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++.
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 6.0, 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 terminal user interface: Ben Krepp, Richard Title,
449 John Bishop, Susan Macchia, Kathy Mann, Satish Pai, India Paul, Steve
450 Rehrauer, and Elena Zannoni. Kim Haase provided HP-specific
451 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 Terminal User Interface when starting.
1116 The Terminal User Interface manages several text windows on the terminal,
1117 showing source, assembly, registers and @value{GDBN} command outputs
1118 (@pxref{TUI, ,@value{GDBN} Text User Interface}).
1119 Do not use this option if you run @value{GDBN} from Emacs
1120 (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1123 @c @cindex @code{--xdb}
1124 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1125 @c For information, see the file @file{xdb_trans.html}, which is usually
1126 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1129 @item -interpreter @var{interp}
1130 @cindex @code{--interpreter}
1131 Use the interpreter @var{interp} for interface with the controlling
1132 program or device. This option is meant to be set by programs which
1133 communicate with @value{GDBN} using it as a back end.
1134 @xref{Interpreters, , Command Interpreters}.
1136 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1137 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1138 The @sc{gdb/mi} Interface}) included in @var{GDBN} version 6.0. The
1139 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3,
1140 can be selected with @samp{--interpreter=mi1}. Earlier @sc{gdb/mi}
1141 interfaces are not supported.
1144 @cindex @code{--write}
1145 Open the executable and core files for both reading and writing. This
1146 is equivalent to the @samp{set write on} command inside @value{GDBN}
1150 @cindex @code{--statistics}
1151 This option causes @value{GDBN} to print statistics about time and
1152 memory usage after it completes each command and returns to the prompt.
1155 @cindex @code{--version}
1156 This option causes @value{GDBN} to print its version number and
1157 no-warranty blurb, and exit.
1162 @section Quitting @value{GDBN}
1163 @cindex exiting @value{GDBN}
1164 @cindex leaving @value{GDBN}
1167 @kindex quit @r{[}@var{expression}@r{]}
1168 @kindex q @r{(@code{quit})}
1169 @item quit @r{[}@var{expression}@r{]}
1171 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1172 @code{q}), or type an end-of-file character (usually @kbd{C-d}). If you
1173 do not supply @var{expression}, @value{GDBN} will terminate normally;
1174 otherwise it will terminate using the result of @var{expression} as the
1179 An interrupt (often @kbd{C-c}) does not exit from @value{GDBN}, but rather
1180 terminates the action of any @value{GDBN} command that is in progress and
1181 returns to @value{GDBN} command level. It is safe to type the interrupt
1182 character at any time because @value{GDBN} does not allow it to take effect
1183 until a time when it is safe.
1185 If you have been using @value{GDBN} to control an attached process or
1186 device, you can release it with the @code{detach} command
1187 (@pxref{Attach, ,Debugging an already-running process}).
1189 @node Shell Commands
1190 @section Shell commands
1192 If you need to execute occasional shell commands during your
1193 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1194 just use the @code{shell} command.
1198 @cindex shell escape
1199 @item shell @var{command string}
1200 Invoke a standard shell to execute @var{command string}.
1201 If it exists, the environment variable @code{SHELL} determines which
1202 shell to run. Otherwise @value{GDBN} uses the default shell
1203 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1206 The utility @code{make} is often needed in development environments.
1207 You do not have to use the @code{shell} command for this purpose in
1212 @cindex calling make
1213 @item make @var{make-args}
1214 Execute the @code{make} program with the specified
1215 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1218 @node Logging output
1219 @section Logging output
1220 @cindex logging @value{GDBN} output
1222 You may want to save the output of @value{GDBN} commands to a file.
1223 There are several commands to control @value{GDBN}'s logging.
1227 @item set logging on
1229 @item set logging off
1231 @item set logging file @var{file}
1232 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1233 @item set logging overwrite [on|off]
1234 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1235 you want @code{set logging on} to overwrite the logfile instead.
1236 @item set logging redirect [on|off]
1237 By default, @value{GDBN} output will go to both the terminal and the logfile.
1238 Set @code{redirect} if you want output to go only to the log file.
1239 @kindex show logging
1241 Show the current values of the logging settings.
1245 @chapter @value{GDBN} Commands
1247 You can abbreviate a @value{GDBN} command to the first few letters of the command
1248 name, if that abbreviation is unambiguous; and you can repeat certain
1249 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1250 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1251 show you the alternatives available, if there is more than one possibility).
1254 * Command Syntax:: How to give commands to @value{GDBN}
1255 * Completion:: Command completion
1256 * Help:: How to ask @value{GDBN} for help
1259 @node Command Syntax
1260 @section Command syntax
1262 A @value{GDBN} command is a single line of input. There is no limit on
1263 how long it can be. It starts with a command name, which is followed by
1264 arguments whose meaning depends on the command name. For example, the
1265 command @code{step} accepts an argument which is the number of times to
1266 step, as in @samp{step 5}. You can also use the @code{step} command
1267 with no arguments. Some commands do not allow any arguments.
1269 @cindex abbreviation
1270 @value{GDBN} command names may always be truncated if that abbreviation is
1271 unambiguous. Other possible command abbreviations are listed in the
1272 documentation for individual commands. In some cases, even ambiguous
1273 abbreviations are allowed; for example, @code{s} is specially defined as
1274 equivalent to @code{step} even though there are other commands whose
1275 names start with @code{s}. You can test abbreviations by using them as
1276 arguments to the @code{help} command.
1278 @cindex repeating commands
1279 @kindex RET @r{(repeat last command)}
1280 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1281 repeat the previous command. Certain commands (for example, @code{run})
1282 will not repeat this way; these are commands whose unintentional
1283 repetition might cause trouble and which you are unlikely to want to
1286 The @code{list} and @code{x} commands, when you repeat them with
1287 @key{RET}, construct new arguments rather than repeating
1288 exactly as typed. This permits easy scanning of source or memory.
1290 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1291 output, in a way similar to the common utility @code{more}
1292 (@pxref{Screen Size,,Screen size}). Since it is easy to press one
1293 @key{RET} too many in this situation, @value{GDBN} disables command
1294 repetition after any command that generates this sort of display.
1296 @kindex # @r{(a comment)}
1298 Any text from a @kbd{#} to the end of the line is a comment; it does
1299 nothing. This is useful mainly in command files (@pxref{Command
1300 Files,,Command files}).
1302 @cindex repeating command sequences
1303 @kindex C-o @r{(operate-and-get-next)}
1304 The @kbd{C-o} binding is useful for repeating a complex sequence of
1305 commands. This command accepts the current line, like @kbd{RET}, and
1306 then fetches the next line relative to the current line from the history
1310 @section Command completion
1313 @cindex word completion
1314 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1315 only one possibility; it can also show you what the valid possibilities
1316 are for the next word in a command, at any time. This works for @value{GDBN}
1317 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1319 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1320 of a word. If there is only one possibility, @value{GDBN} fills in the
1321 word, and waits for you to finish the command (or press @key{RET} to
1322 enter it). For example, if you type
1324 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1325 @c complete accuracy in these examples; space introduced for clarity.
1326 @c If texinfo enhancements make it unnecessary, it would be nice to
1327 @c replace " @key" by "@key" in the following...
1329 (@value{GDBP}) info bre @key{TAB}
1333 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1334 the only @code{info} subcommand beginning with @samp{bre}:
1337 (@value{GDBP}) info breakpoints
1341 You can either press @key{RET} at this point, to run the @code{info
1342 breakpoints} command, or backspace and enter something else, if
1343 @samp{breakpoints} does not look like the command you expected. (If you
1344 were sure you wanted @code{info breakpoints} in the first place, you
1345 might as well just type @key{RET} immediately after @samp{info bre},
1346 to exploit command abbreviations rather than command completion).
1348 If there is more than one possibility for the next word when you press
1349 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1350 characters and try again, or just press @key{TAB} a second time;
1351 @value{GDBN} displays all the possible completions for that word. For
1352 example, you might want to set a breakpoint on a subroutine whose name
1353 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1354 just sounds the bell. Typing @key{TAB} again displays all the
1355 function names in your program that begin with those characters, for
1359 (@value{GDBP}) b make_ @key{TAB}
1360 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1361 make_a_section_from_file make_environ
1362 make_abs_section make_function_type
1363 make_blockvector make_pointer_type
1364 make_cleanup make_reference_type
1365 make_command make_symbol_completion_list
1366 (@value{GDBP}) b make_
1370 After displaying the available possibilities, @value{GDBN} copies your
1371 partial input (@samp{b make_} in the example) so you can finish the
1374 If you just want to see the list of alternatives in the first place, you
1375 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1376 means @kbd{@key{META} ?}. You can type this either by holding down a
1377 key designated as the @key{META} shift on your keyboard (if there is
1378 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1380 @cindex quotes in commands
1381 @cindex completion of quoted strings
1382 Sometimes the string you need, while logically a ``word'', may contain
1383 parentheses or other characters that @value{GDBN} normally excludes from
1384 its notion of a word. To permit word completion to work in this
1385 situation, you may enclose words in @code{'} (single quote marks) in
1386 @value{GDBN} commands.
1388 The most likely situation where you might need this is in typing the
1389 name of a C@t{++} function. This is because C@t{++} allows function
1390 overloading (multiple definitions of the same function, distinguished
1391 by argument type). For example, when you want to set a breakpoint you
1392 may need to distinguish whether you mean the version of @code{name}
1393 that takes an @code{int} parameter, @code{name(int)}, or the version
1394 that takes a @code{float} parameter, @code{name(float)}. To use the
1395 word-completion facilities in this situation, type a single quote
1396 @code{'} at the beginning of the function name. This alerts
1397 @value{GDBN} that it may need to consider more information than usual
1398 when you press @key{TAB} or @kbd{M-?} to request word completion:
1401 (@value{GDBP}) b 'bubble( @kbd{M-?}
1402 bubble(double,double) bubble(int,int)
1403 (@value{GDBP}) b 'bubble(
1406 In some cases, @value{GDBN} can tell that completing a name requires using
1407 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1408 completing as much as it can) if you do not type the quote in the first
1412 (@value{GDBP}) b bub @key{TAB}
1413 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1414 (@value{GDBP}) b 'bubble(
1418 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1419 you have not yet started typing the argument list when you ask for
1420 completion on an overloaded symbol.
1422 For more information about overloaded functions, see @ref{C plus plus
1423 expressions, ,C@t{++} expressions}. You can use the command @code{set
1424 overload-resolution off} to disable overload resolution;
1425 see @ref{Debugging C plus plus, ,@value{GDBN} features for C@t{++}}.
1429 @section Getting help
1430 @cindex online documentation
1433 You can always ask @value{GDBN} itself for information on its commands,
1434 using the command @code{help}.
1437 @kindex h @r{(@code{help})}
1440 You can use @code{help} (abbreviated @code{h}) with no arguments to
1441 display a short list of named classes of commands:
1445 List of classes of commands:
1447 aliases -- Aliases of other commands
1448 breakpoints -- Making program stop at certain points
1449 data -- Examining data
1450 files -- Specifying and examining files
1451 internals -- Maintenance commands
1452 obscure -- Obscure features
1453 running -- Running the program
1454 stack -- Examining the stack
1455 status -- Status inquiries
1456 support -- Support facilities
1457 tracepoints -- Tracing of program execution without@*
1458 stopping the program
1459 user-defined -- User-defined commands
1461 Type "help" followed by a class name for a list of
1462 commands in that class.
1463 Type "help" followed by command name for full
1465 Command name abbreviations are allowed if unambiguous.
1468 @c the above line break eliminates huge line overfull...
1470 @item help @var{class}
1471 Using one of the general help classes as an argument, you can get a
1472 list of the individual commands in that class. For example, here is the
1473 help display for the class @code{status}:
1476 (@value{GDBP}) help status
1481 @c Line break in "show" line falsifies real output, but needed
1482 @c to fit in smallbook page size.
1483 info -- Generic command for showing things
1484 about the program being debugged
1485 show -- Generic command for showing things
1488 Type "help" followed by command name for full
1490 Command name abbreviations are allowed if unambiguous.
1494 @item help @var{command}
1495 With a command name as @code{help} argument, @value{GDBN} displays a
1496 short paragraph on how to use that command.
1499 @item apropos @var{args}
1500 The @code{apropos @var{args}} command searches through all of the @value{GDBN}
1501 commands, and their documentation, for the regular expression specified in
1502 @var{args}. It prints out all matches found. For example:
1513 set symbol-reloading -- Set dynamic symbol table reloading
1514 multiple times in one run
1515 show symbol-reloading -- Show dynamic symbol table reloading
1516 multiple times in one run
1521 @item complete @var{args}
1522 The @code{complete @var{args}} command lists all the possible completions
1523 for the beginning of a command. Use @var{args} to specify the beginning of the
1524 command you want completed. For example:
1530 @noindent results in:
1541 @noindent This is intended for use by @sc{gnu} Emacs.
1544 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1545 and @code{show} to inquire about the state of your program, or the state
1546 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1547 manual introduces each of them in the appropriate context. The listings
1548 under @code{info} and under @code{show} in the Index point to
1549 all the sub-commands. @xref{Index}.
1554 @kindex i @r{(@code{info})}
1556 This command (abbreviated @code{i}) is for describing the state of your
1557 program. For example, you can list the arguments given to your program
1558 with @code{info args}, list the registers currently in use with @code{info
1559 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1560 You can get a complete list of the @code{info} sub-commands with
1561 @w{@code{help info}}.
1565 You can assign the result of an expression to an environment variable with
1566 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1567 @code{set prompt $}.
1571 In contrast to @code{info}, @code{show} is for describing the state of
1572 @value{GDBN} itself.
1573 You can change most of the things you can @code{show}, by using the
1574 related command @code{set}; for example, you can control what number
1575 system is used for displays with @code{set radix}, or simply inquire
1576 which is currently in use with @code{show radix}.
1579 To display all the settable parameters and their current
1580 values, you can use @code{show} with no arguments; you may also use
1581 @code{info set}. Both commands produce the same display.
1582 @c FIXME: "info set" violates the rule that "info" is for state of
1583 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1584 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1588 Here are three miscellaneous @code{show} subcommands, all of which are
1589 exceptional in lacking corresponding @code{set} commands:
1592 @kindex show version
1593 @cindex version number
1595 Show what version of @value{GDBN} is running. You should include this
1596 information in @value{GDBN} bug-reports. If multiple versions of
1597 @value{GDBN} are in use at your site, you may need to determine which
1598 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1599 commands are introduced, and old ones may wither away. Also, many
1600 system vendors ship variant versions of @value{GDBN}, and there are
1601 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1602 The version number is the same as the one announced when you start
1605 @kindex show copying
1607 Display information about permission for copying @value{GDBN}.
1609 @kindex show warranty
1611 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1612 if your version of @value{GDBN} comes with one.
1617 @chapter Running Programs Under @value{GDBN}
1619 When you run a program under @value{GDBN}, you must first generate
1620 debugging information when you compile it.
1622 You may start @value{GDBN} with its arguments, if any, in an environment
1623 of your choice. If you are doing native debugging, you may redirect
1624 your program's input and output, debug an already running process, or
1625 kill a child process.
1628 * Compilation:: Compiling for debugging
1629 * Starting:: Starting your program
1630 * Arguments:: Your program's arguments
1631 * Environment:: Your program's environment
1633 * Working Directory:: Your program's working directory
1634 * Input/Output:: Your program's input and output
1635 * Attach:: Debugging an already-running process
1636 * Kill Process:: Killing the child process
1638 * Threads:: Debugging programs with multiple threads
1639 * Processes:: Debugging programs with multiple processes
1643 @section Compiling for debugging
1645 In order to debug a program effectively, you need to generate
1646 debugging information when you compile it. This debugging information
1647 is stored in the object file; it describes the data type of each
1648 variable or function and the correspondence between source line numbers
1649 and addresses in the executable code.
1651 To request debugging information, specify the @samp{-g} option when you run
1654 Most compilers do not include information about preprocessor macros in
1655 the debugging information if you specify the @option{-g} flag alone,
1656 because this information is rather large. Version 3.1 of @value{NGCC},
1657 the @sc{gnu} C compiler, provides macro information if you specify the
1658 options @option{-gdwarf-2} and @option{-g3}; the former option requests
1659 debugging information in the Dwarf 2 format, and the latter requests
1660 ``extra information''. In the future, we hope to find more compact ways
1661 to represent macro information, so that it can be included with
1664 Many C compilers are unable to handle the @samp{-g} and @samp{-O}
1665 options together. Using those compilers, you cannot generate optimized
1666 executables containing debugging information.
1668 @value{NGCC}, the @sc{gnu} C compiler, supports @samp{-g} with or
1669 without @samp{-O}, making it possible to debug optimized code. We
1670 recommend that you @emph{always} use @samp{-g} whenever you compile a
1671 program. You may think your program is correct, but there is no sense
1672 in pushing your luck.
1674 @cindex optimized code, debugging
1675 @cindex debugging optimized code
1676 When you debug a program compiled with @samp{-g -O}, remember that the
1677 optimizer is rearranging your code; the debugger shows you what is
1678 really there. Do not be too surprised when the execution path does not
1679 exactly match your source file! An extreme example: if you define a
1680 variable, but never use it, @value{GDBN} never sees that
1681 variable---because the compiler optimizes it out of existence.
1683 Some things do not work as well with @samp{-g -O} as with just
1684 @samp{-g}, particularly on machines with instruction scheduling. If in
1685 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1686 please report it to us as a bug (including a test case!).
1688 Older versions of the @sc{gnu} C compiler permitted a variant option
1689 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1690 format; if your @sc{gnu} C compiler has this option, do not use it.
1694 @section Starting your program
1700 @kindex r @r{(@code{run})}
1703 Use the @code{run} command to start your program under @value{GDBN}.
1704 You must first specify the program name (except on VxWorks) with an
1705 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1706 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1707 (@pxref{Files, ,Commands to specify files}).
1711 If you are running your program in an execution environment that
1712 supports processes, @code{run} creates an inferior process and makes
1713 that process run your program. (In environments without processes,
1714 @code{run} jumps to the start of your program.)
1716 The execution of a program is affected by certain information it
1717 receives from its superior. @value{GDBN} provides ways to specify this
1718 information, which you must do @emph{before} starting your program. (You
1719 can change it after starting your program, but such changes only affect
1720 your program the next time you start it.) This information may be
1721 divided into four categories:
1724 @item The @emph{arguments.}
1725 Specify the arguments to give your program as the arguments of the
1726 @code{run} command. If a shell is available on your target, the shell
1727 is used to pass the arguments, so that you may use normal conventions
1728 (such as wildcard expansion or variable substitution) in describing
1730 In Unix systems, you can control which shell is used with the
1731 @code{SHELL} environment variable.
1732 @xref{Arguments, ,Your program's arguments}.
1734 @item The @emph{environment.}
1735 Your program normally inherits its environment from @value{GDBN}, but you can
1736 use the @value{GDBN} commands @code{set environment} and @code{unset
1737 environment} to change parts of the environment that affect
1738 your program. @xref{Environment, ,Your program's environment}.
1740 @item The @emph{working directory.}
1741 Your program inherits its working directory from @value{GDBN}. You can set
1742 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1743 @xref{Working Directory, ,Your program's working directory}.
1745 @item The @emph{standard input and output.}
1746 Your program normally uses the same device for standard input and
1747 standard output as @value{GDBN} is using. You can redirect input and output
1748 in the @code{run} command line, or you can use the @code{tty} command to
1749 set a different device for your program.
1750 @xref{Input/Output, ,Your program's input and output}.
1753 @emph{Warning:} While input and output redirection work, you cannot use
1754 pipes to pass the output of the program you are debugging to another
1755 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1759 When you issue the @code{run} command, your program begins to execute
1760 immediately. @xref{Stopping, ,Stopping and continuing}, for discussion
1761 of how to arrange for your program to stop. Once your program has
1762 stopped, you may call functions in your program, using the @code{print}
1763 or @code{call} commands. @xref{Data, ,Examining Data}.
1765 If the modification time of your symbol file has changed since the last
1766 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1767 table, and reads it again. When it does this, @value{GDBN} tries to retain
1768 your current breakpoints.
1771 @section Your program's arguments
1773 @cindex arguments (to your program)
1774 The arguments to your program can be specified by the arguments of the
1776 They are passed to a shell, which expands wildcard characters and
1777 performs redirection of I/O, and thence to your program. Your
1778 @code{SHELL} environment variable (if it exists) specifies what shell
1779 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1780 the default shell (@file{/bin/sh} on Unix).
1782 On non-Unix systems, the program is usually invoked directly by
1783 @value{GDBN}, which emulates I/O redirection via the appropriate system
1784 calls, and the wildcard characters are expanded by the startup code of
1785 the program, not by the shell.
1787 @code{run} with no arguments uses the same arguments used by the previous
1788 @code{run}, or those set by the @code{set args} command.
1793 Specify the arguments to be used the next time your program is run. If
1794 @code{set args} has no arguments, @code{run} executes your program
1795 with no arguments. Once you have run your program with arguments,
1796 using @code{set args} before the next @code{run} is the only way to run
1797 it again without arguments.
1801 Show the arguments to give your program when it is started.
1805 @section Your program's environment
1807 @cindex environment (of your program)
1808 The @dfn{environment} consists of a set of environment variables and
1809 their values. Environment variables conventionally record such things as
1810 your user name, your home directory, your terminal type, and your search
1811 path for programs to run. Usually you set up environment variables with
1812 the shell and they are inherited by all the other programs you run. When
1813 debugging, it can be useful to try running your program with a modified
1814 environment without having to start @value{GDBN} over again.
1818 @item path @var{directory}
1819 Add @var{directory} to the front of the @code{PATH} environment variable
1820 (the search path for executables) that will be passed to your program.
1821 The value of @code{PATH} used by @value{GDBN} does not change.
1822 You may specify several directory names, separated by whitespace or by a
1823 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1824 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1825 is moved to the front, so it is searched sooner.
1827 You can use the string @samp{$cwd} to refer to whatever is the current
1828 working directory at the time @value{GDBN} searches the path. If you
1829 use @samp{.} instead, it refers to the directory where you executed the
1830 @code{path} command. @value{GDBN} replaces @samp{.} in the
1831 @var{directory} argument (with the current path) before adding
1832 @var{directory} to the search path.
1833 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1834 @c document that, since repeating it would be a no-op.
1838 Display the list of search paths for executables (the @code{PATH}
1839 environment variable).
1841 @kindex show environment
1842 @item show environment @r{[}@var{varname}@r{]}
1843 Print the value of environment variable @var{varname} to be given to
1844 your program when it starts. If you do not supply @var{varname},
1845 print the names and values of all environment variables to be given to
1846 your program. You can abbreviate @code{environment} as @code{env}.
1848 @kindex set environment
1849 @item set environment @var{varname} @r{[}=@var{value}@r{]}
1850 Set environment variable @var{varname} to @var{value}. The value
1851 changes for your program only, not for @value{GDBN} itself. @var{value} may
1852 be any string; the values of environment variables are just strings, and
1853 any interpretation is supplied by your program itself. The @var{value}
1854 parameter is optional; if it is eliminated, the variable is set to a
1856 @c "any string" here does not include leading, trailing
1857 @c blanks. Gnu asks: does anyone care?
1859 For example, this command:
1866 tells the debugged program, when subsequently run, that its user is named
1867 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
1868 are not actually required.)
1870 @kindex unset environment
1871 @item unset environment @var{varname}
1872 Remove variable @var{varname} from the environment to be passed to your
1873 program. This is different from @samp{set env @var{varname} =};
1874 @code{unset environment} removes the variable from the environment,
1875 rather than assigning it an empty value.
1878 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
1880 by your @code{SHELL} environment variable if it exists (or
1881 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
1882 that runs an initialization file---such as @file{.cshrc} for C-shell, or
1883 @file{.bashrc} for BASH---any variables you set in that file affect
1884 your program. You may wish to move setting of environment variables to
1885 files that are only run when you sign on, such as @file{.login} or
1888 @node Working Directory
1889 @section Your program's working directory
1891 @cindex working directory (of your program)
1892 Each time you start your program with @code{run}, it inherits its
1893 working directory from the current working directory of @value{GDBN}.
1894 The @value{GDBN} working directory is initially whatever it inherited
1895 from its parent process (typically the shell), but you can specify a new
1896 working directory in @value{GDBN} with the @code{cd} command.
1898 The @value{GDBN} working directory also serves as a default for the commands
1899 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
1904 @item cd @var{directory}
1905 Set the @value{GDBN} working directory to @var{directory}.
1909 Print the @value{GDBN} working directory.
1913 @section Your program's input and output
1918 By default, the program you run under @value{GDBN} does input and output to
1919 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
1920 to its own terminal modes to interact with you, but it records the terminal
1921 modes your program was using and switches back to them when you continue
1922 running your program.
1925 @kindex info terminal
1927 Displays information recorded by @value{GDBN} about the terminal modes your
1931 You can redirect your program's input and/or output using shell
1932 redirection with the @code{run} command. For example,
1939 starts your program, diverting its output to the file @file{outfile}.
1942 @cindex controlling terminal
1943 Another way to specify where your program should do input and output is
1944 with the @code{tty} command. This command accepts a file name as
1945 argument, and causes this file to be the default for future @code{run}
1946 commands. It also resets the controlling terminal for the child
1947 process, for future @code{run} commands. For example,
1954 directs that processes started with subsequent @code{run} commands
1955 default to do input and output on the terminal @file{/dev/ttyb} and have
1956 that as their controlling terminal.
1958 An explicit redirection in @code{run} overrides the @code{tty} command's
1959 effect on the input/output device, but not its effect on the controlling
1962 When you use the @code{tty} command or redirect input in the @code{run}
1963 command, only the input @emph{for your program} is affected. The input
1964 for @value{GDBN} still comes from your terminal.
1967 @section Debugging an already-running process
1972 @item attach @var{process-id}
1973 This command attaches to a running process---one that was started
1974 outside @value{GDBN}. (@code{info files} shows your active
1975 targets.) The command takes as argument a process ID. The usual way to
1976 find out the process-id of a Unix process is with the @code{ps} utility,
1977 or with the @samp{jobs -l} shell command.
1979 @code{attach} does not repeat if you press @key{RET} a second time after
1980 executing the command.
1983 To use @code{attach}, your program must be running in an environment
1984 which supports processes; for example, @code{attach} does not work for
1985 programs on bare-board targets that lack an operating system. You must
1986 also have permission to send the process a signal.
1988 When you use @code{attach}, the debugger finds the program running in
1989 the process first by looking in the current working directory, then (if
1990 the program is not found) by using the source file search path
1991 (@pxref{Source Path, ,Specifying source directories}). You can also use
1992 the @code{file} command to load the program. @xref{Files, ,Commands to
1995 The first thing @value{GDBN} does after arranging to debug the specified
1996 process is to stop it. You can examine and modify an attached process
1997 with all the @value{GDBN} commands that are ordinarily available when
1998 you start processes with @code{run}. You can insert breakpoints; you
1999 can step and continue; you can modify storage. If you would rather the
2000 process continue running, you may use the @code{continue} command after
2001 attaching @value{GDBN} to the process.
2006 When you have finished debugging the attached process, you can use the
2007 @code{detach} command to release it from @value{GDBN} control. Detaching
2008 the process continues its execution. After the @code{detach} command,
2009 that process and @value{GDBN} become completely independent once more, and you
2010 are ready to @code{attach} another process or start one with @code{run}.
2011 @code{detach} does not repeat if you press @key{RET} again after
2012 executing the command.
2015 If you exit @value{GDBN} or use the @code{run} command while you have an
2016 attached process, you kill that process. By default, @value{GDBN} asks
2017 for confirmation if you try to do either of these things; you can
2018 control whether or not you need to confirm by using the @code{set
2019 confirm} command (@pxref{Messages/Warnings, ,Optional warnings and
2023 @section Killing the child process
2028 Kill the child process in which your program is running under @value{GDBN}.
2031 This command is useful if you wish to debug a core dump instead of a
2032 running process. @value{GDBN} ignores any core dump file while your program
2035 On some operating systems, a program cannot be executed outside @value{GDBN}
2036 while you have breakpoints set on it inside @value{GDBN}. You can use the
2037 @code{kill} command in this situation to permit running your program
2038 outside the debugger.
2040 The @code{kill} command is also useful if you wish to recompile and
2041 relink your program, since on many systems it is impossible to modify an
2042 executable file while it is running in a process. In this case, when you
2043 next type @code{run}, @value{GDBN} notices that the file has changed, and
2044 reads the symbol table again (while trying to preserve your current
2045 breakpoint settings).
2048 @section Debugging programs with multiple threads
2050 @cindex threads of execution
2051 @cindex multiple threads
2052 @cindex switching threads
2053 In some operating systems, such as HP-UX and Solaris, a single program
2054 may have more than one @dfn{thread} of execution. The precise semantics
2055 of threads differ from one operating system to another, but in general
2056 the threads of a single program are akin to multiple processes---except
2057 that they share one address space (that is, they can all examine and
2058 modify the same variables). On the other hand, each thread has its own
2059 registers and execution stack, and perhaps private memory.
2061 @value{GDBN} provides these facilities for debugging multi-thread
2065 @item automatic notification of new threads
2066 @item @samp{thread @var{threadno}}, a command to switch among threads
2067 @item @samp{info threads}, a command to inquire about existing threads
2068 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2069 a command to apply a command to a list of threads
2070 @item thread-specific breakpoints
2074 @emph{Warning:} These facilities are not yet available on every
2075 @value{GDBN} configuration where the operating system supports threads.
2076 If your @value{GDBN} does not support threads, these commands have no
2077 effect. For example, a system without thread support shows no output
2078 from @samp{info threads}, and always rejects the @code{thread} command,
2082 (@value{GDBP}) info threads
2083 (@value{GDBP}) thread 1
2084 Thread ID 1 not known. Use the "info threads" command to
2085 see the IDs of currently known threads.
2087 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2088 @c doesn't support threads"?
2091 @cindex focus of debugging
2092 @cindex current thread
2093 The @value{GDBN} thread debugging facility allows you to observe all
2094 threads while your program runs---but whenever @value{GDBN} takes
2095 control, one thread in particular is always the focus of debugging.
2096 This thread is called the @dfn{current thread}. Debugging commands show
2097 program information from the perspective of the current thread.
2099 @cindex @code{New} @var{systag} message
2100 @cindex thread identifier (system)
2101 @c FIXME-implementors!! It would be more helpful if the [New...] message
2102 @c included GDB's numeric thread handle, so you could just go to that
2103 @c thread without first checking `info threads'.
2104 Whenever @value{GDBN} detects a new thread in your program, it displays
2105 the target system's identification for the thread with a message in the
2106 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2107 whose form varies depending on the particular system. For example, on
2108 LynxOS, you might see
2111 [New process 35 thread 27]
2115 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2116 the @var{systag} is simply something like @samp{process 368}, with no
2119 @c FIXME!! (1) Does the [New...] message appear even for the very first
2120 @c thread of a program, or does it only appear for the
2121 @c second---i.e.@: when it becomes obvious we have a multithread
2123 @c (2) *Is* there necessarily a first thread always? Or do some
2124 @c multithread systems permit starting a program with multiple
2125 @c threads ab initio?
2127 @cindex thread number
2128 @cindex thread identifier (GDB)
2129 For debugging purposes, @value{GDBN} associates its own thread
2130 number---always a single integer---with each thread in your program.
2133 @kindex info threads
2135 Display a summary of all threads currently in your
2136 program. @value{GDBN} displays for each thread (in this order):
2139 @item the thread number assigned by @value{GDBN}
2141 @item the target system's thread identifier (@var{systag})
2143 @item the current stack frame summary for that thread
2147 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2148 indicates the current thread.
2152 @c end table here to get a little more width for example
2155 (@value{GDBP}) info threads
2156 3 process 35 thread 27 0x34e5 in sigpause ()
2157 2 process 35 thread 23 0x34e5 in sigpause ()
2158 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2164 @cindex thread number
2165 @cindex thread identifier (GDB)
2166 For debugging purposes, @value{GDBN} associates its own thread
2167 number---a small integer assigned in thread-creation order---with each
2168 thread in your program.
2170 @cindex @code{New} @var{systag} message, on HP-UX
2171 @cindex thread identifier (system), on HP-UX
2172 @c FIXME-implementors!! It would be more helpful if the [New...] message
2173 @c included GDB's numeric thread handle, so you could just go to that
2174 @c thread without first checking `info threads'.
2175 Whenever @value{GDBN} detects a new thread in your program, it displays
2176 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2177 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2178 whose form varies depending on the particular system. For example, on
2182 [New thread 2 (system thread 26594)]
2186 when @value{GDBN} notices a new thread.
2189 @kindex info threads
2191 Display a summary of all threads currently in your
2192 program. @value{GDBN} displays for each thread (in this order):
2195 @item the thread number assigned by @value{GDBN}
2197 @item the target system's thread identifier (@var{systag})
2199 @item the current stack frame summary for that thread
2203 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2204 indicates the current thread.
2208 @c end table here to get a little more width for example
2211 (@value{GDBP}) info threads
2212 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2214 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2215 from /usr/lib/libc.2
2216 1 system thread 27905 0x7b003498 in _brk () \@*
2217 from /usr/lib/libc.2
2221 @kindex thread @var{threadno}
2222 @item thread @var{threadno}
2223 Make thread number @var{threadno} the current thread. The command
2224 argument @var{threadno} is the internal @value{GDBN} thread number, as
2225 shown in the first field of the @samp{info threads} display.
2226 @value{GDBN} responds by displaying the system identifier of the thread
2227 you selected, and its current stack frame summary:
2230 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2231 (@value{GDBP}) thread 2
2232 [Switching to process 35 thread 23]
2233 0x34e5 in sigpause ()
2237 As with the @samp{[New @dots{}]} message, the form of the text after
2238 @samp{Switching to} depends on your system's conventions for identifying
2241 @kindex thread apply
2242 @item thread apply [@var{threadno}] [@var{all}] @var{args}
2243 The @code{thread apply} command allows you to apply a command to one or
2244 more threads. Specify the numbers of the threads that you want affected
2245 with the command argument @var{threadno}. @var{threadno} is the internal
2246 @value{GDBN} thread number, as shown in the first field of the @samp{info
2247 threads} display. To apply a command to all threads, use
2248 @code{thread apply all} @var{args}.
2251 @cindex automatic thread selection
2252 @cindex switching threads automatically
2253 @cindex threads, automatic switching
2254 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2255 signal, it automatically selects the thread where that breakpoint or
2256 signal happened. @value{GDBN} alerts you to the context switch with a
2257 message of the form @samp{[Switching to @var{systag}]} to identify the
2260 @xref{Thread Stops,,Stopping and starting multi-thread programs}, for
2261 more information about how @value{GDBN} behaves when you stop and start
2262 programs with multiple threads.
2264 @xref{Set Watchpoints,,Setting watchpoints}, for information about
2265 watchpoints in programs with multiple threads.
2268 @section Debugging programs with multiple processes
2270 @cindex fork, debugging programs which call
2271 @cindex multiple processes
2272 @cindex processes, multiple
2273 On most systems, @value{GDBN} has no special support for debugging
2274 programs which create additional processes using the @code{fork}
2275 function. When a program forks, @value{GDBN} will continue to debug the
2276 parent process and the child process will run unimpeded. If you have
2277 set a breakpoint in any code which the child then executes, the child
2278 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2279 will cause it to terminate.
2281 However, if you want to debug the child process there is a workaround
2282 which isn't too painful. Put a call to @code{sleep} in the code which
2283 the child process executes after the fork. It may be useful to sleep
2284 only if a certain environment variable is set, or a certain file exists,
2285 so that the delay need not occur when you don't want to run @value{GDBN}
2286 on the child. While the child is sleeping, use the @code{ps} program to
2287 get its process ID. Then tell @value{GDBN} (a new invocation of
2288 @value{GDBN} if you are also debugging the parent process) to attach to
2289 the child process (@pxref{Attach}). From that point on you can debug
2290 the child process just like any other process which you attached to.
2292 On some systems, @value{GDBN} provides support for debugging programs that
2293 create additional processes using the @code{fork} or @code{vfork} functions.
2294 Currently, the only platforms with this feature are HP-UX (11.x and later
2295 only?) and GNU/Linux (kernel version 2.5.60 and later).
2297 By default, when a program forks, @value{GDBN} will continue to debug
2298 the parent process and the child process will run unimpeded.
2300 If you want to follow the child process instead of the parent process,
2301 use the command @w{@code{set follow-fork-mode}}.
2304 @kindex set follow-fork-mode
2305 @item set follow-fork-mode @var{mode}
2306 Set the debugger response to a program call of @code{fork} or
2307 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2308 process. The @var{mode} can be:
2312 The original process is debugged after a fork. The child process runs
2313 unimpeded. This is the default.
2316 The new process is debugged after a fork. The parent process runs
2321 @item show follow-fork-mode
2322 Display the current debugger response to a @code{fork} or @code{vfork} call.
2325 If you ask to debug a child process and a @code{vfork} is followed by an
2326 @code{exec}, @value{GDBN} executes the new target up to the first
2327 breakpoint in the new target. If you have a breakpoint set on
2328 @code{main} in your original program, the breakpoint will also be set on
2329 the child process's @code{main}.
2331 When a child process is spawned by @code{vfork}, you cannot debug the
2332 child or parent until an @code{exec} call completes.
2334 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2335 call executes, the new target restarts. To restart the parent process,
2336 use the @code{file} command with the parent executable name as its
2339 You can use the @code{catch} command to make @value{GDBN} stop whenever
2340 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2341 Catchpoints, ,Setting catchpoints}.
2344 @chapter Stopping and Continuing
2346 The principal purposes of using a debugger are so that you can stop your
2347 program before it terminates; or so that, if your program runs into
2348 trouble, you can investigate and find out why.
2350 Inside @value{GDBN}, your program may stop for any of several reasons,
2351 such as a signal, a breakpoint, or reaching a new line after a
2352 @value{GDBN} command such as @code{step}. You may then examine and
2353 change variables, set new breakpoints or remove old ones, and then
2354 continue execution. Usually, the messages shown by @value{GDBN} provide
2355 ample explanation of the status of your program---but you can also
2356 explicitly request this information at any time.
2359 @kindex info program
2361 Display information about the status of your program: whether it is
2362 running or not, what process it is, and why it stopped.
2366 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2367 * Continuing and Stepping:: Resuming execution
2369 * Thread Stops:: Stopping and starting multi-thread programs
2373 @section Breakpoints, watchpoints, and catchpoints
2376 A @dfn{breakpoint} makes your program stop whenever a certain point in
2377 the program is reached. For each breakpoint, you can add conditions to
2378 control in finer detail whether your program stops. You can set
2379 breakpoints with the @code{break} command and its variants (@pxref{Set
2380 Breaks, ,Setting breakpoints}), to specify the place where your program
2381 should stop by line number, function name or exact address in the
2384 In HP-UX, SunOS 4.x, SVR4, and Alpha OSF/1 configurations, you can set
2385 breakpoints in shared libraries before the executable is run. There is
2386 a minor limitation on HP-UX systems: you must wait until the executable
2387 is run in order to set breakpoints in shared library routines that are
2388 not called directly by the program (for example, routines that are
2389 arguments in a @code{pthread_create} call).
2392 @cindex memory tracing
2393 @cindex breakpoint on memory address
2394 @cindex breakpoint on variable modification
2395 A @dfn{watchpoint} is a special breakpoint that stops your program
2396 when the value of an expression changes. You must use a different
2397 command to set watchpoints (@pxref{Set Watchpoints, ,Setting
2398 watchpoints}), but aside from that, you can manage a watchpoint like
2399 any other breakpoint: you enable, disable, and delete both breakpoints
2400 and watchpoints using the same commands.
2402 You can arrange to have values from your program displayed automatically
2403 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2407 @cindex breakpoint on events
2408 A @dfn{catchpoint} is another special breakpoint that stops your program
2409 when a certain kind of event occurs, such as the throwing of a C@t{++}
2410 exception or the loading of a library. As with watchpoints, you use a
2411 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2412 catchpoints}), but aside from that, you can manage a catchpoint like any
2413 other breakpoint. (To stop when your program receives a signal, use the
2414 @code{handle} command; see @ref{Signals, ,Signals}.)
2416 @cindex breakpoint numbers
2417 @cindex numbers for breakpoints
2418 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2419 catchpoint when you create it; these numbers are successive integers
2420 starting with one. In many of the commands for controlling various
2421 features of breakpoints you use the breakpoint number to say which
2422 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2423 @dfn{disabled}; if disabled, it has no effect on your program until you
2426 @cindex breakpoint ranges
2427 @cindex ranges of breakpoints
2428 Some @value{GDBN} commands accept a range of breakpoints on which to
2429 operate. A breakpoint range is either a single breakpoint number, like
2430 @samp{5}, or two such numbers, in increasing order, separated by a
2431 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2432 all breakpoint in that range are operated on.
2435 * Set Breaks:: Setting breakpoints
2436 * Set Watchpoints:: Setting watchpoints
2437 * Set Catchpoints:: Setting catchpoints
2438 * Delete Breaks:: Deleting breakpoints
2439 * Disabling:: Disabling breakpoints
2440 * Conditions:: Break conditions
2441 * Break Commands:: Breakpoint command lists
2442 * Breakpoint Menus:: Breakpoint menus
2443 * Error in Breakpoints:: ``Cannot insert breakpoints''
2444 * Breakpoint related warnings:: ``Breakpoint address adjusted...''
2448 @subsection Setting breakpoints
2450 @c FIXME LMB what does GDB do if no code on line of breakpt?
2451 @c consider in particular declaration with/without initialization.
2453 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2456 @kindex b @r{(@code{break})}
2457 @vindex $bpnum@r{, convenience variable}
2458 @cindex latest breakpoint
2459 Breakpoints are set with the @code{break} command (abbreviated
2460 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2461 number of the breakpoint you've set most recently; see @ref{Convenience
2462 Vars,, Convenience variables}, for a discussion of what you can do with
2463 convenience variables.
2465 You have several ways to say where the breakpoint should go.
2468 @item break @var{function}
2469 Set a breakpoint at entry to function @var{function}.
2470 When using source languages that permit overloading of symbols, such as
2471 C@t{++}, @var{function} may refer to more than one possible place to break.
2472 @xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
2474 @item break +@var{offset}
2475 @itemx break -@var{offset}
2476 Set a breakpoint some number of lines forward or back from the position
2477 at which execution stopped in the currently selected @dfn{stack frame}.
2478 (@xref{Frames, ,Frames}, for a description of stack frames.)
2480 @item break @var{linenum}
2481 Set a breakpoint at line @var{linenum} in the current source file.
2482 The current source file is the last file whose source text was printed.
2483 The breakpoint will stop your program just before it executes any of the
2486 @item break @var{filename}:@var{linenum}
2487 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2489 @item break @var{filename}:@var{function}
2490 Set a breakpoint at entry to function @var{function} found in file
2491 @var{filename}. Specifying a file name as well as a function name is
2492 superfluous except when multiple files contain similarly named
2495 @item break *@var{address}
2496 Set a breakpoint at address @var{address}. You can use this to set
2497 breakpoints in parts of your program which do not have debugging
2498 information or source files.
2501 When called without any arguments, @code{break} sets a breakpoint at
2502 the next instruction to be executed in the selected stack frame
2503 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2504 innermost, this makes your program stop as soon as control
2505 returns to that frame. This is similar to the effect of a
2506 @code{finish} command in the frame inside the selected frame---except
2507 that @code{finish} does not leave an active breakpoint. If you use
2508 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2509 the next time it reaches the current location; this may be useful
2512 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2513 least one instruction has been executed. If it did not do this, you
2514 would be unable to proceed past a breakpoint without first disabling the
2515 breakpoint. This rule applies whether or not the breakpoint already
2516 existed when your program stopped.
2518 @item break @dots{} if @var{cond}
2519 Set a breakpoint with condition @var{cond}; evaluate the expression
2520 @var{cond} each time the breakpoint is reached, and stop only if the
2521 value is nonzero---that is, if @var{cond} evaluates as true.
2522 @samp{@dots{}} stands for one of the possible arguments described
2523 above (or no argument) specifying where to break. @xref{Conditions,
2524 ,Break conditions}, for more information on breakpoint conditions.
2527 @item tbreak @var{args}
2528 Set a breakpoint enabled only for one stop. @var{args} are the
2529 same as for the @code{break} command, and the breakpoint is set in the same
2530 way, but the breakpoint is automatically deleted after the first time your
2531 program stops there. @xref{Disabling, ,Disabling breakpoints}.
2534 @item hbreak @var{args}
2535 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2536 @code{break} command and the breakpoint is set in the same way, but the
2537 breakpoint requires hardware support and some target hardware may not
2538 have this support. The main purpose of this is EPROM/ROM code
2539 debugging, so you can set a breakpoint at an instruction without
2540 changing the instruction. This can be used with the new trap-generation
2541 provided by SPARClite DSU and some x86-based targets. These targets
2542 will generate traps when a program accesses some data or instruction
2543 address that is assigned to the debug registers. However the hardware
2544 breakpoint registers can take a limited number of breakpoints. For
2545 example, on the DSU, only two data breakpoints can be set at a time, and
2546 @value{GDBN} will reject this command if more than two are used. Delete
2547 or disable unused hardware breakpoints before setting new ones
2548 (@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}.
2549 @xref{set remote hardware-breakpoint-limit}.
2553 @item thbreak @var{args}
2554 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2555 are the same as for the @code{hbreak} command and the breakpoint is set in
2556 the same way. However, like the @code{tbreak} command,
2557 the breakpoint is automatically deleted after the
2558 first time your program stops there. Also, like the @code{hbreak}
2559 command, the breakpoint requires hardware support and some target hardware
2560 may not have this support. @xref{Disabling, ,Disabling breakpoints}.
2561 See also @ref{Conditions, ,Break conditions}.
2564 @cindex regular expression
2565 @item rbreak @var{regex}
2566 Set breakpoints on all functions matching the regular expression
2567 @var{regex}. This command sets an unconditional breakpoint on all
2568 matches, printing a list of all breakpoints it set. Once these
2569 breakpoints are set, they are treated just like the breakpoints set with
2570 the @code{break} command. You can delete them, disable them, or make
2571 them conditional the same way as any other breakpoint.
2573 The syntax of the regular expression is the standard one used with tools
2574 like @file{grep}. Note that this is different from the syntax used by
2575 shells, so for instance @code{foo*} matches all functions that include
2576 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2577 @code{.*} leading and trailing the regular expression you supply, so to
2578 match only functions that begin with @code{foo}, use @code{^foo}.
2580 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2581 breakpoints on overloaded functions that are not members of any special
2584 @kindex info breakpoints
2585 @cindex @code{$_} and @code{info breakpoints}
2586 @item info breakpoints @r{[}@var{n}@r{]}
2587 @itemx info break @r{[}@var{n}@r{]}
2588 @itemx info watchpoints @r{[}@var{n}@r{]}
2589 Print a table of all breakpoints, watchpoints, and catchpoints set and
2590 not deleted, with the following columns for each breakpoint:
2593 @item Breakpoint Numbers
2595 Breakpoint, watchpoint, or catchpoint.
2597 Whether the breakpoint is marked to be disabled or deleted when hit.
2598 @item Enabled or Disabled
2599 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2600 that are not enabled.
2602 Where the breakpoint is in your program, as a memory address. If the
2603 breakpoint is pending (see below for details) on a future load of a shared library, the address
2604 will be listed as @samp{<PENDING>}.
2606 Where the breakpoint is in the source for your program, as a file and
2607 line number. For a pending breakpoint, the original string passed to
2608 the breakpoint command will be listed as it cannot be resolved until
2609 the appropriate shared library is loaded in the future.
2613 If a breakpoint is conditional, @code{info break} shows the condition on
2614 the line following the affected breakpoint; breakpoint commands, if any,
2615 are listed after that. A pending breakpoint is allowed to have a condition
2616 specified for it. The condition is not parsed for validity until a shared
2617 library is loaded that allows the pending breakpoint to resolve to a
2621 @code{info break} with a breakpoint
2622 number @var{n} as argument lists only that breakpoint. The
2623 convenience variable @code{$_} and the default examining-address for
2624 the @code{x} command are set to the address of the last breakpoint
2625 listed (@pxref{Memory, ,Examining memory}).
2628 @code{info break} displays a count of the number of times the breakpoint
2629 has been hit. This is especially useful in conjunction with the
2630 @code{ignore} command. You can ignore a large number of breakpoint
2631 hits, look at the breakpoint info to see how many times the breakpoint
2632 was hit, and then run again, ignoring one less than that number. This
2633 will get you quickly to the last hit of that breakpoint.
2636 @value{GDBN} allows you to set any number of breakpoints at the same place in
2637 your program. There is nothing silly or meaningless about this. When
2638 the breakpoints are conditional, this is even useful
2639 (@pxref{Conditions, ,Break conditions}).
2641 @cindex pending breakpoints
2642 If a specified breakpoint location cannot be found, @value{GDBN} will
2644 as to whether to make the breakpoint pending on a future shared
2645 library load. This is useful for setting breakpoints at the start of your
2646 @value{GDBN} session for locations that you know will be dynamically loaded
2647 later by the program being debugged. When shared libraries are loaded,
2648 a check is made to see if the load resoloves any pending breakpoint locations.
2649 If a pending breakpoint location has been resolved,
2650 a real breakpoint is created and the original pending breakpoint is removed.
2652 @cindex operations allowed on pending breakpoints
2653 Normal breakpoint operations apply to pending breakpoints as well. You may
2654 specify a condition for a pending breakpoint and/or commands to run when the
2655 breakpoint is reached. You can also enable or disable
2656 the pending breakpoint. When you specify a condition for a pending breakpoint,
2657 the parsing of the condition will be deferred until the point where the
2658 pending breakpoint location is resolved. Disabling a pending breakpoint
2659 tells @value{GDBN} to not attempt to resolve the breakpoint on any subsequent
2660 shared library load. When a pending breakpoint is re-enabled,
2661 @value{GDBN} checks to see if the location is already resolved.
2662 This is done because any number of shared library loads could have
2663 occurred since the time the breakpoint was disabled and one or more
2664 of these loads could resolve the location.
2666 @cindex negative breakpoint numbers
2667 @cindex internal @value{GDBN} breakpoints
2668 @value{GDBN} itself sometimes sets breakpoints in your program for
2669 special purposes, such as proper handling of @code{longjmp} (in C
2670 programs). These internal breakpoints are assigned negative numbers,
2671 starting with @code{-1}; @samp{info breakpoints} does not display them.
2672 You can see these breakpoints with the @value{GDBN} maintenance command
2673 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
2676 @node Set Watchpoints
2677 @subsection Setting watchpoints
2679 @cindex setting watchpoints
2680 @cindex software watchpoints
2681 @cindex hardware watchpoints
2682 You can use a watchpoint to stop execution whenever the value of an
2683 expression changes, without having to predict a particular place where
2686 Depending on your system, watchpoints may be implemented in software or
2687 hardware. @value{GDBN} does software watchpointing by single-stepping your
2688 program and testing the variable's value each time, which is hundreds of
2689 times slower than normal execution. (But this may still be worth it, to
2690 catch errors where you have no clue what part of your program is the
2693 On some systems, such as HP-UX, @sc{gnu}/Linux and some other x86-based targets,
2694 @value{GDBN} includes support for
2695 hardware watchpoints, which do not slow down the running of your
2700 @item watch @var{expr}
2701 Set a watchpoint for an expression. @value{GDBN} will break when @var{expr}
2702 is written into by the program and its value changes.
2705 @item rwatch @var{expr}
2706 Set a watchpoint that will break when watch @var{expr} is read by the program.
2709 @item awatch @var{expr}
2710 Set a watchpoint that will break when @var{expr} is either read or written into
2713 @kindex info watchpoints
2714 @item info watchpoints
2715 This command prints a list of watchpoints, breakpoints, and catchpoints;
2716 it is the same as @code{info break}.
2719 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
2720 watchpoints execute very quickly, and the debugger reports a change in
2721 value at the exact instruction where the change occurs. If @value{GDBN}
2722 cannot set a hardware watchpoint, it sets a software watchpoint, which
2723 executes more slowly and reports the change in value at the next
2724 statement, not the instruction, after the change occurs.
2726 When you issue the @code{watch} command, @value{GDBN} reports
2729 Hardware watchpoint @var{num}: @var{expr}
2733 if it was able to set a hardware watchpoint.
2735 Currently, the @code{awatch} and @code{rwatch} commands can only set
2736 hardware watchpoints, because accesses to data that don't change the
2737 value of the watched expression cannot be detected without examining
2738 every instruction as it is being executed, and @value{GDBN} does not do
2739 that currently. If @value{GDBN} finds that it is unable to set a
2740 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
2741 will print a message like this:
2744 Expression cannot be implemented with read/access watchpoint.
2747 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
2748 data type of the watched expression is wider than what a hardware
2749 watchpoint on the target machine can handle. For example, some systems
2750 can only watch regions that are up to 4 bytes wide; on such systems you
2751 cannot set hardware watchpoints for an expression that yields a
2752 double-precision floating-point number (which is typically 8 bytes
2753 wide). As a work-around, it might be possible to break the large region
2754 into a series of smaller ones and watch them with separate watchpoints.
2756 If you set too many hardware watchpoints, @value{GDBN} might be unable
2757 to insert all of them when you resume the execution of your program.
2758 Since the precise number of active watchpoints is unknown until such
2759 time as the program is about to be resumed, @value{GDBN} might not be
2760 able to warn you about this when you set the watchpoints, and the
2761 warning will be printed only when the program is resumed:
2764 Hardware watchpoint @var{num}: Could not insert watchpoint
2768 If this happens, delete or disable some of the watchpoints.
2770 The SPARClite DSU will generate traps when a program accesses some data
2771 or instruction address that is assigned to the debug registers. For the
2772 data addresses, DSU facilitates the @code{watch} command. However the
2773 hardware breakpoint registers can only take two data watchpoints, and
2774 both watchpoints must be the same kind. For example, you can set two
2775 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
2776 @strong{or} two with @code{awatch} commands, but you cannot set one
2777 watchpoint with one command and the other with a different command.
2778 @value{GDBN} will reject the command if you try to mix watchpoints.
2779 Delete or disable unused watchpoint commands before setting new ones.
2781 If you call a function interactively using @code{print} or @code{call},
2782 any watchpoints you have set will be inactive until @value{GDBN} reaches another
2783 kind of breakpoint or the call completes.
2785 @value{GDBN} automatically deletes watchpoints that watch local
2786 (automatic) variables, or expressions that involve such variables, when
2787 they go out of scope, that is, when the execution leaves the block in
2788 which these variables were defined. In particular, when the program
2789 being debugged terminates, @emph{all} local variables go out of scope,
2790 and so only watchpoints that watch global variables remain set. If you
2791 rerun the program, you will need to set all such watchpoints again. One
2792 way of doing that would be to set a code breakpoint at the entry to the
2793 @code{main} function and when it breaks, set all the watchpoints.
2796 @cindex watchpoints and threads
2797 @cindex threads and watchpoints
2798 @emph{Warning:} In multi-thread programs, watchpoints have only limited
2799 usefulness. With the current watchpoint implementation, @value{GDBN}
2800 can only watch the value of an expression @emph{in a single thread}. If
2801 you are confident that the expression can only change due to the current
2802 thread's activity (and if you are also confident that no other thread
2803 can become current), then you can use watchpoints as usual. However,
2804 @value{GDBN} may not notice when a non-current thread's activity changes
2807 @c FIXME: this is almost identical to the previous paragraph.
2808 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
2809 have only limited usefulness. If @value{GDBN} creates a software
2810 watchpoint, it can only watch the value of an expression @emph{in a
2811 single thread}. If you are confident that the expression can only
2812 change due to the current thread's activity (and if you are also
2813 confident that no other thread can become current), then you can use
2814 software watchpoints as usual. However, @value{GDBN} may not notice
2815 when a non-current thread's activity changes the expression. (Hardware
2816 watchpoints, in contrast, watch an expression in all threads.)
2819 @xref{set remote hardware-watchpoint-limit}.
2821 @node Set Catchpoints
2822 @subsection Setting catchpoints
2823 @cindex catchpoints, setting
2824 @cindex exception handlers
2825 @cindex event handling
2827 You can use @dfn{catchpoints} to cause the debugger to stop for certain
2828 kinds of program events, such as C@t{++} exceptions or the loading of a
2829 shared library. Use the @code{catch} command to set a catchpoint.
2833 @item catch @var{event}
2834 Stop when @var{event} occurs. @var{event} can be any of the following:
2838 The throwing of a C@t{++} exception.
2842 The catching of a C@t{++} exception.
2846 A call to @code{exec}. This is currently only available for HP-UX.
2850 A call to @code{fork}. This is currently only available for HP-UX.
2854 A call to @code{vfork}. This is currently only available for HP-UX.
2857 @itemx load @var{libname}
2859 The dynamic loading of any shared library, or the loading of the library
2860 @var{libname}. This is currently only available for HP-UX.
2863 @itemx unload @var{libname}
2864 @kindex catch unload
2865 The unloading of any dynamically loaded shared library, or the unloading
2866 of the library @var{libname}. This is currently only available for HP-UX.
2869 @item tcatch @var{event}
2870 Set a catchpoint that is enabled only for one stop. The catchpoint is
2871 automatically deleted after the first time the event is caught.
2875 Use the @code{info break} command to list the current catchpoints.
2877 There are currently some limitations to C@t{++} exception handling
2878 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
2882 If you call a function interactively, @value{GDBN} normally returns
2883 control to you when the function has finished executing. If the call
2884 raises an exception, however, the call may bypass the mechanism that
2885 returns control to you and cause your program either to abort or to
2886 simply continue running until it hits a breakpoint, catches a signal
2887 that @value{GDBN} is listening for, or exits. This is the case even if
2888 you set a catchpoint for the exception; catchpoints on exceptions are
2889 disabled within interactive calls.
2892 You cannot raise an exception interactively.
2895 You cannot install an exception handler interactively.
2898 @cindex raise exceptions
2899 Sometimes @code{catch} is not the best way to debug exception handling:
2900 if you need to know exactly where an exception is raised, it is better to
2901 stop @emph{before} the exception handler is called, since that way you
2902 can see the stack before any unwinding takes place. If you set a
2903 breakpoint in an exception handler instead, it may not be easy to find
2904 out where the exception was raised.
2906 To stop just before an exception handler is called, you need some
2907 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
2908 raised by calling a library function named @code{__raise_exception}
2909 which has the following ANSI C interface:
2912 /* @var{addr} is where the exception identifier is stored.
2913 @var{id} is the exception identifier. */
2914 void __raise_exception (void **addr, void *id);
2918 To make the debugger catch all exceptions before any stack
2919 unwinding takes place, set a breakpoint on @code{__raise_exception}
2920 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
2922 With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
2923 that depends on the value of @var{id}, you can stop your program when
2924 a specific exception is raised. You can use multiple conditional
2925 breakpoints to stop your program when any of a number of exceptions are
2930 @subsection Deleting breakpoints
2932 @cindex clearing breakpoints, watchpoints, catchpoints
2933 @cindex deleting breakpoints, watchpoints, catchpoints
2934 It is often necessary to eliminate a breakpoint, watchpoint, or
2935 catchpoint once it has done its job and you no longer want your program
2936 to stop there. This is called @dfn{deleting} the breakpoint. A
2937 breakpoint that has been deleted no longer exists; it is forgotten.
2939 With the @code{clear} command you can delete breakpoints according to
2940 where they are in your program. With the @code{delete} command you can
2941 delete individual breakpoints, watchpoints, or catchpoints by specifying
2942 their breakpoint numbers.
2944 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
2945 automatically ignores breakpoints on the first instruction to be executed
2946 when you continue execution without changing the execution address.
2951 Delete any breakpoints at the next instruction to be executed in the
2952 selected stack frame (@pxref{Selection, ,Selecting a frame}). When
2953 the innermost frame is selected, this is a good way to delete a
2954 breakpoint where your program just stopped.
2956 @item clear @var{function}
2957 @itemx clear @var{filename}:@var{function}
2958 Delete any breakpoints set at entry to the function @var{function}.
2960 @item clear @var{linenum}
2961 @itemx clear @var{filename}:@var{linenum}
2962 Delete any breakpoints set at or within the code of the specified line.
2964 @cindex delete breakpoints
2966 @kindex d @r{(@code{delete})}
2967 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
2968 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
2969 ranges specified as arguments. If no argument is specified, delete all
2970 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
2971 confirm off}). You can abbreviate this command as @code{d}.
2975 @subsection Disabling breakpoints
2977 @kindex disable breakpoints
2978 @kindex enable breakpoints
2979 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
2980 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
2981 it had been deleted, but remembers the information on the breakpoint so
2982 that you can @dfn{enable} it again later.
2984 You disable and enable breakpoints, watchpoints, and catchpoints with
2985 the @code{enable} and @code{disable} commands, optionally specifying one
2986 or more breakpoint numbers as arguments. Use @code{info break} or
2987 @code{info watch} to print a list of breakpoints, watchpoints, and
2988 catchpoints if you do not know which numbers to use.
2990 A breakpoint, watchpoint, or catchpoint can have any of four different
2991 states of enablement:
2995 Enabled. The breakpoint stops your program. A breakpoint set
2996 with the @code{break} command starts out in this state.
2998 Disabled. The breakpoint has no effect on your program.
3000 Enabled once. The breakpoint stops your program, but then becomes
3003 Enabled for deletion. The breakpoint stops your program, but
3004 immediately after it does so it is deleted permanently. A breakpoint
3005 set with the @code{tbreak} command starts out in this state.
3008 You can use the following commands to enable or disable breakpoints,
3009 watchpoints, and catchpoints:
3012 @kindex disable breakpoints
3014 @kindex dis @r{(@code{disable})}
3015 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3016 Disable the specified breakpoints---or all breakpoints, if none are
3017 listed. A disabled breakpoint has no effect but is not forgotten. All
3018 options such as ignore-counts, conditions and commands are remembered in
3019 case the breakpoint is enabled again later. You may abbreviate
3020 @code{disable} as @code{dis}.
3022 @kindex enable breakpoints
3024 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3025 Enable the specified breakpoints (or all defined breakpoints). They
3026 become effective once again in stopping your program.
3028 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3029 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3030 of these breakpoints immediately after stopping your program.
3032 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3033 Enable the specified breakpoints to work once, then die. @value{GDBN}
3034 deletes any of these breakpoints as soon as your program stops there.
3037 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3038 @c confusing: tbreak is also initially enabled.
3039 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3040 ,Setting breakpoints}), breakpoints that you set are initially enabled;
3041 subsequently, they become disabled or enabled only when you use one of
3042 the commands above. (The command @code{until} can set and delete a
3043 breakpoint of its own, but it does not change the state of your other
3044 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3048 @subsection Break conditions
3049 @cindex conditional breakpoints
3050 @cindex breakpoint conditions
3052 @c FIXME what is scope of break condition expr? Context where wanted?
3053 @c in particular for a watchpoint?
3054 The simplest sort of breakpoint breaks every time your program reaches a
3055 specified place. You can also specify a @dfn{condition} for a
3056 breakpoint. A condition is just a Boolean expression in your
3057 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3058 a condition evaluates the expression each time your program reaches it,
3059 and your program stops only if the condition is @emph{true}.
3061 This is the converse of using assertions for program validation; in that
3062 situation, you want to stop when the assertion is violated---that is,
3063 when the condition is false. In C, if you want to test an assertion expressed
3064 by the condition @var{assert}, you should set the condition
3065 @samp{! @var{assert}} on the appropriate breakpoint.
3067 Conditions are also accepted for watchpoints; you may not need them,
3068 since a watchpoint is inspecting the value of an expression anyhow---but
3069 it might be simpler, say, to just set a watchpoint on a variable name,
3070 and specify a condition that tests whether the new value is an interesting
3073 Break conditions can have side effects, and may even call functions in
3074 your program. This can be useful, for example, to activate functions
3075 that log program progress, or to use your own print functions to
3076 format special data structures. The effects are completely predictable
3077 unless there is another enabled breakpoint at the same address. (In
3078 that case, @value{GDBN} might see the other breakpoint first and stop your
3079 program without checking the condition of this one.) Note that
3080 breakpoint commands are usually more convenient and flexible than break
3082 purpose of performing side effects when a breakpoint is reached
3083 (@pxref{Break Commands, ,Breakpoint command lists}).
3085 Break conditions can be specified when a breakpoint is set, by using
3086 @samp{if} in the arguments to the @code{break} command. @xref{Set
3087 Breaks, ,Setting breakpoints}. They can also be changed at any time
3088 with the @code{condition} command.
3090 You can also use the @code{if} keyword with the @code{watch} command.
3091 The @code{catch} command does not recognize the @code{if} keyword;
3092 @code{condition} is the only way to impose a further condition on a
3097 @item condition @var{bnum} @var{expression}
3098 Specify @var{expression} as the break condition for breakpoint,
3099 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3100 breakpoint @var{bnum} stops your program only if the value of
3101 @var{expression} is true (nonzero, in C). When you use
3102 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3103 syntactic correctness, and to determine whether symbols in it have
3104 referents in the context of your breakpoint. If @var{expression} uses
3105 symbols not referenced in the context of the breakpoint, @value{GDBN}
3106 prints an error message:
3109 No symbol "foo" in current context.
3114 not actually evaluate @var{expression} at the time the @code{condition}
3115 command (or a command that sets a breakpoint with a condition, like
3116 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3118 @item condition @var{bnum}
3119 Remove the condition from breakpoint number @var{bnum}. It becomes
3120 an ordinary unconditional breakpoint.
3123 @cindex ignore count (of breakpoint)
3124 A special case of a breakpoint condition is to stop only when the
3125 breakpoint has been reached a certain number of times. This is so
3126 useful that there is a special way to do it, using the @dfn{ignore
3127 count} of the breakpoint. Every breakpoint has an ignore count, which
3128 is an integer. Most of the time, the ignore count is zero, and
3129 therefore has no effect. But if your program reaches a breakpoint whose
3130 ignore count is positive, then instead of stopping, it just decrements
3131 the ignore count by one and continues. As a result, if the ignore count
3132 value is @var{n}, the breakpoint does not stop the next @var{n} times
3133 your program reaches it.
3137 @item ignore @var{bnum} @var{count}
3138 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3139 The next @var{count} times the breakpoint is reached, your program's
3140 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3143 To make the breakpoint stop the next time it is reached, specify
3146 When you use @code{continue} to resume execution of your program from a
3147 breakpoint, you can specify an ignore count directly as an argument to
3148 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3149 Stepping,,Continuing and stepping}.
3151 If a breakpoint has a positive ignore count and a condition, the
3152 condition is not checked. Once the ignore count reaches zero,
3153 @value{GDBN} resumes checking the condition.
3155 You could achieve the effect of the ignore count with a condition such
3156 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3157 is decremented each time. @xref{Convenience Vars, ,Convenience
3161 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3164 @node Break Commands
3165 @subsection Breakpoint command lists
3167 @cindex breakpoint commands
3168 You can give any breakpoint (or watchpoint or catchpoint) a series of
3169 commands to execute when your program stops due to that breakpoint. For
3170 example, you might want to print the values of certain expressions, or
3171 enable other breakpoints.
3176 @item commands @r{[}@var{bnum}@r{]}
3177 @itemx @dots{} @var{command-list} @dots{}
3179 Specify a list of commands for breakpoint number @var{bnum}. The commands
3180 themselves appear on the following lines. Type a line containing just
3181 @code{end} to terminate the commands.
3183 To remove all commands from a breakpoint, type @code{commands} and
3184 follow it immediately with @code{end}; that is, give no commands.
3186 With no @var{bnum} argument, @code{commands} refers to the last
3187 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3188 recently encountered).
3191 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3192 disabled within a @var{command-list}.
3194 You can use breakpoint commands to start your program up again. Simply
3195 use the @code{continue} command, or @code{step}, or any other command
3196 that resumes execution.
3198 Any other commands in the command list, after a command that resumes
3199 execution, are ignored. This is because any time you resume execution
3200 (even with a simple @code{next} or @code{step}), you may encounter
3201 another breakpoint---which could have its own command list, leading to
3202 ambiguities about which list to execute.
3205 If the first command you specify in a command list is @code{silent}, the
3206 usual message about stopping at a breakpoint is not printed. This may
3207 be desirable for breakpoints that are to print a specific message and
3208 then continue. If none of the remaining commands print anything, you
3209 see no sign that the breakpoint was reached. @code{silent} is
3210 meaningful only at the beginning of a breakpoint command list.
3212 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3213 print precisely controlled output, and are often useful in silent
3214 breakpoints. @xref{Output, ,Commands for controlled output}.
3216 For example, here is how you could use breakpoint commands to print the
3217 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3223 printf "x is %d\n",x
3228 One application for breakpoint commands is to compensate for one bug so
3229 you can test for another. Put a breakpoint just after the erroneous line
3230 of code, give it a condition to detect the case in which something
3231 erroneous has been done, and give it commands to assign correct values
3232 to any variables that need them. End with the @code{continue} command
3233 so that your program does not stop, and start with the @code{silent}
3234 command so that no output is produced. Here is an example:
3245 @node Breakpoint Menus
3246 @subsection Breakpoint menus
3248 @cindex symbol overloading
3250 Some programming languages (notably C@t{++} and Objective-C) permit a
3251 single function name
3252 to be defined several times, for application in different contexts.
3253 This is called @dfn{overloading}. When a function name is overloaded,
3254 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3255 a breakpoint. If you realize this is a problem, you can use
3256 something like @samp{break @var{function}(@var{types})} to specify which
3257 particular version of the function you want. Otherwise, @value{GDBN} offers
3258 you a menu of numbered choices for different possible breakpoints, and
3259 waits for your selection with the prompt @samp{>}. The first two
3260 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3261 sets a breakpoint at each definition of @var{function}, and typing
3262 @kbd{0} aborts the @code{break} command without setting any new
3265 For example, the following session excerpt shows an attempt to set a
3266 breakpoint at the overloaded symbol @code{String::after}.
3267 We choose three particular definitions of that function name:
3269 @c FIXME! This is likely to change to show arg type lists, at least
3272 (@value{GDBP}) b String::after
3275 [2] file:String.cc; line number:867
3276 [3] file:String.cc; line number:860
3277 [4] file:String.cc; line number:875
3278 [5] file:String.cc; line number:853
3279 [6] file:String.cc; line number:846
3280 [7] file:String.cc; line number:735
3282 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3283 Breakpoint 2 at 0xb344: file String.cc, line 875.
3284 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3285 Multiple breakpoints were set.
3286 Use the "delete" command to delete unwanted
3292 @c @ifclear BARETARGET
3293 @node Error in Breakpoints
3294 @subsection ``Cannot insert breakpoints''
3296 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3298 Under some operating systems, breakpoints cannot be used in a program if
3299 any other process is running that program. In this situation,
3300 attempting to run or continue a program with a breakpoint causes
3301 @value{GDBN} to print an error message:
3304 Cannot insert breakpoints.
3305 The same program may be running in another process.
3308 When this happens, you have three ways to proceed:
3312 Remove or disable the breakpoints, then continue.
3315 Suspend @value{GDBN}, and copy the file containing your program to a new
3316 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3317 that @value{GDBN} should run your program under that name.
3318 Then start your program again.
3321 Relink your program so that the text segment is nonsharable, using the
3322 linker option @samp{-N}. The operating system limitation may not apply
3323 to nonsharable executables.
3327 A similar message can be printed if you request too many active
3328 hardware-assisted breakpoints and watchpoints:
3330 @c FIXME: the precise wording of this message may change; the relevant
3331 @c source change is not committed yet (Sep 3, 1999).
3333 Stopped; cannot insert breakpoints.
3334 You may have requested too many hardware breakpoints and watchpoints.
3338 This message is printed when you attempt to resume the program, since
3339 only then @value{GDBN} knows exactly how many hardware breakpoints and
3340 watchpoints it needs to insert.
3342 When this message is printed, you need to disable or remove some of the
3343 hardware-assisted breakpoints and watchpoints, and then continue.
3345 @node Breakpoint related warnings
3346 @subsection ``Breakpoint address adjusted...''
3347 @cindex breakpoint address adjusted
3349 Some processor architectures place constraints on the addresses at
3350 which breakpoints may be placed. For architectures thus constrained,
3351 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3352 with the constraints dictated by the architecture.
3354 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3355 a VLIW architecture in which a number of RISC-like instructions may be
3356 bundled together for parallel execution. The FR-V architecture
3357 constrains the location of a breakpoint instruction within such a
3358 bundle to the instruction with the lowest address. @value{GDBN}
3359 honors this constraint by adjusting a breakpoint's address to the
3360 first in the bundle.
3362 It is not uncommon for optimized code to have bundles which contain
3363 instructions from different source statements, thus it may happen that
3364 a breakpoint's address will be adjusted from one source statement to
3365 another. Since this adjustment may significantly alter @value{GDBN}'s
3366 breakpoint related behavior from what the user expects, a warning is
3367 printed when the breakpoint is first set and also when the breakpoint
3370 A warning like the one below is printed when setting a breakpoint
3371 that's been subject to address adjustment:
3374 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3377 Such warnings are printed both for user settable and @value{GDBN}'s
3378 internal breakpoints. If you see one of these warnings, you should
3379 verify that a breakpoint set at the adjusted address will have the
3380 desired affect. If not, the breakpoint in question may be removed and
3381 other breakpoints may be set which will have the desired behavior.
3382 E.g., it may be sufficient to place the breakpoint at a later
3383 instruction. A conditional breakpoint may also be useful in some
3384 cases to prevent the breakpoint from triggering too often.
3386 @value{GDBN} will also issue a warning when stopping at one of these
3387 adjusted breakpoints:
3390 warning: Breakpoint 1 address previously adjusted from 0x00010414
3394 When this warning is encountered, it may be too late to take remedial
3395 action except in cases where the breakpoint is hit earlier or more
3396 frequently than expected.
3398 @node Continuing and Stepping
3399 @section Continuing and stepping
3403 @cindex resuming execution
3404 @dfn{Continuing} means resuming program execution until your program
3405 completes normally. In contrast, @dfn{stepping} means executing just
3406 one more ``step'' of your program, where ``step'' may mean either one
3407 line of source code, or one machine instruction (depending on what
3408 particular command you use). Either when continuing or when stepping,
3409 your program may stop even sooner, due to a breakpoint or a signal. (If
3410 it stops due to a signal, you may want to use @code{handle}, or use
3411 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3415 @kindex c @r{(@code{continue})}
3416 @kindex fg @r{(resume foreground execution)}
3417 @item continue @r{[}@var{ignore-count}@r{]}
3418 @itemx c @r{[}@var{ignore-count}@r{]}
3419 @itemx fg @r{[}@var{ignore-count}@r{]}
3420 Resume program execution, at the address where your program last stopped;
3421 any breakpoints set at that address are bypassed. The optional argument
3422 @var{ignore-count} allows you to specify a further number of times to
3423 ignore a breakpoint at this location; its effect is like that of
3424 @code{ignore} (@pxref{Conditions, ,Break conditions}).
3426 The argument @var{ignore-count} is meaningful only when your program
3427 stopped due to a breakpoint. At other times, the argument to
3428 @code{continue} is ignored.
3430 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3431 debugged program is deemed to be the foreground program) are provided
3432 purely for convenience, and have exactly the same behavior as
3436 To resume execution at a different place, you can use @code{return}
3437 (@pxref{Returning, ,Returning from a function}) to go back to the
3438 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3439 different address}) to go to an arbitrary location in your program.
3441 A typical technique for using stepping is to set a breakpoint
3442 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the
3443 beginning of the function or the section of your program where a problem
3444 is believed to lie, run your program until it stops at that breakpoint,
3445 and then step through the suspect area, examining the variables that are
3446 interesting, until you see the problem happen.
3450 @kindex s @r{(@code{step})}
3452 Continue running your program until control reaches a different source
3453 line, then stop it and return control to @value{GDBN}. This command is
3454 abbreviated @code{s}.
3457 @c "without debugging information" is imprecise; actually "without line
3458 @c numbers in the debugging information". (gcc -g1 has debugging info but
3459 @c not line numbers). But it seems complex to try to make that
3460 @c distinction here.
3461 @emph{Warning:} If you use the @code{step} command while control is
3462 within a function that was compiled without debugging information,
3463 execution proceeds until control reaches a function that does have
3464 debugging information. Likewise, it will not step into a function which
3465 is compiled without debugging information. To step through functions
3466 without debugging information, use the @code{stepi} command, described
3470 The @code{step} command only stops at the first instruction of a source
3471 line. This prevents the multiple stops that could otherwise occur in
3472 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3473 to stop if a function that has debugging information is called within
3474 the line. In other words, @code{step} @emph{steps inside} any functions
3475 called within the line.
3477 Also, the @code{step} command only enters a function if there is line
3478 number information for the function. Otherwise it acts like the
3479 @code{next} command. This avoids problems when using @code{cc -gl}
3480 on MIPS machines. Previously, @code{step} entered subroutines if there
3481 was any debugging information about the routine.
3483 @item step @var{count}
3484 Continue running as in @code{step}, but do so @var{count} times. If a
3485 breakpoint is reached, or a signal not related to stepping occurs before
3486 @var{count} steps, stepping stops right away.
3489 @kindex n @r{(@code{next})}
3490 @item next @r{[}@var{count}@r{]}
3491 Continue to the next source line in the current (innermost) stack frame.
3492 This is similar to @code{step}, but function calls that appear within
3493 the line of code are executed without stopping. Execution stops when
3494 control reaches a different line of code at the original stack level
3495 that was executing when you gave the @code{next} command. This command
3496 is abbreviated @code{n}.
3498 An argument @var{count} is a repeat count, as for @code{step}.
3501 @c FIX ME!! Do we delete this, or is there a way it fits in with
3502 @c the following paragraph? --- Vctoria
3504 @c @code{next} within a function that lacks debugging information acts like
3505 @c @code{step}, but any function calls appearing within the code of the
3506 @c function are executed without stopping.
3508 The @code{next} command only stops at the first instruction of a
3509 source line. This prevents multiple stops that could otherwise occur in
3510 @code{switch} statements, @code{for} loops, etc.
3512 @kindex set step-mode
3514 @cindex functions without line info, and stepping
3515 @cindex stepping into functions with no line info
3516 @itemx set step-mode on
3517 The @code{set step-mode on} command causes the @code{step} command to
3518 stop at the first instruction of a function which contains no debug line
3519 information rather than stepping over it.
3521 This is useful in cases where you may be interested in inspecting the
3522 machine instructions of a function which has no symbolic info and do not
3523 want @value{GDBN} to automatically skip over this function.
3525 @item set step-mode off
3526 Causes the @code{step} command to step over any functions which contains no
3527 debug information. This is the default.
3531 Continue running until just after function in the selected stack frame
3532 returns. Print the returned value (if any).
3534 Contrast this with the @code{return} command (@pxref{Returning,
3535 ,Returning from a function}).
3538 @kindex u @r{(@code{until})}
3541 Continue running until a source line past the current line, in the
3542 current stack frame, is reached. This command is used to avoid single
3543 stepping through a loop more than once. It is like the @code{next}
3544 command, except that when @code{until} encounters a jump, it
3545 automatically continues execution until the program counter is greater
3546 than the address of the jump.
3548 This means that when you reach the end of a loop after single stepping
3549 though it, @code{until} makes your program continue execution until it
3550 exits the loop. In contrast, a @code{next} command at the end of a loop
3551 simply steps back to the beginning of the loop, which forces you to step
3552 through the next iteration.
3554 @code{until} always stops your program if it attempts to exit the current
3557 @code{until} may produce somewhat counterintuitive results if the order
3558 of machine code does not match the order of the source lines. For
3559 example, in the following excerpt from a debugging session, the @code{f}
3560 (@code{frame}) command shows that execution is stopped at line
3561 @code{206}; yet when we use @code{until}, we get to line @code{195}:
3565 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
3567 (@value{GDBP}) until
3568 195 for ( ; argc > 0; NEXTARG) @{
3571 This happened because, for execution efficiency, the compiler had
3572 generated code for the loop closure test at the end, rather than the
3573 start, of the loop---even though the test in a C @code{for}-loop is
3574 written before the body of the loop. The @code{until} command appeared
3575 to step back to the beginning of the loop when it advanced to this
3576 expression; however, it has not really gone to an earlier
3577 statement---not in terms of the actual machine code.
3579 @code{until} with no argument works by means of single
3580 instruction stepping, and hence is slower than @code{until} with an
3583 @item until @var{location}
3584 @itemx u @var{location}
3585 Continue running your program until either the specified location is
3586 reached, or the current stack frame returns. @var{location} is any of
3587 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
3588 ,Setting breakpoints}). This form of the command uses breakpoints, and
3589 hence is quicker than @code{until} without an argument. The specified
3590 location is actually reached only if it is in the current frame. This
3591 implies that @code{until} can be used to skip over recursive function
3592 invocations. For instance in the code below, if the current location is
3593 line @code{96}, issuing @code{until 99} will execute the program up to
3594 line @code{99} in the same invocation of factorial, i.e. after the inner
3595 invocations have returned.
3598 94 int factorial (int value)
3600 96 if (value > 1) @{
3601 97 value *= factorial (value - 1);
3608 @kindex advance @var{location}
3609 @itemx advance @var{location}
3610 Continue running the program up to the given location. An argument is
3611 required, anything of the same form as arguments for the @code{break}
3612 command. Execution will also stop upon exit from the current stack
3613 frame. This command is similar to @code{until}, but @code{advance} will
3614 not skip over recursive function calls, and the target location doesn't
3615 have to be in the same frame as the current one.
3619 @kindex si @r{(@code{stepi})}
3621 @itemx stepi @var{arg}
3623 Execute one machine instruction, then stop and return to the debugger.
3625 It is often useful to do @samp{display/i $pc} when stepping by machine
3626 instructions. This makes @value{GDBN} automatically display the next
3627 instruction to be executed, each time your program stops. @xref{Auto
3628 Display,, Automatic display}.
3630 An argument is a repeat count, as in @code{step}.
3634 @kindex ni @r{(@code{nexti})}
3636 @itemx nexti @var{arg}
3638 Execute one machine instruction, but if it is a function call,
3639 proceed until the function returns.
3641 An argument is a repeat count, as in @code{next}.
3648 A signal is an asynchronous event that can happen in a program. The
3649 operating system defines the possible kinds of signals, and gives each
3650 kind a name and a number. For example, in Unix @code{SIGINT} is the
3651 signal a program gets when you type an interrupt character (often @kbd{C-c});
3652 @code{SIGSEGV} is the signal a program gets from referencing a place in
3653 memory far away from all the areas in use; @code{SIGALRM} occurs when
3654 the alarm clock timer goes off (which happens only if your program has
3655 requested an alarm).
3657 @cindex fatal signals
3658 Some signals, including @code{SIGALRM}, are a normal part of the
3659 functioning of your program. Others, such as @code{SIGSEGV}, indicate
3660 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
3661 program has not specified in advance some other way to handle the signal.
3662 @code{SIGINT} does not indicate an error in your program, but it is normally
3663 fatal so it can carry out the purpose of the interrupt: to kill the program.
3665 @value{GDBN} has the ability to detect any occurrence of a signal in your
3666 program. You can tell @value{GDBN} in advance what to do for each kind of
3669 @cindex handling signals
3670 Normally, @value{GDBN} is set up to let the non-erroneous signals like
3671 @code{SIGALRM} be silently passed to your program
3672 (so as not to interfere with their role in the program's functioning)
3673 but to stop your program immediately whenever an error signal happens.
3674 You can change these settings with the @code{handle} command.
3677 @kindex info signals
3680 Print a table of all the kinds of signals and how @value{GDBN} has been told to
3681 handle each one. You can use this to see the signal numbers of all
3682 the defined types of signals.
3684 @code{info handle} is an alias for @code{info signals}.
3687 @item handle @var{signal} @var{keywords}@dots{}
3688 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
3689 can be the number of a signal or its name (with or without the
3690 @samp{SIG} at the beginning); a list of signal numbers of the form
3691 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
3692 known signals. The @var{keywords} say what change to make.
3696 The keywords allowed by the @code{handle} command can be abbreviated.
3697 Their full names are:
3701 @value{GDBN} should not stop your program when this signal happens. It may
3702 still print a message telling you that the signal has come in.
3705 @value{GDBN} should stop your program when this signal happens. This implies
3706 the @code{print} keyword as well.
3709 @value{GDBN} should print a message when this signal happens.
3712 @value{GDBN} should not mention the occurrence of the signal at all. This
3713 implies the @code{nostop} keyword as well.
3717 @value{GDBN} should allow your program to see this signal; your program
3718 can handle the signal, or else it may terminate if the signal is fatal
3719 and not handled. @code{pass} and @code{noignore} are synonyms.
3723 @value{GDBN} should not allow your program to see this signal.
3724 @code{nopass} and @code{ignore} are synonyms.
3728 When a signal stops your program, the signal is not visible to the
3730 continue. Your program sees the signal then, if @code{pass} is in
3731 effect for the signal in question @emph{at that time}. In other words,
3732 after @value{GDBN} reports a signal, you can use the @code{handle}
3733 command with @code{pass} or @code{nopass} to control whether your
3734 program sees that signal when you continue.
3736 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
3737 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
3738 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
3741 You can also use the @code{signal} command to prevent your program from
3742 seeing a signal, or cause it to see a signal it normally would not see,
3743 or to give it any signal at any time. For example, if your program stopped
3744 due to some sort of memory reference error, you might store correct
3745 values into the erroneous variables and continue, hoping to see more
3746 execution; but your program would probably terminate immediately as
3747 a result of the fatal signal once it saw the signal. To prevent this,
3748 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
3752 @section Stopping and starting multi-thread programs
3754 When your program has multiple threads (@pxref{Threads,, Debugging
3755 programs with multiple threads}), you can choose whether to set
3756 breakpoints on all threads, or on a particular thread.
3759 @cindex breakpoints and threads
3760 @cindex thread breakpoints
3761 @kindex break @dots{} thread @var{threadno}
3762 @item break @var{linespec} thread @var{threadno}
3763 @itemx break @var{linespec} thread @var{threadno} if @dots{}
3764 @var{linespec} specifies source lines; there are several ways of
3765 writing them, but the effect is always to specify some source line.
3767 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
3768 to specify that you only want @value{GDBN} to stop the program when a
3769 particular thread reaches this breakpoint. @var{threadno} is one of the
3770 numeric thread identifiers assigned by @value{GDBN}, shown in the first
3771 column of the @samp{info threads} display.
3773 If you do not specify @samp{thread @var{threadno}} when you set a
3774 breakpoint, the breakpoint applies to @emph{all} threads of your
3777 You can use the @code{thread} qualifier on conditional breakpoints as
3778 well; in this case, place @samp{thread @var{threadno}} before the
3779 breakpoint condition, like this:
3782 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
3787 @cindex stopped threads
3788 @cindex threads, stopped
3789 Whenever your program stops under @value{GDBN} for any reason,
3790 @emph{all} threads of execution stop, not just the current thread. This
3791 allows you to examine the overall state of the program, including
3792 switching between threads, without worrying that things may change
3795 @cindex thread breakpoints and system calls
3796 @cindex system calls and thread breakpoints
3797 @cindex premature return from system calls
3798 There is an unfortunate side effect. If one thread stops for a
3799 breakpoint, or for some other reason, and another thread is blocked in a
3800 system call, then the system call may return prematurely. This is a
3801 consequence of the interaction between multiple threads and the signals
3802 that @value{GDBN} uses to implement breakpoints and other events that
3805 To handle this problem, your program should check the return value of
3806 each system call and react appropriately. This is good programming
3809 For example, do not write code like this:
3815 The call to @code{sleep} will return early if a different thread stops
3816 at a breakpoint or for some other reason.
3818 Instead, write this:
3823 unslept = sleep (unslept);
3826 A system call is allowed to return early, so the system is still
3827 conforming to its specification. But @value{GDBN} does cause your
3828 multi-threaded program to behave differently than it would without
3831 Also, @value{GDBN} uses internal breakpoints in the thread library to
3832 monitor certain events such as thread creation and thread destruction.
3833 When such an event happens, a system call in another thread may return
3834 prematurely, even though your program does not appear to stop.
3836 @cindex continuing threads
3837 @cindex threads, continuing
3838 Conversely, whenever you restart the program, @emph{all} threads start
3839 executing. @emph{This is true even when single-stepping} with commands
3840 like @code{step} or @code{next}.
3842 In particular, @value{GDBN} cannot single-step all threads in lockstep.
3843 Since thread scheduling is up to your debugging target's operating
3844 system (not controlled by @value{GDBN}), other threads may
3845 execute more than one statement while the current thread completes a
3846 single step. Moreover, in general other threads stop in the middle of a
3847 statement, rather than at a clean statement boundary, when the program
3850 You might even find your program stopped in another thread after
3851 continuing or even single-stepping. This happens whenever some other
3852 thread runs into a breakpoint, a signal, or an exception before the
3853 first thread completes whatever you requested.
3855 On some OSes, you can lock the OS scheduler and thus allow only a single
3859 @item set scheduler-locking @var{mode}
3860 Set the scheduler locking mode. If it is @code{off}, then there is no
3861 locking and any thread may run at any time. If @code{on}, then only the
3862 current thread may run when the inferior is resumed. The @code{step}
3863 mode optimizes for single-stepping. It stops other threads from
3864 ``seizing the prompt'' by preempting the current thread while you are
3865 stepping. Other threads will only rarely (or never) get a chance to run
3866 when you step. They are more likely to run when you @samp{next} over a
3867 function call, and they are completely free to run when you use commands
3868 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
3869 thread hits a breakpoint during its timeslice, they will never steal the
3870 @value{GDBN} prompt away from the thread that you are debugging.
3872 @item show scheduler-locking
3873 Display the current scheduler locking mode.
3878 @chapter Examining the Stack
3880 When your program has stopped, the first thing you need to know is where it
3881 stopped and how it got there.
3884 Each time your program performs a function call, information about the call
3886 That information includes the location of the call in your program,
3887 the arguments of the call,
3888 and the local variables of the function being called.
3889 The information is saved in a block of data called a @dfn{stack frame}.
3890 The stack frames are allocated in a region of memory called the @dfn{call
3893 When your program stops, the @value{GDBN} commands for examining the
3894 stack allow you to see all of this information.
3896 @cindex selected frame
3897 One of the stack frames is @dfn{selected} by @value{GDBN} and many
3898 @value{GDBN} commands refer implicitly to the selected frame. In
3899 particular, whenever you ask @value{GDBN} for the value of a variable in
3900 your program, the value is found in the selected frame. There are
3901 special @value{GDBN} commands to select whichever frame you are
3902 interested in. @xref{Selection, ,Selecting a frame}.
3904 When your program stops, @value{GDBN} automatically selects the
3905 currently executing frame and describes it briefly, similar to the
3906 @code{frame} command (@pxref{Frame Info, ,Information about a frame}).
3909 * Frames:: Stack frames
3910 * Backtrace:: Backtraces
3911 * Selection:: Selecting a frame
3912 * Frame Info:: Information on a frame
3917 @section Stack frames
3919 @cindex frame, definition
3921 The call stack is divided up into contiguous pieces called @dfn{stack
3922 frames}, or @dfn{frames} for short; each frame is the data associated
3923 with one call to one function. The frame contains the arguments given
3924 to the function, the function's local variables, and the address at
3925 which the function is executing.
3927 @cindex initial frame
3928 @cindex outermost frame
3929 @cindex innermost frame
3930 When your program is started, the stack has only one frame, that of the
3931 function @code{main}. This is called the @dfn{initial} frame or the
3932 @dfn{outermost} frame. Each time a function is called, a new frame is
3933 made. Each time a function returns, the frame for that function invocation
3934 is eliminated. If a function is recursive, there can be many frames for
3935 the same function. The frame for the function in which execution is
3936 actually occurring is called the @dfn{innermost} frame. This is the most
3937 recently created of all the stack frames that still exist.
3939 @cindex frame pointer
3940 Inside your program, stack frames are identified by their addresses. A
3941 stack frame consists of many bytes, each of which has its own address; each
3942 kind of computer has a convention for choosing one byte whose
3943 address serves as the address of the frame. Usually this address is kept
3944 in a register called the @dfn{frame pointer register} while execution is
3945 going on in that frame.
3947 @cindex frame number
3948 @value{GDBN} assigns numbers to all existing stack frames, starting with
3949 zero for the innermost frame, one for the frame that called it,
3950 and so on upward. These numbers do not really exist in your program;
3951 they are assigned by @value{GDBN} to give you a way of designating stack
3952 frames in @value{GDBN} commands.
3954 @c The -fomit-frame-pointer below perennially causes hbox overflow
3955 @c underflow problems.
3956 @cindex frameless execution
3957 Some compilers provide a way to compile functions so that they operate
3958 without stack frames. (For example, the @value{GCC} option
3960 @samp{-fomit-frame-pointer}
3962 generates functions without a frame.)
3963 This is occasionally done with heavily used library functions to save
3964 the frame setup time. @value{GDBN} has limited facilities for dealing
3965 with these function invocations. If the innermost function invocation
3966 has no stack frame, @value{GDBN} nevertheless regards it as though
3967 it had a separate frame, which is numbered zero as usual, allowing
3968 correct tracing of the function call chain. However, @value{GDBN} has
3969 no provision for frameless functions elsewhere in the stack.
3972 @kindex frame@r{, command}
3973 @cindex current stack frame
3974 @item frame @var{args}
3975 The @code{frame} command allows you to move from one stack frame to another,
3976 and to print the stack frame you select. @var{args} may be either the
3977 address of the frame or the stack frame number. Without an argument,
3978 @code{frame} prints the current stack frame.
3980 @kindex select-frame
3981 @cindex selecting frame silently
3983 The @code{select-frame} command allows you to move from one stack frame
3984 to another without printing the frame. This is the silent version of
3993 @cindex stack traces
3994 A backtrace is a summary of how your program got where it is. It shows one
3995 line per frame, for many frames, starting with the currently executing
3996 frame (frame zero), followed by its caller (frame one), and on up the
4001 @kindex bt @r{(@code{backtrace})}
4004 Print a backtrace of the entire stack: one line per frame for all
4005 frames in the stack.
4007 You can stop the backtrace at any time by typing the system interrupt
4008 character, normally @kbd{C-c}.
4010 @item backtrace @var{n}
4012 Similar, but print only the innermost @var{n} frames.
4014 @item backtrace -@var{n}
4016 Similar, but print only the outermost @var{n} frames.
4021 @kindex info s @r{(@code{info stack})}
4022 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4023 are additional aliases for @code{backtrace}.
4025 Each line in the backtrace shows the frame number and the function name.
4026 The program counter value is also shown---unless you use @code{set
4027 print address off}. The backtrace also shows the source file name and
4028 line number, as well as the arguments to the function. The program
4029 counter value is omitted if it is at the beginning of the code for that
4032 Here is an example of a backtrace. It was made with the command
4033 @samp{bt 3}, so it shows the innermost three frames.
4037 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4039 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4040 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4042 (More stack frames follow...)
4047 The display for frame zero does not begin with a program counter
4048 value, indicating that your program has stopped at the beginning of the
4049 code for line @code{993} of @code{builtin.c}.
4051 @kindex set backtrace past-main
4052 @kindex show backtrace past-main
4053 @kindex set backtrace limit
4054 @kindex show backtrace limit
4056 Most programs have a standard user entry point---a place where system
4057 libraries and startup code transition into user code. For C this is
4058 @code{main}. When @value{GDBN} finds the entry function in a backtrace
4059 it will terminate the backtrace, to avoid tracing into highly
4060 system-specific (and generally uninteresting) code.
4062 If you need to examine the startup code, or limit the number of levels
4063 in a backtrace, you can change this behavior:
4066 @item set backtrace past-main
4067 @itemx set backtrace past-main on
4068 Backtraces will continue past the user entry point.
4070 @item set backtrace past-main off
4071 Backtraces will stop when they encounter the user entry point. This is the
4074 @item show backtrace past-main
4075 Display the current user entry point backtrace policy.
4077 @item set backtrace limit @var{n}
4078 @itemx set backtrace limit 0
4079 @cindex backtrace limit
4080 Limit the backtrace to @var{n} levels. A value of zero means
4083 @item show backtrace limit
4084 Display the current limit on backtrace levels.
4088 @section Selecting a frame
4090 Most commands for examining the stack and other data in your program work on
4091 whichever stack frame is selected at the moment. Here are the commands for
4092 selecting a stack frame; all of them finish by printing a brief description
4093 of the stack frame just selected.
4096 @kindex frame@r{, selecting}
4097 @kindex f @r{(@code{frame})}
4100 Select frame number @var{n}. Recall that frame zero is the innermost
4101 (currently executing) frame, frame one is the frame that called the
4102 innermost one, and so on. The highest-numbered frame is the one for
4105 @item frame @var{addr}
4107 Select the frame at address @var{addr}. This is useful mainly if the
4108 chaining of stack frames has been damaged by a bug, making it
4109 impossible for @value{GDBN} to assign numbers properly to all frames. In
4110 addition, this can be useful when your program has multiple stacks and
4111 switches between them.
4113 On the SPARC architecture, @code{frame} needs two addresses to
4114 select an arbitrary frame: a frame pointer and a stack pointer.
4116 On the MIPS and Alpha architecture, it needs two addresses: a stack
4117 pointer and a program counter.
4119 On the 29k architecture, it needs three addresses: a register stack
4120 pointer, a program counter, and a memory stack pointer.
4121 @c note to future updaters: this is conditioned on a flag
4122 @c SETUP_ARBITRARY_FRAME in the tm-*.h files. The above is up to date
4123 @c as of 27 Jan 1994.
4127 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4128 advances toward the outermost frame, to higher frame numbers, to frames
4129 that have existed longer. @var{n} defaults to one.
4132 @kindex do @r{(@code{down})}
4134 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4135 advances toward the innermost frame, to lower frame numbers, to frames
4136 that were created more recently. @var{n} defaults to one. You may
4137 abbreviate @code{down} as @code{do}.
4140 All of these commands end by printing two lines of output describing the
4141 frame. The first line shows the frame number, the function name, the
4142 arguments, and the source file and line number of execution in that
4143 frame. The second line shows the text of that source line.
4151 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4153 10 read_input_file (argv[i]);
4157 After such a printout, the @code{list} command with no arguments
4158 prints ten lines centered on the point of execution in the frame.
4159 You can also edit the program at the point of execution with your favorite
4160 editing program by typing @code{edit}.
4161 @xref{List, ,Printing source lines},
4165 @kindex down-silently
4167 @item up-silently @var{n}
4168 @itemx down-silently @var{n}
4169 These two commands are variants of @code{up} and @code{down},
4170 respectively; they differ in that they do their work silently, without
4171 causing display of the new frame. They are intended primarily for use
4172 in @value{GDBN} command scripts, where the output might be unnecessary and
4177 @section Information about a frame
4179 There are several other commands to print information about the selected
4185 When used without any argument, this command does not change which
4186 frame is selected, but prints a brief description of the currently
4187 selected stack frame. It can be abbreviated @code{f}. With an
4188 argument, this command is used to select a stack frame.
4189 @xref{Selection, ,Selecting a frame}.
4192 @kindex info f @r{(@code{info frame})}
4195 This command prints a verbose description of the selected stack frame,
4200 the address of the frame
4202 the address of the next frame down (called by this frame)
4204 the address of the next frame up (caller of this frame)
4206 the language in which the source code corresponding to this frame is written
4208 the address of the frame's arguments
4210 the address of the frame's local variables
4212 the program counter saved in it (the address of execution in the caller frame)
4214 which registers were saved in the frame
4217 @noindent The verbose description is useful when
4218 something has gone wrong that has made the stack format fail to fit
4219 the usual conventions.
4221 @item info frame @var{addr}
4222 @itemx info f @var{addr}
4223 Print a verbose description of the frame at address @var{addr}, without
4224 selecting that frame. The selected frame remains unchanged by this
4225 command. This requires the same kind of address (more than one for some
4226 architectures) that you specify in the @code{frame} command.
4227 @xref{Selection, ,Selecting a frame}.
4231 Print the arguments of the selected frame, each on a separate line.
4235 Print the local variables of the selected frame, each on a separate
4236 line. These are all variables (declared either static or automatic)
4237 accessible at the point of execution of the selected frame.
4240 @cindex catch exceptions, list active handlers
4241 @cindex exception handlers, how to list
4243 Print a list of all the exception handlers that are active in the
4244 current stack frame at the current point of execution. To see other
4245 exception handlers, visit the associated frame (using the @code{up},
4246 @code{down}, or @code{frame} commands); then type @code{info catch}.
4247 @xref{Set Catchpoints, , Setting catchpoints}.
4253 @chapter Examining Source Files
4255 @value{GDBN} can print parts of your program's source, since the debugging
4256 information recorded in the program tells @value{GDBN} what source files were
4257 used to build it. When your program stops, @value{GDBN} spontaneously prints
4258 the line where it stopped. Likewise, when you select a stack frame
4259 (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
4260 execution in that frame has stopped. You can print other portions of
4261 source files by explicit command.
4263 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4264 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4265 @value{GDBN} under @sc{gnu} Emacs}.
4268 * List:: Printing source lines
4269 * Edit:: Editing source files
4270 * Search:: Searching source files
4271 * Source Path:: Specifying source directories
4272 * Machine Code:: Source and machine code
4276 @section Printing source lines
4279 @kindex l @r{(@code{list})}
4280 To print lines from a source file, use the @code{list} command
4281 (abbreviated @code{l}). By default, ten lines are printed.
4282 There are several ways to specify what part of the file you want to print.
4284 Here are the forms of the @code{list} command most commonly used:
4287 @item list @var{linenum}
4288 Print lines centered around line number @var{linenum} in the
4289 current source file.
4291 @item list @var{function}
4292 Print lines centered around the beginning of function
4296 Print more lines. If the last lines printed were printed with a
4297 @code{list} command, this prints lines following the last lines
4298 printed; however, if the last line printed was a solitary line printed
4299 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4300 Stack}), this prints lines centered around that line.
4303 Print lines just before the lines last printed.
4306 By default, @value{GDBN} prints ten source lines with any of these forms of
4307 the @code{list} command. You can change this using @code{set listsize}:
4310 @kindex set listsize
4311 @item set listsize @var{count}
4312 Make the @code{list} command display @var{count} source lines (unless
4313 the @code{list} argument explicitly specifies some other number).
4315 @kindex show listsize
4317 Display the number of lines that @code{list} prints.
4320 Repeating a @code{list} command with @key{RET} discards the argument,
4321 so it is equivalent to typing just @code{list}. This is more useful
4322 than listing the same lines again. An exception is made for an
4323 argument of @samp{-}; that argument is preserved in repetition so that
4324 each repetition moves up in the source file.
4327 In general, the @code{list} command expects you to supply zero, one or two
4328 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4329 of writing them, but the effect is always to specify some source line.
4330 Here is a complete description of the possible arguments for @code{list}:
4333 @item list @var{linespec}
4334 Print lines centered around the line specified by @var{linespec}.
4336 @item list @var{first},@var{last}
4337 Print lines from @var{first} to @var{last}. Both arguments are
4340 @item list ,@var{last}
4341 Print lines ending with @var{last}.
4343 @item list @var{first},
4344 Print lines starting with @var{first}.
4347 Print lines just after the lines last printed.
4350 Print lines just before the lines last printed.
4353 As described in the preceding table.
4356 Here are the ways of specifying a single source line---all the
4361 Specifies line @var{number} of the current source file.
4362 When a @code{list} command has two linespecs, this refers to
4363 the same source file as the first linespec.
4366 Specifies the line @var{offset} lines after the last line printed.
4367 When used as the second linespec in a @code{list} command that has
4368 two, this specifies the line @var{offset} lines down from the
4372 Specifies the line @var{offset} lines before the last line printed.
4374 @item @var{filename}:@var{number}
4375 Specifies line @var{number} in the source file @var{filename}.
4377 @item @var{function}
4378 Specifies the line that begins the body of the function @var{function}.
4379 For example: in C, this is the line with the open brace.
4381 @item @var{filename}:@var{function}
4382 Specifies the line of the open-brace that begins the body of the
4383 function @var{function} in the file @var{filename}. You only need the
4384 file name with a function name to avoid ambiguity when there are
4385 identically named functions in different source files.
4387 @item *@var{address}
4388 Specifies the line containing the program address @var{address}.
4389 @var{address} may be any expression.
4393 @section Editing source files
4394 @cindex editing source files
4397 @kindex e @r{(@code{edit})}
4398 To edit the lines in a source file, use the @code{edit} command.
4399 The editing program of your choice
4400 is invoked with the current line set to
4401 the active line in the program.
4402 Alternatively, there are several ways to specify what part of the file you
4403 want to print if you want to see other parts of the program.
4405 Here are the forms of the @code{edit} command most commonly used:
4409 Edit the current source file at the active line number in the program.
4411 @item edit @var{number}
4412 Edit the current source file with @var{number} as the active line number.
4414 @item edit @var{function}
4415 Edit the file containing @var{function} at the beginning of its definition.
4417 @item edit @var{filename}:@var{number}
4418 Specifies line @var{number} in the source file @var{filename}.
4420 @item edit @var{filename}:@var{function}
4421 Specifies the line that begins the body of the
4422 function @var{function} in the file @var{filename}. You only need the
4423 file name with a function name to avoid ambiguity when there are
4424 identically named functions in different source files.
4426 @item edit *@var{address}
4427 Specifies the line containing the program address @var{address}.
4428 @var{address} may be any expression.
4431 @subsection Choosing your editor
4432 You can customize @value{GDBN} to use any editor you want
4434 The only restriction is that your editor (say @code{ex}), recognizes the
4435 following command-line syntax:
4437 ex +@var{number} file
4439 The optional numeric value +@var{number} designates the active line in
4440 the file.}. By default, it is @value{EDITOR}, but you can change this
4441 by setting the environment variable @code{EDITOR} before using
4442 @value{GDBN}. For example, to configure @value{GDBN} to use the
4443 @code{vi} editor, you could use these commands with the @code{sh} shell:
4449 or in the @code{csh} shell,
4451 setenv EDITOR /usr/bin/vi
4456 @section Searching source files
4458 @kindex reverse-search
4460 There are two commands for searching through the current source file for a
4465 @kindex forward-search
4466 @item forward-search @var{regexp}
4467 @itemx search @var{regexp}
4468 The command @samp{forward-search @var{regexp}} checks each line,
4469 starting with the one following the last line listed, for a match for
4470 @var{regexp}. It lists the line that is found. You can use the
4471 synonym @samp{search @var{regexp}} or abbreviate the command name as
4474 @item reverse-search @var{regexp}
4475 The command @samp{reverse-search @var{regexp}} checks each line, starting
4476 with the one before the last line listed and going backward, for a match
4477 for @var{regexp}. It lists the line that is found. You can abbreviate
4478 this command as @code{rev}.
4482 @section Specifying source directories
4485 @cindex directories for source files
4486 Executable programs sometimes do not record the directories of the source
4487 files from which they were compiled, just the names. Even when they do,
4488 the directories could be moved between the compilation and your debugging
4489 session. @value{GDBN} has a list of directories to search for source files;
4490 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
4491 it tries all the directories in the list, in the order they are present
4492 in the list, until it finds a file with the desired name. Note that
4493 the executable search path is @emph{not} used for this purpose. Neither is
4494 the current working directory, unless it happens to be in the source
4497 If @value{GDBN} cannot find a source file in the source path, and the
4498 object program records a directory, @value{GDBN} tries that directory
4499 too. If the source path is empty, and there is no record of the
4500 compilation directory, @value{GDBN} looks in the current directory as a
4503 Whenever you reset or rearrange the source path, @value{GDBN} clears out
4504 any information it has cached about where source files are found and where
4505 each line is in the file.
4509 When you start @value{GDBN}, its source path includes only @samp{cdir}
4510 and @samp{cwd}, in that order.
4511 To add other directories, use the @code{directory} command.
4514 @item directory @var{dirname} @dots{}
4515 @item dir @var{dirname} @dots{}
4516 Add directory @var{dirname} to the front of the source path. Several
4517 directory names may be given to this command, separated by @samp{:}
4518 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
4519 part of absolute file names) or
4520 whitespace. You may specify a directory that is already in the source
4521 path; this moves it forward, so @value{GDBN} searches it sooner.
4525 @vindex $cdir@r{, convenience variable}
4526 @vindex $cwdr@r{, convenience variable}
4527 @cindex compilation directory
4528 @cindex current directory
4529 @cindex working directory
4530 @cindex directory, current
4531 @cindex directory, compilation
4532 You can use the string @samp{$cdir} to refer to the compilation
4533 directory (if one is recorded), and @samp{$cwd} to refer to the current
4534 working directory. @samp{$cwd} is not the same as @samp{.}---the former
4535 tracks the current working directory as it changes during your @value{GDBN}
4536 session, while the latter is immediately expanded to the current
4537 directory at the time you add an entry to the source path.
4540 Reset the source path to empty again. This requires confirmation.
4542 @c RET-repeat for @code{directory} is explicitly disabled, but since
4543 @c repeating it would be a no-op we do not say that. (thanks to RMS)
4545 @item show directories
4546 @kindex show directories
4547 Print the source path: show which directories it contains.
4550 If your source path is cluttered with directories that are no longer of
4551 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
4552 versions of source. You can correct the situation as follows:
4556 Use @code{directory} with no argument to reset the source path to empty.
4559 Use @code{directory} with suitable arguments to reinstall the
4560 directories you want in the source path. You can add all the
4561 directories in one command.
4565 @section Source and machine code
4567 You can use the command @code{info line} to map source lines to program
4568 addresses (and vice versa), and the command @code{disassemble} to display
4569 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
4570 mode, the @code{info line} command causes the arrow to point to the
4571 line specified. Also, @code{info line} prints addresses in symbolic form as
4576 @item info line @var{linespec}
4577 Print the starting and ending addresses of the compiled code for
4578 source line @var{linespec}. You can specify source lines in any of
4579 the ways understood by the @code{list} command (@pxref{List, ,Printing
4583 For example, we can use @code{info line} to discover the location of
4584 the object code for the first line of function
4585 @code{m4_changequote}:
4587 @c FIXME: I think this example should also show the addresses in
4588 @c symbolic form, as they usually would be displayed.
4590 (@value{GDBP}) info line m4_changequote
4591 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
4595 We can also inquire (using @code{*@var{addr}} as the form for
4596 @var{linespec}) what source line covers a particular address:
4598 (@value{GDBP}) info line *0x63ff
4599 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
4602 @cindex @code{$_} and @code{info line}
4603 @kindex x@r{(examine), and} info line
4604 After @code{info line}, the default address for the @code{x} command
4605 is changed to the starting address of the line, so that @samp{x/i} is
4606 sufficient to begin examining the machine code (@pxref{Memory,
4607 ,Examining memory}). Also, this address is saved as the value of the
4608 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
4613 @cindex assembly instructions
4614 @cindex instructions, assembly
4615 @cindex machine instructions
4616 @cindex listing machine instructions
4618 This specialized command dumps a range of memory as machine
4619 instructions. The default memory range is the function surrounding the
4620 program counter of the selected frame. A single argument to this
4621 command is a program counter value; @value{GDBN} dumps the function
4622 surrounding this value. Two arguments specify a range of addresses
4623 (first inclusive, second exclusive) to dump.
4626 The following example shows the disassembly of a range of addresses of
4627 HP PA-RISC 2.0 code:
4630 (@value{GDBP}) disas 0x32c4 0x32e4
4631 Dump of assembler code from 0x32c4 to 0x32e4:
4632 0x32c4 <main+204>: addil 0,dp
4633 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
4634 0x32cc <main+212>: ldil 0x3000,r31
4635 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
4636 0x32d4 <main+220>: ldo 0(r31),rp
4637 0x32d8 <main+224>: addil -0x800,dp
4638 0x32dc <main+228>: ldo 0x588(r1),r26
4639 0x32e0 <main+232>: ldil 0x3000,r31
4640 End of assembler dump.
4643 Some architectures have more than one commonly-used set of instruction
4644 mnemonics or other syntax.
4647 @kindex set disassembly-flavor
4648 @cindex assembly instructions
4649 @cindex instructions, assembly
4650 @cindex machine instructions
4651 @cindex listing machine instructions
4652 @cindex Intel disassembly flavor
4653 @cindex AT&T disassembly flavor
4654 @item set disassembly-flavor @var{instruction-set}
4655 Select the instruction set to use when disassembling the
4656 program via the @code{disassemble} or @code{x/i} commands.
4658 Currently this command is only defined for the Intel x86 family. You
4659 can set @var{instruction-set} to either @code{intel} or @code{att}.
4660 The default is @code{att}, the AT&T flavor used by default by Unix
4661 assemblers for x86-based targets.
4666 @chapter Examining Data
4668 @cindex printing data
4669 @cindex examining data
4672 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
4673 @c document because it is nonstandard... Under Epoch it displays in a
4674 @c different window or something like that.
4675 The usual way to examine data in your program is with the @code{print}
4676 command (abbreviated @code{p}), or its synonym @code{inspect}. It
4677 evaluates and prints the value of an expression of the language your
4678 program is written in (@pxref{Languages, ,Using @value{GDBN} with
4679 Different Languages}).
4682 @item print @var{expr}
4683 @itemx print /@var{f} @var{expr}
4684 @var{expr} is an expression (in the source language). By default the
4685 value of @var{expr} is printed in a format appropriate to its data type;
4686 you can choose a different format by specifying @samp{/@var{f}}, where
4687 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
4691 @itemx print /@var{f}
4692 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
4693 @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
4694 conveniently inspect the same value in an alternative format.
4697 A more low-level way of examining data is with the @code{x} command.
4698 It examines data in memory at a specified address and prints it in a
4699 specified format. @xref{Memory, ,Examining memory}.
4701 If you are interested in information about types, or about how the
4702 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
4703 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
4707 * Expressions:: Expressions
4708 * Variables:: Program variables
4709 * Arrays:: Artificial arrays
4710 * Output Formats:: Output formats
4711 * Memory:: Examining memory
4712 * Auto Display:: Automatic display
4713 * Print Settings:: Print settings
4714 * Value History:: Value history
4715 * Convenience Vars:: Convenience variables
4716 * Registers:: Registers
4717 * Floating Point Hardware:: Floating point hardware
4718 * Vector Unit:: Vector Unit
4719 * Memory Region Attributes:: Memory region attributes
4720 * Dump/Restore Files:: Copy between memory and a file
4721 * Character Sets:: Debugging programs that use a different
4722 character set than GDB does
4726 @section Expressions
4729 @code{print} and many other @value{GDBN} commands accept an expression and
4730 compute its value. Any kind of constant, variable or operator defined
4731 by the programming language you are using is valid in an expression in
4732 @value{GDBN}. This includes conditional expressions, function calls,
4733 casts, and string constants. It also includes preprocessor macros, if
4734 you compiled your program to include this information; see
4737 @value{GDBN} supports array constants in expressions input by
4738 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
4739 you can use the command @code{print @{1, 2, 3@}} to build up an array in
4740 memory that is @code{malloc}ed in the target program.
4742 Because C is so widespread, most of the expressions shown in examples in
4743 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
4744 Languages}, for information on how to use expressions in other
4747 In this section, we discuss operators that you can use in @value{GDBN}
4748 expressions regardless of your programming language.
4750 Casts are supported in all languages, not just in C, because it is so
4751 useful to cast a number into a pointer in order to examine a structure
4752 at that address in memory.
4753 @c FIXME: casts supported---Mod2 true?
4755 @value{GDBN} supports these operators, in addition to those common
4756 to programming languages:
4760 @samp{@@} is a binary operator for treating parts of memory as arrays.
4761 @xref{Arrays, ,Artificial arrays}, for more information.
4764 @samp{::} allows you to specify a variable in terms of the file or
4765 function where it is defined. @xref{Variables, ,Program variables}.
4767 @cindex @{@var{type}@}
4768 @cindex type casting memory
4769 @cindex memory, viewing as typed object
4770 @cindex casts, to view memory
4771 @item @{@var{type}@} @var{addr}
4772 Refers to an object of type @var{type} stored at address @var{addr} in
4773 memory. @var{addr} may be any expression whose value is an integer or
4774 pointer (but parentheses are required around binary operators, just as in
4775 a cast). This construct is allowed regardless of what kind of data is
4776 normally supposed to reside at @var{addr}.
4780 @section Program variables
4782 The most common kind of expression to use is the name of a variable
4785 Variables in expressions are understood in the selected stack frame
4786 (@pxref{Selection, ,Selecting a frame}); they must be either:
4790 global (or file-static)
4797 visible according to the scope rules of the
4798 programming language from the point of execution in that frame
4801 @noindent This means that in the function
4816 you can examine and use the variable @code{a} whenever your program is
4817 executing within the function @code{foo}, but you can only use or
4818 examine the variable @code{b} while your program is executing inside
4819 the block where @code{b} is declared.
4821 @cindex variable name conflict
4822 There is an exception: you can refer to a variable or function whose
4823 scope is a single source file even if the current execution point is not
4824 in this file. But it is possible to have more than one such variable or
4825 function with the same name (in different source files). If that
4826 happens, referring to that name has unpredictable effects. If you wish,
4827 you can specify a static variable in a particular function or file,
4828 using the colon-colon notation:
4830 @cindex colon-colon, context for variables/functions
4832 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
4833 @cindex @code{::}, context for variables/functions
4836 @var{file}::@var{variable}
4837 @var{function}::@var{variable}
4841 Here @var{file} or @var{function} is the name of the context for the
4842 static @var{variable}. In the case of file names, you can use quotes to
4843 make sure @value{GDBN} parses the file name as a single word---for example,
4844 to print a global value of @code{x} defined in @file{f2.c}:
4847 (@value{GDBP}) p 'f2.c'::x
4850 @cindex C@t{++} scope resolution
4851 This use of @samp{::} is very rarely in conflict with the very similar
4852 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
4853 scope resolution operator in @value{GDBN} expressions.
4854 @c FIXME: Um, so what happens in one of those rare cases where it's in
4857 @cindex wrong values
4858 @cindex variable values, wrong
4860 @emph{Warning:} Occasionally, a local variable may appear to have the
4861 wrong value at certain points in a function---just after entry to a new
4862 scope, and just before exit.
4864 You may see this problem when you are stepping by machine instructions.
4865 This is because, on most machines, it takes more than one instruction to
4866 set up a stack frame (including local variable definitions); if you are
4867 stepping by machine instructions, variables may appear to have the wrong
4868 values until the stack frame is completely built. On exit, it usually
4869 also takes more than one machine instruction to destroy a stack frame;
4870 after you begin stepping through that group of instructions, local
4871 variable definitions may be gone.
4873 This may also happen when the compiler does significant optimizations.
4874 To be sure of always seeing accurate values, turn off all optimization
4877 @cindex ``No symbol "foo" in current context''
4878 Another possible effect of compiler optimizations is to optimize
4879 unused variables out of existence, or assign variables to registers (as
4880 opposed to memory addresses). Depending on the support for such cases
4881 offered by the debug info format used by the compiler, @value{GDBN}
4882 might not be able to display values for such local variables. If that
4883 happens, @value{GDBN} will print a message like this:
4886 No symbol "foo" in current context.
4889 To solve such problems, either recompile without optimizations, or use a
4890 different debug info format, if the compiler supports several such
4891 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler
4892 usually supports the @option{-gstabs+} option. @option{-gstabs+}
4893 produces debug info in a format that is superior to formats such as
4894 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
4895 an effective form for debug info. @xref{Debugging Options,,Options
4896 for Debugging Your Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}.
4900 @section Artificial arrays
4902 @cindex artificial array
4903 @kindex @@@r{, referencing memory as an array}
4904 It is often useful to print out several successive objects of the
4905 same type in memory; a section of an array, or an array of
4906 dynamically determined size for which only a pointer exists in the
4909 You can do this by referring to a contiguous span of memory as an
4910 @dfn{artificial array}, using the binary operator @samp{@@}. The left
4911 operand of @samp{@@} should be the first element of the desired array
4912 and be an individual object. The right operand should be the desired length
4913 of the array. The result is an array value whose elements are all of
4914 the type of the left argument. The first element is actually the left
4915 argument; the second element comes from bytes of memory immediately
4916 following those that hold the first element, and so on. Here is an
4917 example. If a program says
4920 int *array = (int *) malloc (len * sizeof (int));
4924 you can print the contents of @code{array} with
4930 The left operand of @samp{@@} must reside in memory. Array values made
4931 with @samp{@@} in this way behave just like other arrays in terms of
4932 subscripting, and are coerced to pointers when used in expressions.
4933 Artificial arrays most often appear in expressions via the value history
4934 (@pxref{Value History, ,Value history}), after printing one out.
4936 Another way to create an artificial array is to use a cast.
4937 This re-interprets a value as if it were an array.
4938 The value need not be in memory:
4940 (@value{GDBP}) p/x (short[2])0x12345678
4941 $1 = @{0x1234, 0x5678@}
4944 As a convenience, if you leave the array length out (as in
4945 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
4946 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
4948 (@value{GDBP}) p/x (short[])0x12345678
4949 $2 = @{0x1234, 0x5678@}
4952 Sometimes the artificial array mechanism is not quite enough; in
4953 moderately complex data structures, the elements of interest may not
4954 actually be adjacent---for example, if you are interested in the values
4955 of pointers in an array. One useful work-around in this situation is
4956 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
4957 variables}) as a counter in an expression that prints the first
4958 interesting value, and then repeat that expression via @key{RET}. For
4959 instance, suppose you have an array @code{dtab} of pointers to
4960 structures, and you are interested in the values of a field @code{fv}
4961 in each structure. Here is an example of what you might type:
4971 @node Output Formats
4972 @section Output formats
4974 @cindex formatted output
4975 @cindex output formats
4976 By default, @value{GDBN} prints a value according to its data type. Sometimes
4977 this is not what you want. For example, you might want to print a number
4978 in hex, or a pointer in decimal. Or you might want to view data in memory
4979 at a certain address as a character string or as an instruction. To do
4980 these things, specify an @dfn{output format} when you print a value.
4982 The simplest use of output formats is to say how to print a value
4983 already computed. This is done by starting the arguments of the
4984 @code{print} command with a slash and a format letter. The format
4985 letters supported are:
4989 Regard the bits of the value as an integer, and print the integer in
4993 Print as integer in signed decimal.
4996 Print as integer in unsigned decimal.
4999 Print as integer in octal.
5002 Print as integer in binary. The letter @samp{t} stands for ``two''.
5003 @footnote{@samp{b} cannot be used because these format letters are also
5004 used with the @code{x} command, where @samp{b} stands for ``byte'';
5005 see @ref{Memory,,Examining memory}.}
5008 @cindex unknown address, locating
5009 @cindex locate address
5010 Print as an address, both absolute in hexadecimal and as an offset from
5011 the nearest preceding symbol. You can use this format used to discover
5012 where (in what function) an unknown address is located:
5015 (@value{GDBP}) p/a 0x54320
5016 $3 = 0x54320 <_initialize_vx+396>
5020 The command @code{info symbol 0x54320} yields similar results.
5021 @xref{Symbols, info symbol}.
5024 Regard as an integer and print it as a character constant.
5027 Regard the bits of the value as a floating point number and print
5028 using typical floating point syntax.
5031 For example, to print the program counter in hex (@pxref{Registers}), type
5038 Note that no space is required before the slash; this is because command
5039 names in @value{GDBN} cannot contain a slash.
5041 To reprint the last value in the value history with a different format,
5042 you can use the @code{print} command with just a format and no
5043 expression. For example, @samp{p/x} reprints the last value in hex.
5046 @section Examining memory
5048 You can use the command @code{x} (for ``examine'') to examine memory in
5049 any of several formats, independently of your program's data types.
5051 @cindex examining memory
5053 @kindex x @r{(examine memory)}
5054 @item x/@var{nfu} @var{addr}
5057 Use the @code{x} command to examine memory.
5060 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5061 much memory to display and how to format it; @var{addr} is an
5062 expression giving the address where you want to start displaying memory.
5063 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5064 Several commands set convenient defaults for @var{addr}.
5067 @item @var{n}, the repeat count
5068 The repeat count is a decimal integer; the default is 1. It specifies
5069 how much memory (counting by units @var{u}) to display.
5070 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5073 @item @var{f}, the display format
5074 The display format is one of the formats used by @code{print},
5075 @samp{s} (null-terminated string), or @samp{i} (machine instruction).
5076 The default is @samp{x} (hexadecimal) initially.
5077 The default changes each time you use either @code{x} or @code{print}.
5079 @item @var{u}, the unit size
5080 The unit size is any of
5086 Halfwords (two bytes).
5088 Words (four bytes). This is the initial default.
5090 Giant words (eight bytes).
5093 Each time you specify a unit size with @code{x}, that size becomes the
5094 default unit the next time you use @code{x}. (For the @samp{s} and
5095 @samp{i} formats, the unit size is ignored and is normally not written.)
5097 @item @var{addr}, starting display address
5098 @var{addr} is the address where you want @value{GDBN} to begin displaying
5099 memory. The expression need not have a pointer value (though it may);
5100 it is always interpreted as an integer address of a byte of memory.
5101 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5102 @var{addr} is usually just after the last address examined---but several
5103 other commands also set the default address: @code{info breakpoints} (to
5104 the address of the last breakpoint listed), @code{info line} (to the
5105 starting address of a line), and @code{print} (if you use it to display
5106 a value from memory).
5109 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5110 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5111 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5112 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5113 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5115 Since the letters indicating unit sizes are all distinct from the
5116 letters specifying output formats, you do not have to remember whether
5117 unit size or format comes first; either order works. The output
5118 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5119 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5121 Even though the unit size @var{u} is ignored for the formats @samp{s}
5122 and @samp{i}, you might still want to use a count @var{n}; for example,
5123 @samp{3i} specifies that you want to see three machine instructions,
5124 including any operands. The command @code{disassemble} gives an
5125 alternative way of inspecting machine instructions; see @ref{Machine
5126 Code,,Source and machine code}.
5128 All the defaults for the arguments to @code{x} are designed to make it
5129 easy to continue scanning memory with minimal specifications each time
5130 you use @code{x}. For example, after you have inspected three machine
5131 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5132 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5133 the repeat count @var{n} is used again; the other arguments default as
5134 for successive uses of @code{x}.
5136 @cindex @code{$_}, @code{$__}, and value history
5137 The addresses and contents printed by the @code{x} command are not saved
5138 in the value history because there is often too much of them and they
5139 would get in the way. Instead, @value{GDBN} makes these values available for
5140 subsequent use in expressions as values of the convenience variables
5141 @code{$_} and @code{$__}. After an @code{x} command, the last address
5142 examined is available for use in expressions in the convenience variable
5143 @code{$_}. The contents of that address, as examined, are available in
5144 the convenience variable @code{$__}.
5146 If the @code{x} command has a repeat count, the address and contents saved
5147 are from the last memory unit printed; this is not the same as the last
5148 address printed if several units were printed on the last line of output.
5151 @section Automatic display
5152 @cindex automatic display
5153 @cindex display of expressions
5155 If you find that you want to print the value of an expression frequently
5156 (to see how it changes), you might want to add it to the @dfn{automatic
5157 display list} so that @value{GDBN} prints its value each time your program stops.
5158 Each expression added to the list is given a number to identify it;
5159 to remove an expression from the list, you specify that number.
5160 The automatic display looks like this:
5164 3: bar[5] = (struct hack *) 0x3804
5168 This display shows item numbers, expressions and their current values. As with
5169 displays you request manually using @code{x} or @code{print}, you can
5170 specify the output format you prefer; in fact, @code{display} decides
5171 whether to use @code{print} or @code{x} depending on how elaborate your
5172 format specification is---it uses @code{x} if you specify a unit size,
5173 or one of the two formats (@samp{i} and @samp{s}) that are only
5174 supported by @code{x}; otherwise it uses @code{print}.
5178 @item display @var{expr}
5179 Add the expression @var{expr} to the list of expressions to display
5180 each time your program stops. @xref{Expressions, ,Expressions}.
5182 @code{display} does not repeat if you press @key{RET} again after using it.
5184 @item display/@var{fmt} @var{expr}
5185 For @var{fmt} specifying only a display format and not a size or
5186 count, add the expression @var{expr} to the auto-display list but
5187 arrange to display it each time in the specified format @var{fmt}.
5188 @xref{Output Formats,,Output formats}.
5190 @item display/@var{fmt} @var{addr}
5191 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
5192 number of units, add the expression @var{addr} as a memory address to
5193 be examined each time your program stops. Examining means in effect
5194 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
5197 For example, @samp{display/i $pc} can be helpful, to see the machine
5198 instruction about to be executed each time execution stops (@samp{$pc}
5199 is a common name for the program counter; @pxref{Registers, ,Registers}).
5202 @kindex delete display
5204 @item undisplay @var{dnums}@dots{}
5205 @itemx delete display @var{dnums}@dots{}
5206 Remove item numbers @var{dnums} from the list of expressions to display.
5208 @code{undisplay} does not repeat if you press @key{RET} after using it.
5209 (Otherwise you would just get the error @samp{No display number @dots{}}.)
5211 @kindex disable display
5212 @item disable display @var{dnums}@dots{}
5213 Disable the display of item numbers @var{dnums}. A disabled display
5214 item is not printed automatically, but is not forgotten. It may be
5215 enabled again later.
5217 @kindex enable display
5218 @item enable display @var{dnums}@dots{}
5219 Enable display of item numbers @var{dnums}. It becomes effective once
5220 again in auto display of its expression, until you specify otherwise.
5223 Display the current values of the expressions on the list, just as is
5224 done when your program stops.
5226 @kindex info display
5228 Print the list of expressions previously set up to display
5229 automatically, each one with its item number, but without showing the
5230 values. This includes disabled expressions, which are marked as such.
5231 It also includes expressions which would not be displayed right now
5232 because they refer to automatic variables not currently available.
5235 If a display expression refers to local variables, then it does not make
5236 sense outside the lexical context for which it was set up. Such an
5237 expression is disabled when execution enters a context where one of its
5238 variables is not defined. For example, if you give the command
5239 @code{display last_char} while inside a function with an argument
5240 @code{last_char}, @value{GDBN} displays this argument while your program
5241 continues to stop inside that function. When it stops elsewhere---where
5242 there is no variable @code{last_char}---the display is disabled
5243 automatically. The next time your program stops where @code{last_char}
5244 is meaningful, you can enable the display expression once again.
5246 @node Print Settings
5247 @section Print settings
5249 @cindex format options
5250 @cindex print settings
5251 @value{GDBN} provides the following ways to control how arrays, structures,
5252 and symbols are printed.
5255 These settings are useful for debugging programs in any language:
5258 @kindex set print address
5259 @item set print address
5260 @itemx set print address on
5261 @value{GDBN} prints memory addresses showing the location of stack
5262 traces, structure values, pointer values, breakpoints, and so forth,
5263 even when it also displays the contents of those addresses. The default
5264 is @code{on}. For example, this is what a stack frame display looks like with
5265 @code{set print address on}:
5270 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
5272 530 if (lquote != def_lquote)
5276 @item set print address off
5277 Do not print addresses when displaying their contents. For example,
5278 this is the same stack frame displayed with @code{set print address off}:
5282 (@value{GDBP}) set print addr off
5284 #0 set_quotes (lq="<<", rq=">>") at input.c:530
5285 530 if (lquote != def_lquote)
5289 You can use @samp{set print address off} to eliminate all machine
5290 dependent displays from the @value{GDBN} interface. For example, with
5291 @code{print address off}, you should get the same text for backtraces on
5292 all machines---whether or not they involve pointer arguments.
5294 @kindex show print address
5295 @item show print address
5296 Show whether or not addresses are to be printed.
5299 When @value{GDBN} prints a symbolic address, it normally prints the
5300 closest earlier symbol plus an offset. If that symbol does not uniquely
5301 identify the address (for example, it is a name whose scope is a single
5302 source file), you may need to clarify. One way to do this is with
5303 @code{info line}, for example @samp{info line *0x4537}. Alternately,
5304 you can set @value{GDBN} to print the source file and line number when
5305 it prints a symbolic address:
5308 @kindex set print symbol-filename
5309 @item set print symbol-filename on
5310 Tell @value{GDBN} to print the source file name and line number of a
5311 symbol in the symbolic form of an address.
5313 @item set print symbol-filename off
5314 Do not print source file name and line number of a symbol. This is the
5317 @kindex show print symbol-filename
5318 @item show print symbol-filename
5319 Show whether or not @value{GDBN} will print the source file name and
5320 line number of a symbol in the symbolic form of an address.
5323 Another situation where it is helpful to show symbol filenames and line
5324 numbers is when disassembling code; @value{GDBN} shows you the line
5325 number and source file that corresponds to each instruction.
5327 Also, you may wish to see the symbolic form only if the address being
5328 printed is reasonably close to the closest earlier symbol:
5331 @kindex set print max-symbolic-offset
5332 @item set print max-symbolic-offset @var{max-offset}
5333 Tell @value{GDBN} to only display the symbolic form of an address if the
5334 offset between the closest earlier symbol and the address is less than
5335 @var{max-offset}. The default is 0, which tells @value{GDBN}
5336 to always print the symbolic form of an address if any symbol precedes it.
5338 @kindex show print max-symbolic-offset
5339 @item show print max-symbolic-offset
5340 Ask how large the maximum offset is that @value{GDBN} prints in a
5344 @cindex wild pointer, interpreting
5345 @cindex pointer, finding referent
5346 If you have a pointer and you are not sure where it points, try
5347 @samp{set print symbol-filename on}. Then you can determine the name
5348 and source file location of the variable where it points, using
5349 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
5350 For example, here @value{GDBN} shows that a variable @code{ptt} points
5351 at another variable @code{t}, defined in @file{hi2.c}:
5354 (@value{GDBP}) set print symbol-filename on
5355 (@value{GDBP}) p/a ptt
5356 $4 = 0xe008 <t in hi2.c>
5360 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
5361 does not show the symbol name and filename of the referent, even with
5362 the appropriate @code{set print} options turned on.
5365 Other settings control how different kinds of objects are printed:
5368 @kindex set print array
5369 @item set print array
5370 @itemx set print array on
5371 Pretty print arrays. This format is more convenient to read,
5372 but uses more space. The default is off.
5374 @item set print array off
5375 Return to compressed format for arrays.
5377 @kindex show print array
5378 @item show print array
5379 Show whether compressed or pretty format is selected for displaying
5382 @kindex set print elements
5383 @item set print elements @var{number-of-elements}
5384 Set a limit on how many elements of an array @value{GDBN} will print.
5385 If @value{GDBN} is printing a large array, it stops printing after it has
5386 printed the number of elements set by the @code{set print elements} command.
5387 This limit also applies to the display of strings.
5388 When @value{GDBN} starts, this limit is set to 200.
5389 Setting @var{number-of-elements} to zero means that the printing is unlimited.
5391 @kindex show print elements
5392 @item show print elements
5393 Display the number of elements of a large array that @value{GDBN} will print.
5394 If the number is 0, then the printing is unlimited.
5396 @kindex set print null-stop
5397 @item set print null-stop
5398 Cause @value{GDBN} to stop printing the characters of an array when the first
5399 @sc{null} is encountered. This is useful when large arrays actually
5400 contain only short strings.
5403 @kindex set print pretty
5404 @item set print pretty on
5405 Cause @value{GDBN} to print structures in an indented format with one member
5406 per line, like this:
5421 @item set print pretty off
5422 Cause @value{GDBN} to print structures in a compact format, like this:
5426 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
5427 meat = 0x54 "Pork"@}
5432 This is the default format.
5434 @kindex show print pretty
5435 @item show print pretty
5436 Show which format @value{GDBN} is using to print structures.
5438 @kindex set print sevenbit-strings
5439 @item set print sevenbit-strings on
5440 Print using only seven-bit characters; if this option is set,
5441 @value{GDBN} displays any eight-bit characters (in strings or
5442 character values) using the notation @code{\}@var{nnn}. This setting is
5443 best if you are working in English (@sc{ascii}) and you use the
5444 high-order bit of characters as a marker or ``meta'' bit.
5446 @item set print sevenbit-strings off
5447 Print full eight-bit characters. This allows the use of more
5448 international character sets, and is the default.
5450 @kindex show print sevenbit-strings
5451 @item show print sevenbit-strings
5452 Show whether or not @value{GDBN} is printing only seven-bit characters.
5454 @kindex set print union
5455 @item set print union on
5456 Tell @value{GDBN} to print unions which are contained in structures. This
5457 is the default setting.
5459 @item set print union off
5460 Tell @value{GDBN} not to print unions which are contained in structures.
5462 @kindex show print union
5463 @item show print union
5464 Ask @value{GDBN} whether or not it will print unions which are contained in
5467 For example, given the declarations
5470 typedef enum @{Tree, Bug@} Species;
5471 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
5472 typedef enum @{Caterpillar, Cocoon, Butterfly@}
5483 struct thing foo = @{Tree, @{Acorn@}@};
5487 with @code{set print union on} in effect @samp{p foo} would print
5490 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
5494 and with @code{set print union off} in effect it would print
5497 $1 = @{it = Tree, form = @{...@}@}
5503 These settings are of interest when debugging C@t{++} programs:
5507 @kindex set print demangle
5508 @item set print demangle
5509 @itemx set print demangle on
5510 Print C@t{++} names in their source form rather than in the encoded
5511 (``mangled'') form passed to the assembler and linker for type-safe
5512 linkage. The default is on.
5514 @kindex show print demangle
5515 @item show print demangle
5516 Show whether C@t{++} names are printed in mangled or demangled form.
5518 @kindex set print asm-demangle
5519 @item set print asm-demangle
5520 @itemx set print asm-demangle on
5521 Print C@t{++} names in their source form rather than their mangled form, even
5522 in assembler code printouts such as instruction disassemblies.
5525 @kindex show print asm-demangle
5526 @item show print asm-demangle
5527 Show whether C@t{++} names in assembly listings are printed in mangled
5530 @kindex set demangle-style
5531 @cindex C@t{++} symbol decoding style
5532 @cindex symbol decoding style, C@t{++}
5533 @item set demangle-style @var{style}
5534 Choose among several encoding schemes used by different compilers to
5535 represent C@t{++} names. The choices for @var{style} are currently:
5539 Allow @value{GDBN} to choose a decoding style by inspecting your program.
5542 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
5543 This is the default.
5546 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
5549 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
5552 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
5553 @strong{Warning:} this setting alone is not sufficient to allow
5554 debugging @code{cfront}-generated executables. @value{GDBN} would
5555 require further enhancement to permit that.
5558 If you omit @var{style}, you will see a list of possible formats.
5560 @kindex show demangle-style
5561 @item show demangle-style
5562 Display the encoding style currently in use for decoding C@t{++} symbols.
5564 @kindex set print object
5565 @item set print object
5566 @itemx set print object on
5567 When displaying a pointer to an object, identify the @emph{actual}
5568 (derived) type of the object rather than the @emph{declared} type, using
5569 the virtual function table.
5571 @item set print object off
5572 Display only the declared type of objects, without reference to the
5573 virtual function table. This is the default setting.
5575 @kindex show print object
5576 @item show print object
5577 Show whether actual, or declared, object types are displayed.
5579 @kindex set print static-members
5580 @item set print static-members
5581 @itemx set print static-members on
5582 Print static members when displaying a C@t{++} object. The default is on.
5584 @item set print static-members off
5585 Do not print static members when displaying a C@t{++} object.
5587 @kindex show print static-members
5588 @item show print static-members
5589 Show whether C@t{++} static members are printed, or not.
5591 @c These don't work with HP ANSI C++ yet.
5592 @kindex set print vtbl
5593 @item set print vtbl
5594 @itemx set print vtbl on
5595 Pretty print C@t{++} virtual function tables. The default is off.
5596 (The @code{vtbl} commands do not work on programs compiled with the HP
5597 ANSI C@t{++} compiler (@code{aCC}).)
5599 @item set print vtbl off
5600 Do not pretty print C@t{++} virtual function tables.
5602 @kindex show print vtbl
5603 @item show print vtbl
5604 Show whether C@t{++} virtual function tables are pretty printed, or not.
5608 @section Value history
5610 @cindex value history
5611 Values printed by the @code{print} command are saved in the @value{GDBN}
5612 @dfn{value history}. This allows you to refer to them in other expressions.
5613 Values are kept until the symbol table is re-read or discarded
5614 (for example with the @code{file} or @code{symbol-file} commands).
5615 When the symbol table changes, the value history is discarded,
5616 since the values may contain pointers back to the types defined in the
5621 @cindex history number
5622 The values printed are given @dfn{history numbers} by which you can
5623 refer to them. These are successive integers starting with one.
5624 @code{print} shows you the history number assigned to a value by
5625 printing @samp{$@var{num} = } before the value; here @var{num} is the
5628 To refer to any previous value, use @samp{$} followed by the value's
5629 history number. The way @code{print} labels its output is designed to
5630 remind you of this. Just @code{$} refers to the most recent value in
5631 the history, and @code{$$} refers to the value before that.
5632 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
5633 is the value just prior to @code{$$}, @code{$$1} is equivalent to
5634 @code{$$}, and @code{$$0} is equivalent to @code{$}.
5636 For example, suppose you have just printed a pointer to a structure and
5637 want to see the contents of the structure. It suffices to type
5643 If you have a chain of structures where the component @code{next} points
5644 to the next one, you can print the contents of the next one with this:
5651 You can print successive links in the chain by repeating this
5652 command---which you can do by just typing @key{RET}.
5654 Note that the history records values, not expressions. If the value of
5655 @code{x} is 4 and you type these commands:
5663 then the value recorded in the value history by the @code{print} command
5664 remains 4 even though the value of @code{x} has changed.
5669 Print the last ten values in the value history, with their item numbers.
5670 This is like @samp{p@ $$9} repeated ten times, except that @code{show
5671 values} does not change the history.
5673 @item show values @var{n}
5674 Print ten history values centered on history item number @var{n}.
5677 Print ten history values just after the values last printed. If no more
5678 values are available, @code{show values +} produces no display.
5681 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
5682 same effect as @samp{show values +}.
5684 @node Convenience Vars
5685 @section Convenience variables
5687 @cindex convenience variables
5688 @value{GDBN} provides @dfn{convenience variables} that you can use within
5689 @value{GDBN} to hold on to a value and refer to it later. These variables
5690 exist entirely within @value{GDBN}; they are not part of your program, and
5691 setting a convenience variable has no direct effect on further execution
5692 of your program. That is why you can use them freely.
5694 Convenience variables are prefixed with @samp{$}. Any name preceded by
5695 @samp{$} can be used for a convenience variable, unless it is one of
5696 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
5697 (Value history references, in contrast, are @emph{numbers} preceded
5698 by @samp{$}. @xref{Value History, ,Value history}.)
5700 You can save a value in a convenience variable with an assignment
5701 expression, just as you would set a variable in your program.
5705 set $foo = *object_ptr
5709 would save in @code{$foo} the value contained in the object pointed to by
5712 Using a convenience variable for the first time creates it, but its
5713 value is @code{void} until you assign a new value. You can alter the
5714 value with another assignment at any time.
5716 Convenience variables have no fixed types. You can assign a convenience
5717 variable any type of value, including structures and arrays, even if
5718 that variable already has a value of a different type. The convenience
5719 variable, when used as an expression, has the type of its current value.
5722 @kindex show convenience
5723 @item show convenience
5724 Print a list of convenience variables used so far, and their values.
5725 Abbreviated @code{show conv}.
5728 One of the ways to use a convenience variable is as a counter to be
5729 incremented or a pointer to be advanced. For example, to print
5730 a field from successive elements of an array of structures:
5734 print bar[$i++]->contents
5738 Repeat that command by typing @key{RET}.
5740 Some convenience variables are created automatically by @value{GDBN} and given
5741 values likely to be useful.
5744 @vindex $_@r{, convenience variable}
5746 The variable @code{$_} is automatically set by the @code{x} command to
5747 the last address examined (@pxref{Memory, ,Examining memory}). Other
5748 commands which provide a default address for @code{x} to examine also
5749 set @code{$_} to that address; these commands include @code{info line}
5750 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
5751 except when set by the @code{x} command, in which case it is a pointer
5752 to the type of @code{$__}.
5754 @vindex $__@r{, convenience variable}
5756 The variable @code{$__} is automatically set by the @code{x} command
5757 to the value found in the last address examined. Its type is chosen
5758 to match the format in which the data was printed.
5761 @vindex $_exitcode@r{, convenience variable}
5762 The variable @code{$_exitcode} is automatically set to the exit code when
5763 the program being debugged terminates.
5766 On HP-UX systems, if you refer to a function or variable name that
5767 begins with a dollar sign, @value{GDBN} searches for a user or system
5768 name first, before it searches for a convenience variable.
5774 You can refer to machine register contents, in expressions, as variables
5775 with names starting with @samp{$}. The names of registers are different
5776 for each machine; use @code{info registers} to see the names used on
5780 @kindex info registers
5781 @item info registers
5782 Print the names and values of all registers except floating-point
5783 and vector registers (in the selected stack frame).
5785 @kindex info all-registers
5786 @cindex floating point registers
5787 @item info all-registers
5788 Print the names and values of all registers, including floating-point
5789 and vector registers (in the selected stack frame).
5791 @item info registers @var{regname} @dots{}
5792 Print the @dfn{relativized} value of each specified register @var{regname}.
5793 As discussed in detail below, register values are normally relative to
5794 the selected stack frame. @var{regname} may be any register name valid on
5795 the machine you are using, with or without the initial @samp{$}.
5798 @value{GDBN} has four ``standard'' register names that are available (in
5799 expressions) on most machines---whenever they do not conflict with an
5800 architecture's canonical mnemonics for registers. The register names
5801 @code{$pc} and @code{$sp} are used for the program counter register and
5802 the stack pointer. @code{$fp} is used for a register that contains a
5803 pointer to the current stack frame, and @code{$ps} is used for a
5804 register that contains the processor status. For example,
5805 you could print the program counter in hex with
5812 or print the instruction to be executed next with
5819 or add four to the stack pointer@footnote{This is a way of removing
5820 one word from the stack, on machines where stacks grow downward in
5821 memory (most machines, nowadays). This assumes that the innermost
5822 stack frame is selected; setting @code{$sp} is not allowed when other
5823 stack frames are selected. To pop entire frames off the stack,
5824 regardless of machine architecture, use @code{return};
5825 see @ref{Returning, ,Returning from a function}.} with
5831 Whenever possible, these four standard register names are available on
5832 your machine even though the machine has different canonical mnemonics,
5833 so long as there is no conflict. The @code{info registers} command
5834 shows the canonical names. For example, on the SPARC, @code{info
5835 registers} displays the processor status register as @code{$psr} but you
5836 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
5837 is an alias for the @sc{eflags} register.
5839 @value{GDBN} always considers the contents of an ordinary register as an
5840 integer when the register is examined in this way. Some machines have
5841 special registers which can hold nothing but floating point; these
5842 registers are considered to have floating point values. There is no way
5843 to refer to the contents of an ordinary register as floating point value
5844 (although you can @emph{print} it as a floating point value with
5845 @samp{print/f $@var{regname}}).
5847 Some registers have distinct ``raw'' and ``virtual'' data formats. This
5848 means that the data format in which the register contents are saved by
5849 the operating system is not the same one that your program normally
5850 sees. For example, the registers of the 68881 floating point
5851 coprocessor are always saved in ``extended'' (raw) format, but all C
5852 programs expect to work with ``double'' (virtual) format. In such
5853 cases, @value{GDBN} normally works with the virtual format only (the format
5854 that makes sense for your program), but the @code{info registers} command
5855 prints the data in both formats.
5857 Normally, register values are relative to the selected stack frame
5858 (@pxref{Selection, ,Selecting a frame}). This means that you get the
5859 value that the register would contain if all stack frames farther in
5860 were exited and their saved registers restored. In order to see the
5861 true contents of hardware registers, you must select the innermost
5862 frame (with @samp{frame 0}).
5864 However, @value{GDBN} must deduce where registers are saved, from the machine
5865 code generated by your compiler. If some registers are not saved, or if
5866 @value{GDBN} is unable to locate the saved registers, the selected stack
5867 frame makes no difference.
5869 @node Floating Point Hardware
5870 @section Floating point hardware
5871 @cindex floating point
5873 Depending on the configuration, @value{GDBN} may be able to give
5874 you more information about the status of the floating point hardware.
5879 Display hardware-dependent information about the floating
5880 point unit. The exact contents and layout vary depending on the
5881 floating point chip. Currently, @samp{info float} is supported on
5882 the ARM and x86 machines.
5886 @section Vector Unit
5889 Depending on the configuration, @value{GDBN} may be able to give you
5890 more information about the status of the vector unit.
5895 Display information about the vector unit. The exact contents and
5896 layout vary depending on the hardware.
5899 @node Memory Region Attributes
5900 @section Memory region attributes
5901 @cindex memory region attributes
5903 @dfn{Memory region attributes} allow you to describe special handling
5904 required by regions of your target's memory. @value{GDBN} uses attributes
5905 to determine whether to allow certain types of memory accesses; whether to
5906 use specific width accesses; and whether to cache target memory.
5908 Defined memory regions can be individually enabled and disabled. When a
5909 memory region is disabled, @value{GDBN} uses the default attributes when
5910 accessing memory in that region. Similarly, if no memory regions have
5911 been defined, @value{GDBN} uses the default attributes when accessing
5914 When a memory region is defined, it is given a number to identify it;
5915 to enable, disable, or remove a memory region, you specify that number.
5919 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
5920 Define memory region bounded by @var{lower} and @var{upper} with
5921 attributes @var{attributes}@dots{}. Note that @var{upper} == 0 is a
5922 special case: it is treated as the the target's maximum memory address.
5923 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
5926 @item delete mem @var{nums}@dots{}
5927 Remove memory regions @var{nums}@dots{}.
5930 @item disable mem @var{nums}@dots{}
5931 Disable memory regions @var{nums}@dots{}.
5932 A disabled memory region is not forgotten.
5933 It may be enabled again later.
5936 @item enable mem @var{nums}@dots{}
5937 Enable memory regions @var{nums}@dots{}.
5941 Print a table of all defined memory regions, with the following columns
5945 @item Memory Region Number
5946 @item Enabled or Disabled.
5947 Enabled memory regions are marked with @samp{y}.
5948 Disabled memory regions are marked with @samp{n}.
5951 The address defining the inclusive lower bound of the memory region.
5954 The address defining the exclusive upper bound of the memory region.
5957 The list of attributes set for this memory region.
5962 @subsection Attributes
5964 @subsubsection Memory Access Mode
5965 The access mode attributes set whether @value{GDBN} may make read or
5966 write accesses to a memory region.
5968 While these attributes prevent @value{GDBN} from performing invalid
5969 memory accesses, they do nothing to prevent the target system, I/O DMA,
5970 etc. from accessing memory.
5974 Memory is read only.
5976 Memory is write only.
5978 Memory is read/write. This is the default.
5981 @subsubsection Memory Access Size
5982 The acccess size attributes tells @value{GDBN} to use specific sized
5983 accesses in the memory region. Often memory mapped device registers
5984 require specific sized accesses. If no access size attribute is
5985 specified, @value{GDBN} may use accesses of any size.
5989 Use 8 bit memory accesses.
5991 Use 16 bit memory accesses.
5993 Use 32 bit memory accesses.
5995 Use 64 bit memory accesses.
5998 @c @subsubsection Hardware/Software Breakpoints
5999 @c The hardware/software breakpoint attributes set whether @value{GDBN}
6000 @c will use hardware or software breakpoints for the internal breakpoints
6001 @c used by the step, next, finish, until, etc. commands.
6005 @c Always use hardware breakpoints
6006 @c @item swbreak (default)
6009 @subsubsection Data Cache
6010 The data cache attributes set whether @value{GDBN} will cache target
6011 memory. While this generally improves performance by reducing debug
6012 protocol overhead, it can lead to incorrect results because @value{GDBN}
6013 does not know about volatile variables or memory mapped device
6018 Enable @value{GDBN} to cache target memory.
6020 Disable @value{GDBN} from caching target memory. This is the default.
6023 @c @subsubsection Memory Write Verification
6024 @c The memory write verification attributes set whether @value{GDBN}
6025 @c will re-reads data after each write to verify the write was successful.
6029 @c @item noverify (default)
6032 @node Dump/Restore Files
6033 @section Copy between memory and a file
6034 @cindex dump/restore files
6035 @cindex append data to a file
6036 @cindex dump data to a file
6037 @cindex restore data from a file
6039 You can use the commands @code{dump}, @code{append}, and
6040 @code{restore} to copy data between target memory and a file. The
6041 @code{dump} and @code{append} commands write data to a file, and the
6042 @code{restore} command reads data from a file back into the inferior's
6043 memory. Files may be in binary, Motorola S-record, Intel hex, or
6044 Tektronix Hex format; however, @value{GDBN} can only append to binary
6050 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6051 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
6052 Dump the contents of memory from @var{start_addr} to @var{end_addr},
6053 or the value of @var{expr}, to @var{filename} in the given format.
6055 The @var{format} parameter may be any one of:
6062 Motorola S-record format.
6064 Tektronix Hex format.
6067 @value{GDBN} uses the same definitions of these formats as the
6068 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
6069 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
6073 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6074 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
6075 Append the contents of memory from @var{start_addr} to @var{end_addr},
6076 or the value of @var{expr}, to @var{filename}, in raw binary form.
6077 (@value{GDBN} can only append data to files in raw binary form.)
6080 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
6081 Restore the contents of file @var{filename} into memory. The
6082 @code{restore} command can automatically recognize any known @sc{bfd}
6083 file format, except for raw binary. To restore a raw binary file you
6084 must specify the optional keyword @code{binary} after the filename.
6086 If @var{bias} is non-zero, its value will be added to the addresses
6087 contained in the file. Binary files always start at address zero, so
6088 they will be restored at address @var{bias}. Other bfd files have
6089 a built-in location; they will be restored at offset @var{bias}
6092 If @var{start} and/or @var{end} are non-zero, then only data between
6093 file offset @var{start} and file offset @var{end} will be restored.
6094 These offsets are relative to the addresses in the file, before
6095 the @var{bias} argument is applied.
6099 @node Character Sets
6100 @section Character Sets
6101 @cindex character sets
6103 @cindex translating between character sets
6104 @cindex host character set
6105 @cindex target character set
6107 If the program you are debugging uses a different character set to
6108 represent characters and strings than the one @value{GDBN} uses itself,
6109 @value{GDBN} can automatically translate between the character sets for
6110 you. The character set @value{GDBN} uses we call the @dfn{host
6111 character set}; the one the inferior program uses we call the
6112 @dfn{target character set}.
6114 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
6115 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
6116 remote protocol (@pxref{Remote,Remote Debugging}) to debug a program
6117 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
6118 then the host character set is Latin-1, and the target character set is
6119 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
6120 target-charset EBCDIC-US}, then @value{GDBN} translates between
6121 @sc{ebcdic} and Latin 1 as you print character or string values, or use
6122 character and string literals in expressions.
6124 @value{GDBN} has no way to automatically recognize which character set
6125 the inferior program uses; you must tell it, using the @code{set
6126 target-charset} command, described below.
6128 Here are the commands for controlling @value{GDBN}'s character set
6132 @item set target-charset @var{charset}
6133 @kindex set target-charset
6134 Set the current target character set to @var{charset}. We list the
6135 character set names @value{GDBN} recognizes below, but if you type
6136 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6137 list the target character sets it supports.
6141 @item set host-charset @var{charset}
6142 @kindex set host-charset
6143 Set the current host character set to @var{charset}.
6145 By default, @value{GDBN} uses a host character set appropriate to the
6146 system it is running on; you can override that default using the
6147 @code{set host-charset} command.
6149 @value{GDBN} can only use certain character sets as its host character
6150 set. We list the character set names @value{GDBN} recognizes below, and
6151 indicate which can be host character sets, but if you type
6152 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6153 list the host character sets it supports.
6155 @item set charset @var{charset}
6157 Set the current host and target character sets to @var{charset}. As
6158 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
6159 @value{GDBN} will list the name of the character sets that can be used
6160 for both host and target.
6164 @kindex show charset
6165 Show the names of the current host and target charsets.
6167 @itemx show host-charset
6168 @kindex show host-charset
6169 Show the name of the current host charset.
6171 @itemx show target-charset
6172 @kindex show target-charset
6173 Show the name of the current target charset.
6177 @value{GDBN} currently includes support for the following character
6183 @cindex ASCII character set
6184 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
6188 @cindex ISO 8859-1 character set
6189 @cindex ISO Latin 1 character set
6190 The ISO Latin 1 character set. This extends @sc{ascii} with accented
6191 characters needed for French, German, and Spanish. @value{GDBN} can use
6192 this as its host character set.
6196 @cindex EBCDIC character set
6197 @cindex IBM1047 character set
6198 Variants of the @sc{ebcdic} character set, used on some of IBM's
6199 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
6200 @value{GDBN} cannot use these as its host character set.
6204 Note that these are all single-byte character sets. More work inside
6205 GDB is needed to support multi-byte or variable-width character
6206 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
6208 Here is an example of @value{GDBN}'s character set support in action.
6209 Assume that the following source code has been placed in the file
6210 @file{charset-test.c}:
6216 = @{72, 101, 108, 108, 111, 44, 32, 119,
6217 111, 114, 108, 100, 33, 10, 0@};
6218 char ibm1047_hello[]
6219 = @{200, 133, 147, 147, 150, 107, 64, 166,
6220 150, 153, 147, 132, 90, 37, 0@};
6224 printf ("Hello, world!\n");
6228 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
6229 containing the string @samp{Hello, world!} followed by a newline,
6230 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
6232 We compile the program, and invoke the debugger on it:
6235 $ gcc -g charset-test.c -o charset-test
6236 $ gdb -nw charset-test
6237 GNU gdb 2001-12-19-cvs
6238 Copyright 2001 Free Software Foundation, Inc.
6243 We can use the @code{show charset} command to see what character sets
6244 @value{GDBN} is currently using to interpret and display characters and
6249 The current host and target character set is `ISO-8859-1'.
6253 For the sake of printing this manual, let's use @sc{ascii} as our
6254 initial character set:
6256 (gdb) set charset ASCII
6258 The current host and target character set is `ASCII'.
6262 Let's assume that @sc{ascii} is indeed the correct character set for our
6263 host system --- in other words, let's assume that if @value{GDBN} prints
6264 characters using the @sc{ascii} character set, our terminal will display
6265 them properly. Since our current target character set is also
6266 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
6269 (gdb) print ascii_hello
6270 $1 = 0x401698 "Hello, world!\n"
6271 (gdb) print ascii_hello[0]
6276 @value{GDBN} uses the target character set for character and string
6277 literals you use in expressions:
6285 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
6288 @value{GDBN} relies on the user to tell it which character set the
6289 target program uses. If we print @code{ibm1047_hello} while our target
6290 character set is still @sc{ascii}, we get jibberish:
6293 (gdb) print ibm1047_hello
6294 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
6295 (gdb) print ibm1047_hello[0]
6300 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
6301 @value{GDBN} tells us the character sets it supports:
6304 (gdb) set target-charset
6305 ASCII EBCDIC-US IBM1047 ISO-8859-1
6306 (gdb) set target-charset
6309 We can select @sc{ibm1047} as our target character set, and examine the
6310 program's strings again. Now the @sc{ascii} string is wrong, but
6311 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
6312 target character set, @sc{ibm1047}, to the host character set,
6313 @sc{ascii}, and they display correctly:
6316 (gdb) set target-charset IBM1047
6318 The current host character set is `ASCII'.
6319 The current target character set is `IBM1047'.
6320 (gdb) print ascii_hello
6321 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
6322 (gdb) print ascii_hello[0]
6324 (gdb) print ibm1047_hello
6325 $8 = 0x4016a8 "Hello, world!\n"
6326 (gdb) print ibm1047_hello[0]
6331 As above, @value{GDBN} uses the target character set for character and
6332 string literals you use in expressions:
6340 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
6345 @chapter C Preprocessor Macros
6347 Some languages, such as C and C++, provide a way to define and invoke
6348 ``preprocessor macros'' which expand into strings of tokens.
6349 @value{GDBN} can evaluate expressions containing macro invocations, show
6350 the result of macro expansion, and show a macro's definition, including
6351 where it was defined.
6353 You may need to compile your program specially to provide @value{GDBN}
6354 with information about preprocessor macros. Most compilers do not
6355 include macros in their debugging information, even when you compile
6356 with the @option{-g} flag. @xref{Compilation}.
6358 A program may define a macro at one point, remove that definition later,
6359 and then provide a different definition after that. Thus, at different
6360 points in the program, a macro may have different definitions, or have
6361 no definition at all. If there is a current stack frame, @value{GDBN}
6362 uses the macros in scope at that frame's source code line. Otherwise,
6363 @value{GDBN} uses the macros in scope at the current listing location;
6366 At the moment, @value{GDBN} does not support the @code{##}
6367 token-splicing operator, the @code{#} stringification operator, or
6368 variable-arity macros.
6370 Whenever @value{GDBN} evaluates an expression, it always expands any
6371 macro invocations present in the expression. @value{GDBN} also provides
6372 the following commands for working with macros explicitly.
6376 @kindex macro expand
6377 @cindex macro expansion, showing the results of preprocessor
6378 @cindex preprocessor macro expansion, showing the results of
6379 @cindex expanding preprocessor macros
6380 @item macro expand @var{expression}
6381 @itemx macro exp @var{expression}
6382 Show the results of expanding all preprocessor macro invocations in
6383 @var{expression}. Since @value{GDBN} simply expands macros, but does
6384 not parse the result, @var{expression} need not be a valid expression;
6385 it can be any string of tokens.
6387 @kindex macro expand-once
6388 @item macro expand-once @var{expression}
6389 @itemx macro exp1 @var{expression}
6390 @i{(This command is not yet implemented.)} Show the results of
6391 expanding those preprocessor macro invocations that appear explicitly in
6392 @var{expression}. Macro invocations appearing in that expansion are
6393 left unchanged. This command allows you to see the effect of a
6394 particular macro more clearly, without being confused by further
6395 expansions. Since @value{GDBN} simply expands macros, but does not
6396 parse the result, @var{expression} need not be a valid expression; it
6397 can be any string of tokens.
6400 @cindex macro definition, showing
6401 @cindex definition, showing a macro's
6402 @item info macro @var{macro}
6403 Show the definition of the macro named @var{macro}, and describe the
6404 source location where that definition was established.
6406 @kindex macro define
6407 @cindex user-defined macros
6408 @cindex defining macros interactively
6409 @cindex macros, user-defined
6410 @item macro define @var{macro} @var{replacement-list}
6411 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
6412 @i{(This command is not yet implemented.)} Introduce a definition for a
6413 preprocessor macro named @var{macro}, invocations of which are replaced
6414 by the tokens given in @var{replacement-list}. The first form of this
6415 command defines an ``object-like'' macro, which takes no arguments; the
6416 second form defines a ``function-like'' macro, which takes the arguments
6417 given in @var{arglist}.
6419 A definition introduced by this command is in scope in every expression
6420 evaluated in @value{GDBN}, until it is removed with the @command{macro
6421 undef} command, described below. The definition overrides all
6422 definitions for @var{macro} present in the program being debugged, as
6423 well as any previous user-supplied definition.
6426 @item macro undef @var{macro}
6427 @i{(This command is not yet implemented.)} Remove any user-supplied
6428 definition for the macro named @var{macro}. This command only affects
6429 definitions provided with the @command{macro define} command, described
6430 above; it cannot remove definitions present in the program being
6435 @cindex macros, example of debugging with
6436 Here is a transcript showing the above commands in action. First, we
6437 show our source files:
6445 #define ADD(x) (M + x)
6450 printf ("Hello, world!\n");
6452 printf ("We're so creative.\n");
6454 printf ("Goodbye, world!\n");
6461 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
6462 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
6463 compiler includes information about preprocessor macros in the debugging
6467 $ gcc -gdwarf-2 -g3 sample.c -o sample
6471 Now, we start @value{GDBN} on our sample program:
6475 GNU gdb 2002-05-06-cvs
6476 Copyright 2002 Free Software Foundation, Inc.
6477 GDB is free software, @dots{}
6481 We can expand macros and examine their definitions, even when the
6482 program is not running. @value{GDBN} uses the current listing position
6483 to decide which macro definitions are in scope:
6489 5 #define ADD(x) (M + x)
6494 10 printf ("Hello, world!\n");
6496 12 printf ("We're so creative.\n");
6497 (gdb) info macro ADD
6498 Defined at /home/jimb/gdb/macros/play/sample.c:5
6499 #define ADD(x) (M + x)
6501 Defined at /home/jimb/gdb/macros/play/sample.h:1
6502 included at /home/jimb/gdb/macros/play/sample.c:2
6504 (gdb) macro expand ADD(1)
6505 expands to: (42 + 1)
6506 (gdb) macro expand-once ADD(1)
6507 expands to: once (M + 1)
6511 In the example above, note that @command{macro expand-once} expands only
6512 the macro invocation explicit in the original text --- the invocation of
6513 @code{ADD} --- but does not expand the invocation of the macro @code{M},
6514 which was introduced by @code{ADD}.
6516 Once the program is running, GDB uses the macro definitions in force at
6517 the source line of the current stack frame:
6521 Breakpoint 1 at 0x8048370: file sample.c, line 10.
6523 Starting program: /home/jimb/gdb/macros/play/sample
6525 Breakpoint 1, main () at sample.c:10
6526 10 printf ("Hello, world!\n");
6530 At line 10, the definition of the macro @code{N} at line 9 is in force:
6534 Defined at /home/jimb/gdb/macros/play/sample.c:9
6536 (gdb) macro expand N Q M
6543 As we step over directives that remove @code{N}'s definition, and then
6544 give it a new definition, @value{GDBN} finds the definition (or lack
6545 thereof) in force at each point:
6550 12 printf ("We're so creative.\n");
6552 The symbol `N' has no definition as a C/C++ preprocessor macro
6553 at /home/jimb/gdb/macros/play/sample.c:12
6556 14 printf ("Goodbye, world!\n");
6558 Defined at /home/jimb/gdb/macros/play/sample.c:13
6560 (gdb) macro expand N Q M
6561 expands to: 1729 < 42
6569 @chapter Tracepoints
6570 @c This chapter is based on the documentation written by Michael
6571 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
6574 In some applications, it is not feasible for the debugger to interrupt
6575 the program's execution long enough for the developer to learn
6576 anything helpful about its behavior. If the program's correctness
6577 depends on its real-time behavior, delays introduced by a debugger
6578 might cause the program to change its behavior drastically, or perhaps
6579 fail, even when the code itself is correct. It is useful to be able
6580 to observe the program's behavior without interrupting it.
6582 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
6583 specify locations in the program, called @dfn{tracepoints}, and
6584 arbitrary expressions to evaluate when those tracepoints are reached.
6585 Later, using the @code{tfind} command, you can examine the values
6586 those expressions had when the program hit the tracepoints. The
6587 expressions may also denote objects in memory---structures or arrays,
6588 for example---whose values @value{GDBN} should record; while visiting
6589 a particular tracepoint, you may inspect those objects as if they were
6590 in memory at that moment. However, because @value{GDBN} records these
6591 values without interacting with you, it can do so quickly and
6592 unobtrusively, hopefully not disturbing the program's behavior.
6594 The tracepoint facility is currently available only for remote
6595 targets. @xref{Targets}. In addition, your remote target must know how
6596 to collect trace data. This functionality is implemented in the remote
6597 stub; however, none of the stubs distributed with @value{GDBN} support
6598 tracepoints as of this writing.
6600 This chapter describes the tracepoint commands and features.
6604 * Analyze Collected Data::
6605 * Tracepoint Variables::
6608 @node Set Tracepoints
6609 @section Commands to Set Tracepoints
6611 Before running such a @dfn{trace experiment}, an arbitrary number of
6612 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
6613 tracepoint has a number assigned to it by @value{GDBN}. Like with
6614 breakpoints, tracepoint numbers are successive integers starting from
6615 one. Many of the commands associated with tracepoints take the
6616 tracepoint number as their argument, to identify which tracepoint to
6619 For each tracepoint, you can specify, in advance, some arbitrary set
6620 of data that you want the target to collect in the trace buffer when
6621 it hits that tracepoint. The collected data can include registers,
6622 local variables, or global data. Later, you can use @value{GDBN}
6623 commands to examine the values these data had at the time the
6626 This section describes commands to set tracepoints and associated
6627 conditions and actions.
6630 * Create and Delete Tracepoints::
6631 * Enable and Disable Tracepoints::
6632 * Tracepoint Passcounts::
6633 * Tracepoint Actions::
6634 * Listing Tracepoints::
6635 * Starting and Stopping Trace Experiment::
6638 @node Create and Delete Tracepoints
6639 @subsection Create and Delete Tracepoints
6642 @cindex set tracepoint
6645 The @code{trace} command is very similar to the @code{break} command.
6646 Its argument can be a source line, a function name, or an address in
6647 the target program. @xref{Set Breaks}. The @code{trace} command
6648 defines a tracepoint, which is a point in the target program where the
6649 debugger will briefly stop, collect some data, and then allow the
6650 program to continue. Setting a tracepoint or changing its commands
6651 doesn't take effect until the next @code{tstart} command; thus, you
6652 cannot change the tracepoint attributes once a trace experiment is
6655 Here are some examples of using the @code{trace} command:
6658 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
6660 (@value{GDBP}) @b{trace +2} // 2 lines forward
6662 (@value{GDBP}) @b{trace my_function} // first source line of function
6664 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
6666 (@value{GDBP}) @b{trace *0x2117c4} // an address
6670 You can abbreviate @code{trace} as @code{tr}.
6673 @cindex last tracepoint number
6674 @cindex recent tracepoint number
6675 @cindex tracepoint number
6676 The convenience variable @code{$tpnum} records the tracepoint number
6677 of the most recently set tracepoint.
6679 @kindex delete tracepoint
6680 @cindex tracepoint deletion
6681 @item delete tracepoint @r{[}@var{num}@r{]}
6682 Permanently delete one or more tracepoints. With no argument, the
6683 default is to delete all tracepoints.
6688 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
6690 (@value{GDBP}) @b{delete trace} // remove all tracepoints
6694 You can abbreviate this command as @code{del tr}.
6697 @node Enable and Disable Tracepoints
6698 @subsection Enable and Disable Tracepoints
6701 @kindex disable tracepoint
6702 @item disable tracepoint @r{[}@var{num}@r{]}
6703 Disable tracepoint @var{num}, or all tracepoints if no argument
6704 @var{num} is given. A disabled tracepoint will have no effect during
6705 the next trace experiment, but it is not forgotten. You can re-enable
6706 a disabled tracepoint using the @code{enable tracepoint} command.
6708 @kindex enable tracepoint
6709 @item enable tracepoint @r{[}@var{num}@r{]}
6710 Enable tracepoint @var{num}, or all tracepoints. The enabled
6711 tracepoints will become effective the next time a trace experiment is
6715 @node Tracepoint Passcounts
6716 @subsection Tracepoint Passcounts
6720 @cindex tracepoint pass count
6721 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
6722 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
6723 automatically stop a trace experiment. If a tracepoint's passcount is
6724 @var{n}, then the trace experiment will be automatically stopped on
6725 the @var{n}'th time that tracepoint is hit. If the tracepoint number
6726 @var{num} is not specified, the @code{passcount} command sets the
6727 passcount of the most recently defined tracepoint. If no passcount is
6728 given, the trace experiment will run until stopped explicitly by the
6734 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
6735 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
6737 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
6738 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
6739 (@value{GDBP}) @b{trace foo}
6740 (@value{GDBP}) @b{pass 3}
6741 (@value{GDBP}) @b{trace bar}
6742 (@value{GDBP}) @b{pass 2}
6743 (@value{GDBP}) @b{trace baz}
6744 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
6745 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
6746 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
6747 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
6751 @node Tracepoint Actions
6752 @subsection Tracepoint Action Lists
6756 @cindex tracepoint actions
6757 @item actions @r{[}@var{num}@r{]}
6758 This command will prompt for a list of actions to be taken when the
6759 tracepoint is hit. If the tracepoint number @var{num} is not
6760 specified, this command sets the actions for the one that was most
6761 recently defined (so that you can define a tracepoint and then say
6762 @code{actions} without bothering about its number). You specify the
6763 actions themselves on the following lines, one action at a time, and
6764 terminate the actions list with a line containing just @code{end}. So
6765 far, the only defined actions are @code{collect} and
6766 @code{while-stepping}.
6768 @cindex remove actions from a tracepoint
6769 To remove all actions from a tracepoint, type @samp{actions @var{num}}
6770 and follow it immediately with @samp{end}.
6773 (@value{GDBP}) @b{collect @var{data}} // collect some data
6775 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
6777 (@value{GDBP}) @b{end} // signals the end of actions.
6780 In the following example, the action list begins with @code{collect}
6781 commands indicating the things to be collected when the tracepoint is
6782 hit. Then, in order to single-step and collect additional data
6783 following the tracepoint, a @code{while-stepping} command is used,
6784 followed by the list of things to be collected while stepping. The
6785 @code{while-stepping} command is terminated by its own separate
6786 @code{end} command. Lastly, the action list is terminated by an
6790 (@value{GDBP}) @b{trace foo}
6791 (@value{GDBP}) @b{actions}
6792 Enter actions for tracepoint 1, one per line:
6801 @kindex collect @r{(tracepoints)}
6802 @item collect @var{expr1}, @var{expr2}, @dots{}
6803 Collect values of the given expressions when the tracepoint is hit.
6804 This command accepts a comma-separated list of any valid expressions.
6805 In addition to global, static, or local variables, the following
6806 special arguments are supported:
6810 collect all registers
6813 collect all function arguments
6816 collect all local variables.
6819 You can give several consecutive @code{collect} commands, each one
6820 with a single argument, or one @code{collect} command with several
6821 arguments separated by commas: the effect is the same.
6823 The command @code{info scope} (@pxref{Symbols, info scope}) is
6824 particularly useful for figuring out what data to collect.
6826 @kindex while-stepping @r{(tracepoints)}
6827 @item while-stepping @var{n}
6828 Perform @var{n} single-step traces after the tracepoint, collecting
6829 new data at each step. The @code{while-stepping} command is
6830 followed by the list of what to collect while stepping (followed by
6831 its own @code{end} command):
6835 > collect $regs, myglobal
6841 You may abbreviate @code{while-stepping} as @code{ws} or
6845 @node Listing Tracepoints
6846 @subsection Listing Tracepoints
6849 @kindex info tracepoints
6850 @cindex information about tracepoints
6851 @item info tracepoints @r{[}@var{num}@r{]}
6852 Display information about the tracepoint @var{num}. If you don't specify
6853 a tracepoint number, displays information about all the tracepoints
6854 defined so far. For each tracepoint, the following information is
6861 whether it is enabled or disabled
6865 its passcount as given by the @code{passcount @var{n}} command
6867 its step count as given by the @code{while-stepping @var{n}} command
6869 where in the source files is the tracepoint set
6871 its action list as given by the @code{actions} command
6875 (@value{GDBP}) @b{info trace}
6876 Num Enb Address PassC StepC What
6877 1 y 0x002117c4 0 0 <gdb_asm>
6878 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
6879 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
6884 This command can be abbreviated @code{info tp}.
6887 @node Starting and Stopping Trace Experiment
6888 @subsection Starting and Stopping Trace Experiment
6892 @cindex start a new trace experiment
6893 @cindex collected data discarded
6895 This command takes no arguments. It starts the trace experiment, and
6896 begins collecting data. This has the side effect of discarding all
6897 the data collected in the trace buffer during the previous trace
6901 @cindex stop a running trace experiment
6903 This command takes no arguments. It ends the trace experiment, and
6904 stops collecting data.
6906 @strong{Note:} a trace experiment and data collection may stop
6907 automatically if any tracepoint's passcount is reached
6908 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
6911 @cindex status of trace data collection
6912 @cindex trace experiment, status of
6914 This command displays the status of the current trace data
6918 Here is an example of the commands we described so far:
6921 (@value{GDBP}) @b{trace gdb_c_test}
6922 (@value{GDBP}) @b{actions}
6923 Enter actions for tracepoint #1, one per line.
6924 > collect $regs,$locals,$args
6929 (@value{GDBP}) @b{tstart}
6930 [time passes @dots{}]
6931 (@value{GDBP}) @b{tstop}
6935 @node Analyze Collected Data
6936 @section Using the collected data
6938 After the tracepoint experiment ends, you use @value{GDBN} commands
6939 for examining the trace data. The basic idea is that each tracepoint
6940 collects a trace @dfn{snapshot} every time it is hit and another
6941 snapshot every time it single-steps. All these snapshots are
6942 consecutively numbered from zero and go into a buffer, and you can
6943 examine them later. The way you examine them is to @dfn{focus} on a
6944 specific trace snapshot. When the remote stub is focused on a trace
6945 snapshot, it will respond to all @value{GDBN} requests for memory and
6946 registers by reading from the buffer which belongs to that snapshot,
6947 rather than from @emph{real} memory or registers of the program being
6948 debugged. This means that @strong{all} @value{GDBN} commands
6949 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
6950 behave as if we were currently debugging the program state as it was
6951 when the tracepoint occurred. Any requests for data that are not in
6952 the buffer will fail.
6955 * tfind:: How to select a trace snapshot
6956 * tdump:: How to display all data for a snapshot
6957 * save-tracepoints:: How to save tracepoints for a future run
6961 @subsection @code{tfind @var{n}}
6964 @cindex select trace snapshot
6965 @cindex find trace snapshot
6966 The basic command for selecting a trace snapshot from the buffer is
6967 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
6968 counting from zero. If no argument @var{n} is given, the next
6969 snapshot is selected.
6971 Here are the various forms of using the @code{tfind} command.
6975 Find the first snapshot in the buffer. This is a synonym for
6976 @code{tfind 0} (since 0 is the number of the first snapshot).
6979 Stop debugging trace snapshots, resume @emph{live} debugging.
6982 Same as @samp{tfind none}.
6985 No argument means find the next trace snapshot.
6988 Find the previous trace snapshot before the current one. This permits
6989 retracing earlier steps.
6991 @item tfind tracepoint @var{num}
6992 Find the next snapshot associated with tracepoint @var{num}. Search
6993 proceeds forward from the last examined trace snapshot. If no
6994 argument @var{num} is given, it means find the next snapshot collected
6995 for the same tracepoint as the current snapshot.
6997 @item tfind pc @var{addr}
6998 Find the next snapshot associated with the value @var{addr} of the
6999 program counter. Search proceeds forward from the last examined trace
7000 snapshot. If no argument @var{addr} is given, it means find the next
7001 snapshot with the same value of PC as the current snapshot.
7003 @item tfind outside @var{addr1}, @var{addr2}
7004 Find the next snapshot whose PC is outside the given range of
7007 @item tfind range @var{addr1}, @var{addr2}
7008 Find the next snapshot whose PC is between @var{addr1} and
7009 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
7011 @item tfind line @r{[}@var{file}:@r{]}@var{n}
7012 Find the next snapshot associated with the source line @var{n}. If
7013 the optional argument @var{file} is given, refer to line @var{n} in
7014 that source file. Search proceeds forward from the last examined
7015 trace snapshot. If no argument @var{n} is given, it means find the
7016 next line other than the one currently being examined; thus saying
7017 @code{tfind line} repeatedly can appear to have the same effect as
7018 stepping from line to line in a @emph{live} debugging session.
7021 The default arguments for the @code{tfind} commands are specifically
7022 designed to make it easy to scan through the trace buffer. For
7023 instance, @code{tfind} with no argument selects the next trace
7024 snapshot, and @code{tfind -} with no argument selects the previous
7025 trace snapshot. So, by giving one @code{tfind} command, and then
7026 simply hitting @key{RET} repeatedly you can examine all the trace
7027 snapshots in order. Or, by saying @code{tfind -} and then hitting
7028 @key{RET} repeatedly you can examine the snapshots in reverse order.
7029 The @code{tfind line} command with no argument selects the snapshot
7030 for the next source line executed. The @code{tfind pc} command with
7031 no argument selects the next snapshot with the same program counter
7032 (PC) as the current frame. The @code{tfind tracepoint} command with
7033 no argument selects the next trace snapshot collected by the same
7034 tracepoint as the current one.
7036 In addition to letting you scan through the trace buffer manually,
7037 these commands make it easy to construct @value{GDBN} scripts that
7038 scan through the trace buffer and print out whatever collected data
7039 you are interested in. Thus, if we want to examine the PC, FP, and SP
7040 registers from each trace frame in the buffer, we can say this:
7043 (@value{GDBP}) @b{tfind start}
7044 (@value{GDBP}) @b{while ($trace_frame != -1)}
7045 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
7046 $trace_frame, $pc, $sp, $fp
7050 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
7051 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
7052 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
7053 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
7054 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
7055 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
7056 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
7057 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
7058 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
7059 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
7060 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
7063 Or, if we want to examine the variable @code{X} at each source line in
7067 (@value{GDBP}) @b{tfind start}
7068 (@value{GDBP}) @b{while ($trace_frame != -1)}
7069 > printf "Frame %d, X == %d\n", $trace_frame, X
7079 @subsection @code{tdump}
7081 @cindex dump all data collected at tracepoint
7082 @cindex tracepoint data, display
7084 This command takes no arguments. It prints all the data collected at
7085 the current trace snapshot.
7088 (@value{GDBP}) @b{trace 444}
7089 (@value{GDBP}) @b{actions}
7090 Enter actions for tracepoint #2, one per line:
7091 > collect $regs, $locals, $args, gdb_long_test
7094 (@value{GDBP}) @b{tstart}
7096 (@value{GDBP}) @b{tfind line 444}
7097 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
7099 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
7101 (@value{GDBP}) @b{tdump}
7102 Data collected at tracepoint 2, trace frame 1:
7103 d0 0xc4aa0085 -995491707
7107 d4 0x71aea3d 119204413
7112 a1 0x3000668 50333288
7115 a4 0x3000698 50333336
7117 fp 0x30bf3c 0x30bf3c
7118 sp 0x30bf34 0x30bf34
7120 pc 0x20b2c8 0x20b2c8
7124 p = 0x20e5b4 "gdb-test"
7131 gdb_long_test = 17 '\021'
7136 @node save-tracepoints
7137 @subsection @code{save-tracepoints @var{filename}}
7138 @kindex save-tracepoints
7139 @cindex save tracepoints for future sessions
7141 This command saves all current tracepoint definitions together with
7142 their actions and passcounts, into a file @file{@var{filename}}
7143 suitable for use in a later debugging session. To read the saved
7144 tracepoint definitions, use the @code{source} command (@pxref{Command
7147 @node Tracepoint Variables
7148 @section Convenience Variables for Tracepoints
7149 @cindex tracepoint variables
7150 @cindex convenience variables for tracepoints
7153 @vindex $trace_frame
7154 @item (int) $trace_frame
7155 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
7156 snapshot is selected.
7159 @item (int) $tracepoint
7160 The tracepoint for the current trace snapshot.
7163 @item (int) $trace_line
7164 The line number for the current trace snapshot.
7167 @item (char []) $trace_file
7168 The source file for the current trace snapshot.
7171 @item (char []) $trace_func
7172 The name of the function containing @code{$tracepoint}.
7175 Note: @code{$trace_file} is not suitable for use in @code{printf},
7176 use @code{output} instead.
7178 Here's a simple example of using these convenience variables for
7179 stepping through all the trace snapshots and printing some of their
7183 (@value{GDBP}) @b{tfind start}
7185 (@value{GDBP}) @b{while $trace_frame != -1}
7186 > output $trace_file
7187 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
7193 @chapter Debugging Programs That Use Overlays
7196 If your program is too large to fit completely in your target system's
7197 memory, you can sometimes use @dfn{overlays} to work around this
7198 problem. @value{GDBN} provides some support for debugging programs that
7202 * How Overlays Work:: A general explanation of overlays.
7203 * Overlay Commands:: Managing overlays in @value{GDBN}.
7204 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
7205 mapped by asking the inferior.
7206 * Overlay Sample Program:: A sample program using overlays.
7209 @node How Overlays Work
7210 @section How Overlays Work
7211 @cindex mapped overlays
7212 @cindex unmapped overlays
7213 @cindex load address, overlay's
7214 @cindex mapped address
7215 @cindex overlay area
7217 Suppose you have a computer whose instruction address space is only 64
7218 kilobytes long, but which has much more memory which can be accessed by
7219 other means: special instructions, segment registers, or memory
7220 management hardware, for example. Suppose further that you want to
7221 adapt a program which is larger than 64 kilobytes to run on this system.
7223 One solution is to identify modules of your program which are relatively
7224 independent, and need not call each other directly; call these modules
7225 @dfn{overlays}. Separate the overlays from the main program, and place
7226 their machine code in the larger memory. Place your main program in
7227 instruction memory, but leave at least enough space there to hold the
7228 largest overlay as well.
7230 Now, to call a function located in an overlay, you must first copy that
7231 overlay's machine code from the large memory into the space set aside
7232 for it in the instruction memory, and then jump to its entry point
7235 @c NB: In the below the mapped area's size is greater or equal to the
7236 @c size of all overlays. This is intentional to remind the developer
7237 @c that overlays don't necessarily need to be the same size.
7241 Data Instruction Larger
7242 Address Space Address Space Address Space
7243 +-----------+ +-----------+ +-----------+
7245 +-----------+ +-----------+ +-----------+<-- overlay 1
7246 | program | | main | .----| overlay 1 | load address
7247 | variables | | program | | +-----------+
7248 | and heap | | | | | |
7249 +-----------+ | | | +-----------+<-- overlay 2
7250 | | +-----------+ | | | load address
7251 +-----------+ | | | .-| overlay 2 |
7253 mapped --->+-----------+ | | +-----------+
7255 | overlay | <-' | | |
7256 | area | <---' +-----------+<-- overlay 3
7257 | | <---. | | load address
7258 +-----------+ `--| overlay 3 |
7265 @anchor{A code overlay}A code overlay
7269 The diagram (@pxref{A code overlay}) shows a system with separate data
7270 and instruction address spaces. To map an overlay, the program copies
7271 its code from the larger address space to the instruction address space.
7272 Since the overlays shown here all use the same mapped address, only one
7273 may be mapped at a time. For a system with a single address space for
7274 data and instructions, the diagram would be similar, except that the
7275 program variables and heap would share an address space with the main
7276 program and the overlay area.
7278 An overlay loaded into instruction memory and ready for use is called a
7279 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
7280 instruction memory. An overlay not present (or only partially present)
7281 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
7282 is its address in the larger memory. The mapped address is also called
7283 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
7284 called the @dfn{load memory address}, or @dfn{LMA}.
7286 Unfortunately, overlays are not a completely transparent way to adapt a
7287 program to limited instruction memory. They introduce a new set of
7288 global constraints you must keep in mind as you design your program:
7293 Before calling or returning to a function in an overlay, your program
7294 must make sure that overlay is actually mapped. Otherwise, the call or
7295 return will transfer control to the right address, but in the wrong
7296 overlay, and your program will probably crash.
7299 If the process of mapping an overlay is expensive on your system, you
7300 will need to choose your overlays carefully to minimize their effect on
7301 your program's performance.
7304 The executable file you load onto your system must contain each
7305 overlay's instructions, appearing at the overlay's load address, not its
7306 mapped address. However, each overlay's instructions must be relocated
7307 and its symbols defined as if the overlay were at its mapped address.
7308 You can use GNU linker scripts to specify different load and relocation
7309 addresses for pieces of your program; see @ref{Overlay Description,,,
7310 ld.info, Using ld: the GNU linker}.
7313 The procedure for loading executable files onto your system must be able
7314 to load their contents into the larger address space as well as the
7315 instruction and data spaces.
7319 The overlay system described above is rather simple, and could be
7320 improved in many ways:
7325 If your system has suitable bank switch registers or memory management
7326 hardware, you could use those facilities to make an overlay's load area
7327 contents simply appear at their mapped address in instruction space.
7328 This would probably be faster than copying the overlay to its mapped
7329 area in the usual way.
7332 If your overlays are small enough, you could set aside more than one
7333 overlay area, and have more than one overlay mapped at a time.
7336 You can use overlays to manage data, as well as instructions. In
7337 general, data overlays are even less transparent to your design than
7338 code overlays: whereas code overlays only require care when you call or
7339 return to functions, data overlays require care every time you access
7340 the data. Also, if you change the contents of a data overlay, you
7341 must copy its contents back out to its load address before you can copy a
7342 different data overlay into the same mapped area.
7347 @node Overlay Commands
7348 @section Overlay Commands
7350 To use @value{GDBN}'s overlay support, each overlay in your program must
7351 correspond to a separate section of the executable file. The section's
7352 virtual memory address and load memory address must be the overlay's
7353 mapped and load addresses. Identifying overlays with sections allows
7354 @value{GDBN} to determine the appropriate address of a function or
7355 variable, depending on whether the overlay is mapped or not.
7357 @value{GDBN}'s overlay commands all start with the word @code{overlay};
7358 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
7363 Disable @value{GDBN}'s overlay support. When overlay support is
7364 disabled, @value{GDBN} assumes that all functions and variables are
7365 always present at their mapped addresses. By default, @value{GDBN}'s
7366 overlay support is disabled.
7368 @item overlay manual
7369 @kindex overlay manual
7370 @cindex manual overlay debugging
7371 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
7372 relies on you to tell it which overlays are mapped, and which are not,
7373 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
7374 commands described below.
7376 @item overlay map-overlay @var{overlay}
7377 @itemx overlay map @var{overlay}
7378 @kindex overlay map-overlay
7379 @cindex map an overlay
7380 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
7381 be the name of the object file section containing the overlay. When an
7382 overlay is mapped, @value{GDBN} assumes it can find the overlay's
7383 functions and variables at their mapped addresses. @value{GDBN} assumes
7384 that any other overlays whose mapped ranges overlap that of
7385 @var{overlay} are now unmapped.
7387 @item overlay unmap-overlay @var{overlay}
7388 @itemx overlay unmap @var{overlay}
7389 @kindex overlay unmap-overlay
7390 @cindex unmap an overlay
7391 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
7392 must be the name of the object file section containing the overlay.
7393 When an overlay is unmapped, @value{GDBN} assumes it can find the
7394 overlay's functions and variables at their load addresses.
7397 @kindex overlay auto
7398 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
7399 consults a data structure the overlay manager maintains in the inferior
7400 to see which overlays are mapped. For details, see @ref{Automatic
7403 @item overlay load-target
7405 @kindex overlay load-target
7406 @cindex reloading the overlay table
7407 Re-read the overlay table from the inferior. Normally, @value{GDBN}
7408 re-reads the table @value{GDBN} automatically each time the inferior
7409 stops, so this command should only be necessary if you have changed the
7410 overlay mapping yourself using @value{GDBN}. This command is only
7411 useful when using automatic overlay debugging.
7413 @item overlay list-overlays
7415 @cindex listing mapped overlays
7416 Display a list of the overlays currently mapped, along with their mapped
7417 addresses, load addresses, and sizes.
7421 Normally, when @value{GDBN} prints a code address, it includes the name
7422 of the function the address falls in:
7426 $3 = @{int ()@} 0x11a0 <main>
7429 When overlay debugging is enabled, @value{GDBN} recognizes code in
7430 unmapped overlays, and prints the names of unmapped functions with
7431 asterisks around them. For example, if @code{foo} is a function in an
7432 unmapped overlay, @value{GDBN} prints it this way:
7436 No sections are mapped.
7438 $5 = @{int (int)@} 0x100000 <*foo*>
7441 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
7446 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
7447 mapped at 0x1016 - 0x104a
7449 $6 = @{int (int)@} 0x1016 <foo>
7452 When overlay debugging is enabled, @value{GDBN} can find the correct
7453 address for functions and variables in an overlay, whether or not the
7454 overlay is mapped. This allows most @value{GDBN} commands, like
7455 @code{break} and @code{disassemble}, to work normally, even on unmapped
7456 code. However, @value{GDBN}'s breakpoint support has some limitations:
7460 @cindex breakpoints in overlays
7461 @cindex overlays, setting breakpoints in
7462 You can set breakpoints in functions in unmapped overlays, as long as
7463 @value{GDBN} can write to the overlay at its load address.
7465 @value{GDBN} can not set hardware or simulator-based breakpoints in
7466 unmapped overlays. However, if you set a breakpoint at the end of your
7467 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
7468 you are using manual overlay management), @value{GDBN} will re-set its
7469 breakpoints properly.
7473 @node Automatic Overlay Debugging
7474 @section Automatic Overlay Debugging
7475 @cindex automatic overlay debugging
7477 @value{GDBN} can automatically track which overlays are mapped and which
7478 are not, given some simple co-operation from the overlay manager in the
7479 inferior. If you enable automatic overlay debugging with the
7480 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
7481 looks in the inferior's memory for certain variables describing the
7482 current state of the overlays.
7484 Here are the variables your overlay manager must define to support
7485 @value{GDBN}'s automatic overlay debugging:
7489 @item @code{_ovly_table}:
7490 This variable must be an array of the following structures:
7495 /* The overlay's mapped address. */
7498 /* The size of the overlay, in bytes. */
7501 /* The overlay's load address. */
7504 /* Non-zero if the overlay is currently mapped;
7506 unsigned long mapped;
7510 @item @code{_novlys}:
7511 This variable must be a four-byte signed integer, holding the total
7512 number of elements in @code{_ovly_table}.
7516 To decide whether a particular overlay is mapped or not, @value{GDBN}
7517 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
7518 @code{lma} members equal the VMA and LMA of the overlay's section in the
7519 executable file. When @value{GDBN} finds a matching entry, it consults
7520 the entry's @code{mapped} member to determine whether the overlay is
7523 In addition, your overlay manager may define a function called
7524 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
7525 will silently set a breakpoint there. If the overlay manager then
7526 calls this function whenever it has changed the overlay table, this
7527 will enable @value{GDBN} to accurately keep track of which overlays
7528 are in program memory, and update any breakpoints that may be set
7529 in overlays. This will allow breakpoints to work even if the
7530 overlays are kept in ROM or other non-writable memory while they
7531 are not being executed.
7533 @node Overlay Sample Program
7534 @section Overlay Sample Program
7535 @cindex overlay example program
7537 When linking a program which uses overlays, you must place the overlays
7538 at their load addresses, while relocating them to run at their mapped
7539 addresses. To do this, you must write a linker script (@pxref{Overlay
7540 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
7541 since linker scripts are specific to a particular host system, target
7542 architecture, and target memory layout, this manual cannot provide
7543 portable sample code demonstrating @value{GDBN}'s overlay support.
7545 However, the @value{GDBN} source distribution does contain an overlaid
7546 program, with linker scripts for a few systems, as part of its test
7547 suite. The program consists of the following files from
7548 @file{gdb/testsuite/gdb.base}:
7552 The main program file.
7554 A simple overlay manager, used by @file{overlays.c}.
7559 Overlay modules, loaded and used by @file{overlays.c}.
7562 Linker scripts for linking the test program on the @code{d10v-elf}
7563 and @code{m32r-elf} targets.
7566 You can build the test program using the @code{d10v-elf} GCC
7567 cross-compiler like this:
7570 $ d10v-elf-gcc -g -c overlays.c
7571 $ d10v-elf-gcc -g -c ovlymgr.c
7572 $ d10v-elf-gcc -g -c foo.c
7573 $ d10v-elf-gcc -g -c bar.c
7574 $ d10v-elf-gcc -g -c baz.c
7575 $ d10v-elf-gcc -g -c grbx.c
7576 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
7577 baz.o grbx.o -Wl,-Td10v.ld -o overlays
7580 The build process is identical for any other architecture, except that
7581 you must substitute the appropriate compiler and linker script for the
7582 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
7586 @chapter Using @value{GDBN} with Different Languages
7589 Although programming languages generally have common aspects, they are
7590 rarely expressed in the same manner. For instance, in ANSI C,
7591 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
7592 Modula-2, it is accomplished by @code{p^}. Values can also be
7593 represented (and displayed) differently. Hex numbers in C appear as
7594 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
7596 @cindex working language
7597 Language-specific information is built into @value{GDBN} for some languages,
7598 allowing you to express operations like the above in your program's
7599 native language, and allowing @value{GDBN} to output values in a manner
7600 consistent with the syntax of your program's native language. The
7601 language you use to build expressions is called the @dfn{working
7605 * Setting:: Switching between source languages
7606 * Show:: Displaying the language
7607 * Checks:: Type and range checks
7608 * Support:: Supported languages
7609 * Unsupported languages:: Unsupported languages
7613 @section Switching between source languages
7615 There are two ways to control the working language---either have @value{GDBN}
7616 set it automatically, or select it manually yourself. You can use the
7617 @code{set language} command for either purpose. On startup, @value{GDBN}
7618 defaults to setting the language automatically. The working language is
7619 used to determine how expressions you type are interpreted, how values
7622 In addition to the working language, every source file that
7623 @value{GDBN} knows about has its own working language. For some object
7624 file formats, the compiler might indicate which language a particular
7625 source file is in. However, most of the time @value{GDBN} infers the
7626 language from the name of the file. The language of a source file
7627 controls whether C@t{++} names are demangled---this way @code{backtrace} can
7628 show each frame appropriately for its own language. There is no way to
7629 set the language of a source file from within @value{GDBN}, but you can
7630 set the language associated with a filename extension. @xref{Show, ,
7631 Displaying the language}.
7633 This is most commonly a problem when you use a program, such
7634 as @code{cfront} or @code{f2c}, that generates C but is written in
7635 another language. In that case, make the
7636 program use @code{#line} directives in its C output; that way
7637 @value{GDBN} will know the correct language of the source code of the original
7638 program, and will display that source code, not the generated C code.
7641 * Filenames:: Filename extensions and languages.
7642 * Manually:: Setting the working language manually
7643 * Automatically:: Having @value{GDBN} infer the source language
7647 @subsection List of filename extensions and languages
7649 If a source file name ends in one of the following extensions, then
7650 @value{GDBN} infers that its language is the one indicated.
7666 Objective-C source file
7673 Modula-2 source file
7677 Assembler source file. This actually behaves almost like C, but
7678 @value{GDBN} does not skip over function prologues when stepping.
7681 In addition, you may set the language associated with a filename
7682 extension. @xref{Show, , Displaying the language}.
7685 @subsection Setting the working language
7687 If you allow @value{GDBN} to set the language automatically,
7688 expressions are interpreted the same way in your debugging session and
7691 @kindex set language
7692 If you wish, you may set the language manually. To do this, issue the
7693 command @samp{set language @var{lang}}, where @var{lang} is the name of
7695 @code{c} or @code{modula-2}.
7696 For a list of the supported languages, type @samp{set language}.
7698 Setting the language manually prevents @value{GDBN} from updating the working
7699 language automatically. This can lead to confusion if you try
7700 to debug a program when the working language is not the same as the
7701 source language, when an expression is acceptable to both
7702 languages---but means different things. For instance, if the current
7703 source file were written in C, and @value{GDBN} was parsing Modula-2, a
7711 might not have the effect you intended. In C, this means to add
7712 @code{b} and @code{c} and place the result in @code{a}. The result
7713 printed would be the value of @code{a}. In Modula-2, this means to compare
7714 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
7717 @subsection Having @value{GDBN} infer the source language
7719 To have @value{GDBN} set the working language automatically, use
7720 @samp{set language local} or @samp{set language auto}. @value{GDBN}
7721 then infers the working language. That is, when your program stops in a
7722 frame (usually by encountering a breakpoint), @value{GDBN} sets the
7723 working language to the language recorded for the function in that
7724 frame. If the language for a frame is unknown (that is, if the function
7725 or block corresponding to the frame was defined in a source file that
7726 does not have a recognized extension), the current working language is
7727 not changed, and @value{GDBN} issues a warning.
7729 This may not seem necessary for most programs, which are written
7730 entirely in one source language. However, program modules and libraries
7731 written in one source language can be used by a main program written in
7732 a different source language. Using @samp{set language auto} in this
7733 case frees you from having to set the working language manually.
7736 @section Displaying the language
7738 The following commands help you find out which language is the
7739 working language, and also what language source files were written in.
7741 @kindex show language
7742 @kindex info frame@r{, show the source language}
7743 @kindex info source@r{, show the source language}
7746 Display the current working language. This is the
7747 language you can use with commands such as @code{print} to
7748 build and compute expressions that may involve variables in your program.
7751 Display the source language for this frame. This language becomes the
7752 working language if you use an identifier from this frame.
7753 @xref{Frame Info, ,Information about a frame}, to identify the other
7754 information listed here.
7757 Display the source language of this source file.
7758 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
7759 information listed here.
7762 In unusual circumstances, you may have source files with extensions
7763 not in the standard list. You can then set the extension associated
7764 with a language explicitly:
7766 @kindex set extension-language
7767 @kindex info extensions
7769 @item set extension-language @var{.ext} @var{language}
7770 Set source files with extension @var{.ext} to be assumed to be in
7771 the source language @var{language}.
7773 @item info extensions
7774 List all the filename extensions and the associated languages.
7778 @section Type and range checking
7781 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
7782 checking are included, but they do not yet have any effect. This
7783 section documents the intended facilities.
7785 @c FIXME remove warning when type/range code added
7787 Some languages are designed to guard you against making seemingly common
7788 errors through a series of compile- and run-time checks. These include
7789 checking the type of arguments to functions and operators, and making
7790 sure mathematical overflows are caught at run time. Checks such as
7791 these help to ensure a program's correctness once it has been compiled
7792 by eliminating type mismatches, and providing active checks for range
7793 errors when your program is running.
7795 @value{GDBN} can check for conditions like the above if you wish.
7796 Although @value{GDBN} does not check the statements in your program, it
7797 can check expressions entered directly into @value{GDBN} for evaluation via
7798 the @code{print} command, for example. As with the working language,
7799 @value{GDBN} can also decide whether or not to check automatically based on
7800 your program's source language. @xref{Support, ,Supported languages},
7801 for the default settings of supported languages.
7804 * Type Checking:: An overview of type checking
7805 * Range Checking:: An overview of range checking
7808 @cindex type checking
7809 @cindex checks, type
7811 @subsection An overview of type checking
7813 Some languages, such as Modula-2, are strongly typed, meaning that the
7814 arguments to operators and functions have to be of the correct type,
7815 otherwise an error occurs. These checks prevent type mismatch
7816 errors from ever causing any run-time problems. For example,
7824 The second example fails because the @code{CARDINAL} 1 is not
7825 type-compatible with the @code{REAL} 2.3.
7827 For the expressions you use in @value{GDBN} commands, you can tell the
7828 @value{GDBN} type checker to skip checking;
7829 to treat any mismatches as errors and abandon the expression;
7830 or to only issue warnings when type mismatches occur,
7831 but evaluate the expression anyway. When you choose the last of
7832 these, @value{GDBN} evaluates expressions like the second example above, but
7833 also issues a warning.
7835 Even if you turn type checking off, there may be other reasons
7836 related to type that prevent @value{GDBN} from evaluating an expression.
7837 For instance, @value{GDBN} does not know how to add an @code{int} and
7838 a @code{struct foo}. These particular type errors have nothing to do
7839 with the language in use, and usually arise from expressions, such as
7840 the one described above, which make little sense to evaluate anyway.
7842 Each language defines to what degree it is strict about type. For
7843 instance, both Modula-2 and C require the arguments to arithmetical
7844 operators to be numbers. In C, enumerated types and pointers can be
7845 represented as numbers, so that they are valid arguments to mathematical
7846 operators. @xref{Support, ,Supported languages}, for further
7847 details on specific languages.
7849 @value{GDBN} provides some additional commands for controlling the type checker:
7851 @kindex set check@r{, type}
7852 @kindex set check type
7853 @kindex show check type
7855 @item set check type auto
7856 Set type checking on or off based on the current working language.
7857 @xref{Support, ,Supported languages}, for the default settings for
7860 @item set check type on
7861 @itemx set check type off
7862 Set type checking on or off, overriding the default setting for the
7863 current working language. Issue a warning if the setting does not
7864 match the language default. If any type mismatches occur in
7865 evaluating an expression while type checking is on, @value{GDBN} prints a
7866 message and aborts evaluation of the expression.
7868 @item set check type warn
7869 Cause the type checker to issue warnings, but to always attempt to
7870 evaluate the expression. Evaluating the expression may still
7871 be impossible for other reasons. For example, @value{GDBN} cannot add
7872 numbers and structures.
7875 Show the current setting of the type checker, and whether or not @value{GDBN}
7876 is setting it automatically.
7879 @cindex range checking
7880 @cindex checks, range
7881 @node Range Checking
7882 @subsection An overview of range checking
7884 In some languages (such as Modula-2), it is an error to exceed the
7885 bounds of a type; this is enforced with run-time checks. Such range
7886 checking is meant to ensure program correctness by making sure
7887 computations do not overflow, or indices on an array element access do
7888 not exceed the bounds of the array.
7890 For expressions you use in @value{GDBN} commands, you can tell
7891 @value{GDBN} to treat range errors in one of three ways: ignore them,
7892 always treat them as errors and abandon the expression, or issue
7893 warnings but evaluate the expression anyway.
7895 A range error can result from numerical overflow, from exceeding an
7896 array index bound, or when you type a constant that is not a member
7897 of any type. Some languages, however, do not treat overflows as an
7898 error. In many implementations of C, mathematical overflow causes the
7899 result to ``wrap around'' to lower values---for example, if @var{m} is
7900 the largest integer value, and @var{s} is the smallest, then
7903 @var{m} + 1 @result{} @var{s}
7906 This, too, is specific to individual languages, and in some cases
7907 specific to individual compilers or machines. @xref{Support, ,
7908 Supported languages}, for further details on specific languages.
7910 @value{GDBN} provides some additional commands for controlling the range checker:
7912 @kindex set check@r{, range}
7913 @kindex set check range
7914 @kindex show check range
7916 @item set check range auto
7917 Set range checking on or off based on the current working language.
7918 @xref{Support, ,Supported languages}, for the default settings for
7921 @item set check range on
7922 @itemx set check range off
7923 Set range checking on or off, overriding the default setting for the
7924 current working language. A warning is issued if the setting does not
7925 match the language default. If a range error occurs and range checking is on,
7926 then a message is printed and evaluation of the expression is aborted.
7928 @item set check range warn
7929 Output messages when the @value{GDBN} range checker detects a range error,
7930 but attempt to evaluate the expression anyway. Evaluating the
7931 expression may still be impossible for other reasons, such as accessing
7932 memory that the process does not own (a typical example from many Unix
7936 Show the current setting of the range checker, and whether or not it is
7937 being set automatically by @value{GDBN}.
7941 @section Supported languages
7943 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, assembly, and Modula-2.
7944 @c This is false ...
7945 Some @value{GDBN} features may be used in expressions regardless of the
7946 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
7947 and the @samp{@{type@}addr} construct (@pxref{Expressions,
7948 ,Expressions}) can be used with the constructs of any supported
7951 The following sections detail to what degree each source language is
7952 supported by @value{GDBN}. These sections are not meant to be language
7953 tutorials or references, but serve only as a reference guide to what the
7954 @value{GDBN} expression parser accepts, and what input and output
7955 formats should look like for different languages. There are many good
7956 books written on each of these languages; please look to these for a
7957 language reference or tutorial.
7961 * Objective-C:: Objective-C
7962 * Modula-2:: Modula-2
7966 @subsection C and C@t{++}
7968 @cindex C and C@t{++}
7969 @cindex expressions in C or C@t{++}
7971 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
7972 to both languages. Whenever this is the case, we discuss those languages
7976 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
7977 @cindex @sc{gnu} C@t{++}
7978 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
7979 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
7980 effectively, you must compile your C@t{++} programs with a supported
7981 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
7982 compiler (@code{aCC}).
7984 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
7985 format; if it doesn't work on your system, try the stabs+ debugging
7986 format. You can select those formats explicitly with the @code{g++}
7987 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
7988 @xref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
7989 CC, gcc.info, Using @sc{gnu} CC}.
7992 * C Operators:: C and C@t{++} operators
7993 * C Constants:: C and C@t{++} constants
7994 * C plus plus expressions:: C@t{++} expressions
7995 * C Defaults:: Default settings for C and C@t{++}
7996 * C Checks:: C and C@t{++} type and range checks
7997 * Debugging C:: @value{GDBN} and C
7998 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
8002 @subsubsection C and C@t{++} operators
8004 @cindex C and C@t{++} operators
8006 Operators must be defined on values of specific types. For instance,
8007 @code{+} is defined on numbers, but not on structures. Operators are
8008 often defined on groups of types.
8010 For the purposes of C and C@t{++}, the following definitions hold:
8015 @emph{Integral types} include @code{int} with any of its storage-class
8016 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
8019 @emph{Floating-point types} include @code{float}, @code{double}, and
8020 @code{long double} (if supported by the target platform).
8023 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
8026 @emph{Scalar types} include all of the above.
8031 The following operators are supported. They are listed here
8032 in order of increasing precedence:
8036 The comma or sequencing operator. Expressions in a comma-separated list
8037 are evaluated from left to right, with the result of the entire
8038 expression being the last expression evaluated.
8041 Assignment. The value of an assignment expression is the value
8042 assigned. Defined on scalar types.
8045 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
8046 and translated to @w{@code{@var{a} = @var{a op b}}}.
8047 @w{@code{@var{op}=}} and @code{=} have the same precedence.
8048 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
8049 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
8052 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
8053 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
8057 Logical @sc{or}. Defined on integral types.
8060 Logical @sc{and}. Defined on integral types.
8063 Bitwise @sc{or}. Defined on integral types.
8066 Bitwise exclusive-@sc{or}. Defined on integral types.
8069 Bitwise @sc{and}. Defined on integral types.
8072 Equality and inequality. Defined on scalar types. The value of these
8073 expressions is 0 for false and non-zero for true.
8075 @item <@r{, }>@r{, }<=@r{, }>=
8076 Less than, greater than, less than or equal, greater than or equal.
8077 Defined on scalar types. The value of these expressions is 0 for false
8078 and non-zero for true.
8081 left shift, and right shift. Defined on integral types.
8084 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8087 Addition and subtraction. Defined on integral types, floating-point types and
8090 @item *@r{, }/@r{, }%
8091 Multiplication, division, and modulus. Multiplication and division are
8092 defined on integral and floating-point types. Modulus is defined on
8096 Increment and decrement. When appearing before a variable, the
8097 operation is performed before the variable is used in an expression;
8098 when appearing after it, the variable's value is used before the
8099 operation takes place.
8102 Pointer dereferencing. Defined on pointer types. Same precedence as
8106 Address operator. Defined on variables. Same precedence as @code{++}.
8108 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
8109 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
8110 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
8111 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
8115 Negative. Defined on integral and floating-point types. Same
8116 precedence as @code{++}.
8119 Logical negation. Defined on integral types. Same precedence as
8123 Bitwise complement operator. Defined on integral types. Same precedence as
8128 Structure member, and pointer-to-structure member. For convenience,
8129 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
8130 pointer based on the stored type information.
8131 Defined on @code{struct} and @code{union} data.
8134 Dereferences of pointers to members.
8137 Array indexing. @code{@var{a}[@var{i}]} is defined as
8138 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
8141 Function parameter list. Same precedence as @code{->}.
8144 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
8145 and @code{class} types.
8148 Doubled colons also represent the @value{GDBN} scope operator
8149 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
8153 If an operator is redefined in the user code, @value{GDBN} usually
8154 attempts to invoke the redefined version instead of using the operator's
8162 @subsubsection C and C@t{++} constants
8164 @cindex C and C@t{++} constants
8166 @value{GDBN} allows you to express the constants of C and C@t{++} in the
8171 Integer constants are a sequence of digits. Octal constants are
8172 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
8173 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
8174 @samp{l}, specifying that the constant should be treated as a
8178 Floating point constants are a sequence of digits, followed by a decimal
8179 point, followed by a sequence of digits, and optionally followed by an
8180 exponent. An exponent is of the form:
8181 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
8182 sequence of digits. The @samp{+} is optional for positive exponents.
8183 A floating-point constant may also end with a letter @samp{f} or
8184 @samp{F}, specifying that the constant should be treated as being of
8185 the @code{float} (as opposed to the default @code{double}) type; or with
8186 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
8190 Enumerated constants consist of enumerated identifiers, or their
8191 integral equivalents.
8194 Character constants are a single character surrounded by single quotes
8195 (@code{'}), or a number---the ordinal value of the corresponding character
8196 (usually its @sc{ascii} value). Within quotes, the single character may
8197 be represented by a letter or by @dfn{escape sequences}, which are of
8198 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
8199 of the character's ordinal value; or of the form @samp{\@var{x}}, where
8200 @samp{@var{x}} is a predefined special character---for example,
8201 @samp{\n} for newline.
8204 String constants are a sequence of character constants surrounded by
8205 double quotes (@code{"}). Any valid character constant (as described
8206 above) may appear. Double quotes within the string must be preceded by
8207 a backslash, so for instance @samp{"a\"b'c"} is a string of five
8211 Pointer constants are an integral value. You can also write pointers
8212 to constants using the C operator @samp{&}.
8215 Array constants are comma-separated lists surrounded by braces @samp{@{}
8216 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
8217 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
8218 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
8222 * C plus plus expressions::
8229 @node C plus plus expressions
8230 @subsubsection C@t{++} expressions
8232 @cindex expressions in C@t{++}
8233 @value{GDBN} expression handling can interpret most C@t{++} expressions.
8235 @cindex debugging C@t{++} programs
8236 @cindex C@t{++} compilers
8237 @cindex debug formats and C@t{++}
8238 @cindex @value{NGCC} and C@t{++}
8240 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
8241 proper compiler and the proper debug format. Currently, @value{GDBN}
8242 works best when debugging C@t{++} code that is compiled with
8243 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
8244 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
8245 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
8246 stabs+ as their default debug format, so you usually don't need to
8247 specify a debug format explicitly. Other compilers and/or debug formats
8248 are likely to work badly or not at all when using @value{GDBN} to debug
8254 @cindex member functions
8256 Member function calls are allowed; you can use expressions like
8259 count = aml->GetOriginal(x, y)
8262 @vindex this@r{, inside C@t{++} member functions}
8263 @cindex namespace in C@t{++}
8265 While a member function is active (in the selected stack frame), your
8266 expressions have the same namespace available as the member function;
8267 that is, @value{GDBN} allows implicit references to the class instance
8268 pointer @code{this} following the same rules as C@t{++}.
8270 @cindex call overloaded functions
8271 @cindex overloaded functions, calling
8272 @cindex type conversions in C@t{++}
8274 You can call overloaded functions; @value{GDBN} resolves the function
8275 call to the right definition, with some restrictions. @value{GDBN} does not
8276 perform overload resolution involving user-defined type conversions,
8277 calls to constructors, or instantiations of templates that do not exist
8278 in the program. It also cannot handle ellipsis argument lists or
8281 It does perform integral conversions and promotions, floating-point
8282 promotions, arithmetic conversions, pointer conversions, conversions of
8283 class objects to base classes, and standard conversions such as those of
8284 functions or arrays to pointers; it requires an exact match on the
8285 number of function arguments.
8287 Overload resolution is always performed, unless you have specified
8288 @code{set overload-resolution off}. @xref{Debugging C plus plus,
8289 ,@value{GDBN} features for C@t{++}}.
8291 You must specify @code{set overload-resolution off} in order to use an
8292 explicit function signature to call an overloaded function, as in
8294 p 'foo(char,int)'('x', 13)
8297 The @value{GDBN} command-completion facility can simplify this;
8298 see @ref{Completion, ,Command completion}.
8300 @cindex reference declarations
8302 @value{GDBN} understands variables declared as C@t{++} references; you can use
8303 them in expressions just as you do in C@t{++} source---they are automatically
8306 In the parameter list shown when @value{GDBN} displays a frame, the values of
8307 reference variables are not displayed (unlike other variables); this
8308 avoids clutter, since references are often used for large structures.
8309 The @emph{address} of a reference variable is always shown, unless
8310 you have specified @samp{set print address off}.
8313 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
8314 expressions can use it just as expressions in your program do. Since
8315 one scope may be defined in another, you can use @code{::} repeatedly if
8316 necessary, for example in an expression like
8317 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
8318 resolving name scope by reference to source files, in both C and C@t{++}
8319 debugging (@pxref{Variables, ,Program variables}).
8322 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
8323 calling virtual functions correctly, printing out virtual bases of
8324 objects, calling functions in a base subobject, casting objects, and
8325 invoking user-defined operators.
8328 @subsubsection C and C@t{++} defaults
8330 @cindex C and C@t{++} defaults
8332 If you allow @value{GDBN} to set type and range checking automatically, they
8333 both default to @code{off} whenever the working language changes to
8334 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
8335 selects the working language.
8337 If you allow @value{GDBN} to set the language automatically, it
8338 recognizes source files whose names end with @file{.c}, @file{.C}, or
8339 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
8340 these files, it sets the working language to C or C@t{++}.
8341 @xref{Automatically, ,Having @value{GDBN} infer the source language},
8342 for further details.
8344 @c Type checking is (a) primarily motivated by Modula-2, and (b)
8345 @c unimplemented. If (b) changes, it might make sense to let this node
8346 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
8349 @subsubsection C and C@t{++} type and range checks
8351 @cindex C and C@t{++} checks
8353 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
8354 is not used. However, if you turn type checking on, @value{GDBN}
8355 considers two variables type equivalent if:
8359 The two variables are structured and have the same structure, union, or
8363 The two variables have the same type name, or types that have been
8364 declared equivalent through @code{typedef}.
8367 @c leaving this out because neither J Gilmore nor R Pesch understand it.
8370 The two @code{struct}, @code{union}, or @code{enum} variables are
8371 declared in the same declaration. (Note: this may not be true for all C
8376 Range checking, if turned on, is done on mathematical operations. Array
8377 indices are not checked, since they are often used to index a pointer
8378 that is not itself an array.
8381 @subsubsection @value{GDBN} and C
8383 The @code{set print union} and @code{show print union} commands apply to
8384 the @code{union} type. When set to @samp{on}, any @code{union} that is
8385 inside a @code{struct} or @code{class} is also printed. Otherwise, it
8386 appears as @samp{@{...@}}.
8388 The @code{@@} operator aids in the debugging of dynamic arrays, formed
8389 with pointers and a memory allocation function. @xref{Expressions,
8393 * Debugging C plus plus::
8396 @node Debugging C plus plus
8397 @subsubsection @value{GDBN} features for C@t{++}
8399 @cindex commands for C@t{++}
8401 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
8402 designed specifically for use with C@t{++}. Here is a summary:
8405 @cindex break in overloaded functions
8406 @item @r{breakpoint menus}
8407 When you want a breakpoint in a function whose name is overloaded,
8408 @value{GDBN} breakpoint menus help you specify which function definition
8409 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
8411 @cindex overloading in C@t{++}
8412 @item rbreak @var{regex}
8413 Setting breakpoints using regular expressions is helpful for setting
8414 breakpoints on overloaded functions that are not members of any special
8416 @xref{Set Breaks, ,Setting breakpoints}.
8418 @cindex C@t{++} exception handling
8421 Debug C@t{++} exception handling using these commands. @xref{Set
8422 Catchpoints, , Setting catchpoints}.
8425 @item ptype @var{typename}
8426 Print inheritance relationships as well as other information for type
8428 @xref{Symbols, ,Examining the Symbol Table}.
8430 @cindex C@t{++} symbol display
8431 @item set print demangle
8432 @itemx show print demangle
8433 @itemx set print asm-demangle
8434 @itemx show print asm-demangle
8435 Control whether C@t{++} symbols display in their source form, both when
8436 displaying code as C@t{++} source and when displaying disassemblies.
8437 @xref{Print Settings, ,Print settings}.
8439 @item set print object
8440 @itemx show print object
8441 Choose whether to print derived (actual) or declared types of objects.
8442 @xref{Print Settings, ,Print settings}.
8444 @item set print vtbl
8445 @itemx show print vtbl
8446 Control the format for printing virtual function tables.
8447 @xref{Print Settings, ,Print settings}.
8448 (The @code{vtbl} commands do not work on programs compiled with the HP
8449 ANSI C@t{++} compiler (@code{aCC}).)
8451 @kindex set overload-resolution
8452 @cindex overloaded functions, overload resolution
8453 @item set overload-resolution on
8454 Enable overload resolution for C@t{++} expression evaluation. The default
8455 is on. For overloaded functions, @value{GDBN} evaluates the arguments
8456 and searches for a function whose signature matches the argument types,
8457 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
8458 expressions}, for details). If it cannot find a match, it emits a
8461 @item set overload-resolution off
8462 Disable overload resolution for C@t{++} expression evaluation. For
8463 overloaded functions that are not class member functions, @value{GDBN}
8464 chooses the first function of the specified name that it finds in the
8465 symbol table, whether or not its arguments are of the correct type. For
8466 overloaded functions that are class member functions, @value{GDBN}
8467 searches for a function whose signature @emph{exactly} matches the
8470 @item @r{Overloaded symbol names}
8471 You can specify a particular definition of an overloaded symbol, using
8472 the same notation that is used to declare such symbols in C@t{++}: type
8473 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
8474 also use the @value{GDBN} command-line word completion facilities to list the
8475 available choices, or to finish the type list for you.
8476 @xref{Completion,, Command completion}, for details on how to do this.
8480 @subsection Objective-C
8483 This section provides information about some commands and command
8484 options that are useful for debugging Objective-C code.
8487 * Method Names in Commands::
8488 * The Print Command with Objective-C::
8491 @node Method Names in Commands, The Print Command with Objective-C, Objective-C, Objective-C
8492 @subsubsection Method Names in Commands
8494 The following commands have been extended to accept Objective-C method
8495 names as line specifications:
8497 @kindex clear@r{, and Objective-C}
8498 @kindex break@r{, and Objective-C}
8499 @kindex info line@r{, and Objective-C}
8500 @kindex jump@r{, and Objective-C}
8501 @kindex list@r{, and Objective-C}
8505 @item @code{info line}
8510 A fully qualified Objective-C method name is specified as
8513 -[@var{Class} @var{methodName}]
8516 where the minus sign is used to indicate an instance method and a
8517 plus sign (not shown) is used to indicate a class method. The class
8518 name @var{Class} and method name @var{methodName} are enclosed in
8519 brackets, similar to the way messages are specified in Objective-C
8520 source code. For example, to set a breakpoint at the @code{create}
8521 instance method of class @code{Fruit} in the program currently being
8525 break -[Fruit create]
8528 To list ten program lines around the @code{initialize} class method,
8532 list +[NSText initialize]
8535 In the current version of @value{GDBN}, the plus or minus sign is
8536 required. In future versions of @value{GDBN}, the plus or minus
8537 sign will be optional, but you can use it to narrow the search. It
8538 is also possible to specify just a method name:
8544 You must specify the complete method name, including any colons. If
8545 your program's source files contain more than one @code{create} method,
8546 you'll be presented with a numbered list of classes that implement that
8547 method. Indicate your choice by number, or type @samp{0} to exit if
8550 As another example, to clear a breakpoint established at the
8551 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
8554 clear -[NSWindow makeKeyAndOrderFront:]
8557 @node The Print Command with Objective-C
8558 @subsubsection The Print Command With Objective-C
8559 @kindex print-object
8560 @kindex po @r{(@code{print-object})}
8562 The print command has also been extended to accept methods. For example:
8565 print -[@var{object} hash]
8568 @cindex print an Objective-C object description
8569 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
8571 will tell @value{GDBN} to send the @code{hash} message to @var{object}
8572 and print the result. Also, an additional command has been added,
8573 @code{print-object} or @code{po} for short, which is meant to print
8574 the description of an object. However, this command may only work
8575 with certain Objective-C libraries that have a particular hook
8576 function, @code{_NSPrintForDebugger}, defined.
8578 @node Modula-2, , Objective-C, Support
8579 @subsection Modula-2
8581 @cindex Modula-2, @value{GDBN} support
8583 The extensions made to @value{GDBN} to support Modula-2 only support
8584 output from the @sc{gnu} Modula-2 compiler (which is currently being
8585 developed). Other Modula-2 compilers are not currently supported, and
8586 attempting to debug executables produced by them is most likely
8587 to give an error as @value{GDBN} reads in the executable's symbol
8590 @cindex expressions in Modula-2
8592 * M2 Operators:: Built-in operators
8593 * Built-In Func/Proc:: Built-in functions and procedures
8594 * M2 Constants:: Modula-2 constants
8595 * M2 Defaults:: Default settings for Modula-2
8596 * Deviations:: Deviations from standard Modula-2
8597 * M2 Checks:: Modula-2 type and range checks
8598 * M2 Scope:: The scope operators @code{::} and @code{.}
8599 * GDB/M2:: @value{GDBN} and Modula-2
8603 @subsubsection Operators
8604 @cindex Modula-2 operators
8606 Operators must be defined on values of specific types. For instance,
8607 @code{+} is defined on numbers, but not on structures. Operators are
8608 often defined on groups of types. For the purposes of Modula-2, the
8609 following definitions hold:
8614 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
8618 @emph{Character types} consist of @code{CHAR} and its subranges.
8621 @emph{Floating-point types} consist of @code{REAL}.
8624 @emph{Pointer types} consist of anything declared as @code{POINTER TO
8628 @emph{Scalar types} consist of all of the above.
8631 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
8634 @emph{Boolean types} consist of @code{BOOLEAN}.
8638 The following operators are supported, and appear in order of
8639 increasing precedence:
8643 Function argument or array index separator.
8646 Assignment. The value of @var{var} @code{:=} @var{value} is
8650 Less than, greater than on integral, floating-point, or enumerated
8654 Less than or equal to, greater than or equal to
8655 on integral, floating-point and enumerated types, or set inclusion on
8656 set types. Same precedence as @code{<}.
8658 @item =@r{, }<>@r{, }#
8659 Equality and two ways of expressing inequality, valid on scalar types.
8660 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
8661 available for inequality, since @code{#} conflicts with the script
8665 Set membership. Defined on set types and the types of their members.
8666 Same precedence as @code{<}.
8669 Boolean disjunction. Defined on boolean types.
8672 Boolean conjunction. Defined on boolean types.
8675 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8678 Addition and subtraction on integral and floating-point types, or union
8679 and difference on set types.
8682 Multiplication on integral and floating-point types, or set intersection
8686 Division on floating-point types, or symmetric set difference on set
8687 types. Same precedence as @code{*}.
8690 Integer division and remainder. Defined on integral types. Same
8691 precedence as @code{*}.
8694 Negative. Defined on @code{INTEGER} and @code{REAL} data.
8697 Pointer dereferencing. Defined on pointer types.
8700 Boolean negation. Defined on boolean types. Same precedence as
8704 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
8705 precedence as @code{^}.
8708 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
8711 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
8715 @value{GDBN} and Modula-2 scope operators.
8719 @emph{Warning:} Sets and their operations are not yet supported, so @value{GDBN}
8720 treats the use of the operator @code{IN}, or the use of operators
8721 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
8722 @code{<=}, and @code{>=} on sets as an error.
8726 @node Built-In Func/Proc
8727 @subsubsection Built-in functions and procedures
8728 @cindex Modula-2 built-ins
8730 Modula-2 also makes available several built-in procedures and functions.
8731 In describing these, the following metavariables are used:
8736 represents an @code{ARRAY} variable.
8739 represents a @code{CHAR} constant or variable.
8742 represents a variable or constant of integral type.
8745 represents an identifier that belongs to a set. Generally used in the
8746 same function with the metavariable @var{s}. The type of @var{s} should
8747 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
8750 represents a variable or constant of integral or floating-point type.
8753 represents a variable or constant of floating-point type.
8759 represents a variable.
8762 represents a variable or constant of one of many types. See the
8763 explanation of the function for details.
8766 All Modula-2 built-in procedures also return a result, described below.
8770 Returns the absolute value of @var{n}.
8773 If @var{c} is a lower case letter, it returns its upper case
8774 equivalent, otherwise it returns its argument.
8777 Returns the character whose ordinal value is @var{i}.
8780 Decrements the value in the variable @var{v} by one. Returns the new value.
8782 @item DEC(@var{v},@var{i})
8783 Decrements the value in the variable @var{v} by @var{i}. Returns the
8786 @item EXCL(@var{m},@var{s})
8787 Removes the element @var{m} from the set @var{s}. Returns the new
8790 @item FLOAT(@var{i})
8791 Returns the floating point equivalent of the integer @var{i}.
8794 Returns the index of the last member of @var{a}.
8797 Increments the value in the variable @var{v} by one. Returns the new value.
8799 @item INC(@var{v},@var{i})
8800 Increments the value in the variable @var{v} by @var{i}. Returns the
8803 @item INCL(@var{m},@var{s})
8804 Adds the element @var{m} to the set @var{s} if it is not already
8805 there. Returns the new set.
8808 Returns the maximum value of the type @var{t}.
8811 Returns the minimum value of the type @var{t}.
8814 Returns boolean TRUE if @var{i} is an odd number.
8817 Returns the ordinal value of its argument. For example, the ordinal
8818 value of a character is its @sc{ascii} value (on machines supporting the
8819 @sc{ascii} character set). @var{x} must be of an ordered type, which include
8820 integral, character and enumerated types.
8823 Returns the size of its argument. @var{x} can be a variable or a type.
8825 @item TRUNC(@var{r})
8826 Returns the integral part of @var{r}.
8828 @item VAL(@var{t},@var{i})
8829 Returns the member of the type @var{t} whose ordinal value is @var{i}.
8833 @emph{Warning:} Sets and their operations are not yet supported, so
8834 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
8838 @cindex Modula-2 constants
8840 @subsubsection Constants
8842 @value{GDBN} allows you to express the constants of Modula-2 in the following
8848 Integer constants are simply a sequence of digits. When used in an
8849 expression, a constant is interpreted to be type-compatible with the
8850 rest of the expression. Hexadecimal integers are specified by a
8851 trailing @samp{H}, and octal integers by a trailing @samp{B}.
8854 Floating point constants appear as a sequence of digits, followed by a
8855 decimal point and another sequence of digits. An optional exponent can
8856 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
8857 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
8858 digits of the floating point constant must be valid decimal (base 10)
8862 Character constants consist of a single character enclosed by a pair of
8863 like quotes, either single (@code{'}) or double (@code{"}). They may
8864 also be expressed by their ordinal value (their @sc{ascii} value, usually)
8865 followed by a @samp{C}.
8868 String constants consist of a sequence of characters enclosed by a
8869 pair of like quotes, either single (@code{'}) or double (@code{"}).
8870 Escape sequences in the style of C are also allowed. @xref{C
8871 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
8875 Enumerated constants consist of an enumerated identifier.
8878 Boolean constants consist of the identifiers @code{TRUE} and
8882 Pointer constants consist of integral values only.
8885 Set constants are not yet supported.
8889 @subsubsection Modula-2 defaults
8890 @cindex Modula-2 defaults
8892 If type and range checking are set automatically by @value{GDBN}, they
8893 both default to @code{on} whenever the working language changes to
8894 Modula-2. This happens regardless of whether you or @value{GDBN}
8895 selected the working language.
8897 If you allow @value{GDBN} to set the language automatically, then entering
8898 code compiled from a file whose name ends with @file{.mod} sets the
8899 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
8900 the language automatically}, for further details.
8903 @subsubsection Deviations from standard Modula-2
8904 @cindex Modula-2, deviations from
8906 A few changes have been made to make Modula-2 programs easier to debug.
8907 This is done primarily via loosening its type strictness:
8911 Unlike in standard Modula-2, pointer constants can be formed by
8912 integers. This allows you to modify pointer variables during
8913 debugging. (In standard Modula-2, the actual address contained in a
8914 pointer variable is hidden from you; it can only be modified
8915 through direct assignment to another pointer variable or expression that
8916 returned a pointer.)
8919 C escape sequences can be used in strings and characters to represent
8920 non-printable characters. @value{GDBN} prints out strings with these
8921 escape sequences embedded. Single non-printable characters are
8922 printed using the @samp{CHR(@var{nnn})} format.
8925 The assignment operator (@code{:=}) returns the value of its right-hand
8929 All built-in procedures both modify @emph{and} return their argument.
8933 @subsubsection Modula-2 type and range checks
8934 @cindex Modula-2 checks
8937 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
8940 @c FIXME remove warning when type/range checks added
8942 @value{GDBN} considers two Modula-2 variables type equivalent if:
8946 They are of types that have been declared equivalent via a @code{TYPE
8947 @var{t1} = @var{t2}} statement
8950 They have been declared on the same line. (Note: This is true of the
8951 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
8954 As long as type checking is enabled, any attempt to combine variables
8955 whose types are not equivalent is an error.
8957 Range checking is done on all mathematical operations, assignment, array
8958 index bounds, and all built-in functions and procedures.
8961 @subsubsection The scope operators @code{::} and @code{.}
8963 @cindex @code{.}, Modula-2 scope operator
8964 @cindex colon, doubled as scope operator
8966 @vindex colon-colon@r{, in Modula-2}
8967 @c Info cannot handle :: but TeX can.
8970 @vindex ::@r{, in Modula-2}
8973 There are a few subtle differences between the Modula-2 scope operator
8974 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
8979 @var{module} . @var{id}
8980 @var{scope} :: @var{id}
8984 where @var{scope} is the name of a module or a procedure,
8985 @var{module} the name of a module, and @var{id} is any declared
8986 identifier within your program, except another module.
8988 Using the @code{::} operator makes @value{GDBN} search the scope
8989 specified by @var{scope} for the identifier @var{id}. If it is not
8990 found in the specified scope, then @value{GDBN} searches all scopes
8991 enclosing the one specified by @var{scope}.
8993 Using the @code{.} operator makes @value{GDBN} search the current scope for
8994 the identifier specified by @var{id} that was imported from the
8995 definition module specified by @var{module}. With this operator, it is
8996 an error if the identifier @var{id} was not imported from definition
8997 module @var{module}, or if @var{id} is not an identifier in
9001 @subsubsection @value{GDBN} and Modula-2
9003 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
9004 Five subcommands of @code{set print} and @code{show print} apply
9005 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
9006 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
9007 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
9008 analogue in Modula-2.
9010 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
9011 with any language, is not useful with Modula-2. Its
9012 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
9013 created in Modula-2 as they can in C or C@t{++}. However, because an
9014 address can be specified by an integral constant, the construct
9015 @samp{@{@var{type}@}@var{adrexp}} is still useful.
9017 @cindex @code{#} in Modula-2
9018 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
9019 interpreted as the beginning of a comment. Use @code{<>} instead.
9021 @node Unsupported languages
9022 @section Unsupported languages
9024 @cindex unsupported languages
9025 @cindex minimal language
9026 In addition to the other fully-supported programming languages,
9027 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
9028 It does not represent a real programming language, but provides a set
9029 of capabilities close to what the C or assembly languages provide.
9030 This should allow most simple operations to be performed while debugging
9031 an application that uses a language currently not supported by @value{GDBN}.
9033 If the language is set to @code{auto}, @value{GDBN} will automatically
9034 select this language if the current frame corresponds to an unsupported
9038 @chapter Examining the Symbol Table
9040 The commands described in this chapter allow you to inquire about the
9041 symbols (names of variables, functions and types) defined in your
9042 program. This information is inherent in the text of your program and
9043 does not change as your program executes. @value{GDBN} finds it in your
9044 program's symbol table, in the file indicated when you started @value{GDBN}
9045 (@pxref{File Options, ,Choosing files}), or by one of the
9046 file-management commands (@pxref{Files, ,Commands to specify files}).
9048 @cindex symbol names
9049 @cindex names of symbols
9050 @cindex quoting names
9051 Occasionally, you may need to refer to symbols that contain unusual
9052 characters, which @value{GDBN} ordinarily treats as word delimiters. The
9053 most frequent case is in referring to static variables in other
9054 source files (@pxref{Variables,,Program variables}). File names
9055 are recorded in object files as debugging symbols, but @value{GDBN} would
9056 ordinarily parse a typical file name, like @file{foo.c}, as the three words
9057 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
9058 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
9065 looks up the value of @code{x} in the scope of the file @file{foo.c}.
9068 @kindex info address
9069 @cindex address of a symbol
9070 @item info address @var{symbol}
9071 Describe where the data for @var{symbol} is stored. For a register
9072 variable, this says which register it is kept in. For a non-register
9073 local variable, this prints the stack-frame offset at which the variable
9076 Note the contrast with @samp{print &@var{symbol}}, which does not work
9077 at all for a register variable, and for a stack local variable prints
9078 the exact address of the current instantiation of the variable.
9081 @cindex symbol from address
9082 @item info symbol @var{addr}
9083 Print the name of a symbol which is stored at the address @var{addr}.
9084 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
9085 nearest symbol and an offset from it:
9088 (@value{GDBP}) info symbol 0x54320
9089 _initialize_vx + 396 in section .text
9093 This is the opposite of the @code{info address} command. You can use
9094 it to find out the name of a variable or a function given its address.
9097 @item whatis @var{expr}
9098 Print the data type of expression @var{expr}. @var{expr} is not
9099 actually evaluated, and any side-effecting operations (such as
9100 assignments or function calls) inside it do not take place.
9101 @xref{Expressions, ,Expressions}.
9104 Print the data type of @code{$}, the last value in the value history.
9107 @item ptype @var{typename}
9108 Print a description of data type @var{typename}. @var{typename} may be
9109 the name of a type, or for C code it may have the form @samp{class
9110 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
9111 @var{union-tag}} or @samp{enum @var{enum-tag}}.
9113 @item ptype @var{expr}
9115 Print a description of the type of expression @var{expr}. @code{ptype}
9116 differs from @code{whatis} by printing a detailed description, instead
9117 of just the name of the type.
9119 For example, for this variable declaration:
9122 struct complex @{double real; double imag;@} v;
9126 the two commands give this output:
9130 (@value{GDBP}) whatis v
9131 type = struct complex
9132 (@value{GDBP}) ptype v
9133 type = struct complex @{
9141 As with @code{whatis}, using @code{ptype} without an argument refers to
9142 the type of @code{$}, the last value in the value history.
9145 @item info types @var{regexp}
9147 Print a brief description of all types whose names match @var{regexp}
9148 (or all types in your program, if you supply no argument). Each
9149 complete typename is matched as though it were a complete line; thus,
9150 @samp{i type value} gives information on all types in your program whose
9151 names include the string @code{value}, but @samp{i type ^value$} gives
9152 information only on types whose complete name is @code{value}.
9154 This command differs from @code{ptype} in two ways: first, like
9155 @code{whatis}, it does not print a detailed description; second, it
9156 lists all source files where a type is defined.
9159 @cindex local variables
9160 @item info scope @var{addr}
9161 List all the variables local to a particular scope. This command
9162 accepts a location---a function name, a source line, or an address
9163 preceded by a @samp{*}, and prints all the variables local to the
9164 scope defined by that location. For example:
9167 (@value{GDBP}) @b{info scope command_line_handler}
9168 Scope for command_line_handler:
9169 Symbol rl is an argument at stack/frame offset 8, length 4.
9170 Symbol linebuffer is in static storage at address 0x150a18, length 4.
9171 Symbol linelength is in static storage at address 0x150a1c, length 4.
9172 Symbol p is a local variable in register $esi, length 4.
9173 Symbol p1 is a local variable in register $ebx, length 4.
9174 Symbol nline is a local variable in register $edx, length 4.
9175 Symbol repeat is a local variable at frame offset -8, length 4.
9179 This command is especially useful for determining what data to collect
9180 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
9185 Show information about the current source file---that is, the source file for
9186 the function containing the current point of execution:
9189 the name of the source file, and the directory containing it,
9191 the directory it was compiled in,
9193 its length, in lines,
9195 which programming language it is written in,
9197 whether the executable includes debugging information for that file, and
9198 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
9200 whether the debugging information includes information about
9201 preprocessor macros.
9205 @kindex info sources
9207 Print the names of all source files in your program for which there is
9208 debugging information, organized into two lists: files whose symbols
9209 have already been read, and files whose symbols will be read when needed.
9211 @kindex info functions
9212 @item info functions
9213 Print the names and data types of all defined functions.
9215 @item info functions @var{regexp}
9216 Print the names and data types of all defined functions
9217 whose names contain a match for regular expression @var{regexp}.
9218 Thus, @samp{info fun step} finds all functions whose names
9219 include @code{step}; @samp{info fun ^step} finds those whose names
9220 start with @code{step}. If a function name contains characters
9221 that conflict with the regular expression language (eg.
9222 @samp{operator*()}), they may be quoted with a backslash.
9224 @kindex info variables
9225 @item info variables
9226 Print the names and data types of all variables that are declared
9227 outside of functions (i.e.@: excluding local variables).
9229 @item info variables @var{regexp}
9230 Print the names and data types of all variables (except for local
9231 variables) whose names contain a match for regular expression
9234 @kindex info classes
9236 @itemx info classes @var{regexp}
9237 Display all Objective-C classes in your program, or
9238 (with the @var{regexp} argument) all those matching a particular regular
9241 @kindex info selectors
9242 @item info selectors
9243 @itemx info selectors @var{regexp}
9244 Display all Objective-C selectors in your program, or
9245 (with the @var{regexp} argument) all those matching a particular regular
9249 This was never implemented.
9250 @kindex info methods
9252 @itemx info methods @var{regexp}
9253 The @code{info methods} command permits the user to examine all defined
9254 methods within C@t{++} program, or (with the @var{regexp} argument) a
9255 specific set of methods found in the various C@t{++} classes. Many
9256 C@t{++} classes provide a large number of methods. Thus, the output
9257 from the @code{ptype} command can be overwhelming and hard to use. The
9258 @code{info-methods} command filters the methods, printing only those
9259 which match the regular-expression @var{regexp}.
9262 @cindex reloading symbols
9263 Some systems allow individual object files that make up your program to
9264 be replaced without stopping and restarting your program. For example,
9265 in VxWorks you can simply recompile a defective object file and keep on
9266 running. If you are running on one of these systems, you can allow
9267 @value{GDBN} to reload the symbols for automatically relinked modules:
9270 @kindex set symbol-reloading
9271 @item set symbol-reloading on
9272 Replace symbol definitions for the corresponding source file when an
9273 object file with a particular name is seen again.
9275 @item set symbol-reloading off
9276 Do not replace symbol definitions when encountering object files of the
9277 same name more than once. This is the default state; if you are not
9278 running on a system that permits automatic relinking of modules, you
9279 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
9280 may discard symbols when linking large programs, that may contain
9281 several modules (from different directories or libraries) with the same
9284 @kindex show symbol-reloading
9285 @item show symbol-reloading
9286 Show the current @code{on} or @code{off} setting.
9289 @kindex set opaque-type-resolution
9290 @item set opaque-type-resolution on
9291 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
9292 declared as a pointer to a @code{struct}, @code{class}, or
9293 @code{union}---for example, @code{struct MyType *}---that is used in one
9294 source file although the full declaration of @code{struct MyType} is in
9295 another source file. The default is on.
9297 A change in the setting of this subcommand will not take effect until
9298 the next time symbols for a file are loaded.
9300 @item set opaque-type-resolution off
9301 Tell @value{GDBN} not to resolve opaque types. In this case, the type
9302 is printed as follows:
9304 @{<no data fields>@}
9307 @kindex show opaque-type-resolution
9308 @item show opaque-type-resolution
9309 Show whether opaque types are resolved or not.
9311 @kindex maint print symbols
9313 @kindex maint print psymbols
9314 @cindex partial symbol dump
9315 @item maint print symbols @var{filename}
9316 @itemx maint print psymbols @var{filename}
9317 @itemx maint print msymbols @var{filename}
9318 Write a dump of debugging symbol data into the file @var{filename}.
9319 These commands are used to debug the @value{GDBN} symbol-reading code. Only
9320 symbols with debugging data are included. If you use @samp{maint print
9321 symbols}, @value{GDBN} includes all the symbols for which it has already
9322 collected full details: that is, @var{filename} reflects symbols for
9323 only those files whose symbols @value{GDBN} has read. You can use the
9324 command @code{info sources} to find out which files these are. If you
9325 use @samp{maint print psymbols} instead, the dump shows information about
9326 symbols that @value{GDBN} only knows partially---that is, symbols defined in
9327 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
9328 @samp{maint print msymbols} dumps just the minimal symbol information
9329 required for each object file from which @value{GDBN} has read some symbols.
9330 @xref{Files, ,Commands to specify files}, for a discussion of how
9331 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
9333 @kindex maint info symtabs
9334 @kindex maint info psymtabs
9335 @cindex listing @value{GDBN}'s internal symbol tables
9336 @cindex symbol tables, listing @value{GDBN}'s internal
9337 @cindex full symbol tables, listing @value{GDBN}'s internal
9338 @cindex partial symbol tables, listing @value{GDBN}'s internal
9339 @item maint info symtabs @r{[} @var{regexp} @r{]}
9340 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
9342 List the @code{struct symtab} or @code{struct partial_symtab}
9343 structures whose names match @var{regexp}. If @var{regexp} is not
9344 given, list them all. The output includes expressions which you can
9345 copy into a @value{GDBN} debugging this one to examine a particular
9346 structure in more detail. For example:
9349 (@value{GDBP}) maint info psymtabs dwarf2read
9350 @{ objfile /home/gnu/build/gdb/gdb
9351 ((struct objfile *) 0x82e69d0)
9352 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
9353 ((struct partial_symtab *) 0x8474b10)
9356 text addresses 0x814d3c8 -- 0x8158074
9357 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
9358 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
9362 (@value{GDBP}) maint info symtabs
9366 We see that there is one partial symbol table whose filename contains
9367 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
9368 and we see that @value{GDBN} has not read in any symtabs yet at all.
9369 If we set a breakpoint on a function, that will cause @value{GDBN} to
9370 read the symtab for the compilation unit containing that function:
9373 (@value{GDBP}) break dwarf2_psymtab_to_symtab
9374 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
9376 (@value{GDBP}) maint info symtabs
9377 @{ objfile /home/gnu/build/gdb/gdb
9378 ((struct objfile *) 0x82e69d0)
9379 @{ symtab /home/gnu/src/gdb/dwarf2read.c
9380 ((struct symtab *) 0x86c1f38)
9383 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
9393 @chapter Altering Execution
9395 Once you think you have found an error in your program, you might want to
9396 find out for certain whether correcting the apparent error would lead to
9397 correct results in the rest of the run. You can find the answer by
9398 experiment, using the @value{GDBN} features for altering execution of the
9401 For example, you can store new values into variables or memory
9402 locations, give your program a signal, restart it at a different
9403 address, or even return prematurely from a function.
9406 * Assignment:: Assignment to variables
9407 * Jumping:: Continuing at a different address
9408 * Signaling:: Giving your program a signal
9409 * Returning:: Returning from a function
9410 * Calling:: Calling your program's functions
9411 * Patching:: Patching your program
9415 @section Assignment to variables
9418 @cindex setting variables
9419 To alter the value of a variable, evaluate an assignment expression.
9420 @xref{Expressions, ,Expressions}. For example,
9427 stores the value 4 into the variable @code{x}, and then prints the
9428 value of the assignment expression (which is 4).
9429 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
9430 information on operators in supported languages.
9432 @kindex set variable
9433 @cindex variables, setting
9434 If you are not interested in seeing the value of the assignment, use the
9435 @code{set} command instead of the @code{print} command. @code{set} is
9436 really the same as @code{print} except that the expression's value is
9437 not printed and is not put in the value history (@pxref{Value History,
9438 ,Value history}). The expression is evaluated only for its effects.
9440 If the beginning of the argument string of the @code{set} command
9441 appears identical to a @code{set} subcommand, use the @code{set
9442 variable} command instead of just @code{set}. This command is identical
9443 to @code{set} except for its lack of subcommands. For example, if your
9444 program has a variable @code{width}, you get an error if you try to set
9445 a new value with just @samp{set width=13}, because @value{GDBN} has the
9446 command @code{set width}:
9449 (@value{GDBP}) whatis width
9451 (@value{GDBP}) p width
9453 (@value{GDBP}) set width=47
9454 Invalid syntax in expression.
9458 The invalid expression, of course, is @samp{=47}. In
9459 order to actually set the program's variable @code{width}, use
9462 (@value{GDBP}) set var width=47
9465 Because the @code{set} command has many subcommands that can conflict
9466 with the names of program variables, it is a good idea to use the
9467 @code{set variable} command instead of just @code{set}. For example, if
9468 your program has a variable @code{g}, you run into problems if you try
9469 to set a new value with just @samp{set g=4}, because @value{GDBN} has
9470 the command @code{set gnutarget}, abbreviated @code{set g}:
9474 (@value{GDBP}) whatis g
9478 (@value{GDBP}) set g=4
9482 The program being debugged has been started already.
9483 Start it from the beginning? (y or n) y
9484 Starting program: /home/smith/cc_progs/a.out
9485 "/home/smith/cc_progs/a.out": can't open to read symbols:
9487 (@value{GDBP}) show g
9488 The current BFD target is "=4".
9493 The program variable @code{g} did not change, and you silently set the
9494 @code{gnutarget} to an invalid value. In order to set the variable
9498 (@value{GDBP}) set var g=4
9501 @value{GDBN} allows more implicit conversions in assignments than C; you can
9502 freely store an integer value into a pointer variable or vice versa,
9503 and you can convert any structure to any other structure that is the
9504 same length or shorter.
9505 @comment FIXME: how do structs align/pad in these conversions?
9506 @comment /doc@cygnus.com 18dec1990
9508 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
9509 construct to generate a value of specified type at a specified address
9510 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
9511 to memory location @code{0x83040} as an integer (which implies a certain size
9512 and representation in memory), and
9515 set @{int@}0x83040 = 4
9519 stores the value 4 into that memory location.
9522 @section Continuing at a different address
9524 Ordinarily, when you continue your program, you do so at the place where
9525 it stopped, with the @code{continue} command. You can instead continue at
9526 an address of your own choosing, with the following commands:
9530 @item jump @var{linespec}
9531 Resume execution at line @var{linespec}. Execution stops again
9532 immediately if there is a breakpoint there. @xref{List, ,Printing
9533 source lines}, for a description of the different forms of
9534 @var{linespec}. It is common practice to use the @code{tbreak} command
9535 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
9538 The @code{jump} command does not change the current stack frame, or
9539 the stack pointer, or the contents of any memory location or any
9540 register other than the program counter. If line @var{linespec} is in
9541 a different function from the one currently executing, the results may
9542 be bizarre if the two functions expect different patterns of arguments or
9543 of local variables. For this reason, the @code{jump} command requests
9544 confirmation if the specified line is not in the function currently
9545 executing. However, even bizarre results are predictable if you are
9546 well acquainted with the machine-language code of your program.
9548 @item jump *@var{address}
9549 Resume execution at the instruction at address @var{address}.
9552 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
9553 On many systems, you can get much the same effect as the @code{jump}
9554 command by storing a new value into the register @code{$pc}. The
9555 difference is that this does not start your program running; it only
9556 changes the address of where it @emph{will} run when you continue. For
9564 makes the next @code{continue} command or stepping command execute at
9565 address @code{0x485}, rather than at the address where your program stopped.
9566 @xref{Continuing and Stepping, ,Continuing and stepping}.
9568 The most common occasion to use the @code{jump} command is to back
9569 up---perhaps with more breakpoints set---over a portion of a program
9570 that has already executed, in order to examine its execution in more
9575 @section Giving your program a signal
9579 @item signal @var{signal}
9580 Resume execution where your program stopped, but immediately give it the
9581 signal @var{signal}. @var{signal} can be the name or the number of a
9582 signal. For example, on many systems @code{signal 2} and @code{signal
9583 SIGINT} are both ways of sending an interrupt signal.
9585 Alternatively, if @var{signal} is zero, continue execution without
9586 giving a signal. This is useful when your program stopped on account of
9587 a signal and would ordinary see the signal when resumed with the
9588 @code{continue} command; @samp{signal 0} causes it to resume without a
9591 @code{signal} does not repeat when you press @key{RET} a second time
9592 after executing the command.
9596 Invoking the @code{signal} command is not the same as invoking the
9597 @code{kill} utility from the shell. Sending a signal with @code{kill}
9598 causes @value{GDBN} to decide what to do with the signal depending on
9599 the signal handling tables (@pxref{Signals}). The @code{signal} command
9600 passes the signal directly to your program.
9604 @section Returning from a function
9607 @cindex returning from a function
9610 @itemx return @var{expression}
9611 You can cancel execution of a function call with the @code{return}
9612 command. If you give an
9613 @var{expression} argument, its value is used as the function's return
9617 When you use @code{return}, @value{GDBN} discards the selected stack frame
9618 (and all frames within it). You can think of this as making the
9619 discarded frame return prematurely. If you wish to specify a value to
9620 be returned, give that value as the argument to @code{return}.
9622 This pops the selected stack frame (@pxref{Selection, ,Selecting a
9623 frame}), and any other frames inside of it, leaving its caller as the
9624 innermost remaining frame. That frame becomes selected. The
9625 specified value is stored in the registers used for returning values
9628 The @code{return} command does not resume execution; it leaves the
9629 program stopped in the state that would exist if the function had just
9630 returned. In contrast, the @code{finish} command (@pxref{Continuing
9631 and Stepping, ,Continuing and stepping}) resumes execution until the
9632 selected stack frame returns naturally.
9635 @section Calling program functions
9637 @cindex calling functions
9640 @item call @var{expr}
9641 Evaluate the expression @var{expr} without displaying @code{void}
9645 You can use this variant of the @code{print} command if you want to
9646 execute a function from your program, but without cluttering the output
9647 with @code{void} returned values. If the result is not void, it
9648 is printed and saved in the value history.
9651 @section Patching programs
9653 @cindex patching binaries
9654 @cindex writing into executables
9655 @cindex writing into corefiles
9657 By default, @value{GDBN} opens the file containing your program's
9658 executable code (or the corefile) read-only. This prevents accidental
9659 alterations to machine code; but it also prevents you from intentionally
9660 patching your program's binary.
9662 If you'd like to be able to patch the binary, you can specify that
9663 explicitly with the @code{set write} command. For example, you might
9664 want to turn on internal debugging flags, or even to make emergency
9670 @itemx set write off
9671 If you specify @samp{set write on}, @value{GDBN} opens executable and
9672 core files for both reading and writing; if you specify @samp{set write
9673 off} (the default), @value{GDBN} opens them read-only.
9675 If you have already loaded a file, you must load it again (using the
9676 @code{exec-file} or @code{core-file} command) after changing @code{set
9677 write}, for your new setting to take effect.
9681 Display whether executable files and core files are opened for writing
9686 @chapter @value{GDBN} Files
9688 @value{GDBN} needs to know the file name of the program to be debugged,
9689 both in order to read its symbol table and in order to start your
9690 program. To debug a core dump of a previous run, you must also tell
9691 @value{GDBN} the name of the core dump file.
9694 * Files:: Commands to specify files
9695 * Separate Debug Files:: Debugging information in separate files
9696 * Symbol Errors:: Errors reading symbol files
9700 @section Commands to specify files
9702 @cindex symbol table
9703 @cindex core dump file
9705 You may want to specify executable and core dump file names. The usual
9706 way to do this is at start-up time, using the arguments to
9707 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
9708 Out of @value{GDBN}}).
9710 Occasionally it is necessary to change to a different file during a
9711 @value{GDBN} session. Or you may run @value{GDBN} and forget to specify
9712 a file you want to use. In these situations the @value{GDBN} commands
9713 to specify new files are useful.
9716 @cindex executable file
9718 @item file @var{filename}
9719 Use @var{filename} as the program to be debugged. It is read for its
9720 symbols and for the contents of pure memory. It is also the program
9721 executed when you use the @code{run} command. If you do not specify a
9722 directory and the file is not found in the @value{GDBN} working directory,
9723 @value{GDBN} uses the environment variable @code{PATH} as a list of
9724 directories to search, just as the shell does when looking for a program
9725 to run. You can change the value of this variable, for both @value{GDBN}
9726 and your program, using the @code{path} command.
9728 On systems with memory-mapped files, an auxiliary file named
9729 @file{@var{filename}.syms} may hold symbol table information for
9730 @var{filename}. If so, @value{GDBN} maps in the symbol table from
9731 @file{@var{filename}.syms}, starting up more quickly. See the
9732 descriptions of the file options @samp{-mapped} and @samp{-readnow}
9733 (available on the command line, and with the commands @code{file},
9734 @code{symbol-file}, or @code{add-symbol-file}, described below),
9735 for more information.
9738 @code{file} with no argument makes @value{GDBN} discard any information it
9739 has on both executable file and the symbol table.
9742 @item exec-file @r{[} @var{filename} @r{]}
9743 Specify that the program to be run (but not the symbol table) is found
9744 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
9745 if necessary to locate your program. Omitting @var{filename} means to
9746 discard information on the executable file.
9749 @item symbol-file @r{[} @var{filename} @r{]}
9750 Read symbol table information from file @var{filename}. @code{PATH} is
9751 searched when necessary. Use the @code{file} command to get both symbol
9752 table and program to run from the same file.
9754 @code{symbol-file} with no argument clears out @value{GDBN} information on your
9755 program's symbol table.
9757 The @code{symbol-file} command causes @value{GDBN} to forget the contents
9758 of its convenience variables, the value history, and all breakpoints and
9759 auto-display expressions. This is because they may contain pointers to
9760 the internal data recording symbols and data types, which are part of
9761 the old symbol table data being discarded inside @value{GDBN}.
9763 @code{symbol-file} does not repeat if you press @key{RET} again after
9766 When @value{GDBN} is configured for a particular environment, it
9767 understands debugging information in whatever format is the standard
9768 generated for that environment; you may use either a @sc{gnu} compiler, or
9769 other compilers that adhere to the local conventions.
9770 Best results are usually obtained from @sc{gnu} compilers; for example,
9771 using @code{@value{GCC}} you can generate debugging information for
9774 For most kinds of object files, with the exception of old SVR3 systems
9775 using COFF, the @code{symbol-file} command does not normally read the
9776 symbol table in full right away. Instead, it scans the symbol table
9777 quickly to find which source files and which symbols are present. The
9778 details are read later, one source file at a time, as they are needed.
9780 The purpose of this two-stage reading strategy is to make @value{GDBN}
9781 start up faster. For the most part, it is invisible except for
9782 occasional pauses while the symbol table details for a particular source
9783 file are being read. (The @code{set verbose} command can turn these
9784 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
9785 warnings and messages}.)
9787 We have not implemented the two-stage strategy for COFF yet. When the
9788 symbol table is stored in COFF format, @code{symbol-file} reads the
9789 symbol table data in full right away. Note that ``stabs-in-COFF''
9790 still does the two-stage strategy, since the debug info is actually
9794 @cindex reading symbols immediately
9795 @cindex symbols, reading immediately
9797 @cindex memory-mapped symbol file
9798 @cindex saving symbol table
9799 @item symbol-file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
9800 @itemx file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
9801 You can override the @value{GDBN} two-stage strategy for reading symbol
9802 tables by using the @samp{-readnow} option with any of the commands that
9803 load symbol table information, if you want to be sure @value{GDBN} has the
9804 entire symbol table available.
9806 If memory-mapped files are available on your system through the
9807 @code{mmap} system call, you can use another option, @samp{-mapped}, to
9808 cause @value{GDBN} to write the symbols for your program into a reusable
9809 file. Future @value{GDBN} debugging sessions map in symbol information
9810 from this auxiliary symbol file (if the program has not changed), rather
9811 than spending time reading the symbol table from the executable
9812 program. Using the @samp{-mapped} option has the same effect as
9813 starting @value{GDBN} with the @samp{-mapped} command-line option.
9815 You can use both options together, to make sure the auxiliary symbol
9816 file has all the symbol information for your program.
9818 The auxiliary symbol file for a program called @var{myprog} is called
9819 @samp{@var{myprog}.syms}. Once this file exists (so long as it is newer
9820 than the corresponding executable), @value{GDBN} always attempts to use
9821 it when you debug @var{myprog}; no special options or commands are
9824 The @file{.syms} file is specific to the host machine where you run
9825 @value{GDBN}. It holds an exact image of the internal @value{GDBN}
9826 symbol table. It cannot be shared across multiple host platforms.
9828 @c FIXME: for now no mention of directories, since this seems to be in
9829 @c flux. 13mar1992 status is that in theory GDB would look either in
9830 @c current dir or in same dir as myprog; but issues like competing
9831 @c GDB's, or clutter in system dirs, mean that in practice right now
9832 @c only current dir is used. FFish says maybe a special GDB hierarchy
9833 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
9838 @item core-file @r{[} @var{filename} @r{]}
9839 Specify the whereabouts of a core dump file to be used as the ``contents
9840 of memory''. Traditionally, core files contain only some parts of the
9841 address space of the process that generated them; @value{GDBN} can access the
9842 executable file itself for other parts.
9844 @code{core-file} with no argument specifies that no core file is
9847 Note that the core file is ignored when your program is actually running
9848 under @value{GDBN}. So, if you have been running your program and you
9849 wish to debug a core file instead, you must kill the subprocess in which
9850 the program is running. To do this, use the @code{kill} command
9851 (@pxref{Kill Process, ,Killing the child process}).
9853 @kindex add-symbol-file
9854 @cindex dynamic linking
9855 @item add-symbol-file @var{filename} @var{address}
9856 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
9857 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
9858 The @code{add-symbol-file} command reads additional symbol table
9859 information from the file @var{filename}. You would use this command
9860 when @var{filename} has been dynamically loaded (by some other means)
9861 into the program that is running. @var{address} should be the memory
9862 address at which the file has been loaded; @value{GDBN} cannot figure
9863 this out for itself. You can additionally specify an arbitrary number
9864 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
9865 section name and base address for that section. You can specify any
9866 @var{address} as an expression.
9868 The symbol table of the file @var{filename} is added to the symbol table
9869 originally read with the @code{symbol-file} command. You can use the
9870 @code{add-symbol-file} command any number of times; the new symbol data
9871 thus read keeps adding to the old. To discard all old symbol data
9872 instead, use the @code{symbol-file} command without any arguments.
9874 @cindex relocatable object files, reading symbols from
9875 @cindex object files, relocatable, reading symbols from
9876 @cindex reading symbols from relocatable object files
9877 @cindex symbols, reading from relocatable object files
9878 @cindex @file{.o} files, reading symbols from
9879 Although @var{filename} is typically a shared library file, an
9880 executable file, or some other object file which has been fully
9881 relocated for loading into a process, you can also load symbolic
9882 information from relocatable @file{.o} files, as long as:
9886 the file's symbolic information refers only to linker symbols defined in
9887 that file, not to symbols defined by other object files,
9889 every section the file's symbolic information refers to has actually
9890 been loaded into the inferior, as it appears in the file, and
9892 you can determine the address at which every section was loaded, and
9893 provide these to the @code{add-symbol-file} command.
9897 Some embedded operating systems, like Sun Chorus and VxWorks, can load
9898 relocatable files into an already running program; such systems
9899 typically make the requirements above easy to meet. However, it's
9900 important to recognize that many native systems use complex link
9901 procedures (@code{.linkonce} section factoring and C++ constructor table
9902 assembly, for example) that make the requirements difficult to meet. In
9903 general, one cannot assume that using @code{add-symbol-file} to read a
9904 relocatable object file's symbolic information will have the same effect
9905 as linking the relocatable object file into the program in the normal
9908 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
9910 You can use the @samp{-mapped} and @samp{-readnow} options just as with
9911 the @code{symbol-file} command, to change how @value{GDBN} manages the symbol
9912 table information for @var{filename}.
9914 @kindex add-shared-symbol-file
9915 @item add-shared-symbol-file
9916 The @code{add-shared-symbol-file} command can be used only under Harris' CXUX
9917 operating system for the Motorola 88k. @value{GDBN} automatically looks for
9918 shared libraries, however if @value{GDBN} does not find yours, you can run
9919 @code{add-shared-symbol-file}. It takes no arguments.
9923 The @code{section} command changes the base address of section SECTION of
9924 the exec file to ADDR. This can be used if the exec file does not contain
9925 section addresses, (such as in the a.out format), or when the addresses
9926 specified in the file itself are wrong. Each section must be changed
9927 separately. The @code{info files} command, described below, lists all
9928 the sections and their addresses.
9934 @code{info files} and @code{info target} are synonymous; both print the
9935 current target (@pxref{Targets, ,Specifying a Debugging Target}),
9936 including the names of the executable and core dump files currently in
9937 use by @value{GDBN}, and the files from which symbols were loaded. The
9938 command @code{help target} lists all possible targets rather than
9941 @kindex maint info sections
9942 @item maint info sections
9943 Another command that can give you extra information about program sections
9944 is @code{maint info sections}. In addition to the section information
9945 displayed by @code{info files}, this command displays the flags and file
9946 offset of each section in the executable and core dump files. In addition,
9947 @code{maint info sections} provides the following command options (which
9948 may be arbitrarily combined):
9952 Display sections for all loaded object files, including shared libraries.
9953 @item @var{sections}
9954 Display info only for named @var{sections}.
9955 @item @var{section-flags}
9956 Display info only for sections for which @var{section-flags} are true.
9957 The section flags that @value{GDBN} currently knows about are:
9960 Section will have space allocated in the process when loaded.
9961 Set for all sections except those containing debug information.
9963 Section will be loaded from the file into the child process memory.
9964 Set for pre-initialized code and data, clear for @code{.bss} sections.
9966 Section needs to be relocated before loading.
9968 Section cannot be modified by the child process.
9970 Section contains executable code only.
9972 Section contains data only (no executable code).
9974 Section will reside in ROM.
9976 Section contains data for constructor/destructor lists.
9978 Section is not empty.
9980 An instruction to the linker to not output the section.
9981 @item COFF_SHARED_LIBRARY
9982 A notification to the linker that the section contains
9983 COFF shared library information.
9985 Section contains common symbols.
9988 @kindex set trust-readonly-sections
9989 @item set trust-readonly-sections on
9990 Tell @value{GDBN} that readonly sections in your object file
9991 really are read-only (i.e.@: that their contents will not change).
9992 In that case, @value{GDBN} can fetch values from these sections
9993 out of the object file, rather than from the target program.
9994 For some targets (notably embedded ones), this can be a significant
9995 enhancement to debugging performance.
9999 @item set trust-readonly-sections off
10000 Tell @value{GDBN} not to trust readonly sections. This means that
10001 the contents of the section might change while the program is running,
10002 and must therefore be fetched from the target when needed.
10005 All file-specifying commands allow both absolute and relative file names
10006 as arguments. @value{GDBN} always converts the file name to an absolute file
10007 name and remembers it that way.
10009 @cindex shared libraries
10010 @value{GDBN} supports HP-UX, SunOS, SVr4, Irix 5, and IBM RS/6000 shared
10013 @value{GDBN} automatically loads symbol definitions from shared libraries
10014 when you use the @code{run} command, or when you examine a core file.
10015 (Before you issue the @code{run} command, @value{GDBN} does not understand
10016 references to a function in a shared library, however---unless you are
10017 debugging a core file).
10019 On HP-UX, if the program loads a library explicitly, @value{GDBN}
10020 automatically loads the symbols at the time of the @code{shl_load} call.
10022 @c FIXME: some @value{GDBN} release may permit some refs to undef
10023 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
10024 @c FIXME...lib; check this from time to time when updating manual
10026 There are times, however, when you may wish to not automatically load
10027 symbol definitions from shared libraries, such as when they are
10028 particularly large or there are many of them.
10030 To control the automatic loading of shared library symbols, use the
10034 @kindex set auto-solib-add
10035 @item set auto-solib-add @var{mode}
10036 If @var{mode} is @code{on}, symbols from all shared object libraries
10037 will be loaded automatically when the inferior begins execution, you
10038 attach to an independently started inferior, or when the dynamic linker
10039 informs @value{GDBN} that a new library has been loaded. If @var{mode}
10040 is @code{off}, symbols must be loaded manually, using the
10041 @code{sharedlibrary} command. The default value is @code{on}.
10043 @kindex show auto-solib-add
10044 @item show auto-solib-add
10045 Display the current autoloading mode.
10048 To explicitly load shared library symbols, use the @code{sharedlibrary}
10052 @kindex info sharedlibrary
10055 @itemx info sharedlibrary
10056 Print the names of the shared libraries which are currently loaded.
10058 @kindex sharedlibrary
10060 @item sharedlibrary @var{regex}
10061 @itemx share @var{regex}
10062 Load shared object library symbols for files matching a
10063 Unix regular expression.
10064 As with files loaded automatically, it only loads shared libraries
10065 required by your program for a core file or after typing @code{run}. If
10066 @var{regex} is omitted all shared libraries required by your program are
10070 On some systems, such as HP-UX systems, @value{GDBN} supports
10071 autoloading shared library symbols until a limiting threshold size is
10072 reached. This provides the benefit of allowing autoloading to remain on
10073 by default, but avoids autoloading excessively large shared libraries,
10074 up to a threshold that is initially set, but which you can modify if you
10077 Beyond that threshold, symbols from shared libraries must be explicitly
10078 loaded. To load these symbols, use the command @code{sharedlibrary
10079 @var{filename}}. The base address of the shared library is determined
10080 automatically by @value{GDBN} and need not be specified.
10082 To display or set the threshold, use the commands:
10085 @kindex set auto-solib-limit
10086 @item set auto-solib-limit @var{threshold}
10087 Set the autoloading size threshold, in an integral number of megabytes.
10088 If @var{threshold} is nonzero and shared library autoloading is enabled,
10089 symbols from all shared object libraries will be loaded until the total
10090 size of the loaded shared library symbols exceeds this threshold.
10091 Otherwise, symbols must be loaded manually, using the
10092 @code{sharedlibrary} command. The default threshold is 100 (i.e.@: 100
10095 @kindex show auto-solib-limit
10096 @item show auto-solib-limit
10097 Display the current autoloading size threshold, in megabytes.
10100 Shared libraries are also supported in many cross or remote debugging
10101 configurations. A copy of the target's libraries need to be present on the
10102 host system; they need to be the same as the target libraries, although the
10103 copies on the target can be stripped as long as the copies on the host are
10106 You need to tell @value{GDBN} where the target libraries are, so that it can
10107 load the correct copies---otherwise, it may try to load the host's libraries.
10108 @value{GDBN} has two variables to specify the search directories for target
10112 @kindex set solib-absolute-prefix
10113 @item set solib-absolute-prefix @var{path}
10114 If this variable is set, @var{path} will be used as a prefix for any
10115 absolute shared library paths; many runtime loaders store the absolute
10116 paths to the shared library in the target program's memory. If you use
10117 @samp{solib-absolute-prefix} to find shared libraries, they need to be laid
10118 out in the same way that they are on the target, with e.g.@: a
10119 @file{/usr/lib} hierarchy under @var{path}.
10121 You can set the default value of @samp{solib-absolute-prefix} by using the
10122 configure-time @samp{--with-sysroot} option.
10124 @kindex show solib-absolute-prefix
10125 @item show solib-absolute-prefix
10126 Display the current shared library prefix.
10128 @kindex set solib-search-path
10129 @item set solib-search-path @var{path}
10130 If this variable is set, @var{path} is a colon-separated list of directories
10131 to search for shared libraries. @samp{solib-search-path} is used after
10132 @samp{solib-absolute-prefix} fails to locate the library, or if the path to
10133 the library is relative instead of absolute. If you want to use
10134 @samp{solib-search-path} instead of @samp{solib-absolute-prefix}, be sure to
10135 set @samp{solib-absolute-prefix} to a nonexistant directory to prevent
10136 @value{GDBN} from finding your host's libraries.
10138 @kindex show solib-search-path
10139 @item show solib-search-path
10140 Display the current shared library search path.
10144 @node Separate Debug Files
10145 @section Debugging Information in Separate Files
10146 @cindex separate debugging information files
10147 @cindex debugging information in separate files
10148 @cindex @file{.debug} subdirectories
10149 @cindex debugging information directory, global
10150 @cindex global debugging information directory
10152 @value{GDBN} allows you to put a program's debugging information in a
10153 file separate from the executable itself, in a way that allows
10154 @value{GDBN} to find and load the debugging information automatically.
10155 Since debugging information can be very large --- sometimes larger
10156 than the executable code itself --- some systems distribute debugging
10157 information for their executables in separate files, which users can
10158 install only when they need to debug a problem.
10160 If an executable's debugging information has been extracted to a
10161 separate file, the executable should contain a @dfn{debug link} giving
10162 the name of the debugging information file (with no directory
10163 components), and a checksum of its contents. (The exact form of a
10164 debug link is described below.) If the full name of the directory
10165 containing the executable is @var{execdir}, and the executable has a
10166 debug link that specifies the name @var{debugfile}, then @value{GDBN}
10167 will automatically search for the debugging information file in three
10172 the directory containing the executable file (that is, it will look
10173 for a file named @file{@var{execdir}/@var{debugfile}},
10175 a subdirectory of that directory named @file{.debug} (that is, the
10176 file @file{@var{execdir}/.debug/@var{debugfile}}, and
10178 a subdirectory of the global debug file directory that includes the
10179 executable's full path, and the name from the link (that is, the file
10180 @file{@var{globaldebugdir}/@var{execdir}/@var{debugfile}}, where
10181 @var{globaldebugdir} is the global debug file directory, and
10182 @var{execdir} has been turned into a relative path).
10185 @value{GDBN} checks under each of these names for a debugging
10186 information file whose checksum matches that given in the link, and
10187 reads the debugging information from the first one it finds.
10189 So, for example, if you ask @value{GDBN} to debug @file{/usr/bin/ls},
10190 which has a link containing the name @file{ls.debug}, and the global
10191 debug directory is @file{/usr/lib/debug}, then @value{GDBN} will look
10192 for debug information in @file{/usr/bin/ls.debug},
10193 @file{/usr/bin/.debug/ls.debug}, and
10194 @file{/usr/lib/debug/usr/bin/ls.debug}.
10196 You can set the global debugging info directory's name, and view the
10197 name @value{GDBN} is currently using.
10201 @kindex set debug-file-directory
10202 @item set debug-file-directory @var{directory}
10203 Set the directory which @value{GDBN} searches for separate debugging
10204 information files to @var{directory}.
10206 @kindex show debug-file-directory
10207 @item show debug-file-directory
10208 Show the directory @value{GDBN} searches for separate debugging
10213 @cindex @code{.gnu_debuglink} sections
10214 @cindex debug links
10215 A debug link is a special section of the executable file named
10216 @code{.gnu_debuglink}. The section must contain:
10220 A filename, with any leading directory components removed, followed by
10223 zero to three bytes of padding, as needed to reach the next four-byte
10224 boundary within the section, and
10226 a four-byte CRC checksum, stored in the same endianness used for the
10227 executable file itself. The checksum is computed on the debugging
10228 information file's full contents by the function given below, passing
10229 zero as the @var{crc} argument.
10232 Any executable file format can carry a debug link, as long as it can
10233 contain a section named @code{.gnu_debuglink} with the contents
10236 The debugging information file itself should be an ordinary
10237 executable, containing a full set of linker symbols, sections, and
10238 debugging information. The sections of the debugging information file
10239 should have the same names, addresses and sizes as the original file,
10240 but they need not contain any data --- much like a @code{.bss} section
10241 in an ordinary executable.
10243 As of December 2002, there is no standard GNU utility to produce
10244 separated executable / debugging information file pairs. Ulrich
10245 Drepper's @file{elfutils} package, starting with version 0.53,
10246 contains a version of the @code{strip} command such that the command
10247 @kbd{strip foo -f foo.debug} removes the debugging information from
10248 the executable file @file{foo}, places it in the file
10249 @file{foo.debug}, and leaves behind a debug link in @file{foo}.
10251 Since there are many different ways to compute CRC's (different
10252 polynomials, reversals, byte ordering, etc.), the simplest way to
10253 describe the CRC used in @code{.gnu_debuglink} sections is to give the
10254 complete code for a function that computes it:
10256 @kindex @code{gnu_debuglink_crc32}
10259 gnu_debuglink_crc32 (unsigned long crc,
10260 unsigned char *buf, size_t len)
10262 static const unsigned long crc32_table[256] =
10264 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
10265 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
10266 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
10267 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
10268 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
10269 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
10270 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
10271 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
10272 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
10273 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
10274 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
10275 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
10276 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
10277 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
10278 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
10279 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
10280 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
10281 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
10282 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
10283 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
10284 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
10285 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
10286 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
10287 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
10288 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
10289 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
10290 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
10291 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
10292 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
10293 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
10294 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
10295 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
10296 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
10297 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
10298 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
10299 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
10300 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
10301 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
10302 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
10303 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
10304 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
10305 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
10306 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
10307 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
10308 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
10309 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
10310 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
10311 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
10312 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
10313 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
10314 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
10317 unsigned char *end;
10319 crc = ~crc & 0xffffffff;
10320 for (end = buf + len; buf < end; ++buf)
10321 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
10322 return ~crc & 0xffffffff;
10327 @node Symbol Errors
10328 @section Errors reading symbol files
10330 While reading a symbol file, @value{GDBN} occasionally encounters problems,
10331 such as symbol types it does not recognize, or known bugs in compiler
10332 output. By default, @value{GDBN} does not notify you of such problems, since
10333 they are relatively common and primarily of interest to people
10334 debugging compilers. If you are interested in seeing information
10335 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
10336 only one message about each such type of problem, no matter how many
10337 times the problem occurs; or you can ask @value{GDBN} to print more messages,
10338 to see how many times the problems occur, with the @code{set
10339 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
10342 The messages currently printed, and their meanings, include:
10345 @item inner block not inside outer block in @var{symbol}
10347 The symbol information shows where symbol scopes begin and end
10348 (such as at the start of a function or a block of statements). This
10349 error indicates that an inner scope block is not fully contained
10350 in its outer scope blocks.
10352 @value{GDBN} circumvents the problem by treating the inner block as if it had
10353 the same scope as the outer block. In the error message, @var{symbol}
10354 may be shown as ``@code{(don't know)}'' if the outer block is not a
10357 @item block at @var{address} out of order
10359 The symbol information for symbol scope blocks should occur in
10360 order of increasing addresses. This error indicates that it does not
10363 @value{GDBN} does not circumvent this problem, and has trouble
10364 locating symbols in the source file whose symbols it is reading. (You
10365 can often determine what source file is affected by specifying
10366 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
10369 @item bad block start address patched
10371 The symbol information for a symbol scope block has a start address
10372 smaller than the address of the preceding source line. This is known
10373 to occur in the SunOS 4.1.1 (and earlier) C compiler.
10375 @value{GDBN} circumvents the problem by treating the symbol scope block as
10376 starting on the previous source line.
10378 @item bad string table offset in symbol @var{n}
10381 Symbol number @var{n} contains a pointer into the string table which is
10382 larger than the size of the string table.
10384 @value{GDBN} circumvents the problem by considering the symbol to have the
10385 name @code{foo}, which may cause other problems if many symbols end up
10388 @item unknown symbol type @code{0x@var{nn}}
10390 The symbol information contains new data types that @value{GDBN} does
10391 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
10392 uncomprehended information, in hexadecimal.
10394 @value{GDBN} circumvents the error by ignoring this symbol information.
10395 This usually allows you to debug your program, though certain symbols
10396 are not accessible. If you encounter such a problem and feel like
10397 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
10398 on @code{complain}, then go up to the function @code{read_dbx_symtab}
10399 and examine @code{*bufp} to see the symbol.
10401 @item stub type has NULL name
10403 @value{GDBN} could not find the full definition for a struct or class.
10405 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
10406 The symbol information for a C@t{++} member function is missing some
10407 information that recent versions of the compiler should have output for
10410 @item info mismatch between compiler and debugger
10412 @value{GDBN} could not parse a type specification output by the compiler.
10417 @chapter Specifying a Debugging Target
10419 @cindex debugging target
10422 A @dfn{target} is the execution environment occupied by your program.
10424 Often, @value{GDBN} runs in the same host environment as your program;
10425 in that case, the debugging target is specified as a side effect when
10426 you use the @code{file} or @code{core} commands. When you need more
10427 flexibility---for example, running @value{GDBN} on a physically separate
10428 host, or controlling a standalone system over a serial port or a
10429 realtime system over a TCP/IP connection---you can use the @code{target}
10430 command to specify one of the target types configured for @value{GDBN}
10431 (@pxref{Target Commands, ,Commands for managing targets}).
10434 * Active Targets:: Active targets
10435 * Target Commands:: Commands for managing targets
10436 * Byte Order:: Choosing target byte order
10437 * Remote:: Remote debugging
10438 * KOD:: Kernel Object Display
10442 @node Active Targets
10443 @section Active targets
10445 @cindex stacking targets
10446 @cindex active targets
10447 @cindex multiple targets
10449 There are three classes of targets: processes, core files, and
10450 executable files. @value{GDBN} can work concurrently on up to three
10451 active targets, one in each class. This allows you to (for example)
10452 start a process and inspect its activity without abandoning your work on
10455 For example, if you execute @samp{gdb a.out}, then the executable file
10456 @code{a.out} is the only active target. If you designate a core file as
10457 well---presumably from a prior run that crashed and coredumped---then
10458 @value{GDBN} has two active targets and uses them in tandem, looking
10459 first in the corefile target, then in the executable file, to satisfy
10460 requests for memory addresses. (Typically, these two classes of target
10461 are complementary, since core files contain only a program's
10462 read-write memory---variables and so on---plus machine status, while
10463 executable files contain only the program text and initialized data.)
10465 When you type @code{run}, your executable file becomes an active process
10466 target as well. When a process target is active, all @value{GDBN}
10467 commands requesting memory addresses refer to that target; addresses in
10468 an active core file or executable file target are obscured while the
10469 process target is active.
10471 Use the @code{core-file} and @code{exec-file} commands to select a new
10472 core file or executable target (@pxref{Files, ,Commands to specify
10473 files}). To specify as a target a process that is already running, use
10474 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
10477 @node Target Commands
10478 @section Commands for managing targets
10481 @item target @var{type} @var{parameters}
10482 Connects the @value{GDBN} host environment to a target machine or
10483 process. A target is typically a protocol for talking to debugging
10484 facilities. You use the argument @var{type} to specify the type or
10485 protocol of the target machine.
10487 Further @var{parameters} are interpreted by the target protocol, but
10488 typically include things like device names or host names to connect
10489 with, process numbers, and baud rates.
10491 The @code{target} command does not repeat if you press @key{RET} again
10492 after executing the command.
10494 @kindex help target
10496 Displays the names of all targets available. To display targets
10497 currently selected, use either @code{info target} or @code{info files}
10498 (@pxref{Files, ,Commands to specify files}).
10500 @item help target @var{name}
10501 Describe a particular target, including any parameters necessary to
10504 @kindex set gnutarget
10505 @item set gnutarget @var{args}
10506 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
10507 knows whether it is reading an @dfn{executable},
10508 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
10509 with the @code{set gnutarget} command. Unlike most @code{target} commands,
10510 with @code{gnutarget} the @code{target} refers to a program, not a machine.
10513 @emph{Warning:} To specify a file format with @code{set gnutarget},
10514 you must know the actual BFD name.
10518 @xref{Files, , Commands to specify files}.
10520 @kindex show gnutarget
10521 @item show gnutarget
10522 Use the @code{show gnutarget} command to display what file format
10523 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
10524 @value{GDBN} will determine the file format for each file automatically,
10525 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
10528 Here are some common targets (available, or not, depending on the GDB
10532 @kindex target exec
10533 @item target exec @var{program}
10534 An executable file. @samp{target exec @var{program}} is the same as
10535 @samp{exec-file @var{program}}.
10537 @kindex target core
10538 @item target core @var{filename}
10539 A core dump file. @samp{target core @var{filename}} is the same as
10540 @samp{core-file @var{filename}}.
10542 @kindex target remote
10543 @item target remote @var{dev}
10544 Remote serial target in GDB-specific protocol. The argument @var{dev}
10545 specifies what serial device to use for the connection (e.g.
10546 @file{/dev/ttya}). @xref{Remote, ,Remote debugging}. @code{target remote}
10547 supports the @code{load} command. This is only useful if you have
10548 some other way of getting the stub to the target system, and you can put
10549 it somewhere in memory where it won't get clobbered by the download.
10553 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
10561 works; however, you cannot assume that a specific memory map, device
10562 drivers, or even basic I/O is available, although some simulators do
10563 provide these. For info about any processor-specific simulator details,
10564 see the appropriate section in @ref{Embedded Processors, ,Embedded
10569 Some configurations may include these targets as well:
10573 @kindex target nrom
10574 @item target nrom @var{dev}
10575 NetROM ROM emulator. This target only supports downloading.
10579 Different targets are available on different configurations of @value{GDBN};
10580 your configuration may have more or fewer targets.
10582 Many remote targets require you to download the executable's code
10583 once you've successfully established a connection.
10587 @kindex load @var{filename}
10588 @item load @var{filename}
10589 Depending on what remote debugging facilities are configured into
10590 @value{GDBN}, the @code{load} command may be available. Where it exists, it
10591 is meant to make @var{filename} (an executable) available for debugging
10592 on the remote system---by downloading, or dynamic linking, for example.
10593 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
10594 the @code{add-symbol-file} command.
10596 If your @value{GDBN} does not have a @code{load} command, attempting to
10597 execute it gets the error message ``@code{You can't do that when your
10598 target is @dots{}}''
10600 The file is loaded at whatever address is specified in the executable.
10601 For some object file formats, you can specify the load address when you
10602 link the program; for other formats, like a.out, the object file format
10603 specifies a fixed address.
10604 @c FIXME! This would be a good place for an xref to the GNU linker doc.
10606 @code{load} does not repeat if you press @key{RET} again after using it.
10610 @section Choosing target byte order
10612 @cindex choosing target byte order
10613 @cindex target byte order
10615 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
10616 offer the ability to run either big-endian or little-endian byte
10617 orders. Usually the executable or symbol will include a bit to
10618 designate the endian-ness, and you will not need to worry about
10619 which to use. However, you may still find it useful to adjust
10620 @value{GDBN}'s idea of processor endian-ness manually.
10623 @kindex set endian big
10624 @item set endian big
10625 Instruct @value{GDBN} to assume the target is big-endian.
10627 @kindex set endian little
10628 @item set endian little
10629 Instruct @value{GDBN} to assume the target is little-endian.
10631 @kindex set endian auto
10632 @item set endian auto
10633 Instruct @value{GDBN} to use the byte order associated with the
10637 Display @value{GDBN}'s current idea of the target byte order.
10641 Note that these commands merely adjust interpretation of symbolic
10642 data on the host, and that they have absolutely no effect on the
10646 @section Remote debugging
10647 @cindex remote debugging
10649 If you are trying to debug a program running on a machine that cannot run
10650 @value{GDBN} in the usual way, it is often useful to use remote debugging.
10651 For example, you might use remote debugging on an operating system kernel,
10652 or on a small system which does not have a general purpose operating system
10653 powerful enough to run a full-featured debugger.
10655 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
10656 to make this work with particular debugging targets. In addition,
10657 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
10658 but not specific to any particular target system) which you can use if you
10659 write the remote stubs---the code that runs on the remote system to
10660 communicate with @value{GDBN}.
10662 Other remote targets may be available in your
10663 configuration of @value{GDBN}; use @code{help target} to list them.
10666 @section Kernel Object Display
10667 @cindex kernel object display
10670 Some targets support kernel object display. Using this facility,
10671 @value{GDBN} communicates specially with the underlying operating system
10672 and can display information about operating system-level objects such as
10673 mutexes and other synchronization objects. Exactly which objects can be
10674 displayed is determined on a per-OS basis.
10677 Use the @code{set os} command to set the operating system. This tells
10678 @value{GDBN} which kernel object display module to initialize:
10681 (@value{GDBP}) set os cisco
10685 The associated command @code{show os} displays the operating system
10686 set with the @code{set os} command; if no operating system has been
10687 set, @code{show os} will display an empty string @samp{""}.
10689 If @code{set os} succeeds, @value{GDBN} will display some information
10690 about the operating system, and will create a new @code{info} command
10691 which can be used to query the target. The @code{info} command is named
10692 after the operating system:
10696 (@value{GDBP}) info cisco
10697 List of Cisco Kernel Objects
10699 any Any and all objects
10702 Further subcommands can be used to query about particular objects known
10705 There is currently no way to determine whether a given operating
10706 system is supported other than to try setting it with @kbd{set os
10707 @var{name}}, where @var{name} is the name of the operating system you
10711 @node Remote Debugging
10712 @chapter Debugging remote programs
10715 * Connecting:: Connecting to a remote target
10716 * Server:: Using the gdbserver program
10717 * NetWare:: Using the gdbserve.nlm program
10718 * Remote configuration:: Remote configuration
10719 * remote stub:: Implementing a remote stub
10723 @section Connecting to a remote target
10725 On the @value{GDBN} host machine, you will need an unstripped copy of
10726 your program, since @value{GDBN} needs symobl and debugging information.
10727 Start up @value{GDBN} as usual, using the name of the local copy of your
10728 program as the first argument.
10730 @cindex serial line, @code{target remote}
10731 If you're using a serial line, you may want to give @value{GDBN} the
10732 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
10733 before the @code{target} command.
10735 After that, use @code{target remote} to establish communications with
10736 the target machine. Its argument specifies how to communicate---either
10737 via a devicename attached to a direct serial line, or a TCP or UDP port
10738 (possibly to a terminal server which in turn has a serial line to the
10739 target). For example, to use a serial line connected to the device
10740 named @file{/dev/ttyb}:
10743 target remote /dev/ttyb
10746 @cindex TCP port, @code{target remote}
10747 To use a TCP connection, use an argument of the form
10748 @code{@var{host}:@var{port}} or @code{tcp:@var{host}:@var{port}}.
10749 For example, to connect to port 2828 on a
10750 terminal server named @code{manyfarms}:
10753 target remote manyfarms:2828
10756 If your remote target is actually running on the same machine as
10757 your debugger session (e.g.@: a simulator of your target running on
10758 the same host), you can omit the hostname. For example, to connect
10759 to port 1234 on your local machine:
10762 target remote :1234
10766 Note that the colon is still required here.
10768 @cindex UDP port, @code{target remote}
10769 To use a UDP connection, use an argument of the form
10770 @code{udp:@var{host}:@var{port}}. For example, to connect to UDP port 2828
10771 on a terminal server named @code{manyfarms}:
10774 target remote udp:manyfarms:2828
10777 When using a UDP connection for remote debugging, you should keep in mind
10778 that the `U' stands for ``Unreliable''. UDP can silently drop packets on
10779 busy or unreliable networks, which will cause havoc with your debugging
10782 Now you can use all the usual commands to examine and change data and to
10783 step and continue the remote program.
10785 @cindex interrupting remote programs
10786 @cindex remote programs, interrupting
10787 Whenever @value{GDBN} is waiting for the remote program, if you type the
10788 interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the
10789 program. This may or may not succeed, depending in part on the hardware
10790 and the serial drivers the remote system uses. If you type the
10791 interrupt character once again, @value{GDBN} displays this prompt:
10794 Interrupted while waiting for the program.
10795 Give up (and stop debugging it)? (y or n)
10798 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
10799 (If you decide you want to try again later, you can use @samp{target
10800 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
10801 goes back to waiting.
10804 @kindex detach (remote)
10806 When you have finished debugging the remote program, you can use the
10807 @code{detach} command to release it from @value{GDBN} control.
10808 Detaching from the target normally resumes its execution, but the results
10809 will depend on your particular remote stub. After the @code{detach}
10810 command, @value{GDBN} is free to connect to another target.
10814 The @code{disconnect} command behaves like @code{detach}, except that
10815 the target is generally not resumed. It will wait for @value{GDBN}
10816 (this instance or another one) to connect and continue debugging. After
10817 the @code{disconnect} command, @value{GDBN} is again free to connect to
10822 @section Using the @code{gdbserver} program
10825 @cindex remote connection without stubs
10826 @code{gdbserver} is a control program for Unix-like systems, which
10827 allows you to connect your program with a remote @value{GDBN} via
10828 @code{target remote}---but without linking in the usual debugging stub.
10830 @code{gdbserver} is not a complete replacement for the debugging stubs,
10831 because it requires essentially the same operating-system facilities
10832 that @value{GDBN} itself does. In fact, a system that can run
10833 @code{gdbserver} to connect to a remote @value{GDBN} could also run
10834 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
10835 because it is a much smaller program than @value{GDBN} itself. It is
10836 also easier to port than all of @value{GDBN}, so you may be able to get
10837 started more quickly on a new system by using @code{gdbserver}.
10838 Finally, if you develop code for real-time systems, you may find that
10839 the tradeoffs involved in real-time operation make it more convenient to
10840 do as much development work as possible on another system, for example
10841 by cross-compiling. You can use @code{gdbserver} to make a similar
10842 choice for debugging.
10844 @value{GDBN} and @code{gdbserver} communicate via either a serial line
10845 or a TCP connection, using the standard @value{GDBN} remote serial
10849 @item On the target machine,
10850 you need to have a copy of the program you want to debug.
10851 @code{gdbserver} does not need your program's symbol table, so you can
10852 strip the program if necessary to save space. @value{GDBN} on the host
10853 system does all the symbol handling.
10855 To use the server, you must tell it how to communicate with @value{GDBN};
10856 the name of your program; and the arguments for your program. The usual
10860 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
10863 @var{comm} is either a device name (to use a serial line) or a TCP
10864 hostname and portnumber. For example, to debug Emacs with the argument
10865 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
10869 target> gdbserver /dev/com1 emacs foo.txt
10872 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
10875 To use a TCP connection instead of a serial line:
10878 target> gdbserver host:2345 emacs foo.txt
10881 The only difference from the previous example is the first argument,
10882 specifying that you are communicating with the host @value{GDBN} via
10883 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
10884 expect a TCP connection from machine @samp{host} to local TCP port 2345.
10885 (Currently, the @samp{host} part is ignored.) You can choose any number
10886 you want for the port number as long as it does not conflict with any
10887 TCP ports already in use on the target system (for example, @code{23} is
10888 reserved for @code{telnet}).@footnote{If you choose a port number that
10889 conflicts with another service, @code{gdbserver} prints an error message
10890 and exits.} You must use the same port number with the host @value{GDBN}
10891 @code{target remote} command.
10893 On some targets, @code{gdbserver} can also attach to running programs.
10894 This is accomplished via the @code{--attach} argument. The syntax is:
10897 target> gdbserver @var{comm} --attach @var{pid}
10900 @var{pid} is the process ID of a currently running process. It isn't necessary
10901 to point @code{gdbserver} at a binary for the running process.
10904 @cindex attach to a program by name
10905 You can debug processes by name instead of process ID if your target has the
10906 @code{pidof} utility:
10909 target> gdbserver @var{comm} --attach `pidof @var{PROGRAM}`
10912 In case more than one copy of @var{PROGRAM} is running, or @var{PROGRAM}
10913 has multiple threads, most versions of @code{pidof} support the
10914 @code{-s} option to only return the first process ID.
10916 @item On the host machine,
10917 connect to your target (@pxref{Connecting,,Connecting to a remote target}).
10918 For TCP connections, you must start up @code{gdbserver} prior to using
10919 the @code{target remote} command. Otherwise you may get an error whose
10920 text depends on the host system, but which usually looks something like
10921 @samp{Connection refused}. You don't need to use the @code{load}
10922 command in @value{GDBN} when using gdbserver, since the program is
10923 already on the target.
10928 @section Using the @code{gdbserve.nlm} program
10930 @kindex gdbserve.nlm
10931 @code{gdbserve.nlm} is a control program for NetWare systems, which
10932 allows you to connect your program with a remote @value{GDBN} via
10933 @code{target remote}.
10935 @value{GDBN} and @code{gdbserve.nlm} communicate via a serial line,
10936 using the standard @value{GDBN} remote serial protocol.
10939 @item On the target machine,
10940 you need to have a copy of the program you want to debug.
10941 @code{gdbserve.nlm} does not need your program's symbol table, so you
10942 can strip the program if necessary to save space. @value{GDBN} on the
10943 host system does all the symbol handling.
10945 To use the server, you must tell it how to communicate with
10946 @value{GDBN}; the name of your program; and the arguments for your
10947 program. The syntax is:
10950 load gdbserve [ BOARD=@var{board} ] [ PORT=@var{port} ]
10951 [ BAUD=@var{baud} ] @var{program} [ @var{args} @dots{} ]
10954 @var{board} and @var{port} specify the serial line; @var{baud} specifies
10955 the baud rate used by the connection. @var{port} and @var{node} default
10956 to 0, @var{baud} defaults to 9600@dmn{bps}.
10958 For example, to debug Emacs with the argument @samp{foo.txt}and
10959 communicate with @value{GDBN} over serial port number 2 or board 1
10960 using a 19200@dmn{bps} connection:
10963 load gdbserve BOARD=1 PORT=2 BAUD=19200 emacs foo.txt
10967 On the @value{GDBN} host machine, connect to your target (@pxref{Connecting,,
10968 Connecting to a remote target}).
10972 @node Remote configuration
10973 @section Remote configuration
10975 The following configuration options are available when debugging remote
10979 @kindex set remote hardware-watchpoint-limit
10980 @kindex set remote hardware-breakpoint-limit
10981 @anchor{set remote hardware-watchpoint-limit}
10982 @anchor{set remote hardware-breakpoint-limit}
10983 @item set remote hardware-watchpoint-limit @var{limit}
10984 @itemx set remote hardware-breakpoint-limit @var{limit}
10985 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
10986 watchpoints. A limit of -1, the default, is treated as unlimited.
10990 @section Implementing a remote stub
10992 @cindex debugging stub, example
10993 @cindex remote stub, example
10994 @cindex stub example, remote debugging
10995 The stub files provided with @value{GDBN} implement the target side of the
10996 communication protocol, and the @value{GDBN} side is implemented in the
10997 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
10998 these subroutines to communicate, and ignore the details. (If you're
10999 implementing your own stub file, you can still ignore the details: start
11000 with one of the existing stub files. @file{sparc-stub.c} is the best
11001 organized, and therefore the easiest to read.)
11003 @cindex remote serial debugging, overview
11004 To debug a program running on another machine (the debugging
11005 @dfn{target} machine), you must first arrange for all the usual
11006 prerequisites for the program to run by itself. For example, for a C
11011 A startup routine to set up the C runtime environment; these usually
11012 have a name like @file{crt0}. The startup routine may be supplied by
11013 your hardware supplier, or you may have to write your own.
11016 A C subroutine library to support your program's
11017 subroutine calls, notably managing input and output.
11020 A way of getting your program to the other machine---for example, a
11021 download program. These are often supplied by the hardware
11022 manufacturer, but you may have to write your own from hardware
11026 The next step is to arrange for your program to use a serial port to
11027 communicate with the machine where @value{GDBN} is running (the @dfn{host}
11028 machine). In general terms, the scheme looks like this:
11032 @value{GDBN} already understands how to use this protocol; when everything
11033 else is set up, you can simply use the @samp{target remote} command
11034 (@pxref{Targets,,Specifying a Debugging Target}).
11036 @item On the target,
11037 you must link with your program a few special-purpose subroutines that
11038 implement the @value{GDBN} remote serial protocol. The file containing these
11039 subroutines is called a @dfn{debugging stub}.
11041 On certain remote targets, you can use an auxiliary program
11042 @code{gdbserver} instead of linking a stub into your program.
11043 @xref{Server,,Using the @code{gdbserver} program}, for details.
11046 The debugging stub is specific to the architecture of the remote
11047 machine; for example, use @file{sparc-stub.c} to debug programs on
11050 @cindex remote serial stub list
11051 These working remote stubs are distributed with @value{GDBN}:
11056 @cindex @file{i386-stub.c}
11059 For Intel 386 and compatible architectures.
11062 @cindex @file{m68k-stub.c}
11063 @cindex Motorola 680x0
11065 For Motorola 680x0 architectures.
11068 @cindex @file{sh-stub.c}
11071 For Renesas SH architectures.
11074 @cindex @file{sparc-stub.c}
11076 For @sc{sparc} architectures.
11078 @item sparcl-stub.c
11079 @cindex @file{sparcl-stub.c}
11082 For Fujitsu @sc{sparclite} architectures.
11086 The @file{README} file in the @value{GDBN} distribution may list other
11087 recently added stubs.
11090 * Stub Contents:: What the stub can do for you
11091 * Bootstrapping:: What you must do for the stub
11092 * Debug Session:: Putting it all together
11095 @node Stub Contents
11096 @subsection What the stub can do for you
11098 @cindex remote serial stub
11099 The debugging stub for your architecture supplies these three
11103 @item set_debug_traps
11104 @kindex set_debug_traps
11105 @cindex remote serial stub, initialization
11106 This routine arranges for @code{handle_exception} to run when your
11107 program stops. You must call this subroutine explicitly near the
11108 beginning of your program.
11110 @item handle_exception
11111 @kindex handle_exception
11112 @cindex remote serial stub, main routine
11113 This is the central workhorse, but your program never calls it
11114 explicitly---the setup code arranges for @code{handle_exception} to
11115 run when a trap is triggered.
11117 @code{handle_exception} takes control when your program stops during
11118 execution (for example, on a breakpoint), and mediates communications
11119 with @value{GDBN} on the host machine. This is where the communications
11120 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
11121 representative on the target machine. It begins by sending summary
11122 information on the state of your program, then continues to execute,
11123 retrieving and transmitting any information @value{GDBN} needs, until you
11124 execute a @value{GDBN} command that makes your program resume; at that point,
11125 @code{handle_exception} returns control to your own code on the target
11129 @cindex @code{breakpoint} subroutine, remote
11130 Use this auxiliary subroutine to make your program contain a
11131 breakpoint. Depending on the particular situation, this may be the only
11132 way for @value{GDBN} to get control. For instance, if your target
11133 machine has some sort of interrupt button, you won't need to call this;
11134 pressing the interrupt button transfers control to
11135 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
11136 simply receiving characters on the serial port may also trigger a trap;
11137 again, in that situation, you don't need to call @code{breakpoint} from
11138 your own program---simply running @samp{target remote} from the host
11139 @value{GDBN} session gets control.
11141 Call @code{breakpoint} if none of these is true, or if you simply want
11142 to make certain your program stops at a predetermined point for the
11143 start of your debugging session.
11146 @node Bootstrapping
11147 @subsection What you must do for the stub
11149 @cindex remote stub, support routines
11150 The debugging stubs that come with @value{GDBN} are set up for a particular
11151 chip architecture, but they have no information about the rest of your
11152 debugging target machine.
11154 First of all you need to tell the stub how to communicate with the
11158 @item int getDebugChar()
11159 @kindex getDebugChar
11160 Write this subroutine to read a single character from the serial port.
11161 It may be identical to @code{getchar} for your target system; a
11162 different name is used to allow you to distinguish the two if you wish.
11164 @item void putDebugChar(int)
11165 @kindex putDebugChar
11166 Write this subroutine to write a single character to the serial port.
11167 It may be identical to @code{putchar} for your target system; a
11168 different name is used to allow you to distinguish the two if you wish.
11171 @cindex control C, and remote debugging
11172 @cindex interrupting remote targets
11173 If you want @value{GDBN} to be able to stop your program while it is
11174 running, you need to use an interrupt-driven serial driver, and arrange
11175 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
11176 character). That is the character which @value{GDBN} uses to tell the
11177 remote system to stop.
11179 Getting the debugging target to return the proper status to @value{GDBN}
11180 probably requires changes to the standard stub; one quick and dirty way
11181 is to just execute a breakpoint instruction (the ``dirty'' part is that
11182 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
11184 Other routines you need to supply are:
11187 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
11188 @kindex exceptionHandler
11189 Write this function to install @var{exception_address} in the exception
11190 handling tables. You need to do this because the stub does not have any
11191 way of knowing what the exception handling tables on your target system
11192 are like (for example, the processor's table might be in @sc{rom},
11193 containing entries which point to a table in @sc{ram}).
11194 @var{exception_number} is the exception number which should be changed;
11195 its meaning is architecture-dependent (for example, different numbers
11196 might represent divide by zero, misaligned access, etc). When this
11197 exception occurs, control should be transferred directly to
11198 @var{exception_address}, and the processor state (stack, registers,
11199 and so on) should be just as it is when a processor exception occurs. So if
11200 you want to use a jump instruction to reach @var{exception_address}, it
11201 should be a simple jump, not a jump to subroutine.
11203 For the 386, @var{exception_address} should be installed as an interrupt
11204 gate so that interrupts are masked while the handler runs. The gate
11205 should be at privilege level 0 (the most privileged level). The
11206 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
11207 help from @code{exceptionHandler}.
11209 @item void flush_i_cache()
11210 @kindex flush_i_cache
11211 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
11212 instruction cache, if any, on your target machine. If there is no
11213 instruction cache, this subroutine may be a no-op.
11215 On target machines that have instruction caches, @value{GDBN} requires this
11216 function to make certain that the state of your program is stable.
11220 You must also make sure this library routine is available:
11223 @item void *memset(void *, int, int)
11225 This is the standard library function @code{memset} that sets an area of
11226 memory to a known value. If you have one of the free versions of
11227 @code{libc.a}, @code{memset} can be found there; otherwise, you must
11228 either obtain it from your hardware manufacturer, or write your own.
11231 If you do not use the GNU C compiler, you may need other standard
11232 library subroutines as well; this varies from one stub to another,
11233 but in general the stubs are likely to use any of the common library
11234 subroutines which @code{@value{GCC}} generates as inline code.
11237 @node Debug Session
11238 @subsection Putting it all together
11240 @cindex remote serial debugging summary
11241 In summary, when your program is ready to debug, you must follow these
11246 Make sure you have defined the supporting low-level routines
11247 (@pxref{Bootstrapping,,What you must do for the stub}):
11249 @code{getDebugChar}, @code{putDebugChar},
11250 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
11254 Insert these lines near the top of your program:
11262 For the 680x0 stub only, you need to provide a variable called
11263 @code{exceptionHook}. Normally you just use:
11266 void (*exceptionHook)() = 0;
11270 but if before calling @code{set_debug_traps}, you set it to point to a
11271 function in your program, that function is called when
11272 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
11273 error). The function indicated by @code{exceptionHook} is called with
11274 one parameter: an @code{int} which is the exception number.
11277 Compile and link together: your program, the @value{GDBN} debugging stub for
11278 your target architecture, and the supporting subroutines.
11281 Make sure you have a serial connection between your target machine and
11282 the @value{GDBN} host, and identify the serial port on the host.
11285 @c The "remote" target now provides a `load' command, so we should
11286 @c document that. FIXME.
11287 Download your program to your target machine (or get it there by
11288 whatever means the manufacturer provides), and start it.
11291 Start @value{GDBN} on the host, and connect to the target
11292 (@pxref{Connecting,,Connecting to a remote target}).
11296 @node Configurations
11297 @chapter Configuration-Specific Information
11299 While nearly all @value{GDBN} commands are available for all native and
11300 cross versions of the debugger, there are some exceptions. This chapter
11301 describes things that are only available in certain configurations.
11303 There are three major categories of configurations: native
11304 configurations, where the host and target are the same, embedded
11305 operating system configurations, which are usually the same for several
11306 different processor architectures, and bare embedded processors, which
11307 are quite different from each other.
11312 * Embedded Processors::
11319 This section describes details specific to particular native
11324 * SVR4 Process Information:: SVR4 process information
11325 * DJGPP Native:: Features specific to the DJGPP port
11326 * Cygwin Native:: Features specific to the Cygwin port
11332 On HP-UX systems, if you refer to a function or variable name that
11333 begins with a dollar sign, @value{GDBN} searches for a user or system
11334 name first, before it searches for a convenience variable.
11336 @node SVR4 Process Information
11337 @subsection SVR4 process information
11340 @cindex process image
11342 Many versions of SVR4 provide a facility called @samp{/proc} that can be
11343 used to examine the image of a running process using file-system
11344 subroutines. If @value{GDBN} is configured for an operating system with
11345 this facility, the command @code{info proc} is available to report on
11346 several kinds of information about the process running your program.
11347 @code{info proc} works only on SVR4 systems that include the
11348 @code{procfs} code. This includes OSF/1 (Digital Unix), Solaris, Irix,
11349 and Unixware, but not HP-UX or @sc{gnu}/Linux, for example.
11354 Summarize available information about the process.
11356 @kindex info proc mappings
11357 @item info proc mappings
11358 Report on the address ranges accessible in the program, with information
11359 on whether your program may read, write, or execute each range.
11361 @comment These sub-options of 'info proc' were not included when
11362 @comment procfs.c was re-written. Keep their descriptions around
11363 @comment against the day when someone finds the time to put them back in.
11364 @kindex info proc times
11365 @item info proc times
11366 Starting time, user CPU time, and system CPU time for your program and
11369 @kindex info proc id
11371 Report on the process IDs related to your program: its own process ID,
11372 the ID of its parent, the process group ID, and the session ID.
11374 @kindex info proc status
11375 @item info proc status
11376 General information on the state of the process. If the process is
11377 stopped, this report includes the reason for stopping, and any signal
11380 @item info proc all
11381 Show all the above information about the process.
11386 @subsection Features for Debugging @sc{djgpp} Programs
11387 @cindex @sc{djgpp} debugging
11388 @cindex native @sc{djgpp} debugging
11389 @cindex MS-DOS-specific commands
11391 @sc{djgpp} is the port of @sc{gnu} development tools to MS-DOS and
11392 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
11393 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
11394 top of real-mode DOS systems and their emulations.
11396 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
11397 defines a few commands specific to the @sc{djgpp} port. This
11398 subsection describes those commands.
11403 This is a prefix of @sc{djgpp}-specific commands which print
11404 information about the target system and important OS structures.
11407 @cindex MS-DOS system info
11408 @cindex free memory information (MS-DOS)
11409 @item info dos sysinfo
11410 This command displays assorted information about the underlying
11411 platform: the CPU type and features, the OS version and flavor, the
11412 DPMI version, and the available conventional and DPMI memory.
11417 @cindex segment descriptor tables
11418 @cindex descriptor tables display
11420 @itemx info dos ldt
11421 @itemx info dos idt
11422 These 3 commands display entries from, respectively, Global, Local,
11423 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
11424 tables are data structures which store a descriptor for each segment
11425 that is currently in use. The segment's selector is an index into a
11426 descriptor table; the table entry for that index holds the
11427 descriptor's base address and limit, and its attributes and access
11430 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
11431 segment (used for both data and the stack), and a DOS segment (which
11432 allows access to DOS/BIOS data structures and absolute addresses in
11433 conventional memory). However, the DPMI host will usually define
11434 additional segments in order to support the DPMI environment.
11436 @cindex garbled pointers
11437 These commands allow to display entries from the descriptor tables.
11438 Without an argument, all entries from the specified table are
11439 displayed. An argument, which should be an integer expression, means
11440 display a single entry whose index is given by the argument. For
11441 example, here's a convenient way to display information about the
11442 debugged program's data segment:
11445 @exdent @code{(@value{GDBP}) info dos ldt $ds}
11446 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
11450 This comes in handy when you want to see whether a pointer is outside
11451 the data segment's limit (i.e.@: @dfn{garbled}).
11453 @cindex page tables display (MS-DOS)
11455 @itemx info dos pte
11456 These two commands display entries from, respectively, the Page
11457 Directory and the Page Tables. Page Directories and Page Tables are
11458 data structures which control how virtual memory addresses are mapped
11459 into physical addresses. A Page Table includes an entry for every
11460 page of memory that is mapped into the program's address space; there
11461 may be several Page Tables, each one holding up to 4096 entries. A
11462 Page Directory has up to 4096 entries, one each for every Page Table
11463 that is currently in use.
11465 Without an argument, @kbd{info dos pde} displays the entire Page
11466 Directory, and @kbd{info dos pte} displays all the entries in all of
11467 the Page Tables. An argument, an integer expression, given to the
11468 @kbd{info dos pde} command means display only that entry from the Page
11469 Directory table. An argument given to the @kbd{info dos pte} command
11470 means display entries from a single Page Table, the one pointed to by
11471 the specified entry in the Page Directory.
11473 @cindex direct memory access (DMA) on MS-DOS
11474 These commands are useful when your program uses @dfn{DMA} (Direct
11475 Memory Access), which needs physical addresses to program the DMA
11478 These commands are supported only with some DPMI servers.
11480 @cindex physical address from linear address
11481 @item info dos address-pte @var{addr}
11482 This command displays the Page Table entry for a specified linear
11483 address. The argument linear address @var{addr} should already have the
11484 appropriate segment's base address added to it, because this command
11485 accepts addresses which may belong to @emph{any} segment. For
11486 example, here's how to display the Page Table entry for the page where
11487 the variable @code{i} is stored:
11490 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
11491 @exdent @code{Page Table entry for address 0x11a00d30:}
11492 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
11496 This says that @code{i} is stored at offset @code{0xd30} from the page
11497 whose physical base address is @code{0x02698000}, and prints all the
11498 attributes of that page.
11500 Note that you must cast the addresses of variables to a @code{char *},
11501 since otherwise the value of @code{__djgpp_base_address}, the base
11502 address of all variables and functions in a @sc{djgpp} program, will
11503 be added using the rules of C pointer arithmetics: if @code{i} is
11504 declared an @code{int}, @value{GDBN} will add 4 times the value of
11505 @code{__djgpp_base_address} to the address of @code{i}.
11507 Here's another example, it displays the Page Table entry for the
11511 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
11512 @exdent @code{Page Table entry for address 0x29110:}
11513 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
11517 (The @code{+ 3} offset is because the transfer buffer's address is the
11518 3rd member of the @code{_go32_info_block} structure.) The output of
11519 this command clearly shows that addresses in conventional memory are
11520 mapped 1:1, i.e.@: the physical and linear addresses are identical.
11522 This command is supported only with some DPMI servers.
11525 @node Cygwin Native
11526 @subsection Features for Debugging MS Windows PE executables
11527 @cindex MS Windows debugging
11528 @cindex native Cygwin debugging
11529 @cindex Cygwin-specific commands
11531 @value{GDBN} supports native debugging of MS Windows programs, including
11532 DLLs with and without symbolic debugging information. There are various
11533 additional Cygwin-specific commands, described in this subsection. The
11534 subsubsection @pxref{Non-debug DLL symbols} describes working with DLLs
11535 that have no debugging symbols.
11541 This is a prefix of MS Windows specific commands which print
11542 information about the target system and important OS structures.
11544 @item info w32 selector
11545 This command displays information returned by
11546 the Win32 API @code{GetThreadSelectorEntry} function.
11547 It takes an optional argument that is evaluated to
11548 a long value to give the information about this given selector.
11549 Without argument, this command displays information
11550 about the the six segment registers.
11554 This is a Cygwin specific alias of info shared.
11556 @kindex dll-symbols
11558 This command loads symbols from a dll similarly to
11559 add-sym command but without the need to specify a base address.
11561 @kindex set new-console
11562 @item set new-console @var{mode}
11563 If @var{mode} is @code{on} the debuggee will
11564 be started in a new console on next start.
11565 If @var{mode} is @code{off}i, the debuggee will
11566 be started in the same console as the debugger.
11568 @kindex show new-console
11569 @item show new-console
11570 Displays whether a new console is used
11571 when the debuggee is started.
11573 @kindex set new-group
11574 @item set new-group @var{mode}
11575 This boolean value controls whether the debuggee should
11576 start a new group or stay in the same group as the debugger.
11577 This affects the way the Windows OS handles
11580 @kindex show new-group
11581 @item show new-group
11582 Displays current value of new-group boolean.
11584 @kindex set debugevents
11585 @item set debugevents
11586 This boolean value adds debug output concerning events seen by the debugger.
11588 @kindex set debugexec
11589 @item set debugexec
11590 This boolean value adds debug output concerning execute events
11591 seen by the debugger.
11593 @kindex set debugexceptions
11594 @item set debugexceptions
11595 This boolean value adds debug ouptut concerning exception events
11596 seen by the debugger.
11598 @kindex set debugmemory
11599 @item set debugmemory
11600 This boolean value adds debug ouptut concerning memory events
11601 seen by the debugger.
11605 This boolean values specifies whether the debuggee is called
11606 via a shell or directly (default value is on).
11610 Displays if the debuggee will be started with a shell.
11615 * Non-debug DLL symbols:: Support for DLLs without debugging symbols
11618 @node Non-debug DLL symbols
11619 @subsubsection Support for DLLs without debugging symbols
11620 @cindex DLLs with no debugging symbols
11621 @cindex Minimal symbols and DLLs
11623 Very often on windows, some of the DLLs that your program relies on do
11624 not include symbolic debugging information (for example,
11625 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
11626 symbols in a DLL, it relies on the minimal amount of symbolic
11627 information contained in the DLL's export table. This subsubsection
11628 describes working with such symbols, known internally to @value{GDBN} as
11629 ``minimal symbols''.
11631 Note that before the debugged program has started execution, no DLLs
11632 will have been loaded. The easiest way around this problem is simply to
11633 start the program --- either by setting a breakpoint or letting the
11634 program run once to completion. It is also possible to force
11635 @value{GDBN} to load a particular DLL before starting the executable ---
11636 see the shared library information in @pxref{Files} or the
11637 @code{dll-symbols} command in @pxref{Cygwin Native}. Currently,
11638 explicitly loading symbols from a DLL with no debugging information will
11639 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
11640 which may adversely affect symbol lookup performance.
11642 @subsubsection DLL name prefixes
11644 In keeping with the naming conventions used by the Microsoft debugging
11645 tools, DLL export symbols are made available with a prefix based on the
11646 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
11647 also entered into the symbol table, so @code{CreateFileA} is often
11648 sufficient. In some cases there will be name clashes within a program
11649 (particularly if the executable itself includes full debugging symbols)
11650 necessitating the use of the fully qualified name when referring to the
11651 contents of the DLL. Use single-quotes around the name to avoid the
11652 exclamation mark (``!'') being interpreted as a language operator.
11654 Note that the internal name of the DLL may be all upper-case, even
11655 though the file name of the DLL is lower-case, or vice-versa. Since
11656 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
11657 some confusion. If in doubt, try the @code{info functions} and
11658 @code{info variables} commands or even @code{maint print msymbols} (see
11659 @pxref{Symbols}). Here's an example:
11662 (gdb) info function CreateFileA
11663 All functions matching regular expression "CreateFileA":
11665 Non-debugging symbols:
11666 0x77e885f4 CreateFileA
11667 0x77e885f4 KERNEL32!CreateFileA
11671 (gdb) info function !
11672 All functions matching regular expression "!":
11674 Non-debugging symbols:
11675 0x6100114c cygwin1!__assert
11676 0x61004034 cygwin1!_dll_crt0@@0
11677 0x61004240 cygwin1!dll_crt0(per_process *)
11681 @subsubsection Working with minimal symbols
11683 Symbols extracted from a DLL's export table do not contain very much
11684 type information. All that @value{GDBN} can do is guess whether a symbol
11685 refers to a function or variable depending on the linker section that
11686 contains the symbol. Also note that the actual contents of the memory
11687 contained in a DLL are not available unless the program is running. This
11688 means that you cannot examine the contents of a variable or disassemble
11689 a function within a DLL without a running program.
11691 Variables are generally treated as pointers and dereferenced
11692 automatically. For this reason, it is often necessary to prefix a
11693 variable name with the address-of operator (``&'') and provide explicit
11694 type information in the command. Here's an example of the type of
11698 (gdb) print 'cygwin1!__argv'
11703 (gdb) x 'cygwin1!__argv'
11704 0x10021610: "\230y\""
11707 And two possible solutions:
11710 (gdb) print ((char **)'cygwin1!__argv')[0]
11711 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
11715 (gdb) x/2x &'cygwin1!__argv'
11716 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
11717 (gdb) x/x 0x10021608
11718 0x10021608: 0x0022fd98
11719 (gdb) x/s 0x0022fd98
11720 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
11723 Setting a break point within a DLL is possible even before the program
11724 starts execution. However, under these circumstances, @value{GDBN} can't
11725 examine the initial instructions of the function in order to skip the
11726 function's frame set-up code. You can work around this by using ``*&''
11727 to set the breakpoint at a raw memory address:
11730 (gdb) break *&'python22!PyOS_Readline'
11731 Breakpoint 1 at 0x1e04eff0
11734 The author of these extensions is not entirely convinced that setting a
11735 break point within a shared DLL like @file{kernel32.dll} is completely
11739 @section Embedded Operating Systems
11741 This section describes configurations involving the debugging of
11742 embedded operating systems that are available for several different
11746 * VxWorks:: Using @value{GDBN} with VxWorks
11749 @value{GDBN} includes the ability to debug programs running on
11750 various real-time operating systems.
11753 @subsection Using @value{GDBN} with VxWorks
11759 @kindex target vxworks
11760 @item target vxworks @var{machinename}
11761 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
11762 is the target system's machine name or IP address.
11766 On VxWorks, @code{load} links @var{filename} dynamically on the
11767 current target system as well as adding its symbols in @value{GDBN}.
11769 @value{GDBN} enables developers to spawn and debug tasks running on networked
11770 VxWorks targets from a Unix host. Already-running tasks spawned from
11771 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
11772 both the Unix host and on the VxWorks target. The program
11773 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
11774 installed with the name @code{vxgdb}, to distinguish it from a
11775 @value{GDBN} for debugging programs on the host itself.)
11778 @item VxWorks-timeout @var{args}
11779 @kindex vxworks-timeout
11780 All VxWorks-based targets now support the option @code{vxworks-timeout}.
11781 This option is set by the user, and @var{args} represents the number of
11782 seconds @value{GDBN} waits for responses to rpc's. You might use this if
11783 your VxWorks target is a slow software simulator or is on the far side
11784 of a thin network line.
11787 The following information on connecting to VxWorks was current when
11788 this manual was produced; newer releases of VxWorks may use revised
11791 @kindex INCLUDE_RDB
11792 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
11793 to include the remote debugging interface routines in the VxWorks
11794 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
11795 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
11796 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
11797 source debugging task @code{tRdbTask} when VxWorks is booted. For more
11798 information on configuring and remaking VxWorks, see the manufacturer's
11800 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
11802 Once you have included @file{rdb.a} in your VxWorks system image and set
11803 your Unix execution search path to find @value{GDBN}, you are ready to
11804 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
11805 @code{vxgdb}, depending on your installation).
11807 @value{GDBN} comes up showing the prompt:
11814 * VxWorks Connection:: Connecting to VxWorks
11815 * VxWorks Download:: VxWorks download
11816 * VxWorks Attach:: Running tasks
11819 @node VxWorks Connection
11820 @subsubsection Connecting to VxWorks
11822 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
11823 network. To connect to a target whose host name is ``@code{tt}'', type:
11826 (vxgdb) target vxworks tt
11830 @value{GDBN} displays messages like these:
11833 Attaching remote machine across net...
11838 @value{GDBN} then attempts to read the symbol tables of any object modules
11839 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
11840 these files by searching the directories listed in the command search
11841 path (@pxref{Environment, ,Your program's environment}); if it fails
11842 to find an object file, it displays a message such as:
11845 prog.o: No such file or directory.
11848 When this happens, add the appropriate directory to the search path with
11849 the @value{GDBN} command @code{path}, and execute the @code{target}
11852 @node VxWorks Download
11853 @subsubsection VxWorks download
11855 @cindex download to VxWorks
11856 If you have connected to the VxWorks target and you want to debug an
11857 object that has not yet been loaded, you can use the @value{GDBN}
11858 @code{load} command to download a file from Unix to VxWorks
11859 incrementally. The object file given as an argument to the @code{load}
11860 command is actually opened twice: first by the VxWorks target in order
11861 to download the code, then by @value{GDBN} in order to read the symbol
11862 table. This can lead to problems if the current working directories on
11863 the two systems differ. If both systems have NFS mounted the same
11864 filesystems, you can avoid these problems by using absolute paths.
11865 Otherwise, it is simplest to set the working directory on both systems
11866 to the directory in which the object file resides, and then to reference
11867 the file by its name, without any path. For instance, a program
11868 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
11869 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
11870 program, type this on VxWorks:
11873 -> cd "@var{vxpath}/vw/demo/rdb"
11877 Then, in @value{GDBN}, type:
11880 (vxgdb) cd @var{hostpath}/vw/demo/rdb
11881 (vxgdb) load prog.o
11884 @value{GDBN} displays a response similar to this:
11887 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
11890 You can also use the @code{load} command to reload an object module
11891 after editing and recompiling the corresponding source file. Note that
11892 this makes @value{GDBN} delete all currently-defined breakpoints,
11893 auto-displays, and convenience variables, and to clear the value
11894 history. (This is necessary in order to preserve the integrity of
11895 debugger's data structures that reference the target system's symbol
11898 @node VxWorks Attach
11899 @subsubsection Running tasks
11901 @cindex running VxWorks tasks
11902 You can also attach to an existing task using the @code{attach} command as
11906 (vxgdb) attach @var{task}
11910 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
11911 or suspended when you attach to it. Running tasks are suspended at
11912 the time of attachment.
11914 @node Embedded Processors
11915 @section Embedded Processors
11917 This section goes into details specific to particular embedded
11923 * H8/300:: Renesas H8/300
11924 * H8/500:: Renesas H8/500
11925 * M32R/D:: Renesas M32R/D
11926 * M68K:: Motorola M68K
11927 * MIPS Embedded:: MIPS Embedded
11928 * OpenRISC 1000:: OpenRisc 1000
11929 * PA:: HP PA Embedded
11932 * Sparclet:: Tsqware Sparclet
11933 * Sparclite:: Fujitsu Sparclite
11934 * ST2000:: Tandem ST2000
11935 * Z8000:: Zilog Z8000
11944 @item target rdi @var{dev}
11945 ARM Angel monitor, via RDI library interface to ADP protocol. You may
11946 use this target to communicate with both boards running the Angel
11947 monitor, or with the EmbeddedICE JTAG debug device.
11950 @item target rdp @var{dev}
11956 @subsection Renesas H8/300
11960 @kindex target hms@r{, with H8/300}
11961 @item target hms @var{dev}
11962 A Renesas SH, H8/300, or H8/500 board, attached via serial line to your host.
11963 Use special commands @code{device} and @code{speed} to control the serial
11964 line and the communications speed used.
11966 @kindex target e7000@r{, with H8/300}
11967 @item target e7000 @var{dev}
11968 E7000 emulator for Renesas H8 and SH.
11970 @kindex target sh3@r{, with H8/300}
11971 @kindex target sh3e@r{, with H8/300}
11972 @item target sh3 @var{dev}
11973 @itemx target sh3e @var{dev}
11974 Renesas SH-3 and SH-3E target systems.
11978 @cindex download to H8/300 or H8/500
11979 @cindex H8/300 or H8/500 download
11980 @cindex download to Renesas SH
11981 @cindex Renesas SH download
11982 When you select remote debugging to a Renesas SH, H8/300, or H8/500
11983 board, the @code{load} command downloads your program to the Renesas
11984 board and also opens it as the current executable target for
11985 @value{GDBN} on your host (like the @code{file} command).
11987 @value{GDBN} needs to know these things to talk to your
11988 Renesas SH, H8/300, or H8/500:
11992 that you want to use @samp{target hms}, the remote debugging interface
11993 for Renesas microprocessors, or @samp{target e7000}, the in-circuit
11994 emulator for the Renesas SH and the Renesas 300H. (@samp{target hms} is
11995 the default when @value{GDBN} is configured specifically for the Renesas SH,
11996 H8/300, or H8/500.)
11999 what serial device connects your host to your Renesas board (the first
12000 serial device available on your host is the default).
12003 what speed to use over the serial device.
12007 * Renesas Boards:: Connecting to Renesas boards.
12008 * Renesas ICE:: Using the E7000 In-Circuit Emulator.
12009 * Renesas Special:: Special @value{GDBN} commands for Renesas micros.
12012 @node Renesas Boards
12013 @subsubsection Connecting to Renesas boards
12015 @c only for Unix hosts
12017 @cindex serial device, Renesas micros
12018 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
12019 need to explicitly set the serial device. The default @var{port} is the
12020 first available port on your host. This is only necessary on Unix
12021 hosts, where it is typically something like @file{/dev/ttya}.
12024 @cindex serial line speed, Renesas micros
12025 @code{@value{GDBN}} has another special command to set the communications
12026 speed: @samp{speed @var{bps}}. This command also is only used from Unix
12027 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
12028 the DOS @code{mode} command (for instance,
12029 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
12031 The @samp{device} and @samp{speed} commands are available only when you
12032 use a Unix host to debug your Renesas microprocessor programs. If you
12034 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
12035 called @code{asynctsr} to communicate with the development board
12036 through a PC serial port. You must also use the DOS @code{mode} command
12037 to set up the serial port on the DOS side.
12039 The following sample session illustrates the steps needed to start a
12040 program under @value{GDBN} control on an H8/300. The example uses a
12041 sample H8/300 program called @file{t.x}. The procedure is the same for
12042 the Renesas SH and the H8/500.
12044 First hook up your development board. In this example, we use a
12045 board attached to serial port @code{COM2}; if you use a different serial
12046 port, substitute its name in the argument of the @code{mode} command.
12047 When you call @code{asynctsr}, the auxiliary comms program used by the
12048 debugger, you give it just the numeric part of the serial port's name;
12049 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
12053 C:\H8300\TEST> asynctsr 2
12054 C:\H8300\TEST> mode com2:9600,n,8,1,p
12056 Resident portion of MODE loaded
12058 COM2: 9600, n, 8, 1, p
12063 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
12064 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
12065 disable it, or even boot without it, to use @code{asynctsr} to control
12066 your development board.
12069 @kindex target hms@r{, and serial protocol}
12070 Now that serial communications are set up, and the development board is
12071 connected, you can start up @value{GDBN}. Call @code{@value{GDBP}} with
12072 the name of your program as the argument. @code{@value{GDBN}} prompts
12073 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
12074 commands to begin your debugging session: @samp{target hms} to specify
12075 cross-debugging to the Renesas board, and the @code{load} command to
12076 download your program to the board. @code{load} displays the names of
12077 the program's sections, and a @samp{*} for each 2K of data downloaded.
12078 (If you want to refresh @value{GDBN} data on symbols or on the
12079 executable file without downloading, use the @value{GDBN} commands
12080 @code{file} or @code{symbol-file}. These commands, and @code{load}
12081 itself, are described in @ref{Files,,Commands to specify files}.)
12084 (eg-C:\H8300\TEST) @value{GDBP} t.x
12085 @value{GDBN} is free software and you are welcome to distribute copies
12086 of it under certain conditions; type "show copying" to see
12088 There is absolutely no warranty for @value{GDBN}; type "show warranty"
12090 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
12091 (@value{GDBP}) target hms
12092 Connected to remote H8/300 HMS system.
12093 (@value{GDBP}) load t.x
12094 .text : 0x8000 .. 0xabde ***********
12095 .data : 0xabde .. 0xad30 *
12096 .stack : 0xf000 .. 0xf014 *
12099 At this point, you're ready to run or debug your program. From here on,
12100 you can use all the usual @value{GDBN} commands. The @code{break} command
12101 sets breakpoints; the @code{run} command starts your program;
12102 @code{print} or @code{x} display data; the @code{continue} command
12103 resumes execution after stopping at a breakpoint. You can use the
12104 @code{help} command at any time to find out more about @value{GDBN} commands.
12106 Remember, however, that @emph{operating system} facilities aren't
12107 available on your development board; for example, if your program hangs,
12108 you can't send an interrupt---but you can press the @sc{reset} switch!
12110 Use the @sc{reset} button on the development board
12113 to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has
12114 no way to pass an interrupt signal to the development board); and
12117 to return to the @value{GDBN} command prompt after your program finishes
12118 normally. The communications protocol provides no other way for @value{GDBN}
12119 to detect program completion.
12122 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
12123 development board as a ``normal exit'' of your program.
12126 @subsubsection Using the E7000 in-circuit emulator
12128 @kindex target e7000@r{, with Renesas ICE}
12129 You can use the E7000 in-circuit emulator to develop code for either the
12130 Renesas SH or the H8/300H. Use one of these forms of the @samp{target
12131 e7000} command to connect @value{GDBN} to your E7000:
12134 @item target e7000 @var{port} @var{speed}
12135 Use this form if your E7000 is connected to a serial port. The
12136 @var{port} argument identifies what serial port to use (for example,
12137 @samp{com2}). The third argument is the line speed in bits per second
12138 (for example, @samp{9600}).
12140 @item target e7000 @var{hostname}
12141 If your E7000 is installed as a host on a TCP/IP network, you can just
12142 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
12145 @node Renesas Special
12146 @subsubsection Special @value{GDBN} commands for Renesas micros
12148 Some @value{GDBN} commands are available only for the H8/300:
12152 @kindex set machine
12153 @kindex show machine
12154 @item set machine h8300
12155 @itemx set machine h8300h
12156 Condition @value{GDBN} for one of the two variants of the H8/300
12157 architecture with @samp{set machine}. You can use @samp{show machine}
12158 to check which variant is currently in effect.
12167 @kindex set memory @var{mod}
12168 @cindex memory models, H8/500
12169 @item set memory @var{mod}
12171 Specify which H8/500 memory model (@var{mod}) you are using with
12172 @samp{set memory}; check which memory model is in effect with @samp{show
12173 memory}. The accepted values for @var{mod} are @code{small},
12174 @code{big}, @code{medium}, and @code{compact}.
12179 @subsection Renesas M32R/D
12183 @kindex target m32r
12184 @item target m32r @var{dev}
12185 Renesas M32R/D ROM monitor.
12187 @kindex target m32rsdi
12188 @item target m32rsdi @var{dev}
12189 Renesas M32R SDI server, connected via parallel port to the board.
12196 The Motorola m68k configuration includes ColdFire support, and
12197 target command for the following ROM monitors.
12201 @kindex target abug
12202 @item target abug @var{dev}
12203 ABug ROM monitor for M68K.
12205 @kindex target cpu32bug
12206 @item target cpu32bug @var{dev}
12207 CPU32BUG monitor, running on a CPU32 (M68K) board.
12209 @kindex target dbug
12210 @item target dbug @var{dev}
12211 dBUG ROM monitor for Motorola ColdFire.
12214 @item target est @var{dev}
12215 EST-300 ICE monitor, running on a CPU32 (M68K) board.
12217 @kindex target rom68k
12218 @item target rom68k @var{dev}
12219 ROM 68K monitor, running on an M68K IDP board.
12225 @kindex target rombug
12226 @item target rombug @var{dev}
12227 ROMBUG ROM monitor for OS/9000.
12231 @node MIPS Embedded
12232 @subsection MIPS Embedded
12234 @cindex MIPS boards
12235 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
12236 MIPS board attached to a serial line. This is available when
12237 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
12240 Use these @value{GDBN} commands to specify the connection to your target board:
12243 @item target mips @var{port}
12244 @kindex target mips @var{port}
12245 To run a program on the board, start up @code{@value{GDBP}} with the
12246 name of your program as the argument. To connect to the board, use the
12247 command @samp{target mips @var{port}}, where @var{port} is the name of
12248 the serial port connected to the board. If the program has not already
12249 been downloaded to the board, you may use the @code{load} command to
12250 download it. You can then use all the usual @value{GDBN} commands.
12252 For example, this sequence connects to the target board through a serial
12253 port, and loads and runs a program called @var{prog} through the
12257 host$ @value{GDBP} @var{prog}
12258 @value{GDBN} is free software and @dots{}
12259 (@value{GDBP}) target mips /dev/ttyb
12260 (@value{GDBP}) load @var{prog}
12264 @item target mips @var{hostname}:@var{portnumber}
12265 On some @value{GDBN} host configurations, you can specify a TCP
12266 connection (for instance, to a serial line managed by a terminal
12267 concentrator) instead of a serial port, using the syntax
12268 @samp{@var{hostname}:@var{portnumber}}.
12270 @item target pmon @var{port}
12271 @kindex target pmon @var{port}
12274 @item target ddb @var{port}
12275 @kindex target ddb @var{port}
12276 NEC's DDB variant of PMON for Vr4300.
12278 @item target lsi @var{port}
12279 @kindex target lsi @var{port}
12280 LSI variant of PMON.
12282 @kindex target r3900
12283 @item target r3900 @var{dev}
12284 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
12286 @kindex target array
12287 @item target array @var{dev}
12288 Array Tech LSI33K RAID controller board.
12294 @value{GDBN} also supports these special commands for MIPS targets:
12297 @item set processor @var{args}
12298 @itemx show processor
12299 @kindex set processor @var{args}
12300 @kindex show processor
12301 Use the @code{set processor} command to set the type of MIPS
12302 processor when you want to access processor-type-specific registers.
12303 For example, @code{set processor @var{r3041}} tells @value{GDBN}
12304 to use the CPU registers appropriate for the 3041 chip.
12305 Use the @code{show processor} command to see what MIPS processor @value{GDBN}
12306 is using. Use the @code{info reg} command to see what registers
12307 @value{GDBN} is using.
12309 @item set mipsfpu double
12310 @itemx set mipsfpu single
12311 @itemx set mipsfpu none
12312 @itemx show mipsfpu
12313 @kindex set mipsfpu
12314 @kindex show mipsfpu
12315 @cindex MIPS remote floating point
12316 @cindex floating point, MIPS remote
12317 If your target board does not support the MIPS floating point
12318 coprocessor, you should use the command @samp{set mipsfpu none} (if you
12319 need this, you may wish to put the command in your @value{GDBN} init
12320 file). This tells @value{GDBN} how to find the return value of
12321 functions which return floating point values. It also allows
12322 @value{GDBN} to avoid saving the floating point registers when calling
12323 functions on the board. If you are using a floating point coprocessor
12324 with only single precision floating point support, as on the @sc{r4650}
12325 processor, use the command @samp{set mipsfpu single}. The default
12326 double precision floating point coprocessor may be selected using
12327 @samp{set mipsfpu double}.
12329 In previous versions the only choices were double precision or no
12330 floating point, so @samp{set mipsfpu on} will select double precision
12331 and @samp{set mipsfpu off} will select no floating point.
12333 As usual, you can inquire about the @code{mipsfpu} variable with
12334 @samp{show mipsfpu}.
12336 @item set remotedebug @var{n}
12337 @itemx show remotedebug
12338 @kindex set remotedebug@r{, MIPS protocol}
12339 @kindex show remotedebug@r{, MIPS protocol}
12340 @cindex @code{remotedebug}, MIPS protocol
12341 @cindex MIPS @code{remotedebug} protocol
12342 @c FIXME! For this to be useful, you must know something about the MIPS
12343 @c FIXME...protocol. Where is it described?
12344 You can see some debugging information about communications with the board
12345 by setting the @code{remotedebug} variable. If you set it to @code{1} using
12346 @samp{set remotedebug 1}, every packet is displayed. If you set it
12347 to @code{2}, every character is displayed. You can check the current value
12348 at any time with the command @samp{show remotedebug}.
12350 @item set timeout @var{seconds}
12351 @itemx set retransmit-timeout @var{seconds}
12352 @itemx show timeout
12353 @itemx show retransmit-timeout
12354 @cindex @code{timeout}, MIPS protocol
12355 @cindex @code{retransmit-timeout}, MIPS protocol
12356 @kindex set timeout
12357 @kindex show timeout
12358 @kindex set retransmit-timeout
12359 @kindex show retransmit-timeout
12360 You can control the timeout used while waiting for a packet, in the MIPS
12361 remote protocol, with the @code{set timeout @var{seconds}} command. The
12362 default is 5 seconds. Similarly, you can control the timeout used while
12363 waiting for an acknowledgement of a packet with the @code{set
12364 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
12365 You can inspect both values with @code{show timeout} and @code{show
12366 retransmit-timeout}. (These commands are @emph{only} available when
12367 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
12369 The timeout set by @code{set timeout} does not apply when @value{GDBN}
12370 is waiting for your program to stop. In that case, @value{GDBN} waits
12371 forever because it has no way of knowing how long the program is going
12372 to run before stopping.
12375 @node OpenRISC 1000
12376 @subsection OpenRISC 1000
12377 @cindex OpenRISC 1000
12379 @cindex or1k boards
12380 See OR1k Architecture document (@uref{www.opencores.org}) for more information
12381 about platform and commands.
12385 @kindex target jtag
12386 @item target jtag jtag://@var{host}:@var{port}
12388 Connects to remote JTAG server.
12389 JTAG remote server can be either an or1ksim or JTAG server,
12390 connected via parallel port to the board.
12392 Example: @code{target jtag jtag://localhost:9999}
12395 @item or1ksim @var{command}
12396 If connected to @code{or1ksim} OpenRISC 1000 Architectural
12397 Simulator, proprietary commands can be executed.
12399 @kindex info or1k spr
12400 @item info or1k spr
12401 Displays spr groups.
12403 @item info or1k spr @var{group}
12404 @itemx info or1k spr @var{groupno}
12405 Displays register names in selected group.
12407 @item info or1k spr @var{group} @var{register}
12408 @itemx info or1k spr @var{register}
12409 @itemx info or1k spr @var{groupno} @var{registerno}
12410 @itemx info or1k spr @var{registerno}
12411 Shows information about specified spr register.
12414 @item spr @var{group} @var{register} @var{value}
12415 @itemx spr @var{register @var{value}}
12416 @itemx spr @var{groupno} @var{registerno @var{value}}
12417 @itemx spr @var{registerno @var{value}}
12418 Writes @var{value} to specified spr register.
12421 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
12422 It is very similar to @value{GDBN} trace, except it does not interfere with normal
12423 program execution and is thus much faster. Hardware breakpoints/watchpoint
12424 triggers can be set using:
12427 Load effective address/data
12429 Store effective address/data
12431 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
12436 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
12437 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
12439 @code{htrace} commands:
12440 @cindex OpenRISC 1000 htrace
12443 @item hwatch @var{conditional}
12444 Set hardware watchpoint on combination of Load/Store Effecive Address(es)
12445 or Data. For example:
12447 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
12449 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
12451 @kindex htrace info
12453 Display information about current HW trace configuration.
12455 @kindex htrace trigger
12456 @item htrace trigger @var{conditional}
12457 Set starting criteria for HW trace.
12459 @kindex htrace qualifier
12460 @item htrace qualifier @var{conditional}
12461 Set acquisition qualifier for HW trace.
12463 @kindex htrace stop
12464 @item htrace stop @var{conditional}
12465 Set HW trace stopping criteria.
12467 @kindex htrace record
12468 @item htrace record [@var{data}]*
12469 Selects the data to be recorded, when qualifier is met and HW trace was
12472 @kindex htrace enable
12473 @item htrace enable
12474 @kindex htrace disable
12475 @itemx htrace disable
12476 Enables/disables the HW trace.
12478 @kindex htrace rewind
12479 @item htrace rewind [@var{filename}]
12480 Clears currently recorded trace data.
12482 If filename is specified, new trace file is made and any newly collected data
12483 will be written there.
12485 @kindex htrace print
12486 @item htrace print [@var{start} [@var{len}]]
12487 Prints trace buffer, using current record configuration.
12489 @kindex htrace mode continuous
12490 @item htrace mode continuous
12491 Set continuous trace mode.
12493 @kindex htrace mode suspend
12494 @item htrace mode suspend
12495 Set suspend trace mode.
12500 @subsection PowerPC
12504 @kindex target dink32
12505 @item target dink32 @var{dev}
12506 DINK32 ROM monitor.
12508 @kindex target ppcbug
12509 @item target ppcbug @var{dev}
12510 @kindex target ppcbug1
12511 @item target ppcbug1 @var{dev}
12512 PPCBUG ROM monitor for PowerPC.
12515 @item target sds @var{dev}
12516 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
12521 @subsection HP PA Embedded
12525 @kindex target op50n
12526 @item target op50n @var{dev}
12527 OP50N monitor, running on an OKI HPPA board.
12529 @kindex target w89k
12530 @item target w89k @var{dev}
12531 W89K monitor, running on a Winbond HPPA board.
12536 @subsection Renesas SH
12540 @kindex target hms@r{, with Renesas SH}
12541 @item target hms @var{dev}
12542 A Renesas SH board attached via serial line to your host. Use special
12543 commands @code{device} and @code{speed} to control the serial line and
12544 the communications speed used.
12546 @kindex target e7000@r{, with Renesas SH}
12547 @item target e7000 @var{dev}
12548 E7000 emulator for Renesas SH.
12550 @kindex target sh3@r{, with SH}
12551 @kindex target sh3e@r{, with SH}
12552 @item target sh3 @var{dev}
12553 @item target sh3e @var{dev}
12554 Renesas SH-3 and SH-3E target systems.
12559 @subsection Tsqware Sparclet
12563 @value{GDBN} enables developers to debug tasks running on
12564 Sparclet targets from a Unix host.
12565 @value{GDBN} uses code that runs on
12566 both the Unix host and on the Sparclet target. The program
12567 @code{@value{GDBP}} is installed and executed on the Unix host.
12570 @item remotetimeout @var{args}
12571 @kindex remotetimeout
12572 @value{GDBN} supports the option @code{remotetimeout}.
12573 This option is set by the user, and @var{args} represents the number of
12574 seconds @value{GDBN} waits for responses.
12577 @cindex compiling, on Sparclet
12578 When compiling for debugging, include the options @samp{-g} to get debug
12579 information and @samp{-Ttext} to relocate the program to where you wish to
12580 load it on the target. You may also want to add the options @samp{-n} or
12581 @samp{-N} in order to reduce the size of the sections. Example:
12584 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
12587 You can use @code{objdump} to verify that the addresses are what you intended:
12590 sparclet-aout-objdump --headers --syms prog
12593 @cindex running, on Sparclet
12595 your Unix execution search path to find @value{GDBN}, you are ready to
12596 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
12597 (or @code{sparclet-aout-gdb}, depending on your installation).
12599 @value{GDBN} comes up showing the prompt:
12606 * Sparclet File:: Setting the file to debug
12607 * Sparclet Connection:: Connecting to Sparclet
12608 * Sparclet Download:: Sparclet download
12609 * Sparclet Execution:: Running and debugging
12612 @node Sparclet File
12613 @subsubsection Setting file to debug
12615 The @value{GDBN} command @code{file} lets you choose with program to debug.
12618 (gdbslet) file prog
12622 @value{GDBN} then attempts to read the symbol table of @file{prog}.
12623 @value{GDBN} locates
12624 the file by searching the directories listed in the command search
12626 If the file was compiled with debug information (option "-g"), source
12627 files will be searched as well.
12628 @value{GDBN} locates
12629 the source files by searching the directories listed in the directory search
12630 path (@pxref{Environment, ,Your program's environment}).
12632 to find a file, it displays a message such as:
12635 prog: No such file or directory.
12638 When this happens, add the appropriate directories to the search paths with
12639 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
12640 @code{target} command again.
12642 @node Sparclet Connection
12643 @subsubsection Connecting to Sparclet
12645 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
12646 To connect to a target on serial port ``@code{ttya}'', type:
12649 (gdbslet) target sparclet /dev/ttya
12650 Remote target sparclet connected to /dev/ttya
12651 main () at ../prog.c:3
12655 @value{GDBN} displays messages like these:
12661 @node Sparclet Download
12662 @subsubsection Sparclet download
12664 @cindex download to Sparclet
12665 Once connected to the Sparclet target,
12666 you can use the @value{GDBN}
12667 @code{load} command to download the file from the host to the target.
12668 The file name and load offset should be given as arguments to the @code{load}
12670 Since the file format is aout, the program must be loaded to the starting
12671 address. You can use @code{objdump} to find out what this value is. The load
12672 offset is an offset which is added to the VMA (virtual memory address)
12673 of each of the file's sections.
12674 For instance, if the program
12675 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
12676 and bss at 0x12010170, in @value{GDBN}, type:
12679 (gdbslet) load prog 0x12010000
12680 Loading section .text, size 0xdb0 vma 0x12010000
12683 If the code is loaded at a different address then what the program was linked
12684 to, you may need to use the @code{section} and @code{add-symbol-file} commands
12685 to tell @value{GDBN} where to map the symbol table.
12687 @node Sparclet Execution
12688 @subsubsection Running and debugging
12690 @cindex running and debugging Sparclet programs
12691 You can now begin debugging the task using @value{GDBN}'s execution control
12692 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
12693 manual for the list of commands.
12697 Breakpoint 1 at 0x12010000: file prog.c, line 3.
12699 Starting program: prog
12700 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
12701 3 char *symarg = 0;
12703 4 char *execarg = "hello!";
12708 @subsection Fujitsu Sparclite
12712 @kindex target sparclite
12713 @item target sparclite @var{dev}
12714 Fujitsu sparclite boards, used only for the purpose of loading.
12715 You must use an additional command to debug the program.
12716 For example: target remote @var{dev} using @value{GDBN} standard
12722 @subsection Tandem ST2000
12724 @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
12727 To connect your ST2000 to the host system, see the manufacturer's
12728 manual. Once the ST2000 is physically attached, you can run:
12731 target st2000 @var{dev} @var{speed}
12735 to establish it as your debugging environment. @var{dev} is normally
12736 the name of a serial device, such as @file{/dev/ttya}, connected to the
12737 ST2000 via a serial line. You can instead specify @var{dev} as a TCP
12738 connection (for example, to a serial line attached via a terminal
12739 concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
12741 The @code{load} and @code{attach} commands are @emph{not} defined for
12742 this target; you must load your program into the ST2000 as you normally
12743 would for standalone operation. @value{GDBN} reads debugging information
12744 (such as symbols) from a separate, debugging version of the program
12745 available on your host computer.
12746 @c FIXME!! This is terribly vague; what little content is here is
12747 @c basically hearsay.
12749 @cindex ST2000 auxiliary commands
12750 These auxiliary @value{GDBN} commands are available to help you with the ST2000
12754 @item st2000 @var{command}
12755 @kindex st2000 @var{cmd}
12756 @cindex STDBUG commands (ST2000)
12757 @cindex commands to STDBUG (ST2000)
12758 Send a @var{command} to the STDBUG monitor. See the manufacturer's
12759 manual for available commands.
12762 @cindex connect (to STDBUG)
12763 Connect the controlling terminal to the STDBUG command monitor. When
12764 you are done interacting with STDBUG, typing either of two character
12765 sequences gets you back to the @value{GDBN} command prompt:
12766 @kbd{@key{RET}~.} (Return, followed by tilde and period) or
12767 @kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D).
12771 @subsection Zilog Z8000
12774 @cindex simulator, Z8000
12775 @cindex Zilog Z8000 simulator
12777 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
12780 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
12781 unsegmented variant of the Z8000 architecture) or the Z8001 (the
12782 segmented variant). The simulator recognizes which architecture is
12783 appropriate by inspecting the object code.
12786 @item target sim @var{args}
12788 @kindex target sim@r{, with Z8000}
12789 Debug programs on a simulated CPU. If the simulator supports setup
12790 options, specify them via @var{args}.
12794 After specifying this target, you can debug programs for the simulated
12795 CPU in the same style as programs for your host computer; use the
12796 @code{file} command to load a new program image, the @code{run} command
12797 to run your program, and so on.
12799 As well as making available all the usual machine registers
12800 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
12801 additional items of information as specially named registers:
12806 Counts clock-ticks in the simulator.
12809 Counts instructions run in the simulator.
12812 Execution time in 60ths of a second.
12816 You can refer to these values in @value{GDBN} expressions with the usual
12817 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
12818 conditional breakpoint that suspends only after at least 5000
12819 simulated clock ticks.
12821 @node Architectures
12822 @section Architectures
12824 This section describes characteristics of architectures that affect
12825 all uses of @value{GDBN} with the architecture, both native and cross.
12838 @kindex set rstack_high_address
12839 @cindex AMD 29K register stack
12840 @cindex register stack, AMD29K
12841 @item set rstack_high_address @var{address}
12842 On AMD 29000 family processors, registers are saved in a separate
12843 @dfn{register stack}. There is no way for @value{GDBN} to determine the
12844 extent of this stack. Normally, @value{GDBN} just assumes that the
12845 stack is ``large enough''. This may result in @value{GDBN} referencing
12846 memory locations that do not exist. If necessary, you can get around
12847 this problem by specifying the ending address of the register stack with
12848 the @code{set rstack_high_address} command. The argument should be an
12849 address, which you probably want to precede with @samp{0x} to specify in
12852 @kindex show rstack_high_address
12853 @item show rstack_high_address
12854 Display the current limit of the register stack, on AMD 29000 family
12862 See the following section.
12867 @cindex stack on Alpha
12868 @cindex stack on MIPS
12869 @cindex Alpha stack
12871 Alpha- and MIPS-based computers use an unusual stack frame, which
12872 sometimes requires @value{GDBN} to search backward in the object code to
12873 find the beginning of a function.
12875 @cindex response time, MIPS debugging
12876 To improve response time (especially for embedded applications, where
12877 @value{GDBN} may be restricted to a slow serial line for this search)
12878 you may want to limit the size of this search, using one of these
12882 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
12883 @item set heuristic-fence-post @var{limit}
12884 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
12885 search for the beginning of a function. A value of @var{0} (the
12886 default) means there is no limit. However, except for @var{0}, the
12887 larger the limit the more bytes @code{heuristic-fence-post} must search
12888 and therefore the longer it takes to run.
12890 @item show heuristic-fence-post
12891 Display the current limit.
12895 These commands are available @emph{only} when @value{GDBN} is configured
12896 for debugging programs on Alpha or MIPS processors.
12899 @node Controlling GDB
12900 @chapter Controlling @value{GDBN}
12902 You can alter the way @value{GDBN} interacts with you by using the
12903 @code{set} command. For commands controlling how @value{GDBN} displays
12904 data, see @ref{Print Settings, ,Print settings}. Other settings are
12909 * Editing:: Command editing
12910 * History:: Command history
12911 * Screen Size:: Screen size
12912 * Numbers:: Numbers
12913 * ABI:: Configuring the current ABI
12914 * Messages/Warnings:: Optional warnings and messages
12915 * Debugging Output:: Optional messages about internal happenings
12923 @value{GDBN} indicates its readiness to read a command by printing a string
12924 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
12925 can change the prompt string with the @code{set prompt} command. For
12926 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
12927 the prompt in one of the @value{GDBN} sessions so that you can always tell
12928 which one you are talking to.
12930 @emph{Note:} @code{set prompt} does not add a space for you after the
12931 prompt you set. This allows you to set a prompt which ends in a space
12932 or a prompt that does not.
12936 @item set prompt @var{newprompt}
12937 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
12939 @kindex show prompt
12941 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
12945 @section Command editing
12947 @cindex command line editing
12949 @value{GDBN} reads its input commands via the @dfn{readline} interface. This
12950 @sc{gnu} library provides consistent behavior for programs which provide a
12951 command line interface to the user. Advantages are @sc{gnu} Emacs-style
12952 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
12953 substitution, and a storage and recall of command history across
12954 debugging sessions.
12956 You may control the behavior of command line editing in @value{GDBN} with the
12957 command @code{set}.
12960 @kindex set editing
12963 @itemx set editing on
12964 Enable command line editing (enabled by default).
12966 @item set editing off
12967 Disable command line editing.
12969 @kindex show editing
12971 Show whether command line editing is enabled.
12975 @section Command history
12977 @value{GDBN} can keep track of the commands you type during your
12978 debugging sessions, so that you can be certain of precisely what
12979 happened. Use these commands to manage the @value{GDBN} command
12983 @cindex history substitution
12984 @cindex history file
12985 @kindex set history filename
12986 @kindex GDBHISTFILE
12987 @item set history filename @var{fname}
12988 Set the name of the @value{GDBN} command history file to @var{fname}.
12989 This is the file where @value{GDBN} reads an initial command history
12990 list, and where it writes the command history from this session when it
12991 exits. You can access this list through history expansion or through
12992 the history command editing characters listed below. This file defaults
12993 to the value of the environment variable @code{GDBHISTFILE}, or to
12994 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
12997 @cindex history save
12998 @kindex set history save
12999 @item set history save
13000 @itemx set history save on
13001 Record command history in a file, whose name may be specified with the
13002 @code{set history filename} command. By default, this option is disabled.
13004 @item set history save off
13005 Stop recording command history in a file.
13007 @cindex history size
13008 @kindex set history size
13009 @item set history size @var{size}
13010 Set the number of commands which @value{GDBN} keeps in its history list.
13011 This defaults to the value of the environment variable
13012 @code{HISTSIZE}, or to 256 if this variable is not set.
13015 @cindex history expansion
13016 History expansion assigns special meaning to the character @kbd{!}.
13017 @ifset have-readline-appendices
13018 @xref{Event Designators}.
13021 Since @kbd{!} is also the logical not operator in C, history expansion
13022 is off by default. If you decide to enable history expansion with the
13023 @code{set history expansion on} command, you may sometimes need to
13024 follow @kbd{!} (when it is used as logical not, in an expression) with
13025 a space or a tab to prevent it from being expanded. The readline
13026 history facilities do not attempt substitution on the strings
13027 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
13029 The commands to control history expansion are:
13032 @kindex set history expansion
13033 @item set history expansion on
13034 @itemx set history expansion
13035 Enable history expansion. History expansion is off by default.
13037 @item set history expansion off
13038 Disable history expansion.
13040 The readline code comes with more complete documentation of
13041 editing and history expansion features. Users unfamiliar with @sc{gnu} Emacs
13042 or @code{vi} may wish to read it.
13043 @ifset have-readline-appendices
13044 @xref{Command Line Editing}.
13048 @kindex show history
13050 @itemx show history filename
13051 @itemx show history save
13052 @itemx show history size
13053 @itemx show history expansion
13054 These commands display the state of the @value{GDBN} history parameters.
13055 @code{show history} by itself displays all four states.
13061 @item show commands
13062 Display the last ten commands in the command history.
13064 @item show commands @var{n}
13065 Print ten commands centered on command number @var{n}.
13067 @item show commands +
13068 Print ten commands just after the commands last printed.
13072 @section Screen size
13073 @cindex size of screen
13074 @cindex pauses in output
13076 Certain commands to @value{GDBN} may produce large amounts of
13077 information output to the screen. To help you read all of it,
13078 @value{GDBN} pauses and asks you for input at the end of each page of
13079 output. Type @key{RET} when you want to continue the output, or @kbd{q}
13080 to discard the remaining output. Also, the screen width setting
13081 determines when to wrap lines of output. Depending on what is being
13082 printed, @value{GDBN} tries to break the line at a readable place,
13083 rather than simply letting it overflow onto the following line.
13085 Normally @value{GDBN} knows the size of the screen from the terminal
13086 driver software. For example, on Unix @value{GDBN} uses the termcap data base
13087 together with the value of the @code{TERM} environment variable and the
13088 @code{stty rows} and @code{stty cols} settings. If this is not correct,
13089 you can override it with the @code{set height} and @code{set
13096 @kindex show height
13097 @item set height @var{lpp}
13099 @itemx set width @var{cpl}
13101 These @code{set} commands specify a screen height of @var{lpp} lines and
13102 a screen width of @var{cpl} characters. The associated @code{show}
13103 commands display the current settings.
13105 If you specify a height of zero lines, @value{GDBN} does not pause during
13106 output no matter how long the output is. This is useful if output is to a
13107 file or to an editor buffer.
13109 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
13110 from wrapping its output.
13115 @cindex number representation
13116 @cindex entering numbers
13118 You can always enter numbers in octal, decimal, or hexadecimal in
13119 @value{GDBN} by the usual conventions: octal numbers begin with
13120 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
13121 begin with @samp{0x}. Numbers that begin with none of these are, by
13122 default, entered in base 10; likewise, the default display for
13123 numbers---when no particular format is specified---is base 10. You can
13124 change the default base for both input and output with the @code{set
13128 @kindex set input-radix
13129 @item set input-radix @var{base}
13130 Set the default base for numeric input. Supported choices
13131 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
13132 specified either unambiguously or using the current default radix; for
13142 sets the base to decimal. On the other hand, @samp{set radix 10}
13143 leaves the radix unchanged no matter what it was.
13145 @kindex set output-radix
13146 @item set output-radix @var{base}
13147 Set the default base for numeric display. Supported choices
13148 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
13149 specified either unambiguously or using the current default radix.
13151 @kindex show input-radix
13152 @item show input-radix
13153 Display the current default base for numeric input.
13155 @kindex show output-radix
13156 @item show output-radix
13157 Display the current default base for numeric display.
13161 @section Configuring the current ABI
13163 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
13164 application automatically. However, sometimes you need to override its
13165 conclusions. Use these commands to manage @value{GDBN}'s view of the
13172 One @value{GDBN} configuration can debug binaries for multiple operating
13173 system targets, either via remote debugging or native emulation.
13174 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
13175 but you can override its conclusion using the @code{set osabi} command.
13176 One example where this is useful is in debugging of binaries which use
13177 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
13178 not have the same identifying marks that the standard C library for your
13183 Show the OS ABI currently in use.
13186 With no argument, show the list of registered available OS ABI's.
13188 @item set osabi @var{abi}
13189 Set the current OS ABI to @var{abi}.
13192 @cindex float promotion
13193 @kindex set coerce-float-to-double
13195 Generally, the way that an argument of type @code{float} is passed to a
13196 function depends on whether the function is prototyped. For a prototyped
13197 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
13198 according to the architecture's convention for @code{float}. For unprototyped
13199 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
13200 @code{double} and then passed.
13202 Unfortunately, some forms of debug information do not reliably indicate whether
13203 a function is prototyped. If @value{GDBN} calls a function that is not marked
13204 as prototyped, it consults @kbd{set coerce-float-to-double}.
13207 @item set coerce-float-to-double
13208 @itemx set coerce-float-to-double on
13209 Arguments of type @code{float} will be promoted to @code{double} when passed
13210 to an unprototyped function. This is the default setting.
13212 @item set coerce-float-to-double off
13213 Arguments of type @code{float} will be passed directly to unprototyped
13218 @kindex show cp-abi
13219 @value{GDBN} needs to know the ABI used for your program's C@t{++}
13220 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
13221 used to build your application. @value{GDBN} only fully supports
13222 programs with a single C@t{++} ABI; if your program contains code using
13223 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
13224 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
13225 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
13226 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
13227 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
13228 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
13233 Show the C@t{++} ABI currently in use.
13236 With no argument, show the list of supported C@t{++} ABI's.
13238 @item set cp-abi @var{abi}
13239 @itemx set cp-abi auto
13240 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
13243 @node Messages/Warnings
13244 @section Optional warnings and messages
13246 By default, @value{GDBN} is silent about its inner workings. If you are
13247 running on a slow machine, you may want to use the @code{set verbose}
13248 command. This makes @value{GDBN} tell you when it does a lengthy
13249 internal operation, so you will not think it has crashed.
13251 Currently, the messages controlled by @code{set verbose} are those
13252 which announce that the symbol table for a source file is being read;
13253 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
13256 @kindex set verbose
13257 @item set verbose on
13258 Enables @value{GDBN} output of certain informational messages.
13260 @item set verbose off
13261 Disables @value{GDBN} output of certain informational messages.
13263 @kindex show verbose
13265 Displays whether @code{set verbose} is on or off.
13268 By default, if @value{GDBN} encounters bugs in the symbol table of an
13269 object file, it is silent; but if you are debugging a compiler, you may
13270 find this information useful (@pxref{Symbol Errors, ,Errors reading
13275 @kindex set complaints
13276 @item set complaints @var{limit}
13277 Permits @value{GDBN} to output @var{limit} complaints about each type of
13278 unusual symbols before becoming silent about the problem. Set
13279 @var{limit} to zero to suppress all complaints; set it to a large number
13280 to prevent complaints from being suppressed.
13282 @kindex show complaints
13283 @item show complaints
13284 Displays how many symbol complaints @value{GDBN} is permitted to produce.
13288 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
13289 lot of stupid questions to confirm certain commands. For example, if
13290 you try to run a program which is already running:
13294 The program being debugged has been started already.
13295 Start it from the beginning? (y or n)
13298 If you are willing to unflinchingly face the consequences of your own
13299 commands, you can disable this ``feature'':
13303 @kindex set confirm
13305 @cindex confirmation
13306 @cindex stupid questions
13307 @item set confirm off
13308 Disables confirmation requests.
13310 @item set confirm on
13311 Enables confirmation requests (the default).
13313 @kindex show confirm
13315 Displays state of confirmation requests.
13319 @node Debugging Output
13320 @section Optional messages about internal happenings
13322 @kindex set debug arch
13323 @item set debug arch
13324 Turns on or off display of gdbarch debugging info. The default is off
13325 @kindex show debug arch
13326 @item show debug arch
13327 Displays the current state of displaying gdbarch debugging info.
13328 @kindex set debug event
13329 @item set debug event
13330 Turns on or off display of @value{GDBN} event debugging info. The
13332 @kindex show debug event
13333 @item show debug event
13334 Displays the current state of displaying @value{GDBN} event debugging
13336 @kindex set debug expression
13337 @item set debug expression
13338 Turns on or off display of @value{GDBN} expression debugging info. The
13340 @kindex show debug expression
13341 @item show debug expression
13342 Displays the current state of displaying @value{GDBN} expression
13344 @kindex set debug frame
13345 @item set debug frame
13346 Turns on or off display of @value{GDBN} frame debugging info. The
13348 @kindex show debug frame
13349 @item show debug frame
13350 Displays the current state of displaying @value{GDBN} frame debugging
13352 @kindex set debug overload
13353 @item set debug overload
13354 Turns on or off display of @value{GDBN} C@t{++} overload debugging
13355 info. This includes info such as ranking of functions, etc. The default
13357 @kindex show debug overload
13358 @item show debug overload
13359 Displays the current state of displaying @value{GDBN} C@t{++} overload
13361 @kindex set debug remote
13362 @cindex packets, reporting on stdout
13363 @cindex serial connections, debugging
13364 @item set debug remote
13365 Turns on or off display of reports on all packets sent back and forth across
13366 the serial line to the remote machine. The info is printed on the
13367 @value{GDBN} standard output stream. The default is off.
13368 @kindex show debug remote
13369 @item show debug remote
13370 Displays the state of display of remote packets.
13371 @kindex set debug serial
13372 @item set debug serial
13373 Turns on or off display of @value{GDBN} serial debugging info. The
13375 @kindex show debug serial
13376 @item show debug serial
13377 Displays the current state of displaying @value{GDBN} serial debugging
13379 @kindex set debug target
13380 @item set debug target
13381 Turns on or off display of @value{GDBN} target debugging info. This info
13382 includes what is going on at the target level of GDB, as it happens. The
13384 @kindex show debug target
13385 @item show debug target
13386 Displays the current state of displaying @value{GDBN} target debugging
13388 @kindex set debug varobj
13389 @item set debug varobj
13390 Turns on or off display of @value{GDBN} variable object debugging
13391 info. The default is off.
13392 @kindex show debug varobj
13393 @item show debug varobj
13394 Displays the current state of displaying @value{GDBN} variable object
13399 @chapter Canned Sequences of Commands
13401 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
13402 command lists}), @value{GDBN} provides two ways to store sequences of
13403 commands for execution as a unit: user-defined commands and command
13407 * Define:: User-defined commands
13408 * Hooks:: User-defined command hooks
13409 * Command Files:: Command files
13410 * Output:: Commands for controlled output
13414 @section User-defined commands
13416 @cindex user-defined command
13417 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
13418 which you assign a new name as a command. This is done with the
13419 @code{define} command. User commands may accept up to 10 arguments
13420 separated by whitespace. Arguments are accessed within the user command
13421 via @var{$arg0@dots{}$arg9}. A trivial example:
13425 print $arg0 + $arg1 + $arg2
13429 To execute the command use:
13436 This defines the command @code{adder}, which prints the sum of
13437 its three arguments. Note the arguments are text substitutions, so they may
13438 reference variables, use complex expressions, or even perform inferior
13444 @item define @var{commandname}
13445 Define a command named @var{commandname}. If there is already a command
13446 by that name, you are asked to confirm that you want to redefine it.
13448 The definition of the command is made up of other @value{GDBN} command lines,
13449 which are given following the @code{define} command. The end of these
13450 commands is marked by a line containing @code{end}.
13455 Takes a single argument, which is an expression to evaluate.
13456 It is followed by a series of commands that are executed
13457 only if the expression is true (nonzero).
13458 There can then optionally be a line @code{else}, followed
13459 by a series of commands that are only executed if the expression
13460 was false. The end of the list is marked by a line containing @code{end}.
13464 The syntax is similar to @code{if}: the command takes a single argument,
13465 which is an expression to evaluate, and must be followed by the commands to
13466 execute, one per line, terminated by an @code{end}.
13467 The commands are executed repeatedly as long as the expression
13471 @item document @var{commandname}
13472 Document the user-defined command @var{commandname}, so that it can be
13473 accessed by @code{help}. The command @var{commandname} must already be
13474 defined. This command reads lines of documentation just as @code{define}
13475 reads the lines of the command definition, ending with @code{end}.
13476 After the @code{document} command is finished, @code{help} on command
13477 @var{commandname} displays the documentation you have written.
13479 You may use the @code{document} command again to change the
13480 documentation of a command. Redefining the command with @code{define}
13481 does not change the documentation.
13483 @kindex help user-defined
13484 @item help user-defined
13485 List all user-defined commands, with the first line of the documentation
13490 @itemx show user @var{commandname}
13491 Display the @value{GDBN} commands used to define @var{commandname} (but
13492 not its documentation). If no @var{commandname} is given, display the
13493 definitions for all user-defined commands.
13495 @kindex show max-user-call-depth
13496 @kindex set max-user-call-depth
13497 @item show max-user-call-depth
13498 @itemx set max-user-call-depth
13499 The value of @code{max-user-call-depth} controls how many recursion
13500 levels are allowed in user-defined commands before GDB suspects an
13501 infinite recursion and aborts the command.
13505 When user-defined commands are executed, the
13506 commands of the definition are not printed. An error in any command
13507 stops execution of the user-defined command.
13509 If used interactively, commands that would ask for confirmation proceed
13510 without asking when used inside a user-defined command. Many @value{GDBN}
13511 commands that normally print messages to say what they are doing omit the
13512 messages when used in a user-defined command.
13515 @section User-defined command hooks
13516 @cindex command hooks
13517 @cindex hooks, for commands
13518 @cindex hooks, pre-command
13522 You may define @dfn{hooks}, which are a special kind of user-defined
13523 command. Whenever you run the command @samp{foo}, if the user-defined
13524 command @samp{hook-foo} exists, it is executed (with no arguments)
13525 before that command.
13527 @cindex hooks, post-command
13530 A hook may also be defined which is run after the command you executed.
13531 Whenever you run the command @samp{foo}, if the user-defined command
13532 @samp{hookpost-foo} exists, it is executed (with no arguments) after
13533 that command. Post-execution hooks may exist simultaneously with
13534 pre-execution hooks, for the same command.
13536 It is valid for a hook to call the command which it hooks. If this
13537 occurs, the hook is not re-executed, thereby avoiding infinte recursion.
13539 @c It would be nice if hookpost could be passed a parameter indicating
13540 @c if the command it hooks executed properly or not. FIXME!
13542 @kindex stop@r{, a pseudo-command}
13543 In addition, a pseudo-command, @samp{stop} exists. Defining
13544 (@samp{hook-stop}) makes the associated commands execute every time
13545 execution stops in your program: before breakpoint commands are run,
13546 displays are printed, or the stack frame is printed.
13548 For example, to ignore @code{SIGALRM} signals while
13549 single-stepping, but treat them normally during normal execution,
13554 handle SIGALRM nopass
13558 handle SIGALRM pass
13561 define hook-continue
13562 handle SIGLARM pass
13566 As a further example, to hook at the begining and end of the @code{echo}
13567 command, and to add extra text to the beginning and end of the message,
13575 define hookpost-echo
13579 (@value{GDBP}) echo Hello World
13580 <<<---Hello World--->>>
13585 You can define a hook for any single-word command in @value{GDBN}, but
13586 not for command aliases; you should define a hook for the basic command
13587 name, e.g. @code{backtrace} rather than @code{bt}.
13588 @c FIXME! So how does Joe User discover whether a command is an alias
13590 If an error occurs during the execution of your hook, execution of
13591 @value{GDBN} commands stops and @value{GDBN} issues a prompt
13592 (before the command that you actually typed had a chance to run).
13594 If you try to define a hook which does not match any known command, you
13595 get a warning from the @code{define} command.
13597 @node Command Files
13598 @section Command files
13600 @cindex command files
13601 A command file for @value{GDBN} is a file of lines that are @value{GDBN}
13602 commands. Comments (lines starting with @kbd{#}) may also be included.
13603 An empty line in a command file does nothing; it does not mean to repeat
13604 the last command, as it would from the terminal.
13607 @cindex @file{.gdbinit}
13608 @cindex @file{gdb.ini}
13609 When you start @value{GDBN}, it automatically executes commands from its
13610 @dfn{init files}, normally called @file{.gdbinit}@footnote{The DJGPP
13611 port of @value{GDBN} uses the name @file{gdb.ini} instead, due to the
13612 limitations of file names imposed by DOS filesystems.}.
13613 During startup, @value{GDBN} does the following:
13617 Reads the init file (if any) in your home directory@footnote{On
13618 DOS/Windows systems, the home directory is the one pointed to by the
13619 @code{HOME} environment variable.}.
13622 Processes command line options and operands.
13625 Reads the init file (if any) in the current working directory.
13628 Reads command files specified by the @samp{-x} option.
13631 The init file in your home directory can set options (such as @samp{set
13632 complaints}) that affect subsequent processing of command line options
13633 and operands. Init files are not executed if you use the @samp{-nx}
13634 option (@pxref{Mode Options, ,Choosing modes}).
13636 @cindex init file name
13637 On some configurations of @value{GDBN}, the init file is known by a
13638 different name (these are typically environments where a specialized
13639 form of @value{GDBN} may need to coexist with other forms, hence a
13640 different name for the specialized version's init file). These are the
13641 environments with special init file names:
13643 @cindex @file{.vxgdbinit}
13646 VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit}
13648 @cindex @file{.os68gdbinit}
13650 OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit}
13652 @cindex @file{.esgdbinit}
13654 ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit}
13657 You can also request the execution of a command file with the
13658 @code{source} command:
13662 @item source @var{filename}
13663 Execute the command file @var{filename}.
13666 The lines in a command file are executed sequentially. They are not
13667 printed as they are executed. An error in any command terminates
13668 execution of the command file and control is returned to the console.
13670 Commands that would ask for confirmation if used interactively proceed
13671 without asking when used in a command file. Many @value{GDBN} commands that
13672 normally print messages to say what they are doing omit the messages
13673 when called from command files.
13675 @value{GDBN} also accepts command input from standard input. In this
13676 mode, normal output goes to standard output and error output goes to
13677 standard error. Errors in a command file supplied on standard input do
13678 not terminate execution of the command file --- execution continues with
13682 gdb < cmds > log 2>&1
13685 (The syntax above will vary depending on the shell used.) This example
13686 will execute commands from the file @file{cmds}. All output and errors
13687 would be directed to @file{log}.
13690 @section Commands for controlled output
13692 During the execution of a command file or a user-defined command, normal
13693 @value{GDBN} output is suppressed; the only output that appears is what is
13694 explicitly printed by the commands in the definition. This section
13695 describes three commands useful for generating exactly the output you
13700 @item echo @var{text}
13701 @c I do not consider backslash-space a standard C escape sequence
13702 @c because it is not in ANSI.
13703 Print @var{text}. Nonprinting characters can be included in
13704 @var{text} using C escape sequences, such as @samp{\n} to print a
13705 newline. @strong{No newline is printed unless you specify one.}
13706 In addition to the standard C escape sequences, a backslash followed
13707 by a space stands for a space. This is useful for displaying a
13708 string with spaces at the beginning or the end, since leading and
13709 trailing spaces are otherwise trimmed from all arguments.
13710 To print @samp{@w{ }and foo =@w{ }}, use the command
13711 @samp{echo \@w{ }and foo = \@w{ }}.
13713 A backslash at the end of @var{text} can be used, as in C, to continue
13714 the command onto subsequent lines. For example,
13717 echo This is some text\n\
13718 which is continued\n\
13719 onto several lines.\n
13722 produces the same output as
13725 echo This is some text\n
13726 echo which is continued\n
13727 echo onto several lines.\n
13731 @item output @var{expression}
13732 Print the value of @var{expression} and nothing but that value: no
13733 newlines, no @samp{$@var{nn} = }. The value is not entered in the
13734 value history either. @xref{Expressions, ,Expressions}, for more information
13737 @item output/@var{fmt} @var{expression}
13738 Print the value of @var{expression} in format @var{fmt}. You can use
13739 the same formats as for @code{print}. @xref{Output Formats,,Output
13740 formats}, for more information.
13743 @item printf @var{string}, @var{expressions}@dots{}
13744 Print the values of the @var{expressions} under the control of
13745 @var{string}. The @var{expressions} are separated by commas and may be
13746 either numbers or pointers. Their values are printed as specified by
13747 @var{string}, exactly as if your program were to execute the C
13749 @c FIXME: the above implies that at least all ANSI C formats are
13750 @c supported, but it isn't true: %E and %G don't work (or so it seems).
13751 @c Either this is a bug, or the manual should document what formats are
13755 printf (@var{string}, @var{expressions}@dots{});
13758 For example, you can print two values in hex like this:
13761 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
13764 The only backslash-escape sequences that you can use in the format
13765 string are the simple ones that consist of backslash followed by a
13770 @chapter Command Interpreters
13771 @cindex command interpreters
13773 @value{GDBN} supports multiple command interpreters, and some command
13774 infrastructure to allow users or user interface writers to switch
13775 between interpreters or run commands in other interpreters.
13777 @value{GDBN} currently supports two command interpreters, the console
13778 interpreter (sometimes called the command-line interpreter or @sc{cli})
13779 and the machine interface interpreter (or @sc{gdb/mi}). This manual
13780 describes both of these interfaces in great detail.
13782 By default, @value{GDBN} will start with the console interpreter.
13783 However, the user may choose to start @value{GDBN} with another
13784 interpreter by specifying the @option{-i} or @option{--interpreter}
13785 startup options. Defined interpreters include:
13789 @cindex console interpreter
13790 The traditional console or command-line interpreter. This is the most often
13791 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
13792 @value{GDBN} will use this interpreter.
13795 @cindex mi interpreter
13796 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
13797 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
13798 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
13802 @cindex mi2 interpreter
13803 The current @sc{gdb/mi} interface.
13806 @cindex mi1 interpreter
13807 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
13811 @cindex invoke another interpreter
13812 The interpreter being used by @value{GDBN} may not be dynamically
13813 switched at runtime. Although possible, this could lead to a very
13814 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
13815 enters the command "interpreter-set console" in a console view,
13816 @value{GDBN} would switch to using the console interpreter, rendering
13817 the IDE inoperable!
13819 @kindex interpreter-exec
13820 Although you may only choose a single interpreter at startup, you may execute
13821 commands in any interpreter from the current interpreter using the appropriate
13822 command. If you are running the console interpreter, simply use the
13823 @code{interpreter-exec} command:
13826 interpreter-exec mi "-data-list-register-names"
13829 @sc{gdb/mi} has a similar command, although it is only available in versions of
13830 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
13833 @chapter @value{GDBN} Text User Interface
13837 * TUI Overview:: TUI overview
13838 * TUI Keys:: TUI key bindings
13839 * TUI Single Key Mode:: TUI single key mode
13840 * TUI Commands:: TUI specific commands
13841 * TUI Configuration:: TUI configuration variables
13844 The @value{GDBN} Text User Interface, TUI in short,
13845 is a terminal interface which uses the @code{curses} library
13846 to show the source file, the assembly output, the program registers
13847 and @value{GDBN} commands in separate text windows.
13848 The TUI is available only when @value{GDBN} is configured
13849 with the @code{--enable-tui} configure option (@pxref{Configure Options}).
13852 @section TUI overview
13854 The TUI has two display modes that can be switched while
13859 A curses (or TUI) mode in which it displays several text
13860 windows on the terminal.
13863 A standard mode which corresponds to the @value{GDBN} configured without
13867 In the TUI mode, @value{GDBN} can display several text window
13872 This window is the @value{GDBN} command window with the @value{GDBN}
13873 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
13874 managed using readline but through the TUI. The @emph{command}
13875 window is always visible.
13878 The source window shows the source file of the program. The current
13879 line as well as active breakpoints are displayed in this window.
13882 The assembly window shows the disassembly output of the program.
13885 This window shows the processor registers. It detects when
13886 a register is changed and when this is the case, registers that have
13887 changed are highlighted.
13891 The source and assembly windows show the current program position
13892 by highlighting the current line and marking them with the @samp{>} marker.
13893 Breakpoints are also indicated with two markers. A first one
13894 indicates the breakpoint type:
13898 Breakpoint which was hit at least once.
13901 Breakpoint which was never hit.
13904 Hardware breakpoint which was hit at least once.
13907 Hardware breakpoint which was never hit.
13911 The second marker indicates whether the breakpoint is enabled or not:
13915 Breakpoint is enabled.
13918 Breakpoint is disabled.
13922 The source, assembly and register windows are attached to the thread
13923 and the frame position. They are updated when the current thread
13924 changes, when the frame changes or when the program counter changes.
13925 These three windows are arranged by the TUI according to several
13926 layouts. The layout defines which of these three windows are visible.
13927 The following layouts are available:
13937 source and assembly
13940 source and registers
13943 assembly and registers
13947 On top of the command window a status line gives various information
13948 concerning the current process begin debugged. The status line is
13949 updated when the information it shows changes. The following fields
13954 Indicates the current gdb target
13955 (@pxref{Targets, ,Specifying a Debugging Target}).
13958 Gives information about the current process or thread number.
13959 When no process is being debugged, this field is set to @code{No process}.
13962 Gives the current function name for the selected frame.
13963 The name is demangled if demangling is turned on (@pxref{Print Settings}).
13964 When there is no symbol corresponding to the current program counter
13965 the string @code{??} is displayed.
13968 Indicates the current line number for the selected frame.
13969 When the current line number is not known the string @code{??} is displayed.
13972 Indicates the current program counter address.
13977 @section TUI Key Bindings
13978 @cindex TUI key bindings
13980 The TUI installs several key bindings in the readline keymaps
13981 (@pxref{Command Line Editing}).
13982 They allow to leave or enter in the TUI mode or they operate
13983 directly on the TUI layout and windows. The TUI also provides
13984 a @emph{SingleKey} keymap which binds several keys directly to
13985 @value{GDBN} commands. The following key bindings
13986 are installed for both TUI mode and the @value{GDBN} standard mode.
13995 Enter or leave the TUI mode. When the TUI mode is left,
13996 the curses window management is left and @value{GDBN} operates using
13997 its standard mode writing on the terminal directly. When the TUI
13998 mode is entered, the control is given back to the curses windows.
13999 The screen is then refreshed.
14003 Use a TUI layout with only one window. The layout will
14004 either be @samp{source} or @samp{assembly}. When the TUI mode
14005 is not active, it will switch to the TUI mode.
14007 Think of this key binding as the Emacs @kbd{C-x 1} binding.
14011 Use a TUI layout with at least two windows. When the current
14012 layout shows already two windows, a next layout with two windows is used.
14013 When a new layout is chosen, one window will always be common to the
14014 previous layout and the new one.
14016 Think of it as the Emacs @kbd{C-x 2} binding.
14020 Change the active window. The TUI associates several key bindings
14021 (like scrolling and arrow keys) to the active window. This command
14022 gives the focus to the next TUI window.
14024 Think of it as the Emacs @kbd{C-x o} binding.
14028 Use the TUI @emph{SingleKey} keymap that binds single key to gdb commands
14029 (@pxref{TUI Single Key Mode}).
14033 The following key bindings are handled only by the TUI mode:
14038 Scroll the active window one page up.
14042 Scroll the active window one page down.
14046 Scroll the active window one line up.
14050 Scroll the active window one line down.
14054 Scroll the active window one column left.
14058 Scroll the active window one column right.
14062 Refresh the screen.
14066 In the TUI mode, the arrow keys are used by the active window
14067 for scrolling. This means they are available for readline when the
14068 active window is the command window. When the command window
14069 does not have the focus, it is necessary to use other readline
14070 key bindings such as @key{C-p}, @key{C-n}, @key{C-b} and @key{C-f}.
14072 @node TUI Single Key Mode
14073 @section TUI Single Key Mode
14074 @cindex TUI single key mode
14076 The TUI provides a @emph{SingleKey} mode in which it installs a particular
14077 key binding in the readline keymaps to connect single keys to
14081 @kindex c @r{(SingleKey TUI key)}
14085 @kindex d @r{(SingleKey TUI key)}
14089 @kindex f @r{(SingleKey TUI key)}
14093 @kindex n @r{(SingleKey TUI key)}
14097 @kindex q @r{(SingleKey TUI key)}
14099 exit the @emph{SingleKey} mode.
14101 @kindex r @r{(SingleKey TUI key)}
14105 @kindex s @r{(SingleKey TUI key)}
14109 @kindex u @r{(SingleKey TUI key)}
14113 @kindex v @r{(SingleKey TUI key)}
14117 @kindex w @r{(SingleKey TUI key)}
14123 Other keys temporarily switch to the @value{GDBN} command prompt.
14124 The key that was pressed is inserted in the editing buffer so that
14125 it is possible to type most @value{GDBN} commands without interaction
14126 with the TUI @emph{SingleKey} mode. Once the command is entered the TUI
14127 @emph{SingleKey} mode is restored. The only way to permanently leave
14128 this mode is by hitting @key{q} or @samp{@key{C-x} @key{s}}.
14132 @section TUI specific commands
14133 @cindex TUI commands
14135 The TUI has specific commands to control the text windows.
14136 These commands are always available, that is they do not depend on
14137 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
14138 is in the standard mode, using these commands will automatically switch
14144 List and give the size of all displayed windows.
14147 @kindex layout next
14148 Display the next layout.
14151 @kindex layout prev
14152 Display the previous layout.
14156 Display the source window only.
14160 Display the assembly window only.
14163 @kindex layout split
14164 Display the source and assembly window.
14167 @kindex layout regs
14168 Display the register window together with the source or assembly window.
14170 @item focus next | prev | src | asm | regs | split
14172 Set the focus to the named window.
14173 This command allows to change the active window so that scrolling keys
14174 can be affected to another window.
14178 Refresh the screen. This is similar to using @key{C-L} key.
14182 Update the source window and the current execution point.
14184 @item winheight @var{name} +@var{count}
14185 @itemx winheight @var{name} -@var{count}
14187 Change the height of the window @var{name} by @var{count}
14188 lines. Positive counts increase the height, while negative counts
14193 @node TUI Configuration
14194 @section TUI configuration variables
14195 @cindex TUI configuration variables
14197 The TUI has several configuration variables that control the
14198 appearance of windows on the terminal.
14201 @item set tui border-kind @var{kind}
14202 @kindex set tui border-kind
14203 Select the border appearance for the source, assembly and register windows.
14204 The possible values are the following:
14207 Use a space character to draw the border.
14210 Use ascii characters + - and | to draw the border.
14213 Use the Alternate Character Set to draw the border. The border is
14214 drawn using character line graphics if the terminal supports them.
14218 @item set tui active-border-mode @var{mode}
14219 @kindex set tui active-border-mode
14220 Select the attributes to display the border of the active window.
14221 The possible values are @code{normal}, @code{standout}, @code{reverse},
14222 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
14224 @item set tui border-mode @var{mode}
14225 @kindex set tui border-mode
14226 Select the attributes to display the border of other windows.
14227 The @var{mode} can be one of the following:
14230 Use normal attributes to display the border.
14236 Use reverse video mode.
14239 Use half bright mode.
14241 @item half-standout
14242 Use half bright and standout mode.
14245 Use extra bright or bold mode.
14247 @item bold-standout
14248 Use extra bright or bold and standout mode.
14255 @chapter Using @value{GDBN} under @sc{gnu} Emacs
14258 @cindex @sc{gnu} Emacs
14259 A special interface allows you to use @sc{gnu} Emacs to view (and
14260 edit) the source files for the program you are debugging with
14263 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
14264 executable file you want to debug as an argument. This command starts
14265 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
14266 created Emacs buffer.
14267 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
14269 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
14274 All ``terminal'' input and output goes through the Emacs buffer.
14277 This applies both to @value{GDBN} commands and their output, and to the input
14278 and output done by the program you are debugging.
14280 This is useful because it means that you can copy the text of previous
14281 commands and input them again; you can even use parts of the output
14284 All the facilities of Emacs' Shell mode are available for interacting
14285 with your program. In particular, you can send signals the usual
14286 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
14291 @value{GDBN} displays source code through Emacs.
14294 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
14295 source file for that frame and puts an arrow (@samp{=>}) at the
14296 left margin of the current line. Emacs uses a separate buffer for
14297 source display, and splits the screen to show both your @value{GDBN} session
14300 Explicit @value{GDBN} @code{list} or search commands still produce output as
14301 usual, but you probably have no reason to use them from Emacs.
14303 If you specify an absolute file name when prompted for the @kbd{M-x
14304 gdb} argument, then Emacs sets your current working directory to where
14305 your program resides. If you only specify the file name, then Emacs
14306 sets your current working directory to to the directory associated
14307 with the previous buffer. In this case, @value{GDBN} may find your
14308 program by searching your environment's @code{PATH} variable, but on
14309 some operating systems it might not find the source. So, although the
14310 @value{GDBN} input and output session proceeds normally, the auxiliary
14311 buffer does not display the current source and line of execution.
14313 The initial working directory of @value{GDBN} is printed on the top
14314 line of the @value{GDBN} I/O buffer and this serves as a default for
14315 the commands that specify files for @value{GDBN} to operate
14316 on. @xref{Files, ,Commands to specify files}.
14318 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
14319 need to call @value{GDBN} by a different name (for example, if you
14320 keep several configurations around, with different names) you can
14321 customize the Emacs variable @code{gud-gdb-command-name} to run the
14324 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
14325 addition to the standard Shell mode commands:
14329 Describe the features of Emacs' @value{GDBN} Mode.
14332 Execute to another source line, like the @value{GDBN} @code{step} command; also
14333 update the display window to show the current file and location.
14336 Execute to next source line in this function, skipping all function
14337 calls, like the @value{GDBN} @code{next} command. Then update the display window
14338 to show the current file and location.
14341 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
14342 display window accordingly.
14345 Execute until exit from the selected stack frame, like the @value{GDBN}
14346 @code{finish} command.
14349 Continue execution of your program, like the @value{GDBN} @code{continue}
14353 Go up the number of frames indicated by the numeric argument
14354 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
14355 like the @value{GDBN} @code{up} command.
14358 Go down the number of frames indicated by the numeric argument, like the
14359 @value{GDBN} @code{down} command.
14362 In any source file, the Emacs command @kbd{C-x SPC} (@code{gud-break})
14363 tells @value{GDBN} to set a breakpoint on the source line point is on.
14365 If you type @kbd{M-x speedbar}, then Emacs displays a separate frame which
14366 shows a backtrace when the @value{GDBN} I/O buffer is current. Move
14367 point to any frame in the stack and type @key{RET} to make it become the
14368 current frame and display the associated source in the source buffer.
14369 Alternatively, click @kbd{Mouse-2} to make the selected frame become the
14372 If you accidentally delete the source-display buffer, an easy way to get
14373 it back is to type the command @code{f} in the @value{GDBN} buffer, to
14374 request a frame display; when you run under Emacs, this recreates
14375 the source buffer if necessary to show you the context of the current
14378 The source files displayed in Emacs are in ordinary Emacs buffers
14379 which are visiting the source files in the usual way. You can edit
14380 the files with these buffers if you wish; but keep in mind that @value{GDBN}
14381 communicates with Emacs in terms of line numbers. If you add or
14382 delete lines from the text, the line numbers that @value{GDBN} knows cease
14383 to correspond properly with the code.
14385 The description given here is for GNU Emacs version 21.3 and a more
14386 detailed description of its interaction with @value{GDBN} is given in
14387 the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu} Emacs Manual}).
14389 @c The following dropped because Epoch is nonstandard. Reactivate
14390 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
14392 @kindex Emacs Epoch environment
14396 Version 18 of @sc{gnu} Emacs has a built-in window system
14397 called the @code{epoch}
14398 environment. Users of this environment can use a new command,
14399 @code{inspect} which performs identically to @code{print} except that
14400 each value is printed in its own window.
14405 @chapter The @sc{gdb/mi} Interface
14407 @unnumberedsec Function and Purpose
14409 @cindex @sc{gdb/mi}, its purpose
14410 @sc{gdb/mi} is a line based machine oriented text interface to @value{GDBN}. It is
14411 specifically intended to support the development of systems which use
14412 the debugger as just one small component of a larger system.
14414 This chapter is a specification of the @sc{gdb/mi} interface. It is written
14415 in the form of a reference manual.
14417 Note that @sc{gdb/mi} is still under construction, so some of the
14418 features described below are incomplete and subject to change.
14420 @unnumberedsec Notation and Terminology
14422 @cindex notational conventions, for @sc{gdb/mi}
14423 This chapter uses the following notation:
14427 @code{|} separates two alternatives.
14430 @code{[ @var{something} ]} indicates that @var{something} is optional:
14431 it may or may not be given.
14434 @code{( @var{group} )*} means that @var{group} inside the parentheses
14435 may repeat zero or more times.
14438 @code{( @var{group} )+} means that @var{group} inside the parentheses
14439 may repeat one or more times.
14442 @code{"@var{string}"} means a literal @var{string}.
14446 @heading Dependencies
14449 @heading Acknowledgments
14451 In alphabetic order: Andrew Cagney, Fernando Nasser, Stan Shebs and
14455 * GDB/MI Command Syntax::
14456 * GDB/MI Compatibility with CLI::
14457 * GDB/MI Output Records::
14458 * GDB/MI Command Description Format::
14459 * GDB/MI Breakpoint Table Commands::
14460 * GDB/MI Data Manipulation::
14461 * GDB/MI Program Control::
14462 * GDB/MI Miscellaneous Commands::
14464 * GDB/MI Kod Commands::
14465 * GDB/MI Memory Overlay Commands::
14466 * GDB/MI Signal Handling Commands::
14468 * GDB/MI Stack Manipulation::
14469 * GDB/MI Symbol Query::
14470 * GDB/MI Target Manipulation::
14471 * GDB/MI Thread Commands::
14472 * GDB/MI Tracepoint Commands::
14473 * GDB/MI Variable Objects::
14476 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14477 @node GDB/MI Command Syntax
14478 @section @sc{gdb/mi} Command Syntax
14481 * GDB/MI Input Syntax::
14482 * GDB/MI Output Syntax::
14483 * GDB/MI Simple Examples::
14486 @node GDB/MI Input Syntax
14487 @subsection @sc{gdb/mi} Input Syntax
14489 @cindex input syntax for @sc{gdb/mi}
14490 @cindex @sc{gdb/mi}, input syntax
14492 @item @var{command} @expansion{}
14493 @code{@var{cli-command} | @var{mi-command}}
14495 @item @var{cli-command} @expansion{}
14496 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
14497 @var{cli-command} is any existing @value{GDBN} CLI command.
14499 @item @var{mi-command} @expansion{}
14500 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
14501 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
14503 @item @var{token} @expansion{}
14504 "any sequence of digits"
14506 @item @var{option} @expansion{}
14507 @code{"-" @var{parameter} [ " " @var{parameter} ]}
14509 @item @var{parameter} @expansion{}
14510 @code{@var{non-blank-sequence} | @var{c-string}}
14512 @item @var{operation} @expansion{}
14513 @emph{any of the operations described in this chapter}
14515 @item @var{non-blank-sequence} @expansion{}
14516 @emph{anything, provided it doesn't contain special characters such as
14517 "-", @var{nl}, """ and of course " "}
14519 @item @var{c-string} @expansion{}
14520 @code{""" @var{seven-bit-iso-c-string-content} """}
14522 @item @var{nl} @expansion{}
14531 The CLI commands are still handled by the @sc{mi} interpreter; their
14532 output is described below.
14535 The @code{@var{token}}, when present, is passed back when the command
14539 Some @sc{mi} commands accept optional arguments as part of the parameter
14540 list. Each option is identified by a leading @samp{-} (dash) and may be
14541 followed by an optional argument parameter. Options occur first in the
14542 parameter list and can be delimited from normal parameters using
14543 @samp{--} (this is useful when some parameters begin with a dash).
14550 We want easy access to the existing CLI syntax (for debugging).
14553 We want it to be easy to spot a @sc{mi} operation.
14556 @node GDB/MI Output Syntax
14557 @subsection @sc{gdb/mi} Output Syntax
14559 @cindex output syntax of @sc{gdb/mi}
14560 @cindex @sc{gdb/mi}, output syntax
14561 The output from @sc{gdb/mi} consists of zero or more out-of-band records
14562 followed, optionally, by a single result record. This result record
14563 is for the most recent command. The sequence of output records is
14564 terminated by @samp{(@value{GDBP})}.
14566 If an input command was prefixed with a @code{@var{token}} then the
14567 corresponding output for that command will also be prefixed by that same
14571 @item @var{output} @expansion{}
14572 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
14574 @item @var{result-record} @expansion{}
14575 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
14577 @item @var{out-of-band-record} @expansion{}
14578 @code{@var{async-record} | @var{stream-record}}
14580 @item @var{async-record} @expansion{}
14581 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
14583 @item @var{exec-async-output} @expansion{}
14584 @code{[ @var{token} ] "*" @var{async-output}}
14586 @item @var{status-async-output} @expansion{}
14587 @code{[ @var{token} ] "+" @var{async-output}}
14589 @item @var{notify-async-output} @expansion{}
14590 @code{[ @var{token} ] "=" @var{async-output}}
14592 @item @var{async-output} @expansion{}
14593 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
14595 @item @var{result-class} @expansion{}
14596 @code{"done" | "running" | "connected" | "error" | "exit"}
14598 @item @var{async-class} @expansion{}
14599 @code{"stopped" | @var{others}} (where @var{others} will be added
14600 depending on the needs---this is still in development).
14602 @item @var{result} @expansion{}
14603 @code{ @var{variable} "=" @var{value}}
14605 @item @var{variable} @expansion{}
14606 @code{ @var{string} }
14608 @item @var{value} @expansion{}
14609 @code{ @var{const} | @var{tuple} | @var{list} }
14611 @item @var{const} @expansion{}
14612 @code{@var{c-string}}
14614 @item @var{tuple} @expansion{}
14615 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
14617 @item @var{list} @expansion{}
14618 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
14619 @var{result} ( "," @var{result} )* "]" }
14621 @item @var{stream-record} @expansion{}
14622 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
14624 @item @var{console-stream-output} @expansion{}
14625 @code{"~" @var{c-string}}
14627 @item @var{target-stream-output} @expansion{}
14628 @code{"@@" @var{c-string}}
14630 @item @var{log-stream-output} @expansion{}
14631 @code{"&" @var{c-string}}
14633 @item @var{nl} @expansion{}
14636 @item @var{token} @expansion{}
14637 @emph{any sequence of digits}.
14645 All output sequences end in a single line containing a period.
14648 The @code{@var{token}} is from the corresponding request. If an execution
14649 command is interrupted by the @samp{-exec-interrupt} command, the
14650 @var{token} associated with the @samp{*stopped} message is the one of the
14651 original execution command, not the one of the interrupt command.
14654 @cindex status output in @sc{gdb/mi}
14655 @var{status-async-output} contains on-going status information about the
14656 progress of a slow operation. It can be discarded. All status output is
14657 prefixed by @samp{+}.
14660 @cindex async output in @sc{gdb/mi}
14661 @var{exec-async-output} contains asynchronous state change on the target
14662 (stopped, started, disappeared). All async output is prefixed by
14666 @cindex notify output in @sc{gdb/mi}
14667 @var{notify-async-output} contains supplementary information that the
14668 client should handle (e.g., a new breakpoint information). All notify
14669 output is prefixed by @samp{=}.
14672 @cindex console output in @sc{gdb/mi}
14673 @var{console-stream-output} is output that should be displayed as is in the
14674 console. It is the textual response to a CLI command. All the console
14675 output is prefixed by @samp{~}.
14678 @cindex target output in @sc{gdb/mi}
14679 @var{target-stream-output} is the output produced by the target program.
14680 All the target output is prefixed by @samp{@@}.
14683 @cindex log output in @sc{gdb/mi}
14684 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
14685 instance messages that should be displayed as part of an error log. All
14686 the log output is prefixed by @samp{&}.
14689 @cindex list output in @sc{gdb/mi}
14690 New @sc{gdb/mi} commands should only output @var{lists} containing
14696 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
14697 details about the various output records.
14699 @node GDB/MI Simple Examples
14700 @subsection Simple Examples of @sc{gdb/mi} Interaction
14701 @cindex @sc{gdb/mi}, simple examples
14703 This subsection presents several simple examples of interaction using
14704 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
14705 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
14706 the output received from @sc{gdb/mi}.
14708 @subsubheading Target Stop
14709 @c Ummm... There is no "-stop" command. This assumes async, no?
14710 Here's an example of stopping the inferior process:
14721 <- *stop,reason="stop",address="0x123",source="a.c:123"
14725 @subsubheading Simple CLI Command
14727 Here's an example of a simple CLI command being passed through
14728 @sc{gdb/mi} and on to the CLI.
14738 @subsubheading Command With Side Effects
14741 -> -symbol-file xyz.exe
14742 <- *breakpoint,nr="3",address="0x123",source="a.c:123"
14746 @subsubheading A Bad Command
14748 Here's what happens if you pass a non-existent command:
14752 <- ^error,msg="Undefined MI command: rubbish"
14756 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14757 @node GDB/MI Compatibility with CLI
14758 @section @sc{gdb/mi} Compatibility with CLI
14760 @cindex compatibility, @sc{gdb/mi} and CLI
14761 @cindex @sc{gdb/mi}, compatibility with CLI
14762 To help users familiar with @value{GDBN}'s existing CLI interface, @sc{gdb/mi}
14763 accepts existing CLI commands. As specified by the syntax, such
14764 commands can be directly entered into the @sc{gdb/mi} interface and @value{GDBN} will
14767 This mechanism is provided as an aid to developers of @sc{gdb/mi}
14768 clients and not as a reliable interface into the CLI. Since the command
14769 is being interpreteted in an environment that assumes @sc{gdb/mi}
14770 behaviour, the exact output of such commands is likely to end up being
14771 an un-supported hybrid of @sc{gdb/mi} and CLI output.
14773 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14774 @node GDB/MI Output Records
14775 @section @sc{gdb/mi} Output Records
14778 * GDB/MI Result Records::
14779 * GDB/MI Stream Records::
14780 * GDB/MI Out-of-band Records::
14783 @node GDB/MI Result Records
14784 @subsection @sc{gdb/mi} Result Records
14786 @cindex result records in @sc{gdb/mi}
14787 @cindex @sc{gdb/mi}, result records
14788 In addition to a number of out-of-band notifications, the response to a
14789 @sc{gdb/mi} command includes one of the following result indications:
14793 @item "^done" [ "," @var{results} ]
14794 The synchronous operation was successful, @code{@var{results}} are the return
14799 @c Is this one correct? Should it be an out-of-band notification?
14800 The asynchronous operation was successfully started. The target is
14803 @item "^error" "," @var{c-string}
14805 The operation failed. The @code{@var{c-string}} contains the corresponding
14809 @node GDB/MI Stream Records
14810 @subsection @sc{gdb/mi} Stream Records
14812 @cindex @sc{gdb/mi}, stream records
14813 @cindex stream records in @sc{gdb/mi}
14814 @value{GDBN} internally maintains a number of output streams: the console, the
14815 target, and the log. The output intended for each of these streams is
14816 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
14818 Each stream record begins with a unique @dfn{prefix character} which
14819 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
14820 Syntax}). In addition to the prefix, each stream record contains a
14821 @code{@var{string-output}}. This is either raw text (with an implicit new
14822 line) or a quoted C string (which does not contain an implicit newline).
14825 @item "~" @var{string-output}
14826 The console output stream contains text that should be displayed in the
14827 CLI console window. It contains the textual responses to CLI commands.
14829 @item "@@" @var{string-output}
14830 The target output stream contains any textual output from the running
14833 @item "&" @var{string-output}
14834 The log stream contains debugging messages being produced by @value{GDBN}'s
14838 @node GDB/MI Out-of-band Records
14839 @subsection @sc{gdb/mi} Out-of-band Records
14841 @cindex out-of-band records in @sc{gdb/mi}
14842 @cindex @sc{gdb/mi}, out-of-band records
14843 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
14844 additional changes that have occurred. Those changes can either be a
14845 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
14846 target activity (e.g., target stopped).
14848 The following is a preliminary list of possible out-of-band records.
14855 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14856 @node GDB/MI Command Description Format
14857 @section @sc{gdb/mi} Command Description Format
14859 The remaining sections describe blocks of commands. Each block of
14860 commands is laid out in a fashion similar to this section.
14862 Note the the line breaks shown in the examples are here only for
14863 readability. They don't appear in the real output.
14864 Also note that the commands with a non-available example (N.A.@:) are
14865 not yet implemented.
14867 @subheading Motivation
14869 The motivation for this collection of commands.
14871 @subheading Introduction
14873 A brief introduction to this collection of commands as a whole.
14875 @subheading Commands
14877 For each command in the block, the following is described:
14879 @subsubheading Synopsis
14882 -command @var{args}@dots{}
14885 @subsubheading @value{GDBN} Command
14887 The corresponding @value{GDBN} CLI command.
14889 @subsubheading Result
14891 @subsubheading Out-of-band
14893 @subsubheading Notes
14895 @subsubheading Example
14898 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14899 @node GDB/MI Breakpoint Table Commands
14900 @section @sc{gdb/mi} Breakpoint table commands
14902 @cindex breakpoint commands for @sc{gdb/mi}
14903 @cindex @sc{gdb/mi}, breakpoint commands
14904 This section documents @sc{gdb/mi} commands for manipulating
14907 @subheading The @code{-break-after} Command
14908 @findex -break-after
14910 @subsubheading Synopsis
14913 -break-after @var{number} @var{count}
14916 The breakpoint number @var{number} is not in effect until it has been
14917 hit @var{count} times. To see how this is reflected in the output of
14918 the @samp{-break-list} command, see the description of the
14919 @samp{-break-list} command below.
14921 @subsubheading @value{GDBN} Command
14923 The corresponding @value{GDBN} command is @samp{ignore}.
14925 @subsubheading Example
14930 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",line="5"@}
14937 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
14938 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14939 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14940 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14941 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14942 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14943 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14944 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
14945 addr="0x000100d0",func="main",file="hello.c",line="5",times="0",
14951 @subheading The @code{-break-catch} Command
14952 @findex -break-catch
14954 @subheading The @code{-break-commands} Command
14955 @findex -break-commands
14959 @subheading The @code{-break-condition} Command
14960 @findex -break-condition
14962 @subsubheading Synopsis
14965 -break-condition @var{number} @var{expr}
14968 Breakpoint @var{number} will stop the program only if the condition in
14969 @var{expr} is true. The condition becomes part of the
14970 @samp{-break-list} output (see the description of the @samp{-break-list}
14973 @subsubheading @value{GDBN} Command
14975 The corresponding @value{GDBN} command is @samp{condition}.
14977 @subsubheading Example
14981 -break-condition 1 1
14985 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
14986 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14987 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14988 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14989 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14990 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14991 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14992 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
14993 addr="0x000100d0",func="main",file="hello.c",line="5",cond="1",
14994 times="0",ignore="3"@}]@}
14998 @subheading The @code{-break-delete} Command
14999 @findex -break-delete
15001 @subsubheading Synopsis
15004 -break-delete ( @var{breakpoint} )+
15007 Delete the breakpoint(s) whose number(s) are specified in the argument
15008 list. This is obviously reflected in the breakpoint list.
15010 @subsubheading @value{GDBN} command
15012 The corresponding @value{GDBN} command is @samp{delete}.
15014 @subsubheading Example
15022 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
15023 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15024 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15025 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15026 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15027 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15028 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15033 @subheading The @code{-break-disable} Command
15034 @findex -break-disable
15036 @subsubheading Synopsis
15039 -break-disable ( @var{breakpoint} )+
15042 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
15043 break list is now set to @samp{n} for the named @var{breakpoint}(s).
15045 @subsubheading @value{GDBN} Command
15047 The corresponding @value{GDBN} command is @samp{disable}.
15049 @subsubheading Example
15057 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15058 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15059 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15060 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15061 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15062 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15063 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15064 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
15065 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
15069 @subheading The @code{-break-enable} Command
15070 @findex -break-enable
15072 @subsubheading Synopsis
15075 -break-enable ( @var{breakpoint} )+
15078 Enable (previously disabled) @var{breakpoint}(s).
15080 @subsubheading @value{GDBN} Command
15082 The corresponding @value{GDBN} command is @samp{enable}.
15084 @subsubheading Example
15092 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15093 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15094 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15095 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15096 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15097 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15098 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15099 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
15100 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
15104 @subheading The @code{-break-info} Command
15105 @findex -break-info
15107 @subsubheading Synopsis
15110 -break-info @var{breakpoint}
15114 Get information about a single breakpoint.
15116 @subsubheading @value{GDBN} command
15118 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
15120 @subsubheading Example
15123 @subheading The @code{-break-insert} Command
15124 @findex -break-insert
15126 @subsubheading Synopsis
15129 -break-insert [ -t ] [ -h ] [ -r ]
15130 [ -c @var{condition} ] [ -i @var{ignore-count} ]
15131 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
15135 If specified, @var{line}, can be one of:
15142 @item filename:linenum
15143 @item filename:function
15147 The possible optional parameters of this command are:
15151 Insert a tempoary breakpoint.
15153 Insert a hardware breakpoint.
15154 @item -c @var{condition}
15155 Make the breakpoint conditional on @var{condition}.
15156 @item -i @var{ignore-count}
15157 Initialize the @var{ignore-count}.
15159 Insert a regular breakpoint in all the functions whose names match the
15160 given regular expression. Other flags are not applicable to regular
15164 @subsubheading Result
15166 The result is in the form:
15169 ^done,bkptno="@var{number}",func="@var{funcname}",
15170 file="@var{filename}",line="@var{lineno}"
15174 where @var{number} is the @value{GDBN} number for this breakpoint, @var{funcname}
15175 is the name of the function where the breakpoint was inserted,
15176 @var{filename} is the name of the source file which contains this
15177 function, and @var{lineno} is the source line number within that file.
15179 Note: this format is open to change.
15180 @c An out-of-band breakpoint instead of part of the result?
15182 @subsubheading @value{GDBN} Command
15184 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
15185 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
15187 @subsubheading Example
15192 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
15194 -break-insert -t foo
15195 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",line="11"@}
15198 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15199 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15200 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15201 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15202 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15203 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15204 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15205 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15206 addr="0x0001072c", func="main",file="recursive2.c",line="4",times="0"@},
15207 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
15208 addr="0x00010774",func="foo",file="recursive2.c",line="11",times="0"@}]@}
15210 -break-insert -r foo.*
15211 ~int foo(int, int);
15212 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c",line="11"@}
15216 @subheading The @code{-break-list} Command
15217 @findex -break-list
15219 @subsubheading Synopsis
15225 Displays the list of inserted breakpoints, showing the following fields:
15229 number of the breakpoint
15231 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
15233 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
15236 is the breakpoint enabled or no: @samp{y} or @samp{n}
15238 memory location at which the breakpoint is set
15240 logical location of the breakpoint, expressed by function name, file
15243 number of times the breakpoint has been hit
15246 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
15247 @code{body} field is an empty list.
15249 @subsubheading @value{GDBN} Command
15251 The corresponding @value{GDBN} command is @samp{info break}.
15253 @subsubheading Example
15258 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15259 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15260 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15261 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15262 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15263 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15264 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15265 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15266 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
15267 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
15268 addr="0x00010114",func="foo",file="hello.c",line="13",times="0"@}]@}
15272 Here's an example of the result when there are no breakpoints:
15277 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
15278 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15279 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15280 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15281 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15282 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15283 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15288 @subheading The @code{-break-watch} Command
15289 @findex -break-watch
15291 @subsubheading Synopsis
15294 -break-watch [ -a | -r ]
15297 Create a watchpoint. With the @samp{-a} option it will create an
15298 @dfn{access} watchpoint, i.e. a watchpoint that triggers either on a
15299 read from or on a write to the memory location. With the @samp{-r}
15300 option, the watchpoint created is a @dfn{read} watchpoint, i.e. it will
15301 trigger only when the memory location is accessed for reading. Without
15302 either of the options, the watchpoint created is a regular watchpoint,
15303 i.e. it will trigger when the memory location is accessed for writing.
15304 @xref{Set Watchpoints, , Setting watchpoints}.
15306 Note that @samp{-break-list} will report a single list of watchpoints and
15307 breakpoints inserted.
15309 @subsubheading @value{GDBN} Command
15311 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
15314 @subsubheading Example
15316 Setting a watchpoint on a variable in the @code{main} function:
15321 ^done,wpt=@{number="2",exp="x"@}
15325 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
15326 value=@{old="-268439212",new="55"@},
15327 frame=@{func="main",args=[],file="recursive2.c",line="5"@}
15331 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
15332 the program execution twice: first for the variable changing value, then
15333 for the watchpoint going out of scope.
15338 ^done,wpt=@{number="5",exp="C"@}
15342 ^done,reason="watchpoint-trigger",
15343 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
15344 frame=@{func="callee4",args=[],
15345 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
15349 ^done,reason="watchpoint-scope",wpnum="5",
15350 frame=@{func="callee3",args=[@{name="strarg",
15351 value="0x11940 \"A string argument.\""@}],
15352 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
15356 Listing breakpoints and watchpoints, at different points in the program
15357 execution. Note that once the watchpoint goes out of scope, it is
15363 ^done,wpt=@{number="2",exp="C"@}
15366 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15367 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15368 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15369 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15370 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15371 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15372 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15373 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15374 addr="0x00010734",func="callee4",
15375 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
15376 bkpt=@{number="2",type="watchpoint",disp="keep",
15377 enabled="y",addr="",what="C",times="0"@}]@}
15381 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
15382 value=@{old="-276895068",new="3"@},
15383 frame=@{func="callee4",args=[],
15384 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
15387 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15388 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15389 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15390 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15391 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15392 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15393 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15394 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15395 addr="0x00010734",func="callee4",
15396 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
15397 bkpt=@{number="2",type="watchpoint",disp="keep",
15398 enabled="y",addr="",what="C",times="-5"@}]@}
15402 ^done,reason="watchpoint-scope",wpnum="2",
15403 frame=@{func="callee3",args=[@{name="strarg",
15404 value="0x11940 \"A string argument.\""@}],
15405 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
15408 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15409 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15410 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15411 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15412 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15413 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15414 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15415 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15416 addr="0x00010734",func="callee4",
15417 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@}]@}
15421 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15422 @node GDB/MI Data Manipulation
15423 @section @sc{gdb/mi} Data Manipulation
15425 @cindex data manipulation, in @sc{gdb/mi}
15426 @cindex @sc{gdb/mi}, data manipulation
15427 This section describes the @sc{gdb/mi} commands that manipulate data:
15428 examine memory and registers, evaluate expressions, etc.
15430 @c REMOVED FROM THE INTERFACE.
15431 @c @subheading -data-assign
15432 @c Change the value of a program variable. Plenty of side effects.
15433 @c @subsubheading GDB command
15435 @c @subsubheading Example
15438 @subheading The @code{-data-disassemble} Command
15439 @findex -data-disassemble
15441 @subsubheading Synopsis
15445 [ -s @var{start-addr} -e @var{end-addr} ]
15446 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
15454 @item @var{start-addr}
15455 is the beginning address (or @code{$pc})
15456 @item @var{end-addr}
15458 @item @var{filename}
15459 is the name of the file to disassemble
15460 @item @var{linenum}
15461 is the line number to disassemble around
15463 is the the number of disassembly lines to be produced. If it is -1,
15464 the whole function will be disassembled, in case no @var{end-addr} is
15465 specified. If @var{end-addr} is specified as a non-zero value, and
15466 @var{lines} is lower than the number of disassembly lines between
15467 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
15468 displayed; if @var{lines} is higher than the number of lines between
15469 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
15472 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
15476 @subsubheading Result
15478 The output for each instruction is composed of four fields:
15487 Note that whatever included in the instruction field, is not manipulated
15488 directely by @sc{gdb/mi}, i.e. it is not possible to adjust its format.
15490 @subsubheading @value{GDBN} Command
15492 There's no direct mapping from this command to the CLI.
15494 @subsubheading Example
15496 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
15500 -data-disassemble -s $pc -e "$pc + 20" -- 0
15503 @{address="0x000107c0",func-name="main",offset="4",
15504 inst="mov 2, %o0"@},
15505 @{address="0x000107c4",func-name="main",offset="8",
15506 inst="sethi %hi(0x11800), %o2"@},
15507 @{address="0x000107c8",func-name="main",offset="12",
15508 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
15509 @{address="0x000107cc",func-name="main",offset="16",
15510 inst="sethi %hi(0x11800), %o2"@},
15511 @{address="0x000107d0",func-name="main",offset="20",
15512 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
15516 Disassemble the whole @code{main} function. Line 32 is part of
15520 -data-disassemble -f basics.c -l 32 -- 0
15522 @{address="0x000107bc",func-name="main",offset="0",
15523 inst="save %sp, -112, %sp"@},
15524 @{address="0x000107c0",func-name="main",offset="4",
15525 inst="mov 2, %o0"@},
15526 @{address="0x000107c4",func-name="main",offset="8",
15527 inst="sethi %hi(0x11800), %o2"@},
15529 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
15530 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
15534 Disassemble 3 instructions from the start of @code{main}:
15538 -data-disassemble -f basics.c -l 32 -n 3 -- 0
15540 @{address="0x000107bc",func-name="main",offset="0",
15541 inst="save %sp, -112, %sp"@},
15542 @{address="0x000107c0",func-name="main",offset="4",
15543 inst="mov 2, %o0"@},
15544 @{address="0x000107c4",func-name="main",offset="8",
15545 inst="sethi %hi(0x11800), %o2"@}]
15549 Disassemble 3 instructions from the start of @code{main} in mixed mode:
15553 -data-disassemble -f basics.c -l 32 -n 3 -- 1
15555 src_and_asm_line=@{line="31",
15556 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
15557 testsuite/gdb.mi/basics.c",line_asm_insn=[
15558 @{address="0x000107bc",func-name="main",offset="0",
15559 inst="save %sp, -112, %sp"@}]@},
15560 src_and_asm_line=@{line="32",
15561 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
15562 testsuite/gdb.mi/basics.c",line_asm_insn=[
15563 @{address="0x000107c0",func-name="main",offset="4",
15564 inst="mov 2, %o0"@},
15565 @{address="0x000107c4",func-name="main",offset="8",
15566 inst="sethi %hi(0x11800), %o2"@}]@}]
15571 @subheading The @code{-data-evaluate-expression} Command
15572 @findex -data-evaluate-expression
15574 @subsubheading Synopsis
15577 -data-evaluate-expression @var{expr}
15580 Evaluate @var{expr} as an expression. The expression could contain an
15581 inferior function call. The function call will execute synchronously.
15582 If the expression contains spaces, it must be enclosed in double quotes.
15584 @subsubheading @value{GDBN} Command
15586 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
15587 @samp{call}. In @code{gdbtk} only, there's a corresponding
15588 @samp{gdb_eval} command.
15590 @subsubheading Example
15592 In the following example, the numbers that precede the commands are the
15593 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
15594 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
15598 211-data-evaluate-expression A
15601 311-data-evaluate-expression &A
15602 311^done,value="0xefffeb7c"
15604 411-data-evaluate-expression A+3
15607 511-data-evaluate-expression "A + 3"
15613 @subheading The @code{-data-list-changed-registers} Command
15614 @findex -data-list-changed-registers
15616 @subsubheading Synopsis
15619 -data-list-changed-registers
15622 Display a list of the registers that have changed.
15624 @subsubheading @value{GDBN} Command
15626 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
15627 has the corresponding command @samp{gdb_changed_register_list}.
15629 @subsubheading Example
15631 On a PPC MBX board:
15639 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
15640 args=[],file="try.c",line="5"@}
15642 -data-list-changed-registers
15643 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
15644 "10","11","13","14","15","16","17","18","19","20","21","22","23",
15645 "24","25","26","27","28","30","31","64","65","66","67","69"]
15650 @subheading The @code{-data-list-register-names} Command
15651 @findex -data-list-register-names
15653 @subsubheading Synopsis
15656 -data-list-register-names [ ( @var{regno} )+ ]
15659 Show a list of register names for the current target. If no arguments
15660 are given, it shows a list of the names of all the registers. If
15661 integer numbers are given as arguments, it will print a list of the
15662 names of the registers corresponding to the arguments. To ensure
15663 consistency between a register name and its number, the output list may
15664 include empty register names.
15666 @subsubheading @value{GDBN} Command
15668 @value{GDBN} does not have a command which corresponds to
15669 @samp{-data-list-register-names}. In @code{gdbtk} there is a
15670 corresponding command @samp{gdb_regnames}.
15672 @subsubheading Example
15674 For the PPC MBX board:
15677 -data-list-register-names
15678 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
15679 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
15680 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
15681 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
15682 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
15683 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
15684 "", "pc","ps","cr","lr","ctr","xer"]
15686 -data-list-register-names 1 2 3
15687 ^done,register-names=["r1","r2","r3"]
15691 @subheading The @code{-data-list-register-values} Command
15692 @findex -data-list-register-values
15694 @subsubheading Synopsis
15697 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
15700 Display the registers' contents. @var{fmt} is the format according to
15701 which the registers' contents are to be returned, followed by an optional
15702 list of numbers specifying the registers to display. A missing list of
15703 numbers indicates that the contents of all the registers must be returned.
15705 Allowed formats for @var{fmt} are:
15722 @subsubheading @value{GDBN} Command
15724 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
15725 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
15727 @subsubheading Example
15729 For a PPC MBX board (note: line breaks are for readability only, they
15730 don't appear in the actual output):
15734 -data-list-register-values r 64 65
15735 ^done,register-values=[@{number="64",value="0xfe00a300"@},
15736 @{number="65",value="0x00029002"@}]
15738 -data-list-register-values x
15739 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
15740 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
15741 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
15742 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
15743 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
15744 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
15745 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
15746 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
15747 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
15748 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
15749 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
15750 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
15751 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
15752 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
15753 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
15754 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
15755 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
15756 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
15757 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
15758 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
15759 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
15760 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
15761 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
15762 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
15763 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
15764 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
15765 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
15766 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
15767 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
15768 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
15769 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
15770 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
15771 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
15772 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
15773 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
15774 @{number="69",value="0x20002b03"@}]
15779 @subheading The @code{-data-read-memory} Command
15780 @findex -data-read-memory
15782 @subsubheading Synopsis
15785 -data-read-memory [ -o @var{byte-offset} ]
15786 @var{address} @var{word-format} @var{word-size}
15787 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
15794 @item @var{address}
15795 An expression specifying the address of the first memory word to be
15796 read. Complex expressions containing embedded white space should be
15797 quoted using the C convention.
15799 @item @var{word-format}
15800 The format to be used to print the memory words. The notation is the
15801 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
15804 @item @var{word-size}
15805 The size of each memory word in bytes.
15807 @item @var{nr-rows}
15808 The number of rows in the output table.
15810 @item @var{nr-cols}
15811 The number of columns in the output table.
15814 If present, indicates that each row should include an @sc{ascii} dump. The
15815 value of @var{aschar} is used as a padding character when a byte is not a
15816 member of the printable @sc{ascii} character set (printable @sc{ascii}
15817 characters are those whose code is between 32 and 126, inclusively).
15819 @item @var{byte-offset}
15820 An offset to add to the @var{address} before fetching memory.
15823 This command displays memory contents as a table of @var{nr-rows} by
15824 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
15825 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
15826 (returned as @samp{total-bytes}). Should less than the requested number
15827 of bytes be returned by the target, the missing words are identified
15828 using @samp{N/A}. The number of bytes read from the target is returned
15829 in @samp{nr-bytes} and the starting address used to read memory in
15832 The address of the next/previous row or page is available in
15833 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
15836 @subsubheading @value{GDBN} Command
15838 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
15839 @samp{gdb_get_mem} memory read command.
15841 @subsubheading Example
15843 Read six bytes of memory starting at @code{bytes+6} but then offset by
15844 @code{-6} bytes. Format as three rows of two columns. One byte per
15845 word. Display each word in hex.
15849 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
15850 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
15851 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
15852 prev-page="0x0000138a",memory=[
15853 @{addr="0x00001390",data=["0x00","0x01"]@},
15854 @{addr="0x00001392",data=["0x02","0x03"]@},
15855 @{addr="0x00001394",data=["0x04","0x05"]@}]
15859 Read two bytes of memory starting at address @code{shorts + 64} and
15860 display as a single word formatted in decimal.
15864 5-data-read-memory shorts+64 d 2 1 1
15865 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
15866 next-row="0x00001512",prev-row="0x0000150e",
15867 next-page="0x00001512",prev-page="0x0000150e",memory=[
15868 @{addr="0x00001510",data=["128"]@}]
15872 Read thirty two bytes of memory starting at @code{bytes+16} and format
15873 as eight rows of four columns. Include a string encoding with @samp{x}
15874 used as the non-printable character.
15878 4-data-read-memory bytes+16 x 1 8 4 x
15879 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
15880 next-row="0x000013c0",prev-row="0x0000139c",
15881 next-page="0x000013c0",prev-page="0x00001380",memory=[
15882 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
15883 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
15884 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
15885 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
15886 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
15887 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
15888 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
15889 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
15893 @subheading The @code{-display-delete} Command
15894 @findex -display-delete
15896 @subsubheading Synopsis
15899 -display-delete @var{number}
15902 Delete the display @var{number}.
15904 @subsubheading @value{GDBN} Command
15906 The corresponding @value{GDBN} command is @samp{delete display}.
15908 @subsubheading Example
15912 @subheading The @code{-display-disable} Command
15913 @findex -display-disable
15915 @subsubheading Synopsis
15918 -display-disable @var{number}
15921 Disable display @var{number}.
15923 @subsubheading @value{GDBN} Command
15925 The corresponding @value{GDBN} command is @samp{disable display}.
15927 @subsubheading Example
15931 @subheading The @code{-display-enable} Command
15932 @findex -display-enable
15934 @subsubheading Synopsis
15937 -display-enable @var{number}
15940 Enable display @var{number}.
15942 @subsubheading @value{GDBN} Command
15944 The corresponding @value{GDBN} command is @samp{enable display}.
15946 @subsubheading Example
15950 @subheading The @code{-display-insert} Command
15951 @findex -display-insert
15953 @subsubheading Synopsis
15956 -display-insert @var{expression}
15959 Display @var{expression} every time the program stops.
15961 @subsubheading @value{GDBN} Command
15963 The corresponding @value{GDBN} command is @samp{display}.
15965 @subsubheading Example
15969 @subheading The @code{-display-list} Command
15970 @findex -display-list
15972 @subsubheading Synopsis
15978 List the displays. Do not show the current values.
15980 @subsubheading @value{GDBN} Command
15982 The corresponding @value{GDBN} command is @samp{info display}.
15984 @subsubheading Example
15988 @subheading The @code{-environment-cd} Command
15989 @findex -environment-cd
15991 @subsubheading Synopsis
15994 -environment-cd @var{pathdir}
15997 Set @value{GDBN}'s working directory.
15999 @subsubheading @value{GDBN} Command
16001 The corresponding @value{GDBN} command is @samp{cd}.
16003 @subsubheading Example
16007 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
16013 @subheading The @code{-environment-directory} Command
16014 @findex -environment-directory
16016 @subsubheading Synopsis
16019 -environment-directory [ -r ] [ @var{pathdir} ]+
16022 Add directories @var{pathdir} to beginning of search path for source files.
16023 If the @samp{-r} option is used, the search path is reset to the default
16024 search path. If directories @var{pathdir} are supplied in addition to the
16025 @samp{-r} option, the search path is first reset and then addition
16027 Multiple directories may be specified, separated by blanks. Specifying
16028 multiple directories in a single command
16029 results in the directories added to the beginning of the
16030 search path in the same order they were presented in the command.
16031 If blanks are needed as
16032 part of a directory name, double-quotes should be used around
16033 the name. In the command output, the path will show up separated
16034 by the system directory-separator character. The directory-seperator
16035 character must not be used
16036 in any directory name.
16037 If no directories are specified, the current search path is displayed.
16039 @subsubheading @value{GDBN} Command
16041 The corresponding @value{GDBN} command is @samp{dir}.
16043 @subsubheading Example
16047 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
16048 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
16050 -environment-directory ""
16051 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
16053 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
16054 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
16056 -environment-directory -r
16057 ^done,source-path="$cdir:$cwd"
16062 @subheading The @code{-environment-path} Command
16063 @findex -environment-path
16065 @subsubheading Synopsis
16068 -environment-path [ -r ] [ @var{pathdir} ]+
16071 Add directories @var{pathdir} to beginning of search path for object files.
16072 If the @samp{-r} option is used, the search path is reset to the original
16073 search path that existed at gdb start-up. If directories @var{pathdir} are
16074 supplied in addition to the
16075 @samp{-r} option, the search path is first reset and then addition
16077 Multiple directories may be specified, separated by blanks. Specifying
16078 multiple directories in a single command
16079 results in the directories added to the beginning of the
16080 search path in the same order they were presented in the command.
16081 If blanks are needed as
16082 part of a directory name, double-quotes should be used around
16083 the name. In the command output, the path will show up separated
16084 by the system directory-separator character. The directory-seperator
16085 character must not be used
16086 in any directory name.
16087 If no directories are specified, the current path is displayed.
16090 @subsubheading @value{GDBN} Command
16092 The corresponding @value{GDBN} command is @samp{path}.
16094 @subsubheading Example
16099 ^done,path="/usr/bin"
16101 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
16102 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
16104 -environment-path -r /usr/local/bin
16105 ^done,path="/usr/local/bin:/usr/bin"
16110 @subheading The @code{-environment-pwd} Command
16111 @findex -environment-pwd
16113 @subsubheading Synopsis
16119 Show the current working directory.
16121 @subsubheading @value{GDBN} command
16123 The corresponding @value{GDBN} command is @samp{pwd}.
16125 @subsubheading Example
16130 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
16134 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16135 @node GDB/MI Program Control
16136 @section @sc{gdb/mi} Program control
16138 @subsubheading Program termination
16140 As a result of execution, the inferior program can run to completion, if
16141 it doesn't encounter any breakpoints. In this case the output will
16142 include an exit code, if the program has exited exceptionally.
16144 @subsubheading Examples
16147 Program exited normally:
16155 *stopped,reason="exited-normally"
16160 Program exited exceptionally:
16168 *stopped,reason="exited",exit-code="01"
16172 Another way the program can terminate is if it receives a signal such as
16173 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
16177 *stopped,reason="exited-signalled",signal-name="SIGINT",
16178 signal-meaning="Interrupt"
16182 @subheading The @code{-exec-abort} Command
16183 @findex -exec-abort
16185 @subsubheading Synopsis
16191 Kill the inferior running program.
16193 @subsubheading @value{GDBN} Command
16195 The corresponding @value{GDBN} command is @samp{kill}.
16197 @subsubheading Example
16201 @subheading The @code{-exec-arguments} Command
16202 @findex -exec-arguments
16204 @subsubheading Synopsis
16207 -exec-arguments @var{args}
16210 Set the inferior program arguments, to be used in the next
16213 @subsubheading @value{GDBN} Command
16215 The corresponding @value{GDBN} command is @samp{set args}.
16217 @subsubheading Example
16220 Don't have one around.
16223 @subheading The @code{-exec-continue} Command
16224 @findex -exec-continue
16226 @subsubheading Synopsis
16232 Asynchronous command. Resumes the execution of the inferior program
16233 until a breakpoint is encountered, or until the inferior exits.
16235 @subsubheading @value{GDBN} Command
16237 The corresponding @value{GDBN} corresponding is @samp{continue}.
16239 @subsubheading Example
16246 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
16247 file="hello.c",line="13"@}
16252 @subheading The @code{-exec-finish} Command
16253 @findex -exec-finish
16255 @subsubheading Synopsis
16261 Asynchronous command. Resumes the execution of the inferior program
16262 until the current function is exited. Displays the results returned by
16265 @subsubheading @value{GDBN} Command
16267 The corresponding @value{GDBN} command is @samp{finish}.
16269 @subsubheading Example
16271 Function returning @code{void}.
16278 *stopped,reason="function-finished",frame=@{func="main",args=[],
16279 file="hello.c",line="7"@}
16283 Function returning other than @code{void}. The name of the internal
16284 @value{GDBN} variable storing the result is printed, together with the
16291 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
16292 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
16293 file="recursive2.c",line="14"@},
16294 gdb-result-var="$1",return-value="0"
16299 @subheading The @code{-exec-interrupt} Command
16300 @findex -exec-interrupt
16302 @subsubheading Synopsis
16308 Asynchronous command. Interrupts the background execution of the target.
16309 Note how the token associated with the stop message is the one for the
16310 execution command that has been interrupted. The token for the interrupt
16311 itself only appears in the @samp{^done} output. If the user is trying to
16312 interrupt a non-running program, an error message will be printed.
16314 @subsubheading @value{GDBN} Command
16316 The corresponding @value{GDBN} command is @samp{interrupt}.
16318 @subsubheading Example
16329 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
16330 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",line="13"@}
16335 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
16340 @subheading The @code{-exec-next} Command
16343 @subsubheading Synopsis
16349 Asynchronous command. Resumes execution of the inferior program, stopping
16350 when the beginning of the next source line is reached.
16352 @subsubheading @value{GDBN} Command
16354 The corresponding @value{GDBN} command is @samp{next}.
16356 @subsubheading Example
16362 *stopped,reason="end-stepping-range",line="8",file="hello.c"
16367 @subheading The @code{-exec-next-instruction} Command
16368 @findex -exec-next-instruction
16370 @subsubheading Synopsis
16373 -exec-next-instruction
16376 Asynchronous command. Executes one machine instruction. If the
16377 instruction is a function call continues until the function returns. If
16378 the program stops at an instruction in the middle of a source line, the
16379 address will be printed as well.
16381 @subsubheading @value{GDBN} Command
16383 The corresponding @value{GDBN} command is @samp{nexti}.
16385 @subsubheading Example
16389 -exec-next-instruction
16393 *stopped,reason="end-stepping-range",
16394 addr="0x000100d4",line="5",file="hello.c"
16399 @subheading The @code{-exec-return} Command
16400 @findex -exec-return
16402 @subsubheading Synopsis
16408 Makes current function return immediately. Doesn't execute the inferior.
16409 Displays the new current frame.
16411 @subsubheading @value{GDBN} Command
16413 The corresponding @value{GDBN} command is @samp{return}.
16415 @subsubheading Example
16419 200-break-insert callee4
16420 200^done,bkpt=@{number="1",addr="0x00010734",
16421 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
16426 000*stopped,reason="breakpoint-hit",bkptno="1",
16427 frame=@{func="callee4",args=[],
16428 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
16434 111^done,frame=@{level="0",func="callee3",
16435 args=[@{name="strarg",
16436 value="0x11940 \"A string argument.\""@}],
16437 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
16442 @subheading The @code{-exec-run} Command
16445 @subsubheading Synopsis
16451 Asynchronous command. Starts execution of the inferior from the
16452 beginning. The inferior executes until either a breakpoint is
16453 encountered or the program exits.
16455 @subsubheading @value{GDBN} Command
16457 The corresponding @value{GDBN} command is @samp{run}.
16459 @subsubheading Example
16464 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
16469 *stopped,reason="breakpoint-hit",bkptno="1",
16470 frame=@{func="main",args=[],file="recursive2.c",line="4"@}
16475 @subheading The @code{-exec-show-arguments} Command
16476 @findex -exec-show-arguments
16478 @subsubheading Synopsis
16481 -exec-show-arguments
16484 Print the arguments of the program.
16486 @subsubheading @value{GDBN} Command
16488 The corresponding @value{GDBN} command is @samp{show args}.
16490 @subsubheading Example
16493 @c @subheading -exec-signal
16495 @subheading The @code{-exec-step} Command
16498 @subsubheading Synopsis
16504 Asynchronous command. Resumes execution of the inferior program, stopping
16505 when the beginning of the next source line is reached, if the next
16506 source line is not a function call. If it is, stop at the first
16507 instruction of the called function.
16509 @subsubheading @value{GDBN} Command
16511 The corresponding @value{GDBN} command is @samp{step}.
16513 @subsubheading Example
16515 Stepping into a function:
16521 *stopped,reason="end-stepping-range",
16522 frame=@{func="foo",args=[@{name="a",value="10"@},
16523 @{name="b",value="0"@}],file="recursive2.c",line="11"@}
16533 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
16538 @subheading The @code{-exec-step-instruction} Command
16539 @findex -exec-step-instruction
16541 @subsubheading Synopsis
16544 -exec-step-instruction
16547 Asynchronous command. Resumes the inferior which executes one machine
16548 instruction. The output, once @value{GDBN} has stopped, will vary depending on
16549 whether we have stopped in the middle of a source line or not. In the
16550 former case, the address at which the program stopped will be printed as
16553 @subsubheading @value{GDBN} Command
16555 The corresponding @value{GDBN} command is @samp{stepi}.
16557 @subsubheading Example
16561 -exec-step-instruction
16565 *stopped,reason="end-stepping-range",
16566 frame=@{func="foo",args=[],file="try.c",line="10"@}
16568 -exec-step-instruction
16572 *stopped,reason="end-stepping-range",
16573 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",line="10"@}
16578 @subheading The @code{-exec-until} Command
16579 @findex -exec-until
16581 @subsubheading Synopsis
16584 -exec-until [ @var{location} ]
16587 Asynchronous command. Executes the inferior until the @var{location}
16588 specified in the argument is reached. If there is no argument, the inferior
16589 executes until a source line greater than the current one is reached.
16590 The reason for stopping in this case will be @samp{location-reached}.
16592 @subsubheading @value{GDBN} Command
16594 The corresponding @value{GDBN} command is @samp{until}.
16596 @subsubheading Example
16600 -exec-until recursive2.c:6
16604 *stopped,reason="location-reached",frame=@{func="main",args=[],
16605 file="recursive2.c",line="6"@}
16610 @subheading -file-clear
16611 Is this going away????
16615 @subheading The @code{-file-exec-and-symbols} Command
16616 @findex -file-exec-and-symbols
16618 @subsubheading Synopsis
16621 -file-exec-and-symbols @var{file}
16624 Specify the executable file to be debugged. This file is the one from
16625 which the symbol table is also read. If no file is specified, the
16626 command clears the executable and symbol information. If breakpoints
16627 are set when using this command with no arguments, @value{GDBN} will produce
16628 error messages. Otherwise, no output is produced, except a completion
16631 @subsubheading @value{GDBN} Command
16633 The corresponding @value{GDBN} command is @samp{file}.
16635 @subsubheading Example
16639 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
16645 @subheading The @code{-file-exec-file} Command
16646 @findex -file-exec-file
16648 @subsubheading Synopsis
16651 -file-exec-file @var{file}
16654 Specify the executable file to be debugged. Unlike
16655 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
16656 from this file. If used without argument, @value{GDBN} clears the information
16657 about the executable file. No output is produced, except a completion
16660 @subsubheading @value{GDBN} Command
16662 The corresponding @value{GDBN} command is @samp{exec-file}.
16664 @subsubheading Example
16668 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
16674 @subheading The @code{-file-list-exec-sections} Command
16675 @findex -file-list-exec-sections
16677 @subsubheading Synopsis
16680 -file-list-exec-sections
16683 List the sections of the current executable file.
16685 @subsubheading @value{GDBN} Command
16687 The @value{GDBN} command @samp{info file} shows, among the rest, the same
16688 information as this command. @code{gdbtk} has a corresponding command
16689 @samp{gdb_load_info}.
16691 @subsubheading Example
16695 @subheading The @code{-file-list-exec-source-file} Command
16696 @findex -file-list-exec-source-file
16698 @subsubheading Synopsis
16701 -file-list-exec-source-file
16704 List the line number, the current source file, and the absolute path
16705 to the current source file for the current executable.
16707 @subsubheading @value{GDBN} Command
16709 There's no @value{GDBN} command which directly corresponds to this one.
16711 @subsubheading Example
16715 123-file-list-exec-source-file
16716 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
16721 @subheading The @code{-file-list-exec-source-files} Command
16722 @findex -file-list-exec-source-files
16724 @subsubheading Synopsis
16727 -file-list-exec-source-files
16730 List the source files for the current executable.
16732 @subsubheading @value{GDBN} Command
16734 There's no @value{GDBN} command which directly corresponds to this one.
16735 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
16737 @subsubheading Example
16741 @subheading The @code{-file-list-shared-libraries} Command
16742 @findex -file-list-shared-libraries
16744 @subsubheading Synopsis
16747 -file-list-shared-libraries
16750 List the shared libraries in the program.
16752 @subsubheading @value{GDBN} Command
16754 The corresponding @value{GDBN} command is @samp{info shared}.
16756 @subsubheading Example
16760 @subheading The @code{-file-list-symbol-files} Command
16761 @findex -file-list-symbol-files
16763 @subsubheading Synopsis
16766 -file-list-symbol-files
16771 @subsubheading @value{GDBN} Command
16773 The corresponding @value{GDBN} command is @samp{info file} (part of it).
16775 @subsubheading Example
16779 @subheading The @code{-file-symbol-file} Command
16780 @findex -file-symbol-file
16782 @subsubheading Synopsis
16785 -file-symbol-file @var{file}
16788 Read symbol table info from the specified @var{file} argument. When
16789 used without arguments, clears @value{GDBN}'s symbol table info. No output is
16790 produced, except for a completion notification.
16792 @subsubheading @value{GDBN} Command
16794 The corresponding @value{GDBN} command is @samp{symbol-file}.
16796 @subsubheading Example
16800 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
16805 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16806 @node GDB/MI Miscellaneous Commands
16807 @section Miscellaneous @value{GDBN} commands in @sc{gdb/mi}
16809 @c @subheading -gdb-complete
16811 @subheading The @code{-gdb-exit} Command
16814 @subsubheading Synopsis
16820 Exit @value{GDBN} immediately.
16822 @subsubheading @value{GDBN} Command
16824 Approximately corresponds to @samp{quit}.
16826 @subsubheading Example
16833 @subheading The @code{-gdb-set} Command
16836 @subsubheading Synopsis
16842 Set an internal @value{GDBN} variable.
16843 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
16845 @subsubheading @value{GDBN} Command
16847 The corresponding @value{GDBN} command is @samp{set}.
16849 @subsubheading Example
16859 @subheading The @code{-gdb-show} Command
16862 @subsubheading Synopsis
16868 Show the current value of a @value{GDBN} variable.
16870 @subsubheading @value{GDBN} command
16872 The corresponding @value{GDBN} command is @samp{show}.
16874 @subsubheading Example
16883 @c @subheading -gdb-source
16886 @subheading The @code{-gdb-version} Command
16887 @findex -gdb-version
16889 @subsubheading Synopsis
16895 Show version information for @value{GDBN}. Used mostly in testing.
16897 @subsubheading @value{GDBN} Command
16899 There's no equivalent @value{GDBN} command. @value{GDBN} by default shows this
16900 information when you start an interactive session.
16902 @subsubheading Example
16904 @c This example modifies the actual output from GDB to avoid overfull
16910 ~Copyright 2000 Free Software Foundation, Inc.
16911 ~GDB is free software, covered by the GNU General Public License, and
16912 ~you are welcome to change it and/or distribute copies of it under
16913 ~ certain conditions.
16914 ~Type "show copying" to see the conditions.
16915 ~There is absolutely no warranty for GDB. Type "show warranty" for
16917 ~This GDB was configured as
16918 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
16923 @subheading The @code{-interpreter-exec} Command
16924 @findex -interpreter-exec
16926 @subheading Synopsis
16929 -interpreter-exec @var{interpreter} @var{command}
16932 Execute the specified @var{command} in the given @var{interpreter}.
16934 @subheading @value{GDBN} Command
16936 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
16938 @subheading Example
16942 -interpreter-exec console "break main"
16943 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
16944 &"During symbol reading, bad structure-type format.\n"
16945 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
16951 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16952 @node GDB/MI Kod Commands
16953 @section @sc{gdb/mi} Kod Commands
16955 The Kod commands are not implemented.
16957 @c @subheading -kod-info
16959 @c @subheading -kod-list
16961 @c @subheading -kod-list-object-types
16963 @c @subheading -kod-show
16965 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16966 @node GDB/MI Memory Overlay Commands
16967 @section @sc{gdb/mi} Memory Overlay Commands
16969 The memory overlay commands are not implemented.
16971 @c @subheading -overlay-auto
16973 @c @subheading -overlay-list-mapping-state
16975 @c @subheading -overlay-list-overlays
16977 @c @subheading -overlay-map
16979 @c @subheading -overlay-off
16981 @c @subheading -overlay-on
16983 @c @subheading -overlay-unmap
16985 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16986 @node GDB/MI Signal Handling Commands
16987 @section @sc{gdb/mi} Signal Handling Commands
16989 Signal handling commands are not implemented.
16991 @c @subheading -signal-handle
16993 @c @subheading -signal-list-handle-actions
16995 @c @subheading -signal-list-signal-types
16999 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17000 @node GDB/MI Stack Manipulation
17001 @section @sc{gdb/mi} Stack Manipulation Commands
17004 @subheading The @code{-stack-info-frame} Command
17005 @findex -stack-info-frame
17007 @subsubheading Synopsis
17013 Get info on the current frame.
17015 @subsubheading @value{GDBN} Command
17017 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
17018 (without arguments).
17020 @subsubheading Example
17023 @subheading The @code{-stack-info-depth} Command
17024 @findex -stack-info-depth
17026 @subsubheading Synopsis
17029 -stack-info-depth [ @var{max-depth} ]
17032 Return the depth of the stack. If the integer argument @var{max-depth}
17033 is specified, do not count beyond @var{max-depth} frames.
17035 @subsubheading @value{GDBN} Command
17037 There's no equivalent @value{GDBN} command.
17039 @subsubheading Example
17041 For a stack with frame levels 0 through 11:
17048 -stack-info-depth 4
17051 -stack-info-depth 12
17054 -stack-info-depth 11
17057 -stack-info-depth 13
17062 @subheading The @code{-stack-list-arguments} Command
17063 @findex -stack-list-arguments
17065 @subsubheading Synopsis
17068 -stack-list-arguments @var{show-values}
17069 [ @var{low-frame} @var{high-frame} ]
17072 Display a list of the arguments for the frames between @var{low-frame}
17073 and @var{high-frame} (inclusive). If @var{low-frame} and
17074 @var{high-frame} are not provided, list the arguments for the whole call
17077 The @var{show-values} argument must have a value of 0 or 1. A value of
17078 0 means that only the names of the arguments are listed, a value of 1
17079 means that both names and values of the arguments are printed.
17081 @subsubheading @value{GDBN} Command
17083 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
17084 @samp{gdb_get_args} command which partially overlaps with the
17085 functionality of @samp{-stack-list-arguments}.
17087 @subsubheading Example
17094 frame=@{level="0",addr="0x00010734",func="callee4",
17095 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
17096 frame=@{level="1",addr="0x0001076c",func="callee3",
17097 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
17098 frame=@{level="2",addr="0x0001078c",func="callee2",
17099 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
17100 frame=@{level="3",addr="0x000107b4",func="callee1",
17101 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
17102 frame=@{level="4",addr="0x000107e0",func="main",
17103 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
17105 -stack-list-arguments 0
17108 frame=@{level="0",args=[]@},
17109 frame=@{level="1",args=[name="strarg"]@},
17110 frame=@{level="2",args=[name="intarg",name="strarg"]@},
17111 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
17112 frame=@{level="4",args=[]@}]
17114 -stack-list-arguments 1
17117 frame=@{level="0",args=[]@},
17119 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
17120 frame=@{level="2",args=[
17121 @{name="intarg",value="2"@},
17122 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
17123 @{frame=@{level="3",args=[
17124 @{name="intarg",value="2"@},
17125 @{name="strarg",value="0x11940 \"A string argument.\""@},
17126 @{name="fltarg",value="3.5"@}]@},
17127 frame=@{level="4",args=[]@}]
17129 -stack-list-arguments 0 2 2
17130 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
17132 -stack-list-arguments 1 2 2
17133 ^done,stack-args=[frame=@{level="2",
17134 args=[@{name="intarg",value="2"@},
17135 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
17139 @c @subheading -stack-list-exception-handlers
17142 @subheading The @code{-stack-list-frames} Command
17143 @findex -stack-list-frames
17145 @subsubheading Synopsis
17148 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
17151 List the frames currently on the stack. For each frame it displays the
17156 The frame number, 0 being the topmost frame, i.e. the innermost function.
17158 The @code{$pc} value for that frame.
17162 File name of the source file where the function lives.
17164 Line number corresponding to the @code{$pc}.
17167 If invoked without arguments, this command prints a backtrace for the
17168 whole stack. If given two integer arguments, it shows the frames whose
17169 levels are between the two arguments (inclusive). If the two arguments
17170 are equal, it shows the single frame at the corresponding level.
17172 @subsubheading @value{GDBN} Command
17174 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
17176 @subsubheading Example
17178 Full stack backtrace:
17184 [frame=@{level="0",addr="0x0001076c",func="foo",
17185 file="recursive2.c",line="11"@},
17186 frame=@{level="1",addr="0x000107a4",func="foo",
17187 file="recursive2.c",line="14"@},
17188 frame=@{level="2",addr="0x000107a4",func="foo",
17189 file="recursive2.c",line="14"@},
17190 frame=@{level="3",addr="0x000107a4",func="foo",
17191 file="recursive2.c",line="14"@},
17192 frame=@{level="4",addr="0x000107a4",func="foo",
17193 file="recursive2.c",line="14"@},
17194 frame=@{level="5",addr="0x000107a4",func="foo",
17195 file="recursive2.c",line="14"@},
17196 frame=@{level="6",addr="0x000107a4",func="foo",
17197 file="recursive2.c",line="14"@},
17198 frame=@{level="7",addr="0x000107a4",func="foo",
17199 file="recursive2.c",line="14"@},
17200 frame=@{level="8",addr="0x000107a4",func="foo",
17201 file="recursive2.c",line="14"@},
17202 frame=@{level="9",addr="0x000107a4",func="foo",
17203 file="recursive2.c",line="14"@},
17204 frame=@{level="10",addr="0x000107a4",func="foo",
17205 file="recursive2.c",line="14"@},
17206 frame=@{level="11",addr="0x00010738",func="main",
17207 file="recursive2.c",line="4"@}]
17211 Show frames between @var{low_frame} and @var{high_frame}:
17215 -stack-list-frames 3 5
17217 [frame=@{level="3",addr="0x000107a4",func="foo",
17218 file="recursive2.c",line="14"@},
17219 frame=@{level="4",addr="0x000107a4",func="foo",
17220 file="recursive2.c",line="14"@},
17221 frame=@{level="5",addr="0x000107a4",func="foo",
17222 file="recursive2.c",line="14"@}]
17226 Show a single frame:
17230 -stack-list-frames 3 3
17232 [frame=@{level="3",addr="0x000107a4",func="foo",
17233 file="recursive2.c",line="14"@}]
17238 @subheading The @code{-stack-list-locals} Command
17239 @findex -stack-list-locals
17241 @subsubheading Synopsis
17244 -stack-list-locals @var{print-values}
17247 Display the local variable names for the current frame. With an
17248 argument of 0 or @code{--no-values}, prints only the names of the variables.
17249 With argument of 1 or @code{--all-values}, prints also their values. With
17250 argument of 2 or @code{--simple-values}, prints the name, type and value for
17251 simple data types and the name and type for arrays, structures and
17252 unions. In this last case, the idea is that the user can see the
17253 value of simple data types immediately and he can create variable
17254 objects for other data types if he wishes to explore their values in
17257 @subsubheading @value{GDBN} Command
17259 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
17261 @subsubheading Example
17265 -stack-list-locals 0
17266 ^done,locals=[name="A",name="B",name="C"]
17268 -stack-list-locals --all-values
17269 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
17270 @{name="C",value="@{1, 2, 3@}"@}]
17271 -stack-list-locals --simple-values
17272 ^done,locals=[@{name="A",type="int",value="1"@},
17273 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
17278 @subheading The @code{-stack-select-frame} Command
17279 @findex -stack-select-frame
17281 @subsubheading Synopsis
17284 -stack-select-frame @var{framenum}
17287 Change the current frame. Select a different frame @var{framenum} on
17290 @subsubheading @value{GDBN} Command
17292 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
17293 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
17295 @subsubheading Example
17299 -stack-select-frame 2
17304 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17305 @node GDB/MI Symbol Query
17306 @section @sc{gdb/mi} Symbol Query Commands
17309 @subheading The @code{-symbol-info-address} Command
17310 @findex -symbol-info-address
17312 @subsubheading Synopsis
17315 -symbol-info-address @var{symbol}
17318 Describe where @var{symbol} is stored.
17320 @subsubheading @value{GDBN} Command
17322 The corresponding @value{GDBN} command is @samp{info address}.
17324 @subsubheading Example
17328 @subheading The @code{-symbol-info-file} Command
17329 @findex -symbol-info-file
17331 @subsubheading Synopsis
17337 Show the file for the symbol.
17339 @subsubheading @value{GDBN} Command
17341 There's no equivalent @value{GDBN} command. @code{gdbtk} has
17342 @samp{gdb_find_file}.
17344 @subsubheading Example
17348 @subheading The @code{-symbol-info-function} Command
17349 @findex -symbol-info-function
17351 @subsubheading Synopsis
17354 -symbol-info-function
17357 Show which function the symbol lives in.
17359 @subsubheading @value{GDBN} Command
17361 @samp{gdb_get_function} in @code{gdbtk}.
17363 @subsubheading Example
17367 @subheading The @code{-symbol-info-line} Command
17368 @findex -symbol-info-line
17370 @subsubheading Synopsis
17376 Show the core addresses of the code for a source line.
17378 @subsubheading @value{GDBN} Command
17380 The corresponding @value{GDBN} command is @samp{info line}.
17381 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
17383 @subsubheading Example
17387 @subheading The @code{-symbol-info-symbol} Command
17388 @findex -symbol-info-symbol
17390 @subsubheading Synopsis
17393 -symbol-info-symbol @var{addr}
17396 Describe what symbol is at location @var{addr}.
17398 @subsubheading @value{GDBN} Command
17400 The corresponding @value{GDBN} command is @samp{info symbol}.
17402 @subsubheading Example
17406 @subheading The @code{-symbol-list-functions} Command
17407 @findex -symbol-list-functions
17409 @subsubheading Synopsis
17412 -symbol-list-functions
17415 List the functions in the executable.
17417 @subsubheading @value{GDBN} Command
17419 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
17420 @samp{gdb_search} in @code{gdbtk}.
17422 @subsubheading Example
17426 @subheading The @code{-symbol-list-lines} Command
17427 @findex -symbol-list-lines
17429 @subsubheading Synopsis
17432 -symbol-list-lines @var{filename}
17435 Print the list of lines that contain code and their associated program
17436 addresses for the given source filename. The entries are sorted in
17437 ascending PC order.
17439 @subsubheading @value{GDBN} Command
17441 There is no corresponding @value{GDBN} command.
17443 @subsubheading Example
17446 -symbol-list-lines basics.c
17447 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
17452 @subheading The @code{-symbol-list-types} Command
17453 @findex -symbol-list-types
17455 @subsubheading Synopsis
17461 List all the type names.
17463 @subsubheading @value{GDBN} Command
17465 The corresponding commands are @samp{info types} in @value{GDBN},
17466 @samp{gdb_search} in @code{gdbtk}.
17468 @subsubheading Example
17472 @subheading The @code{-symbol-list-variables} Command
17473 @findex -symbol-list-variables
17475 @subsubheading Synopsis
17478 -symbol-list-variables
17481 List all the global and static variable names.
17483 @subsubheading @value{GDBN} Command
17485 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
17487 @subsubheading Example
17491 @subheading The @code{-symbol-locate} Command
17492 @findex -symbol-locate
17494 @subsubheading Synopsis
17500 @subsubheading @value{GDBN} Command
17502 @samp{gdb_loc} in @code{gdbtk}.
17504 @subsubheading Example
17508 @subheading The @code{-symbol-type} Command
17509 @findex -symbol-type
17511 @subsubheading Synopsis
17514 -symbol-type @var{variable}
17517 Show type of @var{variable}.
17519 @subsubheading @value{GDBN} Command
17521 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
17522 @samp{gdb_obj_variable}.
17524 @subsubheading Example
17528 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17529 @node GDB/MI Target Manipulation
17530 @section @sc{gdb/mi} Target Manipulation Commands
17533 @subheading The @code{-target-attach} Command
17534 @findex -target-attach
17536 @subsubheading Synopsis
17539 -target-attach @var{pid} | @var{file}
17542 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
17544 @subsubheading @value{GDBN} command
17546 The corresponding @value{GDBN} command is @samp{attach}.
17548 @subsubheading Example
17552 @subheading The @code{-target-compare-sections} Command
17553 @findex -target-compare-sections
17555 @subsubheading Synopsis
17558 -target-compare-sections [ @var{section} ]
17561 Compare data of section @var{section} on target to the exec file.
17562 Without the argument, all sections are compared.
17564 @subsubheading @value{GDBN} Command
17566 The @value{GDBN} equivalent is @samp{compare-sections}.
17568 @subsubheading Example
17572 @subheading The @code{-target-detach} Command
17573 @findex -target-detach
17575 @subsubheading Synopsis
17581 Disconnect from the remote target. There's no output.
17583 @subsubheading @value{GDBN} command
17585 The corresponding @value{GDBN} command is @samp{detach}.
17587 @subsubheading Example
17597 @subheading The @code{-target-disconnect} Command
17598 @findex -target-disconnect
17600 @subsubheading Synopsis
17606 Disconnect from the remote target. There's no output.
17608 @subsubheading @value{GDBN} command
17610 The corresponding @value{GDBN} command is @samp{disconnect}.
17612 @subsubheading Example
17622 @subheading The @code{-target-download} Command
17623 @findex -target-download
17625 @subsubheading Synopsis
17631 Loads the executable onto the remote target.
17632 It prints out an update message every half second, which includes the fields:
17636 The name of the section.
17638 The size of what has been sent so far for that section.
17640 The size of the section.
17642 The total size of what was sent so far (the current and the previous sections).
17644 The size of the overall executable to download.
17648 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
17649 @sc{gdb/mi} Output Syntax}).
17651 In addition, it prints the name and size of the sections, as they are
17652 downloaded. These messages include the following fields:
17656 The name of the section.
17658 The size of the section.
17660 The size of the overall executable to download.
17664 At the end, a summary is printed.
17666 @subsubheading @value{GDBN} Command
17668 The corresponding @value{GDBN} command is @samp{load}.
17670 @subsubheading Example
17672 Note: each status message appears on a single line. Here the messages
17673 have been broken down so that they can fit onto a page.
17678 +download,@{section=".text",section-size="6668",total-size="9880"@}
17679 +download,@{section=".text",section-sent="512",section-size="6668",
17680 total-sent="512",total-size="9880"@}
17681 +download,@{section=".text",section-sent="1024",section-size="6668",
17682 total-sent="1024",total-size="9880"@}
17683 +download,@{section=".text",section-sent="1536",section-size="6668",
17684 total-sent="1536",total-size="9880"@}
17685 +download,@{section=".text",section-sent="2048",section-size="6668",
17686 total-sent="2048",total-size="9880"@}
17687 +download,@{section=".text",section-sent="2560",section-size="6668",
17688 total-sent="2560",total-size="9880"@}
17689 +download,@{section=".text",section-sent="3072",section-size="6668",
17690 total-sent="3072",total-size="9880"@}
17691 +download,@{section=".text",section-sent="3584",section-size="6668",
17692 total-sent="3584",total-size="9880"@}
17693 +download,@{section=".text",section-sent="4096",section-size="6668",
17694 total-sent="4096",total-size="9880"@}
17695 +download,@{section=".text",section-sent="4608",section-size="6668",
17696 total-sent="4608",total-size="9880"@}
17697 +download,@{section=".text",section-sent="5120",section-size="6668",
17698 total-sent="5120",total-size="9880"@}
17699 +download,@{section=".text",section-sent="5632",section-size="6668",
17700 total-sent="5632",total-size="9880"@}
17701 +download,@{section=".text",section-sent="6144",section-size="6668",
17702 total-sent="6144",total-size="9880"@}
17703 +download,@{section=".text",section-sent="6656",section-size="6668",
17704 total-sent="6656",total-size="9880"@}
17705 +download,@{section=".init",section-size="28",total-size="9880"@}
17706 +download,@{section=".fini",section-size="28",total-size="9880"@}
17707 +download,@{section=".data",section-size="3156",total-size="9880"@}
17708 +download,@{section=".data",section-sent="512",section-size="3156",
17709 total-sent="7236",total-size="9880"@}
17710 +download,@{section=".data",section-sent="1024",section-size="3156",
17711 total-sent="7748",total-size="9880"@}
17712 +download,@{section=".data",section-sent="1536",section-size="3156",
17713 total-sent="8260",total-size="9880"@}
17714 +download,@{section=".data",section-sent="2048",section-size="3156",
17715 total-sent="8772",total-size="9880"@}
17716 +download,@{section=".data",section-sent="2560",section-size="3156",
17717 total-sent="9284",total-size="9880"@}
17718 +download,@{section=".data",section-sent="3072",section-size="3156",
17719 total-sent="9796",total-size="9880"@}
17720 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
17726 @subheading The @code{-target-exec-status} Command
17727 @findex -target-exec-status
17729 @subsubheading Synopsis
17732 -target-exec-status
17735 Provide information on the state of the target (whether it is running or
17736 not, for instance).
17738 @subsubheading @value{GDBN} Command
17740 There's no equivalent @value{GDBN} command.
17742 @subsubheading Example
17746 @subheading The @code{-target-list-available-targets} Command
17747 @findex -target-list-available-targets
17749 @subsubheading Synopsis
17752 -target-list-available-targets
17755 List the possible targets to connect to.
17757 @subsubheading @value{GDBN} Command
17759 The corresponding @value{GDBN} command is @samp{help target}.
17761 @subsubheading Example
17765 @subheading The @code{-target-list-current-targets} Command
17766 @findex -target-list-current-targets
17768 @subsubheading Synopsis
17771 -target-list-current-targets
17774 Describe the current target.
17776 @subsubheading @value{GDBN} Command
17778 The corresponding information is printed by @samp{info file} (among
17781 @subsubheading Example
17785 @subheading The @code{-target-list-parameters} Command
17786 @findex -target-list-parameters
17788 @subsubheading Synopsis
17791 -target-list-parameters
17796 @subsubheading @value{GDBN} Command
17800 @subsubheading Example
17804 @subheading The @code{-target-select} Command
17805 @findex -target-select
17807 @subsubheading Synopsis
17810 -target-select @var{type} @var{parameters @dots{}}
17813 Connect @value{GDBN} to the remote target. This command takes two args:
17817 The type of target, for instance @samp{async}, @samp{remote}, etc.
17818 @item @var{parameters}
17819 Device names, host names and the like. @xref{Target Commands, ,
17820 Commands for managing targets}, for more details.
17823 The output is a connection notification, followed by the address at
17824 which the target program is, in the following form:
17827 ^connected,addr="@var{address}",func="@var{function name}",
17828 args=[@var{arg list}]
17831 @subsubheading @value{GDBN} Command
17833 The corresponding @value{GDBN} command is @samp{target}.
17835 @subsubheading Example
17839 -target-select async /dev/ttya
17840 ^connected,addr="0xfe00a300",func="??",args=[]
17844 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17845 @node GDB/MI Thread Commands
17846 @section @sc{gdb/mi} Thread Commands
17849 @subheading The @code{-thread-info} Command
17850 @findex -thread-info
17852 @subsubheading Synopsis
17858 @subsubheading @value{GDBN} command
17862 @subsubheading Example
17866 @subheading The @code{-thread-list-all-threads} Command
17867 @findex -thread-list-all-threads
17869 @subsubheading Synopsis
17872 -thread-list-all-threads
17875 @subsubheading @value{GDBN} Command
17877 The equivalent @value{GDBN} command is @samp{info threads}.
17879 @subsubheading Example
17883 @subheading The @code{-thread-list-ids} Command
17884 @findex -thread-list-ids
17886 @subsubheading Synopsis
17892 Produces a list of the currently known @value{GDBN} thread ids. At the
17893 end of the list it also prints the total number of such threads.
17895 @subsubheading @value{GDBN} Command
17897 Part of @samp{info threads} supplies the same information.
17899 @subsubheading Example
17901 No threads present, besides the main process:
17906 ^done,thread-ids=@{@},number-of-threads="0"
17916 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
17917 number-of-threads="3"
17922 @subheading The @code{-thread-select} Command
17923 @findex -thread-select
17925 @subsubheading Synopsis
17928 -thread-select @var{threadnum}
17931 Make @var{threadnum} the current thread. It prints the number of the new
17932 current thread, and the topmost frame for that thread.
17934 @subsubheading @value{GDBN} Command
17936 The corresponding @value{GDBN} command is @samp{thread}.
17938 @subsubheading Example
17945 *stopped,reason="end-stepping-range",thread-id="2",line="187",
17946 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
17950 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
17951 number-of-threads="3"
17954 ^done,new-thread-id="3",
17955 frame=@{level="0",func="vprintf",
17956 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
17957 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
17961 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17962 @node GDB/MI Tracepoint Commands
17963 @section @sc{gdb/mi} Tracepoint Commands
17965 The tracepoint commands are not yet implemented.
17967 @c @subheading -trace-actions
17969 @c @subheading -trace-delete
17971 @c @subheading -trace-disable
17973 @c @subheading -trace-dump
17975 @c @subheading -trace-enable
17977 @c @subheading -trace-exists
17979 @c @subheading -trace-find
17981 @c @subheading -trace-frame-number
17983 @c @subheading -trace-info
17985 @c @subheading -trace-insert
17987 @c @subheading -trace-list
17989 @c @subheading -trace-pass-count
17991 @c @subheading -trace-save
17993 @c @subheading -trace-start
17995 @c @subheading -trace-stop
17998 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17999 @node GDB/MI Variable Objects
18000 @section @sc{gdb/mi} Variable Objects
18003 @subheading Motivation for Variable Objects in @sc{gdb/mi}
18005 For the implementation of a variable debugger window (locals, watched
18006 expressions, etc.), we are proposing the adaptation of the existing code
18007 used by @code{Insight}.
18009 The two main reasons for that are:
18013 It has been proven in practice (it is already on its second generation).
18016 It will shorten development time (needless to say how important it is
18020 The original interface was designed to be used by Tcl code, so it was
18021 slightly changed so it could be used through @sc{gdb/mi}. This section
18022 describes the @sc{gdb/mi} operations that will be available and gives some
18023 hints about their use.
18025 @emph{Note}: In addition to the set of operations described here, we
18026 expect the @sc{gui} implementation of a variable window to require, at
18027 least, the following operations:
18030 @item @code{-gdb-show} @code{output-radix}
18031 @item @code{-stack-list-arguments}
18032 @item @code{-stack-list-locals}
18033 @item @code{-stack-select-frame}
18036 @subheading Introduction to Variable Objects in @sc{gdb/mi}
18038 @cindex variable objects in @sc{gdb/mi}
18039 The basic idea behind variable objects is the creation of a named object
18040 to represent a variable, an expression, a memory location or even a CPU
18041 register. For each object created, a set of operations is available for
18042 examining or changing its properties.
18044 Furthermore, complex data types, such as C structures, are represented
18045 in a tree format. For instance, the @code{struct} type variable is the
18046 root and the children will represent the struct members. If a child
18047 is itself of a complex type, it will also have children of its own.
18048 Appropriate language differences are handled for C, C@t{++} and Java.
18050 When returning the actual values of the objects, this facility allows
18051 for the individual selection of the display format used in the result
18052 creation. It can be chosen among: binary, decimal, hexadecimal, octal
18053 and natural. Natural refers to a default format automatically
18054 chosen based on the variable type (like decimal for an @code{int}, hex
18055 for pointers, etc.).
18057 The following is the complete set of @sc{gdb/mi} operations defined to
18058 access this functionality:
18060 @multitable @columnfractions .4 .6
18061 @item @strong{Operation}
18062 @tab @strong{Description}
18064 @item @code{-var-create}
18065 @tab create a variable object
18066 @item @code{-var-delete}
18067 @tab delete the variable object and its children
18068 @item @code{-var-set-format}
18069 @tab set the display format of this variable
18070 @item @code{-var-show-format}
18071 @tab show the display format of this variable
18072 @item @code{-var-info-num-children}
18073 @tab tells how many children this object has
18074 @item @code{-var-list-children}
18075 @tab return a list of the object's children
18076 @item @code{-var-info-type}
18077 @tab show the type of this variable object
18078 @item @code{-var-info-expression}
18079 @tab print what this variable object represents
18080 @item @code{-var-show-attributes}
18081 @tab is this variable editable? does it exist here?
18082 @item @code{-var-evaluate-expression}
18083 @tab get the value of this variable
18084 @item @code{-var-assign}
18085 @tab set the value of this variable
18086 @item @code{-var-update}
18087 @tab update the variable and its children
18090 In the next subsection we describe each operation in detail and suggest
18091 how it can be used.
18093 @subheading Description And Use of Operations on Variable Objects
18095 @subheading The @code{-var-create} Command
18096 @findex -var-create
18098 @subsubheading Synopsis
18101 -var-create @{@var{name} | "-"@}
18102 @{@var{frame-addr} | "*"@} @var{expression}
18105 This operation creates a variable object, which allows the monitoring of
18106 a variable, the result of an expression, a memory cell or a CPU
18109 The @var{name} parameter is the string by which the object can be
18110 referenced. It must be unique. If @samp{-} is specified, the varobj
18111 system will generate a string ``varNNNNNN'' automatically. It will be
18112 unique provided that one does not specify @var{name} on that format.
18113 The command fails if a duplicate name is found.
18115 The frame under which the expression should be evaluated can be
18116 specified by @var{frame-addr}. A @samp{*} indicates that the current
18117 frame should be used.
18119 @var{expression} is any expression valid on the current language set (must not
18120 begin with a @samp{*}), or one of the following:
18124 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
18127 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
18130 @samp{$@var{regname}} --- a CPU register name
18133 @subsubheading Result
18135 This operation returns the name, number of children and the type of the
18136 object created. Type is returned as a string as the ones generated by
18137 the @value{GDBN} CLI:
18140 name="@var{name}",numchild="N",type="@var{type}"
18144 @subheading The @code{-var-delete} Command
18145 @findex -var-delete
18147 @subsubheading Synopsis
18150 -var-delete @var{name}
18153 Deletes a previously created variable object and all of its children.
18155 Returns an error if the object @var{name} is not found.
18158 @subheading The @code{-var-set-format} Command
18159 @findex -var-set-format
18161 @subsubheading Synopsis
18164 -var-set-format @var{name} @var{format-spec}
18167 Sets the output format for the value of the object @var{name} to be
18170 The syntax for the @var{format-spec} is as follows:
18173 @var{format-spec} @expansion{}
18174 @{binary | decimal | hexadecimal | octal | natural@}
18178 @subheading The @code{-var-show-format} Command
18179 @findex -var-show-format
18181 @subsubheading Synopsis
18184 -var-show-format @var{name}
18187 Returns the format used to display the value of the object @var{name}.
18190 @var{format} @expansion{}
18195 @subheading The @code{-var-info-num-children} Command
18196 @findex -var-info-num-children
18198 @subsubheading Synopsis
18201 -var-info-num-children @var{name}
18204 Returns the number of children of a variable object @var{name}:
18211 @subheading The @code{-var-list-children} Command
18212 @findex -var-list-children
18214 @subsubheading Synopsis
18217 -var-list-children [@var{print-values}] @var{name}
18220 Returns a list of the children of the specified variable object. With
18221 just the variable object name as an argument or with an optional
18222 preceding argument of 0 or @code{--no-values}, prints only the names of the
18223 variables. With an optional preceding argument of 1 or @code{--all-values},
18224 also prints their values.
18226 @subsubheading Example
18230 -var-list-children n
18231 numchild=@var{n},children=[@{name=@var{name},
18232 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
18234 -var-list-children --all-values n
18235 numchild=@var{n},children=[@{name=@var{name},
18236 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
18240 @subheading The @code{-var-info-type} Command
18241 @findex -var-info-type
18243 @subsubheading Synopsis
18246 -var-info-type @var{name}
18249 Returns the type of the specified variable @var{name}. The type is
18250 returned as a string in the same format as it is output by the
18254 type=@var{typename}
18258 @subheading The @code{-var-info-expression} Command
18259 @findex -var-info-expression
18261 @subsubheading Synopsis
18264 -var-info-expression @var{name}
18267 Returns what is represented by the variable object @var{name}:
18270 lang=@var{lang-spec},exp=@var{expression}
18274 where @var{lang-spec} is @code{@{"C" | "C++" | "Java"@}}.
18276 @subheading The @code{-var-show-attributes} Command
18277 @findex -var-show-attributes
18279 @subsubheading Synopsis
18282 -var-show-attributes @var{name}
18285 List attributes of the specified variable object @var{name}:
18288 status=@var{attr} [ ( ,@var{attr} )* ]
18292 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
18294 @subheading The @code{-var-evaluate-expression} Command
18295 @findex -var-evaluate-expression
18297 @subsubheading Synopsis
18300 -var-evaluate-expression @var{name}
18303 Evaluates the expression that is represented by the specified variable
18304 object and returns its value as a string in the current format specified
18311 Note that one must invoke @code{-var-list-children} for a variable
18312 before the value of a child variable can be evaluated.
18314 @subheading The @code{-var-assign} Command
18315 @findex -var-assign
18317 @subsubheading Synopsis
18320 -var-assign @var{name} @var{expression}
18323 Assigns the value of @var{expression} to the variable object specified
18324 by @var{name}. The object must be @samp{editable}. If the variable's
18325 value is altered by the assign, the variable will show up in any
18326 subsequent @code{-var-update} list.
18328 @subsubheading Example
18336 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
18340 @subheading The @code{-var-update} Command
18341 @findex -var-update
18343 @subsubheading Synopsis
18346 -var-update @{@var{name} | "*"@}
18349 Update the value of the variable object @var{name} by evaluating its
18350 expression after fetching all the new values from memory or registers.
18351 A @samp{*} causes all existing variable objects to be updated.
18355 @chapter @value{GDBN} Annotations
18357 This chapter describes annotations in @value{GDBN}. Annotations were
18358 designed to interface @value{GDBN} to graphical user interfaces or other
18359 similar programs which want to interact with @value{GDBN} at a
18360 relatively high level.
18362 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
18366 This is Edition @value{EDITION}, @value{DATE}.
18370 * Annotations Overview:: What annotations are; the general syntax.
18371 * Server Prefix:: Issuing a command without affecting user state.
18372 * Prompting:: Annotations marking @value{GDBN}'s need for input.
18373 * Errors:: Annotations for error messages.
18374 * Invalidation:: Some annotations describe things now invalid.
18375 * Annotations for Running::
18376 Whether the program is running, how it stopped, etc.
18377 * Source Annotations:: Annotations describing source code.
18380 @node Annotations Overview
18381 @section What is an Annotation?
18382 @cindex annotations
18384 Annotations start with a newline character, two @samp{control-z}
18385 characters, and the name of the annotation. If there is no additional
18386 information associated with this annotation, the name of the annotation
18387 is followed immediately by a newline. If there is additional
18388 information, the name of the annotation is followed by a space, the
18389 additional information, and a newline. The additional information
18390 cannot contain newline characters.
18392 Any output not beginning with a newline and two @samp{control-z}
18393 characters denotes literal output from @value{GDBN}. Currently there is
18394 no need for @value{GDBN} to output a newline followed by two
18395 @samp{control-z} characters, but if there was such a need, the
18396 annotations could be extended with an @samp{escape} annotation which
18397 means those three characters as output.
18399 The annotation @var{level}, which is specified using the
18400 @option{--annotate} command line option (@pxref{Mode Options}), controls
18401 how much information @value{GDBN} prints together with its prompt,
18402 values of expressions, source lines, and other types of output. Level 0
18403 is for no anntations, level 1 is for use when @value{GDBN} is run as a
18404 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
18405 for programs that control @value{GDBN}, and level 2 annotations have
18406 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
18407 Interface, annotate, GDB's Obsolete Annotations}). This chapter
18408 describes level 3 annotations.
18410 A simple example of starting up @value{GDBN} with annotations is:
18413 $ @kbd{gdb --annotate=3}
18415 Copyright 2003 Free Software Foundation, Inc.
18416 GDB is free software, covered by the GNU General Public License,
18417 and you are welcome to change it and/or distribute copies of it
18418 under certain conditions.
18419 Type "show copying" to see the conditions.
18420 There is absolutely no warranty for GDB. Type "show warranty"
18422 This GDB was configured as "i386-pc-linux-gnu"
18433 Here @samp{quit} is input to @value{GDBN}; the rest is output from
18434 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
18435 denotes a @samp{control-z} character) are annotations; the rest is
18436 output from @value{GDBN}.
18438 @node Server Prefix
18439 @section The Server Prefix
18440 @cindex server prefix for annotations
18442 To issue a command to @value{GDBN} without affecting certain aspects of
18443 the state which is seen by users, prefix it with @samp{server }. This
18444 means that this command will not affect the command history, nor will it
18445 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
18446 pressed on a line by itself.
18448 The server prefix does not affect the recording of values into the value
18449 history; to print a value without recording it into the value history,
18450 use the @code{output} command instead of the @code{print} command.
18453 @section Annotation for @value{GDBN} Input
18455 @cindex annotations for prompts
18456 When @value{GDBN} prompts for input, it annotates this fact so it is possible
18457 to know when to send output, when the output from a given command is
18460 Different kinds of input each have a different @dfn{input type}. Each
18461 input type has three annotations: a @code{pre-} annotation, which
18462 denotes the beginning of any prompt which is being output, a plain
18463 annotation, which denotes the end of the prompt, and then a @code{post-}
18464 annotation which denotes the end of any echo which may (or may not) be
18465 associated with the input. For example, the @code{prompt} input type
18466 features the following annotations:
18474 The input types are
18479 @findex post-prompt
18481 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
18483 @findex pre-commands
18485 @findex post-commands
18487 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
18488 command. The annotations are repeated for each command which is input.
18490 @findex pre-overload-choice
18491 @findex overload-choice
18492 @findex post-overload-choice
18493 @item overload-choice
18494 When @value{GDBN} wants the user to select between various overloaded functions.
18500 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
18502 @findex pre-prompt-for-continue
18503 @findex prompt-for-continue
18504 @findex post-prompt-for-continue
18505 @item prompt-for-continue
18506 When @value{GDBN} is asking the user to press return to continue. Note: Don't
18507 expect this to work well; instead use @code{set height 0} to disable
18508 prompting. This is because the counting of lines is buggy in the
18509 presence of annotations.
18514 @cindex annotations for errors, warnings and interrupts
18521 This annotation occurs right before @value{GDBN} responds to an interrupt.
18528 This annotation occurs right before @value{GDBN} responds to an error.
18530 Quit and error annotations indicate that any annotations which @value{GDBN} was
18531 in the middle of may end abruptly. For example, if a
18532 @code{value-history-begin} annotation is followed by a @code{error}, one
18533 cannot expect to receive the matching @code{value-history-end}. One
18534 cannot expect not to receive it either, however; an error annotation
18535 does not necessarily mean that @value{GDBN} is immediately returning all the way
18538 @findex error-begin
18539 A quit or error annotation may be preceded by
18545 Any output between that and the quit or error annotation is the error
18548 Warning messages are not yet annotated.
18549 @c If we want to change that, need to fix warning(), type_error(),
18550 @c range_error(), and possibly other places.
18553 @section Invalidation Notices
18555 @cindex annotations for invalidation messages
18556 The following annotations say that certain pieces of state may have
18560 @findex frames-invalid
18561 @item ^Z^Zframes-invalid
18563 The frames (for example, output from the @code{backtrace} command) may
18566 @findex breakpoints-invalid
18567 @item ^Z^Zbreakpoints-invalid
18569 The breakpoints may have changed. For example, the user just added or
18570 deleted a breakpoint.
18573 @node Annotations for Running
18574 @section Running the Program
18575 @cindex annotations for running programs
18579 When the program starts executing due to a @value{GDBN} command such as
18580 @code{step} or @code{continue},
18586 is output. When the program stops,
18592 is output. Before the @code{stopped} annotation, a variety of
18593 annotations describe how the program stopped.
18597 @item ^Z^Zexited @var{exit-status}
18598 The program exited, and @var{exit-status} is the exit status (zero for
18599 successful exit, otherwise nonzero).
18602 @findex signal-name
18603 @findex signal-name-end
18604 @findex signal-string
18605 @findex signal-string-end
18606 @item ^Z^Zsignalled
18607 The program exited with a signal. After the @code{^Z^Zsignalled}, the
18608 annotation continues:
18614 ^Z^Zsignal-name-end
18618 ^Z^Zsignal-string-end
18623 where @var{name} is the name of the signal, such as @code{SIGILL} or
18624 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
18625 as @code{Illegal Instruction} or @code{Segmentation fault}.
18626 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
18627 user's benefit and have no particular format.
18631 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
18632 just saying that the program received the signal, not that it was
18633 terminated with it.
18636 @item ^Z^Zbreakpoint @var{number}
18637 The program hit breakpoint number @var{number}.
18640 @item ^Z^Zwatchpoint @var{number}
18641 The program hit watchpoint number @var{number}.
18644 @node Source Annotations
18645 @section Displaying Source
18646 @cindex annotations for source display
18649 The following annotation is used instead of displaying source code:
18652 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
18655 where @var{filename} is an absolute file name indicating which source
18656 file, @var{line} is the line number within that file (where 1 is the
18657 first line in the file), @var{character} is the character position
18658 within the file (where 0 is the first character in the file) (for most
18659 debug formats this will necessarily point to the beginning of a line),
18660 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
18661 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
18662 @var{addr} is the address in the target program associated with the
18663 source which is being displayed. @var{addr} is in the form @samp{0x}
18664 followed by one or more lowercase hex digits (note that this does not
18665 depend on the language).
18668 @chapter Reporting Bugs in @value{GDBN}
18669 @cindex bugs in @value{GDBN}
18670 @cindex reporting bugs in @value{GDBN}
18672 Your bug reports play an essential role in making @value{GDBN} reliable.
18674 Reporting a bug may help you by bringing a solution to your problem, or it
18675 may not. But in any case the principal function of a bug report is to help
18676 the entire community by making the next version of @value{GDBN} work better. Bug
18677 reports are your contribution to the maintenance of @value{GDBN}.
18679 In order for a bug report to serve its purpose, you must include the
18680 information that enables us to fix the bug.
18683 * Bug Criteria:: Have you found a bug?
18684 * Bug Reporting:: How to report bugs
18688 @section Have you found a bug?
18689 @cindex bug criteria
18691 If you are not sure whether you have found a bug, here are some guidelines:
18694 @cindex fatal signal
18695 @cindex debugger crash
18696 @cindex crash of debugger
18698 If the debugger gets a fatal signal, for any input whatever, that is a
18699 @value{GDBN} bug. Reliable debuggers never crash.
18701 @cindex error on valid input
18703 If @value{GDBN} produces an error message for valid input, that is a
18704 bug. (Note that if you're cross debugging, the problem may also be
18705 somewhere in the connection to the target.)
18707 @cindex invalid input
18709 If @value{GDBN} does not produce an error message for invalid input,
18710 that is a bug. However, you should note that your idea of
18711 ``invalid input'' might be our idea of ``an extension'' or ``support
18712 for traditional practice''.
18715 If you are an experienced user of debugging tools, your suggestions
18716 for improvement of @value{GDBN} are welcome in any case.
18719 @node Bug Reporting
18720 @section How to report bugs
18721 @cindex bug reports
18722 @cindex @value{GDBN} bugs, reporting
18724 A number of companies and individuals offer support for @sc{gnu} products.
18725 If you obtained @value{GDBN} from a support organization, we recommend you
18726 contact that organization first.
18728 You can find contact information for many support companies and
18729 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
18731 @c should add a web page ref...
18733 In any event, we also recommend that you submit bug reports for
18734 @value{GDBN}. The prefered method is to submit them directly using
18735 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
18736 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
18739 @strong{Do not send bug reports to @samp{info-gdb}, or to
18740 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
18741 not want to receive bug reports. Those that do have arranged to receive
18744 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
18745 serves as a repeater. The mailing list and the newsgroup carry exactly
18746 the same messages. Often people think of posting bug reports to the
18747 newsgroup instead of mailing them. This appears to work, but it has one
18748 problem which can be crucial: a newsgroup posting often lacks a mail
18749 path back to the sender. Thus, if we need to ask for more information,
18750 we may be unable to reach you. For this reason, it is better to send
18751 bug reports to the mailing list.
18753 The fundamental principle of reporting bugs usefully is this:
18754 @strong{report all the facts}. If you are not sure whether to state a
18755 fact or leave it out, state it!
18757 Often people omit facts because they think they know what causes the
18758 problem and assume that some details do not matter. Thus, you might
18759 assume that the name of the variable you use in an example does not matter.
18760 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
18761 stray memory reference which happens to fetch from the location where that
18762 name is stored in memory; perhaps, if the name were different, the contents
18763 of that location would fool the debugger into doing the right thing despite
18764 the bug. Play it safe and give a specific, complete example. That is the
18765 easiest thing for you to do, and the most helpful.
18767 Keep in mind that the purpose of a bug report is to enable us to fix the
18768 bug. It may be that the bug has been reported previously, but neither
18769 you nor we can know that unless your bug report is complete and
18772 Sometimes people give a few sketchy facts and ask, ``Does this ring a
18773 bell?'' Those bug reports are useless, and we urge everyone to
18774 @emph{refuse to respond to them} except to chide the sender to report
18777 To enable us to fix the bug, you should include all these things:
18781 The version of @value{GDBN}. @value{GDBN} announces it if you start
18782 with no arguments; you can also print it at any time using @code{show
18785 Without this, we will not know whether there is any point in looking for
18786 the bug in the current version of @value{GDBN}.
18789 The type of machine you are using, and the operating system name and
18793 What compiler (and its version) was used to compile @value{GDBN}---e.g.
18794 ``@value{GCC}--2.8.1''.
18797 What compiler (and its version) was used to compile the program you are
18798 debugging---e.g. ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
18799 C Compiler''. For GCC, you can say @code{gcc --version} to get this
18800 information; for other compilers, see the documentation for those
18804 The command arguments you gave the compiler to compile your example and
18805 observe the bug. For example, did you use @samp{-O}? To guarantee
18806 you will not omit something important, list them all. A copy of the
18807 Makefile (or the output from make) is sufficient.
18809 If we were to try to guess the arguments, we would probably guess wrong
18810 and then we might not encounter the bug.
18813 A complete input script, and all necessary source files, that will
18817 A description of what behavior you observe that you believe is
18818 incorrect. For example, ``It gets a fatal signal.''
18820 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
18821 will certainly notice it. But if the bug is incorrect output, we might
18822 not notice unless it is glaringly wrong. You might as well not give us
18823 a chance to make a mistake.
18825 Even if the problem you experience is a fatal signal, you should still
18826 say so explicitly. Suppose something strange is going on, such as, your
18827 copy of @value{GDBN} is out of synch, or you have encountered a bug in
18828 the C library on your system. (This has happened!) Your copy might
18829 crash and ours would not. If you told us to expect a crash, then when
18830 ours fails to crash, we would know that the bug was not happening for
18831 us. If you had not told us to expect a crash, then we would not be able
18832 to draw any conclusion from our observations.
18835 If you wish to suggest changes to the @value{GDBN} source, send us context
18836 diffs. If you even discuss something in the @value{GDBN} source, refer to
18837 it by context, not by line number.
18839 The line numbers in our development sources will not match those in your
18840 sources. Your line numbers would convey no useful information to us.
18844 Here are some things that are not necessary:
18848 A description of the envelope of the bug.
18850 Often people who encounter a bug spend a lot of time investigating
18851 which changes to the input file will make the bug go away and which
18852 changes will not affect it.
18854 This is often time consuming and not very useful, because the way we
18855 will find the bug is by running a single example under the debugger
18856 with breakpoints, not by pure deduction from a series of examples.
18857 We recommend that you save your time for something else.
18859 Of course, if you can find a simpler example to report @emph{instead}
18860 of the original one, that is a convenience for us. Errors in the
18861 output will be easier to spot, running under the debugger will take
18862 less time, and so on.
18864 However, simplification is not vital; if you do not want to do this,
18865 report the bug anyway and send us the entire test case you used.
18868 A patch for the bug.
18870 A patch for the bug does help us if it is a good one. But do not omit
18871 the necessary information, such as the test case, on the assumption that
18872 a patch is all we need. We might see problems with your patch and decide
18873 to fix the problem another way, or we might not understand it at all.
18875 Sometimes with a program as complicated as @value{GDBN} it is very hard to
18876 construct an example that will make the program follow a certain path
18877 through the code. If you do not send us the example, we will not be able
18878 to construct one, so we will not be able to verify that the bug is fixed.
18880 And if we cannot understand what bug you are trying to fix, or why your
18881 patch should be an improvement, we will not install it. A test case will
18882 help us to understand.
18885 A guess about what the bug is or what it depends on.
18887 Such guesses are usually wrong. Even we cannot guess right about such
18888 things without first using the debugger to find the facts.
18891 @c The readline documentation is distributed with the readline code
18892 @c and consists of the two following files:
18894 @c inc-hist.texinfo
18895 @c Use -I with makeinfo to point to the appropriate directory,
18896 @c environment var TEXINPUTS with TeX.
18897 @include rluser.texinfo
18898 @include inc-hist.texinfo
18901 @node Formatting Documentation
18902 @appendix Formatting Documentation
18904 @cindex @value{GDBN} reference card
18905 @cindex reference card
18906 The @value{GDBN} 4 release includes an already-formatted reference card, ready
18907 for printing with PostScript or Ghostscript, in the @file{gdb}
18908 subdirectory of the main source directory@footnote{In
18909 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
18910 release.}. If you can use PostScript or Ghostscript with your printer,
18911 you can print the reference card immediately with @file{refcard.ps}.
18913 The release also includes the source for the reference card. You
18914 can format it, using @TeX{}, by typing:
18920 The @value{GDBN} reference card is designed to print in @dfn{landscape}
18921 mode on US ``letter'' size paper;
18922 that is, on a sheet 11 inches wide by 8.5 inches
18923 high. You will need to specify this form of printing as an option to
18924 your @sc{dvi} output program.
18926 @cindex documentation
18928 All the documentation for @value{GDBN} comes as part of the machine-readable
18929 distribution. The documentation is written in Texinfo format, which is
18930 a documentation system that uses a single source file to produce both
18931 on-line information and a printed manual. You can use one of the Info
18932 formatting commands to create the on-line version of the documentation
18933 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
18935 @value{GDBN} includes an already formatted copy of the on-line Info
18936 version of this manual in the @file{gdb} subdirectory. The main Info
18937 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
18938 subordinate files matching @samp{gdb.info*} in the same directory. If
18939 necessary, you can print out these files, or read them with any editor;
18940 but they are easier to read using the @code{info} subsystem in @sc{gnu}
18941 Emacs or the standalone @code{info} program, available as part of the
18942 @sc{gnu} Texinfo distribution.
18944 If you want to format these Info files yourself, you need one of the
18945 Info formatting programs, such as @code{texinfo-format-buffer} or
18948 If you have @code{makeinfo} installed, and are in the top level
18949 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
18950 version @value{GDBVN}), you can make the Info file by typing:
18957 If you want to typeset and print copies of this manual, you need @TeX{},
18958 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
18959 Texinfo definitions file.
18961 @TeX{} is a typesetting program; it does not print files directly, but
18962 produces output files called @sc{dvi} files. To print a typeset
18963 document, you need a program to print @sc{dvi} files. If your system
18964 has @TeX{} installed, chances are it has such a program. The precise
18965 command to use depends on your system; @kbd{lpr -d} is common; another
18966 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
18967 require a file name without any extension or a @samp{.dvi} extension.
18969 @TeX{} also requires a macro definitions file called
18970 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
18971 written in Texinfo format. On its own, @TeX{} cannot either read or
18972 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
18973 and is located in the @file{gdb-@var{version-number}/texinfo}
18976 If you have @TeX{} and a @sc{dvi} printer program installed, you can
18977 typeset and print this manual. First switch to the the @file{gdb}
18978 subdirectory of the main source directory (for example, to
18979 @file{gdb-@value{GDBVN}/gdb}) and type:
18985 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
18987 @node Installing GDB
18988 @appendix Installing @value{GDBN}
18989 @cindex configuring @value{GDBN}
18990 @cindex installation
18991 @cindex configuring @value{GDBN}, and source tree subdirectories
18993 @value{GDBN} comes with a @code{configure} script that automates the process
18994 of preparing @value{GDBN} for installation; you can then use @code{make} to
18995 build the @code{gdb} program.
18997 @c irrelevant in info file; it's as current as the code it lives with.
18998 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
18999 look at the @file{README} file in the sources; we may have improved the
19000 installation procedures since publishing this manual.}
19003 The @value{GDBN} distribution includes all the source code you need for
19004 @value{GDBN} in a single directory, whose name is usually composed by
19005 appending the version number to @samp{gdb}.
19007 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
19008 @file{gdb-@value{GDBVN}} directory. That directory contains:
19011 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
19012 script for configuring @value{GDBN} and all its supporting libraries
19014 @item gdb-@value{GDBVN}/gdb
19015 the source specific to @value{GDBN} itself
19017 @item gdb-@value{GDBVN}/bfd
19018 source for the Binary File Descriptor library
19020 @item gdb-@value{GDBVN}/include
19021 @sc{gnu} include files
19023 @item gdb-@value{GDBVN}/libiberty
19024 source for the @samp{-liberty} free software library
19026 @item gdb-@value{GDBVN}/opcodes
19027 source for the library of opcode tables and disassemblers
19029 @item gdb-@value{GDBVN}/readline
19030 source for the @sc{gnu} command-line interface
19032 @item gdb-@value{GDBVN}/glob
19033 source for the @sc{gnu} filename pattern-matching subroutine
19035 @item gdb-@value{GDBVN}/mmalloc
19036 source for the @sc{gnu} memory-mapped malloc package
19039 The simplest way to configure and build @value{GDBN} is to run @code{configure}
19040 from the @file{gdb-@var{version-number}} source directory, which in
19041 this example is the @file{gdb-@value{GDBVN}} directory.
19043 First switch to the @file{gdb-@var{version-number}} source directory
19044 if you are not already in it; then run @code{configure}. Pass the
19045 identifier for the platform on which @value{GDBN} will run as an
19051 cd gdb-@value{GDBVN}
19052 ./configure @var{host}
19057 where @var{host} is an identifier such as @samp{sun4} or
19058 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
19059 (You can often leave off @var{host}; @code{configure} tries to guess the
19060 correct value by examining your system.)
19062 Running @samp{configure @var{host}} and then running @code{make} builds the
19063 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
19064 libraries, then @code{gdb} itself. The configured source files, and the
19065 binaries, are left in the corresponding source directories.
19068 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
19069 system does not recognize this automatically when you run a different
19070 shell, you may need to run @code{sh} on it explicitly:
19073 sh configure @var{host}
19076 If you run @code{configure} from a directory that contains source
19077 directories for multiple libraries or programs, such as the
19078 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
19079 creates configuration files for every directory level underneath (unless
19080 you tell it not to, with the @samp{--norecursion} option).
19082 You should run the @code{configure} script from the top directory in the
19083 source tree, the @file{gdb-@var{version-number}} directory. If you run
19084 @code{configure} from one of the subdirectories, you will configure only
19085 that subdirectory. That is usually not what you want. In particular,
19086 if you run the first @code{configure} from the @file{gdb} subdirectory
19087 of the @file{gdb-@var{version-number}} directory, you will omit the
19088 configuration of @file{bfd}, @file{readline}, and other sibling
19089 directories of the @file{gdb} subdirectory. This leads to build errors
19090 about missing include files such as @file{bfd/bfd.h}.
19092 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
19093 However, you should make sure that the shell on your path (named by
19094 the @samp{SHELL} environment variable) is publicly readable. Remember
19095 that @value{GDBN} uses the shell to start your program---some systems refuse to
19096 let @value{GDBN} debug child processes whose programs are not readable.
19099 * Separate Objdir:: Compiling @value{GDBN} in another directory
19100 * Config Names:: Specifying names for hosts and targets
19101 * Configure Options:: Summary of options for configure
19104 @node Separate Objdir
19105 @section Compiling @value{GDBN} in another directory
19107 If you want to run @value{GDBN} versions for several host or target machines,
19108 you need a different @code{gdb} compiled for each combination of
19109 host and target. @code{configure} is designed to make this easy by
19110 allowing you to generate each configuration in a separate subdirectory,
19111 rather than in the source directory. If your @code{make} program
19112 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
19113 @code{make} in each of these directories builds the @code{gdb}
19114 program specified there.
19116 To build @code{gdb} in a separate directory, run @code{configure}
19117 with the @samp{--srcdir} option to specify where to find the source.
19118 (You also need to specify a path to find @code{configure}
19119 itself from your working directory. If the path to @code{configure}
19120 would be the same as the argument to @samp{--srcdir}, you can leave out
19121 the @samp{--srcdir} option; it is assumed.)
19123 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
19124 separate directory for a Sun 4 like this:
19128 cd gdb-@value{GDBVN}
19131 ../gdb-@value{GDBVN}/configure sun4
19136 When @code{configure} builds a configuration using a remote source
19137 directory, it creates a tree for the binaries with the same structure
19138 (and using the same names) as the tree under the source directory. In
19139 the example, you'd find the Sun 4 library @file{libiberty.a} in the
19140 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
19141 @file{gdb-sun4/gdb}.
19143 Make sure that your path to the @file{configure} script has just one
19144 instance of @file{gdb} in it. If your path to @file{configure} looks
19145 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
19146 one subdirectory of @value{GDBN}, not the whole package. This leads to
19147 build errors about missing include files such as @file{bfd/bfd.h}.
19149 One popular reason to build several @value{GDBN} configurations in separate
19150 directories is to configure @value{GDBN} for cross-compiling (where
19151 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
19152 programs that run on another machine---the @dfn{target}).
19153 You specify a cross-debugging target by
19154 giving the @samp{--target=@var{target}} option to @code{configure}.
19156 When you run @code{make} to build a program or library, you must run
19157 it in a configured directory---whatever directory you were in when you
19158 called @code{configure} (or one of its subdirectories).
19160 The @code{Makefile} that @code{configure} generates in each source
19161 directory also runs recursively. If you type @code{make} in a source
19162 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
19163 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
19164 will build all the required libraries, and then build GDB.
19166 When you have multiple hosts or targets configured in separate
19167 directories, you can run @code{make} on them in parallel (for example,
19168 if they are NFS-mounted on each of the hosts); they will not interfere
19172 @section Specifying names for hosts and targets
19174 The specifications used for hosts and targets in the @code{configure}
19175 script are based on a three-part naming scheme, but some short predefined
19176 aliases are also supported. The full naming scheme encodes three pieces
19177 of information in the following pattern:
19180 @var{architecture}-@var{vendor}-@var{os}
19183 For example, you can use the alias @code{sun4} as a @var{host} argument,
19184 or as the value for @var{target} in a @code{--target=@var{target}}
19185 option. The equivalent full name is @samp{sparc-sun-sunos4}.
19187 The @code{configure} script accompanying @value{GDBN} does not provide
19188 any query facility to list all supported host and target names or
19189 aliases. @code{configure} calls the Bourne shell script
19190 @code{config.sub} to map abbreviations to full names; you can read the
19191 script, if you wish, or you can use it to test your guesses on
19192 abbreviations---for example:
19195 % sh config.sub i386-linux
19197 % sh config.sub alpha-linux
19198 alpha-unknown-linux-gnu
19199 % sh config.sub hp9k700
19201 % sh config.sub sun4
19202 sparc-sun-sunos4.1.1
19203 % sh config.sub sun3
19204 m68k-sun-sunos4.1.1
19205 % sh config.sub i986v
19206 Invalid configuration `i986v': machine `i986v' not recognized
19210 @code{config.sub} is also distributed in the @value{GDBN} source
19211 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
19213 @node Configure Options
19214 @section @code{configure} options
19216 Here is a summary of the @code{configure} options and arguments that
19217 are most often useful for building @value{GDBN}. @code{configure} also has
19218 several other options not listed here. @inforef{What Configure
19219 Does,,configure.info}, for a full explanation of @code{configure}.
19222 configure @r{[}--help@r{]}
19223 @r{[}--prefix=@var{dir}@r{]}
19224 @r{[}--exec-prefix=@var{dir}@r{]}
19225 @r{[}--srcdir=@var{dirname}@r{]}
19226 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
19227 @r{[}--target=@var{target}@r{]}
19232 You may introduce options with a single @samp{-} rather than
19233 @samp{--} if you prefer; but you may abbreviate option names if you use
19238 Display a quick summary of how to invoke @code{configure}.
19240 @item --prefix=@var{dir}
19241 Configure the source to install programs and files under directory
19244 @item --exec-prefix=@var{dir}
19245 Configure the source to install programs under directory
19248 @c avoid splitting the warning from the explanation:
19250 @item --srcdir=@var{dirname}
19251 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
19252 @code{make} that implements the @code{VPATH} feature.}@*
19253 Use this option to make configurations in directories separate from the
19254 @value{GDBN} source directories. Among other things, you can use this to
19255 build (or maintain) several configurations simultaneously, in separate
19256 directories. @code{configure} writes configuration specific files in
19257 the current directory, but arranges for them to use the source in the
19258 directory @var{dirname}. @code{configure} creates directories under
19259 the working directory in parallel to the source directories below
19262 @item --norecursion
19263 Configure only the directory level where @code{configure} is executed; do not
19264 propagate configuration to subdirectories.
19266 @item --target=@var{target}
19267 Configure @value{GDBN} for cross-debugging programs running on the specified
19268 @var{target}. Without this option, @value{GDBN} is configured to debug
19269 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
19271 There is no convenient way to generate a list of all available targets.
19273 @item @var{host} @dots{}
19274 Configure @value{GDBN} to run on the specified @var{host}.
19276 There is no convenient way to generate a list of all available hosts.
19279 There are many other options available as well, but they are generally
19280 needed for special purposes only.
19282 @node Maintenance Commands
19283 @appendix Maintenance Commands
19284 @cindex maintenance commands
19285 @cindex internal commands
19287 In addition to commands intended for @value{GDBN} users, @value{GDBN}
19288 includes a number of commands intended for @value{GDBN} developers.
19289 These commands are provided here for reference.
19292 @kindex maint info breakpoints
19293 @item @anchor{maint info breakpoints}maint info breakpoints
19294 Using the same format as @samp{info breakpoints}, display both the
19295 breakpoints you've set explicitly, and those @value{GDBN} is using for
19296 internal purposes. Internal breakpoints are shown with negative
19297 breakpoint numbers. The type column identifies what kind of breakpoint
19302 Normal, explicitly set breakpoint.
19305 Normal, explicitly set watchpoint.
19308 Internal breakpoint, used to handle correctly stepping through
19309 @code{longjmp} calls.
19311 @item longjmp resume
19312 Internal breakpoint at the target of a @code{longjmp}.
19315 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
19318 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
19321 Shared library events.
19325 @kindex maint internal-error
19326 @kindex maint internal-warning
19327 @item maint internal-error
19328 @itemx maint internal-warning
19329 Cause @value{GDBN} to call the internal function @code{internal_error}
19330 or @code{internal_warning} and hence behave as though an internal error
19331 or internal warning has been detected. In addition to reporting the
19332 internal problem, these functions give the user the opportunity to
19333 either quit @value{GDBN} or create a core file of the current
19334 @value{GDBN} session.
19337 (gdb) @kbd{maint internal-error testing, 1, 2}
19338 @dots{}/maint.c:121: internal-error: testing, 1, 2
19339 A problem internal to GDB has been detected. Further
19340 debugging may prove unreliable.
19341 Quit this debugging session? (y or n) @kbd{n}
19342 Create a core file? (y or n) @kbd{n}
19346 Takes an optional parameter that is used as the text of the error or
19349 @kindex maint print dummy-frames
19350 @item maint print dummy-frames
19352 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
19357 (gdb) @kbd{print add(2,3)}
19358 Breakpoint 2, add (a=2, b=3) at @dots{}
19360 The program being debugged stopped while in a function called from GDB.
19362 (gdb) @kbd{maint print dummy-frames}
19363 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
19364 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
19365 call_lo=0x01014000 call_hi=0x01014001
19369 Takes an optional file parameter.
19371 @kindex maint print registers
19372 @kindex maint print raw-registers
19373 @kindex maint print cooked-registers
19374 @kindex maint print register-groups
19375 @item maint print registers
19376 @itemx maint print raw-registers
19377 @itemx maint print cooked-registers
19378 @itemx maint print register-groups
19379 Print @value{GDBN}'s internal register data structures.
19381 The command @code{maint print raw-registers} includes the contents of
19382 the raw register cache; the command @code{maint print cooked-registers}
19383 includes the (cooked) value of all registers; and the command
19384 @code{maint print register-groups} includes the groups that each
19385 register is a member of. @xref{Registers,, Registers, gdbint,
19386 @value{GDBN} Internals}.
19388 Takes an optional file parameter.
19390 @kindex maint print reggroups
19391 @item maint print reggroups
19392 Print @value{GDBN}'s internal register group data structures.
19394 Takes an optional file parameter.
19397 (gdb) @kbd{maint print reggroups}
19408 @kindex maint set profile
19409 @kindex maint show profile
19410 @cindex profiling GDB
19411 @item maint set profile
19412 @itemx maint show profile
19413 Control profiling of @value{GDBN}.
19415 Profiling will be disabled until you use the @samp{maint set profile}
19416 command to enable it. When you enable profiling, the system will begin
19417 collecting timing and execution count data; when you disable profiling or
19418 exit @value{GDBN}, the results will be written to a log file. Remember that
19419 if you use profiling, @value{GDBN} will overwrite the profiling log file
19420 (often called @file{gmon.out}). If you have a record of important profiling
19421 data in a @file{gmon.out} file, be sure to move it to a safe location.
19423 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
19424 compiled with the @samp{-pg} compiler option.
19429 @node Remote Protocol
19430 @appendix @value{GDBN} Remote Serial Protocol
19435 * Stop Reply Packets::
19436 * General Query Packets::
19437 * Register Packet Format::
19439 * File-I/O remote protocol extension::
19445 There may be occasions when you need to know something about the
19446 protocol---for example, if there is only one serial port to your target
19447 machine, you might want your program to do something special if it
19448 recognizes a packet meant for @value{GDBN}.
19450 In the examples below, @samp{->} and @samp{<-} are used to indicate
19451 transmitted and received data respectfully.
19453 @cindex protocol, @value{GDBN} remote serial
19454 @cindex serial protocol, @value{GDBN} remote
19455 @cindex remote serial protocol
19456 All @value{GDBN} commands and responses (other than acknowledgments) are
19457 sent as a @var{packet}. A @var{packet} is introduced with the character
19458 @samp{$}, the actual @var{packet-data}, and the terminating character
19459 @samp{#} followed by a two-digit @var{checksum}:
19462 @code{$}@var{packet-data}@code{#}@var{checksum}
19466 @cindex checksum, for @value{GDBN} remote
19468 The two-digit @var{checksum} is computed as the modulo 256 sum of all
19469 characters between the leading @samp{$} and the trailing @samp{#} (an
19470 eight bit unsigned checksum).
19472 Implementors should note that prior to @value{GDBN} 5.0 the protocol
19473 specification also included an optional two-digit @var{sequence-id}:
19476 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
19479 @cindex sequence-id, for @value{GDBN} remote
19481 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
19482 has never output @var{sequence-id}s. Stubs that handle packets added
19483 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
19485 @cindex acknowledgment, for @value{GDBN} remote
19486 When either the host or the target machine receives a packet, the first
19487 response expected is an acknowledgment: either @samp{+} (to indicate
19488 the package was received correctly) or @samp{-} (to request
19492 -> @code{$}@var{packet-data}@code{#}@var{checksum}
19497 The host (@value{GDBN}) sends @var{command}s, and the target (the
19498 debugging stub incorporated in your program) sends a @var{response}. In
19499 the case of step and continue @var{command}s, the response is only sent
19500 when the operation has completed (the target has again stopped).
19502 @var{packet-data} consists of a sequence of characters with the
19503 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
19506 Fields within the packet should be separated using @samp{,} @samp{;} or
19507 @cindex remote protocol, field separator
19508 @samp{:}. Except where otherwise noted all numbers are represented in
19509 @sc{hex} with leading zeros suppressed.
19511 Implementors should note that prior to @value{GDBN} 5.0, the character
19512 @samp{:} could not appear as the third character in a packet (as it
19513 would potentially conflict with the @var{sequence-id}).
19515 Response @var{data} can be run-length encoded to save space. A @samp{*}
19516 means that the next character is an @sc{ascii} encoding giving a repeat count
19517 which stands for that many repetitions of the character preceding the
19518 @samp{*}. The encoding is @code{n+29}, yielding a printable character
19519 where @code{n >=3} (which is where rle starts to win). The printable
19520 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
19521 value greater than 126 should not be used.
19528 means the same as "0000".
19530 The error response returned for some packets includes a two character
19531 error number. That number is not well defined.
19533 For any @var{command} not supported by the stub, an empty response
19534 (@samp{$#00}) should be returned. That way it is possible to extend the
19535 protocol. A newer @value{GDBN} can tell if a packet is supported based
19538 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
19539 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
19545 The following table provides a complete list of all currently defined
19546 @var{command}s and their corresponding response @var{data}.
19550 @item @code{!} --- extended mode
19551 @cindex @code{!} packet
19553 Enable extended mode. In extended mode, the remote server is made
19554 persistent. The @samp{R} packet is used to restart the program being
19560 The remote target both supports and has enabled extended mode.
19563 @item @code{?} --- last signal
19564 @cindex @code{?} packet
19566 Indicate the reason the target halted. The reply is the same as for
19570 @xref{Stop Reply Packets}, for the reply specifications.
19572 @item @code{a} --- reserved
19574 Reserved for future use.
19576 @item @code{A}@var{arglen}@code{,}@var{argnum}@code{,}@var{arg}@code{,@dots{}} --- set program arguments @strong{(reserved)}
19577 @cindex @code{A} packet
19579 Initialized @samp{argv[]} array passed into program. @var{arglen}
19580 specifies the number of bytes in the hex encoded byte stream @var{arg}.
19581 See @code{gdbserver} for more details.
19589 @item @code{b}@var{baud} --- set baud @strong{(deprecated)}
19590 @cindex @code{b} packet
19592 Change the serial line speed to @var{baud}.
19594 JTC: @emph{When does the transport layer state change? When it's
19595 received, or after the ACK is transmitted. In either case, there are
19596 problems if the command or the acknowledgment packet is dropped.}
19598 Stan: @emph{If people really wanted to add something like this, and get
19599 it working for the first time, they ought to modify ser-unix.c to send
19600 some kind of out-of-band message to a specially-setup stub and have the
19601 switch happen "in between" packets, so that from remote protocol's point
19602 of view, nothing actually happened.}
19604 @item @code{B}@var{addr},@var{mode} --- set breakpoint @strong{(deprecated)}
19605 @cindex @code{B} packet
19607 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
19608 breakpoint at @var{addr}.
19610 This packet has been replaced by the @samp{Z} and @samp{z} packets
19611 (@pxref{insert breakpoint or watchpoint packet}).
19613 @item @code{c}@var{addr} --- continue
19614 @cindex @code{c} packet
19616 @var{addr} is address to resume. If @var{addr} is omitted, resume at
19620 @xref{Stop Reply Packets}, for the reply specifications.
19622 @item @code{C}@var{sig}@code{;}@var{addr} --- continue with signal
19623 @cindex @code{C} packet
19625 Continue with signal @var{sig} (hex signal number). If
19626 @code{;}@var{addr} is omitted, resume at same address.
19629 @xref{Stop Reply Packets}, for the reply specifications.
19631 @item @code{d} --- toggle debug @strong{(deprecated)}
19632 @cindex @code{d} packet
19636 @item @code{D} --- detach
19637 @cindex @code{D} packet
19639 Detach @value{GDBN} from the remote system. Sent to the remote target
19640 before @value{GDBN} disconnects via the @code{detach} command.
19644 @item @emph{no response}
19645 @value{GDBN} does not check for any response after sending this packet.
19648 @item @code{e} --- reserved
19650 Reserved for future use.
19652 @item @code{E} --- reserved
19654 Reserved for future use.
19656 @item @code{f} --- reserved
19658 Reserved for future use.
19660 @item @code{F}@var{RC}@code{,}@var{EE}@code{,}@var{CF}@code{;}@var{XX} --- Reply to target's F packet.
19661 @cindex @code{F} packet
19663 This packet is send by @value{GDBN} as reply to a @code{F} request packet
19664 sent by the target. This is part of the File-I/O protocol extension.
19665 @xref{File-I/O remote protocol extension}, for the specification.
19667 @item @code{g} --- read registers
19668 @anchor{read registers packet}
19669 @cindex @code{g} packet
19671 Read general registers.
19675 @item @var{XX@dots{}}
19676 Each byte of register data is described by two hex digits. The bytes
19677 with the register are transmitted in target byte order. The size of
19678 each register and their position within the @samp{g} @var{packet} are
19679 determined by the @value{GDBN} internal macros
19680 @var{DEPRECATED_REGISTER_RAW_SIZE} and @var{REGISTER_NAME} macros. The
19681 specification of several standard @code{g} packets is specified below.
19686 @item @code{G}@var{XX@dots{}} --- write regs
19687 @cindex @code{G} packet
19689 @xref{read registers packet}, for a description of the @var{XX@dots{}}
19700 @item @code{h} --- reserved
19702 Reserved for future use.
19704 @item @code{H}@var{c}@var{t@dots{}} --- set thread
19705 @cindex @code{H} packet
19707 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
19708 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
19709 should be @samp{c} for step and continue operations, @samp{g} for other
19710 operations. The thread designator @var{t@dots{}} may be -1, meaning all
19711 the threads, a thread number, or zero which means pick any thread.
19722 @c 'H': How restrictive (or permissive) is the thread model. If a
19723 @c thread is selected and stopped, are other threads allowed
19724 @c to continue to execute? As I mentioned above, I think the
19725 @c semantics of each command when a thread is selected must be
19726 @c described. For example:
19728 @c 'g': If the stub supports threads and a specific thread is
19729 @c selected, returns the register block from that thread;
19730 @c otherwise returns current registers.
19732 @c 'G' If the stub supports threads and a specific thread is
19733 @c selected, sets the registers of the register block of
19734 @c that thread; otherwise sets current registers.
19736 @item @code{i}@var{addr}@code{,}@var{nnn} --- cycle step @strong{(draft)}
19737 @anchor{cycle step packet}
19738 @cindex @code{i} packet
19740 Step the remote target by a single clock cycle. If @code{,}@var{nnn} is
19741 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
19742 step starting at that address.
19744 @item @code{I} --- signal then cycle step @strong{(reserved)}
19745 @cindex @code{I} packet
19747 @xref{step with signal packet}. @xref{cycle step packet}.
19749 @item @code{j} --- reserved
19751 Reserved for future use.
19753 @item @code{J} --- reserved
19755 Reserved for future use.
19757 @item @code{k} --- kill request
19758 @cindex @code{k} packet
19760 FIXME: @emph{There is no description of how to operate when a specific
19761 thread context has been selected (i.e.@: does 'k' kill only that
19764 @item @code{K} --- reserved
19766 Reserved for future use.
19768 @item @code{l} --- reserved
19770 Reserved for future use.
19772 @item @code{L} --- reserved
19774 Reserved for future use.
19776 @item @code{m}@var{addr}@code{,}@var{length} --- read memory
19777 @cindex @code{m} packet
19779 Read @var{length} bytes of memory starting at address @var{addr}.
19780 Neither @value{GDBN} nor the stub assume that sized memory transfers are
19781 assumed using word aligned accesses. FIXME: @emph{A word aligned memory
19782 transfer mechanism is needed.}
19786 @item @var{XX@dots{}}
19787 @var{XX@dots{}} is mem contents. Can be fewer bytes than requested if able
19788 to read only part of the data. Neither @value{GDBN} nor the stub assume
19789 that sized memory transfers are assumed using word aligned
19790 accesses. FIXME: @emph{A word aligned memory transfer mechanism is
19796 @item @code{M}@var{addr},@var{length}@code{:}@var{XX@dots{}} --- write mem
19797 @cindex @code{M} packet
19799 Write @var{length} bytes of memory starting at address @var{addr}.
19800 @var{XX@dots{}} is the data.
19807 for an error (this includes the case where only part of the data was
19811 @item @code{n} --- reserved
19813 Reserved for future use.
19815 @item @code{N} --- reserved
19817 Reserved for future use.
19819 @item @code{o} --- reserved
19821 Reserved for future use.
19823 @item @code{O} --- reserved
19825 Reserved for future use.
19827 @item @code{p}@var{n@dots{}} --- read reg @strong{(reserved)}
19828 @cindex @code{p} packet
19830 @xref{write register packet}.
19834 @item @var{r@dots{}.}
19835 The hex encoded value of the register in target byte order.
19838 @item @code{P}@var{n@dots{}}@code{=}@var{r@dots{}} --- write register
19839 @anchor{write register packet}
19840 @cindex @code{P} packet
19842 Write register @var{n@dots{}} with value @var{r@dots{}}, which contains two hex
19843 digits for each byte in the register (target byte order).
19853 @item @code{q}@var{query} --- general query
19854 @anchor{general query packet}
19855 @cindex @code{q} packet
19857 Request info about @var{query}. In general @value{GDBN} queries have a
19858 leading upper case letter. Custom vendor queries should use a company
19859 prefix (in lower case) ex: @samp{qfsf.var}. @var{query} may optionally
19860 be followed by a @samp{,} or @samp{;} separated list. Stubs must ensure
19861 that they match the full @var{query} name.
19865 @item @var{XX@dots{}}
19866 Hex encoded data from query. The reply can not be empty.
19870 Indicating an unrecognized @var{query}.
19873 @item @code{Q}@var{var}@code{=}@var{val} --- general set
19874 @cindex @code{Q} packet
19876 Set value of @var{var} to @var{val}.
19878 @xref{general query packet}, for a discussion of naming conventions.
19880 @item @code{r} --- reset @strong{(deprecated)}
19881 @cindex @code{r} packet
19883 Reset the entire system.
19885 @item @code{R}@var{XX} --- remote restart
19886 @cindex @code{R} packet
19888 Restart the program being debugged. @var{XX}, while needed, is ignored.
19889 This packet is only available in extended mode.
19893 @item @emph{no reply}
19894 The @samp{R} packet has no reply.
19897 @item @code{s}@var{addr} --- step
19898 @cindex @code{s} packet
19900 @var{addr} is address to resume. If @var{addr} is omitted, resume at
19904 @xref{Stop Reply Packets}, for the reply specifications.
19906 @item @code{S}@var{sig}@code{;}@var{addr} --- step with signal
19907 @anchor{step with signal packet}
19908 @cindex @code{S} packet
19910 Like @samp{C} but step not continue.
19913 @xref{Stop Reply Packets}, for the reply specifications.
19915 @item @code{t}@var{addr}@code{:}@var{PP}@code{,}@var{MM} --- search
19916 @cindex @code{t} packet
19918 Search backwards starting at address @var{addr} for a match with pattern
19919 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
19920 @var{addr} must be at least 3 digits.
19922 @item @code{T}@var{XX} --- thread alive
19923 @cindex @code{T} packet
19925 Find out if the thread XX is alive.
19930 thread is still alive
19935 @item @code{u} --- reserved
19937 Reserved for future use.
19939 @item @code{U} --- reserved
19941 Reserved for future use.
19943 @item @code{v} --- verbose packet prefix
19945 Packets starting with @code{v} are identified by a multi-letter name,
19946 up to the first @code{;} or @code{?} (or the end of the packet).
19948 @item @code{vCont}[;@var{action}[@code{:}@var{tid}]]... --- extended resume
19949 @cindex @code{vCont} packet
19951 Resume the inferior. Different actions may be specified for each thread.
19952 If an action is specified with no @var{tid}, then it is applied to any
19953 threads that don't have a specific action specified; if no default action is
19954 specified then other threads should remain stopped. Specifying multiple
19955 default actions is an error; specifying no actions is also an error.
19956 Thread IDs are specified in hexadecimal. Currently supported actions are:
19962 Continue with signal @var{sig}. @var{sig} should be two hex digits.
19966 Step with signal @var{sig}. @var{sig} should be two hex digits.
19969 The optional @var{addr} argument normally associated with these packets is
19970 not supported in @code{vCont}.
19973 @xref{Stop Reply Packets}, for the reply specifications.
19975 @item @code{vCont?} --- extended resume query
19976 @cindex @code{vCont?} packet
19978 Query support for the @code{vCont} packet.
19982 @item @code{vCont}[;@var{action}]...
19983 The @code{vCont} packet is supported. Each @var{action} is a supported
19984 command in the @code{vCont} packet.
19986 The @code{vCont} packet is not supported.
19989 @item @code{V} --- reserved
19991 Reserved for future use.
19993 @item @code{w} --- reserved
19995 Reserved for future use.
19997 @item @code{W} --- reserved
19999 Reserved for future use.
20001 @item @code{x} --- reserved
20003 Reserved for future use.
20005 @item @code{X}@var{addr}@code{,}@var{length}@var{:}@var{XX@dots{}} --- write mem (binary)
20006 @cindex @code{X} packet
20008 @var{addr} is address, @var{length} is number of bytes, @var{XX@dots{}}
20009 is binary data. The characters @code{$}, @code{#}, and @code{0x7d} are
20010 escaped using @code{0x7d}.
20020 @item @code{y} --- reserved
20022 Reserved for future use.
20024 @item @code{Y} reserved
20026 Reserved for future use.
20028 @item @code{z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- remove breakpoint or watchpoint @strong{(draft)}
20029 @itemx @code{Z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- insert breakpoint or watchpoint @strong{(draft)}
20030 @anchor{insert breakpoint or watchpoint packet}
20031 @cindex @code{z} packet
20032 @cindex @code{Z} packets
20034 Insert (@code{Z}) or remove (@code{z}) a @var{type} breakpoint or
20035 watchpoint starting at address @var{address} and covering the next
20036 @var{length} bytes.
20038 Each breakpoint and watchpoint packet @var{type} is documented
20041 @emph{Implementation notes: A remote target shall return an empty string
20042 for an unrecognized breakpoint or watchpoint packet @var{type}. A
20043 remote target shall support either both or neither of a given
20044 @code{Z}@var{type}@dots{} and @code{z}@var{type}@dots{} packet pair. To
20045 avoid potential problems with duplicate packets, the operations should
20046 be implemented in an idempotent way.}
20048 @item @code{z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- remove memory breakpoint @strong{(draft)}
20049 @item @code{Z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- insert memory breakpoint @strong{(draft)}
20050 @cindex @code{z0} packet
20051 @cindex @code{Z0} packet
20053 Insert (@code{Z0}) or remove (@code{z0}) a memory breakpoint at address
20054 @code{addr} of size @code{length}.
20056 A memory breakpoint is implemented by replacing the instruction at
20057 @var{addr} with a software breakpoint or trap instruction. The
20058 @code{length} is used by targets that indicates the size of the
20059 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
20060 @sc{mips} can insert either a 2 or 4 byte breakpoint).
20062 @emph{Implementation note: It is possible for a target to copy or move
20063 code that contains memory breakpoints (e.g., when implementing
20064 overlays). The behavior of this packet, in the presence of such a
20065 target, is not defined.}
20077 @item @code{z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- remove hardware breakpoint @strong{(draft)}
20078 @item @code{Z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- insert hardware breakpoint @strong{(draft)}
20079 @cindex @code{z1} packet
20080 @cindex @code{Z1} packet
20082 Insert (@code{Z1}) or remove (@code{z1}) a hardware breakpoint at
20083 address @code{addr} of size @code{length}.
20085 A hardware breakpoint is implemented using a mechanism that is not
20086 dependant on being able to modify the target's memory.
20088 @emph{Implementation note: A hardware breakpoint is not affected by code
20101 @item @code{z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- remove write watchpoint @strong{(draft)}
20102 @item @code{Z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- insert write watchpoint @strong{(draft)}
20103 @cindex @code{z2} packet
20104 @cindex @code{Z2} packet
20106 Insert (@code{Z2}) or remove (@code{z2}) a write watchpoint.
20118 @item @code{z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- remove read watchpoint @strong{(draft)}
20119 @item @code{Z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- insert read watchpoint @strong{(draft)}
20120 @cindex @code{z3} packet
20121 @cindex @code{Z3} packet
20123 Insert (@code{Z3}) or remove (@code{z3}) a read watchpoint.
20135 @item @code{z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- remove access watchpoint @strong{(draft)}
20136 @item @code{Z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- insert access watchpoint @strong{(draft)}
20137 @cindex @code{z4} packet
20138 @cindex @code{Z4} packet
20140 Insert (@code{Z4}) or remove (@code{z4}) an access watchpoint.
20154 @node Stop Reply Packets
20155 @section Stop Reply Packets
20156 @cindex stop reply packets
20158 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
20159 receive any of the below as a reply. In the case of the @samp{C},
20160 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
20161 when the target halts. In the below the exact meaning of @samp{signal
20162 number} is poorly defined. In general one of the UNIX signal numbering
20163 conventions is used.
20168 @var{AA} is the signal number
20170 @item @code{T}@var{AA}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}
20171 @cindex @code{T} packet reply
20173 @var{AA} = two hex digit signal number; @var{n...} = register number
20174 (hex), @var{r...} = target byte ordered register contents, size defined
20175 by @code{DEPRECATED_REGISTER_RAW_SIZE}; @var{n...} = @samp{thread},
20176 @var{r...} = thread process ID, this is a hex integer; @var{n...} =
20177 (@samp{watch} | @samp{rwatch} | @samp{awatch}, @var{r...} = data
20178 address, this is a hex integer; @var{n...} = other string not starting
20179 with valid hex digit. @value{GDBN} should ignore this @var{n...},
20180 @var{r...} pair and go on to the next. This way we can extend the
20185 The process exited, and @var{AA} is the exit status. This is only
20186 applicable to certain targets.
20190 The process terminated with signal @var{AA}.
20192 @item O@var{XX@dots{}}
20194 @var{XX@dots{}} is hex encoding of @sc{ascii} data. This can happen at
20195 any time while the program is running and the debugger should continue
20196 to wait for @samp{W}, @samp{T}, etc.
20198 @item F@var{call-id}@code{,}@var{parameter@dots{}}
20200 @var{call-id} is the identifier which says which host system call should
20201 be called. This is just the name of the function. Translation into the
20202 correct system call is only applicable as it's defined in @value{GDBN}.
20203 @xref{File-I/O remote protocol extension}, for a list of implemented
20206 @var{parameter@dots{}} is a list of parameters as defined for this very
20209 The target replies with this packet when it expects @value{GDBN} to call
20210 a host system call on behalf of the target. @value{GDBN} replies with
20211 an appropriate @code{F} packet and keeps up waiting for the next reply
20212 packet from the target. The latest @samp{C}, @samp{c}, @samp{S} or
20213 @samp{s} action is expected to be continued.
20214 @xref{File-I/O remote protocol extension}, for more details.
20218 @node General Query Packets
20219 @section General Query Packets
20221 The following set and query packets have already been defined.
20225 @item @code{q}@code{C} --- current thread
20227 Return the current thread id.
20231 @item @code{QC}@var{pid}
20232 Where @var{pid} is a HEX encoded 16 bit process id.
20234 Any other reply implies the old pid.
20237 @item @code{q}@code{fThreadInfo} -- all thread ids
20239 @code{q}@code{sThreadInfo}
20241 Obtain a list of active thread ids from the target (OS). Since there
20242 may be too many active threads to fit into one reply packet, this query
20243 works iteratively: it may require more than one query/reply sequence to
20244 obtain the entire list of threads. The first query of the sequence will
20245 be the @code{qf}@code{ThreadInfo} query; subsequent queries in the
20246 sequence will be the @code{qs}@code{ThreadInfo} query.
20248 NOTE: replaces the @code{qL} query (see below).
20252 @item @code{m}@var{id}
20254 @item @code{m}@var{id},@var{id}@dots{}
20255 a comma-separated list of thread ids
20257 (lower case 'el') denotes end of list.
20260 In response to each query, the target will reply with a list of one or
20261 more thread ids, in big-endian hex, separated by commas. @value{GDBN}
20262 will respond to each reply with a request for more thread ids (using the
20263 @code{qs} form of the query), until the target responds with @code{l}
20264 (lower-case el, for @code{'last'}).
20266 @item @code{q}@code{ThreadExtraInfo}@code{,}@var{id} --- extra thread info
20268 Where @var{id} is a thread-id in big-endian hex. Obtain a printable
20269 string description of a thread's attributes from the target OS. This
20270 string may contain anything that the target OS thinks is interesting for
20271 @value{GDBN} to tell the user about the thread. The string is displayed
20272 in @value{GDBN}'s @samp{info threads} display. Some examples of
20273 possible thread extra info strings are ``Runnable'', or ``Blocked on
20278 @item @var{XX@dots{}}
20279 Where @var{XX@dots{}} is a hex encoding of @sc{ascii} data, comprising
20280 the printable string containing the extra information about the thread's
20284 @item @code{q}@code{L}@var{startflag}@var{threadcount}@var{nextthread} --- query @var{LIST} or @var{threadLIST} @strong{(deprecated)}
20286 Obtain thread information from RTOS. Where: @var{startflag} (one hex
20287 digit) is one to indicate the first query and zero to indicate a
20288 subsequent query; @var{threadcount} (two hex digits) is the maximum
20289 number of threads the response packet can contain; and @var{nextthread}
20290 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
20291 returned in the response as @var{argthread}.
20293 NOTE: this query is replaced by the @code{q}@code{fThreadInfo} query
20298 @item @code{q}@code{M}@var{count}@var{done}@var{argthread}@var{thread@dots{}}
20299 Where: @var{count} (two hex digits) is the number of threads being
20300 returned; @var{done} (one hex digit) is zero to indicate more threads
20301 and one indicates no further threads; @var{argthreadid} (eight hex
20302 digits) is @var{nextthread} from the request packet; @var{thread@dots{}}
20303 is a sequence of thread IDs from the target. @var{threadid} (eight hex
20304 digits). See @code{remote.c:parse_threadlist_response()}.
20307 @item @code{q}@code{CRC:}@var{addr}@code{,}@var{length} --- compute CRC of memory block
20311 @item @code{E}@var{NN}
20312 An error (such as memory fault)
20313 @item @code{C}@var{CRC32}
20314 A 32 bit cyclic redundancy check of the specified memory region.
20317 @item @code{q}@code{Offsets} --- query sect offs
20319 Get section offsets that the target used when re-locating the downloaded
20320 image. @emph{Note: while a @code{Bss} offset is included in the
20321 response, @value{GDBN} ignores this and instead applies the @code{Data}
20322 offset to the @code{Bss} section.}
20326 @item @code{Text=}@var{xxx}@code{;Data=}@var{yyy}@code{;Bss=}@var{zzz}
20329 @item @code{q}@code{P}@var{mode}@var{threadid} --- thread info request
20331 Returns information on @var{threadid}. Where: @var{mode} is a hex
20332 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
20339 See @code{remote.c:remote_unpack_thread_info_response()}.
20341 @item @code{q}@code{Rcmd,}@var{command} --- remote command
20343 @var{command} (hex encoded) is passed to the local interpreter for
20344 execution. Invalid commands should be reported using the output string.
20345 Before the final result packet, the target may also respond with a
20346 number of intermediate @code{O}@var{output} console output packets.
20347 @emph{Implementors should note that providing access to a stubs's
20348 interpreter may have security implications}.
20353 A command response with no output.
20355 A command response with the hex encoded output string @var{OUTPUT}.
20356 @item @code{E}@var{NN}
20357 Indicate a badly formed request.
20359 When @samp{q}@samp{Rcmd} is not recognized.
20362 @item @code{qSymbol::} --- symbol lookup
20364 Notify the target that @value{GDBN} is prepared to serve symbol lookup
20365 requests. Accept requests from the target for the values of symbols.
20370 The target does not need to look up any (more) symbols.
20371 @item @code{qSymbol:}@var{sym_name}
20372 The target requests the value of symbol @var{sym_name} (hex encoded).
20373 @value{GDBN} may provide the value by using the
20374 @code{qSymbol:}@var{sym_value}:@var{sym_name} message, described below.
20377 @item @code{qSymbol:}@var{sym_value}:@var{sym_name} --- symbol value
20379 Set the value of @var{sym_name} to @var{sym_value}.
20381 @var{sym_name} (hex encoded) is the name of a symbol whose value the
20382 target has previously requested.
20384 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
20385 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
20391 The target does not need to look up any (more) symbols.
20392 @item @code{qSymbol:}@var{sym_name}
20393 The target requests the value of a new symbol @var{sym_name} (hex
20394 encoded). @value{GDBN} will continue to supply the values of symbols
20395 (if available), until the target ceases to request them.
20400 @node Register Packet Format
20401 @section Register Packet Format
20403 The following @samp{g}/@samp{G} packets have previously been defined.
20404 In the below, some thirty-two bit registers are transferred as
20405 sixty-four bits. Those registers should be zero/sign extended (which?)
20406 to fill the space allocated. Register bytes are transfered in target
20407 byte order. The two nibbles within a register byte are transfered
20408 most-significant - least-significant.
20414 All registers are transfered as thirty-two bit quantities in the order:
20415 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
20416 registers; fsr; fir; fp.
20420 All registers are transfered as sixty-four bit quantities (including
20421 thirty-two bit registers such as @code{sr}). The ordering is the same
20429 Example sequence of a target being re-started. Notice how the restart
20430 does not get any direct output:
20435 @emph{target restarts}
20438 <- @code{T001:1234123412341234}
20442 Example sequence of a target being stepped by a single instruction:
20445 -> @code{G1445@dots{}}
20450 <- @code{T001:1234123412341234}
20454 <- @code{1455@dots{}}
20458 @node File-I/O remote protocol extension
20459 @section File-I/O remote protocol extension
20460 @cindex File-I/O remote protocol extension
20463 * File-I/O Overview::
20464 * Protocol basics::
20465 * The F request packet::
20466 * The F reply packet::
20467 * Memory transfer::
20468 * The Ctrl-C message::
20470 * The isatty call::
20471 * The system call::
20472 * List of supported calls::
20473 * Protocol specific representation of datatypes::
20475 * File-I/O Examples::
20478 @node File-I/O Overview
20479 @subsection File-I/O Overview
20480 @cindex file-i/o overview
20482 The File I/O remote protocol extension (short: File-I/O) allows the
20483 target to use the hosts file system and console I/O when calling various
20484 system calls. System calls on the target system are translated into a
20485 remote protocol packet to the host system which then performs the needed
20486 actions and returns with an adequate response packet to the target system.
20487 This simulates file system operations even on targets that lack file systems.
20489 The protocol is defined host- and target-system independent. It uses
20490 it's own independent representation of datatypes and values. Both,
20491 @value{GDBN} and the target's @value{GDBN} stub are responsible for
20492 translating the system dependent values into the unified protocol values
20493 when data is transmitted.
20495 The communication is synchronous. A system call is possible only
20496 when GDB is waiting for the @samp{C}, @samp{c}, @samp{S} or @samp{s}
20497 packets. While @value{GDBN} handles the request for a system call,
20498 the target is stopped to allow deterministic access to the target's
20499 memory. Therefore File-I/O is not interuptible by target signals. It
20500 is possible to interrupt File-I/O by a user interrupt (Ctrl-C), though.
20502 The target's request to perform a host system call does not finish
20503 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
20504 after finishing the system call, the target returns to continuing the
20505 previous activity (continue, step). No additional continue or step
20506 request from @value{GDBN} is required.
20510 <- target requests 'system call X'
20511 target is stopped, @value{GDBN} executes system call
20512 -> GDB returns result
20513 ... target continues, GDB returns to wait for the target
20514 <- target hits breakpoint and sends a Txx packet
20517 The protocol is only used for files on the host file system and
20518 for I/O on the console. Character or block special devices, pipes,
20519 named pipes or sockets or any other communication method on the host
20520 system are not supported by this protocol.
20522 @node Protocol basics
20523 @subsection Protocol basics
20524 @cindex protocol basics, file-i/o
20526 The File-I/O protocol uses the @code{F} packet, as request as well
20527 as as reply packet. Since a File-I/O system call can only occur when
20528 @value{GDBN} is waiting for the continuing or stepping target, the
20529 File-I/O request is a reply that @value{GDBN} has to expect as a result
20530 of a former @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
20531 This @code{F} packet contains all information needed to allow @value{GDBN}
20532 to call the appropriate host system call:
20536 A unique identifier for the requested system call.
20539 All parameters to the system call. Pointers are given as addresses
20540 in the target memory address space. Pointers to strings are given as
20541 pointer/length pair. Numerical values are given as they are.
20542 Numerical control values are given in a protocol specific representation.
20546 At that point @value{GDBN} has to perform the following actions.
20550 If parameter pointer values are given, which point to data needed as input
20551 to a system call, @value{GDBN} requests this data from the target with a
20552 standard @code{m} packet request. This additional communication has to be
20553 expected by the target implementation and is handled as any other @code{m}
20557 @value{GDBN} translates all value from protocol representation to host
20558 representation as needed. Datatypes are coerced into the host types.
20561 @value{GDBN} calls the system call
20564 It then coerces datatypes back to protocol representation.
20567 If pointer parameters in the request packet point to buffer space in which
20568 a system call is expected to copy data to, the data is transmitted to the
20569 target using a @code{M} or @code{X} packet. This packet has to be expected
20570 by the target implementation and is handled as any other @code{M} or @code{X}
20575 Eventually @value{GDBN} replies with another @code{F} packet which contains all
20576 necessary information for the target to continue. This at least contains
20583 @code{errno}, if has been changed by the system call.
20590 After having done the needed type and value coercion, the target continues
20591 the latest continue or step action.
20593 @node The F request packet
20594 @subsection The @code{F} request packet
20595 @cindex file-i/o request packet
20596 @cindex @code{F} request packet
20598 The @code{F} request packet has the following format:
20603 @code{F}@var{call-id}@code{,}@var{parameter@dots{}}
20606 @var{call-id} is the identifier to indicate the host system call to be called.
20607 This is just the name of the function.
20609 @var{parameter@dots{}} are the parameters to the system call.
20613 Parameters are hexadecimal integer values, either the real values in case
20614 of scalar datatypes, as pointers to target buffer space in case of compound
20615 datatypes and unspecified memory areas or as pointer/length pairs in case
20616 of string parameters. These are appended to the call-id, each separated
20617 from its predecessor by a comma. All values are transmitted in ASCII
20618 string representation, pointer/length pairs separated by a slash.
20620 @node The F reply packet
20621 @subsection The @code{F} reply packet
20622 @cindex file-i/o reply packet
20623 @cindex @code{F} reply packet
20625 The @code{F} reply packet has the following format:
20630 @code{F}@var{retcode}@code{,}@var{errno}@code{,}@var{Ctrl-C flag}@code{;}@var{call specific attachment}
20633 @var{retcode} is the return code of the system call as hexadecimal value.
20635 @var{errno} is the errno set by the call, in protocol specific representation.
20636 This parameter can be omitted if the call was successful.
20638 @var{Ctrl-C flag} is only send if the user requested a break. In this
20639 case, @var{errno} must be send as well, even if the call was successful.
20640 The @var{Ctrl-C flag} itself consists of the character 'C':
20647 or, if the call was interupted before the host call has been performed:
20654 assuming 4 is the protocol specific representation of @code{EINTR}.
20658 @node Memory transfer
20659 @subsection Memory transfer
20660 @cindex memory transfer, in file-i/o protocol
20662 Structured data which is transferred using a memory read or write as e.g.@:
20663 a @code{struct stat} is expected to be in a protocol specific format with
20664 all scalar multibyte datatypes being big endian. This should be done by
20665 the target before the @code{F} packet is sent resp.@: by @value{GDBN} before
20666 it transfers memory to the target. Transferred pointers to structured
20667 data should point to the already coerced data at any time.
20669 @node The Ctrl-C message
20670 @subsection The Ctrl-C message
20671 @cindex ctrl-c message, in file-i/o protocol
20673 A special case is, if the @var{Ctrl-C flag} is set in the @value{GDBN}
20674 reply packet. In this case the target should behave, as if it had
20675 gotten a break message. The meaning for the target is ``system call
20676 interupted by @code{SIGINT}''. Consequentially, the target should actually stop
20677 (as with a break message) and return to @value{GDBN} with a @code{T02}
20678 packet. In this case, it's important for the target to know, in which
20679 state the system call was interrupted. Since this action is by design
20680 not an atomic operation, we have to differ between two cases:
20684 The system call hasn't been performed on the host yet.
20687 The system call on the host has been finished.
20691 These two states can be distinguished by the target by the value of the
20692 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
20693 call hasn't been performed. This is equivalent to the @code{EINTR} handling
20694 on POSIX systems. In any other case, the target may presume that the
20695 system call has been finished --- successful or not --- and should behave
20696 as if the break message arrived right after the system call.
20698 @value{GDBN} must behave reliable. If the system call has not been called
20699 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
20700 @code{errno} in the packet. If the system call on the host has been finished
20701 before the user requests a break, the full action must be finshed by
20702 @value{GDBN}. This requires sending @code{M} or @code{X} packets as they fit.
20703 The @code{F} packet may only be send when either nothing has happened
20704 or the full action has been completed.
20707 @subsection Console I/O
20708 @cindex console i/o as part of file-i/o
20710 By default and if not explicitely closed by the target system, the file
20711 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
20712 on the @value{GDBN} console is handled as any other file output operation
20713 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
20714 by @value{GDBN} so that after the target read request from file descriptor
20715 0 all following typing is buffered until either one of the following
20720 The user presses @kbd{Ctrl-C}. The behaviour is as explained above, the
20722 system call is treated as finished.
20725 The user presses @kbd{Enter}. This is treated as end of input with a trailing
20729 The user presses @kbd{Ctrl-D}. This is treated as end of input. No trailing
20730 character, especially no Ctrl-D is appended to the input.
20734 If the user has typed more characters as fit in the buffer given to
20735 the read call, the trailing characters are buffered in @value{GDBN} until
20736 either another @code{read(0, @dots{})} is requested by the target or debugging
20737 is stopped on users request.
20739 @node The isatty call
20740 @subsection The isatty(3) call
20741 @cindex isatty call, file-i/o protocol
20743 A special case in this protocol is the library call @code{isatty} which
20744 is implemented as it's own call inside of this protocol. It returns
20745 1 to the target if the file descriptor given as parameter is attached
20746 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
20747 would require implementing @code{ioctl} and would be more complex than
20750 @node The system call
20751 @subsection The system(3) call
20752 @cindex system call, file-i/o protocol
20754 The other special case in this protocol is the @code{system} call which
20755 is implemented as it's own call, too. @value{GDBN} is taking over the full
20756 task of calling the necessary host calls to perform the @code{system}
20757 call. The return value of @code{system} is simplified before it's returned
20758 to the target. Basically, the only signal transmitted back is @code{EINTR}
20759 in case the user pressed @kbd{Ctrl-C}. Otherwise the return value consists
20760 entirely of the exit status of the called command.
20762 Due to security concerns, the @code{system} call is refused to be called
20763 by @value{GDBN} by default. The user has to allow this call explicitly by
20767 @kindex set remote system-call-allowed 1
20768 @item @code{set remote system-call-allowed 1}
20771 Disabling the @code{system} call is done by
20774 @kindex set remote system-call-allowed 0
20775 @item @code{set remote system-call-allowed 0}
20778 The current setting is shown by typing
20781 @kindex show remote system-call-allowed
20782 @item @code{show remote system-call-allowed}
20785 @node List of supported calls
20786 @subsection List of supported calls
20787 @cindex list of supported file-i/o calls
20804 @unnumberedsubsubsec open
20805 @cindex open, file-i/o system call
20809 int open(const char *pathname, int flags);
20810 int open(const char *pathname, int flags, mode_t mode);
20813 Fopen,pathptr/len,flags,mode
20817 @code{flags} is the bitwise or of the following values:
20821 If the file does not exist it will be created. The host
20822 rules apply as far as file ownership and time stamps
20826 When used with O_CREAT, if the file already exists it is
20827 an error and open() fails.
20830 If the file already exists and the open mode allows
20831 writing (O_RDWR or O_WRONLY is given) it will be
20832 truncated to length 0.
20835 The file is opened in append mode.
20838 The file is opened for reading only.
20841 The file is opened for writing only.
20844 The file is opened for reading and writing.
20847 Each other bit is silently ignored.
20852 @code{mode} is the bitwise or of the following values:
20856 User has read permission.
20859 User has write permission.
20862 Group has read permission.
20865 Group has write permission.
20868 Others have read permission.
20871 Others have write permission.
20874 Each other bit is silently ignored.
20879 @exdent Return value:
20880 open returns the new file descriptor or -1 if an error
20888 pathname already exists and O_CREAT and O_EXCL were used.
20891 pathname refers to a directory.
20894 The requested access is not allowed.
20897 pathname was too long.
20900 A directory component in pathname does not exist.
20903 pathname refers to a device, pipe, named pipe or socket.
20906 pathname refers to a file on a read-only filesystem and
20907 write access was requested.
20910 pathname is an invalid pointer value.
20913 No space on device to create the file.
20916 The process already has the maximum number of files open.
20919 The limit on the total number of files open on the system
20923 The call was interrupted by the user.
20927 @unnumberedsubsubsec close
20928 @cindex close, file-i/o system call
20937 @exdent Return value:
20938 close returns zero on success, or -1 if an error occurred.
20945 fd isn't a valid open file descriptor.
20948 The call was interrupted by the user.
20952 @unnumberedsubsubsec read
20953 @cindex read, file-i/o system call
20957 int read(int fd, void *buf, unsigned int count);
20960 Fread,fd,bufptr,count
20962 @exdent Return value:
20963 On success, the number of bytes read is returned.
20964 Zero indicates end of file. If count is zero, read
20965 returns zero as well. On error, -1 is returned.
20972 fd is not a valid file descriptor or is not open for
20976 buf is an invalid pointer value.
20979 The call was interrupted by the user.
20983 @unnumberedsubsubsec write
20984 @cindex write, file-i/o system call
20988 int write(int fd, const void *buf, unsigned int count);
20991 Fwrite,fd,bufptr,count
20993 @exdent Return value:
20994 On success, the number of bytes written are returned.
20995 Zero indicates nothing was written. On error, -1
21003 fd is not a valid file descriptor or is not open for
21007 buf is an invalid pointer value.
21010 An attempt was made to write a file that exceeds the
21011 host specific maximum file size allowed.
21014 No space on device to write the data.
21017 The call was interrupted by the user.
21021 @unnumberedsubsubsec lseek
21022 @cindex lseek, file-i/o system call
21026 long lseek (int fd, long offset, int flag);
21029 Flseek,fd,offset,flag
21032 @code{flag} is one of:
21036 The offset is set to offset bytes.
21039 The offset is set to its current location plus offset
21043 The offset is set to the size of the file plus offset
21048 @exdent Return value:
21049 On success, the resulting unsigned offset in bytes from
21050 the beginning of the file is returned. Otherwise, a
21051 value of -1 is returned.
21058 fd is not a valid open file descriptor.
21061 fd is associated with the @value{GDBN} console.
21064 flag is not a proper value.
21067 The call was interrupted by the user.
21071 @unnumberedsubsubsec rename
21072 @cindex rename, file-i/o system call
21076 int rename(const char *oldpath, const char *newpath);
21079 Frename,oldpathptr/len,newpathptr/len
21081 @exdent Return value:
21082 On success, zero is returned. On error, -1 is returned.
21089 newpath is an existing directory, but oldpath is not a
21093 newpath is a non-empty directory.
21096 oldpath or newpath is a directory that is in use by some
21100 An attempt was made to make a directory a subdirectory
21104 A component used as a directory in oldpath or new
21105 path is not a directory. Or oldpath is a directory
21106 and newpath exists but is not a directory.
21109 oldpathptr or newpathptr are invalid pointer values.
21112 No access to the file or the path of the file.
21116 oldpath or newpath was too long.
21119 A directory component in oldpath or newpath does not exist.
21122 The file is on a read-only filesystem.
21125 The device containing the file has no room for the new
21129 The call was interrupted by the user.
21133 @unnumberedsubsubsec unlink
21134 @cindex unlink, file-i/o system call
21138 int unlink(const char *pathname);
21141 Funlink,pathnameptr/len
21143 @exdent Return value:
21144 On success, zero is returned. On error, -1 is returned.
21151 No access to the file or the path of the file.
21154 The system does not allow unlinking of directories.
21157 The file pathname cannot be unlinked because it's
21158 being used by another process.
21161 pathnameptr is an invalid pointer value.
21164 pathname was too long.
21167 A directory component in pathname does not exist.
21170 A component of the path is not a directory.
21173 The file is on a read-only filesystem.
21176 The call was interrupted by the user.
21180 @unnumberedsubsubsec stat/fstat
21181 @cindex fstat, file-i/o system call
21182 @cindex stat, file-i/o system call
21186 int stat(const char *pathname, struct stat *buf);
21187 int fstat(int fd, struct stat *buf);
21190 Fstat,pathnameptr/len,bufptr
21193 @exdent Return value:
21194 On success, zero is returned. On error, -1 is returned.
21201 fd is not a valid open file.
21204 A directory component in pathname does not exist or the
21205 path is an empty string.
21208 A component of the path is not a directory.
21211 pathnameptr is an invalid pointer value.
21214 No access to the file or the path of the file.
21217 pathname was too long.
21220 The call was interrupted by the user.
21224 @unnumberedsubsubsec gettimeofday
21225 @cindex gettimeofday, file-i/o system call
21229 int gettimeofday(struct timeval *tv, void *tz);
21232 Fgettimeofday,tvptr,tzptr
21234 @exdent Return value:
21235 On success, 0 is returned, -1 otherwise.
21242 tz is a non-NULL pointer.
21245 tvptr and/or tzptr is an invalid pointer value.
21249 @unnumberedsubsubsec isatty
21250 @cindex isatty, file-i/o system call
21254 int isatty(int fd);
21259 @exdent Return value:
21260 Returns 1 if fd refers to the @value{GDBN} console, 0 otherwise.
21267 The call was interrupted by the user.
21271 @unnumberedsubsubsec system
21272 @cindex system, file-i/o system call
21276 int system(const char *command);
21279 Fsystem,commandptr/len
21281 @exdent Return value:
21282 The value returned is -1 on error and the return status
21283 of the command otherwise. Only the exit status of the
21284 command is returned, which is extracted from the hosts
21285 system return value by calling WEXITSTATUS(retval).
21286 In case /bin/sh could not be executed, 127 is returned.
21293 The call was interrupted by the user.
21296 @node Protocol specific representation of datatypes
21297 @subsection Protocol specific representation of datatypes
21298 @cindex protocol specific representation of datatypes, in file-i/o protocol
21301 * Integral datatypes::
21307 @node Integral datatypes
21308 @unnumberedsubsubsec Integral datatypes
21309 @cindex integral datatypes, in file-i/o protocol
21311 The integral datatypes used in the system calls are
21314 int@r{,} unsigned int@r{,} long@r{,} unsigned long@r{,} mode_t @r{and} time_t
21317 @code{Int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
21318 implemented as 32 bit values in this protocol.
21320 @code{Long} and @code{unsigned long} are implemented as 64 bit types.
21322 @xref{Limits}, for corresponding MIN and MAX values (similar to those
21323 in @file{limits.h}) to allow range checking on host and target.
21325 @code{time_t} datatypes are defined as seconds since the Epoch.
21327 All integral datatypes transferred as part of a memory read or write of a
21328 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
21331 @node Pointer values
21332 @unnumberedsubsubsec Pointer values
21333 @cindex pointer values, in file-i/o protocol
21335 Pointers to target data are transmitted as they are. An exception
21336 is made for pointers to buffers for which the length isn't
21337 transmitted as part of the function call, namely strings. Strings
21338 are transmitted as a pointer/length pair, both as hex values, e.g.@:
21345 which is a pointer to data of length 18 bytes at position 0x1aaf.
21346 The length is defined as the full string length in bytes, including
21347 the trailing null byte. Example:
21350 ``hello, world'' at address 0x123456
21361 @unnumberedsubsubsec struct stat
21362 @cindex struct stat, in file-i/o protocol
21364 The buffer of type struct stat used by the target and @value{GDBN} is defined
21369 unsigned int st_dev; /* device */
21370 unsigned int st_ino; /* inode */
21371 mode_t st_mode; /* protection */
21372 unsigned int st_nlink; /* number of hard links */
21373 unsigned int st_uid; /* user ID of owner */
21374 unsigned int st_gid; /* group ID of owner */
21375 unsigned int st_rdev; /* device type (if inode device) */
21376 unsigned long st_size; /* total size, in bytes */
21377 unsigned long st_blksize; /* blocksize for filesystem I/O */
21378 unsigned long st_blocks; /* number of blocks allocated */
21379 time_t st_atime; /* time of last access */
21380 time_t st_mtime; /* time of last modification */
21381 time_t st_ctime; /* time of last change */
21385 The integral datatypes are conforming to the definitions given in the
21386 approriate section (see @ref{Integral datatypes}, for details) so this
21387 structure is of size 64 bytes.
21389 The values of several fields have a restricted meaning and/or
21396 st_ino: No valid meaning for the target. Transmitted unchanged.
21398 st_mode: Valid mode bits are described in Appendix C. Any other
21399 bits have currently no meaning for the target.
21401 st_uid: No valid meaning for the target. Transmitted unchanged.
21403 st_gid: No valid meaning for the target. Transmitted unchanged.
21405 st_rdev: No valid meaning for the target. Transmitted unchanged.
21407 st_atime, st_mtime, st_ctime:
21408 These values have a host and file system dependent
21409 accuracy. Especially on Windows hosts the file systems
21410 don't support exact timing values.
21413 The target gets a struct stat of the above representation and is
21414 responsible to coerce it to the target representation before
21417 Note that due to size differences between the host and target
21418 representation of stat members, these members could eventually
21419 get truncated on the target.
21421 @node struct timeval
21422 @unnumberedsubsubsec struct timeval
21423 @cindex struct timeval, in file-i/o protocol
21425 The buffer of type struct timeval used by the target and @value{GDBN}
21426 is defined as follows:
21430 time_t tv_sec; /* second */
21431 long tv_usec; /* microsecond */
21435 The integral datatypes are conforming to the definitions given in the
21436 approriate section (see @ref{Integral datatypes}, for details) so this
21437 structure is of size 8 bytes.
21440 @subsection Constants
21441 @cindex constants, in file-i/o protocol
21443 The following values are used for the constants inside of the
21444 protocol. @value{GDBN} and target are resposible to translate these
21445 values before and after the call as needed.
21456 @unnumberedsubsubsec Open flags
21457 @cindex open flags, in file-i/o protocol
21459 All values are given in hexadecimal representation.
21471 @node mode_t values
21472 @unnumberedsubsubsec mode_t values
21473 @cindex mode_t values, in file-i/o protocol
21475 All values are given in octal representation.
21492 @unnumberedsubsubsec Errno values
21493 @cindex errno values, in file-i/o protocol
21495 All values are given in decimal representation.
21520 EUNKNOWN is used as a fallback error value if a host system returns
21521 any error value not in the list of supported error numbers.
21524 @unnumberedsubsubsec Lseek flags
21525 @cindex lseek flags, in file-i/o protocol
21534 @unnumberedsubsubsec Limits
21535 @cindex limits, in file-i/o protocol
21537 All values are given in decimal representation.
21540 INT_MIN -2147483648
21542 UINT_MAX 4294967295
21543 LONG_MIN -9223372036854775808
21544 LONG_MAX 9223372036854775807
21545 ULONG_MAX 18446744073709551615
21548 @node File-I/O Examples
21549 @subsection File-I/O Examples
21550 @cindex file-i/o examples
21552 Example sequence of a write call, file descriptor 3, buffer is at target
21553 address 0x1234, 6 bytes should be written:
21556 <- @code{Fwrite,3,1234,6}
21557 @emph{request memory read from target}
21560 @emph{return "6 bytes written"}
21564 Example sequence of a read call, file descriptor 3, buffer is at target
21565 address 0x1234, 6 bytes should be read:
21568 <- @code{Fread,3,1234,6}
21569 @emph{request memory write to target}
21570 -> @code{X1234,6:XXXXXX}
21571 @emph{return "6 bytes read"}
21575 Example sequence of a read call, call fails on the host due to invalid
21576 file descriptor (EBADF):
21579 <- @code{Fread,3,1234,6}
21583 Example sequence of a read call, user presses Ctrl-C before syscall on
21587 <- @code{Fread,3,1234,6}
21592 Example sequence of a read call, user presses Ctrl-C after syscall on
21596 <- @code{Fread,3,1234,6}
21597 -> @code{X1234,6:XXXXXX}
21601 @include agentexpr.texi
21613 % I think something like @colophon should be in texinfo. In the
21615 \long\def\colophon{\hbox to0pt{}\vfill
21616 \centerline{The body of this manual is set in}
21617 \centerline{\fontname\tenrm,}
21618 \centerline{with headings in {\bf\fontname\tenbf}}
21619 \centerline{and examples in {\tt\fontname\tentt}.}
21620 \centerline{{\it\fontname\tenit\/},}
21621 \centerline{{\bf\fontname\tenbf}, and}
21622 \centerline{{\sl\fontname\tensl\/}}
21623 \centerline{are used for emphasis.}\vfill}
21625 % Blame: doc@cygnus.com, 1991.