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
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 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 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) 1988-2003 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 * Copying:: GNU General Public License says
160 how you can copy and share GDB
161 * GNU Free Documentation License:: The license for this documentation
170 @unnumbered Summary of @value{GDBN}
172 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
173 going on ``inside'' another program while it executes---or what another
174 program was doing at the moment it crashed.
176 @value{GDBN} can do four main kinds of things (plus other things in support of
177 these) to help you catch bugs in the act:
181 Start your program, specifying anything that might affect its behavior.
184 Make your program stop on specified conditions.
187 Examine what has happened, when your program has stopped.
190 Change things in your program, so you can experiment with correcting the
191 effects of one bug and go on to learn about another.
194 You can use @value{GDBN} to debug programs written in C and C++.
195 For more information, see @ref{Support,,Supported languages}.
196 For more information, see @ref{C,,C and C++}.
199 Support for Modula-2 is partial. For information on Modula-2, see
200 @ref{Modula-2,,Modula-2}.
203 Debugging Pascal programs which use sets, subranges, file variables, or
204 nested functions does not currently work. @value{GDBN} does not support
205 entering expressions, printing values, or similar features using Pascal
209 @value{GDBN} can be used to debug programs written in Fortran, although
210 it may be necessary to refer to some variables with a trailing
213 @value{GDBN} can be used to debug programs written in Objective-C,
214 using either the Apple/NeXT or the GNU Objective-C runtime.
217 * Free Software:: Freely redistributable software
218 * Contributors:: Contributors to GDB
222 @unnumberedsec Free software
224 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
225 General Public License
226 (GPL). The GPL gives you the freedom to copy or adapt a licensed
227 program---but every person getting a copy also gets with it the
228 freedom to modify that copy (which means that they must get access to
229 the source code), and the freedom to distribute further copies.
230 Typical software companies use copyrights to limit your freedoms; the
231 Free Software Foundation uses the GPL to preserve these freedoms.
233 Fundamentally, the General Public License is a license which says that
234 you have these freedoms and that you cannot take these freedoms away
237 @unnumberedsec Free Software Needs Free Documentation
239 The biggest deficiency in the free software community today is not in
240 the software---it is the lack of good free documentation that we can
241 include with the free software. Many of our most important
242 programs do not come with free reference manuals and free introductory
243 texts. Documentation is an essential part of any software package;
244 when an important free software package does not come with a free
245 manual and a free tutorial, that is a major gap. We have many such
248 Consider Perl, for instance. The tutorial manuals that people
249 normally use are non-free. How did this come about? Because the
250 authors of those manuals published them with restrictive terms---no
251 copying, no modification, source files not available---which exclude
252 them from the free software world.
254 That wasn't the first time this sort of thing happened, and it was far
255 from the last. Many times we have heard a GNU user eagerly describe a
256 manual that he is writing, his intended contribution to the community,
257 only to learn that he had ruined everything by signing a publication
258 contract to make it non-free.
260 Free documentation, like free software, is a matter of freedom, not
261 price. The problem with the non-free manual is not that publishers
262 charge a price for printed copies---that in itself is fine. (The Free
263 Software Foundation sells printed copies of manuals, too.) The
264 problem is the restrictions on the use of the manual. Free manuals
265 are available in source code form, and give you permission to copy and
266 modify. Non-free manuals do not allow this.
268 The criteria of freedom for a free manual are roughly the same as for
269 free software. Redistribution (including the normal kinds of
270 commercial redistribution) must be permitted, so that the manual can
271 accompany every copy of the program, both on-line and on paper.
273 Permission for modification of the technical content is crucial too.
274 When people modify the software, adding or changing features, if they
275 are conscientious they will change the manual too---so they can
276 provide accurate and clear documentation for the modified program. A
277 manual that leaves you no choice but to write a new manual to document
278 a changed version of the program is not really available to our
281 Some kinds of limits on the way modification is handled are
282 acceptable. For example, requirements to preserve the original
283 author's copyright notice, the distribution terms, or the list of
284 authors, are ok. It is also no problem to require modified versions
285 to include notice that they were modified. Even entire sections that
286 may not be deleted or changed are acceptable, as long as they deal
287 with nontechnical topics (like this one). These kinds of restrictions
288 are acceptable because they don't obstruct the community's normal use
291 However, it must be possible to modify all the @emph{technical}
292 content of the manual, and then distribute the result in all the usual
293 media, through all the usual channels. Otherwise, the restrictions
294 obstruct the use of the manual, it is not free, and we need another
295 manual to replace it.
297 Please spread the word about this issue. Our community continues to
298 lose manuals to proprietary publishing. If we spread the word that
299 free software needs free reference manuals and free tutorials, perhaps
300 the next person who wants to contribute by writing documentation will
301 realize, before it is too late, that only free manuals contribute to
302 the free software community.
304 If you are writing documentation, please insist on publishing it under
305 the GNU Free Documentation License or another free documentation
306 license. Remember that this decision requires your approval---you
307 don't have to let the publisher decide. Some commercial publishers
308 will use a free license if you insist, but they will not propose the
309 option; it is up to you to raise the issue and say firmly that this is
310 what you want. If the publisher you are dealing with refuses, please
311 try other publishers. If you're not sure whether a proposed license
312 is free, write to @email{licensing@@gnu.org}.
314 You can encourage commercial publishers to sell more free, copylefted
315 manuals and tutorials by buying them, and particularly by buying
316 copies from the publishers that paid for their writing or for major
317 improvements. Meanwhile, try to avoid buying non-free documentation
318 at all. Check the distribution terms of a manual before you buy it,
319 and insist that whoever seeks your business must respect your freedom.
320 Check the history of the book, and try to reward the publishers that
321 have paid or pay the authors to work on it.
323 The Free Software Foundation maintains a list of free documentation
324 published by other publishers, at
325 @url{http://www.fsf.org/doc/other-free-books.html}.
328 @unnumberedsec Contributors to @value{GDBN}
330 Richard Stallman was the original author of @value{GDBN}, and of many
331 other @sc{gnu} programs. Many others have contributed to its
332 development. This section attempts to credit major contributors. One
333 of the virtues of free software is that everyone is free to contribute
334 to it; with regret, we cannot actually acknowledge everyone here. The
335 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
336 blow-by-blow account.
338 Changes much prior to version 2.0 are lost in the mists of time.
341 @emph{Plea:} Additions to this section are particularly welcome. If you
342 or your friends (or enemies, to be evenhanded) have been unfairly
343 omitted from this list, we would like to add your names!
346 So that they may not regard their many labors as thankless, we
347 particularly thank those who shepherded @value{GDBN} through major
349 Andrew Cagney (releases 5.3, 5.2, 5.1 and 5.0);
350 Jim Blandy (release 4.18);
351 Jason Molenda (release 4.17);
352 Stan Shebs (release 4.14);
353 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
354 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
355 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
356 Jim Kingdon (releases 3.5, 3.4, and 3.3);
357 and Randy Smith (releases 3.2, 3.1, and 3.0).
359 Richard Stallman, assisted at various times by Peter TerMaat, Chris
360 Hanson, and Richard Mlynarik, handled releases through 2.8.
362 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
363 in @value{GDBN}, with significant additional contributions from Per
364 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
365 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
366 much general update work leading to release 3.0).
368 @value{GDBN} uses the BFD subroutine library to examine multiple
369 object-file formats; BFD was a joint project of David V.
370 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
372 David Johnson wrote the original COFF support; Pace Willison did
373 the original support for encapsulated COFF.
375 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
377 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
378 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
380 Jean-Daniel Fekete contributed Sun 386i support.
381 Chris Hanson improved the HP9000 support.
382 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
383 David Johnson contributed Encore Umax support.
384 Jyrki Kuoppala contributed Altos 3068 support.
385 Jeff Law contributed HP PA and SOM support.
386 Keith Packard contributed NS32K support.
387 Doug Rabson contributed Acorn Risc Machine support.
388 Bob Rusk contributed Harris Nighthawk CX-UX support.
389 Chris Smith contributed Convex support (and Fortran debugging).
390 Jonathan Stone contributed Pyramid support.
391 Michael Tiemann contributed SPARC support.
392 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
393 Pace Willison contributed Intel 386 support.
394 Jay Vosburgh contributed Symmetry support.
395 Marko Mlinar contributed OpenRISC 1000 support.
397 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
399 Rich Schaefer and Peter Schauer helped with support of SunOS shared
402 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
403 about several machine instruction sets.
405 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
406 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
407 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
408 and RDI targets, respectively.
410 Brian Fox is the author of the readline libraries providing
411 command-line editing and command history.
413 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
414 Modula-2 support, and contributed the Languages chapter of this manual.
416 Fred Fish wrote most of the support for Unix System Vr4.
417 He also enhanced the command-completion support to cover C@t{++} overloaded
420 Hitachi America, Ltd. sponsored the support for H8/300, H8/500, and
423 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
425 Mitsubishi sponsored the support for D10V, D30V, and M32R/D processors.
427 Toshiba sponsored the support for the TX39 Mips processor.
429 Matsushita sponsored the support for the MN10200 and MN10300 processors.
431 Fujitsu sponsored the support for SPARClite and FR30 processors.
433 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
436 Michael Snyder added support for tracepoints.
438 Stu Grossman wrote gdbserver.
440 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
441 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
443 The following people at the Hewlett-Packard Company contributed
444 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
445 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
446 compiler, and the terminal user interface: Ben Krepp, Richard Title,
447 John Bishop, Susan Macchia, Kathy Mann, Satish Pai, India Paul, Steve
448 Rehrauer, and Elena Zannoni. Kim Haase provided HP-specific
449 information in this manual.
451 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
452 Robert Hoehne made significant contributions to the DJGPP port.
454 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
455 development since 1991. Cygnus engineers who have worked on @value{GDBN}
456 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
457 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
458 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
459 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
460 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
461 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
462 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
463 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
464 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
465 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
466 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
467 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
468 Zuhn have made contributions both large and small.
470 Jim Blandy added support for preprocessor macros, while working for Red
474 @chapter A Sample @value{GDBN} Session
476 You can use this manual at your leisure to read all about @value{GDBN}.
477 However, a handful of commands are enough to get started using the
478 debugger. This chapter illustrates those commands.
481 In this sample session, we emphasize user input like this: @b{input},
482 to make it easier to pick out from the surrounding output.
485 @c FIXME: this example may not be appropriate for some configs, where
486 @c FIXME...primary interest is in remote use.
488 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
489 processor) exhibits the following bug: sometimes, when we change its
490 quote strings from the default, the commands used to capture one macro
491 definition within another stop working. In the following short @code{m4}
492 session, we define a macro @code{foo} which expands to @code{0000}; we
493 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
494 same thing. However, when we change the open quote string to
495 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
496 procedure fails to define a new synonym @code{baz}:
505 @b{define(bar,defn(`foo'))}
509 @b{changequote(<QUOTE>,<UNQUOTE>)}
511 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
514 m4: End of input: 0: fatal error: EOF in string
518 Let us use @value{GDBN} to try to see what is going on.
521 $ @b{@value{GDBP} m4}
522 @c FIXME: this falsifies the exact text played out, to permit smallbook
523 @c FIXME... format to come out better.
524 @value{GDBN} is free software and you are welcome to distribute copies
525 of it under certain conditions; type "show copying" to see
527 There is absolutely no warranty for @value{GDBN}; type "show warranty"
530 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
535 @value{GDBN} reads only enough symbol data to know where to find the
536 rest when needed; as a result, the first prompt comes up very quickly.
537 We now tell @value{GDBN} to use a narrower display width than usual, so
538 that examples fit in this manual.
541 (@value{GDBP}) @b{set width 70}
545 We need to see how the @code{m4} built-in @code{changequote} works.
546 Having looked at the source, we know the relevant subroutine is
547 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
548 @code{break} command.
551 (@value{GDBP}) @b{break m4_changequote}
552 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
556 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
557 control; as long as control does not reach the @code{m4_changequote}
558 subroutine, the program runs as usual:
561 (@value{GDBP}) @b{run}
562 Starting program: /work/Editorial/gdb/gnu/m4/m4
570 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
571 suspends execution of @code{m4}, displaying information about the
572 context where it stops.
575 @b{changequote(<QUOTE>,<UNQUOTE>)}
577 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
579 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
583 Now we use the command @code{n} (@code{next}) to advance execution to
584 the next line of the current function.
588 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
593 @code{set_quotes} looks like a promising subroutine. We can go into it
594 by using the command @code{s} (@code{step}) instead of @code{next}.
595 @code{step} goes to the next line to be executed in @emph{any}
596 subroutine, so it steps into @code{set_quotes}.
600 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
602 530 if (lquote != def_lquote)
606 The display that shows the subroutine where @code{m4} is now
607 suspended (and its arguments) is called a stack frame display. It
608 shows a summary of the stack. We can use the @code{backtrace}
609 command (which can also be spelled @code{bt}), to see where we are
610 in the stack as a whole: the @code{backtrace} command displays a
611 stack frame for each active subroutine.
614 (@value{GDBP}) @b{bt}
615 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
617 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
619 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
620 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
622 #4 0x79dc in expand_input () at macro.c:40
623 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
627 We step through a few more lines to see what happens. The first two
628 times, we can use @samp{s}; the next two times we use @code{n} to avoid
629 falling into the @code{xstrdup} subroutine.
633 0x3b5c 532 if (rquote != def_rquote)
635 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
636 def_lquote : xstrdup(lq);
638 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
641 538 len_lquote = strlen(rquote);
645 The last line displayed looks a little odd; we can examine the variables
646 @code{lquote} and @code{rquote} to see if they are in fact the new left
647 and right quotes we specified. We use the command @code{p}
648 (@code{print}) to see their values.
651 (@value{GDBP}) @b{p lquote}
652 $1 = 0x35d40 "<QUOTE>"
653 (@value{GDBP}) @b{p rquote}
654 $2 = 0x35d50 "<UNQUOTE>"
658 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
659 To look at some context, we can display ten lines of source
660 surrounding the current line with the @code{l} (@code{list}) command.
666 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
668 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
671 538 len_lquote = strlen(rquote);
672 539 len_rquote = strlen(lquote);
679 Let us step past the two lines that set @code{len_lquote} and
680 @code{len_rquote}, and then examine the values of those variables.
684 539 len_rquote = strlen(lquote);
687 (@value{GDBP}) @b{p len_lquote}
689 (@value{GDBP}) @b{p len_rquote}
694 That certainly looks wrong, assuming @code{len_lquote} and
695 @code{len_rquote} are meant to be the lengths of @code{lquote} and
696 @code{rquote} respectively. We can set them to better values using
697 the @code{p} command, since it can print the value of
698 any expression---and that expression can include subroutine calls and
702 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
704 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
709 Is that enough to fix the problem of using the new quotes with the
710 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
711 executing with the @code{c} (@code{continue}) command, and then try the
712 example that caused trouble initially:
718 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
725 Success! The new quotes now work just as well as the default ones. The
726 problem seems to have been just the two typos defining the wrong
727 lengths. We allow @code{m4} exit by giving it an EOF as input:
731 Program exited normally.
735 The message @samp{Program exited normally.} is from @value{GDBN}; it
736 indicates @code{m4} has finished executing. We can end our @value{GDBN}
737 session with the @value{GDBN} @code{quit} command.
740 (@value{GDBP}) @b{quit}
744 @chapter Getting In and Out of @value{GDBN}
746 This chapter discusses how to start @value{GDBN}, and how to get out of it.
750 type @samp{@value{GDBP}} to start @value{GDBN}.
752 type @kbd{quit} or @kbd{C-d} to exit.
756 * Invoking GDB:: How to start @value{GDBN}
757 * Quitting GDB:: How to quit @value{GDBN}
758 * Shell Commands:: How to use shell commands inside @value{GDBN}
762 @section Invoking @value{GDBN}
764 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
765 @value{GDBN} reads commands from the terminal until you tell it to exit.
767 You can also run @code{@value{GDBP}} with a variety of arguments and options,
768 to specify more of your debugging environment at the outset.
770 The command-line options described here are designed
771 to cover a variety of situations; in some environments, some of these
772 options may effectively be unavailable.
774 The most usual way to start @value{GDBN} is with one argument,
775 specifying an executable program:
778 @value{GDBP} @var{program}
782 You can also start with both an executable program and a core file
786 @value{GDBP} @var{program} @var{core}
789 You can, instead, specify a process ID as a second argument, if you want
790 to debug a running process:
793 @value{GDBP} @var{program} 1234
797 would attach @value{GDBN} to process @code{1234} (unless you also have a file
798 named @file{1234}; @value{GDBN} does check for a core file first).
800 Taking advantage of the second command-line argument requires a fairly
801 complete operating system; when you use @value{GDBN} as a remote
802 debugger attached to a bare board, there may not be any notion of
803 ``process'', and there is often no way to get a core dump. @value{GDBN}
804 will warn you if it is unable to attach or to read core dumps.
806 You can optionally have @code{@value{GDBP}} pass any arguments after the
807 executable file to the inferior using @code{--args}. This option stops
810 gdb --args gcc -O2 -c foo.c
812 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
813 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
815 You can run @code{@value{GDBP}} without printing the front material, which describes
816 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
823 You can further control how @value{GDBN} starts up by using command-line
824 options. @value{GDBN} itself can remind you of the options available.
834 to display all available options and briefly describe their use
835 (@samp{@value{GDBP} -h} is a shorter equivalent).
837 All options and command line arguments you give are processed
838 in sequential order. The order makes a difference when the
839 @samp{-x} option is used.
843 * File Options:: Choosing files
844 * Mode Options:: Choosing modes
848 @subsection Choosing files
850 When @value{GDBN} starts, it reads any arguments other than options as
851 specifying an executable file and core file (or process ID). This is
852 the same as if the arguments were specified by the @samp{-se} and
853 @samp{-c} (or @samp{-p} options respectively. (@value{GDBN} reads the
854 first argument that does not have an associated option flag as
855 equivalent to the @samp{-se} option followed by that argument; and the
856 second argument that does not have an associated option flag, if any, as
857 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
858 If the second argument begins with a decimal digit, @value{GDBN} will
859 first attempt to attach to it as a process, and if that fails, attempt
860 to open it as a corefile. If you have a corefile whose name begins with
861 a digit, you can prevent @value{GDBN} from treating it as a pid by
862 prefixing it with @file{./}, eg. @file{./12345}.
864 If @value{GDBN} has not been configured to included core file support,
865 such as for most embedded targets, then it will complain about a second
866 argument and ignore it.
868 Many options have both long and short forms; both are shown in the
869 following list. @value{GDBN} also recognizes the long forms if you truncate
870 them, so long as enough of the option is present to be unambiguous.
871 (If you prefer, you can flag option arguments with @samp{--} rather
872 than @samp{-}, though we illustrate the more usual convention.)
874 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
875 @c way, both those who look for -foo and --foo in the index, will find
879 @item -symbols @var{file}
881 @cindex @code{--symbols}
883 Read symbol table from file @var{file}.
885 @item -exec @var{file}
887 @cindex @code{--exec}
889 Use file @var{file} as the executable file to execute when appropriate,
890 and for examining pure data in conjunction with a core dump.
894 Read symbol table from file @var{file} and use it as the executable
897 @item -core @var{file}
899 @cindex @code{--core}
901 Use file @var{file} as a core dump to examine.
903 @item -c @var{number}
904 @item -pid @var{number}
905 @itemx -p @var{number}
908 Connect to process ID @var{number}, as with the @code{attach} command.
909 If there is no such process, @value{GDBN} will attempt to open a core
910 file named @var{number}.
912 @item -command @var{file}
914 @cindex @code{--command}
916 Execute @value{GDBN} commands from file @var{file}. @xref{Command
917 Files,, Command files}.
919 @item -directory @var{directory}
920 @itemx -d @var{directory}
921 @cindex @code{--directory}
923 Add @var{directory} to the path to search for source files.
927 @cindex @code{--mapped}
929 @emph{Warning: this option depends on operating system facilities that are not
930 supported on all systems.}@*
931 If memory-mapped files are available on your system through the @code{mmap}
932 system call, you can use this option
933 to have @value{GDBN} write the symbols from your
934 program into a reusable file in the current directory. If the program you are debugging is
935 called @file{/tmp/fred}, the mapped symbol file is @file{/tmp/fred.syms}.
936 Future @value{GDBN} debugging sessions notice the presence of this file,
937 and can quickly map in symbol information from it, rather than reading
938 the symbol table from the executable program.
940 The @file{.syms} file is specific to the host machine where @value{GDBN}
941 is run. It holds an exact image of the internal @value{GDBN} symbol
942 table. It cannot be shared across multiple host platforms.
946 @cindex @code{--readnow}
948 Read each symbol file's entire symbol table immediately, rather than
949 the default, which is to read it incrementally as it is needed.
950 This makes startup slower, but makes future operations faster.
954 You typically combine the @code{-mapped} and @code{-readnow} options in
955 order to build a @file{.syms} file that contains complete symbol
956 information. (@xref{Files,,Commands to specify files}, for information
957 on @file{.syms} files.) A simple @value{GDBN} invocation to do nothing
958 but build a @file{.syms} file for future use is:
961 gdb -batch -nx -mapped -readnow programname
965 @subsection Choosing modes
967 You can run @value{GDBN} in various alternative modes---for example, in
968 batch mode or quiet mode.
975 Do not execute commands found in any initialization files. Normally,
976 @value{GDBN} executes the commands in these files after all the command
977 options and arguments have been processed. @xref{Command Files,,Command
983 @cindex @code{--quiet}
984 @cindex @code{--silent}
986 ``Quiet''. Do not print the introductory and copyright messages. These
987 messages are also suppressed in batch mode.
990 @cindex @code{--batch}
991 Run in batch mode. Exit with status @code{0} after processing all the
992 command files specified with @samp{-x} (and all commands from
993 initialization files, if not inhibited with @samp{-n}). Exit with
994 nonzero status if an error occurs in executing the @value{GDBN} commands
995 in the command files.
997 Batch mode may be useful for running @value{GDBN} as a filter, for
998 example to download and run a program on another computer; in order to
999 make this more useful, the message
1002 Program exited normally.
1006 (which is ordinarily issued whenever a program running under
1007 @value{GDBN} control terminates) is not issued when running in batch
1012 @cindex @code{--nowindows}
1014 ``No windows''. If @value{GDBN} comes with a graphical user interface
1015 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1016 interface. If no GUI is available, this option has no effect.
1020 @cindex @code{--windows}
1022 If @value{GDBN} includes a GUI, then this option requires it to be
1025 @item -cd @var{directory}
1027 Run @value{GDBN} using @var{directory} as its working directory,
1028 instead of the current directory.
1032 @cindex @code{--fullname}
1034 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1035 subprocess. It tells @value{GDBN} to output the full file name and line
1036 number in a standard, recognizable fashion each time a stack frame is
1037 displayed (which includes each time your program stops). This
1038 recognizable format looks like two @samp{\032} characters, followed by
1039 the file name, line number and character position separated by colons,
1040 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1041 @samp{\032} characters as a signal to display the source code for the
1045 @cindex @code{--epoch}
1046 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1047 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1048 routines so as to allow Epoch to display values of expressions in a
1051 @item -annotate @var{level}
1052 @cindex @code{--annotate}
1053 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1054 effect is identical to using @samp{set annotate @var{level}}
1055 (@pxref{Annotations}).
1056 Annotation level controls how much information does @value{GDBN} print
1057 together with its prompt, values of expressions, source lines, and other
1058 types of output. Level 0 is the normal, level 1 is for use when
1059 @value{GDBN} is run as a subprocess of @sc{gnu} Emacs, level 2 is the
1060 maximum annotation suitable for programs that control @value{GDBN}.
1063 @cindex @code{--async}
1064 Use the asynchronous event loop for the command-line interface.
1065 @value{GDBN} processes all events, such as user keyboard input, via a
1066 special event loop. This allows @value{GDBN} to accept and process user
1067 commands in parallel with the debugged process being
1068 run@footnote{@value{GDBN} built with @sc{djgpp} tools for
1069 MS-DOS/MS-Windows supports this mode of operation, but the event loop is
1070 suspended when the debuggee runs.}, so you don't need to wait for
1071 control to return to @value{GDBN} before you type the next command.
1072 (@emph{Note:} as of version 5.1, the target side of the asynchronous
1073 operation is not yet in place, so @samp{-async} does not work fully
1075 @c FIXME: when the target side of the event loop is done, the above NOTE
1076 @c should be removed.
1078 When the standard input is connected to a terminal device, @value{GDBN}
1079 uses the asynchronous event loop by default, unless disabled by the
1080 @samp{-noasync} option.
1083 @cindex @code{--noasync}
1084 Disable the asynchronous event loop for the command-line interface.
1087 @cindex @code{--args}
1088 Change interpretation of command line so that arguments following the
1089 executable file are passed as command line arguments to the inferior.
1090 This option stops option processing.
1092 @item -baud @var{bps}
1094 @cindex @code{--baud}
1096 Set the line speed (baud rate or bits per second) of any serial
1097 interface used by @value{GDBN} for remote debugging.
1099 @item -tty @var{device}
1100 @itemx -t @var{device}
1101 @cindex @code{--tty}
1103 Run using @var{device} for your program's standard input and output.
1104 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1106 @c resolve the situation of these eventually
1108 @cindex @code{--tui}
1109 Activate the Terminal User Interface when starting.
1110 The Terminal User Interface manages several text windows on the terminal,
1111 showing source, assembly, registers and @value{GDBN} command outputs
1112 (@pxref{TUI, ,@value{GDBN} Text User Interface}).
1113 Do not use this option if you run @value{GDBN} from Emacs
1114 (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1117 @c @cindex @code{--xdb}
1118 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1119 @c For information, see the file @file{xdb_trans.html}, which is usually
1120 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1123 @item -interpreter @var{interp}
1124 @cindex @code{--interpreter}
1125 Use the interpreter @var{interp} for interface with the controlling
1126 program or device. This option is meant to be set by programs which
1127 communicate with @value{GDBN} using it as a back end.
1128 @xref{Interpreters, , Command Interpreters}.
1130 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1131 @value{GDBN} to use the current @dfn{@sc{gdb/mi} interface}
1132 (@pxref{GDB/MI, , The @sc{gdb/mi} Interface}). The previous @sc{gdb/mi}
1133 interface, included in @value{GDBN} version 5.3, can be selected with
1134 @samp{--interpreter=mi1}. Earlier @sc{gdb/mi} interfaces
1138 @cindex @code{--write}
1139 Open the executable and core files for both reading and writing. This
1140 is equivalent to the @samp{set write on} command inside @value{GDBN}
1144 @cindex @code{--statistics}
1145 This option causes @value{GDBN} to print statistics about time and
1146 memory usage after it completes each command and returns to the prompt.
1149 @cindex @code{--version}
1150 This option causes @value{GDBN} to print its version number and
1151 no-warranty blurb, and exit.
1156 @section Quitting @value{GDBN}
1157 @cindex exiting @value{GDBN}
1158 @cindex leaving @value{GDBN}
1161 @kindex quit @r{[}@var{expression}@r{]}
1162 @kindex q @r{(@code{quit})}
1163 @item quit @r{[}@var{expression}@r{]}
1165 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1166 @code{q}), or type an end-of-file character (usually @kbd{C-d}). If you
1167 do not supply @var{expression}, @value{GDBN} will terminate normally;
1168 otherwise it will terminate using the result of @var{expression} as the
1173 An interrupt (often @kbd{C-c}) does not exit from @value{GDBN}, but rather
1174 terminates the action of any @value{GDBN} command that is in progress and
1175 returns to @value{GDBN} command level. It is safe to type the interrupt
1176 character at any time because @value{GDBN} does not allow it to take effect
1177 until a time when it is safe.
1179 If you have been using @value{GDBN} to control an attached process or
1180 device, you can release it with the @code{detach} command
1181 (@pxref{Attach, ,Debugging an already-running process}).
1183 @node Shell Commands
1184 @section Shell commands
1186 If you need to execute occasional shell commands during your
1187 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1188 just use the @code{shell} command.
1192 @cindex shell escape
1193 @item shell @var{command string}
1194 Invoke a standard shell to execute @var{command string}.
1195 If it exists, the environment variable @code{SHELL} determines which
1196 shell to run. Otherwise @value{GDBN} uses the default shell
1197 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1200 The utility @code{make} is often needed in development environments.
1201 You do not have to use the @code{shell} command for this purpose in
1206 @cindex calling make
1207 @item make @var{make-args}
1208 Execute the @code{make} program with the specified
1209 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1213 @chapter @value{GDBN} Commands
1215 You can abbreviate a @value{GDBN} command to the first few letters of the command
1216 name, if that abbreviation is unambiguous; and you can repeat certain
1217 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1218 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1219 show you the alternatives available, if there is more than one possibility).
1222 * Command Syntax:: How to give commands to @value{GDBN}
1223 * Completion:: Command completion
1224 * Help:: How to ask @value{GDBN} for help
1227 @node Command Syntax
1228 @section Command syntax
1230 A @value{GDBN} command is a single line of input. There is no limit on
1231 how long it can be. It starts with a command name, which is followed by
1232 arguments whose meaning depends on the command name. For example, the
1233 command @code{step} accepts an argument which is the number of times to
1234 step, as in @samp{step 5}. You can also use the @code{step} command
1235 with no arguments. Some commands do not allow any arguments.
1237 @cindex abbreviation
1238 @value{GDBN} command names may always be truncated if that abbreviation is
1239 unambiguous. Other possible command abbreviations are listed in the
1240 documentation for individual commands. In some cases, even ambiguous
1241 abbreviations are allowed; for example, @code{s} is specially defined as
1242 equivalent to @code{step} even though there are other commands whose
1243 names start with @code{s}. You can test abbreviations by using them as
1244 arguments to the @code{help} command.
1246 @cindex repeating commands
1247 @kindex RET @r{(repeat last command)}
1248 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1249 repeat the previous command. Certain commands (for example, @code{run})
1250 will not repeat this way; these are commands whose unintentional
1251 repetition might cause trouble and which you are unlikely to want to
1254 The @code{list} and @code{x} commands, when you repeat them with
1255 @key{RET}, construct new arguments rather than repeating
1256 exactly as typed. This permits easy scanning of source or memory.
1258 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1259 output, in a way similar to the common utility @code{more}
1260 (@pxref{Screen Size,,Screen size}). Since it is easy to press one
1261 @key{RET} too many in this situation, @value{GDBN} disables command
1262 repetition after any command that generates this sort of display.
1264 @kindex # @r{(a comment)}
1266 Any text from a @kbd{#} to the end of the line is a comment; it does
1267 nothing. This is useful mainly in command files (@pxref{Command
1268 Files,,Command files}).
1270 @cindex repeating command sequences
1271 @kindex C-o @r{(operate-and-get-next)}
1272 The @kbd{C-o} binding is useful for repeating a complex sequence of
1273 commands. This command accepts the current line, like @kbd{RET}, and
1274 then fetches the next line relative to the current line from the history
1278 @section Command completion
1281 @cindex word completion
1282 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1283 only one possibility; it can also show you what the valid possibilities
1284 are for the next word in a command, at any time. This works for @value{GDBN}
1285 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1287 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1288 of a word. If there is only one possibility, @value{GDBN} fills in the
1289 word, and waits for you to finish the command (or press @key{RET} to
1290 enter it). For example, if you type
1292 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1293 @c complete accuracy in these examples; space introduced for clarity.
1294 @c If texinfo enhancements make it unnecessary, it would be nice to
1295 @c replace " @key" by "@key" in the following...
1297 (@value{GDBP}) info bre @key{TAB}
1301 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1302 the only @code{info} subcommand beginning with @samp{bre}:
1305 (@value{GDBP}) info breakpoints
1309 You can either press @key{RET} at this point, to run the @code{info
1310 breakpoints} command, or backspace and enter something else, if
1311 @samp{breakpoints} does not look like the command you expected. (If you
1312 were sure you wanted @code{info breakpoints} in the first place, you
1313 might as well just type @key{RET} immediately after @samp{info bre},
1314 to exploit command abbreviations rather than command completion).
1316 If there is more than one possibility for the next word when you press
1317 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1318 characters and try again, or just press @key{TAB} a second time;
1319 @value{GDBN} displays all the possible completions for that word. For
1320 example, you might want to set a breakpoint on a subroutine whose name
1321 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1322 just sounds the bell. Typing @key{TAB} again displays all the
1323 function names in your program that begin with those characters, for
1327 (@value{GDBP}) b make_ @key{TAB}
1328 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1329 make_a_section_from_file make_environ
1330 make_abs_section make_function_type
1331 make_blockvector make_pointer_type
1332 make_cleanup make_reference_type
1333 make_command make_symbol_completion_list
1334 (@value{GDBP}) b make_
1338 After displaying the available possibilities, @value{GDBN} copies your
1339 partial input (@samp{b make_} in the example) so you can finish the
1342 If you just want to see the list of alternatives in the first place, you
1343 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1344 means @kbd{@key{META} ?}. You can type this either by holding down a
1345 key designated as the @key{META} shift on your keyboard (if there is
1346 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1348 @cindex quotes in commands
1349 @cindex completion of quoted strings
1350 Sometimes the string you need, while logically a ``word'', may contain
1351 parentheses or other characters that @value{GDBN} normally excludes from
1352 its notion of a word. To permit word completion to work in this
1353 situation, you may enclose words in @code{'} (single quote marks) in
1354 @value{GDBN} commands.
1356 The most likely situation where you might need this is in typing the
1357 name of a C@t{++} function. This is because C@t{++} allows function
1358 overloading (multiple definitions of the same function, distinguished
1359 by argument type). For example, when you want to set a breakpoint you
1360 may need to distinguish whether you mean the version of @code{name}
1361 that takes an @code{int} parameter, @code{name(int)}, or the version
1362 that takes a @code{float} parameter, @code{name(float)}. To use the
1363 word-completion facilities in this situation, type a single quote
1364 @code{'} at the beginning of the function name. This alerts
1365 @value{GDBN} that it may need to consider more information than usual
1366 when you press @key{TAB} or @kbd{M-?} to request word completion:
1369 (@value{GDBP}) b 'bubble( @kbd{M-?}
1370 bubble(double,double) bubble(int,int)
1371 (@value{GDBP}) b 'bubble(
1374 In some cases, @value{GDBN} can tell that completing a name requires using
1375 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1376 completing as much as it can) if you do not type the quote in the first
1380 (@value{GDBP}) b bub @key{TAB}
1381 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1382 (@value{GDBP}) b 'bubble(
1386 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1387 you have not yet started typing the argument list when you ask for
1388 completion on an overloaded symbol.
1390 For more information about overloaded functions, see @ref{C plus plus
1391 expressions, ,C@t{++} expressions}. You can use the command @code{set
1392 overload-resolution off} to disable overload resolution;
1393 see @ref{Debugging C plus plus, ,@value{GDBN} features for C@t{++}}.
1397 @section Getting help
1398 @cindex online documentation
1401 You can always ask @value{GDBN} itself for information on its commands,
1402 using the command @code{help}.
1405 @kindex h @r{(@code{help})}
1408 You can use @code{help} (abbreviated @code{h}) with no arguments to
1409 display a short list of named classes of commands:
1413 List of classes of commands:
1415 aliases -- Aliases of other commands
1416 breakpoints -- Making program stop at certain points
1417 data -- Examining data
1418 files -- Specifying and examining files
1419 internals -- Maintenance commands
1420 obscure -- Obscure features
1421 running -- Running the program
1422 stack -- Examining the stack
1423 status -- Status inquiries
1424 support -- Support facilities
1425 tracepoints -- Tracing of program execution without@*
1426 stopping the program
1427 user-defined -- User-defined commands
1429 Type "help" followed by a class name for a list of
1430 commands in that class.
1431 Type "help" followed by command name for full
1433 Command name abbreviations are allowed if unambiguous.
1436 @c the above line break eliminates huge line overfull...
1438 @item help @var{class}
1439 Using one of the general help classes as an argument, you can get a
1440 list of the individual commands in that class. For example, here is the
1441 help display for the class @code{status}:
1444 (@value{GDBP}) help status
1449 @c Line break in "show" line falsifies real output, but needed
1450 @c to fit in smallbook page size.
1451 info -- Generic command for showing things
1452 about the program being debugged
1453 show -- Generic command for showing things
1456 Type "help" followed by command name for full
1458 Command name abbreviations are allowed if unambiguous.
1462 @item help @var{command}
1463 With a command name as @code{help} argument, @value{GDBN} displays a
1464 short paragraph on how to use that command.
1467 @item apropos @var{args}
1468 The @code{apropos @var{args}} command searches through all of the @value{GDBN}
1469 commands, and their documentation, for the regular expression specified in
1470 @var{args}. It prints out all matches found. For example:
1481 set symbol-reloading -- Set dynamic symbol table reloading
1482 multiple times in one run
1483 show symbol-reloading -- Show dynamic symbol table reloading
1484 multiple times in one run
1489 @item complete @var{args}
1490 The @code{complete @var{args}} command lists all the possible completions
1491 for the beginning of a command. Use @var{args} to specify the beginning of the
1492 command you want completed. For example:
1498 @noindent results in:
1509 @noindent This is intended for use by @sc{gnu} Emacs.
1512 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1513 and @code{show} to inquire about the state of your program, or the state
1514 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1515 manual introduces each of them in the appropriate context. The listings
1516 under @code{info} and under @code{show} in the Index point to
1517 all the sub-commands. @xref{Index}.
1522 @kindex i @r{(@code{info})}
1524 This command (abbreviated @code{i}) is for describing the state of your
1525 program. For example, you can list the arguments given to your program
1526 with @code{info args}, list the registers currently in use with @code{info
1527 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1528 You can get a complete list of the @code{info} sub-commands with
1529 @w{@code{help info}}.
1533 You can assign the result of an expression to an environment variable with
1534 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1535 @code{set prompt $}.
1539 In contrast to @code{info}, @code{show} is for describing the state of
1540 @value{GDBN} itself.
1541 You can change most of the things you can @code{show}, by using the
1542 related command @code{set}; for example, you can control what number
1543 system is used for displays with @code{set radix}, or simply inquire
1544 which is currently in use with @code{show radix}.
1547 To display all the settable parameters and their current
1548 values, you can use @code{show} with no arguments; you may also use
1549 @code{info set}. Both commands produce the same display.
1550 @c FIXME: "info set" violates the rule that "info" is for state of
1551 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1552 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1556 Here are three miscellaneous @code{show} subcommands, all of which are
1557 exceptional in lacking corresponding @code{set} commands:
1560 @kindex show version
1561 @cindex version number
1563 Show what version of @value{GDBN} is running. You should include this
1564 information in @value{GDBN} bug-reports. If multiple versions of
1565 @value{GDBN} are in use at your site, you may need to determine which
1566 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1567 commands are introduced, and old ones may wither away. Also, many
1568 system vendors ship variant versions of @value{GDBN}, and there are
1569 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1570 The version number is the same as the one announced when you start
1573 @kindex show copying
1575 Display information about permission for copying @value{GDBN}.
1577 @kindex show warranty
1579 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1580 if your version of @value{GDBN} comes with one.
1585 @chapter Running Programs Under @value{GDBN}
1587 When you run a program under @value{GDBN}, you must first generate
1588 debugging information when you compile it.
1590 You may start @value{GDBN} with its arguments, if any, in an environment
1591 of your choice. If you are doing native debugging, you may redirect
1592 your program's input and output, debug an already running process, or
1593 kill a child process.
1596 * Compilation:: Compiling for debugging
1597 * Starting:: Starting your program
1598 * Arguments:: Your program's arguments
1599 * Environment:: Your program's environment
1601 * Working Directory:: Your program's working directory
1602 * Input/Output:: Your program's input and output
1603 * Attach:: Debugging an already-running process
1604 * Kill Process:: Killing the child process
1606 * Threads:: Debugging programs with multiple threads
1607 * Processes:: Debugging programs with multiple processes
1611 @section Compiling for debugging
1613 In order to debug a program effectively, you need to generate
1614 debugging information when you compile it. This debugging information
1615 is stored in the object file; it describes the data type of each
1616 variable or function and the correspondence between source line numbers
1617 and addresses in the executable code.
1619 To request debugging information, specify the @samp{-g} option when you run
1622 Most compilers do not include information about preprocessor macros in
1623 the debugging information if you specify the @option{-g} flag alone,
1624 because this information is rather large. Version 3.1 of @value{NGCC},
1625 the @sc{gnu} C compiler, provides macro information if you specify the
1626 options @option{-gdwarf-2} and @option{-g3}; the former option requests
1627 debugging information in the Dwarf 2 format, and the latter requests
1628 ``extra information''. In the future, we hope to find more compact ways
1629 to represent macro information, so that it can be included with
1632 Many C compilers are unable to handle the @samp{-g} and @samp{-O}
1633 options together. Using those compilers, you cannot generate optimized
1634 executables containing debugging information.
1636 @value{NGCC}, the @sc{gnu} C compiler, supports @samp{-g} with or
1637 without @samp{-O}, making it possible to debug optimized code. We
1638 recommend that you @emph{always} use @samp{-g} whenever you compile a
1639 program. You may think your program is correct, but there is no sense
1640 in pushing your luck.
1642 @cindex optimized code, debugging
1643 @cindex debugging optimized code
1644 When you debug a program compiled with @samp{-g -O}, remember that the
1645 optimizer is rearranging your code; the debugger shows you what is
1646 really there. Do not be too surprised when the execution path does not
1647 exactly match your source file! An extreme example: if you define a
1648 variable, but never use it, @value{GDBN} never sees that
1649 variable---because the compiler optimizes it out of existence.
1651 Some things do not work as well with @samp{-g -O} as with just
1652 @samp{-g}, particularly on machines with instruction scheduling. If in
1653 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1654 please report it to us as a bug (including a test case!).
1656 Older versions of the @sc{gnu} C compiler permitted a variant option
1657 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1658 format; if your @sc{gnu} C compiler has this option, do not use it.
1662 @section Starting your program
1668 @kindex r @r{(@code{run})}
1671 Use the @code{run} command to start your program under @value{GDBN}.
1672 You must first specify the program name (except on VxWorks) with an
1673 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1674 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1675 (@pxref{Files, ,Commands to specify files}).
1679 If you are running your program in an execution environment that
1680 supports processes, @code{run} creates an inferior process and makes
1681 that process run your program. (In environments without processes,
1682 @code{run} jumps to the start of your program.)
1684 The execution of a program is affected by certain information it
1685 receives from its superior. @value{GDBN} provides ways to specify this
1686 information, which you must do @emph{before} starting your program. (You
1687 can change it after starting your program, but such changes only affect
1688 your program the next time you start it.) This information may be
1689 divided into four categories:
1692 @item The @emph{arguments.}
1693 Specify the arguments to give your program as the arguments of the
1694 @code{run} command. If a shell is available on your target, the shell
1695 is used to pass the arguments, so that you may use normal conventions
1696 (such as wildcard expansion or variable substitution) in describing
1698 In Unix systems, you can control which shell is used with the
1699 @code{SHELL} environment variable.
1700 @xref{Arguments, ,Your program's arguments}.
1702 @item The @emph{environment.}
1703 Your program normally inherits its environment from @value{GDBN}, but you can
1704 use the @value{GDBN} commands @code{set environment} and @code{unset
1705 environment} to change parts of the environment that affect
1706 your program. @xref{Environment, ,Your program's environment}.
1708 @item The @emph{working directory.}
1709 Your program inherits its working directory from @value{GDBN}. You can set
1710 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1711 @xref{Working Directory, ,Your program's working directory}.
1713 @item The @emph{standard input and output.}
1714 Your program normally uses the same device for standard input and
1715 standard output as @value{GDBN} is using. You can redirect input and output
1716 in the @code{run} command line, or you can use the @code{tty} command to
1717 set a different device for your program.
1718 @xref{Input/Output, ,Your program's input and output}.
1721 @emph{Warning:} While input and output redirection work, you cannot use
1722 pipes to pass the output of the program you are debugging to another
1723 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1727 When you issue the @code{run} command, your program begins to execute
1728 immediately. @xref{Stopping, ,Stopping and continuing}, for discussion
1729 of how to arrange for your program to stop. Once your program has
1730 stopped, you may call functions in your program, using the @code{print}
1731 or @code{call} commands. @xref{Data, ,Examining Data}.
1733 If the modification time of your symbol file has changed since the last
1734 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1735 table, and reads it again. When it does this, @value{GDBN} tries to retain
1736 your current breakpoints.
1739 @section Your program's arguments
1741 @cindex arguments (to your program)
1742 The arguments to your program can be specified by the arguments of the
1744 They are passed to a shell, which expands wildcard characters and
1745 performs redirection of I/O, and thence to your program. Your
1746 @code{SHELL} environment variable (if it exists) specifies what shell
1747 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1748 the default shell (@file{/bin/sh} on Unix).
1750 On non-Unix systems, the program is usually invoked directly by
1751 @value{GDBN}, which emulates I/O redirection via the appropriate system
1752 calls, and the wildcard characters are expanded by the startup code of
1753 the program, not by the shell.
1755 @code{run} with no arguments uses the same arguments used by the previous
1756 @code{run}, or those set by the @code{set args} command.
1761 Specify the arguments to be used the next time your program is run. If
1762 @code{set args} has no arguments, @code{run} executes your program
1763 with no arguments. Once you have run your program with arguments,
1764 using @code{set args} before the next @code{run} is the only way to run
1765 it again without arguments.
1769 Show the arguments to give your program when it is started.
1773 @section Your program's environment
1775 @cindex environment (of your program)
1776 The @dfn{environment} consists of a set of environment variables and
1777 their values. Environment variables conventionally record such things as
1778 your user name, your home directory, your terminal type, and your search
1779 path for programs to run. Usually you set up environment variables with
1780 the shell and they are inherited by all the other programs you run. When
1781 debugging, it can be useful to try running your program with a modified
1782 environment without having to start @value{GDBN} over again.
1786 @item path @var{directory}
1787 Add @var{directory} to the front of the @code{PATH} environment variable
1788 (the search path for executables) that will be passed to your program.
1789 The value of @code{PATH} used by @value{GDBN} does not change.
1790 You may specify several directory names, separated by whitespace or by a
1791 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1792 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1793 is moved to the front, so it is searched sooner.
1795 You can use the string @samp{$cwd} to refer to whatever is the current
1796 working directory at the time @value{GDBN} searches the path. If you
1797 use @samp{.} instead, it refers to the directory where you executed the
1798 @code{path} command. @value{GDBN} replaces @samp{.} in the
1799 @var{directory} argument (with the current path) before adding
1800 @var{directory} to the search path.
1801 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1802 @c document that, since repeating it would be a no-op.
1806 Display the list of search paths for executables (the @code{PATH}
1807 environment variable).
1809 @kindex show environment
1810 @item show environment @r{[}@var{varname}@r{]}
1811 Print the value of environment variable @var{varname} to be given to
1812 your program when it starts. If you do not supply @var{varname},
1813 print the names and values of all environment variables to be given to
1814 your program. You can abbreviate @code{environment} as @code{env}.
1816 @kindex set environment
1817 @item set environment @var{varname} @r{[}=@var{value}@r{]}
1818 Set environment variable @var{varname} to @var{value}. The value
1819 changes for your program only, not for @value{GDBN} itself. @var{value} may
1820 be any string; the values of environment variables are just strings, and
1821 any interpretation is supplied by your program itself. The @var{value}
1822 parameter is optional; if it is eliminated, the variable is set to a
1824 @c "any string" here does not include leading, trailing
1825 @c blanks. Gnu asks: does anyone care?
1827 For example, this command:
1834 tells the debugged program, when subsequently run, that its user is named
1835 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
1836 are not actually required.)
1838 @kindex unset environment
1839 @item unset environment @var{varname}
1840 Remove variable @var{varname} from the environment to be passed to your
1841 program. This is different from @samp{set env @var{varname} =};
1842 @code{unset environment} removes the variable from the environment,
1843 rather than assigning it an empty value.
1846 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
1848 by your @code{SHELL} environment variable if it exists (or
1849 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
1850 that runs an initialization file---such as @file{.cshrc} for C-shell, or
1851 @file{.bashrc} for BASH---any variables you set in that file affect
1852 your program. You may wish to move setting of environment variables to
1853 files that are only run when you sign on, such as @file{.login} or
1856 @node Working Directory
1857 @section Your program's working directory
1859 @cindex working directory (of your program)
1860 Each time you start your program with @code{run}, it inherits its
1861 working directory from the current working directory of @value{GDBN}.
1862 The @value{GDBN} working directory is initially whatever it inherited
1863 from its parent process (typically the shell), but you can specify a new
1864 working directory in @value{GDBN} with the @code{cd} command.
1866 The @value{GDBN} working directory also serves as a default for the commands
1867 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
1872 @item cd @var{directory}
1873 Set the @value{GDBN} working directory to @var{directory}.
1877 Print the @value{GDBN} working directory.
1881 @section Your program's input and output
1886 By default, the program you run under @value{GDBN} does input and output to
1887 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
1888 to its own terminal modes to interact with you, but it records the terminal
1889 modes your program was using and switches back to them when you continue
1890 running your program.
1893 @kindex info terminal
1895 Displays information recorded by @value{GDBN} about the terminal modes your
1899 You can redirect your program's input and/or output using shell
1900 redirection with the @code{run} command. For example,
1907 starts your program, diverting its output to the file @file{outfile}.
1910 @cindex controlling terminal
1911 Another way to specify where your program should do input and output is
1912 with the @code{tty} command. This command accepts a file name as
1913 argument, and causes this file to be the default for future @code{run}
1914 commands. It also resets the controlling terminal for the child
1915 process, for future @code{run} commands. For example,
1922 directs that processes started with subsequent @code{run} commands
1923 default to do input and output on the terminal @file{/dev/ttyb} and have
1924 that as their controlling terminal.
1926 An explicit redirection in @code{run} overrides the @code{tty} command's
1927 effect on the input/output device, but not its effect on the controlling
1930 When you use the @code{tty} command or redirect input in the @code{run}
1931 command, only the input @emph{for your program} is affected. The input
1932 for @value{GDBN} still comes from your terminal.
1935 @section Debugging an already-running process
1940 @item attach @var{process-id}
1941 This command attaches to a running process---one that was started
1942 outside @value{GDBN}. (@code{info files} shows your active
1943 targets.) The command takes as argument a process ID. The usual way to
1944 find out the process-id of a Unix process is with the @code{ps} utility,
1945 or with the @samp{jobs -l} shell command.
1947 @code{attach} does not repeat if you press @key{RET} a second time after
1948 executing the command.
1951 To use @code{attach}, your program must be running in an environment
1952 which supports processes; for example, @code{attach} does not work for
1953 programs on bare-board targets that lack an operating system. You must
1954 also have permission to send the process a signal.
1956 When you use @code{attach}, the debugger finds the program running in
1957 the process first by looking in the current working directory, then (if
1958 the program is not found) by using the source file search path
1959 (@pxref{Source Path, ,Specifying source directories}). You can also use
1960 the @code{file} command to load the program. @xref{Files, ,Commands to
1963 The first thing @value{GDBN} does after arranging to debug the specified
1964 process is to stop it. You can examine and modify an attached process
1965 with all the @value{GDBN} commands that are ordinarily available when
1966 you start processes with @code{run}. You can insert breakpoints; you
1967 can step and continue; you can modify storage. If you would rather the
1968 process continue running, you may use the @code{continue} command after
1969 attaching @value{GDBN} to the process.
1974 When you have finished debugging the attached process, you can use the
1975 @code{detach} command to release it from @value{GDBN} control. Detaching
1976 the process continues its execution. After the @code{detach} command,
1977 that process and @value{GDBN} become completely independent once more, and you
1978 are ready to @code{attach} another process or start one with @code{run}.
1979 @code{detach} does not repeat if you press @key{RET} again after
1980 executing the command.
1983 If you exit @value{GDBN} or use the @code{run} command while you have an
1984 attached process, you kill that process. By default, @value{GDBN} asks
1985 for confirmation if you try to do either of these things; you can
1986 control whether or not you need to confirm by using the @code{set
1987 confirm} command (@pxref{Messages/Warnings, ,Optional warnings and
1991 @section Killing the child process
1996 Kill the child process in which your program is running under @value{GDBN}.
1999 This command is useful if you wish to debug a core dump instead of a
2000 running process. @value{GDBN} ignores any core dump file while your program
2003 On some operating systems, a program cannot be executed outside @value{GDBN}
2004 while you have breakpoints set on it inside @value{GDBN}. You can use the
2005 @code{kill} command in this situation to permit running your program
2006 outside the debugger.
2008 The @code{kill} command is also useful if you wish to recompile and
2009 relink your program, since on many systems it is impossible to modify an
2010 executable file while it is running in a process. In this case, when you
2011 next type @code{run}, @value{GDBN} notices that the file has changed, and
2012 reads the symbol table again (while trying to preserve your current
2013 breakpoint settings).
2016 @section Debugging programs with multiple threads
2018 @cindex threads of execution
2019 @cindex multiple threads
2020 @cindex switching threads
2021 In some operating systems, such as HP-UX and Solaris, a single program
2022 may have more than one @dfn{thread} of execution. The precise semantics
2023 of threads differ from one operating system to another, but in general
2024 the threads of a single program are akin to multiple processes---except
2025 that they share one address space (that is, they can all examine and
2026 modify the same variables). On the other hand, each thread has its own
2027 registers and execution stack, and perhaps private memory.
2029 @value{GDBN} provides these facilities for debugging multi-thread
2033 @item automatic notification of new threads
2034 @item @samp{thread @var{threadno}}, a command to switch among threads
2035 @item @samp{info threads}, a command to inquire about existing threads
2036 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2037 a command to apply a command to a list of threads
2038 @item thread-specific breakpoints
2042 @emph{Warning:} These facilities are not yet available on every
2043 @value{GDBN} configuration where the operating system supports threads.
2044 If your @value{GDBN} does not support threads, these commands have no
2045 effect. For example, a system without thread support shows no output
2046 from @samp{info threads}, and always rejects the @code{thread} command,
2050 (@value{GDBP}) info threads
2051 (@value{GDBP}) thread 1
2052 Thread ID 1 not known. Use the "info threads" command to
2053 see the IDs of currently known threads.
2055 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2056 @c doesn't support threads"?
2059 @cindex focus of debugging
2060 @cindex current thread
2061 The @value{GDBN} thread debugging facility allows you to observe all
2062 threads while your program runs---but whenever @value{GDBN} takes
2063 control, one thread in particular is always the focus of debugging.
2064 This thread is called the @dfn{current thread}. Debugging commands show
2065 program information from the perspective of the current thread.
2067 @cindex @code{New} @var{systag} message
2068 @cindex thread identifier (system)
2069 @c FIXME-implementors!! It would be more helpful if the [New...] message
2070 @c included GDB's numeric thread handle, so you could just go to that
2071 @c thread without first checking `info threads'.
2072 Whenever @value{GDBN} detects a new thread in your program, it displays
2073 the target system's identification for the thread with a message in the
2074 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2075 whose form varies depending on the particular system. For example, on
2076 LynxOS, you might see
2079 [New process 35 thread 27]
2083 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2084 the @var{systag} is simply something like @samp{process 368}, with no
2087 @c FIXME!! (1) Does the [New...] message appear even for the very first
2088 @c thread of a program, or does it only appear for the
2089 @c second---i.e.@: when it becomes obvious we have a multithread
2091 @c (2) *Is* there necessarily a first thread always? Or do some
2092 @c multithread systems permit starting a program with multiple
2093 @c threads ab initio?
2095 @cindex thread number
2096 @cindex thread identifier (GDB)
2097 For debugging purposes, @value{GDBN} associates its own thread
2098 number---always a single integer---with each thread in your program.
2101 @kindex info threads
2103 Display a summary of all threads currently in your
2104 program. @value{GDBN} displays for each thread (in this order):
2107 @item the thread number assigned by @value{GDBN}
2109 @item the target system's thread identifier (@var{systag})
2111 @item the current stack frame summary for that thread
2115 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2116 indicates the current thread.
2120 @c end table here to get a little more width for example
2123 (@value{GDBP}) info threads
2124 3 process 35 thread 27 0x34e5 in sigpause ()
2125 2 process 35 thread 23 0x34e5 in sigpause ()
2126 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2132 @cindex thread number
2133 @cindex thread identifier (GDB)
2134 For debugging purposes, @value{GDBN} associates its own thread
2135 number---a small integer assigned in thread-creation order---with each
2136 thread in your program.
2138 @cindex @code{New} @var{systag} message, on HP-UX
2139 @cindex thread identifier (system), on HP-UX
2140 @c FIXME-implementors!! It would be more helpful if the [New...] message
2141 @c included GDB's numeric thread handle, so you could just go to that
2142 @c thread without first checking `info threads'.
2143 Whenever @value{GDBN} detects a new thread in your program, it displays
2144 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2145 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2146 whose form varies depending on the particular system. For example, on
2150 [New thread 2 (system thread 26594)]
2154 when @value{GDBN} notices a new thread.
2157 @kindex info threads
2159 Display a summary of all threads currently in your
2160 program. @value{GDBN} displays for each thread (in this order):
2163 @item the thread number assigned by @value{GDBN}
2165 @item the target system's thread identifier (@var{systag})
2167 @item the current stack frame summary for that thread
2171 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2172 indicates the current thread.
2176 @c end table here to get a little more width for example
2179 (@value{GDBP}) info threads
2180 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2182 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2183 from /usr/lib/libc.2
2184 1 system thread 27905 0x7b003498 in _brk () \@*
2185 from /usr/lib/libc.2
2189 @kindex thread @var{threadno}
2190 @item thread @var{threadno}
2191 Make thread number @var{threadno} the current thread. The command
2192 argument @var{threadno} is the internal @value{GDBN} thread number, as
2193 shown in the first field of the @samp{info threads} display.
2194 @value{GDBN} responds by displaying the system identifier of the thread
2195 you selected, and its current stack frame summary:
2198 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2199 (@value{GDBP}) thread 2
2200 [Switching to process 35 thread 23]
2201 0x34e5 in sigpause ()
2205 As with the @samp{[New @dots{}]} message, the form of the text after
2206 @samp{Switching to} depends on your system's conventions for identifying
2209 @kindex thread apply
2210 @item thread apply [@var{threadno}] [@var{all}] @var{args}
2211 The @code{thread apply} command allows you to apply a command to one or
2212 more threads. Specify the numbers of the threads that you want affected
2213 with the command argument @var{threadno}. @var{threadno} is the internal
2214 @value{GDBN} thread number, as shown in the first field of the @samp{info
2215 threads} display. To apply a command to all threads, use
2216 @code{thread apply all} @var{args}.
2219 @cindex automatic thread selection
2220 @cindex switching threads automatically
2221 @cindex threads, automatic switching
2222 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2223 signal, it automatically selects the thread where that breakpoint or
2224 signal happened. @value{GDBN} alerts you to the context switch with a
2225 message of the form @samp{[Switching to @var{systag}]} to identify the
2228 @xref{Thread Stops,,Stopping and starting multi-thread programs}, for
2229 more information about how @value{GDBN} behaves when you stop and start
2230 programs with multiple threads.
2232 @xref{Set Watchpoints,,Setting watchpoints}, for information about
2233 watchpoints in programs with multiple threads.
2236 @section Debugging programs with multiple processes
2238 @cindex fork, debugging programs which call
2239 @cindex multiple processes
2240 @cindex processes, multiple
2241 On most systems, @value{GDBN} has no special support for debugging
2242 programs which create additional processes using the @code{fork}
2243 function. When a program forks, @value{GDBN} will continue to debug the
2244 parent process and the child process will run unimpeded. If you have
2245 set a breakpoint in any code which the child then executes, the child
2246 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2247 will cause it to terminate.
2249 However, if you want to debug the child process there is a workaround
2250 which isn't too painful. Put a call to @code{sleep} in the code which
2251 the child process executes after the fork. It may be useful to sleep
2252 only if a certain environment variable is set, or a certain file exists,
2253 so that the delay need not occur when you don't want to run @value{GDBN}
2254 on the child. While the child is sleeping, use the @code{ps} program to
2255 get its process ID. Then tell @value{GDBN} (a new invocation of
2256 @value{GDBN} if you are also debugging the parent process) to attach to
2257 the child process (@pxref{Attach}). From that point on you can debug
2258 the child process just like any other process which you attached to.
2260 On HP-UX (11.x and later only?), @value{GDBN} provides support for
2261 debugging programs that create additional processes using the
2262 @code{fork} or @code{vfork} function.
2264 By default, when a program forks, @value{GDBN} will continue to debug
2265 the parent process and the child process will run unimpeded.
2267 If you want to follow the child process instead of the parent process,
2268 use the command @w{@code{set follow-fork-mode}}.
2271 @kindex set follow-fork-mode
2272 @item set follow-fork-mode @var{mode}
2273 Set the debugger response to a program call of @code{fork} or
2274 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2275 process. The @var{mode} can be:
2279 The original process is debugged after a fork. The child process runs
2280 unimpeded. This is the default.
2283 The new process is debugged after a fork. The parent process runs
2287 The debugger will ask for one of the above choices.
2290 @item show follow-fork-mode
2291 Display the current debugger response to a @code{fork} or @code{vfork} call.
2294 If you ask to debug a child process and a @code{vfork} is followed by an
2295 @code{exec}, @value{GDBN} executes the new target up to the first
2296 breakpoint in the new target. If you have a breakpoint set on
2297 @code{main} in your original program, the breakpoint will also be set on
2298 the child process's @code{main}.
2300 When a child process is spawned by @code{vfork}, you cannot debug the
2301 child or parent until an @code{exec} call completes.
2303 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2304 call executes, the new target restarts. To restart the parent process,
2305 use the @code{file} command with the parent executable name as its
2308 You can use the @code{catch} command to make @value{GDBN} stop whenever
2309 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2310 Catchpoints, ,Setting catchpoints}.
2313 @chapter Stopping and Continuing
2315 The principal purposes of using a debugger are so that you can stop your
2316 program before it terminates; or so that, if your program runs into
2317 trouble, you can investigate and find out why.
2319 Inside @value{GDBN}, your program may stop for any of several reasons,
2320 such as a signal, a breakpoint, or reaching a new line after a
2321 @value{GDBN} command such as @code{step}. You may then examine and
2322 change variables, set new breakpoints or remove old ones, and then
2323 continue execution. Usually, the messages shown by @value{GDBN} provide
2324 ample explanation of the status of your program---but you can also
2325 explicitly request this information at any time.
2328 @kindex info program
2330 Display information about the status of your program: whether it is
2331 running or not, what process it is, and why it stopped.
2335 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2336 * Continuing and Stepping:: Resuming execution
2338 * Thread Stops:: Stopping and starting multi-thread programs
2342 @section Breakpoints, watchpoints, and catchpoints
2345 A @dfn{breakpoint} makes your program stop whenever a certain point in
2346 the program is reached. For each breakpoint, you can add conditions to
2347 control in finer detail whether your program stops. You can set
2348 breakpoints with the @code{break} command and its variants (@pxref{Set
2349 Breaks, ,Setting breakpoints}), to specify the place where your program
2350 should stop by line number, function name or exact address in the
2353 In HP-UX, SunOS 4.x, SVR4, and Alpha OSF/1 configurations, you can set
2354 breakpoints in shared libraries before the executable is run. There is
2355 a minor limitation on HP-UX systems: you must wait until the executable
2356 is run in order to set breakpoints in shared library routines that are
2357 not called directly by the program (for example, routines that are
2358 arguments in a @code{pthread_create} call).
2361 @cindex memory tracing
2362 @cindex breakpoint on memory address
2363 @cindex breakpoint on variable modification
2364 A @dfn{watchpoint} is a special breakpoint that stops your program
2365 when the value of an expression changes. You must use a different
2366 command to set watchpoints (@pxref{Set Watchpoints, ,Setting
2367 watchpoints}), but aside from that, you can manage a watchpoint like
2368 any other breakpoint: you enable, disable, and delete both breakpoints
2369 and watchpoints using the same commands.
2371 You can arrange to have values from your program displayed automatically
2372 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2376 @cindex breakpoint on events
2377 A @dfn{catchpoint} is another special breakpoint that stops your program
2378 when a certain kind of event occurs, such as the throwing of a C@t{++}
2379 exception or the loading of a library. As with watchpoints, you use a
2380 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2381 catchpoints}), but aside from that, you can manage a catchpoint like any
2382 other breakpoint. (To stop when your program receives a signal, use the
2383 @code{handle} command; see @ref{Signals, ,Signals}.)
2385 @cindex breakpoint numbers
2386 @cindex numbers for breakpoints
2387 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2388 catchpoint when you create it; these numbers are successive integers
2389 starting with one. In many of the commands for controlling various
2390 features of breakpoints you use the breakpoint number to say which
2391 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2392 @dfn{disabled}; if disabled, it has no effect on your program until you
2395 @cindex breakpoint ranges
2396 @cindex ranges of breakpoints
2397 Some @value{GDBN} commands accept a range of breakpoints on which to
2398 operate. A breakpoint range is either a single breakpoint number, like
2399 @samp{5}, or two such numbers, in increasing order, separated by a
2400 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2401 all breakpoint in that range are operated on.
2404 * Set Breaks:: Setting breakpoints
2405 * Set Watchpoints:: Setting watchpoints
2406 * Set Catchpoints:: Setting catchpoints
2407 * Delete Breaks:: Deleting breakpoints
2408 * Disabling:: Disabling breakpoints
2409 * Conditions:: Break conditions
2410 * Break Commands:: Breakpoint command lists
2411 * Breakpoint Menus:: Breakpoint menus
2412 * Error in Breakpoints:: ``Cannot insert breakpoints''
2416 @subsection Setting breakpoints
2418 @c FIXME LMB what does GDB do if no code on line of breakpt?
2419 @c consider in particular declaration with/without initialization.
2421 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2424 @kindex b @r{(@code{break})}
2425 @vindex $bpnum@r{, convenience variable}
2426 @cindex latest breakpoint
2427 Breakpoints are set with the @code{break} command (abbreviated
2428 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2429 number of the breakpoint you've set most recently; see @ref{Convenience
2430 Vars,, Convenience variables}, for a discussion of what you can do with
2431 convenience variables.
2433 You have several ways to say where the breakpoint should go.
2436 @item break @var{function}
2437 Set a breakpoint at entry to function @var{function}.
2438 When using source languages that permit overloading of symbols, such as
2439 C@t{++}, @var{function} may refer to more than one possible place to break.
2440 @xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
2442 @item break +@var{offset}
2443 @itemx break -@var{offset}
2444 Set a breakpoint some number of lines forward or back from the position
2445 at which execution stopped in the currently selected @dfn{stack frame}.
2446 (@xref{Frames, ,Frames}, for a description of stack frames.)
2448 @item break @var{linenum}
2449 Set a breakpoint at line @var{linenum} in the current source file.
2450 The current source file is the last file whose source text was printed.
2451 The breakpoint will stop your program just before it executes any of the
2454 @item break @var{filename}:@var{linenum}
2455 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2457 @item break @var{filename}:@var{function}
2458 Set a breakpoint at entry to function @var{function} found in file
2459 @var{filename}. Specifying a file name as well as a function name is
2460 superfluous except when multiple files contain similarly named
2463 @item break *@var{address}
2464 Set a breakpoint at address @var{address}. You can use this to set
2465 breakpoints in parts of your program which do not have debugging
2466 information or source files.
2469 When called without any arguments, @code{break} sets a breakpoint at
2470 the next instruction to be executed in the selected stack frame
2471 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2472 innermost, this makes your program stop as soon as control
2473 returns to that frame. This is similar to the effect of a
2474 @code{finish} command in the frame inside the selected frame---except
2475 that @code{finish} does not leave an active breakpoint. If you use
2476 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2477 the next time it reaches the current location; this may be useful
2480 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2481 least one instruction has been executed. If it did not do this, you
2482 would be unable to proceed past a breakpoint without first disabling the
2483 breakpoint. This rule applies whether or not the breakpoint already
2484 existed when your program stopped.
2486 @item break @dots{} if @var{cond}
2487 Set a breakpoint with condition @var{cond}; evaluate the expression
2488 @var{cond} each time the breakpoint is reached, and stop only if the
2489 value is nonzero---that is, if @var{cond} evaluates as true.
2490 @samp{@dots{}} stands for one of the possible arguments described
2491 above (or no argument) specifying where to break. @xref{Conditions,
2492 ,Break conditions}, for more information on breakpoint conditions.
2495 @item tbreak @var{args}
2496 Set a breakpoint enabled only for one stop. @var{args} are the
2497 same as for the @code{break} command, and the breakpoint is set in the same
2498 way, but the breakpoint is automatically deleted after the first time your
2499 program stops there. @xref{Disabling, ,Disabling breakpoints}.
2502 @item hbreak @var{args}
2503 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2504 @code{break} command and the breakpoint is set in the same way, but the
2505 breakpoint requires hardware support and some target hardware may not
2506 have this support. The main purpose of this is EPROM/ROM code
2507 debugging, so you can set a breakpoint at an instruction without
2508 changing the instruction. This can be used with the new trap-generation
2509 provided by SPARClite DSU and some x86-based targets. These targets
2510 will generate traps when a program accesses some data or instruction
2511 address that is assigned to the debug registers. However the hardware
2512 breakpoint registers can take a limited number of breakpoints. For
2513 example, on the DSU, only two data breakpoints can be set at a time, and
2514 @value{GDBN} will reject this command if more than two are used. Delete
2515 or disable unused hardware breakpoints before setting new ones
2516 (@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}.
2517 @xref{set remote hardware-breakpoint-limit}.
2521 @item thbreak @var{args}
2522 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2523 are the same as for the @code{hbreak} command and the breakpoint is set in
2524 the same way. However, like the @code{tbreak} command,
2525 the breakpoint is automatically deleted after the
2526 first time your program stops there. Also, like the @code{hbreak}
2527 command, the breakpoint requires hardware support and some target hardware
2528 may not have this support. @xref{Disabling, ,Disabling breakpoints}.
2529 See also @ref{Conditions, ,Break conditions}.
2532 @cindex regular expression
2533 @item rbreak @var{regex}
2534 Set breakpoints on all functions matching the regular expression
2535 @var{regex}. This command sets an unconditional breakpoint on all
2536 matches, printing a list of all breakpoints it set. Once these
2537 breakpoints are set, they are treated just like the breakpoints set with
2538 the @code{break} command. You can delete them, disable them, or make
2539 them conditional the same way as any other breakpoint.
2541 The syntax of the regular expression is the standard one used with tools
2542 like @file{grep}. Note that this is different from the syntax used by
2543 shells, so for instance @code{foo*} matches all functions that include
2544 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2545 @code{.*} leading and trailing the regular expression you supply, so to
2546 match only functions that begin with @code{foo}, use @code{^foo}.
2548 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2549 breakpoints on overloaded functions that are not members of any special
2552 @kindex info breakpoints
2553 @cindex @code{$_} and @code{info breakpoints}
2554 @item info breakpoints @r{[}@var{n}@r{]}
2555 @itemx info break @r{[}@var{n}@r{]}
2556 @itemx info watchpoints @r{[}@var{n}@r{]}
2557 Print a table of all breakpoints, watchpoints, and catchpoints set and
2558 not deleted, with the following columns for each breakpoint:
2561 @item Breakpoint Numbers
2563 Breakpoint, watchpoint, or catchpoint.
2565 Whether the breakpoint is marked to be disabled or deleted when hit.
2566 @item Enabled or Disabled
2567 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2568 that are not enabled.
2570 Where the breakpoint is in your program, as a memory address.
2572 Where the breakpoint is in the source for your program, as a file and
2577 If a breakpoint is conditional, @code{info break} shows the condition on
2578 the line following the affected breakpoint; breakpoint commands, if any,
2579 are listed after that.
2582 @code{info break} with a breakpoint
2583 number @var{n} as argument lists only that breakpoint. The
2584 convenience variable @code{$_} and the default examining-address for
2585 the @code{x} command are set to the address of the last breakpoint
2586 listed (@pxref{Memory, ,Examining memory}).
2589 @code{info break} displays a count of the number of times the breakpoint
2590 has been hit. This is especially useful in conjunction with the
2591 @code{ignore} command. You can ignore a large number of breakpoint
2592 hits, look at the breakpoint info to see how many times the breakpoint
2593 was hit, and then run again, ignoring one less than that number. This
2594 will get you quickly to the last hit of that breakpoint.
2597 @value{GDBN} allows you to set any number of breakpoints at the same place in
2598 your program. There is nothing silly or meaningless about this. When
2599 the breakpoints are conditional, this is even useful
2600 (@pxref{Conditions, ,Break conditions}).
2602 @cindex negative breakpoint numbers
2603 @cindex internal @value{GDBN} breakpoints
2604 @value{GDBN} itself sometimes sets breakpoints in your program for
2605 special purposes, such as proper handling of @code{longjmp} (in C
2606 programs). These internal breakpoints are assigned negative numbers,
2607 starting with @code{-1}; @samp{info breakpoints} does not display them.
2608 You can see these breakpoints with the @value{GDBN} maintenance command
2609 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
2612 @node Set Watchpoints
2613 @subsection Setting watchpoints
2615 @cindex setting watchpoints
2616 @cindex software watchpoints
2617 @cindex hardware watchpoints
2618 You can use a watchpoint to stop execution whenever the value of an
2619 expression changes, without having to predict a particular place where
2622 Depending on your system, watchpoints may be implemented in software or
2623 hardware. @value{GDBN} does software watchpointing by single-stepping your
2624 program and testing the variable's value each time, which is hundreds of
2625 times slower than normal execution. (But this may still be worth it, to
2626 catch errors where you have no clue what part of your program is the
2629 On some systems, such as HP-UX, @sc{gnu}/Linux and some other x86-based targets,
2630 @value{GDBN} includes support for
2631 hardware watchpoints, which do not slow down the running of your
2636 @item watch @var{expr}
2637 Set a watchpoint for an expression. @value{GDBN} will break when @var{expr}
2638 is written into by the program and its value changes.
2641 @item rwatch @var{expr}
2642 Set a watchpoint that will break when watch @var{expr} is read by the program.
2645 @item awatch @var{expr}
2646 Set a watchpoint that will break when @var{expr} is either read or written into
2649 @kindex info watchpoints
2650 @item info watchpoints
2651 This command prints a list of watchpoints, breakpoints, and catchpoints;
2652 it is the same as @code{info break}.
2655 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
2656 watchpoints execute very quickly, and the debugger reports a change in
2657 value at the exact instruction where the change occurs. If @value{GDBN}
2658 cannot set a hardware watchpoint, it sets a software watchpoint, which
2659 executes more slowly and reports the change in value at the next
2660 statement, not the instruction, after the change occurs.
2662 When you issue the @code{watch} command, @value{GDBN} reports
2665 Hardware watchpoint @var{num}: @var{expr}
2669 if it was able to set a hardware watchpoint.
2671 Currently, the @code{awatch} and @code{rwatch} commands can only set
2672 hardware watchpoints, because accesses to data that don't change the
2673 value of the watched expression cannot be detected without examining
2674 every instruction as it is being executed, and @value{GDBN} does not do
2675 that currently. If @value{GDBN} finds that it is unable to set a
2676 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
2677 will print a message like this:
2680 Expression cannot be implemented with read/access watchpoint.
2683 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
2684 data type of the watched expression is wider than what a hardware
2685 watchpoint on the target machine can handle. For example, some systems
2686 can only watch regions that are up to 4 bytes wide; on such systems you
2687 cannot set hardware watchpoints for an expression that yields a
2688 double-precision floating-point number (which is typically 8 bytes
2689 wide). As a work-around, it might be possible to break the large region
2690 into a series of smaller ones and watch them with separate watchpoints.
2692 If you set too many hardware watchpoints, @value{GDBN} might be unable
2693 to insert all of them when you resume the execution of your program.
2694 Since the precise number of active watchpoints is unknown until such
2695 time as the program is about to be resumed, @value{GDBN} might not be
2696 able to warn you about this when you set the watchpoints, and the
2697 warning will be printed only when the program is resumed:
2700 Hardware watchpoint @var{num}: Could not insert watchpoint
2704 If this happens, delete or disable some of the watchpoints.
2706 The SPARClite DSU will generate traps when a program accesses some data
2707 or instruction address that is assigned to the debug registers. For the
2708 data addresses, DSU facilitates the @code{watch} command. However the
2709 hardware breakpoint registers can only take two data watchpoints, and
2710 both watchpoints must be the same kind. For example, you can set two
2711 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
2712 @strong{or} two with @code{awatch} commands, but you cannot set one
2713 watchpoint with one command and the other with a different command.
2714 @value{GDBN} will reject the command if you try to mix watchpoints.
2715 Delete or disable unused watchpoint commands before setting new ones.
2717 If you call a function interactively using @code{print} or @code{call},
2718 any watchpoints you have set will be inactive until @value{GDBN} reaches another
2719 kind of breakpoint or the call completes.
2721 @value{GDBN} automatically deletes watchpoints that watch local
2722 (automatic) variables, or expressions that involve such variables, when
2723 they go out of scope, that is, when the execution leaves the block in
2724 which these variables were defined. In particular, when the program
2725 being debugged terminates, @emph{all} local variables go out of scope,
2726 and so only watchpoints that watch global variables remain set. If you
2727 rerun the program, you will need to set all such watchpoints again. One
2728 way of doing that would be to set a code breakpoint at the entry to the
2729 @code{main} function and when it breaks, set all the watchpoints.
2732 @cindex watchpoints and threads
2733 @cindex threads and watchpoints
2734 @emph{Warning:} In multi-thread programs, watchpoints have only limited
2735 usefulness. With the current watchpoint implementation, @value{GDBN}
2736 can only watch the value of an expression @emph{in a single thread}. If
2737 you are confident that the expression can only change due to the current
2738 thread's activity (and if you are also confident that no other thread
2739 can become current), then you can use watchpoints as usual. However,
2740 @value{GDBN} may not notice when a non-current thread's activity changes
2743 @c FIXME: this is almost identical to the previous paragraph.
2744 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
2745 have only limited usefulness. If @value{GDBN} creates a software
2746 watchpoint, it can only watch the value of an expression @emph{in a
2747 single thread}. If you are confident that the expression can only
2748 change due to the current thread's activity (and if you are also
2749 confident that no other thread can become current), then you can use
2750 software watchpoints as usual. However, @value{GDBN} may not notice
2751 when a non-current thread's activity changes the expression. (Hardware
2752 watchpoints, in contrast, watch an expression in all threads.)
2755 @xref{set remote hardware-watchpoint-limit}.
2757 @node Set Catchpoints
2758 @subsection Setting catchpoints
2759 @cindex catchpoints, setting
2760 @cindex exception handlers
2761 @cindex event handling
2763 You can use @dfn{catchpoints} to cause the debugger to stop for certain
2764 kinds of program events, such as C@t{++} exceptions or the loading of a
2765 shared library. Use the @code{catch} command to set a catchpoint.
2769 @item catch @var{event}
2770 Stop when @var{event} occurs. @var{event} can be any of the following:
2774 The throwing of a C@t{++} exception.
2778 The catching of a C@t{++} exception.
2782 A call to @code{exec}. This is currently only available for HP-UX.
2786 A call to @code{fork}. This is currently only available for HP-UX.
2790 A call to @code{vfork}. This is currently only available for HP-UX.
2793 @itemx load @var{libname}
2795 The dynamic loading of any shared library, or the loading of the library
2796 @var{libname}. This is currently only available for HP-UX.
2799 @itemx unload @var{libname}
2800 @kindex catch unload
2801 The unloading of any dynamically loaded shared library, or the unloading
2802 of the library @var{libname}. This is currently only available for HP-UX.
2805 @item tcatch @var{event}
2806 Set a catchpoint that is enabled only for one stop. The catchpoint is
2807 automatically deleted after the first time the event is caught.
2811 Use the @code{info break} command to list the current catchpoints.
2813 There are currently some limitations to C@t{++} exception handling
2814 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
2818 If you call a function interactively, @value{GDBN} normally returns
2819 control to you when the function has finished executing. If the call
2820 raises an exception, however, the call may bypass the mechanism that
2821 returns control to you and cause your program either to abort or to
2822 simply continue running until it hits a breakpoint, catches a signal
2823 that @value{GDBN} is listening for, or exits. This is the case even if
2824 you set a catchpoint for the exception; catchpoints on exceptions are
2825 disabled within interactive calls.
2828 You cannot raise an exception interactively.
2831 You cannot install an exception handler interactively.
2834 @cindex raise exceptions
2835 Sometimes @code{catch} is not the best way to debug exception handling:
2836 if you need to know exactly where an exception is raised, it is better to
2837 stop @emph{before} the exception handler is called, since that way you
2838 can see the stack before any unwinding takes place. If you set a
2839 breakpoint in an exception handler instead, it may not be easy to find
2840 out where the exception was raised.
2842 To stop just before an exception handler is called, you need some
2843 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
2844 raised by calling a library function named @code{__raise_exception}
2845 which has the following ANSI C interface:
2848 /* @var{addr} is where the exception identifier is stored.
2849 @var{id} is the exception identifier. */
2850 void __raise_exception (void **addr, void *id);
2854 To make the debugger catch all exceptions before any stack
2855 unwinding takes place, set a breakpoint on @code{__raise_exception}
2856 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
2858 With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
2859 that depends on the value of @var{id}, you can stop your program when
2860 a specific exception is raised. You can use multiple conditional
2861 breakpoints to stop your program when any of a number of exceptions are
2866 @subsection Deleting breakpoints
2868 @cindex clearing breakpoints, watchpoints, catchpoints
2869 @cindex deleting breakpoints, watchpoints, catchpoints
2870 It is often necessary to eliminate a breakpoint, watchpoint, or
2871 catchpoint once it has done its job and you no longer want your program
2872 to stop there. This is called @dfn{deleting} the breakpoint. A
2873 breakpoint that has been deleted no longer exists; it is forgotten.
2875 With the @code{clear} command you can delete breakpoints according to
2876 where they are in your program. With the @code{delete} command you can
2877 delete individual breakpoints, watchpoints, or catchpoints by specifying
2878 their breakpoint numbers.
2880 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
2881 automatically ignores breakpoints on the first instruction to be executed
2882 when you continue execution without changing the execution address.
2887 Delete any breakpoints at the next instruction to be executed in the
2888 selected stack frame (@pxref{Selection, ,Selecting a frame}). When
2889 the innermost frame is selected, this is a good way to delete a
2890 breakpoint where your program just stopped.
2892 @item clear @var{function}
2893 @itemx clear @var{filename}:@var{function}
2894 Delete any breakpoints set at entry to the function @var{function}.
2896 @item clear @var{linenum}
2897 @itemx clear @var{filename}:@var{linenum}
2898 Delete any breakpoints set at or within the code of the specified line.
2900 @cindex delete breakpoints
2902 @kindex d @r{(@code{delete})}
2903 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
2904 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
2905 ranges specified as arguments. If no argument is specified, delete all
2906 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
2907 confirm off}). You can abbreviate this command as @code{d}.
2911 @subsection Disabling breakpoints
2913 @kindex disable breakpoints
2914 @kindex enable breakpoints
2915 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
2916 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
2917 it had been deleted, but remembers the information on the breakpoint so
2918 that you can @dfn{enable} it again later.
2920 You disable and enable breakpoints, watchpoints, and catchpoints with
2921 the @code{enable} and @code{disable} commands, optionally specifying one
2922 or more breakpoint numbers as arguments. Use @code{info break} or
2923 @code{info watch} to print a list of breakpoints, watchpoints, and
2924 catchpoints if you do not know which numbers to use.
2926 A breakpoint, watchpoint, or catchpoint can have any of four different
2927 states of enablement:
2931 Enabled. The breakpoint stops your program. A breakpoint set
2932 with the @code{break} command starts out in this state.
2934 Disabled. The breakpoint has no effect on your program.
2936 Enabled once. The breakpoint stops your program, but then becomes
2939 Enabled for deletion. The breakpoint stops your program, but
2940 immediately after it does so it is deleted permanently. A breakpoint
2941 set with the @code{tbreak} command starts out in this state.
2944 You can use the following commands to enable or disable breakpoints,
2945 watchpoints, and catchpoints:
2948 @kindex disable breakpoints
2950 @kindex dis @r{(@code{disable})}
2951 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
2952 Disable the specified breakpoints---or all breakpoints, if none are
2953 listed. A disabled breakpoint has no effect but is not forgotten. All
2954 options such as ignore-counts, conditions and commands are remembered in
2955 case the breakpoint is enabled again later. You may abbreviate
2956 @code{disable} as @code{dis}.
2958 @kindex enable breakpoints
2960 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
2961 Enable the specified breakpoints (or all defined breakpoints). They
2962 become effective once again in stopping your program.
2964 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
2965 Enable the specified breakpoints temporarily. @value{GDBN} disables any
2966 of these breakpoints immediately after stopping your program.
2968 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
2969 Enable the specified breakpoints to work once, then die. @value{GDBN}
2970 deletes any of these breakpoints as soon as your program stops there.
2973 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
2974 @c confusing: tbreak is also initially enabled.
2975 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
2976 ,Setting breakpoints}), breakpoints that you set are initially enabled;
2977 subsequently, they become disabled or enabled only when you use one of
2978 the commands above. (The command @code{until} can set and delete a
2979 breakpoint of its own, but it does not change the state of your other
2980 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
2984 @subsection Break conditions
2985 @cindex conditional breakpoints
2986 @cindex breakpoint conditions
2988 @c FIXME what is scope of break condition expr? Context where wanted?
2989 @c in particular for a watchpoint?
2990 The simplest sort of breakpoint breaks every time your program reaches a
2991 specified place. You can also specify a @dfn{condition} for a
2992 breakpoint. A condition is just a Boolean expression in your
2993 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
2994 a condition evaluates the expression each time your program reaches it,
2995 and your program stops only if the condition is @emph{true}.
2997 This is the converse of using assertions for program validation; in that
2998 situation, you want to stop when the assertion is violated---that is,
2999 when the condition is false. In C, if you want to test an assertion expressed
3000 by the condition @var{assert}, you should set the condition
3001 @samp{! @var{assert}} on the appropriate breakpoint.
3003 Conditions are also accepted for watchpoints; you may not need them,
3004 since a watchpoint is inspecting the value of an expression anyhow---but
3005 it might be simpler, say, to just set a watchpoint on a variable name,
3006 and specify a condition that tests whether the new value is an interesting
3009 Break conditions can have side effects, and may even call functions in
3010 your program. This can be useful, for example, to activate functions
3011 that log program progress, or to use your own print functions to
3012 format special data structures. The effects are completely predictable
3013 unless there is another enabled breakpoint at the same address. (In
3014 that case, @value{GDBN} might see the other breakpoint first and stop your
3015 program without checking the condition of this one.) Note that
3016 breakpoint commands are usually more convenient and flexible than break
3018 purpose of performing side effects when a breakpoint is reached
3019 (@pxref{Break Commands, ,Breakpoint command lists}).
3021 Break conditions can be specified when a breakpoint is set, by using
3022 @samp{if} in the arguments to the @code{break} command. @xref{Set
3023 Breaks, ,Setting breakpoints}. They can also be changed at any time
3024 with the @code{condition} command.
3026 You can also use the @code{if} keyword with the @code{watch} command.
3027 The @code{catch} command does not recognize the @code{if} keyword;
3028 @code{condition} is the only way to impose a further condition on a
3033 @item condition @var{bnum} @var{expression}
3034 Specify @var{expression} as the break condition for breakpoint,
3035 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3036 breakpoint @var{bnum} stops your program only if the value of
3037 @var{expression} is true (nonzero, in C). When you use
3038 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3039 syntactic correctness, and to determine whether symbols in it have
3040 referents in the context of your breakpoint. If @var{expression} uses
3041 symbols not referenced in the context of the breakpoint, @value{GDBN}
3042 prints an error message:
3045 No symbol "foo" in current context.
3050 not actually evaluate @var{expression} at the time the @code{condition}
3051 command (or a command that sets a breakpoint with a condition, like
3052 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3054 @item condition @var{bnum}
3055 Remove the condition from breakpoint number @var{bnum}. It becomes
3056 an ordinary unconditional breakpoint.
3059 @cindex ignore count (of breakpoint)
3060 A special case of a breakpoint condition is to stop only when the
3061 breakpoint has been reached a certain number of times. This is so
3062 useful that there is a special way to do it, using the @dfn{ignore
3063 count} of the breakpoint. Every breakpoint has an ignore count, which
3064 is an integer. Most of the time, the ignore count is zero, and
3065 therefore has no effect. But if your program reaches a breakpoint whose
3066 ignore count is positive, then instead of stopping, it just decrements
3067 the ignore count by one and continues. As a result, if the ignore count
3068 value is @var{n}, the breakpoint does not stop the next @var{n} times
3069 your program reaches it.
3073 @item ignore @var{bnum} @var{count}
3074 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3075 The next @var{count} times the breakpoint is reached, your program's
3076 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3079 To make the breakpoint stop the next time it is reached, specify
3082 When you use @code{continue} to resume execution of your program from a
3083 breakpoint, you can specify an ignore count directly as an argument to
3084 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3085 Stepping,,Continuing and stepping}.
3087 If a breakpoint has a positive ignore count and a condition, the
3088 condition is not checked. Once the ignore count reaches zero,
3089 @value{GDBN} resumes checking the condition.
3091 You could achieve the effect of the ignore count with a condition such
3092 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3093 is decremented each time. @xref{Convenience Vars, ,Convenience
3097 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3100 @node Break Commands
3101 @subsection Breakpoint command lists
3103 @cindex breakpoint commands
3104 You can give any breakpoint (or watchpoint or catchpoint) a series of
3105 commands to execute when your program stops due to that breakpoint. For
3106 example, you might want to print the values of certain expressions, or
3107 enable other breakpoints.
3112 @item commands @r{[}@var{bnum}@r{]}
3113 @itemx @dots{} @var{command-list} @dots{}
3115 Specify a list of commands for breakpoint number @var{bnum}. The commands
3116 themselves appear on the following lines. Type a line containing just
3117 @code{end} to terminate the commands.
3119 To remove all commands from a breakpoint, type @code{commands} and
3120 follow it immediately with @code{end}; that is, give no commands.
3122 With no @var{bnum} argument, @code{commands} refers to the last
3123 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3124 recently encountered).
3127 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3128 disabled within a @var{command-list}.
3130 You can use breakpoint commands to start your program up again. Simply
3131 use the @code{continue} command, or @code{step}, or any other command
3132 that resumes execution.
3134 Any other commands in the command list, after a command that resumes
3135 execution, are ignored. This is because any time you resume execution
3136 (even with a simple @code{next} or @code{step}), you may encounter
3137 another breakpoint---which could have its own command list, leading to
3138 ambiguities about which list to execute.
3141 If the first command you specify in a command list is @code{silent}, the
3142 usual message about stopping at a breakpoint is not printed. This may
3143 be desirable for breakpoints that are to print a specific message and
3144 then continue. If none of the remaining commands print anything, you
3145 see no sign that the breakpoint was reached. @code{silent} is
3146 meaningful only at the beginning of a breakpoint command list.
3148 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3149 print precisely controlled output, and are often useful in silent
3150 breakpoints. @xref{Output, ,Commands for controlled output}.
3152 For example, here is how you could use breakpoint commands to print the
3153 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3159 printf "x is %d\n",x
3164 One application for breakpoint commands is to compensate for one bug so
3165 you can test for another. Put a breakpoint just after the erroneous line
3166 of code, give it a condition to detect the case in which something
3167 erroneous has been done, and give it commands to assign correct values
3168 to any variables that need them. End with the @code{continue} command
3169 so that your program does not stop, and start with the @code{silent}
3170 command so that no output is produced. Here is an example:
3181 @node Breakpoint Menus
3182 @subsection Breakpoint menus
3184 @cindex symbol overloading
3186 Some programming languages (notably C@t{++} and Objective-C) permit a
3187 single function name
3188 to be defined several times, for application in different contexts.
3189 This is called @dfn{overloading}. When a function name is overloaded,
3190 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3191 a breakpoint. If you realize this is a problem, you can use
3192 something like @samp{break @var{function}(@var{types})} to specify which
3193 particular version of the function you want. Otherwise, @value{GDBN} offers
3194 you a menu of numbered choices for different possible breakpoints, and
3195 waits for your selection with the prompt @samp{>}. The first two
3196 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3197 sets a breakpoint at each definition of @var{function}, and typing
3198 @kbd{0} aborts the @code{break} command without setting any new
3201 For example, the following session excerpt shows an attempt to set a
3202 breakpoint at the overloaded symbol @code{String::after}.
3203 We choose three particular definitions of that function name:
3205 @c FIXME! This is likely to change to show arg type lists, at least
3208 (@value{GDBP}) b String::after
3211 [2] file:String.cc; line number:867
3212 [3] file:String.cc; line number:860
3213 [4] file:String.cc; line number:875
3214 [5] file:String.cc; line number:853
3215 [6] file:String.cc; line number:846
3216 [7] file:String.cc; line number:735
3218 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3219 Breakpoint 2 at 0xb344: file String.cc, line 875.
3220 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3221 Multiple breakpoints were set.
3222 Use the "delete" command to delete unwanted
3228 @c @ifclear BARETARGET
3229 @node Error in Breakpoints
3230 @subsection ``Cannot insert breakpoints''
3232 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3234 Under some operating systems, breakpoints cannot be used in a program if
3235 any other process is running that program. In this situation,
3236 attempting to run or continue a program with a breakpoint causes
3237 @value{GDBN} to print an error message:
3240 Cannot insert breakpoints.
3241 The same program may be running in another process.
3244 When this happens, you have three ways to proceed:
3248 Remove or disable the breakpoints, then continue.
3251 Suspend @value{GDBN}, and copy the file containing your program to a new
3252 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3253 that @value{GDBN} should run your program under that name.
3254 Then start your program again.
3257 Relink your program so that the text segment is nonsharable, using the
3258 linker option @samp{-N}. The operating system limitation may not apply
3259 to nonsharable executables.
3263 A similar message can be printed if you request too many active
3264 hardware-assisted breakpoints and watchpoints:
3266 @c FIXME: the precise wording of this message may change; the relevant
3267 @c source change is not committed yet (Sep 3, 1999).
3269 Stopped; cannot insert breakpoints.
3270 You may have requested too many hardware breakpoints and watchpoints.
3274 This message is printed when you attempt to resume the program, since
3275 only then @value{GDBN} knows exactly how many hardware breakpoints and
3276 watchpoints it needs to insert.
3278 When this message is printed, you need to disable or remove some of the
3279 hardware-assisted breakpoints and watchpoints, and then continue.
3282 @node Continuing and Stepping
3283 @section Continuing and stepping
3287 @cindex resuming execution
3288 @dfn{Continuing} means resuming program execution until your program
3289 completes normally. In contrast, @dfn{stepping} means executing just
3290 one more ``step'' of your program, where ``step'' may mean either one
3291 line of source code, or one machine instruction (depending on what
3292 particular command you use). Either when continuing or when stepping,
3293 your program may stop even sooner, due to a breakpoint or a signal. (If
3294 it stops due to a signal, you may want to use @code{handle}, or use
3295 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3299 @kindex c @r{(@code{continue})}
3300 @kindex fg @r{(resume foreground execution)}
3301 @item continue @r{[}@var{ignore-count}@r{]}
3302 @itemx c @r{[}@var{ignore-count}@r{]}
3303 @itemx fg @r{[}@var{ignore-count}@r{]}
3304 Resume program execution, at the address where your program last stopped;
3305 any breakpoints set at that address are bypassed. The optional argument
3306 @var{ignore-count} allows you to specify a further number of times to
3307 ignore a breakpoint at this location; its effect is like that of
3308 @code{ignore} (@pxref{Conditions, ,Break conditions}).
3310 The argument @var{ignore-count} is meaningful only when your program
3311 stopped due to a breakpoint. At other times, the argument to
3312 @code{continue} is ignored.
3314 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3315 debugged program is deemed to be the foreground program) are provided
3316 purely for convenience, and have exactly the same behavior as
3320 To resume execution at a different place, you can use @code{return}
3321 (@pxref{Returning, ,Returning from a function}) to go back to the
3322 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3323 different address}) to go to an arbitrary location in your program.
3325 A typical technique for using stepping is to set a breakpoint
3326 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the
3327 beginning of the function or the section of your program where a problem
3328 is believed to lie, run your program until it stops at that breakpoint,
3329 and then step through the suspect area, examining the variables that are
3330 interesting, until you see the problem happen.
3334 @kindex s @r{(@code{step})}
3336 Continue running your program until control reaches a different source
3337 line, then stop it and return control to @value{GDBN}. This command is
3338 abbreviated @code{s}.
3341 @c "without debugging information" is imprecise; actually "without line
3342 @c numbers in the debugging information". (gcc -g1 has debugging info but
3343 @c not line numbers). But it seems complex to try to make that
3344 @c distinction here.
3345 @emph{Warning:} If you use the @code{step} command while control is
3346 within a function that was compiled without debugging information,
3347 execution proceeds until control reaches a function that does have
3348 debugging information. Likewise, it will not step into a function which
3349 is compiled without debugging information. To step through functions
3350 without debugging information, use the @code{stepi} command, described
3354 The @code{step} command only stops at the first instruction of a source
3355 line. This prevents the multiple stops that could otherwise occur in
3356 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3357 to stop if a function that has debugging information is called within
3358 the line. In other words, @code{step} @emph{steps inside} any functions
3359 called within the line.
3361 Also, the @code{step} command only enters a function if there is line
3362 number information for the function. Otherwise it acts like the
3363 @code{next} command. This avoids problems when using @code{cc -gl}
3364 on MIPS machines. Previously, @code{step} entered subroutines if there
3365 was any debugging information about the routine.
3367 @item step @var{count}
3368 Continue running as in @code{step}, but do so @var{count} times. If a
3369 breakpoint is reached, or a signal not related to stepping occurs before
3370 @var{count} steps, stepping stops right away.
3373 @kindex n @r{(@code{next})}
3374 @item next @r{[}@var{count}@r{]}
3375 Continue to the next source line in the current (innermost) stack frame.
3376 This is similar to @code{step}, but function calls that appear within
3377 the line of code are executed without stopping. Execution stops when
3378 control reaches a different line of code at the original stack level
3379 that was executing when you gave the @code{next} command. This command
3380 is abbreviated @code{n}.
3382 An argument @var{count} is a repeat count, as for @code{step}.
3385 @c FIX ME!! Do we delete this, or is there a way it fits in with
3386 @c the following paragraph? --- Vctoria
3388 @c @code{next} within a function that lacks debugging information acts like
3389 @c @code{step}, but any function calls appearing within the code of the
3390 @c function are executed without stopping.
3392 The @code{next} command only stops at the first instruction of a
3393 source line. This prevents multiple stops that could otherwise occur in
3394 @code{switch} statements, @code{for} loops, etc.
3396 @kindex set step-mode
3398 @cindex functions without line info, and stepping
3399 @cindex stepping into functions with no line info
3400 @itemx set step-mode on
3401 The @code{set step-mode on} command causes the @code{step} command to
3402 stop at the first instruction of a function which contains no debug line
3403 information rather than stepping over it.
3405 This is useful in cases where you may be interested in inspecting the
3406 machine instructions of a function which has no symbolic info and do not
3407 want @value{GDBN} to automatically skip over this function.
3409 @item set step-mode off
3410 Causes the @code{step} command to step over any functions which contains no
3411 debug information. This is the default.
3415 Continue running until just after function in the selected stack frame
3416 returns. Print the returned value (if any).
3418 Contrast this with the @code{return} command (@pxref{Returning,
3419 ,Returning from a function}).
3422 @kindex u @r{(@code{until})}
3425 Continue running until a source line past the current line, in the
3426 current stack frame, is reached. This command is used to avoid single
3427 stepping through a loop more than once. It is like the @code{next}
3428 command, except that when @code{until} encounters a jump, it
3429 automatically continues execution until the program counter is greater
3430 than the address of the jump.
3432 This means that when you reach the end of a loop after single stepping
3433 though it, @code{until} makes your program continue execution until it
3434 exits the loop. In contrast, a @code{next} command at the end of a loop
3435 simply steps back to the beginning of the loop, which forces you to step
3436 through the next iteration.
3438 @code{until} always stops your program if it attempts to exit the current
3441 @code{until} may produce somewhat counterintuitive results if the order
3442 of machine code does not match the order of the source lines. For
3443 example, in the following excerpt from a debugging session, the @code{f}
3444 (@code{frame}) command shows that execution is stopped at line
3445 @code{206}; yet when we use @code{until}, we get to line @code{195}:
3449 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
3451 (@value{GDBP}) until
3452 195 for ( ; argc > 0; NEXTARG) @{
3455 This happened because, for execution efficiency, the compiler had
3456 generated code for the loop closure test at the end, rather than the
3457 start, of the loop---even though the test in a C @code{for}-loop is
3458 written before the body of the loop. The @code{until} command appeared
3459 to step back to the beginning of the loop when it advanced to this
3460 expression; however, it has not really gone to an earlier
3461 statement---not in terms of the actual machine code.
3463 @code{until} with no argument works by means of single
3464 instruction stepping, and hence is slower than @code{until} with an
3467 @item until @var{location}
3468 @itemx u @var{location}
3469 Continue running your program until either the specified location is
3470 reached, or the current stack frame returns. @var{location} is any of
3471 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
3472 ,Setting breakpoints}). This form of the command uses breakpoints, and
3473 hence is quicker than @code{until} without an argument. The specified
3474 location is actually reached only if it is in the current frame. This
3475 implies that @code{until} can be used to skip over recursive function
3476 invocations. For instance in the code below, if the current location is
3477 line @code{96}, issuing @code{until 99} will execute the program up to
3478 line @code{99} in the same invocation of factorial, i.e. after the inner
3479 invocations have returned.
3482 94 int factorial (int value)
3484 96 if (value > 1) @{
3485 97 value *= factorial (value - 1);
3492 @kindex advance @var{location}
3493 @itemx advance @var{location}
3494 Continue running the program up to the given location. An argument is
3495 required, anything of the same form as arguments for the @code{break}
3496 command. Execution will also stop upon exit from the current stack
3497 frame. This command is similar to @code{until}, but @code{advance} will
3498 not skip over recursive function calls, and the target location doesn't
3499 have to be in the same frame as the current one.
3503 @kindex si @r{(@code{stepi})}
3505 @itemx stepi @var{arg}
3507 Execute one machine instruction, then stop and return to the debugger.
3509 It is often useful to do @samp{display/i $pc} when stepping by machine
3510 instructions. This makes @value{GDBN} automatically display the next
3511 instruction to be executed, each time your program stops. @xref{Auto
3512 Display,, Automatic display}.
3514 An argument is a repeat count, as in @code{step}.
3518 @kindex ni @r{(@code{nexti})}
3520 @itemx nexti @var{arg}
3522 Execute one machine instruction, but if it is a function call,
3523 proceed until the function returns.
3525 An argument is a repeat count, as in @code{next}.
3532 A signal is an asynchronous event that can happen in a program. The
3533 operating system defines the possible kinds of signals, and gives each
3534 kind a name and a number. For example, in Unix @code{SIGINT} is the
3535 signal a program gets when you type an interrupt character (often @kbd{C-c});
3536 @code{SIGSEGV} is the signal a program gets from referencing a place in
3537 memory far away from all the areas in use; @code{SIGALRM} occurs when
3538 the alarm clock timer goes off (which happens only if your program has
3539 requested an alarm).
3541 @cindex fatal signals
3542 Some signals, including @code{SIGALRM}, are a normal part of the
3543 functioning of your program. Others, such as @code{SIGSEGV}, indicate
3544 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
3545 program has not specified in advance some other way to handle the signal.
3546 @code{SIGINT} does not indicate an error in your program, but it is normally
3547 fatal so it can carry out the purpose of the interrupt: to kill the program.
3549 @value{GDBN} has the ability to detect any occurrence of a signal in your
3550 program. You can tell @value{GDBN} in advance what to do for each kind of
3553 @cindex handling signals
3554 Normally, @value{GDBN} is set up to let the non-erroneous signals like
3555 @code{SIGALRM} be silently passed to your program
3556 (so as not to interfere with their role in the program's functioning)
3557 but to stop your program immediately whenever an error signal happens.
3558 You can change these settings with the @code{handle} command.
3561 @kindex info signals
3564 Print a table of all the kinds of signals and how @value{GDBN} has been told to
3565 handle each one. You can use this to see the signal numbers of all
3566 the defined types of signals.
3568 @code{info handle} is an alias for @code{info signals}.
3571 @item handle @var{signal} @var{keywords}@dots{}
3572 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
3573 can be the number of a signal or its name (with or without the
3574 @samp{SIG} at the beginning); a list of signal numbers of the form
3575 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
3576 known signals. The @var{keywords} say what change to make.
3580 The keywords allowed by the @code{handle} command can be abbreviated.
3581 Their full names are:
3585 @value{GDBN} should not stop your program when this signal happens. It may
3586 still print a message telling you that the signal has come in.
3589 @value{GDBN} should stop your program when this signal happens. This implies
3590 the @code{print} keyword as well.
3593 @value{GDBN} should print a message when this signal happens.
3596 @value{GDBN} should not mention the occurrence of the signal at all. This
3597 implies the @code{nostop} keyword as well.
3601 @value{GDBN} should allow your program to see this signal; your program
3602 can handle the signal, or else it may terminate if the signal is fatal
3603 and not handled. @code{pass} and @code{noignore} are synonyms.
3607 @value{GDBN} should not allow your program to see this signal.
3608 @code{nopass} and @code{ignore} are synonyms.
3612 When a signal stops your program, the signal is not visible to the
3614 continue. Your program sees the signal then, if @code{pass} is in
3615 effect for the signal in question @emph{at that time}. In other words,
3616 after @value{GDBN} reports a signal, you can use the @code{handle}
3617 command with @code{pass} or @code{nopass} to control whether your
3618 program sees that signal when you continue.
3620 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
3621 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
3622 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
3625 You can also use the @code{signal} command to prevent your program from
3626 seeing a signal, or cause it to see a signal it normally would not see,
3627 or to give it any signal at any time. For example, if your program stopped
3628 due to some sort of memory reference error, you might store correct
3629 values into the erroneous variables and continue, hoping to see more
3630 execution; but your program would probably terminate immediately as
3631 a result of the fatal signal once it saw the signal. To prevent this,
3632 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
3636 @section Stopping and starting multi-thread programs
3638 When your program has multiple threads (@pxref{Threads,, Debugging
3639 programs with multiple threads}), you can choose whether to set
3640 breakpoints on all threads, or on a particular thread.
3643 @cindex breakpoints and threads
3644 @cindex thread breakpoints
3645 @kindex break @dots{} thread @var{threadno}
3646 @item break @var{linespec} thread @var{threadno}
3647 @itemx break @var{linespec} thread @var{threadno} if @dots{}
3648 @var{linespec} specifies source lines; there are several ways of
3649 writing them, but the effect is always to specify some source line.
3651 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
3652 to specify that you only want @value{GDBN} to stop the program when a
3653 particular thread reaches this breakpoint. @var{threadno} is one of the
3654 numeric thread identifiers assigned by @value{GDBN}, shown in the first
3655 column of the @samp{info threads} display.
3657 If you do not specify @samp{thread @var{threadno}} when you set a
3658 breakpoint, the breakpoint applies to @emph{all} threads of your
3661 You can use the @code{thread} qualifier on conditional breakpoints as
3662 well; in this case, place @samp{thread @var{threadno}} before the
3663 breakpoint condition, like this:
3666 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
3671 @cindex stopped threads
3672 @cindex threads, stopped
3673 Whenever your program stops under @value{GDBN} for any reason,
3674 @emph{all} threads of execution stop, not just the current thread. This
3675 allows you to examine the overall state of the program, including
3676 switching between threads, without worrying that things may change
3679 @cindex continuing threads
3680 @cindex threads, continuing
3681 Conversely, whenever you restart the program, @emph{all} threads start
3682 executing. @emph{This is true even when single-stepping} with commands
3683 like @code{step} or @code{next}.
3685 In particular, @value{GDBN} cannot single-step all threads in lockstep.
3686 Since thread scheduling is up to your debugging target's operating
3687 system (not controlled by @value{GDBN}), other threads may
3688 execute more than one statement while the current thread completes a
3689 single step. Moreover, in general other threads stop in the middle of a
3690 statement, rather than at a clean statement boundary, when the program
3693 You might even find your program stopped in another thread after
3694 continuing or even single-stepping. This happens whenever some other
3695 thread runs into a breakpoint, a signal, or an exception before the
3696 first thread completes whatever you requested.
3698 On some OSes, you can lock the OS scheduler and thus allow only a single
3702 @item set scheduler-locking @var{mode}
3703 Set the scheduler locking mode. If it is @code{off}, then there is no
3704 locking and any thread may run at any time. If @code{on}, then only the
3705 current thread may run when the inferior is resumed. The @code{step}
3706 mode optimizes for single-stepping. It stops other threads from
3707 ``seizing the prompt'' by preempting the current thread while you are
3708 stepping. Other threads will only rarely (or never) get a chance to run
3709 when you step. They are more likely to run when you @samp{next} over a
3710 function call, and they are completely free to run when you use commands
3711 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
3712 thread hits a breakpoint during its timeslice, they will never steal the
3713 @value{GDBN} prompt away from the thread that you are debugging.
3715 @item show scheduler-locking
3716 Display the current scheduler locking mode.
3721 @chapter Examining the Stack
3723 When your program has stopped, the first thing you need to know is where it
3724 stopped and how it got there.
3727 Each time your program performs a function call, information about the call
3729 That information includes the location of the call in your program,
3730 the arguments of the call,
3731 and the local variables of the function being called.
3732 The information is saved in a block of data called a @dfn{stack frame}.
3733 The stack frames are allocated in a region of memory called the @dfn{call
3736 When your program stops, the @value{GDBN} commands for examining the
3737 stack allow you to see all of this information.
3739 @cindex selected frame
3740 One of the stack frames is @dfn{selected} by @value{GDBN} and many
3741 @value{GDBN} commands refer implicitly to the selected frame. In
3742 particular, whenever you ask @value{GDBN} for the value of a variable in
3743 your program, the value is found in the selected frame. There are
3744 special @value{GDBN} commands to select whichever frame you are
3745 interested in. @xref{Selection, ,Selecting a frame}.
3747 When your program stops, @value{GDBN} automatically selects the
3748 currently executing frame and describes it briefly, similar to the
3749 @code{frame} command (@pxref{Frame Info, ,Information about a frame}).
3752 * Frames:: Stack frames
3753 * Backtrace:: Backtraces
3754 * Selection:: Selecting a frame
3755 * Frame Info:: Information on a frame
3760 @section Stack frames
3762 @cindex frame, definition
3764 The call stack is divided up into contiguous pieces called @dfn{stack
3765 frames}, or @dfn{frames} for short; each frame is the data associated
3766 with one call to one function. The frame contains the arguments given
3767 to the function, the function's local variables, and the address at
3768 which the function is executing.
3770 @cindex initial frame
3771 @cindex outermost frame
3772 @cindex innermost frame
3773 When your program is started, the stack has only one frame, that of the
3774 function @code{main}. This is called the @dfn{initial} frame or the
3775 @dfn{outermost} frame. Each time a function is called, a new frame is
3776 made. Each time a function returns, the frame for that function invocation
3777 is eliminated. If a function is recursive, there can be many frames for
3778 the same function. The frame for the function in which execution is
3779 actually occurring is called the @dfn{innermost} frame. This is the most
3780 recently created of all the stack frames that still exist.
3782 @cindex frame pointer
3783 Inside your program, stack frames are identified by their addresses. A
3784 stack frame consists of many bytes, each of which has its own address; each
3785 kind of computer has a convention for choosing one byte whose
3786 address serves as the address of the frame. Usually this address is kept
3787 in a register called the @dfn{frame pointer register} while execution is
3788 going on in that frame.
3790 @cindex frame number
3791 @value{GDBN} assigns numbers to all existing stack frames, starting with
3792 zero for the innermost frame, one for the frame that called it,
3793 and so on upward. These numbers do not really exist in your program;
3794 they are assigned by @value{GDBN} to give you a way of designating stack
3795 frames in @value{GDBN} commands.
3797 @c The -fomit-frame-pointer below perennially causes hbox overflow
3798 @c underflow problems.
3799 @cindex frameless execution
3800 Some compilers provide a way to compile functions so that they operate
3801 without stack frames. (For example, the @value{GCC} option
3803 @samp{-fomit-frame-pointer}
3805 generates functions without a frame.)
3806 This is occasionally done with heavily used library functions to save
3807 the frame setup time. @value{GDBN} has limited facilities for dealing
3808 with these function invocations. If the innermost function invocation
3809 has no stack frame, @value{GDBN} nevertheless regards it as though
3810 it had a separate frame, which is numbered zero as usual, allowing
3811 correct tracing of the function call chain. However, @value{GDBN} has
3812 no provision for frameless functions elsewhere in the stack.
3815 @kindex frame@r{, command}
3816 @cindex current stack frame
3817 @item frame @var{args}
3818 The @code{frame} command allows you to move from one stack frame to another,
3819 and to print the stack frame you select. @var{args} may be either the
3820 address of the frame or the stack frame number. Without an argument,
3821 @code{frame} prints the current stack frame.
3823 @kindex select-frame
3824 @cindex selecting frame silently
3826 The @code{select-frame} command allows you to move from one stack frame
3827 to another without printing the frame. This is the silent version of
3836 @cindex stack traces
3837 A backtrace is a summary of how your program got where it is. It shows one
3838 line per frame, for many frames, starting with the currently executing
3839 frame (frame zero), followed by its caller (frame one), and on up the
3844 @kindex bt @r{(@code{backtrace})}
3847 Print a backtrace of the entire stack: one line per frame for all
3848 frames in the stack.
3850 You can stop the backtrace at any time by typing the system interrupt
3851 character, normally @kbd{C-c}.
3853 @item backtrace @var{n}
3855 Similar, but print only the innermost @var{n} frames.
3857 @item backtrace -@var{n}
3859 Similar, but print only the outermost @var{n} frames.
3864 @kindex info s @r{(@code{info stack})}
3865 The names @code{where} and @code{info stack} (abbreviated @code{info s})
3866 are additional aliases for @code{backtrace}.
3868 Each line in the backtrace shows the frame number and the function name.
3869 The program counter value is also shown---unless you use @code{set
3870 print address off}. The backtrace also shows the source file name and
3871 line number, as well as the arguments to the function. The program
3872 counter value is omitted if it is at the beginning of the code for that
3875 Here is an example of a backtrace. It was made with the command
3876 @samp{bt 3}, so it shows the innermost three frames.
3880 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
3882 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
3883 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
3885 (More stack frames follow...)
3890 The display for frame zero does not begin with a program counter
3891 value, indicating that your program has stopped at the beginning of the
3892 code for line @code{993} of @code{builtin.c}.
3894 @kindex set backtrace-below-main
3895 @kindex show backtrace-below-main
3897 Most programs have a standard entry point---a place where system libraries
3898 and startup code transition into user code. For C this is @code{main}.
3899 When @value{GDBN} finds the entry function in a backtrace it will terminate
3900 the backtrace, to avoid tracing into highly system-specific (and generally
3901 uninteresting) code. If you need to examine the startup code, then you can
3902 change this behavior.
3905 @item set backtrace-below-main off
3906 Backtraces will stop when they encounter the user entry point. This is the
3909 @item set backtrace-below-main
3910 @itemx set backtrace-below-main on
3911 Backtraces will continue past the user entry point to the top of the stack.
3913 @item show backtrace-below-main
3914 Display the current backtrace policy.
3918 @section Selecting a frame
3920 Most commands for examining the stack and other data in your program work on
3921 whichever stack frame is selected at the moment. Here are the commands for
3922 selecting a stack frame; all of them finish by printing a brief description
3923 of the stack frame just selected.
3926 @kindex frame@r{, selecting}
3927 @kindex f @r{(@code{frame})}
3930 Select frame number @var{n}. Recall that frame zero is the innermost
3931 (currently executing) frame, frame one is the frame that called the
3932 innermost one, and so on. The highest-numbered frame is the one for
3935 @item frame @var{addr}
3937 Select the frame at address @var{addr}. This is useful mainly if the
3938 chaining of stack frames has been damaged by a bug, making it
3939 impossible for @value{GDBN} to assign numbers properly to all frames. In
3940 addition, this can be useful when your program has multiple stacks and
3941 switches between them.
3943 On the SPARC architecture, @code{frame} needs two addresses to
3944 select an arbitrary frame: a frame pointer and a stack pointer.
3946 On the MIPS and Alpha architecture, it needs two addresses: a stack
3947 pointer and a program counter.
3949 On the 29k architecture, it needs three addresses: a register stack
3950 pointer, a program counter, and a memory stack pointer.
3951 @c note to future updaters: this is conditioned on a flag
3952 @c SETUP_ARBITRARY_FRAME in the tm-*.h files. The above is up to date
3953 @c as of 27 Jan 1994.
3957 Move @var{n} frames up the stack. For positive numbers @var{n}, this
3958 advances toward the outermost frame, to higher frame numbers, to frames
3959 that have existed longer. @var{n} defaults to one.
3962 @kindex do @r{(@code{down})}
3964 Move @var{n} frames down the stack. For positive numbers @var{n}, this
3965 advances toward the innermost frame, to lower frame numbers, to frames
3966 that were created more recently. @var{n} defaults to one. You may
3967 abbreviate @code{down} as @code{do}.
3970 All of these commands end by printing two lines of output describing the
3971 frame. The first line shows the frame number, the function name, the
3972 arguments, and the source file and line number of execution in that
3973 frame. The second line shows the text of that source line.
3981 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
3983 10 read_input_file (argv[i]);
3987 After such a printout, the @code{list} command with no arguments
3988 prints ten lines centered on the point of execution in the frame.
3989 You can also edit the program at the point of execution with your favorite
3990 editing program by typing @code{edit}.
3991 @xref{List, ,Printing source lines},
3995 @kindex down-silently
3997 @item up-silently @var{n}
3998 @itemx down-silently @var{n}
3999 These two commands are variants of @code{up} and @code{down},
4000 respectively; they differ in that they do their work silently, without
4001 causing display of the new frame. They are intended primarily for use
4002 in @value{GDBN} command scripts, where the output might be unnecessary and
4007 @section Information about a frame
4009 There are several other commands to print information about the selected
4015 When used without any argument, this command does not change which
4016 frame is selected, but prints a brief description of the currently
4017 selected stack frame. It can be abbreviated @code{f}. With an
4018 argument, this command is used to select a stack frame.
4019 @xref{Selection, ,Selecting a frame}.
4022 @kindex info f @r{(@code{info frame})}
4025 This command prints a verbose description of the selected stack frame,
4030 the address of the frame
4032 the address of the next frame down (called by this frame)
4034 the address of the next frame up (caller of this frame)
4036 the language in which the source code corresponding to this frame is written
4038 the address of the frame's arguments
4040 the address of the frame's local variables
4042 the program counter saved in it (the address of execution in the caller frame)
4044 which registers were saved in the frame
4047 @noindent The verbose description is useful when
4048 something has gone wrong that has made the stack format fail to fit
4049 the usual conventions.
4051 @item info frame @var{addr}
4052 @itemx info f @var{addr}
4053 Print a verbose description of the frame at address @var{addr}, without
4054 selecting that frame. The selected frame remains unchanged by this
4055 command. This requires the same kind of address (more than one for some
4056 architectures) that you specify in the @code{frame} command.
4057 @xref{Selection, ,Selecting a frame}.
4061 Print the arguments of the selected frame, each on a separate line.
4065 Print the local variables of the selected frame, each on a separate
4066 line. These are all variables (declared either static or automatic)
4067 accessible at the point of execution of the selected frame.
4070 @cindex catch exceptions, list active handlers
4071 @cindex exception handlers, how to list
4073 Print a list of all the exception handlers that are active in the
4074 current stack frame at the current point of execution. To see other
4075 exception handlers, visit the associated frame (using the @code{up},
4076 @code{down}, or @code{frame} commands); then type @code{info catch}.
4077 @xref{Set Catchpoints, , Setting catchpoints}.
4083 @chapter Examining Source Files
4085 @value{GDBN} can print parts of your program's source, since the debugging
4086 information recorded in the program tells @value{GDBN} what source files were
4087 used to build it. When your program stops, @value{GDBN} spontaneously prints
4088 the line where it stopped. Likewise, when you select a stack frame
4089 (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
4090 execution in that frame has stopped. You can print other portions of
4091 source files by explicit command.
4093 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4094 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4095 @value{GDBN} under @sc{gnu} Emacs}.
4098 * List:: Printing source lines
4099 * Edit:: Editing source files
4100 * Search:: Searching source files
4101 * Source Path:: Specifying source directories
4102 * Machine Code:: Source and machine code
4106 @section Printing source lines
4109 @kindex l @r{(@code{list})}
4110 To print lines from a source file, use the @code{list} command
4111 (abbreviated @code{l}). By default, ten lines are printed.
4112 There are several ways to specify what part of the file you want to print.
4114 Here are the forms of the @code{list} command most commonly used:
4117 @item list @var{linenum}
4118 Print lines centered around line number @var{linenum} in the
4119 current source file.
4121 @item list @var{function}
4122 Print lines centered around the beginning of function
4126 Print more lines. If the last lines printed were printed with a
4127 @code{list} command, this prints lines following the last lines
4128 printed; however, if the last line printed was a solitary line printed
4129 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4130 Stack}), this prints lines centered around that line.
4133 Print lines just before the lines last printed.
4136 By default, @value{GDBN} prints ten source lines with any of these forms of
4137 the @code{list} command. You can change this using @code{set listsize}:
4140 @kindex set listsize
4141 @item set listsize @var{count}
4142 Make the @code{list} command display @var{count} source lines (unless
4143 the @code{list} argument explicitly specifies some other number).
4145 @kindex show listsize
4147 Display the number of lines that @code{list} prints.
4150 Repeating a @code{list} command with @key{RET} discards the argument,
4151 so it is equivalent to typing just @code{list}. This is more useful
4152 than listing the same lines again. An exception is made for an
4153 argument of @samp{-}; that argument is preserved in repetition so that
4154 each repetition moves up in the source file.
4157 In general, the @code{list} command expects you to supply zero, one or two
4158 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4159 of writing them, but the effect is always to specify some source line.
4160 Here is a complete description of the possible arguments for @code{list}:
4163 @item list @var{linespec}
4164 Print lines centered around the line specified by @var{linespec}.
4166 @item list @var{first},@var{last}
4167 Print lines from @var{first} to @var{last}. Both arguments are
4170 @item list ,@var{last}
4171 Print lines ending with @var{last}.
4173 @item list @var{first},
4174 Print lines starting with @var{first}.
4177 Print lines just after the lines last printed.
4180 Print lines just before the lines last printed.
4183 As described in the preceding table.
4186 Here are the ways of specifying a single source line---all the
4191 Specifies line @var{number} of the current source file.
4192 When a @code{list} command has two linespecs, this refers to
4193 the same source file as the first linespec.
4196 Specifies the line @var{offset} lines after the last line printed.
4197 When used as the second linespec in a @code{list} command that has
4198 two, this specifies the line @var{offset} lines down from the
4202 Specifies the line @var{offset} lines before the last line printed.
4204 @item @var{filename}:@var{number}
4205 Specifies line @var{number} in the source file @var{filename}.
4207 @item @var{function}
4208 Specifies the line that begins the body of the function @var{function}.
4209 For example: in C, this is the line with the open brace.
4211 @item @var{filename}:@var{function}
4212 Specifies the line of the open-brace that begins the body of the
4213 function @var{function} in the file @var{filename}. You only need the
4214 file name with a function name to avoid ambiguity when there are
4215 identically named functions in different source files.
4217 @item *@var{address}
4218 Specifies the line containing the program address @var{address}.
4219 @var{address} may be any expression.
4223 @section Editing source files
4224 @cindex editing source files
4227 @kindex e @r{(@code{edit})}
4228 To edit the lines in a source file, use the @code{edit} command.
4229 The editing program of your choice
4230 is invoked with the current line set to
4231 the active line in the program.
4232 Alternatively, there are several ways to specify what part of the file you
4233 want to print if you want to see other parts of the program.
4235 Here are the forms of the @code{edit} command most commonly used:
4239 Edit the current source file at the active line number in the program.
4241 @item edit @var{number}
4242 Edit the current source file with @var{number} as the active line number.
4244 @item edit @var{function}
4245 Edit the file containing @var{function} at the beginning of its definition.
4247 @item edit @var{filename}:@var{number}
4248 Specifies line @var{number} in the source file @var{filename}.
4250 @item edit @var{filename}:@var{function}
4251 Specifies the line that begins the body of the
4252 function @var{function} in the file @var{filename}. You only need the
4253 file name with a function name to avoid ambiguity when there are
4254 identically named functions in different source files.
4256 @item edit *@var{address}
4257 Specifies the line containing the program address @var{address}.
4258 @var{address} may be any expression.
4261 @subsection Choosing your editor
4262 You can customize @value{GDBN} to use any editor you want
4264 The only restriction is that your editor (say @code{ex}), recognizes the
4265 following command-line syntax:
4267 ex +@var{number} file
4269 The optional numeric value +@var{number} designates the active line in
4270 the file.}. By default, it is @value{EDITOR}, but you can change this
4271 by setting the environment variable @code{EDITOR} before using
4272 @value{GDBN}. For example, to configure @value{GDBN} to use the
4273 @code{vi} editor, you could use these commands with the @code{sh} shell:
4279 or in the @code{csh} shell,
4281 setenv EDITOR /usr/bin/vi
4286 @section Searching source files
4288 @kindex reverse-search
4290 There are two commands for searching through the current source file for a
4295 @kindex forward-search
4296 @item forward-search @var{regexp}
4297 @itemx search @var{regexp}
4298 The command @samp{forward-search @var{regexp}} checks each line,
4299 starting with the one following the last line listed, for a match for
4300 @var{regexp}. It lists the line that is found. You can use the
4301 synonym @samp{search @var{regexp}} or abbreviate the command name as
4304 @item reverse-search @var{regexp}
4305 The command @samp{reverse-search @var{regexp}} checks each line, starting
4306 with the one before the last line listed and going backward, for a match
4307 for @var{regexp}. It lists the line that is found. You can abbreviate
4308 this command as @code{rev}.
4312 @section Specifying source directories
4315 @cindex directories for source files
4316 Executable programs sometimes do not record the directories of the source
4317 files from which they were compiled, just the names. Even when they do,
4318 the directories could be moved between the compilation and your debugging
4319 session. @value{GDBN} has a list of directories to search for source files;
4320 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
4321 it tries all the directories in the list, in the order they are present
4322 in the list, until it finds a file with the desired name. Note that
4323 the executable search path is @emph{not} used for this purpose. Neither is
4324 the current working directory, unless it happens to be in the source
4327 If @value{GDBN} cannot find a source file in the source path, and the
4328 object program records a directory, @value{GDBN} tries that directory
4329 too. If the source path is empty, and there is no record of the
4330 compilation directory, @value{GDBN} looks in the current directory as a
4333 Whenever you reset or rearrange the source path, @value{GDBN} clears out
4334 any information it has cached about where source files are found and where
4335 each line is in the file.
4339 When you start @value{GDBN}, its source path includes only @samp{cdir}
4340 and @samp{cwd}, in that order.
4341 To add other directories, use the @code{directory} command.
4344 @item directory @var{dirname} @dots{}
4345 @item dir @var{dirname} @dots{}
4346 Add directory @var{dirname} to the front of the source path. Several
4347 directory names may be given to this command, separated by @samp{:}
4348 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
4349 part of absolute file names) or
4350 whitespace. You may specify a directory that is already in the source
4351 path; this moves it forward, so @value{GDBN} searches it sooner.
4355 @vindex $cdir@r{, convenience variable}
4356 @vindex $cwdr@r{, convenience variable}
4357 @cindex compilation directory
4358 @cindex current directory
4359 @cindex working directory
4360 @cindex directory, current
4361 @cindex directory, compilation
4362 You can use the string @samp{$cdir} to refer to the compilation
4363 directory (if one is recorded), and @samp{$cwd} to refer to the current
4364 working directory. @samp{$cwd} is not the same as @samp{.}---the former
4365 tracks the current working directory as it changes during your @value{GDBN}
4366 session, while the latter is immediately expanded to the current
4367 directory at the time you add an entry to the source path.
4370 Reset the source path to empty again. This requires confirmation.
4372 @c RET-repeat for @code{directory} is explicitly disabled, but since
4373 @c repeating it would be a no-op we do not say that. (thanks to RMS)
4375 @item show directories
4376 @kindex show directories
4377 Print the source path: show which directories it contains.
4380 If your source path is cluttered with directories that are no longer of
4381 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
4382 versions of source. You can correct the situation as follows:
4386 Use @code{directory} with no argument to reset the source path to empty.
4389 Use @code{directory} with suitable arguments to reinstall the
4390 directories you want in the source path. You can add all the
4391 directories in one command.
4395 @section Source and machine code
4397 You can use the command @code{info line} to map source lines to program
4398 addresses (and vice versa), and the command @code{disassemble} to display
4399 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
4400 mode, the @code{info line} command causes the arrow to point to the
4401 line specified. Also, @code{info line} prints addresses in symbolic form as
4406 @item info line @var{linespec}
4407 Print the starting and ending addresses of the compiled code for
4408 source line @var{linespec}. You can specify source lines in any of
4409 the ways understood by the @code{list} command (@pxref{List, ,Printing
4413 For example, we can use @code{info line} to discover the location of
4414 the object code for the first line of function
4415 @code{m4_changequote}:
4417 @c FIXME: I think this example should also show the addresses in
4418 @c symbolic form, as they usually would be displayed.
4420 (@value{GDBP}) info line m4_changequote
4421 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
4425 We can also inquire (using @code{*@var{addr}} as the form for
4426 @var{linespec}) what source line covers a particular address:
4428 (@value{GDBP}) info line *0x63ff
4429 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
4432 @cindex @code{$_} and @code{info line}
4433 @kindex x@r{(examine), and} info line
4434 After @code{info line}, the default address for the @code{x} command
4435 is changed to the starting address of the line, so that @samp{x/i} is
4436 sufficient to begin examining the machine code (@pxref{Memory,
4437 ,Examining memory}). Also, this address is saved as the value of the
4438 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
4443 @cindex assembly instructions
4444 @cindex instructions, assembly
4445 @cindex machine instructions
4446 @cindex listing machine instructions
4448 This specialized command dumps a range of memory as machine
4449 instructions. The default memory range is the function surrounding the
4450 program counter of the selected frame. A single argument to this
4451 command is a program counter value; @value{GDBN} dumps the function
4452 surrounding this value. Two arguments specify a range of addresses
4453 (first inclusive, second exclusive) to dump.
4456 The following example shows the disassembly of a range of addresses of
4457 HP PA-RISC 2.0 code:
4460 (@value{GDBP}) disas 0x32c4 0x32e4
4461 Dump of assembler code from 0x32c4 to 0x32e4:
4462 0x32c4 <main+204>: addil 0,dp
4463 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
4464 0x32cc <main+212>: ldil 0x3000,r31
4465 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
4466 0x32d4 <main+220>: ldo 0(r31),rp
4467 0x32d8 <main+224>: addil -0x800,dp
4468 0x32dc <main+228>: ldo 0x588(r1),r26
4469 0x32e0 <main+232>: ldil 0x3000,r31
4470 End of assembler dump.
4473 Some architectures have more than one commonly-used set of instruction
4474 mnemonics or other syntax.
4477 @kindex set disassembly-flavor
4478 @cindex assembly instructions
4479 @cindex instructions, assembly
4480 @cindex machine instructions
4481 @cindex listing machine instructions
4482 @cindex Intel disassembly flavor
4483 @cindex AT&T disassembly flavor
4484 @item set disassembly-flavor @var{instruction-set}
4485 Select the instruction set to use when disassembling the
4486 program via the @code{disassemble} or @code{x/i} commands.
4488 Currently this command is only defined for the Intel x86 family. You
4489 can set @var{instruction-set} to either @code{intel} or @code{att}.
4490 The default is @code{att}, the AT&T flavor used by default by Unix
4491 assemblers for x86-based targets.
4496 @chapter Examining Data
4498 @cindex printing data
4499 @cindex examining data
4502 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
4503 @c document because it is nonstandard... Under Epoch it displays in a
4504 @c different window or something like that.
4505 The usual way to examine data in your program is with the @code{print}
4506 command (abbreviated @code{p}), or its synonym @code{inspect}. It
4507 evaluates and prints the value of an expression of the language your
4508 program is written in (@pxref{Languages, ,Using @value{GDBN} with
4509 Different Languages}).
4512 @item print @var{expr}
4513 @itemx print /@var{f} @var{expr}
4514 @var{expr} is an expression (in the source language). By default the
4515 value of @var{expr} is printed in a format appropriate to its data type;
4516 you can choose a different format by specifying @samp{/@var{f}}, where
4517 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
4521 @itemx print /@var{f}
4522 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
4523 @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
4524 conveniently inspect the same value in an alternative format.
4527 A more low-level way of examining data is with the @code{x} command.
4528 It examines data in memory at a specified address and prints it in a
4529 specified format. @xref{Memory, ,Examining memory}.
4531 If you are interested in information about types, or about how the
4532 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
4533 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
4537 * Expressions:: Expressions
4538 * Variables:: Program variables
4539 * Arrays:: Artificial arrays
4540 * Output Formats:: Output formats
4541 * Memory:: Examining memory
4542 * Auto Display:: Automatic display
4543 * Print Settings:: Print settings
4544 * Value History:: Value history
4545 * Convenience Vars:: Convenience variables
4546 * Registers:: Registers
4547 * Floating Point Hardware:: Floating point hardware
4548 * Vector Unit:: Vector Unit
4549 * Memory Region Attributes:: Memory region attributes
4550 * Dump/Restore Files:: Copy between memory and a file
4551 * Character Sets:: Debugging programs that use a different
4552 character set than GDB does
4556 @section Expressions
4559 @code{print} and many other @value{GDBN} commands accept an expression and
4560 compute its value. Any kind of constant, variable or operator defined
4561 by the programming language you are using is valid in an expression in
4562 @value{GDBN}. This includes conditional expressions, function calls,
4563 casts, and string constants. It also includes preprocessor macros, if
4564 you compiled your program to include this information; see
4567 @value{GDBN} supports array constants in expressions input by
4568 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
4569 you can use the command @code{print @{1, 2, 3@}} to build up an array in
4570 memory that is @code{malloc}ed in the target program.
4572 Because C is so widespread, most of the expressions shown in examples in
4573 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
4574 Languages}, for information on how to use expressions in other
4577 In this section, we discuss operators that you can use in @value{GDBN}
4578 expressions regardless of your programming language.
4580 Casts are supported in all languages, not just in C, because it is so
4581 useful to cast a number into a pointer in order to examine a structure
4582 at that address in memory.
4583 @c FIXME: casts supported---Mod2 true?
4585 @value{GDBN} supports these operators, in addition to those common
4586 to programming languages:
4590 @samp{@@} is a binary operator for treating parts of memory as arrays.
4591 @xref{Arrays, ,Artificial arrays}, for more information.
4594 @samp{::} allows you to specify a variable in terms of the file or
4595 function where it is defined. @xref{Variables, ,Program variables}.
4597 @cindex @{@var{type}@}
4598 @cindex type casting memory
4599 @cindex memory, viewing as typed object
4600 @cindex casts, to view memory
4601 @item @{@var{type}@} @var{addr}
4602 Refers to an object of type @var{type} stored at address @var{addr} in
4603 memory. @var{addr} may be any expression whose value is an integer or
4604 pointer (but parentheses are required around binary operators, just as in
4605 a cast). This construct is allowed regardless of what kind of data is
4606 normally supposed to reside at @var{addr}.
4610 @section Program variables
4612 The most common kind of expression to use is the name of a variable
4615 Variables in expressions are understood in the selected stack frame
4616 (@pxref{Selection, ,Selecting a frame}); they must be either:
4620 global (or file-static)
4627 visible according to the scope rules of the
4628 programming language from the point of execution in that frame
4631 @noindent This means that in the function
4646 you can examine and use the variable @code{a} whenever your program is
4647 executing within the function @code{foo}, but you can only use or
4648 examine the variable @code{b} while your program is executing inside
4649 the block where @code{b} is declared.
4651 @cindex variable name conflict
4652 There is an exception: you can refer to a variable or function whose
4653 scope is a single source file even if the current execution point is not
4654 in this file. But it is possible to have more than one such variable or
4655 function with the same name (in different source files). If that
4656 happens, referring to that name has unpredictable effects. If you wish,
4657 you can specify a static variable in a particular function or file,
4658 using the colon-colon notation:
4660 @cindex colon-colon, context for variables/functions
4662 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
4663 @cindex @code{::}, context for variables/functions
4666 @var{file}::@var{variable}
4667 @var{function}::@var{variable}
4671 Here @var{file} or @var{function} is the name of the context for the
4672 static @var{variable}. In the case of file names, you can use quotes to
4673 make sure @value{GDBN} parses the file name as a single word---for example,
4674 to print a global value of @code{x} defined in @file{f2.c}:
4677 (@value{GDBP}) p 'f2.c'::x
4680 @cindex C@t{++} scope resolution
4681 This use of @samp{::} is very rarely in conflict with the very similar
4682 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
4683 scope resolution operator in @value{GDBN} expressions.
4684 @c FIXME: Um, so what happens in one of those rare cases where it's in
4687 @cindex wrong values
4688 @cindex variable values, wrong
4690 @emph{Warning:} Occasionally, a local variable may appear to have the
4691 wrong value at certain points in a function---just after entry to a new
4692 scope, and just before exit.
4694 You may see this problem when you are stepping by machine instructions.
4695 This is because, on most machines, it takes more than one instruction to
4696 set up a stack frame (including local variable definitions); if you are
4697 stepping by machine instructions, variables may appear to have the wrong
4698 values until the stack frame is completely built. On exit, it usually
4699 also takes more than one machine instruction to destroy a stack frame;
4700 after you begin stepping through that group of instructions, local
4701 variable definitions may be gone.
4703 This may also happen when the compiler does significant optimizations.
4704 To be sure of always seeing accurate values, turn off all optimization
4707 @cindex ``No symbol "foo" in current context''
4708 Another possible effect of compiler optimizations is to optimize
4709 unused variables out of existence, or assign variables to registers (as
4710 opposed to memory addresses). Depending on the support for such cases
4711 offered by the debug info format used by the compiler, @value{GDBN}
4712 might not be able to display values for such local variables. If that
4713 happens, @value{GDBN} will print a message like this:
4716 No symbol "foo" in current context.
4719 To solve such problems, either recompile without optimizations, or use a
4720 different debug info format, if the compiler supports several such
4721 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler
4722 usually supports the @option{-gstabs+} option. @option{-gstabs+}
4723 produces debug info in a format that is superior to formats such as
4724 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
4725 an effective form for debug info. @xref{Debugging Options,,Options
4726 for Debugging Your Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}.
4730 @section Artificial arrays
4732 @cindex artificial array
4733 @kindex @@@r{, referencing memory as an array}
4734 It is often useful to print out several successive objects of the
4735 same type in memory; a section of an array, or an array of
4736 dynamically determined size for which only a pointer exists in the
4739 You can do this by referring to a contiguous span of memory as an
4740 @dfn{artificial array}, using the binary operator @samp{@@}. The left
4741 operand of @samp{@@} should be the first element of the desired array
4742 and be an individual object. The right operand should be the desired length
4743 of the array. The result is an array value whose elements are all of
4744 the type of the left argument. The first element is actually the left
4745 argument; the second element comes from bytes of memory immediately
4746 following those that hold the first element, and so on. Here is an
4747 example. If a program says
4750 int *array = (int *) malloc (len * sizeof (int));
4754 you can print the contents of @code{array} with
4760 The left operand of @samp{@@} must reside in memory. Array values made
4761 with @samp{@@} in this way behave just like other arrays in terms of
4762 subscripting, and are coerced to pointers when used in expressions.
4763 Artificial arrays most often appear in expressions via the value history
4764 (@pxref{Value History, ,Value history}), after printing one out.
4766 Another way to create an artificial array is to use a cast.
4767 This re-interprets a value as if it were an array.
4768 The value need not be in memory:
4770 (@value{GDBP}) p/x (short[2])0x12345678
4771 $1 = @{0x1234, 0x5678@}
4774 As a convenience, if you leave the array length out (as in
4775 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
4776 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
4778 (@value{GDBP}) p/x (short[])0x12345678
4779 $2 = @{0x1234, 0x5678@}
4782 Sometimes the artificial array mechanism is not quite enough; in
4783 moderately complex data structures, the elements of interest may not
4784 actually be adjacent---for example, if you are interested in the values
4785 of pointers in an array. One useful work-around in this situation is
4786 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
4787 variables}) as a counter in an expression that prints the first
4788 interesting value, and then repeat that expression via @key{RET}. For
4789 instance, suppose you have an array @code{dtab} of pointers to
4790 structures, and you are interested in the values of a field @code{fv}
4791 in each structure. Here is an example of what you might type:
4801 @node Output Formats
4802 @section Output formats
4804 @cindex formatted output
4805 @cindex output formats
4806 By default, @value{GDBN} prints a value according to its data type. Sometimes
4807 this is not what you want. For example, you might want to print a number
4808 in hex, or a pointer in decimal. Or you might want to view data in memory
4809 at a certain address as a character string or as an instruction. To do
4810 these things, specify an @dfn{output format} when you print a value.
4812 The simplest use of output formats is to say how to print a value
4813 already computed. This is done by starting the arguments of the
4814 @code{print} command with a slash and a format letter. The format
4815 letters supported are:
4819 Regard the bits of the value as an integer, and print the integer in
4823 Print as integer in signed decimal.
4826 Print as integer in unsigned decimal.
4829 Print as integer in octal.
4832 Print as integer in binary. The letter @samp{t} stands for ``two''.
4833 @footnote{@samp{b} cannot be used because these format letters are also
4834 used with the @code{x} command, where @samp{b} stands for ``byte'';
4835 see @ref{Memory,,Examining memory}.}
4838 @cindex unknown address, locating
4839 @cindex locate address
4840 Print as an address, both absolute in hexadecimal and as an offset from
4841 the nearest preceding symbol. You can use this format used to discover
4842 where (in what function) an unknown address is located:
4845 (@value{GDBP}) p/a 0x54320
4846 $3 = 0x54320 <_initialize_vx+396>
4850 The command @code{info symbol 0x54320} yields similar results.
4851 @xref{Symbols, info symbol}.
4854 Regard as an integer and print it as a character constant.
4857 Regard the bits of the value as a floating point number and print
4858 using typical floating point syntax.
4861 For example, to print the program counter in hex (@pxref{Registers}), type
4868 Note that no space is required before the slash; this is because command
4869 names in @value{GDBN} cannot contain a slash.
4871 To reprint the last value in the value history with a different format,
4872 you can use the @code{print} command with just a format and no
4873 expression. For example, @samp{p/x} reprints the last value in hex.
4876 @section Examining memory
4878 You can use the command @code{x} (for ``examine'') to examine memory in
4879 any of several formats, independently of your program's data types.
4881 @cindex examining memory
4883 @kindex x @r{(examine memory)}
4884 @item x/@var{nfu} @var{addr}
4887 Use the @code{x} command to examine memory.
4890 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
4891 much memory to display and how to format it; @var{addr} is an
4892 expression giving the address where you want to start displaying memory.
4893 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
4894 Several commands set convenient defaults for @var{addr}.
4897 @item @var{n}, the repeat count
4898 The repeat count is a decimal integer; the default is 1. It specifies
4899 how much memory (counting by units @var{u}) to display.
4900 @c This really is **decimal**; unaffected by 'set radix' as of GDB
4903 @item @var{f}, the display format
4904 The display format is one of the formats used by @code{print},
4905 @samp{s} (null-terminated string), or @samp{i} (machine instruction).
4906 The default is @samp{x} (hexadecimal) initially.
4907 The default changes each time you use either @code{x} or @code{print}.
4909 @item @var{u}, the unit size
4910 The unit size is any of
4916 Halfwords (two bytes).
4918 Words (four bytes). This is the initial default.
4920 Giant words (eight bytes).
4923 Each time you specify a unit size with @code{x}, that size becomes the
4924 default unit the next time you use @code{x}. (For the @samp{s} and
4925 @samp{i} formats, the unit size is ignored and is normally not written.)
4927 @item @var{addr}, starting display address
4928 @var{addr} is the address where you want @value{GDBN} to begin displaying
4929 memory. The expression need not have a pointer value (though it may);
4930 it is always interpreted as an integer address of a byte of memory.
4931 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
4932 @var{addr} is usually just after the last address examined---but several
4933 other commands also set the default address: @code{info breakpoints} (to
4934 the address of the last breakpoint listed), @code{info line} (to the
4935 starting address of a line), and @code{print} (if you use it to display
4936 a value from memory).
4939 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
4940 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
4941 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
4942 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
4943 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
4945 Since the letters indicating unit sizes are all distinct from the
4946 letters specifying output formats, you do not have to remember whether
4947 unit size or format comes first; either order works. The output
4948 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
4949 (However, the count @var{n} must come first; @samp{wx4} does not work.)
4951 Even though the unit size @var{u} is ignored for the formats @samp{s}
4952 and @samp{i}, you might still want to use a count @var{n}; for example,
4953 @samp{3i} specifies that you want to see three machine instructions,
4954 including any operands. The command @code{disassemble} gives an
4955 alternative way of inspecting machine instructions; see @ref{Machine
4956 Code,,Source and machine code}.
4958 All the defaults for the arguments to @code{x} are designed to make it
4959 easy to continue scanning memory with minimal specifications each time
4960 you use @code{x}. For example, after you have inspected three machine
4961 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
4962 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
4963 the repeat count @var{n} is used again; the other arguments default as
4964 for successive uses of @code{x}.
4966 @cindex @code{$_}, @code{$__}, and value history
4967 The addresses and contents printed by the @code{x} command are not saved
4968 in the value history because there is often too much of them and they
4969 would get in the way. Instead, @value{GDBN} makes these values available for
4970 subsequent use in expressions as values of the convenience variables
4971 @code{$_} and @code{$__}. After an @code{x} command, the last address
4972 examined is available for use in expressions in the convenience variable
4973 @code{$_}. The contents of that address, as examined, are available in
4974 the convenience variable @code{$__}.
4976 If the @code{x} command has a repeat count, the address and contents saved
4977 are from the last memory unit printed; this is not the same as the last
4978 address printed if several units were printed on the last line of output.
4981 @section Automatic display
4982 @cindex automatic display
4983 @cindex display of expressions
4985 If you find that you want to print the value of an expression frequently
4986 (to see how it changes), you might want to add it to the @dfn{automatic
4987 display list} so that @value{GDBN} prints its value each time your program stops.
4988 Each expression added to the list is given a number to identify it;
4989 to remove an expression from the list, you specify that number.
4990 The automatic display looks like this:
4994 3: bar[5] = (struct hack *) 0x3804
4998 This display shows item numbers, expressions and their current values. As with
4999 displays you request manually using @code{x} or @code{print}, you can
5000 specify the output format you prefer; in fact, @code{display} decides
5001 whether to use @code{print} or @code{x} depending on how elaborate your
5002 format specification is---it uses @code{x} if you specify a unit size,
5003 or one of the two formats (@samp{i} and @samp{s}) that are only
5004 supported by @code{x}; otherwise it uses @code{print}.
5008 @item display @var{expr}
5009 Add the expression @var{expr} to the list of expressions to display
5010 each time your program stops. @xref{Expressions, ,Expressions}.
5012 @code{display} does not repeat if you press @key{RET} again after using it.
5014 @item display/@var{fmt} @var{expr}
5015 For @var{fmt} specifying only a display format and not a size or
5016 count, add the expression @var{expr} to the auto-display list but
5017 arrange to display it each time in the specified format @var{fmt}.
5018 @xref{Output Formats,,Output formats}.
5020 @item display/@var{fmt} @var{addr}
5021 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
5022 number of units, add the expression @var{addr} as a memory address to
5023 be examined each time your program stops. Examining means in effect
5024 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
5027 For example, @samp{display/i $pc} can be helpful, to see the machine
5028 instruction about to be executed each time execution stops (@samp{$pc}
5029 is a common name for the program counter; @pxref{Registers, ,Registers}).
5032 @kindex delete display
5034 @item undisplay @var{dnums}@dots{}
5035 @itemx delete display @var{dnums}@dots{}
5036 Remove item numbers @var{dnums} from the list of expressions to display.
5038 @code{undisplay} does not repeat if you press @key{RET} after using it.
5039 (Otherwise you would just get the error @samp{No display number @dots{}}.)
5041 @kindex disable display
5042 @item disable display @var{dnums}@dots{}
5043 Disable the display of item numbers @var{dnums}. A disabled display
5044 item is not printed automatically, but is not forgotten. It may be
5045 enabled again later.
5047 @kindex enable display
5048 @item enable display @var{dnums}@dots{}
5049 Enable display of item numbers @var{dnums}. It becomes effective once
5050 again in auto display of its expression, until you specify otherwise.
5053 Display the current values of the expressions on the list, just as is
5054 done when your program stops.
5056 @kindex info display
5058 Print the list of expressions previously set up to display
5059 automatically, each one with its item number, but without showing the
5060 values. This includes disabled expressions, which are marked as such.
5061 It also includes expressions which would not be displayed right now
5062 because they refer to automatic variables not currently available.
5065 If a display expression refers to local variables, then it does not make
5066 sense outside the lexical context for which it was set up. Such an
5067 expression is disabled when execution enters a context where one of its
5068 variables is not defined. For example, if you give the command
5069 @code{display last_char} while inside a function with an argument
5070 @code{last_char}, @value{GDBN} displays this argument while your program
5071 continues to stop inside that function. When it stops elsewhere---where
5072 there is no variable @code{last_char}---the display is disabled
5073 automatically. The next time your program stops where @code{last_char}
5074 is meaningful, you can enable the display expression once again.
5076 @node Print Settings
5077 @section Print settings
5079 @cindex format options
5080 @cindex print settings
5081 @value{GDBN} provides the following ways to control how arrays, structures,
5082 and symbols are printed.
5085 These settings are useful for debugging programs in any language:
5088 @kindex set print address
5089 @item set print address
5090 @itemx set print address on
5091 @value{GDBN} prints memory addresses showing the location of stack
5092 traces, structure values, pointer values, breakpoints, and so forth,
5093 even when it also displays the contents of those addresses. The default
5094 is @code{on}. For example, this is what a stack frame display looks like with
5095 @code{set print address on}:
5100 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
5102 530 if (lquote != def_lquote)
5106 @item set print address off
5107 Do not print addresses when displaying their contents. For example,
5108 this is the same stack frame displayed with @code{set print address off}:
5112 (@value{GDBP}) set print addr off
5114 #0 set_quotes (lq="<<", rq=">>") at input.c:530
5115 530 if (lquote != def_lquote)
5119 You can use @samp{set print address off} to eliminate all machine
5120 dependent displays from the @value{GDBN} interface. For example, with
5121 @code{print address off}, you should get the same text for backtraces on
5122 all machines---whether or not they involve pointer arguments.
5124 @kindex show print address
5125 @item show print address
5126 Show whether or not addresses are to be printed.
5129 When @value{GDBN} prints a symbolic address, it normally prints the
5130 closest earlier symbol plus an offset. If that symbol does not uniquely
5131 identify the address (for example, it is a name whose scope is a single
5132 source file), you may need to clarify. One way to do this is with
5133 @code{info line}, for example @samp{info line *0x4537}. Alternately,
5134 you can set @value{GDBN} to print the source file and line number when
5135 it prints a symbolic address:
5138 @kindex set print symbol-filename
5139 @item set print symbol-filename on
5140 Tell @value{GDBN} to print the source file name and line number of a
5141 symbol in the symbolic form of an address.
5143 @item set print symbol-filename off
5144 Do not print source file name and line number of a symbol. This is the
5147 @kindex show print symbol-filename
5148 @item show print symbol-filename
5149 Show whether or not @value{GDBN} will print the source file name and
5150 line number of a symbol in the symbolic form of an address.
5153 Another situation where it is helpful to show symbol filenames and line
5154 numbers is when disassembling code; @value{GDBN} shows you the line
5155 number and source file that corresponds to each instruction.
5157 Also, you may wish to see the symbolic form only if the address being
5158 printed is reasonably close to the closest earlier symbol:
5161 @kindex set print max-symbolic-offset
5162 @item set print max-symbolic-offset @var{max-offset}
5163 Tell @value{GDBN} to only display the symbolic form of an address if the
5164 offset between the closest earlier symbol and the address is less than
5165 @var{max-offset}. The default is 0, which tells @value{GDBN}
5166 to always print the symbolic form of an address if any symbol precedes it.
5168 @kindex show print max-symbolic-offset
5169 @item show print max-symbolic-offset
5170 Ask how large the maximum offset is that @value{GDBN} prints in a
5174 @cindex wild pointer, interpreting
5175 @cindex pointer, finding referent
5176 If you have a pointer and you are not sure where it points, try
5177 @samp{set print symbol-filename on}. Then you can determine the name
5178 and source file location of the variable where it points, using
5179 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
5180 For example, here @value{GDBN} shows that a variable @code{ptt} points
5181 at another variable @code{t}, defined in @file{hi2.c}:
5184 (@value{GDBP}) set print symbol-filename on
5185 (@value{GDBP}) p/a ptt
5186 $4 = 0xe008 <t in hi2.c>
5190 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
5191 does not show the symbol name and filename of the referent, even with
5192 the appropriate @code{set print} options turned on.
5195 Other settings control how different kinds of objects are printed:
5198 @kindex set print array
5199 @item set print array
5200 @itemx set print array on
5201 Pretty print arrays. This format is more convenient to read,
5202 but uses more space. The default is off.
5204 @item set print array off
5205 Return to compressed format for arrays.
5207 @kindex show print array
5208 @item show print array
5209 Show whether compressed or pretty format is selected for displaying
5212 @kindex set print elements
5213 @item set print elements @var{number-of-elements}
5214 Set a limit on how many elements of an array @value{GDBN} will print.
5215 If @value{GDBN} is printing a large array, it stops printing after it has
5216 printed the number of elements set by the @code{set print elements} command.
5217 This limit also applies to the display of strings.
5218 When @value{GDBN} starts, this limit is set to 200.
5219 Setting @var{number-of-elements} to zero means that the printing is unlimited.
5221 @kindex show print elements
5222 @item show print elements
5223 Display the number of elements of a large array that @value{GDBN} will print.
5224 If the number is 0, then the printing is unlimited.
5226 @kindex set print null-stop
5227 @item set print null-stop
5228 Cause @value{GDBN} to stop printing the characters of an array when the first
5229 @sc{null} is encountered. This is useful when large arrays actually
5230 contain only short strings.
5233 @kindex set print pretty
5234 @item set print pretty on
5235 Cause @value{GDBN} to print structures in an indented format with one member
5236 per line, like this:
5251 @item set print pretty off
5252 Cause @value{GDBN} to print structures in a compact format, like this:
5256 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
5257 meat = 0x54 "Pork"@}
5262 This is the default format.
5264 @kindex show print pretty
5265 @item show print pretty
5266 Show which format @value{GDBN} is using to print structures.
5268 @kindex set print sevenbit-strings
5269 @item set print sevenbit-strings on
5270 Print using only seven-bit characters; if this option is set,
5271 @value{GDBN} displays any eight-bit characters (in strings or
5272 character values) using the notation @code{\}@var{nnn}. This setting is
5273 best if you are working in English (@sc{ascii}) and you use the
5274 high-order bit of characters as a marker or ``meta'' bit.
5276 @item set print sevenbit-strings off
5277 Print full eight-bit characters. This allows the use of more
5278 international character sets, and is the default.
5280 @kindex show print sevenbit-strings
5281 @item show print sevenbit-strings
5282 Show whether or not @value{GDBN} is printing only seven-bit characters.
5284 @kindex set print union
5285 @item set print union on
5286 Tell @value{GDBN} to print unions which are contained in structures. This
5287 is the default setting.
5289 @item set print union off
5290 Tell @value{GDBN} not to print unions which are contained in structures.
5292 @kindex show print union
5293 @item show print union
5294 Ask @value{GDBN} whether or not it will print unions which are contained in
5297 For example, given the declarations
5300 typedef enum @{Tree, Bug@} Species;
5301 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
5302 typedef enum @{Caterpillar, Cocoon, Butterfly@}
5313 struct thing foo = @{Tree, @{Acorn@}@};
5317 with @code{set print union on} in effect @samp{p foo} would print
5320 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
5324 and with @code{set print union off} in effect it would print
5327 $1 = @{it = Tree, form = @{...@}@}
5333 These settings are of interest when debugging C@t{++} programs:
5337 @kindex set print demangle
5338 @item set print demangle
5339 @itemx set print demangle on
5340 Print C@t{++} names in their source form rather than in the encoded
5341 (``mangled'') form passed to the assembler and linker for type-safe
5342 linkage. The default is on.
5344 @kindex show print demangle
5345 @item show print demangle
5346 Show whether C@t{++} names are printed in mangled or demangled form.
5348 @kindex set print asm-demangle
5349 @item set print asm-demangle
5350 @itemx set print asm-demangle on
5351 Print C@t{++} names in their source form rather than their mangled form, even
5352 in assembler code printouts such as instruction disassemblies.
5355 @kindex show print asm-demangle
5356 @item show print asm-demangle
5357 Show whether C@t{++} names in assembly listings are printed in mangled
5360 @kindex set demangle-style
5361 @cindex C@t{++} symbol decoding style
5362 @cindex symbol decoding style, C@t{++}
5363 @item set demangle-style @var{style}
5364 Choose among several encoding schemes used by different compilers to
5365 represent C@t{++} names. The choices for @var{style} are currently:
5369 Allow @value{GDBN} to choose a decoding style by inspecting your program.
5372 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
5373 This is the default.
5376 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
5379 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
5382 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
5383 @strong{Warning:} this setting alone is not sufficient to allow
5384 debugging @code{cfront}-generated executables. @value{GDBN} would
5385 require further enhancement to permit that.
5388 If you omit @var{style}, you will see a list of possible formats.
5390 @kindex show demangle-style
5391 @item show demangle-style
5392 Display the encoding style currently in use for decoding C@t{++} symbols.
5394 @kindex set print object
5395 @item set print object
5396 @itemx set print object on
5397 When displaying a pointer to an object, identify the @emph{actual}
5398 (derived) type of the object rather than the @emph{declared} type, using
5399 the virtual function table.
5401 @item set print object off
5402 Display only the declared type of objects, without reference to the
5403 virtual function table. This is the default setting.
5405 @kindex show print object
5406 @item show print object
5407 Show whether actual, or declared, object types are displayed.
5409 @kindex set print static-members
5410 @item set print static-members
5411 @itemx set print static-members on
5412 Print static members when displaying a C@t{++} object. The default is on.
5414 @item set print static-members off
5415 Do not print static members when displaying a C@t{++} object.
5417 @kindex show print static-members
5418 @item show print static-members
5419 Show whether C@t{++} static members are printed, or not.
5421 @c These don't work with HP ANSI C++ yet.
5422 @kindex set print vtbl
5423 @item set print vtbl
5424 @itemx set print vtbl on
5425 Pretty print C@t{++} virtual function tables. The default is off.
5426 (The @code{vtbl} commands do not work on programs compiled with the HP
5427 ANSI C@t{++} compiler (@code{aCC}).)
5429 @item set print vtbl off
5430 Do not pretty print C@t{++} virtual function tables.
5432 @kindex show print vtbl
5433 @item show print vtbl
5434 Show whether C@t{++} virtual function tables are pretty printed, or not.
5438 @section Value history
5440 @cindex value history
5441 Values printed by the @code{print} command are saved in the @value{GDBN}
5442 @dfn{value history}. This allows you to refer to them in other expressions.
5443 Values are kept until the symbol table is re-read or discarded
5444 (for example with the @code{file} or @code{symbol-file} commands).
5445 When the symbol table changes, the value history is discarded,
5446 since the values may contain pointers back to the types defined in the
5451 @cindex history number
5452 The values printed are given @dfn{history numbers} by which you can
5453 refer to them. These are successive integers starting with one.
5454 @code{print} shows you the history number assigned to a value by
5455 printing @samp{$@var{num} = } before the value; here @var{num} is the
5458 To refer to any previous value, use @samp{$} followed by the value's
5459 history number. The way @code{print} labels its output is designed to
5460 remind you of this. Just @code{$} refers to the most recent value in
5461 the history, and @code{$$} refers to the value before that.
5462 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
5463 is the value just prior to @code{$$}, @code{$$1} is equivalent to
5464 @code{$$}, and @code{$$0} is equivalent to @code{$}.
5466 For example, suppose you have just printed a pointer to a structure and
5467 want to see the contents of the structure. It suffices to type
5473 If you have a chain of structures where the component @code{next} points
5474 to the next one, you can print the contents of the next one with this:
5481 You can print successive links in the chain by repeating this
5482 command---which you can do by just typing @key{RET}.
5484 Note that the history records values, not expressions. If the value of
5485 @code{x} is 4 and you type these commands:
5493 then the value recorded in the value history by the @code{print} command
5494 remains 4 even though the value of @code{x} has changed.
5499 Print the last ten values in the value history, with their item numbers.
5500 This is like @samp{p@ $$9} repeated ten times, except that @code{show
5501 values} does not change the history.
5503 @item show values @var{n}
5504 Print ten history values centered on history item number @var{n}.
5507 Print ten history values just after the values last printed. If no more
5508 values are available, @code{show values +} produces no display.
5511 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
5512 same effect as @samp{show values +}.
5514 @node Convenience Vars
5515 @section Convenience variables
5517 @cindex convenience variables
5518 @value{GDBN} provides @dfn{convenience variables} that you can use within
5519 @value{GDBN} to hold on to a value and refer to it later. These variables
5520 exist entirely within @value{GDBN}; they are not part of your program, and
5521 setting a convenience variable has no direct effect on further execution
5522 of your program. That is why you can use them freely.
5524 Convenience variables are prefixed with @samp{$}. Any name preceded by
5525 @samp{$} can be used for a convenience variable, unless it is one of
5526 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
5527 (Value history references, in contrast, are @emph{numbers} preceded
5528 by @samp{$}. @xref{Value History, ,Value history}.)
5530 You can save a value in a convenience variable with an assignment
5531 expression, just as you would set a variable in your program.
5535 set $foo = *object_ptr
5539 would save in @code{$foo} the value contained in the object pointed to by
5542 Using a convenience variable for the first time creates it, but its
5543 value is @code{void} until you assign a new value. You can alter the
5544 value with another assignment at any time.
5546 Convenience variables have no fixed types. You can assign a convenience
5547 variable any type of value, including structures and arrays, even if
5548 that variable already has a value of a different type. The convenience
5549 variable, when used as an expression, has the type of its current value.
5552 @kindex show convenience
5553 @item show convenience
5554 Print a list of convenience variables used so far, and their values.
5555 Abbreviated @code{show conv}.
5558 One of the ways to use a convenience variable is as a counter to be
5559 incremented or a pointer to be advanced. For example, to print
5560 a field from successive elements of an array of structures:
5564 print bar[$i++]->contents
5568 Repeat that command by typing @key{RET}.
5570 Some convenience variables are created automatically by @value{GDBN} and given
5571 values likely to be useful.
5574 @vindex $_@r{, convenience variable}
5576 The variable @code{$_} is automatically set by the @code{x} command to
5577 the last address examined (@pxref{Memory, ,Examining memory}). Other
5578 commands which provide a default address for @code{x} to examine also
5579 set @code{$_} to that address; these commands include @code{info line}
5580 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
5581 except when set by the @code{x} command, in which case it is a pointer
5582 to the type of @code{$__}.
5584 @vindex $__@r{, convenience variable}
5586 The variable @code{$__} is automatically set by the @code{x} command
5587 to the value found in the last address examined. Its type is chosen
5588 to match the format in which the data was printed.
5591 @vindex $_exitcode@r{, convenience variable}
5592 The variable @code{$_exitcode} is automatically set to the exit code when
5593 the program being debugged terminates.
5596 On HP-UX systems, if you refer to a function or variable name that
5597 begins with a dollar sign, @value{GDBN} searches for a user or system
5598 name first, before it searches for a convenience variable.
5604 You can refer to machine register contents, in expressions, as variables
5605 with names starting with @samp{$}. The names of registers are different
5606 for each machine; use @code{info registers} to see the names used on
5610 @kindex info registers
5611 @item info registers
5612 Print the names and values of all registers except floating-point
5613 and vector registers (in the selected stack frame).
5615 @kindex info all-registers
5616 @cindex floating point registers
5617 @item info all-registers
5618 Print the names and values of all registers, including floating-point
5619 and vector registers (in the selected stack frame).
5621 @item info registers @var{regname} @dots{}
5622 Print the @dfn{relativized} value of each specified register @var{regname}.
5623 As discussed in detail below, register values are normally relative to
5624 the selected stack frame. @var{regname} may be any register name valid on
5625 the machine you are using, with or without the initial @samp{$}.
5628 @value{GDBN} has four ``standard'' register names that are available (in
5629 expressions) on most machines---whenever they do not conflict with an
5630 architecture's canonical mnemonics for registers. The register names
5631 @code{$pc} and @code{$sp} are used for the program counter register and
5632 the stack pointer. @code{$fp} is used for a register that contains a
5633 pointer to the current stack frame, and @code{$ps} is used for a
5634 register that contains the processor status. For example,
5635 you could print the program counter in hex with
5642 or print the instruction to be executed next with
5649 or add four to the stack pointer@footnote{This is a way of removing
5650 one word from the stack, on machines where stacks grow downward in
5651 memory (most machines, nowadays). This assumes that the innermost
5652 stack frame is selected; setting @code{$sp} is not allowed when other
5653 stack frames are selected. To pop entire frames off the stack,
5654 regardless of machine architecture, use @code{return};
5655 see @ref{Returning, ,Returning from a function}.} with
5661 Whenever possible, these four standard register names are available on
5662 your machine even though the machine has different canonical mnemonics,
5663 so long as there is no conflict. The @code{info registers} command
5664 shows the canonical names. For example, on the SPARC, @code{info
5665 registers} displays the processor status register as @code{$psr} but you
5666 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
5667 is an alias for the @sc{eflags} register.
5669 @value{GDBN} always considers the contents of an ordinary register as an
5670 integer when the register is examined in this way. Some machines have
5671 special registers which can hold nothing but floating point; these
5672 registers are considered to have floating point values. There is no way
5673 to refer to the contents of an ordinary register as floating point value
5674 (although you can @emph{print} it as a floating point value with
5675 @samp{print/f $@var{regname}}).
5677 Some registers have distinct ``raw'' and ``virtual'' data formats. This
5678 means that the data format in which the register contents are saved by
5679 the operating system is not the same one that your program normally
5680 sees. For example, the registers of the 68881 floating point
5681 coprocessor are always saved in ``extended'' (raw) format, but all C
5682 programs expect to work with ``double'' (virtual) format. In such
5683 cases, @value{GDBN} normally works with the virtual format only (the format
5684 that makes sense for your program), but the @code{info registers} command
5685 prints the data in both formats.
5687 Normally, register values are relative to the selected stack frame
5688 (@pxref{Selection, ,Selecting a frame}). This means that you get the
5689 value that the register would contain if all stack frames farther in
5690 were exited and their saved registers restored. In order to see the
5691 true contents of hardware registers, you must select the innermost
5692 frame (with @samp{frame 0}).
5694 However, @value{GDBN} must deduce where registers are saved, from the machine
5695 code generated by your compiler. If some registers are not saved, or if
5696 @value{GDBN} is unable to locate the saved registers, the selected stack
5697 frame makes no difference.
5699 @node Floating Point Hardware
5700 @section Floating point hardware
5701 @cindex floating point
5703 Depending on the configuration, @value{GDBN} may be able to give
5704 you more information about the status of the floating point hardware.
5709 Display hardware-dependent information about the floating
5710 point unit. The exact contents and layout vary depending on the
5711 floating point chip. Currently, @samp{info float} is supported on
5712 the ARM and x86 machines.
5716 @section Vector Unit
5719 Depending on the configuration, @value{GDBN} may be able to give you
5720 more information about the status of the vector unit.
5725 Display information about the vector unit. The exact contents and
5726 layout vary depending on the hardware.
5729 @node Memory Region Attributes
5730 @section Memory region attributes
5731 @cindex memory region attributes
5733 @dfn{Memory region attributes} allow you to describe special handling
5734 required by regions of your target's memory. @value{GDBN} uses attributes
5735 to determine whether to allow certain types of memory accesses; whether to
5736 use specific width accesses; and whether to cache target memory.
5738 Defined memory regions can be individually enabled and disabled. When a
5739 memory region is disabled, @value{GDBN} uses the default attributes when
5740 accessing memory in that region. Similarly, if no memory regions have
5741 been defined, @value{GDBN} uses the default attributes when accessing
5744 When a memory region is defined, it is given a number to identify it;
5745 to enable, disable, or remove a memory region, you specify that number.
5749 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
5750 Define memory region bounded by @var{lower} and @var{upper} with
5751 attributes @var{attributes}@dots{}. Note that @var{upper} == 0 is a
5752 special case: it is treated as the the target's maximum memory address.
5753 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
5756 @item delete mem @var{nums}@dots{}
5757 Remove memory regions @var{nums}@dots{}.
5760 @item disable mem @var{nums}@dots{}
5761 Disable memory regions @var{nums}@dots{}.
5762 A disabled memory region is not forgotten.
5763 It may be enabled again later.
5766 @item enable mem @var{nums}@dots{}
5767 Enable memory regions @var{nums}@dots{}.
5771 Print a table of all defined memory regions, with the following columns
5775 @item Memory Region Number
5776 @item Enabled or Disabled.
5777 Enabled memory regions are marked with @samp{y}.
5778 Disabled memory regions are marked with @samp{n}.
5781 The address defining the inclusive lower bound of the memory region.
5784 The address defining the exclusive upper bound of the memory region.
5787 The list of attributes set for this memory region.
5792 @subsection Attributes
5794 @subsubsection Memory Access Mode
5795 The access mode attributes set whether @value{GDBN} may make read or
5796 write accesses to a memory region.
5798 While these attributes prevent @value{GDBN} from performing invalid
5799 memory accesses, they do nothing to prevent the target system, I/O DMA,
5800 etc. from accessing memory.
5804 Memory is read only.
5806 Memory is write only.
5808 Memory is read/write. This is the default.
5811 @subsubsection Memory Access Size
5812 The acccess size attributes tells @value{GDBN} to use specific sized
5813 accesses in the memory region. Often memory mapped device registers
5814 require specific sized accesses. If no access size attribute is
5815 specified, @value{GDBN} may use accesses of any size.
5819 Use 8 bit memory accesses.
5821 Use 16 bit memory accesses.
5823 Use 32 bit memory accesses.
5825 Use 64 bit memory accesses.
5828 @c @subsubsection Hardware/Software Breakpoints
5829 @c The hardware/software breakpoint attributes set whether @value{GDBN}
5830 @c will use hardware or software breakpoints for the internal breakpoints
5831 @c used by the step, next, finish, until, etc. commands.
5835 @c Always use hardware breakpoints
5836 @c @item swbreak (default)
5839 @subsubsection Data Cache
5840 The data cache attributes set whether @value{GDBN} will cache target
5841 memory. While this generally improves performance by reducing debug
5842 protocol overhead, it can lead to incorrect results because @value{GDBN}
5843 does not know about volatile variables or memory mapped device
5848 Enable @value{GDBN} to cache target memory.
5850 Disable @value{GDBN} from caching target memory. This is the default.
5853 @c @subsubsection Memory Write Verification
5854 @c The memory write verification attributes set whether @value{GDBN}
5855 @c will re-reads data after each write to verify the write was successful.
5859 @c @item noverify (default)
5862 @node Dump/Restore Files
5863 @section Copy between memory and a file
5864 @cindex dump/restore files
5865 @cindex append data to a file
5866 @cindex dump data to a file
5867 @cindex restore data from a file
5869 You can use the commands @code{dump}, @code{append}, and
5870 @code{restore} to copy data between target memory and a file. The
5871 @code{dump} and @code{append} commands write data to a file, and the
5872 @code{restore} command reads data from a file back into the inferior's
5873 memory. Files may be in binary, Motorola S-record, Intel hex, or
5874 Tektronix Hex format; however, @value{GDBN} can only append to binary
5880 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
5881 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
5882 Dump the contents of memory from @var{start_addr} to @var{end_addr},
5883 or the value of @var{expr}, to @var{filename} in the given format.
5885 The @var{format} parameter may be any one of:
5892 Motorola S-record format.
5894 Tektronix Hex format.
5897 @value{GDBN} uses the same definitions of these formats as the
5898 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
5899 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
5903 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
5904 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
5905 Append the contents of memory from @var{start_addr} to @var{end_addr},
5906 or the value of @var{expr}, to @var{filename}, in raw binary form.
5907 (@value{GDBN} can only append data to files in raw binary form.)
5910 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
5911 Restore the contents of file @var{filename} into memory. The
5912 @code{restore} command can automatically recognize any known @sc{bfd}
5913 file format, except for raw binary. To restore a raw binary file you
5914 must specify the optional keyword @code{binary} after the filename.
5916 If @var{bias} is non-zero, its value will be added to the addresses
5917 contained in the file. Binary files always start at address zero, so
5918 they will be restored at address @var{bias}. Other bfd files have
5919 a built-in location; they will be restored at offset @var{bias}
5922 If @var{start} and/or @var{end} are non-zero, then only data between
5923 file offset @var{start} and file offset @var{end} will be restored.
5924 These offsets are relative to the addresses in the file, before
5925 the @var{bias} argument is applied.
5929 @node Character Sets
5930 @section Character Sets
5931 @cindex character sets
5933 @cindex translating between character sets
5934 @cindex host character set
5935 @cindex target character set
5937 If the program you are debugging uses a different character set to
5938 represent characters and strings than the one @value{GDBN} uses itself,
5939 @value{GDBN} can automatically translate between the character sets for
5940 you. The character set @value{GDBN} uses we call the @dfn{host
5941 character set}; the one the inferior program uses we call the
5942 @dfn{target character set}.
5944 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
5945 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
5946 remote protocol (@pxref{Remote,Remote Debugging}) to debug a program
5947 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
5948 then the host character set is Latin-1, and the target character set is
5949 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
5950 target-charset EBCDIC-US}, then @value{GDBN} translates between
5951 @sc{ebcdic} and Latin 1 as you print character or string values, or use
5952 character and string literals in expressions.
5954 @value{GDBN} has no way to automatically recognize which character set
5955 the inferior program uses; you must tell it, using the @code{set
5956 target-charset} command, described below.
5958 Here are the commands for controlling @value{GDBN}'s character set
5962 @item set target-charset @var{charset}
5963 @kindex set target-charset
5964 Set the current target character set to @var{charset}. We list the
5965 character set names @value{GDBN} recognizes below, but if you type
5966 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
5967 list the target character sets it supports.
5971 @item set host-charset @var{charset}
5972 @kindex set host-charset
5973 Set the current host character set to @var{charset}.
5975 By default, @value{GDBN} uses a host character set appropriate to the
5976 system it is running on; you can override that default using the
5977 @code{set host-charset} command.
5979 @value{GDBN} can only use certain character sets as its host character
5980 set. We list the character set names @value{GDBN} recognizes below, and
5981 indicate which can be host character sets, but if you type
5982 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
5983 list the host character sets it supports.
5985 @item set charset @var{charset}
5987 Set the current host and target character sets to @var{charset}. As
5988 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
5989 @value{GDBN} will list the name of the character sets that can be used
5990 for both host and target.
5994 @kindex show charset
5995 Show the names of the current host and target charsets.
5997 @itemx show host-charset
5998 @kindex show host-charset
5999 Show the name of the current host charset.
6001 @itemx show target-charset
6002 @kindex show target-charset
6003 Show the name of the current target charset.
6007 @value{GDBN} currently includes support for the following character
6013 @cindex ASCII character set
6014 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
6018 @cindex ISO 8859-1 character set
6019 @cindex ISO Latin 1 character set
6020 The ISO Latin 1 character set. This extends @sc{ascii} with accented
6021 characters needed for French, German, and Spanish. @value{GDBN} can use
6022 this as its host character set.
6026 @cindex EBCDIC character set
6027 @cindex IBM1047 character set
6028 Variants of the @sc{ebcdic} character set, used on some of IBM's
6029 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
6030 @value{GDBN} cannot use these as its host character set.
6034 Note that these are all single-byte character sets. More work inside
6035 GDB is needed to support multi-byte or variable-width character
6036 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
6038 Here is an example of @value{GDBN}'s character set support in action.
6039 Assume that the following source code has been placed in the file
6040 @file{charset-test.c}:
6046 = @{72, 101, 108, 108, 111, 44, 32, 119,
6047 111, 114, 108, 100, 33, 10, 0@};
6048 char ibm1047_hello[]
6049 = @{200, 133, 147, 147, 150, 107, 64, 166,
6050 150, 153, 147, 132, 90, 37, 0@};
6054 printf ("Hello, world!\n");
6058 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
6059 containing the string @samp{Hello, world!} followed by a newline,
6060 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
6062 We compile the program, and invoke the debugger on it:
6065 $ gcc -g charset-test.c -o charset-test
6066 $ gdb -nw charset-test
6067 GNU gdb 2001-12-19-cvs
6068 Copyright 2001 Free Software Foundation, Inc.
6073 We can use the @code{show charset} command to see what character sets
6074 @value{GDBN} is currently using to interpret and display characters and
6079 The current host and target character set is `ISO-8859-1'.
6083 For the sake of printing this manual, let's use @sc{ascii} as our
6084 initial character set:
6086 (gdb) set charset ASCII
6088 The current host and target character set is `ASCII'.
6092 Let's assume that @sc{ascii} is indeed the correct character set for our
6093 host system --- in other words, let's assume that if @value{GDBN} prints
6094 characters using the @sc{ascii} character set, our terminal will display
6095 them properly. Since our current target character set is also
6096 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
6099 (gdb) print ascii_hello
6100 $1 = 0x401698 "Hello, world!\n"
6101 (gdb) print ascii_hello[0]
6106 @value{GDBN} uses the target character set for character and string
6107 literals you use in expressions:
6115 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
6118 @value{GDBN} relies on the user to tell it which character set the
6119 target program uses. If we print @code{ibm1047_hello} while our target
6120 character set is still @sc{ascii}, we get jibberish:
6123 (gdb) print ibm1047_hello
6124 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
6125 (gdb) print ibm1047_hello[0]
6130 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
6131 @value{GDBN} tells us the character sets it supports:
6134 (gdb) set target-charset
6135 ASCII EBCDIC-US IBM1047 ISO-8859-1
6136 (gdb) set target-charset
6139 We can select @sc{ibm1047} as our target character set, and examine the
6140 program's strings again. Now the @sc{ascii} string is wrong, but
6141 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
6142 target character set, @sc{ibm1047}, to the host character set,
6143 @sc{ascii}, and they display correctly:
6146 (gdb) set target-charset IBM1047
6148 The current host character set is `ASCII'.
6149 The current target character set is `IBM1047'.
6150 (gdb) print ascii_hello
6151 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
6152 (gdb) print ascii_hello[0]
6154 (gdb) print ibm1047_hello
6155 $8 = 0x4016a8 "Hello, world!\n"
6156 (gdb) print ibm1047_hello[0]
6161 As above, @value{GDBN} uses the target character set for character and
6162 string literals you use in expressions:
6170 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
6175 @chapter C Preprocessor Macros
6177 Some languages, such as C and C++, provide a way to define and invoke
6178 ``preprocessor macros'' which expand into strings of tokens.
6179 @value{GDBN} can evaluate expressions containing macro invocations, show
6180 the result of macro expansion, and show a macro's definition, including
6181 where it was defined.
6183 You may need to compile your program specially to provide @value{GDBN}
6184 with information about preprocessor macros. Most compilers do not
6185 include macros in their debugging information, even when you compile
6186 with the @option{-g} flag. @xref{Compilation}.
6188 A program may define a macro at one point, remove that definition later,
6189 and then provide a different definition after that. Thus, at different
6190 points in the program, a macro may have different definitions, or have
6191 no definition at all. If there is a current stack frame, @value{GDBN}
6192 uses the macros in scope at that frame's source code line. Otherwise,
6193 @value{GDBN} uses the macros in scope at the current listing location;
6196 At the moment, @value{GDBN} does not support the @code{##}
6197 token-splicing operator, the @code{#} stringification operator, or
6198 variable-arity macros.
6200 Whenever @value{GDBN} evaluates an expression, it always expands any
6201 macro invocations present in the expression. @value{GDBN} also provides
6202 the following commands for working with macros explicitly.
6206 @kindex macro expand
6207 @cindex macro expansion, showing the results of preprocessor
6208 @cindex preprocessor macro expansion, showing the results of
6209 @cindex expanding preprocessor macros
6210 @item macro expand @var{expression}
6211 @itemx macro exp @var{expression}
6212 Show the results of expanding all preprocessor macro invocations in
6213 @var{expression}. Since @value{GDBN} simply expands macros, but does
6214 not parse the result, @var{expression} need not be a valid expression;
6215 it can be any string of tokens.
6217 @kindex macro expand-once
6218 @item macro expand-once @var{expression}
6219 @itemx macro exp1 @var{expression}
6220 @i{(This command is not yet implemented.)} Show the results of
6221 expanding those preprocessor macro invocations that appear explicitly in
6222 @var{expression}. Macro invocations appearing in that expansion are
6223 left unchanged. This command allows you to see the effect of a
6224 particular macro more clearly, without being confused by further
6225 expansions. Since @value{GDBN} simply expands macros, but does not
6226 parse the result, @var{expression} need not be a valid expression; it
6227 can be any string of tokens.
6230 @cindex macro definition, showing
6231 @cindex definition, showing a macro's
6232 @item info macro @var{macro}
6233 Show the definition of the macro named @var{macro}, and describe the
6234 source location where that definition was established.
6236 @kindex macro define
6237 @cindex user-defined macros
6238 @cindex defining macros interactively
6239 @cindex macros, user-defined
6240 @item macro define @var{macro} @var{replacement-list}
6241 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
6242 @i{(This command is not yet implemented.)} Introduce a definition for a
6243 preprocessor macro named @var{macro}, invocations of which are replaced
6244 by the tokens given in @var{replacement-list}. The first form of this
6245 command defines an ``object-like'' macro, which takes no arguments; the
6246 second form defines a ``function-like'' macro, which takes the arguments
6247 given in @var{arglist}.
6249 A definition introduced by this command is in scope in every expression
6250 evaluated in @value{GDBN}, until it is removed with the @command{macro
6251 undef} command, described below. The definition overrides all
6252 definitions for @var{macro} present in the program being debugged, as
6253 well as any previous user-supplied definition.
6256 @item macro undef @var{macro}
6257 @i{(This command is not yet implemented.)} Remove any user-supplied
6258 definition for the macro named @var{macro}. This command only affects
6259 definitions provided with the @command{macro define} command, described
6260 above; it cannot remove definitions present in the program being
6265 @cindex macros, example of debugging with
6266 Here is a transcript showing the above commands in action. First, we
6267 show our source files:
6275 #define ADD(x) (M + x)
6280 printf ("Hello, world!\n");
6282 printf ("We're so creative.\n");
6284 printf ("Goodbye, world!\n");
6291 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
6292 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
6293 compiler includes information about preprocessor macros in the debugging
6297 $ gcc -gdwarf-2 -g3 sample.c -o sample
6301 Now, we start @value{GDBN} on our sample program:
6305 GNU gdb 2002-05-06-cvs
6306 Copyright 2002 Free Software Foundation, Inc.
6307 GDB is free software, @dots{}
6311 We can expand macros and examine their definitions, even when the
6312 program is not running. @value{GDBN} uses the current listing position
6313 to decide which macro definitions are in scope:
6319 5 #define ADD(x) (M + x)
6324 10 printf ("Hello, world!\n");
6326 12 printf ("We're so creative.\n");
6327 (gdb) info macro ADD
6328 Defined at /home/jimb/gdb/macros/play/sample.c:5
6329 #define ADD(x) (M + x)
6331 Defined at /home/jimb/gdb/macros/play/sample.h:1
6332 included at /home/jimb/gdb/macros/play/sample.c:2
6334 (gdb) macro expand ADD(1)
6335 expands to: (42 + 1)
6336 (gdb) macro expand-once ADD(1)
6337 expands to: once (M + 1)
6341 In the example above, note that @command{macro expand-once} expands only
6342 the macro invocation explicit in the original text --- the invocation of
6343 @code{ADD} --- but does not expand the invocation of the macro @code{M},
6344 which was introduced by @code{ADD}.
6346 Once the program is running, GDB uses the macro definitions in force at
6347 the source line of the current stack frame:
6351 Breakpoint 1 at 0x8048370: file sample.c, line 10.
6353 Starting program: /home/jimb/gdb/macros/play/sample
6355 Breakpoint 1, main () at sample.c:10
6356 10 printf ("Hello, world!\n");
6360 At line 10, the definition of the macro @code{N} at line 9 is in force:
6364 Defined at /home/jimb/gdb/macros/play/sample.c:9
6366 (gdb) macro expand N Q M
6373 As we step over directives that remove @code{N}'s definition, and then
6374 give it a new definition, @value{GDBN} finds the definition (or lack
6375 thereof) in force at each point:
6380 12 printf ("We're so creative.\n");
6382 The symbol `N' has no definition as a C/C++ preprocessor macro
6383 at /home/jimb/gdb/macros/play/sample.c:12
6386 14 printf ("Goodbye, world!\n");
6388 Defined at /home/jimb/gdb/macros/play/sample.c:13
6390 (gdb) macro expand N Q M
6391 expands to: 1729 < 42
6399 @chapter Tracepoints
6400 @c This chapter is based on the documentation written by Michael
6401 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
6404 In some applications, it is not feasible for the debugger to interrupt
6405 the program's execution long enough for the developer to learn
6406 anything helpful about its behavior. If the program's correctness
6407 depends on its real-time behavior, delays introduced by a debugger
6408 might cause the program to change its behavior drastically, or perhaps
6409 fail, even when the code itself is correct. It is useful to be able
6410 to observe the program's behavior without interrupting it.
6412 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
6413 specify locations in the program, called @dfn{tracepoints}, and
6414 arbitrary expressions to evaluate when those tracepoints are reached.
6415 Later, using the @code{tfind} command, you can examine the values
6416 those expressions had when the program hit the tracepoints. The
6417 expressions may also denote objects in memory---structures or arrays,
6418 for example---whose values @value{GDBN} should record; while visiting
6419 a particular tracepoint, you may inspect those objects as if they were
6420 in memory at that moment. However, because @value{GDBN} records these
6421 values without interacting with you, it can do so quickly and
6422 unobtrusively, hopefully not disturbing the program's behavior.
6424 The tracepoint facility is currently available only for remote
6425 targets. @xref{Targets}. In addition, your remote target must know how
6426 to collect trace data. This functionality is implemented in the remote
6427 stub; however, none of the stubs distributed with @value{GDBN} support
6428 tracepoints as of this writing.
6430 This chapter describes the tracepoint commands and features.
6434 * Analyze Collected Data::
6435 * Tracepoint Variables::
6438 @node Set Tracepoints
6439 @section Commands to Set Tracepoints
6441 Before running such a @dfn{trace experiment}, an arbitrary number of
6442 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
6443 tracepoint has a number assigned to it by @value{GDBN}. Like with
6444 breakpoints, tracepoint numbers are successive integers starting from
6445 one. Many of the commands associated with tracepoints take the
6446 tracepoint number as their argument, to identify which tracepoint to
6449 For each tracepoint, you can specify, in advance, some arbitrary set
6450 of data that you want the target to collect in the trace buffer when
6451 it hits that tracepoint. The collected data can include registers,
6452 local variables, or global data. Later, you can use @value{GDBN}
6453 commands to examine the values these data had at the time the
6456 This section describes commands to set tracepoints and associated
6457 conditions and actions.
6460 * Create and Delete Tracepoints::
6461 * Enable and Disable Tracepoints::
6462 * Tracepoint Passcounts::
6463 * Tracepoint Actions::
6464 * Listing Tracepoints::
6465 * Starting and Stopping Trace Experiment::
6468 @node Create and Delete Tracepoints
6469 @subsection Create and Delete Tracepoints
6472 @cindex set tracepoint
6475 The @code{trace} command is very similar to the @code{break} command.
6476 Its argument can be a source line, a function name, or an address in
6477 the target program. @xref{Set Breaks}. The @code{trace} command
6478 defines a tracepoint, which is a point in the target program where the
6479 debugger will briefly stop, collect some data, and then allow the
6480 program to continue. Setting a tracepoint or changing its commands
6481 doesn't take effect until the next @code{tstart} command; thus, you
6482 cannot change the tracepoint attributes once a trace experiment is
6485 Here are some examples of using the @code{trace} command:
6488 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
6490 (@value{GDBP}) @b{trace +2} // 2 lines forward
6492 (@value{GDBP}) @b{trace my_function} // first source line of function
6494 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
6496 (@value{GDBP}) @b{trace *0x2117c4} // an address
6500 You can abbreviate @code{trace} as @code{tr}.
6503 @cindex last tracepoint number
6504 @cindex recent tracepoint number
6505 @cindex tracepoint number
6506 The convenience variable @code{$tpnum} records the tracepoint number
6507 of the most recently set tracepoint.
6509 @kindex delete tracepoint
6510 @cindex tracepoint deletion
6511 @item delete tracepoint @r{[}@var{num}@r{]}
6512 Permanently delete one or more tracepoints. With no argument, the
6513 default is to delete all tracepoints.
6518 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
6520 (@value{GDBP}) @b{delete trace} // remove all tracepoints
6524 You can abbreviate this command as @code{del tr}.
6527 @node Enable and Disable Tracepoints
6528 @subsection Enable and Disable Tracepoints
6531 @kindex disable tracepoint
6532 @item disable tracepoint @r{[}@var{num}@r{]}
6533 Disable tracepoint @var{num}, or all tracepoints if no argument
6534 @var{num} is given. A disabled tracepoint will have no effect during
6535 the next trace experiment, but it is not forgotten. You can re-enable
6536 a disabled tracepoint using the @code{enable tracepoint} command.
6538 @kindex enable tracepoint
6539 @item enable tracepoint @r{[}@var{num}@r{]}
6540 Enable tracepoint @var{num}, or all tracepoints. The enabled
6541 tracepoints will become effective the next time a trace experiment is
6545 @node Tracepoint Passcounts
6546 @subsection Tracepoint Passcounts
6550 @cindex tracepoint pass count
6551 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
6552 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
6553 automatically stop a trace experiment. If a tracepoint's passcount is
6554 @var{n}, then the trace experiment will be automatically stopped on
6555 the @var{n}'th time that tracepoint is hit. If the tracepoint number
6556 @var{num} is not specified, the @code{passcount} command sets the
6557 passcount of the most recently defined tracepoint. If no passcount is
6558 given, the trace experiment will run until stopped explicitly by the
6564 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
6565 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
6567 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
6568 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
6569 (@value{GDBP}) @b{trace foo}
6570 (@value{GDBP}) @b{pass 3}
6571 (@value{GDBP}) @b{trace bar}
6572 (@value{GDBP}) @b{pass 2}
6573 (@value{GDBP}) @b{trace baz}
6574 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
6575 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
6576 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
6577 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
6581 @node Tracepoint Actions
6582 @subsection Tracepoint Action Lists
6586 @cindex tracepoint actions
6587 @item actions @r{[}@var{num}@r{]}
6588 This command will prompt for a list of actions to be taken when the
6589 tracepoint is hit. If the tracepoint number @var{num} is not
6590 specified, this command sets the actions for the one that was most
6591 recently defined (so that you can define a tracepoint and then say
6592 @code{actions} without bothering about its number). You specify the
6593 actions themselves on the following lines, one action at a time, and
6594 terminate the actions list with a line containing just @code{end}. So
6595 far, the only defined actions are @code{collect} and
6596 @code{while-stepping}.
6598 @cindex remove actions from a tracepoint
6599 To remove all actions from a tracepoint, type @samp{actions @var{num}}
6600 and follow it immediately with @samp{end}.
6603 (@value{GDBP}) @b{collect @var{data}} // collect some data
6605 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
6607 (@value{GDBP}) @b{end} // signals the end of actions.
6610 In the following example, the action list begins with @code{collect}
6611 commands indicating the things to be collected when the tracepoint is
6612 hit. Then, in order to single-step and collect additional data
6613 following the tracepoint, a @code{while-stepping} command is used,
6614 followed by the list of things to be collected while stepping. The
6615 @code{while-stepping} command is terminated by its own separate
6616 @code{end} command. Lastly, the action list is terminated by an
6620 (@value{GDBP}) @b{trace foo}
6621 (@value{GDBP}) @b{actions}
6622 Enter actions for tracepoint 1, one per line:
6631 @kindex collect @r{(tracepoints)}
6632 @item collect @var{expr1}, @var{expr2}, @dots{}
6633 Collect values of the given expressions when the tracepoint is hit.
6634 This command accepts a comma-separated list of any valid expressions.
6635 In addition to global, static, or local variables, the following
6636 special arguments are supported:
6640 collect all registers
6643 collect all function arguments
6646 collect all local variables.
6649 You can give several consecutive @code{collect} commands, each one
6650 with a single argument, or one @code{collect} command with several
6651 arguments separated by commas: the effect is the same.
6653 The command @code{info scope} (@pxref{Symbols, info scope}) is
6654 particularly useful for figuring out what data to collect.
6656 @kindex while-stepping @r{(tracepoints)}
6657 @item while-stepping @var{n}
6658 Perform @var{n} single-step traces after the tracepoint, collecting
6659 new data at each step. The @code{while-stepping} command is
6660 followed by the list of what to collect while stepping (followed by
6661 its own @code{end} command):
6665 > collect $regs, myglobal
6671 You may abbreviate @code{while-stepping} as @code{ws} or
6675 @node Listing Tracepoints
6676 @subsection Listing Tracepoints
6679 @kindex info tracepoints
6680 @cindex information about tracepoints
6681 @item info tracepoints @r{[}@var{num}@r{]}
6682 Display information about the tracepoint @var{num}. If you don't specify
6683 a tracepoint number, displays information about all the tracepoints
6684 defined so far. For each tracepoint, the following information is
6691 whether it is enabled or disabled
6695 its passcount as given by the @code{passcount @var{n}} command
6697 its step count as given by the @code{while-stepping @var{n}} command
6699 where in the source files is the tracepoint set
6701 its action list as given by the @code{actions} command
6705 (@value{GDBP}) @b{info trace}
6706 Num Enb Address PassC StepC What
6707 1 y 0x002117c4 0 0 <gdb_asm>
6708 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
6709 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
6714 This command can be abbreviated @code{info tp}.
6717 @node Starting and Stopping Trace Experiment
6718 @subsection Starting and Stopping Trace Experiment
6722 @cindex start a new trace experiment
6723 @cindex collected data discarded
6725 This command takes no arguments. It starts the trace experiment, and
6726 begins collecting data. This has the side effect of discarding all
6727 the data collected in the trace buffer during the previous trace
6731 @cindex stop a running trace experiment
6733 This command takes no arguments. It ends the trace experiment, and
6734 stops collecting data.
6736 @strong{Note:} a trace experiment and data collection may stop
6737 automatically if any tracepoint's passcount is reached
6738 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
6741 @cindex status of trace data collection
6742 @cindex trace experiment, status of
6744 This command displays the status of the current trace data
6748 Here is an example of the commands we described so far:
6751 (@value{GDBP}) @b{trace gdb_c_test}
6752 (@value{GDBP}) @b{actions}
6753 Enter actions for tracepoint #1, one per line.
6754 > collect $regs,$locals,$args
6759 (@value{GDBP}) @b{tstart}
6760 [time passes @dots{}]
6761 (@value{GDBP}) @b{tstop}
6765 @node Analyze Collected Data
6766 @section Using the collected data
6768 After the tracepoint experiment ends, you use @value{GDBN} commands
6769 for examining the trace data. The basic idea is that each tracepoint
6770 collects a trace @dfn{snapshot} every time it is hit and another
6771 snapshot every time it single-steps. All these snapshots are
6772 consecutively numbered from zero and go into a buffer, and you can
6773 examine them later. The way you examine them is to @dfn{focus} on a
6774 specific trace snapshot. When the remote stub is focused on a trace
6775 snapshot, it will respond to all @value{GDBN} requests for memory and
6776 registers by reading from the buffer which belongs to that snapshot,
6777 rather than from @emph{real} memory or registers of the program being
6778 debugged. This means that @strong{all} @value{GDBN} commands
6779 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
6780 behave as if we were currently debugging the program state as it was
6781 when the tracepoint occurred. Any requests for data that are not in
6782 the buffer will fail.
6785 * tfind:: How to select a trace snapshot
6786 * tdump:: How to display all data for a snapshot
6787 * save-tracepoints:: How to save tracepoints for a future run
6791 @subsection @code{tfind @var{n}}
6794 @cindex select trace snapshot
6795 @cindex find trace snapshot
6796 The basic command for selecting a trace snapshot from the buffer is
6797 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
6798 counting from zero. If no argument @var{n} is given, the next
6799 snapshot is selected.
6801 Here are the various forms of using the @code{tfind} command.
6805 Find the first snapshot in the buffer. This is a synonym for
6806 @code{tfind 0} (since 0 is the number of the first snapshot).
6809 Stop debugging trace snapshots, resume @emph{live} debugging.
6812 Same as @samp{tfind none}.
6815 No argument means find the next trace snapshot.
6818 Find the previous trace snapshot before the current one. This permits
6819 retracing earlier steps.
6821 @item tfind tracepoint @var{num}
6822 Find the next snapshot associated with tracepoint @var{num}. Search
6823 proceeds forward from the last examined trace snapshot. If no
6824 argument @var{num} is given, it means find the next snapshot collected
6825 for the same tracepoint as the current snapshot.
6827 @item tfind pc @var{addr}
6828 Find the next snapshot associated with the value @var{addr} of the
6829 program counter. Search proceeds forward from the last examined trace
6830 snapshot. If no argument @var{addr} is given, it means find the next
6831 snapshot with the same value of PC as the current snapshot.
6833 @item tfind outside @var{addr1}, @var{addr2}
6834 Find the next snapshot whose PC is outside the given range of
6837 @item tfind range @var{addr1}, @var{addr2}
6838 Find the next snapshot whose PC is between @var{addr1} and
6839 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
6841 @item tfind line @r{[}@var{file}:@r{]}@var{n}
6842 Find the next snapshot associated with the source line @var{n}. If
6843 the optional argument @var{file} is given, refer to line @var{n} in
6844 that source file. Search proceeds forward from the last examined
6845 trace snapshot. If no argument @var{n} is given, it means find the
6846 next line other than the one currently being examined; thus saying
6847 @code{tfind line} repeatedly can appear to have the same effect as
6848 stepping from line to line in a @emph{live} debugging session.
6851 The default arguments for the @code{tfind} commands are specifically
6852 designed to make it easy to scan through the trace buffer. For
6853 instance, @code{tfind} with no argument selects the next trace
6854 snapshot, and @code{tfind -} with no argument selects the previous
6855 trace snapshot. So, by giving one @code{tfind} command, and then
6856 simply hitting @key{RET} repeatedly you can examine all the trace
6857 snapshots in order. Or, by saying @code{tfind -} and then hitting
6858 @key{RET} repeatedly you can examine the snapshots in reverse order.
6859 The @code{tfind line} command with no argument selects the snapshot
6860 for the next source line executed. The @code{tfind pc} command with
6861 no argument selects the next snapshot with the same program counter
6862 (PC) as the current frame. The @code{tfind tracepoint} command with
6863 no argument selects the next trace snapshot collected by the same
6864 tracepoint as the current one.
6866 In addition to letting you scan through the trace buffer manually,
6867 these commands make it easy to construct @value{GDBN} scripts that
6868 scan through the trace buffer and print out whatever collected data
6869 you are interested in. Thus, if we want to examine the PC, FP, and SP
6870 registers from each trace frame in the buffer, we can say this:
6873 (@value{GDBP}) @b{tfind start}
6874 (@value{GDBP}) @b{while ($trace_frame != -1)}
6875 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
6876 $trace_frame, $pc, $sp, $fp
6880 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
6881 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
6882 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
6883 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
6884 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
6885 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
6886 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
6887 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
6888 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
6889 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
6890 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
6893 Or, if we want to examine the variable @code{X} at each source line in
6897 (@value{GDBP}) @b{tfind start}
6898 (@value{GDBP}) @b{while ($trace_frame != -1)}
6899 > printf "Frame %d, X == %d\n", $trace_frame, X
6909 @subsection @code{tdump}
6911 @cindex dump all data collected at tracepoint
6912 @cindex tracepoint data, display
6914 This command takes no arguments. It prints all the data collected at
6915 the current trace snapshot.
6918 (@value{GDBP}) @b{trace 444}
6919 (@value{GDBP}) @b{actions}
6920 Enter actions for tracepoint #2, one per line:
6921 > collect $regs, $locals, $args, gdb_long_test
6924 (@value{GDBP}) @b{tstart}
6926 (@value{GDBP}) @b{tfind line 444}
6927 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
6929 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
6931 (@value{GDBP}) @b{tdump}
6932 Data collected at tracepoint 2, trace frame 1:
6933 d0 0xc4aa0085 -995491707
6937 d4 0x71aea3d 119204413
6942 a1 0x3000668 50333288
6945 a4 0x3000698 50333336
6947 fp 0x30bf3c 0x30bf3c
6948 sp 0x30bf34 0x30bf34
6950 pc 0x20b2c8 0x20b2c8
6954 p = 0x20e5b4 "gdb-test"
6961 gdb_long_test = 17 '\021'
6966 @node save-tracepoints
6967 @subsection @code{save-tracepoints @var{filename}}
6968 @kindex save-tracepoints
6969 @cindex save tracepoints for future sessions
6971 This command saves all current tracepoint definitions together with
6972 their actions and passcounts, into a file @file{@var{filename}}
6973 suitable for use in a later debugging session. To read the saved
6974 tracepoint definitions, use the @code{source} command (@pxref{Command
6977 @node Tracepoint Variables
6978 @section Convenience Variables for Tracepoints
6979 @cindex tracepoint variables
6980 @cindex convenience variables for tracepoints
6983 @vindex $trace_frame
6984 @item (int) $trace_frame
6985 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
6986 snapshot is selected.
6989 @item (int) $tracepoint
6990 The tracepoint for the current trace snapshot.
6993 @item (int) $trace_line
6994 The line number for the current trace snapshot.
6997 @item (char []) $trace_file
6998 The source file for the current trace snapshot.
7001 @item (char []) $trace_func
7002 The name of the function containing @code{$tracepoint}.
7005 Note: @code{$trace_file} is not suitable for use in @code{printf},
7006 use @code{output} instead.
7008 Here's a simple example of using these convenience variables for
7009 stepping through all the trace snapshots and printing some of their
7013 (@value{GDBP}) @b{tfind start}
7015 (@value{GDBP}) @b{while $trace_frame != -1}
7016 > output $trace_file
7017 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
7023 @chapter Debugging Programs That Use Overlays
7026 If your program is too large to fit completely in your target system's
7027 memory, you can sometimes use @dfn{overlays} to work around this
7028 problem. @value{GDBN} provides some support for debugging programs that
7032 * How Overlays Work:: A general explanation of overlays.
7033 * Overlay Commands:: Managing overlays in @value{GDBN}.
7034 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
7035 mapped by asking the inferior.
7036 * Overlay Sample Program:: A sample program using overlays.
7039 @node How Overlays Work
7040 @section How Overlays Work
7041 @cindex mapped overlays
7042 @cindex unmapped overlays
7043 @cindex load address, overlay's
7044 @cindex mapped address
7045 @cindex overlay area
7047 Suppose you have a computer whose instruction address space is only 64
7048 kilobytes long, but which has much more memory which can be accessed by
7049 other means: special instructions, segment registers, or memory
7050 management hardware, for example. Suppose further that you want to
7051 adapt a program which is larger than 64 kilobytes to run on this system.
7053 One solution is to identify modules of your program which are relatively
7054 independent, and need not call each other directly; call these modules
7055 @dfn{overlays}. Separate the overlays from the main program, and place
7056 their machine code in the larger memory. Place your main program in
7057 instruction memory, but leave at least enough space there to hold the
7058 largest overlay as well.
7060 Now, to call a function located in an overlay, you must first copy that
7061 overlay's machine code from the large memory into the space set aside
7062 for it in the instruction memory, and then jump to its entry point
7065 @c NB: In the below the mapped area's size is greater or equal to the
7066 @c size of all overlays. This is intentional to remind the developer
7067 @c that overlays don't necessarily need to be the same size.
7071 Data Instruction Larger
7072 Address Space Address Space Address Space
7073 +-----------+ +-----------+ +-----------+
7075 +-----------+ +-----------+ +-----------+<-- overlay 1
7076 | program | | main | .----| overlay 1 | load address
7077 | variables | | program | | +-----------+
7078 | and heap | | | | | |
7079 +-----------+ | | | +-----------+<-- overlay 2
7080 | | +-----------+ | | | load address
7081 +-----------+ | | | .-| overlay 2 |
7083 mapped --->+-----------+ | | +-----------+
7085 | overlay | <-' | | |
7086 | area | <---' +-----------+<-- overlay 3
7087 | | <---. | | load address
7088 +-----------+ `--| overlay 3 |
7095 @anchor{A code overlay}A code overlay
7099 The diagram (@pxref{A code overlay}) shows a system with separate data
7100 and instruction address spaces. To map an overlay, the program copies
7101 its code from the larger address space to the instruction address space.
7102 Since the overlays shown here all use the same mapped address, only one
7103 may be mapped at a time. For a system with a single address space for
7104 data and instructions, the diagram would be similar, except that the
7105 program variables and heap would share an address space with the main
7106 program and the overlay area.
7108 An overlay loaded into instruction memory and ready for use is called a
7109 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
7110 instruction memory. An overlay not present (or only partially present)
7111 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
7112 is its address in the larger memory. The mapped address is also called
7113 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
7114 called the @dfn{load memory address}, or @dfn{LMA}.
7116 Unfortunately, overlays are not a completely transparent way to adapt a
7117 program to limited instruction memory. They introduce a new set of
7118 global constraints you must keep in mind as you design your program:
7123 Before calling or returning to a function in an overlay, your program
7124 must make sure that overlay is actually mapped. Otherwise, the call or
7125 return will transfer control to the right address, but in the wrong
7126 overlay, and your program will probably crash.
7129 If the process of mapping an overlay is expensive on your system, you
7130 will need to choose your overlays carefully to minimize their effect on
7131 your program's performance.
7134 The executable file you load onto your system must contain each
7135 overlay's instructions, appearing at the overlay's load address, not its
7136 mapped address. However, each overlay's instructions must be relocated
7137 and its symbols defined as if the overlay were at its mapped address.
7138 You can use GNU linker scripts to specify different load and relocation
7139 addresses for pieces of your program; see @ref{Overlay Description,,,
7140 ld.info, Using ld: the GNU linker}.
7143 The procedure for loading executable files onto your system must be able
7144 to load their contents into the larger address space as well as the
7145 instruction and data spaces.
7149 The overlay system described above is rather simple, and could be
7150 improved in many ways:
7155 If your system has suitable bank switch registers or memory management
7156 hardware, you could use those facilities to make an overlay's load area
7157 contents simply appear at their mapped address in instruction space.
7158 This would probably be faster than copying the overlay to its mapped
7159 area in the usual way.
7162 If your overlays are small enough, you could set aside more than one
7163 overlay area, and have more than one overlay mapped at a time.
7166 You can use overlays to manage data, as well as instructions. In
7167 general, data overlays are even less transparent to your design than
7168 code overlays: whereas code overlays only require care when you call or
7169 return to functions, data overlays require care every time you access
7170 the data. Also, if you change the contents of a data overlay, you
7171 must copy its contents back out to its load address before you can copy a
7172 different data overlay into the same mapped area.
7177 @node Overlay Commands
7178 @section Overlay Commands
7180 To use @value{GDBN}'s overlay support, each overlay in your program must
7181 correspond to a separate section of the executable file. The section's
7182 virtual memory address and load memory address must be the overlay's
7183 mapped and load addresses. Identifying overlays with sections allows
7184 @value{GDBN} to determine the appropriate address of a function or
7185 variable, depending on whether the overlay is mapped or not.
7187 @value{GDBN}'s overlay commands all start with the word @code{overlay};
7188 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
7193 Disable @value{GDBN}'s overlay support. When overlay support is
7194 disabled, @value{GDBN} assumes that all functions and variables are
7195 always present at their mapped addresses. By default, @value{GDBN}'s
7196 overlay support is disabled.
7198 @item overlay manual
7199 @kindex overlay manual
7200 @cindex manual overlay debugging
7201 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
7202 relies on you to tell it which overlays are mapped, and which are not,
7203 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
7204 commands described below.
7206 @item overlay map-overlay @var{overlay}
7207 @itemx overlay map @var{overlay}
7208 @kindex overlay map-overlay
7209 @cindex map an overlay
7210 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
7211 be the name of the object file section containing the overlay. When an
7212 overlay is mapped, @value{GDBN} assumes it can find the overlay's
7213 functions and variables at their mapped addresses. @value{GDBN} assumes
7214 that any other overlays whose mapped ranges overlap that of
7215 @var{overlay} are now unmapped.
7217 @item overlay unmap-overlay @var{overlay}
7218 @itemx overlay unmap @var{overlay}
7219 @kindex overlay unmap-overlay
7220 @cindex unmap an overlay
7221 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
7222 must be the name of the object file section containing the overlay.
7223 When an overlay is unmapped, @value{GDBN} assumes it can find the
7224 overlay's functions and variables at their load addresses.
7227 @kindex overlay auto
7228 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
7229 consults a data structure the overlay manager maintains in the inferior
7230 to see which overlays are mapped. For details, see @ref{Automatic
7233 @item overlay load-target
7235 @kindex overlay load-target
7236 @cindex reloading the overlay table
7237 Re-read the overlay table from the inferior. Normally, @value{GDBN}
7238 re-reads the table @value{GDBN} automatically each time the inferior
7239 stops, so this command should only be necessary if you have changed the
7240 overlay mapping yourself using @value{GDBN}. This command is only
7241 useful when using automatic overlay debugging.
7243 @item overlay list-overlays
7245 @cindex listing mapped overlays
7246 Display a list of the overlays currently mapped, along with their mapped
7247 addresses, load addresses, and sizes.
7251 Normally, when @value{GDBN} prints a code address, it includes the name
7252 of the function the address falls in:
7256 $3 = @{int ()@} 0x11a0 <main>
7259 When overlay debugging is enabled, @value{GDBN} recognizes code in
7260 unmapped overlays, and prints the names of unmapped functions with
7261 asterisks around them. For example, if @code{foo} is a function in an
7262 unmapped overlay, @value{GDBN} prints it this way:
7266 No sections are mapped.
7268 $5 = @{int (int)@} 0x100000 <*foo*>
7271 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
7276 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
7277 mapped at 0x1016 - 0x104a
7279 $6 = @{int (int)@} 0x1016 <foo>
7282 When overlay debugging is enabled, @value{GDBN} can find the correct
7283 address for functions and variables in an overlay, whether or not the
7284 overlay is mapped. This allows most @value{GDBN} commands, like
7285 @code{break} and @code{disassemble}, to work normally, even on unmapped
7286 code. However, @value{GDBN}'s breakpoint support has some limitations:
7290 @cindex breakpoints in overlays
7291 @cindex overlays, setting breakpoints in
7292 You can set breakpoints in functions in unmapped overlays, as long as
7293 @value{GDBN} can write to the overlay at its load address.
7295 @value{GDBN} can not set hardware or simulator-based breakpoints in
7296 unmapped overlays. However, if you set a breakpoint at the end of your
7297 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
7298 you are using manual overlay management), @value{GDBN} will re-set its
7299 breakpoints properly.
7303 @node Automatic Overlay Debugging
7304 @section Automatic Overlay Debugging
7305 @cindex automatic overlay debugging
7307 @value{GDBN} can automatically track which overlays are mapped and which
7308 are not, given some simple co-operation from the overlay manager in the
7309 inferior. If you enable automatic overlay debugging with the
7310 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
7311 looks in the inferior's memory for certain variables describing the
7312 current state of the overlays.
7314 Here are the variables your overlay manager must define to support
7315 @value{GDBN}'s automatic overlay debugging:
7319 @item @code{_ovly_table}:
7320 This variable must be an array of the following structures:
7325 /* The overlay's mapped address. */
7328 /* The size of the overlay, in bytes. */
7331 /* The overlay's load address. */
7334 /* Non-zero if the overlay is currently mapped;
7336 unsigned long mapped;
7340 @item @code{_novlys}:
7341 This variable must be a four-byte signed integer, holding the total
7342 number of elements in @code{_ovly_table}.
7346 To decide whether a particular overlay is mapped or not, @value{GDBN}
7347 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
7348 @code{lma} members equal the VMA and LMA of the overlay's section in the
7349 executable file. When @value{GDBN} finds a matching entry, it consults
7350 the entry's @code{mapped} member to determine whether the overlay is
7353 In addition, your overlay manager may define a function called
7354 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
7355 will silently set a breakpoint there. If the overlay manager then
7356 calls this function whenever it has changed the overlay table, this
7357 will enable @value{GDBN} to accurately keep track of which overlays
7358 are in program memory, and update any breakpoints that may be set
7359 in overlays. This will allow breakpoints to work even if the
7360 overlays are kept in ROM or other non-writable memory while they
7361 are not being executed.
7363 @node Overlay Sample Program
7364 @section Overlay Sample Program
7365 @cindex overlay example program
7367 When linking a program which uses overlays, you must place the overlays
7368 at their load addresses, while relocating them to run at their mapped
7369 addresses. To do this, you must write a linker script (@pxref{Overlay
7370 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
7371 since linker scripts are specific to a particular host system, target
7372 architecture, and target memory layout, this manual cannot provide
7373 portable sample code demonstrating @value{GDBN}'s overlay support.
7375 However, the @value{GDBN} source distribution does contain an overlaid
7376 program, with linker scripts for a few systems, as part of its test
7377 suite. The program consists of the following files from
7378 @file{gdb/testsuite/gdb.base}:
7382 The main program file.
7384 A simple overlay manager, used by @file{overlays.c}.
7389 Overlay modules, loaded and used by @file{overlays.c}.
7392 Linker scripts for linking the test program on the @code{d10v-elf}
7393 and @code{m32r-elf} targets.
7396 You can build the test program using the @code{d10v-elf} GCC
7397 cross-compiler like this:
7400 $ d10v-elf-gcc -g -c overlays.c
7401 $ d10v-elf-gcc -g -c ovlymgr.c
7402 $ d10v-elf-gcc -g -c foo.c
7403 $ d10v-elf-gcc -g -c bar.c
7404 $ d10v-elf-gcc -g -c baz.c
7405 $ d10v-elf-gcc -g -c grbx.c
7406 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
7407 baz.o grbx.o -Wl,-Td10v.ld -o overlays
7410 The build process is identical for any other architecture, except that
7411 you must substitute the appropriate compiler and linker script for the
7412 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
7416 @chapter Using @value{GDBN} with Different Languages
7419 Although programming languages generally have common aspects, they are
7420 rarely expressed in the same manner. For instance, in ANSI C,
7421 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
7422 Modula-2, it is accomplished by @code{p^}. Values can also be
7423 represented (and displayed) differently. Hex numbers in C appear as
7424 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
7426 @cindex working language
7427 Language-specific information is built into @value{GDBN} for some languages,
7428 allowing you to express operations like the above in your program's
7429 native language, and allowing @value{GDBN} to output values in a manner
7430 consistent with the syntax of your program's native language. The
7431 language you use to build expressions is called the @dfn{working
7435 * Setting:: Switching between source languages
7436 * Show:: Displaying the language
7437 * Checks:: Type and range checks
7438 * Support:: Supported languages
7442 @section Switching between source languages
7444 There are two ways to control the working language---either have @value{GDBN}
7445 set it automatically, or select it manually yourself. You can use the
7446 @code{set language} command for either purpose. On startup, @value{GDBN}
7447 defaults to setting the language automatically. The working language is
7448 used to determine how expressions you type are interpreted, how values
7451 In addition to the working language, every source file that
7452 @value{GDBN} knows about has its own working language. For some object
7453 file formats, the compiler might indicate which language a particular
7454 source file is in. However, most of the time @value{GDBN} infers the
7455 language from the name of the file. The language of a source file
7456 controls whether C@t{++} names are demangled---this way @code{backtrace} can
7457 show each frame appropriately for its own language. There is no way to
7458 set the language of a source file from within @value{GDBN}, but you can
7459 set the language associated with a filename extension. @xref{Show, ,
7460 Displaying the language}.
7462 This is most commonly a problem when you use a program, such
7463 as @code{cfront} or @code{f2c}, that generates C but is written in
7464 another language. In that case, make the
7465 program use @code{#line} directives in its C output; that way
7466 @value{GDBN} will know the correct language of the source code of the original
7467 program, and will display that source code, not the generated C code.
7470 * Filenames:: Filename extensions and languages.
7471 * Manually:: Setting the working language manually
7472 * Automatically:: Having @value{GDBN} infer the source language
7476 @subsection List of filename extensions and languages
7478 If a source file name ends in one of the following extensions, then
7479 @value{GDBN} infers that its language is the one indicated.
7495 Objective-C source file
7502 Modula-2 source file
7506 Assembler source file. This actually behaves almost like C, but
7507 @value{GDBN} does not skip over function prologues when stepping.
7510 In addition, you may set the language associated with a filename
7511 extension. @xref{Show, , Displaying the language}.
7514 @subsection Setting the working language
7516 If you allow @value{GDBN} to set the language automatically,
7517 expressions are interpreted the same way in your debugging session and
7520 @kindex set language
7521 If you wish, you may set the language manually. To do this, issue the
7522 command @samp{set language @var{lang}}, where @var{lang} is the name of
7524 @code{c} or @code{modula-2}.
7525 For a list of the supported languages, type @samp{set language}.
7527 Setting the language manually prevents @value{GDBN} from updating the working
7528 language automatically. This can lead to confusion if you try
7529 to debug a program when the working language is not the same as the
7530 source language, when an expression is acceptable to both
7531 languages---but means different things. For instance, if the current
7532 source file were written in C, and @value{GDBN} was parsing Modula-2, a
7540 might not have the effect you intended. In C, this means to add
7541 @code{b} and @code{c} and place the result in @code{a}. The result
7542 printed would be the value of @code{a}. In Modula-2, this means to compare
7543 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
7546 @subsection Having @value{GDBN} infer the source language
7548 To have @value{GDBN} set the working language automatically, use
7549 @samp{set language local} or @samp{set language auto}. @value{GDBN}
7550 then infers the working language. That is, when your program stops in a
7551 frame (usually by encountering a breakpoint), @value{GDBN} sets the
7552 working language to the language recorded for the function in that
7553 frame. If the language for a frame is unknown (that is, if the function
7554 or block corresponding to the frame was defined in a source file that
7555 does not have a recognized extension), the current working language is
7556 not changed, and @value{GDBN} issues a warning.
7558 This may not seem necessary for most programs, which are written
7559 entirely in one source language. However, program modules and libraries
7560 written in one source language can be used by a main program written in
7561 a different source language. Using @samp{set language auto} in this
7562 case frees you from having to set the working language manually.
7565 @section Displaying the language
7567 The following commands help you find out which language is the
7568 working language, and also what language source files were written in.
7570 @kindex show language
7571 @kindex info frame@r{, show the source language}
7572 @kindex info source@r{, show the source language}
7575 Display the current working language. This is the
7576 language you can use with commands such as @code{print} to
7577 build and compute expressions that may involve variables in your program.
7580 Display the source language for this frame. This language becomes the
7581 working language if you use an identifier from this frame.
7582 @xref{Frame Info, ,Information about a frame}, to identify the other
7583 information listed here.
7586 Display the source language of this source file.
7587 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
7588 information listed here.
7591 In unusual circumstances, you may have source files with extensions
7592 not in the standard list. You can then set the extension associated
7593 with a language explicitly:
7595 @kindex set extension-language
7596 @kindex info extensions
7598 @item set extension-language @var{.ext} @var{language}
7599 Set source files with extension @var{.ext} to be assumed to be in
7600 the source language @var{language}.
7602 @item info extensions
7603 List all the filename extensions and the associated languages.
7607 @section Type and range checking
7610 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
7611 checking are included, but they do not yet have any effect. This
7612 section documents the intended facilities.
7614 @c FIXME remove warning when type/range code added
7616 Some languages are designed to guard you against making seemingly common
7617 errors through a series of compile- and run-time checks. These include
7618 checking the type of arguments to functions and operators, and making
7619 sure mathematical overflows are caught at run time. Checks such as
7620 these help to ensure a program's correctness once it has been compiled
7621 by eliminating type mismatches, and providing active checks for range
7622 errors when your program is running.
7624 @value{GDBN} can check for conditions like the above if you wish.
7625 Although @value{GDBN} does not check the statements in your program, it
7626 can check expressions entered directly into @value{GDBN} for evaluation via
7627 the @code{print} command, for example. As with the working language,
7628 @value{GDBN} can also decide whether or not to check automatically based on
7629 your program's source language. @xref{Support, ,Supported languages},
7630 for the default settings of supported languages.
7633 * Type Checking:: An overview of type checking
7634 * Range Checking:: An overview of range checking
7637 @cindex type checking
7638 @cindex checks, type
7640 @subsection An overview of type checking
7642 Some languages, such as Modula-2, are strongly typed, meaning that the
7643 arguments to operators and functions have to be of the correct type,
7644 otherwise an error occurs. These checks prevent type mismatch
7645 errors from ever causing any run-time problems. For example,
7653 The second example fails because the @code{CARDINAL} 1 is not
7654 type-compatible with the @code{REAL} 2.3.
7656 For the expressions you use in @value{GDBN} commands, you can tell the
7657 @value{GDBN} type checker to skip checking;
7658 to treat any mismatches as errors and abandon the expression;
7659 or to only issue warnings when type mismatches occur,
7660 but evaluate the expression anyway. When you choose the last of
7661 these, @value{GDBN} evaluates expressions like the second example above, but
7662 also issues a warning.
7664 Even if you turn type checking off, there may be other reasons
7665 related to type that prevent @value{GDBN} from evaluating an expression.
7666 For instance, @value{GDBN} does not know how to add an @code{int} and
7667 a @code{struct foo}. These particular type errors have nothing to do
7668 with the language in use, and usually arise from expressions, such as
7669 the one described above, which make little sense to evaluate anyway.
7671 Each language defines to what degree it is strict about type. For
7672 instance, both Modula-2 and C require the arguments to arithmetical
7673 operators to be numbers. In C, enumerated types and pointers can be
7674 represented as numbers, so that they are valid arguments to mathematical
7675 operators. @xref{Support, ,Supported languages}, for further
7676 details on specific languages.
7678 @value{GDBN} provides some additional commands for controlling the type checker:
7680 @kindex set check@r{, type}
7681 @kindex set check type
7682 @kindex show check type
7684 @item set check type auto
7685 Set type checking on or off based on the current working language.
7686 @xref{Support, ,Supported languages}, for the default settings for
7689 @item set check type on
7690 @itemx set check type off
7691 Set type checking on or off, overriding the default setting for the
7692 current working language. Issue a warning if the setting does not
7693 match the language default. If any type mismatches occur in
7694 evaluating an expression while type checking is on, @value{GDBN} prints a
7695 message and aborts evaluation of the expression.
7697 @item set check type warn
7698 Cause the type checker to issue warnings, but to always attempt to
7699 evaluate the expression. Evaluating the expression may still
7700 be impossible for other reasons. For example, @value{GDBN} cannot add
7701 numbers and structures.
7704 Show the current setting of the type checker, and whether or not @value{GDBN}
7705 is setting it automatically.
7708 @cindex range checking
7709 @cindex checks, range
7710 @node Range Checking
7711 @subsection An overview of range checking
7713 In some languages (such as Modula-2), it is an error to exceed the
7714 bounds of a type; this is enforced with run-time checks. Such range
7715 checking is meant to ensure program correctness by making sure
7716 computations do not overflow, or indices on an array element access do
7717 not exceed the bounds of the array.
7719 For expressions you use in @value{GDBN} commands, you can tell
7720 @value{GDBN} to treat range errors in one of three ways: ignore them,
7721 always treat them as errors and abandon the expression, or issue
7722 warnings but evaluate the expression anyway.
7724 A range error can result from numerical overflow, from exceeding an
7725 array index bound, or when you type a constant that is not a member
7726 of any type. Some languages, however, do not treat overflows as an
7727 error. In many implementations of C, mathematical overflow causes the
7728 result to ``wrap around'' to lower values---for example, if @var{m} is
7729 the largest integer value, and @var{s} is the smallest, then
7732 @var{m} + 1 @result{} @var{s}
7735 This, too, is specific to individual languages, and in some cases
7736 specific to individual compilers or machines. @xref{Support, ,
7737 Supported languages}, for further details on specific languages.
7739 @value{GDBN} provides some additional commands for controlling the range checker:
7741 @kindex set check@r{, range}
7742 @kindex set check range
7743 @kindex show check range
7745 @item set check range auto
7746 Set range checking on or off based on the current working language.
7747 @xref{Support, ,Supported languages}, for the default settings for
7750 @item set check range on
7751 @itemx set check range off
7752 Set range checking on or off, overriding the default setting for the
7753 current working language. A warning is issued if the setting does not
7754 match the language default. If a range error occurs and range checking is on,
7755 then a message is printed and evaluation of the expression is aborted.
7757 @item set check range warn
7758 Output messages when the @value{GDBN} range checker detects a range error,
7759 but attempt to evaluate the expression anyway. Evaluating the
7760 expression may still be impossible for other reasons, such as accessing
7761 memory that the process does not own (a typical example from many Unix
7765 Show the current setting of the range checker, and whether or not it is
7766 being set automatically by @value{GDBN}.
7770 @section Supported languages
7772 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, assembly, and Modula-2.
7773 @c This is false ...
7774 Some @value{GDBN} features may be used in expressions regardless of the
7775 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
7776 and the @samp{@{type@}addr} construct (@pxref{Expressions,
7777 ,Expressions}) can be used with the constructs of any supported
7780 The following sections detail to what degree each source language is
7781 supported by @value{GDBN}. These sections are not meant to be language
7782 tutorials or references, but serve only as a reference guide to what the
7783 @value{GDBN} expression parser accepts, and what input and output
7784 formats should look like for different languages. There are many good
7785 books written on each of these languages; please look to these for a
7786 language reference or tutorial.
7790 * Objective-C:: Objective-C
7791 * Modula-2:: Modula-2
7795 @subsection C and C@t{++}
7797 @cindex C and C@t{++}
7798 @cindex expressions in C or C@t{++}
7800 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
7801 to both languages. Whenever this is the case, we discuss those languages
7805 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
7806 @cindex @sc{gnu} C@t{++}
7807 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
7808 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
7809 effectively, you must compile your C@t{++} programs with a supported
7810 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
7811 compiler (@code{aCC}).
7813 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
7814 format; if it doesn't work on your system, try the stabs+ debugging
7815 format. You can select those formats explicitly with the @code{g++}
7816 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
7817 @xref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
7818 CC, gcc.info, Using @sc{gnu} CC}.
7821 * C Operators:: C and C@t{++} operators
7822 * C Constants:: C and C@t{++} constants
7823 * C plus plus expressions:: C@t{++} expressions
7824 * C Defaults:: Default settings for C and C@t{++}
7825 * C Checks:: C and C@t{++} type and range checks
7826 * Debugging C:: @value{GDBN} and C
7827 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
7831 @subsubsection C and C@t{++} operators
7833 @cindex C and C@t{++} operators
7835 Operators must be defined on values of specific types. For instance,
7836 @code{+} is defined on numbers, but not on structures. Operators are
7837 often defined on groups of types.
7839 For the purposes of C and C@t{++}, the following definitions hold:
7844 @emph{Integral types} include @code{int} with any of its storage-class
7845 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
7848 @emph{Floating-point types} include @code{float}, @code{double}, and
7849 @code{long double} (if supported by the target platform).
7852 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
7855 @emph{Scalar types} include all of the above.
7860 The following operators are supported. They are listed here
7861 in order of increasing precedence:
7865 The comma or sequencing operator. Expressions in a comma-separated list
7866 are evaluated from left to right, with the result of the entire
7867 expression being the last expression evaluated.
7870 Assignment. The value of an assignment expression is the value
7871 assigned. Defined on scalar types.
7874 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
7875 and translated to @w{@code{@var{a} = @var{a op b}}}.
7876 @w{@code{@var{op}=}} and @code{=} have the same precedence.
7877 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
7878 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
7881 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
7882 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
7886 Logical @sc{or}. Defined on integral types.
7889 Logical @sc{and}. Defined on integral types.
7892 Bitwise @sc{or}. Defined on integral types.
7895 Bitwise exclusive-@sc{or}. Defined on integral types.
7898 Bitwise @sc{and}. Defined on integral types.
7901 Equality and inequality. Defined on scalar types. The value of these
7902 expressions is 0 for false and non-zero for true.
7904 @item <@r{, }>@r{, }<=@r{, }>=
7905 Less than, greater than, less than or equal, greater than or equal.
7906 Defined on scalar types. The value of these expressions is 0 for false
7907 and non-zero for true.
7910 left shift, and right shift. Defined on integral types.
7913 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
7916 Addition and subtraction. Defined on integral types, floating-point types and
7919 @item *@r{, }/@r{, }%
7920 Multiplication, division, and modulus. Multiplication and division are
7921 defined on integral and floating-point types. Modulus is defined on
7925 Increment and decrement. When appearing before a variable, the
7926 operation is performed before the variable is used in an expression;
7927 when appearing after it, the variable's value is used before the
7928 operation takes place.
7931 Pointer dereferencing. Defined on pointer types. Same precedence as
7935 Address operator. Defined on variables. Same precedence as @code{++}.
7937 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
7938 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
7939 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
7940 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
7944 Negative. Defined on integral and floating-point types. Same
7945 precedence as @code{++}.
7948 Logical negation. Defined on integral types. Same precedence as
7952 Bitwise complement operator. Defined on integral types. Same precedence as
7957 Structure member, and pointer-to-structure member. For convenience,
7958 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
7959 pointer based on the stored type information.
7960 Defined on @code{struct} and @code{union} data.
7963 Dereferences of pointers to members.
7966 Array indexing. @code{@var{a}[@var{i}]} is defined as
7967 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
7970 Function parameter list. Same precedence as @code{->}.
7973 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
7974 and @code{class} types.
7977 Doubled colons also represent the @value{GDBN} scope operator
7978 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
7982 If an operator is redefined in the user code, @value{GDBN} usually
7983 attempts to invoke the redefined version instead of using the operator's
7991 @subsubsection C and C@t{++} constants
7993 @cindex C and C@t{++} constants
7995 @value{GDBN} allows you to express the constants of C and C@t{++} in the
8000 Integer constants are a sequence of digits. Octal constants are
8001 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
8002 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
8003 @samp{l}, specifying that the constant should be treated as a
8007 Floating point constants are a sequence of digits, followed by a decimal
8008 point, followed by a sequence of digits, and optionally followed by an
8009 exponent. An exponent is of the form:
8010 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
8011 sequence of digits. The @samp{+} is optional for positive exponents.
8012 A floating-point constant may also end with a letter @samp{f} or
8013 @samp{F}, specifying that the constant should be treated as being of
8014 the @code{float} (as opposed to the default @code{double}) type; or with
8015 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
8019 Enumerated constants consist of enumerated identifiers, or their
8020 integral equivalents.
8023 Character constants are a single character surrounded by single quotes
8024 (@code{'}), or a number---the ordinal value of the corresponding character
8025 (usually its @sc{ascii} value). Within quotes, the single character may
8026 be represented by a letter or by @dfn{escape sequences}, which are of
8027 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
8028 of the character's ordinal value; or of the form @samp{\@var{x}}, where
8029 @samp{@var{x}} is a predefined special character---for example,
8030 @samp{\n} for newline.
8033 String constants are a sequence of character constants surrounded by
8034 double quotes (@code{"}). Any valid character constant (as described
8035 above) may appear. Double quotes within the string must be preceded by
8036 a backslash, so for instance @samp{"a\"b'c"} is a string of five
8040 Pointer constants are an integral value. You can also write pointers
8041 to constants using the C operator @samp{&}.
8044 Array constants are comma-separated lists surrounded by braces @samp{@{}
8045 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
8046 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
8047 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
8051 * C plus plus expressions::
8058 @node C plus plus expressions
8059 @subsubsection C@t{++} expressions
8061 @cindex expressions in C@t{++}
8062 @value{GDBN} expression handling can interpret most C@t{++} expressions.
8064 @cindex debugging C@t{++} programs
8065 @cindex C@t{++} compilers
8066 @cindex debug formats and C@t{++}
8067 @cindex @value{NGCC} and C@t{++}
8069 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
8070 proper compiler and the proper debug format. Currently, @value{GDBN}
8071 works best when debugging C@t{++} code that is compiled with
8072 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
8073 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
8074 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
8075 stabs+ as their default debug format, so you usually don't need to
8076 specify a debug format explicitly. Other compilers and/or debug formats
8077 are likely to work badly or not at all when using @value{GDBN} to debug
8083 @cindex member functions
8085 Member function calls are allowed; you can use expressions like
8088 count = aml->GetOriginal(x, y)
8091 @vindex this@r{, inside C@t{++} member functions}
8092 @cindex namespace in C@t{++}
8094 While a member function is active (in the selected stack frame), your
8095 expressions have the same namespace available as the member function;
8096 that is, @value{GDBN} allows implicit references to the class instance
8097 pointer @code{this} following the same rules as C@t{++}.
8099 @cindex call overloaded functions
8100 @cindex overloaded functions, calling
8101 @cindex type conversions in C@t{++}
8103 You can call overloaded functions; @value{GDBN} resolves the function
8104 call to the right definition, with some restrictions. @value{GDBN} does not
8105 perform overload resolution involving user-defined type conversions,
8106 calls to constructors, or instantiations of templates that do not exist
8107 in the program. It also cannot handle ellipsis argument lists or
8110 It does perform integral conversions and promotions, floating-point
8111 promotions, arithmetic conversions, pointer conversions, conversions of
8112 class objects to base classes, and standard conversions such as those of
8113 functions or arrays to pointers; it requires an exact match on the
8114 number of function arguments.
8116 Overload resolution is always performed, unless you have specified
8117 @code{set overload-resolution off}. @xref{Debugging C plus plus,
8118 ,@value{GDBN} features for C@t{++}}.
8120 You must specify @code{set overload-resolution off} in order to use an
8121 explicit function signature to call an overloaded function, as in
8123 p 'foo(char,int)'('x', 13)
8126 The @value{GDBN} command-completion facility can simplify this;
8127 see @ref{Completion, ,Command completion}.
8129 @cindex reference declarations
8131 @value{GDBN} understands variables declared as C@t{++} references; you can use
8132 them in expressions just as you do in C@t{++} source---they are automatically
8135 In the parameter list shown when @value{GDBN} displays a frame, the values of
8136 reference variables are not displayed (unlike other variables); this
8137 avoids clutter, since references are often used for large structures.
8138 The @emph{address} of a reference variable is always shown, unless
8139 you have specified @samp{set print address off}.
8142 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
8143 expressions can use it just as expressions in your program do. Since
8144 one scope may be defined in another, you can use @code{::} repeatedly if
8145 necessary, for example in an expression like
8146 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
8147 resolving name scope by reference to source files, in both C and C@t{++}
8148 debugging (@pxref{Variables, ,Program variables}).
8151 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
8152 calling virtual functions correctly, printing out virtual bases of
8153 objects, calling functions in a base subobject, casting objects, and
8154 invoking user-defined operators.
8157 @subsubsection C and C@t{++} defaults
8159 @cindex C and C@t{++} defaults
8161 If you allow @value{GDBN} to set type and range checking automatically, they
8162 both default to @code{off} whenever the working language changes to
8163 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
8164 selects the working language.
8166 If you allow @value{GDBN} to set the language automatically, it
8167 recognizes source files whose names end with @file{.c}, @file{.C}, or
8168 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
8169 these files, it sets the working language to C or C@t{++}.
8170 @xref{Automatically, ,Having @value{GDBN} infer the source language},
8171 for further details.
8173 @c Type checking is (a) primarily motivated by Modula-2, and (b)
8174 @c unimplemented. If (b) changes, it might make sense to let this node
8175 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
8178 @subsubsection C and C@t{++} type and range checks
8180 @cindex C and C@t{++} checks
8182 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
8183 is not used. However, if you turn type checking on, @value{GDBN}
8184 considers two variables type equivalent if:
8188 The two variables are structured and have the same structure, union, or
8192 The two variables have the same type name, or types that have been
8193 declared equivalent through @code{typedef}.
8196 @c leaving this out because neither J Gilmore nor R Pesch understand it.
8199 The two @code{struct}, @code{union}, or @code{enum} variables are
8200 declared in the same declaration. (Note: this may not be true for all C
8205 Range checking, if turned on, is done on mathematical operations. Array
8206 indices are not checked, since they are often used to index a pointer
8207 that is not itself an array.
8210 @subsubsection @value{GDBN} and C
8212 The @code{set print union} and @code{show print union} commands apply to
8213 the @code{union} type. When set to @samp{on}, any @code{union} that is
8214 inside a @code{struct} or @code{class} is also printed. Otherwise, it
8215 appears as @samp{@{...@}}.
8217 The @code{@@} operator aids in the debugging of dynamic arrays, formed
8218 with pointers and a memory allocation function. @xref{Expressions,
8222 * Debugging C plus plus::
8225 @node Debugging C plus plus
8226 @subsubsection @value{GDBN} features for C@t{++}
8228 @cindex commands for C@t{++}
8230 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
8231 designed specifically for use with C@t{++}. Here is a summary:
8234 @cindex break in overloaded functions
8235 @item @r{breakpoint menus}
8236 When you want a breakpoint in a function whose name is overloaded,
8237 @value{GDBN} breakpoint menus help you specify which function definition
8238 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
8240 @cindex overloading in C@t{++}
8241 @item rbreak @var{regex}
8242 Setting breakpoints using regular expressions is helpful for setting
8243 breakpoints on overloaded functions that are not members of any special
8245 @xref{Set Breaks, ,Setting breakpoints}.
8247 @cindex C@t{++} exception handling
8250 Debug C@t{++} exception handling using these commands. @xref{Set
8251 Catchpoints, , Setting catchpoints}.
8254 @item ptype @var{typename}
8255 Print inheritance relationships as well as other information for type
8257 @xref{Symbols, ,Examining the Symbol Table}.
8259 @cindex C@t{++} symbol display
8260 @item set print demangle
8261 @itemx show print demangle
8262 @itemx set print asm-demangle
8263 @itemx show print asm-demangle
8264 Control whether C@t{++} symbols display in their source form, both when
8265 displaying code as C@t{++} source and when displaying disassemblies.
8266 @xref{Print Settings, ,Print settings}.
8268 @item set print object
8269 @itemx show print object
8270 Choose whether to print derived (actual) or declared types of objects.
8271 @xref{Print Settings, ,Print settings}.
8273 @item set print vtbl
8274 @itemx show print vtbl
8275 Control the format for printing virtual function tables.
8276 @xref{Print Settings, ,Print settings}.
8277 (The @code{vtbl} commands do not work on programs compiled with the HP
8278 ANSI C@t{++} compiler (@code{aCC}).)
8280 @kindex set overload-resolution
8281 @cindex overloaded functions, overload resolution
8282 @item set overload-resolution on
8283 Enable overload resolution for C@t{++} expression evaluation. The default
8284 is on. For overloaded functions, @value{GDBN} evaluates the arguments
8285 and searches for a function whose signature matches the argument types,
8286 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
8287 expressions}, for details). If it cannot find a match, it emits a
8290 @item set overload-resolution off
8291 Disable overload resolution for C@t{++} expression evaluation. For
8292 overloaded functions that are not class member functions, @value{GDBN}
8293 chooses the first function of the specified name that it finds in the
8294 symbol table, whether or not its arguments are of the correct type. For
8295 overloaded functions that are class member functions, @value{GDBN}
8296 searches for a function whose signature @emph{exactly} matches the
8299 @item @r{Overloaded symbol names}
8300 You can specify a particular definition of an overloaded symbol, using
8301 the same notation that is used to declare such symbols in C@t{++}: type
8302 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
8303 also use the @value{GDBN} command-line word completion facilities to list the
8304 available choices, or to finish the type list for you.
8305 @xref{Completion,, Command completion}, for details on how to do this.
8309 @subsection Objective-C
8312 This section provides information about some commands and command
8313 options that are useful for debugging Objective-C code.
8316 * Method Names in Commands::
8317 * The Print Command with Objective-C::
8320 @node Method Names in Commands, The Print Command with Objective-C, Objective-C, Objective-C
8321 @subsubsection Method Names in Commands
8323 The following commands have been extended to accept Objective-C method
8324 names as line specifications:
8326 @kindex clear@r{, and Objective-C}
8327 @kindex break@r{, and Objective-C}
8328 @kindex info line@r{, and Objective-C}
8329 @kindex jump@r{, and Objective-C}
8330 @kindex list@r{, and Objective-C}
8334 @item @code{info line}
8339 A fully qualified Objective-C method name is specified as
8342 -[@var{Class} @var{methodName}]
8345 where the minus sign is used to indicate an instance method and a plus
8346 sign (not shown) is used to indicate a class method. The
8347 class name @var{Class} and method name @var{methoName} are enclosed in
8348 brackets, similar to the way messages are specified in Objective-C source
8349 code. For example, to set a breakpoint at the @code{create} instance method of
8350 class @code{Fruit} in the program currently being debugged, enter:
8353 break -[Fruit create]
8356 To list ten program lines around the @code{initialize} class method,
8360 list +[NSText initialize]
8363 In the current version of GDB, the plus or minus sign is required. In
8364 future versions of GDB, the plus or minus sign will be optional, but you
8365 can use it to narrow the search. It is also possible to specify just a
8372 You must specify the complete method name, including any colons. If
8373 your program's source files contain more than one @code{create} method,
8374 you'll be presented with a numbered list of classes that implement that
8375 method. Indicate your choice by number, or type @samp{0} to exit if
8378 As another example, to clear a breakpoint established at the
8379 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
8382 clear -[NSWindow makeKeyAndOrderFront:]
8385 @node The Print Command with Objective-C
8386 @subsubsection The Print Command With Objective-C
8388 The print command has also been extended to accept methods. For example:
8391 print -[object hash]
8394 @cindex print an Objective-C object description
8395 will tell gdb to send the -hash message to object and print the
8396 result. Also an additional command has been added, @code{print-object}
8397 or @code{po} for short, which is meant to print the description of an
8398 object. However, this command may only work with certain Objective-C
8399 libraries that have a particular hook function, called
8400 @code{_NSPrintForDebugger} defined.
8402 @node Modula-2, , Objective-C, Support
8403 @subsection Modula-2
8405 @cindex Modula-2, @value{GDBN} support
8407 The extensions made to @value{GDBN} to support Modula-2 only support
8408 output from the @sc{gnu} Modula-2 compiler (which is currently being
8409 developed). Other Modula-2 compilers are not currently supported, and
8410 attempting to debug executables produced by them is most likely
8411 to give an error as @value{GDBN} reads in the executable's symbol
8414 @cindex expressions in Modula-2
8416 * M2 Operators:: Built-in operators
8417 * Built-In Func/Proc:: Built-in functions and procedures
8418 * M2 Constants:: Modula-2 constants
8419 * M2 Defaults:: Default settings for Modula-2
8420 * Deviations:: Deviations from standard Modula-2
8421 * M2 Checks:: Modula-2 type and range checks
8422 * M2 Scope:: The scope operators @code{::} and @code{.}
8423 * GDB/M2:: @value{GDBN} and Modula-2
8427 @subsubsection Operators
8428 @cindex Modula-2 operators
8430 Operators must be defined on values of specific types. For instance,
8431 @code{+} is defined on numbers, but not on structures. Operators are
8432 often defined on groups of types. For the purposes of Modula-2, the
8433 following definitions hold:
8438 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
8442 @emph{Character types} consist of @code{CHAR} and its subranges.
8445 @emph{Floating-point types} consist of @code{REAL}.
8448 @emph{Pointer types} consist of anything declared as @code{POINTER TO
8452 @emph{Scalar types} consist of all of the above.
8455 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
8458 @emph{Boolean types} consist of @code{BOOLEAN}.
8462 The following operators are supported, and appear in order of
8463 increasing precedence:
8467 Function argument or array index separator.
8470 Assignment. The value of @var{var} @code{:=} @var{value} is
8474 Less than, greater than on integral, floating-point, or enumerated
8478 Less than or equal to, greater than or equal to
8479 on integral, floating-point and enumerated types, or set inclusion on
8480 set types. Same precedence as @code{<}.
8482 @item =@r{, }<>@r{, }#
8483 Equality and two ways of expressing inequality, valid on scalar types.
8484 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
8485 available for inequality, since @code{#} conflicts with the script
8489 Set membership. Defined on set types and the types of their members.
8490 Same precedence as @code{<}.
8493 Boolean disjunction. Defined on boolean types.
8496 Boolean conjunction. Defined on boolean types.
8499 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8502 Addition and subtraction on integral and floating-point types, or union
8503 and difference on set types.
8506 Multiplication on integral and floating-point types, or set intersection
8510 Division on floating-point types, or symmetric set difference on set
8511 types. Same precedence as @code{*}.
8514 Integer division and remainder. Defined on integral types. Same
8515 precedence as @code{*}.
8518 Negative. Defined on @code{INTEGER} and @code{REAL} data.
8521 Pointer dereferencing. Defined on pointer types.
8524 Boolean negation. Defined on boolean types. Same precedence as
8528 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
8529 precedence as @code{^}.
8532 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
8535 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
8539 @value{GDBN} and Modula-2 scope operators.
8543 @emph{Warning:} Sets and their operations are not yet supported, so @value{GDBN}
8544 treats the use of the operator @code{IN}, or the use of operators
8545 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
8546 @code{<=}, and @code{>=} on sets as an error.
8550 @node Built-In Func/Proc
8551 @subsubsection Built-in functions and procedures
8552 @cindex Modula-2 built-ins
8554 Modula-2 also makes available several built-in procedures and functions.
8555 In describing these, the following metavariables are used:
8560 represents an @code{ARRAY} variable.
8563 represents a @code{CHAR} constant or variable.
8566 represents a variable or constant of integral type.
8569 represents an identifier that belongs to a set. Generally used in the
8570 same function with the metavariable @var{s}. The type of @var{s} should
8571 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
8574 represents a variable or constant of integral or floating-point type.
8577 represents a variable or constant of floating-point type.
8583 represents a variable.
8586 represents a variable or constant of one of many types. See the
8587 explanation of the function for details.
8590 All Modula-2 built-in procedures also return a result, described below.
8594 Returns the absolute value of @var{n}.
8597 If @var{c} is a lower case letter, it returns its upper case
8598 equivalent, otherwise it returns its argument.
8601 Returns the character whose ordinal value is @var{i}.
8604 Decrements the value in the variable @var{v} by one. Returns the new value.
8606 @item DEC(@var{v},@var{i})
8607 Decrements the value in the variable @var{v} by @var{i}. Returns the
8610 @item EXCL(@var{m},@var{s})
8611 Removes the element @var{m} from the set @var{s}. Returns the new
8614 @item FLOAT(@var{i})
8615 Returns the floating point equivalent of the integer @var{i}.
8618 Returns the index of the last member of @var{a}.
8621 Increments the value in the variable @var{v} by one. Returns the new value.
8623 @item INC(@var{v},@var{i})
8624 Increments the value in the variable @var{v} by @var{i}. Returns the
8627 @item INCL(@var{m},@var{s})
8628 Adds the element @var{m} to the set @var{s} if it is not already
8629 there. Returns the new set.
8632 Returns the maximum value of the type @var{t}.
8635 Returns the minimum value of the type @var{t}.
8638 Returns boolean TRUE if @var{i} is an odd number.
8641 Returns the ordinal value of its argument. For example, the ordinal
8642 value of a character is its @sc{ascii} value (on machines supporting the
8643 @sc{ascii} character set). @var{x} must be of an ordered type, which include
8644 integral, character and enumerated types.
8647 Returns the size of its argument. @var{x} can be a variable or a type.
8649 @item TRUNC(@var{r})
8650 Returns the integral part of @var{r}.
8652 @item VAL(@var{t},@var{i})
8653 Returns the member of the type @var{t} whose ordinal value is @var{i}.
8657 @emph{Warning:} Sets and their operations are not yet supported, so
8658 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
8662 @cindex Modula-2 constants
8664 @subsubsection Constants
8666 @value{GDBN} allows you to express the constants of Modula-2 in the following
8672 Integer constants are simply a sequence of digits. When used in an
8673 expression, a constant is interpreted to be type-compatible with the
8674 rest of the expression. Hexadecimal integers are specified by a
8675 trailing @samp{H}, and octal integers by a trailing @samp{B}.
8678 Floating point constants appear as a sequence of digits, followed by a
8679 decimal point and another sequence of digits. An optional exponent can
8680 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
8681 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
8682 digits of the floating point constant must be valid decimal (base 10)
8686 Character constants consist of a single character enclosed by a pair of
8687 like quotes, either single (@code{'}) or double (@code{"}). They may
8688 also be expressed by their ordinal value (their @sc{ascii} value, usually)
8689 followed by a @samp{C}.
8692 String constants consist of a sequence of characters enclosed by a
8693 pair of like quotes, either single (@code{'}) or double (@code{"}).
8694 Escape sequences in the style of C are also allowed. @xref{C
8695 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
8699 Enumerated constants consist of an enumerated identifier.
8702 Boolean constants consist of the identifiers @code{TRUE} and
8706 Pointer constants consist of integral values only.
8709 Set constants are not yet supported.
8713 @subsubsection Modula-2 defaults
8714 @cindex Modula-2 defaults
8716 If type and range checking are set automatically by @value{GDBN}, they
8717 both default to @code{on} whenever the working language changes to
8718 Modula-2. This happens regardless of whether you or @value{GDBN}
8719 selected the working language.
8721 If you allow @value{GDBN} to set the language automatically, then entering
8722 code compiled from a file whose name ends with @file{.mod} sets the
8723 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
8724 the language automatically}, for further details.
8727 @subsubsection Deviations from standard Modula-2
8728 @cindex Modula-2, deviations from
8730 A few changes have been made to make Modula-2 programs easier to debug.
8731 This is done primarily via loosening its type strictness:
8735 Unlike in standard Modula-2, pointer constants can be formed by
8736 integers. This allows you to modify pointer variables during
8737 debugging. (In standard Modula-2, the actual address contained in a
8738 pointer variable is hidden from you; it can only be modified
8739 through direct assignment to another pointer variable or expression that
8740 returned a pointer.)
8743 C escape sequences can be used in strings and characters to represent
8744 non-printable characters. @value{GDBN} prints out strings with these
8745 escape sequences embedded. Single non-printable characters are
8746 printed using the @samp{CHR(@var{nnn})} format.
8749 The assignment operator (@code{:=}) returns the value of its right-hand
8753 All built-in procedures both modify @emph{and} return their argument.
8757 @subsubsection Modula-2 type and range checks
8758 @cindex Modula-2 checks
8761 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
8764 @c FIXME remove warning when type/range checks added
8766 @value{GDBN} considers two Modula-2 variables type equivalent if:
8770 They are of types that have been declared equivalent via a @code{TYPE
8771 @var{t1} = @var{t2}} statement
8774 They have been declared on the same line. (Note: This is true of the
8775 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
8778 As long as type checking is enabled, any attempt to combine variables
8779 whose types are not equivalent is an error.
8781 Range checking is done on all mathematical operations, assignment, array
8782 index bounds, and all built-in functions and procedures.
8785 @subsubsection The scope operators @code{::} and @code{.}
8787 @cindex @code{.}, Modula-2 scope operator
8788 @cindex colon, doubled as scope operator
8790 @vindex colon-colon@r{, in Modula-2}
8791 @c Info cannot handle :: but TeX can.
8794 @vindex ::@r{, in Modula-2}
8797 There are a few subtle differences between the Modula-2 scope operator
8798 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
8803 @var{module} . @var{id}
8804 @var{scope} :: @var{id}
8808 where @var{scope} is the name of a module or a procedure,
8809 @var{module} the name of a module, and @var{id} is any declared
8810 identifier within your program, except another module.
8812 Using the @code{::} operator makes @value{GDBN} search the scope
8813 specified by @var{scope} for the identifier @var{id}. If it is not
8814 found in the specified scope, then @value{GDBN} searches all scopes
8815 enclosing the one specified by @var{scope}.
8817 Using the @code{.} operator makes @value{GDBN} search the current scope for
8818 the identifier specified by @var{id} that was imported from the
8819 definition module specified by @var{module}. With this operator, it is
8820 an error if the identifier @var{id} was not imported from definition
8821 module @var{module}, or if @var{id} is not an identifier in
8825 @subsubsection @value{GDBN} and Modula-2
8827 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
8828 Five subcommands of @code{set print} and @code{show print} apply
8829 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
8830 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
8831 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
8832 analogue in Modula-2.
8834 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
8835 with any language, is not useful with Modula-2. Its
8836 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
8837 created in Modula-2 as they can in C or C@t{++}. However, because an
8838 address can be specified by an integral constant, the construct
8839 @samp{@{@var{type}@}@var{adrexp}} is still useful.
8841 @cindex @code{#} in Modula-2
8842 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
8843 interpreted as the beginning of a comment. Use @code{<>} instead.
8846 @chapter Examining the Symbol Table
8848 The commands described in this chapter allow you to inquire about the
8849 symbols (names of variables, functions and types) defined in your
8850 program. This information is inherent in the text of your program and
8851 does not change as your program executes. @value{GDBN} finds it in your
8852 program's symbol table, in the file indicated when you started @value{GDBN}
8853 (@pxref{File Options, ,Choosing files}), or by one of the
8854 file-management commands (@pxref{Files, ,Commands to specify files}).
8856 @cindex symbol names
8857 @cindex names of symbols
8858 @cindex quoting names
8859 Occasionally, you may need to refer to symbols that contain unusual
8860 characters, which @value{GDBN} ordinarily treats as word delimiters. The
8861 most frequent case is in referring to static variables in other
8862 source files (@pxref{Variables,,Program variables}). File names
8863 are recorded in object files as debugging symbols, but @value{GDBN} would
8864 ordinarily parse a typical file name, like @file{foo.c}, as the three words
8865 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
8866 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
8873 looks up the value of @code{x} in the scope of the file @file{foo.c}.
8876 @kindex info address
8877 @cindex address of a symbol
8878 @item info address @var{symbol}
8879 Describe where the data for @var{symbol} is stored. For a register
8880 variable, this says which register it is kept in. For a non-register
8881 local variable, this prints the stack-frame offset at which the variable
8884 Note the contrast with @samp{print &@var{symbol}}, which does not work
8885 at all for a register variable, and for a stack local variable prints
8886 the exact address of the current instantiation of the variable.
8889 @cindex symbol from address
8890 @item info symbol @var{addr}
8891 Print the name of a symbol which is stored at the address @var{addr}.
8892 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
8893 nearest symbol and an offset from it:
8896 (@value{GDBP}) info symbol 0x54320
8897 _initialize_vx + 396 in section .text
8901 This is the opposite of the @code{info address} command. You can use
8902 it to find out the name of a variable or a function given its address.
8905 @item whatis @var{expr}
8906 Print the data type of expression @var{expr}. @var{expr} is not
8907 actually evaluated, and any side-effecting operations (such as
8908 assignments or function calls) inside it do not take place.
8909 @xref{Expressions, ,Expressions}.
8912 Print the data type of @code{$}, the last value in the value history.
8915 @item ptype @var{typename}
8916 Print a description of data type @var{typename}. @var{typename} may be
8917 the name of a type, or for C code it may have the form @samp{class
8918 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
8919 @var{union-tag}} or @samp{enum @var{enum-tag}}.
8921 @item ptype @var{expr}
8923 Print a description of the type of expression @var{expr}. @code{ptype}
8924 differs from @code{whatis} by printing a detailed description, instead
8925 of just the name of the type.
8927 For example, for this variable declaration:
8930 struct complex @{double real; double imag;@} v;
8934 the two commands give this output:
8938 (@value{GDBP}) whatis v
8939 type = struct complex
8940 (@value{GDBP}) ptype v
8941 type = struct complex @{
8949 As with @code{whatis}, using @code{ptype} without an argument refers to
8950 the type of @code{$}, the last value in the value history.
8953 @item info types @var{regexp}
8955 Print a brief description of all types whose names match @var{regexp}
8956 (or all types in your program, if you supply no argument). Each
8957 complete typename is matched as though it were a complete line; thus,
8958 @samp{i type value} gives information on all types in your program whose
8959 names include the string @code{value}, but @samp{i type ^value$} gives
8960 information only on types whose complete name is @code{value}.
8962 This command differs from @code{ptype} in two ways: first, like
8963 @code{whatis}, it does not print a detailed description; second, it
8964 lists all source files where a type is defined.
8967 @cindex local variables
8968 @item info scope @var{addr}
8969 List all the variables local to a particular scope. This command
8970 accepts a location---a function name, a source line, or an address
8971 preceded by a @samp{*}, and prints all the variables local to the
8972 scope defined by that location. For example:
8975 (@value{GDBP}) @b{info scope command_line_handler}
8976 Scope for command_line_handler:
8977 Symbol rl is an argument at stack/frame offset 8, length 4.
8978 Symbol linebuffer is in static storage at address 0x150a18, length 4.
8979 Symbol linelength is in static storage at address 0x150a1c, length 4.
8980 Symbol p is a local variable in register $esi, length 4.
8981 Symbol p1 is a local variable in register $ebx, length 4.
8982 Symbol nline is a local variable in register $edx, length 4.
8983 Symbol repeat is a local variable at frame offset -8, length 4.
8987 This command is especially useful for determining what data to collect
8988 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
8993 Show information about the current source file---that is, the source file for
8994 the function containing the current point of execution:
8997 the name of the source file, and the directory containing it,
8999 the directory it was compiled in,
9001 its length, in lines,
9003 which programming language it is written in,
9005 whether the executable includes debugging information for that file, and
9006 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
9008 whether the debugging information includes information about
9009 preprocessor macros.
9013 @kindex info sources
9015 Print the names of all source files in your program for which there is
9016 debugging information, organized into two lists: files whose symbols
9017 have already been read, and files whose symbols will be read when needed.
9019 @kindex info functions
9020 @item info functions
9021 Print the names and data types of all defined functions.
9023 @item info functions @var{regexp}
9024 Print the names and data types of all defined functions
9025 whose names contain a match for regular expression @var{regexp}.
9026 Thus, @samp{info fun step} finds all functions whose names
9027 include @code{step}; @samp{info fun ^step} finds those whose names
9028 start with @code{step}. If a function name contains characters
9029 that conflict with the regular expression language (eg.
9030 @samp{operator*()}), they may be quoted with a backslash.
9032 @kindex info variables
9033 @item info variables
9034 Print the names and data types of all variables that are declared
9035 outside of functions (i.e.@: excluding local variables).
9037 @item info variables @var{regexp}
9038 Print the names and data types of all variables (except for local
9039 variables) whose names contain a match for regular expression
9042 @kindex info classes
9044 @itemx info classes @var{regexp}
9045 Display all Objective-C classes in your program, or
9046 (with the @var{regexp} argument) all those matching a particular regular
9049 @kindex info selectors
9050 @item info selectors
9051 @itemx info selectors @var{regexp}
9052 Display all Objective-C selectors in your program, or
9053 (with the @var{regexp} argument) all those matching a particular regular
9057 This was never implemented.
9058 @kindex info methods
9060 @itemx info methods @var{regexp}
9061 The @code{info methods} command permits the user to examine all defined
9062 methods within C@t{++} program, or (with the @var{regexp} argument) a
9063 specific set of methods found in the various C@t{++} classes. Many
9064 C@t{++} classes provide a large number of methods. Thus, the output
9065 from the @code{ptype} command can be overwhelming and hard to use. The
9066 @code{info-methods} command filters the methods, printing only those
9067 which match the regular-expression @var{regexp}.
9070 @cindex reloading symbols
9071 Some systems allow individual object files that make up your program to
9072 be replaced without stopping and restarting your program. For example,
9073 in VxWorks you can simply recompile a defective object file and keep on
9074 running. If you are running on one of these systems, you can allow
9075 @value{GDBN} to reload the symbols for automatically relinked modules:
9078 @kindex set symbol-reloading
9079 @item set symbol-reloading on
9080 Replace symbol definitions for the corresponding source file when an
9081 object file with a particular name is seen again.
9083 @item set symbol-reloading off
9084 Do not replace symbol definitions when encountering object files of the
9085 same name more than once. This is the default state; if you are not
9086 running on a system that permits automatic relinking of modules, you
9087 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
9088 may discard symbols when linking large programs, that may contain
9089 several modules (from different directories or libraries) with the same
9092 @kindex show symbol-reloading
9093 @item show symbol-reloading
9094 Show the current @code{on} or @code{off} setting.
9097 @kindex set opaque-type-resolution
9098 @item set opaque-type-resolution on
9099 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
9100 declared as a pointer to a @code{struct}, @code{class}, or
9101 @code{union}---for example, @code{struct MyType *}---that is used in one
9102 source file although the full declaration of @code{struct MyType} is in
9103 another source file. The default is on.
9105 A change in the setting of this subcommand will not take effect until
9106 the next time symbols for a file are loaded.
9108 @item set opaque-type-resolution off
9109 Tell @value{GDBN} not to resolve opaque types. In this case, the type
9110 is printed as follows:
9112 @{<no data fields>@}
9115 @kindex show opaque-type-resolution
9116 @item show opaque-type-resolution
9117 Show whether opaque types are resolved or not.
9119 @kindex maint print symbols
9121 @kindex maint print psymbols
9122 @cindex partial symbol dump
9123 @item maint print symbols @var{filename}
9124 @itemx maint print psymbols @var{filename}
9125 @itemx maint print msymbols @var{filename}
9126 Write a dump of debugging symbol data into the file @var{filename}.
9127 These commands are used to debug the @value{GDBN} symbol-reading code. Only
9128 symbols with debugging data are included. If you use @samp{maint print
9129 symbols}, @value{GDBN} includes all the symbols for which it has already
9130 collected full details: that is, @var{filename} reflects symbols for
9131 only those files whose symbols @value{GDBN} has read. You can use the
9132 command @code{info sources} to find out which files these are. If you
9133 use @samp{maint print psymbols} instead, the dump shows information about
9134 symbols that @value{GDBN} only knows partially---that is, symbols defined in
9135 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
9136 @samp{maint print msymbols} dumps just the minimal symbol information
9137 required for each object file from which @value{GDBN} has read some symbols.
9138 @xref{Files, ,Commands to specify files}, for a discussion of how
9139 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
9141 @kindex maint info symtabs
9142 @kindex maint info psymtabs
9143 @cindex listing @value{GDBN}'s internal symbol tables
9144 @cindex symbol tables, listing @value{GDBN}'s internal
9145 @cindex full symbol tables, listing @value{GDBN}'s internal
9146 @cindex partial symbol tables, listing @value{GDBN}'s internal
9147 @item maint info symtabs @r{[} @var{regexp} @r{]}
9148 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
9150 List the @code{struct symtab} or @code{struct partial_symtab}
9151 structures whose names match @var{regexp}. If @var{regexp} is not
9152 given, list them all. The output includes expressions which you can
9153 copy into a @value{GDBN} debugging this one to examine a particular
9154 structure in more detail. For example:
9157 (@value{GDBP}) maint info psymtabs dwarf2read
9158 @{ objfile /home/gnu/build/gdb/gdb
9159 ((struct objfile *) 0x82e69d0)
9160 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
9161 ((struct partial_symtab *) 0x8474b10)
9164 text addresses 0x814d3c8 -- 0x8158074
9165 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
9166 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
9170 (@value{GDBP}) maint info symtabs
9174 We see that there is one partial symbol table whose filename contains
9175 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
9176 and we see that @value{GDBN} has not read in any symtabs yet at all.
9177 If we set a breakpoint on a function, that will cause @value{GDBN} to
9178 read the symtab for the compilation unit containing that function:
9181 (@value{GDBP}) break dwarf2_psymtab_to_symtab
9182 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
9184 (@value{GDBP}) maint info symtabs
9185 @{ objfile /home/gnu/build/gdb/gdb
9186 ((struct objfile *) 0x82e69d0)
9187 @{ symtab /home/gnu/src/gdb/dwarf2read.c
9188 ((struct symtab *) 0x86c1f38)
9191 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
9201 @chapter Altering Execution
9203 Once you think you have found an error in your program, you might want to
9204 find out for certain whether correcting the apparent error would lead to
9205 correct results in the rest of the run. You can find the answer by
9206 experiment, using the @value{GDBN} features for altering execution of the
9209 For example, you can store new values into variables or memory
9210 locations, give your program a signal, restart it at a different
9211 address, or even return prematurely from a function.
9214 * Assignment:: Assignment to variables
9215 * Jumping:: Continuing at a different address
9216 * Signaling:: Giving your program a signal
9217 * Returning:: Returning from a function
9218 * Calling:: Calling your program's functions
9219 * Patching:: Patching your program
9223 @section Assignment to variables
9226 @cindex setting variables
9227 To alter the value of a variable, evaluate an assignment expression.
9228 @xref{Expressions, ,Expressions}. For example,
9235 stores the value 4 into the variable @code{x}, and then prints the
9236 value of the assignment expression (which is 4).
9237 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
9238 information on operators in supported languages.
9240 @kindex set variable
9241 @cindex variables, setting
9242 If you are not interested in seeing the value of the assignment, use the
9243 @code{set} command instead of the @code{print} command. @code{set} is
9244 really the same as @code{print} except that the expression's value is
9245 not printed and is not put in the value history (@pxref{Value History,
9246 ,Value history}). The expression is evaluated only for its effects.
9248 If the beginning of the argument string of the @code{set} command
9249 appears identical to a @code{set} subcommand, use the @code{set
9250 variable} command instead of just @code{set}. This command is identical
9251 to @code{set} except for its lack of subcommands. For example, if your
9252 program has a variable @code{width}, you get an error if you try to set
9253 a new value with just @samp{set width=13}, because @value{GDBN} has the
9254 command @code{set width}:
9257 (@value{GDBP}) whatis width
9259 (@value{GDBP}) p width
9261 (@value{GDBP}) set width=47
9262 Invalid syntax in expression.
9266 The invalid expression, of course, is @samp{=47}. In
9267 order to actually set the program's variable @code{width}, use
9270 (@value{GDBP}) set var width=47
9273 Because the @code{set} command has many subcommands that can conflict
9274 with the names of program variables, it is a good idea to use the
9275 @code{set variable} command instead of just @code{set}. For example, if
9276 your program has a variable @code{g}, you run into problems if you try
9277 to set a new value with just @samp{set g=4}, because @value{GDBN} has
9278 the command @code{set gnutarget}, abbreviated @code{set g}:
9282 (@value{GDBP}) whatis g
9286 (@value{GDBP}) set g=4
9290 The program being debugged has been started already.
9291 Start it from the beginning? (y or n) y
9292 Starting program: /home/smith/cc_progs/a.out
9293 "/home/smith/cc_progs/a.out": can't open to read symbols:
9295 (@value{GDBP}) show g
9296 The current BFD target is "=4".
9301 The program variable @code{g} did not change, and you silently set the
9302 @code{gnutarget} to an invalid value. In order to set the variable
9306 (@value{GDBP}) set var g=4
9309 @value{GDBN} allows more implicit conversions in assignments than C; you can
9310 freely store an integer value into a pointer variable or vice versa,
9311 and you can convert any structure to any other structure that is the
9312 same length or shorter.
9313 @comment FIXME: how do structs align/pad in these conversions?
9314 @comment /doc@cygnus.com 18dec1990
9316 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
9317 construct to generate a value of specified type at a specified address
9318 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
9319 to memory location @code{0x83040} as an integer (which implies a certain size
9320 and representation in memory), and
9323 set @{int@}0x83040 = 4
9327 stores the value 4 into that memory location.
9330 @section Continuing at a different address
9332 Ordinarily, when you continue your program, you do so at the place where
9333 it stopped, with the @code{continue} command. You can instead continue at
9334 an address of your own choosing, with the following commands:
9338 @item jump @var{linespec}
9339 Resume execution at line @var{linespec}. Execution stops again
9340 immediately if there is a breakpoint there. @xref{List, ,Printing
9341 source lines}, for a description of the different forms of
9342 @var{linespec}. It is common practice to use the @code{tbreak} command
9343 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
9346 The @code{jump} command does not change the current stack frame, or
9347 the stack pointer, or the contents of any memory location or any
9348 register other than the program counter. If line @var{linespec} is in
9349 a different function from the one currently executing, the results may
9350 be bizarre if the two functions expect different patterns of arguments or
9351 of local variables. For this reason, the @code{jump} command requests
9352 confirmation if the specified line is not in the function currently
9353 executing. However, even bizarre results are predictable if you are
9354 well acquainted with the machine-language code of your program.
9356 @item jump *@var{address}
9357 Resume execution at the instruction at address @var{address}.
9360 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
9361 On many systems, you can get much the same effect as the @code{jump}
9362 command by storing a new value into the register @code{$pc}. The
9363 difference is that this does not start your program running; it only
9364 changes the address of where it @emph{will} run when you continue. For
9372 makes the next @code{continue} command or stepping command execute at
9373 address @code{0x485}, rather than at the address where your program stopped.
9374 @xref{Continuing and Stepping, ,Continuing and stepping}.
9376 The most common occasion to use the @code{jump} command is to back
9377 up---perhaps with more breakpoints set---over a portion of a program
9378 that has already executed, in order to examine its execution in more
9383 @section Giving your program a signal
9387 @item signal @var{signal}
9388 Resume execution where your program stopped, but immediately give it the
9389 signal @var{signal}. @var{signal} can be the name or the number of a
9390 signal. For example, on many systems @code{signal 2} and @code{signal
9391 SIGINT} are both ways of sending an interrupt signal.
9393 Alternatively, if @var{signal} is zero, continue execution without
9394 giving a signal. This is useful when your program stopped on account of
9395 a signal and would ordinary see the signal when resumed with the
9396 @code{continue} command; @samp{signal 0} causes it to resume without a
9399 @code{signal} does not repeat when you press @key{RET} a second time
9400 after executing the command.
9404 Invoking the @code{signal} command is not the same as invoking the
9405 @code{kill} utility from the shell. Sending a signal with @code{kill}
9406 causes @value{GDBN} to decide what to do with the signal depending on
9407 the signal handling tables (@pxref{Signals}). The @code{signal} command
9408 passes the signal directly to your program.
9412 @section Returning from a function
9415 @cindex returning from a function
9418 @itemx return @var{expression}
9419 You can cancel execution of a function call with the @code{return}
9420 command. If you give an
9421 @var{expression} argument, its value is used as the function's return
9425 When you use @code{return}, @value{GDBN} discards the selected stack frame
9426 (and all frames within it). You can think of this as making the
9427 discarded frame return prematurely. If you wish to specify a value to
9428 be returned, give that value as the argument to @code{return}.
9430 This pops the selected stack frame (@pxref{Selection, ,Selecting a
9431 frame}), and any other frames inside of it, leaving its caller as the
9432 innermost remaining frame. That frame becomes selected. The
9433 specified value is stored in the registers used for returning values
9436 The @code{return} command does not resume execution; it leaves the
9437 program stopped in the state that would exist if the function had just
9438 returned. In contrast, the @code{finish} command (@pxref{Continuing
9439 and Stepping, ,Continuing and stepping}) resumes execution until the
9440 selected stack frame returns naturally.
9443 @section Calling program functions
9445 @cindex calling functions
9448 @item call @var{expr}
9449 Evaluate the expression @var{expr} without displaying @code{void}
9453 You can use this variant of the @code{print} command if you want to
9454 execute a function from your program, but without cluttering the output
9455 with @code{void} returned values. If the result is not void, it
9456 is printed and saved in the value history.
9459 @section Patching programs
9461 @cindex patching binaries
9462 @cindex writing into executables
9463 @cindex writing into corefiles
9465 By default, @value{GDBN} opens the file containing your program's
9466 executable code (or the corefile) read-only. This prevents accidental
9467 alterations to machine code; but it also prevents you from intentionally
9468 patching your program's binary.
9470 If you'd like to be able to patch the binary, you can specify that
9471 explicitly with the @code{set write} command. For example, you might
9472 want to turn on internal debugging flags, or even to make emergency
9478 @itemx set write off
9479 If you specify @samp{set write on}, @value{GDBN} opens executable and
9480 core files for both reading and writing; if you specify @samp{set write
9481 off} (the default), @value{GDBN} opens them read-only.
9483 If you have already loaded a file, you must load it again (using the
9484 @code{exec-file} or @code{core-file} command) after changing @code{set
9485 write}, for your new setting to take effect.
9489 Display whether executable files and core files are opened for writing
9494 @chapter @value{GDBN} Files
9496 @value{GDBN} needs to know the file name of the program to be debugged,
9497 both in order to read its symbol table and in order to start your
9498 program. To debug a core dump of a previous run, you must also tell
9499 @value{GDBN} the name of the core dump file.
9502 * Files:: Commands to specify files
9503 * Separate Debug Files:: Debugging information in separate files
9504 * Symbol Errors:: Errors reading symbol files
9508 @section Commands to specify files
9510 @cindex symbol table
9511 @cindex core dump file
9513 You may want to specify executable and core dump file names. The usual
9514 way to do this is at start-up time, using the arguments to
9515 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
9516 Out of @value{GDBN}}).
9518 Occasionally it is necessary to change to a different file during a
9519 @value{GDBN} session. Or you may run @value{GDBN} and forget to specify
9520 a file you want to use. In these situations the @value{GDBN} commands
9521 to specify new files are useful.
9524 @cindex executable file
9526 @item file @var{filename}
9527 Use @var{filename} as the program to be debugged. It is read for its
9528 symbols and for the contents of pure memory. It is also the program
9529 executed when you use the @code{run} command. If you do not specify a
9530 directory and the file is not found in the @value{GDBN} working directory,
9531 @value{GDBN} uses the environment variable @code{PATH} as a list of
9532 directories to search, just as the shell does when looking for a program
9533 to run. You can change the value of this variable, for both @value{GDBN}
9534 and your program, using the @code{path} command.
9536 On systems with memory-mapped files, an auxiliary file named
9537 @file{@var{filename}.syms} may hold symbol table information for
9538 @var{filename}. If so, @value{GDBN} maps in the symbol table from
9539 @file{@var{filename}.syms}, starting up more quickly. See the
9540 descriptions of the file options @samp{-mapped} and @samp{-readnow}
9541 (available on the command line, and with the commands @code{file},
9542 @code{symbol-file}, or @code{add-symbol-file}, described below),
9543 for more information.
9546 @code{file} with no argument makes @value{GDBN} discard any information it
9547 has on both executable file and the symbol table.
9550 @item exec-file @r{[} @var{filename} @r{]}
9551 Specify that the program to be run (but not the symbol table) is found
9552 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
9553 if necessary to locate your program. Omitting @var{filename} means to
9554 discard information on the executable file.
9557 @item symbol-file @r{[} @var{filename} @r{]}
9558 Read symbol table information from file @var{filename}. @code{PATH} is
9559 searched when necessary. Use the @code{file} command to get both symbol
9560 table and program to run from the same file.
9562 @code{symbol-file} with no argument clears out @value{GDBN} information on your
9563 program's symbol table.
9565 The @code{symbol-file} command causes @value{GDBN} to forget the contents
9566 of its convenience variables, the value history, and all breakpoints and
9567 auto-display expressions. This is because they may contain pointers to
9568 the internal data recording symbols and data types, which are part of
9569 the old symbol table data being discarded inside @value{GDBN}.
9571 @code{symbol-file} does not repeat if you press @key{RET} again after
9574 When @value{GDBN} is configured for a particular environment, it
9575 understands debugging information in whatever format is the standard
9576 generated for that environment; you may use either a @sc{gnu} compiler, or
9577 other compilers that adhere to the local conventions.
9578 Best results are usually obtained from @sc{gnu} compilers; for example,
9579 using @code{@value{GCC}} you can generate debugging information for
9582 For most kinds of object files, with the exception of old SVR3 systems
9583 using COFF, the @code{symbol-file} command does not normally read the
9584 symbol table in full right away. Instead, it scans the symbol table
9585 quickly to find which source files and which symbols are present. The
9586 details are read later, one source file at a time, as they are needed.
9588 The purpose of this two-stage reading strategy is to make @value{GDBN}
9589 start up faster. For the most part, it is invisible except for
9590 occasional pauses while the symbol table details for a particular source
9591 file are being read. (The @code{set verbose} command can turn these
9592 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
9593 warnings and messages}.)
9595 We have not implemented the two-stage strategy for COFF yet. When the
9596 symbol table is stored in COFF format, @code{symbol-file} reads the
9597 symbol table data in full right away. Note that ``stabs-in-COFF''
9598 still does the two-stage strategy, since the debug info is actually
9602 @cindex reading symbols immediately
9603 @cindex symbols, reading immediately
9605 @cindex memory-mapped symbol file
9606 @cindex saving symbol table
9607 @item symbol-file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
9608 @itemx file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
9609 You can override the @value{GDBN} two-stage strategy for reading symbol
9610 tables by using the @samp{-readnow} option with any of the commands that
9611 load symbol table information, if you want to be sure @value{GDBN} has the
9612 entire symbol table available.
9614 If memory-mapped files are available on your system through the
9615 @code{mmap} system call, you can use another option, @samp{-mapped}, to
9616 cause @value{GDBN} to write the symbols for your program into a reusable
9617 file. Future @value{GDBN} debugging sessions map in symbol information
9618 from this auxiliary symbol file (if the program has not changed), rather
9619 than spending time reading the symbol table from the executable
9620 program. Using the @samp{-mapped} option has the same effect as
9621 starting @value{GDBN} with the @samp{-mapped} command-line option.
9623 You can use both options together, to make sure the auxiliary symbol
9624 file has all the symbol information for your program.
9626 The auxiliary symbol file for a program called @var{myprog} is called
9627 @samp{@var{myprog}.syms}. Once this file exists (so long as it is newer
9628 than the corresponding executable), @value{GDBN} always attempts to use
9629 it when you debug @var{myprog}; no special options or commands are
9632 The @file{.syms} file is specific to the host machine where you run
9633 @value{GDBN}. It holds an exact image of the internal @value{GDBN}
9634 symbol table. It cannot be shared across multiple host platforms.
9636 @c FIXME: for now no mention of directories, since this seems to be in
9637 @c flux. 13mar1992 status is that in theory GDB would look either in
9638 @c current dir or in same dir as myprog; but issues like competing
9639 @c GDB's, or clutter in system dirs, mean that in practice right now
9640 @c only current dir is used. FFish says maybe a special GDB hierarchy
9641 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
9646 @item core-file @r{[} @var{filename} @r{]}
9647 Specify the whereabouts of a core dump file to be used as the ``contents
9648 of memory''. Traditionally, core files contain only some parts of the
9649 address space of the process that generated them; @value{GDBN} can access the
9650 executable file itself for other parts.
9652 @code{core-file} with no argument specifies that no core file is
9655 Note that the core file is ignored when your program is actually running
9656 under @value{GDBN}. So, if you have been running your program and you
9657 wish to debug a core file instead, you must kill the subprocess in which
9658 the program is running. To do this, use the @code{kill} command
9659 (@pxref{Kill Process, ,Killing the child process}).
9661 @kindex add-symbol-file
9662 @cindex dynamic linking
9663 @item add-symbol-file @var{filename} @var{address}
9664 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
9665 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
9666 The @code{add-symbol-file} command reads additional symbol table
9667 information from the file @var{filename}. You would use this command
9668 when @var{filename} has been dynamically loaded (by some other means)
9669 into the program that is running. @var{address} should be the memory
9670 address at which the file has been loaded; @value{GDBN} cannot figure
9671 this out for itself. You can additionally specify an arbitrary number
9672 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
9673 section name and base address for that section. You can specify any
9674 @var{address} as an expression.
9676 The symbol table of the file @var{filename} is added to the symbol table
9677 originally read with the @code{symbol-file} command. You can use the
9678 @code{add-symbol-file} command any number of times; the new symbol data
9679 thus read keeps adding to the old. To discard all old symbol data
9680 instead, use the @code{symbol-file} command without any arguments.
9682 @cindex relocatable object files, reading symbols from
9683 @cindex object files, relocatable, reading symbols from
9684 @cindex reading symbols from relocatable object files
9685 @cindex symbols, reading from relocatable object files
9686 @cindex @file{.o} files, reading symbols from
9687 Although @var{filename} is typically a shared library file, an
9688 executable file, or some other object file which has been fully
9689 relocated for loading into a process, you can also load symbolic
9690 information from relocatable @file{.o} files, as long as:
9694 the file's symbolic information refers only to linker symbols defined in
9695 that file, not to symbols defined by other object files,
9697 every section the file's symbolic information refers to has actually
9698 been loaded into the inferior, as it appears in the file, and
9700 you can determine the address at which every section was loaded, and
9701 provide these to the @code{add-symbol-file} command.
9705 Some embedded operating systems, like Sun Chorus and VxWorks, can load
9706 relocatable files into an already running program; such systems
9707 typically make the requirements above easy to meet. However, it's
9708 important to recognize that many native systems use complex link
9709 procedures (@code{.linkonce} section factoring and C++ constructor table
9710 assembly, for example) that make the requirements difficult to meet. In
9711 general, one cannot assume that using @code{add-symbol-file} to read a
9712 relocatable object file's symbolic information will have the same effect
9713 as linking the relocatable object file into the program in the normal
9716 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
9718 You can use the @samp{-mapped} and @samp{-readnow} options just as with
9719 the @code{symbol-file} command, to change how @value{GDBN} manages the symbol
9720 table information for @var{filename}.
9722 @kindex add-shared-symbol-file
9723 @item add-shared-symbol-file
9724 The @code{add-shared-symbol-file} command can be used only under Harris' CXUX
9725 operating system for the Motorola 88k. @value{GDBN} automatically looks for
9726 shared libraries, however if @value{GDBN} does not find yours, you can run
9727 @code{add-shared-symbol-file}. It takes no arguments.
9731 The @code{section} command changes the base address of section SECTION of
9732 the exec file to ADDR. This can be used if the exec file does not contain
9733 section addresses, (such as in the a.out format), or when the addresses
9734 specified in the file itself are wrong. Each section must be changed
9735 separately. The @code{info files} command, described below, lists all
9736 the sections and their addresses.
9742 @code{info files} and @code{info target} are synonymous; both print the
9743 current target (@pxref{Targets, ,Specifying a Debugging Target}),
9744 including the names of the executable and core dump files currently in
9745 use by @value{GDBN}, and the files from which symbols were loaded. The
9746 command @code{help target} lists all possible targets rather than
9749 @kindex maint info sections
9750 @item maint info sections
9751 Another command that can give you extra information about program sections
9752 is @code{maint info sections}. In addition to the section information
9753 displayed by @code{info files}, this command displays the flags and file
9754 offset of each section in the executable and core dump files. In addition,
9755 @code{maint info sections} provides the following command options (which
9756 may be arbitrarily combined):
9760 Display sections for all loaded object files, including shared libraries.
9761 @item @var{sections}
9762 Display info only for named @var{sections}.
9763 @item @var{section-flags}
9764 Display info only for sections for which @var{section-flags} are true.
9765 The section flags that @value{GDBN} currently knows about are:
9768 Section will have space allocated in the process when loaded.
9769 Set for all sections except those containing debug information.
9771 Section will be loaded from the file into the child process memory.
9772 Set for pre-initialized code and data, clear for @code{.bss} sections.
9774 Section needs to be relocated before loading.
9776 Section cannot be modified by the child process.
9778 Section contains executable code only.
9780 Section contains data only (no executable code).
9782 Section will reside in ROM.
9784 Section contains data for constructor/destructor lists.
9786 Section is not empty.
9788 An instruction to the linker to not output the section.
9789 @item COFF_SHARED_LIBRARY
9790 A notification to the linker that the section contains
9791 COFF shared library information.
9793 Section contains common symbols.
9796 @kindex set trust-readonly-sections
9797 @item set trust-readonly-sections on
9798 Tell @value{GDBN} that readonly sections in your object file
9799 really are read-only (i.e.@: that their contents will not change).
9800 In that case, @value{GDBN} can fetch values from these sections
9801 out of the object file, rather than from the target program.
9802 For some targets (notably embedded ones), this can be a significant
9803 enhancement to debugging performance.
9807 @item set trust-readonly-sections off
9808 Tell @value{GDBN} not to trust readonly sections. This means that
9809 the contents of the section might change while the program is running,
9810 and must therefore be fetched from the target when needed.
9813 All file-specifying commands allow both absolute and relative file names
9814 as arguments. @value{GDBN} always converts the file name to an absolute file
9815 name and remembers it that way.
9817 @cindex shared libraries
9818 @value{GDBN} supports HP-UX, SunOS, SVr4, Irix 5, and IBM RS/6000 shared
9821 @value{GDBN} automatically loads symbol definitions from shared libraries
9822 when you use the @code{run} command, or when you examine a core file.
9823 (Before you issue the @code{run} command, @value{GDBN} does not understand
9824 references to a function in a shared library, however---unless you are
9825 debugging a core file).
9827 On HP-UX, if the program loads a library explicitly, @value{GDBN}
9828 automatically loads the symbols at the time of the @code{shl_load} call.
9830 @c FIXME: some @value{GDBN} release may permit some refs to undef
9831 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
9832 @c FIXME...lib; check this from time to time when updating manual
9834 There are times, however, when you may wish to not automatically load
9835 symbol definitions from shared libraries, such as when they are
9836 particularly large or there are many of them.
9838 To control the automatic loading of shared library symbols, use the
9842 @kindex set auto-solib-add
9843 @item set auto-solib-add @var{mode}
9844 If @var{mode} is @code{on}, symbols from all shared object libraries
9845 will be loaded automatically when the inferior begins execution, you
9846 attach to an independently started inferior, or when the dynamic linker
9847 informs @value{GDBN} that a new library has been loaded. If @var{mode}
9848 is @code{off}, symbols must be loaded manually, using the
9849 @code{sharedlibrary} command. The default value is @code{on}.
9851 @kindex show auto-solib-add
9852 @item show auto-solib-add
9853 Display the current autoloading mode.
9856 To explicitly load shared library symbols, use the @code{sharedlibrary}
9860 @kindex info sharedlibrary
9863 @itemx info sharedlibrary
9864 Print the names of the shared libraries which are currently loaded.
9866 @kindex sharedlibrary
9868 @item sharedlibrary @var{regex}
9869 @itemx share @var{regex}
9870 Load shared object library symbols for files matching a
9871 Unix regular expression.
9872 As with files loaded automatically, it only loads shared libraries
9873 required by your program for a core file or after typing @code{run}. If
9874 @var{regex} is omitted all shared libraries required by your program are
9878 On some systems, such as HP-UX systems, @value{GDBN} supports
9879 autoloading shared library symbols until a limiting threshold size is
9880 reached. This provides the benefit of allowing autoloading to remain on
9881 by default, but avoids autoloading excessively large shared libraries,
9882 up to a threshold that is initially set, but which you can modify if you
9885 Beyond that threshold, symbols from shared libraries must be explicitly
9886 loaded. To load these symbols, use the command @code{sharedlibrary
9887 @var{filename}}. The base address of the shared library is determined
9888 automatically by @value{GDBN} and need not be specified.
9890 To display or set the threshold, use the commands:
9893 @kindex set auto-solib-limit
9894 @item set auto-solib-limit @var{threshold}
9895 Set the autoloading size threshold, in an integral number of megabytes.
9896 If @var{threshold} is nonzero and shared library autoloading is enabled,
9897 symbols from all shared object libraries will be loaded until the total
9898 size of the loaded shared library symbols exceeds this threshold.
9899 Otherwise, symbols must be loaded manually, using the
9900 @code{sharedlibrary} command. The default threshold is 100 (i.e.@: 100
9903 @kindex show auto-solib-limit
9904 @item show auto-solib-limit
9905 Display the current autoloading size threshold, in megabytes.
9908 Shared libraries are also supported in many cross or remote debugging
9909 configurations. A copy of the target's libraries need to be present on the
9910 host system; they need to be the same as the target libraries, although the
9911 copies on the target can be stripped as long as the copies on the host are
9914 You need to tell @value{GDBN} where the target libraries are, so that it can
9915 load the correct copies---otherwise, it may try to load the host's libraries.
9916 @value{GDBN} has two variables to specify the search directories for target
9920 @kindex set solib-absolute-prefix
9921 @item set solib-absolute-prefix @var{path}
9922 If this variable is set, @var{path} will be used as a prefix for any
9923 absolute shared library paths; many runtime loaders store the absolute
9924 paths to the shared library in the target program's memory. If you use
9925 @samp{solib-absolute-prefix} to find shared libraries, they need to be laid
9926 out in the same way that they are on the target, with e.g.@: a
9927 @file{/usr/lib} hierarchy under @var{path}.
9929 You can set the default value of @samp{solib-absolute-prefix} by using the
9930 configure-time @samp{--with-sysroot} option.
9932 @kindex show solib-absolute-prefix
9933 @item show solib-absolute-prefix
9934 Display the current shared library prefix.
9936 @kindex set solib-search-path
9937 @item set solib-search-path @var{path}
9938 If this variable is set, @var{path} is a colon-separated list of directories
9939 to search for shared libraries. @samp{solib-search-path} is used after
9940 @samp{solib-absolute-prefix} fails to locate the library, or if the path to
9941 the library is relative instead of absolute. If you want to use
9942 @samp{solib-search-path} instead of @samp{solib-absolute-prefix}, be sure to
9943 set @samp{solib-absolute-prefix} to a nonexistant directory to prevent
9944 @value{GDBN} from finding your host's libraries.
9946 @kindex show solib-search-path
9947 @item show solib-search-path
9948 Display the current shared library search path.
9952 @node Separate Debug Files
9953 @section Debugging Information in Separate Files
9954 @cindex separate debugging information files
9955 @cindex debugging information in separate files
9956 @cindex @file{.debug} subdirectories
9957 @cindex debugging information directory, global
9958 @cindex global debugging information directory
9960 @value{GDBN} allows you to put a program's debugging information in a
9961 file separate from the executable itself, in a way that allows
9962 @value{GDBN} to find and load the debugging information automatically.
9963 Since debugging information can be very large --- sometimes larger
9964 than the executable code itself --- some systems distribute debugging
9965 information for their executables in separate files, which users can
9966 install only when they need to debug a problem.
9968 If an executable's debugging information has been extracted to a
9969 separate file, the executable should contain a @dfn{debug link} giving
9970 the name of the debugging information file (with no directory
9971 components), and a checksum of its contents. (The exact form of a
9972 debug link is described below.) If the full name of the directory
9973 containing the executable is @var{execdir}, and the executable has a
9974 debug link that specifies the name @var{debugfile}, then @value{GDBN}
9975 will automatically search for the debugging information file in three
9980 the directory containing the executable file (that is, it will look
9981 for a file named @file{@var{execdir}/@var{debugfile}},
9983 a subdirectory of that directory named @file{.debug} (that is, the
9984 file @file{@var{execdir}/.debug/@var{debugfile}}, and
9986 a subdirectory of the global debug file directory that includes the
9987 executable's full path, and the name from the link (that is, the file
9988 @file{@var{globaldebugdir}/@var{execdir}/@var{debugfile}}, where
9989 @var{globaldebugdir} is the global debug file directory, and
9990 @var{execdir} has been turned into a relative path).
9993 @value{GDBN} checks under each of these names for a debugging
9994 information file whose checksum matches that given in the link, and
9995 reads the debugging information from the first one it finds.
9997 So, for example, if you ask @value{GDBN} to debug @file{/usr/bin/ls},
9998 which has a link containing the name @file{ls.debug}, and the global
9999 debug directory is @file{/usr/lib/debug}, then @value{GDBN} will look
10000 for debug information in @file{/usr/bin/ls.debug},
10001 @file{/usr/bin/.debug/ls.debug}, and
10002 @file{/usr/lib/debug/usr/bin/ls.debug}.
10004 You can set the global debugging info directory's name, and view the
10005 name @value{GDBN} is currently using.
10009 @kindex set debug-file-directory
10010 @item set debug-file-directory @var{directory}
10011 Set the directory which @value{GDBN} searches for separate debugging
10012 information files to @var{directory}.
10014 @kindex show debug-file-directory
10015 @item show debug-file-directory
10016 Show the directory @value{GDBN} searches for separate debugging
10021 @cindex @code{.gnu_debuglink} sections
10022 @cindex debug links
10023 A debug link is a special section of the executable file named
10024 @code{.gnu_debuglink}. The section must contain:
10028 A filename, with any leading directory components removed, followed by
10031 zero to three bytes of padding, as needed to reach the next four-byte
10032 boundary within the section, and
10034 a four-byte CRC checksum, stored in the same endianness used for the
10035 executable file itself. The checksum is computed on the debugging
10036 information file's full contents by the function given below, passing
10037 zero as the @var{crc} argument.
10040 Any executable file format can carry a debug link, as long as it can
10041 contain a section named @code{.gnu_debuglink} with the contents
10044 The debugging information file itself should be an ordinary
10045 executable, containing a full set of linker symbols, sections, and
10046 debugging information. The sections of the debugging information file
10047 should have the same names, addresses and sizes as the original file,
10048 but they need not contain any data --- much like a @code{.bss} section
10049 in an ordinary executable.
10051 As of December 2002, there is no standard GNU utility to produce
10052 separated executable / debugging information file pairs. Ulrich
10053 Drepper's @file{elfutils} package, starting with version 0.53,
10054 contains a version of the @code{strip} command such that the command
10055 @kbd{strip foo -f foo.debug} removes the debugging information from
10056 the executable file @file{foo}, places it in the file
10057 @file{foo.debug}, and leaves behind a debug link in @file{foo}.
10059 Since there are many different ways to compute CRC's (different
10060 polynomials, reversals, byte ordering, etc.), the simplest way to
10061 describe the CRC used in @code{.gnu_debuglink} sections is to give the
10062 complete code for a function that computes it:
10064 @kindex @code{gnu_debuglink_crc32}
10067 gnu_debuglink_crc32 (unsigned long crc,
10068 unsigned char *buf, size_t len)
10070 static const unsigned long crc32_table[256] =
10072 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
10073 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
10074 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
10075 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
10076 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
10077 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
10078 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
10079 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
10080 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
10081 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
10082 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
10083 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
10084 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
10085 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
10086 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
10087 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
10088 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
10089 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
10090 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
10091 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
10092 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
10093 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
10094 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
10095 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
10096 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
10097 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
10098 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
10099 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
10100 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
10101 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
10102 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
10103 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
10104 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
10105 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
10106 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
10107 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
10108 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
10109 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
10110 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
10111 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
10112 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
10113 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
10114 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
10115 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
10116 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
10117 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
10118 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
10119 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
10120 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
10121 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
10122 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
10125 unsigned char *end;
10127 crc = ~crc & 0xffffffff;
10128 for (end = buf + len; buf < end; ++buf)
10129 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
10130 return ~crc & 0xffffffff;
10135 @node Symbol Errors
10136 @section Errors reading symbol files
10138 While reading a symbol file, @value{GDBN} occasionally encounters problems,
10139 such as symbol types it does not recognize, or known bugs in compiler
10140 output. By default, @value{GDBN} does not notify you of such problems, since
10141 they are relatively common and primarily of interest to people
10142 debugging compilers. If you are interested in seeing information
10143 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
10144 only one message about each such type of problem, no matter how many
10145 times the problem occurs; or you can ask @value{GDBN} to print more messages,
10146 to see how many times the problems occur, with the @code{set
10147 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
10150 The messages currently printed, and their meanings, include:
10153 @item inner block not inside outer block in @var{symbol}
10155 The symbol information shows where symbol scopes begin and end
10156 (such as at the start of a function or a block of statements). This
10157 error indicates that an inner scope block is not fully contained
10158 in its outer scope blocks.
10160 @value{GDBN} circumvents the problem by treating the inner block as if it had
10161 the same scope as the outer block. In the error message, @var{symbol}
10162 may be shown as ``@code{(don't know)}'' if the outer block is not a
10165 @item block at @var{address} out of order
10167 The symbol information for symbol scope blocks should occur in
10168 order of increasing addresses. This error indicates that it does not
10171 @value{GDBN} does not circumvent this problem, and has trouble
10172 locating symbols in the source file whose symbols it is reading. (You
10173 can often determine what source file is affected by specifying
10174 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
10177 @item bad block start address patched
10179 The symbol information for a symbol scope block has a start address
10180 smaller than the address of the preceding source line. This is known
10181 to occur in the SunOS 4.1.1 (and earlier) C compiler.
10183 @value{GDBN} circumvents the problem by treating the symbol scope block as
10184 starting on the previous source line.
10186 @item bad string table offset in symbol @var{n}
10189 Symbol number @var{n} contains a pointer into the string table which is
10190 larger than the size of the string table.
10192 @value{GDBN} circumvents the problem by considering the symbol to have the
10193 name @code{foo}, which may cause other problems if many symbols end up
10196 @item unknown symbol type @code{0x@var{nn}}
10198 The symbol information contains new data types that @value{GDBN} does
10199 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
10200 uncomprehended information, in hexadecimal.
10202 @value{GDBN} circumvents the error by ignoring this symbol information.
10203 This usually allows you to debug your program, though certain symbols
10204 are not accessible. If you encounter such a problem and feel like
10205 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
10206 on @code{complain}, then go up to the function @code{read_dbx_symtab}
10207 and examine @code{*bufp} to see the symbol.
10209 @item stub type has NULL name
10211 @value{GDBN} could not find the full definition for a struct or class.
10213 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
10214 The symbol information for a C@t{++} member function is missing some
10215 information that recent versions of the compiler should have output for
10218 @item info mismatch between compiler and debugger
10220 @value{GDBN} could not parse a type specification output by the compiler.
10225 @chapter Specifying a Debugging Target
10227 @cindex debugging target
10230 A @dfn{target} is the execution environment occupied by your program.
10232 Often, @value{GDBN} runs in the same host environment as your program;
10233 in that case, the debugging target is specified as a side effect when
10234 you use the @code{file} or @code{core} commands. When you need more
10235 flexibility---for example, running @value{GDBN} on a physically separate
10236 host, or controlling a standalone system over a serial port or a
10237 realtime system over a TCP/IP connection---you can use the @code{target}
10238 command to specify one of the target types configured for @value{GDBN}
10239 (@pxref{Target Commands, ,Commands for managing targets}).
10242 * Active Targets:: Active targets
10243 * Target Commands:: Commands for managing targets
10244 * Byte Order:: Choosing target byte order
10245 * Remote:: Remote debugging
10246 * KOD:: Kernel Object Display
10250 @node Active Targets
10251 @section Active targets
10253 @cindex stacking targets
10254 @cindex active targets
10255 @cindex multiple targets
10257 There are three classes of targets: processes, core files, and
10258 executable files. @value{GDBN} can work concurrently on up to three
10259 active targets, one in each class. This allows you to (for example)
10260 start a process and inspect its activity without abandoning your work on
10263 For example, if you execute @samp{gdb a.out}, then the executable file
10264 @code{a.out} is the only active target. If you designate a core file as
10265 well---presumably from a prior run that crashed and coredumped---then
10266 @value{GDBN} has two active targets and uses them in tandem, looking
10267 first in the corefile target, then in the executable file, to satisfy
10268 requests for memory addresses. (Typically, these two classes of target
10269 are complementary, since core files contain only a program's
10270 read-write memory---variables and so on---plus machine status, while
10271 executable files contain only the program text and initialized data.)
10273 When you type @code{run}, your executable file becomes an active process
10274 target as well. When a process target is active, all @value{GDBN}
10275 commands requesting memory addresses refer to that target; addresses in
10276 an active core file or executable file target are obscured while the
10277 process target is active.
10279 Use the @code{core-file} and @code{exec-file} commands to select a new
10280 core file or executable target (@pxref{Files, ,Commands to specify
10281 files}). To specify as a target a process that is already running, use
10282 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
10285 @node Target Commands
10286 @section Commands for managing targets
10289 @item target @var{type} @var{parameters}
10290 Connects the @value{GDBN} host environment to a target machine or
10291 process. A target is typically a protocol for talking to debugging
10292 facilities. You use the argument @var{type} to specify the type or
10293 protocol of the target machine.
10295 Further @var{parameters} are interpreted by the target protocol, but
10296 typically include things like device names or host names to connect
10297 with, process numbers, and baud rates.
10299 The @code{target} command does not repeat if you press @key{RET} again
10300 after executing the command.
10302 @kindex help target
10304 Displays the names of all targets available. To display targets
10305 currently selected, use either @code{info target} or @code{info files}
10306 (@pxref{Files, ,Commands to specify files}).
10308 @item help target @var{name}
10309 Describe a particular target, including any parameters necessary to
10312 @kindex set gnutarget
10313 @item set gnutarget @var{args}
10314 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
10315 knows whether it is reading an @dfn{executable},
10316 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
10317 with the @code{set gnutarget} command. Unlike most @code{target} commands,
10318 with @code{gnutarget} the @code{target} refers to a program, not a machine.
10321 @emph{Warning:} To specify a file format with @code{set gnutarget},
10322 you must know the actual BFD name.
10326 @xref{Files, , Commands to specify files}.
10328 @kindex show gnutarget
10329 @item show gnutarget
10330 Use the @code{show gnutarget} command to display what file format
10331 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
10332 @value{GDBN} will determine the file format for each file automatically,
10333 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
10336 Here are some common targets (available, or not, depending on the GDB
10340 @kindex target exec
10341 @item target exec @var{program}
10342 An executable file. @samp{target exec @var{program}} is the same as
10343 @samp{exec-file @var{program}}.
10345 @kindex target core
10346 @item target core @var{filename}
10347 A core dump file. @samp{target core @var{filename}} is the same as
10348 @samp{core-file @var{filename}}.
10350 @kindex target remote
10351 @item target remote @var{dev}
10352 Remote serial target in GDB-specific protocol. The argument @var{dev}
10353 specifies what serial device to use for the connection (e.g.
10354 @file{/dev/ttya}). @xref{Remote, ,Remote debugging}. @code{target remote}
10355 supports the @code{load} command. This is only useful if you have
10356 some other way of getting the stub to the target system, and you can put
10357 it somewhere in memory where it won't get clobbered by the download.
10361 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
10369 works; however, you cannot assume that a specific memory map, device
10370 drivers, or even basic I/O is available, although some simulators do
10371 provide these. For info about any processor-specific simulator details,
10372 see the appropriate section in @ref{Embedded Processors, ,Embedded
10377 Some configurations may include these targets as well:
10381 @kindex target nrom
10382 @item target nrom @var{dev}
10383 NetROM ROM emulator. This target only supports downloading.
10387 Different targets are available on different configurations of @value{GDBN};
10388 your configuration may have more or fewer targets.
10390 Many remote targets require you to download the executable's code
10391 once you've successfully established a connection.
10395 @kindex load @var{filename}
10396 @item load @var{filename}
10397 Depending on what remote debugging facilities are configured into
10398 @value{GDBN}, the @code{load} command may be available. Where it exists, it
10399 is meant to make @var{filename} (an executable) available for debugging
10400 on the remote system---by downloading, or dynamic linking, for example.
10401 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
10402 the @code{add-symbol-file} command.
10404 If your @value{GDBN} does not have a @code{load} command, attempting to
10405 execute it gets the error message ``@code{You can't do that when your
10406 target is @dots{}}''
10408 The file is loaded at whatever address is specified in the executable.
10409 For some object file formats, you can specify the load address when you
10410 link the program; for other formats, like a.out, the object file format
10411 specifies a fixed address.
10412 @c FIXME! This would be a good place for an xref to the GNU linker doc.
10414 @code{load} does not repeat if you press @key{RET} again after using it.
10418 @section Choosing target byte order
10420 @cindex choosing target byte order
10421 @cindex target byte order
10423 Some types of processors, such as the MIPS, PowerPC, and Hitachi SH,
10424 offer the ability to run either big-endian or little-endian byte
10425 orders. Usually the executable or symbol will include a bit to
10426 designate the endian-ness, and you will not need to worry about
10427 which to use. However, you may still find it useful to adjust
10428 @value{GDBN}'s idea of processor endian-ness manually.
10431 @kindex set endian big
10432 @item set endian big
10433 Instruct @value{GDBN} to assume the target is big-endian.
10435 @kindex set endian little
10436 @item set endian little
10437 Instruct @value{GDBN} to assume the target is little-endian.
10439 @kindex set endian auto
10440 @item set endian auto
10441 Instruct @value{GDBN} to use the byte order associated with the
10445 Display @value{GDBN}'s current idea of the target byte order.
10449 Note that these commands merely adjust interpretation of symbolic
10450 data on the host, and that they have absolutely no effect on the
10454 @section Remote debugging
10455 @cindex remote debugging
10457 If you are trying to debug a program running on a machine that cannot run
10458 @value{GDBN} in the usual way, it is often useful to use remote debugging.
10459 For example, you might use remote debugging on an operating system kernel,
10460 or on a small system which does not have a general purpose operating system
10461 powerful enough to run a full-featured debugger.
10463 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
10464 to make this work with particular debugging targets. In addition,
10465 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
10466 but not specific to any particular target system) which you can use if you
10467 write the remote stubs---the code that runs on the remote system to
10468 communicate with @value{GDBN}.
10470 Other remote targets may be available in your
10471 configuration of @value{GDBN}; use @code{help target} to list them.
10474 @section Kernel Object Display
10476 @cindex kernel object display
10477 @cindex kernel object
10480 Some targets support kernel object display. Using this facility,
10481 @value{GDBN} communicates specially with the underlying operating system
10482 and can display information about operating system-level objects such as
10483 mutexes and other synchronization objects. Exactly which objects can be
10484 displayed is determined on a per-OS basis.
10486 Use the @code{set os} command to set the operating system. This tells
10487 @value{GDBN} which kernel object display module to initialize:
10490 (@value{GDBP}) set os cisco
10493 If @code{set os} succeeds, @value{GDBN} will display some information
10494 about the operating system, and will create a new @code{info} command
10495 which can be used to query the target. The @code{info} command is named
10496 after the operating system:
10499 (@value{GDBP}) info cisco
10500 List of Cisco Kernel Objects
10502 any Any and all objects
10505 Further subcommands can be used to query about particular objects known
10508 There is currently no way to determine whether a given operating system
10509 is supported other than to try it.
10512 @node Remote Debugging
10513 @chapter Debugging remote programs
10516 * Server:: Using the gdbserver program
10517 * NetWare:: Using the gdbserve.nlm program
10518 * Remote configuration:: Remote configuration
10519 * remote stub:: Implementing a remote stub
10523 @section Using the @code{gdbserver} program
10526 @cindex remote connection without stubs
10527 @code{gdbserver} is a control program for Unix-like systems, which
10528 allows you to connect your program with a remote @value{GDBN} via
10529 @code{target remote}---but without linking in the usual debugging stub.
10531 @code{gdbserver} is not a complete replacement for the debugging stubs,
10532 because it requires essentially the same operating-system facilities
10533 that @value{GDBN} itself does. In fact, a system that can run
10534 @code{gdbserver} to connect to a remote @value{GDBN} could also run
10535 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
10536 because it is a much smaller program than @value{GDBN} itself. It is
10537 also easier to port than all of @value{GDBN}, so you may be able to get
10538 started more quickly on a new system by using @code{gdbserver}.
10539 Finally, if you develop code for real-time systems, you may find that
10540 the tradeoffs involved in real-time operation make it more convenient to
10541 do as much development work as possible on another system, for example
10542 by cross-compiling. You can use @code{gdbserver} to make a similar
10543 choice for debugging.
10545 @value{GDBN} and @code{gdbserver} communicate via either a serial line
10546 or a TCP connection, using the standard @value{GDBN} remote serial
10550 @item On the target machine,
10551 you need to have a copy of the program you want to debug.
10552 @code{gdbserver} does not need your program's symbol table, so you can
10553 strip the program if necessary to save space. @value{GDBN} on the host
10554 system does all the symbol handling.
10556 To use the server, you must tell it how to communicate with @value{GDBN};
10557 the name of your program; and the arguments for your program. The usual
10561 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
10564 @var{comm} is either a device name (to use a serial line) or a TCP
10565 hostname and portnumber. For example, to debug Emacs with the argument
10566 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
10570 target> gdbserver /dev/com1 emacs foo.txt
10573 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
10576 To use a TCP connection instead of a serial line:
10579 target> gdbserver host:2345 emacs foo.txt
10582 The only difference from the previous example is the first argument,
10583 specifying that you are communicating with the host @value{GDBN} via
10584 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
10585 expect a TCP connection from machine @samp{host} to local TCP port 2345.
10586 (Currently, the @samp{host} part is ignored.) You can choose any number
10587 you want for the port number as long as it does not conflict with any
10588 TCP ports already in use on the target system (for example, @code{23} is
10589 reserved for @code{telnet}).@footnote{If you choose a port number that
10590 conflicts with another service, @code{gdbserver} prints an error message
10591 and exits.} You must use the same port number with the host @value{GDBN}
10592 @code{target remote} command.
10594 On some targets, @code{gdbserver} can also attach to running programs.
10595 This is accomplished via the @code{--attach} argument. The syntax is:
10598 target> gdbserver @var{comm} --attach @var{pid}
10601 @var{pid} is the process ID of a currently running process. It isn't necessary
10602 to point @code{gdbserver} at a binary for the running process.
10604 @item On the @value{GDBN} host machine,
10605 you need an unstripped copy of your program, since @value{GDBN} needs
10606 symbols and debugging information. Start up @value{GDBN} as usual,
10607 using the name of the local copy of your program as the first argument.
10608 (You may also need the @w{@samp{--baud}} option if the serial line is
10609 running at anything other than 9600@dmn{bps}.) After that, use @code{target
10610 remote} to establish communications with @code{gdbserver}. Its argument
10611 is either a device name (usually a serial device, like
10612 @file{/dev/ttyb}), or a TCP port descriptor in the form
10613 @code{@var{host}:@var{PORT}}. For example:
10616 (@value{GDBP}) target remote /dev/ttyb
10620 communicates with the server via serial line @file{/dev/ttyb}, and
10623 (@value{GDBP}) target remote the-target:2345
10627 communicates via a TCP connection to port 2345 on host @w{@file{the-target}}.
10628 For TCP connections, you must start up @code{gdbserver} prior to using
10629 the @code{target remote} command. Otherwise you may get an error whose
10630 text depends on the host system, but which usually looks something like
10631 @samp{Connection refused}.
10635 @section Using the @code{gdbserve.nlm} program
10637 @kindex gdbserve.nlm
10638 @code{gdbserve.nlm} is a control program for NetWare systems, which
10639 allows you to connect your program with a remote @value{GDBN} via
10640 @code{target remote}.
10642 @value{GDBN} and @code{gdbserve.nlm} communicate via a serial line,
10643 using the standard @value{GDBN} remote serial protocol.
10646 @item On the target machine,
10647 you need to have a copy of the program you want to debug.
10648 @code{gdbserve.nlm} does not need your program's symbol table, so you
10649 can strip the program if necessary to save space. @value{GDBN} on the
10650 host system does all the symbol handling.
10652 To use the server, you must tell it how to communicate with
10653 @value{GDBN}; the name of your program; and the arguments for your
10654 program. The syntax is:
10657 load gdbserve [ BOARD=@var{board} ] [ PORT=@var{port} ]
10658 [ BAUD=@var{baud} ] @var{program} [ @var{args} @dots{} ]
10661 @var{board} and @var{port} specify the serial line; @var{baud} specifies
10662 the baud rate used by the connection. @var{port} and @var{node} default
10663 to 0, @var{baud} defaults to 9600@dmn{bps}.
10665 For example, to debug Emacs with the argument @samp{foo.txt}and
10666 communicate with @value{GDBN} over serial port number 2 or board 1
10667 using a 19200@dmn{bps} connection:
10670 load gdbserve BOARD=1 PORT=2 BAUD=19200 emacs foo.txt
10673 @item On the @value{GDBN} host machine,
10674 you need an unstripped copy of your program, since @value{GDBN} needs
10675 symbols and debugging information. Start up @value{GDBN} as usual,
10676 using the name of the local copy of your program as the first argument.
10677 (You may also need the @w{@samp{--baud}} option if the serial line is
10678 running at anything other than 9600@dmn{bps}. After that, use @code{target
10679 remote} to establish communications with @code{gdbserve.nlm}. Its
10680 argument is a device name (usually a serial device, like
10681 @file{/dev/ttyb}). For example:
10684 (@value{GDBP}) target remote /dev/ttyb
10688 communications with the server via serial line @file{/dev/ttyb}.
10691 @node Remote configuration
10692 @section Remote configuration
10694 The following configuration options are available when debugging remote
10698 @kindex set remote hardware-watchpoint-limit
10699 @kindex set remote hardware-breakpoint-limit
10700 @anchor{set remote hardware-watchpoint-limit}
10701 @anchor{set remote hardware-breakpoint-limit}
10702 @item set remote hardware-watchpoint-limit @var{limit}
10703 @itemx set remote hardware-breakpoint-limit @var{limit}
10704 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
10705 watchpoints. A limit of -1, the default, is treated as unlimited.
10709 @section Implementing a remote stub
10711 @cindex debugging stub, example
10712 @cindex remote stub, example
10713 @cindex stub example, remote debugging
10714 The stub files provided with @value{GDBN} implement the target side of the
10715 communication protocol, and the @value{GDBN} side is implemented in the
10716 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
10717 these subroutines to communicate, and ignore the details. (If you're
10718 implementing your own stub file, you can still ignore the details: start
10719 with one of the existing stub files. @file{sparc-stub.c} is the best
10720 organized, and therefore the easiest to read.)
10722 @cindex remote serial debugging, overview
10723 To debug a program running on another machine (the debugging
10724 @dfn{target} machine), you must first arrange for all the usual
10725 prerequisites for the program to run by itself. For example, for a C
10730 A startup routine to set up the C runtime environment; these usually
10731 have a name like @file{crt0}. The startup routine may be supplied by
10732 your hardware supplier, or you may have to write your own.
10735 A C subroutine library to support your program's
10736 subroutine calls, notably managing input and output.
10739 A way of getting your program to the other machine---for example, a
10740 download program. These are often supplied by the hardware
10741 manufacturer, but you may have to write your own from hardware
10745 The next step is to arrange for your program to use a serial port to
10746 communicate with the machine where @value{GDBN} is running (the @dfn{host}
10747 machine). In general terms, the scheme looks like this:
10751 @value{GDBN} already understands how to use this protocol; when everything
10752 else is set up, you can simply use the @samp{target remote} command
10753 (@pxref{Targets,,Specifying a Debugging Target}).
10755 @item On the target,
10756 you must link with your program a few special-purpose subroutines that
10757 implement the @value{GDBN} remote serial protocol. The file containing these
10758 subroutines is called a @dfn{debugging stub}.
10760 On certain remote targets, you can use an auxiliary program
10761 @code{gdbserver} instead of linking a stub into your program.
10762 @xref{Server,,Using the @code{gdbserver} program}, for details.
10765 The debugging stub is specific to the architecture of the remote
10766 machine; for example, use @file{sparc-stub.c} to debug programs on
10769 @cindex remote serial stub list
10770 These working remote stubs are distributed with @value{GDBN}:
10775 @cindex @file{i386-stub.c}
10778 For Intel 386 and compatible architectures.
10781 @cindex @file{m68k-stub.c}
10782 @cindex Motorola 680x0
10784 For Motorola 680x0 architectures.
10787 @cindex @file{sh-stub.c}
10790 For Hitachi SH architectures.
10793 @cindex @file{sparc-stub.c}
10795 For @sc{sparc} architectures.
10797 @item sparcl-stub.c
10798 @cindex @file{sparcl-stub.c}
10801 For Fujitsu @sc{sparclite} architectures.
10805 The @file{README} file in the @value{GDBN} distribution may list other
10806 recently added stubs.
10809 * Stub Contents:: What the stub can do for you
10810 * Bootstrapping:: What you must do for the stub
10811 * Debug Session:: Putting it all together
10814 @node Stub Contents
10815 @subsection What the stub can do for you
10817 @cindex remote serial stub
10818 The debugging stub for your architecture supplies these three
10822 @item set_debug_traps
10823 @kindex set_debug_traps
10824 @cindex remote serial stub, initialization
10825 This routine arranges for @code{handle_exception} to run when your
10826 program stops. You must call this subroutine explicitly near the
10827 beginning of your program.
10829 @item handle_exception
10830 @kindex handle_exception
10831 @cindex remote serial stub, main routine
10832 This is the central workhorse, but your program never calls it
10833 explicitly---the setup code arranges for @code{handle_exception} to
10834 run when a trap is triggered.
10836 @code{handle_exception} takes control when your program stops during
10837 execution (for example, on a breakpoint), and mediates communications
10838 with @value{GDBN} on the host machine. This is where the communications
10839 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
10840 representative on the target machine. It begins by sending summary
10841 information on the state of your program, then continues to execute,
10842 retrieving and transmitting any information @value{GDBN} needs, until you
10843 execute a @value{GDBN} command that makes your program resume; at that point,
10844 @code{handle_exception} returns control to your own code on the target
10848 @cindex @code{breakpoint} subroutine, remote
10849 Use this auxiliary subroutine to make your program contain a
10850 breakpoint. Depending on the particular situation, this may be the only
10851 way for @value{GDBN} to get control. For instance, if your target
10852 machine has some sort of interrupt button, you won't need to call this;
10853 pressing the interrupt button transfers control to
10854 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
10855 simply receiving characters on the serial port may also trigger a trap;
10856 again, in that situation, you don't need to call @code{breakpoint} from
10857 your own program---simply running @samp{target remote} from the host
10858 @value{GDBN} session gets control.
10860 Call @code{breakpoint} if none of these is true, or if you simply want
10861 to make certain your program stops at a predetermined point for the
10862 start of your debugging session.
10865 @node Bootstrapping
10866 @subsection What you must do for the stub
10868 @cindex remote stub, support routines
10869 The debugging stubs that come with @value{GDBN} are set up for a particular
10870 chip architecture, but they have no information about the rest of your
10871 debugging target machine.
10873 First of all you need to tell the stub how to communicate with the
10877 @item int getDebugChar()
10878 @kindex getDebugChar
10879 Write this subroutine to read a single character from the serial port.
10880 It may be identical to @code{getchar} for your target system; a
10881 different name is used to allow you to distinguish the two if you wish.
10883 @item void putDebugChar(int)
10884 @kindex putDebugChar
10885 Write this subroutine to write a single character to the serial port.
10886 It may be identical to @code{putchar} for your target system; a
10887 different name is used to allow you to distinguish the two if you wish.
10890 @cindex control C, and remote debugging
10891 @cindex interrupting remote targets
10892 If you want @value{GDBN} to be able to stop your program while it is
10893 running, you need to use an interrupt-driven serial driver, and arrange
10894 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
10895 character). That is the character which @value{GDBN} uses to tell the
10896 remote system to stop.
10898 Getting the debugging target to return the proper status to @value{GDBN}
10899 probably requires changes to the standard stub; one quick and dirty way
10900 is to just execute a breakpoint instruction (the ``dirty'' part is that
10901 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
10903 Other routines you need to supply are:
10906 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
10907 @kindex exceptionHandler
10908 Write this function to install @var{exception_address} in the exception
10909 handling tables. You need to do this because the stub does not have any
10910 way of knowing what the exception handling tables on your target system
10911 are like (for example, the processor's table might be in @sc{rom},
10912 containing entries which point to a table in @sc{ram}).
10913 @var{exception_number} is the exception number which should be changed;
10914 its meaning is architecture-dependent (for example, different numbers
10915 might represent divide by zero, misaligned access, etc). When this
10916 exception occurs, control should be transferred directly to
10917 @var{exception_address}, and the processor state (stack, registers,
10918 and so on) should be just as it is when a processor exception occurs. So if
10919 you want to use a jump instruction to reach @var{exception_address}, it
10920 should be a simple jump, not a jump to subroutine.
10922 For the 386, @var{exception_address} should be installed as an interrupt
10923 gate so that interrupts are masked while the handler runs. The gate
10924 should be at privilege level 0 (the most privileged level). The
10925 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
10926 help from @code{exceptionHandler}.
10928 @item void flush_i_cache()
10929 @kindex flush_i_cache
10930 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
10931 instruction cache, if any, on your target machine. If there is no
10932 instruction cache, this subroutine may be a no-op.
10934 On target machines that have instruction caches, @value{GDBN} requires this
10935 function to make certain that the state of your program is stable.
10939 You must also make sure this library routine is available:
10942 @item void *memset(void *, int, int)
10944 This is the standard library function @code{memset} that sets an area of
10945 memory to a known value. If you have one of the free versions of
10946 @code{libc.a}, @code{memset} can be found there; otherwise, you must
10947 either obtain it from your hardware manufacturer, or write your own.
10950 If you do not use the GNU C compiler, you may need other standard
10951 library subroutines as well; this varies from one stub to another,
10952 but in general the stubs are likely to use any of the common library
10953 subroutines which @code{@value{GCC}} generates as inline code.
10956 @node Debug Session
10957 @subsection Putting it all together
10959 @cindex remote serial debugging summary
10960 In summary, when your program is ready to debug, you must follow these
10965 Make sure you have defined the supporting low-level routines
10966 (@pxref{Bootstrapping,,What you must do for the stub}):
10968 @code{getDebugChar}, @code{putDebugChar},
10969 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
10973 Insert these lines near the top of your program:
10981 For the 680x0 stub only, you need to provide a variable called
10982 @code{exceptionHook}. Normally you just use:
10985 void (*exceptionHook)() = 0;
10989 but if before calling @code{set_debug_traps}, you set it to point to a
10990 function in your program, that function is called when
10991 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
10992 error). The function indicated by @code{exceptionHook} is called with
10993 one parameter: an @code{int} which is the exception number.
10996 Compile and link together: your program, the @value{GDBN} debugging stub for
10997 your target architecture, and the supporting subroutines.
11000 Make sure you have a serial connection between your target machine and
11001 the @value{GDBN} host, and identify the serial port on the host.
11004 @c The "remote" target now provides a `load' command, so we should
11005 @c document that. FIXME.
11006 Download your program to your target machine (or get it there by
11007 whatever means the manufacturer provides), and start it.
11010 To start remote debugging, run @value{GDBN} on the host machine, and specify
11011 as an executable file the program that is running in the remote machine.
11012 This tells @value{GDBN} how to find your program's symbols and the contents
11016 @cindex serial line, @code{target remote}
11017 Establish communication using the @code{target remote} command.
11018 Its argument specifies how to communicate with the target
11019 machine---either via a devicename attached to a direct serial line, or a
11020 TCP or UDP port (usually to a terminal server which in turn has a serial line
11021 to the target). For example, to use a serial line connected to the
11022 device named @file{/dev/ttyb}:
11025 target remote /dev/ttyb
11028 @cindex TCP port, @code{target remote}
11029 To use a TCP connection, use an argument of the form
11030 @code{@var{host}:@var{port}} or @code{tcp:@var{host}:@var{port}}.
11031 For example, to connect to port 2828 on a
11032 terminal server named @code{manyfarms}:
11035 target remote manyfarms:2828
11038 If your remote target is actually running on the same machine as
11039 your debugger session (e.g.@: a simulator of your target running on
11040 the same host), you can omit the hostname. For example, to connect
11041 to port 1234 on your local machine:
11044 target remote :1234
11048 Note that the colon is still required here.
11050 @cindex UDP port, @code{target remote}
11051 To use a UDP connection, use an argument of the form
11052 @code{udp:@var{host}:@var{port}}. For example, to connect to UDP port 2828
11053 on a terminal server named @code{manyfarms}:
11056 target remote udp:manyfarms:2828
11059 When using a UDP connection for remote debugging, you should keep in mind
11060 that the `U' stands for ``Unreliable''. UDP can silently drop packets on
11061 busy or unreliable networks, which will cause havoc with your debugging
11066 Now you can use all the usual commands to examine and change data and to
11067 step and continue the remote program.
11069 To resume the remote program and stop debugging it, use the @code{detach}
11072 @cindex interrupting remote programs
11073 @cindex remote programs, interrupting
11074 Whenever @value{GDBN} is waiting for the remote program, if you type the
11075 interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the
11076 program. This may or may not succeed, depending in part on the hardware
11077 and the serial drivers the remote system uses. If you type the
11078 interrupt character once again, @value{GDBN} displays this prompt:
11081 Interrupted while waiting for the program.
11082 Give up (and stop debugging it)? (y or n)
11085 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
11086 (If you decide you want to try again later, you can use @samp{target
11087 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
11088 goes back to waiting.
11091 @node Configurations
11092 @chapter Configuration-Specific Information
11094 While nearly all @value{GDBN} commands are available for all native and
11095 cross versions of the debugger, there are some exceptions. This chapter
11096 describes things that are only available in certain configurations.
11098 There are three major categories of configurations: native
11099 configurations, where the host and target are the same, embedded
11100 operating system configurations, which are usually the same for several
11101 different processor architectures, and bare embedded processors, which
11102 are quite different from each other.
11107 * Embedded Processors::
11114 This section describes details specific to particular native
11119 * SVR4 Process Information:: SVR4 process information
11120 * DJGPP Native:: Features specific to the DJGPP port
11121 * Cygwin Native:: Features specific to the Cygwin port
11127 On HP-UX systems, if you refer to a function or variable name that
11128 begins with a dollar sign, @value{GDBN} searches for a user or system
11129 name first, before it searches for a convenience variable.
11131 @node SVR4 Process Information
11132 @subsection SVR4 process information
11135 @cindex process image
11137 Many versions of SVR4 provide a facility called @samp{/proc} that can be
11138 used to examine the image of a running process using file-system
11139 subroutines. If @value{GDBN} is configured for an operating system with
11140 this facility, the command @code{info proc} is available to report on
11141 several kinds of information about the process running your program.
11142 @code{info proc} works only on SVR4 systems that include the
11143 @code{procfs} code. This includes OSF/1 (Digital Unix), Solaris, Irix,
11144 and Unixware, but not HP-UX or @sc{gnu}/Linux, for example.
11149 Summarize available information about the process.
11151 @kindex info proc mappings
11152 @item info proc mappings
11153 Report on the address ranges accessible in the program, with information
11154 on whether your program may read, write, or execute each range.
11156 @comment These sub-options of 'info proc' were not included when
11157 @comment procfs.c was re-written. Keep their descriptions around
11158 @comment against the day when someone finds the time to put them back in.
11159 @kindex info proc times
11160 @item info proc times
11161 Starting time, user CPU time, and system CPU time for your program and
11164 @kindex info proc id
11166 Report on the process IDs related to your program: its own process ID,
11167 the ID of its parent, the process group ID, and the session ID.
11169 @kindex info proc status
11170 @item info proc status
11171 General information on the state of the process. If the process is
11172 stopped, this report includes the reason for stopping, and any signal
11175 @item info proc all
11176 Show all the above information about the process.
11181 @subsection Features for Debugging @sc{djgpp} Programs
11182 @cindex @sc{djgpp} debugging
11183 @cindex native @sc{djgpp} debugging
11184 @cindex MS-DOS-specific commands
11186 @sc{djgpp} is the port of @sc{gnu} development tools to MS-DOS and
11187 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
11188 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
11189 top of real-mode DOS systems and their emulations.
11191 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
11192 defines a few commands specific to the @sc{djgpp} port. This
11193 subsection describes those commands.
11198 This is a prefix of @sc{djgpp}-specific commands which print
11199 information about the target system and important OS structures.
11202 @cindex MS-DOS system info
11203 @cindex free memory information (MS-DOS)
11204 @item info dos sysinfo
11205 This command displays assorted information about the underlying
11206 platform: the CPU type and features, the OS version and flavor, the
11207 DPMI version, and the available conventional and DPMI memory.
11212 @cindex segment descriptor tables
11213 @cindex descriptor tables display
11215 @itemx info dos ldt
11216 @itemx info dos idt
11217 These 3 commands display entries from, respectively, Global, Local,
11218 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
11219 tables are data structures which store a descriptor for each segment
11220 that is currently in use. The segment's selector is an index into a
11221 descriptor table; the table entry for that index holds the
11222 descriptor's base address and limit, and its attributes and access
11225 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
11226 segment (used for both data and the stack), and a DOS segment (which
11227 allows access to DOS/BIOS data structures and absolute addresses in
11228 conventional memory). However, the DPMI host will usually define
11229 additional segments in order to support the DPMI environment.
11231 @cindex garbled pointers
11232 These commands allow to display entries from the descriptor tables.
11233 Without an argument, all entries from the specified table are
11234 displayed. An argument, which should be an integer expression, means
11235 display a single entry whose index is given by the argument. For
11236 example, here's a convenient way to display information about the
11237 debugged program's data segment:
11240 @exdent @code{(@value{GDBP}) info dos ldt $ds}
11241 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
11245 This comes in handy when you want to see whether a pointer is outside
11246 the data segment's limit (i.e.@: @dfn{garbled}).
11248 @cindex page tables display (MS-DOS)
11250 @itemx info dos pte
11251 These two commands display entries from, respectively, the Page
11252 Directory and the Page Tables. Page Directories and Page Tables are
11253 data structures which control how virtual memory addresses are mapped
11254 into physical addresses. A Page Table includes an entry for every
11255 page of memory that is mapped into the program's address space; there
11256 may be several Page Tables, each one holding up to 4096 entries. A
11257 Page Directory has up to 4096 entries, one each for every Page Table
11258 that is currently in use.
11260 Without an argument, @kbd{info dos pde} displays the entire Page
11261 Directory, and @kbd{info dos pte} displays all the entries in all of
11262 the Page Tables. An argument, an integer expression, given to the
11263 @kbd{info dos pde} command means display only that entry from the Page
11264 Directory table. An argument given to the @kbd{info dos pte} command
11265 means display entries from a single Page Table, the one pointed to by
11266 the specified entry in the Page Directory.
11268 @cindex direct memory access (DMA) on MS-DOS
11269 These commands are useful when your program uses @dfn{DMA} (Direct
11270 Memory Access), which needs physical addresses to program the DMA
11273 These commands are supported only with some DPMI servers.
11275 @cindex physical address from linear address
11276 @item info dos address-pte @var{addr}
11277 This command displays the Page Table entry for a specified linear
11278 address. The argument linear address @var{addr} should already have the
11279 appropriate segment's base address added to it, because this command
11280 accepts addresses which may belong to @emph{any} segment. For
11281 example, here's how to display the Page Table entry for the page where
11282 the variable @code{i} is stored:
11285 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
11286 @exdent @code{Page Table entry for address 0x11a00d30:}
11287 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
11291 This says that @code{i} is stored at offset @code{0xd30} from the page
11292 whose physical base address is @code{0x02698000}, and prints all the
11293 attributes of that page.
11295 Note that you must cast the addresses of variables to a @code{char *},
11296 since otherwise the value of @code{__djgpp_base_address}, the base
11297 address of all variables and functions in a @sc{djgpp} program, will
11298 be added using the rules of C pointer arithmetics: if @code{i} is
11299 declared an @code{int}, @value{GDBN} will add 4 times the value of
11300 @code{__djgpp_base_address} to the address of @code{i}.
11302 Here's another example, it displays the Page Table entry for the
11306 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
11307 @exdent @code{Page Table entry for address 0x29110:}
11308 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
11312 (The @code{+ 3} offset is because the transfer buffer's address is the
11313 3rd member of the @code{_go32_info_block} structure.) The output of
11314 this command clearly shows that addresses in conventional memory are
11315 mapped 1:1, i.e.@: the physical and linear addresses are identical.
11317 This command is supported only with some DPMI servers.
11320 @node Cygwin Native
11321 @subsection Features for Debugging MS Windows PE executables
11322 @cindex MS Windows debugging
11323 @cindex native Cygwin debugging
11324 @cindex Cygwin-specific commands
11326 @value{GDBN} supports native debugging of MS Windows programs, including
11327 DLLs with and without symbolic debugging information. There are various
11328 additional Cygwin-specific commands, described in this subsection. The
11329 subsubsection @pxref{Non-debug DLL symbols} describes working with DLLs
11330 that have no debugging symbols.
11336 This is a prefix of MS Windows specific commands which print
11337 information about the target system and important OS structures.
11339 @item info w32 selector
11340 This command displays information returned by
11341 the Win32 API @code{GetThreadSelectorEntry} function.
11342 It takes an optional argument that is evaluated to
11343 a long value to give the information about this given selector.
11344 Without argument, this command displays information
11345 about the the six segment registers.
11349 This is a Cygwin specific alias of info shared.
11351 @kindex dll-symbols
11353 This command loads symbols from a dll similarly to
11354 add-sym command but without the need to specify a base address.
11356 @kindex set new-console
11357 @item set new-console @var{mode}
11358 If @var{mode} is @code{on} the debuggee will
11359 be started in a new console on next start.
11360 If @var{mode} is @code{off}i, the debuggee will
11361 be started in the same console as the debugger.
11363 @kindex show new-console
11364 @item show new-console
11365 Displays whether a new console is used
11366 when the debuggee is started.
11368 @kindex set new-group
11369 @item set new-group @var{mode}
11370 This boolean value controls whether the debuggee should
11371 start a new group or stay in the same group as the debugger.
11372 This affects the way the Windows OS handles
11375 @kindex show new-group
11376 @item show new-group
11377 Displays current value of new-group boolean.
11379 @kindex set debugevents
11380 @item set debugevents
11381 This boolean value adds debug output concerning events seen by the debugger.
11383 @kindex set debugexec
11384 @item set debugexec
11385 This boolean value adds debug output concerning execute events
11386 seen by the debugger.
11388 @kindex set debugexceptions
11389 @item set debugexceptions
11390 This boolean value adds debug ouptut concerning exception events
11391 seen by the debugger.
11393 @kindex set debugmemory
11394 @item set debugmemory
11395 This boolean value adds debug ouptut concerning memory events
11396 seen by the debugger.
11400 This boolean values specifies whether the debuggee is called
11401 via a shell or directly (default value is on).
11405 Displays if the debuggee will be started with a shell.
11410 * Non-debug DLL symbols:: Support for DLLs without debugging symbols
11413 @node Non-debug DLL symbols
11414 @subsubsection Support for DLLs without debugging symbols
11415 @cindex DLLs with no debugging symbols
11416 @cindex Minimal symbols and DLLs
11418 Very often on windows, some of the DLLs that your program relies on do
11419 not include symbolic debugging information (for example,
11420 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
11421 symbols in a DLL, it relies on the minimal amount of symbolic
11422 information contained in the DLL's export table. This subsubsection
11423 describes working with such symbols, known internally to @value{GDBN} as
11424 ``minimal symbols''.
11426 Note that before the debugged program has started execution, no DLLs
11427 will have been loaded. The easiest way around this problem is simply to
11428 start the program --- either by setting a breakpoint or letting the
11429 program run once to completion. It is also possible to force
11430 @value{GDBN} to load a particular DLL before starting the executable ---
11431 see the shared library information in @pxref{Files} or the
11432 @code{dll-symbols} command in @pxref{Cygwin Native}. Currently,
11433 explicitly loading symbols from a DLL with no debugging information will
11434 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
11435 which may adversely affect symbol lookup performance.
11437 @subsubsection DLL name prefixes
11439 In keeping with the naming conventions used by the Microsoft debugging
11440 tools, DLL export symbols are made available with a prefix based on the
11441 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
11442 also entered into the symbol table, so @code{CreateFileA} is often
11443 sufficient. In some cases there will be name clashes within a program
11444 (particularly if the executable itself includes full debugging symbols)
11445 necessitating the use of the fully qualified name when referring to the
11446 contents of the DLL. Use single-quotes around the name to avoid the
11447 exclamation mark (``!'') being interpreted as a language operator.
11449 Note that the internal name of the DLL may be all upper-case, even
11450 though the file name of the DLL is lower-case, or vice-versa. Since
11451 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
11452 some confusion. If in doubt, try the @code{info functions} and
11453 @code{info variables} commands or even @code{maint print msymbols} (see
11454 @pxref{Symbols}). Here's an example:
11457 (gdb) info function CreateFileA
11458 All functions matching regular expression "CreateFileA":
11460 Non-debugging symbols:
11461 0x77e885f4 CreateFileA
11462 0x77e885f4 KERNEL32!CreateFileA
11466 (gdb) info function !
11467 All functions matching regular expression "!":
11469 Non-debugging symbols:
11470 0x6100114c cygwin1!__assert
11471 0x61004034 cygwin1!_dll_crt0@@0
11472 0x61004240 cygwin1!dll_crt0(per_process *)
11476 @subsubsection Working with minimal symbols
11478 Symbols extracted from a DLL's export table do not contain very much
11479 type information. All that @value{GDBN} can do is guess whether a symbol
11480 refers to a function or variable depending on the linker section that
11481 contains the symbol. Also note that the actual contents of the memory
11482 contained in a DLL are not available unless the program is running. This
11483 means that you cannot examine the contents of a variable or disassemble
11484 a function within a DLL without a running program.
11486 Variables are generally treated as pointers and dereferenced
11487 automatically. For this reason, it is often necessary to prefix a
11488 variable name with the address-of operator (``&'') and provide explicit
11489 type information in the command. Here's an example of the type of
11493 (gdb) print 'cygwin1!__argv'
11498 (gdb) x 'cygwin1!__argv'
11499 0x10021610: "\230y\""
11502 And two possible solutions:
11505 (gdb) print ((char **)'cygwin1!__argv')[0]
11506 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
11510 (gdb) x/2x &'cygwin1!__argv'
11511 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
11512 (gdb) x/x 0x10021608
11513 0x10021608: 0x0022fd98
11514 (gdb) x/s 0x0022fd98
11515 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
11518 Setting a break point within a DLL is possible even before the program
11519 starts execution. However, under these circumstances, @value{GDBN} can't
11520 examine the initial instructions of the function in order to skip the
11521 function's frame set-up code. You can work around this by using ``*&''
11522 to set the breakpoint at a raw memory address:
11525 (gdb) break *&'python22!PyOS_Readline'
11526 Breakpoint 1 at 0x1e04eff0
11529 The author of these extensions is not entirely convinced that setting a
11530 break point within a shared DLL like @file{kernel32.dll} is completely
11534 @section Embedded Operating Systems
11536 This section describes configurations involving the debugging of
11537 embedded operating systems that are available for several different
11541 * VxWorks:: Using @value{GDBN} with VxWorks
11544 @value{GDBN} includes the ability to debug programs running on
11545 various real-time operating systems.
11548 @subsection Using @value{GDBN} with VxWorks
11554 @kindex target vxworks
11555 @item target vxworks @var{machinename}
11556 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
11557 is the target system's machine name or IP address.
11561 On VxWorks, @code{load} links @var{filename} dynamically on the
11562 current target system as well as adding its symbols in @value{GDBN}.
11564 @value{GDBN} enables developers to spawn and debug tasks running on networked
11565 VxWorks targets from a Unix host. Already-running tasks spawned from
11566 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
11567 both the Unix host and on the VxWorks target. The program
11568 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
11569 installed with the name @code{vxgdb}, to distinguish it from a
11570 @value{GDBN} for debugging programs on the host itself.)
11573 @item VxWorks-timeout @var{args}
11574 @kindex vxworks-timeout
11575 All VxWorks-based targets now support the option @code{vxworks-timeout}.
11576 This option is set by the user, and @var{args} represents the number of
11577 seconds @value{GDBN} waits for responses to rpc's. You might use this if
11578 your VxWorks target is a slow software simulator or is on the far side
11579 of a thin network line.
11582 The following information on connecting to VxWorks was current when
11583 this manual was produced; newer releases of VxWorks may use revised
11586 @kindex INCLUDE_RDB
11587 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
11588 to include the remote debugging interface routines in the VxWorks
11589 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
11590 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
11591 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
11592 source debugging task @code{tRdbTask} when VxWorks is booted. For more
11593 information on configuring and remaking VxWorks, see the manufacturer's
11595 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
11597 Once you have included @file{rdb.a} in your VxWorks system image and set
11598 your Unix execution search path to find @value{GDBN}, you are ready to
11599 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
11600 @code{vxgdb}, depending on your installation).
11602 @value{GDBN} comes up showing the prompt:
11609 * VxWorks Connection:: Connecting to VxWorks
11610 * VxWorks Download:: VxWorks download
11611 * VxWorks Attach:: Running tasks
11614 @node VxWorks Connection
11615 @subsubsection Connecting to VxWorks
11617 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
11618 network. To connect to a target whose host name is ``@code{tt}'', type:
11621 (vxgdb) target vxworks tt
11625 @value{GDBN} displays messages like these:
11628 Attaching remote machine across net...
11633 @value{GDBN} then attempts to read the symbol tables of any object modules
11634 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
11635 these files by searching the directories listed in the command search
11636 path (@pxref{Environment, ,Your program's environment}); if it fails
11637 to find an object file, it displays a message such as:
11640 prog.o: No such file or directory.
11643 When this happens, add the appropriate directory to the search path with
11644 the @value{GDBN} command @code{path}, and execute the @code{target}
11647 @node VxWorks Download
11648 @subsubsection VxWorks download
11650 @cindex download to VxWorks
11651 If you have connected to the VxWorks target and you want to debug an
11652 object that has not yet been loaded, you can use the @value{GDBN}
11653 @code{load} command to download a file from Unix to VxWorks
11654 incrementally. The object file given as an argument to the @code{load}
11655 command is actually opened twice: first by the VxWorks target in order
11656 to download the code, then by @value{GDBN} in order to read the symbol
11657 table. This can lead to problems if the current working directories on
11658 the two systems differ. If both systems have NFS mounted the same
11659 filesystems, you can avoid these problems by using absolute paths.
11660 Otherwise, it is simplest to set the working directory on both systems
11661 to the directory in which the object file resides, and then to reference
11662 the file by its name, without any path. For instance, a program
11663 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
11664 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
11665 program, type this on VxWorks:
11668 -> cd "@var{vxpath}/vw/demo/rdb"
11672 Then, in @value{GDBN}, type:
11675 (vxgdb) cd @var{hostpath}/vw/demo/rdb
11676 (vxgdb) load prog.o
11679 @value{GDBN} displays a response similar to this:
11682 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
11685 You can also use the @code{load} command to reload an object module
11686 after editing and recompiling the corresponding source file. Note that
11687 this makes @value{GDBN} delete all currently-defined breakpoints,
11688 auto-displays, and convenience variables, and to clear the value
11689 history. (This is necessary in order to preserve the integrity of
11690 debugger's data structures that reference the target system's symbol
11693 @node VxWorks Attach
11694 @subsubsection Running tasks
11696 @cindex running VxWorks tasks
11697 You can also attach to an existing task using the @code{attach} command as
11701 (vxgdb) attach @var{task}
11705 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
11706 or suspended when you attach to it. Running tasks are suspended at
11707 the time of attachment.
11709 @node Embedded Processors
11710 @section Embedded Processors
11712 This section goes into details specific to particular embedded
11718 * H8/300:: Hitachi H8/300
11719 * H8/500:: Hitachi H8/500
11720 * M32R/D:: Mitsubishi M32R/D
11721 * M68K:: Motorola M68K
11722 * MIPS Embedded:: MIPS Embedded
11723 * OpenRISC 1000:: OpenRisc 1000
11724 * PA:: HP PA Embedded
11727 * Sparclet:: Tsqware Sparclet
11728 * Sparclite:: Fujitsu Sparclite
11729 * ST2000:: Tandem ST2000
11730 * Z8000:: Zilog Z8000
11739 @item target rdi @var{dev}
11740 ARM Angel monitor, via RDI library interface to ADP protocol. You may
11741 use this target to communicate with both boards running the Angel
11742 monitor, or with the EmbeddedICE JTAG debug device.
11745 @item target rdp @var{dev}
11751 @subsection Hitachi H8/300
11755 @kindex target hms@r{, with H8/300}
11756 @item target hms @var{dev}
11757 A Hitachi SH, H8/300, or H8/500 board, attached via serial line to your host.
11758 Use special commands @code{device} and @code{speed} to control the serial
11759 line and the communications speed used.
11761 @kindex target e7000@r{, with H8/300}
11762 @item target e7000 @var{dev}
11763 E7000 emulator for Hitachi H8 and SH.
11765 @kindex target sh3@r{, with H8/300}
11766 @kindex target sh3e@r{, with H8/300}
11767 @item target sh3 @var{dev}
11768 @itemx target sh3e @var{dev}
11769 Hitachi SH-3 and SH-3E target systems.
11773 @cindex download to H8/300 or H8/500
11774 @cindex H8/300 or H8/500 download
11775 @cindex download to Hitachi SH
11776 @cindex Hitachi SH download
11777 When you select remote debugging to a Hitachi SH, H8/300, or H8/500
11778 board, the @code{load} command downloads your program to the Hitachi
11779 board and also opens it as the current executable target for
11780 @value{GDBN} on your host (like the @code{file} command).
11782 @value{GDBN} needs to know these things to talk to your
11783 Hitachi SH, H8/300, or H8/500:
11787 that you want to use @samp{target hms}, the remote debugging interface
11788 for Hitachi microprocessors, or @samp{target e7000}, the in-circuit
11789 emulator for the Hitachi SH and the Hitachi 300H. (@samp{target hms} is
11790 the default when @value{GDBN} is configured specifically for the Hitachi SH,
11791 H8/300, or H8/500.)
11794 what serial device connects your host to your Hitachi board (the first
11795 serial device available on your host is the default).
11798 what speed to use over the serial device.
11802 * Hitachi Boards:: Connecting to Hitachi boards.
11803 * Hitachi ICE:: Using the E7000 In-Circuit Emulator.
11804 * Hitachi Special:: Special @value{GDBN} commands for Hitachi micros.
11807 @node Hitachi Boards
11808 @subsubsection Connecting to Hitachi boards
11810 @c only for Unix hosts
11812 @cindex serial device, Hitachi micros
11813 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
11814 need to explicitly set the serial device. The default @var{port} is the
11815 first available port on your host. This is only necessary on Unix
11816 hosts, where it is typically something like @file{/dev/ttya}.
11819 @cindex serial line speed, Hitachi micros
11820 @code{@value{GDBN}} has another special command to set the communications
11821 speed: @samp{speed @var{bps}}. This command also is only used from Unix
11822 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
11823 the DOS @code{mode} command (for instance,
11824 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
11826 The @samp{device} and @samp{speed} commands are available only when you
11827 use a Unix host to debug your Hitachi microprocessor programs. If you
11829 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
11830 called @code{asynctsr} to communicate with the development board
11831 through a PC serial port. You must also use the DOS @code{mode} command
11832 to set up the serial port on the DOS side.
11834 The following sample session illustrates the steps needed to start a
11835 program under @value{GDBN} control on an H8/300. The example uses a
11836 sample H8/300 program called @file{t.x}. The procedure is the same for
11837 the Hitachi SH and the H8/500.
11839 First hook up your development board. In this example, we use a
11840 board attached to serial port @code{COM2}; if you use a different serial
11841 port, substitute its name in the argument of the @code{mode} command.
11842 When you call @code{asynctsr}, the auxiliary comms program used by the
11843 debugger, you give it just the numeric part of the serial port's name;
11844 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
11848 C:\H8300\TEST> asynctsr 2
11849 C:\H8300\TEST> mode com2:9600,n,8,1,p
11851 Resident portion of MODE loaded
11853 COM2: 9600, n, 8, 1, p
11858 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
11859 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
11860 disable it, or even boot without it, to use @code{asynctsr} to control
11861 your development board.
11864 @kindex target hms@r{, and serial protocol}
11865 Now that serial communications are set up, and the development board is
11866 connected, you can start up @value{GDBN}. Call @code{@value{GDBP}} with
11867 the name of your program as the argument. @code{@value{GDBN}} prompts
11868 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
11869 commands to begin your debugging session: @samp{target hms} to specify
11870 cross-debugging to the Hitachi board, and the @code{load} command to
11871 download your program to the board. @code{load} displays the names of
11872 the program's sections, and a @samp{*} for each 2K of data downloaded.
11873 (If you want to refresh @value{GDBN} data on symbols or on the
11874 executable file without downloading, use the @value{GDBN} commands
11875 @code{file} or @code{symbol-file}. These commands, and @code{load}
11876 itself, are described in @ref{Files,,Commands to specify files}.)
11879 (eg-C:\H8300\TEST) @value{GDBP} t.x
11880 @value{GDBN} is free software and you are welcome to distribute copies
11881 of it under certain conditions; type "show copying" to see
11883 There is absolutely no warranty for @value{GDBN}; type "show warranty"
11885 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
11886 (@value{GDBP}) target hms
11887 Connected to remote H8/300 HMS system.
11888 (@value{GDBP}) load t.x
11889 .text : 0x8000 .. 0xabde ***********
11890 .data : 0xabde .. 0xad30 *
11891 .stack : 0xf000 .. 0xf014 *
11894 At this point, you're ready to run or debug your program. From here on,
11895 you can use all the usual @value{GDBN} commands. The @code{break} command
11896 sets breakpoints; the @code{run} command starts your program;
11897 @code{print} or @code{x} display data; the @code{continue} command
11898 resumes execution after stopping at a breakpoint. You can use the
11899 @code{help} command at any time to find out more about @value{GDBN} commands.
11901 Remember, however, that @emph{operating system} facilities aren't
11902 available on your development board; for example, if your program hangs,
11903 you can't send an interrupt---but you can press the @sc{reset} switch!
11905 Use the @sc{reset} button on the development board
11908 to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has
11909 no way to pass an interrupt signal to the development board); and
11912 to return to the @value{GDBN} command prompt after your program finishes
11913 normally. The communications protocol provides no other way for @value{GDBN}
11914 to detect program completion.
11917 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
11918 development board as a ``normal exit'' of your program.
11921 @subsubsection Using the E7000 in-circuit emulator
11923 @kindex target e7000@r{, with Hitachi ICE}
11924 You can use the E7000 in-circuit emulator to develop code for either the
11925 Hitachi SH or the H8/300H. Use one of these forms of the @samp{target
11926 e7000} command to connect @value{GDBN} to your E7000:
11929 @item target e7000 @var{port} @var{speed}
11930 Use this form if your E7000 is connected to a serial port. The
11931 @var{port} argument identifies what serial port to use (for example,
11932 @samp{com2}). The third argument is the line speed in bits per second
11933 (for example, @samp{9600}).
11935 @item target e7000 @var{hostname}
11936 If your E7000 is installed as a host on a TCP/IP network, you can just
11937 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
11940 @node Hitachi Special
11941 @subsubsection Special @value{GDBN} commands for Hitachi micros
11943 Some @value{GDBN} commands are available only for the H8/300:
11947 @kindex set machine
11948 @kindex show machine
11949 @item set machine h8300
11950 @itemx set machine h8300h
11951 Condition @value{GDBN} for one of the two variants of the H8/300
11952 architecture with @samp{set machine}. You can use @samp{show machine}
11953 to check which variant is currently in effect.
11962 @kindex set memory @var{mod}
11963 @cindex memory models, H8/500
11964 @item set memory @var{mod}
11966 Specify which H8/500 memory model (@var{mod}) you are using with
11967 @samp{set memory}; check which memory model is in effect with @samp{show
11968 memory}. The accepted values for @var{mod} are @code{small},
11969 @code{big}, @code{medium}, and @code{compact}.
11974 @subsection Mitsubishi M32R/D
11978 @kindex target m32r
11979 @item target m32r @var{dev}
11980 Mitsubishi M32R/D ROM monitor.
11987 The Motorola m68k configuration includes ColdFire support, and
11988 target command for the following ROM monitors.
11992 @kindex target abug
11993 @item target abug @var{dev}
11994 ABug ROM monitor for M68K.
11996 @kindex target cpu32bug
11997 @item target cpu32bug @var{dev}
11998 CPU32BUG monitor, running on a CPU32 (M68K) board.
12000 @kindex target dbug
12001 @item target dbug @var{dev}
12002 dBUG ROM monitor for Motorola ColdFire.
12005 @item target est @var{dev}
12006 EST-300 ICE monitor, running on a CPU32 (M68K) board.
12008 @kindex target rom68k
12009 @item target rom68k @var{dev}
12010 ROM 68K monitor, running on an M68K IDP board.
12016 @kindex target rombug
12017 @item target rombug @var{dev}
12018 ROMBUG ROM monitor for OS/9000.
12022 @node MIPS Embedded
12023 @subsection MIPS Embedded
12025 @cindex MIPS boards
12026 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
12027 MIPS board attached to a serial line. This is available when
12028 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
12031 Use these @value{GDBN} commands to specify the connection to your target board:
12034 @item target mips @var{port}
12035 @kindex target mips @var{port}
12036 To run a program on the board, start up @code{@value{GDBP}} with the
12037 name of your program as the argument. To connect to the board, use the
12038 command @samp{target mips @var{port}}, where @var{port} is the name of
12039 the serial port connected to the board. If the program has not already
12040 been downloaded to the board, you may use the @code{load} command to
12041 download it. You can then use all the usual @value{GDBN} commands.
12043 For example, this sequence connects to the target board through a serial
12044 port, and loads and runs a program called @var{prog} through the
12048 host$ @value{GDBP} @var{prog}
12049 @value{GDBN} is free software and @dots{}
12050 (@value{GDBP}) target mips /dev/ttyb
12051 (@value{GDBP}) load @var{prog}
12055 @item target mips @var{hostname}:@var{portnumber}
12056 On some @value{GDBN} host configurations, you can specify a TCP
12057 connection (for instance, to a serial line managed by a terminal
12058 concentrator) instead of a serial port, using the syntax
12059 @samp{@var{hostname}:@var{portnumber}}.
12061 @item target pmon @var{port}
12062 @kindex target pmon @var{port}
12065 @item target ddb @var{port}
12066 @kindex target ddb @var{port}
12067 NEC's DDB variant of PMON for Vr4300.
12069 @item target lsi @var{port}
12070 @kindex target lsi @var{port}
12071 LSI variant of PMON.
12073 @kindex target r3900
12074 @item target r3900 @var{dev}
12075 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
12077 @kindex target array
12078 @item target array @var{dev}
12079 Array Tech LSI33K RAID controller board.
12085 @value{GDBN} also supports these special commands for MIPS targets:
12088 @item set processor @var{args}
12089 @itemx show processor
12090 @kindex set processor @var{args}
12091 @kindex show processor
12092 Use the @code{set processor} command to set the type of MIPS
12093 processor when you want to access processor-type-specific registers.
12094 For example, @code{set processor @var{r3041}} tells @value{GDBN}
12095 to use the CPU registers appropriate for the 3041 chip.
12096 Use the @code{show processor} command to see what MIPS processor @value{GDBN}
12097 is using. Use the @code{info reg} command to see what registers
12098 @value{GDBN} is using.
12100 @item set mipsfpu double
12101 @itemx set mipsfpu single
12102 @itemx set mipsfpu none
12103 @itemx show mipsfpu
12104 @kindex set mipsfpu
12105 @kindex show mipsfpu
12106 @cindex MIPS remote floating point
12107 @cindex floating point, MIPS remote
12108 If your target board does not support the MIPS floating point
12109 coprocessor, you should use the command @samp{set mipsfpu none} (if you
12110 need this, you may wish to put the command in your @value{GDBN} init
12111 file). This tells @value{GDBN} how to find the return value of
12112 functions which return floating point values. It also allows
12113 @value{GDBN} to avoid saving the floating point registers when calling
12114 functions on the board. If you are using a floating point coprocessor
12115 with only single precision floating point support, as on the @sc{r4650}
12116 processor, use the command @samp{set mipsfpu single}. The default
12117 double precision floating point coprocessor may be selected using
12118 @samp{set mipsfpu double}.
12120 In previous versions the only choices were double precision or no
12121 floating point, so @samp{set mipsfpu on} will select double precision
12122 and @samp{set mipsfpu off} will select no floating point.
12124 As usual, you can inquire about the @code{mipsfpu} variable with
12125 @samp{show mipsfpu}.
12127 @item set remotedebug @var{n}
12128 @itemx show remotedebug
12129 @kindex set remotedebug@r{, MIPS protocol}
12130 @kindex show remotedebug@r{, MIPS protocol}
12131 @cindex @code{remotedebug}, MIPS protocol
12132 @cindex MIPS @code{remotedebug} protocol
12133 @c FIXME! For this to be useful, you must know something about the MIPS
12134 @c FIXME...protocol. Where is it described?
12135 You can see some debugging information about communications with the board
12136 by setting the @code{remotedebug} variable. If you set it to @code{1} using
12137 @samp{set remotedebug 1}, every packet is displayed. If you set it
12138 to @code{2}, every character is displayed. You can check the current value
12139 at any time with the command @samp{show remotedebug}.
12141 @item set timeout @var{seconds}
12142 @itemx set retransmit-timeout @var{seconds}
12143 @itemx show timeout
12144 @itemx show retransmit-timeout
12145 @cindex @code{timeout}, MIPS protocol
12146 @cindex @code{retransmit-timeout}, MIPS protocol
12147 @kindex set timeout
12148 @kindex show timeout
12149 @kindex set retransmit-timeout
12150 @kindex show retransmit-timeout
12151 You can control the timeout used while waiting for a packet, in the MIPS
12152 remote protocol, with the @code{set timeout @var{seconds}} command. The
12153 default is 5 seconds. Similarly, you can control the timeout used while
12154 waiting for an acknowledgement of a packet with the @code{set
12155 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
12156 You can inspect both values with @code{show timeout} and @code{show
12157 retransmit-timeout}. (These commands are @emph{only} available when
12158 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
12160 The timeout set by @code{set timeout} does not apply when @value{GDBN}
12161 is waiting for your program to stop. In that case, @value{GDBN} waits
12162 forever because it has no way of knowing how long the program is going
12163 to run before stopping.
12166 @node OpenRISC 1000
12167 @subsection OpenRISC 1000
12168 @cindex OpenRISC 1000
12170 @cindex or1k boards
12171 See OR1k Architecture document (@uref{www.opencores.org}) for more information
12172 about platform and commands.
12176 @kindex target jtag
12177 @item target jtag jtag://@var{host}:@var{port}
12179 Connects to remote JTAG server.
12180 JTAG remote server can be either an or1ksim or JTAG server,
12181 connected via parallel port to the board.
12183 Example: @code{target jtag jtag://localhost:9999}
12186 @item or1ksim @var{command}
12187 If connected to @code{or1ksim} OpenRISC 1000 Architectural
12188 Simulator, proprietary commands can be executed.
12190 @kindex info or1k spr
12191 @item info or1k spr
12192 Displays spr groups.
12194 @item info or1k spr @var{group}
12195 @itemx info or1k spr @var{groupno}
12196 Displays register names in selected group.
12198 @item info or1k spr @var{group} @var{register}
12199 @itemx info or1k spr @var{register}
12200 @itemx info or1k spr @var{groupno} @var{registerno}
12201 @itemx info or1k spr @var{registerno}
12202 Shows information about specified spr register.
12205 @item spr @var{group} @var{register} @var{value}
12206 @itemx spr @var{register @var{value}}
12207 @itemx spr @var{groupno} @var{registerno @var{value}}
12208 @itemx spr @var{registerno @var{value}}
12209 Writes @var{value} to specified spr register.
12212 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
12213 It is very similar to @value{GDBN} trace, except it does not interfere with normal
12214 program execution and is thus much faster. Hardware breakpoints/watchpoint
12215 triggers can be set using:
12218 Load effective address/data
12220 Store effective address/data
12222 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
12227 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
12228 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
12230 @code{htrace} commands:
12231 @cindex OpenRISC 1000 htrace
12234 @item hwatch @var{conditional}
12235 Set hardware watchpoint on combination of Load/Store Effecive Address(es)
12236 or Data. For example:
12238 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
12240 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
12242 @kindex htrace info
12244 Display information about current HW trace configuration.
12246 @kindex htrace trigger
12247 @item htrace trigger @var{conditional}
12248 Set starting criteria for HW trace.
12250 @kindex htrace qualifier
12251 @item htrace qualifier @var{conditional}
12252 Set acquisition qualifier for HW trace.
12254 @kindex htrace stop
12255 @item htrace stop @var{conditional}
12256 Set HW trace stopping criteria.
12258 @kindex htrace record
12259 @item htrace record [@var{data}]*
12260 Selects the data to be recorded, when qualifier is met and HW trace was
12263 @kindex htrace enable
12264 @item htrace enable
12265 @kindex htrace disable
12266 @itemx htrace disable
12267 Enables/disables the HW trace.
12269 @kindex htrace rewind
12270 @item htrace rewind [@var{filename}]
12271 Clears currently recorded trace data.
12273 If filename is specified, new trace file is made and any newly collected data
12274 will be written there.
12276 @kindex htrace print
12277 @item htrace print [@var{start} [@var{len}]]
12278 Prints trace buffer, using current record configuration.
12280 @kindex htrace mode continuous
12281 @item htrace mode continuous
12282 Set continuous trace mode.
12284 @kindex htrace mode suspend
12285 @item htrace mode suspend
12286 Set suspend trace mode.
12291 @subsection PowerPC
12295 @kindex target dink32
12296 @item target dink32 @var{dev}
12297 DINK32 ROM monitor.
12299 @kindex target ppcbug
12300 @item target ppcbug @var{dev}
12301 @kindex target ppcbug1
12302 @item target ppcbug1 @var{dev}
12303 PPCBUG ROM monitor for PowerPC.
12306 @item target sds @var{dev}
12307 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
12312 @subsection HP PA Embedded
12316 @kindex target op50n
12317 @item target op50n @var{dev}
12318 OP50N monitor, running on an OKI HPPA board.
12320 @kindex target w89k
12321 @item target w89k @var{dev}
12322 W89K monitor, running on a Winbond HPPA board.
12327 @subsection Hitachi SH
12331 @kindex target hms@r{, with Hitachi SH}
12332 @item target hms @var{dev}
12333 A Hitachi SH board attached via serial line to your host. Use special
12334 commands @code{device} and @code{speed} to control the serial line and
12335 the communications speed used.
12337 @kindex target e7000@r{, with Hitachi SH}
12338 @item target e7000 @var{dev}
12339 E7000 emulator for Hitachi SH.
12341 @kindex target sh3@r{, with SH}
12342 @kindex target sh3e@r{, with SH}
12343 @item target sh3 @var{dev}
12344 @item target sh3e @var{dev}
12345 Hitachi SH-3 and SH-3E target systems.
12350 @subsection Tsqware Sparclet
12354 @value{GDBN} enables developers to debug tasks running on
12355 Sparclet targets from a Unix host.
12356 @value{GDBN} uses code that runs on
12357 both the Unix host and on the Sparclet target. The program
12358 @code{@value{GDBP}} is installed and executed on the Unix host.
12361 @item remotetimeout @var{args}
12362 @kindex remotetimeout
12363 @value{GDBN} supports the option @code{remotetimeout}.
12364 This option is set by the user, and @var{args} represents the number of
12365 seconds @value{GDBN} waits for responses.
12368 @cindex compiling, on Sparclet
12369 When compiling for debugging, include the options @samp{-g} to get debug
12370 information and @samp{-Ttext} to relocate the program to where you wish to
12371 load it on the target. You may also want to add the options @samp{-n} or
12372 @samp{-N} in order to reduce the size of the sections. Example:
12375 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
12378 You can use @code{objdump} to verify that the addresses are what you intended:
12381 sparclet-aout-objdump --headers --syms prog
12384 @cindex running, on Sparclet
12386 your Unix execution search path to find @value{GDBN}, you are ready to
12387 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
12388 (or @code{sparclet-aout-gdb}, depending on your installation).
12390 @value{GDBN} comes up showing the prompt:
12397 * Sparclet File:: Setting the file to debug
12398 * Sparclet Connection:: Connecting to Sparclet
12399 * Sparclet Download:: Sparclet download
12400 * Sparclet Execution:: Running and debugging
12403 @node Sparclet File
12404 @subsubsection Setting file to debug
12406 The @value{GDBN} command @code{file} lets you choose with program to debug.
12409 (gdbslet) file prog
12413 @value{GDBN} then attempts to read the symbol table of @file{prog}.
12414 @value{GDBN} locates
12415 the file by searching the directories listed in the command search
12417 If the file was compiled with debug information (option "-g"), source
12418 files will be searched as well.
12419 @value{GDBN} locates
12420 the source files by searching the directories listed in the directory search
12421 path (@pxref{Environment, ,Your program's environment}).
12423 to find a file, it displays a message such as:
12426 prog: No such file or directory.
12429 When this happens, add the appropriate directories to the search paths with
12430 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
12431 @code{target} command again.
12433 @node Sparclet Connection
12434 @subsubsection Connecting to Sparclet
12436 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
12437 To connect to a target on serial port ``@code{ttya}'', type:
12440 (gdbslet) target sparclet /dev/ttya
12441 Remote target sparclet connected to /dev/ttya
12442 main () at ../prog.c:3
12446 @value{GDBN} displays messages like these:
12452 @node Sparclet Download
12453 @subsubsection Sparclet download
12455 @cindex download to Sparclet
12456 Once connected to the Sparclet target,
12457 you can use the @value{GDBN}
12458 @code{load} command to download the file from the host to the target.
12459 The file name and load offset should be given as arguments to the @code{load}
12461 Since the file format is aout, the program must be loaded to the starting
12462 address. You can use @code{objdump} to find out what this value is. The load
12463 offset is an offset which is added to the VMA (virtual memory address)
12464 of each of the file's sections.
12465 For instance, if the program
12466 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
12467 and bss at 0x12010170, in @value{GDBN}, type:
12470 (gdbslet) load prog 0x12010000
12471 Loading section .text, size 0xdb0 vma 0x12010000
12474 If the code is loaded at a different address then what the program was linked
12475 to, you may need to use the @code{section} and @code{add-symbol-file} commands
12476 to tell @value{GDBN} where to map the symbol table.
12478 @node Sparclet Execution
12479 @subsubsection Running and debugging
12481 @cindex running and debugging Sparclet programs
12482 You can now begin debugging the task using @value{GDBN}'s execution control
12483 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
12484 manual for the list of commands.
12488 Breakpoint 1 at 0x12010000: file prog.c, line 3.
12490 Starting program: prog
12491 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
12492 3 char *symarg = 0;
12494 4 char *execarg = "hello!";
12499 @subsection Fujitsu Sparclite
12503 @kindex target sparclite
12504 @item target sparclite @var{dev}
12505 Fujitsu sparclite boards, used only for the purpose of loading.
12506 You must use an additional command to debug the program.
12507 For example: target remote @var{dev} using @value{GDBN} standard
12513 @subsection Tandem ST2000
12515 @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
12518 To connect your ST2000 to the host system, see the manufacturer's
12519 manual. Once the ST2000 is physically attached, you can run:
12522 target st2000 @var{dev} @var{speed}
12526 to establish it as your debugging environment. @var{dev} is normally
12527 the name of a serial device, such as @file{/dev/ttya}, connected to the
12528 ST2000 via a serial line. You can instead specify @var{dev} as a TCP
12529 connection (for example, to a serial line attached via a terminal
12530 concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
12532 The @code{load} and @code{attach} commands are @emph{not} defined for
12533 this target; you must load your program into the ST2000 as you normally
12534 would for standalone operation. @value{GDBN} reads debugging information
12535 (such as symbols) from a separate, debugging version of the program
12536 available on your host computer.
12537 @c FIXME!! This is terribly vague; what little content is here is
12538 @c basically hearsay.
12540 @cindex ST2000 auxiliary commands
12541 These auxiliary @value{GDBN} commands are available to help you with the ST2000
12545 @item st2000 @var{command}
12546 @kindex st2000 @var{cmd}
12547 @cindex STDBUG commands (ST2000)
12548 @cindex commands to STDBUG (ST2000)
12549 Send a @var{command} to the STDBUG monitor. See the manufacturer's
12550 manual for available commands.
12553 @cindex connect (to STDBUG)
12554 Connect the controlling terminal to the STDBUG command monitor. When
12555 you are done interacting with STDBUG, typing either of two character
12556 sequences gets you back to the @value{GDBN} command prompt:
12557 @kbd{@key{RET}~.} (Return, followed by tilde and period) or
12558 @kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D).
12562 @subsection Zilog Z8000
12565 @cindex simulator, Z8000
12566 @cindex Zilog Z8000 simulator
12568 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
12571 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
12572 unsegmented variant of the Z8000 architecture) or the Z8001 (the
12573 segmented variant). The simulator recognizes which architecture is
12574 appropriate by inspecting the object code.
12577 @item target sim @var{args}
12579 @kindex target sim@r{, with Z8000}
12580 Debug programs on a simulated CPU. If the simulator supports setup
12581 options, specify them via @var{args}.
12585 After specifying this target, you can debug programs for the simulated
12586 CPU in the same style as programs for your host computer; use the
12587 @code{file} command to load a new program image, the @code{run} command
12588 to run your program, and so on.
12590 As well as making available all the usual machine registers
12591 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
12592 additional items of information as specially named registers:
12597 Counts clock-ticks in the simulator.
12600 Counts instructions run in the simulator.
12603 Execution time in 60ths of a second.
12607 You can refer to these values in @value{GDBN} expressions with the usual
12608 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
12609 conditional breakpoint that suspends only after at least 5000
12610 simulated clock ticks.
12612 @node Architectures
12613 @section Architectures
12615 This section describes characteristics of architectures that affect
12616 all uses of @value{GDBN} with the architecture, both native and cross.
12629 @kindex set rstack_high_address
12630 @cindex AMD 29K register stack
12631 @cindex register stack, AMD29K
12632 @item set rstack_high_address @var{address}
12633 On AMD 29000 family processors, registers are saved in a separate
12634 @dfn{register stack}. There is no way for @value{GDBN} to determine the
12635 extent of this stack. Normally, @value{GDBN} just assumes that the
12636 stack is ``large enough''. This may result in @value{GDBN} referencing
12637 memory locations that do not exist. If necessary, you can get around
12638 this problem by specifying the ending address of the register stack with
12639 the @code{set rstack_high_address} command. The argument should be an
12640 address, which you probably want to precede with @samp{0x} to specify in
12643 @kindex show rstack_high_address
12644 @item show rstack_high_address
12645 Display the current limit of the register stack, on AMD 29000 family
12653 See the following section.
12658 @cindex stack on Alpha
12659 @cindex stack on MIPS
12660 @cindex Alpha stack
12662 Alpha- and MIPS-based computers use an unusual stack frame, which
12663 sometimes requires @value{GDBN} to search backward in the object code to
12664 find the beginning of a function.
12666 @cindex response time, MIPS debugging
12667 To improve response time (especially for embedded applications, where
12668 @value{GDBN} may be restricted to a slow serial line for this search)
12669 you may want to limit the size of this search, using one of these
12673 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
12674 @item set heuristic-fence-post @var{limit}
12675 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
12676 search for the beginning of a function. A value of @var{0} (the
12677 default) means there is no limit. However, except for @var{0}, the
12678 larger the limit the more bytes @code{heuristic-fence-post} must search
12679 and therefore the longer it takes to run.
12681 @item show heuristic-fence-post
12682 Display the current limit.
12686 These commands are available @emph{only} when @value{GDBN} is configured
12687 for debugging programs on Alpha or MIPS processors.
12690 @node Controlling GDB
12691 @chapter Controlling @value{GDBN}
12693 You can alter the way @value{GDBN} interacts with you by using the
12694 @code{set} command. For commands controlling how @value{GDBN} displays
12695 data, see @ref{Print Settings, ,Print settings}. Other settings are
12700 * Editing:: Command editing
12701 * History:: Command history
12702 * Screen Size:: Screen size
12703 * Numbers:: Numbers
12704 * ABI:: Configuring the current ABI
12705 * Messages/Warnings:: Optional warnings and messages
12706 * Debugging Output:: Optional messages about internal happenings
12714 @value{GDBN} indicates its readiness to read a command by printing a string
12715 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
12716 can change the prompt string with the @code{set prompt} command. For
12717 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
12718 the prompt in one of the @value{GDBN} sessions so that you can always tell
12719 which one you are talking to.
12721 @emph{Note:} @code{set prompt} does not add a space for you after the
12722 prompt you set. This allows you to set a prompt which ends in a space
12723 or a prompt that does not.
12727 @item set prompt @var{newprompt}
12728 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
12730 @kindex show prompt
12732 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
12736 @section Command editing
12738 @cindex command line editing
12740 @value{GDBN} reads its input commands via the @dfn{readline} interface. This
12741 @sc{gnu} library provides consistent behavior for programs which provide a
12742 command line interface to the user. Advantages are @sc{gnu} Emacs-style
12743 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
12744 substitution, and a storage and recall of command history across
12745 debugging sessions.
12747 You may control the behavior of command line editing in @value{GDBN} with the
12748 command @code{set}.
12751 @kindex set editing
12754 @itemx set editing on
12755 Enable command line editing (enabled by default).
12757 @item set editing off
12758 Disable command line editing.
12760 @kindex show editing
12762 Show whether command line editing is enabled.
12766 @section Command history
12768 @value{GDBN} can keep track of the commands you type during your
12769 debugging sessions, so that you can be certain of precisely what
12770 happened. Use these commands to manage the @value{GDBN} command
12774 @cindex history substitution
12775 @cindex history file
12776 @kindex set history filename
12777 @kindex GDBHISTFILE
12778 @item set history filename @var{fname}
12779 Set the name of the @value{GDBN} command history file to @var{fname}.
12780 This is the file where @value{GDBN} reads an initial command history
12781 list, and where it writes the command history from this session when it
12782 exits. You can access this list through history expansion or through
12783 the history command editing characters listed below. This file defaults
12784 to the value of the environment variable @code{GDBHISTFILE}, or to
12785 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
12788 @cindex history save
12789 @kindex set history save
12790 @item set history save
12791 @itemx set history save on
12792 Record command history in a file, whose name may be specified with the
12793 @code{set history filename} command. By default, this option is disabled.
12795 @item set history save off
12796 Stop recording command history in a file.
12798 @cindex history size
12799 @kindex set history size
12800 @item set history size @var{size}
12801 Set the number of commands which @value{GDBN} keeps in its history list.
12802 This defaults to the value of the environment variable
12803 @code{HISTSIZE}, or to 256 if this variable is not set.
12806 @cindex history expansion
12807 History expansion assigns special meaning to the character @kbd{!}.
12808 @ifset have-readline-appendices
12809 @xref{Event Designators}.
12812 Since @kbd{!} is also the logical not operator in C, history expansion
12813 is off by default. If you decide to enable history expansion with the
12814 @code{set history expansion on} command, you may sometimes need to
12815 follow @kbd{!} (when it is used as logical not, in an expression) with
12816 a space or a tab to prevent it from being expanded. The readline
12817 history facilities do not attempt substitution on the strings
12818 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
12820 The commands to control history expansion are:
12823 @kindex set history expansion
12824 @item set history expansion on
12825 @itemx set history expansion
12826 Enable history expansion. History expansion is off by default.
12828 @item set history expansion off
12829 Disable history expansion.
12831 The readline code comes with more complete documentation of
12832 editing and history expansion features. Users unfamiliar with @sc{gnu} Emacs
12833 or @code{vi} may wish to read it.
12834 @ifset have-readline-appendices
12835 @xref{Command Line Editing}.
12839 @kindex show history
12841 @itemx show history filename
12842 @itemx show history save
12843 @itemx show history size
12844 @itemx show history expansion
12845 These commands display the state of the @value{GDBN} history parameters.
12846 @code{show history} by itself displays all four states.
12852 @item show commands
12853 Display the last ten commands in the command history.
12855 @item show commands @var{n}
12856 Print ten commands centered on command number @var{n}.
12858 @item show commands +
12859 Print ten commands just after the commands last printed.
12863 @section Screen size
12864 @cindex size of screen
12865 @cindex pauses in output
12867 Certain commands to @value{GDBN} may produce large amounts of
12868 information output to the screen. To help you read all of it,
12869 @value{GDBN} pauses and asks you for input at the end of each page of
12870 output. Type @key{RET} when you want to continue the output, or @kbd{q}
12871 to discard the remaining output. Also, the screen width setting
12872 determines when to wrap lines of output. Depending on what is being
12873 printed, @value{GDBN} tries to break the line at a readable place,
12874 rather than simply letting it overflow onto the following line.
12876 Normally @value{GDBN} knows the size of the screen from the terminal
12877 driver software. For example, on Unix @value{GDBN} uses the termcap data base
12878 together with the value of the @code{TERM} environment variable and the
12879 @code{stty rows} and @code{stty cols} settings. If this is not correct,
12880 you can override it with the @code{set height} and @code{set
12887 @kindex show height
12888 @item set height @var{lpp}
12890 @itemx set width @var{cpl}
12892 These @code{set} commands specify a screen height of @var{lpp} lines and
12893 a screen width of @var{cpl} characters. The associated @code{show}
12894 commands display the current settings.
12896 If you specify a height of zero lines, @value{GDBN} does not pause during
12897 output no matter how long the output is. This is useful if output is to a
12898 file or to an editor buffer.
12900 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
12901 from wrapping its output.
12906 @cindex number representation
12907 @cindex entering numbers
12909 You can always enter numbers in octal, decimal, or hexadecimal in
12910 @value{GDBN} by the usual conventions: octal numbers begin with
12911 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
12912 begin with @samp{0x}. Numbers that begin with none of these are, by
12913 default, entered in base 10; likewise, the default display for
12914 numbers---when no particular format is specified---is base 10. You can
12915 change the default base for both input and output with the @code{set
12919 @kindex set input-radix
12920 @item set input-radix @var{base}
12921 Set the default base for numeric input. Supported choices
12922 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
12923 specified either unambiguously or using the current default radix; for
12933 sets the base to decimal. On the other hand, @samp{set radix 10}
12934 leaves the radix unchanged no matter what it was.
12936 @kindex set output-radix
12937 @item set output-radix @var{base}
12938 Set the default base for numeric display. Supported choices
12939 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
12940 specified either unambiguously or using the current default radix.
12942 @kindex show input-radix
12943 @item show input-radix
12944 Display the current default base for numeric input.
12946 @kindex show output-radix
12947 @item show output-radix
12948 Display the current default base for numeric display.
12952 @section Configuring the current ABI
12954 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
12955 application automatically. However, sometimes you need to override its
12956 conclusions. Use these commands to manage @value{GDBN}'s view of the
12963 One @value{GDBN} configuration can debug binaries for multiple operating
12964 system targets, either via remote debugging or native emulation.
12965 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
12966 but you can override its conclusion using the @code{set osabi} command.
12967 One example where this is useful is in debugging of binaries which use
12968 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
12969 not have the same identifying marks that the standard C library for your
12974 Show the OS ABI currently in use.
12977 With no argument, show the list of registered available OS ABI's.
12979 @item set osabi @var{abi}
12980 Set the current OS ABI to @var{abi}.
12983 @cindex float promotion
12984 @kindex set coerce-float-to-double
12986 Generally, the way that an argument of type @code{float} is passed to a
12987 function depends on whether the function is prototyped. For a prototyped
12988 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
12989 according to the architecture's convention for @code{float}. For unprototyped
12990 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
12991 @code{double} and then passed.
12993 Unfortunately, some forms of debug information do not reliably indicate whether
12994 a function is prototyped. If @value{GDBN} calls a function that is not marked
12995 as prototyped, it consults @kbd{set coerce-float-to-double}.
12998 @item set coerce-float-to-double
12999 @itemx set coerce-float-to-double on
13000 Arguments of type @code{float} will be promoted to @code{double} when passed
13001 to an unprototyped function. This is the default setting.
13003 @item set coerce-float-to-double off
13004 Arguments of type @code{float} will be passed directly to unprototyped
13009 @kindex show cp-abi
13010 @value{GDBN} needs to know the ABI used for your program's C@t{++}
13011 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
13012 used to build your application. @value{GDBN} only fully supports
13013 programs with a single C@t{++} ABI; if your program contains code using
13014 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
13015 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
13016 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
13017 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
13018 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
13019 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
13024 Show the C@t{++} ABI currently in use.
13027 With no argument, show the list of supported C@t{++} ABI's.
13029 @item set cp-abi @var{abi}
13030 @itemx set cp-abi auto
13031 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
13034 @node Messages/Warnings
13035 @section Optional warnings and messages
13037 By default, @value{GDBN} is silent about its inner workings. If you are
13038 running on a slow machine, you may want to use the @code{set verbose}
13039 command. This makes @value{GDBN} tell you when it does a lengthy
13040 internal operation, so you will not think it has crashed.
13042 Currently, the messages controlled by @code{set verbose} are those
13043 which announce that the symbol table for a source file is being read;
13044 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
13047 @kindex set verbose
13048 @item set verbose on
13049 Enables @value{GDBN} output of certain informational messages.
13051 @item set verbose off
13052 Disables @value{GDBN} output of certain informational messages.
13054 @kindex show verbose
13056 Displays whether @code{set verbose} is on or off.
13059 By default, if @value{GDBN} encounters bugs in the symbol table of an
13060 object file, it is silent; but if you are debugging a compiler, you may
13061 find this information useful (@pxref{Symbol Errors, ,Errors reading
13066 @kindex set complaints
13067 @item set complaints @var{limit}
13068 Permits @value{GDBN} to output @var{limit} complaints about each type of
13069 unusual symbols before becoming silent about the problem. Set
13070 @var{limit} to zero to suppress all complaints; set it to a large number
13071 to prevent complaints from being suppressed.
13073 @kindex show complaints
13074 @item show complaints
13075 Displays how many symbol complaints @value{GDBN} is permitted to produce.
13079 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
13080 lot of stupid questions to confirm certain commands. For example, if
13081 you try to run a program which is already running:
13085 The program being debugged has been started already.
13086 Start it from the beginning? (y or n)
13089 If you are willing to unflinchingly face the consequences of your own
13090 commands, you can disable this ``feature'':
13094 @kindex set confirm
13096 @cindex confirmation
13097 @cindex stupid questions
13098 @item set confirm off
13099 Disables confirmation requests.
13101 @item set confirm on
13102 Enables confirmation requests (the default).
13104 @kindex show confirm
13106 Displays state of confirmation requests.
13110 @node Debugging Output
13111 @section Optional messages about internal happenings
13113 @kindex set debug arch
13114 @item set debug arch
13115 Turns on or off display of gdbarch debugging info. The default is off
13116 @kindex show debug arch
13117 @item show debug arch
13118 Displays the current state of displaying gdbarch debugging info.
13119 @kindex set debug event
13120 @item set debug event
13121 Turns on or off display of @value{GDBN} event debugging info. The
13123 @kindex show debug event
13124 @item show debug event
13125 Displays the current state of displaying @value{GDBN} event debugging
13127 @kindex set debug expression
13128 @item set debug expression
13129 Turns on or off display of @value{GDBN} expression debugging info. The
13131 @kindex show debug expression
13132 @item show debug expression
13133 Displays the current state of displaying @value{GDBN} expression
13135 @kindex set debug frame
13136 @item set debug frame
13137 Turns on or off display of @value{GDBN} frame debugging info. The
13139 @kindex show debug frame
13140 @item show debug frame
13141 Displays the current state of displaying @value{GDBN} frame debugging
13143 @kindex set debug overload
13144 @item set debug overload
13145 Turns on or off display of @value{GDBN} C@t{++} overload debugging
13146 info. This includes info such as ranking of functions, etc. The default
13148 @kindex show debug overload
13149 @item show debug overload
13150 Displays the current state of displaying @value{GDBN} C@t{++} overload
13152 @kindex set debug remote
13153 @cindex packets, reporting on stdout
13154 @cindex serial connections, debugging
13155 @item set debug remote
13156 Turns on or off display of reports on all packets sent back and forth across
13157 the serial line to the remote machine. The info is printed on the
13158 @value{GDBN} standard output stream. The default is off.
13159 @kindex show debug remote
13160 @item show debug remote
13161 Displays the state of display of remote packets.
13162 @kindex set debug serial
13163 @item set debug serial
13164 Turns on or off display of @value{GDBN} serial debugging info. The
13166 @kindex show debug serial
13167 @item show debug serial
13168 Displays the current state of displaying @value{GDBN} serial debugging
13170 @kindex set debug target
13171 @item set debug target
13172 Turns on or off display of @value{GDBN} target debugging info. This info
13173 includes what is going on at the target level of GDB, as it happens. The
13175 @kindex show debug target
13176 @item show debug target
13177 Displays the current state of displaying @value{GDBN} target debugging
13179 @kindex set debug varobj
13180 @item set debug varobj
13181 Turns on or off display of @value{GDBN} variable object debugging
13182 info. The default is off.
13183 @kindex show debug varobj
13184 @item show debug varobj
13185 Displays the current state of displaying @value{GDBN} variable object
13190 @chapter Canned Sequences of Commands
13192 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
13193 command lists}), @value{GDBN} provides two ways to store sequences of
13194 commands for execution as a unit: user-defined commands and command
13198 * Define:: User-defined commands
13199 * Hooks:: User-defined command hooks
13200 * Command Files:: Command files
13201 * Output:: Commands for controlled output
13205 @section User-defined commands
13207 @cindex user-defined command
13208 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
13209 which you assign a new name as a command. This is done with the
13210 @code{define} command. User commands may accept up to 10 arguments
13211 separated by whitespace. Arguments are accessed within the user command
13212 via @var{$arg0@dots{}$arg9}. A trivial example:
13216 print $arg0 + $arg1 + $arg2
13220 To execute the command use:
13227 This defines the command @code{adder}, which prints the sum of
13228 its three arguments. Note the arguments are text substitutions, so they may
13229 reference variables, use complex expressions, or even perform inferior
13235 @item define @var{commandname}
13236 Define a command named @var{commandname}. If there is already a command
13237 by that name, you are asked to confirm that you want to redefine it.
13239 The definition of the command is made up of other @value{GDBN} command lines,
13240 which are given following the @code{define} command. The end of these
13241 commands is marked by a line containing @code{end}.
13246 Takes a single argument, which is an expression to evaluate.
13247 It is followed by a series of commands that are executed
13248 only if the expression is true (nonzero).
13249 There can then optionally be a line @code{else}, followed
13250 by a series of commands that are only executed if the expression
13251 was false. The end of the list is marked by a line containing @code{end}.
13255 The syntax is similar to @code{if}: the command takes a single argument,
13256 which is an expression to evaluate, and must be followed by the commands to
13257 execute, one per line, terminated by an @code{end}.
13258 The commands are executed repeatedly as long as the expression
13262 @item document @var{commandname}
13263 Document the user-defined command @var{commandname}, so that it can be
13264 accessed by @code{help}. The command @var{commandname} must already be
13265 defined. This command reads lines of documentation just as @code{define}
13266 reads the lines of the command definition, ending with @code{end}.
13267 After the @code{document} command is finished, @code{help} on command
13268 @var{commandname} displays the documentation you have written.
13270 You may use the @code{document} command again to change the
13271 documentation of a command. Redefining the command with @code{define}
13272 does not change the documentation.
13274 @kindex help user-defined
13275 @item help user-defined
13276 List all user-defined commands, with the first line of the documentation
13281 @itemx show user @var{commandname}
13282 Display the @value{GDBN} commands used to define @var{commandname} (but
13283 not its documentation). If no @var{commandname} is given, display the
13284 definitions for all user-defined commands.
13286 @kindex show max-user-call-depth
13287 @kindex set max-user-call-depth
13288 @item show max-user-call-depth
13289 @itemx set max-user-call-depth
13290 The value of @code{max-user-call-depth} controls how many recursion
13291 levels are allowed in user-defined commands before GDB suspects an
13292 infinite recursion and aborts the command.
13296 When user-defined commands are executed, the
13297 commands of the definition are not printed. An error in any command
13298 stops execution of the user-defined command.
13300 If used interactively, commands that would ask for confirmation proceed
13301 without asking when used inside a user-defined command. Many @value{GDBN}
13302 commands that normally print messages to say what they are doing omit the
13303 messages when used in a user-defined command.
13306 @section User-defined command hooks
13307 @cindex command hooks
13308 @cindex hooks, for commands
13309 @cindex hooks, pre-command
13313 You may define @dfn{hooks}, which are a special kind of user-defined
13314 command. Whenever you run the command @samp{foo}, if the user-defined
13315 command @samp{hook-foo} exists, it is executed (with no arguments)
13316 before that command.
13318 @cindex hooks, post-command
13321 A hook may also be defined which is run after the command you executed.
13322 Whenever you run the command @samp{foo}, if the user-defined command
13323 @samp{hookpost-foo} exists, it is executed (with no arguments) after
13324 that command. Post-execution hooks may exist simultaneously with
13325 pre-execution hooks, for the same command.
13327 It is valid for a hook to call the command which it hooks. If this
13328 occurs, the hook is not re-executed, thereby avoiding infinte recursion.
13330 @c It would be nice if hookpost could be passed a parameter indicating
13331 @c if the command it hooks executed properly or not. FIXME!
13333 @kindex stop@r{, a pseudo-command}
13334 In addition, a pseudo-command, @samp{stop} exists. Defining
13335 (@samp{hook-stop}) makes the associated commands execute every time
13336 execution stops in your program: before breakpoint commands are run,
13337 displays are printed, or the stack frame is printed.
13339 For example, to ignore @code{SIGALRM} signals while
13340 single-stepping, but treat them normally during normal execution,
13345 handle SIGALRM nopass
13349 handle SIGALRM pass
13352 define hook-continue
13353 handle SIGLARM pass
13357 As a further example, to hook at the begining and end of the @code{echo}
13358 command, and to add extra text to the beginning and end of the message,
13366 define hookpost-echo
13370 (@value{GDBP}) echo Hello World
13371 <<<---Hello World--->>>
13376 You can define a hook for any single-word command in @value{GDBN}, but
13377 not for command aliases; you should define a hook for the basic command
13378 name, e.g. @code{backtrace} rather than @code{bt}.
13379 @c FIXME! So how does Joe User discover whether a command is an alias
13381 If an error occurs during the execution of your hook, execution of
13382 @value{GDBN} commands stops and @value{GDBN} issues a prompt
13383 (before the command that you actually typed had a chance to run).
13385 If you try to define a hook which does not match any known command, you
13386 get a warning from the @code{define} command.
13388 @node Command Files
13389 @section Command files
13391 @cindex command files
13392 A command file for @value{GDBN} is a file of lines that are @value{GDBN}
13393 commands. Comments (lines starting with @kbd{#}) may also be included.
13394 An empty line in a command file does nothing; it does not mean to repeat
13395 the last command, as it would from the terminal.
13398 @cindex @file{.gdbinit}
13399 @cindex @file{gdb.ini}
13400 When you start @value{GDBN}, it automatically executes commands from its
13401 @dfn{init files}, normally called @file{.gdbinit}@footnote{The DJGPP
13402 port of @value{GDBN} uses the name @file{gdb.ini} instead, due to the
13403 limitations of file names imposed by DOS filesystems.}.
13404 During startup, @value{GDBN} does the following:
13408 Reads the init file (if any) in your home directory@footnote{On
13409 DOS/Windows systems, the home directory is the one pointed to by the
13410 @code{HOME} environment variable.}.
13413 Processes command line options and operands.
13416 Reads the init file (if any) in the current working directory.
13419 Reads command files specified by the @samp{-x} option.
13422 The init file in your home directory can set options (such as @samp{set
13423 complaints}) that affect subsequent processing of command line options
13424 and operands. Init files are not executed if you use the @samp{-nx}
13425 option (@pxref{Mode Options, ,Choosing modes}).
13427 @cindex init file name
13428 On some configurations of @value{GDBN}, the init file is known by a
13429 different name (these are typically environments where a specialized
13430 form of @value{GDBN} may need to coexist with other forms, hence a
13431 different name for the specialized version's init file). These are the
13432 environments with special init file names:
13434 @cindex @file{.vxgdbinit}
13437 VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit}
13439 @cindex @file{.os68gdbinit}
13441 OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit}
13443 @cindex @file{.esgdbinit}
13445 ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit}
13448 You can also request the execution of a command file with the
13449 @code{source} command:
13453 @item source @var{filename}
13454 Execute the command file @var{filename}.
13457 The lines in a command file are executed sequentially. They are not
13458 printed as they are executed. An error in any command terminates
13459 execution of the command file and control is returned to the console.
13461 Commands that would ask for confirmation if used interactively proceed
13462 without asking when used in a command file. Many @value{GDBN} commands that
13463 normally print messages to say what they are doing omit the messages
13464 when called from command files.
13466 @value{GDBN} also accepts command input from standard input. In this
13467 mode, normal output goes to standard output and error output goes to
13468 standard error. Errors in a command file supplied on standard input do
13469 not terminate execution of the command file --- execution continues with
13473 gdb < cmds > log 2>&1
13476 (The syntax above will vary depending on the shell used.) This example
13477 will execute commands from the file @file{cmds}. All output and errors
13478 would be directed to @file{log}.
13481 @section Commands for controlled output
13483 During the execution of a command file or a user-defined command, normal
13484 @value{GDBN} output is suppressed; the only output that appears is what is
13485 explicitly printed by the commands in the definition. This section
13486 describes three commands useful for generating exactly the output you
13491 @item echo @var{text}
13492 @c I do not consider backslash-space a standard C escape sequence
13493 @c because it is not in ANSI.
13494 Print @var{text}. Nonprinting characters can be included in
13495 @var{text} using C escape sequences, such as @samp{\n} to print a
13496 newline. @strong{No newline is printed unless you specify one.}
13497 In addition to the standard C escape sequences, a backslash followed
13498 by a space stands for a space. This is useful for displaying a
13499 string with spaces at the beginning or the end, since leading and
13500 trailing spaces are otherwise trimmed from all arguments.
13501 To print @samp{@w{ }and foo =@w{ }}, use the command
13502 @samp{echo \@w{ }and foo = \@w{ }}.
13504 A backslash at the end of @var{text} can be used, as in C, to continue
13505 the command onto subsequent lines. For example,
13508 echo This is some text\n\
13509 which is continued\n\
13510 onto several lines.\n
13513 produces the same output as
13516 echo This is some text\n
13517 echo which is continued\n
13518 echo onto several lines.\n
13522 @item output @var{expression}
13523 Print the value of @var{expression} and nothing but that value: no
13524 newlines, no @samp{$@var{nn} = }. The value is not entered in the
13525 value history either. @xref{Expressions, ,Expressions}, for more information
13528 @item output/@var{fmt} @var{expression}
13529 Print the value of @var{expression} in format @var{fmt}. You can use
13530 the same formats as for @code{print}. @xref{Output Formats,,Output
13531 formats}, for more information.
13534 @item printf @var{string}, @var{expressions}@dots{}
13535 Print the values of the @var{expressions} under the control of
13536 @var{string}. The @var{expressions} are separated by commas and may be
13537 either numbers or pointers. Their values are printed as specified by
13538 @var{string}, exactly as if your program were to execute the C
13540 @c FIXME: the above implies that at least all ANSI C formats are
13541 @c supported, but it isn't true: %E and %G don't work (or so it seems).
13542 @c Either this is a bug, or the manual should document what formats are
13546 printf (@var{string}, @var{expressions}@dots{});
13549 For example, you can print two values in hex like this:
13552 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
13555 The only backslash-escape sequences that you can use in the format
13556 string are the simple ones that consist of backslash followed by a
13561 @chapter Command Interpreters
13562 @cindex command interpreters
13564 @value{GDBN} supports multiple command interpreters, and some command
13565 infrastructure to allow users or user interface writers to switch
13566 between interpreters or run commands in other interpreters.
13568 @value{GDBN} currently supports two command interpreters, the console
13569 interpreter (sometimes called the command-line interpreter or @sc{cli})
13570 and the machine interface interpreter (or @sc{gdb/mi}). This manual
13571 describes both of these interfaces in great detail.
13573 By default, @value{GDBN} will start with the console interpreter.
13574 However, the user may choose to start @value{GDBN} with another
13575 interpreter by specifying the @option{-i} or @option{--interpreter}
13576 startup options. Defined interpreters include:
13580 @cindex console interpreter
13581 The traditional console or command-line interpreter. This is the most often
13582 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
13583 @value{GDBN} will use this interpreter.
13586 @cindex mi interpreter
13587 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
13588 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
13589 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
13593 @cindex mi2 interpreter
13594 The current @sc{gdb/mi} interface.
13597 @cindex mi1 interpreter
13598 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
13602 @cindex invoke another interpreter
13603 The interpreter being used by @value{GDBN} may not be dynamically
13604 switched at runtime. Although possible, this could lead to a very
13605 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
13606 enters the command "interpreter-set console" in a console view,
13607 @value{GDBN} would switch to using the console interpreter, rendering
13608 the IDE inoperable!
13610 @kindex interpreter-exec
13611 Although you may only choose a single interpreter at startup, you may execute
13612 commands in any interpreter from the current interpreter using the appropriate
13613 command. If you are running the console interpreter, simply use the
13614 @code{interpreter-exec} command:
13617 interpreter-exec mi "-data-list-register-names"
13620 @sc{gdb/mi} has a similar command, although it is only available in versions of
13621 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
13624 @chapter @value{GDBN} Text User Interface
13628 * TUI Overview:: TUI overview
13629 * TUI Keys:: TUI key bindings
13630 * TUI Single Key Mode:: TUI single key mode
13631 * TUI Commands:: TUI specific commands
13632 * TUI Configuration:: TUI configuration variables
13635 The @value{GDBN} Text User Interface, TUI in short,
13636 is a terminal interface which uses the @code{curses} library
13637 to show the source file, the assembly output, the program registers
13638 and @value{GDBN} commands in separate text windows.
13639 The TUI is available only when @value{GDBN} is configured
13640 with the @code{--enable-tui} configure option (@pxref{Configure Options}).
13643 @section TUI overview
13645 The TUI has two display modes that can be switched while
13650 A curses (or TUI) mode in which it displays several text
13651 windows on the terminal.
13654 A standard mode which corresponds to the @value{GDBN} configured without
13658 In the TUI mode, @value{GDBN} can display several text window
13663 This window is the @value{GDBN} command window with the @value{GDBN}
13664 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
13665 managed using readline but through the TUI. The @emph{command}
13666 window is always visible.
13669 The source window shows the source file of the program. The current
13670 line as well as active breakpoints are displayed in this window.
13673 The assembly window shows the disassembly output of the program.
13676 This window shows the processor registers. It detects when
13677 a register is changed and when this is the case, registers that have
13678 changed are highlighted.
13682 The source and assembly windows show the current program position
13683 by highlighting the current line and marking them with the @samp{>} marker.
13684 Breakpoints are also indicated with two markers. A first one
13685 indicates the breakpoint type:
13689 Breakpoint which was hit at least once.
13692 Breakpoint which was never hit.
13695 Hardware breakpoint which was hit at least once.
13698 Hardware breakpoint which was never hit.
13702 The second marker indicates whether the breakpoint is enabled or not:
13706 Breakpoint is enabled.
13709 Breakpoint is disabled.
13713 The source, assembly and register windows are attached to the thread
13714 and the frame position. They are updated when the current thread
13715 changes, when the frame changes or when the program counter changes.
13716 These three windows are arranged by the TUI according to several
13717 layouts. The layout defines which of these three windows are visible.
13718 The following layouts are available:
13728 source and assembly
13731 source and registers
13734 assembly and registers
13738 On top of the command window a status line gives various information
13739 concerning the current process begin debugged. The status line is
13740 updated when the information it shows changes. The following fields
13745 Indicates the current gdb target
13746 (@pxref{Targets, ,Specifying a Debugging Target}).
13749 Gives information about the current process or thread number.
13750 When no process is being debugged, this field is set to @code{No process}.
13753 Gives the current function name for the selected frame.
13754 The name is demangled if demangling is turned on (@pxref{Print Settings}).
13755 When there is no symbol corresponding to the current program counter
13756 the string @code{??} is displayed.
13759 Indicates the current line number for the selected frame.
13760 When the current line number is not known the string @code{??} is displayed.
13763 Indicates the current program counter address.
13768 @section TUI Key Bindings
13769 @cindex TUI key bindings
13771 The TUI installs several key bindings in the readline keymaps
13772 (@pxref{Command Line Editing}).
13773 They allow to leave or enter in the TUI mode or they operate
13774 directly on the TUI layout and windows. The TUI also provides
13775 a @emph{SingleKey} keymap which binds several keys directly to
13776 @value{GDBN} commands. The following key bindings
13777 are installed for both TUI mode and the @value{GDBN} standard mode.
13786 Enter or leave the TUI mode. When the TUI mode is left,
13787 the curses window management is left and @value{GDBN} operates using
13788 its standard mode writing on the terminal directly. When the TUI
13789 mode is entered, the control is given back to the curses windows.
13790 The screen is then refreshed.
13794 Use a TUI layout with only one window. The layout will
13795 either be @samp{source} or @samp{assembly}. When the TUI mode
13796 is not active, it will switch to the TUI mode.
13798 Think of this key binding as the Emacs @kbd{C-x 1} binding.
13802 Use a TUI layout with at least two windows. When the current
13803 layout shows already two windows, a next layout with two windows is used.
13804 When a new layout is chosen, one window will always be common to the
13805 previous layout and the new one.
13807 Think of it as the Emacs @kbd{C-x 2} binding.
13811 Use the TUI @emph{SingleKey} keymap that binds single key to gdb commands
13812 (@pxref{TUI Single Key Mode}).
13816 The following key bindings are handled only by the TUI mode:
13821 Scroll the active window one page up.
13825 Scroll the active window one page down.
13829 Scroll the active window one line up.
13833 Scroll the active window one line down.
13837 Scroll the active window one column left.
13841 Scroll the active window one column right.
13845 Refresh the screen.
13849 In the TUI mode, the arrow keys are used by the active window
13850 for scrolling. This means they are not available for readline. It is
13851 necessary to use other readline key bindings such as @key{C-p}, @key{C-n},
13852 @key{C-b} and @key{C-f}.
13854 @node TUI Single Key Mode
13855 @section TUI Single Key Mode
13856 @cindex TUI single key mode
13858 The TUI provides a @emph{SingleKey} mode in which it installs a particular
13859 key binding in the readline keymaps to connect single keys to
13863 @kindex c @r{(SingleKey TUI key)}
13867 @kindex d @r{(SingleKey TUI key)}
13871 @kindex f @r{(SingleKey TUI key)}
13875 @kindex n @r{(SingleKey TUI key)}
13879 @kindex q @r{(SingleKey TUI key)}
13881 exit the @emph{SingleKey} mode.
13883 @kindex r @r{(SingleKey TUI key)}
13887 @kindex s @r{(SingleKey TUI key)}
13891 @kindex u @r{(SingleKey TUI key)}
13895 @kindex v @r{(SingleKey TUI key)}
13899 @kindex w @r{(SingleKey TUI key)}
13905 Other keys temporarily switch to the @value{GDBN} command prompt.
13906 The key that was pressed is inserted in the editing buffer so that
13907 it is possible to type most @value{GDBN} commands without interaction
13908 with the TUI @emph{SingleKey} mode. Once the command is entered the TUI
13909 @emph{SingleKey} mode is restored. The only way to permanently leave
13910 this mode is by hitting @key{q} or @samp{@key{C-x} @key{s}}.
13914 @section TUI specific commands
13915 @cindex TUI commands
13917 The TUI has specific commands to control the text windows.
13918 These commands are always available, that is they do not depend on
13919 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
13920 is in the standard mode, using these commands will automatically switch
13926 List and give the size of all displayed windows.
13929 @kindex layout next
13930 Display the next layout.
13933 @kindex layout prev
13934 Display the previous layout.
13938 Display the source window only.
13942 Display the assembly window only.
13945 @kindex layout split
13946 Display the source and assembly window.
13949 @kindex layout regs
13950 Display the register window together with the source or assembly window.
13952 @item focus next | prev | src | asm | regs | split
13954 Set the focus to the named window.
13955 This command allows to change the active window so that scrolling keys
13956 can be affected to another window.
13960 Refresh the screen. This is similar to using @key{C-L} key.
13964 Update the source window and the current execution point.
13966 @item winheight @var{name} +@var{count}
13967 @itemx winheight @var{name} -@var{count}
13969 Change the height of the window @var{name} by @var{count}
13970 lines. Positive counts increase the height, while negative counts
13975 @node TUI Configuration
13976 @section TUI configuration variables
13977 @cindex TUI configuration variables
13979 The TUI has several configuration variables that control the
13980 appearance of windows on the terminal.
13983 @item set tui border-kind @var{kind}
13984 @kindex set tui border-kind
13985 Select the border appearance for the source, assembly and register windows.
13986 The possible values are the following:
13989 Use a space character to draw the border.
13992 Use ascii characters + - and | to draw the border.
13995 Use the Alternate Character Set to draw the border. The border is
13996 drawn using character line graphics if the terminal supports them.
14000 @item set tui active-border-mode @var{mode}
14001 @kindex set tui active-border-mode
14002 Select the attributes to display the border of the active window.
14003 The possible values are @code{normal}, @code{standout}, @code{reverse},
14004 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
14006 @item set tui border-mode @var{mode}
14007 @kindex set tui border-mode
14008 Select the attributes to display the border of other windows.
14009 The @var{mode} can be one of the following:
14012 Use normal attributes to display the border.
14018 Use reverse video mode.
14021 Use half bright mode.
14023 @item half-standout
14024 Use half bright and standout mode.
14027 Use extra bright or bold mode.
14029 @item bold-standout
14030 Use extra bright or bold and standout mode.
14037 @chapter Using @value{GDBN} under @sc{gnu} Emacs
14040 @cindex @sc{gnu} Emacs
14041 A special interface allows you to use @sc{gnu} Emacs to view (and
14042 edit) the source files for the program you are debugging with
14045 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
14046 executable file you want to debug as an argument. This command starts
14047 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
14048 created Emacs buffer.
14049 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
14051 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
14056 All ``terminal'' input and output goes through the Emacs buffer.
14059 This applies both to @value{GDBN} commands and their output, and to the input
14060 and output done by the program you are debugging.
14062 This is useful because it means that you can copy the text of previous
14063 commands and input them again; you can even use parts of the output
14066 All the facilities of Emacs' Shell mode are available for interacting
14067 with your program. In particular, you can send signals the usual
14068 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
14073 @value{GDBN} displays source code through Emacs.
14076 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
14077 source file for that frame and puts an arrow (@samp{=>}) at the
14078 left margin of the current line. Emacs uses a separate buffer for
14079 source display, and splits the screen to show both your @value{GDBN} session
14082 Explicit @value{GDBN} @code{list} or search commands still produce output as
14083 usual, but you probably have no reason to use them from Emacs.
14086 @emph{Warning:} If the directory where your program resides is not your
14087 current directory, it can be easy to confuse Emacs about the location of
14088 the source files, in which case the auxiliary display buffer does not
14089 appear to show your source. @value{GDBN} can find programs by searching your
14090 environment's @code{PATH} variable, so the @value{GDBN} input and output
14091 session proceeds normally; but Emacs does not get enough information
14092 back from @value{GDBN} to locate the source files in this situation. To
14093 avoid this problem, either start @value{GDBN} mode from the directory where
14094 your program resides, or specify an absolute file name when prompted for the
14095 @kbd{M-x gdb} argument.
14097 A similar confusion can result if you use the @value{GDBN} @code{file} command to
14098 switch to debugging a program in some other location, from an existing
14099 @value{GDBN} buffer in Emacs.
14102 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If
14103 you need to call @value{GDBN} by a different name (for example, if you keep
14104 several configurations around, with different names) you can set the
14105 Emacs variable @code{gdb-command-name}; for example,
14108 (setq gdb-command-name "mygdb")
14112 (preceded by @kbd{M-:} or @kbd{ESC :}, or typed in the @code{*scratch*} buffer, or
14113 in your @file{.emacs} file) makes Emacs call the program named
14114 ``@code{mygdb}'' instead.
14116 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
14117 addition to the standard Shell mode commands:
14121 Describe the features of Emacs' @value{GDBN} Mode.
14124 Execute to another source line, like the @value{GDBN} @code{step} command; also
14125 update the display window to show the current file and location.
14128 Execute to next source line in this function, skipping all function
14129 calls, like the @value{GDBN} @code{next} command. Then update the display window
14130 to show the current file and location.
14133 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
14134 display window accordingly.
14136 @item M-x gdb-nexti
14137 Execute to next instruction, using the @value{GDBN} @code{nexti} command; update
14138 display window accordingly.
14141 Execute until exit from the selected stack frame, like the @value{GDBN}
14142 @code{finish} command.
14145 Continue execution of your program, like the @value{GDBN} @code{continue}
14148 @emph{Warning:} In Emacs v19, this command is @kbd{C-c C-p}.
14151 Go up the number of frames indicated by the numeric argument
14152 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
14153 like the @value{GDBN} @code{up} command.
14155 @emph{Warning:} In Emacs v19, this command is @kbd{C-c C-u}.
14158 Go down the number of frames indicated by the numeric argument, like the
14159 @value{GDBN} @code{down} command.
14161 @emph{Warning:} In Emacs v19, this command is @kbd{C-c C-d}.
14164 Read the number where the cursor is positioned, and insert it at the end
14165 of the @value{GDBN} I/O buffer. For example, if you wish to disassemble code
14166 around an address that was displayed earlier, type @kbd{disassemble};
14167 then move the cursor to the address display, and pick up the
14168 argument for @code{disassemble} by typing @kbd{C-x &}.
14170 You can customize this further by defining elements of the list
14171 @code{gdb-print-command}; once it is defined, you can format or
14172 otherwise process numbers picked up by @kbd{C-x &} before they are
14173 inserted. A numeric argument to @kbd{C-x &} indicates that you
14174 wish special formatting, and also acts as an index to pick an element of the
14175 list. If the list element is a string, the number to be inserted is
14176 formatted using the Emacs function @code{format}; otherwise the number
14177 is passed as an argument to the corresponding list element.
14180 In any source file, the Emacs command @kbd{C-x SPC} (@code{gdb-break})
14181 tells @value{GDBN} to set a breakpoint on the source line point is on.
14183 If you accidentally delete the source-display buffer, an easy way to get
14184 it back is to type the command @code{f} in the @value{GDBN} buffer, to
14185 request a frame display; when you run under Emacs, this recreates
14186 the source buffer if necessary to show you the context of the current
14189 The source files displayed in Emacs are in ordinary Emacs buffers
14190 which are visiting the source files in the usual way. You can edit
14191 the files with these buffers if you wish; but keep in mind that @value{GDBN}
14192 communicates with Emacs in terms of line numbers. If you add or
14193 delete lines from the text, the line numbers that @value{GDBN} knows cease
14194 to correspond properly with the code.
14196 @c The following dropped because Epoch is nonstandard. Reactivate
14197 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
14199 @kindex Emacs Epoch environment
14203 Version 18 of @sc{gnu} Emacs has a built-in window system
14204 called the @code{epoch}
14205 environment. Users of this environment can use a new command,
14206 @code{inspect} which performs identically to @code{print} except that
14207 each value is printed in its own window.
14212 @chapter The @sc{gdb/mi} Interface
14214 @unnumberedsec Function and Purpose
14216 @cindex @sc{gdb/mi}, its purpose
14217 @sc{gdb/mi} is a line based machine oriented text interface to @value{GDBN}. It is
14218 specifically intended to support the development of systems which use
14219 the debugger as just one small component of a larger system.
14221 This chapter is a specification of the @sc{gdb/mi} interface. It is written
14222 in the form of a reference manual.
14224 Note that @sc{gdb/mi} is still under construction, so some of the
14225 features described below are incomplete and subject to change.
14227 @unnumberedsec Notation and Terminology
14229 @cindex notational conventions, for @sc{gdb/mi}
14230 This chapter uses the following notation:
14234 @code{|} separates two alternatives.
14237 @code{[ @var{something} ]} indicates that @var{something} is optional:
14238 it may or may not be given.
14241 @code{( @var{group} )*} means that @var{group} inside the parentheses
14242 may repeat zero or more times.
14245 @code{( @var{group} )+} means that @var{group} inside the parentheses
14246 may repeat one or more times.
14249 @code{"@var{string}"} means a literal @var{string}.
14253 @heading Dependencies
14256 @heading Acknowledgments
14258 In alphabetic order: Andrew Cagney, Fernando Nasser, Stan Shebs and
14262 * GDB/MI Command Syntax::
14263 * GDB/MI Compatibility with CLI::
14264 * GDB/MI Output Records::
14265 * GDB/MI Command Description Format::
14266 * GDB/MI Breakpoint Table Commands::
14267 * GDB/MI Data Manipulation::
14268 * GDB/MI Program Control::
14269 * GDB/MI Miscellaneous Commands::
14271 * GDB/MI Kod Commands::
14272 * GDB/MI Memory Overlay Commands::
14273 * GDB/MI Signal Handling Commands::
14275 * GDB/MI Stack Manipulation::
14276 * GDB/MI Symbol Query::
14277 * GDB/MI Target Manipulation::
14278 * GDB/MI Thread Commands::
14279 * GDB/MI Tracepoint Commands::
14280 * GDB/MI Variable Objects::
14283 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14284 @node GDB/MI Command Syntax
14285 @section @sc{gdb/mi} Command Syntax
14288 * GDB/MI Input Syntax::
14289 * GDB/MI Output Syntax::
14290 * GDB/MI Simple Examples::
14293 @node GDB/MI Input Syntax
14294 @subsection @sc{gdb/mi} Input Syntax
14296 @cindex input syntax for @sc{gdb/mi}
14297 @cindex @sc{gdb/mi}, input syntax
14299 @item @var{command} @expansion{}
14300 @code{@var{cli-command} | @var{mi-command}}
14302 @item @var{cli-command} @expansion{}
14303 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
14304 @var{cli-command} is any existing @value{GDBN} CLI command.
14306 @item @var{mi-command} @expansion{}
14307 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
14308 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
14310 @item @var{token} @expansion{}
14311 "any sequence of digits"
14313 @item @var{option} @expansion{}
14314 @code{"-" @var{parameter} [ " " @var{parameter} ]}
14316 @item @var{parameter} @expansion{}
14317 @code{@var{non-blank-sequence} | @var{c-string}}
14319 @item @var{operation} @expansion{}
14320 @emph{any of the operations described in this chapter}
14322 @item @var{non-blank-sequence} @expansion{}
14323 @emph{anything, provided it doesn't contain special characters such as
14324 "-", @var{nl}, """ and of course " "}
14326 @item @var{c-string} @expansion{}
14327 @code{""" @var{seven-bit-iso-c-string-content} """}
14329 @item @var{nl} @expansion{}
14338 The CLI commands are still handled by the @sc{mi} interpreter; their
14339 output is described below.
14342 The @code{@var{token}}, when present, is passed back when the command
14346 Some @sc{mi} commands accept optional arguments as part of the parameter
14347 list. Each option is identified by a leading @samp{-} (dash) and may be
14348 followed by an optional argument parameter. Options occur first in the
14349 parameter list and can be delimited from normal parameters using
14350 @samp{--} (this is useful when some parameters begin with a dash).
14357 We want easy access to the existing CLI syntax (for debugging).
14360 We want it to be easy to spot a @sc{mi} operation.
14363 @node GDB/MI Output Syntax
14364 @subsection @sc{gdb/mi} Output Syntax
14366 @cindex output syntax of @sc{gdb/mi}
14367 @cindex @sc{gdb/mi}, output syntax
14368 The output from @sc{gdb/mi} consists of zero or more out-of-band records
14369 followed, optionally, by a single result record. This result record
14370 is for the most recent command. The sequence of output records is
14371 terminated by @samp{(@value{GDBP})}.
14373 If an input command was prefixed with a @code{@var{token}} then the
14374 corresponding output for that command will also be prefixed by that same
14378 @item @var{output} @expansion{}
14379 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
14381 @item @var{result-record} @expansion{}
14382 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
14384 @item @var{out-of-band-record} @expansion{}
14385 @code{@var{async-record} | @var{stream-record}}
14387 @item @var{async-record} @expansion{}
14388 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
14390 @item @var{exec-async-output} @expansion{}
14391 @code{[ @var{token} ] "*" @var{async-output}}
14393 @item @var{status-async-output} @expansion{}
14394 @code{[ @var{token} ] "+" @var{async-output}}
14396 @item @var{notify-async-output} @expansion{}
14397 @code{[ @var{token} ] "=" @var{async-output}}
14399 @item @var{async-output} @expansion{}
14400 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
14402 @item @var{result-class} @expansion{}
14403 @code{"done" | "running" | "connected" | "error" | "exit"}
14405 @item @var{async-class} @expansion{}
14406 @code{"stopped" | @var{others}} (where @var{others} will be added
14407 depending on the needs---this is still in development).
14409 @item @var{result} @expansion{}
14410 @code{ @var{variable} "=" @var{value}}
14412 @item @var{variable} @expansion{}
14413 @code{ @var{string} }
14415 @item @var{value} @expansion{}
14416 @code{ @var{const} | @var{tuple} | @var{list} }
14418 @item @var{const} @expansion{}
14419 @code{@var{c-string}}
14421 @item @var{tuple} @expansion{}
14422 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
14424 @item @var{list} @expansion{}
14425 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
14426 @var{result} ( "," @var{result} )* "]" }
14428 @item @var{stream-record} @expansion{}
14429 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
14431 @item @var{console-stream-output} @expansion{}
14432 @code{"~" @var{c-string}}
14434 @item @var{target-stream-output} @expansion{}
14435 @code{"@@" @var{c-string}}
14437 @item @var{log-stream-output} @expansion{}
14438 @code{"&" @var{c-string}}
14440 @item @var{nl} @expansion{}
14443 @item @var{token} @expansion{}
14444 @emph{any sequence of digits}.
14452 All output sequences end in a single line containing a period.
14455 The @code{@var{token}} is from the corresponding request. If an execution
14456 command is interrupted by the @samp{-exec-interrupt} command, the
14457 @var{token} associated with the @samp{*stopped} message is the one of the
14458 original execution command, not the one of the interrupt command.
14461 @cindex status output in @sc{gdb/mi}
14462 @var{status-async-output} contains on-going status information about the
14463 progress of a slow operation. It can be discarded. All status output is
14464 prefixed by @samp{+}.
14467 @cindex async output in @sc{gdb/mi}
14468 @var{exec-async-output} contains asynchronous state change on the target
14469 (stopped, started, disappeared). All async output is prefixed by
14473 @cindex notify output in @sc{gdb/mi}
14474 @var{notify-async-output} contains supplementary information that the
14475 client should handle (e.g., a new breakpoint information). All notify
14476 output is prefixed by @samp{=}.
14479 @cindex console output in @sc{gdb/mi}
14480 @var{console-stream-output} is output that should be displayed as is in the
14481 console. It is the textual response to a CLI command. All the console
14482 output is prefixed by @samp{~}.
14485 @cindex target output in @sc{gdb/mi}
14486 @var{target-stream-output} is the output produced by the target program.
14487 All the target output is prefixed by @samp{@@}.
14490 @cindex log output in @sc{gdb/mi}
14491 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
14492 instance messages that should be displayed as part of an error log. All
14493 the log output is prefixed by @samp{&}.
14496 @cindex list output in @sc{gdb/mi}
14497 New @sc{gdb/mi} commands should only output @var{lists} containing
14503 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
14504 details about the various output records.
14506 @node GDB/MI Simple Examples
14507 @subsection Simple Examples of @sc{gdb/mi} Interaction
14508 @cindex @sc{gdb/mi}, simple examples
14510 This subsection presents several simple examples of interaction using
14511 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
14512 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
14513 the output received from @sc{gdb/mi}.
14515 @subsubheading Target Stop
14516 @c Ummm... There is no "-stop" command. This assumes async, no?
14517 Here's an example of stopping the inferior process:
14528 <- *stop,reason="stop",address="0x123",source="a.c:123"
14532 @subsubheading Simple CLI Command
14534 Here's an example of a simple CLI command being passed through
14535 @sc{gdb/mi} and on to the CLI.
14545 @subsubheading Command With Side Effects
14548 -> -symbol-file xyz.exe
14549 <- *breakpoint,nr="3",address="0x123",source="a.c:123"
14553 @subsubheading A Bad Command
14555 Here's what happens if you pass a non-existent command:
14559 <- ^error,msg="Undefined MI command: rubbish"
14563 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14564 @node GDB/MI Compatibility with CLI
14565 @section @sc{gdb/mi} Compatibility with CLI
14567 @cindex compatibility, @sc{gdb/mi} and CLI
14568 @cindex @sc{gdb/mi}, compatibility with CLI
14569 To help users familiar with @value{GDBN}'s existing CLI interface, @sc{gdb/mi}
14570 accepts existing CLI commands. As specified by the syntax, such
14571 commands can be directly entered into the @sc{gdb/mi} interface and @value{GDBN} will
14574 This mechanism is provided as an aid to developers of @sc{gdb/mi}
14575 clients and not as a reliable interface into the CLI. Since the command
14576 is being interpreteted in an environment that assumes @sc{gdb/mi}
14577 behaviour, the exact output of such commands is likely to end up being
14578 an un-supported hybrid of @sc{gdb/mi} and CLI output.
14580 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14581 @node GDB/MI Output Records
14582 @section @sc{gdb/mi} Output Records
14585 * GDB/MI Result Records::
14586 * GDB/MI Stream Records::
14587 * GDB/MI Out-of-band Records::
14590 @node GDB/MI Result Records
14591 @subsection @sc{gdb/mi} Result Records
14593 @cindex result records in @sc{gdb/mi}
14594 @cindex @sc{gdb/mi}, result records
14595 In addition to a number of out-of-band notifications, the response to a
14596 @sc{gdb/mi} command includes one of the following result indications:
14600 @item "^done" [ "," @var{results} ]
14601 The synchronous operation was successful, @code{@var{results}} are the return
14606 @c Is this one correct? Should it be an out-of-band notification?
14607 The asynchronous operation was successfully started. The target is
14610 @item "^error" "," @var{c-string}
14612 The operation failed. The @code{@var{c-string}} contains the corresponding
14616 @node GDB/MI Stream Records
14617 @subsection @sc{gdb/mi} Stream Records
14619 @cindex @sc{gdb/mi}, stream records
14620 @cindex stream records in @sc{gdb/mi}
14621 @value{GDBN} internally maintains a number of output streams: the console, the
14622 target, and the log. The output intended for each of these streams is
14623 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
14625 Each stream record begins with a unique @dfn{prefix character} which
14626 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
14627 Syntax}). In addition to the prefix, each stream record contains a
14628 @code{@var{string-output}}. This is either raw text (with an implicit new
14629 line) or a quoted C string (which does not contain an implicit newline).
14632 @item "~" @var{string-output}
14633 The console output stream contains text that should be displayed in the
14634 CLI console window. It contains the textual responses to CLI commands.
14636 @item "@@" @var{string-output}
14637 The target output stream contains any textual output from the running
14640 @item "&" @var{string-output}
14641 The log stream contains debugging messages being produced by @value{GDBN}'s
14645 @node GDB/MI Out-of-band Records
14646 @subsection @sc{gdb/mi} Out-of-band Records
14648 @cindex out-of-band records in @sc{gdb/mi}
14649 @cindex @sc{gdb/mi}, out-of-band records
14650 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
14651 additional changes that have occurred. Those changes can either be a
14652 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
14653 target activity (e.g., target stopped).
14655 The following is a preliminary list of possible out-of-band records.
14662 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14663 @node GDB/MI Command Description Format
14664 @section @sc{gdb/mi} Command Description Format
14666 The remaining sections describe blocks of commands. Each block of
14667 commands is laid out in a fashion similar to this section.
14669 Note the the line breaks shown in the examples are here only for
14670 readability. They don't appear in the real output.
14671 Also note that the commands with a non-available example (N.A.@:) are
14672 not yet implemented.
14674 @subheading Motivation
14676 The motivation for this collection of commands.
14678 @subheading Introduction
14680 A brief introduction to this collection of commands as a whole.
14682 @subheading Commands
14684 For each command in the block, the following is described:
14686 @subsubheading Synopsis
14689 -command @var{args}@dots{}
14692 @subsubheading @value{GDBN} Command
14694 The corresponding @value{GDBN} CLI command.
14696 @subsubheading Result
14698 @subsubheading Out-of-band
14700 @subsubheading Notes
14702 @subsubheading Example
14705 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14706 @node GDB/MI Breakpoint Table Commands
14707 @section @sc{gdb/mi} Breakpoint table commands
14709 @cindex breakpoint commands for @sc{gdb/mi}
14710 @cindex @sc{gdb/mi}, breakpoint commands
14711 This section documents @sc{gdb/mi} commands for manipulating
14714 @subheading The @code{-break-after} Command
14715 @findex -break-after
14717 @subsubheading Synopsis
14720 -break-after @var{number} @var{count}
14723 The breakpoint number @var{number} is not in effect until it has been
14724 hit @var{count} times. To see how this is reflected in the output of
14725 the @samp{-break-list} command, see the description of the
14726 @samp{-break-list} command below.
14728 @subsubheading @value{GDBN} Command
14730 The corresponding @value{GDBN} command is @samp{ignore}.
14732 @subsubheading Example
14737 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",line="5"@}
14744 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
14745 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14746 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14747 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14748 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14749 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14750 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14751 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
14752 addr="0x000100d0",func="main",file="hello.c",line="5",times="0",
14758 @subheading The @code{-break-catch} Command
14759 @findex -break-catch
14761 @subheading The @code{-break-commands} Command
14762 @findex -break-commands
14766 @subheading The @code{-break-condition} Command
14767 @findex -break-condition
14769 @subsubheading Synopsis
14772 -break-condition @var{number} @var{expr}
14775 Breakpoint @var{number} will stop the program only if the condition in
14776 @var{expr} is true. The condition becomes part of the
14777 @samp{-break-list} output (see the description of the @samp{-break-list}
14780 @subsubheading @value{GDBN} Command
14782 The corresponding @value{GDBN} command is @samp{condition}.
14784 @subsubheading Example
14788 -break-condition 1 1
14792 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
14793 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14794 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14795 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14796 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14797 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14798 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14799 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
14800 addr="0x000100d0",func="main",file="hello.c",line="5",cond="1",
14801 times="0",ignore="3"@}]@}
14805 @subheading The @code{-break-delete} Command
14806 @findex -break-delete
14808 @subsubheading Synopsis
14811 -break-delete ( @var{breakpoint} )+
14814 Delete the breakpoint(s) whose number(s) are specified in the argument
14815 list. This is obviously reflected in the breakpoint list.
14817 @subsubheading @value{GDBN} command
14819 The corresponding @value{GDBN} command is @samp{delete}.
14821 @subsubheading Example
14829 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
14830 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14831 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14832 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14833 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14834 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14835 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14840 @subheading The @code{-break-disable} Command
14841 @findex -break-disable
14843 @subsubheading Synopsis
14846 -break-disable ( @var{breakpoint} )+
14849 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
14850 break list is now set to @samp{n} for the named @var{breakpoint}(s).
14852 @subsubheading @value{GDBN} Command
14854 The corresponding @value{GDBN} command is @samp{disable}.
14856 @subsubheading Example
14864 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
14865 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14866 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14867 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14868 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14869 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14870 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14871 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
14872 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
14876 @subheading The @code{-break-enable} Command
14877 @findex -break-enable
14879 @subsubheading Synopsis
14882 -break-enable ( @var{breakpoint} )+
14885 Enable (previously disabled) @var{breakpoint}(s).
14887 @subsubheading @value{GDBN} Command
14889 The corresponding @value{GDBN} command is @samp{enable}.
14891 @subsubheading Example
14899 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
14900 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14901 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14902 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14903 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14904 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14905 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14906 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
14907 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
14911 @subheading The @code{-break-info} Command
14912 @findex -break-info
14914 @subsubheading Synopsis
14917 -break-info @var{breakpoint}
14921 Get information about a single breakpoint.
14923 @subsubheading @value{GDBN} command
14925 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
14927 @subsubheading Example
14930 @subheading The @code{-break-insert} Command
14931 @findex -break-insert
14933 @subsubheading Synopsis
14936 -break-insert [ -t ] [ -h ] [ -r ]
14937 [ -c @var{condition} ] [ -i @var{ignore-count} ]
14938 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
14942 If specified, @var{line}, can be one of:
14949 @item filename:linenum
14950 @item filename:function
14954 The possible optional parameters of this command are:
14958 Insert a tempoary breakpoint.
14960 Insert a hardware breakpoint.
14961 @item -c @var{condition}
14962 Make the breakpoint conditional on @var{condition}.
14963 @item -i @var{ignore-count}
14964 Initialize the @var{ignore-count}.
14966 Insert a regular breakpoint in all the functions whose names match the
14967 given regular expression. Other flags are not applicable to regular
14971 @subsubheading Result
14973 The result is in the form:
14976 ^done,bkptno="@var{number}",func="@var{funcname}",
14977 file="@var{filename}",line="@var{lineno}"
14981 where @var{number} is the @value{GDBN} number for this breakpoint, @var{funcname}
14982 is the name of the function where the breakpoint was inserted,
14983 @var{filename} is the name of the source file which contains this
14984 function, and @var{lineno} is the source line number within that file.
14986 Note: this format is open to change.
14987 @c An out-of-band breakpoint instead of part of the result?
14989 @subsubheading @value{GDBN} Command
14991 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
14992 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
14994 @subsubheading Example
14999 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
15001 -break-insert -t foo
15002 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",line="11"@}
15005 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15006 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15007 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15008 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15009 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15010 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15011 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15012 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15013 addr="0x0001072c", func="main",file="recursive2.c",line="4",times="0"@},
15014 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
15015 addr="0x00010774",func="foo",file="recursive2.c",line="11",times="0"@}]@}
15017 -break-insert -r foo.*
15018 ~int foo(int, int);
15019 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c",line="11"@}
15023 @subheading The @code{-break-list} Command
15024 @findex -break-list
15026 @subsubheading Synopsis
15032 Displays the list of inserted breakpoints, showing the following fields:
15036 number of the breakpoint
15038 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
15040 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
15043 is the breakpoint enabled or no: @samp{y} or @samp{n}
15045 memory location at which the breakpoint is set
15047 logical location of the breakpoint, expressed by function name, file
15050 number of times the breakpoint has been hit
15053 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
15054 @code{body} field is an empty list.
15056 @subsubheading @value{GDBN} Command
15058 The corresponding @value{GDBN} command is @samp{info break}.
15060 @subsubheading Example
15065 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15066 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15067 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15068 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15069 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15070 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15071 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15072 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15073 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
15074 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
15075 addr="0x00010114",func="foo",file="hello.c",line="13",times="0"@}]@}
15079 Here's an example of the result when there are no breakpoints:
15084 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
15085 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15086 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15087 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15088 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15089 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15090 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15095 @subheading The @code{-break-watch} Command
15096 @findex -break-watch
15098 @subsubheading Synopsis
15101 -break-watch [ -a | -r ]
15104 Create a watchpoint. With the @samp{-a} option it will create an
15105 @dfn{access} watchpoint, i.e. a watchpoint that triggers either on a
15106 read from or on a write to the memory location. With the @samp{-r}
15107 option, the watchpoint created is a @dfn{read} watchpoint, i.e. it will
15108 trigger only when the memory location is accessed for reading. Without
15109 either of the options, the watchpoint created is a regular watchpoint,
15110 i.e. it will trigger when the memory location is accessed for writing.
15111 @xref{Set Watchpoints, , Setting watchpoints}.
15113 Note that @samp{-break-list} will report a single list of watchpoints and
15114 breakpoints inserted.
15116 @subsubheading @value{GDBN} Command
15118 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
15121 @subsubheading Example
15123 Setting a watchpoint on a variable in the @code{main} function:
15128 ^done,wpt=@{number="2",exp="x"@}
15132 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
15133 value=@{old="-268439212",new="55"@},
15134 frame=@{func="main",args=[],file="recursive2.c",line="5"@}
15138 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
15139 the program execution twice: first for the variable changing value, then
15140 for the watchpoint going out of scope.
15145 ^done,wpt=@{number="5",exp="C"@}
15149 ^done,reason="watchpoint-trigger",
15150 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
15151 frame=@{func="callee4",args=[],
15152 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
15156 ^done,reason="watchpoint-scope",wpnum="5",
15157 frame=@{func="callee3",args=[@{name="strarg",
15158 value="0x11940 \"A string argument.\""@}],
15159 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
15163 Listing breakpoints and watchpoints, at different points in the program
15164 execution. Note that once the watchpoint goes out of scope, it is
15170 ^done,wpt=@{number="2",exp="C"@}
15173 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15174 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15175 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15176 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15177 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15178 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15179 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15180 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15181 addr="0x00010734",func="callee4",
15182 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
15183 bkpt=@{number="2",type="watchpoint",disp="keep",
15184 enabled="y",addr="",what="C",times="0"@}]@}
15188 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
15189 value=@{old="-276895068",new="3"@},
15190 frame=@{func="callee4",args=[],
15191 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
15194 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15195 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15196 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15197 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15198 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15199 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15200 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15201 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15202 addr="0x00010734",func="callee4",
15203 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
15204 bkpt=@{number="2",type="watchpoint",disp="keep",
15205 enabled="y",addr="",what="C",times="-5"@}]@}
15209 ^done,reason="watchpoint-scope",wpnum="2",
15210 frame=@{func="callee3",args=[@{name="strarg",
15211 value="0x11940 \"A string argument.\""@}],
15212 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
15215 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15216 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15217 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15218 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15219 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15220 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15221 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15222 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15223 addr="0x00010734",func="callee4",
15224 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@}]@}
15228 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15229 @node GDB/MI Data Manipulation
15230 @section @sc{gdb/mi} Data Manipulation
15232 @cindex data manipulation, in @sc{gdb/mi}
15233 @cindex @sc{gdb/mi}, data manipulation
15234 This section describes the @sc{gdb/mi} commands that manipulate data:
15235 examine memory and registers, evaluate expressions, etc.
15237 @c REMOVED FROM THE INTERFACE.
15238 @c @subheading -data-assign
15239 @c Change the value of a program variable. Plenty of side effects.
15240 @c @subsubheading GDB command
15242 @c @subsubheading Example
15245 @subheading The @code{-data-disassemble} Command
15246 @findex -data-disassemble
15248 @subsubheading Synopsis
15252 [ -s @var{start-addr} -e @var{end-addr} ]
15253 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
15261 @item @var{start-addr}
15262 is the beginning address (or @code{$pc})
15263 @item @var{end-addr}
15265 @item @var{filename}
15266 is the name of the file to disassemble
15267 @item @var{linenum}
15268 is the line number to disassemble around
15270 is the the number of disassembly lines to be produced. If it is -1,
15271 the whole function will be disassembled, in case no @var{end-addr} is
15272 specified. If @var{end-addr} is specified as a non-zero value, and
15273 @var{lines} is lower than the number of disassembly lines between
15274 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
15275 displayed; if @var{lines} is higher than the number of lines between
15276 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
15279 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
15283 @subsubheading Result
15285 The output for each instruction is composed of four fields:
15294 Note that whatever included in the instruction field, is not manipulated
15295 directely by @sc{gdb/mi}, i.e. it is not possible to adjust its format.
15297 @subsubheading @value{GDBN} Command
15299 There's no direct mapping from this command to the CLI.
15301 @subsubheading Example
15303 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
15307 -data-disassemble -s $pc -e "$pc + 20" -- 0
15310 @{address="0x000107c0",func-name="main",offset="4",
15311 inst="mov 2, %o0"@},
15312 @{address="0x000107c4",func-name="main",offset="8",
15313 inst="sethi %hi(0x11800), %o2"@},
15314 @{address="0x000107c8",func-name="main",offset="12",
15315 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
15316 @{address="0x000107cc",func-name="main",offset="16",
15317 inst="sethi %hi(0x11800), %o2"@},
15318 @{address="0x000107d0",func-name="main",offset="20",
15319 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
15323 Disassemble the whole @code{main} function. Line 32 is part of
15327 -data-disassemble -f basics.c -l 32 -- 0
15329 @{address="0x000107bc",func-name="main",offset="0",
15330 inst="save %sp, -112, %sp"@},
15331 @{address="0x000107c0",func-name="main",offset="4",
15332 inst="mov 2, %o0"@},
15333 @{address="0x000107c4",func-name="main",offset="8",
15334 inst="sethi %hi(0x11800), %o2"@},
15336 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
15337 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
15341 Disassemble 3 instructions from the start of @code{main}:
15345 -data-disassemble -f basics.c -l 32 -n 3 -- 0
15347 @{address="0x000107bc",func-name="main",offset="0",
15348 inst="save %sp, -112, %sp"@},
15349 @{address="0x000107c0",func-name="main",offset="4",
15350 inst="mov 2, %o0"@},
15351 @{address="0x000107c4",func-name="main",offset="8",
15352 inst="sethi %hi(0x11800), %o2"@}]
15356 Disassemble 3 instructions from the start of @code{main} in mixed mode:
15360 -data-disassemble -f basics.c -l 32 -n 3 -- 1
15362 src_and_asm_line=@{line="31",
15363 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
15364 testsuite/gdb.mi/basics.c",line_asm_insn=[
15365 @{address="0x000107bc",func-name="main",offset="0",
15366 inst="save %sp, -112, %sp"@}]@},
15367 src_and_asm_line=@{line="32",
15368 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
15369 testsuite/gdb.mi/basics.c",line_asm_insn=[
15370 @{address="0x000107c0",func-name="main",offset="4",
15371 inst="mov 2, %o0"@},
15372 @{address="0x000107c4",func-name="main",offset="8",
15373 inst="sethi %hi(0x11800), %o2"@}]@}]
15378 @subheading The @code{-data-evaluate-expression} Command
15379 @findex -data-evaluate-expression
15381 @subsubheading Synopsis
15384 -data-evaluate-expression @var{expr}
15387 Evaluate @var{expr} as an expression. The expression could contain an
15388 inferior function call. The function call will execute synchronously.
15389 If the expression contains spaces, it must be enclosed in double quotes.
15391 @subsubheading @value{GDBN} Command
15393 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
15394 @samp{call}. In @code{gdbtk} only, there's a corresponding
15395 @samp{gdb_eval} command.
15397 @subsubheading Example
15399 In the following example, the numbers that precede the commands are the
15400 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
15401 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
15405 211-data-evaluate-expression A
15408 311-data-evaluate-expression &A
15409 311^done,value="0xefffeb7c"
15411 411-data-evaluate-expression A+3
15414 511-data-evaluate-expression "A + 3"
15420 @subheading The @code{-data-list-changed-registers} Command
15421 @findex -data-list-changed-registers
15423 @subsubheading Synopsis
15426 -data-list-changed-registers
15429 Display a list of the registers that have changed.
15431 @subsubheading @value{GDBN} Command
15433 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
15434 has the corresponding command @samp{gdb_changed_register_list}.
15436 @subsubheading Example
15438 On a PPC MBX board:
15446 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
15447 args=[],file="try.c",line="5"@}
15449 -data-list-changed-registers
15450 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
15451 "10","11","13","14","15","16","17","18","19","20","21","22","23",
15452 "24","25","26","27","28","30","31","64","65","66","67","69"]
15457 @subheading The @code{-data-list-register-names} Command
15458 @findex -data-list-register-names
15460 @subsubheading Synopsis
15463 -data-list-register-names [ ( @var{regno} )+ ]
15466 Show a list of register names for the current target. If no arguments
15467 are given, it shows a list of the names of all the registers. If
15468 integer numbers are given as arguments, it will print a list of the
15469 names of the registers corresponding to the arguments. To ensure
15470 consistency between a register name and its number, the output list may
15471 include empty register names.
15473 @subsubheading @value{GDBN} Command
15475 @value{GDBN} does not have a command which corresponds to
15476 @samp{-data-list-register-names}. In @code{gdbtk} there is a
15477 corresponding command @samp{gdb_regnames}.
15479 @subsubheading Example
15481 For the PPC MBX board:
15484 -data-list-register-names
15485 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
15486 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
15487 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
15488 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
15489 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
15490 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
15491 "", "pc","ps","cr","lr","ctr","xer"]
15493 -data-list-register-names 1 2 3
15494 ^done,register-names=["r1","r2","r3"]
15498 @subheading The @code{-data-list-register-values} Command
15499 @findex -data-list-register-values
15501 @subsubheading Synopsis
15504 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
15507 Display the registers' contents. @var{fmt} is the format according to
15508 which the registers' contents are to be returned, followed by an optional
15509 list of numbers specifying the registers to display. A missing list of
15510 numbers indicates that the contents of all the registers must be returned.
15512 Allowed formats for @var{fmt} are:
15529 @subsubheading @value{GDBN} Command
15531 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
15532 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
15534 @subsubheading Example
15536 For a PPC MBX board (note: line breaks are for readability only, they
15537 don't appear in the actual output):
15541 -data-list-register-values r 64 65
15542 ^done,register-values=[@{number="64",value="0xfe00a300"@},
15543 @{number="65",value="0x00029002"@}]
15545 -data-list-register-values x
15546 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
15547 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
15548 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
15549 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
15550 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
15551 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
15552 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
15553 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
15554 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
15555 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
15556 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
15557 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
15558 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
15559 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
15560 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
15561 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
15562 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
15563 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
15564 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
15565 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
15566 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
15567 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
15568 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
15569 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
15570 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
15571 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
15572 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
15573 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
15574 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
15575 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
15576 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
15577 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
15578 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
15579 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
15580 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
15581 @{number="69",value="0x20002b03"@}]
15586 @subheading The @code{-data-read-memory} Command
15587 @findex -data-read-memory
15589 @subsubheading Synopsis
15592 -data-read-memory [ -o @var{byte-offset} ]
15593 @var{address} @var{word-format} @var{word-size}
15594 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
15601 @item @var{address}
15602 An expression specifying the address of the first memory word to be
15603 read. Complex expressions containing embedded white space should be
15604 quoted using the C convention.
15606 @item @var{word-format}
15607 The format to be used to print the memory words. The notation is the
15608 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
15611 @item @var{word-size}
15612 The size of each memory word in bytes.
15614 @item @var{nr-rows}
15615 The number of rows in the output table.
15617 @item @var{nr-cols}
15618 The number of columns in the output table.
15621 If present, indicates that each row should include an @sc{ascii} dump. The
15622 value of @var{aschar} is used as a padding character when a byte is not a
15623 member of the printable @sc{ascii} character set (printable @sc{ascii}
15624 characters are those whose code is between 32 and 126, inclusively).
15626 @item @var{byte-offset}
15627 An offset to add to the @var{address} before fetching memory.
15630 This command displays memory contents as a table of @var{nr-rows} by
15631 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
15632 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
15633 (returned as @samp{total-bytes}). Should less than the requested number
15634 of bytes be returned by the target, the missing words are identified
15635 using @samp{N/A}. The number of bytes read from the target is returned
15636 in @samp{nr-bytes} and the starting address used to read memory in
15639 The address of the next/previous row or page is available in
15640 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
15643 @subsubheading @value{GDBN} Command
15645 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
15646 @samp{gdb_get_mem} memory read command.
15648 @subsubheading Example
15650 Read six bytes of memory starting at @code{bytes+6} but then offset by
15651 @code{-6} bytes. Format as three rows of two columns. One byte per
15652 word. Display each word in hex.
15656 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
15657 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
15658 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
15659 prev-page="0x0000138a",memory=[
15660 @{addr="0x00001390",data=["0x00","0x01"]@},
15661 @{addr="0x00001392",data=["0x02","0x03"]@},
15662 @{addr="0x00001394",data=["0x04","0x05"]@}]
15666 Read two bytes of memory starting at address @code{shorts + 64} and
15667 display as a single word formatted in decimal.
15671 5-data-read-memory shorts+64 d 2 1 1
15672 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
15673 next-row="0x00001512",prev-row="0x0000150e",
15674 next-page="0x00001512",prev-page="0x0000150e",memory=[
15675 @{addr="0x00001510",data=["128"]@}]
15679 Read thirty two bytes of memory starting at @code{bytes+16} and format
15680 as eight rows of four columns. Include a string encoding with @samp{x}
15681 used as the non-printable character.
15685 4-data-read-memory bytes+16 x 1 8 4 x
15686 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
15687 next-row="0x000013c0",prev-row="0x0000139c",
15688 next-page="0x000013c0",prev-page="0x00001380",memory=[
15689 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
15690 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
15691 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
15692 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
15693 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
15694 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
15695 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
15696 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
15700 @subheading The @code{-display-delete} Command
15701 @findex -display-delete
15703 @subsubheading Synopsis
15706 -display-delete @var{number}
15709 Delete the display @var{number}.
15711 @subsubheading @value{GDBN} Command
15713 The corresponding @value{GDBN} command is @samp{delete display}.
15715 @subsubheading Example
15719 @subheading The @code{-display-disable} Command
15720 @findex -display-disable
15722 @subsubheading Synopsis
15725 -display-disable @var{number}
15728 Disable display @var{number}.
15730 @subsubheading @value{GDBN} Command
15732 The corresponding @value{GDBN} command is @samp{disable display}.
15734 @subsubheading Example
15738 @subheading The @code{-display-enable} Command
15739 @findex -display-enable
15741 @subsubheading Synopsis
15744 -display-enable @var{number}
15747 Enable display @var{number}.
15749 @subsubheading @value{GDBN} Command
15751 The corresponding @value{GDBN} command is @samp{enable display}.
15753 @subsubheading Example
15757 @subheading The @code{-display-insert} Command
15758 @findex -display-insert
15760 @subsubheading Synopsis
15763 -display-insert @var{expression}
15766 Display @var{expression} every time the program stops.
15768 @subsubheading @value{GDBN} Command
15770 The corresponding @value{GDBN} command is @samp{display}.
15772 @subsubheading Example
15776 @subheading The @code{-display-list} Command
15777 @findex -display-list
15779 @subsubheading Synopsis
15785 List the displays. Do not show the current values.
15787 @subsubheading @value{GDBN} Command
15789 The corresponding @value{GDBN} command is @samp{info display}.
15791 @subsubheading Example
15795 @subheading The @code{-environment-cd} Command
15796 @findex -environment-cd
15798 @subsubheading Synopsis
15801 -environment-cd @var{pathdir}
15804 Set @value{GDBN}'s working directory.
15806 @subsubheading @value{GDBN} Command
15808 The corresponding @value{GDBN} command is @samp{cd}.
15810 @subsubheading Example
15814 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
15820 @subheading The @code{-environment-directory} Command
15821 @findex -environment-directory
15823 @subsubheading Synopsis
15826 -environment-directory [ -r ] [ @var{pathdir} ]+
15829 Add directories @var{pathdir} to beginning of search path for source files.
15830 If the @samp{-r} option is used, the search path is reset to the default
15831 search path. If directories @var{pathdir} are supplied in addition to the
15832 @samp{-r} option, the search path is first reset and then addition
15834 Multiple directories may be specified, separated by blanks. Specifying
15835 multiple directories in a single command
15836 results in the directories added to the beginning of the
15837 search path in the same order they were presented in the command.
15838 If blanks are needed as
15839 part of a directory name, double-quotes should be used around
15840 the name. In the command output, the path will show up separated
15841 by the system directory-separator character. The directory-seperator
15842 character must not be used
15843 in any directory name.
15844 If no directories are specified, the current search path is displayed.
15846 @subsubheading @value{GDBN} Command
15848 The corresponding @value{GDBN} command is @samp{dir}.
15850 @subsubheading Example
15854 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
15855 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
15857 -environment-directory ""
15858 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
15860 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
15861 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
15863 -environment-directory -r
15864 ^done,source-path="$cdir:$cwd"
15869 @subheading The @code{-environment-path} Command
15870 @findex -environment-path
15872 @subsubheading Synopsis
15875 -environment-path [ -r ] [ @var{pathdir} ]+
15878 Add directories @var{pathdir} to beginning of search path for object files.
15879 If the @samp{-r} option is used, the search path is reset to the original
15880 search path that existed at gdb start-up. If directories @var{pathdir} are
15881 supplied in addition to the
15882 @samp{-r} option, the search path is first reset and then addition
15884 Multiple directories may be specified, separated by blanks. Specifying
15885 multiple directories in a single command
15886 results in the directories added to the beginning of the
15887 search path in the same order they were presented in the command.
15888 If blanks are needed as
15889 part of a directory name, double-quotes should be used around
15890 the name. In the command output, the path will show up separated
15891 by the system directory-separator character. The directory-seperator
15892 character must not be used
15893 in any directory name.
15894 If no directories are specified, the current path is displayed.
15897 @subsubheading @value{GDBN} Command
15899 The corresponding @value{GDBN} command is @samp{path}.
15901 @subsubheading Example
15906 ^done,path="/usr/bin"
15908 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
15909 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
15911 -environment-path -r /usr/local/bin
15912 ^done,path="/usr/local/bin:/usr/bin"
15917 @subheading The @code{-environment-pwd} Command
15918 @findex -environment-pwd
15920 @subsubheading Synopsis
15926 Show the current working directory.
15928 @subsubheading @value{GDBN} command
15930 The corresponding @value{GDBN} command is @samp{pwd}.
15932 @subsubheading Example
15937 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
15941 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15942 @node GDB/MI Program Control
15943 @section @sc{gdb/mi} Program control
15945 @subsubheading Program termination
15947 As a result of execution, the inferior program can run to completion, if
15948 it doesn't encounter any breakpoints. In this case the output will
15949 include an exit code, if the program has exited exceptionally.
15951 @subsubheading Examples
15954 Program exited normally:
15962 *stopped,reason="exited-normally"
15967 Program exited exceptionally:
15975 *stopped,reason="exited",exit-code="01"
15979 Another way the program can terminate is if it receives a signal such as
15980 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
15984 *stopped,reason="exited-signalled",signal-name="SIGINT",
15985 signal-meaning="Interrupt"
15989 @subheading The @code{-exec-abort} Command
15990 @findex -exec-abort
15992 @subsubheading Synopsis
15998 Kill the inferior running program.
16000 @subsubheading @value{GDBN} Command
16002 The corresponding @value{GDBN} command is @samp{kill}.
16004 @subsubheading Example
16008 @subheading The @code{-exec-arguments} Command
16009 @findex -exec-arguments
16011 @subsubheading Synopsis
16014 -exec-arguments @var{args}
16017 Set the inferior program arguments, to be used in the next
16020 @subsubheading @value{GDBN} Command
16022 The corresponding @value{GDBN} command is @samp{set args}.
16024 @subsubheading Example
16027 Don't have one around.
16030 @subheading The @code{-exec-continue} Command
16031 @findex -exec-continue
16033 @subsubheading Synopsis
16039 Asynchronous command. Resumes the execution of the inferior program
16040 until a breakpoint is encountered, or until the inferior exits.
16042 @subsubheading @value{GDBN} Command
16044 The corresponding @value{GDBN} corresponding is @samp{continue}.
16046 @subsubheading Example
16053 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
16054 file="hello.c",line="13"@}
16059 @subheading The @code{-exec-finish} Command
16060 @findex -exec-finish
16062 @subsubheading Synopsis
16068 Asynchronous command. Resumes the execution of the inferior program
16069 until the current function is exited. Displays the results returned by
16072 @subsubheading @value{GDBN} Command
16074 The corresponding @value{GDBN} command is @samp{finish}.
16076 @subsubheading Example
16078 Function returning @code{void}.
16085 *stopped,reason="function-finished",frame=@{func="main",args=[],
16086 file="hello.c",line="7"@}
16090 Function returning other than @code{void}. The name of the internal
16091 @value{GDBN} variable storing the result is printed, together with the
16098 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
16099 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
16100 file="recursive2.c",line="14"@},
16101 gdb-result-var="$1",return-value="0"
16106 @subheading The @code{-exec-interrupt} Command
16107 @findex -exec-interrupt
16109 @subsubheading Synopsis
16115 Asynchronous command. Interrupts the background execution of the target.
16116 Note how the token associated with the stop message is the one for the
16117 execution command that has been interrupted. The token for the interrupt
16118 itself only appears in the @samp{^done} output. If the user is trying to
16119 interrupt a non-running program, an error message will be printed.
16121 @subsubheading @value{GDBN} Command
16123 The corresponding @value{GDBN} command is @samp{interrupt}.
16125 @subsubheading Example
16136 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
16137 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",line="13"@}
16142 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
16147 @subheading The @code{-exec-next} Command
16150 @subsubheading Synopsis
16156 Asynchronous command. Resumes execution of the inferior program, stopping
16157 when the beginning of the next source line is reached.
16159 @subsubheading @value{GDBN} Command
16161 The corresponding @value{GDBN} command is @samp{next}.
16163 @subsubheading Example
16169 *stopped,reason="end-stepping-range",line="8",file="hello.c"
16174 @subheading The @code{-exec-next-instruction} Command
16175 @findex -exec-next-instruction
16177 @subsubheading Synopsis
16180 -exec-next-instruction
16183 Asynchronous command. Executes one machine instruction. If the
16184 instruction is a function call continues until the function returns. If
16185 the program stops at an instruction in the middle of a source line, the
16186 address will be printed as well.
16188 @subsubheading @value{GDBN} Command
16190 The corresponding @value{GDBN} command is @samp{nexti}.
16192 @subsubheading Example
16196 -exec-next-instruction
16200 *stopped,reason="end-stepping-range",
16201 addr="0x000100d4",line="5",file="hello.c"
16206 @subheading The @code{-exec-return} Command
16207 @findex -exec-return
16209 @subsubheading Synopsis
16215 Makes current function return immediately. Doesn't execute the inferior.
16216 Displays the new current frame.
16218 @subsubheading @value{GDBN} Command
16220 The corresponding @value{GDBN} command is @samp{return}.
16222 @subsubheading Example
16226 200-break-insert callee4
16227 200^done,bkpt=@{number="1",addr="0x00010734",
16228 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
16233 000*stopped,reason="breakpoint-hit",bkptno="1",
16234 frame=@{func="callee4",args=[],
16235 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
16241 111^done,frame=@{level="0",func="callee3",
16242 args=[@{name="strarg",
16243 value="0x11940 \"A string argument.\""@}],
16244 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
16249 @subheading The @code{-exec-run} Command
16252 @subsubheading Synopsis
16258 Asynchronous command. Starts execution of the inferior from the
16259 beginning. The inferior executes until either a breakpoint is
16260 encountered or the program exits.
16262 @subsubheading @value{GDBN} Command
16264 The corresponding @value{GDBN} command is @samp{run}.
16266 @subsubheading Example
16271 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
16276 *stopped,reason="breakpoint-hit",bkptno="1",
16277 frame=@{func="main",args=[],file="recursive2.c",line="4"@}
16282 @subheading The @code{-exec-show-arguments} Command
16283 @findex -exec-show-arguments
16285 @subsubheading Synopsis
16288 -exec-show-arguments
16291 Print the arguments of the program.
16293 @subsubheading @value{GDBN} Command
16295 The corresponding @value{GDBN} command is @samp{show args}.
16297 @subsubheading Example
16300 @c @subheading -exec-signal
16302 @subheading The @code{-exec-step} Command
16305 @subsubheading Synopsis
16311 Asynchronous command. Resumes execution of the inferior program, stopping
16312 when the beginning of the next source line is reached, if the next
16313 source line is not a function call. If it is, stop at the first
16314 instruction of the called function.
16316 @subsubheading @value{GDBN} Command
16318 The corresponding @value{GDBN} command is @samp{step}.
16320 @subsubheading Example
16322 Stepping into a function:
16328 *stopped,reason="end-stepping-range",
16329 frame=@{func="foo",args=[@{name="a",value="10"@},
16330 @{name="b",value="0"@}],file="recursive2.c",line="11"@}
16340 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
16345 @subheading The @code{-exec-step-instruction} Command
16346 @findex -exec-step-instruction
16348 @subsubheading Synopsis
16351 -exec-step-instruction
16354 Asynchronous command. Resumes the inferior which executes one machine
16355 instruction. The output, once @value{GDBN} has stopped, will vary depending on
16356 whether we have stopped in the middle of a source line or not. In the
16357 former case, the address at which the program stopped will be printed as
16360 @subsubheading @value{GDBN} Command
16362 The corresponding @value{GDBN} command is @samp{stepi}.
16364 @subsubheading Example
16368 -exec-step-instruction
16372 *stopped,reason="end-stepping-range",
16373 frame=@{func="foo",args=[],file="try.c",line="10"@}
16375 -exec-step-instruction
16379 *stopped,reason="end-stepping-range",
16380 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",line="10"@}
16385 @subheading The @code{-exec-until} Command
16386 @findex -exec-until
16388 @subsubheading Synopsis
16391 -exec-until [ @var{location} ]
16394 Asynchronous command. Executes the inferior until the @var{location}
16395 specified in the argument is reached. If there is no argument, the inferior
16396 executes until a source line greater than the current one is reached.
16397 The reason for stopping in this case will be @samp{location-reached}.
16399 @subsubheading @value{GDBN} Command
16401 The corresponding @value{GDBN} command is @samp{until}.
16403 @subsubheading Example
16407 -exec-until recursive2.c:6
16411 *stopped,reason="location-reached",frame=@{func="main",args=[],
16412 file="recursive2.c",line="6"@}
16417 @subheading -file-clear
16418 Is this going away????
16422 @subheading The @code{-file-exec-and-symbols} Command
16423 @findex -file-exec-and-symbols
16425 @subsubheading Synopsis
16428 -file-exec-and-symbols @var{file}
16431 Specify the executable file to be debugged. This file is the one from
16432 which the symbol table is also read. If no file is specified, the
16433 command clears the executable and symbol information. If breakpoints
16434 are set when using this command with no arguments, @value{GDBN} will produce
16435 error messages. Otherwise, no output is produced, except a completion
16438 @subsubheading @value{GDBN} Command
16440 The corresponding @value{GDBN} command is @samp{file}.
16442 @subsubheading Example
16446 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
16452 @subheading The @code{-file-exec-file} Command
16453 @findex -file-exec-file
16455 @subsubheading Synopsis
16458 -file-exec-file @var{file}
16461 Specify the executable file to be debugged. Unlike
16462 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
16463 from this file. If used without argument, @value{GDBN} clears the information
16464 about the executable file. No output is produced, except a completion
16467 @subsubheading @value{GDBN} Command
16469 The corresponding @value{GDBN} command is @samp{exec-file}.
16471 @subsubheading Example
16475 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
16481 @subheading The @code{-file-list-exec-sections} Command
16482 @findex -file-list-exec-sections
16484 @subsubheading Synopsis
16487 -file-list-exec-sections
16490 List the sections of the current executable file.
16492 @subsubheading @value{GDBN} Command
16494 The @value{GDBN} command @samp{info file} shows, among the rest, the same
16495 information as this command. @code{gdbtk} has a corresponding command
16496 @samp{gdb_load_info}.
16498 @subsubheading Example
16502 @subheading The @code{-file-list-exec-source-file} Command
16503 @findex -file-list-exec-source-file
16505 @subsubheading Synopsis
16508 -file-list-exec-source-file
16511 List the line number, the current source file, and the absolute path
16512 to the current source file for the current executable.
16514 @subsubheading @value{GDBN} Command
16516 There's no @value{GDBN} command which directly corresponds to this one.
16518 @subsubheading Example
16522 123-file-list-exec-source-file
16523 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
16528 @subheading The @code{-file-list-exec-source-files} Command
16529 @findex -file-list-exec-source-files
16531 @subsubheading Synopsis
16534 -file-list-exec-source-files
16537 List the source files for the current executable.
16539 @subsubheading @value{GDBN} Command
16541 There's no @value{GDBN} command which directly corresponds to this one.
16542 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
16544 @subsubheading Example
16548 @subheading The @code{-file-list-shared-libraries} Command
16549 @findex -file-list-shared-libraries
16551 @subsubheading Synopsis
16554 -file-list-shared-libraries
16557 List the shared libraries in the program.
16559 @subsubheading @value{GDBN} Command
16561 The corresponding @value{GDBN} command is @samp{info shared}.
16563 @subsubheading Example
16567 @subheading The @code{-file-list-symbol-files} Command
16568 @findex -file-list-symbol-files
16570 @subsubheading Synopsis
16573 -file-list-symbol-files
16578 @subsubheading @value{GDBN} Command
16580 The corresponding @value{GDBN} command is @samp{info file} (part of it).
16582 @subsubheading Example
16586 @subheading The @code{-file-symbol-file} Command
16587 @findex -file-symbol-file
16589 @subsubheading Synopsis
16592 -file-symbol-file @var{file}
16595 Read symbol table info from the specified @var{file} argument. When
16596 used without arguments, clears @value{GDBN}'s symbol table info. No output is
16597 produced, except for a completion notification.
16599 @subsubheading @value{GDBN} Command
16601 The corresponding @value{GDBN} command is @samp{symbol-file}.
16603 @subsubheading Example
16607 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
16612 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16613 @node GDB/MI Miscellaneous Commands
16614 @section Miscellaneous @value{GDBN} commands in @sc{gdb/mi}
16616 @c @subheading -gdb-complete
16618 @subheading The @code{-gdb-exit} Command
16621 @subsubheading Synopsis
16627 Exit @value{GDBN} immediately.
16629 @subsubheading @value{GDBN} Command
16631 Approximately corresponds to @samp{quit}.
16633 @subsubheading Example
16640 @subheading The @code{-gdb-set} Command
16643 @subsubheading Synopsis
16649 Set an internal @value{GDBN} variable.
16650 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
16652 @subsubheading @value{GDBN} Command
16654 The corresponding @value{GDBN} command is @samp{set}.
16656 @subsubheading Example
16666 @subheading The @code{-gdb-show} Command
16669 @subsubheading Synopsis
16675 Show the current value of a @value{GDBN} variable.
16677 @subsubheading @value{GDBN} command
16679 The corresponding @value{GDBN} command is @samp{show}.
16681 @subsubheading Example
16690 @c @subheading -gdb-source
16693 @subheading The @code{-gdb-version} Command
16694 @findex -gdb-version
16696 @subsubheading Synopsis
16702 Show version information for @value{GDBN}. Used mostly in testing.
16704 @subsubheading @value{GDBN} Command
16706 There's no equivalent @value{GDBN} command. @value{GDBN} by default shows this
16707 information when you start an interactive session.
16709 @subsubheading Example
16711 @c This example modifies the actual output from GDB to avoid overfull
16717 ~Copyright 2000 Free Software Foundation, Inc.
16718 ~GDB is free software, covered by the GNU General Public License, and
16719 ~you are welcome to change it and/or distribute copies of it under
16720 ~ certain conditions.
16721 ~Type "show copying" to see the conditions.
16722 ~There is absolutely no warranty for GDB. Type "show warranty" for
16724 ~This GDB was configured as
16725 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
16730 @subheading The @code{-interpreter-exec} Command
16731 @findex -interpreter-exec
16733 @subheading Synopsis
16736 -interpreter-exec @var{interpreter} @var{command}
16739 Execute the specified @var{command} in the given @var{interpreter}.
16741 @subheading @value{GDBN} Command
16743 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
16745 @subheading Example
16749 -interpreter-exec console "break main"
16750 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
16751 &"During symbol reading, bad structure-type format.\n"
16752 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
16758 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16759 @node GDB/MI Kod Commands
16760 @section @sc{gdb/mi} Kod Commands
16762 The Kod commands are not implemented.
16764 @c @subheading -kod-info
16766 @c @subheading -kod-list
16768 @c @subheading -kod-list-object-types
16770 @c @subheading -kod-show
16772 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16773 @node GDB/MI Memory Overlay Commands
16774 @section @sc{gdb/mi} Memory Overlay Commands
16776 The memory overlay commands are not implemented.
16778 @c @subheading -overlay-auto
16780 @c @subheading -overlay-list-mapping-state
16782 @c @subheading -overlay-list-overlays
16784 @c @subheading -overlay-map
16786 @c @subheading -overlay-off
16788 @c @subheading -overlay-on
16790 @c @subheading -overlay-unmap
16792 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16793 @node GDB/MI Signal Handling Commands
16794 @section @sc{gdb/mi} Signal Handling Commands
16796 Signal handling commands are not implemented.
16798 @c @subheading -signal-handle
16800 @c @subheading -signal-list-handle-actions
16802 @c @subheading -signal-list-signal-types
16806 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16807 @node GDB/MI Stack Manipulation
16808 @section @sc{gdb/mi} Stack Manipulation Commands
16811 @subheading The @code{-stack-info-frame} Command
16812 @findex -stack-info-frame
16814 @subsubheading Synopsis
16820 Get info on the current frame.
16822 @subsubheading @value{GDBN} Command
16824 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
16825 (without arguments).
16827 @subsubheading Example
16830 @subheading The @code{-stack-info-depth} Command
16831 @findex -stack-info-depth
16833 @subsubheading Synopsis
16836 -stack-info-depth [ @var{max-depth} ]
16839 Return the depth of the stack. If the integer argument @var{max-depth}
16840 is specified, do not count beyond @var{max-depth} frames.
16842 @subsubheading @value{GDBN} Command
16844 There's no equivalent @value{GDBN} command.
16846 @subsubheading Example
16848 For a stack with frame levels 0 through 11:
16855 -stack-info-depth 4
16858 -stack-info-depth 12
16861 -stack-info-depth 11
16864 -stack-info-depth 13
16869 @subheading The @code{-stack-list-arguments} Command
16870 @findex -stack-list-arguments
16872 @subsubheading Synopsis
16875 -stack-list-arguments @var{show-values}
16876 [ @var{low-frame} @var{high-frame} ]
16879 Display a list of the arguments for the frames between @var{low-frame}
16880 and @var{high-frame} (inclusive). If @var{low-frame} and
16881 @var{high-frame} are not provided, list the arguments for the whole call
16884 The @var{show-values} argument must have a value of 0 or 1. A value of
16885 0 means that only the names of the arguments are listed, a value of 1
16886 means that both names and values of the arguments are printed.
16888 @subsubheading @value{GDBN} Command
16890 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
16891 @samp{gdb_get_args} command which partially overlaps with the
16892 functionality of @samp{-stack-list-arguments}.
16894 @subsubheading Example
16901 frame=@{level="0",addr="0x00010734",func="callee4",
16902 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
16903 frame=@{level="1",addr="0x0001076c",func="callee3",
16904 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
16905 frame=@{level="2",addr="0x0001078c",func="callee2",
16906 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
16907 frame=@{level="3",addr="0x000107b4",func="callee1",
16908 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
16909 frame=@{level="4",addr="0x000107e0",func="main",
16910 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
16912 -stack-list-arguments 0
16915 frame=@{level="0",args=[]@},
16916 frame=@{level="1",args=[name="strarg"]@},
16917 frame=@{level="2",args=[name="intarg",name="strarg"]@},
16918 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
16919 frame=@{level="4",args=[]@}]
16921 -stack-list-arguments 1
16924 frame=@{level="0",args=[]@},
16926 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
16927 frame=@{level="2",args=[
16928 @{name="intarg",value="2"@},
16929 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
16930 @{frame=@{level="3",args=[
16931 @{name="intarg",value="2"@},
16932 @{name="strarg",value="0x11940 \"A string argument.\""@},
16933 @{name="fltarg",value="3.5"@}]@},
16934 frame=@{level="4",args=[]@}]
16936 -stack-list-arguments 0 2 2
16937 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
16939 -stack-list-arguments 1 2 2
16940 ^done,stack-args=[frame=@{level="2",
16941 args=[@{name="intarg",value="2"@},
16942 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
16946 @c @subheading -stack-list-exception-handlers
16949 @subheading The @code{-stack-list-frames} Command
16950 @findex -stack-list-frames
16952 @subsubheading Synopsis
16955 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
16958 List the frames currently on the stack. For each frame it displays the
16963 The frame number, 0 being the topmost frame, i.e. the innermost function.
16965 The @code{$pc} value for that frame.
16969 File name of the source file where the function lives.
16971 Line number corresponding to the @code{$pc}.
16974 If invoked without arguments, this command prints a backtrace for the
16975 whole stack. If given two integer arguments, it shows the frames whose
16976 levels are between the two arguments (inclusive). If the two arguments
16977 are equal, it shows the single frame at the corresponding level.
16979 @subsubheading @value{GDBN} Command
16981 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
16983 @subsubheading Example
16985 Full stack backtrace:
16991 [frame=@{level="0",addr="0x0001076c",func="foo",
16992 file="recursive2.c",line="11"@},
16993 frame=@{level="1",addr="0x000107a4",func="foo",
16994 file="recursive2.c",line="14"@},
16995 frame=@{level="2",addr="0x000107a4",func="foo",
16996 file="recursive2.c",line="14"@},
16997 frame=@{level="3",addr="0x000107a4",func="foo",
16998 file="recursive2.c",line="14"@},
16999 frame=@{level="4",addr="0x000107a4",func="foo",
17000 file="recursive2.c",line="14"@},
17001 frame=@{level="5",addr="0x000107a4",func="foo",
17002 file="recursive2.c",line="14"@},
17003 frame=@{level="6",addr="0x000107a4",func="foo",
17004 file="recursive2.c",line="14"@},
17005 frame=@{level="7",addr="0x000107a4",func="foo",
17006 file="recursive2.c",line="14"@},
17007 frame=@{level="8",addr="0x000107a4",func="foo",
17008 file="recursive2.c",line="14"@},
17009 frame=@{level="9",addr="0x000107a4",func="foo",
17010 file="recursive2.c",line="14"@},
17011 frame=@{level="10",addr="0x000107a4",func="foo",
17012 file="recursive2.c",line="14"@},
17013 frame=@{level="11",addr="0x00010738",func="main",
17014 file="recursive2.c",line="4"@}]
17018 Show frames between @var{low_frame} and @var{high_frame}:
17022 -stack-list-frames 3 5
17024 [frame=@{level="3",addr="0x000107a4",func="foo",
17025 file="recursive2.c",line="14"@},
17026 frame=@{level="4",addr="0x000107a4",func="foo",
17027 file="recursive2.c",line="14"@},
17028 frame=@{level="5",addr="0x000107a4",func="foo",
17029 file="recursive2.c",line="14"@}]
17033 Show a single frame:
17037 -stack-list-frames 3 3
17039 [frame=@{level="3",addr="0x000107a4",func="foo",
17040 file="recursive2.c",line="14"@}]
17045 @subheading The @code{-stack-list-locals} Command
17046 @findex -stack-list-locals
17048 @subsubheading Synopsis
17051 -stack-list-locals @var{print-values}
17054 Display the local variable names for the current frame. With an
17055 argument of 0 prints only the names of the variables, with argument of 1
17056 prints also their values.
17058 @subsubheading @value{GDBN} Command
17060 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
17062 @subsubheading Example
17066 -stack-list-locals 0
17067 ^done,locals=[name="A",name="B",name="C"]
17069 -stack-list-locals 1
17070 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
17071 @{name="C",value="3"@}]
17076 @subheading The @code{-stack-select-frame} Command
17077 @findex -stack-select-frame
17079 @subsubheading Synopsis
17082 -stack-select-frame @var{framenum}
17085 Change the current frame. Select a different frame @var{framenum} on
17088 @subsubheading @value{GDBN} Command
17090 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
17091 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
17093 @subsubheading Example
17097 -stack-select-frame 2
17102 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17103 @node GDB/MI Symbol Query
17104 @section @sc{gdb/mi} Symbol Query Commands
17107 @subheading The @code{-symbol-info-address} Command
17108 @findex -symbol-info-address
17110 @subsubheading Synopsis
17113 -symbol-info-address @var{symbol}
17116 Describe where @var{symbol} is stored.
17118 @subsubheading @value{GDBN} Command
17120 The corresponding @value{GDBN} command is @samp{info address}.
17122 @subsubheading Example
17126 @subheading The @code{-symbol-info-file} Command
17127 @findex -symbol-info-file
17129 @subsubheading Synopsis
17135 Show the file for the symbol.
17137 @subsubheading @value{GDBN} Command
17139 There's no equivalent @value{GDBN} command. @code{gdbtk} has
17140 @samp{gdb_find_file}.
17142 @subsubheading Example
17146 @subheading The @code{-symbol-info-function} Command
17147 @findex -symbol-info-function
17149 @subsubheading Synopsis
17152 -symbol-info-function
17155 Show which function the symbol lives in.
17157 @subsubheading @value{GDBN} Command
17159 @samp{gdb_get_function} in @code{gdbtk}.
17161 @subsubheading Example
17165 @subheading The @code{-symbol-info-line} Command
17166 @findex -symbol-info-line
17168 @subsubheading Synopsis
17174 Show the core addresses of the code for a source line.
17176 @subsubheading @value{GDBN} Command
17178 The corresponding @value{GDBN} comamnd is @samp{info line}.
17179 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
17181 @subsubheading Example
17185 @subheading The @code{-symbol-info-symbol} Command
17186 @findex -symbol-info-symbol
17188 @subsubheading Synopsis
17191 -symbol-info-symbol @var{addr}
17194 Describe what symbol is at location @var{addr}.
17196 @subsubheading @value{GDBN} Command
17198 The corresponding @value{GDBN} command is @samp{info symbol}.
17200 @subsubheading Example
17204 @subheading The @code{-symbol-list-functions} Command
17205 @findex -symbol-list-functions
17207 @subsubheading Synopsis
17210 -symbol-list-functions
17213 List the functions in the executable.
17215 @subsubheading @value{GDBN} Command
17217 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
17218 @samp{gdb_search} in @code{gdbtk}.
17220 @subsubheading Example
17224 @subheading The @code{-symbol-list-lines} Command
17225 @findex -symbol-list-lines
17227 @subsubheading Synopsis
17230 -symbol-list-lines @var{filename}
17233 Print the list of lines that contain code and their associated program
17234 addresses for the given source filename. The entries are sorted in
17235 ascending PC order.
17237 @subsubheading @value{GDBN} Command
17239 There is no corresponding @value{GDBN} command.
17241 @subsubheading Example
17244 -symbol-list-lines basics.c
17245 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
17250 @subheading The @code{-symbol-list-types} Command
17251 @findex -symbol-list-types
17253 @subsubheading Synopsis
17259 List all the type names.
17261 @subsubheading @value{GDBN} Command
17263 The corresponding commands are @samp{info types} in @value{GDBN},
17264 @samp{gdb_search} in @code{gdbtk}.
17266 @subsubheading Example
17270 @subheading The @code{-symbol-list-variables} Command
17271 @findex -symbol-list-variables
17273 @subsubheading Synopsis
17276 -symbol-list-variables
17279 List all the global and static variable names.
17281 @subsubheading @value{GDBN} Command
17283 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
17285 @subsubheading Example
17289 @subheading The @code{-symbol-locate} Command
17290 @findex -symbol-locate
17292 @subsubheading Synopsis
17298 @subsubheading @value{GDBN} Command
17300 @samp{gdb_loc} in @code{gdbtk}.
17302 @subsubheading Example
17306 @subheading The @code{-symbol-type} Command
17307 @findex -symbol-type
17309 @subsubheading Synopsis
17312 -symbol-type @var{variable}
17315 Show type of @var{variable}.
17317 @subsubheading @value{GDBN} Command
17319 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
17320 @samp{gdb_obj_variable}.
17322 @subsubheading Example
17326 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17327 @node GDB/MI Target Manipulation
17328 @section @sc{gdb/mi} Target Manipulation Commands
17331 @subheading The @code{-target-attach} Command
17332 @findex -target-attach
17334 @subsubheading Synopsis
17337 -target-attach @var{pid} | @var{file}
17340 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
17342 @subsubheading @value{GDBN} command
17344 The corresponding @value{GDBN} command is @samp{attach}.
17346 @subsubheading Example
17350 @subheading The @code{-target-compare-sections} Command
17351 @findex -target-compare-sections
17353 @subsubheading Synopsis
17356 -target-compare-sections [ @var{section} ]
17359 Compare data of section @var{section} on target to the exec file.
17360 Without the argument, all sections are compared.
17362 @subsubheading @value{GDBN} Command
17364 The @value{GDBN} equivalent is @samp{compare-sections}.
17366 @subsubheading Example
17370 @subheading The @code{-target-detach} Command
17371 @findex -target-detach
17373 @subsubheading Synopsis
17379 Disconnect from the remote target. There's no output.
17381 @subsubheading @value{GDBN} command
17383 The corresponding @value{GDBN} command is @samp{detach}.
17385 @subsubheading Example
17395 @subheading The @code{-target-download} Command
17396 @findex -target-download
17398 @subsubheading Synopsis
17404 Loads the executable onto the remote target.
17405 It prints out an update message every half second, which includes the fields:
17409 The name of the section.
17411 The size of what has been sent so far for that section.
17413 The size of the section.
17415 The total size of what was sent so far (the current and the previous sections).
17417 The size of the overall executable to download.
17421 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
17422 @sc{gdb/mi} Output Syntax}).
17424 In addition, it prints the name and size of the sections, as they are
17425 downloaded. These messages include the following fields:
17429 The name of the section.
17431 The size of the section.
17433 The size of the overall executable to download.
17437 At the end, a summary is printed.
17439 @subsubheading @value{GDBN} Command
17441 The corresponding @value{GDBN} command is @samp{load}.
17443 @subsubheading Example
17445 Note: each status message appears on a single line. Here the messages
17446 have been broken down so that they can fit onto a page.
17451 +download,@{section=".text",section-size="6668",total-size="9880"@}
17452 +download,@{section=".text",section-sent="512",section-size="6668",
17453 total-sent="512",total-size="9880"@}
17454 +download,@{section=".text",section-sent="1024",section-size="6668",
17455 total-sent="1024",total-size="9880"@}
17456 +download,@{section=".text",section-sent="1536",section-size="6668",
17457 total-sent="1536",total-size="9880"@}
17458 +download,@{section=".text",section-sent="2048",section-size="6668",
17459 total-sent="2048",total-size="9880"@}
17460 +download,@{section=".text",section-sent="2560",section-size="6668",
17461 total-sent="2560",total-size="9880"@}
17462 +download,@{section=".text",section-sent="3072",section-size="6668",
17463 total-sent="3072",total-size="9880"@}
17464 +download,@{section=".text",section-sent="3584",section-size="6668",
17465 total-sent="3584",total-size="9880"@}
17466 +download,@{section=".text",section-sent="4096",section-size="6668",
17467 total-sent="4096",total-size="9880"@}
17468 +download,@{section=".text",section-sent="4608",section-size="6668",
17469 total-sent="4608",total-size="9880"@}
17470 +download,@{section=".text",section-sent="5120",section-size="6668",
17471 total-sent="5120",total-size="9880"@}
17472 +download,@{section=".text",section-sent="5632",section-size="6668",
17473 total-sent="5632",total-size="9880"@}
17474 +download,@{section=".text",section-sent="6144",section-size="6668",
17475 total-sent="6144",total-size="9880"@}
17476 +download,@{section=".text",section-sent="6656",section-size="6668",
17477 total-sent="6656",total-size="9880"@}
17478 +download,@{section=".init",section-size="28",total-size="9880"@}
17479 +download,@{section=".fini",section-size="28",total-size="9880"@}
17480 +download,@{section=".data",section-size="3156",total-size="9880"@}
17481 +download,@{section=".data",section-sent="512",section-size="3156",
17482 total-sent="7236",total-size="9880"@}
17483 +download,@{section=".data",section-sent="1024",section-size="3156",
17484 total-sent="7748",total-size="9880"@}
17485 +download,@{section=".data",section-sent="1536",section-size="3156",
17486 total-sent="8260",total-size="9880"@}
17487 +download,@{section=".data",section-sent="2048",section-size="3156",
17488 total-sent="8772",total-size="9880"@}
17489 +download,@{section=".data",section-sent="2560",section-size="3156",
17490 total-sent="9284",total-size="9880"@}
17491 +download,@{section=".data",section-sent="3072",section-size="3156",
17492 total-sent="9796",total-size="9880"@}
17493 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
17499 @subheading The @code{-target-exec-status} Command
17500 @findex -target-exec-status
17502 @subsubheading Synopsis
17505 -target-exec-status
17508 Provide information on the state of the target (whether it is running or
17509 not, for instance).
17511 @subsubheading @value{GDBN} Command
17513 There's no equivalent @value{GDBN} command.
17515 @subsubheading Example
17519 @subheading The @code{-target-list-available-targets} Command
17520 @findex -target-list-available-targets
17522 @subsubheading Synopsis
17525 -target-list-available-targets
17528 List the possible targets to connect to.
17530 @subsubheading @value{GDBN} Command
17532 The corresponding @value{GDBN} command is @samp{help target}.
17534 @subsubheading Example
17538 @subheading The @code{-target-list-current-targets} Command
17539 @findex -target-list-current-targets
17541 @subsubheading Synopsis
17544 -target-list-current-targets
17547 Describe the current target.
17549 @subsubheading @value{GDBN} Command
17551 The corresponding information is printed by @samp{info file} (among
17554 @subsubheading Example
17558 @subheading The @code{-target-list-parameters} Command
17559 @findex -target-list-parameters
17561 @subsubheading Synopsis
17564 -target-list-parameters
17569 @subsubheading @value{GDBN} Command
17573 @subsubheading Example
17577 @subheading The @code{-target-select} Command
17578 @findex -target-select
17580 @subsubheading Synopsis
17583 -target-select @var{type} @var{parameters @dots{}}
17586 Connect @value{GDBN} to the remote target. This command takes two args:
17590 The type of target, for instance @samp{async}, @samp{remote}, etc.
17591 @item @var{parameters}
17592 Device names, host names and the like. @xref{Target Commands, ,
17593 Commands for managing targets}, for more details.
17596 The output is a connection notification, followed by the address at
17597 which the target program is, in the following form:
17600 ^connected,addr="@var{address}",func="@var{function name}",
17601 args=[@var{arg list}]
17604 @subsubheading @value{GDBN} Command
17606 The corresponding @value{GDBN} command is @samp{target}.
17608 @subsubheading Example
17612 -target-select async /dev/ttya
17613 ^connected,addr="0xfe00a300",func="??",args=[]
17617 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17618 @node GDB/MI Thread Commands
17619 @section @sc{gdb/mi} Thread Commands
17622 @subheading The @code{-thread-info} Command
17623 @findex -thread-info
17625 @subsubheading Synopsis
17631 @subsubheading @value{GDBN} command
17635 @subsubheading Example
17639 @subheading The @code{-thread-list-all-threads} Command
17640 @findex -thread-list-all-threads
17642 @subsubheading Synopsis
17645 -thread-list-all-threads
17648 @subsubheading @value{GDBN} Command
17650 The equivalent @value{GDBN} command is @samp{info threads}.
17652 @subsubheading Example
17656 @subheading The @code{-thread-list-ids} Command
17657 @findex -thread-list-ids
17659 @subsubheading Synopsis
17665 Produces a list of the currently known @value{GDBN} thread ids. At the
17666 end of the list it also prints the total number of such threads.
17668 @subsubheading @value{GDBN} Command
17670 Part of @samp{info threads} supplies the same information.
17672 @subsubheading Example
17674 No threads present, besides the main process:
17679 ^done,thread-ids=@{@},number-of-threads="0"
17689 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
17690 number-of-threads="3"
17695 @subheading The @code{-thread-select} Command
17696 @findex -thread-select
17698 @subsubheading Synopsis
17701 -thread-select @var{threadnum}
17704 Make @var{threadnum} the current thread. It prints the number of the new
17705 current thread, and the topmost frame for that thread.
17707 @subsubheading @value{GDBN} Command
17709 The corresponding @value{GDBN} command is @samp{thread}.
17711 @subsubheading Example
17718 *stopped,reason="end-stepping-range",thread-id="2",line="187",
17719 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
17723 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
17724 number-of-threads="3"
17727 ^done,new-thread-id="3",
17728 frame=@{level="0",func="vprintf",
17729 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
17730 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
17734 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17735 @node GDB/MI Tracepoint Commands
17736 @section @sc{gdb/mi} Tracepoint Commands
17738 The tracepoint commands are not yet implemented.
17740 @c @subheading -trace-actions
17742 @c @subheading -trace-delete
17744 @c @subheading -trace-disable
17746 @c @subheading -trace-dump
17748 @c @subheading -trace-enable
17750 @c @subheading -trace-exists
17752 @c @subheading -trace-find
17754 @c @subheading -trace-frame-number
17756 @c @subheading -trace-info
17758 @c @subheading -trace-insert
17760 @c @subheading -trace-list
17762 @c @subheading -trace-pass-count
17764 @c @subheading -trace-save
17766 @c @subheading -trace-start
17768 @c @subheading -trace-stop
17771 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17772 @node GDB/MI Variable Objects
17773 @section @sc{gdb/mi} Variable Objects
17776 @subheading Motivation for Variable Objects in @sc{gdb/mi}
17778 For the implementation of a variable debugger window (locals, watched
17779 expressions, etc.), we are proposing the adaptation of the existing code
17780 used by @code{Insight}.
17782 The two main reasons for that are:
17786 It has been proven in practice (it is already on its second generation).
17789 It will shorten development time (needless to say how important it is
17793 The original interface was designed to be used by Tcl code, so it was
17794 slightly changed so it could be used through @sc{gdb/mi}. This section
17795 describes the @sc{gdb/mi} operations that will be available and gives some
17796 hints about their use.
17798 @emph{Note}: In addition to the set of operations described here, we
17799 expect the @sc{gui} implementation of a variable window to require, at
17800 least, the following operations:
17803 @item @code{-gdb-show} @code{output-radix}
17804 @item @code{-stack-list-arguments}
17805 @item @code{-stack-list-locals}
17806 @item @code{-stack-select-frame}
17809 @subheading Introduction to Variable Objects in @sc{gdb/mi}
17811 @cindex variable objects in @sc{gdb/mi}
17812 The basic idea behind variable objects is the creation of a named object
17813 to represent a variable, an expression, a memory location or even a CPU
17814 register. For each object created, a set of operations is available for
17815 examining or changing its properties.
17817 Furthermore, complex data types, such as C structures, are represented
17818 in a tree format. For instance, the @code{struct} type variable is the
17819 root and the children will represent the struct members. If a child
17820 is itself of a complex type, it will also have children of its own.
17821 Appropriate language differences are handled for C, C@t{++} and Java.
17823 When returning the actual values of the objects, this facility allows
17824 for the individual selection of the display format used in the result
17825 creation. It can be chosen among: binary, decimal, hexadecimal, octal
17826 and natural. Natural refers to a default format automatically
17827 chosen based on the variable type (like decimal for an @code{int}, hex
17828 for pointers, etc.).
17830 The following is the complete set of @sc{gdb/mi} operations defined to
17831 access this functionality:
17833 @multitable @columnfractions .4 .6
17834 @item @strong{Operation}
17835 @tab @strong{Description}
17837 @item @code{-var-create}
17838 @tab create a variable object
17839 @item @code{-var-delete}
17840 @tab delete the variable object and its children
17841 @item @code{-var-set-format}
17842 @tab set the display format of this variable
17843 @item @code{-var-show-format}
17844 @tab show the display format of this variable
17845 @item @code{-var-info-num-children}
17846 @tab tells how many children this object has
17847 @item @code{-var-list-children}
17848 @tab return a list of the object's children
17849 @item @code{-var-info-type}
17850 @tab show the type of this variable object
17851 @item @code{-var-info-expression}
17852 @tab print what this variable object represents
17853 @item @code{-var-show-attributes}
17854 @tab is this variable editable? does it exist here?
17855 @item @code{-var-evaluate-expression}
17856 @tab get the value of this variable
17857 @item @code{-var-assign}
17858 @tab set the value of this variable
17859 @item @code{-var-update}
17860 @tab update the variable and its children
17863 In the next subsection we describe each operation in detail and suggest
17864 how it can be used.
17866 @subheading Description And Use of Operations on Variable Objects
17868 @subheading The @code{-var-create} Command
17869 @findex -var-create
17871 @subsubheading Synopsis
17874 -var-create @{@var{name} | "-"@}
17875 @{@var{frame-addr} | "*"@} @var{expression}
17878 This operation creates a variable object, which allows the monitoring of
17879 a variable, the result of an expression, a memory cell or a CPU
17882 The @var{name} parameter is the string by which the object can be
17883 referenced. It must be unique. If @samp{-} is specified, the varobj
17884 system will generate a string ``varNNNNNN'' automatically. It will be
17885 unique provided that one does not specify @var{name} on that format.
17886 The command fails if a duplicate name is found.
17888 The frame under which the expression should be evaluated can be
17889 specified by @var{frame-addr}. A @samp{*} indicates that the current
17890 frame should be used.
17892 @var{expression} is any expression valid on the current language set (must not
17893 begin with a @samp{*}), or one of the following:
17897 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
17900 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
17903 @samp{$@var{regname}} --- a CPU register name
17906 @subsubheading Result
17908 This operation returns the name, number of children and the type of the
17909 object created. Type is returned as a string as the ones generated by
17910 the @value{GDBN} CLI:
17913 name="@var{name}",numchild="N",type="@var{type}"
17917 @subheading The @code{-var-delete} Command
17918 @findex -var-delete
17920 @subsubheading Synopsis
17923 -var-delete @var{name}
17926 Deletes a previously created variable object and all of its children.
17928 Returns an error if the object @var{name} is not found.
17931 @subheading The @code{-var-set-format} Command
17932 @findex -var-set-format
17934 @subsubheading Synopsis
17937 -var-set-format @var{name} @var{format-spec}
17940 Sets the output format for the value of the object @var{name} to be
17943 The syntax for the @var{format-spec} is as follows:
17946 @var{format-spec} @expansion{}
17947 @{binary | decimal | hexadecimal | octal | natural@}
17951 @subheading The @code{-var-show-format} Command
17952 @findex -var-show-format
17954 @subsubheading Synopsis
17957 -var-show-format @var{name}
17960 Returns the format used to display the value of the object @var{name}.
17963 @var{format} @expansion{}
17968 @subheading The @code{-var-info-num-children} Command
17969 @findex -var-info-num-children
17971 @subsubheading Synopsis
17974 -var-info-num-children @var{name}
17977 Returns the number of children of a variable object @var{name}:
17984 @subheading The @code{-var-list-children} Command
17985 @findex -var-list-children
17987 @subsubheading Synopsis
17990 -var-list-children @var{name}
17993 Returns a list of the children of the specified variable object:
17996 numchild=@var{n},children=[@{name=@var{name},
17997 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
18001 @subheading The @code{-var-info-type} Command
18002 @findex -var-info-type
18004 @subsubheading Synopsis
18007 -var-info-type @var{name}
18010 Returns the type of the specified variable @var{name}. The type is
18011 returned as a string in the same format as it is output by the
18015 type=@var{typename}
18019 @subheading The @code{-var-info-expression} Command
18020 @findex -var-info-expression
18022 @subsubheading Synopsis
18025 -var-info-expression @var{name}
18028 Returns what is represented by the variable object @var{name}:
18031 lang=@var{lang-spec},exp=@var{expression}
18035 where @var{lang-spec} is @code{@{"C" | "C++" | "Java"@}}.
18037 @subheading The @code{-var-show-attributes} Command
18038 @findex -var-show-attributes
18040 @subsubheading Synopsis
18043 -var-show-attributes @var{name}
18046 List attributes of the specified variable object @var{name}:
18049 status=@var{attr} [ ( ,@var{attr} )* ]
18053 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
18055 @subheading The @code{-var-evaluate-expression} Command
18056 @findex -var-evaluate-expression
18058 @subsubheading Synopsis
18061 -var-evaluate-expression @var{name}
18064 Evaluates the expression that is represented by the specified variable
18065 object and returns its value as a string in the current format specified
18072 Note that one must invoke @code{-var-list-children} for a variable
18073 before the value of a child variable can be evaluated.
18075 @subheading The @code{-var-assign} Command
18076 @findex -var-assign
18078 @subsubheading Synopsis
18081 -var-assign @var{name} @var{expression}
18084 Assigns the value of @var{expression} to the variable object specified
18085 by @var{name}. The object must be @samp{editable}. If the variable's
18086 value is altered by the assign, the variable will show up in any
18087 subsequent @code{-var-update} list.
18089 @subsubheading Example
18097 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
18101 @subheading The @code{-var-update} Command
18102 @findex -var-update
18104 @subsubheading Synopsis
18107 -var-update @{@var{name} | "*"@}
18110 Update the value of the variable object @var{name} by evaluating its
18111 expression after fetching all the new values from memory or registers.
18112 A @samp{*} causes all existing variable objects to be updated.
18116 @chapter @value{GDBN} Annotations
18118 This chapter describes annotations in @value{GDBN}. Annotations are
18119 designed to interface @value{GDBN} to graphical user interfaces or
18120 other similar programs which want to interact with @value{GDBN} at a
18121 relatively high level.
18124 This is Edition @value{EDITION}, @value{DATE}.
18128 * Annotations Overview:: What annotations are; the general syntax.
18129 * Server Prefix:: Issuing a command without affecting user state.
18130 * Value Annotations:: Values are marked as such.
18131 * Frame Annotations:: Stack frames are annotated.
18132 * Displays:: @value{GDBN} can be told to display something periodically.
18133 * Prompting:: Annotations marking @value{GDBN}'s need for input.
18134 * Errors:: Annotations for error messages.
18135 * Breakpoint Info:: Information on breakpoints.
18136 * Invalidation:: Some annotations describe things now invalid.
18137 * Annotations for Running::
18138 Whether the program is running, how it stopped, etc.
18139 * Source Annotations:: Annotations describing source code.
18140 * TODO:: Annotations which might be added in the future.
18143 @node Annotations Overview
18144 @section What is an Annotation?
18145 @cindex annotations
18147 To produce annotations, start @value{GDBN} with the @code{--annotate=2} option.
18149 Annotations start with a newline character, two @samp{control-z}
18150 characters, and the name of the annotation. If there is no additional
18151 information associated with this annotation, the name of the annotation
18152 is followed immediately by a newline. If there is additional
18153 information, the name of the annotation is followed by a space, the
18154 additional information, and a newline. The additional information
18155 cannot contain newline characters.
18157 Any output not beginning with a newline and two @samp{control-z}
18158 characters denotes literal output from @value{GDBN}. Currently there is
18159 no need for @value{GDBN} to output a newline followed by two
18160 @samp{control-z} characters, but if there was such a need, the
18161 annotations could be extended with an @samp{escape} annotation which
18162 means those three characters as output.
18164 A simple example of starting up @value{GDBN} with annotations is:
18169 Copyright 2000 Free Software Foundation, Inc.
18170 GDB is free software, covered by the GNU General Public License,
18171 and you are welcome to change it and/or distribute copies of it
18172 under certain conditions.
18173 Type "show copying" to see the conditions.
18174 There is absolutely no warranty for GDB. Type "show warranty"
18176 This GDB was configured as "sparc-sun-sunos4.1.3"
18187 Here @samp{quit} is input to @value{GDBN}; the rest is output from
18188 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
18189 denotes a @samp{control-z} character) are annotations; the rest is
18190 output from @value{GDBN}.
18192 @node Server Prefix
18193 @section The Server Prefix
18194 @cindex server prefix for annotations
18196 To issue a command to @value{GDBN} without affecting certain aspects of
18197 the state which is seen by users, prefix it with @samp{server }. This
18198 means that this command will not affect the command history, nor will it
18199 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
18200 pressed on a line by itself.
18202 The server prefix does not affect the recording of values into the value
18203 history; to print a value without recording it into the value history,
18204 use the @code{output} command instead of the @code{print} command.
18206 @node Value Annotations
18209 @cindex annotations for values
18210 When a value is printed in various contexts, @value{GDBN} uses
18211 annotations to delimit the value from the surrounding text.
18213 @findex value-history-begin
18214 @findex value-history-value
18215 @findex value-history-end
18216 If a value is printed using @code{print} and added to the value history,
18217 the annotation looks like
18220 ^Z^Zvalue-history-begin @var{history-number} @var{value-flags}
18221 @var{history-string}
18222 ^Z^Zvalue-history-value
18224 ^Z^Zvalue-history-end
18228 where @var{history-number} is the number it is getting in the value
18229 history, @var{history-string} is a string, such as @samp{$5 = }, which
18230 introduces the value to the user, @var{the-value} is the output
18231 corresponding to the value itself, and @var{value-flags} is @samp{*} for
18232 a value which can be dereferenced and @samp{-} for a value which cannot.
18234 @findex value-begin
18236 If the value is not added to the value history (it is an invalid float
18237 or it is printed with the @code{output} command), the annotation is similar:
18240 ^Z^Zvalue-begin @var{value-flags}
18246 @findex arg-name-end
18249 When @value{GDBN} prints an argument to a function (for example, in the output
18250 from the @code{backtrace} command), it annotates it as follows:
18254 @var{argument-name}
18256 @var{separator-string}
18257 ^Z^Zarg-value @var{value-flags}
18263 where @var{argument-name} is the name of the argument,
18264 @var{separator-string} is text which separates the name from the value
18265 for the user's benefit (such as @samp{=}), and @var{value-flags} and
18266 @var{the-value} have the same meanings as in a
18267 @code{value-history-begin} annotation.
18269 @findex field-begin
18270 @findex field-name-end
18271 @findex field-value
18273 When printing a structure, @value{GDBN} annotates it as follows:
18276 ^Z^Zfield-begin @var{value-flags}
18279 @var{separator-string}
18286 where @var{field-name} is the name of the field, @var{separator-string}
18287 is text which separates the name from the value for the user's benefit
18288 (such as @samp{=}), and @var{value-flags} and @var{the-value} have the
18289 same meanings as in a @code{value-history-begin} annotation.
18291 When printing an array, @value{GDBN} annotates it as follows:
18294 ^Z^Zarray-section-begin @var{array-index} @var{value-flags}
18298 where @var{array-index} is the index of the first element being
18299 annotated and @var{value-flags} has the same meaning as in a
18300 @code{value-history-begin} annotation. This is followed by any number
18301 of elements, where is element can be either a single element:
18305 @samp{,} @var{whitespace} ; @r{omitted for the first element}
18310 or a repeated element
18313 @findex elt-rep-end
18315 @samp{,} @var{whitespace} ; @r{omitted for the first element}
18317 ^Z^Zelt-rep @var{number-of-repetitions}
18318 @var{repetition-string}
18322 In both cases, @var{the-value} is the output for the value of the
18323 element and @var{whitespace} can contain spaces, tabs, and newlines. In
18324 the repeated case, @var{number-of-repetitions} is the number of
18325 consecutive array elements which contain that value, and
18326 @var{repetition-string} is a string which is designed to convey to the
18327 user that repetition is being depicted.
18329 @findex array-section-end
18330 Once all the array elements have been output, the array annotation is
18334 ^Z^Zarray-section-end
18337 @node Frame Annotations
18340 @cindex annotations for frames
18341 Whenever @value{GDBN} prints a frame, it annotates it. For example, this applies
18342 to frames printed when @value{GDBN} stops, output from commands such as
18343 @code{backtrace} or @code{up}, etc.
18345 @findex frame-begin
18346 The frame annotation begins with
18349 ^Z^Zframe-begin @var{level} @var{address}
18354 where @var{level} is the number of the frame (0 is the innermost frame,
18355 and other frames have positive numbers), @var{address} is the address of
18356 the code executing in that frame, and @var{level-string} is a string
18357 designed to convey the level to the user. @var{address} is in the form
18358 @samp{0x} followed by one or more lowercase hex digits (note that this
18359 does not depend on the language). The frame ends with
18366 Between these annotations is the main body of the frame, which can
18371 @findex function-call
18374 @var{function-call-string}
18377 where @var{function-call-string} is text designed to convey to the user
18378 that this frame is associated with a function call made by @value{GDBN} to a
18379 function in the program being debugged.
18382 @findex signal-handler-caller
18384 ^Z^Zsignal-handler-caller
18385 @var{signal-handler-caller-string}
18388 where @var{signal-handler-caller-string} is text designed to convey to
18389 the user that this frame is associated with whatever mechanism is used
18390 by this operating system to call a signal handler (it is the frame which
18391 calls the signal handler, not the frame for the signal handler itself).
18396 @findex frame-address
18397 @findex frame-address-end
18398 This can optionally (depending on whether this is thought of as
18399 interesting information for the user to see) begin with
18404 ^Z^Zframe-address-end
18405 @var{separator-string}
18408 where @var{address} is the address executing in the frame (the same
18409 address as in the @code{frame-begin} annotation, but printed in a form
18410 which is intended for user consumption---in particular, the syntax varies
18411 depending on the language), and @var{separator-string} is a string
18412 intended to separate this address from what follows for the user's
18415 @findex frame-function-name
18420 ^Z^Zframe-function-name
18421 @var{function-name}
18426 where @var{function-name} is the name of the function executing in the
18427 frame, or @samp{??} if not known, and @var{arguments} are the arguments
18428 to the frame, with parentheses around them (each argument is annotated
18429 individually as well, @pxref{Value Annotations}).
18431 @findex frame-source-begin
18432 @findex frame-source-file
18433 @findex frame-source-file-end
18434 @findex frame-source-line
18435 @findex frame-source-end
18436 If source information is available, a reference to it is then printed:
18439 ^Z^Zframe-source-begin
18440 @var{source-intro-string}
18441 ^Z^Zframe-source-file
18443 ^Z^Zframe-source-file-end
18445 ^Z^Zframe-source-line
18447 ^Z^Zframe-source-end
18450 where @var{source-intro-string} separates for the user's benefit the
18451 reference from the text which precedes it, @var{filename} is the name of
18452 the source file, and @var{line-number} is the line number within that
18453 file (the first line is line 1).
18455 @findex frame-where
18456 If @value{GDBN} prints some information about where the frame is from (which
18457 library, which load segment, etc.; currently only done on the RS/6000),
18458 it is annotated with
18465 Then, if source is to actually be displayed for this frame (for example,
18466 this is not true for output from the @code{backtrace} command), then a
18467 @code{source} annotation (@pxref{Source Annotations}) is displayed. Unlike
18468 most annotations, this is output instead of the normal text which would be
18469 output, not in addition.
18475 @findex display-begin
18476 @findex display-number-end
18477 @findex display-format
18478 @findex display-expression
18479 @findex display-expression-end
18480 @findex display-value
18481 @findex display-end
18482 @cindex annotations for display
18483 When @value{GDBN} is told to display something using the @code{display} command,
18484 the results of the display are annotated:
18489 ^Z^Zdisplay-number-end
18490 @var{number-separator}
18493 ^Z^Zdisplay-expression
18495 ^Z^Zdisplay-expression-end
18496 @var{expression-separator}
18503 where @var{number} is the number of the display, @var{number-separator}
18504 is intended to separate the number from what follows for the user,
18505 @var{format} includes information such as the size, format, or other
18506 information about how the value is being displayed, @var{expression} is
18507 the expression being displayed, @var{expression-separator} is intended
18508 to separate the expression from the text that follows for the user,
18509 and @var{value} is the actual value being displayed.
18512 @section Annotation for @value{GDBN} Input
18514 @cindex annotations for prompts
18515 When @value{GDBN} prompts for input, it annotates this fact so it is possible
18516 to know when to send output, when the output from a given command is
18519 Different kinds of input each have a different @dfn{input type}. Each
18520 input type has three annotations: a @code{pre-} annotation, which
18521 denotes the beginning of any prompt which is being output, a plain
18522 annotation, which denotes the end of the prompt, and then a @code{post-}
18523 annotation which denotes the end of any echo which may (or may not) be
18524 associated with the input. For example, the @code{prompt} input type
18525 features the following annotations:
18533 The input types are
18538 @findex post-prompt
18540 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
18542 @findex pre-commands
18544 @findex post-commands
18546 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
18547 command. The annotations are repeated for each command which is input.
18549 @findex pre-overload-choice
18550 @findex overload-choice
18551 @findex post-overload-choice
18552 @item overload-choice
18553 When @value{GDBN} wants the user to select between various overloaded functions.
18559 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
18561 @findex pre-prompt-for-continue
18562 @findex prompt-for-continue
18563 @findex post-prompt-for-continue
18564 @item prompt-for-continue
18565 When @value{GDBN} is asking the user to press return to continue. Note: Don't
18566 expect this to work well; instead use @code{set height 0} to disable
18567 prompting. This is because the counting of lines is buggy in the
18568 presence of annotations.
18573 @cindex annotations for errors, warnings and interrupts
18580 This annotation occurs right before @value{GDBN} responds to an interrupt.
18587 This annotation occurs right before @value{GDBN} responds to an error.
18589 Quit and error annotations indicate that any annotations which @value{GDBN} was
18590 in the middle of may end abruptly. For example, if a
18591 @code{value-history-begin} annotation is followed by a @code{error}, one
18592 cannot expect to receive the matching @code{value-history-end}. One
18593 cannot expect not to receive it either, however; an error annotation
18594 does not necessarily mean that @value{GDBN} is immediately returning all the way
18597 @findex error-begin
18598 A quit or error annotation may be preceded by
18604 Any output between that and the quit or error annotation is the error
18607 Warning messages are not yet annotated.
18608 @c If we want to change that, need to fix warning(), type_error(),
18609 @c range_error(), and possibly other places.
18611 @node Breakpoint Info
18612 @section Information on Breakpoints
18614 @cindex annotations for breakpoints
18615 The output from the @code{info breakpoints} command is annotated as follows:
18617 @findex breakpoints-headers
18618 @findex breakpoints-table
18620 ^Z^Zbreakpoints-headers
18622 ^Z^Zbreakpoints-table
18626 where @var{header-entry} has the same syntax as an entry (see below) but
18627 instead of containing data, it contains strings which are intended to
18628 convey the meaning of each field to the user. This is followed by any
18629 number of entries. If a field does not apply for this entry, it is
18630 omitted. Fields may contain trailing whitespace. Each entry consists
18659 Note that @var{address} is intended for user consumption---the syntax
18660 varies depending on the language.
18662 The output ends with
18664 @findex breakpoints-table-end
18666 ^Z^Zbreakpoints-table-end
18670 @section Invalidation Notices
18672 @cindex annotations for invalidation messages
18673 The following annotations say that certain pieces of state may have
18677 @findex frames-invalid
18678 @item ^Z^Zframes-invalid
18680 The frames (for example, output from the @code{backtrace} command) may
18683 @findex breakpoints-invalid
18684 @item ^Z^Zbreakpoints-invalid
18686 The breakpoints may have changed. For example, the user just added or
18687 deleted a breakpoint.
18690 @node Annotations for Running
18691 @section Running the Program
18692 @cindex annotations for running programs
18696 When the program starts executing due to a @value{GDBN} command such as
18697 @code{step} or @code{continue},
18703 is output. When the program stops,
18709 is output. Before the @code{stopped} annotation, a variety of
18710 annotations describe how the program stopped.
18714 @item ^Z^Zexited @var{exit-status}
18715 The program exited, and @var{exit-status} is the exit status (zero for
18716 successful exit, otherwise nonzero).
18719 @findex signal-name
18720 @findex signal-name-end
18721 @findex signal-string
18722 @findex signal-string-end
18723 @item ^Z^Zsignalled
18724 The program exited with a signal. After the @code{^Z^Zsignalled}, the
18725 annotation continues:
18731 ^Z^Zsignal-name-end
18735 ^Z^Zsignal-string-end
18740 where @var{name} is the name of the signal, such as @code{SIGILL} or
18741 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
18742 as @code{Illegal Instruction} or @code{Segmentation fault}.
18743 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
18744 user's benefit and have no particular format.
18748 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
18749 just saying that the program received the signal, not that it was
18750 terminated with it.
18753 @item ^Z^Zbreakpoint @var{number}
18754 The program hit breakpoint number @var{number}.
18757 @item ^Z^Zwatchpoint @var{number}
18758 The program hit watchpoint number @var{number}.
18761 @node Source Annotations
18762 @section Displaying Source
18763 @cindex annotations for source display
18766 The following annotation is used instead of displaying source code:
18769 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
18772 where @var{filename} is an absolute file name indicating which source
18773 file, @var{line} is the line number within that file (where 1 is the
18774 first line in the file), @var{character} is the character position
18775 within the file (where 0 is the first character in the file) (for most
18776 debug formats this will necessarily point to the beginning of a line),
18777 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
18778 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
18779 @var{addr} is the address in the target program associated with the
18780 source which is being displayed. @var{addr} is in the form @samp{0x}
18781 followed by one or more lowercase hex digits (note that this does not
18782 depend on the language).
18785 @section Annotations We Might Want in the Future
18789 the target might have changed (registers, heap contents, or
18790 execution status). For performance, we might eventually want
18791 to hit `registers-invalid' and `all-registers-invalid' with
18794 - systematic annotation for set/show parameters (including
18795 invalidation notices).
18797 - similarly, `info' returns a list of candidates for invalidation
18802 @chapter Reporting Bugs in @value{GDBN}
18803 @cindex bugs in @value{GDBN}
18804 @cindex reporting bugs in @value{GDBN}
18806 Your bug reports play an essential role in making @value{GDBN} reliable.
18808 Reporting a bug may help you by bringing a solution to your problem, or it
18809 may not. But in any case the principal function of a bug report is to help
18810 the entire community by making the next version of @value{GDBN} work better. Bug
18811 reports are your contribution to the maintenance of @value{GDBN}.
18813 In order for a bug report to serve its purpose, you must include the
18814 information that enables us to fix the bug.
18817 * Bug Criteria:: Have you found a bug?
18818 * Bug Reporting:: How to report bugs
18822 @section Have you found a bug?
18823 @cindex bug criteria
18825 If you are not sure whether you have found a bug, here are some guidelines:
18828 @cindex fatal signal
18829 @cindex debugger crash
18830 @cindex crash of debugger
18832 If the debugger gets a fatal signal, for any input whatever, that is a
18833 @value{GDBN} bug. Reliable debuggers never crash.
18835 @cindex error on valid input
18837 If @value{GDBN} produces an error message for valid input, that is a
18838 bug. (Note that if you're cross debugging, the problem may also be
18839 somewhere in the connection to the target.)
18841 @cindex invalid input
18843 If @value{GDBN} does not produce an error message for invalid input,
18844 that is a bug. However, you should note that your idea of
18845 ``invalid input'' might be our idea of ``an extension'' or ``support
18846 for traditional practice''.
18849 If you are an experienced user of debugging tools, your suggestions
18850 for improvement of @value{GDBN} are welcome in any case.
18853 @node Bug Reporting
18854 @section How to report bugs
18855 @cindex bug reports
18856 @cindex @value{GDBN} bugs, reporting
18858 A number of companies and individuals offer support for @sc{gnu} products.
18859 If you obtained @value{GDBN} from a support organization, we recommend you
18860 contact that organization first.
18862 You can find contact information for many support companies and
18863 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
18865 @c should add a web page ref...
18867 In any event, we also recommend that you submit bug reports for
18868 @value{GDBN}. The prefered method is to submit them directly using
18869 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
18870 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
18873 @strong{Do not send bug reports to @samp{info-gdb}, or to
18874 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
18875 not want to receive bug reports. Those that do have arranged to receive
18878 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
18879 serves as a repeater. The mailing list and the newsgroup carry exactly
18880 the same messages. Often people think of posting bug reports to the
18881 newsgroup instead of mailing them. This appears to work, but it has one
18882 problem which can be crucial: a newsgroup posting often lacks a mail
18883 path back to the sender. Thus, if we need to ask for more information,
18884 we may be unable to reach you. For this reason, it is better to send
18885 bug reports to the mailing list.
18887 The fundamental principle of reporting bugs usefully is this:
18888 @strong{report all the facts}. If you are not sure whether to state a
18889 fact or leave it out, state it!
18891 Often people omit facts because they think they know what causes the
18892 problem and assume that some details do not matter. Thus, you might
18893 assume that the name of the variable you use in an example does not matter.
18894 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
18895 stray memory reference which happens to fetch from the location where that
18896 name is stored in memory; perhaps, if the name were different, the contents
18897 of that location would fool the debugger into doing the right thing despite
18898 the bug. Play it safe and give a specific, complete example. That is the
18899 easiest thing for you to do, and the most helpful.
18901 Keep in mind that the purpose of a bug report is to enable us to fix the
18902 bug. It may be that the bug has been reported previously, but neither
18903 you nor we can know that unless your bug report is complete and
18906 Sometimes people give a few sketchy facts and ask, ``Does this ring a
18907 bell?'' Those bug reports are useless, and we urge everyone to
18908 @emph{refuse to respond to them} except to chide the sender to report
18911 To enable us to fix the bug, you should include all these things:
18915 The version of @value{GDBN}. @value{GDBN} announces it if you start
18916 with no arguments; you can also print it at any time using @code{show
18919 Without this, we will not know whether there is any point in looking for
18920 the bug in the current version of @value{GDBN}.
18923 The type of machine you are using, and the operating system name and
18927 What compiler (and its version) was used to compile @value{GDBN}---e.g.
18928 ``@value{GCC}--2.8.1''.
18931 What compiler (and its version) was used to compile the program you are
18932 debugging---e.g. ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
18933 C Compiler''. For GCC, you can say @code{gcc --version} to get this
18934 information; for other compilers, see the documentation for those
18938 The command arguments you gave the compiler to compile your example and
18939 observe the bug. For example, did you use @samp{-O}? To guarantee
18940 you will not omit something important, list them all. A copy of the
18941 Makefile (or the output from make) is sufficient.
18943 If we were to try to guess the arguments, we would probably guess wrong
18944 and then we might not encounter the bug.
18947 A complete input script, and all necessary source files, that will
18951 A description of what behavior you observe that you believe is
18952 incorrect. For example, ``It gets a fatal signal.''
18954 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
18955 will certainly notice it. But if the bug is incorrect output, we might
18956 not notice unless it is glaringly wrong. You might as well not give us
18957 a chance to make a mistake.
18959 Even if the problem you experience is a fatal signal, you should still
18960 say so explicitly. Suppose something strange is going on, such as, your
18961 copy of @value{GDBN} is out of synch, or you have encountered a bug in
18962 the C library on your system. (This has happened!) Your copy might
18963 crash and ours would not. If you told us to expect a crash, then when
18964 ours fails to crash, we would know that the bug was not happening for
18965 us. If you had not told us to expect a crash, then we would not be able
18966 to draw any conclusion from our observations.
18969 If you wish to suggest changes to the @value{GDBN} source, send us context
18970 diffs. If you even discuss something in the @value{GDBN} source, refer to
18971 it by context, not by line number.
18973 The line numbers in our development sources will not match those in your
18974 sources. Your line numbers would convey no useful information to us.
18978 Here are some things that are not necessary:
18982 A description of the envelope of the bug.
18984 Often people who encounter a bug spend a lot of time investigating
18985 which changes to the input file will make the bug go away and which
18986 changes will not affect it.
18988 This is often time consuming and not very useful, because the way we
18989 will find the bug is by running a single example under the debugger
18990 with breakpoints, not by pure deduction from a series of examples.
18991 We recommend that you save your time for something else.
18993 Of course, if you can find a simpler example to report @emph{instead}
18994 of the original one, that is a convenience for us. Errors in the
18995 output will be easier to spot, running under the debugger will take
18996 less time, and so on.
18998 However, simplification is not vital; if you do not want to do this,
18999 report the bug anyway and send us the entire test case you used.
19002 A patch for the bug.
19004 A patch for the bug does help us if it is a good one. But do not omit
19005 the necessary information, such as the test case, on the assumption that
19006 a patch is all we need. We might see problems with your patch and decide
19007 to fix the problem another way, or we might not understand it at all.
19009 Sometimes with a program as complicated as @value{GDBN} it is very hard to
19010 construct an example that will make the program follow a certain path
19011 through the code. If you do not send us the example, we will not be able
19012 to construct one, so we will not be able to verify that the bug is fixed.
19014 And if we cannot understand what bug you are trying to fix, or why your
19015 patch should be an improvement, we will not install it. A test case will
19016 help us to understand.
19019 A guess about what the bug is or what it depends on.
19021 Such guesses are usually wrong. Even we cannot guess right about such
19022 things without first using the debugger to find the facts.
19025 @c The readline documentation is distributed with the readline code
19026 @c and consists of the two following files:
19028 @c inc-hist.texinfo
19029 @c Use -I with makeinfo to point to the appropriate directory,
19030 @c environment var TEXINPUTS with TeX.
19031 @include rluser.texinfo
19032 @include inc-hist.texinfo
19035 @node Formatting Documentation
19036 @appendix Formatting Documentation
19038 @cindex @value{GDBN} reference card
19039 @cindex reference card
19040 The @value{GDBN} 4 release includes an already-formatted reference card, ready
19041 for printing with PostScript or Ghostscript, in the @file{gdb}
19042 subdirectory of the main source directory@footnote{In
19043 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
19044 release.}. If you can use PostScript or Ghostscript with your printer,
19045 you can print the reference card immediately with @file{refcard.ps}.
19047 The release also includes the source for the reference card. You
19048 can format it, using @TeX{}, by typing:
19054 The @value{GDBN} reference card is designed to print in @dfn{landscape}
19055 mode on US ``letter'' size paper;
19056 that is, on a sheet 11 inches wide by 8.5 inches
19057 high. You will need to specify this form of printing as an option to
19058 your @sc{dvi} output program.
19060 @cindex documentation
19062 All the documentation for @value{GDBN} comes as part of the machine-readable
19063 distribution. The documentation is written in Texinfo format, which is
19064 a documentation system that uses a single source file to produce both
19065 on-line information and a printed manual. You can use one of the Info
19066 formatting commands to create the on-line version of the documentation
19067 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
19069 @value{GDBN} includes an already formatted copy of the on-line Info
19070 version of this manual in the @file{gdb} subdirectory. The main Info
19071 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
19072 subordinate files matching @samp{gdb.info*} in the same directory. If
19073 necessary, you can print out these files, or read them with any editor;
19074 but they are easier to read using the @code{info} subsystem in @sc{gnu}
19075 Emacs or the standalone @code{info} program, available as part of the
19076 @sc{gnu} Texinfo distribution.
19078 If you want to format these Info files yourself, you need one of the
19079 Info formatting programs, such as @code{texinfo-format-buffer} or
19082 If you have @code{makeinfo} installed, and are in the top level
19083 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
19084 version @value{GDBVN}), you can make the Info file by typing:
19091 If you want to typeset and print copies of this manual, you need @TeX{},
19092 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
19093 Texinfo definitions file.
19095 @TeX{} is a typesetting program; it does not print files directly, but
19096 produces output files called @sc{dvi} files. To print a typeset
19097 document, you need a program to print @sc{dvi} files. If your system
19098 has @TeX{} installed, chances are it has such a program. The precise
19099 command to use depends on your system; @kbd{lpr -d} is common; another
19100 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
19101 require a file name without any extension or a @samp{.dvi} extension.
19103 @TeX{} also requires a macro definitions file called
19104 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
19105 written in Texinfo format. On its own, @TeX{} cannot either read or
19106 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
19107 and is located in the @file{gdb-@var{version-number}/texinfo}
19110 If you have @TeX{} and a @sc{dvi} printer program installed, you can
19111 typeset and print this manual. First switch to the the @file{gdb}
19112 subdirectory of the main source directory (for example, to
19113 @file{gdb-@value{GDBVN}/gdb}) and type:
19119 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
19121 @node Installing GDB
19122 @appendix Installing @value{GDBN}
19123 @cindex configuring @value{GDBN}
19124 @cindex installation
19125 @cindex configuring @value{GDBN}, and source tree subdirectories
19127 @value{GDBN} comes with a @code{configure} script that automates the process
19128 of preparing @value{GDBN} for installation; you can then use @code{make} to
19129 build the @code{gdb} program.
19131 @c irrelevant in info file; it's as current as the code it lives with.
19132 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
19133 look at the @file{README} file in the sources; we may have improved the
19134 installation procedures since publishing this manual.}
19137 The @value{GDBN} distribution includes all the source code you need for
19138 @value{GDBN} in a single directory, whose name is usually composed by
19139 appending the version number to @samp{gdb}.
19141 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
19142 @file{gdb-@value{GDBVN}} directory. That directory contains:
19145 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
19146 script for configuring @value{GDBN} and all its supporting libraries
19148 @item gdb-@value{GDBVN}/gdb
19149 the source specific to @value{GDBN} itself
19151 @item gdb-@value{GDBVN}/bfd
19152 source for the Binary File Descriptor library
19154 @item gdb-@value{GDBVN}/include
19155 @sc{gnu} include files
19157 @item gdb-@value{GDBVN}/libiberty
19158 source for the @samp{-liberty} free software library
19160 @item gdb-@value{GDBVN}/opcodes
19161 source for the library of opcode tables and disassemblers
19163 @item gdb-@value{GDBVN}/readline
19164 source for the @sc{gnu} command-line interface
19166 @item gdb-@value{GDBVN}/glob
19167 source for the @sc{gnu} filename pattern-matching subroutine
19169 @item gdb-@value{GDBVN}/mmalloc
19170 source for the @sc{gnu} memory-mapped malloc package
19173 The simplest way to configure and build @value{GDBN} is to run @code{configure}
19174 from the @file{gdb-@var{version-number}} source directory, which in
19175 this example is the @file{gdb-@value{GDBVN}} directory.
19177 First switch to the @file{gdb-@var{version-number}} source directory
19178 if you are not already in it; then run @code{configure}. Pass the
19179 identifier for the platform on which @value{GDBN} will run as an
19185 cd gdb-@value{GDBVN}
19186 ./configure @var{host}
19191 where @var{host} is an identifier such as @samp{sun4} or
19192 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
19193 (You can often leave off @var{host}; @code{configure} tries to guess the
19194 correct value by examining your system.)
19196 Running @samp{configure @var{host}} and then running @code{make} builds the
19197 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
19198 libraries, then @code{gdb} itself. The configured source files, and the
19199 binaries, are left in the corresponding source directories.
19202 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
19203 system does not recognize this automatically when you run a different
19204 shell, you may need to run @code{sh} on it explicitly:
19207 sh configure @var{host}
19210 If you run @code{configure} from a directory that contains source
19211 directories for multiple libraries or programs, such as the
19212 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
19213 creates configuration files for every directory level underneath (unless
19214 you tell it not to, with the @samp{--norecursion} option).
19216 You should run the @code{configure} script from the top directory in the
19217 source tree, the @file{gdb-@var{version-number}} directory. If you run
19218 @code{configure} from one of the subdirectories, you will configure only
19219 that subdirectory. That is usually not what you want. In particular,
19220 if you run the first @code{configure} from the @file{gdb} subdirectory
19221 of the @file{gdb-@var{version-number}} directory, you will omit the
19222 configuration of @file{bfd}, @file{readline}, and other sibling
19223 directories of the @file{gdb} subdirectory. This leads to build errors
19224 about missing include files such as @file{bfd/bfd.h}.
19226 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
19227 However, you should make sure that the shell on your path (named by
19228 the @samp{SHELL} environment variable) is publicly readable. Remember
19229 that @value{GDBN} uses the shell to start your program---some systems refuse to
19230 let @value{GDBN} debug child processes whose programs are not readable.
19233 * Separate Objdir:: Compiling @value{GDBN} in another directory
19234 * Config Names:: Specifying names for hosts and targets
19235 * Configure Options:: Summary of options for configure
19238 @node Separate Objdir
19239 @section Compiling @value{GDBN} in another directory
19241 If you want to run @value{GDBN} versions for several host or target machines,
19242 you need a different @code{gdb} compiled for each combination of
19243 host and target. @code{configure} is designed to make this easy by
19244 allowing you to generate each configuration in a separate subdirectory,
19245 rather than in the source directory. If your @code{make} program
19246 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
19247 @code{make} in each of these directories builds the @code{gdb}
19248 program specified there.
19250 To build @code{gdb} in a separate directory, run @code{configure}
19251 with the @samp{--srcdir} option to specify where to find the source.
19252 (You also need to specify a path to find @code{configure}
19253 itself from your working directory. If the path to @code{configure}
19254 would be the same as the argument to @samp{--srcdir}, you can leave out
19255 the @samp{--srcdir} option; it is assumed.)
19257 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
19258 separate directory for a Sun 4 like this:
19262 cd gdb-@value{GDBVN}
19265 ../gdb-@value{GDBVN}/configure sun4
19270 When @code{configure} builds a configuration using a remote source
19271 directory, it creates a tree for the binaries with the same structure
19272 (and using the same names) as the tree under the source directory. In
19273 the example, you'd find the Sun 4 library @file{libiberty.a} in the
19274 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
19275 @file{gdb-sun4/gdb}.
19277 Make sure that your path to the @file{configure} script has just one
19278 instance of @file{gdb} in it. If your path to @file{configure} looks
19279 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
19280 one subdirectory of @value{GDBN}, not the whole package. This leads to
19281 build errors about missing include files such as @file{bfd/bfd.h}.
19283 One popular reason to build several @value{GDBN} configurations in separate
19284 directories is to configure @value{GDBN} for cross-compiling (where
19285 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
19286 programs that run on another machine---the @dfn{target}).
19287 You specify a cross-debugging target by
19288 giving the @samp{--target=@var{target}} option to @code{configure}.
19290 When you run @code{make} to build a program or library, you must run
19291 it in a configured directory---whatever directory you were in when you
19292 called @code{configure} (or one of its subdirectories).
19294 The @code{Makefile} that @code{configure} generates in each source
19295 directory also runs recursively. If you type @code{make} in a source
19296 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
19297 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
19298 will build all the required libraries, and then build GDB.
19300 When you have multiple hosts or targets configured in separate
19301 directories, you can run @code{make} on them in parallel (for example,
19302 if they are NFS-mounted on each of the hosts); they will not interfere
19306 @section Specifying names for hosts and targets
19308 The specifications used for hosts and targets in the @code{configure}
19309 script are based on a three-part naming scheme, but some short predefined
19310 aliases are also supported. The full naming scheme encodes three pieces
19311 of information in the following pattern:
19314 @var{architecture}-@var{vendor}-@var{os}
19317 For example, you can use the alias @code{sun4} as a @var{host} argument,
19318 or as the value for @var{target} in a @code{--target=@var{target}}
19319 option. The equivalent full name is @samp{sparc-sun-sunos4}.
19321 The @code{configure} script accompanying @value{GDBN} does not provide
19322 any query facility to list all supported host and target names or
19323 aliases. @code{configure} calls the Bourne shell script
19324 @code{config.sub} to map abbreviations to full names; you can read the
19325 script, if you wish, or you can use it to test your guesses on
19326 abbreviations---for example:
19329 % sh config.sub i386-linux
19331 % sh config.sub alpha-linux
19332 alpha-unknown-linux-gnu
19333 % sh config.sub hp9k700
19335 % sh config.sub sun4
19336 sparc-sun-sunos4.1.1
19337 % sh config.sub sun3
19338 m68k-sun-sunos4.1.1
19339 % sh config.sub i986v
19340 Invalid configuration `i986v': machine `i986v' not recognized
19344 @code{config.sub} is also distributed in the @value{GDBN} source
19345 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
19347 @node Configure Options
19348 @section @code{configure} options
19350 Here is a summary of the @code{configure} options and arguments that
19351 are most often useful for building @value{GDBN}. @code{configure} also has
19352 several other options not listed here. @inforef{What Configure
19353 Does,,configure.info}, for a full explanation of @code{configure}.
19356 configure @r{[}--help@r{]}
19357 @r{[}--prefix=@var{dir}@r{]}
19358 @r{[}--exec-prefix=@var{dir}@r{]}
19359 @r{[}--srcdir=@var{dirname}@r{]}
19360 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
19361 @r{[}--target=@var{target}@r{]}
19366 You may introduce options with a single @samp{-} rather than
19367 @samp{--} if you prefer; but you may abbreviate option names if you use
19372 Display a quick summary of how to invoke @code{configure}.
19374 @item --prefix=@var{dir}
19375 Configure the source to install programs and files under directory
19378 @item --exec-prefix=@var{dir}
19379 Configure the source to install programs under directory
19382 @c avoid splitting the warning from the explanation:
19384 @item --srcdir=@var{dirname}
19385 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
19386 @code{make} that implements the @code{VPATH} feature.}@*
19387 Use this option to make configurations in directories separate from the
19388 @value{GDBN} source directories. Among other things, you can use this to
19389 build (or maintain) several configurations simultaneously, in separate
19390 directories. @code{configure} writes configuration specific files in
19391 the current directory, but arranges for them to use the source in the
19392 directory @var{dirname}. @code{configure} creates directories under
19393 the working directory in parallel to the source directories below
19396 @item --norecursion
19397 Configure only the directory level where @code{configure} is executed; do not
19398 propagate configuration to subdirectories.
19400 @item --target=@var{target}
19401 Configure @value{GDBN} for cross-debugging programs running on the specified
19402 @var{target}. Without this option, @value{GDBN} is configured to debug
19403 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
19405 There is no convenient way to generate a list of all available targets.
19407 @item @var{host} @dots{}
19408 Configure @value{GDBN} to run on the specified @var{host}.
19410 There is no convenient way to generate a list of all available hosts.
19413 There are many other options available as well, but they are generally
19414 needed for special purposes only.
19416 @node Maintenance Commands
19417 @appendix Maintenance Commands
19418 @cindex maintenance commands
19419 @cindex internal commands
19421 In addition to commands intended for @value{GDBN} users, @value{GDBN}
19422 includes a number of commands intended for @value{GDBN} developers.
19423 These commands are provided here for reference.
19426 @kindex maint info breakpoints
19427 @item @anchor{maint info breakpoints}maint info breakpoints
19428 Using the same format as @samp{info breakpoints}, display both the
19429 breakpoints you've set explicitly, and those @value{GDBN} is using for
19430 internal purposes. Internal breakpoints are shown with negative
19431 breakpoint numbers. The type column identifies what kind of breakpoint
19436 Normal, explicitly set breakpoint.
19439 Normal, explicitly set watchpoint.
19442 Internal breakpoint, used to handle correctly stepping through
19443 @code{longjmp} calls.
19445 @item longjmp resume
19446 Internal breakpoint at the target of a @code{longjmp}.
19449 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
19452 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
19455 Shared library events.
19459 @kindex maint internal-error
19460 @kindex maint internal-warning
19461 @item maint internal-error
19462 @itemx maint internal-warning
19463 Cause @value{GDBN} to call the internal function @code{internal_error}
19464 or @code{internal_warning} and hence behave as though an internal error
19465 or internal warning has been detected. In addition to reporting the
19466 internal problem, these functions give the user the opportunity to
19467 either quit @value{GDBN} or create a core file of the current
19468 @value{GDBN} session.
19471 (gdb) @kbd{maint internal-error testing, 1, 2}
19472 @dots{}/maint.c:121: internal-error: testing, 1, 2
19473 A problem internal to GDB has been detected. Further
19474 debugging may prove unreliable.
19475 Quit this debugging session? (y or n) @kbd{n}
19476 Create a core file? (y or n) @kbd{n}
19480 Takes an optional parameter that is used as the text of the error or
19483 @kindex maint print dummy-frames
19484 @item maint print dummy-frames
19486 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
19491 (gdb) @kbd{print add(2,3)}
19492 Breakpoint 2, add (a=2, b=3) at @dots{}
19494 The program being debugged stopped while in a function called from GDB.
19496 (gdb) @kbd{maint print dummy-frames}
19497 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
19498 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
19499 call_lo=0x01014000 call_hi=0x01014001
19503 Takes an optional file parameter.
19505 @kindex maint print registers
19506 @kindex maint print raw-registers
19507 @kindex maint print cooked-registers
19508 @kindex maint print register-groups
19509 @item maint print registers
19510 @itemx maint print raw-registers
19511 @itemx maint print cooked-registers
19512 @itemx maint print register-groups
19513 Print @value{GDBN}'s internal register data structures.
19515 The command @code{maint print raw-registers} includes the contents of
19516 the raw register cache; the command @code{maint print cooked-registers}
19517 includes the (cooked) value of all registers; and the command
19518 @code{maint print register-groups} includes the groups that each
19519 register is a member of. @xref{Registers,, Registers, gdbint,
19520 @value{GDBN} Internals}.
19522 Takes an optional file parameter.
19524 @kindex maint print reggroups
19525 @item maint print reggroups
19526 Print @value{GDBN}'s internal register group data structures.
19528 Takes an optional file parameter.
19531 (gdb) @kbd{maint print reggroups}
19542 @kindex maint set profile
19543 @kindex maint show profile
19544 @cindex profiling GDB
19545 @item maint set profile
19546 @itemx maint show profile
19547 Control profiling of @value{GDBN}.
19549 Profiling will be disabled until you use the @samp{maint set profile}
19550 command to enable it. When you enable profiling, the system will begin
19551 collecting timing and execution count data; when you disable profiling or
19552 exit @value{GDBN}, the results will be written to a log file. Remember that
19553 if you use profiling, @value{GDBN} will overwrite the profiling log file
19554 (often called @file{gmon.out}). If you have a record of important profiling
19555 data in a @file{gmon.out} file, be sure to move it to a safe location.
19557 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
19558 compiled with the @samp{-pg} compiler option.
19563 @node Remote Protocol
19564 @appendix @value{GDBN} Remote Serial Protocol
19569 * Stop Reply Packets::
19570 * General Query Packets::
19571 * Register Packet Format::
19573 * File-I/O remote protocol extension::
19579 There may be occasions when you need to know something about the
19580 protocol---for example, if there is only one serial port to your target
19581 machine, you might want your program to do something special if it
19582 recognizes a packet meant for @value{GDBN}.
19584 In the examples below, @samp{->} and @samp{<-} are used to indicate
19585 transmitted and received data respectfully.
19587 @cindex protocol, @value{GDBN} remote serial
19588 @cindex serial protocol, @value{GDBN} remote
19589 @cindex remote serial protocol
19590 All @value{GDBN} commands and responses (other than acknowledgments) are
19591 sent as a @var{packet}. A @var{packet} is introduced with the character
19592 @samp{$}, the actual @var{packet-data}, and the terminating character
19593 @samp{#} followed by a two-digit @var{checksum}:
19596 @code{$}@var{packet-data}@code{#}@var{checksum}
19600 @cindex checksum, for @value{GDBN} remote
19602 The two-digit @var{checksum} is computed as the modulo 256 sum of all
19603 characters between the leading @samp{$} and the trailing @samp{#} (an
19604 eight bit unsigned checksum).
19606 Implementors should note that prior to @value{GDBN} 5.0 the protocol
19607 specification also included an optional two-digit @var{sequence-id}:
19610 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
19613 @cindex sequence-id, for @value{GDBN} remote
19615 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
19616 has never output @var{sequence-id}s. Stubs that handle packets added
19617 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
19619 @cindex acknowledgment, for @value{GDBN} remote
19620 When either the host or the target machine receives a packet, the first
19621 response expected is an acknowledgment: either @samp{+} (to indicate
19622 the package was received correctly) or @samp{-} (to request
19626 -> @code{$}@var{packet-data}@code{#}@var{checksum}
19631 The host (@value{GDBN}) sends @var{command}s, and the target (the
19632 debugging stub incorporated in your program) sends a @var{response}. In
19633 the case of step and continue @var{command}s, the response is only sent
19634 when the operation has completed (the target has again stopped).
19636 @var{packet-data} consists of a sequence of characters with the
19637 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
19640 Fields within the packet should be separated using @samp{,} @samp{;} or
19641 @cindex remote protocol, field separator
19642 @samp{:}. Except where otherwise noted all numbers are represented in
19643 @sc{hex} with leading zeros suppressed.
19645 Implementors should note that prior to @value{GDBN} 5.0, the character
19646 @samp{:} could not appear as the third character in a packet (as it
19647 would potentially conflict with the @var{sequence-id}).
19649 Response @var{data} can be run-length encoded to save space. A @samp{*}
19650 means that the next character is an @sc{ascii} encoding giving a repeat count
19651 which stands for that many repetitions of the character preceding the
19652 @samp{*}. The encoding is @code{n+29}, yielding a printable character
19653 where @code{n >=3} (which is where rle starts to win). The printable
19654 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
19655 value greater than 126 should not be used.
19657 Some remote systems have used a different run-length encoding mechanism
19658 loosely refered to as the cisco encoding. Following the @samp{*}
19659 character are two hex digits that indicate the size of the packet.
19666 means the same as "0000".
19668 The error response returned for some packets includes a two character
19669 error number. That number is not well defined.
19671 For any @var{command} not supported by the stub, an empty response
19672 (@samp{$#00}) should be returned. That way it is possible to extend the
19673 protocol. A newer @value{GDBN} can tell if a packet is supported based
19676 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
19677 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
19683 The following table provides a complete list of all currently defined
19684 @var{command}s and their corresponding response @var{data}.
19688 @item @code{!} --- extended mode
19689 @cindex @code{!} packet
19691 Enable extended mode. In extended mode, the remote server is made
19692 persistent. The @samp{R} packet is used to restart the program being
19698 The remote target both supports and has enabled extended mode.
19701 @item @code{?} --- last signal
19702 @cindex @code{?} packet
19704 Indicate the reason the target halted. The reply is the same as for
19708 @xref{Stop Reply Packets}, for the reply specifications.
19710 @item @code{a} --- reserved
19712 Reserved for future use.
19714 @item @code{A}@var{arglen}@code{,}@var{argnum}@code{,}@var{arg}@code{,@dots{}} --- set program arguments @strong{(reserved)}
19715 @cindex @code{A} packet
19717 Initialized @samp{argv[]} array passed into program. @var{arglen}
19718 specifies the number of bytes in the hex encoded byte stream @var{arg}.
19719 See @code{gdbserver} for more details.
19727 @item @code{b}@var{baud} --- set baud @strong{(deprecated)}
19728 @cindex @code{b} packet
19730 Change the serial line speed to @var{baud}.
19732 JTC: @emph{When does the transport layer state change? When it's
19733 received, or after the ACK is transmitted. In either case, there are
19734 problems if the command or the acknowledgment packet is dropped.}
19736 Stan: @emph{If people really wanted to add something like this, and get
19737 it working for the first time, they ought to modify ser-unix.c to send
19738 some kind of out-of-band message to a specially-setup stub and have the
19739 switch happen "in between" packets, so that from remote protocol's point
19740 of view, nothing actually happened.}
19742 @item @code{B}@var{addr},@var{mode} --- set breakpoint @strong{(deprecated)}
19743 @cindex @code{B} packet
19745 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
19746 breakpoint at @var{addr}.
19748 This packet has been replaced by the @samp{Z} and @samp{z} packets
19749 (@pxref{insert breakpoint or watchpoint packet}).
19751 @item @code{c}@var{addr} --- continue
19752 @cindex @code{c} packet
19754 @var{addr} is address to resume. If @var{addr} is omitted, resume at
19758 @xref{Stop Reply Packets}, for the reply specifications.
19760 @item @code{C}@var{sig}@code{;}@var{addr} --- continue with signal
19761 @cindex @code{C} packet
19763 Continue with signal @var{sig} (hex signal number). If
19764 @code{;}@var{addr} is omitted, resume at same address.
19767 @xref{Stop Reply Packets}, for the reply specifications.
19769 @item @code{d} --- toggle debug @strong{(deprecated)}
19770 @cindex @code{d} packet
19774 @item @code{D} --- detach
19775 @cindex @code{D} packet
19777 Detach @value{GDBN} from the remote system. Sent to the remote target
19778 before @value{GDBN} disconnects.
19782 @item @emph{no response}
19783 @value{GDBN} does not check for any response after sending this packet.
19786 @item @code{e} --- reserved
19788 Reserved for future use.
19790 @item @code{E} --- reserved
19792 Reserved for future use.
19794 @item @code{f} --- reserved
19796 Reserved for future use.
19798 @item @code{F}@var{RC}@code{,}@var{EE}@code{,}@var{CF}@code{;}@var{XX} --- Reply to target's F packet.
19799 @cindex @code{F} packet
19801 This packet is send by @value{GDBN} as reply to a @code{F} request packet
19802 sent by the target. This is part of the File-I/O protocol extension.
19803 @xref{File-I/O remote protocol extension}, for the specification.
19805 @item @code{g} --- read registers
19806 @anchor{read registers packet}
19807 @cindex @code{g} packet
19809 Read general registers.
19813 @item @var{XX@dots{}}
19814 Each byte of register data is described by two hex digits. The bytes
19815 with the register are transmitted in target byte order. The size of
19816 each register and their position within the @samp{g} @var{packet} are
19817 determined by the @value{GDBN} internal macros @var{REGISTER_RAW_SIZE}
19818 and @var{REGISTER_NAME} macros. The specification of several standard
19819 @code{g} packets is specified below.
19824 @item @code{G}@var{XX@dots{}} --- write regs
19825 @cindex @code{G} packet
19827 @xref{read registers packet}, for a description of the @var{XX@dots{}}
19838 @item @code{h} --- reserved
19840 Reserved for future use.
19842 @item @code{H}@var{c}@var{t@dots{}} --- set thread
19843 @cindex @code{H} packet
19845 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
19846 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
19847 should be @samp{c} for step and continue operations, @samp{g} for other
19848 operations. The thread designator @var{t@dots{}} may be -1, meaning all
19849 the threads, a thread number, or zero which means pick any thread.
19860 @c 'H': How restrictive (or permissive) is the thread model. If a
19861 @c thread is selected and stopped, are other threads allowed
19862 @c to continue to execute? As I mentioned above, I think the
19863 @c semantics of each command when a thread is selected must be
19864 @c described. For example:
19866 @c 'g': If the stub supports threads and a specific thread is
19867 @c selected, returns the register block from that thread;
19868 @c otherwise returns current registers.
19870 @c 'G' If the stub supports threads and a specific thread is
19871 @c selected, sets the registers of the register block of
19872 @c that thread; otherwise sets current registers.
19874 @item @code{i}@var{addr}@code{,}@var{nnn} --- cycle step @strong{(draft)}
19875 @anchor{cycle step packet}
19876 @cindex @code{i} packet
19878 Step the remote target by a single clock cycle. If @code{,}@var{nnn} is
19879 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
19880 step starting at that address.
19882 @item @code{I} --- signal then cycle step @strong{(reserved)}
19883 @cindex @code{I} packet
19885 @xref{step with signal packet}. @xref{cycle step packet}.
19887 @item @code{j} --- reserved
19889 Reserved for future use.
19891 @item @code{J} --- reserved
19893 Reserved for future use.
19895 @item @code{k} --- kill request
19896 @cindex @code{k} packet
19898 FIXME: @emph{There is no description of how to operate when a specific
19899 thread context has been selected (i.e.@: does 'k' kill only that
19902 @item @code{K} --- reserved
19904 Reserved for future use.
19906 @item @code{l} --- reserved
19908 Reserved for future use.
19910 @item @code{L} --- reserved
19912 Reserved for future use.
19914 @item @code{m}@var{addr}@code{,}@var{length} --- read memory
19915 @cindex @code{m} packet
19917 Read @var{length} bytes of memory starting at address @var{addr}.
19918 Neither @value{GDBN} nor the stub assume that sized memory transfers are
19919 assumed using word aligned accesses. FIXME: @emph{A word aligned memory
19920 transfer mechanism is needed.}
19924 @item @var{XX@dots{}}
19925 @var{XX@dots{}} is mem contents. Can be fewer bytes than requested if able
19926 to read only part of the data. Neither @value{GDBN} nor the stub assume
19927 that sized memory transfers are assumed using word aligned
19928 accesses. FIXME: @emph{A word aligned memory transfer mechanism is
19934 @item @code{M}@var{addr},@var{length}@code{:}@var{XX@dots{}} --- write mem
19935 @cindex @code{M} packet
19937 Write @var{length} bytes of memory starting at address @var{addr}.
19938 @var{XX@dots{}} is the data.
19945 for an error (this includes the case where only part of the data was
19949 @item @code{n} --- reserved
19951 Reserved for future use.
19953 @item @code{N} --- reserved
19955 Reserved for future use.
19957 @item @code{o} --- reserved
19959 Reserved for future use.
19961 @item @code{O} --- reserved
19963 Reserved for future use.
19965 @item @code{p}@var{n@dots{}} --- read reg @strong{(reserved)}
19966 @cindex @code{p} packet
19968 @xref{write register packet}.
19972 @item @var{r@dots{}.}
19973 The hex encoded value of the register in target byte order.
19976 @item @code{P}@var{n@dots{}}@code{=}@var{r@dots{}} --- write register
19977 @anchor{write register packet}
19978 @cindex @code{P} packet
19980 Write register @var{n@dots{}} with value @var{r@dots{}}, which contains two hex
19981 digits for each byte in the register (target byte order).
19991 @item @code{q}@var{query} --- general query
19992 @anchor{general query packet}
19993 @cindex @code{q} packet
19995 Request info about @var{query}. In general @value{GDBN} queries have a
19996 leading upper case letter. Custom vendor queries should use a company
19997 prefix (in lower case) ex: @samp{qfsf.var}. @var{query} may optionally
19998 be followed by a @samp{,} or @samp{;} separated list. Stubs must ensure
19999 that they match the full @var{query} name.
20003 @item @var{XX@dots{}}
20004 Hex encoded data from query. The reply can not be empty.
20008 Indicating an unrecognized @var{query}.
20011 @item @code{Q}@var{var}@code{=}@var{val} --- general set
20012 @cindex @code{Q} packet
20014 Set value of @var{var} to @var{val}.
20016 @xref{general query packet}, for a discussion of naming conventions.
20018 @item @code{r} --- reset @strong{(deprecated)}
20019 @cindex @code{r} packet
20021 Reset the entire system.
20023 @item @code{R}@var{XX} --- remote restart
20024 @cindex @code{R} packet
20026 Restart the program being debugged. @var{XX}, while needed, is ignored.
20027 This packet is only available in extended mode.
20031 @item @emph{no reply}
20032 The @samp{R} packet has no reply.
20035 @item @code{s}@var{addr} --- step
20036 @cindex @code{s} packet
20038 @var{addr} is address to resume. If @var{addr} is omitted, resume at
20042 @xref{Stop Reply Packets}, for the reply specifications.
20044 @item @code{S}@var{sig}@code{;}@var{addr} --- step with signal
20045 @anchor{step with signal packet}
20046 @cindex @code{S} packet
20048 Like @samp{C} but step not continue.
20051 @xref{Stop Reply Packets}, for the reply specifications.
20053 @item @code{t}@var{addr}@code{:}@var{PP}@code{,}@var{MM} --- search
20054 @cindex @code{t} packet
20056 Search backwards starting at address @var{addr} for a match with pattern
20057 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
20058 @var{addr} must be at least 3 digits.
20060 @item @code{T}@var{XX} --- thread alive
20061 @cindex @code{T} packet
20063 Find out if the thread XX is alive.
20068 thread is still alive
20073 @item @code{u} --- reserved
20075 Reserved for future use.
20077 @item @code{U} --- reserved
20079 Reserved for future use.
20081 @item @code{v} --- reserved
20083 Reserved for future use.
20085 @item @code{V} --- reserved
20087 Reserved for future use.
20089 @item @code{w} --- reserved
20091 Reserved for future use.
20093 @item @code{W} --- reserved
20095 Reserved for future use.
20097 @item @code{x} --- reserved
20099 Reserved for future use.
20101 @item @code{X}@var{addr}@code{,}@var{length}@var{:}@var{XX@dots{}} --- write mem (binary)
20102 @cindex @code{X} packet
20104 @var{addr} is address, @var{length} is number of bytes, @var{XX@dots{}}
20105 is binary data. The characters @code{$}, @code{#}, and @code{0x7d} are
20106 escaped using @code{0x7d}.
20116 @item @code{y} --- reserved
20118 Reserved for future use.
20120 @item @code{Y} reserved
20122 Reserved for future use.
20124 @item @code{z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- remove breakpoint or watchpoint @strong{(draft)}
20125 @itemx @code{Z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- insert breakpoint or watchpoint @strong{(draft)}
20126 @anchor{insert breakpoint or watchpoint packet}
20127 @cindex @code{z} packet
20128 @cindex @code{Z} packets
20130 Insert (@code{Z}) or remove (@code{z}) a @var{type} breakpoint or
20131 watchpoint starting at address @var{address} and covering the next
20132 @var{length} bytes.
20134 Each breakpoint and watchpoint packet @var{type} is documented
20137 @emph{Implementation notes: A remote target shall return an empty string
20138 for an unrecognized breakpoint or watchpoint packet @var{type}. A
20139 remote target shall support either both or neither of a given
20140 @code{Z}@var{type}@dots{} and @code{z}@var{type}@dots{} packet pair. To
20141 avoid potential problems with duplicate packets, the operations should
20142 be implemented in an idempotent way.}
20144 @item @code{z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- remove memory breakpoint @strong{(draft)}
20145 @item @code{Z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- insert memory breakpoint @strong{(draft)}
20146 @cindex @code{z0} packet
20147 @cindex @code{Z0} packet
20149 Insert (@code{Z0}) or remove (@code{z0}) a memory breakpoint at address
20150 @code{addr} of size @code{length}.
20152 A memory breakpoint is implemented by replacing the instruction at
20153 @var{addr} with a software breakpoint or trap instruction. The
20154 @code{length} is used by targets that indicates the size of the
20155 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
20156 @sc{mips} can insert either a 2 or 4 byte breakpoint).
20158 @emph{Implementation note: It is possible for a target to copy or move
20159 code that contains memory breakpoints (e.g., when implementing
20160 overlays). The behavior of this packet, in the presence of such a
20161 target, is not defined.}
20173 @item @code{z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- remove hardware breakpoint @strong{(draft)}
20174 @item @code{Z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- insert hardware breakpoint @strong{(draft)}
20175 @cindex @code{z1} packet
20176 @cindex @code{Z1} packet
20178 Insert (@code{Z1}) or remove (@code{z1}) a hardware breakpoint at
20179 address @code{addr} of size @code{length}.
20181 A hardware breakpoint is implemented using a mechanism that is not
20182 dependant on being able to modify the target's memory.
20184 @emph{Implementation note: A hardware breakpoint is not affected by code
20197 @item @code{z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- remove write watchpoint @strong{(draft)}
20198 @item @code{Z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- insert write watchpoint @strong{(draft)}
20199 @cindex @code{z2} packet
20200 @cindex @code{Z2} packet
20202 Insert (@code{Z2}) or remove (@code{z2}) a write watchpoint.
20214 @item @code{z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- remove read watchpoint @strong{(draft)}
20215 @item @code{Z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- insert read watchpoint @strong{(draft)}
20216 @cindex @code{z3} packet
20217 @cindex @code{Z3} packet
20219 Insert (@code{Z3}) or remove (@code{z3}) a read watchpoint.
20231 @item @code{z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- remove access watchpoint @strong{(draft)}
20232 @item @code{Z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- insert access watchpoint @strong{(draft)}
20233 @cindex @code{z4} packet
20234 @cindex @code{Z4} packet
20236 Insert (@code{Z4}) or remove (@code{z4}) an access watchpoint.
20250 @node Stop Reply Packets
20251 @section Stop Reply Packets
20252 @cindex stop reply packets
20254 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
20255 receive any of the below as a reply. In the case of the @samp{C},
20256 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
20257 when the target halts. In the below the exact meaning of @samp{signal
20258 number} is poorly defined. In general one of the UNIX signal numbering
20259 conventions is used.
20264 @var{AA} is the signal number
20266 @item @code{T}@var{AA}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}
20267 @cindex @code{T} packet reply
20269 @var{AA} = two hex digit signal number; @var{n...} = register number
20270 (hex), @var{r...} = target byte ordered register contents, size defined
20271 by @code{REGISTER_RAW_SIZE}; @var{n...} = @samp{thread}, @var{r...} =
20272 thread process ID, this is a hex integer; @var{n...} = (@samp{watch} |
20273 @samp{rwatch} | @samp{awatch}, @var{r...} = data address, this is a hex
20274 integer; @var{n...} = other string not starting with valid hex digit.
20275 @value{GDBN} should ignore this @var{n...}, @var{r...} pair and go on
20276 to the next. This way we can extend the protocol.
20280 The process exited, and @var{AA} is the exit status. This is only
20281 applicable to certain targets.
20285 The process terminated with signal @var{AA}.
20287 @item N@var{AA};@var{t@dots{}};@var{d@dots{}};@var{b@dots{}} @strong{(obsolete)}
20289 @var{AA} = signal number; @var{t@dots{}} = address of symbol
20290 @code{_start}; @var{d@dots{}} = base of data section; @var{b@dots{}} =
20291 base of bss section. @emph{Note: only used by Cisco Systems targets.
20292 The difference between this reply and the @samp{qOffsets} query is that
20293 the @samp{N} packet may arrive spontaneously whereas the @samp{qOffsets}
20294 is a query initiated by the host debugger.}
20296 @item O@var{XX@dots{}}
20298 @var{XX@dots{}} is hex encoding of @sc{ascii} data. This can happen at
20299 any time while the program is running and the debugger should continue
20300 to wait for @samp{W}, @samp{T}, etc.
20302 @item F@var{call-id}@code{,}@var{parameter@dots{}}
20304 @var{call-id} is the identifier which says which host system call should
20305 be called. This is just the name of the function. Translation into the
20306 correct system call is only applicable as it's defined in @value{GDBN}.
20307 @xref{File-I/O remote protocol extension}, for a list of implemented
20310 @var{parameter@dots{}} is a list of parameters as defined for this very
20313 The target replies with this packet when it expects @value{GDBN} to call
20314 a host system call on behalf of the target. @value{GDBN} replies with
20315 an appropriate @code{F} packet and keeps up waiting for the next reply
20316 packet from the target. The latest @samp{C}, @samp{c}, @samp{S} or
20317 @samp{s} action is expected to be continued.
20318 @xref{File-I/O remote protocol extension}, for more details.
20322 @node General Query Packets
20323 @section General Query Packets
20325 The following set and query packets have already been defined.
20329 @item @code{q}@code{C} --- current thread
20331 Return the current thread id.
20335 @item @code{QC}@var{pid}
20336 Where @var{pid} is a HEX encoded 16 bit process id.
20338 Any other reply implies the old pid.
20341 @item @code{q}@code{fThreadInfo} -- all thread ids
20343 @code{q}@code{sThreadInfo}
20345 Obtain a list of active thread ids from the target (OS). Since there
20346 may be too many active threads to fit into one reply packet, this query
20347 works iteratively: it may require more than one query/reply sequence to
20348 obtain the entire list of threads. The first query of the sequence will
20349 be the @code{qf}@code{ThreadInfo} query; subsequent queries in the
20350 sequence will be the @code{qs}@code{ThreadInfo} query.
20352 NOTE: replaces the @code{qL} query (see below).
20356 @item @code{m}@var{id}
20358 @item @code{m}@var{id},@var{id}@dots{}
20359 a comma-separated list of thread ids
20361 (lower case 'el') denotes end of list.
20364 In response to each query, the target will reply with a list of one or
20365 more thread ids, in big-endian hex, separated by commas. @value{GDBN}
20366 will respond to each reply with a request for more thread ids (using the
20367 @code{qs} form of the query), until the target responds with @code{l}
20368 (lower-case el, for @code{'last'}).
20370 @item @code{q}@code{ThreadExtraInfo}@code{,}@var{id} --- extra thread info
20372 Where @var{id} is a thread-id in big-endian hex. Obtain a printable
20373 string description of a thread's attributes from the target OS. This
20374 string may contain anything that the target OS thinks is interesting for
20375 @value{GDBN} to tell the user about the thread. The string is displayed
20376 in @value{GDBN}'s @samp{info threads} display. Some examples of
20377 possible thread extra info strings are ``Runnable'', or ``Blocked on
20382 @item @var{XX@dots{}}
20383 Where @var{XX@dots{}} is a hex encoding of @sc{ascii} data, comprising
20384 the printable string containing the extra information about the thread's
20388 @item @code{q}@code{L}@var{startflag}@var{threadcount}@var{nextthread} --- query @var{LIST} or @var{threadLIST} @strong{(deprecated)}
20390 Obtain thread information from RTOS. Where: @var{startflag} (one hex
20391 digit) is one to indicate the first query and zero to indicate a
20392 subsequent query; @var{threadcount} (two hex digits) is the maximum
20393 number of threads the response packet can contain; and @var{nextthread}
20394 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
20395 returned in the response as @var{argthread}.
20397 NOTE: this query is replaced by the @code{q}@code{fThreadInfo} query
20402 @item @code{q}@code{M}@var{count}@var{done}@var{argthread}@var{thread@dots{}}
20403 Where: @var{count} (two hex digits) is the number of threads being
20404 returned; @var{done} (one hex digit) is zero to indicate more threads
20405 and one indicates no further threads; @var{argthreadid} (eight hex
20406 digits) is @var{nextthread} from the request packet; @var{thread@dots{}}
20407 is a sequence of thread IDs from the target. @var{threadid} (eight hex
20408 digits). See @code{remote.c:parse_threadlist_response()}.
20411 @item @code{q}@code{CRC:}@var{addr}@code{,}@var{length} --- compute CRC of memory block
20415 @item @code{E}@var{NN}
20416 An error (such as memory fault)
20417 @item @code{C}@var{CRC32}
20418 A 32 bit cyclic redundancy check of the specified memory region.
20421 @item @code{q}@code{Offsets} --- query sect offs
20423 Get section offsets that the target used when re-locating the downloaded
20424 image. @emph{Note: while a @code{Bss} offset is included in the
20425 response, @value{GDBN} ignores this and instead applies the @code{Data}
20426 offset to the @code{Bss} section.}
20430 @item @code{Text=}@var{xxx}@code{;Data=}@var{yyy}@code{;Bss=}@var{zzz}
20433 @item @code{q}@code{P}@var{mode}@var{threadid} --- thread info request
20435 Returns information on @var{threadid}. Where: @var{mode} is a hex
20436 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
20443 See @code{remote.c:remote_unpack_thread_info_response()}.
20445 @item @code{q}@code{Rcmd,}@var{command} --- remote command
20447 @var{command} (hex encoded) is passed to the local interpreter for
20448 execution. Invalid commands should be reported using the output string.
20449 Before the final result packet, the target may also respond with a
20450 number of intermediate @code{O}@var{output} console output packets.
20451 @emph{Implementors should note that providing access to a stubs's
20452 interpreter may have security implications}.
20457 A command response with no output.
20459 A command response with the hex encoded output string @var{OUTPUT}.
20460 @item @code{E}@var{NN}
20461 Indicate a badly formed request.
20463 When @samp{q}@samp{Rcmd} is not recognized.
20466 @item @code{qSymbol::} --- symbol lookup
20468 Notify the target that @value{GDBN} is prepared to serve symbol lookup
20469 requests. Accept requests from the target for the values of symbols.
20474 The target does not need to look up any (more) symbols.
20475 @item @code{qSymbol:}@var{sym_name}
20476 The target requests the value of symbol @var{sym_name} (hex encoded).
20477 @value{GDBN} may provide the value by using the
20478 @code{qSymbol:}@var{sym_value}:@var{sym_name} message, described below.
20481 @item @code{qSymbol:}@var{sym_value}:@var{sym_name} --- symbol value
20483 Set the value of @var{sym_name} to @var{sym_value}.
20485 @var{sym_name} (hex encoded) is the name of a symbol whose value the
20486 target has previously requested.
20488 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
20489 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
20495 The target does not need to look up any (more) symbols.
20496 @item @code{qSymbol:}@var{sym_name}
20497 The target requests the value of a new symbol @var{sym_name} (hex
20498 encoded). @value{GDBN} will continue to supply the values of symbols
20499 (if available), until the target ceases to request them.
20504 @node Register Packet Format
20505 @section Register Packet Format
20507 The following @samp{g}/@samp{G} packets have previously been defined.
20508 In the below, some thirty-two bit registers are transferred as
20509 sixty-four bits. Those registers should be zero/sign extended (which?)
20510 to fill the space allocated. Register bytes are transfered in target
20511 byte order. The two nibbles within a register byte are transfered
20512 most-significant - least-significant.
20518 All registers are transfered as thirty-two bit quantities in the order:
20519 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
20520 registers; fsr; fir; fp.
20524 All registers are transfered as sixty-four bit quantities (including
20525 thirty-two bit registers such as @code{sr}). The ordering is the same
20533 Example sequence of a target being re-started. Notice how the restart
20534 does not get any direct output:
20539 @emph{target restarts}
20542 <- @code{T001:1234123412341234}
20546 Example sequence of a target being stepped by a single instruction:
20549 -> @code{G1445@dots{}}
20554 <- @code{T001:1234123412341234}
20558 <- @code{1455@dots{}}
20562 @node File-I/O remote protocol extension
20563 @section File-I/O remote protocol extension
20564 @cindex File-I/O remote protocol extension
20567 * File-I/O Overview::
20568 * Protocol basics::
20569 * The `F' request packet::
20570 * The `F' reply packet::
20571 * Memory transfer::
20572 * The Ctrl-C message::
20574 * The isatty call::
20575 * The system call::
20576 * List of supported calls::
20577 * Protocol specific representation of datatypes::
20579 * File-I/O Examples::
20582 @node File-I/O Overview
20583 @subsection File-I/O Overview
20584 @cindex file-i/o overview
20586 The File I/O remote protocol extension (short: File-I/O) allows the
20587 target to use the hosts file system and console I/O when calling various
20588 system calls. System calls on the target system are translated into a
20589 remote protocol packet to the host system which then performs the needed
20590 actions and returns with an adequate response packet to the target system.
20591 This simulates file system operations even on targets that lack file systems.
20593 The protocol is defined host- and target-system independent. It uses
20594 it's own independent representation of datatypes and values. Both,
20595 @value{GDBN} and the target's @value{GDBN} stub are responsible for
20596 translating the system dependent values into the unified protocol values
20597 when data is transmitted.
20599 The communication is synchronous. A system call is possible only
20600 when GDB is waiting for the @samp{C}, @samp{c}, @samp{S} or @samp{s}
20601 packets. While @value{GDBN} handles the request for a system call,
20602 the target is stopped to allow deterministic access to the target's
20603 memory. Therefore File-I/O is not interuptible by target signals. It
20604 is possible to interrupt File-I/O by a user interrupt (Ctrl-C), though.
20606 The target's request to perform a host system call does not finish
20607 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
20608 after finishing the system call, the target returns to continuing the
20609 previous activity (continue, step). No additional continue or step
20610 request from @value{GDBN} is required.
20614 <- target requests 'system call X'
20615 target is stopped, @value{GDBN} executes system call
20616 -> GDB returns result
20617 ... target continues, GDB returns to wait for the target
20618 <- target hits breakpoint and sends a Txx packet
20621 The protocol is only used for files on the host file system and
20622 for I/O on the console. Character or block special devices, pipes,
20623 named pipes or sockets or any other communication method on the host
20624 system are not supported by this protocol.
20626 @node Protocol basics
20627 @subsection Protocol basics
20628 @cindex protocol basics, file-i/o
20630 The File-I/O protocol uses the @code{F} packet, as request as well
20631 as as reply packet. Since a File-I/O system call can only occur when
20632 @value{GDBN} is waiting for the continuing or stepping target, the
20633 File-I/O request is a reply that @value{GDBN} has to expect as a result
20634 of a former @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
20635 This @code{F} packet contains all information needed to allow @value{GDBN}
20636 to call the appropriate host system call:
20640 A unique identifier for the requested system call.
20643 All parameters to the system call. Pointers are given as addresses
20644 in the target memory address space. Pointers to strings are given as
20645 pointer/length pair. Numerical values are given as they are.
20646 Numerical control values are given in a protocol specific representation.
20650 At that point @value{GDBN} has to perform the following actions.
20654 If parameter pointer values are given, which point to data needed as input
20655 to a system call, @value{GDBN} requests this data from the target with a
20656 standard @code{m} packet request. This additional communication has to be
20657 expected by the target implementation and is handled as any other @code{m}
20661 @value{GDBN} translates all value from protocol representation to host
20662 representation as needed. Datatypes are coerced into the host types.
20665 @value{GDBN} calls the system call
20668 It then coerces datatypes back to protocol representation.
20671 If pointer parameters in the request packet point to buffer space in which
20672 a system call is expected to copy data to, the data is transmitted to the
20673 target using a @code{M} or @code{X} packet. This packet has to be expected
20674 by the target implementation and is handled as any other @code{M} or @code{X}
20679 Eventually @value{GDBN} replies with another @code{F} packet which contains all
20680 necessary information for the target to continue. This at least contains
20687 @code{errno}, if has been changed by the system call.
20694 After having done the needed type and value coercion, the target continues
20695 the latest continue or step action.
20697 @node The `F' request packet
20698 @subsection The @code{F} request packet
20699 @cindex file-i/o request packet
20700 @cindex @code{F} request packet
20702 The @code{F} request packet has the following format:
20707 @code{F}@var{call-id}@code{,}@var{parameter@dots{}}
20710 @var{call-id} is the identifier to indicate the host system call to be called.
20711 This is just the name of the function.
20713 @var{parameter@dots{}} are the parameters to the system call.
20717 Parameters are hexadecimal integer values, either the real values in case
20718 of scalar datatypes, as pointers to target buffer space in case of compound
20719 datatypes and unspecified memory areas or as pointer/length pairs in case
20720 of string parameters. These are appended to the call-id, each separated
20721 from its predecessor by a comma. All values are transmitted in ASCII
20722 string representation, pointer/length pairs separated by a slash.
20724 @node The `F' reply packet
20725 @subsection The @code{F} reply packet
20726 @cindex file-i/o reply packet
20727 @cindex @code{F} reply packet
20729 The @code{F} reply packet has the following format:
20734 @code{F}@var{retcode}@code{,}@var{errno}@code{,}@var{Ctrl-C flag}@code{;}@var{call specific attachment}
20737 @var{retcode} is the return code of the system call as hexadecimal value.
20739 @var{errno} is the errno set by the call, in protocol specific representation.
20740 This parameter can be omitted if the call was successful.
20742 @var{Ctrl-C flag} is only send if the user requested a break. In this
20743 case, @var{errno} must be send as well, even if the call was successful.
20744 The @var{Ctrl-C flag} itself consists of the character 'C':
20751 or, if the call was interupted before the host call has been performed:
20758 assuming 4 is the protocol specific representation of @code{EINTR}.
20762 @node Memory transfer
20763 @subsection Memory transfer
20764 @cindex memory transfer, in file-i/o protocol
20766 Structured data which is transferred using a memory read or write as e.g.@:
20767 a @code{struct stat} is expected to be in a protocol specific format with
20768 all scalar multibyte datatypes being big endian. This should be done by
20769 the target before the @code{F} packet is sent resp.@: by @value{GDBN} before
20770 it transfers memory to the target. Transferred pointers to structured
20771 data should point to the already coerced data at any time.
20773 @node The Ctrl-C message
20774 @subsection The Ctrl-C message
20775 @cindex ctrl-c message, in file-i/o protocol
20777 A special case is, if the @var{Ctrl-C flag} is set in the @value{GDBN}
20778 reply packet. In this case the target should behave, as if it had
20779 gotten a break message. The meaning for the target is ``system call
20780 interupted by @code{SIGINT}''. Consequentially, the target should actually stop
20781 (as with a break message) and return to @value{GDBN} with a @code{T02}
20782 packet. In this case, it's important for the target to know, in which
20783 state the system call was interrupted. Since this action is by design
20784 not an atomic operation, we have to differ between two cases:
20788 The system call hasn't been performed on the host yet.
20791 The system call on the host has been finished.
20795 These two states can be distinguished by the target by the value of the
20796 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
20797 call hasn't been performed. This is equivalent to the @code{EINTR} handling
20798 on POSIX systems. In any other case, the target may presume that the
20799 system call has been finished --- successful or not --- and should behave
20800 as if the break message arrived right after the system call.
20802 @value{GDBN} must behave reliable. If the system call has not been called
20803 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
20804 @code{errno} in the packet. If the system call on the host has been finished
20805 before the user requests a break, the full action must be finshed by
20806 @value{GDBN}. This requires sending @code{M} or @code{X} packets as they fit.
20807 The @code{F} packet may only be send when either nothing has happened
20808 or the full action has been completed.
20811 @subsection Console I/O
20812 @cindex console i/o as part of file-i/o
20814 By default and if not explicitely closed by the target system, the file
20815 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
20816 on the @value{GDBN} console is handled as any other file output operation
20817 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
20818 by @value{GDBN} so that after the target read request from file descriptor
20819 0 all following typing is buffered until either one of the following
20824 The user presses @kbd{Ctrl-C}. The behaviour is as explained above, the
20826 system call is treated as finished.
20829 The user presses @kbd{Enter}. This is treated as end of input with a trailing
20833 The user presses @kbd{Ctrl-D}. This is treated as end of input. No trailing
20834 character, especially no Ctrl-D is appended to the input.
20838 If the user has typed more characters as fit in the buffer given to
20839 the read call, the trailing characters are buffered in @value{GDBN} until
20840 either another @code{read(0, @dots{})} is requested by the target or debugging
20841 is stopped on users request.
20843 @node The isatty call
20844 @subsection The isatty(3) call
20845 @cindex isatty call, file-i/o protocol
20847 A special case in this protocol is the library call @code{isatty} which
20848 is implemented as it's own call inside of this protocol. It returns
20849 1 to the target if the file descriptor given as parameter is attached
20850 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
20851 would require implementing @code{ioctl} and would be more complex than
20854 @node The system call
20855 @subsection The system(3) call
20856 @cindex system call, file-i/o protocol
20858 The other special case in this protocol is the @code{system} call which
20859 is implemented as it's own call, too. @value{GDBN} is taking over the full
20860 task of calling the necessary host calls to perform the @code{system}
20861 call. The return value of @code{system} is simplified before it's returned
20862 to the target. Basically, the only signal transmitted back is @code{EINTR}
20863 in case the user pressed @kbd{Ctrl-C}. Otherwise the return value consists
20864 entirely of the exit status of the called command.
20866 Due to security concerns, the @code{system} call is refused to be called
20867 by @value{GDBN} by default. The user has to allow this call explicitly by
20871 @kindex set remote system-call-allowed 1
20872 @item @code{set remote system-call-allowed 1}
20875 Disabling the @code{system} call is done by
20878 @kindex set remote system-call-allowed 0
20879 @item @code{set remote system-call-allowed 0}
20882 The current setting is shown by typing
20885 @kindex show remote system-call-allowed
20886 @item @code{show remote system-call-allowed}
20889 @node List of supported calls
20890 @subsection List of supported calls
20891 @cindex list of supported file-i/o calls
20908 @unnumberedsubsubsec open
20909 @cindex open, file-i/o system call
20913 int open(const char *pathname, int flags);
20914 int open(const char *pathname, int flags, mode_t mode);
20917 Fopen,pathptr/len,flags,mode
20921 @code{flags} is the bitwise or of the following values:
20925 If the file does not exist it will be created. The host
20926 rules apply as far as file ownership and time stamps
20930 When used with O_CREAT, if the file already exists it is
20931 an error and open() fails.
20934 If the file already exists and the open mode allows
20935 writing (O_RDWR or O_WRONLY is given) it will be
20936 truncated to length 0.
20939 The file is opened in append mode.
20942 The file is opened for reading only.
20945 The file is opened for writing only.
20948 The file is opened for reading and writing.
20951 Each other bit is silently ignored.
20956 @code{mode} is the bitwise or of the following values:
20960 User has read permission.
20963 User has write permission.
20966 Group has read permission.
20969 Group has write permission.
20972 Others have read permission.
20975 Others have write permission.
20978 Each other bit is silently ignored.
20983 @exdent Return value:
20984 open returns the new file descriptor or -1 if an error
20992 pathname already exists and O_CREAT and O_EXCL were used.
20995 pathname refers to a directory.
20998 The requested access is not allowed.
21001 pathname was too long.
21004 A directory component in pathname does not exist.
21007 pathname refers to a device, pipe, named pipe or socket.
21010 pathname refers to a file on a read-only filesystem and
21011 write access was requested.
21014 pathname is an invalid pointer value.
21017 No space on device to create the file.
21020 The process already has the maximum number of files open.
21023 The limit on the total number of files open on the system
21027 The call was interrupted by the user.
21031 @unnumberedsubsubsec close
21032 @cindex close, file-i/o system call
21041 @exdent Return value:
21042 close returns zero on success, or -1 if an error occurred.
21049 fd isn't a valid open file descriptor.
21052 The call was interrupted by the user.
21056 @unnumberedsubsubsec read
21057 @cindex read, file-i/o system call
21061 int read(int fd, void *buf, unsigned int count);
21064 Fread,fd,bufptr,count
21066 @exdent Return value:
21067 On success, the number of bytes read is returned.
21068 Zero indicates end of file. If count is zero, read
21069 returns zero as well. On error, -1 is returned.
21076 fd is not a valid file descriptor or is not open for
21080 buf is an invalid pointer value.
21083 The call was interrupted by the user.
21087 @unnumberedsubsubsec write
21088 @cindex write, file-i/o system call
21092 int write(int fd, const void *buf, unsigned int count);
21095 Fwrite,fd,bufptr,count
21097 @exdent Return value:
21098 On success, the number of bytes written are returned.
21099 Zero indicates nothing was written. On error, -1
21107 fd is not a valid file descriptor or is not open for
21111 buf is an invalid pointer value.
21114 An attempt was made to write a file that exceeds the
21115 host specific maximum file size allowed.
21118 No space on device to write the data.
21121 The call was interrupted by the user.
21125 @unnumberedsubsubsec lseek
21126 @cindex lseek, file-i/o system call
21130 long lseek (int fd, long offset, int flag);
21133 Flseek,fd,offset,flag
21136 @code{flag} is one of:
21140 The offset is set to offset bytes.
21143 The offset is set to its current location plus offset
21147 The offset is set to the size of the file plus offset
21152 @exdent Return value:
21153 On success, the resulting unsigned offset in bytes from
21154 the beginning of the file is returned. Otherwise, a
21155 value of -1 is returned.
21162 fd is not a valid open file descriptor.
21165 fd is associated with the @value{GDBN} console.
21168 flag is not a proper value.
21171 The call was interrupted by the user.
21175 @unnumberedsubsubsec rename
21176 @cindex rename, file-i/o system call
21180 int rename(const char *oldpath, const char *newpath);
21183 Frename,oldpathptr/len,newpathptr/len
21185 @exdent Return value:
21186 On success, zero is returned. On error, -1 is returned.
21193 newpath is an existing directory, but oldpath is not a
21197 newpath is a non-empty directory.
21200 oldpath or newpath is a directory that is in use by some
21204 An attempt was made to make a directory a subdirectory
21208 A component used as a directory in oldpath or new
21209 path is not a directory. Or oldpath is a directory
21210 and newpath exists but is not a directory.
21213 oldpathptr or newpathptr are invalid pointer values.
21216 No access to the file or the path of the file.
21220 oldpath or newpath was too long.
21223 A directory component in oldpath or newpath does not exist.
21226 The file is on a read-only filesystem.
21229 The device containing the file has no room for the new
21233 The call was interrupted by the user.
21237 @unnumberedsubsubsec unlink
21238 @cindex unlink, file-i/o system call
21242 int unlink(const char *pathname);
21245 Funlink,pathnameptr/len
21247 @exdent Return value:
21248 On success, zero is returned. On error, -1 is returned.
21255 No access to the file or the path of the file.
21258 The system does not allow unlinking of directories.
21261 The file pathname cannot be unlinked because it's
21262 being used by another process.
21265 pathnameptr is an invalid pointer value.
21268 pathname was too long.
21271 A directory component in pathname does not exist.
21274 A component of the path is not a directory.
21277 The file is on a read-only filesystem.
21280 The call was interrupted by the user.
21284 @unnumberedsubsubsec stat/fstat
21285 @cindex fstat, file-i/o system call
21286 @cindex stat, file-i/o system call
21290 int stat(const char *pathname, struct stat *buf);
21291 int fstat(int fd, struct stat *buf);
21294 Fstat,pathnameptr/len,bufptr
21297 @exdent Return value:
21298 On success, zero is returned. On error, -1 is returned.
21305 fd is not a valid open file.
21308 A directory component in pathname does not exist or the
21309 path is an empty string.
21312 A component of the path is not a directory.
21315 pathnameptr is an invalid pointer value.
21318 No access to the file or the path of the file.
21321 pathname was too long.
21324 The call was interrupted by the user.
21328 @unnumberedsubsubsec gettimeofday
21329 @cindex gettimeofday, file-i/o system call
21333 int gettimeofday(struct timeval *tv, void *tz);
21336 Fgettimeofday,tvptr,tzptr
21338 @exdent Return value:
21339 On success, 0 is returned, -1 otherwise.
21346 tz is a non-NULL pointer.
21349 tvptr and/or tzptr is an invalid pointer value.
21353 @unnumberedsubsubsec isatty
21354 @cindex isatty, file-i/o system call
21358 int isatty(int fd);
21363 @exdent Return value:
21364 Returns 1 if fd refers to the @value{GDBN} console, 0 otherwise.
21371 The call was interrupted by the user.
21375 @unnumberedsubsubsec system
21376 @cindex system, file-i/o system call
21380 int system(const char *command);
21383 Fsystem,commandptr/len
21385 @exdent Return value:
21386 The value returned is -1 on error and the return status
21387 of the command otherwise. Only the exit status of the
21388 command is returned, which is extracted from the hosts
21389 system return value by calling WEXITSTATUS(retval).
21390 In case /bin/sh could not be executed, 127 is returned.
21397 The call was interrupted by the user.
21400 @node Protocol specific representation of datatypes
21401 @subsection Protocol specific representation of datatypes
21402 @cindex protocol specific representation of datatypes, in file-i/o protocol
21405 * Integral datatypes::
21411 @node Integral datatypes
21412 @unnumberedsubsubsec Integral datatypes
21413 @cindex integral datatypes, in file-i/o protocol
21415 The integral datatypes used in the system calls are
21418 int@r{,} unsigned int@r{,} long@r{,} unsigned long@r{,} mode_t @r{and} time_t
21421 @code{Int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
21422 implemented as 32 bit values in this protocol.
21424 @code{Long} and @code{unsigned long} are implemented as 64 bit types.
21426 @xref{Limits}, for corresponding MIN and MAX values (similar to those
21427 in @file{limits.h}) to allow range checking on host and target.
21429 @code{time_t} datatypes are defined as seconds since the Epoch.
21431 All integral datatypes transferred as part of a memory read or write of a
21432 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
21435 @node Pointer values
21436 @unnumberedsubsubsec Pointer values
21437 @cindex pointer values, in file-i/o protocol
21439 Pointers to target data are transmitted as they are. An exception
21440 is made for pointers to buffers for which the length isn't
21441 transmitted as part of the function call, namely strings. Strings
21442 are transmitted as a pointer/length pair, both as hex values, e.g.@:
21449 which is a pointer to data of length 18 bytes at position 0x1aaf.
21450 The length is defined as the full string length in bytes, including
21451 the trailing null byte. Example:
21454 ``hello, world'' at address 0x123456
21465 @unnumberedsubsubsec struct stat
21466 @cindex struct stat, in file-i/o protocol
21468 The buffer of type struct stat used by the target and @value{GDBN} is defined
21473 unsigned int st_dev; /* device */
21474 unsigned int st_ino; /* inode */
21475 mode_t st_mode; /* protection */
21476 unsigned int st_nlink; /* number of hard links */
21477 unsigned int st_uid; /* user ID of owner */
21478 unsigned int st_gid; /* group ID of owner */
21479 unsigned int st_rdev; /* device type (if inode device) */
21480 unsigned long st_size; /* total size, in bytes */
21481 unsigned long st_blksize; /* blocksize for filesystem I/O */
21482 unsigned long st_blocks; /* number of blocks allocated */
21483 time_t st_atime; /* time of last access */
21484 time_t st_mtime; /* time of last modification */
21485 time_t st_ctime; /* time of last change */
21489 The integral datatypes are conforming to the definitions given in the
21490 approriate section (see @ref{Integral datatypes}, for details) so this
21491 structure is of size 64 bytes.
21493 The values of several fields have a restricted meaning and/or
21500 st_ino: No valid meaning for the target. Transmitted unchanged.
21502 st_mode: Valid mode bits are described in Appendix C. Any other
21503 bits have currently no meaning for the target.
21505 st_uid: No valid meaning for the target. Transmitted unchanged.
21507 st_gid: No valid meaning for the target. Transmitted unchanged.
21509 st_rdev: No valid meaning for the target. Transmitted unchanged.
21511 st_atime, st_mtime, st_ctime:
21512 These values have a host and file system dependent
21513 accuracy. Especially on Windows hosts the file systems
21514 don't support exact timing values.
21517 The target gets a struct stat of the above representation and is
21518 responsible to coerce it to the target representation before
21521 Note that due to size differences between the host and target
21522 representation of stat members, these members could eventually
21523 get truncated on the target.
21525 @node struct timeval
21526 @unnumberedsubsubsec struct timeval
21527 @cindex struct timeval, in file-i/o protocol
21529 The buffer of type struct timeval used by the target and @value{GDBN}
21530 is defined as follows:
21534 time_t tv_sec; /* second */
21535 long tv_usec; /* microsecond */
21539 The integral datatypes are conforming to the definitions given in the
21540 approriate section (see @ref{Integral datatypes}, for details) so this
21541 structure is of size 8 bytes.
21544 @subsection Constants
21545 @cindex constants, in file-i/o protocol
21547 The following values are used for the constants inside of the
21548 protocol. @value{GDBN} and target are resposible to translate these
21549 values before and after the call as needed.
21560 @unnumberedsubsubsec Open flags
21561 @cindex open flags, in file-i/o protocol
21563 All values are given in hexadecimal representation.
21575 @node mode_t values
21576 @unnumberedsubsubsec mode_t values
21577 @cindex mode_t values, in file-i/o protocol
21579 All values are given in octal representation.
21596 @unnumberedsubsubsec Errno values
21597 @cindex errno values, in file-i/o protocol
21599 All values are given in decimal representation.
21624 EUNKNOWN is used as a fallback error value if a host system returns
21625 any error value not in the list of supported error numbers.
21628 @unnumberedsubsubsec Lseek flags
21629 @cindex lseek flags, in file-i/o protocol
21638 @unnumberedsubsubsec Limits
21639 @cindex limits, in file-i/o protocol
21641 All values are given in decimal representation.
21644 INT_MIN -2147483648
21646 UINT_MAX 4294967295
21647 LONG_MIN -9223372036854775808
21648 LONG_MAX 9223372036854775807
21649 ULONG_MAX 18446744073709551615
21652 @node File-I/O Examples
21653 @subsection File-I/O Examples
21654 @cindex file-i/o examples
21656 Example sequence of a write call, file descriptor 3, buffer is at target
21657 address 0x1234, 6 bytes should be written:
21660 <- @code{Fwrite,3,1234,6}
21661 @emph{request memory read from target}
21664 @emph{return "6 bytes written"}
21668 Example sequence of a read call, file descriptor 3, buffer is at target
21669 address 0x1234, 6 bytes should be read:
21672 <- @code{Fread,3,1234,6}
21673 @emph{request memory write to target}
21674 -> @code{X1234,6:XXXXXX}
21675 @emph{return "6 bytes read"}
21679 Example sequence of a read call, call fails on the host due to invalid
21680 file descriptor (EBADF):
21683 <- @code{Fread,3,1234,6}
21687 Example sequence of a read call, user presses Ctrl-C before syscall on
21691 <- @code{Fread,3,1234,6}
21696 Example sequence of a read call, user presses Ctrl-C after syscall on
21700 <- @code{Fread,3,1234,6}
21701 -> @code{X1234,6:XXXXXX}
21715 % I think something like @colophon should be in texinfo. In the
21717 \long\def\colophon{\hbox to0pt{}\vfill
21718 \centerline{The body of this manual is set in}
21719 \centerline{\fontname\tenrm,}
21720 \centerline{with headings in {\bf\fontname\tenbf}}
21721 \centerline{and examples in {\tt\fontname\tentt}.}
21722 \centerline{{\it\fontname\tenit\/},}
21723 \centerline{{\bf\fontname\tenbf}, and}
21724 \centerline{{\sl\fontname\tensl\/}}
21725 \centerline{are used for emphasis.}\vfill}
21727 % Blame: doc@cygnus.com, 1991.