} as @code{tr}.
6722 @cindex last tracepoint number
6723 @cindex recent tracepoint number
6724 @cindex tracepoint number
6725 The convenience variable @code{$tpnum} records the tracepoint number
6726 of the most recently set tracepoint.
6728 @kindex delete tracepoint
6729 @cindex tracepoint deletion
6730 @item delete tracepoint @r{[}@var{num}@r{]}
6731 Permanently delete one or more tracepoints. With no argument, the
6732 default is to delete all tracepoints.
6737 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
6739 (@value{GDBP}) @b{delete trace} // remove all tracepoints
6743 You can abbreviate this command as @code{del tr}.
6746 @node Enable and Disable Tracepoints
6747 @subsection Enable and Disable Tracepoints
6750 @kindex disable tracepoint
6751 @item disable tracepoint @r{[}@var{num}@r{]}
6752 Disable tracepoint @var{num}, or all tracepoints if no argument
6753 @var{num} is given. A disabled tracepoint will have no effect during
6754 the next trace experiment, but it is not forgotten. You can re-enable
6755 a disabled tracepoint using the @code{enable tracepoint} command.
6757 @kindex enable tracepoint
6758 @item enable tracepoint @r{[}@var{num}@r{]}
6759 Enable tracepoint @var{num}, or all tracepoints. The enabled
6760 tracepoints will become effective the next time a trace experiment is
6764 @node Tracepoint Passcounts
6765 @subsection Tracepoint Passcounts
6769 @cindex tracepoint pass count
6770 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
6771 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
6772 automatically stop a trace experiment. If a tracepoint's passcount is
6773 @var{n}, then the trace experiment will be automatically stopped on
6774 the @var{n}'th time that tracepoint is hit. If the tracepoint number
6775 @var{num} is not specified, the @code{passcount} command sets the
6776 passcount of the most recently defined tracepoint. If no passcount is
6777 given, the trace experiment will run until stopped explicitly by the
6783 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
6784 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
6786 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
6787 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
6788 (@value{GDBP}) @b{trace foo}
6789 (@value{GDBP}) @b{pass 3}
6790 (@value{GDBP}) @b{trace bar}
6791 (@value{GDBP}) @b{pass 2}
6792 (@value{GDBP}) @b{trace baz}
6793 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
6794 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
6795 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
6796 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
6800 @node Tracepoint Actions
6801 @subsection Tracepoint Action Lists
6805 @cindex tracepoint actions
6806 @item actions @r{[}@var{num}@r{]}
6807 This command will prompt for a list of actions to be taken when the
6808 tracepoint is hit. If the tracepoint number @var{num} is not
6809 specified, this command sets the actions for the one that was most
6810 recently defined (so that you can define a tracepoint and then say
6811 @code{actions} without bothering about its number). You specify the
6812 actions themselves on the following lines, one action at a time, and
6813 terminate the actions list with a line containing just @code{end}. So
6814 far, the only defined actions are @code{collect} and
6815 @code{while-stepping}.
6817 @cindex remove actions from a tracepoint
6818 To remove all actions from a tracepoint, type @samp{actions @var{num}}
6819 and follow it immediately with @samp{end}.
6822 (@value{GDBP}) @b{collect @var{data}} // collect some data
6824 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
6826 (@value{GDBP}) @b{end} // signals the end of actions.
6829 In the following example, the action list begins with @code{collect}
6830 commands indicating the things to be collected when the tracepoint is
6831 hit. Then, in order to single-step and collect additional data
6832 following the tracepoint, a @code{while-stepping} command is used,
6833 followed by the list of things to be collected while stepping. The
6834 @code{while-stepping} command is terminated by its own separate
6835 @code{end} command. Lastly, the action list is terminated by an
6839 (@value{GDBP}) @b{trace foo}
6840 (@value{GDBP}) @b{actions}
6841 Enter actions for tracepoint 1, one per line:
6850 @kindex collect @r{(tracepoints)}
6851 @item collect @var{expr1}, @var{expr2}, @dots{}
6852 Collect values of the given expressions when the tracepoint is hit.
6853 This command accepts a comma-separated list of any valid expressions.
6854 In addition to global, static, or local variables, the following
6855 special arguments are supported:
6859 collect all registers
6862 collect all function arguments
6865 collect all local variables.
6868 You can give several consecutive @code{collect} commands, each one
6869 with a single argument, or one @code{collect} command with several
6870 arguments separated by commas: the effect is the same.
6872 The command @code{info scope} (@pxref{Symbols, info scope}) is
6873 particularly useful for figuring out what data to collect.
6875 @kindex while-stepping @r{(tracepoints)}
6876 @item while-stepping @var{n}
6877 Perform @var{n} single-step traces after the tracepoint, collecting
6878 new data at each step. The @code{while-stepping} command is
6879 followed by the list of what to collect while stepping (followed by
6880 its own @code{end} command):
6884 > collect $regs, myglobal
6890 You may abbreviate @code{while-stepping} as @code{ws} or
6894 @node Listing Tracepoints
6895 @subsection Listing Tracepoints
6898 @kindex info tracepoints
6899 @cindex information about tracepoints
6900 @item info tracepoints @r{[}@var{num}@r{]}
6901 Display information about the tracepoint @var{num}. If you don't specify
6902 a tracepoint number, displays information about all the tracepoints
6903 defined so far. For each tracepoint, the following information is
6910 whether it is enabled or disabled
6914 its passcount as given by the @code{passcount @var{n}} command
6916 its step count as given by the @code{while-stepping @var{n}} command
6918 where in the source files is the tracepoint set
6920 its action list as given by the @code{actions} command
6924 (@value{GDBP}) @b{info trace}
6925 Num Enb Address PassC StepC What
6926 1 y 0x002117c4 0 0 <gdb_asm>
6927 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
6928 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
6933 This command can be abbreviated @code{info tp}.
6936 @node Starting and Stopping Trace Experiment
6937 @subsection Starting and Stopping Trace Experiment
6941 @cindex start a new trace experiment
6942 @cindex collected data discarded
6944 This command takes no arguments. It starts the trace experiment, and
6945 begins collecting data. This has the side effect of discarding all
6946 the data collected in the trace buffer during the previous trace
6950 @cindex stop a running trace experiment
6952 This command takes no arguments. It ends the trace experiment, and
6953 stops collecting data.
6955 @strong{Note:} a trace experiment and data collection may stop
6956 automatically if any tracepoint's passcount is reached
6957 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
6960 @cindex status of trace data collection
6961 @cindex trace experiment, status of
6963 This command displays the status of the current trace data
6967 Here is an example of the commands we described so far:
6970 (@value{GDBP}) @b{trace gdb_c_test}
6971 (@value{GDBP}) @b{actions}
6972 Enter actions for tracepoint #1, one per line.
6973 > collect $regs,$locals,$args
6978 (@value{GDBP}) @b{tstart}
6979 [time passes @dots{}]
6980 (@value{GDBP}) @b{tstop}
6984 @node Analyze Collected Data
6985 @section Using the collected data
6987 After the tracepoint experiment ends, you use @value{GDBN} commands
6988 for examining the trace data. The basic idea is that each tracepoint
6989 collects a trace @dfn{snapshot} every time it is hit and another
6990 snapshot every time it single-steps. All these snapshots are
6991 consecutively numbered from zero and go into a buffer, and you can
6992 examine them later. The way you examine them is to @dfn{focus} on a
6993 specific trace snapshot. When the remote stub is focused on a trace
6994 snapshot, it will respond to all @value{GDBN} requests for memory and
6995 registers by reading from the buffer which belongs to that snapshot,
6996 rather than from @emph{real} memory or registers of the program being
6997 debugged. This means that @strong{all} @value{GDBN} commands
6998 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
6999 behave as if we were currently debugging the program state as it was
7000 when the tracepoint occurred. Any requests for data that are not in
7001 the buffer will fail.
7004 * tfind:: How to select a trace snapshot
7005 * tdump:: How to display all data for a snapshot
7006 * save-tracepoints:: How to save tracepoints for a future run
7010 @subsection @code{tfind @var{n}}
7013 @cindex select trace snapshot
7014 @cindex find trace snapshot
7015 The basic command for selecting a trace snapshot from the buffer is
7016 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
7017 counting from zero. If no argument @var{n} is given, the next
7018 snapshot is selected.
7020 Here are the various forms of using the @code{tfind} command.
7024 Find the first snapshot in the buffer. This is a synonym for
7025 @code{tfind 0} (since 0 is the number of the first snapshot).
7028 Stop debugging trace snapshots, resume @emph{live} debugging.
7031 Same as @samp{tfind none}.
7034 No argument means find the next trace snapshot.
7037 Find the previous trace snapshot before the current one. This permits
7038 retracing earlier steps.
7040 @item tfind tracepoint @var{num}
7041 Find the next snapshot associated with tracepoint @var{num}. Search
7042 proceeds forward from the last examined trace snapshot. If no
7043 argument @var{num} is given, it means find the next snapshot collected
7044 for the same tracepoint as the current snapshot.
7046 @item tfind pc @var{addr}
7047 Find the next snapshot associated with the value @var{addr} of the
7048 program counter. Search proceeds forward from the last examined trace
7049 snapshot. If no argument @var{addr} is given, it means find the next
7050 snapshot with the same value of PC as the current snapshot.
7052 @item tfind outside @var{addr1}, @var{addr2}
7053 Find the next snapshot whose PC is outside the given range of
7056 @item tfind range @var{addr1}, @var{addr2}
7057 Find the next snapshot whose PC is between @var{addr1} and
7058 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
7060 @item tfind line @r{[}@var{file}:@r{]}@var{n}
7061 Find the next snapshot associated with the source line @var{n}. If
7062 the optional argument @var{file} is given, refer to line @var{n} in
7063 that source file. Search proceeds forward from the last examined
7064 trace snapshot. If no argument @var{n} is given, it means find the
7065 next line other than the one currently being examined; thus saying
7066 @code{tfind line} repeatedly can appear to have the same effect as
7067 stepping from line to line in a @emph{live} debugging session.
7070 The default arguments for the @code{tfind} commands are specifically
7071 designed to make it easy to scan through the trace buffer. For
7072 instance, @code{tfind} with no argument selects the next trace
7073 snapshot, and @code{tfind -} with no argument selects the previous
7074 trace snapshot. So, by giving one @code{tfind} command, and then
7075 simply hitting @key{RET} repeatedly you can examine all the trace
7076 snapshots in order. Or, by saying @code{tfind -} and then hitting
7077 @key{RET} repeatedly you can examine the snapshots in reverse order.
7078 The @code{tfind line} command with no argument selects the snapshot
7079 for the next source line executed. The @code{tfind pc} command with
7080 no argument selects the next snapshot with the same program counter
7081 (PC) as the current frame. The @code{tfind tracepoint} command with
7082 no argument selects the next trace snapshot collected by the same
7083 tracepoint as the current one.
7085 In addition to letting you scan through the trace buffer manually,
7086 these commands make it easy to construct @value{GDBN} scripts that
7087 scan through the trace buffer and print out whatever collected data
7088 you are interested in. Thus, if we want to examine the PC, FP, and SP
7089 registers from each trace frame in the buffer, we can say this:
7092 (@value{GDBP}) @b{tfind start}
7093 (@value{GDBP}) @b{while ($trace_frame != -1)}
7094 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
7095 $trace_frame, $pc, $sp, $fp
7099 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
7100 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
7101 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
7102 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
7103 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
7104 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
7105 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
7106 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
7107 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
7108 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
7109 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
7112 Or, if we want to examine the variable @code{X} at each source line in
7116 (@value{GDBP}) @b{tfind start}
7117 (@value{GDBP}) @b{while ($trace_frame != -1)}
7118 > printf "Frame %d, X == %d\n", $trace_frame, X
7128 @subsection @code{tdump}
7130 @cindex dump all data collected at tracepoint
7131 @cindex tracepoint data, display
7133 This command takes no arguments. It prints all the data collected at
7134 the current trace snapshot.
7137 (@value{GDBP}) @b{trace 444}
7138 (@value{GDBP}) @b{actions}
7139 Enter actions for tracepoint #2, one per line:
7140 > collect $regs, $locals, $args, gdb_long_test
7143 (@value{GDBP}) @b{tstart}
7145 (@value{GDBP}) @b{tfind line 444}
7146 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
7148 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
7150 (@value{GDBP}) @b{tdump}
7151 Data collected at tracepoint 2, trace frame 1:
7152 d0 0xc4aa0085 -995491707
7156 d4 0x71aea3d 119204413
7161 a1 0x3000668 50333288
7164 a4 0x3000698 50333336
7166 fp 0x30bf3c 0x30bf3c
7167 sp 0x30bf34 0x30bf34
7169 pc 0x20b2c8 0x20b2c8
7173 p = 0x20e5b4 "gdb-test"
7180 gdb_long_test = 17 '\021'
7185 @node save-tracepoints
7186 @subsection @code{save-tracepoints @var{filename}}
7187 @kindex save-tracepoints
7188 @cindex save tracepoints for future sessions
7190 This command saves all current tracepoint definitions together with
7191 their actions and passcounts, into a file @file{@var{filename}}
7192 suitable for use in a later debugging session. To read the saved
7193 tracepoint definitions, use the @code{source} command (@pxref{Command
7196 @node Tracepoint Variables
7197 @section Convenience Variables for Tracepoints
7198 @cindex tracepoint variables
7199 @cindex convenience variables for tracepoints
7202 @vindex $trace_frame
7203 @item (int) $trace_frame
7204 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
7205 snapshot is selected.
7208 @item (int) $tracepoint
7209 The tracepoint for the current trace snapshot.
7212 @item (int) $trace_line
7213 The line number for the current trace snapshot.
7216 @item (char []) $trace_file
7217 The source file for the current trace snapshot.
7220 @item (char []) $trace_func
7221 The name of the function containing @code{$tracepoint}.
7224 Note: @code{$trace_file} is not suitable for use in @code{printf},
7225 use @code{output} instead.
7227 Here's a simple example of using these convenience variables for
7228 stepping through all the trace snapshots and printing some of their
7232 (@value{GDBP}) @b{tfind start}
7234 (@value{GDBP}) @b{while $trace_frame != -1}
7235 > output $trace_file
7236 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
7242 @chapter Debugging Programs That Use Overlays
7245 If your program is too large to fit completely in your target system's
7246 memory, you can sometimes use @dfn{overlays} to work around this
7247 problem. @value{GDBN} provides some support for debugging programs that
7251 * How Overlays Work:: A general explanation of overlays.
7252 * Overlay Commands:: Managing overlays in @value{GDBN}.
7253 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
7254 mapped by asking the inferior.
7255 * Overlay Sample Program:: A sample program using overlays.
7258 @node How Overlays Work
7259 @section How Overlays Work
7260 @cindex mapped overlays
7261 @cindex unmapped overlays
7262 @cindex load address, overlay's
7263 @cindex mapped address
7264 @cindex overlay area
7266 Suppose you have a computer whose instruction address space is only 64
7267 kilobytes long, but which has much more memory which can be accessed by
7268 other means: special instructions, segment registers, or memory
7269 management hardware, for example. Suppose further that you want to
7270 adapt a program which is larger than 64 kilobytes to run on this system.
7272 One solution is to identify modules of your program which are relatively
7273 independent, and need not call each other directly; call these modules
7274 @dfn{overlays}. Separate the overlays from the main program, and place
7275 their machine code in the larger memory. Place your main program in
7276 instruction memory, but leave at least enough space there to hold the
7277 largest overlay as well.
7279 Now, to call a function located in an overlay, you must first copy that
7280 overlay's machine code from the large memory into the space set aside
7281 for it in the instruction memory, and then jump to its entry point
7284 @c NB: In the below the mapped area's size is greater or equal to the
7285 @c size of all overlays. This is intentional to remind the developer
7286 @c that overlays don't necessarily need to be the same size.
7290 Data Instruction Larger
7291 Address Space Address Space Address Space
7292 +-----------+ +-----------+ +-----------+
7294 +-----------+ +-----------+ +-----------+<-- overlay 1
7295 | program | | main | .----| overlay 1 | load address
7296 | variables | | program | | +-----------+
7297 | and heap | | | | | |
7298 +-----------+ | | | +-----------+<-- overlay 2
7299 | | +-----------+ | | | load address
7300 +-----------+ | | | .-| overlay 2 |
7302 mapped --->+-----------+ | | +-----------+
7304 | overlay | <-' | | |
7305 | area | <---' +-----------+<-- overlay 3
7306 | | <---. | | load address
7307 +-----------+ `--| overlay 3 |
7314 @anchor{A code overlay}A code overlay
7318 The diagram (@pxref{A code overlay}) shows a system with separate data
7319 and instruction address spaces. To map an overlay, the program copies
7320 its code from the larger address space to the instruction address space.
7321 Since the overlays shown here all use the same mapped address, only one
7322 may be mapped at a time. For a system with a single address space for
7323 data and instructions, the diagram would be similar, except that the
7324 program variables and heap would share an address space with the main
7325 program and the overlay area.
7327 An overlay loaded into instruction memory and ready for use is called a
7328 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
7329 instruction memory. An overlay not present (or only partially present)
7330 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
7331 is its address in the larger memory. The mapped address is also called
7332 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
7333 called the @dfn{load memory address}, or @dfn{LMA}.
7335 Unfortunately, overlays are not a completely transparent way to adapt a
7336 program to limited instruction memory. They introduce a new set of
7337 global constraints you must keep in mind as you design your program:
7342 Before calling or returning to a function in an overlay, your program
7343 must make sure that overlay is actually mapped. Otherwise, the call or
7344 return will transfer control to the right address, but in the wrong
7345 overlay, and your program will probably crash.
7348 If the process of mapping an overlay is expensive on your system, you
7349 will need to choose your overlays carefully to minimize their effect on
7350 your program's performance.
7353 The executable file you load onto your system must contain each
7354 overlay's instructions, appearing at the overlay's load address, not its
7355 mapped address. However, each overlay's instructions must be relocated
7356 and its symbols defined as if the overlay were at its mapped address.
7357 You can use GNU linker scripts to specify different load and relocation
7358 addresses for pieces of your program; see @ref{Overlay Description,,,
7359 ld.info, Using ld: the GNU linker}.
7362 The procedure for loading executable files onto your system must be able
7363 to load their contents into the larger address space as well as the
7364 instruction and data spaces.
7368 The overlay system described above is rather simple, and could be
7369 improved in many ways:
7374 If your system has suitable bank switch registers or memory management
7375 hardware, you could use those facilities to make an overlay's load area
7376 contents simply appear at their mapped address in instruction space.
7377 This would probably be faster than copying the overlay to its mapped
7378 area in the usual way.
7381 If your overlays are small enough, you could set aside more than one
7382 overlay area, and have more than one overlay mapped at a time.
7385 You can use overlays to manage data, as well as instructions. In
7386 general, data overlays are even less transparent to your design than
7387 code overlays: whereas code overlays only require care when you call or
7388 return to functions, data overlays require care every time you access
7389 the data. Also, if you change the contents of a data overlay, you
7390 must copy its contents back out to its load address before you can copy a
7391 different data overlay into the same mapped area.
7396 @node Overlay Commands
7397 @section Overlay Commands
7399 To use @value{GDBN}'s overlay support, each overlay in your program must
7400 correspond to a separate section of the executable file. The section's
7401 virtual memory address and load memory address must be the overlay's
7402 mapped and load addresses. Identifying overlays with sections allows
7403 @value{GDBN} to determine the appropriate address of a function or
7404 variable, depending on whether the overlay is mapped or not.
7406 @value{GDBN}'s overlay commands all start with the word @code{overlay};
7407 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
7412 Disable @value{GDBN}'s overlay support. When overlay support is
7413 disabled, @value{GDBN} assumes that all functions and variables are
7414 always present at their mapped addresses. By default, @value{GDBN}'s
7415 overlay support is disabled.
7417 @item overlay manual
7418 @cindex manual overlay debugging
7419 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
7420 relies on you to tell it which overlays are mapped, and which are not,
7421 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
7422 commands described below.
7424 @item overlay map-overlay @var{overlay}
7425 @itemx overlay map @var{overlay}
7426 @cindex map an overlay
7427 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
7428 be the name of the object file section containing the overlay. When an
7429 overlay is mapped, @value{GDBN} assumes it can find the overlay's
7430 functions and variables at their mapped addresses. @value{GDBN} assumes
7431 that any other overlays whose mapped ranges overlap that of
7432 @var{overlay} are now unmapped.
7434 @item overlay unmap-overlay @var{overlay}
7435 @itemx overlay unmap @var{overlay}
7436 @cindex unmap an overlay
7437 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
7438 must be the name of the object file section containing the overlay.
7439 When an overlay is unmapped, @value{GDBN} assumes it can find the
7440 overlay's functions and variables at their load addresses.
7443 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
7444 consults a data structure the overlay manager maintains in the inferior
7445 to see which overlays are mapped. For details, see @ref{Automatic
7448 @item overlay load-target
7450 @cindex reloading the overlay table
7451 Re-read the overlay table from the inferior. Normally, @value{GDBN}
7452 re-reads the table @value{GDBN} automatically each time the inferior
7453 stops, so this command should only be necessary if you have changed the
7454 overlay mapping yourself using @value{GDBN}. This command is only
7455 useful when using automatic overlay debugging.
7457 @item overlay list-overlays
7459 @cindex listing mapped overlays
7460 Display a list of the overlays currently mapped, along with their mapped
7461 addresses, load addresses, and sizes.
7465 Normally, when @value{GDBN} prints a code address, it includes the name
7466 of the function the address falls in:
7470 $3 = @{int ()@} 0x11a0 <main>
7473 When overlay debugging is enabled, @value{GDBN} recognizes code in
7474 unmapped overlays, and prints the names of unmapped functions with
7475 asterisks around them. For example, if @code{foo} is a function in an
7476 unmapped overlay, @value{GDBN} prints it this way:
7480 No sections are mapped.
7482 $5 = @{int (int)@} 0x100000 <*foo*>
7485 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
7490 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
7491 mapped at 0x1016 - 0x104a
7493 $6 = @{int (int)@} 0x1016 <foo>
7496 When overlay debugging is enabled, @value{GDBN} can find the correct
7497 address for functions and variables in an overlay, whether or not the
7498 overlay is mapped. This allows most @value{GDBN} commands, like
7499 @code{break} and @code{disassemble}, to work normally, even on unmapped
7500 code. However, @value{GDBN}'s breakpoint support has some limitations:
7504 @cindex breakpoints in overlays
7505 @cindex overlays, setting breakpoints in
7506 You can set breakpoints in functions in unmapped overlays, as long as
7507 @value{GDBN} can write to the overlay at its load address.
7509 @value{GDBN} can not set hardware or simulator-based breakpoints in
7510 unmapped overlays. However, if you set a breakpoint at the end of your
7511 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
7512 you are using manual overlay management), @value{GDBN} will re-set its
7513 breakpoints properly.
7517 @node Automatic Overlay Debugging
7518 @section Automatic Overlay Debugging
7519 @cindex automatic overlay debugging
7521 @value{GDBN} can automatically track which overlays are mapped and which
7522 are not, given some simple co-operation from the overlay manager in the
7523 inferior. If you enable automatic overlay debugging with the
7524 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
7525 looks in the inferior's memory for certain variables describing the
7526 current state of the overlays.
7528 Here are the variables your overlay manager must define to support
7529 @value{GDBN}'s automatic overlay debugging:
7533 @item @code{_ovly_table}:
7534 This variable must be an array of the following structures:
7539 /* The overlay's mapped address. */
7542 /* The size of the overlay, in bytes. */
7545 /* The overlay's load address. */
7548 /* Non-zero if the overlay is currently mapped;
7550 unsigned long mapped;
7554 @item @code{_novlys}:
7555 This variable must be a four-byte signed integer, holding the total
7556 number of elements in @code{_ovly_table}.
7560 To decide whether a particular overlay is mapped or not, @value{GDBN}
7561 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
7562 @code{lma} members equal the VMA and LMA of the overlay's section in the
7563 executable file. When @value{GDBN} finds a matching entry, it consults
7564 the entry's @code{mapped} member to determine whether the overlay is
7567 In addition, your overlay manager may define a function called
7568 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
7569 will silently set a breakpoint there. If the overlay manager then
7570 calls this function whenever it has changed the overlay table, this
7571 will enable @value{GDBN} to accurately keep track of which overlays
7572 are in program memory, and update any breakpoints that may be set
7573 in overlays. This will allow breakpoints to work even if the
7574 overlays are kept in ROM or other non-writable memory while they
7575 are not being executed.
7577 @node Overlay Sample Program
7578 @section Overlay Sample Program
7579 @cindex overlay example program
7581 When linking a program which uses overlays, you must place the overlays
7582 at their load addresses, while relocating them to run at their mapped
7583 addresses. To do this, you must write a linker script (@pxref{Overlay
7584 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
7585 since linker scripts are specific to a particular host system, target
7586 architecture, and target memory layout, this manual cannot provide
7587 portable sample code demonstrating @value{GDBN}'s overlay support.
7589 However, the @value{GDBN} source distribution does contain an overlaid
7590 program, with linker scripts for a few systems, as part of its test
7591 suite. The program consists of the following files from
7592 @file{gdb/testsuite/gdb.base}:
7596 The main program file.
7598 A simple overlay manager, used by @file{overlays.c}.
7603 Overlay modules, loaded and used by @file{overlays.c}.
7606 Linker scripts for linking the test program on the @code{d10v-elf}
7607 and @code{m32r-elf} targets.
7610 You can build the test program using the @code{d10v-elf} GCC
7611 cross-compiler like this:
7614 $ d10v-elf-gcc -g -c overlays.c
7615 $ d10v-elf-gcc -g -c ovlymgr.c
7616 $ d10v-elf-gcc -g -c foo.c
7617 $ d10v-elf-gcc -g -c bar.c
7618 $ d10v-elf-gcc -g -c baz.c
7619 $ d10v-elf-gcc -g -c grbx.c
7620 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
7621 baz.o grbx.o -Wl,-Td10v.ld -o overlays
7624 The build process is identical for any other architecture, except that
7625 you must substitute the appropriate compiler and linker script for the
7626 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
7630 @chapter Using @value{GDBN} with Different Languages
7633 Although programming languages generally have common aspects, they are
7634 rarely expressed in the same manner. For instance, in ANSI C,
7635 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
7636 Modula-2, it is accomplished by @code{p^}. Values can also be
7637 represented (and displayed) differently. Hex numbers in C appear as
7638 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
7640 @cindex working language
7641 Language-specific information is built into @value{GDBN} for some languages,
7642 allowing you to express operations like the above in your program's
7643 native language, and allowing @value{GDBN} to output values in a manner
7644 consistent with the syntax of your program's native language. The
7645 language you use to build expressions is called the @dfn{working
7649 * Setting:: Switching between source languages
7650 * Show:: Displaying the language
7651 * Checks:: Type and range checks
7652 * Support:: Supported languages
7653 * Unsupported languages:: Unsupported languages
7657 @section Switching between source languages
7659 There are two ways to control the working language---either have @value{GDBN}
7660 set it automatically, or select it manually yourself. You can use the
7661 @code{set language} command for either purpose. On startup, @value{GDBN}
7662 defaults to setting the language automatically. The working language is
7663 used to determine how expressions you type are interpreted, how values
7666 In addition to the working language, every source file that
7667 @value{GDBN} knows about has its own working language. For some object
7668 file formats, the compiler might indicate which language a particular
7669 source file is in. However, most of the time @value{GDBN} infers the
7670 language from the name of the file. The language of a source file
7671 controls whether C@t{++} names are demangled---this way @code{backtrace} can
7672 show each frame appropriately for its own language. There is no way to
7673 set the language of a source file from within @value{GDBN}, but you can
7674 set the language associated with a filename extension. @xref{Show, ,
7675 Displaying the language}.
7677 This is most commonly a problem when you use a program, such
7678 as @code{cfront} or @code{f2c}, that generates C but is written in
7679 another language. In that case, make the
7680 program use @code{#line} directives in its C output; that way
7681 @value{GDBN} will know the correct language of the source code of the original
7682 program, and will display that source code, not the generated C code.
7685 * Filenames:: Filename extensions and languages.
7686 * Manually:: Setting the working language manually
7687 * Automatically:: Having @value{GDBN} infer the source language
7691 @subsection List of filename extensions and languages
7693 If a source file name ends in one of the following extensions, then
7694 @value{GDBN} infers that its language is the one indicated.
7710 Objective-C source file
7717 Modula-2 source file
7721 Assembler source file. This actually behaves almost like C, but
7722 @value{GDBN} does not skip over function prologues when stepping.
7725 In addition, you may set the language associated with a filename
7726 extension. @xref{Show, , Displaying the language}.
7729 @subsection Setting the working language
7731 If you allow @value{GDBN} to set the language automatically,
7732 expressions are interpreted the same way in your debugging session and
7735 @kindex set language
7736 If you wish, you may set the language manually. To do this, issue the
7737 command @samp{set language @var{lang}}, where @var{lang} is the name of
7739 @code{c} or @code{modula-2}.
7740 For a list of the supported languages, type @samp{set language}.
7742 Setting the language manually prevents @value{GDBN} from updating the working
7743 language automatically. This can lead to confusion if you try
7744 to debug a program when the working language is not the same as the
7745 source language, when an expression is acceptable to both
7746 languages---but means different things. For instance, if the current
7747 source file were written in C, and @value{GDBN} was parsing Modula-2, a
7755 might not have the effect you intended. In C, this means to add
7756 @code{b} and @code{c} and place the result in @code{a}. The result
7757 printed would be the value of @code{a}. In Modula-2, this means to compare
7758 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
7761 @subsection Having @value{GDBN} infer the source language
7763 To have @value{GDBN} set the working language automatically, use
7764 @samp{set language local} or @samp{set language auto}. @value{GDBN}
7765 then infers the working language. That is, when your program stops in a
7766 frame (usually by encountering a breakpoint), @value{GDBN} sets the
7767 working language to the language recorded for the function in that
7768 frame. If the language for a frame is unknown (that is, if the function
7769 or block corresponding to the frame was defined in a source file that
7770 does not have a recognized extension), the current working language is
7771 not changed, and @value{GDBN} issues a warning.
7773 This may not seem necessary for most programs, which are written
7774 entirely in one source language. However, program modules and libraries
7775 written in one source language can be used by a main program written in
7776 a different source language. Using @samp{set language auto} in this
7777 case frees you from having to set the working language manually.
7780 @section Displaying the language
7782 The following commands help you find out which language is the
7783 working language, and also what language source files were written in.
7785 @kindex show language
7788 Display the current working language. This is the
7789 language you can use with commands such as @code{print} to
7790 build and compute expressions that may involve variables in your program.
7793 @kindex info frame@r{, show the source language}
7794 Display the source language for this frame. This language becomes the
7795 working language if you use an identifier from this frame.
7796 @xref{Frame Info, ,Information about a frame}, to identify the other
7797 information listed here.
7800 @kindex info source@r{, show the source language}
7801 Display the source language of this source file.
7802 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
7803 information listed here.
7806 In unusual circumstances, you may have source files with extensions
7807 not in the standard list. You can then set the extension associated
7808 with a language explicitly:
7810 @kindex set extension-language
7811 @kindex info extensions
7813 @item set extension-language @var{.ext} @var{language}
7814 Set source files with extension @var{.ext} to be assumed to be in
7815 the source language @var{language}.
7817 @item info extensions
7818 List all the filename extensions and the associated languages.
7822 @section Type and range checking
7825 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
7826 checking are included, but they do not yet have any effect. This
7827 section documents the intended facilities.
7829 @c FIXME remove warning when type/range code added
7831 Some languages are designed to guard you against making seemingly common
7832 errors through a series of compile- and run-time checks. These include
7833 checking the type of arguments to functions and operators, and making
7834 sure mathematical overflows are caught at run time. Checks such as
7835 these help to ensure a program's correctness once it has been compiled
7836 by eliminating type mismatches, and providing active checks for range
7837 errors when your program is running.
7839 @value{GDBN} can check for conditions like the above if you wish.
7840 Although @value{GDBN} does not check the statements in your program, it
7841 can check expressions entered directly into @value{GDBN} for evaluation via
7842 the @code{print} command, for example. As with the working language,
7843 @value{GDBN} can also decide whether or not to check automatically based on
7844 your program's source language. @xref{Support, ,Supported languages},
7845 for the default settings of supported languages.
7848 * Type Checking:: An overview of type checking
7849 * Range Checking:: An overview of range checking
7852 @cindex type checking
7853 @cindex checks, type
7855 @subsection An overview of type checking
7857 Some languages, such as Modula-2, are strongly typed, meaning that the
7858 arguments to operators and functions have to be of the correct type,
7859 otherwise an error occurs. These checks prevent type mismatch
7860 errors from ever causing any run-time problems. For example,
7868 The second example fails because the @code{CARDINAL} 1 is not
7869 type-compatible with the @code{REAL} 2.3.
7871 For the expressions you use in @value{GDBN} commands, you can tell the
7872 @value{GDBN} type checker to skip checking;
7873 to treat any mismatches as errors and abandon the expression;
7874 or to only issue warnings when type mismatches occur,
7875 but evaluate the expression anyway. When you choose the last of
7876 these, @value{GDBN} evaluates expressions like the second example above, but
7877 also issues a warning.
7879 Even if you turn type checking off, there may be other reasons
7880 related to type that prevent @value{GDBN} from evaluating an expression.
7881 For instance, @value{GDBN} does not know how to add an @code{int} and
7882 a @code{struct foo}. These particular type errors have nothing to do
7883 with the language in use, and usually arise from expressions, such as
7884 the one described above, which make little sense to evaluate anyway.
7886 Each language defines to what degree it is strict about type. For
7887 instance, both Modula-2 and C require the arguments to arithmetical
7888 operators to be numbers. In C, enumerated types and pointers can be
7889 represented as numbers, so that they are valid arguments to mathematical
7890 operators. @xref{Support, ,Supported languages}, for further
7891 details on specific languages.
7893 @value{GDBN} provides some additional commands for controlling the type checker:
7895 @kindex set check type
7896 @kindex show check type
7898 @item set check type auto
7899 Set type checking on or off based on the current working language.
7900 @xref{Support, ,Supported languages}, for the default settings for
7903 @item set check type on
7904 @itemx set check type off
7905 Set type checking on or off, overriding the default setting for the
7906 current working language. Issue a warning if the setting does not
7907 match the language default. If any type mismatches occur in
7908 evaluating an expression while type checking is on, @value{GDBN} prints a
7909 message and aborts evaluation of the expression.
7911 @item set check type warn
7912 Cause the type checker to issue warnings, but to always attempt to
7913 evaluate the expression. Evaluating the expression may still
7914 be impossible for other reasons. For example, @value{GDBN} cannot add
7915 numbers and structures.
7918 Show the current setting of the type checker, and whether or not @value{GDBN}
7919 is setting it automatically.
7922 @cindex range checking
7923 @cindex checks, range
7924 @node Range Checking
7925 @subsection An overview of range checking
7927 In some languages (such as Modula-2), it is an error to exceed the
7928 bounds of a type; this is enforced with run-time checks. Such range
7929 checking is meant to ensure program correctness by making sure
7930 computations do not overflow, or indices on an array element access do
7931 not exceed the bounds of the array.
7933 For expressions you use in @value{GDBN} commands, you can tell
7934 @value{GDBN} to treat range errors in one of three ways: ignore them,
7935 always treat them as errors and abandon the expression, or issue
7936 warnings but evaluate the expression anyway.
7938 A range error can result from numerical overflow, from exceeding an
7939 array index bound, or when you type a constant that is not a member
7940 of any type. Some languages, however, do not treat overflows as an
7941 error. In many implementations of C, mathematical overflow causes the
7942 result to ``wrap around'' to lower values---for example, if @var{m} is
7943 the largest integer value, and @var{s} is the smallest, then
7946 @var{m} + 1 @result{} @var{s}
7949 This, too, is specific to individual languages, and in some cases
7950 specific to individual compilers or machines. @xref{Support, ,
7951 Supported languages}, for further details on specific languages.
7953 @value{GDBN} provides some additional commands for controlling the range checker:
7955 @kindex set check range
7956 @kindex show check range
7958 @item set check range auto
7959 Set range checking on or off based on the current working language.
7960 @xref{Support, ,Supported languages}, for the default settings for
7963 @item set check range on
7964 @itemx set check range off
7965 Set range checking on or off, overriding the default setting for the
7966 current working language. A warning is issued if the setting does not
7967 match the language default. If a range error occurs and range checking is on,
7968 then a message is printed and evaluation of the expression is aborted.
7970 @item set check range warn
7971 Output messages when the @value{GDBN} range checker detects a range error,
7972 but attempt to evaluate the expression anyway. Evaluating the
7973 expression may still be impossible for other reasons, such as accessing
7974 memory that the process does not own (a typical example from many Unix
7978 Show the current setting of the range checker, and whether or not it is
7979 being set automatically by @value{GDBN}.
7983 @section Supported languages
7985 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, assembly, and Modula-2.
7986 @c This is false ...
7987 Some @value{GDBN} features may be used in expressions regardless of the
7988 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
7989 and the @samp{@{type@}addr} construct (@pxref{Expressions,
7990 ,Expressions}) can be used with the constructs of any supported
7993 The following sections detail to what degree each source language is
7994 supported by @value{GDBN}. These sections are not meant to be language
7995 tutorials or references, but serve only as a reference guide to what the
7996 @value{GDBN} expression parser accepts, and what input and output
7997 formats should look like for different languages. There are many good
7998 books written on each of these languages; please look to these for a
7999 language reference or tutorial.
8003 * Objective-C:: Objective-C
8004 * Modula-2:: Modula-2
8008 @subsection C and C@t{++}
8010 @cindex C and C@t{++}
8011 @cindex expressions in C or C@t{++}
8013 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
8014 to both languages. Whenever this is the case, we discuss those languages
8018 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
8019 @cindex @sc{gnu} C@t{++}
8020 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
8021 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
8022 effectively, you must compile your C@t{++} programs with a supported
8023 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
8024 compiler (@code{aCC}).
8026 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
8027 format; if it doesn't work on your system, try the stabs+ debugging
8028 format. You can select those formats explicitly with the @code{g++}
8029 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
8030 @xref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
8031 CC, gcc.info, Using @sc{gnu} CC}.
8034 * C Operators:: C and C@t{++} operators
8035 * C Constants:: C and C@t{++} constants
8036 * C plus plus expressions:: C@t{++} expressions
8037 * C Defaults:: Default settings for C and C@t{++}
8038 * C Checks:: C and C@t{++} type and range checks
8039 * Debugging C:: @value{GDBN} and C
8040 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
8044 @subsubsection C and C@t{++} operators
8046 @cindex C and C@t{++} operators
8048 Operators must be defined on values of specific types. For instance,
8049 @code{+} is defined on numbers, but not on structures. Operators are
8050 often defined on groups of types.
8052 For the purposes of C and C@t{++}, the following definitions hold:
8057 @emph{Integral types} include @code{int} with any of its storage-class
8058 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
8061 @emph{Floating-point types} include @code{float}, @code{double}, and
8062 @code{long double} (if supported by the target platform).
8065 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
8068 @emph{Scalar types} include all of the above.
8073 The following operators are supported. They are listed here
8074 in order of increasing precedence:
8078 The comma or sequencing operator. Expressions in a comma-separated list
8079 are evaluated from left to right, with the result of the entire
8080 expression being the last expression evaluated.
8083 Assignment. The value of an assignment expression is the value
8084 assigned. Defined on scalar types.
8087 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
8088 and translated to @w{@code{@var{a} = @var{a op b}}}.
8089 @w{@code{@var{op}=}} and @code{=} have the same precedence.
8090 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
8091 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
8094 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
8095 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
8099 Logical @sc{or}. Defined on integral types.
8102 Logical @sc{and}. Defined on integral types.
8105 Bitwise @sc{or}. Defined on integral types.
8108 Bitwise exclusive-@sc{or}. Defined on integral types.
8111 Bitwise @sc{and}. Defined on integral types.
8114 Equality and inequality. Defined on scalar types. The value of these
8115 expressions is 0 for false and non-zero for true.
8117 @item <@r{, }>@r{, }<=@r{, }>=
8118 Less than, greater than, less than or equal, greater than or equal.
8119 Defined on scalar types. The value of these expressions is 0 for false
8120 and non-zero for true.
8123 left shift, and right shift. Defined on integral types.
8126 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8129 Addition and subtraction. Defined on integral types, floating-point types and
8132 @item *@r{, }/@r{, }%
8133 Multiplication, division, and modulus. Multiplication and division are
8134 defined on integral and floating-point types. Modulus is defined on
8138 Increment and decrement. When appearing before a variable, the
8139 operation is performed before the variable is used in an expression;
8140 when appearing after it, the variable's value is used before the
8141 operation takes place.
8144 Pointer dereferencing. Defined on pointer types. Same precedence as
8148 Address operator. Defined on variables. Same precedence as @code{++}.
8150 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
8151 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
8152 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
8153 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
8157 Negative. Defined on integral and floating-point types. Same
8158 precedence as @code{++}.
8161 Logical negation. Defined on integral types. Same precedence as
8165 Bitwise complement operator. Defined on integral types. Same precedence as
8170 Structure member, and pointer-to-structure member. For convenience,
8171 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
8172 pointer based on the stored type information.
8173 Defined on @code{struct} and @code{union} data.
8176 Dereferences of pointers to members.
8179 Array indexing. @code{@var{a}[@var{i}]} is defined as
8180 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
8183 Function parameter list. Same precedence as @code{->}.
8186 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
8187 and @code{class} types.
8190 Doubled colons also represent the @value{GDBN} scope operator
8191 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
8195 If an operator is redefined in the user code, @value{GDBN} usually
8196 attempts to invoke the redefined version instead of using the operator's
8204 @subsubsection C and C@t{++} constants
8206 @cindex C and C@t{++} constants
8208 @value{GDBN} allows you to express the constants of C and C@t{++} in the
8213 Integer constants are a sequence of digits. Octal constants are
8214 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
8215 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
8216 @samp{l}, specifying that the constant should be treated as a
8220 Floating point constants are a sequence of digits, followed by a decimal
8221 point, followed by a sequence of digits, and optionally followed by an
8222 exponent. An exponent is of the form:
8223 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
8224 sequence of digits. The @samp{+} is optional for positive exponents.
8225 A floating-point constant may also end with a letter @samp{f} or
8226 @samp{F}, specifying that the constant should be treated as being of
8227 the @code{float} (as opposed to the default @code{double}) type; or with
8228 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
8232 Enumerated constants consist of enumerated identifiers, or their
8233 integral equivalents.
8236 Character constants are a single character surrounded by single quotes
8237 (@code{'}), or a number---the ordinal value of the corresponding character
8238 (usually its @sc{ascii} value). Within quotes, the single character may
8239 be represented by a letter or by @dfn{escape sequences}, which are of
8240 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
8241 of the character's ordinal value; or of the form @samp{\@var{x}}, where
8242 @samp{@var{x}} is a predefined special character---for example,
8243 @samp{\n} for newline.
8246 String constants are a sequence of character constants surrounded by
8247 double quotes (@code{"}). Any valid character constant (as described
8248 above) may appear. Double quotes within the string must be preceded by
8249 a backslash, so for instance @samp{"a\"b'c"} is a string of five
8253 Pointer constants are an integral value. You can also write pointers
8254 to constants using the C operator @samp{&}.
8257 Array constants are comma-separated lists surrounded by braces @samp{@{}
8258 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
8259 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
8260 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
8264 * C plus plus expressions::
8271 @node C plus plus expressions
8272 @subsubsection C@t{++} expressions
8274 @cindex expressions in C@t{++}
8275 @value{GDBN} expression handling can interpret most C@t{++} expressions.
8277 @cindex debugging C@t{++} programs
8278 @cindex C@t{++} compilers
8279 @cindex debug formats and C@t{++}
8280 @cindex @value{NGCC} and C@t{++}
8282 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
8283 proper compiler and the proper debug format. Currently, @value{GDBN}
8284 works best when debugging C@t{++} code that is compiled with
8285 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
8286 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
8287 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
8288 stabs+ as their default debug format, so you usually don't need to
8289 specify a debug format explicitly. Other compilers and/or debug formats
8290 are likely to work badly or not at all when using @value{GDBN} to debug
8296 @cindex member functions
8298 Member function calls are allowed; you can use expressions like
8301 count = aml->GetOriginal(x, y)
8304 @vindex this@r{, inside C@t{++} member functions}
8305 @cindex namespace in C@t{++}
8307 While a member function is active (in the selected stack frame), your
8308 expressions have the same namespace available as the member function;
8309 that is, @value{GDBN} allows implicit references to the class instance
8310 pointer @code{this} following the same rules as C@t{++}.
8312 @cindex call overloaded functions
8313 @cindex overloaded functions, calling
8314 @cindex type conversions in C@t{++}
8316 You can call overloaded functions; @value{GDBN} resolves the function
8317 call to the right definition, with some restrictions. @value{GDBN} does not
8318 perform overload resolution involving user-defined type conversions,
8319 calls to constructors, or instantiations of templates that do not exist
8320 in the program. It also cannot handle ellipsis argument lists or
8323 It does perform integral conversions and promotions, floating-point
8324 promotions, arithmetic conversions, pointer conversions, conversions of
8325 class objects to base classes, and standard conversions such as those of
8326 functions or arrays to pointers; it requires an exact match on the
8327 number of function arguments.
8329 Overload resolution is always performed, unless you have specified
8330 @code{set overload-resolution off}. @xref{Debugging C plus plus,
8331 ,@value{GDBN} features for C@t{++}}.
8333 You must specify @code{set overload-resolution off} in order to use an
8334 explicit function signature to call an overloaded function, as in
8336 p 'foo(char,int)'('x', 13)
8339 The @value{GDBN} command-completion facility can simplify this;
8340 see @ref{Completion, ,Command completion}.
8342 @cindex reference declarations
8344 @value{GDBN} understands variables declared as C@t{++} references; you can use
8345 them in expressions just as you do in C@t{++} source---they are automatically
8348 In the parameter list shown when @value{GDBN} displays a frame, the values of
8349 reference variables are not displayed (unlike other variables); this
8350 avoids clutter, since references are often used for large structures.
8351 The @emph{address} of a reference variable is always shown, unless
8352 you have specified @samp{set print address off}.
8355 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
8356 expressions can use it just as expressions in your program do. Since
8357 one scope may be defined in another, you can use @code{::} repeatedly if
8358 necessary, for example in an expression like
8359 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
8360 resolving name scope by reference to source files, in both C and C@t{++}
8361 debugging (@pxref{Variables, ,Program variables}).
8364 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
8365 calling virtual functions correctly, printing out virtual bases of
8366 objects, calling functions in a base subobject, casting objects, and
8367 invoking user-defined operators.
8370 @subsubsection C and C@t{++} defaults
8372 @cindex C and C@t{++} defaults
8374 If you allow @value{GDBN} to set type and range checking automatically, they
8375 both default to @code{off} whenever the working language changes to
8376 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
8377 selects the working language.
8379 If you allow @value{GDBN} to set the language automatically, it
8380 recognizes source files whose names end with @file{.c}, @file{.C}, or
8381 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
8382 these files, it sets the working language to C or C@t{++}.
8383 @xref{Automatically, ,Having @value{GDBN} infer the source language},
8384 for further details.
8386 @c Type checking is (a) primarily motivated by Modula-2, and (b)
8387 @c unimplemented. If (b) changes, it might make sense to let this node
8388 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
8391 @subsubsection C and C@t{++} type and range checks
8393 @cindex C and C@t{++} checks
8395 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
8396 is not used. However, if you turn type checking on, @value{GDBN}
8397 considers two variables type equivalent if:
8401 The two variables are structured and have the same structure, union, or
8405 The two variables have the same type name, or types that have been
8406 declared equivalent through @code{typedef}.
8409 @c leaving this out because neither J Gilmore nor R Pesch understand it.
8412 The two @code{struct}, @code{union}, or @code{enum} variables are
8413 declared in the same declaration. (Note: this may not be true for all C
8418 Range checking, if turned on, is done on mathematical operations. Array
8419 indices are not checked, since they are often used to index a pointer
8420 that is not itself an array.
8423 @subsubsection @value{GDBN} and C
8425 The @code{set print union} and @code{show print union} commands apply to
8426 the @code{union} type. When set to @samp{on}, any @code{union} that is
8427 inside a @code{struct} or @code{class} is also printed. Otherwise, it
8428 appears as @samp{@{...@}}.
8430 The @code{@@} operator aids in the debugging of dynamic arrays, formed
8431 with pointers and a memory allocation function. @xref{Expressions,
8435 * Debugging C plus plus::
8438 @node Debugging C plus plus
8439 @subsubsection @value{GDBN} features for C@t{++}
8441 @cindex commands for C@t{++}
8443 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
8444 designed specifically for use with C@t{++}. Here is a summary:
8447 @cindex break in overloaded functions
8448 @item @r{breakpoint menus}
8449 When you want a breakpoint in a function whose name is overloaded,
8450 @value{GDBN} breakpoint menus help you specify which function definition
8451 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
8453 @cindex overloading in C@t{++}
8454 @item rbreak @var{regex}
8455 Setting breakpoints using regular expressions is helpful for setting
8456 breakpoints on overloaded functions that are not members of any special
8458 @xref{Set Breaks, ,Setting breakpoints}.
8460 @cindex C@t{++} exception handling
8463 Debug C@t{++} exception handling using these commands. @xref{Set
8464 Catchpoints, , Setting catchpoints}.
8467 @item ptype @var{typename}
8468 Print inheritance relationships as well as other information for type
8470 @xref{Symbols, ,Examining the Symbol Table}.
8472 @cindex C@t{++} symbol display
8473 @item set print demangle
8474 @itemx show print demangle
8475 @itemx set print asm-demangle
8476 @itemx show print asm-demangle
8477 Control whether C@t{++} symbols display in their source form, both when
8478 displaying code as C@t{++} source and when displaying disassemblies.
8479 @xref{Print Settings, ,Print settings}.
8481 @item set print object
8482 @itemx show print object
8483 Choose whether to print derived (actual) or declared types of objects.
8484 @xref{Print Settings, ,Print settings}.
8486 @item set print vtbl
8487 @itemx show print vtbl
8488 Control the format for printing virtual function tables.
8489 @xref{Print Settings, ,Print settings}.
8490 (The @code{vtbl} commands do not work on programs compiled with the HP
8491 ANSI C@t{++} compiler (@code{aCC}).)
8493 @kindex set overload-resolution
8494 @cindex overloaded functions, overload resolution
8495 @item set overload-resolution on
8496 Enable overload resolution for C@t{++} expression evaluation. The default
8497 is on. For overloaded functions, @value{GDBN} evaluates the arguments
8498 and searches for a function whose signature matches the argument types,
8499 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
8500 expressions}, for details). If it cannot find a match, it emits a
8503 @item set overload-resolution off
8504 Disable overload resolution for C@t{++} expression evaluation. For
8505 overloaded functions that are not class member functions, @value{GDBN}
8506 chooses the first function of the specified name that it finds in the
8507 symbol table, whether or not its arguments are of the correct type. For
8508 overloaded functions that are class member functions, @value{GDBN}
8509 searches for a function whose signature @emph{exactly} matches the
8512 @item @r{Overloaded symbol names}
8513 You can specify a particular definition of an overloaded symbol, using
8514 the same notation that is used to declare such symbols in C@t{++}: type
8515 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
8516 also use the @value{GDBN} command-line word completion facilities to list the
8517 available choices, or to finish the type list for you.
8518 @xref{Completion,, Command completion}, for details on how to do this.
8522 @subsection Objective-C
8525 This section provides information about some commands and command
8526 options that are useful for debugging Objective-C code.
8529 * Method Names in Commands::
8530 * The Print Command with Objective-C::
8533 @node Method Names in Commands, The Print Command with Objective-C, Objective-C, Objective-C
8534 @subsubsection Method Names in Commands
8536 The following commands have been extended to accept Objective-C method
8537 names as line specifications:
8539 @kindex clear@r{, and Objective-C}
8540 @kindex break@r{, and Objective-C}
8541 @kindex info line@r{, and Objective-C}
8542 @kindex jump@r{, and Objective-C}
8543 @kindex list@r{, and Objective-C}
8547 @item @code{info line}
8552 A fully qualified Objective-C method name is specified as
8555 -[@var{Class} @var{methodName}]
8558 where the minus sign is used to indicate an instance method and a
8559 plus sign (not shown) is used to indicate a class method. The class
8560 name @var{Class} and method name @var{methodName} are enclosed in
8561 brackets, similar to the way messages are specified in Objective-C
8562 source code. For example, to set a breakpoint at the @code{create}
8563 instance method of class @code{Fruit} in the program currently being
8567 break -[Fruit create]
8570 To list ten program lines around the @code{initialize} class method,
8574 list +[NSText initialize]
8577 In the current version of @value{GDBN}, the plus or minus sign is
8578 required. In future versions of @value{GDBN}, the plus or minus
8579 sign will be optional, but you can use it to narrow the search. It
8580 is also possible to specify just a method name:
8586 You must specify the complete method name, including any colons. If
8587 your program's source files contain more than one @code{create} method,
8588 you'll be presented with a numbered list of classes that implement that
8589 method. Indicate your choice by number, or type @samp{0} to exit if
8592 As another example, to clear a breakpoint established at the
8593 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
8596 clear -[NSWindow makeKeyAndOrderFront:]
8599 @node The Print Command with Objective-C
8600 @subsubsection The Print Command With Objective-C
8601 @kindex print-object
8602 @kindex po @r{(@code{print-object})}
8604 The print command has also been extended to accept methods. For example:
8607 print -[@var{object} hash]
8610 @cindex print an Objective-C object description
8611 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
8613 will tell @value{GDBN} to send the @code{hash} message to @var{object}
8614 and print the result. Also, an additional command has been added,
8615 @code{print-object} or @code{po} for short, which is meant to print
8616 the description of an object. However, this command may only work
8617 with certain Objective-C libraries that have a particular hook
8618 function, @code{_NSPrintForDebugger}, defined.
8620 @node Modula-2, , Objective-C, Support
8621 @subsection Modula-2
8623 @cindex Modula-2, @value{GDBN} support
8625 The extensions made to @value{GDBN} to support Modula-2 only support
8626 output from the @sc{gnu} Modula-2 compiler (which is currently being
8627 developed). Other Modula-2 compilers are not currently supported, and
8628 attempting to debug executables produced by them is most likely
8629 to give an error as @value{GDBN} reads in the executable's symbol
8632 @cindex expressions in Modula-2
8634 * M2 Operators:: Built-in operators
8635 * Built-In Func/Proc:: Built-in functions and procedures
8636 * M2 Constants:: Modula-2 constants
8637 * M2 Defaults:: Default settings for Modula-2
8638 * Deviations:: Deviations from standard Modula-2
8639 * M2 Checks:: Modula-2 type and range checks
8640 * M2 Scope:: The scope operators @code{::} and @code{.}
8641 * GDB/M2:: @value{GDBN} and Modula-2
8645 @subsubsection Operators
8646 @cindex Modula-2 operators
8648 Operators must be defined on values of specific types. For instance,
8649 @code{+} is defined on numbers, but not on structures. Operators are
8650 often defined on groups of types. For the purposes of Modula-2, the
8651 following definitions hold:
8656 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
8660 @emph{Character types} consist of @code{CHAR} and its subranges.
8663 @emph{Floating-point types} consist of @code{REAL}.
8666 @emph{Pointer types} consist of anything declared as @code{POINTER TO
8670 @emph{Scalar types} consist of all of the above.
8673 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
8676 @emph{Boolean types} consist of @code{BOOLEAN}.
8680 The following operators are supported, and appear in order of
8681 increasing precedence:
8685 Function argument or array index separator.
8688 Assignment. The value of @var{var} @code{:=} @var{value} is
8692 Less than, greater than on integral, floating-point, or enumerated
8696 Less than or equal to, greater than or equal to
8697 on integral, floating-point and enumerated types, or set inclusion on
8698 set types. Same precedence as @code{<}.
8700 @item =@r{, }<>@r{, }#
8701 Equality and two ways of expressing inequality, valid on scalar types.
8702 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
8703 available for inequality, since @code{#} conflicts with the script
8707 Set membership. Defined on set types and the types of their members.
8708 Same precedence as @code{<}.
8711 Boolean disjunction. Defined on boolean types.
8714 Boolean conjunction. Defined on boolean types.
8717 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8720 Addition and subtraction on integral and floating-point types, or union
8721 and difference on set types.
8724 Multiplication on integral and floating-point types, or set intersection
8728 Division on floating-point types, or symmetric set difference on set
8729 types. Same precedence as @code{*}.
8732 Integer division and remainder. Defined on integral types. Same
8733 precedence as @code{*}.
8736 Negative. Defined on @code{INTEGER} and @code{REAL} data.
8739 Pointer dereferencing. Defined on pointer types.
8742 Boolean negation. Defined on boolean types. Same precedence as
8746 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
8747 precedence as @code{^}.
8750 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
8753 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
8757 @value{GDBN} and Modula-2 scope operators.
8761 @emph{Warning:} Sets and their operations are not yet supported, so @value{GDBN}
8762 treats the use of the operator @code{IN}, or the use of operators
8763 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
8764 @code{<=}, and @code{>=} on sets as an error.
8768 @node Built-In Func/Proc
8769 @subsubsection Built-in functions and procedures
8770 @cindex Modula-2 built-ins
8772 Modula-2 also makes available several built-in procedures and functions.
8773 In describing these, the following metavariables are used:
8778 represents an @code{ARRAY} variable.
8781 represents a @code{CHAR} constant or variable.
8784 represents a variable or constant of integral type.
8787 represents an identifier that belongs to a set. Generally used in the
8788 same function with the metavariable @var{s}. The type of @var{s} should
8789 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
8792 represents a variable or constant of integral or floating-point type.
8795 represents a variable or constant of floating-point type.
8801 represents a variable.
8804 represents a variable or constant of one of many types. See the
8805 explanation of the function for details.
8808 All Modula-2 built-in procedures also return a result, described below.
8812 Returns the absolute value of @var{n}.
8815 If @var{c} is a lower case letter, it returns its upper case
8816 equivalent, otherwise it returns its argument.
8819 Returns the character whose ordinal value is @var{i}.
8822 Decrements the value in the variable @var{v} by one. Returns the new value.
8824 @item DEC(@var{v},@var{i})
8825 Decrements the value in the variable @var{v} by @var{i}. Returns the
8828 @item EXCL(@var{m},@var{s})
8829 Removes the element @var{m} from the set @var{s}. Returns the new
8832 @item FLOAT(@var{i})
8833 Returns the floating point equivalent of the integer @var{i}.
8836 Returns the index of the last member of @var{a}.
8839 Increments the value in the variable @var{v} by one. Returns the new value.
8841 @item INC(@var{v},@var{i})
8842 Increments the value in the variable @var{v} by @var{i}. Returns the
8845 @item INCL(@var{m},@var{s})
8846 Adds the element @var{m} to the set @var{s} if it is not already
8847 there. Returns the new set.
8850 Returns the maximum value of the type @var{t}.
8853 Returns the minimum value of the type @var{t}.
8856 Returns boolean TRUE if @var{i} is an odd number.
8859 Returns the ordinal value of its argument. For example, the ordinal
8860 value of a character is its @sc{ascii} value (on machines supporting the
8861 @sc{ascii} character set). @var{x} must be of an ordered type, which include
8862 integral, character and enumerated types.
8865 Returns the size of its argument. @var{x} can be a variable or a type.
8867 @item TRUNC(@var{r})
8868 Returns the integral part of @var{r}.
8870 @item VAL(@var{t},@var{i})
8871 Returns the member of the type @var{t} whose ordinal value is @var{i}.
8875 @emph{Warning:} Sets and their operations are not yet supported, so
8876 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
8880 @cindex Modula-2 constants
8882 @subsubsection Constants
8884 @value{GDBN} allows you to express the constants of Modula-2 in the following
8890 Integer constants are simply a sequence of digits. When used in an
8891 expression, a constant is interpreted to be type-compatible with the
8892 rest of the expression. Hexadecimal integers are specified by a
8893 trailing @samp{H}, and octal integers by a trailing @samp{B}.
8896 Floating point constants appear as a sequence of digits, followed by a
8897 decimal point and another sequence of digits. An optional exponent can
8898 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
8899 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
8900 digits of the floating point constant must be valid decimal (base 10)
8904 Character constants consist of a single character enclosed by a pair of
8905 like quotes, either single (@code{'}) or double (@code{"}). They may
8906 also be expressed by their ordinal value (their @sc{ascii} value, usually)
8907 followed by a @samp{C}.
8910 String constants consist of a sequence of characters enclosed by a
8911 pair of like quotes, either single (@code{'}) or double (@code{"}).
8912 Escape sequences in the style of C are also allowed. @xref{C
8913 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
8917 Enumerated constants consist of an enumerated identifier.
8920 Boolean constants consist of the identifiers @code{TRUE} and
8924 Pointer constants consist of integral values only.
8927 Set constants are not yet supported.
8931 @subsubsection Modula-2 defaults
8932 @cindex Modula-2 defaults
8934 If type and range checking are set automatically by @value{GDBN}, they
8935 both default to @code{on} whenever the working language changes to
8936 Modula-2. This happens regardless of whether you or @value{GDBN}
8937 selected the working language.
8939 If you allow @value{GDBN} to set the language automatically, then entering
8940 code compiled from a file whose name ends with @file{.mod} sets the
8941 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
8942 the language automatically}, for further details.
8945 @subsubsection Deviations from standard Modula-2
8946 @cindex Modula-2, deviations from
8948 A few changes have been made to make Modula-2 programs easier to debug.
8949 This is done primarily via loosening its type strictness:
8953 Unlike in standard Modula-2, pointer constants can be formed by
8954 integers. This allows you to modify pointer variables during
8955 debugging. (In standard Modula-2, the actual address contained in a
8956 pointer variable is hidden from you; it can only be modified
8957 through direct assignment to another pointer variable or expression that
8958 returned a pointer.)
8961 C escape sequences can be used in strings and characters to represent
8962 non-printable characters. @value{GDBN} prints out strings with these
8963 escape sequences embedded. Single non-printable characters are
8964 printed using the @samp{CHR(@var{nnn})} format.
8967 The assignment operator (@code{:=}) returns the value of its right-hand
8971 All built-in procedures both modify @emph{and} return their argument.
8975 @subsubsection Modula-2 type and range checks
8976 @cindex Modula-2 checks
8979 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
8982 @c FIXME remove warning when type/range checks added
8984 @value{GDBN} considers two Modula-2 variables type equivalent if:
8988 They are of types that have been declared equivalent via a @code{TYPE
8989 @var{t1} = @var{t2}} statement
8992 They have been declared on the same line. (Note: This is true of the
8993 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
8996 As long as type checking is enabled, any attempt to combine variables
8997 whose types are not equivalent is an error.
8999 Range checking is done on all mathematical operations, assignment, array
9000 index bounds, and all built-in functions and procedures.
9003 @subsubsection The scope operators @code{::} and @code{.}
9005 @cindex @code{.}, Modula-2 scope operator
9006 @cindex colon, doubled as scope operator
9008 @vindex colon-colon@r{, in Modula-2}
9009 @c Info cannot handle :: but TeX can.
9012 @vindex ::@r{, in Modula-2}
9015 There are a few subtle differences between the Modula-2 scope operator
9016 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
9021 @var{module} . @var{id}
9022 @var{scope} :: @var{id}
9026 where @var{scope} is the name of a module or a procedure,
9027 @var{module} the name of a module, and @var{id} is any declared
9028 identifier within your program, except another module.
9030 Using the @code{::} operator makes @value{GDBN} search the scope
9031 specified by @var{scope} for the identifier @var{id}. If it is not
9032 found in the specified scope, then @value{GDBN} searches all scopes
9033 enclosing the one specified by @var{scope}.
9035 Using the @code{.} operator makes @value{GDBN} search the current scope for
9036 the identifier specified by @var{id} that was imported from the
9037 definition module specified by @var{module}. With this operator, it is
9038 an error if the identifier @var{id} was not imported from definition
9039 module @var{module}, or if @var{id} is not an identifier in
9043 @subsubsection @value{GDBN} and Modula-2
9045 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
9046 Five subcommands of @code{set print} and @code{show print} apply
9047 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
9048 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
9049 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
9050 analogue in Modula-2.
9052 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
9053 with any language, is not useful with Modula-2. Its
9054 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
9055 created in Modula-2 as they can in C or C@t{++}. However, because an
9056 address can be specified by an integral constant, the construct
9057 @samp{@{@var{type}@}@var{adrexp}} is still useful.
9059 @cindex @code{#} in Modula-2
9060 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
9061 interpreted as the beginning of a comment. Use @code{<>} instead.
9063 @node Unsupported languages
9064 @section Unsupported languages
9066 @cindex unsupported languages
9067 @cindex minimal language
9068 In addition to the other fully-supported programming languages,
9069 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
9070 It does not represent a real programming language, but provides a set
9071 of capabilities close to what the C or assembly languages provide.
9072 This should allow most simple operations to be performed while debugging
9073 an application that uses a language currently not supported by @value{GDBN}.
9075 If the language is set to @code{auto}, @value{GDBN} will automatically
9076 select this language if the current frame corresponds to an unsupported
9080 @chapter Examining the Symbol Table
9082 The commands described in this chapter allow you to inquire about the
9083 symbols (names of variables, functions and types) defined in your
9084 program. This information is inherent in the text of your program and
9085 does not change as your program executes. @value{GDBN} finds it in your
9086 program's symbol table, in the file indicated when you started @value{GDBN}
9087 (@pxref{File Options, ,Choosing files}), or by one of the
9088 file-management commands (@pxref{Files, ,Commands to specify files}).
9090 @cindex symbol names
9091 @cindex names of symbols
9092 @cindex quoting names
9093 Occasionally, you may need to refer to symbols that contain unusual
9094 characters, which @value{GDBN} ordinarily treats as word delimiters. The
9095 most frequent case is in referring to static variables in other
9096 source files (@pxref{Variables,,Program variables}). File names
9097 are recorded in object files as debugging symbols, but @value{GDBN} would
9098 ordinarily parse a typical file name, like @file{foo.c}, as the three words
9099 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
9100 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
9107 looks up the value of @code{x} in the scope of the file @file{foo.c}.
9110 @kindex info address
9111 @cindex address of a symbol
9112 @item info address @var{symbol}
9113 Describe where the data for @var{symbol} is stored. For a register
9114 variable, this says which register it is kept in. For a non-register
9115 local variable, this prints the stack-frame offset at which the variable
9118 Note the contrast with @samp{print &@var{symbol}}, which does not work
9119 at all for a register variable, and for a stack local variable prints
9120 the exact address of the current instantiation of the variable.
9123 @cindex symbol from address
9124 @item info symbol @var{addr}
9125 Print the name of a symbol which is stored at the address @var{addr}.
9126 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
9127 nearest symbol and an offset from it:
9130 (@value{GDBP}) info symbol 0x54320
9131 _initialize_vx + 396 in section .text
9135 This is the opposite of the @code{info address} command. You can use
9136 it to find out the name of a variable or a function given its address.
9139 @item whatis @var{expr}
9140 Print the data type of expression @var{expr}. @var{expr} is not
9141 actually evaluated, and any side-effecting operations (such as
9142 assignments or function calls) inside it do not take place.
9143 @xref{Expressions, ,Expressions}.
9146 Print the data type of @code{$}, the last value in the value history.
9149 @item ptype @var{typename}
9150 Print a description of data type @var{typename}. @var{typename} may be
9151 the name of a type, or for C code it may have the form @samp{class
9152 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
9153 @var{union-tag}} or @samp{enum @var{enum-tag}}.
9155 @item ptype @var{expr}
9157 Print a description of the type of expression @var{expr}. @code{ptype}
9158 differs from @code{whatis} by printing a detailed description, instead
9159 of just the name of the type.
9161 For example, for this variable declaration:
9164 struct complex @{double real; double imag;@} v;
9168 the two commands give this output:
9172 (@value{GDBP}) whatis v
9173 type = struct complex
9174 (@value{GDBP}) ptype v
9175 type = struct complex @{
9183 As with @code{whatis}, using @code{ptype} without an argument refers to
9184 the type of @code{$}, the last value in the value history.
9187 @item info types @var{regexp}
9189 Print a brief description of all types whose names match @var{regexp}
9190 (or all types in your program, if you supply no argument). Each
9191 complete typename is matched as though it were a complete line; thus,
9192 @samp{i type value} gives information on all types in your program whose
9193 names include the string @code{value}, but @samp{i type ^value$} gives
9194 information only on types whose complete name is @code{value}.
9196 This command differs from @code{ptype} in two ways: first, like
9197 @code{whatis}, it does not print a detailed description; second, it
9198 lists all source files where a type is defined.
9201 @cindex local variables
9202 @item info scope @var{addr}
9203 List all the variables local to a particular scope. This command
9204 accepts a location---a function name, a source line, or an address
9205 preceded by a @samp{*}, and prints all the variables local to the
9206 scope defined by that location. For example:
9209 (@value{GDBP}) @b{info scope command_line_handler}
9210 Scope for command_line_handler:
9211 Symbol rl is an argument at stack/frame offset 8, length 4.
9212 Symbol linebuffer is in static storage at address 0x150a18, length 4.
9213 Symbol linelength is in static storage at address 0x150a1c, length 4.
9214 Symbol p is a local variable in register $esi, length 4.
9215 Symbol p1 is a local variable in register $ebx, length 4.
9216 Symbol nline is a local variable in register $edx, length 4.
9217 Symbol repeat is a local variable at frame offset -8, length 4.
9221 This command is especially useful for determining what data to collect
9222 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
9227 Show information about the current source file---that is, the source file for
9228 the function containing the current point of execution:
9231 the name of the source file, and the directory containing it,
9233 the directory it was compiled in,
9235 its length, in lines,
9237 which programming language it is written in,
9239 whether the executable includes debugging information for that file, and
9240 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
9242 whether the debugging information includes information about
9243 preprocessor macros.
9247 @kindex info sources
9249 Print the names of all source files in your program for which there is
9250 debugging information, organized into two lists: files whose symbols
9251 have already been read, and files whose symbols will be read when needed.
9253 @kindex info functions
9254 @item info functions
9255 Print the names and data types of all defined functions.
9257 @item info functions @var{regexp}
9258 Print the names and data types of all defined functions
9259 whose names contain a match for regular expression @var{regexp}.
9260 Thus, @samp{info fun step} finds all functions whose names
9261 include @code{step}; @samp{info fun ^step} finds those whose names
9262 start with @code{step}. If a function name contains characters
9263 that conflict with the regular expression language (eg.
9264 @samp{operator*()}), they may be quoted with a backslash.
9266 @kindex info variables
9267 @item info variables
9268 Print the names and data types of all variables that are declared
9269 outside of functions (i.e.@: excluding local variables).
9271 @item info variables @var{regexp}
9272 Print the names and data types of all variables (except for local
9273 variables) whose names contain a match for regular expression
9276 @kindex info classes
9278 @itemx info classes @var{regexp}
9279 Display all Objective-C classes in your program, or
9280 (with the @var{regexp} argument) all those matching a particular regular
9283 @kindex info selectors
9284 @item info selectors
9285 @itemx info selectors @var{regexp}
9286 Display all Objective-C selectors in your program, or
9287 (with the @var{regexp} argument) all those matching a particular regular
9291 This was never implemented.
9292 @kindex info methods
9294 @itemx info methods @var{regexp}
9295 The @code{info methods} command permits the user to examine all defined
9296 methods within C@t{++} program, or (with the @var{regexp} argument) a
9297 specific set of methods found in the various C@t{++} classes. Many
9298 C@t{++} classes provide a large number of methods. Thus, the output
9299 from the @code{ptype} command can be overwhelming and hard to use. The
9300 @code{info-methods} command filters the methods, printing only those
9301 which match the regular-expression @var{regexp}.
9304 @cindex reloading symbols
9305 Some systems allow individual object files that make up your program to
9306 be replaced without stopping and restarting your program. For example,
9307 in VxWorks you can simply recompile a defective object file and keep on
9308 running. If you are running on one of these systems, you can allow
9309 @value{GDBN} to reload the symbols for automatically relinked modules:
9312 @kindex set symbol-reloading
9313 @item set symbol-reloading on
9314 Replace symbol definitions for the corresponding source file when an
9315 object file with a particular name is seen again.
9317 @item set symbol-reloading off
9318 Do not replace symbol definitions when encountering object files of the
9319 same name more than once. This is the default state; if you are not
9320 running on a system that permits automatic relinking of modules, you
9321 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
9322 may discard symbols when linking large programs, that may contain
9323 several modules (from different directories or libraries) with the same
9326 @kindex show symbol-reloading
9327 @item show symbol-reloading
9328 Show the current @code{on} or @code{off} setting.
9331 @kindex set opaque-type-resolution
9332 @item set opaque-type-resolution on
9333 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
9334 declared as a pointer to a @code{struct}, @code{class}, or
9335 @code{union}---for example, @code{struct MyType *}---that is used in one
9336 source file although the full declaration of @code{struct MyType} is in
9337 another source file. The default is on.
9339 A change in the setting of this subcommand will not take effect until
9340 the next time symbols for a file are loaded.
9342 @item set opaque-type-resolution off
9343 Tell @value{GDBN} not to resolve opaque types. In this case, the type
9344 is printed as follows:
9346 @{<no data fields>@}
9349 @kindex show opaque-type-resolution
9350 @item show opaque-type-resolution
9351 Show whether opaque types are resolved or not.
9353 @kindex maint print symbols
9355 @kindex maint print psymbols
9356 @cindex partial symbol dump
9357 @item maint print symbols @var{filename}
9358 @itemx maint print psymbols @var{filename}
9359 @itemx maint print msymbols @var{filename}
9360 Write a dump of debugging symbol data into the file @var{filename}.
9361 These commands are used to debug the @value{GDBN} symbol-reading code. Only
9362 symbols with debugging data are included. If you use @samp{maint print
9363 symbols}, @value{GDBN} includes all the symbols for which it has already
9364 collected full details: that is, @var{filename} reflects symbols for
9365 only those files whose symbols @value{GDBN} has read. You can use the
9366 command @code{info sources} to find out which files these are. If you
9367 use @samp{maint print psymbols} instead, the dump shows information about
9368 symbols that @value{GDBN} only knows partially---that is, symbols defined in
9369 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
9370 @samp{maint print msymbols} dumps just the minimal symbol information
9371 required for each object file from which @value{GDBN} has read some symbols.
9372 @xref{Files, ,Commands to specify files}, for a discussion of how
9373 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
9375 @kindex maint info symtabs
9376 @kindex maint info psymtabs
9377 @cindex listing @value{GDBN}'s internal symbol tables
9378 @cindex symbol tables, listing @value{GDBN}'s internal
9379 @cindex full symbol tables, listing @value{GDBN}'s internal
9380 @cindex partial symbol tables, listing @value{GDBN}'s internal
9381 @item maint info symtabs @r{[} @var{regexp} @r{]}
9382 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
9384 List the @code{struct symtab} or @code{struct partial_symtab}
9385 structures whose names match @var{regexp}. If @var{regexp} is not
9386 given, list them all. The output includes expressions which you can
9387 copy into a @value{GDBN} debugging this one to examine a particular
9388 structure in more detail. For example:
9391 (@value{GDBP}) maint info psymtabs dwarf2read
9392 @{ objfile /home/gnu/build/gdb/gdb
9393 ((struct objfile *) 0x82e69d0)
9394 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
9395 ((struct partial_symtab *) 0x8474b10)
9398 text addresses 0x814d3c8 -- 0x8158074
9399 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
9400 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
9404 (@value{GDBP}) maint info symtabs
9408 We see that there is one partial symbol table whose filename contains
9409 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
9410 and we see that @value{GDBN} has not read in any symtabs yet at all.
9411 If we set a breakpoint on a function, that will cause @value{GDBN} to
9412 read the symtab for the compilation unit containing that function:
9415 (@value{GDBP}) break dwarf2_psymtab_to_symtab
9416 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
9418 (@value{GDBP}) maint info symtabs
9419 @{ objfile /home/gnu/build/gdb/gdb
9420 ((struct objfile *) 0x82e69d0)
9421 @{ symtab /home/gnu/src/gdb/dwarf2read.c
9422 ((struct symtab *) 0x86c1f38)
9425 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
9435 @chapter Altering Execution
9437 Once you think you have found an error in your program, you might want to
9438 find out for certain whether correcting the apparent error would lead to
9439 correct results in the rest of the run. You can find the answer by
9440 experiment, using the @value{GDBN} features for altering execution of the
9443 For example, you can store new values into variables or memory
9444 locations, give your program a signal, restart it at a different
9445 address, or even return prematurely from a function.
9448 * Assignment:: Assignment to variables
9449 * Jumping:: Continuing at a different address
9450 * Signaling:: Giving your program a signal
9451 * Returning:: Returning from a function
9452 * Calling:: Calling your program's functions
9453 * Patching:: Patching your program
9457 @section Assignment to variables
9460 @cindex setting variables
9461 To alter the value of a variable, evaluate an assignment expression.
9462 @xref{Expressions, ,Expressions}. For example,
9469 stores the value 4 into the variable @code{x}, and then prints the
9470 value of the assignment expression (which is 4).
9471 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
9472 information on operators in supported languages.
9474 @kindex set variable
9475 @cindex variables, setting
9476 If you are not interested in seeing the value of the assignment, use the
9477 @code{set} command instead of the @code{print} command. @code{set} is
9478 really the same as @code{print} except that the expression's value is
9479 not printed and is not put in the value history (@pxref{Value History,
9480 ,Value history}). The expression is evaluated only for its effects.
9482 If the beginning of the argument string of the @code{set} command
9483 appears identical to a @code{set} subcommand, use the @code{set
9484 variable} command instead of just @code{set}. This command is identical
9485 to @code{set} except for its lack of subcommands. For example, if your
9486 program has a variable @code{width}, you get an error if you try to set
9487 a new value with just @samp{set width=13}, because @value{GDBN} has the
9488 command @code{set width}:
9491 (@value{GDBP}) whatis width
9493 (@value{GDBP}) p width
9495 (@value{GDBP}) set width=47
9496 Invalid syntax in expression.
9500 The invalid expression, of course, is @samp{=47}. In
9501 order to actually set the program's variable @code{width}, use
9504 (@value{GDBP}) set var width=47
9507 Because the @code{set} command has many subcommands that can conflict
9508 with the names of program variables, it is a good idea to use the
9509 @code{set variable} command instead of just @code{set}. For example, if
9510 your program has a variable @code{g}, you run into problems if you try
9511 to set a new value with just @samp{set g=4}, because @value{GDBN} has
9512 the command @code{set gnutarget}, abbreviated @code{set g}:
9516 (@value{GDBP}) whatis g
9520 (@value{GDBP}) set g=4
9524 The program being debugged has been started already.
9525 Start it from the beginning? (y or n) y
9526 Starting program: /home/smith/cc_progs/a.out
9527 "/home/smith/cc_progs/a.out": can't open to read symbols:
9529 (@value{GDBP}) show g
9530 The current BFD target is "=4".
9535 The program variable @code{g} did not change, and you silently set the
9536 @code{gnutarget} to an invalid value. In order to set the variable
9540 (@value{GDBP}) set var g=4
9543 @value{GDBN} allows more implicit conversions in assignments than C; you can
9544 freely store an integer value into a pointer variable or vice versa,
9545 and you can convert any structure to any other structure that is the
9546 same length or shorter.
9547 @comment FIXME: how do structs align/pad in these conversions?
9548 @comment /doc@cygnus.com 18dec1990
9550 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
9551 construct to generate a value of specified type at a specified address
9552 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
9553 to memory location @code{0x83040} as an integer (which implies a certain size
9554 and representation in memory), and
9557 set @{int@}0x83040 = 4
9561 stores the value 4 into that memory location.
9564 @section Continuing at a different address
9566 Ordinarily, when you continue your program, you do so at the place where
9567 it stopped, with the @code{continue} command. You can instead continue at
9568 an address of your own choosing, with the following commands:
9572 @item jump @var{linespec}
9573 Resume execution at line @var{linespec}. Execution stops again
9574 immediately if there is a breakpoint there. @xref{List, ,Printing
9575 source lines}, for a description of the different forms of
9576 @var{linespec}. It is common practice to use the @code{tbreak} command
9577 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
9580 The @code{jump} command does not change the current stack frame, or
9581 the stack pointer, or the contents of any memory location or any
9582 register other than the program counter. If line @var{linespec} is in
9583 a different function from the one currently executing, the results may
9584 be bizarre if the two functions expect different patterns of arguments or
9585 of local variables. For this reason, the @code{jump} command requests
9586 confirmation if the specified line is not in the function currently
9587 executing. However, even bizarre results are predictable if you are
9588 well acquainted with the machine-language code of your program.
9590 @item jump *@var{address}
9591 Resume execution at the instruction at address @var{address}.
9594 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
9595 On many systems, you can get much the same effect as the @code{jump}
9596 command by storing a new value into the register @code{$pc}. The
9597 difference is that this does not start your program running; it only
9598 changes the address of where it @emph{will} run when you continue. For
9606 makes the next @code{continue} command or stepping command execute at
9607 address @code{0x485}, rather than at the address where your program stopped.
9608 @xref{Continuing and Stepping, ,Continuing and stepping}.
9610 The most common occasion to use the @code{jump} command is to back
9611 up---perhaps with more breakpoints set---over a portion of a program
9612 that has already executed, in order to examine its execution in more
9617 @section Giving your program a signal
9621 @item signal @var{signal}
9622 Resume execution where your program stopped, but immediately give it the
9623 signal @var{signal}. @var{signal} can be the name or the number of a
9624 signal. For example, on many systems @code{signal 2} and @code{signal
9625 SIGINT} are both ways of sending an interrupt signal.
9627 Alternatively, if @var{signal} is zero, continue execution without
9628 giving a signal. This is useful when your program stopped on account of
9629 a signal and would ordinary see the signal when resumed with the
9630 @code{continue} command; @samp{signal 0} causes it to resume without a
9633 @code{signal} does not repeat when you press @key{RET} a second time
9634 after executing the command.
9638 Invoking the @code{signal} command is not the same as invoking the
9639 @code{kill} utility from the shell. Sending a signal with @code{kill}
9640 causes @value{GDBN} to decide what to do with the signal depending on
9641 the signal handling tables (@pxref{Signals}). The @code{signal} command
9642 passes the signal directly to your program.
9646 @section Returning from a function
9649 @cindex returning from a function
9652 @itemx return @var{expression}
9653 You can cancel execution of a function call with the @code{return}
9654 command. If you give an
9655 @var{expression} argument, its value is used as the function's return
9659 When you use @code{return}, @value{GDBN} discards the selected stack frame
9660 (and all frames within it). You can think of this as making the
9661 discarded frame return prematurely. If you wish to specify a value to
9662 be returned, give that value as the argument to @code{return}.
9664 This pops the selected stack frame (@pxref{Selection, ,Selecting a
9665 frame}), and any other frames inside of it, leaving its caller as the
9666 innermost remaining frame. That frame becomes selected. The
9667 specified value is stored in the registers used for returning values
9670 The @code{return} command does not resume execution; it leaves the
9671 program stopped in the state that would exist if the function had just
9672 returned. In contrast, the @code{finish} command (@pxref{Continuing
9673 and Stepping, ,Continuing and stepping}) resumes execution until the
9674 selected stack frame returns naturally.
9677 @section Calling program functions
9679 @cindex calling functions
9682 @item call @var{expr}
9683 Evaluate the expression @var{expr} without displaying @code{void}
9687 You can use this variant of the @code{print} command if you want to
9688 execute a function from your program, but without cluttering the output
9689 with @code{void} returned values. If the result is not void, it
9690 is printed and saved in the value history.
9693 @section Patching programs
9695 @cindex patching binaries
9696 @cindex writing into executables
9697 @cindex writing into corefiles
9699 By default, @value{GDBN} opens the file containing your program's
9700 executable code (or the corefile) read-only. This prevents accidental
9701 alterations to machine code; but it also prevents you from intentionally
9702 patching your program's binary.
9704 If you'd like to be able to patch the binary, you can specify that
9705 explicitly with the @code{set write} command. For example, you might
9706 want to turn on internal debugging flags, or even to make emergency
9712 @itemx set write off
9713 If you specify @samp{set write on}, @value{GDBN} opens executable and
9714 core files for both reading and writing; if you specify @samp{set write
9715 off} (the default), @value{GDBN} opens them read-only.
9717 If you have already loaded a file, you must load it again (using the
9718 @code{exec-file} or @code{core-file} command) after changing @code{set
9719 write}, for your new setting to take effect.
9723 Display whether executable files and core files are opened for writing
9728 @chapter @value{GDBN} Files
9730 @value{GDBN} needs to know the file name of the program to be debugged,
9731 both in order to read its symbol table and in order to start your
9732 program. To debug a core dump of a previous run, you must also tell
9733 @value{GDBN} the name of the core dump file.
9736 * Files:: Commands to specify files
9737 * Separate Debug Files:: Debugging information in separate files
9738 * Symbol Errors:: Errors reading symbol files
9742 @section Commands to specify files
9744 @cindex symbol table
9745 @cindex core dump file
9747 You may want to specify executable and core dump file names. The usual
9748 way to do this is at start-up time, using the arguments to
9749 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
9750 Out of @value{GDBN}}).
9752 Occasionally it is necessary to change to a different file during a
9753 @value{GDBN} session. Or you may run @value{GDBN} and forget to specify
9754 a file you want to use. In these situations the @value{GDBN} commands
9755 to specify new files are useful.
9758 @cindex executable file
9760 @item file @var{filename}
9761 Use @var{filename} as the program to be debugged. It is read for its
9762 symbols and for the contents of pure memory. It is also the program
9763 executed when you use the @code{run} command. If you do not specify a
9764 directory and the file is not found in the @value{GDBN} working directory,
9765 @value{GDBN} uses the environment variable @code{PATH} as a list of
9766 directories to search, just as the shell does when looking for a program
9767 to run. You can change the value of this variable, for both @value{GDBN}
9768 and your program, using the @code{path} command.
9770 On systems with memory-mapped files, an auxiliary file named
9771 @file{@var{filename}.syms} may hold symbol table information for
9772 @var{filename}. If so, @value{GDBN} maps in the symbol table from
9773 @file{@var{filename}.syms}, starting up more quickly. See the
9774 descriptions of the file options @samp{-mapped} and @samp{-readnow}
9775 (available on the command line, and with the commands @code{file},
9776 @code{symbol-file}, or @code{add-symbol-file}, described below),
9777 for more information.
9780 @code{file} with no argument makes @value{GDBN} discard any information it
9781 has on both executable file and the symbol table.
9784 @item exec-file @r{[} @var{filename} @r{]}
9785 Specify that the program to be run (but not the symbol table) is found
9786 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
9787 if necessary to locate your program. Omitting @var{filename} means to
9788 discard information on the executable file.
9791 @item symbol-file @r{[} @var{filename} @r{]}
9792 Read symbol table information from file @var{filename}. @code{PATH} is
9793 searched when necessary. Use the @code{file} command to get both symbol
9794 table and program to run from the same file.
9796 @code{symbol-file} with no argument clears out @value{GDBN} information on your
9797 program's symbol table.
9799 The @code{symbol-file} command causes @value{GDBN} to forget the contents
9800 of its convenience variables, the value history, and all breakpoints and
9801 auto-display expressions. This is because they may contain pointers to
9802 the internal data recording symbols and data types, which are part of
9803 the old symbol table data being discarded inside @value{GDBN}.
9805 @code{symbol-file} does not repeat if you press @key{RET} again after
9808 When @value{GDBN} is configured for a particular environment, it
9809 understands debugging information in whatever format is the standard
9810 generated for that environment; you may use either a @sc{gnu} compiler, or
9811 other compilers that adhere to the local conventions.
9812 Best results are usually obtained from @sc{gnu} compilers; for example,
9813 using @code{@value{GCC}} you can generate debugging information for
9816 For most kinds of object files, with the exception of old SVR3 systems
9817 using COFF, the @code{symbol-file} command does not normally read the
9818 symbol table in full right away. Instead, it scans the symbol table
9819 quickly to find which source files and which symbols are present. The
9820 details are read later, one source file at a time, as they are needed.
9822 The purpose of this two-stage reading strategy is to make @value{GDBN}
9823 start up faster. For the most part, it is invisible except for
9824 occasional pauses while the symbol table details for a particular source
9825 file are being read. (The @code{set verbose} command can turn these
9826 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
9827 warnings and messages}.)
9829 We have not implemented the two-stage strategy for COFF yet. When the
9830 symbol table is stored in COFF format, @code{symbol-file} reads the
9831 symbol table data in full right away. Note that ``stabs-in-COFF''
9832 still does the two-stage strategy, since the debug info is actually
9836 @cindex reading symbols immediately
9837 @cindex symbols, reading immediately
9839 @cindex memory-mapped symbol file
9840 @cindex saving symbol table
9841 @item symbol-file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
9842 @itemx file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
9843 You can override the @value{GDBN} two-stage strategy for reading symbol
9844 tables by using the @samp{-readnow} option with any of the commands that
9845 load symbol table information, if you want to be sure @value{GDBN} has the
9846 entire symbol table available.
9848 If memory-mapped files are available on your system through the
9849 @code{mmap} system call, you can use another option, @samp{-mapped}, to
9850 cause @value{GDBN} to write the symbols for your program into a reusable
9851 file. Future @value{GDBN} debugging sessions map in symbol information
9852 from this auxiliary symbol file (if the program has not changed), rather
9853 than spending time reading the symbol table from the executable
9854 program. Using the @samp{-mapped} option has the same effect as
9855 starting @value{GDBN} with the @samp{-mapped} command-line option.
9857 You can use both options together, to make sure the auxiliary symbol
9858 file has all the symbol information for your program.
9860 The auxiliary symbol file for a program called @var{myprog} is called
9861 @samp{@var{myprog}.syms}. Once this file exists (so long as it is newer
9862 than the corresponding executable), @value{GDBN} always attempts to use
9863 it when you debug @var{myprog}; no special options or commands are
9866 The @file{.syms} file is specific to the host machine where you run
9867 @value{GDBN}. It holds an exact image of the internal @value{GDBN}
9868 symbol table. It cannot be shared across multiple host platforms.
9870 @c FIXME: for now no mention of directories, since this seems to be in
9871 @c flux. 13mar1992 status is that in theory GDB would look either in
9872 @c current dir or in same dir as myprog; but issues like competing
9873 @c GDB's, or clutter in system dirs, mean that in practice right now
9874 @c only current dir is used. FFish says maybe a special GDB hierarchy
9875 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
9879 @item core-file @r{[} @var{filename} @r{]}
9881 Specify the whereabouts of a core dump file to be used as the ``contents
9882 of memory''. Traditionally, core files contain only some parts of the
9883 address space of the process that generated them; @value{GDBN} can access the
9884 executable file itself for other parts.
9886 @code{core-file} with no argument specifies that no core file is
9889 Note that the core file is ignored when your program is actually running
9890 under @value{GDBN}. So, if you have been running your program and you
9891 wish to debug a core file instead, you must kill the subprocess in which
9892 the program is running. To do this, use the @code{kill} command
9893 (@pxref{Kill Process, ,Killing the child process}).
9895 @kindex add-symbol-file
9896 @cindex dynamic linking
9897 @item add-symbol-file @var{filename} @var{address}
9898 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
9899 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
9900 The @code{add-symbol-file} command reads additional symbol table
9901 information from the file @var{filename}. You would use this command
9902 when @var{filename} has been dynamically loaded (by some other means)
9903 into the program that is running. @var{address} should be the memory
9904 address at which the file has been loaded; @value{GDBN} cannot figure
9905 this out for itself. You can additionally specify an arbitrary number
9906 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
9907 section name and base address for that section. You can specify any
9908 @var{address} as an expression.
9910 The symbol table of the file @var{filename} is added to the symbol table
9911 originally read with the @code{symbol-file} command. You can use the
9912 @code{add-symbol-file} command any number of times; the new symbol data
9913 thus read keeps adding to the old. To discard all old symbol data
9914 instead, use the @code{symbol-file} command without any arguments.
9916 @cindex relocatable object files, reading symbols from
9917 @cindex object files, relocatable, reading symbols from
9918 @cindex reading symbols from relocatable object files
9919 @cindex symbols, reading from relocatable object files
9920 @cindex @file{.o} files, reading symbols from
9921 Although @var{filename} is typically a shared library file, an
9922 executable file, or some other object file which has been fully
9923 relocated for loading into a process, you can also load symbolic
9924 information from relocatable @file{.o} files, as long as:
9928 the file's symbolic information refers only to linker symbols defined in
9929 that file, not to symbols defined by other object files,
9931 every section the file's symbolic information refers to has actually
9932 been loaded into the inferior, as it appears in the file, and
9934 you can determine the address at which every section was loaded, and
9935 provide these to the @code{add-symbol-file} command.
9939 Some embedded operating systems, like Sun Chorus and VxWorks, can load
9940 relocatable files into an already running program; such systems
9941 typically make the requirements above easy to meet. However, it's
9942 important to recognize that many native systems use complex link
9943 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
9944 assembly, for example) that make the requirements difficult to meet. In
9945 general, one cannot assume that using @code{add-symbol-file} to read a
9946 relocatable object file's symbolic information will have the same effect
9947 as linking the relocatable object file into the program in the normal
9950 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
9952 You can use the @samp{-mapped} and @samp{-readnow} options just as with
9953 the @code{symbol-file} command, to change how @value{GDBN} manages the symbol
9954 table information for @var{filename}.
9956 @kindex add-shared-symbol-file
9957 @item add-shared-symbol-file
9958 The @code{add-shared-symbol-file} command can be used only under Harris' CXUX
9959 operating system for the Motorola 88k. @value{GDBN} automatically looks for
9960 shared libraries, however if @value{GDBN} does not find yours, you can run
9961 @code{add-shared-symbol-file}. It takes no arguments.
9965 The @code{section} command changes the base address of section SECTION of
9966 the exec file to ADDR. This can be used if the exec file does not contain
9967 section addresses, (such as in the a.out format), or when the addresses
9968 specified in the file itself are wrong. Each section must be changed
9969 separately. The @code{info files} command, described below, lists all
9970 the sections and their addresses.
9976 @code{info files} and @code{info target} are synonymous; both print the
9977 current target (@pxref{Targets, ,Specifying a Debugging Target}),
9978 including the names of the executable and core dump files currently in
9979 use by @value{GDBN}, and the files from which symbols were loaded. The
9980 command @code{help target} lists all possible targets rather than
9983 @kindex maint info sections
9984 @item maint info sections
9985 Another command that can give you extra information about program sections
9986 is @code{maint info sections}. In addition to the section information
9987 displayed by @code{info files}, this command displays the flags and file
9988 offset of each section in the executable and core dump files. In addition,
9989 @code{maint info sections} provides the following command options (which
9990 may be arbitrarily combined):
9994 Display sections for all loaded object files, including shared libraries.
9995 @item @var{sections}
9996 Display info only for named @var{sections}.
9997 @item @var{section-flags}
9998 Display info only for sections for which @var{section-flags} are true.
9999 The section flags that @value{GDBN} currently knows about are:
10002 Section will have space allocated in the process when loaded.
10003 Set for all sections except those containing debug information.
10005 Section will be loaded from the file into the child process memory.
10006 Set for pre-initialized code and data, clear for @code{.bss} sections.
10008 Section needs to be relocated before loading.
10010 Section cannot be modified by the child process.
10012 Section contains executable code only.
10014 Section contains data only (no executable code).
10016 Section will reside in ROM.
10018 Section contains data for constructor/destructor lists.
10020 Section is not empty.
10022 An instruction to the linker to not output the section.
10023 @item COFF_SHARED_LIBRARY
10024 A notification to the linker that the section contains
10025 COFF shared library information.
10027 Section contains common symbols.
10030 @kindex set trust-readonly-sections
10031 @item set trust-readonly-sections on
10032 Tell @value{GDBN} that readonly sections in your object file
10033 really are read-only (i.e.@: that their contents will not change).
10034 In that case, @value{GDBN} can fetch values from these sections
10035 out of the object file, rather than from the target program.
10036 For some targets (notably embedded ones), this can be a significant
10037 enhancement to debugging performance.
10039 The default is off.
10041 @item set trust-readonly-sections off
10042 Tell @value{GDBN} not to trust readonly sections. This means that
10043 the contents of the section might change while the program is running,
10044 and must therefore be fetched from the target when needed.
10047 All file-specifying commands allow both absolute and relative file names
10048 as arguments. @value{GDBN} always converts the file name to an absolute file
10049 name and remembers it that way.
10051 @cindex shared libraries
10052 @value{GDBN} supports HP-UX, SunOS, SVr4, Irix 5, and IBM RS/6000 shared
10055 @value{GDBN} automatically loads symbol definitions from shared libraries
10056 when you use the @code{run} command, or when you examine a core file.
10057 (Before you issue the @code{run} command, @value{GDBN} does not understand
10058 references to a function in a shared library, however---unless you are
10059 debugging a core file).
10061 On HP-UX, if the program loads a library explicitly, @value{GDBN}
10062 automatically loads the symbols at the time of the @code{shl_load} call.
10064 @c FIXME: some @value{GDBN} release may permit some refs to undef
10065 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
10066 @c FIXME...lib; check this from time to time when updating manual
10068 There are times, however, when you may wish to not automatically load
10069 symbol definitions from shared libraries, such as when they are
10070 particularly large or there are many of them.
10072 To control the automatic loading of shared library symbols, use the
10076 @kindex set auto-solib-add
10077 @item set auto-solib-add @var{mode}
10078 If @var{mode} is @code{on}, symbols from all shared object libraries
10079 will be loaded automatically when the inferior begins execution, you
10080 attach to an independently started inferior, or when the dynamic linker
10081 informs @value{GDBN} that a new library has been loaded. If @var{mode}
10082 is @code{off}, symbols must be loaded manually, using the
10083 @code{sharedlibrary} command. The default value is @code{on}.
10085 @kindex show auto-solib-add
10086 @item show auto-solib-add
10087 Display the current autoloading mode.
10090 To explicitly load shared library symbols, use the @code{sharedlibrary}
10094 @kindex info sharedlibrary
10097 @itemx info sharedlibrary
10098 Print the names of the shared libraries which are currently loaded.
10100 @kindex sharedlibrary
10102 @item sharedlibrary @var{regex}
10103 @itemx share @var{regex}
10104 Load shared object library symbols for files matching a
10105 Unix regular expression.
10106 As with files loaded automatically, it only loads shared libraries
10107 required by your program for a core file or after typing @code{run}. If
10108 @var{regex} is omitted all shared libraries required by your program are
10112 On some systems, such as HP-UX systems, @value{GDBN} supports
10113 autoloading shared library symbols until a limiting threshold size is
10114 reached. This provides the benefit of allowing autoloading to remain on
10115 by default, but avoids autoloading excessively large shared libraries,
10116 up to a threshold that is initially set, but which you can modify if you
10119 Beyond that threshold, symbols from shared libraries must be explicitly
10120 loaded. To load these symbols, use the command @code{sharedlibrary
10121 @var{filename}}. The base address of the shared library is determined
10122 automatically by @value{GDBN} and need not be specified.
10124 To display or set the threshold, use the commands:
10127 @kindex set auto-solib-limit
10128 @item set auto-solib-limit @var{threshold}
10129 Set the autoloading size threshold, in an integral number of megabytes.
10130 If @var{threshold} is nonzero and shared library autoloading is enabled,
10131 symbols from all shared object libraries will be loaded until the total
10132 size of the loaded shared library symbols exceeds this threshold.
10133 Otherwise, symbols must be loaded manually, using the
10134 @code{sharedlibrary} command. The default threshold is 100 (i.e.@: 100
10137 @kindex show auto-solib-limit
10138 @item show auto-solib-limit
10139 Display the current autoloading size threshold, in megabytes.
10142 Shared libraries are also supported in many cross or remote debugging
10143 configurations. A copy of the target's libraries need to be present on the
10144 host system; they need to be the same as the target libraries, although the
10145 copies on the target can be stripped as long as the copies on the host are
10148 You need to tell @value{GDBN} where the target libraries are, so that it can
10149 load the correct copies---otherwise, it may try to load the host's libraries.
10150 @value{GDBN} has two variables to specify the search directories for target
10154 @kindex set solib-absolute-prefix
10155 @item set solib-absolute-prefix @var{path}
10156 If this variable is set, @var{path} will be used as a prefix for any
10157 absolute shared library paths; many runtime loaders store the absolute
10158 paths to the shared library in the target program's memory. If you use
10159 @samp{solib-absolute-prefix} to find shared libraries, they need to be laid
10160 out in the same way that they are on the target, with e.g.@: a
10161 @file{/usr/lib} hierarchy under @var{path}.
10163 You can set the default value of @samp{solib-absolute-prefix} by using the
10164 configure-time @samp{--with-sysroot} option.
10166 @kindex show solib-absolute-prefix
10167 @item show solib-absolute-prefix
10168 Display the current shared library prefix.
10170 @kindex set solib-search-path
10171 @item set solib-search-path @var{path}
10172 If this variable is set, @var{path} is a colon-separated list of directories
10173 to search for shared libraries. @samp{solib-search-path} is used after
10174 @samp{solib-absolute-prefix} fails to locate the library, or if the path to
10175 the library is relative instead of absolute. If you want to use
10176 @samp{solib-search-path} instead of @samp{solib-absolute-prefix}, be sure to
10177 set @samp{solib-absolute-prefix} to a nonexistant directory to prevent
10178 @value{GDBN} from finding your host's libraries.
10180 @kindex show solib-search-path
10181 @item show solib-search-path
10182 Display the current shared library search path.
10186 @node Separate Debug Files
10187 @section Debugging Information in Separate Files
10188 @cindex separate debugging information files
10189 @cindex debugging information in separate files
10190 @cindex @file{.debug} subdirectories
10191 @cindex debugging information directory, global
10192 @cindex global debugging information directory
10194 @value{GDBN} allows you to put a program's debugging information in a
10195 file separate from the executable itself, in a way that allows
10196 @value{GDBN} to find and load the debugging information automatically.
10197 Since debugging information can be very large --- sometimes larger
10198 than the executable code itself --- some systems distribute debugging
10199 information for their executables in separate files, which users can
10200 install only when they need to debug a problem.
10202 If an executable's debugging information has been extracted to a
10203 separate file, the executable should contain a @dfn{debug link} giving
10204 the name of the debugging information file (with no directory
10205 components), and a checksum of its contents. (The exact form of a
10206 debug link is described below.) If the full name of the directory
10207 containing the executable is @var{execdir}, and the executable has a
10208 debug link that specifies the name @var{debugfile}, then @value{GDBN}
10209 will automatically search for the debugging information file in three
10214 the directory containing the executable file (that is, it will look
10215 for a file named @file{@var{execdir}/@var{debugfile}},
10217 a subdirectory of that directory named @file{.debug} (that is, the
10218 file @file{@var{execdir}/.debug/@var{debugfile}}, and
10220 a subdirectory of the global debug file directory that includes the
10221 executable's full path, and the name from the link (that is, the file
10222 @file{@var{globaldebugdir}/@var{execdir}/@var{debugfile}}, where
10223 @var{globaldebugdir} is the global debug file directory, and
10224 @var{execdir} has been turned into a relative path).
10227 @value{GDBN} checks under each of these names for a debugging
10228 information file whose checksum matches that given in the link, and
10229 reads the debugging information from the first one it finds.
10231 So, for example, if you ask @value{GDBN} to debug @file{/usr/bin/ls},
10232 which has a link containing the name @file{ls.debug}, and the global
10233 debug directory is @file{/usr/lib/debug}, then @value{GDBN} will look
10234 for debug information in @file{/usr/bin/ls.debug},
10235 @file{/usr/bin/.debug/ls.debug}, and
10236 @file{/usr/lib/debug/usr/bin/ls.debug}.
10238 You can set the global debugging info directory's name, and view the
10239 name @value{GDBN} is currently using.
10243 @kindex set debug-file-directory
10244 @item set debug-file-directory @var{directory}
10245 Set the directory which @value{GDBN} searches for separate debugging
10246 information files to @var{directory}.
10248 @kindex show debug-file-directory
10249 @item show debug-file-directory
10250 Show the directory @value{GDBN} searches for separate debugging
10255 @cindex @code{.gnu_debuglink} sections
10256 @cindex debug links
10257 A debug link is a special section of the executable file named
10258 @code{.gnu_debuglink}. The section must contain:
10262 A filename, with any leading directory components removed, followed by
10265 zero to three bytes of padding, as needed to reach the next four-byte
10266 boundary within the section, and
10268 a four-byte CRC checksum, stored in the same endianness used for the
10269 executable file itself. The checksum is computed on the debugging
10270 information file's full contents by the function given below, passing
10271 zero as the @var{crc} argument.
10274 Any executable file format can carry a debug link, as long as it can
10275 contain a section named @code{.gnu_debuglink} with the contents
10278 The debugging information file itself should be an ordinary
10279 executable, containing a full set of linker symbols, sections, and
10280 debugging information. The sections of the debugging information file
10281 should have the same names, addresses and sizes as the original file,
10282 but they need not contain any data --- much like a @code{.bss} section
10283 in an ordinary executable.
10285 As of December 2002, there is no standard GNU utility to produce
10286 separated executable / debugging information file pairs. Ulrich
10287 Drepper's @file{elfutils} package, starting with version 0.53,
10288 contains a version of the @code{strip} command such that the command
10289 @kbd{strip foo -f foo.debug} removes the debugging information from
10290 the executable file @file{foo}, places it in the file
10291 @file{foo.debug}, and leaves behind a debug link in @file{foo}.
10293 Since there are many different ways to compute CRC's (different
10294 polynomials, reversals, byte ordering, etc.), the simplest way to
10295 describe the CRC used in @code{.gnu_debuglink} sections is to give the
10296 complete code for a function that computes it:
10298 @kindex gnu_debuglink_crc32
10301 gnu_debuglink_crc32 (unsigned long crc,
10302 unsigned char *buf, size_t len)
10304 static const unsigned long crc32_table[256] =
10306 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
10307 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
10308 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
10309 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
10310 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
10311 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
10312 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
10313 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
10314 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
10315 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
10316 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
10317 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
10318 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
10319 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
10320 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
10321 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
10322 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
10323 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
10324 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
10325 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
10326 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
10327 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
10328 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
10329 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
10330 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
10331 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
10332 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
10333 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
10334 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
10335 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
10336 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
10337 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
10338 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
10339 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
10340 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
10341 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
10342 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
10343 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
10344 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
10345 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
10346 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
10347 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
10348 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
10349 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
10350 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
10351 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
10352 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
10353 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
10354 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
10355 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
10356 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
10359 unsigned char *end;
10361 crc = ~crc & 0xffffffff;
10362 for (end = buf + len; buf < end; ++buf)
10363 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
10364 return ~crc & 0xffffffff;
10369 @node Symbol Errors
10370 @section Errors reading symbol files
10372 While reading a symbol file, @value{GDBN} occasionally encounters problems,
10373 such as symbol types it does not recognize, or known bugs in compiler
10374 output. By default, @value{GDBN} does not notify you of such problems, since
10375 they are relatively common and primarily of interest to people
10376 debugging compilers. If you are interested in seeing information
10377 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
10378 only one message about each such type of problem, no matter how many
10379 times the problem occurs; or you can ask @value{GDBN} to print more messages,
10380 to see how many times the problems occur, with the @code{set
10381 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
10384 The messages currently printed, and their meanings, include:
10387 @item inner block not inside outer block in @var{symbol}
10389 The symbol information shows where symbol scopes begin and end
10390 (such as at the start of a function or a block of statements). This
10391 error indicates that an inner scope block is not fully contained
10392 in its outer scope blocks.
10394 @value{GDBN} circumvents the problem by treating the inner block as if it had
10395 the same scope as the outer block. In the error message, @var{symbol}
10396 may be shown as ``@code{(don't know)}'' if the outer block is not a
10399 @item block at @var{address} out of order
10401 The symbol information for symbol scope blocks should occur in
10402 order of increasing addresses. This error indicates that it does not
10405 @value{GDBN} does not circumvent this problem, and has trouble
10406 locating symbols in the source file whose symbols it is reading. (You
10407 can often determine what source file is affected by specifying
10408 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
10411 @item bad block start address patched
10413 The symbol information for a symbol scope block has a start address
10414 smaller than the address of the preceding source line. This is known
10415 to occur in the SunOS 4.1.1 (and earlier) C compiler.
10417 @value{GDBN} circumvents the problem by treating the symbol scope block as
10418 starting on the previous source line.
10420 @item bad string table offset in symbol @var{n}
10423 Symbol number @var{n} contains a pointer into the string table which is
10424 larger than the size of the string table.
10426 @value{GDBN} circumvents the problem by considering the symbol to have the
10427 name @code{foo}, which may cause other problems if many symbols end up
10430 @item unknown symbol type @code{0x@var{nn}}
10432 The symbol information contains new data types that @value{GDBN} does
10433 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
10434 uncomprehended information, in hexadecimal.
10436 @value{GDBN} circumvents the error by ignoring this symbol information.
10437 This usually allows you to debug your program, though certain symbols
10438 are not accessible. If you encounter such a problem and feel like
10439 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
10440 on @code{complain}, then go up to the function @code{read_dbx_symtab}
10441 and examine @code{*bufp} to see the symbol.
10443 @item stub type has NULL name
10445 @value{GDBN} could not find the full definition for a struct or class.
10447 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
10448 The symbol information for a C@t{++} member function is missing some
10449 information that recent versions of the compiler should have output for
10452 @item info mismatch between compiler and debugger
10454 @value{GDBN} could not parse a type specification output by the compiler.
10459 @chapter Specifying a Debugging Target
10461 @cindex debugging target
10464 A @dfn{target} is the execution environment occupied by your program.
10466 Often, @value{GDBN} runs in the same host environment as your program;
10467 in that case, the debugging target is specified as a side effect when
10468 you use the @code{file} or @code{core} commands. When you need more
10469 flexibility---for example, running @value{GDBN} on a physically separate
10470 host, or controlling a standalone system over a serial port or a
10471 realtime system over a TCP/IP connection---you can use the @code{target}
10472 command to specify one of the target types configured for @value{GDBN}
10473 (@pxref{Target Commands, ,Commands for managing targets}).
10476 * Active Targets:: Active targets
10477 * Target Commands:: Commands for managing targets
10478 * Byte Order:: Choosing target byte order
10479 * Remote:: Remote debugging
10480 * KOD:: Kernel Object Display
10484 @node Active Targets
10485 @section Active targets
10487 @cindex stacking targets
10488 @cindex active targets
10489 @cindex multiple targets
10491 There are three classes of targets: processes, core files, and
10492 executable files. @value{GDBN} can work concurrently on up to three
10493 active targets, one in each class. This allows you to (for example)
10494 start a process and inspect its activity without abandoning your work on
10497 For example, if you execute @samp{gdb a.out}, then the executable file
10498 @code{a.out} is the only active target. If you designate a core file as
10499 well---presumably from a prior run that crashed and coredumped---then
10500 @value{GDBN} has two active targets and uses them in tandem, looking
10501 first in the corefile target, then in the executable file, to satisfy
10502 requests for memory addresses. (Typically, these two classes of target
10503 are complementary, since core files contain only a program's
10504 read-write memory---variables and so on---plus machine status, while
10505 executable files contain only the program text and initialized data.)
10507 When you type @code{run}, your executable file becomes an active process
10508 target as well. When a process target is active, all @value{GDBN}
10509 commands requesting memory addresses refer to that target; addresses in
10510 an active core file or executable file target are obscured while the
10511 process target is active.
10513 Use the @code{core-file} and @code{exec-file} commands to select a new
10514 core file or executable target (@pxref{Files, ,Commands to specify
10515 files}). To specify as a target a process that is already running, use
10516 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
10519 @node Target Commands
10520 @section Commands for managing targets
10523 @item target @var{type} @var{parameters}
10524 Connects the @value{GDBN} host environment to a target machine or
10525 process. A target is typically a protocol for talking to debugging
10526 facilities. You use the argument @var{type} to specify the type or
10527 protocol of the target machine.
10529 Further @var{parameters} are interpreted by the target protocol, but
10530 typically include things like device names or host names to connect
10531 with, process numbers, and baud rates.
10533 The @code{target} command does not repeat if you press @key{RET} again
10534 after executing the command.
10536 @kindex help target
10538 Displays the names of all targets available. To display targets
10539 currently selected, use either @code{info target} or @code{info files}
10540 (@pxref{Files, ,Commands to specify files}).
10542 @item help target @var{name}
10543 Describe a particular target, including any parameters necessary to
10546 @kindex set gnutarget
10547 @item set gnutarget @var{args}
10548 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
10549 knows whether it is reading an @dfn{executable},
10550 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
10551 with the @code{set gnutarget} command. Unlike most @code{target} commands,
10552 with @code{gnutarget} the @code{target} refers to a program, not a machine.
10555 @emph{Warning:} To specify a file format with @code{set gnutarget},
10556 you must know the actual BFD name.
10560 @xref{Files, , Commands to specify files}.
10562 @kindex show gnutarget
10563 @item show gnutarget
10564 Use the @code{show gnutarget} command to display what file format
10565 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
10566 @value{GDBN} will determine the file format for each file automatically,
10567 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
10570 @cindex common targets
10571 Here are some common targets (available, or not, depending on the GDB
10576 @item target exec @var{program}
10577 @cindex executable file target
10578 An executable file. @samp{target exec @var{program}} is the same as
10579 @samp{exec-file @var{program}}.
10581 @item target core @var{filename}
10582 @cindex core dump file target
10583 A core dump file. @samp{target core @var{filename}} is the same as
10584 @samp{core-file @var{filename}}.
10586 @item target remote @var{dev}
10587 @cindex remote target
10588 Remote serial target in GDB-specific protocol. The argument @var{dev}
10589 specifies what serial device to use for the connection (e.g.
10590 @file{/dev/ttya}). @xref{Remote, ,Remote debugging}. @code{target remote}
10591 supports the @code{load} command. This is only useful if you have
10592 some other way of getting the stub to the target system, and you can put
10593 it somewhere in memory where it won't get clobbered by the download.
10596 @cindex built-in simulator target
10597 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
10605 works; however, you cannot assume that a specific memory map, device
10606 drivers, or even basic I/O is available, although some simulators do
10607 provide these. For info about any processor-specific simulator details,
10608 see the appropriate section in @ref{Embedded Processors, ,Embedded
10613 Some configurations may include these targets as well:
10617 @item target nrom @var{dev}
10618 @cindex NetROM ROM emulator target
10619 NetROM ROM emulator. This target only supports downloading.
10623 Different targets are available on different configurations of @value{GDBN};
10624 your configuration may have more or fewer targets.
10626 Many remote targets require you to download the executable's code
10627 once you've successfully established a connection.
10631 @kindex load @var{filename}
10632 @item load @var{filename}
10633 Depending on what remote debugging facilities are configured into
10634 @value{GDBN}, the @code{load} command may be available. Where it exists, it
10635 is meant to make @var{filename} (an executable) available for debugging
10636 on the remote system---by downloading, or dynamic linking, for example.
10637 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
10638 the @code{add-symbol-file} command.
10640 If your @value{GDBN} does not have a @code{load} command, attempting to
10641 execute it gets the error message ``@code{You can't do that when your
10642 target is @dots{}}''
10644 The file is loaded at whatever address is specified in the executable.
10645 For some object file formats, you can specify the load address when you
10646 link the program; for other formats, like a.out, the object file format
10647 specifies a fixed address.
10648 @c FIXME! This would be a good place for an xref to the GNU linker doc.
10650 @code{load} does not repeat if you press @key{RET} again after using it.
10654 @section Choosing target byte order
10656 @cindex choosing target byte order
10657 @cindex target byte order
10659 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
10660 offer the ability to run either big-endian or little-endian byte
10661 orders. Usually the executable or symbol will include a bit to
10662 designate the endian-ness, and you will not need to worry about
10663 which to use. However, you may still find it useful to adjust
10664 @value{GDBN}'s idea of processor endian-ness manually.
10668 @item set endian big
10669 Instruct @value{GDBN} to assume the target is big-endian.
10671 @item set endian little
10672 Instruct @value{GDBN} to assume the target is little-endian.
10674 @item set endian auto
10675 Instruct @value{GDBN} to use the byte order associated with the
10679 Display @value{GDBN}'s current idea of the target byte order.
10683 Note that these commands merely adjust interpretation of symbolic
10684 data on the host, and that they have absolutely no effect on the
10688 @section Remote debugging
10689 @cindex remote debugging
10691 If you are trying to debug a program running on a machine that cannot run
10692 @value{GDBN} in the usual way, it is often useful to use remote debugging.
10693 For example, you might use remote debugging on an operating system kernel,
10694 or on a small system which does not have a general purpose operating system
10695 powerful enough to run a full-featured debugger.
10697 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
10698 to make this work with particular debugging targets. In addition,
10699 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
10700 but not specific to any particular target system) which you can use if you
10701 write the remote stubs---the code that runs on the remote system to
10702 communicate with @value{GDBN}.
10704 Other remote targets may be available in your
10705 configuration of @value{GDBN}; use @code{help target} to list them.
10708 @section Kernel Object Display
10709 @cindex kernel object display
10712 Some targets support kernel object display. Using this facility,
10713 @value{GDBN} communicates specially with the underlying operating system
10714 and can display information about operating system-level objects such as
10715 mutexes and other synchronization objects. Exactly which objects can be
10716 displayed is determined on a per-OS basis.
10719 Use the @code{set os} command to set the operating system. This tells
10720 @value{GDBN} which kernel object display module to initialize:
10723 (@value{GDBP}) set os cisco
10727 The associated command @code{show os} displays the operating system
10728 set with the @code{set os} command; if no operating system has been
10729 set, @code{show os} will display an empty string @samp{""}.
10731 If @code{set os} succeeds, @value{GDBN} will display some information
10732 about the operating system, and will create a new @code{info} command
10733 which can be used to query the target. The @code{info} command is named
10734 after the operating system:
10738 (@value{GDBP}) info cisco
10739 List of Cisco Kernel Objects
10741 any Any and all objects
10744 Further subcommands can be used to query about particular objects known
10747 There is currently no way to determine whether a given operating
10748 system is supported other than to try setting it with @kbd{set os
10749 @var{name}}, where @var{name} is the name of the operating system you
10753 @node Remote Debugging
10754 @chapter Debugging remote programs
10757 * Connecting:: Connecting to a remote target
10758 * Server:: Using the gdbserver program
10759 * NetWare:: Using the gdbserve.nlm program
10760 * Remote configuration:: Remote configuration
10761 * remote stub:: Implementing a remote stub
10765 @section Connecting to a remote target
10767 On the @value{GDBN} host machine, you will need an unstripped copy of
10768 your program, since @value{GDBN} needs symobl and debugging information.
10769 Start up @value{GDBN} as usual, using the name of the local copy of your
10770 program as the first argument.
10772 @cindex serial line, @code{target remote}
10773 If you're using a serial line, you may want to give @value{GDBN} the
10774 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
10775 before the @code{target} command.
10777 After that, use @code{target remote} to establish communications with
10778 the target machine. Its argument specifies how to communicate---either
10779 via a devicename attached to a direct serial line, or a TCP or UDP port
10780 (possibly to a terminal server which in turn has a serial line to the
10781 target). For example, to use a serial line connected to the device
10782 named @file{/dev/ttyb}:
10785 target remote /dev/ttyb
10788 @cindex TCP port, @code{target remote}
10789 To use a TCP connection, use an argument of the form
10790 @code{@var{host}:@var{port}} or @code{tcp:@var{host}:@var{port}}.
10791 For example, to connect to port 2828 on a
10792 terminal server named @code{manyfarms}:
10795 target remote manyfarms:2828
10798 If your remote target is actually running on the same machine as
10799 your debugger session (e.g.@: a simulator of your target running on
10800 the same host), you can omit the hostname. For example, to connect
10801 to port 1234 on your local machine:
10804 target remote :1234
10808 Note that the colon is still required here.
10810 @cindex UDP port, @code{target remote}
10811 To use a UDP connection, use an argument of the form
10812 @code{udp:@var{host}:@var{port}}. For example, to connect to UDP port 2828
10813 on a terminal server named @code{manyfarms}:
10816 target remote udp:manyfarms:2828
10819 When using a UDP connection for remote debugging, you should keep in mind
10820 that the `U' stands for ``Unreliable''. UDP can silently drop packets on
10821 busy or unreliable networks, which will cause havoc with your debugging
10824 Now you can use all the usual commands to examine and change data and to
10825 step and continue the remote program.
10827 @cindex interrupting remote programs
10828 @cindex remote programs, interrupting
10829 Whenever @value{GDBN} is waiting for the remote program, if you type the
10830 interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the
10831 program. This may or may not succeed, depending in part on the hardware
10832 and the serial drivers the remote system uses. If you type the
10833 interrupt character once again, @value{GDBN} displays this prompt:
10836 Interrupted while waiting for the program.
10837 Give up (and stop debugging it)? (y or n)
10840 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
10841 (If you decide you want to try again later, you can use @samp{target
10842 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
10843 goes back to waiting.
10846 @kindex detach (remote)
10848 When you have finished debugging the remote program, you can use the
10849 @code{detach} command to release it from @value{GDBN} control.
10850 Detaching from the target normally resumes its execution, but the results
10851 will depend on your particular remote stub. After the @code{detach}
10852 command, @value{GDBN} is free to connect to another target.
10856 The @code{disconnect} command behaves like @code{detach}, except that
10857 the target is generally not resumed. It will wait for @value{GDBN}
10858 (this instance or another one) to connect and continue debugging. After
10859 the @code{disconnect} command, @value{GDBN} is again free to connect to
10864 @section Using the @code{gdbserver} program
10867 @cindex remote connection without stubs
10868 @code{gdbserver} is a control program for Unix-like systems, which
10869 allows you to connect your program with a remote @value{GDBN} via
10870 @code{target remote}---but without linking in the usual debugging stub.
10872 @code{gdbserver} is not a complete replacement for the debugging stubs,
10873 because it requires essentially the same operating-system facilities
10874 that @value{GDBN} itself does. In fact, a system that can run
10875 @code{gdbserver} to connect to a remote @value{GDBN} could also run
10876 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
10877 because it is a much smaller program than @value{GDBN} itself. It is
10878 also easier to port than all of @value{GDBN}, so you may be able to get
10879 started more quickly on a new system by using @code{gdbserver}.
10880 Finally, if you develop code for real-time systems, you may find that
10881 the tradeoffs involved in real-time operation make it more convenient to
10882 do as much development work as possible on another system, for example
10883 by cross-compiling. You can use @code{gdbserver} to make a similar
10884 choice for debugging.
10886 @value{GDBN} and @code{gdbserver} communicate via either a serial line
10887 or a TCP connection, using the standard @value{GDBN} remote serial
10891 @item On the target machine,
10892 you need to have a copy of the program you want to debug.
10893 @code{gdbserver} does not need your program's symbol table, so you can
10894 strip the program if necessary to save space. @value{GDBN} on the host
10895 system does all the symbol handling.
10897 To use the server, you must tell it how to communicate with @value{GDBN};
10898 the name of your program; and the arguments for your program. The usual
10902 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
10905 @var{comm} is either a device name (to use a serial line) or a TCP
10906 hostname and portnumber. For example, to debug Emacs with the argument
10907 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
10911 target> gdbserver /dev/com1 emacs foo.txt
10914 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
10917 To use a TCP connection instead of a serial line:
10920 target> gdbserver host:2345 emacs foo.txt
10923 The only difference from the previous example is the first argument,
10924 specifying that you are communicating with the host @value{GDBN} via
10925 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
10926 expect a TCP connection from machine @samp{host} to local TCP port 2345.
10927 (Currently, the @samp{host} part is ignored.) You can choose any number
10928 you want for the port number as long as it does not conflict with any
10929 TCP ports already in use on the target system (for example, @code{23} is
10930 reserved for @code{telnet}).@footnote{If you choose a port number that
10931 conflicts with another service, @code{gdbserver} prints an error message
10932 and exits.} You must use the same port number with the host @value{GDBN}
10933 @code{target remote} command.
10935 On some targets, @code{gdbserver} can also attach to running programs.
10936 This is accomplished via the @code{--attach} argument. The syntax is:
10939 target> gdbserver @var{comm} --attach @var{pid}
10942 @var{pid} is the process ID of a currently running process. It isn't necessary
10943 to point @code{gdbserver} at a binary for the running process.
10946 @cindex attach to a program by name
10947 You can debug processes by name instead of process ID if your target has the
10948 @code{pidof} utility:
10951 target> gdbserver @var{comm} --attach `pidof @var{PROGRAM}`
10954 In case more than one copy of @var{PROGRAM} is running, or @var{PROGRAM}
10955 has multiple threads, most versions of @code{pidof} support the
10956 @code{-s} option to only return the first process ID.
10958 @item On the host machine,
10959 connect to your target (@pxref{Connecting,,Connecting to a remote target}).
10960 For TCP connections, you must start up @code{gdbserver} prior to using
10961 the @code{target remote} command. Otherwise you may get an error whose
10962 text depends on the host system, but which usually looks something like
10963 @samp{Connection refused}. You don't need to use the @code{load}
10964 command in @value{GDBN} when using gdbserver, since the program is
10965 already on the target.
10970 @section Using the @code{gdbserve.nlm} program
10972 @kindex gdbserve.nlm
10973 @code{gdbserve.nlm} is a control program for NetWare systems, which
10974 allows you to connect your program with a remote @value{GDBN} via
10975 @code{target remote}.
10977 @value{GDBN} and @code{gdbserve.nlm} communicate via a serial line,
10978 using the standard @value{GDBN} remote serial protocol.
10981 @item On the target machine,
10982 you need to have a copy of the program you want to debug.
10983 @code{gdbserve.nlm} does not need your program's symbol table, so you
10984 can strip the program if necessary to save space. @value{GDBN} on the
10985 host system does all the symbol handling.
10987 To use the server, you must tell it how to communicate with
10988 @value{GDBN}; the name of your program; and the arguments for your
10989 program. The syntax is:
10992 load gdbserve [ BOARD=@var{board} ] [ PORT=@var{port} ]
10993 [ BAUD=@var{baud} ] @var{program} [ @var{args} @dots{} ]
10996 @var{board} and @var{port} specify the serial line; @var{baud} specifies
10997 the baud rate used by the connection. @var{port} and @var{node} default
10998 to 0, @var{baud} defaults to 9600@dmn{bps}.
11000 For example, to debug Emacs with the argument @samp{foo.txt}and
11001 communicate with @value{GDBN} over serial port number 2 or board 1
11002 using a 19200@dmn{bps} connection:
11005 load gdbserve BOARD=1 PORT=2 BAUD=19200 emacs foo.txt
11009 On the @value{GDBN} host machine, connect to your target (@pxref{Connecting,,
11010 Connecting to a remote target}).
11014 @node Remote configuration
11015 @section Remote configuration
11017 The following configuration options are available when debugging remote
11021 @kindex set remote hardware-watchpoint-limit
11022 @kindex set remote hardware-breakpoint-limit
11023 @anchor{set remote hardware-watchpoint-limit}
11024 @anchor{set remote hardware-breakpoint-limit}
11025 @item set remote hardware-watchpoint-limit @var{limit}
11026 @itemx set remote hardware-breakpoint-limit @var{limit}
11027 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
11028 watchpoints. A limit of -1, the default, is treated as unlimited.
11032 @section Implementing a remote stub
11034 @cindex debugging stub, example
11035 @cindex remote stub, example
11036 @cindex stub example, remote debugging
11037 The stub files provided with @value{GDBN} implement the target side of the
11038 communication protocol, and the @value{GDBN} side is implemented in the
11039 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
11040 these subroutines to communicate, and ignore the details. (If you're
11041 implementing your own stub file, you can still ignore the details: start
11042 with one of the existing stub files. @file{sparc-stub.c} is the best
11043 organized, and therefore the easiest to read.)
11045 @cindex remote serial debugging, overview
11046 To debug a program running on another machine (the debugging
11047 @dfn{target} machine), you must first arrange for all the usual
11048 prerequisites for the program to run by itself. For example, for a C
11053 A startup routine to set up the C runtime environment; these usually
11054 have a name like @file{crt0}. The startup routine may be supplied by
11055 your hardware supplier, or you may have to write your own.
11058 A C subroutine library to support your program's
11059 subroutine calls, notably managing input and output.
11062 A way of getting your program to the other machine---for example, a
11063 download program. These are often supplied by the hardware
11064 manufacturer, but you may have to write your own from hardware
11068 The next step is to arrange for your program to use a serial port to
11069 communicate with the machine where @value{GDBN} is running (the @dfn{host}
11070 machine). In general terms, the scheme looks like this:
11074 @value{GDBN} already understands how to use this protocol; when everything
11075 else is set up, you can simply use the @samp{target remote} command
11076 (@pxref{Targets,,Specifying a Debugging Target}).
11078 @item On the target,
11079 you must link with your program a few special-purpose subroutines that
11080 implement the @value{GDBN} remote serial protocol. The file containing these
11081 subroutines is called a @dfn{debugging stub}.
11083 On certain remote targets, you can use an auxiliary program
11084 @code{gdbserver} instead of linking a stub into your program.
11085 @xref{Server,,Using the @code{gdbserver} program}, for details.
11088 The debugging stub is specific to the architecture of the remote
11089 machine; for example, use @file{sparc-stub.c} to debug programs on
11092 @cindex remote serial stub list
11093 These working remote stubs are distributed with @value{GDBN}:
11098 @cindex @file{i386-stub.c}
11101 For Intel 386 and compatible architectures.
11104 @cindex @file{m68k-stub.c}
11105 @cindex Motorola 680x0
11107 For Motorola 680x0 architectures.
11110 @cindex @file{sh-stub.c}
11113 For Renesas SH architectures.
11116 @cindex @file{sparc-stub.c}
11118 For @sc{sparc} architectures.
11120 @item sparcl-stub.c
11121 @cindex @file{sparcl-stub.c}
11124 For Fujitsu @sc{sparclite} architectures.
11128 The @file{README} file in the @value{GDBN} distribution may list other
11129 recently added stubs.
11132 * Stub Contents:: What the stub can do for you
11133 * Bootstrapping:: What you must do for the stub
11134 * Debug Session:: Putting it all together
11137 @node Stub Contents
11138 @subsection What the stub can do for you
11140 @cindex remote serial stub
11141 The debugging stub for your architecture supplies these three
11145 @item set_debug_traps
11146 @findex set_debug_traps
11147 @cindex remote serial stub, initialization
11148 This routine arranges for @code{handle_exception} to run when your
11149 program stops. You must call this subroutine explicitly near the
11150 beginning of your program.
11152 @item handle_exception
11153 @findex handle_exception
11154 @cindex remote serial stub, main routine
11155 This is the central workhorse, but your program never calls it
11156 explicitly---the setup code arranges for @code{handle_exception} to
11157 run when a trap is triggered.
11159 @code{handle_exception} takes control when your program stops during
11160 execution (for example, on a breakpoint), and mediates communications
11161 with @value{GDBN} on the host machine. This is where the communications
11162 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
11163 representative on the target machine. It begins by sending summary
11164 information on the state of your program, then continues to execute,
11165 retrieving and transmitting any information @value{GDBN} needs, until you
11166 execute a @value{GDBN} command that makes your program resume; at that point,
11167 @code{handle_exception} returns control to your own code on the target
11171 @cindex @code{breakpoint} subroutine, remote
11172 Use this auxiliary subroutine to make your program contain a
11173 breakpoint. Depending on the particular situation, this may be the only
11174 way for @value{GDBN} to get control. For instance, if your target
11175 machine has some sort of interrupt button, you won't need to call this;
11176 pressing the interrupt button transfers control to
11177 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
11178 simply receiving characters on the serial port may also trigger a trap;
11179 again, in that situation, you don't need to call @code{breakpoint} from
11180 your own program---simply running @samp{target remote} from the host
11181 @value{GDBN} session gets control.
11183 Call @code{breakpoint} if none of these is true, or if you simply want
11184 to make certain your program stops at a predetermined point for the
11185 start of your debugging session.
11188 @node Bootstrapping
11189 @subsection What you must do for the stub
11191 @cindex remote stub, support routines
11192 The debugging stubs that come with @value{GDBN} are set up for a particular
11193 chip architecture, but they have no information about the rest of your
11194 debugging target machine.
11196 First of all you need to tell the stub how to communicate with the
11200 @item int getDebugChar()
11201 @findex getDebugChar
11202 Write this subroutine to read a single character from the serial port.
11203 It may be identical to @code{getchar} for your target system; a
11204 different name is used to allow you to distinguish the two if you wish.
11206 @item void putDebugChar(int)
11207 @findex putDebugChar
11208 Write this subroutine to write a single character to the serial port.
11209 It may be identical to @code{putchar} for your target system; a
11210 different name is used to allow you to distinguish the two if you wish.
11213 @cindex control C, and remote debugging
11214 @cindex interrupting remote targets
11215 If you want @value{GDBN} to be able to stop your program while it is
11216 running, you need to use an interrupt-driven serial driver, and arrange
11217 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
11218 character). That is the character which @value{GDBN} uses to tell the
11219 remote system to stop.
11221 Getting the debugging target to return the proper status to @value{GDBN}
11222 probably requires changes to the standard stub; one quick and dirty way
11223 is to just execute a breakpoint instruction (the ``dirty'' part is that
11224 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
11226 Other routines you need to supply are:
11229 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
11230 @findex exceptionHandler
11231 Write this function to install @var{exception_address} in the exception
11232 handling tables. You need to do this because the stub does not have any
11233 way of knowing what the exception handling tables on your target system
11234 are like (for example, the processor's table might be in @sc{rom},
11235 containing entries which point to a table in @sc{ram}).
11236 @var{exception_number} is the exception number which should be changed;
11237 its meaning is architecture-dependent (for example, different numbers
11238 might represent divide by zero, misaligned access, etc). When this
11239 exception occurs, control should be transferred directly to
11240 @var{exception_address}, and the processor state (stack, registers,
11241 and so on) should be just as it is when a processor exception occurs. So if
11242 you want to use a jump instruction to reach @var{exception_address}, it
11243 should be a simple jump, not a jump to subroutine.
11245 For the 386, @var{exception_address} should be installed as an interrupt
11246 gate so that interrupts are masked while the handler runs. The gate
11247 should be at privilege level 0 (the most privileged level). The
11248 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
11249 help from @code{exceptionHandler}.
11251 @item void flush_i_cache()
11252 @findex flush_i_cache
11253 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
11254 instruction cache, if any, on your target machine. If there is no
11255 instruction cache, this subroutine may be a no-op.
11257 On target machines that have instruction caches, @value{GDBN} requires this
11258 function to make certain that the state of your program is stable.
11262 You must also make sure this library routine is available:
11265 @item void *memset(void *, int, int)
11267 This is the standard library function @code{memset} that sets an area of
11268 memory to a known value. If you have one of the free versions of
11269 @code{libc.a}, @code{memset} can be found there; otherwise, you must
11270 either obtain it from your hardware manufacturer, or write your own.
11273 If you do not use the GNU C compiler, you may need other standard
11274 library subroutines as well; this varies from one stub to another,
11275 but in general the stubs are likely to use any of the common library
11276 subroutines which @code{@value{GCC}} generates as inline code.
11279 @node Debug Session
11280 @subsection Putting it all together
11282 @cindex remote serial debugging summary
11283 In summary, when your program is ready to debug, you must follow these
11288 Make sure you have defined the supporting low-level routines
11289 (@pxref{Bootstrapping,,What you must do for the stub}):
11291 @code{getDebugChar}, @code{putDebugChar},
11292 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
11296 Insert these lines near the top of your program:
11304 For the 680x0 stub only, you need to provide a variable called
11305 @code{exceptionHook}. Normally you just use:
11308 void (*exceptionHook)() = 0;
11312 but if before calling @code{set_debug_traps}, you set it to point to a
11313 function in your program, that function is called when
11314 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
11315 error). The function indicated by @code{exceptionHook} is called with
11316 one parameter: an @code{int} which is the exception number.
11319 Compile and link together: your program, the @value{GDBN} debugging stub for
11320 your target architecture, and the supporting subroutines.
11323 Make sure you have a serial connection between your target machine and
11324 the @value{GDBN} host, and identify the serial port on the host.
11327 @c The "remote" target now provides a `load' command, so we should
11328 @c document that. FIXME.
11329 Download your program to your target machine (or get it there by
11330 whatever means the manufacturer provides), and start it.
11333 Start @value{GDBN} on the host, and connect to the target
11334 (@pxref{Connecting,,Connecting to a remote target}).
11338 @node Configurations
11339 @chapter Configuration-Specific Information
11341 While nearly all @value{GDBN} commands are available for all native and
11342 cross versions of the debugger, there are some exceptions. This chapter
11343 describes things that are only available in certain configurations.
11345 There are three major categories of configurations: native
11346 configurations, where the host and target are the same, embedded
11347 operating system configurations, which are usually the same for several
11348 different processor architectures, and bare embedded processors, which
11349 are quite different from each other.
11354 * Embedded Processors::
11361 This section describes details specific to particular native
11366 * BSD libkvm Interface:: Debugging BSD kernel memory images
11367 * SVR4 Process Information:: SVR4 process information
11368 * DJGPP Native:: Features specific to the DJGPP port
11369 * Cygwin Native:: Features specific to the Cygwin port
11375 On HP-UX systems, if you refer to a function or variable name that
11376 begins with a dollar sign, @value{GDBN} searches for a user or system
11377 name first, before it searches for a convenience variable.
11379 @node BSD libkvm Interface
11380 @subsection BSD libkvm Interface
11383 @cindex kernel memory image
11384 @cindex kernel crash dump
11386 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
11387 interface that provides a uniform interface for accessing kernel virtual
11388 memory images, including live systems and crash dumps. @value{GDBN}
11389 uses this interface to allow you to debug live kernels and kernel crash
11390 dumps on many native BSD configurations. This is implemented as a
11391 special @code{kvm} debugging target. For debugging a live system, load
11392 the currently running kernel into @value{GDBN} and connect to the
11396 (@value{GDBP}) @b{target kvm}
11399 For debugging crash dumps, provide the file name of the crash dump as an
11403 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
11406 Once connected to the @code{kvm} target, the following commands are
11412 Set current context from pcb address.
11415 Set current context from proc address. This command isn't available on
11416 modern FreeBSD systems.
11419 @node SVR4 Process Information
11420 @subsection SVR4 process information
11423 @cindex process image
11425 Many versions of SVR4 provide a facility called @samp{/proc} that can be
11426 used to examine the image of a running process using file-system
11427 subroutines. If @value{GDBN} is configured for an operating system with
11428 this facility, the command @code{info proc} is available to report on
11429 several kinds of information about the process running your program.
11430 @code{info proc} works only on SVR4 systems that include the
11431 @code{procfs} code. This includes OSF/1 (Digital Unix), Solaris, Irix,
11432 and Unixware, but not HP-UX or @sc{gnu}/Linux, for example.
11437 Summarize available information about the process.
11439 @kindex info proc mappings
11440 @item info proc mappings
11441 Report on the address ranges accessible in the program, with information
11442 on whether your program may read, write, or execute each range.
11444 @comment These sub-options of 'info proc' were not included when
11445 @comment procfs.c was re-written. Keep their descriptions around
11446 @comment against the day when someone finds the time to put them back in.
11447 @kindex info proc times
11448 @item info proc times
11449 Starting time, user CPU time, and system CPU time for your program and
11452 @kindex info proc id
11454 Report on the process IDs related to your program: its own process ID,
11455 the ID of its parent, the process group ID, and the session ID.
11457 @kindex info proc status
11458 @item info proc status
11459 General information on the state of the process. If the process is
11460 stopped, this report includes the reason for stopping, and any signal
11463 @item info proc all
11464 Show all the above information about the process.
11469 @subsection Features for Debugging @sc{djgpp} Programs
11470 @cindex @sc{djgpp} debugging
11471 @cindex native @sc{djgpp} debugging
11472 @cindex MS-DOS-specific commands
11474 @sc{djgpp} is the port of @sc{gnu} development tools to MS-DOS and
11475 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
11476 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
11477 top of real-mode DOS systems and their emulations.
11479 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
11480 defines a few commands specific to the @sc{djgpp} port. This
11481 subsection describes those commands.
11486 This is a prefix of @sc{djgpp}-specific commands which print
11487 information about the target system and important OS structures.
11490 @cindex MS-DOS system info
11491 @cindex free memory information (MS-DOS)
11492 @item info dos sysinfo
11493 This command displays assorted information about the underlying
11494 platform: the CPU type and features, the OS version and flavor, the
11495 DPMI version, and the available conventional and DPMI memory.
11500 @cindex segment descriptor tables
11501 @cindex descriptor tables display
11503 @itemx info dos ldt
11504 @itemx info dos idt
11505 These 3 commands display entries from, respectively, Global, Local,
11506 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
11507 tables are data structures which store a descriptor for each segment
11508 that is currently in use. The segment's selector is an index into a
11509 descriptor table; the table entry for that index holds the
11510 descriptor's base address and limit, and its attributes and access
11513 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
11514 segment (used for both data and the stack), and a DOS segment (which
11515 allows access to DOS/BIOS data structures and absolute addresses in
11516 conventional memory). However, the DPMI host will usually define
11517 additional segments in order to support the DPMI environment.
11519 @cindex garbled pointers
11520 These commands allow to display entries from the descriptor tables.
11521 Without an argument, all entries from the specified table are
11522 displayed. An argument, which should be an integer expression, means
11523 display a single entry whose index is given by the argument. For
11524 example, here's a convenient way to display information about the
11525 debugged program's data segment:
11528 @exdent @code{(@value{GDBP}) info dos ldt $ds}
11529 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
11533 This comes in handy when you want to see whether a pointer is outside
11534 the data segment's limit (i.e.@: @dfn{garbled}).
11536 @cindex page tables display (MS-DOS)
11538 @itemx info dos pte
11539 These two commands display entries from, respectively, the Page
11540 Directory and the Page Tables. Page Directories and Page Tables are
11541 data structures which control how virtual memory addresses are mapped
11542 into physical addresses. A Page Table includes an entry for every
11543 page of memory that is mapped into the program's address space; there
11544 may be several Page Tables, each one holding up to 4096 entries. A
11545 Page Directory has up to 4096 entries, one each for every Page Table
11546 that is currently in use.
11548 Without an argument, @kbd{info dos pde} displays the entire Page
11549 Directory, and @kbd{info dos pte} displays all the entries in all of
11550 the Page Tables. An argument, an integer expression, given to the
11551 @kbd{info dos pde} command means display only that entry from the Page
11552 Directory table. An argument given to the @kbd{info dos pte} command
11553 means display entries from a single Page Table, the one pointed to by
11554 the specified entry in the Page Directory.
11556 @cindex direct memory access (DMA) on MS-DOS
11557 These commands are useful when your program uses @dfn{DMA} (Direct
11558 Memory Access), which needs physical addresses to program the DMA
11561 These commands are supported only with some DPMI servers.
11563 @cindex physical address from linear address
11564 @item info dos address-pte @var{addr}
11565 This command displays the Page Table entry for a specified linear
11566 address. The argument linear address @var{addr} should already have the
11567 appropriate segment's base address added to it, because this command
11568 accepts addresses which may belong to @emph{any} segment. For
11569 example, here's how to display the Page Table entry for the page where
11570 the variable @code{i} is stored:
11573 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
11574 @exdent @code{Page Table entry for address 0x11a00d30:}
11575 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
11579 This says that @code{i} is stored at offset @code{0xd30} from the page
11580 whose physical base address is @code{0x02698000}, and prints all the
11581 attributes of that page.
11583 Note that you must cast the addresses of variables to a @code{char *},
11584 since otherwise the value of @code{__djgpp_base_address}, the base
11585 address of all variables and functions in a @sc{djgpp} program, will
11586 be added using the rules of C pointer arithmetics: if @code{i} is
11587 declared an @code{int}, @value{GDBN} will add 4 times the value of
11588 @code{__djgpp_base_address} to the address of @code{i}.
11590 Here's another example, it displays the Page Table entry for the
11594 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
11595 @exdent @code{Page Table entry for address 0x29110:}
11596 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
11600 (The @code{+ 3} offset is because the transfer buffer's address is the
11601 3rd member of the @code{_go32_info_block} structure.) The output of
11602 this command clearly shows that addresses in conventional memory are
11603 mapped 1:1, i.e.@: the physical and linear addresses are identical.
11605 This command is supported only with some DPMI servers.
11608 @node Cygwin Native
11609 @subsection Features for Debugging MS Windows PE executables
11610 @cindex MS Windows debugging
11611 @cindex native Cygwin debugging
11612 @cindex Cygwin-specific commands
11614 @value{GDBN} supports native debugging of MS Windows programs, including
11615 DLLs with and without symbolic debugging information. There are various
11616 additional Cygwin-specific commands, described in this subsection. The
11617 subsubsection @pxref{Non-debug DLL symbols} describes working with DLLs
11618 that have no debugging symbols.
11624 This is a prefix of MS Windows specific commands which print
11625 information about the target system and important OS structures.
11627 @item info w32 selector
11628 This command displays information returned by
11629 the Win32 API @code{GetThreadSelectorEntry} function.
11630 It takes an optional argument that is evaluated to
11631 a long value to give the information about this given selector.
11632 Without argument, this command displays information
11633 about the the six segment registers.
11637 This is a Cygwin specific alias of info shared.
11639 @kindex dll-symbols
11641 This command loads symbols from a dll similarly to
11642 add-sym command but without the need to specify a base address.
11644 @kindex set new-console
11645 @item set new-console @var{mode}
11646 If @var{mode} is @code{on} the debuggee will
11647 be started in a new console on next start.
11648 If @var{mode} is @code{off}i, the debuggee will
11649 be started in the same console as the debugger.
11651 @kindex show new-console
11652 @item show new-console
11653 Displays whether a new console is used
11654 when the debuggee is started.
11656 @kindex set new-group
11657 @item set new-group @var{mode}
11658 This boolean value controls whether the debuggee should
11659 start a new group or stay in the same group as the debugger.
11660 This affects the way the Windows OS handles
11663 @kindex show new-group
11664 @item show new-group
11665 Displays current value of new-group boolean.
11667 @kindex set debugevents
11668 @item set debugevents
11669 This boolean value adds debug output concerning events seen by the debugger.
11671 @kindex set debugexec
11672 @item set debugexec
11673 This boolean value adds debug output concerning execute events
11674 seen by the debugger.
11676 @kindex set debugexceptions
11677 @item set debugexceptions
11678 This boolean value adds debug ouptut concerning exception events
11679 seen by the debugger.
11681 @kindex set debugmemory
11682 @item set debugmemory
11683 This boolean value adds debug ouptut concerning memory events
11684 seen by the debugger.
11688 This boolean values specifies whether the debuggee is called
11689 via a shell or directly (default value is on).
11693 Displays if the debuggee will be started with a shell.
11698 * Non-debug DLL symbols:: Support for DLLs without debugging symbols
11701 @node Non-debug DLL symbols
11702 @subsubsection Support for DLLs without debugging symbols
11703 @cindex DLLs with no debugging symbols
11704 @cindex Minimal symbols and DLLs
11706 Very often on windows, some of the DLLs that your program relies on do
11707 not include symbolic debugging information (for example,
11708 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
11709 symbols in a DLL, it relies on the minimal amount of symbolic
11710 information contained in the DLL's export table. This subsubsection
11711 describes working with such symbols, known internally to @value{GDBN} as
11712 ``minimal symbols''.
11714 Note that before the debugged program has started execution, no DLLs
11715 will have been loaded. The easiest way around this problem is simply to
11716 start the program --- either by setting a breakpoint or letting the
11717 program run once to completion. It is also possible to force
11718 @value{GDBN} to load a particular DLL before starting the executable ---
11719 see the shared library information in @pxref{Files} or the
11720 @code{dll-symbols} command in @pxref{Cygwin Native}. Currently,
11721 explicitly loading symbols from a DLL with no debugging information will
11722 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
11723 which may adversely affect symbol lookup performance.
11725 @subsubsection DLL name prefixes
11727 In keeping with the naming conventions used by the Microsoft debugging
11728 tools, DLL export symbols are made available with a prefix based on the
11729 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
11730 also entered into the symbol table, so @code{CreateFileA} is often
11731 sufficient. In some cases there will be name clashes within a program
11732 (particularly if the executable itself includes full debugging symbols)
11733 necessitating the use of the fully qualified name when referring to the
11734 contents of the DLL. Use single-quotes around the name to avoid the
11735 exclamation mark (``!'') being interpreted as a language operator.
11737 Note that the internal name of the DLL may be all upper-case, even
11738 though the file name of the DLL is lower-case, or vice-versa. Since
11739 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
11740 some confusion. If in doubt, try the @code{info functions} and
11741 @code{info variables} commands or even @code{maint print msymbols} (see
11742 @pxref{Symbols}). Here's an example:
11745 (gdb) info function CreateFileA
11746 All functions matching regular expression "CreateFileA":
11748 Non-debugging symbols:
11749 0x77e885f4 CreateFileA
11750 0x77e885f4 KERNEL32!CreateFileA
11754 (gdb) info function !
11755 All functions matching regular expression "!":
11757 Non-debugging symbols:
11758 0x6100114c cygwin1!__assert
11759 0x61004034 cygwin1!_dll_crt0@@0
11760 0x61004240 cygwin1!dll_crt0(per_process *)
11764 @subsubsection Working with minimal symbols
11766 Symbols extracted from a DLL's export table do not contain very much
11767 type information. All that @value{GDBN} can do is guess whether a symbol
11768 refers to a function or variable depending on the linker section that
11769 contains the symbol. Also note that the actual contents of the memory
11770 contained in a DLL are not available unless the program is running. This
11771 means that you cannot examine the contents of a variable or disassemble
11772 a function within a DLL without a running program.
11774 Variables are generally treated as pointers and dereferenced
11775 automatically. For this reason, it is often necessary to prefix a
11776 variable name with the address-of operator (``&'') and provide explicit
11777 type information in the command. Here's an example of the type of
11781 (gdb) print 'cygwin1!__argv'
11786 (gdb) x 'cygwin1!__argv'
11787 0x10021610: "\230y\""
11790 And two possible solutions:
11793 (gdb) print ((char **)'cygwin1!__argv')[0]
11794 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
11798 (gdb) x/2x &'cygwin1!__argv'
11799 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
11800 (gdb) x/x 0x10021608
11801 0x10021608: 0x0022fd98
11802 (gdb) x/s 0x0022fd98
11803 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
11806 Setting a break point within a DLL is possible even before the program
11807 starts execution. However, under these circumstances, @value{GDBN} can't
11808 examine the initial instructions of the function in order to skip the
11809 function's frame set-up code. You can work around this by using ``*&''
11810 to set the breakpoint at a raw memory address:
11813 (gdb) break *&'python22!PyOS_Readline'
11814 Breakpoint 1 at 0x1e04eff0
11817 The author of these extensions is not entirely convinced that setting a
11818 break point within a shared DLL like @file{kernel32.dll} is completely
11822 @section Embedded Operating Systems
11824 This section describes configurations involving the debugging of
11825 embedded operating systems that are available for several different
11829 * VxWorks:: Using @value{GDBN} with VxWorks
11832 @value{GDBN} includes the ability to debug programs running on
11833 various real-time operating systems.
11836 @subsection Using @value{GDBN} with VxWorks
11842 @kindex target vxworks
11843 @item target vxworks @var{machinename}
11844 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
11845 is the target system's machine name or IP address.
11849 On VxWorks, @code{load} links @var{filename} dynamically on the
11850 current target system as well as adding its symbols in @value{GDBN}.
11852 @value{GDBN} enables developers to spawn and debug tasks running on networked
11853 VxWorks targets from a Unix host. Already-running tasks spawned from
11854 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
11855 both the Unix host and on the VxWorks target. The program
11856 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
11857 installed with the name @code{vxgdb}, to distinguish it from a
11858 @value{GDBN} for debugging programs on the host itself.)
11861 @item VxWorks-timeout @var{args}
11862 @kindex vxworks-timeout
11863 All VxWorks-based targets now support the option @code{vxworks-timeout}.
11864 This option is set by the user, and @var{args} represents the number of
11865 seconds @value{GDBN} waits for responses to rpc's. You might use this if
11866 your VxWorks target is a slow software simulator or is on the far side
11867 of a thin network line.
11870 The following information on connecting to VxWorks was current when
11871 this manual was produced; newer releases of VxWorks may use revised
11874 @findex INCLUDE_RDB
11875 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
11876 to include the remote debugging interface routines in the VxWorks
11877 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
11878 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
11879 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
11880 source debugging task @code{tRdbTask} when VxWorks is booted. For more
11881 information on configuring and remaking VxWorks, see the manufacturer's
11883 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
11885 Once you have included @file{rdb.a} in your VxWorks system image and set
11886 your Unix execution search path to find @value{GDBN}, you are ready to
11887 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
11888 @code{vxgdb}, depending on your installation).
11890 @value{GDBN} comes up showing the prompt:
11897 * VxWorks Connection:: Connecting to VxWorks
11898 * VxWorks Download:: VxWorks download
11899 * VxWorks Attach:: Running tasks
11902 @node VxWorks Connection
11903 @subsubsection Connecting to VxWorks
11905 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
11906 network. To connect to a target whose host name is ``@code{tt}'', type:
11909 (vxgdb) target vxworks tt
11913 @value{GDBN} displays messages like these:
11916 Attaching remote machine across net...
11921 @value{GDBN} then attempts to read the symbol tables of any object modules
11922 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
11923 these files by searching the directories listed in the command search
11924 path (@pxref{Environment, ,Your program's environment}); if it fails
11925 to find an object file, it displays a message such as:
11928 prog.o: No such file or directory.
11931 When this happens, add the appropriate directory to the search path with
11932 the @value{GDBN} command @code{path}, and execute the @code{target}
11935 @node VxWorks Download
11936 @subsubsection VxWorks download
11938 @cindex download to VxWorks
11939 If you have connected to the VxWorks target and you want to debug an
11940 object that has not yet been loaded, you can use the @value{GDBN}
11941 @code{load} command to download a file from Unix to VxWorks
11942 incrementally. The object file given as an argument to the @code{load}
11943 command is actually opened twice: first by the VxWorks target in order
11944 to download the code, then by @value{GDBN} in order to read the symbol
11945 table. This can lead to problems if the current working directories on
11946 the two systems differ. If both systems have NFS mounted the same
11947 filesystems, you can avoid these problems by using absolute paths.
11948 Otherwise, it is simplest to set the working directory on both systems
11949 to the directory in which the object file resides, and then to reference
11950 the file by its name, without any path. For instance, a program
11951 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
11952 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
11953 program, type this on VxWorks:
11956 -> cd "@var{vxpath}/vw/demo/rdb"
11960 Then, in @value{GDBN}, type:
11963 (vxgdb) cd @var{hostpath}/vw/demo/rdb
11964 (vxgdb) load prog.o
11967 @value{GDBN} displays a response similar to this:
11970 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
11973 You can also use the @code{load} command to reload an object module
11974 after editing and recompiling the corresponding source file. Note that
11975 this makes @value{GDBN} delete all currently-defined breakpoints,
11976 auto-displays, and convenience variables, and to clear the value
11977 history. (This is necessary in order to preserve the integrity of
11978 debugger's data structures that reference the target system's symbol
11981 @node VxWorks Attach
11982 @subsubsection Running tasks
11984 @cindex running VxWorks tasks
11985 You can also attach to an existing task using the @code{attach} command as
11989 (vxgdb) attach @var{task}
11993 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
11994 or suspended when you attach to it. Running tasks are suspended at
11995 the time of attachment.
11997 @node Embedded Processors
11998 @section Embedded Processors
12000 This section goes into details specific to particular embedded
12006 * H8/300:: Renesas H8/300
12007 * H8/500:: Renesas H8/500
12008 * M32R/D:: Renesas M32R/D
12009 * M68K:: Motorola M68K
12010 * MIPS Embedded:: MIPS Embedded
12011 * OpenRISC 1000:: OpenRisc 1000
12012 * PA:: HP PA Embedded
12015 * Sparclet:: Tsqware Sparclet
12016 * Sparclite:: Fujitsu Sparclite
12017 * ST2000:: Tandem ST2000
12018 * Z8000:: Zilog Z8000
12027 @item target rdi @var{dev}
12028 ARM Angel monitor, via RDI library interface to ADP protocol. You may
12029 use this target to communicate with both boards running the Angel
12030 monitor, or with the EmbeddedICE JTAG debug device.
12033 @item target rdp @var{dev}
12039 @subsection Renesas H8/300
12043 @kindex target hms@r{, with H8/300}
12044 @item target hms @var{dev}
12045 A Renesas SH, H8/300, or H8/500 board, attached via serial line to your host.
12046 Use special commands @code{device} and @code{speed} to control the serial
12047 line and the communications speed used.
12049 @kindex target e7000@r{, with H8/300}
12050 @item target e7000 @var{dev}
12051 E7000 emulator for Renesas H8 and SH.
12053 @kindex target sh3@r{, with H8/300}
12054 @kindex target sh3e@r{, with H8/300}
12055 @item target sh3 @var{dev}
12056 @itemx target sh3e @var{dev}
12057 Renesas SH-3 and SH-3E target systems.
12061 @cindex download to H8/300 or H8/500
12062 @cindex H8/300 or H8/500 download
12063 @cindex download to Renesas SH
12064 @cindex Renesas SH download
12065 When you select remote debugging to a Renesas SH, H8/300, or H8/500
12066 board, the @code{load} command downloads your program to the Renesas
12067 board and also opens it as the current executable target for
12068 @value{GDBN} on your host (like the @code{file} command).
12070 @value{GDBN} needs to know these things to talk to your
12071 Renesas SH, H8/300, or H8/500:
12075 that you want to use @samp{target hms}, the remote debugging interface
12076 for Renesas microprocessors, or @samp{target e7000}, the in-circuit
12077 emulator for the Renesas SH and the Renesas 300H. (@samp{target hms} is
12078 the default when @value{GDBN} is configured specifically for the Renesas SH,
12079 H8/300, or H8/500.)
12082 what serial device connects your host to your Renesas board (the first
12083 serial device available on your host is the default).
12086 what speed to use over the serial device.
12090 * Renesas Boards:: Connecting to Renesas boards.
12091 * Renesas ICE:: Using the E7000 In-Circuit Emulator.
12092 * Renesas Special:: Special @value{GDBN} commands for Renesas micros.
12095 @node Renesas Boards
12096 @subsubsection Connecting to Renesas boards
12098 @c only for Unix hosts
12100 @cindex serial device, Renesas micros
12101 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
12102 need to explicitly set the serial device. The default @var{port} is the
12103 first available port on your host. This is only necessary on Unix
12104 hosts, where it is typically something like @file{/dev/ttya}.
12107 @cindex serial line speed, Renesas micros
12108 @code{@value{GDBN}} has another special command to set the communications
12109 speed: @samp{speed @var{bps}}. This command also is only used from Unix
12110 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
12111 the DOS @code{mode} command (for instance,
12112 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
12114 The @samp{device} and @samp{speed} commands are available only when you
12115 use a Unix host to debug your Renesas microprocessor programs. If you
12117 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
12118 called @code{asynctsr} to communicate with the development board
12119 through a PC serial port. You must also use the DOS @code{mode} command
12120 to set up the serial port on the DOS side.
12122 The following sample session illustrates the steps needed to start a
12123 program under @value{GDBN} control on an H8/300. The example uses a
12124 sample H8/300 program called @file{t.x}. The procedure is the same for
12125 the Renesas SH and the H8/500.
12127 First hook up your development board. In this example, we use a
12128 board attached to serial port @code{COM2}; if you use a different serial
12129 port, substitute its name in the argument of the @code{mode} command.
12130 When you call @code{asynctsr}, the auxiliary comms program used by the
12131 debugger, you give it just the numeric part of the serial port's name;
12132 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
12136 C:\H8300\TEST> asynctsr 2
12137 C:\H8300\TEST> mode com2:9600,n,8,1,p
12139 Resident portion of MODE loaded
12141 COM2: 9600, n, 8, 1, p
12146 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
12147 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
12148 disable it, or even boot without it, to use @code{asynctsr} to control
12149 your development board.
12152 @kindex target hms@r{, and serial protocol}
12153 Now that serial communications are set up, and the development board is
12154 connected, you can start up @value{GDBN}. Call @code{@value{GDBP}} with
12155 the name of your program as the argument. @code{@value{GDBN}} prompts
12156 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
12157 commands to begin your debugging session: @samp{target hms} to specify
12158 cross-debugging to the Renesas board, and the @code{load} command to
12159 download your program to the board. @code{load} displays the names of
12160 the program's sections, and a @samp{*} for each 2K of data downloaded.
12161 (If you want to refresh @value{GDBN} data on symbols or on the
12162 executable file without downloading, use the @value{GDBN} commands
12163 @code{file} or @code{symbol-file}. These commands, and @code{load}
12164 itself, are described in @ref{Files,,Commands to specify files}.)
12167 (eg-C:\H8300\TEST) @value{GDBP} t.x
12168 @value{GDBN} is free software and you are welcome to distribute copies
12169 of it under certain conditions; type "show copying" to see
12171 There is absolutely no warranty for @value{GDBN}; type "show warranty"
12173 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
12174 (@value{GDBP}) target hms
12175 Connected to remote H8/300 HMS system.
12176 (@value{GDBP}) load t.x
12177 .text : 0x8000 .. 0xabde ***********
12178 .data : 0xabde .. 0xad30 *
12179 .stack : 0xf000 .. 0xf014 *
12182 At this point, you're ready to run or debug your program. From here on,
12183 you can use all the usual @value{GDBN} commands. The @code{break} command
12184 sets breakpoints; the @code{run} command starts your program;
12185 @code{print} or @code{x} display data; the @code{continue} command
12186 resumes execution after stopping at a breakpoint. You can use the
12187 @code{help} command at any time to find out more about @value{GDBN} commands.
12189 Remember, however, that @emph{operating system} facilities aren't
12190 available on your development board; for example, if your program hangs,
12191 you can't send an interrupt---but you can press the @sc{reset} switch!
12193 Use the @sc{reset} button on the development board
12196 to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has
12197 no way to pass an interrupt signal to the development board); and
12200 to return to the @value{GDBN} command prompt after your program finishes
12201 normally. The communications protocol provides no other way for @value{GDBN}
12202 to detect program completion.
12205 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
12206 development board as a ``normal exit'' of your program.
12209 @subsubsection Using the E7000 in-circuit emulator
12211 @kindex target e7000@r{, with Renesas ICE}
12212 You can use the E7000 in-circuit emulator to develop code for either the
12213 Renesas SH or the H8/300H. Use one of these forms of the @samp{target
12214 e7000} command to connect @value{GDBN} to your E7000:
12217 @item target e7000 @var{port} @var{speed}
12218 Use this form if your E7000 is connected to a serial port. The
12219 @var{port} argument identifies what serial port to use (for example,
12220 @samp{com2}). The third argument is the line speed in bits per second
12221 (for example, @samp{9600}).
12223 @item target e7000 @var{hostname}
12224 If your E7000 is installed as a host on a TCP/IP network, you can just
12225 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
12228 @node Renesas Special
12229 @subsubsection Special @value{GDBN} commands for Renesas micros
12231 Some @value{GDBN} commands are available only for the H8/300:
12235 @kindex set machine
12236 @kindex show machine
12237 @item set machine h8300
12238 @itemx set machine h8300h
12239 Condition @value{GDBN} for one of the two variants of the H8/300
12240 architecture with @samp{set machine}. You can use @samp{show machine}
12241 to check which variant is currently in effect.
12250 @kindex set memory @var{mod}
12251 @cindex memory models, H8/500
12252 @item set memory @var{mod}
12254 Specify which H8/500 memory model (@var{mod}) you are using with
12255 @samp{set memory}; check which memory model is in effect with @samp{show
12256 memory}. The accepted values for @var{mod} are @code{small},
12257 @code{big}, @code{medium}, and @code{compact}.
12262 @subsection Renesas M32R/D
12266 @kindex target m32r
12267 @item target m32r @var{dev}
12268 Renesas M32R/D ROM monitor.
12270 @kindex target m32rsdi
12271 @item target m32rsdi @var{dev}
12272 Renesas M32R SDI server, connected via parallel port to the board.
12279 The Motorola m68k configuration includes ColdFire support, and
12280 target command for the following ROM monitors.
12284 @kindex target abug
12285 @item target abug @var{dev}
12286 ABug ROM monitor for M68K.
12288 @kindex target cpu32bug
12289 @item target cpu32bug @var{dev}
12290 CPU32BUG monitor, running on a CPU32 (M68K) board.
12292 @kindex target dbug
12293 @item target dbug @var{dev}
12294 dBUG ROM monitor for Motorola ColdFire.
12297 @item target est @var{dev}
12298 EST-300 ICE monitor, running on a CPU32 (M68K) board.
12300 @kindex target rom68k
12301 @item target rom68k @var{dev}
12302 ROM 68K monitor, running on an M68K IDP board.
12308 @kindex target rombug
12309 @item target rombug @var{dev}
12310 ROMBUG ROM monitor for OS/9000.
12314 @node MIPS Embedded
12315 @subsection MIPS Embedded
12317 @cindex MIPS boards
12318 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
12319 MIPS board attached to a serial line. This is available when
12320 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
12323 Use these @value{GDBN} commands to specify the connection to your target board:
12326 @item target mips @var{port}
12327 @kindex target mips @var{port}
12328 To run a program on the board, start up @code{@value{GDBP}} with the
12329 name of your program as the argument. To connect to the board, use the
12330 command @samp{target mips @var{port}}, where @var{port} is the name of
12331 the serial port connected to the board. If the program has not already
12332 been downloaded to the board, you may use the @code{load} command to
12333 download it. You can then use all the usual @value{GDBN} commands.
12335 For example, this sequence connects to the target board through a serial
12336 port, and loads and runs a program called @var{prog} through the
12340 host$ @value{GDBP} @var{prog}
12341 @value{GDBN} is free software and @dots{}
12342 (@value{GDBP}) target mips /dev/ttyb
12343 (@value{GDBP}) load @var{prog}
12347 @item target mips @var{hostname}:@var{portnumber}
12348 On some @value{GDBN} host configurations, you can specify a TCP
12349 connection (for instance, to a serial line managed by a terminal
12350 concentrator) instead of a serial port, using the syntax
12351 @samp{@var{hostname}:@var{portnumber}}.
12353 @item target pmon @var{port}
12354 @kindex target pmon @var{port}
12357 @item target ddb @var{port}
12358 @kindex target ddb @var{port}
12359 NEC's DDB variant of PMON for Vr4300.
12361 @item target lsi @var{port}
12362 @kindex target lsi @var{port}
12363 LSI variant of PMON.
12365 @kindex target r3900
12366 @item target r3900 @var{dev}
12367 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
12369 @kindex target array
12370 @item target array @var{dev}
12371 Array Tech LSI33K RAID controller board.
12377 @value{GDBN} also supports these special commands for MIPS targets:
12380 @item set processor @var{args}
12381 @itemx show processor
12382 @kindex set processor @var{args}
12383 @kindex show processor
12384 Use the @code{set processor} command to set the type of MIPS
12385 processor when you want to access processor-type-specific registers.
12386 For example, @code{set processor @var{r3041}} tells @value{GDBN}
12387 to use the CPU registers appropriate for the 3041 chip.
12388 Use the @code{show processor} command to see what MIPS processor @value{GDBN}
12389 is using. Use the @code{info reg} command to see what registers
12390 @value{GDBN} is using.
12392 @item set mipsfpu double
12393 @itemx set mipsfpu single
12394 @itemx set mipsfpu none
12395 @itemx show mipsfpu
12396 @kindex set mipsfpu
12397 @kindex show mipsfpu
12398 @cindex MIPS remote floating point
12399 @cindex floating point, MIPS remote
12400 If your target board does not support the MIPS floating point
12401 coprocessor, you should use the command @samp{set mipsfpu none} (if you
12402 need this, you may wish to put the command in your @value{GDBN} init
12403 file). This tells @value{GDBN} how to find the return value of
12404 functions which return floating point values. It also allows
12405 @value{GDBN} to avoid saving the floating point registers when calling
12406 functions on the board. If you are using a floating point coprocessor
12407 with only single precision floating point support, as on the @sc{r4650}
12408 processor, use the command @samp{set mipsfpu single}. The default
12409 double precision floating point coprocessor may be selected using
12410 @samp{set mipsfpu double}.
12412 In previous versions the only choices were double precision or no
12413 floating point, so @samp{set mipsfpu on} will select double precision
12414 and @samp{set mipsfpu off} will select no floating point.
12416 As usual, you can inquire about the @code{mipsfpu} variable with
12417 @samp{show mipsfpu}.
12419 @item set remotedebug @var{n}
12420 @itemx show remotedebug
12421 @kindex set remotedebug@r{, MIPS protocol}
12422 @kindex show remotedebug@r{, MIPS protocol}
12423 @cindex @code{remotedebug}, MIPS protocol
12424 @cindex MIPS @code{remotedebug} protocol
12425 @c FIXME! For this to be useful, you must know something about the MIPS
12426 @c FIXME...protocol. Where is it described?
12427 You can see some debugging information about communications with the board
12428 by setting the @code{remotedebug} variable. If you set it to @code{1} using
12429 @samp{set remotedebug 1}, every packet is displayed. If you set it
12430 to @code{2}, every character is displayed. You can check the current value
12431 at any time with the command @samp{show remotedebug}.
12433 @item set timeout @var{seconds}
12434 @itemx set retransmit-timeout @var{seconds}
12435 @itemx show timeout
12436 @itemx show retransmit-timeout
12437 @cindex @code{timeout}, MIPS protocol
12438 @cindex @code{retransmit-timeout}, MIPS protocol
12439 @kindex set timeout
12440 @kindex show timeout
12441 @kindex set retransmit-timeout
12442 @kindex show retransmit-timeout
12443 You can control the timeout used while waiting for a packet, in the MIPS
12444 remote protocol, with the @code{set timeout @var{seconds}} command. The
12445 default is 5 seconds. Similarly, you can control the timeout used while
12446 waiting for an acknowledgement of a packet with the @code{set
12447 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
12448 You can inspect both values with @code{show timeout} and @code{show
12449 retransmit-timeout}. (These commands are @emph{only} available when
12450 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
12452 The timeout set by @code{set timeout} does not apply when @value{GDBN}
12453 is waiting for your program to stop. In that case, @value{GDBN} waits
12454 forever because it has no way of knowing how long the program is going
12455 to run before stopping.
12458 @node OpenRISC 1000
12459 @subsection OpenRISC 1000
12460 @cindex OpenRISC 1000
12462 @cindex or1k boards
12463 See OR1k Architecture document (@uref{www.opencores.org}) for more information
12464 about platform and commands.
12468 @kindex target jtag
12469 @item target jtag jtag://@var{host}:@var{port}
12471 Connects to remote JTAG server.
12472 JTAG remote server can be either an or1ksim or JTAG server,
12473 connected via parallel port to the board.
12475 Example: @code{target jtag jtag://localhost:9999}
12478 @item or1ksim @var{command}
12479 If connected to @code{or1ksim} OpenRISC 1000 Architectural
12480 Simulator, proprietary commands can be executed.
12482 @kindex info or1k spr
12483 @item info or1k spr
12484 Displays spr groups.
12486 @item info or1k spr @var{group}
12487 @itemx info or1k spr @var{groupno}
12488 Displays register names in selected group.
12490 @item info or1k spr @var{group} @var{register}
12491 @itemx info or1k spr @var{register}
12492 @itemx info or1k spr @var{groupno} @var{registerno}
12493 @itemx info or1k spr @var{registerno}
12494 Shows information about specified spr register.
12497 @item spr @var{group} @var{register} @var{value}
12498 @itemx spr @var{register @var{value}}
12499 @itemx spr @var{groupno} @var{registerno @var{value}}
12500 @itemx spr @var{registerno @var{value}}
12501 Writes @var{value} to specified spr register.
12504 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
12505 It is very similar to @value{GDBN} trace, except it does not interfere with normal
12506 program execution and is thus much faster. Hardware breakpoints/watchpoint
12507 triggers can be set using:
12510 Load effective address/data
12512 Store effective address/data
12514 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
12519 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
12520 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
12522 @code{htrace} commands:
12523 @cindex OpenRISC 1000 htrace
12526 @item hwatch @var{conditional}
12527 Set hardware watchpoint on combination of Load/Store Effecive Address(es)
12528 or Data. For example:
12530 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
12532 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
12536 Display information about current HW trace configuration.
12538 @item htrace trigger @var{conditional}
12539 Set starting criteria for HW trace.
12541 @item htrace qualifier @var{conditional}
12542 Set acquisition qualifier for HW trace.
12544 @item htrace stop @var{conditional}
12545 Set HW trace stopping criteria.
12547 @item htrace record [@var{data}]*
12548 Selects the data to be recorded, when qualifier is met and HW trace was
12551 @item htrace enable
12552 @itemx htrace disable
12553 Enables/disables the HW trace.
12555 @item htrace rewind [@var{filename}]
12556 Clears currently recorded trace data.
12558 If filename is specified, new trace file is made and any newly collected data
12559 will be written there.
12561 @item htrace print [@var{start} [@var{len}]]
12562 Prints trace buffer, using current record configuration.
12564 @item htrace mode continuous
12565 Set continuous trace mode.
12567 @item htrace mode suspend
12568 Set suspend trace mode.
12573 @subsection PowerPC
12577 @kindex target dink32
12578 @item target dink32 @var{dev}
12579 DINK32 ROM monitor.
12581 @kindex target ppcbug
12582 @item target ppcbug @var{dev}
12583 @kindex target ppcbug1
12584 @item target ppcbug1 @var{dev}
12585 PPCBUG ROM monitor for PowerPC.
12588 @item target sds @var{dev}
12589 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
12594 @subsection HP PA Embedded
12598 @kindex target op50n
12599 @item target op50n @var{dev}
12600 OP50N monitor, running on an OKI HPPA board.
12602 @kindex target w89k
12603 @item target w89k @var{dev}
12604 W89K monitor, running on a Winbond HPPA board.
12609 @subsection Renesas SH
12613 @kindex target hms@r{, with Renesas SH}
12614 @item target hms @var{dev}
12615 A Renesas SH board attached via serial line to your host. Use special
12616 commands @code{device} and @code{speed} to control the serial line and
12617 the communications speed used.
12619 @kindex target e7000@r{, with Renesas SH}
12620 @item target e7000 @var{dev}
12621 E7000 emulator for Renesas SH.
12623 @kindex target sh3@r{, with SH}
12624 @kindex target sh3e@r{, with SH}
12625 @item target sh3 @var{dev}
12626 @item target sh3e @var{dev}
12627 Renesas SH-3 and SH-3E target systems.
12632 @subsection Tsqware Sparclet
12636 @value{GDBN} enables developers to debug tasks running on
12637 Sparclet targets from a Unix host.
12638 @value{GDBN} uses code that runs on
12639 both the Unix host and on the Sparclet target. The program
12640 @code{@value{GDBP}} is installed and executed on the Unix host.
12643 @item remotetimeout @var{args}
12644 @kindex remotetimeout
12645 @value{GDBN} supports the option @code{remotetimeout}.
12646 This option is set by the user, and @var{args} represents the number of
12647 seconds @value{GDBN} waits for responses.
12650 @cindex compiling, on Sparclet
12651 When compiling for debugging, include the options @samp{-g} to get debug
12652 information and @samp{-Ttext} to relocate the program to where you wish to
12653 load it on the target. You may also want to add the options @samp{-n} or
12654 @samp{-N} in order to reduce the size of the sections. Example:
12657 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
12660 You can use @code{objdump} to verify that the addresses are what you intended:
12663 sparclet-aout-objdump --headers --syms prog
12666 @cindex running, on Sparclet
12668 your Unix execution search path to find @value{GDBN}, you are ready to
12669 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
12670 (or @code{sparclet-aout-gdb}, depending on your installation).
12672 @value{GDBN} comes up showing the prompt:
12679 * Sparclet File:: Setting the file to debug
12680 * Sparclet Connection:: Connecting to Sparclet
12681 * Sparclet Download:: Sparclet download
12682 * Sparclet Execution:: Running and debugging
12685 @node Sparclet File
12686 @subsubsection Setting file to debug
12688 The @value{GDBN} command @code{file} lets you choose with program to debug.
12691 (gdbslet) file prog
12695 @value{GDBN} then attempts to read the symbol table of @file{prog}.
12696 @value{GDBN} locates
12697 the file by searching the directories listed in the command search
12699 If the file was compiled with debug information (option "-g"), source
12700 files will be searched as well.
12701 @value{GDBN} locates
12702 the source files by searching the directories listed in the directory search
12703 path (@pxref{Environment, ,Your program's environment}).
12705 to find a file, it displays a message such as:
12708 prog: No such file or directory.
12711 When this happens, add the appropriate directories to the search paths with
12712 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
12713 @code{target} command again.
12715 @node Sparclet Connection
12716 @subsubsection Connecting to Sparclet
12718 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
12719 To connect to a target on serial port ``@code{ttya}'', type:
12722 (gdbslet) target sparclet /dev/ttya
12723 Remote target sparclet connected to /dev/ttya
12724 main () at ../prog.c:3
12728 @value{GDBN} displays messages like these:
12734 @node Sparclet Download
12735 @subsubsection Sparclet download
12737 @cindex download to Sparclet
12738 Once connected to the Sparclet target,
12739 you can use the @value{GDBN}
12740 @code{load} command to download the file from the host to the target.
12741 The file name and load offset should be given as arguments to the @code{load}
12743 Since the file format is aout, the program must be loaded to the starting
12744 address. You can use @code{objdump} to find out what this value is. The load
12745 offset is an offset which is added to the VMA (virtual memory address)
12746 of each of the file's sections.
12747 For instance, if the program
12748 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
12749 and bss at 0x12010170, in @value{GDBN}, type:
12752 (gdbslet) load prog 0x12010000
12753 Loading section .text, size 0xdb0 vma 0x12010000
12756 If the code is loaded at a different address then what the program was linked
12757 to, you may need to use the @code{section} and @code{add-symbol-file} commands
12758 to tell @value{GDBN} where to map the symbol table.
12760 @node Sparclet Execution
12761 @subsubsection Running and debugging
12763 @cindex running and debugging Sparclet programs
12764 You can now begin debugging the task using @value{GDBN}'s execution control
12765 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
12766 manual for the list of commands.
12770 Breakpoint 1 at 0x12010000: file prog.c, line 3.
12772 Starting program: prog
12773 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
12774 3 char *symarg = 0;
12776 4 char *execarg = "hello!";
12781 @subsection Fujitsu Sparclite
12785 @kindex target sparclite
12786 @item target sparclite @var{dev}
12787 Fujitsu sparclite boards, used only for the purpose of loading.
12788 You must use an additional command to debug the program.
12789 For example: target remote @var{dev} using @value{GDBN} standard
12795 @subsection Tandem ST2000
12797 @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
12800 To connect your ST2000 to the host system, see the manufacturer's
12801 manual. Once the ST2000 is physically attached, you can run:
12804 target st2000 @var{dev} @var{speed}
12808 to establish it as your debugging environment. @var{dev} is normally
12809 the name of a serial device, such as @file{/dev/ttya}, connected to the
12810 ST2000 via a serial line. You can instead specify @var{dev} as a TCP
12811 connection (for example, to a serial line attached via a terminal
12812 concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
12814 The @code{load} and @code{attach} commands are @emph{not} defined for
12815 this target; you must load your program into the ST2000 as you normally
12816 would for standalone operation. @value{GDBN} reads debugging information
12817 (such as symbols) from a separate, debugging version of the program
12818 available on your host computer.
12819 @c FIXME!! This is terribly vague; what little content is here is
12820 @c basically hearsay.
12822 @cindex ST2000 auxiliary commands
12823 These auxiliary @value{GDBN} commands are available to help you with the ST2000
12827 @item st2000 @var{command}
12828 @kindex st2000 @var{cmd}
12829 @cindex STDBUG commands (ST2000)
12830 @cindex commands to STDBUG (ST2000)
12831 Send a @var{command} to the STDBUG monitor. See the manufacturer's
12832 manual for available commands.
12835 @cindex connect (to STDBUG)
12836 Connect the controlling terminal to the STDBUG command monitor. When
12837 you are done interacting with STDBUG, typing either of two character
12838 sequences gets you back to the @value{GDBN} command prompt:
12839 @kbd{@key{RET}~.} (Return, followed by tilde and period) or
12840 @kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D).
12844 @subsection Zilog Z8000
12847 @cindex simulator, Z8000
12848 @cindex Zilog Z8000 simulator
12850 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
12853 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
12854 unsegmented variant of the Z8000 architecture) or the Z8001 (the
12855 segmented variant). The simulator recognizes which architecture is
12856 appropriate by inspecting the object code.
12859 @item target sim @var{args}
12861 @kindex target sim@r{, with Z8000}
12862 Debug programs on a simulated CPU. If the simulator supports setup
12863 options, specify them via @var{args}.
12867 After specifying this target, you can debug programs for the simulated
12868 CPU in the same style as programs for your host computer; use the
12869 @code{file} command to load a new program image, the @code{run} command
12870 to run your program, and so on.
12872 As well as making available all the usual machine registers
12873 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
12874 additional items of information as specially named registers:
12879 Counts clock-ticks in the simulator.
12882 Counts instructions run in the simulator.
12885 Execution time in 60ths of a second.
12889 You can refer to these values in @value{GDBN} expressions with the usual
12890 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
12891 conditional breakpoint that suspends only after at least 5000
12892 simulated clock ticks.
12894 @node Architectures
12895 @section Architectures
12897 This section describes characteristics of architectures that affect
12898 all uses of @value{GDBN} with the architecture, both native and cross.
12911 @kindex set rstack_high_address
12912 @cindex AMD 29K register stack
12913 @cindex register stack, AMD29K
12914 @item set rstack_high_address @var{address}
12915 On AMD 29000 family processors, registers are saved in a separate
12916 @dfn{register stack}. There is no way for @value{GDBN} to determine the
12917 extent of this stack. Normally, @value{GDBN} just assumes that the
12918 stack is ``large enough''. This may result in @value{GDBN} referencing
12919 memory locations that do not exist. If necessary, you can get around
12920 this problem by specifying the ending address of the register stack with
12921 the @code{set rstack_high_address} command. The argument should be an
12922 address, which you probably want to precede with @samp{0x} to specify in
12925 @kindex show rstack_high_address
12926 @item show rstack_high_address
12927 Display the current limit of the register stack, on AMD 29000 family
12935 See the following section.
12940 @cindex stack on Alpha
12941 @cindex stack on MIPS
12942 @cindex Alpha stack
12944 Alpha- and MIPS-based computers use an unusual stack frame, which
12945 sometimes requires @value{GDBN} to search backward in the object code to
12946 find the beginning of a function.
12948 @cindex response time, MIPS debugging
12949 To improve response time (especially for embedded applications, where
12950 @value{GDBN} may be restricted to a slow serial line for this search)
12951 you may want to limit the size of this search, using one of these
12955 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
12956 @item set heuristic-fence-post @var{limit}
12957 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
12958 search for the beginning of a function. A value of @var{0} (the
12959 default) means there is no limit. However, except for @var{0}, the
12960 larger the limit the more bytes @code{heuristic-fence-post} must search
12961 and therefore the longer it takes to run.
12963 @item show heuristic-fence-post
12964 Display the current limit.
12968 These commands are available @emph{only} when @value{GDBN} is configured
12969 for debugging programs on Alpha or MIPS processors.
12972 @node Controlling GDB
12973 @chapter Controlling @value{GDBN}
12975 You can alter the way @value{GDBN} interacts with you by using the
12976 @code{set} command. For commands controlling how @value{GDBN} displays
12977 data, see @ref{Print Settings, ,Print settings}. Other settings are
12982 * Editing:: Command editing
12983 * History:: Command history
12984 * Screen Size:: Screen size
12985 * Numbers:: Numbers
12986 * ABI:: Configuring the current ABI
12987 * Messages/Warnings:: Optional warnings and messages
12988 * Debugging Output:: Optional messages about internal happenings
12996 @value{GDBN} indicates its readiness to read a command by printing a string
12997 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
12998 can change the prompt string with the @code{set prompt} command. For
12999 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
13000 the prompt in one of the @value{GDBN} sessions so that you can always tell
13001 which one you are talking to.
13003 @emph{Note:} @code{set prompt} does not add a space for you after the
13004 prompt you set. This allows you to set a prompt which ends in a space
13005 or a prompt that does not.
13009 @item set prompt @var{newprompt}
13010 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
13012 @kindex show prompt
13014 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
13018 @section Command editing
13020 @cindex command line editing
13022 @value{GDBN} reads its input commands via the @dfn{readline} interface. This
13023 @sc{gnu} library provides consistent behavior for programs which provide a
13024 command line interface to the user. Advantages are @sc{gnu} Emacs-style
13025 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
13026 substitution, and a storage and recall of command history across
13027 debugging sessions.
13029 You may control the behavior of command line editing in @value{GDBN} with the
13030 command @code{set}.
13033 @kindex set editing
13036 @itemx set editing on
13037 Enable command line editing (enabled by default).
13039 @item set editing off
13040 Disable command line editing.
13042 @kindex show editing
13044 Show whether command line editing is enabled.
13048 @section Command history
13050 @value{GDBN} can keep track of the commands you type during your
13051 debugging sessions, so that you can be certain of precisely what
13052 happened. Use these commands to manage the @value{GDBN} command
13056 @cindex history substitution
13057 @cindex history file
13058 @kindex set history filename
13059 @cindex @env{GDBHISTFILE}, environment variable
13060 @item set history filename @var{fname}
13061 Set the name of the @value{GDBN} command history file to @var{fname}.
13062 This is the file where @value{GDBN} reads an initial command history
13063 list, and where it writes the command history from this session when it
13064 exits. You can access this list through history expansion or through
13065 the history command editing characters listed below. This file defaults
13066 to the value of the environment variable @code{GDBHISTFILE}, or to
13067 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
13070 @cindex history save
13071 @kindex set history
13072 @item set history save
13073 @itemx set history save on
13074 Record command history in a file, whose name may be specified with the
13075 @code{set history filename} command. By default, this option is disabled.
13077 @item set history save off
13078 Stop recording command history in a file.
13080 @cindex history size
13081 @item set history size @var{size}
13082 Set the number of commands which @value{GDBN} keeps in its history list.
13083 This defaults to the value of the environment variable
13084 @code{HISTSIZE}, or to 256 if this variable is not set.
13087 @cindex history expansion
13088 History expansion assigns special meaning to the character @kbd{!}.
13089 @ifset have-readline-appendices
13090 @xref{Event Designators}.
13093 Since @kbd{!} is also the logical not operator in C, history expansion
13094 is off by default. If you decide to enable history expansion with the
13095 @code{set history expansion on} command, you may sometimes need to
13096 follow @kbd{!} (when it is used as logical not, in an expression) with
13097 a space or a tab to prevent it from being expanded. The readline
13098 history facilities do not attempt substitution on the strings
13099 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
13101 The commands to control history expansion are:
13104 @item set history expansion on
13105 @itemx set history expansion
13106 @cindex history expansion
13107 Enable history expansion. History expansion is off by default.
13109 @item set history expansion off
13110 Disable history expansion.
13112 The readline code comes with more complete documentation of
13113 editing and history expansion features. Users unfamiliar with @sc{gnu} Emacs
13114 or @code{vi} may wish to read it.
13115 @ifset have-readline-appendices
13116 @xref{Command Line Editing}.
13120 @kindex show history
13122 @itemx show history filename
13123 @itemx show history save
13124 @itemx show history size
13125 @itemx show history expansion
13126 These commands display the state of the @value{GDBN} history parameters.
13127 @code{show history} by itself displays all four states.
13133 @item show commands
13134 Display the last ten commands in the command history.
13136 @item show commands @var{n}
13137 Print ten commands centered on command number @var{n}.
13139 @item show commands +
13140 Print ten commands just after the commands last printed.
13144 @section Screen size
13145 @cindex size of screen
13146 @cindex pauses in output
13148 Certain commands to @value{GDBN} may produce large amounts of
13149 information output to the screen. To help you read all of it,
13150 @value{GDBN} pauses and asks you for input at the end of each page of
13151 output. Type @key{RET} when you want to continue the output, or @kbd{q}
13152 to discard the remaining output. Also, the screen width setting
13153 determines when to wrap lines of output. Depending on what is being
13154 printed, @value{GDBN} tries to break the line at a readable place,
13155 rather than simply letting it overflow onto the following line.
13157 Normally @value{GDBN} knows the size of the screen from the terminal
13158 driver software. For example, on Unix @value{GDBN} uses the termcap data base
13159 together with the value of the @code{TERM} environment variable and the
13160 @code{stty rows} and @code{stty cols} settings. If this is not correct,
13161 you can override it with the @code{set height} and @code{set
13168 @kindex show height
13169 @item set height @var{lpp}
13171 @itemx set width @var{cpl}
13173 These @code{set} commands specify a screen height of @var{lpp} lines and
13174 a screen width of @var{cpl} characters. The associated @code{show}
13175 commands display the current settings.
13177 If you specify a height of zero lines, @value{GDBN} does not pause during
13178 output no matter how long the output is. This is useful if output is to a
13179 file or to an editor buffer.
13181 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
13182 from wrapping its output.
13187 @cindex number representation
13188 @cindex entering numbers
13190 You can always enter numbers in octal, decimal, or hexadecimal in
13191 @value{GDBN} by the usual conventions: octal numbers begin with
13192 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
13193 begin with @samp{0x}. Numbers that begin with none of these are, by
13194 default, entered in base 10; likewise, the default display for
13195 numbers---when no particular format is specified---is base 10. You can
13196 change the default base for both input and output with the @code{set
13200 @kindex set input-radix
13201 @item set input-radix @var{base}
13202 Set the default base for numeric input. Supported choices
13203 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
13204 specified either unambiguously or using the current default radix; for
13214 sets the base to decimal. On the other hand, @samp{set radix 10}
13215 leaves the radix unchanged no matter what it was.
13217 @kindex set output-radix
13218 @item set output-radix @var{base}
13219 Set the default base for numeric display. Supported choices
13220 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
13221 specified either unambiguously or using the current default radix.
13223 @kindex show input-radix
13224 @item show input-radix
13225 Display the current default base for numeric input.
13227 @kindex show output-radix
13228 @item show output-radix
13229 Display the current default base for numeric display.
13233 @section Configuring the current ABI
13235 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
13236 application automatically. However, sometimes you need to override its
13237 conclusions. Use these commands to manage @value{GDBN}'s view of the
13244 One @value{GDBN} configuration can debug binaries for multiple operating
13245 system targets, either via remote debugging or native emulation.
13246 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
13247 but you can override its conclusion using the @code{set osabi} command.
13248 One example where this is useful is in debugging of binaries which use
13249 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
13250 not have the same identifying marks that the standard C library for your
13255 Show the OS ABI currently in use.
13258 With no argument, show the list of registered available OS ABI's.
13260 @item set osabi @var{abi}
13261 Set the current OS ABI to @var{abi}.
13264 @cindex float promotion
13265 @kindex set coerce-float-to-double
13267 Generally, the way that an argument of type @code{float} is passed to a
13268 function depends on whether the function is prototyped. For a prototyped
13269 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
13270 according to the architecture's convention for @code{float}. For unprototyped
13271 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
13272 @code{double} and then passed.
13274 Unfortunately, some forms of debug information do not reliably indicate whether
13275 a function is prototyped. If @value{GDBN} calls a function that is not marked
13276 as prototyped, it consults @kbd{set coerce-float-to-double}.
13279 @item set coerce-float-to-double
13280 @itemx set coerce-float-to-double on
13281 Arguments of type @code{float} will be promoted to @code{double} when passed
13282 to an unprototyped function. This is the default setting.
13284 @item set coerce-float-to-double off
13285 Arguments of type @code{float} will be passed directly to unprototyped
13290 @kindex show cp-abi
13291 @value{GDBN} needs to know the ABI used for your program's C@t{++}
13292 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
13293 used to build your application. @value{GDBN} only fully supports
13294 programs with a single C@t{++} ABI; if your program contains code using
13295 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
13296 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
13297 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
13298 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
13299 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
13300 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
13305 Show the C@t{++} ABI currently in use.
13308 With no argument, show the list of supported C@t{++} ABI's.
13310 @item set cp-abi @var{abi}
13311 @itemx set cp-abi auto
13312 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
13315 @node Messages/Warnings
13316 @section Optional warnings and messages
13318 By default, @value{GDBN} is silent about its inner workings. If you are
13319 running on a slow machine, you may want to use the @code{set verbose}
13320 command. This makes @value{GDBN} tell you when it does a lengthy
13321 internal operation, so you will not think it has crashed.
13323 Currently, the messages controlled by @code{set verbose} are those
13324 which announce that the symbol table for a source file is being read;
13325 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
13328 @kindex set verbose
13329 @item set verbose on
13330 Enables @value{GDBN} output of certain informational messages.
13332 @item set verbose off
13333 Disables @value{GDBN} output of certain informational messages.
13335 @kindex show verbose
13337 Displays whether @code{set verbose} is on or off.
13340 By default, if @value{GDBN} encounters bugs in the symbol table of an
13341 object file, it is silent; but if you are debugging a compiler, you may
13342 find this information useful (@pxref{Symbol Errors, ,Errors reading
13347 @kindex set complaints
13348 @item set complaints @var{limit}
13349 Permits @value{GDBN} to output @var{limit} complaints about each type of
13350 unusual symbols before becoming silent about the problem. Set
13351 @var{limit} to zero to suppress all complaints; set it to a large number
13352 to prevent complaints from being suppressed.
13354 @kindex show complaints
13355 @item show complaints
13356 Displays how many symbol complaints @value{GDBN} is permitted to produce.
13360 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
13361 lot of stupid questions to confirm certain commands. For example, if
13362 you try to run a program which is already running:
13366 The program being debugged has been started already.
13367 Start it from the beginning? (y or n)
13370 If you are willing to unflinchingly face the consequences of your own
13371 commands, you can disable this ``feature'':
13375 @kindex set confirm
13377 @cindex confirmation
13378 @cindex stupid questions
13379 @item set confirm off
13380 Disables confirmation requests.
13382 @item set confirm on
13383 Enables confirmation requests (the default).
13385 @kindex show confirm
13387 Displays state of confirmation requests.
13391 @node Debugging Output
13392 @section Optional messages about internal happenings
13393 @cindex optional debugging messages
13397 @cindex gdbarch debugging info
13398 @item set debug arch
13399 Turns on or off display of gdbarch debugging info. The default is off
13401 @item show debug arch
13402 Displays the current state of displaying gdbarch debugging info.
13403 @item set debug event
13404 @cindex event debugging info
13405 Turns on or off display of @value{GDBN} event debugging info. The
13407 @item show debug event
13408 Displays the current state of displaying @value{GDBN} event debugging
13410 @item set debug expression
13411 @cindex expression debugging info
13412 Turns on or off display of @value{GDBN} expression debugging info. The
13414 @item show debug expression
13415 Displays the current state of displaying @value{GDBN} expression
13417 @item set debug frame
13418 @cindex frame debugging info
13419 Turns on or off display of @value{GDBN} frame debugging info. The
13421 @item show debug frame
13422 Displays the current state of displaying @value{GDBN} frame debugging
13424 @item set debug observer
13425 @cindex observer debugging info
13426 Turns on or off display of @value{GDBN} observer debugging. This
13427 includes info such as the notification of observable events.
13428 @item show debug observer
13429 Displays the current state of observer debugging.
13430 @item set debug overload
13431 @cindex C@t{++} overload debugging info
13432 Turns on or off display of @value{GDBN} C@t{++} overload debugging
13433 info. This includes info such as ranking of functions, etc. The default
13435 @item show debug overload
13436 Displays the current state of displaying @value{GDBN} C@t{++} overload
13438 @cindex packets, reporting on stdout
13439 @cindex serial connections, debugging
13440 @item set debug remote
13441 Turns on or off display of reports on all packets sent back and forth across
13442 the serial line to the remote machine. The info is printed on the
13443 @value{GDBN} standard output stream. The default is off.
13444 @item show debug remote
13445 Displays the state of display of remote packets.
13446 @item set debug serial
13447 Turns on or off display of @value{GDBN} serial debugging info. The
13449 @item show debug serial
13450 Displays the current state of displaying @value{GDBN} serial debugging
13452 @item set debug target
13453 @cindex target debugging info
13454 Turns on or off display of @value{GDBN} target debugging info. This info
13455 includes what is going on at the target level of GDB, as it happens. The
13456 default is 0. Set it to 1 to track events, and to 2 to also track the
13457 value of large memory transfers. Changes to this flag do not take effect
13458 until the next time you connect to a target or use the @code{run} command.
13459 @item show debug target
13460 Displays the current state of displaying @value{GDBN} target debugging
13462 @item set debug varobj
13463 @cindex variable object debugging info
13464 Turns on or off display of @value{GDBN} variable object debugging
13465 info. The default is off.
13466 @item show debug varobj
13467 Displays the current state of displaying @value{GDBN} variable object
13472 @chapter Canned Sequences of Commands
13474 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
13475 command lists}), @value{GDBN} provides two ways to store sequences of
13476 commands for execution as a unit: user-defined commands and command
13480 * Define:: User-defined commands
13481 * Hooks:: User-defined command hooks
13482 * Command Files:: Command files
13483 * Output:: Commands for controlled output
13487 @section User-defined commands
13489 @cindex user-defined command
13490 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
13491 which you assign a new name as a command. This is done with the
13492 @code{define} command. User commands may accept up to 10 arguments
13493 separated by whitespace. Arguments are accessed within the user command
13494 via @var{$arg0@dots{}$arg9}. A trivial example:
13498 print $arg0 + $arg1 + $arg2
13502 To execute the command use:
13509 This defines the command @code{adder}, which prints the sum of
13510 its three arguments. Note the arguments are text substitutions, so they may
13511 reference variables, use complex expressions, or even perform inferior
13517 @item define @var{commandname}
13518 Define a command named @var{commandname}. If there is already a command
13519 by that name, you are asked to confirm that you want to redefine it.
13521 The definition of the command is made up of other @value{GDBN} command lines,
13522 which are given following the @code{define} command. The end of these
13523 commands is marked by a line containing @code{end}.
13528 Takes a single argument, which is an expression to evaluate.
13529 It is followed by a series of commands that are executed
13530 only if the expression is true (nonzero).
13531 There can then optionally be a line @code{else}, followed
13532 by a series of commands that are only executed if the expression
13533 was false. The end of the list is marked by a line containing @code{end}.
13537 The syntax is similar to @code{if}: the command takes a single argument,
13538 which is an expression to evaluate, and must be followed by the commands to
13539 execute, one per line, terminated by an @code{end}.
13540 The commands are executed repeatedly as long as the expression
13544 @item document @var{commandname}
13545 Document the user-defined command @var{commandname}, so that it can be
13546 accessed by @code{help}. The command @var{commandname} must already be
13547 defined. This command reads lines of documentation just as @code{define}
13548 reads the lines of the command definition, ending with @code{end}.
13549 After the @code{document} command is finished, @code{help} on command
13550 @var{commandname} displays the documentation you have written.
13552 You may use the @code{document} command again to change the
13553 documentation of a command. Redefining the command with @code{define}
13554 does not change the documentation.
13556 @kindex help user-defined
13557 @item help user-defined
13558 List all user-defined commands, with the first line of the documentation
13563 @itemx show user @var{commandname}
13564 Display the @value{GDBN} commands used to define @var{commandname} (but
13565 not its documentation). If no @var{commandname} is given, display the
13566 definitions for all user-defined commands.
13568 @kindex show max-user-call-depth
13569 @kindex set max-user-call-depth
13570 @item show max-user-call-depth
13571 @itemx set max-user-call-depth
13572 The value of @code{max-user-call-depth} controls how many recursion
13573 levels are allowed in user-defined commands before GDB suspects an
13574 infinite recursion and aborts the command.
13578 When user-defined commands are executed, the
13579 commands of the definition are not printed. An error in any command
13580 stops execution of the user-defined command.
13582 If used interactively, commands that would ask for confirmation proceed
13583 without asking when used inside a user-defined command. Many @value{GDBN}
13584 commands that normally print messages to say what they are doing omit the
13585 messages when used in a user-defined command.
13588 @section User-defined command hooks
13589 @cindex command hooks
13590 @cindex hooks, for commands
13591 @cindex hooks, pre-command
13594 You may define @dfn{hooks}, which are a special kind of user-defined
13595 command. Whenever you run the command @samp{foo}, if the user-defined
13596 command @samp{hook-foo} exists, it is executed (with no arguments)
13597 before that command.
13599 @cindex hooks, post-command
13601 A hook may also be defined which is run after the command you executed.
13602 Whenever you run the command @samp{foo}, if the user-defined command
13603 @samp{hookpost-foo} exists, it is executed (with no arguments) after
13604 that command. Post-execution hooks may exist simultaneously with
13605 pre-execution hooks, for the same command.
13607 It is valid for a hook to call the command which it hooks. If this
13608 occurs, the hook is not re-executed, thereby avoiding infinte recursion.
13610 @c It would be nice if hookpost could be passed a parameter indicating
13611 @c if the command it hooks executed properly or not. FIXME!
13613 @kindex stop@r{, a pseudo-command}
13614 In addition, a pseudo-command, @samp{stop} exists. Defining
13615 (@samp{hook-stop}) makes the associated commands execute every time
13616 execution stops in your program: before breakpoint commands are run,
13617 displays are printed, or the stack frame is printed.
13619 For example, to ignore @code{SIGALRM} signals while
13620 single-stepping, but treat them normally during normal execution,
13625 handle SIGALRM nopass
13629 handle SIGALRM pass
13632 define hook-continue
13633 handle SIGLARM pass
13637 As a further example, to hook at the begining and end of the @code{echo}
13638 command, and to add extra text to the beginning and end of the message,
13646 define hookpost-echo
13650 (@value{GDBP}) echo Hello World
13651 <<<---Hello World--->>>
13656 You can define a hook for any single-word command in @value{GDBN}, but
13657 not for command aliases; you should define a hook for the basic command
13658 name, e.g. @code{backtrace} rather than @code{bt}.
13659 @c FIXME! So how does Joe User discover whether a command is an alias
13661 If an error occurs during the execution of your hook, execution of
13662 @value{GDBN} commands stops and @value{GDBN} issues a prompt
13663 (before the command that you actually typed had a chance to run).
13665 If you try to define a hook which does not match any known command, you
13666 get a warning from the @code{define} command.
13668 @node Command Files
13669 @section Command files
13671 @cindex command files
13672 A command file for @value{GDBN} is a file of lines that are @value{GDBN}
13673 commands. Comments (lines starting with @kbd{#}) may also be included.
13674 An empty line in a command file does nothing; it does not mean to repeat
13675 the last command, as it would from the terminal.
13678 @cindex @file{.gdbinit}
13679 @cindex @file{gdb.ini}
13680 When you start @value{GDBN}, it automatically executes commands from its
13681 @dfn{init files}, normally called @file{.gdbinit}@footnote{The DJGPP
13682 port of @value{GDBN} uses the name @file{gdb.ini} instead, due to the
13683 limitations of file names imposed by DOS filesystems.}.
13684 During startup, @value{GDBN} does the following:
13688 Reads the init file (if any) in your home directory@footnote{On
13689 DOS/Windows systems, the home directory is the one pointed to by the
13690 @code{HOME} environment variable.}.
13693 Processes command line options and operands.
13696 Reads the init file (if any) in the current working directory.
13699 Reads command files specified by the @samp{-x} option.
13702 The init file in your home directory can set options (such as @samp{set
13703 complaints}) that affect subsequent processing of command line options
13704 and operands. Init files are not executed if you use the @samp{-nx}
13705 option (@pxref{Mode Options, ,Choosing modes}).
13707 @cindex init file name
13708 On some configurations of @value{GDBN}, the init file is known by a
13709 different name (these are typically environments where a specialized
13710 form of @value{GDBN} may need to coexist with other forms, hence a
13711 different name for the specialized version's init file). These are the
13712 environments with special init file names:
13714 @cindex @file{.vxgdbinit}
13717 VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit}
13719 @cindex @file{.os68gdbinit}
13721 OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit}
13723 @cindex @file{.esgdbinit}
13725 ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit}
13728 You can also request the execution of a command file with the
13729 @code{source} command:
13733 @item source @var{filename}
13734 Execute the command file @var{filename}.
13737 The lines in a command file are executed sequentially. They are not
13738 printed as they are executed. An error in any command terminates
13739 execution of the command file and control is returned to the console.
13741 Commands that would ask for confirmation if used interactively proceed
13742 without asking when used in a command file. Many @value{GDBN} commands that
13743 normally print messages to say what they are doing omit the messages
13744 when called from command files.
13746 @value{GDBN} also accepts command input from standard input. In this
13747 mode, normal output goes to standard output and error output goes to
13748 standard error. Errors in a command file supplied on standard input do
13749 not terminate execution of the command file --- execution continues with
13753 gdb < cmds > log 2>&1
13756 (The syntax above will vary depending on the shell used.) This example
13757 will execute commands from the file @file{cmds}. All output and errors
13758 would be directed to @file{log}.
13761 @section Commands for controlled output
13763 During the execution of a command file or a user-defined command, normal
13764 @value{GDBN} output is suppressed; the only output that appears is what is
13765 explicitly printed by the commands in the definition. This section
13766 describes three commands useful for generating exactly the output you
13771 @item echo @var{text}
13772 @c I do not consider backslash-space a standard C escape sequence
13773 @c because it is not in ANSI.
13774 Print @var{text}. Nonprinting characters can be included in
13775 @var{text} using C escape sequences, such as @samp{\n} to print a
13776 newline. @strong{No newline is printed unless you specify one.}
13777 In addition to the standard C escape sequences, a backslash followed
13778 by a space stands for a space. This is useful for displaying a
13779 string with spaces at the beginning or the end, since leading and
13780 trailing spaces are otherwise trimmed from all arguments.
13781 To print @samp{@w{ }and foo =@w{ }}, use the command
13782 @samp{echo \@w{ }and foo = \@w{ }}.
13784 A backslash at the end of @var{text} can be used, as in C, to continue
13785 the command onto subsequent lines. For example,
13788 echo This is some text\n\
13789 which is continued\n\
13790 onto several lines.\n
13793 produces the same output as
13796 echo This is some text\n
13797 echo which is continued\n
13798 echo onto several lines.\n
13802 @item output @var{expression}
13803 Print the value of @var{expression} and nothing but that value: no
13804 newlines, no @samp{$@var{nn} = }. The value is not entered in the
13805 value history either. @xref{Expressions, ,Expressions}, for more information
13808 @item output/@var{fmt} @var{expression}
13809 Print the value of @var{expression} in format @var{fmt}. You can use
13810 the same formats as for @code{print}. @xref{Output Formats,,Output
13811 formats}, for more information.
13814 @item printf @var{string}, @var{expressions}@dots{}
13815 Print the values of the @var{expressions} under the control of
13816 @var{string}. The @var{expressions} are separated by commas and may be
13817 either numbers or pointers. Their values are printed as specified by
13818 @var{string}, exactly as if your program were to execute the C
13820 @c FIXME: the above implies that at least all ANSI C formats are
13821 @c supported, but it isn't true: %E and %G don't work (or so it seems).
13822 @c Either this is a bug, or the manual should document what formats are
13826 printf (@var{string}, @var{expressions}@dots{});
13829 For example, you can print two values in hex like this:
13832 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
13835 The only backslash-escape sequences that you can use in the format
13836 string are the simple ones that consist of backslash followed by a
13841 @chapter Command Interpreters
13842 @cindex command interpreters
13844 @value{GDBN} supports multiple command interpreters, and some command
13845 infrastructure to allow users or user interface writers to switch
13846 between interpreters or run commands in other interpreters.
13848 @value{GDBN} currently supports two command interpreters, the console
13849 interpreter (sometimes called the command-line interpreter or @sc{cli})
13850 and the machine interface interpreter (or @sc{gdb/mi}). This manual
13851 describes both of these interfaces in great detail.
13853 By default, @value{GDBN} will start with the console interpreter.
13854 However, the user may choose to start @value{GDBN} with another
13855 interpreter by specifying the @option{-i} or @option{--interpreter}
13856 startup options. Defined interpreters include:
13860 @cindex console interpreter
13861 The traditional console or command-line interpreter. This is the most often
13862 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
13863 @value{GDBN} will use this interpreter.
13866 @cindex mi interpreter
13867 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
13868 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
13869 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
13873 @cindex mi2 interpreter
13874 The current @sc{gdb/mi} interface.
13877 @cindex mi1 interpreter
13878 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
13882 @cindex invoke another interpreter
13883 The interpreter being used by @value{GDBN} may not be dynamically
13884 switched at runtime. Although possible, this could lead to a very
13885 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
13886 enters the command "interpreter-set console" in a console view,
13887 @value{GDBN} would switch to using the console interpreter, rendering
13888 the IDE inoperable!
13890 @kindex interpreter-exec
13891 Although you may only choose a single interpreter at startup, you may execute
13892 commands in any interpreter from the current interpreter using the appropriate
13893 command. If you are running the console interpreter, simply use the
13894 @code{interpreter-exec} command:
13897 interpreter-exec mi "-data-list-register-names"
13900 @sc{gdb/mi} has a similar command, although it is only available in versions of
13901 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
13904 @chapter @value{GDBN} Text User Interface
13906 @cindex Text User Interface
13909 * TUI Overview:: TUI overview
13910 * TUI Keys:: TUI key bindings
13911 * TUI Single Key Mode:: TUI single key mode
13912 * TUI Commands:: TUI specific commands
13913 * TUI Configuration:: TUI configuration variables
13916 The @value{GDBN} Text User Interface, TUI in short, is a terminal
13917 interface which uses the @code{curses} library to show the source
13918 file, the assembly output, the program registers and @value{GDBN}
13919 commands in separate text windows.
13921 The TUI is enabled by invoking @value{GDBN} using either
13923 @samp{gdbtui} or @samp{gdb -tui}.
13926 @section TUI overview
13928 The TUI has two display modes that can be switched while
13933 A curses (or TUI) mode in which it displays several text
13934 windows on the terminal.
13937 A standard mode which corresponds to the @value{GDBN} configured without
13941 In the TUI mode, @value{GDBN} can display several text window
13946 This window is the @value{GDBN} command window with the @value{GDBN}
13947 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
13948 managed using readline but through the TUI. The @emph{command}
13949 window is always visible.
13952 The source window shows the source file of the program. The current
13953 line as well as active breakpoints are displayed in this window.
13956 The assembly window shows the disassembly output of the program.
13959 This window shows the processor registers. It detects when
13960 a register is changed and when this is the case, registers that have
13961 changed are highlighted.
13965 The source and assembly windows show the current program position
13966 by highlighting the current line and marking them with the @samp{>} marker.
13967 Breakpoints are also indicated with two markers. A first one
13968 indicates the breakpoint type:
13972 Breakpoint which was hit at least once.
13975 Breakpoint which was never hit.
13978 Hardware breakpoint which was hit at least once.
13981 Hardware breakpoint which was never hit.
13985 The second marker indicates whether the breakpoint is enabled or not:
13989 Breakpoint is enabled.
13992 Breakpoint is disabled.
13996 The source, assembly and register windows are attached to the thread
13997 and the frame position. They are updated when the current thread
13998 changes, when the frame changes or when the program counter changes.
13999 These three windows are arranged by the TUI according to several
14000 layouts. The layout defines which of these three windows are visible.
14001 The following layouts are available:
14011 source and assembly
14014 source and registers
14017 assembly and registers
14021 On top of the command window a status line gives various information
14022 concerning the current process begin debugged. The status line is
14023 updated when the information it shows changes. The following fields
14028 Indicates the current gdb target
14029 (@pxref{Targets, ,Specifying a Debugging Target}).
14032 Gives information about the current process or thread number.
14033 When no process is being debugged, this field is set to @code{No process}.
14036 Gives the current function name for the selected frame.
14037 The name is demangled if demangling is turned on (@pxref{Print Settings}).
14038 When there is no symbol corresponding to the current program counter
14039 the string @code{??} is displayed.
14042 Indicates the current line number for the selected frame.
14043 When the current line number is not known the string @code{??} is displayed.
14046 Indicates the current program counter address.
14051 @section TUI Key Bindings
14052 @cindex TUI key bindings
14054 The TUI installs several key bindings in the readline keymaps
14055 (@pxref{Command Line Editing}).
14056 They allow to leave or enter in the TUI mode or they operate
14057 directly on the TUI layout and windows. The TUI also provides
14058 a @emph{SingleKey} keymap which binds several keys directly to
14059 @value{GDBN} commands. The following key bindings
14060 are installed for both TUI mode and the @value{GDBN} standard mode.
14069 Enter or leave the TUI mode. When the TUI mode is left,
14070 the curses window management is left and @value{GDBN} operates using
14071 its standard mode writing on the terminal directly. When the TUI
14072 mode is entered, the control is given back to the curses windows.
14073 The screen is then refreshed.
14077 Use a TUI layout with only one window. The layout will
14078 either be @samp{source} or @samp{assembly}. When the TUI mode
14079 is not active, it will switch to the TUI mode.
14081 Think of this key binding as the Emacs @kbd{C-x 1} binding.
14085 Use a TUI layout with at least two windows. When the current
14086 layout shows already two windows, a next layout with two windows is used.
14087 When a new layout is chosen, one window will always be common to the
14088 previous layout and the new one.
14090 Think of it as the Emacs @kbd{C-x 2} binding.
14094 Change the active window. The TUI associates several key bindings
14095 (like scrolling and arrow keys) to the active window. This command
14096 gives the focus to the next TUI window.
14098 Think of it as the Emacs @kbd{C-x o} binding.
14102 Use the TUI @emph{SingleKey} keymap that binds single key to gdb commands
14103 (@pxref{TUI Single Key Mode}).
14107 The following key bindings are handled only by the TUI mode:
14112 Scroll the active window one page up.
14116 Scroll the active window one page down.
14120 Scroll the active window one line up.
14124 Scroll the active window one line down.
14128 Scroll the active window one column left.
14132 Scroll the active window one column right.
14136 Refresh the screen.
14140 In the TUI mode, the arrow keys are used by the active window
14141 for scrolling. This means they are available for readline when the
14142 active window is the command window. When the command window
14143 does not have the focus, it is necessary to use other readline
14144 key bindings such as @key{C-p}, @key{C-n}, @key{C-b} and @key{C-f}.
14146 @node TUI Single Key Mode
14147 @section TUI Single Key Mode
14148 @cindex TUI single key mode
14150 The TUI provides a @emph{SingleKey} mode in which it installs a particular
14151 key binding in the readline keymaps to connect single keys to
14155 @kindex c @r{(SingleKey TUI key)}
14159 @kindex d @r{(SingleKey TUI key)}
14163 @kindex f @r{(SingleKey TUI key)}
14167 @kindex n @r{(SingleKey TUI key)}
14171 @kindex q @r{(SingleKey TUI key)}
14173 exit the @emph{SingleKey} mode.
14175 @kindex r @r{(SingleKey TUI key)}
14179 @kindex s @r{(SingleKey TUI key)}
14183 @kindex u @r{(SingleKey TUI key)}
14187 @kindex v @r{(SingleKey TUI key)}
14191 @kindex w @r{(SingleKey TUI key)}
14197 Other keys temporarily switch to the @value{GDBN} command prompt.
14198 The key that was pressed is inserted in the editing buffer so that
14199 it is possible to type most @value{GDBN} commands without interaction
14200 with the TUI @emph{SingleKey} mode. Once the command is entered the TUI
14201 @emph{SingleKey} mode is restored. The only way to permanently leave
14202 this mode is by hitting @key{q} or @samp{@key{C-x} @key{s}}.
14206 @section TUI specific commands
14207 @cindex TUI commands
14209 The TUI has specific commands to control the text windows.
14210 These commands are always available, that is they do not depend on
14211 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
14212 is in the standard mode, using these commands will automatically switch
14218 List and give the size of all displayed windows.
14222 Display the next layout.
14225 Display the previous layout.
14228 Display the source window only.
14231 Display the assembly window only.
14234 Display the source and assembly window.
14237 Display the register window together with the source or assembly window.
14239 @item focus next | prev | src | asm | regs | split
14241 Set the focus to the named window.
14242 This command allows to change the active window so that scrolling keys
14243 can be affected to another window.
14247 Refresh the screen. This is similar to using @key{C-L} key.
14249 @item tui reg float
14251 Show the floating point registers in the register window.
14253 @item tui reg general
14254 Show the general registers in the register window.
14257 Show the next register group. The list of register groups as well as
14258 their order is target specific. The predefined register groups are the
14259 following: @code{general}, @code{float}, @code{system}, @code{vector},
14260 @code{all}, @code{save}, @code{restore}.
14262 @item tui reg system
14263 Show the system registers in the register window.
14267 Update the source window and the current execution point.
14269 @item winheight @var{name} +@var{count}
14270 @itemx winheight @var{name} -@var{count}
14272 Change the height of the window @var{name} by @var{count}
14273 lines. Positive counts increase the height, while negative counts
14278 @node TUI Configuration
14279 @section TUI configuration variables
14280 @cindex TUI configuration variables
14282 The TUI has several configuration variables that control the
14283 appearance of windows on the terminal.
14286 @item set tui border-kind @var{kind}
14287 @kindex set tui border-kind
14288 Select the border appearance for the source, assembly and register windows.
14289 The possible values are the following:
14292 Use a space character to draw the border.
14295 Use ascii characters + - and | to draw the border.
14298 Use the Alternate Character Set to draw the border. The border is
14299 drawn using character line graphics if the terminal supports them.
14303 @item set tui active-border-mode @var{mode}
14304 @kindex set tui active-border-mode
14305 Select the attributes to display the border of the active window.
14306 The possible values are @code{normal}, @code{standout}, @code{reverse},
14307 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
14309 @item set tui border-mode @var{mode}
14310 @kindex set tui border-mode
14311 Select the attributes to display the border of other windows.
14312 The @var{mode} can be one of the following:
14315 Use normal attributes to display the border.
14321 Use reverse video mode.
14324 Use half bright mode.
14326 @item half-standout
14327 Use half bright and standout mode.
14330 Use extra bright or bold mode.
14332 @item bold-standout
14333 Use extra bright or bold and standout mode.
14340 @chapter Using @value{GDBN} under @sc{gnu} Emacs
14343 @cindex @sc{gnu} Emacs
14344 A special interface allows you to use @sc{gnu} Emacs to view (and
14345 edit) the source files for the program you are debugging with
14348 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
14349 executable file you want to debug as an argument. This command starts
14350 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
14351 created Emacs buffer.
14352 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
14354 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
14359 All ``terminal'' input and output goes through the Emacs buffer.
14362 This applies both to @value{GDBN} commands and their output, and to the input
14363 and output done by the program you are debugging.
14365 This is useful because it means that you can copy the text of previous
14366 commands and input them again; you can even use parts of the output
14369 All the facilities of Emacs' Shell mode are available for interacting
14370 with your program. In particular, you can send signals the usual
14371 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
14376 @value{GDBN} displays source code through Emacs.
14379 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
14380 source file for that frame and puts an arrow (@samp{=>}) at the
14381 left margin of the current line. Emacs uses a separate buffer for
14382 source display, and splits the screen to show both your @value{GDBN} session
14385 Explicit @value{GDBN} @code{list} or search commands still produce output as
14386 usual, but you probably have no reason to use them from Emacs.
14388 If you specify an absolute file name when prompted for the @kbd{M-x
14389 gdb} argument, then Emacs sets your current working directory to where
14390 your program resides. If you only specify the file name, then Emacs
14391 sets your current working directory to to the directory associated
14392 with the previous buffer. In this case, @value{GDBN} may find your
14393 program by searching your environment's @code{PATH} variable, but on
14394 some operating systems it might not find the source. So, although the
14395 @value{GDBN} input and output session proceeds normally, the auxiliary
14396 buffer does not display the current source and line of execution.
14398 The initial working directory of @value{GDBN} is printed on the top
14399 line of the @value{GDBN} I/O buffer and this serves as a default for
14400 the commands that specify files for @value{GDBN} to operate
14401 on. @xref{Files, ,Commands to specify files}.
14403 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
14404 need to call @value{GDBN} by a different name (for example, if you
14405 keep several configurations around, with different names) you can
14406 customize the Emacs variable @code{gud-gdb-command-name} to run the
14409 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
14410 addition to the standard Shell mode commands:
14414 Describe the features of Emacs' @value{GDBN} Mode.
14417 Execute to another source line, like the @value{GDBN} @code{step} command; also
14418 update the display window to show the current file and location.
14421 Execute to next source line in this function, skipping all function
14422 calls, like the @value{GDBN} @code{next} command. Then update the display window
14423 to show the current file and location.
14426 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
14427 display window accordingly.
14430 Execute until exit from the selected stack frame, like the @value{GDBN}
14431 @code{finish} command.
14434 Continue execution of your program, like the @value{GDBN} @code{continue}
14438 Go up the number of frames indicated by the numeric argument
14439 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
14440 like the @value{GDBN} @code{up} command.
14443 Go down the number of frames indicated by the numeric argument, like the
14444 @value{GDBN} @code{down} command.
14447 In any source file, the Emacs command @kbd{C-x SPC} (@code{gud-break})
14448 tells @value{GDBN} to set a breakpoint on the source line point is on.
14450 If you type @kbd{M-x speedbar}, then Emacs displays a separate frame which
14451 shows a backtrace when the @value{GDBN} I/O buffer is current. Move
14452 point to any frame in the stack and type @key{RET} to make it become the
14453 current frame and display the associated source in the source buffer.
14454 Alternatively, click @kbd{Mouse-2} to make the selected frame become the
14457 If you accidentally delete the source-display buffer, an easy way to get
14458 it back is to type the command @code{f} in the @value{GDBN} buffer, to
14459 request a frame display; when you run under Emacs, this recreates
14460 the source buffer if necessary to show you the context of the current
14463 The source files displayed in Emacs are in ordinary Emacs buffers
14464 which are visiting the source files in the usual way. You can edit
14465 the files with these buffers if you wish; but keep in mind that @value{GDBN}
14466 communicates with Emacs in terms of line numbers. If you add or
14467 delete lines from the text, the line numbers that @value{GDBN} knows cease
14468 to correspond properly with the code.
14470 The description given here is for GNU Emacs version 21.3 and a more
14471 detailed description of its interaction with @value{GDBN} is given in
14472 the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu} Emacs Manual}).
14474 @c The following dropped because Epoch is nonstandard. Reactivate
14475 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
14477 @kindex Emacs Epoch environment
14481 Version 18 of @sc{gnu} Emacs has a built-in window system
14482 called the @code{epoch}
14483 environment. Users of this environment can use a new command,
14484 @code{inspect} which performs identically to @code{print} except that
14485 each value is printed in its own window.
14490 @chapter The @sc{gdb/mi} Interface
14492 @unnumberedsec Function and Purpose
14494 @cindex @sc{gdb/mi}, its purpose
14495 @sc{gdb/mi} is a line based machine oriented text interface to @value{GDBN}. It is
14496 specifically intended to support the development of systems which use
14497 the debugger as just one small component of a larger system.
14499 This chapter is a specification of the @sc{gdb/mi} interface. It is written
14500 in the form of a reference manual.
14502 Note that @sc{gdb/mi} is still under construction, so some of the
14503 features described below are incomplete and subject to change.
14505 @unnumberedsec Notation and Terminology
14507 @cindex notational conventions, for @sc{gdb/mi}
14508 This chapter uses the following notation:
14512 @code{|} separates two alternatives.
14515 @code{[ @var{something} ]} indicates that @var{something} is optional:
14516 it may or may not be given.
14519 @code{( @var{group} )*} means that @var{group} inside the parentheses
14520 may repeat zero or more times.
14523 @code{( @var{group} )+} means that @var{group} inside the parentheses
14524 may repeat one or more times.
14527 @code{"@var{string}"} means a literal @var{string}.
14531 @heading Dependencies
14534 @heading Acknowledgments
14536 In alphabetic order: Andrew Cagney, Fernando Nasser, Stan Shebs and
14540 * GDB/MI Command Syntax::
14541 * GDB/MI Compatibility with CLI::
14542 * GDB/MI Output Records::
14543 * GDB/MI Command Description Format::
14544 * GDB/MI Breakpoint Table Commands::
14545 * GDB/MI Data Manipulation::
14546 * GDB/MI Program Control::
14547 * GDB/MI Miscellaneous Commands::
14549 * GDB/MI Kod Commands::
14550 * GDB/MI Memory Overlay Commands::
14551 * GDB/MI Signal Handling Commands::
14553 * GDB/MI Stack Manipulation::
14554 * GDB/MI Symbol Query::
14555 * GDB/MI Target Manipulation::
14556 * GDB/MI Thread Commands::
14557 * GDB/MI Tracepoint Commands::
14558 * GDB/MI Variable Objects::
14561 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14562 @node GDB/MI Command Syntax
14563 @section @sc{gdb/mi} Command Syntax
14566 * GDB/MI Input Syntax::
14567 * GDB/MI Output Syntax::
14568 * GDB/MI Simple Examples::
14571 @node GDB/MI Input Syntax
14572 @subsection @sc{gdb/mi} Input Syntax
14574 @cindex input syntax for @sc{gdb/mi}
14575 @cindex @sc{gdb/mi}, input syntax
14577 @item @var{command} @expansion{}
14578 @code{@var{cli-command} | @var{mi-command}}
14580 @item @var{cli-command} @expansion{}
14581 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
14582 @var{cli-command} is any existing @value{GDBN} CLI command.
14584 @item @var{mi-command} @expansion{}
14585 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
14586 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
14588 @item @var{token} @expansion{}
14589 "any sequence of digits"
14591 @item @var{option} @expansion{}
14592 @code{"-" @var{parameter} [ " " @var{parameter} ]}
14594 @item @var{parameter} @expansion{}
14595 @code{@var{non-blank-sequence} | @var{c-string}}
14597 @item @var{operation} @expansion{}
14598 @emph{any of the operations described in this chapter}
14600 @item @var{non-blank-sequence} @expansion{}
14601 @emph{anything, provided it doesn't contain special characters such as
14602 "-", @var{nl}, """ and of course " "}
14604 @item @var{c-string} @expansion{}
14605 @code{""" @var{seven-bit-iso-c-string-content} """}
14607 @item @var{nl} @expansion{}
14616 The CLI commands are still handled by the @sc{mi} interpreter; their
14617 output is described below.
14620 The @code{@var{token}}, when present, is passed back when the command
14624 Some @sc{mi} commands accept optional arguments as part of the parameter
14625 list. Each option is identified by a leading @samp{-} (dash) and may be
14626 followed by an optional argument parameter. Options occur first in the
14627 parameter list and can be delimited from normal parameters using
14628 @samp{--} (this is useful when some parameters begin with a dash).
14635 We want easy access to the existing CLI syntax (for debugging).
14638 We want it to be easy to spot a @sc{mi} operation.
14641 @node GDB/MI Output Syntax
14642 @subsection @sc{gdb/mi} Output Syntax
14644 @cindex output syntax of @sc{gdb/mi}
14645 @cindex @sc{gdb/mi}, output syntax
14646 The output from @sc{gdb/mi} consists of zero or more out-of-band records
14647 followed, optionally, by a single result record. This result record
14648 is for the most recent command. The sequence of output records is
14649 terminated by @samp{(@value{GDBP})}.
14651 If an input command was prefixed with a @code{@var{token}} then the
14652 corresponding output for that command will also be prefixed by that same
14656 @item @var{output} @expansion{}
14657 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
14659 @item @var{result-record} @expansion{}
14660 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
14662 @item @var{out-of-band-record} @expansion{}
14663 @code{@var{async-record} | @var{stream-record}}
14665 @item @var{async-record} @expansion{}
14666 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
14668 @item @var{exec-async-output} @expansion{}
14669 @code{[ @var{token} ] "*" @var{async-output}}
14671 @item @var{status-async-output} @expansion{}
14672 @code{[ @var{token} ] "+" @var{async-output}}
14674 @item @var{notify-async-output} @expansion{}
14675 @code{[ @var{token} ] "=" @var{async-output}}
14677 @item @var{async-output} @expansion{}
14678 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
14680 @item @var{result-class} @expansion{}
14681 @code{"done" | "running" | "connected" | "error" | "exit"}
14683 @item @var{async-class} @expansion{}
14684 @code{"stopped" | @var{others}} (where @var{others} will be added
14685 depending on the needs---this is still in development).
14687 @item @var{result} @expansion{}
14688 @code{ @var{variable} "=" @var{value}}
14690 @item @var{variable} @expansion{}
14691 @code{ @var{string} }
14693 @item @var{value} @expansion{}
14694 @code{ @var{const} | @var{tuple} | @var{list} }
14696 @item @var{const} @expansion{}
14697 @code{@var{c-string}}
14699 @item @var{tuple} @expansion{}
14700 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
14702 @item @var{list} @expansion{}
14703 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
14704 @var{result} ( "," @var{result} )* "]" }
14706 @item @var{stream-record} @expansion{}
14707 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
14709 @item @var{console-stream-output} @expansion{}
14710 @code{"~" @var{c-string}}
14712 @item @var{target-stream-output} @expansion{}
14713 @code{"@@" @var{c-string}}
14715 @item @var{log-stream-output} @expansion{}
14716 @code{"&" @var{c-string}}
14718 @item @var{nl} @expansion{}
14721 @item @var{token} @expansion{}
14722 @emph{any sequence of digits}.
14730 All output sequences end in a single line containing a period.
14733 The @code{@var{token}} is from the corresponding request. If an execution
14734 command is interrupted by the @samp{-exec-interrupt} command, the
14735 @var{token} associated with the @samp{*stopped} message is the one of the
14736 original execution command, not the one of the interrupt command.
14739 @cindex status output in @sc{gdb/mi}
14740 @var{status-async-output} contains on-going status information about the
14741 progress of a slow operation. It can be discarded. All status output is
14742 prefixed by @samp{+}.
14745 @cindex async output in @sc{gdb/mi}
14746 @var{exec-async-output} contains asynchronous state change on the target
14747 (stopped, started, disappeared). All async output is prefixed by
14751 @cindex notify output in @sc{gdb/mi}
14752 @var{notify-async-output} contains supplementary information that the
14753 client should handle (e.g., a new breakpoint information). All notify
14754 output is prefixed by @samp{=}.
14757 @cindex console output in @sc{gdb/mi}
14758 @var{console-stream-output} is output that should be displayed as is in the
14759 console. It is the textual response to a CLI command. All the console
14760 output is prefixed by @samp{~}.
14763 @cindex target output in @sc{gdb/mi}
14764 @var{target-stream-output} is the output produced by the target program.
14765 All the target output is prefixed by @samp{@@}.
14768 @cindex log output in @sc{gdb/mi}
14769 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
14770 instance messages that should be displayed as part of an error log. All
14771 the log output is prefixed by @samp{&}.
14774 @cindex list output in @sc{gdb/mi}
14775 New @sc{gdb/mi} commands should only output @var{lists} containing
14781 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
14782 details about the various output records.
14784 @node GDB/MI Simple Examples
14785 @subsection Simple Examples of @sc{gdb/mi} Interaction
14786 @cindex @sc{gdb/mi}, simple examples
14788 This subsection presents several simple examples of interaction using
14789 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
14790 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
14791 the output received from @sc{gdb/mi}.
14793 @subsubheading Target Stop
14794 @c Ummm... There is no "-stop" command. This assumes async, no?
14795 Here's an example of stopping the inferior process:
14806 <- *stop,reason="stop",address="0x123",source="a.c:123"
14810 @subsubheading Simple CLI Command
14812 Here's an example of a simple CLI command being passed through
14813 @sc{gdb/mi} and on to the CLI.
14823 @subsubheading Command With Side Effects
14826 -> -symbol-file xyz.exe
14827 <- *breakpoint,nr="3",address="0x123",source="a.c:123"
14831 @subsubheading A Bad Command
14833 Here's what happens if you pass a non-existent command:
14837 <- ^error,msg="Undefined MI command: rubbish"
14841 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14842 @node GDB/MI Compatibility with CLI
14843 @section @sc{gdb/mi} Compatibility with CLI
14845 @cindex compatibility, @sc{gdb/mi} and CLI
14846 @cindex @sc{gdb/mi}, compatibility with CLI
14847 To help users familiar with @value{GDBN}'s existing CLI interface, @sc{gdb/mi}
14848 accepts existing CLI commands. As specified by the syntax, such
14849 commands can be directly entered into the @sc{gdb/mi} interface and @value{GDBN} will
14852 This mechanism is provided as an aid to developers of @sc{gdb/mi}
14853 clients and not as a reliable interface into the CLI. Since the command
14854 is being interpreteted in an environment that assumes @sc{gdb/mi}
14855 behaviour, the exact output of such commands is likely to end up being
14856 an un-supported hybrid of @sc{gdb/mi} and CLI output.
14858 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14859 @node GDB/MI Output Records
14860 @section @sc{gdb/mi} Output Records
14863 * GDB/MI Result Records::
14864 * GDB/MI Stream Records::
14865 * GDB/MI Out-of-band Records::
14868 @node GDB/MI Result Records
14869 @subsection @sc{gdb/mi} Result Records
14871 @cindex result records in @sc{gdb/mi}
14872 @cindex @sc{gdb/mi}, result records
14873 In addition to a number of out-of-band notifications, the response to a
14874 @sc{gdb/mi} command includes one of the following result indications:
14878 @item "^done" [ "," @var{results} ]
14879 The synchronous operation was successful, @code{@var{results}} are the return
14884 @c Is this one correct? Should it be an out-of-band notification?
14885 The asynchronous operation was successfully started. The target is
14888 @item "^error" "," @var{c-string}
14890 The operation failed. The @code{@var{c-string}} contains the corresponding
14894 @node GDB/MI Stream Records
14895 @subsection @sc{gdb/mi} Stream Records
14897 @cindex @sc{gdb/mi}, stream records
14898 @cindex stream records in @sc{gdb/mi}
14899 @value{GDBN} internally maintains a number of output streams: the console, the
14900 target, and the log. The output intended for each of these streams is
14901 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
14903 Each stream record begins with a unique @dfn{prefix character} which
14904 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
14905 Syntax}). In addition to the prefix, each stream record contains a
14906 @code{@var{string-output}}. This is either raw text (with an implicit new
14907 line) or a quoted C string (which does not contain an implicit newline).
14910 @item "~" @var{string-output}
14911 The console output stream contains text that should be displayed in the
14912 CLI console window. It contains the textual responses to CLI commands.
14914 @item "@@" @var{string-output}
14915 The target output stream contains any textual output from the running
14918 @item "&" @var{string-output}
14919 The log stream contains debugging messages being produced by @value{GDBN}'s
14923 @node GDB/MI Out-of-band Records
14924 @subsection @sc{gdb/mi} Out-of-band Records
14926 @cindex out-of-band records in @sc{gdb/mi}
14927 @cindex @sc{gdb/mi}, out-of-band records
14928 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
14929 additional changes that have occurred. Those changes can either be a
14930 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
14931 target activity (e.g., target stopped).
14933 The following is a preliminary list of possible out-of-band records.
14940 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14941 @node GDB/MI Command Description Format
14942 @section @sc{gdb/mi} Command Description Format
14944 The remaining sections describe blocks of commands. Each block of
14945 commands is laid out in a fashion similar to this section.
14947 Note the the line breaks shown in the examples are here only for
14948 readability. They don't appear in the real output.
14949 Also note that the commands with a non-available example (N.A.@:) are
14950 not yet implemented.
14952 @subheading Motivation
14954 The motivation for this collection of commands.
14956 @subheading Introduction
14958 A brief introduction to this collection of commands as a whole.
14960 @subheading Commands
14962 For each command in the block, the following is described:
14964 @subsubheading Synopsis
14967 -command @var{args}@dots{}
14970 @subsubheading @value{GDBN} Command
14972 The corresponding @value{GDBN} CLI command.
14974 @subsubheading Result
14976 @subsubheading Out-of-band
14978 @subsubheading Notes
14980 @subsubheading Example
14983 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14984 @node GDB/MI Breakpoint Table Commands
14985 @section @sc{gdb/mi} Breakpoint table commands
14987 @cindex breakpoint commands for @sc{gdb/mi}
14988 @cindex @sc{gdb/mi}, breakpoint commands
14989 This section documents @sc{gdb/mi} commands for manipulating
14992 @subheading The @code{-break-after} Command
14993 @findex -break-after
14995 @subsubheading Synopsis
14998 -break-after @var{number} @var{count}
15001 The breakpoint number @var{number} is not in effect until it has been
15002 hit @var{count} times. To see how this is reflected in the output of
15003 the @samp{-break-list} command, see the description of the
15004 @samp{-break-list} command below.
15006 @subsubheading @value{GDBN} Command
15008 The corresponding @value{GDBN} command is @samp{ignore}.
15010 @subsubheading Example
15015 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",line="5"@}
15022 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15023 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15024 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15025 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15026 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15027 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15028 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15029 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15030 addr="0x000100d0",func="main",file="hello.c",line="5",times="0",
15036 @subheading The @code{-break-catch} Command
15037 @findex -break-catch
15039 @subheading The @code{-break-commands} Command
15040 @findex -break-commands
15044 @subheading The @code{-break-condition} Command
15045 @findex -break-condition
15047 @subsubheading Synopsis
15050 -break-condition @var{number} @var{expr}
15053 Breakpoint @var{number} will stop the program only if the condition in
15054 @var{expr} is true. The condition becomes part of the
15055 @samp{-break-list} output (see the description of the @samp{-break-list}
15058 @subsubheading @value{GDBN} Command
15060 The corresponding @value{GDBN} command is @samp{condition}.
15062 @subsubheading Example
15066 -break-condition 1 1
15070 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15071 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15072 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15073 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15074 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15075 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15076 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15077 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15078 addr="0x000100d0",func="main",file="hello.c",line="5",cond="1",
15079 times="0",ignore="3"@}]@}
15083 @subheading The @code{-break-delete} Command
15084 @findex -break-delete
15086 @subsubheading Synopsis
15089 -break-delete ( @var{breakpoint} )+
15092 Delete the breakpoint(s) whose number(s) are specified in the argument
15093 list. This is obviously reflected in the breakpoint list.
15095 @subsubheading @value{GDBN} command
15097 The corresponding @value{GDBN} command is @samp{delete}.
15099 @subsubheading Example
15107 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
15108 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15109 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15110 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15111 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15112 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15113 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15118 @subheading The @code{-break-disable} Command
15119 @findex -break-disable
15121 @subsubheading Synopsis
15124 -break-disable ( @var{breakpoint} )+
15127 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
15128 break list is now set to @samp{n} for the named @var{breakpoint}(s).
15130 @subsubheading @value{GDBN} Command
15132 The corresponding @value{GDBN} command is @samp{disable}.
15134 @subsubheading Example
15142 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15143 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15144 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15145 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15146 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15147 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15148 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15149 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
15150 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
15154 @subheading The @code{-break-enable} Command
15155 @findex -break-enable
15157 @subsubheading Synopsis
15160 -break-enable ( @var{breakpoint} )+
15163 Enable (previously disabled) @var{breakpoint}(s).
15165 @subsubheading @value{GDBN} Command
15167 The corresponding @value{GDBN} command is @samp{enable}.
15169 @subsubheading Example
15177 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15178 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15179 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15180 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15181 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15182 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15183 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15184 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
15185 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
15189 @subheading The @code{-break-info} Command
15190 @findex -break-info
15192 @subsubheading Synopsis
15195 -break-info @var{breakpoint}
15199 Get information about a single breakpoint.
15201 @subsubheading @value{GDBN} command
15203 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
15205 @subsubheading Example
15208 @subheading The @code{-break-insert} Command
15209 @findex -break-insert
15211 @subsubheading Synopsis
15214 -break-insert [ -t ] [ -h ] [ -r ]
15215 [ -c @var{condition} ] [ -i @var{ignore-count} ]
15216 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
15220 If specified, @var{line}, can be one of:
15227 @item filename:linenum
15228 @item filename:function
15232 The possible optional parameters of this command are:
15236 Insert a tempoary breakpoint.
15238 Insert a hardware breakpoint.
15239 @item -c @var{condition}
15240 Make the breakpoint conditional on @var{condition}.
15241 @item -i @var{ignore-count}
15242 Initialize the @var{ignore-count}.
15244 Insert a regular breakpoint in all the functions whose names match the
15245 given regular expression. Other flags are not applicable to regular
15249 @subsubheading Result
15251 The result is in the form:
15254 ^done,bkptno="@var{number}",func="@var{funcname}",
15255 file="@var{filename}",line="@var{lineno}"
15259 where @var{number} is the @value{GDBN} number for this breakpoint, @var{funcname}
15260 is the name of the function where the breakpoint was inserted,
15261 @var{filename} is the name of the source file which contains this
15262 function, and @var{lineno} is the source line number within that file.
15264 Note: this format is open to change.
15265 @c An out-of-band breakpoint instead of part of the result?
15267 @subsubheading @value{GDBN} Command
15269 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
15270 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
15272 @subsubheading Example
15277 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
15279 -break-insert -t foo
15280 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",line="11"@}
15283 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15284 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15285 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15286 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15287 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15288 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15289 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15290 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15291 addr="0x0001072c", func="main",file="recursive2.c",line="4",times="0"@},
15292 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
15293 addr="0x00010774",func="foo",file="recursive2.c",line="11",times="0"@}]@}
15295 -break-insert -r foo.*
15296 ~int foo(int, int);
15297 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c",line="11"@}
15301 @subheading The @code{-break-list} Command
15302 @findex -break-list
15304 @subsubheading Synopsis
15310 Displays the list of inserted breakpoints, showing the following fields:
15314 number of the breakpoint
15316 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
15318 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
15321 is the breakpoint enabled or no: @samp{y} or @samp{n}
15323 memory location at which the breakpoint is set
15325 logical location of the breakpoint, expressed by function name, file
15328 number of times the breakpoint has been hit
15331 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
15332 @code{body} field is an empty list.
15334 @subsubheading @value{GDBN} Command
15336 The corresponding @value{GDBN} command is @samp{info break}.
15338 @subsubheading Example
15343 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15344 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15345 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15346 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15347 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15348 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15349 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15350 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15351 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
15352 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
15353 addr="0x00010114",func="foo",file="hello.c",line="13",times="0"@}]@}
15357 Here's an example of the result when there are no breakpoints:
15362 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
15363 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15364 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15365 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15366 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15367 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15368 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15373 @subheading The @code{-break-watch} Command
15374 @findex -break-watch
15376 @subsubheading Synopsis
15379 -break-watch [ -a | -r ]
15382 Create a watchpoint. With the @samp{-a} option it will create an
15383 @dfn{access} watchpoint, i.e. a watchpoint that triggers either on a
15384 read from or on a write to the memory location. With the @samp{-r}
15385 option, the watchpoint created is a @dfn{read} watchpoint, i.e. it will
15386 trigger only when the memory location is accessed for reading. Without
15387 either of the options, the watchpoint created is a regular watchpoint,
15388 i.e. it will trigger when the memory location is accessed for writing.
15389 @xref{Set Watchpoints, , Setting watchpoints}.
15391 Note that @samp{-break-list} will report a single list of watchpoints and
15392 breakpoints inserted.
15394 @subsubheading @value{GDBN} Command
15396 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
15399 @subsubheading Example
15401 Setting a watchpoint on a variable in the @code{main} function:
15406 ^done,wpt=@{number="2",exp="x"@}
15410 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
15411 value=@{old="-268439212",new="55"@},
15412 frame=@{func="main",args=[],file="recursive2.c",line="5"@}
15416 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
15417 the program execution twice: first for the variable changing value, then
15418 for the watchpoint going out of scope.
15423 ^done,wpt=@{number="5",exp="C"@}
15427 ^done,reason="watchpoint-trigger",
15428 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
15429 frame=@{func="callee4",args=[],
15430 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
15434 ^done,reason="watchpoint-scope",wpnum="5",
15435 frame=@{func="callee3",args=[@{name="strarg",
15436 value="0x11940 \"A string argument.\""@}],
15437 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
15441 Listing breakpoints and watchpoints, at different points in the program
15442 execution. Note that once the watchpoint goes out of scope, it is
15448 ^done,wpt=@{number="2",exp="C"@}
15451 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15452 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15453 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15454 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15455 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15456 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15457 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15458 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15459 addr="0x00010734",func="callee4",
15460 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
15461 bkpt=@{number="2",type="watchpoint",disp="keep",
15462 enabled="y",addr="",what="C",times="0"@}]@}
15466 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
15467 value=@{old="-276895068",new="3"@},
15468 frame=@{func="callee4",args=[],
15469 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
15472 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15473 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15474 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15475 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15476 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15477 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15478 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15479 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15480 addr="0x00010734",func="callee4",
15481 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
15482 bkpt=@{number="2",type="watchpoint",disp="keep",
15483 enabled="y",addr="",what="C",times="-5"@}]@}
15487 ^done,reason="watchpoint-scope",wpnum="2",
15488 frame=@{func="callee3",args=[@{name="strarg",
15489 value="0x11940 \"A string argument.\""@}],
15490 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
15493 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15494 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15495 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15496 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15497 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15498 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15499 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15500 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15501 addr="0x00010734",func="callee4",
15502 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@}]@}
15506 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15507 @node GDB/MI Data Manipulation
15508 @section @sc{gdb/mi} Data Manipulation
15510 @cindex data manipulation, in @sc{gdb/mi}
15511 @cindex @sc{gdb/mi}, data manipulation
15512 This section describes the @sc{gdb/mi} commands that manipulate data:
15513 examine memory and registers, evaluate expressions, etc.
15515 @c REMOVED FROM THE INTERFACE.
15516 @c @subheading -data-assign
15517 @c Change the value of a program variable. Plenty of side effects.
15518 @c @subsubheading GDB command
15520 @c @subsubheading Example
15523 @subheading The @code{-data-disassemble} Command
15524 @findex -data-disassemble
15526 @subsubheading Synopsis
15530 [ -s @var{start-addr} -e @var{end-addr} ]
15531 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
15539 @item @var{start-addr}
15540 is the beginning address (or @code{$pc})
15541 @item @var{end-addr}
15543 @item @var{filename}
15544 is the name of the file to disassemble
15545 @item @var{linenum}
15546 is the line number to disassemble around
15548 is the the number of disassembly lines to be produced. If it is -1,
15549 the whole function will be disassembled, in case no @var{end-addr} is
15550 specified. If @var{end-addr} is specified as a non-zero value, and
15551 @var{lines} is lower than the number of disassembly lines between
15552 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
15553 displayed; if @var{lines} is higher than the number of lines between
15554 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
15557 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
15561 @subsubheading Result
15563 The output for each instruction is composed of four fields:
15572 Note that whatever included in the instruction field, is not manipulated
15573 directely by @sc{gdb/mi}, i.e. it is not possible to adjust its format.
15575 @subsubheading @value{GDBN} Command
15577 There's no direct mapping from this command to the CLI.
15579 @subsubheading Example
15581 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
15585 -data-disassemble -s $pc -e "$pc + 20" -- 0
15588 @{address="0x000107c0",func-name="main",offset="4",
15589 inst="mov 2, %o0"@},
15590 @{address="0x000107c4",func-name="main",offset="8",
15591 inst="sethi %hi(0x11800), %o2"@},
15592 @{address="0x000107c8",func-name="main",offset="12",
15593 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
15594 @{address="0x000107cc",func-name="main",offset="16",
15595 inst="sethi %hi(0x11800), %o2"@},
15596 @{address="0x000107d0",func-name="main",offset="20",
15597 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
15601 Disassemble the whole @code{main} function. Line 32 is part of
15605 -data-disassemble -f basics.c -l 32 -- 0
15607 @{address="0x000107bc",func-name="main",offset="0",
15608 inst="save %sp, -112, %sp"@},
15609 @{address="0x000107c0",func-name="main",offset="4",
15610 inst="mov 2, %o0"@},
15611 @{address="0x000107c4",func-name="main",offset="8",
15612 inst="sethi %hi(0x11800), %o2"@},
15614 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
15615 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
15619 Disassemble 3 instructions from the start of @code{main}:
15623 -data-disassemble -f basics.c -l 32 -n 3 -- 0
15625 @{address="0x000107bc",func-name="main",offset="0",
15626 inst="save %sp, -112, %sp"@},
15627 @{address="0x000107c0",func-name="main",offset="4",
15628 inst="mov 2, %o0"@},
15629 @{address="0x000107c4",func-name="main",offset="8",
15630 inst="sethi %hi(0x11800), %o2"@}]
15634 Disassemble 3 instructions from the start of @code{main} in mixed mode:
15638 -data-disassemble -f basics.c -l 32 -n 3 -- 1
15640 src_and_asm_line=@{line="31",
15641 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
15642 testsuite/gdb.mi/basics.c",line_asm_insn=[
15643 @{address="0x000107bc",func-name="main",offset="0",
15644 inst="save %sp, -112, %sp"@}]@},
15645 src_and_asm_line=@{line="32",
15646 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
15647 testsuite/gdb.mi/basics.c",line_asm_insn=[
15648 @{address="0x000107c0",func-name="main",offset="4",
15649 inst="mov 2, %o0"@},
15650 @{address="0x000107c4",func-name="main",offset="8",
15651 inst="sethi %hi(0x11800), %o2"@}]@}]
15656 @subheading The @code{-data-evaluate-expression} Command
15657 @findex -data-evaluate-expression
15659 @subsubheading Synopsis
15662 -data-evaluate-expression @var{expr}
15665 Evaluate @var{expr} as an expression. The expression could contain an
15666 inferior function call. The function call will execute synchronously.
15667 If the expression contains spaces, it must be enclosed in double quotes.
15669 @subsubheading @value{GDBN} Command
15671 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
15672 @samp{call}. In @code{gdbtk} only, there's a corresponding
15673 @samp{gdb_eval} command.
15675 @subsubheading Example
15677 In the following example, the numbers that precede the commands are the
15678 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
15679 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
15683 211-data-evaluate-expression A
15686 311-data-evaluate-expression &A
15687 311^done,value="0xefffeb7c"
15689 411-data-evaluate-expression A+3
15692 511-data-evaluate-expression "A + 3"
15698 @subheading The @code{-data-list-changed-registers} Command
15699 @findex -data-list-changed-registers
15701 @subsubheading Synopsis
15704 -data-list-changed-registers
15707 Display a list of the registers that have changed.
15709 @subsubheading @value{GDBN} Command
15711 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
15712 has the corresponding command @samp{gdb_changed_register_list}.
15714 @subsubheading Example
15716 On a PPC MBX board:
15724 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
15725 args=[],file="try.c",line="5"@}
15727 -data-list-changed-registers
15728 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
15729 "10","11","13","14","15","16","17","18","19","20","21","22","23",
15730 "24","25","26","27","28","30","31","64","65","66","67","69"]
15735 @subheading The @code{-data-list-register-names} Command
15736 @findex -data-list-register-names
15738 @subsubheading Synopsis
15741 -data-list-register-names [ ( @var{regno} )+ ]
15744 Show a list of register names for the current target. If no arguments
15745 are given, it shows a list of the names of all the registers. If
15746 integer numbers are given as arguments, it will print a list of the
15747 names of the registers corresponding to the arguments. To ensure
15748 consistency between a register name and its number, the output list may
15749 include empty register names.
15751 @subsubheading @value{GDBN} Command
15753 @value{GDBN} does not have a command which corresponds to
15754 @samp{-data-list-register-names}. In @code{gdbtk} there is a
15755 corresponding command @samp{gdb_regnames}.
15757 @subsubheading Example
15759 For the PPC MBX board:
15762 -data-list-register-names
15763 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
15764 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
15765 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
15766 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
15767 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
15768 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
15769 "", "pc","ps","cr","lr","ctr","xer"]
15771 -data-list-register-names 1 2 3
15772 ^done,register-names=["r1","r2","r3"]
15776 @subheading The @code{-data-list-register-values} Command
15777 @findex -data-list-register-values
15779 @subsubheading Synopsis
15782 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
15785 Display the registers' contents. @var{fmt} is the format according to
15786 which the registers' contents are to be returned, followed by an optional
15787 list of numbers specifying the registers to display. A missing list of
15788 numbers indicates that the contents of all the registers must be returned.
15790 Allowed formats for @var{fmt} are:
15807 @subsubheading @value{GDBN} Command
15809 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
15810 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
15812 @subsubheading Example
15814 For a PPC MBX board (note: line breaks are for readability only, they
15815 don't appear in the actual output):
15819 -data-list-register-values r 64 65
15820 ^done,register-values=[@{number="64",value="0xfe00a300"@},
15821 @{number="65",value="0x00029002"@}]
15823 -data-list-register-values x
15824 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
15825 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
15826 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
15827 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
15828 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
15829 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
15830 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
15831 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
15832 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
15833 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
15834 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
15835 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
15836 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
15837 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
15838 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
15839 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
15840 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
15841 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
15842 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
15843 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
15844 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
15845 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
15846 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
15847 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
15848 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
15849 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
15850 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
15851 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
15852 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
15853 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
15854 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
15855 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
15856 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
15857 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
15858 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
15859 @{number="69",value="0x20002b03"@}]
15864 @subheading The @code{-data-read-memory} Command
15865 @findex -data-read-memory
15867 @subsubheading Synopsis
15870 -data-read-memory [ -o @var{byte-offset} ]
15871 @var{address} @var{word-format} @var{word-size}
15872 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
15879 @item @var{address}
15880 An expression specifying the address of the first memory word to be
15881 read. Complex expressions containing embedded white space should be
15882 quoted using the C convention.
15884 @item @var{word-format}
15885 The format to be used to print the memory words. The notation is the
15886 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
15889 @item @var{word-size}
15890 The size of each memory word in bytes.
15892 @item @var{nr-rows}
15893 The number of rows in the output table.
15895 @item @var{nr-cols}
15896 The number of columns in the output table.
15899 If present, indicates that each row should include an @sc{ascii} dump. The
15900 value of @var{aschar} is used as a padding character when a byte is not a
15901 member of the printable @sc{ascii} character set (printable @sc{ascii}
15902 characters are those whose code is between 32 and 126, inclusively).
15904 @item @var{byte-offset}
15905 An offset to add to the @var{address} before fetching memory.
15908 This command displays memory contents as a table of @var{nr-rows} by
15909 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
15910 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
15911 (returned as @samp{total-bytes}). Should less than the requested number
15912 of bytes be returned by the target, the missing words are identified
15913 using @samp{N/A}. The number of bytes read from the target is returned
15914 in @samp{nr-bytes} and the starting address used to read memory in
15917 The address of the next/previous row or page is available in
15918 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
15921 @subsubheading @value{GDBN} Command
15923 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
15924 @samp{gdb_get_mem} memory read command.
15926 @subsubheading Example
15928 Read six bytes of memory starting at @code{bytes+6} but then offset by
15929 @code{-6} bytes. Format as three rows of two columns. One byte per
15930 word. Display each word in hex.
15934 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
15935 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
15936 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
15937 prev-page="0x0000138a",memory=[
15938 @{addr="0x00001390",data=["0x00","0x01"]@},
15939 @{addr="0x00001392",data=["0x02","0x03"]@},
15940 @{addr="0x00001394",data=["0x04","0x05"]@}]
15944 Read two bytes of memory starting at address @code{shorts + 64} and
15945 display as a single word formatted in decimal.
15949 5-data-read-memory shorts+64 d 2 1 1
15950 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
15951 next-row="0x00001512",prev-row="0x0000150e",
15952 next-page="0x00001512",prev-page="0x0000150e",memory=[
15953 @{addr="0x00001510",data=["128"]@}]
15957 Read thirty two bytes of memory starting at @code{bytes+16} and format
15958 as eight rows of four columns. Include a string encoding with @samp{x}
15959 used as the non-printable character.
15963 4-data-read-memory bytes+16 x 1 8 4 x
15964 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
15965 next-row="0x000013c0",prev-row="0x0000139c",
15966 next-page="0x000013c0",prev-page="0x00001380",memory=[
15967 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
15968 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
15969 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
15970 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
15971 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
15972 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
15973 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
15974 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
15978 @subheading The @code{-display-delete} Command
15979 @findex -display-delete
15981 @subsubheading Synopsis
15984 -display-delete @var{number}
15987 Delete the display @var{number}.
15989 @subsubheading @value{GDBN} Command
15991 The corresponding @value{GDBN} command is @samp{delete display}.
15993 @subsubheading Example
15997 @subheading The @code{-display-disable} Command
15998 @findex -display-disable
16000 @subsubheading Synopsis
16003 -display-disable @var{number}
16006 Disable display @var{number}.
16008 @subsubheading @value{GDBN} Command
16010 The corresponding @value{GDBN} command is @samp{disable display}.
16012 @subsubheading Example
16016 @subheading The @code{-display-enable} Command
16017 @findex -display-enable
16019 @subsubheading Synopsis
16022 -display-enable @var{number}
16025 Enable display @var{number}.
16027 @subsubheading @value{GDBN} Command
16029 The corresponding @value{GDBN} command is @samp{enable display}.
16031 @subsubheading Example
16035 @subheading The @code{-display-insert} Command
16036 @findex -display-insert
16038 @subsubheading Synopsis
16041 -display-insert @var{expression}
16044 Display @var{expression} every time the program stops.
16046 @subsubheading @value{GDBN} Command
16048 The corresponding @value{GDBN} command is @samp{display}.
16050 @subsubheading Example
16054 @subheading The @code{-display-list} Command
16055 @findex -display-list
16057 @subsubheading Synopsis
16063 List the displays. Do not show the current values.
16065 @subsubheading @value{GDBN} Command
16067 The corresponding @value{GDBN} command is @samp{info display}.
16069 @subsubheading Example
16073 @subheading The @code{-environment-cd} Command
16074 @findex -environment-cd
16076 @subsubheading Synopsis
16079 -environment-cd @var{pathdir}
16082 Set @value{GDBN}'s working directory.
16084 @subsubheading @value{GDBN} Command
16086 The corresponding @value{GDBN} command is @samp{cd}.
16088 @subsubheading Example
16092 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
16098 @subheading The @code{-environment-directory} Command
16099 @findex -environment-directory
16101 @subsubheading Synopsis
16104 -environment-directory [ -r ] [ @var{pathdir} ]+
16107 Add directories @var{pathdir} to beginning of search path for source files.
16108 If the @samp{-r} option is used, the search path is reset to the default
16109 search path. If directories @var{pathdir} are supplied in addition to the
16110 @samp{-r} option, the search path is first reset and then addition
16112 Multiple directories may be specified, separated by blanks. Specifying
16113 multiple directories in a single command
16114 results in the directories added to the beginning of the
16115 search path in the same order they were presented in the command.
16116 If blanks are needed as
16117 part of a directory name, double-quotes should be used around
16118 the name. In the command output, the path will show up separated
16119 by the system directory-separator character. The directory-seperator
16120 character must not be used
16121 in any directory name.
16122 If no directories are specified, the current search path is displayed.
16124 @subsubheading @value{GDBN} Command
16126 The corresponding @value{GDBN} command is @samp{dir}.
16128 @subsubheading Example
16132 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
16133 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
16135 -environment-directory ""
16136 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
16138 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
16139 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
16141 -environment-directory -r
16142 ^done,source-path="$cdir:$cwd"
16147 @subheading The @code{-environment-path} Command
16148 @findex -environment-path
16150 @subsubheading Synopsis
16153 -environment-path [ -r ] [ @var{pathdir} ]+
16156 Add directories @var{pathdir} to beginning of search path for object files.
16157 If the @samp{-r} option is used, the search path is reset to the original
16158 search path that existed at gdb start-up. If directories @var{pathdir} are
16159 supplied in addition to the
16160 @samp{-r} option, the search path is first reset and then addition
16162 Multiple directories may be specified, separated by blanks. Specifying
16163 multiple directories in a single command
16164 results in the directories added to the beginning of the
16165 search path in the same order they were presented in the command.
16166 If blanks are needed as
16167 part of a directory name, double-quotes should be used around
16168 the name. In the command output, the path will show up separated
16169 by the system directory-separator character. The directory-seperator
16170 character must not be used
16171 in any directory name.
16172 If no directories are specified, the current path is displayed.
16175 @subsubheading @value{GDBN} Command
16177 The corresponding @value{GDBN} command is @samp{path}.
16179 @subsubheading Example
16184 ^done,path="/usr/bin"
16186 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
16187 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
16189 -environment-path -r /usr/local/bin
16190 ^done,path="/usr/local/bin:/usr/bin"
16195 @subheading The @code{-environment-pwd} Command
16196 @findex -environment-pwd
16198 @subsubheading Synopsis
16204 Show the current working directory.
16206 @subsubheading @value{GDBN} command
16208 The corresponding @value{GDBN} command is @samp{pwd}.
16210 @subsubheading Example
16215 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
16219 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16220 @node GDB/MI Program Control
16221 @section @sc{gdb/mi} Program control
16223 @subsubheading Program termination
16225 As a result of execution, the inferior program can run to completion, if
16226 it doesn't encounter any breakpoints. In this case the output will
16227 include an exit code, if the program has exited exceptionally.
16229 @subsubheading Examples
16232 Program exited normally:
16240 *stopped,reason="exited-normally"
16245 Program exited exceptionally:
16253 *stopped,reason="exited",exit-code="01"
16257 Another way the program can terminate is if it receives a signal such as
16258 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
16262 *stopped,reason="exited-signalled",signal-name="SIGINT",
16263 signal-meaning="Interrupt"
16267 @subheading The @code{-exec-abort} Command
16268 @findex -exec-abort
16270 @subsubheading Synopsis
16276 Kill the inferior running program.
16278 @subsubheading @value{GDBN} Command
16280 The corresponding @value{GDBN} command is @samp{kill}.
16282 @subsubheading Example
16286 @subheading The @code{-exec-arguments} Command
16287 @findex -exec-arguments
16289 @subsubheading Synopsis
16292 -exec-arguments @var{args}
16295 Set the inferior program arguments, to be used in the next
16298 @subsubheading @value{GDBN} Command
16300 The corresponding @value{GDBN} command is @samp{set args}.
16302 @subsubheading Example
16305 Don't have one around.
16308 @subheading The @code{-exec-continue} Command
16309 @findex -exec-continue
16311 @subsubheading Synopsis
16317 Asynchronous command. Resumes the execution of the inferior program
16318 until a breakpoint is encountered, or until the inferior exits.
16320 @subsubheading @value{GDBN} Command
16322 The corresponding @value{GDBN} corresponding is @samp{continue}.
16324 @subsubheading Example
16331 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
16332 file="hello.c",line="13"@}
16337 @subheading The @code{-exec-finish} Command
16338 @findex -exec-finish
16340 @subsubheading Synopsis
16346 Asynchronous command. Resumes the execution of the inferior program
16347 until the current function is exited. Displays the results returned by
16350 @subsubheading @value{GDBN} Command
16352 The corresponding @value{GDBN} command is @samp{finish}.
16354 @subsubheading Example
16356 Function returning @code{void}.
16363 *stopped,reason="function-finished",frame=@{func="main",args=[],
16364 file="hello.c",line="7"@}
16368 Function returning other than @code{void}. The name of the internal
16369 @value{GDBN} variable storing the result is printed, together with the
16376 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
16377 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
16378 file="recursive2.c",line="14"@},
16379 gdb-result-var="$1",return-value="0"
16384 @subheading The @code{-exec-interrupt} Command
16385 @findex -exec-interrupt
16387 @subsubheading Synopsis
16393 Asynchronous command. Interrupts the background execution of the target.
16394 Note how the token associated with the stop message is the one for the
16395 execution command that has been interrupted. The token for the interrupt
16396 itself only appears in the @samp{^done} output. If the user is trying to
16397 interrupt a non-running program, an error message will be printed.
16399 @subsubheading @value{GDBN} Command
16401 The corresponding @value{GDBN} command is @samp{interrupt}.
16403 @subsubheading Example
16414 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
16415 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",line="13"@}
16420 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
16425 @subheading The @code{-exec-next} Command
16428 @subsubheading Synopsis
16434 Asynchronous command. Resumes execution of the inferior program, stopping
16435 when the beginning of the next source line is reached.
16437 @subsubheading @value{GDBN} Command
16439 The corresponding @value{GDBN} command is @samp{next}.
16441 @subsubheading Example
16447 *stopped,reason="end-stepping-range",line="8",file="hello.c"
16452 @subheading The @code{-exec-next-instruction} Command
16453 @findex -exec-next-instruction
16455 @subsubheading Synopsis
16458 -exec-next-instruction
16461 Asynchronous command. Executes one machine instruction. If the
16462 instruction is a function call continues until the function returns. If
16463 the program stops at an instruction in the middle of a source line, the
16464 address will be printed as well.
16466 @subsubheading @value{GDBN} Command
16468 The corresponding @value{GDBN} command is @samp{nexti}.
16470 @subsubheading Example
16474 -exec-next-instruction
16478 *stopped,reason="end-stepping-range",
16479 addr="0x000100d4",line="5",file="hello.c"
16484 @subheading The @code{-exec-return} Command
16485 @findex -exec-return
16487 @subsubheading Synopsis
16493 Makes current function return immediately. Doesn't execute the inferior.
16494 Displays the new current frame.
16496 @subsubheading @value{GDBN} Command
16498 The corresponding @value{GDBN} command is @samp{return}.
16500 @subsubheading Example
16504 200-break-insert callee4
16505 200^done,bkpt=@{number="1",addr="0x00010734",
16506 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
16511 000*stopped,reason="breakpoint-hit",bkptno="1",
16512 frame=@{func="callee4",args=[],
16513 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
16519 111^done,frame=@{level="0",func="callee3",
16520 args=[@{name="strarg",
16521 value="0x11940 \"A string argument.\""@}],
16522 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
16527 @subheading The @code{-exec-run} Command
16530 @subsubheading Synopsis
16536 Asynchronous command. Starts execution of the inferior from the
16537 beginning. The inferior executes until either a breakpoint is
16538 encountered or the program exits.
16540 @subsubheading @value{GDBN} Command
16542 The corresponding @value{GDBN} command is @samp{run}.
16544 @subsubheading Example
16549 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
16554 *stopped,reason="breakpoint-hit",bkptno="1",
16555 frame=@{func="main",args=[],file="recursive2.c",line="4"@}
16560 @subheading The @code{-exec-show-arguments} Command
16561 @findex -exec-show-arguments
16563 @subsubheading Synopsis
16566 -exec-show-arguments
16569 Print the arguments of the program.
16571 @subsubheading @value{GDBN} Command
16573 The corresponding @value{GDBN} command is @samp{show args}.
16575 @subsubheading Example
16578 @c @subheading -exec-signal
16580 @subheading The @code{-exec-step} Command
16583 @subsubheading Synopsis
16589 Asynchronous command. Resumes execution of the inferior program, stopping
16590 when the beginning of the next source line is reached, if the next
16591 source line is not a function call. If it is, stop at the first
16592 instruction of the called function.
16594 @subsubheading @value{GDBN} Command
16596 The corresponding @value{GDBN} command is @samp{step}.
16598 @subsubheading Example
16600 Stepping into a function:
16606 *stopped,reason="end-stepping-range",
16607 frame=@{func="foo",args=[@{name="a",value="10"@},
16608 @{name="b",value="0"@}],file="recursive2.c",line="11"@}
16618 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
16623 @subheading The @code{-exec-step-instruction} Command
16624 @findex -exec-step-instruction
16626 @subsubheading Synopsis
16629 -exec-step-instruction
16632 Asynchronous command. Resumes the inferior which executes one machine
16633 instruction. The output, once @value{GDBN} has stopped, will vary depending on
16634 whether we have stopped in the middle of a source line or not. In the
16635 former case, the address at which the program stopped will be printed as
16638 @subsubheading @value{GDBN} Command
16640 The corresponding @value{GDBN} command is @samp{stepi}.
16642 @subsubheading Example
16646 -exec-step-instruction
16650 *stopped,reason="end-stepping-range",
16651 frame=@{func="foo",args=[],file="try.c",line="10"@}
16653 -exec-step-instruction
16657 *stopped,reason="end-stepping-range",
16658 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",line="10"@}
16663 @subheading The @code{-exec-until} Command
16664 @findex -exec-until
16666 @subsubheading Synopsis
16669 -exec-until [ @var{location} ]
16672 Asynchronous command. Executes the inferior until the @var{location}
16673 specified in the argument is reached. If there is no argument, the inferior
16674 executes until a source line greater than the current one is reached.
16675 The reason for stopping in this case will be @samp{location-reached}.
16677 @subsubheading @value{GDBN} Command
16679 The corresponding @value{GDBN} command is @samp{until}.
16681 @subsubheading Example
16685 -exec-until recursive2.c:6
16689 *stopped,reason="location-reached",frame=@{func="main",args=[],
16690 file="recursive2.c",line="6"@}
16695 @subheading -file-clear
16696 Is this going away????
16700 @subheading The @code{-file-exec-and-symbols} Command
16701 @findex -file-exec-and-symbols
16703 @subsubheading Synopsis
16706 -file-exec-and-symbols @var{file}
16709 Specify the executable file to be debugged. This file is the one from
16710 which the symbol table is also read. If no file is specified, the
16711 command clears the executable and symbol information. If breakpoints
16712 are set when using this command with no arguments, @value{GDBN} will produce
16713 error messages. Otherwise, no output is produced, except a completion
16716 @subsubheading @value{GDBN} Command
16718 The corresponding @value{GDBN} command is @samp{file}.
16720 @subsubheading Example
16724 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
16730 @subheading The @code{-file-exec-file} Command
16731 @findex -file-exec-file
16733 @subsubheading Synopsis
16736 -file-exec-file @var{file}
16739 Specify the executable file to be debugged. Unlike
16740 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
16741 from this file. If used without argument, @value{GDBN} clears the information
16742 about the executable file. No output is produced, except a completion
16745 @subsubheading @value{GDBN} Command
16747 The corresponding @value{GDBN} command is @samp{exec-file}.
16749 @subsubheading Example
16753 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
16759 @subheading The @code{-file-list-exec-sections} Command
16760 @findex -file-list-exec-sections
16762 @subsubheading Synopsis
16765 -file-list-exec-sections
16768 List the sections of the current executable file.
16770 @subsubheading @value{GDBN} Command
16772 The @value{GDBN} command @samp{info file} shows, among the rest, the same
16773 information as this command. @code{gdbtk} has a corresponding command
16774 @samp{gdb_load_info}.
16776 @subsubheading Example
16780 @subheading The @code{-file-list-exec-source-file} Command
16781 @findex -file-list-exec-source-file
16783 @subsubheading Synopsis
16786 -file-list-exec-source-file
16789 List the line number, the current source file, and the absolute path
16790 to the current source file for the current executable.
16792 @subsubheading @value{GDBN} Command
16794 There's no @value{GDBN} command which directly corresponds to this one.
16796 @subsubheading Example
16800 123-file-list-exec-source-file
16801 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
16806 @subheading The @code{-file-list-exec-source-files} Command
16807 @findex -file-list-exec-source-files
16809 @subsubheading Synopsis
16812 -file-list-exec-source-files
16815 List the source files for the current executable.
16817 It will always output the filename, but only when GDB can find the absolute
16818 file name of a source file, will it output the fullname.
16820 @subsubheading @value{GDBN} Command
16822 There's no @value{GDBN} command which directly corresponds to this one.
16823 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
16825 @subsubheading Example
16828 -file-list-exec-source-files
16830 @{file=foo.c,fullname=/home/foo.c@},
16831 @{file=/home/bar.c,fullname=/home/bar.c@},
16832 @{file=gdb_could_not_find_fullpath.c@}]
16836 @subheading The @code{-file-list-shared-libraries} Command
16837 @findex -file-list-shared-libraries
16839 @subsubheading Synopsis
16842 -file-list-shared-libraries
16845 List the shared libraries in the program.
16847 @subsubheading @value{GDBN} Command
16849 The corresponding @value{GDBN} command is @samp{info shared}.
16851 @subsubheading Example
16855 @subheading The @code{-file-list-symbol-files} Command
16856 @findex -file-list-symbol-files
16858 @subsubheading Synopsis
16861 -file-list-symbol-files
16866 @subsubheading @value{GDBN} Command
16868 The corresponding @value{GDBN} command is @samp{info file} (part of it).
16870 @subsubheading Example
16874 @subheading The @code{-file-symbol-file} Command
16875 @findex -file-symbol-file
16877 @subsubheading Synopsis
16880 -file-symbol-file @var{file}
16883 Read symbol table info from the specified @var{file} argument. When
16884 used without arguments, clears @value{GDBN}'s symbol table info. No output is
16885 produced, except for a completion notification.
16887 @subsubheading @value{GDBN} Command
16889 The corresponding @value{GDBN} command is @samp{symbol-file}.
16891 @subsubheading Example
16895 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
16900 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16901 @node GDB/MI Miscellaneous Commands
16902 @section Miscellaneous @value{GDBN} commands in @sc{gdb/mi}
16904 @c @subheading -gdb-complete
16906 @subheading The @code{-gdb-exit} Command
16909 @subsubheading Synopsis
16915 Exit @value{GDBN} immediately.
16917 @subsubheading @value{GDBN} Command
16919 Approximately corresponds to @samp{quit}.
16921 @subsubheading Example
16928 @subheading The @code{-gdb-set} Command
16931 @subsubheading Synopsis
16937 Set an internal @value{GDBN} variable.
16938 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
16940 @subsubheading @value{GDBN} Command
16942 The corresponding @value{GDBN} command is @samp{set}.
16944 @subsubheading Example
16954 @subheading The @code{-gdb-show} Command
16957 @subsubheading Synopsis
16963 Show the current value of a @value{GDBN} variable.
16965 @subsubheading @value{GDBN} command
16967 The corresponding @value{GDBN} command is @samp{show}.
16969 @subsubheading Example
16978 @c @subheading -gdb-source
16981 @subheading The @code{-gdb-version} Command
16982 @findex -gdb-version
16984 @subsubheading Synopsis
16990 Show version information for @value{GDBN}. Used mostly in testing.
16992 @subsubheading @value{GDBN} Command
16994 There's no equivalent @value{GDBN} command. @value{GDBN} by default shows this
16995 information when you start an interactive session.
16997 @subsubheading Example
16999 @c This example modifies the actual output from GDB to avoid overfull
17005 ~Copyright 2000 Free Software Foundation, Inc.
17006 ~GDB is free software, covered by the GNU General Public License, and
17007 ~you are welcome to change it and/or distribute copies of it under
17008 ~ certain conditions.
17009 ~Type "show copying" to see the conditions.
17010 ~There is absolutely no warranty for GDB. Type "show warranty" for
17012 ~This GDB was configured as
17013 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
17018 @subheading The @code{-interpreter-exec} Command
17019 @findex -interpreter-exec
17021 @subheading Synopsis
17024 -interpreter-exec @var{interpreter} @var{command}
17027 Execute the specified @var{command} in the given @var{interpreter}.
17029 @subheading @value{GDBN} Command
17031 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
17033 @subheading Example
17037 -interpreter-exec console "break main"
17038 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
17039 &"During symbol reading, bad structure-type format.\n"
17040 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
17046 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17047 @node GDB/MI Kod Commands
17048 @section @sc{gdb/mi} Kod Commands
17050 The Kod commands are not implemented.
17052 @c @subheading -kod-info
17054 @c @subheading -kod-list
17056 @c @subheading -kod-list-object-types
17058 @c @subheading -kod-show
17060 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17061 @node GDB/MI Memory Overlay Commands
17062 @section @sc{gdb/mi} Memory Overlay Commands
17064 The memory overlay commands are not implemented.
17066 @c @subheading -overlay-auto
17068 @c @subheading -overlay-list-mapping-state
17070 @c @subheading -overlay-list-overlays
17072 @c @subheading -overlay-map
17074 @c @subheading -overlay-off
17076 @c @subheading -overlay-on
17078 @c @subheading -overlay-unmap
17080 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17081 @node GDB/MI Signal Handling Commands
17082 @section @sc{gdb/mi} Signal Handling Commands
17084 Signal handling commands are not implemented.
17086 @c @subheading -signal-handle
17088 @c @subheading -signal-list-handle-actions
17090 @c @subheading -signal-list-signal-types
17094 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17095 @node GDB/MI Stack Manipulation
17096 @section @sc{gdb/mi} Stack Manipulation Commands
17099 @subheading The @code{-stack-info-frame} Command
17100 @findex -stack-info-frame
17102 @subsubheading Synopsis
17108 Get info on the current frame.
17110 @subsubheading @value{GDBN} Command
17112 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
17113 (without arguments).
17115 @subsubheading Example
17118 @subheading The @code{-stack-info-depth} Command
17119 @findex -stack-info-depth
17121 @subsubheading Synopsis
17124 -stack-info-depth [ @var{max-depth} ]
17127 Return the depth of the stack. If the integer argument @var{max-depth}
17128 is specified, do not count beyond @var{max-depth} frames.
17130 @subsubheading @value{GDBN} Command
17132 There's no equivalent @value{GDBN} command.
17134 @subsubheading Example
17136 For a stack with frame levels 0 through 11:
17143 -stack-info-depth 4
17146 -stack-info-depth 12
17149 -stack-info-depth 11
17152 -stack-info-depth 13
17157 @subheading The @code{-stack-list-arguments} Command
17158 @findex -stack-list-arguments
17160 @subsubheading Synopsis
17163 -stack-list-arguments @var{show-values}
17164 [ @var{low-frame} @var{high-frame} ]
17167 Display a list of the arguments for the frames between @var{low-frame}
17168 and @var{high-frame} (inclusive). If @var{low-frame} and
17169 @var{high-frame} are not provided, list the arguments for the whole call
17172 The @var{show-values} argument must have a value of 0 or 1. A value of
17173 0 means that only the names of the arguments are listed, a value of 1
17174 means that both names and values of the arguments are printed.
17176 @subsubheading @value{GDBN} Command
17178 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
17179 @samp{gdb_get_args} command which partially overlaps with the
17180 functionality of @samp{-stack-list-arguments}.
17182 @subsubheading Example
17189 frame=@{level="0",addr="0x00010734",func="callee4",
17190 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
17191 frame=@{level="1",addr="0x0001076c",func="callee3",
17192 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
17193 frame=@{level="2",addr="0x0001078c",func="callee2",
17194 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
17195 frame=@{level="3",addr="0x000107b4",func="callee1",
17196 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
17197 frame=@{level="4",addr="0x000107e0",func="main",
17198 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
17200 -stack-list-arguments 0
17203 frame=@{level="0",args=[]@},
17204 frame=@{level="1",args=[name="strarg"]@},
17205 frame=@{level="2",args=[name="intarg",name="strarg"]@},
17206 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
17207 frame=@{level="4",args=[]@}]
17209 -stack-list-arguments 1
17212 frame=@{level="0",args=[]@},
17214 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
17215 frame=@{level="2",args=[
17216 @{name="intarg",value="2"@},
17217 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
17218 @{frame=@{level="3",args=[
17219 @{name="intarg",value="2"@},
17220 @{name="strarg",value="0x11940 \"A string argument.\""@},
17221 @{name="fltarg",value="3.5"@}]@},
17222 frame=@{level="4",args=[]@}]
17224 -stack-list-arguments 0 2 2
17225 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
17227 -stack-list-arguments 1 2 2
17228 ^done,stack-args=[frame=@{level="2",
17229 args=[@{name="intarg",value="2"@},
17230 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
17234 @c @subheading -stack-list-exception-handlers
17237 @subheading The @code{-stack-list-frames} Command
17238 @findex -stack-list-frames
17240 @subsubheading Synopsis
17243 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
17246 List the frames currently on the stack. For each frame it displays the
17251 The frame number, 0 being the topmost frame, i.e. the innermost function.
17253 The @code{$pc} value for that frame.
17257 File name of the source file where the function lives.
17259 Line number corresponding to the @code{$pc}.
17262 If invoked without arguments, this command prints a backtrace for the
17263 whole stack. If given two integer arguments, it shows the frames whose
17264 levels are between the two arguments (inclusive). If the two arguments
17265 are equal, it shows the single frame at the corresponding level.
17267 @subsubheading @value{GDBN} Command
17269 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
17271 @subsubheading Example
17273 Full stack backtrace:
17279 [frame=@{level="0",addr="0x0001076c",func="foo",
17280 file="recursive2.c",line="11"@},
17281 frame=@{level="1",addr="0x000107a4",func="foo",
17282 file="recursive2.c",line="14"@},
17283 frame=@{level="2",addr="0x000107a4",func="foo",
17284 file="recursive2.c",line="14"@},
17285 frame=@{level="3",addr="0x000107a4",func="foo",
17286 file="recursive2.c",line="14"@},
17287 frame=@{level="4",addr="0x000107a4",func="foo",
17288 file="recursive2.c",line="14"@},
17289 frame=@{level="5",addr="0x000107a4",func="foo",
17290 file="recursive2.c",line="14"@},
17291 frame=@{level="6",addr="0x000107a4",func="foo",
17292 file="recursive2.c",line="14"@},
17293 frame=@{level="7",addr="0x000107a4",func="foo",
17294 file="recursive2.c",line="14"@},
17295 frame=@{level="8",addr="0x000107a4",func="foo",
17296 file="recursive2.c",line="14"@},
17297 frame=@{level="9",addr="0x000107a4",func="foo",
17298 file="recursive2.c",line="14"@},
17299 frame=@{level="10",addr="0x000107a4",func="foo",
17300 file="recursive2.c",line="14"@},
17301 frame=@{level="11",addr="0x00010738",func="main",
17302 file="recursive2.c",line="4"@}]
17306 Show frames between @var{low_frame} and @var{high_frame}:
17310 -stack-list-frames 3 5
17312 [frame=@{level="3",addr="0x000107a4",func="foo",
17313 file="recursive2.c",line="14"@},
17314 frame=@{level="4",addr="0x000107a4",func="foo",
17315 file="recursive2.c",line="14"@},
17316 frame=@{level="5",addr="0x000107a4",func="foo",
17317 file="recursive2.c",line="14"@}]
17321 Show a single frame:
17325 -stack-list-frames 3 3
17327 [frame=@{level="3",addr="0x000107a4",func="foo",
17328 file="recursive2.c",line="14"@}]
17333 @subheading The @code{-stack-list-locals} Command
17334 @findex -stack-list-locals
17336 @subsubheading Synopsis
17339 -stack-list-locals @var{print-values}
17342 Display the local variable names for the current frame. With an
17343 argument of 0 or @code{--no-values}, prints only the names of the variables.
17344 With argument of 1 or @code{--all-values}, prints also their values. With
17345 argument of 2 or @code{--simple-values}, prints the name, type and value for
17346 simple data types and the name and type for arrays, structures and
17347 unions. In this last case, the idea is that the user can see the
17348 value of simple data types immediately and he can create variable
17349 objects for other data types if he wishes to explore their values in
17352 @subsubheading @value{GDBN} Command
17354 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
17356 @subsubheading Example
17360 -stack-list-locals 0
17361 ^done,locals=[name="A",name="B",name="C"]
17363 -stack-list-locals --all-values
17364 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
17365 @{name="C",value="@{1, 2, 3@}"@}]
17366 -stack-list-locals --simple-values
17367 ^done,locals=[@{name="A",type="int",value="1"@},
17368 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
17373 @subheading The @code{-stack-select-frame} Command
17374 @findex -stack-select-frame
17376 @subsubheading Synopsis
17379 -stack-select-frame @var{framenum}
17382 Change the current frame. Select a different frame @var{framenum} on
17385 @subsubheading @value{GDBN} Command
17387 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
17388 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
17390 @subsubheading Example
17394 -stack-select-frame 2
17399 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17400 @node GDB/MI Symbol Query
17401 @section @sc{gdb/mi} Symbol Query Commands
17404 @subheading The @code{-symbol-info-address} Command
17405 @findex -symbol-info-address
17407 @subsubheading Synopsis
17410 -symbol-info-address @var{symbol}
17413 Describe where @var{symbol} is stored.
17415 @subsubheading @value{GDBN} Command
17417 The corresponding @value{GDBN} command is @samp{info address}.
17419 @subsubheading Example
17423 @subheading The @code{-symbol-info-file} Command
17424 @findex -symbol-info-file
17426 @subsubheading Synopsis
17432 Show the file for the symbol.
17434 @subsubheading @value{GDBN} Command
17436 There's no equivalent @value{GDBN} command. @code{gdbtk} has
17437 @samp{gdb_find_file}.
17439 @subsubheading Example
17443 @subheading The @code{-symbol-info-function} Command
17444 @findex -symbol-info-function
17446 @subsubheading Synopsis
17449 -symbol-info-function
17452 Show which function the symbol lives in.
17454 @subsubheading @value{GDBN} Command
17456 @samp{gdb_get_function} in @code{gdbtk}.
17458 @subsubheading Example
17462 @subheading The @code{-symbol-info-line} Command
17463 @findex -symbol-info-line
17465 @subsubheading Synopsis
17471 Show the core addresses of the code for a source line.
17473 @subsubheading @value{GDBN} Command
17475 The corresponding @value{GDBN} command is @samp{info line}.
17476 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
17478 @subsubheading Example
17482 @subheading The @code{-symbol-info-symbol} Command
17483 @findex -symbol-info-symbol
17485 @subsubheading Synopsis
17488 -symbol-info-symbol @var{addr}
17491 Describe what symbol is at location @var{addr}.
17493 @subsubheading @value{GDBN} Command
17495 The corresponding @value{GDBN} command is @samp{info symbol}.
17497 @subsubheading Example
17501 @subheading The @code{-symbol-list-functions} Command
17502 @findex -symbol-list-functions
17504 @subsubheading Synopsis
17507 -symbol-list-functions
17510 List the functions in the executable.
17512 @subsubheading @value{GDBN} Command
17514 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
17515 @samp{gdb_search} in @code{gdbtk}.
17517 @subsubheading Example
17521 @subheading The @code{-symbol-list-lines} Command
17522 @findex -symbol-list-lines
17524 @subsubheading Synopsis
17527 -symbol-list-lines @var{filename}
17530 Print the list of lines that contain code and their associated program
17531 addresses for the given source filename. The entries are sorted in
17532 ascending PC order.
17534 @subsubheading @value{GDBN} Command
17536 There is no corresponding @value{GDBN} command.
17538 @subsubheading Example
17541 -symbol-list-lines basics.c
17542 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
17547 @subheading The @code{-symbol-list-types} Command
17548 @findex -symbol-list-types
17550 @subsubheading Synopsis
17556 List all the type names.
17558 @subsubheading @value{GDBN} Command
17560 The corresponding commands are @samp{info types} in @value{GDBN},
17561 @samp{gdb_search} in @code{gdbtk}.
17563 @subsubheading Example
17567 @subheading The @code{-symbol-list-variables} Command
17568 @findex -symbol-list-variables
17570 @subsubheading Synopsis
17573 -symbol-list-variables
17576 List all the global and static variable names.
17578 @subsubheading @value{GDBN} Command
17580 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
17582 @subsubheading Example
17586 @subheading The @code{-symbol-locate} Command
17587 @findex -symbol-locate
17589 @subsubheading Synopsis
17595 @subsubheading @value{GDBN} Command
17597 @samp{gdb_loc} in @code{gdbtk}.
17599 @subsubheading Example
17603 @subheading The @code{-symbol-type} Command
17604 @findex -symbol-type
17606 @subsubheading Synopsis
17609 -symbol-type @var{variable}
17612 Show type of @var{variable}.
17614 @subsubheading @value{GDBN} Command
17616 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
17617 @samp{gdb_obj_variable}.
17619 @subsubheading Example
17623 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17624 @node GDB/MI Target Manipulation
17625 @section @sc{gdb/mi} Target Manipulation Commands
17628 @subheading The @code{-target-attach} Command
17629 @findex -target-attach
17631 @subsubheading Synopsis
17634 -target-attach @var{pid} | @var{file}
17637 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
17639 @subsubheading @value{GDBN} command
17641 The corresponding @value{GDBN} command is @samp{attach}.
17643 @subsubheading Example
17647 @subheading The @code{-target-compare-sections} Command
17648 @findex -target-compare-sections
17650 @subsubheading Synopsis
17653 -target-compare-sections [ @var{section} ]
17656 Compare data of section @var{section} on target to the exec file.
17657 Without the argument, all sections are compared.
17659 @subsubheading @value{GDBN} Command
17661 The @value{GDBN} equivalent is @samp{compare-sections}.
17663 @subsubheading Example
17667 @subheading The @code{-target-detach} Command
17668 @findex -target-detach
17670 @subsubheading Synopsis
17676 Disconnect from the remote target. There's no output.
17678 @subsubheading @value{GDBN} command
17680 The corresponding @value{GDBN} command is @samp{detach}.
17682 @subsubheading Example
17692 @subheading The @code{-target-disconnect} Command
17693 @findex -target-disconnect
17695 @subsubheading Synopsis
17701 Disconnect from the remote target. There's no output.
17703 @subsubheading @value{GDBN} command
17705 The corresponding @value{GDBN} command is @samp{disconnect}.
17707 @subsubheading Example
17717 @subheading The @code{-target-download} Command
17718 @findex -target-download
17720 @subsubheading Synopsis
17726 Loads the executable onto the remote target.
17727 It prints out an update message every half second, which includes the fields:
17731 The name of the section.
17733 The size of what has been sent so far for that section.
17735 The size of the section.
17737 The total size of what was sent so far (the current and the previous sections).
17739 The size of the overall executable to download.
17743 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
17744 @sc{gdb/mi} Output Syntax}).
17746 In addition, it prints the name and size of the sections, as they are
17747 downloaded. These messages include the following fields:
17751 The name of the section.
17753 The size of the section.
17755 The size of the overall executable to download.
17759 At the end, a summary is printed.
17761 @subsubheading @value{GDBN} Command
17763 The corresponding @value{GDBN} command is @samp{load}.
17765 @subsubheading Example
17767 Note: each status message appears on a single line. Here the messages
17768 have been broken down so that they can fit onto a page.
17773 +download,@{section=".text",section-size="6668",total-size="9880"@}
17774 +download,@{section=".text",section-sent="512",section-size="6668",
17775 total-sent="512",total-size="9880"@}
17776 +download,@{section=".text",section-sent="1024",section-size="6668",
17777 total-sent="1024",total-size="9880"@}
17778 +download,@{section=".text",section-sent="1536",section-size="6668",
17779 total-sent="1536",total-size="9880"@}
17780 +download,@{section=".text",section-sent="2048",section-size="6668",
17781 total-sent="2048",total-size="9880"@}
17782 +download,@{section=".text",section-sent="2560",section-size="6668",
17783 total-sent="2560",total-size="9880"@}
17784 +download,@{section=".text",section-sent="3072",section-size="6668",
17785 total-sent="3072",total-size="9880"@}
17786 +download,@{section=".text",section-sent="3584",section-size="6668",
17787 total-sent="3584",total-size="9880"@}
17788 +download,@{section=".text",section-sent="4096",section-size="6668",
17789 total-sent="4096",total-size="9880"@}
17790 +download,@{section=".text",section-sent="4608",section-size="6668",
17791 total-sent="4608",total-size="9880"@}
17792 +download,@{section=".text",section-sent="5120",section-size="6668",
17793 total-sent="5120",total-size="9880"@}
17794 +download,@{section=".text",section-sent="5632",section-size="6668",
17795 total-sent="5632",total-size="9880"@}
17796 +download,@{section=".text",section-sent="6144",section-size="6668",
17797 total-sent="6144",total-size="9880"@}
17798 +download,@{section=".text",section-sent="6656",section-size="6668",
17799 total-sent="6656",total-size="9880"@}
17800 +download,@{section=".init",section-size="28",total-size="9880"@}
17801 +download,@{section=".fini",section-size="28",total-size="9880"@}
17802 +download,@{section=".data",section-size="3156",total-size="9880"@}
17803 +download,@{section=".data",section-sent="512",section-size="3156",
17804 total-sent="7236",total-size="9880"@}
17805 +download,@{section=".data",section-sent="1024",section-size="3156",
17806 total-sent="7748",total-size="9880"@}
17807 +download,@{section=".data",section-sent="1536",section-size="3156",
17808 total-sent="8260",total-size="9880"@}
17809 +download,@{section=".data",section-sent="2048",section-size="3156",
17810 total-sent="8772",total-size="9880"@}
17811 +download,@{section=".data",section-sent="2560",section-size="3156",
17812 total-sent="9284",total-size="9880"@}
17813 +download,@{section=".data",section-sent="3072",section-size="3156",
17814 total-sent="9796",total-size="9880"@}
17815 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
17821 @subheading The @code{-target-exec-status} Command
17822 @findex -target-exec-status
17824 @subsubheading Synopsis
17827 -target-exec-status
17830 Provide information on the state of the target (whether it is running or
17831 not, for instance).
17833 @subsubheading @value{GDBN} Command
17835 There's no equivalent @value{GDBN} command.
17837 @subsubheading Example
17841 @subheading The @code{-target-list-available-targets} Command
17842 @findex -target-list-available-targets
17844 @subsubheading Synopsis
17847 -target-list-available-targets
17850 List the possible targets to connect to.
17852 @subsubheading @value{GDBN} Command
17854 The corresponding @value{GDBN} command is @samp{help target}.
17856 @subsubheading Example
17860 @subheading The @code{-target-list-current-targets} Command
17861 @findex -target-list-current-targets
17863 @subsubheading Synopsis
17866 -target-list-current-targets
17869 Describe the current target.
17871 @subsubheading @value{GDBN} Command
17873 The corresponding information is printed by @samp{info file} (among
17876 @subsubheading Example
17880 @subheading The @code{-target-list-parameters} Command
17881 @findex -target-list-parameters
17883 @subsubheading Synopsis
17886 -target-list-parameters
17891 @subsubheading @value{GDBN} Command
17895 @subsubheading Example
17899 @subheading The @code{-target-select} Command
17900 @findex -target-select
17902 @subsubheading Synopsis
17905 -target-select @var{type} @var{parameters @dots{}}
17908 Connect @value{GDBN} to the remote target. This command takes two args:
17912 The type of target, for instance @samp{async}, @samp{remote}, etc.
17913 @item @var{parameters}
17914 Device names, host names and the like. @xref{Target Commands, ,
17915 Commands for managing targets}, for more details.
17918 The output is a connection notification, followed by the address at
17919 which the target program is, in the following form:
17922 ^connected,addr="@var{address}",func="@var{function name}",
17923 args=[@var{arg list}]
17926 @subsubheading @value{GDBN} Command
17928 The corresponding @value{GDBN} command is @samp{target}.
17930 @subsubheading Example
17934 -target-select async /dev/ttya
17935 ^connected,addr="0xfe00a300",func="??",args=[]
17939 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17940 @node GDB/MI Thread Commands
17941 @section @sc{gdb/mi} Thread Commands
17944 @subheading The @code{-thread-info} Command
17945 @findex -thread-info
17947 @subsubheading Synopsis
17953 @subsubheading @value{GDBN} command
17957 @subsubheading Example
17961 @subheading The @code{-thread-list-all-threads} Command
17962 @findex -thread-list-all-threads
17964 @subsubheading Synopsis
17967 -thread-list-all-threads
17970 @subsubheading @value{GDBN} Command
17972 The equivalent @value{GDBN} command is @samp{info threads}.
17974 @subsubheading Example
17978 @subheading The @code{-thread-list-ids} Command
17979 @findex -thread-list-ids
17981 @subsubheading Synopsis
17987 Produces a list of the currently known @value{GDBN} thread ids. At the
17988 end of the list it also prints the total number of such threads.
17990 @subsubheading @value{GDBN} Command
17992 Part of @samp{info threads} supplies the same information.
17994 @subsubheading Example
17996 No threads present, besides the main process:
18001 ^done,thread-ids=@{@},number-of-threads="0"
18011 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18012 number-of-threads="3"
18017 @subheading The @code{-thread-select} Command
18018 @findex -thread-select
18020 @subsubheading Synopsis
18023 -thread-select @var{threadnum}
18026 Make @var{threadnum} the current thread. It prints the number of the new
18027 current thread, and the topmost frame for that thread.
18029 @subsubheading @value{GDBN} Command
18031 The corresponding @value{GDBN} command is @samp{thread}.
18033 @subsubheading Example
18040 *stopped,reason="end-stepping-range",thread-id="2",line="187",
18041 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
18045 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18046 number-of-threads="3"
18049 ^done,new-thread-id="3",
18050 frame=@{level="0",func="vprintf",
18051 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
18052 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
18056 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18057 @node GDB/MI Tracepoint Commands
18058 @section @sc{gdb/mi} Tracepoint Commands
18060 The tracepoint commands are not yet implemented.
18062 @c @subheading -trace-actions
18064 @c @subheading -trace-delete
18066 @c @subheading -trace-disable
18068 @c @subheading -trace-dump
18070 @c @subheading -trace-enable
18072 @c @subheading -trace-exists
18074 @c @subheading -trace-find
18076 @c @subheading -trace-frame-number
18078 @c @subheading -trace-info
18080 @c @subheading -trace-insert
18082 @c @subheading -trace-list
18084 @c @subheading -trace-pass-count
18086 @c @subheading -trace-save
18088 @c @subheading -trace-start
18090 @c @subheading -trace-stop
18093 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18094 @node GDB/MI Variable Objects
18095 @section @sc{gdb/mi} Variable Objects
18098 @subheading Motivation for Variable Objects in @sc{gdb/mi}
18100 For the implementation of a variable debugger window (locals, watched
18101 expressions, etc.), we are proposing the adaptation of the existing code
18102 used by @code{Insight}.
18104 The two main reasons for that are:
18108 It has been proven in practice (it is already on its second generation).
18111 It will shorten development time (needless to say how important it is
18115 The original interface was designed to be used by Tcl code, so it was
18116 slightly changed so it could be used through @sc{gdb/mi}. This section
18117 describes the @sc{gdb/mi} operations that will be available and gives some
18118 hints about their use.
18120 @emph{Note}: In addition to the set of operations described here, we
18121 expect the @sc{gui} implementation of a variable window to require, at
18122 least, the following operations:
18125 @item @code{-gdb-show} @code{output-radix}
18126 @item @code{-stack-list-arguments}
18127 @item @code{-stack-list-locals}
18128 @item @code{-stack-select-frame}
18131 @subheading Introduction to Variable Objects in @sc{gdb/mi}
18133 @cindex variable objects in @sc{gdb/mi}
18134 The basic idea behind variable objects is the creation of a named object
18135 to represent a variable, an expression, a memory location or even a CPU
18136 register. For each object created, a set of operations is available for
18137 examining or changing its properties.
18139 Furthermore, complex data types, such as C structures, are represented
18140 in a tree format. For instance, the @code{struct} type variable is the
18141 root and the children will represent the struct members. If a child
18142 is itself of a complex type, it will also have children of its own.
18143 Appropriate language differences are handled for C, C@t{++} and Java.
18145 When returning the actual values of the objects, this facility allows
18146 for the individual selection of the display format used in the result
18147 creation. It can be chosen among: binary, decimal, hexadecimal, octal
18148 and natural. Natural refers to a default format automatically
18149 chosen based on the variable type (like decimal for an @code{int}, hex
18150 for pointers, etc.).
18152 The following is the complete set of @sc{gdb/mi} operations defined to
18153 access this functionality:
18155 @multitable @columnfractions .4 .6
18156 @item @strong{Operation}
18157 @tab @strong{Description}
18159 @item @code{-var-create}
18160 @tab create a variable object
18161 @item @code{-var-delete}
18162 @tab delete the variable object and its children
18163 @item @code{-var-set-format}
18164 @tab set the display format of this variable
18165 @item @code{-var-show-format}
18166 @tab show the display format of this variable
18167 @item @code{-var-info-num-children}
18168 @tab tells how many children this object has
18169 @item @code{-var-list-children}
18170 @tab return a list of the object's children
18171 @item @code{-var-info-type}
18172 @tab show the type of this variable object
18173 @item @code{-var-info-expression}
18174 @tab print what this variable object represents
18175 @item @code{-var-show-attributes}
18176 @tab is this variable editable? does it exist here?
18177 @item @code{-var-evaluate-expression}
18178 @tab get the value of this variable
18179 @item @code{-var-assign}
18180 @tab set the value of this variable
18181 @item @code{-var-update}
18182 @tab update the variable and its children
18185 In the next subsection we describe each operation in detail and suggest
18186 how it can be used.
18188 @subheading Description And Use of Operations on Variable Objects
18190 @subheading The @code{-var-create} Command
18191 @findex -var-create
18193 @subsubheading Synopsis
18196 -var-create @{@var{name} | "-"@}
18197 @{@var{frame-addr} | "*"@} @var{expression}
18200 This operation creates a variable object, which allows the monitoring of
18201 a variable, the result of an expression, a memory cell or a CPU
18204 The @var{name} parameter is the string by which the object can be
18205 referenced. It must be unique. If @samp{-} is specified, the varobj
18206 system will generate a string ``varNNNNNN'' automatically. It will be
18207 unique provided that one does not specify @var{name} on that format.
18208 The command fails if a duplicate name is found.
18210 The frame under which the expression should be evaluated can be
18211 specified by @var{frame-addr}. A @samp{*} indicates that the current
18212 frame should be used.
18214 @var{expression} is any expression valid on the current language set (must not
18215 begin with a @samp{*}), or one of the following:
18219 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
18222 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
18225 @samp{$@var{regname}} --- a CPU register name
18228 @subsubheading Result
18230 This operation returns the name, number of children and the type of the
18231 object created. Type is returned as a string as the ones generated by
18232 the @value{GDBN} CLI:
18235 name="@var{name}",numchild="N",type="@var{type}"
18239 @subheading The @code{-var-delete} Command
18240 @findex -var-delete
18242 @subsubheading Synopsis
18245 -var-delete @var{name}
18248 Deletes a previously created variable object and all of its children.
18250 Returns an error if the object @var{name} is not found.
18253 @subheading The @code{-var-set-format} Command
18254 @findex -var-set-format
18256 @subsubheading Synopsis
18259 -var-set-format @var{name} @var{format-spec}
18262 Sets the output format for the value of the object @var{name} to be
18265 The syntax for the @var{format-spec} is as follows:
18268 @var{format-spec} @expansion{}
18269 @{binary | decimal | hexadecimal | octal | natural@}
18273 @subheading The @code{-var-show-format} Command
18274 @findex -var-show-format
18276 @subsubheading Synopsis
18279 -var-show-format @var{name}
18282 Returns the format used to display the value of the object @var{name}.
18285 @var{format} @expansion{}
18290 @subheading The @code{-var-info-num-children} Command
18291 @findex -var-info-num-children
18293 @subsubheading Synopsis
18296 -var-info-num-children @var{name}
18299 Returns the number of children of a variable object @var{name}:
18306 @subheading The @code{-var-list-children} Command
18307 @findex -var-list-children
18309 @subsubheading Synopsis
18312 -var-list-children [@var{print-values}] @var{name}
18315 Returns a list of the children of the specified variable object. With
18316 just the variable object name as an argument or with an optional
18317 preceding argument of 0 or @code{--no-values}, prints only the names of the
18318 variables. With an optional preceding argument of 1 or @code{--all-values},
18319 also prints their values.
18321 @subsubheading Example
18325 -var-list-children n
18326 numchild=@var{n},children=[@{name=@var{name},
18327 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
18329 -var-list-children --all-values n
18330 numchild=@var{n},children=[@{name=@var{name},
18331 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
18335 @subheading The @code{-var-info-type} Command
18336 @findex -var-info-type
18338 @subsubheading Synopsis
18341 -var-info-type @var{name}
18344 Returns the type of the specified variable @var{name}. The type is
18345 returned as a string in the same format as it is output by the
18349 type=@var{typename}
18353 @subheading The @code{-var-info-expression} Command
18354 @findex -var-info-expression
18356 @subsubheading Synopsis
18359 -var-info-expression @var{name}
18362 Returns what is represented by the variable object @var{name}:
18365 lang=@var{lang-spec},exp=@var{expression}
18369 where @var{lang-spec} is @code{@{"C" | "C++" | "Java"@}}.
18371 @subheading The @code{-var-show-attributes} Command
18372 @findex -var-show-attributes
18374 @subsubheading Synopsis
18377 -var-show-attributes @var{name}
18380 List attributes of the specified variable object @var{name}:
18383 status=@var{attr} [ ( ,@var{attr} )* ]
18387 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
18389 @subheading The @code{-var-evaluate-expression} Command
18390 @findex -var-evaluate-expression
18392 @subsubheading Synopsis
18395 -var-evaluate-expression @var{name}
18398 Evaluates the expression that is represented by the specified variable
18399 object and returns its value as a string in the current format specified
18406 Note that one must invoke @code{-var-list-children} for a variable
18407 before the value of a child variable can be evaluated.
18409 @subheading The @code{-var-assign} Command
18410 @findex -var-assign
18412 @subsubheading Synopsis
18415 -var-assign @var{name} @var{expression}
18418 Assigns the value of @var{expression} to the variable object specified
18419 by @var{name}. The object must be @samp{editable}. If the variable's
18420 value is altered by the assign, the variable will show up in any
18421 subsequent @code{-var-update} list.
18423 @subsubheading Example
18431 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
18435 @subheading The @code{-var-update} Command
18436 @findex -var-update
18438 @subsubheading Synopsis
18441 -var-update @{@var{name} | "*"@}
18444 Update the value of the variable object @var{name} by evaluating its
18445 expression after fetching all the new values from memory or registers.
18446 A @samp{*} causes all existing variable objects to be updated.
18450 @chapter @value{GDBN} Annotations
18452 This chapter describes annotations in @value{GDBN}. Annotations were
18453 designed to interface @value{GDBN} to graphical user interfaces or other
18454 similar programs which want to interact with @value{GDBN} at a
18455 relatively high level.
18457 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
18461 This is Edition @value{EDITION}, @value{DATE}.
18465 * Annotations Overview:: What annotations are; the general syntax.
18466 * Server Prefix:: Issuing a command without affecting user state.
18467 * Prompting:: Annotations marking @value{GDBN}'s need for input.
18468 * Errors:: Annotations for error messages.
18469 * Invalidation:: Some annotations describe things now invalid.
18470 * Annotations for Running::
18471 Whether the program is running, how it stopped, etc.
18472 * Source Annotations:: Annotations describing source code.
18475 @node Annotations Overview
18476 @section What is an Annotation?
18477 @cindex annotations
18479 Annotations start with a newline character, two @samp{control-z}
18480 characters, and the name of the annotation. If there is no additional
18481 information associated with this annotation, the name of the annotation
18482 is followed immediately by a newline. If there is additional
18483 information, the name of the annotation is followed by a space, the
18484 additional information, and a newline. The additional information
18485 cannot contain newline characters.
18487 Any output not beginning with a newline and two @samp{control-z}
18488 characters denotes literal output from @value{GDBN}. Currently there is
18489 no need for @value{GDBN} to output a newline followed by two
18490 @samp{control-z} characters, but if there was such a need, the
18491 annotations could be extended with an @samp{escape} annotation which
18492 means those three characters as output.
18494 The annotation @var{level}, which is specified using the
18495 @option{--annotate} command line option (@pxref{Mode Options}), controls
18496 how much information @value{GDBN} prints together with its prompt,
18497 values of expressions, source lines, and other types of output. Level 0
18498 is for no anntations, level 1 is for use when @value{GDBN} is run as a
18499 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
18500 for programs that control @value{GDBN}, and level 2 annotations have
18501 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
18502 Interface, annotate, GDB's Obsolete Annotations}). This chapter
18503 describes level 3 annotations.
18505 A simple example of starting up @value{GDBN} with annotations is:
18508 $ @kbd{gdb --annotate=3}
18510 Copyright 2003 Free Software Foundation, Inc.
18511 GDB is free software, covered by the GNU General Public License,
18512 and you are welcome to change it and/or distribute copies of it
18513 under certain conditions.
18514 Type "show copying" to see the conditions.
18515 There is absolutely no warranty for GDB. Type "show warranty"
18517 This GDB was configured as "i386-pc-linux-gnu"
18528 Here @samp{quit} is input to @value{GDBN}; the rest is output from
18529 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
18530 denotes a @samp{control-z} character) are annotations; the rest is
18531 output from @value{GDBN}.
18533 @node Server Prefix
18534 @section The Server Prefix
18535 @cindex server prefix for annotations
18537 To issue a command to @value{GDBN} without affecting certain aspects of
18538 the state which is seen by users, prefix it with @samp{server }. This
18539 means that this command will not affect the command history, nor will it
18540 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
18541 pressed on a line by itself.
18543 The server prefix does not affect the recording of values into the value
18544 history; to print a value without recording it into the value history,
18545 use the @code{output} command instead of the @code{print} command.
18548 @section Annotation for @value{GDBN} Input
18550 @cindex annotations for prompts
18551 When @value{GDBN} prompts for input, it annotates this fact so it is possible
18552 to know when to send output, when the output from a given command is
18555 Different kinds of input each have a different @dfn{input type}. Each
18556 input type has three annotations: a @code{pre-} annotation, which
18557 denotes the beginning of any prompt which is being output, a plain
18558 annotation, which denotes the end of the prompt, and then a @code{post-}
18559 annotation which denotes the end of any echo which may (or may not) be
18560 associated with the input. For example, the @code{prompt} input type
18561 features the following annotations:
18569 The input types are
18574 @findex post-prompt
18576 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
18578 @findex pre-commands
18580 @findex post-commands
18582 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
18583 command. The annotations are repeated for each command which is input.
18585 @findex pre-overload-choice
18586 @findex overload-choice
18587 @findex post-overload-choice
18588 @item overload-choice
18589 When @value{GDBN} wants the user to select between various overloaded functions.
18595 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
18597 @findex pre-prompt-for-continue
18598 @findex prompt-for-continue
18599 @findex post-prompt-for-continue
18600 @item prompt-for-continue
18601 When @value{GDBN} is asking the user to press return to continue. Note: Don't
18602 expect this to work well; instead use @code{set height 0} to disable
18603 prompting. This is because the counting of lines is buggy in the
18604 presence of annotations.
18609 @cindex annotations for errors, warnings and interrupts
18616 This annotation occurs right before @value{GDBN} responds to an interrupt.
18623 This annotation occurs right before @value{GDBN} responds to an error.
18625 Quit and error annotations indicate that any annotations which @value{GDBN} was
18626 in the middle of may end abruptly. For example, if a
18627 @code{value-history-begin} annotation is followed by a @code{error}, one
18628 cannot expect to receive the matching @code{value-history-end}. One
18629 cannot expect not to receive it either, however; an error annotation
18630 does not necessarily mean that @value{GDBN} is immediately returning all the way
18633 @findex error-begin
18634 A quit or error annotation may be preceded by
18640 Any output between that and the quit or error annotation is the error
18643 Warning messages are not yet annotated.
18644 @c If we want to change that, need to fix warning(), type_error(),
18645 @c range_error(), and possibly other places.
18648 @section Invalidation Notices
18650 @cindex annotations for invalidation messages
18651 The following annotations say that certain pieces of state may have
18655 @findex frames-invalid
18656 @item ^Z^Zframes-invalid
18658 The frames (for example, output from the @code{backtrace} command) may
18661 @findex breakpoints-invalid
18662 @item ^Z^Zbreakpoints-invalid
18664 The breakpoints may have changed. For example, the user just added or
18665 deleted a breakpoint.
18668 @node Annotations for Running
18669 @section Running the Program
18670 @cindex annotations for running programs
18674 When the program starts executing due to a @value{GDBN} command such as
18675 @code{step} or @code{continue},
18681 is output. When the program stops,
18687 is output. Before the @code{stopped} annotation, a variety of
18688 annotations describe how the program stopped.
18692 @item ^Z^Zexited @var{exit-status}
18693 The program exited, and @var{exit-status} is the exit status (zero for
18694 successful exit, otherwise nonzero).
18697 @findex signal-name
18698 @findex signal-name-end
18699 @findex signal-string
18700 @findex signal-string-end
18701 @item ^Z^Zsignalled
18702 The program exited with a signal. After the @code{^Z^Zsignalled}, the
18703 annotation continues:
18709 ^Z^Zsignal-name-end
18713 ^Z^Zsignal-string-end
18718 where @var{name} is the name of the signal, such as @code{SIGILL} or
18719 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
18720 as @code{Illegal Instruction} or @code{Segmentation fault}.
18721 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
18722 user's benefit and have no particular format.
18726 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
18727 just saying that the program received the signal, not that it was
18728 terminated with it.
18731 @item ^Z^Zbreakpoint @var{number}
18732 The program hit breakpoint number @var{number}.
18735 @item ^Z^Zwatchpoint @var{number}
18736 The program hit watchpoint number @var{number}.
18739 @node Source Annotations
18740 @section Displaying Source
18741 @cindex annotations for source display
18744 The following annotation is used instead of displaying source code:
18747 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
18750 where @var{filename} is an absolute file name indicating which source
18751 file, @var{line} is the line number within that file (where 1 is the
18752 first line in the file), @var{character} is the character position
18753 within the file (where 0 is the first character in the file) (for most
18754 debug formats this will necessarily point to the beginning of a line),
18755 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
18756 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
18757 @var{addr} is the address in the target program associated with the
18758 source which is being displayed. @var{addr} is in the form @samp{0x}
18759 followed by one or more lowercase hex digits (note that this does not
18760 depend on the language).
18763 @chapter Reporting Bugs in @value{GDBN}
18764 @cindex bugs in @value{GDBN}
18765 @cindex reporting bugs in @value{GDBN}
18767 Your bug reports play an essential role in making @value{GDBN} reliable.
18769 Reporting a bug may help you by bringing a solution to your problem, or it
18770 may not. But in any case the principal function of a bug report is to help
18771 the entire community by making the next version of @value{GDBN} work better. Bug
18772 reports are your contribution to the maintenance of @value{GDBN}.
18774 In order for a bug report to serve its purpose, you must include the
18775 information that enables us to fix the bug.
18778 * Bug Criteria:: Have you found a bug?
18779 * Bug Reporting:: How to report bugs
18783 @section Have you found a bug?
18784 @cindex bug criteria
18786 If you are not sure whether you have found a bug, here are some guidelines:
18789 @cindex fatal signal
18790 @cindex debugger crash
18791 @cindex crash of debugger
18793 If the debugger gets a fatal signal, for any input whatever, that is a
18794 @value{GDBN} bug. Reliable debuggers never crash.
18796 @cindex error on valid input
18798 If @value{GDBN} produces an error message for valid input, that is a
18799 bug. (Note that if you're cross debugging, the problem may also be
18800 somewhere in the connection to the target.)
18802 @cindex invalid input
18804 If @value{GDBN} does not produce an error message for invalid input,
18805 that is a bug. However, you should note that your idea of
18806 ``invalid input'' might be our idea of ``an extension'' or ``support
18807 for traditional practice''.
18810 If you are an experienced user of debugging tools, your suggestions
18811 for improvement of @value{GDBN} are welcome in any case.
18814 @node Bug Reporting
18815 @section How to report bugs
18816 @cindex bug reports
18817 @cindex @value{GDBN} bugs, reporting
18819 A number of companies and individuals offer support for @sc{gnu} products.
18820 If you obtained @value{GDBN} from a support organization, we recommend you
18821 contact that organization first.
18823 You can find contact information for many support companies and
18824 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
18826 @c should add a web page ref...
18828 In any event, we also recommend that you submit bug reports for
18829 @value{GDBN}. The prefered method is to submit them directly using
18830 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
18831 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
18834 @strong{Do not send bug reports to @samp{info-gdb}, or to
18835 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
18836 not want to receive bug reports. Those that do have arranged to receive
18839 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
18840 serves as a repeater. The mailing list and the newsgroup carry exactly
18841 the same messages. Often people think of posting bug reports to the
18842 newsgroup instead of mailing them. This appears to work, but it has one
18843 problem which can be crucial: a newsgroup posting often lacks a mail
18844 path back to the sender. Thus, if we need to ask for more information,
18845 we may be unable to reach you. For this reason, it is better to send
18846 bug reports to the mailing list.
18848 The fundamental principle of reporting bugs usefully is this:
18849 @strong{report all the facts}. If you are not sure whether to state a
18850 fact or leave it out, state it!
18852 Often people omit facts because they think they know what causes the
18853 problem and assume that some details do not matter. Thus, you might
18854 assume that the name of the variable you use in an example does not matter.
18855 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
18856 stray memory reference which happens to fetch from the location where that
18857 name is stored in memory; perhaps, if the name were different, the contents
18858 of that location would fool the debugger into doing the right thing despite
18859 the bug. Play it safe and give a specific, complete example. That is the
18860 easiest thing for you to do, and the most helpful.
18862 Keep in mind that the purpose of a bug report is to enable us to fix the
18863 bug. It may be that the bug has been reported previously, but neither
18864 you nor we can know that unless your bug report is complete and
18867 Sometimes people give a few sketchy facts and ask, ``Does this ring a
18868 bell?'' Those bug reports are useless, and we urge everyone to
18869 @emph{refuse to respond to them} except to chide the sender to report
18872 To enable us to fix the bug, you should include all these things:
18876 The version of @value{GDBN}. @value{GDBN} announces it if you start
18877 with no arguments; you can also print it at any time using @code{show
18880 Without this, we will not know whether there is any point in looking for
18881 the bug in the current version of @value{GDBN}.
18884 The type of machine you are using, and the operating system name and
18888 What compiler (and its version) was used to compile @value{GDBN}---e.g.
18889 ``@value{GCC}--2.8.1''.
18892 What compiler (and its version) was used to compile the program you are
18893 debugging---e.g. ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
18894 C Compiler''. For GCC, you can say @code{gcc --version} to get this
18895 information; for other compilers, see the documentation for those
18899 The command arguments you gave the compiler to compile your example and
18900 observe the bug. For example, did you use @samp{-O}? To guarantee
18901 you will not omit something important, list them all. A copy of the
18902 Makefile (or the output from make) is sufficient.
18904 If we were to try to guess the arguments, we would probably guess wrong
18905 and then we might not encounter the bug.
18908 A complete input script, and all necessary source files, that will
18912 A description of what behavior you observe that you believe is
18913 incorrect. For example, ``It gets a fatal signal.''
18915 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
18916 will certainly notice it. But if the bug is incorrect output, we might
18917 not notice unless it is glaringly wrong. You might as well not give us
18918 a chance to make a mistake.
18920 Even if the problem you experience is a fatal signal, you should still
18921 say so explicitly. Suppose something strange is going on, such as, your
18922 copy of @value{GDBN} is out of synch, or you have encountered a bug in
18923 the C library on your system. (This has happened!) Your copy might
18924 crash and ours would not. If you told us to expect a crash, then when
18925 ours fails to crash, we would know that the bug was not happening for
18926 us. If you had not told us to expect a crash, then we would not be able
18927 to draw any conclusion from our observations.
18930 @cindex recording a session script
18931 To collect all this information, you can use a session recording program
18932 such as @command{script}, which is available on many Unix systems.
18933 Just run your @value{GDBN} session inside @command{script} and then
18934 include the @file{typescript} file with your bug report.
18936 Another way to record a @value{GDBN} session is to run @value{GDBN}
18937 inside Emacs and then save the entire buffer to a file.
18940 If you wish to suggest changes to the @value{GDBN} source, send us context
18941 diffs. If you even discuss something in the @value{GDBN} source, refer to
18942 it by context, not by line number.
18944 The line numbers in our development sources will not match those in your
18945 sources. Your line numbers would convey no useful information to us.
18949 Here are some things that are not necessary:
18953 A description of the envelope of the bug.
18955 Often people who encounter a bug spend a lot of time investigating
18956 which changes to the input file will make the bug go away and which
18957 changes will not affect it.
18959 This is often time consuming and not very useful, because the way we
18960 will find the bug is by running a single example under the debugger
18961 with breakpoints, not by pure deduction from a series of examples.
18962 We recommend that you save your time for something else.
18964 Of course, if you can find a simpler example to report @emph{instead}
18965 of the original one, that is a convenience for us. Errors in the
18966 output will be easier to spot, running under the debugger will take
18967 less time, and so on.
18969 However, simplification is not vital; if you do not want to do this,
18970 report the bug anyway and send us the entire test case you used.
18973 A patch for the bug.
18975 A patch for the bug does help us if it is a good one. But do not omit
18976 the necessary information, such as the test case, on the assumption that
18977 a patch is all we need. We might see problems with your patch and decide
18978 to fix the problem another way, or we might not understand it at all.
18980 Sometimes with a program as complicated as @value{GDBN} it is very hard to
18981 construct an example that will make the program follow a certain path
18982 through the code. If you do not send us the example, we will not be able
18983 to construct one, so we will not be able to verify that the bug is fixed.
18985 And if we cannot understand what bug you are trying to fix, or why your
18986 patch should be an improvement, we will not install it. A test case will
18987 help us to understand.
18990 A guess about what the bug is or what it depends on.
18992 Such guesses are usually wrong. Even we cannot guess right about such
18993 things without first using the debugger to find the facts.
18996 @c The readline documentation is distributed with the readline code
18997 @c and consists of the two following files:
18999 @c inc-hist.texinfo
19000 @c Use -I with makeinfo to point to the appropriate directory,
19001 @c environment var TEXINPUTS with TeX.
19002 @include rluser.texinfo
19003 @include inc-hist.texinfo
19006 @node Formatting Documentation
19007 @appendix Formatting Documentation
19009 @cindex @value{GDBN} reference card
19010 @cindex reference card
19011 The @value{GDBN} 4 release includes an already-formatted reference card, ready
19012 for printing with PostScript or Ghostscript, in the @file{gdb}
19013 subdirectory of the main source directory@footnote{In
19014 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
19015 release.}. If you can use PostScript or Ghostscript with your printer,
19016 you can print the reference card immediately with @file{refcard.ps}.
19018 The release also includes the source for the reference card. You
19019 can format it, using @TeX{}, by typing:
19025 The @value{GDBN} reference card is designed to print in @dfn{landscape}
19026 mode on US ``letter'' size paper;
19027 that is, on a sheet 11 inches wide by 8.5 inches
19028 high. You will need to specify this form of printing as an option to
19029 your @sc{dvi} output program.
19031 @cindex documentation
19033 All the documentation for @value{GDBN} comes as part of the machine-readable
19034 distribution. The documentation is written in Texinfo format, which is
19035 a documentation system that uses a single source file to produce both
19036 on-line information and a printed manual. You can use one of the Info
19037 formatting commands to create the on-line version of the documentation
19038 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
19040 @value{GDBN} includes an already formatted copy of the on-line Info
19041 version of this manual in the @file{gdb} subdirectory. The main Info
19042 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
19043 subordinate files matching @samp{gdb.info*} in the same directory. If
19044 necessary, you can print out these files, or read them with any editor;
19045 but they are easier to read using the @code{info} subsystem in @sc{gnu}
19046 Emacs or the standalone @code{info} program, available as part of the
19047 @sc{gnu} Texinfo distribution.
19049 If you want to format these Info files yourself, you need one of the
19050 Info formatting programs, such as @code{texinfo-format-buffer} or
19053 If you have @code{makeinfo} installed, and are in the top level
19054 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
19055 version @value{GDBVN}), you can make the Info file by typing:
19062 If you want to typeset and print copies of this manual, you need @TeX{},
19063 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
19064 Texinfo definitions file.
19066 @TeX{} is a typesetting program; it does not print files directly, but
19067 produces output files called @sc{dvi} files. To print a typeset
19068 document, you need a program to print @sc{dvi} files. If your system
19069 has @TeX{} installed, chances are it has such a program. The precise
19070 command to use depends on your system; @kbd{lpr -d} is common; another
19071 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
19072 require a file name without any extension or a @samp{.dvi} extension.
19074 @TeX{} also requires a macro definitions file called
19075 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
19076 written in Texinfo format. On its own, @TeX{} cannot either read or
19077 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
19078 and is located in the @file{gdb-@var{version-number}/texinfo}
19081 If you have @TeX{} and a @sc{dvi} printer program installed, you can
19082 typeset and print this manual. First switch to the the @file{gdb}
19083 subdirectory of the main source directory (for example, to
19084 @file{gdb-@value{GDBVN}/gdb}) and type:
19090 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
19092 @node Installing GDB
19093 @appendix Installing @value{GDBN}
19094 @cindex configuring @value{GDBN}
19095 @cindex installation
19096 @cindex configuring @value{GDBN}, and source tree subdirectories
19098 @value{GDBN} comes with a @code{configure} script that automates the process
19099 of preparing @value{GDBN} for installation; you can then use @code{make} to
19100 build the @code{gdb} program.
19102 @c irrelevant in info file; it's as current as the code it lives with.
19103 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
19104 look at the @file{README} file in the sources; we may have improved the
19105 installation procedures since publishing this manual.}
19108 The @value{GDBN} distribution includes all the source code you need for
19109 @value{GDBN} in a single directory, whose name is usually composed by
19110 appending the version number to @samp{gdb}.
19112 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
19113 @file{gdb-@value{GDBVN}} directory. That directory contains:
19116 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
19117 script for configuring @value{GDBN} and all its supporting libraries
19119 @item gdb-@value{GDBVN}/gdb
19120 the source specific to @value{GDBN} itself
19122 @item gdb-@value{GDBVN}/bfd
19123 source for the Binary File Descriptor library
19125 @item gdb-@value{GDBVN}/include
19126 @sc{gnu} include files
19128 @item gdb-@value{GDBVN}/libiberty
19129 source for the @samp{-liberty} free software library
19131 @item gdb-@value{GDBVN}/opcodes
19132 source for the library of opcode tables and disassemblers
19134 @item gdb-@value{GDBVN}/readline
19135 source for the @sc{gnu} command-line interface
19137 @item gdb-@value{GDBVN}/glob
19138 source for the @sc{gnu} filename pattern-matching subroutine
19140 @item gdb-@value{GDBVN}/mmalloc
19141 source for the @sc{gnu} memory-mapped malloc package
19144 The simplest way to configure and build @value{GDBN} is to run @code{configure}
19145 from the @file{gdb-@var{version-number}} source directory, which in
19146 this example is the @file{gdb-@value{GDBVN}} directory.
19148 First switch to the @file{gdb-@var{version-number}} source directory
19149 if you are not already in it; then run @code{configure}. Pass the
19150 identifier for the platform on which @value{GDBN} will run as an
19156 cd gdb-@value{GDBVN}
19157 ./configure @var{host}
19162 where @var{host} is an identifier such as @samp{sun4} or
19163 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
19164 (You can often leave off @var{host}; @code{configure} tries to guess the
19165 correct value by examining your system.)
19167 Running @samp{configure @var{host}} and then running @code{make} builds the
19168 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
19169 libraries, then @code{gdb} itself. The configured source files, and the
19170 binaries, are left in the corresponding source directories.
19173 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
19174 system does not recognize this automatically when you run a different
19175 shell, you may need to run @code{sh} on it explicitly:
19178 sh configure @var{host}
19181 If you run @code{configure} from a directory that contains source
19182 directories for multiple libraries or programs, such as the
19183 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
19184 creates configuration files for every directory level underneath (unless
19185 you tell it not to, with the @samp{--norecursion} option).
19187 You should run the @code{configure} script from the top directory in the
19188 source tree, the @file{gdb-@var{version-number}} directory. If you run
19189 @code{configure} from one of the subdirectories, you will configure only
19190 that subdirectory. That is usually not what you want. In particular,
19191 if you run the first @code{configure} from the @file{gdb} subdirectory
19192 of the @file{gdb-@var{version-number}} directory, you will omit the
19193 configuration of @file{bfd}, @file{readline}, and other sibling
19194 directories of the @file{gdb} subdirectory. This leads to build errors
19195 about missing include files such as @file{bfd/bfd.h}.
19197 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
19198 However, you should make sure that the shell on your path (named by
19199 the @samp{SHELL} environment variable) is publicly readable. Remember
19200 that @value{GDBN} uses the shell to start your program---some systems refuse to
19201 let @value{GDBN} debug child processes whose programs are not readable.
19204 * Separate Objdir:: Compiling @value{GDBN} in another directory
19205 * Config Names:: Specifying names for hosts and targets
19206 * Configure Options:: Summary of options for configure
19209 @node Separate Objdir
19210 @section Compiling @value{GDBN} in another directory
19212 If you want to run @value{GDBN} versions for several host or target machines,
19213 you need a different @code{gdb} compiled for each combination of
19214 host and target. @code{configure} is designed to make this easy by
19215 allowing you to generate each configuration in a separate subdirectory,
19216 rather than in the source directory. If your @code{make} program
19217 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
19218 @code{make} in each of these directories builds the @code{gdb}
19219 program specified there.
19221 To build @code{gdb} in a separate directory, run @code{configure}
19222 with the @samp{--srcdir} option to specify where to find the source.
19223 (You also need to specify a path to find @code{configure}
19224 itself from your working directory. If the path to @code{configure}
19225 would be the same as the argument to @samp{--srcdir}, you can leave out
19226 the @samp{--srcdir} option; it is assumed.)
19228 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
19229 separate directory for a Sun 4 like this:
19233 cd gdb-@value{GDBVN}
19236 ../gdb-@value{GDBVN}/configure sun4
19241 When @code{configure} builds a configuration using a remote source
19242 directory, it creates a tree for the binaries with the same structure
19243 (and using the same names) as the tree under the source directory. In
19244 the example, you'd find the Sun 4 library @file{libiberty.a} in the
19245 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
19246 @file{gdb-sun4/gdb}.
19248 Make sure that your path to the @file{configure} script has just one
19249 instance of @file{gdb} in it. If your path to @file{configure} looks
19250 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
19251 one subdirectory of @value{GDBN}, not the whole package. This leads to
19252 build errors about missing include files such as @file{bfd/bfd.h}.
19254 One popular reason to build several @value{GDBN} configurations in separate
19255 directories is to configure @value{GDBN} for cross-compiling (where
19256 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
19257 programs that run on another machine---the @dfn{target}).
19258 You specify a cross-debugging target by
19259 giving the @samp{--target=@var{target}} option to @code{configure}.
19261 When you run @code{make} to build a program or library, you must run
19262 it in a configured directory---whatever directory you were in when you
19263 called @code{configure} (or one of its subdirectories).
19265 The @code{Makefile} that @code{configure} generates in each source
19266 directory also runs recursively. If you type @code{make} in a source
19267 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
19268 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
19269 will build all the required libraries, and then build GDB.
19271 When you have multiple hosts or targets configured in separate
19272 directories, you can run @code{make} on them in parallel (for example,
19273 if they are NFS-mounted on each of the hosts); they will not interfere
19277 @section Specifying names for hosts and targets
19279 The specifications used for hosts and targets in the @code{configure}
19280 script are based on a three-part naming scheme, but some short predefined
19281 aliases are also supported. The full naming scheme encodes three pieces
19282 of information in the following pattern:
19285 @var{architecture}-@var{vendor}-@var{os}
19288 For example, you can use the alias @code{sun4} as a @var{host} argument,
19289 or as the value for @var{target} in a @code{--target=@var{target}}
19290 option. The equivalent full name is @samp{sparc-sun-sunos4}.
19292 The @code{configure} script accompanying @value{GDBN} does not provide
19293 any query facility to list all supported host and target names or
19294 aliases. @code{configure} calls the Bourne shell script
19295 @code{config.sub} to map abbreviations to full names; you can read the
19296 script, if you wish, or you can use it to test your guesses on
19297 abbreviations---for example:
19300 % sh config.sub i386-linux
19302 % sh config.sub alpha-linux
19303 alpha-unknown-linux-gnu
19304 % sh config.sub hp9k700
19306 % sh config.sub sun4
19307 sparc-sun-sunos4.1.1
19308 % sh config.sub sun3
19309 m68k-sun-sunos4.1.1
19310 % sh config.sub i986v
19311 Invalid configuration `i986v': machine `i986v' not recognized
19315 @code{config.sub} is also distributed in the @value{GDBN} source
19316 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
19318 @node Configure Options
19319 @section @code{configure} options
19321 Here is a summary of the @code{configure} options and arguments that
19322 are most often useful for building @value{GDBN}. @code{configure} also has
19323 several other options not listed here. @inforef{What Configure
19324 Does,,configure.info}, for a full explanation of @code{configure}.
19327 configure @r{[}--help@r{]}
19328 @r{[}--prefix=@var{dir}@r{]}
19329 @r{[}--exec-prefix=@var{dir}@r{]}
19330 @r{[}--srcdir=@var{dirname}@r{]}
19331 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
19332 @r{[}--target=@var{target}@r{]}
19337 You may introduce options with a single @samp{-} rather than
19338 @samp{--} if you prefer; but you may abbreviate option names if you use
19343 Display a quick summary of how to invoke @code{configure}.
19345 @item --prefix=@var{dir}
19346 Configure the source to install programs and files under directory
19349 @item --exec-prefix=@var{dir}
19350 Configure the source to install programs under directory
19353 @c avoid splitting the warning from the explanation:
19355 @item --srcdir=@var{dirname}
19356 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
19357 @code{make} that implements the @code{VPATH} feature.}@*
19358 Use this option to make configurations in directories separate from the
19359 @value{GDBN} source directories. Among other things, you can use this to
19360 build (or maintain) several configurations simultaneously, in separate
19361 directories. @code{configure} writes configuration specific files in
19362 the current directory, but arranges for them to use the source in the
19363 directory @var{dirname}. @code{configure} creates directories under
19364 the working directory in parallel to the source directories below
19367 @item --norecursion
19368 Configure only the directory level where @code{configure} is executed; do not
19369 propagate configuration to subdirectories.
19371 @item --target=@var{target}
19372 Configure @value{GDBN} for cross-debugging programs running on the specified
19373 @var{target}. Without this option, @value{GDBN} is configured to debug
19374 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
19376 There is no convenient way to generate a list of all available targets.
19378 @item @var{host} @dots{}
19379 Configure @value{GDBN} to run on the specified @var{host}.
19381 There is no convenient way to generate a list of all available hosts.
19384 There are many other options available as well, but they are generally
19385 needed for special purposes only.
19387 @node Maintenance Commands
19388 @appendix Maintenance Commands
19389 @cindex maintenance commands
19390 @cindex internal commands
19392 In addition to commands intended for @value{GDBN} users, @value{GDBN}
19393 includes a number of commands intended for @value{GDBN} developers.
19394 These commands are provided here for reference.
19397 @kindex maint info breakpoints
19398 @item @anchor{maint info breakpoints}maint info breakpoints
19399 Using the same format as @samp{info breakpoints}, display both the
19400 breakpoints you've set explicitly, and those @value{GDBN} is using for
19401 internal purposes. Internal breakpoints are shown with negative
19402 breakpoint numbers. The type column identifies what kind of breakpoint
19407 Normal, explicitly set breakpoint.
19410 Normal, explicitly set watchpoint.
19413 Internal breakpoint, used to handle correctly stepping through
19414 @code{longjmp} calls.
19416 @item longjmp resume
19417 Internal breakpoint at the target of a @code{longjmp}.
19420 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
19423 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
19426 Shared library events.
19430 @kindex maint internal-error
19431 @kindex maint internal-warning
19432 @item maint internal-error
19433 @itemx maint internal-warning
19434 Cause @value{GDBN} to call the internal function @code{internal_error}
19435 or @code{internal_warning} and hence behave as though an internal error
19436 or internal warning has been detected. In addition to reporting the
19437 internal problem, these functions give the user the opportunity to
19438 either quit @value{GDBN} or create a core file of the current
19439 @value{GDBN} session.
19442 (gdb) @kbd{maint internal-error testing, 1, 2}
19443 @dots{}/maint.c:121: internal-error: testing, 1, 2
19444 A problem internal to GDB has been detected. Further
19445 debugging may prove unreliable.
19446 Quit this debugging session? (y or n) @kbd{n}
19447 Create a core file? (y or n) @kbd{n}
19451 Takes an optional parameter that is used as the text of the error or
19454 @kindex maint print dummy-frames
19455 @item maint print dummy-frames
19457 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
19462 (gdb) @kbd{print add(2,3)}
19463 Breakpoint 2, add (a=2, b=3) at @dots{}
19465 The program being debugged stopped while in a function called from GDB.
19467 (gdb) @kbd{maint print dummy-frames}
19468 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
19469 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
19470 call_lo=0x01014000 call_hi=0x01014001
19474 Takes an optional file parameter.
19476 @kindex maint print registers
19477 @kindex maint print raw-registers
19478 @kindex maint print cooked-registers
19479 @kindex maint print register-groups
19480 @item maint print registers
19481 @itemx maint print raw-registers
19482 @itemx maint print cooked-registers
19483 @itemx maint print register-groups
19484 Print @value{GDBN}'s internal register data structures.
19486 The command @code{maint print raw-registers} includes the contents of
19487 the raw register cache; the command @code{maint print cooked-registers}
19488 includes the (cooked) value of all registers; and the command
19489 @code{maint print register-groups} includes the groups that each
19490 register is a member of. @xref{Registers,, Registers, gdbint,
19491 @value{GDBN} Internals}.
19493 Takes an optional file parameter.
19495 @kindex maint print reggroups
19496 @item maint print reggroups
19497 Print @value{GDBN}'s internal register group data structures.
19499 Takes an optional file parameter.
19502 (gdb) @kbd{maint print reggroups}
19513 @kindex maint set profile
19514 @kindex maint show profile
19515 @cindex profiling GDB
19516 @item maint set profile
19517 @itemx maint show profile
19518 Control profiling of @value{GDBN}.
19520 Profiling will be disabled until you use the @samp{maint set profile}
19521 command to enable it. When you enable profiling, the system will begin
19522 collecting timing and execution count data; when you disable profiling or
19523 exit @value{GDBN}, the results will be written to a log file. Remember that
19524 if you use profiling, @value{GDBN} will overwrite the profiling log file
19525 (often called @file{gmon.out}). If you have a record of important profiling
19526 data in a @file{gmon.out} file, be sure to move it to a safe location.
19528 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
19529 compiled with the @samp{-pg} compiler option.
19534 @node Remote Protocol
19535 @appendix @value{GDBN} Remote Serial Protocol
19540 * Stop Reply Packets::
19541 * General Query Packets::
19542 * Register Packet Format::
19544 * File-I/O remote protocol extension::
19550 There may be occasions when you need to know something about the
19551 protocol---for example, if there is only one serial port to your target
19552 machine, you might want your program to do something special if it
19553 recognizes a packet meant for @value{GDBN}.
19555 In the examples below, @samp{->} and @samp{<-} are used to indicate
19556 transmitted and received data respectfully.
19558 @cindex protocol, @value{GDBN} remote serial
19559 @cindex serial protocol, @value{GDBN} remote
19560 @cindex remote serial protocol
19561 All @value{GDBN} commands and responses (other than acknowledgments) are
19562 sent as a @var{packet}. A @var{packet} is introduced with the character
19563 @samp{$}, the actual @var{packet-data}, and the terminating character
19564 @samp{#} followed by a two-digit @var{checksum}:
19567 @code{$}@var{packet-data}@code{#}@var{checksum}
19571 @cindex checksum, for @value{GDBN} remote
19573 The two-digit @var{checksum} is computed as the modulo 256 sum of all
19574 characters between the leading @samp{$} and the trailing @samp{#} (an
19575 eight bit unsigned checksum).
19577 Implementors should note that prior to @value{GDBN} 5.0 the protocol
19578 specification also included an optional two-digit @var{sequence-id}:
19581 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
19584 @cindex sequence-id, for @value{GDBN} remote
19586 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
19587 has never output @var{sequence-id}s. Stubs that handle packets added
19588 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
19590 @cindex acknowledgment, for @value{GDBN} remote
19591 When either the host or the target machine receives a packet, the first
19592 response expected is an acknowledgment: either @samp{+} (to indicate
19593 the package was received correctly) or @samp{-} (to request
19597 -> @code{$}@var{packet-data}@code{#}@var{checksum}
19602 The host (@value{GDBN}) sends @var{command}s, and the target (the
19603 debugging stub incorporated in your program) sends a @var{response}. In
19604 the case of step and continue @var{command}s, the response is only sent
19605 when the operation has completed (the target has again stopped).
19607 @var{packet-data} consists of a sequence of characters with the
19608 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
19611 Fields within the packet should be separated using @samp{,} @samp{;} or
19612 @cindex remote protocol, field separator
19613 @samp{:}. Except where otherwise noted all numbers are represented in
19614 @sc{hex} with leading zeros suppressed.
19616 Implementors should note that prior to @value{GDBN} 5.0, the character
19617 @samp{:} could not appear as the third character in a packet (as it
19618 would potentially conflict with the @var{sequence-id}).
19620 Response @var{data} can be run-length encoded to save space. A @samp{*}
19621 means that the next character is an @sc{ascii} encoding giving a repeat count
19622 which stands for that many repetitions of the character preceding the
19623 @samp{*}. The encoding is @code{n+29}, yielding a printable character
19624 where @code{n >=3} (which is where rle starts to win). The printable
19625 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
19626 value greater than 126 should not be used.
19633 means the same as "0000".
19635 The error response returned for some packets includes a two character
19636 error number. That number is not well defined.
19638 For any @var{command} not supported by the stub, an empty response
19639 (@samp{$#00}) should be returned. That way it is possible to extend the
19640 protocol. A newer @value{GDBN} can tell if a packet is supported based
19643 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
19644 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
19650 The following table provides a complete list of all currently defined
19651 @var{command}s and their corresponding response @var{data}.
19655 @item @code{!} --- extended mode
19656 @cindex @code{!} packet
19658 Enable extended mode. In extended mode, the remote server is made
19659 persistent. The @samp{R} packet is used to restart the program being
19665 The remote target both supports and has enabled extended mode.
19668 @item @code{?} --- last signal
19669 @cindex @code{?} packet
19671 Indicate the reason the target halted. The reply is the same as for
19675 @xref{Stop Reply Packets}, for the reply specifications.
19677 @item @code{a} --- reserved
19679 Reserved for future use.
19681 @item @code{A}@var{arglen}@code{,}@var{argnum}@code{,}@var{arg}@code{,@dots{}} --- set program arguments @strong{(reserved)}
19682 @cindex @code{A} packet
19684 Initialized @samp{argv[]} array passed into program. @var{arglen}
19685 specifies the number of bytes in the hex encoded byte stream @var{arg}.
19686 See @code{gdbserver} for more details.
19694 @item @code{b}@var{baud} --- set baud @strong{(deprecated)}
19695 @cindex @code{b} packet
19697 Change the serial line speed to @var{baud}.
19699 JTC: @emph{When does the transport layer state change? When it's
19700 received, or after the ACK is transmitted. In either case, there are
19701 problems if the command or the acknowledgment packet is dropped.}
19703 Stan: @emph{If people really wanted to add something like this, and get
19704 it working for the first time, they ought to modify ser-unix.c to send
19705 some kind of out-of-band message to a specially-setup stub and have the
19706 switch happen "in between" packets, so that from remote protocol's point
19707 of view, nothing actually happened.}
19709 @item @code{B}@var{addr},@var{mode} --- set breakpoint @strong{(deprecated)}
19710 @cindex @code{B} packet
19712 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
19713 breakpoint at @var{addr}.
19715 This packet has been replaced by the @samp{Z} and @samp{z} packets
19716 (@pxref{insert breakpoint or watchpoint packet}).
19718 @item @code{c}@var{addr} --- continue
19719 @cindex @code{c} packet
19721 @var{addr} is address to resume. If @var{addr} is omitted, resume at
19725 @xref{Stop Reply Packets}, for the reply specifications.
19727 @item @code{C}@var{sig}@code{;}@var{addr} --- continue with signal
19728 @cindex @code{C} packet
19730 Continue with signal @var{sig} (hex signal number). If
19731 @code{;}@var{addr} is omitted, resume at same address.
19734 @xref{Stop Reply Packets}, for the reply specifications.
19736 @item @code{d} --- toggle debug @strong{(deprecated)}
19737 @cindex @code{d} packet
19741 @item @code{D} --- detach
19742 @cindex @code{D} packet
19744 Detach @value{GDBN} from the remote system. Sent to the remote target
19745 before @value{GDBN} disconnects via the @code{detach} command.
19749 @item @emph{no response}
19750 @value{GDBN} does not check for any response after sending this packet.
19753 @item @code{e} --- reserved
19755 Reserved for future use.
19757 @item @code{E} --- reserved
19759 Reserved for future use.
19761 @item @code{f} --- reserved
19763 Reserved for future use.
19765 @item @code{F}@var{RC}@code{,}@var{EE}@code{,}@var{CF}@code{;}@var{XX} --- Reply to target's F packet.
19766 @cindex @code{F} packet
19768 This packet is send by @value{GDBN} as reply to a @code{F} request packet
19769 sent by the target. This is part of the File-I/O protocol extension.
19770 @xref{File-I/O remote protocol extension}, for the specification.
19772 @item @code{g} --- read registers
19773 @anchor{read registers packet}
19774 @cindex @code{g} packet
19776 Read general registers.
19780 @item @var{XX@dots{}}
19781 Each byte of register data is described by two hex digits. The bytes
19782 with the register are transmitted in target byte order. The size of
19783 each register and their position within the @samp{g} @var{packet} are
19784 determined by the @value{GDBN} internal macros
19785 @var{DEPRECATED_REGISTER_RAW_SIZE} and @var{REGISTER_NAME} macros. The
19786 specification of several standard @code{g} packets is specified below.
19791 @item @code{G}@var{XX@dots{}} --- write regs
19792 @cindex @code{G} packet
19794 @xref{read registers packet}, for a description of the @var{XX@dots{}}
19805 @item @code{h} --- reserved
19807 Reserved for future use.
19809 @item @code{H}@var{c}@var{t@dots{}} --- set thread
19810 @cindex @code{H} packet
19812 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
19813 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
19814 should be @samp{c} for step and continue operations, @samp{g} for other
19815 operations. The thread designator @var{t@dots{}} may be -1, meaning all
19816 the threads, a thread number, or zero which means pick any thread.
19827 @c 'H': How restrictive (or permissive) is the thread model. If a
19828 @c thread is selected and stopped, are other threads allowed
19829 @c to continue to execute? As I mentioned above, I think the
19830 @c semantics of each command when a thread is selected must be
19831 @c described. For example:
19833 @c 'g': If the stub supports threads and a specific thread is
19834 @c selected, returns the register block from that thread;
19835 @c otherwise returns current registers.
19837 @c 'G' If the stub supports threads and a specific thread is
19838 @c selected, sets the registers of the register block of
19839 @c that thread; otherwise sets current registers.
19841 @item @code{i}@var{addr}@code{,}@var{nnn} --- cycle step @strong{(draft)}
19842 @anchor{cycle step packet}
19843 @cindex @code{i} packet
19845 Step the remote target by a single clock cycle. If @code{,}@var{nnn} is
19846 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
19847 step starting at that address.
19849 @item @code{I} --- signal then cycle step @strong{(reserved)}
19850 @cindex @code{I} packet
19852 @xref{step with signal packet}. @xref{cycle step packet}.
19854 @item @code{j} --- reserved
19856 Reserved for future use.
19858 @item @code{J} --- reserved
19860 Reserved for future use.
19862 @item @code{k} --- kill request
19863 @cindex @code{k} packet
19865 FIXME: @emph{There is no description of how to operate when a specific
19866 thread context has been selected (i.e.@: does 'k' kill only that
19869 @item @code{K} --- reserved
19871 Reserved for future use.
19873 @item @code{l} --- reserved
19875 Reserved for future use.
19877 @item @code{L} --- reserved
19879 Reserved for future use.
19881 @item @code{m}@var{addr}@code{,}@var{length} --- read memory
19882 @cindex @code{m} packet
19884 Read @var{length} bytes of memory starting at address @var{addr}.
19885 Neither @value{GDBN} nor the stub assume that sized memory transfers are
19886 assumed using word aligned accesses. FIXME: @emph{A word aligned memory
19887 transfer mechanism is needed.}
19891 @item @var{XX@dots{}}
19892 @var{XX@dots{}} is mem contents. Can be fewer bytes than requested if able
19893 to read only part of the data. Neither @value{GDBN} nor the stub assume
19894 that sized memory transfers are assumed using word aligned
19895 accesses. FIXME: @emph{A word aligned memory transfer mechanism is
19901 @item @code{M}@var{addr},@var{length}@code{:}@var{XX@dots{}} --- write mem
19902 @cindex @code{M} packet
19904 Write @var{length} bytes of memory starting at address @var{addr}.
19905 @var{XX@dots{}} is the data.
19912 for an error (this includes the case where only part of the data was
19916 @item @code{n} --- reserved
19918 Reserved for future use.
19920 @item @code{N} --- reserved
19922 Reserved for future use.
19924 @item @code{o} --- reserved
19926 Reserved for future use.
19928 @item @code{O} --- reserved
19930 Reserved for future use.
19932 @item @code{p}@var{n@dots{}} --- read reg @strong{(reserved)}
19933 @cindex @code{p} packet
19935 @xref{write register packet}.
19939 @item @var{r@dots{}.}
19940 The hex encoded value of the register in target byte order.
19943 @item @code{P}@var{n@dots{}}@code{=}@var{r@dots{}} --- write register
19944 @anchor{write register packet}
19945 @cindex @code{P} packet
19947 Write register @var{n@dots{}} with value @var{r@dots{}}, which contains two hex
19948 digits for each byte in the register (target byte order).
19958 @item @code{q}@var{query} --- general query
19959 @anchor{general query packet}
19960 @cindex @code{q} packet
19962 Request info about @var{query}. In general @value{GDBN} queries have a
19963 leading upper case letter. Custom vendor queries should use a company
19964 prefix (in lower case) ex: @samp{qfsf.var}. @var{query} may optionally
19965 be followed by a @samp{,} or @samp{;} separated list. Stubs must ensure
19966 that they match the full @var{query} name.
19970 @item @var{XX@dots{}}
19971 Hex encoded data from query. The reply can not be empty.
19975 Indicating an unrecognized @var{query}.
19978 @item @code{Q}@var{var}@code{=}@var{val} --- general set
19979 @cindex @code{Q} packet
19981 Set value of @var{var} to @var{val}.
19983 @xref{general query packet}, for a discussion of naming conventions.
19985 @item @code{r} --- reset @strong{(deprecated)}
19986 @cindex @code{r} packet
19988 Reset the entire system.
19990 @item @code{R}@var{XX} --- remote restart
19991 @cindex @code{R} packet
19993 Restart the program being debugged. @var{XX}, while needed, is ignored.
19994 This packet is only available in extended mode.
19998 @item @emph{no reply}
19999 The @samp{R} packet has no reply.
20002 @item @code{s}@var{addr} --- step
20003 @cindex @code{s} packet
20005 @var{addr} is address to resume. If @var{addr} is omitted, resume at
20009 @xref{Stop Reply Packets}, for the reply specifications.
20011 @item @code{S}@var{sig}@code{;}@var{addr} --- step with signal
20012 @anchor{step with signal packet}
20013 @cindex @code{S} packet
20015 Like @samp{C} but step not continue.
20018 @xref{Stop Reply Packets}, for the reply specifications.
20020 @item @code{t}@var{addr}@code{:}@var{PP}@code{,}@var{MM} --- search
20021 @cindex @code{t} packet
20023 Search backwards starting at address @var{addr} for a match with pattern
20024 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
20025 @var{addr} must be at least 3 digits.
20027 @item @code{T}@var{XX} --- thread alive
20028 @cindex @code{T} packet
20030 Find out if the thread XX is alive.
20035 thread is still alive
20040 @item @code{u} --- reserved
20042 Reserved for future use.
20044 @item @code{U} --- reserved
20046 Reserved for future use.
20048 @item @code{v} --- verbose packet prefix
20050 Packets starting with @code{v} are identified by a multi-letter name,
20051 up to the first @code{;} or @code{?} (or the end of the packet).
20053 @item @code{vCont}[;@var{action}[@code{:}@var{tid}]]... --- extended resume
20054 @cindex @code{vCont} packet
20056 Resume the inferior. Different actions may be specified for each thread.
20057 If an action is specified with no @var{tid}, then it is applied to any
20058 threads that don't have a specific action specified; if no default action is
20059 specified then other threads should remain stopped. Specifying multiple
20060 default actions is an error; specifying no actions is also an error.
20061 Thread IDs are specified in hexadecimal. Currently supported actions are:
20067 Continue with signal @var{sig}. @var{sig} should be two hex digits.
20071 Step with signal @var{sig}. @var{sig} should be two hex digits.
20074 The optional @var{addr} argument normally associated with these packets is
20075 not supported in @code{vCont}.
20078 @xref{Stop Reply Packets}, for the reply specifications.
20080 @item @code{vCont?} --- extended resume query
20081 @cindex @code{vCont?} packet
20083 Query support for the @code{vCont} packet.
20087 @item @code{vCont}[;@var{action}]...
20088 The @code{vCont} packet is supported. Each @var{action} is a supported
20089 command in the @code{vCont} packet.
20091 The @code{vCont} packet is not supported.
20094 @item @code{V} --- reserved
20096 Reserved for future use.
20098 @item @code{w} --- reserved
20100 Reserved for future use.
20102 @item @code{W} --- reserved
20104 Reserved for future use.
20106 @item @code{x} --- reserved
20108 Reserved for future use.
20110 @item @code{X}@var{addr}@code{,}@var{length}@var{:}@var{XX@dots{}} --- write mem (binary)
20111 @cindex @code{X} packet
20113 @var{addr} is address, @var{length} is number of bytes, @var{XX@dots{}}
20114 is binary data. The characters @code{$}, @code{#}, and @code{0x7d} are
20115 escaped using @code{0x7d}.
20125 @item @code{y} --- reserved
20127 Reserved for future use.
20129 @item @code{Y} reserved
20131 Reserved for future use.
20133 @item @code{z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- remove breakpoint or watchpoint @strong{(draft)}
20134 @itemx @code{Z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- insert breakpoint or watchpoint @strong{(draft)}
20135 @anchor{insert breakpoint or watchpoint packet}
20136 @cindex @code{z} packet
20137 @cindex @code{Z} packets
20139 Insert (@code{Z}) or remove (@code{z}) a @var{type} breakpoint or
20140 watchpoint starting at address @var{address} and covering the next
20141 @var{length} bytes.
20143 Each breakpoint and watchpoint packet @var{type} is documented
20146 @emph{Implementation notes: A remote target shall return an empty string
20147 for an unrecognized breakpoint or watchpoint packet @var{type}. A
20148 remote target shall support either both or neither of a given
20149 @code{Z}@var{type}@dots{} and @code{z}@var{type}@dots{} packet pair. To
20150 avoid potential problems with duplicate packets, the operations should
20151 be implemented in an idempotent way.}
20153 @item @code{z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- remove memory breakpoint @strong{(draft)}
20154 @item @code{Z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- insert memory breakpoint @strong{(draft)}
20155 @cindex @code{z0} packet
20156 @cindex @code{Z0} packet
20158 Insert (@code{Z0}) or remove (@code{z0}) a memory breakpoint at address
20159 @code{addr} of size @code{length}.
20161 A memory breakpoint is implemented by replacing the instruction at
20162 @var{addr} with a software breakpoint or trap instruction. The
20163 @code{length} is used by targets that indicates the size of the
20164 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
20165 @sc{mips} can insert either a 2 or 4 byte breakpoint).
20167 @emph{Implementation note: It is possible for a target to copy or move
20168 code that contains memory breakpoints (e.g., when implementing
20169 overlays). The behavior of this packet, in the presence of such a
20170 target, is not defined.}
20182 @item @code{z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- remove hardware breakpoint @strong{(draft)}
20183 @item @code{Z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- insert hardware breakpoint @strong{(draft)}
20184 @cindex @code{z1} packet
20185 @cindex @code{Z1} packet
20187 Insert (@code{Z1}) or remove (@code{z1}) a hardware breakpoint at
20188 address @code{addr} of size @code{length}.
20190 A hardware breakpoint is implemented using a mechanism that is not
20191 dependant on being able to modify the target's memory.
20193 @emph{Implementation note: A hardware breakpoint is not affected by code
20206 @item @code{z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- remove write watchpoint @strong{(draft)}
20207 @item @code{Z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- insert write watchpoint @strong{(draft)}
20208 @cindex @code{z2} packet
20209 @cindex @code{Z2} packet
20211 Insert (@code{Z2}) or remove (@code{z2}) a write watchpoint.
20223 @item @code{z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- remove read watchpoint @strong{(draft)}
20224 @item @code{Z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- insert read watchpoint @strong{(draft)}
20225 @cindex @code{z3} packet
20226 @cindex @code{Z3} packet
20228 Insert (@code{Z3}) or remove (@code{z3}) a read watchpoint.
20240 @item @code{z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- remove access watchpoint @strong{(draft)}
20241 @item @code{Z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- insert access watchpoint @strong{(draft)}
20242 @cindex @code{z4} packet
20243 @cindex @code{Z4} packet
20245 Insert (@code{Z4}) or remove (@code{z4}) an access watchpoint.
20259 @node Stop Reply Packets
20260 @section Stop Reply Packets
20261 @cindex stop reply packets
20263 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
20264 receive any of the below as a reply. In the case of the @samp{C},
20265 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
20266 when the target halts. In the below the exact meaning of @samp{signal
20267 number} is poorly defined. In general one of the UNIX signal numbering
20268 conventions is used.
20273 @var{AA} is the signal number
20275 @item @code{T}@var{AA}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}
20276 @cindex @code{T} packet reply
20278 @var{AA} = two hex digit signal number; @var{n...} = register number
20279 (hex), @var{r...} = target byte ordered register contents, size defined
20280 by @code{DEPRECATED_REGISTER_RAW_SIZE}; @var{n...} = @samp{thread},
20281 @var{r...} = thread process ID, this is a hex integer; @var{n...} =
20282 (@samp{watch} | @samp{rwatch} | @samp{awatch}, @var{r...} = data
20283 address, this is a hex integer; @var{n...} = other string not starting
20284 with valid hex digit. @value{GDBN} should ignore this @var{n...},
20285 @var{r...} pair and go on to the next. This way we can extend the
20290 The process exited, and @var{AA} is the exit status. This is only
20291 applicable to certain targets.
20295 The process terminated with signal @var{AA}.
20297 @item O@var{XX@dots{}}
20299 @var{XX@dots{}} is hex encoding of @sc{ascii} data. This can happen at
20300 any time while the program is running and the debugger should continue
20301 to wait for @samp{W}, @samp{T}, etc.
20303 @item F@var{call-id}@code{,}@var{parameter@dots{}}
20305 @var{call-id} is the identifier which says which host system call should
20306 be called. This is just the name of the function. Translation into the
20307 correct system call is only applicable as it's defined in @value{GDBN}.
20308 @xref{File-I/O remote protocol extension}, for a list of implemented
20311 @var{parameter@dots{}} is a list of parameters as defined for this very
20314 The target replies with this packet when it expects @value{GDBN} to call
20315 a host system call on behalf of the target. @value{GDBN} replies with
20316 an appropriate @code{F} packet and keeps up waiting for the next reply
20317 packet from the target. The latest @samp{C}, @samp{c}, @samp{S} or
20318 @samp{s} action is expected to be continued.
20319 @xref{File-I/O remote protocol extension}, for more details.
20323 @node General Query Packets
20324 @section General Query Packets
20326 The following set and query packets have already been defined.
20330 @item @code{q}@code{C} --- current thread
20332 Return the current thread id.
20336 @item @code{QC}@var{pid}
20337 Where @var{pid} is a HEX encoded 16 bit process id.
20339 Any other reply implies the old pid.
20342 @item @code{q}@code{fThreadInfo} -- all thread ids
20344 @code{q}@code{sThreadInfo}
20346 Obtain a list of active thread ids from the target (OS). Since there
20347 may be too many active threads to fit into one reply packet, this query
20348 works iteratively: it may require more than one query/reply sequence to
20349 obtain the entire list of threads. The first query of the sequence will
20350 be the @code{qf}@code{ThreadInfo} query; subsequent queries in the
20351 sequence will be the @code{qs}@code{ThreadInfo} query.
20353 NOTE: replaces the @code{qL} query (see below).
20357 @item @code{m}@var{id}
20359 @item @code{m}@var{id},@var{id}@dots{}
20360 a comma-separated list of thread ids
20362 (lower case 'el') denotes end of list.
20365 In response to each query, the target will reply with a list of one or
20366 more thread ids, in big-endian hex, separated by commas. @value{GDBN}
20367 will respond to each reply with a request for more thread ids (using the
20368 @code{qs} form of the query), until the target responds with @code{l}
20369 (lower-case el, for @code{'last'}).
20371 @item @code{q}@code{ThreadExtraInfo}@code{,}@var{id} --- extra thread info
20373 Where @var{id} is a thread-id in big-endian hex. Obtain a printable
20374 string description of a thread's attributes from the target OS. This
20375 string may contain anything that the target OS thinks is interesting for
20376 @value{GDBN} to tell the user about the thread. The string is displayed
20377 in @value{GDBN}'s @samp{info threads} display. Some examples of
20378 possible thread extra info strings are ``Runnable'', or ``Blocked on
20383 @item @var{XX@dots{}}
20384 Where @var{XX@dots{}} is a hex encoding of @sc{ascii} data, comprising
20385 the printable string containing the extra information about the thread's
20389 @item @code{q}@code{L}@var{startflag}@var{threadcount}@var{nextthread} --- query @var{LIST} or @var{threadLIST} @strong{(deprecated)}
20391 Obtain thread information from RTOS. Where: @var{startflag} (one hex
20392 digit) is one to indicate the first query and zero to indicate a
20393 subsequent query; @var{threadcount} (two hex digits) is the maximum
20394 number of threads the response packet can contain; and @var{nextthread}
20395 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
20396 returned in the response as @var{argthread}.
20398 NOTE: this query is replaced by the @code{q}@code{fThreadInfo} query
20403 @item @code{q}@code{M}@var{count}@var{done}@var{argthread}@var{thread@dots{}}
20404 Where: @var{count} (two hex digits) is the number of threads being
20405 returned; @var{done} (one hex digit) is zero to indicate more threads
20406 and one indicates no further threads; @var{argthreadid} (eight hex
20407 digits) is @var{nextthread} from the request packet; @var{thread@dots{}}
20408 is a sequence of thread IDs from the target. @var{threadid} (eight hex
20409 digits). See @code{remote.c:parse_threadlist_response()}.
20412 @item @code{q}@code{CRC:}@var{addr}@code{,}@var{length} --- compute CRC of memory block
20416 @item @code{E}@var{NN}
20417 An error (such as memory fault)
20418 @item @code{C}@var{CRC32}
20419 A 32 bit cyclic redundancy check of the specified memory region.
20422 @item @code{q}@code{Offsets} --- query sect offs
20424 Get section offsets that the target used when re-locating the downloaded
20425 image. @emph{Note: while a @code{Bss} offset is included in the
20426 response, @value{GDBN} ignores this and instead applies the @code{Data}
20427 offset to the @code{Bss} section.}
20431 @item @code{Text=}@var{xxx}@code{;Data=}@var{yyy}@code{;Bss=}@var{zzz}
20434 @item @code{q}@code{P}@var{mode}@var{threadid} --- thread info request
20436 Returns information on @var{threadid}. Where: @var{mode} is a hex
20437 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
20444 See @code{remote.c:remote_unpack_thread_info_response()}.
20446 @item @code{q}@code{Rcmd,}@var{command} --- remote command
20448 @var{command} (hex encoded) is passed to the local interpreter for
20449 execution. Invalid commands should be reported using the output string.
20450 Before the final result packet, the target may also respond with a
20451 number of intermediate @code{O}@var{output} console output packets.
20452 @emph{Implementors should note that providing access to a stubs's
20453 interpreter may have security implications}.
20458 A command response with no output.
20460 A command response with the hex encoded output string @var{OUTPUT}.
20461 @item @code{E}@var{NN}
20462 Indicate a badly formed request.
20464 When @samp{q}@samp{Rcmd} is not recognized.
20467 @item @code{qSymbol::} --- symbol lookup
20469 Notify the target that @value{GDBN} is prepared to serve symbol lookup
20470 requests. Accept requests from the target for the values of symbols.
20475 The target does not need to look up any (more) symbols.
20476 @item @code{qSymbol:}@var{sym_name}
20477 The target requests the value of symbol @var{sym_name} (hex encoded).
20478 @value{GDBN} may provide the value by using the
20479 @code{qSymbol:}@var{sym_value}:@var{sym_name} message, described below.
20482 @item @code{qSymbol:}@var{sym_value}:@var{sym_name} --- symbol value
20484 Set the value of @var{sym_name} to @var{sym_value}.
20486 @var{sym_name} (hex encoded) is the name of a symbol whose value the
20487 target has previously requested.
20489 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
20490 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
20496 The target does not need to look up any (more) symbols.
20497 @item @code{qSymbol:}@var{sym_name}
20498 The target requests the value of a new symbol @var{sym_name} (hex
20499 encoded). @value{GDBN} will continue to supply the values of symbols
20500 (if available), until the target ceases to request them.
20503 @item @code{qPart}:@var{object}:@code{read}:@var{annex}:@var{offset},@var{length} --- read special data
20505 Read uninterpreted bytes from the target's special data area
20506 identified by the keyword @code{object}.
20507 Request @var{length} bytes starting at @var{offset} bytes into the data.
20508 The content and encoding of @var{annex} is specific to the object;
20509 it can supply additional details about what data to access.
20511 Here are the specific requests of this form defined so far.
20512 All @samp{@code{qPart}:@var{object}:@code{read}:@dots{}}
20513 requests use the same reply formats, listed below.
20516 @item @code{qPart}:@code{auxv}:@code{read}::@var{offset},@var{length}
20517 Access the target's @dfn{auxiliary vector}. @xref{Auxiliary Vector}.
20518 Note @var{annex} must be empty.
20524 The @var{offset} in the request is at the end of the data.
20525 There is no more data to be read.
20527 @item @var{XX@dots{}}
20528 Hex encoded data bytes read.
20529 This may be fewer bytes than the @var{length} in the request.
20532 The request was malformed, or @var{annex} was invalid.
20534 @item @code{E}@var{nn}
20535 The offset was invalid, or there was an error encountered reading the data.
20536 @var{nn} is a hex-encoded @code{errno} value.
20538 @item @code{""} (empty)
20539 An empty reply indicates the @var{object} or @var{annex} string was not
20540 recognized by the stub.
20543 @item @code{qPart}:@var{object}:@code{write}:@var{annex}:@var{offset}:@var{data@dots{}}
20545 Write uninterpreted bytes into the target's special data area
20546 identified by the keyword @code{object},
20547 starting at @var{offset} bytes into the data.
20548 @var{data@dots{}} is the hex-encoded data to be written.
20549 The content and encoding of @var{annex} is specific to the object;
20550 it can supply additional details about what data to access.
20552 No requests of this form are presently in use. This specification
20553 serves as a placeholder to document the common format that new
20554 specific request specifications ought to use.
20559 @var{nn} (hex encoded) is the number of bytes written.
20560 This may be fewer bytes than supplied in the request.
20563 The request was malformed, or @var{annex} was invalid.
20565 @item @code{E}@var{nn}
20566 The offset was invalid, or there was an error encountered writing the data.
20567 @var{nn} is a hex-encoded @code{errno} value.
20569 @item @code{""} (empty)
20570 An empty reply indicates the @var{object} or @var{annex} string was not
20571 recognized by the stub, or that the object does not support writing.
20574 @item @code{qPart}:@var{object}:@var{operation}:@dots{}
20575 Requests of this form may be added in the future. When a stub does
20576 not recognize the @var{object} keyword, or its support for
20577 @var{object} does not recognize the @var{operation} keyword,
20578 the stub must respond with an empty packet.
20581 @node Register Packet Format
20582 @section Register Packet Format
20584 The following @samp{g}/@samp{G} packets have previously been defined.
20585 In the below, some thirty-two bit registers are transferred as
20586 sixty-four bits. Those registers should be zero/sign extended (which?)
20587 to fill the space allocated. Register bytes are transfered in target
20588 byte order. The two nibbles within a register byte are transfered
20589 most-significant - least-significant.
20595 All registers are transfered as thirty-two bit quantities in the order:
20596 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
20597 registers; fsr; fir; fp.
20601 All registers are transfered as sixty-four bit quantities (including
20602 thirty-two bit registers such as @code{sr}). The ordering is the same
20610 Example sequence of a target being re-started. Notice how the restart
20611 does not get any direct output:
20616 @emph{target restarts}
20619 <- @code{T001:1234123412341234}
20623 Example sequence of a target being stepped by a single instruction:
20626 -> @code{G1445@dots{}}
20631 <- @code{T001:1234123412341234}
20635 <- @code{1455@dots{}}
20639 @node File-I/O remote protocol extension
20640 @section File-I/O remote protocol extension
20641 @cindex File-I/O remote protocol extension
20644 * File-I/O Overview::
20645 * Protocol basics::
20646 * The F request packet::
20647 * The F reply packet::
20648 * Memory transfer::
20649 * The Ctrl-C message::
20651 * The isatty call::
20652 * The system call::
20653 * List of supported calls::
20654 * Protocol specific representation of datatypes::
20656 * File-I/O Examples::
20659 @node File-I/O Overview
20660 @subsection File-I/O Overview
20661 @cindex file-i/o overview
20663 The File I/O remote protocol extension (short: File-I/O) allows the
20664 target to use the hosts file system and console I/O when calling various
20665 system calls. System calls on the target system are translated into a
20666 remote protocol packet to the host system which then performs the needed
20667 actions and returns with an adequate response packet to the target system.
20668 This simulates file system operations even on targets that lack file systems.
20670 The protocol is defined host- and target-system independent. It uses
20671 it's own independent representation of datatypes and values. Both,
20672 @value{GDBN} and the target's @value{GDBN} stub are responsible for
20673 translating the system dependent values into the unified protocol values
20674 when data is transmitted.
20676 The communication is synchronous. A system call is possible only
20677 when GDB is waiting for the @samp{C}, @samp{c}, @samp{S} or @samp{s}
20678 packets. While @value{GDBN} handles the request for a system call,
20679 the target is stopped to allow deterministic access to the target's
20680 memory. Therefore File-I/O is not interuptible by target signals. It
20681 is possible to interrupt File-I/O by a user interrupt (Ctrl-C), though.
20683 The target's request to perform a host system call does not finish
20684 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
20685 after finishing the system call, the target returns to continuing the
20686 previous activity (continue, step). No additional continue or step
20687 request from @value{GDBN} is required.
20691 <- target requests 'system call X'
20692 target is stopped, @value{GDBN} executes system call
20693 -> GDB returns result
20694 ... target continues, GDB returns to wait for the target
20695 <- target hits breakpoint and sends a Txx packet
20698 The protocol is only used for files on the host file system and
20699 for I/O on the console. Character or block special devices, pipes,
20700 named pipes or sockets or any other communication method on the host
20701 system are not supported by this protocol.
20703 @node Protocol basics
20704 @subsection Protocol basics
20705 @cindex protocol basics, file-i/o
20707 The File-I/O protocol uses the @code{F} packet, as request as well
20708 as as reply packet. Since a File-I/O system call can only occur when
20709 @value{GDBN} is waiting for the continuing or stepping target, the
20710 File-I/O request is a reply that @value{GDBN} has to expect as a result
20711 of a former @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
20712 This @code{F} packet contains all information needed to allow @value{GDBN}
20713 to call the appropriate host system call:
20717 A unique identifier for the requested system call.
20720 All parameters to the system call. Pointers are given as addresses
20721 in the target memory address space. Pointers to strings are given as
20722 pointer/length pair. Numerical values are given as they are.
20723 Numerical control values are given in a protocol specific representation.
20727 At that point @value{GDBN} has to perform the following actions.
20731 If parameter pointer values are given, which point to data needed as input
20732 to a system call, @value{GDBN} requests this data from the target with a
20733 standard @code{m} packet request. This additional communication has to be
20734 expected by the target implementation and is handled as any other @code{m}
20738 @value{GDBN} translates all value from protocol representation to host
20739 representation as needed. Datatypes are coerced into the host types.
20742 @value{GDBN} calls the system call
20745 It then coerces datatypes back to protocol representation.
20748 If pointer parameters in the request packet point to buffer space in which
20749 a system call is expected to copy data to, the data is transmitted to the
20750 target using a @code{M} or @code{X} packet. This packet has to be expected
20751 by the target implementation and is handled as any other @code{M} or @code{X}
20756 Eventually @value{GDBN} replies with another @code{F} packet which contains all
20757 necessary information for the target to continue. This at least contains
20764 @code{errno}, if has been changed by the system call.
20771 After having done the needed type and value coercion, the target continues
20772 the latest continue or step action.
20774 @node The F request packet
20775 @subsection The @code{F} request packet
20776 @cindex file-i/o request packet
20777 @cindex @code{F} request packet
20779 The @code{F} request packet has the following format:
20784 @code{F}@var{call-id}@code{,}@var{parameter@dots{}}
20787 @var{call-id} is the identifier to indicate the host system call to be called.
20788 This is just the name of the function.
20790 @var{parameter@dots{}} are the parameters to the system call.
20794 Parameters are hexadecimal integer values, either the real values in case
20795 of scalar datatypes, as pointers to target buffer space in case of compound
20796 datatypes and unspecified memory areas or as pointer/length pairs in case
20797 of string parameters. These are appended to the call-id, each separated
20798 from its predecessor by a comma. All values are transmitted in ASCII
20799 string representation, pointer/length pairs separated by a slash.
20801 @node The F reply packet
20802 @subsection The @code{F} reply packet
20803 @cindex file-i/o reply packet
20804 @cindex @code{F} reply packet
20806 The @code{F} reply packet has the following format:
20811 @code{F}@var{retcode}@code{,}@var{errno}@code{,}@var{Ctrl-C flag}@code{;}@var{call specific attachment}
20814 @var{retcode} is the return code of the system call as hexadecimal value.
20816 @var{errno} is the errno set by the call, in protocol specific representation.
20817 This parameter can be omitted if the call was successful.
20819 @var{Ctrl-C flag} is only send if the user requested a break. In this
20820 case, @var{errno} must be send as well, even if the call was successful.
20821 The @var{Ctrl-C flag} itself consists of the character 'C':
20828 or, if the call was interupted before the host call has been performed:
20835 assuming 4 is the protocol specific representation of @code{EINTR}.
20839 @node Memory transfer
20840 @subsection Memory transfer
20841 @cindex memory transfer, in file-i/o protocol
20843 Structured data which is transferred using a memory read or write as e.g.@:
20844 a @code{struct stat} is expected to be in a protocol specific format with
20845 all scalar multibyte datatypes being big endian. This should be done by
20846 the target before the @code{F} packet is sent resp.@: by @value{GDBN} before
20847 it transfers memory to the target. Transferred pointers to structured
20848 data should point to the already coerced data at any time.
20850 @node The Ctrl-C message
20851 @subsection The Ctrl-C message
20852 @cindex ctrl-c message, in file-i/o protocol
20854 A special case is, if the @var{Ctrl-C flag} is set in the @value{GDBN}
20855 reply packet. In this case the target should behave, as if it had
20856 gotten a break message. The meaning for the target is ``system call
20857 interupted by @code{SIGINT}''. Consequentially, the target should actually stop
20858 (as with a break message) and return to @value{GDBN} with a @code{T02}
20859 packet. In this case, it's important for the target to know, in which
20860 state the system call was interrupted. Since this action is by design
20861 not an atomic operation, we have to differ between two cases:
20865 The system call hasn't been performed on the host yet.
20868 The system call on the host has been finished.
20872 These two states can be distinguished by the target by the value of the
20873 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
20874 call hasn't been performed. This is equivalent to the @code{EINTR} handling
20875 on POSIX systems. In any other case, the target may presume that the
20876 system call has been finished --- successful or not --- and should behave
20877 as if the break message arrived right after the system call.
20879 @value{GDBN} must behave reliable. If the system call has not been called
20880 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
20881 @code{errno} in the packet. If the system call on the host has been finished
20882 before the user requests a break, the full action must be finshed by
20883 @value{GDBN}. This requires sending @code{M} or @code{X} packets as they fit.
20884 The @code{F} packet may only be send when either nothing has happened
20885 or the full action has been completed.
20888 @subsection Console I/O
20889 @cindex console i/o as part of file-i/o
20891 By default and if not explicitely closed by the target system, the file
20892 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
20893 on the @value{GDBN} console is handled as any other file output operation
20894 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
20895 by @value{GDBN} so that after the target read request from file descriptor
20896 0 all following typing is buffered until either one of the following
20901 The user presses @kbd{Ctrl-C}. The behaviour is as explained above, the
20903 system call is treated as finished.
20906 The user presses @kbd{Enter}. This is treated as end of input with a trailing
20910 The user presses @kbd{Ctrl-D}. This is treated as end of input. No trailing
20911 character, especially no Ctrl-D is appended to the input.
20915 If the user has typed more characters as fit in the buffer given to
20916 the read call, the trailing characters are buffered in @value{GDBN} until
20917 either another @code{read(0, @dots{})} is requested by the target or debugging
20918 is stopped on users request.
20920 @node The isatty call
20921 @subsection The isatty(3) call
20922 @cindex isatty call, file-i/o protocol
20924 A special case in this protocol is the library call @code{isatty} which
20925 is implemented as it's own call inside of this protocol. It returns
20926 1 to the target if the file descriptor given as parameter is attached
20927 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
20928 would require implementing @code{ioctl} and would be more complex than
20931 @node The system call
20932 @subsection The system(3) call
20933 @cindex system call, file-i/o protocol
20935 The other special case in this protocol is the @code{system} call which
20936 is implemented as it's own call, too. @value{GDBN} is taking over the full
20937 task of calling the necessary host calls to perform the @code{system}
20938 call. The return value of @code{system} is simplified before it's returned
20939 to the target. Basically, the only signal transmitted back is @code{EINTR}
20940 in case the user pressed @kbd{Ctrl-C}. Otherwise the return value consists
20941 entirely of the exit status of the called command.
20943 Due to security concerns, the @code{system} call is refused to be called
20944 by @value{GDBN} by default. The user has to allow this call explicitly by
20948 @kindex set remote system-call-allowed 1
20949 @item @code{set remote system-call-allowed 1}
20952 Disabling the @code{system} call is done by
20955 @kindex set remote system-call-allowed 0
20956 @item @code{set remote system-call-allowed 0}
20959 The current setting is shown by typing
20962 @kindex show remote system-call-allowed
20963 @item @code{show remote system-call-allowed}
20966 @node List of supported calls
20967 @subsection List of supported calls
20968 @cindex list of supported file-i/o calls
20985 @unnumberedsubsubsec open
20986 @cindex open, file-i/o system call
20990 int open(const char *pathname, int flags);
20991 int open(const char *pathname, int flags, mode_t mode);
20994 Fopen,pathptr/len,flags,mode
20998 @code{flags} is the bitwise or of the following values:
21002 If the file does not exist it will be created. The host
21003 rules apply as far as file ownership and time stamps
21007 When used with O_CREAT, if the file already exists it is
21008 an error and open() fails.
21011 If the file already exists and the open mode allows
21012 writing (O_RDWR or O_WRONLY is given) it will be
21013 truncated to length 0.
21016 The file is opened in append mode.
21019 The file is opened for reading only.
21022 The file is opened for writing only.
21025 The file is opened for reading and writing.
21028 Each other bit is silently ignored.
21033 @code{mode} is the bitwise or of the following values:
21037 User has read permission.
21040 User has write permission.
21043 Group has read permission.
21046 Group has write permission.
21049 Others have read permission.
21052 Others have write permission.
21055 Each other bit is silently ignored.
21060 @exdent Return value:
21061 open returns the new file descriptor or -1 if an error
21069 pathname already exists and O_CREAT and O_EXCL were used.
21072 pathname refers to a directory.
21075 The requested access is not allowed.
21078 pathname was too long.
21081 A directory component in pathname does not exist.
21084 pathname refers to a device, pipe, named pipe or socket.
21087 pathname refers to a file on a read-only filesystem and
21088 write access was requested.
21091 pathname is an invalid pointer value.
21094 No space on device to create the file.
21097 The process already has the maximum number of files open.
21100 The limit on the total number of files open on the system
21104 The call was interrupted by the user.
21108 @unnumberedsubsubsec close
21109 @cindex close, file-i/o system call
21118 @exdent Return value:
21119 close returns zero on success, or -1 if an error occurred.
21126 fd isn't a valid open file descriptor.
21129 The call was interrupted by the user.
21133 @unnumberedsubsubsec read
21134 @cindex read, file-i/o system call
21138 int read(int fd, void *buf, unsigned int count);
21141 Fread,fd,bufptr,count
21143 @exdent Return value:
21144 On success, the number of bytes read is returned.
21145 Zero indicates end of file. If count is zero, read
21146 returns zero as well. On error, -1 is returned.
21153 fd is not a valid file descriptor or is not open for
21157 buf is an invalid pointer value.
21160 The call was interrupted by the user.
21164 @unnumberedsubsubsec write
21165 @cindex write, file-i/o system call
21169 int write(int fd, const void *buf, unsigned int count);
21172 Fwrite,fd,bufptr,count
21174 @exdent Return value:
21175 On success, the number of bytes written are returned.
21176 Zero indicates nothing was written. On error, -1
21184 fd is not a valid file descriptor or is not open for
21188 buf is an invalid pointer value.
21191 An attempt was made to write a file that exceeds the
21192 host specific maximum file size allowed.
21195 No space on device to write the data.
21198 The call was interrupted by the user.
21202 @unnumberedsubsubsec lseek
21203 @cindex lseek, file-i/o system call
21207 long lseek (int fd, long offset, int flag);
21210 Flseek,fd,offset,flag
21213 @code{flag} is one of:
21217 The offset is set to offset bytes.
21220 The offset is set to its current location plus offset
21224 The offset is set to the size of the file plus offset
21229 @exdent Return value:
21230 On success, the resulting unsigned offset in bytes from
21231 the beginning of the file is returned. Otherwise, a
21232 value of -1 is returned.
21239 fd is not a valid open file descriptor.
21242 fd is associated with the @value{GDBN} console.
21245 flag is not a proper value.
21248 The call was interrupted by the user.
21252 @unnumberedsubsubsec rename
21253 @cindex rename, file-i/o system call
21257 int rename(const char *oldpath, const char *newpath);
21260 Frename,oldpathptr/len,newpathptr/len
21262 @exdent Return value:
21263 On success, zero is returned. On error, -1 is returned.
21270 newpath is an existing directory, but oldpath is not a
21274 newpath is a non-empty directory.
21277 oldpath or newpath is a directory that is in use by some
21281 An attempt was made to make a directory a subdirectory
21285 A component used as a directory in oldpath or new
21286 path is not a directory. Or oldpath is a directory
21287 and newpath exists but is not a directory.
21290 oldpathptr or newpathptr are invalid pointer values.
21293 No access to the file or the path of the file.
21297 oldpath or newpath was too long.
21300 A directory component in oldpath or newpath does not exist.
21303 The file is on a read-only filesystem.
21306 The device containing the file has no room for the new
21310 The call was interrupted by the user.
21314 @unnumberedsubsubsec unlink
21315 @cindex unlink, file-i/o system call
21319 int unlink(const char *pathname);
21322 Funlink,pathnameptr/len
21324 @exdent Return value:
21325 On success, zero is returned. On error, -1 is returned.
21332 No access to the file or the path of the file.
21335 The system does not allow unlinking of directories.
21338 The file pathname cannot be unlinked because it's
21339 being used by another process.
21342 pathnameptr is an invalid pointer value.
21345 pathname was too long.
21348 A directory component in pathname does not exist.
21351 A component of the path is not a directory.
21354 The file is on a read-only filesystem.
21357 The call was interrupted by the user.
21361 @unnumberedsubsubsec stat/fstat
21362 @cindex fstat, file-i/o system call
21363 @cindex stat, file-i/o system call
21367 int stat(const char *pathname, struct stat *buf);
21368 int fstat(int fd, struct stat *buf);
21371 Fstat,pathnameptr/len,bufptr
21374 @exdent Return value:
21375 On success, zero is returned. On error, -1 is returned.
21382 fd is not a valid open file.
21385 A directory component in pathname does not exist or the
21386 path is an empty string.
21389 A component of the path is not a directory.
21392 pathnameptr is an invalid pointer value.
21395 No access to the file or the path of the file.
21398 pathname was too long.
21401 The call was interrupted by the user.
21405 @unnumberedsubsubsec gettimeofday
21406 @cindex gettimeofday, file-i/o system call
21410 int gettimeofday(struct timeval *tv, void *tz);
21413 Fgettimeofday,tvptr,tzptr
21415 @exdent Return value:
21416 On success, 0 is returned, -1 otherwise.
21423 tz is a non-NULL pointer.
21426 tvptr and/or tzptr is an invalid pointer value.
21430 @unnumberedsubsubsec isatty
21431 @cindex isatty, file-i/o system call
21435 int isatty(int fd);
21440 @exdent Return value:
21441 Returns 1 if fd refers to the @value{GDBN} console, 0 otherwise.
21448 The call was interrupted by the user.
21452 @unnumberedsubsubsec system
21453 @cindex system, file-i/o system call
21457 int system(const char *command);
21460 Fsystem,commandptr/len
21462 @exdent Return value:
21463 The value returned is -1 on error and the return status
21464 of the command otherwise. Only the exit status of the
21465 command is returned, which is extracted from the hosts
21466 system return value by calling WEXITSTATUS(retval).
21467 In case /bin/sh could not be executed, 127 is returned.
21474 The call was interrupted by the user.
21477 @node Protocol specific representation of datatypes
21478 @subsection Protocol specific representation of datatypes
21479 @cindex protocol specific representation of datatypes, in file-i/o protocol
21482 * Integral datatypes::
21488 @node Integral datatypes
21489 @unnumberedsubsubsec Integral datatypes
21490 @cindex integral datatypes, in file-i/o protocol
21492 The integral datatypes used in the system calls are
21495 int@r{,} unsigned int@r{,} long@r{,} unsigned long@r{,} mode_t @r{and} time_t
21498 @code{Int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
21499 implemented as 32 bit values in this protocol.
21501 @code{Long} and @code{unsigned long} are implemented as 64 bit types.
21503 @xref{Limits}, for corresponding MIN and MAX values (similar to those
21504 in @file{limits.h}) to allow range checking on host and target.
21506 @code{time_t} datatypes are defined as seconds since the Epoch.
21508 All integral datatypes transferred as part of a memory read or write of a
21509 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
21512 @node Pointer values
21513 @unnumberedsubsubsec Pointer values
21514 @cindex pointer values, in file-i/o protocol
21516 Pointers to target data are transmitted as they are. An exception
21517 is made for pointers to buffers for which the length isn't
21518 transmitted as part of the function call, namely strings. Strings
21519 are transmitted as a pointer/length pair, both as hex values, e.g.@:
21526 which is a pointer to data of length 18 bytes at position 0x1aaf.
21527 The length is defined as the full string length in bytes, including
21528 the trailing null byte. Example:
21531 ``hello, world'' at address 0x123456
21542 @unnumberedsubsubsec struct stat
21543 @cindex struct stat, in file-i/o protocol
21545 The buffer of type struct stat used by the target and @value{GDBN} is defined
21550 unsigned int st_dev; /* device */
21551 unsigned int st_ino; /* inode */
21552 mode_t st_mode; /* protection */
21553 unsigned int st_nlink; /* number of hard links */
21554 unsigned int st_uid; /* user ID of owner */
21555 unsigned int st_gid; /* group ID of owner */
21556 unsigned int st_rdev; /* device type (if inode device) */
21557 unsigned long st_size; /* total size, in bytes */
21558 unsigned long st_blksize; /* blocksize for filesystem I/O */
21559 unsigned long st_blocks; /* number of blocks allocated */
21560 time_t st_atime; /* time of last access */
21561 time_t st_mtime; /* time of last modification */
21562 time_t st_ctime; /* time of last change */
21566 The integral datatypes are conforming to the definitions given in the
21567 approriate section (see @ref{Integral datatypes}, for details) so this
21568 structure is of size 64 bytes.
21570 The values of several fields have a restricted meaning and/or
21577 st_ino: No valid meaning for the target. Transmitted unchanged.
21579 st_mode: Valid mode bits are described in Appendix C. Any other
21580 bits have currently no meaning for the target.
21582 st_uid: No valid meaning for the target. Transmitted unchanged.
21584 st_gid: No valid meaning for the target. Transmitted unchanged.
21586 st_rdev: No valid meaning for the target. Transmitted unchanged.
21588 st_atime, st_mtime, st_ctime:
21589 These values have a host and file system dependent
21590 accuracy. Especially on Windows hosts the file systems
21591 don't support exact timing values.
21594 The target gets a struct stat of the above representation and is
21595 responsible to coerce it to the target representation before
21598 Note that due to size differences between the host and target
21599 representation of stat members, these members could eventually
21600 get truncated on the target.
21602 @node struct timeval
21603 @unnumberedsubsubsec struct timeval
21604 @cindex struct timeval, in file-i/o protocol
21606 The buffer of type struct timeval used by the target and @value{GDBN}
21607 is defined as follows:
21611 time_t tv_sec; /* second */
21612 long tv_usec; /* microsecond */
21616 The integral datatypes are conforming to the definitions given in the
21617 approriate section (see @ref{Integral datatypes}, for details) so this
21618 structure is of size 8 bytes.
21621 @subsection Constants
21622 @cindex constants, in file-i/o protocol
21624 The following values are used for the constants inside of the
21625 protocol. @value{GDBN} and target are resposible to translate these
21626 values before and after the call as needed.
21637 @unnumberedsubsubsec Open flags
21638 @cindex open flags, in file-i/o protocol
21640 All values are given in hexadecimal representation.
21652 @node mode_t values
21653 @unnumberedsubsubsec mode_t values
21654 @cindex mode_t values, in file-i/o protocol
21656 All values are given in octal representation.
21673 @unnumberedsubsubsec Errno values
21674 @cindex errno values, in file-i/o protocol
21676 All values are given in decimal representation.
21701 EUNKNOWN is used as a fallback error value if a host system returns
21702 any error value not in the list of supported error numbers.
21705 @unnumberedsubsubsec Lseek flags
21706 @cindex lseek flags, in file-i/o protocol
21715 @unnumberedsubsubsec Limits
21716 @cindex limits, in file-i/o protocol
21718 All values are given in decimal representation.
21721 INT_MIN -2147483648
21723 UINT_MAX 4294967295
21724 LONG_MIN -9223372036854775808
21725 LONG_MAX 9223372036854775807
21726 ULONG_MAX 18446744073709551615
21729 @node File-I/O Examples
21730 @subsection File-I/O Examples
21731 @cindex file-i/o examples
21733 Example sequence of a write call, file descriptor 3, buffer is at target
21734 address 0x1234, 6 bytes should be written:
21737 <- @code{Fwrite,3,1234,6}
21738 @emph{request memory read from target}
21741 @emph{return "6 bytes written"}
21745 Example sequence of a read call, file descriptor 3, buffer is at target
21746 address 0x1234, 6 bytes should be read:
21749 <- @code{Fread,3,1234,6}
21750 @emph{request memory write to target}
21751 -> @code{X1234,6:XXXXXX}
21752 @emph{return "6 bytes read"}
21756 Example sequence of a read call, call fails on the host due to invalid
21757 file descriptor (EBADF):
21760 <- @code{Fread,3,1234,6}
21764 Example sequence of a read call, user presses Ctrl-C before syscall on
21768 <- @code{Fread,3,1234,6}
21773 Example sequence of a read call, user presses Ctrl-C after syscall on
21777 <- @code{Fread,3,1234,6}
21778 -> @code{X1234,6:XXXXXX}
21782 @include agentexpr.texi
21796 % I think something like @colophon should be in texinfo. In the
21798 \long\def\colophon{\hbox to0pt{}\vfill
21799 \centerline{The body of this manual is set in}
21800 \centerline{\fontname\tenrm,}
21801 \centerline{with headings in {\bf\fontname\tenbf}}
21802 \centerline{and examples in {\tt\fontname\tentt}.}
21803 \centerline{{\it\fontname\tenit\/},}
21804 \centerline{{\bf\fontname\tenbf}, and}
21805 \centerline{{\sl\fontname\tensl\/}}
21806 \centerline{are used for emphasis.}\vfill}
21808 % Blame: doc@cygnus.com, 1991.