1 \input texinfo @c -*-texinfo-*-
2 @c Copyright 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,
3 @c 1999, 2000, 2001, 2002, 2003, 2004, 2005
4 @c Free Software Foundation, Inc.
7 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
8 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
25 @c readline appendices use @vindex, @findex and @ftable,
26 @c annotate.texi and gdbmi use @findex.
30 @c !!set GDB manual's edition---not the same as GDB version!
31 @c This is updated by GNU Press.
34 @c !!set GDB edit command default editor
37 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
39 @c This is a dir.info fragment to support semi-automated addition of
40 @c manuals to an info tree.
41 @dircategory Software development
43 * Gdb: (gdb). The GNU debugger.
47 This file documents the @sc{gnu} debugger @value{GDBN}.
50 This is the @value{EDITION} Edition, of @cite{Debugging with
51 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
52 Version @value{GDBVN}.
54 Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,@*
55 1999, 2000, 2001, 2002, 2003, 2004, 2005@*
56 Free Software Foundation, Inc.
58 Permission is granted to copy, distribute and/or modify this document
59 under the terms of the GNU Free Documentation License, Version 1.1 or
60 any later version published by the Free Software Foundation; with the
61 Invariant Sections being ``Free Software'' and ``Free Software Needs
62 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
63 and with the Back-Cover Texts as in (a) below.
65 (a) The Free Software Foundation's Back-Cover Text is: ``You have
66 freedom to copy and modify this GNU Manual, like GNU software. Copies
67 published by the Free Software Foundation raise funds for GNU
72 @title Debugging with @value{GDBN}
73 @subtitle The @sc{gnu} Source-Level Debugger
75 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
76 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
80 \hfill (Send bugs and comments on @value{GDBN} to bug-gdb\@gnu.org.)\par
81 \hfill {\it Debugging with @value{GDBN}}\par
82 \hfill \TeX{}info \texinfoversion\par
86 @vskip 0pt plus 1filll
87 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,
88 1996, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
89 Free Software Foundation, Inc.
91 Published by the Free Software Foundation @*
92 59 Temple Place - Suite 330, @*
93 Boston, MA 02111-1307 USA @*
96 Permission is granted to copy, distribute and/or modify this document
97 under the terms of the GNU Free Documentation License, Version 1.1 or
98 any later version published by the Free Software Foundation; with the
99 Invariant Sections being ``Free Software'' and ``Free Software Needs
100 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
101 and with the Back-Cover Texts as in (a) below.
103 (a) The Free Software Foundation's Back-Cover Text is: ``You have
104 freedom to copy and modify this GNU Manual, like GNU software. Copies
105 published by the Free Software Foundation raise funds for GNU
111 @node Top, Summary, (dir), (dir)
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN} Version
120 Copyright (C) 1988-2005 Free Software Foundation, Inc.
123 * Summary:: Summary of @value{GDBN}
124 * Sample Session:: A sample @value{GDBN} session
126 * Invocation:: Getting in and out of @value{GDBN}
127 * Commands:: @value{GDBN} commands
128 * Running:: Running programs under @value{GDBN}
129 * Stopping:: Stopping and continuing
130 * Stack:: Examining the stack
131 * Source:: Examining source files
132 * Data:: Examining data
133 * Macros:: Preprocessor Macros
134 * Tracepoints:: Debugging remote targets non-intrusively
135 * Overlays:: Debugging programs that use overlays
137 * Languages:: Using @value{GDBN} with different languages
139 * Symbols:: Examining the symbol table
140 * Altering:: Altering execution
141 * GDB Files:: @value{GDBN} files
142 * Targets:: Specifying a debugging target
143 * Remote Debugging:: Debugging remote programs
144 * Configurations:: Configuration-specific information
145 * Controlling GDB:: Controlling @value{GDBN}
146 * Sequences:: Canned sequences of commands
147 * TUI:: @value{GDBN} Text User Interface
148 * Interpreters:: Command Interpreters
149 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
150 * Annotations:: @value{GDBN}'s annotation interface.
151 * GDB/MI:: @value{GDBN}'s Machine Interface.
153 * GDB Bugs:: Reporting bugs in @value{GDBN}
154 * Formatting Documentation:: How to format and print @value{GDBN} documentation
156 * Command Line Editing:: Command Line Editing
157 * Using History Interactively:: Using History Interactively
158 * Installing GDB:: Installing GDB
159 * Maintenance Commands:: Maintenance Commands
160 * Remote Protocol:: GDB Remote Serial Protocol
161 * Agent Expressions:: The GDB Agent Expression Mechanism
162 * Copying:: GNU General Public License says
163 how you can copy and share GDB
164 * GNU Free Documentation License:: The license for this documentation
173 @unnumbered Summary of @value{GDBN}
175 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
176 going on ``inside'' another program while it executes---or what another
177 program was doing at the moment it crashed.
179 @value{GDBN} can do four main kinds of things (plus other things in support of
180 these) to help you catch bugs in the act:
184 Start your program, specifying anything that might affect its behavior.
187 Make your program stop on specified conditions.
190 Examine what has happened, when your program has stopped.
193 Change things in your program, so you can experiment with correcting the
194 effects of one bug and go on to learn about another.
197 You can use @value{GDBN} to debug programs written in C and C@t{++}.
198 For more information, see @ref{Supported languages,,Supported languages}.
199 For more information, see @ref{C,,C and C++}.
202 Support for Modula-2 is partial. For information on Modula-2, see
203 @ref{Modula-2,,Modula-2}.
206 Debugging Pascal programs which use sets, subranges, file variables, or
207 nested functions does not currently work. @value{GDBN} does not support
208 entering expressions, printing values, or similar features using Pascal
212 @value{GDBN} can be used to debug programs written in Fortran, although
213 it may be necessary to refer to some variables with a trailing
216 @value{GDBN} can be used to debug programs written in Objective-C,
217 using either the Apple/NeXT or the GNU Objective-C runtime.
220 * Free Software:: Freely redistributable software
221 * Contributors:: Contributors to GDB
225 @unnumberedsec Free software
227 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
228 General Public License
229 (GPL). The GPL gives you the freedom to copy or adapt a licensed
230 program---but every person getting a copy also gets with it the
231 freedom to modify that copy (which means that they must get access to
232 the source code), and the freedom to distribute further copies.
233 Typical software companies use copyrights to limit your freedoms; the
234 Free Software Foundation uses the GPL to preserve these freedoms.
236 Fundamentally, the General Public License is a license which says that
237 you have these freedoms and that you cannot take these freedoms away
240 @unnumberedsec Free Software Needs Free Documentation
242 The biggest deficiency in the free software community today is not in
243 the software---it is the lack of good free documentation that we can
244 include with the free software. Many of our most important
245 programs do not come with free reference manuals and free introductory
246 texts. Documentation is an essential part of any software package;
247 when an important free software package does not come with a free
248 manual and a free tutorial, that is a major gap. We have many such
251 Consider Perl, for instance. The tutorial manuals that people
252 normally use are non-free. How did this come about? Because the
253 authors of those manuals published them with restrictive terms---no
254 copying, no modification, source files not available---which exclude
255 them from the free software world.
257 That wasn't the first time this sort of thing happened, and it was far
258 from the last. Many times we have heard a GNU user eagerly describe a
259 manual that he is writing, his intended contribution to the community,
260 only to learn that he had ruined everything by signing a publication
261 contract to make it non-free.
263 Free documentation, like free software, is a matter of freedom, not
264 price. The problem with the non-free manual is not that publishers
265 charge a price for printed copies---that in itself is fine. (The Free
266 Software Foundation sells printed copies of manuals, too.) The
267 problem is the restrictions on the use of the manual. Free manuals
268 are available in source code form, and give you permission to copy and
269 modify. Non-free manuals do not allow this.
271 The criteria of freedom for a free manual are roughly the same as for
272 free software. Redistribution (including the normal kinds of
273 commercial redistribution) must be permitted, so that the manual can
274 accompany every copy of the program, both on-line and on paper.
276 Permission for modification of the technical content is crucial too.
277 When people modify the software, adding or changing features, if they
278 are conscientious they will change the manual too---so they can
279 provide accurate and clear documentation for the modified program. A
280 manual that leaves you no choice but to write a new manual to document
281 a changed version of the program is not really available to our
284 Some kinds of limits on the way modification is handled are
285 acceptable. For example, requirements to preserve the original
286 author's copyright notice, the distribution terms, or the list of
287 authors, are ok. It is also no problem to require modified versions
288 to include notice that they were modified. Even entire sections that
289 may not be deleted or changed are acceptable, as long as they deal
290 with nontechnical topics (like this one). These kinds of restrictions
291 are acceptable because they don't obstruct the community's normal use
294 However, it must be possible to modify all the @emph{technical}
295 content of the manual, and then distribute the result in all the usual
296 media, through all the usual channels. Otherwise, the restrictions
297 obstruct the use of the manual, it is not free, and we need another
298 manual to replace it.
300 Please spread the word about this issue. Our community continues to
301 lose manuals to proprietary publishing. If we spread the word that
302 free software needs free reference manuals and free tutorials, perhaps
303 the next person who wants to contribute by writing documentation will
304 realize, before it is too late, that only free manuals contribute to
305 the free software community.
307 If you are writing documentation, please insist on publishing it under
308 the GNU Free Documentation License or another free documentation
309 license. Remember that this decision requires your approval---you
310 don't have to let the publisher decide. Some commercial publishers
311 will use a free license if you insist, but they will not propose the
312 option; it is up to you to raise the issue and say firmly that this is
313 what you want. If the publisher you are dealing with refuses, please
314 try other publishers. If you're not sure whether a proposed license
315 is free, write to @email{licensing@@gnu.org}.
317 You can encourage commercial publishers to sell more free, copylefted
318 manuals and tutorials by buying them, and particularly by buying
319 copies from the publishers that paid for their writing or for major
320 improvements. Meanwhile, try to avoid buying non-free documentation
321 at all. Check the distribution terms of a manual before you buy it,
322 and insist that whoever seeks your business must respect your freedom.
323 Check the history of the book, and try to reward the publishers that
324 have paid or pay the authors to work on it.
326 The Free Software Foundation maintains a list of free documentation
327 published by other publishers, at
328 @url{http://www.fsf.org/doc/other-free-books.html}.
331 @unnumberedsec Contributors to @value{GDBN}
333 Richard Stallman was the original author of @value{GDBN}, and of many
334 other @sc{gnu} programs. Many others have contributed to its
335 development. This section attempts to credit major contributors. One
336 of the virtues of free software is that everyone is free to contribute
337 to it; with regret, we cannot actually acknowledge everyone here. The
338 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
339 blow-by-blow account.
341 Changes much prior to version 2.0 are lost in the mists of time.
344 @emph{Plea:} Additions to this section are particularly welcome. If you
345 or your friends (or enemies, to be evenhanded) have been unfairly
346 omitted from this list, we would like to add your names!
349 So that they may not regard their many labors as thankless, we
350 particularly thank those who shepherded @value{GDBN} through major
352 Andrew Cagney (releases 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
353 Jim Blandy (release 4.18);
354 Jason Molenda (release 4.17);
355 Stan Shebs (release 4.14);
356 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
357 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
358 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
359 Jim Kingdon (releases 3.5, 3.4, and 3.3);
360 and Randy Smith (releases 3.2, 3.1, and 3.0).
362 Richard Stallman, assisted at various times by Peter TerMaat, Chris
363 Hanson, and Richard Mlynarik, handled releases through 2.8.
365 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
366 in @value{GDBN}, with significant additional contributions from Per
367 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
368 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
369 much general update work leading to release 3.0).
371 @value{GDBN} uses the BFD subroutine library to examine multiple
372 object-file formats; BFD was a joint project of David V.
373 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
375 David Johnson wrote the original COFF support; Pace Willison did
376 the original support for encapsulated COFF.
378 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
380 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
381 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
383 Jean-Daniel Fekete contributed Sun 386i support.
384 Chris Hanson improved the HP9000 support.
385 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
386 David Johnson contributed Encore Umax support.
387 Jyrki Kuoppala contributed Altos 3068 support.
388 Jeff Law contributed HP PA and SOM support.
389 Keith Packard contributed NS32K support.
390 Doug Rabson contributed Acorn Risc Machine support.
391 Bob Rusk contributed Harris Nighthawk CX-UX support.
392 Chris Smith contributed Convex support (and Fortran debugging).
393 Jonathan Stone contributed Pyramid support.
394 Michael Tiemann contributed SPARC support.
395 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
396 Pace Willison contributed Intel 386 support.
397 Jay Vosburgh contributed Symmetry support.
398 Marko Mlinar contributed OpenRISC 1000 support.
400 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
402 Rich Schaefer and Peter Schauer helped with support of SunOS shared
405 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
406 about several machine instruction sets.
408 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
409 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
410 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
411 and RDI targets, respectively.
413 Brian Fox is the author of the readline libraries providing
414 command-line editing and command history.
416 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
417 Modula-2 support, and contributed the Languages chapter of this manual.
419 Fred Fish wrote most of the support for Unix System Vr4.
420 He also enhanced the command-completion support to cover C@t{++} overloaded
423 Hitachi America (now Renesas America), Ltd. sponsored the support for
424 H8/300, H8/500, and Super-H processors.
426 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
428 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
431 Toshiba sponsored the support for the TX39 Mips processor.
433 Matsushita sponsored the support for the MN10200 and MN10300 processors.
435 Fujitsu sponsored the support for SPARClite and FR30 processors.
437 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
440 Michael Snyder added support for tracepoints.
442 Stu Grossman wrote gdbserver.
444 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
445 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
447 The following people at the Hewlett-Packard Company contributed
448 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
449 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
450 compiler, and the Text User Interface (nee Terminal User Interface):
451 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
452 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
453 provided HP-specific information in this manual.
455 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
456 Robert Hoehne made significant contributions to the DJGPP port.
458 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
459 development since 1991. Cygnus engineers who have worked on @value{GDBN}
460 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
461 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
462 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
463 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
464 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
465 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
466 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
467 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
468 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
469 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
470 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
471 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
472 Zuhn have made contributions both large and small.
474 Jim Blandy added support for preprocessor macros, while working for Red
478 @chapter A Sample @value{GDBN} Session
480 You can use this manual at your leisure to read all about @value{GDBN}.
481 However, a handful of commands are enough to get started using the
482 debugger. This chapter illustrates those commands.
485 In this sample session, we emphasize user input like this: @b{input},
486 to make it easier to pick out from the surrounding output.
489 @c FIXME: this example may not be appropriate for some configs, where
490 @c FIXME...primary interest is in remote use.
492 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
493 processor) exhibits the following bug: sometimes, when we change its
494 quote strings from the default, the commands used to capture one macro
495 definition within another stop working. In the following short @code{m4}
496 session, we define a macro @code{foo} which expands to @code{0000}; we
497 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
498 same thing. However, when we change the open quote string to
499 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
500 procedure fails to define a new synonym @code{baz}:
509 @b{define(bar,defn(`foo'))}
513 @b{changequote(<QUOTE>,<UNQUOTE>)}
515 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
518 m4: End of input: 0: fatal error: EOF in string
522 Let us use @value{GDBN} to try to see what is going on.
525 $ @b{@value{GDBP} m4}
526 @c FIXME: this falsifies the exact text played out, to permit smallbook
527 @c FIXME... format to come out better.
528 @value{GDBN} is free software and you are welcome to distribute copies
529 of it under certain conditions; type "show copying" to see
531 There is absolutely no warranty for @value{GDBN}; type "show warranty"
534 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
539 @value{GDBN} reads only enough symbol data to know where to find the
540 rest when needed; as a result, the first prompt comes up very quickly.
541 We now tell @value{GDBN} to use a narrower display width than usual, so
542 that examples fit in this manual.
545 (@value{GDBP}) @b{set width 70}
549 We need to see how the @code{m4} built-in @code{changequote} works.
550 Having looked at the source, we know the relevant subroutine is
551 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
552 @code{break} command.
555 (@value{GDBP}) @b{break m4_changequote}
556 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
560 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
561 control; as long as control does not reach the @code{m4_changequote}
562 subroutine, the program runs as usual:
565 (@value{GDBP}) @b{run}
566 Starting program: /work/Editorial/gdb/gnu/m4/m4
574 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
575 suspends execution of @code{m4}, displaying information about the
576 context where it stops.
579 @b{changequote(<QUOTE>,<UNQUOTE>)}
581 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
583 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
587 Now we use the command @code{n} (@code{next}) to advance execution to
588 the next line of the current function.
592 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
597 @code{set_quotes} looks like a promising subroutine. We can go into it
598 by using the command @code{s} (@code{step}) instead of @code{next}.
599 @code{step} goes to the next line to be executed in @emph{any}
600 subroutine, so it steps into @code{set_quotes}.
604 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
606 530 if (lquote != def_lquote)
610 The display that shows the subroutine where @code{m4} is now
611 suspended (and its arguments) is called a stack frame display. It
612 shows a summary of the stack. We can use the @code{backtrace}
613 command (which can also be spelled @code{bt}), to see where we are
614 in the stack as a whole: the @code{backtrace} command displays a
615 stack frame for each active subroutine.
618 (@value{GDBP}) @b{bt}
619 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
621 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
623 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
624 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
626 #4 0x79dc in expand_input () at macro.c:40
627 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
631 We step through a few more lines to see what happens. The first two
632 times, we can use @samp{s}; the next two times we use @code{n} to avoid
633 falling into the @code{xstrdup} subroutine.
637 0x3b5c 532 if (rquote != def_rquote)
639 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
640 def_lquote : xstrdup(lq);
642 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
645 538 len_lquote = strlen(rquote);
649 The last line displayed looks a little odd; we can examine the variables
650 @code{lquote} and @code{rquote} to see if they are in fact the new left
651 and right quotes we specified. We use the command @code{p}
652 (@code{print}) to see their values.
655 (@value{GDBP}) @b{p lquote}
656 $1 = 0x35d40 "<QUOTE>"
657 (@value{GDBP}) @b{p rquote}
658 $2 = 0x35d50 "<UNQUOTE>"
662 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
663 To look at some context, we can display ten lines of source
664 surrounding the current line with the @code{l} (@code{list}) command.
670 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
672 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
675 538 len_lquote = strlen(rquote);
676 539 len_rquote = strlen(lquote);
683 Let us step past the two lines that set @code{len_lquote} and
684 @code{len_rquote}, and then examine the values of those variables.
688 539 len_rquote = strlen(lquote);
691 (@value{GDBP}) @b{p len_lquote}
693 (@value{GDBP}) @b{p len_rquote}
698 That certainly looks wrong, assuming @code{len_lquote} and
699 @code{len_rquote} are meant to be the lengths of @code{lquote} and
700 @code{rquote} respectively. We can set them to better values using
701 the @code{p} command, since it can print the value of
702 any expression---and that expression can include subroutine calls and
706 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
708 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
713 Is that enough to fix the problem of using the new quotes with the
714 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
715 executing with the @code{c} (@code{continue}) command, and then try the
716 example that caused trouble initially:
722 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
729 Success! The new quotes now work just as well as the default ones. The
730 problem seems to have been just the two typos defining the wrong
731 lengths. We allow @code{m4} exit by giving it an EOF as input:
735 Program exited normally.
739 The message @samp{Program exited normally.} is from @value{GDBN}; it
740 indicates @code{m4} has finished executing. We can end our @value{GDBN}
741 session with the @value{GDBN} @code{quit} command.
744 (@value{GDBP}) @b{quit}
748 @chapter Getting In and Out of @value{GDBN}
750 This chapter discusses how to start @value{GDBN}, and how to get out of it.
754 type @samp{@value{GDBP}} to start @value{GDBN}.
756 type @kbd{quit} or @kbd{C-d} to exit.
760 * Invoking GDB:: How to start @value{GDBN}
761 * Quitting GDB:: How to quit @value{GDBN}
762 * Shell Commands:: How to use shell commands inside @value{GDBN}
763 * Logging output:: How to log @value{GDBN}'s output to a file
767 @section Invoking @value{GDBN}
769 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
770 @value{GDBN} reads commands from the terminal until you tell it to exit.
772 You can also run @code{@value{GDBP}} with a variety of arguments and options,
773 to specify more of your debugging environment at the outset.
775 The command-line options described here are designed
776 to cover a variety of situations; in some environments, some of these
777 options may effectively be unavailable.
779 The most usual way to start @value{GDBN} is with one argument,
780 specifying an executable program:
783 @value{GDBP} @var{program}
787 You can also start with both an executable program and a core file
791 @value{GDBP} @var{program} @var{core}
794 You can, instead, specify a process ID as a second argument, if you want
795 to debug a running process:
798 @value{GDBP} @var{program} 1234
802 would attach @value{GDBN} to process @code{1234} (unless you also have a file
803 named @file{1234}; @value{GDBN} does check for a core file first).
805 Taking advantage of the second command-line argument requires a fairly
806 complete operating system; when you use @value{GDBN} as a remote
807 debugger attached to a bare board, there may not be any notion of
808 ``process'', and there is often no way to get a core dump. @value{GDBN}
809 will warn you if it is unable to attach or to read core dumps.
811 You can optionally have @code{@value{GDBP}} pass any arguments after the
812 executable file to the inferior using @code{--args}. This option stops
815 gdb --args gcc -O2 -c foo.c
817 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
818 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
820 You can run @code{@value{GDBP}} without printing the front material, which describes
821 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
828 You can further control how @value{GDBN} starts up by using command-line
829 options. @value{GDBN} itself can remind you of the options available.
839 to display all available options and briefly describe their use
840 (@samp{@value{GDBP} -h} is a shorter equivalent).
842 All options and command line arguments you give are processed
843 in sequential order. The order makes a difference when the
844 @samp{-x} option is used.
848 * File Options:: Choosing files
849 * Mode Options:: Choosing modes
853 @subsection Choosing files
855 When @value{GDBN} starts, it reads any arguments other than options as
856 specifying an executable file and core file (or process ID). This is
857 the same as if the arguments were specified by the @samp{-se} and
858 @samp{-c} (or @samp{-p} options respectively. (@value{GDBN} reads the
859 first argument that does not have an associated option flag as
860 equivalent to the @samp{-se} option followed by that argument; and the
861 second argument that does not have an associated option flag, if any, as
862 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
863 If the second argument begins with a decimal digit, @value{GDBN} will
864 first attempt to attach to it as a process, and if that fails, attempt
865 to open it as a corefile. If you have a corefile whose name begins with
866 a digit, you can prevent @value{GDBN} from treating it as a pid by
867 prefixing it with @file{./}, eg. @file{./12345}.
869 If @value{GDBN} has not been configured to included core file support,
870 such as for most embedded targets, then it will complain about a second
871 argument and ignore it.
873 Many options have both long and short forms; both are shown in the
874 following list. @value{GDBN} also recognizes the long forms if you truncate
875 them, so long as enough of the option is present to be unambiguous.
876 (If you prefer, you can flag option arguments with @samp{--} rather
877 than @samp{-}, though we illustrate the more usual convention.)
879 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
880 @c way, both those who look for -foo and --foo in the index, will find
884 @item -symbols @var{file}
886 @cindex @code{--symbols}
888 Read symbol table from file @var{file}.
890 @item -exec @var{file}
892 @cindex @code{--exec}
894 Use file @var{file} as the executable file to execute when appropriate,
895 and for examining pure data in conjunction with a core dump.
899 Read symbol table from file @var{file} and use it as the executable
902 @item -core @var{file}
904 @cindex @code{--core}
906 Use file @var{file} as a core dump to examine.
908 @item -c @var{number}
909 @item -pid @var{number}
910 @itemx -p @var{number}
913 Connect to process ID @var{number}, as with the @code{attach} command.
914 If there is no such process, @value{GDBN} will attempt to open a core
915 file named @var{number}.
917 @item -command @var{file}
919 @cindex @code{--command}
921 Execute @value{GDBN} commands from file @var{file}. @xref{Command
922 Files,, Command files}.
924 @item -directory @var{directory}
925 @itemx -d @var{directory}
926 @cindex @code{--directory}
928 Add @var{directory} to the path to search for source files.
932 @cindex @code{--mapped}
934 @emph{Warning: this option depends on operating system facilities that are not
935 supported on all systems.}@*
936 If memory-mapped files are available on your system through the @code{mmap}
937 system call, you can use this option
938 to have @value{GDBN} write the symbols from your
939 program into a reusable file in the current directory. If the program you are debugging is
940 called @file{/tmp/fred}, the mapped symbol file is @file{/tmp/fred.syms}.
941 Future @value{GDBN} debugging sessions notice the presence of this file,
942 and can quickly map in symbol information from it, rather than reading
943 the symbol table from the executable program.
945 The @file{.syms} file is specific to the host machine where @value{GDBN}
946 is run. It holds an exact image of the internal @value{GDBN} symbol
947 table. It cannot be shared across multiple host platforms.
951 @cindex @code{--readnow}
953 Read each symbol file's entire symbol table immediately, rather than
954 the default, which is to read it incrementally as it is needed.
955 This makes startup slower, but makes future operations faster.
959 You typically combine the @code{-mapped} and @code{-readnow} options in
960 order to build a @file{.syms} file that contains complete symbol
961 information. (@xref{Files,,Commands to specify files}, for information
962 on @file{.syms} files.) A simple @value{GDBN} invocation to do nothing
963 but build a @file{.syms} file for future use is:
966 gdb -batch -nx -mapped -readnow programname
970 @subsection Choosing modes
972 You can run @value{GDBN} in various alternative modes---for example, in
973 batch mode or quiet mode.
980 Do not execute commands found in any initialization files. Normally,
981 @value{GDBN} executes the commands in these files after all the command
982 options and arguments have been processed. @xref{Command Files,,Command
988 @cindex @code{--quiet}
989 @cindex @code{--silent}
991 ``Quiet''. Do not print the introductory and copyright messages. These
992 messages are also suppressed in batch mode.
995 @cindex @code{--batch}
996 Run in batch mode. Exit with status @code{0} after processing all the
997 command files specified with @samp{-x} (and all commands from
998 initialization files, if not inhibited with @samp{-n}). Exit with
999 nonzero status if an error occurs in executing the @value{GDBN} commands
1000 in the command files.
1002 Batch mode may be useful for running @value{GDBN} as a filter, for
1003 example to download and run a program on another computer; in order to
1004 make this more useful, the message
1007 Program exited normally.
1011 (which is ordinarily issued whenever a program running under
1012 @value{GDBN} control terminates) is not issued when running in batch
1017 @cindex @code{--nowindows}
1019 ``No windows''. If @value{GDBN} comes with a graphical user interface
1020 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1021 interface. If no GUI is available, this option has no effect.
1025 @cindex @code{--windows}
1027 If @value{GDBN} includes a GUI, then this option requires it to be
1030 @item -cd @var{directory}
1032 Run @value{GDBN} using @var{directory} as its working directory,
1033 instead of the current directory.
1037 @cindex @code{--fullname}
1039 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1040 subprocess. It tells @value{GDBN} to output the full file name and line
1041 number in a standard, recognizable fashion each time a stack frame is
1042 displayed (which includes each time your program stops). This
1043 recognizable format looks like two @samp{\032} characters, followed by
1044 the file name, line number and character position separated by colons,
1045 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1046 @samp{\032} characters as a signal to display the source code for the
1050 @cindex @code{--epoch}
1051 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1052 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1053 routines so as to allow Epoch to display values of expressions in a
1056 @item -annotate @var{level}
1057 @cindex @code{--annotate}
1058 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1059 effect is identical to using @samp{set annotate @var{level}}
1060 (@pxref{Annotations}). The annotation @var{level} controls how much
1061 information @value{GDBN} prints together with its prompt, values of
1062 expressions, source lines, and other types of output. Level 0 is the
1063 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1064 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1065 that control @value{GDBN}, and level 2 has been deprecated.
1067 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
1071 @cindex @code{--args}
1072 Change interpretation of command line so that arguments following the
1073 executable file are passed as command line arguments to the inferior.
1074 This option stops option processing.
1076 @item -baud @var{bps}
1078 @cindex @code{--baud}
1080 Set the line speed (baud rate or bits per second) of any serial
1081 interface used by @value{GDBN} for remote debugging.
1083 @item -l @var{timeout}
1085 Set the timeout (in seconds) of any communication used by @value{GDBN}
1086 for remote debugging.
1088 @item -tty @var{device}
1089 @itemx -t @var{device}
1090 @cindex @code{--tty}
1092 Run using @var{device} for your program's standard input and output.
1093 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1095 @c resolve the situation of these eventually
1097 @cindex @code{--tui}
1098 Activate the @dfn{Text User Interface} when starting. The Text User
1099 Interface manages several text windows on the terminal, showing
1100 source, assembly, registers and @value{GDBN} command outputs
1101 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1102 Text User Interface can be enabled by invoking the program
1103 @samp{gdbtui}. Do not use this option if you run @value{GDBN} from
1104 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1107 @c @cindex @code{--xdb}
1108 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1109 @c For information, see the file @file{xdb_trans.html}, which is usually
1110 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1113 @item -interpreter @var{interp}
1114 @cindex @code{--interpreter}
1115 Use the interpreter @var{interp} for interface with the controlling
1116 program or device. This option is meant to be set by programs which
1117 communicate with @value{GDBN} using it as a back end.
1118 @xref{Interpreters, , Command Interpreters}.
1120 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1121 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1122 The @sc{gdb/mi} Interface}) included since @var{GDBN} version 6.0. The
1123 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1124 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1125 @sc{gdb/mi} interfaces are no longer supported.
1128 @cindex @code{--write}
1129 Open the executable and core files for both reading and writing. This
1130 is equivalent to the @samp{set write on} command inside @value{GDBN}
1134 @cindex @code{--statistics}
1135 This option causes @value{GDBN} to print statistics about time and
1136 memory usage after it completes each command and returns to the prompt.
1139 @cindex @code{--version}
1140 This option causes @value{GDBN} to print its version number and
1141 no-warranty blurb, and exit.
1146 @section Quitting @value{GDBN}
1147 @cindex exiting @value{GDBN}
1148 @cindex leaving @value{GDBN}
1151 @kindex quit @r{[}@var{expression}@r{]}
1152 @kindex q @r{(@code{quit})}
1153 @item quit @r{[}@var{expression}@r{]}
1155 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1156 @code{q}), or type an end-of-file character (usually @kbd{C-d}). If you
1157 do not supply @var{expression}, @value{GDBN} will terminate normally;
1158 otherwise it will terminate using the result of @var{expression} as the
1163 An interrupt (often @kbd{C-c}) does not exit from @value{GDBN}, but rather
1164 terminates the action of any @value{GDBN} command that is in progress and
1165 returns to @value{GDBN} command level. It is safe to type the interrupt
1166 character at any time because @value{GDBN} does not allow it to take effect
1167 until a time when it is safe.
1169 If you have been using @value{GDBN} to control an attached process or
1170 device, you can release it with the @code{detach} command
1171 (@pxref{Attach, ,Debugging an already-running process}).
1173 @node Shell Commands
1174 @section Shell commands
1176 If you need to execute occasional shell commands during your
1177 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1178 just use the @code{shell} command.
1182 @cindex shell escape
1183 @item shell @var{command string}
1184 Invoke a standard shell to execute @var{command string}.
1185 If it exists, the environment variable @code{SHELL} determines which
1186 shell to run. Otherwise @value{GDBN} uses the default shell
1187 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1190 The utility @code{make} is often needed in development environments.
1191 You do not have to use the @code{shell} command for this purpose in
1196 @cindex calling make
1197 @item make @var{make-args}
1198 Execute the @code{make} program with the specified
1199 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1202 @node Logging output
1203 @section Logging output
1204 @cindex logging @value{GDBN} output
1205 @cindex save @value{GDBN} output to a file
1207 You may want to save the output of @value{GDBN} commands to a file.
1208 There are several commands to control @value{GDBN}'s logging.
1212 @item set logging on
1214 @item set logging off
1216 @cindex logging file name
1217 @item set logging file @var{file}
1218 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1219 @item set logging overwrite [on|off]
1220 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1221 you want @code{set logging on} to overwrite the logfile instead.
1222 @item set logging redirect [on|off]
1223 By default, @value{GDBN} output will go to both the terminal and the logfile.
1224 Set @code{redirect} if you want output to go only to the log file.
1225 @kindex show logging
1227 Show the current values of the logging settings.
1231 @chapter @value{GDBN} Commands
1233 You can abbreviate a @value{GDBN} command to the first few letters of the command
1234 name, if that abbreviation is unambiguous; and you can repeat certain
1235 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1236 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1237 show you the alternatives available, if there is more than one possibility).
1240 * Command Syntax:: How to give commands to @value{GDBN}
1241 * Completion:: Command completion
1242 * Help:: How to ask @value{GDBN} for help
1245 @node Command Syntax
1246 @section Command syntax
1248 A @value{GDBN} command is a single line of input. There is no limit on
1249 how long it can be. It starts with a command name, which is followed by
1250 arguments whose meaning depends on the command name. For example, the
1251 command @code{step} accepts an argument which is the number of times to
1252 step, as in @samp{step 5}. You can also use the @code{step} command
1253 with no arguments. Some commands do not allow any arguments.
1255 @cindex abbreviation
1256 @value{GDBN} command names may always be truncated if that abbreviation is
1257 unambiguous. Other possible command abbreviations are listed in the
1258 documentation for individual commands. In some cases, even ambiguous
1259 abbreviations are allowed; for example, @code{s} is specially defined as
1260 equivalent to @code{step} even though there are other commands whose
1261 names start with @code{s}. You can test abbreviations by using them as
1262 arguments to the @code{help} command.
1264 @cindex repeating commands
1265 @kindex RET @r{(repeat last command)}
1266 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1267 repeat the previous command. Certain commands (for example, @code{run})
1268 will not repeat this way; these are commands whose unintentional
1269 repetition might cause trouble and which you are unlikely to want to
1272 The @code{list} and @code{x} commands, when you repeat them with
1273 @key{RET}, construct new arguments rather than repeating
1274 exactly as typed. This permits easy scanning of source or memory.
1276 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1277 output, in a way similar to the common utility @code{more}
1278 (@pxref{Screen Size,,Screen size}). Since it is easy to press one
1279 @key{RET} too many in this situation, @value{GDBN} disables command
1280 repetition after any command that generates this sort of display.
1282 @kindex # @r{(a comment)}
1284 Any text from a @kbd{#} to the end of the line is a comment; it does
1285 nothing. This is useful mainly in command files (@pxref{Command
1286 Files,,Command files}).
1288 @cindex repeating command sequences
1289 @kindex C-o @r{(operate-and-get-next)}
1290 The @kbd{C-o} binding is useful for repeating a complex sequence of
1291 commands. This command accepts the current line, like @kbd{RET}, and
1292 then fetches the next line relative to the current line from the history
1296 @section Command completion
1299 @cindex word completion
1300 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1301 only one possibility; it can also show you what the valid possibilities
1302 are for the next word in a command, at any time. This works for @value{GDBN}
1303 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1305 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1306 of a word. If there is only one possibility, @value{GDBN} fills in the
1307 word, and waits for you to finish the command (or press @key{RET} to
1308 enter it). For example, if you type
1310 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1311 @c complete accuracy in these examples; space introduced for clarity.
1312 @c If texinfo enhancements make it unnecessary, it would be nice to
1313 @c replace " @key" by "@key" in the following...
1315 (@value{GDBP}) info bre @key{TAB}
1319 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1320 the only @code{info} subcommand beginning with @samp{bre}:
1323 (@value{GDBP}) info breakpoints
1327 You can either press @key{RET} at this point, to run the @code{info
1328 breakpoints} command, or backspace and enter something else, if
1329 @samp{breakpoints} does not look like the command you expected. (If you
1330 were sure you wanted @code{info breakpoints} in the first place, you
1331 might as well just type @key{RET} immediately after @samp{info bre},
1332 to exploit command abbreviations rather than command completion).
1334 If there is more than one possibility for the next word when you press
1335 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1336 characters and try again, or just press @key{TAB} a second time;
1337 @value{GDBN} displays all the possible completions for that word. For
1338 example, you might want to set a breakpoint on a subroutine whose name
1339 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1340 just sounds the bell. Typing @key{TAB} again displays all the
1341 function names in your program that begin with those characters, for
1345 (@value{GDBP}) b make_ @key{TAB}
1346 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1347 make_a_section_from_file make_environ
1348 make_abs_section make_function_type
1349 make_blockvector make_pointer_type
1350 make_cleanup make_reference_type
1351 make_command make_symbol_completion_list
1352 (@value{GDBP}) b make_
1356 After displaying the available possibilities, @value{GDBN} copies your
1357 partial input (@samp{b make_} in the example) so you can finish the
1360 If you just want to see the list of alternatives in the first place, you
1361 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1362 means @kbd{@key{META} ?}. You can type this either by holding down a
1363 key designated as the @key{META} shift on your keyboard (if there is
1364 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1366 @cindex quotes in commands
1367 @cindex completion of quoted strings
1368 Sometimes the string you need, while logically a ``word'', may contain
1369 parentheses or other characters that @value{GDBN} normally excludes from
1370 its notion of a word. To permit word completion to work in this
1371 situation, you may enclose words in @code{'} (single quote marks) in
1372 @value{GDBN} commands.
1374 The most likely situation where you might need this is in typing the
1375 name of a C@t{++} function. This is because C@t{++} allows function
1376 overloading (multiple definitions of the same function, distinguished
1377 by argument type). For example, when you want to set a breakpoint you
1378 may need to distinguish whether you mean the version of @code{name}
1379 that takes an @code{int} parameter, @code{name(int)}, or the version
1380 that takes a @code{float} parameter, @code{name(float)}. To use the
1381 word-completion facilities in this situation, type a single quote
1382 @code{'} at the beginning of the function name. This alerts
1383 @value{GDBN} that it may need to consider more information than usual
1384 when you press @key{TAB} or @kbd{M-?} to request word completion:
1387 (@value{GDBP}) b 'bubble( @kbd{M-?}
1388 bubble(double,double) bubble(int,int)
1389 (@value{GDBP}) b 'bubble(
1392 In some cases, @value{GDBN} can tell that completing a name requires using
1393 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1394 completing as much as it can) if you do not type the quote in the first
1398 (@value{GDBP}) b bub @key{TAB}
1399 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1400 (@value{GDBP}) b 'bubble(
1404 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1405 you have not yet started typing the argument list when you ask for
1406 completion on an overloaded symbol.
1408 For more information about overloaded functions, see @ref{C plus plus
1409 expressions, ,C@t{++} expressions}. You can use the command @code{set
1410 overload-resolution off} to disable overload resolution;
1411 see @ref{Debugging C plus plus, ,@value{GDBN} features for C@t{++}}.
1415 @section Getting help
1416 @cindex online documentation
1419 You can always ask @value{GDBN} itself for information on its commands,
1420 using the command @code{help}.
1423 @kindex h @r{(@code{help})}
1426 You can use @code{help} (abbreviated @code{h}) with no arguments to
1427 display a short list of named classes of commands:
1431 List of classes of commands:
1433 aliases -- Aliases of other commands
1434 breakpoints -- Making program stop at certain points
1435 data -- Examining data
1436 files -- Specifying and examining files
1437 internals -- Maintenance commands
1438 obscure -- Obscure features
1439 running -- Running the program
1440 stack -- Examining the stack
1441 status -- Status inquiries
1442 support -- Support facilities
1443 tracepoints -- Tracing of program execution without@*
1444 stopping the program
1445 user-defined -- User-defined commands
1447 Type "help" followed by a class name for a list of
1448 commands in that class.
1449 Type "help" followed by command name for full
1451 Command name abbreviations are allowed if unambiguous.
1454 @c the above line break eliminates huge line overfull...
1456 @item help @var{class}
1457 Using one of the general help classes as an argument, you can get a
1458 list of the individual commands in that class. For example, here is the
1459 help display for the class @code{status}:
1462 (@value{GDBP}) help status
1467 @c Line break in "show" line falsifies real output, but needed
1468 @c to fit in smallbook page size.
1469 info -- Generic command for showing things
1470 about the program being debugged
1471 show -- Generic command for showing things
1474 Type "help" followed by command name for full
1476 Command name abbreviations are allowed if unambiguous.
1480 @item help @var{command}
1481 With a command name as @code{help} argument, @value{GDBN} displays a
1482 short paragraph on how to use that command.
1485 @item apropos @var{args}
1486 The @code{apropos} command searches through all of the @value{GDBN}
1487 commands, and their documentation, for the regular expression specified in
1488 @var{args}. It prints out all matches found. For example:
1499 set symbol-reloading -- Set dynamic symbol table reloading
1500 multiple times in one run
1501 show symbol-reloading -- Show dynamic symbol table reloading
1502 multiple times in one run
1507 @item complete @var{args}
1508 The @code{complete @var{args}} command lists all the possible completions
1509 for the beginning of a command. Use @var{args} to specify the beginning of the
1510 command you want completed. For example:
1516 @noindent results in:
1527 @noindent This is intended for use by @sc{gnu} Emacs.
1530 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1531 and @code{show} to inquire about the state of your program, or the state
1532 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1533 manual introduces each of them in the appropriate context. The listings
1534 under @code{info} and under @code{show} in the Index point to
1535 all the sub-commands. @xref{Index}.
1540 @kindex i @r{(@code{info})}
1542 This command (abbreviated @code{i}) is for describing the state of your
1543 program. For example, you can list the arguments given to your program
1544 with @code{info args}, list the registers currently in use with @code{info
1545 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1546 You can get a complete list of the @code{info} sub-commands with
1547 @w{@code{help info}}.
1551 You can assign the result of an expression to an environment variable with
1552 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1553 @code{set prompt $}.
1557 In contrast to @code{info}, @code{show} is for describing the state of
1558 @value{GDBN} itself.
1559 You can change most of the things you can @code{show}, by using the
1560 related command @code{set}; for example, you can control what number
1561 system is used for displays with @code{set radix}, or simply inquire
1562 which is currently in use with @code{show radix}.
1565 To display all the settable parameters and their current
1566 values, you can use @code{show} with no arguments; you may also use
1567 @code{info set}. Both commands produce the same display.
1568 @c FIXME: "info set" violates the rule that "info" is for state of
1569 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1570 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1574 Here are three miscellaneous @code{show} subcommands, all of which are
1575 exceptional in lacking corresponding @code{set} commands:
1578 @kindex show version
1579 @cindex @value{GDBN} version number
1581 Show what version of @value{GDBN} is running. You should include this
1582 information in @value{GDBN} bug-reports. If multiple versions of
1583 @value{GDBN} are in use at your site, you may need to determine which
1584 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1585 commands are introduced, and old ones may wither away. Also, many
1586 system vendors ship variant versions of @value{GDBN}, and there are
1587 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1588 The version number is the same as the one announced when you start
1591 @kindex show copying
1592 @kindex info copying
1593 @cindex display @value{GDBN} copyright
1596 Display information about permission for copying @value{GDBN}.
1598 @kindex show warranty
1599 @kindex info warranty
1601 @itemx info warranty
1602 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1603 if your version of @value{GDBN} comes with one.
1608 @chapter Running Programs Under @value{GDBN}
1610 When you run a program under @value{GDBN}, you must first generate
1611 debugging information when you compile it.
1613 You may start @value{GDBN} with its arguments, if any, in an environment
1614 of your choice. If you are doing native debugging, you may redirect
1615 your program's input and output, debug an already running process, or
1616 kill a child process.
1619 * Compilation:: Compiling for debugging
1620 * Starting:: Starting your program
1621 * Arguments:: Your program's arguments
1622 * Environment:: Your program's environment
1624 * Working Directory:: Your program's working directory
1625 * Input/Output:: Your program's input and output
1626 * Attach:: Debugging an already-running process
1627 * Kill Process:: Killing the child process
1629 * Threads:: Debugging programs with multiple threads
1630 * Processes:: Debugging programs with multiple processes
1634 @section Compiling for debugging
1636 In order to debug a program effectively, you need to generate
1637 debugging information when you compile it. This debugging information
1638 is stored in the object file; it describes the data type of each
1639 variable or function and the correspondence between source line numbers
1640 and addresses in the executable code.
1642 To request debugging information, specify the @samp{-g} option when you run
1645 Most compilers do not include information about preprocessor macros in
1646 the debugging information if you specify the @option{-g} flag alone,
1647 because this information is rather large. Version 3.1 of @value{NGCC},
1648 the @sc{gnu} C compiler, provides macro information if you specify the
1649 options @option{-gdwarf-2} and @option{-g3}; the former option requests
1650 debugging information in the Dwarf 2 format, and the latter requests
1651 ``extra information''. In the future, we hope to find more compact ways
1652 to represent macro information, so that it can be included with
1655 Many C compilers are unable to handle the @samp{-g} and @samp{-O}
1656 options together. Using those compilers, you cannot generate optimized
1657 executables containing debugging information.
1659 @value{NGCC}, the @sc{gnu} C compiler, supports @samp{-g} with or
1660 without @samp{-O}, making it possible to debug optimized code. We
1661 recommend that you @emph{always} use @samp{-g} whenever you compile a
1662 program. You may think your program is correct, but there is no sense
1663 in pushing your luck.
1665 @cindex optimized code, debugging
1666 @cindex debugging optimized code
1667 When you debug a program compiled with @samp{-g -O}, remember that the
1668 optimizer is rearranging your code; the debugger shows you what is
1669 really there. Do not be too surprised when the execution path does not
1670 exactly match your source file! An extreme example: if you define a
1671 variable, but never use it, @value{GDBN} never sees that
1672 variable---because the compiler optimizes it out of existence.
1674 Some things do not work as well with @samp{-g -O} as with just
1675 @samp{-g}, particularly on machines with instruction scheduling. If in
1676 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1677 please report it to us as a bug (including a test case!).
1678 @xref{Variables}, for more information about debugging optimized code.
1680 Older versions of the @sc{gnu} C compiler permitted a variant option
1681 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1682 format; if your @sc{gnu} C compiler has this option, do not use it.
1686 @section Starting your program
1692 @kindex r @r{(@code{run})}
1695 Use the @code{run} command to start your program under @value{GDBN}.
1696 You must first specify the program name (except on VxWorks) with an
1697 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1698 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1699 (@pxref{Files, ,Commands to specify files}).
1703 If you are running your program in an execution environment that
1704 supports processes, @code{run} creates an inferior process and makes
1705 that process run your program. (In environments without processes,
1706 @code{run} jumps to the start of your program.)
1708 The execution of a program is affected by certain information it
1709 receives from its superior. @value{GDBN} provides ways to specify this
1710 information, which you must do @emph{before} starting your program. (You
1711 can change it after starting your program, but such changes only affect
1712 your program the next time you start it.) This information may be
1713 divided into four categories:
1716 @item The @emph{arguments.}
1717 Specify the arguments to give your program as the arguments of the
1718 @code{run} command. If a shell is available on your target, the shell
1719 is used to pass the arguments, so that you may use normal conventions
1720 (such as wildcard expansion or variable substitution) in describing
1722 In Unix systems, you can control which shell is used with the
1723 @code{SHELL} environment variable.
1724 @xref{Arguments, ,Your program's arguments}.
1726 @item The @emph{environment.}
1727 Your program normally inherits its environment from @value{GDBN}, but you can
1728 use the @value{GDBN} commands @code{set environment} and @code{unset
1729 environment} to change parts of the environment that affect
1730 your program. @xref{Environment, ,Your program's environment}.
1732 @item The @emph{working directory.}
1733 Your program inherits its working directory from @value{GDBN}. You can set
1734 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1735 @xref{Working Directory, ,Your program's working directory}.
1737 @item The @emph{standard input and output.}
1738 Your program normally uses the same device for standard input and
1739 standard output as @value{GDBN} is using. You can redirect input and output
1740 in the @code{run} command line, or you can use the @code{tty} command to
1741 set a different device for your program.
1742 @xref{Input/Output, ,Your program's input and output}.
1745 @emph{Warning:} While input and output redirection work, you cannot use
1746 pipes to pass the output of the program you are debugging to another
1747 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1751 When you issue the @code{run} command, your program begins to execute
1752 immediately. @xref{Stopping, ,Stopping and continuing}, for discussion
1753 of how to arrange for your program to stop. Once your program has
1754 stopped, you may call functions in your program, using the @code{print}
1755 or @code{call} commands. @xref{Data, ,Examining Data}.
1757 If the modification time of your symbol file has changed since the last
1758 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1759 table, and reads it again. When it does this, @value{GDBN} tries to retain
1760 your current breakpoints.
1765 @cindex run to main procedure
1766 The name of the main procedure can vary from language to language.
1767 With C or C@t{++}, the main procedure name is always @code{main}, but
1768 other languages such as Ada do not require a specific name for their
1769 main procedure. The debugger provides a convenient way to start the
1770 execution of the program and to stop at the beginning of the main
1771 procedure, depending on the language used.
1773 The @samp{start} command does the equivalent of setting a temporary
1774 breakpoint at the beginning of the main procedure and then invoking
1775 the @samp{run} command.
1777 @cindex elaboration phase
1778 Some programs contain an @dfn{elaboration} phase where some startup code is
1779 executed before the main procedure is called. This depends on the
1780 languages used to write your program. In C@t{++}, for instance,
1781 constructors for static and global objects are executed before
1782 @code{main} is called. It is therefore possible that the debugger stops
1783 before reaching the main procedure. However, the temporary breakpoint
1784 will remain to halt execution.
1786 Specify the arguments to give to your program as arguments to the
1787 @samp{start} command. These arguments will be given verbatim to the
1788 underlying @samp{run} command. Note that the same arguments will be
1789 reused if no argument is provided during subsequent calls to
1790 @samp{start} or @samp{run}.
1792 It is sometimes necessary to debug the program during elaboration. In
1793 these cases, using the @code{start} command would stop the execution of
1794 your program too late, as the program would have already completed the
1795 elaboration phase. Under these circumstances, insert breakpoints in your
1796 elaboration code before running your program.
1800 @section Your program's arguments
1802 @cindex arguments (to your program)
1803 The arguments to your program can be specified by the arguments of the
1805 They are passed to a shell, which expands wildcard characters and
1806 performs redirection of I/O, and thence to your program. Your
1807 @code{SHELL} environment variable (if it exists) specifies what shell
1808 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1809 the default shell (@file{/bin/sh} on Unix).
1811 On non-Unix systems, the program is usually invoked directly by
1812 @value{GDBN}, which emulates I/O redirection via the appropriate system
1813 calls, and the wildcard characters are expanded by the startup code of
1814 the program, not by the shell.
1816 @code{run} with no arguments uses the same arguments used by the previous
1817 @code{run}, or those set by the @code{set args} command.
1822 Specify the arguments to be used the next time your program is run. If
1823 @code{set args} has no arguments, @code{run} executes your program
1824 with no arguments. Once you have run your program with arguments,
1825 using @code{set args} before the next @code{run} is the only way to run
1826 it again without arguments.
1830 Show the arguments to give your program when it is started.
1834 @section Your program's environment
1836 @cindex environment (of your program)
1837 The @dfn{environment} consists of a set of environment variables and
1838 their values. Environment variables conventionally record such things as
1839 your user name, your home directory, your terminal type, and your search
1840 path for programs to run. Usually you set up environment variables with
1841 the shell and they are inherited by all the other programs you run. When
1842 debugging, it can be useful to try running your program with a modified
1843 environment without having to start @value{GDBN} over again.
1847 @item path @var{directory}
1848 Add @var{directory} to the front of the @code{PATH} environment variable
1849 (the search path for executables) that will be passed to your program.
1850 The value of @code{PATH} used by @value{GDBN} does not change.
1851 You may specify several directory names, separated by whitespace or by a
1852 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1853 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1854 is moved to the front, so it is searched sooner.
1856 You can use the string @samp{$cwd} to refer to whatever is the current
1857 working directory at the time @value{GDBN} searches the path. If you
1858 use @samp{.} instead, it refers to the directory where you executed the
1859 @code{path} command. @value{GDBN} replaces @samp{.} in the
1860 @var{directory} argument (with the current path) before adding
1861 @var{directory} to the search path.
1862 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1863 @c document that, since repeating it would be a no-op.
1867 Display the list of search paths for executables (the @code{PATH}
1868 environment variable).
1870 @kindex show environment
1871 @item show environment @r{[}@var{varname}@r{]}
1872 Print the value of environment variable @var{varname} to be given to
1873 your program when it starts. If you do not supply @var{varname},
1874 print the names and values of all environment variables to be given to
1875 your program. You can abbreviate @code{environment} as @code{env}.
1877 @kindex set environment
1878 @item set environment @var{varname} @r{[}=@var{value}@r{]}
1879 Set environment variable @var{varname} to @var{value}. The value
1880 changes for your program only, not for @value{GDBN} itself. @var{value} may
1881 be any string; the values of environment variables are just strings, and
1882 any interpretation is supplied by your program itself. The @var{value}
1883 parameter is optional; if it is eliminated, the variable is set to a
1885 @c "any string" here does not include leading, trailing
1886 @c blanks. Gnu asks: does anyone care?
1888 For example, this command:
1895 tells the debugged program, when subsequently run, that its user is named
1896 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
1897 are not actually required.)
1899 @kindex unset environment
1900 @item unset environment @var{varname}
1901 Remove variable @var{varname} from the environment to be passed to your
1902 program. This is different from @samp{set env @var{varname} =};
1903 @code{unset environment} removes the variable from the environment,
1904 rather than assigning it an empty value.
1907 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
1909 by your @code{SHELL} environment variable if it exists (or
1910 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
1911 that runs an initialization file---such as @file{.cshrc} for C-shell, or
1912 @file{.bashrc} for BASH---any variables you set in that file affect
1913 your program. You may wish to move setting of environment variables to
1914 files that are only run when you sign on, such as @file{.login} or
1917 @node Working Directory
1918 @section Your program's working directory
1920 @cindex working directory (of your program)
1921 Each time you start your program with @code{run}, it inherits its
1922 working directory from the current working directory of @value{GDBN}.
1923 The @value{GDBN} working directory is initially whatever it inherited
1924 from its parent process (typically the shell), but you can specify a new
1925 working directory in @value{GDBN} with the @code{cd} command.
1927 The @value{GDBN} working directory also serves as a default for the commands
1928 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
1933 @item cd @var{directory}
1934 Set the @value{GDBN} working directory to @var{directory}.
1938 Print the @value{GDBN} working directory.
1941 It is generally impossible to find the current working directory of
1942 the process being debugged (since a program can change its directory
1943 during its run). If you work on a system where @value{GDBN} is
1944 configured with the @file{/proc} support, you can use the @code{info
1945 proc} command (@pxref{SVR4 Process Information}) to find out the
1946 current working directory of the debuggee.
1949 @section Your program's input and output
1954 By default, the program you run under @value{GDBN} does input and output to
1955 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
1956 to its own terminal modes to interact with you, but it records the terminal
1957 modes your program was using and switches back to them when you continue
1958 running your program.
1961 @kindex info terminal
1963 Displays information recorded by @value{GDBN} about the terminal modes your
1967 You can redirect your program's input and/or output using shell
1968 redirection with the @code{run} command. For example,
1975 starts your program, diverting its output to the file @file{outfile}.
1978 @cindex controlling terminal
1979 Another way to specify where your program should do input and output is
1980 with the @code{tty} command. This command accepts a file name as
1981 argument, and causes this file to be the default for future @code{run}
1982 commands. It also resets the controlling terminal for the child
1983 process, for future @code{run} commands. For example,
1990 directs that processes started with subsequent @code{run} commands
1991 default to do input and output on the terminal @file{/dev/ttyb} and have
1992 that as their controlling terminal.
1994 An explicit redirection in @code{run} overrides the @code{tty} command's
1995 effect on the input/output device, but not its effect on the controlling
1998 When you use the @code{tty} command or redirect input in the @code{run}
1999 command, only the input @emph{for your program} is affected. The input
2000 for @value{GDBN} still comes from your terminal.
2003 @section Debugging an already-running process
2008 @item attach @var{process-id}
2009 This command attaches to a running process---one that was started
2010 outside @value{GDBN}. (@code{info files} shows your active
2011 targets.) The command takes as argument a process ID. The usual way to
2012 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2013 or with the @samp{jobs -l} shell command.
2015 @code{attach} does not repeat if you press @key{RET} a second time after
2016 executing the command.
2019 To use @code{attach}, your program must be running in an environment
2020 which supports processes; for example, @code{attach} does not work for
2021 programs on bare-board targets that lack an operating system. You must
2022 also have permission to send the process a signal.
2024 When you use @code{attach}, the debugger finds the program running in
2025 the process first by looking in the current working directory, then (if
2026 the program is not found) by using the source file search path
2027 (@pxref{Source Path, ,Specifying source directories}). You can also use
2028 the @code{file} command to load the program. @xref{Files, ,Commands to
2031 The first thing @value{GDBN} does after arranging to debug the specified
2032 process is to stop it. You can examine and modify an attached process
2033 with all the @value{GDBN} commands that are ordinarily available when
2034 you start processes with @code{run}. You can insert breakpoints; you
2035 can step and continue; you can modify storage. If you would rather the
2036 process continue running, you may use the @code{continue} command after
2037 attaching @value{GDBN} to the process.
2042 When you have finished debugging the attached process, you can use the
2043 @code{detach} command to release it from @value{GDBN} control. Detaching
2044 the process continues its execution. After the @code{detach} command,
2045 that process and @value{GDBN} become completely independent once more, and you
2046 are ready to @code{attach} another process or start one with @code{run}.
2047 @code{detach} does not repeat if you press @key{RET} again after
2048 executing the command.
2051 If you exit @value{GDBN} or use the @code{run} command while you have an
2052 attached process, you kill that process. By default, @value{GDBN} asks
2053 for confirmation if you try to do either of these things; you can
2054 control whether or not you need to confirm by using the @code{set
2055 confirm} command (@pxref{Messages/Warnings, ,Optional warnings and
2059 @section Killing the child process
2064 Kill the child process in which your program is running under @value{GDBN}.
2067 This command is useful if you wish to debug a core dump instead of a
2068 running process. @value{GDBN} ignores any core dump file while your program
2071 On some operating systems, a program cannot be executed outside @value{GDBN}
2072 while you have breakpoints set on it inside @value{GDBN}. You can use the
2073 @code{kill} command in this situation to permit running your program
2074 outside the debugger.
2076 The @code{kill} command is also useful if you wish to recompile and
2077 relink your program, since on many systems it is impossible to modify an
2078 executable file while it is running in a process. In this case, when you
2079 next type @code{run}, @value{GDBN} notices that the file has changed, and
2080 reads the symbol table again (while trying to preserve your current
2081 breakpoint settings).
2084 @section Debugging programs with multiple threads
2086 @cindex threads of execution
2087 @cindex multiple threads
2088 @cindex switching threads
2089 In some operating systems, such as HP-UX and Solaris, a single program
2090 may have more than one @dfn{thread} of execution. The precise semantics
2091 of threads differ from one operating system to another, but in general
2092 the threads of a single program are akin to multiple processes---except
2093 that they share one address space (that is, they can all examine and
2094 modify the same variables). On the other hand, each thread has its own
2095 registers and execution stack, and perhaps private memory.
2097 @value{GDBN} provides these facilities for debugging multi-thread
2101 @item automatic notification of new threads
2102 @item @samp{thread @var{threadno}}, a command to switch among threads
2103 @item @samp{info threads}, a command to inquire about existing threads
2104 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2105 a command to apply a command to a list of threads
2106 @item thread-specific breakpoints
2110 @emph{Warning:} These facilities are not yet available on every
2111 @value{GDBN} configuration where the operating system supports threads.
2112 If your @value{GDBN} does not support threads, these commands have no
2113 effect. For example, a system without thread support shows no output
2114 from @samp{info threads}, and always rejects the @code{thread} command,
2118 (@value{GDBP}) info threads
2119 (@value{GDBP}) thread 1
2120 Thread ID 1 not known. Use the "info threads" command to
2121 see the IDs of currently known threads.
2123 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2124 @c doesn't support threads"?
2127 @cindex focus of debugging
2128 @cindex current thread
2129 The @value{GDBN} thread debugging facility allows you to observe all
2130 threads while your program runs---but whenever @value{GDBN} takes
2131 control, one thread in particular is always the focus of debugging.
2132 This thread is called the @dfn{current thread}. Debugging commands show
2133 program information from the perspective of the current thread.
2135 @cindex @code{New} @var{systag} message
2136 @cindex thread identifier (system)
2137 @c FIXME-implementors!! It would be more helpful if the [New...] message
2138 @c included GDB's numeric thread handle, so you could just go to that
2139 @c thread without first checking `info threads'.
2140 Whenever @value{GDBN} detects a new thread in your program, it displays
2141 the target system's identification for the thread with a message in the
2142 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2143 whose form varies depending on the particular system. For example, on
2144 LynxOS, you might see
2147 [New process 35 thread 27]
2151 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2152 the @var{systag} is simply something like @samp{process 368}, with no
2155 @c FIXME!! (1) Does the [New...] message appear even for the very first
2156 @c thread of a program, or does it only appear for the
2157 @c second---i.e.@: when it becomes obvious we have a multithread
2159 @c (2) *Is* there necessarily a first thread always? Or do some
2160 @c multithread systems permit starting a program with multiple
2161 @c threads ab initio?
2163 @cindex thread number
2164 @cindex thread identifier (GDB)
2165 For debugging purposes, @value{GDBN} associates its own thread
2166 number---always a single integer---with each thread in your program.
2169 @kindex info threads
2171 Display a summary of all threads currently in your
2172 program. @value{GDBN} displays for each thread (in this order):
2176 the thread number assigned by @value{GDBN}
2179 the target system's thread identifier (@var{systag})
2182 the current stack frame summary for that thread
2186 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2187 indicates the current thread.
2191 @c end table here to get a little more width for example
2194 (@value{GDBP}) info threads
2195 3 process 35 thread 27 0x34e5 in sigpause ()
2196 2 process 35 thread 23 0x34e5 in sigpause ()
2197 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2203 @cindex debugging multithreaded programs (on HP-UX)
2204 @cindex thread identifier (GDB), on HP-UX
2205 For debugging purposes, @value{GDBN} associates its own thread
2206 number---a small integer assigned in thread-creation order---with each
2207 thread in your program.
2209 @cindex @code{New} @var{systag} message, on HP-UX
2210 @cindex thread identifier (system), on HP-UX
2211 @c FIXME-implementors!! It would be more helpful if the [New...] message
2212 @c included GDB's numeric thread handle, so you could just go to that
2213 @c thread without first checking `info threads'.
2214 Whenever @value{GDBN} detects a new thread in your program, it displays
2215 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2216 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2217 whose form varies depending on the particular system. For example, on
2221 [New thread 2 (system thread 26594)]
2225 when @value{GDBN} notices a new thread.
2228 @kindex info threads (HP-UX)
2230 Display a summary of all threads currently in your
2231 program. @value{GDBN} displays for each thread (in this order):
2234 @item the thread number assigned by @value{GDBN}
2236 @item the target system's thread identifier (@var{systag})
2238 @item the current stack frame summary for that thread
2242 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2243 indicates the current thread.
2247 @c end table here to get a little more width for example
2250 (@value{GDBP}) info threads
2251 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2253 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2254 from /usr/lib/libc.2
2255 1 system thread 27905 0x7b003498 in _brk () \@*
2256 from /usr/lib/libc.2
2260 @kindex thread @var{threadno}
2261 @item thread @var{threadno}
2262 Make thread number @var{threadno} the current thread. The command
2263 argument @var{threadno} is the internal @value{GDBN} thread number, as
2264 shown in the first field of the @samp{info threads} display.
2265 @value{GDBN} responds by displaying the system identifier of the thread
2266 you selected, and its current stack frame summary:
2269 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2270 (@value{GDBP}) thread 2
2271 [Switching to process 35 thread 23]
2272 0x34e5 in sigpause ()
2276 As with the @samp{[New @dots{}]} message, the form of the text after
2277 @samp{Switching to} depends on your system's conventions for identifying
2280 @kindex thread apply
2281 @item thread apply [@var{threadno}] [@var{all}] @var{args}
2282 The @code{thread apply} command allows you to apply a command to one or
2283 more threads. Specify the numbers of the threads that you want affected
2284 with the command argument @var{threadno}. @var{threadno} is the internal
2285 @value{GDBN} thread number, as shown in the first field of the @samp{info
2286 threads} display. To apply a command to all threads, use
2287 @code{thread apply all} @var{args}.
2290 @cindex automatic thread selection
2291 @cindex switching threads automatically
2292 @cindex threads, automatic switching
2293 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2294 signal, it automatically selects the thread where that breakpoint or
2295 signal happened. @value{GDBN} alerts you to the context switch with a
2296 message of the form @samp{[Switching to @var{systag}]} to identify the
2299 @xref{Thread Stops,,Stopping and starting multi-thread programs}, for
2300 more information about how @value{GDBN} behaves when you stop and start
2301 programs with multiple threads.
2303 @xref{Set Watchpoints,,Setting watchpoints}, for information about
2304 watchpoints in programs with multiple threads.
2307 @section Debugging programs with multiple processes
2309 @cindex fork, debugging programs which call
2310 @cindex multiple processes
2311 @cindex processes, multiple
2312 On most systems, @value{GDBN} has no special support for debugging
2313 programs which create additional processes using the @code{fork}
2314 function. When a program forks, @value{GDBN} will continue to debug the
2315 parent process and the child process will run unimpeded. If you have
2316 set a breakpoint in any code which the child then executes, the child
2317 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2318 will cause it to terminate.
2320 However, if you want to debug the child process there is a workaround
2321 which isn't too painful. Put a call to @code{sleep} in the code which
2322 the child process executes after the fork. It may be useful to sleep
2323 only if a certain environment variable is set, or a certain file exists,
2324 so that the delay need not occur when you don't want to run @value{GDBN}
2325 on the child. While the child is sleeping, use the @code{ps} program to
2326 get its process ID. Then tell @value{GDBN} (a new invocation of
2327 @value{GDBN} if you are also debugging the parent process) to attach to
2328 the child process (@pxref{Attach}). From that point on you can debug
2329 the child process just like any other process which you attached to.
2331 On some systems, @value{GDBN} provides support for debugging programs that
2332 create additional processes using the @code{fork} or @code{vfork} functions.
2333 Currently, the only platforms with this feature are HP-UX (11.x and later
2334 only?) and GNU/Linux (kernel version 2.5.60 and later).
2336 By default, when a program forks, @value{GDBN} will continue to debug
2337 the parent process and the child process will run unimpeded.
2339 If you want to follow the child process instead of the parent process,
2340 use the command @w{@code{set follow-fork-mode}}.
2343 @kindex set follow-fork-mode
2344 @item set follow-fork-mode @var{mode}
2345 Set the debugger response to a program call of @code{fork} or
2346 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2347 process. The @var{mode} argument can be:
2351 The original process is debugged after a fork. The child process runs
2352 unimpeded. This is the default.
2355 The new process is debugged after a fork. The parent process runs
2360 @kindex show follow-fork-mode
2361 @item show follow-fork-mode
2362 Display the current debugger response to a @code{fork} or @code{vfork} call.
2365 If you ask to debug a child process and a @code{vfork} is followed by an
2366 @code{exec}, @value{GDBN} executes the new target up to the first
2367 breakpoint in the new target. If you have a breakpoint set on
2368 @code{main} in your original program, the breakpoint will also be set on
2369 the child process's @code{main}.
2371 When a child process is spawned by @code{vfork}, you cannot debug the
2372 child or parent until an @code{exec} call completes.
2374 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2375 call executes, the new target restarts. To restart the parent process,
2376 use the @code{file} command with the parent executable name as its
2379 You can use the @code{catch} command to make @value{GDBN} stop whenever
2380 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2381 Catchpoints, ,Setting catchpoints}.
2384 @chapter Stopping and Continuing
2386 The principal purposes of using a debugger are so that you can stop your
2387 program before it terminates; or so that, if your program runs into
2388 trouble, you can investigate and find out why.
2390 Inside @value{GDBN}, your program may stop for any of several reasons,
2391 such as a signal, a breakpoint, or reaching a new line after a
2392 @value{GDBN} command such as @code{step}. You may then examine and
2393 change variables, set new breakpoints or remove old ones, and then
2394 continue execution. Usually, the messages shown by @value{GDBN} provide
2395 ample explanation of the status of your program---but you can also
2396 explicitly request this information at any time.
2399 @kindex info program
2401 Display information about the status of your program: whether it is
2402 running or not, what process it is, and why it stopped.
2406 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2407 * Continuing and Stepping:: Resuming execution
2409 * Thread Stops:: Stopping and starting multi-thread programs
2413 @section Breakpoints, watchpoints, and catchpoints
2416 A @dfn{breakpoint} makes your program stop whenever a certain point in
2417 the program is reached. For each breakpoint, you can add conditions to
2418 control in finer detail whether your program stops. You can set
2419 breakpoints with the @code{break} command and its variants (@pxref{Set
2420 Breaks, ,Setting breakpoints}), to specify the place where your program
2421 should stop by line number, function name or exact address in the
2424 On some systems, you can set breakpoints in shared libraries before
2425 the executable is run. There is a minor limitation on HP-UX systems:
2426 you must wait until the executable is run in order to set breakpoints
2427 in shared library routines that are not called directly by the program
2428 (for example, routines that are arguments in a @code{pthread_create}
2432 @cindex memory tracing
2433 @cindex breakpoint on memory address
2434 @cindex breakpoint on variable modification
2435 A @dfn{watchpoint} is a special breakpoint that stops your program
2436 when the value of an expression changes. You must use a different
2437 command to set watchpoints (@pxref{Set Watchpoints, ,Setting
2438 watchpoints}), but aside from that, you can manage a watchpoint like
2439 any other breakpoint: you enable, disable, and delete both breakpoints
2440 and watchpoints using the same commands.
2442 You can arrange to have values from your program displayed automatically
2443 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2447 @cindex breakpoint on events
2448 A @dfn{catchpoint} is another special breakpoint that stops your program
2449 when a certain kind of event occurs, such as the throwing of a C@t{++}
2450 exception or the loading of a library. As with watchpoints, you use a
2451 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2452 catchpoints}), but aside from that, you can manage a catchpoint like any
2453 other breakpoint. (To stop when your program receives a signal, use the
2454 @code{handle} command; see @ref{Signals, ,Signals}.)
2456 @cindex breakpoint numbers
2457 @cindex numbers for breakpoints
2458 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2459 catchpoint when you create it; these numbers are successive integers
2460 starting with one. In many of the commands for controlling various
2461 features of breakpoints you use the breakpoint number to say which
2462 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2463 @dfn{disabled}; if disabled, it has no effect on your program until you
2466 @cindex breakpoint ranges
2467 @cindex ranges of breakpoints
2468 Some @value{GDBN} commands accept a range of breakpoints on which to
2469 operate. A breakpoint range is either a single breakpoint number, like
2470 @samp{5}, or two such numbers, in increasing order, separated by a
2471 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2472 all breakpoint in that range are operated on.
2475 * Set Breaks:: Setting breakpoints
2476 * Set Watchpoints:: Setting watchpoints
2477 * Set Catchpoints:: Setting catchpoints
2478 * Delete Breaks:: Deleting breakpoints
2479 * Disabling:: Disabling breakpoints
2480 * Conditions:: Break conditions
2481 * Break Commands:: Breakpoint command lists
2482 * Breakpoint Menus:: Breakpoint menus
2483 * Error in Breakpoints:: ``Cannot insert breakpoints''
2484 * Breakpoint related warnings:: ``Breakpoint address adjusted...''
2488 @subsection Setting breakpoints
2490 @c FIXME LMB what does GDB do if no code on line of breakpt?
2491 @c consider in particular declaration with/without initialization.
2493 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2496 @kindex b @r{(@code{break})}
2497 @vindex $bpnum@r{, convenience variable}
2498 @cindex latest breakpoint
2499 Breakpoints are set with the @code{break} command (abbreviated
2500 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2501 number of the breakpoint you've set most recently; see @ref{Convenience
2502 Vars,, Convenience variables}, for a discussion of what you can do with
2503 convenience variables.
2505 You have several ways to say where the breakpoint should go.
2508 @item break @var{function}
2509 Set a breakpoint at entry to function @var{function}.
2510 When using source languages that permit overloading of symbols, such as
2511 C@t{++}, @var{function} may refer to more than one possible place to break.
2512 @xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
2514 @item break +@var{offset}
2515 @itemx break -@var{offset}
2516 Set a breakpoint some number of lines forward or back from the position
2517 at which execution stopped in the currently selected @dfn{stack frame}.
2518 (@xref{Frames, ,Frames}, for a description of stack frames.)
2520 @item break @var{linenum}
2521 Set a breakpoint at line @var{linenum} in the current source file.
2522 The current source file is the last file whose source text was printed.
2523 The breakpoint will stop your program just before it executes any of the
2526 @item break @var{filename}:@var{linenum}
2527 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2529 @item break @var{filename}:@var{function}
2530 Set a breakpoint at entry to function @var{function} found in file
2531 @var{filename}. Specifying a file name as well as a function name is
2532 superfluous except when multiple files contain similarly named
2535 @item break *@var{address}
2536 Set a breakpoint at address @var{address}. You can use this to set
2537 breakpoints in parts of your program which do not have debugging
2538 information or source files.
2541 When called without any arguments, @code{break} sets a breakpoint at
2542 the next instruction to be executed in the selected stack frame
2543 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2544 innermost, this makes your program stop as soon as control
2545 returns to that frame. This is similar to the effect of a
2546 @code{finish} command in the frame inside the selected frame---except
2547 that @code{finish} does not leave an active breakpoint. If you use
2548 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2549 the next time it reaches the current location; this may be useful
2552 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2553 least one instruction has been executed. If it did not do this, you
2554 would be unable to proceed past a breakpoint without first disabling the
2555 breakpoint. This rule applies whether or not the breakpoint already
2556 existed when your program stopped.
2558 @item break @dots{} if @var{cond}
2559 Set a breakpoint with condition @var{cond}; evaluate the expression
2560 @var{cond} each time the breakpoint is reached, and stop only if the
2561 value is nonzero---that is, if @var{cond} evaluates as true.
2562 @samp{@dots{}} stands for one of the possible arguments described
2563 above (or no argument) specifying where to break. @xref{Conditions,
2564 ,Break conditions}, for more information on breakpoint conditions.
2567 @item tbreak @var{args}
2568 Set a breakpoint enabled only for one stop. @var{args} are the
2569 same as for the @code{break} command, and the breakpoint is set in the same
2570 way, but the breakpoint is automatically deleted after the first time your
2571 program stops there. @xref{Disabling, ,Disabling breakpoints}.
2574 @item hbreak @var{args}
2575 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2576 @code{break} command and the breakpoint is set in the same way, but the
2577 breakpoint requires hardware support and some target hardware may not
2578 have this support. The main purpose of this is EPROM/ROM code
2579 debugging, so you can set a breakpoint at an instruction without
2580 changing the instruction. This can be used with the new trap-generation
2581 provided by SPARClite DSU and most x86-based targets. These targets
2582 will generate traps when a program accesses some data or instruction
2583 address that is assigned to the debug registers. However the hardware
2584 breakpoint registers can take a limited number of breakpoints. For
2585 example, on the DSU, only two data breakpoints can be set at a time, and
2586 @value{GDBN} will reject this command if more than two are used. Delete
2587 or disable unused hardware breakpoints before setting new ones
2588 (@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}.
2589 For remote targets, you can restrict the number of hardware
2590 breakpoints @value{GDBN} will use, see @ref{set remote
2591 hardware-breakpoint-limit}.
2595 @item thbreak @var{args}
2596 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2597 are the same as for the @code{hbreak} command and the breakpoint is set in
2598 the same way. However, like the @code{tbreak} command,
2599 the breakpoint is automatically deleted after the
2600 first time your program stops there. Also, like the @code{hbreak}
2601 command, the breakpoint requires hardware support and some target hardware
2602 may not have this support. @xref{Disabling, ,Disabling breakpoints}.
2603 See also @ref{Conditions, ,Break conditions}.
2606 @cindex regular expression
2607 @item rbreak @var{regex}
2608 Set breakpoints on all functions matching the regular expression
2609 @var{regex}. This command sets an unconditional breakpoint on all
2610 matches, printing a list of all breakpoints it set. Once these
2611 breakpoints are set, they are treated just like the breakpoints set with
2612 the @code{break} command. You can delete them, disable them, or make
2613 them conditional the same way as any other breakpoint.
2615 The syntax of the regular expression is the standard one used with tools
2616 like @file{grep}. Note that this is different from the syntax used by
2617 shells, so for instance @code{foo*} matches all functions that include
2618 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2619 @code{.*} leading and trailing the regular expression you supply, so to
2620 match only functions that begin with @code{foo}, use @code{^foo}.
2622 @cindex non-member C@t{++} functions, set breakpoint in
2623 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2624 breakpoints on overloaded functions that are not members of any special
2627 @cindex set breakpoints on all functions
2628 The @code{rbreak} command can be used to set breakpoints in
2629 @strong{all} the functions in a program, like this:
2632 (@value{GDBP}) rbreak .
2635 @kindex info breakpoints
2636 @cindex @code{$_} and @code{info breakpoints}
2637 @item info breakpoints @r{[}@var{n}@r{]}
2638 @itemx info break @r{[}@var{n}@r{]}
2639 @itemx info watchpoints @r{[}@var{n}@r{]}
2640 Print a table of all breakpoints, watchpoints, and catchpoints set and
2641 not deleted, with the following columns for each breakpoint:
2644 @item Breakpoint Numbers
2646 Breakpoint, watchpoint, or catchpoint.
2648 Whether the breakpoint is marked to be disabled or deleted when hit.
2649 @item Enabled or Disabled
2650 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2651 that are not enabled.
2653 Where the breakpoint is in your program, as a memory address. If the
2654 breakpoint is pending (see below for details) on a future load of a shared library, the address
2655 will be listed as @samp{<PENDING>}.
2657 Where the breakpoint is in the source for your program, as a file and
2658 line number. For a pending breakpoint, the original string passed to
2659 the breakpoint command will be listed as it cannot be resolved until
2660 the appropriate shared library is loaded in the future.
2664 If a breakpoint is conditional, @code{info break} shows the condition on
2665 the line following the affected breakpoint; breakpoint commands, if any,
2666 are listed after that. A pending breakpoint is allowed to have a condition
2667 specified for it. The condition is not parsed for validity until a shared
2668 library is loaded that allows the pending breakpoint to resolve to a
2672 @code{info break} with a breakpoint
2673 number @var{n} as argument lists only that breakpoint. The
2674 convenience variable @code{$_} and the default examining-address for
2675 the @code{x} command are set to the address of the last breakpoint
2676 listed (@pxref{Memory, ,Examining memory}).
2679 @code{info break} displays a count of the number of times the breakpoint
2680 has been hit. This is especially useful in conjunction with the
2681 @code{ignore} command. You can ignore a large number of breakpoint
2682 hits, look at the breakpoint info to see how many times the breakpoint
2683 was hit, and then run again, ignoring one less than that number. This
2684 will get you quickly to the last hit of that breakpoint.
2687 @value{GDBN} allows you to set any number of breakpoints at the same place in
2688 your program. There is nothing silly or meaningless about this. When
2689 the breakpoints are conditional, this is even useful
2690 (@pxref{Conditions, ,Break conditions}).
2692 @cindex pending breakpoints
2693 If a specified breakpoint location cannot be found, it may be due to the fact
2694 that the location is in a shared library that is yet to be loaded. In such
2695 a case, you may want @value{GDBN} to create a special breakpoint (known as
2696 a @dfn{pending breakpoint}) that
2697 attempts to resolve itself in the future when an appropriate shared library
2700 Pending breakpoints are useful to set at the start of your
2701 @value{GDBN} session for locations that you know will be dynamically loaded
2702 later by the program being debugged. When shared libraries are loaded,
2703 a check is made to see if the load resolves any pending breakpoint locations.
2704 If a pending breakpoint location gets resolved,
2705 a regular breakpoint is created and the original pending breakpoint is removed.
2707 @value{GDBN} provides some additional commands for controlling pending
2710 @kindex set breakpoint pending
2711 @kindex show breakpoint pending
2713 @item set breakpoint pending auto
2714 This is the default behavior. When @value{GDBN} cannot find the breakpoint
2715 location, it queries you whether a pending breakpoint should be created.
2717 @item set breakpoint pending on
2718 This indicates that an unrecognized breakpoint location should automatically
2719 result in a pending breakpoint being created.
2721 @item set breakpoint pending off
2722 This indicates that pending breakpoints are not to be created. Any
2723 unrecognized breakpoint location results in an error. This setting does
2724 not affect any pending breakpoints previously created.
2726 @item show breakpoint pending
2727 Show the current behavior setting for creating pending breakpoints.
2730 @cindex operations allowed on pending breakpoints
2731 Normal breakpoint operations apply to pending breakpoints as well. You may
2732 specify a condition for a pending breakpoint and/or commands to run when the
2733 breakpoint is reached. You can also enable or disable
2734 the pending breakpoint. When you specify a condition for a pending breakpoint,
2735 the parsing of the condition will be deferred until the point where the
2736 pending breakpoint location is resolved. Disabling a pending breakpoint
2737 tells @value{GDBN} to not attempt to resolve the breakpoint on any subsequent
2738 shared library load. When a pending breakpoint is re-enabled,
2739 @value{GDBN} checks to see if the location is already resolved.
2740 This is done because any number of shared library loads could have
2741 occurred since the time the breakpoint was disabled and one or more
2742 of these loads could resolve the location.
2744 @cindex negative breakpoint numbers
2745 @cindex internal @value{GDBN} breakpoints
2746 @value{GDBN} itself sometimes sets breakpoints in your program for
2747 special purposes, such as proper handling of @code{longjmp} (in C
2748 programs). These internal breakpoints are assigned negative numbers,
2749 starting with @code{-1}; @samp{info breakpoints} does not display them.
2750 You can see these breakpoints with the @value{GDBN} maintenance command
2751 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
2754 @node Set Watchpoints
2755 @subsection Setting watchpoints
2757 @cindex setting watchpoints
2758 You can use a watchpoint to stop execution whenever the value of an
2759 expression changes, without having to predict a particular place where
2762 @cindex software watchpoints
2763 @cindex hardware watchpoints
2764 Depending on your system, watchpoints may be implemented in software or
2765 hardware. @value{GDBN} does software watchpointing by single-stepping your
2766 program and testing the variable's value each time, which is hundreds of
2767 times slower than normal execution. (But this may still be worth it, to
2768 catch errors where you have no clue what part of your program is the
2771 On some systems, such as HP-UX, @sc{gnu}/Linux and most other
2772 x86-based targets, @value{GDBN} includes support for hardware
2773 watchpoints, which do not slow down the running of your program.
2777 @item watch @var{expr}
2778 Set a watchpoint for an expression. @value{GDBN} will break when @var{expr}
2779 is written into by the program and its value changes.
2782 @item rwatch @var{expr}
2783 Set a watchpoint that will break when the value of @var{expr} is read
2787 @item awatch @var{expr}
2788 Set a watchpoint that will break when @var{expr} is either read from
2789 or written into by the program.
2791 @kindex info watchpoints
2792 @item info watchpoints
2793 This command prints a list of watchpoints, breakpoints, and catchpoints;
2794 it is the same as @code{info break} (@pxref{Set Breaks}).
2797 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
2798 watchpoints execute very quickly, and the debugger reports a change in
2799 value at the exact instruction where the change occurs. If @value{GDBN}
2800 cannot set a hardware watchpoint, it sets a software watchpoint, which
2801 executes more slowly and reports the change in value at the next
2802 @emph{statement}, not the instruction, after the change occurs.
2804 @vindex can-use-hw-watchpoints
2805 @cindex use only software watchpoints
2806 You can force @value{GDBN} to use only software watchpoints with the
2807 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
2808 zero, @value{GDBN} will never try to use hardware watchpoints, even if
2809 the underlying system supports them. (Note that hardware-assisted
2810 watchpoints that were set @emph{before} setting
2811 @code{can-use-hw-watchpoints} to zero will still use the hardware
2812 mechanism of watching expressiion values.)
2815 @item set can-use-hw-watchpoints
2816 @kindex set can-use-hw-watchpoints
2817 Set whether or not to use hardware watchpoints.
2819 @item show can-use-hw-watchpoints
2820 @kindex show can-use-hw-watchpoints
2821 Show the current mode of using hardware watchpoints.
2824 For remote targets, you can restrict the number of hardware
2825 watchpoints @value{GDBN} will use, see @ref{set remote
2826 hardware-breakpoint-limit}.
2828 When you issue the @code{watch} command, @value{GDBN} reports
2831 Hardware watchpoint @var{num}: @var{expr}
2835 if it was able to set a hardware watchpoint.
2837 Currently, the @code{awatch} and @code{rwatch} commands can only set
2838 hardware watchpoints, because accesses to data that don't change the
2839 value of the watched expression cannot be detected without examining
2840 every instruction as it is being executed, and @value{GDBN} does not do
2841 that currently. If @value{GDBN} finds that it is unable to set a
2842 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
2843 will print a message like this:
2846 Expression cannot be implemented with read/access watchpoint.
2849 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
2850 data type of the watched expression is wider than what a hardware
2851 watchpoint on the target machine can handle. For example, some systems
2852 can only watch regions that are up to 4 bytes wide; on such systems you
2853 cannot set hardware watchpoints for an expression that yields a
2854 double-precision floating-point number (which is typically 8 bytes
2855 wide). As a work-around, it might be possible to break the large region
2856 into a series of smaller ones and watch them with separate watchpoints.
2858 If you set too many hardware watchpoints, @value{GDBN} might be unable
2859 to insert all of them when you resume the execution of your program.
2860 Since the precise number of active watchpoints is unknown until such
2861 time as the program is about to be resumed, @value{GDBN} might not be
2862 able to warn you about this when you set the watchpoints, and the
2863 warning will be printed only when the program is resumed:
2866 Hardware watchpoint @var{num}: Could not insert watchpoint
2870 If this happens, delete or disable some of the watchpoints.
2872 The SPARClite DSU will generate traps when a program accesses some data
2873 or instruction address that is assigned to the debug registers. For the
2874 data addresses, DSU facilitates the @code{watch} command. However the
2875 hardware breakpoint registers can only take two data watchpoints, and
2876 both watchpoints must be the same kind. For example, you can set two
2877 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
2878 @strong{or} two with @code{awatch} commands, but you cannot set one
2879 watchpoint with one command and the other with a different command.
2880 @value{GDBN} will reject the command if you try to mix watchpoints.
2881 Delete or disable unused watchpoint commands before setting new ones.
2883 If you call a function interactively using @code{print} or @code{call},
2884 any watchpoints you have set will be inactive until @value{GDBN} reaches another
2885 kind of breakpoint or the call completes.
2887 @value{GDBN} automatically deletes watchpoints that watch local
2888 (automatic) variables, or expressions that involve such variables, when
2889 they go out of scope, that is, when the execution leaves the block in
2890 which these variables were defined. In particular, when the program
2891 being debugged terminates, @emph{all} local variables go out of scope,
2892 and so only watchpoints that watch global variables remain set. If you
2893 rerun the program, you will need to set all such watchpoints again. One
2894 way of doing that would be to set a code breakpoint at the entry to the
2895 @code{main} function and when it breaks, set all the watchpoints.
2898 @cindex watchpoints and threads
2899 @cindex threads and watchpoints
2900 @emph{Warning:} In multi-thread programs, watchpoints have only limited
2901 usefulness. With the current watchpoint implementation, @value{GDBN}
2902 can only watch the value of an expression @emph{in a single thread}. If
2903 you are confident that the expression can only change due to the current
2904 thread's activity (and if you are also confident that no other thread
2905 can become current), then you can use watchpoints as usual. However,
2906 @value{GDBN} may not notice when a non-current thread's activity changes
2909 @c FIXME: this is almost identical to the previous paragraph.
2910 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
2911 have only limited usefulness. If @value{GDBN} creates a software
2912 watchpoint, it can only watch the value of an expression @emph{in a
2913 single thread}. If you are confident that the expression can only
2914 change due to the current thread's activity (and if you are also
2915 confident that no other thread can become current), then you can use
2916 software watchpoints as usual. However, @value{GDBN} may not notice
2917 when a non-current thread's activity changes the expression. (Hardware
2918 watchpoints, in contrast, watch an expression in all threads.)
2921 @xref{set remote hardware-watchpoint-limit}.
2923 @node Set Catchpoints
2924 @subsection Setting catchpoints
2925 @cindex catchpoints, setting
2926 @cindex exception handlers
2927 @cindex event handling
2929 You can use @dfn{catchpoints} to cause the debugger to stop for certain
2930 kinds of program events, such as C@t{++} exceptions or the loading of a
2931 shared library. Use the @code{catch} command to set a catchpoint.
2935 @item catch @var{event}
2936 Stop when @var{event} occurs. @var{event} can be any of the following:
2939 @cindex stop on C@t{++} exceptions
2940 The throwing of a C@t{++} exception.
2943 The catching of a C@t{++} exception.
2946 @cindex break on fork/exec
2947 A call to @code{exec}. This is currently only available for HP-UX.
2950 A call to @code{fork}. This is currently only available for HP-UX.
2953 A call to @code{vfork}. This is currently only available for HP-UX.
2956 @itemx load @var{libname}
2957 @cindex break on load/unload of shared library
2958 The dynamic loading of any shared library, or the loading of the library
2959 @var{libname}. This is currently only available for HP-UX.
2962 @itemx unload @var{libname}
2963 The unloading of any dynamically loaded shared library, or the unloading
2964 of the library @var{libname}. This is currently only available for HP-UX.
2967 @item tcatch @var{event}
2968 Set a catchpoint that is enabled only for one stop. The catchpoint is
2969 automatically deleted after the first time the event is caught.
2973 Use the @code{info break} command to list the current catchpoints.
2975 There are currently some limitations to C@t{++} exception handling
2976 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
2980 If you call a function interactively, @value{GDBN} normally returns
2981 control to you when the function has finished executing. If the call
2982 raises an exception, however, the call may bypass the mechanism that
2983 returns control to you and cause your program either to abort or to
2984 simply continue running until it hits a breakpoint, catches a signal
2985 that @value{GDBN} is listening for, or exits. This is the case even if
2986 you set a catchpoint for the exception; catchpoints on exceptions are
2987 disabled within interactive calls.
2990 You cannot raise an exception interactively.
2993 You cannot install an exception handler interactively.
2996 @cindex raise exceptions
2997 Sometimes @code{catch} is not the best way to debug exception handling:
2998 if you need to know exactly where an exception is raised, it is better to
2999 stop @emph{before} the exception handler is called, since that way you
3000 can see the stack before any unwinding takes place. If you set a
3001 breakpoint in an exception handler instead, it may not be easy to find
3002 out where the exception was raised.
3004 To stop just before an exception handler is called, you need some
3005 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3006 raised by calling a library function named @code{__raise_exception}
3007 which has the following ANSI C interface:
3010 /* @var{addr} is where the exception identifier is stored.
3011 @var{id} is the exception identifier. */
3012 void __raise_exception (void **addr, void *id);
3016 To make the debugger catch all exceptions before any stack
3017 unwinding takes place, set a breakpoint on @code{__raise_exception}
3018 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
3020 With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
3021 that depends on the value of @var{id}, you can stop your program when
3022 a specific exception is raised. You can use multiple conditional
3023 breakpoints to stop your program when any of a number of exceptions are
3028 @subsection Deleting breakpoints
3030 @cindex clearing breakpoints, watchpoints, catchpoints
3031 @cindex deleting breakpoints, watchpoints, catchpoints
3032 It is often necessary to eliminate a breakpoint, watchpoint, or
3033 catchpoint once it has done its job and you no longer want your program
3034 to stop there. This is called @dfn{deleting} the breakpoint. A
3035 breakpoint that has been deleted no longer exists; it is forgotten.
3037 With the @code{clear} command you can delete breakpoints according to
3038 where they are in your program. With the @code{delete} command you can
3039 delete individual breakpoints, watchpoints, or catchpoints by specifying
3040 their breakpoint numbers.
3042 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3043 automatically ignores breakpoints on the first instruction to be executed
3044 when you continue execution without changing the execution address.
3049 Delete any breakpoints at the next instruction to be executed in the
3050 selected stack frame (@pxref{Selection, ,Selecting a frame}). When
3051 the innermost frame is selected, this is a good way to delete a
3052 breakpoint where your program just stopped.
3054 @item clear @var{function}
3055 @itemx clear @var{filename}:@var{function}
3056 Delete any breakpoints set at entry to the named @var{function}.
3058 @item clear @var{linenum}
3059 @itemx clear @var{filename}:@var{linenum}
3060 Delete any breakpoints set at or within the code of the specified
3061 @var{linenum} of the specified @var{filename}.
3063 @cindex delete breakpoints
3065 @kindex d @r{(@code{delete})}
3066 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3067 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3068 ranges specified as arguments. If no argument is specified, delete all
3069 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3070 confirm off}). You can abbreviate this command as @code{d}.
3074 @subsection Disabling breakpoints
3076 @cindex enable/disable a breakpoint
3077 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3078 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3079 it had been deleted, but remembers the information on the breakpoint so
3080 that you can @dfn{enable} it again later.
3082 You disable and enable breakpoints, watchpoints, and catchpoints with
3083 the @code{enable} and @code{disable} commands, optionally specifying one
3084 or more breakpoint numbers as arguments. Use @code{info break} or
3085 @code{info watch} to print a list of breakpoints, watchpoints, and
3086 catchpoints if you do not know which numbers to use.
3088 A breakpoint, watchpoint, or catchpoint can have any of four different
3089 states of enablement:
3093 Enabled. The breakpoint stops your program. A breakpoint set
3094 with the @code{break} command starts out in this state.
3096 Disabled. The breakpoint has no effect on your program.
3098 Enabled once. The breakpoint stops your program, but then becomes
3101 Enabled for deletion. The breakpoint stops your program, but
3102 immediately after it does so it is deleted permanently. A breakpoint
3103 set with the @code{tbreak} command starts out in this state.
3106 You can use the following commands to enable or disable breakpoints,
3107 watchpoints, and catchpoints:
3111 @kindex dis @r{(@code{disable})}
3112 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3113 Disable the specified breakpoints---or all breakpoints, if none are
3114 listed. A disabled breakpoint has no effect but is not forgotten. All
3115 options such as ignore-counts, conditions and commands are remembered in
3116 case the breakpoint is enabled again later. You may abbreviate
3117 @code{disable} as @code{dis}.
3120 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3121 Enable the specified breakpoints (or all defined breakpoints). They
3122 become effective once again in stopping your program.
3124 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3125 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3126 of these breakpoints immediately after stopping your program.
3128 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3129 Enable the specified breakpoints to work once, then die. @value{GDBN}
3130 deletes any of these breakpoints as soon as your program stops there.
3131 Breakpoints set by the @code{tbreak} command start out in this state.
3134 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3135 @c confusing: tbreak is also initially enabled.
3136 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3137 ,Setting breakpoints}), breakpoints that you set are initially enabled;
3138 subsequently, they become disabled or enabled only when you use one of
3139 the commands above. (The command @code{until} can set and delete a
3140 breakpoint of its own, but it does not change the state of your other
3141 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3145 @subsection Break conditions
3146 @cindex conditional breakpoints
3147 @cindex breakpoint conditions
3149 @c FIXME what is scope of break condition expr? Context where wanted?
3150 @c in particular for a watchpoint?
3151 The simplest sort of breakpoint breaks every time your program reaches a
3152 specified place. You can also specify a @dfn{condition} for a
3153 breakpoint. A condition is just a Boolean expression in your
3154 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3155 a condition evaluates the expression each time your program reaches it,
3156 and your program stops only if the condition is @emph{true}.
3158 This is the converse of using assertions for program validation; in that
3159 situation, you want to stop when the assertion is violated---that is,
3160 when the condition is false. In C, if you want to test an assertion expressed
3161 by the condition @var{assert}, you should set the condition
3162 @samp{! @var{assert}} on the appropriate breakpoint.
3164 Conditions are also accepted for watchpoints; you may not need them,
3165 since a watchpoint is inspecting the value of an expression anyhow---but
3166 it might be simpler, say, to just set a watchpoint on a variable name,
3167 and specify a condition that tests whether the new value is an interesting
3170 Break conditions can have side effects, and may even call functions in
3171 your program. This can be useful, for example, to activate functions
3172 that log program progress, or to use your own print functions to
3173 format special data structures. The effects are completely predictable
3174 unless there is another enabled breakpoint at the same address. (In
3175 that case, @value{GDBN} might see the other breakpoint first and stop your
3176 program without checking the condition of this one.) Note that
3177 breakpoint commands are usually more convenient and flexible than break
3179 purpose of performing side effects when a breakpoint is reached
3180 (@pxref{Break Commands, ,Breakpoint command lists}).
3182 Break conditions can be specified when a breakpoint is set, by using
3183 @samp{if} in the arguments to the @code{break} command. @xref{Set
3184 Breaks, ,Setting breakpoints}. They can also be changed at any time
3185 with the @code{condition} command.
3187 You can also use the @code{if} keyword with the @code{watch} command.
3188 The @code{catch} command does not recognize the @code{if} keyword;
3189 @code{condition} is the only way to impose a further condition on a
3194 @item condition @var{bnum} @var{expression}
3195 Specify @var{expression} as the break condition for breakpoint,
3196 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3197 breakpoint @var{bnum} stops your program only if the value of
3198 @var{expression} is true (nonzero, in C). When you use
3199 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3200 syntactic correctness, and to determine whether symbols in it have
3201 referents in the context of your breakpoint. If @var{expression} uses
3202 symbols not referenced in the context of the breakpoint, @value{GDBN}
3203 prints an error message:
3206 No symbol "foo" in current context.
3211 not actually evaluate @var{expression} at the time the @code{condition}
3212 command (or a command that sets a breakpoint with a condition, like
3213 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3215 @item condition @var{bnum}
3216 Remove the condition from breakpoint number @var{bnum}. It becomes
3217 an ordinary unconditional breakpoint.
3220 @cindex ignore count (of breakpoint)
3221 A special case of a breakpoint condition is to stop only when the
3222 breakpoint has been reached a certain number of times. This is so
3223 useful that there is a special way to do it, using the @dfn{ignore
3224 count} of the breakpoint. Every breakpoint has an ignore count, which
3225 is an integer. Most of the time, the ignore count is zero, and
3226 therefore has no effect. But if your program reaches a breakpoint whose
3227 ignore count is positive, then instead of stopping, it just decrements
3228 the ignore count by one and continues. As a result, if the ignore count
3229 value is @var{n}, the breakpoint does not stop the next @var{n} times
3230 your program reaches it.
3234 @item ignore @var{bnum} @var{count}
3235 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3236 The next @var{count} times the breakpoint is reached, your program's
3237 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3240 To make the breakpoint stop the next time it is reached, specify
3243 When you use @code{continue} to resume execution of your program from a
3244 breakpoint, you can specify an ignore count directly as an argument to
3245 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3246 Stepping,,Continuing and stepping}.
3248 If a breakpoint has a positive ignore count and a condition, the
3249 condition is not checked. Once the ignore count reaches zero,
3250 @value{GDBN} resumes checking the condition.
3252 You could achieve the effect of the ignore count with a condition such
3253 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3254 is decremented each time. @xref{Convenience Vars, ,Convenience
3258 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3261 @node Break Commands
3262 @subsection Breakpoint command lists
3264 @cindex breakpoint commands
3265 You can give any breakpoint (or watchpoint or catchpoint) a series of
3266 commands to execute when your program stops due to that breakpoint. For
3267 example, you might want to print the values of certain expressions, or
3268 enable other breakpoints.
3273 @item commands @r{[}@var{bnum}@r{]}
3274 @itemx @dots{} @var{command-list} @dots{}
3276 Specify a list of commands for breakpoint number @var{bnum}. The commands
3277 themselves appear on the following lines. Type a line containing just
3278 @code{end} to terminate the commands.
3280 To remove all commands from a breakpoint, type @code{commands} and
3281 follow it immediately with @code{end}; that is, give no commands.
3283 With no @var{bnum} argument, @code{commands} refers to the last
3284 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3285 recently encountered).
3288 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3289 disabled within a @var{command-list}.
3291 You can use breakpoint commands to start your program up again. Simply
3292 use the @code{continue} command, or @code{step}, or any other command
3293 that resumes execution.
3295 Any other commands in the command list, after a command that resumes
3296 execution, are ignored. This is because any time you resume execution
3297 (even with a simple @code{next} or @code{step}), you may encounter
3298 another breakpoint---which could have its own command list, leading to
3299 ambiguities about which list to execute.
3302 If the first command you specify in a command list is @code{silent}, the
3303 usual message about stopping at a breakpoint is not printed. This may
3304 be desirable for breakpoints that are to print a specific message and
3305 then continue. If none of the remaining commands print anything, you
3306 see no sign that the breakpoint was reached. @code{silent} is
3307 meaningful only at the beginning of a breakpoint command list.
3309 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3310 print precisely controlled output, and are often useful in silent
3311 breakpoints. @xref{Output, ,Commands for controlled output}.
3313 For example, here is how you could use breakpoint commands to print the
3314 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3320 printf "x is %d\n",x
3325 One application for breakpoint commands is to compensate for one bug so
3326 you can test for another. Put a breakpoint just after the erroneous line
3327 of code, give it a condition to detect the case in which something
3328 erroneous has been done, and give it commands to assign correct values
3329 to any variables that need them. End with the @code{continue} command
3330 so that your program does not stop, and start with the @code{silent}
3331 command so that no output is produced. Here is an example:
3342 @node Breakpoint Menus
3343 @subsection Breakpoint menus
3345 @cindex symbol overloading
3347 Some programming languages (notably C@t{++} and Objective-C) permit a
3348 single function name
3349 to be defined several times, for application in different contexts.
3350 This is called @dfn{overloading}. When a function name is overloaded,
3351 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3352 a breakpoint. If you realize this is a problem, you can use
3353 something like @samp{break @var{function}(@var{types})} to specify which
3354 particular version of the function you want. Otherwise, @value{GDBN} offers
3355 you a menu of numbered choices for different possible breakpoints, and
3356 waits for your selection with the prompt @samp{>}. The first two
3357 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3358 sets a breakpoint at each definition of @var{function}, and typing
3359 @kbd{0} aborts the @code{break} command without setting any new
3362 For example, the following session excerpt shows an attempt to set a
3363 breakpoint at the overloaded symbol @code{String::after}.
3364 We choose three particular definitions of that function name:
3366 @c FIXME! This is likely to change to show arg type lists, at least
3369 (@value{GDBP}) b String::after
3372 [2] file:String.cc; line number:867
3373 [3] file:String.cc; line number:860
3374 [4] file:String.cc; line number:875
3375 [5] file:String.cc; line number:853
3376 [6] file:String.cc; line number:846
3377 [7] file:String.cc; line number:735
3379 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3380 Breakpoint 2 at 0xb344: file String.cc, line 875.
3381 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3382 Multiple breakpoints were set.
3383 Use the "delete" command to delete unwanted
3389 @c @ifclear BARETARGET
3390 @node Error in Breakpoints
3391 @subsection ``Cannot insert breakpoints''
3393 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3395 Under some operating systems, breakpoints cannot be used in a program if
3396 any other process is running that program. In this situation,
3397 attempting to run or continue a program with a breakpoint causes
3398 @value{GDBN} to print an error message:
3401 Cannot insert breakpoints.
3402 The same program may be running in another process.
3405 When this happens, you have three ways to proceed:
3409 Remove or disable the breakpoints, then continue.
3412 Suspend @value{GDBN}, and copy the file containing your program to a new
3413 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3414 that @value{GDBN} should run your program under that name.
3415 Then start your program again.
3418 Relink your program so that the text segment is nonsharable, using the
3419 linker option @samp{-N}. The operating system limitation may not apply
3420 to nonsharable executables.
3424 A similar message can be printed if you request too many active
3425 hardware-assisted breakpoints and watchpoints:
3427 @c FIXME: the precise wording of this message may change; the relevant
3428 @c source change is not committed yet (Sep 3, 1999).
3430 Stopped; cannot insert breakpoints.
3431 You may have requested too many hardware breakpoints and watchpoints.
3435 This message is printed when you attempt to resume the program, since
3436 only then @value{GDBN} knows exactly how many hardware breakpoints and
3437 watchpoints it needs to insert.
3439 When this message is printed, you need to disable or remove some of the
3440 hardware-assisted breakpoints and watchpoints, and then continue.
3442 @node Breakpoint related warnings
3443 @subsection ``Breakpoint address adjusted...''
3444 @cindex breakpoint address adjusted
3446 Some processor architectures place constraints on the addresses at
3447 which breakpoints may be placed. For architectures thus constrained,
3448 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3449 with the constraints dictated by the architecture.
3451 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3452 a VLIW architecture in which a number of RISC-like instructions may be
3453 bundled together for parallel execution. The FR-V architecture
3454 constrains the location of a breakpoint instruction within such a
3455 bundle to the instruction with the lowest address. @value{GDBN}
3456 honors this constraint by adjusting a breakpoint's address to the
3457 first in the bundle.
3459 It is not uncommon for optimized code to have bundles which contain
3460 instructions from different source statements, thus it may happen that
3461 a breakpoint's address will be adjusted from one source statement to
3462 another. Since this adjustment may significantly alter @value{GDBN}'s
3463 breakpoint related behavior from what the user expects, a warning is
3464 printed when the breakpoint is first set and also when the breakpoint
3467 A warning like the one below is printed when setting a breakpoint
3468 that's been subject to address adjustment:
3471 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3474 Such warnings are printed both for user settable and @value{GDBN}'s
3475 internal breakpoints. If you see one of these warnings, you should
3476 verify that a breakpoint set at the adjusted address will have the
3477 desired affect. If not, the breakpoint in question may be removed and
3478 other breakpoints may be set which will have the desired behavior.
3479 E.g., it may be sufficient to place the breakpoint at a later
3480 instruction. A conditional breakpoint may also be useful in some
3481 cases to prevent the breakpoint from triggering too often.
3483 @value{GDBN} will also issue a warning when stopping at one of these
3484 adjusted breakpoints:
3487 warning: Breakpoint 1 address previously adjusted from 0x00010414
3491 When this warning is encountered, it may be too late to take remedial
3492 action except in cases where the breakpoint is hit earlier or more
3493 frequently than expected.
3495 @node Continuing and Stepping
3496 @section Continuing and stepping
3500 @cindex resuming execution
3501 @dfn{Continuing} means resuming program execution until your program
3502 completes normally. In contrast, @dfn{stepping} means executing just
3503 one more ``step'' of your program, where ``step'' may mean either one
3504 line of source code, or one machine instruction (depending on what
3505 particular command you use). Either when continuing or when stepping,
3506 your program may stop even sooner, due to a breakpoint or a signal. (If
3507 it stops due to a signal, you may want to use @code{handle}, or use
3508 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3512 @kindex c @r{(@code{continue})}
3513 @kindex fg @r{(resume foreground execution)}
3514 @item continue @r{[}@var{ignore-count}@r{]}
3515 @itemx c @r{[}@var{ignore-count}@r{]}
3516 @itemx fg @r{[}@var{ignore-count}@r{]}
3517 Resume program execution, at the address where your program last stopped;
3518 any breakpoints set at that address are bypassed. The optional argument
3519 @var{ignore-count} allows you to specify a further number of times to
3520 ignore a breakpoint at this location; its effect is like that of
3521 @code{ignore} (@pxref{Conditions, ,Break conditions}).
3523 The argument @var{ignore-count} is meaningful only when your program
3524 stopped due to a breakpoint. At other times, the argument to
3525 @code{continue} is ignored.
3527 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3528 debugged program is deemed to be the foreground program) are provided
3529 purely for convenience, and have exactly the same behavior as
3533 To resume execution at a different place, you can use @code{return}
3534 (@pxref{Returning, ,Returning from a function}) to go back to the
3535 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3536 different address}) to go to an arbitrary location in your program.
3538 A typical technique for using stepping is to set a breakpoint
3539 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the
3540 beginning of the function or the section of your program where a problem
3541 is believed to lie, run your program until it stops at that breakpoint,
3542 and then step through the suspect area, examining the variables that are
3543 interesting, until you see the problem happen.
3547 @kindex s @r{(@code{step})}
3549 Continue running your program until control reaches a different source
3550 line, then stop it and return control to @value{GDBN}. This command is
3551 abbreviated @code{s}.
3554 @c "without debugging information" is imprecise; actually "without line
3555 @c numbers in the debugging information". (gcc -g1 has debugging info but
3556 @c not line numbers). But it seems complex to try to make that
3557 @c distinction here.
3558 @emph{Warning:} If you use the @code{step} command while control is
3559 within a function that was compiled without debugging information,
3560 execution proceeds until control reaches a function that does have
3561 debugging information. Likewise, it will not step into a function which
3562 is compiled without debugging information. To step through functions
3563 without debugging information, use the @code{stepi} command, described
3567 The @code{step} command only stops at the first instruction of a source
3568 line. This prevents the multiple stops that could otherwise occur in
3569 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3570 to stop if a function that has debugging information is called within
3571 the line. In other words, @code{step} @emph{steps inside} any functions
3572 called within the line.
3574 Also, the @code{step} command only enters a function if there is line
3575 number information for the function. Otherwise it acts like the
3576 @code{next} command. This avoids problems when using @code{cc -gl}
3577 on MIPS machines. Previously, @code{step} entered subroutines if there
3578 was any debugging information about the routine.
3580 @item step @var{count}
3581 Continue running as in @code{step}, but do so @var{count} times. If a
3582 breakpoint is reached, or a signal not related to stepping occurs before
3583 @var{count} steps, stepping stops right away.
3586 @kindex n @r{(@code{next})}
3587 @item next @r{[}@var{count}@r{]}
3588 Continue to the next source line in the current (innermost) stack frame.
3589 This is similar to @code{step}, but function calls that appear within
3590 the line of code are executed without stopping. Execution stops when
3591 control reaches a different line of code at the original stack level
3592 that was executing when you gave the @code{next} command. This command
3593 is abbreviated @code{n}.
3595 An argument @var{count} is a repeat count, as for @code{step}.
3598 @c FIX ME!! Do we delete this, or is there a way it fits in with
3599 @c the following paragraph? --- Vctoria
3601 @c @code{next} within a function that lacks debugging information acts like
3602 @c @code{step}, but any function calls appearing within the code of the
3603 @c function are executed without stopping.
3605 The @code{next} command only stops at the first instruction of a
3606 source line. This prevents multiple stops that could otherwise occur in
3607 @code{switch} statements, @code{for} loops, etc.
3609 @kindex set step-mode
3611 @cindex functions without line info, and stepping
3612 @cindex stepping into functions with no line info
3613 @itemx set step-mode on
3614 The @code{set step-mode on} command causes the @code{step} command to
3615 stop at the first instruction of a function which contains no debug line
3616 information rather than stepping over it.
3618 This is useful in cases where you may be interested in inspecting the
3619 machine instructions of a function which has no symbolic info and do not
3620 want @value{GDBN} to automatically skip over this function.
3622 @item set step-mode off
3623 Causes the @code{step} command to step over any functions which contains no
3624 debug information. This is the default.
3626 @item show step-mode
3627 Show whether @value{GDBN} will stop in or step over functions without
3628 source line debug information.
3632 Continue running until just after function in the selected stack frame
3633 returns. Print the returned value (if any).
3635 Contrast this with the @code{return} command (@pxref{Returning,
3636 ,Returning from a function}).
3639 @kindex u @r{(@code{until})}
3640 @cindex run until specified location
3643 Continue running until a source line past the current line, in the
3644 current stack frame, is reached. This command is used to avoid single
3645 stepping through a loop more than once. It is like the @code{next}
3646 command, except that when @code{until} encounters a jump, it
3647 automatically continues execution until the program counter is greater
3648 than the address of the jump.
3650 This means that when you reach the end of a loop after single stepping
3651 though it, @code{until} makes your program continue execution until it
3652 exits the loop. In contrast, a @code{next} command at the end of a loop
3653 simply steps back to the beginning of the loop, which forces you to step
3654 through the next iteration.
3656 @code{until} always stops your program if it attempts to exit the current
3659 @code{until} may produce somewhat counterintuitive results if the order
3660 of machine code does not match the order of the source lines. For
3661 example, in the following excerpt from a debugging session, the @code{f}
3662 (@code{frame}) command shows that execution is stopped at line
3663 @code{206}; yet when we use @code{until}, we get to line @code{195}:
3667 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
3669 (@value{GDBP}) until
3670 195 for ( ; argc > 0; NEXTARG) @{
3673 This happened because, for execution efficiency, the compiler had
3674 generated code for the loop closure test at the end, rather than the
3675 start, of the loop---even though the test in a C @code{for}-loop is
3676 written before the body of the loop. The @code{until} command appeared
3677 to step back to the beginning of the loop when it advanced to this
3678 expression; however, it has not really gone to an earlier
3679 statement---not in terms of the actual machine code.
3681 @code{until} with no argument works by means of single
3682 instruction stepping, and hence is slower than @code{until} with an
3685 @item until @var{location}
3686 @itemx u @var{location}
3687 Continue running your program until either the specified location is
3688 reached, or the current stack frame returns. @var{location} is any of
3689 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
3690 ,Setting breakpoints}). This form of the command uses breakpoints, and
3691 hence is quicker than @code{until} without an argument. The specified
3692 location is actually reached only if it is in the current frame. This
3693 implies that @code{until} can be used to skip over recursive function
3694 invocations. For instance in the code below, if the current location is
3695 line @code{96}, issuing @code{until 99} will execute the program up to
3696 line @code{99} in the same invocation of factorial, i.e. after the inner
3697 invocations have returned.
3700 94 int factorial (int value)
3702 96 if (value > 1) @{
3703 97 value *= factorial (value - 1);
3710 @kindex advance @var{location}
3711 @itemx advance @var{location}
3712 Continue running the program up to the given @var{location}. An argument is
3713 required, which should be of the same form as arguments for the @code{break}
3714 command. Execution will also stop upon exit from the current stack
3715 frame. This command is similar to @code{until}, but @code{advance} will
3716 not skip over recursive function calls, and the target location doesn't
3717 have to be in the same frame as the current one.
3721 @kindex si @r{(@code{stepi})}
3723 @itemx stepi @var{arg}
3725 Execute one machine instruction, then stop and return to the debugger.
3727 It is often useful to do @samp{display/i $pc} when stepping by machine
3728 instructions. This makes @value{GDBN} automatically display the next
3729 instruction to be executed, each time your program stops. @xref{Auto
3730 Display,, Automatic display}.
3732 An argument is a repeat count, as in @code{step}.
3736 @kindex ni @r{(@code{nexti})}
3738 @itemx nexti @var{arg}
3740 Execute one machine instruction, but if it is a function call,
3741 proceed until the function returns.
3743 An argument is a repeat count, as in @code{next}.
3750 A signal is an asynchronous event that can happen in a program. The
3751 operating system defines the possible kinds of signals, and gives each
3752 kind a name and a number. For example, in Unix @code{SIGINT} is the
3753 signal a program gets when you type an interrupt character (often @kbd{C-c});
3754 @code{SIGSEGV} is the signal a program gets from referencing a place in
3755 memory far away from all the areas in use; @code{SIGALRM} occurs when
3756 the alarm clock timer goes off (which happens only if your program has
3757 requested an alarm).
3759 @cindex fatal signals
3760 Some signals, including @code{SIGALRM}, are a normal part of the
3761 functioning of your program. Others, such as @code{SIGSEGV}, indicate
3762 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
3763 program has not specified in advance some other way to handle the signal.
3764 @code{SIGINT} does not indicate an error in your program, but it is normally
3765 fatal so it can carry out the purpose of the interrupt: to kill the program.
3767 @value{GDBN} has the ability to detect any occurrence of a signal in your
3768 program. You can tell @value{GDBN} in advance what to do for each kind of
3771 @cindex handling signals
3772 Normally, @value{GDBN} is set up to let the non-erroneous signals like
3773 @code{SIGALRM} be silently passed to your program
3774 (so as not to interfere with their role in the program's functioning)
3775 but to stop your program immediately whenever an error signal happens.
3776 You can change these settings with the @code{handle} command.
3779 @kindex info signals
3783 Print a table of all the kinds of signals and how @value{GDBN} has been told to
3784 handle each one. You can use this to see the signal numbers of all
3785 the defined types of signals.
3787 @code{info handle} is an alias for @code{info signals}.
3790 @item handle @var{signal} @var{keywords}@dots{}
3791 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
3792 can be the number of a signal or its name (with or without the
3793 @samp{SIG} at the beginning); a list of signal numbers of the form
3794 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
3795 known signals. The @var{keywords} say what change to make.
3799 The keywords allowed by the @code{handle} command can be abbreviated.
3800 Their full names are:
3804 @value{GDBN} should not stop your program when this signal happens. It may
3805 still print a message telling you that the signal has come in.
3808 @value{GDBN} should stop your program when this signal happens. This implies
3809 the @code{print} keyword as well.
3812 @value{GDBN} should print a message when this signal happens.
3815 @value{GDBN} should not mention the occurrence of the signal at all. This
3816 implies the @code{nostop} keyword as well.
3820 @value{GDBN} should allow your program to see this signal; your program
3821 can handle the signal, or else it may terminate if the signal is fatal
3822 and not handled. @code{pass} and @code{noignore} are synonyms.
3826 @value{GDBN} should not allow your program to see this signal.
3827 @code{nopass} and @code{ignore} are synonyms.
3831 When a signal stops your program, the signal is not visible to the
3833 continue. Your program sees the signal then, if @code{pass} is in
3834 effect for the signal in question @emph{at that time}. In other words,
3835 after @value{GDBN} reports a signal, you can use the @code{handle}
3836 command with @code{pass} or @code{nopass} to control whether your
3837 program sees that signal when you continue.
3839 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
3840 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
3841 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
3844 You can also use the @code{signal} command to prevent your program from
3845 seeing a signal, or cause it to see a signal it normally would not see,
3846 or to give it any signal at any time. For example, if your program stopped
3847 due to some sort of memory reference error, you might store correct
3848 values into the erroneous variables and continue, hoping to see more
3849 execution; but your program would probably terminate immediately as
3850 a result of the fatal signal once it saw the signal. To prevent this,
3851 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
3855 @section Stopping and starting multi-thread programs
3857 When your program has multiple threads (@pxref{Threads,, Debugging
3858 programs with multiple threads}), you can choose whether to set
3859 breakpoints on all threads, or on a particular thread.
3862 @cindex breakpoints and threads
3863 @cindex thread breakpoints
3864 @kindex break @dots{} thread @var{threadno}
3865 @item break @var{linespec} thread @var{threadno}
3866 @itemx break @var{linespec} thread @var{threadno} if @dots{}
3867 @var{linespec} specifies source lines; there are several ways of
3868 writing them, but the effect is always to specify some source line.
3870 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
3871 to specify that you only want @value{GDBN} to stop the program when a
3872 particular thread reaches this breakpoint. @var{threadno} is one of the
3873 numeric thread identifiers assigned by @value{GDBN}, shown in the first
3874 column of the @samp{info threads} display.
3876 If you do not specify @samp{thread @var{threadno}} when you set a
3877 breakpoint, the breakpoint applies to @emph{all} threads of your
3880 You can use the @code{thread} qualifier on conditional breakpoints as
3881 well; in this case, place @samp{thread @var{threadno}} before the
3882 breakpoint condition, like this:
3885 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
3890 @cindex stopped threads
3891 @cindex threads, stopped
3892 Whenever your program stops under @value{GDBN} for any reason,
3893 @emph{all} threads of execution stop, not just the current thread. This
3894 allows you to examine the overall state of the program, including
3895 switching between threads, without worrying that things may change
3898 @cindex thread breakpoints and system calls
3899 @cindex system calls and thread breakpoints
3900 @cindex premature return from system calls
3901 There is an unfortunate side effect. If one thread stops for a
3902 breakpoint, or for some other reason, and another thread is blocked in a
3903 system call, then the system call may return prematurely. This is a
3904 consequence of the interaction between multiple threads and the signals
3905 that @value{GDBN} uses to implement breakpoints and other events that
3908 To handle this problem, your program should check the return value of
3909 each system call and react appropriately. This is good programming
3912 For example, do not write code like this:
3918 The call to @code{sleep} will return early if a different thread stops
3919 at a breakpoint or for some other reason.
3921 Instead, write this:
3926 unslept = sleep (unslept);
3929 A system call is allowed to return early, so the system is still
3930 conforming to its specification. But @value{GDBN} does cause your
3931 multi-threaded program to behave differently than it would without
3934 Also, @value{GDBN} uses internal breakpoints in the thread library to
3935 monitor certain events such as thread creation and thread destruction.
3936 When such an event happens, a system call in another thread may return
3937 prematurely, even though your program does not appear to stop.
3939 @cindex continuing threads
3940 @cindex threads, continuing
3941 Conversely, whenever you restart the program, @emph{all} threads start
3942 executing. @emph{This is true even when single-stepping} with commands
3943 like @code{step} or @code{next}.
3945 In particular, @value{GDBN} cannot single-step all threads in lockstep.
3946 Since thread scheduling is up to your debugging target's operating
3947 system (not controlled by @value{GDBN}), other threads may
3948 execute more than one statement while the current thread completes a
3949 single step. Moreover, in general other threads stop in the middle of a
3950 statement, rather than at a clean statement boundary, when the program
3953 You might even find your program stopped in another thread after
3954 continuing or even single-stepping. This happens whenever some other
3955 thread runs into a breakpoint, a signal, or an exception before the
3956 first thread completes whatever you requested.
3958 On some OSes, you can lock the OS scheduler and thus allow only a single
3962 @item set scheduler-locking @var{mode}
3963 @cindex scheduler locking mode
3964 @cindex lock scheduler
3965 Set the scheduler locking mode. If it is @code{off}, then there is no
3966 locking and any thread may run at any time. If @code{on}, then only the
3967 current thread may run when the inferior is resumed. The @code{step}
3968 mode optimizes for single-stepping. It stops other threads from
3969 ``seizing the prompt'' by preempting the current thread while you are
3970 stepping. Other threads will only rarely (or never) get a chance to run
3971 when you step. They are more likely to run when you @samp{next} over a
3972 function call, and they are completely free to run when you use commands
3973 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
3974 thread hits a breakpoint during its timeslice, they will never steal the
3975 @value{GDBN} prompt away from the thread that you are debugging.
3977 @item show scheduler-locking
3978 Display the current scheduler locking mode.
3983 @chapter Examining the Stack
3985 When your program has stopped, the first thing you need to know is where it
3986 stopped and how it got there.
3989 Each time your program performs a function call, information about the call
3991 That information includes the location of the call in your program,
3992 the arguments of the call,
3993 and the local variables of the function being called.
3994 The information is saved in a block of data called a @dfn{stack frame}.
3995 The stack frames are allocated in a region of memory called the @dfn{call
3998 When your program stops, the @value{GDBN} commands for examining the
3999 stack allow you to see all of this information.
4001 @cindex selected frame
4002 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4003 @value{GDBN} commands refer implicitly to the selected frame. In
4004 particular, whenever you ask @value{GDBN} for the value of a variable in
4005 your program, the value is found in the selected frame. There are
4006 special @value{GDBN} commands to select whichever frame you are
4007 interested in. @xref{Selection, ,Selecting a frame}.
4009 When your program stops, @value{GDBN} automatically selects the
4010 currently executing frame and describes it briefly, similar to the
4011 @code{frame} command (@pxref{Frame Info, ,Information about a frame}).
4014 * Frames:: Stack frames
4015 * Backtrace:: Backtraces
4016 * Selection:: Selecting a frame
4017 * Frame Info:: Information on a frame
4022 @section Stack frames
4024 @cindex frame, definition
4026 The call stack is divided up into contiguous pieces called @dfn{stack
4027 frames}, or @dfn{frames} for short; each frame is the data associated
4028 with one call to one function. The frame contains the arguments given
4029 to the function, the function's local variables, and the address at
4030 which the function is executing.
4032 @cindex initial frame
4033 @cindex outermost frame
4034 @cindex innermost frame
4035 When your program is started, the stack has only one frame, that of the
4036 function @code{main}. This is called the @dfn{initial} frame or the
4037 @dfn{outermost} frame. Each time a function is called, a new frame is
4038 made. Each time a function returns, the frame for that function invocation
4039 is eliminated. If a function is recursive, there can be many frames for
4040 the same function. The frame for the function in which execution is
4041 actually occurring is called the @dfn{innermost} frame. This is the most
4042 recently created of all the stack frames that still exist.
4044 @cindex frame pointer
4045 Inside your program, stack frames are identified by their addresses. A
4046 stack frame consists of many bytes, each of which has its own address; each
4047 kind of computer has a convention for choosing one byte whose
4048 address serves as the address of the frame. Usually this address is kept
4049 in a register called the @dfn{frame pointer register} while execution is
4050 going on in that frame.
4052 @cindex frame number
4053 @value{GDBN} assigns numbers to all existing stack frames, starting with
4054 zero for the innermost frame, one for the frame that called it,
4055 and so on upward. These numbers do not really exist in your program;
4056 they are assigned by @value{GDBN} to give you a way of designating stack
4057 frames in @value{GDBN} commands.
4059 @c The -fomit-frame-pointer below perennially causes hbox overflow
4060 @c underflow problems.
4061 @cindex frameless execution
4062 Some compilers provide a way to compile functions so that they operate
4063 without stack frames. (For example, the @value{GCC} option
4065 @samp{-fomit-frame-pointer}
4067 generates functions without a frame.)
4068 This is occasionally done with heavily used library functions to save
4069 the frame setup time. @value{GDBN} has limited facilities for dealing
4070 with these function invocations. If the innermost function invocation
4071 has no stack frame, @value{GDBN} nevertheless regards it as though
4072 it had a separate frame, which is numbered zero as usual, allowing
4073 correct tracing of the function call chain. However, @value{GDBN} has
4074 no provision for frameless functions elsewhere in the stack.
4077 @kindex frame@r{, command}
4078 @cindex current stack frame
4079 @item frame @var{args}
4080 The @code{frame} command allows you to move from one stack frame to another,
4081 and to print the stack frame you select. @var{args} may be either the
4082 address of the frame or the stack frame number. Without an argument,
4083 @code{frame} prints the current stack frame.
4085 @kindex select-frame
4086 @cindex selecting frame silently
4088 The @code{select-frame} command allows you to move from one stack frame
4089 to another without printing the frame. This is the silent version of
4097 @cindex call stack traces
4098 A backtrace is a summary of how your program got where it is. It shows one
4099 line per frame, for many frames, starting with the currently executing
4100 frame (frame zero), followed by its caller (frame one), and on up the
4105 @kindex bt @r{(@code{backtrace})}
4108 Print a backtrace of the entire stack: one line per frame for all
4109 frames in the stack.
4111 You can stop the backtrace at any time by typing the system interrupt
4112 character, normally @kbd{C-c}.
4114 @item backtrace @var{n}
4116 Similar, but print only the innermost @var{n} frames.
4118 @item backtrace -@var{n}
4120 Similar, but print only the outermost @var{n} frames.
4125 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4126 are additional aliases for @code{backtrace}.
4128 Each line in the backtrace shows the frame number and the function name.
4129 The program counter value is also shown---unless you use @code{set
4130 print address off}. The backtrace also shows the source file name and
4131 line number, as well as the arguments to the function. The program
4132 counter value is omitted if it is at the beginning of the code for that
4135 Here is an example of a backtrace. It was made with the command
4136 @samp{bt 3}, so it shows the innermost three frames.
4140 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4142 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4143 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4145 (More stack frames follow...)
4150 The display for frame zero does not begin with a program counter
4151 value, indicating that your program has stopped at the beginning of the
4152 code for line @code{993} of @code{builtin.c}.
4154 @cindex backtrace beyond @code{main} function
4155 @cindex program entry point
4156 @cindex startup code, and backtrace
4157 Most programs have a standard user entry point---a place where system
4158 libraries and startup code transition into user code. For C this is
4159 @code{main}. When @value{GDBN} finds the entry function in a backtrace
4160 it will terminate the backtrace, to avoid tracing into highly
4161 system-specific (and generally uninteresting) code.
4163 If you need to examine the startup code, or limit the number of levels
4164 in a backtrace, you can change this behavior:
4167 @item set backtrace past-main
4168 @itemx set backtrace past-main on
4169 @kindex set backtrace
4170 Backtraces will continue past the user entry point.
4172 @item set backtrace past-main off
4173 Backtraces will stop when they encounter the user entry point. This is the
4176 @item show backtrace past-main
4177 @kindex show backtrace
4178 Display the current user entry point backtrace policy.
4180 @item set backtrace past-entry
4181 @itemx set backtrace past-entry on
4182 Backtraces will continue past the internal entry point of an application.
4183 This entry point is encoded by the linker when the application is built,
4184 and is likely before the user entry point @code{main} (or equivalent) is called.
4186 @item set backtrace past-entry off
4187 Backtraces will stop when they encouter the internal entry point of an
4188 application. This is the default.
4190 @item show backtrace past-entry
4191 Display the current internal entry point backtrace policy.
4193 @item set backtrace limit @var{n}
4194 @itemx set backtrace limit 0
4195 @cindex backtrace limit
4196 Limit the backtrace to @var{n} levels. A value of zero means
4199 @item show backtrace limit
4200 Display the current limit on backtrace levels.
4204 @section Selecting a frame
4206 Most commands for examining the stack and other data in your program work on
4207 whichever stack frame is selected at the moment. Here are the commands for
4208 selecting a stack frame; all of them finish by printing a brief description
4209 of the stack frame just selected.
4212 @kindex frame@r{, selecting}
4213 @kindex f @r{(@code{frame})}
4216 Select frame number @var{n}. Recall that frame zero is the innermost
4217 (currently executing) frame, frame one is the frame that called the
4218 innermost one, and so on. The highest-numbered frame is the one for
4221 @item frame @var{addr}
4223 Select the frame at address @var{addr}. This is useful mainly if the
4224 chaining of stack frames has been damaged by a bug, making it
4225 impossible for @value{GDBN} to assign numbers properly to all frames. In
4226 addition, this can be useful when your program has multiple stacks and
4227 switches between them.
4229 On the SPARC architecture, @code{frame} needs two addresses to
4230 select an arbitrary frame: a frame pointer and a stack pointer.
4232 On the MIPS and Alpha architecture, it needs two addresses: a stack
4233 pointer and a program counter.
4235 On the 29k architecture, it needs three addresses: a register stack
4236 pointer, a program counter, and a memory stack pointer.
4237 @c note to future updaters: this is conditioned on a flag
4238 @c SETUP_ARBITRARY_FRAME in the tm-*.h files. The above is up to date
4239 @c as of 27 Jan 1994.
4243 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4244 advances toward the outermost frame, to higher frame numbers, to frames
4245 that have existed longer. @var{n} defaults to one.
4248 @kindex do @r{(@code{down})}
4250 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4251 advances toward the innermost frame, to lower frame numbers, to frames
4252 that were created more recently. @var{n} defaults to one. You may
4253 abbreviate @code{down} as @code{do}.
4256 All of these commands end by printing two lines of output describing the
4257 frame. The first line shows the frame number, the function name, the
4258 arguments, and the source file and line number of execution in that
4259 frame. The second line shows the text of that source line.
4267 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4269 10 read_input_file (argv[i]);
4273 After such a printout, the @code{list} command with no arguments
4274 prints ten lines centered on the point of execution in the frame.
4275 You can also edit the program at the point of execution with your favorite
4276 editing program by typing @code{edit}.
4277 @xref{List, ,Printing source lines},
4281 @kindex down-silently
4283 @item up-silently @var{n}
4284 @itemx down-silently @var{n}
4285 These two commands are variants of @code{up} and @code{down},
4286 respectively; they differ in that they do their work silently, without
4287 causing display of the new frame. They are intended primarily for use
4288 in @value{GDBN} command scripts, where the output might be unnecessary and
4293 @section Information about a frame
4295 There are several other commands to print information about the selected
4301 When used without any argument, this command does not change which
4302 frame is selected, but prints a brief description of the currently
4303 selected stack frame. It can be abbreviated @code{f}. With an
4304 argument, this command is used to select a stack frame.
4305 @xref{Selection, ,Selecting a frame}.
4308 @kindex info f @r{(@code{info frame})}
4311 This command prints a verbose description of the selected stack frame,
4316 the address of the frame
4318 the address of the next frame down (called by this frame)
4320 the address of the next frame up (caller of this frame)
4322 the language in which the source code corresponding to this frame is written
4324 the address of the frame's arguments
4326 the address of the frame's local variables
4328 the program counter saved in it (the address of execution in the caller frame)
4330 which registers were saved in the frame
4333 @noindent The verbose description is useful when
4334 something has gone wrong that has made the stack format fail to fit
4335 the usual conventions.
4337 @item info frame @var{addr}
4338 @itemx info f @var{addr}
4339 Print a verbose description of the frame at address @var{addr}, without
4340 selecting that frame. The selected frame remains unchanged by this
4341 command. This requires the same kind of address (more than one for some
4342 architectures) that you specify in the @code{frame} command.
4343 @xref{Selection, ,Selecting a frame}.
4347 Print the arguments of the selected frame, each on a separate line.
4351 Print the local variables of the selected frame, each on a separate
4352 line. These are all variables (declared either static or automatic)
4353 accessible at the point of execution of the selected frame.
4356 @cindex catch exceptions, list active handlers
4357 @cindex exception handlers, how to list
4359 Print a list of all the exception handlers that are active in the
4360 current stack frame at the current point of execution. To see other
4361 exception handlers, visit the associated frame (using the @code{up},
4362 @code{down}, or @code{frame} commands); then type @code{info catch}.
4363 @xref{Set Catchpoints, , Setting catchpoints}.
4369 @chapter Examining Source Files
4371 @value{GDBN} can print parts of your program's source, since the debugging
4372 information recorded in the program tells @value{GDBN} what source files were
4373 used to build it. When your program stops, @value{GDBN} spontaneously prints
4374 the line where it stopped. Likewise, when you select a stack frame
4375 (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
4376 execution in that frame has stopped. You can print other portions of
4377 source files by explicit command.
4379 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4380 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4381 @value{GDBN} under @sc{gnu} Emacs}.
4384 * List:: Printing source lines
4385 * Edit:: Editing source files
4386 * Search:: Searching source files
4387 * Source Path:: Specifying source directories
4388 * Machine Code:: Source and machine code
4392 @section Printing source lines
4395 @kindex l @r{(@code{list})}
4396 To print lines from a source file, use the @code{list} command
4397 (abbreviated @code{l}). By default, ten lines are printed.
4398 There are several ways to specify what part of the file you want to print.
4400 Here are the forms of the @code{list} command most commonly used:
4403 @item list @var{linenum}
4404 Print lines centered around line number @var{linenum} in the
4405 current source file.
4407 @item list @var{function}
4408 Print lines centered around the beginning of function
4412 Print more lines. If the last lines printed were printed with a
4413 @code{list} command, this prints lines following the last lines
4414 printed; however, if the last line printed was a solitary line printed
4415 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4416 Stack}), this prints lines centered around that line.
4419 Print lines just before the lines last printed.
4422 @cindex @code{list}, how many lines to display
4423 By default, @value{GDBN} prints ten source lines with any of these forms of
4424 the @code{list} command. You can change this using @code{set listsize}:
4427 @kindex set listsize
4428 @item set listsize @var{count}
4429 Make the @code{list} command display @var{count} source lines (unless
4430 the @code{list} argument explicitly specifies some other number).
4432 @kindex show listsize
4434 Display the number of lines that @code{list} prints.
4437 Repeating a @code{list} command with @key{RET} discards the argument,
4438 so it is equivalent to typing just @code{list}. This is more useful
4439 than listing the same lines again. An exception is made for an
4440 argument of @samp{-}; that argument is preserved in repetition so that
4441 each repetition moves up in the source file.
4444 In general, the @code{list} command expects you to supply zero, one or two
4445 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4446 of writing them, but the effect is always to specify some source line.
4447 Here is a complete description of the possible arguments for @code{list}:
4450 @item list @var{linespec}
4451 Print lines centered around the line specified by @var{linespec}.
4453 @item list @var{first},@var{last}
4454 Print lines from @var{first} to @var{last}. Both arguments are
4457 @item list ,@var{last}
4458 Print lines ending with @var{last}.
4460 @item list @var{first},
4461 Print lines starting with @var{first}.
4464 Print lines just after the lines last printed.
4467 Print lines just before the lines last printed.
4470 As described in the preceding table.
4473 Here are the ways of specifying a single source line---all the
4478 Specifies line @var{number} of the current source file.
4479 When a @code{list} command has two linespecs, this refers to
4480 the same source file as the first linespec.
4483 Specifies the line @var{offset} lines after the last line printed.
4484 When used as the second linespec in a @code{list} command that has
4485 two, this specifies the line @var{offset} lines down from the
4489 Specifies the line @var{offset} lines before the last line printed.
4491 @item @var{filename}:@var{number}
4492 Specifies line @var{number} in the source file @var{filename}.
4494 @item @var{function}
4495 Specifies the line that begins the body of the function @var{function}.
4496 For example: in C, this is the line with the open brace.
4498 @item @var{filename}:@var{function}
4499 Specifies the line of the open-brace that begins the body of the
4500 function @var{function} in the file @var{filename}. You only need the
4501 file name with a function name to avoid ambiguity when there are
4502 identically named functions in different source files.
4504 @item *@var{address}
4505 Specifies the line containing the program address @var{address}.
4506 @var{address} may be any expression.
4510 @section Editing source files
4511 @cindex editing source files
4514 @kindex e @r{(@code{edit})}
4515 To edit the lines in a source file, use the @code{edit} command.
4516 The editing program of your choice
4517 is invoked with the current line set to
4518 the active line in the program.
4519 Alternatively, there are several ways to specify what part of the file you
4520 want to print if you want to see other parts of the program.
4522 Here are the forms of the @code{edit} command most commonly used:
4526 Edit the current source file at the active line number in the program.
4528 @item edit @var{number}
4529 Edit the current source file with @var{number} as the active line number.
4531 @item edit @var{function}
4532 Edit the file containing @var{function} at the beginning of its definition.
4534 @item edit @var{filename}:@var{number}
4535 Specifies line @var{number} in the source file @var{filename}.
4537 @item edit @var{filename}:@var{function}
4538 Specifies the line that begins the body of the
4539 function @var{function} in the file @var{filename}. You only need the
4540 file name with a function name to avoid ambiguity when there are
4541 identically named functions in different source files.
4543 @item edit *@var{address}
4544 Specifies the line containing the program address @var{address}.
4545 @var{address} may be any expression.
4548 @subsection Choosing your editor
4549 You can customize @value{GDBN} to use any editor you want
4551 The only restriction is that your editor (say @code{ex}), recognizes the
4552 following command-line syntax:
4554 ex +@var{number} file
4556 The optional numeric value +@var{number} specifies the number of the line in
4557 the file where to start editing.}.
4558 By default, it is @file{@value{EDITOR}}, but you can change this
4559 by setting the environment variable @code{EDITOR} before using
4560 @value{GDBN}. For example, to configure @value{GDBN} to use the
4561 @code{vi} editor, you could use these commands with the @code{sh} shell:
4567 or in the @code{csh} shell,
4569 setenv EDITOR /usr/bin/vi
4574 @section Searching source files
4575 @cindex searching source files
4577 There are two commands for searching through the current source file for a
4582 @kindex forward-search
4583 @item forward-search @var{regexp}
4584 @itemx search @var{regexp}
4585 The command @samp{forward-search @var{regexp}} checks each line,
4586 starting with the one following the last line listed, for a match for
4587 @var{regexp}. It lists the line that is found. You can use the
4588 synonym @samp{search @var{regexp}} or abbreviate the command name as
4591 @kindex reverse-search
4592 @item reverse-search @var{regexp}
4593 The command @samp{reverse-search @var{regexp}} checks each line, starting
4594 with the one before the last line listed and going backward, for a match
4595 for @var{regexp}. It lists the line that is found. You can abbreviate
4596 this command as @code{rev}.
4600 @section Specifying source directories
4603 @cindex directories for source files
4604 Executable programs sometimes do not record the directories of the source
4605 files from which they were compiled, just the names. Even when they do,
4606 the directories could be moved between the compilation and your debugging
4607 session. @value{GDBN} has a list of directories to search for source files;
4608 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
4609 it tries all the directories in the list, in the order they are present
4610 in the list, until it finds a file with the desired name.
4612 For example, suppose an executable references the file
4613 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
4614 @file{/mnt/cross}. The file is first looked up literally; if this
4615 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
4616 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
4617 message is printed. @value{GDBN} does not look up the parts of the
4618 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
4619 Likewise, the subdirectories of the source path are not searched: if
4620 the source path is @file{/mnt/cross}, and the binary refers to
4621 @file{foo.c}, @value{GDBN} would not find it under
4622 @file{/mnt/cross/usr/src/foo-1.0/lib}.
4624 Plain file names, relative file names with leading directories, file
4625 names containing dots, etc.@: are all treated as described above; for
4626 instance, if the source path is @file{/mnt/cross}, and the source file
4627 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
4628 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
4629 that---@file{/mnt/cross/foo.c}.
4631 Note that the executable search path is @emph{not} used to locate the
4632 source files. Neither is the current working directory, unless it
4633 happens to be in the source path.
4635 Whenever you reset or rearrange the source path, @value{GDBN} clears out
4636 any information it has cached about where source files are found and where
4637 each line is in the file.
4641 When you start @value{GDBN}, its source path includes only @samp{cdir}
4642 and @samp{cwd}, in that order.
4643 To add other directories, use the @code{directory} command.
4646 @item directory @var{dirname} @dots{}
4647 @item dir @var{dirname} @dots{}
4648 Add directory @var{dirname} to the front of the source path. Several
4649 directory names may be given to this command, separated by @samp{:}
4650 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
4651 part of absolute file names) or
4652 whitespace. You may specify a directory that is already in the source
4653 path; this moves it forward, so @value{GDBN} searches it sooner.
4657 @vindex $cdir@r{, convenience variable}
4658 @vindex $cwdr@r{, convenience variable}
4659 @cindex compilation directory
4660 @cindex current directory
4661 @cindex working directory
4662 @cindex directory, current
4663 @cindex directory, compilation
4664 You can use the string @samp{$cdir} to refer to the compilation
4665 directory (if one is recorded), and @samp{$cwd} to refer to the current
4666 working directory. @samp{$cwd} is not the same as @samp{.}---the former
4667 tracks the current working directory as it changes during your @value{GDBN}
4668 session, while the latter is immediately expanded to the current
4669 directory at the time you add an entry to the source path.
4672 Reset the source path to empty again. This requires confirmation.
4674 @c RET-repeat for @code{directory} is explicitly disabled, but since
4675 @c repeating it would be a no-op we do not say that. (thanks to RMS)
4677 @item show directories
4678 @kindex show directories
4679 Print the source path: show which directories it contains.
4682 If your source path is cluttered with directories that are no longer of
4683 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
4684 versions of source. You can correct the situation as follows:
4688 Use @code{directory} with no argument to reset the source path to empty.
4691 Use @code{directory} with suitable arguments to reinstall the
4692 directories you want in the source path. You can add all the
4693 directories in one command.
4697 @section Source and machine code
4698 @cindex source line and its code address
4700 You can use the command @code{info line} to map source lines to program
4701 addresses (and vice versa), and the command @code{disassemble} to display
4702 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
4703 mode, the @code{info line} command causes the arrow to point to the
4704 line specified. Also, @code{info line} prints addresses in symbolic form as
4709 @item info line @var{linespec}
4710 Print the starting and ending addresses of the compiled code for
4711 source line @var{linespec}. You can specify source lines in any of
4712 the ways understood by the @code{list} command (@pxref{List, ,Printing
4716 For example, we can use @code{info line} to discover the location of
4717 the object code for the first line of function
4718 @code{m4_changequote}:
4720 @c FIXME: I think this example should also show the addresses in
4721 @c symbolic form, as they usually would be displayed.
4723 (@value{GDBP}) info line m4_changequote
4724 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
4728 @cindex code address and its source line
4729 We can also inquire (using @code{*@var{addr}} as the form for
4730 @var{linespec}) what source line covers a particular address:
4732 (@value{GDBP}) info line *0x63ff
4733 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
4736 @cindex @code{$_} and @code{info line}
4737 @cindex @code{x} command, default address
4738 @kindex x@r{(examine), and} info line
4739 After @code{info line}, the default address for the @code{x} command
4740 is changed to the starting address of the line, so that @samp{x/i} is
4741 sufficient to begin examining the machine code (@pxref{Memory,
4742 ,Examining memory}). Also, this address is saved as the value of the
4743 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
4748 @cindex assembly instructions
4749 @cindex instructions, assembly
4750 @cindex machine instructions
4751 @cindex listing machine instructions
4753 This specialized command dumps a range of memory as machine
4754 instructions. The default memory range is the function surrounding the
4755 program counter of the selected frame. A single argument to this
4756 command is a program counter value; @value{GDBN} dumps the function
4757 surrounding this value. Two arguments specify a range of addresses
4758 (first inclusive, second exclusive) to dump.
4761 The following example shows the disassembly of a range of addresses of
4762 HP PA-RISC 2.0 code:
4765 (@value{GDBP}) disas 0x32c4 0x32e4
4766 Dump of assembler code from 0x32c4 to 0x32e4:
4767 0x32c4 <main+204>: addil 0,dp
4768 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
4769 0x32cc <main+212>: ldil 0x3000,r31
4770 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
4771 0x32d4 <main+220>: ldo 0(r31),rp
4772 0x32d8 <main+224>: addil -0x800,dp
4773 0x32dc <main+228>: ldo 0x588(r1),r26
4774 0x32e0 <main+232>: ldil 0x3000,r31
4775 End of assembler dump.
4778 Some architectures have more than one commonly-used set of instruction
4779 mnemonics or other syntax.
4782 @kindex set disassembly-flavor
4783 @cindex Intel disassembly flavor
4784 @cindex AT&T disassembly flavor
4785 @item set disassembly-flavor @var{instruction-set}
4786 Select the instruction set to use when disassembling the
4787 program via the @code{disassemble} or @code{x/i} commands.
4789 Currently this command is only defined for the Intel x86 family. You
4790 can set @var{instruction-set} to either @code{intel} or @code{att}.
4791 The default is @code{att}, the AT&T flavor used by default by Unix
4792 assemblers for x86-based targets.
4794 @kindex show disassembly-flavor
4795 @item show disassembly-flavor
4796 Show the current setting of the disassembly flavor.
4801 @chapter Examining Data
4803 @cindex printing data
4804 @cindex examining data
4807 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
4808 @c document because it is nonstandard... Under Epoch it displays in a
4809 @c different window or something like that.
4810 The usual way to examine data in your program is with the @code{print}
4811 command (abbreviated @code{p}), or its synonym @code{inspect}. It
4812 evaluates and prints the value of an expression of the language your
4813 program is written in (@pxref{Languages, ,Using @value{GDBN} with
4814 Different Languages}).
4817 @item print @var{expr}
4818 @itemx print /@var{f} @var{expr}
4819 @var{expr} is an expression (in the source language). By default the
4820 value of @var{expr} is printed in a format appropriate to its data type;
4821 you can choose a different format by specifying @samp{/@var{f}}, where
4822 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
4826 @itemx print /@var{f}
4827 @cindex reprint the last value
4828 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
4829 @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
4830 conveniently inspect the same value in an alternative format.
4833 A more low-level way of examining data is with the @code{x} command.
4834 It examines data in memory at a specified address and prints it in a
4835 specified format. @xref{Memory, ,Examining memory}.
4837 If you are interested in information about types, or about how the
4838 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
4839 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
4843 * Expressions:: Expressions
4844 * Variables:: Program variables
4845 * Arrays:: Artificial arrays
4846 * Output Formats:: Output formats
4847 * Memory:: Examining memory
4848 * Auto Display:: Automatic display
4849 * Print Settings:: Print settings
4850 * Value History:: Value history
4851 * Convenience Vars:: Convenience variables
4852 * Registers:: Registers
4853 * Floating Point Hardware:: Floating point hardware
4854 * Vector Unit:: Vector Unit
4855 * Auxiliary Vector:: Auxiliary data provided by operating system
4856 * Memory Region Attributes:: Memory region attributes
4857 * Dump/Restore Files:: Copy between memory and a file
4858 * Core File Generation:: Cause a program dump its core
4859 * Character Sets:: Debugging programs that use a different
4860 character set than GDB does
4861 * Caching Remote Data:: Data caching for remote targets
4865 @section Expressions
4868 @code{print} and many other @value{GDBN} commands accept an expression and
4869 compute its value. Any kind of constant, variable or operator defined
4870 by the programming language you are using is valid in an expression in
4871 @value{GDBN}. This includes conditional expressions, function calls,
4872 casts, and string constants. It also includes preprocessor macros, if
4873 you compiled your program to include this information; see
4876 @cindex arrays in expressions
4877 @value{GDBN} supports array constants in expressions input by
4878 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
4879 you can use the command @code{print @{1, 2, 3@}} to build up an array in
4880 memory that is @code{malloc}ed in the target program.
4882 Because C is so widespread, most of the expressions shown in examples in
4883 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
4884 Languages}, for information on how to use expressions in other
4887 In this section, we discuss operators that you can use in @value{GDBN}
4888 expressions regardless of your programming language.
4890 @cindex casts, in expressions
4891 Casts are supported in all languages, not just in C, because it is so
4892 useful to cast a number into a pointer in order to examine a structure
4893 at that address in memory.
4894 @c FIXME: casts supported---Mod2 true?
4896 @value{GDBN} supports these operators, in addition to those common
4897 to programming languages:
4901 @samp{@@} is a binary operator for treating parts of memory as arrays.
4902 @xref{Arrays, ,Artificial arrays}, for more information.
4905 @samp{::} allows you to specify a variable in terms of the file or
4906 function where it is defined. @xref{Variables, ,Program variables}.
4908 @cindex @{@var{type}@}
4909 @cindex type casting memory
4910 @cindex memory, viewing as typed object
4911 @cindex casts, to view memory
4912 @item @{@var{type}@} @var{addr}
4913 Refers to an object of type @var{type} stored at address @var{addr} in
4914 memory. @var{addr} may be any expression whose value is an integer or
4915 pointer (but parentheses are required around binary operators, just as in
4916 a cast). This construct is allowed regardless of what kind of data is
4917 normally supposed to reside at @var{addr}.
4921 @section Program variables
4923 The most common kind of expression to use is the name of a variable
4926 Variables in expressions are understood in the selected stack frame
4927 (@pxref{Selection, ,Selecting a frame}); they must be either:
4931 global (or file-static)
4938 visible according to the scope rules of the
4939 programming language from the point of execution in that frame
4942 @noindent This means that in the function
4957 you can examine and use the variable @code{a} whenever your program is
4958 executing within the function @code{foo}, but you can only use or
4959 examine the variable @code{b} while your program is executing inside
4960 the block where @code{b} is declared.
4962 @cindex variable name conflict
4963 There is an exception: you can refer to a variable or function whose
4964 scope is a single source file even if the current execution point is not
4965 in this file. But it is possible to have more than one such variable or
4966 function with the same name (in different source files). If that
4967 happens, referring to that name has unpredictable effects. If you wish,
4968 you can specify a static variable in a particular function or file,
4969 using the colon-colon (@code{::}) notation:
4971 @cindex colon-colon, context for variables/functions
4973 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
4974 @cindex @code{::}, context for variables/functions
4977 @var{file}::@var{variable}
4978 @var{function}::@var{variable}
4982 Here @var{file} or @var{function} is the name of the context for the
4983 static @var{variable}. In the case of file names, you can use quotes to
4984 make sure @value{GDBN} parses the file name as a single word---for example,
4985 to print a global value of @code{x} defined in @file{f2.c}:
4988 (@value{GDBP}) p 'f2.c'::x
4991 @cindex C@t{++} scope resolution
4992 This use of @samp{::} is very rarely in conflict with the very similar
4993 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
4994 scope resolution operator in @value{GDBN} expressions.
4995 @c FIXME: Um, so what happens in one of those rare cases where it's in
4998 @cindex wrong values
4999 @cindex variable values, wrong
5000 @cindex function entry/exit, wrong values of variables
5001 @cindex optimized code, wrong values of variables
5003 @emph{Warning:} Occasionally, a local variable may appear to have the
5004 wrong value at certain points in a function---just after entry to a new
5005 scope, and just before exit.
5007 You may see this problem when you are stepping by machine instructions.
5008 This is because, on most machines, it takes more than one instruction to
5009 set up a stack frame (including local variable definitions); if you are
5010 stepping by machine instructions, variables may appear to have the wrong
5011 values until the stack frame is completely built. On exit, it usually
5012 also takes more than one machine instruction to destroy a stack frame;
5013 after you begin stepping through that group of instructions, local
5014 variable definitions may be gone.
5016 This may also happen when the compiler does significant optimizations.
5017 To be sure of always seeing accurate values, turn off all optimization
5020 @cindex ``No symbol "foo" in current context''
5021 Another possible effect of compiler optimizations is to optimize
5022 unused variables out of existence, or assign variables to registers (as
5023 opposed to memory addresses). Depending on the support for such cases
5024 offered by the debug info format used by the compiler, @value{GDBN}
5025 might not be able to display values for such local variables. If that
5026 happens, @value{GDBN} will print a message like this:
5029 No symbol "foo" in current context.
5032 To solve such problems, either recompile without optimizations, or use a
5033 different debug info format, if the compiler supports several such
5034 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
5035 usually supports the @option{-gstabs+} option. @option{-gstabs+}
5036 produces debug info in a format that is superior to formats such as
5037 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
5038 an effective form for debug info. @xref{Debugging Options,,Options
5039 for Debugging Your Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}.
5040 @xref{C, , Debugging C++}, for more info about debug info formats
5041 that are best suited to C@t{++} programs.
5044 @section Artificial arrays
5046 @cindex artificial array
5048 @kindex @@@r{, referencing memory as an array}
5049 It is often useful to print out several successive objects of the
5050 same type in memory; a section of an array, or an array of
5051 dynamically determined size for which only a pointer exists in the
5054 You can do this by referring to a contiguous span of memory as an
5055 @dfn{artificial array}, using the binary operator @samp{@@}. The left
5056 operand of @samp{@@} should be the first element of the desired array
5057 and be an individual object. The right operand should be the desired length
5058 of the array. The result is an array value whose elements are all of
5059 the type of the left argument. The first element is actually the left
5060 argument; the second element comes from bytes of memory immediately
5061 following those that hold the first element, and so on. Here is an
5062 example. If a program says
5065 int *array = (int *) malloc (len * sizeof (int));
5069 you can print the contents of @code{array} with
5075 The left operand of @samp{@@} must reside in memory. Array values made
5076 with @samp{@@} in this way behave just like other arrays in terms of
5077 subscripting, and are coerced to pointers when used in expressions.
5078 Artificial arrays most often appear in expressions via the value history
5079 (@pxref{Value History, ,Value history}), after printing one out.
5081 Another way to create an artificial array is to use a cast.
5082 This re-interprets a value as if it were an array.
5083 The value need not be in memory:
5085 (@value{GDBP}) p/x (short[2])0x12345678
5086 $1 = @{0x1234, 0x5678@}
5089 As a convenience, if you leave the array length out (as in
5090 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5091 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5093 (@value{GDBP}) p/x (short[])0x12345678
5094 $2 = @{0x1234, 0x5678@}
5097 Sometimes the artificial array mechanism is not quite enough; in
5098 moderately complex data structures, the elements of interest may not
5099 actually be adjacent---for example, if you are interested in the values
5100 of pointers in an array. One useful work-around in this situation is
5101 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5102 variables}) as a counter in an expression that prints the first
5103 interesting value, and then repeat that expression via @key{RET}. For
5104 instance, suppose you have an array @code{dtab} of pointers to
5105 structures, and you are interested in the values of a field @code{fv}
5106 in each structure. Here is an example of what you might type:
5116 @node Output Formats
5117 @section Output formats
5119 @cindex formatted output
5120 @cindex output formats
5121 By default, @value{GDBN} prints a value according to its data type. Sometimes
5122 this is not what you want. For example, you might want to print a number
5123 in hex, or a pointer in decimal. Or you might want to view data in memory
5124 at a certain address as a character string or as an instruction. To do
5125 these things, specify an @dfn{output format} when you print a value.
5127 The simplest use of output formats is to say how to print a value
5128 already computed. This is done by starting the arguments of the
5129 @code{print} command with a slash and a format letter. The format
5130 letters supported are:
5134 Regard the bits of the value as an integer, and print the integer in
5138 Print as integer in signed decimal.
5141 Print as integer in unsigned decimal.
5144 Print as integer in octal.
5147 Print as integer in binary. The letter @samp{t} stands for ``two''.
5148 @footnote{@samp{b} cannot be used because these format letters are also
5149 used with the @code{x} command, where @samp{b} stands for ``byte'';
5150 see @ref{Memory,,Examining memory}.}
5153 @cindex unknown address, locating
5154 @cindex locate address
5155 Print as an address, both absolute in hexadecimal and as an offset from
5156 the nearest preceding symbol. You can use this format used to discover
5157 where (in what function) an unknown address is located:
5160 (@value{GDBP}) p/a 0x54320
5161 $3 = 0x54320 <_initialize_vx+396>
5165 The command @code{info symbol 0x54320} yields similar results.
5166 @xref{Symbols, info symbol}.
5169 Regard as an integer and print it as a character constant.
5172 Regard the bits of the value as a floating point number and print
5173 using typical floating point syntax.
5176 For example, to print the program counter in hex (@pxref{Registers}), type
5183 Note that no space is required before the slash; this is because command
5184 names in @value{GDBN} cannot contain a slash.
5186 To reprint the last value in the value history with a different format,
5187 you can use the @code{print} command with just a format and no
5188 expression. For example, @samp{p/x} reprints the last value in hex.
5191 @section Examining memory
5193 You can use the command @code{x} (for ``examine'') to examine memory in
5194 any of several formats, independently of your program's data types.
5196 @cindex examining memory
5198 @kindex x @r{(examine memory)}
5199 @item x/@var{nfu} @var{addr}
5202 Use the @code{x} command to examine memory.
5205 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5206 much memory to display and how to format it; @var{addr} is an
5207 expression giving the address where you want to start displaying memory.
5208 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5209 Several commands set convenient defaults for @var{addr}.
5212 @item @var{n}, the repeat count
5213 The repeat count is a decimal integer; the default is 1. It specifies
5214 how much memory (counting by units @var{u}) to display.
5215 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5218 @item @var{f}, the display format
5219 The display format is one of the formats used by @code{print},
5220 @samp{s} (null-terminated string), or @samp{i} (machine instruction).
5221 The default is @samp{x} (hexadecimal) initially.
5222 The default changes each time you use either @code{x} or @code{print}.
5224 @item @var{u}, the unit size
5225 The unit size is any of
5231 Halfwords (two bytes).
5233 Words (four bytes). This is the initial default.
5235 Giant words (eight bytes).
5238 Each time you specify a unit size with @code{x}, that size becomes the
5239 default unit the next time you use @code{x}. (For the @samp{s} and
5240 @samp{i} formats, the unit size is ignored and is normally not written.)
5242 @item @var{addr}, starting display address
5243 @var{addr} is the address where you want @value{GDBN} to begin displaying
5244 memory. The expression need not have a pointer value (though it may);
5245 it is always interpreted as an integer address of a byte of memory.
5246 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5247 @var{addr} is usually just after the last address examined---but several
5248 other commands also set the default address: @code{info breakpoints} (to
5249 the address of the last breakpoint listed), @code{info line} (to the
5250 starting address of a line), and @code{print} (if you use it to display
5251 a value from memory).
5254 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5255 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5256 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5257 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5258 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5260 Since the letters indicating unit sizes are all distinct from the
5261 letters specifying output formats, you do not have to remember whether
5262 unit size or format comes first; either order works. The output
5263 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5264 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5266 Even though the unit size @var{u} is ignored for the formats @samp{s}
5267 and @samp{i}, you might still want to use a count @var{n}; for example,
5268 @samp{3i} specifies that you want to see three machine instructions,
5269 including any operands. The command @code{disassemble} gives an
5270 alternative way of inspecting machine instructions; see @ref{Machine
5271 Code,,Source and machine code}.
5273 All the defaults for the arguments to @code{x} are designed to make it
5274 easy to continue scanning memory with minimal specifications each time
5275 you use @code{x}. For example, after you have inspected three machine
5276 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5277 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5278 the repeat count @var{n} is used again; the other arguments default as
5279 for successive uses of @code{x}.
5281 @cindex @code{$_}, @code{$__}, and value history
5282 The addresses and contents printed by the @code{x} command are not saved
5283 in the value history because there is often too much of them and they
5284 would get in the way. Instead, @value{GDBN} makes these values available for
5285 subsequent use in expressions as values of the convenience variables
5286 @code{$_} and @code{$__}. After an @code{x} command, the last address
5287 examined is available for use in expressions in the convenience variable
5288 @code{$_}. The contents of that address, as examined, are available in
5289 the convenience variable @code{$__}.
5291 If the @code{x} command has a repeat count, the address and contents saved
5292 are from the last memory unit printed; this is not the same as the last
5293 address printed if several units were printed on the last line of output.
5295 @cindex remote memory comparison
5296 @cindex verify remote memory image
5297 When you are debugging a program running on a remote target machine
5298 (@pxref{Remote}), you may wish to verify the program's image in the
5299 remote machine's memory against the executable file you downloaded to
5300 the target. The @code{compare-sections} command is provided for such
5304 @kindex compare-sections
5305 @item compare-sections @r{[}@var{section-name}@r{]}
5306 Compare the data of a loadable section @var{section-name} in the
5307 executable file of the program being debugged with the same section in
5308 the remote machine's memory, and report any mismatches. With no
5309 arguments, compares all loadable sections. This command's
5310 availability depends on the target's support for the @code{"qCRC"}
5315 @section Automatic display
5316 @cindex automatic display
5317 @cindex display of expressions
5319 If you find that you want to print the value of an expression frequently
5320 (to see how it changes), you might want to add it to the @dfn{automatic
5321 display list} so that @value{GDBN} prints its value each time your program stops.
5322 Each expression added to the list is given a number to identify it;
5323 to remove an expression from the list, you specify that number.
5324 The automatic display looks like this:
5328 3: bar[5] = (struct hack *) 0x3804
5332 This display shows item numbers, expressions and their current values. As with
5333 displays you request manually using @code{x} or @code{print}, you can
5334 specify the output format you prefer; in fact, @code{display} decides
5335 whether to use @code{print} or @code{x} depending on how elaborate your
5336 format specification is---it uses @code{x} if you specify a unit size,
5337 or one of the two formats (@samp{i} and @samp{s}) that are only
5338 supported by @code{x}; otherwise it uses @code{print}.
5342 @item display @var{expr}
5343 Add the expression @var{expr} to the list of expressions to display
5344 each time your program stops. @xref{Expressions, ,Expressions}.
5346 @code{display} does not repeat if you press @key{RET} again after using it.
5348 @item display/@var{fmt} @var{expr}
5349 For @var{fmt} specifying only a display format and not a size or
5350 count, add the expression @var{expr} to the auto-display list but
5351 arrange to display it each time in the specified format @var{fmt}.
5352 @xref{Output Formats,,Output formats}.
5354 @item display/@var{fmt} @var{addr}
5355 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
5356 number of units, add the expression @var{addr} as a memory address to
5357 be examined each time your program stops. Examining means in effect
5358 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
5361 For example, @samp{display/i $pc} can be helpful, to see the machine
5362 instruction about to be executed each time execution stops (@samp{$pc}
5363 is a common name for the program counter; @pxref{Registers, ,Registers}).
5366 @kindex delete display
5368 @item undisplay @var{dnums}@dots{}
5369 @itemx delete display @var{dnums}@dots{}
5370 Remove item numbers @var{dnums} from the list of expressions to display.
5372 @code{undisplay} does not repeat if you press @key{RET} after using it.
5373 (Otherwise you would just get the error @samp{No display number @dots{}}.)
5375 @kindex disable display
5376 @item disable display @var{dnums}@dots{}
5377 Disable the display of item numbers @var{dnums}. A disabled display
5378 item is not printed automatically, but is not forgotten. It may be
5379 enabled again later.
5381 @kindex enable display
5382 @item enable display @var{dnums}@dots{}
5383 Enable display of item numbers @var{dnums}. It becomes effective once
5384 again in auto display of its expression, until you specify otherwise.
5387 Display the current values of the expressions on the list, just as is
5388 done when your program stops.
5390 @kindex info display
5392 Print the list of expressions previously set up to display
5393 automatically, each one with its item number, but without showing the
5394 values. This includes disabled expressions, which are marked as such.
5395 It also includes expressions which would not be displayed right now
5396 because they refer to automatic variables not currently available.
5399 @cindex display disabled out of scope
5400 If a display expression refers to local variables, then it does not make
5401 sense outside the lexical context for which it was set up. Such an
5402 expression is disabled when execution enters a context where one of its
5403 variables is not defined. For example, if you give the command
5404 @code{display last_char} while inside a function with an argument
5405 @code{last_char}, @value{GDBN} displays this argument while your program
5406 continues to stop inside that function. When it stops elsewhere---where
5407 there is no variable @code{last_char}---the display is disabled
5408 automatically. The next time your program stops where @code{last_char}
5409 is meaningful, you can enable the display expression once again.
5411 @node Print Settings
5412 @section Print settings
5414 @cindex format options
5415 @cindex print settings
5416 @value{GDBN} provides the following ways to control how arrays, structures,
5417 and symbols are printed.
5420 These settings are useful for debugging programs in any language:
5424 @item set print address
5425 @itemx set print address on
5426 @cindex print/don't print memory addresses
5427 @value{GDBN} prints memory addresses showing the location of stack
5428 traces, structure values, pointer values, breakpoints, and so forth,
5429 even when it also displays the contents of those addresses. The default
5430 is @code{on}. For example, this is what a stack frame display looks like with
5431 @code{set print address on}:
5436 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
5438 530 if (lquote != def_lquote)
5442 @item set print address off
5443 Do not print addresses when displaying their contents. For example,
5444 this is the same stack frame displayed with @code{set print address off}:
5448 (@value{GDBP}) set print addr off
5450 #0 set_quotes (lq="<<", rq=">>") at input.c:530
5451 530 if (lquote != def_lquote)
5455 You can use @samp{set print address off} to eliminate all machine
5456 dependent displays from the @value{GDBN} interface. For example, with
5457 @code{print address off}, you should get the same text for backtraces on
5458 all machines---whether or not they involve pointer arguments.
5461 @item show print address
5462 Show whether or not addresses are to be printed.
5465 When @value{GDBN} prints a symbolic address, it normally prints the
5466 closest earlier symbol plus an offset. If that symbol does not uniquely
5467 identify the address (for example, it is a name whose scope is a single
5468 source file), you may need to clarify. One way to do this is with
5469 @code{info line}, for example @samp{info line *0x4537}. Alternately,
5470 you can set @value{GDBN} to print the source file and line number when
5471 it prints a symbolic address:
5474 @item set print symbol-filename on
5475 @cindex source file and line of a symbol
5476 @cindex symbol, source file and line
5477 Tell @value{GDBN} to print the source file name and line number of a
5478 symbol in the symbolic form of an address.
5480 @item set print symbol-filename off
5481 Do not print source file name and line number of a symbol. This is the
5484 @item show print symbol-filename
5485 Show whether or not @value{GDBN} will print the source file name and
5486 line number of a symbol in the symbolic form of an address.
5489 Another situation where it is helpful to show symbol filenames and line
5490 numbers is when disassembling code; @value{GDBN} shows you the line
5491 number and source file that corresponds to each instruction.
5493 Also, you may wish to see the symbolic form only if the address being
5494 printed is reasonably close to the closest earlier symbol:
5497 @item set print max-symbolic-offset @var{max-offset}
5498 @cindex maximum value for offset of closest symbol
5499 Tell @value{GDBN} to only display the symbolic form of an address if the
5500 offset between the closest earlier symbol and the address is less than
5501 @var{max-offset}. The default is 0, which tells @value{GDBN}
5502 to always print the symbolic form of an address if any symbol precedes it.
5504 @item show print max-symbolic-offset
5505 Ask how large the maximum offset is that @value{GDBN} prints in a
5509 @cindex wild pointer, interpreting
5510 @cindex pointer, finding referent
5511 If you have a pointer and you are not sure where it points, try
5512 @samp{set print symbol-filename on}. Then you can determine the name
5513 and source file location of the variable where it points, using
5514 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
5515 For example, here @value{GDBN} shows that a variable @code{ptt} points
5516 at another variable @code{t}, defined in @file{hi2.c}:
5519 (@value{GDBP}) set print symbol-filename on
5520 (@value{GDBP}) p/a ptt
5521 $4 = 0xe008 <t in hi2.c>
5525 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
5526 does not show the symbol name and filename of the referent, even with
5527 the appropriate @code{set print} options turned on.
5530 Other settings control how different kinds of objects are printed:
5533 @item set print array
5534 @itemx set print array on
5535 @cindex pretty print arrays
5536 Pretty print arrays. This format is more convenient to read,
5537 but uses more space. The default is off.
5539 @item set print array off
5540 Return to compressed format for arrays.
5542 @item show print array
5543 Show whether compressed or pretty format is selected for displaying
5546 @item set print elements @var{number-of-elements}
5547 @cindex number of array elements to print
5548 @cindex limit on number of printed array elements
5549 Set a limit on how many elements of an array @value{GDBN} will print.
5550 If @value{GDBN} is printing a large array, it stops printing after it has
5551 printed the number of elements set by the @code{set print elements} command.
5552 This limit also applies to the display of strings.
5553 When @value{GDBN} starts, this limit is set to 200.
5554 Setting @var{number-of-elements} to zero means that the printing is unlimited.
5556 @item show print elements
5557 Display the number of elements of a large array that @value{GDBN} will print.
5558 If the number is 0, then the printing is unlimited.
5560 @item set print repeats
5561 @cindex repeated array elements
5562 Set the threshold for suppressing display of repeated array
5563 elelments. When the number of consecutive identical elements of an
5564 array exceeds the threshold, @value{GDBN} prints the string
5565 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
5566 identical repetitions, instead of displaying the identical elements
5567 themselves. Setting the threshold to zero will cause all elements to
5568 be individually printed. The default threshold is 10.
5570 @item show print repeats
5571 Display the current threshold for printing repeated identical
5574 @item set print null-stop
5575 @cindex @sc{null} elements in arrays
5576 Cause @value{GDBN} to stop printing the characters of an array when the first
5577 @sc{null} is encountered. This is useful when large arrays actually
5578 contain only short strings.
5581 @item show print null-stop
5582 Show whether @value{GDBN} stops printing an array on the first
5583 @sc{null} character.
5585 @item set print pretty on
5586 @cindex print structures in indented form
5587 @cindex indentation in structure display
5588 Cause @value{GDBN} to print structures in an indented format with one member
5589 per line, like this:
5604 @item set print pretty off
5605 Cause @value{GDBN} to print structures in a compact format, like this:
5609 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
5610 meat = 0x54 "Pork"@}
5615 This is the default format.
5617 @item show print pretty
5618 Show which format @value{GDBN} is using to print structures.
5620 @item set print sevenbit-strings on
5621 @cindex eight-bit characters in strings
5622 @cindex octal escapes in strings
5623 Print using only seven-bit characters; if this option is set,
5624 @value{GDBN} displays any eight-bit characters (in strings or
5625 character values) using the notation @code{\}@var{nnn}. This setting is
5626 best if you are working in English (@sc{ascii}) and you use the
5627 high-order bit of characters as a marker or ``meta'' bit.
5629 @item set print sevenbit-strings off
5630 Print full eight-bit characters. This allows the use of more
5631 international character sets, and is the default.
5633 @item show print sevenbit-strings
5634 Show whether or not @value{GDBN} is printing only seven-bit characters.
5636 @item set print union on
5637 @cindex unions in structures, printing
5638 Tell @value{GDBN} to print unions which are contained in structures
5639 and other unions. This is the default setting.
5641 @item set print union off
5642 Tell @value{GDBN} not to print unions which are contained in
5643 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
5646 @item show print union
5647 Ask @value{GDBN} whether or not it will print unions which are contained in
5648 structures and other unions.
5650 For example, given the declarations
5653 typedef enum @{Tree, Bug@} Species;
5654 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
5655 typedef enum @{Caterpillar, Cocoon, Butterfly@}
5666 struct thing foo = @{Tree, @{Acorn@}@};
5670 with @code{set print union on} in effect @samp{p foo} would print
5673 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
5677 and with @code{set print union off} in effect it would print
5680 $1 = @{it = Tree, form = @{...@}@}
5684 @code{set print union} affects programs written in C-like languages
5690 These settings are of interest when debugging C@t{++} programs:
5693 @cindex demangling C@t{++} names
5694 @item set print demangle
5695 @itemx set print demangle on
5696 Print C@t{++} names in their source form rather than in the encoded
5697 (``mangled'') form passed to the assembler and linker for type-safe
5698 linkage. The default is on.
5700 @item show print demangle
5701 Show whether C@t{++} names are printed in mangled or demangled form.
5703 @item set print asm-demangle
5704 @itemx set print asm-demangle on
5705 Print C@t{++} names in their source form rather than their mangled form, even
5706 in assembler code printouts such as instruction disassemblies.
5709 @item show print asm-demangle
5710 Show whether C@t{++} names in assembly listings are printed in mangled
5713 @cindex C@t{++} symbol decoding style
5714 @cindex symbol decoding style, C@t{++}
5715 @kindex set demangle-style
5716 @item set demangle-style @var{style}
5717 Choose among several encoding schemes used by different compilers to
5718 represent C@t{++} names. The choices for @var{style} are currently:
5722 Allow @value{GDBN} to choose a decoding style by inspecting your program.
5725 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
5726 This is the default.
5729 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
5732 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
5735 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
5736 @strong{Warning:} this setting alone is not sufficient to allow
5737 debugging @code{cfront}-generated executables. @value{GDBN} would
5738 require further enhancement to permit that.
5741 If you omit @var{style}, you will see a list of possible formats.
5743 @item show demangle-style
5744 Display the encoding style currently in use for decoding C@t{++} symbols.
5746 @item set print object
5747 @itemx set print object on
5748 @cindex derived type of an object, printing
5749 @cindex display derived types
5750 When displaying a pointer to an object, identify the @emph{actual}
5751 (derived) type of the object rather than the @emph{declared} type, using
5752 the virtual function table.
5754 @item set print object off
5755 Display only the declared type of objects, without reference to the
5756 virtual function table. This is the default setting.
5758 @item show print object
5759 Show whether actual, or declared, object types are displayed.
5761 @item set print static-members
5762 @itemx set print static-members on
5763 @cindex static members of C@t{++} objects
5764 Print static members when displaying a C@t{++} object. The default is on.
5766 @item set print static-members off
5767 Do not print static members when displaying a C@t{++} object.
5769 @item show print static-members
5770 Show whether C@t{++} static members are printed or not.
5772 @item set print pascal_static-members
5773 @itemx set print pascal_static-members on
5774 @cindex static members of Pacal objects
5775 @cindex Pacal objects, static members display
5776 Print static members when displaying a Pascal object. The default is on.
5778 @item set print pascal_static-members off
5779 Do not print static members when displaying a Pascal object.
5781 @item show print pascal_static-members
5782 Show whether Pascal static members are printed or not.
5784 @c These don't work with HP ANSI C++ yet.
5785 @item set print vtbl
5786 @itemx set print vtbl on
5787 @cindex pretty print C@t{++} virtual function tables
5788 @cindex virtual functions (C@t{++}) display
5789 @cindex VTBL display
5790 Pretty print C@t{++} virtual function tables. The default is off.
5791 (The @code{vtbl} commands do not work on programs compiled with the HP
5792 ANSI C@t{++} compiler (@code{aCC}).)
5794 @item set print vtbl off
5795 Do not pretty print C@t{++} virtual function tables.
5797 @item show print vtbl
5798 Show whether C@t{++} virtual function tables are pretty printed, or not.
5802 @section Value history
5804 @cindex value history
5805 @cindex history of values printed by @value{GDBN}
5806 Values printed by the @code{print} command are saved in the @value{GDBN}
5807 @dfn{value history}. This allows you to refer to them in other expressions.
5808 Values are kept until the symbol table is re-read or discarded
5809 (for example with the @code{file} or @code{symbol-file} commands).
5810 When the symbol table changes, the value history is discarded,
5811 since the values may contain pointers back to the types defined in the
5816 @cindex history number
5817 The values printed are given @dfn{history numbers} by which you can
5818 refer to them. These are successive integers starting with one.
5819 @code{print} shows you the history number assigned to a value by
5820 printing @samp{$@var{num} = } before the value; here @var{num} is the
5823 To refer to any previous value, use @samp{$} followed by the value's
5824 history number. The way @code{print} labels its output is designed to
5825 remind you of this. Just @code{$} refers to the most recent value in
5826 the history, and @code{$$} refers to the value before that.
5827 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
5828 is the value just prior to @code{$$}, @code{$$1} is equivalent to
5829 @code{$$}, and @code{$$0} is equivalent to @code{$}.
5831 For example, suppose you have just printed a pointer to a structure and
5832 want to see the contents of the structure. It suffices to type
5838 If you have a chain of structures where the component @code{next} points
5839 to the next one, you can print the contents of the next one with this:
5846 You can print successive links in the chain by repeating this
5847 command---which you can do by just typing @key{RET}.
5849 Note that the history records values, not expressions. If the value of
5850 @code{x} is 4 and you type these commands:
5858 then the value recorded in the value history by the @code{print} command
5859 remains 4 even though the value of @code{x} has changed.
5864 Print the last ten values in the value history, with their item numbers.
5865 This is like @samp{p@ $$9} repeated ten times, except that @code{show
5866 values} does not change the history.
5868 @item show values @var{n}
5869 Print ten history values centered on history item number @var{n}.
5872 Print ten history values just after the values last printed. If no more
5873 values are available, @code{show values +} produces no display.
5876 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
5877 same effect as @samp{show values +}.
5879 @node Convenience Vars
5880 @section Convenience variables
5882 @cindex convenience variables
5883 @cindex user-defined variables
5884 @value{GDBN} provides @dfn{convenience variables} that you can use within
5885 @value{GDBN} to hold on to a value and refer to it later. These variables
5886 exist entirely within @value{GDBN}; they are not part of your program, and
5887 setting a convenience variable has no direct effect on further execution
5888 of your program. That is why you can use them freely.
5890 Convenience variables are prefixed with @samp{$}. Any name preceded by
5891 @samp{$} can be used for a convenience variable, unless it is one of
5892 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
5893 (Value history references, in contrast, are @emph{numbers} preceded
5894 by @samp{$}. @xref{Value History, ,Value history}.)
5896 You can save a value in a convenience variable with an assignment
5897 expression, just as you would set a variable in your program.
5901 set $foo = *object_ptr
5905 would save in @code{$foo} the value contained in the object pointed to by
5908 Using a convenience variable for the first time creates it, but its
5909 value is @code{void} until you assign a new value. You can alter the
5910 value with another assignment at any time.
5912 Convenience variables have no fixed types. You can assign a convenience
5913 variable any type of value, including structures and arrays, even if
5914 that variable already has a value of a different type. The convenience
5915 variable, when used as an expression, has the type of its current value.
5918 @kindex show convenience
5919 @cindex show all user variables
5920 @item show convenience
5921 Print a list of convenience variables used so far, and their values.
5922 Abbreviated @code{show conv}.
5925 One of the ways to use a convenience variable is as a counter to be
5926 incremented or a pointer to be advanced. For example, to print
5927 a field from successive elements of an array of structures:
5931 print bar[$i++]->contents
5935 Repeat that command by typing @key{RET}.
5937 Some convenience variables are created automatically by @value{GDBN} and given
5938 values likely to be useful.
5941 @vindex $_@r{, convenience variable}
5943 The variable @code{$_} is automatically set by the @code{x} command to
5944 the last address examined (@pxref{Memory, ,Examining memory}). Other
5945 commands which provide a default address for @code{x} to examine also
5946 set @code{$_} to that address; these commands include @code{info line}
5947 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
5948 except when set by the @code{x} command, in which case it is a pointer
5949 to the type of @code{$__}.
5951 @vindex $__@r{, convenience variable}
5953 The variable @code{$__} is automatically set by the @code{x} command
5954 to the value found in the last address examined. Its type is chosen
5955 to match the format in which the data was printed.
5958 @vindex $_exitcode@r{, convenience variable}
5959 The variable @code{$_exitcode} is automatically set to the exit code when
5960 the program being debugged terminates.
5963 On HP-UX systems, if you refer to a function or variable name that
5964 begins with a dollar sign, @value{GDBN} searches for a user or system
5965 name first, before it searches for a convenience variable.
5971 You can refer to machine register contents, in expressions, as variables
5972 with names starting with @samp{$}. The names of registers are different
5973 for each machine; use @code{info registers} to see the names used on
5977 @kindex info registers
5978 @item info registers
5979 Print the names and values of all registers except floating-point
5980 and vector registers (in the selected stack frame).
5982 @kindex info all-registers
5983 @cindex floating point registers
5984 @item info all-registers
5985 Print the names and values of all registers, including floating-point
5986 and vector registers (in the selected stack frame).
5988 @item info registers @var{regname} @dots{}
5989 Print the @dfn{relativized} value of each specified register @var{regname}.
5990 As discussed in detail below, register values are normally relative to
5991 the selected stack frame. @var{regname} may be any register name valid on
5992 the machine you are using, with or without the initial @samp{$}.
5995 @value{GDBN} has four ``standard'' register names that are available (in
5996 expressions) on most machines---whenever they do not conflict with an
5997 architecture's canonical mnemonics for registers. The register names
5998 @code{$pc} and @code{$sp} are used for the program counter register and
5999 the stack pointer. @code{$fp} is used for a register that contains a
6000 pointer to the current stack frame, and @code{$ps} is used for a
6001 register that contains the processor status. For example,
6002 you could print the program counter in hex with
6009 or print the instruction to be executed next with
6016 or add four to the stack pointer@footnote{This is a way of removing
6017 one word from the stack, on machines where stacks grow downward in
6018 memory (most machines, nowadays). This assumes that the innermost
6019 stack frame is selected; setting @code{$sp} is not allowed when other
6020 stack frames are selected. To pop entire frames off the stack,
6021 regardless of machine architecture, use @code{return};
6022 see @ref{Returning, ,Returning from a function}.} with
6028 Whenever possible, these four standard register names are available on
6029 your machine even though the machine has different canonical mnemonics,
6030 so long as there is no conflict. The @code{info registers} command
6031 shows the canonical names. For example, on the SPARC, @code{info
6032 registers} displays the processor status register as @code{$psr} but you
6033 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
6034 is an alias for the @sc{eflags} register.
6036 @value{GDBN} always considers the contents of an ordinary register as an
6037 integer when the register is examined in this way. Some machines have
6038 special registers which can hold nothing but floating point; these
6039 registers are considered to have floating point values. There is no way
6040 to refer to the contents of an ordinary register as floating point value
6041 (although you can @emph{print} it as a floating point value with
6042 @samp{print/f $@var{regname}}).
6044 Some registers have distinct ``raw'' and ``virtual'' data formats. This
6045 means that the data format in which the register contents are saved by
6046 the operating system is not the same one that your program normally
6047 sees. For example, the registers of the 68881 floating point
6048 coprocessor are always saved in ``extended'' (raw) format, but all C
6049 programs expect to work with ``double'' (virtual) format. In such
6050 cases, @value{GDBN} normally works with the virtual format only (the format
6051 that makes sense for your program), but the @code{info registers} command
6052 prints the data in both formats.
6054 Normally, register values are relative to the selected stack frame
6055 (@pxref{Selection, ,Selecting a frame}). This means that you get the
6056 value that the register would contain if all stack frames farther in
6057 were exited and their saved registers restored. In order to see the
6058 true contents of hardware registers, you must select the innermost
6059 frame (with @samp{frame 0}).
6061 However, @value{GDBN} must deduce where registers are saved, from the machine
6062 code generated by your compiler. If some registers are not saved, or if
6063 @value{GDBN} is unable to locate the saved registers, the selected stack
6064 frame makes no difference.
6066 @node Floating Point Hardware
6067 @section Floating point hardware
6068 @cindex floating point
6070 Depending on the configuration, @value{GDBN} may be able to give
6071 you more information about the status of the floating point hardware.
6076 Display hardware-dependent information about the floating
6077 point unit. The exact contents and layout vary depending on the
6078 floating point chip. Currently, @samp{info float} is supported on
6079 the ARM and x86 machines.
6083 @section Vector Unit
6086 Depending on the configuration, @value{GDBN} may be able to give you
6087 more information about the status of the vector unit.
6092 Display information about the vector unit. The exact contents and
6093 layout vary depending on the hardware.
6096 @node Auxiliary Vector
6097 @section Operating system auxiliary vector
6098 @cindex auxiliary vector
6099 @cindex vector, auxiliary
6101 Some operating systems supply an @dfn{auxiliary vector} to programs at
6102 startup. This is akin to the arguments and environment that you
6103 specify for a program, but contains a system-dependent variety of
6104 binary values that tell system libraries important details about the
6105 hardware, operating system, and process. Each value's purpose is
6106 identified by an integer tag; the meanings are well-known but system-specific.
6107 Depending on the configuration and operating system facilities,
6108 @value{GDBN} may be able to show you this information. For remote
6109 targets, this functionality may further depend on the remote stub's
6110 support of the @samp{qPart:auxv:read} packet, see @ref{Remote
6111 configuration, auxiliary vector}.
6116 Display the auxiliary vector of the inferior, which can be either a
6117 live process or a core dump file. @value{GDBN} prints each tag value
6118 numerically, and also shows names and text descriptions for recognized
6119 tags. Some values in the vector are numbers, some bit masks, and some
6120 pointers to strings or other data. @value{GDBN} displays each value in the
6121 most appropriate form for a recognized tag, and in hexadecimal for
6122 an unrecognized tag.
6125 @node Memory Region Attributes
6126 @section Memory region attributes
6127 @cindex memory region attributes
6129 @dfn{Memory region attributes} allow you to describe special handling
6130 required by regions of your target's memory. @value{GDBN} uses attributes
6131 to determine whether to allow certain types of memory accesses; whether to
6132 use specific width accesses; and whether to cache target memory.
6134 Defined memory regions can be individually enabled and disabled. When a
6135 memory region is disabled, @value{GDBN} uses the default attributes when
6136 accessing memory in that region. Similarly, if no memory regions have
6137 been defined, @value{GDBN} uses the default attributes when accessing
6140 When a memory region is defined, it is given a number to identify it;
6141 to enable, disable, or remove a memory region, you specify that number.
6145 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
6146 Define a memory region bounded by @var{lower} and @var{upper} with
6147 attributes @var{attributes}@dots{}, and add it to the list of regions
6148 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
6149 case: it is treated as the the target's maximum memory address.
6150 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
6153 @item delete mem @var{nums}@dots{}
6154 Remove memory regions @var{nums}@dots{} from the list of regions
6155 monitored by @value{GDBN}.
6158 @item disable mem @var{nums}@dots{}
6159 Disable monitoring of memory regions @var{nums}@dots{}.
6160 A disabled memory region is not forgotten.
6161 It may be enabled again later.
6164 @item enable mem @var{nums}@dots{}
6165 Enable monitoring of memory regions @var{nums}@dots{}.
6169 Print a table of all defined memory regions, with the following columns
6173 @item Memory Region Number
6174 @item Enabled or Disabled.
6175 Enabled memory regions are marked with @samp{y}.
6176 Disabled memory regions are marked with @samp{n}.
6179 The address defining the inclusive lower bound of the memory region.
6182 The address defining the exclusive upper bound of the memory region.
6185 The list of attributes set for this memory region.
6190 @subsection Attributes
6192 @subsubsection Memory Access Mode
6193 The access mode attributes set whether @value{GDBN} may make read or
6194 write accesses to a memory region.
6196 While these attributes prevent @value{GDBN} from performing invalid
6197 memory accesses, they do nothing to prevent the target system, I/O DMA,
6198 etc. from accessing memory.
6202 Memory is read only.
6204 Memory is write only.
6206 Memory is read/write. This is the default.
6209 @subsubsection Memory Access Size
6210 The acccess size attributes tells @value{GDBN} to use specific sized
6211 accesses in the memory region. Often memory mapped device registers
6212 require specific sized accesses. If no access size attribute is
6213 specified, @value{GDBN} may use accesses of any size.
6217 Use 8 bit memory accesses.
6219 Use 16 bit memory accesses.
6221 Use 32 bit memory accesses.
6223 Use 64 bit memory accesses.
6226 @c @subsubsection Hardware/Software Breakpoints
6227 @c The hardware/software breakpoint attributes set whether @value{GDBN}
6228 @c will use hardware or software breakpoints for the internal breakpoints
6229 @c used by the step, next, finish, until, etc. commands.
6233 @c Always use hardware breakpoints
6234 @c @item swbreak (default)
6237 @subsubsection Data Cache
6238 The data cache attributes set whether @value{GDBN} will cache target
6239 memory. While this generally improves performance by reducing debug
6240 protocol overhead, it can lead to incorrect results because @value{GDBN}
6241 does not know about volatile variables or memory mapped device
6246 Enable @value{GDBN} to cache target memory.
6248 Disable @value{GDBN} from caching target memory. This is the default.
6251 @c @subsubsection Memory Write Verification
6252 @c The memory write verification attributes set whether @value{GDBN}
6253 @c will re-reads data after each write to verify the write was successful.
6257 @c @item noverify (default)
6260 @node Dump/Restore Files
6261 @section Copy between memory and a file
6262 @cindex dump/restore files
6263 @cindex append data to a file
6264 @cindex dump data to a file
6265 @cindex restore data from a file
6267 You can use the commands @code{dump}, @code{append}, and
6268 @code{restore} to copy data between target memory and a file. The
6269 @code{dump} and @code{append} commands write data to a file, and the
6270 @code{restore} command reads data from a file back into the inferior's
6271 memory. Files may be in binary, Motorola S-record, Intel hex, or
6272 Tektronix Hex format; however, @value{GDBN} can only append to binary
6278 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6279 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
6280 Dump the contents of memory from @var{start_addr} to @var{end_addr},
6281 or the value of @var{expr}, to @var{filename} in the given format.
6283 The @var{format} parameter may be any one of:
6290 Motorola S-record format.
6292 Tektronix Hex format.
6295 @value{GDBN} uses the same definitions of these formats as the
6296 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
6297 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
6301 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6302 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
6303 Append the contents of memory from @var{start_addr} to @var{end_addr},
6304 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
6305 (@value{GDBN} can only append data to files in raw binary form.)
6308 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
6309 Restore the contents of file @var{filename} into memory. The
6310 @code{restore} command can automatically recognize any known @sc{bfd}
6311 file format, except for raw binary. To restore a raw binary file you
6312 must specify the optional keyword @code{binary} after the filename.
6314 If @var{bias} is non-zero, its value will be added to the addresses
6315 contained in the file. Binary files always start at address zero, so
6316 they will be restored at address @var{bias}. Other bfd files have
6317 a built-in location; they will be restored at offset @var{bias}
6320 If @var{start} and/or @var{end} are non-zero, then only data between
6321 file offset @var{start} and file offset @var{end} will be restored.
6322 These offsets are relative to the addresses in the file, before
6323 the @var{bias} argument is applied.
6327 @node Core File Generation
6328 @section How to Produce a Core File from Your Program
6329 @cindex dump core from inferior
6331 A @dfn{core file} or @dfn{core dump} is a file that records the memory
6332 image of a running process and its process status (register values
6333 etc.). Its primary use is post-mortem debugging of a program that
6334 crashed while it ran outside a debugger. A program that crashes
6335 automatically produces a core file, unless this feature is disabled by
6336 the user. @xref{Files}, for information on invoking @value{GDBN} in
6337 the post-mortem debugging mode.
6339 Occasionally, you may wish to produce a core file of the program you
6340 are debugging in order to preserve a snapshot of its state.
6341 @value{GDBN} has a special command for that.
6345 @kindex generate-core-file
6346 @item generate-core-file [@var{file}]
6347 @itemx gcore [@var{file}]
6348 Produce a core dump of the inferior process. The optional argument
6349 @var{file} specifies the file name where to put the core dump. If not
6350 specified, the file name defaults to @file{core.@var{pid}}, where
6351 @var{pid} is the inferior process ID.
6353 Note that this command is implemented only for some systems (as of
6354 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
6357 @node Character Sets
6358 @section Character Sets
6359 @cindex character sets
6361 @cindex translating between character sets
6362 @cindex host character set
6363 @cindex target character set
6365 If the program you are debugging uses a different character set to
6366 represent characters and strings than the one @value{GDBN} uses itself,
6367 @value{GDBN} can automatically translate between the character sets for
6368 you. The character set @value{GDBN} uses we call the @dfn{host
6369 character set}; the one the inferior program uses we call the
6370 @dfn{target character set}.
6372 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
6373 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
6374 remote protocol (@pxref{Remote,Remote Debugging}) to debug a program
6375 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
6376 then the host character set is Latin-1, and the target character set is
6377 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
6378 target-charset EBCDIC-US}, then @value{GDBN} translates between
6379 @sc{ebcdic} and Latin 1 as you print character or string values, or use
6380 character and string literals in expressions.
6382 @value{GDBN} has no way to automatically recognize which character set
6383 the inferior program uses; you must tell it, using the @code{set
6384 target-charset} command, described below.
6386 Here are the commands for controlling @value{GDBN}'s character set
6390 @item set target-charset @var{charset}
6391 @kindex set target-charset
6392 Set the current target character set to @var{charset}. We list the
6393 character set names @value{GDBN} recognizes below, but if you type
6394 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6395 list the target character sets it supports.
6399 @item set host-charset @var{charset}
6400 @kindex set host-charset
6401 Set the current host character set to @var{charset}.
6403 By default, @value{GDBN} uses a host character set appropriate to the
6404 system it is running on; you can override that default using the
6405 @code{set host-charset} command.
6407 @value{GDBN} can only use certain character sets as its host character
6408 set. We list the character set names @value{GDBN} recognizes below, and
6409 indicate which can be host character sets, but if you type
6410 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6411 list the host character sets it supports.
6413 @item set charset @var{charset}
6415 Set the current host and target character sets to @var{charset}. As
6416 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
6417 @value{GDBN} will list the name of the character sets that can be used
6418 for both host and target.
6422 @kindex show charset
6423 Show the names of the current host and target charsets.
6425 @itemx show host-charset
6426 @kindex show host-charset
6427 Show the name of the current host charset.
6429 @itemx show target-charset
6430 @kindex show target-charset
6431 Show the name of the current target charset.
6435 @value{GDBN} currently includes support for the following character
6441 @cindex ASCII character set
6442 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
6446 @cindex ISO 8859-1 character set
6447 @cindex ISO Latin 1 character set
6448 The ISO Latin 1 character set. This extends @sc{ascii} with accented
6449 characters needed for French, German, and Spanish. @value{GDBN} can use
6450 this as its host character set.
6454 @cindex EBCDIC character set
6455 @cindex IBM1047 character set
6456 Variants of the @sc{ebcdic} character set, used on some of IBM's
6457 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
6458 @value{GDBN} cannot use these as its host character set.
6462 Note that these are all single-byte character sets. More work inside
6463 GDB is needed to support multi-byte or variable-width character
6464 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
6466 Here is an example of @value{GDBN}'s character set support in action.
6467 Assume that the following source code has been placed in the file
6468 @file{charset-test.c}:
6474 = @{72, 101, 108, 108, 111, 44, 32, 119,
6475 111, 114, 108, 100, 33, 10, 0@};
6476 char ibm1047_hello[]
6477 = @{200, 133, 147, 147, 150, 107, 64, 166,
6478 150, 153, 147, 132, 90, 37, 0@};
6482 printf ("Hello, world!\n");
6486 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
6487 containing the string @samp{Hello, world!} followed by a newline,
6488 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
6490 We compile the program, and invoke the debugger on it:
6493 $ gcc -g charset-test.c -o charset-test
6494 $ gdb -nw charset-test
6495 GNU gdb 2001-12-19-cvs
6496 Copyright 2001 Free Software Foundation, Inc.
6501 We can use the @code{show charset} command to see what character sets
6502 @value{GDBN} is currently using to interpret and display characters and
6506 (@value{GDBP}) show charset
6507 The current host and target character set is `ISO-8859-1'.
6511 For the sake of printing this manual, let's use @sc{ascii} as our
6512 initial character set:
6514 (@value{GDBP}) set charset ASCII
6515 (@value{GDBP}) show charset
6516 The current host and target character set is `ASCII'.
6520 Let's assume that @sc{ascii} is indeed the correct character set for our
6521 host system --- in other words, let's assume that if @value{GDBN} prints
6522 characters using the @sc{ascii} character set, our terminal will display
6523 them properly. Since our current target character set is also
6524 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
6527 (@value{GDBP}) print ascii_hello
6528 $1 = 0x401698 "Hello, world!\n"
6529 (@value{GDBP}) print ascii_hello[0]
6534 @value{GDBN} uses the target character set for character and string
6535 literals you use in expressions:
6538 (@value{GDBP}) print '+'
6543 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
6546 @value{GDBN} relies on the user to tell it which character set the
6547 target program uses. If we print @code{ibm1047_hello} while our target
6548 character set is still @sc{ascii}, we get jibberish:
6551 (@value{GDBP}) print ibm1047_hello
6552 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
6553 (@value{GDBP}) print ibm1047_hello[0]
6558 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
6559 @value{GDBN} tells us the character sets it supports:
6562 (@value{GDBP}) set target-charset
6563 ASCII EBCDIC-US IBM1047 ISO-8859-1
6564 (@value{GDBP}) set target-charset
6567 We can select @sc{ibm1047} as our target character set, and examine the
6568 program's strings again. Now the @sc{ascii} string is wrong, but
6569 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
6570 target character set, @sc{ibm1047}, to the host character set,
6571 @sc{ascii}, and they display correctly:
6574 (@value{GDBP}) set target-charset IBM1047
6575 (@value{GDBP}) show charset
6576 The current host character set is `ASCII'.
6577 The current target character set is `IBM1047'.
6578 (@value{GDBP}) print ascii_hello
6579 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
6580 (@value{GDBP}) print ascii_hello[0]
6582 (@value{GDBP}) print ibm1047_hello
6583 $8 = 0x4016a8 "Hello, world!\n"
6584 (@value{GDBP}) print ibm1047_hello[0]
6589 As above, @value{GDBN} uses the target character set for character and
6590 string literals you use in expressions:
6593 (@value{GDBP}) print '+'
6598 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
6601 @node Caching Remote Data
6602 @section Caching Data of Remote Targets
6603 @cindex caching data of remote targets
6605 @value{GDBN} can cache data exchanged between the debugger and a
6606 remote target (@pxref{Remote}). Such caching generally improves
6607 performance, because it reduces the overhead of the remote protocol by
6608 bundling memory reads and writes into large chunks. Unfortunately,
6609 @value{GDBN} does not currently know anything about volatile
6610 registers, and thus data caching will produce incorrect results when
6611 volatile registers are in use.
6614 @kindex set remotecache
6615 @item set remotecache on
6616 @itemx set remotecache off
6617 Set caching state for remote targets. When @code{ON}, use data
6618 caching. By default, this option is @code{OFF}.
6620 @kindex show remotecache
6621 @item show remotecache
6622 Show the current state of data caching for remote targets.
6626 Print the information about the data cache performance. The
6627 information displayed includes: the dcache width and depth; and for
6628 each cache line, how many times it was referenced, and its data and
6629 state (dirty, bad, ok, etc.). This command is useful for debugging
6630 the data cache operation.
6635 @chapter C Preprocessor Macros
6637 Some languages, such as C and C@t{++}, provide a way to define and invoke
6638 ``preprocessor macros'' which expand into strings of tokens.
6639 @value{GDBN} can evaluate expressions containing macro invocations, show
6640 the result of macro expansion, and show a macro's definition, including
6641 where it was defined.
6643 You may need to compile your program specially to provide @value{GDBN}
6644 with information about preprocessor macros. Most compilers do not
6645 include macros in their debugging information, even when you compile
6646 with the @option{-g} flag. @xref{Compilation}.
6648 A program may define a macro at one point, remove that definition later,
6649 and then provide a different definition after that. Thus, at different
6650 points in the program, a macro may have different definitions, or have
6651 no definition at all. If there is a current stack frame, @value{GDBN}
6652 uses the macros in scope at that frame's source code line. Otherwise,
6653 @value{GDBN} uses the macros in scope at the current listing location;
6656 At the moment, @value{GDBN} does not support the @code{##}
6657 token-splicing operator, the @code{#} stringification operator, or
6658 variable-arity macros.
6660 Whenever @value{GDBN} evaluates an expression, it always expands any
6661 macro invocations present in the expression. @value{GDBN} also provides
6662 the following commands for working with macros explicitly.
6666 @kindex macro expand
6667 @cindex macro expansion, showing the results of preprocessor
6668 @cindex preprocessor macro expansion, showing the results of
6669 @cindex expanding preprocessor macros
6670 @item macro expand @var{expression}
6671 @itemx macro exp @var{expression}
6672 Show the results of expanding all preprocessor macro invocations in
6673 @var{expression}. Since @value{GDBN} simply expands macros, but does
6674 not parse the result, @var{expression} need not be a valid expression;
6675 it can be any string of tokens.
6678 @item macro expand-once @var{expression}
6679 @itemx macro exp1 @var{expression}
6680 @cindex expand macro once
6681 @i{(This command is not yet implemented.)} Show the results of
6682 expanding those preprocessor macro invocations that appear explicitly in
6683 @var{expression}. Macro invocations appearing in that expansion are
6684 left unchanged. This command allows you to see the effect of a
6685 particular macro more clearly, without being confused by further
6686 expansions. Since @value{GDBN} simply expands macros, but does not
6687 parse the result, @var{expression} need not be a valid expression; it
6688 can be any string of tokens.
6691 @cindex macro definition, showing
6692 @cindex definition, showing a macro's
6693 @item info macro @var{macro}
6694 Show the definition of the macro named @var{macro}, and describe the
6695 source location where that definition was established.
6697 @kindex macro define
6698 @cindex user-defined macros
6699 @cindex defining macros interactively
6700 @cindex macros, user-defined
6701 @item macro define @var{macro} @var{replacement-list}
6702 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
6703 @i{(This command is not yet implemented.)} Introduce a definition for a
6704 preprocessor macro named @var{macro}, invocations of which are replaced
6705 by the tokens given in @var{replacement-list}. The first form of this
6706 command defines an ``object-like'' macro, which takes no arguments; the
6707 second form defines a ``function-like'' macro, which takes the arguments
6708 given in @var{arglist}.
6710 A definition introduced by this command is in scope in every expression
6711 evaluated in @value{GDBN}, until it is removed with the @command{macro
6712 undef} command, described below. The definition overrides all
6713 definitions for @var{macro} present in the program being debugged, as
6714 well as any previous user-supplied definition.
6717 @item macro undef @var{macro}
6718 @i{(This command is not yet implemented.)} Remove any user-supplied
6719 definition for the macro named @var{macro}. This command only affects
6720 definitions provided with the @command{macro define} command, described
6721 above; it cannot remove definitions present in the program being
6726 @i{(This command is not yet implemented.)} List all the macros
6727 defined using the @code{macro define} command.
6730 @cindex macros, example of debugging with
6731 Here is a transcript showing the above commands in action. First, we
6732 show our source files:
6740 #define ADD(x) (M + x)
6745 printf ("Hello, world!\n");
6747 printf ("We're so creative.\n");
6749 printf ("Goodbye, world!\n");
6756 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
6757 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
6758 compiler includes information about preprocessor macros in the debugging
6762 $ gcc -gdwarf-2 -g3 sample.c -o sample
6766 Now, we start @value{GDBN} on our sample program:
6770 GNU gdb 2002-05-06-cvs
6771 Copyright 2002 Free Software Foundation, Inc.
6772 GDB is free software, @dots{}
6776 We can expand macros and examine their definitions, even when the
6777 program is not running. @value{GDBN} uses the current listing position
6778 to decide which macro definitions are in scope:
6781 (@value{GDBP}) list main
6784 5 #define ADD(x) (M + x)
6789 10 printf ("Hello, world!\n");
6791 12 printf ("We're so creative.\n");
6792 (@value{GDBP}) info macro ADD
6793 Defined at /home/jimb/gdb/macros/play/sample.c:5
6794 #define ADD(x) (M + x)
6795 (@value{GDBP}) info macro Q
6796 Defined at /home/jimb/gdb/macros/play/sample.h:1
6797 included at /home/jimb/gdb/macros/play/sample.c:2
6799 (@value{GDBP}) macro expand ADD(1)
6800 expands to: (42 + 1)
6801 (@value{GDBP}) macro expand-once ADD(1)
6802 expands to: once (M + 1)
6806 In the example above, note that @command{macro expand-once} expands only
6807 the macro invocation explicit in the original text --- the invocation of
6808 @code{ADD} --- but does not expand the invocation of the macro @code{M},
6809 which was introduced by @code{ADD}.
6811 Once the program is running, GDB uses the macro definitions in force at
6812 the source line of the current stack frame:
6815 (@value{GDBP}) break main
6816 Breakpoint 1 at 0x8048370: file sample.c, line 10.
6818 Starting program: /home/jimb/gdb/macros/play/sample
6820 Breakpoint 1, main () at sample.c:10
6821 10 printf ("Hello, world!\n");
6825 At line 10, the definition of the macro @code{N} at line 9 is in force:
6828 (@value{GDBP}) info macro N
6829 Defined at /home/jimb/gdb/macros/play/sample.c:9
6831 (@value{GDBP}) macro expand N Q M
6833 (@value{GDBP}) print N Q M
6838 As we step over directives that remove @code{N}'s definition, and then
6839 give it a new definition, @value{GDBN} finds the definition (or lack
6840 thereof) in force at each point:
6845 12 printf ("We're so creative.\n");
6846 (@value{GDBP}) info macro N
6847 The symbol `N' has no definition as a C/C++ preprocessor macro
6848 at /home/jimb/gdb/macros/play/sample.c:12
6851 14 printf ("Goodbye, world!\n");
6852 (@value{GDBP}) info macro N
6853 Defined at /home/jimb/gdb/macros/play/sample.c:13
6855 (@value{GDBP}) macro expand N Q M
6856 expands to: 1729 < 42
6857 (@value{GDBP}) print N Q M
6864 @chapter Tracepoints
6865 @c This chapter is based on the documentation written by Michael
6866 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
6869 In some applications, it is not feasible for the debugger to interrupt
6870 the program's execution long enough for the developer to learn
6871 anything helpful about its behavior. If the program's correctness
6872 depends on its real-time behavior, delays introduced by a debugger
6873 might cause the program to change its behavior drastically, or perhaps
6874 fail, even when the code itself is correct. It is useful to be able
6875 to observe the program's behavior without interrupting it.
6877 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
6878 specify locations in the program, called @dfn{tracepoints}, and
6879 arbitrary expressions to evaluate when those tracepoints are reached.
6880 Later, using the @code{tfind} command, you can examine the values
6881 those expressions had when the program hit the tracepoints. The
6882 expressions may also denote objects in memory---structures or arrays,
6883 for example---whose values @value{GDBN} should record; while visiting
6884 a particular tracepoint, you may inspect those objects as if they were
6885 in memory at that moment. However, because @value{GDBN} records these
6886 values without interacting with you, it can do so quickly and
6887 unobtrusively, hopefully not disturbing the program's behavior.
6889 The tracepoint facility is currently available only for remote
6890 targets. @xref{Targets}. In addition, your remote target must know how
6891 to collect trace data. This functionality is implemented in the remote
6892 stub; however, none of the stubs distributed with @value{GDBN} support
6893 tracepoints as of this writing.
6895 This chapter describes the tracepoint commands and features.
6899 * Analyze Collected Data::
6900 * Tracepoint Variables::
6903 @node Set Tracepoints
6904 @section Commands to Set Tracepoints
6906 Before running such a @dfn{trace experiment}, an arbitrary number of
6907 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
6908 tracepoint has a number assigned to it by @value{GDBN}. Like with
6909 breakpoints, tracepoint numbers are successive integers starting from
6910 one. Many of the commands associated with tracepoints take the
6911 tracepoint number as their argument, to identify which tracepoint to
6914 For each tracepoint, you can specify, in advance, some arbitrary set
6915 of data that you want the target to collect in the trace buffer when
6916 it hits that tracepoint. The collected data can include registers,
6917 local variables, or global data. Later, you can use @value{GDBN}
6918 commands to examine the values these data had at the time the
6921 This section describes commands to set tracepoints and associated
6922 conditions and actions.
6925 * Create and Delete Tracepoints::
6926 * Enable and Disable Tracepoints::
6927 * Tracepoint Passcounts::
6928 * Tracepoint Actions::
6929 * Listing Tracepoints::
6930 * Starting and Stopping Trace Experiment::
6933 @node Create and Delete Tracepoints
6934 @subsection Create and Delete Tracepoints
6937 @cindex set tracepoint
6940 The @code{trace} command is very similar to the @code{break} command.
6941 Its argument can be a source line, a function name, or an address in
6942 the target program. @xref{Set Breaks}. The @code{trace} command
6943 defines a tracepoint, which is a point in the target program where the
6944 debugger will briefly stop, collect some data, and then allow the
6945 program to continue. Setting a tracepoint or changing its commands
6946 doesn't take effect until the next @code{tstart} command; thus, you
6947 cannot change the tracepoint attributes once a trace experiment is
6950 Here are some examples of using the @code{trace} command:
6953 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
6955 (@value{GDBP}) @b{trace +2} // 2 lines forward
6957 (@value{GDBP}) @b{trace my_function} // first source line of function
6959 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
6961 (@value{GDBP}) @b{trace *0x2117c4} // an address
6965 You can abbreviate @code{trace} as @code{tr}.
6968 @cindex last tracepoint number
6969 @cindex recent tracepoint number
6970 @cindex tracepoint number
6971 The convenience variable @code{$tpnum} records the tracepoint number
6972 of the most recently set tracepoint.
6974 @kindex delete tracepoint
6975 @cindex tracepoint deletion
6976 @item delete tracepoint @r{[}@var{num}@r{]}
6977 Permanently delete one or more tracepoints. With no argument, the
6978 default is to delete all tracepoints.
6983 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
6985 (@value{GDBP}) @b{delete trace} // remove all tracepoints
6989 You can abbreviate this command as @code{del tr}.
6992 @node Enable and Disable Tracepoints
6993 @subsection Enable and Disable Tracepoints
6996 @kindex disable tracepoint
6997 @item disable tracepoint @r{[}@var{num}@r{]}
6998 Disable tracepoint @var{num}, or all tracepoints if no argument
6999 @var{num} is given. A disabled tracepoint will have no effect during
7000 the next trace experiment, but it is not forgotten. You can re-enable
7001 a disabled tracepoint using the @code{enable tracepoint} command.
7003 @kindex enable tracepoint
7004 @item enable tracepoint @r{[}@var{num}@r{]}
7005 Enable tracepoint @var{num}, or all tracepoints. The enabled
7006 tracepoints will become effective the next time a trace experiment is
7010 @node Tracepoint Passcounts
7011 @subsection Tracepoint Passcounts
7015 @cindex tracepoint pass count
7016 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
7017 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
7018 automatically stop a trace experiment. If a tracepoint's passcount is
7019 @var{n}, then the trace experiment will be automatically stopped on
7020 the @var{n}'th time that tracepoint is hit. If the tracepoint number
7021 @var{num} is not specified, the @code{passcount} command sets the
7022 passcount of the most recently defined tracepoint. If no passcount is
7023 given, the trace experiment will run until stopped explicitly by the
7029 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
7030 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
7032 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
7033 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
7034 (@value{GDBP}) @b{trace foo}
7035 (@value{GDBP}) @b{pass 3}
7036 (@value{GDBP}) @b{trace bar}
7037 (@value{GDBP}) @b{pass 2}
7038 (@value{GDBP}) @b{trace baz}
7039 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
7040 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
7041 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
7042 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
7046 @node Tracepoint Actions
7047 @subsection Tracepoint Action Lists
7051 @cindex tracepoint actions
7052 @item actions @r{[}@var{num}@r{]}
7053 This command will prompt for a list of actions to be taken when the
7054 tracepoint is hit. If the tracepoint number @var{num} is not
7055 specified, this command sets the actions for the one that was most
7056 recently defined (so that you can define a tracepoint and then say
7057 @code{actions} without bothering about its number). You specify the
7058 actions themselves on the following lines, one action at a time, and
7059 terminate the actions list with a line containing just @code{end}. So
7060 far, the only defined actions are @code{collect} and
7061 @code{while-stepping}.
7063 @cindex remove actions from a tracepoint
7064 To remove all actions from a tracepoint, type @samp{actions @var{num}}
7065 and follow it immediately with @samp{end}.
7068 (@value{GDBP}) @b{collect @var{data}} // collect some data
7070 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
7072 (@value{GDBP}) @b{end} // signals the end of actions.
7075 In the following example, the action list begins with @code{collect}
7076 commands indicating the things to be collected when the tracepoint is
7077 hit. Then, in order to single-step and collect additional data
7078 following the tracepoint, a @code{while-stepping} command is used,
7079 followed by the list of things to be collected while stepping. The
7080 @code{while-stepping} command is terminated by its own separate
7081 @code{end} command. Lastly, the action list is terminated by an
7085 (@value{GDBP}) @b{trace foo}
7086 (@value{GDBP}) @b{actions}
7087 Enter actions for tracepoint 1, one per line:
7096 @kindex collect @r{(tracepoints)}
7097 @item collect @var{expr1}, @var{expr2}, @dots{}
7098 Collect values of the given expressions when the tracepoint is hit.
7099 This command accepts a comma-separated list of any valid expressions.
7100 In addition to global, static, or local variables, the following
7101 special arguments are supported:
7105 collect all registers
7108 collect all function arguments
7111 collect all local variables.
7114 You can give several consecutive @code{collect} commands, each one
7115 with a single argument, or one @code{collect} command with several
7116 arguments separated by commas: the effect is the same.
7118 The command @code{info scope} (@pxref{Symbols, info scope}) is
7119 particularly useful for figuring out what data to collect.
7121 @kindex while-stepping @r{(tracepoints)}
7122 @item while-stepping @var{n}
7123 Perform @var{n} single-step traces after the tracepoint, collecting
7124 new data at each step. The @code{while-stepping} command is
7125 followed by the list of what to collect while stepping (followed by
7126 its own @code{end} command):
7130 > collect $regs, myglobal
7136 You may abbreviate @code{while-stepping} as @code{ws} or
7140 @node Listing Tracepoints
7141 @subsection Listing Tracepoints
7144 @kindex info tracepoints
7146 @cindex information about tracepoints
7147 @item info tracepoints @r{[}@var{num}@r{]}
7148 Display information about the tracepoint @var{num}. If you don't specify
7149 a tracepoint number, displays information about all the tracepoints
7150 defined so far. For each tracepoint, the following information is
7157 whether it is enabled or disabled
7161 its passcount as given by the @code{passcount @var{n}} command
7163 its step count as given by the @code{while-stepping @var{n}} command
7165 where in the source files is the tracepoint set
7167 its action list as given by the @code{actions} command
7171 (@value{GDBP}) @b{info trace}
7172 Num Enb Address PassC StepC What
7173 1 y 0x002117c4 0 0 <gdb_asm>
7174 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
7175 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
7180 This command can be abbreviated @code{info tp}.
7183 @node Starting and Stopping Trace Experiment
7184 @subsection Starting and Stopping Trace Experiment
7188 @cindex start a new trace experiment
7189 @cindex collected data discarded
7191 This command takes no arguments. It starts the trace experiment, and
7192 begins collecting data. This has the side effect of discarding all
7193 the data collected in the trace buffer during the previous trace
7197 @cindex stop a running trace experiment
7199 This command takes no arguments. It ends the trace experiment, and
7200 stops collecting data.
7202 @strong{Note}: a trace experiment and data collection may stop
7203 automatically if any tracepoint's passcount is reached
7204 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
7207 @cindex status of trace data collection
7208 @cindex trace experiment, status of
7210 This command displays the status of the current trace data
7214 Here is an example of the commands we described so far:
7217 (@value{GDBP}) @b{trace gdb_c_test}
7218 (@value{GDBP}) @b{actions}
7219 Enter actions for tracepoint #1, one per line.
7220 > collect $regs,$locals,$args
7225 (@value{GDBP}) @b{tstart}
7226 [time passes @dots{}]
7227 (@value{GDBP}) @b{tstop}
7231 @node Analyze Collected Data
7232 @section Using the collected data
7234 After the tracepoint experiment ends, you use @value{GDBN} commands
7235 for examining the trace data. The basic idea is that each tracepoint
7236 collects a trace @dfn{snapshot} every time it is hit and another
7237 snapshot every time it single-steps. All these snapshots are
7238 consecutively numbered from zero and go into a buffer, and you can
7239 examine them later. The way you examine them is to @dfn{focus} on a
7240 specific trace snapshot. When the remote stub is focused on a trace
7241 snapshot, it will respond to all @value{GDBN} requests for memory and
7242 registers by reading from the buffer which belongs to that snapshot,
7243 rather than from @emph{real} memory or registers of the program being
7244 debugged. This means that @strong{all} @value{GDBN} commands
7245 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
7246 behave as if we were currently debugging the program state as it was
7247 when the tracepoint occurred. Any requests for data that are not in
7248 the buffer will fail.
7251 * tfind:: How to select a trace snapshot
7252 * tdump:: How to display all data for a snapshot
7253 * save-tracepoints:: How to save tracepoints for a future run
7257 @subsection @code{tfind @var{n}}
7260 @cindex select trace snapshot
7261 @cindex find trace snapshot
7262 The basic command for selecting a trace snapshot from the buffer is
7263 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
7264 counting from zero. If no argument @var{n} is given, the next
7265 snapshot is selected.
7267 Here are the various forms of using the @code{tfind} command.
7271 Find the first snapshot in the buffer. This is a synonym for
7272 @code{tfind 0} (since 0 is the number of the first snapshot).
7275 Stop debugging trace snapshots, resume @emph{live} debugging.
7278 Same as @samp{tfind none}.
7281 No argument means find the next trace snapshot.
7284 Find the previous trace snapshot before the current one. This permits
7285 retracing earlier steps.
7287 @item tfind tracepoint @var{num}
7288 Find the next snapshot associated with tracepoint @var{num}. Search
7289 proceeds forward from the last examined trace snapshot. If no
7290 argument @var{num} is given, it means find the next snapshot collected
7291 for the same tracepoint as the current snapshot.
7293 @item tfind pc @var{addr}
7294 Find the next snapshot associated with the value @var{addr} of the
7295 program counter. Search proceeds forward from the last examined trace
7296 snapshot. If no argument @var{addr} is given, it means find the next
7297 snapshot with the same value of PC as the current snapshot.
7299 @item tfind outside @var{addr1}, @var{addr2}
7300 Find the next snapshot whose PC is outside the given range of
7303 @item tfind range @var{addr1}, @var{addr2}
7304 Find the next snapshot whose PC is between @var{addr1} and
7305 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
7307 @item tfind line @r{[}@var{file}:@r{]}@var{n}
7308 Find the next snapshot associated with the source line @var{n}. If
7309 the optional argument @var{file} is given, refer to line @var{n} in
7310 that source file. Search proceeds forward from the last examined
7311 trace snapshot. If no argument @var{n} is given, it means find the
7312 next line other than the one currently being examined; thus saying
7313 @code{tfind line} repeatedly can appear to have the same effect as
7314 stepping from line to line in a @emph{live} debugging session.
7317 The default arguments for the @code{tfind} commands are specifically
7318 designed to make it easy to scan through the trace buffer. For
7319 instance, @code{tfind} with no argument selects the next trace
7320 snapshot, and @code{tfind -} with no argument selects the previous
7321 trace snapshot. So, by giving one @code{tfind} command, and then
7322 simply hitting @key{RET} repeatedly you can examine all the trace
7323 snapshots in order. Or, by saying @code{tfind -} and then hitting
7324 @key{RET} repeatedly you can examine the snapshots in reverse order.
7325 The @code{tfind line} command with no argument selects the snapshot
7326 for the next source line executed. The @code{tfind pc} command with
7327 no argument selects the next snapshot with the same program counter
7328 (PC) as the current frame. The @code{tfind tracepoint} command with
7329 no argument selects the next trace snapshot collected by the same
7330 tracepoint as the current one.
7332 In addition to letting you scan through the trace buffer manually,
7333 these commands make it easy to construct @value{GDBN} scripts that
7334 scan through the trace buffer and print out whatever collected data
7335 you are interested in. Thus, if we want to examine the PC, FP, and SP
7336 registers from each trace frame in the buffer, we can say this:
7339 (@value{GDBP}) @b{tfind start}
7340 (@value{GDBP}) @b{while ($trace_frame != -1)}
7341 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
7342 $trace_frame, $pc, $sp, $fp
7346 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
7347 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
7348 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
7349 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
7350 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
7351 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
7352 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
7353 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
7354 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
7355 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
7356 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
7359 Or, if we want to examine the variable @code{X} at each source line in
7363 (@value{GDBP}) @b{tfind start}
7364 (@value{GDBP}) @b{while ($trace_frame != -1)}
7365 > printf "Frame %d, X == %d\n", $trace_frame, X
7375 @subsection @code{tdump}
7377 @cindex dump all data collected at tracepoint
7378 @cindex tracepoint data, display
7380 This command takes no arguments. It prints all the data collected at
7381 the current trace snapshot.
7384 (@value{GDBP}) @b{trace 444}
7385 (@value{GDBP}) @b{actions}
7386 Enter actions for tracepoint #2, one per line:
7387 > collect $regs, $locals, $args, gdb_long_test
7390 (@value{GDBP}) @b{tstart}
7392 (@value{GDBP}) @b{tfind line 444}
7393 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
7395 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
7397 (@value{GDBP}) @b{tdump}
7398 Data collected at tracepoint 2, trace frame 1:
7399 d0 0xc4aa0085 -995491707
7403 d4 0x71aea3d 119204413
7408 a1 0x3000668 50333288
7411 a4 0x3000698 50333336
7413 fp 0x30bf3c 0x30bf3c
7414 sp 0x30bf34 0x30bf34
7416 pc 0x20b2c8 0x20b2c8
7420 p = 0x20e5b4 "gdb-test"
7427 gdb_long_test = 17 '\021'
7432 @node save-tracepoints
7433 @subsection @code{save-tracepoints @var{filename}}
7434 @kindex save-tracepoints
7435 @cindex save tracepoints for future sessions
7437 This command saves all current tracepoint definitions together with
7438 their actions and passcounts, into a file @file{@var{filename}}
7439 suitable for use in a later debugging session. To read the saved
7440 tracepoint definitions, use the @code{source} command (@pxref{Command
7443 @node Tracepoint Variables
7444 @section Convenience Variables for Tracepoints
7445 @cindex tracepoint variables
7446 @cindex convenience variables for tracepoints
7449 @vindex $trace_frame
7450 @item (int) $trace_frame
7451 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
7452 snapshot is selected.
7455 @item (int) $tracepoint
7456 The tracepoint for the current trace snapshot.
7459 @item (int) $trace_line
7460 The line number for the current trace snapshot.
7463 @item (char []) $trace_file
7464 The source file for the current trace snapshot.
7467 @item (char []) $trace_func
7468 The name of the function containing @code{$tracepoint}.
7471 Note: @code{$trace_file} is not suitable for use in @code{printf},
7472 use @code{output} instead.
7474 Here's a simple example of using these convenience variables for
7475 stepping through all the trace snapshots and printing some of their
7479 (@value{GDBP}) @b{tfind start}
7481 (@value{GDBP}) @b{while $trace_frame != -1}
7482 > output $trace_file
7483 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
7489 @chapter Debugging Programs That Use Overlays
7492 If your program is too large to fit completely in your target system's
7493 memory, you can sometimes use @dfn{overlays} to work around this
7494 problem. @value{GDBN} provides some support for debugging programs that
7498 * How Overlays Work:: A general explanation of overlays.
7499 * Overlay Commands:: Managing overlays in @value{GDBN}.
7500 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
7501 mapped by asking the inferior.
7502 * Overlay Sample Program:: A sample program using overlays.
7505 @node How Overlays Work
7506 @section How Overlays Work
7507 @cindex mapped overlays
7508 @cindex unmapped overlays
7509 @cindex load address, overlay's
7510 @cindex mapped address
7511 @cindex overlay area
7513 Suppose you have a computer whose instruction address space is only 64
7514 kilobytes long, but which has much more memory which can be accessed by
7515 other means: special instructions, segment registers, or memory
7516 management hardware, for example. Suppose further that you want to
7517 adapt a program which is larger than 64 kilobytes to run on this system.
7519 One solution is to identify modules of your program which are relatively
7520 independent, and need not call each other directly; call these modules
7521 @dfn{overlays}. Separate the overlays from the main program, and place
7522 their machine code in the larger memory. Place your main program in
7523 instruction memory, but leave at least enough space there to hold the
7524 largest overlay as well.
7526 Now, to call a function located in an overlay, you must first copy that
7527 overlay's machine code from the large memory into the space set aside
7528 for it in the instruction memory, and then jump to its entry point
7531 @c NB: In the below the mapped area's size is greater or equal to the
7532 @c size of all overlays. This is intentional to remind the developer
7533 @c that overlays don't necessarily need to be the same size.
7537 Data Instruction Larger
7538 Address Space Address Space Address Space
7539 +-----------+ +-----------+ +-----------+
7541 +-----------+ +-----------+ +-----------+<-- overlay 1
7542 | program | | main | .----| overlay 1 | load address
7543 | variables | | program | | +-----------+
7544 | and heap | | | | | |
7545 +-----------+ | | | +-----------+<-- overlay 2
7546 | | +-----------+ | | | load address
7547 +-----------+ | | | .-| overlay 2 |
7549 mapped --->+-----------+ | | +-----------+
7551 | overlay | <-' | | |
7552 | area | <---' +-----------+<-- overlay 3
7553 | | <---. | | load address
7554 +-----------+ `--| overlay 3 |
7561 @anchor{A code overlay}A code overlay
7565 The diagram (@pxref{A code overlay}) shows a system with separate data
7566 and instruction address spaces. To map an overlay, the program copies
7567 its code from the larger address space to the instruction address space.
7568 Since the overlays shown here all use the same mapped address, only one
7569 may be mapped at a time. For a system with a single address space for
7570 data and instructions, the diagram would be similar, except that the
7571 program variables and heap would share an address space with the main
7572 program and the overlay area.
7574 An overlay loaded into instruction memory and ready for use is called a
7575 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
7576 instruction memory. An overlay not present (or only partially present)
7577 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
7578 is its address in the larger memory. The mapped address is also called
7579 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
7580 called the @dfn{load memory address}, or @dfn{LMA}.
7582 Unfortunately, overlays are not a completely transparent way to adapt a
7583 program to limited instruction memory. They introduce a new set of
7584 global constraints you must keep in mind as you design your program:
7589 Before calling or returning to a function in an overlay, your program
7590 must make sure that overlay is actually mapped. Otherwise, the call or
7591 return will transfer control to the right address, but in the wrong
7592 overlay, and your program will probably crash.
7595 If the process of mapping an overlay is expensive on your system, you
7596 will need to choose your overlays carefully to minimize their effect on
7597 your program's performance.
7600 The executable file you load onto your system must contain each
7601 overlay's instructions, appearing at the overlay's load address, not its
7602 mapped address. However, each overlay's instructions must be relocated
7603 and its symbols defined as if the overlay were at its mapped address.
7604 You can use GNU linker scripts to specify different load and relocation
7605 addresses for pieces of your program; see @ref{Overlay Description,,,
7606 ld.info, Using ld: the GNU linker}.
7609 The procedure for loading executable files onto your system must be able
7610 to load their contents into the larger address space as well as the
7611 instruction and data spaces.
7615 The overlay system described above is rather simple, and could be
7616 improved in many ways:
7621 If your system has suitable bank switch registers or memory management
7622 hardware, you could use those facilities to make an overlay's load area
7623 contents simply appear at their mapped address in instruction space.
7624 This would probably be faster than copying the overlay to its mapped
7625 area in the usual way.
7628 If your overlays are small enough, you could set aside more than one
7629 overlay area, and have more than one overlay mapped at a time.
7632 You can use overlays to manage data, as well as instructions. In
7633 general, data overlays are even less transparent to your design than
7634 code overlays: whereas code overlays only require care when you call or
7635 return to functions, data overlays require care every time you access
7636 the data. Also, if you change the contents of a data overlay, you
7637 must copy its contents back out to its load address before you can copy a
7638 different data overlay into the same mapped area.
7643 @node Overlay Commands
7644 @section Overlay Commands
7646 To use @value{GDBN}'s overlay support, each overlay in your program must
7647 correspond to a separate section of the executable file. The section's
7648 virtual memory address and load memory address must be the overlay's
7649 mapped and load addresses. Identifying overlays with sections allows
7650 @value{GDBN} to determine the appropriate address of a function or
7651 variable, depending on whether the overlay is mapped or not.
7653 @value{GDBN}'s overlay commands all start with the word @code{overlay};
7654 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
7659 Disable @value{GDBN}'s overlay support. When overlay support is
7660 disabled, @value{GDBN} assumes that all functions and variables are
7661 always present at their mapped addresses. By default, @value{GDBN}'s
7662 overlay support is disabled.
7664 @item overlay manual
7665 @cindex manual overlay debugging
7666 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
7667 relies on you to tell it which overlays are mapped, and which are not,
7668 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
7669 commands described below.
7671 @item overlay map-overlay @var{overlay}
7672 @itemx overlay map @var{overlay}
7673 @cindex map an overlay
7674 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
7675 be the name of the object file section containing the overlay. When an
7676 overlay is mapped, @value{GDBN} assumes it can find the overlay's
7677 functions and variables at their mapped addresses. @value{GDBN} assumes
7678 that any other overlays whose mapped ranges overlap that of
7679 @var{overlay} are now unmapped.
7681 @item overlay unmap-overlay @var{overlay}
7682 @itemx overlay unmap @var{overlay}
7683 @cindex unmap an overlay
7684 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
7685 must be the name of the object file section containing the overlay.
7686 When an overlay is unmapped, @value{GDBN} assumes it can find the
7687 overlay's functions and variables at their load addresses.
7690 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
7691 consults a data structure the overlay manager maintains in the inferior
7692 to see which overlays are mapped. For details, see @ref{Automatic
7695 @item overlay load-target
7697 @cindex reloading the overlay table
7698 Re-read the overlay table from the inferior. Normally, @value{GDBN}
7699 re-reads the table @value{GDBN} automatically each time the inferior
7700 stops, so this command should only be necessary if you have changed the
7701 overlay mapping yourself using @value{GDBN}. This command is only
7702 useful when using automatic overlay debugging.
7704 @item overlay list-overlays
7706 @cindex listing mapped overlays
7707 Display a list of the overlays currently mapped, along with their mapped
7708 addresses, load addresses, and sizes.
7712 Normally, when @value{GDBN} prints a code address, it includes the name
7713 of the function the address falls in:
7716 (@value{GDBP}) print main
7717 $3 = @{int ()@} 0x11a0 <main>
7720 When overlay debugging is enabled, @value{GDBN} recognizes code in
7721 unmapped overlays, and prints the names of unmapped functions with
7722 asterisks around them. For example, if @code{foo} is a function in an
7723 unmapped overlay, @value{GDBN} prints it this way:
7726 (@value{GDBP}) overlay list
7727 No sections are mapped.
7728 (@value{GDBP}) print foo
7729 $5 = @{int (int)@} 0x100000 <*foo*>
7732 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
7736 (@value{GDBP}) overlay list
7737 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
7738 mapped at 0x1016 - 0x104a
7739 (@value{GDBP}) print foo
7740 $6 = @{int (int)@} 0x1016 <foo>
7743 When overlay debugging is enabled, @value{GDBN} can find the correct
7744 address for functions and variables in an overlay, whether or not the
7745 overlay is mapped. This allows most @value{GDBN} commands, like
7746 @code{break} and @code{disassemble}, to work normally, even on unmapped
7747 code. However, @value{GDBN}'s breakpoint support has some limitations:
7751 @cindex breakpoints in overlays
7752 @cindex overlays, setting breakpoints in
7753 You can set breakpoints in functions in unmapped overlays, as long as
7754 @value{GDBN} can write to the overlay at its load address.
7756 @value{GDBN} can not set hardware or simulator-based breakpoints in
7757 unmapped overlays. However, if you set a breakpoint at the end of your
7758 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
7759 you are using manual overlay management), @value{GDBN} will re-set its
7760 breakpoints properly.
7764 @node Automatic Overlay Debugging
7765 @section Automatic Overlay Debugging
7766 @cindex automatic overlay debugging
7768 @value{GDBN} can automatically track which overlays are mapped and which
7769 are not, given some simple co-operation from the overlay manager in the
7770 inferior. If you enable automatic overlay debugging with the
7771 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
7772 looks in the inferior's memory for certain variables describing the
7773 current state of the overlays.
7775 Here are the variables your overlay manager must define to support
7776 @value{GDBN}'s automatic overlay debugging:
7780 @item @code{_ovly_table}:
7781 This variable must be an array of the following structures:
7786 /* The overlay's mapped address. */
7789 /* The size of the overlay, in bytes. */
7792 /* The overlay's load address. */
7795 /* Non-zero if the overlay is currently mapped;
7797 unsigned long mapped;
7801 @item @code{_novlys}:
7802 This variable must be a four-byte signed integer, holding the total
7803 number of elements in @code{_ovly_table}.
7807 To decide whether a particular overlay is mapped or not, @value{GDBN}
7808 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
7809 @code{lma} members equal the VMA and LMA of the overlay's section in the
7810 executable file. When @value{GDBN} finds a matching entry, it consults
7811 the entry's @code{mapped} member to determine whether the overlay is
7814 In addition, your overlay manager may define a function called
7815 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
7816 will silently set a breakpoint there. If the overlay manager then
7817 calls this function whenever it has changed the overlay table, this
7818 will enable @value{GDBN} to accurately keep track of which overlays
7819 are in program memory, and update any breakpoints that may be set
7820 in overlays. This will allow breakpoints to work even if the
7821 overlays are kept in ROM or other non-writable memory while they
7822 are not being executed.
7824 @node Overlay Sample Program
7825 @section Overlay Sample Program
7826 @cindex overlay example program
7828 When linking a program which uses overlays, you must place the overlays
7829 at their load addresses, while relocating them to run at their mapped
7830 addresses. To do this, you must write a linker script (@pxref{Overlay
7831 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
7832 since linker scripts are specific to a particular host system, target
7833 architecture, and target memory layout, this manual cannot provide
7834 portable sample code demonstrating @value{GDBN}'s overlay support.
7836 However, the @value{GDBN} source distribution does contain an overlaid
7837 program, with linker scripts for a few systems, as part of its test
7838 suite. The program consists of the following files from
7839 @file{gdb/testsuite/gdb.base}:
7843 The main program file.
7845 A simple overlay manager, used by @file{overlays.c}.
7850 Overlay modules, loaded and used by @file{overlays.c}.
7853 Linker scripts for linking the test program on the @code{d10v-elf}
7854 and @code{m32r-elf} targets.
7857 You can build the test program using the @code{d10v-elf} GCC
7858 cross-compiler like this:
7861 $ d10v-elf-gcc -g -c overlays.c
7862 $ d10v-elf-gcc -g -c ovlymgr.c
7863 $ d10v-elf-gcc -g -c foo.c
7864 $ d10v-elf-gcc -g -c bar.c
7865 $ d10v-elf-gcc -g -c baz.c
7866 $ d10v-elf-gcc -g -c grbx.c
7867 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
7868 baz.o grbx.o -Wl,-Td10v.ld -o overlays
7871 The build process is identical for any other architecture, except that
7872 you must substitute the appropriate compiler and linker script for the
7873 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
7877 @chapter Using @value{GDBN} with Different Languages
7880 Although programming languages generally have common aspects, they are
7881 rarely expressed in the same manner. For instance, in ANSI C,
7882 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
7883 Modula-2, it is accomplished by @code{p^}. Values can also be
7884 represented (and displayed) differently. Hex numbers in C appear as
7885 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
7887 @cindex working language
7888 Language-specific information is built into @value{GDBN} for some languages,
7889 allowing you to express operations like the above in your program's
7890 native language, and allowing @value{GDBN} to output values in a manner
7891 consistent with the syntax of your program's native language. The
7892 language you use to build expressions is called the @dfn{working
7896 * Setting:: Switching between source languages
7897 * Show:: Displaying the language
7898 * Checks:: Type and range checks
7899 * Supported languages:: Supported languages
7900 * Unsupported languages:: Unsupported languages
7904 @section Switching between source languages
7906 There are two ways to control the working language---either have @value{GDBN}
7907 set it automatically, or select it manually yourself. You can use the
7908 @code{set language} command for either purpose. On startup, @value{GDBN}
7909 defaults to setting the language automatically. The working language is
7910 used to determine how expressions you type are interpreted, how values
7913 In addition to the working language, every source file that
7914 @value{GDBN} knows about has its own working language. For some object
7915 file formats, the compiler might indicate which language a particular
7916 source file is in. However, most of the time @value{GDBN} infers the
7917 language from the name of the file. The language of a source file
7918 controls whether C@t{++} names are demangled---this way @code{backtrace} can
7919 show each frame appropriately for its own language. There is no way to
7920 set the language of a source file from within @value{GDBN}, but you can
7921 set the language associated with a filename extension. @xref{Show, ,
7922 Displaying the language}.
7924 This is most commonly a problem when you use a program, such
7925 as @code{cfront} or @code{f2c}, that generates C but is written in
7926 another language. In that case, make the
7927 program use @code{#line} directives in its C output; that way
7928 @value{GDBN} will know the correct language of the source code of the original
7929 program, and will display that source code, not the generated C code.
7932 * Filenames:: Filename extensions and languages.
7933 * Manually:: Setting the working language manually
7934 * Automatically:: Having @value{GDBN} infer the source language
7938 @subsection List of filename extensions and languages
7940 If a source file name ends in one of the following extensions, then
7941 @value{GDBN} infers that its language is the one indicated.
7962 Objective-C source file
7969 Modula-2 source file
7973 Assembler source file. This actually behaves almost like C, but
7974 @value{GDBN} does not skip over function prologues when stepping.
7977 In addition, you may set the language associated with a filename
7978 extension. @xref{Show, , Displaying the language}.
7981 @subsection Setting the working language
7983 If you allow @value{GDBN} to set the language automatically,
7984 expressions are interpreted the same way in your debugging session and
7987 @kindex set language
7988 If you wish, you may set the language manually. To do this, issue the
7989 command @samp{set language @var{lang}}, where @var{lang} is the name of
7991 @code{c} or @code{modula-2}.
7992 For a list of the supported languages, type @samp{set language}.
7994 Setting the language manually prevents @value{GDBN} from updating the working
7995 language automatically. This can lead to confusion if you try
7996 to debug a program when the working language is not the same as the
7997 source language, when an expression is acceptable to both
7998 languages---but means different things. For instance, if the current
7999 source file were written in C, and @value{GDBN} was parsing Modula-2, a
8007 might not have the effect you intended. In C, this means to add
8008 @code{b} and @code{c} and place the result in @code{a}. The result
8009 printed would be the value of @code{a}. In Modula-2, this means to compare
8010 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
8013 @subsection Having @value{GDBN} infer the source language
8015 To have @value{GDBN} set the working language automatically, use
8016 @samp{set language local} or @samp{set language auto}. @value{GDBN}
8017 then infers the working language. That is, when your program stops in a
8018 frame (usually by encountering a breakpoint), @value{GDBN} sets the
8019 working language to the language recorded for the function in that
8020 frame. If the language for a frame is unknown (that is, if the function
8021 or block corresponding to the frame was defined in a source file that
8022 does not have a recognized extension), the current working language is
8023 not changed, and @value{GDBN} issues a warning.
8025 This may not seem necessary for most programs, which are written
8026 entirely in one source language. However, program modules and libraries
8027 written in one source language can be used by a main program written in
8028 a different source language. Using @samp{set language auto} in this
8029 case frees you from having to set the working language manually.
8032 @section Displaying the language
8034 The following commands help you find out which language is the
8035 working language, and also what language source files were written in.
8039 @kindex show language
8040 Display the current working language. This is the
8041 language you can use with commands such as @code{print} to
8042 build and compute expressions that may involve variables in your program.
8045 @kindex info frame@r{, show the source language}
8046 Display the source language for this frame. This language becomes the
8047 working language if you use an identifier from this frame.
8048 @xref{Frame Info, ,Information about a frame}, to identify the other
8049 information listed here.
8052 @kindex info source@r{, show the source language}
8053 Display the source language of this source file.
8054 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
8055 information listed here.
8058 In unusual circumstances, you may have source files with extensions
8059 not in the standard list. You can then set the extension associated
8060 with a language explicitly:
8063 @item set extension-language @var{ext} @var{language}
8064 @kindex set extension-language
8065 Tell @value{GDBN} that source files with extension @var{ext} are to be
8066 assumed as written in the source language @var{language}.
8068 @item info extensions
8069 @kindex info extensions
8070 List all the filename extensions and the associated languages.
8074 @section Type and range checking
8077 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
8078 checking are included, but they do not yet have any effect. This
8079 section documents the intended facilities.
8081 @c FIXME remove warning when type/range code added
8083 Some languages are designed to guard you against making seemingly common
8084 errors through a series of compile- and run-time checks. These include
8085 checking the type of arguments to functions and operators, and making
8086 sure mathematical overflows are caught at run time. Checks such as
8087 these help to ensure a program's correctness once it has been compiled
8088 by eliminating type mismatches, and providing active checks for range
8089 errors when your program is running.
8091 @value{GDBN} can check for conditions like the above if you wish.
8092 Although @value{GDBN} does not check the statements in your program,
8093 it can check expressions entered directly into @value{GDBN} for
8094 evaluation via the @code{print} command, for example. As with the
8095 working language, @value{GDBN} can also decide whether or not to check
8096 automatically based on your program's source language.
8097 @xref{Supported languages, ,Supported languages}, for the default
8098 settings of supported languages.
8101 * Type Checking:: An overview of type checking
8102 * Range Checking:: An overview of range checking
8105 @cindex type checking
8106 @cindex checks, type
8108 @subsection An overview of type checking
8110 Some languages, such as Modula-2, are strongly typed, meaning that the
8111 arguments to operators and functions have to be of the correct type,
8112 otherwise an error occurs. These checks prevent type mismatch
8113 errors from ever causing any run-time problems. For example,
8121 The second example fails because the @code{CARDINAL} 1 is not
8122 type-compatible with the @code{REAL} 2.3.
8124 For the expressions you use in @value{GDBN} commands, you can tell the
8125 @value{GDBN} type checker to skip checking;
8126 to treat any mismatches as errors and abandon the expression;
8127 or to only issue warnings when type mismatches occur,
8128 but evaluate the expression anyway. When you choose the last of
8129 these, @value{GDBN} evaluates expressions like the second example above, but
8130 also issues a warning.
8132 Even if you turn type checking off, there may be other reasons
8133 related to type that prevent @value{GDBN} from evaluating an expression.
8134 For instance, @value{GDBN} does not know how to add an @code{int} and
8135 a @code{struct foo}. These particular type errors have nothing to do
8136 with the language in use, and usually arise from expressions, such as
8137 the one described above, which make little sense to evaluate anyway.
8139 Each language defines to what degree it is strict about type. For
8140 instance, both Modula-2 and C require the arguments to arithmetical
8141 operators to be numbers. In C, enumerated types and pointers can be
8142 represented as numbers, so that they are valid arguments to mathematical
8143 operators. @xref{Supported languages, ,Supported languages}, for further
8144 details on specific languages.
8146 @value{GDBN} provides some additional commands for controlling the type checker:
8148 @kindex set check type
8149 @kindex show check type
8151 @item set check type auto
8152 Set type checking on or off based on the current working language.
8153 @xref{Supported languages, ,Supported languages}, for the default settings for
8156 @item set check type on
8157 @itemx set check type off
8158 Set type checking on or off, overriding the default setting for the
8159 current working language. Issue a warning if the setting does not
8160 match the language default. If any type mismatches occur in
8161 evaluating an expression while type checking is on, @value{GDBN} prints a
8162 message and aborts evaluation of the expression.
8164 @item set check type warn
8165 Cause the type checker to issue warnings, but to always attempt to
8166 evaluate the expression. Evaluating the expression may still
8167 be impossible for other reasons. For example, @value{GDBN} cannot add
8168 numbers and structures.
8171 Show the current setting of the type checker, and whether or not @value{GDBN}
8172 is setting it automatically.
8175 @cindex range checking
8176 @cindex checks, range
8177 @node Range Checking
8178 @subsection An overview of range checking
8180 In some languages (such as Modula-2), it is an error to exceed the
8181 bounds of a type; this is enforced with run-time checks. Such range
8182 checking is meant to ensure program correctness by making sure
8183 computations do not overflow, or indices on an array element access do
8184 not exceed the bounds of the array.
8186 For expressions you use in @value{GDBN} commands, you can tell
8187 @value{GDBN} to treat range errors in one of three ways: ignore them,
8188 always treat them as errors and abandon the expression, or issue
8189 warnings but evaluate the expression anyway.
8191 A range error can result from numerical overflow, from exceeding an
8192 array index bound, or when you type a constant that is not a member
8193 of any type. Some languages, however, do not treat overflows as an
8194 error. In many implementations of C, mathematical overflow causes the
8195 result to ``wrap around'' to lower values---for example, if @var{m} is
8196 the largest integer value, and @var{s} is the smallest, then
8199 @var{m} + 1 @result{} @var{s}
8202 This, too, is specific to individual languages, and in some cases
8203 specific to individual compilers or machines. @xref{Supported languages, ,
8204 Supported languages}, for further details on specific languages.
8206 @value{GDBN} provides some additional commands for controlling the range checker:
8208 @kindex set check range
8209 @kindex show check range
8211 @item set check range auto
8212 Set range checking on or off based on the current working language.
8213 @xref{Supported languages, ,Supported languages}, for the default settings for
8216 @item set check range on
8217 @itemx set check range off
8218 Set range checking on or off, overriding the default setting for the
8219 current working language. A warning is issued if the setting does not
8220 match the language default. If a range error occurs and range checking is on,
8221 then a message is printed and evaluation of the expression is aborted.
8223 @item set check range warn
8224 Output messages when the @value{GDBN} range checker detects a range error,
8225 but attempt to evaluate the expression anyway. Evaluating the
8226 expression may still be impossible for other reasons, such as accessing
8227 memory that the process does not own (a typical example from many Unix
8231 Show the current setting of the range checker, and whether or not it is
8232 being set automatically by @value{GDBN}.
8235 @node Supported languages
8236 @section Supported languages
8238 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
8239 assembly, Modula-2, and Ada.
8240 @c This is false ...
8241 Some @value{GDBN} features may be used in expressions regardless of the
8242 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
8243 and the @samp{@{type@}addr} construct (@pxref{Expressions,
8244 ,Expressions}) can be used with the constructs of any supported
8247 The following sections detail to what degree each source language is
8248 supported by @value{GDBN}. These sections are not meant to be language
8249 tutorials or references, but serve only as a reference guide to what the
8250 @value{GDBN} expression parser accepts, and what input and output
8251 formats should look like for different languages. There are many good
8252 books written on each of these languages; please look to these for a
8253 language reference or tutorial.
8257 * Objective-C:: Objective-C
8260 * Modula-2:: Modula-2
8265 @subsection C and C@t{++}
8267 @cindex C and C@t{++}
8268 @cindex expressions in C or C@t{++}
8270 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
8271 to both languages. Whenever this is the case, we discuss those languages
8275 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
8276 @cindex @sc{gnu} C@t{++}
8277 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
8278 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
8279 effectively, you must compile your C@t{++} programs with a supported
8280 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
8281 compiler (@code{aCC}).
8283 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
8284 format; if it doesn't work on your system, try the stabs+ debugging
8285 format. You can select those formats explicitly with the @code{g++}
8286 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
8287 @xref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
8288 CC, gcc.info, Using @sc{gnu} CC}.
8291 * C Operators:: C and C@t{++} operators
8292 * C Constants:: C and C@t{++} constants
8293 * C plus plus expressions:: C@t{++} expressions
8294 * C Defaults:: Default settings for C and C@t{++}
8295 * C Checks:: C and C@t{++} type and range checks
8296 * Debugging C:: @value{GDBN} and C
8297 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
8301 @subsubsection C and C@t{++} operators
8303 @cindex C and C@t{++} operators
8305 Operators must be defined on values of specific types. For instance,
8306 @code{+} is defined on numbers, but not on structures. Operators are
8307 often defined on groups of types.
8309 For the purposes of C and C@t{++}, the following definitions hold:
8314 @emph{Integral types} include @code{int} with any of its storage-class
8315 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
8318 @emph{Floating-point types} include @code{float}, @code{double}, and
8319 @code{long double} (if supported by the target platform).
8322 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
8325 @emph{Scalar types} include all of the above.
8330 The following operators are supported. They are listed here
8331 in order of increasing precedence:
8335 The comma or sequencing operator. Expressions in a comma-separated list
8336 are evaluated from left to right, with the result of the entire
8337 expression being the last expression evaluated.
8340 Assignment. The value of an assignment expression is the value
8341 assigned. Defined on scalar types.
8344 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
8345 and translated to @w{@code{@var{a} = @var{a op b}}}.
8346 @w{@code{@var{op}=}} and @code{=} have the same precedence.
8347 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
8348 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
8351 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
8352 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
8356 Logical @sc{or}. Defined on integral types.
8359 Logical @sc{and}. Defined on integral types.
8362 Bitwise @sc{or}. Defined on integral types.
8365 Bitwise exclusive-@sc{or}. Defined on integral types.
8368 Bitwise @sc{and}. Defined on integral types.
8371 Equality and inequality. Defined on scalar types. The value of these
8372 expressions is 0 for false and non-zero for true.
8374 @item <@r{, }>@r{, }<=@r{, }>=
8375 Less than, greater than, less than or equal, greater than or equal.
8376 Defined on scalar types. The value of these expressions is 0 for false
8377 and non-zero for true.
8380 left shift, and right shift. Defined on integral types.
8383 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8386 Addition and subtraction. Defined on integral types, floating-point types and
8389 @item *@r{, }/@r{, }%
8390 Multiplication, division, and modulus. Multiplication and division are
8391 defined on integral and floating-point types. Modulus is defined on
8395 Increment and decrement. When appearing before a variable, the
8396 operation is performed before the variable is used in an expression;
8397 when appearing after it, the variable's value is used before the
8398 operation takes place.
8401 Pointer dereferencing. Defined on pointer types. Same precedence as
8405 Address operator. Defined on variables. Same precedence as @code{++}.
8407 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
8408 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
8409 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
8410 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
8414 Negative. Defined on integral and floating-point types. Same
8415 precedence as @code{++}.
8418 Logical negation. Defined on integral types. Same precedence as
8422 Bitwise complement operator. Defined on integral types. Same precedence as
8427 Structure member, and pointer-to-structure member. For convenience,
8428 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
8429 pointer based on the stored type information.
8430 Defined on @code{struct} and @code{union} data.
8433 Dereferences of pointers to members.
8436 Array indexing. @code{@var{a}[@var{i}]} is defined as
8437 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
8440 Function parameter list. Same precedence as @code{->}.
8443 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
8444 and @code{class} types.
8447 Doubled colons also represent the @value{GDBN} scope operator
8448 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
8452 If an operator is redefined in the user code, @value{GDBN} usually
8453 attempts to invoke the redefined version instead of using the operator's
8461 @subsubsection C and C@t{++} constants
8463 @cindex C and C@t{++} constants
8465 @value{GDBN} allows you to express the constants of C and C@t{++} in the
8470 Integer constants are a sequence of digits. Octal constants are
8471 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
8472 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
8473 @samp{l}, specifying that the constant should be treated as a
8477 Floating point constants are a sequence of digits, followed by a decimal
8478 point, followed by a sequence of digits, and optionally followed by an
8479 exponent. An exponent is of the form:
8480 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
8481 sequence of digits. The @samp{+} is optional for positive exponents.
8482 A floating-point constant may also end with a letter @samp{f} or
8483 @samp{F}, specifying that the constant should be treated as being of
8484 the @code{float} (as opposed to the default @code{double}) type; or with
8485 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
8489 Enumerated constants consist of enumerated identifiers, or their
8490 integral equivalents.
8493 Character constants are a single character surrounded by single quotes
8494 (@code{'}), or a number---the ordinal value of the corresponding character
8495 (usually its @sc{ascii} value). Within quotes, the single character may
8496 be represented by a letter or by @dfn{escape sequences}, which are of
8497 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
8498 of the character's ordinal value; or of the form @samp{\@var{x}}, where
8499 @samp{@var{x}} is a predefined special character---for example,
8500 @samp{\n} for newline.
8503 String constants are a sequence of character constants surrounded by
8504 double quotes (@code{"}). Any valid character constant (as described
8505 above) may appear. Double quotes within the string must be preceded by
8506 a backslash, so for instance @samp{"a\"b'c"} is a string of five
8510 Pointer constants are an integral value. You can also write pointers
8511 to constants using the C operator @samp{&}.
8514 Array constants are comma-separated lists surrounded by braces @samp{@{}
8515 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
8516 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
8517 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
8521 * C plus plus expressions::
8528 @node C plus plus expressions
8529 @subsubsection C@t{++} expressions
8531 @cindex expressions in C@t{++}
8532 @value{GDBN} expression handling can interpret most C@t{++} expressions.
8534 @cindex debugging C@t{++} programs
8535 @cindex C@t{++} compilers
8536 @cindex debug formats and C@t{++}
8537 @cindex @value{NGCC} and C@t{++}
8539 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
8540 proper compiler and the proper debug format. Currently, @value{GDBN}
8541 works best when debugging C@t{++} code that is compiled with
8542 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
8543 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
8544 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
8545 stabs+ as their default debug format, so you usually don't need to
8546 specify a debug format explicitly. Other compilers and/or debug formats
8547 are likely to work badly or not at all when using @value{GDBN} to debug
8553 @cindex member functions
8555 Member function calls are allowed; you can use expressions like
8558 count = aml->GetOriginal(x, y)
8561 @vindex this@r{, inside C@t{++} member functions}
8562 @cindex namespace in C@t{++}
8564 While a member function is active (in the selected stack frame), your
8565 expressions have the same namespace available as the member function;
8566 that is, @value{GDBN} allows implicit references to the class instance
8567 pointer @code{this} following the same rules as C@t{++}.
8569 @cindex call overloaded functions
8570 @cindex overloaded functions, calling
8571 @cindex type conversions in C@t{++}
8573 You can call overloaded functions; @value{GDBN} resolves the function
8574 call to the right definition, with some restrictions. @value{GDBN} does not
8575 perform overload resolution involving user-defined type conversions,
8576 calls to constructors, or instantiations of templates that do not exist
8577 in the program. It also cannot handle ellipsis argument lists or
8580 It does perform integral conversions and promotions, floating-point
8581 promotions, arithmetic conversions, pointer conversions, conversions of
8582 class objects to base classes, and standard conversions such as those of
8583 functions or arrays to pointers; it requires an exact match on the
8584 number of function arguments.
8586 Overload resolution is always performed, unless you have specified
8587 @code{set overload-resolution off}. @xref{Debugging C plus plus,
8588 ,@value{GDBN} features for C@t{++}}.
8590 You must specify @code{set overload-resolution off} in order to use an
8591 explicit function signature to call an overloaded function, as in
8593 p 'foo(char,int)'('x', 13)
8596 The @value{GDBN} command-completion facility can simplify this;
8597 see @ref{Completion, ,Command completion}.
8599 @cindex reference declarations
8601 @value{GDBN} understands variables declared as C@t{++} references; you can use
8602 them in expressions just as you do in C@t{++} source---they are automatically
8605 In the parameter list shown when @value{GDBN} displays a frame, the values of
8606 reference variables are not displayed (unlike other variables); this
8607 avoids clutter, since references are often used for large structures.
8608 The @emph{address} of a reference variable is always shown, unless
8609 you have specified @samp{set print address off}.
8612 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
8613 expressions can use it just as expressions in your program do. Since
8614 one scope may be defined in another, you can use @code{::} repeatedly if
8615 necessary, for example in an expression like
8616 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
8617 resolving name scope by reference to source files, in both C and C@t{++}
8618 debugging (@pxref{Variables, ,Program variables}).
8621 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
8622 calling virtual functions correctly, printing out virtual bases of
8623 objects, calling functions in a base subobject, casting objects, and
8624 invoking user-defined operators.
8627 @subsubsection C and C@t{++} defaults
8629 @cindex C and C@t{++} defaults
8631 If you allow @value{GDBN} to set type and range checking automatically, they
8632 both default to @code{off} whenever the working language changes to
8633 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
8634 selects the working language.
8636 If you allow @value{GDBN} to set the language automatically, it
8637 recognizes source files whose names end with @file{.c}, @file{.C}, or
8638 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
8639 these files, it sets the working language to C or C@t{++}.
8640 @xref{Automatically, ,Having @value{GDBN} infer the source language},
8641 for further details.
8643 @c Type checking is (a) primarily motivated by Modula-2, and (b)
8644 @c unimplemented. If (b) changes, it might make sense to let this node
8645 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
8648 @subsubsection C and C@t{++} type and range checks
8650 @cindex C and C@t{++} checks
8652 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
8653 is not used. However, if you turn type checking on, @value{GDBN}
8654 considers two variables type equivalent if:
8658 The two variables are structured and have the same structure, union, or
8662 The two variables have the same type name, or types that have been
8663 declared equivalent through @code{typedef}.
8666 @c leaving this out because neither J Gilmore nor R Pesch understand it.
8669 The two @code{struct}, @code{union}, or @code{enum} variables are
8670 declared in the same declaration. (Note: this may not be true for all C
8675 Range checking, if turned on, is done on mathematical operations. Array
8676 indices are not checked, since they are often used to index a pointer
8677 that is not itself an array.
8680 @subsubsection @value{GDBN} and C
8682 The @code{set print union} and @code{show print union} commands apply to
8683 the @code{union} type. When set to @samp{on}, any @code{union} that is
8684 inside a @code{struct} or @code{class} is also printed. Otherwise, it
8685 appears as @samp{@{...@}}.
8687 The @code{@@} operator aids in the debugging of dynamic arrays, formed
8688 with pointers and a memory allocation function. @xref{Expressions,
8692 * Debugging C plus plus::
8695 @node Debugging C plus plus
8696 @subsubsection @value{GDBN} features for C@t{++}
8698 @cindex commands for C@t{++}
8700 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
8701 designed specifically for use with C@t{++}. Here is a summary:
8704 @cindex break in overloaded functions
8705 @item @r{breakpoint menus}
8706 When you want a breakpoint in a function whose name is overloaded,
8707 @value{GDBN} breakpoint menus help you specify which function definition
8708 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
8710 @cindex overloading in C@t{++}
8711 @item rbreak @var{regex}
8712 Setting breakpoints using regular expressions is helpful for setting
8713 breakpoints on overloaded functions that are not members of any special
8715 @xref{Set Breaks, ,Setting breakpoints}.
8717 @cindex C@t{++} exception handling
8720 Debug C@t{++} exception handling using these commands. @xref{Set
8721 Catchpoints, , Setting catchpoints}.
8724 @item ptype @var{typename}
8725 Print inheritance relationships as well as other information for type
8727 @xref{Symbols, ,Examining the Symbol Table}.
8729 @cindex C@t{++} symbol display
8730 @item set print demangle
8731 @itemx show print demangle
8732 @itemx set print asm-demangle
8733 @itemx show print asm-demangle
8734 Control whether C@t{++} symbols display in their source form, both when
8735 displaying code as C@t{++} source and when displaying disassemblies.
8736 @xref{Print Settings, ,Print settings}.
8738 @item set print object
8739 @itemx show print object
8740 Choose whether to print derived (actual) or declared types of objects.
8741 @xref{Print Settings, ,Print settings}.
8743 @item set print vtbl
8744 @itemx show print vtbl
8745 Control the format for printing virtual function tables.
8746 @xref{Print Settings, ,Print settings}.
8747 (The @code{vtbl} commands do not work on programs compiled with the HP
8748 ANSI C@t{++} compiler (@code{aCC}).)
8750 @kindex set overload-resolution
8751 @cindex overloaded functions, overload resolution
8752 @item set overload-resolution on
8753 Enable overload resolution for C@t{++} expression evaluation. The default
8754 is on. For overloaded functions, @value{GDBN} evaluates the arguments
8755 and searches for a function whose signature matches the argument types,
8756 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
8757 expressions}, for details). If it cannot find a match, it emits a
8760 @item set overload-resolution off
8761 Disable overload resolution for C@t{++} expression evaluation. For
8762 overloaded functions that are not class member functions, @value{GDBN}
8763 chooses the first function of the specified name that it finds in the
8764 symbol table, whether or not its arguments are of the correct type. For
8765 overloaded functions that are class member functions, @value{GDBN}
8766 searches for a function whose signature @emph{exactly} matches the
8769 @kindex show overload-resolution
8770 @item show overload-resolution
8771 Show the current setting of overload resolution.
8773 @item @r{Overloaded symbol names}
8774 You can specify a particular definition of an overloaded symbol, using
8775 the same notation that is used to declare such symbols in C@t{++}: type
8776 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
8777 also use the @value{GDBN} command-line word completion facilities to list the
8778 available choices, or to finish the type list for you.
8779 @xref{Completion,, Command completion}, for details on how to do this.
8783 @subsection Objective-C
8786 This section provides information about some commands and command
8787 options that are useful for debugging Objective-C code.
8790 * Method Names in Commands::
8791 * The Print Command with Objective-C::
8794 @node Method Names in Commands, The Print Command with Objective-C, Objective-C, Objective-C
8795 @subsubsection Method Names in Commands
8797 The following commands have been extended to accept Objective-C method
8798 names as line specifications:
8800 @kindex clear@r{, and Objective-C}
8801 @kindex break@r{, and Objective-C}
8802 @kindex info line@r{, and Objective-C}
8803 @kindex jump@r{, and Objective-C}
8804 @kindex list@r{, and Objective-C}
8808 @item @code{info line}
8813 A fully qualified Objective-C method name is specified as
8816 -[@var{Class} @var{methodName}]
8819 where the minus sign is used to indicate an instance method and a
8820 plus sign (not shown) is used to indicate a class method. The class
8821 name @var{Class} and method name @var{methodName} are enclosed in
8822 brackets, similar to the way messages are specified in Objective-C
8823 source code. For example, to set a breakpoint at the @code{create}
8824 instance method of class @code{Fruit} in the program currently being
8828 break -[Fruit create]
8831 To list ten program lines around the @code{initialize} class method,
8835 list +[NSText initialize]
8838 In the current version of @value{GDBN}, the plus or minus sign is
8839 required. In future versions of @value{GDBN}, the plus or minus
8840 sign will be optional, but you can use it to narrow the search. It
8841 is also possible to specify just a method name:
8847 You must specify the complete method name, including any colons. If
8848 your program's source files contain more than one @code{create} method,
8849 you'll be presented with a numbered list of classes that implement that
8850 method. Indicate your choice by number, or type @samp{0} to exit if
8853 As another example, to clear a breakpoint established at the
8854 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
8857 clear -[NSWindow makeKeyAndOrderFront:]
8860 @node The Print Command with Objective-C
8861 @subsubsection The Print Command With Objective-C
8862 @kindex print-object
8863 @kindex po @r{(@code{print-object})}
8865 The print command has also been extended to accept methods. For example:
8868 print -[@var{object} hash]
8871 @cindex print an Objective-C object description
8872 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
8874 will tell @value{GDBN} to send the @code{hash} message to @var{object}
8875 and print the result. Also, an additional command has been added,
8876 @code{print-object} or @code{po} for short, which is meant to print
8877 the description of an object. However, this command may only work
8878 with certain Objective-C libraries that have a particular hook
8879 function, @code{_NSPrintForDebugger}, defined.
8883 @cindex Fortran-specific support in @value{GDBN}
8886 @cindex @code{COMMON} blocks, Fortran
8888 @item info common @r{[}@var{common-name}@r{]}
8889 This command prints the values contained in the Fortran @code{COMMON}
8890 block whose name is @var{common-name}. With no argument, the names of
8891 all @code{COMMON} blocks visible at current program location are
8895 Fortran symbols are usually case-insensitive, so @value{GDBN} by
8896 default uses case-insensitive matches for Fortran symbols. You can
8897 change that with the @samp{set case-insensitive} command, see
8898 @ref{Symbols}, for the details.
8903 @cindex Pascal support in @value{GDBN}, limitations
8904 Debugging Pascal programs which use sets, subranges, file variables, or
8905 nested functions does not currently work. @value{GDBN} does not support
8906 entering expressions, printing values, or similar features using Pascal
8909 The Pascal-specific command @code{set print pascal_static-members}
8910 controls whether static members of Pascal objects are displayed.
8911 @xref{Print Settings, pascal_static-members}.
8914 @subsection Modula-2
8916 @cindex Modula-2, @value{GDBN} support
8918 The extensions made to @value{GDBN} to support Modula-2 only support
8919 output from the @sc{gnu} Modula-2 compiler (which is currently being
8920 developed). Other Modula-2 compilers are not currently supported, and
8921 attempting to debug executables produced by them is most likely
8922 to give an error as @value{GDBN} reads in the executable's symbol
8925 @cindex expressions in Modula-2
8927 * M2 Operators:: Built-in operators
8928 * Built-In Func/Proc:: Built-in functions and procedures
8929 * M2 Constants:: Modula-2 constants
8930 * M2 Defaults:: Default settings for Modula-2
8931 * Deviations:: Deviations from standard Modula-2
8932 * M2 Checks:: Modula-2 type and range checks
8933 * M2 Scope:: The scope operators @code{::} and @code{.}
8934 * GDB/M2:: @value{GDBN} and Modula-2
8938 @subsubsection Operators
8939 @cindex Modula-2 operators
8941 Operators must be defined on values of specific types. For instance,
8942 @code{+} is defined on numbers, but not on structures. Operators are
8943 often defined on groups of types. For the purposes of Modula-2, the
8944 following definitions hold:
8949 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
8953 @emph{Character types} consist of @code{CHAR} and its subranges.
8956 @emph{Floating-point types} consist of @code{REAL}.
8959 @emph{Pointer types} consist of anything declared as @code{POINTER TO
8963 @emph{Scalar types} consist of all of the above.
8966 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
8969 @emph{Boolean types} consist of @code{BOOLEAN}.
8973 The following operators are supported, and appear in order of
8974 increasing precedence:
8978 Function argument or array index separator.
8981 Assignment. The value of @var{var} @code{:=} @var{value} is
8985 Less than, greater than on integral, floating-point, or enumerated
8989 Less than or equal to, greater than or equal to
8990 on integral, floating-point and enumerated types, or set inclusion on
8991 set types. Same precedence as @code{<}.
8993 @item =@r{, }<>@r{, }#
8994 Equality and two ways of expressing inequality, valid on scalar types.
8995 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
8996 available for inequality, since @code{#} conflicts with the script
9000 Set membership. Defined on set types and the types of their members.
9001 Same precedence as @code{<}.
9004 Boolean disjunction. Defined on boolean types.
9007 Boolean conjunction. Defined on boolean types.
9010 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9013 Addition and subtraction on integral and floating-point types, or union
9014 and difference on set types.
9017 Multiplication on integral and floating-point types, or set intersection
9021 Division on floating-point types, or symmetric set difference on set
9022 types. Same precedence as @code{*}.
9025 Integer division and remainder. Defined on integral types. Same
9026 precedence as @code{*}.
9029 Negative. Defined on @code{INTEGER} and @code{REAL} data.
9032 Pointer dereferencing. Defined on pointer types.
9035 Boolean negation. Defined on boolean types. Same precedence as
9039 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
9040 precedence as @code{^}.
9043 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
9046 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
9050 @value{GDBN} and Modula-2 scope operators.
9054 @emph{Warning:} Sets and their operations are not yet supported, so @value{GDBN}
9055 treats the use of the operator @code{IN}, or the use of operators
9056 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
9057 @code{<=}, and @code{>=} on sets as an error.
9061 @node Built-In Func/Proc
9062 @subsubsection Built-in functions and procedures
9063 @cindex Modula-2 built-ins
9065 Modula-2 also makes available several built-in procedures and functions.
9066 In describing these, the following metavariables are used:
9071 represents an @code{ARRAY} variable.
9074 represents a @code{CHAR} constant or variable.
9077 represents a variable or constant of integral type.
9080 represents an identifier that belongs to a set. Generally used in the
9081 same function with the metavariable @var{s}. The type of @var{s} should
9082 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
9085 represents a variable or constant of integral or floating-point type.
9088 represents a variable or constant of floating-point type.
9094 represents a variable.
9097 represents a variable or constant of one of many types. See the
9098 explanation of the function for details.
9101 All Modula-2 built-in procedures also return a result, described below.
9105 Returns the absolute value of @var{n}.
9108 If @var{c} is a lower case letter, it returns its upper case
9109 equivalent, otherwise it returns its argument.
9112 Returns the character whose ordinal value is @var{i}.
9115 Decrements the value in the variable @var{v} by one. Returns the new value.
9117 @item DEC(@var{v},@var{i})
9118 Decrements the value in the variable @var{v} by @var{i}. Returns the
9121 @item EXCL(@var{m},@var{s})
9122 Removes the element @var{m} from the set @var{s}. Returns the new
9125 @item FLOAT(@var{i})
9126 Returns the floating point equivalent of the integer @var{i}.
9129 Returns the index of the last member of @var{a}.
9132 Increments the value in the variable @var{v} by one. Returns the new value.
9134 @item INC(@var{v},@var{i})
9135 Increments the value in the variable @var{v} by @var{i}. Returns the
9138 @item INCL(@var{m},@var{s})
9139 Adds the element @var{m} to the set @var{s} if it is not already
9140 there. Returns the new set.
9143 Returns the maximum value of the type @var{t}.
9146 Returns the minimum value of the type @var{t}.
9149 Returns boolean TRUE if @var{i} is an odd number.
9152 Returns the ordinal value of its argument. For example, the ordinal
9153 value of a character is its @sc{ascii} value (on machines supporting the
9154 @sc{ascii} character set). @var{x} must be of an ordered type, which include
9155 integral, character and enumerated types.
9158 Returns the size of its argument. @var{x} can be a variable or a type.
9160 @item TRUNC(@var{r})
9161 Returns the integral part of @var{r}.
9163 @item VAL(@var{t},@var{i})
9164 Returns the member of the type @var{t} whose ordinal value is @var{i}.
9168 @emph{Warning:} Sets and their operations are not yet supported, so
9169 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
9173 @cindex Modula-2 constants
9175 @subsubsection Constants
9177 @value{GDBN} allows you to express the constants of Modula-2 in the following
9183 Integer constants are simply a sequence of digits. When used in an
9184 expression, a constant is interpreted to be type-compatible with the
9185 rest of the expression. Hexadecimal integers are specified by a
9186 trailing @samp{H}, and octal integers by a trailing @samp{B}.
9189 Floating point constants appear as a sequence of digits, followed by a
9190 decimal point and another sequence of digits. An optional exponent can
9191 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
9192 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
9193 digits of the floating point constant must be valid decimal (base 10)
9197 Character constants consist of a single character enclosed by a pair of
9198 like quotes, either single (@code{'}) or double (@code{"}). They may
9199 also be expressed by their ordinal value (their @sc{ascii} value, usually)
9200 followed by a @samp{C}.
9203 String constants consist of a sequence of characters enclosed by a
9204 pair of like quotes, either single (@code{'}) or double (@code{"}).
9205 Escape sequences in the style of C are also allowed. @xref{C
9206 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
9210 Enumerated constants consist of an enumerated identifier.
9213 Boolean constants consist of the identifiers @code{TRUE} and
9217 Pointer constants consist of integral values only.
9220 Set constants are not yet supported.
9224 @subsubsection Modula-2 defaults
9225 @cindex Modula-2 defaults
9227 If type and range checking are set automatically by @value{GDBN}, they
9228 both default to @code{on} whenever the working language changes to
9229 Modula-2. This happens regardless of whether you or @value{GDBN}
9230 selected the working language.
9232 If you allow @value{GDBN} to set the language automatically, then entering
9233 code compiled from a file whose name ends with @file{.mod} sets the
9234 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
9235 the language automatically}, for further details.
9238 @subsubsection Deviations from standard Modula-2
9239 @cindex Modula-2, deviations from
9241 A few changes have been made to make Modula-2 programs easier to debug.
9242 This is done primarily via loosening its type strictness:
9246 Unlike in standard Modula-2, pointer constants can be formed by
9247 integers. This allows you to modify pointer variables during
9248 debugging. (In standard Modula-2, the actual address contained in a
9249 pointer variable is hidden from you; it can only be modified
9250 through direct assignment to another pointer variable or expression that
9251 returned a pointer.)
9254 C escape sequences can be used in strings and characters to represent
9255 non-printable characters. @value{GDBN} prints out strings with these
9256 escape sequences embedded. Single non-printable characters are
9257 printed using the @samp{CHR(@var{nnn})} format.
9260 The assignment operator (@code{:=}) returns the value of its right-hand
9264 All built-in procedures both modify @emph{and} return their argument.
9268 @subsubsection Modula-2 type and range checks
9269 @cindex Modula-2 checks
9272 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
9275 @c FIXME remove warning when type/range checks added
9277 @value{GDBN} considers two Modula-2 variables type equivalent if:
9281 They are of types that have been declared equivalent via a @code{TYPE
9282 @var{t1} = @var{t2}} statement
9285 They have been declared on the same line. (Note: This is true of the
9286 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
9289 As long as type checking is enabled, any attempt to combine variables
9290 whose types are not equivalent is an error.
9292 Range checking is done on all mathematical operations, assignment, array
9293 index bounds, and all built-in functions and procedures.
9296 @subsubsection The scope operators @code{::} and @code{.}
9298 @cindex @code{.}, Modula-2 scope operator
9299 @cindex colon, doubled as scope operator
9301 @vindex colon-colon@r{, in Modula-2}
9302 @c Info cannot handle :: but TeX can.
9305 @vindex ::@r{, in Modula-2}
9308 There are a few subtle differences between the Modula-2 scope operator
9309 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
9314 @var{module} . @var{id}
9315 @var{scope} :: @var{id}
9319 where @var{scope} is the name of a module or a procedure,
9320 @var{module} the name of a module, and @var{id} is any declared
9321 identifier within your program, except another module.
9323 Using the @code{::} operator makes @value{GDBN} search the scope
9324 specified by @var{scope} for the identifier @var{id}. If it is not
9325 found in the specified scope, then @value{GDBN} searches all scopes
9326 enclosing the one specified by @var{scope}.
9328 Using the @code{.} operator makes @value{GDBN} search the current scope for
9329 the identifier specified by @var{id} that was imported from the
9330 definition module specified by @var{module}. With this operator, it is
9331 an error if the identifier @var{id} was not imported from definition
9332 module @var{module}, or if @var{id} is not an identifier in
9336 @subsubsection @value{GDBN} and Modula-2
9338 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
9339 Five subcommands of @code{set print} and @code{show print} apply
9340 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
9341 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
9342 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
9343 analogue in Modula-2.
9345 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
9346 with any language, is not useful with Modula-2. Its
9347 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
9348 created in Modula-2 as they can in C or C@t{++}. However, because an
9349 address can be specified by an integral constant, the construct
9350 @samp{@{@var{type}@}@var{adrexp}} is still useful.
9352 @cindex @code{#} in Modula-2
9353 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
9354 interpreted as the beginning of a comment. Use @code{<>} instead.
9360 The extensions made to @value{GDBN} for Ada only support
9361 output from the @sc{gnu} Ada (GNAT) compiler.
9362 Other Ada compilers are not currently supported, and
9363 attempting to debug executables produced by them is most likely
9367 @cindex expressions in Ada
9369 * Ada Mode Intro:: General remarks on the Ada syntax
9370 and semantics supported by Ada mode
9372 * Omissions from Ada:: Restrictions on the Ada expression syntax.
9373 * Additions to Ada:: Extensions of the Ada expression syntax.
9374 * Stopping Before Main Program:: Debugging the program during elaboration.
9375 * Ada Glitches:: Known peculiarities of Ada mode.
9378 @node Ada Mode Intro
9379 @subsubsection Introduction
9380 @cindex Ada mode, general
9382 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
9383 syntax, with some extensions.
9384 The philosophy behind the design of this subset is
9388 That @value{GDBN} should provide basic literals and access to operations for
9389 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
9390 leaving more sophisticated computations to subprograms written into the
9391 program (which therefore may be called from @value{GDBN}).
9394 That type safety and strict adherence to Ada language restrictions
9395 are not particularly important to the @value{GDBN} user.
9398 That brevity is important to the @value{GDBN} user.
9401 Thus, for brevity, the debugger acts as if there were
9402 implicit @code{with} and @code{use} clauses in effect for all user-written
9403 packages, making it unnecessary to fully qualify most names with
9404 their packages, regardless of context. Where this causes ambiguity,
9405 @value{GDBN} asks the user's intent.
9407 The debugger will start in Ada mode if it detects an Ada main program.
9408 As for other languages, it will enter Ada mode when stopped in a program that
9409 was translated from an Ada source file.
9411 While in Ada mode, you may use `@t{--}' for comments. This is useful
9412 mostly for documenting command files. The standard @value{GDBN} comment
9413 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
9414 middle (to allow based literals).
9416 The debugger supports limited overloading. Given a subprogram call in which
9417 the function symbol has multiple definitions, it will use the number of
9418 actual parameters and some information about their types to attempt to narrow
9419 the set of definitions. It also makes very limited use of context, preferring
9420 procedures to functions in the context of the @code{call} command, and
9421 functions to procedures elsewhere.
9423 @node Omissions from Ada
9424 @subsubsection Omissions from Ada
9425 @cindex Ada, omissions from
9427 Here are the notable omissions from the subset:
9431 Only a subset of the attributes are supported:
9435 @t{'First}, @t{'Last}, and @t{'Length}
9436 on array objects (not on types and subtypes).
9439 @t{'Min} and @t{'Max}.
9442 @t{'Pos} and @t{'Val}.
9448 @t{'Range} on array objects (not subtypes), but only as the right
9449 operand of the membership (@code{in}) operator.
9452 @t{'Access}, @t{'Unchecked_Access}, and
9453 @t{'Unrestricted_Access} (a GNAT extension).
9461 @code{Characters.Latin_1} are not available and
9462 concatenation is not implemented. Thus, escape characters in strings are
9463 not currently available.
9466 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
9467 equality of representations. They will generally work correctly
9468 for strings and arrays whose elements have integer or enumeration types.
9469 They may not work correctly for arrays whose element
9470 types have user-defined equality, for arrays of real values
9471 (in particular, IEEE-conformant floating point, because of negative
9472 zeroes and NaNs), and for arrays whose elements contain unused bits with
9473 indeterminate values.
9476 The other component-by-component array operations (@code{and}, @code{or},
9477 @code{xor}, @code{not}, and relational tests other than equality)
9478 are not implemented.
9481 There are no record or array aggregates.
9484 Calls to dispatching subprograms are not implemented.
9487 The overloading algorithm is much more limited (i.e., less selective)
9488 than that of real Ada. It makes only limited use of the context in which a subexpression
9489 appears to resolve its meaning, and it is much looser in its rules for allowing
9490 type matches. As a result, some function calls will be ambiguous, and the user
9491 will be asked to choose the proper resolution.
9494 The @code{new} operator is not implemented.
9497 Entry calls are not implemented.
9500 Aside from printing, arithmetic operations on the native VAX floating-point
9501 formats are not supported.
9504 It is not possible to slice a packed array.
9507 @node Additions to Ada
9508 @subsubsection Additions to Ada
9509 @cindex Ada, deviations from
9511 As it does for other languages, @value{GDBN} makes certain generic
9512 extensions to Ada (@pxref{Expressions}):
9516 If the expression @var{E} is a variable residing in memory
9517 (typically a local variable or array element) and @var{N} is
9518 a positive integer, then @code{@var{E}@@@var{N}} displays the values of
9519 @var{E} and the @var{N}-1 adjacent variables following it in memory as an array.
9520 In Ada, this operator is generally not necessary, since its prime use
9521 is in displaying parts of an array, and slicing will usually do this in Ada.
9522 However, there are occasional uses when debugging programs
9523 in which certain debugging information has been optimized away.
9526 @code{@var{B}::@var{var}} means ``the variable named @var{var} that appears
9527 in function or file @var{B}.'' When @var{B} is a file name, you must typically
9528 surround it in single quotes.
9531 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
9532 @var{type} that appears at address @var{addr}.''
9535 A name starting with @samp{$} is a convenience variable
9536 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
9539 In addition, @value{GDBN} provides a few other shortcuts and outright additions specific
9544 The assignment statement is allowed as an expression, returning
9545 its right-hand operand as its value. Thus, you may enter
9549 print A(tmp := y + 1)
9553 The semicolon is allowed as an ``operator,'' returning as its value
9554 the value of its right-hand operand.
9555 This allows, for example,
9556 complex conditional breaks:
9560 condition 1 (report(i); k += 1; A(k) > 100)
9564 Rather than use catenation and symbolic character names to introduce special
9565 characters into strings, one may instead use a special bracket notation,
9566 which is also used to print strings. A sequence of characters of the form
9567 @samp{["@var{XX}"]} within a string or character literal denotes the
9568 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
9569 sequence of characters @samp{["""]} also denotes a single quotation mark
9570 in strings. For example,
9572 "One line.["0a"]Next line.["0a"]"
9575 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF}) after each
9579 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
9580 @t{'Max} is optional (and is ignored in any case). For example, it is valid
9588 When printing arrays, @value{GDBN} uses positional notation when the
9589 array has a lower bound of 1, and uses a modified named notation otherwise.
9590 For example, a one-dimensional array of three integers with a lower bound of 3 might print as
9597 That is, in contrast to valid Ada, only the first component has a @code{=>}
9601 You may abbreviate attributes in expressions with any unique,
9602 multi-character subsequence of
9603 their names (an exact match gets preference).
9604 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
9605 in place of @t{a'length}.
9608 @cindex quoting Ada internal identifiers
9609 Since Ada is case-insensitive, the debugger normally maps identifiers you type
9610 to lower case. The GNAT compiler uses upper-case characters for
9611 some of its internal identifiers, which are normally of no interest to users.
9612 For the rare occasions when you actually have to look at them,
9613 enclose them in angle brackets to avoid the lower-case mapping.
9616 @value{GDBP} print <JMPBUF_SAVE>[0]
9620 Printing an object of class-wide type or dereferencing an
9621 access-to-class-wide value will display all the components of the object's
9622 specific type (as indicated by its run-time tag). Likewise, component
9623 selection on such a value will operate on the specific type of the
9628 @node Stopping Before Main Program
9629 @subsubsection Stopping at the Very Beginning
9631 @cindex breakpointing Ada elaboration code
9632 It is sometimes necessary to debug the program during elaboration, and
9633 before reaching the main procedure.
9634 As defined in the Ada Reference
9635 Manual, the elaboration code is invoked from a procedure called
9636 @code{adainit}. To run your program up to the beginning of
9637 elaboration, simply use the following two commands:
9638 @code{tbreak adainit} and @code{run}.
9641 @subsubsection Known Peculiarities of Ada Mode
9642 @cindex Ada, problems
9644 Besides the omissions listed previously (@pxref{Omissions from Ada}),
9645 we know of several problems with and limitations of Ada mode in
9647 some of which will be fixed with planned future releases of the debugger
9648 and the GNU Ada compiler.
9652 Currently, the debugger
9653 has insufficient information to determine whether certain pointers represent
9654 pointers to objects or the objects themselves.
9655 Thus, the user may have to tack an extra @code{.all} after an expression
9656 to get it printed properly.
9659 Static constants that the compiler chooses not to materialize as objects in
9660 storage are invisible to the debugger.
9663 Named parameter associations in function argument lists are ignored (the
9664 argument lists are treated as positional).
9667 Many useful library packages are currently invisible to the debugger.
9670 Fixed-point arithmetic, conversions, input, and output is carried out using
9671 floating-point arithmetic, and may give results that only approximate those on
9675 The type of the @t{'Address} attribute may not be @code{System.Address}.
9678 The GNAT compiler never generates the prefix @code{Standard} for any of
9679 the standard symbols defined by the Ada language. @value{GDBN} knows about
9680 this: it will strip the prefix from names when you use it, and will never
9681 look for a name you have so qualified among local symbols, nor match against
9682 symbols in other packages or subprograms. If you have
9683 defined entities anywhere in your program other than parameters and
9684 local variables whose simple names match names in @code{Standard},
9685 GNAT's lack of qualification here can cause confusion. When this happens,
9686 you can usually resolve the confusion
9687 by qualifying the problematic names with package
9688 @code{Standard} explicitly.
9691 @node Unsupported languages
9692 @section Unsupported languages
9694 @cindex unsupported languages
9695 @cindex minimal language
9696 In addition to the other fully-supported programming languages,
9697 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
9698 It does not represent a real programming language, but provides a set
9699 of capabilities close to what the C or assembly languages provide.
9700 This should allow most simple operations to be performed while debugging
9701 an application that uses a language currently not supported by @value{GDBN}.
9703 If the language is set to @code{auto}, @value{GDBN} will automatically
9704 select this language if the current frame corresponds to an unsupported
9708 @chapter Examining the Symbol Table
9710 The commands described in this chapter allow you to inquire about the
9711 symbols (names of variables, functions and types) defined in your
9712 program. This information is inherent in the text of your program and
9713 does not change as your program executes. @value{GDBN} finds it in your
9714 program's symbol table, in the file indicated when you started @value{GDBN}
9715 (@pxref{File Options, ,Choosing files}), or by one of the
9716 file-management commands (@pxref{Files, ,Commands to specify files}).
9718 @cindex symbol names
9719 @cindex names of symbols
9720 @cindex quoting names
9721 Occasionally, you may need to refer to symbols that contain unusual
9722 characters, which @value{GDBN} ordinarily treats as word delimiters. The
9723 most frequent case is in referring to static variables in other
9724 source files (@pxref{Variables,,Program variables}). File names
9725 are recorded in object files as debugging symbols, but @value{GDBN} would
9726 ordinarily parse a typical file name, like @file{foo.c}, as the three words
9727 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
9728 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
9735 looks up the value of @code{x} in the scope of the file @file{foo.c}.
9738 @cindex case-insensitive symbol names
9739 @cindex case sensitivity in symbol names
9740 @kindex set case-sensitive
9741 @item set case-sensitive on
9742 @itemx set case-sensitive off
9743 @itemx set case-sensitive auto
9744 Normally, when @value{GDBN} looks up symbols, it matches their names
9745 with case sensitivity determined by the current source language.
9746 Occasionally, you may wish to control that. The command @code{set
9747 case-sensitive} lets you do that by specifying @code{on} for
9748 case-sensitive matches or @code{off} for case-insensitive ones. If
9749 you specify @code{auto}, case sensitivity is reset to the default
9750 suitable for the source language. The default is case-sensitive
9751 matches for all languages except for Fortran, for which the default is
9752 case-insensitive matches.
9754 @kindex show case-sensitive
9755 @item show case-sensitive
9756 This command shows the current setting of case sensitivity for symbols
9759 @kindex info address
9760 @cindex address of a symbol
9761 @item info address @var{symbol}
9762 Describe where the data for @var{symbol} is stored. For a register
9763 variable, this says which register it is kept in. For a non-register
9764 local variable, this prints the stack-frame offset at which the variable
9767 Note the contrast with @samp{print &@var{symbol}}, which does not work
9768 at all for a register variable, and for a stack local variable prints
9769 the exact address of the current instantiation of the variable.
9772 @cindex symbol from address
9773 @cindex closest symbol and offset for an address
9774 @item info symbol @var{addr}
9775 Print the name of a symbol which is stored at the address @var{addr}.
9776 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
9777 nearest symbol and an offset from it:
9780 (@value{GDBP}) info symbol 0x54320
9781 _initialize_vx + 396 in section .text
9785 This is the opposite of the @code{info address} command. You can use
9786 it to find out the name of a variable or a function given its address.
9789 @item whatis @var{expr}
9790 Print the data type of expression @var{expr}. @var{expr} is not
9791 actually evaluated, and any side-effecting operations (such as
9792 assignments or function calls) inside it do not take place.
9793 @xref{Expressions, ,Expressions}.
9796 Print the data type of @code{$}, the last value in the value history.
9799 @item ptype @var{typename}
9800 Print a description of data type @var{typename}. @var{typename} may be
9801 the name of a type, or for C code it may have the form @samp{class
9802 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
9803 @var{union-tag}} or @samp{enum @var{enum-tag}}.
9805 @item ptype @var{expr}
9807 Print a description of the type of expression @var{expr}. @code{ptype}
9808 differs from @code{whatis} by printing a detailed description, instead
9809 of just the name of the type.
9811 For example, for this variable declaration:
9814 struct complex @{double real; double imag;@} v;
9818 the two commands give this output:
9822 (@value{GDBP}) whatis v
9823 type = struct complex
9824 (@value{GDBP}) ptype v
9825 type = struct complex @{
9833 As with @code{whatis}, using @code{ptype} without an argument refers to
9834 the type of @code{$}, the last value in the value history.
9837 @item info types @var{regexp}
9839 Print a brief description of all types whose names match the regular
9840 expression @var{regexp} (or all types in your program, if you supply
9841 no argument). Each complete typename is matched as though it were a
9842 complete line; thus, @samp{i type value} gives information on all
9843 types in your program whose names include the string @code{value}, but
9844 @samp{i type ^value$} gives information only on types whose complete
9845 name is @code{value}.
9847 This command differs from @code{ptype} in two ways: first, like
9848 @code{whatis}, it does not print a detailed description; second, it
9849 lists all source files where a type is defined.
9852 @cindex local variables
9853 @item info scope @var{location}
9854 List all the variables local to a particular scope. This command
9855 accepts a @var{location} argument---a function name, a source line, or
9856 an address preceded by a @samp{*}, and prints all the variables local
9857 to the scope defined by that location. For example:
9860 (@value{GDBP}) @b{info scope command_line_handler}
9861 Scope for command_line_handler:
9862 Symbol rl is an argument at stack/frame offset 8, length 4.
9863 Symbol linebuffer is in static storage at address 0x150a18, length 4.
9864 Symbol linelength is in static storage at address 0x150a1c, length 4.
9865 Symbol p is a local variable in register $esi, length 4.
9866 Symbol p1 is a local variable in register $ebx, length 4.
9867 Symbol nline is a local variable in register $edx, length 4.
9868 Symbol repeat is a local variable at frame offset -8, length 4.
9872 This command is especially useful for determining what data to collect
9873 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
9878 Show information about the current source file---that is, the source file for
9879 the function containing the current point of execution:
9882 the name of the source file, and the directory containing it,
9884 the directory it was compiled in,
9886 its length, in lines,
9888 which programming language it is written in,
9890 whether the executable includes debugging information for that file, and
9891 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
9893 whether the debugging information includes information about
9894 preprocessor macros.
9898 @kindex info sources
9900 Print the names of all source files in your program for which there is
9901 debugging information, organized into two lists: files whose symbols
9902 have already been read, and files whose symbols will be read when needed.
9904 @kindex info functions
9905 @item info functions
9906 Print the names and data types of all defined functions.
9908 @item info functions @var{regexp}
9909 Print the names and data types of all defined functions
9910 whose names contain a match for regular expression @var{regexp}.
9911 Thus, @samp{info fun step} finds all functions whose names
9912 include @code{step}; @samp{info fun ^step} finds those whose names
9913 start with @code{step}. If a function name contains characters
9914 that conflict with the regular expression language (eg.
9915 @samp{operator*()}), they may be quoted with a backslash.
9917 @kindex info variables
9918 @item info variables
9919 Print the names and data types of all variables that are declared
9920 outside of functions (i.e.@: excluding local variables).
9922 @item info variables @var{regexp}
9923 Print the names and data types of all variables (except for local
9924 variables) whose names contain a match for regular expression
9927 @kindex info classes
9929 @itemx info classes @var{regexp}
9930 Display all Objective-C classes in your program, or
9931 (with the @var{regexp} argument) all those matching a particular regular
9934 @kindex info selectors
9935 @item info selectors
9936 @itemx info selectors @var{regexp}
9937 Display all Objective-C selectors in your program, or
9938 (with the @var{regexp} argument) all those matching a particular regular
9942 This was never implemented.
9943 @kindex info methods
9945 @itemx info methods @var{regexp}
9946 The @code{info methods} command permits the user to examine all defined
9947 methods within C@t{++} program, or (with the @var{regexp} argument) a
9948 specific set of methods found in the various C@t{++} classes. Many
9949 C@t{++} classes provide a large number of methods. Thus, the output
9950 from the @code{ptype} command can be overwhelming and hard to use. The
9951 @code{info-methods} command filters the methods, printing only those
9952 which match the regular-expression @var{regexp}.
9955 @cindex reloading symbols
9956 Some systems allow individual object files that make up your program to
9957 be replaced without stopping and restarting your program. For example,
9958 in VxWorks you can simply recompile a defective object file and keep on
9959 running. If you are running on one of these systems, you can allow
9960 @value{GDBN} to reload the symbols for automatically relinked modules:
9963 @kindex set symbol-reloading
9964 @item set symbol-reloading on
9965 Replace symbol definitions for the corresponding source file when an
9966 object file with a particular name is seen again.
9968 @item set symbol-reloading off
9969 Do not replace symbol definitions when encountering object files of the
9970 same name more than once. This is the default state; if you are not
9971 running on a system that permits automatic relinking of modules, you
9972 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
9973 may discard symbols when linking large programs, that may contain
9974 several modules (from different directories or libraries) with the same
9977 @kindex show symbol-reloading
9978 @item show symbol-reloading
9979 Show the current @code{on} or @code{off} setting.
9982 @cindex opaque data types
9983 @kindex set opaque-type-resolution
9984 @item set opaque-type-resolution on
9985 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
9986 declared as a pointer to a @code{struct}, @code{class}, or
9987 @code{union}---for example, @code{struct MyType *}---that is used in one
9988 source file although the full declaration of @code{struct MyType} is in
9989 another source file. The default is on.
9991 A change in the setting of this subcommand will not take effect until
9992 the next time symbols for a file are loaded.
9994 @item set opaque-type-resolution off
9995 Tell @value{GDBN} not to resolve opaque types. In this case, the type
9996 is printed as follows:
9998 @{<no data fields>@}
10001 @kindex show opaque-type-resolution
10002 @item show opaque-type-resolution
10003 Show whether opaque types are resolved or not.
10005 @kindex maint print symbols
10006 @cindex symbol dump
10007 @kindex maint print psymbols
10008 @cindex partial symbol dump
10009 @item maint print symbols @var{filename}
10010 @itemx maint print psymbols @var{filename}
10011 @itemx maint print msymbols @var{filename}
10012 Write a dump of debugging symbol data into the file @var{filename}.
10013 These commands are used to debug the @value{GDBN} symbol-reading code. Only
10014 symbols with debugging data are included. If you use @samp{maint print
10015 symbols}, @value{GDBN} includes all the symbols for which it has already
10016 collected full details: that is, @var{filename} reflects symbols for
10017 only those files whose symbols @value{GDBN} has read. You can use the
10018 command @code{info sources} to find out which files these are. If you
10019 use @samp{maint print psymbols} instead, the dump shows information about
10020 symbols that @value{GDBN} only knows partially---that is, symbols defined in
10021 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
10022 @samp{maint print msymbols} dumps just the minimal symbol information
10023 required for each object file from which @value{GDBN} has read some symbols.
10024 @xref{Files, ,Commands to specify files}, for a discussion of how
10025 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
10027 @kindex maint info symtabs
10028 @kindex maint info psymtabs
10029 @cindex listing @value{GDBN}'s internal symbol tables
10030 @cindex symbol tables, listing @value{GDBN}'s internal
10031 @cindex full symbol tables, listing @value{GDBN}'s internal
10032 @cindex partial symbol tables, listing @value{GDBN}'s internal
10033 @item maint info symtabs @r{[} @var{regexp} @r{]}
10034 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
10036 List the @code{struct symtab} or @code{struct partial_symtab}
10037 structures whose names match @var{regexp}. If @var{regexp} is not
10038 given, list them all. The output includes expressions which you can
10039 copy into a @value{GDBN} debugging this one to examine a particular
10040 structure in more detail. For example:
10043 (@value{GDBP}) maint info psymtabs dwarf2read
10044 @{ objfile /home/gnu/build/gdb/gdb
10045 ((struct objfile *) 0x82e69d0)
10046 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
10047 ((struct partial_symtab *) 0x8474b10)
10050 text addresses 0x814d3c8 -- 0x8158074
10051 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
10052 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
10053 dependencies (none)
10056 (@value{GDBP}) maint info symtabs
10060 We see that there is one partial symbol table whose filename contains
10061 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
10062 and we see that @value{GDBN} has not read in any symtabs yet at all.
10063 If we set a breakpoint on a function, that will cause @value{GDBN} to
10064 read the symtab for the compilation unit containing that function:
10067 (@value{GDBP}) break dwarf2_psymtab_to_symtab
10068 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
10070 (@value{GDBP}) maint info symtabs
10071 @{ objfile /home/gnu/build/gdb/gdb
10072 ((struct objfile *) 0x82e69d0)
10073 @{ symtab /home/gnu/src/gdb/dwarf2read.c
10074 ((struct symtab *) 0x86c1f38)
10077 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
10078 debugformat DWARF 2
10087 @chapter Altering Execution
10089 Once you think you have found an error in your program, you might want to
10090 find out for certain whether correcting the apparent error would lead to
10091 correct results in the rest of the run. You can find the answer by
10092 experiment, using the @value{GDBN} features for altering execution of the
10095 For example, you can store new values into variables or memory
10096 locations, give your program a signal, restart it at a different
10097 address, or even return prematurely from a function.
10100 * Assignment:: Assignment to variables
10101 * Jumping:: Continuing at a different address
10102 * Signaling:: Giving your program a signal
10103 * Returning:: Returning from a function
10104 * Calling:: Calling your program's functions
10105 * Patching:: Patching your program
10109 @section Assignment to variables
10112 @cindex setting variables
10113 To alter the value of a variable, evaluate an assignment expression.
10114 @xref{Expressions, ,Expressions}. For example,
10121 stores the value 4 into the variable @code{x}, and then prints the
10122 value of the assignment expression (which is 4).
10123 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
10124 information on operators in supported languages.
10126 @kindex set variable
10127 @cindex variables, setting
10128 If you are not interested in seeing the value of the assignment, use the
10129 @code{set} command instead of the @code{print} command. @code{set} is
10130 really the same as @code{print} except that the expression's value is
10131 not printed and is not put in the value history (@pxref{Value History,
10132 ,Value history}). The expression is evaluated only for its effects.
10134 If the beginning of the argument string of the @code{set} command
10135 appears identical to a @code{set} subcommand, use the @code{set
10136 variable} command instead of just @code{set}. This command is identical
10137 to @code{set} except for its lack of subcommands. For example, if your
10138 program has a variable @code{width}, you get an error if you try to set
10139 a new value with just @samp{set width=13}, because @value{GDBN} has the
10140 command @code{set width}:
10143 (@value{GDBP}) whatis width
10145 (@value{GDBP}) p width
10147 (@value{GDBP}) set width=47
10148 Invalid syntax in expression.
10152 The invalid expression, of course, is @samp{=47}. In
10153 order to actually set the program's variable @code{width}, use
10156 (@value{GDBP}) set var width=47
10159 Because the @code{set} command has many subcommands that can conflict
10160 with the names of program variables, it is a good idea to use the
10161 @code{set variable} command instead of just @code{set}. For example, if
10162 your program has a variable @code{g}, you run into problems if you try
10163 to set a new value with just @samp{set g=4}, because @value{GDBN} has
10164 the command @code{set gnutarget}, abbreviated @code{set g}:
10168 (@value{GDBP}) whatis g
10172 (@value{GDBP}) set g=4
10176 The program being debugged has been started already.
10177 Start it from the beginning? (y or n) y
10178 Starting program: /home/smith/cc_progs/a.out
10179 "/home/smith/cc_progs/a.out": can't open to read symbols:
10180 Invalid bfd target.
10181 (@value{GDBP}) show g
10182 The current BFD target is "=4".
10187 The program variable @code{g} did not change, and you silently set the
10188 @code{gnutarget} to an invalid value. In order to set the variable
10192 (@value{GDBP}) set var g=4
10195 @value{GDBN} allows more implicit conversions in assignments than C; you can
10196 freely store an integer value into a pointer variable or vice versa,
10197 and you can convert any structure to any other structure that is the
10198 same length or shorter.
10199 @comment FIXME: how do structs align/pad in these conversions?
10200 @comment /doc@cygnus.com 18dec1990
10202 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
10203 construct to generate a value of specified type at a specified address
10204 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
10205 to memory location @code{0x83040} as an integer (which implies a certain size
10206 and representation in memory), and
10209 set @{int@}0x83040 = 4
10213 stores the value 4 into that memory location.
10216 @section Continuing at a different address
10218 Ordinarily, when you continue your program, you do so at the place where
10219 it stopped, with the @code{continue} command. You can instead continue at
10220 an address of your own choosing, with the following commands:
10224 @item jump @var{linespec}
10225 Resume execution at line @var{linespec}. Execution stops again
10226 immediately if there is a breakpoint there. @xref{List, ,Printing
10227 source lines}, for a description of the different forms of
10228 @var{linespec}. It is common practice to use the @code{tbreak} command
10229 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
10232 The @code{jump} command does not change the current stack frame, or
10233 the stack pointer, or the contents of any memory location or any
10234 register other than the program counter. If line @var{linespec} is in
10235 a different function from the one currently executing, the results may
10236 be bizarre if the two functions expect different patterns of arguments or
10237 of local variables. For this reason, the @code{jump} command requests
10238 confirmation if the specified line is not in the function currently
10239 executing. However, even bizarre results are predictable if you are
10240 well acquainted with the machine-language code of your program.
10242 @item jump *@var{address}
10243 Resume execution at the instruction at address @var{address}.
10246 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
10247 On many systems, you can get much the same effect as the @code{jump}
10248 command by storing a new value into the register @code{$pc}. The
10249 difference is that this does not start your program running; it only
10250 changes the address of where it @emph{will} run when you continue. For
10258 makes the next @code{continue} command or stepping command execute at
10259 address @code{0x485}, rather than at the address where your program stopped.
10260 @xref{Continuing and Stepping, ,Continuing and stepping}.
10262 The most common occasion to use the @code{jump} command is to back
10263 up---perhaps with more breakpoints set---over a portion of a program
10264 that has already executed, in order to examine its execution in more
10269 @section Giving your program a signal
10270 @cindex deliver a signal to a program
10274 @item signal @var{signal}
10275 Resume execution where your program stopped, but immediately give it the
10276 signal @var{signal}. @var{signal} can be the name or the number of a
10277 signal. For example, on many systems @code{signal 2} and @code{signal
10278 SIGINT} are both ways of sending an interrupt signal.
10280 Alternatively, if @var{signal} is zero, continue execution without
10281 giving a signal. This is useful when your program stopped on account of
10282 a signal and would ordinary see the signal when resumed with the
10283 @code{continue} command; @samp{signal 0} causes it to resume without a
10286 @code{signal} does not repeat when you press @key{RET} a second time
10287 after executing the command.
10291 Invoking the @code{signal} command is not the same as invoking the
10292 @code{kill} utility from the shell. Sending a signal with @code{kill}
10293 causes @value{GDBN} to decide what to do with the signal depending on
10294 the signal handling tables (@pxref{Signals}). The @code{signal} command
10295 passes the signal directly to your program.
10299 @section Returning from a function
10302 @cindex returning from a function
10305 @itemx return @var{expression}
10306 You can cancel execution of a function call with the @code{return}
10307 command. If you give an
10308 @var{expression} argument, its value is used as the function's return
10312 When you use @code{return}, @value{GDBN} discards the selected stack frame
10313 (and all frames within it). You can think of this as making the
10314 discarded frame return prematurely. If you wish to specify a value to
10315 be returned, give that value as the argument to @code{return}.
10317 This pops the selected stack frame (@pxref{Selection, ,Selecting a
10318 frame}), and any other frames inside of it, leaving its caller as the
10319 innermost remaining frame. That frame becomes selected. The
10320 specified value is stored in the registers used for returning values
10323 The @code{return} command does not resume execution; it leaves the
10324 program stopped in the state that would exist if the function had just
10325 returned. In contrast, the @code{finish} command (@pxref{Continuing
10326 and Stepping, ,Continuing and stepping}) resumes execution until the
10327 selected stack frame returns naturally.
10330 @section Calling program functions
10333 @cindex calling functions
10334 @cindex inferior functions, calling
10335 @item print @var{expr}
10336 Evaluate the expression @var{expr} and display the resuling value.
10337 @var{expr} may include calls to functions in the program being
10341 @item call @var{expr}
10342 Evaluate the expression @var{expr} without displaying @code{void}
10345 You can use this variant of the @code{print} command if you want to
10346 execute a function from your program that does not return anything
10347 (a.k.a.@: @dfn{a void function}), but without cluttering the output
10348 with @code{void} returned values that @value{GDBN} will otherwise
10349 print. If the result is not void, it is printed and saved in the
10353 It is possible for the function you call via the @code{print} or
10354 @code{call} command to generate a signal (e.g., if there's a bug in
10355 the function, or if you passed it incorrect arguments). What happens
10356 in that case is controlled by the @code{set unwindonsignal} command.
10359 @item set unwindonsignal
10360 @kindex set unwindonsignal
10361 @cindex unwind stack in called functions
10362 @cindex call dummy stack unwinding
10363 Set unwinding of the stack if a signal is received while in a function
10364 that @value{GDBN} called in the program being debugged. If set to on,
10365 @value{GDBN} unwinds the stack it created for the call and restores
10366 the context to what it was before the call. If set to off (the
10367 default), @value{GDBN} stops in the frame where the signal was
10370 @item show unwindonsignal
10371 @kindex show unwindonsignal
10372 Show the current setting of stack unwinding in the functions called by
10376 @cindex weak alias functions
10377 Sometimes, a function you wish to call is actually a @dfn{weak alias}
10378 for another function. In such case, @value{GDBN} might not pick up
10379 the type information, including the types of the function arguments,
10380 which causes @value{GDBN} to call the inferior function incorrectly.
10381 As a result, the called function will function erroneously and may
10382 even crash. A solution to that is to use the name of the aliased
10386 @section Patching programs
10388 @cindex patching binaries
10389 @cindex writing into executables
10390 @cindex writing into corefiles
10392 By default, @value{GDBN} opens the file containing your program's
10393 executable code (or the corefile) read-only. This prevents accidental
10394 alterations to machine code; but it also prevents you from intentionally
10395 patching your program's binary.
10397 If you'd like to be able to patch the binary, you can specify that
10398 explicitly with the @code{set write} command. For example, you might
10399 want to turn on internal debugging flags, or even to make emergency
10405 @itemx set write off
10406 If you specify @samp{set write on}, @value{GDBN} opens executable and
10407 core files for both reading and writing; if you specify @samp{set write
10408 off} (the default), @value{GDBN} opens them read-only.
10410 If you have already loaded a file, you must load it again (using the
10411 @code{exec-file} or @code{core-file} command) after changing @code{set
10412 write}, for your new setting to take effect.
10416 Display whether executable files and core files are opened for writing
10417 as well as reading.
10421 @chapter @value{GDBN} Files
10423 @value{GDBN} needs to know the file name of the program to be debugged,
10424 both in order to read its symbol table and in order to start your
10425 program. To debug a core dump of a previous run, you must also tell
10426 @value{GDBN} the name of the core dump file.
10429 * Files:: Commands to specify files
10430 * Separate Debug Files:: Debugging information in separate files
10431 * Symbol Errors:: Errors reading symbol files
10435 @section Commands to specify files
10437 @cindex symbol table
10438 @cindex core dump file
10440 You may want to specify executable and core dump file names. The usual
10441 way to do this is at start-up time, using the arguments to
10442 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
10443 Out of @value{GDBN}}).
10445 Occasionally it is necessary to change to a different file during a
10446 @value{GDBN} session. Or you may run @value{GDBN} and forget to specify
10447 a file you want to use. In these situations the @value{GDBN} commands
10448 to specify new files are useful.
10451 @cindex executable file
10453 @item file @var{filename}
10454 Use @var{filename} as the program to be debugged. It is read for its
10455 symbols and for the contents of pure memory. It is also the program
10456 executed when you use the @code{run} command. If you do not specify a
10457 directory and the file is not found in the @value{GDBN} working directory,
10458 @value{GDBN} uses the environment variable @code{PATH} as a list of
10459 directories to search, just as the shell does when looking for a program
10460 to run. You can change the value of this variable, for both @value{GDBN}
10461 and your program, using the @code{path} command.
10463 On systems with memory-mapped files, an auxiliary file named
10464 @file{@var{filename}.syms} may hold symbol table information for
10465 @var{filename}. If so, @value{GDBN} maps in the symbol table from
10466 @file{@var{filename}.syms}, starting up more quickly. See the
10467 descriptions of the file options @samp{-mapped} and @samp{-readnow}
10468 (available on the command line, see @ref{File Options, , -readnow},
10469 and with the commands @code{file}, @code{symbol-file}, or
10470 @code{add-symbol-file}, described below), for more information.
10473 @code{file} with no argument makes @value{GDBN} discard any information it
10474 has on both executable file and the symbol table.
10477 @item exec-file @r{[} @var{filename} @r{]}
10478 Specify that the program to be run (but not the symbol table) is found
10479 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
10480 if necessary to locate your program. Omitting @var{filename} means to
10481 discard information on the executable file.
10483 @kindex symbol-file
10484 @item symbol-file @r{[} @var{filename} @r{]}
10485 Read symbol table information from file @var{filename}. @code{PATH} is
10486 searched when necessary. Use the @code{file} command to get both symbol
10487 table and program to run from the same file.
10489 @code{symbol-file} with no argument clears out @value{GDBN} information on your
10490 program's symbol table.
10492 The @code{symbol-file} command causes @value{GDBN} to forget the contents
10493 of its convenience variables, the value history, and all breakpoints and
10494 auto-display expressions. This is because they may contain pointers to
10495 the internal data recording symbols and data types, which are part of
10496 the old symbol table data being discarded inside @value{GDBN}.
10498 @code{symbol-file} does not repeat if you press @key{RET} again after
10501 When @value{GDBN} is configured for a particular environment, it
10502 understands debugging information in whatever format is the standard
10503 generated for that environment; you may use either a @sc{gnu} compiler, or
10504 other compilers that adhere to the local conventions.
10505 Best results are usually obtained from @sc{gnu} compilers; for example,
10506 using @code{@value{GCC}} you can generate debugging information for
10509 For most kinds of object files, with the exception of old SVR3 systems
10510 using COFF, the @code{symbol-file} command does not normally read the
10511 symbol table in full right away. Instead, it scans the symbol table
10512 quickly to find which source files and which symbols are present. The
10513 details are read later, one source file at a time, as they are needed.
10515 The purpose of this two-stage reading strategy is to make @value{GDBN}
10516 start up faster. For the most part, it is invisible except for
10517 occasional pauses while the symbol table details for a particular source
10518 file are being read. (The @code{set verbose} command can turn these
10519 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
10520 warnings and messages}.)
10522 We have not implemented the two-stage strategy for COFF yet. When the
10523 symbol table is stored in COFF format, @code{symbol-file} reads the
10524 symbol table data in full right away. Note that ``stabs-in-COFF''
10525 still does the two-stage strategy, since the debug info is actually
10529 @cindex reading symbols immediately
10530 @cindex symbols, reading immediately
10532 @cindex memory-mapped symbol file
10533 @cindex saving symbol table
10534 @item symbol-file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10535 @itemx file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10536 You can override the @value{GDBN} two-stage strategy for reading symbol
10537 tables by using the @samp{-readnow} option with any of the commands that
10538 load symbol table information, if you want to be sure @value{GDBN} has the
10539 entire symbol table available.
10541 If memory-mapped files are available on your system through the
10542 @code{mmap} system call, you can use another option, @samp{-mapped}, to
10543 cause @value{GDBN} to write the symbols for your program into a reusable
10544 file. Future @value{GDBN} debugging sessions map in symbol information
10545 from this auxiliary symbol file (if the program has not changed), rather
10546 than spending time reading the symbol table from the executable
10547 program. Using the @samp{-mapped} option has the same effect as
10548 starting @value{GDBN} with the @samp{-mapped} command-line option.
10550 You can use both options together, to make sure the auxiliary symbol
10551 file has all the symbol information for your program.
10553 The auxiliary symbol file for a program called @var{myprog} is called
10554 @samp{@var{myprog}.syms}. Once this file exists (so long as it is newer
10555 than the corresponding executable), @value{GDBN} always attempts to use
10556 it when you debug @var{myprog}; no special options or commands are
10559 The @file{.syms} file is specific to the host machine where you run
10560 @value{GDBN}. It holds an exact image of the internal @value{GDBN}
10561 symbol table. It cannot be shared across multiple host platforms.
10563 @c FIXME: for now no mention of directories, since this seems to be in
10564 @c flux. 13mar1992 status is that in theory GDB would look either in
10565 @c current dir or in same dir as myprog; but issues like competing
10566 @c GDB's, or clutter in system dirs, mean that in practice right now
10567 @c only current dir is used. FFish says maybe a special GDB hierarchy
10568 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
10572 @item core-file @r{[}@var{filename}@r{]}
10574 Specify the whereabouts of a core dump file to be used as the ``contents
10575 of memory''. Traditionally, core files contain only some parts of the
10576 address space of the process that generated them; @value{GDBN} can access the
10577 executable file itself for other parts.
10579 @code{core-file} with no argument specifies that no core file is
10582 Note that the core file is ignored when your program is actually running
10583 under @value{GDBN}. So, if you have been running your program and you
10584 wish to debug a core file instead, you must kill the subprocess in which
10585 the program is running. To do this, use the @code{kill} command
10586 (@pxref{Kill Process, ,Killing the child process}).
10588 @kindex add-symbol-file
10589 @cindex dynamic linking
10590 @item add-symbol-file @var{filename} @var{address}
10591 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10592 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
10593 The @code{add-symbol-file} command reads additional symbol table
10594 information from the file @var{filename}. You would use this command
10595 when @var{filename} has been dynamically loaded (by some other means)
10596 into the program that is running. @var{address} should be the memory
10597 address at which the file has been loaded; @value{GDBN} cannot figure
10598 this out for itself. You can additionally specify an arbitrary number
10599 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
10600 section name and base address for that section. You can specify any
10601 @var{address} as an expression.
10603 The symbol table of the file @var{filename} is added to the symbol table
10604 originally read with the @code{symbol-file} command. You can use the
10605 @code{add-symbol-file} command any number of times; the new symbol data
10606 thus read keeps adding to the old. To discard all old symbol data
10607 instead, use the @code{symbol-file} command without any arguments.
10609 @cindex relocatable object files, reading symbols from
10610 @cindex object files, relocatable, reading symbols from
10611 @cindex reading symbols from relocatable object files
10612 @cindex symbols, reading from relocatable object files
10613 @cindex @file{.o} files, reading symbols from
10614 Although @var{filename} is typically a shared library file, an
10615 executable file, or some other object file which has been fully
10616 relocated for loading into a process, you can also load symbolic
10617 information from relocatable @file{.o} files, as long as:
10621 the file's symbolic information refers only to linker symbols defined in
10622 that file, not to symbols defined by other object files,
10624 every section the file's symbolic information refers to has actually
10625 been loaded into the inferior, as it appears in the file, and
10627 you can determine the address at which every section was loaded, and
10628 provide these to the @code{add-symbol-file} command.
10632 Some embedded operating systems, like Sun Chorus and VxWorks, can load
10633 relocatable files into an already running program; such systems
10634 typically make the requirements above easy to meet. However, it's
10635 important to recognize that many native systems use complex link
10636 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
10637 assembly, for example) that make the requirements difficult to meet. In
10638 general, one cannot assume that using @code{add-symbol-file} to read a
10639 relocatable object file's symbolic information will have the same effect
10640 as linking the relocatable object file into the program in the normal
10643 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
10645 You can use the @samp{-mapped} and @samp{-readnow} options just as with
10646 the @code{symbol-file} command, to change how @value{GDBN} manages the symbol
10647 table information for @var{filename}.
10649 @kindex add-shared-symbol-files
10651 @item add-shared-symbol-files @var{library-file}
10652 @itemx assf @var{library-file}
10653 The @code{add-shared-symbol-files} command can currently be used only
10654 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
10655 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
10656 @value{GDBN} automatically looks for shared libraries, however if
10657 @value{GDBN} does not find yours, you can invoke
10658 @code{add-shared-symbol-files}. It takes one argument: the shared
10659 library's file name. @code{assf} is a shorthand alias for
10660 @code{add-shared-symbol-files}.
10663 @item section @var{section} @var{addr}
10664 The @code{section} command changes the base address of the named
10665 @var{section} of the exec file to @var{addr}. This can be used if the
10666 exec file does not contain section addresses, (such as in the
10667 @code{a.out} format), or when the addresses specified in the file
10668 itself are wrong. Each section must be changed separately. The
10669 @code{info files} command, described below, lists all the sections and
10673 @kindex info target
10676 @code{info files} and @code{info target} are synonymous; both print the
10677 current target (@pxref{Targets, ,Specifying a Debugging Target}),
10678 including the names of the executable and core dump files currently in
10679 use by @value{GDBN}, and the files from which symbols were loaded. The
10680 command @code{help target} lists all possible targets rather than
10683 @kindex maint info sections
10684 @item maint info sections
10685 Another command that can give you extra information about program sections
10686 is @code{maint info sections}. In addition to the section information
10687 displayed by @code{info files}, this command displays the flags and file
10688 offset of each section in the executable and core dump files. In addition,
10689 @code{maint info sections} provides the following command options (which
10690 may be arbitrarily combined):
10694 Display sections for all loaded object files, including shared libraries.
10695 @item @var{sections}
10696 Display info only for named @var{sections}.
10697 @item @var{section-flags}
10698 Display info only for sections for which @var{section-flags} are true.
10699 The section flags that @value{GDBN} currently knows about are:
10702 Section will have space allocated in the process when loaded.
10703 Set for all sections except those containing debug information.
10705 Section will be loaded from the file into the child process memory.
10706 Set for pre-initialized code and data, clear for @code{.bss} sections.
10708 Section needs to be relocated before loading.
10710 Section cannot be modified by the child process.
10712 Section contains executable code only.
10714 Section contains data only (no executable code).
10716 Section will reside in ROM.
10718 Section contains data for constructor/destructor lists.
10720 Section is not empty.
10722 An instruction to the linker to not output the section.
10723 @item COFF_SHARED_LIBRARY
10724 A notification to the linker that the section contains
10725 COFF shared library information.
10727 Section contains common symbols.
10730 @kindex set trust-readonly-sections
10731 @cindex read-only sections
10732 @item set trust-readonly-sections on
10733 Tell @value{GDBN} that readonly sections in your object file
10734 really are read-only (i.e.@: that their contents will not change).
10735 In that case, @value{GDBN} can fetch values from these sections
10736 out of the object file, rather than from the target program.
10737 For some targets (notably embedded ones), this can be a significant
10738 enhancement to debugging performance.
10740 The default is off.
10742 @item set trust-readonly-sections off
10743 Tell @value{GDBN} not to trust readonly sections. This means that
10744 the contents of the section might change while the program is running,
10745 and must therefore be fetched from the target when needed.
10747 @item show trust-readonly-sections
10748 Show the current setting of trusting readonly sections.
10751 All file-specifying commands allow both absolute and relative file names
10752 as arguments. @value{GDBN} always converts the file name to an absolute file
10753 name and remembers it that way.
10755 @cindex shared libraries
10756 @value{GDBN} supports GNU/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
10757 and IBM RS/6000 AIX shared libraries.
10759 @value{GDBN} automatically loads symbol definitions from shared libraries
10760 when you use the @code{run} command, or when you examine a core file.
10761 (Before you issue the @code{run} command, @value{GDBN} does not understand
10762 references to a function in a shared library, however---unless you are
10763 debugging a core file).
10765 On HP-UX, if the program loads a library explicitly, @value{GDBN}
10766 automatically loads the symbols at the time of the @code{shl_load} call.
10768 @c FIXME: some @value{GDBN} release may permit some refs to undef
10769 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
10770 @c FIXME...lib; check this from time to time when updating manual
10772 There are times, however, when you may wish to not automatically load
10773 symbol definitions from shared libraries, such as when they are
10774 particularly large or there are many of them.
10776 To control the automatic loading of shared library symbols, use the
10780 @kindex set auto-solib-add
10781 @item set auto-solib-add @var{mode}
10782 If @var{mode} is @code{on}, symbols from all shared object libraries
10783 will be loaded automatically when the inferior begins execution, you
10784 attach to an independently started inferior, or when the dynamic linker
10785 informs @value{GDBN} that a new library has been loaded. If @var{mode}
10786 is @code{off}, symbols must be loaded manually, using the
10787 @code{sharedlibrary} command. The default value is @code{on}.
10789 @cindex memory used for symbol tables
10790 If your program uses lots of shared libraries with debug info that
10791 takes large amounts of memory, you can decrease the @value{GDBN}
10792 memory footprint by preventing it from automatically loading the
10793 symbols from shared libraries. To that end, type @kbd{set
10794 auto-solib-add off} before running the inferior, then load each
10795 library whose debug symbols you do need with @kbd{sharedlibrary
10796 @var{regexp}}, where @var{regexp} is a regular expresion that matches
10797 the libraries whose symbols you want to be loaded.
10799 @kindex show auto-solib-add
10800 @item show auto-solib-add
10801 Display the current autoloading mode.
10804 To explicitly load shared library symbols, use the @code{sharedlibrary}
10808 @kindex info sharedlibrary
10811 @itemx info sharedlibrary
10812 Print the names of the shared libraries which are currently loaded.
10814 @kindex sharedlibrary
10816 @item sharedlibrary @var{regex}
10817 @itemx share @var{regex}
10818 Load shared object library symbols for files matching a
10819 Unix regular expression.
10820 As with files loaded automatically, it only loads shared libraries
10821 required by your program for a core file or after typing @code{run}. If
10822 @var{regex} is omitted all shared libraries required by your program are
10826 On some systems, such as HP-UX systems, @value{GDBN} supports
10827 autoloading shared library symbols until a limiting threshold size is
10828 reached. This provides the benefit of allowing autoloading to remain on
10829 by default, but avoids autoloading excessively large shared libraries,
10830 up to a threshold that is initially set, but which you can modify if you
10833 Beyond that threshold, symbols from shared libraries must be explicitly
10834 loaded. To load these symbols, use the command @code{sharedlibrary
10835 @var{filename}}. The base address of the shared library is determined
10836 automatically by @value{GDBN} and need not be specified.
10838 To display or set the threshold, use the commands:
10841 @kindex set auto-solib-limit
10842 @item set auto-solib-limit @var{threshold}
10843 Set the autoloading size threshold, in an integral number of megabytes.
10844 If @var{threshold} is nonzero and shared library autoloading is enabled,
10845 symbols from all shared object libraries will be loaded until the total
10846 size of the loaded shared library symbols exceeds this threshold.
10847 Otherwise, symbols must be loaded manually, using the
10848 @code{sharedlibrary} command. The default threshold is 100 (i.e.@: 100
10851 @kindex show auto-solib-limit
10852 @item show auto-solib-limit
10853 Display the current autoloading size threshold, in megabytes.
10856 Shared libraries are also supported in many cross or remote debugging
10857 configurations. A copy of the target's libraries need to be present on the
10858 host system; they need to be the same as the target libraries, although the
10859 copies on the target can be stripped as long as the copies on the host are
10862 You need to tell @value{GDBN} where the target libraries are, so that it can
10863 load the correct copies---otherwise, it may try to load the host's libraries.
10864 @value{GDBN} has two variables to specify the search directories for target
10868 @kindex set solib-absolute-prefix
10869 @item set solib-absolute-prefix @var{path}
10870 If this variable is set, @var{path} will be used as a prefix for any
10871 absolute shared library paths; many runtime loaders store the absolute
10872 paths to the shared library in the target program's memory. If you use
10873 @samp{solib-absolute-prefix} to find shared libraries, they need to be laid
10874 out in the same way that they are on the target, with e.g.@: a
10875 @file{/usr/lib} hierarchy under @var{path}.
10877 You can set the default value of @samp{solib-absolute-prefix} by using the
10878 configure-time @samp{--with-sysroot} option.
10880 @kindex show solib-absolute-prefix
10881 @item show solib-absolute-prefix
10882 Display the current shared library prefix.
10884 @kindex set solib-search-path
10885 @item set solib-search-path @var{path}
10886 If this variable is set, @var{path} is a colon-separated list of directories
10887 to search for shared libraries. @samp{solib-search-path} is used after
10888 @samp{solib-absolute-prefix} fails to locate the library, or if the path to
10889 the library is relative instead of absolute. If you want to use
10890 @samp{solib-search-path} instead of @samp{solib-absolute-prefix}, be sure to
10891 set @samp{solib-absolute-prefix} to a nonexistant directory to prevent
10892 @value{GDBN} from finding your host's libraries.
10894 @kindex show solib-search-path
10895 @item show solib-search-path
10896 Display the current shared library search path.
10900 @node Separate Debug Files
10901 @section Debugging Information in Separate Files
10902 @cindex separate debugging information files
10903 @cindex debugging information in separate files
10904 @cindex @file{.debug} subdirectories
10905 @cindex debugging information directory, global
10906 @cindex global debugging information directory
10908 @value{GDBN} allows you to put a program's debugging information in a
10909 file separate from the executable itself, in a way that allows
10910 @value{GDBN} to find and load the debugging information automatically.
10911 Since debugging information can be very large --- sometimes larger
10912 than the executable code itself --- some systems distribute debugging
10913 information for their executables in separate files, which users can
10914 install only when they need to debug a problem.
10916 If an executable's debugging information has been extracted to a
10917 separate file, the executable should contain a @dfn{debug link} giving
10918 the name of the debugging information file (with no directory
10919 components), and a checksum of its contents. (The exact form of a
10920 debug link is described below.) If the full name of the directory
10921 containing the executable is @var{execdir}, and the executable has a
10922 debug link that specifies the name @var{debugfile}, then @value{GDBN}
10923 will automatically search for the debugging information file in three
10928 the directory containing the executable file (that is, it will look
10929 for a file named @file{@var{execdir}/@var{debugfile}},
10931 a subdirectory of that directory named @file{.debug} (that is, the
10932 file @file{@var{execdir}/.debug/@var{debugfile}}, and
10934 a subdirectory of the global debug file directory that includes the
10935 executable's full path, and the name from the link (that is, the file
10936 @file{@var{globaldebugdir}/@var{execdir}/@var{debugfile}}, where
10937 @var{globaldebugdir} is the global debug file directory, and
10938 @var{execdir} has been turned into a relative path).
10941 @value{GDBN} checks under each of these names for a debugging
10942 information file whose checksum matches that given in the link, and
10943 reads the debugging information from the first one it finds.
10945 So, for example, if you ask @value{GDBN} to debug @file{/usr/bin/ls},
10946 which has a link containing the name @file{ls.debug}, and the global
10947 debug directory is @file{/usr/lib/debug}, then @value{GDBN} will look
10948 for debug information in @file{/usr/bin/ls.debug},
10949 @file{/usr/bin/.debug/ls.debug}, and
10950 @file{/usr/lib/debug/usr/bin/ls.debug}.
10952 You can set the global debugging info directory's name, and view the
10953 name @value{GDBN} is currently using.
10957 @kindex set debug-file-directory
10958 @item set debug-file-directory @var{directory}
10959 Set the directory which @value{GDBN} searches for separate debugging
10960 information files to @var{directory}.
10962 @kindex show debug-file-directory
10963 @item show debug-file-directory
10964 Show the directory @value{GDBN} searches for separate debugging
10969 @cindex @code{.gnu_debuglink} sections
10970 @cindex debug links
10971 A debug link is a special section of the executable file named
10972 @code{.gnu_debuglink}. The section must contain:
10976 A filename, with any leading directory components removed, followed by
10979 zero to three bytes of padding, as needed to reach the next four-byte
10980 boundary within the section, and
10982 a four-byte CRC checksum, stored in the same endianness used for the
10983 executable file itself. The checksum is computed on the debugging
10984 information file's full contents by the function given below, passing
10985 zero as the @var{crc} argument.
10988 Any executable file format can carry a debug link, as long as it can
10989 contain a section named @code{.gnu_debuglink} with the contents
10992 The debugging information file itself should be an ordinary
10993 executable, containing a full set of linker symbols, sections, and
10994 debugging information. The sections of the debugging information file
10995 should have the same names, addresses and sizes as the original file,
10996 but they need not contain any data --- much like a @code{.bss} section
10997 in an ordinary executable.
10999 As of December 2002, there is no standard GNU utility to produce
11000 separated executable / debugging information file pairs. Ulrich
11001 Drepper's @file{elfutils} package, starting with version 0.53,
11002 contains a version of the @code{strip} command such that the command
11003 @kbd{strip foo -f foo.debug} removes the debugging information from
11004 the executable file @file{foo}, places it in the file
11005 @file{foo.debug}, and leaves behind a debug link in @file{foo}.
11007 Since there are many different ways to compute CRC's (different
11008 polynomials, reversals, byte ordering, etc.), the simplest way to
11009 describe the CRC used in @code{.gnu_debuglink} sections is to give the
11010 complete code for a function that computes it:
11012 @kindex gnu_debuglink_crc32
11015 gnu_debuglink_crc32 (unsigned long crc,
11016 unsigned char *buf, size_t len)
11018 static const unsigned long crc32_table[256] =
11020 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
11021 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
11022 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
11023 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
11024 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
11025 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
11026 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
11027 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
11028 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
11029 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
11030 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
11031 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
11032 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
11033 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
11034 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
11035 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
11036 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
11037 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
11038 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
11039 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
11040 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
11041 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
11042 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
11043 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
11044 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
11045 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
11046 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
11047 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
11048 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
11049 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
11050 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
11051 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
11052 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
11053 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
11054 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
11055 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
11056 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
11057 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
11058 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
11059 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
11060 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
11061 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
11062 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
11063 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
11064 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
11065 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
11066 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
11067 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
11068 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
11069 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
11070 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
11073 unsigned char *end;
11075 crc = ~crc & 0xffffffff;
11076 for (end = buf + len; buf < end; ++buf)
11077 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
11078 return ~crc & 0xffffffff;
11083 @node Symbol Errors
11084 @section Errors reading symbol files
11086 While reading a symbol file, @value{GDBN} occasionally encounters problems,
11087 such as symbol types it does not recognize, or known bugs in compiler
11088 output. By default, @value{GDBN} does not notify you of such problems, since
11089 they are relatively common and primarily of interest to people
11090 debugging compilers. If you are interested in seeing information
11091 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
11092 only one message about each such type of problem, no matter how many
11093 times the problem occurs; or you can ask @value{GDBN} to print more messages,
11094 to see how many times the problems occur, with the @code{set
11095 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
11098 The messages currently printed, and their meanings, include:
11101 @item inner block not inside outer block in @var{symbol}
11103 The symbol information shows where symbol scopes begin and end
11104 (such as at the start of a function or a block of statements). This
11105 error indicates that an inner scope block is not fully contained
11106 in its outer scope blocks.
11108 @value{GDBN} circumvents the problem by treating the inner block as if it had
11109 the same scope as the outer block. In the error message, @var{symbol}
11110 may be shown as ``@code{(don't know)}'' if the outer block is not a
11113 @item block at @var{address} out of order
11115 The symbol information for symbol scope blocks should occur in
11116 order of increasing addresses. This error indicates that it does not
11119 @value{GDBN} does not circumvent this problem, and has trouble
11120 locating symbols in the source file whose symbols it is reading. (You
11121 can often determine what source file is affected by specifying
11122 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
11125 @item bad block start address patched
11127 The symbol information for a symbol scope block has a start address
11128 smaller than the address of the preceding source line. This is known
11129 to occur in the SunOS 4.1.1 (and earlier) C compiler.
11131 @value{GDBN} circumvents the problem by treating the symbol scope block as
11132 starting on the previous source line.
11134 @item bad string table offset in symbol @var{n}
11137 Symbol number @var{n} contains a pointer into the string table which is
11138 larger than the size of the string table.
11140 @value{GDBN} circumvents the problem by considering the symbol to have the
11141 name @code{foo}, which may cause other problems if many symbols end up
11144 @item unknown symbol type @code{0x@var{nn}}
11146 The symbol information contains new data types that @value{GDBN} does
11147 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
11148 uncomprehended information, in hexadecimal.
11150 @value{GDBN} circumvents the error by ignoring this symbol information.
11151 This usually allows you to debug your program, though certain symbols
11152 are not accessible. If you encounter such a problem and feel like
11153 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
11154 on @code{complain}, then go up to the function @code{read_dbx_symtab}
11155 and examine @code{*bufp} to see the symbol.
11157 @item stub type has NULL name
11159 @value{GDBN} could not find the full definition for a struct or class.
11161 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
11162 The symbol information for a C@t{++} member function is missing some
11163 information that recent versions of the compiler should have output for
11166 @item info mismatch between compiler and debugger
11168 @value{GDBN} could not parse a type specification output by the compiler.
11173 @chapter Specifying a Debugging Target
11175 @cindex debugging target
11176 A @dfn{target} is the execution environment occupied by your program.
11178 Often, @value{GDBN} runs in the same host environment as your program;
11179 in that case, the debugging target is specified as a side effect when
11180 you use the @code{file} or @code{core} commands. When you need more
11181 flexibility---for example, running @value{GDBN} on a physically separate
11182 host, or controlling a standalone system over a serial port or a
11183 realtime system over a TCP/IP connection---you can use the @code{target}
11184 command to specify one of the target types configured for @value{GDBN}
11185 (@pxref{Target Commands, ,Commands for managing targets}).
11187 @cindex target architecture
11188 It is possible to build @value{GDBN} for several different @dfn{target
11189 architectures}. When @value{GDBN} is built like that, you can choose
11190 one of the available architectures with the @kbd{set architecture}
11194 @kindex set architecture
11195 @kindex show architecture
11196 @item set architecture @var{arch}
11197 This command sets the current target architecture to @var{arch}. The
11198 value of @var{arch} can be @code{"auto"}, in addition to one of the
11199 supported architectures.
11201 @item show architecture
11202 Show the current target architecture.
11204 @item set processor
11206 @kindex set processor
11207 @kindex show processor
11208 These are alias commands for, respectively, @code{set architecture}
11209 and @code{show architecture}.
11213 * Active Targets:: Active targets
11214 * Target Commands:: Commands for managing targets
11215 * Byte Order:: Choosing target byte order
11216 * Remote:: Remote debugging
11217 * KOD:: Kernel Object Display
11221 @node Active Targets
11222 @section Active targets
11224 @cindex stacking targets
11225 @cindex active targets
11226 @cindex multiple targets
11228 There are three classes of targets: processes, core files, and
11229 executable files. @value{GDBN} can work concurrently on up to three
11230 active targets, one in each class. This allows you to (for example)
11231 start a process and inspect its activity without abandoning your work on
11234 For example, if you execute @samp{gdb a.out}, then the executable file
11235 @code{a.out} is the only active target. If you designate a core file as
11236 well---presumably from a prior run that crashed and coredumped---then
11237 @value{GDBN} has two active targets and uses them in tandem, looking
11238 first in the corefile target, then in the executable file, to satisfy
11239 requests for memory addresses. (Typically, these two classes of target
11240 are complementary, since core files contain only a program's
11241 read-write memory---variables and so on---plus machine status, while
11242 executable files contain only the program text and initialized data.)
11244 When you type @code{run}, your executable file becomes an active process
11245 target as well. When a process target is active, all @value{GDBN}
11246 commands requesting memory addresses refer to that target; addresses in
11247 an active core file or executable file target are obscured while the
11248 process target is active.
11250 Use the @code{core-file} and @code{exec-file} commands to select a new
11251 core file or executable target (@pxref{Files, ,Commands to specify
11252 files}). To specify as a target a process that is already running, use
11253 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
11256 @node Target Commands
11257 @section Commands for managing targets
11260 @item target @var{type} @var{parameters}
11261 Connects the @value{GDBN} host environment to a target machine or
11262 process. A target is typically a protocol for talking to debugging
11263 facilities. You use the argument @var{type} to specify the type or
11264 protocol of the target machine.
11266 Further @var{parameters} are interpreted by the target protocol, but
11267 typically include things like device names or host names to connect
11268 with, process numbers, and baud rates.
11270 The @code{target} command does not repeat if you press @key{RET} again
11271 after executing the command.
11273 @kindex help target
11275 Displays the names of all targets available. To display targets
11276 currently selected, use either @code{info target} or @code{info files}
11277 (@pxref{Files, ,Commands to specify files}).
11279 @item help target @var{name}
11280 Describe a particular target, including any parameters necessary to
11283 @kindex set gnutarget
11284 @item set gnutarget @var{args}
11285 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
11286 knows whether it is reading an @dfn{executable},
11287 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
11288 with the @code{set gnutarget} command. Unlike most @code{target} commands,
11289 with @code{gnutarget} the @code{target} refers to a program, not a machine.
11292 @emph{Warning:} To specify a file format with @code{set gnutarget},
11293 you must know the actual BFD name.
11297 @xref{Files, , Commands to specify files}.
11299 @kindex show gnutarget
11300 @item show gnutarget
11301 Use the @code{show gnutarget} command to display what file format
11302 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
11303 @value{GDBN} will determine the file format for each file automatically,
11304 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
11307 @cindex common targets
11308 Here are some common targets (available, or not, depending on the GDB
11313 @item target exec @var{program}
11314 @cindex executable file target
11315 An executable file. @samp{target exec @var{program}} is the same as
11316 @samp{exec-file @var{program}}.
11318 @item target core @var{filename}
11319 @cindex core dump file target
11320 A core dump file. @samp{target core @var{filename}} is the same as
11321 @samp{core-file @var{filename}}.
11323 @item target remote @var{dev}
11324 @cindex remote target
11325 Remote serial target in GDB-specific protocol. The argument @var{dev}
11326 specifies what serial device to use for the connection (e.g.
11327 @file{/dev/ttya}). @xref{Remote, ,Remote debugging}. @code{target remote}
11328 supports the @code{load} command. This is only useful if you have
11329 some other way of getting the stub to the target system, and you can put
11330 it somewhere in memory where it won't get clobbered by the download.
11333 @cindex built-in simulator target
11334 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
11342 works; however, you cannot assume that a specific memory map, device
11343 drivers, or even basic I/O is available, although some simulators do
11344 provide these. For info about any processor-specific simulator details,
11345 see the appropriate section in @ref{Embedded Processors, ,Embedded
11350 Some configurations may include these targets as well:
11354 @item target nrom @var{dev}
11355 @cindex NetROM ROM emulator target
11356 NetROM ROM emulator. This target only supports downloading.
11360 Different targets are available on different configurations of @value{GDBN};
11361 your configuration may have more or fewer targets.
11363 Many remote targets require you to download the executable's code
11364 once you've successfully established a connection. You may wish to
11365 control the size of the data chunks used by @value{GDBN} to download
11366 program parts to the remote target.
11369 @kindex set download-write-size
11370 @item set download-write-size @var{size}
11371 Set the write size used when downloading a program. Only used when
11372 downloading a program onto a remote target. Specify zero or a
11373 negative value to disable blocked writes. The actual size of each
11374 transfer is also limited by the size of the target packet and the
11377 @kindex show download-write-size
11378 @item show download-write-size
11379 Show the current value of the write size.
11384 @kindex load @var{filename}
11385 @item load @var{filename}
11386 Depending on what remote debugging facilities are configured into
11387 @value{GDBN}, the @code{load} command may be available. Where it exists, it
11388 is meant to make @var{filename} (an executable) available for debugging
11389 on the remote system---by downloading, or dynamic linking, for example.
11390 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
11391 the @code{add-symbol-file} command.
11393 If your @value{GDBN} does not have a @code{load} command, attempting to
11394 execute it gets the error message ``@code{You can't do that when your
11395 target is @dots{}}''
11397 The file is loaded at whatever address is specified in the executable.
11398 For some object file formats, you can specify the load address when you
11399 link the program; for other formats, like a.out, the object file format
11400 specifies a fixed address.
11401 @c FIXME! This would be a good place for an xref to the GNU linker doc.
11403 @code{load} does not repeat if you press @key{RET} again after using it.
11407 @section Choosing target byte order
11409 @cindex choosing target byte order
11410 @cindex target byte order
11412 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
11413 offer the ability to run either big-endian or little-endian byte
11414 orders. Usually the executable or symbol will include a bit to
11415 designate the endian-ness, and you will not need to worry about
11416 which to use. However, you may still find it useful to adjust
11417 @value{GDBN}'s idea of processor endian-ness manually.
11421 @item set endian big
11422 Instruct @value{GDBN} to assume the target is big-endian.
11424 @item set endian little
11425 Instruct @value{GDBN} to assume the target is little-endian.
11427 @item set endian auto
11428 Instruct @value{GDBN} to use the byte order associated with the
11432 Display @value{GDBN}'s current idea of the target byte order.
11436 Note that these commands merely adjust interpretation of symbolic
11437 data on the host, and that they have absolutely no effect on the
11441 @section Remote debugging
11442 @cindex remote debugging
11444 If you are trying to debug a program running on a machine that cannot run
11445 @value{GDBN} in the usual way, it is often useful to use remote debugging.
11446 For example, you might use remote debugging on an operating system kernel,
11447 or on a small system which does not have a general purpose operating system
11448 powerful enough to run a full-featured debugger.
11450 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
11451 to make this work with particular debugging targets. In addition,
11452 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
11453 but not specific to any particular target system) which you can use if you
11454 write the remote stubs---the code that runs on the remote system to
11455 communicate with @value{GDBN}.
11457 Other remote targets may be available in your
11458 configuration of @value{GDBN}; use @code{help target} to list them.
11461 @section Kernel Object Display
11462 @cindex kernel object display
11465 Some targets support kernel object display. Using this facility,
11466 @value{GDBN} communicates specially with the underlying operating system
11467 and can display information about operating system-level objects such as
11468 mutexes and other synchronization objects. Exactly which objects can be
11469 displayed is determined on a per-OS basis.
11472 Use the @code{set os} command to set the operating system. This tells
11473 @value{GDBN} which kernel object display module to initialize:
11476 (@value{GDBP}) set os cisco
11480 The associated command @code{show os} displays the operating system
11481 set with the @code{set os} command; if no operating system has been
11482 set, @code{show os} will display an empty string @samp{""}.
11484 If @code{set os} succeeds, @value{GDBN} will display some information
11485 about the operating system, and will create a new @code{info} command
11486 which can be used to query the target. The @code{info} command is named
11487 after the operating system:
11491 (@value{GDBP}) info cisco
11492 List of Cisco Kernel Objects
11494 any Any and all objects
11497 Further subcommands can be used to query about particular objects known
11500 There is currently no way to determine whether a given operating
11501 system is supported other than to try setting it with @kbd{set os
11502 @var{name}}, where @var{name} is the name of the operating system you
11506 @node Remote Debugging
11507 @chapter Debugging remote programs
11510 * Connecting:: Connecting to a remote target
11511 * Server:: Using the gdbserver program
11512 * NetWare:: Using the gdbserve.nlm program
11513 * Remote configuration:: Remote configuration
11514 * remote stub:: Implementing a remote stub
11518 @section Connecting to a remote target
11520 On the @value{GDBN} host machine, you will need an unstripped copy of
11521 your program, since @value{GDBN} needs symobl and debugging information.
11522 Start up @value{GDBN} as usual, using the name of the local copy of your
11523 program as the first argument.
11525 @cindex serial line, @code{target remote}
11526 If you're using a serial line, you may want to give @value{GDBN} the
11527 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
11528 (@pxref{Remote configuration, set remotebaud}) before the
11529 @code{target} command.
11531 After that, use @code{target remote} to establish communications with
11532 the target machine. Its argument specifies how to communicate---either
11533 via a devicename attached to a direct serial line, or a TCP or UDP port
11534 (possibly to a terminal server which in turn has a serial line to the
11535 target). For example, to use a serial line connected to the device
11536 named @file{/dev/ttyb}:
11539 target remote /dev/ttyb
11542 @cindex TCP port, @code{target remote}
11543 To use a TCP connection, use an argument of the form
11544 @code{@var{host}:@var{port}} or @code{tcp:@var{host}:@var{port}}.
11545 For example, to connect to port 2828 on a
11546 terminal server named @code{manyfarms}:
11549 target remote manyfarms:2828
11552 If your remote target is actually running on the same machine as
11553 your debugger session (e.g.@: a simulator of your target running on
11554 the same host), you can omit the hostname. For example, to connect
11555 to port 1234 on your local machine:
11558 target remote :1234
11562 Note that the colon is still required here.
11564 @cindex UDP port, @code{target remote}
11565 To use a UDP connection, use an argument of the form
11566 @code{udp:@var{host}:@var{port}}. For example, to connect to UDP port 2828
11567 on a terminal server named @code{manyfarms}:
11570 target remote udp:manyfarms:2828
11573 When using a UDP connection for remote debugging, you should keep in mind
11574 that the `U' stands for ``Unreliable''. UDP can silently drop packets on
11575 busy or unreliable networks, which will cause havoc with your debugging
11578 Now you can use all the usual commands to examine and change data and to
11579 step and continue the remote program.
11581 @cindex interrupting remote programs
11582 @cindex remote programs, interrupting
11583 Whenever @value{GDBN} is waiting for the remote program, if you type the
11584 interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the
11585 program. This may or may not succeed, depending in part on the hardware
11586 and the serial drivers the remote system uses. If you type the
11587 interrupt character once again, @value{GDBN} displays this prompt:
11590 Interrupted while waiting for the program.
11591 Give up (and stop debugging it)? (y or n)
11594 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
11595 (If you decide you want to try again later, you can use @samp{target
11596 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
11597 goes back to waiting.
11600 @kindex detach (remote)
11602 When you have finished debugging the remote program, you can use the
11603 @code{detach} command to release it from @value{GDBN} control.
11604 Detaching from the target normally resumes its execution, but the results
11605 will depend on your particular remote stub. After the @code{detach}
11606 command, @value{GDBN} is free to connect to another target.
11610 The @code{disconnect} command behaves like @code{detach}, except that
11611 the target is generally not resumed. It will wait for @value{GDBN}
11612 (this instance or another one) to connect and continue debugging. After
11613 the @code{disconnect} command, @value{GDBN} is again free to connect to
11616 @cindex send command to remote monitor
11618 @item monitor @var{cmd}
11619 This command allows you to send commands directly to the remote
11624 @section Using the @code{gdbserver} program
11627 @cindex remote connection without stubs
11628 @code{gdbserver} is a control program for Unix-like systems, which
11629 allows you to connect your program with a remote @value{GDBN} via
11630 @code{target remote}---but without linking in the usual debugging stub.
11632 @code{gdbserver} is not a complete replacement for the debugging stubs,
11633 because it requires essentially the same operating-system facilities
11634 that @value{GDBN} itself does. In fact, a system that can run
11635 @code{gdbserver} to connect to a remote @value{GDBN} could also run
11636 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
11637 because it is a much smaller program than @value{GDBN} itself. It is
11638 also easier to port than all of @value{GDBN}, so you may be able to get
11639 started more quickly on a new system by using @code{gdbserver}.
11640 Finally, if you develop code for real-time systems, you may find that
11641 the tradeoffs involved in real-time operation make it more convenient to
11642 do as much development work as possible on another system, for example
11643 by cross-compiling. You can use @code{gdbserver} to make a similar
11644 choice for debugging.
11646 @value{GDBN} and @code{gdbserver} communicate via either a serial line
11647 or a TCP connection, using the standard @value{GDBN} remote serial
11651 @item On the target machine,
11652 you need to have a copy of the program you want to debug.
11653 @code{gdbserver} does not need your program's symbol table, so you can
11654 strip the program if necessary to save space. @value{GDBN} on the host
11655 system does all the symbol handling.
11657 To use the server, you must tell it how to communicate with @value{GDBN};
11658 the name of your program; and the arguments for your program. The usual
11662 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
11665 @var{comm} is either a device name (to use a serial line) or a TCP
11666 hostname and portnumber. For example, to debug Emacs with the argument
11667 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
11671 target> gdbserver /dev/com1 emacs foo.txt
11674 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
11677 To use a TCP connection instead of a serial line:
11680 target> gdbserver host:2345 emacs foo.txt
11683 The only difference from the previous example is the first argument,
11684 specifying that you are communicating with the host @value{GDBN} via
11685 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
11686 expect a TCP connection from machine @samp{host} to local TCP port 2345.
11687 (Currently, the @samp{host} part is ignored.) You can choose any number
11688 you want for the port number as long as it does not conflict with any
11689 TCP ports already in use on the target system (for example, @code{23} is
11690 reserved for @code{telnet}).@footnote{If you choose a port number that
11691 conflicts with another service, @code{gdbserver} prints an error message
11692 and exits.} You must use the same port number with the host @value{GDBN}
11693 @code{target remote} command.
11695 On some targets, @code{gdbserver} can also attach to running programs.
11696 This is accomplished via the @code{--attach} argument. The syntax is:
11699 target> gdbserver @var{comm} --attach @var{pid}
11702 @var{pid} is the process ID of a currently running process. It isn't necessary
11703 to point @code{gdbserver} at a binary for the running process.
11706 @cindex attach to a program by name
11707 You can debug processes by name instead of process ID if your target has the
11708 @code{pidof} utility:
11711 target> gdbserver @var{comm} --attach `pidof @var{PROGRAM}`
11714 In case more than one copy of @var{PROGRAM} is running, or @var{PROGRAM}
11715 has multiple threads, most versions of @code{pidof} support the
11716 @code{-s} option to only return the first process ID.
11718 @item On the host machine,
11719 connect to your target (@pxref{Connecting,,Connecting to a remote target}).
11720 For TCP connections, you must start up @code{gdbserver} prior to using
11721 the @code{target remote} command. Otherwise you may get an error whose
11722 text depends on the host system, but which usually looks something like
11723 @samp{Connection refused}. You don't need to use the @code{load}
11724 command in @value{GDBN} when using gdbserver, since the program is
11725 already on the target.
11730 @section Using the @code{gdbserve.nlm} program
11732 @kindex gdbserve.nlm
11733 @code{gdbserve.nlm} is a control program for NetWare systems, which
11734 allows you to connect your program with a remote @value{GDBN} via
11735 @code{target remote}.
11737 @value{GDBN} and @code{gdbserve.nlm} communicate via a serial line,
11738 using the standard @value{GDBN} remote serial protocol.
11741 @item On the target machine,
11742 you need to have a copy of the program you want to debug.
11743 @code{gdbserve.nlm} does not need your program's symbol table, so you
11744 can strip the program if necessary to save space. @value{GDBN} on the
11745 host system does all the symbol handling.
11747 To use the server, you must tell it how to communicate with
11748 @value{GDBN}; the name of your program; and the arguments for your
11749 program. The syntax is:
11752 load gdbserve [ BOARD=@var{board} ] [ PORT=@var{port} ]
11753 [ BAUD=@var{baud} ] @var{program} [ @var{args} @dots{} ]
11756 @var{board} and @var{port} specify the serial line; @var{baud} specifies
11757 the baud rate used by the connection. @var{port} and @var{node} default
11758 to 0, @var{baud} defaults to 9600@dmn{bps}.
11760 For example, to debug Emacs with the argument @samp{foo.txt}and
11761 communicate with @value{GDBN} over serial port number 2 or board 1
11762 using a 19200@dmn{bps} connection:
11765 load gdbserve BOARD=1 PORT=2 BAUD=19200 emacs foo.txt
11769 On the @value{GDBN} host machine, connect to your target (@pxref{Connecting,,
11770 Connecting to a remote target}).
11774 @node Remote configuration
11775 @section Remote configuration
11778 @kindex show remote
11779 This section documents the configuration options available when
11780 debugging remote programs. For the options related to the File I/O
11781 extensions of the remote protocol, see @ref{The system call,
11782 system-call-allowed}.
11785 @item set remoteaddresssize @var{bits}
11786 @cindex adress size for remote targets
11787 @cindex bits in remote address
11788 Set the maximum size of address in a memory packet to the specified
11789 number of bits. @value{GDBN} will mask off the address bits above
11790 that number, when it passes addresses to the remote target. The
11791 default value is the number of bits in the target's address.
11793 @item show remoteaddresssize
11794 Show the current value of remote address size in bits.
11796 @item set remotebaud @var{n}
11797 @cindex baud rate for remote targets
11798 Set the baud rate for the remote serial I/O to @var{n} baud. The
11799 value is used to set the speed of the serial port used for debugging
11802 @item show remotebaud
11803 Show the current speed of the remote connection.
11805 @item set remotebreak
11806 @cindex interrupt remote programs
11807 @cindex BREAK signal instead of Ctrl-C
11808 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
11809 when you press the @key{Ctrl-C} key to interrupt the program running
11810 on the remote. If set to off, @value{GDBN} sends the @samp{Strl-C}
11811 character instead. The default is off, since most remote systems
11812 expect to see @samp{Ctrl-C} as the interrupt signal.
11814 @item show remotebreak
11815 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
11816 interrupt the remote program.
11818 @item set remotedebug
11819 @cindex debug remote protocol
11820 @cindex remote protocol debugging
11821 @cindex display remote packets
11822 Control the debugging of the remote protocol. When enabled, each
11823 packet sent to or received from the remote target is displayed. The
11826 @item show remotedebug
11827 Show the current setting of the remote protocol debugging.
11829 @item set remotedevice @var{device}
11830 @cindex serial port name
11831 Set the name of the serial port through which to communicate to the
11832 remote target to @var{device}. This is the device used by
11833 @value{GDBN} to open the serial communications line to the remote
11834 target. There's no default, so you must set a valid port name for the
11835 remote serial communications to work. (Some varieties of the
11836 @code{target} command accept the port name as part of their
11839 @item show remotedevice
11840 Show the current name of the serial port.
11842 @item set remotelogbase @var{base}
11843 Set the base (a.k.a.@: radix) of logging serial protocol
11844 communications to @var{base}. Supported values of @var{base} are:
11845 @code{ascii}, @code{octal}, and @code{hex}. The default is
11848 @item show remotelogbase
11849 Show the current setting of the radix for logging remote serial
11852 @item set remotelogfile @var{file}
11853 @cindex record serial communications on file
11854 Record remote serial communications on the named @var{file}. The
11855 default is not to record at all.
11857 @item show remotelogfile.
11858 Show the current setting of the file name on which to record the
11859 serial communications.
11861 @item set remotetimeout @var{num}
11862 @cindex timeout for serial communications
11863 @cindex remote timeout
11864 Set the timeout limit to wait for the remote target to respond to
11865 @var{num} seconds. The default is 2 seconds.
11867 @item show remotetimeout
11868 Show the current number of seconds to wait for the remote target
11871 @cindex limit hardware breakpoints and watchpoints
11872 @cindex remote target, limit break- and watchpoints
11873 @anchor{set remote hardware-watchpoint-limit}
11874 @anchor{set remote hardware-breakpoint-limit}
11875 @item set remote hardware-watchpoint-limit @var{limit}
11876 @itemx set remote hardware-breakpoint-limit @var{limit}
11877 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
11878 watchpoints. A limit of -1, the default, is treated as unlimited.
11880 @item set remote fetch-register-packet
11881 @itemx set remote set-register-packet
11882 @itemx set remote P-packet
11883 @itemx set remote p-packet
11885 @cindex fetch registers from remote targets
11886 @cindex set registers in remote targets
11887 Determine whether @value{GDBN} can set and fetch registers from the
11888 remote target using the @samp{P} packets. The default depends on the
11889 remote stub's support of the @samp{P} packets (@value{GDBN} queries
11890 the stub when this packet is first required).
11892 @item show remote fetch-register-packet
11893 @itemx show remote set-register-packet
11894 @itemx show remote P-packet
11895 @itemx show remote p-packet
11896 Show the current setting of using the @samp{P} packets for setting and
11897 fetching registers from the remote target.
11899 @cindex binary downloads
11901 @item set remote binary-download-packet
11902 @itemx set remote X-packet
11903 Determine whether @value{GDBN} sends downloads in binary mode using
11904 the @samp{X} packets. The default is on.
11906 @item show remote binary-download-packet
11907 @itemx show remote X-packet
11908 Show the current setting of using the @samp{X} packets for binary
11911 @item set remote read-aux-vector-packet
11912 @cindex auxiliary vector of remote target
11913 @cindex @code{auxv}, and remote targets
11914 Set the use of the remote protocol's @samp{qPart:auxv:read} (target
11915 auxiliary vector read) request. This request is used to fetch the
11916 remote target's @dfn{auxiliary vector}, see @ref{Auxiliary Vector}.
11917 The default setting depends on the remote stub's support of this
11918 request (@value{GDBN} queries the stub when this request is first
11919 required). @xref{General Query Packets, qPart}, for more information
11920 about this request.
11922 @item show remote read-aux-vector-packet
11923 Show the current setting of use of the @samp{qPart:auxv:read} request.
11925 @item set remote symbol-lookup-packet
11926 @cindex remote symbol lookup request
11927 Set the use of the remote protocol's @samp{qSymbol} (target symbol
11928 lookup) request. This request is used to communicate symbol
11929 information to the remote target, e.g., whenever a new shared library
11930 is loaded by the remote (@pxref{Files, shared libraries}). The
11931 default setting depends on the remote stub's support of this request
11932 (@value{GDBN} queries the stub when this request is first required).
11933 @xref{General Query Packets, qSymbol}, for more information about this
11936 @item show remote symbol-lookup-packet
11937 Show the current setting of use of the @samp{qSymbol} request.
11939 @item set remote verbose-resume-packet
11940 @cindex resume remote target
11941 @cindex signal thread, and remote targets
11942 @cindex single-step thread, and remote targets
11943 @cindex thread-specific operations on remote targets
11944 Set the use of the remote protocol's @samp{vCont} (descriptive resume)
11945 request. This request is used to resume specific threads in the
11946 remote target, and to single-step or signal them. The default setting
11947 depends on the remote stub's support of this request (@value{GDBN}
11948 queries the stub when this request is first required). This setting
11949 affects debugging of multithreaded programs: if @samp{vCont} cannot be
11950 used, @value{GDBN} might be unable to single-step a specific thread,
11951 especially under @code{set scheduler-locking off}; it is also
11952 impossible to pause a specific thread. @xref{Packets, vCont}, for
11955 @item show remote verbose-resume-packet
11956 Show the current setting of use of the @samp{vCont} request
11958 @item set remote software-breakpoint-packet
11959 @itemx set remote hardware-breakpoint-packet
11960 @itemx set remote write-watchpoint-packet
11961 @itemx set remote read-watchpoint-packet
11962 @itemx set remote access-watchpoint-packet
11963 @itemx set remote Z-packet
11965 @cindex remote hardware breakpoints and watchpoints
11966 These commands enable or disable the use of @samp{Z} packets for
11967 setting breakpoints and watchpoints in the remote target. The default
11968 depends on the remote stub's support of the @samp{Z} packets
11969 (@value{GDBN} queries the stub when each packet is first required).
11970 The command @code{set remote Z-packet}, kept for back-compatibility,
11971 turns on or off all the features that require the use of @samp{Z}
11974 @item show remote software-breakpoint-packet
11975 @itemx show remote hardware-breakpoint-packet
11976 @itemx show remote write-watchpoint-packet
11977 @itemx show remote read-watchpoint-packet
11978 @itemx show remote access-watchpoint-packet
11979 @itemx show remote Z-packet
11980 Show the current setting of @samp{Z} packets usage.
11984 @section Implementing a remote stub
11986 @cindex debugging stub, example
11987 @cindex remote stub, example
11988 @cindex stub example, remote debugging
11989 The stub files provided with @value{GDBN} implement the target side of the
11990 communication protocol, and the @value{GDBN} side is implemented in the
11991 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
11992 these subroutines to communicate, and ignore the details. (If you're
11993 implementing your own stub file, you can still ignore the details: start
11994 with one of the existing stub files. @file{sparc-stub.c} is the best
11995 organized, and therefore the easiest to read.)
11997 @cindex remote serial debugging, overview
11998 To debug a program running on another machine (the debugging
11999 @dfn{target} machine), you must first arrange for all the usual
12000 prerequisites for the program to run by itself. For example, for a C
12005 A startup routine to set up the C runtime environment; these usually
12006 have a name like @file{crt0}. The startup routine may be supplied by
12007 your hardware supplier, or you may have to write your own.
12010 A C subroutine library to support your program's
12011 subroutine calls, notably managing input and output.
12014 A way of getting your program to the other machine---for example, a
12015 download program. These are often supplied by the hardware
12016 manufacturer, but you may have to write your own from hardware
12020 The next step is to arrange for your program to use a serial port to
12021 communicate with the machine where @value{GDBN} is running (the @dfn{host}
12022 machine). In general terms, the scheme looks like this:
12026 @value{GDBN} already understands how to use this protocol; when everything
12027 else is set up, you can simply use the @samp{target remote} command
12028 (@pxref{Targets,,Specifying a Debugging Target}).
12030 @item On the target,
12031 you must link with your program a few special-purpose subroutines that
12032 implement the @value{GDBN} remote serial protocol. The file containing these
12033 subroutines is called a @dfn{debugging stub}.
12035 On certain remote targets, you can use an auxiliary program
12036 @code{gdbserver} instead of linking a stub into your program.
12037 @xref{Server,,Using the @code{gdbserver} program}, for details.
12040 The debugging stub is specific to the architecture of the remote
12041 machine; for example, use @file{sparc-stub.c} to debug programs on
12044 @cindex remote serial stub list
12045 These working remote stubs are distributed with @value{GDBN}:
12050 @cindex @file{i386-stub.c}
12053 For Intel 386 and compatible architectures.
12056 @cindex @file{m68k-stub.c}
12057 @cindex Motorola 680x0
12059 For Motorola 680x0 architectures.
12062 @cindex @file{sh-stub.c}
12065 For Renesas SH architectures.
12068 @cindex @file{sparc-stub.c}
12070 For @sc{sparc} architectures.
12072 @item sparcl-stub.c
12073 @cindex @file{sparcl-stub.c}
12076 For Fujitsu @sc{sparclite} architectures.
12080 The @file{README} file in the @value{GDBN} distribution may list other
12081 recently added stubs.
12084 * Stub Contents:: What the stub can do for you
12085 * Bootstrapping:: What you must do for the stub
12086 * Debug Session:: Putting it all together
12089 @node Stub Contents
12090 @subsection What the stub can do for you
12092 @cindex remote serial stub
12093 The debugging stub for your architecture supplies these three
12097 @item set_debug_traps
12098 @findex set_debug_traps
12099 @cindex remote serial stub, initialization
12100 This routine arranges for @code{handle_exception} to run when your
12101 program stops. You must call this subroutine explicitly near the
12102 beginning of your program.
12104 @item handle_exception
12105 @findex handle_exception
12106 @cindex remote serial stub, main routine
12107 This is the central workhorse, but your program never calls it
12108 explicitly---the setup code arranges for @code{handle_exception} to
12109 run when a trap is triggered.
12111 @code{handle_exception} takes control when your program stops during
12112 execution (for example, on a breakpoint), and mediates communications
12113 with @value{GDBN} on the host machine. This is where the communications
12114 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
12115 representative on the target machine. It begins by sending summary
12116 information on the state of your program, then continues to execute,
12117 retrieving and transmitting any information @value{GDBN} needs, until you
12118 execute a @value{GDBN} command that makes your program resume; at that point,
12119 @code{handle_exception} returns control to your own code on the target
12123 @cindex @code{breakpoint} subroutine, remote
12124 Use this auxiliary subroutine to make your program contain a
12125 breakpoint. Depending on the particular situation, this may be the only
12126 way for @value{GDBN} to get control. For instance, if your target
12127 machine has some sort of interrupt button, you won't need to call this;
12128 pressing the interrupt button transfers control to
12129 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
12130 simply receiving characters on the serial port may also trigger a trap;
12131 again, in that situation, you don't need to call @code{breakpoint} from
12132 your own program---simply running @samp{target remote} from the host
12133 @value{GDBN} session gets control.
12135 Call @code{breakpoint} if none of these is true, or if you simply want
12136 to make certain your program stops at a predetermined point for the
12137 start of your debugging session.
12140 @node Bootstrapping
12141 @subsection What you must do for the stub
12143 @cindex remote stub, support routines
12144 The debugging stubs that come with @value{GDBN} are set up for a particular
12145 chip architecture, but they have no information about the rest of your
12146 debugging target machine.
12148 First of all you need to tell the stub how to communicate with the
12152 @item int getDebugChar()
12153 @findex getDebugChar
12154 Write this subroutine to read a single character from the serial port.
12155 It may be identical to @code{getchar} for your target system; a
12156 different name is used to allow you to distinguish the two if you wish.
12158 @item void putDebugChar(int)
12159 @findex putDebugChar
12160 Write this subroutine to write a single character to the serial port.
12161 It may be identical to @code{putchar} for your target system; a
12162 different name is used to allow you to distinguish the two if you wish.
12165 @cindex control C, and remote debugging
12166 @cindex interrupting remote targets
12167 If you want @value{GDBN} to be able to stop your program while it is
12168 running, you need to use an interrupt-driven serial driver, and arrange
12169 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
12170 character). That is the character which @value{GDBN} uses to tell the
12171 remote system to stop.
12173 Getting the debugging target to return the proper status to @value{GDBN}
12174 probably requires changes to the standard stub; one quick and dirty way
12175 is to just execute a breakpoint instruction (the ``dirty'' part is that
12176 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
12178 Other routines you need to supply are:
12181 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
12182 @findex exceptionHandler
12183 Write this function to install @var{exception_address} in the exception
12184 handling tables. You need to do this because the stub does not have any
12185 way of knowing what the exception handling tables on your target system
12186 are like (for example, the processor's table might be in @sc{rom},
12187 containing entries which point to a table in @sc{ram}).
12188 @var{exception_number} is the exception number which should be changed;
12189 its meaning is architecture-dependent (for example, different numbers
12190 might represent divide by zero, misaligned access, etc). When this
12191 exception occurs, control should be transferred directly to
12192 @var{exception_address}, and the processor state (stack, registers,
12193 and so on) should be just as it is when a processor exception occurs. So if
12194 you want to use a jump instruction to reach @var{exception_address}, it
12195 should be a simple jump, not a jump to subroutine.
12197 For the 386, @var{exception_address} should be installed as an interrupt
12198 gate so that interrupts are masked while the handler runs. The gate
12199 should be at privilege level 0 (the most privileged level). The
12200 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
12201 help from @code{exceptionHandler}.
12203 @item void flush_i_cache()
12204 @findex flush_i_cache
12205 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
12206 instruction cache, if any, on your target machine. If there is no
12207 instruction cache, this subroutine may be a no-op.
12209 On target machines that have instruction caches, @value{GDBN} requires this
12210 function to make certain that the state of your program is stable.
12214 You must also make sure this library routine is available:
12217 @item void *memset(void *, int, int)
12219 This is the standard library function @code{memset} that sets an area of
12220 memory to a known value. If you have one of the free versions of
12221 @code{libc.a}, @code{memset} can be found there; otherwise, you must
12222 either obtain it from your hardware manufacturer, or write your own.
12225 If you do not use the GNU C compiler, you may need other standard
12226 library subroutines as well; this varies from one stub to another,
12227 but in general the stubs are likely to use any of the common library
12228 subroutines which @code{@value{GCC}} generates as inline code.
12231 @node Debug Session
12232 @subsection Putting it all together
12234 @cindex remote serial debugging summary
12235 In summary, when your program is ready to debug, you must follow these
12240 Make sure you have defined the supporting low-level routines
12241 (@pxref{Bootstrapping,,What you must do for the stub}):
12243 @code{getDebugChar}, @code{putDebugChar},
12244 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
12248 Insert these lines near the top of your program:
12256 For the 680x0 stub only, you need to provide a variable called
12257 @code{exceptionHook}. Normally you just use:
12260 void (*exceptionHook)() = 0;
12264 but if before calling @code{set_debug_traps}, you set it to point to a
12265 function in your program, that function is called when
12266 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
12267 error). The function indicated by @code{exceptionHook} is called with
12268 one parameter: an @code{int} which is the exception number.
12271 Compile and link together: your program, the @value{GDBN} debugging stub for
12272 your target architecture, and the supporting subroutines.
12275 Make sure you have a serial connection between your target machine and
12276 the @value{GDBN} host, and identify the serial port on the host.
12279 @c The "remote" target now provides a `load' command, so we should
12280 @c document that. FIXME.
12281 Download your program to your target machine (or get it there by
12282 whatever means the manufacturer provides), and start it.
12285 Start @value{GDBN} on the host, and connect to the target
12286 (@pxref{Connecting,,Connecting to a remote target}).
12290 @node Configurations
12291 @chapter Configuration-Specific Information
12293 While nearly all @value{GDBN} commands are available for all native and
12294 cross versions of the debugger, there are some exceptions. This chapter
12295 describes things that are only available in certain configurations.
12297 There are three major categories of configurations: native
12298 configurations, where the host and target are the same, embedded
12299 operating system configurations, which are usually the same for several
12300 different processor architectures, and bare embedded processors, which
12301 are quite different from each other.
12306 * Embedded Processors::
12313 This section describes details specific to particular native
12318 * BSD libkvm Interface:: Debugging BSD kernel memory images
12319 * SVR4 Process Information:: SVR4 process information
12320 * DJGPP Native:: Features specific to the DJGPP port
12321 * Cygwin Native:: Features specific to the Cygwin port
12322 * Hurd Native:: Features specific to @sc{gnu} Hurd
12328 On HP-UX systems, if you refer to a function or variable name that
12329 begins with a dollar sign, @value{GDBN} searches for a user or system
12330 name first, before it searches for a convenience variable.
12333 @node BSD libkvm Interface
12334 @subsection BSD libkvm Interface
12337 @cindex kernel memory image
12338 @cindex kernel crash dump
12340 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
12341 interface that provides a uniform interface for accessing kernel virtual
12342 memory images, including live systems and crash dumps. @value{GDBN}
12343 uses this interface to allow you to debug live kernels and kernel crash
12344 dumps on many native BSD configurations. This is implemented as a
12345 special @code{kvm} debugging target. For debugging a live system, load
12346 the currently running kernel into @value{GDBN} and connect to the
12350 (@value{GDBP}) @b{target kvm}
12353 For debugging crash dumps, provide the file name of the crash dump as an
12357 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
12360 Once connected to the @code{kvm} target, the following commands are
12366 Set current context from pcb address.
12369 Set current context from proc address. This command isn't available on
12370 modern FreeBSD systems.
12373 @node SVR4 Process Information
12374 @subsection SVR4 process information
12376 @cindex examine process image
12377 @cindex process info via @file{/proc}
12379 Many versions of SVR4 and compatible systems provide a facility called
12380 @samp{/proc} that can be used to examine the image of a running
12381 process using file-system subroutines. If @value{GDBN} is configured
12382 for an operating system with this facility, the command @code{info
12383 proc} is available to report information about the process running
12384 your program, or about any process running on your system. @code{info
12385 proc} works only on SVR4 systems that include the @code{procfs} code.
12386 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
12387 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
12393 @itemx info proc @var{process-id}
12394 Summarize available information about any running process. If a
12395 process ID is specified by @var{process-id}, display information about
12396 that process; otherwise display information about the program being
12397 debugged. The summary includes the debugged process ID, the command
12398 line used to invoke it, its current working directory, and its
12399 executable file's absolute file name.
12401 On some systems, @var{process-id} can be of the form
12402 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
12403 within a process. If the optional @var{pid} part is missing, it means
12404 a thread from the process being debugged (the leading @samp{/} still
12405 needs to be present, or else @value{GDBN} will interpret the number as
12406 a process ID rather than a thread ID).
12408 @item info proc mappings
12409 @cindex memory address space mappings
12410 Report the memory address space ranges accessible in the program, with
12411 information on whether the process has read, write, or execute access
12412 rights to each range. On @sc{gnu}/Linux systems, each memory range
12413 includes the object file which is mapped to that range, instead of the
12414 memory access rights to that range.
12416 @item info proc stat
12417 @itemx info proc status
12418 @cindex process detailed status information
12419 These subcommands are specific to @sc{gnu}/Linux systems. They show
12420 the process-related information, including the user ID and group ID;
12421 how many threads are there in the process; its virtual memory usage;
12422 the signals that are pending, blocked, and ignored; its TTY; its
12423 consumption of system and user time; its stack size; its @samp{nice}
12424 value; etc. For more information, see the @samp{proc(5)} man page
12425 (type @kbd{man 5 proc} from your shell prompt).
12427 @item info proc all
12428 Show all the information about the process described under all of the
12429 above @code{info proc} subcommands.
12432 @comment These sub-options of 'info proc' were not included when
12433 @comment procfs.c was re-written. Keep their descriptions around
12434 @comment against the day when someone finds the time to put them back in.
12435 @kindex info proc times
12436 @item info proc times
12437 Starting time, user CPU time, and system CPU time for your program and
12440 @kindex info proc id
12442 Report on the process IDs related to your program: its own process ID,
12443 the ID of its parent, the process group ID, and the session ID.
12448 @subsection Features for Debugging @sc{djgpp} Programs
12449 @cindex @sc{djgpp} debugging
12450 @cindex native @sc{djgpp} debugging
12451 @cindex MS-DOS-specific commands
12453 @sc{djgpp} is the port of @sc{gnu} development tools to MS-DOS and
12454 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
12455 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
12456 top of real-mode DOS systems and their emulations.
12458 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
12459 defines a few commands specific to the @sc{djgpp} port. This
12460 subsection describes those commands.
12465 This is a prefix of @sc{djgpp}-specific commands which print
12466 information about the target system and important OS structures.
12469 @cindex MS-DOS system info
12470 @cindex free memory information (MS-DOS)
12471 @item info dos sysinfo
12472 This command displays assorted information about the underlying
12473 platform: the CPU type and features, the OS version and flavor, the
12474 DPMI version, and the available conventional and DPMI memory.
12479 @cindex segment descriptor tables
12480 @cindex descriptor tables display
12482 @itemx info dos ldt
12483 @itemx info dos idt
12484 These 3 commands display entries from, respectively, Global, Local,
12485 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
12486 tables are data structures which store a descriptor for each segment
12487 that is currently in use. The segment's selector is an index into a
12488 descriptor table; the table entry for that index holds the
12489 descriptor's base address and limit, and its attributes and access
12492 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
12493 segment (used for both data and the stack), and a DOS segment (which
12494 allows access to DOS/BIOS data structures and absolute addresses in
12495 conventional memory). However, the DPMI host will usually define
12496 additional segments in order to support the DPMI environment.
12498 @cindex garbled pointers
12499 These commands allow to display entries from the descriptor tables.
12500 Without an argument, all entries from the specified table are
12501 displayed. An argument, which should be an integer expression, means
12502 display a single entry whose index is given by the argument. For
12503 example, here's a convenient way to display information about the
12504 debugged program's data segment:
12507 @exdent @code{(@value{GDBP}) info dos ldt $ds}
12508 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
12512 This comes in handy when you want to see whether a pointer is outside
12513 the data segment's limit (i.e.@: @dfn{garbled}).
12515 @cindex page tables display (MS-DOS)
12517 @itemx info dos pte
12518 These two commands display entries from, respectively, the Page
12519 Directory and the Page Tables. Page Directories and Page Tables are
12520 data structures which control how virtual memory addresses are mapped
12521 into physical addresses. A Page Table includes an entry for every
12522 page of memory that is mapped into the program's address space; there
12523 may be several Page Tables, each one holding up to 4096 entries. A
12524 Page Directory has up to 4096 entries, one each for every Page Table
12525 that is currently in use.
12527 Without an argument, @kbd{info dos pde} displays the entire Page
12528 Directory, and @kbd{info dos pte} displays all the entries in all of
12529 the Page Tables. An argument, an integer expression, given to the
12530 @kbd{info dos pde} command means display only that entry from the Page
12531 Directory table. An argument given to the @kbd{info dos pte} command
12532 means display entries from a single Page Table, the one pointed to by
12533 the specified entry in the Page Directory.
12535 @cindex direct memory access (DMA) on MS-DOS
12536 These commands are useful when your program uses @dfn{DMA} (Direct
12537 Memory Access), which needs physical addresses to program the DMA
12540 These commands are supported only with some DPMI servers.
12542 @cindex physical address from linear address
12543 @item info dos address-pte @var{addr}
12544 This command displays the Page Table entry for a specified linear
12545 address. The argument linear address @var{addr} should already have the
12546 appropriate segment's base address added to it, because this command
12547 accepts addresses which may belong to @emph{any} segment. For
12548 example, here's how to display the Page Table entry for the page where
12549 the variable @code{i} is stored:
12552 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
12553 @exdent @code{Page Table entry for address 0x11a00d30:}
12554 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
12558 This says that @code{i} is stored at offset @code{0xd30} from the page
12559 whose physical base address is @code{0x02698000}, and prints all the
12560 attributes of that page.
12562 Note that you must cast the addresses of variables to a @code{char *},
12563 since otherwise the value of @code{__djgpp_base_address}, the base
12564 address of all variables and functions in a @sc{djgpp} program, will
12565 be added using the rules of C pointer arithmetics: if @code{i} is
12566 declared an @code{int}, @value{GDBN} will add 4 times the value of
12567 @code{__djgpp_base_address} to the address of @code{i}.
12569 Here's another example, it displays the Page Table entry for the
12573 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
12574 @exdent @code{Page Table entry for address 0x29110:}
12575 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
12579 (The @code{+ 3} offset is because the transfer buffer's address is the
12580 3rd member of the @code{_go32_info_block} structure.) The output of
12581 this command clearly shows that addresses in conventional memory are
12582 mapped 1:1, i.e.@: the physical and linear addresses are identical.
12584 This command is supported only with some DPMI servers.
12587 In addition to native debugging, the DJGPP port supports remote
12588 debugging via a serial data link. The following commands are specific
12589 to remote serial debugging in the DJGPP port of @value{GDBN}.
12592 @kindex set com1base
12593 @kindex set com1irq
12594 @kindex set com2base
12595 @kindex set com2irq
12596 @kindex set com3base
12597 @kindex set com3irq
12598 @kindex set com4base
12599 @kindex set com4irq
12600 @item set com1base @var{addr}
12601 This command sets the base I/O port address of the @file{COM1} serial
12604 @item set com1irq @var{irq}
12605 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
12606 for the @file{COM1} serial port.
12608 There are similar commands @samp{set com2base}, @samp{set com3irq},
12609 etc.@: for setting the port address and the @code{IRQ} lines for the
12612 @kindex show com1base
12613 @kindex show com1irq
12614 @kindex show com2base
12615 @kindex show com2irq
12616 @kindex show com3base
12617 @kindex show com3irq
12618 @kindex show com4base
12619 @kindex show com4irq
12620 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
12621 display the current settings of the base address and the @code{IRQ}
12622 lines used by the COM ports.
12626 @node Cygwin Native
12627 @subsection Features for Debugging MS Windows PE executables
12628 @cindex MS Windows debugging
12629 @cindex native Cygwin debugging
12630 @cindex Cygwin-specific commands
12632 @value{GDBN} supports native debugging of MS Windows programs, including
12633 DLLs with and without symbolic debugging information. There are various
12634 additional Cygwin-specific commands, described in this subsection. The
12635 subsubsection @pxref{Non-debug DLL symbols} describes working with DLLs
12636 that have no debugging symbols.
12642 This is a prefix of MS Windows specific commands which print
12643 information about the target system and important OS structures.
12645 @item info w32 selector
12646 This command displays information returned by
12647 the Win32 API @code{GetThreadSelectorEntry} function.
12648 It takes an optional argument that is evaluated to
12649 a long value to give the information about this given selector.
12650 Without argument, this command displays information
12651 about the the six segment registers.
12655 This is a Cygwin specific alias of info shared.
12657 @kindex dll-symbols
12659 This command loads symbols from a dll similarly to
12660 add-sym command but without the need to specify a base address.
12662 @kindex set new-console
12663 @item set new-console @var{mode}
12664 If @var{mode} is @code{on} the debuggee will
12665 be started in a new console on next start.
12666 If @var{mode} is @code{off}i, the debuggee will
12667 be started in the same console as the debugger.
12669 @kindex show new-console
12670 @item show new-console
12671 Displays whether a new console is used
12672 when the debuggee is started.
12674 @kindex set new-group
12675 @item set new-group @var{mode}
12676 This boolean value controls whether the debuggee should
12677 start a new group or stay in the same group as the debugger.
12678 This affects the way the Windows OS handles
12681 @kindex show new-group
12682 @item show new-group
12683 Displays current value of new-group boolean.
12685 @kindex set debugevents
12686 @item set debugevents
12687 This boolean value adds debug output concerning events seen by the debugger.
12689 @kindex set debugexec
12690 @item set debugexec
12691 This boolean value adds debug output concerning execute events
12692 seen by the debugger.
12694 @kindex set debugexceptions
12695 @item set debugexceptions
12696 This boolean value adds debug ouptut concerning exception events
12697 seen by the debugger.
12699 @kindex set debugmemory
12700 @item set debugmemory
12701 This boolean value adds debug ouptut concerning memory events
12702 seen by the debugger.
12706 This boolean values specifies whether the debuggee is called
12707 via a shell or directly (default value is on).
12711 Displays if the debuggee will be started with a shell.
12716 * Non-debug DLL symbols:: Support for DLLs without debugging symbols
12719 @node Non-debug DLL symbols
12720 @subsubsection Support for DLLs without debugging symbols
12721 @cindex DLLs with no debugging symbols
12722 @cindex Minimal symbols and DLLs
12724 Very often on windows, some of the DLLs that your program relies on do
12725 not include symbolic debugging information (for example,
12726 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
12727 symbols in a DLL, it relies on the minimal amount of symbolic
12728 information contained in the DLL's export table. This subsubsection
12729 describes working with such symbols, known internally to @value{GDBN} as
12730 ``minimal symbols''.
12732 Note that before the debugged program has started execution, no DLLs
12733 will have been loaded. The easiest way around this problem is simply to
12734 start the program --- either by setting a breakpoint or letting the
12735 program run once to completion. It is also possible to force
12736 @value{GDBN} to load a particular DLL before starting the executable ---
12737 see the shared library information in @pxref{Files} or the
12738 @code{dll-symbols} command in @pxref{Cygwin Native}. Currently,
12739 explicitly loading symbols from a DLL with no debugging information will
12740 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
12741 which may adversely affect symbol lookup performance.
12743 @subsubsection DLL name prefixes
12745 In keeping with the naming conventions used by the Microsoft debugging
12746 tools, DLL export symbols are made available with a prefix based on the
12747 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
12748 also entered into the symbol table, so @code{CreateFileA} is often
12749 sufficient. In some cases there will be name clashes within a program
12750 (particularly if the executable itself includes full debugging symbols)
12751 necessitating the use of the fully qualified name when referring to the
12752 contents of the DLL. Use single-quotes around the name to avoid the
12753 exclamation mark (``!'') being interpreted as a language operator.
12755 Note that the internal name of the DLL may be all upper-case, even
12756 though the file name of the DLL is lower-case, or vice-versa. Since
12757 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
12758 some confusion. If in doubt, try the @code{info functions} and
12759 @code{info variables} commands or even @code{maint print msymbols} (see
12760 @pxref{Symbols}). Here's an example:
12763 (@value{GDBP}) info function CreateFileA
12764 All functions matching regular expression "CreateFileA":
12766 Non-debugging symbols:
12767 0x77e885f4 CreateFileA
12768 0x77e885f4 KERNEL32!CreateFileA
12772 (@value{GDBP}) info function !
12773 All functions matching regular expression "!":
12775 Non-debugging symbols:
12776 0x6100114c cygwin1!__assert
12777 0x61004034 cygwin1!_dll_crt0@@0
12778 0x61004240 cygwin1!dll_crt0(per_process *)
12782 @subsubsection Working with minimal symbols
12784 Symbols extracted from a DLL's export table do not contain very much
12785 type information. All that @value{GDBN} can do is guess whether a symbol
12786 refers to a function or variable depending on the linker section that
12787 contains the symbol. Also note that the actual contents of the memory
12788 contained in a DLL are not available unless the program is running. This
12789 means that you cannot examine the contents of a variable or disassemble
12790 a function within a DLL without a running program.
12792 Variables are generally treated as pointers and dereferenced
12793 automatically. For this reason, it is often necessary to prefix a
12794 variable name with the address-of operator (``&'') and provide explicit
12795 type information in the command. Here's an example of the type of
12799 (@value{GDBP}) print 'cygwin1!__argv'
12804 (@value{GDBP}) x 'cygwin1!__argv'
12805 0x10021610: "\230y\""
12808 And two possible solutions:
12811 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
12812 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
12816 (@value{GDBP}) x/2x &'cygwin1!__argv'
12817 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
12818 (@value{GDBP}) x/x 0x10021608
12819 0x10021608: 0x0022fd98
12820 (@value{GDBP}) x/s 0x0022fd98
12821 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
12824 Setting a break point within a DLL is possible even before the program
12825 starts execution. However, under these circumstances, @value{GDBN} can't
12826 examine the initial instructions of the function in order to skip the
12827 function's frame set-up code. You can work around this by using ``*&''
12828 to set the breakpoint at a raw memory address:
12831 (@value{GDBP}) break *&'python22!PyOS_Readline'
12832 Breakpoint 1 at 0x1e04eff0
12835 The author of these extensions is not entirely convinced that setting a
12836 break point within a shared DLL like @file{kernel32.dll} is completely
12840 @subsection Commands specific to @sc{gnu} Hurd systems
12841 @cindex @sc{gnu} Hurd debugging
12843 This subsection describes @value{GDBN} commands specific to the
12844 @sc{gnu} Hurd native debugging.
12849 @kindex set signals@r{, Hurd command}
12850 @kindex set sigs@r{, Hurd command}
12851 This command toggles the state of inferior signal interception by
12852 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
12853 affected by this command. @code{sigs} is a shorthand alias for
12858 @kindex show signals@r{, Hurd command}
12859 @kindex show sigs@r{, Hurd command}
12860 Show the current state of intercepting inferior's signals.
12862 @item set signal-thread
12863 @itemx set sigthread
12864 @kindex set signal-thread
12865 @kindex set sigthread
12866 This command tells @value{GDBN} which thread is the @code{libc} signal
12867 thread. That thread is run when a signal is delivered to a running
12868 process. @code{set sigthread} is the shorthand alias of @code{set
12871 @item show signal-thread
12872 @itemx show sigthread
12873 @kindex show signal-thread
12874 @kindex show sigthread
12875 These two commands show which thread will run when the inferior is
12876 delivered a signal.
12879 @kindex set stopped@r{, Hurd command}
12880 This commands tells @value{GDBN} that the inferior process is stopped,
12881 as with the @code{SIGSTOP} signal. The stopped process can be
12882 continued by delivering a signal to it.
12885 @kindex show stopped@r{, Hurd command}
12886 This command shows whether @value{GDBN} thinks the debuggee is
12889 @item set exceptions
12890 @kindex set exceptions@r{, Hurd command}
12891 Use this command to turn off trapping of exceptions in the inferior.
12892 When exception trapping is off, neither breakpoints nor
12893 single-stepping will work. To restore the default, set exception
12896 @item show exceptions
12897 @kindex show exceptions@r{, Hurd command}
12898 Show the current state of trapping exceptions in the inferior.
12900 @item set task pause
12901 @kindex set task@r{, Hurd commands}
12902 @cindex task attributes (@sc{gnu} Hurd)
12903 @cindex pause current task (@sc{gnu} Hurd)
12904 This command toggles task suspension when @value{GDBN} has control.
12905 Setting it to on takes effect immediately, and the task is suspended
12906 whenever @value{GDBN} gets control. Setting it to off will take
12907 effect the next time the inferior is continued. If this option is set
12908 to off, you can use @code{set thread default pause on} or @code{set
12909 thread pause on} (see below) to pause individual threads.
12911 @item show task pause
12912 @kindex show task@r{, Hurd commands}
12913 Show the current state of task suspension.
12915 @item set task detach-suspend-count
12916 @cindex task suspend count
12917 @cindex detach from task, @sc{gnu} Hurd
12918 This command sets the suspend count the task will be left with when
12919 @value{GDBN} detaches from it.
12921 @item show task detach-suspend-count
12922 Show the suspend count the task will be left with when detaching.
12924 @item set task exception-port
12925 @itemx set task excp
12926 @cindex task exception port, @sc{gnu} Hurd
12927 This command sets the task exception port to which @value{GDBN} will
12928 forward exceptions. The argument should be the value of the @dfn{send
12929 rights} of the task. @code{set task excp} is a shorthand alias.
12931 @item set noninvasive
12932 @cindex noninvasive task options
12933 This command switches @value{GDBN} to a mode that is the least
12934 invasive as far as interfering with the inferior is concerned. This
12935 is the same as using @code{set task pause}, @code{set exceptions}, and
12936 @code{set signals} to values opposite to the defaults.
12938 @item info send-rights
12939 @itemx info receive-rights
12940 @itemx info port-rights
12941 @itemx info port-sets
12942 @itemx info dead-names
12945 @cindex send rights, @sc{gnu} Hurd
12946 @cindex receive rights, @sc{gnu} Hurd
12947 @cindex port rights, @sc{gnu} Hurd
12948 @cindex port sets, @sc{gnu} Hurd
12949 @cindex dead names, @sc{gnu} Hurd
12950 These commands display information about, respectively, send rights,
12951 receive rights, port rights, port sets, and dead names of a task.
12952 There are also shorthand aliases: @code{info ports} for @code{info
12953 port-rights} and @code{info psets} for @code{info port-sets}.
12955 @item set thread pause
12956 @kindex set thread@r{, Hurd command}
12957 @cindex thread properties, @sc{gnu} Hurd
12958 @cindex pause current thread (@sc{gnu} Hurd)
12959 This command toggles current thread suspension when @value{GDBN} has
12960 control. Setting it to on takes effect immediately, and the current
12961 thread is suspended whenever @value{GDBN} gets control. Setting it to
12962 off will take effect the next time the inferior is continued.
12963 Normally, this command has no effect, since when @value{GDBN} has
12964 control, the whole task is suspended. However, if you used @code{set
12965 task pause off} (see above), this command comes in handy to suspend
12966 only the current thread.
12968 @item show thread pause
12969 @kindex show thread@r{, Hurd command}
12970 This command shows the state of current thread suspension.
12972 @item set thread run
12973 This comamnd sets whether the current thread is allowed to run.
12975 @item show thread run
12976 Show whether the current thread is allowed to run.
12978 @item set thread detach-suspend-count
12979 @cindex thread suspend count, @sc{gnu} Hurd
12980 @cindex detach from thread, @sc{gnu} Hurd
12981 This command sets the suspend count @value{GDBN} will leave on a
12982 thread when detaching. This number is relative to the suspend count
12983 found by @value{GDBN} when it notices the thread; use @code{set thread
12984 takeover-suspend-count} to force it to an absolute value.
12986 @item show thread detach-suspend-count
12987 Show the suspend count @value{GDBN} will leave on the thread when
12990 @item set thread exception-port
12991 @itemx set thread excp
12992 Set the thread exception port to which to forward exceptions. This
12993 overrides the port set by @code{set task exception-port} (see above).
12994 @code{set thread excp} is the shorthand alias.
12996 @item set thread takeover-suspend-count
12997 Normally, @value{GDBN}'s thread suspend counts are relative to the
12998 value @value{GDBN} finds when it notices each thread. This command
12999 changes the suspend counts to be absolute instead.
13001 @item set thread default
13002 @itemx show thread default
13003 @cindex thread default settings, @sc{gnu} Hurd
13004 Each of the above @code{set thread} commands has a @code{set thread
13005 default} counterpart (e.g., @code{set thread default pause}, @code{set
13006 thread default exception-port}, etc.). The @code{thread default}
13007 variety of commands sets the default thread properties for all
13008 threads; you can then change the properties of individual threads with
13009 the non-default commands.
13014 @section Embedded Operating Systems
13016 This section describes configurations involving the debugging of
13017 embedded operating systems that are available for several different
13021 * VxWorks:: Using @value{GDBN} with VxWorks
13024 @value{GDBN} includes the ability to debug programs running on
13025 various real-time operating systems.
13028 @subsection Using @value{GDBN} with VxWorks
13034 @kindex target vxworks
13035 @item target vxworks @var{machinename}
13036 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
13037 is the target system's machine name or IP address.
13041 On VxWorks, @code{load} links @var{filename} dynamically on the
13042 current target system as well as adding its symbols in @value{GDBN}.
13044 @value{GDBN} enables developers to spawn and debug tasks running on networked
13045 VxWorks targets from a Unix host. Already-running tasks spawned from
13046 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
13047 both the Unix host and on the VxWorks target. The program
13048 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
13049 installed with the name @code{vxgdb}, to distinguish it from a
13050 @value{GDBN} for debugging programs on the host itself.)
13053 @item VxWorks-timeout @var{args}
13054 @kindex vxworks-timeout
13055 All VxWorks-based targets now support the option @code{vxworks-timeout}.
13056 This option is set by the user, and @var{args} represents the number of
13057 seconds @value{GDBN} waits for responses to rpc's. You might use this if
13058 your VxWorks target is a slow software simulator or is on the far side
13059 of a thin network line.
13062 The following information on connecting to VxWorks was current when
13063 this manual was produced; newer releases of VxWorks may use revised
13066 @findex INCLUDE_RDB
13067 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
13068 to include the remote debugging interface routines in the VxWorks
13069 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
13070 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
13071 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
13072 source debugging task @code{tRdbTask} when VxWorks is booted. For more
13073 information on configuring and remaking VxWorks, see the manufacturer's
13075 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
13077 Once you have included @file{rdb.a} in your VxWorks system image and set
13078 your Unix execution search path to find @value{GDBN}, you are ready to
13079 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
13080 @code{vxgdb}, depending on your installation).
13082 @value{GDBN} comes up showing the prompt:
13089 * VxWorks Connection:: Connecting to VxWorks
13090 * VxWorks Download:: VxWorks download
13091 * VxWorks Attach:: Running tasks
13094 @node VxWorks Connection
13095 @subsubsection Connecting to VxWorks
13097 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
13098 network. To connect to a target whose host name is ``@code{tt}'', type:
13101 (vxgdb) target vxworks tt
13105 @value{GDBN} displays messages like these:
13108 Attaching remote machine across net...
13113 @value{GDBN} then attempts to read the symbol tables of any object modules
13114 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
13115 these files by searching the directories listed in the command search
13116 path (@pxref{Environment, ,Your program's environment}); if it fails
13117 to find an object file, it displays a message such as:
13120 prog.o: No such file or directory.
13123 When this happens, add the appropriate directory to the search path with
13124 the @value{GDBN} command @code{path}, and execute the @code{target}
13127 @node VxWorks Download
13128 @subsubsection VxWorks download
13130 @cindex download to VxWorks
13131 If you have connected to the VxWorks target and you want to debug an
13132 object that has not yet been loaded, you can use the @value{GDBN}
13133 @code{load} command to download a file from Unix to VxWorks
13134 incrementally. The object file given as an argument to the @code{load}
13135 command is actually opened twice: first by the VxWorks target in order
13136 to download the code, then by @value{GDBN} in order to read the symbol
13137 table. This can lead to problems if the current working directories on
13138 the two systems differ. If both systems have NFS mounted the same
13139 filesystems, you can avoid these problems by using absolute paths.
13140 Otherwise, it is simplest to set the working directory on both systems
13141 to the directory in which the object file resides, and then to reference
13142 the file by its name, without any path. For instance, a program
13143 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
13144 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
13145 program, type this on VxWorks:
13148 -> cd "@var{vxpath}/vw/demo/rdb"
13152 Then, in @value{GDBN}, type:
13155 (vxgdb) cd @var{hostpath}/vw/demo/rdb
13156 (vxgdb) load prog.o
13159 @value{GDBN} displays a response similar to this:
13162 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
13165 You can also use the @code{load} command to reload an object module
13166 after editing and recompiling the corresponding source file. Note that
13167 this makes @value{GDBN} delete all currently-defined breakpoints,
13168 auto-displays, and convenience variables, and to clear the value
13169 history. (This is necessary in order to preserve the integrity of
13170 debugger's data structures that reference the target system's symbol
13173 @node VxWorks Attach
13174 @subsubsection Running tasks
13176 @cindex running VxWorks tasks
13177 You can also attach to an existing task using the @code{attach} command as
13181 (vxgdb) attach @var{task}
13185 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
13186 or suspended when you attach to it. Running tasks are suspended at
13187 the time of attachment.
13189 @node Embedded Processors
13190 @section Embedded Processors
13192 This section goes into details specific to particular embedded
13198 * H8/300:: Renesas H8/300
13199 * H8/500:: Renesas H8/500
13200 * M32R/D:: Renesas M32R/D
13201 * M68K:: Motorola M68K
13202 * MIPS Embedded:: MIPS Embedded
13203 * OpenRISC 1000:: OpenRisc 1000
13204 * PA:: HP PA Embedded
13207 * Sparclet:: Tsqware Sparclet
13208 * Sparclite:: Fujitsu Sparclite
13209 * ST2000:: Tandem ST2000
13210 * Z8000:: Zilog Z8000
13219 @item target rdi @var{dev}
13220 ARM Angel monitor, via RDI library interface to ADP protocol. You may
13221 use this target to communicate with both boards running the Angel
13222 monitor, or with the EmbeddedICE JTAG debug device.
13225 @item target rdp @var{dev}
13231 @subsection Renesas H8/300
13235 @kindex target hms@r{, with H8/300}
13236 @item target hms @var{dev}
13237 A Renesas SH, H8/300, or H8/500 board, attached via serial line to your host.
13238 Use special commands @code{device} and @code{speed} to control the serial
13239 line and the communications speed used.
13241 @kindex target e7000@r{, with H8/300}
13242 @item target e7000 @var{dev}
13243 E7000 emulator for Renesas H8 and SH.
13245 @kindex target sh3@r{, with H8/300}
13246 @kindex target sh3e@r{, with H8/300}
13247 @item target sh3 @var{dev}
13248 @itemx target sh3e @var{dev}
13249 Renesas SH-3 and SH-3E target systems.
13253 @cindex download to H8/300 or H8/500
13254 @cindex H8/300 or H8/500 download
13255 @cindex download to Renesas SH
13256 @cindex Renesas SH download
13257 When you select remote debugging to a Renesas SH, H8/300, or H8/500
13258 board, the @code{load} command downloads your program to the Renesas
13259 board and also opens it as the current executable target for
13260 @value{GDBN} on your host (like the @code{file} command).
13262 @value{GDBN} needs to know these things to talk to your
13263 Renesas SH, H8/300, or H8/500:
13267 that you want to use @samp{target hms}, the remote debugging interface
13268 for Renesas microprocessors, or @samp{target e7000}, the in-circuit
13269 emulator for the Renesas SH and the Renesas 300H. (@samp{target hms} is
13270 the default when @value{GDBN} is configured specifically for the Renesas SH,
13271 H8/300, or H8/500.)
13274 what serial device connects your host to your Renesas board (the first
13275 serial device available on your host is the default).
13278 what speed to use over the serial device.
13282 * Renesas Boards:: Connecting to Renesas boards.
13283 * Renesas ICE:: Using the E7000 In-Circuit Emulator.
13284 * Renesas Special:: Special @value{GDBN} commands for Renesas micros.
13287 @node Renesas Boards
13288 @subsubsection Connecting to Renesas boards
13290 @c only for Unix hosts
13292 @cindex serial device, Renesas micros
13293 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
13294 need to explicitly set the serial device. The default @var{port} is the
13295 first available port on your host. This is only necessary on Unix
13296 hosts, where it is typically something like @file{/dev/ttya}.
13299 @cindex serial line speed, Renesas micros
13300 @code{@value{GDBN}} has another special command to set the communications
13301 speed: @samp{speed @var{bps}}. This command also is only used from Unix
13302 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
13303 the DOS @code{mode} command (for instance,
13304 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
13306 The @samp{device} and @samp{speed} commands are available only when you
13307 use a Unix host to debug your Renesas microprocessor programs. If you
13309 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
13310 called @code{asynctsr} to communicate with the development board
13311 through a PC serial port. You must also use the DOS @code{mode} command
13312 to set up the serial port on the DOS side.
13314 The following sample session illustrates the steps needed to start a
13315 program under @value{GDBN} control on an H8/300. The example uses a
13316 sample H8/300 program called @file{t.x}. The procedure is the same for
13317 the Renesas SH and the H8/500.
13319 First hook up your development board. In this example, we use a
13320 board attached to serial port @code{COM2}; if you use a different serial
13321 port, substitute its name in the argument of the @code{mode} command.
13322 When you call @code{asynctsr}, the auxiliary comms program used by the
13323 debugger, you give it just the numeric part of the serial port's name;
13324 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
13328 C:\H8300\TEST> asynctsr 2
13329 C:\H8300\TEST> mode com2:9600,n,8,1,p
13331 Resident portion of MODE loaded
13333 COM2: 9600, n, 8, 1, p
13338 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
13339 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
13340 disable it, or even boot without it, to use @code{asynctsr} to control
13341 your development board.
13344 @kindex target hms@r{, and serial protocol}
13345 Now that serial communications are set up, and the development board is
13346 connected, you can start up @value{GDBN}. Call @code{@value{GDBN}} with
13347 the name of your program as the argument. @code{@value{GDBN}} prompts
13348 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
13349 commands to begin your debugging session: @samp{target hms} to specify
13350 cross-debugging to the Renesas board, and the @code{load} command to
13351 download your program to the board. @code{load} displays the names of
13352 the program's sections, and a @samp{*} for each 2K of data downloaded.
13353 (If you want to refresh @value{GDBN} data on symbols or on the
13354 executable file without downloading, use the @value{GDBN} commands
13355 @code{file} or @code{symbol-file}. These commands, and @code{load}
13356 itself, are described in @ref{Files,,Commands to specify files}.)
13359 (eg-C:\H8300\TEST) @value{GDBP} t.x
13360 @value{GDBN} is free software and you are welcome to distribute copies
13361 of it under certain conditions; type "show copying" to see
13363 There is absolutely no warranty for @value{GDBN}; type "show warranty"
13365 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
13366 (@value{GDBP}) target hms
13367 Connected to remote H8/300 HMS system.
13368 (@value{GDBP}) load t.x
13369 .text : 0x8000 .. 0xabde ***********
13370 .data : 0xabde .. 0xad30 *
13371 .stack : 0xf000 .. 0xf014 *
13374 At this point, you're ready to run or debug your program. From here on,
13375 you can use all the usual @value{GDBN} commands. The @code{break} command
13376 sets breakpoints; the @code{run} command starts your program;
13377 @code{print} or @code{x} display data; the @code{continue} command
13378 resumes execution after stopping at a breakpoint. You can use the
13379 @code{help} command at any time to find out more about @value{GDBN} commands.
13381 Remember, however, that @emph{operating system} facilities aren't
13382 available on your development board; for example, if your program hangs,
13383 you can't send an interrupt---but you can press the @sc{reset} switch!
13385 Use the @sc{reset} button on the development board
13388 to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has
13389 no way to pass an interrupt signal to the development board); and
13392 to return to the @value{GDBN} command prompt after your program finishes
13393 normally. The communications protocol provides no other way for @value{GDBN}
13394 to detect program completion.
13397 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
13398 development board as a ``normal exit'' of your program.
13401 @subsubsection Using the E7000 in-circuit emulator
13403 @kindex target e7000@r{, with Renesas ICE}
13404 You can use the E7000 in-circuit emulator to develop code for either the
13405 Renesas SH or the H8/300H. Use one of these forms of the @samp{target
13406 e7000} command to connect @value{GDBN} to your E7000:
13409 @item target e7000 @var{port} @var{speed}
13410 Use this form if your E7000 is connected to a serial port. The
13411 @var{port} argument identifies what serial port to use (for example,
13412 @samp{com2}). The third argument is the line speed in bits per second
13413 (for example, @samp{9600}).
13415 @item target e7000 @var{hostname}
13416 If your E7000 is installed as a host on a TCP/IP network, you can just
13417 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
13420 @node Renesas Special
13421 @subsubsection Special @value{GDBN} commands for Renesas micros
13423 Some @value{GDBN} commands are available only for the H8/300:
13427 @kindex set machine
13428 @kindex show machine
13429 @item set machine h8300
13430 @itemx set machine h8300h
13431 Condition @value{GDBN} for one of the two variants of the H8/300
13432 architecture with @samp{set machine}. You can use @samp{show machine}
13433 to check which variant is currently in effect.
13442 @kindex set memory @var{mod}
13443 @cindex memory models, H8/500
13444 @item set memory @var{mod}
13446 Specify which H8/500 memory model (@var{mod}) you are using with
13447 @samp{set memory}; check which memory model is in effect with @samp{show
13448 memory}. The accepted values for @var{mod} are @code{small},
13449 @code{big}, @code{medium}, and @code{compact}.
13454 @subsection Renesas M32R/D
13458 @kindex target m32r
13459 @item target m32r @var{dev}
13460 Renesas M32R/D ROM monitor.
13462 @kindex target m32rsdi
13463 @item target m32rsdi @var{dev}
13464 Renesas M32R SDI server, connected via parallel port to the board.
13471 The Motorola m68k configuration includes ColdFire support, and
13472 target command for the following ROM monitors.
13476 @kindex target abug
13477 @item target abug @var{dev}
13478 ABug ROM monitor for M68K.
13480 @kindex target cpu32bug
13481 @item target cpu32bug @var{dev}
13482 CPU32BUG monitor, running on a CPU32 (M68K) board.
13484 @kindex target dbug
13485 @item target dbug @var{dev}
13486 dBUG ROM monitor for Motorola ColdFire.
13489 @item target est @var{dev}
13490 EST-300 ICE monitor, running on a CPU32 (M68K) board.
13492 @kindex target rom68k
13493 @item target rom68k @var{dev}
13494 ROM 68K monitor, running on an M68K IDP board.
13500 @kindex target rombug
13501 @item target rombug @var{dev}
13502 ROMBUG ROM monitor for OS/9000.
13506 @node MIPS Embedded
13507 @subsection MIPS Embedded
13509 @cindex MIPS boards
13510 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
13511 MIPS board attached to a serial line. This is available when
13512 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
13515 Use these @value{GDBN} commands to specify the connection to your target board:
13518 @item target mips @var{port}
13519 @kindex target mips @var{port}
13520 To run a program on the board, start up @code{@value{GDBP}} with the
13521 name of your program as the argument. To connect to the board, use the
13522 command @samp{target mips @var{port}}, where @var{port} is the name of
13523 the serial port connected to the board. If the program has not already
13524 been downloaded to the board, you may use the @code{load} command to
13525 download it. You can then use all the usual @value{GDBN} commands.
13527 For example, this sequence connects to the target board through a serial
13528 port, and loads and runs a program called @var{prog} through the
13532 host$ @value{GDBP} @var{prog}
13533 @value{GDBN} is free software and @dots{}
13534 (@value{GDBP}) target mips /dev/ttyb
13535 (@value{GDBP}) load @var{prog}
13539 @item target mips @var{hostname}:@var{portnumber}
13540 On some @value{GDBN} host configurations, you can specify a TCP
13541 connection (for instance, to a serial line managed by a terminal
13542 concentrator) instead of a serial port, using the syntax
13543 @samp{@var{hostname}:@var{portnumber}}.
13545 @item target pmon @var{port}
13546 @kindex target pmon @var{port}
13549 @item target ddb @var{port}
13550 @kindex target ddb @var{port}
13551 NEC's DDB variant of PMON for Vr4300.
13553 @item target lsi @var{port}
13554 @kindex target lsi @var{port}
13555 LSI variant of PMON.
13557 @kindex target r3900
13558 @item target r3900 @var{dev}
13559 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
13561 @kindex target array
13562 @item target array @var{dev}
13563 Array Tech LSI33K RAID controller board.
13569 @value{GDBN} also supports these special commands for MIPS targets:
13572 @item set mipsfpu double
13573 @itemx set mipsfpu single
13574 @itemx set mipsfpu none
13575 @itemx show mipsfpu
13576 @kindex set mipsfpu
13577 @kindex show mipsfpu
13578 @cindex MIPS remote floating point
13579 @cindex floating point, MIPS remote
13580 If your target board does not support the MIPS floating point
13581 coprocessor, you should use the command @samp{set mipsfpu none} (if you
13582 need this, you may wish to put the command in your @value{GDBN} init
13583 file). This tells @value{GDBN} how to find the return value of
13584 functions which return floating point values. It also allows
13585 @value{GDBN} to avoid saving the floating point registers when calling
13586 functions on the board. If you are using a floating point coprocessor
13587 with only single precision floating point support, as on the @sc{r4650}
13588 processor, use the command @samp{set mipsfpu single}. The default
13589 double precision floating point coprocessor may be selected using
13590 @samp{set mipsfpu double}.
13592 In previous versions the only choices were double precision or no
13593 floating point, so @samp{set mipsfpu on} will select double precision
13594 and @samp{set mipsfpu off} will select no floating point.
13596 As usual, you can inquire about the @code{mipsfpu} variable with
13597 @samp{show mipsfpu}.
13599 @item set timeout @var{seconds}
13600 @itemx set retransmit-timeout @var{seconds}
13601 @itemx show timeout
13602 @itemx show retransmit-timeout
13603 @cindex @code{timeout}, MIPS protocol
13604 @cindex @code{retransmit-timeout}, MIPS protocol
13605 @kindex set timeout
13606 @kindex show timeout
13607 @kindex set retransmit-timeout
13608 @kindex show retransmit-timeout
13609 You can control the timeout used while waiting for a packet, in the MIPS
13610 remote protocol, with the @code{set timeout @var{seconds}} command. The
13611 default is 5 seconds. Similarly, you can control the timeout used while
13612 waiting for an acknowledgement of a packet with the @code{set
13613 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
13614 You can inspect both values with @code{show timeout} and @code{show
13615 retransmit-timeout}. (These commands are @emph{only} available when
13616 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
13618 The timeout set by @code{set timeout} does not apply when @value{GDBN}
13619 is waiting for your program to stop. In that case, @value{GDBN} waits
13620 forever because it has no way of knowing how long the program is going
13621 to run before stopping.
13624 @node OpenRISC 1000
13625 @subsection OpenRISC 1000
13626 @cindex OpenRISC 1000
13628 @cindex or1k boards
13629 See OR1k Architecture document (@uref{www.opencores.org}) for more information
13630 about platform and commands.
13634 @kindex target jtag
13635 @item target jtag jtag://@var{host}:@var{port}
13637 Connects to remote JTAG server.
13638 JTAG remote server can be either an or1ksim or JTAG server,
13639 connected via parallel port to the board.
13641 Example: @code{target jtag jtag://localhost:9999}
13644 @item or1ksim @var{command}
13645 If connected to @code{or1ksim} OpenRISC 1000 Architectural
13646 Simulator, proprietary commands can be executed.
13648 @kindex info or1k spr
13649 @item info or1k spr
13650 Displays spr groups.
13652 @item info or1k spr @var{group}
13653 @itemx info or1k spr @var{groupno}
13654 Displays register names in selected group.
13656 @item info or1k spr @var{group} @var{register}
13657 @itemx info or1k spr @var{register}
13658 @itemx info or1k spr @var{groupno} @var{registerno}
13659 @itemx info or1k spr @var{registerno}
13660 Shows information about specified spr register.
13663 @item spr @var{group} @var{register} @var{value}
13664 @itemx spr @var{register @var{value}}
13665 @itemx spr @var{groupno} @var{registerno @var{value}}
13666 @itemx spr @var{registerno @var{value}}
13667 Writes @var{value} to specified spr register.
13670 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
13671 It is very similar to @value{GDBN} trace, except it does not interfere with normal
13672 program execution and is thus much faster. Hardware breakpoints/watchpoint
13673 triggers can be set using:
13676 Load effective address/data
13678 Store effective address/data
13680 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
13685 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
13686 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
13688 @code{htrace} commands:
13689 @cindex OpenRISC 1000 htrace
13692 @item hwatch @var{conditional}
13693 Set hardware watchpoint on combination of Load/Store Effecive Address(es)
13694 or Data. For example:
13696 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
13698 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
13702 Display information about current HW trace configuration.
13704 @item htrace trigger @var{conditional}
13705 Set starting criteria for HW trace.
13707 @item htrace qualifier @var{conditional}
13708 Set acquisition qualifier for HW trace.
13710 @item htrace stop @var{conditional}
13711 Set HW trace stopping criteria.
13713 @item htrace record [@var{data}]*
13714 Selects the data to be recorded, when qualifier is met and HW trace was
13717 @item htrace enable
13718 @itemx htrace disable
13719 Enables/disables the HW trace.
13721 @item htrace rewind [@var{filename}]
13722 Clears currently recorded trace data.
13724 If filename is specified, new trace file is made and any newly collected data
13725 will be written there.
13727 @item htrace print [@var{start} [@var{len}]]
13728 Prints trace buffer, using current record configuration.
13730 @item htrace mode continuous
13731 Set continuous trace mode.
13733 @item htrace mode suspend
13734 Set suspend trace mode.
13739 @subsection PowerPC
13743 @kindex target dink32
13744 @item target dink32 @var{dev}
13745 DINK32 ROM monitor.
13747 @kindex target ppcbug
13748 @item target ppcbug @var{dev}
13749 @kindex target ppcbug1
13750 @item target ppcbug1 @var{dev}
13751 PPCBUG ROM monitor for PowerPC.
13754 @item target sds @var{dev}
13755 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
13760 @subsection HP PA Embedded
13764 @kindex target op50n
13765 @item target op50n @var{dev}
13766 OP50N monitor, running on an OKI HPPA board.
13768 @kindex target w89k
13769 @item target w89k @var{dev}
13770 W89K monitor, running on a Winbond HPPA board.
13775 @subsection Renesas SH
13779 @kindex target hms@r{, with Renesas SH}
13780 @item target hms @var{dev}
13781 A Renesas SH board attached via serial line to your host. Use special
13782 commands @code{device} and @code{speed} to control the serial line and
13783 the communications speed used.
13785 @kindex target e7000@r{, with Renesas SH}
13786 @item target e7000 @var{dev}
13787 E7000 emulator for Renesas SH.
13789 @kindex target sh3@r{, with SH}
13790 @kindex target sh3e@r{, with SH}
13791 @item target sh3 @var{dev}
13792 @item target sh3e @var{dev}
13793 Renesas SH-3 and SH-3E target systems.
13798 @subsection Tsqware Sparclet
13802 @value{GDBN} enables developers to debug tasks running on
13803 Sparclet targets from a Unix host.
13804 @value{GDBN} uses code that runs on
13805 both the Unix host and on the Sparclet target. The program
13806 @code{@value{GDBP}} is installed and executed on the Unix host.
13809 @item remotetimeout @var{args}
13810 @kindex remotetimeout
13811 @value{GDBN} supports the option @code{remotetimeout}.
13812 This option is set by the user, and @var{args} represents the number of
13813 seconds @value{GDBN} waits for responses.
13816 @cindex compiling, on Sparclet
13817 When compiling for debugging, include the options @samp{-g} to get debug
13818 information and @samp{-Ttext} to relocate the program to where you wish to
13819 load it on the target. You may also want to add the options @samp{-n} or
13820 @samp{-N} in order to reduce the size of the sections. Example:
13823 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
13826 You can use @code{objdump} to verify that the addresses are what you intended:
13829 sparclet-aout-objdump --headers --syms prog
13832 @cindex running, on Sparclet
13834 your Unix execution search path to find @value{GDBN}, you are ready to
13835 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
13836 (or @code{sparclet-aout-gdb}, depending on your installation).
13838 @value{GDBN} comes up showing the prompt:
13845 * Sparclet File:: Setting the file to debug
13846 * Sparclet Connection:: Connecting to Sparclet
13847 * Sparclet Download:: Sparclet download
13848 * Sparclet Execution:: Running and debugging
13851 @node Sparclet File
13852 @subsubsection Setting file to debug
13854 The @value{GDBN} command @code{file} lets you choose with program to debug.
13857 (gdbslet) file prog
13861 @value{GDBN} then attempts to read the symbol table of @file{prog}.
13862 @value{GDBN} locates
13863 the file by searching the directories listed in the command search
13865 If the file was compiled with debug information (option "-g"), source
13866 files will be searched as well.
13867 @value{GDBN} locates
13868 the source files by searching the directories listed in the directory search
13869 path (@pxref{Environment, ,Your program's environment}).
13871 to find a file, it displays a message such as:
13874 prog: No such file or directory.
13877 When this happens, add the appropriate directories to the search paths with
13878 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
13879 @code{target} command again.
13881 @node Sparclet Connection
13882 @subsubsection Connecting to Sparclet
13884 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
13885 To connect to a target on serial port ``@code{ttya}'', type:
13888 (gdbslet) target sparclet /dev/ttya
13889 Remote target sparclet connected to /dev/ttya
13890 main () at ../prog.c:3
13894 @value{GDBN} displays messages like these:
13900 @node Sparclet Download
13901 @subsubsection Sparclet download
13903 @cindex download to Sparclet
13904 Once connected to the Sparclet target,
13905 you can use the @value{GDBN}
13906 @code{load} command to download the file from the host to the target.
13907 The file name and load offset should be given as arguments to the @code{load}
13909 Since the file format is aout, the program must be loaded to the starting
13910 address. You can use @code{objdump} to find out what this value is. The load
13911 offset is an offset which is added to the VMA (virtual memory address)
13912 of each of the file's sections.
13913 For instance, if the program
13914 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
13915 and bss at 0x12010170, in @value{GDBN}, type:
13918 (gdbslet) load prog 0x12010000
13919 Loading section .text, size 0xdb0 vma 0x12010000
13922 If the code is loaded at a different address then what the program was linked
13923 to, you may need to use the @code{section} and @code{add-symbol-file} commands
13924 to tell @value{GDBN} where to map the symbol table.
13926 @node Sparclet Execution
13927 @subsubsection Running and debugging
13929 @cindex running and debugging Sparclet programs
13930 You can now begin debugging the task using @value{GDBN}'s execution control
13931 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
13932 manual for the list of commands.
13936 Breakpoint 1 at 0x12010000: file prog.c, line 3.
13938 Starting program: prog
13939 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
13940 3 char *symarg = 0;
13942 4 char *execarg = "hello!";
13947 @subsection Fujitsu Sparclite
13951 @kindex target sparclite
13952 @item target sparclite @var{dev}
13953 Fujitsu sparclite boards, used only for the purpose of loading.
13954 You must use an additional command to debug the program.
13955 For example: target remote @var{dev} using @value{GDBN} standard
13961 @subsection Tandem ST2000
13963 @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
13966 To connect your ST2000 to the host system, see the manufacturer's
13967 manual. Once the ST2000 is physically attached, you can run:
13970 target st2000 @var{dev} @var{speed}
13974 to establish it as your debugging environment. @var{dev} is normally
13975 the name of a serial device, such as @file{/dev/ttya}, connected to the
13976 ST2000 via a serial line. You can instead specify @var{dev} as a TCP
13977 connection (for example, to a serial line attached via a terminal
13978 concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
13980 The @code{load} and @code{attach} commands are @emph{not} defined for
13981 this target; you must load your program into the ST2000 as you normally
13982 would for standalone operation. @value{GDBN} reads debugging information
13983 (such as symbols) from a separate, debugging version of the program
13984 available on your host computer.
13985 @c FIXME!! This is terribly vague; what little content is here is
13986 @c basically hearsay.
13988 @cindex ST2000 auxiliary commands
13989 These auxiliary @value{GDBN} commands are available to help you with the ST2000
13993 @item st2000 @var{command}
13994 @kindex st2000 @var{cmd}
13995 @cindex STDBUG commands (ST2000)
13996 @cindex commands to STDBUG (ST2000)
13997 Send a @var{command} to the STDBUG monitor. See the manufacturer's
13998 manual for available commands.
14001 @cindex connect (to STDBUG)
14002 Connect the controlling terminal to the STDBUG command monitor. When
14003 you are done interacting with STDBUG, typing either of two character
14004 sequences gets you back to the @value{GDBN} command prompt:
14005 @kbd{@key{RET}~.} (Return, followed by tilde and period) or
14006 @kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D).
14010 @subsection Zilog Z8000
14013 @cindex simulator, Z8000
14014 @cindex Zilog Z8000 simulator
14016 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
14019 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
14020 unsegmented variant of the Z8000 architecture) or the Z8001 (the
14021 segmented variant). The simulator recognizes which architecture is
14022 appropriate by inspecting the object code.
14025 @item target sim @var{args}
14027 @kindex target sim@r{, with Z8000}
14028 Debug programs on a simulated CPU. If the simulator supports setup
14029 options, specify them via @var{args}.
14033 After specifying this target, you can debug programs for the simulated
14034 CPU in the same style as programs for your host computer; use the
14035 @code{file} command to load a new program image, the @code{run} command
14036 to run your program, and so on.
14038 As well as making available all the usual machine registers
14039 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
14040 additional items of information as specially named registers:
14045 Counts clock-ticks in the simulator.
14048 Counts instructions run in the simulator.
14051 Execution time in 60ths of a second.
14055 You can refer to these values in @value{GDBN} expressions with the usual
14056 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
14057 conditional breakpoint that suspends only after at least 5000
14058 simulated clock ticks.
14060 @node Architectures
14061 @section Architectures
14063 This section describes characteristics of architectures that affect
14064 all uses of @value{GDBN} with the architecture, both native and cross.
14074 @subsection x86 Architecture-specific issues.
14077 @item set struct-convention @var{mode}
14078 @kindex set struct-convention
14079 @cindex struct return convention
14080 @cindex struct/union returned in registers
14081 Set the convention used by the inferior to return @code{struct}s and
14082 @code{union}s from functions to @var{mode}. Possible values of
14083 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
14084 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
14085 are returned on the stack, while @code{"reg"} means that a
14086 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
14087 be returned in a register.
14089 @item show struct-convention
14090 @kindex show struct-convention
14091 Show the current setting of the convention to return @code{struct}s
14100 @kindex set rstack_high_address
14101 @cindex AMD 29K register stack
14102 @cindex register stack, AMD29K
14103 @item set rstack_high_address @var{address}
14104 On AMD 29000 family processors, registers are saved in a separate
14105 @dfn{register stack}. There is no way for @value{GDBN} to determine the
14106 extent of this stack. Normally, @value{GDBN} just assumes that the
14107 stack is ``large enough''. This may result in @value{GDBN} referencing
14108 memory locations that do not exist. If necessary, you can get around
14109 this problem by specifying the ending address of the register stack with
14110 the @code{set rstack_high_address} command. The argument should be an
14111 address, which you probably want to precede with @samp{0x} to specify in
14114 @kindex show rstack_high_address
14115 @item show rstack_high_address
14116 Display the current limit of the register stack, on AMD 29000 family
14124 See the following section.
14129 @cindex stack on Alpha
14130 @cindex stack on MIPS
14131 @cindex Alpha stack
14133 Alpha- and MIPS-based computers use an unusual stack frame, which
14134 sometimes requires @value{GDBN} to search backward in the object code to
14135 find the beginning of a function.
14137 @cindex response time, MIPS debugging
14138 To improve response time (especially for embedded applications, where
14139 @value{GDBN} may be restricted to a slow serial line for this search)
14140 you may want to limit the size of this search, using one of these
14144 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
14145 @item set heuristic-fence-post @var{limit}
14146 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
14147 search for the beginning of a function. A value of @var{0} (the
14148 default) means there is no limit. However, except for @var{0}, the
14149 larger the limit the more bytes @code{heuristic-fence-post} must search
14150 and therefore the longer it takes to run.
14152 @item show heuristic-fence-post
14153 Display the current limit.
14157 These commands are available @emph{only} when @value{GDBN} is configured
14158 for debugging programs on Alpha or MIPS processors.
14161 @node Controlling GDB
14162 @chapter Controlling @value{GDBN}
14164 You can alter the way @value{GDBN} interacts with you by using the
14165 @code{set} command. For commands controlling how @value{GDBN} displays
14166 data, see @ref{Print Settings, ,Print settings}. Other settings are
14171 * Editing:: Command editing
14172 * History:: Command history
14173 * Screen Size:: Screen size
14174 * Numbers:: Numbers
14175 * ABI:: Configuring the current ABI
14176 * Messages/Warnings:: Optional warnings and messages
14177 * Debugging Output:: Optional messages about internal happenings
14185 @value{GDBN} indicates its readiness to read a command by printing a string
14186 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
14187 can change the prompt string with the @code{set prompt} command. For
14188 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
14189 the prompt in one of the @value{GDBN} sessions so that you can always tell
14190 which one you are talking to.
14192 @emph{Note:} @code{set prompt} does not add a space for you after the
14193 prompt you set. This allows you to set a prompt which ends in a space
14194 or a prompt that does not.
14198 @item set prompt @var{newprompt}
14199 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
14201 @kindex show prompt
14203 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
14207 @section Command editing
14209 @cindex command line editing
14211 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
14212 @sc{gnu} library provides consistent behavior for programs which provide a
14213 command line interface to the user. Advantages are @sc{gnu} Emacs-style
14214 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
14215 substitution, and a storage and recall of command history across
14216 debugging sessions.
14218 You may control the behavior of command line editing in @value{GDBN} with the
14219 command @code{set}.
14222 @kindex set editing
14225 @itemx set editing on
14226 Enable command line editing (enabled by default).
14228 @item set editing off
14229 Disable command line editing.
14231 @kindex show editing
14233 Show whether command line editing is enabled.
14236 @xref{Command Line Editing}, for more details about the Readline
14237 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
14238 encouraged to read that chapter.
14241 @section Command history
14242 @cindex command history
14244 @value{GDBN} can keep track of the commands you type during your
14245 debugging sessions, so that you can be certain of precisely what
14246 happened. Use these commands to manage the @value{GDBN} command
14249 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
14250 package, to provide the history facility. @xref{Using History
14251 Interactively}, for the detailed description of the History library.
14253 Here is the description of @value{GDBN} commands related to command
14257 @cindex history substitution
14258 @cindex history file
14259 @kindex set history filename
14260 @cindex @env{GDBHISTFILE}, environment variable
14261 @item set history filename @var{fname}
14262 Set the name of the @value{GDBN} command history file to @var{fname}.
14263 This is the file where @value{GDBN} reads an initial command history
14264 list, and where it writes the command history from this session when it
14265 exits. You can access this list through history expansion or through
14266 the history command editing characters listed below. This file defaults
14267 to the value of the environment variable @code{GDBHISTFILE}, or to
14268 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
14271 @cindex save command history
14272 @kindex set history save
14273 @item set history save
14274 @itemx set history save on
14275 Record command history in a file, whose name may be specified with the
14276 @code{set history filename} command. By default, this option is disabled.
14278 @item set history save off
14279 Stop recording command history in a file.
14281 @cindex history size
14282 @kindex set history size
14283 @item set history size @var{size}
14284 Set the number of commands which @value{GDBN} keeps in its history list.
14285 This defaults to the value of the environment variable
14286 @code{HISTSIZE}, or to 256 if this variable is not set.
14289 History expansion assigns special meaning to the character @kbd{!}.
14290 @xref{Event Designators}, for more details.
14292 @cindex history expansion, turn on/off
14293 Since @kbd{!} is also the logical not operator in C, history expansion
14294 is off by default. If you decide to enable history expansion with the
14295 @code{set history expansion on} command, you may sometimes need to
14296 follow @kbd{!} (when it is used as logical not, in an expression) with
14297 a space or a tab to prevent it from being expanded. The readline
14298 history facilities do not attempt substitution on the strings
14299 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
14301 The commands to control history expansion are:
14304 @item set history expansion on
14305 @itemx set history expansion
14306 @kindex set history expansion
14307 Enable history expansion. History expansion is off by default.
14309 @item set history expansion off
14310 Disable history expansion.
14313 @kindex show history
14315 @itemx show history filename
14316 @itemx show history save
14317 @itemx show history size
14318 @itemx show history expansion
14319 These commands display the state of the @value{GDBN} history parameters.
14320 @code{show history} by itself displays all four states.
14325 @kindex show commands
14326 @cindex show last commands
14327 @cindex display command history
14328 @item show commands
14329 Display the last ten commands in the command history.
14331 @item show commands @var{n}
14332 Print ten commands centered on command number @var{n}.
14334 @item show commands +
14335 Print ten commands just after the commands last printed.
14339 @section Screen size
14340 @cindex size of screen
14341 @cindex pauses in output
14343 Certain commands to @value{GDBN} may produce large amounts of
14344 information output to the screen. To help you read all of it,
14345 @value{GDBN} pauses and asks you for input at the end of each page of
14346 output. Type @key{RET} when you want to continue the output, or @kbd{q}
14347 to discard the remaining output. Also, the screen width setting
14348 determines when to wrap lines of output. Depending on what is being
14349 printed, @value{GDBN} tries to break the line at a readable place,
14350 rather than simply letting it overflow onto the following line.
14352 Normally @value{GDBN} knows the size of the screen from the terminal
14353 driver software. For example, on Unix @value{GDBN} uses the termcap data base
14354 together with the value of the @code{TERM} environment variable and the
14355 @code{stty rows} and @code{stty cols} settings. If this is not correct,
14356 you can override it with the @code{set height} and @code{set
14363 @kindex show height
14364 @item set height @var{lpp}
14366 @itemx set width @var{cpl}
14368 These @code{set} commands specify a screen height of @var{lpp} lines and
14369 a screen width of @var{cpl} characters. The associated @code{show}
14370 commands display the current settings.
14372 If you specify a height of zero lines, @value{GDBN} does not pause during
14373 output no matter how long the output is. This is useful if output is to a
14374 file or to an editor buffer.
14376 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
14377 from wrapping its output.
14379 @item set pagination on
14380 @itemx set pagination off
14381 @kindex set pagination
14382 Turn the output pagination on or off; the default is on. Turning
14383 pagination off is the alternative to @code{set height 0}.
14385 @item show pagination
14386 @kindex show pagination
14387 Show the current pagination mode.
14392 @cindex number representation
14393 @cindex entering numbers
14395 You can always enter numbers in octal, decimal, or hexadecimal in
14396 @value{GDBN} by the usual conventions: octal numbers begin with
14397 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
14398 begin with @samp{0x}. Numbers that begin with none of these are, by
14399 default, entered in base 10; likewise, the default display for
14400 numbers---when no particular format is specified---is base 10. You can
14401 change the default base for both input and output with the @code{set
14405 @kindex set input-radix
14406 @item set input-radix @var{base}
14407 Set the default base for numeric input. Supported choices
14408 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
14409 specified either unambiguously or using the current default radix; for
14413 set input-radix 012
14414 set input-radix 10.
14415 set input-radix 0xa
14419 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
14420 leaves the input radix unchanged, no matter what it was.
14422 @kindex set output-radix
14423 @item set output-radix @var{base}
14424 Set the default base for numeric display. Supported choices
14425 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
14426 specified either unambiguously or using the current default radix.
14428 @kindex show input-radix
14429 @item show input-radix
14430 Display the current default base for numeric input.
14432 @kindex show output-radix
14433 @item show output-radix
14434 Display the current default base for numeric display.
14436 @item set radix @r{[}@var{base}@r{]}
14440 These commands set and show the default base for both input and output
14441 of numbers. @code{set radix} sets the radix of input and output to
14442 the same base; without an argument, it resets the radix back to its
14443 default value of 10.
14448 @section Configuring the current ABI
14450 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
14451 application automatically. However, sometimes you need to override its
14452 conclusions. Use these commands to manage @value{GDBN}'s view of the
14459 One @value{GDBN} configuration can debug binaries for multiple operating
14460 system targets, either via remote debugging or native emulation.
14461 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
14462 but you can override its conclusion using the @code{set osabi} command.
14463 One example where this is useful is in debugging of binaries which use
14464 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
14465 not have the same identifying marks that the standard C library for your
14470 Show the OS ABI currently in use.
14473 With no argument, show the list of registered available OS ABI's.
14475 @item set osabi @var{abi}
14476 Set the current OS ABI to @var{abi}.
14479 @cindex float promotion
14481 Generally, the way that an argument of type @code{float} is passed to a
14482 function depends on whether the function is prototyped. For a prototyped
14483 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
14484 according to the architecture's convention for @code{float}. For unprototyped
14485 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
14486 @code{double} and then passed.
14488 Unfortunately, some forms of debug information do not reliably indicate whether
14489 a function is prototyped. If @value{GDBN} calls a function that is not marked
14490 as prototyped, it consults @kbd{set coerce-float-to-double}.
14493 @kindex set coerce-float-to-double
14494 @item set coerce-float-to-double
14495 @itemx set coerce-float-to-double on
14496 Arguments of type @code{float} will be promoted to @code{double} when passed
14497 to an unprototyped function. This is the default setting.
14499 @item set coerce-float-to-double off
14500 Arguments of type @code{float} will be passed directly to unprototyped
14503 @kindex show coerce-float-to-double
14504 @item show coerce-float-to-double
14505 Show the current setting of promoting @code{float} to @code{double}.
14509 @kindex show cp-abi
14510 @value{GDBN} needs to know the ABI used for your program's C@t{++}
14511 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
14512 used to build your application. @value{GDBN} only fully supports
14513 programs with a single C@t{++} ABI; if your program contains code using
14514 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
14515 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
14516 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
14517 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
14518 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
14519 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
14524 Show the C@t{++} ABI currently in use.
14527 With no argument, show the list of supported C@t{++} ABI's.
14529 @item set cp-abi @var{abi}
14530 @itemx set cp-abi auto
14531 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
14534 @node Messages/Warnings
14535 @section Optional warnings and messages
14537 @cindex verbose operation
14538 @cindex optional warnings
14539 By default, @value{GDBN} is silent about its inner workings. If you are
14540 running on a slow machine, you may want to use the @code{set verbose}
14541 command. This makes @value{GDBN} tell you when it does a lengthy
14542 internal operation, so you will not think it has crashed.
14544 Currently, the messages controlled by @code{set verbose} are those
14545 which announce that the symbol table for a source file is being read;
14546 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
14549 @kindex set verbose
14550 @item set verbose on
14551 Enables @value{GDBN} output of certain informational messages.
14553 @item set verbose off
14554 Disables @value{GDBN} output of certain informational messages.
14556 @kindex show verbose
14558 Displays whether @code{set verbose} is on or off.
14561 By default, if @value{GDBN} encounters bugs in the symbol table of an
14562 object file, it is silent; but if you are debugging a compiler, you may
14563 find this information useful (@pxref{Symbol Errors, ,Errors reading
14568 @kindex set complaints
14569 @item set complaints @var{limit}
14570 Permits @value{GDBN} to output @var{limit} complaints about each type of
14571 unusual symbols before becoming silent about the problem. Set
14572 @var{limit} to zero to suppress all complaints; set it to a large number
14573 to prevent complaints from being suppressed.
14575 @kindex show complaints
14576 @item show complaints
14577 Displays how many symbol complaints @value{GDBN} is permitted to produce.
14581 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
14582 lot of stupid questions to confirm certain commands. For example, if
14583 you try to run a program which is already running:
14587 The program being debugged has been started already.
14588 Start it from the beginning? (y or n)
14591 If you are willing to unflinchingly face the consequences of your own
14592 commands, you can disable this ``feature'':
14596 @kindex set confirm
14598 @cindex confirmation
14599 @cindex stupid questions
14600 @item set confirm off
14601 Disables confirmation requests.
14603 @item set confirm on
14604 Enables confirmation requests (the default).
14606 @kindex show confirm
14608 Displays state of confirmation requests.
14612 @node Debugging Output
14613 @section Optional messages about internal happenings
14614 @cindex optional debugging messages
14617 @kindex set exec-done-display
14618 @item set exec-done-display
14619 Turns on or off the notification of asynchronous commands'
14620 completion. When on, @value{GDBN} will print a message when an
14621 asynchronous command finishes its execution. The default is off.
14622 @kindex show exec-done-display
14623 @item show exec-done-display
14624 Displays the current setting of asynchronous command completion
14627 @cindex gdbarch debugging info
14628 @cindex architecture debugging info
14629 @item set debug arch
14630 Turns on or off display of gdbarch debugging info. The default is off
14632 @item show debug arch
14633 Displays the current state of displaying gdbarch debugging info.
14634 @item set debug event
14635 @cindex event debugging info
14636 Turns on or off display of @value{GDBN} event debugging info. The
14638 @item show debug event
14639 Displays the current state of displaying @value{GDBN} event debugging
14641 @item set debug expression
14642 @cindex expression debugging info
14643 Turns on or off display of @value{GDBN} expression debugging info. The
14645 @item show debug expression
14646 Displays the current state of displaying @value{GDBN} expression
14648 @item set debug frame
14649 @cindex frame debugging info
14650 Turns on or off display of @value{GDBN} frame debugging info. The
14652 @item show debug frame
14653 Displays the current state of displaying @value{GDBN} frame debugging
14655 @item set debug infrun
14656 @cindex inferior debugging info
14657 Turns on or off display of @value{GDBN} debugging info for running the inferior.
14658 The default is off. @file{infrun.c} contains GDB's runtime state machine used
14659 for implementing operations such as single-stepping the inferior.
14660 @item show debug infrun
14661 Displays the current state of @value{GDBN} inferior debugging.
14662 @item set debug observer
14663 @cindex observer debugging info
14664 Turns on or off display of @value{GDBN} observer debugging. This
14665 includes info such as the notification of observable events.
14666 @item show debug observer
14667 Displays the current state of observer debugging.
14668 @item set debug overload
14669 @cindex C@t{++} overload debugging info
14670 Turns on or off display of @value{GDBN} C@t{++} overload debugging
14671 info. This includes info such as ranking of functions, etc. The default
14673 @item show debug overload
14674 Displays the current state of displaying @value{GDBN} C@t{++} overload
14676 @cindex packets, reporting on stdout
14677 @cindex serial connections, debugging
14678 @item set debug remote
14679 Turns on or off display of reports on all packets sent back and forth across
14680 the serial line to the remote machine. The info is printed on the
14681 @value{GDBN} standard output stream. The default is off.
14682 @item show debug remote
14683 Displays the state of display of remote packets.
14684 @item set debug serial
14685 Turns on or off display of @value{GDBN} serial debugging info. The
14687 @item show debug serial
14688 Displays the current state of displaying @value{GDBN} serial debugging
14690 @item set debug target
14691 @cindex target debugging info
14692 Turns on or off display of @value{GDBN} target debugging info. This info
14693 includes what is going on at the target level of GDB, as it happens. The
14694 default is 0. Set it to 1 to track events, and to 2 to also track the
14695 value of large memory transfers. Changes to this flag do not take effect
14696 until the next time you connect to a target or use the @code{run} command.
14697 @item show debug target
14698 Displays the current state of displaying @value{GDBN} target debugging
14700 @item set debug varobj
14701 @cindex variable object debugging info
14702 Turns on or off display of @value{GDBN} variable object debugging
14703 info. The default is off.
14704 @item show debug varobj
14705 Displays the current state of displaying @value{GDBN} variable object
14710 @chapter Canned Sequences of Commands
14712 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
14713 command lists}), @value{GDBN} provides two ways to store sequences of
14714 commands for execution as a unit: user-defined commands and command
14718 * Define:: User-defined commands
14719 * Hooks:: User-defined command hooks
14720 * Command Files:: Command files
14721 * Output:: Commands for controlled output
14725 @section User-defined commands
14727 @cindex user-defined command
14728 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
14729 which you assign a new name as a command. This is done with the
14730 @code{define} command. User commands may accept up to 10 arguments
14731 separated by whitespace. Arguments are accessed within the user command
14732 via @var{$arg0@dots{}$arg9}. A trivial example:
14736 print $arg0 + $arg1 + $arg2
14740 To execute the command use:
14747 This defines the command @code{adder}, which prints the sum of
14748 its three arguments. Note the arguments are text substitutions, so they may
14749 reference variables, use complex expressions, or even perform inferior
14755 @item define @var{commandname}
14756 Define a command named @var{commandname}. If there is already a command
14757 by that name, you are asked to confirm that you want to redefine it.
14759 The definition of the command is made up of other @value{GDBN} command lines,
14760 which are given following the @code{define} command. The end of these
14761 commands is marked by a line containing @code{end}.
14767 Takes a single argument, which is an expression to evaluate.
14768 It is followed by a series of commands that are executed
14769 only if the expression is true (nonzero).
14770 There can then optionally be a line @code{else}, followed
14771 by a series of commands that are only executed if the expression
14772 was false. The end of the list is marked by a line containing @code{end}.
14776 The syntax is similar to @code{if}: the command takes a single argument,
14777 which is an expression to evaluate, and must be followed by the commands to
14778 execute, one per line, terminated by an @code{end}.
14779 The commands are executed repeatedly as long as the expression
14783 @item document @var{commandname}
14784 Document the user-defined command @var{commandname}, so that it can be
14785 accessed by @code{help}. The command @var{commandname} must already be
14786 defined. This command reads lines of documentation just as @code{define}
14787 reads the lines of the command definition, ending with @code{end}.
14788 After the @code{document} command is finished, @code{help} on command
14789 @var{commandname} displays the documentation you have written.
14791 You may use the @code{document} command again to change the
14792 documentation of a command. Redefining the command with @code{define}
14793 does not change the documentation.
14795 @kindex help user-defined
14796 @item help user-defined
14797 List all user-defined commands, with the first line of the documentation
14802 @itemx show user @var{commandname}
14803 Display the @value{GDBN} commands used to define @var{commandname} (but
14804 not its documentation). If no @var{commandname} is given, display the
14805 definitions for all user-defined commands.
14807 @cindex infinite recusrion in user-defined commands
14808 @kindex show max-user-call-depth
14809 @kindex set max-user-call-depth
14810 @item show max-user-call-depth
14811 @itemx set max-user-call-depth
14812 The value of @code{max-user-call-depth} controls how many recursion
14813 levels are allowed in user-defined commands before GDB suspects an
14814 infinite recursion and aborts the command.
14818 When user-defined commands are executed, the
14819 commands of the definition are not printed. An error in any command
14820 stops execution of the user-defined command.
14822 If used interactively, commands that would ask for confirmation proceed
14823 without asking when used inside a user-defined command. Many @value{GDBN}
14824 commands that normally print messages to say what they are doing omit the
14825 messages when used in a user-defined command.
14828 @section User-defined command hooks
14829 @cindex command hooks
14830 @cindex hooks, for commands
14831 @cindex hooks, pre-command
14834 You may define @dfn{hooks}, which are a special kind of user-defined
14835 command. Whenever you run the command @samp{foo}, if the user-defined
14836 command @samp{hook-foo} exists, it is executed (with no arguments)
14837 before that command.
14839 @cindex hooks, post-command
14841 A hook may also be defined which is run after the command you executed.
14842 Whenever you run the command @samp{foo}, if the user-defined command
14843 @samp{hookpost-foo} exists, it is executed (with no arguments) after
14844 that command. Post-execution hooks may exist simultaneously with
14845 pre-execution hooks, for the same command.
14847 It is valid for a hook to call the command which it hooks. If this
14848 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
14850 @c It would be nice if hookpost could be passed a parameter indicating
14851 @c if the command it hooks executed properly or not. FIXME!
14853 @kindex stop@r{, a pseudo-command}
14854 In addition, a pseudo-command, @samp{stop} exists. Defining
14855 (@samp{hook-stop}) makes the associated commands execute every time
14856 execution stops in your program: before breakpoint commands are run,
14857 displays are printed, or the stack frame is printed.
14859 For example, to ignore @code{SIGALRM} signals while
14860 single-stepping, but treat them normally during normal execution,
14865 handle SIGALRM nopass
14869 handle SIGALRM pass
14872 define hook-continue
14873 handle SIGLARM pass
14877 As a further example, to hook at the begining and end of the @code{echo}
14878 command, and to add extra text to the beginning and end of the message,
14886 define hookpost-echo
14890 (@value{GDBP}) echo Hello World
14891 <<<---Hello World--->>>
14896 You can define a hook for any single-word command in @value{GDBN}, but
14897 not for command aliases; you should define a hook for the basic command
14898 name, e.g. @code{backtrace} rather than @code{bt}.
14899 @c FIXME! So how does Joe User discover whether a command is an alias
14901 If an error occurs during the execution of your hook, execution of
14902 @value{GDBN} commands stops and @value{GDBN} issues a prompt
14903 (before the command that you actually typed had a chance to run).
14905 If you try to define a hook which does not match any known command, you
14906 get a warning from the @code{define} command.
14908 @node Command Files
14909 @section Command files
14911 @cindex command files
14912 A command file for @value{GDBN} is a file of lines that are @value{GDBN}
14913 commands. Comments (lines starting with @kbd{#}) may also be included.
14914 An empty line in a command file does nothing; it does not mean to repeat
14915 the last command, as it would from the terminal.
14918 @cindex @file{.gdbinit}
14919 @cindex @file{gdb.ini}
14920 When you start @value{GDBN}, it automatically executes commands from its
14921 @dfn{init files}, normally called @file{.gdbinit}@footnote{The DJGPP
14922 port of @value{GDBN} uses the name @file{gdb.ini} instead, due to the
14923 limitations of file names imposed by DOS filesystems.}.
14924 During startup, @value{GDBN} does the following:
14928 Reads the init file (if any) in your home directory@footnote{On
14929 DOS/Windows systems, the home directory is the one pointed to by the
14930 @code{HOME} environment variable.}.
14933 Processes command line options and operands.
14936 Reads the init file (if any) in the current working directory.
14939 Reads command files specified by the @samp{-x} option.
14942 The init file in your home directory can set options (such as @samp{set
14943 complaints}) that affect subsequent processing of command line options
14944 and operands. Init files are not executed if you use the @samp{-nx}
14945 option (@pxref{Mode Options, ,Choosing modes}).
14947 @cindex init file name
14948 On some configurations of @value{GDBN}, the init file is known by a
14949 different name (these are typically environments where a specialized
14950 form of @value{GDBN} may need to coexist with other forms, hence a
14951 different name for the specialized version's init file). These are the
14952 environments with special init file names:
14954 @cindex @file{.vxgdbinit}
14957 VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit}
14959 @cindex @file{.os68gdbinit}
14961 OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit}
14963 @cindex @file{.esgdbinit}
14965 ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit}
14968 You can also request the execution of a command file with the
14969 @code{source} command:
14973 @item source @var{filename}
14974 Execute the command file @var{filename}.
14977 The lines in a command file are executed sequentially. They are not
14978 printed as they are executed. An error in any command terminates
14979 execution of the command file and control is returned to the console.
14981 Commands that would ask for confirmation if used interactively proceed
14982 without asking when used in a command file. Many @value{GDBN} commands that
14983 normally print messages to say what they are doing omit the messages
14984 when called from command files.
14986 @value{GDBN} also accepts command input from standard input. In this
14987 mode, normal output goes to standard output and error output goes to
14988 standard error. Errors in a command file supplied on standard input do
14989 not terminate execution of the command file --- execution continues with
14993 gdb < cmds > log 2>&1
14996 (The syntax above will vary depending on the shell used.) This example
14997 will execute commands from the file @file{cmds}. All output and errors
14998 would be directed to @file{log}.
15001 @section Commands for controlled output
15003 During the execution of a command file or a user-defined command, normal
15004 @value{GDBN} output is suppressed; the only output that appears is what is
15005 explicitly printed by the commands in the definition. This section
15006 describes three commands useful for generating exactly the output you
15011 @item echo @var{text}
15012 @c I do not consider backslash-space a standard C escape sequence
15013 @c because it is not in ANSI.
15014 Print @var{text}. Nonprinting characters can be included in
15015 @var{text} using C escape sequences, such as @samp{\n} to print a
15016 newline. @strong{No newline is printed unless you specify one.}
15017 In addition to the standard C escape sequences, a backslash followed
15018 by a space stands for a space. This is useful for displaying a
15019 string with spaces at the beginning or the end, since leading and
15020 trailing spaces are otherwise trimmed from all arguments.
15021 To print @samp{@w{ }and foo =@w{ }}, use the command
15022 @samp{echo \@w{ }and foo = \@w{ }}.
15024 A backslash at the end of @var{text} can be used, as in C, to continue
15025 the command onto subsequent lines. For example,
15028 echo This is some text\n\
15029 which is continued\n\
15030 onto several lines.\n
15033 produces the same output as
15036 echo This is some text\n
15037 echo which is continued\n
15038 echo onto several lines.\n
15042 @item output @var{expression}
15043 Print the value of @var{expression} and nothing but that value: no
15044 newlines, no @samp{$@var{nn} = }. The value is not entered in the
15045 value history either. @xref{Expressions, ,Expressions}, for more information
15048 @item output/@var{fmt} @var{expression}
15049 Print the value of @var{expression} in format @var{fmt}. You can use
15050 the same formats as for @code{print}. @xref{Output Formats,,Output
15051 formats}, for more information.
15054 @item printf @var{string}, @var{expressions}@dots{}
15055 Print the values of the @var{expressions} under the control of
15056 @var{string}. The @var{expressions} are separated by commas and may be
15057 either numbers or pointers. Their values are printed as specified by
15058 @var{string}, exactly as if your program were to execute the C
15060 @c FIXME: the above implies that at least all ANSI C formats are
15061 @c supported, but it isn't true: %E and %G don't work (or so it seems).
15062 @c Either this is a bug, or the manual should document what formats are
15066 printf (@var{string}, @var{expressions}@dots{});
15069 For example, you can print two values in hex like this:
15072 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
15075 The only backslash-escape sequences that you can use in the format
15076 string are the simple ones that consist of backslash followed by a
15081 @chapter Command Interpreters
15082 @cindex command interpreters
15084 @value{GDBN} supports multiple command interpreters, and some command
15085 infrastructure to allow users or user interface writers to switch
15086 between interpreters or run commands in other interpreters.
15088 @value{GDBN} currently supports two command interpreters, the console
15089 interpreter (sometimes called the command-line interpreter or @sc{cli})
15090 and the machine interface interpreter (or @sc{gdb/mi}). This manual
15091 describes both of these interfaces in great detail.
15093 By default, @value{GDBN} will start with the console interpreter.
15094 However, the user may choose to start @value{GDBN} with another
15095 interpreter by specifying the @option{-i} or @option{--interpreter}
15096 startup options. Defined interpreters include:
15100 @cindex console interpreter
15101 The traditional console or command-line interpreter. This is the most often
15102 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
15103 @value{GDBN} will use this interpreter.
15106 @cindex mi interpreter
15107 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
15108 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
15109 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
15113 @cindex mi2 interpreter
15114 The current @sc{gdb/mi} interface.
15117 @cindex mi1 interpreter
15118 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
15122 @cindex invoke another interpreter
15123 The interpreter being used by @value{GDBN} may not be dynamically
15124 switched at runtime. Although possible, this could lead to a very
15125 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
15126 enters the command "interpreter-set console" in a console view,
15127 @value{GDBN} would switch to using the console interpreter, rendering
15128 the IDE inoperable!
15130 @kindex interpreter-exec
15131 Although you may only choose a single interpreter at startup, you may execute
15132 commands in any interpreter from the current interpreter using the appropriate
15133 command. If you are running the console interpreter, simply use the
15134 @code{interpreter-exec} command:
15137 interpreter-exec mi "-data-list-register-names"
15140 @sc{gdb/mi} has a similar command, although it is only available in versions of
15141 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
15144 @chapter @value{GDBN} Text User Interface
15146 @cindex Text User Interface
15149 * TUI Overview:: TUI overview
15150 * TUI Keys:: TUI key bindings
15151 * TUI Single Key Mode:: TUI single key mode
15152 * TUI Commands:: TUI specific commands
15153 * TUI Configuration:: TUI configuration variables
15156 The @value{GDBN} Text User Interface, TUI in short, is a terminal
15157 interface which uses the @code{curses} library to show the source
15158 file, the assembly output, the program registers and @value{GDBN}
15159 commands in separate text windows.
15161 The TUI is enabled by invoking @value{GDBN} using either
15163 @samp{gdbtui} or @samp{gdb -tui}.
15166 @section TUI overview
15168 The TUI has two display modes that can be switched while
15173 A curses (or TUI) mode in which it displays several text
15174 windows on the terminal.
15177 A standard mode which corresponds to the @value{GDBN} configured without
15181 In the TUI mode, @value{GDBN} can display several text window
15186 This window is the @value{GDBN} command window with the @value{GDBN}
15187 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
15188 managed using readline but through the TUI. The @emph{command}
15189 window is always visible.
15192 The source window shows the source file of the program. The current
15193 line as well as active breakpoints are displayed in this window.
15196 The assembly window shows the disassembly output of the program.
15199 This window shows the processor registers. It detects when
15200 a register is changed and when this is the case, registers that have
15201 changed are highlighted.
15205 The source and assembly windows show the current program position
15206 by highlighting the current line and marking them with the @samp{>} marker.
15207 Breakpoints are also indicated with two markers. A first one
15208 indicates the breakpoint type:
15212 Breakpoint which was hit at least once.
15215 Breakpoint which was never hit.
15218 Hardware breakpoint which was hit at least once.
15221 Hardware breakpoint which was never hit.
15225 The second marker indicates whether the breakpoint is enabled or not:
15229 Breakpoint is enabled.
15232 Breakpoint is disabled.
15236 The source, assembly and register windows are attached to the thread
15237 and the frame position. They are updated when the current thread
15238 changes, when the frame changes or when the program counter changes.
15239 These three windows are arranged by the TUI according to several
15240 layouts. The layout defines which of these three windows are visible.
15241 The following layouts are available:
15251 source and assembly
15254 source and registers
15257 assembly and registers
15261 On top of the command window a status line gives various information
15262 concerning the current process begin debugged. The status line is
15263 updated when the information it shows changes. The following fields
15268 Indicates the current gdb target
15269 (@pxref{Targets, ,Specifying a Debugging Target}).
15272 Gives information about the current process or thread number.
15273 When no process is being debugged, this field is set to @code{No process}.
15276 Gives the current function name for the selected frame.
15277 The name is demangled if demangling is turned on (@pxref{Print Settings}).
15278 When there is no symbol corresponding to the current program counter
15279 the string @code{??} is displayed.
15282 Indicates the current line number for the selected frame.
15283 When the current line number is not known the string @code{??} is displayed.
15286 Indicates the current program counter address.
15291 @section TUI Key Bindings
15292 @cindex TUI key bindings
15294 The TUI installs several key bindings in the readline keymaps
15295 (@pxref{Command Line Editing}).
15296 They allow to leave or enter in the TUI mode or they operate
15297 directly on the TUI layout and windows. The TUI also provides
15298 a @emph{SingleKey} keymap which binds several keys directly to
15299 @value{GDBN} commands. The following key bindings
15300 are installed for both TUI mode and the @value{GDBN} standard mode.
15309 Enter or leave the TUI mode. When the TUI mode is left,
15310 the curses window management is left and @value{GDBN} operates using
15311 its standard mode writing on the terminal directly. When the TUI
15312 mode is entered, the control is given back to the curses windows.
15313 The screen is then refreshed.
15317 Use a TUI layout with only one window. The layout will
15318 either be @samp{source} or @samp{assembly}. When the TUI mode
15319 is not active, it will switch to the TUI mode.
15321 Think of this key binding as the Emacs @kbd{C-x 1} binding.
15325 Use a TUI layout with at least two windows. When the current
15326 layout shows already two windows, a next layout with two windows is used.
15327 When a new layout is chosen, one window will always be common to the
15328 previous layout and the new one.
15330 Think of it as the Emacs @kbd{C-x 2} binding.
15334 Change the active window. The TUI associates several key bindings
15335 (like scrolling and arrow keys) to the active window. This command
15336 gives the focus to the next TUI window.
15338 Think of it as the Emacs @kbd{C-x o} binding.
15342 Use the TUI @emph{SingleKey} keymap that binds single key to gdb commands
15343 (@pxref{TUI Single Key Mode}).
15347 The following key bindings are handled only by the TUI mode:
15352 Scroll the active window one page up.
15356 Scroll the active window one page down.
15360 Scroll the active window one line up.
15364 Scroll the active window one line down.
15368 Scroll the active window one column left.
15372 Scroll the active window one column right.
15376 Refresh the screen.
15380 In the TUI mode, the arrow keys are used by the active window
15381 for scrolling. This means they are available for readline when the
15382 active window is the command window. When the command window
15383 does not have the focus, it is necessary to use other readline
15384 key bindings such as @key{C-p}, @key{C-n}, @key{C-b} and @key{C-f}.
15386 @node TUI Single Key Mode
15387 @section TUI Single Key Mode
15388 @cindex TUI single key mode
15390 The TUI provides a @emph{SingleKey} mode in which it installs a particular
15391 key binding in the readline keymaps to connect single keys to
15395 @kindex c @r{(SingleKey TUI key)}
15399 @kindex d @r{(SingleKey TUI key)}
15403 @kindex f @r{(SingleKey TUI key)}
15407 @kindex n @r{(SingleKey TUI key)}
15411 @kindex q @r{(SingleKey TUI key)}
15413 exit the @emph{SingleKey} mode.
15415 @kindex r @r{(SingleKey TUI key)}
15419 @kindex s @r{(SingleKey TUI key)}
15423 @kindex u @r{(SingleKey TUI key)}
15427 @kindex v @r{(SingleKey TUI key)}
15431 @kindex w @r{(SingleKey TUI key)}
15437 Other keys temporarily switch to the @value{GDBN} command prompt.
15438 The key that was pressed is inserted in the editing buffer so that
15439 it is possible to type most @value{GDBN} commands without interaction
15440 with the TUI @emph{SingleKey} mode. Once the command is entered the TUI
15441 @emph{SingleKey} mode is restored. The only way to permanently leave
15442 this mode is by hitting @key{q} or @samp{@key{C-x} @key{s}}.
15446 @section TUI specific commands
15447 @cindex TUI commands
15449 The TUI has specific commands to control the text windows.
15450 These commands are always available, that is they do not depend on
15451 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
15452 is in the standard mode, using these commands will automatically switch
15458 List and give the size of all displayed windows.
15462 Display the next layout.
15465 Display the previous layout.
15468 Display the source window only.
15471 Display the assembly window only.
15474 Display the source and assembly window.
15477 Display the register window together with the source or assembly window.
15479 @item focus next | prev | src | asm | regs | split
15481 Set the focus to the named window.
15482 This command allows to change the active window so that scrolling keys
15483 can be affected to another window.
15487 Refresh the screen. This is similar to using @key{C-L} key.
15489 @item tui reg float
15491 Show the floating point registers in the register window.
15493 @item tui reg general
15494 Show the general registers in the register window.
15497 Show the next register group. The list of register groups as well as
15498 their order is target specific. The predefined register groups are the
15499 following: @code{general}, @code{float}, @code{system}, @code{vector},
15500 @code{all}, @code{save}, @code{restore}.
15502 @item tui reg system
15503 Show the system registers in the register window.
15507 Update the source window and the current execution point.
15509 @item winheight @var{name} +@var{count}
15510 @itemx winheight @var{name} -@var{count}
15512 Change the height of the window @var{name} by @var{count}
15513 lines. Positive counts increase the height, while negative counts
15518 @node TUI Configuration
15519 @section TUI configuration variables
15520 @cindex TUI configuration variables
15522 The TUI has several configuration variables that control the
15523 appearance of windows on the terminal.
15526 @item set tui border-kind @var{kind}
15527 @kindex set tui border-kind
15528 Select the border appearance for the source, assembly and register windows.
15529 The possible values are the following:
15532 Use a space character to draw the border.
15535 Use ascii characters + - and | to draw the border.
15538 Use the Alternate Character Set to draw the border. The border is
15539 drawn using character line graphics if the terminal supports them.
15543 @item set tui active-border-mode @var{mode}
15544 @kindex set tui active-border-mode
15545 Select the attributes to display the border of the active window.
15546 The possible values are @code{normal}, @code{standout}, @code{reverse},
15547 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
15549 @item set tui border-mode @var{mode}
15550 @kindex set tui border-mode
15551 Select the attributes to display the border of other windows.
15552 The @var{mode} can be one of the following:
15555 Use normal attributes to display the border.
15561 Use reverse video mode.
15564 Use half bright mode.
15566 @item half-standout
15567 Use half bright and standout mode.
15570 Use extra bright or bold mode.
15572 @item bold-standout
15573 Use extra bright or bold and standout mode.
15580 @chapter Using @value{GDBN} under @sc{gnu} Emacs
15583 @cindex @sc{gnu} Emacs
15584 A special interface allows you to use @sc{gnu} Emacs to view (and
15585 edit) the source files for the program you are debugging with
15588 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
15589 executable file you want to debug as an argument. This command starts
15590 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
15591 created Emacs buffer.
15592 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
15594 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
15599 All ``terminal'' input and output goes through the Emacs buffer.
15602 This applies both to @value{GDBN} commands and their output, and to the input
15603 and output done by the program you are debugging.
15605 This is useful because it means that you can copy the text of previous
15606 commands and input them again; you can even use parts of the output
15609 All the facilities of Emacs' Shell mode are available for interacting
15610 with your program. In particular, you can send signals the usual
15611 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
15616 @value{GDBN} displays source code through Emacs.
15619 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
15620 source file for that frame and puts an arrow (@samp{=>}) at the
15621 left margin of the current line. Emacs uses a separate buffer for
15622 source display, and splits the screen to show both your @value{GDBN} session
15625 Explicit @value{GDBN} @code{list} or search commands still produce output as
15626 usual, but you probably have no reason to use them from Emacs.
15628 If you specify an absolute file name when prompted for the @kbd{M-x
15629 gdb} argument, then Emacs sets your current working directory to where
15630 your program resides. If you only specify the file name, then Emacs
15631 sets your current working directory to to the directory associated
15632 with the previous buffer. In this case, @value{GDBN} may find your
15633 program by searching your environment's @code{PATH} variable, but on
15634 some operating systems it might not find the source. So, although the
15635 @value{GDBN} input and output session proceeds normally, the auxiliary
15636 buffer does not display the current source and line of execution.
15638 The initial working directory of @value{GDBN} is printed on the top
15639 line of the @value{GDBN} I/O buffer and this serves as a default for
15640 the commands that specify files for @value{GDBN} to operate
15641 on. @xref{Files, ,Commands to specify files}.
15643 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
15644 need to call @value{GDBN} by a different name (for example, if you
15645 keep several configurations around, with different names) you can
15646 customize the Emacs variable @code{gud-gdb-command-name} to run the
15649 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
15650 addition to the standard Shell mode commands:
15654 Describe the features of Emacs' @value{GDBN} Mode.
15657 Execute to another source line, like the @value{GDBN} @code{step} command; also
15658 update the display window to show the current file and location.
15661 Execute to next source line in this function, skipping all function
15662 calls, like the @value{GDBN} @code{next} command. Then update the display window
15663 to show the current file and location.
15666 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
15667 display window accordingly.
15670 Execute until exit from the selected stack frame, like the @value{GDBN}
15671 @code{finish} command.
15674 Continue execution of your program, like the @value{GDBN} @code{continue}
15678 Go up the number of frames indicated by the numeric argument
15679 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
15680 like the @value{GDBN} @code{up} command.
15683 Go down the number of frames indicated by the numeric argument, like the
15684 @value{GDBN} @code{down} command.
15687 In any source file, the Emacs command @kbd{C-x SPC} (@code{gud-break})
15688 tells @value{GDBN} to set a breakpoint on the source line point is on.
15690 If you type @kbd{M-x speedbar}, then Emacs displays a separate frame which
15691 shows a backtrace when the @value{GDBN} I/O buffer is current. Move
15692 point to any frame in the stack and type @key{RET} to make it become the
15693 current frame and display the associated source in the source buffer.
15694 Alternatively, click @kbd{Mouse-2} to make the selected frame become the
15697 If you accidentally delete the source-display buffer, an easy way to get
15698 it back is to type the command @code{f} in the @value{GDBN} buffer, to
15699 request a frame display; when you run under Emacs, this recreates
15700 the source buffer if necessary to show you the context of the current
15703 The source files displayed in Emacs are in ordinary Emacs buffers
15704 which are visiting the source files in the usual way. You can edit
15705 the files with these buffers if you wish; but keep in mind that @value{GDBN}
15706 communicates with Emacs in terms of line numbers. If you add or
15707 delete lines from the text, the line numbers that @value{GDBN} knows cease
15708 to correspond properly with the code.
15710 The description given here is for GNU Emacs version 21.3 and a more
15711 detailed description of its interaction with @value{GDBN} is given in
15712 the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu} Emacs Manual}).
15714 @c The following dropped because Epoch is nonstandard. Reactivate
15715 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
15717 @kindex Emacs Epoch environment
15721 Version 18 of @sc{gnu} Emacs has a built-in window system
15722 called the @code{epoch}
15723 environment. Users of this environment can use a new command,
15724 @code{inspect} which performs identically to @code{print} except that
15725 each value is printed in its own window.
15730 @chapter The @sc{gdb/mi} Interface
15732 @unnumberedsec Function and Purpose
15734 @cindex @sc{gdb/mi}, its purpose
15735 @sc{gdb/mi} is a line based machine oriented text interface to @value{GDBN}. It is
15736 specifically intended to support the development of systems which use
15737 the debugger as just one small component of a larger system.
15739 This chapter is a specification of the @sc{gdb/mi} interface. It is written
15740 in the form of a reference manual.
15742 Note that @sc{gdb/mi} is still under construction, so some of the
15743 features described below are incomplete and subject to change.
15745 @unnumberedsec Notation and Terminology
15747 @cindex notational conventions, for @sc{gdb/mi}
15748 This chapter uses the following notation:
15752 @code{|} separates two alternatives.
15755 @code{[ @var{something} ]} indicates that @var{something} is optional:
15756 it may or may not be given.
15759 @code{( @var{group} )*} means that @var{group} inside the parentheses
15760 may repeat zero or more times.
15763 @code{( @var{group} )+} means that @var{group} inside the parentheses
15764 may repeat one or more times.
15767 @code{"@var{string}"} means a literal @var{string}.
15771 @heading Dependencies
15774 @heading Acknowledgments
15776 In alphabetic order: Andrew Cagney, Fernando Nasser, Stan Shebs and
15780 * GDB/MI Command Syntax::
15781 * GDB/MI Compatibility with CLI::
15782 * GDB/MI Output Records::
15783 * GDB/MI Command Description Format::
15784 * GDB/MI Breakpoint Table Commands::
15785 * GDB/MI Data Manipulation::
15786 * GDB/MI Program Control::
15787 * GDB/MI Miscellaneous Commands::
15789 * GDB/MI Kod Commands::
15790 * GDB/MI Memory Overlay Commands::
15791 * GDB/MI Signal Handling Commands::
15793 * GDB/MI Stack Manipulation::
15794 * GDB/MI Symbol Query::
15795 * GDB/MI Target Manipulation::
15796 * GDB/MI Thread Commands::
15797 * GDB/MI Tracepoint Commands::
15798 * GDB/MI Variable Objects::
15801 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15802 @node GDB/MI Command Syntax
15803 @section @sc{gdb/mi} Command Syntax
15806 * GDB/MI Input Syntax::
15807 * GDB/MI Output Syntax::
15808 * GDB/MI Simple Examples::
15811 @node GDB/MI Input Syntax
15812 @subsection @sc{gdb/mi} Input Syntax
15814 @cindex input syntax for @sc{gdb/mi}
15815 @cindex @sc{gdb/mi}, input syntax
15817 @item @var{command} @expansion{}
15818 @code{@var{cli-command} | @var{mi-command}}
15820 @item @var{cli-command} @expansion{}
15821 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
15822 @var{cli-command} is any existing @value{GDBN} CLI command.
15824 @item @var{mi-command} @expansion{}
15825 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
15826 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
15828 @item @var{token} @expansion{}
15829 "any sequence of digits"
15831 @item @var{option} @expansion{}
15832 @code{"-" @var{parameter} [ " " @var{parameter} ]}
15834 @item @var{parameter} @expansion{}
15835 @code{@var{non-blank-sequence} | @var{c-string}}
15837 @item @var{operation} @expansion{}
15838 @emph{any of the operations described in this chapter}
15840 @item @var{non-blank-sequence} @expansion{}
15841 @emph{anything, provided it doesn't contain special characters such as
15842 "-", @var{nl}, """ and of course " "}
15844 @item @var{c-string} @expansion{}
15845 @code{""" @var{seven-bit-iso-c-string-content} """}
15847 @item @var{nl} @expansion{}
15856 The CLI commands are still handled by the @sc{mi} interpreter; their
15857 output is described below.
15860 The @code{@var{token}}, when present, is passed back when the command
15864 Some @sc{mi} commands accept optional arguments as part of the parameter
15865 list. Each option is identified by a leading @samp{-} (dash) and may be
15866 followed by an optional argument parameter. Options occur first in the
15867 parameter list and can be delimited from normal parameters using
15868 @samp{--} (this is useful when some parameters begin with a dash).
15875 We want easy access to the existing CLI syntax (for debugging).
15878 We want it to be easy to spot a @sc{mi} operation.
15881 @node GDB/MI Output Syntax
15882 @subsection @sc{gdb/mi} Output Syntax
15884 @cindex output syntax of @sc{gdb/mi}
15885 @cindex @sc{gdb/mi}, output syntax
15886 The output from @sc{gdb/mi} consists of zero or more out-of-band records
15887 followed, optionally, by a single result record. This result record
15888 is for the most recent command. The sequence of output records is
15889 terminated by @samp{(@value{GDBP})}.
15891 If an input command was prefixed with a @code{@var{token}} then the
15892 corresponding output for that command will also be prefixed by that same
15896 @item @var{output} @expansion{}
15897 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(@value{GDBP})" @var{nl}}
15899 @item @var{result-record} @expansion{}
15900 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
15902 @item @var{out-of-band-record} @expansion{}
15903 @code{@var{async-record} | @var{stream-record}}
15905 @item @var{async-record} @expansion{}
15906 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
15908 @item @var{exec-async-output} @expansion{}
15909 @code{[ @var{token} ] "*" @var{async-output}}
15911 @item @var{status-async-output} @expansion{}
15912 @code{[ @var{token} ] "+" @var{async-output}}
15914 @item @var{notify-async-output} @expansion{}
15915 @code{[ @var{token} ] "=" @var{async-output}}
15917 @item @var{async-output} @expansion{}
15918 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
15920 @item @var{result-class} @expansion{}
15921 @code{"done" | "running" | "connected" | "error" | "exit"}
15923 @item @var{async-class} @expansion{}
15924 @code{"stopped" | @var{others}} (where @var{others} will be added
15925 depending on the needs---this is still in development).
15927 @item @var{result} @expansion{}
15928 @code{ @var{variable} "=" @var{value}}
15930 @item @var{variable} @expansion{}
15931 @code{ @var{string} }
15933 @item @var{value} @expansion{}
15934 @code{ @var{const} | @var{tuple} | @var{list} }
15936 @item @var{const} @expansion{}
15937 @code{@var{c-string}}
15939 @item @var{tuple} @expansion{}
15940 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
15942 @item @var{list} @expansion{}
15943 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
15944 @var{result} ( "," @var{result} )* "]" }
15946 @item @var{stream-record} @expansion{}
15947 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
15949 @item @var{console-stream-output} @expansion{}
15950 @code{"~" @var{c-string}}
15952 @item @var{target-stream-output} @expansion{}
15953 @code{"@@" @var{c-string}}
15955 @item @var{log-stream-output} @expansion{}
15956 @code{"&" @var{c-string}}
15958 @item @var{nl} @expansion{}
15961 @item @var{token} @expansion{}
15962 @emph{any sequence of digits}.
15970 All output sequences end in a single line containing a period.
15973 The @code{@var{token}} is from the corresponding request. If an execution
15974 command is interrupted by the @samp{-exec-interrupt} command, the
15975 @var{token} associated with the @samp{*stopped} message is the one of the
15976 original execution command, not the one of the interrupt command.
15979 @cindex status output in @sc{gdb/mi}
15980 @var{status-async-output} contains on-going status information about the
15981 progress of a slow operation. It can be discarded. All status output is
15982 prefixed by @samp{+}.
15985 @cindex async output in @sc{gdb/mi}
15986 @var{exec-async-output} contains asynchronous state change on the target
15987 (stopped, started, disappeared). All async output is prefixed by
15991 @cindex notify output in @sc{gdb/mi}
15992 @var{notify-async-output} contains supplementary information that the
15993 client should handle (e.g., a new breakpoint information). All notify
15994 output is prefixed by @samp{=}.
15997 @cindex console output in @sc{gdb/mi}
15998 @var{console-stream-output} is output that should be displayed as is in the
15999 console. It is the textual response to a CLI command. All the console
16000 output is prefixed by @samp{~}.
16003 @cindex target output in @sc{gdb/mi}
16004 @var{target-stream-output} is the output produced by the target program.
16005 All the target output is prefixed by @samp{@@}.
16008 @cindex log output in @sc{gdb/mi}
16009 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
16010 instance messages that should be displayed as part of an error log. All
16011 the log output is prefixed by @samp{&}.
16014 @cindex list output in @sc{gdb/mi}
16015 New @sc{gdb/mi} commands should only output @var{lists} containing
16021 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
16022 details about the various output records.
16024 @node GDB/MI Simple Examples
16025 @subsection Simple Examples of @sc{gdb/mi} Interaction
16026 @cindex @sc{gdb/mi}, simple examples
16028 This subsection presents several simple examples of interaction using
16029 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
16030 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
16031 the output received from @sc{gdb/mi}.
16033 @subsubheading Target Stop
16034 @c Ummm... There is no "-stop" command. This assumes async, no?
16035 Here's an example of stopping the inferior process:
16046 <- *stop,reason="stop",address="0x123",source="a.c:123"
16050 @subsubheading Simple CLI Command
16052 Here's an example of a simple CLI command being passed through
16053 @sc{gdb/mi} and on to the CLI.
16063 @subsubheading Command With Side Effects
16066 -> -symbol-file xyz.exe
16067 <- *breakpoint,nr="3",address="0x123",source="a.c:123"
16071 @subsubheading A Bad Command
16073 Here's what happens if you pass a non-existent command:
16077 <- ^error,msg="Undefined MI command: rubbish"
16081 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16082 @node GDB/MI Compatibility with CLI
16083 @section @sc{gdb/mi} Compatibility with CLI
16085 @cindex compatibility, @sc{gdb/mi} and CLI
16086 @cindex @sc{gdb/mi}, compatibility with CLI
16087 To help users familiar with @value{GDBN}'s existing CLI interface, @sc{gdb/mi}
16088 accepts existing CLI commands. As specified by the syntax, such
16089 commands can be directly entered into the @sc{gdb/mi} interface and @value{GDBN} will
16092 This mechanism is provided as an aid to developers of @sc{gdb/mi}
16093 clients and not as a reliable interface into the CLI. Since the command
16094 is being interpreteted in an environment that assumes @sc{gdb/mi}
16095 behaviour, the exact output of such commands is likely to end up being
16096 an un-supported hybrid of @sc{gdb/mi} and CLI output.
16098 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16099 @node GDB/MI Output Records
16100 @section @sc{gdb/mi} Output Records
16103 * GDB/MI Result Records::
16104 * GDB/MI Stream Records::
16105 * GDB/MI Out-of-band Records::
16108 @node GDB/MI Result Records
16109 @subsection @sc{gdb/mi} Result Records
16111 @cindex result records in @sc{gdb/mi}
16112 @cindex @sc{gdb/mi}, result records
16113 In addition to a number of out-of-band notifications, the response to a
16114 @sc{gdb/mi} command includes one of the following result indications:
16118 @item "^done" [ "," @var{results} ]
16119 The synchronous operation was successful, @code{@var{results}} are the return
16124 @c Is this one correct? Should it be an out-of-band notification?
16125 The asynchronous operation was successfully started. The target is
16128 @item "^error" "," @var{c-string}
16130 The operation failed. The @code{@var{c-string}} contains the corresponding
16134 @node GDB/MI Stream Records
16135 @subsection @sc{gdb/mi} Stream Records
16137 @cindex @sc{gdb/mi}, stream records
16138 @cindex stream records in @sc{gdb/mi}
16139 @value{GDBN} internally maintains a number of output streams: the console, the
16140 target, and the log. The output intended for each of these streams is
16141 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
16143 Each stream record begins with a unique @dfn{prefix character} which
16144 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
16145 Syntax}). In addition to the prefix, each stream record contains a
16146 @code{@var{string-output}}. This is either raw text (with an implicit new
16147 line) or a quoted C string (which does not contain an implicit newline).
16150 @item "~" @var{string-output}
16151 The console output stream contains text that should be displayed in the
16152 CLI console window. It contains the textual responses to CLI commands.
16154 @item "@@" @var{string-output}
16155 The target output stream contains any textual output from the running
16158 @item "&" @var{string-output}
16159 The log stream contains debugging messages being produced by @value{GDBN}'s
16163 @node GDB/MI Out-of-band Records
16164 @subsection @sc{gdb/mi} Out-of-band Records
16166 @cindex out-of-band records in @sc{gdb/mi}
16167 @cindex @sc{gdb/mi}, out-of-band records
16168 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
16169 additional changes that have occurred. Those changes can either be a
16170 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
16171 target activity (e.g., target stopped).
16173 The following is a preliminary list of possible out-of-band records.
16180 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16181 @node GDB/MI Command Description Format
16182 @section @sc{gdb/mi} Command Description Format
16184 The remaining sections describe blocks of commands. Each block of
16185 commands is laid out in a fashion similar to this section.
16187 Note the the line breaks shown in the examples are here only for
16188 readability. They don't appear in the real output.
16189 Also note that the commands with a non-available example (N.A.@:) are
16190 not yet implemented.
16192 @subheading Motivation
16194 The motivation for this collection of commands.
16196 @subheading Introduction
16198 A brief introduction to this collection of commands as a whole.
16200 @subheading Commands
16202 For each command in the block, the following is described:
16204 @subsubheading Synopsis
16207 -command @var{args}@dots{}
16210 @subsubheading @value{GDBN} Command
16212 The corresponding @value{GDBN} CLI command.
16214 @subsubheading Result
16216 @subsubheading Out-of-band
16218 @subsubheading Notes
16220 @subsubheading Example
16223 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16224 @node GDB/MI Breakpoint Table Commands
16225 @section @sc{gdb/mi} Breakpoint table commands
16227 @cindex breakpoint commands for @sc{gdb/mi}
16228 @cindex @sc{gdb/mi}, breakpoint commands
16229 This section documents @sc{gdb/mi} commands for manipulating
16232 @subheading The @code{-break-after} Command
16233 @findex -break-after
16235 @subsubheading Synopsis
16238 -break-after @var{number} @var{count}
16241 The breakpoint number @var{number} is not in effect until it has been
16242 hit @var{count} times. To see how this is reflected in the output of
16243 the @samp{-break-list} command, see the description of the
16244 @samp{-break-list} command below.
16246 @subsubheading @value{GDBN} Command
16248 The corresponding @value{GDBN} command is @samp{ignore}.
16250 @subsubheading Example
16255 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",line="5"@}
16262 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
16263 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
16264 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
16265 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
16266 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
16267 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
16268 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
16269 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
16270 addr="0x000100d0",func="main",file="hello.c",line="5",times="0",
16276 @subheading The @code{-break-catch} Command
16277 @findex -break-catch
16279 @subheading The @code{-break-commands} Command
16280 @findex -break-commands
16284 @subheading The @code{-break-condition} Command
16285 @findex -break-condition
16287 @subsubheading Synopsis
16290 -break-condition @var{number} @var{expr}
16293 Breakpoint @var{number} will stop the program only if the condition in
16294 @var{expr} is true. The condition becomes part of the
16295 @samp{-break-list} output (see the description of the @samp{-break-list}
16298 @subsubheading @value{GDBN} Command
16300 The corresponding @value{GDBN} command is @samp{condition}.
16302 @subsubheading Example
16306 -break-condition 1 1
16310 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
16311 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
16312 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
16313 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
16314 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
16315 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
16316 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
16317 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
16318 addr="0x000100d0",func="main",file="hello.c",line="5",cond="1",
16319 times="0",ignore="3"@}]@}
16323 @subheading The @code{-break-delete} Command
16324 @findex -break-delete
16326 @subsubheading Synopsis
16329 -break-delete ( @var{breakpoint} )+
16332 Delete the breakpoint(s) whose number(s) are specified in the argument
16333 list. This is obviously reflected in the breakpoint list.
16335 @subsubheading @value{GDBN} command
16337 The corresponding @value{GDBN} command is @samp{delete}.
16339 @subsubheading Example
16347 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
16348 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
16349 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
16350 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
16351 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
16352 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
16353 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
16358 @subheading The @code{-break-disable} Command
16359 @findex -break-disable
16361 @subsubheading Synopsis
16364 -break-disable ( @var{breakpoint} )+
16367 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
16368 break list is now set to @samp{n} for the named @var{breakpoint}(s).
16370 @subsubheading @value{GDBN} Command
16372 The corresponding @value{GDBN} command is @samp{disable}.
16374 @subsubheading Example
16382 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
16383 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
16384 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
16385 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
16386 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
16387 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
16388 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
16389 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
16390 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
16394 @subheading The @code{-break-enable} Command
16395 @findex -break-enable
16397 @subsubheading Synopsis
16400 -break-enable ( @var{breakpoint} )+
16403 Enable (previously disabled) @var{breakpoint}(s).
16405 @subsubheading @value{GDBN} Command
16407 The corresponding @value{GDBN} command is @samp{enable}.
16409 @subsubheading Example
16417 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
16418 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
16419 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
16420 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
16421 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
16422 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
16423 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
16424 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
16425 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
16429 @subheading The @code{-break-info} Command
16430 @findex -break-info
16432 @subsubheading Synopsis
16435 -break-info @var{breakpoint}
16439 Get information about a single breakpoint.
16441 @subsubheading @value{GDBN} command
16443 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
16445 @subsubheading Example
16448 @subheading The @code{-break-insert} Command
16449 @findex -break-insert
16451 @subsubheading Synopsis
16454 -break-insert [ -t ] [ -h ] [ -r ]
16455 [ -c @var{condition} ] [ -i @var{ignore-count} ]
16456 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
16460 If specified, @var{line}, can be one of:
16467 @item filename:linenum
16468 @item filename:function
16472 The possible optional parameters of this command are:
16476 Insert a tempoary breakpoint.
16478 Insert a hardware breakpoint.
16479 @item -c @var{condition}
16480 Make the breakpoint conditional on @var{condition}.
16481 @item -i @var{ignore-count}
16482 Initialize the @var{ignore-count}.
16484 Insert a regular breakpoint in all the functions whose names match the
16485 given regular expression. Other flags are not applicable to regular
16489 @subsubheading Result
16491 The result is in the form:
16494 ^done,bkptno="@var{number}",func="@var{funcname}",
16495 file="@var{filename}",line="@var{lineno}"
16499 where @var{number} is the @value{GDBN} number for this breakpoint, @var{funcname}
16500 is the name of the function where the breakpoint was inserted,
16501 @var{filename} is the name of the source file which contains this
16502 function, and @var{lineno} is the source line number within that file.
16504 Note: this format is open to change.
16505 @c An out-of-band breakpoint instead of part of the result?
16507 @subsubheading @value{GDBN} Command
16509 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
16510 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
16512 @subsubheading Example
16517 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
16519 -break-insert -t foo
16520 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",line="11"@}
16523 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
16524 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
16525 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
16526 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
16527 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
16528 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
16529 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
16530 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
16531 addr="0x0001072c", func="main",file="recursive2.c",line="4",times="0"@},
16532 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
16533 addr="0x00010774",func="foo",file="recursive2.c",line="11",times="0"@}]@}
16535 -break-insert -r foo.*
16536 ~int foo(int, int);
16537 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c",line="11"@}
16541 @subheading The @code{-break-list} Command
16542 @findex -break-list
16544 @subsubheading Synopsis
16550 Displays the list of inserted breakpoints, showing the following fields:
16554 number of the breakpoint
16556 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
16558 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
16561 is the breakpoint enabled or no: @samp{y} or @samp{n}
16563 memory location at which the breakpoint is set
16565 logical location of the breakpoint, expressed by function name, file
16568 number of times the breakpoint has been hit
16571 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
16572 @code{body} field is an empty list.
16574 @subsubheading @value{GDBN} Command
16576 The corresponding @value{GDBN} command is @samp{info break}.
16578 @subsubheading Example
16583 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
16584 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
16585 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
16586 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
16587 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
16588 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
16589 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
16590 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
16591 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
16592 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
16593 addr="0x00010114",func="foo",file="hello.c",line="13",times="0"@}]@}
16597 Here's an example of the result when there are no breakpoints:
16602 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
16603 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
16604 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
16605 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
16606 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
16607 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
16608 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
16613 @subheading The @code{-break-watch} Command
16614 @findex -break-watch
16616 @subsubheading Synopsis
16619 -break-watch [ -a | -r ]
16622 Create a watchpoint. With the @samp{-a} option it will create an
16623 @dfn{access} watchpoint, i.e. a watchpoint that triggers either on a
16624 read from or on a write to the memory location. With the @samp{-r}
16625 option, the watchpoint created is a @dfn{read} watchpoint, i.e. it will
16626 trigger only when the memory location is accessed for reading. Without
16627 either of the options, the watchpoint created is a regular watchpoint,
16628 i.e. it will trigger when the memory location is accessed for writing.
16629 @xref{Set Watchpoints, , Setting watchpoints}.
16631 Note that @samp{-break-list} will report a single list of watchpoints and
16632 breakpoints inserted.
16634 @subsubheading @value{GDBN} Command
16636 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
16639 @subsubheading Example
16641 Setting a watchpoint on a variable in the @code{main} function:
16646 ^done,wpt=@{number="2",exp="x"@}
16650 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
16651 value=@{old="-268439212",new="55"@},
16652 frame=@{func="main",args=[],file="recursive2.c",line="5"@}
16656 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
16657 the program execution twice: first for the variable changing value, then
16658 for the watchpoint going out of scope.
16663 ^done,wpt=@{number="5",exp="C"@}
16667 ^done,reason="watchpoint-trigger",
16668 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
16669 frame=@{func="callee4",args=[],
16670 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
16674 ^done,reason="watchpoint-scope",wpnum="5",
16675 frame=@{func="callee3",args=[@{name="strarg",
16676 value="0x11940 \"A string argument.\""@}],
16677 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
16681 Listing breakpoints and watchpoints, at different points in the program
16682 execution. Note that once the watchpoint goes out of scope, it is
16688 ^done,wpt=@{number="2",exp="C"@}
16691 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
16692 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
16693 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
16694 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
16695 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
16696 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
16697 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
16698 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
16699 addr="0x00010734",func="callee4",
16700 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
16701 bkpt=@{number="2",type="watchpoint",disp="keep",
16702 enabled="y",addr="",what="C",times="0"@}]@}
16706 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
16707 value=@{old="-276895068",new="3"@},
16708 frame=@{func="callee4",args=[],
16709 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
16712 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
16713 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
16714 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
16715 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
16716 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
16717 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
16718 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
16719 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
16720 addr="0x00010734",func="callee4",
16721 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
16722 bkpt=@{number="2",type="watchpoint",disp="keep",
16723 enabled="y",addr="",what="C",times="-5"@}]@}
16727 ^done,reason="watchpoint-scope",wpnum="2",
16728 frame=@{func="callee3",args=[@{name="strarg",
16729 value="0x11940 \"A string argument.\""@}],
16730 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
16733 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
16734 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
16735 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
16736 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
16737 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
16738 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
16739 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
16740 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
16741 addr="0x00010734",func="callee4",
16742 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@}]@}
16746 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16747 @node GDB/MI Data Manipulation
16748 @section @sc{gdb/mi} Data Manipulation
16750 @cindex data manipulation, in @sc{gdb/mi}
16751 @cindex @sc{gdb/mi}, data manipulation
16752 This section describes the @sc{gdb/mi} commands that manipulate data:
16753 examine memory and registers, evaluate expressions, etc.
16755 @c REMOVED FROM THE INTERFACE.
16756 @c @subheading -data-assign
16757 @c Change the value of a program variable. Plenty of side effects.
16758 @c @subsubheading GDB command
16760 @c @subsubheading Example
16763 @subheading The @code{-data-disassemble} Command
16764 @findex -data-disassemble
16766 @subsubheading Synopsis
16770 [ -s @var{start-addr} -e @var{end-addr} ]
16771 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
16779 @item @var{start-addr}
16780 is the beginning address (or @code{$pc})
16781 @item @var{end-addr}
16783 @item @var{filename}
16784 is the name of the file to disassemble
16785 @item @var{linenum}
16786 is the line number to disassemble around
16788 is the the number of disassembly lines to be produced. If it is -1,
16789 the whole function will be disassembled, in case no @var{end-addr} is
16790 specified. If @var{end-addr} is specified as a non-zero value, and
16791 @var{lines} is lower than the number of disassembly lines between
16792 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
16793 displayed; if @var{lines} is higher than the number of lines between
16794 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
16797 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
16801 @subsubheading Result
16803 The output for each instruction is composed of four fields:
16812 Note that whatever included in the instruction field, is not manipulated
16813 directely by @sc{gdb/mi}, i.e. it is not possible to adjust its format.
16815 @subsubheading @value{GDBN} Command
16817 There's no direct mapping from this command to the CLI.
16819 @subsubheading Example
16821 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
16825 -data-disassemble -s $pc -e "$pc + 20" -- 0
16828 @{address="0x000107c0",func-name="main",offset="4",
16829 inst="mov 2, %o0"@},
16830 @{address="0x000107c4",func-name="main",offset="8",
16831 inst="sethi %hi(0x11800), %o2"@},
16832 @{address="0x000107c8",func-name="main",offset="12",
16833 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
16834 @{address="0x000107cc",func-name="main",offset="16",
16835 inst="sethi %hi(0x11800), %o2"@},
16836 @{address="0x000107d0",func-name="main",offset="20",
16837 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
16841 Disassemble the whole @code{main} function. Line 32 is part of
16845 -data-disassemble -f basics.c -l 32 -- 0
16847 @{address="0x000107bc",func-name="main",offset="0",
16848 inst="save %sp, -112, %sp"@},
16849 @{address="0x000107c0",func-name="main",offset="4",
16850 inst="mov 2, %o0"@},
16851 @{address="0x000107c4",func-name="main",offset="8",
16852 inst="sethi %hi(0x11800), %o2"@},
16854 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
16855 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
16859 Disassemble 3 instructions from the start of @code{main}:
16863 -data-disassemble -f basics.c -l 32 -n 3 -- 0
16865 @{address="0x000107bc",func-name="main",offset="0",
16866 inst="save %sp, -112, %sp"@},
16867 @{address="0x000107c0",func-name="main",offset="4",
16868 inst="mov 2, %o0"@},
16869 @{address="0x000107c4",func-name="main",offset="8",
16870 inst="sethi %hi(0x11800), %o2"@}]
16874 Disassemble 3 instructions from the start of @code{main} in mixed mode:
16878 -data-disassemble -f basics.c -l 32 -n 3 -- 1
16880 src_and_asm_line=@{line="31",
16881 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
16882 testsuite/gdb.mi/basics.c",line_asm_insn=[
16883 @{address="0x000107bc",func-name="main",offset="0",
16884 inst="save %sp, -112, %sp"@}]@},
16885 src_and_asm_line=@{line="32",
16886 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
16887 testsuite/gdb.mi/basics.c",line_asm_insn=[
16888 @{address="0x000107c0",func-name="main",offset="4",
16889 inst="mov 2, %o0"@},
16890 @{address="0x000107c4",func-name="main",offset="8",
16891 inst="sethi %hi(0x11800), %o2"@}]@}]
16896 @subheading The @code{-data-evaluate-expression} Command
16897 @findex -data-evaluate-expression
16899 @subsubheading Synopsis
16902 -data-evaluate-expression @var{expr}
16905 Evaluate @var{expr} as an expression. The expression could contain an
16906 inferior function call. The function call will execute synchronously.
16907 If the expression contains spaces, it must be enclosed in double quotes.
16909 @subsubheading @value{GDBN} Command
16911 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
16912 @samp{call}. In @code{gdbtk} only, there's a corresponding
16913 @samp{gdb_eval} command.
16915 @subsubheading Example
16917 In the following example, the numbers that precede the commands are the
16918 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
16919 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
16923 211-data-evaluate-expression A
16926 311-data-evaluate-expression &A
16927 311^done,value="0xefffeb7c"
16929 411-data-evaluate-expression A+3
16932 511-data-evaluate-expression "A + 3"
16938 @subheading The @code{-data-list-changed-registers} Command
16939 @findex -data-list-changed-registers
16941 @subsubheading Synopsis
16944 -data-list-changed-registers
16947 Display a list of the registers that have changed.
16949 @subsubheading @value{GDBN} Command
16951 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
16952 has the corresponding command @samp{gdb_changed_register_list}.
16954 @subsubheading Example
16956 On a PPC MBX board:
16964 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
16965 args=[],file="try.c",line="5"@}
16967 -data-list-changed-registers
16968 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
16969 "10","11","13","14","15","16","17","18","19","20","21","22","23",
16970 "24","25","26","27","28","30","31","64","65","66","67","69"]
16975 @subheading The @code{-data-list-register-names} Command
16976 @findex -data-list-register-names
16978 @subsubheading Synopsis
16981 -data-list-register-names [ ( @var{regno} )+ ]
16984 Show a list of register names for the current target. If no arguments
16985 are given, it shows a list of the names of all the registers. If
16986 integer numbers are given as arguments, it will print a list of the
16987 names of the registers corresponding to the arguments. To ensure
16988 consistency between a register name and its number, the output list may
16989 include empty register names.
16991 @subsubheading @value{GDBN} Command
16993 @value{GDBN} does not have a command which corresponds to
16994 @samp{-data-list-register-names}. In @code{gdbtk} there is a
16995 corresponding command @samp{gdb_regnames}.
16997 @subsubheading Example
16999 For the PPC MBX board:
17002 -data-list-register-names
17003 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
17004 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
17005 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
17006 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
17007 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
17008 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
17009 "", "pc","ps","cr","lr","ctr","xer"]
17011 -data-list-register-names 1 2 3
17012 ^done,register-names=["r1","r2","r3"]
17016 @subheading The @code{-data-list-register-values} Command
17017 @findex -data-list-register-values
17019 @subsubheading Synopsis
17022 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
17025 Display the registers' contents. @var{fmt} is the format according to
17026 which the registers' contents are to be returned, followed by an optional
17027 list of numbers specifying the registers to display. A missing list of
17028 numbers indicates that the contents of all the registers must be returned.
17030 Allowed formats for @var{fmt} are:
17047 @subsubheading @value{GDBN} Command
17049 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
17050 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
17052 @subsubheading Example
17054 For a PPC MBX board (note: line breaks are for readability only, they
17055 don't appear in the actual output):
17059 -data-list-register-values r 64 65
17060 ^done,register-values=[@{number="64",value="0xfe00a300"@},
17061 @{number="65",value="0x00029002"@}]
17063 -data-list-register-values x
17064 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
17065 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
17066 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
17067 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
17068 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
17069 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
17070 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
17071 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
17072 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
17073 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
17074 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
17075 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
17076 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
17077 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
17078 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
17079 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
17080 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
17081 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
17082 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
17083 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
17084 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
17085 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
17086 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
17087 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
17088 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
17089 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
17090 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
17091 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
17092 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
17093 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
17094 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
17095 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
17096 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
17097 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
17098 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
17099 @{number="69",value="0x20002b03"@}]
17104 @subheading The @code{-data-read-memory} Command
17105 @findex -data-read-memory
17107 @subsubheading Synopsis
17110 -data-read-memory [ -o @var{byte-offset} ]
17111 @var{address} @var{word-format} @var{word-size}
17112 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
17119 @item @var{address}
17120 An expression specifying the address of the first memory word to be
17121 read. Complex expressions containing embedded white space should be
17122 quoted using the C convention.
17124 @item @var{word-format}
17125 The format to be used to print the memory words. The notation is the
17126 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
17129 @item @var{word-size}
17130 The size of each memory word in bytes.
17132 @item @var{nr-rows}
17133 The number of rows in the output table.
17135 @item @var{nr-cols}
17136 The number of columns in the output table.
17139 If present, indicates that each row should include an @sc{ascii} dump. The
17140 value of @var{aschar} is used as a padding character when a byte is not a
17141 member of the printable @sc{ascii} character set (printable @sc{ascii}
17142 characters are those whose code is between 32 and 126, inclusively).
17144 @item @var{byte-offset}
17145 An offset to add to the @var{address} before fetching memory.
17148 This command displays memory contents as a table of @var{nr-rows} by
17149 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
17150 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
17151 (returned as @samp{total-bytes}). Should less than the requested number
17152 of bytes be returned by the target, the missing words are identified
17153 using @samp{N/A}. The number of bytes read from the target is returned
17154 in @samp{nr-bytes} and the starting address used to read memory in
17157 The address of the next/previous row or page is available in
17158 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
17161 @subsubheading @value{GDBN} Command
17163 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
17164 @samp{gdb_get_mem} memory read command.
17166 @subsubheading Example
17168 Read six bytes of memory starting at @code{bytes+6} but then offset by
17169 @code{-6} bytes. Format as three rows of two columns. One byte per
17170 word. Display each word in hex.
17174 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
17175 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
17176 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
17177 prev-page="0x0000138a",memory=[
17178 @{addr="0x00001390",data=["0x00","0x01"]@},
17179 @{addr="0x00001392",data=["0x02","0x03"]@},
17180 @{addr="0x00001394",data=["0x04","0x05"]@}]
17184 Read two bytes of memory starting at address @code{shorts + 64} and
17185 display as a single word formatted in decimal.
17189 5-data-read-memory shorts+64 d 2 1 1
17190 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
17191 next-row="0x00001512",prev-row="0x0000150e",
17192 next-page="0x00001512",prev-page="0x0000150e",memory=[
17193 @{addr="0x00001510",data=["128"]@}]
17197 Read thirty two bytes of memory starting at @code{bytes+16} and format
17198 as eight rows of four columns. Include a string encoding with @samp{x}
17199 used as the non-printable character.
17203 4-data-read-memory bytes+16 x 1 8 4 x
17204 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
17205 next-row="0x000013c0",prev-row="0x0000139c",
17206 next-page="0x000013c0",prev-page="0x00001380",memory=[
17207 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
17208 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
17209 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
17210 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
17211 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
17212 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
17213 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
17214 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
17218 @subheading The @code{-display-delete} Command
17219 @findex -display-delete
17221 @subsubheading Synopsis
17224 -display-delete @var{number}
17227 Delete the display @var{number}.
17229 @subsubheading @value{GDBN} Command
17231 The corresponding @value{GDBN} command is @samp{delete display}.
17233 @subsubheading Example
17237 @subheading The @code{-display-disable} Command
17238 @findex -display-disable
17240 @subsubheading Synopsis
17243 -display-disable @var{number}
17246 Disable display @var{number}.
17248 @subsubheading @value{GDBN} Command
17250 The corresponding @value{GDBN} command is @samp{disable display}.
17252 @subsubheading Example
17256 @subheading The @code{-display-enable} Command
17257 @findex -display-enable
17259 @subsubheading Synopsis
17262 -display-enable @var{number}
17265 Enable display @var{number}.
17267 @subsubheading @value{GDBN} Command
17269 The corresponding @value{GDBN} command is @samp{enable display}.
17271 @subsubheading Example
17275 @subheading The @code{-display-insert} Command
17276 @findex -display-insert
17278 @subsubheading Synopsis
17281 -display-insert @var{expression}
17284 Display @var{expression} every time the program stops.
17286 @subsubheading @value{GDBN} Command
17288 The corresponding @value{GDBN} command is @samp{display}.
17290 @subsubheading Example
17294 @subheading The @code{-display-list} Command
17295 @findex -display-list
17297 @subsubheading Synopsis
17303 List the displays. Do not show the current values.
17305 @subsubheading @value{GDBN} Command
17307 The corresponding @value{GDBN} command is @samp{info display}.
17309 @subsubheading Example
17313 @subheading The @code{-environment-cd} Command
17314 @findex -environment-cd
17316 @subsubheading Synopsis
17319 -environment-cd @var{pathdir}
17322 Set @value{GDBN}'s working directory.
17324 @subsubheading @value{GDBN} Command
17326 The corresponding @value{GDBN} command is @samp{cd}.
17328 @subsubheading Example
17332 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
17338 @subheading The @code{-environment-directory} Command
17339 @findex -environment-directory
17341 @subsubheading Synopsis
17344 -environment-directory [ -r ] [ @var{pathdir} ]+
17347 Add directories @var{pathdir} to beginning of search path for source files.
17348 If the @samp{-r} option is used, the search path is reset to the default
17349 search path. If directories @var{pathdir} are supplied in addition to the
17350 @samp{-r} option, the search path is first reset and then addition
17352 Multiple directories may be specified, separated by blanks. Specifying
17353 multiple directories in a single command
17354 results in the directories added to the beginning of the
17355 search path in the same order they were presented in the command.
17356 If blanks are needed as
17357 part of a directory name, double-quotes should be used around
17358 the name. In the command output, the path will show up separated
17359 by the system directory-separator character. The directory-seperator
17360 character must not be used
17361 in any directory name.
17362 If no directories are specified, the current search path is displayed.
17364 @subsubheading @value{GDBN} Command
17366 The corresponding @value{GDBN} command is @samp{dir}.
17368 @subsubheading Example
17372 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
17373 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
17375 -environment-directory ""
17376 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
17378 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
17379 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
17381 -environment-directory -r
17382 ^done,source-path="$cdir:$cwd"
17387 @subheading The @code{-environment-path} Command
17388 @findex -environment-path
17390 @subsubheading Synopsis
17393 -environment-path [ -r ] [ @var{pathdir} ]+
17396 Add directories @var{pathdir} to beginning of search path for object files.
17397 If the @samp{-r} option is used, the search path is reset to the original
17398 search path that existed at gdb start-up. If directories @var{pathdir} are
17399 supplied in addition to the
17400 @samp{-r} option, the search path is first reset and then addition
17402 Multiple directories may be specified, separated by blanks. Specifying
17403 multiple directories in a single command
17404 results in the directories added to the beginning of the
17405 search path in the same order they were presented in the command.
17406 If blanks are needed as
17407 part of a directory name, double-quotes should be used around
17408 the name. In the command output, the path will show up separated
17409 by the system directory-separator character. The directory-seperator
17410 character must not be used
17411 in any directory name.
17412 If no directories are specified, the current path is displayed.
17415 @subsubheading @value{GDBN} Command
17417 The corresponding @value{GDBN} command is @samp{path}.
17419 @subsubheading Example
17424 ^done,path="/usr/bin"
17426 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
17427 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
17429 -environment-path -r /usr/local/bin
17430 ^done,path="/usr/local/bin:/usr/bin"
17435 @subheading The @code{-environment-pwd} Command
17436 @findex -environment-pwd
17438 @subsubheading Synopsis
17444 Show the current working directory.
17446 @subsubheading @value{GDBN} command
17448 The corresponding @value{GDBN} command is @samp{pwd}.
17450 @subsubheading Example
17455 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
17459 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17460 @node GDB/MI Program Control
17461 @section @sc{gdb/mi} Program control
17463 @subsubheading Program termination
17465 As a result of execution, the inferior program can run to completion, if
17466 it doesn't encounter any breakpoints. In this case the output will
17467 include an exit code, if the program has exited exceptionally.
17469 @subsubheading Examples
17472 Program exited normally:
17480 *stopped,reason="exited-normally"
17485 Program exited exceptionally:
17493 *stopped,reason="exited",exit-code="01"
17497 Another way the program can terminate is if it receives a signal such as
17498 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
17502 *stopped,reason="exited-signalled",signal-name="SIGINT",
17503 signal-meaning="Interrupt"
17507 @subheading The @code{-exec-abort} Command
17508 @findex -exec-abort
17510 @subsubheading Synopsis
17516 Kill the inferior running program.
17518 @subsubheading @value{GDBN} Command
17520 The corresponding @value{GDBN} command is @samp{kill}.
17522 @subsubheading Example
17526 @subheading The @code{-exec-arguments} Command
17527 @findex -exec-arguments
17529 @subsubheading Synopsis
17532 -exec-arguments @var{args}
17535 Set the inferior program arguments, to be used in the next
17538 @subsubheading @value{GDBN} Command
17540 The corresponding @value{GDBN} command is @samp{set args}.
17542 @subsubheading Example
17545 Don't have one around.
17548 @subheading The @code{-exec-continue} Command
17549 @findex -exec-continue
17551 @subsubheading Synopsis
17557 Asynchronous command. Resumes the execution of the inferior program
17558 until a breakpoint is encountered, or until the inferior exits.
17560 @subsubheading @value{GDBN} Command
17562 The corresponding @value{GDBN} corresponding is @samp{continue}.
17564 @subsubheading Example
17571 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
17572 file="hello.c",line="13"@}
17577 @subheading The @code{-exec-finish} Command
17578 @findex -exec-finish
17580 @subsubheading Synopsis
17586 Asynchronous command. Resumes the execution of the inferior program
17587 until the current function is exited. Displays the results returned by
17590 @subsubheading @value{GDBN} Command
17592 The corresponding @value{GDBN} command is @samp{finish}.
17594 @subsubheading Example
17596 Function returning @code{void}.
17603 *stopped,reason="function-finished",frame=@{func="main",args=[],
17604 file="hello.c",line="7"@}
17608 Function returning other than @code{void}. The name of the internal
17609 @value{GDBN} variable storing the result is printed, together with the
17616 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
17617 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
17618 file="recursive2.c",line="14"@},
17619 gdb-result-var="$1",return-value="0"
17624 @subheading The @code{-exec-interrupt} Command
17625 @findex -exec-interrupt
17627 @subsubheading Synopsis
17633 Asynchronous command. Interrupts the background execution of the target.
17634 Note how the token associated with the stop message is the one for the
17635 execution command that has been interrupted. The token for the interrupt
17636 itself only appears in the @samp{^done} output. If the user is trying to
17637 interrupt a non-running program, an error message will be printed.
17639 @subsubheading @value{GDBN} Command
17641 The corresponding @value{GDBN} command is @samp{interrupt}.
17643 @subsubheading Example
17654 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
17655 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",line="13"@}
17660 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
17665 @subheading The @code{-exec-next} Command
17668 @subsubheading Synopsis
17674 Asynchronous command. Resumes execution of the inferior program, stopping
17675 when the beginning of the next source line is reached.
17677 @subsubheading @value{GDBN} Command
17679 The corresponding @value{GDBN} command is @samp{next}.
17681 @subsubheading Example
17687 *stopped,reason="end-stepping-range",line="8",file="hello.c"
17692 @subheading The @code{-exec-next-instruction} Command
17693 @findex -exec-next-instruction
17695 @subsubheading Synopsis
17698 -exec-next-instruction
17701 Asynchronous command. Executes one machine instruction. If the
17702 instruction is a function call continues until the function returns. If
17703 the program stops at an instruction in the middle of a source line, the
17704 address will be printed as well.
17706 @subsubheading @value{GDBN} Command
17708 The corresponding @value{GDBN} command is @samp{nexti}.
17710 @subsubheading Example
17714 -exec-next-instruction
17718 *stopped,reason="end-stepping-range",
17719 addr="0x000100d4",line="5",file="hello.c"
17724 @subheading The @code{-exec-return} Command
17725 @findex -exec-return
17727 @subsubheading Synopsis
17733 Makes current function return immediately. Doesn't execute the inferior.
17734 Displays the new current frame.
17736 @subsubheading @value{GDBN} Command
17738 The corresponding @value{GDBN} command is @samp{return}.
17740 @subsubheading Example
17744 200-break-insert callee4
17745 200^done,bkpt=@{number="1",addr="0x00010734",
17746 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
17751 000*stopped,reason="breakpoint-hit",bkptno="1",
17752 frame=@{func="callee4",args=[],
17753 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
17759 111^done,frame=@{level="0",func="callee3",
17760 args=[@{name="strarg",
17761 value="0x11940 \"A string argument.\""@}],
17762 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
17767 @subheading The @code{-exec-run} Command
17770 @subsubheading Synopsis
17776 Asynchronous command. Starts execution of the inferior from the
17777 beginning. The inferior executes until either a breakpoint is
17778 encountered or the program exits.
17780 @subsubheading @value{GDBN} Command
17782 The corresponding @value{GDBN} command is @samp{run}.
17784 @subsubheading Example
17789 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
17794 *stopped,reason="breakpoint-hit",bkptno="1",
17795 frame=@{func="main",args=[],file="recursive2.c",line="4"@}
17800 @subheading The @code{-exec-show-arguments} Command
17801 @findex -exec-show-arguments
17803 @subsubheading Synopsis
17806 -exec-show-arguments
17809 Print the arguments of the program.
17811 @subsubheading @value{GDBN} Command
17813 The corresponding @value{GDBN} command is @samp{show args}.
17815 @subsubheading Example
17818 @c @subheading -exec-signal
17820 @subheading The @code{-exec-step} Command
17823 @subsubheading Synopsis
17829 Asynchronous command. Resumes execution of the inferior program, stopping
17830 when the beginning of the next source line is reached, if the next
17831 source line is not a function call. If it is, stop at the first
17832 instruction of the called function.
17834 @subsubheading @value{GDBN} Command
17836 The corresponding @value{GDBN} command is @samp{step}.
17838 @subsubheading Example
17840 Stepping into a function:
17846 *stopped,reason="end-stepping-range",
17847 frame=@{func="foo",args=[@{name="a",value="10"@},
17848 @{name="b",value="0"@}],file="recursive2.c",line="11"@}
17858 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
17863 @subheading The @code{-exec-step-instruction} Command
17864 @findex -exec-step-instruction
17866 @subsubheading Synopsis
17869 -exec-step-instruction
17872 Asynchronous command. Resumes the inferior which executes one machine
17873 instruction. The output, once @value{GDBN} has stopped, will vary depending on
17874 whether we have stopped in the middle of a source line or not. In the
17875 former case, the address at which the program stopped will be printed as
17878 @subsubheading @value{GDBN} Command
17880 The corresponding @value{GDBN} command is @samp{stepi}.
17882 @subsubheading Example
17886 -exec-step-instruction
17890 *stopped,reason="end-stepping-range",
17891 frame=@{func="foo",args=[],file="try.c",line="10"@}
17893 -exec-step-instruction
17897 *stopped,reason="end-stepping-range",
17898 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",line="10"@}
17903 @subheading The @code{-exec-until} Command
17904 @findex -exec-until
17906 @subsubheading Synopsis
17909 -exec-until [ @var{location} ]
17912 Asynchronous command. Executes the inferior until the @var{location}
17913 specified in the argument is reached. If there is no argument, the inferior
17914 executes until a source line greater than the current one is reached.
17915 The reason for stopping in this case will be @samp{location-reached}.
17917 @subsubheading @value{GDBN} Command
17919 The corresponding @value{GDBN} command is @samp{until}.
17921 @subsubheading Example
17925 -exec-until recursive2.c:6
17929 *stopped,reason="location-reached",frame=@{func="main",args=[],
17930 file="recursive2.c",line="6"@}
17935 @subheading -file-clear
17936 Is this going away????
17940 @subheading The @code{-file-exec-and-symbols} Command
17941 @findex -file-exec-and-symbols
17943 @subsubheading Synopsis
17946 -file-exec-and-symbols @var{file}
17949 Specify the executable file to be debugged. This file is the one from
17950 which the symbol table is also read. If no file is specified, the
17951 command clears the executable and symbol information. If breakpoints
17952 are set when using this command with no arguments, @value{GDBN} will produce
17953 error messages. Otherwise, no output is produced, except a completion
17956 @subsubheading @value{GDBN} Command
17958 The corresponding @value{GDBN} command is @samp{file}.
17960 @subsubheading Example
17964 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
17970 @subheading The @code{-file-exec-file} Command
17971 @findex -file-exec-file
17973 @subsubheading Synopsis
17976 -file-exec-file @var{file}
17979 Specify the executable file to be debugged. Unlike
17980 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
17981 from this file. If used without argument, @value{GDBN} clears the information
17982 about the executable file. No output is produced, except a completion
17985 @subsubheading @value{GDBN} Command
17987 The corresponding @value{GDBN} command is @samp{exec-file}.
17989 @subsubheading Example
17993 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
17999 @subheading The @code{-file-list-exec-sections} Command
18000 @findex -file-list-exec-sections
18002 @subsubheading Synopsis
18005 -file-list-exec-sections
18008 List the sections of the current executable file.
18010 @subsubheading @value{GDBN} Command
18012 The @value{GDBN} command @samp{info file} shows, among the rest, the same
18013 information as this command. @code{gdbtk} has a corresponding command
18014 @samp{gdb_load_info}.
18016 @subsubheading Example
18020 @subheading The @code{-file-list-exec-source-file} Command
18021 @findex -file-list-exec-source-file
18023 @subsubheading Synopsis
18026 -file-list-exec-source-file
18029 List the line number, the current source file, and the absolute path
18030 to the current source file for the current executable.
18032 @subsubheading @value{GDBN} Command
18034 There's no @value{GDBN} command which directly corresponds to this one.
18036 @subsubheading Example
18040 123-file-list-exec-source-file
18041 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
18046 @subheading The @code{-file-list-exec-source-files} Command
18047 @findex -file-list-exec-source-files
18049 @subsubheading Synopsis
18052 -file-list-exec-source-files
18055 List the source files for the current executable.
18057 It will always output the filename, but only when GDB can find the absolute
18058 file name of a source file, will it output the fullname.
18060 @subsubheading @value{GDBN} Command
18062 There's no @value{GDBN} command which directly corresponds to this one.
18063 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
18065 @subsubheading Example
18068 -file-list-exec-source-files
18070 @{file=foo.c,fullname=/home/foo.c@},
18071 @{file=/home/bar.c,fullname=/home/bar.c@},
18072 @{file=gdb_could_not_find_fullpath.c@}]
18076 @subheading The @code{-file-list-shared-libraries} Command
18077 @findex -file-list-shared-libraries
18079 @subsubheading Synopsis
18082 -file-list-shared-libraries
18085 List the shared libraries in the program.
18087 @subsubheading @value{GDBN} Command
18089 The corresponding @value{GDBN} command is @samp{info shared}.
18091 @subsubheading Example
18095 @subheading The @code{-file-list-symbol-files} Command
18096 @findex -file-list-symbol-files
18098 @subsubheading Synopsis
18101 -file-list-symbol-files
18106 @subsubheading @value{GDBN} Command
18108 The corresponding @value{GDBN} command is @samp{info file} (part of it).
18110 @subsubheading Example
18114 @subheading The @code{-file-symbol-file} Command
18115 @findex -file-symbol-file
18117 @subsubheading Synopsis
18120 -file-symbol-file @var{file}
18123 Read symbol table info from the specified @var{file} argument. When
18124 used without arguments, clears @value{GDBN}'s symbol table info. No output is
18125 produced, except for a completion notification.
18127 @subsubheading @value{GDBN} Command
18129 The corresponding @value{GDBN} command is @samp{symbol-file}.
18131 @subsubheading Example
18135 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
18140 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18141 @node GDB/MI Miscellaneous Commands
18142 @section Miscellaneous @value{GDBN} commands in @sc{gdb/mi}
18144 @c @subheading -gdb-complete
18146 @subheading The @code{-gdb-exit} Command
18149 @subsubheading Synopsis
18155 Exit @value{GDBN} immediately.
18157 @subsubheading @value{GDBN} Command
18159 Approximately corresponds to @samp{quit}.
18161 @subsubheading Example
18168 @subheading The @code{-gdb-set} Command
18171 @subsubheading Synopsis
18177 Set an internal @value{GDBN} variable.
18178 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
18180 @subsubheading @value{GDBN} Command
18182 The corresponding @value{GDBN} command is @samp{set}.
18184 @subsubheading Example
18194 @subheading The @code{-gdb-show} Command
18197 @subsubheading Synopsis
18203 Show the current value of a @value{GDBN} variable.
18205 @subsubheading @value{GDBN} command
18207 The corresponding @value{GDBN} command is @samp{show}.
18209 @subsubheading Example
18218 @c @subheading -gdb-source
18221 @subheading The @code{-gdb-version} Command
18222 @findex -gdb-version
18224 @subsubheading Synopsis
18230 Show version information for @value{GDBN}. Used mostly in testing.
18232 @subsubheading @value{GDBN} Command
18234 There's no equivalent @value{GDBN} command. @value{GDBN} by default shows this
18235 information when you start an interactive session.
18237 @subsubheading Example
18239 @c This example modifies the actual output from GDB to avoid overfull
18245 ~Copyright 2000 Free Software Foundation, Inc.
18246 ~GDB is free software, covered by the GNU General Public License, and
18247 ~you are welcome to change it and/or distribute copies of it under
18248 ~ certain conditions.
18249 ~Type "show copying" to see the conditions.
18250 ~There is absolutely no warranty for GDB. Type "show warranty" for
18252 ~This GDB was configured as
18253 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
18258 @subheading The @code{-interpreter-exec} Command
18259 @findex -interpreter-exec
18261 @subheading Synopsis
18264 -interpreter-exec @var{interpreter} @var{command}
18267 Execute the specified @var{command} in the given @var{interpreter}.
18269 @subheading @value{GDBN} Command
18271 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
18273 @subheading Example
18277 -interpreter-exec console "break main"
18278 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
18279 &"During symbol reading, bad structure-type format.\n"
18280 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
18286 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18287 @node GDB/MI Kod Commands
18288 @section @sc{gdb/mi} Kod Commands
18290 The Kod commands are not implemented.
18292 @c @subheading -kod-info
18294 @c @subheading -kod-list
18296 @c @subheading -kod-list-object-types
18298 @c @subheading -kod-show
18300 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18301 @node GDB/MI Memory Overlay Commands
18302 @section @sc{gdb/mi} Memory Overlay Commands
18304 The memory overlay commands are not implemented.
18306 @c @subheading -overlay-auto
18308 @c @subheading -overlay-list-mapping-state
18310 @c @subheading -overlay-list-overlays
18312 @c @subheading -overlay-map
18314 @c @subheading -overlay-off
18316 @c @subheading -overlay-on
18318 @c @subheading -overlay-unmap
18320 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18321 @node GDB/MI Signal Handling Commands
18322 @section @sc{gdb/mi} Signal Handling Commands
18324 Signal handling commands are not implemented.
18326 @c @subheading -signal-handle
18328 @c @subheading -signal-list-handle-actions
18330 @c @subheading -signal-list-signal-types
18334 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18335 @node GDB/MI Stack Manipulation
18336 @section @sc{gdb/mi} Stack Manipulation Commands
18339 @subheading The @code{-stack-info-frame} Command
18340 @findex -stack-info-frame
18342 @subsubheading Synopsis
18348 Get info on the current frame.
18350 @subsubheading @value{GDBN} Command
18352 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
18353 (without arguments).
18355 @subsubheading Example
18358 @subheading The @code{-stack-info-depth} Command
18359 @findex -stack-info-depth
18361 @subsubheading Synopsis
18364 -stack-info-depth [ @var{max-depth} ]
18367 Return the depth of the stack. If the integer argument @var{max-depth}
18368 is specified, do not count beyond @var{max-depth} frames.
18370 @subsubheading @value{GDBN} Command
18372 There's no equivalent @value{GDBN} command.
18374 @subsubheading Example
18376 For a stack with frame levels 0 through 11:
18383 -stack-info-depth 4
18386 -stack-info-depth 12
18389 -stack-info-depth 11
18392 -stack-info-depth 13
18397 @subheading The @code{-stack-list-arguments} Command
18398 @findex -stack-list-arguments
18400 @subsubheading Synopsis
18403 -stack-list-arguments @var{show-values}
18404 [ @var{low-frame} @var{high-frame} ]
18407 Display a list of the arguments for the frames between @var{low-frame}
18408 and @var{high-frame} (inclusive). If @var{low-frame} and
18409 @var{high-frame} are not provided, list the arguments for the whole call
18412 The @var{show-values} argument must have a value of 0 or 1. A value of
18413 0 means that only the names of the arguments are listed, a value of 1
18414 means that both names and values of the arguments are printed.
18416 @subsubheading @value{GDBN} Command
18418 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
18419 @samp{gdb_get_args} command which partially overlaps with the
18420 functionality of @samp{-stack-list-arguments}.
18422 @subsubheading Example
18429 frame=@{level="0",addr="0x00010734",func="callee4",
18430 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
18431 frame=@{level="1",addr="0x0001076c",func="callee3",
18432 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
18433 frame=@{level="2",addr="0x0001078c",func="callee2",
18434 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
18435 frame=@{level="3",addr="0x000107b4",func="callee1",
18436 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
18437 frame=@{level="4",addr="0x000107e0",func="main",
18438 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
18440 -stack-list-arguments 0
18443 frame=@{level="0",args=[]@},
18444 frame=@{level="1",args=[name="strarg"]@},
18445 frame=@{level="2",args=[name="intarg",name="strarg"]@},
18446 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
18447 frame=@{level="4",args=[]@}]
18449 -stack-list-arguments 1
18452 frame=@{level="0",args=[]@},
18454 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
18455 frame=@{level="2",args=[
18456 @{name="intarg",value="2"@},
18457 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
18458 @{frame=@{level="3",args=[
18459 @{name="intarg",value="2"@},
18460 @{name="strarg",value="0x11940 \"A string argument.\""@},
18461 @{name="fltarg",value="3.5"@}]@},
18462 frame=@{level="4",args=[]@}]
18464 -stack-list-arguments 0 2 2
18465 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
18467 -stack-list-arguments 1 2 2
18468 ^done,stack-args=[frame=@{level="2",
18469 args=[@{name="intarg",value="2"@},
18470 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
18474 @c @subheading -stack-list-exception-handlers
18477 @subheading The @code{-stack-list-frames} Command
18478 @findex -stack-list-frames
18480 @subsubheading Synopsis
18483 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
18486 List the frames currently on the stack. For each frame it displays the
18491 The frame number, 0 being the topmost frame, i.e. the innermost function.
18493 The @code{$pc} value for that frame.
18497 File name of the source file where the function lives.
18499 Line number corresponding to the @code{$pc}.
18502 If invoked without arguments, this command prints a backtrace for the
18503 whole stack. If given two integer arguments, it shows the frames whose
18504 levels are between the two arguments (inclusive). If the two arguments
18505 are equal, it shows the single frame at the corresponding level.
18507 @subsubheading @value{GDBN} Command
18509 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
18511 @subsubheading Example
18513 Full stack backtrace:
18519 [frame=@{level="0",addr="0x0001076c",func="foo",
18520 file="recursive2.c",line="11"@},
18521 frame=@{level="1",addr="0x000107a4",func="foo",
18522 file="recursive2.c",line="14"@},
18523 frame=@{level="2",addr="0x000107a4",func="foo",
18524 file="recursive2.c",line="14"@},
18525 frame=@{level="3",addr="0x000107a4",func="foo",
18526 file="recursive2.c",line="14"@},
18527 frame=@{level="4",addr="0x000107a4",func="foo",
18528 file="recursive2.c",line="14"@},
18529 frame=@{level="5",addr="0x000107a4",func="foo",
18530 file="recursive2.c",line="14"@},
18531 frame=@{level="6",addr="0x000107a4",func="foo",
18532 file="recursive2.c",line="14"@},
18533 frame=@{level="7",addr="0x000107a4",func="foo",
18534 file="recursive2.c",line="14"@},
18535 frame=@{level="8",addr="0x000107a4",func="foo",
18536 file="recursive2.c",line="14"@},
18537 frame=@{level="9",addr="0x000107a4",func="foo",
18538 file="recursive2.c",line="14"@},
18539 frame=@{level="10",addr="0x000107a4",func="foo",
18540 file="recursive2.c",line="14"@},
18541 frame=@{level="11",addr="0x00010738",func="main",
18542 file="recursive2.c",line="4"@}]
18546 Show frames between @var{low_frame} and @var{high_frame}:
18550 -stack-list-frames 3 5
18552 [frame=@{level="3",addr="0x000107a4",func="foo",
18553 file="recursive2.c",line="14"@},
18554 frame=@{level="4",addr="0x000107a4",func="foo",
18555 file="recursive2.c",line="14"@},
18556 frame=@{level="5",addr="0x000107a4",func="foo",
18557 file="recursive2.c",line="14"@}]
18561 Show a single frame:
18565 -stack-list-frames 3 3
18567 [frame=@{level="3",addr="0x000107a4",func="foo",
18568 file="recursive2.c",line="14"@}]
18573 @subheading The @code{-stack-list-locals} Command
18574 @findex -stack-list-locals
18576 @subsubheading Synopsis
18579 -stack-list-locals @var{print-values}
18582 Display the local variable names for the current frame. With an
18583 argument of 0 or @code{--no-values}, prints only the names of the variables.
18584 With argument of 1 or @code{--all-values}, prints also their values. With
18585 argument of 2 or @code{--simple-values}, prints the name, type and value for
18586 simple data types and the name and type for arrays, structures and
18587 unions. In this last case, the idea is that the user can see the
18588 value of simple data types immediately and he can create variable
18589 objects for other data types if he wishes to explore their values in
18592 @subsubheading @value{GDBN} Command
18594 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
18596 @subsubheading Example
18600 -stack-list-locals 0
18601 ^done,locals=[name="A",name="B",name="C"]
18603 -stack-list-locals --all-values
18604 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
18605 @{name="C",value="@{1, 2, 3@}"@}]
18606 -stack-list-locals --simple-values
18607 ^done,locals=[@{name="A",type="int",value="1"@},
18608 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
18613 @subheading The @code{-stack-select-frame} Command
18614 @findex -stack-select-frame
18616 @subsubheading Synopsis
18619 -stack-select-frame @var{framenum}
18622 Change the current frame. Select a different frame @var{framenum} on
18625 @subsubheading @value{GDBN} Command
18627 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
18628 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
18630 @subsubheading Example
18634 -stack-select-frame 2
18639 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18640 @node GDB/MI Symbol Query
18641 @section @sc{gdb/mi} Symbol Query Commands
18644 @subheading The @code{-symbol-info-address} Command
18645 @findex -symbol-info-address
18647 @subsubheading Synopsis
18650 -symbol-info-address @var{symbol}
18653 Describe where @var{symbol} is stored.
18655 @subsubheading @value{GDBN} Command
18657 The corresponding @value{GDBN} command is @samp{info address}.
18659 @subsubheading Example
18663 @subheading The @code{-symbol-info-file} Command
18664 @findex -symbol-info-file
18666 @subsubheading Synopsis
18672 Show the file for the symbol.
18674 @subsubheading @value{GDBN} Command
18676 There's no equivalent @value{GDBN} command. @code{gdbtk} has
18677 @samp{gdb_find_file}.
18679 @subsubheading Example
18683 @subheading The @code{-symbol-info-function} Command
18684 @findex -symbol-info-function
18686 @subsubheading Synopsis
18689 -symbol-info-function
18692 Show which function the symbol lives in.
18694 @subsubheading @value{GDBN} Command
18696 @samp{gdb_get_function} in @code{gdbtk}.
18698 @subsubheading Example
18702 @subheading The @code{-symbol-info-line} Command
18703 @findex -symbol-info-line
18705 @subsubheading Synopsis
18711 Show the core addresses of the code for a source line.
18713 @subsubheading @value{GDBN} Command
18715 The corresponding @value{GDBN} command is @samp{info line}.
18716 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
18718 @subsubheading Example
18722 @subheading The @code{-symbol-info-symbol} Command
18723 @findex -symbol-info-symbol
18725 @subsubheading Synopsis
18728 -symbol-info-symbol @var{addr}
18731 Describe what symbol is at location @var{addr}.
18733 @subsubheading @value{GDBN} Command
18735 The corresponding @value{GDBN} command is @samp{info symbol}.
18737 @subsubheading Example
18741 @subheading The @code{-symbol-list-functions} Command
18742 @findex -symbol-list-functions
18744 @subsubheading Synopsis
18747 -symbol-list-functions
18750 List the functions in the executable.
18752 @subsubheading @value{GDBN} Command
18754 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
18755 @samp{gdb_search} in @code{gdbtk}.
18757 @subsubheading Example
18761 @subheading The @code{-symbol-list-lines} Command
18762 @findex -symbol-list-lines
18764 @subsubheading Synopsis
18767 -symbol-list-lines @var{filename}
18770 Print the list of lines that contain code and their associated program
18771 addresses for the given source filename. The entries are sorted in
18772 ascending PC order.
18774 @subsubheading @value{GDBN} Command
18776 There is no corresponding @value{GDBN} command.
18778 @subsubheading Example
18781 -symbol-list-lines basics.c
18782 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
18787 @subheading The @code{-symbol-list-types} Command
18788 @findex -symbol-list-types
18790 @subsubheading Synopsis
18796 List all the type names.
18798 @subsubheading @value{GDBN} Command
18800 The corresponding commands are @samp{info types} in @value{GDBN},
18801 @samp{gdb_search} in @code{gdbtk}.
18803 @subsubheading Example
18807 @subheading The @code{-symbol-list-variables} Command
18808 @findex -symbol-list-variables
18810 @subsubheading Synopsis
18813 -symbol-list-variables
18816 List all the global and static variable names.
18818 @subsubheading @value{GDBN} Command
18820 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
18822 @subsubheading Example
18826 @subheading The @code{-symbol-locate} Command
18827 @findex -symbol-locate
18829 @subsubheading Synopsis
18835 @subsubheading @value{GDBN} Command
18837 @samp{gdb_loc} in @code{gdbtk}.
18839 @subsubheading Example
18843 @subheading The @code{-symbol-type} Command
18844 @findex -symbol-type
18846 @subsubheading Synopsis
18849 -symbol-type @var{variable}
18852 Show type of @var{variable}.
18854 @subsubheading @value{GDBN} Command
18856 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
18857 @samp{gdb_obj_variable}.
18859 @subsubheading Example
18863 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18864 @node GDB/MI Target Manipulation
18865 @section @sc{gdb/mi} Target Manipulation Commands
18868 @subheading The @code{-target-attach} Command
18869 @findex -target-attach
18871 @subsubheading Synopsis
18874 -target-attach @var{pid} | @var{file}
18877 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
18879 @subsubheading @value{GDBN} command
18881 The corresponding @value{GDBN} command is @samp{attach}.
18883 @subsubheading Example
18887 @subheading The @code{-target-compare-sections} Command
18888 @findex -target-compare-sections
18890 @subsubheading Synopsis
18893 -target-compare-sections [ @var{section} ]
18896 Compare data of section @var{section} on target to the exec file.
18897 Without the argument, all sections are compared.
18899 @subsubheading @value{GDBN} Command
18901 The @value{GDBN} equivalent is @samp{compare-sections}.
18903 @subsubheading Example
18907 @subheading The @code{-target-detach} Command
18908 @findex -target-detach
18910 @subsubheading Synopsis
18916 Disconnect from the remote target. There's no output.
18918 @subsubheading @value{GDBN} command
18920 The corresponding @value{GDBN} command is @samp{detach}.
18922 @subsubheading Example
18932 @subheading The @code{-target-disconnect} Command
18933 @findex -target-disconnect
18935 @subsubheading Synopsis
18941 Disconnect from the remote target. There's no output.
18943 @subsubheading @value{GDBN} command
18945 The corresponding @value{GDBN} command is @samp{disconnect}.
18947 @subsubheading Example
18957 @subheading The @code{-target-download} Command
18958 @findex -target-download
18960 @subsubheading Synopsis
18966 Loads the executable onto the remote target.
18967 It prints out an update message every half second, which includes the fields:
18971 The name of the section.
18973 The size of what has been sent so far for that section.
18975 The size of the section.
18977 The total size of what was sent so far (the current and the previous sections).
18979 The size of the overall executable to download.
18983 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
18984 @sc{gdb/mi} Output Syntax}).
18986 In addition, it prints the name and size of the sections, as they are
18987 downloaded. These messages include the following fields:
18991 The name of the section.
18993 The size of the section.
18995 The size of the overall executable to download.
18999 At the end, a summary is printed.
19001 @subsubheading @value{GDBN} Command
19003 The corresponding @value{GDBN} command is @samp{load}.
19005 @subsubheading Example
19007 Note: each status message appears on a single line. Here the messages
19008 have been broken down so that they can fit onto a page.
19013 +download,@{section=".text",section-size="6668",total-size="9880"@}
19014 +download,@{section=".text",section-sent="512",section-size="6668",
19015 total-sent="512",total-size="9880"@}
19016 +download,@{section=".text",section-sent="1024",section-size="6668",
19017 total-sent="1024",total-size="9880"@}
19018 +download,@{section=".text",section-sent="1536",section-size="6668",
19019 total-sent="1536",total-size="9880"@}
19020 +download,@{section=".text",section-sent="2048",section-size="6668",
19021 total-sent="2048",total-size="9880"@}
19022 +download,@{section=".text",section-sent="2560",section-size="6668",
19023 total-sent="2560",total-size="9880"@}
19024 +download,@{section=".text",section-sent="3072",section-size="6668",
19025 total-sent="3072",total-size="9880"@}
19026 +download,@{section=".text",section-sent="3584",section-size="6668",
19027 total-sent="3584",total-size="9880"@}
19028 +download,@{section=".text",section-sent="4096",section-size="6668",
19029 total-sent="4096",total-size="9880"@}
19030 +download,@{section=".text",section-sent="4608",section-size="6668",
19031 total-sent="4608",total-size="9880"@}
19032 +download,@{section=".text",section-sent="5120",section-size="6668",
19033 total-sent="5120",total-size="9880"@}
19034 +download,@{section=".text",section-sent="5632",section-size="6668",
19035 total-sent="5632",total-size="9880"@}
19036 +download,@{section=".text",section-sent="6144",section-size="6668",
19037 total-sent="6144",total-size="9880"@}
19038 +download,@{section=".text",section-sent="6656",section-size="6668",
19039 total-sent="6656",total-size="9880"@}
19040 +download,@{section=".init",section-size="28",total-size="9880"@}
19041 +download,@{section=".fini",section-size="28",total-size="9880"@}
19042 +download,@{section=".data",section-size="3156",total-size="9880"@}
19043 +download,@{section=".data",section-sent="512",section-size="3156",
19044 total-sent="7236",total-size="9880"@}
19045 +download,@{section=".data",section-sent="1024",section-size="3156",
19046 total-sent="7748",total-size="9880"@}
19047 +download,@{section=".data",section-sent="1536",section-size="3156",
19048 total-sent="8260",total-size="9880"@}
19049 +download,@{section=".data",section-sent="2048",section-size="3156",
19050 total-sent="8772",total-size="9880"@}
19051 +download,@{section=".data",section-sent="2560",section-size="3156",
19052 total-sent="9284",total-size="9880"@}
19053 +download,@{section=".data",section-sent="3072",section-size="3156",
19054 total-sent="9796",total-size="9880"@}
19055 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
19061 @subheading The @code{-target-exec-status} Command
19062 @findex -target-exec-status
19064 @subsubheading Synopsis
19067 -target-exec-status
19070 Provide information on the state of the target (whether it is running or
19071 not, for instance).
19073 @subsubheading @value{GDBN} Command
19075 There's no equivalent @value{GDBN} command.
19077 @subsubheading Example
19081 @subheading The @code{-target-list-available-targets} Command
19082 @findex -target-list-available-targets
19084 @subsubheading Synopsis
19087 -target-list-available-targets
19090 List the possible targets to connect to.
19092 @subsubheading @value{GDBN} Command
19094 The corresponding @value{GDBN} command is @samp{help target}.
19096 @subsubheading Example
19100 @subheading The @code{-target-list-current-targets} Command
19101 @findex -target-list-current-targets
19103 @subsubheading Synopsis
19106 -target-list-current-targets
19109 Describe the current target.
19111 @subsubheading @value{GDBN} Command
19113 The corresponding information is printed by @samp{info file} (among
19116 @subsubheading Example
19120 @subheading The @code{-target-list-parameters} Command
19121 @findex -target-list-parameters
19123 @subsubheading Synopsis
19126 -target-list-parameters
19131 @subsubheading @value{GDBN} Command
19135 @subsubheading Example
19139 @subheading The @code{-target-select} Command
19140 @findex -target-select
19142 @subsubheading Synopsis
19145 -target-select @var{type} @var{parameters @dots{}}
19148 Connect @value{GDBN} to the remote target. This command takes two args:
19152 The type of target, for instance @samp{async}, @samp{remote}, etc.
19153 @item @var{parameters}
19154 Device names, host names and the like. @xref{Target Commands, ,
19155 Commands for managing targets}, for more details.
19158 The output is a connection notification, followed by the address at
19159 which the target program is, in the following form:
19162 ^connected,addr="@var{address}",func="@var{function name}",
19163 args=[@var{arg list}]
19166 @subsubheading @value{GDBN} Command
19168 The corresponding @value{GDBN} command is @samp{target}.
19170 @subsubheading Example
19174 -target-select async /dev/ttya
19175 ^connected,addr="0xfe00a300",func="??",args=[]
19179 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19180 @node GDB/MI Thread Commands
19181 @section @sc{gdb/mi} Thread Commands
19184 @subheading The @code{-thread-info} Command
19185 @findex -thread-info
19187 @subsubheading Synopsis
19193 @subsubheading @value{GDBN} command
19197 @subsubheading Example
19201 @subheading The @code{-thread-list-all-threads} Command
19202 @findex -thread-list-all-threads
19204 @subsubheading Synopsis
19207 -thread-list-all-threads
19210 @subsubheading @value{GDBN} Command
19212 The equivalent @value{GDBN} command is @samp{info threads}.
19214 @subsubheading Example
19218 @subheading The @code{-thread-list-ids} Command
19219 @findex -thread-list-ids
19221 @subsubheading Synopsis
19227 Produces a list of the currently known @value{GDBN} thread ids. At the
19228 end of the list it also prints the total number of such threads.
19230 @subsubheading @value{GDBN} Command
19232 Part of @samp{info threads} supplies the same information.
19234 @subsubheading Example
19236 No threads present, besides the main process:
19241 ^done,thread-ids=@{@},number-of-threads="0"
19251 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
19252 number-of-threads="3"
19257 @subheading The @code{-thread-select} Command
19258 @findex -thread-select
19260 @subsubheading Synopsis
19263 -thread-select @var{threadnum}
19266 Make @var{threadnum} the current thread. It prints the number of the new
19267 current thread, and the topmost frame for that thread.
19269 @subsubheading @value{GDBN} Command
19271 The corresponding @value{GDBN} command is @samp{thread}.
19273 @subsubheading Example
19280 *stopped,reason="end-stepping-range",thread-id="2",line="187",
19281 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
19285 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
19286 number-of-threads="3"
19289 ^done,new-thread-id="3",
19290 frame=@{level="0",func="vprintf",
19291 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
19292 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
19296 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19297 @node GDB/MI Tracepoint Commands
19298 @section @sc{gdb/mi} Tracepoint Commands
19300 The tracepoint commands are not yet implemented.
19302 @c @subheading -trace-actions
19304 @c @subheading -trace-delete
19306 @c @subheading -trace-disable
19308 @c @subheading -trace-dump
19310 @c @subheading -trace-enable
19312 @c @subheading -trace-exists
19314 @c @subheading -trace-find
19316 @c @subheading -trace-frame-number
19318 @c @subheading -trace-info
19320 @c @subheading -trace-insert
19322 @c @subheading -trace-list
19324 @c @subheading -trace-pass-count
19326 @c @subheading -trace-save
19328 @c @subheading -trace-start
19330 @c @subheading -trace-stop
19333 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19334 @node GDB/MI Variable Objects
19335 @section @sc{gdb/mi} Variable Objects
19338 @subheading Motivation for Variable Objects in @sc{gdb/mi}
19340 For the implementation of a variable debugger window (locals, watched
19341 expressions, etc.), we are proposing the adaptation of the existing code
19342 used by @code{Insight}.
19344 The two main reasons for that are:
19348 It has been proven in practice (it is already on its second generation).
19351 It will shorten development time (needless to say how important it is
19355 The original interface was designed to be used by Tcl code, so it was
19356 slightly changed so it could be used through @sc{gdb/mi}. This section
19357 describes the @sc{gdb/mi} operations that will be available and gives some
19358 hints about their use.
19360 @emph{Note}: In addition to the set of operations described here, we
19361 expect the @sc{gui} implementation of a variable window to require, at
19362 least, the following operations:
19365 @item @code{-gdb-show} @code{output-radix}
19366 @item @code{-stack-list-arguments}
19367 @item @code{-stack-list-locals}
19368 @item @code{-stack-select-frame}
19371 @subheading Introduction to Variable Objects in @sc{gdb/mi}
19373 @cindex variable objects in @sc{gdb/mi}
19374 The basic idea behind variable objects is the creation of a named object
19375 to represent a variable, an expression, a memory location or even a CPU
19376 register. For each object created, a set of operations is available for
19377 examining or changing its properties.
19379 Furthermore, complex data types, such as C structures, are represented
19380 in a tree format. For instance, the @code{struct} type variable is the
19381 root and the children will represent the struct members. If a child
19382 is itself of a complex type, it will also have children of its own.
19383 Appropriate language differences are handled for C, C@t{++} and Java.
19385 When returning the actual values of the objects, this facility allows
19386 for the individual selection of the display format used in the result
19387 creation. It can be chosen among: binary, decimal, hexadecimal, octal
19388 and natural. Natural refers to a default format automatically
19389 chosen based on the variable type (like decimal for an @code{int}, hex
19390 for pointers, etc.).
19392 The following is the complete set of @sc{gdb/mi} operations defined to
19393 access this functionality:
19395 @multitable @columnfractions .4 .6
19396 @item @strong{Operation}
19397 @tab @strong{Description}
19399 @item @code{-var-create}
19400 @tab create a variable object
19401 @item @code{-var-delete}
19402 @tab delete the variable object and its children
19403 @item @code{-var-set-format}
19404 @tab set the display format of this variable
19405 @item @code{-var-show-format}
19406 @tab show the display format of this variable
19407 @item @code{-var-info-num-children}
19408 @tab tells how many children this object has
19409 @item @code{-var-list-children}
19410 @tab return a list of the object's children
19411 @item @code{-var-info-type}
19412 @tab show the type of this variable object
19413 @item @code{-var-info-expression}
19414 @tab print what this variable object represents
19415 @item @code{-var-show-attributes}
19416 @tab is this variable editable? does it exist here?
19417 @item @code{-var-evaluate-expression}
19418 @tab get the value of this variable
19419 @item @code{-var-assign}
19420 @tab set the value of this variable
19421 @item @code{-var-update}
19422 @tab update the variable and its children
19425 In the next subsection we describe each operation in detail and suggest
19426 how it can be used.
19428 @subheading Description And Use of Operations on Variable Objects
19430 @subheading The @code{-var-create} Command
19431 @findex -var-create
19433 @subsubheading Synopsis
19436 -var-create @{@var{name} | "-"@}
19437 @{@var{frame-addr} | "*"@} @var{expression}
19440 This operation creates a variable object, which allows the monitoring of
19441 a variable, the result of an expression, a memory cell or a CPU
19444 The @var{name} parameter is the string by which the object can be
19445 referenced. It must be unique. If @samp{-} is specified, the varobj
19446 system will generate a string ``varNNNNNN'' automatically. It will be
19447 unique provided that one does not specify @var{name} on that format.
19448 The command fails if a duplicate name is found.
19450 The frame under which the expression should be evaluated can be
19451 specified by @var{frame-addr}. A @samp{*} indicates that the current
19452 frame should be used.
19454 @var{expression} is any expression valid on the current language set (must not
19455 begin with a @samp{*}), or one of the following:
19459 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
19462 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
19465 @samp{$@var{regname}} --- a CPU register name
19468 @subsubheading Result
19470 This operation returns the name, number of children and the type of the
19471 object created. Type is returned as a string as the ones generated by
19472 the @value{GDBN} CLI:
19475 name="@var{name}",numchild="N",type="@var{type}"
19479 @subheading The @code{-var-delete} Command
19480 @findex -var-delete
19482 @subsubheading Synopsis
19485 -var-delete @var{name}
19488 Deletes a previously created variable object and all of its children.
19490 Returns an error if the object @var{name} is not found.
19493 @subheading The @code{-var-set-format} Command
19494 @findex -var-set-format
19496 @subsubheading Synopsis
19499 -var-set-format @var{name} @var{format-spec}
19502 Sets the output format for the value of the object @var{name} to be
19505 The syntax for the @var{format-spec} is as follows:
19508 @var{format-spec} @expansion{}
19509 @{binary | decimal | hexadecimal | octal | natural@}
19513 @subheading The @code{-var-show-format} Command
19514 @findex -var-show-format
19516 @subsubheading Synopsis
19519 -var-show-format @var{name}
19522 Returns the format used to display the value of the object @var{name}.
19525 @var{format} @expansion{}
19530 @subheading The @code{-var-info-num-children} Command
19531 @findex -var-info-num-children
19533 @subsubheading Synopsis
19536 -var-info-num-children @var{name}
19539 Returns the number of children of a variable object @var{name}:
19546 @subheading The @code{-var-list-children} Command
19547 @findex -var-list-children
19549 @subsubheading Synopsis
19552 -var-list-children [@var{print-values}] @var{name}
19555 Returns a list of the children of the specified variable object. With
19556 just the variable object name as an argument or with an optional
19557 preceding argument of 0 or @code{--no-values}, prints only the names of the
19558 variables. With an optional preceding argument of 1 or @code{--all-values},
19559 also prints their values.
19561 @subsubheading Example
19565 -var-list-children n
19566 numchild=@var{n},children=[@{name=@var{name},
19567 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
19569 -var-list-children --all-values n
19570 numchild=@var{n},children=[@{name=@var{name},
19571 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
19575 @subheading The @code{-var-info-type} Command
19576 @findex -var-info-type
19578 @subsubheading Synopsis
19581 -var-info-type @var{name}
19584 Returns the type of the specified variable @var{name}. The type is
19585 returned as a string in the same format as it is output by the
19589 type=@var{typename}
19593 @subheading The @code{-var-info-expression} Command
19594 @findex -var-info-expression
19596 @subsubheading Synopsis
19599 -var-info-expression @var{name}
19602 Returns what is represented by the variable object @var{name}:
19605 lang=@var{lang-spec},exp=@var{expression}
19609 where @var{lang-spec} is @code{@{"C" | "C++" | "Java"@}}.
19611 @subheading The @code{-var-show-attributes} Command
19612 @findex -var-show-attributes
19614 @subsubheading Synopsis
19617 -var-show-attributes @var{name}
19620 List attributes of the specified variable object @var{name}:
19623 status=@var{attr} [ ( ,@var{attr} )* ]
19627 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
19629 @subheading The @code{-var-evaluate-expression} Command
19630 @findex -var-evaluate-expression
19632 @subsubheading Synopsis
19635 -var-evaluate-expression @var{name}
19638 Evaluates the expression that is represented by the specified variable
19639 object and returns its value as a string in the current format specified
19646 Note that one must invoke @code{-var-list-children} for a variable
19647 before the value of a child variable can be evaluated.
19649 @subheading The @code{-var-assign} Command
19650 @findex -var-assign
19652 @subsubheading Synopsis
19655 -var-assign @var{name} @var{expression}
19658 Assigns the value of @var{expression} to the variable object specified
19659 by @var{name}. The object must be @samp{editable}. If the variable's
19660 value is altered by the assign, the variable will show up in any
19661 subsequent @code{-var-update} list.
19663 @subsubheading Example
19671 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
19675 @subheading The @code{-var-update} Command
19676 @findex -var-update
19678 @subsubheading Synopsis
19681 -var-update @{@var{name} | "*"@}
19684 Update the value of the variable object @var{name} by evaluating its
19685 expression after fetching all the new values from memory or registers.
19686 A @samp{*} causes all existing variable objects to be updated.
19690 @chapter @value{GDBN} Annotations
19692 This chapter describes annotations in @value{GDBN}. Annotations were
19693 designed to interface @value{GDBN} to graphical user interfaces or other
19694 similar programs which want to interact with @value{GDBN} at a
19695 relatively high level.
19697 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
19701 This is Edition @value{EDITION}, @value{DATE}.
19705 * Annotations Overview:: What annotations are; the general syntax.
19706 * Server Prefix:: Issuing a command without affecting user state.
19707 * Prompting:: Annotations marking @value{GDBN}'s need for input.
19708 * Errors:: Annotations for error messages.
19709 * Invalidation:: Some annotations describe things now invalid.
19710 * Annotations for Running::
19711 Whether the program is running, how it stopped, etc.
19712 * Source Annotations:: Annotations describing source code.
19715 @node Annotations Overview
19716 @section What is an Annotation?
19717 @cindex annotations
19719 Annotations start with a newline character, two @samp{control-z}
19720 characters, and the name of the annotation. If there is no additional
19721 information associated with this annotation, the name of the annotation
19722 is followed immediately by a newline. If there is additional
19723 information, the name of the annotation is followed by a space, the
19724 additional information, and a newline. The additional information
19725 cannot contain newline characters.
19727 Any output not beginning with a newline and two @samp{control-z}
19728 characters denotes literal output from @value{GDBN}. Currently there is
19729 no need for @value{GDBN} to output a newline followed by two
19730 @samp{control-z} characters, but if there was such a need, the
19731 annotations could be extended with an @samp{escape} annotation which
19732 means those three characters as output.
19734 The annotation @var{level}, which is specified using the
19735 @option{--annotate} command line option (@pxref{Mode Options}), controls
19736 how much information @value{GDBN} prints together with its prompt,
19737 values of expressions, source lines, and other types of output. Level 0
19738 is for no anntations, level 1 is for use when @value{GDBN} is run as a
19739 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
19740 for programs that control @value{GDBN}, and level 2 annotations have
19741 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
19742 Interface, annotate, GDB's Obsolete Annotations}).
19745 @kindex set annotate
19746 @item set annotate @var{level}
19747 The @value{GDB} command @code{set annotate} sets the level of
19748 annotations to the specified @var{level}.
19750 @item show annotate
19751 @kindex show annotate
19752 Show the current annotation level.
19755 This chapter describes level 3 annotations.
19757 A simple example of starting up @value{GDBN} with annotations is:
19760 $ @kbd{gdb --annotate=3}
19762 Copyright 2003 Free Software Foundation, Inc.
19763 GDB is free software, covered by the GNU General Public License,
19764 and you are welcome to change it and/or distribute copies of it
19765 under certain conditions.
19766 Type "show copying" to see the conditions.
19767 There is absolutely no warranty for GDB. Type "show warranty"
19769 This GDB was configured as "i386-pc-linux-gnu"
19780 Here @samp{quit} is input to @value{GDBN}; the rest is output from
19781 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
19782 denotes a @samp{control-z} character) are annotations; the rest is
19783 output from @value{GDBN}.
19785 @node Server Prefix
19786 @section The Server Prefix
19787 @cindex server prefix for annotations
19789 To issue a command to @value{GDBN} without affecting certain aspects of
19790 the state which is seen by users, prefix it with @samp{server }. This
19791 means that this command will not affect the command history, nor will it
19792 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
19793 pressed on a line by itself.
19795 The server prefix does not affect the recording of values into the value
19796 history; to print a value without recording it into the value history,
19797 use the @code{output} command instead of the @code{print} command.
19800 @section Annotation for @value{GDBN} Input
19802 @cindex annotations for prompts
19803 When @value{GDBN} prompts for input, it annotates this fact so it is possible
19804 to know when to send output, when the output from a given command is
19807 Different kinds of input each have a different @dfn{input type}. Each
19808 input type has three annotations: a @code{pre-} annotation, which
19809 denotes the beginning of any prompt which is being output, a plain
19810 annotation, which denotes the end of the prompt, and then a @code{post-}
19811 annotation which denotes the end of any echo which may (or may not) be
19812 associated with the input. For example, the @code{prompt} input type
19813 features the following annotations:
19821 The input types are
19826 @findex post-prompt
19828 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
19830 @findex pre-commands
19832 @findex post-commands
19834 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
19835 command. The annotations are repeated for each command which is input.
19837 @findex pre-overload-choice
19838 @findex overload-choice
19839 @findex post-overload-choice
19840 @item overload-choice
19841 When @value{GDBN} wants the user to select between various overloaded functions.
19847 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
19849 @findex pre-prompt-for-continue
19850 @findex prompt-for-continue
19851 @findex post-prompt-for-continue
19852 @item prompt-for-continue
19853 When @value{GDBN} is asking the user to press return to continue. Note: Don't
19854 expect this to work well; instead use @code{set height 0} to disable
19855 prompting. This is because the counting of lines is buggy in the
19856 presence of annotations.
19861 @cindex annotations for errors, warnings and interrupts
19868 This annotation occurs right before @value{GDBN} responds to an interrupt.
19875 This annotation occurs right before @value{GDBN} responds to an error.
19877 Quit and error annotations indicate that any annotations which @value{GDBN} was
19878 in the middle of may end abruptly. For example, if a
19879 @code{value-history-begin} annotation is followed by a @code{error}, one
19880 cannot expect to receive the matching @code{value-history-end}. One
19881 cannot expect not to receive it either, however; an error annotation
19882 does not necessarily mean that @value{GDBN} is immediately returning all the way
19885 @findex error-begin
19886 A quit or error annotation may be preceded by
19892 Any output between that and the quit or error annotation is the error
19895 Warning messages are not yet annotated.
19896 @c If we want to change that, need to fix warning(), type_error(),
19897 @c range_error(), and possibly other places.
19900 @section Invalidation Notices
19902 @cindex annotations for invalidation messages
19903 The following annotations say that certain pieces of state may have
19907 @findex frames-invalid
19908 @item ^Z^Zframes-invalid
19910 The frames (for example, output from the @code{backtrace} command) may
19913 @findex breakpoints-invalid
19914 @item ^Z^Zbreakpoints-invalid
19916 The breakpoints may have changed. For example, the user just added or
19917 deleted a breakpoint.
19920 @node Annotations for Running
19921 @section Running the Program
19922 @cindex annotations for running programs
19926 When the program starts executing due to a @value{GDBN} command such as
19927 @code{step} or @code{continue},
19933 is output. When the program stops,
19939 is output. Before the @code{stopped} annotation, a variety of
19940 annotations describe how the program stopped.
19944 @item ^Z^Zexited @var{exit-status}
19945 The program exited, and @var{exit-status} is the exit status (zero for
19946 successful exit, otherwise nonzero).
19949 @findex signal-name
19950 @findex signal-name-end
19951 @findex signal-string
19952 @findex signal-string-end
19953 @item ^Z^Zsignalled
19954 The program exited with a signal. After the @code{^Z^Zsignalled}, the
19955 annotation continues:
19961 ^Z^Zsignal-name-end
19965 ^Z^Zsignal-string-end
19970 where @var{name} is the name of the signal, such as @code{SIGILL} or
19971 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
19972 as @code{Illegal Instruction} or @code{Segmentation fault}.
19973 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
19974 user's benefit and have no particular format.
19978 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
19979 just saying that the program received the signal, not that it was
19980 terminated with it.
19983 @item ^Z^Zbreakpoint @var{number}
19984 The program hit breakpoint number @var{number}.
19987 @item ^Z^Zwatchpoint @var{number}
19988 The program hit watchpoint number @var{number}.
19991 @node Source Annotations
19992 @section Displaying Source
19993 @cindex annotations for source display
19996 The following annotation is used instead of displaying source code:
19999 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
20002 where @var{filename} is an absolute file name indicating which source
20003 file, @var{line} is the line number within that file (where 1 is the
20004 first line in the file), @var{character} is the character position
20005 within the file (where 0 is the first character in the file) (for most
20006 debug formats this will necessarily point to the beginning of a line),
20007 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
20008 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
20009 @var{addr} is the address in the target program associated with the
20010 source which is being displayed. @var{addr} is in the form @samp{0x}
20011 followed by one or more lowercase hex digits (note that this does not
20012 depend on the language).
20015 @chapter Reporting Bugs in @value{GDBN}
20016 @cindex bugs in @value{GDBN}
20017 @cindex reporting bugs in @value{GDBN}
20019 Your bug reports play an essential role in making @value{GDBN} reliable.
20021 Reporting a bug may help you by bringing a solution to your problem, or it
20022 may not. But in any case the principal function of a bug report is to help
20023 the entire community by making the next version of @value{GDBN} work better. Bug
20024 reports are your contribution to the maintenance of @value{GDBN}.
20026 In order for a bug report to serve its purpose, you must include the
20027 information that enables us to fix the bug.
20030 * Bug Criteria:: Have you found a bug?
20031 * Bug Reporting:: How to report bugs
20035 @section Have you found a bug?
20036 @cindex bug criteria
20038 If you are not sure whether you have found a bug, here are some guidelines:
20041 @cindex fatal signal
20042 @cindex debugger crash
20043 @cindex crash of debugger
20045 If the debugger gets a fatal signal, for any input whatever, that is a
20046 @value{GDBN} bug. Reliable debuggers never crash.
20048 @cindex error on valid input
20050 If @value{GDBN} produces an error message for valid input, that is a
20051 bug. (Note that if you're cross debugging, the problem may also be
20052 somewhere in the connection to the target.)
20054 @cindex invalid input
20056 If @value{GDBN} does not produce an error message for invalid input,
20057 that is a bug. However, you should note that your idea of
20058 ``invalid input'' might be our idea of ``an extension'' or ``support
20059 for traditional practice''.
20062 If you are an experienced user of debugging tools, your suggestions
20063 for improvement of @value{GDBN} are welcome in any case.
20066 @node Bug Reporting
20067 @section How to report bugs
20068 @cindex bug reports
20069 @cindex @value{GDBN} bugs, reporting
20071 A number of companies and individuals offer support for @sc{gnu} products.
20072 If you obtained @value{GDBN} from a support organization, we recommend you
20073 contact that organization first.
20075 You can find contact information for many support companies and
20076 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
20078 @c should add a web page ref...
20080 In any event, we also recommend that you submit bug reports for
20081 @value{GDBN}. The prefered method is to submit them directly using
20082 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
20083 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
20086 @strong{Do not send bug reports to @samp{info-gdb}, or to
20087 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
20088 not want to receive bug reports. Those that do have arranged to receive
20091 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
20092 serves as a repeater. The mailing list and the newsgroup carry exactly
20093 the same messages. Often people think of posting bug reports to the
20094 newsgroup instead of mailing them. This appears to work, but it has one
20095 problem which can be crucial: a newsgroup posting often lacks a mail
20096 path back to the sender. Thus, if we need to ask for more information,
20097 we may be unable to reach you. For this reason, it is better to send
20098 bug reports to the mailing list.
20100 The fundamental principle of reporting bugs usefully is this:
20101 @strong{report all the facts}. If you are not sure whether to state a
20102 fact or leave it out, state it!
20104 Often people omit facts because they think they know what causes the
20105 problem and assume that some details do not matter. Thus, you might
20106 assume that the name of the variable you use in an example does not matter.
20107 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
20108 stray memory reference which happens to fetch from the location where that
20109 name is stored in memory; perhaps, if the name were different, the contents
20110 of that location would fool the debugger into doing the right thing despite
20111 the bug. Play it safe and give a specific, complete example. That is the
20112 easiest thing for you to do, and the most helpful.
20114 Keep in mind that the purpose of a bug report is to enable us to fix the
20115 bug. It may be that the bug has been reported previously, but neither
20116 you nor we can know that unless your bug report is complete and
20119 Sometimes people give a few sketchy facts and ask, ``Does this ring a
20120 bell?'' Those bug reports are useless, and we urge everyone to
20121 @emph{refuse to respond to them} except to chide the sender to report
20124 To enable us to fix the bug, you should include all these things:
20128 The version of @value{GDBN}. @value{GDBN} announces it if you start
20129 with no arguments; you can also print it at any time using @code{show
20132 Without this, we will not know whether there is any point in looking for
20133 the bug in the current version of @value{GDBN}.
20136 The type of machine you are using, and the operating system name and
20140 What compiler (and its version) was used to compile @value{GDBN}---e.g.
20141 ``@value{GCC}--2.8.1''.
20144 What compiler (and its version) was used to compile the program you are
20145 debugging---e.g. ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
20146 C Compiler''. For GCC, you can say @code{gcc --version} to get this
20147 information; for other compilers, see the documentation for those
20151 The command arguments you gave the compiler to compile your example and
20152 observe the bug. For example, did you use @samp{-O}? To guarantee
20153 you will not omit something important, list them all. A copy of the
20154 Makefile (or the output from make) is sufficient.
20156 If we were to try to guess the arguments, we would probably guess wrong
20157 and then we might not encounter the bug.
20160 A complete input script, and all necessary source files, that will
20164 A description of what behavior you observe that you believe is
20165 incorrect. For example, ``It gets a fatal signal.''
20167 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
20168 will certainly notice it. But if the bug is incorrect output, we might
20169 not notice unless it is glaringly wrong. You might as well not give us
20170 a chance to make a mistake.
20172 Even if the problem you experience is a fatal signal, you should still
20173 say so explicitly. Suppose something strange is going on, such as, your
20174 copy of @value{GDBN} is out of synch, or you have encountered a bug in
20175 the C library on your system. (This has happened!) Your copy might
20176 crash and ours would not. If you told us to expect a crash, then when
20177 ours fails to crash, we would know that the bug was not happening for
20178 us. If you had not told us to expect a crash, then we would not be able
20179 to draw any conclusion from our observations.
20182 @cindex recording a session script
20183 To collect all this information, you can use a session recording program
20184 such as @command{script}, which is available on many Unix systems.
20185 Just run your @value{GDBN} session inside @command{script} and then
20186 include the @file{typescript} file with your bug report.
20188 Another way to record a @value{GDBN} session is to run @value{GDBN}
20189 inside Emacs and then save the entire buffer to a file.
20192 If you wish to suggest changes to the @value{GDBN} source, send us context
20193 diffs. If you even discuss something in the @value{GDBN} source, refer to
20194 it by context, not by line number.
20196 The line numbers in our development sources will not match those in your
20197 sources. Your line numbers would convey no useful information to us.
20201 Here are some things that are not necessary:
20205 A description of the envelope of the bug.
20207 Often people who encounter a bug spend a lot of time investigating
20208 which changes to the input file will make the bug go away and which
20209 changes will not affect it.
20211 This is often time consuming and not very useful, because the way we
20212 will find the bug is by running a single example under the debugger
20213 with breakpoints, not by pure deduction from a series of examples.
20214 We recommend that you save your time for something else.
20216 Of course, if you can find a simpler example to report @emph{instead}
20217 of the original one, that is a convenience for us. Errors in the
20218 output will be easier to spot, running under the debugger will take
20219 less time, and so on.
20221 However, simplification is not vital; if you do not want to do this,
20222 report the bug anyway and send us the entire test case you used.
20225 A patch for the bug.
20227 A patch for the bug does help us if it is a good one. But do not omit
20228 the necessary information, such as the test case, on the assumption that
20229 a patch is all we need. We might see problems with your patch and decide
20230 to fix the problem another way, or we might not understand it at all.
20232 Sometimes with a program as complicated as @value{GDBN} it is very hard to
20233 construct an example that will make the program follow a certain path
20234 through the code. If you do not send us the example, we will not be able
20235 to construct one, so we will not be able to verify that the bug is fixed.
20237 And if we cannot understand what bug you are trying to fix, or why your
20238 patch should be an improvement, we will not install it. A test case will
20239 help us to understand.
20242 A guess about what the bug is or what it depends on.
20244 Such guesses are usually wrong. Even we cannot guess right about such
20245 things without first using the debugger to find the facts.
20248 @c The readline documentation is distributed with the readline code
20249 @c and consists of the two following files:
20251 @c inc-hist.texinfo
20252 @c Use -I with makeinfo to point to the appropriate directory,
20253 @c environment var TEXINPUTS with TeX.
20254 @include rluser.texinfo
20255 @include inc-hist.texinfo
20258 @node Formatting Documentation
20259 @appendix Formatting Documentation
20261 @cindex @value{GDBN} reference card
20262 @cindex reference card
20263 The @value{GDBN} 4 release includes an already-formatted reference card, ready
20264 for printing with PostScript or Ghostscript, in the @file{gdb}
20265 subdirectory of the main source directory@footnote{In
20266 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
20267 release.}. If you can use PostScript or Ghostscript with your printer,
20268 you can print the reference card immediately with @file{refcard.ps}.
20270 The release also includes the source for the reference card. You
20271 can format it, using @TeX{}, by typing:
20277 The @value{GDBN} reference card is designed to print in @dfn{landscape}
20278 mode on US ``letter'' size paper;
20279 that is, on a sheet 11 inches wide by 8.5 inches
20280 high. You will need to specify this form of printing as an option to
20281 your @sc{dvi} output program.
20283 @cindex documentation
20285 All the documentation for @value{GDBN} comes as part of the machine-readable
20286 distribution. The documentation is written in Texinfo format, which is
20287 a documentation system that uses a single source file to produce both
20288 on-line information and a printed manual. You can use one of the Info
20289 formatting commands to create the on-line version of the documentation
20290 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
20292 @value{GDBN} includes an already formatted copy of the on-line Info
20293 version of this manual in the @file{gdb} subdirectory. The main Info
20294 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
20295 subordinate files matching @samp{gdb.info*} in the same directory. If
20296 necessary, you can print out these files, or read them with any editor;
20297 but they are easier to read using the @code{info} subsystem in @sc{gnu}
20298 Emacs or the standalone @code{info} program, available as part of the
20299 @sc{gnu} Texinfo distribution.
20301 If you want to format these Info files yourself, you need one of the
20302 Info formatting programs, such as @code{texinfo-format-buffer} or
20305 If you have @code{makeinfo} installed, and are in the top level
20306 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
20307 version @value{GDBVN}), you can make the Info file by typing:
20314 If you want to typeset and print copies of this manual, you need @TeX{},
20315 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
20316 Texinfo definitions file.
20318 @TeX{} is a typesetting program; it does not print files directly, but
20319 produces output files called @sc{dvi} files. To print a typeset
20320 document, you need a program to print @sc{dvi} files. If your system
20321 has @TeX{} installed, chances are it has such a program. The precise
20322 command to use depends on your system; @kbd{lpr -d} is common; another
20323 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
20324 require a file name without any extension or a @samp{.dvi} extension.
20326 @TeX{} also requires a macro definitions file called
20327 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
20328 written in Texinfo format. On its own, @TeX{} cannot either read or
20329 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
20330 and is located in the @file{gdb-@var{version-number}/texinfo}
20333 If you have @TeX{} and a @sc{dvi} printer program installed, you can
20334 typeset and print this manual. First switch to the the @file{gdb}
20335 subdirectory of the main source directory (for example, to
20336 @file{gdb-@value{GDBVN}/gdb}) and type:
20342 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
20344 @node Installing GDB
20345 @appendix Installing @value{GDBN}
20346 @cindex configuring @value{GDBN}
20347 @cindex installation
20348 @cindex configuring @value{GDBN}, and source tree subdirectories
20350 @value{GDBN} comes with a @code{configure} script that automates the process
20351 of preparing @value{GDBN} for installation; you can then use @code{make} to
20352 build the @code{gdb} program.
20354 @c irrelevant in info file; it's as current as the code it lives with.
20355 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
20356 look at the @file{README} file in the sources; we may have improved the
20357 installation procedures since publishing this manual.}
20360 The @value{GDBN} distribution includes all the source code you need for
20361 @value{GDBN} in a single directory, whose name is usually composed by
20362 appending the version number to @samp{gdb}.
20364 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
20365 @file{gdb-@value{GDBVN}} directory. That directory contains:
20368 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
20369 script for configuring @value{GDBN} and all its supporting libraries
20371 @item gdb-@value{GDBVN}/gdb
20372 the source specific to @value{GDBN} itself
20374 @item gdb-@value{GDBVN}/bfd
20375 source for the Binary File Descriptor library
20377 @item gdb-@value{GDBVN}/include
20378 @sc{gnu} include files
20380 @item gdb-@value{GDBVN}/libiberty
20381 source for the @samp{-liberty} free software library
20383 @item gdb-@value{GDBVN}/opcodes
20384 source for the library of opcode tables and disassemblers
20386 @item gdb-@value{GDBVN}/readline
20387 source for the @sc{gnu} command-line interface
20389 @item gdb-@value{GDBVN}/glob
20390 source for the @sc{gnu} filename pattern-matching subroutine
20392 @item gdb-@value{GDBVN}/mmalloc
20393 source for the @sc{gnu} memory-mapped malloc package
20396 The simplest way to configure and build @value{GDBN} is to run @code{configure}
20397 from the @file{gdb-@var{version-number}} source directory, which in
20398 this example is the @file{gdb-@value{GDBVN}} directory.
20400 First switch to the @file{gdb-@var{version-number}} source directory
20401 if you are not already in it; then run @code{configure}. Pass the
20402 identifier for the platform on which @value{GDBN} will run as an
20408 cd gdb-@value{GDBVN}
20409 ./configure @var{host}
20414 where @var{host} is an identifier such as @samp{sun4} or
20415 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
20416 (You can often leave off @var{host}; @code{configure} tries to guess the
20417 correct value by examining your system.)
20419 Running @samp{configure @var{host}} and then running @code{make} builds the
20420 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
20421 libraries, then @code{gdb} itself. The configured source files, and the
20422 binaries, are left in the corresponding source directories.
20425 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
20426 system does not recognize this automatically when you run a different
20427 shell, you may need to run @code{sh} on it explicitly:
20430 sh configure @var{host}
20433 If you run @code{configure} from a directory that contains source
20434 directories for multiple libraries or programs, such as the
20435 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
20436 creates configuration files for every directory level underneath (unless
20437 you tell it not to, with the @samp{--norecursion} option).
20439 You should run the @code{configure} script from the top directory in the
20440 source tree, the @file{gdb-@var{version-number}} directory. If you run
20441 @code{configure} from one of the subdirectories, you will configure only
20442 that subdirectory. That is usually not what you want. In particular,
20443 if you run the first @code{configure} from the @file{gdb} subdirectory
20444 of the @file{gdb-@var{version-number}} directory, you will omit the
20445 configuration of @file{bfd}, @file{readline}, and other sibling
20446 directories of the @file{gdb} subdirectory. This leads to build errors
20447 about missing include files such as @file{bfd/bfd.h}.
20449 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
20450 However, you should make sure that the shell on your path (named by
20451 the @samp{SHELL} environment variable) is publicly readable. Remember
20452 that @value{GDBN} uses the shell to start your program---some systems refuse to
20453 let @value{GDBN} debug child processes whose programs are not readable.
20456 * Separate Objdir:: Compiling @value{GDBN} in another directory
20457 * Config Names:: Specifying names for hosts and targets
20458 * Configure Options:: Summary of options for configure
20461 @node Separate Objdir
20462 @section Compiling @value{GDBN} in another directory
20464 If you want to run @value{GDBN} versions for several host or target machines,
20465 you need a different @code{gdb} compiled for each combination of
20466 host and target. @code{configure} is designed to make this easy by
20467 allowing you to generate each configuration in a separate subdirectory,
20468 rather than in the source directory. If your @code{make} program
20469 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
20470 @code{make} in each of these directories builds the @code{gdb}
20471 program specified there.
20473 To build @code{gdb} in a separate directory, run @code{configure}
20474 with the @samp{--srcdir} option to specify where to find the source.
20475 (You also need to specify a path to find @code{configure}
20476 itself from your working directory. If the path to @code{configure}
20477 would be the same as the argument to @samp{--srcdir}, you can leave out
20478 the @samp{--srcdir} option; it is assumed.)
20480 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
20481 separate directory for a Sun 4 like this:
20485 cd gdb-@value{GDBVN}
20488 ../gdb-@value{GDBVN}/configure sun4
20493 When @code{configure} builds a configuration using a remote source
20494 directory, it creates a tree for the binaries with the same structure
20495 (and using the same names) as the tree under the source directory. In
20496 the example, you'd find the Sun 4 library @file{libiberty.a} in the
20497 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
20498 @file{gdb-sun4/gdb}.
20500 Make sure that your path to the @file{configure} script has just one
20501 instance of @file{gdb} in it. If your path to @file{configure} looks
20502 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
20503 one subdirectory of @value{GDBN}, not the whole package. This leads to
20504 build errors about missing include files such as @file{bfd/bfd.h}.
20506 One popular reason to build several @value{GDBN} configurations in separate
20507 directories is to configure @value{GDBN} for cross-compiling (where
20508 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
20509 programs that run on another machine---the @dfn{target}).
20510 You specify a cross-debugging target by
20511 giving the @samp{--target=@var{target}} option to @code{configure}.
20513 When you run @code{make} to build a program or library, you must run
20514 it in a configured directory---whatever directory you were in when you
20515 called @code{configure} (or one of its subdirectories).
20517 The @code{Makefile} that @code{configure} generates in each source
20518 directory also runs recursively. If you type @code{make} in a source
20519 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
20520 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
20521 will build all the required libraries, and then build GDB.
20523 When you have multiple hosts or targets configured in separate
20524 directories, you can run @code{make} on them in parallel (for example,
20525 if they are NFS-mounted on each of the hosts); they will not interfere
20529 @section Specifying names for hosts and targets
20531 The specifications used for hosts and targets in the @code{configure}
20532 script are based on a three-part naming scheme, but some short predefined
20533 aliases are also supported. The full naming scheme encodes three pieces
20534 of information in the following pattern:
20537 @var{architecture}-@var{vendor}-@var{os}
20540 For example, you can use the alias @code{sun4} as a @var{host} argument,
20541 or as the value for @var{target} in a @code{--target=@var{target}}
20542 option. The equivalent full name is @samp{sparc-sun-sunos4}.
20544 The @code{configure} script accompanying @value{GDBN} does not provide
20545 any query facility to list all supported host and target names or
20546 aliases. @code{configure} calls the Bourne shell script
20547 @code{config.sub} to map abbreviations to full names; you can read the
20548 script, if you wish, or you can use it to test your guesses on
20549 abbreviations---for example:
20552 % sh config.sub i386-linux
20554 % sh config.sub alpha-linux
20555 alpha-unknown-linux-gnu
20556 % sh config.sub hp9k700
20558 % sh config.sub sun4
20559 sparc-sun-sunos4.1.1
20560 % sh config.sub sun3
20561 m68k-sun-sunos4.1.1
20562 % sh config.sub i986v
20563 Invalid configuration `i986v': machine `i986v' not recognized
20567 @code{config.sub} is also distributed in the @value{GDBN} source
20568 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
20570 @node Configure Options
20571 @section @code{configure} options
20573 Here is a summary of the @code{configure} options and arguments that
20574 are most often useful for building @value{GDBN}. @code{configure} also has
20575 several other options not listed here. @inforef{What Configure
20576 Does,,configure.info}, for a full explanation of @code{configure}.
20579 configure @r{[}--help@r{]}
20580 @r{[}--prefix=@var{dir}@r{]}
20581 @r{[}--exec-prefix=@var{dir}@r{]}
20582 @r{[}--srcdir=@var{dirname}@r{]}
20583 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
20584 @r{[}--target=@var{target}@r{]}
20589 You may introduce options with a single @samp{-} rather than
20590 @samp{--} if you prefer; but you may abbreviate option names if you use
20595 Display a quick summary of how to invoke @code{configure}.
20597 @item --prefix=@var{dir}
20598 Configure the source to install programs and files under directory
20601 @item --exec-prefix=@var{dir}
20602 Configure the source to install programs under directory
20605 @c avoid splitting the warning from the explanation:
20607 @item --srcdir=@var{dirname}
20608 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
20609 @code{make} that implements the @code{VPATH} feature.}@*
20610 Use this option to make configurations in directories separate from the
20611 @value{GDBN} source directories. Among other things, you can use this to
20612 build (or maintain) several configurations simultaneously, in separate
20613 directories. @code{configure} writes configuration specific files in
20614 the current directory, but arranges for them to use the source in the
20615 directory @var{dirname}. @code{configure} creates directories under
20616 the working directory in parallel to the source directories below
20619 @item --norecursion
20620 Configure only the directory level where @code{configure} is executed; do not
20621 propagate configuration to subdirectories.
20623 @item --target=@var{target}
20624 Configure @value{GDBN} for cross-debugging programs running on the specified
20625 @var{target}. Without this option, @value{GDBN} is configured to debug
20626 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
20628 There is no convenient way to generate a list of all available targets.
20630 @item @var{host} @dots{}
20631 Configure @value{GDBN} to run on the specified @var{host}.
20633 There is no convenient way to generate a list of all available hosts.
20636 There are many other options available as well, but they are generally
20637 needed for special purposes only.
20639 @node Maintenance Commands
20640 @appendix Maintenance Commands
20641 @cindex maintenance commands
20642 @cindex internal commands
20644 In addition to commands intended for @value{GDBN} users, @value{GDBN}
20645 includes a number of commands intended for @value{GDBN} developers,
20646 that are not documented elsewhere in this manual. These commands are
20647 provided here for reference.
20650 @kindex maint agent
20651 @item maint agent @var{expression}
20652 Translate the given @var{expression} into remote agent bytecodes.
20653 This command is useful for debugging the Agent Expression mechanism
20654 (@pxref{Agent Expressions}).
20656 @kindex maint info breakpoints
20657 @item @anchor{maint info breakpoints}maint info breakpoints
20658 Using the same format as @samp{info breakpoints}, display both the
20659 breakpoints you've set explicitly, and those @value{GDBN} is using for
20660 internal purposes. Internal breakpoints are shown with negative
20661 breakpoint numbers. The type column identifies what kind of breakpoint
20666 Normal, explicitly set breakpoint.
20669 Normal, explicitly set watchpoint.
20672 Internal breakpoint, used to handle correctly stepping through
20673 @code{longjmp} calls.
20675 @item longjmp resume
20676 Internal breakpoint at the target of a @code{longjmp}.
20679 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
20682 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
20685 Shared library events.
20689 @kindex maint check-symtabs
20690 @item maint check-symtabs
20691 Check the consistency of psymtabs and symtabs.
20693 @kindex maint cplus first_component
20694 @item maint cplus first_component @var{name}
20695 Print the first C@t{++} class/namespace component of @var{name}.
20697 @kindex maint cplus namespace
20698 @item maint cplus namespace
20699 Print the list of possible C@t{++} namespaces.
20701 @kindex maint demangle
20702 @item maint demangle @var{name}
20703 Demangle a C@t{++} or Objective-C manled @var{name}.
20705 @kindex maint deprecate
20706 @kindex maint undeprecate
20707 @cindex deprecated commands
20708 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
20709 @itemx maint undeprecate @var{command}
20710 Deprecate or undeprecate the named @var{command}. Deprecated commands
20711 cause @value{GDBN} to issue a warning when you use them. The optional
20712 argument @var{replacement} says which newer command should be used in
20713 favor of the deprecated one; if it is given, @value{GDBN} will mention
20714 the replacement as part of the warning.
20716 @kindex maint dump-me
20717 @item maint dump-me
20718 Cause a fatal signal in the debugger and force it to dump its core.
20720 @kindex maint internal-error
20721 @kindex maint internal-warning
20722 @item maint internal-error @r{[}@var{message-text}@r{]}
20723 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
20724 Cause @value{GDBN} to call the internal function @code{internal_error}
20725 or @code{internal_warning} and hence behave as though an internal error
20726 or internal warning has been detected. In addition to reporting the
20727 internal problem, these functions give the user the opportunity to
20728 either quit @value{GDBN} or create a core file of the current
20729 @value{GDBN} session.
20731 These commands take an optional parameter @var{message-text} that is
20732 used as the text of the error or warning message.
20734 Here's an example of using @code{indernal-error}:
20737 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
20738 @dots{}/maint.c:121: internal-error: testing, 1, 2
20739 A problem internal to GDB has been detected. Further
20740 debugging may prove unreliable.
20741 Quit this debugging session? (y or n) @kbd{n}
20742 Create a core file? (y or n) @kbd{n}
20746 @kindex maint packet
20747 @item maint packet @var{text}
20748 If @value{GDBN} is talking to an inferior via the serial protocol,
20749 then this command sends the string @var{text} to the inferior, and
20750 displays the response packet. @value{GDBN} supplies the initial
20751 @samp{$} character, the terminating @samp{#} character, and the
20754 @kindex maint print architecture
20755 @item maint print architecture @r{[}@var{file}@r{]}
20756 Print the entire architecture configuration. The optional argument
20757 @var{file} names the file where the output goes.
20759 @kindex maint print dummy-frames
20760 @item maint print dummy-frames
20762 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
20765 (@value{GDBP}) @kbd{b add}
20767 (@value{GDBP}) @kbd{print add(2,3)}
20768 Breakpoint 2, add (a=2, b=3) at @dots{}
20770 The program being debugged stopped while in a function called from GDB.
20772 (@value{GDBP}) @kbd{maint print dummy-frames}
20773 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
20774 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
20775 call_lo=0x01014000 call_hi=0x01014001
20779 Takes an optional file parameter.
20781 @kindex maint print registers
20782 @kindex maint print raw-registers
20783 @kindex maint print cooked-registers
20784 @kindex maint print register-groups
20785 @item maint print registers @r{[}@var{file}@r{]}
20786 @itemx maint print raw-registers @r{[}@var{file}@r{]}
20787 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
20788 @itemx maint print register-groups @r{[}@var{file}@r{]}
20789 Print @value{GDBN}'s internal register data structures.
20791 The command @code{maint print raw-registers} includes the contents of
20792 the raw register cache; the command @code{maint print cooked-registers}
20793 includes the (cooked) value of all registers; and the command
20794 @code{maint print register-groups} includes the groups that each
20795 register is a member of. @xref{Registers,, Registers, gdbint,
20796 @value{GDBN} Internals}.
20798 These commands take an optional parameter, a file name to which to
20799 write the information.
20801 @kindex maint print reggroups
20802 @item maint print reggroups @r{[}@var{file}@r{]}
20803 Print @value{GDBN}'s internal register group data structures. The
20804 optional argument @var{file} tells to what file to write the
20807 The register groups info looks like this:
20810 (@value{GDBP}) @kbd{maint print reggroups}
20823 This command forces @value{GDBN} to flush its internal register cache.
20825 @kindex maint print objfiles
20826 @cindex info for known object files
20827 @item maint print objfiles
20828 Print a dump of all known object files. For each object file, this
20829 command prints its name, address in memory, and all of its psymtabs
20832 @kindex maint print statistics
20833 @cindex bcache statistics
20834 @item maint print statistics
20835 This command prints, for each object file in the program, various data
20836 about that object file followed by the byte cache (@dfn{bcache})
20837 statistics for the object file. The objfile data includes the number
20838 of minimal, partical, full, and stabs symbols, the number of types
20839 defined by the objfile, the number of as yet unexpanded psym tables,
20840 the number of line tables and string tables, and the amount of memory
20841 used by the various tables. The bcache statistics include the counts,
20842 sizes, and counts of duplicates of all and unique objects, max,
20843 average, and median entry size, total memory used and its overhead and
20844 savings, and various measures of the hash table size and chain
20847 @kindex maint print type
20848 @cindex type chain of a data type
20849 @item maint print type @var{expr}
20850 Print the type chain for a type specified by @var{expr}. The argument
20851 can be either a type name or a symbol. If it is a symbol, the type of
20852 that symbol is described. The type chain produced by this command is
20853 a recursive definition of the data type as stored in @value{GDBN}'s
20854 data structures, including its flags and contained types.
20856 @kindex maint set dwarf2 max-cache-age
20857 @kindex maint show dwarf2 max-cache-age
20858 @item maint set dwarf2 max-cache-age
20859 @itemx maint show dwarf2 max-cache-age
20860 Control the DWARF 2 compilation unit cache.
20862 @cindex DWARF 2 compilation units cache
20863 In object files with inter-compilation-unit references, such as those
20864 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
20865 reader needs to frequently refer to previously read compilation units.
20866 This setting controls how long a compilation unit will remain in the
20867 cache if it is not referenced. A higher limit means that cached
20868 compilation units will be stored in memory longer, and more total
20869 memory will be used. Setting it to zero disables caching, which will
20870 slow down @value{GDBN} startup, but reduce memory consumption.
20872 @kindex maint set profile
20873 @kindex maint show profile
20874 @cindex profiling GDB
20875 @item maint set profile
20876 @itemx maint show profile
20877 Control profiling of @value{GDBN}.
20879 Profiling will be disabled until you use the @samp{maint set profile}
20880 command to enable it. When you enable profiling, the system will begin
20881 collecting timing and execution count data; when you disable profiling or
20882 exit @value{GDBN}, the results will be written to a log file. Remember that
20883 if you use profiling, @value{GDBN} will overwrite the profiling log file
20884 (often called @file{gmon.out}). If you have a record of important profiling
20885 data in a @file{gmon.out} file, be sure to move it to a safe location.
20887 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
20888 compiled with the @samp{-pg} compiler option.
20890 @kindex maint show-debug-regs
20891 @cindex x86 hardware debug registers
20892 @item maint show-debug-regs
20893 Control whether to show variables that mirror the x86 hardware debug
20894 registers. Use @code{ON} to enable, @code{OFF} to disable. If
20895 enabled, the debug registers values are shown when GDB inserts or
20896 removes a hardware breakpoint or watchpoint, and when the inferior
20897 triggers a hardware-assisted breakpoint or watchpoint.
20899 @kindex maint space
20900 @cindex memory used by commands
20902 Control whether to display memory usage for each command. If set to a
20903 nonzero value, @value{GDBN} will display how much memory each command
20904 took, following the command's own output. This can also be requested
20905 by invoking @value{GDBN} with the @option{--statistics} command-line
20906 switch (@pxref{Mode Options}).
20909 @cindex time of command execution
20911 Control whether to display the execution time for each command. If
20912 set to a nonzero value, @value{GDBN} will display how much time it
20913 took to execute each command, following the command's own output.
20914 This can also be requested by invoking @value{GDBN} with the
20915 @option{--statistics} command-line switch (@pxref{Mode Options}).
20917 @kindex maint translate-address
20918 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
20919 Find the symbol stored at the location specified by the address
20920 @var{addr} and an optional section name @var{section}. If found,
20921 @value{GDBN} prints the name of the closest symbol and an offset from
20922 the symbol's location to the specified address. This is similar to
20923 the @code{info address} command (@pxref{Symbols}), except that this
20924 command also allows to find symbols in other sections.
20928 The following command is useful for non-interactive invocations of
20929 @value{GDBN}, such as in the test suite.
20932 @item set watchdog @var{nsec}
20933 @kindex set watchdog
20934 @cindex watchdog timer
20935 @cindex timeout for commands
20936 Set the maximum number of seconds @value{GDBN} will wait for the
20937 target operation to finish. If this time expires, @value{GDBN}
20938 reports and error and the command is aborted.
20940 @item show watchdog
20941 Show the current setting of the target wait timeout.
20944 @node Remote Protocol
20945 @appendix @value{GDBN} Remote Serial Protocol
20950 * Stop Reply Packets::
20951 * General Query Packets::
20952 * Register Packet Format::
20954 * File-I/O remote protocol extension::
20960 There may be occasions when you need to know something about the
20961 protocol---for example, if there is only one serial port to your target
20962 machine, you might want your program to do something special if it
20963 recognizes a packet meant for @value{GDBN}.
20965 In the examples below, @samp{->} and @samp{<-} are used to indicate
20966 transmitted and received data respectfully.
20968 @cindex protocol, @value{GDBN} remote serial
20969 @cindex serial protocol, @value{GDBN} remote
20970 @cindex remote serial protocol
20971 All @value{GDBN} commands and responses (other than acknowledgments) are
20972 sent as a @var{packet}. A @var{packet} is introduced with the character
20973 @samp{$}, the actual @var{packet-data}, and the terminating character
20974 @samp{#} followed by a two-digit @var{checksum}:
20977 @code{$}@var{packet-data}@code{#}@var{checksum}
20981 @cindex checksum, for @value{GDBN} remote
20983 The two-digit @var{checksum} is computed as the modulo 256 sum of all
20984 characters between the leading @samp{$} and the trailing @samp{#} (an
20985 eight bit unsigned checksum).
20987 Implementors should note that prior to @value{GDBN} 5.0 the protocol
20988 specification also included an optional two-digit @var{sequence-id}:
20991 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
20994 @cindex sequence-id, for @value{GDBN} remote
20996 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
20997 has never output @var{sequence-id}s. Stubs that handle packets added
20998 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
21000 @cindex acknowledgment, for @value{GDBN} remote
21001 When either the host or the target machine receives a packet, the first
21002 response expected is an acknowledgment: either @samp{+} (to indicate
21003 the package was received correctly) or @samp{-} (to request
21007 -> @code{$}@var{packet-data}@code{#}@var{checksum}
21012 The host (@value{GDBN}) sends @var{command}s, and the target (the
21013 debugging stub incorporated in your program) sends a @var{response}. In
21014 the case of step and continue @var{command}s, the response is only sent
21015 when the operation has completed (the target has again stopped).
21017 @var{packet-data} consists of a sequence of characters with the
21018 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
21021 Fields within the packet should be separated using @samp{,} @samp{;} or
21022 @cindex remote protocol, field separator
21023 @samp{:}. Except where otherwise noted all numbers are represented in
21024 @sc{hex} with leading zeros suppressed.
21026 Implementors should note that prior to @value{GDBN} 5.0, the character
21027 @samp{:} could not appear as the third character in a packet (as it
21028 would potentially conflict with the @var{sequence-id}).
21030 Response @var{data} can be run-length encoded to save space. A @samp{*}
21031 means that the next character is an @sc{ascii} encoding giving a repeat count
21032 which stands for that many repetitions of the character preceding the
21033 @samp{*}. The encoding is @code{n+29}, yielding a printable character
21034 where @code{n >=3} (which is where rle starts to win). The printable
21035 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
21036 value greater than 126 should not be used.
21043 means the same as "0000".
21045 The error response returned for some packets includes a two character
21046 error number. That number is not well defined.
21048 For any @var{command} not supported by the stub, an empty response
21049 (@samp{$#00}) should be returned. That way it is possible to extend the
21050 protocol. A newer @value{GDBN} can tell if a packet is supported based
21053 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
21054 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
21060 The following table provides a complete list of all currently defined
21061 @var{command}s and their corresponding response @var{data}.
21062 @xref{File-I/O remote protocol extension}, for details about the File
21063 I/O extension of the remote protocol.
21067 @item @code{!} --- extended mode
21068 @cindex @code{!} packet
21070 Enable extended mode. In extended mode, the remote server is made
21071 persistent. The @samp{R} packet is used to restart the program being
21077 The remote target both supports and has enabled extended mode.
21080 @item @code{?} --- last signal
21081 @cindex @code{?} packet
21083 Indicate the reason the target halted. The reply is the same as for
21087 @xref{Stop Reply Packets}, for the reply specifications.
21089 @item @code{a} --- reserved
21091 Reserved for future use.
21093 @item @code{A}@var{arglen}@code{,}@var{argnum}@code{,}@var{arg}@code{,@dots{}} --- set program arguments @strong{(reserved)}
21094 @cindex @code{A} packet
21096 Initialized @samp{argv[]} array passed into program. @var{arglen}
21097 specifies the number of bytes in the hex encoded byte stream @var{arg}.
21098 See @code{gdbserver} for more details.
21106 @item @code{b}@var{baud} --- set baud @strong{(deprecated)}
21107 @cindex @code{b} packet
21109 Change the serial line speed to @var{baud}.
21111 JTC: @emph{When does the transport layer state change? When it's
21112 received, or after the ACK is transmitted. In either case, there are
21113 problems if the command or the acknowledgment packet is dropped.}
21115 Stan: @emph{If people really wanted to add something like this, and get
21116 it working for the first time, they ought to modify ser-unix.c to send
21117 some kind of out-of-band message to a specially-setup stub and have the
21118 switch happen "in between" packets, so that from remote protocol's point
21119 of view, nothing actually happened.}
21121 @item @code{B}@var{addr},@var{mode} --- set breakpoint @strong{(deprecated)}
21122 @cindex @code{B} packet
21124 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
21125 breakpoint at @var{addr}.
21127 This packet has been replaced by the @samp{Z} and @samp{z} packets
21128 (@pxref{insert breakpoint or watchpoint packet}).
21130 @item @code{c}@var{addr} --- continue
21131 @cindex @code{c} packet
21133 @var{addr} is address to resume. If @var{addr} is omitted, resume at
21137 @xref{Stop Reply Packets}, for the reply specifications.
21139 @item @code{C}@var{sig}@code{;}@var{addr} --- continue with signal
21140 @cindex @code{C} packet
21142 Continue with signal @var{sig} (hex signal number). If
21143 @code{;}@var{addr} is omitted, resume at same address.
21146 @xref{Stop Reply Packets}, for the reply specifications.
21148 @item @code{d} --- toggle debug @strong{(deprecated)}
21149 @cindex @code{d} packet
21153 @item @code{D} --- detach
21154 @cindex @code{D} packet
21156 Detach @value{GDBN} from the remote system. Sent to the remote target
21157 before @value{GDBN} disconnects via the @code{detach} command.
21161 @item @emph{no response}
21162 @value{GDBN} does not check for any response after sending this packet.
21165 @item @code{e} --- reserved
21167 Reserved for future use.
21169 @item @code{E} --- reserved
21171 Reserved for future use.
21173 @item @code{f} --- reserved
21175 Reserved for future use.
21177 @item @code{F}@var{RC}@code{,}@var{EE}@code{,}@var{CF}@code{;}@var{XX} --- Reply to target's F packet.
21178 @cindex @code{F} packet
21180 This packet is send by @value{GDBN} as reply to a @code{F} request packet
21181 sent by the target. This is part of the File-I/O protocol extension.
21182 @xref{File-I/O remote protocol extension}, for the specification.
21184 @item @code{g} --- read registers
21185 @anchor{read registers packet}
21186 @cindex @code{g} packet
21188 Read general registers.
21192 @item @var{XX@dots{}}
21193 Each byte of register data is described by two hex digits. The bytes
21194 with the register are transmitted in target byte order. The size of
21195 each register and their position within the @samp{g} @var{packet} are
21196 determined by the @value{GDBN} internal macros
21197 @var{DEPRECATED_REGISTER_RAW_SIZE} and @var{REGISTER_NAME} macros. The
21198 specification of several standard @code{g} packets is specified below.
21203 @item @code{G}@var{XX@dots{}} --- write regs
21204 @cindex @code{G} packet
21206 @xref{read registers packet}, for a description of the @var{XX@dots{}}
21217 @item @code{h} --- reserved
21219 Reserved for future use.
21221 @item @code{H}@var{c}@var{t@dots{}} --- set thread
21222 @cindex @code{H} packet
21224 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
21225 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
21226 should be @samp{c} for step and continue operations, @samp{g} for other
21227 operations. The thread designator @var{t@dots{}} may be -1, meaning all
21228 the threads, a thread number, or zero which means pick any thread.
21239 @c 'H': How restrictive (or permissive) is the thread model. If a
21240 @c thread is selected and stopped, are other threads allowed
21241 @c to continue to execute? As I mentioned above, I think the
21242 @c semantics of each command when a thread is selected must be
21243 @c described. For example:
21245 @c 'g': If the stub supports threads and a specific thread is
21246 @c selected, returns the register block from that thread;
21247 @c otherwise returns current registers.
21249 @c 'G' If the stub supports threads and a specific thread is
21250 @c selected, sets the registers of the register block of
21251 @c that thread; otherwise sets current registers.
21253 @item @code{i}@var{addr}@code{,}@var{nnn} --- cycle step @strong{(draft)}
21254 @anchor{cycle step packet}
21255 @cindex @code{i} packet
21257 Step the remote target by a single clock cycle. If @code{,}@var{nnn} is
21258 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
21259 step starting at that address.
21261 @item @code{I} --- signal then cycle step @strong{(reserved)}
21262 @cindex @code{I} packet
21264 @xref{step with signal packet}. @xref{cycle step packet}.
21266 @item @code{j} --- reserved
21268 Reserved for future use.
21270 @item @code{J} --- reserved
21272 Reserved for future use.
21274 @item @code{k} --- kill request
21275 @cindex @code{k} packet
21277 FIXME: @emph{There is no description of how to operate when a specific
21278 thread context has been selected (i.e.@: does 'k' kill only that
21281 @item @code{K} --- reserved
21283 Reserved for future use.
21285 @item @code{l} --- reserved
21287 Reserved for future use.
21289 @item @code{L} --- reserved
21291 Reserved for future use.
21293 @item @code{m}@var{addr}@code{,}@var{length} --- read memory
21294 @cindex @code{m} packet
21296 Read @var{length} bytes of memory starting at address @var{addr}.
21297 Neither @value{GDBN} nor the stub assume that sized memory transfers are
21298 assumed using word aligned accesses. FIXME: @emph{A word aligned memory
21299 transfer mechanism is needed.}
21303 @item @var{XX@dots{}}
21304 @var{XX@dots{}} is mem contents. Can be fewer bytes than requested if able
21305 to read only part of the data. Neither @value{GDBN} nor the stub assume
21306 that sized memory transfers are assumed using word aligned
21307 accesses. FIXME: @emph{A word aligned memory transfer mechanism is
21313 @item @code{M}@var{addr},@var{length}@code{:}@var{XX@dots{}} --- write mem
21314 @cindex @code{M} packet
21316 Write @var{length} bytes of memory starting at address @var{addr}.
21317 @var{XX@dots{}} is the data.
21324 for an error (this includes the case where only part of the data was
21328 @item @code{n} --- reserved
21330 Reserved for future use.
21332 @item @code{N} --- reserved
21334 Reserved for future use.
21336 @item @code{o} --- reserved
21338 Reserved for future use.
21340 @item @code{O} --- reserved
21342 @item @code{p}@var{hex number of register} --- read register packet
21343 @cindex @code{p} packet
21345 @xref{read registers packet}, for a description of how the returned
21346 register value is encoded.
21350 @item @var{XX@dots{}}
21351 the register's value
21355 Indicating an unrecognized @var{query}.
21358 @item @code{P}@var{n@dots{}}@code{=}@var{r@dots{}} --- write register
21359 @anchor{write register packet}
21360 @cindex @code{P} packet
21362 Write register @var{n@dots{}} with value @var{r@dots{}}, which contains two hex
21363 digits for each byte in the register (target byte order).
21373 @item @code{q}@var{query} --- general query
21374 @anchor{general query packet}
21375 @cindex @code{q} packet
21377 Request info about @var{query}. In general @value{GDBN} queries have a
21378 leading upper case letter. Custom vendor queries should use a company
21379 prefix (in lower case) ex: @samp{qfsf.var}. @var{query} may optionally
21380 be followed by a @samp{,} or @samp{;} separated list. Stubs must ensure
21381 that they match the full @var{query} name.
21385 @item @var{XX@dots{}}
21386 Hex encoded data from query. The reply can not be empty.
21390 Indicating an unrecognized @var{query}.
21393 @item @code{Q}@var{var}@code{=}@var{val} --- general set
21394 @cindex @code{Q} packet
21396 Set value of @var{var} to @var{val}.
21398 @xref{general query packet}, for a discussion of naming conventions.
21400 @item @code{r} --- reset @strong{(deprecated)}
21401 @cindex @code{r} packet
21403 Reset the entire system.
21405 @item @code{R}@var{XX} --- remote restart
21406 @cindex @code{R} packet
21408 Restart the program being debugged. @var{XX}, while needed, is ignored.
21409 This packet is only available in extended mode.
21413 @item @emph{no reply}
21414 The @samp{R} packet has no reply.
21417 @item @code{s}@var{addr} --- step
21418 @cindex @code{s} packet
21420 @var{addr} is address to resume. If @var{addr} is omitted, resume at
21424 @xref{Stop Reply Packets}, for the reply specifications.
21426 @item @code{S}@var{sig}@code{;}@var{addr} --- step with signal
21427 @anchor{step with signal packet}
21428 @cindex @code{S} packet
21430 Like @samp{C} but step not continue.
21433 @xref{Stop Reply Packets}, for the reply specifications.
21435 @item @code{t}@var{addr}@code{:}@var{PP}@code{,}@var{MM} --- search
21436 @cindex @code{t} packet
21438 Search backwards starting at address @var{addr} for a match with pattern
21439 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
21440 @var{addr} must be at least 3 digits.
21442 @item @code{T}@var{XX} --- thread alive
21443 @cindex @code{T} packet
21445 Find out if the thread XX is alive.
21450 thread is still alive
21455 @item @code{u} --- reserved
21457 Reserved for future use.
21459 @item @code{U} --- reserved
21461 Reserved for future use.
21463 @item @code{v} --- verbose packet prefix
21465 Packets starting with @code{v} are identified by a multi-letter name,
21466 up to the first @code{;} or @code{?} (or the end of the packet).
21468 @item @code{vCont}[;@var{action}[@code{:}@var{tid}]]... --- extended resume
21469 @cindex @code{vCont} packet
21471 Resume the inferior. Different actions may be specified for each thread.
21472 If an action is specified with no @var{tid}, then it is applied to any
21473 threads that don't have a specific action specified; if no default action is
21474 specified then other threads should remain stopped. Specifying multiple
21475 default actions is an error; specifying no actions is also an error.
21476 Thread IDs are specified in hexadecimal. Currently supported actions are:
21482 Continue with signal @var{sig}. @var{sig} should be two hex digits.
21486 Step with signal @var{sig}. @var{sig} should be two hex digits.
21489 The optional @var{addr} argument normally associated with these packets is
21490 not supported in @code{vCont}.
21493 @xref{Stop Reply Packets}, for the reply specifications.
21495 @item @code{vCont?} --- extended resume query
21496 @cindex @code{vCont?} packet
21498 Query support for the @code{vCont} packet.
21502 @item @code{vCont}[;@var{action}]...
21503 The @code{vCont} packet is supported. Each @var{action} is a supported
21504 command in the @code{vCont} packet.
21506 The @code{vCont} packet is not supported.
21509 @item @code{V} --- reserved
21511 Reserved for future use.
21513 @item @code{w} --- reserved
21515 Reserved for future use.
21517 @item @code{W} --- reserved
21519 Reserved for future use.
21521 @item @code{x} --- reserved
21523 Reserved for future use.
21525 @item @code{X}@var{addr}@code{,}@var{length}@var{:}@var{XX@dots{}} --- write mem (binary)
21526 @cindex @code{X} packet
21528 @var{addr} is address, @var{length} is number of bytes, @var{XX@dots{}}
21529 is binary data. The characters @code{$}, @code{#}, and @code{0x7d} are
21530 escaped using @code{0x7d}, and then XORed with @code{0x20}.
21531 For example, @code{0x7d} would be transmitted as @code{0x7d 0x5d}.
21541 @item @code{y} --- reserved
21543 Reserved for future use.
21545 @item @code{Y} reserved
21547 Reserved for future use.
21549 @item @code{z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- remove breakpoint or watchpoint @strong{(draft)}
21550 @itemx @code{Z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- insert breakpoint or watchpoint @strong{(draft)}
21551 @anchor{insert breakpoint or watchpoint packet}
21552 @cindex @code{z} packet
21553 @cindex @code{Z} packets
21555 Insert (@code{Z}) or remove (@code{z}) a @var{type} breakpoint or
21556 watchpoint starting at address @var{address} and covering the next
21557 @var{length} bytes.
21559 Each breakpoint and watchpoint packet @var{type} is documented
21562 @emph{Implementation notes: A remote target shall return an empty string
21563 for an unrecognized breakpoint or watchpoint packet @var{type}. A
21564 remote target shall support either both or neither of a given
21565 @code{Z}@var{type}@dots{} and @code{z}@var{type}@dots{} packet pair. To
21566 avoid potential problems with duplicate packets, the operations should
21567 be implemented in an idempotent way.}
21569 @item @code{z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- remove memory breakpoint @strong{(draft)}
21570 @item @code{Z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- insert memory breakpoint @strong{(draft)}
21571 @cindex @code{z0} packet
21572 @cindex @code{Z0} packet
21574 Insert (@code{Z0}) or remove (@code{z0}) a memory breakpoint at address
21575 @code{addr} of size @code{length}.
21577 A memory breakpoint is implemented by replacing the instruction at
21578 @var{addr} with a software breakpoint or trap instruction. The
21579 @code{length} is used by targets that indicates the size of the
21580 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
21581 @sc{mips} can insert either a 2 or 4 byte breakpoint).
21583 @emph{Implementation note: It is possible for a target to copy or move
21584 code that contains memory breakpoints (e.g., when implementing
21585 overlays). The behavior of this packet, in the presence of such a
21586 target, is not defined.}
21598 @item @code{z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- remove hardware breakpoint @strong{(draft)}
21599 @item @code{Z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- insert hardware breakpoint @strong{(draft)}
21600 @cindex @code{z1} packet
21601 @cindex @code{Z1} packet
21603 Insert (@code{Z1}) or remove (@code{z1}) a hardware breakpoint at
21604 address @code{addr} of size @code{length}.
21606 A hardware breakpoint is implemented using a mechanism that is not
21607 dependant on being able to modify the target's memory.
21609 @emph{Implementation note: A hardware breakpoint is not affected by code
21622 @item @code{z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- remove write watchpoint @strong{(draft)}
21623 @item @code{Z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- insert write watchpoint @strong{(draft)}
21624 @cindex @code{z2} packet
21625 @cindex @code{Z2} packet
21627 Insert (@code{Z2}) or remove (@code{z2}) a write watchpoint.
21639 @item @code{z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- remove read watchpoint @strong{(draft)}
21640 @item @code{Z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- insert read watchpoint @strong{(draft)}
21641 @cindex @code{z3} packet
21642 @cindex @code{Z3} packet
21644 Insert (@code{Z3}) or remove (@code{z3}) a read watchpoint.
21656 @item @code{z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- remove access watchpoint @strong{(draft)}
21657 @item @code{Z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- insert access watchpoint @strong{(draft)}
21658 @cindex @code{z4} packet
21659 @cindex @code{Z4} packet
21661 Insert (@code{Z4}) or remove (@code{z4}) an access watchpoint.
21675 @node Stop Reply Packets
21676 @section Stop Reply Packets
21677 @cindex stop reply packets
21679 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
21680 receive any of the below as a reply. In the case of the @samp{C},
21681 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
21682 when the target halts. In the below the exact meaning of @samp{signal
21683 number} is poorly defined. In general one of the UNIX signal numbering
21684 conventions is used.
21689 @var{AA} is the signal number
21691 @item @code{T}@var{AA}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}
21692 @cindex @code{T} packet reply
21694 @var{AA} = two hex digit signal number; @var{n...} = register number
21695 (hex), @var{r...} = target byte ordered register contents, size defined
21696 by @code{DEPRECATED_REGISTER_RAW_SIZE}; @var{n...} = @samp{thread},
21697 @var{r...} = thread process ID, this is a hex integer; @var{n...} =
21698 (@samp{watch} | @samp{rwatch} | @samp{awatch}, @var{r...} = data
21699 address, this is a hex integer; @var{n...} = other string not starting
21700 with valid hex digit. @value{GDBN} should ignore this @var{n...},
21701 @var{r...} pair and go on to the next. This way we can extend the
21706 The process exited, and @var{AA} is the exit status. This is only
21707 applicable to certain targets.
21711 The process terminated with signal @var{AA}.
21713 @item O@var{XX@dots{}}
21715 @var{XX@dots{}} is hex encoding of @sc{ascii} data. This can happen at
21716 any time while the program is running and the debugger should continue
21717 to wait for @samp{W}, @samp{T}, etc.
21719 @item F@var{call-id}@code{,}@var{parameter@dots{}}
21721 @var{call-id} is the identifier which says which host system call should
21722 be called. This is just the name of the function. Translation into the
21723 correct system call is only applicable as it's defined in @value{GDBN}.
21724 @xref{File-I/O remote protocol extension}, for a list of implemented
21727 @var{parameter@dots{}} is a list of parameters as defined for this very
21730 The target replies with this packet when it expects @value{GDBN} to call
21731 a host system call on behalf of the target. @value{GDBN} replies with
21732 an appropriate @code{F} packet and keeps up waiting for the next reply
21733 packet from the target. The latest @samp{C}, @samp{c}, @samp{S} or
21734 @samp{s} action is expected to be continued.
21735 @xref{File-I/O remote protocol extension}, for more details.
21739 @node General Query Packets
21740 @section General Query Packets
21741 @cindex remote query requests
21743 The following set and query packets have already been defined.
21747 @item @code{q}@code{C} --- current thread
21748 @cindex current thread, remote request
21749 @cindex @code{qC} packet
21750 Return the current thread id.
21754 @item @code{QC}@var{pid}
21755 Where @var{pid} is an unsigned hexidecimal process id.
21757 Any other reply implies the old pid.
21760 @item @code{q}@code{fThreadInfo} -- all thread ids
21761 @cindex list active threads, remote request
21762 @cindex @code{qfThreadInfo} packet
21763 @code{q}@code{sThreadInfo}
21765 Obtain a list of active thread ids from the target (OS). Since there
21766 may be too many active threads to fit into one reply packet, this query
21767 works iteratively: it may require more than one query/reply sequence to
21768 obtain the entire list of threads. The first query of the sequence will
21769 be the @code{qf}@code{ThreadInfo} query; subsequent queries in the
21770 sequence will be the @code{qs}@code{ThreadInfo} query.
21772 NOTE: replaces the @code{qL} query (see below).
21776 @item @code{m}@var{id}
21778 @item @code{m}@var{id},@var{id}@dots{}
21779 a comma-separated list of thread ids
21781 (lower case 'el') denotes end of list.
21784 In response to each query, the target will reply with a list of one or
21785 more thread ids, in big-endian unsigned hex, separated by commas.
21786 @value{GDBN} will respond to each reply with a request for more thread
21787 ids (using the @code{qs} form of the query), until the target responds
21788 with @code{l} (lower-case el, for @code{'last'}).
21790 @item @code{q}@code{ThreadExtraInfo}@code{,}@var{id} --- extra thread info
21791 @cindex thread attributes info, remote request
21792 @cindex @code{qThreadExtraInfo} packet
21793 Where @var{id} is a thread-id in big-endian hex. Obtain a printable
21794 string description of a thread's attributes from the target OS. This
21795 string may contain anything that the target OS thinks is interesting for
21796 @value{GDBN} to tell the user about the thread. The string is displayed
21797 in @value{GDBN}'s @samp{info threads} display. Some examples of
21798 possible thread extra info strings are ``Runnable'', or ``Blocked on
21803 @item @var{XX@dots{}}
21804 Where @var{XX@dots{}} is a hex encoding of @sc{ascii} data, comprising
21805 the printable string containing the extra information about the thread's
21809 @item @code{q}@code{L}@var{startflag}@var{threadcount}@var{nextthread} --- query @var{LIST} or @var{threadLIST} @strong{(deprecated)}
21811 Obtain thread information from RTOS. Where: @var{startflag} (one hex
21812 digit) is one to indicate the first query and zero to indicate a
21813 subsequent query; @var{threadcount} (two hex digits) is the maximum
21814 number of threads the response packet can contain; and @var{nextthread}
21815 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
21816 returned in the response as @var{argthread}.
21818 NOTE: this query is replaced by the @code{q}@code{fThreadInfo} query
21823 @item @code{q}@code{M}@var{count}@var{done}@var{argthread}@var{thread@dots{}}
21824 Where: @var{count} (two hex digits) is the number of threads being
21825 returned; @var{done} (one hex digit) is zero to indicate more threads
21826 and one indicates no further threads; @var{argthreadid} (eight hex
21827 digits) is @var{nextthread} from the request packet; @var{thread@dots{}}
21828 is a sequence of thread IDs from the target. @var{threadid} (eight hex
21829 digits). See @code{remote.c:parse_threadlist_response()}.
21832 @item @code{q}@code{CRC:}@var{addr}@code{,}@var{length} --- compute CRC of memory block
21833 @cindex CRC of memory block, remote request
21834 @cindex @code{qCRC} packet
21837 @item @code{E}@var{NN}
21838 An error (such as memory fault)
21839 @item @code{C}@var{CRC32}
21840 A 32 bit cyclic redundancy check of the specified memory region.
21843 @item @code{q}@code{Offsets} --- query sect offs
21844 @cindex section offsets, remote request
21845 @cindex @code{qOffsets} packet
21846 Get section offsets that the target used when re-locating the downloaded
21847 image. @emph{Note: while a @code{Bss} offset is included in the
21848 response, @value{GDBN} ignores this and instead applies the @code{Data}
21849 offset to the @code{Bss} section.}
21853 @item @code{Text=}@var{xxx}@code{;Data=}@var{yyy}@code{;Bss=}@var{zzz}
21856 @item @code{q}@code{P}@var{mode}@var{threadid} --- thread info request
21857 @cindex thread information, remote request
21858 @cindex @code{qP} packet
21859 Returns information on @var{threadid}. Where: @var{mode} is a hex
21860 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
21867 See @code{remote.c:remote_unpack_thread_info_response()}.
21869 @item @code{q}@code{Rcmd,}@var{command} --- remote command
21870 @cindex execute remote command, remote request
21871 @cindex @code{qRcmd} packet
21872 @var{command} (hex encoded) is passed to the local interpreter for
21873 execution. Invalid commands should be reported using the output string.
21874 Before the final result packet, the target may also respond with a
21875 number of intermediate @code{O}@var{output} console output packets.
21876 @emph{Implementors should note that providing access to a stubs's
21877 interpreter may have security implications}.
21882 A command response with no output.
21884 A command response with the hex encoded output string @var{OUTPUT}.
21885 @item @code{E}@var{NN}
21886 Indicate a badly formed request.
21888 When @samp{q}@samp{Rcmd} is not recognized.
21891 @item @code{qSymbol::} --- symbol lookup
21892 @cindex symbol lookup, remote request
21893 @cindex @code{qSymbol} packet
21894 Notify the target that @value{GDBN} is prepared to serve symbol lookup
21895 requests. Accept requests from the target for the values of symbols.
21900 The target does not need to look up any (more) symbols.
21901 @item @code{qSymbol:}@var{sym_name}
21902 The target requests the value of symbol @var{sym_name} (hex encoded).
21903 @value{GDBN} may provide the value by using the
21904 @code{qSymbol:}@var{sym_value}:@var{sym_name} message, described below.
21907 @item @code{qSymbol:}@var{sym_value}:@var{sym_name} --- symbol value
21909 Set the value of @var{sym_name} to @var{sym_value}.
21911 @var{sym_name} (hex encoded) is the name of a symbol whose value the
21912 target has previously requested.
21914 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
21915 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
21921 The target does not need to look up any (more) symbols.
21922 @item @code{qSymbol:}@var{sym_name}
21923 The target requests the value of a new symbol @var{sym_name} (hex
21924 encoded). @value{GDBN} will continue to supply the values of symbols
21925 (if available), until the target ceases to request them.
21928 @item @code{qPart}:@var{object}:@code{read}:@var{annex}:@var{offset},@var{length} --- read special data
21929 @cindex read special object, remote request
21930 @cindex @code{qPart} packet
21931 Read uninterpreted bytes from the target's special data area
21932 identified by the keyword @code{object}.
21933 Request @var{length} bytes starting at @var{offset} bytes into the data.
21934 The content and encoding of @var{annex} is specific to the object;
21935 it can supply additional details about what data to access.
21937 Here are the specific requests of this form defined so far.
21938 All @samp{@code{qPart}:@var{object}:@code{read}:@dots{}}
21939 requests use the same reply formats, listed below.
21942 @item @code{qPart}:@code{auxv}:@code{read}::@var{offset},@var{length}
21943 Access the target's @dfn{auxiliary vector}. @xref{Auxiliary Vector},
21944 and see @ref{Remote configuration, read-aux-vector-packet}.
21945 Note @var{annex} must be empty.
21951 The @var{offset} in the request is at the end of the data.
21952 There is no more data to be read.
21954 @item @var{XX@dots{}}
21955 Hex encoded data bytes read.
21956 This may be fewer bytes than the @var{length} in the request.
21959 The request was malformed, or @var{annex} was invalid.
21961 @item @code{E}@var{nn}
21962 The offset was invalid, or there was an error encountered reading the data.
21963 @var{nn} is a hex-encoded @code{errno} value.
21965 @item @code{""} (empty)
21966 An empty reply indicates the @var{object} or @var{annex} string was not
21967 recognized by the stub.
21970 @item @code{qPart}:@var{object}:@code{write}:@var{annex}:@var{offset}:@var{data@dots{}}
21971 @cindex write data into object, remote request
21972 Write uninterpreted bytes into the target's special data area
21973 identified by the keyword @code{object},
21974 starting at @var{offset} bytes into the data.
21975 @var{data@dots{}} is the hex-encoded data to be written.
21976 The content and encoding of @var{annex} is specific to the object;
21977 it can supply additional details about what data to access.
21979 No requests of this form are presently in use. This specification
21980 serves as a placeholder to document the common format that new
21981 specific request specifications ought to use.
21986 @var{nn} (hex encoded) is the number of bytes written.
21987 This may be fewer bytes than supplied in the request.
21990 The request was malformed, or @var{annex} was invalid.
21992 @item @code{E}@var{nn}
21993 The offset was invalid, or there was an error encountered writing the data.
21994 @var{nn} is a hex-encoded @code{errno} value.
21996 @item @code{""} (empty)
21997 An empty reply indicates the @var{object} or @var{annex} string was not
21998 recognized by the stub, or that the object does not support writing.
22001 @item @code{qPart}:@var{object}:@var{operation}:@dots{}
22002 Requests of this form may be added in the future. When a stub does
22003 not recognize the @var{object} keyword, or its support for
22004 @var{object} does not recognize the @var{operation} keyword,
22005 the stub must respond with an empty packet.
22007 @item @code{qGetTLSAddr}:@var{thread-id},@var{offset},@var{lm} --- get thread local storage address
22008 @cindex get thread-local storage address, remote request
22009 @cindex @code{qGetTLSAddr} packet
22010 Fetch the address associated with thread local storage specified
22011 by @var{thread-id}, @var{offset}, and @var{lm}.
22013 @var{thread-id} is the (big endian, hex encoded) thread id associated with the
22014 thread for which to fetch the TLS address.
22016 @var{offset} is the (big endian, hex encoded) offset associated with the
22017 thread local variable. (This offset is obtained from the debug
22018 information associated with the variable.)
22020 @var{lm} is the (big endian, hex encoded) OS/ABI specific encoding of the
22021 the load module associated with the thread local storage. For example,
22022 a @sc{gnu}/Linux system will pass the link map address of the shared
22023 object associated with the thread local storage under consideration.
22024 Other operating environments may choose to represent the load module
22025 differently, so the precise meaning of this parameter will vary.
22029 @item @var{XX@dots{}}
22030 Hex encoded (big endian) bytes representing the address of the thread
22031 local storage requested.
22033 @item @code{E}@var{nn} (where @var{nn} are hex digits)
22036 @item @code{""} (empty)
22037 An empty reply indicates that @code{qGetTLSAddr} is not supported by the stub.
22042 @node Register Packet Format
22043 @section Register Packet Format
22045 The following @samp{g}/@samp{G} packets have previously been defined.
22046 In the below, some thirty-two bit registers are transferred as
22047 sixty-four bits. Those registers should be zero/sign extended (which?)
22048 to fill the space allocated. Register bytes are transfered in target
22049 byte order. The two nibbles within a register byte are transfered
22050 most-significant - least-significant.
22056 All registers are transfered as thirty-two bit quantities in the order:
22057 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
22058 registers; fsr; fir; fp.
22062 All registers are transfered as sixty-four bit quantities (including
22063 thirty-two bit registers such as @code{sr}). The ordering is the same
22071 Example sequence of a target being re-started. Notice how the restart
22072 does not get any direct output:
22077 @emph{target restarts}
22080 <- @code{T001:1234123412341234}
22084 Example sequence of a target being stepped by a single instruction:
22087 -> @code{G1445@dots{}}
22092 <- @code{T001:1234123412341234}
22096 <- @code{1455@dots{}}
22100 @node File-I/O remote protocol extension
22101 @section File-I/O remote protocol extension
22102 @cindex File-I/O remote protocol extension
22105 * File-I/O Overview::
22106 * Protocol basics::
22107 * The F request packet::
22108 * The F reply packet::
22109 * Memory transfer::
22110 * The Ctrl-C message::
22112 * The isatty call::
22113 * The system call::
22114 * List of supported calls::
22115 * Protocol specific representation of datatypes::
22117 * File-I/O Examples::
22120 @node File-I/O Overview
22121 @subsection File-I/O Overview
22122 @cindex file-i/o overview
22124 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
22125 target to use the host's file system and console I/O when calling various
22126 system calls. System calls on the target system are translated into a
22127 remote protocol packet to the host system which then performs the needed
22128 actions and returns with an adequate response packet to the target system.
22129 This simulates file system operations even on targets that lack file systems.
22131 The protocol is defined host- and target-system independent. It uses
22132 its own independent representation of datatypes and values. Both,
22133 @value{GDBN} and the target's @value{GDBN} stub are responsible for
22134 translating the system dependent values into the unified protocol values
22135 when data is transmitted.
22137 The communication is synchronous. A system call is possible only
22138 when GDB is waiting for the @samp{C}, @samp{c}, @samp{S} or @samp{s}
22139 packets. While @value{GDBN} handles the request for a system call,
22140 the target is stopped to allow deterministic access to the target's
22141 memory. Therefore File-I/O is not interuptible by target signals. It
22142 is possible to interrupt File-I/O by a user interrupt (Ctrl-C), though.
22144 The target's request to perform a host system call does not finish
22145 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
22146 after finishing the system call, the target returns to continuing the
22147 previous activity (continue, step). No additional continue or step
22148 request from @value{GDBN} is required.
22151 (@value{GDBP}) continue
22152 <- target requests 'system call X'
22153 target is stopped, @value{GDBN} executes system call
22154 -> GDB returns result
22155 ... target continues, GDB returns to wait for the target
22156 <- target hits breakpoint and sends a Txx packet
22159 The protocol is only used for files on the host file system and
22160 for I/O on the console. Character or block special devices, pipes,
22161 named pipes or sockets or any other communication method on the host
22162 system are not supported by this protocol.
22164 @node Protocol basics
22165 @subsection Protocol basics
22166 @cindex protocol basics, file-i/o
22168 The File-I/O protocol uses the @code{F} packet, as request as well
22169 as as reply packet. Since a File-I/O system call can only occur when
22170 @value{GDBN} is waiting for the continuing or stepping target, the
22171 File-I/O request is a reply that @value{GDBN} has to expect as a result
22172 of a former @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
22173 This @code{F} packet contains all information needed to allow @value{GDBN}
22174 to call the appropriate host system call:
22178 A unique identifier for the requested system call.
22181 All parameters to the system call. Pointers are given as addresses
22182 in the target memory address space. Pointers to strings are given as
22183 pointer/length pair. Numerical values are given as they are.
22184 Numerical control values are given in a protocol specific representation.
22188 At that point @value{GDBN} has to perform the following actions.
22192 If parameter pointer values are given, which point to data needed as input
22193 to a system call, @value{GDBN} requests this data from the target with a
22194 standard @code{m} packet request. This additional communication has to be
22195 expected by the target implementation and is handled as any other @code{m}
22199 @value{GDBN} translates all value from protocol representation to host
22200 representation as needed. Datatypes are coerced into the host types.
22203 @value{GDBN} calls the system call
22206 It then coerces datatypes back to protocol representation.
22209 If pointer parameters in the request packet point to buffer space in which
22210 a system call is expected to copy data to, the data is transmitted to the
22211 target using a @code{M} or @code{X} packet. This packet has to be expected
22212 by the target implementation and is handled as any other @code{M} or @code{X}
22217 Eventually @value{GDBN} replies with another @code{F} packet which contains all
22218 necessary information for the target to continue. This at least contains
22225 @code{errno}, if has been changed by the system call.
22232 After having done the needed type and value coercion, the target continues
22233 the latest continue or step action.
22235 @node The F request packet
22236 @subsection The @code{F} request packet
22237 @cindex file-i/o request packet
22238 @cindex @code{F} request packet
22240 The @code{F} request packet has the following format:
22245 @code{F}@var{call-id}@code{,}@var{parameter@dots{}}
22248 @var{call-id} is the identifier to indicate the host system call to be called.
22249 This is just the name of the function.
22251 @var{parameter@dots{}} are the parameters to the system call.
22255 Parameters are hexadecimal integer values, either the real values in case
22256 of scalar datatypes, as pointers to target buffer space in case of compound
22257 datatypes and unspecified memory areas or as pointer/length pairs in case
22258 of string parameters. These are appended to the call-id, each separated
22259 from its predecessor by a comma. All values are transmitted in ASCII
22260 string representation, pointer/length pairs separated by a slash.
22262 @node The F reply packet
22263 @subsection The @code{F} reply packet
22264 @cindex file-i/o reply packet
22265 @cindex @code{F} reply packet
22267 The @code{F} reply packet has the following format:
22272 @code{F}@var{retcode}@code{,}@var{errno}@code{,}@var{Ctrl-C flag}@code{;}@var{call specific attachment}
22275 @var{retcode} is the return code of the system call as hexadecimal value.
22277 @var{errno} is the errno set by the call, in protocol specific representation.
22278 This parameter can be omitted if the call was successful.
22280 @var{Ctrl-C flag} is only send if the user requested a break. In this
22281 case, @var{errno} must be send as well, even if the call was successful.
22282 The @var{Ctrl-C flag} itself consists of the character 'C':
22289 or, if the call was interupted before the host call has been performed:
22296 assuming 4 is the protocol specific representation of @code{EINTR}.
22300 @node Memory transfer
22301 @subsection Memory transfer
22302 @cindex memory transfer, in file-i/o protocol
22304 Structured data which is transferred using a memory read or write as e.g.@:
22305 a @code{struct stat} is expected to be in a protocol specific format with
22306 all scalar multibyte datatypes being big endian. This should be done by
22307 the target before the @code{F} packet is sent resp.@: by @value{GDBN} before
22308 it transfers memory to the target. Transferred pointers to structured
22309 data should point to the already coerced data at any time.
22311 @node The Ctrl-C message
22312 @subsection The Ctrl-C message
22313 @cindex ctrl-c message, in file-i/o protocol
22315 A special case is, if the @var{Ctrl-C flag} is set in the @value{GDBN}
22316 reply packet. In this case the target should behave, as if it had
22317 gotten a break message. The meaning for the target is ``system call
22318 interupted by @code{SIGINT}''. Consequentially, the target should actually stop
22319 (as with a break message) and return to @value{GDBN} with a @code{T02}
22320 packet. In this case, it's important for the target to know, in which
22321 state the system call was interrupted. Since this action is by design
22322 not an atomic operation, we have to differ between two cases:
22326 The system call hasn't been performed on the host yet.
22329 The system call on the host has been finished.
22333 These two states can be distinguished by the target by the value of the
22334 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
22335 call hasn't been performed. This is equivalent to the @code{EINTR} handling
22336 on POSIX systems. In any other case, the target may presume that the
22337 system call has been finished --- successful or not --- and should behave
22338 as if the break message arrived right after the system call.
22340 @value{GDBN} must behave reliable. If the system call has not been called
22341 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
22342 @code{errno} in the packet. If the system call on the host has been finished
22343 before the user requests a break, the full action must be finshed by
22344 @value{GDBN}. This requires sending @code{M} or @code{X} packets as they fit.
22345 The @code{F} packet may only be send when either nothing has happened
22346 or the full action has been completed.
22349 @subsection Console I/O
22350 @cindex console i/o as part of file-i/o
22352 By default and if not explicitely closed by the target system, the file
22353 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
22354 on the @value{GDBN} console is handled as any other file output operation
22355 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
22356 by @value{GDBN} so that after the target read request from file descriptor
22357 0 all following typing is buffered until either one of the following
22362 The user presses @kbd{Ctrl-C}. The behaviour is as explained above, the
22364 system call is treated as finished.
22367 The user presses @kbd{Enter}. This is treated as end of input with a trailing
22371 The user presses @kbd{Ctrl-D}. This is treated as end of input. No trailing
22372 character, especially no Ctrl-D is appended to the input.
22376 If the user has typed more characters as fit in the buffer given to
22377 the read call, the trailing characters are buffered in @value{GDBN} until
22378 either another @code{read(0, @dots{})} is requested by the target or debugging
22379 is stopped on users request.
22381 @node The isatty call
22382 @subsection The isatty(3) call
22383 @cindex isatty call, file-i/o protocol
22385 A special case in this protocol is the library call @code{isatty} which
22386 is implemented as its own call inside of this protocol. It returns
22387 1 to the target if the file descriptor given as parameter is attached
22388 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
22389 would require implementing @code{ioctl} and would be more complex than
22392 @node The system call
22393 @subsection The system(3) call
22394 @cindex system call, file-i/o protocol
22396 The other special case in this protocol is the @code{system} call which
22397 is implemented as its own call, too. @value{GDBN} is taking over the full
22398 task of calling the necessary host calls to perform the @code{system}
22399 call. The return value of @code{system} is simplified before it's returned
22400 to the target. Basically, the only signal transmitted back is @code{EINTR}
22401 in case the user pressed @kbd{Ctrl-C}. Otherwise the return value consists
22402 entirely of the exit status of the called command.
22404 Due to security concerns, the @code{system} call is by default refused
22405 by @value{GDBN}. The user has to allow this call explicitly with the
22406 @kbd{set remote system-call-allowed 1} command.
22409 @item set remote system-call-allowed
22410 @kindex set remote system-call-allowed
22411 Control whether to allow the @code{system} calls in the File I/O
22412 protocol for the remote target. The default is zero (disabled).
22414 @item show remote system-call-allowed
22415 @kindex show remote system-call-allowed
22416 Show the current setting of system calls for the remote File I/O
22420 @node List of supported calls
22421 @subsection List of supported calls
22422 @cindex list of supported file-i/o calls
22439 @unnumberedsubsubsec open
22440 @cindex open, file-i/o system call
22444 int open(const char *pathname, int flags);
22445 int open(const char *pathname, int flags, mode_t mode);
22448 Fopen,pathptr/len,flags,mode
22452 @code{flags} is the bitwise or of the following values:
22456 If the file does not exist it will be created. The host
22457 rules apply as far as file ownership and time stamps
22461 When used with O_CREAT, if the file already exists it is
22462 an error and open() fails.
22465 If the file already exists and the open mode allows
22466 writing (O_RDWR or O_WRONLY is given) it will be
22467 truncated to length 0.
22470 The file is opened in append mode.
22473 The file is opened for reading only.
22476 The file is opened for writing only.
22479 The file is opened for reading and writing.
22482 Each other bit is silently ignored.
22487 @code{mode} is the bitwise or of the following values:
22491 User has read permission.
22494 User has write permission.
22497 Group has read permission.
22500 Group has write permission.
22503 Others have read permission.
22506 Others have write permission.
22509 Each other bit is silently ignored.
22514 @exdent Return value:
22515 open returns the new file descriptor or -1 if an error
22523 pathname already exists and O_CREAT and O_EXCL were used.
22526 pathname refers to a directory.
22529 The requested access is not allowed.
22532 pathname was too long.
22535 A directory component in pathname does not exist.
22538 pathname refers to a device, pipe, named pipe or socket.
22541 pathname refers to a file on a read-only filesystem and
22542 write access was requested.
22545 pathname is an invalid pointer value.
22548 No space on device to create the file.
22551 The process already has the maximum number of files open.
22554 The limit on the total number of files open on the system
22558 The call was interrupted by the user.
22562 @unnumberedsubsubsec close
22563 @cindex close, file-i/o system call
22572 @exdent Return value:
22573 close returns zero on success, or -1 if an error occurred.
22580 fd isn't a valid open file descriptor.
22583 The call was interrupted by the user.
22587 @unnumberedsubsubsec read
22588 @cindex read, file-i/o system call
22592 int read(int fd, void *buf, unsigned int count);
22595 Fread,fd,bufptr,count
22597 @exdent Return value:
22598 On success, the number of bytes read is returned.
22599 Zero indicates end of file. If count is zero, read
22600 returns zero as well. On error, -1 is returned.
22607 fd is not a valid file descriptor or is not open for
22611 buf is an invalid pointer value.
22614 The call was interrupted by the user.
22618 @unnumberedsubsubsec write
22619 @cindex write, file-i/o system call
22623 int write(int fd, const void *buf, unsigned int count);
22626 Fwrite,fd,bufptr,count
22628 @exdent Return value:
22629 On success, the number of bytes written are returned.
22630 Zero indicates nothing was written. On error, -1
22638 fd is not a valid file descriptor or is not open for
22642 buf is an invalid pointer value.
22645 An attempt was made to write a file that exceeds the
22646 host specific maximum file size allowed.
22649 No space on device to write the data.
22652 The call was interrupted by the user.
22656 @unnumberedsubsubsec lseek
22657 @cindex lseek, file-i/o system call
22661 long lseek (int fd, long offset, int flag);
22664 Flseek,fd,offset,flag
22667 @code{flag} is one of:
22671 The offset is set to offset bytes.
22674 The offset is set to its current location plus offset
22678 The offset is set to the size of the file plus offset
22683 @exdent Return value:
22684 On success, the resulting unsigned offset in bytes from
22685 the beginning of the file is returned. Otherwise, a
22686 value of -1 is returned.
22693 fd is not a valid open file descriptor.
22696 fd is associated with the @value{GDBN} console.
22699 flag is not a proper value.
22702 The call was interrupted by the user.
22706 @unnumberedsubsubsec rename
22707 @cindex rename, file-i/o system call
22711 int rename(const char *oldpath, const char *newpath);
22714 Frename,oldpathptr/len,newpathptr/len
22716 @exdent Return value:
22717 On success, zero is returned. On error, -1 is returned.
22724 newpath is an existing directory, but oldpath is not a
22728 newpath is a non-empty directory.
22731 oldpath or newpath is a directory that is in use by some
22735 An attempt was made to make a directory a subdirectory
22739 A component used as a directory in oldpath or new
22740 path is not a directory. Or oldpath is a directory
22741 and newpath exists but is not a directory.
22744 oldpathptr or newpathptr are invalid pointer values.
22747 No access to the file or the path of the file.
22751 oldpath or newpath was too long.
22754 A directory component in oldpath or newpath does not exist.
22757 The file is on a read-only filesystem.
22760 The device containing the file has no room for the new
22764 The call was interrupted by the user.
22768 @unnumberedsubsubsec unlink
22769 @cindex unlink, file-i/o system call
22773 int unlink(const char *pathname);
22776 Funlink,pathnameptr/len
22778 @exdent Return value:
22779 On success, zero is returned. On error, -1 is returned.
22786 No access to the file or the path of the file.
22789 The system does not allow unlinking of directories.
22792 The file pathname cannot be unlinked because it's
22793 being used by another process.
22796 pathnameptr is an invalid pointer value.
22799 pathname was too long.
22802 A directory component in pathname does not exist.
22805 A component of the path is not a directory.
22808 The file is on a read-only filesystem.
22811 The call was interrupted by the user.
22815 @unnumberedsubsubsec stat/fstat
22816 @cindex fstat, file-i/o system call
22817 @cindex stat, file-i/o system call
22821 int stat(const char *pathname, struct stat *buf);
22822 int fstat(int fd, struct stat *buf);
22825 Fstat,pathnameptr/len,bufptr
22828 @exdent Return value:
22829 On success, zero is returned. On error, -1 is returned.
22836 fd is not a valid open file.
22839 A directory component in pathname does not exist or the
22840 path is an empty string.
22843 A component of the path is not a directory.
22846 pathnameptr is an invalid pointer value.
22849 No access to the file or the path of the file.
22852 pathname was too long.
22855 The call was interrupted by the user.
22859 @unnumberedsubsubsec gettimeofday
22860 @cindex gettimeofday, file-i/o system call
22864 int gettimeofday(struct timeval *tv, void *tz);
22867 Fgettimeofday,tvptr,tzptr
22869 @exdent Return value:
22870 On success, 0 is returned, -1 otherwise.
22877 tz is a non-NULL pointer.
22880 tvptr and/or tzptr is an invalid pointer value.
22884 @unnumberedsubsubsec isatty
22885 @cindex isatty, file-i/o system call
22889 int isatty(int fd);
22894 @exdent Return value:
22895 Returns 1 if fd refers to the @value{GDBN} console, 0 otherwise.
22902 The call was interrupted by the user.
22906 @unnumberedsubsubsec system
22907 @cindex system, file-i/o system call
22911 int system(const char *command);
22914 Fsystem,commandptr/len
22916 @exdent Return value:
22917 The value returned is -1 on error and the return status
22918 of the command otherwise. Only the exit status of the
22919 command is returned, which is extracted from the hosts
22920 system return value by calling WEXITSTATUS(retval).
22921 In case /bin/sh could not be executed, 127 is returned.
22928 The call was interrupted by the user.
22931 @node Protocol specific representation of datatypes
22932 @subsection Protocol specific representation of datatypes
22933 @cindex protocol specific representation of datatypes, in file-i/o protocol
22936 * Integral datatypes::
22942 @node Integral datatypes
22943 @unnumberedsubsubsec Integral datatypes
22944 @cindex integral datatypes, in file-i/o protocol
22946 The integral datatypes used in the system calls are
22949 int@r{,} unsigned int@r{,} long@r{,} unsigned long@r{,} mode_t @r{and} time_t
22952 @code{Int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
22953 implemented as 32 bit values in this protocol.
22955 @code{Long} and @code{unsigned long} are implemented as 64 bit types.
22957 @xref{Limits}, for corresponding MIN and MAX values (similar to those
22958 in @file{limits.h}) to allow range checking on host and target.
22960 @code{time_t} datatypes are defined as seconds since the Epoch.
22962 All integral datatypes transferred as part of a memory read or write of a
22963 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
22966 @node Pointer values
22967 @unnumberedsubsubsec Pointer values
22968 @cindex pointer values, in file-i/o protocol
22970 Pointers to target data are transmitted as they are. An exception
22971 is made for pointers to buffers for which the length isn't
22972 transmitted as part of the function call, namely strings. Strings
22973 are transmitted as a pointer/length pair, both as hex values, e.g.@:
22980 which is a pointer to data of length 18 bytes at position 0x1aaf.
22981 The length is defined as the full string length in bytes, including
22982 the trailing null byte. Example:
22985 ``hello, world'' at address 0x123456
22996 @unnumberedsubsubsec struct stat
22997 @cindex struct stat, in file-i/o protocol
22999 The buffer of type struct stat used by the target and @value{GDBN} is defined
23004 unsigned int st_dev; /* device */
23005 unsigned int st_ino; /* inode */
23006 mode_t st_mode; /* protection */
23007 unsigned int st_nlink; /* number of hard links */
23008 unsigned int st_uid; /* user ID of owner */
23009 unsigned int st_gid; /* group ID of owner */
23010 unsigned int st_rdev; /* device type (if inode device) */
23011 unsigned long st_size; /* total size, in bytes */
23012 unsigned long st_blksize; /* blocksize for filesystem I/O */
23013 unsigned long st_blocks; /* number of blocks allocated */
23014 time_t st_atime; /* time of last access */
23015 time_t st_mtime; /* time of last modification */
23016 time_t st_ctime; /* time of last change */
23020 The integral datatypes are conforming to the definitions given in the
23021 approriate section (see @ref{Integral datatypes}, for details) so this
23022 structure is of size 64 bytes.
23024 The values of several fields have a restricted meaning and/or
23031 st_ino: No valid meaning for the target. Transmitted unchanged.
23033 st_mode: Valid mode bits are described in Appendix C. Any other
23034 bits have currently no meaning for the target.
23036 st_uid: No valid meaning for the target. Transmitted unchanged.
23038 st_gid: No valid meaning for the target. Transmitted unchanged.
23040 st_rdev: No valid meaning for the target. Transmitted unchanged.
23042 st_atime, st_mtime, st_ctime:
23043 These values have a host and file system dependent
23044 accuracy. Especially on Windows hosts the file systems
23045 don't support exact timing values.
23048 The target gets a struct stat of the above representation and is
23049 responsible to coerce it to the target representation before
23052 Note that due to size differences between the host and target
23053 representation of stat members, these members could eventually
23054 get truncated on the target.
23056 @node struct timeval
23057 @unnumberedsubsubsec struct timeval
23058 @cindex struct timeval, in file-i/o protocol
23060 The buffer of type struct timeval used by the target and @value{GDBN}
23061 is defined as follows:
23065 time_t tv_sec; /* second */
23066 long tv_usec; /* microsecond */
23070 The integral datatypes are conforming to the definitions given in the
23071 approriate section (see @ref{Integral datatypes}, for details) so this
23072 structure is of size 8 bytes.
23075 @subsection Constants
23076 @cindex constants, in file-i/o protocol
23078 The following values are used for the constants inside of the
23079 protocol. @value{GDBN} and target are resposible to translate these
23080 values before and after the call as needed.
23091 @unnumberedsubsubsec Open flags
23092 @cindex open flags, in file-i/o protocol
23094 All values are given in hexadecimal representation.
23106 @node mode_t values
23107 @unnumberedsubsubsec mode_t values
23108 @cindex mode_t values, in file-i/o protocol
23110 All values are given in octal representation.
23127 @unnumberedsubsubsec Errno values
23128 @cindex errno values, in file-i/o protocol
23130 All values are given in decimal representation.
23155 EUNKNOWN is used as a fallback error value if a host system returns
23156 any error value not in the list of supported error numbers.
23159 @unnumberedsubsubsec Lseek flags
23160 @cindex lseek flags, in file-i/o protocol
23169 @unnumberedsubsubsec Limits
23170 @cindex limits, in file-i/o protocol
23172 All values are given in decimal representation.
23175 INT_MIN -2147483648
23177 UINT_MAX 4294967295
23178 LONG_MIN -9223372036854775808
23179 LONG_MAX 9223372036854775807
23180 ULONG_MAX 18446744073709551615
23183 @node File-I/O Examples
23184 @subsection File-I/O Examples
23185 @cindex file-i/o examples
23187 Example sequence of a write call, file descriptor 3, buffer is at target
23188 address 0x1234, 6 bytes should be written:
23191 <- @code{Fwrite,3,1234,6}
23192 @emph{request memory read from target}
23195 @emph{return "6 bytes written"}
23199 Example sequence of a read call, file descriptor 3, buffer is at target
23200 address 0x1234, 6 bytes should be read:
23203 <- @code{Fread,3,1234,6}
23204 @emph{request memory write to target}
23205 -> @code{X1234,6:XXXXXX}
23206 @emph{return "6 bytes read"}
23210 Example sequence of a read call, call fails on the host due to invalid
23211 file descriptor (EBADF):
23214 <- @code{Fread,3,1234,6}
23218 Example sequence of a read call, user presses Ctrl-C before syscall on
23222 <- @code{Fread,3,1234,6}
23227 Example sequence of a read call, user presses Ctrl-C after syscall on
23231 <- @code{Fread,3,1234,6}
23232 -> @code{X1234,6:XXXXXX}
23236 @include agentexpr.texi
23250 % I think something like @colophon should be in texinfo. In the
23252 \long\def\colophon{\hbox to0pt{}\vfill
23253 \centerline{The body of this manual is set in}
23254 \centerline{\fontname\tenrm,}
23255 \centerline{with headings in {\bf\fontname\tenbf}}
23256 \centerline{and examples in {\tt\fontname\tentt}.}
23257 \centerline{{\it\fontname\tenit\/},}
23258 \centerline{{\bf\fontname\tenbf}, and}
23259 \centerline{{\sl\fontname\tensl\/}}
23260 \centerline{are used for emphasis.}\vfill}
23262 % Blame: doc@cygnus.com, 1991.