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 Programming & development tools.
43 * Gdb: (gdb). The @sc{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{--async}
1070 Use the asynchronous event loop for the command-line interface.
1071 @value{GDBN} processes all events, such as user keyboard input, via a
1072 special event loop. This allows @value{GDBN} to accept and process user
1073 commands in parallel with the debugged process being
1074 run@footnote{@value{GDBN} built with @sc{djgpp} tools for
1075 MS-DOS/MS-Windows supports this mode of operation, but the event loop is
1076 suspended when the debuggee runs.}, so you don't need to wait for
1077 control to return to @value{GDBN} before you type the next command.
1078 (@emph{Note:} as of version 5.1, the target side of the asynchronous
1079 operation is not yet in place, so @samp{-async} does not work fully
1081 @c FIXME: when the target side of the event loop is done, the above NOTE
1082 @c should be removed.
1084 When the standard input is connected to a terminal device, @value{GDBN}
1085 uses the asynchronous event loop by default, unless disabled by the
1086 @samp{-noasync} option.
1089 @cindex @code{--noasync}
1090 Disable the asynchronous event loop for the command-line interface.
1093 @cindex @code{--args}
1094 Change interpretation of command line so that arguments following the
1095 executable file are passed as command line arguments to the inferior.
1096 This option stops option processing.
1098 @item -baud @var{bps}
1100 @cindex @code{--baud}
1102 Set the line speed (baud rate or bits per second) of any serial
1103 interface used by @value{GDBN} for remote debugging.
1105 @item -tty @var{device}
1106 @itemx -t @var{device}
1107 @cindex @code{--tty}
1109 Run using @var{device} for your program's standard input and output.
1110 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1112 @c resolve the situation of these eventually
1114 @cindex @code{--tui}
1115 Activate the @dfn{Text User Interface} when starting. The Text User
1116 Interface manages several text windows on the terminal, showing
1117 source, assembly, registers and @value{GDBN} command outputs
1118 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1119 Text User Interface can be enabled by invoking the program
1120 @samp{gdbtui}. Do not use this option if you run @value{GDBN} from
1121 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1124 @c @cindex @code{--xdb}
1125 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1126 @c For information, see the file @file{xdb_trans.html}, which is usually
1127 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1130 @item -interpreter @var{interp}
1131 @cindex @code{--interpreter}
1132 Use the interpreter @var{interp} for interface with the controlling
1133 program or device. This option is meant to be set by programs which
1134 communicate with @value{GDBN} using it as a back end.
1135 @xref{Interpreters, , Command Interpreters}.
1137 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1138 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1139 The @sc{gdb/mi} Interface}) included since @var{GDBN} version 6.0. The
1140 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1141 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1142 @sc{gdb/mi} interfaces are no longer supported.
1145 @cindex @code{--write}
1146 Open the executable and core files for both reading and writing. This
1147 is equivalent to the @samp{set write on} command inside @value{GDBN}
1151 @cindex @code{--statistics}
1152 This option causes @value{GDBN} to print statistics about time and
1153 memory usage after it completes each command and returns to the prompt.
1156 @cindex @code{--version}
1157 This option causes @value{GDBN} to print its version number and
1158 no-warranty blurb, and exit.
1163 @section Quitting @value{GDBN}
1164 @cindex exiting @value{GDBN}
1165 @cindex leaving @value{GDBN}
1168 @kindex quit @r{[}@var{expression}@r{]}
1169 @kindex q @r{(@code{quit})}
1170 @item quit @r{[}@var{expression}@r{]}
1172 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1173 @code{q}), or type an end-of-file character (usually @kbd{C-d}). If you
1174 do not supply @var{expression}, @value{GDBN} will terminate normally;
1175 otherwise it will terminate using the result of @var{expression} as the
1180 An interrupt (often @kbd{C-c}) does not exit from @value{GDBN}, but rather
1181 terminates the action of any @value{GDBN} command that is in progress and
1182 returns to @value{GDBN} command level. It is safe to type the interrupt
1183 character at any time because @value{GDBN} does not allow it to take effect
1184 until a time when it is safe.
1186 If you have been using @value{GDBN} to control an attached process or
1187 device, you can release it with the @code{detach} command
1188 (@pxref{Attach, ,Debugging an already-running process}).
1190 @node Shell Commands
1191 @section Shell commands
1193 If you need to execute occasional shell commands during your
1194 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1195 just use the @code{shell} command.
1199 @cindex shell escape
1200 @item shell @var{command string}
1201 Invoke a standard shell to execute @var{command string}.
1202 If it exists, the environment variable @code{SHELL} determines which
1203 shell to run. Otherwise @value{GDBN} uses the default shell
1204 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1207 The utility @code{make} is often needed in development environments.
1208 You do not have to use the @code{shell} command for this purpose in
1213 @cindex calling make
1214 @item make @var{make-args}
1215 Execute the @code{make} program with the specified
1216 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1219 @node Logging output
1220 @section Logging output
1221 @cindex logging @value{GDBN} output
1223 You may want to save the output of @value{GDBN} commands to a file.
1224 There are several commands to control @value{GDBN}'s logging.
1228 @item set logging on
1230 @item set logging off
1232 @item set logging file @var{file}
1233 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1234 @item set logging overwrite [on|off]
1235 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1236 you want @code{set logging on} to overwrite the logfile instead.
1237 @item set logging redirect [on|off]
1238 By default, @value{GDBN} output will go to both the terminal and the logfile.
1239 Set @code{redirect} if you want output to go only to the log file.
1240 @kindex show logging
1242 Show the current values of the logging settings.
1246 @chapter @value{GDBN} Commands
1248 You can abbreviate a @value{GDBN} command to the first few letters of the command
1249 name, if that abbreviation is unambiguous; and you can repeat certain
1250 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1251 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1252 show you the alternatives available, if there is more than one possibility).
1255 * Command Syntax:: How to give commands to @value{GDBN}
1256 * Completion:: Command completion
1257 * Help:: How to ask @value{GDBN} for help
1260 @node Command Syntax
1261 @section Command syntax
1263 A @value{GDBN} command is a single line of input. There is no limit on
1264 how long it can be. It starts with a command name, which is followed by
1265 arguments whose meaning depends on the command name. For example, the
1266 command @code{step} accepts an argument which is the number of times to
1267 step, as in @samp{step 5}. You can also use the @code{step} command
1268 with no arguments. Some commands do not allow any arguments.
1270 @cindex abbreviation
1271 @value{GDBN} command names may always be truncated if that abbreviation is
1272 unambiguous. Other possible command abbreviations are listed in the
1273 documentation for individual commands. In some cases, even ambiguous
1274 abbreviations are allowed; for example, @code{s} is specially defined as
1275 equivalent to @code{step} even though there are other commands whose
1276 names start with @code{s}. You can test abbreviations by using them as
1277 arguments to the @code{help} command.
1279 @cindex repeating commands
1280 @kindex RET @r{(repeat last command)}
1281 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1282 repeat the previous command. Certain commands (for example, @code{run})
1283 will not repeat this way; these are commands whose unintentional
1284 repetition might cause trouble and which you are unlikely to want to
1287 The @code{list} and @code{x} commands, when you repeat them with
1288 @key{RET}, construct new arguments rather than repeating
1289 exactly as typed. This permits easy scanning of source or memory.
1291 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1292 output, in a way similar to the common utility @code{more}
1293 (@pxref{Screen Size,,Screen size}). Since it is easy to press one
1294 @key{RET} too many in this situation, @value{GDBN} disables command
1295 repetition after any command that generates this sort of display.
1297 @kindex # @r{(a comment)}
1299 Any text from a @kbd{#} to the end of the line is a comment; it does
1300 nothing. This is useful mainly in command files (@pxref{Command
1301 Files,,Command files}).
1303 @cindex repeating command sequences
1304 @kindex C-o @r{(operate-and-get-next)}
1305 The @kbd{C-o} binding is useful for repeating a complex sequence of
1306 commands. This command accepts the current line, like @kbd{RET}, and
1307 then fetches the next line relative to the current line from the history
1311 @section Command completion
1314 @cindex word completion
1315 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1316 only one possibility; it can also show you what the valid possibilities
1317 are for the next word in a command, at any time. This works for @value{GDBN}
1318 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1320 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1321 of a word. If there is only one possibility, @value{GDBN} fills in the
1322 word, and waits for you to finish the command (or press @key{RET} to
1323 enter it). For example, if you type
1325 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1326 @c complete accuracy in these examples; space introduced for clarity.
1327 @c If texinfo enhancements make it unnecessary, it would be nice to
1328 @c replace " @key" by "@key" in the following...
1330 (@value{GDBP}) info bre @key{TAB}
1334 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1335 the only @code{info} subcommand beginning with @samp{bre}:
1338 (@value{GDBP}) info breakpoints
1342 You can either press @key{RET} at this point, to run the @code{info
1343 breakpoints} command, or backspace and enter something else, if
1344 @samp{breakpoints} does not look like the command you expected. (If you
1345 were sure you wanted @code{info breakpoints} in the first place, you
1346 might as well just type @key{RET} immediately after @samp{info bre},
1347 to exploit command abbreviations rather than command completion).
1349 If there is more than one possibility for the next word when you press
1350 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1351 characters and try again, or just press @key{TAB} a second time;
1352 @value{GDBN} displays all the possible completions for that word. For
1353 example, you might want to set a breakpoint on a subroutine whose name
1354 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1355 just sounds the bell. Typing @key{TAB} again displays all the
1356 function names in your program that begin with those characters, for
1360 (@value{GDBP}) b make_ @key{TAB}
1361 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1362 make_a_section_from_file make_environ
1363 make_abs_section make_function_type
1364 make_blockvector make_pointer_type
1365 make_cleanup make_reference_type
1366 make_command make_symbol_completion_list
1367 (@value{GDBP}) b make_
1371 After displaying the available possibilities, @value{GDBN} copies your
1372 partial input (@samp{b make_} in the example) so you can finish the
1375 If you just want to see the list of alternatives in the first place, you
1376 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1377 means @kbd{@key{META} ?}. You can type this either by holding down a
1378 key designated as the @key{META} shift on your keyboard (if there is
1379 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1381 @cindex quotes in commands
1382 @cindex completion of quoted strings
1383 Sometimes the string you need, while logically a ``word'', may contain
1384 parentheses or other characters that @value{GDBN} normally excludes from
1385 its notion of a word. To permit word completion to work in this
1386 situation, you may enclose words in @code{'} (single quote marks) in
1387 @value{GDBN} commands.
1389 The most likely situation where you might need this is in typing the
1390 name of a C@t{++} function. This is because C@t{++} allows function
1391 overloading (multiple definitions of the same function, distinguished
1392 by argument type). For example, when you want to set a breakpoint you
1393 may need to distinguish whether you mean the version of @code{name}
1394 that takes an @code{int} parameter, @code{name(int)}, or the version
1395 that takes a @code{float} parameter, @code{name(float)}. To use the
1396 word-completion facilities in this situation, type a single quote
1397 @code{'} at the beginning of the function name. This alerts
1398 @value{GDBN} that it may need to consider more information than usual
1399 when you press @key{TAB} or @kbd{M-?} to request word completion:
1402 (@value{GDBP}) b 'bubble( @kbd{M-?}
1403 bubble(double,double) bubble(int,int)
1404 (@value{GDBP}) b 'bubble(
1407 In some cases, @value{GDBN} can tell that completing a name requires using
1408 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1409 completing as much as it can) if you do not type the quote in the first
1413 (@value{GDBP}) b bub @key{TAB}
1414 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1415 (@value{GDBP}) b 'bubble(
1419 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1420 you have not yet started typing the argument list when you ask for
1421 completion on an overloaded symbol.
1423 For more information about overloaded functions, see @ref{C plus plus
1424 expressions, ,C@t{++} expressions}. You can use the command @code{set
1425 overload-resolution off} to disable overload resolution;
1426 see @ref{Debugging C plus plus, ,@value{GDBN} features for C@t{++}}.
1430 @section Getting help
1431 @cindex online documentation
1434 You can always ask @value{GDBN} itself for information on its commands,
1435 using the command @code{help}.
1438 @kindex h @r{(@code{help})}
1441 You can use @code{help} (abbreviated @code{h}) with no arguments to
1442 display a short list of named classes of commands:
1446 List of classes of commands:
1448 aliases -- Aliases of other commands
1449 breakpoints -- Making program stop at certain points
1450 data -- Examining data
1451 files -- Specifying and examining files
1452 internals -- Maintenance commands
1453 obscure -- Obscure features
1454 running -- Running the program
1455 stack -- Examining the stack
1456 status -- Status inquiries
1457 support -- Support facilities
1458 tracepoints -- Tracing of program execution without@*
1459 stopping the program
1460 user-defined -- User-defined commands
1462 Type "help" followed by a class name for a list of
1463 commands in that class.
1464 Type "help" followed by command name for full
1466 Command name abbreviations are allowed if unambiguous.
1469 @c the above line break eliminates huge line overfull...
1471 @item help @var{class}
1472 Using one of the general help classes as an argument, you can get a
1473 list of the individual commands in that class. For example, here is the
1474 help display for the class @code{status}:
1477 (@value{GDBP}) help status
1482 @c Line break in "show" line falsifies real output, but needed
1483 @c to fit in smallbook page size.
1484 info -- Generic command for showing things
1485 about the program being debugged
1486 show -- Generic command for showing things
1489 Type "help" followed by command name for full
1491 Command name abbreviations are allowed if unambiguous.
1495 @item help @var{command}
1496 With a command name as @code{help} argument, @value{GDBN} displays a
1497 short paragraph on how to use that command.
1500 @item apropos @var{args}
1501 The @code{apropos @var{args}} command searches through all of the @value{GDBN}
1502 commands, and their documentation, for the regular expression specified in
1503 @var{args}. It prints out all matches found. For example:
1514 set symbol-reloading -- Set dynamic symbol table reloading
1515 multiple times in one run
1516 show symbol-reloading -- Show dynamic symbol table reloading
1517 multiple times in one run
1522 @item complete @var{args}
1523 The @code{complete @var{args}} command lists all the possible completions
1524 for the beginning of a command. Use @var{args} to specify the beginning of the
1525 command you want completed. For example:
1531 @noindent results in:
1542 @noindent This is intended for use by @sc{gnu} Emacs.
1545 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1546 and @code{show} to inquire about the state of your program, or the state
1547 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1548 manual introduces each of them in the appropriate context. The listings
1549 under @code{info} and under @code{show} in the Index point to
1550 all the sub-commands. @xref{Index}.
1555 @kindex i @r{(@code{info})}
1557 This command (abbreviated @code{i}) is for describing the state of your
1558 program. For example, you can list the arguments given to your program
1559 with @code{info args}, list the registers currently in use with @code{info
1560 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1561 You can get a complete list of the @code{info} sub-commands with
1562 @w{@code{help info}}.
1566 You can assign the result of an expression to an environment variable with
1567 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1568 @code{set prompt $}.
1572 In contrast to @code{info}, @code{show} is for describing the state of
1573 @value{GDBN} itself.
1574 You can change most of the things you can @code{show}, by using the
1575 related command @code{set}; for example, you can control what number
1576 system is used for displays with @code{set radix}, or simply inquire
1577 which is currently in use with @code{show radix}.
1580 To display all the settable parameters and their current
1581 values, you can use @code{show} with no arguments; you may also use
1582 @code{info set}. Both commands produce the same display.
1583 @c FIXME: "info set" violates the rule that "info" is for state of
1584 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1585 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1589 Here are three miscellaneous @code{show} subcommands, all of which are
1590 exceptional in lacking corresponding @code{set} commands:
1593 @kindex show version
1594 @cindex version number
1596 Show what version of @value{GDBN} is running. You should include this
1597 information in @value{GDBN} bug-reports. If multiple versions of
1598 @value{GDBN} are in use at your site, you may need to determine which
1599 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1600 commands are introduced, and old ones may wither away. Also, many
1601 system vendors ship variant versions of @value{GDBN}, and there are
1602 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1603 The version number is the same as the one announced when you start
1606 @kindex show copying
1608 Display information about permission for copying @value{GDBN}.
1610 @kindex show warranty
1612 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1613 if your version of @value{GDBN} comes with one.
1618 @chapter Running Programs Under @value{GDBN}
1620 When you run a program under @value{GDBN}, you must first generate
1621 debugging information when you compile it.
1623 You may start @value{GDBN} with its arguments, if any, in an environment
1624 of your choice. If you are doing native debugging, you may redirect
1625 your program's input and output, debug an already running process, or
1626 kill a child process.
1629 * Compilation:: Compiling for debugging
1630 * Starting:: Starting your program
1631 * Arguments:: Your program's arguments
1632 * Environment:: Your program's environment
1634 * Working Directory:: Your program's working directory
1635 * Input/Output:: Your program's input and output
1636 * Attach:: Debugging an already-running process
1637 * Kill Process:: Killing the child process
1639 * Threads:: Debugging programs with multiple threads
1640 * Processes:: Debugging programs with multiple processes
1644 @section Compiling for debugging
1646 In order to debug a program effectively, you need to generate
1647 debugging information when you compile it. This debugging information
1648 is stored in the object file; it describes the data type of each
1649 variable or function and the correspondence between source line numbers
1650 and addresses in the executable code.
1652 To request debugging information, specify the @samp{-g} option when you run
1655 Most compilers do not include information about preprocessor macros in
1656 the debugging information if you specify the @option{-g} flag alone,
1657 because this information is rather large. Version 3.1 of @value{NGCC},
1658 the @sc{gnu} C compiler, provides macro information if you specify the
1659 options @option{-gdwarf-2} and @option{-g3}; the former option requests
1660 debugging information in the Dwarf 2 format, and the latter requests
1661 ``extra information''. In the future, we hope to find more compact ways
1662 to represent macro information, so that it can be included with
1665 Many C compilers are unable to handle the @samp{-g} and @samp{-O}
1666 options together. Using those compilers, you cannot generate optimized
1667 executables containing debugging information.
1669 @value{NGCC}, the @sc{gnu} C compiler, supports @samp{-g} with or
1670 without @samp{-O}, making it possible to debug optimized code. We
1671 recommend that you @emph{always} use @samp{-g} whenever you compile a
1672 program. You may think your program is correct, but there is no sense
1673 in pushing your luck.
1675 @cindex optimized code, debugging
1676 @cindex debugging optimized code
1677 When you debug a program compiled with @samp{-g -O}, remember that the
1678 optimizer is rearranging your code; the debugger shows you what is
1679 really there. Do not be too surprised when the execution path does not
1680 exactly match your source file! An extreme example: if you define a
1681 variable, but never use it, @value{GDBN} never sees that
1682 variable---because the compiler optimizes it out of existence.
1684 Some things do not work as well with @samp{-g -O} as with just
1685 @samp{-g}, particularly on machines with instruction scheduling. If in
1686 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1687 please report it to us as a bug (including a test case!).
1689 Older versions of the @sc{gnu} C compiler permitted a variant option
1690 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1691 format; if your @sc{gnu} C compiler has this option, do not use it.
1695 @section Starting your program
1701 @kindex r @r{(@code{run})}
1704 Use the @code{run} command to start your program under @value{GDBN}.
1705 You must first specify the program name (except on VxWorks) with an
1706 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1707 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1708 (@pxref{Files, ,Commands to specify files}).
1712 If you are running your program in an execution environment that
1713 supports processes, @code{run} creates an inferior process and makes
1714 that process run your program. (In environments without processes,
1715 @code{run} jumps to the start of your program.)
1717 The execution of a program is affected by certain information it
1718 receives from its superior. @value{GDBN} provides ways to specify this
1719 information, which you must do @emph{before} starting your program. (You
1720 can change it after starting your program, but such changes only affect
1721 your program the next time you start it.) This information may be
1722 divided into four categories:
1725 @item The @emph{arguments.}
1726 Specify the arguments to give your program as the arguments of the
1727 @code{run} command. If a shell is available on your target, the shell
1728 is used to pass the arguments, so that you may use normal conventions
1729 (such as wildcard expansion or variable substitution) in describing
1731 In Unix systems, you can control which shell is used with the
1732 @code{SHELL} environment variable.
1733 @xref{Arguments, ,Your program's arguments}.
1735 @item The @emph{environment.}
1736 Your program normally inherits its environment from @value{GDBN}, but you can
1737 use the @value{GDBN} commands @code{set environment} and @code{unset
1738 environment} to change parts of the environment that affect
1739 your program. @xref{Environment, ,Your program's environment}.
1741 @item The @emph{working directory.}
1742 Your program inherits its working directory from @value{GDBN}. You can set
1743 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1744 @xref{Working Directory, ,Your program's working directory}.
1746 @item The @emph{standard input and output.}
1747 Your program normally uses the same device for standard input and
1748 standard output as @value{GDBN} is using. You can redirect input and output
1749 in the @code{run} command line, or you can use the @code{tty} command to
1750 set a different device for your program.
1751 @xref{Input/Output, ,Your program's input and output}.
1754 @emph{Warning:} While input and output redirection work, you cannot use
1755 pipes to pass the output of the program you are debugging to another
1756 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1760 When you issue the @code{run} command, your program begins to execute
1761 immediately. @xref{Stopping, ,Stopping and continuing}, for discussion
1762 of how to arrange for your program to stop. Once your program has
1763 stopped, you may call functions in your program, using the @code{print}
1764 or @code{call} commands. @xref{Data, ,Examining Data}.
1766 If the modification time of your symbol file has changed since the last
1767 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1768 table, and reads it again. When it does this, @value{GDBN} tries to retain
1769 your current breakpoints.
1772 @section Your program's arguments
1774 @cindex arguments (to your program)
1775 The arguments to your program can be specified by the arguments of the
1777 They are passed to a shell, which expands wildcard characters and
1778 performs redirection of I/O, and thence to your program. Your
1779 @code{SHELL} environment variable (if it exists) specifies what shell
1780 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1781 the default shell (@file{/bin/sh} on Unix).
1783 On non-Unix systems, the program is usually invoked directly by
1784 @value{GDBN}, which emulates I/O redirection via the appropriate system
1785 calls, and the wildcard characters are expanded by the startup code of
1786 the program, not by the shell.
1788 @code{run} with no arguments uses the same arguments used by the previous
1789 @code{run}, or those set by the @code{set args} command.
1794 Specify the arguments to be used the next time your program is run. If
1795 @code{set args} has no arguments, @code{run} executes your program
1796 with no arguments. Once you have run your program with arguments,
1797 using @code{set args} before the next @code{run} is the only way to run
1798 it again without arguments.
1802 Show the arguments to give your program when it is started.
1806 @section Your program's environment
1808 @cindex environment (of your program)
1809 The @dfn{environment} consists of a set of environment variables and
1810 their values. Environment variables conventionally record such things as
1811 your user name, your home directory, your terminal type, and your search
1812 path for programs to run. Usually you set up environment variables with
1813 the shell and they are inherited by all the other programs you run. When
1814 debugging, it can be useful to try running your program with a modified
1815 environment without having to start @value{GDBN} over again.
1819 @item path @var{directory}
1820 Add @var{directory} to the front of the @code{PATH} environment variable
1821 (the search path for executables) that will be passed to your program.
1822 The value of @code{PATH} used by @value{GDBN} does not change.
1823 You may specify several directory names, separated by whitespace or by a
1824 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1825 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1826 is moved to the front, so it is searched sooner.
1828 You can use the string @samp{$cwd} to refer to whatever is the current
1829 working directory at the time @value{GDBN} searches the path. If you
1830 use @samp{.} instead, it refers to the directory where you executed the
1831 @code{path} command. @value{GDBN} replaces @samp{.} in the
1832 @var{directory} argument (with the current path) before adding
1833 @var{directory} to the search path.
1834 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1835 @c document that, since repeating it would be a no-op.
1839 Display the list of search paths for executables (the @code{PATH}
1840 environment variable).
1842 @kindex show environment
1843 @item show environment @r{[}@var{varname}@r{]}
1844 Print the value of environment variable @var{varname} to be given to
1845 your program when it starts. If you do not supply @var{varname},
1846 print the names and values of all environment variables to be given to
1847 your program. You can abbreviate @code{environment} as @code{env}.
1849 @kindex set environment
1850 @item set environment @var{varname} @r{[}=@var{value}@r{]}
1851 Set environment variable @var{varname} to @var{value}. The value
1852 changes for your program only, not for @value{GDBN} itself. @var{value} may
1853 be any string; the values of environment variables are just strings, and
1854 any interpretation is supplied by your program itself. The @var{value}
1855 parameter is optional; if it is eliminated, the variable is set to a
1857 @c "any string" here does not include leading, trailing
1858 @c blanks. Gnu asks: does anyone care?
1860 For example, this command:
1867 tells the debugged program, when subsequently run, that its user is named
1868 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
1869 are not actually required.)
1871 @kindex unset environment
1872 @item unset environment @var{varname}
1873 Remove variable @var{varname} from the environment to be passed to your
1874 program. This is different from @samp{set env @var{varname} =};
1875 @code{unset environment} removes the variable from the environment,
1876 rather than assigning it an empty value.
1879 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
1881 by your @code{SHELL} environment variable if it exists (or
1882 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
1883 that runs an initialization file---such as @file{.cshrc} for C-shell, or
1884 @file{.bashrc} for BASH---any variables you set in that file affect
1885 your program. You may wish to move setting of environment variables to
1886 files that are only run when you sign on, such as @file{.login} or
1889 @node Working Directory
1890 @section Your program's working directory
1892 @cindex working directory (of your program)
1893 Each time you start your program with @code{run}, it inherits its
1894 working directory from the current working directory of @value{GDBN}.
1895 The @value{GDBN} working directory is initially whatever it inherited
1896 from its parent process (typically the shell), but you can specify a new
1897 working directory in @value{GDBN} with the @code{cd} command.
1899 The @value{GDBN} working directory also serves as a default for the commands
1900 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
1905 @item cd @var{directory}
1906 Set the @value{GDBN} working directory to @var{directory}.
1910 Print the @value{GDBN} working directory.
1914 @section Your program's input and output
1919 By default, the program you run under @value{GDBN} does input and output to
1920 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
1921 to its own terminal modes to interact with you, but it records the terminal
1922 modes your program was using and switches back to them when you continue
1923 running your program.
1926 @kindex info terminal
1928 Displays information recorded by @value{GDBN} about the terminal modes your
1932 You can redirect your program's input and/or output using shell
1933 redirection with the @code{run} command. For example,
1940 starts your program, diverting its output to the file @file{outfile}.
1943 @cindex controlling terminal
1944 Another way to specify where your program should do input and output is
1945 with the @code{tty} command. This command accepts a file name as
1946 argument, and causes this file to be the default for future @code{run}
1947 commands. It also resets the controlling terminal for the child
1948 process, for future @code{run} commands. For example,
1955 directs that processes started with subsequent @code{run} commands
1956 default to do input and output on the terminal @file{/dev/ttyb} and have
1957 that as their controlling terminal.
1959 An explicit redirection in @code{run} overrides the @code{tty} command's
1960 effect on the input/output device, but not its effect on the controlling
1963 When you use the @code{tty} command or redirect input in the @code{run}
1964 command, only the input @emph{for your program} is affected. The input
1965 for @value{GDBN} still comes from your terminal.
1968 @section Debugging an already-running process
1973 @item attach @var{process-id}
1974 This command attaches to a running process---one that was started
1975 outside @value{GDBN}. (@code{info files} shows your active
1976 targets.) The command takes as argument a process ID. The usual way to
1977 find out the process-id of a Unix process is with the @code{ps} utility,
1978 or with the @samp{jobs -l} shell command.
1980 @code{attach} does not repeat if you press @key{RET} a second time after
1981 executing the command.
1984 To use @code{attach}, your program must be running in an environment
1985 which supports processes; for example, @code{attach} does not work for
1986 programs on bare-board targets that lack an operating system. You must
1987 also have permission to send the process a signal.
1989 When you use @code{attach}, the debugger finds the program running in
1990 the process first by looking in the current working directory, then (if
1991 the program is not found) by using the source file search path
1992 (@pxref{Source Path, ,Specifying source directories}). You can also use
1993 the @code{file} command to load the program. @xref{Files, ,Commands to
1996 The first thing @value{GDBN} does after arranging to debug the specified
1997 process is to stop it. You can examine and modify an attached process
1998 with all the @value{GDBN} commands that are ordinarily available when
1999 you start processes with @code{run}. You can insert breakpoints; you
2000 can step and continue; you can modify storage. If you would rather the
2001 process continue running, you may use the @code{continue} command after
2002 attaching @value{GDBN} to the process.
2007 When you have finished debugging the attached process, you can use the
2008 @code{detach} command to release it from @value{GDBN} control. Detaching
2009 the process continues its execution. After the @code{detach} command,
2010 that process and @value{GDBN} become completely independent once more, and you
2011 are ready to @code{attach} another process or start one with @code{run}.
2012 @code{detach} does not repeat if you press @key{RET} again after
2013 executing the command.
2016 If you exit @value{GDBN} or use the @code{run} command while you have an
2017 attached process, you kill that process. By default, @value{GDBN} asks
2018 for confirmation if you try to do either of these things; you can
2019 control whether or not you need to confirm by using the @code{set
2020 confirm} command (@pxref{Messages/Warnings, ,Optional warnings and
2024 @section Killing the child process
2029 Kill the child process in which your program is running under @value{GDBN}.
2032 This command is useful if you wish to debug a core dump instead of a
2033 running process. @value{GDBN} ignores any core dump file while your program
2036 On some operating systems, a program cannot be executed outside @value{GDBN}
2037 while you have breakpoints set on it inside @value{GDBN}. You can use the
2038 @code{kill} command in this situation to permit running your program
2039 outside the debugger.
2041 The @code{kill} command is also useful if you wish to recompile and
2042 relink your program, since on many systems it is impossible to modify an
2043 executable file while it is running in a process. In this case, when you
2044 next type @code{run}, @value{GDBN} notices that the file has changed, and
2045 reads the symbol table again (while trying to preserve your current
2046 breakpoint settings).
2049 @section Debugging programs with multiple threads
2051 @cindex threads of execution
2052 @cindex multiple threads
2053 @cindex switching threads
2054 In some operating systems, such as HP-UX and Solaris, a single program
2055 may have more than one @dfn{thread} of execution. The precise semantics
2056 of threads differ from one operating system to another, but in general
2057 the threads of a single program are akin to multiple processes---except
2058 that they share one address space (that is, they can all examine and
2059 modify the same variables). On the other hand, each thread has its own
2060 registers and execution stack, and perhaps private memory.
2062 @value{GDBN} provides these facilities for debugging multi-thread
2066 @item automatic notification of new threads
2067 @item @samp{thread @var{threadno}}, a command to switch among threads
2068 @item @samp{info threads}, a command to inquire about existing threads
2069 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2070 a command to apply a command to a list of threads
2071 @item thread-specific breakpoints
2075 @emph{Warning:} These facilities are not yet available on every
2076 @value{GDBN} configuration where the operating system supports threads.
2077 If your @value{GDBN} does not support threads, these commands have no
2078 effect. For example, a system without thread support shows no output
2079 from @samp{info threads}, and always rejects the @code{thread} command,
2083 (@value{GDBP}) info threads
2084 (@value{GDBP}) thread 1
2085 Thread ID 1 not known. Use the "info threads" command to
2086 see the IDs of currently known threads.
2088 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2089 @c doesn't support threads"?
2092 @cindex focus of debugging
2093 @cindex current thread
2094 The @value{GDBN} thread debugging facility allows you to observe all
2095 threads while your program runs---but whenever @value{GDBN} takes
2096 control, one thread in particular is always the focus of debugging.
2097 This thread is called the @dfn{current thread}. Debugging commands show
2098 program information from the perspective of the current thread.
2100 @cindex @code{New} @var{systag} message
2101 @cindex thread identifier (system)
2102 @c FIXME-implementors!! It would be more helpful if the [New...] message
2103 @c included GDB's numeric thread handle, so you could just go to that
2104 @c thread without first checking `info threads'.
2105 Whenever @value{GDBN} detects a new thread in your program, it displays
2106 the target system's identification for the thread with a message in the
2107 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2108 whose form varies depending on the particular system. For example, on
2109 LynxOS, you might see
2112 [New process 35 thread 27]
2116 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2117 the @var{systag} is simply something like @samp{process 368}, with no
2120 @c FIXME!! (1) Does the [New...] message appear even for the very first
2121 @c thread of a program, or does it only appear for the
2122 @c second---i.e.@: when it becomes obvious we have a multithread
2124 @c (2) *Is* there necessarily a first thread always? Or do some
2125 @c multithread systems permit starting a program with multiple
2126 @c threads ab initio?
2128 @cindex thread number
2129 @cindex thread identifier (GDB)
2130 For debugging purposes, @value{GDBN} associates its own thread
2131 number---always a single integer---with each thread in your program.
2134 @kindex info threads
2136 Display a summary of all threads currently in your
2137 program. @value{GDBN} displays for each thread (in this order):
2140 @item the thread number assigned by @value{GDBN}
2142 @item the target system's thread identifier (@var{systag})
2144 @item the current stack frame summary for that thread
2148 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2149 indicates the current thread.
2153 @c end table here to get a little more width for example
2156 (@value{GDBP}) info threads
2157 3 process 35 thread 27 0x34e5 in sigpause ()
2158 2 process 35 thread 23 0x34e5 in sigpause ()
2159 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2165 @cindex thread number
2166 @cindex thread identifier (GDB)
2167 For debugging purposes, @value{GDBN} associates its own thread
2168 number---a small integer assigned in thread-creation order---with each
2169 thread in your program.
2171 @cindex @code{New} @var{systag} message, on HP-UX
2172 @cindex thread identifier (system), on HP-UX
2173 @c FIXME-implementors!! It would be more helpful if the [New...] message
2174 @c included GDB's numeric thread handle, so you could just go to that
2175 @c thread without first checking `info threads'.
2176 Whenever @value{GDBN} detects a new thread in your program, it displays
2177 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2178 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2179 whose form varies depending on the particular system. For example, on
2183 [New thread 2 (system thread 26594)]
2187 when @value{GDBN} notices a new thread.
2190 @kindex info threads
2192 Display a summary of all threads currently in your
2193 program. @value{GDBN} displays for each thread (in this order):
2196 @item the thread number assigned by @value{GDBN}
2198 @item the target system's thread identifier (@var{systag})
2200 @item the current stack frame summary for that thread
2204 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2205 indicates the current thread.
2209 @c end table here to get a little more width for example
2212 (@value{GDBP}) info threads
2213 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2215 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2216 from /usr/lib/libc.2
2217 1 system thread 27905 0x7b003498 in _brk () \@*
2218 from /usr/lib/libc.2
2222 @kindex thread @var{threadno}
2223 @item thread @var{threadno}
2224 Make thread number @var{threadno} the current thread. The command
2225 argument @var{threadno} is the internal @value{GDBN} thread number, as
2226 shown in the first field of the @samp{info threads} display.
2227 @value{GDBN} responds by displaying the system identifier of the thread
2228 you selected, and its current stack frame summary:
2231 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2232 (@value{GDBP}) thread 2
2233 [Switching to process 35 thread 23]
2234 0x34e5 in sigpause ()
2238 As with the @samp{[New @dots{}]} message, the form of the text after
2239 @samp{Switching to} depends on your system's conventions for identifying
2242 @kindex thread apply
2243 @item thread apply [@var{threadno}] [@var{all}] @var{args}
2244 The @code{thread apply} command allows you to apply a command to one or
2245 more threads. Specify the numbers of the threads that you want affected
2246 with the command argument @var{threadno}. @var{threadno} is the internal
2247 @value{GDBN} thread number, as shown in the first field of the @samp{info
2248 threads} display. To apply a command to all threads, use
2249 @code{thread apply all} @var{args}.
2252 @cindex automatic thread selection
2253 @cindex switching threads automatically
2254 @cindex threads, automatic switching
2255 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2256 signal, it automatically selects the thread where that breakpoint or
2257 signal happened. @value{GDBN} alerts you to the context switch with a
2258 message of the form @samp{[Switching to @var{systag}]} to identify the
2261 @xref{Thread Stops,,Stopping and starting multi-thread programs}, for
2262 more information about how @value{GDBN} behaves when you stop and start
2263 programs with multiple threads.
2265 @xref{Set Watchpoints,,Setting watchpoints}, for information about
2266 watchpoints in programs with multiple threads.
2269 @section Debugging programs with multiple processes
2271 @cindex fork, debugging programs which call
2272 @cindex multiple processes
2273 @cindex processes, multiple
2274 On most systems, @value{GDBN} has no special support for debugging
2275 programs which create additional processes using the @code{fork}
2276 function. When a program forks, @value{GDBN} will continue to debug the
2277 parent process and the child process will run unimpeded. If you have
2278 set a breakpoint in any code which the child then executes, the child
2279 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2280 will cause it to terminate.
2282 However, if you want to debug the child process there is a workaround
2283 which isn't too painful. Put a call to @code{sleep} in the code which
2284 the child process executes after the fork. It may be useful to sleep
2285 only if a certain environment variable is set, or a certain file exists,
2286 so that the delay need not occur when you don't want to run @value{GDBN}
2287 on the child. While the child is sleeping, use the @code{ps} program to
2288 get its process ID. Then tell @value{GDBN} (a new invocation of
2289 @value{GDBN} if you are also debugging the parent process) to attach to
2290 the child process (@pxref{Attach}). From that point on you can debug
2291 the child process just like any other process which you attached to.
2293 On some systems, @value{GDBN} provides support for debugging programs that
2294 create additional processes using the @code{fork} or @code{vfork} functions.
2295 Currently, the only platforms with this feature are HP-UX (11.x and later
2296 only?) and GNU/Linux (kernel version 2.5.60 and later).
2298 By default, when a program forks, @value{GDBN} will continue to debug
2299 the parent process and the child process will run unimpeded.
2301 If you want to follow the child process instead of the parent process,
2302 use the command @w{@code{set follow-fork-mode}}.
2305 @kindex set follow-fork-mode
2306 @item set follow-fork-mode @var{mode}
2307 Set the debugger response to a program call of @code{fork} or
2308 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2309 process. The @var{mode} can be:
2313 The original process is debugged after a fork. The child process runs
2314 unimpeded. This is the default.
2317 The new process is debugged after a fork. The parent process runs
2322 @item show follow-fork-mode
2323 Display the current debugger response to a @code{fork} or @code{vfork} call.
2326 If you ask to debug a child process and a @code{vfork} is followed by an
2327 @code{exec}, @value{GDBN} executes the new target up to the first
2328 breakpoint in the new target. If you have a breakpoint set on
2329 @code{main} in your original program, the breakpoint will also be set on
2330 the child process's @code{main}.
2332 When a child process is spawned by @code{vfork}, you cannot debug the
2333 child or parent until an @code{exec} call completes.
2335 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2336 call executes, the new target restarts. To restart the parent process,
2337 use the @code{file} command with the parent executable name as its
2340 You can use the @code{catch} command to make @value{GDBN} stop whenever
2341 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2342 Catchpoints, ,Setting catchpoints}.
2345 @chapter Stopping and Continuing
2347 The principal purposes of using a debugger are so that you can stop your
2348 program before it terminates; or so that, if your program runs into
2349 trouble, you can investigate and find out why.
2351 Inside @value{GDBN}, your program may stop for any of several reasons,
2352 such as a signal, a breakpoint, or reaching a new line after a
2353 @value{GDBN} command such as @code{step}. You may then examine and
2354 change variables, set new breakpoints or remove old ones, and then
2355 continue execution. Usually, the messages shown by @value{GDBN} provide
2356 ample explanation of the status of your program---but you can also
2357 explicitly request this information at any time.
2360 @kindex info program
2362 Display information about the status of your program: whether it is
2363 running or not, what process it is, and why it stopped.
2367 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2368 * Continuing and Stepping:: Resuming execution
2370 * Thread Stops:: Stopping and starting multi-thread programs
2374 @section Breakpoints, watchpoints, and catchpoints
2377 A @dfn{breakpoint} makes your program stop whenever a certain point in
2378 the program is reached. For each breakpoint, you can add conditions to
2379 control in finer detail whether your program stops. You can set
2380 breakpoints with the @code{break} command and its variants (@pxref{Set
2381 Breaks, ,Setting breakpoints}), to specify the place where your program
2382 should stop by line number, function name or exact address in the
2385 In HP-UX, SunOS 4.x, SVR4, and Alpha OSF/1 configurations, you can set
2386 breakpoints in shared libraries before the executable is run. There is
2387 a minor limitation on HP-UX systems: you must wait until the executable
2388 is run in order to set breakpoints in shared library routines that are
2389 not called directly by the program (for example, routines that are
2390 arguments in a @code{pthread_create} call).
2393 @cindex memory tracing
2394 @cindex breakpoint on memory address
2395 @cindex breakpoint on variable modification
2396 A @dfn{watchpoint} is a special breakpoint that stops your program
2397 when the value of an expression changes. You must use a different
2398 command to set watchpoints (@pxref{Set Watchpoints, ,Setting
2399 watchpoints}), but aside from that, you can manage a watchpoint like
2400 any other breakpoint: you enable, disable, and delete both breakpoints
2401 and watchpoints using the same commands.
2403 You can arrange to have values from your program displayed automatically
2404 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2408 @cindex breakpoint on events
2409 A @dfn{catchpoint} is another special breakpoint that stops your program
2410 when a certain kind of event occurs, such as the throwing of a C@t{++}
2411 exception or the loading of a library. As with watchpoints, you use a
2412 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2413 catchpoints}), but aside from that, you can manage a catchpoint like any
2414 other breakpoint. (To stop when your program receives a signal, use the
2415 @code{handle} command; see @ref{Signals, ,Signals}.)
2417 @cindex breakpoint numbers
2418 @cindex numbers for breakpoints
2419 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2420 catchpoint when you create it; these numbers are successive integers
2421 starting with one. In many of the commands for controlling various
2422 features of breakpoints you use the breakpoint number to say which
2423 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2424 @dfn{disabled}; if disabled, it has no effect on your program until you
2427 @cindex breakpoint ranges
2428 @cindex ranges of breakpoints
2429 Some @value{GDBN} commands accept a range of breakpoints on which to
2430 operate. A breakpoint range is either a single breakpoint number, like
2431 @samp{5}, or two such numbers, in increasing order, separated by a
2432 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2433 all breakpoint in that range are operated on.
2436 * Set Breaks:: Setting breakpoints
2437 * Set Watchpoints:: Setting watchpoints
2438 * Set Catchpoints:: Setting catchpoints
2439 * Delete Breaks:: Deleting breakpoints
2440 * Disabling:: Disabling breakpoints
2441 * Conditions:: Break conditions
2442 * Break Commands:: Breakpoint command lists
2443 * Breakpoint Menus:: Breakpoint menus
2444 * Error in Breakpoints:: ``Cannot insert breakpoints''
2445 * Breakpoint related warnings:: ``Breakpoint address adjusted...''
2449 @subsection Setting breakpoints
2451 @c FIXME LMB what does GDB do if no code on line of breakpt?
2452 @c consider in particular declaration with/without initialization.
2454 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2457 @kindex b @r{(@code{break})}
2458 @vindex $bpnum@r{, convenience variable}
2459 @cindex latest breakpoint
2460 Breakpoints are set with the @code{break} command (abbreviated
2461 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2462 number of the breakpoint you've set most recently; see @ref{Convenience
2463 Vars,, Convenience variables}, for a discussion of what you can do with
2464 convenience variables.
2466 You have several ways to say where the breakpoint should go.
2469 @item break @var{function}
2470 Set a breakpoint at entry to function @var{function}.
2471 When using source languages that permit overloading of symbols, such as
2472 C@t{++}, @var{function} may refer to more than one possible place to break.
2473 @xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
2475 @item break +@var{offset}
2476 @itemx break -@var{offset}
2477 Set a breakpoint some number of lines forward or back from the position
2478 at which execution stopped in the currently selected @dfn{stack frame}.
2479 (@xref{Frames, ,Frames}, for a description of stack frames.)
2481 @item break @var{linenum}
2482 Set a breakpoint at line @var{linenum} in the current source file.
2483 The current source file is the last file whose source text was printed.
2484 The breakpoint will stop your program just before it executes any of the
2487 @item break @var{filename}:@var{linenum}
2488 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2490 @item break @var{filename}:@var{function}
2491 Set a breakpoint at entry to function @var{function} found in file
2492 @var{filename}. Specifying a file name as well as a function name is
2493 superfluous except when multiple files contain similarly named
2496 @item break *@var{address}
2497 Set a breakpoint at address @var{address}. You can use this to set
2498 breakpoints in parts of your program which do not have debugging
2499 information or source files.
2502 When called without any arguments, @code{break} sets a breakpoint at
2503 the next instruction to be executed in the selected stack frame
2504 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2505 innermost, this makes your program stop as soon as control
2506 returns to that frame. This is similar to the effect of a
2507 @code{finish} command in the frame inside the selected frame---except
2508 that @code{finish} does not leave an active breakpoint. If you use
2509 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2510 the next time it reaches the current location; this may be useful
2513 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2514 least one instruction has been executed. If it did not do this, you
2515 would be unable to proceed past a breakpoint without first disabling the
2516 breakpoint. This rule applies whether or not the breakpoint already
2517 existed when your program stopped.
2519 @item break @dots{} if @var{cond}
2520 Set a breakpoint with condition @var{cond}; evaluate the expression
2521 @var{cond} each time the breakpoint is reached, and stop only if the
2522 value is nonzero---that is, if @var{cond} evaluates as true.
2523 @samp{@dots{}} stands for one of the possible arguments described
2524 above (or no argument) specifying where to break. @xref{Conditions,
2525 ,Break conditions}, for more information on breakpoint conditions.
2528 @item tbreak @var{args}
2529 Set a breakpoint enabled only for one stop. @var{args} are the
2530 same as for the @code{break} command, and the breakpoint is set in the same
2531 way, but the breakpoint is automatically deleted after the first time your
2532 program stops there. @xref{Disabling, ,Disabling breakpoints}.
2535 @item hbreak @var{args}
2536 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2537 @code{break} command and the breakpoint is set in the same way, but the
2538 breakpoint requires hardware support and some target hardware may not
2539 have this support. The main purpose of this is EPROM/ROM code
2540 debugging, so you can set a breakpoint at an instruction without
2541 changing the instruction. This can be used with the new trap-generation
2542 provided by SPARClite DSU and some x86-based targets. These targets
2543 will generate traps when a program accesses some data or instruction
2544 address that is assigned to the debug registers. However the hardware
2545 breakpoint registers can take a limited number of breakpoints. For
2546 example, on the DSU, only two data breakpoints can be set at a time, and
2547 @value{GDBN} will reject this command if more than two are used. Delete
2548 or disable unused hardware breakpoints before setting new ones
2549 (@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}.
2550 @xref{set remote hardware-breakpoint-limit}.
2554 @item thbreak @var{args}
2555 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2556 are the same as for the @code{hbreak} command and the breakpoint is set in
2557 the same way. However, like the @code{tbreak} command,
2558 the breakpoint is automatically deleted after the
2559 first time your program stops there. Also, like the @code{hbreak}
2560 command, the breakpoint requires hardware support and some target hardware
2561 may not have this support. @xref{Disabling, ,Disabling breakpoints}.
2562 See also @ref{Conditions, ,Break conditions}.
2565 @cindex regular expression
2566 @item rbreak @var{regex}
2567 Set breakpoints on all functions matching the regular expression
2568 @var{regex}. This command sets an unconditional breakpoint on all
2569 matches, printing a list of all breakpoints it set. Once these
2570 breakpoints are set, they are treated just like the breakpoints set with
2571 the @code{break} command. You can delete them, disable them, or make
2572 them conditional the same way as any other breakpoint.
2574 The syntax of the regular expression is the standard one used with tools
2575 like @file{grep}. Note that this is different from the syntax used by
2576 shells, so for instance @code{foo*} matches all functions that include
2577 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2578 @code{.*} leading and trailing the regular expression you supply, so to
2579 match only functions that begin with @code{foo}, use @code{^foo}.
2581 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2582 breakpoints on overloaded functions that are not members of any special
2585 @kindex info breakpoints
2586 @cindex @code{$_} and @code{info breakpoints}
2587 @item info breakpoints @r{[}@var{n}@r{]}
2588 @itemx info break @r{[}@var{n}@r{]}
2589 @itemx info watchpoints @r{[}@var{n}@r{]}
2590 Print a table of all breakpoints, watchpoints, and catchpoints set and
2591 not deleted, with the following columns for each breakpoint:
2594 @item Breakpoint Numbers
2596 Breakpoint, watchpoint, or catchpoint.
2598 Whether the breakpoint is marked to be disabled or deleted when hit.
2599 @item Enabled or Disabled
2600 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2601 that are not enabled.
2603 Where the breakpoint is in your program, as a memory address. If the
2604 breakpoint is pending (see below for details) on a future load of a shared library, the address
2605 will be listed as @samp{<PENDING>}.
2607 Where the breakpoint is in the source for your program, as a file and
2608 line number. For a pending breakpoint, the original string passed to
2609 the breakpoint command will be listed as it cannot be resolved until
2610 the appropriate shared library is loaded in the future.
2614 If a breakpoint is conditional, @code{info break} shows the condition on
2615 the line following the affected breakpoint; breakpoint commands, if any,
2616 are listed after that. A pending breakpoint is allowed to have a condition
2617 specified for it. The condition is not parsed for validity until a shared
2618 library is loaded that allows the pending breakpoint to resolve to a
2622 @code{info break} with a breakpoint
2623 number @var{n} as argument lists only that breakpoint. The
2624 convenience variable @code{$_} and the default examining-address for
2625 the @code{x} command are set to the address of the last breakpoint
2626 listed (@pxref{Memory, ,Examining memory}).
2629 @code{info break} displays a count of the number of times the breakpoint
2630 has been hit. This is especially useful in conjunction with the
2631 @code{ignore} command. You can ignore a large number of breakpoint
2632 hits, look at the breakpoint info to see how many times the breakpoint
2633 was hit, and then run again, ignoring one less than that number. This
2634 will get you quickly to the last hit of that breakpoint.
2637 @value{GDBN} allows you to set any number of breakpoints at the same place in
2638 your program. There is nothing silly or meaningless about this. When
2639 the breakpoints are conditional, this is even useful
2640 (@pxref{Conditions, ,Break conditions}).
2642 @cindex pending breakpoints
2643 If a specified breakpoint location cannot be found, it may be due to the fact
2644 that the location is in a shared library that is yet to be loaded. In such
2645 a case, you may want @value{GDBN} to create a special breakpoint (known as
2646 a @dfn{pending breakpoint}) that
2647 attempts to resolve itself in the future when an appropriate shared library
2650 Pending breakpoints are useful to set at the start of your
2651 @value{GDBN} session for locations that you know will be dynamically loaded
2652 later by the program being debugged. When shared libraries are loaded,
2653 a check is made to see if the load resolves any pending breakpoint locations.
2654 If a pending breakpoint location gets resolved,
2655 a regular breakpoint is created and the original pending breakpoint is removed.
2657 @value{GDBN} provides some additional commands for controlling pending
2660 @kindex set breakpoint pending
2661 @kindex show breakpoint pending
2663 @item set breakpoint pending auto
2664 This is the default behavior. When @value{GDBN} cannot find the breakpoint
2665 location, it queries you whether a pending breakpoint should be created.
2667 @item set breakpoint pending on
2668 This indicates that an unrecognized breakpoint location should automatically
2669 result in a pending breakpoint being created.
2671 @item set breakpoint pending off
2672 This indicates that pending breakpoints are not to be created. Any
2673 unrecognized breakpoint location results in an error. This setting does
2674 not affect any pending breakpoints previously created.
2676 @item show breakpoint pending
2677 Show the current behavior setting for creating pending breakpoints.
2680 @cindex operations allowed on pending breakpoints
2681 Normal breakpoint operations apply to pending breakpoints as well. You may
2682 specify a condition for a pending breakpoint and/or commands to run when the
2683 breakpoint is reached. You can also enable or disable
2684 the pending breakpoint. When you specify a condition for a pending breakpoint,
2685 the parsing of the condition will be deferred until the point where the
2686 pending breakpoint location is resolved. Disabling a pending breakpoint
2687 tells @value{GDBN} to not attempt to resolve the breakpoint on any subsequent
2688 shared library load. When a pending breakpoint is re-enabled,
2689 @value{GDBN} checks to see if the location is already resolved.
2690 This is done because any number of shared library loads could have
2691 occurred since the time the breakpoint was disabled and one or more
2692 of these loads could resolve the location.
2694 @cindex negative breakpoint numbers
2695 @cindex internal @value{GDBN} breakpoints
2696 @value{GDBN} itself sometimes sets breakpoints in your program for
2697 special purposes, such as proper handling of @code{longjmp} (in C
2698 programs). These internal breakpoints are assigned negative numbers,
2699 starting with @code{-1}; @samp{info breakpoints} does not display them.
2700 You can see these breakpoints with the @value{GDBN} maintenance command
2701 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
2704 @node Set Watchpoints
2705 @subsection Setting watchpoints
2707 @cindex setting watchpoints
2708 @cindex software watchpoints
2709 @cindex hardware watchpoints
2710 You can use a watchpoint to stop execution whenever the value of an
2711 expression changes, without having to predict a particular place where
2714 Depending on your system, watchpoints may be implemented in software or
2715 hardware. @value{GDBN} does software watchpointing by single-stepping your
2716 program and testing the variable's value each time, which is hundreds of
2717 times slower than normal execution. (But this may still be worth it, to
2718 catch errors where you have no clue what part of your program is the
2721 On some systems, such as HP-UX, @sc{gnu}/Linux and some other x86-based targets,
2722 @value{GDBN} includes support for
2723 hardware watchpoints, which do not slow down the running of your
2728 @item watch @var{expr}
2729 Set a watchpoint for an expression. @value{GDBN} will break when @var{expr}
2730 is written into by the program and its value changes.
2733 @item rwatch @var{expr}
2734 Set a watchpoint that will break when watch @var{expr} is read by the program.
2737 @item awatch @var{expr}
2738 Set a watchpoint that will break when @var{expr} is either read or written into
2741 @kindex info watchpoints
2742 @item info watchpoints
2743 This command prints a list of watchpoints, breakpoints, and catchpoints;
2744 it is the same as @code{info break}.
2747 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
2748 watchpoints execute very quickly, and the debugger reports a change in
2749 value at the exact instruction where the change occurs. If @value{GDBN}
2750 cannot set a hardware watchpoint, it sets a software watchpoint, which
2751 executes more slowly and reports the change in value at the next
2752 statement, not the instruction, after the change occurs.
2754 When you issue the @code{watch} command, @value{GDBN} reports
2757 Hardware watchpoint @var{num}: @var{expr}
2761 if it was able to set a hardware watchpoint.
2763 Currently, the @code{awatch} and @code{rwatch} commands can only set
2764 hardware watchpoints, because accesses to data that don't change the
2765 value of the watched expression cannot be detected without examining
2766 every instruction as it is being executed, and @value{GDBN} does not do
2767 that currently. If @value{GDBN} finds that it is unable to set a
2768 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
2769 will print a message like this:
2772 Expression cannot be implemented with read/access watchpoint.
2775 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
2776 data type of the watched expression is wider than what a hardware
2777 watchpoint on the target machine can handle. For example, some systems
2778 can only watch regions that are up to 4 bytes wide; on such systems you
2779 cannot set hardware watchpoints for an expression that yields a
2780 double-precision floating-point number (which is typically 8 bytes
2781 wide). As a work-around, it might be possible to break the large region
2782 into a series of smaller ones and watch them with separate watchpoints.
2784 If you set too many hardware watchpoints, @value{GDBN} might be unable
2785 to insert all of them when you resume the execution of your program.
2786 Since the precise number of active watchpoints is unknown until such
2787 time as the program is about to be resumed, @value{GDBN} might not be
2788 able to warn you about this when you set the watchpoints, and the
2789 warning will be printed only when the program is resumed:
2792 Hardware watchpoint @var{num}: Could not insert watchpoint
2796 If this happens, delete or disable some of the watchpoints.
2798 The SPARClite DSU will generate traps when a program accesses some data
2799 or instruction address that is assigned to the debug registers. For the
2800 data addresses, DSU facilitates the @code{watch} command. However the
2801 hardware breakpoint registers can only take two data watchpoints, and
2802 both watchpoints must be the same kind. For example, you can set two
2803 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
2804 @strong{or} two with @code{awatch} commands, but you cannot set one
2805 watchpoint with one command and the other with a different command.
2806 @value{GDBN} will reject the command if you try to mix watchpoints.
2807 Delete or disable unused watchpoint commands before setting new ones.
2809 If you call a function interactively using @code{print} or @code{call},
2810 any watchpoints you have set will be inactive until @value{GDBN} reaches another
2811 kind of breakpoint or the call completes.
2813 @value{GDBN} automatically deletes watchpoints that watch local
2814 (automatic) variables, or expressions that involve such variables, when
2815 they go out of scope, that is, when the execution leaves the block in
2816 which these variables were defined. In particular, when the program
2817 being debugged terminates, @emph{all} local variables go out of scope,
2818 and so only watchpoints that watch global variables remain set. If you
2819 rerun the program, you will need to set all such watchpoints again. One
2820 way of doing that would be to set a code breakpoint at the entry to the
2821 @code{main} function and when it breaks, set all the watchpoints.
2824 @cindex watchpoints and threads
2825 @cindex threads and watchpoints
2826 @emph{Warning:} In multi-thread programs, watchpoints have only limited
2827 usefulness. With the current watchpoint implementation, @value{GDBN}
2828 can only watch the value of an expression @emph{in a single thread}. If
2829 you are confident that the expression can only change due to the current
2830 thread's activity (and if you are also confident that no other thread
2831 can become current), then you can use watchpoints as usual. However,
2832 @value{GDBN} may not notice when a non-current thread's activity changes
2835 @c FIXME: this is almost identical to the previous paragraph.
2836 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
2837 have only limited usefulness. If @value{GDBN} creates a software
2838 watchpoint, it can only watch the value of an expression @emph{in a
2839 single thread}. If you are confident that the expression can only
2840 change due to the current thread's activity (and if you are also
2841 confident that no other thread can become current), then you can use
2842 software watchpoints as usual. However, @value{GDBN} may not notice
2843 when a non-current thread's activity changes the expression. (Hardware
2844 watchpoints, in contrast, watch an expression in all threads.)
2847 @xref{set remote hardware-watchpoint-limit}.
2849 @node Set Catchpoints
2850 @subsection Setting catchpoints
2851 @cindex catchpoints, setting
2852 @cindex exception handlers
2853 @cindex event handling
2855 You can use @dfn{catchpoints} to cause the debugger to stop for certain
2856 kinds of program events, such as C@t{++} exceptions or the loading of a
2857 shared library. Use the @code{catch} command to set a catchpoint.
2861 @item catch @var{event}
2862 Stop when @var{event} occurs. @var{event} can be any of the following:
2866 The throwing of a C@t{++} exception.
2870 The catching of a C@t{++} exception.
2874 A call to @code{exec}. This is currently only available for HP-UX.
2878 A call to @code{fork}. This is currently only available for HP-UX.
2882 A call to @code{vfork}. This is currently only available for HP-UX.
2885 @itemx load @var{libname}
2887 The dynamic loading of any shared library, or the loading of the library
2888 @var{libname}. This is currently only available for HP-UX.
2891 @itemx unload @var{libname}
2892 @kindex catch unload
2893 The unloading of any dynamically loaded shared library, or the unloading
2894 of the library @var{libname}. This is currently only available for HP-UX.
2897 @item tcatch @var{event}
2898 Set a catchpoint that is enabled only for one stop. The catchpoint is
2899 automatically deleted after the first time the event is caught.
2903 Use the @code{info break} command to list the current catchpoints.
2905 There are currently some limitations to C@t{++} exception handling
2906 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
2910 If you call a function interactively, @value{GDBN} normally returns
2911 control to you when the function has finished executing. If the call
2912 raises an exception, however, the call may bypass the mechanism that
2913 returns control to you and cause your program either to abort or to
2914 simply continue running until it hits a breakpoint, catches a signal
2915 that @value{GDBN} is listening for, or exits. This is the case even if
2916 you set a catchpoint for the exception; catchpoints on exceptions are
2917 disabled within interactive calls.
2920 You cannot raise an exception interactively.
2923 You cannot install an exception handler interactively.
2926 @cindex raise exceptions
2927 Sometimes @code{catch} is not the best way to debug exception handling:
2928 if you need to know exactly where an exception is raised, it is better to
2929 stop @emph{before} the exception handler is called, since that way you
2930 can see the stack before any unwinding takes place. If you set a
2931 breakpoint in an exception handler instead, it may not be easy to find
2932 out where the exception was raised.
2934 To stop just before an exception handler is called, you need some
2935 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
2936 raised by calling a library function named @code{__raise_exception}
2937 which has the following ANSI C interface:
2940 /* @var{addr} is where the exception identifier is stored.
2941 @var{id} is the exception identifier. */
2942 void __raise_exception (void **addr, void *id);
2946 To make the debugger catch all exceptions before any stack
2947 unwinding takes place, set a breakpoint on @code{__raise_exception}
2948 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
2950 With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
2951 that depends on the value of @var{id}, you can stop your program when
2952 a specific exception is raised. You can use multiple conditional
2953 breakpoints to stop your program when any of a number of exceptions are
2958 @subsection Deleting breakpoints
2960 @cindex clearing breakpoints, watchpoints, catchpoints
2961 @cindex deleting breakpoints, watchpoints, catchpoints
2962 It is often necessary to eliminate a breakpoint, watchpoint, or
2963 catchpoint once it has done its job and you no longer want your program
2964 to stop there. This is called @dfn{deleting} the breakpoint. A
2965 breakpoint that has been deleted no longer exists; it is forgotten.
2967 With the @code{clear} command you can delete breakpoints according to
2968 where they are in your program. With the @code{delete} command you can
2969 delete individual breakpoints, watchpoints, or catchpoints by specifying
2970 their breakpoint numbers.
2972 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
2973 automatically ignores breakpoints on the first instruction to be executed
2974 when you continue execution without changing the execution address.
2979 Delete any breakpoints at the next instruction to be executed in the
2980 selected stack frame (@pxref{Selection, ,Selecting a frame}). When
2981 the innermost frame is selected, this is a good way to delete a
2982 breakpoint where your program just stopped.
2984 @item clear @var{function}
2985 @itemx clear @var{filename}:@var{function}
2986 Delete any breakpoints set at entry to the function @var{function}.
2988 @item clear @var{linenum}
2989 @itemx clear @var{filename}:@var{linenum}
2990 Delete any breakpoints set at or within the code of the specified line.
2992 @cindex delete breakpoints
2994 @kindex d @r{(@code{delete})}
2995 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
2996 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
2997 ranges specified as arguments. If no argument is specified, delete all
2998 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
2999 confirm off}). You can abbreviate this command as @code{d}.
3003 @subsection Disabling breakpoints
3005 @kindex disable breakpoints
3006 @kindex enable breakpoints
3007 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3008 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3009 it had been deleted, but remembers the information on the breakpoint so
3010 that you can @dfn{enable} it again later.
3012 You disable and enable breakpoints, watchpoints, and catchpoints with
3013 the @code{enable} and @code{disable} commands, optionally specifying one
3014 or more breakpoint numbers as arguments. Use @code{info break} or
3015 @code{info watch} to print a list of breakpoints, watchpoints, and
3016 catchpoints if you do not know which numbers to use.
3018 A breakpoint, watchpoint, or catchpoint can have any of four different
3019 states of enablement:
3023 Enabled. The breakpoint stops your program. A breakpoint set
3024 with the @code{break} command starts out in this state.
3026 Disabled. The breakpoint has no effect on your program.
3028 Enabled once. The breakpoint stops your program, but then becomes
3031 Enabled for deletion. The breakpoint stops your program, but
3032 immediately after it does so it is deleted permanently. A breakpoint
3033 set with the @code{tbreak} command starts out in this state.
3036 You can use the following commands to enable or disable breakpoints,
3037 watchpoints, and catchpoints:
3040 @kindex disable breakpoints
3042 @kindex dis @r{(@code{disable})}
3043 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3044 Disable the specified breakpoints---or all breakpoints, if none are
3045 listed. A disabled breakpoint has no effect but is not forgotten. All
3046 options such as ignore-counts, conditions and commands are remembered in
3047 case the breakpoint is enabled again later. You may abbreviate
3048 @code{disable} as @code{dis}.
3050 @kindex enable breakpoints
3052 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3053 Enable the specified breakpoints (or all defined breakpoints). They
3054 become effective once again in stopping your program.
3056 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3057 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3058 of these breakpoints immediately after stopping your program.
3060 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3061 Enable the specified breakpoints to work once, then die. @value{GDBN}
3062 deletes any of these breakpoints as soon as your program stops there.
3065 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3066 @c confusing: tbreak is also initially enabled.
3067 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3068 ,Setting breakpoints}), breakpoints that you set are initially enabled;
3069 subsequently, they become disabled or enabled only when you use one of
3070 the commands above. (The command @code{until} can set and delete a
3071 breakpoint of its own, but it does not change the state of your other
3072 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3076 @subsection Break conditions
3077 @cindex conditional breakpoints
3078 @cindex breakpoint conditions
3080 @c FIXME what is scope of break condition expr? Context where wanted?
3081 @c in particular for a watchpoint?
3082 The simplest sort of breakpoint breaks every time your program reaches a
3083 specified place. You can also specify a @dfn{condition} for a
3084 breakpoint. A condition is just a Boolean expression in your
3085 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3086 a condition evaluates the expression each time your program reaches it,
3087 and your program stops only if the condition is @emph{true}.
3089 This is the converse of using assertions for program validation; in that
3090 situation, you want to stop when the assertion is violated---that is,
3091 when the condition is false. In C, if you want to test an assertion expressed
3092 by the condition @var{assert}, you should set the condition
3093 @samp{! @var{assert}} on the appropriate breakpoint.
3095 Conditions are also accepted for watchpoints; you may not need them,
3096 since a watchpoint is inspecting the value of an expression anyhow---but
3097 it might be simpler, say, to just set a watchpoint on a variable name,
3098 and specify a condition that tests whether the new value is an interesting
3101 Break conditions can have side effects, and may even call functions in
3102 your program. This can be useful, for example, to activate functions
3103 that log program progress, or to use your own print functions to
3104 format special data structures. The effects are completely predictable
3105 unless there is another enabled breakpoint at the same address. (In
3106 that case, @value{GDBN} might see the other breakpoint first and stop your
3107 program without checking the condition of this one.) Note that
3108 breakpoint commands are usually more convenient and flexible than break
3110 purpose of performing side effects when a breakpoint is reached
3111 (@pxref{Break Commands, ,Breakpoint command lists}).
3113 Break conditions can be specified when a breakpoint is set, by using
3114 @samp{if} in the arguments to the @code{break} command. @xref{Set
3115 Breaks, ,Setting breakpoints}. They can also be changed at any time
3116 with the @code{condition} command.
3118 You can also use the @code{if} keyword with the @code{watch} command.
3119 The @code{catch} command does not recognize the @code{if} keyword;
3120 @code{condition} is the only way to impose a further condition on a
3125 @item condition @var{bnum} @var{expression}
3126 Specify @var{expression} as the break condition for breakpoint,
3127 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3128 breakpoint @var{bnum} stops your program only if the value of
3129 @var{expression} is true (nonzero, in C). When you use
3130 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3131 syntactic correctness, and to determine whether symbols in it have
3132 referents in the context of your breakpoint. If @var{expression} uses
3133 symbols not referenced in the context of the breakpoint, @value{GDBN}
3134 prints an error message:
3137 No symbol "foo" in current context.
3142 not actually evaluate @var{expression} at the time the @code{condition}
3143 command (or a command that sets a breakpoint with a condition, like
3144 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3146 @item condition @var{bnum}
3147 Remove the condition from breakpoint number @var{bnum}. It becomes
3148 an ordinary unconditional breakpoint.
3151 @cindex ignore count (of breakpoint)
3152 A special case of a breakpoint condition is to stop only when the
3153 breakpoint has been reached a certain number of times. This is so
3154 useful that there is a special way to do it, using the @dfn{ignore
3155 count} of the breakpoint. Every breakpoint has an ignore count, which
3156 is an integer. Most of the time, the ignore count is zero, and
3157 therefore has no effect. But if your program reaches a breakpoint whose
3158 ignore count is positive, then instead of stopping, it just decrements
3159 the ignore count by one and continues. As a result, if the ignore count
3160 value is @var{n}, the breakpoint does not stop the next @var{n} times
3161 your program reaches it.
3165 @item ignore @var{bnum} @var{count}
3166 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3167 The next @var{count} times the breakpoint is reached, your program's
3168 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3171 To make the breakpoint stop the next time it is reached, specify
3174 When you use @code{continue} to resume execution of your program from a
3175 breakpoint, you can specify an ignore count directly as an argument to
3176 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3177 Stepping,,Continuing and stepping}.
3179 If a breakpoint has a positive ignore count and a condition, the
3180 condition is not checked. Once the ignore count reaches zero,
3181 @value{GDBN} resumes checking the condition.
3183 You could achieve the effect of the ignore count with a condition such
3184 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3185 is decremented each time. @xref{Convenience Vars, ,Convenience
3189 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3192 @node Break Commands
3193 @subsection Breakpoint command lists
3195 @cindex breakpoint commands
3196 You can give any breakpoint (or watchpoint or catchpoint) a series of
3197 commands to execute when your program stops due to that breakpoint. For
3198 example, you might want to print the values of certain expressions, or
3199 enable other breakpoints.
3204 @item commands @r{[}@var{bnum}@r{]}
3205 @itemx @dots{} @var{command-list} @dots{}
3207 Specify a list of commands for breakpoint number @var{bnum}. The commands
3208 themselves appear on the following lines. Type a line containing just
3209 @code{end} to terminate the commands.
3211 To remove all commands from a breakpoint, type @code{commands} and
3212 follow it immediately with @code{end}; that is, give no commands.
3214 With no @var{bnum} argument, @code{commands} refers to the last
3215 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3216 recently encountered).
3219 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3220 disabled within a @var{command-list}.
3222 You can use breakpoint commands to start your program up again. Simply
3223 use the @code{continue} command, or @code{step}, or any other command
3224 that resumes execution.
3226 Any other commands in the command list, after a command that resumes
3227 execution, are ignored. This is because any time you resume execution
3228 (even with a simple @code{next} or @code{step}), you may encounter
3229 another breakpoint---which could have its own command list, leading to
3230 ambiguities about which list to execute.
3233 If the first command you specify in a command list is @code{silent}, the
3234 usual message about stopping at a breakpoint is not printed. This may
3235 be desirable for breakpoints that are to print a specific message and
3236 then continue. If none of the remaining commands print anything, you
3237 see no sign that the breakpoint was reached. @code{silent} is
3238 meaningful only at the beginning of a breakpoint command list.
3240 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3241 print precisely controlled output, and are often useful in silent
3242 breakpoints. @xref{Output, ,Commands for controlled output}.
3244 For example, here is how you could use breakpoint commands to print the
3245 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3251 printf "x is %d\n",x
3256 One application for breakpoint commands is to compensate for one bug so
3257 you can test for another. Put a breakpoint just after the erroneous line
3258 of code, give it a condition to detect the case in which something
3259 erroneous has been done, and give it commands to assign correct values
3260 to any variables that need them. End with the @code{continue} command
3261 so that your program does not stop, and start with the @code{silent}
3262 command so that no output is produced. Here is an example:
3273 @node Breakpoint Menus
3274 @subsection Breakpoint menus
3276 @cindex symbol overloading
3278 Some programming languages (notably C@t{++} and Objective-C) permit a
3279 single function name
3280 to be defined several times, for application in different contexts.
3281 This is called @dfn{overloading}. When a function name is overloaded,
3282 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3283 a breakpoint. If you realize this is a problem, you can use
3284 something like @samp{break @var{function}(@var{types})} to specify which
3285 particular version of the function you want. Otherwise, @value{GDBN} offers
3286 you a menu of numbered choices for different possible breakpoints, and
3287 waits for your selection with the prompt @samp{>}. The first two
3288 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3289 sets a breakpoint at each definition of @var{function}, and typing
3290 @kbd{0} aborts the @code{break} command without setting any new
3293 For example, the following session excerpt shows an attempt to set a
3294 breakpoint at the overloaded symbol @code{String::after}.
3295 We choose three particular definitions of that function name:
3297 @c FIXME! This is likely to change to show arg type lists, at least
3300 (@value{GDBP}) b String::after
3303 [2] file:String.cc; line number:867
3304 [3] file:String.cc; line number:860
3305 [4] file:String.cc; line number:875
3306 [5] file:String.cc; line number:853
3307 [6] file:String.cc; line number:846
3308 [7] file:String.cc; line number:735
3310 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3311 Breakpoint 2 at 0xb344: file String.cc, line 875.
3312 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3313 Multiple breakpoints were set.
3314 Use the "delete" command to delete unwanted
3320 @c @ifclear BARETARGET
3321 @node Error in Breakpoints
3322 @subsection ``Cannot insert breakpoints''
3324 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3326 Under some operating systems, breakpoints cannot be used in a program if
3327 any other process is running that program. In this situation,
3328 attempting to run or continue a program with a breakpoint causes
3329 @value{GDBN} to print an error message:
3332 Cannot insert breakpoints.
3333 The same program may be running in another process.
3336 When this happens, you have three ways to proceed:
3340 Remove or disable the breakpoints, then continue.
3343 Suspend @value{GDBN}, and copy the file containing your program to a new
3344 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3345 that @value{GDBN} should run your program under that name.
3346 Then start your program again.
3349 Relink your program so that the text segment is nonsharable, using the
3350 linker option @samp{-N}. The operating system limitation may not apply
3351 to nonsharable executables.
3355 A similar message can be printed if you request too many active
3356 hardware-assisted breakpoints and watchpoints:
3358 @c FIXME: the precise wording of this message may change; the relevant
3359 @c source change is not committed yet (Sep 3, 1999).
3361 Stopped; cannot insert breakpoints.
3362 You may have requested too many hardware breakpoints and watchpoints.
3366 This message is printed when you attempt to resume the program, since
3367 only then @value{GDBN} knows exactly how many hardware breakpoints and
3368 watchpoints it needs to insert.
3370 When this message is printed, you need to disable or remove some of the
3371 hardware-assisted breakpoints and watchpoints, and then continue.
3373 @node Breakpoint related warnings
3374 @subsection ``Breakpoint address adjusted...''
3375 @cindex breakpoint address adjusted
3377 Some processor architectures place constraints on the addresses at
3378 which breakpoints may be placed. For architectures thus constrained,
3379 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3380 with the constraints dictated by the architecture.
3382 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3383 a VLIW architecture in which a number of RISC-like instructions may be
3384 bundled together for parallel execution. The FR-V architecture
3385 constrains the location of a breakpoint instruction within such a
3386 bundle to the instruction with the lowest address. @value{GDBN}
3387 honors this constraint by adjusting a breakpoint's address to the
3388 first in the bundle.
3390 It is not uncommon for optimized code to have bundles which contain
3391 instructions from different source statements, thus it may happen that
3392 a breakpoint's address will be adjusted from one source statement to
3393 another. Since this adjustment may significantly alter @value{GDBN}'s
3394 breakpoint related behavior from what the user expects, a warning is
3395 printed when the breakpoint is first set and also when the breakpoint
3398 A warning like the one below is printed when setting a breakpoint
3399 that's been subject to address adjustment:
3402 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3405 Such warnings are printed both for user settable and @value{GDBN}'s
3406 internal breakpoints. If you see one of these warnings, you should
3407 verify that a breakpoint set at the adjusted address will have the
3408 desired affect. If not, the breakpoint in question may be removed and
3409 other breakpoints may be set which will have the desired behavior.
3410 E.g., it may be sufficient to place the breakpoint at a later
3411 instruction. A conditional breakpoint may also be useful in some
3412 cases to prevent the breakpoint from triggering too often.
3414 @value{GDBN} will also issue a warning when stopping at one of these
3415 adjusted breakpoints:
3418 warning: Breakpoint 1 address previously adjusted from 0x00010414
3422 When this warning is encountered, it may be too late to take remedial
3423 action except in cases where the breakpoint is hit earlier or more
3424 frequently than expected.
3426 @node Continuing and Stepping
3427 @section Continuing and stepping
3431 @cindex resuming execution
3432 @dfn{Continuing} means resuming program execution until your program
3433 completes normally. In contrast, @dfn{stepping} means executing just
3434 one more ``step'' of your program, where ``step'' may mean either one
3435 line of source code, or one machine instruction (depending on what
3436 particular command you use). Either when continuing or when stepping,
3437 your program may stop even sooner, due to a breakpoint or a signal. (If
3438 it stops due to a signal, you may want to use @code{handle}, or use
3439 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3443 @kindex c @r{(@code{continue})}
3444 @kindex fg @r{(resume foreground execution)}
3445 @item continue @r{[}@var{ignore-count}@r{]}
3446 @itemx c @r{[}@var{ignore-count}@r{]}
3447 @itemx fg @r{[}@var{ignore-count}@r{]}
3448 Resume program execution, at the address where your program last stopped;
3449 any breakpoints set at that address are bypassed. The optional argument
3450 @var{ignore-count} allows you to specify a further number of times to
3451 ignore a breakpoint at this location; its effect is like that of
3452 @code{ignore} (@pxref{Conditions, ,Break conditions}).
3454 The argument @var{ignore-count} is meaningful only when your program
3455 stopped due to a breakpoint. At other times, the argument to
3456 @code{continue} is ignored.
3458 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3459 debugged program is deemed to be the foreground program) are provided
3460 purely for convenience, and have exactly the same behavior as
3464 To resume execution at a different place, you can use @code{return}
3465 (@pxref{Returning, ,Returning from a function}) to go back to the
3466 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3467 different address}) to go to an arbitrary location in your program.
3469 A typical technique for using stepping is to set a breakpoint
3470 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the
3471 beginning of the function or the section of your program where a problem
3472 is believed to lie, run your program until it stops at that breakpoint,
3473 and then step through the suspect area, examining the variables that are
3474 interesting, until you see the problem happen.
3478 @kindex s @r{(@code{step})}
3480 Continue running your program until control reaches a different source
3481 line, then stop it and return control to @value{GDBN}. This command is
3482 abbreviated @code{s}.
3485 @c "without debugging information" is imprecise; actually "without line
3486 @c numbers in the debugging information". (gcc -g1 has debugging info but
3487 @c not line numbers). But it seems complex to try to make that
3488 @c distinction here.
3489 @emph{Warning:} If you use the @code{step} command while control is
3490 within a function that was compiled without debugging information,
3491 execution proceeds until control reaches a function that does have
3492 debugging information. Likewise, it will not step into a function which
3493 is compiled without debugging information. To step through functions
3494 without debugging information, use the @code{stepi} command, described
3498 The @code{step} command only stops at the first instruction of a source
3499 line. This prevents the multiple stops that could otherwise occur in
3500 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3501 to stop if a function that has debugging information is called within
3502 the line. In other words, @code{step} @emph{steps inside} any functions
3503 called within the line.
3505 Also, the @code{step} command only enters a function if there is line
3506 number information for the function. Otherwise it acts like the
3507 @code{next} command. This avoids problems when using @code{cc -gl}
3508 on MIPS machines. Previously, @code{step} entered subroutines if there
3509 was any debugging information about the routine.
3511 @item step @var{count}
3512 Continue running as in @code{step}, but do so @var{count} times. If a
3513 breakpoint is reached, or a signal not related to stepping occurs before
3514 @var{count} steps, stepping stops right away.
3517 @kindex n @r{(@code{next})}
3518 @item next @r{[}@var{count}@r{]}
3519 Continue to the next source line in the current (innermost) stack frame.
3520 This is similar to @code{step}, but function calls that appear within
3521 the line of code are executed without stopping. Execution stops when
3522 control reaches a different line of code at the original stack level
3523 that was executing when you gave the @code{next} command. This command
3524 is abbreviated @code{n}.
3526 An argument @var{count} is a repeat count, as for @code{step}.
3529 @c FIX ME!! Do we delete this, or is there a way it fits in with
3530 @c the following paragraph? --- Vctoria
3532 @c @code{next} within a function that lacks debugging information acts like
3533 @c @code{step}, but any function calls appearing within the code of the
3534 @c function are executed without stopping.
3536 The @code{next} command only stops at the first instruction of a
3537 source line. This prevents multiple stops that could otherwise occur in
3538 @code{switch} statements, @code{for} loops, etc.
3540 @kindex set step-mode
3542 @cindex functions without line info, and stepping
3543 @cindex stepping into functions with no line info
3544 @itemx set step-mode on
3545 The @code{set step-mode on} command causes the @code{step} command to
3546 stop at the first instruction of a function which contains no debug line
3547 information rather than stepping over it.
3549 This is useful in cases where you may be interested in inspecting the
3550 machine instructions of a function which has no symbolic info and do not
3551 want @value{GDBN} to automatically skip over this function.
3553 @item set step-mode off
3554 Causes the @code{step} command to step over any functions which contains no
3555 debug information. This is the default.
3559 Continue running until just after function in the selected stack frame
3560 returns. Print the returned value (if any).
3562 Contrast this with the @code{return} command (@pxref{Returning,
3563 ,Returning from a function}).
3566 @kindex u @r{(@code{until})}
3569 Continue running until a source line past the current line, in the
3570 current stack frame, is reached. This command is used to avoid single
3571 stepping through a loop more than once. It is like the @code{next}
3572 command, except that when @code{until} encounters a jump, it
3573 automatically continues execution until the program counter is greater
3574 than the address of the jump.
3576 This means that when you reach the end of a loop after single stepping
3577 though it, @code{until} makes your program continue execution until it
3578 exits the loop. In contrast, a @code{next} command at the end of a loop
3579 simply steps back to the beginning of the loop, which forces you to step
3580 through the next iteration.
3582 @code{until} always stops your program if it attempts to exit the current
3585 @code{until} may produce somewhat counterintuitive results if the order
3586 of machine code does not match the order of the source lines. For
3587 example, in the following excerpt from a debugging session, the @code{f}
3588 (@code{frame}) command shows that execution is stopped at line
3589 @code{206}; yet when we use @code{until}, we get to line @code{195}:
3593 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
3595 (@value{GDBP}) until
3596 195 for ( ; argc > 0; NEXTARG) @{
3599 This happened because, for execution efficiency, the compiler had
3600 generated code for the loop closure test at the end, rather than the
3601 start, of the loop---even though the test in a C @code{for}-loop is
3602 written before the body of the loop. The @code{until} command appeared
3603 to step back to the beginning of the loop when it advanced to this
3604 expression; however, it has not really gone to an earlier
3605 statement---not in terms of the actual machine code.
3607 @code{until} with no argument works by means of single
3608 instruction stepping, and hence is slower than @code{until} with an
3611 @item until @var{location}
3612 @itemx u @var{location}
3613 Continue running your program until either the specified location is
3614 reached, or the current stack frame returns. @var{location} is any of
3615 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
3616 ,Setting breakpoints}). This form of the command uses breakpoints, and
3617 hence is quicker than @code{until} without an argument. The specified
3618 location is actually reached only if it is in the current frame. This
3619 implies that @code{until} can be used to skip over recursive function
3620 invocations. For instance in the code below, if the current location is
3621 line @code{96}, issuing @code{until 99} will execute the program up to
3622 line @code{99} in the same invocation of factorial, i.e. after the inner
3623 invocations have returned.
3626 94 int factorial (int value)
3628 96 if (value > 1) @{
3629 97 value *= factorial (value - 1);
3636 @kindex advance @var{location}
3637 @itemx advance @var{location}
3638 Continue running the program up to the given location. An argument is
3639 required, anything of the same form as arguments for the @code{break}
3640 command. Execution will also stop upon exit from the current stack
3641 frame. This command is similar to @code{until}, but @code{advance} will
3642 not skip over recursive function calls, and the target location doesn't
3643 have to be in the same frame as the current one.
3647 @kindex si @r{(@code{stepi})}
3649 @itemx stepi @var{arg}
3651 Execute one machine instruction, then stop and return to the debugger.
3653 It is often useful to do @samp{display/i $pc} when stepping by machine
3654 instructions. This makes @value{GDBN} automatically display the next
3655 instruction to be executed, each time your program stops. @xref{Auto
3656 Display,, Automatic display}.
3658 An argument is a repeat count, as in @code{step}.
3662 @kindex ni @r{(@code{nexti})}
3664 @itemx nexti @var{arg}
3666 Execute one machine instruction, but if it is a function call,
3667 proceed until the function returns.
3669 An argument is a repeat count, as in @code{next}.
3676 A signal is an asynchronous event that can happen in a program. The
3677 operating system defines the possible kinds of signals, and gives each
3678 kind a name and a number. For example, in Unix @code{SIGINT} is the
3679 signal a program gets when you type an interrupt character (often @kbd{C-c});
3680 @code{SIGSEGV} is the signal a program gets from referencing a place in
3681 memory far away from all the areas in use; @code{SIGALRM} occurs when
3682 the alarm clock timer goes off (which happens only if your program has
3683 requested an alarm).
3685 @cindex fatal signals
3686 Some signals, including @code{SIGALRM}, are a normal part of the
3687 functioning of your program. Others, such as @code{SIGSEGV}, indicate
3688 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
3689 program has not specified in advance some other way to handle the signal.
3690 @code{SIGINT} does not indicate an error in your program, but it is normally
3691 fatal so it can carry out the purpose of the interrupt: to kill the program.
3693 @value{GDBN} has the ability to detect any occurrence of a signal in your
3694 program. You can tell @value{GDBN} in advance what to do for each kind of
3697 @cindex handling signals
3698 Normally, @value{GDBN} is set up to let the non-erroneous signals like
3699 @code{SIGALRM} be silently passed to your program
3700 (so as not to interfere with their role in the program's functioning)
3701 but to stop your program immediately whenever an error signal happens.
3702 You can change these settings with the @code{handle} command.
3705 @kindex info signals
3708 Print a table of all the kinds of signals and how @value{GDBN} has been told to
3709 handle each one. You can use this to see the signal numbers of all
3710 the defined types of signals.
3712 @code{info handle} is an alias for @code{info signals}.
3715 @item handle @var{signal} @var{keywords}@dots{}
3716 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
3717 can be the number of a signal or its name (with or without the
3718 @samp{SIG} at the beginning); a list of signal numbers of the form
3719 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
3720 known signals. The @var{keywords} say what change to make.
3724 The keywords allowed by the @code{handle} command can be abbreviated.
3725 Their full names are:
3729 @value{GDBN} should not stop your program when this signal happens. It may
3730 still print a message telling you that the signal has come in.
3733 @value{GDBN} should stop your program when this signal happens. This implies
3734 the @code{print} keyword as well.
3737 @value{GDBN} should print a message when this signal happens.
3740 @value{GDBN} should not mention the occurrence of the signal at all. This
3741 implies the @code{nostop} keyword as well.
3745 @value{GDBN} should allow your program to see this signal; your program
3746 can handle the signal, or else it may terminate if the signal is fatal
3747 and not handled. @code{pass} and @code{noignore} are synonyms.
3751 @value{GDBN} should not allow your program to see this signal.
3752 @code{nopass} and @code{ignore} are synonyms.
3756 When a signal stops your program, the signal is not visible to the
3758 continue. Your program sees the signal then, if @code{pass} is in
3759 effect for the signal in question @emph{at that time}. In other words,
3760 after @value{GDBN} reports a signal, you can use the @code{handle}
3761 command with @code{pass} or @code{nopass} to control whether your
3762 program sees that signal when you continue.
3764 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
3765 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
3766 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
3769 You can also use the @code{signal} command to prevent your program from
3770 seeing a signal, or cause it to see a signal it normally would not see,
3771 or to give it any signal at any time. For example, if your program stopped
3772 due to some sort of memory reference error, you might store correct
3773 values into the erroneous variables and continue, hoping to see more
3774 execution; but your program would probably terminate immediately as
3775 a result of the fatal signal once it saw the signal. To prevent this,
3776 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
3780 @section Stopping and starting multi-thread programs
3782 When your program has multiple threads (@pxref{Threads,, Debugging
3783 programs with multiple threads}), you can choose whether to set
3784 breakpoints on all threads, or on a particular thread.
3787 @cindex breakpoints and threads
3788 @cindex thread breakpoints
3789 @kindex break @dots{} thread @var{threadno}
3790 @item break @var{linespec} thread @var{threadno}
3791 @itemx break @var{linespec} thread @var{threadno} if @dots{}
3792 @var{linespec} specifies source lines; there are several ways of
3793 writing them, but the effect is always to specify some source line.
3795 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
3796 to specify that you only want @value{GDBN} to stop the program when a
3797 particular thread reaches this breakpoint. @var{threadno} is one of the
3798 numeric thread identifiers assigned by @value{GDBN}, shown in the first
3799 column of the @samp{info threads} display.
3801 If you do not specify @samp{thread @var{threadno}} when you set a
3802 breakpoint, the breakpoint applies to @emph{all} threads of your
3805 You can use the @code{thread} qualifier on conditional breakpoints as
3806 well; in this case, place @samp{thread @var{threadno}} before the
3807 breakpoint condition, like this:
3810 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
3815 @cindex stopped threads
3816 @cindex threads, stopped
3817 Whenever your program stops under @value{GDBN} for any reason,
3818 @emph{all} threads of execution stop, not just the current thread. This
3819 allows you to examine the overall state of the program, including
3820 switching between threads, without worrying that things may change
3823 @cindex thread breakpoints and system calls
3824 @cindex system calls and thread breakpoints
3825 @cindex premature return from system calls
3826 There is an unfortunate side effect. If one thread stops for a
3827 breakpoint, or for some other reason, and another thread is blocked in a
3828 system call, then the system call may return prematurely. This is a
3829 consequence of the interaction between multiple threads and the signals
3830 that @value{GDBN} uses to implement breakpoints and other events that
3833 To handle this problem, your program should check the return value of
3834 each system call and react appropriately. This is good programming
3837 For example, do not write code like this:
3843 The call to @code{sleep} will return early if a different thread stops
3844 at a breakpoint or for some other reason.
3846 Instead, write this:
3851 unslept = sleep (unslept);
3854 A system call is allowed to return early, so the system is still
3855 conforming to its specification. But @value{GDBN} does cause your
3856 multi-threaded program to behave differently than it would without
3859 Also, @value{GDBN} uses internal breakpoints in the thread library to
3860 monitor certain events such as thread creation and thread destruction.
3861 When such an event happens, a system call in another thread may return
3862 prematurely, even though your program does not appear to stop.
3864 @cindex continuing threads
3865 @cindex threads, continuing
3866 Conversely, whenever you restart the program, @emph{all} threads start
3867 executing. @emph{This is true even when single-stepping} with commands
3868 like @code{step} or @code{next}.
3870 In particular, @value{GDBN} cannot single-step all threads in lockstep.
3871 Since thread scheduling is up to your debugging target's operating
3872 system (not controlled by @value{GDBN}), other threads may
3873 execute more than one statement while the current thread completes a
3874 single step. Moreover, in general other threads stop in the middle of a
3875 statement, rather than at a clean statement boundary, when the program
3878 You might even find your program stopped in another thread after
3879 continuing or even single-stepping. This happens whenever some other
3880 thread runs into a breakpoint, a signal, or an exception before the
3881 first thread completes whatever you requested.
3883 On some OSes, you can lock the OS scheduler and thus allow only a single
3887 @item set scheduler-locking @var{mode}
3888 Set the scheduler locking mode. If it is @code{off}, then there is no
3889 locking and any thread may run at any time. If @code{on}, then only the
3890 current thread may run when the inferior is resumed. The @code{step}
3891 mode optimizes for single-stepping. It stops other threads from
3892 ``seizing the prompt'' by preempting the current thread while you are
3893 stepping. Other threads will only rarely (or never) get a chance to run
3894 when you step. They are more likely to run when you @samp{next} over a
3895 function call, and they are completely free to run when you use commands
3896 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
3897 thread hits a breakpoint during its timeslice, they will never steal the
3898 @value{GDBN} prompt away from the thread that you are debugging.
3900 @item show scheduler-locking
3901 Display the current scheduler locking mode.
3906 @chapter Examining the Stack
3908 When your program has stopped, the first thing you need to know is where it
3909 stopped and how it got there.
3912 Each time your program performs a function call, information about the call
3914 That information includes the location of the call in your program,
3915 the arguments of the call,
3916 and the local variables of the function being called.
3917 The information is saved in a block of data called a @dfn{stack frame}.
3918 The stack frames are allocated in a region of memory called the @dfn{call
3921 When your program stops, the @value{GDBN} commands for examining the
3922 stack allow you to see all of this information.
3924 @cindex selected frame
3925 One of the stack frames is @dfn{selected} by @value{GDBN} and many
3926 @value{GDBN} commands refer implicitly to the selected frame. In
3927 particular, whenever you ask @value{GDBN} for the value of a variable in
3928 your program, the value is found in the selected frame. There are
3929 special @value{GDBN} commands to select whichever frame you are
3930 interested in. @xref{Selection, ,Selecting a frame}.
3932 When your program stops, @value{GDBN} automatically selects the
3933 currently executing frame and describes it briefly, similar to the
3934 @code{frame} command (@pxref{Frame Info, ,Information about a frame}).
3937 * Frames:: Stack frames
3938 * Backtrace:: Backtraces
3939 * Selection:: Selecting a frame
3940 * Frame Info:: Information on a frame
3945 @section Stack frames
3947 @cindex frame, definition
3949 The call stack is divided up into contiguous pieces called @dfn{stack
3950 frames}, or @dfn{frames} for short; each frame is the data associated
3951 with one call to one function. The frame contains the arguments given
3952 to the function, the function's local variables, and the address at
3953 which the function is executing.
3955 @cindex initial frame
3956 @cindex outermost frame
3957 @cindex innermost frame
3958 When your program is started, the stack has only one frame, that of the
3959 function @code{main}. This is called the @dfn{initial} frame or the
3960 @dfn{outermost} frame. Each time a function is called, a new frame is
3961 made. Each time a function returns, the frame for that function invocation
3962 is eliminated. If a function is recursive, there can be many frames for
3963 the same function. The frame for the function in which execution is
3964 actually occurring is called the @dfn{innermost} frame. This is the most
3965 recently created of all the stack frames that still exist.
3967 @cindex frame pointer
3968 Inside your program, stack frames are identified by their addresses. A
3969 stack frame consists of many bytes, each of which has its own address; each
3970 kind of computer has a convention for choosing one byte whose
3971 address serves as the address of the frame. Usually this address is kept
3972 in a register called the @dfn{frame pointer register} while execution is
3973 going on in that frame.
3975 @cindex frame number
3976 @value{GDBN} assigns numbers to all existing stack frames, starting with
3977 zero for the innermost frame, one for the frame that called it,
3978 and so on upward. These numbers do not really exist in your program;
3979 they are assigned by @value{GDBN} to give you a way of designating stack
3980 frames in @value{GDBN} commands.
3982 @c The -fomit-frame-pointer below perennially causes hbox overflow
3983 @c underflow problems.
3984 @cindex frameless execution
3985 Some compilers provide a way to compile functions so that they operate
3986 without stack frames. (For example, the @value{GCC} option
3988 @samp{-fomit-frame-pointer}
3990 generates functions without a frame.)
3991 This is occasionally done with heavily used library functions to save
3992 the frame setup time. @value{GDBN} has limited facilities for dealing
3993 with these function invocations. If the innermost function invocation
3994 has no stack frame, @value{GDBN} nevertheless regards it as though
3995 it had a separate frame, which is numbered zero as usual, allowing
3996 correct tracing of the function call chain. However, @value{GDBN} has
3997 no provision for frameless functions elsewhere in the stack.
4000 @kindex frame@r{, command}
4001 @cindex current stack frame
4002 @item frame @var{args}
4003 The @code{frame} command allows you to move from one stack frame to another,
4004 and to print the stack frame you select. @var{args} may be either the
4005 address of the frame or the stack frame number. Without an argument,
4006 @code{frame} prints the current stack frame.
4008 @kindex select-frame
4009 @cindex selecting frame silently
4011 The @code{select-frame} command allows you to move from one stack frame
4012 to another without printing the frame. This is the silent version of
4021 @cindex stack traces
4022 A backtrace is a summary of how your program got where it is. It shows one
4023 line per frame, for many frames, starting with the currently executing
4024 frame (frame zero), followed by its caller (frame one), and on up the
4029 @kindex bt @r{(@code{backtrace})}
4032 Print a backtrace of the entire stack: one line per frame for all
4033 frames in the stack.
4035 You can stop the backtrace at any time by typing the system interrupt
4036 character, normally @kbd{C-c}.
4038 @item backtrace @var{n}
4040 Similar, but print only the innermost @var{n} frames.
4042 @item backtrace -@var{n}
4044 Similar, but print only the outermost @var{n} frames.
4049 @kindex info s @r{(@code{info stack})}
4050 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4051 are additional aliases for @code{backtrace}.
4053 Each line in the backtrace shows the frame number and the function name.
4054 The program counter value is also shown---unless you use @code{set
4055 print address off}. The backtrace also shows the source file name and
4056 line number, as well as the arguments to the function. The program
4057 counter value is omitted if it is at the beginning of the code for that
4060 Here is an example of a backtrace. It was made with the command
4061 @samp{bt 3}, so it shows the innermost three frames.
4065 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4067 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4068 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4070 (More stack frames follow...)
4075 The display for frame zero does not begin with a program counter
4076 value, indicating that your program has stopped at the beginning of the
4077 code for line @code{993} of @code{builtin.c}.
4079 @kindex set backtrace past-main
4080 @kindex show backtrace past-main
4081 @kindex set backtrace limit
4082 @kindex show backtrace limit
4084 Most programs have a standard user entry point---a place where system
4085 libraries and startup code transition into user code. For C this is
4086 @code{main}. When @value{GDBN} finds the entry function in a backtrace
4087 it will terminate the backtrace, to avoid tracing into highly
4088 system-specific (and generally uninteresting) code.
4090 If you need to examine the startup code, or limit the number of levels
4091 in a backtrace, you can change this behavior:
4094 @item set backtrace past-main
4095 @itemx set backtrace past-main on
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 Display the current user entry point backtrace policy.
4105 @item set backtrace limit @var{n}
4106 @itemx set backtrace limit 0
4107 @cindex backtrace limit
4108 Limit the backtrace to @var{n} levels. A value of zero means
4111 @item show backtrace limit
4112 Display the current limit on backtrace levels.
4116 @section Selecting a frame
4118 Most commands for examining the stack and other data in your program work on
4119 whichever stack frame is selected at the moment. Here are the commands for
4120 selecting a stack frame; all of them finish by printing a brief description
4121 of the stack frame just selected.
4124 @kindex frame@r{, selecting}
4125 @kindex f @r{(@code{frame})}
4128 Select frame number @var{n}. Recall that frame zero is the innermost
4129 (currently executing) frame, frame one is the frame that called the
4130 innermost one, and so on. The highest-numbered frame is the one for
4133 @item frame @var{addr}
4135 Select the frame at address @var{addr}. This is useful mainly if the
4136 chaining of stack frames has been damaged by a bug, making it
4137 impossible for @value{GDBN} to assign numbers properly to all frames. In
4138 addition, this can be useful when your program has multiple stacks and
4139 switches between them.
4141 On the SPARC architecture, @code{frame} needs two addresses to
4142 select an arbitrary frame: a frame pointer and a stack pointer.
4144 On the MIPS and Alpha architecture, it needs two addresses: a stack
4145 pointer and a program counter.
4147 On the 29k architecture, it needs three addresses: a register stack
4148 pointer, a program counter, and a memory stack pointer.
4149 @c note to future updaters: this is conditioned on a flag
4150 @c SETUP_ARBITRARY_FRAME in the tm-*.h files. The above is up to date
4151 @c as of 27 Jan 1994.
4155 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4156 advances toward the outermost frame, to higher frame numbers, to frames
4157 that have existed longer. @var{n} defaults to one.
4160 @kindex do @r{(@code{down})}
4162 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4163 advances toward the innermost frame, to lower frame numbers, to frames
4164 that were created more recently. @var{n} defaults to one. You may
4165 abbreviate @code{down} as @code{do}.
4168 All of these commands end by printing two lines of output describing the
4169 frame. The first line shows the frame number, the function name, the
4170 arguments, and the source file and line number of execution in that
4171 frame. The second line shows the text of that source line.
4179 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4181 10 read_input_file (argv[i]);
4185 After such a printout, the @code{list} command with no arguments
4186 prints ten lines centered on the point of execution in the frame.
4187 You can also edit the program at the point of execution with your favorite
4188 editing program by typing @code{edit}.
4189 @xref{List, ,Printing source lines},
4193 @kindex down-silently
4195 @item up-silently @var{n}
4196 @itemx down-silently @var{n}
4197 These two commands are variants of @code{up} and @code{down},
4198 respectively; they differ in that they do their work silently, without
4199 causing display of the new frame. They are intended primarily for use
4200 in @value{GDBN} command scripts, where the output might be unnecessary and
4205 @section Information about a frame
4207 There are several other commands to print information about the selected
4213 When used without any argument, this command does not change which
4214 frame is selected, but prints a brief description of the currently
4215 selected stack frame. It can be abbreviated @code{f}. With an
4216 argument, this command is used to select a stack frame.
4217 @xref{Selection, ,Selecting a frame}.
4220 @kindex info f @r{(@code{info frame})}
4223 This command prints a verbose description of the selected stack frame,
4228 the address of the frame
4230 the address of the next frame down (called by this frame)
4232 the address of the next frame up (caller of this frame)
4234 the language in which the source code corresponding to this frame is written
4236 the address of the frame's arguments
4238 the address of the frame's local variables
4240 the program counter saved in it (the address of execution in the caller frame)
4242 which registers were saved in the frame
4245 @noindent The verbose description is useful when
4246 something has gone wrong that has made the stack format fail to fit
4247 the usual conventions.
4249 @item info frame @var{addr}
4250 @itemx info f @var{addr}
4251 Print a verbose description of the frame at address @var{addr}, without
4252 selecting that frame. The selected frame remains unchanged by this
4253 command. This requires the same kind of address (more than one for some
4254 architectures) that you specify in the @code{frame} command.
4255 @xref{Selection, ,Selecting a frame}.
4259 Print the arguments of the selected frame, each on a separate line.
4263 Print the local variables of the selected frame, each on a separate
4264 line. These are all variables (declared either static or automatic)
4265 accessible at the point of execution of the selected frame.
4268 @cindex catch exceptions, list active handlers
4269 @cindex exception handlers, how to list
4271 Print a list of all the exception handlers that are active in the
4272 current stack frame at the current point of execution. To see other
4273 exception handlers, visit the associated frame (using the @code{up},
4274 @code{down}, or @code{frame} commands); then type @code{info catch}.
4275 @xref{Set Catchpoints, , Setting catchpoints}.
4281 @chapter Examining Source Files
4283 @value{GDBN} can print parts of your program's source, since the debugging
4284 information recorded in the program tells @value{GDBN} what source files were
4285 used to build it. When your program stops, @value{GDBN} spontaneously prints
4286 the line where it stopped. Likewise, when you select a stack frame
4287 (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
4288 execution in that frame has stopped. You can print other portions of
4289 source files by explicit command.
4291 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4292 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4293 @value{GDBN} under @sc{gnu} Emacs}.
4296 * List:: Printing source lines
4297 * Edit:: Editing source files
4298 * Search:: Searching source files
4299 * Source Path:: Specifying source directories
4300 * Machine Code:: Source and machine code
4304 @section Printing source lines
4307 @kindex l @r{(@code{list})}
4308 To print lines from a source file, use the @code{list} command
4309 (abbreviated @code{l}). By default, ten lines are printed.
4310 There are several ways to specify what part of the file you want to print.
4312 Here are the forms of the @code{list} command most commonly used:
4315 @item list @var{linenum}
4316 Print lines centered around line number @var{linenum} in the
4317 current source file.
4319 @item list @var{function}
4320 Print lines centered around the beginning of function
4324 Print more lines. If the last lines printed were printed with a
4325 @code{list} command, this prints lines following the last lines
4326 printed; however, if the last line printed was a solitary line printed
4327 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4328 Stack}), this prints lines centered around that line.
4331 Print lines just before the lines last printed.
4334 By default, @value{GDBN} prints ten source lines with any of these forms of
4335 the @code{list} command. You can change this using @code{set listsize}:
4338 @kindex set listsize
4339 @item set listsize @var{count}
4340 Make the @code{list} command display @var{count} source lines (unless
4341 the @code{list} argument explicitly specifies some other number).
4343 @kindex show listsize
4345 Display the number of lines that @code{list} prints.
4348 Repeating a @code{list} command with @key{RET} discards the argument,
4349 so it is equivalent to typing just @code{list}. This is more useful
4350 than listing the same lines again. An exception is made for an
4351 argument of @samp{-}; that argument is preserved in repetition so that
4352 each repetition moves up in the source file.
4355 In general, the @code{list} command expects you to supply zero, one or two
4356 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4357 of writing them, but the effect is always to specify some source line.
4358 Here is a complete description of the possible arguments for @code{list}:
4361 @item list @var{linespec}
4362 Print lines centered around the line specified by @var{linespec}.
4364 @item list @var{first},@var{last}
4365 Print lines from @var{first} to @var{last}. Both arguments are
4368 @item list ,@var{last}
4369 Print lines ending with @var{last}.
4371 @item list @var{first},
4372 Print lines starting with @var{first}.
4375 Print lines just after the lines last printed.
4378 Print lines just before the lines last printed.
4381 As described in the preceding table.
4384 Here are the ways of specifying a single source line---all the
4389 Specifies line @var{number} of the current source file.
4390 When a @code{list} command has two linespecs, this refers to
4391 the same source file as the first linespec.
4394 Specifies the line @var{offset} lines after the last line printed.
4395 When used as the second linespec in a @code{list} command that has
4396 two, this specifies the line @var{offset} lines down from the
4400 Specifies the line @var{offset} lines before the last line printed.
4402 @item @var{filename}:@var{number}
4403 Specifies line @var{number} in the source file @var{filename}.
4405 @item @var{function}
4406 Specifies the line that begins the body of the function @var{function}.
4407 For example: in C, this is the line with the open brace.
4409 @item @var{filename}:@var{function}
4410 Specifies the line of the open-brace that begins the body of the
4411 function @var{function} in the file @var{filename}. You only need the
4412 file name with a function name to avoid ambiguity when there are
4413 identically named functions in different source files.
4415 @item *@var{address}
4416 Specifies the line containing the program address @var{address}.
4417 @var{address} may be any expression.
4421 @section Editing source files
4422 @cindex editing source files
4425 @kindex e @r{(@code{edit})}
4426 To edit the lines in a source file, use the @code{edit} command.
4427 The editing program of your choice
4428 is invoked with the current line set to
4429 the active line in the program.
4430 Alternatively, there are several ways to specify what part of the file you
4431 want to print if you want to see other parts of the program.
4433 Here are the forms of the @code{edit} command most commonly used:
4437 Edit the current source file at the active line number in the program.
4439 @item edit @var{number}
4440 Edit the current source file with @var{number} as the active line number.
4442 @item edit @var{function}
4443 Edit the file containing @var{function} at the beginning of its definition.
4445 @item edit @var{filename}:@var{number}
4446 Specifies line @var{number} in the source file @var{filename}.
4448 @item edit @var{filename}:@var{function}
4449 Specifies the line that begins the body of the
4450 function @var{function} in the file @var{filename}. You only need the
4451 file name with a function name to avoid ambiguity when there are
4452 identically named functions in different source files.
4454 @item edit *@var{address}
4455 Specifies the line containing the program address @var{address}.
4456 @var{address} may be any expression.
4459 @subsection Choosing your editor
4460 You can customize @value{GDBN} to use any editor you want
4462 The only restriction is that your editor (say @code{ex}), recognizes the
4463 following command-line syntax:
4465 ex +@var{number} file
4467 The optional numeric value +@var{number} designates the active line in
4468 the file.}. By default, it is @value{EDITOR}, but you can change this
4469 by setting the environment variable @code{EDITOR} before using
4470 @value{GDBN}. For example, to configure @value{GDBN} to use the
4471 @code{vi} editor, you could use these commands with the @code{sh} shell:
4477 or in the @code{csh} shell,
4479 setenv EDITOR /usr/bin/vi
4484 @section Searching source files
4486 @kindex reverse-search
4488 There are two commands for searching through the current source file for a
4493 @kindex forward-search
4494 @item forward-search @var{regexp}
4495 @itemx search @var{regexp}
4496 The command @samp{forward-search @var{regexp}} checks each line,
4497 starting with the one following the last line listed, for a match for
4498 @var{regexp}. It lists the line that is found. You can use the
4499 synonym @samp{search @var{regexp}} or abbreviate the command name as
4502 @item reverse-search @var{regexp}
4503 The command @samp{reverse-search @var{regexp}} checks each line, starting
4504 with the one before the last line listed and going backward, for a match
4505 for @var{regexp}. It lists the line that is found. You can abbreviate
4506 this command as @code{rev}.
4510 @section Specifying source directories
4513 @cindex directories for source files
4514 Executable programs sometimes do not record the directories of the source
4515 files from which they were compiled, just the names. Even when they do,
4516 the directories could be moved between the compilation and your debugging
4517 session. @value{GDBN} has a list of directories to search for source files;
4518 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
4519 it tries all the directories in the list, in the order they are present
4520 in the list, until it finds a file with the desired name. Note that
4521 the executable search path is @emph{not} used for this purpose. Neither is
4522 the current working directory, unless it happens to be in the source
4525 If @value{GDBN} cannot find a source file in the source path, and the
4526 object program records a directory, @value{GDBN} tries that directory
4527 too. If the source path is empty, and there is no record of the
4528 compilation directory, @value{GDBN} looks in the current directory as a
4531 Whenever you reset or rearrange the source path, @value{GDBN} clears out
4532 any information it has cached about where source files are found and where
4533 each line is in the file.
4537 When you start @value{GDBN}, its source path includes only @samp{cdir}
4538 and @samp{cwd}, in that order.
4539 To add other directories, use the @code{directory} command.
4542 @item directory @var{dirname} @dots{}
4543 @item dir @var{dirname} @dots{}
4544 Add directory @var{dirname} to the front of the source path. Several
4545 directory names may be given to this command, separated by @samp{:}
4546 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
4547 part of absolute file names) or
4548 whitespace. You may specify a directory that is already in the source
4549 path; this moves it forward, so @value{GDBN} searches it sooner.
4553 @vindex $cdir@r{, convenience variable}
4554 @vindex $cwdr@r{, convenience variable}
4555 @cindex compilation directory
4556 @cindex current directory
4557 @cindex working directory
4558 @cindex directory, current
4559 @cindex directory, compilation
4560 You can use the string @samp{$cdir} to refer to the compilation
4561 directory (if one is recorded), and @samp{$cwd} to refer to the current
4562 working directory. @samp{$cwd} is not the same as @samp{.}---the former
4563 tracks the current working directory as it changes during your @value{GDBN}
4564 session, while the latter is immediately expanded to the current
4565 directory at the time you add an entry to the source path.
4568 Reset the source path to empty again. This requires confirmation.
4570 @c RET-repeat for @code{directory} is explicitly disabled, but since
4571 @c repeating it would be a no-op we do not say that. (thanks to RMS)
4573 @item show directories
4574 @kindex show directories
4575 Print the source path: show which directories it contains.
4578 If your source path is cluttered with directories that are no longer of
4579 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
4580 versions of source. You can correct the situation as follows:
4584 Use @code{directory} with no argument to reset the source path to empty.
4587 Use @code{directory} with suitable arguments to reinstall the
4588 directories you want in the source path. You can add all the
4589 directories in one command.
4593 @section Source and machine code
4595 You can use the command @code{info line} to map source lines to program
4596 addresses (and vice versa), and the command @code{disassemble} to display
4597 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
4598 mode, the @code{info line} command causes the arrow to point to the
4599 line specified. Also, @code{info line} prints addresses in symbolic form as
4604 @item info line @var{linespec}
4605 Print the starting and ending addresses of the compiled code for
4606 source line @var{linespec}. You can specify source lines in any of
4607 the ways understood by the @code{list} command (@pxref{List, ,Printing
4611 For example, we can use @code{info line} to discover the location of
4612 the object code for the first line of function
4613 @code{m4_changequote}:
4615 @c FIXME: I think this example should also show the addresses in
4616 @c symbolic form, as they usually would be displayed.
4618 (@value{GDBP}) info line m4_changequote
4619 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
4623 We can also inquire (using @code{*@var{addr}} as the form for
4624 @var{linespec}) what source line covers a particular address:
4626 (@value{GDBP}) info line *0x63ff
4627 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
4630 @cindex @code{$_} and @code{info line}
4631 @kindex x@r{(examine), and} info line
4632 After @code{info line}, the default address for the @code{x} command
4633 is changed to the starting address of the line, so that @samp{x/i} is
4634 sufficient to begin examining the machine code (@pxref{Memory,
4635 ,Examining memory}). Also, this address is saved as the value of the
4636 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
4641 @cindex assembly instructions
4642 @cindex instructions, assembly
4643 @cindex machine instructions
4644 @cindex listing machine instructions
4646 This specialized command dumps a range of memory as machine
4647 instructions. The default memory range is the function surrounding the
4648 program counter of the selected frame. A single argument to this
4649 command is a program counter value; @value{GDBN} dumps the function
4650 surrounding this value. Two arguments specify a range of addresses
4651 (first inclusive, second exclusive) to dump.
4654 The following example shows the disassembly of a range of addresses of
4655 HP PA-RISC 2.0 code:
4658 (@value{GDBP}) disas 0x32c4 0x32e4
4659 Dump of assembler code from 0x32c4 to 0x32e4:
4660 0x32c4 <main+204>: addil 0,dp
4661 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
4662 0x32cc <main+212>: ldil 0x3000,r31
4663 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
4664 0x32d4 <main+220>: ldo 0(r31),rp
4665 0x32d8 <main+224>: addil -0x800,dp
4666 0x32dc <main+228>: ldo 0x588(r1),r26
4667 0x32e0 <main+232>: ldil 0x3000,r31
4668 End of assembler dump.
4671 Some architectures have more than one commonly-used set of instruction
4672 mnemonics or other syntax.
4675 @kindex set disassembly-flavor
4676 @cindex assembly instructions
4677 @cindex instructions, assembly
4678 @cindex machine instructions
4679 @cindex listing machine instructions
4680 @cindex Intel disassembly flavor
4681 @cindex AT&T disassembly flavor
4682 @item set disassembly-flavor @var{instruction-set}
4683 Select the instruction set to use when disassembling the
4684 program via the @code{disassemble} or @code{x/i} commands.
4686 Currently this command is only defined for the Intel x86 family. You
4687 can set @var{instruction-set} to either @code{intel} or @code{att}.
4688 The default is @code{att}, the AT&T flavor used by default by Unix
4689 assemblers for x86-based targets.
4694 @chapter Examining Data
4696 @cindex printing data
4697 @cindex examining data
4700 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
4701 @c document because it is nonstandard... Under Epoch it displays in a
4702 @c different window or something like that.
4703 The usual way to examine data in your program is with the @code{print}
4704 command (abbreviated @code{p}), or its synonym @code{inspect}. It
4705 evaluates and prints the value of an expression of the language your
4706 program is written in (@pxref{Languages, ,Using @value{GDBN} with
4707 Different Languages}).
4710 @item print @var{expr}
4711 @itemx print /@var{f} @var{expr}
4712 @var{expr} is an expression (in the source language). By default the
4713 value of @var{expr} is printed in a format appropriate to its data type;
4714 you can choose a different format by specifying @samp{/@var{f}}, where
4715 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
4719 @itemx print /@var{f}
4720 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
4721 @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
4722 conveniently inspect the same value in an alternative format.
4725 A more low-level way of examining data is with the @code{x} command.
4726 It examines data in memory at a specified address and prints it in a
4727 specified format. @xref{Memory, ,Examining memory}.
4729 If you are interested in information about types, or about how the
4730 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
4731 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
4735 * Expressions:: Expressions
4736 * Variables:: Program variables
4737 * Arrays:: Artificial arrays
4738 * Output Formats:: Output formats
4739 * Memory:: Examining memory
4740 * Auto Display:: Automatic display
4741 * Print Settings:: Print settings
4742 * Value History:: Value history
4743 * Convenience Vars:: Convenience variables
4744 * Registers:: Registers
4745 * Floating Point Hardware:: Floating point hardware
4746 * Vector Unit:: Vector Unit
4747 * Auxiliary Vector:: Auxiliary data provided by operating system
4748 * Memory Region Attributes:: Memory region attributes
4749 * Dump/Restore Files:: Copy between memory and a file
4750 * Character Sets:: Debugging programs that use a different
4751 character set than GDB does
4755 @section Expressions
4758 @code{print} and many other @value{GDBN} commands accept an expression and
4759 compute its value. Any kind of constant, variable or operator defined
4760 by the programming language you are using is valid in an expression in
4761 @value{GDBN}. This includes conditional expressions, function calls,
4762 casts, and string constants. It also includes preprocessor macros, if
4763 you compiled your program to include this information; see
4766 @value{GDBN} supports array constants in expressions input by
4767 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
4768 you can use the command @code{print @{1, 2, 3@}} to build up an array in
4769 memory that is @code{malloc}ed in the target program.
4771 Because C is so widespread, most of the expressions shown in examples in
4772 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
4773 Languages}, for information on how to use expressions in other
4776 In this section, we discuss operators that you can use in @value{GDBN}
4777 expressions regardless of your programming language.
4779 Casts are supported in all languages, not just in C, because it is so
4780 useful to cast a number into a pointer in order to examine a structure
4781 at that address in memory.
4782 @c FIXME: casts supported---Mod2 true?
4784 @value{GDBN} supports these operators, in addition to those common
4785 to programming languages:
4789 @samp{@@} is a binary operator for treating parts of memory as arrays.
4790 @xref{Arrays, ,Artificial arrays}, for more information.
4793 @samp{::} allows you to specify a variable in terms of the file or
4794 function where it is defined. @xref{Variables, ,Program variables}.
4796 @cindex @{@var{type}@}
4797 @cindex type casting memory
4798 @cindex memory, viewing as typed object
4799 @cindex casts, to view memory
4800 @item @{@var{type}@} @var{addr}
4801 Refers to an object of type @var{type} stored at address @var{addr} in
4802 memory. @var{addr} may be any expression whose value is an integer or
4803 pointer (but parentheses are required around binary operators, just as in
4804 a cast). This construct is allowed regardless of what kind of data is
4805 normally supposed to reside at @var{addr}.
4809 @section Program variables
4811 The most common kind of expression to use is the name of a variable
4814 Variables in expressions are understood in the selected stack frame
4815 (@pxref{Selection, ,Selecting a frame}); they must be either:
4819 global (or file-static)
4826 visible according to the scope rules of the
4827 programming language from the point of execution in that frame
4830 @noindent This means that in the function
4845 you can examine and use the variable @code{a} whenever your program is
4846 executing within the function @code{foo}, but you can only use or
4847 examine the variable @code{b} while your program is executing inside
4848 the block where @code{b} is declared.
4850 @cindex variable name conflict
4851 There is an exception: you can refer to a variable or function whose
4852 scope is a single source file even if the current execution point is not
4853 in this file. But it is possible to have more than one such variable or
4854 function with the same name (in different source files). If that
4855 happens, referring to that name has unpredictable effects. If you wish,
4856 you can specify a static variable in a particular function or file,
4857 using the colon-colon notation:
4859 @cindex colon-colon, context for variables/functions
4861 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
4862 @cindex @code{::}, context for variables/functions
4865 @var{file}::@var{variable}
4866 @var{function}::@var{variable}
4870 Here @var{file} or @var{function} is the name of the context for the
4871 static @var{variable}. In the case of file names, you can use quotes to
4872 make sure @value{GDBN} parses the file name as a single word---for example,
4873 to print a global value of @code{x} defined in @file{f2.c}:
4876 (@value{GDBP}) p 'f2.c'::x
4879 @cindex C@t{++} scope resolution
4880 This use of @samp{::} is very rarely in conflict with the very similar
4881 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
4882 scope resolution operator in @value{GDBN} expressions.
4883 @c FIXME: Um, so what happens in one of those rare cases where it's in
4886 @cindex wrong values
4887 @cindex variable values, wrong
4889 @emph{Warning:} Occasionally, a local variable may appear to have the
4890 wrong value at certain points in a function---just after entry to a new
4891 scope, and just before exit.
4893 You may see this problem when you are stepping by machine instructions.
4894 This is because, on most machines, it takes more than one instruction to
4895 set up a stack frame (including local variable definitions); if you are
4896 stepping by machine instructions, variables may appear to have the wrong
4897 values until the stack frame is completely built. On exit, it usually
4898 also takes more than one machine instruction to destroy a stack frame;
4899 after you begin stepping through that group of instructions, local
4900 variable definitions may be gone.
4902 This may also happen when the compiler does significant optimizations.
4903 To be sure of always seeing accurate values, turn off all optimization
4906 @cindex ``No symbol "foo" in current context''
4907 Another possible effect of compiler optimizations is to optimize
4908 unused variables out of existence, or assign variables to registers (as
4909 opposed to memory addresses). Depending on the support for such cases
4910 offered by the debug info format used by the compiler, @value{GDBN}
4911 might not be able to display values for such local variables. If that
4912 happens, @value{GDBN} will print a message like this:
4915 No symbol "foo" in current context.
4918 To solve such problems, either recompile without optimizations, or use a
4919 different debug info format, if the compiler supports several such
4920 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler
4921 usually supports the @option{-gstabs+} option. @option{-gstabs+}
4922 produces debug info in a format that is superior to formats such as
4923 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
4924 an effective form for debug info. @xref{Debugging Options,,Options
4925 for Debugging Your Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}.
4929 @section Artificial arrays
4931 @cindex artificial array
4932 @kindex @@@r{, referencing memory as an array}
4933 It is often useful to print out several successive objects of the
4934 same type in memory; a section of an array, or an array of
4935 dynamically determined size for which only a pointer exists in the
4938 You can do this by referring to a contiguous span of memory as an
4939 @dfn{artificial array}, using the binary operator @samp{@@}. The left
4940 operand of @samp{@@} should be the first element of the desired array
4941 and be an individual object. The right operand should be the desired length
4942 of the array. The result is an array value whose elements are all of
4943 the type of the left argument. The first element is actually the left
4944 argument; the second element comes from bytes of memory immediately
4945 following those that hold the first element, and so on. Here is an
4946 example. If a program says
4949 int *array = (int *) malloc (len * sizeof (int));
4953 you can print the contents of @code{array} with
4959 The left operand of @samp{@@} must reside in memory. Array values made
4960 with @samp{@@} in this way behave just like other arrays in terms of
4961 subscripting, and are coerced to pointers when used in expressions.
4962 Artificial arrays most often appear in expressions via the value history
4963 (@pxref{Value History, ,Value history}), after printing one out.
4965 Another way to create an artificial array is to use a cast.
4966 This re-interprets a value as if it were an array.
4967 The value need not be in memory:
4969 (@value{GDBP}) p/x (short[2])0x12345678
4970 $1 = @{0x1234, 0x5678@}
4973 As a convenience, if you leave the array length out (as in
4974 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
4975 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
4977 (@value{GDBP}) p/x (short[])0x12345678
4978 $2 = @{0x1234, 0x5678@}
4981 Sometimes the artificial array mechanism is not quite enough; in
4982 moderately complex data structures, the elements of interest may not
4983 actually be adjacent---for example, if you are interested in the values
4984 of pointers in an array. One useful work-around in this situation is
4985 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
4986 variables}) as a counter in an expression that prints the first
4987 interesting value, and then repeat that expression via @key{RET}. For
4988 instance, suppose you have an array @code{dtab} of pointers to
4989 structures, and you are interested in the values of a field @code{fv}
4990 in each structure. Here is an example of what you might type:
5000 @node Output Formats
5001 @section Output formats
5003 @cindex formatted output
5004 @cindex output formats
5005 By default, @value{GDBN} prints a value according to its data type. Sometimes
5006 this is not what you want. For example, you might want to print a number
5007 in hex, or a pointer in decimal. Or you might want to view data in memory
5008 at a certain address as a character string or as an instruction. To do
5009 these things, specify an @dfn{output format} when you print a value.
5011 The simplest use of output formats is to say how to print a value
5012 already computed. This is done by starting the arguments of the
5013 @code{print} command with a slash and a format letter. The format
5014 letters supported are:
5018 Regard the bits of the value as an integer, and print the integer in
5022 Print as integer in signed decimal.
5025 Print as integer in unsigned decimal.
5028 Print as integer in octal.
5031 Print as integer in binary. The letter @samp{t} stands for ``two''.
5032 @footnote{@samp{b} cannot be used because these format letters are also
5033 used with the @code{x} command, where @samp{b} stands for ``byte'';
5034 see @ref{Memory,,Examining memory}.}
5037 @cindex unknown address, locating
5038 @cindex locate address
5039 Print as an address, both absolute in hexadecimal and as an offset from
5040 the nearest preceding symbol. You can use this format used to discover
5041 where (in what function) an unknown address is located:
5044 (@value{GDBP}) p/a 0x54320
5045 $3 = 0x54320 <_initialize_vx+396>
5049 The command @code{info symbol 0x54320} yields similar results.
5050 @xref{Symbols, info symbol}.
5053 Regard as an integer and print it as a character constant.
5056 Regard the bits of the value as a floating point number and print
5057 using typical floating point syntax.
5060 For example, to print the program counter in hex (@pxref{Registers}), type
5067 Note that no space is required before the slash; this is because command
5068 names in @value{GDBN} cannot contain a slash.
5070 To reprint the last value in the value history with a different format,
5071 you can use the @code{print} command with just a format and no
5072 expression. For example, @samp{p/x} reprints the last value in hex.
5075 @section Examining memory
5077 You can use the command @code{x} (for ``examine'') to examine memory in
5078 any of several formats, independently of your program's data types.
5080 @cindex examining memory
5082 @kindex x @r{(examine memory)}
5083 @item x/@var{nfu} @var{addr}
5086 Use the @code{x} command to examine memory.
5089 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5090 much memory to display and how to format it; @var{addr} is an
5091 expression giving the address where you want to start displaying memory.
5092 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5093 Several commands set convenient defaults for @var{addr}.
5096 @item @var{n}, the repeat count
5097 The repeat count is a decimal integer; the default is 1. It specifies
5098 how much memory (counting by units @var{u}) to display.
5099 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5102 @item @var{f}, the display format
5103 The display format is one of the formats used by @code{print},
5104 @samp{s} (null-terminated string), or @samp{i} (machine instruction).
5105 The default is @samp{x} (hexadecimal) initially.
5106 The default changes each time you use either @code{x} or @code{print}.
5108 @item @var{u}, the unit size
5109 The unit size is any of
5115 Halfwords (two bytes).
5117 Words (four bytes). This is the initial default.
5119 Giant words (eight bytes).
5122 Each time you specify a unit size with @code{x}, that size becomes the
5123 default unit the next time you use @code{x}. (For the @samp{s} and
5124 @samp{i} formats, the unit size is ignored and is normally not written.)
5126 @item @var{addr}, starting display address
5127 @var{addr} is the address where you want @value{GDBN} to begin displaying
5128 memory. The expression need not have a pointer value (though it may);
5129 it is always interpreted as an integer address of a byte of memory.
5130 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5131 @var{addr} is usually just after the last address examined---but several
5132 other commands also set the default address: @code{info breakpoints} (to
5133 the address of the last breakpoint listed), @code{info line} (to the
5134 starting address of a line), and @code{print} (if you use it to display
5135 a value from memory).
5138 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5139 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5140 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5141 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5142 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5144 Since the letters indicating unit sizes are all distinct from the
5145 letters specifying output formats, you do not have to remember whether
5146 unit size or format comes first; either order works. The output
5147 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5148 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5150 Even though the unit size @var{u} is ignored for the formats @samp{s}
5151 and @samp{i}, you might still want to use a count @var{n}; for example,
5152 @samp{3i} specifies that you want to see three machine instructions,
5153 including any operands. The command @code{disassemble} gives an
5154 alternative way of inspecting machine instructions; see @ref{Machine
5155 Code,,Source and machine code}.
5157 All the defaults for the arguments to @code{x} are designed to make it
5158 easy to continue scanning memory with minimal specifications each time
5159 you use @code{x}. For example, after you have inspected three machine
5160 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5161 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5162 the repeat count @var{n} is used again; the other arguments default as
5163 for successive uses of @code{x}.
5165 @cindex @code{$_}, @code{$__}, and value history
5166 The addresses and contents printed by the @code{x} command are not saved
5167 in the value history because there is often too much of them and they
5168 would get in the way. Instead, @value{GDBN} makes these values available for
5169 subsequent use in expressions as values of the convenience variables
5170 @code{$_} and @code{$__}. After an @code{x} command, the last address
5171 examined is available for use in expressions in the convenience variable
5172 @code{$_}. The contents of that address, as examined, are available in
5173 the convenience variable @code{$__}.
5175 If the @code{x} command has a repeat count, the address and contents saved
5176 are from the last memory unit printed; this is not the same as the last
5177 address printed if several units were printed on the last line of output.
5180 @section Automatic display
5181 @cindex automatic display
5182 @cindex display of expressions
5184 If you find that you want to print the value of an expression frequently
5185 (to see how it changes), you might want to add it to the @dfn{automatic
5186 display list} so that @value{GDBN} prints its value each time your program stops.
5187 Each expression added to the list is given a number to identify it;
5188 to remove an expression from the list, you specify that number.
5189 The automatic display looks like this:
5193 3: bar[5] = (struct hack *) 0x3804
5197 This display shows item numbers, expressions and their current values. As with
5198 displays you request manually using @code{x} or @code{print}, you can
5199 specify the output format you prefer; in fact, @code{display} decides
5200 whether to use @code{print} or @code{x} depending on how elaborate your
5201 format specification is---it uses @code{x} if you specify a unit size,
5202 or one of the two formats (@samp{i} and @samp{s}) that are only
5203 supported by @code{x}; otherwise it uses @code{print}.
5207 @item display @var{expr}
5208 Add the expression @var{expr} to the list of expressions to display
5209 each time your program stops. @xref{Expressions, ,Expressions}.
5211 @code{display} does not repeat if you press @key{RET} again after using it.
5213 @item display/@var{fmt} @var{expr}
5214 For @var{fmt} specifying only a display format and not a size or
5215 count, add the expression @var{expr} to the auto-display list but
5216 arrange to display it each time in the specified format @var{fmt}.
5217 @xref{Output Formats,,Output formats}.
5219 @item display/@var{fmt} @var{addr}
5220 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
5221 number of units, add the expression @var{addr} as a memory address to
5222 be examined each time your program stops. Examining means in effect
5223 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
5226 For example, @samp{display/i $pc} can be helpful, to see the machine
5227 instruction about to be executed each time execution stops (@samp{$pc}
5228 is a common name for the program counter; @pxref{Registers, ,Registers}).
5231 @kindex delete display
5233 @item undisplay @var{dnums}@dots{}
5234 @itemx delete display @var{dnums}@dots{}
5235 Remove item numbers @var{dnums} from the list of expressions to display.
5237 @code{undisplay} does not repeat if you press @key{RET} after using it.
5238 (Otherwise you would just get the error @samp{No display number @dots{}}.)
5240 @kindex disable display
5241 @item disable display @var{dnums}@dots{}
5242 Disable the display of item numbers @var{dnums}. A disabled display
5243 item is not printed automatically, but is not forgotten. It may be
5244 enabled again later.
5246 @kindex enable display
5247 @item enable display @var{dnums}@dots{}
5248 Enable display of item numbers @var{dnums}. It becomes effective once
5249 again in auto display of its expression, until you specify otherwise.
5252 Display the current values of the expressions on the list, just as is
5253 done when your program stops.
5255 @kindex info display
5257 Print the list of expressions previously set up to display
5258 automatically, each one with its item number, but without showing the
5259 values. This includes disabled expressions, which are marked as such.
5260 It also includes expressions which would not be displayed right now
5261 because they refer to automatic variables not currently available.
5264 If a display expression refers to local variables, then it does not make
5265 sense outside the lexical context for which it was set up. Such an
5266 expression is disabled when execution enters a context where one of its
5267 variables is not defined. For example, if you give the command
5268 @code{display last_char} while inside a function with an argument
5269 @code{last_char}, @value{GDBN} displays this argument while your program
5270 continues to stop inside that function. When it stops elsewhere---where
5271 there is no variable @code{last_char}---the display is disabled
5272 automatically. The next time your program stops where @code{last_char}
5273 is meaningful, you can enable the display expression once again.
5275 @node Print Settings
5276 @section Print settings
5278 @cindex format options
5279 @cindex print settings
5280 @value{GDBN} provides the following ways to control how arrays, structures,
5281 and symbols are printed.
5284 These settings are useful for debugging programs in any language:
5287 @kindex set print address
5288 @item set print address
5289 @itemx set print address on
5290 @value{GDBN} prints memory addresses showing the location of stack
5291 traces, structure values, pointer values, breakpoints, and so forth,
5292 even when it also displays the contents of those addresses. The default
5293 is @code{on}. For example, this is what a stack frame display looks like with
5294 @code{set print address on}:
5299 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
5301 530 if (lquote != def_lquote)
5305 @item set print address off
5306 Do not print addresses when displaying their contents. For example,
5307 this is the same stack frame displayed with @code{set print address off}:
5311 (@value{GDBP}) set print addr off
5313 #0 set_quotes (lq="<<", rq=">>") at input.c:530
5314 530 if (lquote != def_lquote)
5318 You can use @samp{set print address off} to eliminate all machine
5319 dependent displays from the @value{GDBN} interface. For example, with
5320 @code{print address off}, you should get the same text for backtraces on
5321 all machines---whether or not they involve pointer arguments.
5323 @kindex show print address
5324 @item show print address
5325 Show whether or not addresses are to be printed.
5328 When @value{GDBN} prints a symbolic address, it normally prints the
5329 closest earlier symbol plus an offset. If that symbol does not uniquely
5330 identify the address (for example, it is a name whose scope is a single
5331 source file), you may need to clarify. One way to do this is with
5332 @code{info line}, for example @samp{info line *0x4537}. Alternately,
5333 you can set @value{GDBN} to print the source file and line number when
5334 it prints a symbolic address:
5337 @kindex set print symbol-filename
5338 @item set print symbol-filename on
5339 Tell @value{GDBN} to print the source file name and line number of a
5340 symbol in the symbolic form of an address.
5342 @item set print symbol-filename off
5343 Do not print source file name and line number of a symbol. This is the
5346 @kindex show print symbol-filename
5347 @item show print symbol-filename
5348 Show whether or not @value{GDBN} will print the source file name and
5349 line number of a symbol in the symbolic form of an address.
5352 Another situation where it is helpful to show symbol filenames and line
5353 numbers is when disassembling code; @value{GDBN} shows you the line
5354 number and source file that corresponds to each instruction.
5356 Also, you may wish to see the symbolic form only if the address being
5357 printed is reasonably close to the closest earlier symbol:
5360 @kindex set print max-symbolic-offset
5361 @item set print max-symbolic-offset @var{max-offset}
5362 Tell @value{GDBN} to only display the symbolic form of an address if the
5363 offset between the closest earlier symbol and the address is less than
5364 @var{max-offset}. The default is 0, which tells @value{GDBN}
5365 to always print the symbolic form of an address if any symbol precedes it.
5367 @kindex show print max-symbolic-offset
5368 @item show print max-symbolic-offset
5369 Ask how large the maximum offset is that @value{GDBN} prints in a
5373 @cindex wild pointer, interpreting
5374 @cindex pointer, finding referent
5375 If you have a pointer and you are not sure where it points, try
5376 @samp{set print symbol-filename on}. Then you can determine the name
5377 and source file location of the variable where it points, using
5378 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
5379 For example, here @value{GDBN} shows that a variable @code{ptt} points
5380 at another variable @code{t}, defined in @file{hi2.c}:
5383 (@value{GDBP}) set print symbol-filename on
5384 (@value{GDBP}) p/a ptt
5385 $4 = 0xe008 <t in hi2.c>
5389 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
5390 does not show the symbol name and filename of the referent, even with
5391 the appropriate @code{set print} options turned on.
5394 Other settings control how different kinds of objects are printed:
5397 @kindex set print array
5398 @item set print array
5399 @itemx set print array on
5400 Pretty print arrays. This format is more convenient to read,
5401 but uses more space. The default is off.
5403 @item set print array off
5404 Return to compressed format for arrays.
5406 @kindex show print array
5407 @item show print array
5408 Show whether compressed or pretty format is selected for displaying
5411 @kindex set print elements
5412 @item set print elements @var{number-of-elements}
5413 Set a limit on how many elements of an array @value{GDBN} will print.
5414 If @value{GDBN} is printing a large array, it stops printing after it has
5415 printed the number of elements set by the @code{set print elements} command.
5416 This limit also applies to the display of strings.
5417 When @value{GDBN} starts, this limit is set to 200.
5418 Setting @var{number-of-elements} to zero means that the printing is unlimited.
5420 @kindex show print elements
5421 @item show print elements
5422 Display the number of elements of a large array that @value{GDBN} will print.
5423 If the number is 0, then the printing is unlimited.
5425 @kindex set print null-stop
5426 @item set print null-stop
5427 Cause @value{GDBN} to stop printing the characters of an array when the first
5428 @sc{null} is encountered. This is useful when large arrays actually
5429 contain only short strings.
5432 @kindex set print pretty
5433 @item set print pretty on
5434 Cause @value{GDBN} to print structures in an indented format with one member
5435 per line, like this:
5450 @item set print pretty off
5451 Cause @value{GDBN} to print structures in a compact format, like this:
5455 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
5456 meat = 0x54 "Pork"@}
5461 This is the default format.
5463 @kindex show print pretty
5464 @item show print pretty
5465 Show which format @value{GDBN} is using to print structures.
5467 @kindex set print sevenbit-strings
5468 @item set print sevenbit-strings on
5469 Print using only seven-bit characters; if this option is set,
5470 @value{GDBN} displays any eight-bit characters (in strings or
5471 character values) using the notation @code{\}@var{nnn}. This setting is
5472 best if you are working in English (@sc{ascii}) and you use the
5473 high-order bit of characters as a marker or ``meta'' bit.
5475 @item set print sevenbit-strings off
5476 Print full eight-bit characters. This allows the use of more
5477 international character sets, and is the default.
5479 @kindex show print sevenbit-strings
5480 @item show print sevenbit-strings
5481 Show whether or not @value{GDBN} is printing only seven-bit characters.
5483 @kindex set print union
5484 @item set print union on
5485 Tell @value{GDBN} to print unions which are contained in structures. This
5486 is the default setting.
5488 @item set print union off
5489 Tell @value{GDBN} not to print unions which are contained in structures.
5491 @kindex show print union
5492 @item show print union
5493 Ask @value{GDBN} whether or not it will print unions which are contained in
5496 For example, given the declarations
5499 typedef enum @{Tree, Bug@} Species;
5500 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
5501 typedef enum @{Caterpillar, Cocoon, Butterfly@}
5512 struct thing foo = @{Tree, @{Acorn@}@};
5516 with @code{set print union on} in effect @samp{p foo} would print
5519 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
5523 and with @code{set print union off} in effect it would print
5526 $1 = @{it = Tree, form = @{...@}@}
5532 These settings are of interest when debugging C@t{++} programs:
5536 @kindex set print demangle
5537 @item set print demangle
5538 @itemx set print demangle on
5539 Print C@t{++} names in their source form rather than in the encoded
5540 (``mangled'') form passed to the assembler and linker for type-safe
5541 linkage. The default is on.
5543 @kindex show print demangle
5544 @item show print demangle
5545 Show whether C@t{++} names are printed in mangled or demangled form.
5547 @kindex set print asm-demangle
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 @kindex show print asm-demangle
5555 @item show print asm-demangle
5556 Show whether C@t{++} names in assembly listings are printed in mangled
5559 @kindex set demangle-style
5560 @cindex C@t{++} symbol decoding style
5561 @cindex symbol decoding style, C@t{++}
5562 @item set demangle-style @var{style}
5563 Choose among several encoding schemes used by different compilers to
5564 represent C@t{++} names. The choices for @var{style} are currently:
5568 Allow @value{GDBN} to choose a decoding style by inspecting your program.
5571 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
5572 This is the default.
5575 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
5578 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
5581 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
5582 @strong{Warning:} this setting alone is not sufficient to allow
5583 debugging @code{cfront}-generated executables. @value{GDBN} would
5584 require further enhancement to permit that.
5587 If you omit @var{style}, you will see a list of possible formats.
5589 @kindex show demangle-style
5590 @item show demangle-style
5591 Display the encoding style currently in use for decoding C@t{++} symbols.
5593 @kindex set print object
5594 @item set print object
5595 @itemx set print object on
5596 When displaying a pointer to an object, identify the @emph{actual}
5597 (derived) type of the object rather than the @emph{declared} type, using
5598 the virtual function table.
5600 @item set print object off
5601 Display only the declared type of objects, without reference to the
5602 virtual function table. This is the default setting.
5604 @kindex show print object
5605 @item show print object
5606 Show whether actual, or declared, object types are displayed.
5608 @kindex set print static-members
5609 @item set print static-members
5610 @itemx set print static-members on
5611 Print static members when displaying a C@t{++} object. The default is on.
5613 @item set print static-members off
5614 Do not print static members when displaying a C@t{++} object.
5616 @kindex show print static-members
5617 @item show print static-members
5618 Show whether C@t{++} static members are printed, or not.
5620 @c These don't work with HP ANSI C++ yet.
5621 @kindex set print vtbl
5622 @item set print vtbl
5623 @itemx set print vtbl on
5624 Pretty print C@t{++} virtual function tables. The default is off.
5625 (The @code{vtbl} commands do not work on programs compiled with the HP
5626 ANSI C@t{++} compiler (@code{aCC}).)
5628 @item set print vtbl off
5629 Do not pretty print C@t{++} virtual function tables.
5631 @kindex show print vtbl
5632 @item show print vtbl
5633 Show whether C@t{++} virtual function tables are pretty printed, or not.
5637 @section Value history
5639 @cindex value history
5640 Values printed by the @code{print} command are saved in the @value{GDBN}
5641 @dfn{value history}. This allows you to refer to them in other expressions.
5642 Values are kept until the symbol table is re-read or discarded
5643 (for example with the @code{file} or @code{symbol-file} commands).
5644 When the symbol table changes, the value history is discarded,
5645 since the values may contain pointers back to the types defined in the
5650 @cindex history number
5651 The values printed are given @dfn{history numbers} by which you can
5652 refer to them. These are successive integers starting with one.
5653 @code{print} shows you the history number assigned to a value by
5654 printing @samp{$@var{num} = } before the value; here @var{num} is the
5657 To refer to any previous value, use @samp{$} followed by the value's
5658 history number. The way @code{print} labels its output is designed to
5659 remind you of this. Just @code{$} refers to the most recent value in
5660 the history, and @code{$$} refers to the value before that.
5661 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
5662 is the value just prior to @code{$$}, @code{$$1} is equivalent to
5663 @code{$$}, and @code{$$0} is equivalent to @code{$}.
5665 For example, suppose you have just printed a pointer to a structure and
5666 want to see the contents of the structure. It suffices to type
5672 If you have a chain of structures where the component @code{next} points
5673 to the next one, you can print the contents of the next one with this:
5680 You can print successive links in the chain by repeating this
5681 command---which you can do by just typing @key{RET}.
5683 Note that the history records values, not expressions. If the value of
5684 @code{x} is 4 and you type these commands:
5692 then the value recorded in the value history by the @code{print} command
5693 remains 4 even though the value of @code{x} has changed.
5698 Print the last ten values in the value history, with their item numbers.
5699 This is like @samp{p@ $$9} repeated ten times, except that @code{show
5700 values} does not change the history.
5702 @item show values @var{n}
5703 Print ten history values centered on history item number @var{n}.
5706 Print ten history values just after the values last printed. If no more
5707 values are available, @code{show values +} produces no display.
5710 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
5711 same effect as @samp{show values +}.
5713 @node Convenience Vars
5714 @section Convenience variables
5716 @cindex convenience variables
5717 @value{GDBN} provides @dfn{convenience variables} that you can use within
5718 @value{GDBN} to hold on to a value and refer to it later. These variables
5719 exist entirely within @value{GDBN}; they are not part of your program, and
5720 setting a convenience variable has no direct effect on further execution
5721 of your program. That is why you can use them freely.
5723 Convenience variables are prefixed with @samp{$}. Any name preceded by
5724 @samp{$} can be used for a convenience variable, unless it is one of
5725 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
5726 (Value history references, in contrast, are @emph{numbers} preceded
5727 by @samp{$}. @xref{Value History, ,Value history}.)
5729 You can save a value in a convenience variable with an assignment
5730 expression, just as you would set a variable in your program.
5734 set $foo = *object_ptr
5738 would save in @code{$foo} the value contained in the object pointed to by
5741 Using a convenience variable for the first time creates it, but its
5742 value is @code{void} until you assign a new value. You can alter the
5743 value with another assignment at any time.
5745 Convenience variables have no fixed types. You can assign a convenience
5746 variable any type of value, including structures and arrays, even if
5747 that variable already has a value of a different type. The convenience
5748 variable, when used as an expression, has the type of its current value.
5751 @kindex show convenience
5752 @item show convenience
5753 Print a list of convenience variables used so far, and their values.
5754 Abbreviated @code{show conv}.
5757 One of the ways to use a convenience variable is as a counter to be
5758 incremented or a pointer to be advanced. For example, to print
5759 a field from successive elements of an array of structures:
5763 print bar[$i++]->contents
5767 Repeat that command by typing @key{RET}.
5769 Some convenience variables are created automatically by @value{GDBN} and given
5770 values likely to be useful.
5773 @vindex $_@r{, convenience variable}
5775 The variable @code{$_} is automatically set by the @code{x} command to
5776 the last address examined (@pxref{Memory, ,Examining memory}). Other
5777 commands which provide a default address for @code{x} to examine also
5778 set @code{$_} to that address; these commands include @code{info line}
5779 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
5780 except when set by the @code{x} command, in which case it is a pointer
5781 to the type of @code{$__}.
5783 @vindex $__@r{, convenience variable}
5785 The variable @code{$__} is automatically set by the @code{x} command
5786 to the value found in the last address examined. Its type is chosen
5787 to match the format in which the data was printed.
5790 @vindex $_exitcode@r{, convenience variable}
5791 The variable @code{$_exitcode} is automatically set to the exit code when
5792 the program being debugged terminates.
5795 On HP-UX systems, if you refer to a function or variable name that
5796 begins with a dollar sign, @value{GDBN} searches for a user or system
5797 name first, before it searches for a convenience variable.
5803 You can refer to machine register contents, in expressions, as variables
5804 with names starting with @samp{$}. The names of registers are different
5805 for each machine; use @code{info registers} to see the names used on
5809 @kindex info registers
5810 @item info registers
5811 Print the names and values of all registers except floating-point
5812 and vector registers (in the selected stack frame).
5814 @kindex info all-registers
5815 @cindex floating point registers
5816 @item info all-registers
5817 Print the names and values of all registers, including floating-point
5818 and vector registers (in the selected stack frame).
5820 @item info registers @var{regname} @dots{}
5821 Print the @dfn{relativized} value of each specified register @var{regname}.
5822 As discussed in detail below, register values are normally relative to
5823 the selected stack frame. @var{regname} may be any register name valid on
5824 the machine you are using, with or without the initial @samp{$}.
5827 @value{GDBN} has four ``standard'' register names that are available (in
5828 expressions) on most machines---whenever they do not conflict with an
5829 architecture's canonical mnemonics for registers. The register names
5830 @code{$pc} and @code{$sp} are used for the program counter register and
5831 the stack pointer. @code{$fp} is used for a register that contains a
5832 pointer to the current stack frame, and @code{$ps} is used for a
5833 register that contains the processor status. For example,
5834 you could print the program counter in hex with
5841 or print the instruction to be executed next with
5848 or add four to the stack pointer@footnote{This is a way of removing
5849 one word from the stack, on machines where stacks grow downward in
5850 memory (most machines, nowadays). This assumes that the innermost
5851 stack frame is selected; setting @code{$sp} is not allowed when other
5852 stack frames are selected. To pop entire frames off the stack,
5853 regardless of machine architecture, use @code{return};
5854 see @ref{Returning, ,Returning from a function}.} with
5860 Whenever possible, these four standard register names are available on
5861 your machine even though the machine has different canonical mnemonics,
5862 so long as there is no conflict. The @code{info registers} command
5863 shows the canonical names. For example, on the SPARC, @code{info
5864 registers} displays the processor status register as @code{$psr} but you
5865 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
5866 is an alias for the @sc{eflags} register.
5868 @value{GDBN} always considers the contents of an ordinary register as an
5869 integer when the register is examined in this way. Some machines have
5870 special registers which can hold nothing but floating point; these
5871 registers are considered to have floating point values. There is no way
5872 to refer to the contents of an ordinary register as floating point value
5873 (although you can @emph{print} it as a floating point value with
5874 @samp{print/f $@var{regname}}).
5876 Some registers have distinct ``raw'' and ``virtual'' data formats. This
5877 means that the data format in which the register contents are saved by
5878 the operating system is not the same one that your program normally
5879 sees. For example, the registers of the 68881 floating point
5880 coprocessor are always saved in ``extended'' (raw) format, but all C
5881 programs expect to work with ``double'' (virtual) format. In such
5882 cases, @value{GDBN} normally works with the virtual format only (the format
5883 that makes sense for your program), but the @code{info registers} command
5884 prints the data in both formats.
5886 Normally, register values are relative to the selected stack frame
5887 (@pxref{Selection, ,Selecting a frame}). This means that you get the
5888 value that the register would contain if all stack frames farther in
5889 were exited and their saved registers restored. In order to see the
5890 true contents of hardware registers, you must select the innermost
5891 frame (with @samp{frame 0}).
5893 However, @value{GDBN} must deduce where registers are saved, from the machine
5894 code generated by your compiler. If some registers are not saved, or if
5895 @value{GDBN} is unable to locate the saved registers, the selected stack
5896 frame makes no difference.
5898 @node Floating Point Hardware
5899 @section Floating point hardware
5900 @cindex floating point
5902 Depending on the configuration, @value{GDBN} may be able to give
5903 you more information about the status of the floating point hardware.
5908 Display hardware-dependent information about the floating
5909 point unit. The exact contents and layout vary depending on the
5910 floating point chip. Currently, @samp{info float} is supported on
5911 the ARM and x86 machines.
5915 @section Vector Unit
5918 Depending on the configuration, @value{GDBN} may be able to give you
5919 more information about the status of the vector unit.
5924 Display information about the vector unit. The exact contents and
5925 layout vary depending on the hardware.
5928 @node Auxiliary Vector
5929 @section Operating system auxiliary vector
5930 @cindex auxiliary vector
5931 @cindex vector, auxiliary
5933 Some operating systems supply an @dfn{auxiliary vector} to programs at
5934 startup. This is akin to the arguments and environment that you
5935 specify for a program, but contains a system-dependent variety of
5936 binary values that tell system libraries important details about the
5937 hardware, operating system, and process. Each value's purpose is
5938 identified by an integer tag; the meanings are well-known but system-specific.
5939 Depending on the configuration and operating system facilities,
5940 @value{GDBN} may be able to show you this information.
5945 Display the auxiliary vector of the inferior, which can be either a
5946 live process or a core dump file. @value{GDBN} prints each tag value
5947 numerically, and also shows names and text descriptions for recognized
5948 tags. Some values in the vector are numbers, some bit masks, and some
5949 pointers to strings or other data. @value{GDBN} displays each value in the
5950 most appropriate form for a recognized tag, and in hexadecimal for
5951 an unrecognized tag.
5954 @node Memory Region Attributes
5955 @section Memory region attributes
5956 @cindex memory region attributes
5958 @dfn{Memory region attributes} allow you to describe special handling
5959 required by regions of your target's memory. @value{GDBN} uses attributes
5960 to determine whether to allow certain types of memory accesses; whether to
5961 use specific width accesses; and whether to cache target memory.
5963 Defined memory regions can be individually enabled and disabled. When a
5964 memory region is disabled, @value{GDBN} uses the default attributes when
5965 accessing memory in that region. Similarly, if no memory regions have
5966 been defined, @value{GDBN} uses the default attributes when accessing
5969 When a memory region is defined, it is given a number to identify it;
5970 to enable, disable, or remove a memory region, you specify that number.
5974 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
5975 Define memory region bounded by @var{lower} and @var{upper} with
5976 attributes @var{attributes}@dots{}. Note that @var{upper} == 0 is a
5977 special case: it is treated as the the target's maximum memory address.
5978 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
5981 @item delete mem @var{nums}@dots{}
5982 Remove memory regions @var{nums}@dots{}.
5985 @item disable mem @var{nums}@dots{}
5986 Disable memory regions @var{nums}@dots{}.
5987 A disabled memory region is not forgotten.
5988 It may be enabled again later.
5991 @item enable mem @var{nums}@dots{}
5992 Enable memory regions @var{nums}@dots{}.
5996 Print a table of all defined memory regions, with the following columns
6000 @item Memory Region Number
6001 @item Enabled or Disabled.
6002 Enabled memory regions are marked with @samp{y}.
6003 Disabled memory regions are marked with @samp{n}.
6006 The address defining the inclusive lower bound of the memory region.
6009 The address defining the exclusive upper bound of the memory region.
6012 The list of attributes set for this memory region.
6017 @subsection Attributes
6019 @subsubsection Memory Access Mode
6020 The access mode attributes set whether @value{GDBN} may make read or
6021 write accesses to a memory region.
6023 While these attributes prevent @value{GDBN} from performing invalid
6024 memory accesses, they do nothing to prevent the target system, I/O DMA,
6025 etc. from accessing memory.
6029 Memory is read only.
6031 Memory is write only.
6033 Memory is read/write. This is the default.
6036 @subsubsection Memory Access Size
6037 The acccess size attributes tells @value{GDBN} to use specific sized
6038 accesses in the memory region. Often memory mapped device registers
6039 require specific sized accesses. If no access size attribute is
6040 specified, @value{GDBN} may use accesses of any size.
6044 Use 8 bit memory accesses.
6046 Use 16 bit memory accesses.
6048 Use 32 bit memory accesses.
6050 Use 64 bit memory accesses.
6053 @c @subsubsection Hardware/Software Breakpoints
6054 @c The hardware/software breakpoint attributes set whether @value{GDBN}
6055 @c will use hardware or software breakpoints for the internal breakpoints
6056 @c used by the step, next, finish, until, etc. commands.
6060 @c Always use hardware breakpoints
6061 @c @item swbreak (default)
6064 @subsubsection Data Cache
6065 The data cache attributes set whether @value{GDBN} will cache target
6066 memory. While this generally improves performance by reducing debug
6067 protocol overhead, it can lead to incorrect results because @value{GDBN}
6068 does not know about volatile variables or memory mapped device
6073 Enable @value{GDBN} to cache target memory.
6075 Disable @value{GDBN} from caching target memory. This is the default.
6078 @c @subsubsection Memory Write Verification
6079 @c The memory write verification attributes set whether @value{GDBN}
6080 @c will re-reads data after each write to verify the write was successful.
6084 @c @item noverify (default)
6087 @node Dump/Restore Files
6088 @section Copy between memory and a file
6089 @cindex dump/restore files
6090 @cindex append data to a file
6091 @cindex dump data to a file
6092 @cindex restore data from a file
6094 You can use the commands @code{dump}, @code{append}, and
6095 @code{restore} to copy data between target memory and a file. The
6096 @code{dump} and @code{append} commands write data to a file, and the
6097 @code{restore} command reads data from a file back into the inferior's
6098 memory. Files may be in binary, Motorola S-record, Intel hex, or
6099 Tektronix Hex format; however, @value{GDBN} can only append to binary
6105 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6106 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
6107 Dump the contents of memory from @var{start_addr} to @var{end_addr},
6108 or the value of @var{expr}, to @var{filename} in the given format.
6110 The @var{format} parameter may be any one of:
6117 Motorola S-record format.
6119 Tektronix Hex format.
6122 @value{GDBN} uses the same definitions of these formats as the
6123 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
6124 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
6128 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6129 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
6130 Append the contents of memory from @var{start_addr} to @var{end_addr},
6131 or the value of @var{expr}, to @var{filename}, in raw binary form.
6132 (@value{GDBN} can only append data to files in raw binary form.)
6135 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
6136 Restore the contents of file @var{filename} into memory. The
6137 @code{restore} command can automatically recognize any known @sc{bfd}
6138 file format, except for raw binary. To restore a raw binary file you
6139 must specify the optional keyword @code{binary} after the filename.
6141 If @var{bias} is non-zero, its value will be added to the addresses
6142 contained in the file. Binary files always start at address zero, so
6143 they will be restored at address @var{bias}. Other bfd files have
6144 a built-in location; they will be restored at offset @var{bias}
6147 If @var{start} and/or @var{end} are non-zero, then only data between
6148 file offset @var{start} and file offset @var{end} will be restored.
6149 These offsets are relative to the addresses in the file, before
6150 the @var{bias} argument is applied.
6154 @node Character Sets
6155 @section Character Sets
6156 @cindex character sets
6158 @cindex translating between character sets
6159 @cindex host character set
6160 @cindex target character set
6162 If the program you are debugging uses a different character set to
6163 represent characters and strings than the one @value{GDBN} uses itself,
6164 @value{GDBN} can automatically translate between the character sets for
6165 you. The character set @value{GDBN} uses we call the @dfn{host
6166 character set}; the one the inferior program uses we call the
6167 @dfn{target character set}.
6169 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
6170 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
6171 remote protocol (@pxref{Remote,Remote Debugging}) to debug a program
6172 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
6173 then the host character set is Latin-1, and the target character set is
6174 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
6175 target-charset EBCDIC-US}, then @value{GDBN} translates between
6176 @sc{ebcdic} and Latin 1 as you print character or string values, or use
6177 character and string literals in expressions.
6179 @value{GDBN} has no way to automatically recognize which character set
6180 the inferior program uses; you must tell it, using the @code{set
6181 target-charset} command, described below.
6183 Here are the commands for controlling @value{GDBN}'s character set
6187 @item set target-charset @var{charset}
6188 @kindex set target-charset
6189 Set the current target character set to @var{charset}. We list the
6190 character set names @value{GDBN} recognizes below, but if you type
6191 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6192 list the target character sets it supports.
6196 @item set host-charset @var{charset}
6197 @kindex set host-charset
6198 Set the current host character set to @var{charset}.
6200 By default, @value{GDBN} uses a host character set appropriate to the
6201 system it is running on; you can override that default using the
6202 @code{set host-charset} command.
6204 @value{GDBN} can only use certain character sets as its host character
6205 set. We list the character set names @value{GDBN} recognizes below, and
6206 indicate which can be host character sets, but if you type
6207 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6208 list the host character sets it supports.
6210 @item set charset @var{charset}
6212 Set the current host and target character sets to @var{charset}. As
6213 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
6214 @value{GDBN} will list the name of the character sets that can be used
6215 for both host and target.
6219 @kindex show charset
6220 Show the names of the current host and target charsets.
6222 @itemx show host-charset
6223 @kindex show host-charset
6224 Show the name of the current host charset.
6226 @itemx show target-charset
6227 @kindex show target-charset
6228 Show the name of the current target charset.
6232 @value{GDBN} currently includes support for the following character
6238 @cindex ASCII character set
6239 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
6243 @cindex ISO 8859-1 character set
6244 @cindex ISO Latin 1 character set
6245 The ISO Latin 1 character set. This extends @sc{ascii} with accented
6246 characters needed for French, German, and Spanish. @value{GDBN} can use
6247 this as its host character set.
6251 @cindex EBCDIC character set
6252 @cindex IBM1047 character set
6253 Variants of the @sc{ebcdic} character set, used on some of IBM's
6254 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
6255 @value{GDBN} cannot use these as its host character set.
6259 Note that these are all single-byte character sets. More work inside
6260 GDB is needed to support multi-byte or variable-width character
6261 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
6263 Here is an example of @value{GDBN}'s character set support in action.
6264 Assume that the following source code has been placed in the file
6265 @file{charset-test.c}:
6271 = @{72, 101, 108, 108, 111, 44, 32, 119,
6272 111, 114, 108, 100, 33, 10, 0@};
6273 char ibm1047_hello[]
6274 = @{200, 133, 147, 147, 150, 107, 64, 166,
6275 150, 153, 147, 132, 90, 37, 0@};
6279 printf ("Hello, world!\n");
6283 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
6284 containing the string @samp{Hello, world!} followed by a newline,
6285 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
6287 We compile the program, and invoke the debugger on it:
6290 $ gcc -g charset-test.c -o charset-test
6291 $ gdb -nw charset-test
6292 GNU gdb 2001-12-19-cvs
6293 Copyright 2001 Free Software Foundation, Inc.
6298 We can use the @code{show charset} command to see what character sets
6299 @value{GDBN} is currently using to interpret and display characters and
6304 The current host and target character set is `ISO-8859-1'.
6308 For the sake of printing this manual, let's use @sc{ascii} as our
6309 initial character set:
6311 (gdb) set charset ASCII
6313 The current host and target character set is `ASCII'.
6317 Let's assume that @sc{ascii} is indeed the correct character set for our
6318 host system --- in other words, let's assume that if @value{GDBN} prints
6319 characters using the @sc{ascii} character set, our terminal will display
6320 them properly. Since our current target character set is also
6321 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
6324 (gdb) print ascii_hello
6325 $1 = 0x401698 "Hello, world!\n"
6326 (gdb) print ascii_hello[0]
6331 @value{GDBN} uses the target character set for character and string
6332 literals you use in expressions:
6340 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
6343 @value{GDBN} relies on the user to tell it which character set the
6344 target program uses. If we print @code{ibm1047_hello} while our target
6345 character set is still @sc{ascii}, we get jibberish:
6348 (gdb) print ibm1047_hello
6349 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
6350 (gdb) print ibm1047_hello[0]
6355 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
6356 @value{GDBN} tells us the character sets it supports:
6359 (gdb) set target-charset
6360 ASCII EBCDIC-US IBM1047 ISO-8859-1
6361 (gdb) set target-charset
6364 We can select @sc{ibm1047} as our target character set, and examine the
6365 program's strings again. Now the @sc{ascii} string is wrong, but
6366 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
6367 target character set, @sc{ibm1047}, to the host character set,
6368 @sc{ascii}, and they display correctly:
6371 (gdb) set target-charset IBM1047
6373 The current host character set is `ASCII'.
6374 The current target character set is `IBM1047'.
6375 (gdb) print ascii_hello
6376 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
6377 (gdb) print ascii_hello[0]
6379 (gdb) print ibm1047_hello
6380 $8 = 0x4016a8 "Hello, world!\n"
6381 (gdb) print ibm1047_hello[0]
6386 As above, @value{GDBN} uses the target character set for character and
6387 string literals you use in expressions:
6395 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
6400 @chapter C Preprocessor Macros
6402 Some languages, such as C and C@t{++}, provide a way to define and invoke
6403 ``preprocessor macros'' which expand into strings of tokens.
6404 @value{GDBN} can evaluate expressions containing macro invocations, show
6405 the result of macro expansion, and show a macro's definition, including
6406 where it was defined.
6408 You may need to compile your program specially to provide @value{GDBN}
6409 with information about preprocessor macros. Most compilers do not
6410 include macros in their debugging information, even when you compile
6411 with the @option{-g} flag. @xref{Compilation}.
6413 A program may define a macro at one point, remove that definition later,
6414 and then provide a different definition after that. Thus, at different
6415 points in the program, a macro may have different definitions, or have
6416 no definition at all. If there is a current stack frame, @value{GDBN}
6417 uses the macros in scope at that frame's source code line. Otherwise,
6418 @value{GDBN} uses the macros in scope at the current listing location;
6421 At the moment, @value{GDBN} does not support the @code{##}
6422 token-splicing operator, the @code{#} stringification operator, or
6423 variable-arity macros.
6425 Whenever @value{GDBN} evaluates an expression, it always expands any
6426 macro invocations present in the expression. @value{GDBN} also provides
6427 the following commands for working with macros explicitly.
6431 @kindex macro expand
6432 @cindex macro expansion, showing the results of preprocessor
6433 @cindex preprocessor macro expansion, showing the results of
6434 @cindex expanding preprocessor macros
6435 @item macro expand @var{expression}
6436 @itemx macro exp @var{expression}
6437 Show the results of expanding all preprocessor macro invocations in
6438 @var{expression}. Since @value{GDBN} simply expands macros, but does
6439 not parse the result, @var{expression} need not be a valid expression;
6440 it can be any string of tokens.
6442 @kindex macro expand-once
6443 @item macro expand-once @var{expression}
6444 @itemx macro exp1 @var{expression}
6445 @i{(This command is not yet implemented.)} Show the results of
6446 expanding those preprocessor macro invocations that appear explicitly in
6447 @var{expression}. Macro invocations appearing in that expansion are
6448 left unchanged. This command allows you to see the effect of a
6449 particular macro more clearly, without being confused by further
6450 expansions. Since @value{GDBN} simply expands macros, but does not
6451 parse the result, @var{expression} need not be a valid expression; it
6452 can be any string of tokens.
6455 @cindex macro definition, showing
6456 @cindex definition, showing a macro's
6457 @item info macro @var{macro}
6458 Show the definition of the macro named @var{macro}, and describe the
6459 source location where that definition was established.
6461 @kindex macro define
6462 @cindex user-defined macros
6463 @cindex defining macros interactively
6464 @cindex macros, user-defined
6465 @item macro define @var{macro} @var{replacement-list}
6466 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
6467 @i{(This command is not yet implemented.)} Introduce a definition for a
6468 preprocessor macro named @var{macro}, invocations of which are replaced
6469 by the tokens given in @var{replacement-list}. The first form of this
6470 command defines an ``object-like'' macro, which takes no arguments; the
6471 second form defines a ``function-like'' macro, which takes the arguments
6472 given in @var{arglist}.
6474 A definition introduced by this command is in scope in every expression
6475 evaluated in @value{GDBN}, until it is removed with the @command{macro
6476 undef} command, described below. The definition overrides all
6477 definitions for @var{macro} present in the program being debugged, as
6478 well as any previous user-supplied definition.
6481 @item macro undef @var{macro}
6482 @i{(This command is not yet implemented.)} Remove any user-supplied
6483 definition for the macro named @var{macro}. This command only affects
6484 definitions provided with the @command{macro define} command, described
6485 above; it cannot remove definitions present in the program being
6490 @cindex macros, example of debugging with
6491 Here is a transcript showing the above commands in action. First, we
6492 show our source files:
6500 #define ADD(x) (M + x)
6505 printf ("Hello, world!\n");
6507 printf ("We're so creative.\n");
6509 printf ("Goodbye, world!\n");
6516 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
6517 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
6518 compiler includes information about preprocessor macros in the debugging
6522 $ gcc -gdwarf-2 -g3 sample.c -o sample
6526 Now, we start @value{GDBN} on our sample program:
6530 GNU gdb 2002-05-06-cvs
6531 Copyright 2002 Free Software Foundation, Inc.
6532 GDB is free software, @dots{}
6536 We can expand macros and examine their definitions, even when the
6537 program is not running. @value{GDBN} uses the current listing position
6538 to decide which macro definitions are in scope:
6544 5 #define ADD(x) (M + x)
6549 10 printf ("Hello, world!\n");
6551 12 printf ("We're so creative.\n");
6552 (gdb) info macro ADD
6553 Defined at /home/jimb/gdb/macros/play/sample.c:5
6554 #define ADD(x) (M + x)
6556 Defined at /home/jimb/gdb/macros/play/sample.h:1
6557 included at /home/jimb/gdb/macros/play/sample.c:2
6559 (gdb) macro expand ADD(1)
6560 expands to: (42 + 1)
6561 (gdb) macro expand-once ADD(1)
6562 expands to: once (M + 1)
6566 In the example above, note that @command{macro expand-once} expands only
6567 the macro invocation explicit in the original text --- the invocation of
6568 @code{ADD} --- but does not expand the invocation of the macro @code{M},
6569 which was introduced by @code{ADD}.
6571 Once the program is running, GDB uses the macro definitions in force at
6572 the source line of the current stack frame:
6576 Breakpoint 1 at 0x8048370: file sample.c, line 10.
6578 Starting program: /home/jimb/gdb/macros/play/sample
6580 Breakpoint 1, main () at sample.c:10
6581 10 printf ("Hello, world!\n");
6585 At line 10, the definition of the macro @code{N} at line 9 is in force:
6589 Defined at /home/jimb/gdb/macros/play/sample.c:9
6591 (gdb) macro expand N Q M
6598 As we step over directives that remove @code{N}'s definition, and then
6599 give it a new definition, @value{GDBN} finds the definition (or lack
6600 thereof) in force at each point:
6605 12 printf ("We're so creative.\n");
6607 The symbol `N' has no definition as a C/C++ preprocessor macro
6608 at /home/jimb/gdb/macros/play/sample.c:12
6611 14 printf ("Goodbye, world!\n");
6613 Defined at /home/jimb/gdb/macros/play/sample.c:13
6615 (gdb) macro expand N Q M
6616 expands to: 1729 < 42
6624 @chapter Tracepoints
6625 @c This chapter is based on the documentation written by Michael
6626 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
6629 In some applications, it is not feasible for the debugger to interrupt
6630 the program's execution long enough for the developer to learn
6631 anything helpful about its behavior. If the program's correctness
6632 depends on its real-time behavior, delays introduced by a debugger
6633 might cause the program to change its behavior drastically, or perhaps
6634 fail, even when the code itself is correct. It is useful to be able
6635 to observe the program's behavior without interrupting it.
6637 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
6638 specify locations in the program, called @dfn{tracepoints}, and
6639 arbitrary expressions to evaluate when those tracepoints are reached.
6640 Later, using the @code{tfind} command, you can examine the values
6641 those expressions had when the program hit the tracepoints. The
6642 expressions may also denote objects in memory---structures or arrays,
6643 for example---whose values @value{GDBN} should record; while visiting
6644 a particular tracepoint, you may inspect those objects as if they were
6645 in memory at that moment. However, because @value{GDBN} records these
6646 values without interacting with you, it can do so quickly and
6647 unobtrusively, hopefully not disturbing the program's behavior.
6649 The tracepoint facility is currently available only for remote
6650 targets. @xref{Targets}. In addition, your remote target must know how
6651 to collect trace data. This functionality is implemented in the remote
6652 stub; however, none of the stubs distributed with @value{GDBN} support
6653 tracepoints as of this writing.
6655 This chapter describes the tracepoint commands and features.
6659 * Analyze Collected Data::
6660 * Tracepoint Variables::
6663 @node Set Tracepoints
6664 @section Commands to Set Tracepoints
6666 Before running such a @dfn{trace experiment}, an arbitrary number of
6667 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
6668 tracepoint has a number assigned to it by @value{GDBN}. Like with
6669 breakpoints, tracepoint numbers are successive integers starting from
6670 one. Many of the commands associated with tracepoints take the
6671 tracepoint number as their argument, to identify which tracepoint to
6674 For each tracepoint, you can specify, in advance, some arbitrary set
6675 of data that you want the target to collect in the trace buffer when
6676 it hits that tracepoint. The collected data can include registers,
6677 local variables, or global data. Later, you can use @value{GDBN}
6678 commands to examine the values these data had at the time the
6681 This section describes commands to set tracepoints and associated
6682 conditions and actions.
6685 * Create and Delete Tracepoints::
6686 * Enable and Disable Tracepoints::
6687 * Tracepoint Passcounts::
6688 * Tracepoint Actions::
6689 * Listing Tracepoints::
6690 * Starting and Stopping Trace Experiment::
6693 @node Create and Delete Tracepoints
6694 @subsection Create and Delete Tracepoints
6697 @cindex set tracepoint
6700 The @code{trace} command is very similar to the @code{break} command.
6701 Its argument can be a source line, a function name, or an address in
6702 the target program. @xref{Set Breaks}. The @code{trace} command
6703 defines a tracepoint, which is a point in the target program where the
6704 debugger will briefly stop, collect some data, and then allow the
6705 program to continue. Setting a tracepoint or changing its commands
6706 doesn't take effect until the next @code{tstart} command; thus, you
6707 cannot change the tracepoint attributes once a trace experiment is
6710 Here are some examples of using the @code{trace} command:
6713 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
6715 (@value{GDBP}) @b{trace +2} // 2 lines forward
6717 (@value{GDBP}) @b{trace my_function} // first source line of function
6719 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
6721 (@value{GDBP}) @b{trace *0x2117c4} // an address
6725 You can abbreviate @code{trace} as @code{tr}.
6728 @cindex last tracepoint number
6729 @cindex recent tracepoint number
6730 @cindex tracepoint number
6731 The convenience variable @code{$tpnum} records the tracepoint number
6732 of the most recently set tracepoint.
6734 @kindex delete tracepoint
6735 @cindex tracepoint deletion
6736 @item delete tracepoint @r{[}@var{num}@r{]}
6737 Permanently delete one or more tracepoints. With no argument, the
6738 default is to delete all tracepoints.
6743 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
6745 (@value{GDBP}) @b{delete trace} // remove all tracepoints
6749 You can abbreviate this command as @code{del tr}.
6752 @node Enable and Disable Tracepoints
6753 @subsection Enable and Disable Tracepoints
6756 @kindex disable tracepoint
6757 @item disable tracepoint @r{[}@var{num}@r{]}
6758 Disable tracepoint @var{num}, or all tracepoints if no argument
6759 @var{num} is given. A disabled tracepoint will have no effect during
6760 the next trace experiment, but it is not forgotten. You can re-enable
6761 a disabled tracepoint using the @code{enable tracepoint} command.
6763 @kindex enable tracepoint
6764 @item enable tracepoint @r{[}@var{num}@r{]}
6765 Enable tracepoint @var{num}, or all tracepoints. The enabled
6766 tracepoints will become effective the next time a trace experiment is
6770 @node Tracepoint Passcounts
6771 @subsection Tracepoint Passcounts
6775 @cindex tracepoint pass count
6776 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
6777 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
6778 automatically stop a trace experiment. If a tracepoint's passcount is
6779 @var{n}, then the trace experiment will be automatically stopped on
6780 the @var{n}'th time that tracepoint is hit. If the tracepoint number
6781 @var{num} is not specified, the @code{passcount} command sets the
6782 passcount of the most recently defined tracepoint. If no passcount is
6783 given, the trace experiment will run until stopped explicitly by the
6789 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
6790 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
6792 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
6793 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
6794 (@value{GDBP}) @b{trace foo}
6795 (@value{GDBP}) @b{pass 3}
6796 (@value{GDBP}) @b{trace bar}
6797 (@value{GDBP}) @b{pass 2}
6798 (@value{GDBP}) @b{trace baz}
6799 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
6800 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
6801 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
6802 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
6806 @node Tracepoint Actions
6807 @subsection Tracepoint Action Lists
6811 @cindex tracepoint actions
6812 @item actions @r{[}@var{num}@r{]}
6813 This command will prompt for a list of actions to be taken when the
6814 tracepoint is hit. If the tracepoint number @var{num} is not
6815 specified, this command sets the actions for the one that was most
6816 recently defined (so that you can define a tracepoint and then say
6817 @code{actions} without bothering about its number). You specify the
6818 actions themselves on the following lines, one action at a time, and
6819 terminate the actions list with a line containing just @code{end}. So
6820 far, the only defined actions are @code{collect} and
6821 @code{while-stepping}.
6823 @cindex remove actions from a tracepoint
6824 To remove all actions from a tracepoint, type @samp{actions @var{num}}
6825 and follow it immediately with @samp{end}.
6828 (@value{GDBP}) @b{collect @var{data}} // collect some data
6830 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
6832 (@value{GDBP}) @b{end} // signals the end of actions.
6835 In the following example, the action list begins with @code{collect}
6836 commands indicating the things to be collected when the tracepoint is
6837 hit. Then, in order to single-step and collect additional data
6838 following the tracepoint, a @code{while-stepping} command is used,
6839 followed by the list of things to be collected while stepping. The
6840 @code{while-stepping} command is terminated by its own separate
6841 @code{end} command. Lastly, the action list is terminated by an
6845 (@value{GDBP}) @b{trace foo}
6846 (@value{GDBP}) @b{actions}
6847 Enter actions for tracepoint 1, one per line:
6856 @kindex collect @r{(tracepoints)}
6857 @item collect @var{expr1}, @var{expr2}, @dots{}
6858 Collect values of the given expressions when the tracepoint is hit.
6859 This command accepts a comma-separated list of any valid expressions.
6860 In addition to global, static, or local variables, the following
6861 special arguments are supported:
6865 collect all registers
6868 collect all function arguments
6871 collect all local variables.
6874 You can give several consecutive @code{collect} commands, each one
6875 with a single argument, or one @code{collect} command with several
6876 arguments separated by commas: the effect is the same.
6878 The command @code{info scope} (@pxref{Symbols, info scope}) is
6879 particularly useful for figuring out what data to collect.
6881 @kindex while-stepping @r{(tracepoints)}
6882 @item while-stepping @var{n}
6883 Perform @var{n} single-step traces after the tracepoint, collecting
6884 new data at each step. The @code{while-stepping} command is
6885 followed by the list of what to collect while stepping (followed by
6886 its own @code{end} command):
6890 > collect $regs, myglobal
6896 You may abbreviate @code{while-stepping} as @code{ws} or
6900 @node Listing Tracepoints
6901 @subsection Listing Tracepoints
6904 @kindex info tracepoints
6905 @cindex information about tracepoints
6906 @item info tracepoints @r{[}@var{num}@r{]}
6907 Display information about the tracepoint @var{num}. If you don't specify
6908 a tracepoint number, displays information about all the tracepoints
6909 defined so far. For each tracepoint, the following information is
6916 whether it is enabled or disabled
6920 its passcount as given by the @code{passcount @var{n}} command
6922 its step count as given by the @code{while-stepping @var{n}} command
6924 where in the source files is the tracepoint set
6926 its action list as given by the @code{actions} command
6930 (@value{GDBP}) @b{info trace}
6931 Num Enb Address PassC StepC What
6932 1 y 0x002117c4 0 0 <gdb_asm>
6933 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
6934 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
6939 This command can be abbreviated @code{info tp}.
6942 @node Starting and Stopping Trace Experiment
6943 @subsection Starting and Stopping Trace Experiment
6947 @cindex start a new trace experiment
6948 @cindex collected data discarded
6950 This command takes no arguments. It starts the trace experiment, and
6951 begins collecting data. This has the side effect of discarding all
6952 the data collected in the trace buffer during the previous trace
6956 @cindex stop a running trace experiment
6958 This command takes no arguments. It ends the trace experiment, and
6959 stops collecting data.
6961 @strong{Note:} a trace experiment and data collection may stop
6962 automatically if any tracepoint's passcount is reached
6963 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
6966 @cindex status of trace data collection
6967 @cindex trace experiment, status of
6969 This command displays the status of the current trace data
6973 Here is an example of the commands we described so far:
6976 (@value{GDBP}) @b{trace gdb_c_test}
6977 (@value{GDBP}) @b{actions}
6978 Enter actions for tracepoint #1, one per line.
6979 > collect $regs,$locals,$args
6984 (@value{GDBP}) @b{tstart}
6985 [time passes @dots{}]
6986 (@value{GDBP}) @b{tstop}
6990 @node Analyze Collected Data
6991 @section Using the collected data
6993 After the tracepoint experiment ends, you use @value{GDBN} commands
6994 for examining the trace data. The basic idea is that each tracepoint
6995 collects a trace @dfn{snapshot} every time it is hit and another
6996 snapshot every time it single-steps. All these snapshots are
6997 consecutively numbered from zero and go into a buffer, and you can
6998 examine them later. The way you examine them is to @dfn{focus} on a
6999 specific trace snapshot. When the remote stub is focused on a trace
7000 snapshot, it will respond to all @value{GDBN} requests for memory and
7001 registers by reading from the buffer which belongs to that snapshot,
7002 rather than from @emph{real} memory or registers of the program being
7003 debugged. This means that @strong{all} @value{GDBN} commands
7004 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
7005 behave as if we were currently debugging the program state as it was
7006 when the tracepoint occurred. Any requests for data that are not in
7007 the buffer will fail.
7010 * tfind:: How to select a trace snapshot
7011 * tdump:: How to display all data for a snapshot
7012 * save-tracepoints:: How to save tracepoints for a future run
7016 @subsection @code{tfind @var{n}}
7019 @cindex select trace snapshot
7020 @cindex find trace snapshot
7021 The basic command for selecting a trace snapshot from the buffer is
7022 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
7023 counting from zero. If no argument @var{n} is given, the next
7024 snapshot is selected.
7026 Here are the various forms of using the @code{tfind} command.
7030 Find the first snapshot in the buffer. This is a synonym for
7031 @code{tfind 0} (since 0 is the number of the first snapshot).
7034 Stop debugging trace snapshots, resume @emph{live} debugging.
7037 Same as @samp{tfind none}.
7040 No argument means find the next trace snapshot.
7043 Find the previous trace snapshot before the current one. This permits
7044 retracing earlier steps.
7046 @item tfind tracepoint @var{num}
7047 Find the next snapshot associated with tracepoint @var{num}. Search
7048 proceeds forward from the last examined trace snapshot. If no
7049 argument @var{num} is given, it means find the next snapshot collected
7050 for the same tracepoint as the current snapshot.
7052 @item tfind pc @var{addr}
7053 Find the next snapshot associated with the value @var{addr} of the
7054 program counter. Search proceeds forward from the last examined trace
7055 snapshot. If no argument @var{addr} is given, it means find the next
7056 snapshot with the same value of PC as the current snapshot.
7058 @item tfind outside @var{addr1}, @var{addr2}
7059 Find the next snapshot whose PC is outside the given range of
7062 @item tfind range @var{addr1}, @var{addr2}
7063 Find the next snapshot whose PC is between @var{addr1} and
7064 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
7066 @item tfind line @r{[}@var{file}:@r{]}@var{n}
7067 Find the next snapshot associated with the source line @var{n}. If
7068 the optional argument @var{file} is given, refer to line @var{n} in
7069 that source file. Search proceeds forward from the last examined
7070 trace snapshot. If no argument @var{n} is given, it means find the
7071 next line other than the one currently being examined; thus saying
7072 @code{tfind line} repeatedly can appear to have the same effect as
7073 stepping from line to line in a @emph{live} debugging session.
7076 The default arguments for the @code{tfind} commands are specifically
7077 designed to make it easy to scan through the trace buffer. For
7078 instance, @code{tfind} with no argument selects the next trace
7079 snapshot, and @code{tfind -} with no argument selects the previous
7080 trace snapshot. So, by giving one @code{tfind} command, and then
7081 simply hitting @key{RET} repeatedly you can examine all the trace
7082 snapshots in order. Or, by saying @code{tfind -} and then hitting
7083 @key{RET} repeatedly you can examine the snapshots in reverse order.
7084 The @code{tfind line} command with no argument selects the snapshot
7085 for the next source line executed. The @code{tfind pc} command with
7086 no argument selects the next snapshot with the same program counter
7087 (PC) as the current frame. The @code{tfind tracepoint} command with
7088 no argument selects the next trace snapshot collected by the same
7089 tracepoint as the current one.
7091 In addition to letting you scan through the trace buffer manually,
7092 these commands make it easy to construct @value{GDBN} scripts that
7093 scan through the trace buffer and print out whatever collected data
7094 you are interested in. Thus, if we want to examine the PC, FP, and SP
7095 registers from each trace frame in the buffer, we can say this:
7098 (@value{GDBP}) @b{tfind start}
7099 (@value{GDBP}) @b{while ($trace_frame != -1)}
7100 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
7101 $trace_frame, $pc, $sp, $fp
7105 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
7106 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
7107 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
7108 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
7109 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
7110 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
7111 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
7112 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
7113 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
7114 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
7115 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
7118 Or, if we want to examine the variable @code{X} at each source line in
7122 (@value{GDBP}) @b{tfind start}
7123 (@value{GDBP}) @b{while ($trace_frame != -1)}
7124 > printf "Frame %d, X == %d\n", $trace_frame, X
7134 @subsection @code{tdump}
7136 @cindex dump all data collected at tracepoint
7137 @cindex tracepoint data, display
7139 This command takes no arguments. It prints all the data collected at
7140 the current trace snapshot.
7143 (@value{GDBP}) @b{trace 444}
7144 (@value{GDBP}) @b{actions}
7145 Enter actions for tracepoint #2, one per line:
7146 > collect $regs, $locals, $args, gdb_long_test
7149 (@value{GDBP}) @b{tstart}
7151 (@value{GDBP}) @b{tfind line 444}
7152 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
7154 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
7156 (@value{GDBP}) @b{tdump}
7157 Data collected at tracepoint 2, trace frame 1:
7158 d0 0xc4aa0085 -995491707
7162 d4 0x71aea3d 119204413
7167 a1 0x3000668 50333288
7170 a4 0x3000698 50333336
7172 fp 0x30bf3c 0x30bf3c
7173 sp 0x30bf34 0x30bf34
7175 pc 0x20b2c8 0x20b2c8
7179 p = 0x20e5b4 "gdb-test"
7186 gdb_long_test = 17 '\021'
7191 @node save-tracepoints
7192 @subsection @code{save-tracepoints @var{filename}}
7193 @kindex save-tracepoints
7194 @cindex save tracepoints for future sessions
7196 This command saves all current tracepoint definitions together with
7197 their actions and passcounts, into a file @file{@var{filename}}
7198 suitable for use in a later debugging session. To read the saved
7199 tracepoint definitions, use the @code{source} command (@pxref{Command
7202 @node Tracepoint Variables
7203 @section Convenience Variables for Tracepoints
7204 @cindex tracepoint variables
7205 @cindex convenience variables for tracepoints
7208 @vindex $trace_frame
7209 @item (int) $trace_frame
7210 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
7211 snapshot is selected.
7214 @item (int) $tracepoint
7215 The tracepoint for the current trace snapshot.
7218 @item (int) $trace_line
7219 The line number for the current trace snapshot.
7222 @item (char []) $trace_file
7223 The source file for the current trace snapshot.
7226 @item (char []) $trace_func
7227 The name of the function containing @code{$tracepoint}.
7230 Note: @code{$trace_file} is not suitable for use in @code{printf},
7231 use @code{output} instead.
7233 Here's a simple example of using these convenience variables for
7234 stepping through all the trace snapshots and printing some of their
7238 (@value{GDBP}) @b{tfind start}
7240 (@value{GDBP}) @b{while $trace_frame != -1}
7241 > output $trace_file
7242 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
7248 @chapter Debugging Programs That Use Overlays
7251 If your program is too large to fit completely in your target system's
7252 memory, you can sometimes use @dfn{overlays} to work around this
7253 problem. @value{GDBN} provides some support for debugging programs that
7257 * How Overlays Work:: A general explanation of overlays.
7258 * Overlay Commands:: Managing overlays in @value{GDBN}.
7259 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
7260 mapped by asking the inferior.
7261 * Overlay Sample Program:: A sample program using overlays.
7264 @node How Overlays Work
7265 @section How Overlays Work
7266 @cindex mapped overlays
7267 @cindex unmapped overlays
7268 @cindex load address, overlay's
7269 @cindex mapped address
7270 @cindex overlay area
7272 Suppose you have a computer whose instruction address space is only 64
7273 kilobytes long, but which has much more memory which can be accessed by
7274 other means: special instructions, segment registers, or memory
7275 management hardware, for example. Suppose further that you want to
7276 adapt a program which is larger than 64 kilobytes to run on this system.
7278 One solution is to identify modules of your program which are relatively
7279 independent, and need not call each other directly; call these modules
7280 @dfn{overlays}. Separate the overlays from the main program, and place
7281 their machine code in the larger memory. Place your main program in
7282 instruction memory, but leave at least enough space there to hold the
7283 largest overlay as well.
7285 Now, to call a function located in an overlay, you must first copy that
7286 overlay's machine code from the large memory into the space set aside
7287 for it in the instruction memory, and then jump to its entry point
7290 @c NB: In the below the mapped area's size is greater or equal to the
7291 @c size of all overlays. This is intentional to remind the developer
7292 @c that overlays don't necessarily need to be the same size.
7296 Data Instruction Larger
7297 Address Space Address Space Address Space
7298 +-----------+ +-----------+ +-----------+
7300 +-----------+ +-----------+ +-----------+<-- overlay 1
7301 | program | | main | .----| overlay 1 | load address
7302 | variables | | program | | +-----------+
7303 | and heap | | | | | |
7304 +-----------+ | | | +-----------+<-- overlay 2
7305 | | +-----------+ | | | load address
7306 +-----------+ | | | .-| overlay 2 |
7308 mapped --->+-----------+ | | +-----------+
7310 | overlay | <-' | | |
7311 | area | <---' +-----------+<-- overlay 3
7312 | | <---. | | load address
7313 +-----------+ `--| overlay 3 |
7320 @anchor{A code overlay}A code overlay
7324 The diagram (@pxref{A code overlay}) shows a system with separate data
7325 and instruction address spaces. To map an overlay, the program copies
7326 its code from the larger address space to the instruction address space.
7327 Since the overlays shown here all use the same mapped address, only one
7328 may be mapped at a time. For a system with a single address space for
7329 data and instructions, the diagram would be similar, except that the
7330 program variables and heap would share an address space with the main
7331 program and the overlay area.
7333 An overlay loaded into instruction memory and ready for use is called a
7334 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
7335 instruction memory. An overlay not present (or only partially present)
7336 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
7337 is its address in the larger memory. The mapped address is also called
7338 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
7339 called the @dfn{load memory address}, or @dfn{LMA}.
7341 Unfortunately, overlays are not a completely transparent way to adapt a
7342 program to limited instruction memory. They introduce a new set of
7343 global constraints you must keep in mind as you design your program:
7348 Before calling or returning to a function in an overlay, your program
7349 must make sure that overlay is actually mapped. Otherwise, the call or
7350 return will transfer control to the right address, but in the wrong
7351 overlay, and your program will probably crash.
7354 If the process of mapping an overlay is expensive on your system, you
7355 will need to choose your overlays carefully to minimize their effect on
7356 your program's performance.
7359 The executable file you load onto your system must contain each
7360 overlay's instructions, appearing at the overlay's load address, not its
7361 mapped address. However, each overlay's instructions must be relocated
7362 and its symbols defined as if the overlay were at its mapped address.
7363 You can use GNU linker scripts to specify different load and relocation
7364 addresses for pieces of your program; see @ref{Overlay Description,,,
7365 ld.info, Using ld: the GNU linker}.
7368 The procedure for loading executable files onto your system must be able
7369 to load their contents into the larger address space as well as the
7370 instruction and data spaces.
7374 The overlay system described above is rather simple, and could be
7375 improved in many ways:
7380 If your system has suitable bank switch registers or memory management
7381 hardware, you could use those facilities to make an overlay's load area
7382 contents simply appear at their mapped address in instruction space.
7383 This would probably be faster than copying the overlay to its mapped
7384 area in the usual way.
7387 If your overlays are small enough, you could set aside more than one
7388 overlay area, and have more than one overlay mapped at a time.
7391 You can use overlays to manage data, as well as instructions. In
7392 general, data overlays are even less transparent to your design than
7393 code overlays: whereas code overlays only require care when you call or
7394 return to functions, data overlays require care every time you access
7395 the data. Also, if you change the contents of a data overlay, you
7396 must copy its contents back out to its load address before you can copy a
7397 different data overlay into the same mapped area.
7402 @node Overlay Commands
7403 @section Overlay Commands
7405 To use @value{GDBN}'s overlay support, each overlay in your program must
7406 correspond to a separate section of the executable file. The section's
7407 virtual memory address and load memory address must be the overlay's
7408 mapped and load addresses. Identifying overlays with sections allows
7409 @value{GDBN} to determine the appropriate address of a function or
7410 variable, depending on whether the overlay is mapped or not.
7412 @value{GDBN}'s overlay commands all start with the word @code{overlay};
7413 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
7418 Disable @value{GDBN}'s overlay support. When overlay support is
7419 disabled, @value{GDBN} assumes that all functions and variables are
7420 always present at their mapped addresses. By default, @value{GDBN}'s
7421 overlay support is disabled.
7423 @item overlay manual
7424 @kindex overlay manual
7425 @cindex manual overlay debugging
7426 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
7427 relies on you to tell it which overlays are mapped, and which are not,
7428 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
7429 commands described below.
7431 @item overlay map-overlay @var{overlay}
7432 @itemx overlay map @var{overlay}
7433 @kindex overlay map-overlay
7434 @cindex map an overlay
7435 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
7436 be the name of the object file section containing the overlay. When an
7437 overlay is mapped, @value{GDBN} assumes it can find the overlay's
7438 functions and variables at their mapped addresses. @value{GDBN} assumes
7439 that any other overlays whose mapped ranges overlap that of
7440 @var{overlay} are now unmapped.
7442 @item overlay unmap-overlay @var{overlay}
7443 @itemx overlay unmap @var{overlay}
7444 @kindex overlay unmap-overlay
7445 @cindex unmap an overlay
7446 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
7447 must be the name of the object file section containing the overlay.
7448 When an overlay is unmapped, @value{GDBN} assumes it can find the
7449 overlay's functions and variables at their load addresses.
7452 @kindex overlay auto
7453 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
7454 consults a data structure the overlay manager maintains in the inferior
7455 to see which overlays are mapped. For details, see @ref{Automatic
7458 @item overlay load-target
7460 @kindex overlay load-target
7461 @cindex reloading the overlay table
7462 Re-read the overlay table from the inferior. Normally, @value{GDBN}
7463 re-reads the table @value{GDBN} automatically each time the inferior
7464 stops, so this command should only be necessary if you have changed the
7465 overlay mapping yourself using @value{GDBN}. This command is only
7466 useful when using automatic overlay debugging.
7468 @item overlay list-overlays
7470 @cindex listing mapped overlays
7471 Display a list of the overlays currently mapped, along with their mapped
7472 addresses, load addresses, and sizes.
7476 Normally, when @value{GDBN} prints a code address, it includes the name
7477 of the function the address falls in:
7481 $3 = @{int ()@} 0x11a0 <main>
7484 When overlay debugging is enabled, @value{GDBN} recognizes code in
7485 unmapped overlays, and prints the names of unmapped functions with
7486 asterisks around them. For example, if @code{foo} is a function in an
7487 unmapped overlay, @value{GDBN} prints it this way:
7491 No sections are mapped.
7493 $5 = @{int (int)@} 0x100000 <*foo*>
7496 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
7501 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
7502 mapped at 0x1016 - 0x104a
7504 $6 = @{int (int)@} 0x1016 <foo>
7507 When overlay debugging is enabled, @value{GDBN} can find the correct
7508 address for functions and variables in an overlay, whether or not the
7509 overlay is mapped. This allows most @value{GDBN} commands, like
7510 @code{break} and @code{disassemble}, to work normally, even on unmapped
7511 code. However, @value{GDBN}'s breakpoint support has some limitations:
7515 @cindex breakpoints in overlays
7516 @cindex overlays, setting breakpoints in
7517 You can set breakpoints in functions in unmapped overlays, as long as
7518 @value{GDBN} can write to the overlay at its load address.
7520 @value{GDBN} can not set hardware or simulator-based breakpoints in
7521 unmapped overlays. However, if you set a breakpoint at the end of your
7522 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
7523 you are using manual overlay management), @value{GDBN} will re-set its
7524 breakpoints properly.
7528 @node Automatic Overlay Debugging
7529 @section Automatic Overlay Debugging
7530 @cindex automatic overlay debugging
7532 @value{GDBN} can automatically track which overlays are mapped and which
7533 are not, given some simple co-operation from the overlay manager in the
7534 inferior. If you enable automatic overlay debugging with the
7535 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
7536 looks in the inferior's memory for certain variables describing the
7537 current state of the overlays.
7539 Here are the variables your overlay manager must define to support
7540 @value{GDBN}'s automatic overlay debugging:
7544 @item @code{_ovly_table}:
7545 This variable must be an array of the following structures:
7550 /* The overlay's mapped address. */
7553 /* The size of the overlay, in bytes. */
7556 /* The overlay's load address. */
7559 /* Non-zero if the overlay is currently mapped;
7561 unsigned long mapped;
7565 @item @code{_novlys}:
7566 This variable must be a four-byte signed integer, holding the total
7567 number of elements in @code{_ovly_table}.
7571 To decide whether a particular overlay is mapped or not, @value{GDBN}
7572 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
7573 @code{lma} members equal the VMA and LMA of the overlay's section in the
7574 executable file. When @value{GDBN} finds a matching entry, it consults
7575 the entry's @code{mapped} member to determine whether the overlay is
7578 In addition, your overlay manager may define a function called
7579 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
7580 will silently set a breakpoint there. If the overlay manager then
7581 calls this function whenever it has changed the overlay table, this
7582 will enable @value{GDBN} to accurately keep track of which overlays
7583 are in program memory, and update any breakpoints that may be set
7584 in overlays. This will allow breakpoints to work even if the
7585 overlays are kept in ROM or other non-writable memory while they
7586 are not being executed.
7588 @node Overlay Sample Program
7589 @section Overlay Sample Program
7590 @cindex overlay example program
7592 When linking a program which uses overlays, you must place the overlays
7593 at their load addresses, while relocating them to run at their mapped
7594 addresses. To do this, you must write a linker script (@pxref{Overlay
7595 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
7596 since linker scripts are specific to a particular host system, target
7597 architecture, and target memory layout, this manual cannot provide
7598 portable sample code demonstrating @value{GDBN}'s overlay support.
7600 However, the @value{GDBN} source distribution does contain an overlaid
7601 program, with linker scripts for a few systems, as part of its test
7602 suite. The program consists of the following files from
7603 @file{gdb/testsuite/gdb.base}:
7607 The main program file.
7609 A simple overlay manager, used by @file{overlays.c}.
7614 Overlay modules, loaded and used by @file{overlays.c}.
7617 Linker scripts for linking the test program on the @code{d10v-elf}
7618 and @code{m32r-elf} targets.
7621 You can build the test program using the @code{d10v-elf} GCC
7622 cross-compiler like this:
7625 $ d10v-elf-gcc -g -c overlays.c
7626 $ d10v-elf-gcc -g -c ovlymgr.c
7627 $ d10v-elf-gcc -g -c foo.c
7628 $ d10v-elf-gcc -g -c bar.c
7629 $ d10v-elf-gcc -g -c baz.c
7630 $ d10v-elf-gcc -g -c grbx.c
7631 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
7632 baz.o grbx.o -Wl,-Td10v.ld -o overlays
7635 The build process is identical for any other architecture, except that
7636 you must substitute the appropriate compiler and linker script for the
7637 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
7641 @chapter Using @value{GDBN} with Different Languages
7644 Although programming languages generally have common aspects, they are
7645 rarely expressed in the same manner. For instance, in ANSI C,
7646 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
7647 Modula-2, it is accomplished by @code{p^}. Values can also be
7648 represented (and displayed) differently. Hex numbers in C appear as
7649 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
7651 @cindex working language
7652 Language-specific information is built into @value{GDBN} for some languages,
7653 allowing you to express operations like the above in your program's
7654 native language, and allowing @value{GDBN} to output values in a manner
7655 consistent with the syntax of your program's native language. The
7656 language you use to build expressions is called the @dfn{working
7660 * Setting:: Switching between source languages
7661 * Show:: Displaying the language
7662 * Checks:: Type and range checks
7663 * Support:: Supported languages
7664 * Unsupported languages:: Unsupported languages
7668 @section Switching between source languages
7670 There are two ways to control the working language---either have @value{GDBN}
7671 set it automatically, or select it manually yourself. You can use the
7672 @code{set language} command for either purpose. On startup, @value{GDBN}
7673 defaults to setting the language automatically. The working language is
7674 used to determine how expressions you type are interpreted, how values
7677 In addition to the working language, every source file that
7678 @value{GDBN} knows about has its own working language. For some object
7679 file formats, the compiler might indicate which language a particular
7680 source file is in. However, most of the time @value{GDBN} infers the
7681 language from the name of the file. The language of a source file
7682 controls whether C@t{++} names are demangled---this way @code{backtrace} can
7683 show each frame appropriately for its own language. There is no way to
7684 set the language of a source file from within @value{GDBN}, but you can
7685 set the language associated with a filename extension. @xref{Show, ,
7686 Displaying the language}.
7688 This is most commonly a problem when you use a program, such
7689 as @code{cfront} or @code{f2c}, that generates C but is written in
7690 another language. In that case, make the
7691 program use @code{#line} directives in its C output; that way
7692 @value{GDBN} will know the correct language of the source code of the original
7693 program, and will display that source code, not the generated C code.
7696 * Filenames:: Filename extensions and languages.
7697 * Manually:: Setting the working language manually
7698 * Automatically:: Having @value{GDBN} infer the source language
7702 @subsection List of filename extensions and languages
7704 If a source file name ends in one of the following extensions, then
7705 @value{GDBN} infers that its language is the one indicated.
7721 Objective-C source file
7728 Modula-2 source file
7732 Assembler source file. This actually behaves almost like C, but
7733 @value{GDBN} does not skip over function prologues when stepping.
7736 In addition, you may set the language associated with a filename
7737 extension. @xref{Show, , Displaying the language}.
7740 @subsection Setting the working language
7742 If you allow @value{GDBN} to set the language automatically,
7743 expressions are interpreted the same way in your debugging session and
7746 @kindex set language
7747 If you wish, you may set the language manually. To do this, issue the
7748 command @samp{set language @var{lang}}, where @var{lang} is the name of
7750 @code{c} or @code{modula-2}.
7751 For a list of the supported languages, type @samp{set language}.
7753 Setting the language manually prevents @value{GDBN} from updating the working
7754 language automatically. This can lead to confusion if you try
7755 to debug a program when the working language is not the same as the
7756 source language, when an expression is acceptable to both
7757 languages---but means different things. For instance, if the current
7758 source file were written in C, and @value{GDBN} was parsing Modula-2, a
7766 might not have the effect you intended. In C, this means to add
7767 @code{b} and @code{c} and place the result in @code{a}. The result
7768 printed would be the value of @code{a}. In Modula-2, this means to compare
7769 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
7772 @subsection Having @value{GDBN} infer the source language
7774 To have @value{GDBN} set the working language automatically, use
7775 @samp{set language local} or @samp{set language auto}. @value{GDBN}
7776 then infers the working language. That is, when your program stops in a
7777 frame (usually by encountering a breakpoint), @value{GDBN} sets the
7778 working language to the language recorded for the function in that
7779 frame. If the language for a frame is unknown (that is, if the function
7780 or block corresponding to the frame was defined in a source file that
7781 does not have a recognized extension), the current working language is
7782 not changed, and @value{GDBN} issues a warning.
7784 This may not seem necessary for most programs, which are written
7785 entirely in one source language. However, program modules and libraries
7786 written in one source language can be used by a main program written in
7787 a different source language. Using @samp{set language auto} in this
7788 case frees you from having to set the working language manually.
7791 @section Displaying the language
7793 The following commands help you find out which language is the
7794 working language, and also what language source files were written in.
7796 @kindex show language
7797 @kindex info frame@r{, show the source language}
7798 @kindex info source@r{, show the source language}
7801 Display the current working language. This is the
7802 language you can use with commands such as @code{print} to
7803 build and compute expressions that may involve variables in your program.
7806 Display the source language for this frame. This language becomes the
7807 working language if you use an identifier from this frame.
7808 @xref{Frame Info, ,Information about a frame}, to identify the other
7809 information listed here.
7812 Display the source language of this source file.
7813 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
7814 information listed here.
7817 In unusual circumstances, you may have source files with extensions
7818 not in the standard list. You can then set the extension associated
7819 with a language explicitly:
7821 @kindex set extension-language
7822 @kindex info extensions
7824 @item set extension-language @var{.ext} @var{language}
7825 Set source files with extension @var{.ext} to be assumed to be in
7826 the source language @var{language}.
7828 @item info extensions
7829 List all the filename extensions and the associated languages.
7833 @section Type and range checking
7836 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
7837 checking are included, but they do not yet have any effect. This
7838 section documents the intended facilities.
7840 @c FIXME remove warning when type/range code added
7842 Some languages are designed to guard you against making seemingly common
7843 errors through a series of compile- and run-time checks. These include
7844 checking the type of arguments to functions and operators, and making
7845 sure mathematical overflows are caught at run time. Checks such as
7846 these help to ensure a program's correctness once it has been compiled
7847 by eliminating type mismatches, and providing active checks for range
7848 errors when your program is running.
7850 @value{GDBN} can check for conditions like the above if you wish.
7851 Although @value{GDBN} does not check the statements in your program, it
7852 can check expressions entered directly into @value{GDBN} for evaluation via
7853 the @code{print} command, for example. As with the working language,
7854 @value{GDBN} can also decide whether or not to check automatically based on
7855 your program's source language. @xref{Support, ,Supported languages},
7856 for the default settings of supported languages.
7859 * Type Checking:: An overview of type checking
7860 * Range Checking:: An overview of range checking
7863 @cindex type checking
7864 @cindex checks, type
7866 @subsection An overview of type checking
7868 Some languages, such as Modula-2, are strongly typed, meaning that the
7869 arguments to operators and functions have to be of the correct type,
7870 otherwise an error occurs. These checks prevent type mismatch
7871 errors from ever causing any run-time problems. For example,
7879 The second example fails because the @code{CARDINAL} 1 is not
7880 type-compatible with the @code{REAL} 2.3.
7882 For the expressions you use in @value{GDBN} commands, you can tell the
7883 @value{GDBN} type checker to skip checking;
7884 to treat any mismatches as errors and abandon the expression;
7885 or to only issue warnings when type mismatches occur,
7886 but evaluate the expression anyway. When you choose the last of
7887 these, @value{GDBN} evaluates expressions like the second example above, but
7888 also issues a warning.
7890 Even if you turn type checking off, there may be other reasons
7891 related to type that prevent @value{GDBN} from evaluating an expression.
7892 For instance, @value{GDBN} does not know how to add an @code{int} and
7893 a @code{struct foo}. These particular type errors have nothing to do
7894 with the language in use, and usually arise from expressions, such as
7895 the one described above, which make little sense to evaluate anyway.
7897 Each language defines to what degree it is strict about type. For
7898 instance, both Modula-2 and C require the arguments to arithmetical
7899 operators to be numbers. In C, enumerated types and pointers can be
7900 represented as numbers, so that they are valid arguments to mathematical
7901 operators. @xref{Support, ,Supported languages}, for further
7902 details on specific languages.
7904 @value{GDBN} provides some additional commands for controlling the type checker:
7906 @kindex set check@r{, type}
7907 @kindex set check type
7908 @kindex show check type
7910 @item set check type auto
7911 Set type checking on or off based on the current working language.
7912 @xref{Support, ,Supported languages}, for the default settings for
7915 @item set check type on
7916 @itemx set check type off
7917 Set type checking on or off, overriding the default setting for the
7918 current working language. Issue a warning if the setting does not
7919 match the language default. If any type mismatches occur in
7920 evaluating an expression while type checking is on, @value{GDBN} prints a
7921 message and aborts evaluation of the expression.
7923 @item set check type warn
7924 Cause the type checker to issue warnings, but to always attempt to
7925 evaluate the expression. Evaluating the expression may still
7926 be impossible for other reasons. For example, @value{GDBN} cannot add
7927 numbers and structures.
7930 Show the current setting of the type checker, and whether or not @value{GDBN}
7931 is setting it automatically.
7934 @cindex range checking
7935 @cindex checks, range
7936 @node Range Checking
7937 @subsection An overview of range checking
7939 In some languages (such as Modula-2), it is an error to exceed the
7940 bounds of a type; this is enforced with run-time checks. Such range
7941 checking is meant to ensure program correctness by making sure
7942 computations do not overflow, or indices on an array element access do
7943 not exceed the bounds of the array.
7945 For expressions you use in @value{GDBN} commands, you can tell
7946 @value{GDBN} to treat range errors in one of three ways: ignore them,
7947 always treat them as errors and abandon the expression, or issue
7948 warnings but evaluate the expression anyway.
7950 A range error can result from numerical overflow, from exceeding an
7951 array index bound, or when you type a constant that is not a member
7952 of any type. Some languages, however, do not treat overflows as an
7953 error. In many implementations of C, mathematical overflow causes the
7954 result to ``wrap around'' to lower values---for example, if @var{m} is
7955 the largest integer value, and @var{s} is the smallest, then
7958 @var{m} + 1 @result{} @var{s}
7961 This, too, is specific to individual languages, and in some cases
7962 specific to individual compilers or machines. @xref{Support, ,
7963 Supported languages}, for further details on specific languages.
7965 @value{GDBN} provides some additional commands for controlling the range checker:
7967 @kindex set check@r{, range}
7968 @kindex set check range
7969 @kindex show check range
7971 @item set check range auto
7972 Set range checking on or off based on the current working language.
7973 @xref{Support, ,Supported languages}, for the default settings for
7976 @item set check range on
7977 @itemx set check range off
7978 Set range checking on or off, overriding the default setting for the
7979 current working language. A warning is issued if the setting does not
7980 match the language default. If a range error occurs and range checking is on,
7981 then a message is printed and evaluation of the expression is aborted.
7983 @item set check range warn
7984 Output messages when the @value{GDBN} range checker detects a range error,
7985 but attempt to evaluate the expression anyway. Evaluating the
7986 expression may still be impossible for other reasons, such as accessing
7987 memory that the process does not own (a typical example from many Unix
7991 Show the current setting of the range checker, and whether or not it is
7992 being set automatically by @value{GDBN}.
7996 @section Supported languages
7998 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, assembly, and Modula-2.
7999 @c This is false ...
8000 Some @value{GDBN} features may be used in expressions regardless of the
8001 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
8002 and the @samp{@{type@}addr} construct (@pxref{Expressions,
8003 ,Expressions}) can be used with the constructs of any supported
8006 The following sections detail to what degree each source language is
8007 supported by @value{GDBN}. These sections are not meant to be language
8008 tutorials or references, but serve only as a reference guide to what the
8009 @value{GDBN} expression parser accepts, and what input and output
8010 formats should look like for different languages. There are many good
8011 books written on each of these languages; please look to these for a
8012 language reference or tutorial.
8016 * Objective-C:: Objective-C
8017 * Modula-2:: Modula-2
8021 @subsection C and C@t{++}
8023 @cindex C and C@t{++}
8024 @cindex expressions in C or C@t{++}
8026 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
8027 to both languages. Whenever this is the case, we discuss those languages
8031 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
8032 @cindex @sc{gnu} C@t{++}
8033 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
8034 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
8035 effectively, you must compile your C@t{++} programs with a supported
8036 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
8037 compiler (@code{aCC}).
8039 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
8040 format; if it doesn't work on your system, try the stabs+ debugging
8041 format. You can select those formats explicitly with the @code{g++}
8042 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
8043 @xref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
8044 CC, gcc.info, Using @sc{gnu} CC}.
8047 * C Operators:: C and C@t{++} operators
8048 * C Constants:: C and C@t{++} constants
8049 * C plus plus expressions:: C@t{++} expressions
8050 * C Defaults:: Default settings for C and C@t{++}
8051 * C Checks:: C and C@t{++} type and range checks
8052 * Debugging C:: @value{GDBN} and C
8053 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
8057 @subsubsection C and C@t{++} operators
8059 @cindex C and C@t{++} operators
8061 Operators must be defined on values of specific types. For instance,
8062 @code{+} is defined on numbers, but not on structures. Operators are
8063 often defined on groups of types.
8065 For the purposes of C and C@t{++}, the following definitions hold:
8070 @emph{Integral types} include @code{int} with any of its storage-class
8071 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
8074 @emph{Floating-point types} include @code{float}, @code{double}, and
8075 @code{long double} (if supported by the target platform).
8078 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
8081 @emph{Scalar types} include all of the above.
8086 The following operators are supported. They are listed here
8087 in order of increasing precedence:
8091 The comma or sequencing operator. Expressions in a comma-separated list
8092 are evaluated from left to right, with the result of the entire
8093 expression being the last expression evaluated.
8096 Assignment. The value of an assignment expression is the value
8097 assigned. Defined on scalar types.
8100 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
8101 and translated to @w{@code{@var{a} = @var{a op b}}}.
8102 @w{@code{@var{op}=}} and @code{=} have the same precedence.
8103 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
8104 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
8107 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
8108 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
8112 Logical @sc{or}. Defined on integral types.
8115 Logical @sc{and}. Defined on integral types.
8118 Bitwise @sc{or}. Defined on integral types.
8121 Bitwise exclusive-@sc{or}. Defined on integral types.
8124 Bitwise @sc{and}. Defined on integral types.
8127 Equality and inequality. Defined on scalar types. The value of these
8128 expressions is 0 for false and non-zero for true.
8130 @item <@r{, }>@r{, }<=@r{, }>=
8131 Less than, greater than, less than or equal, greater than or equal.
8132 Defined on scalar types. The value of these expressions is 0 for false
8133 and non-zero for true.
8136 left shift, and right shift. Defined on integral types.
8139 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8142 Addition and subtraction. Defined on integral types, floating-point types and
8145 @item *@r{, }/@r{, }%
8146 Multiplication, division, and modulus. Multiplication and division are
8147 defined on integral and floating-point types. Modulus is defined on
8151 Increment and decrement. When appearing before a variable, the
8152 operation is performed before the variable is used in an expression;
8153 when appearing after it, the variable's value is used before the
8154 operation takes place.
8157 Pointer dereferencing. Defined on pointer types. Same precedence as
8161 Address operator. Defined on variables. Same precedence as @code{++}.
8163 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
8164 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
8165 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
8166 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
8170 Negative. Defined on integral and floating-point types. Same
8171 precedence as @code{++}.
8174 Logical negation. Defined on integral types. Same precedence as
8178 Bitwise complement operator. Defined on integral types. Same precedence as
8183 Structure member, and pointer-to-structure member. For convenience,
8184 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
8185 pointer based on the stored type information.
8186 Defined on @code{struct} and @code{union} data.
8189 Dereferences of pointers to members.
8192 Array indexing. @code{@var{a}[@var{i}]} is defined as
8193 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
8196 Function parameter list. Same precedence as @code{->}.
8199 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
8200 and @code{class} types.
8203 Doubled colons also represent the @value{GDBN} scope operator
8204 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
8208 If an operator is redefined in the user code, @value{GDBN} usually
8209 attempts to invoke the redefined version instead of using the operator's
8217 @subsubsection C and C@t{++} constants
8219 @cindex C and C@t{++} constants
8221 @value{GDBN} allows you to express the constants of C and C@t{++} in the
8226 Integer constants are a sequence of digits. Octal constants are
8227 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
8228 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
8229 @samp{l}, specifying that the constant should be treated as a
8233 Floating point constants are a sequence of digits, followed by a decimal
8234 point, followed by a sequence of digits, and optionally followed by an
8235 exponent. An exponent is of the form:
8236 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
8237 sequence of digits. The @samp{+} is optional for positive exponents.
8238 A floating-point constant may also end with a letter @samp{f} or
8239 @samp{F}, specifying that the constant should be treated as being of
8240 the @code{float} (as opposed to the default @code{double}) type; or with
8241 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
8245 Enumerated constants consist of enumerated identifiers, or their
8246 integral equivalents.
8249 Character constants are a single character surrounded by single quotes
8250 (@code{'}), or a number---the ordinal value of the corresponding character
8251 (usually its @sc{ascii} value). Within quotes, the single character may
8252 be represented by a letter or by @dfn{escape sequences}, which are of
8253 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
8254 of the character's ordinal value; or of the form @samp{\@var{x}}, where
8255 @samp{@var{x}} is a predefined special character---for example,
8256 @samp{\n} for newline.
8259 String constants are a sequence of character constants surrounded by
8260 double quotes (@code{"}). Any valid character constant (as described
8261 above) may appear. Double quotes within the string must be preceded by
8262 a backslash, so for instance @samp{"a\"b'c"} is a string of five
8266 Pointer constants are an integral value. You can also write pointers
8267 to constants using the C operator @samp{&}.
8270 Array constants are comma-separated lists surrounded by braces @samp{@{}
8271 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
8272 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
8273 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
8277 * C plus plus expressions::
8284 @node C plus plus expressions
8285 @subsubsection C@t{++} expressions
8287 @cindex expressions in C@t{++}
8288 @value{GDBN} expression handling can interpret most C@t{++} expressions.
8290 @cindex debugging C@t{++} programs
8291 @cindex C@t{++} compilers
8292 @cindex debug formats and C@t{++}
8293 @cindex @value{NGCC} and C@t{++}
8295 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
8296 proper compiler and the proper debug format. Currently, @value{GDBN}
8297 works best when debugging C@t{++} code that is compiled with
8298 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
8299 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
8300 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
8301 stabs+ as their default debug format, so you usually don't need to
8302 specify a debug format explicitly. Other compilers and/or debug formats
8303 are likely to work badly or not at all when using @value{GDBN} to debug
8309 @cindex member functions
8311 Member function calls are allowed; you can use expressions like
8314 count = aml->GetOriginal(x, y)
8317 @vindex this@r{, inside C@t{++} member functions}
8318 @cindex namespace in C@t{++}
8320 While a member function is active (in the selected stack frame), your
8321 expressions have the same namespace available as the member function;
8322 that is, @value{GDBN} allows implicit references to the class instance
8323 pointer @code{this} following the same rules as C@t{++}.
8325 @cindex call overloaded functions
8326 @cindex overloaded functions, calling
8327 @cindex type conversions in C@t{++}
8329 You can call overloaded functions; @value{GDBN} resolves the function
8330 call to the right definition, with some restrictions. @value{GDBN} does not
8331 perform overload resolution involving user-defined type conversions,
8332 calls to constructors, or instantiations of templates that do not exist
8333 in the program. It also cannot handle ellipsis argument lists or
8336 It does perform integral conversions and promotions, floating-point
8337 promotions, arithmetic conversions, pointer conversions, conversions of
8338 class objects to base classes, and standard conversions such as those of
8339 functions or arrays to pointers; it requires an exact match on the
8340 number of function arguments.
8342 Overload resolution is always performed, unless you have specified
8343 @code{set overload-resolution off}. @xref{Debugging C plus plus,
8344 ,@value{GDBN} features for C@t{++}}.
8346 You must specify @code{set overload-resolution off} in order to use an
8347 explicit function signature to call an overloaded function, as in
8349 p 'foo(char,int)'('x', 13)
8352 The @value{GDBN} command-completion facility can simplify this;
8353 see @ref{Completion, ,Command completion}.
8355 @cindex reference declarations
8357 @value{GDBN} understands variables declared as C@t{++} references; you can use
8358 them in expressions just as you do in C@t{++} source---they are automatically
8361 In the parameter list shown when @value{GDBN} displays a frame, the values of
8362 reference variables are not displayed (unlike other variables); this
8363 avoids clutter, since references are often used for large structures.
8364 The @emph{address} of a reference variable is always shown, unless
8365 you have specified @samp{set print address off}.
8368 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
8369 expressions can use it just as expressions in your program do. Since
8370 one scope may be defined in another, you can use @code{::} repeatedly if
8371 necessary, for example in an expression like
8372 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
8373 resolving name scope by reference to source files, in both C and C@t{++}
8374 debugging (@pxref{Variables, ,Program variables}).
8377 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
8378 calling virtual functions correctly, printing out virtual bases of
8379 objects, calling functions in a base subobject, casting objects, and
8380 invoking user-defined operators.
8383 @subsubsection C and C@t{++} defaults
8385 @cindex C and C@t{++} defaults
8387 If you allow @value{GDBN} to set type and range checking automatically, they
8388 both default to @code{off} whenever the working language changes to
8389 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
8390 selects the working language.
8392 If you allow @value{GDBN} to set the language automatically, it
8393 recognizes source files whose names end with @file{.c}, @file{.C}, or
8394 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
8395 these files, it sets the working language to C or C@t{++}.
8396 @xref{Automatically, ,Having @value{GDBN} infer the source language},
8397 for further details.
8399 @c Type checking is (a) primarily motivated by Modula-2, and (b)
8400 @c unimplemented. If (b) changes, it might make sense to let this node
8401 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
8404 @subsubsection C and C@t{++} type and range checks
8406 @cindex C and C@t{++} checks
8408 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
8409 is not used. However, if you turn type checking on, @value{GDBN}
8410 considers two variables type equivalent if:
8414 The two variables are structured and have the same structure, union, or
8418 The two variables have the same type name, or types that have been
8419 declared equivalent through @code{typedef}.
8422 @c leaving this out because neither J Gilmore nor R Pesch understand it.
8425 The two @code{struct}, @code{union}, or @code{enum} variables are
8426 declared in the same declaration. (Note: this may not be true for all C
8431 Range checking, if turned on, is done on mathematical operations. Array
8432 indices are not checked, since they are often used to index a pointer
8433 that is not itself an array.
8436 @subsubsection @value{GDBN} and C
8438 The @code{set print union} and @code{show print union} commands apply to
8439 the @code{union} type. When set to @samp{on}, any @code{union} that is
8440 inside a @code{struct} or @code{class} is also printed. Otherwise, it
8441 appears as @samp{@{...@}}.
8443 The @code{@@} operator aids in the debugging of dynamic arrays, formed
8444 with pointers and a memory allocation function. @xref{Expressions,
8448 * Debugging C plus plus::
8451 @node Debugging C plus plus
8452 @subsubsection @value{GDBN} features for C@t{++}
8454 @cindex commands for C@t{++}
8456 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
8457 designed specifically for use with C@t{++}. Here is a summary:
8460 @cindex break in overloaded functions
8461 @item @r{breakpoint menus}
8462 When you want a breakpoint in a function whose name is overloaded,
8463 @value{GDBN} breakpoint menus help you specify which function definition
8464 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
8466 @cindex overloading in C@t{++}
8467 @item rbreak @var{regex}
8468 Setting breakpoints using regular expressions is helpful for setting
8469 breakpoints on overloaded functions that are not members of any special
8471 @xref{Set Breaks, ,Setting breakpoints}.
8473 @cindex C@t{++} exception handling
8476 Debug C@t{++} exception handling using these commands. @xref{Set
8477 Catchpoints, , Setting catchpoints}.
8480 @item ptype @var{typename}
8481 Print inheritance relationships as well as other information for type
8483 @xref{Symbols, ,Examining the Symbol Table}.
8485 @cindex C@t{++} symbol display
8486 @item set print demangle
8487 @itemx show print demangle
8488 @itemx set print asm-demangle
8489 @itemx show print asm-demangle
8490 Control whether C@t{++} symbols display in their source form, both when
8491 displaying code as C@t{++} source and when displaying disassemblies.
8492 @xref{Print Settings, ,Print settings}.
8494 @item set print object
8495 @itemx show print object
8496 Choose whether to print derived (actual) or declared types of objects.
8497 @xref{Print Settings, ,Print settings}.
8499 @item set print vtbl
8500 @itemx show print vtbl
8501 Control the format for printing virtual function tables.
8502 @xref{Print Settings, ,Print settings}.
8503 (The @code{vtbl} commands do not work on programs compiled with the HP
8504 ANSI C@t{++} compiler (@code{aCC}).)
8506 @kindex set overload-resolution
8507 @cindex overloaded functions, overload resolution
8508 @item set overload-resolution on
8509 Enable overload resolution for C@t{++} expression evaluation. The default
8510 is on. For overloaded functions, @value{GDBN} evaluates the arguments
8511 and searches for a function whose signature matches the argument types,
8512 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
8513 expressions}, for details). If it cannot find a match, it emits a
8516 @item set overload-resolution off
8517 Disable overload resolution for C@t{++} expression evaluation. For
8518 overloaded functions that are not class member functions, @value{GDBN}
8519 chooses the first function of the specified name that it finds in the
8520 symbol table, whether or not its arguments are of the correct type. For
8521 overloaded functions that are class member functions, @value{GDBN}
8522 searches for a function whose signature @emph{exactly} matches the
8525 @item @r{Overloaded symbol names}
8526 You can specify a particular definition of an overloaded symbol, using
8527 the same notation that is used to declare such symbols in C@t{++}: type
8528 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
8529 also use the @value{GDBN} command-line word completion facilities to list the
8530 available choices, or to finish the type list for you.
8531 @xref{Completion,, Command completion}, for details on how to do this.
8535 @subsection Objective-C
8538 This section provides information about some commands and command
8539 options that are useful for debugging Objective-C code.
8542 * Method Names in Commands::
8543 * The Print Command with Objective-C::
8546 @node Method Names in Commands, The Print Command with Objective-C, Objective-C, Objective-C
8547 @subsubsection Method Names in Commands
8549 The following commands have been extended to accept Objective-C method
8550 names as line specifications:
8552 @kindex clear@r{, and Objective-C}
8553 @kindex break@r{, and Objective-C}
8554 @kindex info line@r{, and Objective-C}
8555 @kindex jump@r{, and Objective-C}
8556 @kindex list@r{, and Objective-C}
8560 @item @code{info line}
8565 A fully qualified Objective-C method name is specified as
8568 -[@var{Class} @var{methodName}]
8571 where the minus sign is used to indicate an instance method and a
8572 plus sign (not shown) is used to indicate a class method. The class
8573 name @var{Class} and method name @var{methodName} are enclosed in
8574 brackets, similar to the way messages are specified in Objective-C
8575 source code. For example, to set a breakpoint at the @code{create}
8576 instance method of class @code{Fruit} in the program currently being
8580 break -[Fruit create]
8583 To list ten program lines around the @code{initialize} class method,
8587 list +[NSText initialize]
8590 In the current version of @value{GDBN}, the plus or minus sign is
8591 required. In future versions of @value{GDBN}, the plus or minus
8592 sign will be optional, but you can use it to narrow the search. It
8593 is also possible to specify just a method name:
8599 You must specify the complete method name, including any colons. If
8600 your program's source files contain more than one @code{create} method,
8601 you'll be presented with a numbered list of classes that implement that
8602 method. Indicate your choice by number, or type @samp{0} to exit if
8605 As another example, to clear a breakpoint established at the
8606 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
8609 clear -[NSWindow makeKeyAndOrderFront:]
8612 @node The Print Command with Objective-C
8613 @subsubsection The Print Command With Objective-C
8614 @kindex print-object
8615 @kindex po @r{(@code{print-object})}
8617 The print command has also been extended to accept methods. For example:
8620 print -[@var{object} hash]
8623 @cindex print an Objective-C object description
8624 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
8626 will tell @value{GDBN} to send the @code{hash} message to @var{object}
8627 and print the result. Also, an additional command has been added,
8628 @code{print-object} or @code{po} for short, which is meant to print
8629 the description of an object. However, this command may only work
8630 with certain Objective-C libraries that have a particular hook
8631 function, @code{_NSPrintForDebugger}, defined.
8633 @node Modula-2, , Objective-C, Support
8634 @subsection Modula-2
8636 @cindex Modula-2, @value{GDBN} support
8638 The extensions made to @value{GDBN} to support Modula-2 only support
8639 output from the @sc{gnu} Modula-2 compiler (which is currently being
8640 developed). Other Modula-2 compilers are not currently supported, and
8641 attempting to debug executables produced by them is most likely
8642 to give an error as @value{GDBN} reads in the executable's symbol
8645 @cindex expressions in Modula-2
8647 * M2 Operators:: Built-in operators
8648 * Built-In Func/Proc:: Built-in functions and procedures
8649 * M2 Constants:: Modula-2 constants
8650 * M2 Defaults:: Default settings for Modula-2
8651 * Deviations:: Deviations from standard Modula-2
8652 * M2 Checks:: Modula-2 type and range checks
8653 * M2 Scope:: The scope operators @code{::} and @code{.}
8654 * GDB/M2:: @value{GDBN} and Modula-2
8658 @subsubsection Operators
8659 @cindex Modula-2 operators
8661 Operators must be defined on values of specific types. For instance,
8662 @code{+} is defined on numbers, but not on structures. Operators are
8663 often defined on groups of types. For the purposes of Modula-2, the
8664 following definitions hold:
8669 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
8673 @emph{Character types} consist of @code{CHAR} and its subranges.
8676 @emph{Floating-point types} consist of @code{REAL}.
8679 @emph{Pointer types} consist of anything declared as @code{POINTER TO
8683 @emph{Scalar types} consist of all of the above.
8686 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
8689 @emph{Boolean types} consist of @code{BOOLEAN}.
8693 The following operators are supported, and appear in order of
8694 increasing precedence:
8698 Function argument or array index separator.
8701 Assignment. The value of @var{var} @code{:=} @var{value} is
8705 Less than, greater than on integral, floating-point, or enumerated
8709 Less than or equal to, greater than or equal to
8710 on integral, floating-point and enumerated types, or set inclusion on
8711 set types. Same precedence as @code{<}.
8713 @item =@r{, }<>@r{, }#
8714 Equality and two ways of expressing inequality, valid on scalar types.
8715 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
8716 available for inequality, since @code{#} conflicts with the script
8720 Set membership. Defined on set types and the types of their members.
8721 Same precedence as @code{<}.
8724 Boolean disjunction. Defined on boolean types.
8727 Boolean conjunction. Defined on boolean types.
8730 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8733 Addition and subtraction on integral and floating-point types, or union
8734 and difference on set types.
8737 Multiplication on integral and floating-point types, or set intersection
8741 Division on floating-point types, or symmetric set difference on set
8742 types. Same precedence as @code{*}.
8745 Integer division and remainder. Defined on integral types. Same
8746 precedence as @code{*}.
8749 Negative. Defined on @code{INTEGER} and @code{REAL} data.
8752 Pointer dereferencing. Defined on pointer types.
8755 Boolean negation. Defined on boolean types. Same precedence as
8759 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
8760 precedence as @code{^}.
8763 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
8766 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
8770 @value{GDBN} and Modula-2 scope operators.
8774 @emph{Warning:} Sets and their operations are not yet supported, so @value{GDBN}
8775 treats the use of the operator @code{IN}, or the use of operators
8776 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
8777 @code{<=}, and @code{>=} on sets as an error.
8781 @node Built-In Func/Proc
8782 @subsubsection Built-in functions and procedures
8783 @cindex Modula-2 built-ins
8785 Modula-2 also makes available several built-in procedures and functions.
8786 In describing these, the following metavariables are used:
8791 represents an @code{ARRAY} variable.
8794 represents a @code{CHAR} constant or variable.
8797 represents a variable or constant of integral type.
8800 represents an identifier that belongs to a set. Generally used in the
8801 same function with the metavariable @var{s}. The type of @var{s} should
8802 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
8805 represents a variable or constant of integral or floating-point type.
8808 represents a variable or constant of floating-point type.
8814 represents a variable.
8817 represents a variable or constant of one of many types. See the
8818 explanation of the function for details.
8821 All Modula-2 built-in procedures also return a result, described below.
8825 Returns the absolute value of @var{n}.
8828 If @var{c} is a lower case letter, it returns its upper case
8829 equivalent, otherwise it returns its argument.
8832 Returns the character whose ordinal value is @var{i}.
8835 Decrements the value in the variable @var{v} by one. Returns the new value.
8837 @item DEC(@var{v},@var{i})
8838 Decrements the value in the variable @var{v} by @var{i}. Returns the
8841 @item EXCL(@var{m},@var{s})
8842 Removes the element @var{m} from the set @var{s}. Returns the new
8845 @item FLOAT(@var{i})
8846 Returns the floating point equivalent of the integer @var{i}.
8849 Returns the index of the last member of @var{a}.
8852 Increments the value in the variable @var{v} by one. Returns the new value.
8854 @item INC(@var{v},@var{i})
8855 Increments the value in the variable @var{v} by @var{i}. Returns the
8858 @item INCL(@var{m},@var{s})
8859 Adds the element @var{m} to the set @var{s} if it is not already
8860 there. Returns the new set.
8863 Returns the maximum value of the type @var{t}.
8866 Returns the minimum value of the type @var{t}.
8869 Returns boolean TRUE if @var{i} is an odd number.
8872 Returns the ordinal value of its argument. For example, the ordinal
8873 value of a character is its @sc{ascii} value (on machines supporting the
8874 @sc{ascii} character set). @var{x} must be of an ordered type, which include
8875 integral, character and enumerated types.
8878 Returns the size of its argument. @var{x} can be a variable or a type.
8880 @item TRUNC(@var{r})
8881 Returns the integral part of @var{r}.
8883 @item VAL(@var{t},@var{i})
8884 Returns the member of the type @var{t} whose ordinal value is @var{i}.
8888 @emph{Warning:} Sets and their operations are not yet supported, so
8889 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
8893 @cindex Modula-2 constants
8895 @subsubsection Constants
8897 @value{GDBN} allows you to express the constants of Modula-2 in the following
8903 Integer constants are simply a sequence of digits. When used in an
8904 expression, a constant is interpreted to be type-compatible with the
8905 rest of the expression. Hexadecimal integers are specified by a
8906 trailing @samp{H}, and octal integers by a trailing @samp{B}.
8909 Floating point constants appear as a sequence of digits, followed by a
8910 decimal point and another sequence of digits. An optional exponent can
8911 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
8912 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
8913 digits of the floating point constant must be valid decimal (base 10)
8917 Character constants consist of a single character enclosed by a pair of
8918 like quotes, either single (@code{'}) or double (@code{"}). They may
8919 also be expressed by their ordinal value (their @sc{ascii} value, usually)
8920 followed by a @samp{C}.
8923 String constants consist of a sequence of characters enclosed by a
8924 pair of like quotes, either single (@code{'}) or double (@code{"}).
8925 Escape sequences in the style of C are also allowed. @xref{C
8926 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
8930 Enumerated constants consist of an enumerated identifier.
8933 Boolean constants consist of the identifiers @code{TRUE} and
8937 Pointer constants consist of integral values only.
8940 Set constants are not yet supported.
8944 @subsubsection Modula-2 defaults
8945 @cindex Modula-2 defaults
8947 If type and range checking are set automatically by @value{GDBN}, they
8948 both default to @code{on} whenever the working language changes to
8949 Modula-2. This happens regardless of whether you or @value{GDBN}
8950 selected the working language.
8952 If you allow @value{GDBN} to set the language automatically, then entering
8953 code compiled from a file whose name ends with @file{.mod} sets the
8954 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
8955 the language automatically}, for further details.
8958 @subsubsection Deviations from standard Modula-2
8959 @cindex Modula-2, deviations from
8961 A few changes have been made to make Modula-2 programs easier to debug.
8962 This is done primarily via loosening its type strictness:
8966 Unlike in standard Modula-2, pointer constants can be formed by
8967 integers. This allows you to modify pointer variables during
8968 debugging. (In standard Modula-2, the actual address contained in a
8969 pointer variable is hidden from you; it can only be modified
8970 through direct assignment to another pointer variable or expression that
8971 returned a pointer.)
8974 C escape sequences can be used in strings and characters to represent
8975 non-printable characters. @value{GDBN} prints out strings with these
8976 escape sequences embedded. Single non-printable characters are
8977 printed using the @samp{CHR(@var{nnn})} format.
8980 The assignment operator (@code{:=}) returns the value of its right-hand
8984 All built-in procedures both modify @emph{and} return their argument.
8988 @subsubsection Modula-2 type and range checks
8989 @cindex Modula-2 checks
8992 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
8995 @c FIXME remove warning when type/range checks added
8997 @value{GDBN} considers two Modula-2 variables type equivalent if:
9001 They are of types that have been declared equivalent via a @code{TYPE
9002 @var{t1} = @var{t2}} statement
9005 They have been declared on the same line. (Note: This is true of the
9006 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
9009 As long as type checking is enabled, any attempt to combine variables
9010 whose types are not equivalent is an error.
9012 Range checking is done on all mathematical operations, assignment, array
9013 index bounds, and all built-in functions and procedures.
9016 @subsubsection The scope operators @code{::} and @code{.}
9018 @cindex @code{.}, Modula-2 scope operator
9019 @cindex colon, doubled as scope operator
9021 @vindex colon-colon@r{, in Modula-2}
9022 @c Info cannot handle :: but TeX can.
9025 @vindex ::@r{, in Modula-2}
9028 There are a few subtle differences between the Modula-2 scope operator
9029 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
9034 @var{module} . @var{id}
9035 @var{scope} :: @var{id}
9039 where @var{scope} is the name of a module or a procedure,
9040 @var{module} the name of a module, and @var{id} is any declared
9041 identifier within your program, except another module.
9043 Using the @code{::} operator makes @value{GDBN} search the scope
9044 specified by @var{scope} for the identifier @var{id}. If it is not
9045 found in the specified scope, then @value{GDBN} searches all scopes
9046 enclosing the one specified by @var{scope}.
9048 Using the @code{.} operator makes @value{GDBN} search the current scope for
9049 the identifier specified by @var{id} that was imported from the
9050 definition module specified by @var{module}. With this operator, it is
9051 an error if the identifier @var{id} was not imported from definition
9052 module @var{module}, or if @var{id} is not an identifier in
9056 @subsubsection @value{GDBN} and Modula-2
9058 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
9059 Five subcommands of @code{set print} and @code{show print} apply
9060 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
9061 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
9062 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
9063 analogue in Modula-2.
9065 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
9066 with any language, is not useful with Modula-2. Its
9067 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
9068 created in Modula-2 as they can in C or C@t{++}. However, because an
9069 address can be specified by an integral constant, the construct
9070 @samp{@{@var{type}@}@var{adrexp}} is still useful.
9072 @cindex @code{#} in Modula-2
9073 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
9074 interpreted as the beginning of a comment. Use @code{<>} instead.
9076 @node Unsupported languages
9077 @section Unsupported languages
9079 @cindex unsupported languages
9080 @cindex minimal language
9081 In addition to the other fully-supported programming languages,
9082 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
9083 It does not represent a real programming language, but provides a set
9084 of capabilities close to what the C or assembly languages provide.
9085 This should allow most simple operations to be performed while debugging
9086 an application that uses a language currently not supported by @value{GDBN}.
9088 If the language is set to @code{auto}, @value{GDBN} will automatically
9089 select this language if the current frame corresponds to an unsupported
9093 @chapter Examining the Symbol Table
9095 The commands described in this chapter allow you to inquire about the
9096 symbols (names of variables, functions and types) defined in your
9097 program. This information is inherent in the text of your program and
9098 does not change as your program executes. @value{GDBN} finds it in your
9099 program's symbol table, in the file indicated when you started @value{GDBN}
9100 (@pxref{File Options, ,Choosing files}), or by one of the
9101 file-management commands (@pxref{Files, ,Commands to specify files}).
9103 @cindex symbol names
9104 @cindex names of symbols
9105 @cindex quoting names
9106 Occasionally, you may need to refer to symbols that contain unusual
9107 characters, which @value{GDBN} ordinarily treats as word delimiters. The
9108 most frequent case is in referring to static variables in other
9109 source files (@pxref{Variables,,Program variables}). File names
9110 are recorded in object files as debugging symbols, but @value{GDBN} would
9111 ordinarily parse a typical file name, like @file{foo.c}, as the three words
9112 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
9113 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
9120 looks up the value of @code{x} in the scope of the file @file{foo.c}.
9123 @kindex info address
9124 @cindex address of a symbol
9125 @item info address @var{symbol}
9126 Describe where the data for @var{symbol} is stored. For a register
9127 variable, this says which register it is kept in. For a non-register
9128 local variable, this prints the stack-frame offset at which the variable
9131 Note the contrast with @samp{print &@var{symbol}}, which does not work
9132 at all for a register variable, and for a stack local variable prints
9133 the exact address of the current instantiation of the variable.
9136 @cindex symbol from address
9137 @item info symbol @var{addr}
9138 Print the name of a symbol which is stored at the address @var{addr}.
9139 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
9140 nearest symbol and an offset from it:
9143 (@value{GDBP}) info symbol 0x54320
9144 _initialize_vx + 396 in section .text
9148 This is the opposite of the @code{info address} command. You can use
9149 it to find out the name of a variable or a function given its address.
9152 @item whatis @var{expr}
9153 Print the data type of expression @var{expr}. @var{expr} is not
9154 actually evaluated, and any side-effecting operations (such as
9155 assignments or function calls) inside it do not take place.
9156 @xref{Expressions, ,Expressions}.
9159 Print the data type of @code{$}, the last value in the value history.
9162 @item ptype @var{typename}
9163 Print a description of data type @var{typename}. @var{typename} may be
9164 the name of a type, or for C code it may have the form @samp{class
9165 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
9166 @var{union-tag}} or @samp{enum @var{enum-tag}}.
9168 @item ptype @var{expr}
9170 Print a description of the type of expression @var{expr}. @code{ptype}
9171 differs from @code{whatis} by printing a detailed description, instead
9172 of just the name of the type.
9174 For example, for this variable declaration:
9177 struct complex @{double real; double imag;@} v;
9181 the two commands give this output:
9185 (@value{GDBP}) whatis v
9186 type = struct complex
9187 (@value{GDBP}) ptype v
9188 type = struct complex @{
9196 As with @code{whatis}, using @code{ptype} without an argument refers to
9197 the type of @code{$}, the last value in the value history.
9200 @item info types @var{regexp}
9202 Print a brief description of all types whose names match @var{regexp}
9203 (or all types in your program, if you supply no argument). Each
9204 complete typename is matched as though it were a complete line; thus,
9205 @samp{i type value} gives information on all types in your program whose
9206 names include the string @code{value}, but @samp{i type ^value$} gives
9207 information only on types whose complete name is @code{value}.
9209 This command differs from @code{ptype} in two ways: first, like
9210 @code{whatis}, it does not print a detailed description; second, it
9211 lists all source files where a type is defined.
9214 @cindex local variables
9215 @item info scope @var{addr}
9216 List all the variables local to a particular scope. This command
9217 accepts a location---a function name, a source line, or an address
9218 preceded by a @samp{*}, and prints all the variables local to the
9219 scope defined by that location. For example:
9222 (@value{GDBP}) @b{info scope command_line_handler}
9223 Scope for command_line_handler:
9224 Symbol rl is an argument at stack/frame offset 8, length 4.
9225 Symbol linebuffer is in static storage at address 0x150a18, length 4.
9226 Symbol linelength is in static storage at address 0x150a1c, length 4.
9227 Symbol p is a local variable in register $esi, length 4.
9228 Symbol p1 is a local variable in register $ebx, length 4.
9229 Symbol nline is a local variable in register $edx, length 4.
9230 Symbol repeat is a local variable at frame offset -8, length 4.
9234 This command is especially useful for determining what data to collect
9235 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
9240 Show information about the current source file---that is, the source file for
9241 the function containing the current point of execution:
9244 the name of the source file, and the directory containing it,
9246 the directory it was compiled in,
9248 its length, in lines,
9250 which programming language it is written in,
9252 whether the executable includes debugging information for that file, and
9253 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
9255 whether the debugging information includes information about
9256 preprocessor macros.
9260 @kindex info sources
9262 Print the names of all source files in your program for which there is
9263 debugging information, organized into two lists: files whose symbols
9264 have already been read, and files whose symbols will be read when needed.
9266 @kindex info functions
9267 @item info functions
9268 Print the names and data types of all defined functions.
9270 @item info functions @var{regexp}
9271 Print the names and data types of all defined functions
9272 whose names contain a match for regular expression @var{regexp}.
9273 Thus, @samp{info fun step} finds all functions whose names
9274 include @code{step}; @samp{info fun ^step} finds those whose names
9275 start with @code{step}. If a function name contains characters
9276 that conflict with the regular expression language (eg.
9277 @samp{operator*()}), they may be quoted with a backslash.
9279 @kindex info variables
9280 @item info variables
9281 Print the names and data types of all variables that are declared
9282 outside of functions (i.e.@: excluding local variables).
9284 @item info variables @var{regexp}
9285 Print the names and data types of all variables (except for local
9286 variables) whose names contain a match for regular expression
9289 @kindex info classes
9291 @itemx info classes @var{regexp}
9292 Display all Objective-C classes in your program, or
9293 (with the @var{regexp} argument) all those matching a particular regular
9296 @kindex info selectors
9297 @item info selectors
9298 @itemx info selectors @var{regexp}
9299 Display all Objective-C selectors in your program, or
9300 (with the @var{regexp} argument) all those matching a particular regular
9304 This was never implemented.
9305 @kindex info methods
9307 @itemx info methods @var{regexp}
9308 The @code{info methods} command permits the user to examine all defined
9309 methods within C@t{++} program, or (with the @var{regexp} argument) a
9310 specific set of methods found in the various C@t{++} classes. Many
9311 C@t{++} classes provide a large number of methods. Thus, the output
9312 from the @code{ptype} command can be overwhelming and hard to use. The
9313 @code{info-methods} command filters the methods, printing only those
9314 which match the regular-expression @var{regexp}.
9317 @cindex reloading symbols
9318 Some systems allow individual object files that make up your program to
9319 be replaced without stopping and restarting your program. For example,
9320 in VxWorks you can simply recompile a defective object file and keep on
9321 running. If you are running on one of these systems, you can allow
9322 @value{GDBN} to reload the symbols for automatically relinked modules:
9325 @kindex set symbol-reloading
9326 @item set symbol-reloading on
9327 Replace symbol definitions for the corresponding source file when an
9328 object file with a particular name is seen again.
9330 @item set symbol-reloading off
9331 Do not replace symbol definitions when encountering object files of the
9332 same name more than once. This is the default state; if you are not
9333 running on a system that permits automatic relinking of modules, you
9334 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
9335 may discard symbols when linking large programs, that may contain
9336 several modules (from different directories or libraries) with the same
9339 @kindex show symbol-reloading
9340 @item show symbol-reloading
9341 Show the current @code{on} or @code{off} setting.
9344 @kindex set opaque-type-resolution
9345 @item set opaque-type-resolution on
9346 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
9347 declared as a pointer to a @code{struct}, @code{class}, or
9348 @code{union}---for example, @code{struct MyType *}---that is used in one
9349 source file although the full declaration of @code{struct MyType} is in
9350 another source file. The default is on.
9352 A change in the setting of this subcommand will not take effect until
9353 the next time symbols for a file are loaded.
9355 @item set opaque-type-resolution off
9356 Tell @value{GDBN} not to resolve opaque types. In this case, the type
9357 is printed as follows:
9359 @{<no data fields>@}
9362 @kindex show opaque-type-resolution
9363 @item show opaque-type-resolution
9364 Show whether opaque types are resolved or not.
9366 @kindex maint print symbols
9368 @kindex maint print psymbols
9369 @cindex partial symbol dump
9370 @item maint print symbols @var{filename}
9371 @itemx maint print psymbols @var{filename}
9372 @itemx maint print msymbols @var{filename}
9373 Write a dump of debugging symbol data into the file @var{filename}.
9374 These commands are used to debug the @value{GDBN} symbol-reading code. Only
9375 symbols with debugging data are included. If you use @samp{maint print
9376 symbols}, @value{GDBN} includes all the symbols for which it has already
9377 collected full details: that is, @var{filename} reflects symbols for
9378 only those files whose symbols @value{GDBN} has read. You can use the
9379 command @code{info sources} to find out which files these are. If you
9380 use @samp{maint print psymbols} instead, the dump shows information about
9381 symbols that @value{GDBN} only knows partially---that is, symbols defined in
9382 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
9383 @samp{maint print msymbols} dumps just the minimal symbol information
9384 required for each object file from which @value{GDBN} has read some symbols.
9385 @xref{Files, ,Commands to specify files}, for a discussion of how
9386 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
9388 @kindex maint info symtabs
9389 @kindex maint info psymtabs
9390 @cindex listing @value{GDBN}'s internal symbol tables
9391 @cindex symbol tables, listing @value{GDBN}'s internal
9392 @cindex full symbol tables, listing @value{GDBN}'s internal
9393 @cindex partial symbol tables, listing @value{GDBN}'s internal
9394 @item maint info symtabs @r{[} @var{regexp} @r{]}
9395 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
9397 List the @code{struct symtab} or @code{struct partial_symtab}
9398 structures whose names match @var{regexp}. If @var{regexp} is not
9399 given, list them all. The output includes expressions which you can
9400 copy into a @value{GDBN} debugging this one to examine a particular
9401 structure in more detail. For example:
9404 (@value{GDBP}) maint info psymtabs dwarf2read
9405 @{ objfile /home/gnu/build/gdb/gdb
9406 ((struct objfile *) 0x82e69d0)
9407 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
9408 ((struct partial_symtab *) 0x8474b10)
9411 text addresses 0x814d3c8 -- 0x8158074
9412 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
9413 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
9417 (@value{GDBP}) maint info symtabs
9421 We see that there is one partial symbol table whose filename contains
9422 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
9423 and we see that @value{GDBN} has not read in any symtabs yet at all.
9424 If we set a breakpoint on a function, that will cause @value{GDBN} to
9425 read the symtab for the compilation unit containing that function:
9428 (@value{GDBP}) break dwarf2_psymtab_to_symtab
9429 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
9431 (@value{GDBP}) maint info symtabs
9432 @{ objfile /home/gnu/build/gdb/gdb
9433 ((struct objfile *) 0x82e69d0)
9434 @{ symtab /home/gnu/src/gdb/dwarf2read.c
9435 ((struct symtab *) 0x86c1f38)
9438 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
9448 @chapter Altering Execution
9450 Once you think you have found an error in your program, you might want to
9451 find out for certain whether correcting the apparent error would lead to
9452 correct results in the rest of the run. You can find the answer by
9453 experiment, using the @value{GDBN} features for altering execution of the
9456 For example, you can store new values into variables or memory
9457 locations, give your program a signal, restart it at a different
9458 address, or even return prematurely from a function.
9461 * Assignment:: Assignment to variables
9462 * Jumping:: Continuing at a different address
9463 * Signaling:: Giving your program a signal
9464 * Returning:: Returning from a function
9465 * Calling:: Calling your program's functions
9466 * Patching:: Patching your program
9470 @section Assignment to variables
9473 @cindex setting variables
9474 To alter the value of a variable, evaluate an assignment expression.
9475 @xref{Expressions, ,Expressions}. For example,
9482 stores the value 4 into the variable @code{x}, and then prints the
9483 value of the assignment expression (which is 4).
9484 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
9485 information on operators in supported languages.
9487 @kindex set variable
9488 @cindex variables, setting
9489 If you are not interested in seeing the value of the assignment, use the
9490 @code{set} command instead of the @code{print} command. @code{set} is
9491 really the same as @code{print} except that the expression's value is
9492 not printed and is not put in the value history (@pxref{Value History,
9493 ,Value history}). The expression is evaluated only for its effects.
9495 If the beginning of the argument string of the @code{set} command
9496 appears identical to a @code{set} subcommand, use the @code{set
9497 variable} command instead of just @code{set}. This command is identical
9498 to @code{set} except for its lack of subcommands. For example, if your
9499 program has a variable @code{width}, you get an error if you try to set
9500 a new value with just @samp{set width=13}, because @value{GDBN} has the
9501 command @code{set width}:
9504 (@value{GDBP}) whatis width
9506 (@value{GDBP}) p width
9508 (@value{GDBP}) set width=47
9509 Invalid syntax in expression.
9513 The invalid expression, of course, is @samp{=47}. In
9514 order to actually set the program's variable @code{width}, use
9517 (@value{GDBP}) set var width=47
9520 Because the @code{set} command has many subcommands that can conflict
9521 with the names of program variables, it is a good idea to use the
9522 @code{set variable} command instead of just @code{set}. For example, if
9523 your program has a variable @code{g}, you run into problems if you try
9524 to set a new value with just @samp{set g=4}, because @value{GDBN} has
9525 the command @code{set gnutarget}, abbreviated @code{set g}:
9529 (@value{GDBP}) whatis g
9533 (@value{GDBP}) set g=4
9537 The program being debugged has been started already.
9538 Start it from the beginning? (y or n) y
9539 Starting program: /home/smith/cc_progs/a.out
9540 "/home/smith/cc_progs/a.out": can't open to read symbols:
9542 (@value{GDBP}) show g
9543 The current BFD target is "=4".
9548 The program variable @code{g} did not change, and you silently set the
9549 @code{gnutarget} to an invalid value. In order to set the variable
9553 (@value{GDBP}) set var g=4
9556 @value{GDBN} allows more implicit conversions in assignments than C; you can
9557 freely store an integer value into a pointer variable or vice versa,
9558 and you can convert any structure to any other structure that is the
9559 same length or shorter.
9560 @comment FIXME: how do structs align/pad in these conversions?
9561 @comment /doc@cygnus.com 18dec1990
9563 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
9564 construct to generate a value of specified type at a specified address
9565 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
9566 to memory location @code{0x83040} as an integer (which implies a certain size
9567 and representation in memory), and
9570 set @{int@}0x83040 = 4
9574 stores the value 4 into that memory location.
9577 @section Continuing at a different address
9579 Ordinarily, when you continue your program, you do so at the place where
9580 it stopped, with the @code{continue} command. You can instead continue at
9581 an address of your own choosing, with the following commands:
9585 @item jump @var{linespec}
9586 Resume execution at line @var{linespec}. Execution stops again
9587 immediately if there is a breakpoint there. @xref{List, ,Printing
9588 source lines}, for a description of the different forms of
9589 @var{linespec}. It is common practice to use the @code{tbreak} command
9590 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
9593 The @code{jump} command does not change the current stack frame, or
9594 the stack pointer, or the contents of any memory location or any
9595 register other than the program counter. If line @var{linespec} is in
9596 a different function from the one currently executing, the results may
9597 be bizarre if the two functions expect different patterns of arguments or
9598 of local variables. For this reason, the @code{jump} command requests
9599 confirmation if the specified line is not in the function currently
9600 executing. However, even bizarre results are predictable if you are
9601 well acquainted with the machine-language code of your program.
9603 @item jump *@var{address}
9604 Resume execution at the instruction at address @var{address}.
9607 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
9608 On many systems, you can get much the same effect as the @code{jump}
9609 command by storing a new value into the register @code{$pc}. The
9610 difference is that this does not start your program running; it only
9611 changes the address of where it @emph{will} run when you continue. For
9619 makes the next @code{continue} command or stepping command execute at
9620 address @code{0x485}, rather than at the address where your program stopped.
9621 @xref{Continuing and Stepping, ,Continuing and stepping}.
9623 The most common occasion to use the @code{jump} command is to back
9624 up---perhaps with more breakpoints set---over a portion of a program
9625 that has already executed, in order to examine its execution in more
9630 @section Giving your program a signal
9634 @item signal @var{signal}
9635 Resume execution where your program stopped, but immediately give it the
9636 signal @var{signal}. @var{signal} can be the name or the number of a
9637 signal. For example, on many systems @code{signal 2} and @code{signal
9638 SIGINT} are both ways of sending an interrupt signal.
9640 Alternatively, if @var{signal} is zero, continue execution without
9641 giving a signal. This is useful when your program stopped on account of
9642 a signal and would ordinary see the signal when resumed with the
9643 @code{continue} command; @samp{signal 0} causes it to resume without a
9646 @code{signal} does not repeat when you press @key{RET} a second time
9647 after executing the command.
9651 Invoking the @code{signal} command is not the same as invoking the
9652 @code{kill} utility from the shell. Sending a signal with @code{kill}
9653 causes @value{GDBN} to decide what to do with the signal depending on
9654 the signal handling tables (@pxref{Signals}). The @code{signal} command
9655 passes the signal directly to your program.
9659 @section Returning from a function
9662 @cindex returning from a function
9665 @itemx return @var{expression}
9666 You can cancel execution of a function call with the @code{return}
9667 command. If you give an
9668 @var{expression} argument, its value is used as the function's return
9672 When you use @code{return}, @value{GDBN} discards the selected stack frame
9673 (and all frames within it). You can think of this as making the
9674 discarded frame return prematurely. If you wish to specify a value to
9675 be returned, give that value as the argument to @code{return}.
9677 This pops the selected stack frame (@pxref{Selection, ,Selecting a
9678 frame}), and any other frames inside of it, leaving its caller as the
9679 innermost remaining frame. That frame becomes selected. The
9680 specified value is stored in the registers used for returning values
9683 The @code{return} command does not resume execution; it leaves the
9684 program stopped in the state that would exist if the function had just
9685 returned. In contrast, the @code{finish} command (@pxref{Continuing
9686 and Stepping, ,Continuing and stepping}) resumes execution until the
9687 selected stack frame returns naturally.
9690 @section Calling program functions
9692 @cindex calling functions
9695 @item call @var{expr}
9696 Evaluate the expression @var{expr} without displaying @code{void}
9700 You can use this variant of the @code{print} command if you want to
9701 execute a function from your program, but without cluttering the output
9702 with @code{void} returned values. If the result is not void, it
9703 is printed and saved in the value history.
9706 @section Patching programs
9708 @cindex patching binaries
9709 @cindex writing into executables
9710 @cindex writing into corefiles
9712 By default, @value{GDBN} opens the file containing your program's
9713 executable code (or the corefile) read-only. This prevents accidental
9714 alterations to machine code; but it also prevents you from intentionally
9715 patching your program's binary.
9717 If you'd like to be able to patch the binary, you can specify that
9718 explicitly with the @code{set write} command. For example, you might
9719 want to turn on internal debugging flags, or even to make emergency
9725 @itemx set write off
9726 If you specify @samp{set write on}, @value{GDBN} opens executable and
9727 core files for both reading and writing; if you specify @samp{set write
9728 off} (the default), @value{GDBN} opens them read-only.
9730 If you have already loaded a file, you must load it again (using the
9731 @code{exec-file} or @code{core-file} command) after changing @code{set
9732 write}, for your new setting to take effect.
9736 Display whether executable files and core files are opened for writing
9741 @chapter @value{GDBN} Files
9743 @value{GDBN} needs to know the file name of the program to be debugged,
9744 both in order to read its symbol table and in order to start your
9745 program. To debug a core dump of a previous run, you must also tell
9746 @value{GDBN} the name of the core dump file.
9749 * Files:: Commands to specify files
9750 * Separate Debug Files:: Debugging information in separate files
9751 * Symbol Errors:: Errors reading symbol files
9755 @section Commands to specify files
9757 @cindex symbol table
9758 @cindex core dump file
9760 You may want to specify executable and core dump file names. The usual
9761 way to do this is at start-up time, using the arguments to
9762 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
9763 Out of @value{GDBN}}).
9765 Occasionally it is necessary to change to a different file during a
9766 @value{GDBN} session. Or you may run @value{GDBN} and forget to specify
9767 a file you want to use. In these situations the @value{GDBN} commands
9768 to specify new files are useful.
9771 @cindex executable file
9773 @item file @var{filename}
9774 Use @var{filename} as the program to be debugged. It is read for its
9775 symbols and for the contents of pure memory. It is also the program
9776 executed when you use the @code{run} command. If you do not specify a
9777 directory and the file is not found in the @value{GDBN} working directory,
9778 @value{GDBN} uses the environment variable @code{PATH} as a list of
9779 directories to search, just as the shell does when looking for a program
9780 to run. You can change the value of this variable, for both @value{GDBN}
9781 and your program, using the @code{path} command.
9783 On systems with memory-mapped files, an auxiliary file named
9784 @file{@var{filename}.syms} may hold symbol table information for
9785 @var{filename}. If so, @value{GDBN} maps in the symbol table from
9786 @file{@var{filename}.syms}, starting up more quickly. See the
9787 descriptions of the file options @samp{-mapped} and @samp{-readnow}
9788 (available on the command line, and with the commands @code{file},
9789 @code{symbol-file}, or @code{add-symbol-file}, described below),
9790 for more information.
9793 @code{file} with no argument makes @value{GDBN} discard any information it
9794 has on both executable file and the symbol table.
9797 @item exec-file @r{[} @var{filename} @r{]}
9798 Specify that the program to be run (but not the symbol table) is found
9799 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
9800 if necessary to locate your program. Omitting @var{filename} means to
9801 discard information on the executable file.
9804 @item symbol-file @r{[} @var{filename} @r{]}
9805 Read symbol table information from file @var{filename}. @code{PATH} is
9806 searched when necessary. Use the @code{file} command to get both symbol
9807 table and program to run from the same file.
9809 @code{symbol-file} with no argument clears out @value{GDBN} information on your
9810 program's symbol table.
9812 The @code{symbol-file} command causes @value{GDBN} to forget the contents
9813 of its convenience variables, the value history, and all breakpoints and
9814 auto-display expressions. This is because they may contain pointers to
9815 the internal data recording symbols and data types, which are part of
9816 the old symbol table data being discarded inside @value{GDBN}.
9818 @code{symbol-file} does not repeat if you press @key{RET} again after
9821 When @value{GDBN} is configured for a particular environment, it
9822 understands debugging information in whatever format is the standard
9823 generated for that environment; you may use either a @sc{gnu} compiler, or
9824 other compilers that adhere to the local conventions.
9825 Best results are usually obtained from @sc{gnu} compilers; for example,
9826 using @code{@value{GCC}} you can generate debugging information for
9829 For most kinds of object files, with the exception of old SVR3 systems
9830 using COFF, the @code{symbol-file} command does not normally read the
9831 symbol table in full right away. Instead, it scans the symbol table
9832 quickly to find which source files and which symbols are present. The
9833 details are read later, one source file at a time, as they are needed.
9835 The purpose of this two-stage reading strategy is to make @value{GDBN}
9836 start up faster. For the most part, it is invisible except for
9837 occasional pauses while the symbol table details for a particular source
9838 file are being read. (The @code{set verbose} command can turn these
9839 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
9840 warnings and messages}.)
9842 We have not implemented the two-stage strategy for COFF yet. When the
9843 symbol table is stored in COFF format, @code{symbol-file} reads the
9844 symbol table data in full right away. Note that ``stabs-in-COFF''
9845 still does the two-stage strategy, since the debug info is actually
9849 @cindex reading symbols immediately
9850 @cindex symbols, reading immediately
9852 @cindex memory-mapped symbol file
9853 @cindex saving symbol table
9854 @item symbol-file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
9855 @itemx file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
9856 You can override the @value{GDBN} two-stage strategy for reading symbol
9857 tables by using the @samp{-readnow} option with any of the commands that
9858 load symbol table information, if you want to be sure @value{GDBN} has the
9859 entire symbol table available.
9861 If memory-mapped files are available on your system through the
9862 @code{mmap} system call, you can use another option, @samp{-mapped}, to
9863 cause @value{GDBN} to write the symbols for your program into a reusable
9864 file. Future @value{GDBN} debugging sessions map in symbol information
9865 from this auxiliary symbol file (if the program has not changed), rather
9866 than spending time reading the symbol table from the executable
9867 program. Using the @samp{-mapped} option has the same effect as
9868 starting @value{GDBN} with the @samp{-mapped} command-line option.
9870 You can use both options together, to make sure the auxiliary symbol
9871 file has all the symbol information for your program.
9873 The auxiliary symbol file for a program called @var{myprog} is called
9874 @samp{@var{myprog}.syms}. Once this file exists (so long as it is newer
9875 than the corresponding executable), @value{GDBN} always attempts to use
9876 it when you debug @var{myprog}; no special options or commands are
9879 The @file{.syms} file is specific to the host machine where you run
9880 @value{GDBN}. It holds an exact image of the internal @value{GDBN}
9881 symbol table. It cannot be shared across multiple host platforms.
9883 @c FIXME: for now no mention of directories, since this seems to be in
9884 @c flux. 13mar1992 status is that in theory GDB would look either in
9885 @c current dir or in same dir as myprog; but issues like competing
9886 @c GDB's, or clutter in system dirs, mean that in practice right now
9887 @c only current dir is used. FFish says maybe a special GDB hierarchy
9888 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
9893 @item core-file @r{[} @var{filename} @r{]}
9894 Specify the whereabouts of a core dump file to be used as the ``contents
9895 of memory''. Traditionally, core files contain only some parts of the
9896 address space of the process that generated them; @value{GDBN} can access the
9897 executable file itself for other parts.
9899 @code{core-file} with no argument specifies that no core file is
9902 Note that the core file is ignored when your program is actually running
9903 under @value{GDBN}. So, if you have been running your program and you
9904 wish to debug a core file instead, you must kill the subprocess in which
9905 the program is running. To do this, use the @code{kill} command
9906 (@pxref{Kill Process, ,Killing the child process}).
9908 @kindex add-symbol-file
9909 @cindex dynamic linking
9910 @item add-symbol-file @var{filename} @var{address}
9911 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
9912 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
9913 The @code{add-symbol-file} command reads additional symbol table
9914 information from the file @var{filename}. You would use this command
9915 when @var{filename} has been dynamically loaded (by some other means)
9916 into the program that is running. @var{address} should be the memory
9917 address at which the file has been loaded; @value{GDBN} cannot figure
9918 this out for itself. You can additionally specify an arbitrary number
9919 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
9920 section name and base address for that section. You can specify any
9921 @var{address} as an expression.
9923 The symbol table of the file @var{filename} is added to the symbol table
9924 originally read with the @code{symbol-file} command. You can use the
9925 @code{add-symbol-file} command any number of times; the new symbol data
9926 thus read keeps adding to the old. To discard all old symbol data
9927 instead, use the @code{symbol-file} command without any arguments.
9929 @cindex relocatable object files, reading symbols from
9930 @cindex object files, relocatable, reading symbols from
9931 @cindex reading symbols from relocatable object files
9932 @cindex symbols, reading from relocatable object files
9933 @cindex @file{.o} files, reading symbols from
9934 Although @var{filename} is typically a shared library file, an
9935 executable file, or some other object file which has been fully
9936 relocated for loading into a process, you can also load symbolic
9937 information from relocatable @file{.o} files, as long as:
9941 the file's symbolic information refers only to linker symbols defined in
9942 that file, not to symbols defined by other object files,
9944 every section the file's symbolic information refers to has actually
9945 been loaded into the inferior, as it appears in the file, and
9947 you can determine the address at which every section was loaded, and
9948 provide these to the @code{add-symbol-file} command.
9952 Some embedded operating systems, like Sun Chorus and VxWorks, can load
9953 relocatable files into an already running program; such systems
9954 typically make the requirements above easy to meet. However, it's
9955 important to recognize that many native systems use complex link
9956 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
9957 assembly, for example) that make the requirements difficult to meet. In
9958 general, one cannot assume that using @code{add-symbol-file} to read a
9959 relocatable object file's symbolic information will have the same effect
9960 as linking the relocatable object file into the program in the normal
9963 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
9965 You can use the @samp{-mapped} and @samp{-readnow} options just as with
9966 the @code{symbol-file} command, to change how @value{GDBN} manages the symbol
9967 table information for @var{filename}.
9969 @kindex add-shared-symbol-file
9970 @item add-shared-symbol-file
9971 The @code{add-shared-symbol-file} command can be used only under Harris' CXUX
9972 operating system for the Motorola 88k. @value{GDBN} automatically looks for
9973 shared libraries, however if @value{GDBN} does not find yours, you can run
9974 @code{add-shared-symbol-file}. It takes no arguments.
9978 The @code{section} command changes the base address of section SECTION of
9979 the exec file to ADDR. This can be used if the exec file does not contain
9980 section addresses, (such as in the a.out format), or when the addresses
9981 specified in the file itself are wrong. Each section must be changed
9982 separately. The @code{info files} command, described below, lists all
9983 the sections and their addresses.
9989 @code{info files} and @code{info target} are synonymous; both print the
9990 current target (@pxref{Targets, ,Specifying a Debugging Target}),
9991 including the names of the executable and core dump files currently in
9992 use by @value{GDBN}, and the files from which symbols were loaded. The
9993 command @code{help target} lists all possible targets rather than
9996 @kindex maint info sections
9997 @item maint info sections
9998 Another command that can give you extra information about program sections
9999 is @code{maint info sections}. In addition to the section information
10000 displayed by @code{info files}, this command displays the flags and file
10001 offset of each section in the executable and core dump files. In addition,
10002 @code{maint info sections} provides the following command options (which
10003 may be arbitrarily combined):
10007 Display sections for all loaded object files, including shared libraries.
10008 @item @var{sections}
10009 Display info only for named @var{sections}.
10010 @item @var{section-flags}
10011 Display info only for sections for which @var{section-flags} are true.
10012 The section flags that @value{GDBN} currently knows about are:
10015 Section will have space allocated in the process when loaded.
10016 Set for all sections except those containing debug information.
10018 Section will be loaded from the file into the child process memory.
10019 Set for pre-initialized code and data, clear for @code{.bss} sections.
10021 Section needs to be relocated before loading.
10023 Section cannot be modified by the child process.
10025 Section contains executable code only.
10027 Section contains data only (no executable code).
10029 Section will reside in ROM.
10031 Section contains data for constructor/destructor lists.
10033 Section is not empty.
10035 An instruction to the linker to not output the section.
10036 @item COFF_SHARED_LIBRARY
10037 A notification to the linker that the section contains
10038 COFF shared library information.
10040 Section contains common symbols.
10043 @kindex set trust-readonly-sections
10044 @item set trust-readonly-sections on
10045 Tell @value{GDBN} that readonly sections in your object file
10046 really are read-only (i.e.@: that their contents will not change).
10047 In that case, @value{GDBN} can fetch values from these sections
10048 out of the object file, rather than from the target program.
10049 For some targets (notably embedded ones), this can be a significant
10050 enhancement to debugging performance.
10052 The default is off.
10054 @item set trust-readonly-sections off
10055 Tell @value{GDBN} not to trust readonly sections. This means that
10056 the contents of the section might change while the program is running,
10057 and must therefore be fetched from the target when needed.
10060 All file-specifying commands allow both absolute and relative file names
10061 as arguments. @value{GDBN} always converts the file name to an absolute file
10062 name and remembers it that way.
10064 @cindex shared libraries
10065 @value{GDBN} supports HP-UX, SunOS, SVr4, Irix 5, and IBM RS/6000 shared
10068 @value{GDBN} automatically loads symbol definitions from shared libraries
10069 when you use the @code{run} command, or when you examine a core file.
10070 (Before you issue the @code{run} command, @value{GDBN} does not understand
10071 references to a function in a shared library, however---unless you are
10072 debugging a core file).
10074 On HP-UX, if the program loads a library explicitly, @value{GDBN}
10075 automatically loads the symbols at the time of the @code{shl_load} call.
10077 @c FIXME: some @value{GDBN} release may permit some refs to undef
10078 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
10079 @c FIXME...lib; check this from time to time when updating manual
10081 There are times, however, when you may wish to not automatically load
10082 symbol definitions from shared libraries, such as when they are
10083 particularly large or there are many of them.
10085 To control the automatic loading of shared library symbols, use the
10089 @kindex set auto-solib-add
10090 @item set auto-solib-add @var{mode}
10091 If @var{mode} is @code{on}, symbols from all shared object libraries
10092 will be loaded automatically when the inferior begins execution, you
10093 attach to an independently started inferior, or when the dynamic linker
10094 informs @value{GDBN} that a new library has been loaded. If @var{mode}
10095 is @code{off}, symbols must be loaded manually, using the
10096 @code{sharedlibrary} command. The default value is @code{on}.
10098 @kindex show auto-solib-add
10099 @item show auto-solib-add
10100 Display the current autoloading mode.
10103 To explicitly load shared library symbols, use the @code{sharedlibrary}
10107 @kindex info sharedlibrary
10110 @itemx info sharedlibrary
10111 Print the names of the shared libraries which are currently loaded.
10113 @kindex sharedlibrary
10115 @item sharedlibrary @var{regex}
10116 @itemx share @var{regex}
10117 Load shared object library symbols for files matching a
10118 Unix regular expression.
10119 As with files loaded automatically, it only loads shared libraries
10120 required by your program for a core file or after typing @code{run}. If
10121 @var{regex} is omitted all shared libraries required by your program are
10125 On some systems, such as HP-UX systems, @value{GDBN} supports
10126 autoloading shared library symbols until a limiting threshold size is
10127 reached. This provides the benefit of allowing autoloading to remain on
10128 by default, but avoids autoloading excessively large shared libraries,
10129 up to a threshold that is initially set, but which you can modify if you
10132 Beyond that threshold, symbols from shared libraries must be explicitly
10133 loaded. To load these symbols, use the command @code{sharedlibrary
10134 @var{filename}}. The base address of the shared library is determined
10135 automatically by @value{GDBN} and need not be specified.
10137 To display or set the threshold, use the commands:
10140 @kindex set auto-solib-limit
10141 @item set auto-solib-limit @var{threshold}
10142 Set the autoloading size threshold, in an integral number of megabytes.
10143 If @var{threshold} is nonzero and shared library autoloading is enabled,
10144 symbols from all shared object libraries will be loaded until the total
10145 size of the loaded shared library symbols exceeds this threshold.
10146 Otherwise, symbols must be loaded manually, using the
10147 @code{sharedlibrary} command. The default threshold is 100 (i.e.@: 100
10150 @kindex show auto-solib-limit
10151 @item show auto-solib-limit
10152 Display the current autoloading size threshold, in megabytes.
10155 Shared libraries are also supported in many cross or remote debugging
10156 configurations. A copy of the target's libraries need to be present on the
10157 host system; they need to be the same as the target libraries, although the
10158 copies on the target can be stripped as long as the copies on the host are
10161 You need to tell @value{GDBN} where the target libraries are, so that it can
10162 load the correct copies---otherwise, it may try to load the host's libraries.
10163 @value{GDBN} has two variables to specify the search directories for target
10167 @kindex set solib-absolute-prefix
10168 @item set solib-absolute-prefix @var{path}
10169 If this variable is set, @var{path} will be used as a prefix for any
10170 absolute shared library paths; many runtime loaders store the absolute
10171 paths to the shared library in the target program's memory. If you use
10172 @samp{solib-absolute-prefix} to find shared libraries, they need to be laid
10173 out in the same way that they are on the target, with e.g.@: a
10174 @file{/usr/lib} hierarchy under @var{path}.
10176 You can set the default value of @samp{solib-absolute-prefix} by using the
10177 configure-time @samp{--with-sysroot} option.
10179 @kindex show solib-absolute-prefix
10180 @item show solib-absolute-prefix
10181 Display the current shared library prefix.
10183 @kindex set solib-search-path
10184 @item set solib-search-path @var{path}
10185 If this variable is set, @var{path} is a colon-separated list of directories
10186 to search for shared libraries. @samp{solib-search-path} is used after
10187 @samp{solib-absolute-prefix} fails to locate the library, or if the path to
10188 the library is relative instead of absolute. If you want to use
10189 @samp{solib-search-path} instead of @samp{solib-absolute-prefix}, be sure to
10190 set @samp{solib-absolute-prefix} to a nonexistant directory to prevent
10191 @value{GDBN} from finding your host's libraries.
10193 @kindex show solib-search-path
10194 @item show solib-search-path
10195 Display the current shared library search path.
10199 @node Separate Debug Files
10200 @section Debugging Information in Separate Files
10201 @cindex separate debugging information files
10202 @cindex debugging information in separate files
10203 @cindex @file{.debug} subdirectories
10204 @cindex debugging information directory, global
10205 @cindex global debugging information directory
10207 @value{GDBN} allows you to put a program's debugging information in a
10208 file separate from the executable itself, in a way that allows
10209 @value{GDBN} to find and load the debugging information automatically.
10210 Since debugging information can be very large --- sometimes larger
10211 than the executable code itself --- some systems distribute debugging
10212 information for their executables in separate files, which users can
10213 install only when they need to debug a problem.
10215 If an executable's debugging information has been extracted to a
10216 separate file, the executable should contain a @dfn{debug link} giving
10217 the name of the debugging information file (with no directory
10218 components), and a checksum of its contents. (The exact form of a
10219 debug link is described below.) If the full name of the directory
10220 containing the executable is @var{execdir}, and the executable has a
10221 debug link that specifies the name @var{debugfile}, then @value{GDBN}
10222 will automatically search for the debugging information file in three
10227 the directory containing the executable file (that is, it will look
10228 for a file named @file{@var{execdir}/@var{debugfile}},
10230 a subdirectory of that directory named @file{.debug} (that is, the
10231 file @file{@var{execdir}/.debug/@var{debugfile}}, and
10233 a subdirectory of the global debug file directory that includes the
10234 executable's full path, and the name from the link (that is, the file
10235 @file{@var{globaldebugdir}/@var{execdir}/@var{debugfile}}, where
10236 @var{globaldebugdir} is the global debug file directory, and
10237 @var{execdir} has been turned into a relative path).
10240 @value{GDBN} checks under each of these names for a debugging
10241 information file whose checksum matches that given in the link, and
10242 reads the debugging information from the first one it finds.
10244 So, for example, if you ask @value{GDBN} to debug @file{/usr/bin/ls},
10245 which has a link containing the name @file{ls.debug}, and the global
10246 debug directory is @file{/usr/lib/debug}, then @value{GDBN} will look
10247 for debug information in @file{/usr/bin/ls.debug},
10248 @file{/usr/bin/.debug/ls.debug}, and
10249 @file{/usr/lib/debug/usr/bin/ls.debug}.
10251 You can set the global debugging info directory's name, and view the
10252 name @value{GDBN} is currently using.
10256 @kindex set debug-file-directory
10257 @item set debug-file-directory @var{directory}
10258 Set the directory which @value{GDBN} searches for separate debugging
10259 information files to @var{directory}.
10261 @kindex show debug-file-directory
10262 @item show debug-file-directory
10263 Show the directory @value{GDBN} searches for separate debugging
10268 @cindex @code{.gnu_debuglink} sections
10269 @cindex debug links
10270 A debug link is a special section of the executable file named
10271 @code{.gnu_debuglink}. The section must contain:
10275 A filename, with any leading directory components removed, followed by
10278 zero to three bytes of padding, as needed to reach the next four-byte
10279 boundary within the section, and
10281 a four-byte CRC checksum, stored in the same endianness used for the
10282 executable file itself. The checksum is computed on the debugging
10283 information file's full contents by the function given below, passing
10284 zero as the @var{crc} argument.
10287 Any executable file format can carry a debug link, as long as it can
10288 contain a section named @code{.gnu_debuglink} with the contents
10291 The debugging information file itself should be an ordinary
10292 executable, containing a full set of linker symbols, sections, and
10293 debugging information. The sections of the debugging information file
10294 should have the same names, addresses and sizes as the original file,
10295 but they need not contain any data --- much like a @code{.bss} section
10296 in an ordinary executable.
10298 As of December 2002, there is no standard GNU utility to produce
10299 separated executable / debugging information file pairs. Ulrich
10300 Drepper's @file{elfutils} package, starting with version 0.53,
10301 contains a version of the @code{strip} command such that the command
10302 @kbd{strip foo -f foo.debug} removes the debugging information from
10303 the executable file @file{foo}, places it in the file
10304 @file{foo.debug}, and leaves behind a debug link in @file{foo}.
10306 Since there are many different ways to compute CRC's (different
10307 polynomials, reversals, byte ordering, etc.), the simplest way to
10308 describe the CRC used in @code{.gnu_debuglink} sections is to give the
10309 complete code for a function that computes it:
10311 @kindex @code{gnu_debuglink_crc32}
10314 gnu_debuglink_crc32 (unsigned long crc,
10315 unsigned char *buf, size_t len)
10317 static const unsigned long crc32_table[256] =
10319 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
10320 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
10321 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
10322 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
10323 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
10324 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
10325 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
10326 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
10327 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
10328 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
10329 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
10330 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
10331 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
10332 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
10333 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
10334 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
10335 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
10336 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
10337 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
10338 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
10339 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
10340 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
10341 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
10342 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
10343 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
10344 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
10345 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
10346 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
10347 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
10348 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
10349 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
10350 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
10351 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
10352 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
10353 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
10354 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
10355 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
10356 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
10357 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
10358 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
10359 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
10360 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
10361 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
10362 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
10363 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
10364 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
10365 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
10366 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
10367 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
10368 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
10369 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
10372 unsigned char *end;
10374 crc = ~crc & 0xffffffff;
10375 for (end = buf + len; buf < end; ++buf)
10376 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
10377 return ~crc & 0xffffffff;
10382 @node Symbol Errors
10383 @section Errors reading symbol files
10385 While reading a symbol file, @value{GDBN} occasionally encounters problems,
10386 such as symbol types it does not recognize, or known bugs in compiler
10387 output. By default, @value{GDBN} does not notify you of such problems, since
10388 they are relatively common and primarily of interest to people
10389 debugging compilers. If you are interested in seeing information
10390 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
10391 only one message about each such type of problem, no matter how many
10392 times the problem occurs; or you can ask @value{GDBN} to print more messages,
10393 to see how many times the problems occur, with the @code{set
10394 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
10397 The messages currently printed, and their meanings, include:
10400 @item inner block not inside outer block in @var{symbol}
10402 The symbol information shows where symbol scopes begin and end
10403 (such as at the start of a function or a block of statements). This
10404 error indicates that an inner scope block is not fully contained
10405 in its outer scope blocks.
10407 @value{GDBN} circumvents the problem by treating the inner block as if it had
10408 the same scope as the outer block. In the error message, @var{symbol}
10409 may be shown as ``@code{(don't know)}'' if the outer block is not a
10412 @item block at @var{address} out of order
10414 The symbol information for symbol scope blocks should occur in
10415 order of increasing addresses. This error indicates that it does not
10418 @value{GDBN} does not circumvent this problem, and has trouble
10419 locating symbols in the source file whose symbols it is reading. (You
10420 can often determine what source file is affected by specifying
10421 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
10424 @item bad block start address patched
10426 The symbol information for a symbol scope block has a start address
10427 smaller than the address of the preceding source line. This is known
10428 to occur in the SunOS 4.1.1 (and earlier) C compiler.
10430 @value{GDBN} circumvents the problem by treating the symbol scope block as
10431 starting on the previous source line.
10433 @item bad string table offset in symbol @var{n}
10436 Symbol number @var{n} contains a pointer into the string table which is
10437 larger than the size of the string table.
10439 @value{GDBN} circumvents the problem by considering the symbol to have the
10440 name @code{foo}, which may cause other problems if many symbols end up
10443 @item unknown symbol type @code{0x@var{nn}}
10445 The symbol information contains new data types that @value{GDBN} does
10446 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
10447 uncomprehended information, in hexadecimal.
10449 @value{GDBN} circumvents the error by ignoring this symbol information.
10450 This usually allows you to debug your program, though certain symbols
10451 are not accessible. If you encounter such a problem and feel like
10452 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
10453 on @code{complain}, then go up to the function @code{read_dbx_symtab}
10454 and examine @code{*bufp} to see the symbol.
10456 @item stub type has NULL name
10458 @value{GDBN} could not find the full definition for a struct or class.
10460 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
10461 The symbol information for a C@t{++} member function is missing some
10462 information that recent versions of the compiler should have output for
10465 @item info mismatch between compiler and debugger
10467 @value{GDBN} could not parse a type specification output by the compiler.
10472 @chapter Specifying a Debugging Target
10474 @cindex debugging target
10477 A @dfn{target} is the execution environment occupied by your program.
10479 Often, @value{GDBN} runs in the same host environment as your program;
10480 in that case, the debugging target is specified as a side effect when
10481 you use the @code{file} or @code{core} commands. When you need more
10482 flexibility---for example, running @value{GDBN} on a physically separate
10483 host, or controlling a standalone system over a serial port or a
10484 realtime system over a TCP/IP connection---you can use the @code{target}
10485 command to specify one of the target types configured for @value{GDBN}
10486 (@pxref{Target Commands, ,Commands for managing targets}).
10489 * Active Targets:: Active targets
10490 * Target Commands:: Commands for managing targets
10491 * Byte Order:: Choosing target byte order
10492 * Remote:: Remote debugging
10493 * KOD:: Kernel Object Display
10497 @node Active Targets
10498 @section Active targets
10500 @cindex stacking targets
10501 @cindex active targets
10502 @cindex multiple targets
10504 There are three classes of targets: processes, core files, and
10505 executable files. @value{GDBN} can work concurrently on up to three
10506 active targets, one in each class. This allows you to (for example)
10507 start a process and inspect its activity without abandoning your work on
10510 For example, if you execute @samp{gdb a.out}, then the executable file
10511 @code{a.out} is the only active target. If you designate a core file as
10512 well---presumably from a prior run that crashed and coredumped---then
10513 @value{GDBN} has two active targets and uses them in tandem, looking
10514 first in the corefile target, then in the executable file, to satisfy
10515 requests for memory addresses. (Typically, these two classes of target
10516 are complementary, since core files contain only a program's
10517 read-write memory---variables and so on---plus machine status, while
10518 executable files contain only the program text and initialized data.)
10520 When you type @code{run}, your executable file becomes an active process
10521 target as well. When a process target is active, all @value{GDBN}
10522 commands requesting memory addresses refer to that target; addresses in
10523 an active core file or executable file target are obscured while the
10524 process target is active.
10526 Use the @code{core-file} and @code{exec-file} commands to select a new
10527 core file or executable target (@pxref{Files, ,Commands to specify
10528 files}). To specify as a target a process that is already running, use
10529 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
10532 @node Target Commands
10533 @section Commands for managing targets
10536 @item target @var{type} @var{parameters}
10537 Connects the @value{GDBN} host environment to a target machine or
10538 process. A target is typically a protocol for talking to debugging
10539 facilities. You use the argument @var{type} to specify the type or
10540 protocol of the target machine.
10542 Further @var{parameters} are interpreted by the target protocol, but
10543 typically include things like device names or host names to connect
10544 with, process numbers, and baud rates.
10546 The @code{target} command does not repeat if you press @key{RET} again
10547 after executing the command.
10549 @kindex help target
10551 Displays the names of all targets available. To display targets
10552 currently selected, use either @code{info target} or @code{info files}
10553 (@pxref{Files, ,Commands to specify files}).
10555 @item help target @var{name}
10556 Describe a particular target, including any parameters necessary to
10559 @kindex set gnutarget
10560 @item set gnutarget @var{args}
10561 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
10562 knows whether it is reading an @dfn{executable},
10563 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
10564 with the @code{set gnutarget} command. Unlike most @code{target} commands,
10565 with @code{gnutarget} the @code{target} refers to a program, not a machine.
10568 @emph{Warning:} To specify a file format with @code{set gnutarget},
10569 you must know the actual BFD name.
10573 @xref{Files, , Commands to specify files}.
10575 @kindex show gnutarget
10576 @item show gnutarget
10577 Use the @code{show gnutarget} command to display what file format
10578 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
10579 @value{GDBN} will determine the file format for each file automatically,
10580 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
10583 Here are some common targets (available, or not, depending on the GDB
10587 @kindex target exec
10588 @item target exec @var{program}
10589 An executable file. @samp{target exec @var{program}} is the same as
10590 @samp{exec-file @var{program}}.
10592 @kindex target core
10593 @item target core @var{filename}
10594 A core dump file. @samp{target core @var{filename}} is the same as
10595 @samp{core-file @var{filename}}.
10597 @kindex target remote
10598 @item target remote @var{dev}
10599 Remote serial target in GDB-specific protocol. The argument @var{dev}
10600 specifies what serial device to use for the connection (e.g.
10601 @file{/dev/ttya}). @xref{Remote, ,Remote debugging}. @code{target remote}
10602 supports the @code{load} command. This is only useful if you have
10603 some other way of getting the stub to the target system, and you can put
10604 it somewhere in memory where it won't get clobbered by the download.
10608 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
10616 works; however, you cannot assume that a specific memory map, device
10617 drivers, or even basic I/O is available, although some simulators do
10618 provide these. For info about any processor-specific simulator details,
10619 see the appropriate section in @ref{Embedded Processors, ,Embedded
10624 Some configurations may include these targets as well:
10628 @kindex target nrom
10629 @item target nrom @var{dev}
10630 NetROM ROM emulator. This target only supports downloading.
10634 Different targets are available on different configurations of @value{GDBN};
10635 your configuration may have more or fewer targets.
10637 Many remote targets require you to download the executable's code
10638 once you've successfully established a connection.
10642 @kindex load @var{filename}
10643 @item load @var{filename}
10644 Depending on what remote debugging facilities are configured into
10645 @value{GDBN}, the @code{load} command may be available. Where it exists, it
10646 is meant to make @var{filename} (an executable) available for debugging
10647 on the remote system---by downloading, or dynamic linking, for example.
10648 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
10649 the @code{add-symbol-file} command.
10651 If your @value{GDBN} does not have a @code{load} command, attempting to
10652 execute it gets the error message ``@code{You can't do that when your
10653 target is @dots{}}''
10655 The file is loaded at whatever address is specified in the executable.
10656 For some object file formats, you can specify the load address when you
10657 link the program; for other formats, like a.out, the object file format
10658 specifies a fixed address.
10659 @c FIXME! This would be a good place for an xref to the GNU linker doc.
10661 @code{load} does not repeat if you press @key{RET} again after using it.
10665 @section Choosing target byte order
10667 @cindex choosing target byte order
10668 @cindex target byte order
10670 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
10671 offer the ability to run either big-endian or little-endian byte
10672 orders. Usually the executable or symbol will include a bit to
10673 designate the endian-ness, and you will not need to worry about
10674 which to use. However, you may still find it useful to adjust
10675 @value{GDBN}'s idea of processor endian-ness manually.
10678 @kindex set endian big
10679 @item set endian big
10680 Instruct @value{GDBN} to assume the target is big-endian.
10682 @kindex set endian little
10683 @item set endian little
10684 Instruct @value{GDBN} to assume the target is little-endian.
10686 @kindex set endian auto
10687 @item set endian auto
10688 Instruct @value{GDBN} to use the byte order associated with the
10692 Display @value{GDBN}'s current idea of the target byte order.
10696 Note that these commands merely adjust interpretation of symbolic
10697 data on the host, and that they have absolutely no effect on the
10701 @section Remote debugging
10702 @cindex remote debugging
10704 If you are trying to debug a program running on a machine that cannot run
10705 @value{GDBN} in the usual way, it is often useful to use remote debugging.
10706 For example, you might use remote debugging on an operating system kernel,
10707 or on a small system which does not have a general purpose operating system
10708 powerful enough to run a full-featured debugger.
10710 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
10711 to make this work with particular debugging targets. In addition,
10712 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
10713 but not specific to any particular target system) which you can use if you
10714 write the remote stubs---the code that runs on the remote system to
10715 communicate with @value{GDBN}.
10717 Other remote targets may be available in your
10718 configuration of @value{GDBN}; use @code{help target} to list them.
10721 @section Kernel Object Display
10722 @cindex kernel object display
10725 Some targets support kernel object display. Using this facility,
10726 @value{GDBN} communicates specially with the underlying operating system
10727 and can display information about operating system-level objects such as
10728 mutexes and other synchronization objects. Exactly which objects can be
10729 displayed is determined on a per-OS basis.
10732 Use the @code{set os} command to set the operating system. This tells
10733 @value{GDBN} which kernel object display module to initialize:
10736 (@value{GDBP}) set os cisco
10740 The associated command @code{show os} displays the operating system
10741 set with the @code{set os} command; if no operating system has been
10742 set, @code{show os} will display an empty string @samp{""}.
10744 If @code{set os} succeeds, @value{GDBN} will display some information
10745 about the operating system, and will create a new @code{info} command
10746 which can be used to query the target. The @code{info} command is named
10747 after the operating system:
10751 (@value{GDBP}) info cisco
10752 List of Cisco Kernel Objects
10754 any Any and all objects
10757 Further subcommands can be used to query about particular objects known
10760 There is currently no way to determine whether a given operating
10761 system is supported other than to try setting it with @kbd{set os
10762 @var{name}}, where @var{name} is the name of the operating system you
10766 @node Remote Debugging
10767 @chapter Debugging remote programs
10770 * Connecting:: Connecting to a remote target
10771 * Server:: Using the gdbserver program
10772 * NetWare:: Using the gdbserve.nlm program
10773 * Remote configuration:: Remote configuration
10774 * remote stub:: Implementing a remote stub
10778 @section Connecting to a remote target
10780 On the @value{GDBN} host machine, you will need an unstripped copy of
10781 your program, since @value{GDBN} needs symobl and debugging information.
10782 Start up @value{GDBN} as usual, using the name of the local copy of your
10783 program as the first argument.
10785 @cindex serial line, @code{target remote}
10786 If you're using a serial line, you may want to give @value{GDBN} the
10787 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
10788 before the @code{target} command.
10790 After that, use @code{target remote} to establish communications with
10791 the target machine. Its argument specifies how to communicate---either
10792 via a devicename attached to a direct serial line, or a TCP or UDP port
10793 (possibly to a terminal server which in turn has a serial line to the
10794 target). For example, to use a serial line connected to the device
10795 named @file{/dev/ttyb}:
10798 target remote /dev/ttyb
10801 @cindex TCP port, @code{target remote}
10802 To use a TCP connection, use an argument of the form
10803 @code{@var{host}:@var{port}} or @code{tcp:@var{host}:@var{port}}.
10804 For example, to connect to port 2828 on a
10805 terminal server named @code{manyfarms}:
10808 target remote manyfarms:2828
10811 If your remote target is actually running on the same machine as
10812 your debugger session (e.g.@: a simulator of your target running on
10813 the same host), you can omit the hostname. For example, to connect
10814 to port 1234 on your local machine:
10817 target remote :1234
10821 Note that the colon is still required here.
10823 @cindex UDP port, @code{target remote}
10824 To use a UDP connection, use an argument of the form
10825 @code{udp:@var{host}:@var{port}}. For example, to connect to UDP port 2828
10826 on a terminal server named @code{manyfarms}:
10829 target remote udp:manyfarms:2828
10832 When using a UDP connection for remote debugging, you should keep in mind
10833 that the `U' stands for ``Unreliable''. UDP can silently drop packets on
10834 busy or unreliable networks, which will cause havoc with your debugging
10837 Now you can use all the usual commands to examine and change data and to
10838 step and continue the remote program.
10840 @cindex interrupting remote programs
10841 @cindex remote programs, interrupting
10842 Whenever @value{GDBN} is waiting for the remote program, if you type the
10843 interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the
10844 program. This may or may not succeed, depending in part on the hardware
10845 and the serial drivers the remote system uses. If you type the
10846 interrupt character once again, @value{GDBN} displays this prompt:
10849 Interrupted while waiting for the program.
10850 Give up (and stop debugging it)? (y or n)
10853 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
10854 (If you decide you want to try again later, you can use @samp{target
10855 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
10856 goes back to waiting.
10859 @kindex detach (remote)
10861 When you have finished debugging the remote program, you can use the
10862 @code{detach} command to release it from @value{GDBN} control.
10863 Detaching from the target normally resumes its execution, but the results
10864 will depend on your particular remote stub. After the @code{detach}
10865 command, @value{GDBN} is free to connect to another target.
10869 The @code{disconnect} command behaves like @code{detach}, except that
10870 the target is generally not resumed. It will wait for @value{GDBN}
10871 (this instance or another one) to connect and continue debugging. After
10872 the @code{disconnect} command, @value{GDBN} is again free to connect to
10877 @section Using the @code{gdbserver} program
10880 @cindex remote connection without stubs
10881 @code{gdbserver} is a control program for Unix-like systems, which
10882 allows you to connect your program with a remote @value{GDBN} via
10883 @code{target remote}---but without linking in the usual debugging stub.
10885 @code{gdbserver} is not a complete replacement for the debugging stubs,
10886 because it requires essentially the same operating-system facilities
10887 that @value{GDBN} itself does. In fact, a system that can run
10888 @code{gdbserver} to connect to a remote @value{GDBN} could also run
10889 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
10890 because it is a much smaller program than @value{GDBN} itself. It is
10891 also easier to port than all of @value{GDBN}, so you may be able to get
10892 started more quickly on a new system by using @code{gdbserver}.
10893 Finally, if you develop code for real-time systems, you may find that
10894 the tradeoffs involved in real-time operation make it more convenient to
10895 do as much development work as possible on another system, for example
10896 by cross-compiling. You can use @code{gdbserver} to make a similar
10897 choice for debugging.
10899 @value{GDBN} and @code{gdbserver} communicate via either a serial line
10900 or a TCP connection, using the standard @value{GDBN} remote serial
10904 @item On the target machine,
10905 you need to have a copy of the program you want to debug.
10906 @code{gdbserver} does not need your program's symbol table, so you can
10907 strip the program if necessary to save space. @value{GDBN} on the host
10908 system does all the symbol handling.
10910 To use the server, you must tell it how to communicate with @value{GDBN};
10911 the name of your program; and the arguments for your program. The usual
10915 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
10918 @var{comm} is either a device name (to use a serial line) or a TCP
10919 hostname and portnumber. For example, to debug Emacs with the argument
10920 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
10924 target> gdbserver /dev/com1 emacs foo.txt
10927 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
10930 To use a TCP connection instead of a serial line:
10933 target> gdbserver host:2345 emacs foo.txt
10936 The only difference from the previous example is the first argument,
10937 specifying that you are communicating with the host @value{GDBN} via
10938 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
10939 expect a TCP connection from machine @samp{host} to local TCP port 2345.
10940 (Currently, the @samp{host} part is ignored.) You can choose any number
10941 you want for the port number as long as it does not conflict with any
10942 TCP ports already in use on the target system (for example, @code{23} is
10943 reserved for @code{telnet}).@footnote{If you choose a port number that
10944 conflicts with another service, @code{gdbserver} prints an error message
10945 and exits.} You must use the same port number with the host @value{GDBN}
10946 @code{target remote} command.
10948 On some targets, @code{gdbserver} can also attach to running programs.
10949 This is accomplished via the @code{--attach} argument. The syntax is:
10952 target> gdbserver @var{comm} --attach @var{pid}
10955 @var{pid} is the process ID of a currently running process. It isn't necessary
10956 to point @code{gdbserver} at a binary for the running process.
10959 @cindex attach to a program by name
10960 You can debug processes by name instead of process ID if your target has the
10961 @code{pidof} utility:
10964 target> gdbserver @var{comm} --attach `pidof @var{PROGRAM}`
10967 In case more than one copy of @var{PROGRAM} is running, or @var{PROGRAM}
10968 has multiple threads, most versions of @code{pidof} support the
10969 @code{-s} option to only return the first process ID.
10971 @item On the host machine,
10972 connect to your target (@pxref{Connecting,,Connecting to a remote target}).
10973 For TCP connections, you must start up @code{gdbserver} prior to using
10974 the @code{target remote} command. Otherwise you may get an error whose
10975 text depends on the host system, but which usually looks something like
10976 @samp{Connection refused}. You don't need to use the @code{load}
10977 command in @value{GDBN} when using gdbserver, since the program is
10978 already on the target.
10983 @section Using the @code{gdbserve.nlm} program
10985 @kindex gdbserve.nlm
10986 @code{gdbserve.nlm} is a control program for NetWare systems, which
10987 allows you to connect your program with a remote @value{GDBN} via
10988 @code{target remote}.
10990 @value{GDBN} and @code{gdbserve.nlm} communicate via a serial line,
10991 using the standard @value{GDBN} remote serial protocol.
10994 @item On the target machine,
10995 you need to have a copy of the program you want to debug.
10996 @code{gdbserve.nlm} does not need your program's symbol table, so you
10997 can strip the program if necessary to save space. @value{GDBN} on the
10998 host system does all the symbol handling.
11000 To use the server, you must tell it how to communicate with
11001 @value{GDBN}; the name of your program; and the arguments for your
11002 program. The syntax is:
11005 load gdbserve [ BOARD=@var{board} ] [ PORT=@var{port} ]
11006 [ BAUD=@var{baud} ] @var{program} [ @var{args} @dots{} ]
11009 @var{board} and @var{port} specify the serial line; @var{baud} specifies
11010 the baud rate used by the connection. @var{port} and @var{node} default
11011 to 0, @var{baud} defaults to 9600@dmn{bps}.
11013 For example, to debug Emacs with the argument @samp{foo.txt}and
11014 communicate with @value{GDBN} over serial port number 2 or board 1
11015 using a 19200@dmn{bps} connection:
11018 load gdbserve BOARD=1 PORT=2 BAUD=19200 emacs foo.txt
11022 On the @value{GDBN} host machine, connect to your target (@pxref{Connecting,,
11023 Connecting to a remote target}).
11027 @node Remote configuration
11028 @section Remote configuration
11030 The following configuration options are available when debugging remote
11034 @kindex set remote hardware-watchpoint-limit
11035 @kindex set remote hardware-breakpoint-limit
11036 @anchor{set remote hardware-watchpoint-limit}
11037 @anchor{set remote hardware-breakpoint-limit}
11038 @item set remote hardware-watchpoint-limit @var{limit}
11039 @itemx set remote hardware-breakpoint-limit @var{limit}
11040 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
11041 watchpoints. A limit of -1, the default, is treated as unlimited.
11045 @section Implementing a remote stub
11047 @cindex debugging stub, example
11048 @cindex remote stub, example
11049 @cindex stub example, remote debugging
11050 The stub files provided with @value{GDBN} implement the target side of the
11051 communication protocol, and the @value{GDBN} side is implemented in the
11052 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
11053 these subroutines to communicate, and ignore the details. (If you're
11054 implementing your own stub file, you can still ignore the details: start
11055 with one of the existing stub files. @file{sparc-stub.c} is the best
11056 organized, and therefore the easiest to read.)
11058 @cindex remote serial debugging, overview
11059 To debug a program running on another machine (the debugging
11060 @dfn{target} machine), you must first arrange for all the usual
11061 prerequisites for the program to run by itself. For example, for a C
11066 A startup routine to set up the C runtime environment; these usually
11067 have a name like @file{crt0}. The startup routine may be supplied by
11068 your hardware supplier, or you may have to write your own.
11071 A C subroutine library to support your program's
11072 subroutine calls, notably managing input and output.
11075 A way of getting your program to the other machine---for example, a
11076 download program. These are often supplied by the hardware
11077 manufacturer, but you may have to write your own from hardware
11081 The next step is to arrange for your program to use a serial port to
11082 communicate with the machine where @value{GDBN} is running (the @dfn{host}
11083 machine). In general terms, the scheme looks like this:
11087 @value{GDBN} already understands how to use this protocol; when everything
11088 else is set up, you can simply use the @samp{target remote} command
11089 (@pxref{Targets,,Specifying a Debugging Target}).
11091 @item On the target,
11092 you must link with your program a few special-purpose subroutines that
11093 implement the @value{GDBN} remote serial protocol. The file containing these
11094 subroutines is called a @dfn{debugging stub}.
11096 On certain remote targets, you can use an auxiliary program
11097 @code{gdbserver} instead of linking a stub into your program.
11098 @xref{Server,,Using the @code{gdbserver} program}, for details.
11101 The debugging stub is specific to the architecture of the remote
11102 machine; for example, use @file{sparc-stub.c} to debug programs on
11105 @cindex remote serial stub list
11106 These working remote stubs are distributed with @value{GDBN}:
11111 @cindex @file{i386-stub.c}
11114 For Intel 386 and compatible architectures.
11117 @cindex @file{m68k-stub.c}
11118 @cindex Motorola 680x0
11120 For Motorola 680x0 architectures.
11123 @cindex @file{sh-stub.c}
11126 For Renesas SH architectures.
11129 @cindex @file{sparc-stub.c}
11131 For @sc{sparc} architectures.
11133 @item sparcl-stub.c
11134 @cindex @file{sparcl-stub.c}
11137 For Fujitsu @sc{sparclite} architectures.
11141 The @file{README} file in the @value{GDBN} distribution may list other
11142 recently added stubs.
11145 * Stub Contents:: What the stub can do for you
11146 * Bootstrapping:: What you must do for the stub
11147 * Debug Session:: Putting it all together
11150 @node Stub Contents
11151 @subsection What the stub can do for you
11153 @cindex remote serial stub
11154 The debugging stub for your architecture supplies these three
11158 @item set_debug_traps
11159 @kindex set_debug_traps
11160 @cindex remote serial stub, initialization
11161 This routine arranges for @code{handle_exception} to run when your
11162 program stops. You must call this subroutine explicitly near the
11163 beginning of your program.
11165 @item handle_exception
11166 @kindex handle_exception
11167 @cindex remote serial stub, main routine
11168 This is the central workhorse, but your program never calls it
11169 explicitly---the setup code arranges for @code{handle_exception} to
11170 run when a trap is triggered.
11172 @code{handle_exception} takes control when your program stops during
11173 execution (for example, on a breakpoint), and mediates communications
11174 with @value{GDBN} on the host machine. This is where the communications
11175 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
11176 representative on the target machine. It begins by sending summary
11177 information on the state of your program, then continues to execute,
11178 retrieving and transmitting any information @value{GDBN} needs, until you
11179 execute a @value{GDBN} command that makes your program resume; at that point,
11180 @code{handle_exception} returns control to your own code on the target
11184 @cindex @code{breakpoint} subroutine, remote
11185 Use this auxiliary subroutine to make your program contain a
11186 breakpoint. Depending on the particular situation, this may be the only
11187 way for @value{GDBN} to get control. For instance, if your target
11188 machine has some sort of interrupt button, you won't need to call this;
11189 pressing the interrupt button transfers control to
11190 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
11191 simply receiving characters on the serial port may also trigger a trap;
11192 again, in that situation, you don't need to call @code{breakpoint} from
11193 your own program---simply running @samp{target remote} from the host
11194 @value{GDBN} session gets control.
11196 Call @code{breakpoint} if none of these is true, or if you simply want
11197 to make certain your program stops at a predetermined point for the
11198 start of your debugging session.
11201 @node Bootstrapping
11202 @subsection What you must do for the stub
11204 @cindex remote stub, support routines
11205 The debugging stubs that come with @value{GDBN} are set up for a particular
11206 chip architecture, but they have no information about the rest of your
11207 debugging target machine.
11209 First of all you need to tell the stub how to communicate with the
11213 @item int getDebugChar()
11214 @kindex getDebugChar
11215 Write this subroutine to read a single character from the serial port.
11216 It may be identical to @code{getchar} for your target system; a
11217 different name is used to allow you to distinguish the two if you wish.
11219 @item void putDebugChar(int)
11220 @kindex putDebugChar
11221 Write this subroutine to write a single character to the serial port.
11222 It may be identical to @code{putchar} for your target system; a
11223 different name is used to allow you to distinguish the two if you wish.
11226 @cindex control C, and remote debugging
11227 @cindex interrupting remote targets
11228 If you want @value{GDBN} to be able to stop your program while it is
11229 running, you need to use an interrupt-driven serial driver, and arrange
11230 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
11231 character). That is the character which @value{GDBN} uses to tell the
11232 remote system to stop.
11234 Getting the debugging target to return the proper status to @value{GDBN}
11235 probably requires changes to the standard stub; one quick and dirty way
11236 is to just execute a breakpoint instruction (the ``dirty'' part is that
11237 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
11239 Other routines you need to supply are:
11242 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
11243 @kindex exceptionHandler
11244 Write this function to install @var{exception_address} in the exception
11245 handling tables. You need to do this because the stub does not have any
11246 way of knowing what the exception handling tables on your target system
11247 are like (for example, the processor's table might be in @sc{rom},
11248 containing entries which point to a table in @sc{ram}).
11249 @var{exception_number} is the exception number which should be changed;
11250 its meaning is architecture-dependent (for example, different numbers
11251 might represent divide by zero, misaligned access, etc). When this
11252 exception occurs, control should be transferred directly to
11253 @var{exception_address}, and the processor state (stack, registers,
11254 and so on) should be just as it is when a processor exception occurs. So if
11255 you want to use a jump instruction to reach @var{exception_address}, it
11256 should be a simple jump, not a jump to subroutine.
11258 For the 386, @var{exception_address} should be installed as an interrupt
11259 gate so that interrupts are masked while the handler runs. The gate
11260 should be at privilege level 0 (the most privileged level). The
11261 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
11262 help from @code{exceptionHandler}.
11264 @item void flush_i_cache()
11265 @kindex flush_i_cache
11266 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
11267 instruction cache, if any, on your target machine. If there is no
11268 instruction cache, this subroutine may be a no-op.
11270 On target machines that have instruction caches, @value{GDBN} requires this
11271 function to make certain that the state of your program is stable.
11275 You must also make sure this library routine is available:
11278 @item void *memset(void *, int, int)
11280 This is the standard library function @code{memset} that sets an area of
11281 memory to a known value. If you have one of the free versions of
11282 @code{libc.a}, @code{memset} can be found there; otherwise, you must
11283 either obtain it from your hardware manufacturer, or write your own.
11286 If you do not use the GNU C compiler, you may need other standard
11287 library subroutines as well; this varies from one stub to another,
11288 but in general the stubs are likely to use any of the common library
11289 subroutines which @code{@value{GCC}} generates as inline code.
11292 @node Debug Session
11293 @subsection Putting it all together
11295 @cindex remote serial debugging summary
11296 In summary, when your program is ready to debug, you must follow these
11301 Make sure you have defined the supporting low-level routines
11302 (@pxref{Bootstrapping,,What you must do for the stub}):
11304 @code{getDebugChar}, @code{putDebugChar},
11305 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
11309 Insert these lines near the top of your program:
11317 For the 680x0 stub only, you need to provide a variable called
11318 @code{exceptionHook}. Normally you just use:
11321 void (*exceptionHook)() = 0;
11325 but if before calling @code{set_debug_traps}, you set it to point to a
11326 function in your program, that function is called when
11327 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
11328 error). The function indicated by @code{exceptionHook} is called with
11329 one parameter: an @code{int} which is the exception number.
11332 Compile and link together: your program, the @value{GDBN} debugging stub for
11333 your target architecture, and the supporting subroutines.
11336 Make sure you have a serial connection between your target machine and
11337 the @value{GDBN} host, and identify the serial port on the host.
11340 @c The "remote" target now provides a `load' command, so we should
11341 @c document that. FIXME.
11342 Download your program to your target machine (or get it there by
11343 whatever means the manufacturer provides), and start it.
11346 Start @value{GDBN} on the host, and connect to the target
11347 (@pxref{Connecting,,Connecting to a remote target}).
11351 @node Configurations
11352 @chapter Configuration-Specific Information
11354 While nearly all @value{GDBN} commands are available for all native and
11355 cross versions of the debugger, there are some exceptions. This chapter
11356 describes things that are only available in certain configurations.
11358 There are three major categories of configurations: native
11359 configurations, where the host and target are the same, embedded
11360 operating system configurations, which are usually the same for several
11361 different processor architectures, and bare embedded processors, which
11362 are quite different from each other.
11367 * Embedded Processors::
11374 This section describes details specific to particular native
11379 * SVR4 Process Information:: SVR4 process information
11380 * DJGPP Native:: Features specific to the DJGPP port
11381 * Cygwin Native:: Features specific to the Cygwin port
11387 On HP-UX systems, if you refer to a function or variable name that
11388 begins with a dollar sign, @value{GDBN} searches for a user or system
11389 name first, before it searches for a convenience variable.
11391 @node SVR4 Process Information
11392 @subsection SVR4 process information
11395 @cindex process image
11397 Many versions of SVR4 provide a facility called @samp{/proc} that can be
11398 used to examine the image of a running process using file-system
11399 subroutines. If @value{GDBN} is configured for an operating system with
11400 this facility, the command @code{info proc} is available to report on
11401 several kinds of information about the process running your program.
11402 @code{info proc} works only on SVR4 systems that include the
11403 @code{procfs} code. This includes OSF/1 (Digital Unix), Solaris, Irix,
11404 and Unixware, but not HP-UX or @sc{gnu}/Linux, for example.
11409 Summarize available information about the process.
11411 @kindex info proc mappings
11412 @item info proc mappings
11413 Report on the address ranges accessible in the program, with information
11414 on whether your program may read, write, or execute each range.
11416 @comment These sub-options of 'info proc' were not included when
11417 @comment procfs.c was re-written. Keep their descriptions around
11418 @comment against the day when someone finds the time to put them back in.
11419 @kindex info proc times
11420 @item info proc times
11421 Starting time, user CPU time, and system CPU time for your program and
11424 @kindex info proc id
11426 Report on the process IDs related to your program: its own process ID,
11427 the ID of its parent, the process group ID, and the session ID.
11429 @kindex info proc status
11430 @item info proc status
11431 General information on the state of the process. If the process is
11432 stopped, this report includes the reason for stopping, and any signal
11435 @item info proc all
11436 Show all the above information about the process.
11441 @subsection Features for Debugging @sc{djgpp} Programs
11442 @cindex @sc{djgpp} debugging
11443 @cindex native @sc{djgpp} debugging
11444 @cindex MS-DOS-specific commands
11446 @sc{djgpp} is the port of @sc{gnu} development tools to MS-DOS and
11447 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
11448 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
11449 top of real-mode DOS systems and their emulations.
11451 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
11452 defines a few commands specific to the @sc{djgpp} port. This
11453 subsection describes those commands.
11458 This is a prefix of @sc{djgpp}-specific commands which print
11459 information about the target system and important OS structures.
11462 @cindex MS-DOS system info
11463 @cindex free memory information (MS-DOS)
11464 @item info dos sysinfo
11465 This command displays assorted information about the underlying
11466 platform: the CPU type and features, the OS version and flavor, the
11467 DPMI version, and the available conventional and DPMI memory.
11472 @cindex segment descriptor tables
11473 @cindex descriptor tables display
11475 @itemx info dos ldt
11476 @itemx info dos idt
11477 These 3 commands display entries from, respectively, Global, Local,
11478 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
11479 tables are data structures which store a descriptor for each segment
11480 that is currently in use. The segment's selector is an index into a
11481 descriptor table; the table entry for that index holds the
11482 descriptor's base address and limit, and its attributes and access
11485 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
11486 segment (used for both data and the stack), and a DOS segment (which
11487 allows access to DOS/BIOS data structures and absolute addresses in
11488 conventional memory). However, the DPMI host will usually define
11489 additional segments in order to support the DPMI environment.
11491 @cindex garbled pointers
11492 These commands allow to display entries from the descriptor tables.
11493 Without an argument, all entries from the specified table are
11494 displayed. An argument, which should be an integer expression, means
11495 display a single entry whose index is given by the argument. For
11496 example, here's a convenient way to display information about the
11497 debugged program's data segment:
11500 @exdent @code{(@value{GDBP}) info dos ldt $ds}
11501 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
11505 This comes in handy when you want to see whether a pointer is outside
11506 the data segment's limit (i.e.@: @dfn{garbled}).
11508 @cindex page tables display (MS-DOS)
11510 @itemx info dos pte
11511 These two commands display entries from, respectively, the Page
11512 Directory and the Page Tables. Page Directories and Page Tables are
11513 data structures which control how virtual memory addresses are mapped
11514 into physical addresses. A Page Table includes an entry for every
11515 page of memory that is mapped into the program's address space; there
11516 may be several Page Tables, each one holding up to 4096 entries. A
11517 Page Directory has up to 4096 entries, one each for every Page Table
11518 that is currently in use.
11520 Without an argument, @kbd{info dos pde} displays the entire Page
11521 Directory, and @kbd{info dos pte} displays all the entries in all of
11522 the Page Tables. An argument, an integer expression, given to the
11523 @kbd{info dos pde} command means display only that entry from the Page
11524 Directory table. An argument given to the @kbd{info dos pte} command
11525 means display entries from a single Page Table, the one pointed to by
11526 the specified entry in the Page Directory.
11528 @cindex direct memory access (DMA) on MS-DOS
11529 These commands are useful when your program uses @dfn{DMA} (Direct
11530 Memory Access), which needs physical addresses to program the DMA
11533 These commands are supported only with some DPMI servers.
11535 @cindex physical address from linear address
11536 @item info dos address-pte @var{addr}
11537 This command displays the Page Table entry for a specified linear
11538 address. The argument linear address @var{addr} should already have the
11539 appropriate segment's base address added to it, because this command
11540 accepts addresses which may belong to @emph{any} segment. For
11541 example, here's how to display the Page Table entry for the page where
11542 the variable @code{i} is stored:
11545 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
11546 @exdent @code{Page Table entry for address 0x11a00d30:}
11547 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
11551 This says that @code{i} is stored at offset @code{0xd30} from the page
11552 whose physical base address is @code{0x02698000}, and prints all the
11553 attributes of that page.
11555 Note that you must cast the addresses of variables to a @code{char *},
11556 since otherwise the value of @code{__djgpp_base_address}, the base
11557 address of all variables and functions in a @sc{djgpp} program, will
11558 be added using the rules of C pointer arithmetics: if @code{i} is
11559 declared an @code{int}, @value{GDBN} will add 4 times the value of
11560 @code{__djgpp_base_address} to the address of @code{i}.
11562 Here's another example, it displays the Page Table entry for the
11566 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
11567 @exdent @code{Page Table entry for address 0x29110:}
11568 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
11572 (The @code{+ 3} offset is because the transfer buffer's address is the
11573 3rd member of the @code{_go32_info_block} structure.) The output of
11574 this command clearly shows that addresses in conventional memory are
11575 mapped 1:1, i.e.@: the physical and linear addresses are identical.
11577 This command is supported only with some DPMI servers.
11580 @node Cygwin Native
11581 @subsection Features for Debugging MS Windows PE executables
11582 @cindex MS Windows debugging
11583 @cindex native Cygwin debugging
11584 @cindex Cygwin-specific commands
11586 @value{GDBN} supports native debugging of MS Windows programs, including
11587 DLLs with and without symbolic debugging information. There are various
11588 additional Cygwin-specific commands, described in this subsection. The
11589 subsubsection @pxref{Non-debug DLL symbols} describes working with DLLs
11590 that have no debugging symbols.
11596 This is a prefix of MS Windows specific commands which print
11597 information about the target system and important OS structures.
11599 @item info w32 selector
11600 This command displays information returned by
11601 the Win32 API @code{GetThreadSelectorEntry} function.
11602 It takes an optional argument that is evaluated to
11603 a long value to give the information about this given selector.
11604 Without argument, this command displays information
11605 about the the six segment registers.
11609 This is a Cygwin specific alias of info shared.
11611 @kindex dll-symbols
11613 This command loads symbols from a dll similarly to
11614 add-sym command but without the need to specify a base address.
11616 @kindex set new-console
11617 @item set new-console @var{mode}
11618 If @var{mode} is @code{on} the debuggee will
11619 be started in a new console on next start.
11620 If @var{mode} is @code{off}i, the debuggee will
11621 be started in the same console as the debugger.
11623 @kindex show new-console
11624 @item show new-console
11625 Displays whether a new console is used
11626 when the debuggee is started.
11628 @kindex set new-group
11629 @item set new-group @var{mode}
11630 This boolean value controls whether the debuggee should
11631 start a new group or stay in the same group as the debugger.
11632 This affects the way the Windows OS handles
11635 @kindex show new-group
11636 @item show new-group
11637 Displays current value of new-group boolean.
11639 @kindex set debugevents
11640 @item set debugevents
11641 This boolean value adds debug output concerning events seen by the debugger.
11643 @kindex set debugexec
11644 @item set debugexec
11645 This boolean value adds debug output concerning execute events
11646 seen by the debugger.
11648 @kindex set debugexceptions
11649 @item set debugexceptions
11650 This boolean value adds debug ouptut concerning exception events
11651 seen by the debugger.
11653 @kindex set debugmemory
11654 @item set debugmemory
11655 This boolean value adds debug ouptut concerning memory events
11656 seen by the debugger.
11660 This boolean values specifies whether the debuggee is called
11661 via a shell or directly (default value is on).
11665 Displays if the debuggee will be started with a shell.
11670 * Non-debug DLL symbols:: Support for DLLs without debugging symbols
11673 @node Non-debug DLL symbols
11674 @subsubsection Support for DLLs without debugging symbols
11675 @cindex DLLs with no debugging symbols
11676 @cindex Minimal symbols and DLLs
11678 Very often on windows, some of the DLLs that your program relies on do
11679 not include symbolic debugging information (for example,
11680 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
11681 symbols in a DLL, it relies on the minimal amount of symbolic
11682 information contained in the DLL's export table. This subsubsection
11683 describes working with such symbols, known internally to @value{GDBN} as
11684 ``minimal symbols''.
11686 Note that before the debugged program has started execution, no DLLs
11687 will have been loaded. The easiest way around this problem is simply to
11688 start the program --- either by setting a breakpoint or letting the
11689 program run once to completion. It is also possible to force
11690 @value{GDBN} to load a particular DLL before starting the executable ---
11691 see the shared library information in @pxref{Files} or the
11692 @code{dll-symbols} command in @pxref{Cygwin Native}. Currently,
11693 explicitly loading symbols from a DLL with no debugging information will
11694 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
11695 which may adversely affect symbol lookup performance.
11697 @subsubsection DLL name prefixes
11699 In keeping with the naming conventions used by the Microsoft debugging
11700 tools, DLL export symbols are made available with a prefix based on the
11701 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
11702 also entered into the symbol table, so @code{CreateFileA} is often
11703 sufficient. In some cases there will be name clashes within a program
11704 (particularly if the executable itself includes full debugging symbols)
11705 necessitating the use of the fully qualified name when referring to the
11706 contents of the DLL. Use single-quotes around the name to avoid the
11707 exclamation mark (``!'') being interpreted as a language operator.
11709 Note that the internal name of the DLL may be all upper-case, even
11710 though the file name of the DLL is lower-case, or vice-versa. Since
11711 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
11712 some confusion. If in doubt, try the @code{info functions} and
11713 @code{info variables} commands or even @code{maint print msymbols} (see
11714 @pxref{Symbols}). Here's an example:
11717 (gdb) info function CreateFileA
11718 All functions matching regular expression "CreateFileA":
11720 Non-debugging symbols:
11721 0x77e885f4 CreateFileA
11722 0x77e885f4 KERNEL32!CreateFileA
11726 (gdb) info function !
11727 All functions matching regular expression "!":
11729 Non-debugging symbols:
11730 0x6100114c cygwin1!__assert
11731 0x61004034 cygwin1!_dll_crt0@@0
11732 0x61004240 cygwin1!dll_crt0(per_process *)
11736 @subsubsection Working with minimal symbols
11738 Symbols extracted from a DLL's export table do not contain very much
11739 type information. All that @value{GDBN} can do is guess whether a symbol
11740 refers to a function or variable depending on the linker section that
11741 contains the symbol. Also note that the actual contents of the memory
11742 contained in a DLL are not available unless the program is running. This
11743 means that you cannot examine the contents of a variable or disassemble
11744 a function within a DLL without a running program.
11746 Variables are generally treated as pointers and dereferenced
11747 automatically. For this reason, it is often necessary to prefix a
11748 variable name with the address-of operator (``&'') and provide explicit
11749 type information in the command. Here's an example of the type of
11753 (gdb) print 'cygwin1!__argv'
11758 (gdb) x 'cygwin1!__argv'
11759 0x10021610: "\230y\""
11762 And two possible solutions:
11765 (gdb) print ((char **)'cygwin1!__argv')[0]
11766 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
11770 (gdb) x/2x &'cygwin1!__argv'
11771 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
11772 (gdb) x/x 0x10021608
11773 0x10021608: 0x0022fd98
11774 (gdb) x/s 0x0022fd98
11775 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
11778 Setting a break point within a DLL is possible even before the program
11779 starts execution. However, under these circumstances, @value{GDBN} can't
11780 examine the initial instructions of the function in order to skip the
11781 function's frame set-up code. You can work around this by using ``*&''
11782 to set the breakpoint at a raw memory address:
11785 (gdb) break *&'python22!PyOS_Readline'
11786 Breakpoint 1 at 0x1e04eff0
11789 The author of these extensions is not entirely convinced that setting a
11790 break point within a shared DLL like @file{kernel32.dll} is completely
11794 @section Embedded Operating Systems
11796 This section describes configurations involving the debugging of
11797 embedded operating systems that are available for several different
11801 * VxWorks:: Using @value{GDBN} with VxWorks
11804 @value{GDBN} includes the ability to debug programs running on
11805 various real-time operating systems.
11808 @subsection Using @value{GDBN} with VxWorks
11814 @kindex target vxworks
11815 @item target vxworks @var{machinename}
11816 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
11817 is the target system's machine name or IP address.
11821 On VxWorks, @code{load} links @var{filename} dynamically on the
11822 current target system as well as adding its symbols in @value{GDBN}.
11824 @value{GDBN} enables developers to spawn and debug tasks running on networked
11825 VxWorks targets from a Unix host. Already-running tasks spawned from
11826 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
11827 both the Unix host and on the VxWorks target. The program
11828 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
11829 installed with the name @code{vxgdb}, to distinguish it from a
11830 @value{GDBN} for debugging programs on the host itself.)
11833 @item VxWorks-timeout @var{args}
11834 @kindex vxworks-timeout
11835 All VxWorks-based targets now support the option @code{vxworks-timeout}.
11836 This option is set by the user, and @var{args} represents the number of
11837 seconds @value{GDBN} waits for responses to rpc's. You might use this if
11838 your VxWorks target is a slow software simulator or is on the far side
11839 of a thin network line.
11842 The following information on connecting to VxWorks was current when
11843 this manual was produced; newer releases of VxWorks may use revised
11846 @kindex INCLUDE_RDB
11847 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
11848 to include the remote debugging interface routines in the VxWorks
11849 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
11850 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
11851 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
11852 source debugging task @code{tRdbTask} when VxWorks is booted. For more
11853 information on configuring and remaking VxWorks, see the manufacturer's
11855 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
11857 Once you have included @file{rdb.a} in your VxWorks system image and set
11858 your Unix execution search path to find @value{GDBN}, you are ready to
11859 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
11860 @code{vxgdb}, depending on your installation).
11862 @value{GDBN} comes up showing the prompt:
11869 * VxWorks Connection:: Connecting to VxWorks
11870 * VxWorks Download:: VxWorks download
11871 * VxWorks Attach:: Running tasks
11874 @node VxWorks Connection
11875 @subsubsection Connecting to VxWorks
11877 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
11878 network. To connect to a target whose host name is ``@code{tt}'', type:
11881 (vxgdb) target vxworks tt
11885 @value{GDBN} displays messages like these:
11888 Attaching remote machine across net...
11893 @value{GDBN} then attempts to read the symbol tables of any object modules
11894 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
11895 these files by searching the directories listed in the command search
11896 path (@pxref{Environment, ,Your program's environment}); if it fails
11897 to find an object file, it displays a message such as:
11900 prog.o: No such file or directory.
11903 When this happens, add the appropriate directory to the search path with
11904 the @value{GDBN} command @code{path}, and execute the @code{target}
11907 @node VxWorks Download
11908 @subsubsection VxWorks download
11910 @cindex download to VxWorks
11911 If you have connected to the VxWorks target and you want to debug an
11912 object that has not yet been loaded, you can use the @value{GDBN}
11913 @code{load} command to download a file from Unix to VxWorks
11914 incrementally. The object file given as an argument to the @code{load}
11915 command is actually opened twice: first by the VxWorks target in order
11916 to download the code, then by @value{GDBN} in order to read the symbol
11917 table. This can lead to problems if the current working directories on
11918 the two systems differ. If both systems have NFS mounted the same
11919 filesystems, you can avoid these problems by using absolute paths.
11920 Otherwise, it is simplest to set the working directory on both systems
11921 to the directory in which the object file resides, and then to reference
11922 the file by its name, without any path. For instance, a program
11923 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
11924 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
11925 program, type this on VxWorks:
11928 -> cd "@var{vxpath}/vw/demo/rdb"
11932 Then, in @value{GDBN}, type:
11935 (vxgdb) cd @var{hostpath}/vw/demo/rdb
11936 (vxgdb) load prog.o
11939 @value{GDBN} displays a response similar to this:
11942 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
11945 You can also use the @code{load} command to reload an object module
11946 after editing and recompiling the corresponding source file. Note that
11947 this makes @value{GDBN} delete all currently-defined breakpoints,
11948 auto-displays, and convenience variables, and to clear the value
11949 history. (This is necessary in order to preserve the integrity of
11950 debugger's data structures that reference the target system's symbol
11953 @node VxWorks Attach
11954 @subsubsection Running tasks
11956 @cindex running VxWorks tasks
11957 You can also attach to an existing task using the @code{attach} command as
11961 (vxgdb) attach @var{task}
11965 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
11966 or suspended when you attach to it. Running tasks are suspended at
11967 the time of attachment.
11969 @node Embedded Processors
11970 @section Embedded Processors
11972 This section goes into details specific to particular embedded
11978 * H8/300:: Renesas H8/300
11979 * H8/500:: Renesas H8/500
11980 * M32R/D:: Renesas M32R/D
11981 * M68K:: Motorola M68K
11982 * MIPS Embedded:: MIPS Embedded
11983 * OpenRISC 1000:: OpenRisc 1000
11984 * PA:: HP PA Embedded
11987 * Sparclet:: Tsqware Sparclet
11988 * Sparclite:: Fujitsu Sparclite
11989 * ST2000:: Tandem ST2000
11990 * Z8000:: Zilog Z8000
11999 @item target rdi @var{dev}
12000 ARM Angel monitor, via RDI library interface to ADP protocol. You may
12001 use this target to communicate with both boards running the Angel
12002 monitor, or with the EmbeddedICE JTAG debug device.
12005 @item target rdp @var{dev}
12011 @subsection Renesas H8/300
12015 @kindex target hms@r{, with H8/300}
12016 @item target hms @var{dev}
12017 A Renesas SH, H8/300, or H8/500 board, attached via serial line to your host.
12018 Use special commands @code{device} and @code{speed} to control the serial
12019 line and the communications speed used.
12021 @kindex target e7000@r{, with H8/300}
12022 @item target e7000 @var{dev}
12023 E7000 emulator for Renesas H8 and SH.
12025 @kindex target sh3@r{, with H8/300}
12026 @kindex target sh3e@r{, with H8/300}
12027 @item target sh3 @var{dev}
12028 @itemx target sh3e @var{dev}
12029 Renesas SH-3 and SH-3E target systems.
12033 @cindex download to H8/300 or H8/500
12034 @cindex H8/300 or H8/500 download
12035 @cindex download to Renesas SH
12036 @cindex Renesas SH download
12037 When you select remote debugging to a Renesas SH, H8/300, or H8/500
12038 board, the @code{load} command downloads your program to the Renesas
12039 board and also opens it as the current executable target for
12040 @value{GDBN} on your host (like the @code{file} command).
12042 @value{GDBN} needs to know these things to talk to your
12043 Renesas SH, H8/300, or H8/500:
12047 that you want to use @samp{target hms}, the remote debugging interface
12048 for Renesas microprocessors, or @samp{target e7000}, the in-circuit
12049 emulator for the Renesas SH and the Renesas 300H. (@samp{target hms} is
12050 the default when @value{GDBN} is configured specifically for the Renesas SH,
12051 H8/300, or H8/500.)
12054 what serial device connects your host to your Renesas board (the first
12055 serial device available on your host is the default).
12058 what speed to use over the serial device.
12062 * Renesas Boards:: Connecting to Renesas boards.
12063 * Renesas ICE:: Using the E7000 In-Circuit Emulator.
12064 * Renesas Special:: Special @value{GDBN} commands for Renesas micros.
12067 @node Renesas Boards
12068 @subsubsection Connecting to Renesas boards
12070 @c only for Unix hosts
12072 @cindex serial device, Renesas micros
12073 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
12074 need to explicitly set the serial device. The default @var{port} is the
12075 first available port on your host. This is only necessary on Unix
12076 hosts, where it is typically something like @file{/dev/ttya}.
12079 @cindex serial line speed, Renesas micros
12080 @code{@value{GDBN}} has another special command to set the communications
12081 speed: @samp{speed @var{bps}}. This command also is only used from Unix
12082 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
12083 the DOS @code{mode} command (for instance,
12084 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
12086 The @samp{device} and @samp{speed} commands are available only when you
12087 use a Unix host to debug your Renesas microprocessor programs. If you
12089 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
12090 called @code{asynctsr} to communicate with the development board
12091 through a PC serial port. You must also use the DOS @code{mode} command
12092 to set up the serial port on the DOS side.
12094 The following sample session illustrates the steps needed to start a
12095 program under @value{GDBN} control on an H8/300. The example uses a
12096 sample H8/300 program called @file{t.x}. The procedure is the same for
12097 the Renesas SH and the H8/500.
12099 First hook up your development board. In this example, we use a
12100 board attached to serial port @code{COM2}; if you use a different serial
12101 port, substitute its name in the argument of the @code{mode} command.
12102 When you call @code{asynctsr}, the auxiliary comms program used by the
12103 debugger, you give it just the numeric part of the serial port's name;
12104 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
12108 C:\H8300\TEST> asynctsr 2
12109 C:\H8300\TEST> mode com2:9600,n,8,1,p
12111 Resident portion of MODE loaded
12113 COM2: 9600, n, 8, 1, p
12118 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
12119 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
12120 disable it, or even boot without it, to use @code{asynctsr} to control
12121 your development board.
12124 @kindex target hms@r{, and serial protocol}
12125 Now that serial communications are set up, and the development board is
12126 connected, you can start up @value{GDBN}. Call @code{@value{GDBP}} with
12127 the name of your program as the argument. @code{@value{GDBN}} prompts
12128 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
12129 commands to begin your debugging session: @samp{target hms} to specify
12130 cross-debugging to the Renesas board, and the @code{load} command to
12131 download your program to the board. @code{load} displays the names of
12132 the program's sections, and a @samp{*} for each 2K of data downloaded.
12133 (If you want to refresh @value{GDBN} data on symbols or on the
12134 executable file without downloading, use the @value{GDBN} commands
12135 @code{file} or @code{symbol-file}. These commands, and @code{load}
12136 itself, are described in @ref{Files,,Commands to specify files}.)
12139 (eg-C:\H8300\TEST) @value{GDBP} t.x
12140 @value{GDBN} is free software and you are welcome to distribute copies
12141 of it under certain conditions; type "show copying" to see
12143 There is absolutely no warranty for @value{GDBN}; type "show warranty"
12145 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
12146 (@value{GDBP}) target hms
12147 Connected to remote H8/300 HMS system.
12148 (@value{GDBP}) load t.x
12149 .text : 0x8000 .. 0xabde ***********
12150 .data : 0xabde .. 0xad30 *
12151 .stack : 0xf000 .. 0xf014 *
12154 At this point, you're ready to run or debug your program. From here on,
12155 you can use all the usual @value{GDBN} commands. The @code{break} command
12156 sets breakpoints; the @code{run} command starts your program;
12157 @code{print} or @code{x} display data; the @code{continue} command
12158 resumes execution after stopping at a breakpoint. You can use the
12159 @code{help} command at any time to find out more about @value{GDBN} commands.
12161 Remember, however, that @emph{operating system} facilities aren't
12162 available on your development board; for example, if your program hangs,
12163 you can't send an interrupt---but you can press the @sc{reset} switch!
12165 Use the @sc{reset} button on the development board
12168 to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has
12169 no way to pass an interrupt signal to the development board); and
12172 to return to the @value{GDBN} command prompt after your program finishes
12173 normally. The communications protocol provides no other way for @value{GDBN}
12174 to detect program completion.
12177 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
12178 development board as a ``normal exit'' of your program.
12181 @subsubsection Using the E7000 in-circuit emulator
12183 @kindex target e7000@r{, with Renesas ICE}
12184 You can use the E7000 in-circuit emulator to develop code for either the
12185 Renesas SH or the H8/300H. Use one of these forms of the @samp{target
12186 e7000} command to connect @value{GDBN} to your E7000:
12189 @item target e7000 @var{port} @var{speed}
12190 Use this form if your E7000 is connected to a serial port. The
12191 @var{port} argument identifies what serial port to use (for example,
12192 @samp{com2}). The third argument is the line speed in bits per second
12193 (for example, @samp{9600}).
12195 @item target e7000 @var{hostname}
12196 If your E7000 is installed as a host on a TCP/IP network, you can just
12197 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
12200 @node Renesas Special
12201 @subsubsection Special @value{GDBN} commands for Renesas micros
12203 Some @value{GDBN} commands are available only for the H8/300:
12207 @kindex set machine
12208 @kindex show machine
12209 @item set machine h8300
12210 @itemx set machine h8300h
12211 Condition @value{GDBN} for one of the two variants of the H8/300
12212 architecture with @samp{set machine}. You can use @samp{show machine}
12213 to check which variant is currently in effect.
12222 @kindex set memory @var{mod}
12223 @cindex memory models, H8/500
12224 @item set memory @var{mod}
12226 Specify which H8/500 memory model (@var{mod}) you are using with
12227 @samp{set memory}; check which memory model is in effect with @samp{show
12228 memory}. The accepted values for @var{mod} are @code{small},
12229 @code{big}, @code{medium}, and @code{compact}.
12234 @subsection Renesas M32R/D
12238 @kindex target m32r
12239 @item target m32r @var{dev}
12240 Renesas M32R/D ROM monitor.
12242 @kindex target m32rsdi
12243 @item target m32rsdi @var{dev}
12244 Renesas M32R SDI server, connected via parallel port to the board.
12251 The Motorola m68k configuration includes ColdFire support, and
12252 target command for the following ROM monitors.
12256 @kindex target abug
12257 @item target abug @var{dev}
12258 ABug ROM monitor for M68K.
12260 @kindex target cpu32bug
12261 @item target cpu32bug @var{dev}
12262 CPU32BUG monitor, running on a CPU32 (M68K) board.
12264 @kindex target dbug
12265 @item target dbug @var{dev}
12266 dBUG ROM monitor for Motorola ColdFire.
12269 @item target est @var{dev}
12270 EST-300 ICE monitor, running on a CPU32 (M68K) board.
12272 @kindex target rom68k
12273 @item target rom68k @var{dev}
12274 ROM 68K monitor, running on an M68K IDP board.
12280 @kindex target rombug
12281 @item target rombug @var{dev}
12282 ROMBUG ROM monitor for OS/9000.
12286 @node MIPS Embedded
12287 @subsection MIPS Embedded
12289 @cindex MIPS boards
12290 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
12291 MIPS board attached to a serial line. This is available when
12292 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
12295 Use these @value{GDBN} commands to specify the connection to your target board:
12298 @item target mips @var{port}
12299 @kindex target mips @var{port}
12300 To run a program on the board, start up @code{@value{GDBP}} with the
12301 name of your program as the argument. To connect to the board, use the
12302 command @samp{target mips @var{port}}, where @var{port} is the name of
12303 the serial port connected to the board. If the program has not already
12304 been downloaded to the board, you may use the @code{load} command to
12305 download it. You can then use all the usual @value{GDBN} commands.
12307 For example, this sequence connects to the target board through a serial
12308 port, and loads and runs a program called @var{prog} through the
12312 host$ @value{GDBP} @var{prog}
12313 @value{GDBN} is free software and @dots{}
12314 (@value{GDBP}) target mips /dev/ttyb
12315 (@value{GDBP}) load @var{prog}
12319 @item target mips @var{hostname}:@var{portnumber}
12320 On some @value{GDBN} host configurations, you can specify a TCP
12321 connection (for instance, to a serial line managed by a terminal
12322 concentrator) instead of a serial port, using the syntax
12323 @samp{@var{hostname}:@var{portnumber}}.
12325 @item target pmon @var{port}
12326 @kindex target pmon @var{port}
12329 @item target ddb @var{port}
12330 @kindex target ddb @var{port}
12331 NEC's DDB variant of PMON for Vr4300.
12333 @item target lsi @var{port}
12334 @kindex target lsi @var{port}
12335 LSI variant of PMON.
12337 @kindex target r3900
12338 @item target r3900 @var{dev}
12339 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
12341 @kindex target array
12342 @item target array @var{dev}
12343 Array Tech LSI33K RAID controller board.
12349 @value{GDBN} also supports these special commands for MIPS targets:
12352 @item set processor @var{args}
12353 @itemx show processor
12354 @kindex set processor @var{args}
12355 @kindex show processor
12356 Use the @code{set processor} command to set the type of MIPS
12357 processor when you want to access processor-type-specific registers.
12358 For example, @code{set processor @var{r3041}} tells @value{GDBN}
12359 to use the CPU registers appropriate for the 3041 chip.
12360 Use the @code{show processor} command to see what MIPS processor @value{GDBN}
12361 is using. Use the @code{info reg} command to see what registers
12362 @value{GDBN} is using.
12364 @item set mipsfpu double
12365 @itemx set mipsfpu single
12366 @itemx set mipsfpu none
12367 @itemx show mipsfpu
12368 @kindex set mipsfpu
12369 @kindex show mipsfpu
12370 @cindex MIPS remote floating point
12371 @cindex floating point, MIPS remote
12372 If your target board does not support the MIPS floating point
12373 coprocessor, you should use the command @samp{set mipsfpu none} (if you
12374 need this, you may wish to put the command in your @value{GDBN} init
12375 file). This tells @value{GDBN} how to find the return value of
12376 functions which return floating point values. It also allows
12377 @value{GDBN} to avoid saving the floating point registers when calling
12378 functions on the board. If you are using a floating point coprocessor
12379 with only single precision floating point support, as on the @sc{r4650}
12380 processor, use the command @samp{set mipsfpu single}. The default
12381 double precision floating point coprocessor may be selected using
12382 @samp{set mipsfpu double}.
12384 In previous versions the only choices were double precision or no
12385 floating point, so @samp{set mipsfpu on} will select double precision
12386 and @samp{set mipsfpu off} will select no floating point.
12388 As usual, you can inquire about the @code{mipsfpu} variable with
12389 @samp{show mipsfpu}.
12391 @item set remotedebug @var{n}
12392 @itemx show remotedebug
12393 @kindex set remotedebug@r{, MIPS protocol}
12394 @kindex show remotedebug@r{, MIPS protocol}
12395 @cindex @code{remotedebug}, MIPS protocol
12396 @cindex MIPS @code{remotedebug} protocol
12397 @c FIXME! For this to be useful, you must know something about the MIPS
12398 @c FIXME...protocol. Where is it described?
12399 You can see some debugging information about communications with the board
12400 by setting the @code{remotedebug} variable. If you set it to @code{1} using
12401 @samp{set remotedebug 1}, every packet is displayed. If you set it
12402 to @code{2}, every character is displayed. You can check the current value
12403 at any time with the command @samp{show remotedebug}.
12405 @item set timeout @var{seconds}
12406 @itemx set retransmit-timeout @var{seconds}
12407 @itemx show timeout
12408 @itemx show retransmit-timeout
12409 @cindex @code{timeout}, MIPS protocol
12410 @cindex @code{retransmit-timeout}, MIPS protocol
12411 @kindex set timeout
12412 @kindex show timeout
12413 @kindex set retransmit-timeout
12414 @kindex show retransmit-timeout
12415 You can control the timeout used while waiting for a packet, in the MIPS
12416 remote protocol, with the @code{set timeout @var{seconds}} command. The
12417 default is 5 seconds. Similarly, you can control the timeout used while
12418 waiting for an acknowledgement of a packet with the @code{set
12419 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
12420 You can inspect both values with @code{show timeout} and @code{show
12421 retransmit-timeout}. (These commands are @emph{only} available when
12422 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
12424 The timeout set by @code{set timeout} does not apply when @value{GDBN}
12425 is waiting for your program to stop. In that case, @value{GDBN} waits
12426 forever because it has no way of knowing how long the program is going
12427 to run before stopping.
12430 @node OpenRISC 1000
12431 @subsection OpenRISC 1000
12432 @cindex OpenRISC 1000
12434 @cindex or1k boards
12435 See OR1k Architecture document (@uref{www.opencores.org}) for more information
12436 about platform and commands.
12440 @kindex target jtag
12441 @item target jtag jtag://@var{host}:@var{port}
12443 Connects to remote JTAG server.
12444 JTAG remote server can be either an or1ksim or JTAG server,
12445 connected via parallel port to the board.
12447 Example: @code{target jtag jtag://localhost:9999}
12450 @item or1ksim @var{command}
12451 If connected to @code{or1ksim} OpenRISC 1000 Architectural
12452 Simulator, proprietary commands can be executed.
12454 @kindex info or1k spr
12455 @item info or1k spr
12456 Displays spr groups.
12458 @item info or1k spr @var{group}
12459 @itemx info or1k spr @var{groupno}
12460 Displays register names in selected group.
12462 @item info or1k spr @var{group} @var{register}
12463 @itemx info or1k spr @var{register}
12464 @itemx info or1k spr @var{groupno} @var{registerno}
12465 @itemx info or1k spr @var{registerno}
12466 Shows information about specified spr register.
12469 @item spr @var{group} @var{register} @var{value}
12470 @itemx spr @var{register @var{value}}
12471 @itemx spr @var{groupno} @var{registerno @var{value}}
12472 @itemx spr @var{registerno @var{value}}
12473 Writes @var{value} to specified spr register.
12476 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
12477 It is very similar to @value{GDBN} trace, except it does not interfere with normal
12478 program execution and is thus much faster. Hardware breakpoints/watchpoint
12479 triggers can be set using:
12482 Load effective address/data
12484 Store effective address/data
12486 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
12491 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
12492 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
12494 @code{htrace} commands:
12495 @cindex OpenRISC 1000 htrace
12498 @item hwatch @var{conditional}
12499 Set hardware watchpoint on combination of Load/Store Effecive Address(es)
12500 or Data. For example:
12502 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
12504 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
12506 @kindex htrace info
12508 Display information about current HW trace configuration.
12510 @kindex htrace trigger
12511 @item htrace trigger @var{conditional}
12512 Set starting criteria for HW trace.
12514 @kindex htrace qualifier
12515 @item htrace qualifier @var{conditional}
12516 Set acquisition qualifier for HW trace.
12518 @kindex htrace stop
12519 @item htrace stop @var{conditional}
12520 Set HW trace stopping criteria.
12522 @kindex htrace record
12523 @item htrace record [@var{data}]*
12524 Selects the data to be recorded, when qualifier is met and HW trace was
12527 @kindex htrace enable
12528 @item htrace enable
12529 @kindex htrace disable
12530 @itemx htrace disable
12531 Enables/disables the HW trace.
12533 @kindex htrace rewind
12534 @item htrace rewind [@var{filename}]
12535 Clears currently recorded trace data.
12537 If filename is specified, new trace file is made and any newly collected data
12538 will be written there.
12540 @kindex htrace print
12541 @item htrace print [@var{start} [@var{len}]]
12542 Prints trace buffer, using current record configuration.
12544 @kindex htrace mode continuous
12545 @item htrace mode continuous
12546 Set continuous trace mode.
12548 @kindex htrace mode suspend
12549 @item htrace mode suspend
12550 Set suspend trace mode.
12555 @subsection PowerPC
12559 @kindex target dink32
12560 @item target dink32 @var{dev}
12561 DINK32 ROM monitor.
12563 @kindex target ppcbug
12564 @item target ppcbug @var{dev}
12565 @kindex target ppcbug1
12566 @item target ppcbug1 @var{dev}
12567 PPCBUG ROM monitor for PowerPC.
12570 @item target sds @var{dev}
12571 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
12576 @subsection HP PA Embedded
12580 @kindex target op50n
12581 @item target op50n @var{dev}
12582 OP50N monitor, running on an OKI HPPA board.
12584 @kindex target w89k
12585 @item target w89k @var{dev}
12586 W89K monitor, running on a Winbond HPPA board.
12591 @subsection Renesas SH
12595 @kindex target hms@r{, with Renesas SH}
12596 @item target hms @var{dev}
12597 A Renesas SH board attached via serial line to your host. Use special
12598 commands @code{device} and @code{speed} to control the serial line and
12599 the communications speed used.
12601 @kindex target e7000@r{, with Renesas SH}
12602 @item target e7000 @var{dev}
12603 E7000 emulator for Renesas SH.
12605 @kindex target sh3@r{, with SH}
12606 @kindex target sh3e@r{, with SH}
12607 @item target sh3 @var{dev}
12608 @item target sh3e @var{dev}
12609 Renesas SH-3 and SH-3E target systems.
12614 @subsection Tsqware Sparclet
12618 @value{GDBN} enables developers to debug tasks running on
12619 Sparclet targets from a Unix host.
12620 @value{GDBN} uses code that runs on
12621 both the Unix host and on the Sparclet target. The program
12622 @code{@value{GDBP}} is installed and executed on the Unix host.
12625 @item remotetimeout @var{args}
12626 @kindex remotetimeout
12627 @value{GDBN} supports the option @code{remotetimeout}.
12628 This option is set by the user, and @var{args} represents the number of
12629 seconds @value{GDBN} waits for responses.
12632 @cindex compiling, on Sparclet
12633 When compiling for debugging, include the options @samp{-g} to get debug
12634 information and @samp{-Ttext} to relocate the program to where you wish to
12635 load it on the target. You may also want to add the options @samp{-n} or
12636 @samp{-N} in order to reduce the size of the sections. Example:
12639 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
12642 You can use @code{objdump} to verify that the addresses are what you intended:
12645 sparclet-aout-objdump --headers --syms prog
12648 @cindex running, on Sparclet
12650 your Unix execution search path to find @value{GDBN}, you are ready to
12651 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
12652 (or @code{sparclet-aout-gdb}, depending on your installation).
12654 @value{GDBN} comes up showing the prompt:
12661 * Sparclet File:: Setting the file to debug
12662 * Sparclet Connection:: Connecting to Sparclet
12663 * Sparclet Download:: Sparclet download
12664 * Sparclet Execution:: Running and debugging
12667 @node Sparclet File
12668 @subsubsection Setting file to debug
12670 The @value{GDBN} command @code{file} lets you choose with program to debug.
12673 (gdbslet) file prog
12677 @value{GDBN} then attempts to read the symbol table of @file{prog}.
12678 @value{GDBN} locates
12679 the file by searching the directories listed in the command search
12681 If the file was compiled with debug information (option "-g"), source
12682 files will be searched as well.
12683 @value{GDBN} locates
12684 the source files by searching the directories listed in the directory search
12685 path (@pxref{Environment, ,Your program's environment}).
12687 to find a file, it displays a message such as:
12690 prog: No such file or directory.
12693 When this happens, add the appropriate directories to the search paths with
12694 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
12695 @code{target} command again.
12697 @node Sparclet Connection
12698 @subsubsection Connecting to Sparclet
12700 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
12701 To connect to a target on serial port ``@code{ttya}'', type:
12704 (gdbslet) target sparclet /dev/ttya
12705 Remote target sparclet connected to /dev/ttya
12706 main () at ../prog.c:3
12710 @value{GDBN} displays messages like these:
12716 @node Sparclet Download
12717 @subsubsection Sparclet download
12719 @cindex download to Sparclet
12720 Once connected to the Sparclet target,
12721 you can use the @value{GDBN}
12722 @code{load} command to download the file from the host to the target.
12723 The file name and load offset should be given as arguments to the @code{load}
12725 Since the file format is aout, the program must be loaded to the starting
12726 address. You can use @code{objdump} to find out what this value is. The load
12727 offset is an offset which is added to the VMA (virtual memory address)
12728 of each of the file's sections.
12729 For instance, if the program
12730 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
12731 and bss at 0x12010170, in @value{GDBN}, type:
12734 (gdbslet) load prog 0x12010000
12735 Loading section .text, size 0xdb0 vma 0x12010000
12738 If the code is loaded at a different address then what the program was linked
12739 to, you may need to use the @code{section} and @code{add-symbol-file} commands
12740 to tell @value{GDBN} where to map the symbol table.
12742 @node Sparclet Execution
12743 @subsubsection Running and debugging
12745 @cindex running and debugging Sparclet programs
12746 You can now begin debugging the task using @value{GDBN}'s execution control
12747 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
12748 manual for the list of commands.
12752 Breakpoint 1 at 0x12010000: file prog.c, line 3.
12754 Starting program: prog
12755 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
12756 3 char *symarg = 0;
12758 4 char *execarg = "hello!";
12763 @subsection Fujitsu Sparclite
12767 @kindex target sparclite
12768 @item target sparclite @var{dev}
12769 Fujitsu sparclite boards, used only for the purpose of loading.
12770 You must use an additional command to debug the program.
12771 For example: target remote @var{dev} using @value{GDBN} standard
12777 @subsection Tandem ST2000
12779 @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
12782 To connect your ST2000 to the host system, see the manufacturer's
12783 manual. Once the ST2000 is physically attached, you can run:
12786 target st2000 @var{dev} @var{speed}
12790 to establish it as your debugging environment. @var{dev} is normally
12791 the name of a serial device, such as @file{/dev/ttya}, connected to the
12792 ST2000 via a serial line. You can instead specify @var{dev} as a TCP
12793 connection (for example, to a serial line attached via a terminal
12794 concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
12796 The @code{load} and @code{attach} commands are @emph{not} defined for
12797 this target; you must load your program into the ST2000 as you normally
12798 would for standalone operation. @value{GDBN} reads debugging information
12799 (such as symbols) from a separate, debugging version of the program
12800 available on your host computer.
12801 @c FIXME!! This is terribly vague; what little content is here is
12802 @c basically hearsay.
12804 @cindex ST2000 auxiliary commands
12805 These auxiliary @value{GDBN} commands are available to help you with the ST2000
12809 @item st2000 @var{command}
12810 @kindex st2000 @var{cmd}
12811 @cindex STDBUG commands (ST2000)
12812 @cindex commands to STDBUG (ST2000)
12813 Send a @var{command} to the STDBUG monitor. See the manufacturer's
12814 manual for available commands.
12817 @cindex connect (to STDBUG)
12818 Connect the controlling terminal to the STDBUG command monitor. When
12819 you are done interacting with STDBUG, typing either of two character
12820 sequences gets you back to the @value{GDBN} command prompt:
12821 @kbd{@key{RET}~.} (Return, followed by tilde and period) or
12822 @kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D).
12826 @subsection Zilog Z8000
12829 @cindex simulator, Z8000
12830 @cindex Zilog Z8000 simulator
12832 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
12835 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
12836 unsegmented variant of the Z8000 architecture) or the Z8001 (the
12837 segmented variant). The simulator recognizes which architecture is
12838 appropriate by inspecting the object code.
12841 @item target sim @var{args}
12843 @kindex target sim@r{, with Z8000}
12844 Debug programs on a simulated CPU. If the simulator supports setup
12845 options, specify them via @var{args}.
12849 After specifying this target, you can debug programs for the simulated
12850 CPU in the same style as programs for your host computer; use the
12851 @code{file} command to load a new program image, the @code{run} command
12852 to run your program, and so on.
12854 As well as making available all the usual machine registers
12855 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
12856 additional items of information as specially named registers:
12861 Counts clock-ticks in the simulator.
12864 Counts instructions run in the simulator.
12867 Execution time in 60ths of a second.
12871 You can refer to these values in @value{GDBN} expressions with the usual
12872 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
12873 conditional breakpoint that suspends only after at least 5000
12874 simulated clock ticks.
12876 @node Architectures
12877 @section Architectures
12879 This section describes characteristics of architectures that affect
12880 all uses of @value{GDBN} with the architecture, both native and cross.
12893 @kindex set rstack_high_address
12894 @cindex AMD 29K register stack
12895 @cindex register stack, AMD29K
12896 @item set rstack_high_address @var{address}
12897 On AMD 29000 family processors, registers are saved in a separate
12898 @dfn{register stack}. There is no way for @value{GDBN} to determine the
12899 extent of this stack. Normally, @value{GDBN} just assumes that the
12900 stack is ``large enough''. This may result in @value{GDBN} referencing
12901 memory locations that do not exist. If necessary, you can get around
12902 this problem by specifying the ending address of the register stack with
12903 the @code{set rstack_high_address} command. The argument should be an
12904 address, which you probably want to precede with @samp{0x} to specify in
12907 @kindex show rstack_high_address
12908 @item show rstack_high_address
12909 Display the current limit of the register stack, on AMD 29000 family
12917 See the following section.
12922 @cindex stack on Alpha
12923 @cindex stack on MIPS
12924 @cindex Alpha stack
12926 Alpha- and MIPS-based computers use an unusual stack frame, which
12927 sometimes requires @value{GDBN} to search backward in the object code to
12928 find the beginning of a function.
12930 @cindex response time, MIPS debugging
12931 To improve response time (especially for embedded applications, where
12932 @value{GDBN} may be restricted to a slow serial line for this search)
12933 you may want to limit the size of this search, using one of these
12937 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
12938 @item set heuristic-fence-post @var{limit}
12939 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
12940 search for the beginning of a function. A value of @var{0} (the
12941 default) means there is no limit. However, except for @var{0}, the
12942 larger the limit the more bytes @code{heuristic-fence-post} must search
12943 and therefore the longer it takes to run.
12945 @item show heuristic-fence-post
12946 Display the current limit.
12950 These commands are available @emph{only} when @value{GDBN} is configured
12951 for debugging programs on Alpha or MIPS processors.
12954 @node Controlling GDB
12955 @chapter Controlling @value{GDBN}
12957 You can alter the way @value{GDBN} interacts with you by using the
12958 @code{set} command. For commands controlling how @value{GDBN} displays
12959 data, see @ref{Print Settings, ,Print settings}. Other settings are
12964 * Editing:: Command editing
12965 * History:: Command history
12966 * Screen Size:: Screen size
12967 * Numbers:: Numbers
12968 * ABI:: Configuring the current ABI
12969 * Messages/Warnings:: Optional warnings and messages
12970 * Debugging Output:: Optional messages about internal happenings
12978 @value{GDBN} indicates its readiness to read a command by printing a string
12979 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
12980 can change the prompt string with the @code{set prompt} command. For
12981 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
12982 the prompt in one of the @value{GDBN} sessions so that you can always tell
12983 which one you are talking to.
12985 @emph{Note:} @code{set prompt} does not add a space for you after the
12986 prompt you set. This allows you to set a prompt which ends in a space
12987 or a prompt that does not.
12991 @item set prompt @var{newprompt}
12992 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
12994 @kindex show prompt
12996 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
13000 @section Command editing
13002 @cindex command line editing
13004 @value{GDBN} reads its input commands via the @dfn{readline} interface. This
13005 @sc{gnu} library provides consistent behavior for programs which provide a
13006 command line interface to the user. Advantages are @sc{gnu} Emacs-style
13007 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
13008 substitution, and a storage and recall of command history across
13009 debugging sessions.
13011 You may control the behavior of command line editing in @value{GDBN} with the
13012 command @code{set}.
13015 @kindex set editing
13018 @itemx set editing on
13019 Enable command line editing (enabled by default).
13021 @item set editing off
13022 Disable command line editing.
13024 @kindex show editing
13026 Show whether command line editing is enabled.
13030 @section Command history
13032 @value{GDBN} can keep track of the commands you type during your
13033 debugging sessions, so that you can be certain of precisely what
13034 happened. Use these commands to manage the @value{GDBN} command
13038 @cindex history substitution
13039 @cindex history file
13040 @kindex set history filename
13041 @kindex GDBHISTFILE
13042 @item set history filename @var{fname}
13043 Set the name of the @value{GDBN} command history file to @var{fname}.
13044 This is the file where @value{GDBN} reads an initial command history
13045 list, and where it writes the command history from this session when it
13046 exits. You can access this list through history expansion or through
13047 the history command editing characters listed below. This file defaults
13048 to the value of the environment variable @code{GDBHISTFILE}, or to
13049 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
13052 @cindex history save
13053 @kindex set history save
13054 @item set history save
13055 @itemx set history save on
13056 Record command history in a file, whose name may be specified with the
13057 @code{set history filename} command. By default, this option is disabled.
13059 @item set history save off
13060 Stop recording command history in a file.
13062 @cindex history size
13063 @kindex set history size
13064 @item set history size @var{size}
13065 Set the number of commands which @value{GDBN} keeps in its history list.
13066 This defaults to the value of the environment variable
13067 @code{HISTSIZE}, or to 256 if this variable is not set.
13070 @cindex history expansion
13071 History expansion assigns special meaning to the character @kbd{!}.
13072 @ifset have-readline-appendices
13073 @xref{Event Designators}.
13076 Since @kbd{!} is also the logical not operator in C, history expansion
13077 is off by default. If you decide to enable history expansion with the
13078 @code{set history expansion on} command, you may sometimes need to
13079 follow @kbd{!} (when it is used as logical not, in an expression) with
13080 a space or a tab to prevent it from being expanded. The readline
13081 history facilities do not attempt substitution on the strings
13082 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
13084 The commands to control history expansion are:
13087 @kindex set history expansion
13088 @item set history expansion on
13089 @itemx set history expansion
13090 Enable history expansion. History expansion is off by default.
13092 @item set history expansion off
13093 Disable history expansion.
13095 The readline code comes with more complete documentation of
13096 editing and history expansion features. Users unfamiliar with @sc{gnu} Emacs
13097 or @code{vi} may wish to read it.
13098 @ifset have-readline-appendices
13099 @xref{Command Line Editing}.
13103 @kindex show history
13105 @itemx show history filename
13106 @itemx show history save
13107 @itemx show history size
13108 @itemx show history expansion
13109 These commands display the state of the @value{GDBN} history parameters.
13110 @code{show history} by itself displays all four states.
13116 @item show commands
13117 Display the last ten commands in the command history.
13119 @item show commands @var{n}
13120 Print ten commands centered on command number @var{n}.
13122 @item show commands +
13123 Print ten commands just after the commands last printed.
13127 @section Screen size
13128 @cindex size of screen
13129 @cindex pauses in output
13131 Certain commands to @value{GDBN} may produce large amounts of
13132 information output to the screen. To help you read all of it,
13133 @value{GDBN} pauses and asks you for input at the end of each page of
13134 output. Type @key{RET} when you want to continue the output, or @kbd{q}
13135 to discard the remaining output. Also, the screen width setting
13136 determines when to wrap lines of output. Depending on what is being
13137 printed, @value{GDBN} tries to break the line at a readable place,
13138 rather than simply letting it overflow onto the following line.
13140 Normally @value{GDBN} knows the size of the screen from the terminal
13141 driver software. For example, on Unix @value{GDBN} uses the termcap data base
13142 together with the value of the @code{TERM} environment variable and the
13143 @code{stty rows} and @code{stty cols} settings. If this is not correct,
13144 you can override it with the @code{set height} and @code{set
13151 @kindex show height
13152 @item set height @var{lpp}
13154 @itemx set width @var{cpl}
13156 These @code{set} commands specify a screen height of @var{lpp} lines and
13157 a screen width of @var{cpl} characters. The associated @code{show}
13158 commands display the current settings.
13160 If you specify a height of zero lines, @value{GDBN} does not pause during
13161 output no matter how long the output is. This is useful if output is to a
13162 file or to an editor buffer.
13164 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
13165 from wrapping its output.
13170 @cindex number representation
13171 @cindex entering numbers
13173 You can always enter numbers in octal, decimal, or hexadecimal in
13174 @value{GDBN} by the usual conventions: octal numbers begin with
13175 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
13176 begin with @samp{0x}. Numbers that begin with none of these are, by
13177 default, entered in base 10; likewise, the default display for
13178 numbers---when no particular format is specified---is base 10. You can
13179 change the default base for both input and output with the @code{set
13183 @kindex set input-radix
13184 @item set input-radix @var{base}
13185 Set the default base for numeric input. Supported choices
13186 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
13187 specified either unambiguously or using the current default radix; for
13197 sets the base to decimal. On the other hand, @samp{set radix 10}
13198 leaves the radix unchanged no matter what it was.
13200 @kindex set output-radix
13201 @item set output-radix @var{base}
13202 Set the default base for numeric display. 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.
13206 @kindex show input-radix
13207 @item show input-radix
13208 Display the current default base for numeric input.
13210 @kindex show output-radix
13211 @item show output-radix
13212 Display the current default base for numeric display.
13216 @section Configuring the current ABI
13218 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
13219 application automatically. However, sometimes you need to override its
13220 conclusions. Use these commands to manage @value{GDBN}'s view of the
13227 One @value{GDBN} configuration can debug binaries for multiple operating
13228 system targets, either via remote debugging or native emulation.
13229 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
13230 but you can override its conclusion using the @code{set osabi} command.
13231 One example where this is useful is in debugging of binaries which use
13232 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
13233 not have the same identifying marks that the standard C library for your
13238 Show the OS ABI currently in use.
13241 With no argument, show the list of registered available OS ABI's.
13243 @item set osabi @var{abi}
13244 Set the current OS ABI to @var{abi}.
13247 @cindex float promotion
13248 @kindex set coerce-float-to-double
13250 Generally, the way that an argument of type @code{float} is passed to a
13251 function depends on whether the function is prototyped. For a prototyped
13252 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
13253 according to the architecture's convention for @code{float}. For unprototyped
13254 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
13255 @code{double} and then passed.
13257 Unfortunately, some forms of debug information do not reliably indicate whether
13258 a function is prototyped. If @value{GDBN} calls a function that is not marked
13259 as prototyped, it consults @kbd{set coerce-float-to-double}.
13262 @item set coerce-float-to-double
13263 @itemx set coerce-float-to-double on
13264 Arguments of type @code{float} will be promoted to @code{double} when passed
13265 to an unprototyped function. This is the default setting.
13267 @item set coerce-float-to-double off
13268 Arguments of type @code{float} will be passed directly to unprototyped
13273 @kindex show cp-abi
13274 @value{GDBN} needs to know the ABI used for your program's C@t{++}
13275 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
13276 used to build your application. @value{GDBN} only fully supports
13277 programs with a single C@t{++} ABI; if your program contains code using
13278 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
13279 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
13280 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
13281 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
13282 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
13283 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
13288 Show the C@t{++} ABI currently in use.
13291 With no argument, show the list of supported C@t{++} ABI's.
13293 @item set cp-abi @var{abi}
13294 @itemx set cp-abi auto
13295 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
13298 @node Messages/Warnings
13299 @section Optional warnings and messages
13301 By default, @value{GDBN} is silent about its inner workings. If you are
13302 running on a slow machine, you may want to use the @code{set verbose}
13303 command. This makes @value{GDBN} tell you when it does a lengthy
13304 internal operation, so you will not think it has crashed.
13306 Currently, the messages controlled by @code{set verbose} are those
13307 which announce that the symbol table for a source file is being read;
13308 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
13311 @kindex set verbose
13312 @item set verbose on
13313 Enables @value{GDBN} output of certain informational messages.
13315 @item set verbose off
13316 Disables @value{GDBN} output of certain informational messages.
13318 @kindex show verbose
13320 Displays whether @code{set verbose} is on or off.
13323 By default, if @value{GDBN} encounters bugs in the symbol table of an
13324 object file, it is silent; but if you are debugging a compiler, you may
13325 find this information useful (@pxref{Symbol Errors, ,Errors reading
13330 @kindex set complaints
13331 @item set complaints @var{limit}
13332 Permits @value{GDBN} to output @var{limit} complaints about each type of
13333 unusual symbols before becoming silent about the problem. Set
13334 @var{limit} to zero to suppress all complaints; set it to a large number
13335 to prevent complaints from being suppressed.
13337 @kindex show complaints
13338 @item show complaints
13339 Displays how many symbol complaints @value{GDBN} is permitted to produce.
13343 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
13344 lot of stupid questions to confirm certain commands. For example, if
13345 you try to run a program which is already running:
13349 The program being debugged has been started already.
13350 Start it from the beginning? (y or n)
13353 If you are willing to unflinchingly face the consequences of your own
13354 commands, you can disable this ``feature'':
13358 @kindex set confirm
13360 @cindex confirmation
13361 @cindex stupid questions
13362 @item set confirm off
13363 Disables confirmation requests.
13365 @item set confirm on
13366 Enables confirmation requests (the default).
13368 @kindex show confirm
13370 Displays state of confirmation requests.
13374 @node Debugging Output
13375 @section Optional messages about internal happenings
13377 @kindex set debug arch
13378 @item set debug arch
13379 Turns on or off display of gdbarch debugging info. The default is off
13380 @kindex show debug arch
13381 @item show debug arch
13382 Displays the current state of displaying gdbarch debugging info.
13383 @kindex set debug event
13384 @item set debug event
13385 Turns on or off display of @value{GDBN} event debugging info. The
13387 @kindex show debug event
13388 @item show debug event
13389 Displays the current state of displaying @value{GDBN} event debugging
13391 @kindex set debug expression
13392 @item set debug expression
13393 Turns on or off display of @value{GDBN} expression debugging info. The
13395 @kindex show debug expression
13396 @item show debug expression
13397 Displays the current state of displaying @value{GDBN} expression
13399 @kindex set debug frame
13400 @item set debug frame
13401 Turns on or off display of @value{GDBN} frame debugging info. The
13403 @kindex show debug frame
13404 @item show debug frame
13405 Displays the current state of displaying @value{GDBN} frame debugging
13407 @kindex set debug observer
13408 @item set debug observer
13409 Turns on or off display of @value{GDBN} observer debugging. This
13410 includes info such as the notification of observable events.
13411 @kindex show debug observer
13412 @item show debug observer
13413 Displays the current state of observer debugging.
13414 @kindex set debug overload
13415 @item set debug overload
13416 Turns on or off display of @value{GDBN} C@t{++} overload debugging
13417 info. This includes info such as ranking of functions, etc. The default
13419 @kindex show debug overload
13420 @item show debug overload
13421 Displays the current state of displaying @value{GDBN} C@t{++} overload
13423 @kindex set debug remote
13424 @cindex packets, reporting on stdout
13425 @cindex serial connections, debugging
13426 @item set debug remote
13427 Turns on or off display of reports on all packets sent back and forth across
13428 the serial line to the remote machine. The info is printed on the
13429 @value{GDBN} standard output stream. The default is off.
13430 @kindex show debug remote
13431 @item show debug remote
13432 Displays the state of display of remote packets.
13433 @kindex set debug serial
13434 @item set debug serial
13435 Turns on or off display of @value{GDBN} serial debugging info. The
13437 @kindex show debug serial
13438 @item show debug serial
13439 Displays the current state of displaying @value{GDBN} serial debugging
13441 @kindex set debug target
13442 @item set debug target
13443 Turns on or off display of @value{GDBN} target debugging info. This info
13444 includes what is going on at the target level of GDB, as it happens. The
13445 default is 0. Set it to 1 to track events, and to 2 to also track the
13446 value of large memory transfers. Changes to this flag do not take effect
13447 until the next time you connect to a target or use the @code{run} command.
13448 @kindex show debug target
13449 @item show debug target
13450 Displays the current state of displaying @value{GDBN} target debugging
13452 @kindex set debug varobj
13453 @item set debug varobj
13454 Turns on or off display of @value{GDBN} variable object debugging
13455 info. The default is off.
13456 @kindex show debug varobj
13457 @item show debug varobj
13458 Displays the current state of displaying @value{GDBN} variable object
13463 @chapter Canned Sequences of Commands
13465 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
13466 command lists}), @value{GDBN} provides two ways to store sequences of
13467 commands for execution as a unit: user-defined commands and command
13471 * Define:: User-defined commands
13472 * Hooks:: User-defined command hooks
13473 * Command Files:: Command files
13474 * Output:: Commands for controlled output
13478 @section User-defined commands
13480 @cindex user-defined command
13481 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
13482 which you assign a new name as a command. This is done with the
13483 @code{define} command. User commands may accept up to 10 arguments
13484 separated by whitespace. Arguments are accessed within the user command
13485 via @var{$arg0@dots{}$arg9}. A trivial example:
13489 print $arg0 + $arg1 + $arg2
13493 To execute the command use:
13500 This defines the command @code{adder}, which prints the sum of
13501 its three arguments. Note the arguments are text substitutions, so they may
13502 reference variables, use complex expressions, or even perform inferior
13508 @item define @var{commandname}
13509 Define a command named @var{commandname}. If there is already a command
13510 by that name, you are asked to confirm that you want to redefine it.
13512 The definition of the command is made up of other @value{GDBN} command lines,
13513 which are given following the @code{define} command. The end of these
13514 commands is marked by a line containing @code{end}.
13519 Takes a single argument, which is an expression to evaluate.
13520 It is followed by a series of commands that are executed
13521 only if the expression is true (nonzero).
13522 There can then optionally be a line @code{else}, followed
13523 by a series of commands that are only executed if the expression
13524 was false. The end of the list is marked by a line containing @code{end}.
13528 The syntax is similar to @code{if}: the command takes a single argument,
13529 which is an expression to evaluate, and must be followed by the commands to
13530 execute, one per line, terminated by an @code{end}.
13531 The commands are executed repeatedly as long as the expression
13535 @item document @var{commandname}
13536 Document the user-defined command @var{commandname}, so that it can be
13537 accessed by @code{help}. The command @var{commandname} must already be
13538 defined. This command reads lines of documentation just as @code{define}
13539 reads the lines of the command definition, ending with @code{end}.
13540 After the @code{document} command is finished, @code{help} on command
13541 @var{commandname} displays the documentation you have written.
13543 You may use the @code{document} command again to change the
13544 documentation of a command. Redefining the command with @code{define}
13545 does not change the documentation.
13547 @kindex help user-defined
13548 @item help user-defined
13549 List all user-defined commands, with the first line of the documentation
13554 @itemx show user @var{commandname}
13555 Display the @value{GDBN} commands used to define @var{commandname} (but
13556 not its documentation). If no @var{commandname} is given, display the
13557 definitions for all user-defined commands.
13559 @kindex show max-user-call-depth
13560 @kindex set max-user-call-depth
13561 @item show max-user-call-depth
13562 @itemx set max-user-call-depth
13563 The value of @code{max-user-call-depth} controls how many recursion
13564 levels are allowed in user-defined commands before GDB suspects an
13565 infinite recursion and aborts the command.
13569 When user-defined commands are executed, the
13570 commands of the definition are not printed. An error in any command
13571 stops execution of the user-defined command.
13573 If used interactively, commands that would ask for confirmation proceed
13574 without asking when used inside a user-defined command. Many @value{GDBN}
13575 commands that normally print messages to say what they are doing omit the
13576 messages when used in a user-defined command.
13579 @section User-defined command hooks
13580 @cindex command hooks
13581 @cindex hooks, for commands
13582 @cindex hooks, pre-command
13586 You may define @dfn{hooks}, which are a special kind of user-defined
13587 command. Whenever you run the command @samp{foo}, if the user-defined
13588 command @samp{hook-foo} exists, it is executed (with no arguments)
13589 before that command.
13591 @cindex hooks, post-command
13594 A hook may also be defined which is run after the command you executed.
13595 Whenever you run the command @samp{foo}, if the user-defined command
13596 @samp{hookpost-foo} exists, it is executed (with no arguments) after
13597 that command. Post-execution hooks may exist simultaneously with
13598 pre-execution hooks, for the same command.
13600 It is valid for a hook to call the command which it hooks. If this
13601 occurs, the hook is not re-executed, thereby avoiding infinte recursion.
13603 @c It would be nice if hookpost could be passed a parameter indicating
13604 @c if the command it hooks executed properly or not. FIXME!
13606 @kindex stop@r{, a pseudo-command}
13607 In addition, a pseudo-command, @samp{stop} exists. Defining
13608 (@samp{hook-stop}) makes the associated commands execute every time
13609 execution stops in your program: before breakpoint commands are run,
13610 displays are printed, or the stack frame is printed.
13612 For example, to ignore @code{SIGALRM} signals while
13613 single-stepping, but treat them normally during normal execution,
13618 handle SIGALRM nopass
13622 handle SIGALRM pass
13625 define hook-continue
13626 handle SIGLARM pass
13630 As a further example, to hook at the begining and end of the @code{echo}
13631 command, and to add extra text to the beginning and end of the message,
13639 define hookpost-echo
13643 (@value{GDBP}) echo Hello World
13644 <<<---Hello World--->>>
13649 You can define a hook for any single-word command in @value{GDBN}, but
13650 not for command aliases; you should define a hook for the basic command
13651 name, e.g. @code{backtrace} rather than @code{bt}.
13652 @c FIXME! So how does Joe User discover whether a command is an alias
13654 If an error occurs during the execution of your hook, execution of
13655 @value{GDBN} commands stops and @value{GDBN} issues a prompt
13656 (before the command that you actually typed had a chance to run).
13658 If you try to define a hook which does not match any known command, you
13659 get a warning from the @code{define} command.
13661 @node Command Files
13662 @section Command files
13664 @cindex command files
13665 A command file for @value{GDBN} is a file of lines that are @value{GDBN}
13666 commands. Comments (lines starting with @kbd{#}) may also be included.
13667 An empty line in a command file does nothing; it does not mean to repeat
13668 the last command, as it would from the terminal.
13671 @cindex @file{.gdbinit}
13672 @cindex @file{gdb.ini}
13673 When you start @value{GDBN}, it automatically executes commands from its
13674 @dfn{init files}, normally called @file{.gdbinit}@footnote{The DJGPP
13675 port of @value{GDBN} uses the name @file{gdb.ini} instead, due to the
13676 limitations of file names imposed by DOS filesystems.}.
13677 During startup, @value{GDBN} does the following:
13681 Reads the init file (if any) in your home directory@footnote{On
13682 DOS/Windows systems, the home directory is the one pointed to by the
13683 @code{HOME} environment variable.}.
13686 Processes command line options and operands.
13689 Reads the init file (if any) in the current working directory.
13692 Reads command files specified by the @samp{-x} option.
13695 The init file in your home directory can set options (such as @samp{set
13696 complaints}) that affect subsequent processing of command line options
13697 and operands. Init files are not executed if you use the @samp{-nx}
13698 option (@pxref{Mode Options, ,Choosing modes}).
13700 @cindex init file name
13701 On some configurations of @value{GDBN}, the init file is known by a
13702 different name (these are typically environments where a specialized
13703 form of @value{GDBN} may need to coexist with other forms, hence a
13704 different name for the specialized version's init file). These are the
13705 environments with special init file names:
13707 @cindex @file{.vxgdbinit}
13710 VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit}
13712 @cindex @file{.os68gdbinit}
13714 OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit}
13716 @cindex @file{.esgdbinit}
13718 ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit}
13721 You can also request the execution of a command file with the
13722 @code{source} command:
13726 @item source @var{filename}
13727 Execute the command file @var{filename}.
13730 The lines in a command file are executed sequentially. They are not
13731 printed as they are executed. An error in any command terminates
13732 execution of the command file and control is returned to the console.
13734 Commands that would ask for confirmation if used interactively proceed
13735 without asking when used in a command file. Many @value{GDBN} commands that
13736 normally print messages to say what they are doing omit the messages
13737 when called from command files.
13739 @value{GDBN} also accepts command input from standard input. In this
13740 mode, normal output goes to standard output and error output goes to
13741 standard error. Errors in a command file supplied on standard input do
13742 not terminate execution of the command file --- execution continues with
13746 gdb < cmds > log 2>&1
13749 (The syntax above will vary depending on the shell used.) This example
13750 will execute commands from the file @file{cmds}. All output and errors
13751 would be directed to @file{log}.
13754 @section Commands for controlled output
13756 During the execution of a command file or a user-defined command, normal
13757 @value{GDBN} output is suppressed; the only output that appears is what is
13758 explicitly printed by the commands in the definition. This section
13759 describes three commands useful for generating exactly the output you
13764 @item echo @var{text}
13765 @c I do not consider backslash-space a standard C escape sequence
13766 @c because it is not in ANSI.
13767 Print @var{text}. Nonprinting characters can be included in
13768 @var{text} using C escape sequences, such as @samp{\n} to print a
13769 newline. @strong{No newline is printed unless you specify one.}
13770 In addition to the standard C escape sequences, a backslash followed
13771 by a space stands for a space. This is useful for displaying a
13772 string with spaces at the beginning or the end, since leading and
13773 trailing spaces are otherwise trimmed from all arguments.
13774 To print @samp{@w{ }and foo =@w{ }}, use the command
13775 @samp{echo \@w{ }and foo = \@w{ }}.
13777 A backslash at the end of @var{text} can be used, as in C, to continue
13778 the command onto subsequent lines. For example,
13781 echo This is some text\n\
13782 which is continued\n\
13783 onto several lines.\n
13786 produces the same output as
13789 echo This is some text\n
13790 echo which is continued\n
13791 echo onto several lines.\n
13795 @item output @var{expression}
13796 Print the value of @var{expression} and nothing but that value: no
13797 newlines, no @samp{$@var{nn} = }. The value is not entered in the
13798 value history either. @xref{Expressions, ,Expressions}, for more information
13801 @item output/@var{fmt} @var{expression}
13802 Print the value of @var{expression} in format @var{fmt}. You can use
13803 the same formats as for @code{print}. @xref{Output Formats,,Output
13804 formats}, for more information.
13807 @item printf @var{string}, @var{expressions}@dots{}
13808 Print the values of the @var{expressions} under the control of
13809 @var{string}. The @var{expressions} are separated by commas and may be
13810 either numbers or pointers. Their values are printed as specified by
13811 @var{string}, exactly as if your program were to execute the C
13813 @c FIXME: the above implies that at least all ANSI C formats are
13814 @c supported, but it isn't true: %E and %G don't work (or so it seems).
13815 @c Either this is a bug, or the manual should document what formats are
13819 printf (@var{string}, @var{expressions}@dots{});
13822 For example, you can print two values in hex like this:
13825 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
13828 The only backslash-escape sequences that you can use in the format
13829 string are the simple ones that consist of backslash followed by a
13834 @chapter Command Interpreters
13835 @cindex command interpreters
13837 @value{GDBN} supports multiple command interpreters, and some command
13838 infrastructure to allow users or user interface writers to switch
13839 between interpreters or run commands in other interpreters.
13841 @value{GDBN} currently supports two command interpreters, the console
13842 interpreter (sometimes called the command-line interpreter or @sc{cli})
13843 and the machine interface interpreter (or @sc{gdb/mi}). This manual
13844 describes both of these interfaces in great detail.
13846 By default, @value{GDBN} will start with the console interpreter.
13847 However, the user may choose to start @value{GDBN} with another
13848 interpreter by specifying the @option{-i} or @option{--interpreter}
13849 startup options. Defined interpreters include:
13853 @cindex console interpreter
13854 The traditional console or command-line interpreter. This is the most often
13855 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
13856 @value{GDBN} will use this interpreter.
13859 @cindex mi interpreter
13860 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
13861 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
13862 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
13866 @cindex mi2 interpreter
13867 The current @sc{gdb/mi} interface.
13870 @cindex mi1 interpreter
13871 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
13875 @cindex invoke another interpreter
13876 The interpreter being used by @value{GDBN} may not be dynamically
13877 switched at runtime. Although possible, this could lead to a very
13878 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
13879 enters the command "interpreter-set console" in a console view,
13880 @value{GDBN} would switch to using the console interpreter, rendering
13881 the IDE inoperable!
13883 @kindex interpreter-exec
13884 Although you may only choose a single interpreter at startup, you may execute
13885 commands in any interpreter from the current interpreter using the appropriate
13886 command. If you are running the console interpreter, simply use the
13887 @code{interpreter-exec} command:
13890 interpreter-exec mi "-data-list-register-names"
13893 @sc{gdb/mi} has a similar command, although it is only available in versions of
13894 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
13897 @chapter @value{GDBN} Text User Interface
13899 @cindex Text User Interface
13902 * TUI Overview:: TUI overview
13903 * TUI Keys:: TUI key bindings
13904 * TUI Single Key Mode:: TUI single key mode
13905 * TUI Commands:: TUI specific commands
13906 * TUI Configuration:: TUI configuration variables
13909 The @value{GDBN} Text User Interface, TUI in short, is a terminal
13910 interface which uses the @code{curses} library to show the source
13911 file, the assembly output, the program registers and @value{GDBN}
13912 commands in separate text windows.
13914 The TUI is enabled by invoking @value{GDBN} using either
13916 @samp{gdbtui} or @samp{gdb -tui}.
13919 @section TUI overview
13921 The TUI has two display modes that can be switched while
13926 A curses (or TUI) mode in which it displays several text
13927 windows on the terminal.
13930 A standard mode which corresponds to the @value{GDBN} configured without
13934 In the TUI mode, @value{GDBN} can display several text window
13939 This window is the @value{GDBN} command window with the @value{GDBN}
13940 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
13941 managed using readline but through the TUI. The @emph{command}
13942 window is always visible.
13945 The source window shows the source file of the program. The current
13946 line as well as active breakpoints are displayed in this window.
13949 The assembly window shows the disassembly output of the program.
13952 This window shows the processor registers. It detects when
13953 a register is changed and when this is the case, registers that have
13954 changed are highlighted.
13958 The source and assembly windows show the current program position
13959 by highlighting the current line and marking them with the @samp{>} marker.
13960 Breakpoints are also indicated with two markers. A first one
13961 indicates the breakpoint type:
13965 Breakpoint which was hit at least once.
13968 Breakpoint which was never hit.
13971 Hardware breakpoint which was hit at least once.
13974 Hardware breakpoint which was never hit.
13978 The second marker indicates whether the breakpoint is enabled or not:
13982 Breakpoint is enabled.
13985 Breakpoint is disabled.
13989 The source, assembly and register windows are attached to the thread
13990 and the frame position. They are updated when the current thread
13991 changes, when the frame changes or when the program counter changes.
13992 These three windows are arranged by the TUI according to several
13993 layouts. The layout defines which of these three windows are visible.
13994 The following layouts are available:
14004 source and assembly
14007 source and registers
14010 assembly and registers
14014 On top of the command window a status line gives various information
14015 concerning the current process begin debugged. The status line is
14016 updated when the information it shows changes. The following fields
14021 Indicates the current gdb target
14022 (@pxref{Targets, ,Specifying a Debugging Target}).
14025 Gives information about the current process or thread number.
14026 When no process is being debugged, this field is set to @code{No process}.
14029 Gives the current function name for the selected frame.
14030 The name is demangled if demangling is turned on (@pxref{Print Settings}).
14031 When there is no symbol corresponding to the current program counter
14032 the string @code{??} is displayed.
14035 Indicates the current line number for the selected frame.
14036 When the current line number is not known the string @code{??} is displayed.
14039 Indicates the current program counter address.
14044 @section TUI Key Bindings
14045 @cindex TUI key bindings
14047 The TUI installs several key bindings in the readline keymaps
14048 (@pxref{Command Line Editing}).
14049 They allow to leave or enter in the TUI mode or they operate
14050 directly on the TUI layout and windows. The TUI also provides
14051 a @emph{SingleKey} keymap which binds several keys directly to
14052 @value{GDBN} commands. The following key bindings
14053 are installed for both TUI mode and the @value{GDBN} standard mode.
14062 Enter or leave the TUI mode. When the TUI mode is left,
14063 the curses window management is left and @value{GDBN} operates using
14064 its standard mode writing on the terminal directly. When the TUI
14065 mode is entered, the control is given back to the curses windows.
14066 The screen is then refreshed.
14070 Use a TUI layout with only one window. The layout will
14071 either be @samp{source} or @samp{assembly}. When the TUI mode
14072 is not active, it will switch to the TUI mode.
14074 Think of this key binding as the Emacs @kbd{C-x 1} binding.
14078 Use a TUI layout with at least two windows. When the current
14079 layout shows already two windows, a next layout with two windows is used.
14080 When a new layout is chosen, one window will always be common to the
14081 previous layout and the new one.
14083 Think of it as the Emacs @kbd{C-x 2} binding.
14087 Change the active window. The TUI associates several key bindings
14088 (like scrolling and arrow keys) to the active window. This command
14089 gives the focus to the next TUI window.
14091 Think of it as the Emacs @kbd{C-x o} binding.
14095 Use the TUI @emph{SingleKey} keymap that binds single key to gdb commands
14096 (@pxref{TUI Single Key Mode}).
14100 The following key bindings are handled only by the TUI mode:
14105 Scroll the active window one page up.
14109 Scroll the active window one page down.
14113 Scroll the active window one line up.
14117 Scroll the active window one line down.
14121 Scroll the active window one column left.
14125 Scroll the active window one column right.
14129 Refresh the screen.
14133 In the TUI mode, the arrow keys are used by the active window
14134 for scrolling. This means they are available for readline when the
14135 active window is the command window. When the command window
14136 does not have the focus, it is necessary to use other readline
14137 key bindings such as @key{C-p}, @key{C-n}, @key{C-b} and @key{C-f}.
14139 @node TUI Single Key Mode
14140 @section TUI Single Key Mode
14141 @cindex TUI single key mode
14143 The TUI provides a @emph{SingleKey} mode in which it installs a particular
14144 key binding in the readline keymaps to connect single keys to
14148 @kindex c @r{(SingleKey TUI key)}
14152 @kindex d @r{(SingleKey TUI key)}
14156 @kindex f @r{(SingleKey TUI key)}
14160 @kindex n @r{(SingleKey TUI key)}
14164 @kindex q @r{(SingleKey TUI key)}
14166 exit the @emph{SingleKey} mode.
14168 @kindex r @r{(SingleKey TUI key)}
14172 @kindex s @r{(SingleKey TUI key)}
14176 @kindex u @r{(SingleKey TUI key)}
14180 @kindex v @r{(SingleKey TUI key)}
14184 @kindex w @r{(SingleKey TUI key)}
14190 Other keys temporarily switch to the @value{GDBN} command prompt.
14191 The key that was pressed is inserted in the editing buffer so that
14192 it is possible to type most @value{GDBN} commands without interaction
14193 with the TUI @emph{SingleKey} mode. Once the command is entered the TUI
14194 @emph{SingleKey} mode is restored. The only way to permanently leave
14195 this mode is by hitting @key{q} or @samp{@key{C-x} @key{s}}.
14199 @section TUI specific commands
14200 @cindex TUI commands
14202 The TUI has specific commands to control the text windows.
14203 These commands are always available, that is they do not depend on
14204 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
14205 is in the standard mode, using these commands will automatically switch
14211 List and give the size of all displayed windows.
14214 @kindex layout next
14215 Display the next layout.
14218 @kindex layout prev
14219 Display the previous layout.
14223 Display the source window only.
14227 Display the assembly window only.
14230 @kindex layout split
14231 Display the source and assembly window.
14234 @kindex layout regs
14235 Display the register window together with the source or assembly window.
14237 @item focus next | prev | src | asm | regs | split
14239 Set the focus to the named window.
14240 This command allows to change the active window so that scrolling keys
14241 can be affected to another window.
14245 Refresh the screen. This is similar to using @key{C-L} key.
14247 @item tui reg float
14249 Show the floating point registers in the register window.
14251 @item tui reg general
14252 Show the general registers in the register window.
14255 Show the next register group. The list of register groups as well as
14256 their order is target specific. The predefined register groups are the
14257 following: @code{general}, @code{float}, @code{system}, @code{vector},
14258 @code{all}, @code{save}, @code{restore}.
14260 @item tui reg system
14261 Show the system registers in the register window.
14265 Update the source window and the current execution point.
14267 @item winheight @var{name} +@var{count}
14268 @itemx winheight @var{name} -@var{count}
14270 Change the height of the window @var{name} by @var{count}
14271 lines. Positive counts increase the height, while negative counts
14276 @node TUI Configuration
14277 @section TUI configuration variables
14278 @cindex TUI configuration variables
14280 The TUI has several configuration variables that control the
14281 appearance of windows on the terminal.
14284 @item set tui border-kind @var{kind}
14285 @kindex set tui border-kind
14286 Select the border appearance for the source, assembly and register windows.
14287 The possible values are the following:
14290 Use a space character to draw the border.
14293 Use ascii characters + - and | to draw the border.
14296 Use the Alternate Character Set to draw the border. The border is
14297 drawn using character line graphics if the terminal supports them.
14301 @item set tui active-border-mode @var{mode}
14302 @kindex set tui active-border-mode
14303 Select the attributes to display the border of the active window.
14304 The possible values are @code{normal}, @code{standout}, @code{reverse},
14305 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
14307 @item set tui border-mode @var{mode}
14308 @kindex set tui border-mode
14309 Select the attributes to display the border of other windows.
14310 The @var{mode} can be one of the following:
14313 Use normal attributes to display the border.
14319 Use reverse video mode.
14322 Use half bright mode.
14324 @item half-standout
14325 Use half bright and standout mode.
14328 Use extra bright or bold mode.
14330 @item bold-standout
14331 Use extra bright or bold and standout mode.
14338 @chapter Using @value{GDBN} under @sc{gnu} Emacs
14341 @cindex @sc{gnu} Emacs
14342 A special interface allows you to use @sc{gnu} Emacs to view (and
14343 edit) the source files for the program you are debugging with
14346 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
14347 executable file you want to debug as an argument. This command starts
14348 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
14349 created Emacs buffer.
14350 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
14352 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
14357 All ``terminal'' input and output goes through the Emacs buffer.
14360 This applies both to @value{GDBN} commands and their output, and to the input
14361 and output done by the program you are debugging.
14363 This is useful because it means that you can copy the text of previous
14364 commands and input them again; you can even use parts of the output
14367 All the facilities of Emacs' Shell mode are available for interacting
14368 with your program. In particular, you can send signals the usual
14369 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
14374 @value{GDBN} displays source code through Emacs.
14377 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
14378 source file for that frame and puts an arrow (@samp{=>}) at the
14379 left margin of the current line. Emacs uses a separate buffer for
14380 source display, and splits the screen to show both your @value{GDBN} session
14383 Explicit @value{GDBN} @code{list} or search commands still produce output as
14384 usual, but you probably have no reason to use them from Emacs.
14386 If you specify an absolute file name when prompted for the @kbd{M-x
14387 gdb} argument, then Emacs sets your current working directory to where
14388 your program resides. If you only specify the file name, then Emacs
14389 sets your current working directory to to the directory associated
14390 with the previous buffer. In this case, @value{GDBN} may find your
14391 program by searching your environment's @code{PATH} variable, but on
14392 some operating systems it might not find the source. So, although the
14393 @value{GDBN} input and output session proceeds normally, the auxiliary
14394 buffer does not display the current source and line of execution.
14396 The initial working directory of @value{GDBN} is printed on the top
14397 line of the @value{GDBN} I/O buffer and this serves as a default for
14398 the commands that specify files for @value{GDBN} to operate
14399 on. @xref{Files, ,Commands to specify files}.
14401 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
14402 need to call @value{GDBN} by a different name (for example, if you
14403 keep several configurations around, with different names) you can
14404 customize the Emacs variable @code{gud-gdb-command-name} to run the
14407 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
14408 addition to the standard Shell mode commands:
14412 Describe the features of Emacs' @value{GDBN} Mode.
14415 Execute to another source line, like the @value{GDBN} @code{step} command; also
14416 update the display window to show the current file and location.
14419 Execute to next source line in this function, skipping all function
14420 calls, like the @value{GDBN} @code{next} command. Then update the display window
14421 to show the current file and location.
14424 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
14425 display window accordingly.
14428 Execute until exit from the selected stack frame, like the @value{GDBN}
14429 @code{finish} command.
14432 Continue execution of your program, like the @value{GDBN} @code{continue}
14436 Go up the number of frames indicated by the numeric argument
14437 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
14438 like the @value{GDBN} @code{up} command.
14441 Go down the number of frames indicated by the numeric argument, like the
14442 @value{GDBN} @code{down} command.
14445 In any source file, the Emacs command @kbd{C-x SPC} (@code{gud-break})
14446 tells @value{GDBN} to set a breakpoint on the source line point is on.
14448 If you type @kbd{M-x speedbar}, then Emacs displays a separate frame which
14449 shows a backtrace when the @value{GDBN} I/O buffer is current. Move
14450 point to any frame in the stack and type @key{RET} to make it become the
14451 current frame and display the associated source in the source buffer.
14452 Alternatively, click @kbd{Mouse-2} to make the selected frame become the
14455 If you accidentally delete the source-display buffer, an easy way to get
14456 it back is to type the command @code{f} in the @value{GDBN} buffer, to
14457 request a frame display; when you run under Emacs, this recreates
14458 the source buffer if necessary to show you the context of the current
14461 The source files displayed in Emacs are in ordinary Emacs buffers
14462 which are visiting the source files in the usual way. You can edit
14463 the files with these buffers if you wish; but keep in mind that @value{GDBN}
14464 communicates with Emacs in terms of line numbers. If you add or
14465 delete lines from the text, the line numbers that @value{GDBN} knows cease
14466 to correspond properly with the code.
14468 The description given here is for GNU Emacs version 21.3 and a more
14469 detailed description of its interaction with @value{GDBN} is given in
14470 the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu} Emacs Manual}).
14472 @c The following dropped because Epoch is nonstandard. Reactivate
14473 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
14475 @kindex Emacs Epoch environment
14479 Version 18 of @sc{gnu} Emacs has a built-in window system
14480 called the @code{epoch}
14481 environment. Users of this environment can use a new command,
14482 @code{inspect} which performs identically to @code{print} except that
14483 each value is printed in its own window.
14488 @chapter The @sc{gdb/mi} Interface
14490 @unnumberedsec Function and Purpose
14492 @cindex @sc{gdb/mi}, its purpose
14493 @sc{gdb/mi} is a line based machine oriented text interface to @value{GDBN}. It is
14494 specifically intended to support the development of systems which use
14495 the debugger as just one small component of a larger system.
14497 This chapter is a specification of the @sc{gdb/mi} interface. It is written
14498 in the form of a reference manual.
14500 Note that @sc{gdb/mi} is still under construction, so some of the
14501 features described below are incomplete and subject to change.
14503 @unnumberedsec Notation and Terminology
14505 @cindex notational conventions, for @sc{gdb/mi}
14506 This chapter uses the following notation:
14510 @code{|} separates two alternatives.
14513 @code{[ @var{something} ]} indicates that @var{something} is optional:
14514 it may or may not be given.
14517 @code{( @var{group} )*} means that @var{group} inside the parentheses
14518 may repeat zero or more times.
14521 @code{( @var{group} )+} means that @var{group} inside the parentheses
14522 may repeat one or more times.
14525 @code{"@var{string}"} means a literal @var{string}.
14529 @heading Dependencies
14532 @heading Acknowledgments
14534 In alphabetic order: Andrew Cagney, Fernando Nasser, Stan Shebs and
14538 * GDB/MI Command Syntax::
14539 * GDB/MI Compatibility with CLI::
14540 * GDB/MI Output Records::
14541 * GDB/MI Command Description Format::
14542 * GDB/MI Breakpoint Table Commands::
14543 * GDB/MI Data Manipulation::
14544 * GDB/MI Program Control::
14545 * GDB/MI Miscellaneous Commands::
14547 * GDB/MI Kod Commands::
14548 * GDB/MI Memory Overlay Commands::
14549 * GDB/MI Signal Handling Commands::
14551 * GDB/MI Stack Manipulation::
14552 * GDB/MI Symbol Query::
14553 * GDB/MI Target Manipulation::
14554 * GDB/MI Thread Commands::
14555 * GDB/MI Tracepoint Commands::
14556 * GDB/MI Variable Objects::
14559 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14560 @node GDB/MI Command Syntax
14561 @section @sc{gdb/mi} Command Syntax
14564 * GDB/MI Input Syntax::
14565 * GDB/MI Output Syntax::
14566 * GDB/MI Simple Examples::
14569 @node GDB/MI Input Syntax
14570 @subsection @sc{gdb/mi} Input Syntax
14572 @cindex input syntax for @sc{gdb/mi}
14573 @cindex @sc{gdb/mi}, input syntax
14575 @item @var{command} @expansion{}
14576 @code{@var{cli-command} | @var{mi-command}}
14578 @item @var{cli-command} @expansion{}
14579 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
14580 @var{cli-command} is any existing @value{GDBN} CLI command.
14582 @item @var{mi-command} @expansion{}
14583 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
14584 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
14586 @item @var{token} @expansion{}
14587 "any sequence of digits"
14589 @item @var{option} @expansion{}
14590 @code{"-" @var{parameter} [ " " @var{parameter} ]}
14592 @item @var{parameter} @expansion{}
14593 @code{@var{non-blank-sequence} | @var{c-string}}
14595 @item @var{operation} @expansion{}
14596 @emph{any of the operations described in this chapter}
14598 @item @var{non-blank-sequence} @expansion{}
14599 @emph{anything, provided it doesn't contain special characters such as
14600 "-", @var{nl}, """ and of course " "}
14602 @item @var{c-string} @expansion{}
14603 @code{""" @var{seven-bit-iso-c-string-content} """}
14605 @item @var{nl} @expansion{}
14614 The CLI commands are still handled by the @sc{mi} interpreter; their
14615 output is described below.
14618 The @code{@var{token}}, when present, is passed back when the command
14622 Some @sc{mi} commands accept optional arguments as part of the parameter
14623 list. Each option is identified by a leading @samp{-} (dash) and may be
14624 followed by an optional argument parameter. Options occur first in the
14625 parameter list and can be delimited from normal parameters using
14626 @samp{--} (this is useful when some parameters begin with a dash).
14633 We want easy access to the existing CLI syntax (for debugging).
14636 We want it to be easy to spot a @sc{mi} operation.
14639 @node GDB/MI Output Syntax
14640 @subsection @sc{gdb/mi} Output Syntax
14642 @cindex output syntax of @sc{gdb/mi}
14643 @cindex @sc{gdb/mi}, output syntax
14644 The output from @sc{gdb/mi} consists of zero or more out-of-band records
14645 followed, optionally, by a single result record. This result record
14646 is for the most recent command. The sequence of output records is
14647 terminated by @samp{(@value{GDBP})}.
14649 If an input command was prefixed with a @code{@var{token}} then the
14650 corresponding output for that command will also be prefixed by that same
14654 @item @var{output} @expansion{}
14655 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
14657 @item @var{result-record} @expansion{}
14658 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
14660 @item @var{out-of-band-record} @expansion{}
14661 @code{@var{async-record} | @var{stream-record}}
14663 @item @var{async-record} @expansion{}
14664 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
14666 @item @var{exec-async-output} @expansion{}
14667 @code{[ @var{token} ] "*" @var{async-output}}
14669 @item @var{status-async-output} @expansion{}
14670 @code{[ @var{token} ] "+" @var{async-output}}
14672 @item @var{notify-async-output} @expansion{}
14673 @code{[ @var{token} ] "=" @var{async-output}}
14675 @item @var{async-output} @expansion{}
14676 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
14678 @item @var{result-class} @expansion{}
14679 @code{"done" | "running" | "connected" | "error" | "exit"}
14681 @item @var{async-class} @expansion{}
14682 @code{"stopped" | @var{others}} (where @var{others} will be added
14683 depending on the needs---this is still in development).
14685 @item @var{result} @expansion{}
14686 @code{ @var{variable} "=" @var{value}}
14688 @item @var{variable} @expansion{}
14689 @code{ @var{string} }
14691 @item @var{value} @expansion{}
14692 @code{ @var{const} | @var{tuple} | @var{list} }
14694 @item @var{const} @expansion{}
14695 @code{@var{c-string}}
14697 @item @var{tuple} @expansion{}
14698 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
14700 @item @var{list} @expansion{}
14701 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
14702 @var{result} ( "," @var{result} )* "]" }
14704 @item @var{stream-record} @expansion{}
14705 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
14707 @item @var{console-stream-output} @expansion{}
14708 @code{"~" @var{c-string}}
14710 @item @var{target-stream-output} @expansion{}
14711 @code{"@@" @var{c-string}}
14713 @item @var{log-stream-output} @expansion{}
14714 @code{"&" @var{c-string}}
14716 @item @var{nl} @expansion{}
14719 @item @var{token} @expansion{}
14720 @emph{any sequence of digits}.
14728 All output sequences end in a single line containing a period.
14731 The @code{@var{token}} is from the corresponding request. If an execution
14732 command is interrupted by the @samp{-exec-interrupt} command, the
14733 @var{token} associated with the @samp{*stopped} message is the one of the
14734 original execution command, not the one of the interrupt command.
14737 @cindex status output in @sc{gdb/mi}
14738 @var{status-async-output} contains on-going status information about the
14739 progress of a slow operation. It can be discarded. All status output is
14740 prefixed by @samp{+}.
14743 @cindex async output in @sc{gdb/mi}
14744 @var{exec-async-output} contains asynchronous state change on the target
14745 (stopped, started, disappeared). All async output is prefixed by
14749 @cindex notify output in @sc{gdb/mi}
14750 @var{notify-async-output} contains supplementary information that the
14751 client should handle (e.g., a new breakpoint information). All notify
14752 output is prefixed by @samp{=}.
14755 @cindex console output in @sc{gdb/mi}
14756 @var{console-stream-output} is output that should be displayed as is in the
14757 console. It is the textual response to a CLI command. All the console
14758 output is prefixed by @samp{~}.
14761 @cindex target output in @sc{gdb/mi}
14762 @var{target-stream-output} is the output produced by the target program.
14763 All the target output is prefixed by @samp{@@}.
14766 @cindex log output in @sc{gdb/mi}
14767 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
14768 instance messages that should be displayed as part of an error log. All
14769 the log output is prefixed by @samp{&}.
14772 @cindex list output in @sc{gdb/mi}
14773 New @sc{gdb/mi} commands should only output @var{lists} containing
14779 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
14780 details about the various output records.
14782 @node GDB/MI Simple Examples
14783 @subsection Simple Examples of @sc{gdb/mi} Interaction
14784 @cindex @sc{gdb/mi}, simple examples
14786 This subsection presents several simple examples of interaction using
14787 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
14788 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
14789 the output received from @sc{gdb/mi}.
14791 @subsubheading Target Stop
14792 @c Ummm... There is no "-stop" command. This assumes async, no?
14793 Here's an example of stopping the inferior process:
14804 <- *stop,reason="stop",address="0x123",source="a.c:123"
14808 @subsubheading Simple CLI Command
14810 Here's an example of a simple CLI command being passed through
14811 @sc{gdb/mi} and on to the CLI.
14821 @subsubheading Command With Side Effects
14824 -> -symbol-file xyz.exe
14825 <- *breakpoint,nr="3",address="0x123",source="a.c:123"
14829 @subsubheading A Bad Command
14831 Here's what happens if you pass a non-existent command:
14835 <- ^error,msg="Undefined MI command: rubbish"
14839 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14840 @node GDB/MI Compatibility with CLI
14841 @section @sc{gdb/mi} Compatibility with CLI
14843 @cindex compatibility, @sc{gdb/mi} and CLI
14844 @cindex @sc{gdb/mi}, compatibility with CLI
14845 To help users familiar with @value{GDBN}'s existing CLI interface, @sc{gdb/mi}
14846 accepts existing CLI commands. As specified by the syntax, such
14847 commands can be directly entered into the @sc{gdb/mi} interface and @value{GDBN} will
14850 This mechanism is provided as an aid to developers of @sc{gdb/mi}
14851 clients and not as a reliable interface into the CLI. Since the command
14852 is being interpreteted in an environment that assumes @sc{gdb/mi}
14853 behaviour, the exact output of such commands is likely to end up being
14854 an un-supported hybrid of @sc{gdb/mi} and CLI output.
14856 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14857 @node GDB/MI Output Records
14858 @section @sc{gdb/mi} Output Records
14861 * GDB/MI Result Records::
14862 * GDB/MI Stream Records::
14863 * GDB/MI Out-of-band Records::
14866 @node GDB/MI Result Records
14867 @subsection @sc{gdb/mi} Result Records
14869 @cindex result records in @sc{gdb/mi}
14870 @cindex @sc{gdb/mi}, result records
14871 In addition to a number of out-of-band notifications, the response to a
14872 @sc{gdb/mi} command includes one of the following result indications:
14876 @item "^done" [ "," @var{results} ]
14877 The synchronous operation was successful, @code{@var{results}} are the return
14882 @c Is this one correct? Should it be an out-of-band notification?
14883 The asynchronous operation was successfully started. The target is
14886 @item "^error" "," @var{c-string}
14888 The operation failed. The @code{@var{c-string}} contains the corresponding
14892 @node GDB/MI Stream Records
14893 @subsection @sc{gdb/mi} Stream Records
14895 @cindex @sc{gdb/mi}, stream records
14896 @cindex stream records in @sc{gdb/mi}
14897 @value{GDBN} internally maintains a number of output streams: the console, the
14898 target, and the log. The output intended for each of these streams is
14899 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
14901 Each stream record begins with a unique @dfn{prefix character} which
14902 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
14903 Syntax}). In addition to the prefix, each stream record contains a
14904 @code{@var{string-output}}. This is either raw text (with an implicit new
14905 line) or a quoted C string (which does not contain an implicit newline).
14908 @item "~" @var{string-output}
14909 The console output stream contains text that should be displayed in the
14910 CLI console window. It contains the textual responses to CLI commands.
14912 @item "@@" @var{string-output}
14913 The target output stream contains any textual output from the running
14916 @item "&" @var{string-output}
14917 The log stream contains debugging messages being produced by @value{GDBN}'s
14921 @node GDB/MI Out-of-band Records
14922 @subsection @sc{gdb/mi} Out-of-band Records
14924 @cindex out-of-band records in @sc{gdb/mi}
14925 @cindex @sc{gdb/mi}, out-of-band records
14926 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
14927 additional changes that have occurred. Those changes can either be a
14928 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
14929 target activity (e.g., target stopped).
14931 The following is a preliminary list of possible out-of-band records.
14938 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14939 @node GDB/MI Command Description Format
14940 @section @sc{gdb/mi} Command Description Format
14942 The remaining sections describe blocks of commands. Each block of
14943 commands is laid out in a fashion similar to this section.
14945 Note the the line breaks shown in the examples are here only for
14946 readability. They don't appear in the real output.
14947 Also note that the commands with a non-available example (N.A.@:) are
14948 not yet implemented.
14950 @subheading Motivation
14952 The motivation for this collection of commands.
14954 @subheading Introduction
14956 A brief introduction to this collection of commands as a whole.
14958 @subheading Commands
14960 For each command in the block, the following is described:
14962 @subsubheading Synopsis
14965 -command @var{args}@dots{}
14968 @subsubheading @value{GDBN} Command
14970 The corresponding @value{GDBN} CLI command.
14972 @subsubheading Result
14974 @subsubheading Out-of-band
14976 @subsubheading Notes
14978 @subsubheading Example
14981 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14982 @node GDB/MI Breakpoint Table Commands
14983 @section @sc{gdb/mi} Breakpoint table commands
14985 @cindex breakpoint commands for @sc{gdb/mi}
14986 @cindex @sc{gdb/mi}, breakpoint commands
14987 This section documents @sc{gdb/mi} commands for manipulating
14990 @subheading The @code{-break-after} Command
14991 @findex -break-after
14993 @subsubheading Synopsis
14996 -break-after @var{number} @var{count}
14999 The breakpoint number @var{number} is not in effect until it has been
15000 hit @var{count} times. To see how this is reflected in the output of
15001 the @samp{-break-list} command, see the description of the
15002 @samp{-break-list} command below.
15004 @subsubheading @value{GDBN} Command
15006 The corresponding @value{GDBN} command is @samp{ignore}.
15008 @subsubheading Example
15013 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",line="5"@}
15020 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15021 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15022 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15023 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15024 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15025 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15026 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15027 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15028 addr="0x000100d0",func="main",file="hello.c",line="5",times="0",
15034 @subheading The @code{-break-catch} Command
15035 @findex -break-catch
15037 @subheading The @code{-break-commands} Command
15038 @findex -break-commands
15042 @subheading The @code{-break-condition} Command
15043 @findex -break-condition
15045 @subsubheading Synopsis
15048 -break-condition @var{number} @var{expr}
15051 Breakpoint @var{number} will stop the program only if the condition in
15052 @var{expr} is true. The condition becomes part of the
15053 @samp{-break-list} output (see the description of the @samp{-break-list}
15056 @subsubheading @value{GDBN} Command
15058 The corresponding @value{GDBN} command is @samp{condition}.
15060 @subsubheading Example
15064 -break-condition 1 1
15068 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15069 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15070 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15071 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15072 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15073 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15074 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15075 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15076 addr="0x000100d0",func="main",file="hello.c",line="5",cond="1",
15077 times="0",ignore="3"@}]@}
15081 @subheading The @code{-break-delete} Command
15082 @findex -break-delete
15084 @subsubheading Synopsis
15087 -break-delete ( @var{breakpoint} )+
15090 Delete the breakpoint(s) whose number(s) are specified in the argument
15091 list. This is obviously reflected in the breakpoint list.
15093 @subsubheading @value{GDBN} command
15095 The corresponding @value{GDBN} command is @samp{delete}.
15097 @subsubheading Example
15105 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
15106 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15107 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15108 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15109 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15110 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15111 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15116 @subheading The @code{-break-disable} Command
15117 @findex -break-disable
15119 @subsubheading Synopsis
15122 -break-disable ( @var{breakpoint} )+
15125 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
15126 break list is now set to @samp{n} for the named @var{breakpoint}(s).
15128 @subsubheading @value{GDBN} Command
15130 The corresponding @value{GDBN} command is @samp{disable}.
15132 @subsubheading Example
15140 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15141 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15142 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15143 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15144 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15145 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15146 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15147 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
15148 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
15152 @subheading The @code{-break-enable} Command
15153 @findex -break-enable
15155 @subsubheading Synopsis
15158 -break-enable ( @var{breakpoint} )+
15161 Enable (previously disabled) @var{breakpoint}(s).
15163 @subsubheading @value{GDBN} Command
15165 The corresponding @value{GDBN} command is @samp{enable}.
15167 @subsubheading Example
15175 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15176 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15177 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15178 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15179 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15180 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15181 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15182 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
15183 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
15187 @subheading The @code{-break-info} Command
15188 @findex -break-info
15190 @subsubheading Synopsis
15193 -break-info @var{breakpoint}
15197 Get information about a single breakpoint.
15199 @subsubheading @value{GDBN} command
15201 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
15203 @subsubheading Example
15206 @subheading The @code{-break-insert} Command
15207 @findex -break-insert
15209 @subsubheading Synopsis
15212 -break-insert [ -t ] [ -h ] [ -r ]
15213 [ -c @var{condition} ] [ -i @var{ignore-count} ]
15214 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
15218 If specified, @var{line}, can be one of:
15225 @item filename:linenum
15226 @item filename:function
15230 The possible optional parameters of this command are:
15234 Insert a tempoary breakpoint.
15236 Insert a hardware breakpoint.
15237 @item -c @var{condition}
15238 Make the breakpoint conditional on @var{condition}.
15239 @item -i @var{ignore-count}
15240 Initialize the @var{ignore-count}.
15242 Insert a regular breakpoint in all the functions whose names match the
15243 given regular expression. Other flags are not applicable to regular
15247 @subsubheading Result
15249 The result is in the form:
15252 ^done,bkptno="@var{number}",func="@var{funcname}",
15253 file="@var{filename}",line="@var{lineno}"
15257 where @var{number} is the @value{GDBN} number for this breakpoint, @var{funcname}
15258 is the name of the function where the breakpoint was inserted,
15259 @var{filename} is the name of the source file which contains this
15260 function, and @var{lineno} is the source line number within that file.
15262 Note: this format is open to change.
15263 @c An out-of-band breakpoint instead of part of the result?
15265 @subsubheading @value{GDBN} Command
15267 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
15268 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
15270 @subsubheading Example
15275 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
15277 -break-insert -t foo
15278 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",line="11"@}
15281 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15282 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15283 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15284 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15285 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15286 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15287 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15288 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15289 addr="0x0001072c", func="main",file="recursive2.c",line="4",times="0"@},
15290 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
15291 addr="0x00010774",func="foo",file="recursive2.c",line="11",times="0"@}]@}
15293 -break-insert -r foo.*
15294 ~int foo(int, int);
15295 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c",line="11"@}
15299 @subheading The @code{-break-list} Command
15300 @findex -break-list
15302 @subsubheading Synopsis
15308 Displays the list of inserted breakpoints, showing the following fields:
15312 number of the breakpoint
15314 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
15316 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
15319 is the breakpoint enabled or no: @samp{y} or @samp{n}
15321 memory location at which the breakpoint is set
15323 logical location of the breakpoint, expressed by function name, file
15326 number of times the breakpoint has been hit
15329 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
15330 @code{body} field is an empty list.
15332 @subsubheading @value{GDBN} Command
15334 The corresponding @value{GDBN} command is @samp{info break}.
15336 @subsubheading Example
15341 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15342 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15343 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15344 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15345 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15346 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15347 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15348 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15349 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
15350 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
15351 addr="0x00010114",func="foo",file="hello.c",line="13",times="0"@}]@}
15355 Here's an example of the result when there are no breakpoints:
15360 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
15361 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15362 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15363 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15364 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15365 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15366 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15371 @subheading The @code{-break-watch} Command
15372 @findex -break-watch
15374 @subsubheading Synopsis
15377 -break-watch [ -a | -r ]
15380 Create a watchpoint. With the @samp{-a} option it will create an
15381 @dfn{access} watchpoint, i.e. a watchpoint that triggers either on a
15382 read from or on a write to the memory location. With the @samp{-r}
15383 option, the watchpoint created is a @dfn{read} watchpoint, i.e. it will
15384 trigger only when the memory location is accessed for reading. Without
15385 either of the options, the watchpoint created is a regular watchpoint,
15386 i.e. it will trigger when the memory location is accessed for writing.
15387 @xref{Set Watchpoints, , Setting watchpoints}.
15389 Note that @samp{-break-list} will report a single list of watchpoints and
15390 breakpoints inserted.
15392 @subsubheading @value{GDBN} Command
15394 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
15397 @subsubheading Example
15399 Setting a watchpoint on a variable in the @code{main} function:
15404 ^done,wpt=@{number="2",exp="x"@}
15408 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
15409 value=@{old="-268439212",new="55"@},
15410 frame=@{func="main",args=[],file="recursive2.c",line="5"@}
15414 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
15415 the program execution twice: first for the variable changing value, then
15416 for the watchpoint going out of scope.
15421 ^done,wpt=@{number="5",exp="C"@}
15425 ^done,reason="watchpoint-trigger",
15426 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
15427 frame=@{func="callee4",args=[],
15428 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
15432 ^done,reason="watchpoint-scope",wpnum="5",
15433 frame=@{func="callee3",args=[@{name="strarg",
15434 value="0x11940 \"A string argument.\""@}],
15435 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
15439 Listing breakpoints and watchpoints, at different points in the program
15440 execution. Note that once the watchpoint goes out of scope, it is
15446 ^done,wpt=@{number="2",exp="C"@}
15449 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15450 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15451 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15452 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15453 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15454 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15455 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15456 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15457 addr="0x00010734",func="callee4",
15458 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
15459 bkpt=@{number="2",type="watchpoint",disp="keep",
15460 enabled="y",addr="",what="C",times="0"@}]@}
15464 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
15465 value=@{old="-276895068",new="3"@},
15466 frame=@{func="callee4",args=[],
15467 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
15470 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15471 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15472 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15473 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15474 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15475 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15476 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15477 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15478 addr="0x00010734",func="callee4",
15479 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
15480 bkpt=@{number="2",type="watchpoint",disp="keep",
15481 enabled="y",addr="",what="C",times="-5"@}]@}
15485 ^done,reason="watchpoint-scope",wpnum="2",
15486 frame=@{func="callee3",args=[@{name="strarg",
15487 value="0x11940 \"A string argument.\""@}],
15488 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
15491 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15492 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15493 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15494 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15495 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15496 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15497 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15498 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15499 addr="0x00010734",func="callee4",
15500 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@}]@}
15504 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15505 @node GDB/MI Data Manipulation
15506 @section @sc{gdb/mi} Data Manipulation
15508 @cindex data manipulation, in @sc{gdb/mi}
15509 @cindex @sc{gdb/mi}, data manipulation
15510 This section describes the @sc{gdb/mi} commands that manipulate data:
15511 examine memory and registers, evaluate expressions, etc.
15513 @c REMOVED FROM THE INTERFACE.
15514 @c @subheading -data-assign
15515 @c Change the value of a program variable. Plenty of side effects.
15516 @c @subsubheading GDB command
15518 @c @subsubheading Example
15521 @subheading The @code{-data-disassemble} Command
15522 @findex -data-disassemble
15524 @subsubheading Synopsis
15528 [ -s @var{start-addr} -e @var{end-addr} ]
15529 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
15537 @item @var{start-addr}
15538 is the beginning address (or @code{$pc})
15539 @item @var{end-addr}
15541 @item @var{filename}
15542 is the name of the file to disassemble
15543 @item @var{linenum}
15544 is the line number to disassemble around
15546 is the the number of disassembly lines to be produced. If it is -1,
15547 the whole function will be disassembled, in case no @var{end-addr} is
15548 specified. If @var{end-addr} is specified as a non-zero value, and
15549 @var{lines} is lower than the number of disassembly lines between
15550 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
15551 displayed; if @var{lines} is higher than the number of lines between
15552 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
15555 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
15559 @subsubheading Result
15561 The output for each instruction is composed of four fields:
15570 Note that whatever included in the instruction field, is not manipulated
15571 directely by @sc{gdb/mi}, i.e. it is not possible to adjust its format.
15573 @subsubheading @value{GDBN} Command
15575 There's no direct mapping from this command to the CLI.
15577 @subsubheading Example
15579 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
15583 -data-disassemble -s $pc -e "$pc + 20" -- 0
15586 @{address="0x000107c0",func-name="main",offset="4",
15587 inst="mov 2, %o0"@},
15588 @{address="0x000107c4",func-name="main",offset="8",
15589 inst="sethi %hi(0x11800), %o2"@},
15590 @{address="0x000107c8",func-name="main",offset="12",
15591 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
15592 @{address="0x000107cc",func-name="main",offset="16",
15593 inst="sethi %hi(0x11800), %o2"@},
15594 @{address="0x000107d0",func-name="main",offset="20",
15595 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
15599 Disassemble the whole @code{main} function. Line 32 is part of
15603 -data-disassemble -f basics.c -l 32 -- 0
15605 @{address="0x000107bc",func-name="main",offset="0",
15606 inst="save %sp, -112, %sp"@},
15607 @{address="0x000107c0",func-name="main",offset="4",
15608 inst="mov 2, %o0"@},
15609 @{address="0x000107c4",func-name="main",offset="8",
15610 inst="sethi %hi(0x11800), %o2"@},
15612 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
15613 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
15617 Disassemble 3 instructions from the start of @code{main}:
15621 -data-disassemble -f basics.c -l 32 -n 3 -- 0
15623 @{address="0x000107bc",func-name="main",offset="0",
15624 inst="save %sp, -112, %sp"@},
15625 @{address="0x000107c0",func-name="main",offset="4",
15626 inst="mov 2, %o0"@},
15627 @{address="0x000107c4",func-name="main",offset="8",
15628 inst="sethi %hi(0x11800), %o2"@}]
15632 Disassemble 3 instructions from the start of @code{main} in mixed mode:
15636 -data-disassemble -f basics.c -l 32 -n 3 -- 1
15638 src_and_asm_line=@{line="31",
15639 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
15640 testsuite/gdb.mi/basics.c",line_asm_insn=[
15641 @{address="0x000107bc",func-name="main",offset="0",
15642 inst="save %sp, -112, %sp"@}]@},
15643 src_and_asm_line=@{line="32",
15644 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
15645 testsuite/gdb.mi/basics.c",line_asm_insn=[
15646 @{address="0x000107c0",func-name="main",offset="4",
15647 inst="mov 2, %o0"@},
15648 @{address="0x000107c4",func-name="main",offset="8",
15649 inst="sethi %hi(0x11800), %o2"@}]@}]
15654 @subheading The @code{-data-evaluate-expression} Command
15655 @findex -data-evaluate-expression
15657 @subsubheading Synopsis
15660 -data-evaluate-expression @var{expr}
15663 Evaluate @var{expr} as an expression. The expression could contain an
15664 inferior function call. The function call will execute synchronously.
15665 If the expression contains spaces, it must be enclosed in double quotes.
15667 @subsubheading @value{GDBN} Command
15669 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
15670 @samp{call}. In @code{gdbtk} only, there's a corresponding
15671 @samp{gdb_eval} command.
15673 @subsubheading Example
15675 In the following example, the numbers that precede the commands are the
15676 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
15677 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
15681 211-data-evaluate-expression A
15684 311-data-evaluate-expression &A
15685 311^done,value="0xefffeb7c"
15687 411-data-evaluate-expression A+3
15690 511-data-evaluate-expression "A + 3"
15696 @subheading The @code{-data-list-changed-registers} Command
15697 @findex -data-list-changed-registers
15699 @subsubheading Synopsis
15702 -data-list-changed-registers
15705 Display a list of the registers that have changed.
15707 @subsubheading @value{GDBN} Command
15709 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
15710 has the corresponding command @samp{gdb_changed_register_list}.
15712 @subsubheading Example
15714 On a PPC MBX board:
15722 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
15723 args=[],file="try.c",line="5"@}
15725 -data-list-changed-registers
15726 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
15727 "10","11","13","14","15","16","17","18","19","20","21","22","23",
15728 "24","25","26","27","28","30","31","64","65","66","67","69"]
15733 @subheading The @code{-data-list-register-names} Command
15734 @findex -data-list-register-names
15736 @subsubheading Synopsis
15739 -data-list-register-names [ ( @var{regno} )+ ]
15742 Show a list of register names for the current target. If no arguments
15743 are given, it shows a list of the names of all the registers. If
15744 integer numbers are given as arguments, it will print a list of the
15745 names of the registers corresponding to the arguments. To ensure
15746 consistency between a register name and its number, the output list may
15747 include empty register names.
15749 @subsubheading @value{GDBN} Command
15751 @value{GDBN} does not have a command which corresponds to
15752 @samp{-data-list-register-names}. In @code{gdbtk} there is a
15753 corresponding command @samp{gdb_regnames}.
15755 @subsubheading Example
15757 For the PPC MBX board:
15760 -data-list-register-names
15761 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
15762 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
15763 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
15764 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
15765 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
15766 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
15767 "", "pc","ps","cr","lr","ctr","xer"]
15769 -data-list-register-names 1 2 3
15770 ^done,register-names=["r1","r2","r3"]
15774 @subheading The @code{-data-list-register-values} Command
15775 @findex -data-list-register-values
15777 @subsubheading Synopsis
15780 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
15783 Display the registers' contents. @var{fmt} is the format according to
15784 which the registers' contents are to be returned, followed by an optional
15785 list of numbers specifying the registers to display. A missing list of
15786 numbers indicates that the contents of all the registers must be returned.
15788 Allowed formats for @var{fmt} are:
15805 @subsubheading @value{GDBN} Command
15807 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
15808 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
15810 @subsubheading Example
15812 For a PPC MBX board (note: line breaks are for readability only, they
15813 don't appear in the actual output):
15817 -data-list-register-values r 64 65
15818 ^done,register-values=[@{number="64",value="0xfe00a300"@},
15819 @{number="65",value="0x00029002"@}]
15821 -data-list-register-values x
15822 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
15823 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
15824 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
15825 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
15826 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
15827 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
15828 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
15829 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
15830 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
15831 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
15832 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
15833 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
15834 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
15835 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
15836 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
15837 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
15838 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
15839 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
15840 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
15841 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
15842 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
15843 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
15844 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
15845 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
15846 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
15847 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
15848 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
15849 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
15850 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
15851 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
15852 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
15853 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
15854 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
15855 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
15856 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
15857 @{number="69",value="0x20002b03"@}]
15862 @subheading The @code{-data-read-memory} Command
15863 @findex -data-read-memory
15865 @subsubheading Synopsis
15868 -data-read-memory [ -o @var{byte-offset} ]
15869 @var{address} @var{word-format} @var{word-size}
15870 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
15877 @item @var{address}
15878 An expression specifying the address of the first memory word to be
15879 read. Complex expressions containing embedded white space should be
15880 quoted using the C convention.
15882 @item @var{word-format}
15883 The format to be used to print the memory words. The notation is the
15884 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
15887 @item @var{word-size}
15888 The size of each memory word in bytes.
15890 @item @var{nr-rows}
15891 The number of rows in the output table.
15893 @item @var{nr-cols}
15894 The number of columns in the output table.
15897 If present, indicates that each row should include an @sc{ascii} dump. The
15898 value of @var{aschar} is used as a padding character when a byte is not a
15899 member of the printable @sc{ascii} character set (printable @sc{ascii}
15900 characters are those whose code is between 32 and 126, inclusively).
15902 @item @var{byte-offset}
15903 An offset to add to the @var{address} before fetching memory.
15906 This command displays memory contents as a table of @var{nr-rows} by
15907 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
15908 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
15909 (returned as @samp{total-bytes}). Should less than the requested number
15910 of bytes be returned by the target, the missing words are identified
15911 using @samp{N/A}. The number of bytes read from the target is returned
15912 in @samp{nr-bytes} and the starting address used to read memory in
15915 The address of the next/previous row or page is available in
15916 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
15919 @subsubheading @value{GDBN} Command
15921 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
15922 @samp{gdb_get_mem} memory read command.
15924 @subsubheading Example
15926 Read six bytes of memory starting at @code{bytes+6} but then offset by
15927 @code{-6} bytes. Format as three rows of two columns. One byte per
15928 word. Display each word in hex.
15932 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
15933 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
15934 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
15935 prev-page="0x0000138a",memory=[
15936 @{addr="0x00001390",data=["0x00","0x01"]@},
15937 @{addr="0x00001392",data=["0x02","0x03"]@},
15938 @{addr="0x00001394",data=["0x04","0x05"]@}]
15942 Read two bytes of memory starting at address @code{shorts + 64} and
15943 display as a single word formatted in decimal.
15947 5-data-read-memory shorts+64 d 2 1 1
15948 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
15949 next-row="0x00001512",prev-row="0x0000150e",
15950 next-page="0x00001512",prev-page="0x0000150e",memory=[
15951 @{addr="0x00001510",data=["128"]@}]
15955 Read thirty two bytes of memory starting at @code{bytes+16} and format
15956 as eight rows of four columns. Include a string encoding with @samp{x}
15957 used as the non-printable character.
15961 4-data-read-memory bytes+16 x 1 8 4 x
15962 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
15963 next-row="0x000013c0",prev-row="0x0000139c",
15964 next-page="0x000013c0",prev-page="0x00001380",memory=[
15965 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
15966 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
15967 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
15968 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
15969 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
15970 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
15971 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
15972 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
15976 @subheading The @code{-display-delete} Command
15977 @findex -display-delete
15979 @subsubheading Synopsis
15982 -display-delete @var{number}
15985 Delete the display @var{number}.
15987 @subsubheading @value{GDBN} Command
15989 The corresponding @value{GDBN} command is @samp{delete display}.
15991 @subsubheading Example
15995 @subheading The @code{-display-disable} Command
15996 @findex -display-disable
15998 @subsubheading Synopsis
16001 -display-disable @var{number}
16004 Disable display @var{number}.
16006 @subsubheading @value{GDBN} Command
16008 The corresponding @value{GDBN} command is @samp{disable display}.
16010 @subsubheading Example
16014 @subheading The @code{-display-enable} Command
16015 @findex -display-enable
16017 @subsubheading Synopsis
16020 -display-enable @var{number}
16023 Enable display @var{number}.
16025 @subsubheading @value{GDBN} Command
16027 The corresponding @value{GDBN} command is @samp{enable display}.
16029 @subsubheading Example
16033 @subheading The @code{-display-insert} Command
16034 @findex -display-insert
16036 @subsubheading Synopsis
16039 -display-insert @var{expression}
16042 Display @var{expression} every time the program stops.
16044 @subsubheading @value{GDBN} Command
16046 The corresponding @value{GDBN} command is @samp{display}.
16048 @subsubheading Example
16052 @subheading The @code{-display-list} Command
16053 @findex -display-list
16055 @subsubheading Synopsis
16061 List the displays. Do not show the current values.
16063 @subsubheading @value{GDBN} Command
16065 The corresponding @value{GDBN} command is @samp{info display}.
16067 @subsubheading Example
16071 @subheading The @code{-environment-cd} Command
16072 @findex -environment-cd
16074 @subsubheading Synopsis
16077 -environment-cd @var{pathdir}
16080 Set @value{GDBN}'s working directory.
16082 @subsubheading @value{GDBN} Command
16084 The corresponding @value{GDBN} command is @samp{cd}.
16086 @subsubheading Example
16090 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
16096 @subheading The @code{-environment-directory} Command
16097 @findex -environment-directory
16099 @subsubheading Synopsis
16102 -environment-directory [ -r ] [ @var{pathdir} ]+
16105 Add directories @var{pathdir} to beginning of search path for source files.
16106 If the @samp{-r} option is used, the search path is reset to the default
16107 search path. If directories @var{pathdir} are supplied in addition to the
16108 @samp{-r} option, the search path is first reset and then addition
16110 Multiple directories may be specified, separated by blanks. Specifying
16111 multiple directories in a single command
16112 results in the directories added to the beginning of the
16113 search path in the same order they were presented in the command.
16114 If blanks are needed as
16115 part of a directory name, double-quotes should be used around
16116 the name. In the command output, the path will show up separated
16117 by the system directory-separator character. The directory-seperator
16118 character must not be used
16119 in any directory name.
16120 If no directories are specified, the current search path is displayed.
16122 @subsubheading @value{GDBN} Command
16124 The corresponding @value{GDBN} command is @samp{dir}.
16126 @subsubheading Example
16130 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
16131 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
16133 -environment-directory ""
16134 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
16136 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
16137 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
16139 -environment-directory -r
16140 ^done,source-path="$cdir:$cwd"
16145 @subheading The @code{-environment-path} Command
16146 @findex -environment-path
16148 @subsubheading Synopsis
16151 -environment-path [ -r ] [ @var{pathdir} ]+
16154 Add directories @var{pathdir} to beginning of search path for object files.
16155 If the @samp{-r} option is used, the search path is reset to the original
16156 search path that existed at gdb start-up. If directories @var{pathdir} are
16157 supplied in addition to the
16158 @samp{-r} option, the search path is first reset and then addition
16160 Multiple directories may be specified, separated by blanks. Specifying
16161 multiple directories in a single command
16162 results in the directories added to the beginning of the
16163 search path in the same order they were presented in the command.
16164 If blanks are needed as
16165 part of a directory name, double-quotes should be used around
16166 the name. In the command output, the path will show up separated
16167 by the system directory-separator character. The directory-seperator
16168 character must not be used
16169 in any directory name.
16170 If no directories are specified, the current path is displayed.
16173 @subsubheading @value{GDBN} Command
16175 The corresponding @value{GDBN} command is @samp{path}.
16177 @subsubheading Example
16182 ^done,path="/usr/bin"
16184 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
16185 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
16187 -environment-path -r /usr/local/bin
16188 ^done,path="/usr/local/bin:/usr/bin"
16193 @subheading The @code{-environment-pwd} Command
16194 @findex -environment-pwd
16196 @subsubheading Synopsis
16202 Show the current working directory.
16204 @subsubheading @value{GDBN} command
16206 The corresponding @value{GDBN} command is @samp{pwd}.
16208 @subsubheading Example
16213 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
16217 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16218 @node GDB/MI Program Control
16219 @section @sc{gdb/mi} Program control
16221 @subsubheading Program termination
16223 As a result of execution, the inferior program can run to completion, if
16224 it doesn't encounter any breakpoints. In this case the output will
16225 include an exit code, if the program has exited exceptionally.
16227 @subsubheading Examples
16230 Program exited normally:
16238 *stopped,reason="exited-normally"
16243 Program exited exceptionally:
16251 *stopped,reason="exited",exit-code="01"
16255 Another way the program can terminate is if it receives a signal such as
16256 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
16260 *stopped,reason="exited-signalled",signal-name="SIGINT",
16261 signal-meaning="Interrupt"
16265 @subheading The @code{-exec-abort} Command
16266 @findex -exec-abort
16268 @subsubheading Synopsis
16274 Kill the inferior running program.
16276 @subsubheading @value{GDBN} Command
16278 The corresponding @value{GDBN} command is @samp{kill}.
16280 @subsubheading Example
16284 @subheading The @code{-exec-arguments} Command
16285 @findex -exec-arguments
16287 @subsubheading Synopsis
16290 -exec-arguments @var{args}
16293 Set the inferior program arguments, to be used in the next
16296 @subsubheading @value{GDBN} Command
16298 The corresponding @value{GDBN} command is @samp{set args}.
16300 @subsubheading Example
16303 Don't have one around.
16306 @subheading The @code{-exec-continue} Command
16307 @findex -exec-continue
16309 @subsubheading Synopsis
16315 Asynchronous command. Resumes the execution of the inferior program
16316 until a breakpoint is encountered, or until the inferior exits.
16318 @subsubheading @value{GDBN} Command
16320 The corresponding @value{GDBN} corresponding is @samp{continue}.
16322 @subsubheading Example
16329 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
16330 file="hello.c",line="13"@}
16335 @subheading The @code{-exec-finish} Command
16336 @findex -exec-finish
16338 @subsubheading Synopsis
16344 Asynchronous command. Resumes the execution of the inferior program
16345 until the current function is exited. Displays the results returned by
16348 @subsubheading @value{GDBN} Command
16350 The corresponding @value{GDBN} command is @samp{finish}.
16352 @subsubheading Example
16354 Function returning @code{void}.
16361 *stopped,reason="function-finished",frame=@{func="main",args=[],
16362 file="hello.c",line="7"@}
16366 Function returning other than @code{void}. The name of the internal
16367 @value{GDBN} variable storing the result is printed, together with the
16374 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
16375 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
16376 file="recursive2.c",line="14"@},
16377 gdb-result-var="$1",return-value="0"
16382 @subheading The @code{-exec-interrupt} Command
16383 @findex -exec-interrupt
16385 @subsubheading Synopsis
16391 Asynchronous command. Interrupts the background execution of the target.
16392 Note how the token associated with the stop message is the one for the
16393 execution command that has been interrupted. The token for the interrupt
16394 itself only appears in the @samp{^done} output. If the user is trying to
16395 interrupt a non-running program, an error message will be printed.
16397 @subsubheading @value{GDBN} Command
16399 The corresponding @value{GDBN} command is @samp{interrupt}.
16401 @subsubheading Example
16412 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
16413 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",line="13"@}
16418 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
16423 @subheading The @code{-exec-next} Command
16426 @subsubheading Synopsis
16432 Asynchronous command. Resumes execution of the inferior program, stopping
16433 when the beginning of the next source line is reached.
16435 @subsubheading @value{GDBN} Command
16437 The corresponding @value{GDBN} command is @samp{next}.
16439 @subsubheading Example
16445 *stopped,reason="end-stepping-range",line="8",file="hello.c"
16450 @subheading The @code{-exec-next-instruction} Command
16451 @findex -exec-next-instruction
16453 @subsubheading Synopsis
16456 -exec-next-instruction
16459 Asynchronous command. Executes one machine instruction. If the
16460 instruction is a function call continues until the function returns. If
16461 the program stops at an instruction in the middle of a source line, the
16462 address will be printed as well.
16464 @subsubheading @value{GDBN} Command
16466 The corresponding @value{GDBN} command is @samp{nexti}.
16468 @subsubheading Example
16472 -exec-next-instruction
16476 *stopped,reason="end-stepping-range",
16477 addr="0x000100d4",line="5",file="hello.c"
16482 @subheading The @code{-exec-return} Command
16483 @findex -exec-return
16485 @subsubheading Synopsis
16491 Makes current function return immediately. Doesn't execute the inferior.
16492 Displays the new current frame.
16494 @subsubheading @value{GDBN} Command
16496 The corresponding @value{GDBN} command is @samp{return}.
16498 @subsubheading Example
16502 200-break-insert callee4
16503 200^done,bkpt=@{number="1",addr="0x00010734",
16504 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
16509 000*stopped,reason="breakpoint-hit",bkptno="1",
16510 frame=@{func="callee4",args=[],
16511 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
16517 111^done,frame=@{level="0",func="callee3",
16518 args=[@{name="strarg",
16519 value="0x11940 \"A string argument.\""@}],
16520 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
16525 @subheading The @code{-exec-run} Command
16528 @subsubheading Synopsis
16534 Asynchronous command. Starts execution of the inferior from the
16535 beginning. The inferior executes until either a breakpoint is
16536 encountered or the program exits.
16538 @subsubheading @value{GDBN} Command
16540 The corresponding @value{GDBN} command is @samp{run}.
16542 @subsubheading Example
16547 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
16552 *stopped,reason="breakpoint-hit",bkptno="1",
16553 frame=@{func="main",args=[],file="recursive2.c",line="4"@}
16558 @subheading The @code{-exec-show-arguments} Command
16559 @findex -exec-show-arguments
16561 @subsubheading Synopsis
16564 -exec-show-arguments
16567 Print the arguments of the program.
16569 @subsubheading @value{GDBN} Command
16571 The corresponding @value{GDBN} command is @samp{show args}.
16573 @subsubheading Example
16576 @c @subheading -exec-signal
16578 @subheading The @code{-exec-step} Command
16581 @subsubheading Synopsis
16587 Asynchronous command. Resumes execution of the inferior program, stopping
16588 when the beginning of the next source line is reached, if the next
16589 source line is not a function call. If it is, stop at the first
16590 instruction of the called function.
16592 @subsubheading @value{GDBN} Command
16594 The corresponding @value{GDBN} command is @samp{step}.
16596 @subsubheading Example
16598 Stepping into a function:
16604 *stopped,reason="end-stepping-range",
16605 frame=@{func="foo",args=[@{name="a",value="10"@},
16606 @{name="b",value="0"@}],file="recursive2.c",line="11"@}
16616 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
16621 @subheading The @code{-exec-step-instruction} Command
16622 @findex -exec-step-instruction
16624 @subsubheading Synopsis
16627 -exec-step-instruction
16630 Asynchronous command. Resumes the inferior which executes one machine
16631 instruction. The output, once @value{GDBN} has stopped, will vary depending on
16632 whether we have stopped in the middle of a source line or not. In the
16633 former case, the address at which the program stopped will be printed as
16636 @subsubheading @value{GDBN} Command
16638 The corresponding @value{GDBN} command is @samp{stepi}.
16640 @subsubheading Example
16644 -exec-step-instruction
16648 *stopped,reason="end-stepping-range",
16649 frame=@{func="foo",args=[],file="try.c",line="10"@}
16651 -exec-step-instruction
16655 *stopped,reason="end-stepping-range",
16656 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",line="10"@}
16661 @subheading The @code{-exec-until} Command
16662 @findex -exec-until
16664 @subsubheading Synopsis
16667 -exec-until [ @var{location} ]
16670 Asynchronous command. Executes the inferior until the @var{location}
16671 specified in the argument is reached. If there is no argument, the inferior
16672 executes until a source line greater than the current one is reached.
16673 The reason for stopping in this case will be @samp{location-reached}.
16675 @subsubheading @value{GDBN} Command
16677 The corresponding @value{GDBN} command is @samp{until}.
16679 @subsubheading Example
16683 -exec-until recursive2.c:6
16687 *stopped,reason="location-reached",frame=@{func="main",args=[],
16688 file="recursive2.c",line="6"@}
16693 @subheading -file-clear
16694 Is this going away????
16698 @subheading The @code{-file-exec-and-symbols} Command
16699 @findex -file-exec-and-symbols
16701 @subsubheading Synopsis
16704 -file-exec-and-symbols @var{file}
16707 Specify the executable file to be debugged. This file is the one from
16708 which the symbol table is also read. If no file is specified, the
16709 command clears the executable and symbol information. If breakpoints
16710 are set when using this command with no arguments, @value{GDBN} will produce
16711 error messages. Otherwise, no output is produced, except a completion
16714 @subsubheading @value{GDBN} Command
16716 The corresponding @value{GDBN} command is @samp{file}.
16718 @subsubheading Example
16722 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
16728 @subheading The @code{-file-exec-file} Command
16729 @findex -file-exec-file
16731 @subsubheading Synopsis
16734 -file-exec-file @var{file}
16737 Specify the executable file to be debugged. Unlike
16738 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
16739 from this file. If used without argument, @value{GDBN} clears the information
16740 about the executable file. No output is produced, except a completion
16743 @subsubheading @value{GDBN} Command
16745 The corresponding @value{GDBN} command is @samp{exec-file}.
16747 @subsubheading Example
16751 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
16757 @subheading The @code{-file-list-exec-sections} Command
16758 @findex -file-list-exec-sections
16760 @subsubheading Synopsis
16763 -file-list-exec-sections
16766 List the sections of the current executable file.
16768 @subsubheading @value{GDBN} Command
16770 The @value{GDBN} command @samp{info file} shows, among the rest, the same
16771 information as this command. @code{gdbtk} has a corresponding command
16772 @samp{gdb_load_info}.
16774 @subsubheading Example
16778 @subheading The @code{-file-list-exec-source-file} Command
16779 @findex -file-list-exec-source-file
16781 @subsubheading Synopsis
16784 -file-list-exec-source-file
16787 List the line number, the current source file, and the absolute path
16788 to the current source file for the current executable.
16790 @subsubheading @value{GDBN} Command
16792 There's no @value{GDBN} command which directly corresponds to this one.
16794 @subsubheading Example
16798 123-file-list-exec-source-file
16799 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
16804 @subheading The @code{-file-list-exec-source-files} Command
16805 @findex -file-list-exec-source-files
16807 @subsubheading Synopsis
16810 -file-list-exec-source-files
16813 List the source files for the current executable.
16815 @subsubheading @value{GDBN} Command
16817 There's no @value{GDBN} command which directly corresponds to this one.
16818 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
16820 @subsubheading Example
16824 @subheading The @code{-file-list-shared-libraries} Command
16825 @findex -file-list-shared-libraries
16827 @subsubheading Synopsis
16830 -file-list-shared-libraries
16833 List the shared libraries in the program.
16835 @subsubheading @value{GDBN} Command
16837 The corresponding @value{GDBN} command is @samp{info shared}.
16839 @subsubheading Example
16843 @subheading The @code{-file-list-symbol-files} Command
16844 @findex -file-list-symbol-files
16846 @subsubheading Synopsis
16849 -file-list-symbol-files
16854 @subsubheading @value{GDBN} Command
16856 The corresponding @value{GDBN} command is @samp{info file} (part of it).
16858 @subsubheading Example
16862 @subheading The @code{-file-symbol-file} Command
16863 @findex -file-symbol-file
16865 @subsubheading Synopsis
16868 -file-symbol-file @var{file}
16871 Read symbol table info from the specified @var{file} argument. When
16872 used without arguments, clears @value{GDBN}'s symbol table info. No output is
16873 produced, except for a completion notification.
16875 @subsubheading @value{GDBN} Command
16877 The corresponding @value{GDBN} command is @samp{symbol-file}.
16879 @subsubheading Example
16883 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
16888 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16889 @node GDB/MI Miscellaneous Commands
16890 @section Miscellaneous @value{GDBN} commands in @sc{gdb/mi}
16892 @c @subheading -gdb-complete
16894 @subheading The @code{-gdb-exit} Command
16897 @subsubheading Synopsis
16903 Exit @value{GDBN} immediately.
16905 @subsubheading @value{GDBN} Command
16907 Approximately corresponds to @samp{quit}.
16909 @subsubheading Example
16916 @subheading The @code{-gdb-set} Command
16919 @subsubheading Synopsis
16925 Set an internal @value{GDBN} variable.
16926 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
16928 @subsubheading @value{GDBN} Command
16930 The corresponding @value{GDBN} command is @samp{set}.
16932 @subsubheading Example
16942 @subheading The @code{-gdb-show} Command
16945 @subsubheading Synopsis
16951 Show the current value of a @value{GDBN} variable.
16953 @subsubheading @value{GDBN} command
16955 The corresponding @value{GDBN} command is @samp{show}.
16957 @subsubheading Example
16966 @c @subheading -gdb-source
16969 @subheading The @code{-gdb-version} Command
16970 @findex -gdb-version
16972 @subsubheading Synopsis
16978 Show version information for @value{GDBN}. Used mostly in testing.
16980 @subsubheading @value{GDBN} Command
16982 There's no equivalent @value{GDBN} command. @value{GDBN} by default shows this
16983 information when you start an interactive session.
16985 @subsubheading Example
16987 @c This example modifies the actual output from GDB to avoid overfull
16993 ~Copyright 2000 Free Software Foundation, Inc.
16994 ~GDB is free software, covered by the GNU General Public License, and
16995 ~you are welcome to change it and/or distribute copies of it under
16996 ~ certain conditions.
16997 ~Type "show copying" to see the conditions.
16998 ~There is absolutely no warranty for GDB. Type "show warranty" for
17000 ~This GDB was configured as
17001 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
17006 @subheading The @code{-interpreter-exec} Command
17007 @findex -interpreter-exec
17009 @subheading Synopsis
17012 -interpreter-exec @var{interpreter} @var{command}
17015 Execute the specified @var{command} in the given @var{interpreter}.
17017 @subheading @value{GDBN} Command
17019 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
17021 @subheading Example
17025 -interpreter-exec console "break main"
17026 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
17027 &"During symbol reading, bad structure-type format.\n"
17028 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
17034 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17035 @node GDB/MI Kod Commands
17036 @section @sc{gdb/mi} Kod Commands
17038 The Kod commands are not implemented.
17040 @c @subheading -kod-info
17042 @c @subheading -kod-list
17044 @c @subheading -kod-list-object-types
17046 @c @subheading -kod-show
17048 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17049 @node GDB/MI Memory Overlay Commands
17050 @section @sc{gdb/mi} Memory Overlay Commands
17052 The memory overlay commands are not implemented.
17054 @c @subheading -overlay-auto
17056 @c @subheading -overlay-list-mapping-state
17058 @c @subheading -overlay-list-overlays
17060 @c @subheading -overlay-map
17062 @c @subheading -overlay-off
17064 @c @subheading -overlay-on
17066 @c @subheading -overlay-unmap
17068 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17069 @node GDB/MI Signal Handling Commands
17070 @section @sc{gdb/mi} Signal Handling Commands
17072 Signal handling commands are not implemented.
17074 @c @subheading -signal-handle
17076 @c @subheading -signal-list-handle-actions
17078 @c @subheading -signal-list-signal-types
17082 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17083 @node GDB/MI Stack Manipulation
17084 @section @sc{gdb/mi} Stack Manipulation Commands
17087 @subheading The @code{-stack-info-frame} Command
17088 @findex -stack-info-frame
17090 @subsubheading Synopsis
17096 Get info on the current frame.
17098 @subsubheading @value{GDBN} Command
17100 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
17101 (without arguments).
17103 @subsubheading Example
17106 @subheading The @code{-stack-info-depth} Command
17107 @findex -stack-info-depth
17109 @subsubheading Synopsis
17112 -stack-info-depth [ @var{max-depth} ]
17115 Return the depth of the stack. If the integer argument @var{max-depth}
17116 is specified, do not count beyond @var{max-depth} frames.
17118 @subsubheading @value{GDBN} Command
17120 There's no equivalent @value{GDBN} command.
17122 @subsubheading Example
17124 For a stack with frame levels 0 through 11:
17131 -stack-info-depth 4
17134 -stack-info-depth 12
17137 -stack-info-depth 11
17140 -stack-info-depth 13
17145 @subheading The @code{-stack-list-arguments} Command
17146 @findex -stack-list-arguments
17148 @subsubheading Synopsis
17151 -stack-list-arguments @var{show-values}
17152 [ @var{low-frame} @var{high-frame} ]
17155 Display a list of the arguments for the frames between @var{low-frame}
17156 and @var{high-frame} (inclusive). If @var{low-frame} and
17157 @var{high-frame} are not provided, list the arguments for the whole call
17160 The @var{show-values} argument must have a value of 0 or 1. A value of
17161 0 means that only the names of the arguments are listed, a value of 1
17162 means that both names and values of the arguments are printed.
17164 @subsubheading @value{GDBN} Command
17166 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
17167 @samp{gdb_get_args} command which partially overlaps with the
17168 functionality of @samp{-stack-list-arguments}.
17170 @subsubheading Example
17177 frame=@{level="0",addr="0x00010734",func="callee4",
17178 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
17179 frame=@{level="1",addr="0x0001076c",func="callee3",
17180 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
17181 frame=@{level="2",addr="0x0001078c",func="callee2",
17182 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
17183 frame=@{level="3",addr="0x000107b4",func="callee1",
17184 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
17185 frame=@{level="4",addr="0x000107e0",func="main",
17186 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
17188 -stack-list-arguments 0
17191 frame=@{level="0",args=[]@},
17192 frame=@{level="1",args=[name="strarg"]@},
17193 frame=@{level="2",args=[name="intarg",name="strarg"]@},
17194 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
17195 frame=@{level="4",args=[]@}]
17197 -stack-list-arguments 1
17200 frame=@{level="0",args=[]@},
17202 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
17203 frame=@{level="2",args=[
17204 @{name="intarg",value="2"@},
17205 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
17206 @{frame=@{level="3",args=[
17207 @{name="intarg",value="2"@},
17208 @{name="strarg",value="0x11940 \"A string argument.\""@},
17209 @{name="fltarg",value="3.5"@}]@},
17210 frame=@{level="4",args=[]@}]
17212 -stack-list-arguments 0 2 2
17213 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
17215 -stack-list-arguments 1 2 2
17216 ^done,stack-args=[frame=@{level="2",
17217 args=[@{name="intarg",value="2"@},
17218 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
17222 @c @subheading -stack-list-exception-handlers
17225 @subheading The @code{-stack-list-frames} Command
17226 @findex -stack-list-frames
17228 @subsubheading Synopsis
17231 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
17234 List the frames currently on the stack. For each frame it displays the
17239 The frame number, 0 being the topmost frame, i.e. the innermost function.
17241 The @code{$pc} value for that frame.
17245 File name of the source file where the function lives.
17247 Line number corresponding to the @code{$pc}.
17250 If invoked without arguments, this command prints a backtrace for the
17251 whole stack. If given two integer arguments, it shows the frames whose
17252 levels are between the two arguments (inclusive). If the two arguments
17253 are equal, it shows the single frame at the corresponding level.
17255 @subsubheading @value{GDBN} Command
17257 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
17259 @subsubheading Example
17261 Full stack backtrace:
17267 [frame=@{level="0",addr="0x0001076c",func="foo",
17268 file="recursive2.c",line="11"@},
17269 frame=@{level="1",addr="0x000107a4",func="foo",
17270 file="recursive2.c",line="14"@},
17271 frame=@{level="2",addr="0x000107a4",func="foo",
17272 file="recursive2.c",line="14"@},
17273 frame=@{level="3",addr="0x000107a4",func="foo",
17274 file="recursive2.c",line="14"@},
17275 frame=@{level="4",addr="0x000107a4",func="foo",
17276 file="recursive2.c",line="14"@},
17277 frame=@{level="5",addr="0x000107a4",func="foo",
17278 file="recursive2.c",line="14"@},
17279 frame=@{level="6",addr="0x000107a4",func="foo",
17280 file="recursive2.c",line="14"@},
17281 frame=@{level="7",addr="0x000107a4",func="foo",
17282 file="recursive2.c",line="14"@},
17283 frame=@{level="8",addr="0x000107a4",func="foo",
17284 file="recursive2.c",line="14"@},
17285 frame=@{level="9",addr="0x000107a4",func="foo",
17286 file="recursive2.c",line="14"@},
17287 frame=@{level="10",addr="0x000107a4",func="foo",
17288 file="recursive2.c",line="14"@},
17289 frame=@{level="11",addr="0x00010738",func="main",
17290 file="recursive2.c",line="4"@}]
17294 Show frames between @var{low_frame} and @var{high_frame}:
17298 -stack-list-frames 3 5
17300 [frame=@{level="3",addr="0x000107a4",func="foo",
17301 file="recursive2.c",line="14"@},
17302 frame=@{level="4",addr="0x000107a4",func="foo",
17303 file="recursive2.c",line="14"@},
17304 frame=@{level="5",addr="0x000107a4",func="foo",
17305 file="recursive2.c",line="14"@}]
17309 Show a single frame:
17313 -stack-list-frames 3 3
17315 [frame=@{level="3",addr="0x000107a4",func="foo",
17316 file="recursive2.c",line="14"@}]
17321 @subheading The @code{-stack-list-locals} Command
17322 @findex -stack-list-locals
17324 @subsubheading Synopsis
17327 -stack-list-locals @var{print-values}
17330 Display the local variable names for the current frame. With an
17331 argument of 0 or @code{--no-values}, prints only the names of the variables.
17332 With argument of 1 or @code{--all-values}, prints also their values. With
17333 argument of 2 or @code{--simple-values}, prints the name, type and value for
17334 simple data types and the name and type for arrays, structures and
17335 unions. In this last case, the idea is that the user can see the
17336 value of simple data types immediately and he can create variable
17337 objects for other data types if he wishes to explore their values in
17340 @subsubheading @value{GDBN} Command
17342 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
17344 @subsubheading Example
17348 -stack-list-locals 0
17349 ^done,locals=[name="A",name="B",name="C"]
17351 -stack-list-locals --all-values
17352 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
17353 @{name="C",value="@{1, 2, 3@}"@}]
17354 -stack-list-locals --simple-values
17355 ^done,locals=[@{name="A",type="int",value="1"@},
17356 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
17361 @subheading The @code{-stack-select-frame} Command
17362 @findex -stack-select-frame
17364 @subsubheading Synopsis
17367 -stack-select-frame @var{framenum}
17370 Change the current frame. Select a different frame @var{framenum} on
17373 @subsubheading @value{GDBN} Command
17375 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
17376 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
17378 @subsubheading Example
17382 -stack-select-frame 2
17387 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17388 @node GDB/MI Symbol Query
17389 @section @sc{gdb/mi} Symbol Query Commands
17392 @subheading The @code{-symbol-info-address} Command
17393 @findex -symbol-info-address
17395 @subsubheading Synopsis
17398 -symbol-info-address @var{symbol}
17401 Describe where @var{symbol} is stored.
17403 @subsubheading @value{GDBN} Command
17405 The corresponding @value{GDBN} command is @samp{info address}.
17407 @subsubheading Example
17411 @subheading The @code{-symbol-info-file} Command
17412 @findex -symbol-info-file
17414 @subsubheading Synopsis
17420 Show the file for the symbol.
17422 @subsubheading @value{GDBN} Command
17424 There's no equivalent @value{GDBN} command. @code{gdbtk} has
17425 @samp{gdb_find_file}.
17427 @subsubheading Example
17431 @subheading The @code{-symbol-info-function} Command
17432 @findex -symbol-info-function
17434 @subsubheading Synopsis
17437 -symbol-info-function
17440 Show which function the symbol lives in.
17442 @subsubheading @value{GDBN} Command
17444 @samp{gdb_get_function} in @code{gdbtk}.
17446 @subsubheading Example
17450 @subheading The @code{-symbol-info-line} Command
17451 @findex -symbol-info-line
17453 @subsubheading Synopsis
17459 Show the core addresses of the code for a source line.
17461 @subsubheading @value{GDBN} Command
17463 The corresponding @value{GDBN} command is @samp{info line}.
17464 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
17466 @subsubheading Example
17470 @subheading The @code{-symbol-info-symbol} Command
17471 @findex -symbol-info-symbol
17473 @subsubheading Synopsis
17476 -symbol-info-symbol @var{addr}
17479 Describe what symbol is at location @var{addr}.
17481 @subsubheading @value{GDBN} Command
17483 The corresponding @value{GDBN} command is @samp{info symbol}.
17485 @subsubheading Example
17489 @subheading The @code{-symbol-list-functions} Command
17490 @findex -symbol-list-functions
17492 @subsubheading Synopsis
17495 -symbol-list-functions
17498 List the functions in the executable.
17500 @subsubheading @value{GDBN} Command
17502 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
17503 @samp{gdb_search} in @code{gdbtk}.
17505 @subsubheading Example
17509 @subheading The @code{-symbol-list-lines} Command
17510 @findex -symbol-list-lines
17512 @subsubheading Synopsis
17515 -symbol-list-lines @var{filename}
17518 Print the list of lines that contain code and their associated program
17519 addresses for the given source filename. The entries are sorted in
17520 ascending PC order.
17522 @subsubheading @value{GDBN} Command
17524 There is no corresponding @value{GDBN} command.
17526 @subsubheading Example
17529 -symbol-list-lines basics.c
17530 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
17535 @subheading The @code{-symbol-list-types} Command
17536 @findex -symbol-list-types
17538 @subsubheading Synopsis
17544 List all the type names.
17546 @subsubheading @value{GDBN} Command
17548 The corresponding commands are @samp{info types} in @value{GDBN},
17549 @samp{gdb_search} in @code{gdbtk}.
17551 @subsubheading Example
17555 @subheading The @code{-symbol-list-variables} Command
17556 @findex -symbol-list-variables
17558 @subsubheading Synopsis
17561 -symbol-list-variables
17564 List all the global and static variable names.
17566 @subsubheading @value{GDBN} Command
17568 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
17570 @subsubheading Example
17574 @subheading The @code{-symbol-locate} Command
17575 @findex -symbol-locate
17577 @subsubheading Synopsis
17583 @subsubheading @value{GDBN} Command
17585 @samp{gdb_loc} in @code{gdbtk}.
17587 @subsubheading Example
17591 @subheading The @code{-symbol-type} Command
17592 @findex -symbol-type
17594 @subsubheading Synopsis
17597 -symbol-type @var{variable}
17600 Show type of @var{variable}.
17602 @subsubheading @value{GDBN} Command
17604 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
17605 @samp{gdb_obj_variable}.
17607 @subsubheading Example
17611 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17612 @node GDB/MI Target Manipulation
17613 @section @sc{gdb/mi} Target Manipulation Commands
17616 @subheading The @code{-target-attach} Command
17617 @findex -target-attach
17619 @subsubheading Synopsis
17622 -target-attach @var{pid} | @var{file}
17625 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
17627 @subsubheading @value{GDBN} command
17629 The corresponding @value{GDBN} command is @samp{attach}.
17631 @subsubheading Example
17635 @subheading The @code{-target-compare-sections} Command
17636 @findex -target-compare-sections
17638 @subsubheading Synopsis
17641 -target-compare-sections [ @var{section} ]
17644 Compare data of section @var{section} on target to the exec file.
17645 Without the argument, all sections are compared.
17647 @subsubheading @value{GDBN} Command
17649 The @value{GDBN} equivalent is @samp{compare-sections}.
17651 @subsubheading Example
17655 @subheading The @code{-target-detach} Command
17656 @findex -target-detach
17658 @subsubheading Synopsis
17664 Disconnect from the remote target. There's no output.
17666 @subsubheading @value{GDBN} command
17668 The corresponding @value{GDBN} command is @samp{detach}.
17670 @subsubheading Example
17680 @subheading The @code{-target-disconnect} Command
17681 @findex -target-disconnect
17683 @subsubheading Synopsis
17689 Disconnect from the remote target. There's no output.
17691 @subsubheading @value{GDBN} command
17693 The corresponding @value{GDBN} command is @samp{disconnect}.
17695 @subsubheading Example
17705 @subheading The @code{-target-download} Command
17706 @findex -target-download
17708 @subsubheading Synopsis
17714 Loads the executable onto the remote target.
17715 It prints out an update message every half second, which includes the fields:
17719 The name of the section.
17721 The size of what has been sent so far for that section.
17723 The size of the section.
17725 The total size of what was sent so far (the current and the previous sections).
17727 The size of the overall executable to download.
17731 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
17732 @sc{gdb/mi} Output Syntax}).
17734 In addition, it prints the name and size of the sections, as they are
17735 downloaded. These messages include the following fields:
17739 The name of the section.
17741 The size of the section.
17743 The size of the overall executable to download.
17747 At the end, a summary is printed.
17749 @subsubheading @value{GDBN} Command
17751 The corresponding @value{GDBN} command is @samp{load}.
17753 @subsubheading Example
17755 Note: each status message appears on a single line. Here the messages
17756 have been broken down so that they can fit onto a page.
17761 +download,@{section=".text",section-size="6668",total-size="9880"@}
17762 +download,@{section=".text",section-sent="512",section-size="6668",
17763 total-sent="512",total-size="9880"@}
17764 +download,@{section=".text",section-sent="1024",section-size="6668",
17765 total-sent="1024",total-size="9880"@}
17766 +download,@{section=".text",section-sent="1536",section-size="6668",
17767 total-sent="1536",total-size="9880"@}
17768 +download,@{section=".text",section-sent="2048",section-size="6668",
17769 total-sent="2048",total-size="9880"@}
17770 +download,@{section=".text",section-sent="2560",section-size="6668",
17771 total-sent="2560",total-size="9880"@}
17772 +download,@{section=".text",section-sent="3072",section-size="6668",
17773 total-sent="3072",total-size="9880"@}
17774 +download,@{section=".text",section-sent="3584",section-size="6668",
17775 total-sent="3584",total-size="9880"@}
17776 +download,@{section=".text",section-sent="4096",section-size="6668",
17777 total-sent="4096",total-size="9880"@}
17778 +download,@{section=".text",section-sent="4608",section-size="6668",
17779 total-sent="4608",total-size="9880"@}
17780 +download,@{section=".text",section-sent="5120",section-size="6668",
17781 total-sent="5120",total-size="9880"@}
17782 +download,@{section=".text",section-sent="5632",section-size="6668",
17783 total-sent="5632",total-size="9880"@}
17784 +download,@{section=".text",section-sent="6144",section-size="6668",
17785 total-sent="6144",total-size="9880"@}
17786 +download,@{section=".text",section-sent="6656",section-size="6668",
17787 total-sent="6656",total-size="9880"@}
17788 +download,@{section=".init",section-size="28",total-size="9880"@}
17789 +download,@{section=".fini",section-size="28",total-size="9880"@}
17790 +download,@{section=".data",section-size="3156",total-size="9880"@}
17791 +download,@{section=".data",section-sent="512",section-size="3156",
17792 total-sent="7236",total-size="9880"@}
17793 +download,@{section=".data",section-sent="1024",section-size="3156",
17794 total-sent="7748",total-size="9880"@}
17795 +download,@{section=".data",section-sent="1536",section-size="3156",
17796 total-sent="8260",total-size="9880"@}
17797 +download,@{section=".data",section-sent="2048",section-size="3156",
17798 total-sent="8772",total-size="9880"@}
17799 +download,@{section=".data",section-sent="2560",section-size="3156",
17800 total-sent="9284",total-size="9880"@}
17801 +download,@{section=".data",section-sent="3072",section-size="3156",
17802 total-sent="9796",total-size="9880"@}
17803 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
17809 @subheading The @code{-target-exec-status} Command
17810 @findex -target-exec-status
17812 @subsubheading Synopsis
17815 -target-exec-status
17818 Provide information on the state of the target (whether it is running or
17819 not, for instance).
17821 @subsubheading @value{GDBN} Command
17823 There's no equivalent @value{GDBN} command.
17825 @subsubheading Example
17829 @subheading The @code{-target-list-available-targets} Command
17830 @findex -target-list-available-targets
17832 @subsubheading Synopsis
17835 -target-list-available-targets
17838 List the possible targets to connect to.
17840 @subsubheading @value{GDBN} Command
17842 The corresponding @value{GDBN} command is @samp{help target}.
17844 @subsubheading Example
17848 @subheading The @code{-target-list-current-targets} Command
17849 @findex -target-list-current-targets
17851 @subsubheading Synopsis
17854 -target-list-current-targets
17857 Describe the current target.
17859 @subsubheading @value{GDBN} Command
17861 The corresponding information is printed by @samp{info file} (among
17864 @subsubheading Example
17868 @subheading The @code{-target-list-parameters} Command
17869 @findex -target-list-parameters
17871 @subsubheading Synopsis
17874 -target-list-parameters
17879 @subsubheading @value{GDBN} Command
17883 @subsubheading Example
17887 @subheading The @code{-target-select} Command
17888 @findex -target-select
17890 @subsubheading Synopsis
17893 -target-select @var{type} @var{parameters @dots{}}
17896 Connect @value{GDBN} to the remote target. This command takes two args:
17900 The type of target, for instance @samp{async}, @samp{remote}, etc.
17901 @item @var{parameters}
17902 Device names, host names and the like. @xref{Target Commands, ,
17903 Commands for managing targets}, for more details.
17906 The output is a connection notification, followed by the address at
17907 which the target program is, in the following form:
17910 ^connected,addr="@var{address}",func="@var{function name}",
17911 args=[@var{arg list}]
17914 @subsubheading @value{GDBN} Command
17916 The corresponding @value{GDBN} command is @samp{target}.
17918 @subsubheading Example
17922 -target-select async /dev/ttya
17923 ^connected,addr="0xfe00a300",func="??",args=[]
17927 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17928 @node GDB/MI Thread Commands
17929 @section @sc{gdb/mi} Thread Commands
17932 @subheading The @code{-thread-info} Command
17933 @findex -thread-info
17935 @subsubheading Synopsis
17941 @subsubheading @value{GDBN} command
17945 @subsubheading Example
17949 @subheading The @code{-thread-list-all-threads} Command
17950 @findex -thread-list-all-threads
17952 @subsubheading Synopsis
17955 -thread-list-all-threads
17958 @subsubheading @value{GDBN} Command
17960 The equivalent @value{GDBN} command is @samp{info threads}.
17962 @subsubheading Example
17966 @subheading The @code{-thread-list-ids} Command
17967 @findex -thread-list-ids
17969 @subsubheading Synopsis
17975 Produces a list of the currently known @value{GDBN} thread ids. At the
17976 end of the list it also prints the total number of such threads.
17978 @subsubheading @value{GDBN} Command
17980 Part of @samp{info threads} supplies the same information.
17982 @subsubheading Example
17984 No threads present, besides the main process:
17989 ^done,thread-ids=@{@},number-of-threads="0"
17999 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18000 number-of-threads="3"
18005 @subheading The @code{-thread-select} Command
18006 @findex -thread-select
18008 @subsubheading Synopsis
18011 -thread-select @var{threadnum}
18014 Make @var{threadnum} the current thread. It prints the number of the new
18015 current thread, and the topmost frame for that thread.
18017 @subsubheading @value{GDBN} Command
18019 The corresponding @value{GDBN} command is @samp{thread}.
18021 @subsubheading Example
18028 *stopped,reason="end-stepping-range",thread-id="2",line="187",
18029 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
18033 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18034 number-of-threads="3"
18037 ^done,new-thread-id="3",
18038 frame=@{level="0",func="vprintf",
18039 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
18040 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
18044 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18045 @node GDB/MI Tracepoint Commands
18046 @section @sc{gdb/mi} Tracepoint Commands
18048 The tracepoint commands are not yet implemented.
18050 @c @subheading -trace-actions
18052 @c @subheading -trace-delete
18054 @c @subheading -trace-disable
18056 @c @subheading -trace-dump
18058 @c @subheading -trace-enable
18060 @c @subheading -trace-exists
18062 @c @subheading -trace-find
18064 @c @subheading -trace-frame-number
18066 @c @subheading -trace-info
18068 @c @subheading -trace-insert
18070 @c @subheading -trace-list
18072 @c @subheading -trace-pass-count
18074 @c @subheading -trace-save
18076 @c @subheading -trace-start
18078 @c @subheading -trace-stop
18081 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18082 @node GDB/MI Variable Objects
18083 @section @sc{gdb/mi} Variable Objects
18086 @subheading Motivation for Variable Objects in @sc{gdb/mi}
18088 For the implementation of a variable debugger window (locals, watched
18089 expressions, etc.), we are proposing the adaptation of the existing code
18090 used by @code{Insight}.
18092 The two main reasons for that are:
18096 It has been proven in practice (it is already on its second generation).
18099 It will shorten development time (needless to say how important it is
18103 The original interface was designed to be used by Tcl code, so it was
18104 slightly changed so it could be used through @sc{gdb/mi}. This section
18105 describes the @sc{gdb/mi} operations that will be available and gives some
18106 hints about their use.
18108 @emph{Note}: In addition to the set of operations described here, we
18109 expect the @sc{gui} implementation of a variable window to require, at
18110 least, the following operations:
18113 @item @code{-gdb-show} @code{output-radix}
18114 @item @code{-stack-list-arguments}
18115 @item @code{-stack-list-locals}
18116 @item @code{-stack-select-frame}
18119 @subheading Introduction to Variable Objects in @sc{gdb/mi}
18121 @cindex variable objects in @sc{gdb/mi}
18122 The basic idea behind variable objects is the creation of a named object
18123 to represent a variable, an expression, a memory location or even a CPU
18124 register. For each object created, a set of operations is available for
18125 examining or changing its properties.
18127 Furthermore, complex data types, such as C structures, are represented
18128 in a tree format. For instance, the @code{struct} type variable is the
18129 root and the children will represent the struct members. If a child
18130 is itself of a complex type, it will also have children of its own.
18131 Appropriate language differences are handled for C, C@t{++} and Java.
18133 When returning the actual values of the objects, this facility allows
18134 for the individual selection of the display format used in the result
18135 creation. It can be chosen among: binary, decimal, hexadecimal, octal
18136 and natural. Natural refers to a default format automatically
18137 chosen based on the variable type (like decimal for an @code{int}, hex
18138 for pointers, etc.).
18140 The following is the complete set of @sc{gdb/mi} operations defined to
18141 access this functionality:
18143 @multitable @columnfractions .4 .6
18144 @item @strong{Operation}
18145 @tab @strong{Description}
18147 @item @code{-var-create}
18148 @tab create a variable object
18149 @item @code{-var-delete}
18150 @tab delete the variable object and its children
18151 @item @code{-var-set-format}
18152 @tab set the display format of this variable
18153 @item @code{-var-show-format}
18154 @tab show the display format of this variable
18155 @item @code{-var-info-num-children}
18156 @tab tells how many children this object has
18157 @item @code{-var-list-children}
18158 @tab return a list of the object's children
18159 @item @code{-var-info-type}
18160 @tab show the type of this variable object
18161 @item @code{-var-info-expression}
18162 @tab print what this variable object represents
18163 @item @code{-var-show-attributes}
18164 @tab is this variable editable? does it exist here?
18165 @item @code{-var-evaluate-expression}
18166 @tab get the value of this variable
18167 @item @code{-var-assign}
18168 @tab set the value of this variable
18169 @item @code{-var-update}
18170 @tab update the variable and its children
18173 In the next subsection we describe each operation in detail and suggest
18174 how it can be used.
18176 @subheading Description And Use of Operations on Variable Objects
18178 @subheading The @code{-var-create} Command
18179 @findex -var-create
18181 @subsubheading Synopsis
18184 -var-create @{@var{name} | "-"@}
18185 @{@var{frame-addr} | "*"@} @var{expression}
18188 This operation creates a variable object, which allows the monitoring of
18189 a variable, the result of an expression, a memory cell or a CPU
18192 The @var{name} parameter is the string by which the object can be
18193 referenced. It must be unique. If @samp{-} is specified, the varobj
18194 system will generate a string ``varNNNNNN'' automatically. It will be
18195 unique provided that one does not specify @var{name} on that format.
18196 The command fails if a duplicate name is found.
18198 The frame under which the expression should be evaluated can be
18199 specified by @var{frame-addr}. A @samp{*} indicates that the current
18200 frame should be used.
18202 @var{expression} is any expression valid on the current language set (must not
18203 begin with a @samp{*}), or one of the following:
18207 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
18210 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
18213 @samp{$@var{regname}} --- a CPU register name
18216 @subsubheading Result
18218 This operation returns the name, number of children and the type of the
18219 object created. Type is returned as a string as the ones generated by
18220 the @value{GDBN} CLI:
18223 name="@var{name}",numchild="N",type="@var{type}"
18227 @subheading The @code{-var-delete} Command
18228 @findex -var-delete
18230 @subsubheading Synopsis
18233 -var-delete @var{name}
18236 Deletes a previously created variable object and all of its children.
18238 Returns an error if the object @var{name} is not found.
18241 @subheading The @code{-var-set-format} Command
18242 @findex -var-set-format
18244 @subsubheading Synopsis
18247 -var-set-format @var{name} @var{format-spec}
18250 Sets the output format for the value of the object @var{name} to be
18253 The syntax for the @var{format-spec} is as follows:
18256 @var{format-spec} @expansion{}
18257 @{binary | decimal | hexadecimal | octal | natural@}
18261 @subheading The @code{-var-show-format} Command
18262 @findex -var-show-format
18264 @subsubheading Synopsis
18267 -var-show-format @var{name}
18270 Returns the format used to display the value of the object @var{name}.
18273 @var{format} @expansion{}
18278 @subheading The @code{-var-info-num-children} Command
18279 @findex -var-info-num-children
18281 @subsubheading Synopsis
18284 -var-info-num-children @var{name}
18287 Returns the number of children of a variable object @var{name}:
18294 @subheading The @code{-var-list-children} Command
18295 @findex -var-list-children
18297 @subsubheading Synopsis
18300 -var-list-children [@var{print-values}] @var{name}
18303 Returns a list of the children of the specified variable object. With
18304 just the variable object name as an argument or with an optional
18305 preceding argument of 0 or @code{--no-values}, prints only the names of the
18306 variables. With an optional preceding argument of 1 or @code{--all-values},
18307 also prints their values.
18309 @subsubheading Example
18313 -var-list-children n
18314 numchild=@var{n},children=[@{name=@var{name},
18315 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
18317 -var-list-children --all-values n
18318 numchild=@var{n},children=[@{name=@var{name},
18319 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
18323 @subheading The @code{-var-info-type} Command
18324 @findex -var-info-type
18326 @subsubheading Synopsis
18329 -var-info-type @var{name}
18332 Returns the type of the specified variable @var{name}. The type is
18333 returned as a string in the same format as it is output by the
18337 type=@var{typename}
18341 @subheading The @code{-var-info-expression} Command
18342 @findex -var-info-expression
18344 @subsubheading Synopsis
18347 -var-info-expression @var{name}
18350 Returns what is represented by the variable object @var{name}:
18353 lang=@var{lang-spec},exp=@var{expression}
18357 where @var{lang-spec} is @code{@{"C" | "C++" | "Java"@}}.
18359 @subheading The @code{-var-show-attributes} Command
18360 @findex -var-show-attributes
18362 @subsubheading Synopsis
18365 -var-show-attributes @var{name}
18368 List attributes of the specified variable object @var{name}:
18371 status=@var{attr} [ ( ,@var{attr} )* ]
18375 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
18377 @subheading The @code{-var-evaluate-expression} Command
18378 @findex -var-evaluate-expression
18380 @subsubheading Synopsis
18383 -var-evaluate-expression @var{name}
18386 Evaluates the expression that is represented by the specified variable
18387 object and returns its value as a string in the current format specified
18394 Note that one must invoke @code{-var-list-children} for a variable
18395 before the value of a child variable can be evaluated.
18397 @subheading The @code{-var-assign} Command
18398 @findex -var-assign
18400 @subsubheading Synopsis
18403 -var-assign @var{name} @var{expression}
18406 Assigns the value of @var{expression} to the variable object specified
18407 by @var{name}. The object must be @samp{editable}. If the variable's
18408 value is altered by the assign, the variable will show up in any
18409 subsequent @code{-var-update} list.
18411 @subsubheading Example
18419 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
18423 @subheading The @code{-var-update} Command
18424 @findex -var-update
18426 @subsubheading Synopsis
18429 -var-update @{@var{name} | "*"@}
18432 Update the value of the variable object @var{name} by evaluating its
18433 expression after fetching all the new values from memory or registers.
18434 A @samp{*} causes all existing variable objects to be updated.
18438 @chapter @value{GDBN} Annotations
18440 This chapter describes annotations in @value{GDBN}. Annotations were
18441 designed to interface @value{GDBN} to graphical user interfaces or other
18442 similar programs which want to interact with @value{GDBN} at a
18443 relatively high level.
18445 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
18449 This is Edition @value{EDITION}, @value{DATE}.
18453 * Annotations Overview:: What annotations are; the general syntax.
18454 * Server Prefix:: Issuing a command without affecting user state.
18455 * Prompting:: Annotations marking @value{GDBN}'s need for input.
18456 * Errors:: Annotations for error messages.
18457 * Invalidation:: Some annotations describe things now invalid.
18458 * Annotations for Running::
18459 Whether the program is running, how it stopped, etc.
18460 * Source Annotations:: Annotations describing source code.
18463 @node Annotations Overview
18464 @section What is an Annotation?
18465 @cindex annotations
18467 Annotations start with a newline character, two @samp{control-z}
18468 characters, and the name of the annotation. If there is no additional
18469 information associated with this annotation, the name of the annotation
18470 is followed immediately by a newline. If there is additional
18471 information, the name of the annotation is followed by a space, the
18472 additional information, and a newline. The additional information
18473 cannot contain newline characters.
18475 Any output not beginning with a newline and two @samp{control-z}
18476 characters denotes literal output from @value{GDBN}. Currently there is
18477 no need for @value{GDBN} to output a newline followed by two
18478 @samp{control-z} characters, but if there was such a need, the
18479 annotations could be extended with an @samp{escape} annotation which
18480 means those three characters as output.
18482 The annotation @var{level}, which is specified using the
18483 @option{--annotate} command line option (@pxref{Mode Options}), controls
18484 how much information @value{GDBN} prints together with its prompt,
18485 values of expressions, source lines, and other types of output. Level 0
18486 is for no anntations, level 1 is for use when @value{GDBN} is run as a
18487 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
18488 for programs that control @value{GDBN}, and level 2 annotations have
18489 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
18490 Interface, annotate, GDB's Obsolete Annotations}). This chapter
18491 describes level 3 annotations.
18493 A simple example of starting up @value{GDBN} with annotations is:
18496 $ @kbd{gdb --annotate=3}
18498 Copyright 2003 Free Software Foundation, Inc.
18499 GDB is free software, covered by the GNU General Public License,
18500 and you are welcome to change it and/or distribute copies of it
18501 under certain conditions.
18502 Type "show copying" to see the conditions.
18503 There is absolutely no warranty for GDB. Type "show warranty"
18505 This GDB was configured as "i386-pc-linux-gnu"
18516 Here @samp{quit} is input to @value{GDBN}; the rest is output from
18517 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
18518 denotes a @samp{control-z} character) are annotations; the rest is
18519 output from @value{GDBN}.
18521 @node Server Prefix
18522 @section The Server Prefix
18523 @cindex server prefix for annotations
18525 To issue a command to @value{GDBN} without affecting certain aspects of
18526 the state which is seen by users, prefix it with @samp{server }. This
18527 means that this command will not affect the command history, nor will it
18528 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
18529 pressed on a line by itself.
18531 The server prefix does not affect the recording of values into the value
18532 history; to print a value without recording it into the value history,
18533 use the @code{output} command instead of the @code{print} command.
18536 @section Annotation for @value{GDBN} Input
18538 @cindex annotations for prompts
18539 When @value{GDBN} prompts for input, it annotates this fact so it is possible
18540 to know when to send output, when the output from a given command is
18543 Different kinds of input each have a different @dfn{input type}. Each
18544 input type has three annotations: a @code{pre-} annotation, which
18545 denotes the beginning of any prompt which is being output, a plain
18546 annotation, which denotes the end of the prompt, and then a @code{post-}
18547 annotation which denotes the end of any echo which may (or may not) be
18548 associated with the input. For example, the @code{prompt} input type
18549 features the following annotations:
18557 The input types are
18562 @findex post-prompt
18564 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
18566 @findex pre-commands
18568 @findex post-commands
18570 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
18571 command. The annotations are repeated for each command which is input.
18573 @findex pre-overload-choice
18574 @findex overload-choice
18575 @findex post-overload-choice
18576 @item overload-choice
18577 When @value{GDBN} wants the user to select between various overloaded functions.
18583 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
18585 @findex pre-prompt-for-continue
18586 @findex prompt-for-continue
18587 @findex post-prompt-for-continue
18588 @item prompt-for-continue
18589 When @value{GDBN} is asking the user to press return to continue. Note: Don't
18590 expect this to work well; instead use @code{set height 0} to disable
18591 prompting. This is because the counting of lines is buggy in the
18592 presence of annotations.
18597 @cindex annotations for errors, warnings and interrupts
18604 This annotation occurs right before @value{GDBN} responds to an interrupt.
18611 This annotation occurs right before @value{GDBN} responds to an error.
18613 Quit and error annotations indicate that any annotations which @value{GDBN} was
18614 in the middle of may end abruptly. For example, if a
18615 @code{value-history-begin} annotation is followed by a @code{error}, one
18616 cannot expect to receive the matching @code{value-history-end}. One
18617 cannot expect not to receive it either, however; an error annotation
18618 does not necessarily mean that @value{GDBN} is immediately returning all the way
18621 @findex error-begin
18622 A quit or error annotation may be preceded by
18628 Any output between that and the quit or error annotation is the error
18631 Warning messages are not yet annotated.
18632 @c If we want to change that, need to fix warning(), type_error(),
18633 @c range_error(), and possibly other places.
18636 @section Invalidation Notices
18638 @cindex annotations for invalidation messages
18639 The following annotations say that certain pieces of state may have
18643 @findex frames-invalid
18644 @item ^Z^Zframes-invalid
18646 The frames (for example, output from the @code{backtrace} command) may
18649 @findex breakpoints-invalid
18650 @item ^Z^Zbreakpoints-invalid
18652 The breakpoints may have changed. For example, the user just added or
18653 deleted a breakpoint.
18656 @node Annotations for Running
18657 @section Running the Program
18658 @cindex annotations for running programs
18662 When the program starts executing due to a @value{GDBN} command such as
18663 @code{step} or @code{continue},
18669 is output. When the program stops,
18675 is output. Before the @code{stopped} annotation, a variety of
18676 annotations describe how the program stopped.
18680 @item ^Z^Zexited @var{exit-status}
18681 The program exited, and @var{exit-status} is the exit status (zero for
18682 successful exit, otherwise nonzero).
18685 @findex signal-name
18686 @findex signal-name-end
18687 @findex signal-string
18688 @findex signal-string-end
18689 @item ^Z^Zsignalled
18690 The program exited with a signal. After the @code{^Z^Zsignalled}, the
18691 annotation continues:
18697 ^Z^Zsignal-name-end
18701 ^Z^Zsignal-string-end
18706 where @var{name} is the name of the signal, such as @code{SIGILL} or
18707 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
18708 as @code{Illegal Instruction} or @code{Segmentation fault}.
18709 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
18710 user's benefit and have no particular format.
18714 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
18715 just saying that the program received the signal, not that it was
18716 terminated with it.
18719 @item ^Z^Zbreakpoint @var{number}
18720 The program hit breakpoint number @var{number}.
18723 @item ^Z^Zwatchpoint @var{number}
18724 The program hit watchpoint number @var{number}.
18727 @node Source Annotations
18728 @section Displaying Source
18729 @cindex annotations for source display
18732 The following annotation is used instead of displaying source code:
18735 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
18738 where @var{filename} is an absolute file name indicating which source
18739 file, @var{line} is the line number within that file (where 1 is the
18740 first line in the file), @var{character} is the character position
18741 within the file (where 0 is the first character in the file) (for most
18742 debug formats this will necessarily point to the beginning of a line),
18743 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
18744 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
18745 @var{addr} is the address in the target program associated with the
18746 source which is being displayed. @var{addr} is in the form @samp{0x}
18747 followed by one or more lowercase hex digits (note that this does not
18748 depend on the language).
18751 @chapter Reporting Bugs in @value{GDBN}
18752 @cindex bugs in @value{GDBN}
18753 @cindex reporting bugs in @value{GDBN}
18755 Your bug reports play an essential role in making @value{GDBN} reliable.
18757 Reporting a bug may help you by bringing a solution to your problem, or it
18758 may not. But in any case the principal function of a bug report is to help
18759 the entire community by making the next version of @value{GDBN} work better. Bug
18760 reports are your contribution to the maintenance of @value{GDBN}.
18762 In order for a bug report to serve its purpose, you must include the
18763 information that enables us to fix the bug.
18766 * Bug Criteria:: Have you found a bug?
18767 * Bug Reporting:: How to report bugs
18771 @section Have you found a bug?
18772 @cindex bug criteria
18774 If you are not sure whether you have found a bug, here are some guidelines:
18777 @cindex fatal signal
18778 @cindex debugger crash
18779 @cindex crash of debugger
18781 If the debugger gets a fatal signal, for any input whatever, that is a
18782 @value{GDBN} bug. Reliable debuggers never crash.
18784 @cindex error on valid input
18786 If @value{GDBN} produces an error message for valid input, that is a
18787 bug. (Note that if you're cross debugging, the problem may also be
18788 somewhere in the connection to the target.)
18790 @cindex invalid input
18792 If @value{GDBN} does not produce an error message for invalid input,
18793 that is a bug. However, you should note that your idea of
18794 ``invalid input'' might be our idea of ``an extension'' or ``support
18795 for traditional practice''.
18798 If you are an experienced user of debugging tools, your suggestions
18799 for improvement of @value{GDBN} are welcome in any case.
18802 @node Bug Reporting
18803 @section How to report bugs
18804 @cindex bug reports
18805 @cindex @value{GDBN} bugs, reporting
18807 A number of companies and individuals offer support for @sc{gnu} products.
18808 If you obtained @value{GDBN} from a support organization, we recommend you
18809 contact that organization first.
18811 You can find contact information for many support companies and
18812 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
18814 @c should add a web page ref...
18816 In any event, we also recommend that you submit bug reports for
18817 @value{GDBN}. The prefered method is to submit them directly using
18818 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
18819 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
18822 @strong{Do not send bug reports to @samp{info-gdb}, or to
18823 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
18824 not want to receive bug reports. Those that do have arranged to receive
18827 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
18828 serves as a repeater. The mailing list and the newsgroup carry exactly
18829 the same messages. Often people think of posting bug reports to the
18830 newsgroup instead of mailing them. This appears to work, but it has one
18831 problem which can be crucial: a newsgroup posting often lacks a mail
18832 path back to the sender. Thus, if we need to ask for more information,
18833 we may be unable to reach you. For this reason, it is better to send
18834 bug reports to the mailing list.
18836 The fundamental principle of reporting bugs usefully is this:
18837 @strong{report all the facts}. If you are not sure whether to state a
18838 fact or leave it out, state it!
18840 Often people omit facts because they think they know what causes the
18841 problem and assume that some details do not matter. Thus, you might
18842 assume that the name of the variable you use in an example does not matter.
18843 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
18844 stray memory reference which happens to fetch from the location where that
18845 name is stored in memory; perhaps, if the name were different, the contents
18846 of that location would fool the debugger into doing the right thing despite
18847 the bug. Play it safe and give a specific, complete example. That is the
18848 easiest thing for you to do, and the most helpful.
18850 Keep in mind that the purpose of a bug report is to enable us to fix the
18851 bug. It may be that the bug has been reported previously, but neither
18852 you nor we can know that unless your bug report is complete and
18855 Sometimes people give a few sketchy facts and ask, ``Does this ring a
18856 bell?'' Those bug reports are useless, and we urge everyone to
18857 @emph{refuse to respond to them} except to chide the sender to report
18860 To enable us to fix the bug, you should include all these things:
18864 The version of @value{GDBN}. @value{GDBN} announces it if you start
18865 with no arguments; you can also print it at any time using @code{show
18868 Without this, we will not know whether there is any point in looking for
18869 the bug in the current version of @value{GDBN}.
18872 The type of machine you are using, and the operating system name and
18876 What compiler (and its version) was used to compile @value{GDBN}---e.g.
18877 ``@value{GCC}--2.8.1''.
18880 What compiler (and its version) was used to compile the program you are
18881 debugging---e.g. ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
18882 C Compiler''. For GCC, you can say @code{gcc --version} to get this
18883 information; for other compilers, see the documentation for those
18887 The command arguments you gave the compiler to compile your example and
18888 observe the bug. For example, did you use @samp{-O}? To guarantee
18889 you will not omit something important, list them all. A copy of the
18890 Makefile (or the output from make) is sufficient.
18892 If we were to try to guess the arguments, we would probably guess wrong
18893 and then we might not encounter the bug.
18896 A complete input script, and all necessary source files, that will
18900 A description of what behavior you observe that you believe is
18901 incorrect. For example, ``It gets a fatal signal.''
18903 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
18904 will certainly notice it. But if the bug is incorrect output, we might
18905 not notice unless it is glaringly wrong. You might as well not give us
18906 a chance to make a mistake.
18908 Even if the problem you experience is a fatal signal, you should still
18909 say so explicitly. Suppose something strange is going on, such as, your
18910 copy of @value{GDBN} is out of synch, or you have encountered a bug in
18911 the C library on your system. (This has happened!) Your copy might
18912 crash and ours would not. If you told us to expect a crash, then when
18913 ours fails to crash, we would know that the bug was not happening for
18914 us. If you had not told us to expect a crash, then we would not be able
18915 to draw any conclusion from our observations.
18918 If you wish to suggest changes to the @value{GDBN} source, send us context
18919 diffs. If you even discuss something in the @value{GDBN} source, refer to
18920 it by context, not by line number.
18922 The line numbers in our development sources will not match those in your
18923 sources. Your line numbers would convey no useful information to us.
18927 Here are some things that are not necessary:
18931 A description of the envelope of the bug.
18933 Often people who encounter a bug spend a lot of time investigating
18934 which changes to the input file will make the bug go away and which
18935 changes will not affect it.
18937 This is often time consuming and not very useful, because the way we
18938 will find the bug is by running a single example under the debugger
18939 with breakpoints, not by pure deduction from a series of examples.
18940 We recommend that you save your time for something else.
18942 Of course, if you can find a simpler example to report @emph{instead}
18943 of the original one, that is a convenience for us. Errors in the
18944 output will be easier to spot, running under the debugger will take
18945 less time, and so on.
18947 However, simplification is not vital; if you do not want to do this,
18948 report the bug anyway and send us the entire test case you used.
18951 A patch for the bug.
18953 A patch for the bug does help us if it is a good one. But do not omit
18954 the necessary information, such as the test case, on the assumption that
18955 a patch is all we need. We might see problems with your patch and decide
18956 to fix the problem another way, or we might not understand it at all.
18958 Sometimes with a program as complicated as @value{GDBN} it is very hard to
18959 construct an example that will make the program follow a certain path
18960 through the code. If you do not send us the example, we will not be able
18961 to construct one, so we will not be able to verify that the bug is fixed.
18963 And if we cannot understand what bug you are trying to fix, or why your
18964 patch should be an improvement, we will not install it. A test case will
18965 help us to understand.
18968 A guess about what the bug is or what it depends on.
18970 Such guesses are usually wrong. Even we cannot guess right about such
18971 things without first using the debugger to find the facts.
18974 @c The readline documentation is distributed with the readline code
18975 @c and consists of the two following files:
18977 @c inc-hist.texinfo
18978 @c Use -I with makeinfo to point to the appropriate directory,
18979 @c environment var TEXINPUTS with TeX.
18980 @include rluser.texinfo
18981 @include inc-hist.texinfo
18984 @node Formatting Documentation
18985 @appendix Formatting Documentation
18987 @cindex @value{GDBN} reference card
18988 @cindex reference card
18989 The @value{GDBN} 4 release includes an already-formatted reference card, ready
18990 for printing with PostScript or Ghostscript, in the @file{gdb}
18991 subdirectory of the main source directory@footnote{In
18992 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
18993 release.}. If you can use PostScript or Ghostscript with your printer,
18994 you can print the reference card immediately with @file{refcard.ps}.
18996 The release also includes the source for the reference card. You
18997 can format it, using @TeX{}, by typing:
19003 The @value{GDBN} reference card is designed to print in @dfn{landscape}
19004 mode on US ``letter'' size paper;
19005 that is, on a sheet 11 inches wide by 8.5 inches
19006 high. You will need to specify this form of printing as an option to
19007 your @sc{dvi} output program.
19009 @cindex documentation
19011 All the documentation for @value{GDBN} comes as part of the machine-readable
19012 distribution. The documentation is written in Texinfo format, which is
19013 a documentation system that uses a single source file to produce both
19014 on-line information and a printed manual. You can use one of the Info
19015 formatting commands to create the on-line version of the documentation
19016 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
19018 @value{GDBN} includes an already formatted copy of the on-line Info
19019 version of this manual in the @file{gdb} subdirectory. The main Info
19020 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
19021 subordinate files matching @samp{gdb.info*} in the same directory. If
19022 necessary, you can print out these files, or read them with any editor;
19023 but they are easier to read using the @code{info} subsystem in @sc{gnu}
19024 Emacs or the standalone @code{info} program, available as part of the
19025 @sc{gnu} Texinfo distribution.
19027 If you want to format these Info files yourself, you need one of the
19028 Info formatting programs, such as @code{texinfo-format-buffer} or
19031 If you have @code{makeinfo} installed, and are in the top level
19032 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
19033 version @value{GDBVN}), you can make the Info file by typing:
19040 If you want to typeset and print copies of this manual, you need @TeX{},
19041 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
19042 Texinfo definitions file.
19044 @TeX{} is a typesetting program; it does not print files directly, but
19045 produces output files called @sc{dvi} files. To print a typeset
19046 document, you need a program to print @sc{dvi} files. If your system
19047 has @TeX{} installed, chances are it has such a program. The precise
19048 command to use depends on your system; @kbd{lpr -d} is common; another
19049 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
19050 require a file name without any extension or a @samp{.dvi} extension.
19052 @TeX{} also requires a macro definitions file called
19053 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
19054 written in Texinfo format. On its own, @TeX{} cannot either read or
19055 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
19056 and is located in the @file{gdb-@var{version-number}/texinfo}
19059 If you have @TeX{} and a @sc{dvi} printer program installed, you can
19060 typeset and print this manual. First switch to the the @file{gdb}
19061 subdirectory of the main source directory (for example, to
19062 @file{gdb-@value{GDBVN}/gdb}) and type:
19068 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
19070 @node Installing GDB
19071 @appendix Installing @value{GDBN}
19072 @cindex configuring @value{GDBN}
19073 @cindex installation
19074 @cindex configuring @value{GDBN}, and source tree subdirectories
19076 @value{GDBN} comes with a @code{configure} script that automates the process
19077 of preparing @value{GDBN} for installation; you can then use @code{make} to
19078 build the @code{gdb} program.
19080 @c irrelevant in info file; it's as current as the code it lives with.
19081 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
19082 look at the @file{README} file in the sources; we may have improved the
19083 installation procedures since publishing this manual.}
19086 The @value{GDBN} distribution includes all the source code you need for
19087 @value{GDBN} in a single directory, whose name is usually composed by
19088 appending the version number to @samp{gdb}.
19090 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
19091 @file{gdb-@value{GDBVN}} directory. That directory contains:
19094 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
19095 script for configuring @value{GDBN} and all its supporting libraries
19097 @item gdb-@value{GDBVN}/gdb
19098 the source specific to @value{GDBN} itself
19100 @item gdb-@value{GDBVN}/bfd
19101 source for the Binary File Descriptor library
19103 @item gdb-@value{GDBVN}/include
19104 @sc{gnu} include files
19106 @item gdb-@value{GDBVN}/libiberty
19107 source for the @samp{-liberty} free software library
19109 @item gdb-@value{GDBVN}/opcodes
19110 source for the library of opcode tables and disassemblers
19112 @item gdb-@value{GDBVN}/readline
19113 source for the @sc{gnu} command-line interface
19115 @item gdb-@value{GDBVN}/glob
19116 source for the @sc{gnu} filename pattern-matching subroutine
19118 @item gdb-@value{GDBVN}/mmalloc
19119 source for the @sc{gnu} memory-mapped malloc package
19122 The simplest way to configure and build @value{GDBN} is to run @code{configure}
19123 from the @file{gdb-@var{version-number}} source directory, which in
19124 this example is the @file{gdb-@value{GDBVN}} directory.
19126 First switch to the @file{gdb-@var{version-number}} source directory
19127 if you are not already in it; then run @code{configure}. Pass the
19128 identifier for the platform on which @value{GDBN} will run as an
19134 cd gdb-@value{GDBVN}
19135 ./configure @var{host}
19140 where @var{host} is an identifier such as @samp{sun4} or
19141 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
19142 (You can often leave off @var{host}; @code{configure} tries to guess the
19143 correct value by examining your system.)
19145 Running @samp{configure @var{host}} and then running @code{make} builds the
19146 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
19147 libraries, then @code{gdb} itself. The configured source files, and the
19148 binaries, are left in the corresponding source directories.
19151 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
19152 system does not recognize this automatically when you run a different
19153 shell, you may need to run @code{sh} on it explicitly:
19156 sh configure @var{host}
19159 If you run @code{configure} from a directory that contains source
19160 directories for multiple libraries or programs, such as the
19161 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
19162 creates configuration files for every directory level underneath (unless
19163 you tell it not to, with the @samp{--norecursion} option).
19165 You should run the @code{configure} script from the top directory in the
19166 source tree, the @file{gdb-@var{version-number}} directory. If you run
19167 @code{configure} from one of the subdirectories, you will configure only
19168 that subdirectory. That is usually not what you want. In particular,
19169 if you run the first @code{configure} from the @file{gdb} subdirectory
19170 of the @file{gdb-@var{version-number}} directory, you will omit the
19171 configuration of @file{bfd}, @file{readline}, and other sibling
19172 directories of the @file{gdb} subdirectory. This leads to build errors
19173 about missing include files such as @file{bfd/bfd.h}.
19175 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
19176 However, you should make sure that the shell on your path (named by
19177 the @samp{SHELL} environment variable) is publicly readable. Remember
19178 that @value{GDBN} uses the shell to start your program---some systems refuse to
19179 let @value{GDBN} debug child processes whose programs are not readable.
19182 * Separate Objdir:: Compiling @value{GDBN} in another directory
19183 * Config Names:: Specifying names for hosts and targets
19184 * Configure Options:: Summary of options for configure
19187 @node Separate Objdir
19188 @section Compiling @value{GDBN} in another directory
19190 If you want to run @value{GDBN} versions for several host or target machines,
19191 you need a different @code{gdb} compiled for each combination of
19192 host and target. @code{configure} is designed to make this easy by
19193 allowing you to generate each configuration in a separate subdirectory,
19194 rather than in the source directory. If your @code{make} program
19195 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
19196 @code{make} in each of these directories builds the @code{gdb}
19197 program specified there.
19199 To build @code{gdb} in a separate directory, run @code{configure}
19200 with the @samp{--srcdir} option to specify where to find the source.
19201 (You also need to specify a path to find @code{configure}
19202 itself from your working directory. If the path to @code{configure}
19203 would be the same as the argument to @samp{--srcdir}, you can leave out
19204 the @samp{--srcdir} option; it is assumed.)
19206 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
19207 separate directory for a Sun 4 like this:
19211 cd gdb-@value{GDBVN}
19214 ../gdb-@value{GDBVN}/configure sun4
19219 When @code{configure} builds a configuration using a remote source
19220 directory, it creates a tree for the binaries with the same structure
19221 (and using the same names) as the tree under the source directory. In
19222 the example, you'd find the Sun 4 library @file{libiberty.a} in the
19223 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
19224 @file{gdb-sun4/gdb}.
19226 Make sure that your path to the @file{configure} script has just one
19227 instance of @file{gdb} in it. If your path to @file{configure} looks
19228 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
19229 one subdirectory of @value{GDBN}, not the whole package. This leads to
19230 build errors about missing include files such as @file{bfd/bfd.h}.
19232 One popular reason to build several @value{GDBN} configurations in separate
19233 directories is to configure @value{GDBN} for cross-compiling (where
19234 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
19235 programs that run on another machine---the @dfn{target}).
19236 You specify a cross-debugging target by
19237 giving the @samp{--target=@var{target}} option to @code{configure}.
19239 When you run @code{make} to build a program or library, you must run
19240 it in a configured directory---whatever directory you were in when you
19241 called @code{configure} (or one of its subdirectories).
19243 The @code{Makefile} that @code{configure} generates in each source
19244 directory also runs recursively. If you type @code{make} in a source
19245 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
19246 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
19247 will build all the required libraries, and then build GDB.
19249 When you have multiple hosts or targets configured in separate
19250 directories, you can run @code{make} on them in parallel (for example,
19251 if they are NFS-mounted on each of the hosts); they will not interfere
19255 @section Specifying names for hosts and targets
19257 The specifications used for hosts and targets in the @code{configure}
19258 script are based on a three-part naming scheme, but some short predefined
19259 aliases are also supported. The full naming scheme encodes three pieces
19260 of information in the following pattern:
19263 @var{architecture}-@var{vendor}-@var{os}
19266 For example, you can use the alias @code{sun4} as a @var{host} argument,
19267 or as the value for @var{target} in a @code{--target=@var{target}}
19268 option. The equivalent full name is @samp{sparc-sun-sunos4}.
19270 The @code{configure} script accompanying @value{GDBN} does not provide
19271 any query facility to list all supported host and target names or
19272 aliases. @code{configure} calls the Bourne shell script
19273 @code{config.sub} to map abbreviations to full names; you can read the
19274 script, if you wish, or you can use it to test your guesses on
19275 abbreviations---for example:
19278 % sh config.sub i386-linux
19280 % sh config.sub alpha-linux
19281 alpha-unknown-linux-gnu
19282 % sh config.sub hp9k700
19284 % sh config.sub sun4
19285 sparc-sun-sunos4.1.1
19286 % sh config.sub sun3
19287 m68k-sun-sunos4.1.1
19288 % sh config.sub i986v
19289 Invalid configuration `i986v': machine `i986v' not recognized
19293 @code{config.sub} is also distributed in the @value{GDBN} source
19294 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
19296 @node Configure Options
19297 @section @code{configure} options
19299 Here is a summary of the @code{configure} options and arguments that
19300 are most often useful for building @value{GDBN}. @code{configure} also has
19301 several other options not listed here. @inforef{What Configure
19302 Does,,configure.info}, for a full explanation of @code{configure}.
19305 configure @r{[}--help@r{]}
19306 @r{[}--prefix=@var{dir}@r{]}
19307 @r{[}--exec-prefix=@var{dir}@r{]}
19308 @r{[}--srcdir=@var{dirname}@r{]}
19309 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
19310 @r{[}--target=@var{target}@r{]}
19315 You may introduce options with a single @samp{-} rather than
19316 @samp{--} if you prefer; but you may abbreviate option names if you use
19321 Display a quick summary of how to invoke @code{configure}.
19323 @item --prefix=@var{dir}
19324 Configure the source to install programs and files under directory
19327 @item --exec-prefix=@var{dir}
19328 Configure the source to install programs under directory
19331 @c avoid splitting the warning from the explanation:
19333 @item --srcdir=@var{dirname}
19334 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
19335 @code{make} that implements the @code{VPATH} feature.}@*
19336 Use this option to make configurations in directories separate from the
19337 @value{GDBN} source directories. Among other things, you can use this to
19338 build (or maintain) several configurations simultaneously, in separate
19339 directories. @code{configure} writes configuration specific files in
19340 the current directory, but arranges for them to use the source in the
19341 directory @var{dirname}. @code{configure} creates directories under
19342 the working directory in parallel to the source directories below
19345 @item --norecursion
19346 Configure only the directory level where @code{configure} is executed; do not
19347 propagate configuration to subdirectories.
19349 @item --target=@var{target}
19350 Configure @value{GDBN} for cross-debugging programs running on the specified
19351 @var{target}. Without this option, @value{GDBN} is configured to debug
19352 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
19354 There is no convenient way to generate a list of all available targets.
19356 @item @var{host} @dots{}
19357 Configure @value{GDBN} to run on the specified @var{host}.
19359 There is no convenient way to generate a list of all available hosts.
19362 There are many other options available as well, but they are generally
19363 needed for special purposes only.
19365 @node Maintenance Commands
19366 @appendix Maintenance Commands
19367 @cindex maintenance commands
19368 @cindex internal commands
19370 In addition to commands intended for @value{GDBN} users, @value{GDBN}
19371 includes a number of commands intended for @value{GDBN} developers.
19372 These commands are provided here for reference.
19375 @kindex maint info breakpoints
19376 @item @anchor{maint info breakpoints}maint info breakpoints
19377 Using the same format as @samp{info breakpoints}, display both the
19378 breakpoints you've set explicitly, and those @value{GDBN} is using for
19379 internal purposes. Internal breakpoints are shown with negative
19380 breakpoint numbers. The type column identifies what kind of breakpoint
19385 Normal, explicitly set breakpoint.
19388 Normal, explicitly set watchpoint.
19391 Internal breakpoint, used to handle correctly stepping through
19392 @code{longjmp} calls.
19394 @item longjmp resume
19395 Internal breakpoint at the target of a @code{longjmp}.
19398 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
19401 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
19404 Shared library events.
19408 @kindex maint internal-error
19409 @kindex maint internal-warning
19410 @item maint internal-error
19411 @itemx maint internal-warning
19412 Cause @value{GDBN} to call the internal function @code{internal_error}
19413 or @code{internal_warning} and hence behave as though an internal error
19414 or internal warning has been detected. In addition to reporting the
19415 internal problem, these functions give the user the opportunity to
19416 either quit @value{GDBN} or create a core file of the current
19417 @value{GDBN} session.
19420 (gdb) @kbd{maint internal-error testing, 1, 2}
19421 @dots{}/maint.c:121: internal-error: testing, 1, 2
19422 A problem internal to GDB has been detected. Further
19423 debugging may prove unreliable.
19424 Quit this debugging session? (y or n) @kbd{n}
19425 Create a core file? (y or n) @kbd{n}
19429 Takes an optional parameter that is used as the text of the error or
19432 @kindex maint print dummy-frames
19433 @item maint print dummy-frames
19435 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
19440 (gdb) @kbd{print add(2,3)}
19441 Breakpoint 2, add (a=2, b=3) at @dots{}
19443 The program being debugged stopped while in a function called from GDB.
19445 (gdb) @kbd{maint print dummy-frames}
19446 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
19447 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
19448 call_lo=0x01014000 call_hi=0x01014001
19452 Takes an optional file parameter.
19454 @kindex maint print registers
19455 @kindex maint print raw-registers
19456 @kindex maint print cooked-registers
19457 @kindex maint print register-groups
19458 @item maint print registers
19459 @itemx maint print raw-registers
19460 @itemx maint print cooked-registers
19461 @itemx maint print register-groups
19462 Print @value{GDBN}'s internal register data structures.
19464 The command @code{maint print raw-registers} includes the contents of
19465 the raw register cache; the command @code{maint print cooked-registers}
19466 includes the (cooked) value of all registers; and the command
19467 @code{maint print register-groups} includes the groups that each
19468 register is a member of. @xref{Registers,, Registers, gdbint,
19469 @value{GDBN} Internals}.
19471 Takes an optional file parameter.
19473 @kindex maint print reggroups
19474 @item maint print reggroups
19475 Print @value{GDBN}'s internal register group data structures.
19477 Takes an optional file parameter.
19480 (gdb) @kbd{maint print reggroups}
19491 @kindex maint set profile
19492 @kindex maint show profile
19493 @cindex profiling GDB
19494 @item maint set profile
19495 @itemx maint show profile
19496 Control profiling of @value{GDBN}.
19498 Profiling will be disabled until you use the @samp{maint set profile}
19499 command to enable it. When you enable profiling, the system will begin
19500 collecting timing and execution count data; when you disable profiling or
19501 exit @value{GDBN}, the results will be written to a log file. Remember that
19502 if you use profiling, @value{GDBN} will overwrite the profiling log file
19503 (often called @file{gmon.out}). If you have a record of important profiling
19504 data in a @file{gmon.out} file, be sure to move it to a safe location.
19506 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
19507 compiled with the @samp{-pg} compiler option.
19512 @node Remote Protocol
19513 @appendix @value{GDBN} Remote Serial Protocol
19518 * Stop Reply Packets::
19519 * General Query Packets::
19520 * Register Packet Format::
19522 * File-I/O remote protocol extension::
19528 There may be occasions when you need to know something about the
19529 protocol---for example, if there is only one serial port to your target
19530 machine, you might want your program to do something special if it
19531 recognizes a packet meant for @value{GDBN}.
19533 In the examples below, @samp{->} and @samp{<-} are used to indicate
19534 transmitted and received data respectfully.
19536 @cindex protocol, @value{GDBN} remote serial
19537 @cindex serial protocol, @value{GDBN} remote
19538 @cindex remote serial protocol
19539 All @value{GDBN} commands and responses (other than acknowledgments) are
19540 sent as a @var{packet}. A @var{packet} is introduced with the character
19541 @samp{$}, the actual @var{packet-data}, and the terminating character
19542 @samp{#} followed by a two-digit @var{checksum}:
19545 @code{$}@var{packet-data}@code{#}@var{checksum}
19549 @cindex checksum, for @value{GDBN} remote
19551 The two-digit @var{checksum} is computed as the modulo 256 sum of all
19552 characters between the leading @samp{$} and the trailing @samp{#} (an
19553 eight bit unsigned checksum).
19555 Implementors should note that prior to @value{GDBN} 5.0 the protocol
19556 specification also included an optional two-digit @var{sequence-id}:
19559 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
19562 @cindex sequence-id, for @value{GDBN} remote
19564 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
19565 has never output @var{sequence-id}s. Stubs that handle packets added
19566 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
19568 @cindex acknowledgment, for @value{GDBN} remote
19569 When either the host or the target machine receives a packet, the first
19570 response expected is an acknowledgment: either @samp{+} (to indicate
19571 the package was received correctly) or @samp{-} (to request
19575 -> @code{$}@var{packet-data}@code{#}@var{checksum}
19580 The host (@value{GDBN}) sends @var{command}s, and the target (the
19581 debugging stub incorporated in your program) sends a @var{response}. In
19582 the case of step and continue @var{command}s, the response is only sent
19583 when the operation has completed (the target has again stopped).
19585 @var{packet-data} consists of a sequence of characters with the
19586 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
19589 Fields within the packet should be separated using @samp{,} @samp{;} or
19590 @cindex remote protocol, field separator
19591 @samp{:}. Except where otherwise noted all numbers are represented in
19592 @sc{hex} with leading zeros suppressed.
19594 Implementors should note that prior to @value{GDBN} 5.0, the character
19595 @samp{:} could not appear as the third character in a packet (as it
19596 would potentially conflict with the @var{sequence-id}).
19598 Response @var{data} can be run-length encoded to save space. A @samp{*}
19599 means that the next character is an @sc{ascii} encoding giving a repeat count
19600 which stands for that many repetitions of the character preceding the
19601 @samp{*}. The encoding is @code{n+29}, yielding a printable character
19602 where @code{n >=3} (which is where rle starts to win). The printable
19603 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
19604 value greater than 126 should not be used.
19611 means the same as "0000".
19613 The error response returned for some packets includes a two character
19614 error number. That number is not well defined.
19616 For any @var{command} not supported by the stub, an empty response
19617 (@samp{$#00}) should be returned. That way it is possible to extend the
19618 protocol. A newer @value{GDBN} can tell if a packet is supported based
19621 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
19622 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
19628 The following table provides a complete list of all currently defined
19629 @var{command}s and their corresponding response @var{data}.
19633 @item @code{!} --- extended mode
19634 @cindex @code{!} packet
19636 Enable extended mode. In extended mode, the remote server is made
19637 persistent. The @samp{R} packet is used to restart the program being
19643 The remote target both supports and has enabled extended mode.
19646 @item @code{?} --- last signal
19647 @cindex @code{?} packet
19649 Indicate the reason the target halted. The reply is the same as for
19653 @xref{Stop Reply Packets}, for the reply specifications.
19655 @item @code{a} --- reserved
19657 Reserved for future use.
19659 @item @code{A}@var{arglen}@code{,}@var{argnum}@code{,}@var{arg}@code{,@dots{}} --- set program arguments @strong{(reserved)}
19660 @cindex @code{A} packet
19662 Initialized @samp{argv[]} array passed into program. @var{arglen}
19663 specifies the number of bytes in the hex encoded byte stream @var{arg}.
19664 See @code{gdbserver} for more details.
19672 @item @code{b}@var{baud} --- set baud @strong{(deprecated)}
19673 @cindex @code{b} packet
19675 Change the serial line speed to @var{baud}.
19677 JTC: @emph{When does the transport layer state change? When it's
19678 received, or after the ACK is transmitted. In either case, there are
19679 problems if the command or the acknowledgment packet is dropped.}
19681 Stan: @emph{If people really wanted to add something like this, and get
19682 it working for the first time, they ought to modify ser-unix.c to send
19683 some kind of out-of-band message to a specially-setup stub and have the
19684 switch happen "in between" packets, so that from remote protocol's point
19685 of view, nothing actually happened.}
19687 @item @code{B}@var{addr},@var{mode} --- set breakpoint @strong{(deprecated)}
19688 @cindex @code{B} packet
19690 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
19691 breakpoint at @var{addr}.
19693 This packet has been replaced by the @samp{Z} and @samp{z} packets
19694 (@pxref{insert breakpoint or watchpoint packet}).
19696 @item @code{c}@var{addr} --- continue
19697 @cindex @code{c} packet
19699 @var{addr} is address to resume. If @var{addr} is omitted, resume at
19703 @xref{Stop Reply Packets}, for the reply specifications.
19705 @item @code{C}@var{sig}@code{;}@var{addr} --- continue with signal
19706 @cindex @code{C} packet
19708 Continue with signal @var{sig} (hex signal number). If
19709 @code{;}@var{addr} is omitted, resume at same address.
19712 @xref{Stop Reply Packets}, for the reply specifications.
19714 @item @code{d} --- toggle debug @strong{(deprecated)}
19715 @cindex @code{d} packet
19719 @item @code{D} --- detach
19720 @cindex @code{D} packet
19722 Detach @value{GDBN} from the remote system. Sent to the remote target
19723 before @value{GDBN} disconnects via the @code{detach} command.
19727 @item @emph{no response}
19728 @value{GDBN} does not check for any response after sending this packet.
19731 @item @code{e} --- reserved
19733 Reserved for future use.
19735 @item @code{E} --- reserved
19737 Reserved for future use.
19739 @item @code{f} --- reserved
19741 Reserved for future use.
19743 @item @code{F}@var{RC}@code{,}@var{EE}@code{,}@var{CF}@code{;}@var{XX} --- Reply to target's F packet.
19744 @cindex @code{F} packet
19746 This packet is send by @value{GDBN} as reply to a @code{F} request packet
19747 sent by the target. This is part of the File-I/O protocol extension.
19748 @xref{File-I/O remote protocol extension}, for the specification.
19750 @item @code{g} --- read registers
19751 @anchor{read registers packet}
19752 @cindex @code{g} packet
19754 Read general registers.
19758 @item @var{XX@dots{}}
19759 Each byte of register data is described by two hex digits. The bytes
19760 with the register are transmitted in target byte order. The size of
19761 each register and their position within the @samp{g} @var{packet} are
19762 determined by the @value{GDBN} internal macros
19763 @var{DEPRECATED_REGISTER_RAW_SIZE} and @var{REGISTER_NAME} macros. The
19764 specification of several standard @code{g} packets is specified below.
19769 @item @code{G}@var{XX@dots{}} --- write regs
19770 @cindex @code{G} packet
19772 @xref{read registers packet}, for a description of the @var{XX@dots{}}
19783 @item @code{h} --- reserved
19785 Reserved for future use.
19787 @item @code{H}@var{c}@var{t@dots{}} --- set thread
19788 @cindex @code{H} packet
19790 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
19791 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
19792 should be @samp{c} for step and continue operations, @samp{g} for other
19793 operations. The thread designator @var{t@dots{}} may be -1, meaning all
19794 the threads, a thread number, or zero which means pick any thread.
19805 @c 'H': How restrictive (or permissive) is the thread model. If a
19806 @c thread is selected and stopped, are other threads allowed
19807 @c to continue to execute? As I mentioned above, I think the
19808 @c semantics of each command when a thread is selected must be
19809 @c described. For example:
19811 @c 'g': If the stub supports threads and a specific thread is
19812 @c selected, returns the register block from that thread;
19813 @c otherwise returns current registers.
19815 @c 'G' If the stub supports threads and a specific thread is
19816 @c selected, sets the registers of the register block of
19817 @c that thread; otherwise sets current registers.
19819 @item @code{i}@var{addr}@code{,}@var{nnn} --- cycle step @strong{(draft)}
19820 @anchor{cycle step packet}
19821 @cindex @code{i} packet
19823 Step the remote target by a single clock cycle. If @code{,}@var{nnn} is
19824 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
19825 step starting at that address.
19827 @item @code{I} --- signal then cycle step @strong{(reserved)}
19828 @cindex @code{I} packet
19830 @xref{step with signal packet}. @xref{cycle step packet}.
19832 @item @code{j} --- reserved
19834 Reserved for future use.
19836 @item @code{J} --- reserved
19838 Reserved for future use.
19840 @item @code{k} --- kill request
19841 @cindex @code{k} packet
19843 FIXME: @emph{There is no description of how to operate when a specific
19844 thread context has been selected (i.e.@: does 'k' kill only that
19847 @item @code{K} --- reserved
19849 Reserved for future use.
19851 @item @code{l} --- reserved
19853 Reserved for future use.
19855 @item @code{L} --- reserved
19857 Reserved for future use.
19859 @item @code{m}@var{addr}@code{,}@var{length} --- read memory
19860 @cindex @code{m} packet
19862 Read @var{length} bytes of memory starting at address @var{addr}.
19863 Neither @value{GDBN} nor the stub assume that sized memory transfers are
19864 assumed using word aligned accesses. FIXME: @emph{A word aligned memory
19865 transfer mechanism is needed.}
19869 @item @var{XX@dots{}}
19870 @var{XX@dots{}} is mem contents. Can be fewer bytes than requested if able
19871 to read only part of the data. Neither @value{GDBN} nor the stub assume
19872 that sized memory transfers are assumed using word aligned
19873 accesses. FIXME: @emph{A word aligned memory transfer mechanism is
19879 @item @code{M}@var{addr},@var{length}@code{:}@var{XX@dots{}} --- write mem
19880 @cindex @code{M} packet
19882 Write @var{length} bytes of memory starting at address @var{addr}.
19883 @var{XX@dots{}} is the data.
19890 for an error (this includes the case where only part of the data was
19894 @item @code{n} --- reserved
19896 Reserved for future use.
19898 @item @code{N} --- reserved
19900 Reserved for future use.
19902 @item @code{o} --- reserved
19904 Reserved for future use.
19906 @item @code{O} --- reserved
19908 Reserved for future use.
19910 @item @code{p}@var{n@dots{}} --- read reg @strong{(reserved)}
19911 @cindex @code{p} packet
19913 @xref{write register packet}.
19917 @item @var{r@dots{}.}
19918 The hex encoded value of the register in target byte order.
19921 @item @code{P}@var{n@dots{}}@code{=}@var{r@dots{}} --- write register
19922 @anchor{write register packet}
19923 @cindex @code{P} packet
19925 Write register @var{n@dots{}} with value @var{r@dots{}}, which contains two hex
19926 digits for each byte in the register (target byte order).
19936 @item @code{q}@var{query} --- general query
19937 @anchor{general query packet}
19938 @cindex @code{q} packet
19940 Request info about @var{query}. In general @value{GDBN} queries have a
19941 leading upper case letter. Custom vendor queries should use a company
19942 prefix (in lower case) ex: @samp{qfsf.var}. @var{query} may optionally
19943 be followed by a @samp{,} or @samp{;} separated list. Stubs must ensure
19944 that they match the full @var{query} name.
19948 @item @var{XX@dots{}}
19949 Hex encoded data from query. The reply can not be empty.
19953 Indicating an unrecognized @var{query}.
19956 @item @code{Q}@var{var}@code{=}@var{val} --- general set
19957 @cindex @code{Q} packet
19959 Set value of @var{var} to @var{val}.
19961 @xref{general query packet}, for a discussion of naming conventions.
19963 @item @code{r} --- reset @strong{(deprecated)}
19964 @cindex @code{r} packet
19966 Reset the entire system.
19968 @item @code{R}@var{XX} --- remote restart
19969 @cindex @code{R} packet
19971 Restart the program being debugged. @var{XX}, while needed, is ignored.
19972 This packet is only available in extended mode.
19976 @item @emph{no reply}
19977 The @samp{R} packet has no reply.
19980 @item @code{s}@var{addr} --- step
19981 @cindex @code{s} packet
19983 @var{addr} is address to resume. If @var{addr} is omitted, resume at
19987 @xref{Stop Reply Packets}, for the reply specifications.
19989 @item @code{S}@var{sig}@code{;}@var{addr} --- step with signal
19990 @anchor{step with signal packet}
19991 @cindex @code{S} packet
19993 Like @samp{C} but step not continue.
19996 @xref{Stop Reply Packets}, for the reply specifications.
19998 @item @code{t}@var{addr}@code{:}@var{PP}@code{,}@var{MM} --- search
19999 @cindex @code{t} packet
20001 Search backwards starting at address @var{addr} for a match with pattern
20002 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
20003 @var{addr} must be at least 3 digits.
20005 @item @code{T}@var{XX} --- thread alive
20006 @cindex @code{T} packet
20008 Find out if the thread XX is alive.
20013 thread is still alive
20018 @item @code{u} --- reserved
20020 Reserved for future use.
20022 @item @code{U} --- reserved
20024 Reserved for future use.
20026 @item @code{v} --- verbose packet prefix
20028 Packets starting with @code{v} are identified by a multi-letter name,
20029 up to the first @code{;} or @code{?} (or the end of the packet).
20031 @item @code{vCont}[;@var{action}[@code{:}@var{tid}]]... --- extended resume
20032 @cindex @code{vCont} packet
20034 Resume the inferior. Different actions may be specified for each thread.
20035 If an action is specified with no @var{tid}, then it is applied to any
20036 threads that don't have a specific action specified; if no default action is
20037 specified then other threads should remain stopped. Specifying multiple
20038 default actions is an error; specifying no actions is also an error.
20039 Thread IDs are specified in hexadecimal. Currently supported actions are:
20045 Continue with signal @var{sig}. @var{sig} should be two hex digits.
20049 Step with signal @var{sig}. @var{sig} should be two hex digits.
20052 The optional @var{addr} argument normally associated with these packets is
20053 not supported in @code{vCont}.
20056 @xref{Stop Reply Packets}, for the reply specifications.
20058 @item @code{vCont?} --- extended resume query
20059 @cindex @code{vCont?} packet
20061 Query support for the @code{vCont} packet.
20065 @item @code{vCont}[;@var{action}]...
20066 The @code{vCont} packet is supported. Each @var{action} is a supported
20067 command in the @code{vCont} packet.
20069 The @code{vCont} packet is not supported.
20072 @item @code{V} --- reserved
20074 Reserved for future use.
20076 @item @code{w} --- reserved
20078 Reserved for future use.
20080 @item @code{W} --- reserved
20082 Reserved for future use.
20084 @item @code{x} --- reserved
20086 Reserved for future use.
20088 @item @code{X}@var{addr}@code{,}@var{length}@var{:}@var{XX@dots{}} --- write mem (binary)
20089 @cindex @code{X} packet
20091 @var{addr} is address, @var{length} is number of bytes, @var{XX@dots{}}
20092 is binary data. The characters @code{$}, @code{#}, and @code{0x7d} are
20093 escaped using @code{0x7d}.
20103 @item @code{y} --- reserved
20105 Reserved for future use.
20107 @item @code{Y} reserved
20109 Reserved for future use.
20111 @item @code{z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- remove breakpoint or watchpoint @strong{(draft)}
20112 @itemx @code{Z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- insert breakpoint or watchpoint @strong{(draft)}
20113 @anchor{insert breakpoint or watchpoint packet}
20114 @cindex @code{z} packet
20115 @cindex @code{Z} packets
20117 Insert (@code{Z}) or remove (@code{z}) a @var{type} breakpoint or
20118 watchpoint starting at address @var{address} and covering the next
20119 @var{length} bytes.
20121 Each breakpoint and watchpoint packet @var{type} is documented
20124 @emph{Implementation notes: A remote target shall return an empty string
20125 for an unrecognized breakpoint or watchpoint packet @var{type}. A
20126 remote target shall support either both or neither of a given
20127 @code{Z}@var{type}@dots{} and @code{z}@var{type}@dots{} packet pair. To
20128 avoid potential problems with duplicate packets, the operations should
20129 be implemented in an idempotent way.}
20131 @item @code{z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- remove memory breakpoint @strong{(draft)}
20132 @item @code{Z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- insert memory breakpoint @strong{(draft)}
20133 @cindex @code{z0} packet
20134 @cindex @code{Z0} packet
20136 Insert (@code{Z0}) or remove (@code{z0}) a memory breakpoint at address
20137 @code{addr} of size @code{length}.
20139 A memory breakpoint is implemented by replacing the instruction at
20140 @var{addr} with a software breakpoint or trap instruction. The
20141 @code{length} is used by targets that indicates the size of the
20142 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
20143 @sc{mips} can insert either a 2 or 4 byte breakpoint).
20145 @emph{Implementation note: It is possible for a target to copy or move
20146 code that contains memory breakpoints (e.g., when implementing
20147 overlays). The behavior of this packet, in the presence of such a
20148 target, is not defined.}
20160 @item @code{z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- remove hardware breakpoint @strong{(draft)}
20161 @item @code{Z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- insert hardware breakpoint @strong{(draft)}
20162 @cindex @code{z1} packet
20163 @cindex @code{Z1} packet
20165 Insert (@code{Z1}) or remove (@code{z1}) a hardware breakpoint at
20166 address @code{addr} of size @code{length}.
20168 A hardware breakpoint is implemented using a mechanism that is not
20169 dependant on being able to modify the target's memory.
20171 @emph{Implementation note: A hardware breakpoint is not affected by code
20184 @item @code{z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- remove write watchpoint @strong{(draft)}
20185 @item @code{Z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- insert write watchpoint @strong{(draft)}
20186 @cindex @code{z2} packet
20187 @cindex @code{Z2} packet
20189 Insert (@code{Z2}) or remove (@code{z2}) a write watchpoint.
20201 @item @code{z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- remove read watchpoint @strong{(draft)}
20202 @item @code{Z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- insert read watchpoint @strong{(draft)}
20203 @cindex @code{z3} packet
20204 @cindex @code{Z3} packet
20206 Insert (@code{Z3}) or remove (@code{z3}) a read watchpoint.
20218 @item @code{z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- remove access watchpoint @strong{(draft)}
20219 @item @code{Z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- insert access watchpoint @strong{(draft)}
20220 @cindex @code{z4} packet
20221 @cindex @code{Z4} packet
20223 Insert (@code{Z4}) or remove (@code{z4}) an access watchpoint.
20237 @node Stop Reply Packets
20238 @section Stop Reply Packets
20239 @cindex stop reply packets
20241 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
20242 receive any of the below as a reply. In the case of the @samp{C},
20243 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
20244 when the target halts. In the below the exact meaning of @samp{signal
20245 number} is poorly defined. In general one of the UNIX signal numbering
20246 conventions is used.
20251 @var{AA} is the signal number
20253 @item @code{T}@var{AA}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}
20254 @cindex @code{T} packet reply
20256 @var{AA} = two hex digit signal number; @var{n...} = register number
20257 (hex), @var{r...} = target byte ordered register contents, size defined
20258 by @code{DEPRECATED_REGISTER_RAW_SIZE}; @var{n...} = @samp{thread},
20259 @var{r...} = thread process ID, this is a hex integer; @var{n...} =
20260 (@samp{watch} | @samp{rwatch} | @samp{awatch}, @var{r...} = data
20261 address, this is a hex integer; @var{n...} = other string not starting
20262 with valid hex digit. @value{GDBN} should ignore this @var{n...},
20263 @var{r...} pair and go on to the next. This way we can extend the
20268 The process exited, and @var{AA} is the exit status. This is only
20269 applicable to certain targets.
20273 The process terminated with signal @var{AA}.
20275 @item O@var{XX@dots{}}
20277 @var{XX@dots{}} is hex encoding of @sc{ascii} data. This can happen at
20278 any time while the program is running and the debugger should continue
20279 to wait for @samp{W}, @samp{T}, etc.
20281 @item F@var{call-id}@code{,}@var{parameter@dots{}}
20283 @var{call-id} is the identifier which says which host system call should
20284 be called. This is just the name of the function. Translation into the
20285 correct system call is only applicable as it's defined in @value{GDBN}.
20286 @xref{File-I/O remote protocol extension}, for a list of implemented
20289 @var{parameter@dots{}} is a list of parameters as defined for this very
20292 The target replies with this packet when it expects @value{GDBN} to call
20293 a host system call on behalf of the target. @value{GDBN} replies with
20294 an appropriate @code{F} packet and keeps up waiting for the next reply
20295 packet from the target. The latest @samp{C}, @samp{c}, @samp{S} or
20296 @samp{s} action is expected to be continued.
20297 @xref{File-I/O remote protocol extension}, for more details.
20301 @node General Query Packets
20302 @section General Query Packets
20304 The following set and query packets have already been defined.
20308 @item @code{q}@code{C} --- current thread
20310 Return the current thread id.
20314 @item @code{QC}@var{pid}
20315 Where @var{pid} is a HEX encoded 16 bit process id.
20317 Any other reply implies the old pid.
20320 @item @code{q}@code{fThreadInfo} -- all thread ids
20322 @code{q}@code{sThreadInfo}
20324 Obtain a list of active thread ids from the target (OS). Since there
20325 may be too many active threads to fit into one reply packet, this query
20326 works iteratively: it may require more than one query/reply sequence to
20327 obtain the entire list of threads. The first query of the sequence will
20328 be the @code{qf}@code{ThreadInfo} query; subsequent queries in the
20329 sequence will be the @code{qs}@code{ThreadInfo} query.
20331 NOTE: replaces the @code{qL} query (see below).
20335 @item @code{m}@var{id}
20337 @item @code{m}@var{id},@var{id}@dots{}
20338 a comma-separated list of thread ids
20340 (lower case 'el') denotes end of list.
20343 In response to each query, the target will reply with a list of one or
20344 more thread ids, in big-endian hex, separated by commas. @value{GDBN}
20345 will respond to each reply with a request for more thread ids (using the
20346 @code{qs} form of the query), until the target responds with @code{l}
20347 (lower-case el, for @code{'last'}).
20349 @item @code{q}@code{ThreadExtraInfo}@code{,}@var{id} --- extra thread info
20351 Where @var{id} is a thread-id in big-endian hex. Obtain a printable
20352 string description of a thread's attributes from the target OS. This
20353 string may contain anything that the target OS thinks is interesting for
20354 @value{GDBN} to tell the user about the thread. The string is displayed
20355 in @value{GDBN}'s @samp{info threads} display. Some examples of
20356 possible thread extra info strings are ``Runnable'', or ``Blocked on
20361 @item @var{XX@dots{}}
20362 Where @var{XX@dots{}} is a hex encoding of @sc{ascii} data, comprising
20363 the printable string containing the extra information about the thread's
20367 @item @code{q}@code{L}@var{startflag}@var{threadcount}@var{nextthread} --- query @var{LIST} or @var{threadLIST} @strong{(deprecated)}
20369 Obtain thread information from RTOS. Where: @var{startflag} (one hex
20370 digit) is one to indicate the first query and zero to indicate a
20371 subsequent query; @var{threadcount} (two hex digits) is the maximum
20372 number of threads the response packet can contain; and @var{nextthread}
20373 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
20374 returned in the response as @var{argthread}.
20376 NOTE: this query is replaced by the @code{q}@code{fThreadInfo} query
20381 @item @code{q}@code{M}@var{count}@var{done}@var{argthread}@var{thread@dots{}}
20382 Where: @var{count} (two hex digits) is the number of threads being
20383 returned; @var{done} (one hex digit) is zero to indicate more threads
20384 and one indicates no further threads; @var{argthreadid} (eight hex
20385 digits) is @var{nextthread} from the request packet; @var{thread@dots{}}
20386 is a sequence of thread IDs from the target. @var{threadid} (eight hex
20387 digits). See @code{remote.c:parse_threadlist_response()}.
20390 @item @code{q}@code{CRC:}@var{addr}@code{,}@var{length} --- compute CRC of memory block
20394 @item @code{E}@var{NN}
20395 An error (such as memory fault)
20396 @item @code{C}@var{CRC32}
20397 A 32 bit cyclic redundancy check of the specified memory region.
20400 @item @code{q}@code{Offsets} --- query sect offs
20402 Get section offsets that the target used when re-locating the downloaded
20403 image. @emph{Note: while a @code{Bss} offset is included in the
20404 response, @value{GDBN} ignores this and instead applies the @code{Data}
20405 offset to the @code{Bss} section.}
20409 @item @code{Text=}@var{xxx}@code{;Data=}@var{yyy}@code{;Bss=}@var{zzz}
20412 @item @code{q}@code{P}@var{mode}@var{threadid} --- thread info request
20414 Returns information on @var{threadid}. Where: @var{mode} is a hex
20415 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
20422 See @code{remote.c:remote_unpack_thread_info_response()}.
20424 @item @code{q}@code{Rcmd,}@var{command} --- remote command
20426 @var{command} (hex encoded) is passed to the local interpreter for
20427 execution. Invalid commands should be reported using the output string.
20428 Before the final result packet, the target may also respond with a
20429 number of intermediate @code{O}@var{output} console output packets.
20430 @emph{Implementors should note that providing access to a stubs's
20431 interpreter may have security implications}.
20436 A command response with no output.
20438 A command response with the hex encoded output string @var{OUTPUT}.
20439 @item @code{E}@var{NN}
20440 Indicate a badly formed request.
20442 When @samp{q}@samp{Rcmd} is not recognized.
20445 @item @code{qSymbol::} --- symbol lookup
20447 Notify the target that @value{GDBN} is prepared to serve symbol lookup
20448 requests. Accept requests from the target for the values of symbols.
20453 The target does not need to look up any (more) symbols.
20454 @item @code{qSymbol:}@var{sym_name}
20455 The target requests the value of symbol @var{sym_name} (hex encoded).
20456 @value{GDBN} may provide the value by using the
20457 @code{qSymbol:}@var{sym_value}:@var{sym_name} message, described below.
20460 @item @code{qSymbol:}@var{sym_value}:@var{sym_name} --- symbol value
20462 Set the value of @var{sym_name} to @var{sym_value}.
20464 @var{sym_name} (hex encoded) is the name of a symbol whose value the
20465 target has previously requested.
20467 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
20468 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
20474 The target does not need to look up any (more) symbols.
20475 @item @code{qSymbol:}@var{sym_name}
20476 The target requests the value of a new symbol @var{sym_name} (hex
20477 encoded). @value{GDBN} will continue to supply the values of symbols
20478 (if available), until the target ceases to request them.
20481 @item @code{qPart}:@var{object}:@code{read}:@var{annex}:@var{offset},@var{length} --- read special data
20483 Read uninterpreted bytes from the target's special data area
20484 identified by the keyword @code{object}.
20485 Request @var{length} bytes starting at @var{offset} bytes into the data.
20486 The content and encoding of @var{annex} is specific to the object;
20487 it can supply additional details about what data to access.
20489 Here are the specific requests of this form defined so far.
20490 All @samp{@code{qPart}:@var{object}:@code{read}:@dots{}}
20491 requests use the same reply formats, listed below.
20494 @item @code{qPart}:@code{auxv}:@code{read}::@var{offset},@var{length}
20495 Access the target's @dfn{auxiliary vector}. @xref{Auxiliary Vector}.
20496 Note @var{annex} must be empty.
20502 The @var{offset} in the request is at the end of the data.
20503 There is no more data to be read.
20505 @item @var{XX@dots{}}
20506 Hex encoded data bytes read.
20507 This may be fewer bytes than the @var{length} in the request.
20510 The request was malformed, or @var{annex} was invalid.
20512 @item @code{E}@var{nn}
20513 The offset was invalid, or there was an error encountered reading the data.
20514 @var{nn} is a hex-encoded @code{errno} value.
20516 @item @code{""} (empty)
20517 An empty reply indicates the @var{object} or @var{annex} string was not
20518 recognized by the stub.
20521 @item @code{qPart}:@var{object}:@code{write}:@var{annex}:@var{offset}:@var{data@dots{}}
20523 Write uninterpreted bytes into the target's special data area
20524 identified by the keyword @code{object},
20525 starting at @var{offset} bytes into the data.
20526 @var{data@dots{}} is the hex-encoded data to be written.
20527 The content and encoding of @var{annex} is specific to the object;
20528 it can supply additional details about what data to access.
20530 No requests of this form are presently in use. This specification
20531 serves as a placeholder to document the common format that new
20532 specific request specifications ought to use.
20537 @var{nn} (hex encoded) is the number of bytes written.
20538 This may be fewer bytes than supplied in the request.
20541 The request was malformed, or @var{annex} was invalid.
20543 @item @code{E}@var{nn}
20544 The offset was invalid, or there was an error encountered writing the data.
20545 @var{nn} is a hex-encoded @code{errno} value.
20547 @item @code{""} (empty)
20548 An empty reply indicates the @var{object} or @var{annex} string was not
20549 recognized by the stub, or that the object does not support writing.
20552 @item @code{qPart}:@var{object}:@var{operation}:@dots{}
20553 Requests of this form may be added in the future. When a stub does
20554 not recognize the @var{object} keyword, or its support for
20555 @var{object} does not recognize the @var{operation} keyword,
20556 the stub must respond with an empty packet.
20559 @node Register Packet Format
20560 @section Register Packet Format
20562 The following @samp{g}/@samp{G} packets have previously been defined.
20563 In the below, some thirty-two bit registers are transferred as
20564 sixty-four bits. Those registers should be zero/sign extended (which?)
20565 to fill the space allocated. Register bytes are transfered in target
20566 byte order. The two nibbles within a register byte are transfered
20567 most-significant - least-significant.
20573 All registers are transfered as thirty-two bit quantities in the order:
20574 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
20575 registers; fsr; fir; fp.
20579 All registers are transfered as sixty-four bit quantities (including
20580 thirty-two bit registers such as @code{sr}). The ordering is the same
20588 Example sequence of a target being re-started. Notice how the restart
20589 does not get any direct output:
20594 @emph{target restarts}
20597 <- @code{T001:1234123412341234}
20601 Example sequence of a target being stepped by a single instruction:
20604 -> @code{G1445@dots{}}
20609 <- @code{T001:1234123412341234}
20613 <- @code{1455@dots{}}
20617 @node File-I/O remote protocol extension
20618 @section File-I/O remote protocol extension
20619 @cindex File-I/O remote protocol extension
20622 * File-I/O Overview::
20623 * Protocol basics::
20624 * The F request packet::
20625 * The F reply packet::
20626 * Memory transfer::
20627 * The Ctrl-C message::
20629 * The isatty call::
20630 * The system call::
20631 * List of supported calls::
20632 * Protocol specific representation of datatypes::
20634 * File-I/O Examples::
20637 @node File-I/O Overview
20638 @subsection File-I/O Overview
20639 @cindex file-i/o overview
20641 The File I/O remote protocol extension (short: File-I/O) allows the
20642 target to use the hosts file system and console I/O when calling various
20643 system calls. System calls on the target system are translated into a
20644 remote protocol packet to the host system which then performs the needed
20645 actions and returns with an adequate response packet to the target system.
20646 This simulates file system operations even on targets that lack file systems.
20648 The protocol is defined host- and target-system independent. It uses
20649 it's own independent representation of datatypes and values. Both,
20650 @value{GDBN} and the target's @value{GDBN} stub are responsible for
20651 translating the system dependent values into the unified protocol values
20652 when data is transmitted.
20654 The communication is synchronous. A system call is possible only
20655 when GDB is waiting for the @samp{C}, @samp{c}, @samp{S} or @samp{s}
20656 packets. While @value{GDBN} handles the request for a system call,
20657 the target is stopped to allow deterministic access to the target's
20658 memory. Therefore File-I/O is not interuptible by target signals. It
20659 is possible to interrupt File-I/O by a user interrupt (Ctrl-C), though.
20661 The target's request to perform a host system call does not finish
20662 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
20663 after finishing the system call, the target returns to continuing the
20664 previous activity (continue, step). No additional continue or step
20665 request from @value{GDBN} is required.
20669 <- target requests 'system call X'
20670 target is stopped, @value{GDBN} executes system call
20671 -> GDB returns result
20672 ... target continues, GDB returns to wait for the target
20673 <- target hits breakpoint and sends a Txx packet
20676 The protocol is only used for files on the host file system and
20677 for I/O on the console. Character or block special devices, pipes,
20678 named pipes or sockets or any other communication method on the host
20679 system are not supported by this protocol.
20681 @node Protocol basics
20682 @subsection Protocol basics
20683 @cindex protocol basics, file-i/o
20685 The File-I/O protocol uses the @code{F} packet, as request as well
20686 as as reply packet. Since a File-I/O system call can only occur when
20687 @value{GDBN} is waiting for the continuing or stepping target, the
20688 File-I/O request is a reply that @value{GDBN} has to expect as a result
20689 of a former @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
20690 This @code{F} packet contains all information needed to allow @value{GDBN}
20691 to call the appropriate host system call:
20695 A unique identifier for the requested system call.
20698 All parameters to the system call. Pointers are given as addresses
20699 in the target memory address space. Pointers to strings are given as
20700 pointer/length pair. Numerical values are given as they are.
20701 Numerical control values are given in a protocol specific representation.
20705 At that point @value{GDBN} has to perform the following actions.
20709 If parameter pointer values are given, which point to data needed as input
20710 to a system call, @value{GDBN} requests this data from the target with a
20711 standard @code{m} packet request. This additional communication has to be
20712 expected by the target implementation and is handled as any other @code{m}
20716 @value{GDBN} translates all value from protocol representation to host
20717 representation as needed. Datatypes are coerced into the host types.
20720 @value{GDBN} calls the system call
20723 It then coerces datatypes back to protocol representation.
20726 If pointer parameters in the request packet point to buffer space in which
20727 a system call is expected to copy data to, the data is transmitted to the
20728 target using a @code{M} or @code{X} packet. This packet has to be expected
20729 by the target implementation and is handled as any other @code{M} or @code{X}
20734 Eventually @value{GDBN} replies with another @code{F} packet which contains all
20735 necessary information for the target to continue. This at least contains
20742 @code{errno}, if has been changed by the system call.
20749 After having done the needed type and value coercion, the target continues
20750 the latest continue or step action.
20752 @node The F request packet
20753 @subsection The @code{F} request packet
20754 @cindex file-i/o request packet
20755 @cindex @code{F} request packet
20757 The @code{F} request packet has the following format:
20762 @code{F}@var{call-id}@code{,}@var{parameter@dots{}}
20765 @var{call-id} is the identifier to indicate the host system call to be called.
20766 This is just the name of the function.
20768 @var{parameter@dots{}} are the parameters to the system call.
20772 Parameters are hexadecimal integer values, either the real values in case
20773 of scalar datatypes, as pointers to target buffer space in case of compound
20774 datatypes and unspecified memory areas or as pointer/length pairs in case
20775 of string parameters. These are appended to the call-id, each separated
20776 from its predecessor by a comma. All values are transmitted in ASCII
20777 string representation, pointer/length pairs separated by a slash.
20779 @node The F reply packet
20780 @subsection The @code{F} reply packet
20781 @cindex file-i/o reply packet
20782 @cindex @code{F} reply packet
20784 The @code{F} reply packet has the following format:
20789 @code{F}@var{retcode}@code{,}@var{errno}@code{,}@var{Ctrl-C flag}@code{;}@var{call specific attachment}
20792 @var{retcode} is the return code of the system call as hexadecimal value.
20794 @var{errno} is the errno set by the call, in protocol specific representation.
20795 This parameter can be omitted if the call was successful.
20797 @var{Ctrl-C flag} is only send if the user requested a break. In this
20798 case, @var{errno} must be send as well, even if the call was successful.
20799 The @var{Ctrl-C flag} itself consists of the character 'C':
20806 or, if the call was interupted before the host call has been performed:
20813 assuming 4 is the protocol specific representation of @code{EINTR}.
20817 @node Memory transfer
20818 @subsection Memory transfer
20819 @cindex memory transfer, in file-i/o protocol
20821 Structured data which is transferred using a memory read or write as e.g.@:
20822 a @code{struct stat} is expected to be in a protocol specific format with
20823 all scalar multibyte datatypes being big endian. This should be done by
20824 the target before the @code{F} packet is sent resp.@: by @value{GDBN} before
20825 it transfers memory to the target. Transferred pointers to structured
20826 data should point to the already coerced data at any time.
20828 @node The Ctrl-C message
20829 @subsection The Ctrl-C message
20830 @cindex ctrl-c message, in file-i/o protocol
20832 A special case is, if the @var{Ctrl-C flag} is set in the @value{GDBN}
20833 reply packet. In this case the target should behave, as if it had
20834 gotten a break message. The meaning for the target is ``system call
20835 interupted by @code{SIGINT}''. Consequentially, the target should actually stop
20836 (as with a break message) and return to @value{GDBN} with a @code{T02}
20837 packet. In this case, it's important for the target to know, in which
20838 state the system call was interrupted. Since this action is by design
20839 not an atomic operation, we have to differ between two cases:
20843 The system call hasn't been performed on the host yet.
20846 The system call on the host has been finished.
20850 These two states can be distinguished by the target by the value of the
20851 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
20852 call hasn't been performed. This is equivalent to the @code{EINTR} handling
20853 on POSIX systems. In any other case, the target may presume that the
20854 system call has been finished --- successful or not --- and should behave
20855 as if the break message arrived right after the system call.
20857 @value{GDBN} must behave reliable. If the system call has not been called
20858 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
20859 @code{errno} in the packet. If the system call on the host has been finished
20860 before the user requests a break, the full action must be finshed by
20861 @value{GDBN}. This requires sending @code{M} or @code{X} packets as they fit.
20862 The @code{F} packet may only be send when either nothing has happened
20863 or the full action has been completed.
20866 @subsection Console I/O
20867 @cindex console i/o as part of file-i/o
20869 By default and if not explicitely closed by the target system, the file
20870 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
20871 on the @value{GDBN} console is handled as any other file output operation
20872 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
20873 by @value{GDBN} so that after the target read request from file descriptor
20874 0 all following typing is buffered until either one of the following
20879 The user presses @kbd{Ctrl-C}. The behaviour is as explained above, the
20881 system call is treated as finished.
20884 The user presses @kbd{Enter}. This is treated as end of input with a trailing
20888 The user presses @kbd{Ctrl-D}. This is treated as end of input. No trailing
20889 character, especially no Ctrl-D is appended to the input.
20893 If the user has typed more characters as fit in the buffer given to
20894 the read call, the trailing characters are buffered in @value{GDBN} until
20895 either another @code{read(0, @dots{})} is requested by the target or debugging
20896 is stopped on users request.
20898 @node The isatty call
20899 @subsection The isatty(3) call
20900 @cindex isatty call, file-i/o protocol
20902 A special case in this protocol is the library call @code{isatty} which
20903 is implemented as it's own call inside of this protocol. It returns
20904 1 to the target if the file descriptor given as parameter is attached
20905 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
20906 would require implementing @code{ioctl} and would be more complex than
20909 @node The system call
20910 @subsection The system(3) call
20911 @cindex system call, file-i/o protocol
20913 The other special case in this protocol is the @code{system} call which
20914 is implemented as it's own call, too. @value{GDBN} is taking over the full
20915 task of calling the necessary host calls to perform the @code{system}
20916 call. The return value of @code{system} is simplified before it's returned
20917 to the target. Basically, the only signal transmitted back is @code{EINTR}
20918 in case the user pressed @kbd{Ctrl-C}. Otherwise the return value consists
20919 entirely of the exit status of the called command.
20921 Due to security concerns, the @code{system} call is refused to be called
20922 by @value{GDBN} by default. The user has to allow this call explicitly by
20926 @kindex set remote system-call-allowed 1
20927 @item @code{set remote system-call-allowed 1}
20930 Disabling the @code{system} call is done by
20933 @kindex set remote system-call-allowed 0
20934 @item @code{set remote system-call-allowed 0}
20937 The current setting is shown by typing
20940 @kindex show remote system-call-allowed
20941 @item @code{show remote system-call-allowed}
20944 @node List of supported calls
20945 @subsection List of supported calls
20946 @cindex list of supported file-i/o calls
20963 @unnumberedsubsubsec open
20964 @cindex open, file-i/o system call
20968 int open(const char *pathname, int flags);
20969 int open(const char *pathname, int flags, mode_t mode);
20972 Fopen,pathptr/len,flags,mode
20976 @code{flags} is the bitwise or of the following values:
20980 If the file does not exist it will be created. The host
20981 rules apply as far as file ownership and time stamps
20985 When used with O_CREAT, if the file already exists it is
20986 an error and open() fails.
20989 If the file already exists and the open mode allows
20990 writing (O_RDWR or O_WRONLY is given) it will be
20991 truncated to length 0.
20994 The file is opened in append mode.
20997 The file is opened for reading only.
21000 The file is opened for writing only.
21003 The file is opened for reading and writing.
21006 Each other bit is silently ignored.
21011 @code{mode} is the bitwise or of the following values:
21015 User has read permission.
21018 User has write permission.
21021 Group has read permission.
21024 Group has write permission.
21027 Others have read permission.
21030 Others have write permission.
21033 Each other bit is silently ignored.
21038 @exdent Return value:
21039 open returns the new file descriptor or -1 if an error
21047 pathname already exists and O_CREAT and O_EXCL were used.
21050 pathname refers to a directory.
21053 The requested access is not allowed.
21056 pathname was too long.
21059 A directory component in pathname does not exist.
21062 pathname refers to a device, pipe, named pipe or socket.
21065 pathname refers to a file on a read-only filesystem and
21066 write access was requested.
21069 pathname is an invalid pointer value.
21072 No space on device to create the file.
21075 The process already has the maximum number of files open.
21078 The limit on the total number of files open on the system
21082 The call was interrupted by the user.
21086 @unnumberedsubsubsec close
21087 @cindex close, file-i/o system call
21096 @exdent Return value:
21097 close returns zero on success, or -1 if an error occurred.
21104 fd isn't a valid open file descriptor.
21107 The call was interrupted by the user.
21111 @unnumberedsubsubsec read
21112 @cindex read, file-i/o system call
21116 int read(int fd, void *buf, unsigned int count);
21119 Fread,fd,bufptr,count
21121 @exdent Return value:
21122 On success, the number of bytes read is returned.
21123 Zero indicates end of file. If count is zero, read
21124 returns zero as well. On error, -1 is returned.
21131 fd is not a valid file descriptor or is not open for
21135 buf is an invalid pointer value.
21138 The call was interrupted by the user.
21142 @unnumberedsubsubsec write
21143 @cindex write, file-i/o system call
21147 int write(int fd, const void *buf, unsigned int count);
21150 Fwrite,fd,bufptr,count
21152 @exdent Return value:
21153 On success, the number of bytes written are returned.
21154 Zero indicates nothing was written. On error, -1
21162 fd is not a valid file descriptor or is not open for
21166 buf is an invalid pointer value.
21169 An attempt was made to write a file that exceeds the
21170 host specific maximum file size allowed.
21173 No space on device to write the data.
21176 The call was interrupted by the user.
21180 @unnumberedsubsubsec lseek
21181 @cindex lseek, file-i/o system call
21185 long lseek (int fd, long offset, int flag);
21188 Flseek,fd,offset,flag
21191 @code{flag} is one of:
21195 The offset is set to offset bytes.
21198 The offset is set to its current location plus offset
21202 The offset is set to the size of the file plus offset
21207 @exdent Return value:
21208 On success, the resulting unsigned offset in bytes from
21209 the beginning of the file is returned. Otherwise, a
21210 value of -1 is returned.
21217 fd is not a valid open file descriptor.
21220 fd is associated with the @value{GDBN} console.
21223 flag is not a proper value.
21226 The call was interrupted by the user.
21230 @unnumberedsubsubsec rename
21231 @cindex rename, file-i/o system call
21235 int rename(const char *oldpath, const char *newpath);
21238 Frename,oldpathptr/len,newpathptr/len
21240 @exdent Return value:
21241 On success, zero is returned. On error, -1 is returned.
21248 newpath is an existing directory, but oldpath is not a
21252 newpath is a non-empty directory.
21255 oldpath or newpath is a directory that is in use by some
21259 An attempt was made to make a directory a subdirectory
21263 A component used as a directory in oldpath or new
21264 path is not a directory. Or oldpath is a directory
21265 and newpath exists but is not a directory.
21268 oldpathptr or newpathptr are invalid pointer values.
21271 No access to the file or the path of the file.
21275 oldpath or newpath was too long.
21278 A directory component in oldpath or newpath does not exist.
21281 The file is on a read-only filesystem.
21284 The device containing the file has no room for the new
21288 The call was interrupted by the user.
21292 @unnumberedsubsubsec unlink
21293 @cindex unlink, file-i/o system call
21297 int unlink(const char *pathname);
21300 Funlink,pathnameptr/len
21302 @exdent Return value:
21303 On success, zero is returned. On error, -1 is returned.
21310 No access to the file or the path of the file.
21313 The system does not allow unlinking of directories.
21316 The file pathname cannot be unlinked because it's
21317 being used by another process.
21320 pathnameptr is an invalid pointer value.
21323 pathname was too long.
21326 A directory component in pathname does not exist.
21329 A component of the path is not a directory.
21332 The file is on a read-only filesystem.
21335 The call was interrupted by the user.
21339 @unnumberedsubsubsec stat/fstat
21340 @cindex fstat, file-i/o system call
21341 @cindex stat, file-i/o system call
21345 int stat(const char *pathname, struct stat *buf);
21346 int fstat(int fd, struct stat *buf);
21349 Fstat,pathnameptr/len,bufptr
21352 @exdent Return value:
21353 On success, zero is returned. On error, -1 is returned.
21360 fd is not a valid open file.
21363 A directory component in pathname does not exist or the
21364 path is an empty string.
21367 A component of the path is not a directory.
21370 pathnameptr is an invalid pointer value.
21373 No access to the file or the path of the file.
21376 pathname was too long.
21379 The call was interrupted by the user.
21383 @unnumberedsubsubsec gettimeofday
21384 @cindex gettimeofday, file-i/o system call
21388 int gettimeofday(struct timeval *tv, void *tz);
21391 Fgettimeofday,tvptr,tzptr
21393 @exdent Return value:
21394 On success, 0 is returned, -1 otherwise.
21401 tz is a non-NULL pointer.
21404 tvptr and/or tzptr is an invalid pointer value.
21408 @unnumberedsubsubsec isatty
21409 @cindex isatty, file-i/o system call
21413 int isatty(int fd);
21418 @exdent Return value:
21419 Returns 1 if fd refers to the @value{GDBN} console, 0 otherwise.
21426 The call was interrupted by the user.
21430 @unnumberedsubsubsec system
21431 @cindex system, file-i/o system call
21435 int system(const char *command);
21438 Fsystem,commandptr/len
21440 @exdent Return value:
21441 The value returned is -1 on error and the return status
21442 of the command otherwise. Only the exit status of the
21443 command is returned, which is extracted from the hosts
21444 system return value by calling WEXITSTATUS(retval).
21445 In case /bin/sh could not be executed, 127 is returned.
21452 The call was interrupted by the user.
21455 @node Protocol specific representation of datatypes
21456 @subsection Protocol specific representation of datatypes
21457 @cindex protocol specific representation of datatypes, in file-i/o protocol
21460 * Integral datatypes::
21466 @node Integral datatypes
21467 @unnumberedsubsubsec Integral datatypes
21468 @cindex integral datatypes, in file-i/o protocol
21470 The integral datatypes used in the system calls are
21473 int@r{,} unsigned int@r{,} long@r{,} unsigned long@r{,} mode_t @r{and} time_t
21476 @code{Int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
21477 implemented as 32 bit values in this protocol.
21479 @code{Long} and @code{unsigned long} are implemented as 64 bit types.
21481 @xref{Limits}, for corresponding MIN and MAX values (similar to those
21482 in @file{limits.h}) to allow range checking on host and target.
21484 @code{time_t} datatypes are defined as seconds since the Epoch.
21486 All integral datatypes transferred as part of a memory read or write of a
21487 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
21490 @node Pointer values
21491 @unnumberedsubsubsec Pointer values
21492 @cindex pointer values, in file-i/o protocol
21494 Pointers to target data are transmitted as they are. An exception
21495 is made for pointers to buffers for which the length isn't
21496 transmitted as part of the function call, namely strings. Strings
21497 are transmitted as a pointer/length pair, both as hex values, e.g.@:
21504 which is a pointer to data of length 18 bytes at position 0x1aaf.
21505 The length is defined as the full string length in bytes, including
21506 the trailing null byte. Example:
21509 ``hello, world'' at address 0x123456
21520 @unnumberedsubsubsec struct stat
21521 @cindex struct stat, in file-i/o protocol
21523 The buffer of type struct stat used by the target and @value{GDBN} is defined
21528 unsigned int st_dev; /* device */
21529 unsigned int st_ino; /* inode */
21530 mode_t st_mode; /* protection */
21531 unsigned int st_nlink; /* number of hard links */
21532 unsigned int st_uid; /* user ID of owner */
21533 unsigned int st_gid; /* group ID of owner */
21534 unsigned int st_rdev; /* device type (if inode device) */
21535 unsigned long st_size; /* total size, in bytes */
21536 unsigned long st_blksize; /* blocksize for filesystem I/O */
21537 unsigned long st_blocks; /* number of blocks allocated */
21538 time_t st_atime; /* time of last access */
21539 time_t st_mtime; /* time of last modification */
21540 time_t st_ctime; /* time of last change */
21544 The integral datatypes are conforming to the definitions given in the
21545 approriate section (see @ref{Integral datatypes}, for details) so this
21546 structure is of size 64 bytes.
21548 The values of several fields have a restricted meaning and/or
21555 st_ino: No valid meaning for the target. Transmitted unchanged.
21557 st_mode: Valid mode bits are described in Appendix C. Any other
21558 bits have currently no meaning for the target.
21560 st_uid: No valid meaning for the target. Transmitted unchanged.
21562 st_gid: No valid meaning for the target. Transmitted unchanged.
21564 st_rdev: No valid meaning for the target. Transmitted unchanged.
21566 st_atime, st_mtime, st_ctime:
21567 These values have a host and file system dependent
21568 accuracy. Especially on Windows hosts the file systems
21569 don't support exact timing values.
21572 The target gets a struct stat of the above representation and is
21573 responsible to coerce it to the target representation before
21576 Note that due to size differences between the host and target
21577 representation of stat members, these members could eventually
21578 get truncated on the target.
21580 @node struct timeval
21581 @unnumberedsubsubsec struct timeval
21582 @cindex struct timeval, in file-i/o protocol
21584 The buffer of type struct timeval used by the target and @value{GDBN}
21585 is defined as follows:
21589 time_t tv_sec; /* second */
21590 long tv_usec; /* microsecond */
21594 The integral datatypes are conforming to the definitions given in the
21595 approriate section (see @ref{Integral datatypes}, for details) so this
21596 structure is of size 8 bytes.
21599 @subsection Constants
21600 @cindex constants, in file-i/o protocol
21602 The following values are used for the constants inside of the
21603 protocol. @value{GDBN} and target are resposible to translate these
21604 values before and after the call as needed.
21615 @unnumberedsubsubsec Open flags
21616 @cindex open flags, in file-i/o protocol
21618 All values are given in hexadecimal representation.
21630 @node mode_t values
21631 @unnumberedsubsubsec mode_t values
21632 @cindex mode_t values, in file-i/o protocol
21634 All values are given in octal representation.
21651 @unnumberedsubsubsec Errno values
21652 @cindex errno values, in file-i/o protocol
21654 All values are given in decimal representation.
21679 EUNKNOWN is used as a fallback error value if a host system returns
21680 any error value not in the list of supported error numbers.
21683 @unnumberedsubsubsec Lseek flags
21684 @cindex lseek flags, in file-i/o protocol
21693 @unnumberedsubsubsec Limits
21694 @cindex limits, in file-i/o protocol
21696 All values are given in decimal representation.
21699 INT_MIN -2147483648
21701 UINT_MAX 4294967295
21702 LONG_MIN -9223372036854775808
21703 LONG_MAX 9223372036854775807
21704 ULONG_MAX 18446744073709551615
21707 @node File-I/O Examples
21708 @subsection File-I/O Examples
21709 @cindex file-i/o examples
21711 Example sequence of a write call, file descriptor 3, buffer is at target
21712 address 0x1234, 6 bytes should be written:
21715 <- @code{Fwrite,3,1234,6}
21716 @emph{request memory read from target}
21719 @emph{return "6 bytes written"}
21723 Example sequence of a read call, file descriptor 3, buffer is at target
21724 address 0x1234, 6 bytes should be read:
21727 <- @code{Fread,3,1234,6}
21728 @emph{request memory write to target}
21729 -> @code{X1234,6:XXXXXX}
21730 @emph{return "6 bytes read"}
21734 Example sequence of a read call, call fails on the host due to invalid
21735 file descriptor (EBADF):
21738 <- @code{Fread,3,1234,6}
21742 Example sequence of a read call, user presses Ctrl-C before syscall on
21746 <- @code{Fread,3,1234,6}
21751 Example sequence of a read call, user presses Ctrl-C after syscall on
21755 <- @code{Fread,3,1234,6}
21756 -> @code{X1234,6:XXXXXX}
21760 @include agentexpr.texi
21774 % I think something like @colophon should be in texinfo. In the
21776 \long\def\colophon{\hbox to0pt{}\vfill
21777 \centerline{The body of this manual is set in}
21778 \centerline{\fontname\tenrm,}
21779 \centerline{with headings in {\bf\fontname\tenbf}}
21780 \centerline{and examples in {\tt\fontname\tentt}.}
21781 \centerline{{\it\fontname\tenit\/},}
21782 \centerline{{\bf\fontname\tenbf}, and}
21783 \centerline{{\sl\fontname\tensl\/}}
21784 \centerline{are used for emphasis.}\vfill}
21786 % Blame: doc@cygnus.com, 1991.