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 @value{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
1270 repeat. User-defined commands can disable this feature; see
1271 @ref{Define, dont-repeat}.
1273 The @code{list} and @code{x} commands, when you repeat them with
1274 @key{RET}, construct new arguments rather than repeating
1275 exactly as typed. This permits easy scanning of source or memory.
1277 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1278 output, in a way similar to the common utility @code{more}
1279 (@pxref{Screen Size,,Screen size}). Since it is easy to press one
1280 @key{RET} too many in this situation, @value{GDBN} disables command
1281 repetition after any command that generates this sort of display.
1283 @kindex # @r{(a comment)}
1285 Any text from a @kbd{#} to the end of the line is a comment; it does
1286 nothing. This is useful mainly in command files (@pxref{Command
1287 Files,,Command files}).
1289 @cindex repeating command sequences
1290 @kindex C-o @r{(operate-and-get-next)}
1291 The @kbd{C-o} binding is useful for repeating a complex sequence of
1292 commands. This command accepts the current line, like @kbd{RET}, and
1293 then fetches the next line relative to the current line from the history
1297 @section Command completion
1300 @cindex word completion
1301 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1302 only one possibility; it can also show you what the valid possibilities
1303 are for the next word in a command, at any time. This works for @value{GDBN}
1304 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1306 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1307 of a word. If there is only one possibility, @value{GDBN} fills in the
1308 word, and waits for you to finish the command (or press @key{RET} to
1309 enter it). For example, if you type
1311 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1312 @c complete accuracy in these examples; space introduced for clarity.
1313 @c If texinfo enhancements make it unnecessary, it would be nice to
1314 @c replace " @key" by "@key" in the following...
1316 (@value{GDBP}) info bre @key{TAB}
1320 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1321 the only @code{info} subcommand beginning with @samp{bre}:
1324 (@value{GDBP}) info breakpoints
1328 You can either press @key{RET} at this point, to run the @code{info
1329 breakpoints} command, or backspace and enter something else, if
1330 @samp{breakpoints} does not look like the command you expected. (If you
1331 were sure you wanted @code{info breakpoints} in the first place, you
1332 might as well just type @key{RET} immediately after @samp{info bre},
1333 to exploit command abbreviations rather than command completion).
1335 If there is more than one possibility for the next word when you press
1336 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1337 characters and try again, or just press @key{TAB} a second time;
1338 @value{GDBN} displays all the possible completions for that word. For
1339 example, you might want to set a breakpoint on a subroutine whose name
1340 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1341 just sounds the bell. Typing @key{TAB} again displays all the
1342 function names in your program that begin with those characters, for
1346 (@value{GDBP}) b make_ @key{TAB}
1347 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1348 make_a_section_from_file make_environ
1349 make_abs_section make_function_type
1350 make_blockvector make_pointer_type
1351 make_cleanup make_reference_type
1352 make_command make_symbol_completion_list
1353 (@value{GDBP}) b make_
1357 After displaying the available possibilities, @value{GDBN} copies your
1358 partial input (@samp{b make_} in the example) so you can finish the
1361 If you just want to see the list of alternatives in the first place, you
1362 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1363 means @kbd{@key{META} ?}. You can type this either by holding down a
1364 key designated as the @key{META} shift on your keyboard (if there is
1365 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1367 @cindex quotes in commands
1368 @cindex completion of quoted strings
1369 Sometimes the string you need, while logically a ``word'', may contain
1370 parentheses or other characters that @value{GDBN} normally excludes from
1371 its notion of a word. To permit word completion to work in this
1372 situation, you may enclose words in @code{'} (single quote marks) in
1373 @value{GDBN} commands.
1375 The most likely situation where you might need this is in typing the
1376 name of a C@t{++} function. This is because C@t{++} allows function
1377 overloading (multiple definitions of the same function, distinguished
1378 by argument type). For example, when you want to set a breakpoint you
1379 may need to distinguish whether you mean the version of @code{name}
1380 that takes an @code{int} parameter, @code{name(int)}, or the version
1381 that takes a @code{float} parameter, @code{name(float)}. To use the
1382 word-completion facilities in this situation, type a single quote
1383 @code{'} at the beginning of the function name. This alerts
1384 @value{GDBN} that it may need to consider more information than usual
1385 when you press @key{TAB} or @kbd{M-?} to request word completion:
1388 (@value{GDBP}) b 'bubble( @kbd{M-?}
1389 bubble(double,double) bubble(int,int)
1390 (@value{GDBP}) b 'bubble(
1393 In some cases, @value{GDBN} can tell that completing a name requires using
1394 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1395 completing as much as it can) if you do not type the quote in the first
1399 (@value{GDBP}) b bub @key{TAB}
1400 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1401 (@value{GDBP}) b 'bubble(
1405 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1406 you have not yet started typing the argument list when you ask for
1407 completion on an overloaded symbol.
1409 For more information about overloaded functions, see @ref{C plus plus
1410 expressions, ,C@t{++} expressions}. You can use the command @code{set
1411 overload-resolution off} to disable overload resolution;
1412 see @ref{Debugging C plus plus, ,@value{GDBN} features for C@t{++}}.
1416 @section Getting help
1417 @cindex online documentation
1420 You can always ask @value{GDBN} itself for information on its commands,
1421 using the command @code{help}.
1424 @kindex h @r{(@code{help})}
1427 You can use @code{help} (abbreviated @code{h}) with no arguments to
1428 display a short list of named classes of commands:
1432 List of classes of commands:
1434 aliases -- Aliases of other commands
1435 breakpoints -- Making program stop at certain points
1436 data -- Examining data
1437 files -- Specifying and examining files
1438 internals -- Maintenance commands
1439 obscure -- Obscure features
1440 running -- Running the program
1441 stack -- Examining the stack
1442 status -- Status inquiries
1443 support -- Support facilities
1444 tracepoints -- Tracing of program execution without@*
1445 stopping the program
1446 user-defined -- User-defined commands
1448 Type "help" followed by a class name for a list of
1449 commands in that class.
1450 Type "help" followed by command name for full
1452 Command name abbreviations are allowed if unambiguous.
1455 @c the above line break eliminates huge line overfull...
1457 @item help @var{class}
1458 Using one of the general help classes as an argument, you can get a
1459 list of the individual commands in that class. For example, here is the
1460 help display for the class @code{status}:
1463 (@value{GDBP}) help status
1468 @c Line break in "show" line falsifies real output, but needed
1469 @c to fit in smallbook page size.
1470 info -- Generic command for showing things
1471 about the program being debugged
1472 show -- Generic command for showing things
1475 Type "help" followed by command name for full
1477 Command name abbreviations are allowed if unambiguous.
1481 @item help @var{command}
1482 With a command name as @code{help} argument, @value{GDBN} displays a
1483 short paragraph on how to use that command.
1486 @item apropos @var{args}
1487 The @code{apropos} command searches through all of the @value{GDBN}
1488 commands, and their documentation, for the regular expression specified in
1489 @var{args}. It prints out all matches found. For example:
1500 set symbol-reloading -- Set dynamic symbol table reloading
1501 multiple times in one run
1502 show symbol-reloading -- Show dynamic symbol table reloading
1503 multiple times in one run
1508 @item complete @var{args}
1509 The @code{complete @var{args}} command lists all the possible completions
1510 for the beginning of a command. Use @var{args} to specify the beginning of the
1511 command you want completed. For example:
1517 @noindent results in:
1528 @noindent This is intended for use by @sc{gnu} Emacs.
1531 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1532 and @code{show} to inquire about the state of your program, or the state
1533 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1534 manual introduces each of them in the appropriate context. The listings
1535 under @code{info} and under @code{show} in the Index point to
1536 all the sub-commands. @xref{Index}.
1541 @kindex i @r{(@code{info})}
1543 This command (abbreviated @code{i}) is for describing the state of your
1544 program. For example, you can list the arguments given to your program
1545 with @code{info args}, list the registers currently in use with @code{info
1546 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1547 You can get a complete list of the @code{info} sub-commands with
1548 @w{@code{help info}}.
1552 You can assign the result of an expression to an environment variable with
1553 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1554 @code{set prompt $}.
1558 In contrast to @code{info}, @code{show} is for describing the state of
1559 @value{GDBN} itself.
1560 You can change most of the things you can @code{show}, by using the
1561 related command @code{set}; for example, you can control what number
1562 system is used for displays with @code{set radix}, or simply inquire
1563 which is currently in use with @code{show radix}.
1566 To display all the settable parameters and their current
1567 values, you can use @code{show} with no arguments; you may also use
1568 @code{info set}. Both commands produce the same display.
1569 @c FIXME: "info set" violates the rule that "info" is for state of
1570 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1571 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1575 Here are three miscellaneous @code{show} subcommands, all of which are
1576 exceptional in lacking corresponding @code{set} commands:
1579 @kindex show version
1580 @cindex @value{GDBN} version number
1582 Show what version of @value{GDBN} is running. You should include this
1583 information in @value{GDBN} bug-reports. If multiple versions of
1584 @value{GDBN} are in use at your site, you may need to determine which
1585 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1586 commands are introduced, and old ones may wither away. Also, many
1587 system vendors ship variant versions of @value{GDBN}, and there are
1588 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1589 The version number is the same as the one announced when you start
1592 @kindex show copying
1593 @kindex info copying
1594 @cindex display @value{GDBN} copyright
1597 Display information about permission for copying @value{GDBN}.
1599 @kindex show warranty
1600 @kindex info warranty
1602 @itemx info warranty
1603 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1604 if your version of @value{GDBN} comes with one.
1609 @chapter Running Programs Under @value{GDBN}
1611 When you run a program under @value{GDBN}, you must first generate
1612 debugging information when you compile it.
1614 You may start @value{GDBN} with its arguments, if any, in an environment
1615 of your choice. If you are doing native debugging, you may redirect
1616 your program's input and output, debug an already running process, or
1617 kill a child process.
1620 * Compilation:: Compiling for debugging
1621 * Starting:: Starting your program
1622 * Arguments:: Your program's arguments
1623 * Environment:: Your program's environment
1625 * Working Directory:: Your program's working directory
1626 * Input/Output:: Your program's input and output
1627 * Attach:: Debugging an already-running process
1628 * Kill Process:: Killing the child process
1630 * Threads:: Debugging programs with multiple threads
1631 * Processes:: Debugging programs with multiple processes
1635 @section Compiling for debugging
1637 In order to debug a program effectively, you need to generate
1638 debugging information when you compile it. This debugging information
1639 is stored in the object file; it describes the data type of each
1640 variable or function and the correspondence between source line numbers
1641 and addresses in the executable code.
1643 To request debugging information, specify the @samp{-g} option when you run
1646 Most compilers do not include information about preprocessor macros in
1647 the debugging information if you specify the @option{-g} flag alone,
1648 because this information is rather large. Version 3.1 of @value{NGCC},
1649 the @sc{gnu} C compiler, provides macro information if you specify the
1650 options @option{-gdwarf-2} and @option{-g3}; the former option requests
1651 debugging information in the Dwarf 2 format, and the latter requests
1652 ``extra information''. In the future, we hope to find more compact ways
1653 to represent macro information, so that it can be included with
1656 Many C compilers are unable to handle the @samp{-g} and @samp{-O}
1657 options together. Using those compilers, you cannot generate optimized
1658 executables containing debugging information.
1660 @value{NGCC}, the @sc{gnu} C compiler, supports @samp{-g} with or
1661 without @samp{-O}, making it possible to debug optimized code. We
1662 recommend that you @emph{always} use @samp{-g} whenever you compile a
1663 program. You may think your program is correct, but there is no sense
1664 in pushing your luck.
1666 @cindex optimized code, debugging
1667 @cindex debugging optimized code
1668 When you debug a program compiled with @samp{-g -O}, remember that the
1669 optimizer is rearranging your code; the debugger shows you what is
1670 really there. Do not be too surprised when the execution path does not
1671 exactly match your source file! An extreme example: if you define a
1672 variable, but never use it, @value{GDBN} never sees that
1673 variable---because the compiler optimizes it out of existence.
1675 Some things do not work as well with @samp{-g -O} as with just
1676 @samp{-g}, particularly on machines with instruction scheduling. If in
1677 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1678 please report it to us as a bug (including a test case!).
1679 @xref{Variables}, for more information about debugging optimized code.
1681 Older versions of the @sc{gnu} C compiler permitted a variant option
1682 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1683 format; if your @sc{gnu} C compiler has this option, do not use it.
1687 @section Starting your program
1693 @kindex r @r{(@code{run})}
1696 Use the @code{run} command to start your program under @value{GDBN}.
1697 You must first specify the program name (except on VxWorks) with an
1698 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1699 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1700 (@pxref{Files, ,Commands to specify files}).
1704 If you are running your program in an execution environment that
1705 supports processes, @code{run} creates an inferior process and makes
1706 that process run your program. (In environments without processes,
1707 @code{run} jumps to the start of your program.)
1709 The execution of a program is affected by certain information it
1710 receives from its superior. @value{GDBN} provides ways to specify this
1711 information, which you must do @emph{before} starting your program. (You
1712 can change it after starting your program, but such changes only affect
1713 your program the next time you start it.) This information may be
1714 divided into four categories:
1717 @item The @emph{arguments.}
1718 Specify the arguments to give your program as the arguments of the
1719 @code{run} command. If a shell is available on your target, the shell
1720 is used to pass the arguments, so that you may use normal conventions
1721 (such as wildcard expansion or variable substitution) in describing
1723 In Unix systems, you can control which shell is used with the
1724 @code{SHELL} environment variable.
1725 @xref{Arguments, ,Your program's arguments}.
1727 @item The @emph{environment.}
1728 Your program normally inherits its environment from @value{GDBN}, but you can
1729 use the @value{GDBN} commands @code{set environment} and @code{unset
1730 environment} to change parts of the environment that affect
1731 your program. @xref{Environment, ,Your program's environment}.
1733 @item The @emph{working directory.}
1734 Your program inherits its working directory from @value{GDBN}. You can set
1735 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1736 @xref{Working Directory, ,Your program's working directory}.
1738 @item The @emph{standard input and output.}
1739 Your program normally uses the same device for standard input and
1740 standard output as @value{GDBN} is using. You can redirect input and output
1741 in the @code{run} command line, or you can use the @code{tty} command to
1742 set a different device for your program.
1743 @xref{Input/Output, ,Your program's input and output}.
1746 @emph{Warning:} While input and output redirection work, you cannot use
1747 pipes to pass the output of the program you are debugging to another
1748 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1752 When you issue the @code{run} command, your program begins to execute
1753 immediately. @xref{Stopping, ,Stopping and continuing}, for discussion
1754 of how to arrange for your program to stop. Once your program has
1755 stopped, you may call functions in your program, using the @code{print}
1756 or @code{call} commands. @xref{Data, ,Examining Data}.
1758 If the modification time of your symbol file has changed since the last
1759 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1760 table, and reads it again. When it does this, @value{GDBN} tries to retain
1761 your current breakpoints.
1766 @cindex run to main procedure
1767 The name of the main procedure can vary from language to language.
1768 With C or C@t{++}, the main procedure name is always @code{main}, but
1769 other languages such as Ada do not require a specific name for their
1770 main procedure. The debugger provides a convenient way to start the
1771 execution of the program and to stop at the beginning of the main
1772 procedure, depending on the language used.
1774 The @samp{start} command does the equivalent of setting a temporary
1775 breakpoint at the beginning of the main procedure and then invoking
1776 the @samp{run} command.
1778 @cindex elaboration phase
1779 Some programs contain an @dfn{elaboration} phase where some startup code is
1780 executed before the main procedure is called. This depends on the
1781 languages used to write your program. In C@t{++}, for instance,
1782 constructors for static and global objects are executed before
1783 @code{main} is called. It is therefore possible that the debugger stops
1784 before reaching the main procedure. However, the temporary breakpoint
1785 will remain to halt execution.
1787 Specify the arguments to give to your program as arguments to the
1788 @samp{start} command. These arguments will be given verbatim to the
1789 underlying @samp{run} command. Note that the same arguments will be
1790 reused if no argument is provided during subsequent calls to
1791 @samp{start} or @samp{run}.
1793 It is sometimes necessary to debug the program during elaboration. In
1794 these cases, using the @code{start} command would stop the execution of
1795 your program too late, as the program would have already completed the
1796 elaboration phase. Under these circumstances, insert breakpoints in your
1797 elaboration code before running your program.
1801 @section Your program's arguments
1803 @cindex arguments (to your program)
1804 The arguments to your program can be specified by the arguments of the
1806 They are passed to a shell, which expands wildcard characters and
1807 performs redirection of I/O, and thence to your program. Your
1808 @code{SHELL} environment variable (if it exists) specifies what shell
1809 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1810 the default shell (@file{/bin/sh} on Unix).
1812 On non-Unix systems, the program is usually invoked directly by
1813 @value{GDBN}, which emulates I/O redirection via the appropriate system
1814 calls, and the wildcard characters are expanded by the startup code of
1815 the program, not by the shell.
1817 @code{run} with no arguments uses the same arguments used by the previous
1818 @code{run}, or those set by the @code{set args} command.
1823 Specify the arguments to be used the next time your program is run. If
1824 @code{set args} has no arguments, @code{run} executes your program
1825 with no arguments. Once you have run your program with arguments,
1826 using @code{set args} before the next @code{run} is the only way to run
1827 it again without arguments.
1831 Show the arguments to give your program when it is started.
1835 @section Your program's environment
1837 @cindex environment (of your program)
1838 The @dfn{environment} consists of a set of environment variables and
1839 their values. Environment variables conventionally record such things as
1840 your user name, your home directory, your terminal type, and your search
1841 path for programs to run. Usually you set up environment variables with
1842 the shell and they are inherited by all the other programs you run. When
1843 debugging, it can be useful to try running your program with a modified
1844 environment without having to start @value{GDBN} over again.
1848 @item path @var{directory}
1849 Add @var{directory} to the front of the @code{PATH} environment variable
1850 (the search path for executables) that will be passed to your program.
1851 The value of @code{PATH} used by @value{GDBN} does not change.
1852 You may specify several directory names, separated by whitespace or by a
1853 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1854 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1855 is moved to the front, so it is searched sooner.
1857 You can use the string @samp{$cwd} to refer to whatever is the current
1858 working directory at the time @value{GDBN} searches the path. If you
1859 use @samp{.} instead, it refers to the directory where you executed the
1860 @code{path} command. @value{GDBN} replaces @samp{.} in the
1861 @var{directory} argument (with the current path) before adding
1862 @var{directory} to the search path.
1863 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1864 @c document that, since repeating it would be a no-op.
1868 Display the list of search paths for executables (the @code{PATH}
1869 environment variable).
1871 @kindex show environment
1872 @item show environment @r{[}@var{varname}@r{]}
1873 Print the value of environment variable @var{varname} to be given to
1874 your program when it starts. If you do not supply @var{varname},
1875 print the names and values of all environment variables to be given to
1876 your program. You can abbreviate @code{environment} as @code{env}.
1878 @kindex set environment
1879 @item set environment @var{varname} @r{[}=@var{value}@r{]}
1880 Set environment variable @var{varname} to @var{value}. The value
1881 changes for your program only, not for @value{GDBN} itself. @var{value} may
1882 be any string; the values of environment variables are just strings, and
1883 any interpretation is supplied by your program itself. The @var{value}
1884 parameter is optional; if it is eliminated, the variable is set to a
1886 @c "any string" here does not include leading, trailing
1887 @c blanks. Gnu asks: does anyone care?
1889 For example, this command:
1896 tells the debugged program, when subsequently run, that its user is named
1897 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
1898 are not actually required.)
1900 @kindex unset environment
1901 @item unset environment @var{varname}
1902 Remove variable @var{varname} from the environment to be passed to your
1903 program. This is different from @samp{set env @var{varname} =};
1904 @code{unset environment} removes the variable from the environment,
1905 rather than assigning it an empty value.
1908 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
1910 by your @code{SHELL} environment variable if it exists (or
1911 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
1912 that runs an initialization file---such as @file{.cshrc} for C-shell, or
1913 @file{.bashrc} for BASH---any variables you set in that file affect
1914 your program. You may wish to move setting of environment variables to
1915 files that are only run when you sign on, such as @file{.login} or
1918 @node Working Directory
1919 @section Your program's working directory
1921 @cindex working directory (of your program)
1922 Each time you start your program with @code{run}, it inherits its
1923 working directory from the current working directory of @value{GDBN}.
1924 The @value{GDBN} working directory is initially whatever it inherited
1925 from its parent process (typically the shell), but you can specify a new
1926 working directory in @value{GDBN} with the @code{cd} command.
1928 The @value{GDBN} working directory also serves as a default for the commands
1929 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
1934 @cindex change working directory
1935 @item cd @var{directory}
1936 Set the @value{GDBN} working directory to @var{directory}.
1940 Print the @value{GDBN} working directory.
1943 It is generally impossible to find the current working directory of
1944 the process being debugged (since a program can change its directory
1945 during its run). If you work on a system where @value{GDBN} is
1946 configured with the @file{/proc} support, you can use the @code{info
1947 proc} command (@pxref{SVR4 Process Information}) to find out the
1948 current working directory of the debuggee.
1951 @section Your program's input and output
1956 By default, the program you run under @value{GDBN} does input and output to
1957 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
1958 to its own terminal modes to interact with you, but it records the terminal
1959 modes your program was using and switches back to them when you continue
1960 running your program.
1963 @kindex info terminal
1965 Displays information recorded by @value{GDBN} about the terminal modes your
1969 You can redirect your program's input and/or output using shell
1970 redirection with the @code{run} command. For example,
1977 starts your program, diverting its output to the file @file{outfile}.
1980 @cindex controlling terminal
1981 Another way to specify where your program should do input and output is
1982 with the @code{tty} command. This command accepts a file name as
1983 argument, and causes this file to be the default for future @code{run}
1984 commands. It also resets the controlling terminal for the child
1985 process, for future @code{run} commands. For example,
1992 directs that processes started with subsequent @code{run} commands
1993 default to do input and output on the terminal @file{/dev/ttyb} and have
1994 that as their controlling terminal.
1996 An explicit redirection in @code{run} overrides the @code{tty} command's
1997 effect on the input/output device, but not its effect on the controlling
2000 When you use the @code{tty} command or redirect input in the @code{run}
2001 command, only the input @emph{for your program} is affected. The input
2002 for @value{GDBN} still comes from your terminal.
2005 @section Debugging an already-running process
2010 @item attach @var{process-id}
2011 This command attaches to a running process---one that was started
2012 outside @value{GDBN}. (@code{info files} shows your active
2013 targets.) The command takes as argument a process ID. The usual way to
2014 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2015 or with the @samp{jobs -l} shell command.
2017 @code{attach} does not repeat if you press @key{RET} a second time after
2018 executing the command.
2021 To use @code{attach}, your program must be running in an environment
2022 which supports processes; for example, @code{attach} does not work for
2023 programs on bare-board targets that lack an operating system. You must
2024 also have permission to send the process a signal.
2026 When you use @code{attach}, the debugger finds the program running in
2027 the process first by looking in the current working directory, then (if
2028 the program is not found) by using the source file search path
2029 (@pxref{Source Path, ,Specifying source directories}). You can also use
2030 the @code{file} command to load the program. @xref{Files, ,Commands to
2033 The first thing @value{GDBN} does after arranging to debug the specified
2034 process is to stop it. You can examine and modify an attached process
2035 with all the @value{GDBN} commands that are ordinarily available when
2036 you start processes with @code{run}. You can insert breakpoints; you
2037 can step and continue; you can modify storage. If you would rather the
2038 process continue running, you may use the @code{continue} command after
2039 attaching @value{GDBN} to the process.
2044 When you have finished debugging the attached process, you can use the
2045 @code{detach} command to release it from @value{GDBN} control. Detaching
2046 the process continues its execution. After the @code{detach} command,
2047 that process and @value{GDBN} become completely independent once more, and you
2048 are ready to @code{attach} another process or start one with @code{run}.
2049 @code{detach} does not repeat if you press @key{RET} again after
2050 executing the command.
2053 If you exit @value{GDBN} or use the @code{run} command while you have an
2054 attached process, you kill that process. By default, @value{GDBN} asks
2055 for confirmation if you try to do either of these things; you can
2056 control whether or not you need to confirm by using the @code{set
2057 confirm} command (@pxref{Messages/Warnings, ,Optional warnings and
2061 @section Killing the child process
2066 Kill the child process in which your program is running under @value{GDBN}.
2069 This command is useful if you wish to debug a core dump instead of a
2070 running process. @value{GDBN} ignores any core dump file while your program
2073 On some operating systems, a program cannot be executed outside @value{GDBN}
2074 while you have breakpoints set on it inside @value{GDBN}. You can use the
2075 @code{kill} command in this situation to permit running your program
2076 outside the debugger.
2078 The @code{kill} command is also useful if you wish to recompile and
2079 relink your program, since on many systems it is impossible to modify an
2080 executable file while it is running in a process. In this case, when you
2081 next type @code{run}, @value{GDBN} notices that the file has changed, and
2082 reads the symbol table again (while trying to preserve your current
2083 breakpoint settings).
2086 @section Debugging programs with multiple threads
2088 @cindex threads of execution
2089 @cindex multiple threads
2090 @cindex switching threads
2091 In some operating systems, such as HP-UX and Solaris, a single program
2092 may have more than one @dfn{thread} of execution. The precise semantics
2093 of threads differ from one operating system to another, but in general
2094 the threads of a single program are akin to multiple processes---except
2095 that they share one address space (that is, they can all examine and
2096 modify the same variables). On the other hand, each thread has its own
2097 registers and execution stack, and perhaps private memory.
2099 @value{GDBN} provides these facilities for debugging multi-thread
2103 @item automatic notification of new threads
2104 @item @samp{thread @var{threadno}}, a command to switch among threads
2105 @item @samp{info threads}, a command to inquire about existing threads
2106 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2107 a command to apply a command to a list of threads
2108 @item thread-specific breakpoints
2112 @emph{Warning:} These facilities are not yet available on every
2113 @value{GDBN} configuration where the operating system supports threads.
2114 If your @value{GDBN} does not support threads, these commands have no
2115 effect. For example, a system without thread support shows no output
2116 from @samp{info threads}, and always rejects the @code{thread} command,
2120 (@value{GDBP}) info threads
2121 (@value{GDBP}) thread 1
2122 Thread ID 1 not known. Use the "info threads" command to
2123 see the IDs of currently known threads.
2125 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2126 @c doesn't support threads"?
2129 @cindex focus of debugging
2130 @cindex current thread
2131 The @value{GDBN} thread debugging facility allows you to observe all
2132 threads while your program runs---but whenever @value{GDBN} takes
2133 control, one thread in particular is always the focus of debugging.
2134 This thread is called the @dfn{current thread}. Debugging commands show
2135 program information from the perspective of the current thread.
2137 @cindex @code{New} @var{systag} message
2138 @cindex thread identifier (system)
2139 @c FIXME-implementors!! It would be more helpful if the [New...] message
2140 @c included GDB's numeric thread handle, so you could just go to that
2141 @c thread without first checking `info threads'.
2142 Whenever @value{GDBN} detects a new thread in your program, it displays
2143 the target system's identification for the thread with a message in the
2144 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2145 whose form varies depending on the particular system. For example, on
2146 LynxOS, you might see
2149 [New process 35 thread 27]
2153 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2154 the @var{systag} is simply something like @samp{process 368}, with no
2157 @c FIXME!! (1) Does the [New...] message appear even for the very first
2158 @c thread of a program, or does it only appear for the
2159 @c second---i.e.@: when it becomes obvious we have a multithread
2161 @c (2) *Is* there necessarily a first thread always? Or do some
2162 @c multithread systems permit starting a program with multiple
2163 @c threads ab initio?
2165 @cindex thread number
2166 @cindex thread identifier (GDB)
2167 For debugging purposes, @value{GDBN} associates its own thread
2168 number---always a single integer---with each thread in your program.
2171 @kindex info threads
2173 Display a summary of all threads currently in your
2174 program. @value{GDBN} displays for each thread (in this order):
2178 the thread number assigned by @value{GDBN}
2181 the target system's thread identifier (@var{systag})
2184 the current stack frame summary for that thread
2188 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2189 indicates the current thread.
2193 @c end table here to get a little more width for example
2196 (@value{GDBP}) info threads
2197 3 process 35 thread 27 0x34e5 in sigpause ()
2198 2 process 35 thread 23 0x34e5 in sigpause ()
2199 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2205 @cindex debugging multithreaded programs (on HP-UX)
2206 @cindex thread identifier (GDB), on HP-UX
2207 For debugging purposes, @value{GDBN} associates its own thread
2208 number---a small integer assigned in thread-creation order---with each
2209 thread in your program.
2211 @cindex @code{New} @var{systag} message, on HP-UX
2212 @cindex thread identifier (system), on HP-UX
2213 @c FIXME-implementors!! It would be more helpful if the [New...] message
2214 @c included GDB's numeric thread handle, so you could just go to that
2215 @c thread without first checking `info threads'.
2216 Whenever @value{GDBN} detects a new thread in your program, it displays
2217 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2218 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2219 whose form varies depending on the particular system. For example, on
2223 [New thread 2 (system thread 26594)]
2227 when @value{GDBN} notices a new thread.
2230 @kindex info threads (HP-UX)
2232 Display a summary of all threads currently in your
2233 program. @value{GDBN} displays for each thread (in this order):
2236 @item the thread number assigned by @value{GDBN}
2238 @item the target system's thread identifier (@var{systag})
2240 @item the current stack frame summary for that thread
2244 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2245 indicates the current thread.
2249 @c end table here to get a little more width for example
2252 (@value{GDBP}) info threads
2253 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2255 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2256 from /usr/lib/libc.2
2257 1 system thread 27905 0x7b003498 in _brk () \@*
2258 from /usr/lib/libc.2
2261 On Solaris, you can display more information about user threads with a
2262 Solaris-specific command:
2265 @item maint info sol-threads
2266 @kindex maint info sol-threads
2267 @cindex thread info (Solaris)
2268 Display info on Solaris user threads.
2272 @kindex thread @var{threadno}
2273 @item thread @var{threadno}
2274 Make thread number @var{threadno} the current thread. The command
2275 argument @var{threadno} is the internal @value{GDBN} thread number, as
2276 shown in the first field of the @samp{info threads} display.
2277 @value{GDBN} responds by displaying the system identifier of the thread
2278 you selected, and its current stack frame summary:
2281 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2282 (@value{GDBP}) thread 2
2283 [Switching to process 35 thread 23]
2284 0x34e5 in sigpause ()
2288 As with the @samp{[New @dots{}]} message, the form of the text after
2289 @samp{Switching to} depends on your system's conventions for identifying
2292 @kindex thread apply
2293 @item thread apply [@var{threadno}] [@var{all}] @var{args}
2294 The @code{thread apply} command allows you to apply a command to one or
2295 more threads. Specify the numbers of the threads that you want affected
2296 with the command argument @var{threadno}. @var{threadno} is the internal
2297 @value{GDBN} thread number, as shown in the first field of the @samp{info
2298 threads} display. To apply a command to all threads, use
2299 @code{thread apply all} @var{args}.
2302 @cindex automatic thread selection
2303 @cindex switching threads automatically
2304 @cindex threads, automatic switching
2305 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2306 signal, it automatically selects the thread where that breakpoint or
2307 signal happened. @value{GDBN} alerts you to the context switch with a
2308 message of the form @samp{[Switching to @var{systag}]} to identify the
2311 @xref{Thread Stops,,Stopping and starting multi-thread programs}, for
2312 more information about how @value{GDBN} behaves when you stop and start
2313 programs with multiple threads.
2315 @xref{Set Watchpoints,,Setting watchpoints}, for information about
2316 watchpoints in programs with multiple threads.
2319 @section Debugging programs with multiple processes
2321 @cindex fork, debugging programs which call
2322 @cindex multiple processes
2323 @cindex processes, multiple
2324 On most systems, @value{GDBN} has no special support for debugging
2325 programs which create additional processes using the @code{fork}
2326 function. When a program forks, @value{GDBN} will continue to debug the
2327 parent process and the child process will run unimpeded. If you have
2328 set a breakpoint in any code which the child then executes, the child
2329 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2330 will cause it to terminate.
2332 However, if you want to debug the child process there is a workaround
2333 which isn't too painful. Put a call to @code{sleep} in the code which
2334 the child process executes after the fork. It may be useful to sleep
2335 only if a certain environment variable is set, or a certain file exists,
2336 so that the delay need not occur when you don't want to run @value{GDBN}
2337 on the child. While the child is sleeping, use the @code{ps} program to
2338 get its process ID. Then tell @value{GDBN} (a new invocation of
2339 @value{GDBN} if you are also debugging the parent process) to attach to
2340 the child process (@pxref{Attach}). From that point on you can debug
2341 the child process just like any other process which you attached to.
2343 On some systems, @value{GDBN} provides support for debugging programs that
2344 create additional processes using the @code{fork} or @code{vfork} functions.
2345 Currently, the only platforms with this feature are HP-UX (11.x and later
2346 only?) and GNU/Linux (kernel version 2.5.60 and later).
2348 By default, when a program forks, @value{GDBN} will continue to debug
2349 the parent process and the child process will run unimpeded.
2351 If you want to follow the child process instead of the parent process,
2352 use the command @w{@code{set follow-fork-mode}}.
2355 @kindex set follow-fork-mode
2356 @item set follow-fork-mode @var{mode}
2357 Set the debugger response to a program call of @code{fork} or
2358 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2359 process. The @var{mode} argument can be:
2363 The original process is debugged after a fork. The child process runs
2364 unimpeded. This is the default.
2367 The new process is debugged after a fork. The parent process runs
2372 @kindex show follow-fork-mode
2373 @item show follow-fork-mode
2374 Display the current debugger response to a @code{fork} or @code{vfork} call.
2377 If you ask to debug a child process and a @code{vfork} is followed by an
2378 @code{exec}, @value{GDBN} executes the new target up to the first
2379 breakpoint in the new target. If you have a breakpoint set on
2380 @code{main} in your original program, the breakpoint will also be set on
2381 the child process's @code{main}.
2383 When a child process is spawned by @code{vfork}, you cannot debug the
2384 child or parent until an @code{exec} call completes.
2386 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2387 call executes, the new target restarts. To restart the parent process,
2388 use the @code{file} command with the parent executable name as its
2391 You can use the @code{catch} command to make @value{GDBN} stop whenever
2392 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2393 Catchpoints, ,Setting catchpoints}.
2396 @chapter Stopping and Continuing
2398 The principal purposes of using a debugger are so that you can stop your
2399 program before it terminates; or so that, if your program runs into
2400 trouble, you can investigate and find out why.
2402 Inside @value{GDBN}, your program may stop for any of several reasons,
2403 such as a signal, a breakpoint, or reaching a new line after a
2404 @value{GDBN} command such as @code{step}. You may then examine and
2405 change variables, set new breakpoints or remove old ones, and then
2406 continue execution. Usually, the messages shown by @value{GDBN} provide
2407 ample explanation of the status of your program---but you can also
2408 explicitly request this information at any time.
2411 @kindex info program
2413 Display information about the status of your program: whether it is
2414 running or not, what process it is, and why it stopped.
2418 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2419 * Continuing and Stepping:: Resuming execution
2421 * Thread Stops:: Stopping and starting multi-thread programs
2425 @section Breakpoints, watchpoints, and catchpoints
2428 A @dfn{breakpoint} makes your program stop whenever a certain point in
2429 the program is reached. For each breakpoint, you can add conditions to
2430 control in finer detail whether your program stops. You can set
2431 breakpoints with the @code{break} command and its variants (@pxref{Set
2432 Breaks, ,Setting breakpoints}), to specify the place where your program
2433 should stop by line number, function name or exact address in the
2436 On some systems, you can set breakpoints in shared libraries before
2437 the executable is run. There is a minor limitation on HP-UX systems:
2438 you must wait until the executable is run in order to set breakpoints
2439 in shared library routines that are not called directly by the program
2440 (for example, routines that are arguments in a @code{pthread_create}
2444 @cindex memory tracing
2445 @cindex breakpoint on memory address
2446 @cindex breakpoint on variable modification
2447 A @dfn{watchpoint} is a special breakpoint that stops your program
2448 when the value of an expression changes. You must use a different
2449 command to set watchpoints (@pxref{Set Watchpoints, ,Setting
2450 watchpoints}), but aside from that, you can manage a watchpoint like
2451 any other breakpoint: you enable, disable, and delete both breakpoints
2452 and watchpoints using the same commands.
2454 You can arrange to have values from your program displayed automatically
2455 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2459 @cindex breakpoint on events
2460 A @dfn{catchpoint} is another special breakpoint that stops your program
2461 when a certain kind of event occurs, such as the throwing of a C@t{++}
2462 exception or the loading of a library. As with watchpoints, you use a
2463 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2464 catchpoints}), but aside from that, you can manage a catchpoint like any
2465 other breakpoint. (To stop when your program receives a signal, use the
2466 @code{handle} command; see @ref{Signals, ,Signals}.)
2468 @cindex breakpoint numbers
2469 @cindex numbers for breakpoints
2470 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2471 catchpoint when you create it; these numbers are successive integers
2472 starting with one. In many of the commands for controlling various
2473 features of breakpoints you use the breakpoint number to say which
2474 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2475 @dfn{disabled}; if disabled, it has no effect on your program until you
2478 @cindex breakpoint ranges
2479 @cindex ranges of breakpoints
2480 Some @value{GDBN} commands accept a range of breakpoints on which to
2481 operate. A breakpoint range is either a single breakpoint number, like
2482 @samp{5}, or two such numbers, in increasing order, separated by a
2483 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2484 all breakpoint in that range are operated on.
2487 * Set Breaks:: Setting breakpoints
2488 * Set Watchpoints:: Setting watchpoints
2489 * Set Catchpoints:: Setting catchpoints
2490 * Delete Breaks:: Deleting breakpoints
2491 * Disabling:: Disabling breakpoints
2492 * Conditions:: Break conditions
2493 * Break Commands:: Breakpoint command lists
2494 * Breakpoint Menus:: Breakpoint menus
2495 * Error in Breakpoints:: ``Cannot insert breakpoints''
2496 * Breakpoint related warnings:: ``Breakpoint address adjusted...''
2500 @subsection Setting breakpoints
2502 @c FIXME LMB what does GDB do if no code on line of breakpt?
2503 @c consider in particular declaration with/without initialization.
2505 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2508 @kindex b @r{(@code{break})}
2509 @vindex $bpnum@r{, convenience variable}
2510 @cindex latest breakpoint
2511 Breakpoints are set with the @code{break} command (abbreviated
2512 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2513 number of the breakpoint you've set most recently; see @ref{Convenience
2514 Vars,, Convenience variables}, for a discussion of what you can do with
2515 convenience variables.
2517 You have several ways to say where the breakpoint should go.
2520 @item break @var{function}
2521 Set a breakpoint at entry to function @var{function}.
2522 When using source languages that permit overloading of symbols, such as
2523 C@t{++}, @var{function} may refer to more than one possible place to break.
2524 @xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
2526 @item break +@var{offset}
2527 @itemx break -@var{offset}
2528 Set a breakpoint some number of lines forward or back from the position
2529 at which execution stopped in the currently selected @dfn{stack frame}.
2530 (@xref{Frames, ,Frames}, for a description of stack frames.)
2532 @item break @var{linenum}
2533 Set a breakpoint at line @var{linenum} in the current source file.
2534 The current source file is the last file whose source text was printed.
2535 The breakpoint will stop your program just before it executes any of the
2538 @item break @var{filename}:@var{linenum}
2539 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2541 @item break @var{filename}:@var{function}
2542 Set a breakpoint at entry to function @var{function} found in file
2543 @var{filename}. Specifying a file name as well as a function name is
2544 superfluous except when multiple files contain similarly named
2547 @item break *@var{address}
2548 Set a breakpoint at address @var{address}. You can use this to set
2549 breakpoints in parts of your program which do not have debugging
2550 information or source files.
2553 When called without any arguments, @code{break} sets a breakpoint at
2554 the next instruction to be executed in the selected stack frame
2555 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2556 innermost, this makes your program stop as soon as control
2557 returns to that frame. This is similar to the effect of a
2558 @code{finish} command in the frame inside the selected frame---except
2559 that @code{finish} does not leave an active breakpoint. If you use
2560 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2561 the next time it reaches the current location; this may be useful
2564 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2565 least one instruction has been executed. If it did not do this, you
2566 would be unable to proceed past a breakpoint without first disabling the
2567 breakpoint. This rule applies whether or not the breakpoint already
2568 existed when your program stopped.
2570 @item break @dots{} if @var{cond}
2571 Set a breakpoint with condition @var{cond}; evaluate the expression
2572 @var{cond} each time the breakpoint is reached, and stop only if the
2573 value is nonzero---that is, if @var{cond} evaluates as true.
2574 @samp{@dots{}} stands for one of the possible arguments described
2575 above (or no argument) specifying where to break. @xref{Conditions,
2576 ,Break conditions}, for more information on breakpoint conditions.
2579 @item tbreak @var{args}
2580 Set a breakpoint enabled only for one stop. @var{args} are the
2581 same as for the @code{break} command, and the breakpoint is set in the same
2582 way, but the breakpoint is automatically deleted after the first time your
2583 program stops there. @xref{Disabling, ,Disabling breakpoints}.
2586 @cindex hardware breakpoints
2587 @item hbreak @var{args}
2588 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2589 @code{break} command and the breakpoint is set in the same way, but the
2590 breakpoint requires hardware support and some target hardware may not
2591 have this support. The main purpose of this is EPROM/ROM code
2592 debugging, so you can set a breakpoint at an instruction without
2593 changing the instruction. This can be used with the new trap-generation
2594 provided by SPARClite DSU and most x86-based targets. These targets
2595 will generate traps when a program accesses some data or instruction
2596 address that is assigned to the debug registers. However the hardware
2597 breakpoint registers can take a limited number of breakpoints. For
2598 example, on the DSU, only two data breakpoints can be set at a time, and
2599 @value{GDBN} will reject this command if more than two are used. Delete
2600 or disable unused hardware breakpoints before setting new ones
2601 (@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}.
2602 For remote targets, you can restrict the number of hardware
2603 breakpoints @value{GDBN} will use, see @ref{set remote
2604 hardware-breakpoint-limit}.
2608 @item thbreak @var{args}
2609 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2610 are the same as for the @code{hbreak} command and the breakpoint is set in
2611 the same way. However, like the @code{tbreak} command,
2612 the breakpoint is automatically deleted after the
2613 first time your program stops there. Also, like the @code{hbreak}
2614 command, the breakpoint requires hardware support and some target hardware
2615 may not have this support. @xref{Disabling, ,Disabling breakpoints}.
2616 See also @ref{Conditions, ,Break conditions}.
2619 @cindex regular expression
2620 @cindex breakpoints in functions matching a regexp
2621 @cindex set breakpoints in many functions
2622 @item rbreak @var{regex}
2623 Set breakpoints on all functions matching the regular expression
2624 @var{regex}. This command sets an unconditional breakpoint on all
2625 matches, printing a list of all breakpoints it set. Once these
2626 breakpoints are set, they are treated just like the breakpoints set with
2627 the @code{break} command. You can delete them, disable them, or make
2628 them conditional the same way as any other breakpoint.
2630 The syntax of the regular expression is the standard one used with tools
2631 like @file{grep}. Note that this is different from the syntax used by
2632 shells, so for instance @code{foo*} matches all functions that include
2633 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2634 @code{.*} leading and trailing the regular expression you supply, so to
2635 match only functions that begin with @code{foo}, use @code{^foo}.
2637 @cindex non-member C@t{++} functions, set breakpoint in
2638 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2639 breakpoints on overloaded functions that are not members of any special
2642 @cindex set breakpoints on all functions
2643 The @code{rbreak} command can be used to set breakpoints in
2644 @strong{all} the functions in a program, like this:
2647 (@value{GDBP}) rbreak .
2650 @kindex info breakpoints
2651 @cindex @code{$_} and @code{info breakpoints}
2652 @item info breakpoints @r{[}@var{n}@r{]}
2653 @itemx info break @r{[}@var{n}@r{]}
2654 @itemx info watchpoints @r{[}@var{n}@r{]}
2655 Print a table of all breakpoints, watchpoints, and catchpoints set and
2656 not deleted, with the following columns for each breakpoint:
2659 @item Breakpoint Numbers
2661 Breakpoint, watchpoint, or catchpoint.
2663 Whether the breakpoint is marked to be disabled or deleted when hit.
2664 @item Enabled or Disabled
2665 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2666 that are not enabled.
2668 Where the breakpoint is in your program, as a memory address. If the
2669 breakpoint is pending (see below for details) on a future load of a shared library, the address
2670 will be listed as @samp{<PENDING>}.
2672 Where the breakpoint is in the source for your program, as a file and
2673 line number. For a pending breakpoint, the original string passed to
2674 the breakpoint command will be listed as it cannot be resolved until
2675 the appropriate shared library is loaded in the future.
2679 If a breakpoint is conditional, @code{info break} shows the condition on
2680 the line following the affected breakpoint; breakpoint commands, if any,
2681 are listed after that. A pending breakpoint is allowed to have a condition
2682 specified for it. The condition is not parsed for validity until a shared
2683 library is loaded that allows the pending breakpoint to resolve to a
2687 @code{info break} with a breakpoint
2688 number @var{n} as argument lists only that breakpoint. The
2689 convenience variable @code{$_} and the default examining-address for
2690 the @code{x} command are set to the address of the last breakpoint
2691 listed (@pxref{Memory, ,Examining memory}).
2694 @code{info break} displays a count of the number of times the breakpoint
2695 has been hit. This is especially useful in conjunction with the
2696 @code{ignore} command. You can ignore a large number of breakpoint
2697 hits, look at the breakpoint info to see how many times the breakpoint
2698 was hit, and then run again, ignoring one less than that number. This
2699 will get you quickly to the last hit of that breakpoint.
2702 @value{GDBN} allows you to set any number of breakpoints at the same place in
2703 your program. There is nothing silly or meaningless about this. When
2704 the breakpoints are conditional, this is even useful
2705 (@pxref{Conditions, ,Break conditions}).
2707 @cindex pending breakpoints
2708 If a specified breakpoint location cannot be found, it may be due to the fact
2709 that the location is in a shared library that is yet to be loaded. In such
2710 a case, you may want @value{GDBN} to create a special breakpoint (known as
2711 a @dfn{pending breakpoint}) that
2712 attempts to resolve itself in the future when an appropriate shared library
2715 Pending breakpoints are useful to set at the start of your
2716 @value{GDBN} session for locations that you know will be dynamically loaded
2717 later by the program being debugged. When shared libraries are loaded,
2718 a check is made to see if the load resolves any pending breakpoint locations.
2719 If a pending breakpoint location gets resolved,
2720 a regular breakpoint is created and the original pending breakpoint is removed.
2722 @value{GDBN} provides some additional commands for controlling pending
2725 @kindex set breakpoint pending
2726 @kindex show breakpoint pending
2728 @item set breakpoint pending auto
2729 This is the default behavior. When @value{GDBN} cannot find the breakpoint
2730 location, it queries you whether a pending breakpoint should be created.
2732 @item set breakpoint pending on
2733 This indicates that an unrecognized breakpoint location should automatically
2734 result in a pending breakpoint being created.
2736 @item set breakpoint pending off
2737 This indicates that pending breakpoints are not to be created. Any
2738 unrecognized breakpoint location results in an error. This setting does
2739 not affect any pending breakpoints previously created.
2741 @item show breakpoint pending
2742 Show the current behavior setting for creating pending breakpoints.
2745 @cindex operations allowed on pending breakpoints
2746 Normal breakpoint operations apply to pending breakpoints as well. You may
2747 specify a condition for a pending breakpoint and/or commands to run when the
2748 breakpoint is reached. You can also enable or disable
2749 the pending breakpoint. When you specify a condition for a pending breakpoint,
2750 the parsing of the condition will be deferred until the point where the
2751 pending breakpoint location is resolved. Disabling a pending breakpoint
2752 tells @value{GDBN} to not attempt to resolve the breakpoint on any subsequent
2753 shared library load. When a pending breakpoint is re-enabled,
2754 @value{GDBN} checks to see if the location is already resolved.
2755 This is done because any number of shared library loads could have
2756 occurred since the time the breakpoint was disabled and one or more
2757 of these loads could resolve the location.
2759 @cindex negative breakpoint numbers
2760 @cindex internal @value{GDBN} breakpoints
2761 @value{GDBN} itself sometimes sets breakpoints in your program for
2762 special purposes, such as proper handling of @code{longjmp} (in C
2763 programs). These internal breakpoints are assigned negative numbers,
2764 starting with @code{-1}; @samp{info breakpoints} does not display them.
2765 You can see these breakpoints with the @value{GDBN} maintenance command
2766 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
2769 @node Set Watchpoints
2770 @subsection Setting watchpoints
2772 @cindex setting watchpoints
2773 You can use a watchpoint to stop execution whenever the value of an
2774 expression changes, without having to predict a particular place where
2777 @cindex software watchpoints
2778 @cindex hardware watchpoints
2779 Depending on your system, watchpoints may be implemented in software or
2780 hardware. @value{GDBN} does software watchpointing by single-stepping your
2781 program and testing the variable's value each time, which is hundreds of
2782 times slower than normal execution. (But this may still be worth it, to
2783 catch errors where you have no clue what part of your program is the
2786 On some systems, such as HP-UX, @sc{gnu}/Linux and most other
2787 x86-based targets, @value{GDBN} includes support for hardware
2788 watchpoints, which do not slow down the running of your program.
2792 @item watch @var{expr}
2793 Set a watchpoint for an expression. @value{GDBN} will break when @var{expr}
2794 is written into by the program and its value changes.
2797 @item rwatch @var{expr}
2798 Set a watchpoint that will break when the value of @var{expr} is read
2802 @item awatch @var{expr}
2803 Set a watchpoint that will break when @var{expr} is either read from
2804 or written into by the program.
2806 @kindex info watchpoints
2807 @item info watchpoints
2808 This command prints a list of watchpoints, breakpoints, and catchpoints;
2809 it is the same as @code{info break} (@pxref{Set Breaks}).
2812 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
2813 watchpoints execute very quickly, and the debugger reports a change in
2814 value at the exact instruction where the change occurs. If @value{GDBN}
2815 cannot set a hardware watchpoint, it sets a software watchpoint, which
2816 executes more slowly and reports the change in value at the next
2817 @emph{statement}, not the instruction, after the change occurs.
2819 @vindex can-use-hw-watchpoints
2820 @cindex use only software watchpoints
2821 You can force @value{GDBN} to use only software watchpoints with the
2822 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
2823 zero, @value{GDBN} will never try to use hardware watchpoints, even if
2824 the underlying system supports them. (Note that hardware-assisted
2825 watchpoints that were set @emph{before} setting
2826 @code{can-use-hw-watchpoints} to zero will still use the hardware
2827 mechanism of watching expressiion values.)
2830 @item set can-use-hw-watchpoints
2831 @kindex set can-use-hw-watchpoints
2832 Set whether or not to use hardware watchpoints.
2834 @item show can-use-hw-watchpoints
2835 @kindex show can-use-hw-watchpoints
2836 Show the current mode of using hardware watchpoints.
2839 For remote targets, you can restrict the number of hardware
2840 watchpoints @value{GDBN} will use, see @ref{set remote
2841 hardware-breakpoint-limit}.
2843 When you issue the @code{watch} command, @value{GDBN} reports
2846 Hardware watchpoint @var{num}: @var{expr}
2850 if it was able to set a hardware watchpoint.
2852 Currently, the @code{awatch} and @code{rwatch} commands can only set
2853 hardware watchpoints, because accesses to data that don't change the
2854 value of the watched expression cannot be detected without examining
2855 every instruction as it is being executed, and @value{GDBN} does not do
2856 that currently. If @value{GDBN} finds that it is unable to set a
2857 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
2858 will print a message like this:
2861 Expression cannot be implemented with read/access watchpoint.
2864 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
2865 data type of the watched expression is wider than what a hardware
2866 watchpoint on the target machine can handle. For example, some systems
2867 can only watch regions that are up to 4 bytes wide; on such systems you
2868 cannot set hardware watchpoints for an expression that yields a
2869 double-precision floating-point number (which is typically 8 bytes
2870 wide). As a work-around, it might be possible to break the large region
2871 into a series of smaller ones and watch them with separate watchpoints.
2873 If you set too many hardware watchpoints, @value{GDBN} might be unable
2874 to insert all of them when you resume the execution of your program.
2875 Since the precise number of active watchpoints is unknown until such
2876 time as the program is about to be resumed, @value{GDBN} might not be
2877 able to warn you about this when you set the watchpoints, and the
2878 warning will be printed only when the program is resumed:
2881 Hardware watchpoint @var{num}: Could not insert watchpoint
2885 If this happens, delete or disable some of the watchpoints.
2887 The SPARClite DSU will generate traps when a program accesses some data
2888 or instruction address that is assigned to the debug registers. For the
2889 data addresses, DSU facilitates the @code{watch} command. However the
2890 hardware breakpoint registers can only take two data watchpoints, and
2891 both watchpoints must be the same kind. For example, you can set two
2892 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
2893 @strong{or} two with @code{awatch} commands, but you cannot set one
2894 watchpoint with one command and the other with a different command.
2895 @value{GDBN} will reject the command if you try to mix watchpoints.
2896 Delete or disable unused watchpoint commands before setting new ones.
2898 If you call a function interactively using @code{print} or @code{call},
2899 any watchpoints you have set will be inactive until @value{GDBN} reaches another
2900 kind of breakpoint or the call completes.
2902 @value{GDBN} automatically deletes watchpoints that watch local
2903 (automatic) variables, or expressions that involve such variables, when
2904 they go out of scope, that is, when the execution leaves the block in
2905 which these variables were defined. In particular, when the program
2906 being debugged terminates, @emph{all} local variables go out of scope,
2907 and so only watchpoints that watch global variables remain set. If you
2908 rerun the program, you will need to set all such watchpoints again. One
2909 way of doing that would be to set a code breakpoint at the entry to the
2910 @code{main} function and when it breaks, set all the watchpoints.
2913 @cindex watchpoints and threads
2914 @cindex threads and watchpoints
2915 @emph{Warning:} In multi-thread programs, watchpoints have only limited
2916 usefulness. With the current watchpoint implementation, @value{GDBN}
2917 can only watch the value of an expression @emph{in a single thread}. If
2918 you are confident that the expression can only change due to the current
2919 thread's activity (and if you are also confident that no other thread
2920 can become current), then you can use watchpoints as usual. However,
2921 @value{GDBN} may not notice when a non-current thread's activity changes
2924 @c FIXME: this is almost identical to the previous paragraph.
2925 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
2926 have only limited usefulness. If @value{GDBN} creates a software
2927 watchpoint, it can only watch the value of an expression @emph{in a
2928 single thread}. If you are confident that the expression can only
2929 change due to the current thread's activity (and if you are also
2930 confident that no other thread can become current), then you can use
2931 software watchpoints as usual. However, @value{GDBN} may not notice
2932 when a non-current thread's activity changes the expression. (Hardware
2933 watchpoints, in contrast, watch an expression in all threads.)
2936 @xref{set remote hardware-watchpoint-limit}.
2938 @node Set Catchpoints
2939 @subsection Setting catchpoints
2940 @cindex catchpoints, setting
2941 @cindex exception handlers
2942 @cindex event handling
2944 You can use @dfn{catchpoints} to cause the debugger to stop for certain
2945 kinds of program events, such as C@t{++} exceptions or the loading of a
2946 shared library. Use the @code{catch} command to set a catchpoint.
2950 @item catch @var{event}
2951 Stop when @var{event} occurs. @var{event} can be any of the following:
2954 @cindex stop on C@t{++} exceptions
2955 The throwing of a C@t{++} exception.
2958 The catching of a C@t{++} exception.
2961 @cindex break on fork/exec
2962 A call to @code{exec}. This is currently only available for HP-UX.
2965 A call to @code{fork}. This is currently only available for HP-UX.
2968 A call to @code{vfork}. This is currently only available for HP-UX.
2971 @itemx load @var{libname}
2972 @cindex break on load/unload of shared library
2973 The dynamic loading of any shared library, or the loading of the library
2974 @var{libname}. This is currently only available for HP-UX.
2977 @itemx unload @var{libname}
2978 The unloading of any dynamically loaded shared library, or the unloading
2979 of the library @var{libname}. This is currently only available for HP-UX.
2982 @item tcatch @var{event}
2983 Set a catchpoint that is enabled only for one stop. The catchpoint is
2984 automatically deleted after the first time the event is caught.
2988 Use the @code{info break} command to list the current catchpoints.
2990 There are currently some limitations to C@t{++} exception handling
2991 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
2995 If you call a function interactively, @value{GDBN} normally returns
2996 control to you when the function has finished executing. If the call
2997 raises an exception, however, the call may bypass the mechanism that
2998 returns control to you and cause your program either to abort or to
2999 simply continue running until it hits a breakpoint, catches a signal
3000 that @value{GDBN} is listening for, or exits. This is the case even if
3001 you set a catchpoint for the exception; catchpoints on exceptions are
3002 disabled within interactive calls.
3005 You cannot raise an exception interactively.
3008 You cannot install an exception handler interactively.
3011 @cindex raise exceptions
3012 Sometimes @code{catch} is not the best way to debug exception handling:
3013 if you need to know exactly where an exception is raised, it is better to
3014 stop @emph{before} the exception handler is called, since that way you
3015 can see the stack before any unwinding takes place. If you set a
3016 breakpoint in an exception handler instead, it may not be easy to find
3017 out where the exception was raised.
3019 To stop just before an exception handler is called, you need some
3020 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3021 raised by calling a library function named @code{__raise_exception}
3022 which has the following ANSI C interface:
3025 /* @var{addr} is where the exception identifier is stored.
3026 @var{id} is the exception identifier. */
3027 void __raise_exception (void **addr, void *id);
3031 To make the debugger catch all exceptions before any stack
3032 unwinding takes place, set a breakpoint on @code{__raise_exception}
3033 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
3035 With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
3036 that depends on the value of @var{id}, you can stop your program when
3037 a specific exception is raised. You can use multiple conditional
3038 breakpoints to stop your program when any of a number of exceptions are
3043 @subsection Deleting breakpoints
3045 @cindex clearing breakpoints, watchpoints, catchpoints
3046 @cindex deleting breakpoints, watchpoints, catchpoints
3047 It is often necessary to eliminate a breakpoint, watchpoint, or
3048 catchpoint once it has done its job and you no longer want your program
3049 to stop there. This is called @dfn{deleting} the breakpoint. A
3050 breakpoint that has been deleted no longer exists; it is forgotten.
3052 With the @code{clear} command you can delete breakpoints according to
3053 where they are in your program. With the @code{delete} command you can
3054 delete individual breakpoints, watchpoints, or catchpoints by specifying
3055 their breakpoint numbers.
3057 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3058 automatically ignores breakpoints on the first instruction to be executed
3059 when you continue execution without changing the execution address.
3064 Delete any breakpoints at the next instruction to be executed in the
3065 selected stack frame (@pxref{Selection, ,Selecting a frame}). When
3066 the innermost frame is selected, this is a good way to delete a
3067 breakpoint where your program just stopped.
3069 @item clear @var{function}
3070 @itemx clear @var{filename}:@var{function}
3071 Delete any breakpoints set at entry to the named @var{function}.
3073 @item clear @var{linenum}
3074 @itemx clear @var{filename}:@var{linenum}
3075 Delete any breakpoints set at or within the code of the specified
3076 @var{linenum} of the specified @var{filename}.
3078 @cindex delete breakpoints
3080 @kindex d @r{(@code{delete})}
3081 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3082 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3083 ranges specified as arguments. If no argument is specified, delete all
3084 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3085 confirm off}). You can abbreviate this command as @code{d}.
3089 @subsection Disabling breakpoints
3091 @cindex enable/disable a breakpoint
3092 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3093 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3094 it had been deleted, but remembers the information on the breakpoint so
3095 that you can @dfn{enable} it again later.
3097 You disable and enable breakpoints, watchpoints, and catchpoints with
3098 the @code{enable} and @code{disable} commands, optionally specifying one
3099 or more breakpoint numbers as arguments. Use @code{info break} or
3100 @code{info watch} to print a list of breakpoints, watchpoints, and
3101 catchpoints if you do not know which numbers to use.
3103 A breakpoint, watchpoint, or catchpoint can have any of four different
3104 states of enablement:
3108 Enabled. The breakpoint stops your program. A breakpoint set
3109 with the @code{break} command starts out in this state.
3111 Disabled. The breakpoint has no effect on your program.
3113 Enabled once. The breakpoint stops your program, but then becomes
3116 Enabled for deletion. The breakpoint stops your program, but
3117 immediately after it does so it is deleted permanently. A breakpoint
3118 set with the @code{tbreak} command starts out in this state.
3121 You can use the following commands to enable or disable breakpoints,
3122 watchpoints, and catchpoints:
3126 @kindex dis @r{(@code{disable})}
3127 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3128 Disable the specified breakpoints---or all breakpoints, if none are
3129 listed. A disabled breakpoint has no effect but is not forgotten. All
3130 options such as ignore-counts, conditions and commands are remembered in
3131 case the breakpoint is enabled again later. You may abbreviate
3132 @code{disable} as @code{dis}.
3135 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3136 Enable the specified breakpoints (or all defined breakpoints). They
3137 become effective once again in stopping your program.
3139 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3140 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3141 of these breakpoints immediately after stopping your program.
3143 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3144 Enable the specified breakpoints to work once, then die. @value{GDBN}
3145 deletes any of these breakpoints as soon as your program stops there.
3146 Breakpoints set by the @code{tbreak} command start out in this state.
3149 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3150 @c confusing: tbreak is also initially enabled.
3151 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3152 ,Setting breakpoints}), breakpoints that you set are initially enabled;
3153 subsequently, they become disabled or enabled only when you use one of
3154 the commands above. (The command @code{until} can set and delete a
3155 breakpoint of its own, but it does not change the state of your other
3156 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3160 @subsection Break conditions
3161 @cindex conditional breakpoints
3162 @cindex breakpoint conditions
3164 @c FIXME what is scope of break condition expr? Context where wanted?
3165 @c in particular for a watchpoint?
3166 The simplest sort of breakpoint breaks every time your program reaches a
3167 specified place. You can also specify a @dfn{condition} for a
3168 breakpoint. A condition is just a Boolean expression in your
3169 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3170 a condition evaluates the expression each time your program reaches it,
3171 and your program stops only if the condition is @emph{true}.
3173 This is the converse of using assertions for program validation; in that
3174 situation, you want to stop when the assertion is violated---that is,
3175 when the condition is false. In C, if you want to test an assertion expressed
3176 by the condition @var{assert}, you should set the condition
3177 @samp{! @var{assert}} on the appropriate breakpoint.
3179 Conditions are also accepted for watchpoints; you may not need them,
3180 since a watchpoint is inspecting the value of an expression anyhow---but
3181 it might be simpler, say, to just set a watchpoint on a variable name,
3182 and specify a condition that tests whether the new value is an interesting
3185 Break conditions can have side effects, and may even call functions in
3186 your program. This can be useful, for example, to activate functions
3187 that log program progress, or to use your own print functions to
3188 format special data structures. The effects are completely predictable
3189 unless there is another enabled breakpoint at the same address. (In
3190 that case, @value{GDBN} might see the other breakpoint first and stop your
3191 program without checking the condition of this one.) Note that
3192 breakpoint commands are usually more convenient and flexible than break
3194 purpose of performing side effects when a breakpoint is reached
3195 (@pxref{Break Commands, ,Breakpoint command lists}).
3197 Break conditions can be specified when a breakpoint is set, by using
3198 @samp{if} in the arguments to the @code{break} command. @xref{Set
3199 Breaks, ,Setting breakpoints}. They can also be changed at any time
3200 with the @code{condition} command.
3202 You can also use the @code{if} keyword with the @code{watch} command.
3203 The @code{catch} command does not recognize the @code{if} keyword;
3204 @code{condition} is the only way to impose a further condition on a
3209 @item condition @var{bnum} @var{expression}
3210 Specify @var{expression} as the break condition for breakpoint,
3211 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3212 breakpoint @var{bnum} stops your program only if the value of
3213 @var{expression} is true (nonzero, in C). When you use
3214 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3215 syntactic correctness, and to determine whether symbols in it have
3216 referents in the context of your breakpoint. If @var{expression} uses
3217 symbols not referenced in the context of the breakpoint, @value{GDBN}
3218 prints an error message:
3221 No symbol "foo" in current context.
3226 not actually evaluate @var{expression} at the time the @code{condition}
3227 command (or a command that sets a breakpoint with a condition, like
3228 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3230 @item condition @var{bnum}
3231 Remove the condition from breakpoint number @var{bnum}. It becomes
3232 an ordinary unconditional breakpoint.
3235 @cindex ignore count (of breakpoint)
3236 A special case of a breakpoint condition is to stop only when the
3237 breakpoint has been reached a certain number of times. This is so
3238 useful that there is a special way to do it, using the @dfn{ignore
3239 count} of the breakpoint. Every breakpoint has an ignore count, which
3240 is an integer. Most of the time, the ignore count is zero, and
3241 therefore has no effect. But if your program reaches a breakpoint whose
3242 ignore count is positive, then instead of stopping, it just decrements
3243 the ignore count by one and continues. As a result, if the ignore count
3244 value is @var{n}, the breakpoint does not stop the next @var{n} times
3245 your program reaches it.
3249 @item ignore @var{bnum} @var{count}
3250 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3251 The next @var{count} times the breakpoint is reached, your program's
3252 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3255 To make the breakpoint stop the next time it is reached, specify
3258 When you use @code{continue} to resume execution of your program from a
3259 breakpoint, you can specify an ignore count directly as an argument to
3260 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3261 Stepping,,Continuing and stepping}.
3263 If a breakpoint has a positive ignore count and a condition, the
3264 condition is not checked. Once the ignore count reaches zero,
3265 @value{GDBN} resumes checking the condition.
3267 You could achieve the effect of the ignore count with a condition such
3268 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3269 is decremented each time. @xref{Convenience Vars, ,Convenience
3273 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3276 @node Break Commands
3277 @subsection Breakpoint command lists
3279 @cindex breakpoint commands
3280 You can give any breakpoint (or watchpoint or catchpoint) a series of
3281 commands to execute when your program stops due to that breakpoint. For
3282 example, you might want to print the values of certain expressions, or
3283 enable other breakpoints.
3288 @item commands @r{[}@var{bnum}@r{]}
3289 @itemx @dots{} @var{command-list} @dots{}
3291 Specify a list of commands for breakpoint number @var{bnum}. The commands
3292 themselves appear on the following lines. Type a line containing just
3293 @code{end} to terminate the commands.
3295 To remove all commands from a breakpoint, type @code{commands} and
3296 follow it immediately with @code{end}; that is, give no commands.
3298 With no @var{bnum} argument, @code{commands} refers to the last
3299 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3300 recently encountered).
3303 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3304 disabled within a @var{command-list}.
3306 You can use breakpoint commands to start your program up again. Simply
3307 use the @code{continue} command, or @code{step}, or any other command
3308 that resumes execution.
3310 Any other commands in the command list, after a command that resumes
3311 execution, are ignored. This is because any time you resume execution
3312 (even with a simple @code{next} or @code{step}), you may encounter
3313 another breakpoint---which could have its own command list, leading to
3314 ambiguities about which list to execute.
3317 If the first command you specify in a command list is @code{silent}, the
3318 usual message about stopping at a breakpoint is not printed. This may
3319 be desirable for breakpoints that are to print a specific message and
3320 then continue. If none of the remaining commands print anything, you
3321 see no sign that the breakpoint was reached. @code{silent} is
3322 meaningful only at the beginning of a breakpoint command list.
3324 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3325 print precisely controlled output, and are often useful in silent
3326 breakpoints. @xref{Output, ,Commands for controlled output}.
3328 For example, here is how you could use breakpoint commands to print the
3329 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3335 printf "x is %d\n",x
3340 One application for breakpoint commands is to compensate for one bug so
3341 you can test for another. Put a breakpoint just after the erroneous line
3342 of code, give it a condition to detect the case in which something
3343 erroneous has been done, and give it commands to assign correct values
3344 to any variables that need them. End with the @code{continue} command
3345 so that your program does not stop, and start with the @code{silent}
3346 command so that no output is produced. Here is an example:
3357 @node Breakpoint Menus
3358 @subsection Breakpoint menus
3360 @cindex symbol overloading
3362 Some programming languages (notably C@t{++} and Objective-C) permit a
3363 single function name
3364 to be defined several times, for application in different contexts.
3365 This is called @dfn{overloading}. When a function name is overloaded,
3366 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3367 a breakpoint. If you realize this is a problem, you can use
3368 something like @samp{break @var{function}(@var{types})} to specify which
3369 particular version of the function you want. Otherwise, @value{GDBN} offers
3370 you a menu of numbered choices for different possible breakpoints, and
3371 waits for your selection with the prompt @samp{>}. The first two
3372 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3373 sets a breakpoint at each definition of @var{function}, and typing
3374 @kbd{0} aborts the @code{break} command without setting any new
3377 For example, the following session excerpt shows an attempt to set a
3378 breakpoint at the overloaded symbol @code{String::after}.
3379 We choose three particular definitions of that function name:
3381 @c FIXME! This is likely to change to show arg type lists, at least
3384 (@value{GDBP}) b String::after
3387 [2] file:String.cc; line number:867
3388 [3] file:String.cc; line number:860
3389 [4] file:String.cc; line number:875
3390 [5] file:String.cc; line number:853
3391 [6] file:String.cc; line number:846
3392 [7] file:String.cc; line number:735
3394 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3395 Breakpoint 2 at 0xb344: file String.cc, line 875.
3396 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3397 Multiple breakpoints were set.
3398 Use the "delete" command to delete unwanted
3404 @c @ifclear BARETARGET
3405 @node Error in Breakpoints
3406 @subsection ``Cannot insert breakpoints''
3408 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3410 Under some operating systems, breakpoints cannot be used in a program if
3411 any other process is running that program. In this situation,
3412 attempting to run or continue a program with a breakpoint causes
3413 @value{GDBN} to print an error message:
3416 Cannot insert breakpoints.
3417 The same program may be running in another process.
3420 When this happens, you have three ways to proceed:
3424 Remove or disable the breakpoints, then continue.
3427 Suspend @value{GDBN}, and copy the file containing your program to a new
3428 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3429 that @value{GDBN} should run your program under that name.
3430 Then start your program again.
3433 Relink your program so that the text segment is nonsharable, using the
3434 linker option @samp{-N}. The operating system limitation may not apply
3435 to nonsharable executables.
3439 A similar message can be printed if you request too many active
3440 hardware-assisted breakpoints and watchpoints:
3442 @c FIXME: the precise wording of this message may change; the relevant
3443 @c source change is not committed yet (Sep 3, 1999).
3445 Stopped; cannot insert breakpoints.
3446 You may have requested too many hardware breakpoints and watchpoints.
3450 This message is printed when you attempt to resume the program, since
3451 only then @value{GDBN} knows exactly how many hardware breakpoints and
3452 watchpoints it needs to insert.
3454 When this message is printed, you need to disable or remove some of the
3455 hardware-assisted breakpoints and watchpoints, and then continue.
3457 @node Breakpoint related warnings
3458 @subsection ``Breakpoint address adjusted...''
3459 @cindex breakpoint address adjusted
3461 Some processor architectures place constraints on the addresses at
3462 which breakpoints may be placed. For architectures thus constrained,
3463 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3464 with the constraints dictated by the architecture.
3466 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3467 a VLIW architecture in which a number of RISC-like instructions may be
3468 bundled together for parallel execution. The FR-V architecture
3469 constrains the location of a breakpoint instruction within such a
3470 bundle to the instruction with the lowest address. @value{GDBN}
3471 honors this constraint by adjusting a breakpoint's address to the
3472 first in the bundle.
3474 It is not uncommon for optimized code to have bundles which contain
3475 instructions from different source statements, thus it may happen that
3476 a breakpoint's address will be adjusted from one source statement to
3477 another. Since this adjustment may significantly alter @value{GDBN}'s
3478 breakpoint related behavior from what the user expects, a warning is
3479 printed when the breakpoint is first set and also when the breakpoint
3482 A warning like the one below is printed when setting a breakpoint
3483 that's been subject to address adjustment:
3486 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3489 Such warnings are printed both for user settable and @value{GDBN}'s
3490 internal breakpoints. If you see one of these warnings, you should
3491 verify that a breakpoint set at the adjusted address will have the
3492 desired affect. If not, the breakpoint in question may be removed and
3493 other breakpoints may be set which will have the desired behavior.
3494 E.g., it may be sufficient to place the breakpoint at a later
3495 instruction. A conditional breakpoint may also be useful in some
3496 cases to prevent the breakpoint from triggering too often.
3498 @value{GDBN} will also issue a warning when stopping at one of these
3499 adjusted breakpoints:
3502 warning: Breakpoint 1 address previously adjusted from 0x00010414
3506 When this warning is encountered, it may be too late to take remedial
3507 action except in cases where the breakpoint is hit earlier or more
3508 frequently than expected.
3510 @node Continuing and Stepping
3511 @section Continuing and stepping
3515 @cindex resuming execution
3516 @dfn{Continuing} means resuming program execution until your program
3517 completes normally. In contrast, @dfn{stepping} means executing just
3518 one more ``step'' of your program, where ``step'' may mean either one
3519 line of source code, or one machine instruction (depending on what
3520 particular command you use). Either when continuing or when stepping,
3521 your program may stop even sooner, due to a breakpoint or a signal. (If
3522 it stops due to a signal, you may want to use @code{handle}, or use
3523 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3527 @kindex c @r{(@code{continue})}
3528 @kindex fg @r{(resume foreground execution)}
3529 @item continue @r{[}@var{ignore-count}@r{]}
3530 @itemx c @r{[}@var{ignore-count}@r{]}
3531 @itemx fg @r{[}@var{ignore-count}@r{]}
3532 Resume program execution, at the address where your program last stopped;
3533 any breakpoints set at that address are bypassed. The optional argument
3534 @var{ignore-count} allows you to specify a further number of times to
3535 ignore a breakpoint at this location; its effect is like that of
3536 @code{ignore} (@pxref{Conditions, ,Break conditions}).
3538 The argument @var{ignore-count} is meaningful only when your program
3539 stopped due to a breakpoint. At other times, the argument to
3540 @code{continue} is ignored.
3542 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3543 debugged program is deemed to be the foreground program) are provided
3544 purely for convenience, and have exactly the same behavior as
3548 To resume execution at a different place, you can use @code{return}
3549 (@pxref{Returning, ,Returning from a function}) to go back to the
3550 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3551 different address}) to go to an arbitrary location in your program.
3553 A typical technique for using stepping is to set a breakpoint
3554 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the
3555 beginning of the function or the section of your program where a problem
3556 is believed to lie, run your program until it stops at that breakpoint,
3557 and then step through the suspect area, examining the variables that are
3558 interesting, until you see the problem happen.
3562 @kindex s @r{(@code{step})}
3564 Continue running your program until control reaches a different source
3565 line, then stop it and return control to @value{GDBN}. This command is
3566 abbreviated @code{s}.
3569 @c "without debugging information" is imprecise; actually "without line
3570 @c numbers in the debugging information". (gcc -g1 has debugging info but
3571 @c not line numbers). But it seems complex to try to make that
3572 @c distinction here.
3573 @emph{Warning:} If you use the @code{step} command while control is
3574 within a function that was compiled without debugging information,
3575 execution proceeds until control reaches a function that does have
3576 debugging information. Likewise, it will not step into a function which
3577 is compiled without debugging information. To step through functions
3578 without debugging information, use the @code{stepi} command, described
3582 The @code{step} command only stops at the first instruction of a source
3583 line. This prevents the multiple stops that could otherwise occur in
3584 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3585 to stop if a function that has debugging information is called within
3586 the line. In other words, @code{step} @emph{steps inside} any functions
3587 called within the line.
3589 Also, the @code{step} command only enters a function if there is line
3590 number information for the function. Otherwise it acts like the
3591 @code{next} command. This avoids problems when using @code{cc -gl}
3592 on MIPS machines. Previously, @code{step} entered subroutines if there
3593 was any debugging information about the routine.
3595 @item step @var{count}
3596 Continue running as in @code{step}, but do so @var{count} times. If a
3597 breakpoint is reached, or a signal not related to stepping occurs before
3598 @var{count} steps, stepping stops right away.
3601 @kindex n @r{(@code{next})}
3602 @item next @r{[}@var{count}@r{]}
3603 Continue to the next source line in the current (innermost) stack frame.
3604 This is similar to @code{step}, but function calls that appear within
3605 the line of code are executed without stopping. Execution stops when
3606 control reaches a different line of code at the original stack level
3607 that was executing when you gave the @code{next} command. This command
3608 is abbreviated @code{n}.
3610 An argument @var{count} is a repeat count, as for @code{step}.
3613 @c FIX ME!! Do we delete this, or is there a way it fits in with
3614 @c the following paragraph? --- Vctoria
3616 @c @code{next} within a function that lacks debugging information acts like
3617 @c @code{step}, but any function calls appearing within the code of the
3618 @c function are executed without stopping.
3620 The @code{next} command only stops at the first instruction of a
3621 source line. This prevents multiple stops that could otherwise occur in
3622 @code{switch} statements, @code{for} loops, etc.
3624 @kindex set step-mode
3626 @cindex functions without line info, and stepping
3627 @cindex stepping into functions with no line info
3628 @itemx set step-mode on
3629 The @code{set step-mode on} command causes the @code{step} command to
3630 stop at the first instruction of a function which contains no debug line
3631 information rather than stepping over it.
3633 This is useful in cases where you may be interested in inspecting the
3634 machine instructions of a function which has no symbolic info and do not
3635 want @value{GDBN} to automatically skip over this function.
3637 @item set step-mode off
3638 Causes the @code{step} command to step over any functions which contains no
3639 debug information. This is the default.
3641 @item show step-mode
3642 Show whether @value{GDBN} will stop in or step over functions without
3643 source line debug information.
3647 Continue running until just after function in the selected stack frame
3648 returns. Print the returned value (if any).
3650 Contrast this with the @code{return} command (@pxref{Returning,
3651 ,Returning from a function}).
3654 @kindex u @r{(@code{until})}
3655 @cindex run until specified location
3658 Continue running until a source line past the current line, in the
3659 current stack frame, is reached. This command is used to avoid single
3660 stepping through a loop more than once. It is like the @code{next}
3661 command, except that when @code{until} encounters a jump, it
3662 automatically continues execution until the program counter is greater
3663 than the address of the jump.
3665 This means that when you reach the end of a loop after single stepping
3666 though it, @code{until} makes your program continue execution until it
3667 exits the loop. In contrast, a @code{next} command at the end of a loop
3668 simply steps back to the beginning of the loop, which forces you to step
3669 through the next iteration.
3671 @code{until} always stops your program if it attempts to exit the current
3674 @code{until} may produce somewhat counterintuitive results if the order
3675 of machine code does not match the order of the source lines. For
3676 example, in the following excerpt from a debugging session, the @code{f}
3677 (@code{frame}) command shows that execution is stopped at line
3678 @code{206}; yet when we use @code{until}, we get to line @code{195}:
3682 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
3684 (@value{GDBP}) until
3685 195 for ( ; argc > 0; NEXTARG) @{
3688 This happened because, for execution efficiency, the compiler had
3689 generated code for the loop closure test at the end, rather than the
3690 start, of the loop---even though the test in a C @code{for}-loop is
3691 written before the body of the loop. The @code{until} command appeared
3692 to step back to the beginning of the loop when it advanced to this
3693 expression; however, it has not really gone to an earlier
3694 statement---not in terms of the actual machine code.
3696 @code{until} with no argument works by means of single
3697 instruction stepping, and hence is slower than @code{until} with an
3700 @item until @var{location}
3701 @itemx u @var{location}
3702 Continue running your program until either the specified location is
3703 reached, or the current stack frame returns. @var{location} is any of
3704 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
3705 ,Setting breakpoints}). This form of the command uses breakpoints, and
3706 hence is quicker than @code{until} without an argument. The specified
3707 location is actually reached only if it is in the current frame. This
3708 implies that @code{until} can be used to skip over recursive function
3709 invocations. For instance in the code below, if the current location is
3710 line @code{96}, issuing @code{until 99} will execute the program up to
3711 line @code{99} in the same invocation of factorial, i.e. after the inner
3712 invocations have returned.
3715 94 int factorial (int value)
3717 96 if (value > 1) @{
3718 97 value *= factorial (value - 1);
3725 @kindex advance @var{location}
3726 @itemx advance @var{location}
3727 Continue running the program up to the given @var{location}. An argument is
3728 required, which should be of the same form as arguments for the @code{break}
3729 command. Execution will also stop upon exit from the current stack
3730 frame. This command is similar to @code{until}, but @code{advance} will
3731 not skip over recursive function calls, and the target location doesn't
3732 have to be in the same frame as the current one.
3736 @kindex si @r{(@code{stepi})}
3738 @itemx stepi @var{arg}
3740 Execute one machine instruction, then stop and return to the debugger.
3742 It is often useful to do @samp{display/i $pc} when stepping by machine
3743 instructions. This makes @value{GDBN} automatically display the next
3744 instruction to be executed, each time your program stops. @xref{Auto
3745 Display,, Automatic display}.
3747 An argument is a repeat count, as in @code{step}.
3751 @kindex ni @r{(@code{nexti})}
3753 @itemx nexti @var{arg}
3755 Execute one machine instruction, but if it is a function call,
3756 proceed until the function returns.
3758 An argument is a repeat count, as in @code{next}.
3765 A signal is an asynchronous event that can happen in a program. The
3766 operating system defines the possible kinds of signals, and gives each
3767 kind a name and a number. For example, in Unix @code{SIGINT} is the
3768 signal a program gets when you type an interrupt character (often @kbd{C-c});
3769 @code{SIGSEGV} is the signal a program gets from referencing a place in
3770 memory far away from all the areas in use; @code{SIGALRM} occurs when
3771 the alarm clock timer goes off (which happens only if your program has
3772 requested an alarm).
3774 @cindex fatal signals
3775 Some signals, including @code{SIGALRM}, are a normal part of the
3776 functioning of your program. Others, such as @code{SIGSEGV}, indicate
3777 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
3778 program has not specified in advance some other way to handle the signal.
3779 @code{SIGINT} does not indicate an error in your program, but it is normally
3780 fatal so it can carry out the purpose of the interrupt: to kill the program.
3782 @value{GDBN} has the ability to detect any occurrence of a signal in your
3783 program. You can tell @value{GDBN} in advance what to do for each kind of
3786 @cindex handling signals
3787 Normally, @value{GDBN} is set up to let the non-erroneous signals like
3788 @code{SIGALRM} be silently passed to your program
3789 (so as not to interfere with their role in the program's functioning)
3790 but to stop your program immediately whenever an error signal happens.
3791 You can change these settings with the @code{handle} command.
3794 @kindex info signals
3798 Print a table of all the kinds of signals and how @value{GDBN} has been told to
3799 handle each one. You can use this to see the signal numbers of all
3800 the defined types of signals.
3802 @code{info handle} is an alias for @code{info signals}.
3805 @item handle @var{signal} @var{keywords}@dots{}
3806 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
3807 can be the number of a signal or its name (with or without the
3808 @samp{SIG} at the beginning); a list of signal numbers of the form
3809 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
3810 known signals. The @var{keywords} say what change to make.
3814 The keywords allowed by the @code{handle} command can be abbreviated.
3815 Their full names are:
3819 @value{GDBN} should not stop your program when this signal happens. It may
3820 still print a message telling you that the signal has come in.
3823 @value{GDBN} should stop your program when this signal happens. This implies
3824 the @code{print} keyword as well.
3827 @value{GDBN} should print a message when this signal happens.
3830 @value{GDBN} should not mention the occurrence of the signal at all. This
3831 implies the @code{nostop} keyword as well.
3835 @value{GDBN} should allow your program to see this signal; your program
3836 can handle the signal, or else it may terminate if the signal is fatal
3837 and not handled. @code{pass} and @code{noignore} are synonyms.
3841 @value{GDBN} should not allow your program to see this signal.
3842 @code{nopass} and @code{ignore} are synonyms.
3846 When a signal stops your program, the signal is not visible to the
3848 continue. Your program sees the signal then, if @code{pass} is in
3849 effect for the signal in question @emph{at that time}. In other words,
3850 after @value{GDBN} reports a signal, you can use the @code{handle}
3851 command with @code{pass} or @code{nopass} to control whether your
3852 program sees that signal when you continue.
3854 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
3855 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
3856 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
3859 You can also use the @code{signal} command to prevent your program from
3860 seeing a signal, or cause it to see a signal it normally would not see,
3861 or to give it any signal at any time. For example, if your program stopped
3862 due to some sort of memory reference error, you might store correct
3863 values into the erroneous variables and continue, hoping to see more
3864 execution; but your program would probably terminate immediately as
3865 a result of the fatal signal once it saw the signal. To prevent this,
3866 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
3870 @section Stopping and starting multi-thread programs
3872 When your program has multiple threads (@pxref{Threads,, Debugging
3873 programs with multiple threads}), you can choose whether to set
3874 breakpoints on all threads, or on a particular thread.
3877 @cindex breakpoints and threads
3878 @cindex thread breakpoints
3879 @kindex break @dots{} thread @var{threadno}
3880 @item break @var{linespec} thread @var{threadno}
3881 @itemx break @var{linespec} thread @var{threadno} if @dots{}
3882 @var{linespec} specifies source lines; there are several ways of
3883 writing them, but the effect is always to specify some source line.
3885 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
3886 to specify that you only want @value{GDBN} to stop the program when a
3887 particular thread reaches this breakpoint. @var{threadno} is one of the
3888 numeric thread identifiers assigned by @value{GDBN}, shown in the first
3889 column of the @samp{info threads} display.
3891 If you do not specify @samp{thread @var{threadno}} when you set a
3892 breakpoint, the breakpoint applies to @emph{all} threads of your
3895 You can use the @code{thread} qualifier on conditional breakpoints as
3896 well; in this case, place @samp{thread @var{threadno}} before the
3897 breakpoint condition, like this:
3900 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
3905 @cindex stopped threads
3906 @cindex threads, stopped
3907 Whenever your program stops under @value{GDBN} for any reason,
3908 @emph{all} threads of execution stop, not just the current thread. This
3909 allows you to examine the overall state of the program, including
3910 switching between threads, without worrying that things may change
3913 @cindex thread breakpoints and system calls
3914 @cindex system calls and thread breakpoints
3915 @cindex premature return from system calls
3916 There is an unfortunate side effect. If one thread stops for a
3917 breakpoint, or for some other reason, and another thread is blocked in a
3918 system call, then the system call may return prematurely. This is a
3919 consequence of the interaction between multiple threads and the signals
3920 that @value{GDBN} uses to implement breakpoints and other events that
3923 To handle this problem, your program should check the return value of
3924 each system call and react appropriately. This is good programming
3927 For example, do not write code like this:
3933 The call to @code{sleep} will return early if a different thread stops
3934 at a breakpoint or for some other reason.
3936 Instead, write this:
3941 unslept = sleep (unslept);
3944 A system call is allowed to return early, so the system is still
3945 conforming to its specification. But @value{GDBN} does cause your
3946 multi-threaded program to behave differently than it would without
3949 Also, @value{GDBN} uses internal breakpoints in the thread library to
3950 monitor certain events such as thread creation and thread destruction.
3951 When such an event happens, a system call in another thread may return
3952 prematurely, even though your program does not appear to stop.
3954 @cindex continuing threads
3955 @cindex threads, continuing
3956 Conversely, whenever you restart the program, @emph{all} threads start
3957 executing. @emph{This is true even when single-stepping} with commands
3958 like @code{step} or @code{next}.
3960 In particular, @value{GDBN} cannot single-step all threads in lockstep.
3961 Since thread scheduling is up to your debugging target's operating
3962 system (not controlled by @value{GDBN}), other threads may
3963 execute more than one statement while the current thread completes a
3964 single step. Moreover, in general other threads stop in the middle of a
3965 statement, rather than at a clean statement boundary, when the program
3968 You might even find your program stopped in another thread after
3969 continuing or even single-stepping. This happens whenever some other
3970 thread runs into a breakpoint, a signal, or an exception before the
3971 first thread completes whatever you requested.
3973 On some OSes, you can lock the OS scheduler and thus allow only a single
3977 @item set scheduler-locking @var{mode}
3978 @cindex scheduler locking mode
3979 @cindex lock scheduler
3980 Set the scheduler locking mode. If it is @code{off}, then there is no
3981 locking and any thread may run at any time. If @code{on}, then only the
3982 current thread may run when the inferior is resumed. The @code{step}
3983 mode optimizes for single-stepping. It stops other threads from
3984 ``seizing the prompt'' by preempting the current thread while you are
3985 stepping. Other threads will only rarely (or never) get a chance to run
3986 when you step. They are more likely to run when you @samp{next} over a
3987 function call, and they are completely free to run when you use commands
3988 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
3989 thread hits a breakpoint during its timeslice, they will never steal the
3990 @value{GDBN} prompt away from the thread that you are debugging.
3992 @item show scheduler-locking
3993 Display the current scheduler locking mode.
3998 @chapter Examining the Stack
4000 When your program has stopped, the first thing you need to know is where it
4001 stopped and how it got there.
4004 Each time your program performs a function call, information about the call
4006 That information includes the location of the call in your program,
4007 the arguments of the call,
4008 and the local variables of the function being called.
4009 The information is saved in a block of data called a @dfn{stack frame}.
4010 The stack frames are allocated in a region of memory called the @dfn{call
4013 When your program stops, the @value{GDBN} commands for examining the
4014 stack allow you to see all of this information.
4016 @cindex selected frame
4017 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4018 @value{GDBN} commands refer implicitly to the selected frame. In
4019 particular, whenever you ask @value{GDBN} for the value of a variable in
4020 your program, the value is found in the selected frame. There are
4021 special @value{GDBN} commands to select whichever frame you are
4022 interested in. @xref{Selection, ,Selecting a frame}.
4024 When your program stops, @value{GDBN} automatically selects the
4025 currently executing frame and describes it briefly, similar to the
4026 @code{frame} command (@pxref{Frame Info, ,Information about a frame}).
4029 * Frames:: Stack frames
4030 * Backtrace:: Backtraces
4031 * Selection:: Selecting a frame
4032 * Frame Info:: Information on a frame
4037 @section Stack frames
4039 @cindex frame, definition
4041 The call stack is divided up into contiguous pieces called @dfn{stack
4042 frames}, or @dfn{frames} for short; each frame is the data associated
4043 with one call to one function. The frame contains the arguments given
4044 to the function, the function's local variables, and the address at
4045 which the function is executing.
4047 @cindex initial frame
4048 @cindex outermost frame
4049 @cindex innermost frame
4050 When your program is started, the stack has only one frame, that of the
4051 function @code{main}. This is called the @dfn{initial} frame or the
4052 @dfn{outermost} frame. Each time a function is called, a new frame is
4053 made. Each time a function returns, the frame for that function invocation
4054 is eliminated. If a function is recursive, there can be many frames for
4055 the same function. The frame for the function in which execution is
4056 actually occurring is called the @dfn{innermost} frame. This is the most
4057 recently created of all the stack frames that still exist.
4059 @cindex frame pointer
4060 Inside your program, stack frames are identified by their addresses. A
4061 stack frame consists of many bytes, each of which has its own address; each
4062 kind of computer has a convention for choosing one byte whose
4063 address serves as the address of the frame. Usually this address is kept
4064 in a register called the @dfn{frame pointer register} while execution is
4065 going on in that frame.
4067 @cindex frame number
4068 @value{GDBN} assigns numbers to all existing stack frames, starting with
4069 zero for the innermost frame, one for the frame that called it,
4070 and so on upward. These numbers do not really exist in your program;
4071 they are assigned by @value{GDBN} to give you a way of designating stack
4072 frames in @value{GDBN} commands.
4074 @c The -fomit-frame-pointer below perennially causes hbox overflow
4075 @c underflow problems.
4076 @cindex frameless execution
4077 Some compilers provide a way to compile functions so that they operate
4078 without stack frames. (For example, the @value{GCC} option
4080 @samp{-fomit-frame-pointer}
4082 generates functions without a frame.)
4083 This is occasionally done with heavily used library functions to save
4084 the frame setup time. @value{GDBN} has limited facilities for dealing
4085 with these function invocations. If the innermost function invocation
4086 has no stack frame, @value{GDBN} nevertheless regards it as though
4087 it had a separate frame, which is numbered zero as usual, allowing
4088 correct tracing of the function call chain. However, @value{GDBN} has
4089 no provision for frameless functions elsewhere in the stack.
4092 @kindex frame@r{, command}
4093 @cindex current stack frame
4094 @item frame @var{args}
4095 The @code{frame} command allows you to move from one stack frame to another,
4096 and to print the stack frame you select. @var{args} may be either the
4097 address of the frame or the stack frame number. Without an argument,
4098 @code{frame} prints the current stack frame.
4100 @kindex select-frame
4101 @cindex selecting frame silently
4103 The @code{select-frame} command allows you to move from one stack frame
4104 to another without printing the frame. This is the silent version of
4112 @cindex call stack traces
4113 A backtrace is a summary of how your program got where it is. It shows one
4114 line per frame, for many frames, starting with the currently executing
4115 frame (frame zero), followed by its caller (frame one), and on up the
4120 @kindex bt @r{(@code{backtrace})}
4123 Print a backtrace of the entire stack: one line per frame for all
4124 frames in the stack.
4126 You can stop the backtrace at any time by typing the system interrupt
4127 character, normally @kbd{C-c}.
4129 @item backtrace @var{n}
4131 Similar, but print only the innermost @var{n} frames.
4133 @item backtrace -@var{n}
4135 Similar, but print only the outermost @var{n} frames.
4137 @item backtrace full
4138 Print the values of the local variables also.
4144 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4145 are additional aliases for @code{backtrace}.
4147 Each line in the backtrace shows the frame number and the function name.
4148 The program counter value is also shown---unless you use @code{set
4149 print address off}. The backtrace also shows the source file name and
4150 line number, as well as the arguments to the function. The program
4151 counter value is omitted if it is at the beginning of the code for that
4154 Here is an example of a backtrace. It was made with the command
4155 @samp{bt 3}, so it shows the innermost three frames.
4159 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4161 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4162 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4164 (More stack frames follow...)
4169 The display for frame zero does not begin with a program counter
4170 value, indicating that your program has stopped at the beginning of the
4171 code for line @code{993} of @code{builtin.c}.
4173 @cindex backtrace beyond @code{main} function
4174 @cindex program entry point
4175 @cindex startup code, and backtrace
4176 Most programs have a standard user entry point---a place where system
4177 libraries and startup code transition into user code. For C this is
4178 @code{main}. When @value{GDBN} finds the entry function in a backtrace
4179 it will terminate the backtrace, to avoid tracing into highly
4180 system-specific (and generally uninteresting) code.
4182 If you need to examine the startup code, or limit the number of levels
4183 in a backtrace, you can change this behavior:
4186 @item set backtrace past-main
4187 @itemx set backtrace past-main on
4188 @kindex set backtrace
4189 Backtraces will continue past the user entry point.
4191 @item set backtrace past-main off
4192 Backtraces will stop when they encounter the user entry point. This is the
4195 @item show backtrace past-main
4196 @kindex show backtrace
4197 Display the current user entry point backtrace policy.
4199 @item set backtrace past-entry
4200 @itemx set backtrace past-entry on
4201 Backtraces will continue past the internal entry point of an application.
4202 This entry point is encoded by the linker when the application is built,
4203 and is likely before the user entry point @code{main} (or equivalent) is called.
4205 @item set backtrace past-entry off
4206 Backtraces will stop when they encouter the internal entry point of an
4207 application. This is the default.
4209 @item show backtrace past-entry
4210 Display the current internal entry point backtrace policy.
4212 @item set backtrace limit @var{n}
4213 @itemx set backtrace limit 0
4214 @cindex backtrace limit
4215 Limit the backtrace to @var{n} levels. A value of zero means
4218 @item show backtrace limit
4219 Display the current limit on backtrace levels.
4223 @section Selecting a frame
4225 Most commands for examining the stack and other data in your program work on
4226 whichever stack frame is selected at the moment. Here are the commands for
4227 selecting a stack frame; all of them finish by printing a brief description
4228 of the stack frame just selected.
4231 @kindex frame@r{, selecting}
4232 @kindex f @r{(@code{frame})}
4235 Select frame number @var{n}. Recall that frame zero is the innermost
4236 (currently executing) frame, frame one is the frame that called the
4237 innermost one, and so on. The highest-numbered frame is the one for
4240 @item frame @var{addr}
4242 Select the frame at address @var{addr}. This is useful mainly if the
4243 chaining of stack frames has been damaged by a bug, making it
4244 impossible for @value{GDBN} to assign numbers properly to all frames. In
4245 addition, this can be useful when your program has multiple stacks and
4246 switches between them.
4248 On the SPARC architecture, @code{frame} needs two addresses to
4249 select an arbitrary frame: a frame pointer and a stack pointer.
4251 On the MIPS and Alpha architecture, it needs two addresses: a stack
4252 pointer and a program counter.
4254 On the 29k architecture, it needs three addresses: a register stack
4255 pointer, a program counter, and a memory stack pointer.
4256 @c note to future updaters: this is conditioned on a flag
4257 @c SETUP_ARBITRARY_FRAME in the tm-*.h files. The above is up to date
4258 @c as of 27 Jan 1994.
4262 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4263 advances toward the outermost frame, to higher frame numbers, to frames
4264 that have existed longer. @var{n} defaults to one.
4267 @kindex do @r{(@code{down})}
4269 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4270 advances toward the innermost frame, to lower frame numbers, to frames
4271 that were created more recently. @var{n} defaults to one. You may
4272 abbreviate @code{down} as @code{do}.
4275 All of these commands end by printing two lines of output describing the
4276 frame. The first line shows the frame number, the function name, the
4277 arguments, and the source file and line number of execution in that
4278 frame. The second line shows the text of that source line.
4286 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4288 10 read_input_file (argv[i]);
4292 After such a printout, the @code{list} command with no arguments
4293 prints ten lines centered on the point of execution in the frame.
4294 You can also edit the program at the point of execution with your favorite
4295 editing program by typing @code{edit}.
4296 @xref{List, ,Printing source lines},
4300 @kindex down-silently
4302 @item up-silently @var{n}
4303 @itemx down-silently @var{n}
4304 These two commands are variants of @code{up} and @code{down},
4305 respectively; they differ in that they do their work silently, without
4306 causing display of the new frame. They are intended primarily for use
4307 in @value{GDBN} command scripts, where the output might be unnecessary and
4312 @section Information about a frame
4314 There are several other commands to print information about the selected
4320 When used without any argument, this command does not change which
4321 frame is selected, but prints a brief description of the currently
4322 selected stack frame. It can be abbreviated @code{f}. With an
4323 argument, this command is used to select a stack frame.
4324 @xref{Selection, ,Selecting a frame}.
4327 @kindex info f @r{(@code{info frame})}
4330 This command prints a verbose description of the selected stack frame,
4335 the address of the frame
4337 the address of the next frame down (called by this frame)
4339 the address of the next frame up (caller of this frame)
4341 the language in which the source code corresponding to this frame is written
4343 the address of the frame's arguments
4345 the address of the frame's local variables
4347 the program counter saved in it (the address of execution in the caller frame)
4349 which registers were saved in the frame
4352 @noindent The verbose description is useful when
4353 something has gone wrong that has made the stack format fail to fit
4354 the usual conventions.
4356 @item info frame @var{addr}
4357 @itemx info f @var{addr}
4358 Print a verbose description of the frame at address @var{addr}, without
4359 selecting that frame. The selected frame remains unchanged by this
4360 command. This requires the same kind of address (more than one for some
4361 architectures) that you specify in the @code{frame} command.
4362 @xref{Selection, ,Selecting a frame}.
4366 Print the arguments of the selected frame, each on a separate line.
4370 Print the local variables of the selected frame, each on a separate
4371 line. These are all variables (declared either static or automatic)
4372 accessible at the point of execution of the selected frame.
4375 @cindex catch exceptions, list active handlers
4376 @cindex exception handlers, how to list
4378 Print a list of all the exception handlers that are active in the
4379 current stack frame at the current point of execution. To see other
4380 exception handlers, visit the associated frame (using the @code{up},
4381 @code{down}, or @code{frame} commands); then type @code{info catch}.
4382 @xref{Set Catchpoints, , Setting catchpoints}.
4388 @chapter Examining Source Files
4390 @value{GDBN} can print parts of your program's source, since the debugging
4391 information recorded in the program tells @value{GDBN} what source files were
4392 used to build it. When your program stops, @value{GDBN} spontaneously prints
4393 the line where it stopped. Likewise, when you select a stack frame
4394 (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
4395 execution in that frame has stopped. You can print other portions of
4396 source files by explicit command.
4398 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4399 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4400 @value{GDBN} under @sc{gnu} Emacs}.
4403 * List:: Printing source lines
4404 * Edit:: Editing source files
4405 * Search:: Searching source files
4406 * Source Path:: Specifying source directories
4407 * Machine Code:: Source and machine code
4411 @section Printing source lines
4414 @kindex l @r{(@code{list})}
4415 To print lines from a source file, use the @code{list} command
4416 (abbreviated @code{l}). By default, ten lines are printed.
4417 There are several ways to specify what part of the file you want to print.
4419 Here are the forms of the @code{list} command most commonly used:
4422 @item list @var{linenum}
4423 Print lines centered around line number @var{linenum} in the
4424 current source file.
4426 @item list @var{function}
4427 Print lines centered around the beginning of function
4431 Print more lines. If the last lines printed were printed with a
4432 @code{list} command, this prints lines following the last lines
4433 printed; however, if the last line printed was a solitary line printed
4434 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4435 Stack}), this prints lines centered around that line.
4438 Print lines just before the lines last printed.
4441 @cindex @code{list}, how many lines to display
4442 By default, @value{GDBN} prints ten source lines with any of these forms of
4443 the @code{list} command. You can change this using @code{set listsize}:
4446 @kindex set listsize
4447 @item set listsize @var{count}
4448 Make the @code{list} command display @var{count} source lines (unless
4449 the @code{list} argument explicitly specifies some other number).
4451 @kindex show listsize
4453 Display the number of lines that @code{list} prints.
4456 Repeating a @code{list} command with @key{RET} discards the argument,
4457 so it is equivalent to typing just @code{list}. This is more useful
4458 than listing the same lines again. An exception is made for an
4459 argument of @samp{-}; that argument is preserved in repetition so that
4460 each repetition moves up in the source file.
4463 In general, the @code{list} command expects you to supply zero, one or two
4464 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4465 of writing them, but the effect is always to specify some source line.
4466 Here is a complete description of the possible arguments for @code{list}:
4469 @item list @var{linespec}
4470 Print lines centered around the line specified by @var{linespec}.
4472 @item list @var{first},@var{last}
4473 Print lines from @var{first} to @var{last}. Both arguments are
4476 @item list ,@var{last}
4477 Print lines ending with @var{last}.
4479 @item list @var{first},
4480 Print lines starting with @var{first}.
4483 Print lines just after the lines last printed.
4486 Print lines just before the lines last printed.
4489 As described in the preceding table.
4492 Here are the ways of specifying a single source line---all the
4497 Specifies line @var{number} of the current source file.
4498 When a @code{list} command has two linespecs, this refers to
4499 the same source file as the first linespec.
4502 Specifies the line @var{offset} lines after the last line printed.
4503 When used as the second linespec in a @code{list} command that has
4504 two, this specifies the line @var{offset} lines down from the
4508 Specifies the line @var{offset} lines before the last line printed.
4510 @item @var{filename}:@var{number}
4511 Specifies line @var{number} in the source file @var{filename}.
4513 @item @var{function}
4514 Specifies the line that begins the body of the function @var{function}.
4515 For example: in C, this is the line with the open brace.
4517 @item @var{filename}:@var{function}
4518 Specifies the line of the open-brace that begins the body of the
4519 function @var{function} in the file @var{filename}. You only need the
4520 file name with a function name to avoid ambiguity when there are
4521 identically named functions in different source files.
4523 @item *@var{address}
4524 Specifies the line containing the program address @var{address}.
4525 @var{address} may be any expression.
4529 @section Editing source files
4530 @cindex editing source files
4533 @kindex e @r{(@code{edit})}
4534 To edit the lines in a source file, use the @code{edit} command.
4535 The editing program of your choice
4536 is invoked with the current line set to
4537 the active line in the program.
4538 Alternatively, there are several ways to specify what part of the file you
4539 want to print if you want to see other parts of the program.
4541 Here are the forms of the @code{edit} command most commonly used:
4545 Edit the current source file at the active line number in the program.
4547 @item edit @var{number}
4548 Edit the current source file with @var{number} as the active line number.
4550 @item edit @var{function}
4551 Edit the file containing @var{function} at the beginning of its definition.
4553 @item edit @var{filename}:@var{number}
4554 Specifies line @var{number} in the source file @var{filename}.
4556 @item edit @var{filename}:@var{function}
4557 Specifies the line that begins the body of the
4558 function @var{function} in the file @var{filename}. You only need the
4559 file name with a function name to avoid ambiguity when there are
4560 identically named functions in different source files.
4562 @item edit *@var{address}
4563 Specifies the line containing the program address @var{address}.
4564 @var{address} may be any expression.
4567 @subsection Choosing your editor
4568 You can customize @value{GDBN} to use any editor you want
4570 The only restriction is that your editor (say @code{ex}), recognizes the
4571 following command-line syntax:
4573 ex +@var{number} file
4575 The optional numeric value +@var{number} specifies the number of the line in
4576 the file where to start editing.}.
4577 By default, it is @file{@value{EDITOR}}, but you can change this
4578 by setting the environment variable @code{EDITOR} before using
4579 @value{GDBN}. For example, to configure @value{GDBN} to use the
4580 @code{vi} editor, you could use these commands with the @code{sh} shell:
4586 or in the @code{csh} shell,
4588 setenv EDITOR /usr/bin/vi
4593 @section Searching source files
4594 @cindex searching source files
4596 There are two commands for searching through the current source file for a
4601 @kindex forward-search
4602 @item forward-search @var{regexp}
4603 @itemx search @var{regexp}
4604 The command @samp{forward-search @var{regexp}} checks each line,
4605 starting with the one following the last line listed, for a match for
4606 @var{regexp}. It lists the line that is found. You can use the
4607 synonym @samp{search @var{regexp}} or abbreviate the command name as
4610 @kindex reverse-search
4611 @item reverse-search @var{regexp}
4612 The command @samp{reverse-search @var{regexp}} checks each line, starting
4613 with the one before the last line listed and going backward, for a match
4614 for @var{regexp}. It lists the line that is found. You can abbreviate
4615 this command as @code{rev}.
4619 @section Specifying source directories
4622 @cindex directories for source files
4623 Executable programs sometimes do not record the directories of the source
4624 files from which they were compiled, just the names. Even when they do,
4625 the directories could be moved between the compilation and your debugging
4626 session. @value{GDBN} has a list of directories to search for source files;
4627 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
4628 it tries all the directories in the list, in the order they are present
4629 in the list, until it finds a file with the desired name.
4631 For example, suppose an executable references the file
4632 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
4633 @file{/mnt/cross}. The file is first looked up literally; if this
4634 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
4635 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
4636 message is printed. @value{GDBN} does not look up the parts of the
4637 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
4638 Likewise, the subdirectories of the source path are not searched: if
4639 the source path is @file{/mnt/cross}, and the binary refers to
4640 @file{foo.c}, @value{GDBN} would not find it under
4641 @file{/mnt/cross/usr/src/foo-1.0/lib}.
4643 Plain file names, relative file names with leading directories, file
4644 names containing dots, etc.@: are all treated as described above; for
4645 instance, if the source path is @file{/mnt/cross}, and the source file
4646 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
4647 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
4648 that---@file{/mnt/cross/foo.c}.
4650 Note that the executable search path is @emph{not} used to locate the
4651 source files. Neither is the current working directory, unless it
4652 happens to be in the source path.
4654 Whenever you reset or rearrange the source path, @value{GDBN} clears out
4655 any information it has cached about where source files are found and where
4656 each line is in the file.
4660 When you start @value{GDBN}, its source path includes only @samp{cdir}
4661 and @samp{cwd}, in that order.
4662 To add other directories, use the @code{directory} command.
4665 @item directory @var{dirname} @dots{}
4666 @item dir @var{dirname} @dots{}
4667 Add directory @var{dirname} to the front of the source path. Several
4668 directory names may be given to this command, separated by @samp{:}
4669 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
4670 part of absolute file names) or
4671 whitespace. You may specify a directory that is already in the source
4672 path; this moves it forward, so @value{GDBN} searches it sooner.
4676 @vindex $cdir@r{, convenience variable}
4677 @vindex $cwdr@r{, convenience variable}
4678 @cindex compilation directory
4679 @cindex current directory
4680 @cindex working directory
4681 @cindex directory, current
4682 @cindex directory, compilation
4683 You can use the string @samp{$cdir} to refer to the compilation
4684 directory (if one is recorded), and @samp{$cwd} to refer to the current
4685 working directory. @samp{$cwd} is not the same as @samp{.}---the former
4686 tracks the current working directory as it changes during your @value{GDBN}
4687 session, while the latter is immediately expanded to the current
4688 directory at the time you add an entry to the source path.
4691 Reset the source path to empty again. This requires confirmation.
4693 @c RET-repeat for @code{directory} is explicitly disabled, but since
4694 @c repeating it would be a no-op we do not say that. (thanks to RMS)
4696 @item show directories
4697 @kindex show directories
4698 Print the source path: show which directories it contains.
4701 If your source path is cluttered with directories that are no longer of
4702 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
4703 versions of source. You can correct the situation as follows:
4707 Use @code{directory} with no argument to reset the source path to empty.
4710 Use @code{directory} with suitable arguments to reinstall the
4711 directories you want in the source path. You can add all the
4712 directories in one command.
4716 @section Source and machine code
4717 @cindex source line and its code address
4719 You can use the command @code{info line} to map source lines to program
4720 addresses (and vice versa), and the command @code{disassemble} to display
4721 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
4722 mode, the @code{info line} command causes the arrow to point to the
4723 line specified. Also, @code{info line} prints addresses in symbolic form as
4728 @item info line @var{linespec}
4729 Print the starting and ending addresses of the compiled code for
4730 source line @var{linespec}. You can specify source lines in any of
4731 the ways understood by the @code{list} command (@pxref{List, ,Printing
4735 For example, we can use @code{info line} to discover the location of
4736 the object code for the first line of function
4737 @code{m4_changequote}:
4739 @c FIXME: I think this example should also show the addresses in
4740 @c symbolic form, as they usually would be displayed.
4742 (@value{GDBP}) info line m4_changequote
4743 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
4747 @cindex code address and its source line
4748 We can also inquire (using @code{*@var{addr}} as the form for
4749 @var{linespec}) what source line covers a particular address:
4751 (@value{GDBP}) info line *0x63ff
4752 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
4755 @cindex @code{$_} and @code{info line}
4756 @cindex @code{x} command, default address
4757 @kindex x@r{(examine), and} info line
4758 After @code{info line}, the default address for the @code{x} command
4759 is changed to the starting address of the line, so that @samp{x/i} is
4760 sufficient to begin examining the machine code (@pxref{Memory,
4761 ,Examining memory}). Also, this address is saved as the value of the
4762 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
4767 @cindex assembly instructions
4768 @cindex instructions, assembly
4769 @cindex machine instructions
4770 @cindex listing machine instructions
4772 This specialized command dumps a range of memory as machine
4773 instructions. The default memory range is the function surrounding the
4774 program counter of the selected frame. A single argument to this
4775 command is a program counter value; @value{GDBN} dumps the function
4776 surrounding this value. Two arguments specify a range of addresses
4777 (first inclusive, second exclusive) to dump.
4780 The following example shows the disassembly of a range of addresses of
4781 HP PA-RISC 2.0 code:
4784 (@value{GDBP}) disas 0x32c4 0x32e4
4785 Dump of assembler code from 0x32c4 to 0x32e4:
4786 0x32c4 <main+204>: addil 0,dp
4787 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
4788 0x32cc <main+212>: ldil 0x3000,r31
4789 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
4790 0x32d4 <main+220>: ldo 0(r31),rp
4791 0x32d8 <main+224>: addil -0x800,dp
4792 0x32dc <main+228>: ldo 0x588(r1),r26
4793 0x32e0 <main+232>: ldil 0x3000,r31
4794 End of assembler dump.
4797 Some architectures have more than one commonly-used set of instruction
4798 mnemonics or other syntax.
4801 @kindex set disassembly-flavor
4802 @cindex Intel disassembly flavor
4803 @cindex AT&T disassembly flavor
4804 @item set disassembly-flavor @var{instruction-set}
4805 Select the instruction set to use when disassembling the
4806 program via the @code{disassemble} or @code{x/i} commands.
4808 Currently this command is only defined for the Intel x86 family. You
4809 can set @var{instruction-set} to either @code{intel} or @code{att}.
4810 The default is @code{att}, the AT&T flavor used by default by Unix
4811 assemblers for x86-based targets.
4813 @kindex show disassembly-flavor
4814 @item show disassembly-flavor
4815 Show the current setting of the disassembly flavor.
4820 @chapter Examining Data
4822 @cindex printing data
4823 @cindex examining data
4826 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
4827 @c document because it is nonstandard... Under Epoch it displays in a
4828 @c different window or something like that.
4829 The usual way to examine data in your program is with the @code{print}
4830 command (abbreviated @code{p}), or its synonym @code{inspect}. It
4831 evaluates and prints the value of an expression of the language your
4832 program is written in (@pxref{Languages, ,Using @value{GDBN} with
4833 Different Languages}).
4836 @item print @var{expr}
4837 @itemx print /@var{f} @var{expr}
4838 @var{expr} is an expression (in the source language). By default the
4839 value of @var{expr} is printed in a format appropriate to its data type;
4840 you can choose a different format by specifying @samp{/@var{f}}, where
4841 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
4845 @itemx print /@var{f}
4846 @cindex reprint the last value
4847 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
4848 @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
4849 conveniently inspect the same value in an alternative format.
4852 A more low-level way of examining data is with the @code{x} command.
4853 It examines data in memory at a specified address and prints it in a
4854 specified format. @xref{Memory, ,Examining memory}.
4856 If you are interested in information about types, or about how the
4857 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
4858 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
4862 * Expressions:: Expressions
4863 * Variables:: Program variables
4864 * Arrays:: Artificial arrays
4865 * Output Formats:: Output formats
4866 * Memory:: Examining memory
4867 * Auto Display:: Automatic display
4868 * Print Settings:: Print settings
4869 * Value History:: Value history
4870 * Convenience Vars:: Convenience variables
4871 * Registers:: Registers
4872 * Floating Point Hardware:: Floating point hardware
4873 * Vector Unit:: Vector Unit
4874 * OS Information:: Auxiliary data provided by operating system
4875 * Memory Region Attributes:: Memory region attributes
4876 * Dump/Restore Files:: Copy between memory and a file
4877 * Core File Generation:: Cause a program dump its core
4878 * Character Sets:: Debugging programs that use a different
4879 character set than GDB does
4880 * Caching Remote Data:: Data caching for remote targets
4884 @section Expressions
4887 @code{print} and many other @value{GDBN} commands accept an expression and
4888 compute its value. Any kind of constant, variable or operator defined
4889 by the programming language you are using is valid in an expression in
4890 @value{GDBN}. This includes conditional expressions, function calls,
4891 casts, and string constants. It also includes preprocessor macros, if
4892 you compiled your program to include this information; see
4895 @cindex arrays in expressions
4896 @value{GDBN} supports array constants in expressions input by
4897 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
4898 you can use the command @code{print @{1, 2, 3@}} to build up an array in
4899 memory that is @code{malloc}ed in the target program.
4901 Because C is so widespread, most of the expressions shown in examples in
4902 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
4903 Languages}, for information on how to use expressions in other
4906 In this section, we discuss operators that you can use in @value{GDBN}
4907 expressions regardless of your programming language.
4909 @cindex casts, in expressions
4910 Casts are supported in all languages, not just in C, because it is so
4911 useful to cast a number into a pointer in order to examine a structure
4912 at that address in memory.
4913 @c FIXME: casts supported---Mod2 true?
4915 @value{GDBN} supports these operators, in addition to those common
4916 to programming languages:
4920 @samp{@@} is a binary operator for treating parts of memory as arrays.
4921 @xref{Arrays, ,Artificial arrays}, for more information.
4924 @samp{::} allows you to specify a variable in terms of the file or
4925 function where it is defined. @xref{Variables, ,Program variables}.
4927 @cindex @{@var{type}@}
4928 @cindex type casting memory
4929 @cindex memory, viewing as typed object
4930 @cindex casts, to view memory
4931 @item @{@var{type}@} @var{addr}
4932 Refers to an object of type @var{type} stored at address @var{addr} in
4933 memory. @var{addr} may be any expression whose value is an integer or
4934 pointer (but parentheses are required around binary operators, just as in
4935 a cast). This construct is allowed regardless of what kind of data is
4936 normally supposed to reside at @var{addr}.
4940 @section Program variables
4942 The most common kind of expression to use is the name of a variable
4945 Variables in expressions are understood in the selected stack frame
4946 (@pxref{Selection, ,Selecting a frame}); they must be either:
4950 global (or file-static)
4957 visible according to the scope rules of the
4958 programming language from the point of execution in that frame
4961 @noindent This means that in the function
4976 you can examine and use the variable @code{a} whenever your program is
4977 executing within the function @code{foo}, but you can only use or
4978 examine the variable @code{b} while your program is executing inside
4979 the block where @code{b} is declared.
4981 @cindex variable name conflict
4982 There is an exception: you can refer to a variable or function whose
4983 scope is a single source file even if the current execution point is not
4984 in this file. But it is possible to have more than one such variable or
4985 function with the same name (in different source files). If that
4986 happens, referring to that name has unpredictable effects. If you wish,
4987 you can specify a static variable in a particular function or file,
4988 using the colon-colon (@code{::}) notation:
4990 @cindex colon-colon, context for variables/functions
4992 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
4993 @cindex @code{::}, context for variables/functions
4996 @var{file}::@var{variable}
4997 @var{function}::@var{variable}
5001 Here @var{file} or @var{function} is the name of the context for the
5002 static @var{variable}. In the case of file names, you can use quotes to
5003 make sure @value{GDBN} parses the file name as a single word---for example,
5004 to print a global value of @code{x} defined in @file{f2.c}:
5007 (@value{GDBP}) p 'f2.c'::x
5010 @cindex C@t{++} scope resolution
5011 This use of @samp{::} is very rarely in conflict with the very similar
5012 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
5013 scope resolution operator in @value{GDBN} expressions.
5014 @c FIXME: Um, so what happens in one of those rare cases where it's in
5017 @cindex wrong values
5018 @cindex variable values, wrong
5019 @cindex function entry/exit, wrong values of variables
5020 @cindex optimized code, wrong values of variables
5022 @emph{Warning:} Occasionally, a local variable may appear to have the
5023 wrong value at certain points in a function---just after entry to a new
5024 scope, and just before exit.
5026 You may see this problem when you are stepping by machine instructions.
5027 This is because, on most machines, it takes more than one instruction to
5028 set up a stack frame (including local variable definitions); if you are
5029 stepping by machine instructions, variables may appear to have the wrong
5030 values until the stack frame is completely built. On exit, it usually
5031 also takes more than one machine instruction to destroy a stack frame;
5032 after you begin stepping through that group of instructions, local
5033 variable definitions may be gone.
5035 This may also happen when the compiler does significant optimizations.
5036 To be sure of always seeing accurate values, turn off all optimization
5039 @cindex ``No symbol "foo" in current context''
5040 Another possible effect of compiler optimizations is to optimize
5041 unused variables out of existence, or assign variables to registers (as
5042 opposed to memory addresses). Depending on the support for such cases
5043 offered by the debug info format used by the compiler, @value{GDBN}
5044 might not be able to display values for such local variables. If that
5045 happens, @value{GDBN} will print a message like this:
5048 No symbol "foo" in current context.
5051 To solve such problems, either recompile without optimizations, or use a
5052 different debug info format, if the compiler supports several such
5053 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
5054 usually supports the @option{-gstabs+} option. @option{-gstabs+}
5055 produces debug info in a format that is superior to formats such as
5056 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
5057 an effective form for debug info. @xref{Debugging Options,,Options
5058 for Debugging Your Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}.
5059 @xref{C, , Debugging C++}, for more info about debug info formats
5060 that are best suited to C@t{++} programs.
5063 @section Artificial arrays
5065 @cindex artificial array
5067 @kindex @@@r{, referencing memory as an array}
5068 It is often useful to print out several successive objects of the
5069 same type in memory; a section of an array, or an array of
5070 dynamically determined size for which only a pointer exists in the
5073 You can do this by referring to a contiguous span of memory as an
5074 @dfn{artificial array}, using the binary operator @samp{@@}. The left
5075 operand of @samp{@@} should be the first element of the desired array
5076 and be an individual object. The right operand should be the desired length
5077 of the array. The result is an array value whose elements are all of
5078 the type of the left argument. The first element is actually the left
5079 argument; the second element comes from bytes of memory immediately
5080 following those that hold the first element, and so on. Here is an
5081 example. If a program says
5084 int *array = (int *) malloc (len * sizeof (int));
5088 you can print the contents of @code{array} with
5094 The left operand of @samp{@@} must reside in memory. Array values made
5095 with @samp{@@} in this way behave just like other arrays in terms of
5096 subscripting, and are coerced to pointers when used in expressions.
5097 Artificial arrays most often appear in expressions via the value history
5098 (@pxref{Value History, ,Value history}), after printing one out.
5100 Another way to create an artificial array is to use a cast.
5101 This re-interprets a value as if it were an array.
5102 The value need not be in memory:
5104 (@value{GDBP}) p/x (short[2])0x12345678
5105 $1 = @{0x1234, 0x5678@}
5108 As a convenience, if you leave the array length out (as in
5109 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5110 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5112 (@value{GDBP}) p/x (short[])0x12345678
5113 $2 = @{0x1234, 0x5678@}
5116 Sometimes the artificial array mechanism is not quite enough; in
5117 moderately complex data structures, the elements of interest may not
5118 actually be adjacent---for example, if you are interested in the values
5119 of pointers in an array. One useful work-around in this situation is
5120 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5121 variables}) as a counter in an expression that prints the first
5122 interesting value, and then repeat that expression via @key{RET}. For
5123 instance, suppose you have an array @code{dtab} of pointers to
5124 structures, and you are interested in the values of a field @code{fv}
5125 in each structure. Here is an example of what you might type:
5135 @node Output Formats
5136 @section Output formats
5138 @cindex formatted output
5139 @cindex output formats
5140 By default, @value{GDBN} prints a value according to its data type. Sometimes
5141 this is not what you want. For example, you might want to print a number
5142 in hex, or a pointer in decimal. Or you might want to view data in memory
5143 at a certain address as a character string or as an instruction. To do
5144 these things, specify an @dfn{output format} when you print a value.
5146 The simplest use of output formats is to say how to print a value
5147 already computed. This is done by starting the arguments of the
5148 @code{print} command with a slash and a format letter. The format
5149 letters supported are:
5153 Regard the bits of the value as an integer, and print the integer in
5157 Print as integer in signed decimal.
5160 Print as integer in unsigned decimal.
5163 Print as integer in octal.
5166 Print as integer in binary. The letter @samp{t} stands for ``two''.
5167 @footnote{@samp{b} cannot be used because these format letters are also
5168 used with the @code{x} command, where @samp{b} stands for ``byte'';
5169 see @ref{Memory,,Examining memory}.}
5172 @cindex unknown address, locating
5173 @cindex locate address
5174 Print as an address, both absolute in hexadecimal and as an offset from
5175 the nearest preceding symbol. You can use this format used to discover
5176 where (in what function) an unknown address is located:
5179 (@value{GDBP}) p/a 0x54320
5180 $3 = 0x54320 <_initialize_vx+396>
5184 The command @code{info symbol 0x54320} yields similar results.
5185 @xref{Symbols, info symbol}.
5188 Regard as an integer and print it as a character constant.
5191 Regard the bits of the value as a floating point number and print
5192 using typical floating point syntax.
5195 For example, to print the program counter in hex (@pxref{Registers}), type
5202 Note that no space is required before the slash; this is because command
5203 names in @value{GDBN} cannot contain a slash.
5205 To reprint the last value in the value history with a different format,
5206 you can use the @code{print} command with just a format and no
5207 expression. For example, @samp{p/x} reprints the last value in hex.
5210 @section Examining memory
5212 You can use the command @code{x} (for ``examine'') to examine memory in
5213 any of several formats, independently of your program's data types.
5215 @cindex examining memory
5217 @kindex x @r{(examine memory)}
5218 @item x/@var{nfu} @var{addr}
5221 Use the @code{x} command to examine memory.
5224 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5225 much memory to display and how to format it; @var{addr} is an
5226 expression giving the address where you want to start displaying memory.
5227 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5228 Several commands set convenient defaults for @var{addr}.
5231 @item @var{n}, the repeat count
5232 The repeat count is a decimal integer; the default is 1. It specifies
5233 how much memory (counting by units @var{u}) to display.
5234 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5237 @item @var{f}, the display format
5238 The display format is one of the formats used by @code{print},
5239 @samp{s} (null-terminated string), or @samp{i} (machine instruction).
5240 The default is @samp{x} (hexadecimal) initially.
5241 The default changes each time you use either @code{x} or @code{print}.
5243 @item @var{u}, the unit size
5244 The unit size is any of
5250 Halfwords (two bytes).
5252 Words (four bytes). This is the initial default.
5254 Giant words (eight bytes).
5257 Each time you specify a unit size with @code{x}, that size becomes the
5258 default unit the next time you use @code{x}. (For the @samp{s} and
5259 @samp{i} formats, the unit size is ignored and is normally not written.)
5261 @item @var{addr}, starting display address
5262 @var{addr} is the address where you want @value{GDBN} to begin displaying
5263 memory. The expression need not have a pointer value (though it may);
5264 it is always interpreted as an integer address of a byte of memory.
5265 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5266 @var{addr} is usually just after the last address examined---but several
5267 other commands also set the default address: @code{info breakpoints} (to
5268 the address of the last breakpoint listed), @code{info line} (to the
5269 starting address of a line), and @code{print} (if you use it to display
5270 a value from memory).
5273 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5274 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5275 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5276 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5277 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5279 Since the letters indicating unit sizes are all distinct from the
5280 letters specifying output formats, you do not have to remember whether
5281 unit size or format comes first; either order works. The output
5282 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5283 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5285 Even though the unit size @var{u} is ignored for the formats @samp{s}
5286 and @samp{i}, you might still want to use a count @var{n}; for example,
5287 @samp{3i} specifies that you want to see three machine instructions,
5288 including any operands. The command @code{disassemble} gives an
5289 alternative way of inspecting machine instructions; see @ref{Machine
5290 Code,,Source and machine code}.
5292 All the defaults for the arguments to @code{x} are designed to make it
5293 easy to continue scanning memory with minimal specifications each time
5294 you use @code{x}. For example, after you have inspected three machine
5295 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5296 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5297 the repeat count @var{n} is used again; the other arguments default as
5298 for successive uses of @code{x}.
5300 @cindex @code{$_}, @code{$__}, and value history
5301 The addresses and contents printed by the @code{x} command are not saved
5302 in the value history because there is often too much of them and they
5303 would get in the way. Instead, @value{GDBN} makes these values available for
5304 subsequent use in expressions as values of the convenience variables
5305 @code{$_} and @code{$__}. After an @code{x} command, the last address
5306 examined is available for use in expressions in the convenience variable
5307 @code{$_}. The contents of that address, as examined, are available in
5308 the convenience variable @code{$__}.
5310 If the @code{x} command has a repeat count, the address and contents saved
5311 are from the last memory unit printed; this is not the same as the last
5312 address printed if several units were printed on the last line of output.
5314 @cindex remote memory comparison
5315 @cindex verify remote memory image
5316 When you are debugging a program running on a remote target machine
5317 (@pxref{Remote}), you may wish to verify the program's image in the
5318 remote machine's memory against the executable file you downloaded to
5319 the target. The @code{compare-sections} command is provided for such
5323 @kindex compare-sections
5324 @item compare-sections @r{[}@var{section-name}@r{]}
5325 Compare the data of a loadable section @var{section-name} in the
5326 executable file of the program being debugged with the same section in
5327 the remote machine's memory, and report any mismatches. With no
5328 arguments, compares all loadable sections. This command's
5329 availability depends on the target's support for the @code{"qCRC"}
5334 @section Automatic display
5335 @cindex automatic display
5336 @cindex display of expressions
5338 If you find that you want to print the value of an expression frequently
5339 (to see how it changes), you might want to add it to the @dfn{automatic
5340 display list} so that @value{GDBN} prints its value each time your program stops.
5341 Each expression added to the list is given a number to identify it;
5342 to remove an expression from the list, you specify that number.
5343 The automatic display looks like this:
5347 3: bar[5] = (struct hack *) 0x3804
5351 This display shows item numbers, expressions and their current values. As with
5352 displays you request manually using @code{x} or @code{print}, you can
5353 specify the output format you prefer; in fact, @code{display} decides
5354 whether to use @code{print} or @code{x} depending on how elaborate your
5355 format specification is---it uses @code{x} if you specify a unit size,
5356 or one of the two formats (@samp{i} and @samp{s}) that are only
5357 supported by @code{x}; otherwise it uses @code{print}.
5361 @item display @var{expr}
5362 Add the expression @var{expr} to the list of expressions to display
5363 each time your program stops. @xref{Expressions, ,Expressions}.
5365 @code{display} does not repeat if you press @key{RET} again after using it.
5367 @item display/@var{fmt} @var{expr}
5368 For @var{fmt} specifying only a display format and not a size or
5369 count, add the expression @var{expr} to the auto-display list but
5370 arrange to display it each time in the specified format @var{fmt}.
5371 @xref{Output Formats,,Output formats}.
5373 @item display/@var{fmt} @var{addr}
5374 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
5375 number of units, add the expression @var{addr} as a memory address to
5376 be examined each time your program stops. Examining means in effect
5377 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
5380 For example, @samp{display/i $pc} can be helpful, to see the machine
5381 instruction about to be executed each time execution stops (@samp{$pc}
5382 is a common name for the program counter; @pxref{Registers, ,Registers}).
5385 @kindex delete display
5387 @item undisplay @var{dnums}@dots{}
5388 @itemx delete display @var{dnums}@dots{}
5389 Remove item numbers @var{dnums} from the list of expressions to display.
5391 @code{undisplay} does not repeat if you press @key{RET} after using it.
5392 (Otherwise you would just get the error @samp{No display number @dots{}}.)
5394 @kindex disable display
5395 @item disable display @var{dnums}@dots{}
5396 Disable the display of item numbers @var{dnums}. A disabled display
5397 item is not printed automatically, but is not forgotten. It may be
5398 enabled again later.
5400 @kindex enable display
5401 @item enable display @var{dnums}@dots{}
5402 Enable display of item numbers @var{dnums}. It becomes effective once
5403 again in auto display of its expression, until you specify otherwise.
5406 Display the current values of the expressions on the list, just as is
5407 done when your program stops.
5409 @kindex info display
5411 Print the list of expressions previously set up to display
5412 automatically, each one with its item number, but without showing the
5413 values. This includes disabled expressions, which are marked as such.
5414 It also includes expressions which would not be displayed right now
5415 because they refer to automatic variables not currently available.
5418 @cindex display disabled out of scope
5419 If a display expression refers to local variables, then it does not make
5420 sense outside the lexical context for which it was set up. Such an
5421 expression is disabled when execution enters a context where one of its
5422 variables is not defined. For example, if you give the command
5423 @code{display last_char} while inside a function with an argument
5424 @code{last_char}, @value{GDBN} displays this argument while your program
5425 continues to stop inside that function. When it stops elsewhere---where
5426 there is no variable @code{last_char}---the display is disabled
5427 automatically. The next time your program stops where @code{last_char}
5428 is meaningful, you can enable the display expression once again.
5430 @node Print Settings
5431 @section Print settings
5433 @cindex format options
5434 @cindex print settings
5435 @value{GDBN} provides the following ways to control how arrays, structures,
5436 and symbols are printed.
5439 These settings are useful for debugging programs in any language:
5443 @item set print address
5444 @itemx set print address on
5445 @cindex print/don't print memory addresses
5446 @value{GDBN} prints memory addresses showing the location of stack
5447 traces, structure values, pointer values, breakpoints, and so forth,
5448 even when it also displays the contents of those addresses. The default
5449 is @code{on}. For example, this is what a stack frame display looks like with
5450 @code{set print address on}:
5455 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
5457 530 if (lquote != def_lquote)
5461 @item set print address off
5462 Do not print addresses when displaying their contents. For example,
5463 this is the same stack frame displayed with @code{set print address off}:
5467 (@value{GDBP}) set print addr off
5469 #0 set_quotes (lq="<<", rq=">>") at input.c:530
5470 530 if (lquote != def_lquote)
5474 You can use @samp{set print address off} to eliminate all machine
5475 dependent displays from the @value{GDBN} interface. For example, with
5476 @code{print address off}, you should get the same text for backtraces on
5477 all machines---whether or not they involve pointer arguments.
5480 @item show print address
5481 Show whether or not addresses are to be printed.
5484 When @value{GDBN} prints a symbolic address, it normally prints the
5485 closest earlier symbol plus an offset. If that symbol does not uniquely
5486 identify the address (for example, it is a name whose scope is a single
5487 source file), you may need to clarify. One way to do this is with
5488 @code{info line}, for example @samp{info line *0x4537}. Alternately,
5489 you can set @value{GDBN} to print the source file and line number when
5490 it prints a symbolic address:
5493 @item set print symbol-filename on
5494 @cindex source file and line of a symbol
5495 @cindex symbol, source file and line
5496 Tell @value{GDBN} to print the source file name and line number of a
5497 symbol in the symbolic form of an address.
5499 @item set print symbol-filename off
5500 Do not print source file name and line number of a symbol. This is the
5503 @item show print symbol-filename
5504 Show whether or not @value{GDBN} will print the source file name and
5505 line number of a symbol in the symbolic form of an address.
5508 Another situation where it is helpful to show symbol filenames and line
5509 numbers is when disassembling code; @value{GDBN} shows you the line
5510 number and source file that corresponds to each instruction.
5512 Also, you may wish to see the symbolic form only if the address being
5513 printed is reasonably close to the closest earlier symbol:
5516 @item set print max-symbolic-offset @var{max-offset}
5517 @cindex maximum value for offset of closest symbol
5518 Tell @value{GDBN} to only display the symbolic form of an address if the
5519 offset between the closest earlier symbol and the address is less than
5520 @var{max-offset}. The default is 0, which tells @value{GDBN}
5521 to always print the symbolic form of an address if any symbol precedes it.
5523 @item show print max-symbolic-offset
5524 Ask how large the maximum offset is that @value{GDBN} prints in a
5528 @cindex wild pointer, interpreting
5529 @cindex pointer, finding referent
5530 If you have a pointer and you are not sure where it points, try
5531 @samp{set print symbol-filename on}. Then you can determine the name
5532 and source file location of the variable where it points, using
5533 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
5534 For example, here @value{GDBN} shows that a variable @code{ptt} points
5535 at another variable @code{t}, defined in @file{hi2.c}:
5538 (@value{GDBP}) set print symbol-filename on
5539 (@value{GDBP}) p/a ptt
5540 $4 = 0xe008 <t in hi2.c>
5544 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
5545 does not show the symbol name and filename of the referent, even with
5546 the appropriate @code{set print} options turned on.
5549 Other settings control how different kinds of objects are printed:
5552 @item set print array
5553 @itemx set print array on
5554 @cindex pretty print arrays
5555 Pretty print arrays. This format is more convenient to read,
5556 but uses more space. The default is off.
5558 @item set print array off
5559 Return to compressed format for arrays.
5561 @item show print array
5562 Show whether compressed or pretty format is selected for displaying
5565 @item set print elements @var{number-of-elements}
5566 @cindex number of array elements to print
5567 @cindex limit on number of printed array elements
5568 Set a limit on how many elements of an array @value{GDBN} will print.
5569 If @value{GDBN} is printing a large array, it stops printing after it has
5570 printed the number of elements set by the @code{set print elements} command.
5571 This limit also applies to the display of strings.
5572 When @value{GDBN} starts, this limit is set to 200.
5573 Setting @var{number-of-elements} to zero means that the printing is unlimited.
5575 @item show print elements
5576 Display the number of elements of a large array that @value{GDBN} will print.
5577 If the number is 0, then the printing is unlimited.
5579 @item set print repeats
5580 @cindex repeated array elements
5581 Set the threshold for suppressing display of repeated array
5582 elelments. When the number of consecutive identical elements of an
5583 array exceeds the threshold, @value{GDBN} prints the string
5584 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
5585 identical repetitions, instead of displaying the identical elements
5586 themselves. Setting the threshold to zero will cause all elements to
5587 be individually printed. The default threshold is 10.
5589 @item show print repeats
5590 Display the current threshold for printing repeated identical
5593 @item set print null-stop
5594 @cindex @sc{null} elements in arrays
5595 Cause @value{GDBN} to stop printing the characters of an array when the first
5596 @sc{null} is encountered. This is useful when large arrays actually
5597 contain only short strings.
5600 @item show print null-stop
5601 Show whether @value{GDBN} stops printing an array on the first
5602 @sc{null} character.
5604 @item set print pretty on
5605 @cindex print structures in indented form
5606 @cindex indentation in structure display
5607 Cause @value{GDBN} to print structures in an indented format with one member
5608 per line, like this:
5623 @item set print pretty off
5624 Cause @value{GDBN} to print structures in a compact format, like this:
5628 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
5629 meat = 0x54 "Pork"@}
5634 This is the default format.
5636 @item show print pretty
5637 Show which format @value{GDBN} is using to print structures.
5639 @item set print sevenbit-strings on
5640 @cindex eight-bit characters in strings
5641 @cindex octal escapes in strings
5642 Print using only seven-bit characters; if this option is set,
5643 @value{GDBN} displays any eight-bit characters (in strings or
5644 character values) using the notation @code{\}@var{nnn}. This setting is
5645 best if you are working in English (@sc{ascii}) and you use the
5646 high-order bit of characters as a marker or ``meta'' bit.
5648 @item set print sevenbit-strings off
5649 Print full eight-bit characters. This allows the use of more
5650 international character sets, and is the default.
5652 @item show print sevenbit-strings
5653 Show whether or not @value{GDBN} is printing only seven-bit characters.
5655 @item set print union on
5656 @cindex unions in structures, printing
5657 Tell @value{GDBN} to print unions which are contained in structures
5658 and other unions. This is the default setting.
5660 @item set print union off
5661 Tell @value{GDBN} not to print unions which are contained in
5662 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
5665 @item show print union
5666 Ask @value{GDBN} whether or not it will print unions which are contained in
5667 structures and other unions.
5669 For example, given the declarations
5672 typedef enum @{Tree, Bug@} Species;
5673 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
5674 typedef enum @{Caterpillar, Cocoon, Butterfly@}
5685 struct thing foo = @{Tree, @{Acorn@}@};
5689 with @code{set print union on} in effect @samp{p foo} would print
5692 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
5696 and with @code{set print union off} in effect it would print
5699 $1 = @{it = Tree, form = @{...@}@}
5703 @code{set print union} affects programs written in C-like languages
5709 These settings are of interest when debugging C@t{++} programs:
5712 @cindex demangling C@t{++} names
5713 @item set print demangle
5714 @itemx set print demangle on
5715 Print C@t{++} names in their source form rather than in the encoded
5716 (``mangled'') form passed to the assembler and linker for type-safe
5717 linkage. The default is on.
5719 @item show print demangle
5720 Show whether C@t{++} names are printed in mangled or demangled form.
5722 @item set print asm-demangle
5723 @itemx set print asm-demangle on
5724 Print C@t{++} names in their source form rather than their mangled form, even
5725 in assembler code printouts such as instruction disassemblies.
5728 @item show print asm-demangle
5729 Show whether C@t{++} names in assembly listings are printed in mangled
5732 @cindex C@t{++} symbol decoding style
5733 @cindex symbol decoding style, C@t{++}
5734 @kindex set demangle-style
5735 @item set demangle-style @var{style}
5736 Choose among several encoding schemes used by different compilers to
5737 represent C@t{++} names. The choices for @var{style} are currently:
5741 Allow @value{GDBN} to choose a decoding style by inspecting your program.
5744 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
5745 This is the default.
5748 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
5751 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
5754 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
5755 @strong{Warning:} this setting alone is not sufficient to allow
5756 debugging @code{cfront}-generated executables. @value{GDBN} would
5757 require further enhancement to permit that.
5760 If you omit @var{style}, you will see a list of possible formats.
5762 @item show demangle-style
5763 Display the encoding style currently in use for decoding C@t{++} symbols.
5765 @item set print object
5766 @itemx set print object on
5767 @cindex derived type of an object, printing
5768 @cindex display derived types
5769 When displaying a pointer to an object, identify the @emph{actual}
5770 (derived) type of the object rather than the @emph{declared} type, using
5771 the virtual function table.
5773 @item set print object off
5774 Display only the declared type of objects, without reference to the
5775 virtual function table. This is the default setting.
5777 @item show print object
5778 Show whether actual, or declared, object types are displayed.
5780 @item set print static-members
5781 @itemx set print static-members on
5782 @cindex static members of C@t{++} objects
5783 Print static members when displaying a C@t{++} object. The default is on.
5785 @item set print static-members off
5786 Do not print static members when displaying a C@t{++} object.
5788 @item show print static-members
5789 Show whether C@t{++} static members are printed or not.
5791 @item set print pascal_static-members
5792 @itemx set print pascal_static-members on
5793 @cindex static members of Pacal objects
5794 @cindex Pacal objects, static members display
5795 Print static members when displaying a Pascal object. The default is on.
5797 @item set print pascal_static-members off
5798 Do not print static members when displaying a Pascal object.
5800 @item show print pascal_static-members
5801 Show whether Pascal static members are printed or not.
5803 @c These don't work with HP ANSI C++ yet.
5804 @item set print vtbl
5805 @itemx set print vtbl on
5806 @cindex pretty print C@t{++} virtual function tables
5807 @cindex virtual functions (C@t{++}) display
5808 @cindex VTBL display
5809 Pretty print C@t{++} virtual function tables. The default is off.
5810 (The @code{vtbl} commands do not work on programs compiled with the HP
5811 ANSI C@t{++} compiler (@code{aCC}).)
5813 @item set print vtbl off
5814 Do not pretty print C@t{++} virtual function tables.
5816 @item show print vtbl
5817 Show whether C@t{++} virtual function tables are pretty printed, or not.
5821 @section Value history
5823 @cindex value history
5824 @cindex history of values printed by @value{GDBN}
5825 Values printed by the @code{print} command are saved in the @value{GDBN}
5826 @dfn{value history}. This allows you to refer to them in other expressions.
5827 Values are kept until the symbol table is re-read or discarded
5828 (for example with the @code{file} or @code{symbol-file} commands).
5829 When the symbol table changes, the value history is discarded,
5830 since the values may contain pointers back to the types defined in the
5835 @cindex history number
5836 The values printed are given @dfn{history numbers} by which you can
5837 refer to them. These are successive integers starting with one.
5838 @code{print} shows you the history number assigned to a value by
5839 printing @samp{$@var{num} = } before the value; here @var{num} is the
5842 To refer to any previous value, use @samp{$} followed by the value's
5843 history number. The way @code{print} labels its output is designed to
5844 remind you of this. Just @code{$} refers to the most recent value in
5845 the history, and @code{$$} refers to the value before that.
5846 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
5847 is the value just prior to @code{$$}, @code{$$1} is equivalent to
5848 @code{$$}, and @code{$$0} is equivalent to @code{$}.
5850 For example, suppose you have just printed a pointer to a structure and
5851 want to see the contents of the structure. It suffices to type
5857 If you have a chain of structures where the component @code{next} points
5858 to the next one, you can print the contents of the next one with this:
5865 You can print successive links in the chain by repeating this
5866 command---which you can do by just typing @key{RET}.
5868 Note that the history records values, not expressions. If the value of
5869 @code{x} is 4 and you type these commands:
5877 then the value recorded in the value history by the @code{print} command
5878 remains 4 even though the value of @code{x} has changed.
5883 Print the last ten values in the value history, with their item numbers.
5884 This is like @samp{p@ $$9} repeated ten times, except that @code{show
5885 values} does not change the history.
5887 @item show values @var{n}
5888 Print ten history values centered on history item number @var{n}.
5891 Print ten history values just after the values last printed. If no more
5892 values are available, @code{show values +} produces no display.
5895 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
5896 same effect as @samp{show values +}.
5898 @node Convenience Vars
5899 @section Convenience variables
5901 @cindex convenience variables
5902 @cindex user-defined variables
5903 @value{GDBN} provides @dfn{convenience variables} that you can use within
5904 @value{GDBN} to hold on to a value and refer to it later. These variables
5905 exist entirely within @value{GDBN}; they are not part of your program, and
5906 setting a convenience variable has no direct effect on further execution
5907 of your program. That is why you can use them freely.
5909 Convenience variables are prefixed with @samp{$}. Any name preceded by
5910 @samp{$} can be used for a convenience variable, unless it is one of
5911 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
5912 (Value history references, in contrast, are @emph{numbers} preceded
5913 by @samp{$}. @xref{Value History, ,Value history}.)
5915 You can save a value in a convenience variable with an assignment
5916 expression, just as you would set a variable in your program.
5920 set $foo = *object_ptr
5924 would save in @code{$foo} the value contained in the object pointed to by
5927 Using a convenience variable for the first time creates it, but its
5928 value is @code{void} until you assign a new value. You can alter the
5929 value with another assignment at any time.
5931 Convenience variables have no fixed types. You can assign a convenience
5932 variable any type of value, including structures and arrays, even if
5933 that variable already has a value of a different type. The convenience
5934 variable, when used as an expression, has the type of its current value.
5937 @kindex show convenience
5938 @cindex show all user variables
5939 @item show convenience
5940 Print a list of convenience variables used so far, and their values.
5941 Abbreviated @code{show conv}.
5944 One of the ways to use a convenience variable is as a counter to be
5945 incremented or a pointer to be advanced. For example, to print
5946 a field from successive elements of an array of structures:
5950 print bar[$i++]->contents
5954 Repeat that command by typing @key{RET}.
5956 Some convenience variables are created automatically by @value{GDBN} and given
5957 values likely to be useful.
5960 @vindex $_@r{, convenience variable}
5962 The variable @code{$_} is automatically set by the @code{x} command to
5963 the last address examined (@pxref{Memory, ,Examining memory}). Other
5964 commands which provide a default address for @code{x} to examine also
5965 set @code{$_} to that address; these commands include @code{info line}
5966 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
5967 except when set by the @code{x} command, in which case it is a pointer
5968 to the type of @code{$__}.
5970 @vindex $__@r{, convenience variable}
5972 The variable @code{$__} is automatically set by the @code{x} command
5973 to the value found in the last address examined. Its type is chosen
5974 to match the format in which the data was printed.
5977 @vindex $_exitcode@r{, convenience variable}
5978 The variable @code{$_exitcode} is automatically set to the exit code when
5979 the program being debugged terminates.
5982 On HP-UX systems, if you refer to a function or variable name that
5983 begins with a dollar sign, @value{GDBN} searches for a user or system
5984 name first, before it searches for a convenience variable.
5990 You can refer to machine register contents, in expressions, as variables
5991 with names starting with @samp{$}. The names of registers are different
5992 for each machine; use @code{info registers} to see the names used on
5996 @kindex info registers
5997 @item info registers
5998 Print the names and values of all registers except floating-point
5999 and vector registers (in the selected stack frame).
6001 @kindex info all-registers
6002 @cindex floating point registers
6003 @item info all-registers
6004 Print the names and values of all registers, including floating-point
6005 and vector registers (in the selected stack frame).
6007 @item info registers @var{regname} @dots{}
6008 Print the @dfn{relativized} value of each specified register @var{regname}.
6009 As discussed in detail below, register values are normally relative to
6010 the selected stack frame. @var{regname} may be any register name valid on
6011 the machine you are using, with or without the initial @samp{$}.
6014 @value{GDBN} has four ``standard'' register names that are available (in
6015 expressions) on most machines---whenever they do not conflict with an
6016 architecture's canonical mnemonics for registers. The register names
6017 @code{$pc} and @code{$sp} are used for the program counter register and
6018 the stack pointer. @code{$fp} is used for a register that contains a
6019 pointer to the current stack frame, and @code{$ps} is used for a
6020 register that contains the processor status. For example,
6021 you could print the program counter in hex with
6028 or print the instruction to be executed next with
6035 or add four to the stack pointer@footnote{This is a way of removing
6036 one word from the stack, on machines where stacks grow downward in
6037 memory (most machines, nowadays). This assumes that the innermost
6038 stack frame is selected; setting @code{$sp} is not allowed when other
6039 stack frames are selected. To pop entire frames off the stack,
6040 regardless of machine architecture, use @code{return};
6041 see @ref{Returning, ,Returning from a function}.} with
6047 Whenever possible, these four standard register names are available on
6048 your machine even though the machine has different canonical mnemonics,
6049 so long as there is no conflict. The @code{info registers} command
6050 shows the canonical names. For example, on the SPARC, @code{info
6051 registers} displays the processor status register as @code{$psr} but you
6052 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
6053 is an alias for the @sc{eflags} register.
6055 @value{GDBN} always considers the contents of an ordinary register as an
6056 integer when the register is examined in this way. Some machines have
6057 special registers which can hold nothing but floating point; these
6058 registers are considered to have floating point values. There is no way
6059 to refer to the contents of an ordinary register as floating point value
6060 (although you can @emph{print} it as a floating point value with
6061 @samp{print/f $@var{regname}}).
6063 Some registers have distinct ``raw'' and ``virtual'' data formats. This
6064 means that the data format in which the register contents are saved by
6065 the operating system is not the same one that your program normally
6066 sees. For example, the registers of the 68881 floating point
6067 coprocessor are always saved in ``extended'' (raw) format, but all C
6068 programs expect to work with ``double'' (virtual) format. In such
6069 cases, @value{GDBN} normally works with the virtual format only (the format
6070 that makes sense for your program), but the @code{info registers} command
6071 prints the data in both formats.
6073 Normally, register values are relative to the selected stack frame
6074 (@pxref{Selection, ,Selecting a frame}). This means that you get the
6075 value that the register would contain if all stack frames farther in
6076 were exited and their saved registers restored. In order to see the
6077 true contents of hardware registers, you must select the innermost
6078 frame (with @samp{frame 0}).
6080 However, @value{GDBN} must deduce where registers are saved, from the machine
6081 code generated by your compiler. If some registers are not saved, or if
6082 @value{GDBN} is unable to locate the saved registers, the selected stack
6083 frame makes no difference.
6085 @node Floating Point Hardware
6086 @section Floating point hardware
6087 @cindex floating point
6089 Depending on the configuration, @value{GDBN} may be able to give
6090 you more information about the status of the floating point hardware.
6095 Display hardware-dependent information about the floating
6096 point unit. The exact contents and layout vary depending on the
6097 floating point chip. Currently, @samp{info float} is supported on
6098 the ARM and x86 machines.
6102 @section Vector Unit
6105 Depending on the configuration, @value{GDBN} may be able to give you
6106 more information about the status of the vector unit.
6111 Display information about the vector unit. The exact contents and
6112 layout vary depending on the hardware.
6115 @node OS Information
6116 @section Operating system auxiliary information
6117 @cindex OS information
6119 @value{GDBN} provides interfaces to useful OS facilities that can help
6120 you debug your program.
6122 @cindex @code{ptrace} system call
6123 @cindex @code{struct user} contents
6124 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
6125 machines), it interfaces with the inferior via the @code{ptrace}
6126 system call. The operating system creates a special sata structure,
6127 called @code{struct user}, for this interface. You can use the
6128 command @code{info udot} to display the contents of this data
6134 Display the contents of the @code{struct user} maintained by the OS
6135 kernel for the program being debugged. @value{GDBN} displays the
6136 contents of @code{struct user} as a list of hex numbers, similar to
6137 the @code{examine} command.
6140 @cindex auxiliary vector
6141 @cindex vector, auxiliary
6142 Some operating systems supply an @dfn{auxiliary vector} to programs at
6143 startup. This is akin to the arguments and environment that you
6144 specify for a program, but contains a system-dependent variety of
6145 binary values that tell system libraries important details about the
6146 hardware, operating system, and process. Each value's purpose is
6147 identified by an integer tag; the meanings are well-known but system-specific.
6148 Depending on the configuration and operating system facilities,
6149 @value{GDBN} may be able to show you this information. For remote
6150 targets, this functionality may further depend on the remote stub's
6151 support of the @samp{qPart:auxv:read} packet, see @ref{Remote
6152 configuration, auxiliary vector}.
6157 Display the auxiliary vector of the inferior, which can be either a
6158 live process or a core dump file. @value{GDBN} prints each tag value
6159 numerically, and also shows names and text descriptions for recognized
6160 tags. Some values in the vector are numbers, some bit masks, and some
6161 pointers to strings or other data. @value{GDBN} displays each value in the
6162 most appropriate form for a recognized tag, and in hexadecimal for
6163 an unrecognized tag.
6167 @node Memory Region Attributes
6168 @section Memory region attributes
6169 @cindex memory region attributes
6171 @dfn{Memory region attributes} allow you to describe special handling
6172 required by regions of your target's memory. @value{GDBN} uses attributes
6173 to determine whether to allow certain types of memory accesses; whether to
6174 use specific width accesses; and whether to cache target memory.
6176 Defined memory regions can be individually enabled and disabled. When a
6177 memory region is disabled, @value{GDBN} uses the default attributes when
6178 accessing memory in that region. Similarly, if no memory regions have
6179 been defined, @value{GDBN} uses the default attributes when accessing
6182 When a memory region is defined, it is given a number to identify it;
6183 to enable, disable, or remove a memory region, you specify that number.
6187 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
6188 Define a memory region bounded by @var{lower} and @var{upper} with
6189 attributes @var{attributes}@dots{}, and add it to the list of regions
6190 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
6191 case: it is treated as the the target's maximum memory address.
6192 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
6195 @item delete mem @var{nums}@dots{}
6196 Remove memory regions @var{nums}@dots{} from the list of regions
6197 monitored by @value{GDBN}.
6200 @item disable mem @var{nums}@dots{}
6201 Disable monitoring of memory regions @var{nums}@dots{}.
6202 A disabled memory region is not forgotten.
6203 It may be enabled again later.
6206 @item enable mem @var{nums}@dots{}
6207 Enable monitoring of memory regions @var{nums}@dots{}.
6211 Print a table of all defined memory regions, with the following columns
6215 @item Memory Region Number
6216 @item Enabled or Disabled.
6217 Enabled memory regions are marked with @samp{y}.
6218 Disabled memory regions are marked with @samp{n}.
6221 The address defining the inclusive lower bound of the memory region.
6224 The address defining the exclusive upper bound of the memory region.
6227 The list of attributes set for this memory region.
6232 @subsection Attributes
6234 @subsubsection Memory Access Mode
6235 The access mode attributes set whether @value{GDBN} may make read or
6236 write accesses to a memory region.
6238 While these attributes prevent @value{GDBN} from performing invalid
6239 memory accesses, they do nothing to prevent the target system, I/O DMA,
6240 etc. from accessing memory.
6244 Memory is read only.
6246 Memory is write only.
6248 Memory is read/write. This is the default.
6251 @subsubsection Memory Access Size
6252 The acccess size attributes tells @value{GDBN} to use specific sized
6253 accesses in the memory region. Often memory mapped device registers
6254 require specific sized accesses. If no access size attribute is
6255 specified, @value{GDBN} may use accesses of any size.
6259 Use 8 bit memory accesses.
6261 Use 16 bit memory accesses.
6263 Use 32 bit memory accesses.
6265 Use 64 bit memory accesses.
6268 @c @subsubsection Hardware/Software Breakpoints
6269 @c The hardware/software breakpoint attributes set whether @value{GDBN}
6270 @c will use hardware or software breakpoints for the internal breakpoints
6271 @c used by the step, next, finish, until, etc. commands.
6275 @c Always use hardware breakpoints
6276 @c @item swbreak (default)
6279 @subsubsection Data Cache
6280 The data cache attributes set whether @value{GDBN} will cache target
6281 memory. While this generally improves performance by reducing debug
6282 protocol overhead, it can lead to incorrect results because @value{GDBN}
6283 does not know about volatile variables or memory mapped device
6288 Enable @value{GDBN} to cache target memory.
6290 Disable @value{GDBN} from caching target memory. This is the default.
6293 @c @subsubsection Memory Write Verification
6294 @c The memory write verification attributes set whether @value{GDBN}
6295 @c will re-reads data after each write to verify the write was successful.
6299 @c @item noverify (default)
6302 @node Dump/Restore Files
6303 @section Copy between memory and a file
6304 @cindex dump/restore files
6305 @cindex append data to a file
6306 @cindex dump data to a file
6307 @cindex restore data from a file
6309 You can use the commands @code{dump}, @code{append}, and
6310 @code{restore} to copy data between target memory and a file. The
6311 @code{dump} and @code{append} commands write data to a file, and the
6312 @code{restore} command reads data from a file back into the inferior's
6313 memory. Files may be in binary, Motorola S-record, Intel hex, or
6314 Tektronix Hex format; however, @value{GDBN} can only append to binary
6320 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6321 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
6322 Dump the contents of memory from @var{start_addr} to @var{end_addr},
6323 or the value of @var{expr}, to @var{filename} in the given format.
6325 The @var{format} parameter may be any one of:
6332 Motorola S-record format.
6334 Tektronix Hex format.
6337 @value{GDBN} uses the same definitions of these formats as the
6338 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
6339 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
6343 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6344 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
6345 Append the contents of memory from @var{start_addr} to @var{end_addr},
6346 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
6347 (@value{GDBN} can only append data to files in raw binary form.)
6350 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
6351 Restore the contents of file @var{filename} into memory. The
6352 @code{restore} command can automatically recognize any known @sc{bfd}
6353 file format, except for raw binary. To restore a raw binary file you
6354 must specify the optional keyword @code{binary} after the filename.
6356 If @var{bias} is non-zero, its value will be added to the addresses
6357 contained in the file. Binary files always start at address zero, so
6358 they will be restored at address @var{bias}. Other bfd files have
6359 a built-in location; they will be restored at offset @var{bias}
6362 If @var{start} and/or @var{end} are non-zero, then only data between
6363 file offset @var{start} and file offset @var{end} will be restored.
6364 These offsets are relative to the addresses in the file, before
6365 the @var{bias} argument is applied.
6369 @node Core File Generation
6370 @section How to Produce a Core File from Your Program
6371 @cindex dump core from inferior
6373 A @dfn{core file} or @dfn{core dump} is a file that records the memory
6374 image of a running process and its process status (register values
6375 etc.). Its primary use is post-mortem debugging of a program that
6376 crashed while it ran outside a debugger. A program that crashes
6377 automatically produces a core file, unless this feature is disabled by
6378 the user. @xref{Files}, for information on invoking @value{GDBN} in
6379 the post-mortem debugging mode.
6381 Occasionally, you may wish to produce a core file of the program you
6382 are debugging in order to preserve a snapshot of its state.
6383 @value{GDBN} has a special command for that.
6387 @kindex generate-core-file
6388 @item generate-core-file [@var{file}]
6389 @itemx gcore [@var{file}]
6390 Produce a core dump of the inferior process. The optional argument
6391 @var{file} specifies the file name where to put the core dump. If not
6392 specified, the file name defaults to @file{core.@var{pid}}, where
6393 @var{pid} is the inferior process ID.
6395 Note that this command is implemented only for some systems (as of
6396 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
6399 @node Character Sets
6400 @section Character Sets
6401 @cindex character sets
6403 @cindex translating between character sets
6404 @cindex host character set
6405 @cindex target character set
6407 If the program you are debugging uses a different character set to
6408 represent characters and strings than the one @value{GDBN} uses itself,
6409 @value{GDBN} can automatically translate between the character sets for
6410 you. The character set @value{GDBN} uses we call the @dfn{host
6411 character set}; the one the inferior program uses we call the
6412 @dfn{target character set}.
6414 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
6415 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
6416 remote protocol (@pxref{Remote,Remote Debugging}) to debug a program
6417 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
6418 then the host character set is Latin-1, and the target character set is
6419 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
6420 target-charset EBCDIC-US}, then @value{GDBN} translates between
6421 @sc{ebcdic} and Latin 1 as you print character or string values, or use
6422 character and string literals in expressions.
6424 @value{GDBN} has no way to automatically recognize which character set
6425 the inferior program uses; you must tell it, using the @code{set
6426 target-charset} command, described below.
6428 Here are the commands for controlling @value{GDBN}'s character set
6432 @item set target-charset @var{charset}
6433 @kindex set target-charset
6434 Set the current target character set to @var{charset}. We list the
6435 character set names @value{GDBN} recognizes below, but if you type
6436 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6437 list the target character sets it supports.
6441 @item set host-charset @var{charset}
6442 @kindex set host-charset
6443 Set the current host character set to @var{charset}.
6445 By default, @value{GDBN} uses a host character set appropriate to the
6446 system it is running on; you can override that default using the
6447 @code{set host-charset} command.
6449 @value{GDBN} can only use certain character sets as its host character
6450 set. We list the character set names @value{GDBN} recognizes below, and
6451 indicate which can be host character sets, but if you type
6452 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6453 list the host character sets it supports.
6455 @item set charset @var{charset}
6457 Set the current host and target character sets to @var{charset}. As
6458 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
6459 @value{GDBN} will list the name of the character sets that can be used
6460 for both host and target.
6464 @kindex show charset
6465 Show the names of the current host and target charsets.
6467 @itemx show host-charset
6468 @kindex show host-charset
6469 Show the name of the current host charset.
6471 @itemx show target-charset
6472 @kindex show target-charset
6473 Show the name of the current target charset.
6477 @value{GDBN} currently includes support for the following character
6483 @cindex ASCII character set
6484 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
6488 @cindex ISO 8859-1 character set
6489 @cindex ISO Latin 1 character set
6490 The ISO Latin 1 character set. This extends @sc{ascii} with accented
6491 characters needed for French, German, and Spanish. @value{GDBN} can use
6492 this as its host character set.
6496 @cindex EBCDIC character set
6497 @cindex IBM1047 character set
6498 Variants of the @sc{ebcdic} character set, used on some of IBM's
6499 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
6500 @value{GDBN} cannot use these as its host character set.
6504 Note that these are all single-byte character sets. More work inside
6505 GDB is needed to support multi-byte or variable-width character
6506 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
6508 Here is an example of @value{GDBN}'s character set support in action.
6509 Assume that the following source code has been placed in the file
6510 @file{charset-test.c}:
6516 = @{72, 101, 108, 108, 111, 44, 32, 119,
6517 111, 114, 108, 100, 33, 10, 0@};
6518 char ibm1047_hello[]
6519 = @{200, 133, 147, 147, 150, 107, 64, 166,
6520 150, 153, 147, 132, 90, 37, 0@};
6524 printf ("Hello, world!\n");
6528 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
6529 containing the string @samp{Hello, world!} followed by a newline,
6530 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
6532 We compile the program, and invoke the debugger on it:
6535 $ gcc -g charset-test.c -o charset-test
6536 $ gdb -nw charset-test
6537 GNU gdb 2001-12-19-cvs
6538 Copyright 2001 Free Software Foundation, Inc.
6543 We can use the @code{show charset} command to see what character sets
6544 @value{GDBN} is currently using to interpret and display characters and
6548 (@value{GDBP}) show charset
6549 The current host and target character set is `ISO-8859-1'.
6553 For the sake of printing this manual, let's use @sc{ascii} as our
6554 initial character set:
6556 (@value{GDBP}) set charset ASCII
6557 (@value{GDBP}) show charset
6558 The current host and target character set is `ASCII'.
6562 Let's assume that @sc{ascii} is indeed the correct character set for our
6563 host system --- in other words, let's assume that if @value{GDBN} prints
6564 characters using the @sc{ascii} character set, our terminal will display
6565 them properly. Since our current target character set is also
6566 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
6569 (@value{GDBP}) print ascii_hello
6570 $1 = 0x401698 "Hello, world!\n"
6571 (@value{GDBP}) print ascii_hello[0]
6576 @value{GDBN} uses the target character set for character and string
6577 literals you use in expressions:
6580 (@value{GDBP}) print '+'
6585 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
6588 @value{GDBN} relies on the user to tell it which character set the
6589 target program uses. If we print @code{ibm1047_hello} while our target
6590 character set is still @sc{ascii}, we get jibberish:
6593 (@value{GDBP}) print ibm1047_hello
6594 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
6595 (@value{GDBP}) print ibm1047_hello[0]
6600 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
6601 @value{GDBN} tells us the character sets it supports:
6604 (@value{GDBP}) set target-charset
6605 ASCII EBCDIC-US IBM1047 ISO-8859-1
6606 (@value{GDBP}) set target-charset
6609 We can select @sc{ibm1047} as our target character set, and examine the
6610 program's strings again. Now the @sc{ascii} string is wrong, but
6611 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
6612 target character set, @sc{ibm1047}, to the host character set,
6613 @sc{ascii}, and they display correctly:
6616 (@value{GDBP}) set target-charset IBM1047
6617 (@value{GDBP}) show charset
6618 The current host character set is `ASCII'.
6619 The current target character set is `IBM1047'.
6620 (@value{GDBP}) print ascii_hello
6621 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
6622 (@value{GDBP}) print ascii_hello[0]
6624 (@value{GDBP}) print ibm1047_hello
6625 $8 = 0x4016a8 "Hello, world!\n"
6626 (@value{GDBP}) print ibm1047_hello[0]
6631 As above, @value{GDBN} uses the target character set for character and
6632 string literals you use in expressions:
6635 (@value{GDBP}) print '+'
6640 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
6643 @node Caching Remote Data
6644 @section Caching Data of Remote Targets
6645 @cindex caching data of remote targets
6647 @value{GDBN} can cache data exchanged between the debugger and a
6648 remote target (@pxref{Remote}). Such caching generally improves
6649 performance, because it reduces the overhead of the remote protocol by
6650 bundling memory reads and writes into large chunks. Unfortunately,
6651 @value{GDBN} does not currently know anything about volatile
6652 registers, and thus data caching will produce incorrect results when
6653 volatile registers are in use.
6656 @kindex set remotecache
6657 @item set remotecache on
6658 @itemx set remotecache off
6659 Set caching state for remote targets. When @code{ON}, use data
6660 caching. By default, this option is @code{OFF}.
6662 @kindex show remotecache
6663 @item show remotecache
6664 Show the current state of data caching for remote targets.
6668 Print the information about the data cache performance. The
6669 information displayed includes: the dcache width and depth; and for
6670 each cache line, how many times it was referenced, and its data and
6671 state (dirty, bad, ok, etc.). This command is useful for debugging
6672 the data cache operation.
6677 @chapter C Preprocessor Macros
6679 Some languages, such as C and C@t{++}, provide a way to define and invoke
6680 ``preprocessor macros'' which expand into strings of tokens.
6681 @value{GDBN} can evaluate expressions containing macro invocations, show
6682 the result of macro expansion, and show a macro's definition, including
6683 where it was defined.
6685 You may need to compile your program specially to provide @value{GDBN}
6686 with information about preprocessor macros. Most compilers do not
6687 include macros in their debugging information, even when you compile
6688 with the @option{-g} flag. @xref{Compilation}.
6690 A program may define a macro at one point, remove that definition later,
6691 and then provide a different definition after that. Thus, at different
6692 points in the program, a macro may have different definitions, or have
6693 no definition at all. If there is a current stack frame, @value{GDBN}
6694 uses the macros in scope at that frame's source code line. Otherwise,
6695 @value{GDBN} uses the macros in scope at the current listing location;
6698 At the moment, @value{GDBN} does not support the @code{##}
6699 token-splicing operator, the @code{#} stringification operator, or
6700 variable-arity macros.
6702 Whenever @value{GDBN} evaluates an expression, it always expands any
6703 macro invocations present in the expression. @value{GDBN} also provides
6704 the following commands for working with macros explicitly.
6708 @kindex macro expand
6709 @cindex macro expansion, showing the results of preprocessor
6710 @cindex preprocessor macro expansion, showing the results of
6711 @cindex expanding preprocessor macros
6712 @item macro expand @var{expression}
6713 @itemx macro exp @var{expression}
6714 Show the results of expanding all preprocessor macro invocations in
6715 @var{expression}. Since @value{GDBN} simply expands macros, but does
6716 not parse the result, @var{expression} need not be a valid expression;
6717 it can be any string of tokens.
6720 @item macro expand-once @var{expression}
6721 @itemx macro exp1 @var{expression}
6722 @cindex expand macro once
6723 @i{(This command is not yet implemented.)} Show the results of
6724 expanding those preprocessor macro invocations that appear explicitly in
6725 @var{expression}. Macro invocations appearing in that expansion are
6726 left unchanged. This command allows you to see the effect of a
6727 particular macro more clearly, without being confused by further
6728 expansions. Since @value{GDBN} simply expands macros, but does not
6729 parse the result, @var{expression} need not be a valid expression; it
6730 can be any string of tokens.
6733 @cindex macro definition, showing
6734 @cindex definition, showing a macro's
6735 @item info macro @var{macro}
6736 Show the definition of the macro named @var{macro}, and describe the
6737 source location where that definition was established.
6739 @kindex macro define
6740 @cindex user-defined macros
6741 @cindex defining macros interactively
6742 @cindex macros, user-defined
6743 @item macro define @var{macro} @var{replacement-list}
6744 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
6745 @i{(This command is not yet implemented.)} Introduce a definition for a
6746 preprocessor macro named @var{macro}, invocations of which are replaced
6747 by the tokens given in @var{replacement-list}. The first form of this
6748 command defines an ``object-like'' macro, which takes no arguments; the
6749 second form defines a ``function-like'' macro, which takes the arguments
6750 given in @var{arglist}.
6752 A definition introduced by this command is in scope in every expression
6753 evaluated in @value{GDBN}, until it is removed with the @command{macro
6754 undef} command, described below. The definition overrides all
6755 definitions for @var{macro} present in the program being debugged, as
6756 well as any previous user-supplied definition.
6759 @item macro undef @var{macro}
6760 @i{(This command is not yet implemented.)} Remove any user-supplied
6761 definition for the macro named @var{macro}. This command only affects
6762 definitions provided with the @command{macro define} command, described
6763 above; it cannot remove definitions present in the program being
6768 @i{(This command is not yet implemented.)} List all the macros
6769 defined using the @code{macro define} command.
6772 @cindex macros, example of debugging with
6773 Here is a transcript showing the above commands in action. First, we
6774 show our source files:
6782 #define ADD(x) (M + x)
6787 printf ("Hello, world!\n");
6789 printf ("We're so creative.\n");
6791 printf ("Goodbye, world!\n");
6798 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
6799 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
6800 compiler includes information about preprocessor macros in the debugging
6804 $ gcc -gdwarf-2 -g3 sample.c -o sample
6808 Now, we start @value{GDBN} on our sample program:
6812 GNU gdb 2002-05-06-cvs
6813 Copyright 2002 Free Software Foundation, Inc.
6814 GDB is free software, @dots{}
6818 We can expand macros and examine their definitions, even when the
6819 program is not running. @value{GDBN} uses the current listing position
6820 to decide which macro definitions are in scope:
6823 (@value{GDBP}) list main
6826 5 #define ADD(x) (M + x)
6831 10 printf ("Hello, world!\n");
6833 12 printf ("We're so creative.\n");
6834 (@value{GDBP}) info macro ADD
6835 Defined at /home/jimb/gdb/macros/play/sample.c:5
6836 #define ADD(x) (M + x)
6837 (@value{GDBP}) info macro Q
6838 Defined at /home/jimb/gdb/macros/play/sample.h:1
6839 included at /home/jimb/gdb/macros/play/sample.c:2
6841 (@value{GDBP}) macro expand ADD(1)
6842 expands to: (42 + 1)
6843 (@value{GDBP}) macro expand-once ADD(1)
6844 expands to: once (M + 1)
6848 In the example above, note that @command{macro expand-once} expands only
6849 the macro invocation explicit in the original text --- the invocation of
6850 @code{ADD} --- but does not expand the invocation of the macro @code{M},
6851 which was introduced by @code{ADD}.
6853 Once the program is running, GDB uses the macro definitions in force at
6854 the source line of the current stack frame:
6857 (@value{GDBP}) break main
6858 Breakpoint 1 at 0x8048370: file sample.c, line 10.
6860 Starting program: /home/jimb/gdb/macros/play/sample
6862 Breakpoint 1, main () at sample.c:10
6863 10 printf ("Hello, world!\n");
6867 At line 10, the definition of the macro @code{N} at line 9 is in force:
6870 (@value{GDBP}) info macro N
6871 Defined at /home/jimb/gdb/macros/play/sample.c:9
6873 (@value{GDBP}) macro expand N Q M
6875 (@value{GDBP}) print N Q M
6880 As we step over directives that remove @code{N}'s definition, and then
6881 give it a new definition, @value{GDBN} finds the definition (or lack
6882 thereof) in force at each point:
6887 12 printf ("We're so creative.\n");
6888 (@value{GDBP}) info macro N
6889 The symbol `N' has no definition as a C/C++ preprocessor macro
6890 at /home/jimb/gdb/macros/play/sample.c:12
6893 14 printf ("Goodbye, world!\n");
6894 (@value{GDBP}) info macro N
6895 Defined at /home/jimb/gdb/macros/play/sample.c:13
6897 (@value{GDBP}) macro expand N Q M
6898 expands to: 1729 < 42
6899 (@value{GDBP}) print N Q M
6906 @chapter Tracepoints
6907 @c This chapter is based on the documentation written by Michael
6908 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
6911 In some applications, it is not feasible for the debugger to interrupt
6912 the program's execution long enough for the developer to learn
6913 anything helpful about its behavior. If the program's correctness
6914 depends on its real-time behavior, delays introduced by a debugger
6915 might cause the program to change its behavior drastically, or perhaps
6916 fail, even when the code itself is correct. It is useful to be able
6917 to observe the program's behavior without interrupting it.
6919 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
6920 specify locations in the program, called @dfn{tracepoints}, and
6921 arbitrary expressions to evaluate when those tracepoints are reached.
6922 Later, using the @code{tfind} command, you can examine the values
6923 those expressions had when the program hit the tracepoints. The
6924 expressions may also denote objects in memory---structures or arrays,
6925 for example---whose values @value{GDBN} should record; while visiting
6926 a particular tracepoint, you may inspect those objects as if they were
6927 in memory at that moment. However, because @value{GDBN} records these
6928 values without interacting with you, it can do so quickly and
6929 unobtrusively, hopefully not disturbing the program's behavior.
6931 The tracepoint facility is currently available only for remote
6932 targets. @xref{Targets}. In addition, your remote target must know how
6933 to collect trace data. This functionality is implemented in the remote
6934 stub; however, none of the stubs distributed with @value{GDBN} support
6935 tracepoints as of this writing.
6937 This chapter describes the tracepoint commands and features.
6941 * Analyze Collected Data::
6942 * Tracepoint Variables::
6945 @node Set Tracepoints
6946 @section Commands to Set Tracepoints
6948 Before running such a @dfn{trace experiment}, an arbitrary number of
6949 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
6950 tracepoint has a number assigned to it by @value{GDBN}. Like with
6951 breakpoints, tracepoint numbers are successive integers starting from
6952 one. Many of the commands associated with tracepoints take the
6953 tracepoint number as their argument, to identify which tracepoint to
6956 For each tracepoint, you can specify, in advance, some arbitrary set
6957 of data that you want the target to collect in the trace buffer when
6958 it hits that tracepoint. The collected data can include registers,
6959 local variables, or global data. Later, you can use @value{GDBN}
6960 commands to examine the values these data had at the time the
6963 This section describes commands to set tracepoints and associated
6964 conditions and actions.
6967 * Create and Delete Tracepoints::
6968 * Enable and Disable Tracepoints::
6969 * Tracepoint Passcounts::
6970 * Tracepoint Actions::
6971 * Listing Tracepoints::
6972 * Starting and Stopping Trace Experiment::
6975 @node Create and Delete Tracepoints
6976 @subsection Create and Delete Tracepoints
6979 @cindex set tracepoint
6982 The @code{trace} command is very similar to the @code{break} command.
6983 Its argument can be a source line, a function name, or an address in
6984 the target program. @xref{Set Breaks}. The @code{trace} command
6985 defines a tracepoint, which is a point in the target program where the
6986 debugger will briefly stop, collect some data, and then allow the
6987 program to continue. Setting a tracepoint or changing its commands
6988 doesn't take effect until the next @code{tstart} command; thus, you
6989 cannot change the tracepoint attributes once a trace experiment is
6992 Here are some examples of using the @code{trace} command:
6995 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
6997 (@value{GDBP}) @b{trace +2} // 2 lines forward
6999 (@value{GDBP}) @b{trace my_function} // first source line of function
7001 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
7003 (@value{GDBP}) @b{trace *0x2117c4} // an address
7007 You can abbreviate @code{trace} as @code{tr}.
7010 @cindex last tracepoint number
7011 @cindex recent tracepoint number
7012 @cindex tracepoint number
7013 The convenience variable @code{$tpnum} records the tracepoint number
7014 of the most recently set tracepoint.
7016 @kindex delete tracepoint
7017 @cindex tracepoint deletion
7018 @item delete tracepoint @r{[}@var{num}@r{]}
7019 Permanently delete one or more tracepoints. With no argument, the
7020 default is to delete all tracepoints.
7025 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
7027 (@value{GDBP}) @b{delete trace} // remove all tracepoints
7031 You can abbreviate this command as @code{del tr}.
7034 @node Enable and Disable Tracepoints
7035 @subsection Enable and Disable Tracepoints
7038 @kindex disable tracepoint
7039 @item disable tracepoint @r{[}@var{num}@r{]}
7040 Disable tracepoint @var{num}, or all tracepoints if no argument
7041 @var{num} is given. A disabled tracepoint will have no effect during
7042 the next trace experiment, but it is not forgotten. You can re-enable
7043 a disabled tracepoint using the @code{enable tracepoint} command.
7045 @kindex enable tracepoint
7046 @item enable tracepoint @r{[}@var{num}@r{]}
7047 Enable tracepoint @var{num}, or all tracepoints. The enabled
7048 tracepoints will become effective the next time a trace experiment is
7052 @node Tracepoint Passcounts
7053 @subsection Tracepoint Passcounts
7057 @cindex tracepoint pass count
7058 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
7059 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
7060 automatically stop a trace experiment. If a tracepoint's passcount is
7061 @var{n}, then the trace experiment will be automatically stopped on
7062 the @var{n}'th time that tracepoint is hit. If the tracepoint number
7063 @var{num} is not specified, the @code{passcount} command sets the
7064 passcount of the most recently defined tracepoint. If no passcount is
7065 given, the trace experiment will run until stopped explicitly by the
7071 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
7072 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
7074 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
7075 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
7076 (@value{GDBP}) @b{trace foo}
7077 (@value{GDBP}) @b{pass 3}
7078 (@value{GDBP}) @b{trace bar}
7079 (@value{GDBP}) @b{pass 2}
7080 (@value{GDBP}) @b{trace baz}
7081 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
7082 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
7083 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
7084 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
7088 @node Tracepoint Actions
7089 @subsection Tracepoint Action Lists
7093 @cindex tracepoint actions
7094 @item actions @r{[}@var{num}@r{]}
7095 This command will prompt for a list of actions to be taken when the
7096 tracepoint is hit. If the tracepoint number @var{num} is not
7097 specified, this command sets the actions for the one that was most
7098 recently defined (so that you can define a tracepoint and then say
7099 @code{actions} without bothering about its number). You specify the
7100 actions themselves on the following lines, one action at a time, and
7101 terminate the actions list with a line containing just @code{end}. So
7102 far, the only defined actions are @code{collect} and
7103 @code{while-stepping}.
7105 @cindex remove actions from a tracepoint
7106 To remove all actions from a tracepoint, type @samp{actions @var{num}}
7107 and follow it immediately with @samp{end}.
7110 (@value{GDBP}) @b{collect @var{data}} // collect some data
7112 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
7114 (@value{GDBP}) @b{end} // signals the end of actions.
7117 In the following example, the action list begins with @code{collect}
7118 commands indicating the things to be collected when the tracepoint is
7119 hit. Then, in order to single-step and collect additional data
7120 following the tracepoint, a @code{while-stepping} command is used,
7121 followed by the list of things to be collected while stepping. The
7122 @code{while-stepping} command is terminated by its own separate
7123 @code{end} command. Lastly, the action list is terminated by an
7127 (@value{GDBP}) @b{trace foo}
7128 (@value{GDBP}) @b{actions}
7129 Enter actions for tracepoint 1, one per line:
7138 @kindex collect @r{(tracepoints)}
7139 @item collect @var{expr1}, @var{expr2}, @dots{}
7140 Collect values of the given expressions when the tracepoint is hit.
7141 This command accepts a comma-separated list of any valid expressions.
7142 In addition to global, static, or local variables, the following
7143 special arguments are supported:
7147 collect all registers
7150 collect all function arguments
7153 collect all local variables.
7156 You can give several consecutive @code{collect} commands, each one
7157 with a single argument, or one @code{collect} command with several
7158 arguments separated by commas: the effect is the same.
7160 The command @code{info scope} (@pxref{Symbols, info scope}) is
7161 particularly useful for figuring out what data to collect.
7163 @kindex while-stepping @r{(tracepoints)}
7164 @item while-stepping @var{n}
7165 Perform @var{n} single-step traces after the tracepoint, collecting
7166 new data at each step. The @code{while-stepping} command is
7167 followed by the list of what to collect while stepping (followed by
7168 its own @code{end} command):
7172 > collect $regs, myglobal
7178 You may abbreviate @code{while-stepping} as @code{ws} or
7182 @node Listing Tracepoints
7183 @subsection Listing Tracepoints
7186 @kindex info tracepoints
7188 @cindex information about tracepoints
7189 @item info tracepoints @r{[}@var{num}@r{]}
7190 Display information about the tracepoint @var{num}. If you don't specify
7191 a tracepoint number, displays information about all the tracepoints
7192 defined so far. For each tracepoint, the following information is
7199 whether it is enabled or disabled
7203 its passcount as given by the @code{passcount @var{n}} command
7205 its step count as given by the @code{while-stepping @var{n}} command
7207 where in the source files is the tracepoint set
7209 its action list as given by the @code{actions} command
7213 (@value{GDBP}) @b{info trace}
7214 Num Enb Address PassC StepC What
7215 1 y 0x002117c4 0 0 <gdb_asm>
7216 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
7217 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
7222 This command can be abbreviated @code{info tp}.
7225 @node Starting and Stopping Trace Experiment
7226 @subsection Starting and Stopping Trace Experiment
7230 @cindex start a new trace experiment
7231 @cindex collected data discarded
7233 This command takes no arguments. It starts the trace experiment, and
7234 begins collecting data. This has the side effect of discarding all
7235 the data collected in the trace buffer during the previous trace
7239 @cindex stop a running trace experiment
7241 This command takes no arguments. It ends the trace experiment, and
7242 stops collecting data.
7244 @strong{Note}: a trace experiment and data collection may stop
7245 automatically if any tracepoint's passcount is reached
7246 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
7249 @cindex status of trace data collection
7250 @cindex trace experiment, status of
7252 This command displays the status of the current trace data
7256 Here is an example of the commands we described so far:
7259 (@value{GDBP}) @b{trace gdb_c_test}
7260 (@value{GDBP}) @b{actions}
7261 Enter actions for tracepoint #1, one per line.
7262 > collect $regs,$locals,$args
7267 (@value{GDBP}) @b{tstart}
7268 [time passes @dots{}]
7269 (@value{GDBP}) @b{tstop}
7273 @node Analyze Collected Data
7274 @section Using the collected data
7276 After the tracepoint experiment ends, you use @value{GDBN} commands
7277 for examining the trace data. The basic idea is that each tracepoint
7278 collects a trace @dfn{snapshot} every time it is hit and another
7279 snapshot every time it single-steps. All these snapshots are
7280 consecutively numbered from zero and go into a buffer, and you can
7281 examine them later. The way you examine them is to @dfn{focus} on a
7282 specific trace snapshot. When the remote stub is focused on a trace
7283 snapshot, it will respond to all @value{GDBN} requests for memory and
7284 registers by reading from the buffer which belongs to that snapshot,
7285 rather than from @emph{real} memory or registers of the program being
7286 debugged. This means that @strong{all} @value{GDBN} commands
7287 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
7288 behave as if we were currently debugging the program state as it was
7289 when the tracepoint occurred. Any requests for data that are not in
7290 the buffer will fail.
7293 * tfind:: How to select a trace snapshot
7294 * tdump:: How to display all data for a snapshot
7295 * save-tracepoints:: How to save tracepoints for a future run
7299 @subsection @code{tfind @var{n}}
7302 @cindex select trace snapshot
7303 @cindex find trace snapshot
7304 The basic command for selecting a trace snapshot from the buffer is
7305 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
7306 counting from zero. If no argument @var{n} is given, the next
7307 snapshot is selected.
7309 Here are the various forms of using the @code{tfind} command.
7313 Find the first snapshot in the buffer. This is a synonym for
7314 @code{tfind 0} (since 0 is the number of the first snapshot).
7317 Stop debugging trace snapshots, resume @emph{live} debugging.
7320 Same as @samp{tfind none}.
7323 No argument means find the next trace snapshot.
7326 Find the previous trace snapshot before the current one. This permits
7327 retracing earlier steps.
7329 @item tfind tracepoint @var{num}
7330 Find the next snapshot associated with tracepoint @var{num}. Search
7331 proceeds forward from the last examined trace snapshot. If no
7332 argument @var{num} is given, it means find the next snapshot collected
7333 for the same tracepoint as the current snapshot.
7335 @item tfind pc @var{addr}
7336 Find the next snapshot associated with the value @var{addr} of the
7337 program counter. Search proceeds forward from the last examined trace
7338 snapshot. If no argument @var{addr} is given, it means find the next
7339 snapshot with the same value of PC as the current snapshot.
7341 @item tfind outside @var{addr1}, @var{addr2}
7342 Find the next snapshot whose PC is outside the given range of
7345 @item tfind range @var{addr1}, @var{addr2}
7346 Find the next snapshot whose PC is between @var{addr1} and
7347 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
7349 @item tfind line @r{[}@var{file}:@r{]}@var{n}
7350 Find the next snapshot associated with the source line @var{n}. If
7351 the optional argument @var{file} is given, refer to line @var{n} in
7352 that source file. Search proceeds forward from the last examined
7353 trace snapshot. If no argument @var{n} is given, it means find the
7354 next line other than the one currently being examined; thus saying
7355 @code{tfind line} repeatedly can appear to have the same effect as
7356 stepping from line to line in a @emph{live} debugging session.
7359 The default arguments for the @code{tfind} commands are specifically
7360 designed to make it easy to scan through the trace buffer. For
7361 instance, @code{tfind} with no argument selects the next trace
7362 snapshot, and @code{tfind -} with no argument selects the previous
7363 trace snapshot. So, by giving one @code{tfind} command, and then
7364 simply hitting @key{RET} repeatedly you can examine all the trace
7365 snapshots in order. Or, by saying @code{tfind -} and then hitting
7366 @key{RET} repeatedly you can examine the snapshots in reverse order.
7367 The @code{tfind line} command with no argument selects the snapshot
7368 for the next source line executed. The @code{tfind pc} command with
7369 no argument selects the next snapshot with the same program counter
7370 (PC) as the current frame. The @code{tfind tracepoint} command with
7371 no argument selects the next trace snapshot collected by the same
7372 tracepoint as the current one.
7374 In addition to letting you scan through the trace buffer manually,
7375 these commands make it easy to construct @value{GDBN} scripts that
7376 scan through the trace buffer and print out whatever collected data
7377 you are interested in. Thus, if we want to examine the PC, FP, and SP
7378 registers from each trace frame in the buffer, we can say this:
7381 (@value{GDBP}) @b{tfind start}
7382 (@value{GDBP}) @b{while ($trace_frame != -1)}
7383 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
7384 $trace_frame, $pc, $sp, $fp
7388 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
7389 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
7390 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
7391 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
7392 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
7393 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
7394 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
7395 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
7396 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
7397 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
7398 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
7401 Or, if we want to examine the variable @code{X} at each source line in
7405 (@value{GDBP}) @b{tfind start}
7406 (@value{GDBP}) @b{while ($trace_frame != -1)}
7407 > printf "Frame %d, X == %d\n", $trace_frame, X
7417 @subsection @code{tdump}
7419 @cindex dump all data collected at tracepoint
7420 @cindex tracepoint data, display
7422 This command takes no arguments. It prints all the data collected at
7423 the current trace snapshot.
7426 (@value{GDBP}) @b{trace 444}
7427 (@value{GDBP}) @b{actions}
7428 Enter actions for tracepoint #2, one per line:
7429 > collect $regs, $locals, $args, gdb_long_test
7432 (@value{GDBP}) @b{tstart}
7434 (@value{GDBP}) @b{tfind line 444}
7435 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
7437 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
7439 (@value{GDBP}) @b{tdump}
7440 Data collected at tracepoint 2, trace frame 1:
7441 d0 0xc4aa0085 -995491707
7445 d4 0x71aea3d 119204413
7450 a1 0x3000668 50333288
7453 a4 0x3000698 50333336
7455 fp 0x30bf3c 0x30bf3c
7456 sp 0x30bf34 0x30bf34
7458 pc 0x20b2c8 0x20b2c8
7462 p = 0x20e5b4 "gdb-test"
7469 gdb_long_test = 17 '\021'
7474 @node save-tracepoints
7475 @subsection @code{save-tracepoints @var{filename}}
7476 @kindex save-tracepoints
7477 @cindex save tracepoints for future sessions
7479 This command saves all current tracepoint definitions together with
7480 their actions and passcounts, into a file @file{@var{filename}}
7481 suitable for use in a later debugging session. To read the saved
7482 tracepoint definitions, use the @code{source} command (@pxref{Command
7485 @node Tracepoint Variables
7486 @section Convenience Variables for Tracepoints
7487 @cindex tracepoint variables
7488 @cindex convenience variables for tracepoints
7491 @vindex $trace_frame
7492 @item (int) $trace_frame
7493 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
7494 snapshot is selected.
7497 @item (int) $tracepoint
7498 The tracepoint for the current trace snapshot.
7501 @item (int) $trace_line
7502 The line number for the current trace snapshot.
7505 @item (char []) $trace_file
7506 The source file for the current trace snapshot.
7509 @item (char []) $trace_func
7510 The name of the function containing @code{$tracepoint}.
7513 Note: @code{$trace_file} is not suitable for use in @code{printf},
7514 use @code{output} instead.
7516 Here's a simple example of using these convenience variables for
7517 stepping through all the trace snapshots and printing some of their
7521 (@value{GDBP}) @b{tfind start}
7523 (@value{GDBP}) @b{while $trace_frame != -1}
7524 > output $trace_file
7525 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
7531 @chapter Debugging Programs That Use Overlays
7534 If your program is too large to fit completely in your target system's
7535 memory, you can sometimes use @dfn{overlays} to work around this
7536 problem. @value{GDBN} provides some support for debugging programs that
7540 * How Overlays Work:: A general explanation of overlays.
7541 * Overlay Commands:: Managing overlays in @value{GDBN}.
7542 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
7543 mapped by asking the inferior.
7544 * Overlay Sample Program:: A sample program using overlays.
7547 @node How Overlays Work
7548 @section How Overlays Work
7549 @cindex mapped overlays
7550 @cindex unmapped overlays
7551 @cindex load address, overlay's
7552 @cindex mapped address
7553 @cindex overlay area
7555 Suppose you have a computer whose instruction address space is only 64
7556 kilobytes long, but which has much more memory which can be accessed by
7557 other means: special instructions, segment registers, or memory
7558 management hardware, for example. Suppose further that you want to
7559 adapt a program which is larger than 64 kilobytes to run on this system.
7561 One solution is to identify modules of your program which are relatively
7562 independent, and need not call each other directly; call these modules
7563 @dfn{overlays}. Separate the overlays from the main program, and place
7564 their machine code in the larger memory. Place your main program in
7565 instruction memory, but leave at least enough space there to hold the
7566 largest overlay as well.
7568 Now, to call a function located in an overlay, you must first copy that
7569 overlay's machine code from the large memory into the space set aside
7570 for it in the instruction memory, and then jump to its entry point
7573 @c NB: In the below the mapped area's size is greater or equal to the
7574 @c size of all overlays. This is intentional to remind the developer
7575 @c that overlays don't necessarily need to be the same size.
7579 Data Instruction Larger
7580 Address Space Address Space Address Space
7581 +-----------+ +-----------+ +-----------+
7583 +-----------+ +-----------+ +-----------+<-- overlay 1
7584 | program | | main | .----| overlay 1 | load address
7585 | variables | | program | | +-----------+
7586 | and heap | | | | | |
7587 +-----------+ | | | +-----------+<-- overlay 2
7588 | | +-----------+ | | | load address
7589 +-----------+ | | | .-| overlay 2 |
7591 mapped --->+-----------+ | | +-----------+
7593 | overlay | <-' | | |
7594 | area | <---' +-----------+<-- overlay 3
7595 | | <---. | | load address
7596 +-----------+ `--| overlay 3 |
7603 @anchor{A code overlay}A code overlay
7607 The diagram (@pxref{A code overlay}) shows a system with separate data
7608 and instruction address spaces. To map an overlay, the program copies
7609 its code from the larger address space to the instruction address space.
7610 Since the overlays shown here all use the same mapped address, only one
7611 may be mapped at a time. For a system with a single address space for
7612 data and instructions, the diagram would be similar, except that the
7613 program variables and heap would share an address space with the main
7614 program and the overlay area.
7616 An overlay loaded into instruction memory and ready for use is called a
7617 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
7618 instruction memory. An overlay not present (or only partially present)
7619 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
7620 is its address in the larger memory. The mapped address is also called
7621 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
7622 called the @dfn{load memory address}, or @dfn{LMA}.
7624 Unfortunately, overlays are not a completely transparent way to adapt a
7625 program to limited instruction memory. They introduce a new set of
7626 global constraints you must keep in mind as you design your program:
7631 Before calling or returning to a function in an overlay, your program
7632 must make sure that overlay is actually mapped. Otherwise, the call or
7633 return will transfer control to the right address, but in the wrong
7634 overlay, and your program will probably crash.
7637 If the process of mapping an overlay is expensive on your system, you
7638 will need to choose your overlays carefully to minimize their effect on
7639 your program's performance.
7642 The executable file you load onto your system must contain each
7643 overlay's instructions, appearing at the overlay's load address, not its
7644 mapped address. However, each overlay's instructions must be relocated
7645 and its symbols defined as if the overlay were at its mapped address.
7646 You can use GNU linker scripts to specify different load and relocation
7647 addresses for pieces of your program; see @ref{Overlay Description,,,
7648 ld.info, Using ld: the GNU linker}.
7651 The procedure for loading executable files onto your system must be able
7652 to load their contents into the larger address space as well as the
7653 instruction and data spaces.
7657 The overlay system described above is rather simple, and could be
7658 improved in many ways:
7663 If your system has suitable bank switch registers or memory management
7664 hardware, you could use those facilities to make an overlay's load area
7665 contents simply appear at their mapped address in instruction space.
7666 This would probably be faster than copying the overlay to its mapped
7667 area in the usual way.
7670 If your overlays are small enough, you could set aside more than one
7671 overlay area, and have more than one overlay mapped at a time.
7674 You can use overlays to manage data, as well as instructions. In
7675 general, data overlays are even less transparent to your design than
7676 code overlays: whereas code overlays only require care when you call or
7677 return to functions, data overlays require care every time you access
7678 the data. Also, if you change the contents of a data overlay, you
7679 must copy its contents back out to its load address before you can copy a
7680 different data overlay into the same mapped area.
7685 @node Overlay Commands
7686 @section Overlay Commands
7688 To use @value{GDBN}'s overlay support, each overlay in your program must
7689 correspond to a separate section of the executable file. The section's
7690 virtual memory address and load memory address must be the overlay's
7691 mapped and load addresses. Identifying overlays with sections allows
7692 @value{GDBN} to determine the appropriate address of a function or
7693 variable, depending on whether the overlay is mapped or not.
7695 @value{GDBN}'s overlay commands all start with the word @code{overlay};
7696 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
7701 Disable @value{GDBN}'s overlay support. When overlay support is
7702 disabled, @value{GDBN} assumes that all functions and variables are
7703 always present at their mapped addresses. By default, @value{GDBN}'s
7704 overlay support is disabled.
7706 @item overlay manual
7707 @cindex manual overlay debugging
7708 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
7709 relies on you to tell it which overlays are mapped, and which are not,
7710 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
7711 commands described below.
7713 @item overlay map-overlay @var{overlay}
7714 @itemx overlay map @var{overlay}
7715 @cindex map an overlay
7716 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
7717 be the name of the object file section containing the overlay. When an
7718 overlay is mapped, @value{GDBN} assumes it can find the overlay's
7719 functions and variables at their mapped addresses. @value{GDBN} assumes
7720 that any other overlays whose mapped ranges overlap that of
7721 @var{overlay} are now unmapped.
7723 @item overlay unmap-overlay @var{overlay}
7724 @itemx overlay unmap @var{overlay}
7725 @cindex unmap an overlay
7726 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
7727 must be the name of the object file section containing the overlay.
7728 When an overlay is unmapped, @value{GDBN} assumes it can find the
7729 overlay's functions and variables at their load addresses.
7732 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
7733 consults a data structure the overlay manager maintains in the inferior
7734 to see which overlays are mapped. For details, see @ref{Automatic
7737 @item overlay load-target
7739 @cindex reloading the overlay table
7740 Re-read the overlay table from the inferior. Normally, @value{GDBN}
7741 re-reads the table @value{GDBN} automatically each time the inferior
7742 stops, so this command should only be necessary if you have changed the
7743 overlay mapping yourself using @value{GDBN}. This command is only
7744 useful when using automatic overlay debugging.
7746 @item overlay list-overlays
7748 @cindex listing mapped overlays
7749 Display a list of the overlays currently mapped, along with their mapped
7750 addresses, load addresses, and sizes.
7754 Normally, when @value{GDBN} prints a code address, it includes the name
7755 of the function the address falls in:
7758 (@value{GDBP}) print main
7759 $3 = @{int ()@} 0x11a0 <main>
7762 When overlay debugging is enabled, @value{GDBN} recognizes code in
7763 unmapped overlays, and prints the names of unmapped functions with
7764 asterisks around them. For example, if @code{foo} is a function in an
7765 unmapped overlay, @value{GDBN} prints it this way:
7768 (@value{GDBP}) overlay list
7769 No sections are mapped.
7770 (@value{GDBP}) print foo
7771 $5 = @{int (int)@} 0x100000 <*foo*>
7774 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
7778 (@value{GDBP}) overlay list
7779 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
7780 mapped at 0x1016 - 0x104a
7781 (@value{GDBP}) print foo
7782 $6 = @{int (int)@} 0x1016 <foo>
7785 When overlay debugging is enabled, @value{GDBN} can find the correct
7786 address for functions and variables in an overlay, whether or not the
7787 overlay is mapped. This allows most @value{GDBN} commands, like
7788 @code{break} and @code{disassemble}, to work normally, even on unmapped
7789 code. However, @value{GDBN}'s breakpoint support has some limitations:
7793 @cindex breakpoints in overlays
7794 @cindex overlays, setting breakpoints in
7795 You can set breakpoints in functions in unmapped overlays, as long as
7796 @value{GDBN} can write to the overlay at its load address.
7798 @value{GDBN} can not set hardware or simulator-based breakpoints in
7799 unmapped overlays. However, if you set a breakpoint at the end of your
7800 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
7801 you are using manual overlay management), @value{GDBN} will re-set its
7802 breakpoints properly.
7806 @node Automatic Overlay Debugging
7807 @section Automatic Overlay Debugging
7808 @cindex automatic overlay debugging
7810 @value{GDBN} can automatically track which overlays are mapped and which
7811 are not, given some simple co-operation from the overlay manager in the
7812 inferior. If you enable automatic overlay debugging with the
7813 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
7814 looks in the inferior's memory for certain variables describing the
7815 current state of the overlays.
7817 Here are the variables your overlay manager must define to support
7818 @value{GDBN}'s automatic overlay debugging:
7822 @item @code{_ovly_table}:
7823 This variable must be an array of the following structures:
7828 /* The overlay's mapped address. */
7831 /* The size of the overlay, in bytes. */
7834 /* The overlay's load address. */
7837 /* Non-zero if the overlay is currently mapped;
7839 unsigned long mapped;
7843 @item @code{_novlys}:
7844 This variable must be a four-byte signed integer, holding the total
7845 number of elements in @code{_ovly_table}.
7849 To decide whether a particular overlay is mapped or not, @value{GDBN}
7850 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
7851 @code{lma} members equal the VMA and LMA of the overlay's section in the
7852 executable file. When @value{GDBN} finds a matching entry, it consults
7853 the entry's @code{mapped} member to determine whether the overlay is
7856 In addition, your overlay manager may define a function called
7857 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
7858 will silently set a breakpoint there. If the overlay manager then
7859 calls this function whenever it has changed the overlay table, this
7860 will enable @value{GDBN} to accurately keep track of which overlays
7861 are in program memory, and update any breakpoints that may be set
7862 in overlays. This will allow breakpoints to work even if the
7863 overlays are kept in ROM or other non-writable memory while they
7864 are not being executed.
7866 @node Overlay Sample Program
7867 @section Overlay Sample Program
7868 @cindex overlay example program
7870 When linking a program which uses overlays, you must place the overlays
7871 at their load addresses, while relocating them to run at their mapped
7872 addresses. To do this, you must write a linker script (@pxref{Overlay
7873 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
7874 since linker scripts are specific to a particular host system, target
7875 architecture, and target memory layout, this manual cannot provide
7876 portable sample code demonstrating @value{GDBN}'s overlay support.
7878 However, the @value{GDBN} source distribution does contain an overlaid
7879 program, with linker scripts for a few systems, as part of its test
7880 suite. The program consists of the following files from
7881 @file{gdb/testsuite/gdb.base}:
7885 The main program file.
7887 A simple overlay manager, used by @file{overlays.c}.
7892 Overlay modules, loaded and used by @file{overlays.c}.
7895 Linker scripts for linking the test program on the @code{d10v-elf}
7896 and @code{m32r-elf} targets.
7899 You can build the test program using the @code{d10v-elf} GCC
7900 cross-compiler like this:
7903 $ d10v-elf-gcc -g -c overlays.c
7904 $ d10v-elf-gcc -g -c ovlymgr.c
7905 $ d10v-elf-gcc -g -c foo.c
7906 $ d10v-elf-gcc -g -c bar.c
7907 $ d10v-elf-gcc -g -c baz.c
7908 $ d10v-elf-gcc -g -c grbx.c
7909 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
7910 baz.o grbx.o -Wl,-Td10v.ld -o overlays
7913 The build process is identical for any other architecture, except that
7914 you must substitute the appropriate compiler and linker script for the
7915 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
7919 @chapter Using @value{GDBN} with Different Languages
7922 Although programming languages generally have common aspects, they are
7923 rarely expressed in the same manner. For instance, in ANSI C,
7924 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
7925 Modula-2, it is accomplished by @code{p^}. Values can also be
7926 represented (and displayed) differently. Hex numbers in C appear as
7927 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
7929 @cindex working language
7930 Language-specific information is built into @value{GDBN} for some languages,
7931 allowing you to express operations like the above in your program's
7932 native language, and allowing @value{GDBN} to output values in a manner
7933 consistent with the syntax of your program's native language. The
7934 language you use to build expressions is called the @dfn{working
7938 * Setting:: Switching between source languages
7939 * Show:: Displaying the language
7940 * Checks:: Type and range checks
7941 * Supported languages:: Supported languages
7942 * Unsupported languages:: Unsupported languages
7946 @section Switching between source languages
7948 There are two ways to control the working language---either have @value{GDBN}
7949 set it automatically, or select it manually yourself. You can use the
7950 @code{set language} command for either purpose. On startup, @value{GDBN}
7951 defaults to setting the language automatically. The working language is
7952 used to determine how expressions you type are interpreted, how values
7955 In addition to the working language, every source file that
7956 @value{GDBN} knows about has its own working language. For some object
7957 file formats, the compiler might indicate which language a particular
7958 source file is in. However, most of the time @value{GDBN} infers the
7959 language from the name of the file. The language of a source file
7960 controls whether C@t{++} names are demangled---this way @code{backtrace} can
7961 show each frame appropriately for its own language. There is no way to
7962 set the language of a source file from within @value{GDBN}, but you can
7963 set the language associated with a filename extension. @xref{Show, ,
7964 Displaying the language}.
7966 This is most commonly a problem when you use a program, such
7967 as @code{cfront} or @code{f2c}, that generates C but is written in
7968 another language. In that case, make the
7969 program use @code{#line} directives in its C output; that way
7970 @value{GDBN} will know the correct language of the source code of the original
7971 program, and will display that source code, not the generated C code.
7974 * Filenames:: Filename extensions and languages.
7975 * Manually:: Setting the working language manually
7976 * Automatically:: Having @value{GDBN} infer the source language
7980 @subsection List of filename extensions and languages
7982 If a source file name ends in one of the following extensions, then
7983 @value{GDBN} infers that its language is the one indicated.
8004 Objective-C source file
8011 Modula-2 source file
8015 Assembler source file. This actually behaves almost like C, but
8016 @value{GDBN} does not skip over function prologues when stepping.
8019 In addition, you may set the language associated with a filename
8020 extension. @xref{Show, , Displaying the language}.
8023 @subsection Setting the working language
8025 If you allow @value{GDBN} to set the language automatically,
8026 expressions are interpreted the same way in your debugging session and
8029 @kindex set language
8030 If you wish, you may set the language manually. To do this, issue the
8031 command @samp{set language @var{lang}}, where @var{lang} is the name of
8033 @code{c} or @code{modula-2}.
8034 For a list of the supported languages, type @samp{set language}.
8036 Setting the language manually prevents @value{GDBN} from updating the working
8037 language automatically. This can lead to confusion if you try
8038 to debug a program when the working language is not the same as the
8039 source language, when an expression is acceptable to both
8040 languages---but means different things. For instance, if the current
8041 source file were written in C, and @value{GDBN} was parsing Modula-2, a
8049 might not have the effect you intended. In C, this means to add
8050 @code{b} and @code{c} and place the result in @code{a}. The result
8051 printed would be the value of @code{a}. In Modula-2, this means to compare
8052 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
8055 @subsection Having @value{GDBN} infer the source language
8057 To have @value{GDBN} set the working language automatically, use
8058 @samp{set language local} or @samp{set language auto}. @value{GDBN}
8059 then infers the working language. That is, when your program stops in a
8060 frame (usually by encountering a breakpoint), @value{GDBN} sets the
8061 working language to the language recorded for the function in that
8062 frame. If the language for a frame is unknown (that is, if the function
8063 or block corresponding to the frame was defined in a source file that
8064 does not have a recognized extension), the current working language is
8065 not changed, and @value{GDBN} issues a warning.
8067 This may not seem necessary for most programs, which are written
8068 entirely in one source language. However, program modules and libraries
8069 written in one source language can be used by a main program written in
8070 a different source language. Using @samp{set language auto} in this
8071 case frees you from having to set the working language manually.
8074 @section Displaying the language
8076 The following commands help you find out which language is the
8077 working language, and also what language source files were written in.
8081 @kindex show language
8082 Display the current working language. This is the
8083 language you can use with commands such as @code{print} to
8084 build and compute expressions that may involve variables in your program.
8087 @kindex info frame@r{, show the source language}
8088 Display the source language for this frame. This language becomes the
8089 working language if you use an identifier from this frame.
8090 @xref{Frame Info, ,Information about a frame}, to identify the other
8091 information listed here.
8094 @kindex info source@r{, show the source language}
8095 Display the source language of this source file.
8096 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
8097 information listed here.
8100 In unusual circumstances, you may have source files with extensions
8101 not in the standard list. You can then set the extension associated
8102 with a language explicitly:
8105 @item set extension-language @var{ext} @var{language}
8106 @kindex set extension-language
8107 Tell @value{GDBN} that source files with extension @var{ext} are to be
8108 assumed as written in the source language @var{language}.
8110 @item info extensions
8111 @kindex info extensions
8112 List all the filename extensions and the associated languages.
8116 @section Type and range checking
8119 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
8120 checking are included, but they do not yet have any effect. This
8121 section documents the intended facilities.
8123 @c FIXME remove warning when type/range code added
8125 Some languages are designed to guard you against making seemingly common
8126 errors through a series of compile- and run-time checks. These include
8127 checking the type of arguments to functions and operators, and making
8128 sure mathematical overflows are caught at run time. Checks such as
8129 these help to ensure a program's correctness once it has been compiled
8130 by eliminating type mismatches, and providing active checks for range
8131 errors when your program is running.
8133 @value{GDBN} can check for conditions like the above if you wish.
8134 Although @value{GDBN} does not check the statements in your program,
8135 it can check expressions entered directly into @value{GDBN} for
8136 evaluation via the @code{print} command, for example. As with the
8137 working language, @value{GDBN} can also decide whether or not to check
8138 automatically based on your program's source language.
8139 @xref{Supported languages, ,Supported languages}, for the default
8140 settings of supported languages.
8143 * Type Checking:: An overview of type checking
8144 * Range Checking:: An overview of range checking
8147 @cindex type checking
8148 @cindex checks, type
8150 @subsection An overview of type checking
8152 Some languages, such as Modula-2, are strongly typed, meaning that the
8153 arguments to operators and functions have to be of the correct type,
8154 otherwise an error occurs. These checks prevent type mismatch
8155 errors from ever causing any run-time problems. For example,
8163 The second example fails because the @code{CARDINAL} 1 is not
8164 type-compatible with the @code{REAL} 2.3.
8166 For the expressions you use in @value{GDBN} commands, you can tell the
8167 @value{GDBN} type checker to skip checking;
8168 to treat any mismatches as errors and abandon the expression;
8169 or to only issue warnings when type mismatches occur,
8170 but evaluate the expression anyway. When you choose the last of
8171 these, @value{GDBN} evaluates expressions like the second example above, but
8172 also issues a warning.
8174 Even if you turn type checking off, there may be other reasons
8175 related to type that prevent @value{GDBN} from evaluating an expression.
8176 For instance, @value{GDBN} does not know how to add an @code{int} and
8177 a @code{struct foo}. These particular type errors have nothing to do
8178 with the language in use, and usually arise from expressions, such as
8179 the one described above, which make little sense to evaluate anyway.
8181 Each language defines to what degree it is strict about type. For
8182 instance, both Modula-2 and C require the arguments to arithmetical
8183 operators to be numbers. In C, enumerated types and pointers can be
8184 represented as numbers, so that they are valid arguments to mathematical
8185 operators. @xref{Supported languages, ,Supported languages}, for further
8186 details on specific languages.
8188 @value{GDBN} provides some additional commands for controlling the type checker:
8190 @kindex set check type
8191 @kindex show check type
8193 @item set check type auto
8194 Set type checking on or off based on the current working language.
8195 @xref{Supported languages, ,Supported languages}, for the default settings for
8198 @item set check type on
8199 @itemx set check type off
8200 Set type checking on or off, overriding the default setting for the
8201 current working language. Issue a warning if the setting does not
8202 match the language default. If any type mismatches occur in
8203 evaluating an expression while type checking is on, @value{GDBN} prints a
8204 message and aborts evaluation of the expression.
8206 @item set check type warn
8207 Cause the type checker to issue warnings, but to always attempt to
8208 evaluate the expression. Evaluating the expression may still
8209 be impossible for other reasons. For example, @value{GDBN} cannot add
8210 numbers and structures.
8213 Show the current setting of the type checker, and whether or not @value{GDBN}
8214 is setting it automatically.
8217 @cindex range checking
8218 @cindex checks, range
8219 @node Range Checking
8220 @subsection An overview of range checking
8222 In some languages (such as Modula-2), it is an error to exceed the
8223 bounds of a type; this is enforced with run-time checks. Such range
8224 checking is meant to ensure program correctness by making sure
8225 computations do not overflow, or indices on an array element access do
8226 not exceed the bounds of the array.
8228 For expressions you use in @value{GDBN} commands, you can tell
8229 @value{GDBN} to treat range errors in one of three ways: ignore them,
8230 always treat them as errors and abandon the expression, or issue
8231 warnings but evaluate the expression anyway.
8233 A range error can result from numerical overflow, from exceeding an
8234 array index bound, or when you type a constant that is not a member
8235 of any type. Some languages, however, do not treat overflows as an
8236 error. In many implementations of C, mathematical overflow causes the
8237 result to ``wrap around'' to lower values---for example, if @var{m} is
8238 the largest integer value, and @var{s} is the smallest, then
8241 @var{m} + 1 @result{} @var{s}
8244 This, too, is specific to individual languages, and in some cases
8245 specific to individual compilers or machines. @xref{Supported languages, ,
8246 Supported languages}, for further details on specific languages.
8248 @value{GDBN} provides some additional commands for controlling the range checker:
8250 @kindex set check range
8251 @kindex show check range
8253 @item set check range auto
8254 Set range checking on or off based on the current working language.
8255 @xref{Supported languages, ,Supported languages}, for the default settings for
8258 @item set check range on
8259 @itemx set check range off
8260 Set range checking on or off, overriding the default setting for the
8261 current working language. A warning is issued if the setting does not
8262 match the language default. If a range error occurs and range checking is on,
8263 then a message is printed and evaluation of the expression is aborted.
8265 @item set check range warn
8266 Output messages when the @value{GDBN} range checker detects a range error,
8267 but attempt to evaluate the expression anyway. Evaluating the
8268 expression may still be impossible for other reasons, such as accessing
8269 memory that the process does not own (a typical example from many Unix
8273 Show the current setting of the range checker, and whether or not it is
8274 being set automatically by @value{GDBN}.
8277 @node Supported languages
8278 @section Supported languages
8280 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
8281 assembly, Modula-2, and Ada.
8282 @c This is false ...
8283 Some @value{GDBN} features may be used in expressions regardless of the
8284 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
8285 and the @samp{@{type@}addr} construct (@pxref{Expressions,
8286 ,Expressions}) can be used with the constructs of any supported
8289 The following sections detail to what degree each source language is
8290 supported by @value{GDBN}. These sections are not meant to be language
8291 tutorials or references, but serve only as a reference guide to what the
8292 @value{GDBN} expression parser accepts, and what input and output
8293 formats should look like for different languages. There are many good
8294 books written on each of these languages; please look to these for a
8295 language reference or tutorial.
8299 * Objective-C:: Objective-C
8302 * Modula-2:: Modula-2
8307 @subsection C and C@t{++}
8309 @cindex C and C@t{++}
8310 @cindex expressions in C or C@t{++}
8312 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
8313 to both languages. Whenever this is the case, we discuss those languages
8317 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
8318 @cindex @sc{gnu} C@t{++}
8319 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
8320 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
8321 effectively, you must compile your C@t{++} programs with a supported
8322 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
8323 compiler (@code{aCC}).
8325 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
8326 format; if it doesn't work on your system, try the stabs+ debugging
8327 format. You can select those formats explicitly with the @code{g++}
8328 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
8329 @xref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
8330 CC, gcc.info, Using @sc{gnu} CC}.
8333 * C Operators:: C and C@t{++} operators
8334 * C Constants:: C and C@t{++} constants
8335 * C plus plus expressions:: C@t{++} expressions
8336 * C Defaults:: Default settings for C and C@t{++}
8337 * C Checks:: C and C@t{++} type and range checks
8338 * Debugging C:: @value{GDBN} and C
8339 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
8343 @subsubsection C and C@t{++} operators
8345 @cindex C and C@t{++} operators
8347 Operators must be defined on values of specific types. For instance,
8348 @code{+} is defined on numbers, but not on structures. Operators are
8349 often defined on groups of types.
8351 For the purposes of C and C@t{++}, the following definitions hold:
8356 @emph{Integral types} include @code{int} with any of its storage-class
8357 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
8360 @emph{Floating-point types} include @code{float}, @code{double}, and
8361 @code{long double} (if supported by the target platform).
8364 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
8367 @emph{Scalar types} include all of the above.
8372 The following operators are supported. They are listed here
8373 in order of increasing precedence:
8377 The comma or sequencing operator. Expressions in a comma-separated list
8378 are evaluated from left to right, with the result of the entire
8379 expression being the last expression evaluated.
8382 Assignment. The value of an assignment expression is the value
8383 assigned. Defined on scalar types.
8386 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
8387 and translated to @w{@code{@var{a} = @var{a op b}}}.
8388 @w{@code{@var{op}=}} and @code{=} have the same precedence.
8389 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
8390 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
8393 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
8394 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
8398 Logical @sc{or}. Defined on integral types.
8401 Logical @sc{and}. Defined on integral types.
8404 Bitwise @sc{or}. Defined on integral types.
8407 Bitwise exclusive-@sc{or}. Defined on integral types.
8410 Bitwise @sc{and}. Defined on integral types.
8413 Equality and inequality. Defined on scalar types. The value of these
8414 expressions is 0 for false and non-zero for true.
8416 @item <@r{, }>@r{, }<=@r{, }>=
8417 Less than, greater than, less than or equal, greater than or equal.
8418 Defined on scalar types. The value of these expressions is 0 for false
8419 and non-zero for true.
8422 left shift, and right shift. Defined on integral types.
8425 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8428 Addition and subtraction. Defined on integral types, floating-point types and
8431 @item *@r{, }/@r{, }%
8432 Multiplication, division, and modulus. Multiplication and division are
8433 defined on integral and floating-point types. Modulus is defined on
8437 Increment and decrement. When appearing before a variable, the
8438 operation is performed before the variable is used in an expression;
8439 when appearing after it, the variable's value is used before the
8440 operation takes place.
8443 Pointer dereferencing. Defined on pointer types. Same precedence as
8447 Address operator. Defined on variables. Same precedence as @code{++}.
8449 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
8450 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
8451 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
8452 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
8456 Negative. Defined on integral and floating-point types. Same
8457 precedence as @code{++}.
8460 Logical negation. Defined on integral types. Same precedence as
8464 Bitwise complement operator. Defined on integral types. Same precedence as
8469 Structure member, and pointer-to-structure member. For convenience,
8470 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
8471 pointer based on the stored type information.
8472 Defined on @code{struct} and @code{union} data.
8475 Dereferences of pointers to members.
8478 Array indexing. @code{@var{a}[@var{i}]} is defined as
8479 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
8482 Function parameter list. Same precedence as @code{->}.
8485 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
8486 and @code{class} types.
8489 Doubled colons also represent the @value{GDBN} scope operator
8490 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
8494 If an operator is redefined in the user code, @value{GDBN} usually
8495 attempts to invoke the redefined version instead of using the operator's
8503 @subsubsection C and C@t{++} constants
8505 @cindex C and C@t{++} constants
8507 @value{GDBN} allows you to express the constants of C and C@t{++} in the
8512 Integer constants are a sequence of digits. Octal constants are
8513 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
8514 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
8515 @samp{l}, specifying that the constant should be treated as a
8519 Floating point constants are a sequence of digits, followed by a decimal
8520 point, followed by a sequence of digits, and optionally followed by an
8521 exponent. An exponent is of the form:
8522 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
8523 sequence of digits. The @samp{+} is optional for positive exponents.
8524 A floating-point constant may also end with a letter @samp{f} or
8525 @samp{F}, specifying that the constant should be treated as being of
8526 the @code{float} (as opposed to the default @code{double}) type; or with
8527 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
8531 Enumerated constants consist of enumerated identifiers, or their
8532 integral equivalents.
8535 Character constants are a single character surrounded by single quotes
8536 (@code{'}), or a number---the ordinal value of the corresponding character
8537 (usually its @sc{ascii} value). Within quotes, the single character may
8538 be represented by a letter or by @dfn{escape sequences}, which are of
8539 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
8540 of the character's ordinal value; or of the form @samp{\@var{x}}, where
8541 @samp{@var{x}} is a predefined special character---for example,
8542 @samp{\n} for newline.
8545 String constants are a sequence of character constants surrounded by
8546 double quotes (@code{"}). Any valid character constant (as described
8547 above) may appear. Double quotes within the string must be preceded by
8548 a backslash, so for instance @samp{"a\"b'c"} is a string of five
8552 Pointer constants are an integral value. You can also write pointers
8553 to constants using the C operator @samp{&}.
8556 Array constants are comma-separated lists surrounded by braces @samp{@{}
8557 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
8558 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
8559 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
8563 * C plus plus expressions::
8570 @node C plus plus expressions
8571 @subsubsection C@t{++} expressions
8573 @cindex expressions in C@t{++}
8574 @value{GDBN} expression handling can interpret most C@t{++} expressions.
8576 @cindex debugging C@t{++} programs
8577 @cindex C@t{++} compilers
8578 @cindex debug formats and C@t{++}
8579 @cindex @value{NGCC} and C@t{++}
8581 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
8582 proper compiler and the proper debug format. Currently, @value{GDBN}
8583 works best when debugging C@t{++} code that is compiled with
8584 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
8585 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
8586 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
8587 stabs+ as their default debug format, so you usually don't need to
8588 specify a debug format explicitly. Other compilers and/or debug formats
8589 are likely to work badly or not at all when using @value{GDBN} to debug
8595 @cindex member functions
8597 Member function calls are allowed; you can use expressions like
8600 count = aml->GetOriginal(x, y)
8603 @vindex this@r{, inside C@t{++} member functions}
8604 @cindex namespace in C@t{++}
8606 While a member function is active (in the selected stack frame), your
8607 expressions have the same namespace available as the member function;
8608 that is, @value{GDBN} allows implicit references to the class instance
8609 pointer @code{this} following the same rules as C@t{++}.
8611 @cindex call overloaded functions
8612 @cindex overloaded functions, calling
8613 @cindex type conversions in C@t{++}
8615 You can call overloaded functions; @value{GDBN} resolves the function
8616 call to the right definition, with some restrictions. @value{GDBN} does not
8617 perform overload resolution involving user-defined type conversions,
8618 calls to constructors, or instantiations of templates that do not exist
8619 in the program. It also cannot handle ellipsis argument lists or
8622 It does perform integral conversions and promotions, floating-point
8623 promotions, arithmetic conversions, pointer conversions, conversions of
8624 class objects to base classes, and standard conversions such as those of
8625 functions or arrays to pointers; it requires an exact match on the
8626 number of function arguments.
8628 Overload resolution is always performed, unless you have specified
8629 @code{set overload-resolution off}. @xref{Debugging C plus plus,
8630 ,@value{GDBN} features for C@t{++}}.
8632 You must specify @code{set overload-resolution off} in order to use an
8633 explicit function signature to call an overloaded function, as in
8635 p 'foo(char,int)'('x', 13)
8638 The @value{GDBN} command-completion facility can simplify this;
8639 see @ref{Completion, ,Command completion}.
8641 @cindex reference declarations
8643 @value{GDBN} understands variables declared as C@t{++} references; you can use
8644 them in expressions just as you do in C@t{++} source---they are automatically
8647 In the parameter list shown when @value{GDBN} displays a frame, the values of
8648 reference variables are not displayed (unlike other variables); this
8649 avoids clutter, since references are often used for large structures.
8650 The @emph{address} of a reference variable is always shown, unless
8651 you have specified @samp{set print address off}.
8654 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
8655 expressions can use it just as expressions in your program do. Since
8656 one scope may be defined in another, you can use @code{::} repeatedly if
8657 necessary, for example in an expression like
8658 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
8659 resolving name scope by reference to source files, in both C and C@t{++}
8660 debugging (@pxref{Variables, ,Program variables}).
8663 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
8664 calling virtual functions correctly, printing out virtual bases of
8665 objects, calling functions in a base subobject, casting objects, and
8666 invoking user-defined operators.
8669 @subsubsection C and C@t{++} defaults
8671 @cindex C and C@t{++} defaults
8673 If you allow @value{GDBN} to set type and range checking automatically, they
8674 both default to @code{off} whenever the working language changes to
8675 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
8676 selects the working language.
8678 If you allow @value{GDBN} to set the language automatically, it
8679 recognizes source files whose names end with @file{.c}, @file{.C}, or
8680 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
8681 these files, it sets the working language to C or C@t{++}.
8682 @xref{Automatically, ,Having @value{GDBN} infer the source language},
8683 for further details.
8685 @c Type checking is (a) primarily motivated by Modula-2, and (b)
8686 @c unimplemented. If (b) changes, it might make sense to let this node
8687 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
8690 @subsubsection C and C@t{++} type and range checks
8692 @cindex C and C@t{++} checks
8694 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
8695 is not used. However, if you turn type checking on, @value{GDBN}
8696 considers two variables type equivalent if:
8700 The two variables are structured and have the same structure, union, or
8704 The two variables have the same type name, or types that have been
8705 declared equivalent through @code{typedef}.
8708 @c leaving this out because neither J Gilmore nor R Pesch understand it.
8711 The two @code{struct}, @code{union}, or @code{enum} variables are
8712 declared in the same declaration. (Note: this may not be true for all C
8717 Range checking, if turned on, is done on mathematical operations. Array
8718 indices are not checked, since they are often used to index a pointer
8719 that is not itself an array.
8722 @subsubsection @value{GDBN} and C
8724 The @code{set print union} and @code{show print union} commands apply to
8725 the @code{union} type. When set to @samp{on}, any @code{union} that is
8726 inside a @code{struct} or @code{class} is also printed. Otherwise, it
8727 appears as @samp{@{...@}}.
8729 The @code{@@} operator aids in the debugging of dynamic arrays, formed
8730 with pointers and a memory allocation function. @xref{Expressions,
8734 * Debugging C plus plus::
8737 @node Debugging C plus plus
8738 @subsubsection @value{GDBN} features for C@t{++}
8740 @cindex commands for C@t{++}
8742 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
8743 designed specifically for use with C@t{++}. Here is a summary:
8746 @cindex break in overloaded functions
8747 @item @r{breakpoint menus}
8748 When you want a breakpoint in a function whose name is overloaded,
8749 @value{GDBN} breakpoint menus help you specify which function definition
8750 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
8752 @cindex overloading in C@t{++}
8753 @item rbreak @var{regex}
8754 Setting breakpoints using regular expressions is helpful for setting
8755 breakpoints on overloaded functions that are not members of any special
8757 @xref{Set Breaks, ,Setting breakpoints}.
8759 @cindex C@t{++} exception handling
8762 Debug C@t{++} exception handling using these commands. @xref{Set
8763 Catchpoints, , Setting catchpoints}.
8766 @item ptype @var{typename}
8767 Print inheritance relationships as well as other information for type
8769 @xref{Symbols, ,Examining the Symbol Table}.
8771 @cindex C@t{++} symbol display
8772 @item set print demangle
8773 @itemx show print demangle
8774 @itemx set print asm-demangle
8775 @itemx show print asm-demangle
8776 Control whether C@t{++} symbols display in their source form, both when
8777 displaying code as C@t{++} source and when displaying disassemblies.
8778 @xref{Print Settings, ,Print settings}.
8780 @item set print object
8781 @itemx show print object
8782 Choose whether to print derived (actual) or declared types of objects.
8783 @xref{Print Settings, ,Print settings}.
8785 @item set print vtbl
8786 @itemx show print vtbl
8787 Control the format for printing virtual function tables.
8788 @xref{Print Settings, ,Print settings}.
8789 (The @code{vtbl} commands do not work on programs compiled with the HP
8790 ANSI C@t{++} compiler (@code{aCC}).)
8792 @kindex set overload-resolution
8793 @cindex overloaded functions, overload resolution
8794 @item set overload-resolution on
8795 Enable overload resolution for C@t{++} expression evaluation. The default
8796 is on. For overloaded functions, @value{GDBN} evaluates the arguments
8797 and searches for a function whose signature matches the argument types,
8798 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
8799 expressions}, for details). If it cannot find a match, it emits a
8802 @item set overload-resolution off
8803 Disable overload resolution for C@t{++} expression evaluation. For
8804 overloaded functions that are not class member functions, @value{GDBN}
8805 chooses the first function of the specified name that it finds in the
8806 symbol table, whether or not its arguments are of the correct type. For
8807 overloaded functions that are class member functions, @value{GDBN}
8808 searches for a function whose signature @emph{exactly} matches the
8811 @kindex show overload-resolution
8812 @item show overload-resolution
8813 Show the current setting of overload resolution.
8815 @item @r{Overloaded symbol names}
8816 You can specify a particular definition of an overloaded symbol, using
8817 the same notation that is used to declare such symbols in C@t{++}: type
8818 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
8819 also use the @value{GDBN} command-line word completion facilities to list the
8820 available choices, or to finish the type list for you.
8821 @xref{Completion,, Command completion}, for details on how to do this.
8825 @subsection Objective-C
8828 This section provides information about some commands and command
8829 options that are useful for debugging Objective-C code. See also
8830 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
8831 few more commands specific to Objective-C support.
8834 * Method Names in Commands::
8835 * The Print Command with Objective-C::
8838 @node Method Names in Commands, The Print Command with Objective-C, Objective-C, Objective-C
8839 @subsubsection Method Names in Commands
8841 The following commands have been extended to accept Objective-C method
8842 names as line specifications:
8844 @kindex clear@r{, and Objective-C}
8845 @kindex break@r{, and Objective-C}
8846 @kindex info line@r{, and Objective-C}
8847 @kindex jump@r{, and Objective-C}
8848 @kindex list@r{, and Objective-C}
8852 @item @code{info line}
8857 A fully qualified Objective-C method name is specified as
8860 -[@var{Class} @var{methodName}]
8863 where the minus sign is used to indicate an instance method and a
8864 plus sign (not shown) is used to indicate a class method. The class
8865 name @var{Class} and method name @var{methodName} are enclosed in
8866 brackets, similar to the way messages are specified in Objective-C
8867 source code. For example, to set a breakpoint at the @code{create}
8868 instance method of class @code{Fruit} in the program currently being
8872 break -[Fruit create]
8875 To list ten program lines around the @code{initialize} class method,
8879 list +[NSText initialize]
8882 In the current version of @value{GDBN}, the plus or minus sign is
8883 required. In future versions of @value{GDBN}, the plus or minus
8884 sign will be optional, but you can use it to narrow the search. It
8885 is also possible to specify just a method name:
8891 You must specify the complete method name, including any colons. If
8892 your program's source files contain more than one @code{create} method,
8893 you'll be presented with a numbered list of classes that implement that
8894 method. Indicate your choice by number, or type @samp{0} to exit if
8897 As another example, to clear a breakpoint established at the
8898 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
8901 clear -[NSWindow makeKeyAndOrderFront:]
8904 @node The Print Command with Objective-C
8905 @subsubsection The Print Command With Objective-C
8906 @cindex Objective-C, print objects
8907 @kindex print-object
8908 @kindex po @r{(@code{print-object})}
8910 The print command has also been extended to accept methods. For example:
8913 print -[@var{object} hash]
8916 @cindex print an Objective-C object description
8917 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
8919 will tell @value{GDBN} to send the @code{hash} message to @var{object}
8920 and print the result. Also, an additional command has been added,
8921 @code{print-object} or @code{po} for short, which is meant to print
8922 the description of an object. However, this command may only work
8923 with certain Objective-C libraries that have a particular hook
8924 function, @code{_NSPrintForDebugger}, defined.
8928 @cindex Fortran-specific support in @value{GDBN}
8931 @cindex @code{COMMON} blocks, Fortran
8933 @item info common @r{[}@var{common-name}@r{]}
8934 This command prints the values contained in the Fortran @code{COMMON}
8935 block whose name is @var{common-name}. With no argument, the names of
8936 all @code{COMMON} blocks visible at current program location are
8940 Fortran symbols are usually case-insensitive, so @value{GDBN} by
8941 default uses case-insensitive matches for Fortran symbols. You can
8942 change that with the @samp{set case-insensitive} command, see
8943 @ref{Symbols}, for the details.
8948 @cindex Pascal support in @value{GDBN}, limitations
8949 Debugging Pascal programs which use sets, subranges, file variables, or
8950 nested functions does not currently work. @value{GDBN} does not support
8951 entering expressions, printing values, or similar features using Pascal
8954 The Pascal-specific command @code{set print pascal_static-members}
8955 controls whether static members of Pascal objects are displayed.
8956 @xref{Print Settings, pascal_static-members}.
8959 @subsection Modula-2
8961 @cindex Modula-2, @value{GDBN} support
8963 The extensions made to @value{GDBN} to support Modula-2 only support
8964 output from the @sc{gnu} Modula-2 compiler (which is currently being
8965 developed). Other Modula-2 compilers are not currently supported, and
8966 attempting to debug executables produced by them is most likely
8967 to give an error as @value{GDBN} reads in the executable's symbol
8970 @cindex expressions in Modula-2
8972 * M2 Operators:: Built-in operators
8973 * Built-In Func/Proc:: Built-in functions and procedures
8974 * M2 Constants:: Modula-2 constants
8975 * M2 Defaults:: Default settings for Modula-2
8976 * Deviations:: Deviations from standard Modula-2
8977 * M2 Checks:: Modula-2 type and range checks
8978 * M2 Scope:: The scope operators @code{::} and @code{.}
8979 * GDB/M2:: @value{GDBN} and Modula-2
8983 @subsubsection Operators
8984 @cindex Modula-2 operators
8986 Operators must be defined on values of specific types. For instance,
8987 @code{+} is defined on numbers, but not on structures. Operators are
8988 often defined on groups of types. For the purposes of Modula-2, the
8989 following definitions hold:
8994 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
8998 @emph{Character types} consist of @code{CHAR} and its subranges.
9001 @emph{Floating-point types} consist of @code{REAL}.
9004 @emph{Pointer types} consist of anything declared as @code{POINTER TO
9008 @emph{Scalar types} consist of all of the above.
9011 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
9014 @emph{Boolean types} consist of @code{BOOLEAN}.
9018 The following operators are supported, and appear in order of
9019 increasing precedence:
9023 Function argument or array index separator.
9026 Assignment. The value of @var{var} @code{:=} @var{value} is
9030 Less than, greater than on integral, floating-point, or enumerated
9034 Less than or equal to, greater than or equal to
9035 on integral, floating-point and enumerated types, or set inclusion on
9036 set types. Same precedence as @code{<}.
9038 @item =@r{, }<>@r{, }#
9039 Equality and two ways of expressing inequality, valid on scalar types.
9040 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
9041 available for inequality, since @code{#} conflicts with the script
9045 Set membership. Defined on set types and the types of their members.
9046 Same precedence as @code{<}.
9049 Boolean disjunction. Defined on boolean types.
9052 Boolean conjunction. Defined on boolean types.
9055 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9058 Addition and subtraction on integral and floating-point types, or union
9059 and difference on set types.
9062 Multiplication on integral and floating-point types, or set intersection
9066 Division on floating-point types, or symmetric set difference on set
9067 types. Same precedence as @code{*}.
9070 Integer division and remainder. Defined on integral types. Same
9071 precedence as @code{*}.
9074 Negative. Defined on @code{INTEGER} and @code{REAL} data.
9077 Pointer dereferencing. Defined on pointer types.
9080 Boolean negation. Defined on boolean types. Same precedence as
9084 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
9085 precedence as @code{^}.
9088 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
9091 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
9095 @value{GDBN} and Modula-2 scope operators.
9099 @emph{Warning:} Sets and their operations are not yet supported, so @value{GDBN}
9100 treats the use of the operator @code{IN}, or the use of operators
9101 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
9102 @code{<=}, and @code{>=} on sets as an error.
9106 @node Built-In Func/Proc
9107 @subsubsection Built-in functions and procedures
9108 @cindex Modula-2 built-ins
9110 Modula-2 also makes available several built-in procedures and functions.
9111 In describing these, the following metavariables are used:
9116 represents an @code{ARRAY} variable.
9119 represents a @code{CHAR} constant or variable.
9122 represents a variable or constant of integral type.
9125 represents an identifier that belongs to a set. Generally used in the
9126 same function with the metavariable @var{s}. The type of @var{s} should
9127 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
9130 represents a variable or constant of integral or floating-point type.
9133 represents a variable or constant of floating-point type.
9139 represents a variable.
9142 represents a variable or constant of one of many types. See the
9143 explanation of the function for details.
9146 All Modula-2 built-in procedures also return a result, described below.
9150 Returns the absolute value of @var{n}.
9153 If @var{c} is a lower case letter, it returns its upper case
9154 equivalent, otherwise it returns its argument.
9157 Returns the character whose ordinal value is @var{i}.
9160 Decrements the value in the variable @var{v} by one. Returns the new value.
9162 @item DEC(@var{v},@var{i})
9163 Decrements the value in the variable @var{v} by @var{i}. Returns the
9166 @item EXCL(@var{m},@var{s})
9167 Removes the element @var{m} from the set @var{s}. Returns the new
9170 @item FLOAT(@var{i})
9171 Returns the floating point equivalent of the integer @var{i}.
9174 Returns the index of the last member of @var{a}.
9177 Increments the value in the variable @var{v} by one. Returns the new value.
9179 @item INC(@var{v},@var{i})
9180 Increments the value in the variable @var{v} by @var{i}. Returns the
9183 @item INCL(@var{m},@var{s})
9184 Adds the element @var{m} to the set @var{s} if it is not already
9185 there. Returns the new set.
9188 Returns the maximum value of the type @var{t}.
9191 Returns the minimum value of the type @var{t}.
9194 Returns boolean TRUE if @var{i} is an odd number.
9197 Returns the ordinal value of its argument. For example, the ordinal
9198 value of a character is its @sc{ascii} value (on machines supporting the
9199 @sc{ascii} character set). @var{x} must be of an ordered type, which include
9200 integral, character and enumerated types.
9203 Returns the size of its argument. @var{x} can be a variable or a type.
9205 @item TRUNC(@var{r})
9206 Returns the integral part of @var{r}.
9208 @item VAL(@var{t},@var{i})
9209 Returns the member of the type @var{t} whose ordinal value is @var{i}.
9213 @emph{Warning:} Sets and their operations are not yet supported, so
9214 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
9218 @cindex Modula-2 constants
9220 @subsubsection Constants
9222 @value{GDBN} allows you to express the constants of Modula-2 in the following
9228 Integer constants are simply a sequence of digits. When used in an
9229 expression, a constant is interpreted to be type-compatible with the
9230 rest of the expression. Hexadecimal integers are specified by a
9231 trailing @samp{H}, and octal integers by a trailing @samp{B}.
9234 Floating point constants appear as a sequence of digits, followed by a
9235 decimal point and another sequence of digits. An optional exponent can
9236 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
9237 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
9238 digits of the floating point constant must be valid decimal (base 10)
9242 Character constants consist of a single character enclosed by a pair of
9243 like quotes, either single (@code{'}) or double (@code{"}). They may
9244 also be expressed by their ordinal value (their @sc{ascii} value, usually)
9245 followed by a @samp{C}.
9248 String constants consist of a sequence of characters enclosed by a
9249 pair of like quotes, either single (@code{'}) or double (@code{"}).
9250 Escape sequences in the style of C are also allowed. @xref{C
9251 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
9255 Enumerated constants consist of an enumerated identifier.
9258 Boolean constants consist of the identifiers @code{TRUE} and
9262 Pointer constants consist of integral values only.
9265 Set constants are not yet supported.
9269 @subsubsection Modula-2 defaults
9270 @cindex Modula-2 defaults
9272 If type and range checking are set automatically by @value{GDBN}, they
9273 both default to @code{on} whenever the working language changes to
9274 Modula-2. This happens regardless of whether you or @value{GDBN}
9275 selected the working language.
9277 If you allow @value{GDBN} to set the language automatically, then entering
9278 code compiled from a file whose name ends with @file{.mod} sets the
9279 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
9280 the language automatically}, for further details.
9283 @subsubsection Deviations from standard Modula-2
9284 @cindex Modula-2, deviations from
9286 A few changes have been made to make Modula-2 programs easier to debug.
9287 This is done primarily via loosening its type strictness:
9291 Unlike in standard Modula-2, pointer constants can be formed by
9292 integers. This allows you to modify pointer variables during
9293 debugging. (In standard Modula-2, the actual address contained in a
9294 pointer variable is hidden from you; it can only be modified
9295 through direct assignment to another pointer variable or expression that
9296 returned a pointer.)
9299 C escape sequences can be used in strings and characters to represent
9300 non-printable characters. @value{GDBN} prints out strings with these
9301 escape sequences embedded. Single non-printable characters are
9302 printed using the @samp{CHR(@var{nnn})} format.
9305 The assignment operator (@code{:=}) returns the value of its right-hand
9309 All built-in procedures both modify @emph{and} return their argument.
9313 @subsubsection Modula-2 type and range checks
9314 @cindex Modula-2 checks
9317 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
9320 @c FIXME remove warning when type/range checks added
9322 @value{GDBN} considers two Modula-2 variables type equivalent if:
9326 They are of types that have been declared equivalent via a @code{TYPE
9327 @var{t1} = @var{t2}} statement
9330 They have been declared on the same line. (Note: This is true of the
9331 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
9334 As long as type checking is enabled, any attempt to combine variables
9335 whose types are not equivalent is an error.
9337 Range checking is done on all mathematical operations, assignment, array
9338 index bounds, and all built-in functions and procedures.
9341 @subsubsection The scope operators @code{::} and @code{.}
9343 @cindex @code{.}, Modula-2 scope operator
9344 @cindex colon, doubled as scope operator
9346 @vindex colon-colon@r{, in Modula-2}
9347 @c Info cannot handle :: but TeX can.
9350 @vindex ::@r{, in Modula-2}
9353 There are a few subtle differences between the Modula-2 scope operator
9354 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
9359 @var{module} . @var{id}
9360 @var{scope} :: @var{id}
9364 where @var{scope} is the name of a module or a procedure,
9365 @var{module} the name of a module, and @var{id} is any declared
9366 identifier within your program, except another module.
9368 Using the @code{::} operator makes @value{GDBN} search the scope
9369 specified by @var{scope} for the identifier @var{id}. If it is not
9370 found in the specified scope, then @value{GDBN} searches all scopes
9371 enclosing the one specified by @var{scope}.
9373 Using the @code{.} operator makes @value{GDBN} search the current scope for
9374 the identifier specified by @var{id} that was imported from the
9375 definition module specified by @var{module}. With this operator, it is
9376 an error if the identifier @var{id} was not imported from definition
9377 module @var{module}, or if @var{id} is not an identifier in
9381 @subsubsection @value{GDBN} and Modula-2
9383 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
9384 Five subcommands of @code{set print} and @code{show print} apply
9385 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
9386 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
9387 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
9388 analogue in Modula-2.
9390 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
9391 with any language, is not useful with Modula-2. Its
9392 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
9393 created in Modula-2 as they can in C or C@t{++}. However, because an
9394 address can be specified by an integral constant, the construct
9395 @samp{@{@var{type}@}@var{adrexp}} is still useful.
9397 @cindex @code{#} in Modula-2
9398 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
9399 interpreted as the beginning of a comment. Use @code{<>} instead.
9405 The extensions made to @value{GDBN} for Ada only support
9406 output from the @sc{gnu} Ada (GNAT) compiler.
9407 Other Ada compilers are not currently supported, and
9408 attempting to debug executables produced by them is most likely
9412 @cindex expressions in Ada
9414 * Ada Mode Intro:: General remarks on the Ada syntax
9415 and semantics supported by Ada mode
9417 * Omissions from Ada:: Restrictions on the Ada expression syntax.
9418 * Additions to Ada:: Extensions of the Ada expression syntax.
9419 * Stopping Before Main Program:: Debugging the program during elaboration.
9420 * Ada Glitches:: Known peculiarities of Ada mode.
9423 @node Ada Mode Intro
9424 @subsubsection Introduction
9425 @cindex Ada mode, general
9427 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
9428 syntax, with some extensions.
9429 The philosophy behind the design of this subset is
9433 That @value{GDBN} should provide basic literals and access to operations for
9434 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
9435 leaving more sophisticated computations to subprograms written into the
9436 program (which therefore may be called from @value{GDBN}).
9439 That type safety and strict adherence to Ada language restrictions
9440 are not particularly important to the @value{GDBN} user.
9443 That brevity is important to the @value{GDBN} user.
9446 Thus, for brevity, the debugger acts as if there were
9447 implicit @code{with} and @code{use} clauses in effect for all user-written
9448 packages, making it unnecessary to fully qualify most names with
9449 their packages, regardless of context. Where this causes ambiguity,
9450 @value{GDBN} asks the user's intent.
9452 The debugger will start in Ada mode if it detects an Ada main program.
9453 As for other languages, it will enter Ada mode when stopped in a program that
9454 was translated from an Ada source file.
9456 While in Ada mode, you may use `@t{--}' for comments. This is useful
9457 mostly for documenting command files. The standard @value{GDBN} comment
9458 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
9459 middle (to allow based literals).
9461 The debugger supports limited overloading. Given a subprogram call in which
9462 the function symbol has multiple definitions, it will use the number of
9463 actual parameters and some information about their types to attempt to narrow
9464 the set of definitions. It also makes very limited use of context, preferring
9465 procedures to functions in the context of the @code{call} command, and
9466 functions to procedures elsewhere.
9468 @node Omissions from Ada
9469 @subsubsection Omissions from Ada
9470 @cindex Ada, omissions from
9472 Here are the notable omissions from the subset:
9476 Only a subset of the attributes are supported:
9480 @t{'First}, @t{'Last}, and @t{'Length}
9481 on array objects (not on types and subtypes).
9484 @t{'Min} and @t{'Max}.
9487 @t{'Pos} and @t{'Val}.
9493 @t{'Range} on array objects (not subtypes), but only as the right
9494 operand of the membership (@code{in}) operator.
9497 @t{'Access}, @t{'Unchecked_Access}, and
9498 @t{'Unrestricted_Access} (a GNAT extension).
9506 @code{Characters.Latin_1} are not available and
9507 concatenation is not implemented. Thus, escape characters in strings are
9508 not currently available.
9511 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
9512 equality of representations. They will generally work correctly
9513 for strings and arrays whose elements have integer or enumeration types.
9514 They may not work correctly for arrays whose element
9515 types have user-defined equality, for arrays of real values
9516 (in particular, IEEE-conformant floating point, because of negative
9517 zeroes and NaNs), and for arrays whose elements contain unused bits with
9518 indeterminate values.
9521 The other component-by-component array operations (@code{and}, @code{or},
9522 @code{xor}, @code{not}, and relational tests other than equality)
9523 are not implemented.
9526 There are no record or array aggregates.
9529 Calls to dispatching subprograms are not implemented.
9532 The overloading algorithm is much more limited (i.e., less selective)
9533 than that of real Ada. It makes only limited use of the context in which a subexpression
9534 appears to resolve its meaning, and it is much looser in its rules for allowing
9535 type matches. As a result, some function calls will be ambiguous, and the user
9536 will be asked to choose the proper resolution.
9539 The @code{new} operator is not implemented.
9542 Entry calls are not implemented.
9545 Aside from printing, arithmetic operations on the native VAX floating-point
9546 formats are not supported.
9549 It is not possible to slice a packed array.
9552 @node Additions to Ada
9553 @subsubsection Additions to Ada
9554 @cindex Ada, deviations from
9556 As it does for other languages, @value{GDBN} makes certain generic
9557 extensions to Ada (@pxref{Expressions}):
9561 If the expression @var{E} is a variable residing in memory
9562 (typically a local variable or array element) and @var{N} is
9563 a positive integer, then @code{@var{E}@@@var{N}} displays the values of
9564 @var{E} and the @var{N}-1 adjacent variables following it in memory as an array.
9565 In Ada, this operator is generally not necessary, since its prime use
9566 is in displaying parts of an array, and slicing will usually do this in Ada.
9567 However, there are occasional uses when debugging programs
9568 in which certain debugging information has been optimized away.
9571 @code{@var{B}::@var{var}} means ``the variable named @var{var} that appears
9572 in function or file @var{B}.'' When @var{B} is a file name, you must typically
9573 surround it in single quotes.
9576 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
9577 @var{type} that appears at address @var{addr}.''
9580 A name starting with @samp{$} is a convenience variable
9581 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
9584 In addition, @value{GDBN} provides a few other shortcuts and outright additions specific
9589 The assignment statement is allowed as an expression, returning
9590 its right-hand operand as its value. Thus, you may enter
9594 print A(tmp := y + 1)
9598 The semicolon is allowed as an ``operator,'' returning as its value
9599 the value of its right-hand operand.
9600 This allows, for example,
9601 complex conditional breaks:
9605 condition 1 (report(i); k += 1; A(k) > 100)
9609 Rather than use catenation and symbolic character names to introduce special
9610 characters into strings, one may instead use a special bracket notation,
9611 which is also used to print strings. A sequence of characters of the form
9612 @samp{["@var{XX}"]} within a string or character literal denotes the
9613 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
9614 sequence of characters @samp{["""]} also denotes a single quotation mark
9615 in strings. For example,
9617 "One line.["0a"]Next line.["0a"]"
9620 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF}) after each
9624 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
9625 @t{'Max} is optional (and is ignored in any case). For example, it is valid
9633 When printing arrays, @value{GDBN} uses positional notation when the
9634 array has a lower bound of 1, and uses a modified named notation otherwise.
9635 For example, a one-dimensional array of three integers with a lower bound of 3 might print as
9642 That is, in contrast to valid Ada, only the first component has a @code{=>}
9646 You may abbreviate attributes in expressions with any unique,
9647 multi-character subsequence of
9648 their names (an exact match gets preference).
9649 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
9650 in place of @t{a'length}.
9653 @cindex quoting Ada internal identifiers
9654 Since Ada is case-insensitive, the debugger normally maps identifiers you type
9655 to lower case. The GNAT compiler uses upper-case characters for
9656 some of its internal identifiers, which are normally of no interest to users.
9657 For the rare occasions when you actually have to look at them,
9658 enclose them in angle brackets to avoid the lower-case mapping.
9661 @value{GDBP} print <JMPBUF_SAVE>[0]
9665 Printing an object of class-wide type or dereferencing an
9666 access-to-class-wide value will display all the components of the object's
9667 specific type (as indicated by its run-time tag). Likewise, component
9668 selection on such a value will operate on the specific type of the
9673 @node Stopping Before Main Program
9674 @subsubsection Stopping at the Very Beginning
9676 @cindex breakpointing Ada elaboration code
9677 It is sometimes necessary to debug the program during elaboration, and
9678 before reaching the main procedure.
9679 As defined in the Ada Reference
9680 Manual, the elaboration code is invoked from a procedure called
9681 @code{adainit}. To run your program up to the beginning of
9682 elaboration, simply use the following two commands:
9683 @code{tbreak adainit} and @code{run}.
9686 @subsubsection Known Peculiarities of Ada Mode
9687 @cindex Ada, problems
9689 Besides the omissions listed previously (@pxref{Omissions from Ada}),
9690 we know of several problems with and limitations of Ada mode in
9692 some of which will be fixed with planned future releases of the debugger
9693 and the GNU Ada compiler.
9697 Currently, the debugger
9698 has insufficient information to determine whether certain pointers represent
9699 pointers to objects or the objects themselves.
9700 Thus, the user may have to tack an extra @code{.all} after an expression
9701 to get it printed properly.
9704 Static constants that the compiler chooses not to materialize as objects in
9705 storage are invisible to the debugger.
9708 Named parameter associations in function argument lists are ignored (the
9709 argument lists are treated as positional).
9712 Many useful library packages are currently invisible to the debugger.
9715 Fixed-point arithmetic, conversions, input, and output is carried out using
9716 floating-point arithmetic, and may give results that only approximate those on
9720 The type of the @t{'Address} attribute may not be @code{System.Address}.
9723 The GNAT compiler never generates the prefix @code{Standard} for any of
9724 the standard symbols defined by the Ada language. @value{GDBN} knows about
9725 this: it will strip the prefix from names when you use it, and will never
9726 look for a name you have so qualified among local symbols, nor match against
9727 symbols in other packages or subprograms. If you have
9728 defined entities anywhere in your program other than parameters and
9729 local variables whose simple names match names in @code{Standard},
9730 GNAT's lack of qualification here can cause confusion. When this happens,
9731 you can usually resolve the confusion
9732 by qualifying the problematic names with package
9733 @code{Standard} explicitly.
9736 @node Unsupported languages
9737 @section Unsupported languages
9739 @cindex unsupported languages
9740 @cindex minimal language
9741 In addition to the other fully-supported programming languages,
9742 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
9743 It does not represent a real programming language, but provides a set
9744 of capabilities close to what the C or assembly languages provide.
9745 This should allow most simple operations to be performed while debugging
9746 an application that uses a language currently not supported by @value{GDBN}.
9748 If the language is set to @code{auto}, @value{GDBN} will automatically
9749 select this language if the current frame corresponds to an unsupported
9753 @chapter Examining the Symbol Table
9755 The commands described in this chapter allow you to inquire about the
9756 symbols (names of variables, functions and types) defined in your
9757 program. This information is inherent in the text of your program and
9758 does not change as your program executes. @value{GDBN} finds it in your
9759 program's symbol table, in the file indicated when you started @value{GDBN}
9760 (@pxref{File Options, ,Choosing files}), or by one of the
9761 file-management commands (@pxref{Files, ,Commands to specify files}).
9763 @cindex symbol names
9764 @cindex names of symbols
9765 @cindex quoting names
9766 Occasionally, you may need to refer to symbols that contain unusual
9767 characters, which @value{GDBN} ordinarily treats as word delimiters. The
9768 most frequent case is in referring to static variables in other
9769 source files (@pxref{Variables,,Program variables}). File names
9770 are recorded in object files as debugging symbols, but @value{GDBN} would
9771 ordinarily parse a typical file name, like @file{foo.c}, as the three words
9772 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
9773 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
9780 looks up the value of @code{x} in the scope of the file @file{foo.c}.
9783 @cindex case-insensitive symbol names
9784 @cindex case sensitivity in symbol names
9785 @kindex set case-sensitive
9786 @item set case-sensitive on
9787 @itemx set case-sensitive off
9788 @itemx set case-sensitive auto
9789 Normally, when @value{GDBN} looks up symbols, it matches their names
9790 with case sensitivity determined by the current source language.
9791 Occasionally, you may wish to control that. The command @code{set
9792 case-sensitive} lets you do that by specifying @code{on} for
9793 case-sensitive matches or @code{off} for case-insensitive ones. If
9794 you specify @code{auto}, case sensitivity is reset to the default
9795 suitable for the source language. The default is case-sensitive
9796 matches for all languages except for Fortran, for which the default is
9797 case-insensitive matches.
9799 @kindex show case-sensitive
9800 @item show case-sensitive
9801 This command shows the current setting of case sensitivity for symbols
9804 @kindex info address
9805 @cindex address of a symbol
9806 @item info address @var{symbol}
9807 Describe where the data for @var{symbol} is stored. For a register
9808 variable, this says which register it is kept in. For a non-register
9809 local variable, this prints the stack-frame offset at which the variable
9812 Note the contrast with @samp{print &@var{symbol}}, which does not work
9813 at all for a register variable, and for a stack local variable prints
9814 the exact address of the current instantiation of the variable.
9817 @cindex symbol from address
9818 @cindex closest symbol and offset for an address
9819 @item info symbol @var{addr}
9820 Print the name of a symbol which is stored at the address @var{addr}.
9821 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
9822 nearest symbol and an offset from it:
9825 (@value{GDBP}) info symbol 0x54320
9826 _initialize_vx + 396 in section .text
9830 This is the opposite of the @code{info address} command. You can use
9831 it to find out the name of a variable or a function given its address.
9834 @item whatis @var{expr}
9835 Print the data type of expression @var{expr}. @var{expr} is not
9836 actually evaluated, and any side-effecting operations (such as
9837 assignments or function calls) inside it do not take place.
9838 @xref{Expressions, ,Expressions}.
9841 Print the data type of @code{$}, the last value in the value history.
9844 @item ptype @var{typename}
9845 Print a description of data type @var{typename}. @var{typename} may be
9846 the name of a type, or for C code it may have the form @samp{class
9847 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
9848 @var{union-tag}} or @samp{enum @var{enum-tag}}.
9850 @item ptype @var{expr}
9852 Print a description of the type of expression @var{expr}. @code{ptype}
9853 differs from @code{whatis} by printing a detailed description, instead
9854 of just the name of the type.
9856 For example, for this variable declaration:
9859 struct complex @{double real; double imag;@} v;
9863 the two commands give this output:
9867 (@value{GDBP}) whatis v
9868 type = struct complex
9869 (@value{GDBP}) ptype v
9870 type = struct complex @{
9878 As with @code{whatis}, using @code{ptype} without an argument refers to
9879 the type of @code{$}, the last value in the value history.
9882 @item info types @var{regexp}
9884 Print a brief description of all types whose names match the regular
9885 expression @var{regexp} (or all types in your program, if you supply
9886 no argument). Each complete typename is matched as though it were a
9887 complete line; thus, @samp{i type value} gives information on all
9888 types in your program whose names include the string @code{value}, but
9889 @samp{i type ^value$} gives information only on types whose complete
9890 name is @code{value}.
9892 This command differs from @code{ptype} in two ways: first, like
9893 @code{whatis}, it does not print a detailed description; second, it
9894 lists all source files where a type is defined.
9897 @cindex local variables
9898 @item info scope @var{location}
9899 List all the variables local to a particular scope. This command
9900 accepts a @var{location} argument---a function name, a source line, or
9901 an address preceded by a @samp{*}, and prints all the variables local
9902 to the scope defined by that location. For example:
9905 (@value{GDBP}) @b{info scope command_line_handler}
9906 Scope for command_line_handler:
9907 Symbol rl is an argument at stack/frame offset 8, length 4.
9908 Symbol linebuffer is in static storage at address 0x150a18, length 4.
9909 Symbol linelength is in static storage at address 0x150a1c, length 4.
9910 Symbol p is a local variable in register $esi, length 4.
9911 Symbol p1 is a local variable in register $ebx, length 4.
9912 Symbol nline is a local variable in register $edx, length 4.
9913 Symbol repeat is a local variable at frame offset -8, length 4.
9917 This command is especially useful for determining what data to collect
9918 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
9923 Show information about the current source file---that is, the source file for
9924 the function containing the current point of execution:
9927 the name of the source file, and the directory containing it,
9929 the directory it was compiled in,
9931 its length, in lines,
9933 which programming language it is written in,
9935 whether the executable includes debugging information for that file, and
9936 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
9938 whether the debugging information includes information about
9939 preprocessor macros.
9943 @kindex info sources
9945 Print the names of all source files in your program for which there is
9946 debugging information, organized into two lists: files whose symbols
9947 have already been read, and files whose symbols will be read when needed.
9949 @kindex info functions
9950 @item info functions
9951 Print the names and data types of all defined functions.
9953 @item info functions @var{regexp}
9954 Print the names and data types of all defined functions
9955 whose names contain a match for regular expression @var{regexp}.
9956 Thus, @samp{info fun step} finds all functions whose names
9957 include @code{step}; @samp{info fun ^step} finds those whose names
9958 start with @code{step}. If a function name contains characters
9959 that conflict with the regular expression language (eg.
9960 @samp{operator*()}), they may be quoted with a backslash.
9962 @kindex info variables
9963 @item info variables
9964 Print the names and data types of all variables that are declared
9965 outside of functions (i.e.@: excluding local variables).
9967 @item info variables @var{regexp}
9968 Print the names and data types of all variables (except for local
9969 variables) whose names contain a match for regular expression
9972 @kindex info classes
9973 @cindex Objective-C, classes and selectors
9975 @itemx info classes @var{regexp}
9976 Display all Objective-C classes in your program, or
9977 (with the @var{regexp} argument) all those matching a particular regular
9980 @kindex info selectors
9981 @item info selectors
9982 @itemx info selectors @var{regexp}
9983 Display all Objective-C selectors in your program, or
9984 (with the @var{regexp} argument) all those matching a particular regular
9988 This was never implemented.
9989 @kindex info methods
9991 @itemx info methods @var{regexp}
9992 The @code{info methods} command permits the user to examine all defined
9993 methods within C@t{++} program, or (with the @var{regexp} argument) a
9994 specific set of methods found in the various C@t{++} classes. Many
9995 C@t{++} classes provide a large number of methods. Thus, the output
9996 from the @code{ptype} command can be overwhelming and hard to use. The
9997 @code{info-methods} command filters the methods, printing only those
9998 which match the regular-expression @var{regexp}.
10001 @cindex reloading symbols
10002 Some systems allow individual object files that make up your program to
10003 be replaced without stopping and restarting your program. For example,
10004 in VxWorks you can simply recompile a defective object file and keep on
10005 running. If you are running on one of these systems, you can allow
10006 @value{GDBN} to reload the symbols for automatically relinked modules:
10009 @kindex set symbol-reloading
10010 @item set symbol-reloading on
10011 Replace symbol definitions for the corresponding source file when an
10012 object file with a particular name is seen again.
10014 @item set symbol-reloading off
10015 Do not replace symbol definitions when encountering object files of the
10016 same name more than once. This is the default state; if you are not
10017 running on a system that permits automatic relinking of modules, you
10018 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
10019 may discard symbols when linking large programs, that may contain
10020 several modules (from different directories or libraries) with the same
10023 @kindex show symbol-reloading
10024 @item show symbol-reloading
10025 Show the current @code{on} or @code{off} setting.
10028 @cindex opaque data types
10029 @kindex set opaque-type-resolution
10030 @item set opaque-type-resolution on
10031 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
10032 declared as a pointer to a @code{struct}, @code{class}, or
10033 @code{union}---for example, @code{struct MyType *}---that is used in one
10034 source file although the full declaration of @code{struct MyType} is in
10035 another source file. The default is on.
10037 A change in the setting of this subcommand will not take effect until
10038 the next time symbols for a file are loaded.
10040 @item set opaque-type-resolution off
10041 Tell @value{GDBN} not to resolve opaque types. In this case, the type
10042 is printed as follows:
10044 @{<no data fields>@}
10047 @kindex show opaque-type-resolution
10048 @item show opaque-type-resolution
10049 Show whether opaque types are resolved or not.
10051 @kindex maint print symbols
10052 @cindex symbol dump
10053 @kindex maint print psymbols
10054 @cindex partial symbol dump
10055 @item maint print symbols @var{filename}
10056 @itemx maint print psymbols @var{filename}
10057 @itemx maint print msymbols @var{filename}
10058 Write a dump of debugging symbol data into the file @var{filename}.
10059 These commands are used to debug the @value{GDBN} symbol-reading code. Only
10060 symbols with debugging data are included. If you use @samp{maint print
10061 symbols}, @value{GDBN} includes all the symbols for which it has already
10062 collected full details: that is, @var{filename} reflects symbols for
10063 only those files whose symbols @value{GDBN} has read. You can use the
10064 command @code{info sources} to find out which files these are. If you
10065 use @samp{maint print psymbols} instead, the dump shows information about
10066 symbols that @value{GDBN} only knows partially---that is, symbols defined in
10067 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
10068 @samp{maint print msymbols} dumps just the minimal symbol information
10069 required for each object file from which @value{GDBN} has read some symbols.
10070 @xref{Files, ,Commands to specify files}, for a discussion of how
10071 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
10073 @kindex maint info symtabs
10074 @kindex maint info psymtabs
10075 @cindex listing @value{GDBN}'s internal symbol tables
10076 @cindex symbol tables, listing @value{GDBN}'s internal
10077 @cindex full symbol tables, listing @value{GDBN}'s internal
10078 @cindex partial symbol tables, listing @value{GDBN}'s internal
10079 @item maint info symtabs @r{[} @var{regexp} @r{]}
10080 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
10082 List the @code{struct symtab} or @code{struct partial_symtab}
10083 structures whose names match @var{regexp}. If @var{regexp} is not
10084 given, list them all. The output includes expressions which you can
10085 copy into a @value{GDBN} debugging this one to examine a particular
10086 structure in more detail. For example:
10089 (@value{GDBP}) maint info psymtabs dwarf2read
10090 @{ objfile /home/gnu/build/gdb/gdb
10091 ((struct objfile *) 0x82e69d0)
10092 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
10093 ((struct partial_symtab *) 0x8474b10)
10096 text addresses 0x814d3c8 -- 0x8158074
10097 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
10098 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
10099 dependencies (none)
10102 (@value{GDBP}) maint info symtabs
10106 We see that there is one partial symbol table whose filename contains
10107 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
10108 and we see that @value{GDBN} has not read in any symtabs yet at all.
10109 If we set a breakpoint on a function, that will cause @value{GDBN} to
10110 read the symtab for the compilation unit containing that function:
10113 (@value{GDBP}) break dwarf2_psymtab_to_symtab
10114 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
10116 (@value{GDBP}) maint info symtabs
10117 @{ objfile /home/gnu/build/gdb/gdb
10118 ((struct objfile *) 0x82e69d0)
10119 @{ symtab /home/gnu/src/gdb/dwarf2read.c
10120 ((struct symtab *) 0x86c1f38)
10123 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
10124 debugformat DWARF 2
10133 @chapter Altering Execution
10135 Once you think you have found an error in your program, you might want to
10136 find out for certain whether correcting the apparent error would lead to
10137 correct results in the rest of the run. You can find the answer by
10138 experiment, using the @value{GDBN} features for altering execution of the
10141 For example, you can store new values into variables or memory
10142 locations, give your program a signal, restart it at a different
10143 address, or even return prematurely from a function.
10146 * Assignment:: Assignment to variables
10147 * Jumping:: Continuing at a different address
10148 * Signaling:: Giving your program a signal
10149 * Returning:: Returning from a function
10150 * Calling:: Calling your program's functions
10151 * Patching:: Patching your program
10155 @section Assignment to variables
10158 @cindex setting variables
10159 To alter the value of a variable, evaluate an assignment expression.
10160 @xref{Expressions, ,Expressions}. For example,
10167 stores the value 4 into the variable @code{x}, and then prints the
10168 value of the assignment expression (which is 4).
10169 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
10170 information on operators in supported languages.
10172 @kindex set variable
10173 @cindex variables, setting
10174 If you are not interested in seeing the value of the assignment, use the
10175 @code{set} command instead of the @code{print} command. @code{set} is
10176 really the same as @code{print} except that the expression's value is
10177 not printed and is not put in the value history (@pxref{Value History,
10178 ,Value history}). The expression is evaluated only for its effects.
10180 If the beginning of the argument string of the @code{set} command
10181 appears identical to a @code{set} subcommand, use the @code{set
10182 variable} command instead of just @code{set}. This command is identical
10183 to @code{set} except for its lack of subcommands. For example, if your
10184 program has a variable @code{width}, you get an error if you try to set
10185 a new value with just @samp{set width=13}, because @value{GDBN} has the
10186 command @code{set width}:
10189 (@value{GDBP}) whatis width
10191 (@value{GDBP}) p width
10193 (@value{GDBP}) set width=47
10194 Invalid syntax in expression.
10198 The invalid expression, of course, is @samp{=47}. In
10199 order to actually set the program's variable @code{width}, use
10202 (@value{GDBP}) set var width=47
10205 Because the @code{set} command has many subcommands that can conflict
10206 with the names of program variables, it is a good idea to use the
10207 @code{set variable} command instead of just @code{set}. For example, if
10208 your program has a variable @code{g}, you run into problems if you try
10209 to set a new value with just @samp{set g=4}, because @value{GDBN} has
10210 the command @code{set gnutarget}, abbreviated @code{set g}:
10214 (@value{GDBP}) whatis g
10218 (@value{GDBP}) set g=4
10222 The program being debugged has been started already.
10223 Start it from the beginning? (y or n) y
10224 Starting program: /home/smith/cc_progs/a.out
10225 "/home/smith/cc_progs/a.out": can't open to read symbols:
10226 Invalid bfd target.
10227 (@value{GDBP}) show g
10228 The current BFD target is "=4".
10233 The program variable @code{g} did not change, and you silently set the
10234 @code{gnutarget} to an invalid value. In order to set the variable
10238 (@value{GDBP}) set var g=4
10241 @value{GDBN} allows more implicit conversions in assignments than C; you can
10242 freely store an integer value into a pointer variable or vice versa,
10243 and you can convert any structure to any other structure that is the
10244 same length or shorter.
10245 @comment FIXME: how do structs align/pad in these conversions?
10246 @comment /doc@cygnus.com 18dec1990
10248 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
10249 construct to generate a value of specified type at a specified address
10250 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
10251 to memory location @code{0x83040} as an integer (which implies a certain size
10252 and representation in memory), and
10255 set @{int@}0x83040 = 4
10259 stores the value 4 into that memory location.
10262 @section Continuing at a different address
10264 Ordinarily, when you continue your program, you do so at the place where
10265 it stopped, with the @code{continue} command. You can instead continue at
10266 an address of your own choosing, with the following commands:
10270 @item jump @var{linespec}
10271 Resume execution at line @var{linespec}. Execution stops again
10272 immediately if there is a breakpoint there. @xref{List, ,Printing
10273 source lines}, for a description of the different forms of
10274 @var{linespec}. It is common practice to use the @code{tbreak} command
10275 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
10278 The @code{jump} command does not change the current stack frame, or
10279 the stack pointer, or the contents of any memory location or any
10280 register other than the program counter. If line @var{linespec} is in
10281 a different function from the one currently executing, the results may
10282 be bizarre if the two functions expect different patterns of arguments or
10283 of local variables. For this reason, the @code{jump} command requests
10284 confirmation if the specified line is not in the function currently
10285 executing. However, even bizarre results are predictable if you are
10286 well acquainted with the machine-language code of your program.
10288 @item jump *@var{address}
10289 Resume execution at the instruction at address @var{address}.
10292 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
10293 On many systems, you can get much the same effect as the @code{jump}
10294 command by storing a new value into the register @code{$pc}. The
10295 difference is that this does not start your program running; it only
10296 changes the address of where it @emph{will} run when you continue. For
10304 makes the next @code{continue} command or stepping command execute at
10305 address @code{0x485}, rather than at the address where your program stopped.
10306 @xref{Continuing and Stepping, ,Continuing and stepping}.
10308 The most common occasion to use the @code{jump} command is to back
10309 up---perhaps with more breakpoints set---over a portion of a program
10310 that has already executed, in order to examine its execution in more
10315 @section Giving your program a signal
10316 @cindex deliver a signal to a program
10320 @item signal @var{signal}
10321 Resume execution where your program stopped, but immediately give it the
10322 signal @var{signal}. @var{signal} can be the name or the number of a
10323 signal. For example, on many systems @code{signal 2} and @code{signal
10324 SIGINT} are both ways of sending an interrupt signal.
10326 Alternatively, if @var{signal} is zero, continue execution without
10327 giving a signal. This is useful when your program stopped on account of
10328 a signal and would ordinary see the signal when resumed with the
10329 @code{continue} command; @samp{signal 0} causes it to resume without a
10332 @code{signal} does not repeat when you press @key{RET} a second time
10333 after executing the command.
10337 Invoking the @code{signal} command is not the same as invoking the
10338 @code{kill} utility from the shell. Sending a signal with @code{kill}
10339 causes @value{GDBN} to decide what to do with the signal depending on
10340 the signal handling tables (@pxref{Signals}). The @code{signal} command
10341 passes the signal directly to your program.
10345 @section Returning from a function
10348 @cindex returning from a function
10351 @itemx return @var{expression}
10352 You can cancel execution of a function call with the @code{return}
10353 command. If you give an
10354 @var{expression} argument, its value is used as the function's return
10358 When you use @code{return}, @value{GDBN} discards the selected stack frame
10359 (and all frames within it). You can think of this as making the
10360 discarded frame return prematurely. If you wish to specify a value to
10361 be returned, give that value as the argument to @code{return}.
10363 This pops the selected stack frame (@pxref{Selection, ,Selecting a
10364 frame}), and any other frames inside of it, leaving its caller as the
10365 innermost remaining frame. That frame becomes selected. The
10366 specified value is stored in the registers used for returning values
10369 The @code{return} command does not resume execution; it leaves the
10370 program stopped in the state that would exist if the function had just
10371 returned. In contrast, the @code{finish} command (@pxref{Continuing
10372 and Stepping, ,Continuing and stepping}) resumes execution until the
10373 selected stack frame returns naturally.
10376 @section Calling program functions
10379 @cindex calling functions
10380 @cindex inferior functions, calling
10381 @item print @var{expr}
10382 Evaluate the expression @var{expr} and display the resuling value.
10383 @var{expr} may include calls to functions in the program being
10387 @item call @var{expr}
10388 Evaluate the expression @var{expr} without displaying @code{void}
10391 You can use this variant of the @code{print} command if you want to
10392 execute a function from your program that does not return anything
10393 (a.k.a.@: @dfn{a void function}), but without cluttering the output
10394 with @code{void} returned values that @value{GDBN} will otherwise
10395 print. If the result is not void, it is printed and saved in the
10399 It is possible for the function you call via the @code{print} or
10400 @code{call} command to generate a signal (e.g., if there's a bug in
10401 the function, or if you passed it incorrect arguments). What happens
10402 in that case is controlled by the @code{set unwindonsignal} command.
10405 @item set unwindonsignal
10406 @kindex set unwindonsignal
10407 @cindex unwind stack in called functions
10408 @cindex call dummy stack unwinding
10409 Set unwinding of the stack if a signal is received while in a function
10410 that @value{GDBN} called in the program being debugged. If set to on,
10411 @value{GDBN} unwinds the stack it created for the call and restores
10412 the context to what it was before the call. If set to off (the
10413 default), @value{GDBN} stops in the frame where the signal was
10416 @item show unwindonsignal
10417 @kindex show unwindonsignal
10418 Show the current setting of stack unwinding in the functions called by
10422 @cindex weak alias functions
10423 Sometimes, a function you wish to call is actually a @dfn{weak alias}
10424 for another function. In such case, @value{GDBN} might not pick up
10425 the type information, including the types of the function arguments,
10426 which causes @value{GDBN} to call the inferior function incorrectly.
10427 As a result, the called function will function erroneously and may
10428 even crash. A solution to that is to use the name of the aliased
10432 @section Patching programs
10434 @cindex patching binaries
10435 @cindex writing into executables
10436 @cindex writing into corefiles
10438 By default, @value{GDBN} opens the file containing your program's
10439 executable code (or the corefile) read-only. This prevents accidental
10440 alterations to machine code; but it also prevents you from intentionally
10441 patching your program's binary.
10443 If you'd like to be able to patch the binary, you can specify that
10444 explicitly with the @code{set write} command. For example, you might
10445 want to turn on internal debugging flags, or even to make emergency
10451 @itemx set write off
10452 If you specify @samp{set write on}, @value{GDBN} opens executable and
10453 core files for both reading and writing; if you specify @samp{set write
10454 off} (the default), @value{GDBN} opens them read-only.
10456 If you have already loaded a file, you must load it again (using the
10457 @code{exec-file} or @code{core-file} command) after changing @code{set
10458 write}, for your new setting to take effect.
10462 Display whether executable files and core files are opened for writing
10463 as well as reading.
10467 @chapter @value{GDBN} Files
10469 @value{GDBN} needs to know the file name of the program to be debugged,
10470 both in order to read its symbol table and in order to start your
10471 program. To debug a core dump of a previous run, you must also tell
10472 @value{GDBN} the name of the core dump file.
10475 * Files:: Commands to specify files
10476 * Separate Debug Files:: Debugging information in separate files
10477 * Symbol Errors:: Errors reading symbol files
10481 @section Commands to specify files
10483 @cindex symbol table
10484 @cindex core dump file
10486 You may want to specify executable and core dump file names. The usual
10487 way to do this is at start-up time, using the arguments to
10488 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
10489 Out of @value{GDBN}}).
10491 Occasionally it is necessary to change to a different file during a
10492 @value{GDBN} session. Or you may run @value{GDBN} and forget to specify
10493 a file you want to use. In these situations the @value{GDBN} commands
10494 to specify new files are useful.
10497 @cindex executable file
10499 @item file @var{filename}
10500 Use @var{filename} as the program to be debugged. It is read for its
10501 symbols and for the contents of pure memory. It is also the program
10502 executed when you use the @code{run} command. If you do not specify a
10503 directory and the file is not found in the @value{GDBN} working directory,
10504 @value{GDBN} uses the environment variable @code{PATH} as a list of
10505 directories to search, just as the shell does when looking for a program
10506 to run. You can change the value of this variable, for both @value{GDBN}
10507 and your program, using the @code{path} command.
10509 On systems with memory-mapped files, an auxiliary file named
10510 @file{@var{filename}.syms} may hold symbol table information for
10511 @var{filename}. If so, @value{GDBN} maps in the symbol table from
10512 @file{@var{filename}.syms}, starting up more quickly. See the
10513 descriptions of the file options @samp{-mapped} and @samp{-readnow}
10514 (available on the command line, see @ref{File Options, , -readnow},
10515 and with the commands @code{file}, @code{symbol-file}, or
10516 @code{add-symbol-file}, described below), for more information.
10519 @code{file} with no argument makes @value{GDBN} discard any information it
10520 has on both executable file and the symbol table.
10523 @item exec-file @r{[} @var{filename} @r{]}
10524 Specify that the program to be run (but not the symbol table) is found
10525 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
10526 if necessary to locate your program. Omitting @var{filename} means to
10527 discard information on the executable file.
10529 @kindex symbol-file
10530 @item symbol-file @r{[} @var{filename} @r{]}
10531 Read symbol table information from file @var{filename}. @code{PATH} is
10532 searched when necessary. Use the @code{file} command to get both symbol
10533 table and program to run from the same file.
10535 @code{symbol-file} with no argument clears out @value{GDBN} information on your
10536 program's symbol table.
10538 The @code{symbol-file} command causes @value{GDBN} to forget the contents
10539 of its convenience variables, the value history, and all breakpoints and
10540 auto-display expressions. This is because they may contain pointers to
10541 the internal data recording symbols and data types, which are part of
10542 the old symbol table data being discarded inside @value{GDBN}.
10544 @code{symbol-file} does not repeat if you press @key{RET} again after
10547 When @value{GDBN} is configured for a particular environment, it
10548 understands debugging information in whatever format is the standard
10549 generated for that environment; you may use either a @sc{gnu} compiler, or
10550 other compilers that adhere to the local conventions.
10551 Best results are usually obtained from @sc{gnu} compilers; for example,
10552 using @code{@value{GCC}} you can generate debugging information for
10555 For most kinds of object files, with the exception of old SVR3 systems
10556 using COFF, the @code{symbol-file} command does not normally read the
10557 symbol table in full right away. Instead, it scans the symbol table
10558 quickly to find which source files and which symbols are present. The
10559 details are read later, one source file at a time, as they are needed.
10561 The purpose of this two-stage reading strategy is to make @value{GDBN}
10562 start up faster. For the most part, it is invisible except for
10563 occasional pauses while the symbol table details for a particular source
10564 file are being read. (The @code{set verbose} command can turn these
10565 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
10566 warnings and messages}.)
10568 We have not implemented the two-stage strategy for COFF yet. When the
10569 symbol table is stored in COFF format, @code{symbol-file} reads the
10570 symbol table data in full right away. Note that ``stabs-in-COFF''
10571 still does the two-stage strategy, since the debug info is actually
10575 @cindex reading symbols immediately
10576 @cindex symbols, reading immediately
10578 @cindex memory-mapped symbol file
10579 @cindex saving symbol table
10580 @item symbol-file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10581 @itemx file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10582 You can override the @value{GDBN} two-stage strategy for reading symbol
10583 tables by using the @samp{-readnow} option with any of the commands that
10584 load symbol table information, if you want to be sure @value{GDBN} has the
10585 entire symbol table available.
10587 If memory-mapped files are available on your system through the
10588 @code{mmap} system call, you can use another option, @samp{-mapped}, to
10589 cause @value{GDBN} to write the symbols for your program into a reusable
10590 file. Future @value{GDBN} debugging sessions map in symbol information
10591 from this auxiliary symbol file (if the program has not changed), rather
10592 than spending time reading the symbol table from the executable
10593 program. Using the @samp{-mapped} option has the same effect as
10594 starting @value{GDBN} with the @samp{-mapped} command-line option.
10596 You can use both options together, to make sure the auxiliary symbol
10597 file has all the symbol information for your program.
10599 The auxiliary symbol file for a program called @var{myprog} is called
10600 @samp{@var{myprog}.syms}. Once this file exists (so long as it is newer
10601 than the corresponding executable), @value{GDBN} always attempts to use
10602 it when you debug @var{myprog}; no special options or commands are
10605 The @file{.syms} file is specific to the host machine where you run
10606 @value{GDBN}. It holds an exact image of the internal @value{GDBN}
10607 symbol table. It cannot be shared across multiple host platforms.
10609 @c FIXME: for now no mention of directories, since this seems to be in
10610 @c flux. 13mar1992 status is that in theory GDB would look either in
10611 @c current dir or in same dir as myprog; but issues like competing
10612 @c GDB's, or clutter in system dirs, mean that in practice right now
10613 @c only current dir is used. FFish says maybe a special GDB hierarchy
10614 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
10618 @item core-file @r{[}@var{filename}@r{]}
10620 Specify the whereabouts of a core dump file to be used as the ``contents
10621 of memory''. Traditionally, core files contain only some parts of the
10622 address space of the process that generated them; @value{GDBN} can access the
10623 executable file itself for other parts.
10625 @code{core-file} with no argument specifies that no core file is
10628 Note that the core file is ignored when your program is actually running
10629 under @value{GDBN}. So, if you have been running your program and you
10630 wish to debug a core file instead, you must kill the subprocess in which
10631 the program is running. To do this, use the @code{kill} command
10632 (@pxref{Kill Process, ,Killing the child process}).
10634 @kindex add-symbol-file
10635 @cindex dynamic linking
10636 @item add-symbol-file @var{filename} @var{address}
10637 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10638 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
10639 The @code{add-symbol-file} command reads additional symbol table
10640 information from the file @var{filename}. You would use this command
10641 when @var{filename} has been dynamically loaded (by some other means)
10642 into the program that is running. @var{address} should be the memory
10643 address at which the file has been loaded; @value{GDBN} cannot figure
10644 this out for itself. You can additionally specify an arbitrary number
10645 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
10646 section name and base address for that section. You can specify any
10647 @var{address} as an expression.
10649 The symbol table of the file @var{filename} is added to the symbol table
10650 originally read with the @code{symbol-file} command. You can use the
10651 @code{add-symbol-file} command any number of times; the new symbol data
10652 thus read keeps adding to the old. To discard all old symbol data
10653 instead, use the @code{symbol-file} command without any arguments.
10655 @cindex relocatable object files, reading symbols from
10656 @cindex object files, relocatable, reading symbols from
10657 @cindex reading symbols from relocatable object files
10658 @cindex symbols, reading from relocatable object files
10659 @cindex @file{.o} files, reading symbols from
10660 Although @var{filename} is typically a shared library file, an
10661 executable file, or some other object file which has been fully
10662 relocated for loading into a process, you can also load symbolic
10663 information from relocatable @file{.o} files, as long as:
10667 the file's symbolic information refers only to linker symbols defined in
10668 that file, not to symbols defined by other object files,
10670 every section the file's symbolic information refers to has actually
10671 been loaded into the inferior, as it appears in the file, and
10673 you can determine the address at which every section was loaded, and
10674 provide these to the @code{add-symbol-file} command.
10678 Some embedded operating systems, like Sun Chorus and VxWorks, can load
10679 relocatable files into an already running program; such systems
10680 typically make the requirements above easy to meet. However, it's
10681 important to recognize that many native systems use complex link
10682 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
10683 assembly, for example) that make the requirements difficult to meet. In
10684 general, one cannot assume that using @code{add-symbol-file} to read a
10685 relocatable object file's symbolic information will have the same effect
10686 as linking the relocatable object file into the program in the normal
10689 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
10691 You can use the @samp{-mapped} and @samp{-readnow} options just as with
10692 the @code{symbol-file} command, to change how @value{GDBN} manages the symbol
10693 table information for @var{filename}.
10695 @kindex add-symbol-file-from-memory
10696 @cindex @code{syscall DSO}
10697 @cindex load symbols from memory
10698 @item add-symbol-file-from-memory @var{address}
10699 Load symbols from the given @var{address} in a dynamically loaded
10700 object file whose image is mapped directly into the inferior's memory.
10701 For example, the Linux kernel maps a @code{syscall DSO} into each
10702 process's address space; this DSO provides kernel-specific code for
10703 some system calls. The argument can be any expression whose
10704 evaluation yields the address of the file's shared object file header.
10705 For this command to work, you must have used @code{symbol-file} or
10706 @code{exec-file} commands in advance.
10708 @kindex add-shared-symbol-files
10710 @item add-shared-symbol-files @var{library-file}
10711 @itemx assf @var{library-file}
10712 The @code{add-shared-symbol-files} command can currently be used only
10713 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
10714 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
10715 @value{GDBN} automatically looks for shared libraries, however if
10716 @value{GDBN} does not find yours, you can invoke
10717 @code{add-shared-symbol-files}. It takes one argument: the shared
10718 library's file name. @code{assf} is a shorthand alias for
10719 @code{add-shared-symbol-files}.
10722 @item section @var{section} @var{addr}
10723 The @code{section} command changes the base address of the named
10724 @var{section} of the exec file to @var{addr}. This can be used if the
10725 exec file does not contain section addresses, (such as in the
10726 @code{a.out} format), or when the addresses specified in the file
10727 itself are wrong. Each section must be changed separately. The
10728 @code{info files} command, described below, lists all the sections and
10732 @kindex info target
10735 @code{info files} and @code{info target} are synonymous; both print the
10736 current target (@pxref{Targets, ,Specifying a Debugging Target}),
10737 including the names of the executable and core dump files currently in
10738 use by @value{GDBN}, and the files from which symbols were loaded. The
10739 command @code{help target} lists all possible targets rather than
10742 @kindex maint info sections
10743 @item maint info sections
10744 Another command that can give you extra information about program sections
10745 is @code{maint info sections}. In addition to the section information
10746 displayed by @code{info files}, this command displays the flags and file
10747 offset of each section in the executable and core dump files. In addition,
10748 @code{maint info sections} provides the following command options (which
10749 may be arbitrarily combined):
10753 Display sections for all loaded object files, including shared libraries.
10754 @item @var{sections}
10755 Display info only for named @var{sections}.
10756 @item @var{section-flags}
10757 Display info only for sections for which @var{section-flags} are true.
10758 The section flags that @value{GDBN} currently knows about are:
10761 Section will have space allocated in the process when loaded.
10762 Set for all sections except those containing debug information.
10764 Section will be loaded from the file into the child process memory.
10765 Set for pre-initialized code and data, clear for @code{.bss} sections.
10767 Section needs to be relocated before loading.
10769 Section cannot be modified by the child process.
10771 Section contains executable code only.
10773 Section contains data only (no executable code).
10775 Section will reside in ROM.
10777 Section contains data for constructor/destructor lists.
10779 Section is not empty.
10781 An instruction to the linker to not output the section.
10782 @item COFF_SHARED_LIBRARY
10783 A notification to the linker that the section contains
10784 COFF shared library information.
10786 Section contains common symbols.
10789 @kindex set trust-readonly-sections
10790 @cindex read-only sections
10791 @item set trust-readonly-sections on
10792 Tell @value{GDBN} that readonly sections in your object file
10793 really are read-only (i.e.@: that their contents will not change).
10794 In that case, @value{GDBN} can fetch values from these sections
10795 out of the object file, rather than from the target program.
10796 For some targets (notably embedded ones), this can be a significant
10797 enhancement to debugging performance.
10799 The default is off.
10801 @item set trust-readonly-sections off
10802 Tell @value{GDBN} not to trust readonly sections. This means that
10803 the contents of the section might change while the program is running,
10804 and must therefore be fetched from the target when needed.
10806 @item show trust-readonly-sections
10807 Show the current setting of trusting readonly sections.
10810 All file-specifying commands allow both absolute and relative file names
10811 as arguments. @value{GDBN} always converts the file name to an absolute file
10812 name and remembers it that way.
10814 @cindex shared libraries
10815 @value{GDBN} supports GNU/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
10816 and IBM RS/6000 AIX shared libraries.
10818 @value{GDBN} automatically loads symbol definitions from shared libraries
10819 when you use the @code{run} command, or when you examine a core file.
10820 (Before you issue the @code{run} command, @value{GDBN} does not understand
10821 references to a function in a shared library, however---unless you are
10822 debugging a core file).
10824 On HP-UX, if the program loads a library explicitly, @value{GDBN}
10825 automatically loads the symbols at the time of the @code{shl_load} call.
10827 @c FIXME: some @value{GDBN} release may permit some refs to undef
10828 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
10829 @c FIXME...lib; check this from time to time when updating manual
10831 There are times, however, when you may wish to not automatically load
10832 symbol definitions from shared libraries, such as when they are
10833 particularly large or there are many of them.
10835 To control the automatic loading of shared library symbols, use the
10839 @kindex set auto-solib-add
10840 @item set auto-solib-add @var{mode}
10841 If @var{mode} is @code{on}, symbols from all shared object libraries
10842 will be loaded automatically when the inferior begins execution, you
10843 attach to an independently started inferior, or when the dynamic linker
10844 informs @value{GDBN} that a new library has been loaded. If @var{mode}
10845 is @code{off}, symbols must be loaded manually, using the
10846 @code{sharedlibrary} command. The default value is @code{on}.
10848 @cindex memory used for symbol tables
10849 If your program uses lots of shared libraries with debug info that
10850 takes large amounts of memory, you can decrease the @value{GDBN}
10851 memory footprint by preventing it from automatically loading the
10852 symbols from shared libraries. To that end, type @kbd{set
10853 auto-solib-add off} before running the inferior, then load each
10854 library whose debug symbols you do need with @kbd{sharedlibrary
10855 @var{regexp}}, where @var{regexp} is a regular expresion that matches
10856 the libraries whose symbols you want to be loaded.
10858 @kindex show auto-solib-add
10859 @item show auto-solib-add
10860 Display the current autoloading mode.
10863 @cindex load shared library
10864 To explicitly load shared library symbols, use the @code{sharedlibrary}
10868 @kindex info sharedlibrary
10871 @itemx info sharedlibrary
10872 Print the names of the shared libraries which are currently loaded.
10874 @kindex sharedlibrary
10876 @item sharedlibrary @var{regex}
10877 @itemx share @var{regex}
10878 Load shared object library symbols for files matching a
10879 Unix regular expression.
10880 As with files loaded automatically, it only loads shared libraries
10881 required by your program for a core file or after typing @code{run}. If
10882 @var{regex} is omitted all shared libraries required by your program are
10885 @item nosharedlibrary
10886 @kindex nosharedlibrary
10887 @cindex unload symbols from shared libraries
10888 Unload all shared object library symbols. This discards all symbols
10889 that have been loaded from all shared libraries. Symbols from shared
10890 libraries that were loaded by explicit user requests are not
10894 On some systems, such as HP-UX systems, @value{GDBN} supports
10895 autoloading shared library symbols until a limiting threshold size is
10896 reached. This provides the benefit of allowing autoloading to remain on
10897 by default, but avoids autoloading excessively large shared libraries,
10898 up to a threshold that is initially set, but which you can modify if you
10901 Beyond that threshold, symbols from shared libraries must be explicitly
10902 loaded. To load these symbols, use the command @code{sharedlibrary
10903 @var{filename}}. The base address of the shared library is determined
10904 automatically by @value{GDBN} and need not be specified.
10906 To display or set the threshold, use the commands:
10909 @kindex set auto-solib-limit
10910 @item set auto-solib-limit @var{threshold}
10911 Set the autoloading size threshold, in an integral number of megabytes.
10912 If @var{threshold} is nonzero and shared library autoloading is enabled,
10913 symbols from all shared object libraries will be loaded until the total
10914 size of the loaded shared library symbols exceeds this threshold.
10915 Otherwise, symbols must be loaded manually, using the
10916 @code{sharedlibrary} command. The default threshold is 100 (i.e.@: 100
10919 @kindex show auto-solib-limit
10920 @item show auto-solib-limit
10921 Display the current autoloading size threshold, in megabytes.
10924 Sometimes you may wish that @value{GDBN} stops and gives you control
10925 when any of shared library events happen. Use the @code{set
10926 stop-on-solib-events} command for this:
10929 @item set stop-on-solib-events
10930 @kindex set stop-on-solib-events
10931 This command controls whether @value{GDBN} should give you control
10932 when the dynamic linker notifies it about some shared library event.
10933 The most common event of interest is loading or unloading of a new
10936 @item show stop-on-solib-events
10937 @kindex show stop-on-solib-events
10938 Show whether @value{GDBN} stops and gives you control when shared
10939 library events happen.
10942 Shared libraries are also supported in many cross or remote debugging
10943 configurations. A copy of the target's libraries need to be present on the
10944 host system; they need to be the same as the target libraries, although the
10945 copies on the target can be stripped as long as the copies on the host are
10948 You need to tell @value{GDBN} where the target libraries are, so that it can
10949 load the correct copies---otherwise, it may try to load the host's libraries.
10950 @value{GDBN} has two variables to specify the search directories for target
10954 @kindex set solib-absolute-prefix
10955 @item set solib-absolute-prefix @var{path}
10956 If this variable is set, @var{path} will be used as a prefix for any
10957 absolute shared library paths; many runtime loaders store the absolute
10958 paths to the shared library in the target program's memory. If you use
10959 @samp{solib-absolute-prefix} to find shared libraries, they need to be laid
10960 out in the same way that they are on the target, with e.g.@: a
10961 @file{/usr/lib} hierarchy under @var{path}.
10963 You can set the default value of @samp{solib-absolute-prefix} by using the
10964 configure-time @samp{--with-sysroot} option.
10966 @kindex show solib-absolute-prefix
10967 @item show solib-absolute-prefix
10968 Display the current shared library prefix.
10970 @kindex set solib-search-path
10971 @item set solib-search-path @var{path}
10972 If this variable is set, @var{path} is a colon-separated list of directories
10973 to search for shared libraries. @samp{solib-search-path} is used after
10974 @samp{solib-absolute-prefix} fails to locate the library, or if the path to
10975 the library is relative instead of absolute. If you want to use
10976 @samp{solib-search-path} instead of @samp{solib-absolute-prefix}, be sure to
10977 set @samp{solib-absolute-prefix} to a nonexistant directory to prevent
10978 @value{GDBN} from finding your host's libraries.
10980 @kindex show solib-search-path
10981 @item show solib-search-path
10982 Display the current shared library search path.
10986 @node Separate Debug Files
10987 @section Debugging Information in Separate Files
10988 @cindex separate debugging information files
10989 @cindex debugging information in separate files
10990 @cindex @file{.debug} subdirectories
10991 @cindex debugging information directory, global
10992 @cindex global debugging information directory
10994 @value{GDBN} allows you to put a program's debugging information in a
10995 file separate from the executable itself, in a way that allows
10996 @value{GDBN} to find and load the debugging information automatically.
10997 Since debugging information can be very large --- sometimes larger
10998 than the executable code itself --- some systems distribute debugging
10999 information for their executables in separate files, which users can
11000 install only when they need to debug a problem.
11002 If an executable's debugging information has been extracted to a
11003 separate file, the executable should contain a @dfn{debug link} giving
11004 the name of the debugging information file (with no directory
11005 components), and a checksum of its contents. (The exact form of a
11006 debug link is described below.) If the full name of the directory
11007 containing the executable is @var{execdir}, and the executable has a
11008 debug link that specifies the name @var{debugfile}, then @value{GDBN}
11009 will automatically search for the debugging information file in three
11014 the directory containing the executable file (that is, it will look
11015 for a file named @file{@var{execdir}/@var{debugfile}},
11017 a subdirectory of that directory named @file{.debug} (that is, the
11018 file @file{@var{execdir}/.debug/@var{debugfile}}, and
11020 a subdirectory of the global debug file directory that includes the
11021 executable's full path, and the name from the link (that is, the file
11022 @file{@var{globaldebugdir}/@var{execdir}/@var{debugfile}}, where
11023 @var{globaldebugdir} is the global debug file directory, and
11024 @var{execdir} has been turned into a relative path).
11027 @value{GDBN} checks under each of these names for a debugging
11028 information file whose checksum matches that given in the link, and
11029 reads the debugging information from the first one it finds.
11031 So, for example, if you ask @value{GDBN} to debug @file{/usr/bin/ls},
11032 which has a link containing the name @file{ls.debug}, and the global
11033 debug directory is @file{/usr/lib/debug}, then @value{GDBN} will look
11034 for debug information in @file{/usr/bin/ls.debug},
11035 @file{/usr/bin/.debug/ls.debug}, and
11036 @file{/usr/lib/debug/usr/bin/ls.debug}.
11038 You can set the global debugging info directory's name, and view the
11039 name @value{GDBN} is currently using.
11043 @kindex set debug-file-directory
11044 @item set debug-file-directory @var{directory}
11045 Set the directory which @value{GDBN} searches for separate debugging
11046 information files to @var{directory}.
11048 @kindex show debug-file-directory
11049 @item show debug-file-directory
11050 Show the directory @value{GDBN} searches for separate debugging
11055 @cindex @code{.gnu_debuglink} sections
11056 @cindex debug links
11057 A debug link is a special section of the executable file named
11058 @code{.gnu_debuglink}. The section must contain:
11062 A filename, with any leading directory components removed, followed by
11065 zero to three bytes of padding, as needed to reach the next four-byte
11066 boundary within the section, and
11068 a four-byte CRC checksum, stored in the same endianness used for the
11069 executable file itself. The checksum is computed on the debugging
11070 information file's full contents by the function given below, passing
11071 zero as the @var{crc} argument.
11074 Any executable file format can carry a debug link, as long as it can
11075 contain a section named @code{.gnu_debuglink} with the contents
11078 The debugging information file itself should be an ordinary
11079 executable, containing a full set of linker symbols, sections, and
11080 debugging information. The sections of the debugging information file
11081 should have the same names, addresses and sizes as the original file,
11082 but they need not contain any data --- much like a @code{.bss} section
11083 in an ordinary executable.
11085 As of December 2002, there is no standard GNU utility to produce
11086 separated executable / debugging information file pairs. Ulrich
11087 Drepper's @file{elfutils} package, starting with version 0.53,
11088 contains a version of the @code{strip} command such that the command
11089 @kbd{strip foo -f foo.debug} removes the debugging information from
11090 the executable file @file{foo}, places it in the file
11091 @file{foo.debug}, and leaves behind a debug link in @file{foo}.
11093 Since there are many different ways to compute CRC's (different
11094 polynomials, reversals, byte ordering, etc.), the simplest way to
11095 describe the CRC used in @code{.gnu_debuglink} sections is to give the
11096 complete code for a function that computes it:
11098 @kindex gnu_debuglink_crc32
11101 gnu_debuglink_crc32 (unsigned long crc,
11102 unsigned char *buf, size_t len)
11104 static const unsigned long crc32_table[256] =
11106 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
11107 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
11108 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
11109 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
11110 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
11111 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
11112 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
11113 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
11114 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
11115 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
11116 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
11117 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
11118 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
11119 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
11120 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
11121 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
11122 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
11123 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
11124 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
11125 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
11126 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
11127 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
11128 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
11129 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
11130 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
11131 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
11132 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
11133 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
11134 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
11135 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
11136 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
11137 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
11138 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
11139 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
11140 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
11141 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
11142 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
11143 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
11144 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
11145 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
11146 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
11147 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
11148 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
11149 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
11150 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
11151 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
11152 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
11153 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
11154 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
11155 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
11156 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
11159 unsigned char *end;
11161 crc = ~crc & 0xffffffff;
11162 for (end = buf + len; buf < end; ++buf)
11163 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
11164 return ~crc & 0xffffffff;
11169 @node Symbol Errors
11170 @section Errors reading symbol files
11172 While reading a symbol file, @value{GDBN} occasionally encounters problems,
11173 such as symbol types it does not recognize, or known bugs in compiler
11174 output. By default, @value{GDBN} does not notify you of such problems, since
11175 they are relatively common and primarily of interest to people
11176 debugging compilers. If you are interested in seeing information
11177 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
11178 only one message about each such type of problem, no matter how many
11179 times the problem occurs; or you can ask @value{GDBN} to print more messages,
11180 to see how many times the problems occur, with the @code{set
11181 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
11184 The messages currently printed, and their meanings, include:
11187 @item inner block not inside outer block in @var{symbol}
11189 The symbol information shows where symbol scopes begin and end
11190 (such as at the start of a function or a block of statements). This
11191 error indicates that an inner scope block is not fully contained
11192 in its outer scope blocks.
11194 @value{GDBN} circumvents the problem by treating the inner block as if it had
11195 the same scope as the outer block. In the error message, @var{symbol}
11196 may be shown as ``@code{(don't know)}'' if the outer block is not a
11199 @item block at @var{address} out of order
11201 The symbol information for symbol scope blocks should occur in
11202 order of increasing addresses. This error indicates that it does not
11205 @value{GDBN} does not circumvent this problem, and has trouble
11206 locating symbols in the source file whose symbols it is reading. (You
11207 can often determine what source file is affected by specifying
11208 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
11211 @item bad block start address patched
11213 The symbol information for a symbol scope block has a start address
11214 smaller than the address of the preceding source line. This is known
11215 to occur in the SunOS 4.1.1 (and earlier) C compiler.
11217 @value{GDBN} circumvents the problem by treating the symbol scope block as
11218 starting on the previous source line.
11220 @item bad string table offset in symbol @var{n}
11223 Symbol number @var{n} contains a pointer into the string table which is
11224 larger than the size of the string table.
11226 @value{GDBN} circumvents the problem by considering the symbol to have the
11227 name @code{foo}, which may cause other problems if many symbols end up
11230 @item unknown symbol type @code{0x@var{nn}}
11232 The symbol information contains new data types that @value{GDBN} does
11233 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
11234 uncomprehended information, in hexadecimal.
11236 @value{GDBN} circumvents the error by ignoring this symbol information.
11237 This usually allows you to debug your program, though certain symbols
11238 are not accessible. If you encounter such a problem and feel like
11239 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
11240 on @code{complain}, then go up to the function @code{read_dbx_symtab}
11241 and examine @code{*bufp} to see the symbol.
11243 @item stub type has NULL name
11245 @value{GDBN} could not find the full definition for a struct or class.
11247 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
11248 The symbol information for a C@t{++} member function is missing some
11249 information that recent versions of the compiler should have output for
11252 @item info mismatch between compiler and debugger
11254 @value{GDBN} could not parse a type specification output by the compiler.
11259 @chapter Specifying a Debugging Target
11261 @cindex debugging target
11262 A @dfn{target} is the execution environment occupied by your program.
11264 Often, @value{GDBN} runs in the same host environment as your program;
11265 in that case, the debugging target is specified as a side effect when
11266 you use the @code{file} or @code{core} commands. When you need more
11267 flexibility---for example, running @value{GDBN} on a physically separate
11268 host, or controlling a standalone system over a serial port or a
11269 realtime system over a TCP/IP connection---you can use the @code{target}
11270 command to specify one of the target types configured for @value{GDBN}
11271 (@pxref{Target Commands, ,Commands for managing targets}).
11273 @cindex target architecture
11274 It is possible to build @value{GDBN} for several different @dfn{target
11275 architectures}. When @value{GDBN} is built like that, you can choose
11276 one of the available architectures with the @kbd{set architecture}
11280 @kindex set architecture
11281 @kindex show architecture
11282 @item set architecture @var{arch}
11283 This command sets the current target architecture to @var{arch}. The
11284 value of @var{arch} can be @code{"auto"}, in addition to one of the
11285 supported architectures.
11287 @item show architecture
11288 Show the current target architecture.
11290 @item set processor
11292 @kindex set processor
11293 @kindex show processor
11294 These are alias commands for, respectively, @code{set architecture}
11295 and @code{show architecture}.
11299 * Active Targets:: Active targets
11300 * Target Commands:: Commands for managing targets
11301 * Byte Order:: Choosing target byte order
11302 * Remote:: Remote debugging
11303 * KOD:: Kernel Object Display
11307 @node Active Targets
11308 @section Active targets
11310 @cindex stacking targets
11311 @cindex active targets
11312 @cindex multiple targets
11314 There are three classes of targets: processes, core files, and
11315 executable files. @value{GDBN} can work concurrently on up to three
11316 active targets, one in each class. This allows you to (for example)
11317 start a process and inspect its activity without abandoning your work on
11320 For example, if you execute @samp{gdb a.out}, then the executable file
11321 @code{a.out} is the only active target. If you designate a core file as
11322 well---presumably from a prior run that crashed and coredumped---then
11323 @value{GDBN} has two active targets and uses them in tandem, looking
11324 first in the corefile target, then in the executable file, to satisfy
11325 requests for memory addresses. (Typically, these two classes of target
11326 are complementary, since core files contain only a program's
11327 read-write memory---variables and so on---plus machine status, while
11328 executable files contain only the program text and initialized data.)
11330 When you type @code{run}, your executable file becomes an active process
11331 target as well. When a process target is active, all @value{GDBN}
11332 commands requesting memory addresses refer to that target; addresses in
11333 an active core file or executable file target are obscured while the
11334 process target is active.
11336 Use the @code{core-file} and @code{exec-file} commands to select a new
11337 core file or executable target (@pxref{Files, ,Commands to specify
11338 files}). To specify as a target a process that is already running, use
11339 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
11342 @node Target Commands
11343 @section Commands for managing targets
11346 @item target @var{type} @var{parameters}
11347 Connects the @value{GDBN} host environment to a target machine or
11348 process. A target is typically a protocol for talking to debugging
11349 facilities. You use the argument @var{type} to specify the type or
11350 protocol of the target machine.
11352 Further @var{parameters} are interpreted by the target protocol, but
11353 typically include things like device names or host names to connect
11354 with, process numbers, and baud rates.
11356 The @code{target} command does not repeat if you press @key{RET} again
11357 after executing the command.
11359 @kindex help target
11361 Displays the names of all targets available. To display targets
11362 currently selected, use either @code{info target} or @code{info files}
11363 (@pxref{Files, ,Commands to specify files}).
11365 @item help target @var{name}
11366 Describe a particular target, including any parameters necessary to
11369 @kindex set gnutarget
11370 @item set gnutarget @var{args}
11371 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
11372 knows whether it is reading an @dfn{executable},
11373 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
11374 with the @code{set gnutarget} command. Unlike most @code{target} commands,
11375 with @code{gnutarget} the @code{target} refers to a program, not a machine.
11378 @emph{Warning:} To specify a file format with @code{set gnutarget},
11379 you must know the actual BFD name.
11383 @xref{Files, , Commands to specify files}.
11385 @kindex show gnutarget
11386 @item show gnutarget
11387 Use the @code{show gnutarget} command to display what file format
11388 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
11389 @value{GDBN} will determine the file format for each file automatically,
11390 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
11393 @cindex common targets
11394 Here are some common targets (available, or not, depending on the GDB
11399 @item target exec @var{program}
11400 @cindex executable file target
11401 An executable file. @samp{target exec @var{program}} is the same as
11402 @samp{exec-file @var{program}}.
11404 @item target core @var{filename}
11405 @cindex core dump file target
11406 A core dump file. @samp{target core @var{filename}} is the same as
11407 @samp{core-file @var{filename}}.
11409 @item target remote @var{dev}
11410 @cindex remote target
11411 Remote serial target in GDB-specific protocol. The argument @var{dev}
11412 specifies what serial device to use for the connection (e.g.
11413 @file{/dev/ttya}). @xref{Remote, ,Remote debugging}. @code{target remote}
11414 supports the @code{load} command. This is only useful if you have
11415 some other way of getting the stub to the target system, and you can put
11416 it somewhere in memory where it won't get clobbered by the download.
11419 @cindex built-in simulator target
11420 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
11428 works; however, you cannot assume that a specific memory map, device
11429 drivers, or even basic I/O is available, although some simulators do
11430 provide these. For info about any processor-specific simulator details,
11431 see the appropriate section in @ref{Embedded Processors, ,Embedded
11436 Some configurations may include these targets as well:
11440 @item target nrom @var{dev}
11441 @cindex NetROM ROM emulator target
11442 NetROM ROM emulator. This target only supports downloading.
11446 Different targets are available on different configurations of @value{GDBN};
11447 your configuration may have more or fewer targets.
11449 Many remote targets require you to download the executable's code once
11450 you've successfully established a connection. You may wish to control
11451 various aspects of this process, such as the size of the data chunks
11452 used by @value{GDBN} to download program parts to the remote target.
11455 @kindex set download-write-size
11456 @item set download-write-size @var{size}
11457 Set the write size used when downloading a program. Only used when
11458 downloading a program onto a remote target. Specify zero or a
11459 negative value to disable blocked writes. The actual size of each
11460 transfer is also limited by the size of the target packet and the
11463 @kindex show download-write-size
11464 @item show download-write-size
11465 @kindex show download-write-size
11466 Show the current value of the write size.
11469 @kindex set hash@r{, for remote monitors}
11470 @cindex hash mark while downloading
11471 This command controls whether a hash mark @samp{#} is displayed while
11472 downloading a file to the remote monitor. If on, a hash mark is
11473 displayed after each S-record is successfully downloaded to the
11477 @kindex show hash@r{, for remote monitors}
11478 Show the current status of displaying the hash mark.
11480 @item set debug monitor
11481 @kindex set debug monitor
11482 @cindex display remote monitor communications
11483 Enable or disable display of communications messages between
11484 @value{GDBN} and the remote monitor.
11486 @item show debug monitor
11487 @kindex show debug monitor
11488 Show the current status of displaying communications between
11489 @value{GDBN} and the remote monitor.
11494 @kindex load @var{filename}
11495 @item load @var{filename}
11496 Depending on what remote debugging facilities are configured into
11497 @value{GDBN}, the @code{load} command may be available. Where it exists, it
11498 is meant to make @var{filename} (an executable) available for debugging
11499 on the remote system---by downloading, or dynamic linking, for example.
11500 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
11501 the @code{add-symbol-file} command.
11503 If your @value{GDBN} does not have a @code{load} command, attempting to
11504 execute it gets the error message ``@code{You can't do that when your
11505 target is @dots{}}''
11507 The file is loaded at whatever address is specified in the executable.
11508 For some object file formats, you can specify the load address when you
11509 link the program; for other formats, like a.out, the object file format
11510 specifies a fixed address.
11511 @c FIXME! This would be a good place for an xref to the GNU linker doc.
11513 @code{load} does not repeat if you press @key{RET} again after using it.
11517 @section Choosing target byte order
11519 @cindex choosing target byte order
11520 @cindex target byte order
11522 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
11523 offer the ability to run either big-endian or little-endian byte
11524 orders. Usually the executable or symbol will include a bit to
11525 designate the endian-ness, and you will not need to worry about
11526 which to use. However, you may still find it useful to adjust
11527 @value{GDBN}'s idea of processor endian-ness manually.
11531 @item set endian big
11532 Instruct @value{GDBN} to assume the target is big-endian.
11534 @item set endian little
11535 Instruct @value{GDBN} to assume the target is little-endian.
11537 @item set endian auto
11538 Instruct @value{GDBN} to use the byte order associated with the
11542 Display @value{GDBN}'s current idea of the target byte order.
11546 Note that these commands merely adjust interpretation of symbolic
11547 data on the host, and that they have absolutely no effect on the
11551 @section Remote debugging
11552 @cindex remote debugging
11554 If you are trying to debug a program running on a machine that cannot run
11555 @value{GDBN} in the usual way, it is often useful to use remote debugging.
11556 For example, you might use remote debugging on an operating system kernel,
11557 or on a small system which does not have a general purpose operating system
11558 powerful enough to run a full-featured debugger.
11560 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
11561 to make this work with particular debugging targets. In addition,
11562 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
11563 but not specific to any particular target system) which you can use if you
11564 write the remote stubs---the code that runs on the remote system to
11565 communicate with @value{GDBN}.
11567 Other remote targets may be available in your
11568 configuration of @value{GDBN}; use @code{help target} to list them.
11570 Once you've connected to the remote target, @value{GDBN} allows you to
11571 send arbitrary commands to the remote monitor:
11574 @item remote @var{command}
11575 @kindex remote@r{, a command}
11576 @cindex send command to remote monitor
11577 Send an arbitrary @var{command} string to the remote monitor.
11582 @section Kernel Object Display
11583 @cindex kernel object display
11586 Some targets support kernel object display. Using this facility,
11587 @value{GDBN} communicates specially with the underlying operating system
11588 and can display information about operating system-level objects such as
11589 mutexes and other synchronization objects. Exactly which objects can be
11590 displayed is determined on a per-OS basis.
11593 Use the @code{set os} command to set the operating system. This tells
11594 @value{GDBN} which kernel object display module to initialize:
11597 (@value{GDBP}) set os cisco
11601 The associated command @code{show os} displays the operating system
11602 set with the @code{set os} command; if no operating system has been
11603 set, @code{show os} will display an empty string @samp{""}.
11605 If @code{set os} succeeds, @value{GDBN} will display some information
11606 about the operating system, and will create a new @code{info} command
11607 which can be used to query the target. The @code{info} command is named
11608 after the operating system:
11612 (@value{GDBP}) info cisco
11613 List of Cisco Kernel Objects
11615 any Any and all objects
11618 Further subcommands can be used to query about particular objects known
11621 There is currently no way to determine whether a given operating
11622 system is supported other than to try setting it with @kbd{set os
11623 @var{name}}, where @var{name} is the name of the operating system you
11627 @node Remote Debugging
11628 @chapter Debugging remote programs
11631 * Connecting:: Connecting to a remote target
11632 * Server:: Using the gdbserver program
11633 * NetWare:: Using the gdbserve.nlm program
11634 * Remote configuration:: Remote configuration
11635 * remote stub:: Implementing a remote stub
11639 @section Connecting to a remote target
11641 On the @value{GDBN} host machine, you will need an unstripped copy of
11642 your program, since @value{GDBN} needs symobl and debugging information.
11643 Start up @value{GDBN} as usual, using the name of the local copy of your
11644 program as the first argument.
11646 @cindex serial line, @code{target remote}
11647 If you're using a serial line, you may want to give @value{GDBN} the
11648 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
11649 (@pxref{Remote configuration, set remotebaud}) before the
11650 @code{target} command.
11652 After that, use @code{target remote} to establish communications with
11653 the target machine. Its argument specifies how to communicate---either
11654 via a devicename attached to a direct serial line, or a TCP or UDP port
11655 (possibly to a terminal server which in turn has a serial line to the
11656 target). For example, to use a serial line connected to the device
11657 named @file{/dev/ttyb}:
11660 target remote /dev/ttyb
11663 @cindex TCP port, @code{target remote}
11664 To use a TCP connection, use an argument of the form
11665 @code{@var{host}:@var{port}} or @code{tcp:@var{host}:@var{port}}.
11666 For example, to connect to port 2828 on a
11667 terminal server named @code{manyfarms}:
11670 target remote manyfarms:2828
11673 If your remote target is actually running on the same machine as
11674 your debugger session (e.g.@: a simulator of your target running on
11675 the same host), you can omit the hostname. For example, to connect
11676 to port 1234 on your local machine:
11679 target remote :1234
11683 Note that the colon is still required here.
11685 @cindex UDP port, @code{target remote}
11686 To use a UDP connection, use an argument of the form
11687 @code{udp:@var{host}:@var{port}}. For example, to connect to UDP port 2828
11688 on a terminal server named @code{manyfarms}:
11691 target remote udp:manyfarms:2828
11694 When using a UDP connection for remote debugging, you should keep in mind
11695 that the `U' stands for ``Unreliable''. UDP can silently drop packets on
11696 busy or unreliable networks, which will cause havoc with your debugging
11699 Now you can use all the usual commands to examine and change data and to
11700 step and continue the remote program.
11702 @cindex interrupting remote programs
11703 @cindex remote programs, interrupting
11704 Whenever @value{GDBN} is waiting for the remote program, if you type the
11705 interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the
11706 program. This may or may not succeed, depending in part on the hardware
11707 and the serial drivers the remote system uses. If you type the
11708 interrupt character once again, @value{GDBN} displays this prompt:
11711 Interrupted while waiting for the program.
11712 Give up (and stop debugging it)? (y or n)
11715 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
11716 (If you decide you want to try again later, you can use @samp{target
11717 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
11718 goes back to waiting.
11721 @kindex detach (remote)
11723 When you have finished debugging the remote program, you can use the
11724 @code{detach} command to release it from @value{GDBN} control.
11725 Detaching from the target normally resumes its execution, but the results
11726 will depend on your particular remote stub. After the @code{detach}
11727 command, @value{GDBN} is free to connect to another target.
11731 The @code{disconnect} command behaves like @code{detach}, except that
11732 the target is generally not resumed. It will wait for @value{GDBN}
11733 (this instance or another one) to connect and continue debugging. After
11734 the @code{disconnect} command, @value{GDBN} is again free to connect to
11737 @cindex send command to remote monitor
11739 @item monitor @var{cmd}
11740 This command allows you to send commands directly to the remote
11745 @section Using the @code{gdbserver} program
11748 @cindex remote connection without stubs
11749 @code{gdbserver} is a control program for Unix-like systems, which
11750 allows you to connect your program with a remote @value{GDBN} via
11751 @code{target remote}---but without linking in the usual debugging stub.
11753 @code{gdbserver} is not a complete replacement for the debugging stubs,
11754 because it requires essentially the same operating-system facilities
11755 that @value{GDBN} itself does. In fact, a system that can run
11756 @code{gdbserver} to connect to a remote @value{GDBN} could also run
11757 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
11758 because it is a much smaller program than @value{GDBN} itself. It is
11759 also easier to port than all of @value{GDBN}, so you may be able to get
11760 started more quickly on a new system by using @code{gdbserver}.
11761 Finally, if you develop code for real-time systems, you may find that
11762 the tradeoffs involved in real-time operation make it more convenient to
11763 do as much development work as possible on another system, for example
11764 by cross-compiling. You can use @code{gdbserver} to make a similar
11765 choice for debugging.
11767 @value{GDBN} and @code{gdbserver} communicate via either a serial line
11768 or a TCP connection, using the standard @value{GDBN} remote serial
11772 @item On the target machine,
11773 you need to have a copy of the program you want to debug.
11774 @code{gdbserver} does not need your program's symbol table, so you can
11775 strip the program if necessary to save space. @value{GDBN} on the host
11776 system does all the symbol handling.
11778 To use the server, you must tell it how to communicate with @value{GDBN};
11779 the name of your program; and the arguments for your program. The usual
11783 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
11786 @var{comm} is either a device name (to use a serial line) or a TCP
11787 hostname and portnumber. For example, to debug Emacs with the argument
11788 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
11792 target> gdbserver /dev/com1 emacs foo.txt
11795 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
11798 To use a TCP connection instead of a serial line:
11801 target> gdbserver host:2345 emacs foo.txt
11804 The only difference from the previous example is the first argument,
11805 specifying that you are communicating with the host @value{GDBN} via
11806 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
11807 expect a TCP connection from machine @samp{host} to local TCP port 2345.
11808 (Currently, the @samp{host} part is ignored.) You can choose any number
11809 you want for the port number as long as it does not conflict with any
11810 TCP ports already in use on the target system (for example, @code{23} is
11811 reserved for @code{telnet}).@footnote{If you choose a port number that
11812 conflicts with another service, @code{gdbserver} prints an error message
11813 and exits.} You must use the same port number with the host @value{GDBN}
11814 @code{target remote} command.
11816 On some targets, @code{gdbserver} can also attach to running programs.
11817 This is accomplished via the @code{--attach} argument. The syntax is:
11820 target> gdbserver @var{comm} --attach @var{pid}
11823 @var{pid} is the process ID of a currently running process. It isn't necessary
11824 to point @code{gdbserver} at a binary for the running process.
11827 @cindex attach to a program by name
11828 You can debug processes by name instead of process ID if your target has the
11829 @code{pidof} utility:
11832 target> gdbserver @var{comm} --attach `pidof @var{PROGRAM}`
11835 In case more than one copy of @var{PROGRAM} is running, or @var{PROGRAM}
11836 has multiple threads, most versions of @code{pidof} support the
11837 @code{-s} option to only return the first process ID.
11839 @item On the host machine,
11840 connect to your target (@pxref{Connecting,,Connecting to a remote target}).
11841 For TCP connections, you must start up @code{gdbserver} prior to using
11842 the @code{target remote} command. Otherwise you may get an error whose
11843 text depends on the host system, but which usually looks something like
11844 @samp{Connection refused}. You don't need to use the @code{load}
11845 command in @value{GDBN} when using gdbserver, since the program is
11846 already on the target.
11851 @section Using the @code{gdbserve.nlm} program
11853 @kindex gdbserve.nlm
11854 @code{gdbserve.nlm} is a control program for NetWare systems, which
11855 allows you to connect your program with a remote @value{GDBN} via
11856 @code{target remote}.
11858 @value{GDBN} and @code{gdbserve.nlm} communicate via a serial line,
11859 using the standard @value{GDBN} remote serial protocol.
11862 @item On the target machine,
11863 you need to have a copy of the program you want to debug.
11864 @code{gdbserve.nlm} does not need your program's symbol table, so you
11865 can strip the program if necessary to save space. @value{GDBN} on the
11866 host system does all the symbol handling.
11868 To use the server, you must tell it how to communicate with
11869 @value{GDBN}; the name of your program; and the arguments for your
11870 program. The syntax is:
11873 load gdbserve [ BOARD=@var{board} ] [ PORT=@var{port} ]
11874 [ BAUD=@var{baud} ] @var{program} [ @var{args} @dots{} ]
11877 @var{board} and @var{port} specify the serial line; @var{baud} specifies
11878 the baud rate used by the connection. @var{port} and @var{node} default
11879 to 0, @var{baud} defaults to 9600@dmn{bps}.
11881 For example, to debug Emacs with the argument @samp{foo.txt}and
11882 communicate with @value{GDBN} over serial port number 2 or board 1
11883 using a 19200@dmn{bps} connection:
11886 load gdbserve BOARD=1 PORT=2 BAUD=19200 emacs foo.txt
11890 On the @value{GDBN} host machine, connect to your target (@pxref{Connecting,,
11891 Connecting to a remote target}).
11895 @node Remote configuration
11896 @section Remote configuration
11899 @kindex show remote
11900 This section documents the configuration options available when
11901 debugging remote programs. For the options related to the File I/O
11902 extensions of the remote protocol, see @ref{The system call,
11903 system-call-allowed}.
11906 @item set remoteaddresssize @var{bits}
11907 @cindex adress size for remote targets
11908 @cindex bits in remote address
11909 Set the maximum size of address in a memory packet to the specified
11910 number of bits. @value{GDBN} will mask off the address bits above
11911 that number, when it passes addresses to the remote target. The
11912 default value is the number of bits in the target's address.
11914 @item show remoteaddresssize
11915 Show the current value of remote address size in bits.
11917 @item set remotebaud @var{n}
11918 @cindex baud rate for remote targets
11919 Set the baud rate for the remote serial I/O to @var{n} baud. The
11920 value is used to set the speed of the serial port used for debugging
11923 @item show remotebaud
11924 Show the current speed of the remote connection.
11926 @item set remotebreak
11927 @cindex interrupt remote programs
11928 @cindex BREAK signal instead of Ctrl-C
11929 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
11930 when you press the @key{Ctrl-C} key to interrupt the program running
11931 on the remote. If set to off, @value{GDBN} sends the @samp{Strl-C}
11932 character instead. The default is off, since most remote systems
11933 expect to see @samp{Ctrl-C} as the interrupt signal.
11935 @item show remotebreak
11936 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
11937 interrupt the remote program.
11939 @item set remotedebug
11940 @cindex debug remote protocol
11941 @cindex remote protocol debugging
11942 @cindex display remote packets
11943 Control the debugging of the remote protocol. When enabled, each
11944 packet sent to or received from the remote target is displayed. The
11947 @item show remotedebug
11948 Show the current setting of the remote protocol debugging.
11950 @item set remotedevice @var{device}
11951 @cindex serial port name
11952 Set the name of the serial port through which to communicate to the
11953 remote target to @var{device}. This is the device used by
11954 @value{GDBN} to open the serial communications line to the remote
11955 target. There's no default, so you must set a valid port name for the
11956 remote serial communications to work. (Some varieties of the
11957 @code{target} command accept the port name as part of their
11960 @item show remotedevice
11961 Show the current name of the serial port.
11963 @item set remotelogbase @var{base}
11964 Set the base (a.k.a.@: radix) of logging serial protocol
11965 communications to @var{base}. Supported values of @var{base} are:
11966 @code{ascii}, @code{octal}, and @code{hex}. The default is
11969 @item show remotelogbase
11970 Show the current setting of the radix for logging remote serial
11973 @item set remotelogfile @var{file}
11974 @cindex record serial communications on file
11975 Record remote serial communications on the named @var{file}. The
11976 default is not to record at all.
11978 @item show remotelogfile.
11979 Show the current setting of the file name on which to record the
11980 serial communications.
11982 @item set remotetimeout @var{num}
11983 @cindex timeout for serial communications
11984 @cindex remote timeout
11985 Set the timeout limit to wait for the remote target to respond to
11986 @var{num} seconds. The default is 2 seconds.
11988 @item show remotetimeout
11989 Show the current number of seconds to wait for the remote target
11992 @cindex limit hardware breakpoints and watchpoints
11993 @cindex remote target, limit break- and watchpoints
11994 @anchor{set remote hardware-watchpoint-limit}
11995 @anchor{set remote hardware-breakpoint-limit}
11996 @item set remote hardware-watchpoint-limit @var{limit}
11997 @itemx set remote hardware-breakpoint-limit @var{limit}
11998 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
11999 watchpoints. A limit of -1, the default, is treated as unlimited.
12001 @item set remote fetch-register-packet
12002 @itemx set remote set-register-packet
12003 @itemx set remote P-packet
12004 @itemx set remote p-packet
12006 @cindex fetch registers from remote targets
12007 @cindex set registers in remote targets
12008 Determine whether @value{GDBN} can set and fetch registers from the
12009 remote target using the @samp{P} packets. The default depends on the
12010 remote stub's support of the @samp{P} packets (@value{GDBN} queries
12011 the stub when this packet is first required).
12013 @item show remote fetch-register-packet
12014 @itemx show remote set-register-packet
12015 @itemx show remote P-packet
12016 @itemx show remote p-packet
12017 Show the current setting of using the @samp{P} packets for setting and
12018 fetching registers from the remote target.
12020 @cindex binary downloads
12022 @item set remote binary-download-packet
12023 @itemx set remote X-packet
12024 Determine whether @value{GDBN} sends downloads in binary mode using
12025 the @samp{X} packets. The default is on.
12027 @item show remote binary-download-packet
12028 @itemx show remote X-packet
12029 Show the current setting of using the @samp{X} packets for binary
12032 @item set remote read-aux-vector-packet
12033 @cindex auxiliary vector of remote target
12034 @cindex @code{auxv}, and remote targets
12035 Set the use of the remote protocol's @samp{qPart:auxv:read} (target
12036 auxiliary vector read) request. This request is used to fetch the
12037 remote target's @dfn{auxiliary vector}, see @ref{OS Information,
12038 Auxiliary Vector}. The default setting depends on the remote stub's
12039 support of this request (@value{GDBN} queries the stub when this
12040 request is first required). @xref{General Query Packets, qPart}, for
12041 more information about this request.
12043 @item show remote read-aux-vector-packet
12044 Show the current setting of use of the @samp{qPart:auxv:read} request.
12046 @item set remote symbol-lookup-packet
12047 @cindex remote symbol lookup request
12048 Set the use of the remote protocol's @samp{qSymbol} (target symbol
12049 lookup) request. This request is used to communicate symbol
12050 information to the remote target, e.g., whenever a new shared library
12051 is loaded by the remote (@pxref{Files, shared libraries}). The
12052 default setting depends on the remote stub's support of this request
12053 (@value{GDBN} queries the stub when this request is first required).
12054 @xref{General Query Packets, qSymbol}, for more information about this
12057 @item show remote symbol-lookup-packet
12058 Show the current setting of use of the @samp{qSymbol} request.
12060 @item set remote verbose-resume-packet
12061 @cindex resume remote target
12062 @cindex signal thread, and remote targets
12063 @cindex single-step thread, and remote targets
12064 @cindex thread-specific operations on remote targets
12065 Set the use of the remote protocol's @samp{vCont} (descriptive resume)
12066 request. This request is used to resume specific threads in the
12067 remote target, and to single-step or signal them. The default setting
12068 depends on the remote stub's support of this request (@value{GDBN}
12069 queries the stub when this request is first required). This setting
12070 affects debugging of multithreaded programs: if @samp{vCont} cannot be
12071 used, @value{GDBN} might be unable to single-step a specific thread,
12072 especially under @code{set scheduler-locking off}; it is also
12073 impossible to pause a specific thread. @xref{Packets, vCont}, for
12076 @item show remote verbose-resume-packet
12077 Show the current setting of use of the @samp{vCont} request
12079 @item set remote software-breakpoint-packet
12080 @itemx set remote hardware-breakpoint-packet
12081 @itemx set remote write-watchpoint-packet
12082 @itemx set remote read-watchpoint-packet
12083 @itemx set remote access-watchpoint-packet
12084 @itemx set remote Z-packet
12086 @cindex remote hardware breakpoints and watchpoints
12087 These commands enable or disable the use of @samp{Z} packets for
12088 setting breakpoints and watchpoints in the remote target. The default
12089 depends on the remote stub's support of the @samp{Z} packets
12090 (@value{GDBN} queries the stub when each packet is first required).
12091 The command @code{set remote Z-packet}, kept for back-compatibility,
12092 turns on or off all the features that require the use of @samp{Z}
12095 @item show remote software-breakpoint-packet
12096 @itemx show remote hardware-breakpoint-packet
12097 @itemx show remote write-watchpoint-packet
12098 @itemx show remote read-watchpoint-packet
12099 @itemx show remote access-watchpoint-packet
12100 @itemx show remote Z-packet
12101 Show the current setting of @samp{Z} packets usage.
12105 @section Implementing a remote stub
12107 @cindex debugging stub, example
12108 @cindex remote stub, example
12109 @cindex stub example, remote debugging
12110 The stub files provided with @value{GDBN} implement the target side of the
12111 communication protocol, and the @value{GDBN} side is implemented in the
12112 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
12113 these subroutines to communicate, and ignore the details. (If you're
12114 implementing your own stub file, you can still ignore the details: start
12115 with one of the existing stub files. @file{sparc-stub.c} is the best
12116 organized, and therefore the easiest to read.)
12118 @cindex remote serial debugging, overview
12119 To debug a program running on another machine (the debugging
12120 @dfn{target} machine), you must first arrange for all the usual
12121 prerequisites for the program to run by itself. For example, for a C
12126 A startup routine to set up the C runtime environment; these usually
12127 have a name like @file{crt0}. The startup routine may be supplied by
12128 your hardware supplier, or you may have to write your own.
12131 A C subroutine library to support your program's
12132 subroutine calls, notably managing input and output.
12135 A way of getting your program to the other machine---for example, a
12136 download program. These are often supplied by the hardware
12137 manufacturer, but you may have to write your own from hardware
12141 The next step is to arrange for your program to use a serial port to
12142 communicate with the machine where @value{GDBN} is running (the @dfn{host}
12143 machine). In general terms, the scheme looks like this:
12147 @value{GDBN} already understands how to use this protocol; when everything
12148 else is set up, you can simply use the @samp{target remote} command
12149 (@pxref{Targets,,Specifying a Debugging Target}).
12151 @item On the target,
12152 you must link with your program a few special-purpose subroutines that
12153 implement the @value{GDBN} remote serial protocol. The file containing these
12154 subroutines is called a @dfn{debugging stub}.
12156 On certain remote targets, you can use an auxiliary program
12157 @code{gdbserver} instead of linking a stub into your program.
12158 @xref{Server,,Using the @code{gdbserver} program}, for details.
12161 The debugging stub is specific to the architecture of the remote
12162 machine; for example, use @file{sparc-stub.c} to debug programs on
12165 @cindex remote serial stub list
12166 These working remote stubs are distributed with @value{GDBN}:
12171 @cindex @file{i386-stub.c}
12174 For Intel 386 and compatible architectures.
12177 @cindex @file{m68k-stub.c}
12178 @cindex Motorola 680x0
12180 For Motorola 680x0 architectures.
12183 @cindex @file{sh-stub.c}
12186 For Renesas SH architectures.
12189 @cindex @file{sparc-stub.c}
12191 For @sc{sparc} architectures.
12193 @item sparcl-stub.c
12194 @cindex @file{sparcl-stub.c}
12197 For Fujitsu @sc{sparclite} architectures.
12201 The @file{README} file in the @value{GDBN} distribution may list other
12202 recently added stubs.
12205 * Stub Contents:: What the stub can do for you
12206 * Bootstrapping:: What you must do for the stub
12207 * Debug Session:: Putting it all together
12210 @node Stub Contents
12211 @subsection What the stub can do for you
12213 @cindex remote serial stub
12214 The debugging stub for your architecture supplies these three
12218 @item set_debug_traps
12219 @findex set_debug_traps
12220 @cindex remote serial stub, initialization
12221 This routine arranges for @code{handle_exception} to run when your
12222 program stops. You must call this subroutine explicitly near the
12223 beginning of your program.
12225 @item handle_exception
12226 @findex handle_exception
12227 @cindex remote serial stub, main routine
12228 This is the central workhorse, but your program never calls it
12229 explicitly---the setup code arranges for @code{handle_exception} to
12230 run when a trap is triggered.
12232 @code{handle_exception} takes control when your program stops during
12233 execution (for example, on a breakpoint), and mediates communications
12234 with @value{GDBN} on the host machine. This is where the communications
12235 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
12236 representative on the target machine. It begins by sending summary
12237 information on the state of your program, then continues to execute,
12238 retrieving and transmitting any information @value{GDBN} needs, until you
12239 execute a @value{GDBN} command that makes your program resume; at that point,
12240 @code{handle_exception} returns control to your own code on the target
12244 @cindex @code{breakpoint} subroutine, remote
12245 Use this auxiliary subroutine to make your program contain a
12246 breakpoint. Depending on the particular situation, this may be the only
12247 way for @value{GDBN} to get control. For instance, if your target
12248 machine has some sort of interrupt button, you won't need to call this;
12249 pressing the interrupt button transfers control to
12250 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
12251 simply receiving characters on the serial port may also trigger a trap;
12252 again, in that situation, you don't need to call @code{breakpoint} from
12253 your own program---simply running @samp{target remote} from the host
12254 @value{GDBN} session gets control.
12256 Call @code{breakpoint} if none of these is true, or if you simply want
12257 to make certain your program stops at a predetermined point for the
12258 start of your debugging session.
12261 @node Bootstrapping
12262 @subsection What you must do for the stub
12264 @cindex remote stub, support routines
12265 The debugging stubs that come with @value{GDBN} are set up for a particular
12266 chip architecture, but they have no information about the rest of your
12267 debugging target machine.
12269 First of all you need to tell the stub how to communicate with the
12273 @item int getDebugChar()
12274 @findex getDebugChar
12275 Write this subroutine to read a single character from the serial port.
12276 It may be identical to @code{getchar} for your target system; a
12277 different name is used to allow you to distinguish the two if you wish.
12279 @item void putDebugChar(int)
12280 @findex putDebugChar
12281 Write this subroutine to write a single character to the serial port.
12282 It may be identical to @code{putchar} for your target system; a
12283 different name is used to allow you to distinguish the two if you wish.
12286 @cindex control C, and remote debugging
12287 @cindex interrupting remote targets
12288 If you want @value{GDBN} to be able to stop your program while it is
12289 running, you need to use an interrupt-driven serial driver, and arrange
12290 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
12291 character). That is the character which @value{GDBN} uses to tell the
12292 remote system to stop.
12294 Getting the debugging target to return the proper status to @value{GDBN}
12295 probably requires changes to the standard stub; one quick and dirty way
12296 is to just execute a breakpoint instruction (the ``dirty'' part is that
12297 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
12299 Other routines you need to supply are:
12302 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
12303 @findex exceptionHandler
12304 Write this function to install @var{exception_address} in the exception
12305 handling tables. You need to do this because the stub does not have any
12306 way of knowing what the exception handling tables on your target system
12307 are like (for example, the processor's table might be in @sc{rom},
12308 containing entries which point to a table in @sc{ram}).
12309 @var{exception_number} is the exception number which should be changed;
12310 its meaning is architecture-dependent (for example, different numbers
12311 might represent divide by zero, misaligned access, etc). When this
12312 exception occurs, control should be transferred directly to
12313 @var{exception_address}, and the processor state (stack, registers,
12314 and so on) should be just as it is when a processor exception occurs. So if
12315 you want to use a jump instruction to reach @var{exception_address}, it
12316 should be a simple jump, not a jump to subroutine.
12318 For the 386, @var{exception_address} should be installed as an interrupt
12319 gate so that interrupts are masked while the handler runs. The gate
12320 should be at privilege level 0 (the most privileged level). The
12321 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
12322 help from @code{exceptionHandler}.
12324 @item void flush_i_cache()
12325 @findex flush_i_cache
12326 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
12327 instruction cache, if any, on your target machine. If there is no
12328 instruction cache, this subroutine may be a no-op.
12330 On target machines that have instruction caches, @value{GDBN} requires this
12331 function to make certain that the state of your program is stable.
12335 You must also make sure this library routine is available:
12338 @item void *memset(void *, int, int)
12340 This is the standard library function @code{memset} that sets an area of
12341 memory to a known value. If you have one of the free versions of
12342 @code{libc.a}, @code{memset} can be found there; otherwise, you must
12343 either obtain it from your hardware manufacturer, or write your own.
12346 If you do not use the GNU C compiler, you may need other standard
12347 library subroutines as well; this varies from one stub to another,
12348 but in general the stubs are likely to use any of the common library
12349 subroutines which @code{@value{GCC}} generates as inline code.
12352 @node Debug Session
12353 @subsection Putting it all together
12355 @cindex remote serial debugging summary
12356 In summary, when your program is ready to debug, you must follow these
12361 Make sure you have defined the supporting low-level routines
12362 (@pxref{Bootstrapping,,What you must do for the stub}):
12364 @code{getDebugChar}, @code{putDebugChar},
12365 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
12369 Insert these lines near the top of your program:
12377 For the 680x0 stub only, you need to provide a variable called
12378 @code{exceptionHook}. Normally you just use:
12381 void (*exceptionHook)() = 0;
12385 but if before calling @code{set_debug_traps}, you set it to point to a
12386 function in your program, that function is called when
12387 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
12388 error). The function indicated by @code{exceptionHook} is called with
12389 one parameter: an @code{int} which is the exception number.
12392 Compile and link together: your program, the @value{GDBN} debugging stub for
12393 your target architecture, and the supporting subroutines.
12396 Make sure you have a serial connection between your target machine and
12397 the @value{GDBN} host, and identify the serial port on the host.
12400 @c The "remote" target now provides a `load' command, so we should
12401 @c document that. FIXME.
12402 Download your program to your target machine (or get it there by
12403 whatever means the manufacturer provides), and start it.
12406 Start @value{GDBN} on the host, and connect to the target
12407 (@pxref{Connecting,,Connecting to a remote target}).
12411 @node Configurations
12412 @chapter Configuration-Specific Information
12414 While nearly all @value{GDBN} commands are available for all native and
12415 cross versions of the debugger, there are some exceptions. This chapter
12416 describes things that are only available in certain configurations.
12418 There are three major categories of configurations: native
12419 configurations, where the host and target are the same, embedded
12420 operating system configurations, which are usually the same for several
12421 different processor architectures, and bare embedded processors, which
12422 are quite different from each other.
12427 * Embedded Processors::
12434 This section describes details specific to particular native
12439 * BSD libkvm Interface:: Debugging BSD kernel memory images
12440 * SVR4 Process Information:: SVR4 process information
12441 * DJGPP Native:: Features specific to the DJGPP port
12442 * Cygwin Native:: Features specific to the Cygwin port
12443 * Hurd Native:: Features specific to @sc{gnu} Hurd
12444 * Neutrino:: Features specific to QNX Neutrino
12450 On HP-UX systems, if you refer to a function or variable name that
12451 begins with a dollar sign, @value{GDBN} searches for a user or system
12452 name first, before it searches for a convenience variable.
12455 @node BSD libkvm Interface
12456 @subsection BSD libkvm Interface
12459 @cindex kernel memory image
12460 @cindex kernel crash dump
12462 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
12463 interface that provides a uniform interface for accessing kernel virtual
12464 memory images, including live systems and crash dumps. @value{GDBN}
12465 uses this interface to allow you to debug live kernels and kernel crash
12466 dumps on many native BSD configurations. This is implemented as a
12467 special @code{kvm} debugging target. For debugging a live system, load
12468 the currently running kernel into @value{GDBN} and connect to the
12472 (@value{GDBP}) @b{target kvm}
12475 For debugging crash dumps, provide the file name of the crash dump as an
12479 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
12482 Once connected to the @code{kvm} target, the following commands are
12488 Set current context from the @dfn{Process Control Block} (PCB) address.
12491 Set current context from proc address. This command isn't available on
12492 modern FreeBSD systems.
12495 @node SVR4 Process Information
12496 @subsection SVR4 process information
12498 @cindex examine process image
12499 @cindex process info via @file{/proc}
12501 Many versions of SVR4 and compatible systems provide a facility called
12502 @samp{/proc} that can be used to examine the image of a running
12503 process using file-system subroutines. If @value{GDBN} is configured
12504 for an operating system with this facility, the command @code{info
12505 proc} is available to report information about the process running
12506 your program, or about any process running on your system. @code{info
12507 proc} works only on SVR4 systems that include the @code{procfs} code.
12508 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
12509 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
12515 @itemx info proc @var{process-id}
12516 Summarize available information about any running process. If a
12517 process ID is specified by @var{process-id}, display information about
12518 that process; otherwise display information about the program being
12519 debugged. The summary includes the debugged process ID, the command
12520 line used to invoke it, its current working directory, and its
12521 executable file's absolute file name.
12523 On some systems, @var{process-id} can be of the form
12524 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
12525 within a process. If the optional @var{pid} part is missing, it means
12526 a thread from the process being debugged (the leading @samp{/} still
12527 needs to be present, or else @value{GDBN} will interpret the number as
12528 a process ID rather than a thread ID).
12530 @item info proc mappings
12531 @cindex memory address space mappings
12532 Report the memory address space ranges accessible in the program, with
12533 information on whether the process has read, write, or execute access
12534 rights to each range. On @sc{gnu}/Linux systems, each memory range
12535 includes the object file which is mapped to that range, instead of the
12536 memory access rights to that range.
12538 @item info proc stat
12539 @itemx info proc status
12540 @cindex process detailed status information
12541 These subcommands are specific to @sc{gnu}/Linux systems. They show
12542 the process-related information, including the user ID and group ID;
12543 how many threads are there in the process; its virtual memory usage;
12544 the signals that are pending, blocked, and ignored; its TTY; its
12545 consumption of system and user time; its stack size; its @samp{nice}
12546 value; etc. For more information, see the @samp{proc(5)} man page
12547 (type @kbd{man 5 proc} from your shell prompt).
12549 @item info proc all
12550 Show all the information about the process described under all of the
12551 above @code{info proc} subcommands.
12554 @comment These sub-options of 'info proc' were not included when
12555 @comment procfs.c was re-written. Keep their descriptions around
12556 @comment against the day when someone finds the time to put them back in.
12557 @kindex info proc times
12558 @item info proc times
12559 Starting time, user CPU time, and system CPU time for your program and
12562 @kindex info proc id
12564 Report on the process IDs related to your program: its own process ID,
12565 the ID of its parent, the process group ID, and the session ID.
12568 @item set procfs-trace
12569 @kindex set procfs-trace
12570 @cindex @code{procfs} API calls
12571 This command enables and disables tracing of @code{procfs} API calls.
12573 @item show procfs-trace
12574 @kindex show procfs-trace
12575 Show the current state of @code{procfs} API call tracing.
12577 @item set procfs-file @var{file}
12578 @kindex set procfs-file
12579 Tell @value{GDBN} to write @code{procfs} API trace to the named
12580 @var{file}. @value{GDBN} appends the trace info to the previous
12581 contents of the file. The default is to display the trace on the
12584 @item show procfs-file
12585 @kindex show procfs-file
12586 Show the file to which @code{procfs} API trace is written.
12588 @item proc-trace-entry
12589 @itemx proc-trace-exit
12590 @itemx proc-untrace-entry
12591 @itemx proc-untrace-exit
12592 @kindex proc-trace-entry
12593 @kindex proc-trace-exit
12594 @kindex proc-untrace-entry
12595 @kindex proc-untrace-exit
12596 These commands enable and disable tracing of entries into and exits
12597 from the @code{syscall} interface.
12600 @kindex info pidlist
12601 @cindex process list, QNX Neutrino
12602 For QNX Neutrino only, this command displays the list of all the
12603 processes and all the threads within each process.
12606 @kindex info meminfo
12607 @cindex mapinfo list, QNX Neutrino
12608 For QNX Neutrino only, this command displays the list of all mapinfos.
12612 @subsection Features for Debugging @sc{djgpp} Programs
12613 @cindex @sc{djgpp} debugging
12614 @cindex native @sc{djgpp} debugging
12615 @cindex MS-DOS-specific commands
12617 @sc{djgpp} is the port of @sc{gnu} development tools to MS-DOS and
12618 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
12619 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
12620 top of real-mode DOS systems and their emulations.
12622 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
12623 defines a few commands specific to the @sc{djgpp} port. This
12624 subsection describes those commands.
12629 This is a prefix of @sc{djgpp}-specific commands which print
12630 information about the target system and important OS structures.
12633 @cindex MS-DOS system info
12634 @cindex free memory information (MS-DOS)
12635 @item info dos sysinfo
12636 This command displays assorted information about the underlying
12637 platform: the CPU type and features, the OS version and flavor, the
12638 DPMI version, and the available conventional and DPMI memory.
12643 @cindex segment descriptor tables
12644 @cindex descriptor tables display
12646 @itemx info dos ldt
12647 @itemx info dos idt
12648 These 3 commands display entries from, respectively, Global, Local,
12649 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
12650 tables are data structures which store a descriptor for each segment
12651 that is currently in use. The segment's selector is an index into a
12652 descriptor table; the table entry for that index holds the
12653 descriptor's base address and limit, and its attributes and access
12656 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
12657 segment (used for both data and the stack), and a DOS segment (which
12658 allows access to DOS/BIOS data structures and absolute addresses in
12659 conventional memory). However, the DPMI host will usually define
12660 additional segments in order to support the DPMI environment.
12662 @cindex garbled pointers
12663 These commands allow to display entries from the descriptor tables.
12664 Without an argument, all entries from the specified table are
12665 displayed. An argument, which should be an integer expression, means
12666 display a single entry whose index is given by the argument. For
12667 example, here's a convenient way to display information about the
12668 debugged program's data segment:
12671 @exdent @code{(@value{GDBP}) info dos ldt $ds}
12672 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
12676 This comes in handy when you want to see whether a pointer is outside
12677 the data segment's limit (i.e.@: @dfn{garbled}).
12679 @cindex page tables display (MS-DOS)
12681 @itemx info dos pte
12682 These two commands display entries from, respectively, the Page
12683 Directory and the Page Tables. Page Directories and Page Tables are
12684 data structures which control how virtual memory addresses are mapped
12685 into physical addresses. A Page Table includes an entry for every
12686 page of memory that is mapped into the program's address space; there
12687 may be several Page Tables, each one holding up to 4096 entries. A
12688 Page Directory has up to 4096 entries, one each for every Page Table
12689 that is currently in use.
12691 Without an argument, @kbd{info dos pde} displays the entire Page
12692 Directory, and @kbd{info dos pte} displays all the entries in all of
12693 the Page Tables. An argument, an integer expression, given to the
12694 @kbd{info dos pde} command means display only that entry from the Page
12695 Directory table. An argument given to the @kbd{info dos pte} command
12696 means display entries from a single Page Table, the one pointed to by
12697 the specified entry in the Page Directory.
12699 @cindex direct memory access (DMA) on MS-DOS
12700 These commands are useful when your program uses @dfn{DMA} (Direct
12701 Memory Access), which needs physical addresses to program the DMA
12704 These commands are supported only with some DPMI servers.
12706 @cindex physical address from linear address
12707 @item info dos address-pte @var{addr}
12708 This command displays the Page Table entry for a specified linear
12709 address. The argument linear address @var{addr} should already have the
12710 appropriate segment's base address added to it, because this command
12711 accepts addresses which may belong to @emph{any} segment. For
12712 example, here's how to display the Page Table entry for the page where
12713 the variable @code{i} is stored:
12716 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
12717 @exdent @code{Page Table entry for address 0x11a00d30:}
12718 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
12722 This says that @code{i} is stored at offset @code{0xd30} from the page
12723 whose physical base address is @code{0x02698000}, and prints all the
12724 attributes of that page.
12726 Note that you must cast the addresses of variables to a @code{char *},
12727 since otherwise the value of @code{__djgpp_base_address}, the base
12728 address of all variables and functions in a @sc{djgpp} program, will
12729 be added using the rules of C pointer arithmetics: if @code{i} is
12730 declared an @code{int}, @value{GDBN} will add 4 times the value of
12731 @code{__djgpp_base_address} to the address of @code{i}.
12733 Here's another example, it displays the Page Table entry for the
12737 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
12738 @exdent @code{Page Table entry for address 0x29110:}
12739 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
12743 (The @code{+ 3} offset is because the transfer buffer's address is the
12744 3rd member of the @code{_go32_info_block} structure.) The output of
12745 this command clearly shows that addresses in conventional memory are
12746 mapped 1:1, i.e.@: the physical and linear addresses are identical.
12748 This command is supported only with some DPMI servers.
12751 @cindex DOS serial data link, remote debugging
12752 In addition to native debugging, the DJGPP port supports remote
12753 debugging via a serial data link. The following commands are specific
12754 to remote serial debugging in the DJGPP port of @value{GDBN}.
12757 @kindex set com1base
12758 @kindex set com1irq
12759 @kindex set com2base
12760 @kindex set com2irq
12761 @kindex set com3base
12762 @kindex set com3irq
12763 @kindex set com4base
12764 @kindex set com4irq
12765 @item set com1base @var{addr}
12766 This command sets the base I/O port address of the @file{COM1} serial
12769 @item set com1irq @var{irq}
12770 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
12771 for the @file{COM1} serial port.
12773 There are similar commands @samp{set com2base}, @samp{set com3irq},
12774 etc.@: for setting the port address and the @code{IRQ} lines for the
12777 @kindex show com1base
12778 @kindex show com1irq
12779 @kindex show com2base
12780 @kindex show com2irq
12781 @kindex show com3base
12782 @kindex show com3irq
12783 @kindex show com4base
12784 @kindex show com4irq
12785 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
12786 display the current settings of the base address and the @code{IRQ}
12787 lines used by the COM ports.
12790 @kindex info serial
12791 @cindex DOS serial port status
12792 This command prints the status of the 4 DOS serial ports. For each
12793 port, it prints whether it's active or not, its I/O base address and
12794 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
12795 counts of various errors encountered so far.
12799 @node Cygwin Native
12800 @subsection Features for Debugging MS Windows PE executables
12801 @cindex MS Windows debugging
12802 @cindex native Cygwin debugging
12803 @cindex Cygwin-specific commands
12805 @value{GDBN} supports native debugging of MS Windows programs, including
12806 DLLs with and without symbolic debugging information. There are various
12807 additional Cygwin-specific commands, described in this subsection. The
12808 subsubsection @pxref{Non-debug DLL symbols} describes working with DLLs
12809 that have no debugging symbols.
12815 This is a prefix of MS Windows specific commands which print
12816 information about the target system and important OS structures.
12818 @item info w32 selector
12819 This command displays information returned by
12820 the Win32 API @code{GetThreadSelectorEntry} function.
12821 It takes an optional argument that is evaluated to
12822 a long value to give the information about this given selector.
12823 Without argument, this command displays information
12824 about the the six segment registers.
12828 This is a Cygwin specific alias of info shared.
12830 @kindex dll-symbols
12832 This command loads symbols from a dll similarly to
12833 add-sym command but without the need to specify a base address.
12835 @kindex set new-console
12836 @item set new-console @var{mode}
12837 If @var{mode} is @code{on} the debuggee will
12838 be started in a new console on next start.
12839 If @var{mode} is @code{off}i, the debuggee will
12840 be started in the same console as the debugger.
12842 @kindex show new-console
12843 @item show new-console
12844 Displays whether a new console is used
12845 when the debuggee is started.
12847 @kindex set new-group
12848 @item set new-group @var{mode}
12849 This boolean value controls whether the debuggee should
12850 start a new group or stay in the same group as the debugger.
12851 This affects the way the Windows OS handles
12854 @kindex show new-group
12855 @item show new-group
12856 Displays current value of new-group boolean.
12858 @kindex set debugevents
12859 @item set debugevents
12860 This boolean value adds debug output concerning events seen by the debugger.
12862 @kindex set debugexec
12863 @item set debugexec
12864 This boolean value adds debug output concerning execute events
12865 seen by the debugger.
12867 @kindex set debugexceptions
12868 @item set debugexceptions
12869 This boolean value adds debug ouptut concerning exception events
12870 seen by the debugger.
12872 @kindex set debugmemory
12873 @item set debugmemory
12874 This boolean value adds debug ouptut concerning memory events
12875 seen by the debugger.
12879 This boolean values specifies whether the debuggee is called
12880 via a shell or directly (default value is on).
12884 Displays if the debuggee will be started with a shell.
12889 * Non-debug DLL symbols:: Support for DLLs without debugging symbols
12892 @node Non-debug DLL symbols
12893 @subsubsection Support for DLLs without debugging symbols
12894 @cindex DLLs with no debugging symbols
12895 @cindex Minimal symbols and DLLs
12897 Very often on windows, some of the DLLs that your program relies on do
12898 not include symbolic debugging information (for example,
12899 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
12900 symbols in a DLL, it relies on the minimal amount of symbolic
12901 information contained in the DLL's export table. This subsubsection
12902 describes working with such symbols, known internally to @value{GDBN} as
12903 ``minimal symbols''.
12905 Note that before the debugged program has started execution, no DLLs
12906 will have been loaded. The easiest way around this problem is simply to
12907 start the program --- either by setting a breakpoint or letting the
12908 program run once to completion. It is also possible to force
12909 @value{GDBN} to load a particular DLL before starting the executable ---
12910 see the shared library information in @pxref{Files} or the
12911 @code{dll-symbols} command in @pxref{Cygwin Native}. Currently,
12912 explicitly loading symbols from a DLL with no debugging information will
12913 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
12914 which may adversely affect symbol lookup performance.
12916 @subsubsection DLL name prefixes
12918 In keeping with the naming conventions used by the Microsoft debugging
12919 tools, DLL export symbols are made available with a prefix based on the
12920 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
12921 also entered into the symbol table, so @code{CreateFileA} is often
12922 sufficient. In some cases there will be name clashes within a program
12923 (particularly if the executable itself includes full debugging symbols)
12924 necessitating the use of the fully qualified name when referring to the
12925 contents of the DLL. Use single-quotes around the name to avoid the
12926 exclamation mark (``!'') being interpreted as a language operator.
12928 Note that the internal name of the DLL may be all upper-case, even
12929 though the file name of the DLL is lower-case, or vice-versa. Since
12930 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
12931 some confusion. If in doubt, try the @code{info functions} and
12932 @code{info variables} commands or even @code{maint print msymbols} (see
12933 @pxref{Symbols}). Here's an example:
12936 (@value{GDBP}) info function CreateFileA
12937 All functions matching regular expression "CreateFileA":
12939 Non-debugging symbols:
12940 0x77e885f4 CreateFileA
12941 0x77e885f4 KERNEL32!CreateFileA
12945 (@value{GDBP}) info function !
12946 All functions matching regular expression "!":
12948 Non-debugging symbols:
12949 0x6100114c cygwin1!__assert
12950 0x61004034 cygwin1!_dll_crt0@@0
12951 0x61004240 cygwin1!dll_crt0(per_process *)
12955 @subsubsection Working with minimal symbols
12957 Symbols extracted from a DLL's export table do not contain very much
12958 type information. All that @value{GDBN} can do is guess whether a symbol
12959 refers to a function or variable depending on the linker section that
12960 contains the symbol. Also note that the actual contents of the memory
12961 contained in a DLL are not available unless the program is running. This
12962 means that you cannot examine the contents of a variable or disassemble
12963 a function within a DLL without a running program.
12965 Variables are generally treated as pointers and dereferenced
12966 automatically. For this reason, it is often necessary to prefix a
12967 variable name with the address-of operator (``&'') and provide explicit
12968 type information in the command. Here's an example of the type of
12972 (@value{GDBP}) print 'cygwin1!__argv'
12977 (@value{GDBP}) x 'cygwin1!__argv'
12978 0x10021610: "\230y\""
12981 And two possible solutions:
12984 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
12985 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
12989 (@value{GDBP}) x/2x &'cygwin1!__argv'
12990 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
12991 (@value{GDBP}) x/x 0x10021608
12992 0x10021608: 0x0022fd98
12993 (@value{GDBP}) x/s 0x0022fd98
12994 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
12997 Setting a break point within a DLL is possible even before the program
12998 starts execution. However, under these circumstances, @value{GDBN} can't
12999 examine the initial instructions of the function in order to skip the
13000 function's frame set-up code. You can work around this by using ``*&''
13001 to set the breakpoint at a raw memory address:
13004 (@value{GDBP}) break *&'python22!PyOS_Readline'
13005 Breakpoint 1 at 0x1e04eff0
13008 The author of these extensions is not entirely convinced that setting a
13009 break point within a shared DLL like @file{kernel32.dll} is completely
13013 @subsection Commands specific to @sc{gnu} Hurd systems
13014 @cindex @sc{gnu} Hurd debugging
13016 This subsection describes @value{GDBN} commands specific to the
13017 @sc{gnu} Hurd native debugging.
13022 @kindex set signals@r{, Hurd command}
13023 @kindex set sigs@r{, Hurd command}
13024 This command toggles the state of inferior signal interception by
13025 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
13026 affected by this command. @code{sigs} is a shorthand alias for
13031 @kindex show signals@r{, Hurd command}
13032 @kindex show sigs@r{, Hurd command}
13033 Show the current state of intercepting inferior's signals.
13035 @item set signal-thread
13036 @itemx set sigthread
13037 @kindex set signal-thread
13038 @kindex set sigthread
13039 This command tells @value{GDBN} which thread is the @code{libc} signal
13040 thread. That thread is run when a signal is delivered to a running
13041 process. @code{set sigthread} is the shorthand alias of @code{set
13044 @item show signal-thread
13045 @itemx show sigthread
13046 @kindex show signal-thread
13047 @kindex show sigthread
13048 These two commands show which thread will run when the inferior is
13049 delivered a signal.
13052 @kindex set stopped@r{, Hurd command}
13053 This commands tells @value{GDBN} that the inferior process is stopped,
13054 as with the @code{SIGSTOP} signal. The stopped process can be
13055 continued by delivering a signal to it.
13058 @kindex show stopped@r{, Hurd command}
13059 This command shows whether @value{GDBN} thinks the debuggee is
13062 @item set exceptions
13063 @kindex set exceptions@r{, Hurd command}
13064 Use this command to turn off trapping of exceptions in the inferior.
13065 When exception trapping is off, neither breakpoints nor
13066 single-stepping will work. To restore the default, set exception
13069 @item show exceptions
13070 @kindex show exceptions@r{, Hurd command}
13071 Show the current state of trapping exceptions in the inferior.
13073 @item set task pause
13074 @kindex set task@r{, Hurd commands}
13075 @cindex task attributes (@sc{gnu} Hurd)
13076 @cindex pause current task (@sc{gnu} Hurd)
13077 This command toggles task suspension when @value{GDBN} has control.
13078 Setting it to on takes effect immediately, and the task is suspended
13079 whenever @value{GDBN} gets control. Setting it to off will take
13080 effect the next time the inferior is continued. If this option is set
13081 to off, you can use @code{set thread default pause on} or @code{set
13082 thread pause on} (see below) to pause individual threads.
13084 @item show task pause
13085 @kindex show task@r{, Hurd commands}
13086 Show the current state of task suspension.
13088 @item set task detach-suspend-count
13089 @cindex task suspend count
13090 @cindex detach from task, @sc{gnu} Hurd
13091 This command sets the suspend count the task will be left with when
13092 @value{GDBN} detaches from it.
13094 @item show task detach-suspend-count
13095 Show the suspend count the task will be left with when detaching.
13097 @item set task exception-port
13098 @itemx set task excp
13099 @cindex task exception port, @sc{gnu} Hurd
13100 This command sets the task exception port to which @value{GDBN} will
13101 forward exceptions. The argument should be the value of the @dfn{send
13102 rights} of the task. @code{set task excp} is a shorthand alias.
13104 @item set noninvasive
13105 @cindex noninvasive task options
13106 This command switches @value{GDBN} to a mode that is the least
13107 invasive as far as interfering with the inferior is concerned. This
13108 is the same as using @code{set task pause}, @code{set exceptions}, and
13109 @code{set signals} to values opposite to the defaults.
13111 @item info send-rights
13112 @itemx info receive-rights
13113 @itemx info port-rights
13114 @itemx info port-sets
13115 @itemx info dead-names
13118 @cindex send rights, @sc{gnu} Hurd
13119 @cindex receive rights, @sc{gnu} Hurd
13120 @cindex port rights, @sc{gnu} Hurd
13121 @cindex port sets, @sc{gnu} Hurd
13122 @cindex dead names, @sc{gnu} Hurd
13123 These commands display information about, respectively, send rights,
13124 receive rights, port rights, port sets, and dead names of a task.
13125 There are also shorthand aliases: @code{info ports} for @code{info
13126 port-rights} and @code{info psets} for @code{info port-sets}.
13128 @item set thread pause
13129 @kindex set thread@r{, Hurd command}
13130 @cindex thread properties, @sc{gnu} Hurd
13131 @cindex pause current thread (@sc{gnu} Hurd)
13132 This command toggles current thread suspension when @value{GDBN} has
13133 control. Setting it to on takes effect immediately, and the current
13134 thread is suspended whenever @value{GDBN} gets control. Setting it to
13135 off will take effect the next time the inferior is continued.
13136 Normally, this command has no effect, since when @value{GDBN} has
13137 control, the whole task is suspended. However, if you used @code{set
13138 task pause off} (see above), this command comes in handy to suspend
13139 only the current thread.
13141 @item show thread pause
13142 @kindex show thread@r{, Hurd command}
13143 This command shows the state of current thread suspension.
13145 @item set thread run
13146 This comamnd sets whether the current thread is allowed to run.
13148 @item show thread run
13149 Show whether the current thread is allowed to run.
13151 @item set thread detach-suspend-count
13152 @cindex thread suspend count, @sc{gnu} Hurd
13153 @cindex detach from thread, @sc{gnu} Hurd
13154 This command sets the suspend count @value{GDBN} will leave on a
13155 thread when detaching. This number is relative to the suspend count
13156 found by @value{GDBN} when it notices the thread; use @code{set thread
13157 takeover-suspend-count} to force it to an absolute value.
13159 @item show thread detach-suspend-count
13160 Show the suspend count @value{GDBN} will leave on the thread when
13163 @item set thread exception-port
13164 @itemx set thread excp
13165 Set the thread exception port to which to forward exceptions. This
13166 overrides the port set by @code{set task exception-port} (see above).
13167 @code{set thread excp} is the shorthand alias.
13169 @item set thread takeover-suspend-count
13170 Normally, @value{GDBN}'s thread suspend counts are relative to the
13171 value @value{GDBN} finds when it notices each thread. This command
13172 changes the suspend counts to be absolute instead.
13174 @item set thread default
13175 @itemx show thread default
13176 @cindex thread default settings, @sc{gnu} Hurd
13177 Each of the above @code{set thread} commands has a @code{set thread
13178 default} counterpart (e.g., @code{set thread default pause}, @code{set
13179 thread default exception-port}, etc.). The @code{thread default}
13180 variety of commands sets the default thread properties for all
13181 threads; you can then change the properties of individual threads with
13182 the non-default commands.
13187 @subsection QNX Neutrino
13188 @cindex QNX Neutrino
13190 @value{GDBN} provides the following commands specific to the QNX
13194 @item set debug nto-debug
13195 @kindex set debug nto-debug
13196 When set to on, enables debugging messages specific to the QNX
13199 @item show debug nto-debug
13200 @kindex show debug nto-debug
13201 Show the current state of QNX Neutrino messages.
13206 @section Embedded Operating Systems
13208 This section describes configurations involving the debugging of
13209 embedded operating systems that are available for several different
13213 * VxWorks:: Using @value{GDBN} with VxWorks
13216 @value{GDBN} includes the ability to debug programs running on
13217 various real-time operating systems.
13220 @subsection Using @value{GDBN} with VxWorks
13226 @kindex target vxworks
13227 @item target vxworks @var{machinename}
13228 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
13229 is the target system's machine name or IP address.
13233 On VxWorks, @code{load} links @var{filename} dynamically on the
13234 current target system as well as adding its symbols in @value{GDBN}.
13236 @value{GDBN} enables developers to spawn and debug tasks running on networked
13237 VxWorks targets from a Unix host. Already-running tasks spawned from
13238 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
13239 both the Unix host and on the VxWorks target. The program
13240 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
13241 installed with the name @code{vxgdb}, to distinguish it from a
13242 @value{GDBN} for debugging programs on the host itself.)
13245 @item VxWorks-timeout @var{args}
13246 @kindex vxworks-timeout
13247 All VxWorks-based targets now support the option @code{vxworks-timeout}.
13248 This option is set by the user, and @var{args} represents the number of
13249 seconds @value{GDBN} waits for responses to rpc's. You might use this if
13250 your VxWorks target is a slow software simulator or is on the far side
13251 of a thin network line.
13254 The following information on connecting to VxWorks was current when
13255 this manual was produced; newer releases of VxWorks may use revised
13258 @findex INCLUDE_RDB
13259 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
13260 to include the remote debugging interface routines in the VxWorks
13261 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
13262 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
13263 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
13264 source debugging task @code{tRdbTask} when VxWorks is booted. For more
13265 information on configuring and remaking VxWorks, see the manufacturer's
13267 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
13269 Once you have included @file{rdb.a} in your VxWorks system image and set
13270 your Unix execution search path to find @value{GDBN}, you are ready to
13271 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
13272 @code{vxgdb}, depending on your installation).
13274 @value{GDBN} comes up showing the prompt:
13281 * VxWorks Connection:: Connecting to VxWorks
13282 * VxWorks Download:: VxWorks download
13283 * VxWorks Attach:: Running tasks
13286 @node VxWorks Connection
13287 @subsubsection Connecting to VxWorks
13289 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
13290 network. To connect to a target whose host name is ``@code{tt}'', type:
13293 (vxgdb) target vxworks tt
13297 @value{GDBN} displays messages like these:
13300 Attaching remote machine across net...
13305 @value{GDBN} then attempts to read the symbol tables of any object modules
13306 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
13307 these files by searching the directories listed in the command search
13308 path (@pxref{Environment, ,Your program's environment}); if it fails
13309 to find an object file, it displays a message such as:
13312 prog.o: No such file or directory.
13315 When this happens, add the appropriate directory to the search path with
13316 the @value{GDBN} command @code{path}, and execute the @code{target}
13319 @node VxWorks Download
13320 @subsubsection VxWorks download
13322 @cindex download to VxWorks
13323 If you have connected to the VxWorks target and you want to debug an
13324 object that has not yet been loaded, you can use the @value{GDBN}
13325 @code{load} command to download a file from Unix to VxWorks
13326 incrementally. The object file given as an argument to the @code{load}
13327 command is actually opened twice: first by the VxWorks target in order
13328 to download the code, then by @value{GDBN} in order to read the symbol
13329 table. This can lead to problems if the current working directories on
13330 the two systems differ. If both systems have NFS mounted the same
13331 filesystems, you can avoid these problems by using absolute paths.
13332 Otherwise, it is simplest to set the working directory on both systems
13333 to the directory in which the object file resides, and then to reference
13334 the file by its name, without any path. For instance, a program
13335 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
13336 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
13337 program, type this on VxWorks:
13340 -> cd "@var{vxpath}/vw/demo/rdb"
13344 Then, in @value{GDBN}, type:
13347 (vxgdb) cd @var{hostpath}/vw/demo/rdb
13348 (vxgdb) load prog.o
13351 @value{GDBN} displays a response similar to this:
13354 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
13357 You can also use the @code{load} command to reload an object module
13358 after editing and recompiling the corresponding source file. Note that
13359 this makes @value{GDBN} delete all currently-defined breakpoints,
13360 auto-displays, and convenience variables, and to clear the value
13361 history. (This is necessary in order to preserve the integrity of
13362 debugger's data structures that reference the target system's symbol
13365 @node VxWorks Attach
13366 @subsubsection Running tasks
13368 @cindex running VxWorks tasks
13369 You can also attach to an existing task using the @code{attach} command as
13373 (vxgdb) attach @var{task}
13377 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
13378 or suspended when you attach to it. Running tasks are suspended at
13379 the time of attachment.
13381 @node Embedded Processors
13382 @section Embedded Processors
13384 This section goes into details specific to particular embedded
13387 @cindex send command to simulator
13388 Whenever a specific embedded processor has a simulator, @value{GDBN}
13389 allows to send an arbitrary command to the simulator.
13392 @item sim @var{command}
13393 @kindex sim@r{, a command}
13394 Send an arbitrary @var{command} string to the simulator. Consult the
13395 documentation for the specific simulator in use for information about
13396 acceptable commands.
13402 * H8/300:: Renesas H8/300
13403 * H8/500:: Renesas H8/500
13404 * M32R/D:: Renesas M32R/D
13405 * M68K:: Motorola M68K
13406 * MIPS Embedded:: MIPS Embedded
13407 * OpenRISC 1000:: OpenRisc 1000
13408 * PA:: HP PA Embedded
13411 * Sparclet:: Tsqware Sparclet
13412 * Sparclite:: Fujitsu Sparclite
13413 * ST2000:: Tandem ST2000
13414 * Z8000:: Zilog Z8000
13417 * Super-H:: Renesas Super-H
13418 * WinCE:: Windows CE child processes
13427 @item target rdi @var{dev}
13428 ARM Angel monitor, via RDI library interface to ADP protocol. You may
13429 use this target to communicate with both boards running the Angel
13430 monitor, or with the EmbeddedICE JTAG debug device.
13433 @item target rdp @var{dev}
13438 @value{GDBN} provides the following ARM-specific commands:
13441 @item set arm disassembler
13443 This commands selects from a list of disassembly styles. The
13444 @code{"std"} style is the standard style.
13446 @item show arm disassembler
13448 Show the current disassembly style.
13450 @item set arm apcs32
13451 @cindex ARM 32-bit mode
13452 This command toggles ARM operation mode between 32-bit and 26-bit.
13454 @item show arm apcs32
13455 Display the current usage of the ARM 32-bit mode.
13457 @item set arm fpu @var{fputype}
13458 This command sets the ARM floating-point unit (FPU) type. The
13459 argument @var{fputype} can be one of these:
13463 Determine the FPU type by querying the OS ABI.
13465 Software FPU, with mixed-endian doubles on little-endian ARM
13468 GCC-compiled FPA co-processor.
13470 Software FPU with pure-endian doubles.
13476 Show the current type of the FPU.
13479 This command forces @value{GDBN} to use the specified ABI.
13482 Show the currently used ABI.
13484 @item set debug arm
13485 Toggle whether to display ARM-specific debugging messages from the ARM
13486 target support subsystem.
13488 @item show debug arm
13489 Show whether ARM-specific debugging messages are enabled.
13492 The following commands are available when an ARM target is debugged
13493 using the RDI interface:
13496 @item rdilogfile @r{[}@var{file}@r{]}
13498 @cindex ADP (Angel Debugger Protocol) logging
13499 Set the filename for the ADP (Angel Debugger Protocol) packet log.
13500 With an argument, sets the log file to the specified @var{file}. With
13501 no argument, show the current log file name. The default log file is
13504 @item rdilogenable @r{[}@var{arg}@r{]}
13505 @kindex rdilogenable
13506 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
13507 enables logging, with an argument 0 or @code{"no"} disables it. With
13508 no arguments displays the current setting. When logging is enabled,
13509 ADP packets exchanged between @value{GDBN} and the RDI target device
13510 are logged to a file.
13512 @item set rdiromatzero
13513 @kindex set rdiromatzero
13514 @cindex ROM at zero address, RDI
13515 Tell @value{GDBN} whether the target has ROM at address 0. If on,
13516 vector catching is disabled, so that zero address can be used. If off
13517 (the default), vector catching is enabled. For this command to take
13518 effect, it needs to be invoked prior to the @code{target rdi} command.
13520 @item show rdiromatzero
13521 @kindex show rdiromatzero
13522 Show the current setting of ROM at zero address.
13524 @item set rdiheartbeat
13525 @kindex set rdiheartbeat
13526 @cindex RDI heartbeat
13527 Enable or disable RDI heartbeat packets. It is not recommended to
13528 turn on this option, since it confuses ARM and EPI JTAG interface, as
13529 well as the Angel monitor.
13531 @item show rdiheartbeat
13532 @kindex show rdiheartbeat
13533 Show the setting of RDI heartbeat packets.
13538 @subsection Renesas H8/300
13542 @kindex target hms@r{, with H8/300}
13543 @item target hms @var{dev}
13544 A Renesas SH, H8/300, or H8/500 board, attached via serial line to your host.
13545 Use special commands @code{device} and @code{speed} to control the serial
13546 line and the communications speed used.
13548 @kindex target e7000@r{, with H8/300}
13549 @item target e7000 @var{dev}
13550 E7000 emulator for Renesas H8 and SH.
13552 @kindex target sh3@r{, with H8/300}
13553 @kindex target sh3e@r{, with H8/300}
13554 @item target sh3 @var{dev}
13555 @itemx target sh3e @var{dev}
13556 Renesas SH-3 and SH-3E target systems.
13560 @cindex download to H8/300 or H8/500
13561 @cindex H8/300 or H8/500 download
13562 @cindex download to Renesas SH
13563 @cindex Renesas SH download
13564 When you select remote debugging to a Renesas SH, H8/300, or H8/500
13565 board, the @code{load} command downloads your program to the Renesas
13566 board and also opens it as the current executable target for
13567 @value{GDBN} on your host (like the @code{file} command).
13569 @value{GDBN} needs to know these things to talk to your
13570 Renesas SH, H8/300, or H8/500:
13574 that you want to use @samp{target hms}, the remote debugging interface
13575 for Renesas microprocessors, or @samp{target e7000}, the in-circuit
13576 emulator for the Renesas SH and the Renesas 300H. (@samp{target hms} is
13577 the default when @value{GDBN} is configured specifically for the Renesas SH,
13578 H8/300, or H8/500.)
13581 what serial device connects your host to your Renesas board (the first
13582 serial device available on your host is the default).
13585 what speed to use over the serial device.
13589 * Renesas Boards:: Connecting to Renesas boards.
13590 * Renesas ICE:: Using the E7000 In-Circuit Emulator.
13591 * Renesas Special:: Special @value{GDBN} commands for Renesas micros.
13594 @node Renesas Boards
13595 @subsubsection Connecting to Renesas boards
13597 @c only for Unix hosts
13599 @cindex serial device, Renesas micros
13600 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
13601 need to explicitly set the serial device. The default @var{port} is the
13602 first available port on your host. This is only necessary on Unix
13603 hosts, where it is typically something like @file{/dev/ttya}.
13606 @cindex serial line speed, Renesas micros
13607 @code{@value{GDBN}} has another special command to set the communications
13608 speed: @samp{speed @var{bps}}. This command also is only used from Unix
13609 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
13610 the DOS @code{mode} command (for instance,
13611 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
13613 The @samp{device} and @samp{speed} commands are available only when you
13614 use a Unix host to debug your Renesas microprocessor programs. If you
13616 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
13617 called @code{asynctsr} to communicate with the development board
13618 through a PC serial port. You must also use the DOS @code{mode} command
13619 to set up the serial port on the DOS side.
13621 The following sample session illustrates the steps needed to start a
13622 program under @value{GDBN} control on an H8/300. The example uses a
13623 sample H8/300 program called @file{t.x}. The procedure is the same for
13624 the Renesas SH and the H8/500.
13626 First hook up your development board. In this example, we use a
13627 board attached to serial port @code{COM2}; if you use a different serial
13628 port, substitute its name in the argument of the @code{mode} command.
13629 When you call @code{asynctsr}, the auxiliary comms program used by the
13630 debugger, you give it just the numeric part of the serial port's name;
13631 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
13635 C:\H8300\TEST> asynctsr 2
13636 C:\H8300\TEST> mode com2:9600,n,8,1,p
13638 Resident portion of MODE loaded
13640 COM2: 9600, n, 8, 1, p
13645 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
13646 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
13647 disable it, or even boot without it, to use @code{asynctsr} to control
13648 your development board.
13651 @kindex target hms@r{, and serial protocol}
13652 Now that serial communications are set up, and the development board is
13653 connected, you can start up @value{GDBN}. Call @code{@value{GDBN}} with
13654 the name of your program as the argument. @code{@value{GDBN}} prompts
13655 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
13656 commands to begin your debugging session: @samp{target hms} to specify
13657 cross-debugging to the Renesas board, and the @code{load} command to
13658 download your program to the board. @code{load} displays the names of
13659 the program's sections, and a @samp{*} for each 2K of data downloaded.
13660 (If you want to refresh @value{GDBN} data on symbols or on the
13661 executable file without downloading, use the @value{GDBN} commands
13662 @code{file} or @code{symbol-file}. These commands, and @code{load}
13663 itself, are described in @ref{Files,,Commands to specify files}.)
13666 (eg-C:\H8300\TEST) @value{GDBP} t.x
13667 @value{GDBN} is free software and you are welcome to distribute copies
13668 of it under certain conditions; type "show copying" to see
13670 There is absolutely no warranty for @value{GDBN}; type "show warranty"
13672 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
13673 (@value{GDBP}) target hms
13674 Connected to remote H8/300 HMS system.
13675 (@value{GDBP}) load t.x
13676 .text : 0x8000 .. 0xabde ***********
13677 .data : 0xabde .. 0xad30 *
13678 .stack : 0xf000 .. 0xf014 *
13681 At this point, you're ready to run or debug your program. From here on,
13682 you can use all the usual @value{GDBN} commands. The @code{break} command
13683 sets breakpoints; the @code{run} command starts your program;
13684 @code{print} or @code{x} display data; the @code{continue} command
13685 resumes execution after stopping at a breakpoint. You can use the
13686 @code{help} command at any time to find out more about @value{GDBN} commands.
13688 Remember, however, that @emph{operating system} facilities aren't
13689 available on your development board; for example, if your program hangs,
13690 you can't send an interrupt---but you can press the @sc{reset} switch!
13692 Use the @sc{reset} button on the development board
13695 to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has
13696 no way to pass an interrupt signal to the development board); and
13699 to return to the @value{GDBN} command prompt after your program finishes
13700 normally. The communications protocol provides no other way for @value{GDBN}
13701 to detect program completion.
13704 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
13705 development board as a ``normal exit'' of your program.
13708 @subsubsection Using the E7000 in-circuit emulator
13710 @kindex target e7000@r{, with Renesas ICE}
13711 You can use the E7000 in-circuit emulator to develop code for either the
13712 Renesas SH or the H8/300H. Use one of these forms of the @samp{target
13713 e7000} command to connect @value{GDBN} to your E7000:
13716 @item target e7000 @var{port} @var{speed}
13717 Use this form if your E7000 is connected to a serial port. The
13718 @var{port} argument identifies what serial port to use (for example,
13719 @samp{com2}). The third argument is the line speed in bits per second
13720 (for example, @samp{9600}).
13722 @item target e7000 @var{hostname}
13723 If your E7000 is installed as a host on a TCP/IP network, you can just
13724 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
13727 The following special commands are available when debugging with the
13731 @item e7000 @var{command}
13733 @cindex send command to E7000 monitor
13734 This sends the specified @var{command} to the E7000 monitor.
13736 @item ftplogin @var{machine} @var{username} @var{password} @var{dir}
13737 @kindex ftplogin@r{, E7000}
13738 This command records information for subsequent interface with the
13739 E7000 monitor via the FTP protocol: @value{GDBN} will log into the
13740 named @var{machine} using specified @var{username} and @var{password},
13741 and then chdir to the named directory @var{dir}.
13743 @item ftpload @var{file}
13744 @kindex ftpload@r{, E7000}
13745 This command uses credentials recorded by @code{ftplogin} to fetch and
13746 load the named @var{file} from the E7000 monitor.
13749 @kindex drain@r{, E7000}
13750 This command drains any pending text buffers stored on the E7000.
13752 @item set usehardbreakpoints
13753 @itemx show usehardbreakpoints
13754 @kindex set usehardbreakpoints@r{, E7000}
13755 @kindex show usehardbreakpoints@r{, E7000}
13756 @cindex hardware breakpoints, and E7000
13757 These commands set and show the use of hardware breakpoints for all
13758 breakpoints. @xref{Set Breaks, hardware-assisted breakpoint}, for
13759 more information about using hardware breakpoints selectively.
13762 @node Renesas Special
13763 @subsubsection Special @value{GDBN} commands for Renesas micros
13765 Some @value{GDBN} commands are available only for the H8/300:
13769 @kindex set machine
13770 @kindex show machine
13771 @item set machine h8300
13772 @itemx set machine h8300h
13773 Condition @value{GDBN} for one of the two variants of the H8/300
13774 architecture with @samp{set machine}. You can use @samp{show machine}
13775 to check which variant is currently in effect.
13784 @kindex set memory @var{mod}
13785 @cindex memory models, H8/500
13786 @item set memory @var{mod}
13788 Specify which H8/500 memory model (@var{mod}) you are using with
13789 @samp{set memory}; check which memory model is in effect with @samp{show
13790 memory}. The accepted values for @var{mod} are @code{small},
13791 @code{big}, @code{medium}, and @code{compact}.
13796 @subsection Renesas M32R/D and M32R/SDI
13799 @kindex target m32r
13800 @item target m32r @var{dev}
13801 Renesas M32R/D ROM monitor.
13803 @kindex target m32rsdi
13804 @item target m32rsdi @var{dev}
13805 Renesas M32R SDI server, connected via parallel port to the board.
13808 The following @value{GDBN} commands are specific to the M32R monitor:
13811 @item set download-path @var{path}
13812 @kindex set download-path
13813 @cindex find downloadable @sc{srec} files (M32R)
13814 Set the default path for finding donwloadable @sc{srec} files.
13816 @item show download-path
13817 @kindex show download-path
13818 Show the default path for downloadable @sc{srec} files.
13820 @item set board-address @var{addr}
13821 @kindex set board-address
13822 @cindex M32-EVA target board address
13823 Set the IP address for the M32R-EVA target board.
13825 @item show board-address
13826 @kindex show board-address
13827 Show the current IP address of the target board.
13829 @item set server-address @var{addr}
13830 @kindex set server-address
13831 @cindex download server address (M32R)
13832 Set the IP address for the download server, which is the @value{GDBN}'s
13835 @item show server-address
13836 @kindex show server-address
13837 Display the IP address of the download server.
13839 @item upload @r{[}@var{file}@r{]}
13840 @kindex upload@r{, M32R}
13841 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
13842 upload capability. If no @var{file} argument is given, the current
13843 executable file is uploaded.
13845 @item tload @r{[}@var{file}@r{]}
13846 @kindex tload@r{, M32R}
13847 Test the @code{upload} command.
13850 The following commands are available for M32R/SDI:
13855 @cindex reset SDI connection, M32R
13856 This command resets the SDI connection.
13860 This command shows the SDI connection status.
13863 @kindex debug_chaos
13864 @cindex M32R/Chaos debugging
13865 Instructs the remote that M32R/Chaos debugging is to be used.
13867 @item use_debug_dma
13868 @kindex use_debug_dma
13869 Instructs the remote to use the DEBUG_DMA method of accessing memory.
13872 @kindex use_mon_code
13873 Instructs the remote to use the MON_CODE method of accessing memory.
13876 @kindex use_ib_break
13877 Instructs the remote to set breakpoints by IB break.
13879 @item use_dbt_break
13880 @kindex use_dbt_break
13881 Instructs the remote to set breakpoints by DBT.
13887 The Motorola m68k configuration includes ColdFire support, and
13888 target command for the following ROM monitors.
13892 @kindex target abug
13893 @item target abug @var{dev}
13894 ABug ROM monitor for M68K.
13896 @kindex target cpu32bug
13897 @item target cpu32bug @var{dev}
13898 CPU32BUG monitor, running on a CPU32 (M68K) board.
13900 @kindex target dbug
13901 @item target dbug @var{dev}
13902 dBUG ROM monitor for Motorola ColdFire.
13905 @item target est @var{dev}
13906 EST-300 ICE monitor, running on a CPU32 (M68K) board.
13908 @kindex target rom68k
13909 @item target rom68k @var{dev}
13910 ROM 68K monitor, running on an M68K IDP board.
13916 @kindex target rombug
13917 @item target rombug @var{dev}
13918 ROMBUG ROM monitor for OS/9000.
13922 @node MIPS Embedded
13923 @subsection MIPS Embedded
13925 @cindex MIPS boards
13926 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
13927 MIPS board attached to a serial line. This is available when
13928 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
13931 Use these @value{GDBN} commands to specify the connection to your target board:
13934 @item target mips @var{port}
13935 @kindex target mips @var{port}
13936 To run a program on the board, start up @code{@value{GDBP}} with the
13937 name of your program as the argument. To connect to the board, use the
13938 command @samp{target mips @var{port}}, where @var{port} is the name of
13939 the serial port connected to the board. If the program has not already
13940 been downloaded to the board, you may use the @code{load} command to
13941 download it. You can then use all the usual @value{GDBN} commands.
13943 For example, this sequence connects to the target board through a serial
13944 port, and loads and runs a program called @var{prog} through the
13948 host$ @value{GDBP} @var{prog}
13949 @value{GDBN} is free software and @dots{}
13950 (@value{GDBP}) target mips /dev/ttyb
13951 (@value{GDBP}) load @var{prog}
13955 @item target mips @var{hostname}:@var{portnumber}
13956 On some @value{GDBN} host configurations, you can specify a TCP
13957 connection (for instance, to a serial line managed by a terminal
13958 concentrator) instead of a serial port, using the syntax
13959 @samp{@var{hostname}:@var{portnumber}}.
13961 @item target pmon @var{port}
13962 @kindex target pmon @var{port}
13965 @item target ddb @var{port}
13966 @kindex target ddb @var{port}
13967 NEC's DDB variant of PMON for Vr4300.
13969 @item target lsi @var{port}
13970 @kindex target lsi @var{port}
13971 LSI variant of PMON.
13973 @kindex target r3900
13974 @item target r3900 @var{dev}
13975 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
13977 @kindex target array
13978 @item target array @var{dev}
13979 Array Tech LSI33K RAID controller board.
13985 @value{GDBN} also supports these special commands for MIPS targets:
13988 @item set mipsfpu double
13989 @itemx set mipsfpu single
13990 @itemx set mipsfpu none
13991 @itemx set mipsfpu auto
13992 @itemx show mipsfpu
13993 @kindex set mipsfpu
13994 @kindex show mipsfpu
13995 @cindex MIPS remote floating point
13996 @cindex floating point, MIPS remote
13997 If your target board does not support the MIPS floating point
13998 coprocessor, you should use the command @samp{set mipsfpu none} (if you
13999 need this, you may wish to put the command in your @value{GDBN} init
14000 file). This tells @value{GDBN} how to find the return value of
14001 functions which return floating point values. It also allows
14002 @value{GDBN} to avoid saving the floating point registers when calling
14003 functions on the board. If you are using a floating point coprocessor
14004 with only single precision floating point support, as on the @sc{r4650}
14005 processor, use the command @samp{set mipsfpu single}. The default
14006 double precision floating point coprocessor may be selected using
14007 @samp{set mipsfpu double}.
14009 In previous versions the only choices were double precision or no
14010 floating point, so @samp{set mipsfpu on} will select double precision
14011 and @samp{set mipsfpu off} will select no floating point.
14013 As usual, you can inquire about the @code{mipsfpu} variable with
14014 @samp{show mipsfpu}.
14016 @item set timeout @var{seconds}
14017 @itemx set retransmit-timeout @var{seconds}
14018 @itemx show timeout
14019 @itemx show retransmit-timeout
14020 @cindex @code{timeout}, MIPS protocol
14021 @cindex @code{retransmit-timeout}, MIPS protocol
14022 @kindex set timeout
14023 @kindex show timeout
14024 @kindex set retransmit-timeout
14025 @kindex show retransmit-timeout
14026 You can control the timeout used while waiting for a packet, in the MIPS
14027 remote protocol, with the @code{set timeout @var{seconds}} command. The
14028 default is 5 seconds. Similarly, you can control the timeout used while
14029 waiting for an acknowledgement of a packet with the @code{set
14030 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
14031 You can inspect both values with @code{show timeout} and @code{show
14032 retransmit-timeout}. (These commands are @emph{only} available when
14033 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
14035 The timeout set by @code{set timeout} does not apply when @value{GDBN}
14036 is waiting for your program to stop. In that case, @value{GDBN} waits
14037 forever because it has no way of knowing how long the program is going
14038 to run before stopping.
14040 @item set syn-garbage-limit @var{num}
14041 @kindex set syn-garbage-limit@r{, MIPS remote}
14042 @cindex synchronize with remote MIPS target
14043 Limit the maximum number of characters @value{GDBN} should ignore when
14044 it tries to synchronize with the remote target. The default is 10
14045 characters. Setting the limit to -1 means there's no limit.
14047 @item show syn-garbage-limit
14048 @kindex show syn-garbage-limit@r{, MIPS remote}
14049 Show the current limit on the number of characters to ignore when
14050 trying to synchronize with the remote system.
14052 @item set monitor-prompt @var{prompt}
14053 @kindex set monitor-prompt@r{, MIPS remote}
14054 @cindex remote monitor prompt
14055 Tell @value{GDBN} to expect the specified @var{prompt} string from the
14056 remote monitor. The default depends on the target:
14066 @item show monitor-prompt
14067 @kindex show monitor-prompt@r{, MIPS remote}
14068 Show the current strings @value{GDBN} expects as the prompt from the
14071 @item set monitor-warnings
14072 @kindex set monitor-warnings@r{, MIPS remote}
14073 Enable or disable monitor warnings about hardware breakpoints. This
14074 has effect only for the @code{lsi} target. When on, @value{GDBN} will
14075 display warning messages whose codes are returned by the @code{lsi}
14076 PMON monitor for breakpoint commands.
14078 @item show monitor-warnings
14079 @kindex show monitor-warnings@r{, MIPS remote}
14080 Show the current setting of printing monitor warnings.
14082 @item pmon @var{command}
14083 @kindex pmon@r{, MIPS remote}
14084 @cindex send PMON command
14085 This command allows sending an arbitrary @var{command} string to the
14086 monitor. The monitor must be in debug mode for this to work.
14089 @node OpenRISC 1000
14090 @subsection OpenRISC 1000
14091 @cindex OpenRISC 1000
14093 @cindex or1k boards
14094 See OR1k Architecture document (@uref{www.opencores.org}) for more information
14095 about platform and commands.
14099 @kindex target jtag
14100 @item target jtag jtag://@var{host}:@var{port}
14102 Connects to remote JTAG server.
14103 JTAG remote server can be either an or1ksim or JTAG server,
14104 connected via parallel port to the board.
14106 Example: @code{target jtag jtag://localhost:9999}
14109 @item or1ksim @var{command}
14110 If connected to @code{or1ksim} OpenRISC 1000 Architectural
14111 Simulator, proprietary commands can be executed.
14113 @kindex info or1k spr
14114 @item info or1k spr
14115 Displays spr groups.
14117 @item info or1k spr @var{group}
14118 @itemx info or1k spr @var{groupno}
14119 Displays register names in selected group.
14121 @item info or1k spr @var{group} @var{register}
14122 @itemx info or1k spr @var{register}
14123 @itemx info or1k spr @var{groupno} @var{registerno}
14124 @itemx info or1k spr @var{registerno}
14125 Shows information about specified spr register.
14128 @item spr @var{group} @var{register} @var{value}
14129 @itemx spr @var{register @var{value}}
14130 @itemx spr @var{groupno} @var{registerno @var{value}}
14131 @itemx spr @var{registerno @var{value}}
14132 Writes @var{value} to specified spr register.
14135 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
14136 It is very similar to @value{GDBN} trace, except it does not interfere with normal
14137 program execution and is thus much faster. Hardware breakpoints/watchpoint
14138 triggers can be set using:
14141 Load effective address/data
14143 Store effective address/data
14145 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
14150 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
14151 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
14153 @code{htrace} commands:
14154 @cindex OpenRISC 1000 htrace
14157 @item hwatch @var{conditional}
14158 Set hardware watchpoint on combination of Load/Store Effecive Address(es)
14159 or Data. For example:
14161 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14163 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14167 Display information about current HW trace configuration.
14169 @item htrace trigger @var{conditional}
14170 Set starting criteria for HW trace.
14172 @item htrace qualifier @var{conditional}
14173 Set acquisition qualifier for HW trace.
14175 @item htrace stop @var{conditional}
14176 Set HW trace stopping criteria.
14178 @item htrace record [@var{data}]*
14179 Selects the data to be recorded, when qualifier is met and HW trace was
14182 @item htrace enable
14183 @itemx htrace disable
14184 Enables/disables the HW trace.
14186 @item htrace rewind [@var{filename}]
14187 Clears currently recorded trace data.
14189 If filename is specified, new trace file is made and any newly collected data
14190 will be written there.
14192 @item htrace print [@var{start} [@var{len}]]
14193 Prints trace buffer, using current record configuration.
14195 @item htrace mode continuous
14196 Set continuous trace mode.
14198 @item htrace mode suspend
14199 Set suspend trace mode.
14204 @subsection PowerPC
14207 @kindex target dink32
14208 @item target dink32 @var{dev}
14209 DINK32 ROM monitor.
14211 @kindex target ppcbug
14212 @item target ppcbug @var{dev}
14213 @kindex target ppcbug1
14214 @item target ppcbug1 @var{dev}
14215 PPCBUG ROM monitor for PowerPC.
14218 @item target sds @var{dev}
14219 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
14222 @cindex SDS protocol
14223 The following commands specifi to the SDS protocol are supported
14227 @item set sdstimeout @var{nsec}
14228 @kindex set sdstimeout
14229 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
14230 default is 2 seconds.
14232 @item show sdstimeout
14233 @kindex show sdstimeout
14234 Show the current value of the SDS timeout.
14236 @item sds @var{command}
14237 @kindex sds@r{, a command}
14238 Send the specified @var{command} string to the SDS monitor.
14243 @subsection HP PA Embedded
14247 @kindex target op50n
14248 @item target op50n @var{dev}
14249 OP50N monitor, running on an OKI HPPA board.
14251 @kindex target w89k
14252 @item target w89k @var{dev}
14253 W89K monitor, running on a Winbond HPPA board.
14258 @subsection Renesas SH
14262 @kindex target hms@r{, with Renesas SH}
14263 @item target hms @var{dev}
14264 A Renesas SH board attached via serial line to your host. Use special
14265 commands @code{device} and @code{speed} to control the serial line and
14266 the communications speed used.
14268 @kindex target e7000@r{, with Renesas SH}
14269 @item target e7000 @var{dev}
14270 E7000 emulator for Renesas SH.
14272 @kindex target sh3@r{, with SH}
14273 @kindex target sh3e@r{, with SH}
14274 @item target sh3 @var{dev}
14275 @item target sh3e @var{dev}
14276 Renesas SH-3 and SH-3E target systems.
14281 @subsection Tsqware Sparclet
14285 @value{GDBN} enables developers to debug tasks running on
14286 Sparclet targets from a Unix host.
14287 @value{GDBN} uses code that runs on
14288 both the Unix host and on the Sparclet target. The program
14289 @code{@value{GDBP}} is installed and executed on the Unix host.
14292 @item remotetimeout @var{args}
14293 @kindex remotetimeout
14294 @value{GDBN} supports the option @code{remotetimeout}.
14295 This option is set by the user, and @var{args} represents the number of
14296 seconds @value{GDBN} waits for responses.
14299 @cindex compiling, on Sparclet
14300 When compiling for debugging, include the options @samp{-g} to get debug
14301 information and @samp{-Ttext} to relocate the program to where you wish to
14302 load it on the target. You may also want to add the options @samp{-n} or
14303 @samp{-N} in order to reduce the size of the sections. Example:
14306 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
14309 You can use @code{objdump} to verify that the addresses are what you intended:
14312 sparclet-aout-objdump --headers --syms prog
14315 @cindex running, on Sparclet
14317 your Unix execution search path to find @value{GDBN}, you are ready to
14318 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
14319 (or @code{sparclet-aout-gdb}, depending on your installation).
14321 @value{GDBN} comes up showing the prompt:
14328 * Sparclet File:: Setting the file to debug
14329 * Sparclet Connection:: Connecting to Sparclet
14330 * Sparclet Download:: Sparclet download
14331 * Sparclet Execution:: Running and debugging
14334 @node Sparclet File
14335 @subsubsection Setting file to debug
14337 The @value{GDBN} command @code{file} lets you choose with program to debug.
14340 (gdbslet) file prog
14344 @value{GDBN} then attempts to read the symbol table of @file{prog}.
14345 @value{GDBN} locates
14346 the file by searching the directories listed in the command search
14348 If the file was compiled with debug information (option "-g"), source
14349 files will be searched as well.
14350 @value{GDBN} locates
14351 the source files by searching the directories listed in the directory search
14352 path (@pxref{Environment, ,Your program's environment}).
14354 to find a file, it displays a message such as:
14357 prog: No such file or directory.
14360 When this happens, add the appropriate directories to the search paths with
14361 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
14362 @code{target} command again.
14364 @node Sparclet Connection
14365 @subsubsection Connecting to Sparclet
14367 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
14368 To connect to a target on serial port ``@code{ttya}'', type:
14371 (gdbslet) target sparclet /dev/ttya
14372 Remote target sparclet connected to /dev/ttya
14373 main () at ../prog.c:3
14377 @value{GDBN} displays messages like these:
14383 @node Sparclet Download
14384 @subsubsection Sparclet download
14386 @cindex download to Sparclet
14387 Once connected to the Sparclet target,
14388 you can use the @value{GDBN}
14389 @code{load} command to download the file from the host to the target.
14390 The file name and load offset should be given as arguments to the @code{load}
14392 Since the file format is aout, the program must be loaded to the starting
14393 address. You can use @code{objdump} to find out what this value is. The load
14394 offset is an offset which is added to the VMA (virtual memory address)
14395 of each of the file's sections.
14396 For instance, if the program
14397 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
14398 and bss at 0x12010170, in @value{GDBN}, type:
14401 (gdbslet) load prog 0x12010000
14402 Loading section .text, size 0xdb0 vma 0x12010000
14405 If the code is loaded at a different address then what the program was linked
14406 to, you may need to use the @code{section} and @code{add-symbol-file} commands
14407 to tell @value{GDBN} where to map the symbol table.
14409 @node Sparclet Execution
14410 @subsubsection Running and debugging
14412 @cindex running and debugging Sparclet programs
14413 You can now begin debugging the task using @value{GDBN}'s execution control
14414 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
14415 manual for the list of commands.
14419 Breakpoint 1 at 0x12010000: file prog.c, line 3.
14421 Starting program: prog
14422 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
14423 3 char *symarg = 0;
14425 4 char *execarg = "hello!";
14430 @subsection Fujitsu Sparclite
14434 @kindex target sparclite
14435 @item target sparclite @var{dev}
14436 Fujitsu sparclite boards, used only for the purpose of loading.
14437 You must use an additional command to debug the program.
14438 For example: target remote @var{dev} using @value{GDBN} standard
14444 @subsection Tandem ST2000
14446 @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
14449 To connect your ST2000 to the host system, see the manufacturer's
14450 manual. Once the ST2000 is physically attached, you can run:
14453 target st2000 @var{dev} @var{speed}
14457 to establish it as your debugging environment. @var{dev} is normally
14458 the name of a serial device, such as @file{/dev/ttya}, connected to the
14459 ST2000 via a serial line. You can instead specify @var{dev} as a TCP
14460 connection (for example, to a serial line attached via a terminal
14461 concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
14463 The @code{load} and @code{attach} commands are @emph{not} defined for
14464 this target; you must load your program into the ST2000 as you normally
14465 would for standalone operation. @value{GDBN} reads debugging information
14466 (such as symbols) from a separate, debugging version of the program
14467 available on your host computer.
14468 @c FIXME!! This is terribly vague; what little content is here is
14469 @c basically hearsay.
14471 @cindex ST2000 auxiliary commands
14472 These auxiliary @value{GDBN} commands are available to help you with the ST2000
14476 @item st2000 @var{command}
14477 @kindex st2000 @var{cmd}
14478 @cindex STDBUG commands (ST2000)
14479 @cindex commands to STDBUG (ST2000)
14480 Send a @var{command} to the STDBUG monitor. See the manufacturer's
14481 manual for available commands.
14484 @cindex connect (to STDBUG)
14485 Connect the controlling terminal to the STDBUG command monitor. When
14486 you are done interacting with STDBUG, typing either of two character
14487 sequences gets you back to the @value{GDBN} command prompt:
14488 @kbd{@key{RET}~.} (Return, followed by tilde and period) or
14489 @kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D).
14493 @subsection Zilog Z8000
14496 @cindex simulator, Z8000
14497 @cindex Zilog Z8000 simulator
14499 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
14502 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
14503 unsegmented variant of the Z8000 architecture) or the Z8001 (the
14504 segmented variant). The simulator recognizes which architecture is
14505 appropriate by inspecting the object code.
14508 @item target sim @var{args}
14510 @kindex target sim@r{, with Z8000}
14511 Debug programs on a simulated CPU. If the simulator supports setup
14512 options, specify them via @var{args}.
14516 After specifying this target, you can debug programs for the simulated
14517 CPU in the same style as programs for your host computer; use the
14518 @code{file} command to load a new program image, the @code{run} command
14519 to run your program, and so on.
14521 As well as making available all the usual machine registers
14522 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
14523 additional items of information as specially named registers:
14528 Counts clock-ticks in the simulator.
14531 Counts instructions run in the simulator.
14534 Execution time in 60ths of a second.
14538 You can refer to these values in @value{GDBN} expressions with the usual
14539 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
14540 conditional breakpoint that suspends only after at least 5000
14541 simulated clock ticks.
14544 @subsection Atmel AVR
14547 When configured for debugging the Atmel AVR, @value{GDBN} supports the
14548 following AVR-specific commands:
14551 @item info io_registers
14552 @kindex info io_registers@r{, AVR}
14553 @cindex I/O registers (Atmel AVR)
14554 This command displays information about the AVR I/O registers. For
14555 each register, @value{GDBN} prints its number and value.
14562 When configured for debugging CRIS, @value{GDBN} provides the
14563 following CRIS-specific commands:
14566 @item set cris-version @var{ver}
14567 @cindex CRIS version
14568 Set the current CRIS version to @var{ver}. The CRIS version affects
14569 register names and sizes. This command is useful in case
14570 autodetection of the CRIS version fails.
14572 @item show cris-version
14573 Show the current CRIS version.
14575 @item set cris-dwarf2-cfi
14576 @cindex DWARF-2 CFI and CRIS
14577 Set the usage of DWARF-2 CFI for CRIS debugging. The default is off
14578 if using @code{gcc-cris} whose version is below @code{R59}, otherwise
14581 @item show cris-dwarf2-cfi
14582 Show the current state of using DWARF-2 CFI.
14586 @subsection Renesas Super-H
14589 For the Renesas Super-H processor, @value{GDBN} provides these
14594 @kindex regs@r{, Super-H}
14595 Show the values of all Super-H registers.
14599 @subsection Windows CE
14602 The following commands are available for Windows CE:
14605 @item set remotedirectory @var{dir}
14606 @kindex set remotedirectory
14607 Tell @value{GDBN} to upload files from the named directory @var{dir}.
14608 The default is @file{/gdb}, i.e.@: the root directory on the current
14611 @item show remotedirectory
14612 @kindex show remotedirectory
14613 Show the current value of the upload directory.
14615 @item set remoteupload @var{method}
14616 @kindex set remoteupload
14617 Set the method used to upload files to remote device. Valid values
14618 for @var{method} are @samp{always}, @samp{newer}, and @samp{never}.
14619 The default is @samp{newer}.
14621 @item show remoteupload
14622 @kindex show remoteupload
14623 Show the current setting of the upload method.
14625 @item set remoteaddhost
14626 @kindex set remoteaddhost
14627 Tell @value{GDBN} whether to add this host to the remote stub's
14628 arguments when you debug over a network.
14630 @item show remoteaddhost
14631 @kindex show remoteaddhost
14632 Show whether to add this host to remote stub's arguments when
14633 debugging over a network.
14637 @node Architectures
14638 @section Architectures
14640 This section describes characteristics of architectures that affect
14641 all uses of @value{GDBN} with the architecture, both native and cross.
14648 * HPPA:: HP PA architecture
14652 @subsection x86 Architecture-specific issues.
14655 @item set struct-convention @var{mode}
14656 @kindex set struct-convention
14657 @cindex struct return convention
14658 @cindex struct/union returned in registers
14659 Set the convention used by the inferior to return @code{struct}s and
14660 @code{union}s from functions to @var{mode}. Possible values of
14661 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
14662 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
14663 are returned on the stack, while @code{"reg"} means that a
14664 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
14665 be returned in a register.
14667 @item show struct-convention
14668 @kindex show struct-convention
14669 Show the current setting of the convention to return @code{struct}s
14678 @kindex set rstack_high_address
14679 @cindex AMD 29K register stack
14680 @cindex register stack, AMD29K
14681 @item set rstack_high_address @var{address}
14682 On AMD 29000 family processors, registers are saved in a separate
14683 @dfn{register stack}. There is no way for @value{GDBN} to determine the
14684 extent of this stack. Normally, @value{GDBN} just assumes that the
14685 stack is ``large enough''. This may result in @value{GDBN} referencing
14686 memory locations that do not exist. If necessary, you can get around
14687 this problem by specifying the ending address of the register stack with
14688 the @code{set rstack_high_address} command. The argument should be an
14689 address, which you probably want to precede with @samp{0x} to specify in
14692 @kindex show rstack_high_address
14693 @item show rstack_high_address
14694 Display the current limit of the register stack, on AMD 29000 family
14702 See the following section.
14707 @cindex stack on Alpha
14708 @cindex stack on MIPS
14709 @cindex Alpha stack
14711 Alpha- and MIPS-based computers use an unusual stack frame, which
14712 sometimes requires @value{GDBN} to search backward in the object code to
14713 find the beginning of a function.
14715 @cindex response time, MIPS debugging
14716 To improve response time (especially for embedded applications, where
14717 @value{GDBN} may be restricted to a slow serial line for this search)
14718 you may want to limit the size of this search, using one of these
14722 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
14723 @item set heuristic-fence-post @var{limit}
14724 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
14725 search for the beginning of a function. A value of @var{0} (the
14726 default) means there is no limit. However, except for @var{0}, the
14727 larger the limit the more bytes @code{heuristic-fence-post} must search
14728 and therefore the longer it takes to run. You should only need to use
14729 this command when debugging a stripped executable.
14731 @item show heuristic-fence-post
14732 Display the current limit.
14736 These commands are available @emph{only} when @value{GDBN} is configured
14737 for debugging programs on Alpha or MIPS processors.
14739 Several MIPS-specific commands are available when debugging MIPS
14743 @item set mips saved-gpreg-size @var{size}
14744 @kindex set mips saved-gpreg-size
14745 @cindex MIPS GP register size on stack
14746 Set the size of MIPS general-purpose registers saved on the stack.
14747 The argument @var{size} can be one of the following:
14751 32-bit GP registers
14753 64-bit GP registers
14755 Use the target's default setting or autodetect the saved size from the
14756 information contained in the executable. This is the default
14759 @item show mips saved-gpreg-size
14760 @kindex show mips saved-gpreg-size
14761 Show the current size of MIPS GP registers on the stack.
14763 @item set mips stack-arg-size @var{size}
14764 @kindex set mips stack-arg-size
14765 @cindex MIPS stack space for arguments
14766 Set the amount of stack space reserved for arguments to functions.
14767 The argument can be one of @code{"32"}, @code{"64"} or @code{"auto"}
14770 @item set mips abi @var{arg}
14771 @kindex set mips abi
14772 @cindex set ABI for MIPS
14773 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
14774 values of @var{arg} are:
14778 The default ABI associated with the current binary (this is the
14789 @item show mips abi
14790 @kindex show mips abi
14791 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
14794 @itemx show mipsfpu
14795 @xref{MIPS Embedded, set mipsfpu}.
14797 @item set mips mask-address @var{arg}
14798 @kindex set mips mask-address
14799 @cindex MIPS addresses, masking
14800 This command determines whether the most-significant 32 bits of 64-bit
14801 MIPS addresses are masked off. The argument @var{arg} can be
14802 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
14803 setting, which lets @value{GDBN} determine the correct value.
14805 @item show mips mask-address
14806 @kindex show mips mask-address
14807 Show whether the upper 32 bits of MIPS addresses are masked off or
14810 @item set remote-mips64-transfers-32bit-regs
14811 @kindex set remote-mips64-transfers-32bit-regs
14812 This command controls compatibility with 64-bit MIPS targets that
14813 transfer data in 32-bit quantities. If you have an old MIPS 64 target
14814 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
14815 and 64 bits for other registers, set this option to @samp{on}.
14817 @item show remote-mips64-transfers-32bit-regs
14818 @kindex show remote-mips64-transfers-32bit-regs
14819 Show the current setting of compatibility with older MIPS 64 targets.
14821 @item set debug mips
14822 @kindex set debug mips
14823 This command turns on and off debugging messages for the MIPS-specific
14824 target code in @value{GDBN}.
14826 @item show debug mips
14827 @kindex show debug mips
14828 Show the current setting of MIPS debugging messages.
14834 @cindex HPPA support
14836 When @value{GDBN} is debugging te HP PA architecture, it provides the
14837 following special commands:
14840 @item set debug hppa
14841 @kindex set debug hppa
14842 THis command determines whether HPPA architecture specific debugging
14843 messages are to be displayed.
14845 @item show debug hppa
14846 Show whether HPPA debugging messages are displayed.
14848 @item maint print unwind @var{address}
14849 @kindex maint print unwind@r{, HPPA}
14850 This command displays the contents of the unwind table entry at the
14851 given @var{address}.
14856 @node Controlling GDB
14857 @chapter Controlling @value{GDBN}
14859 You can alter the way @value{GDBN} interacts with you by using the
14860 @code{set} command. For commands controlling how @value{GDBN} displays
14861 data, see @ref{Print Settings, ,Print settings}. Other settings are
14866 * Editing:: Command editing
14867 * History:: Command history
14868 * Screen Size:: Screen size
14869 * Numbers:: Numbers
14870 * ABI:: Configuring the current ABI
14871 * Messages/Warnings:: Optional warnings and messages
14872 * Debugging Output:: Optional messages about internal happenings
14880 @value{GDBN} indicates its readiness to read a command by printing a string
14881 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
14882 can change the prompt string with the @code{set prompt} command. For
14883 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
14884 the prompt in one of the @value{GDBN} sessions so that you can always tell
14885 which one you are talking to.
14887 @emph{Note:} @code{set prompt} does not add a space for you after the
14888 prompt you set. This allows you to set a prompt which ends in a space
14889 or a prompt that does not.
14893 @item set prompt @var{newprompt}
14894 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
14896 @kindex show prompt
14898 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
14902 @section Command editing
14904 @cindex command line editing
14906 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
14907 @sc{gnu} library provides consistent behavior for programs which provide a
14908 command line interface to the user. Advantages are @sc{gnu} Emacs-style
14909 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
14910 substitution, and a storage and recall of command history across
14911 debugging sessions.
14913 You may control the behavior of command line editing in @value{GDBN} with the
14914 command @code{set}.
14917 @kindex set editing
14920 @itemx set editing on
14921 Enable command line editing (enabled by default).
14923 @item set editing off
14924 Disable command line editing.
14926 @kindex show editing
14928 Show whether command line editing is enabled.
14931 @xref{Command Line Editing}, for more details about the Readline
14932 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
14933 encouraged to read that chapter.
14936 @section Command history
14937 @cindex command history
14939 @value{GDBN} can keep track of the commands you type during your
14940 debugging sessions, so that you can be certain of precisely what
14941 happened. Use these commands to manage the @value{GDBN} command
14944 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
14945 package, to provide the history facility. @xref{Using History
14946 Interactively}, for the detailed description of the History library.
14948 Here is the description of @value{GDBN} commands related to command
14952 @cindex history substitution
14953 @cindex history file
14954 @kindex set history filename
14955 @cindex @env{GDBHISTFILE}, environment variable
14956 @item set history filename @var{fname}
14957 Set the name of the @value{GDBN} command history file to @var{fname}.
14958 This is the file where @value{GDBN} reads an initial command history
14959 list, and where it writes the command history from this session when it
14960 exits. You can access this list through history expansion or through
14961 the history command editing characters listed below. This file defaults
14962 to the value of the environment variable @code{GDBHISTFILE}, or to
14963 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
14966 @cindex save command history
14967 @kindex set history save
14968 @item set history save
14969 @itemx set history save on
14970 Record command history in a file, whose name may be specified with the
14971 @code{set history filename} command. By default, this option is disabled.
14973 @item set history save off
14974 Stop recording command history in a file.
14976 @cindex history size
14977 @kindex set history size
14978 @item set history size @var{size}
14979 Set the number of commands which @value{GDBN} keeps in its history list.
14980 This defaults to the value of the environment variable
14981 @code{HISTSIZE}, or to 256 if this variable is not set.
14984 History expansion assigns special meaning to the character @kbd{!}.
14985 @xref{Event Designators}, for more details.
14987 @cindex history expansion, turn on/off
14988 Since @kbd{!} is also the logical not operator in C, history expansion
14989 is off by default. If you decide to enable history expansion with the
14990 @code{set history expansion on} command, you may sometimes need to
14991 follow @kbd{!} (when it is used as logical not, in an expression) with
14992 a space or a tab to prevent it from being expanded. The readline
14993 history facilities do not attempt substitution on the strings
14994 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
14996 The commands to control history expansion are:
14999 @item set history expansion on
15000 @itemx set history expansion
15001 @kindex set history expansion
15002 Enable history expansion. History expansion is off by default.
15004 @item set history expansion off
15005 Disable history expansion.
15008 @kindex show history
15010 @itemx show history filename
15011 @itemx show history save
15012 @itemx show history size
15013 @itemx show history expansion
15014 These commands display the state of the @value{GDBN} history parameters.
15015 @code{show history} by itself displays all four states.
15020 @kindex show commands
15021 @cindex show last commands
15022 @cindex display command history
15023 @item show commands
15024 Display the last ten commands in the command history.
15026 @item show commands @var{n}
15027 Print ten commands centered on command number @var{n}.
15029 @item show commands +
15030 Print ten commands just after the commands last printed.
15034 @section Screen size
15035 @cindex size of screen
15036 @cindex pauses in output
15038 Certain commands to @value{GDBN} may produce large amounts of
15039 information output to the screen. To help you read all of it,
15040 @value{GDBN} pauses and asks you for input at the end of each page of
15041 output. Type @key{RET} when you want to continue the output, or @kbd{q}
15042 to discard the remaining output. Also, the screen width setting
15043 determines when to wrap lines of output. Depending on what is being
15044 printed, @value{GDBN} tries to break the line at a readable place,
15045 rather than simply letting it overflow onto the following line.
15047 Normally @value{GDBN} knows the size of the screen from the terminal
15048 driver software. For example, on Unix @value{GDBN} uses the termcap data base
15049 together with the value of the @code{TERM} environment variable and the
15050 @code{stty rows} and @code{stty cols} settings. If this is not correct,
15051 you can override it with the @code{set height} and @code{set
15058 @kindex show height
15059 @item set height @var{lpp}
15061 @itemx set width @var{cpl}
15063 These @code{set} commands specify a screen height of @var{lpp} lines and
15064 a screen width of @var{cpl} characters. The associated @code{show}
15065 commands display the current settings.
15067 If you specify a height of zero lines, @value{GDBN} does not pause during
15068 output no matter how long the output is. This is useful if output is to a
15069 file or to an editor buffer.
15071 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
15072 from wrapping its output.
15074 @item set pagination on
15075 @itemx set pagination off
15076 @kindex set pagination
15077 Turn the output pagination on or off; the default is on. Turning
15078 pagination off is the alternative to @code{set height 0}.
15080 @item show pagination
15081 @kindex show pagination
15082 Show the current pagination mode.
15087 @cindex number representation
15088 @cindex entering numbers
15090 You can always enter numbers in octal, decimal, or hexadecimal in
15091 @value{GDBN} by the usual conventions: octal numbers begin with
15092 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
15093 begin with @samp{0x}. Numbers that begin with none of these are, by
15094 default, entered in base 10; likewise, the default display for
15095 numbers---when no particular format is specified---is base 10. You can
15096 change the default base for both input and output with the @code{set
15100 @kindex set input-radix
15101 @item set input-radix @var{base}
15102 Set the default base for numeric input. Supported choices
15103 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15104 specified either unambiguously or using the current default radix; for
15108 set input-radix 012
15109 set input-radix 10.
15110 set input-radix 0xa
15114 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
15115 leaves the input radix unchanged, no matter what it was.
15117 @kindex set output-radix
15118 @item set output-radix @var{base}
15119 Set the default base for numeric display. Supported choices
15120 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15121 specified either unambiguously or using the current default radix.
15123 @kindex show input-radix
15124 @item show input-radix
15125 Display the current default base for numeric input.
15127 @kindex show output-radix
15128 @item show output-radix
15129 Display the current default base for numeric display.
15131 @item set radix @r{[}@var{base}@r{]}
15135 These commands set and show the default base for both input and output
15136 of numbers. @code{set radix} sets the radix of input and output to
15137 the same base; without an argument, it resets the radix back to its
15138 default value of 10.
15143 @section Configuring the current ABI
15145 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
15146 application automatically. However, sometimes you need to override its
15147 conclusions. Use these commands to manage @value{GDBN}'s view of the
15154 One @value{GDBN} configuration can debug binaries for multiple operating
15155 system targets, either via remote debugging or native emulation.
15156 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
15157 but you can override its conclusion using the @code{set osabi} command.
15158 One example where this is useful is in debugging of binaries which use
15159 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
15160 not have the same identifying marks that the standard C library for your
15165 Show the OS ABI currently in use.
15168 With no argument, show the list of registered available OS ABI's.
15170 @item set osabi @var{abi}
15171 Set the current OS ABI to @var{abi}.
15174 @cindex float promotion
15176 Generally, the way that an argument of type @code{float} is passed to a
15177 function depends on whether the function is prototyped. For a prototyped
15178 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
15179 according to the architecture's convention for @code{float}. For unprototyped
15180 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
15181 @code{double} and then passed.
15183 Unfortunately, some forms of debug information do not reliably indicate whether
15184 a function is prototyped. If @value{GDBN} calls a function that is not marked
15185 as prototyped, it consults @kbd{set coerce-float-to-double}.
15188 @kindex set coerce-float-to-double
15189 @item set coerce-float-to-double
15190 @itemx set coerce-float-to-double on
15191 Arguments of type @code{float} will be promoted to @code{double} when passed
15192 to an unprototyped function. This is the default setting.
15194 @item set coerce-float-to-double off
15195 Arguments of type @code{float} will be passed directly to unprototyped
15198 @kindex show coerce-float-to-double
15199 @item show coerce-float-to-double
15200 Show the current setting of promoting @code{float} to @code{double}.
15204 @kindex show cp-abi
15205 @value{GDBN} needs to know the ABI used for your program's C@t{++}
15206 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
15207 used to build your application. @value{GDBN} only fully supports
15208 programs with a single C@t{++} ABI; if your program contains code using
15209 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
15210 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
15211 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
15212 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
15213 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
15214 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
15219 Show the C@t{++} ABI currently in use.
15222 With no argument, show the list of supported C@t{++} ABI's.
15224 @item set cp-abi @var{abi}
15225 @itemx set cp-abi auto
15226 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
15229 @node Messages/Warnings
15230 @section Optional warnings and messages
15232 @cindex verbose operation
15233 @cindex optional warnings
15234 By default, @value{GDBN} is silent about its inner workings. If you are
15235 running on a slow machine, you may want to use the @code{set verbose}
15236 command. This makes @value{GDBN} tell you when it does a lengthy
15237 internal operation, so you will not think it has crashed.
15239 Currently, the messages controlled by @code{set verbose} are those
15240 which announce that the symbol table for a source file is being read;
15241 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
15244 @kindex set verbose
15245 @item set verbose on
15246 Enables @value{GDBN} output of certain informational messages.
15248 @item set verbose off
15249 Disables @value{GDBN} output of certain informational messages.
15251 @kindex show verbose
15253 Displays whether @code{set verbose} is on or off.
15256 By default, if @value{GDBN} encounters bugs in the symbol table of an
15257 object file, it is silent; but if you are debugging a compiler, you may
15258 find this information useful (@pxref{Symbol Errors, ,Errors reading
15263 @kindex set complaints
15264 @item set complaints @var{limit}
15265 Permits @value{GDBN} to output @var{limit} complaints about each type of
15266 unusual symbols before becoming silent about the problem. Set
15267 @var{limit} to zero to suppress all complaints; set it to a large number
15268 to prevent complaints from being suppressed.
15270 @kindex show complaints
15271 @item show complaints
15272 Displays how many symbol complaints @value{GDBN} is permitted to produce.
15276 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
15277 lot of stupid questions to confirm certain commands. For example, if
15278 you try to run a program which is already running:
15282 The program being debugged has been started already.
15283 Start it from the beginning? (y or n)
15286 If you are willing to unflinchingly face the consequences of your own
15287 commands, you can disable this ``feature'':
15291 @kindex set confirm
15293 @cindex confirmation
15294 @cindex stupid questions
15295 @item set confirm off
15296 Disables confirmation requests.
15298 @item set confirm on
15299 Enables confirmation requests (the default).
15301 @kindex show confirm
15303 Displays state of confirmation requests.
15307 @node Debugging Output
15308 @section Optional messages about internal happenings
15309 @cindex optional debugging messages
15311 @value{GDBN} has commands that enable optional debugging messages from
15312 various @value{GDBN} subsystems; normally these commands are of
15313 interest to @value{GDBN} maintainers, or when reporting a bug. This
15314 section documents those commands.
15317 @kindex set exec-done-display
15318 @item set exec-done-display
15319 Turns on or off the notification of asynchronous commands'
15320 completion. When on, @value{GDBN} will print a message when an
15321 asynchronous command finishes its execution. The default is off.
15322 @kindex show exec-done-display
15323 @item show exec-done-display
15324 Displays the current setting of asynchronous command completion
15327 @cindex gdbarch debugging info
15328 @cindex architecture debugging info
15329 @item set debug arch
15330 Turns on or off display of gdbarch debugging info. The default is off
15332 @item show debug arch
15333 Displays the current state of displaying gdbarch debugging info.
15334 @item set debug aix-thread
15335 @cindex AIX threads
15336 Display debugging messages about inner workings of the AIX thread
15338 @item show debug aix-thread
15339 Show the current state of AIX thread debugging info display.
15340 @item set debug event
15341 @cindex event debugging info
15342 Turns on or off display of @value{GDBN} event debugging info. The
15344 @item show debug event
15345 Displays the current state of displaying @value{GDBN} event debugging
15347 @item set debug expression
15348 @cindex expression debugging info
15349 Turns on or off display of debugging info about @value{GDBN}
15350 expression parsing. The default is off.
15351 @item show debug expression
15352 Displays the current state of displaying debugging info about
15353 @value{GDBN} expression parsing.
15354 @item set debug frame
15355 @cindex frame debugging info
15356 Turns on or off display of @value{GDBN} frame debugging info. The
15358 @item show debug frame
15359 Displays the current state of displaying @value{GDBN} frame debugging
15361 @item set debug infrun
15362 @cindex inferior debugging info
15363 Turns on or off display of @value{GDBN} debugging info for running the inferior.
15364 The default is off. @file{infrun.c} contains GDB's runtime state machine used
15365 for implementing operations such as single-stepping the inferior.
15366 @item show debug infrun
15367 Displays the current state of @value{GDBN} inferior debugging.
15368 @item set debug lin-lwp
15369 @cindex @sc{gnu}/Linux LWP debug messages
15370 @cindex Linux lightweight processes
15371 Turns on or off debugging messages from the Linux LWP debug support.
15372 @item show debug lin-lwp
15373 Show the current state of Linux LWP debugging messages.
15374 @item set debug observer
15375 @cindex observer debugging info
15376 Turns on or off display of @value{GDBN} observer debugging. This
15377 includes info such as the notification of observable events.
15378 @item show debug observer
15379 Displays the current state of observer debugging.
15380 @item set debug overload
15381 @cindex C@t{++} overload debugging info
15382 Turns on or off display of @value{GDBN} C@t{++} overload debugging
15383 info. This includes info such as ranking of functions, etc. The default
15385 @item show debug overload
15386 Displays the current state of displaying @value{GDBN} C@t{++} overload
15388 @cindex packets, reporting on stdout
15389 @cindex serial connections, debugging
15390 @item set debug remote
15391 Turns on or off display of reports on all packets sent back and forth across
15392 the serial line to the remote machine. The info is printed on the
15393 @value{GDBN} standard output stream. The default is off.
15394 @item show debug remote
15395 Displays the state of display of remote packets.
15396 @item set debug serial
15397 Turns on or off display of @value{GDBN} serial debugging info. The
15399 @item show debug serial
15400 Displays the current state of displaying @value{GDBN} serial debugging
15402 @item set debug solib-frv
15403 @cindex FR-V shared-library debugging
15404 Turns on or off debugging messages for FR-V shared-library code.
15405 @item show debug solib-frv
15406 Display the current state of FR-V shared-library code debugging
15408 @item set debug target
15409 @cindex target debugging info
15410 Turns on or off display of @value{GDBN} target debugging info. This info
15411 includes what is going on at the target level of GDB, as it happens. The
15412 default is 0. Set it to 1 to track events, and to 2 to also track the
15413 value of large memory transfers. Changes to this flag do not take effect
15414 until the next time you connect to a target or use the @code{run} command.
15415 @item show debug target
15416 Displays the current state of displaying @value{GDBN} target debugging
15418 @item set debugvarobj
15419 @cindex variable object debugging info
15420 Turns on or off display of @value{GDBN} variable object debugging
15421 info. The default is off.
15422 @item show debugvarobj
15423 Displays the current state of displaying @value{GDBN} variable object
15428 @chapter Canned Sequences of Commands
15430 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
15431 command lists}), @value{GDBN} provides two ways to store sequences of
15432 commands for execution as a unit: user-defined commands and command
15436 * Define:: User-defined commands
15437 * Hooks:: User-defined command hooks
15438 * Command Files:: Command files
15439 * Output:: Commands for controlled output
15443 @section User-defined commands
15445 @cindex user-defined command
15446 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
15447 which you assign a new name as a command. This is done with the
15448 @code{define} command. User commands may accept up to 10 arguments
15449 separated by whitespace. Arguments are accessed within the user command
15450 via @var{$arg0@dots{}$arg9}. A trivial example:
15454 print $arg0 + $arg1 + $arg2
15458 To execute the command use:
15465 This defines the command @code{adder}, which prints the sum of
15466 its three arguments. Note the arguments are text substitutions, so they may
15467 reference variables, use complex expressions, or even perform inferior
15473 @item define @var{commandname}
15474 Define a command named @var{commandname}. If there is already a command
15475 by that name, you are asked to confirm that you want to redefine it.
15477 The definition of the command is made up of other @value{GDBN} command lines,
15478 which are given following the @code{define} command. The end of these
15479 commands is marked by a line containing @code{end}.
15485 Takes a single argument, which is an expression to evaluate.
15486 It is followed by a series of commands that are executed
15487 only if the expression is true (nonzero).
15488 There can then optionally be a line @code{else}, followed
15489 by a series of commands that are only executed if the expression
15490 was false. The end of the list is marked by a line containing @code{end}.
15494 The syntax is similar to @code{if}: the command takes a single argument,
15495 which is an expression to evaluate, and must be followed by the commands to
15496 execute, one per line, terminated by an @code{end}.
15497 The commands are executed repeatedly as long as the expression
15501 @item document @var{commandname}
15502 Document the user-defined command @var{commandname}, so that it can be
15503 accessed by @code{help}. The command @var{commandname} must already be
15504 defined. This command reads lines of documentation just as @code{define}
15505 reads the lines of the command definition, ending with @code{end}.
15506 After the @code{document} command is finished, @code{help} on command
15507 @var{commandname} displays the documentation you have written.
15509 You may use the @code{document} command again to change the
15510 documentation of a command. Redefining the command with @code{define}
15511 does not change the documentation.
15513 @kindex dont-repeat
15514 @cindex don't repeat command
15516 Used inside a user-defined command, this tells @value{GDBN} that this
15517 command should not be repeated when the user hits @key{RET}
15518 (@pxref{Command Syntax, repeat last command}).
15520 @kindex help user-defined
15521 @item help user-defined
15522 List all user-defined commands, with the first line of the documentation
15527 @itemx show user @var{commandname}
15528 Display the @value{GDBN} commands used to define @var{commandname} (but
15529 not its documentation). If no @var{commandname} is given, display the
15530 definitions for all user-defined commands.
15532 @cindex infinite recusrion in user-defined commands
15533 @kindex show max-user-call-depth
15534 @kindex set max-user-call-depth
15535 @item show max-user-call-depth
15536 @itemx set max-user-call-depth
15537 The value of @code{max-user-call-depth} controls how many recursion
15538 levels are allowed in user-defined commands before GDB suspects an
15539 infinite recursion and aborts the command.
15543 When user-defined commands are executed, the
15544 commands of the definition are not printed. An error in any command
15545 stops execution of the user-defined command.
15547 If used interactively, commands that would ask for confirmation proceed
15548 without asking when used inside a user-defined command. Many @value{GDBN}
15549 commands that normally print messages to say what they are doing omit the
15550 messages when used in a user-defined command.
15553 @section User-defined command hooks
15554 @cindex command hooks
15555 @cindex hooks, for commands
15556 @cindex hooks, pre-command
15559 You may define @dfn{hooks}, which are a special kind of user-defined
15560 command. Whenever you run the command @samp{foo}, if the user-defined
15561 command @samp{hook-foo} exists, it is executed (with no arguments)
15562 before that command.
15564 @cindex hooks, post-command
15566 A hook may also be defined which is run after the command you executed.
15567 Whenever you run the command @samp{foo}, if the user-defined command
15568 @samp{hookpost-foo} exists, it is executed (with no arguments) after
15569 that command. Post-execution hooks may exist simultaneously with
15570 pre-execution hooks, for the same command.
15572 It is valid for a hook to call the command which it hooks. If this
15573 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
15575 @c It would be nice if hookpost could be passed a parameter indicating
15576 @c if the command it hooks executed properly or not. FIXME!
15578 @kindex stop@r{, a pseudo-command}
15579 In addition, a pseudo-command, @samp{stop} exists. Defining
15580 (@samp{hook-stop}) makes the associated commands execute every time
15581 execution stops in your program: before breakpoint commands are run,
15582 displays are printed, or the stack frame is printed.
15584 For example, to ignore @code{SIGALRM} signals while
15585 single-stepping, but treat them normally during normal execution,
15590 handle SIGALRM nopass
15594 handle SIGALRM pass
15597 define hook-continue
15598 handle SIGLARM pass
15602 As a further example, to hook at the begining and end of the @code{echo}
15603 command, and to add extra text to the beginning and end of the message,
15611 define hookpost-echo
15615 (@value{GDBP}) echo Hello World
15616 <<<---Hello World--->>>
15621 You can define a hook for any single-word command in @value{GDBN}, but
15622 not for command aliases; you should define a hook for the basic command
15623 name, e.g. @code{backtrace} rather than @code{bt}.
15624 @c FIXME! So how does Joe User discover whether a command is an alias
15626 If an error occurs during the execution of your hook, execution of
15627 @value{GDBN} commands stops and @value{GDBN} issues a prompt
15628 (before the command that you actually typed had a chance to run).
15630 If you try to define a hook which does not match any known command, you
15631 get a warning from the @code{define} command.
15633 @node Command Files
15634 @section Command files
15636 @cindex command files
15637 A command file for @value{GDBN} is a file of lines that are @value{GDBN}
15638 commands. Comments (lines starting with @kbd{#}) may also be included.
15639 An empty line in a command file does nothing; it does not mean to repeat
15640 the last command, as it would from the terminal.
15643 @cindex @file{.gdbinit}
15644 @cindex @file{gdb.ini}
15645 When you start @value{GDBN}, it automatically executes commands from its
15646 @dfn{init files}, normally called @file{.gdbinit}@footnote{The DJGPP
15647 port of @value{GDBN} uses the name @file{gdb.ini} instead, due to the
15648 limitations of file names imposed by DOS filesystems.}.
15649 During startup, @value{GDBN} does the following:
15653 Reads the init file (if any) in your home directory@footnote{On
15654 DOS/Windows systems, the home directory is the one pointed to by the
15655 @code{HOME} environment variable.}.
15658 Processes command line options and operands.
15661 Reads the init file (if any) in the current working directory.
15664 Reads command files specified by the @samp{-x} option.
15667 The init file in your home directory can set options (such as @samp{set
15668 complaints}) that affect subsequent processing of command line options
15669 and operands. Init files are not executed if you use the @samp{-nx}
15670 option (@pxref{Mode Options, ,Choosing modes}).
15672 @cindex init file name
15673 On some configurations of @value{GDBN}, the init file is known by a
15674 different name (these are typically environments where a specialized
15675 form of @value{GDBN} may need to coexist with other forms, hence a
15676 different name for the specialized version's init file). These are the
15677 environments with special init file names:
15679 @cindex @file{.vxgdbinit}
15682 VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit}
15684 @cindex @file{.os68gdbinit}
15686 OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit}
15688 @cindex @file{.esgdbinit}
15690 ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit}
15693 You can also request the execution of a command file with the
15694 @code{source} command:
15698 @item source @var{filename}
15699 Execute the command file @var{filename}.
15702 The lines in a command file are executed sequentially. They are not
15703 printed as they are executed. An error in any command terminates
15704 execution of the command file and control is returned to the console.
15706 Commands that would ask for confirmation if used interactively proceed
15707 without asking when used in a command file. Many @value{GDBN} commands that
15708 normally print messages to say what they are doing omit the messages
15709 when called from command files.
15711 @value{GDBN} also accepts command input from standard input. In this
15712 mode, normal output goes to standard output and error output goes to
15713 standard error. Errors in a command file supplied on standard input do
15714 not terminate execution of the command file --- execution continues with
15718 gdb < cmds > log 2>&1
15721 (The syntax above will vary depending on the shell used.) This example
15722 will execute commands from the file @file{cmds}. All output and errors
15723 would be directed to @file{log}.
15726 @section Commands for controlled output
15728 During the execution of a command file or a user-defined command, normal
15729 @value{GDBN} output is suppressed; the only output that appears is what is
15730 explicitly printed by the commands in the definition. This section
15731 describes three commands useful for generating exactly the output you
15736 @item echo @var{text}
15737 @c I do not consider backslash-space a standard C escape sequence
15738 @c because it is not in ANSI.
15739 Print @var{text}. Nonprinting characters can be included in
15740 @var{text} using C escape sequences, such as @samp{\n} to print a
15741 newline. @strong{No newline is printed unless you specify one.}
15742 In addition to the standard C escape sequences, a backslash followed
15743 by a space stands for a space. This is useful for displaying a
15744 string with spaces at the beginning or the end, since leading and
15745 trailing spaces are otherwise trimmed from all arguments.
15746 To print @samp{@w{ }and foo =@w{ }}, use the command
15747 @samp{echo \@w{ }and foo = \@w{ }}.
15749 A backslash at the end of @var{text} can be used, as in C, to continue
15750 the command onto subsequent lines. For example,
15753 echo This is some text\n\
15754 which is continued\n\
15755 onto several lines.\n
15758 produces the same output as
15761 echo This is some text\n
15762 echo which is continued\n
15763 echo onto several lines.\n
15767 @item output @var{expression}
15768 Print the value of @var{expression} and nothing but that value: no
15769 newlines, no @samp{$@var{nn} = }. The value is not entered in the
15770 value history either. @xref{Expressions, ,Expressions}, for more information
15773 @item output/@var{fmt} @var{expression}
15774 Print the value of @var{expression} in format @var{fmt}. You can use
15775 the same formats as for @code{print}. @xref{Output Formats,,Output
15776 formats}, for more information.
15779 @item printf @var{string}, @var{expressions}@dots{}
15780 Print the values of the @var{expressions} under the control of
15781 @var{string}. The @var{expressions} are separated by commas and may be
15782 either numbers or pointers. Their values are printed as specified by
15783 @var{string}, exactly as if your program were to execute the C
15785 @c FIXME: the above implies that at least all ANSI C formats are
15786 @c supported, but it isn't true: %E and %G don't work (or so it seems).
15787 @c Either this is a bug, or the manual should document what formats are
15791 printf (@var{string}, @var{expressions}@dots{});
15794 For example, you can print two values in hex like this:
15797 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
15800 The only backslash-escape sequences that you can use in the format
15801 string are the simple ones that consist of backslash followed by a
15806 @chapter Command Interpreters
15807 @cindex command interpreters
15809 @value{GDBN} supports multiple command interpreters, and some command
15810 infrastructure to allow users or user interface writers to switch
15811 between interpreters or run commands in other interpreters.
15813 @value{GDBN} currently supports two command interpreters, the console
15814 interpreter (sometimes called the command-line interpreter or @sc{cli})
15815 and the machine interface interpreter (or @sc{gdb/mi}). This manual
15816 describes both of these interfaces in great detail.
15818 By default, @value{GDBN} will start with the console interpreter.
15819 However, the user may choose to start @value{GDBN} with another
15820 interpreter by specifying the @option{-i} or @option{--interpreter}
15821 startup options. Defined interpreters include:
15825 @cindex console interpreter
15826 The traditional console or command-line interpreter. This is the most often
15827 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
15828 @value{GDBN} will use this interpreter.
15831 @cindex mi interpreter
15832 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
15833 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
15834 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
15838 @cindex mi2 interpreter
15839 The current @sc{gdb/mi} interface.
15842 @cindex mi1 interpreter
15843 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
15847 @cindex invoke another interpreter
15848 The interpreter being used by @value{GDBN} may not be dynamically
15849 switched at runtime. Although possible, this could lead to a very
15850 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
15851 enters the command "interpreter-set console" in a console view,
15852 @value{GDBN} would switch to using the console interpreter, rendering
15853 the IDE inoperable!
15855 @kindex interpreter-exec
15856 Although you may only choose a single interpreter at startup, you may execute
15857 commands in any interpreter from the current interpreter using the appropriate
15858 command. If you are running the console interpreter, simply use the
15859 @code{interpreter-exec} command:
15862 interpreter-exec mi "-data-list-register-names"
15865 @sc{gdb/mi} has a similar command, although it is only available in versions of
15866 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
15869 @chapter @value{GDBN} Text User Interface
15871 @cindex Text User Interface
15874 * TUI Overview:: TUI overview
15875 * TUI Keys:: TUI key bindings
15876 * TUI Single Key Mode:: TUI single key mode
15877 * TUI Commands:: TUI specific commands
15878 * TUI Configuration:: TUI configuration variables
15881 The @value{GDBN} Text User Interface, TUI in short, is a terminal
15882 interface which uses the @code{curses} library to show the source
15883 file, the assembly output, the program registers and @value{GDBN}
15884 commands in separate text windows.
15886 The TUI is enabled by invoking @value{GDBN} using either
15888 @samp{gdbtui} or @samp{gdb -tui}.
15891 @section TUI overview
15893 The TUI has two display modes that can be switched while
15898 A curses (or TUI) mode in which it displays several text
15899 windows on the terminal.
15902 A standard mode which corresponds to the @value{GDBN} configured without
15906 In the TUI mode, @value{GDBN} can display several text window
15911 This window is the @value{GDBN} command window with the @value{GDBN}
15912 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
15913 managed using readline but through the TUI. The @emph{command}
15914 window is always visible.
15917 The source window shows the source file of the program. The current
15918 line as well as active breakpoints are displayed in this window.
15921 The assembly window shows the disassembly output of the program.
15924 This window shows the processor registers. It detects when
15925 a register is changed and when this is the case, registers that have
15926 changed are highlighted.
15930 The source and assembly windows show the current program position
15931 by highlighting the current line and marking them with the @samp{>} marker.
15932 Breakpoints are also indicated with two markers. A first one
15933 indicates the breakpoint type:
15937 Breakpoint which was hit at least once.
15940 Breakpoint which was never hit.
15943 Hardware breakpoint which was hit at least once.
15946 Hardware breakpoint which was never hit.
15950 The second marker indicates whether the breakpoint is enabled or not:
15954 Breakpoint is enabled.
15957 Breakpoint is disabled.
15961 The source, assembly and register windows are attached to the thread
15962 and the frame position. They are updated when the current thread
15963 changes, when the frame changes or when the program counter changes.
15964 These three windows are arranged by the TUI according to several
15965 layouts. The layout defines which of these three windows are visible.
15966 The following layouts are available:
15976 source and assembly
15979 source and registers
15982 assembly and registers
15986 On top of the command window a status line gives various information
15987 concerning the current process begin debugged. The status line is
15988 updated when the information it shows changes. The following fields
15993 Indicates the current gdb target
15994 (@pxref{Targets, ,Specifying a Debugging Target}).
15997 Gives information about the current process or thread number.
15998 When no process is being debugged, this field is set to @code{No process}.
16001 Gives the current function name for the selected frame.
16002 The name is demangled if demangling is turned on (@pxref{Print Settings}).
16003 When there is no symbol corresponding to the current program counter
16004 the string @code{??} is displayed.
16007 Indicates the current line number for the selected frame.
16008 When the current line number is not known the string @code{??} is displayed.
16011 Indicates the current program counter address.
16016 @section TUI Key Bindings
16017 @cindex TUI key bindings
16019 The TUI installs several key bindings in the readline keymaps
16020 (@pxref{Command Line Editing}).
16021 They allow to leave or enter in the TUI mode or they operate
16022 directly on the TUI layout and windows. The TUI also provides
16023 a @emph{SingleKey} keymap which binds several keys directly to
16024 @value{GDBN} commands. The following key bindings
16025 are installed for both TUI mode and the @value{GDBN} standard mode.
16034 Enter or leave the TUI mode. When the TUI mode is left,
16035 the curses window management is left and @value{GDBN} operates using
16036 its standard mode writing on the terminal directly. When the TUI
16037 mode is entered, the control is given back to the curses windows.
16038 The screen is then refreshed.
16042 Use a TUI layout with only one window. The layout will
16043 either be @samp{source} or @samp{assembly}. When the TUI mode
16044 is not active, it will switch to the TUI mode.
16046 Think of this key binding as the Emacs @kbd{C-x 1} binding.
16050 Use a TUI layout with at least two windows. When the current
16051 layout shows already two windows, a next layout with two windows is used.
16052 When a new layout is chosen, one window will always be common to the
16053 previous layout and the new one.
16055 Think of it as the Emacs @kbd{C-x 2} binding.
16059 Change the active window. The TUI associates several key bindings
16060 (like scrolling and arrow keys) to the active window. This command
16061 gives the focus to the next TUI window.
16063 Think of it as the Emacs @kbd{C-x o} binding.
16067 Use the TUI @emph{SingleKey} keymap that binds single key to gdb commands
16068 (@pxref{TUI Single Key Mode}).
16072 The following key bindings are handled only by the TUI mode:
16077 Scroll the active window one page up.
16081 Scroll the active window one page down.
16085 Scroll the active window one line up.
16089 Scroll the active window one line down.
16093 Scroll the active window one column left.
16097 Scroll the active window one column right.
16101 Refresh the screen.
16105 In the TUI mode, the arrow keys are used by the active window
16106 for scrolling. This means they are available for readline when the
16107 active window is the command window. When the command window
16108 does not have the focus, it is necessary to use other readline
16109 key bindings such as @key{C-p}, @key{C-n}, @key{C-b} and @key{C-f}.
16111 @node TUI Single Key Mode
16112 @section TUI Single Key Mode
16113 @cindex TUI single key mode
16115 The TUI provides a @emph{SingleKey} mode in which it installs a particular
16116 key binding in the readline keymaps to connect single keys to
16120 @kindex c @r{(SingleKey TUI key)}
16124 @kindex d @r{(SingleKey TUI key)}
16128 @kindex f @r{(SingleKey TUI key)}
16132 @kindex n @r{(SingleKey TUI key)}
16136 @kindex q @r{(SingleKey TUI key)}
16138 exit the @emph{SingleKey} mode.
16140 @kindex r @r{(SingleKey TUI key)}
16144 @kindex s @r{(SingleKey TUI key)}
16148 @kindex u @r{(SingleKey TUI key)}
16152 @kindex v @r{(SingleKey TUI key)}
16156 @kindex w @r{(SingleKey TUI key)}
16162 Other keys temporarily switch to the @value{GDBN} command prompt.
16163 The key that was pressed is inserted in the editing buffer so that
16164 it is possible to type most @value{GDBN} commands without interaction
16165 with the TUI @emph{SingleKey} mode. Once the command is entered the TUI
16166 @emph{SingleKey} mode is restored. The only way to permanently leave
16167 this mode is by hitting @key{q} or @samp{@key{C-x} @key{s}}.
16171 @section TUI specific commands
16172 @cindex TUI commands
16174 The TUI has specific commands to control the text windows.
16175 These commands are always available, that is they do not depend on
16176 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
16177 is in the standard mode, using these commands will automatically switch
16183 List and give the size of all displayed windows.
16187 Display the next layout.
16190 Display the previous layout.
16193 Display the source window only.
16196 Display the assembly window only.
16199 Display the source and assembly window.
16202 Display the register window together with the source or assembly window.
16204 @item focus next | prev | src | asm | regs | split
16206 Set the focus to the named window.
16207 This command allows to change the active window so that scrolling keys
16208 can be affected to another window.
16212 Refresh the screen. This is similar to using @key{C-L} key.
16214 @item tui reg float
16216 Show the floating point registers in the register window.
16218 @item tui reg general
16219 Show the general registers in the register window.
16222 Show the next register group. The list of register groups as well as
16223 their order is target specific. The predefined register groups are the
16224 following: @code{general}, @code{float}, @code{system}, @code{vector},
16225 @code{all}, @code{save}, @code{restore}.
16227 @item tui reg system
16228 Show the system registers in the register window.
16232 Update the source window and the current execution point.
16234 @item winheight @var{name} +@var{count}
16235 @itemx winheight @var{name} -@var{count}
16237 Change the height of the window @var{name} by @var{count}
16238 lines. Positive counts increase the height, while negative counts
16242 @kindex tabset @var{nchars}
16243 Set the width of tab stops to be @var{nchars} characters.
16247 @node TUI Configuration
16248 @section TUI configuration variables
16249 @cindex TUI configuration variables
16251 The TUI has several configuration variables that control the
16252 appearance of windows on the terminal.
16255 @item set tui border-kind @var{kind}
16256 @kindex set tui border-kind
16257 Select the border appearance for the source, assembly and register windows.
16258 The possible values are the following:
16261 Use a space character to draw the border.
16264 Use ascii characters + - and | to draw the border.
16267 Use the Alternate Character Set to draw the border. The border is
16268 drawn using character line graphics if the terminal supports them.
16272 @item set tui active-border-mode @var{mode}
16273 @kindex set tui active-border-mode
16274 Select the attributes to display the border of the active window.
16275 The possible values are @code{normal}, @code{standout}, @code{reverse},
16276 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
16278 @item set tui border-mode @var{mode}
16279 @kindex set tui border-mode
16280 Select the attributes to display the border of other windows.
16281 The @var{mode} can be one of the following:
16284 Use normal attributes to display the border.
16290 Use reverse video mode.
16293 Use half bright mode.
16295 @item half-standout
16296 Use half bright and standout mode.
16299 Use extra bright or bold mode.
16301 @item bold-standout
16302 Use extra bright or bold and standout mode.
16309 @chapter Using @value{GDBN} under @sc{gnu} Emacs
16312 @cindex @sc{gnu} Emacs
16313 A special interface allows you to use @sc{gnu} Emacs to view (and
16314 edit) the source files for the program you are debugging with
16317 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
16318 executable file you want to debug as an argument. This command starts
16319 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
16320 created Emacs buffer.
16321 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
16323 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
16328 All ``terminal'' input and output goes through the Emacs buffer.
16331 This applies both to @value{GDBN} commands and their output, and to the input
16332 and output done by the program you are debugging.
16334 This is useful because it means that you can copy the text of previous
16335 commands and input them again; you can even use parts of the output
16338 All the facilities of Emacs' Shell mode are available for interacting
16339 with your program. In particular, you can send signals the usual
16340 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
16345 @value{GDBN} displays source code through Emacs.
16348 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
16349 source file for that frame and puts an arrow (@samp{=>}) at the
16350 left margin of the current line. Emacs uses a separate buffer for
16351 source display, and splits the screen to show both your @value{GDBN} session
16354 Explicit @value{GDBN} @code{list} or search commands still produce output as
16355 usual, but you probably have no reason to use them from Emacs.
16357 If you specify an absolute file name when prompted for the @kbd{M-x
16358 gdb} argument, then Emacs sets your current working directory to where
16359 your program resides. If you only specify the file name, then Emacs
16360 sets your current working directory to to the directory associated
16361 with the previous buffer. In this case, @value{GDBN} may find your
16362 program by searching your environment's @code{PATH} variable, but on
16363 some operating systems it might not find the source. So, although the
16364 @value{GDBN} input and output session proceeds normally, the auxiliary
16365 buffer does not display the current source and line of execution.
16367 The initial working directory of @value{GDBN} is printed on the top
16368 line of the @value{GDBN} I/O buffer and this serves as a default for
16369 the commands that specify files for @value{GDBN} to operate
16370 on. @xref{Files, ,Commands to specify files}.
16372 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
16373 need to call @value{GDBN} by a different name (for example, if you
16374 keep several configurations around, with different names) you can
16375 customize the Emacs variable @code{gud-gdb-command-name} to run the
16378 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
16379 addition to the standard Shell mode commands:
16383 Describe the features of Emacs' @value{GDBN} Mode.
16386 Execute to another source line, like the @value{GDBN} @code{step} command; also
16387 update the display window to show the current file and location.
16390 Execute to next source line in this function, skipping all function
16391 calls, like the @value{GDBN} @code{next} command. Then update the display window
16392 to show the current file and location.
16395 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
16396 display window accordingly.
16399 Execute until exit from the selected stack frame, like the @value{GDBN}
16400 @code{finish} command.
16403 Continue execution of your program, like the @value{GDBN} @code{continue}
16407 Go up the number of frames indicated by the numeric argument
16408 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
16409 like the @value{GDBN} @code{up} command.
16412 Go down the number of frames indicated by the numeric argument, like the
16413 @value{GDBN} @code{down} command.
16416 In any source file, the Emacs command @kbd{C-x SPC} (@code{gud-break})
16417 tells @value{GDBN} to set a breakpoint on the source line point is on.
16419 If you type @kbd{M-x speedbar}, then Emacs displays a separate frame which
16420 shows a backtrace when the @value{GDBN} I/O buffer is current. Move
16421 point to any frame in the stack and type @key{RET} to make it become the
16422 current frame and display the associated source in the source buffer.
16423 Alternatively, click @kbd{Mouse-2} to make the selected frame become the
16426 If you accidentally delete the source-display buffer, an easy way to get
16427 it back is to type the command @code{f} in the @value{GDBN} buffer, to
16428 request a frame display; when you run under Emacs, this recreates
16429 the source buffer if necessary to show you the context of the current
16432 The source files displayed in Emacs are in ordinary Emacs buffers
16433 which are visiting the source files in the usual way. You can edit
16434 the files with these buffers if you wish; but keep in mind that @value{GDBN}
16435 communicates with Emacs in terms of line numbers. If you add or
16436 delete lines from the text, the line numbers that @value{GDBN} knows cease
16437 to correspond properly with the code.
16439 The description given here is for GNU Emacs version 21.3 and a more
16440 detailed description of its interaction with @value{GDBN} is given in
16441 the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu} Emacs Manual}).
16443 @c The following dropped because Epoch is nonstandard. Reactivate
16444 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
16446 @kindex Emacs Epoch environment
16450 Version 18 of @sc{gnu} Emacs has a built-in window system
16451 called the @code{epoch}
16452 environment. Users of this environment can use a new command,
16453 @code{inspect} which performs identically to @code{print} except that
16454 each value is printed in its own window.
16459 @chapter The @sc{gdb/mi} Interface
16461 @unnumberedsec Function and Purpose
16463 @cindex @sc{gdb/mi}, its purpose
16464 @sc{gdb/mi} is a line based machine oriented text interface to
16465 @value{GDBN} and is activated by specifying using the
16466 @option{--interpreter} command line option (@pxref{Mode Options}). It
16467 is specifically intended to support the development of systems which
16468 use the debugger as just one small component of a larger system.
16470 This chapter is a specification of the @sc{gdb/mi} interface. It is written
16471 in the form of a reference manual.
16473 Note that @sc{gdb/mi} is still under construction, so some of the
16474 features described below are incomplete and subject to change.
16476 @unnumberedsec Notation and Terminology
16478 @cindex notational conventions, for @sc{gdb/mi}
16479 This chapter uses the following notation:
16483 @code{|} separates two alternatives.
16486 @code{[ @var{something} ]} indicates that @var{something} is optional:
16487 it may or may not be given.
16490 @code{( @var{group} )*} means that @var{group} inside the parentheses
16491 may repeat zero or more times.
16494 @code{( @var{group} )+} means that @var{group} inside the parentheses
16495 may repeat one or more times.
16498 @code{"@var{string}"} means a literal @var{string}.
16502 @heading Dependencies
16505 @heading Acknowledgments
16507 In alphabetic order: Andrew Cagney, Fernando Nasser, Stan Shebs and
16511 * GDB/MI Command Syntax::
16512 * GDB/MI Compatibility with CLI::
16513 * GDB/MI Output Records::
16514 * GDB/MI Command Description Format::
16515 * GDB/MI Breakpoint Table Commands::
16516 * GDB/MI Data Manipulation::
16517 * GDB/MI Program Control::
16518 * GDB/MI Miscellaneous Commands::
16520 * GDB/MI Kod Commands::
16521 * GDB/MI Memory Overlay Commands::
16522 * GDB/MI Signal Handling Commands::
16524 * GDB/MI Stack Manipulation::
16525 * GDB/MI Symbol Query::
16526 * GDB/MI Target Manipulation::
16527 * GDB/MI Thread Commands::
16528 * GDB/MI Tracepoint Commands::
16529 * GDB/MI Variable Objects::
16532 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16533 @node GDB/MI Command Syntax
16534 @section @sc{gdb/mi} Command Syntax
16537 * GDB/MI Input Syntax::
16538 * GDB/MI Output Syntax::
16539 * GDB/MI Simple Examples::
16542 @node GDB/MI Input Syntax
16543 @subsection @sc{gdb/mi} Input Syntax
16545 @cindex input syntax for @sc{gdb/mi}
16546 @cindex @sc{gdb/mi}, input syntax
16548 @item @var{command} @expansion{}
16549 @code{@var{cli-command} | @var{mi-command}}
16551 @item @var{cli-command} @expansion{}
16552 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
16553 @var{cli-command} is any existing @value{GDBN} CLI command.
16555 @item @var{mi-command} @expansion{}
16556 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
16557 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
16559 @item @var{token} @expansion{}
16560 "any sequence of digits"
16562 @item @var{option} @expansion{}
16563 @code{"-" @var{parameter} [ " " @var{parameter} ]}
16565 @item @var{parameter} @expansion{}
16566 @code{@var{non-blank-sequence} | @var{c-string}}
16568 @item @var{operation} @expansion{}
16569 @emph{any of the operations described in this chapter}
16571 @item @var{non-blank-sequence} @expansion{}
16572 @emph{anything, provided it doesn't contain special characters such as
16573 "-", @var{nl}, """ and of course " "}
16575 @item @var{c-string} @expansion{}
16576 @code{""" @var{seven-bit-iso-c-string-content} """}
16578 @item @var{nl} @expansion{}
16587 The CLI commands are still handled by the @sc{mi} interpreter; their
16588 output is described below.
16591 The @code{@var{token}}, when present, is passed back when the command
16595 Some @sc{mi} commands accept optional arguments as part of the parameter
16596 list. Each option is identified by a leading @samp{-} (dash) and may be
16597 followed by an optional argument parameter. Options occur first in the
16598 parameter list and can be delimited from normal parameters using
16599 @samp{--} (this is useful when some parameters begin with a dash).
16606 We want easy access to the existing CLI syntax (for debugging).
16609 We want it to be easy to spot a @sc{mi} operation.
16612 @node GDB/MI Output Syntax
16613 @subsection @sc{gdb/mi} Output Syntax
16615 @cindex output syntax of @sc{gdb/mi}
16616 @cindex @sc{gdb/mi}, output syntax
16617 The output from @sc{gdb/mi} consists of zero or more out-of-band records
16618 followed, optionally, by a single result record. This result record
16619 is for the most recent command. The sequence of output records is
16620 terminated by @samp{(@value{GDBP})}.
16622 If an input command was prefixed with a @code{@var{token}} then the
16623 corresponding output for that command will also be prefixed by that same
16627 @item @var{output} @expansion{}
16628 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(@value{GDBP})" @var{nl}}
16630 @item @var{result-record} @expansion{}
16631 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
16633 @item @var{out-of-band-record} @expansion{}
16634 @code{@var{async-record} | @var{stream-record}}
16636 @item @var{async-record} @expansion{}
16637 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
16639 @item @var{exec-async-output} @expansion{}
16640 @code{[ @var{token} ] "*" @var{async-output}}
16642 @item @var{status-async-output} @expansion{}
16643 @code{[ @var{token} ] "+" @var{async-output}}
16645 @item @var{notify-async-output} @expansion{}
16646 @code{[ @var{token} ] "=" @var{async-output}}
16648 @item @var{async-output} @expansion{}
16649 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
16651 @item @var{result-class} @expansion{}
16652 @code{"done" | "running" | "connected" | "error" | "exit"}
16654 @item @var{async-class} @expansion{}
16655 @code{"stopped" | @var{others}} (where @var{others} will be added
16656 depending on the needs---this is still in development).
16658 @item @var{result} @expansion{}
16659 @code{ @var{variable} "=" @var{value}}
16661 @item @var{variable} @expansion{}
16662 @code{ @var{string} }
16664 @item @var{value} @expansion{}
16665 @code{ @var{const} | @var{tuple} | @var{list} }
16667 @item @var{const} @expansion{}
16668 @code{@var{c-string}}
16670 @item @var{tuple} @expansion{}
16671 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
16673 @item @var{list} @expansion{}
16674 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
16675 @var{result} ( "," @var{result} )* "]" }
16677 @item @var{stream-record} @expansion{}
16678 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
16680 @item @var{console-stream-output} @expansion{}
16681 @code{"~" @var{c-string}}
16683 @item @var{target-stream-output} @expansion{}
16684 @code{"@@" @var{c-string}}
16686 @item @var{log-stream-output} @expansion{}
16687 @code{"&" @var{c-string}}
16689 @item @var{nl} @expansion{}
16692 @item @var{token} @expansion{}
16693 @emph{any sequence of digits}.
16701 All output sequences end in a single line containing a period.
16704 The @code{@var{token}} is from the corresponding request. If an execution
16705 command is interrupted by the @samp{-exec-interrupt} command, the
16706 @var{token} associated with the @samp{*stopped} message is the one of the
16707 original execution command, not the one of the interrupt command.
16710 @cindex status output in @sc{gdb/mi}
16711 @var{status-async-output} contains on-going status information about the
16712 progress of a slow operation. It can be discarded. All status output is
16713 prefixed by @samp{+}.
16716 @cindex async output in @sc{gdb/mi}
16717 @var{exec-async-output} contains asynchronous state change on the target
16718 (stopped, started, disappeared). All async output is prefixed by
16722 @cindex notify output in @sc{gdb/mi}
16723 @var{notify-async-output} contains supplementary information that the
16724 client should handle (e.g., a new breakpoint information). All notify
16725 output is prefixed by @samp{=}.
16728 @cindex console output in @sc{gdb/mi}
16729 @var{console-stream-output} is output that should be displayed as is in the
16730 console. It is the textual response to a CLI command. All the console
16731 output is prefixed by @samp{~}.
16734 @cindex target output in @sc{gdb/mi}
16735 @var{target-stream-output} is the output produced by the target program.
16736 All the target output is prefixed by @samp{@@}.
16739 @cindex log output in @sc{gdb/mi}
16740 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
16741 instance messages that should be displayed as part of an error log. All
16742 the log output is prefixed by @samp{&}.
16745 @cindex list output in @sc{gdb/mi}
16746 New @sc{gdb/mi} commands should only output @var{lists} containing
16752 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
16753 details about the various output records.
16755 @node GDB/MI Simple Examples
16756 @subsection Simple Examples of @sc{gdb/mi} Interaction
16757 @cindex @sc{gdb/mi}, simple examples
16759 This subsection presents several simple examples of interaction using
16760 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
16761 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
16762 the output received from @sc{gdb/mi}.
16764 @subsubheading Target Stop
16765 @c Ummm... There is no "-stop" command. This assumes async, no?
16766 Here's an example of stopping the inferior process:
16777 <- *stop,reason="stop",address="0x123",source="a.c:123"
16781 @subsubheading Simple CLI Command
16783 Here's an example of a simple CLI command being passed through
16784 @sc{gdb/mi} and on to the CLI.
16794 @subsubheading Command With Side Effects
16797 -> -symbol-file xyz.exe
16798 <- *breakpoint,nr="3",address="0x123",source="a.c:123"
16802 @subsubheading A Bad Command
16804 Here's what happens if you pass a non-existent command:
16808 <- ^error,msg="Undefined MI command: rubbish"
16812 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16813 @node GDB/MI Compatibility with CLI
16814 @section @sc{gdb/mi} Compatibility with CLI
16816 @cindex compatibility, @sc{gdb/mi} and CLI
16817 @cindex @sc{gdb/mi}, compatibility with CLI
16818 To help users familiar with @value{GDBN}'s existing CLI interface, @sc{gdb/mi}
16819 accepts existing CLI commands. As specified by the syntax, such
16820 commands can be directly entered into the @sc{gdb/mi} interface and @value{GDBN} will
16823 This mechanism is provided as an aid to developers of @sc{gdb/mi}
16824 clients and not as a reliable interface into the CLI. Since the command
16825 is being interpreteted in an environment that assumes @sc{gdb/mi}
16826 behaviour, the exact output of such commands is likely to end up being
16827 an un-supported hybrid of @sc{gdb/mi} and CLI output.
16829 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16830 @node GDB/MI Output Records
16831 @section @sc{gdb/mi} Output Records
16834 * GDB/MI Result Records::
16835 * GDB/MI Stream Records::
16836 * GDB/MI Out-of-band Records::
16839 @node GDB/MI Result Records
16840 @subsection @sc{gdb/mi} Result Records
16842 @cindex result records in @sc{gdb/mi}
16843 @cindex @sc{gdb/mi}, result records
16844 In addition to a number of out-of-band notifications, the response to a
16845 @sc{gdb/mi} command includes one of the following result indications:
16849 @item "^done" [ "," @var{results} ]
16850 The synchronous operation was successful, @code{@var{results}} are the return
16855 @c Is this one correct? Should it be an out-of-band notification?
16856 The asynchronous operation was successfully started. The target is
16859 @item "^error" "," @var{c-string}
16861 The operation failed. The @code{@var{c-string}} contains the corresponding
16865 @node GDB/MI Stream Records
16866 @subsection @sc{gdb/mi} Stream Records
16868 @cindex @sc{gdb/mi}, stream records
16869 @cindex stream records in @sc{gdb/mi}
16870 @value{GDBN} internally maintains a number of output streams: the console, the
16871 target, and the log. The output intended for each of these streams is
16872 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
16874 Each stream record begins with a unique @dfn{prefix character} which
16875 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
16876 Syntax}). In addition to the prefix, each stream record contains a
16877 @code{@var{string-output}}. This is either raw text (with an implicit new
16878 line) or a quoted C string (which does not contain an implicit newline).
16881 @item "~" @var{string-output}
16882 The console output stream contains text that should be displayed in the
16883 CLI console window. It contains the textual responses to CLI commands.
16885 @item "@@" @var{string-output}
16886 The target output stream contains any textual output from the running
16889 @item "&" @var{string-output}
16890 The log stream contains debugging messages being produced by @value{GDBN}'s
16894 @node GDB/MI Out-of-band Records
16895 @subsection @sc{gdb/mi} Out-of-band Records
16897 @cindex out-of-band records in @sc{gdb/mi}
16898 @cindex @sc{gdb/mi}, out-of-band records
16899 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
16900 additional changes that have occurred. Those changes can either be a
16901 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
16902 target activity (e.g., target stopped).
16904 The following is a preliminary list of possible out-of-band records.
16911 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16912 @node GDB/MI Command Description Format
16913 @section @sc{gdb/mi} Command Description Format
16915 The remaining sections describe blocks of commands. Each block of
16916 commands is laid out in a fashion similar to this section.
16918 Note the the line breaks shown in the examples are here only for
16919 readability. They don't appear in the real output.
16920 Also note that the commands with a non-available example (N.A.@:) are
16921 not yet implemented.
16923 @subheading Motivation
16925 The motivation for this collection of commands.
16927 @subheading Introduction
16929 A brief introduction to this collection of commands as a whole.
16931 @subheading Commands
16933 For each command in the block, the following is described:
16935 @subsubheading Synopsis
16938 -command @var{args}@dots{}
16941 @subsubheading @value{GDBN} Command
16943 The corresponding @value{GDBN} CLI command.
16945 @subsubheading Result
16947 @subsubheading Out-of-band
16949 @subsubheading Notes
16951 @subsubheading Example
16954 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16955 @node GDB/MI Breakpoint Table Commands
16956 @section @sc{gdb/mi} Breakpoint table commands
16958 @cindex breakpoint commands for @sc{gdb/mi}
16959 @cindex @sc{gdb/mi}, breakpoint commands
16960 This section documents @sc{gdb/mi} commands for manipulating
16963 @subheading The @code{-break-after} Command
16964 @findex -break-after
16966 @subsubheading Synopsis
16969 -break-after @var{number} @var{count}
16972 The breakpoint number @var{number} is not in effect until it has been
16973 hit @var{count} times. To see how this is reflected in the output of
16974 the @samp{-break-list} command, see the description of the
16975 @samp{-break-list} command below.
16977 @subsubheading @value{GDBN} Command
16979 The corresponding @value{GDBN} command is @samp{ignore}.
16981 @subsubheading Example
16986 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",line="5"@}
16993 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
16994 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
16995 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
16996 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
16997 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
16998 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
16999 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17000 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17001 addr="0x000100d0",func="main",file="hello.c",line="5",times="0",
17007 @subheading The @code{-break-catch} Command
17008 @findex -break-catch
17010 @subheading The @code{-break-commands} Command
17011 @findex -break-commands
17015 @subheading The @code{-break-condition} Command
17016 @findex -break-condition
17018 @subsubheading Synopsis
17021 -break-condition @var{number} @var{expr}
17024 Breakpoint @var{number} will stop the program only if the condition in
17025 @var{expr} is true. The condition becomes part of the
17026 @samp{-break-list} output (see the description of the @samp{-break-list}
17029 @subsubheading @value{GDBN} Command
17031 The corresponding @value{GDBN} command is @samp{condition}.
17033 @subsubheading Example
17037 -break-condition 1 1
17041 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17042 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17043 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17044 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17045 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17046 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17047 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17048 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17049 addr="0x000100d0",func="main",file="hello.c",line="5",cond="1",
17050 times="0",ignore="3"@}]@}
17054 @subheading The @code{-break-delete} Command
17055 @findex -break-delete
17057 @subsubheading Synopsis
17060 -break-delete ( @var{breakpoint} )+
17063 Delete the breakpoint(s) whose number(s) are specified in the argument
17064 list. This is obviously reflected in the breakpoint list.
17066 @subsubheading @value{GDBN} command
17068 The corresponding @value{GDBN} command is @samp{delete}.
17070 @subsubheading Example
17078 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
17079 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17080 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17081 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17082 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17083 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17084 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17089 @subheading The @code{-break-disable} Command
17090 @findex -break-disable
17092 @subsubheading Synopsis
17095 -break-disable ( @var{breakpoint} )+
17098 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
17099 break list is now set to @samp{n} for the named @var{breakpoint}(s).
17101 @subsubheading @value{GDBN} Command
17103 The corresponding @value{GDBN} command is @samp{disable}.
17105 @subsubheading Example
17113 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17114 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17115 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17116 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17117 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17118 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17119 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17120 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
17121 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
17125 @subheading The @code{-break-enable} Command
17126 @findex -break-enable
17128 @subsubheading Synopsis
17131 -break-enable ( @var{breakpoint} )+
17134 Enable (previously disabled) @var{breakpoint}(s).
17136 @subsubheading @value{GDBN} Command
17138 The corresponding @value{GDBN} command is @samp{enable}.
17140 @subsubheading Example
17148 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17149 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17150 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17151 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17152 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17153 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17154 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17155 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
17156 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
17160 @subheading The @code{-break-info} Command
17161 @findex -break-info
17163 @subsubheading Synopsis
17166 -break-info @var{breakpoint}
17170 Get information about a single breakpoint.
17172 @subsubheading @value{GDBN} command
17174 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
17176 @subsubheading Example
17179 @subheading The @code{-break-insert} Command
17180 @findex -break-insert
17182 @subsubheading Synopsis
17185 -break-insert [ -t ] [ -h ] [ -r ]
17186 [ -c @var{condition} ] [ -i @var{ignore-count} ]
17187 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
17191 If specified, @var{line}, can be one of:
17198 @item filename:linenum
17199 @item filename:function
17203 The possible optional parameters of this command are:
17207 Insert a tempoary breakpoint.
17209 Insert a hardware breakpoint.
17210 @item -c @var{condition}
17211 Make the breakpoint conditional on @var{condition}.
17212 @item -i @var{ignore-count}
17213 Initialize the @var{ignore-count}.
17215 Insert a regular breakpoint in all the functions whose names match the
17216 given regular expression. Other flags are not applicable to regular
17220 @subsubheading Result
17222 The result is in the form:
17225 ^done,bkptno="@var{number}",func="@var{funcname}",
17226 file="@var{filename}",line="@var{lineno}"
17230 where @var{number} is the @value{GDBN} number for this breakpoint, @var{funcname}
17231 is the name of the function where the breakpoint was inserted,
17232 @var{filename} is the name of the source file which contains this
17233 function, and @var{lineno} is the source line number within that file.
17235 Note: this format is open to change.
17236 @c An out-of-band breakpoint instead of part of the result?
17238 @subsubheading @value{GDBN} Command
17240 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
17241 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
17243 @subsubheading Example
17248 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
17250 -break-insert -t foo
17251 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",line="11"@}
17254 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17255 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17256 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17257 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17258 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17259 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17260 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17261 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17262 addr="0x0001072c", func="main",file="recursive2.c",line="4",times="0"@},
17263 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
17264 addr="0x00010774",func="foo",file="recursive2.c",line="11",times="0"@}]@}
17266 -break-insert -r foo.*
17267 ~int foo(int, int);
17268 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c",line="11"@}
17272 @subheading The @code{-break-list} Command
17273 @findex -break-list
17275 @subsubheading Synopsis
17281 Displays the list of inserted breakpoints, showing the following fields:
17285 number of the breakpoint
17287 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
17289 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
17292 is the breakpoint enabled or no: @samp{y} or @samp{n}
17294 memory location at which the breakpoint is set
17296 logical location of the breakpoint, expressed by function name, file
17299 number of times the breakpoint has been hit
17302 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
17303 @code{body} field is an empty list.
17305 @subsubheading @value{GDBN} Command
17307 The corresponding @value{GDBN} command is @samp{info break}.
17309 @subsubheading Example
17314 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17315 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17316 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17317 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17318 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17319 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17320 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17321 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17322 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
17323 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
17324 addr="0x00010114",func="foo",file="hello.c",line="13",times="0"@}]@}
17328 Here's an example of the result when there are no breakpoints:
17333 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
17334 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17335 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17336 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17337 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17338 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17339 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17344 @subheading The @code{-break-watch} Command
17345 @findex -break-watch
17347 @subsubheading Synopsis
17350 -break-watch [ -a | -r ]
17353 Create a watchpoint. With the @samp{-a} option it will create an
17354 @dfn{access} watchpoint, i.e. a watchpoint that triggers either on a
17355 read from or on a write to the memory location. With the @samp{-r}
17356 option, the watchpoint created is a @dfn{read} watchpoint, i.e. it will
17357 trigger only when the memory location is accessed for reading. Without
17358 either of the options, the watchpoint created is a regular watchpoint,
17359 i.e. it will trigger when the memory location is accessed for writing.
17360 @xref{Set Watchpoints, , Setting watchpoints}.
17362 Note that @samp{-break-list} will report a single list of watchpoints and
17363 breakpoints inserted.
17365 @subsubheading @value{GDBN} Command
17367 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
17370 @subsubheading Example
17372 Setting a watchpoint on a variable in the @code{main} function:
17377 ^done,wpt=@{number="2",exp="x"@}
17381 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
17382 value=@{old="-268439212",new="55"@},
17383 frame=@{func="main",args=[],file="recursive2.c",line="5"@}
17387 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
17388 the program execution twice: first for the variable changing value, then
17389 for the watchpoint going out of scope.
17394 ^done,wpt=@{number="5",exp="C"@}
17398 ^done,reason="watchpoint-trigger",
17399 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
17400 frame=@{func="callee4",args=[],
17401 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
17405 ^done,reason="watchpoint-scope",wpnum="5",
17406 frame=@{func="callee3",args=[@{name="strarg",
17407 value="0x11940 \"A string argument.\""@}],
17408 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
17412 Listing breakpoints and watchpoints, at different points in the program
17413 execution. Note that once the watchpoint goes out of scope, it is
17419 ^done,wpt=@{number="2",exp="C"@}
17422 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17423 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17424 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17425 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17426 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17427 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17428 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17429 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17430 addr="0x00010734",func="callee4",
17431 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
17432 bkpt=@{number="2",type="watchpoint",disp="keep",
17433 enabled="y",addr="",what="C",times="0"@}]@}
17437 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
17438 value=@{old="-276895068",new="3"@},
17439 frame=@{func="callee4",args=[],
17440 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
17443 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17444 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17445 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17446 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17447 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17448 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17449 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17450 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17451 addr="0x00010734",func="callee4",
17452 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
17453 bkpt=@{number="2",type="watchpoint",disp="keep",
17454 enabled="y",addr="",what="C",times="-5"@}]@}
17458 ^done,reason="watchpoint-scope",wpnum="2",
17459 frame=@{func="callee3",args=[@{name="strarg",
17460 value="0x11940 \"A string argument.\""@}],
17461 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
17464 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17465 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17466 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17467 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17468 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17469 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17470 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17471 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17472 addr="0x00010734",func="callee4",
17473 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@}]@}
17477 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17478 @node GDB/MI Data Manipulation
17479 @section @sc{gdb/mi} Data Manipulation
17481 @cindex data manipulation, in @sc{gdb/mi}
17482 @cindex @sc{gdb/mi}, data manipulation
17483 This section describes the @sc{gdb/mi} commands that manipulate data:
17484 examine memory and registers, evaluate expressions, etc.
17486 @c REMOVED FROM THE INTERFACE.
17487 @c @subheading -data-assign
17488 @c Change the value of a program variable. Plenty of side effects.
17489 @c @subsubheading GDB command
17491 @c @subsubheading Example
17494 @subheading The @code{-data-disassemble} Command
17495 @findex -data-disassemble
17497 @subsubheading Synopsis
17501 [ -s @var{start-addr} -e @var{end-addr} ]
17502 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
17510 @item @var{start-addr}
17511 is the beginning address (or @code{$pc})
17512 @item @var{end-addr}
17514 @item @var{filename}
17515 is the name of the file to disassemble
17516 @item @var{linenum}
17517 is the line number to disassemble around
17519 is the the number of disassembly lines to be produced. If it is -1,
17520 the whole function will be disassembled, in case no @var{end-addr} is
17521 specified. If @var{end-addr} is specified as a non-zero value, and
17522 @var{lines} is lower than the number of disassembly lines between
17523 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
17524 displayed; if @var{lines} is higher than the number of lines between
17525 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
17528 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
17532 @subsubheading Result
17534 The output for each instruction is composed of four fields:
17543 Note that whatever included in the instruction field, is not manipulated
17544 directely by @sc{gdb/mi}, i.e. it is not possible to adjust its format.
17546 @subsubheading @value{GDBN} Command
17548 There's no direct mapping from this command to the CLI.
17550 @subsubheading Example
17552 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
17556 -data-disassemble -s $pc -e "$pc + 20" -- 0
17559 @{address="0x000107c0",func-name="main",offset="4",
17560 inst="mov 2, %o0"@},
17561 @{address="0x000107c4",func-name="main",offset="8",
17562 inst="sethi %hi(0x11800), %o2"@},
17563 @{address="0x000107c8",func-name="main",offset="12",
17564 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
17565 @{address="0x000107cc",func-name="main",offset="16",
17566 inst="sethi %hi(0x11800), %o2"@},
17567 @{address="0x000107d0",func-name="main",offset="20",
17568 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
17572 Disassemble the whole @code{main} function. Line 32 is part of
17576 -data-disassemble -f basics.c -l 32 -- 0
17578 @{address="0x000107bc",func-name="main",offset="0",
17579 inst="save %sp, -112, %sp"@},
17580 @{address="0x000107c0",func-name="main",offset="4",
17581 inst="mov 2, %o0"@},
17582 @{address="0x000107c4",func-name="main",offset="8",
17583 inst="sethi %hi(0x11800), %o2"@},
17585 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
17586 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
17590 Disassemble 3 instructions from the start of @code{main}:
17594 -data-disassemble -f basics.c -l 32 -n 3 -- 0
17596 @{address="0x000107bc",func-name="main",offset="0",
17597 inst="save %sp, -112, %sp"@},
17598 @{address="0x000107c0",func-name="main",offset="4",
17599 inst="mov 2, %o0"@},
17600 @{address="0x000107c4",func-name="main",offset="8",
17601 inst="sethi %hi(0x11800), %o2"@}]
17605 Disassemble 3 instructions from the start of @code{main} in mixed mode:
17609 -data-disassemble -f basics.c -l 32 -n 3 -- 1
17611 src_and_asm_line=@{line="31",
17612 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
17613 testsuite/gdb.mi/basics.c",line_asm_insn=[
17614 @{address="0x000107bc",func-name="main",offset="0",
17615 inst="save %sp, -112, %sp"@}]@},
17616 src_and_asm_line=@{line="32",
17617 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
17618 testsuite/gdb.mi/basics.c",line_asm_insn=[
17619 @{address="0x000107c0",func-name="main",offset="4",
17620 inst="mov 2, %o0"@},
17621 @{address="0x000107c4",func-name="main",offset="8",
17622 inst="sethi %hi(0x11800), %o2"@}]@}]
17627 @subheading The @code{-data-evaluate-expression} Command
17628 @findex -data-evaluate-expression
17630 @subsubheading Synopsis
17633 -data-evaluate-expression @var{expr}
17636 Evaluate @var{expr} as an expression. The expression could contain an
17637 inferior function call. The function call will execute synchronously.
17638 If the expression contains spaces, it must be enclosed in double quotes.
17640 @subsubheading @value{GDBN} Command
17642 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
17643 @samp{call}. In @code{gdbtk} only, there's a corresponding
17644 @samp{gdb_eval} command.
17646 @subsubheading Example
17648 In the following example, the numbers that precede the commands are the
17649 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
17650 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
17654 211-data-evaluate-expression A
17657 311-data-evaluate-expression &A
17658 311^done,value="0xefffeb7c"
17660 411-data-evaluate-expression A+3
17663 511-data-evaluate-expression "A + 3"
17669 @subheading The @code{-data-list-changed-registers} Command
17670 @findex -data-list-changed-registers
17672 @subsubheading Synopsis
17675 -data-list-changed-registers
17678 Display a list of the registers that have changed.
17680 @subsubheading @value{GDBN} Command
17682 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
17683 has the corresponding command @samp{gdb_changed_register_list}.
17685 @subsubheading Example
17687 On a PPC MBX board:
17695 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
17696 args=[],file="try.c",line="5"@}
17698 -data-list-changed-registers
17699 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
17700 "10","11","13","14","15","16","17","18","19","20","21","22","23",
17701 "24","25","26","27","28","30","31","64","65","66","67","69"]
17706 @subheading The @code{-data-list-register-names} Command
17707 @findex -data-list-register-names
17709 @subsubheading Synopsis
17712 -data-list-register-names [ ( @var{regno} )+ ]
17715 Show a list of register names for the current target. If no arguments
17716 are given, it shows a list of the names of all the registers. If
17717 integer numbers are given as arguments, it will print a list of the
17718 names of the registers corresponding to the arguments. To ensure
17719 consistency between a register name and its number, the output list may
17720 include empty register names.
17722 @subsubheading @value{GDBN} Command
17724 @value{GDBN} does not have a command which corresponds to
17725 @samp{-data-list-register-names}. In @code{gdbtk} there is a
17726 corresponding command @samp{gdb_regnames}.
17728 @subsubheading Example
17730 For the PPC MBX board:
17733 -data-list-register-names
17734 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
17735 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
17736 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
17737 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
17738 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
17739 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
17740 "", "pc","ps","cr","lr","ctr","xer"]
17742 -data-list-register-names 1 2 3
17743 ^done,register-names=["r1","r2","r3"]
17747 @subheading The @code{-data-list-register-values} Command
17748 @findex -data-list-register-values
17750 @subsubheading Synopsis
17753 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
17756 Display the registers' contents. @var{fmt} is the format according to
17757 which the registers' contents are to be returned, followed by an optional
17758 list of numbers specifying the registers to display. A missing list of
17759 numbers indicates that the contents of all the registers must be returned.
17761 Allowed formats for @var{fmt} are:
17778 @subsubheading @value{GDBN} Command
17780 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
17781 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
17783 @subsubheading Example
17785 For a PPC MBX board (note: line breaks are for readability only, they
17786 don't appear in the actual output):
17790 -data-list-register-values r 64 65
17791 ^done,register-values=[@{number="64",value="0xfe00a300"@},
17792 @{number="65",value="0x00029002"@}]
17794 -data-list-register-values x
17795 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
17796 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
17797 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
17798 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
17799 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
17800 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
17801 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
17802 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
17803 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
17804 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
17805 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
17806 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
17807 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
17808 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
17809 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
17810 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
17811 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
17812 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
17813 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
17814 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
17815 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
17816 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
17817 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
17818 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
17819 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
17820 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
17821 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
17822 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
17823 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
17824 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
17825 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
17826 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
17827 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
17828 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
17829 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
17830 @{number="69",value="0x20002b03"@}]
17835 @subheading The @code{-data-read-memory} Command
17836 @findex -data-read-memory
17838 @subsubheading Synopsis
17841 -data-read-memory [ -o @var{byte-offset} ]
17842 @var{address} @var{word-format} @var{word-size}
17843 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
17850 @item @var{address}
17851 An expression specifying the address of the first memory word to be
17852 read. Complex expressions containing embedded white space should be
17853 quoted using the C convention.
17855 @item @var{word-format}
17856 The format to be used to print the memory words. The notation is the
17857 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
17860 @item @var{word-size}
17861 The size of each memory word in bytes.
17863 @item @var{nr-rows}
17864 The number of rows in the output table.
17866 @item @var{nr-cols}
17867 The number of columns in the output table.
17870 If present, indicates that each row should include an @sc{ascii} dump. The
17871 value of @var{aschar} is used as a padding character when a byte is not a
17872 member of the printable @sc{ascii} character set (printable @sc{ascii}
17873 characters are those whose code is between 32 and 126, inclusively).
17875 @item @var{byte-offset}
17876 An offset to add to the @var{address} before fetching memory.
17879 This command displays memory contents as a table of @var{nr-rows} by
17880 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
17881 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
17882 (returned as @samp{total-bytes}). Should less than the requested number
17883 of bytes be returned by the target, the missing words are identified
17884 using @samp{N/A}. The number of bytes read from the target is returned
17885 in @samp{nr-bytes} and the starting address used to read memory in
17888 The address of the next/previous row or page is available in
17889 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
17892 @subsubheading @value{GDBN} Command
17894 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
17895 @samp{gdb_get_mem} memory read command.
17897 @subsubheading Example
17899 Read six bytes of memory starting at @code{bytes+6} but then offset by
17900 @code{-6} bytes. Format as three rows of two columns. One byte per
17901 word. Display each word in hex.
17905 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
17906 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
17907 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
17908 prev-page="0x0000138a",memory=[
17909 @{addr="0x00001390",data=["0x00","0x01"]@},
17910 @{addr="0x00001392",data=["0x02","0x03"]@},
17911 @{addr="0x00001394",data=["0x04","0x05"]@}]
17915 Read two bytes of memory starting at address @code{shorts + 64} and
17916 display as a single word formatted in decimal.
17920 5-data-read-memory shorts+64 d 2 1 1
17921 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
17922 next-row="0x00001512",prev-row="0x0000150e",
17923 next-page="0x00001512",prev-page="0x0000150e",memory=[
17924 @{addr="0x00001510",data=["128"]@}]
17928 Read thirty two bytes of memory starting at @code{bytes+16} and format
17929 as eight rows of four columns. Include a string encoding with @samp{x}
17930 used as the non-printable character.
17934 4-data-read-memory bytes+16 x 1 8 4 x
17935 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
17936 next-row="0x000013c0",prev-row="0x0000139c",
17937 next-page="0x000013c0",prev-page="0x00001380",memory=[
17938 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
17939 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
17940 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
17941 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
17942 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
17943 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
17944 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
17945 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
17949 @subheading The @code{-display-delete} Command
17950 @findex -display-delete
17952 @subsubheading Synopsis
17955 -display-delete @var{number}
17958 Delete the display @var{number}.
17960 @subsubheading @value{GDBN} Command
17962 The corresponding @value{GDBN} command is @samp{delete display}.
17964 @subsubheading Example
17968 @subheading The @code{-display-disable} Command
17969 @findex -display-disable
17971 @subsubheading Synopsis
17974 -display-disable @var{number}
17977 Disable display @var{number}.
17979 @subsubheading @value{GDBN} Command
17981 The corresponding @value{GDBN} command is @samp{disable display}.
17983 @subsubheading Example
17987 @subheading The @code{-display-enable} Command
17988 @findex -display-enable
17990 @subsubheading Synopsis
17993 -display-enable @var{number}
17996 Enable display @var{number}.
17998 @subsubheading @value{GDBN} Command
18000 The corresponding @value{GDBN} command is @samp{enable display}.
18002 @subsubheading Example
18006 @subheading The @code{-display-insert} Command
18007 @findex -display-insert
18009 @subsubheading Synopsis
18012 -display-insert @var{expression}
18015 Display @var{expression} every time the program stops.
18017 @subsubheading @value{GDBN} Command
18019 The corresponding @value{GDBN} command is @samp{display}.
18021 @subsubheading Example
18025 @subheading The @code{-display-list} Command
18026 @findex -display-list
18028 @subsubheading Synopsis
18034 List the displays. Do not show the current values.
18036 @subsubheading @value{GDBN} Command
18038 The corresponding @value{GDBN} command is @samp{info display}.
18040 @subsubheading Example
18044 @subheading The @code{-environment-cd} Command
18045 @findex -environment-cd
18047 @subsubheading Synopsis
18050 -environment-cd @var{pathdir}
18053 Set @value{GDBN}'s working directory.
18055 @subsubheading @value{GDBN} Command
18057 The corresponding @value{GDBN} command is @samp{cd}.
18059 @subsubheading Example
18063 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18069 @subheading The @code{-environment-directory} Command
18070 @findex -environment-directory
18072 @subsubheading Synopsis
18075 -environment-directory [ -r ] [ @var{pathdir} ]+
18078 Add directories @var{pathdir} to beginning of search path for source files.
18079 If the @samp{-r} option is used, the search path is reset to the default
18080 search path. If directories @var{pathdir} are supplied in addition to the
18081 @samp{-r} option, the search path is first reset and then addition
18083 Multiple directories may be specified, separated by blanks. Specifying
18084 multiple directories in a single command
18085 results in the directories added to the beginning of the
18086 search path in the same order they were presented in the command.
18087 If blanks are needed as
18088 part of a directory name, double-quotes should be used around
18089 the name. In the command output, the path will show up separated
18090 by the system directory-separator character. The directory-seperator
18091 character must not be used
18092 in any directory name.
18093 If no directories are specified, the current search path is displayed.
18095 @subsubheading @value{GDBN} Command
18097 The corresponding @value{GDBN} command is @samp{dir}.
18099 @subsubheading Example
18103 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18104 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18106 -environment-directory ""
18107 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18109 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
18110 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
18112 -environment-directory -r
18113 ^done,source-path="$cdir:$cwd"
18118 @subheading The @code{-environment-path} Command
18119 @findex -environment-path
18121 @subsubheading Synopsis
18124 -environment-path [ -r ] [ @var{pathdir} ]+
18127 Add directories @var{pathdir} to beginning of search path for object files.
18128 If the @samp{-r} option is used, the search path is reset to the original
18129 search path that existed at gdb start-up. If directories @var{pathdir} are
18130 supplied in addition to the
18131 @samp{-r} option, the search path is first reset and then addition
18133 Multiple directories may be specified, separated by blanks. Specifying
18134 multiple directories in a single command
18135 results in the directories added to the beginning of the
18136 search path in the same order they were presented in the command.
18137 If blanks are needed as
18138 part of a directory name, double-quotes should be used around
18139 the name. In the command output, the path will show up separated
18140 by the system directory-separator character. The directory-seperator
18141 character must not be used
18142 in any directory name.
18143 If no directories are specified, the current path is displayed.
18146 @subsubheading @value{GDBN} Command
18148 The corresponding @value{GDBN} command is @samp{path}.
18150 @subsubheading Example
18155 ^done,path="/usr/bin"
18157 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
18158 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
18160 -environment-path -r /usr/local/bin
18161 ^done,path="/usr/local/bin:/usr/bin"
18166 @subheading The @code{-environment-pwd} Command
18167 @findex -environment-pwd
18169 @subsubheading Synopsis
18175 Show the current working directory.
18177 @subsubheading @value{GDBN} command
18179 The corresponding @value{GDBN} command is @samp{pwd}.
18181 @subsubheading Example
18186 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
18190 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18191 @node GDB/MI Program Control
18192 @section @sc{gdb/mi} Program control
18194 @subsubheading Program termination
18196 As a result of execution, the inferior program can run to completion, if
18197 it doesn't encounter any breakpoints. In this case the output will
18198 include an exit code, if the program has exited exceptionally.
18200 @subsubheading Examples
18203 Program exited normally:
18211 *stopped,reason="exited-normally"
18216 Program exited exceptionally:
18224 *stopped,reason="exited",exit-code="01"
18228 Another way the program can terminate is if it receives a signal such as
18229 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
18233 *stopped,reason="exited-signalled",signal-name="SIGINT",
18234 signal-meaning="Interrupt"
18238 @subheading The @code{-exec-abort} Command
18239 @findex -exec-abort
18241 @subsubheading Synopsis
18247 Kill the inferior running program.
18249 @subsubheading @value{GDBN} Command
18251 The corresponding @value{GDBN} command is @samp{kill}.
18253 @subsubheading Example
18257 @subheading The @code{-exec-arguments} Command
18258 @findex -exec-arguments
18260 @subsubheading Synopsis
18263 -exec-arguments @var{args}
18266 Set the inferior program arguments, to be used in the next
18269 @subsubheading @value{GDBN} Command
18271 The corresponding @value{GDBN} command is @samp{set args}.
18273 @subsubheading Example
18276 Don't have one around.
18279 @subheading The @code{-exec-continue} Command
18280 @findex -exec-continue
18282 @subsubheading Synopsis
18288 Asynchronous command. Resumes the execution of the inferior program
18289 until a breakpoint is encountered, or until the inferior exits.
18291 @subsubheading @value{GDBN} Command
18293 The corresponding @value{GDBN} corresponding is @samp{continue}.
18295 @subsubheading Example
18302 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
18303 file="hello.c",line="13"@}
18308 @subheading The @code{-exec-finish} Command
18309 @findex -exec-finish
18311 @subsubheading Synopsis
18317 Asynchronous command. Resumes the execution of the inferior program
18318 until the current function is exited. Displays the results returned by
18321 @subsubheading @value{GDBN} Command
18323 The corresponding @value{GDBN} command is @samp{finish}.
18325 @subsubheading Example
18327 Function returning @code{void}.
18334 *stopped,reason="function-finished",frame=@{func="main",args=[],
18335 file="hello.c",line="7"@}
18339 Function returning other than @code{void}. The name of the internal
18340 @value{GDBN} variable storing the result is printed, together with the
18347 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
18348 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
18349 file="recursive2.c",line="14"@},
18350 gdb-result-var="$1",return-value="0"
18355 @subheading The @code{-exec-interrupt} Command
18356 @findex -exec-interrupt
18358 @subsubheading Synopsis
18364 Asynchronous command. Interrupts the background execution of the target.
18365 Note how the token associated with the stop message is the one for the
18366 execution command that has been interrupted. The token for the interrupt
18367 itself only appears in the @samp{^done} output. If the user is trying to
18368 interrupt a non-running program, an error message will be printed.
18370 @subsubheading @value{GDBN} Command
18372 The corresponding @value{GDBN} command is @samp{interrupt}.
18374 @subsubheading Example
18385 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
18386 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",line="13"@}
18391 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
18396 @subheading The @code{-exec-next} Command
18399 @subsubheading Synopsis
18405 Asynchronous command. Resumes execution of the inferior program, stopping
18406 when the beginning of the next source line is reached.
18408 @subsubheading @value{GDBN} Command
18410 The corresponding @value{GDBN} command is @samp{next}.
18412 @subsubheading Example
18418 *stopped,reason="end-stepping-range",line="8",file="hello.c"
18423 @subheading The @code{-exec-next-instruction} Command
18424 @findex -exec-next-instruction
18426 @subsubheading Synopsis
18429 -exec-next-instruction
18432 Asynchronous command. Executes one machine instruction. If the
18433 instruction is a function call continues until the function returns. If
18434 the program stops at an instruction in the middle of a source line, the
18435 address will be printed as well.
18437 @subsubheading @value{GDBN} Command
18439 The corresponding @value{GDBN} command is @samp{nexti}.
18441 @subsubheading Example
18445 -exec-next-instruction
18449 *stopped,reason="end-stepping-range",
18450 addr="0x000100d4",line="5",file="hello.c"
18455 @subheading The @code{-exec-return} Command
18456 @findex -exec-return
18458 @subsubheading Synopsis
18464 Makes current function return immediately. Doesn't execute the inferior.
18465 Displays the new current frame.
18467 @subsubheading @value{GDBN} Command
18469 The corresponding @value{GDBN} command is @samp{return}.
18471 @subsubheading Example
18475 200-break-insert callee4
18476 200^done,bkpt=@{number="1",addr="0x00010734",
18477 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
18482 000*stopped,reason="breakpoint-hit",bkptno="1",
18483 frame=@{func="callee4",args=[],
18484 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
18490 111^done,frame=@{level="0",func="callee3",
18491 args=[@{name="strarg",
18492 value="0x11940 \"A string argument.\""@}],
18493 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18498 @subheading The @code{-exec-run} Command
18501 @subsubheading Synopsis
18507 Asynchronous command. Starts execution of the inferior from the
18508 beginning. The inferior executes until either a breakpoint is
18509 encountered or the program exits.
18511 @subsubheading @value{GDBN} Command
18513 The corresponding @value{GDBN} command is @samp{run}.
18515 @subsubheading Example
18520 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
18525 *stopped,reason="breakpoint-hit",bkptno="1",
18526 frame=@{func="main",args=[],file="recursive2.c",line="4"@}
18531 @subheading The @code{-exec-show-arguments} Command
18532 @findex -exec-show-arguments
18534 @subsubheading Synopsis
18537 -exec-show-arguments
18540 Print the arguments of the program.
18542 @subsubheading @value{GDBN} Command
18544 The corresponding @value{GDBN} command is @samp{show args}.
18546 @subsubheading Example
18549 @c @subheading -exec-signal
18551 @subheading The @code{-exec-step} Command
18554 @subsubheading Synopsis
18560 Asynchronous command. Resumes execution of the inferior program, stopping
18561 when the beginning of the next source line is reached, if the next
18562 source line is not a function call. If it is, stop at the first
18563 instruction of the called function.
18565 @subsubheading @value{GDBN} Command
18567 The corresponding @value{GDBN} command is @samp{step}.
18569 @subsubheading Example
18571 Stepping into a function:
18577 *stopped,reason="end-stepping-range",
18578 frame=@{func="foo",args=[@{name="a",value="10"@},
18579 @{name="b",value="0"@}],file="recursive2.c",line="11"@}
18589 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
18594 @subheading The @code{-exec-step-instruction} Command
18595 @findex -exec-step-instruction
18597 @subsubheading Synopsis
18600 -exec-step-instruction
18603 Asynchronous command. Resumes the inferior which executes one machine
18604 instruction. The output, once @value{GDBN} has stopped, will vary depending on
18605 whether we have stopped in the middle of a source line or not. In the
18606 former case, the address at which the program stopped will be printed as
18609 @subsubheading @value{GDBN} Command
18611 The corresponding @value{GDBN} command is @samp{stepi}.
18613 @subsubheading Example
18617 -exec-step-instruction
18621 *stopped,reason="end-stepping-range",
18622 frame=@{func="foo",args=[],file="try.c",line="10"@}
18624 -exec-step-instruction
18628 *stopped,reason="end-stepping-range",
18629 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",line="10"@}
18634 @subheading The @code{-exec-until} Command
18635 @findex -exec-until
18637 @subsubheading Synopsis
18640 -exec-until [ @var{location} ]
18643 Asynchronous command. Executes the inferior until the @var{location}
18644 specified in the argument is reached. If there is no argument, the inferior
18645 executes until a source line greater than the current one is reached.
18646 The reason for stopping in this case will be @samp{location-reached}.
18648 @subsubheading @value{GDBN} Command
18650 The corresponding @value{GDBN} command is @samp{until}.
18652 @subsubheading Example
18656 -exec-until recursive2.c:6
18660 *stopped,reason="location-reached",frame=@{func="main",args=[],
18661 file="recursive2.c",line="6"@}
18666 @subheading -file-clear
18667 Is this going away????
18671 @subheading The @code{-file-exec-and-symbols} Command
18672 @findex -file-exec-and-symbols
18674 @subsubheading Synopsis
18677 -file-exec-and-symbols @var{file}
18680 Specify the executable file to be debugged. This file is the one from
18681 which the symbol table is also read. If no file is specified, the
18682 command clears the executable and symbol information. If breakpoints
18683 are set when using this command with no arguments, @value{GDBN} will produce
18684 error messages. Otherwise, no output is produced, except a completion
18687 @subsubheading @value{GDBN} Command
18689 The corresponding @value{GDBN} command is @samp{file}.
18691 @subsubheading Example
18695 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
18701 @subheading The @code{-file-exec-file} Command
18702 @findex -file-exec-file
18704 @subsubheading Synopsis
18707 -file-exec-file @var{file}
18710 Specify the executable file to be debugged. Unlike
18711 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
18712 from this file. If used without argument, @value{GDBN} clears the information
18713 about the executable file. No output is produced, except a completion
18716 @subsubheading @value{GDBN} Command
18718 The corresponding @value{GDBN} command is @samp{exec-file}.
18720 @subsubheading Example
18724 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
18730 @subheading The @code{-file-list-exec-sections} Command
18731 @findex -file-list-exec-sections
18733 @subsubheading Synopsis
18736 -file-list-exec-sections
18739 List the sections of the current executable file.
18741 @subsubheading @value{GDBN} Command
18743 The @value{GDBN} command @samp{info file} shows, among the rest, the same
18744 information as this command. @code{gdbtk} has a corresponding command
18745 @samp{gdb_load_info}.
18747 @subsubheading Example
18751 @subheading The @code{-file-list-exec-source-file} Command
18752 @findex -file-list-exec-source-file
18754 @subsubheading Synopsis
18757 -file-list-exec-source-file
18760 List the line number, the current source file, and the absolute path
18761 to the current source file for the current executable.
18763 @subsubheading @value{GDBN} Command
18765 There's no @value{GDBN} command which directly corresponds to this one.
18767 @subsubheading Example
18771 123-file-list-exec-source-file
18772 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
18777 @subheading The @code{-file-list-exec-source-files} Command
18778 @findex -file-list-exec-source-files
18780 @subsubheading Synopsis
18783 -file-list-exec-source-files
18786 List the source files for the current executable.
18788 It will always output the filename, but only when GDB can find the absolute
18789 file name of a source file, will it output the fullname.
18791 @subsubheading @value{GDBN} Command
18793 There's no @value{GDBN} command which directly corresponds to this one.
18794 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
18796 @subsubheading Example
18799 -file-list-exec-source-files
18801 @{file=foo.c,fullname=/home/foo.c@},
18802 @{file=/home/bar.c,fullname=/home/bar.c@},
18803 @{file=gdb_could_not_find_fullpath.c@}]
18807 @subheading The @code{-file-list-shared-libraries} Command
18808 @findex -file-list-shared-libraries
18810 @subsubheading Synopsis
18813 -file-list-shared-libraries
18816 List the shared libraries in the program.
18818 @subsubheading @value{GDBN} Command
18820 The corresponding @value{GDBN} command is @samp{info shared}.
18822 @subsubheading Example
18826 @subheading The @code{-file-list-symbol-files} Command
18827 @findex -file-list-symbol-files
18829 @subsubheading Synopsis
18832 -file-list-symbol-files
18837 @subsubheading @value{GDBN} Command
18839 The corresponding @value{GDBN} command is @samp{info file} (part of it).
18841 @subsubheading Example
18845 @subheading The @code{-file-symbol-file} Command
18846 @findex -file-symbol-file
18848 @subsubheading Synopsis
18851 -file-symbol-file @var{file}
18854 Read symbol table info from the specified @var{file} argument. When
18855 used without arguments, clears @value{GDBN}'s symbol table info. No output is
18856 produced, except for a completion notification.
18858 @subsubheading @value{GDBN} Command
18860 The corresponding @value{GDBN} command is @samp{symbol-file}.
18862 @subsubheading Example
18866 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
18871 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18872 @node GDB/MI Miscellaneous Commands
18873 @section Miscellaneous @value{GDBN} commands in @sc{gdb/mi}
18875 @c @subheading -gdb-complete
18877 @subheading The @code{-gdb-exit} Command
18880 @subsubheading Synopsis
18886 Exit @value{GDBN} immediately.
18888 @subsubheading @value{GDBN} Command
18890 Approximately corresponds to @samp{quit}.
18892 @subsubheading Example
18899 @subheading The @code{-gdb-set} Command
18902 @subsubheading Synopsis
18908 Set an internal @value{GDBN} variable.
18909 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
18911 @subsubheading @value{GDBN} Command
18913 The corresponding @value{GDBN} command is @samp{set}.
18915 @subsubheading Example
18925 @subheading The @code{-gdb-show} Command
18928 @subsubheading Synopsis
18934 Show the current value of a @value{GDBN} variable.
18936 @subsubheading @value{GDBN} command
18938 The corresponding @value{GDBN} command is @samp{show}.
18940 @subsubheading Example
18949 @c @subheading -gdb-source
18952 @subheading The @code{-gdb-version} Command
18953 @findex -gdb-version
18955 @subsubheading Synopsis
18961 Show version information for @value{GDBN}. Used mostly in testing.
18963 @subsubheading @value{GDBN} Command
18965 There's no equivalent @value{GDBN} command. @value{GDBN} by default shows this
18966 information when you start an interactive session.
18968 @subsubheading Example
18970 @c This example modifies the actual output from GDB to avoid overfull
18976 ~Copyright 2000 Free Software Foundation, Inc.
18977 ~GDB is free software, covered by the GNU General Public License, and
18978 ~you are welcome to change it and/or distribute copies of it under
18979 ~ certain conditions.
18980 ~Type "show copying" to see the conditions.
18981 ~There is absolutely no warranty for GDB. Type "show warranty" for
18983 ~This GDB was configured as
18984 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
18989 @subheading The @code{-interpreter-exec} Command
18990 @findex -interpreter-exec
18992 @subheading Synopsis
18995 -interpreter-exec @var{interpreter} @var{command}
18998 Execute the specified @var{command} in the given @var{interpreter}.
19000 @subheading @value{GDBN} Command
19002 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
19004 @subheading Example
19008 -interpreter-exec console "break main"
19009 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
19010 &"During symbol reading, bad structure-type format.\n"
19011 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
19017 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19018 @node GDB/MI Kod Commands
19019 @section @sc{gdb/mi} Kod Commands
19021 The Kod commands are not implemented.
19023 @c @subheading -kod-info
19025 @c @subheading -kod-list
19027 @c @subheading -kod-list-object-types
19029 @c @subheading -kod-show
19031 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19032 @node GDB/MI Memory Overlay Commands
19033 @section @sc{gdb/mi} Memory Overlay Commands
19035 The memory overlay commands are not implemented.
19037 @c @subheading -overlay-auto
19039 @c @subheading -overlay-list-mapping-state
19041 @c @subheading -overlay-list-overlays
19043 @c @subheading -overlay-map
19045 @c @subheading -overlay-off
19047 @c @subheading -overlay-on
19049 @c @subheading -overlay-unmap
19051 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19052 @node GDB/MI Signal Handling Commands
19053 @section @sc{gdb/mi} Signal Handling Commands
19055 Signal handling commands are not implemented.
19057 @c @subheading -signal-handle
19059 @c @subheading -signal-list-handle-actions
19061 @c @subheading -signal-list-signal-types
19065 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19066 @node GDB/MI Stack Manipulation
19067 @section @sc{gdb/mi} Stack Manipulation Commands
19070 @subheading The @code{-stack-info-frame} Command
19071 @findex -stack-info-frame
19073 @subsubheading Synopsis
19079 Get info on the current frame.
19081 @subsubheading @value{GDBN} Command
19083 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
19084 (without arguments).
19086 @subsubheading Example
19089 @subheading The @code{-stack-info-depth} Command
19090 @findex -stack-info-depth
19092 @subsubheading Synopsis
19095 -stack-info-depth [ @var{max-depth} ]
19098 Return the depth of the stack. If the integer argument @var{max-depth}
19099 is specified, do not count beyond @var{max-depth} frames.
19101 @subsubheading @value{GDBN} Command
19103 There's no equivalent @value{GDBN} command.
19105 @subsubheading Example
19107 For a stack with frame levels 0 through 11:
19114 -stack-info-depth 4
19117 -stack-info-depth 12
19120 -stack-info-depth 11
19123 -stack-info-depth 13
19128 @subheading The @code{-stack-list-arguments} Command
19129 @findex -stack-list-arguments
19131 @subsubheading Synopsis
19134 -stack-list-arguments @var{show-values}
19135 [ @var{low-frame} @var{high-frame} ]
19138 Display a list of the arguments for the frames between @var{low-frame}
19139 and @var{high-frame} (inclusive). If @var{low-frame} and
19140 @var{high-frame} are not provided, list the arguments for the whole call
19143 The @var{show-values} argument must have a value of 0 or 1. A value of
19144 0 means that only the names of the arguments are listed, a value of 1
19145 means that both names and values of the arguments are printed.
19147 @subsubheading @value{GDBN} Command
19149 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
19150 @samp{gdb_get_args} command which partially overlaps with the
19151 functionality of @samp{-stack-list-arguments}.
19153 @subsubheading Example
19160 frame=@{level="0",addr="0x00010734",func="callee4",
19161 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
19162 frame=@{level="1",addr="0x0001076c",func="callee3",
19163 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
19164 frame=@{level="2",addr="0x0001078c",func="callee2",
19165 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
19166 frame=@{level="3",addr="0x000107b4",func="callee1",
19167 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
19168 frame=@{level="4",addr="0x000107e0",func="main",
19169 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
19171 -stack-list-arguments 0
19174 frame=@{level="0",args=[]@},
19175 frame=@{level="1",args=[name="strarg"]@},
19176 frame=@{level="2",args=[name="intarg",name="strarg"]@},
19177 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
19178 frame=@{level="4",args=[]@}]
19180 -stack-list-arguments 1
19183 frame=@{level="0",args=[]@},
19185 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19186 frame=@{level="2",args=[
19187 @{name="intarg",value="2"@},
19188 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19189 @{frame=@{level="3",args=[
19190 @{name="intarg",value="2"@},
19191 @{name="strarg",value="0x11940 \"A string argument.\""@},
19192 @{name="fltarg",value="3.5"@}]@},
19193 frame=@{level="4",args=[]@}]
19195 -stack-list-arguments 0 2 2
19196 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
19198 -stack-list-arguments 1 2 2
19199 ^done,stack-args=[frame=@{level="2",
19200 args=[@{name="intarg",value="2"@},
19201 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
19205 @c @subheading -stack-list-exception-handlers
19208 @subheading The @code{-stack-list-frames} Command
19209 @findex -stack-list-frames
19211 @subsubheading Synopsis
19214 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
19217 List the frames currently on the stack. For each frame it displays the
19222 The frame number, 0 being the topmost frame, i.e. the innermost function.
19224 The @code{$pc} value for that frame.
19228 File name of the source file where the function lives.
19230 Line number corresponding to the @code{$pc}.
19233 If invoked without arguments, this command prints a backtrace for the
19234 whole stack. If given two integer arguments, it shows the frames whose
19235 levels are between the two arguments (inclusive). If the two arguments
19236 are equal, it shows the single frame at the corresponding level.
19238 @subsubheading @value{GDBN} Command
19240 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
19242 @subsubheading Example
19244 Full stack backtrace:
19250 [frame=@{level="0",addr="0x0001076c",func="foo",
19251 file="recursive2.c",line="11"@},
19252 frame=@{level="1",addr="0x000107a4",func="foo",
19253 file="recursive2.c",line="14"@},
19254 frame=@{level="2",addr="0x000107a4",func="foo",
19255 file="recursive2.c",line="14"@},
19256 frame=@{level="3",addr="0x000107a4",func="foo",
19257 file="recursive2.c",line="14"@},
19258 frame=@{level="4",addr="0x000107a4",func="foo",
19259 file="recursive2.c",line="14"@},
19260 frame=@{level="5",addr="0x000107a4",func="foo",
19261 file="recursive2.c",line="14"@},
19262 frame=@{level="6",addr="0x000107a4",func="foo",
19263 file="recursive2.c",line="14"@},
19264 frame=@{level="7",addr="0x000107a4",func="foo",
19265 file="recursive2.c",line="14"@},
19266 frame=@{level="8",addr="0x000107a4",func="foo",
19267 file="recursive2.c",line="14"@},
19268 frame=@{level="9",addr="0x000107a4",func="foo",
19269 file="recursive2.c",line="14"@},
19270 frame=@{level="10",addr="0x000107a4",func="foo",
19271 file="recursive2.c",line="14"@},
19272 frame=@{level="11",addr="0x00010738",func="main",
19273 file="recursive2.c",line="4"@}]
19277 Show frames between @var{low_frame} and @var{high_frame}:
19281 -stack-list-frames 3 5
19283 [frame=@{level="3",addr="0x000107a4",func="foo",
19284 file="recursive2.c",line="14"@},
19285 frame=@{level="4",addr="0x000107a4",func="foo",
19286 file="recursive2.c",line="14"@},
19287 frame=@{level="5",addr="0x000107a4",func="foo",
19288 file="recursive2.c",line="14"@}]
19292 Show a single frame:
19296 -stack-list-frames 3 3
19298 [frame=@{level="3",addr="0x000107a4",func="foo",
19299 file="recursive2.c",line="14"@}]
19304 @subheading The @code{-stack-list-locals} Command
19305 @findex -stack-list-locals
19307 @subsubheading Synopsis
19310 -stack-list-locals @var{print-values}
19313 Display the local variable names for the current frame. With an
19314 argument of 0 or @code{--no-values}, prints only the names of the variables.
19315 With argument of 1 or @code{--all-values}, prints also their values. With
19316 argument of 2 or @code{--simple-values}, prints the name, type and value for
19317 simple data types and the name and type for arrays, structures and
19318 unions. In this last case, the idea is that the user can see the
19319 value of simple data types immediately and he can create variable
19320 objects for other data types if he wishes to explore their values in
19323 @subsubheading @value{GDBN} Command
19325 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
19327 @subsubheading Example
19331 -stack-list-locals 0
19332 ^done,locals=[name="A",name="B",name="C"]
19334 -stack-list-locals --all-values
19335 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
19336 @{name="C",value="@{1, 2, 3@}"@}]
19337 -stack-list-locals --simple-values
19338 ^done,locals=[@{name="A",type="int",value="1"@},
19339 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
19344 @subheading The @code{-stack-select-frame} Command
19345 @findex -stack-select-frame
19347 @subsubheading Synopsis
19350 -stack-select-frame @var{framenum}
19353 Change the current frame. Select a different frame @var{framenum} on
19356 @subsubheading @value{GDBN} Command
19358 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
19359 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
19361 @subsubheading Example
19365 -stack-select-frame 2
19370 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19371 @node GDB/MI Symbol Query
19372 @section @sc{gdb/mi} Symbol Query Commands
19375 @subheading The @code{-symbol-info-address} Command
19376 @findex -symbol-info-address
19378 @subsubheading Synopsis
19381 -symbol-info-address @var{symbol}
19384 Describe where @var{symbol} is stored.
19386 @subsubheading @value{GDBN} Command
19388 The corresponding @value{GDBN} command is @samp{info address}.
19390 @subsubheading Example
19394 @subheading The @code{-symbol-info-file} Command
19395 @findex -symbol-info-file
19397 @subsubheading Synopsis
19403 Show the file for the symbol.
19405 @subsubheading @value{GDBN} Command
19407 There's no equivalent @value{GDBN} command. @code{gdbtk} has
19408 @samp{gdb_find_file}.
19410 @subsubheading Example
19414 @subheading The @code{-symbol-info-function} Command
19415 @findex -symbol-info-function
19417 @subsubheading Synopsis
19420 -symbol-info-function
19423 Show which function the symbol lives in.
19425 @subsubheading @value{GDBN} Command
19427 @samp{gdb_get_function} in @code{gdbtk}.
19429 @subsubheading Example
19433 @subheading The @code{-symbol-info-line} Command
19434 @findex -symbol-info-line
19436 @subsubheading Synopsis
19442 Show the core addresses of the code for a source line.
19444 @subsubheading @value{GDBN} Command
19446 The corresponding @value{GDBN} command is @samp{info line}.
19447 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
19449 @subsubheading Example
19453 @subheading The @code{-symbol-info-symbol} Command
19454 @findex -symbol-info-symbol
19456 @subsubheading Synopsis
19459 -symbol-info-symbol @var{addr}
19462 Describe what symbol is at location @var{addr}.
19464 @subsubheading @value{GDBN} Command
19466 The corresponding @value{GDBN} command is @samp{info symbol}.
19468 @subsubheading Example
19472 @subheading The @code{-symbol-list-functions} Command
19473 @findex -symbol-list-functions
19475 @subsubheading Synopsis
19478 -symbol-list-functions
19481 List the functions in the executable.
19483 @subsubheading @value{GDBN} Command
19485 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
19486 @samp{gdb_search} in @code{gdbtk}.
19488 @subsubheading Example
19492 @subheading The @code{-symbol-list-lines} Command
19493 @findex -symbol-list-lines
19495 @subsubheading Synopsis
19498 -symbol-list-lines @var{filename}
19501 Print the list of lines that contain code and their associated program
19502 addresses for the given source filename. The entries are sorted in
19503 ascending PC order.
19505 @subsubheading @value{GDBN} Command
19507 There is no corresponding @value{GDBN} command.
19509 @subsubheading Example
19512 -symbol-list-lines basics.c
19513 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
19518 @subheading The @code{-symbol-list-types} Command
19519 @findex -symbol-list-types
19521 @subsubheading Synopsis
19527 List all the type names.
19529 @subsubheading @value{GDBN} Command
19531 The corresponding commands are @samp{info types} in @value{GDBN},
19532 @samp{gdb_search} in @code{gdbtk}.
19534 @subsubheading Example
19538 @subheading The @code{-symbol-list-variables} Command
19539 @findex -symbol-list-variables
19541 @subsubheading Synopsis
19544 -symbol-list-variables
19547 List all the global and static variable names.
19549 @subsubheading @value{GDBN} Command
19551 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
19553 @subsubheading Example
19557 @subheading The @code{-symbol-locate} Command
19558 @findex -symbol-locate
19560 @subsubheading Synopsis
19566 @subsubheading @value{GDBN} Command
19568 @samp{gdb_loc} in @code{gdbtk}.
19570 @subsubheading Example
19574 @subheading The @code{-symbol-type} Command
19575 @findex -symbol-type
19577 @subsubheading Synopsis
19580 -symbol-type @var{variable}
19583 Show type of @var{variable}.
19585 @subsubheading @value{GDBN} Command
19587 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
19588 @samp{gdb_obj_variable}.
19590 @subsubheading Example
19594 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19595 @node GDB/MI Target Manipulation
19596 @section @sc{gdb/mi} Target Manipulation Commands
19599 @subheading The @code{-target-attach} Command
19600 @findex -target-attach
19602 @subsubheading Synopsis
19605 -target-attach @var{pid} | @var{file}
19608 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
19610 @subsubheading @value{GDBN} command
19612 The corresponding @value{GDBN} command is @samp{attach}.
19614 @subsubheading Example
19618 @subheading The @code{-target-compare-sections} Command
19619 @findex -target-compare-sections
19621 @subsubheading Synopsis
19624 -target-compare-sections [ @var{section} ]
19627 Compare data of section @var{section} on target to the exec file.
19628 Without the argument, all sections are compared.
19630 @subsubheading @value{GDBN} Command
19632 The @value{GDBN} equivalent is @samp{compare-sections}.
19634 @subsubheading Example
19638 @subheading The @code{-target-detach} Command
19639 @findex -target-detach
19641 @subsubheading Synopsis
19647 Disconnect from the remote target. There's no output.
19649 @subsubheading @value{GDBN} command
19651 The corresponding @value{GDBN} command is @samp{detach}.
19653 @subsubheading Example
19663 @subheading The @code{-target-disconnect} Command
19664 @findex -target-disconnect
19666 @subsubheading Synopsis
19672 Disconnect from the remote target. There's no output.
19674 @subsubheading @value{GDBN} command
19676 The corresponding @value{GDBN} command is @samp{disconnect}.
19678 @subsubheading Example
19688 @subheading The @code{-target-download} Command
19689 @findex -target-download
19691 @subsubheading Synopsis
19697 Loads the executable onto the remote target.
19698 It prints out an update message every half second, which includes the fields:
19702 The name of the section.
19704 The size of what has been sent so far for that section.
19706 The size of the section.
19708 The total size of what was sent so far (the current and the previous sections).
19710 The size of the overall executable to download.
19714 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
19715 @sc{gdb/mi} Output Syntax}).
19717 In addition, it prints the name and size of the sections, as they are
19718 downloaded. These messages include the following fields:
19722 The name of the section.
19724 The size of the section.
19726 The size of the overall executable to download.
19730 At the end, a summary is printed.
19732 @subsubheading @value{GDBN} Command
19734 The corresponding @value{GDBN} command is @samp{load}.
19736 @subsubheading Example
19738 Note: each status message appears on a single line. Here the messages
19739 have been broken down so that they can fit onto a page.
19744 +download,@{section=".text",section-size="6668",total-size="9880"@}
19745 +download,@{section=".text",section-sent="512",section-size="6668",
19746 total-sent="512",total-size="9880"@}
19747 +download,@{section=".text",section-sent="1024",section-size="6668",
19748 total-sent="1024",total-size="9880"@}
19749 +download,@{section=".text",section-sent="1536",section-size="6668",
19750 total-sent="1536",total-size="9880"@}
19751 +download,@{section=".text",section-sent="2048",section-size="6668",
19752 total-sent="2048",total-size="9880"@}
19753 +download,@{section=".text",section-sent="2560",section-size="6668",
19754 total-sent="2560",total-size="9880"@}
19755 +download,@{section=".text",section-sent="3072",section-size="6668",
19756 total-sent="3072",total-size="9880"@}
19757 +download,@{section=".text",section-sent="3584",section-size="6668",
19758 total-sent="3584",total-size="9880"@}
19759 +download,@{section=".text",section-sent="4096",section-size="6668",
19760 total-sent="4096",total-size="9880"@}
19761 +download,@{section=".text",section-sent="4608",section-size="6668",
19762 total-sent="4608",total-size="9880"@}
19763 +download,@{section=".text",section-sent="5120",section-size="6668",
19764 total-sent="5120",total-size="9880"@}
19765 +download,@{section=".text",section-sent="5632",section-size="6668",
19766 total-sent="5632",total-size="9880"@}
19767 +download,@{section=".text",section-sent="6144",section-size="6668",
19768 total-sent="6144",total-size="9880"@}
19769 +download,@{section=".text",section-sent="6656",section-size="6668",
19770 total-sent="6656",total-size="9880"@}
19771 +download,@{section=".init",section-size="28",total-size="9880"@}
19772 +download,@{section=".fini",section-size="28",total-size="9880"@}
19773 +download,@{section=".data",section-size="3156",total-size="9880"@}
19774 +download,@{section=".data",section-sent="512",section-size="3156",
19775 total-sent="7236",total-size="9880"@}
19776 +download,@{section=".data",section-sent="1024",section-size="3156",
19777 total-sent="7748",total-size="9880"@}
19778 +download,@{section=".data",section-sent="1536",section-size="3156",
19779 total-sent="8260",total-size="9880"@}
19780 +download,@{section=".data",section-sent="2048",section-size="3156",
19781 total-sent="8772",total-size="9880"@}
19782 +download,@{section=".data",section-sent="2560",section-size="3156",
19783 total-sent="9284",total-size="9880"@}
19784 +download,@{section=".data",section-sent="3072",section-size="3156",
19785 total-sent="9796",total-size="9880"@}
19786 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
19792 @subheading The @code{-target-exec-status} Command
19793 @findex -target-exec-status
19795 @subsubheading Synopsis
19798 -target-exec-status
19801 Provide information on the state of the target (whether it is running or
19802 not, for instance).
19804 @subsubheading @value{GDBN} Command
19806 There's no equivalent @value{GDBN} command.
19808 @subsubheading Example
19812 @subheading The @code{-target-list-available-targets} Command
19813 @findex -target-list-available-targets
19815 @subsubheading Synopsis
19818 -target-list-available-targets
19821 List the possible targets to connect to.
19823 @subsubheading @value{GDBN} Command
19825 The corresponding @value{GDBN} command is @samp{help target}.
19827 @subsubheading Example
19831 @subheading The @code{-target-list-current-targets} Command
19832 @findex -target-list-current-targets
19834 @subsubheading Synopsis
19837 -target-list-current-targets
19840 Describe the current target.
19842 @subsubheading @value{GDBN} Command
19844 The corresponding information is printed by @samp{info file} (among
19847 @subsubheading Example
19851 @subheading The @code{-target-list-parameters} Command
19852 @findex -target-list-parameters
19854 @subsubheading Synopsis
19857 -target-list-parameters
19862 @subsubheading @value{GDBN} Command
19866 @subsubheading Example
19870 @subheading The @code{-target-select} Command
19871 @findex -target-select
19873 @subsubheading Synopsis
19876 -target-select @var{type} @var{parameters @dots{}}
19879 Connect @value{GDBN} to the remote target. This command takes two args:
19883 The type of target, for instance @samp{async}, @samp{remote}, etc.
19884 @item @var{parameters}
19885 Device names, host names and the like. @xref{Target Commands, ,
19886 Commands for managing targets}, for more details.
19889 The output is a connection notification, followed by the address at
19890 which the target program is, in the following form:
19893 ^connected,addr="@var{address}",func="@var{function name}",
19894 args=[@var{arg list}]
19897 @subsubheading @value{GDBN} Command
19899 The corresponding @value{GDBN} command is @samp{target}.
19901 @subsubheading Example
19905 -target-select async /dev/ttya
19906 ^connected,addr="0xfe00a300",func="??",args=[]
19910 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19911 @node GDB/MI Thread Commands
19912 @section @sc{gdb/mi} Thread Commands
19915 @subheading The @code{-thread-info} Command
19916 @findex -thread-info
19918 @subsubheading Synopsis
19924 @subsubheading @value{GDBN} command
19928 @subsubheading Example
19932 @subheading The @code{-thread-list-all-threads} Command
19933 @findex -thread-list-all-threads
19935 @subsubheading Synopsis
19938 -thread-list-all-threads
19941 @subsubheading @value{GDBN} Command
19943 The equivalent @value{GDBN} command is @samp{info threads}.
19945 @subsubheading Example
19949 @subheading The @code{-thread-list-ids} Command
19950 @findex -thread-list-ids
19952 @subsubheading Synopsis
19958 Produces a list of the currently known @value{GDBN} thread ids. At the
19959 end of the list it also prints the total number of such threads.
19961 @subsubheading @value{GDBN} Command
19963 Part of @samp{info threads} supplies the same information.
19965 @subsubheading Example
19967 No threads present, besides the main process:
19972 ^done,thread-ids=@{@},number-of-threads="0"
19982 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
19983 number-of-threads="3"
19988 @subheading The @code{-thread-select} Command
19989 @findex -thread-select
19991 @subsubheading Synopsis
19994 -thread-select @var{threadnum}
19997 Make @var{threadnum} the current thread. It prints the number of the new
19998 current thread, and the topmost frame for that thread.
20000 @subsubheading @value{GDBN} Command
20002 The corresponding @value{GDBN} command is @samp{thread}.
20004 @subsubheading Example
20011 *stopped,reason="end-stepping-range",thread-id="2",line="187",
20012 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
20016 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
20017 number-of-threads="3"
20020 ^done,new-thread-id="3",
20021 frame=@{level="0",func="vprintf",
20022 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
20023 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
20027 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20028 @node GDB/MI Tracepoint Commands
20029 @section @sc{gdb/mi} Tracepoint Commands
20031 The tracepoint commands are not yet implemented.
20033 @c @subheading -trace-actions
20035 @c @subheading -trace-delete
20037 @c @subheading -trace-disable
20039 @c @subheading -trace-dump
20041 @c @subheading -trace-enable
20043 @c @subheading -trace-exists
20045 @c @subheading -trace-find
20047 @c @subheading -trace-frame-number
20049 @c @subheading -trace-info
20051 @c @subheading -trace-insert
20053 @c @subheading -trace-list
20055 @c @subheading -trace-pass-count
20057 @c @subheading -trace-save
20059 @c @subheading -trace-start
20061 @c @subheading -trace-stop
20064 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20065 @node GDB/MI Variable Objects
20066 @section @sc{gdb/mi} Variable Objects
20069 @subheading Motivation for Variable Objects in @sc{gdb/mi}
20071 For the implementation of a variable debugger window (locals, watched
20072 expressions, etc.), we are proposing the adaptation of the existing code
20073 used by @code{Insight}.
20075 The two main reasons for that are:
20079 It has been proven in practice (it is already on its second generation).
20082 It will shorten development time (needless to say how important it is
20086 The original interface was designed to be used by Tcl code, so it was
20087 slightly changed so it could be used through @sc{gdb/mi}. This section
20088 describes the @sc{gdb/mi} operations that will be available and gives some
20089 hints about their use.
20091 @emph{Note}: In addition to the set of operations described here, we
20092 expect the @sc{gui} implementation of a variable window to require, at
20093 least, the following operations:
20096 @item @code{-gdb-show} @code{output-radix}
20097 @item @code{-stack-list-arguments}
20098 @item @code{-stack-list-locals}
20099 @item @code{-stack-select-frame}
20102 @subheading Introduction to Variable Objects in @sc{gdb/mi}
20104 @cindex variable objects in @sc{gdb/mi}
20105 The basic idea behind variable objects is the creation of a named object
20106 to represent a variable, an expression, a memory location or even a CPU
20107 register. For each object created, a set of operations is available for
20108 examining or changing its properties.
20110 Furthermore, complex data types, such as C structures, are represented
20111 in a tree format. For instance, the @code{struct} type variable is the
20112 root and the children will represent the struct members. If a child
20113 is itself of a complex type, it will also have children of its own.
20114 Appropriate language differences are handled for C, C@t{++} and Java.
20116 When returning the actual values of the objects, this facility allows
20117 for the individual selection of the display format used in the result
20118 creation. It can be chosen among: binary, decimal, hexadecimal, octal
20119 and natural. Natural refers to a default format automatically
20120 chosen based on the variable type (like decimal for an @code{int}, hex
20121 for pointers, etc.).
20123 The following is the complete set of @sc{gdb/mi} operations defined to
20124 access this functionality:
20126 @multitable @columnfractions .4 .6
20127 @item @strong{Operation}
20128 @tab @strong{Description}
20130 @item @code{-var-create}
20131 @tab create a variable object
20132 @item @code{-var-delete}
20133 @tab delete the variable object and its children
20134 @item @code{-var-set-format}
20135 @tab set the display format of this variable
20136 @item @code{-var-show-format}
20137 @tab show the display format of this variable
20138 @item @code{-var-info-num-children}
20139 @tab tells how many children this object has
20140 @item @code{-var-list-children}
20141 @tab return a list of the object's children
20142 @item @code{-var-info-type}
20143 @tab show the type of this variable object
20144 @item @code{-var-info-expression}
20145 @tab print what this variable object represents
20146 @item @code{-var-show-attributes}
20147 @tab is this variable editable? does it exist here?
20148 @item @code{-var-evaluate-expression}
20149 @tab get the value of this variable
20150 @item @code{-var-assign}
20151 @tab set the value of this variable
20152 @item @code{-var-update}
20153 @tab update the variable and its children
20156 In the next subsection we describe each operation in detail and suggest
20157 how it can be used.
20159 @subheading Description And Use of Operations on Variable Objects
20161 @subheading The @code{-var-create} Command
20162 @findex -var-create
20164 @subsubheading Synopsis
20167 -var-create @{@var{name} | "-"@}
20168 @{@var{frame-addr} | "*"@} @var{expression}
20171 This operation creates a variable object, which allows the monitoring of
20172 a variable, the result of an expression, a memory cell or a CPU
20175 The @var{name} parameter is the string by which the object can be
20176 referenced. It must be unique. If @samp{-} is specified, the varobj
20177 system will generate a string ``varNNNNNN'' automatically. It will be
20178 unique provided that one does not specify @var{name} on that format.
20179 The command fails if a duplicate name is found.
20181 The frame under which the expression should be evaluated can be
20182 specified by @var{frame-addr}. A @samp{*} indicates that the current
20183 frame should be used.
20185 @var{expression} is any expression valid on the current language set (must not
20186 begin with a @samp{*}), or one of the following:
20190 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
20193 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
20196 @samp{$@var{regname}} --- a CPU register name
20199 @subsubheading Result
20201 This operation returns the name, number of children and the type of the
20202 object created. Type is returned as a string as the ones generated by
20203 the @value{GDBN} CLI:
20206 name="@var{name}",numchild="N",type="@var{type}"
20210 @subheading The @code{-var-delete} Command
20211 @findex -var-delete
20213 @subsubheading Synopsis
20216 -var-delete @var{name}
20219 Deletes a previously created variable object and all of its children.
20221 Returns an error if the object @var{name} is not found.
20224 @subheading The @code{-var-set-format} Command
20225 @findex -var-set-format
20227 @subsubheading Synopsis
20230 -var-set-format @var{name} @var{format-spec}
20233 Sets the output format for the value of the object @var{name} to be
20236 The syntax for the @var{format-spec} is as follows:
20239 @var{format-spec} @expansion{}
20240 @{binary | decimal | hexadecimal | octal | natural@}
20244 @subheading The @code{-var-show-format} Command
20245 @findex -var-show-format
20247 @subsubheading Synopsis
20250 -var-show-format @var{name}
20253 Returns the format used to display the value of the object @var{name}.
20256 @var{format} @expansion{}
20261 @subheading The @code{-var-info-num-children} Command
20262 @findex -var-info-num-children
20264 @subsubheading Synopsis
20267 -var-info-num-children @var{name}
20270 Returns the number of children of a variable object @var{name}:
20277 @subheading The @code{-var-list-children} Command
20278 @findex -var-list-children
20280 @subsubheading Synopsis
20283 -var-list-children [@var{print-values}] @var{name}
20286 Returns a list of the children of the specified variable object. With
20287 just the variable object name as an argument or with an optional
20288 preceding argument of 0 or @code{--no-values}, prints only the names of the
20289 variables. With an optional preceding argument of 1 or @code{--all-values},
20290 also prints their values.
20292 @subsubheading Example
20296 -var-list-children n
20297 numchild=@var{n},children=[@{name=@var{name},
20298 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
20300 -var-list-children --all-values n
20301 numchild=@var{n},children=[@{name=@var{name},
20302 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
20306 @subheading The @code{-var-info-type} Command
20307 @findex -var-info-type
20309 @subsubheading Synopsis
20312 -var-info-type @var{name}
20315 Returns the type of the specified variable @var{name}. The type is
20316 returned as a string in the same format as it is output by the
20320 type=@var{typename}
20324 @subheading The @code{-var-info-expression} Command
20325 @findex -var-info-expression
20327 @subsubheading Synopsis
20330 -var-info-expression @var{name}
20333 Returns what is represented by the variable object @var{name}:
20336 lang=@var{lang-spec},exp=@var{expression}
20340 where @var{lang-spec} is @code{@{"C" | "C++" | "Java"@}}.
20342 @subheading The @code{-var-show-attributes} Command
20343 @findex -var-show-attributes
20345 @subsubheading Synopsis
20348 -var-show-attributes @var{name}
20351 List attributes of the specified variable object @var{name}:
20354 status=@var{attr} [ ( ,@var{attr} )* ]
20358 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
20360 @subheading The @code{-var-evaluate-expression} Command
20361 @findex -var-evaluate-expression
20363 @subsubheading Synopsis
20366 -var-evaluate-expression @var{name}
20369 Evaluates the expression that is represented by the specified variable
20370 object and returns its value as a string in the current format specified
20377 Note that one must invoke @code{-var-list-children} for a variable
20378 before the value of a child variable can be evaluated.
20380 @subheading The @code{-var-assign} Command
20381 @findex -var-assign
20383 @subsubheading Synopsis
20386 -var-assign @var{name} @var{expression}
20389 Assigns the value of @var{expression} to the variable object specified
20390 by @var{name}. The object must be @samp{editable}. If the variable's
20391 value is altered by the assign, the variable will show up in any
20392 subsequent @code{-var-update} list.
20394 @subsubheading Example
20402 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
20406 @subheading The @code{-var-update} Command
20407 @findex -var-update
20409 @subsubheading Synopsis
20412 -var-update @{@var{name} | "*"@}
20415 Update the value of the variable object @var{name} by evaluating its
20416 expression after fetching all the new values from memory or registers.
20417 A @samp{*} causes all existing variable objects to be updated.
20421 @chapter @value{GDBN} Annotations
20423 This chapter describes annotations in @value{GDBN}. Annotations were
20424 designed to interface @value{GDBN} to graphical user interfaces or other
20425 similar programs which want to interact with @value{GDBN} at a
20426 relatively high level.
20428 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
20432 This is Edition @value{EDITION}, @value{DATE}.
20436 * Annotations Overview:: What annotations are; the general syntax.
20437 * Server Prefix:: Issuing a command without affecting user state.
20438 * Prompting:: Annotations marking @value{GDBN}'s need for input.
20439 * Errors:: Annotations for error messages.
20440 * Invalidation:: Some annotations describe things now invalid.
20441 * Annotations for Running::
20442 Whether the program is running, how it stopped, etc.
20443 * Source Annotations:: Annotations describing source code.
20446 @node Annotations Overview
20447 @section What is an Annotation?
20448 @cindex annotations
20450 Annotations start with a newline character, two @samp{control-z}
20451 characters, and the name of the annotation. If there is no additional
20452 information associated with this annotation, the name of the annotation
20453 is followed immediately by a newline. If there is additional
20454 information, the name of the annotation is followed by a space, the
20455 additional information, and a newline. The additional information
20456 cannot contain newline characters.
20458 Any output not beginning with a newline and two @samp{control-z}
20459 characters denotes literal output from @value{GDBN}. Currently there is
20460 no need for @value{GDBN} to output a newline followed by two
20461 @samp{control-z} characters, but if there was such a need, the
20462 annotations could be extended with an @samp{escape} annotation which
20463 means those three characters as output.
20465 The annotation @var{level}, which is specified using the
20466 @option{--annotate} command line option (@pxref{Mode Options}), controls
20467 how much information @value{GDBN} prints together with its prompt,
20468 values of expressions, source lines, and other types of output. Level 0
20469 is for no anntations, level 1 is for use when @value{GDBN} is run as a
20470 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
20471 for programs that control @value{GDBN}, and level 2 annotations have
20472 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
20473 Interface, annotate, GDB's Obsolete Annotations}).
20476 @kindex set annotate
20477 @item set annotate @var{level}
20478 The @value{GDB} command @code{set annotate} sets the level of
20479 annotations to the specified @var{level}.
20481 @item show annotate
20482 @kindex show annotate
20483 Show the current annotation level.
20486 This chapter describes level 3 annotations.
20488 A simple example of starting up @value{GDBN} with annotations is:
20491 $ @kbd{gdb --annotate=3}
20493 Copyright 2003 Free Software Foundation, Inc.
20494 GDB is free software, covered by the GNU General Public License,
20495 and you are welcome to change it and/or distribute copies of it
20496 under certain conditions.
20497 Type "show copying" to see the conditions.
20498 There is absolutely no warranty for GDB. Type "show warranty"
20500 This GDB was configured as "i386-pc-linux-gnu"
20511 Here @samp{quit} is input to @value{GDBN}; the rest is output from
20512 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
20513 denotes a @samp{control-z} character) are annotations; the rest is
20514 output from @value{GDBN}.
20516 @node Server Prefix
20517 @section The Server Prefix
20518 @cindex server prefix for annotations
20520 To issue a command to @value{GDBN} without affecting certain aspects of
20521 the state which is seen by users, prefix it with @samp{server }. This
20522 means that this command will not affect the command history, nor will it
20523 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
20524 pressed on a line by itself.
20526 The server prefix does not affect the recording of values into the value
20527 history; to print a value without recording it into the value history,
20528 use the @code{output} command instead of the @code{print} command.
20531 @section Annotation for @value{GDBN} Input
20533 @cindex annotations for prompts
20534 When @value{GDBN} prompts for input, it annotates this fact so it is possible
20535 to know when to send output, when the output from a given command is
20538 Different kinds of input each have a different @dfn{input type}. Each
20539 input type has three annotations: a @code{pre-} annotation, which
20540 denotes the beginning of any prompt which is being output, a plain
20541 annotation, which denotes the end of the prompt, and then a @code{post-}
20542 annotation which denotes the end of any echo which may (or may not) be
20543 associated with the input. For example, the @code{prompt} input type
20544 features the following annotations:
20552 The input types are
20557 @findex post-prompt
20559 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
20561 @findex pre-commands
20563 @findex post-commands
20565 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
20566 command. The annotations are repeated for each command which is input.
20568 @findex pre-overload-choice
20569 @findex overload-choice
20570 @findex post-overload-choice
20571 @item overload-choice
20572 When @value{GDBN} wants the user to select between various overloaded functions.
20578 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
20580 @findex pre-prompt-for-continue
20581 @findex prompt-for-continue
20582 @findex post-prompt-for-continue
20583 @item prompt-for-continue
20584 When @value{GDBN} is asking the user to press return to continue. Note: Don't
20585 expect this to work well; instead use @code{set height 0} to disable
20586 prompting. This is because the counting of lines is buggy in the
20587 presence of annotations.
20592 @cindex annotations for errors, warnings and interrupts
20599 This annotation occurs right before @value{GDBN} responds to an interrupt.
20606 This annotation occurs right before @value{GDBN} responds to an error.
20608 Quit and error annotations indicate that any annotations which @value{GDBN} was
20609 in the middle of may end abruptly. For example, if a
20610 @code{value-history-begin} annotation is followed by a @code{error}, one
20611 cannot expect to receive the matching @code{value-history-end}. One
20612 cannot expect not to receive it either, however; an error annotation
20613 does not necessarily mean that @value{GDBN} is immediately returning all the way
20616 @findex error-begin
20617 A quit or error annotation may be preceded by
20623 Any output between that and the quit or error annotation is the error
20626 Warning messages are not yet annotated.
20627 @c If we want to change that, need to fix warning(), type_error(),
20628 @c range_error(), and possibly other places.
20631 @section Invalidation Notices
20633 @cindex annotations for invalidation messages
20634 The following annotations say that certain pieces of state may have
20638 @findex frames-invalid
20639 @item ^Z^Zframes-invalid
20641 The frames (for example, output from the @code{backtrace} command) may
20644 @findex breakpoints-invalid
20645 @item ^Z^Zbreakpoints-invalid
20647 The breakpoints may have changed. For example, the user just added or
20648 deleted a breakpoint.
20651 @node Annotations for Running
20652 @section Running the Program
20653 @cindex annotations for running programs
20657 When the program starts executing due to a @value{GDBN} command such as
20658 @code{step} or @code{continue},
20664 is output. When the program stops,
20670 is output. Before the @code{stopped} annotation, a variety of
20671 annotations describe how the program stopped.
20675 @item ^Z^Zexited @var{exit-status}
20676 The program exited, and @var{exit-status} is the exit status (zero for
20677 successful exit, otherwise nonzero).
20680 @findex signal-name
20681 @findex signal-name-end
20682 @findex signal-string
20683 @findex signal-string-end
20684 @item ^Z^Zsignalled
20685 The program exited with a signal. After the @code{^Z^Zsignalled}, the
20686 annotation continues:
20692 ^Z^Zsignal-name-end
20696 ^Z^Zsignal-string-end
20701 where @var{name} is the name of the signal, such as @code{SIGILL} or
20702 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
20703 as @code{Illegal Instruction} or @code{Segmentation fault}.
20704 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
20705 user's benefit and have no particular format.
20709 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
20710 just saying that the program received the signal, not that it was
20711 terminated with it.
20714 @item ^Z^Zbreakpoint @var{number}
20715 The program hit breakpoint number @var{number}.
20718 @item ^Z^Zwatchpoint @var{number}
20719 The program hit watchpoint number @var{number}.
20722 @node Source Annotations
20723 @section Displaying Source
20724 @cindex annotations for source display
20727 The following annotation is used instead of displaying source code:
20730 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
20733 where @var{filename} is an absolute file name indicating which source
20734 file, @var{line} is the line number within that file (where 1 is the
20735 first line in the file), @var{character} is the character position
20736 within the file (where 0 is the first character in the file) (for most
20737 debug formats this will necessarily point to the beginning of a line),
20738 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
20739 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
20740 @var{addr} is the address in the target program associated with the
20741 source which is being displayed. @var{addr} is in the form @samp{0x}
20742 followed by one or more lowercase hex digits (note that this does not
20743 depend on the language).
20746 @chapter Reporting Bugs in @value{GDBN}
20747 @cindex bugs in @value{GDBN}
20748 @cindex reporting bugs in @value{GDBN}
20750 Your bug reports play an essential role in making @value{GDBN} reliable.
20752 Reporting a bug may help you by bringing a solution to your problem, or it
20753 may not. But in any case the principal function of a bug report is to help
20754 the entire community by making the next version of @value{GDBN} work better. Bug
20755 reports are your contribution to the maintenance of @value{GDBN}.
20757 In order for a bug report to serve its purpose, you must include the
20758 information that enables us to fix the bug.
20761 * Bug Criteria:: Have you found a bug?
20762 * Bug Reporting:: How to report bugs
20766 @section Have you found a bug?
20767 @cindex bug criteria
20769 If you are not sure whether you have found a bug, here are some guidelines:
20772 @cindex fatal signal
20773 @cindex debugger crash
20774 @cindex crash of debugger
20776 If the debugger gets a fatal signal, for any input whatever, that is a
20777 @value{GDBN} bug. Reliable debuggers never crash.
20779 @cindex error on valid input
20781 If @value{GDBN} produces an error message for valid input, that is a
20782 bug. (Note that if you're cross debugging, the problem may also be
20783 somewhere in the connection to the target.)
20785 @cindex invalid input
20787 If @value{GDBN} does not produce an error message for invalid input,
20788 that is a bug. However, you should note that your idea of
20789 ``invalid input'' might be our idea of ``an extension'' or ``support
20790 for traditional practice''.
20793 If you are an experienced user of debugging tools, your suggestions
20794 for improvement of @value{GDBN} are welcome in any case.
20797 @node Bug Reporting
20798 @section How to report bugs
20799 @cindex bug reports
20800 @cindex @value{GDBN} bugs, reporting
20802 A number of companies and individuals offer support for @sc{gnu} products.
20803 If you obtained @value{GDBN} from a support organization, we recommend you
20804 contact that organization first.
20806 You can find contact information for many support companies and
20807 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
20809 @c should add a web page ref...
20811 In any event, we also recommend that you submit bug reports for
20812 @value{GDBN}. The prefered method is to submit them directly using
20813 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
20814 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
20817 @strong{Do not send bug reports to @samp{info-gdb}, or to
20818 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
20819 not want to receive bug reports. Those that do have arranged to receive
20822 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
20823 serves as a repeater. The mailing list and the newsgroup carry exactly
20824 the same messages. Often people think of posting bug reports to the
20825 newsgroup instead of mailing them. This appears to work, but it has one
20826 problem which can be crucial: a newsgroup posting often lacks a mail
20827 path back to the sender. Thus, if we need to ask for more information,
20828 we may be unable to reach you. For this reason, it is better to send
20829 bug reports to the mailing list.
20831 The fundamental principle of reporting bugs usefully is this:
20832 @strong{report all the facts}. If you are not sure whether to state a
20833 fact or leave it out, state it!
20835 Often people omit facts because they think they know what causes the
20836 problem and assume that some details do not matter. Thus, you might
20837 assume that the name of the variable you use in an example does not matter.
20838 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
20839 stray memory reference which happens to fetch from the location where that
20840 name is stored in memory; perhaps, if the name were different, the contents
20841 of that location would fool the debugger into doing the right thing despite
20842 the bug. Play it safe and give a specific, complete example. That is the
20843 easiest thing for you to do, and the most helpful.
20845 Keep in mind that the purpose of a bug report is to enable us to fix the
20846 bug. It may be that the bug has been reported previously, but neither
20847 you nor we can know that unless your bug report is complete and
20850 Sometimes people give a few sketchy facts and ask, ``Does this ring a
20851 bell?'' Those bug reports are useless, and we urge everyone to
20852 @emph{refuse to respond to them} except to chide the sender to report
20855 To enable us to fix the bug, you should include all these things:
20859 The version of @value{GDBN}. @value{GDBN} announces it if you start
20860 with no arguments; you can also print it at any time using @code{show
20863 Without this, we will not know whether there is any point in looking for
20864 the bug in the current version of @value{GDBN}.
20867 The type of machine you are using, and the operating system name and
20871 What compiler (and its version) was used to compile @value{GDBN}---e.g.
20872 ``@value{GCC}--2.8.1''.
20875 What compiler (and its version) was used to compile the program you are
20876 debugging---e.g. ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
20877 C Compiler''. For GCC, you can say @code{gcc --version} to get this
20878 information; for other compilers, see the documentation for those
20882 The command arguments you gave the compiler to compile your example and
20883 observe the bug. For example, did you use @samp{-O}? To guarantee
20884 you will not omit something important, list them all. A copy of the
20885 Makefile (or the output from make) is sufficient.
20887 If we were to try to guess the arguments, we would probably guess wrong
20888 and then we might not encounter the bug.
20891 A complete input script, and all necessary source files, that will
20895 A description of what behavior you observe that you believe is
20896 incorrect. For example, ``It gets a fatal signal.''
20898 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
20899 will certainly notice it. But if the bug is incorrect output, we might
20900 not notice unless it is glaringly wrong. You might as well not give us
20901 a chance to make a mistake.
20903 Even if the problem you experience is a fatal signal, you should still
20904 say so explicitly. Suppose something strange is going on, such as, your
20905 copy of @value{GDBN} is out of synch, or you have encountered a bug in
20906 the C library on your system. (This has happened!) Your copy might
20907 crash and ours would not. If you told us to expect a crash, then when
20908 ours fails to crash, we would know that the bug was not happening for
20909 us. If you had not told us to expect a crash, then we would not be able
20910 to draw any conclusion from our observations.
20913 @cindex recording a session script
20914 To collect all this information, you can use a session recording program
20915 such as @command{script}, which is available on many Unix systems.
20916 Just run your @value{GDBN} session inside @command{script} and then
20917 include the @file{typescript} file with your bug report.
20919 Another way to record a @value{GDBN} session is to run @value{GDBN}
20920 inside Emacs and then save the entire buffer to a file.
20923 If you wish to suggest changes to the @value{GDBN} source, send us context
20924 diffs. If you even discuss something in the @value{GDBN} source, refer to
20925 it by context, not by line number.
20927 The line numbers in our development sources will not match those in your
20928 sources. Your line numbers would convey no useful information to us.
20932 Here are some things that are not necessary:
20936 A description of the envelope of the bug.
20938 Often people who encounter a bug spend a lot of time investigating
20939 which changes to the input file will make the bug go away and which
20940 changes will not affect it.
20942 This is often time consuming and not very useful, because the way we
20943 will find the bug is by running a single example under the debugger
20944 with breakpoints, not by pure deduction from a series of examples.
20945 We recommend that you save your time for something else.
20947 Of course, if you can find a simpler example to report @emph{instead}
20948 of the original one, that is a convenience for us. Errors in the
20949 output will be easier to spot, running under the debugger will take
20950 less time, and so on.
20952 However, simplification is not vital; if you do not want to do this,
20953 report the bug anyway and send us the entire test case you used.
20956 A patch for the bug.
20958 A patch for the bug does help us if it is a good one. But do not omit
20959 the necessary information, such as the test case, on the assumption that
20960 a patch is all we need. We might see problems with your patch and decide
20961 to fix the problem another way, or we might not understand it at all.
20963 Sometimes with a program as complicated as @value{GDBN} it is very hard to
20964 construct an example that will make the program follow a certain path
20965 through the code. If you do not send us the example, we will not be able
20966 to construct one, so we will not be able to verify that the bug is fixed.
20968 And if we cannot understand what bug you are trying to fix, or why your
20969 patch should be an improvement, we will not install it. A test case will
20970 help us to understand.
20973 A guess about what the bug is or what it depends on.
20975 Such guesses are usually wrong. Even we cannot guess right about such
20976 things without first using the debugger to find the facts.
20979 @c The readline documentation is distributed with the readline code
20980 @c and consists of the two following files:
20982 @c inc-hist.texinfo
20983 @c Use -I with makeinfo to point to the appropriate directory,
20984 @c environment var TEXINPUTS with TeX.
20985 @include rluser.texinfo
20986 @include inc-hist.texinfo
20989 @node Formatting Documentation
20990 @appendix Formatting Documentation
20992 @cindex @value{GDBN} reference card
20993 @cindex reference card
20994 The @value{GDBN} 4 release includes an already-formatted reference card, ready
20995 for printing with PostScript or Ghostscript, in the @file{gdb}
20996 subdirectory of the main source directory@footnote{In
20997 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
20998 release.}. If you can use PostScript or Ghostscript with your printer,
20999 you can print the reference card immediately with @file{refcard.ps}.
21001 The release also includes the source for the reference card. You
21002 can format it, using @TeX{}, by typing:
21008 The @value{GDBN} reference card is designed to print in @dfn{landscape}
21009 mode on US ``letter'' size paper;
21010 that is, on a sheet 11 inches wide by 8.5 inches
21011 high. You will need to specify this form of printing as an option to
21012 your @sc{dvi} output program.
21014 @cindex documentation
21016 All the documentation for @value{GDBN} comes as part of the machine-readable
21017 distribution. The documentation is written in Texinfo format, which is
21018 a documentation system that uses a single source file to produce both
21019 on-line information and a printed manual. You can use one of the Info
21020 formatting commands to create the on-line version of the documentation
21021 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
21023 @value{GDBN} includes an already formatted copy of the on-line Info
21024 version of this manual in the @file{gdb} subdirectory. The main Info
21025 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
21026 subordinate files matching @samp{gdb.info*} in the same directory. If
21027 necessary, you can print out these files, or read them with any editor;
21028 but they are easier to read using the @code{info} subsystem in @sc{gnu}
21029 Emacs or the standalone @code{info} program, available as part of the
21030 @sc{gnu} Texinfo distribution.
21032 If you want to format these Info files yourself, you need one of the
21033 Info formatting programs, such as @code{texinfo-format-buffer} or
21036 If you have @code{makeinfo} installed, and are in the top level
21037 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
21038 version @value{GDBVN}), you can make the Info file by typing:
21045 If you want to typeset and print copies of this manual, you need @TeX{},
21046 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
21047 Texinfo definitions file.
21049 @TeX{} is a typesetting program; it does not print files directly, but
21050 produces output files called @sc{dvi} files. To print a typeset
21051 document, you need a program to print @sc{dvi} files. If your system
21052 has @TeX{} installed, chances are it has such a program. The precise
21053 command to use depends on your system; @kbd{lpr -d} is common; another
21054 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
21055 require a file name without any extension or a @samp{.dvi} extension.
21057 @TeX{} also requires a macro definitions file called
21058 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
21059 written in Texinfo format. On its own, @TeX{} cannot either read or
21060 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
21061 and is located in the @file{gdb-@var{version-number}/texinfo}
21064 If you have @TeX{} and a @sc{dvi} printer program installed, you can
21065 typeset and print this manual. First switch to the the @file{gdb}
21066 subdirectory of the main source directory (for example, to
21067 @file{gdb-@value{GDBVN}/gdb}) and type:
21073 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
21075 @node Installing GDB
21076 @appendix Installing @value{GDBN}
21077 @cindex configuring @value{GDBN}
21078 @cindex installation
21079 @cindex configuring @value{GDBN}, and source tree subdirectories
21081 @value{GDBN} comes with a @code{configure} script that automates the process
21082 of preparing @value{GDBN} for installation; you can then use @code{make} to
21083 build the @code{gdb} program.
21085 @c irrelevant in info file; it's as current as the code it lives with.
21086 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
21087 look at the @file{README} file in the sources; we may have improved the
21088 installation procedures since publishing this manual.}
21091 The @value{GDBN} distribution includes all the source code you need for
21092 @value{GDBN} in a single directory, whose name is usually composed by
21093 appending the version number to @samp{gdb}.
21095 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
21096 @file{gdb-@value{GDBVN}} directory. That directory contains:
21099 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
21100 script for configuring @value{GDBN} and all its supporting libraries
21102 @item gdb-@value{GDBVN}/gdb
21103 the source specific to @value{GDBN} itself
21105 @item gdb-@value{GDBVN}/bfd
21106 source for the Binary File Descriptor library
21108 @item gdb-@value{GDBVN}/include
21109 @sc{gnu} include files
21111 @item gdb-@value{GDBVN}/libiberty
21112 source for the @samp{-liberty} free software library
21114 @item gdb-@value{GDBVN}/opcodes
21115 source for the library of opcode tables and disassemblers
21117 @item gdb-@value{GDBVN}/readline
21118 source for the @sc{gnu} command-line interface
21120 @item gdb-@value{GDBVN}/glob
21121 source for the @sc{gnu} filename pattern-matching subroutine
21123 @item gdb-@value{GDBVN}/mmalloc
21124 source for the @sc{gnu} memory-mapped malloc package
21127 The simplest way to configure and build @value{GDBN} is to run @code{configure}
21128 from the @file{gdb-@var{version-number}} source directory, which in
21129 this example is the @file{gdb-@value{GDBVN}} directory.
21131 First switch to the @file{gdb-@var{version-number}} source directory
21132 if you are not already in it; then run @code{configure}. Pass the
21133 identifier for the platform on which @value{GDBN} will run as an
21139 cd gdb-@value{GDBVN}
21140 ./configure @var{host}
21145 where @var{host} is an identifier such as @samp{sun4} or
21146 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
21147 (You can often leave off @var{host}; @code{configure} tries to guess the
21148 correct value by examining your system.)
21150 Running @samp{configure @var{host}} and then running @code{make} builds the
21151 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
21152 libraries, then @code{gdb} itself. The configured source files, and the
21153 binaries, are left in the corresponding source directories.
21156 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
21157 system does not recognize this automatically when you run a different
21158 shell, you may need to run @code{sh} on it explicitly:
21161 sh configure @var{host}
21164 If you run @code{configure} from a directory that contains source
21165 directories for multiple libraries or programs, such as the
21166 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
21167 creates configuration files for every directory level underneath (unless
21168 you tell it not to, with the @samp{--norecursion} option).
21170 You should run the @code{configure} script from the top directory in the
21171 source tree, the @file{gdb-@var{version-number}} directory. If you run
21172 @code{configure} from one of the subdirectories, you will configure only
21173 that subdirectory. That is usually not what you want. In particular,
21174 if you run the first @code{configure} from the @file{gdb} subdirectory
21175 of the @file{gdb-@var{version-number}} directory, you will omit the
21176 configuration of @file{bfd}, @file{readline}, and other sibling
21177 directories of the @file{gdb} subdirectory. This leads to build errors
21178 about missing include files such as @file{bfd/bfd.h}.
21180 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
21181 However, you should make sure that the shell on your path (named by
21182 the @samp{SHELL} environment variable) is publicly readable. Remember
21183 that @value{GDBN} uses the shell to start your program---some systems refuse to
21184 let @value{GDBN} debug child processes whose programs are not readable.
21187 * Separate Objdir:: Compiling @value{GDBN} in another directory
21188 * Config Names:: Specifying names for hosts and targets
21189 * Configure Options:: Summary of options for configure
21192 @node Separate Objdir
21193 @section Compiling @value{GDBN} in another directory
21195 If you want to run @value{GDBN} versions for several host or target machines,
21196 you need a different @code{gdb} compiled for each combination of
21197 host and target. @code{configure} is designed to make this easy by
21198 allowing you to generate each configuration in a separate subdirectory,
21199 rather than in the source directory. If your @code{make} program
21200 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
21201 @code{make} in each of these directories builds the @code{gdb}
21202 program specified there.
21204 To build @code{gdb} in a separate directory, run @code{configure}
21205 with the @samp{--srcdir} option to specify where to find the source.
21206 (You also need to specify a path to find @code{configure}
21207 itself from your working directory. If the path to @code{configure}
21208 would be the same as the argument to @samp{--srcdir}, you can leave out
21209 the @samp{--srcdir} option; it is assumed.)
21211 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
21212 separate directory for a Sun 4 like this:
21216 cd gdb-@value{GDBVN}
21219 ../gdb-@value{GDBVN}/configure sun4
21224 When @code{configure} builds a configuration using a remote source
21225 directory, it creates a tree for the binaries with the same structure
21226 (and using the same names) as the tree under the source directory. In
21227 the example, you'd find the Sun 4 library @file{libiberty.a} in the
21228 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
21229 @file{gdb-sun4/gdb}.
21231 Make sure that your path to the @file{configure} script has just one
21232 instance of @file{gdb} in it. If your path to @file{configure} looks
21233 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
21234 one subdirectory of @value{GDBN}, not the whole package. This leads to
21235 build errors about missing include files such as @file{bfd/bfd.h}.
21237 One popular reason to build several @value{GDBN} configurations in separate
21238 directories is to configure @value{GDBN} for cross-compiling (where
21239 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
21240 programs that run on another machine---the @dfn{target}).
21241 You specify a cross-debugging target by
21242 giving the @samp{--target=@var{target}} option to @code{configure}.
21244 When you run @code{make} to build a program or library, you must run
21245 it in a configured directory---whatever directory you were in when you
21246 called @code{configure} (or one of its subdirectories).
21248 The @code{Makefile} that @code{configure} generates in each source
21249 directory also runs recursively. If you type @code{make} in a source
21250 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
21251 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
21252 will build all the required libraries, and then build GDB.
21254 When you have multiple hosts or targets configured in separate
21255 directories, you can run @code{make} on them in parallel (for example,
21256 if they are NFS-mounted on each of the hosts); they will not interfere
21260 @section Specifying names for hosts and targets
21262 The specifications used for hosts and targets in the @code{configure}
21263 script are based on a three-part naming scheme, but some short predefined
21264 aliases are also supported. The full naming scheme encodes three pieces
21265 of information in the following pattern:
21268 @var{architecture}-@var{vendor}-@var{os}
21271 For example, you can use the alias @code{sun4} as a @var{host} argument,
21272 or as the value for @var{target} in a @code{--target=@var{target}}
21273 option. The equivalent full name is @samp{sparc-sun-sunos4}.
21275 The @code{configure} script accompanying @value{GDBN} does not provide
21276 any query facility to list all supported host and target names or
21277 aliases. @code{configure} calls the Bourne shell script
21278 @code{config.sub} to map abbreviations to full names; you can read the
21279 script, if you wish, or you can use it to test your guesses on
21280 abbreviations---for example:
21283 % sh config.sub i386-linux
21285 % sh config.sub alpha-linux
21286 alpha-unknown-linux-gnu
21287 % sh config.sub hp9k700
21289 % sh config.sub sun4
21290 sparc-sun-sunos4.1.1
21291 % sh config.sub sun3
21292 m68k-sun-sunos4.1.1
21293 % sh config.sub i986v
21294 Invalid configuration `i986v': machine `i986v' not recognized
21298 @code{config.sub} is also distributed in the @value{GDBN} source
21299 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
21301 @node Configure Options
21302 @section @code{configure} options
21304 Here is a summary of the @code{configure} options and arguments that
21305 are most often useful for building @value{GDBN}. @code{configure} also has
21306 several other options not listed here. @inforef{What Configure
21307 Does,,configure.info}, for a full explanation of @code{configure}.
21310 configure @r{[}--help@r{]}
21311 @r{[}--prefix=@var{dir}@r{]}
21312 @r{[}--exec-prefix=@var{dir}@r{]}
21313 @r{[}--srcdir=@var{dirname}@r{]}
21314 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
21315 @r{[}--target=@var{target}@r{]}
21320 You may introduce options with a single @samp{-} rather than
21321 @samp{--} if you prefer; but you may abbreviate option names if you use
21326 Display a quick summary of how to invoke @code{configure}.
21328 @item --prefix=@var{dir}
21329 Configure the source to install programs and files under directory
21332 @item --exec-prefix=@var{dir}
21333 Configure the source to install programs under directory
21336 @c avoid splitting the warning from the explanation:
21338 @item --srcdir=@var{dirname}
21339 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
21340 @code{make} that implements the @code{VPATH} feature.}@*
21341 Use this option to make configurations in directories separate from the
21342 @value{GDBN} source directories. Among other things, you can use this to
21343 build (or maintain) several configurations simultaneously, in separate
21344 directories. @code{configure} writes configuration specific files in
21345 the current directory, but arranges for them to use the source in the
21346 directory @var{dirname}. @code{configure} creates directories under
21347 the working directory in parallel to the source directories below
21350 @item --norecursion
21351 Configure only the directory level where @code{configure} is executed; do not
21352 propagate configuration to subdirectories.
21354 @item --target=@var{target}
21355 Configure @value{GDBN} for cross-debugging programs running on the specified
21356 @var{target}. Without this option, @value{GDBN} is configured to debug
21357 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
21359 There is no convenient way to generate a list of all available targets.
21361 @item @var{host} @dots{}
21362 Configure @value{GDBN} to run on the specified @var{host}.
21364 There is no convenient way to generate a list of all available hosts.
21367 There are many other options available as well, but they are generally
21368 needed for special purposes only.
21370 @node Maintenance Commands
21371 @appendix Maintenance Commands
21372 @cindex maintenance commands
21373 @cindex internal commands
21375 In addition to commands intended for @value{GDBN} users, @value{GDBN}
21376 includes a number of commands intended for @value{GDBN} developers,
21377 that are not documented elsewhere in this manual. These commands are
21378 provided here for reference. (For commands that turn on debugging
21379 messages, see @ref{Debugging Output}.)
21382 @kindex maint agent
21383 @item maint agent @var{expression}
21384 Translate the given @var{expression} into remote agent bytecodes.
21385 This command is useful for debugging the Agent Expression mechanism
21386 (@pxref{Agent Expressions}).
21388 @kindex maint info breakpoints
21389 @item @anchor{maint info breakpoints}maint info breakpoints
21390 Using the same format as @samp{info breakpoints}, display both the
21391 breakpoints you've set explicitly, and those @value{GDBN} is using for
21392 internal purposes. Internal breakpoints are shown with negative
21393 breakpoint numbers. The type column identifies what kind of breakpoint
21398 Normal, explicitly set breakpoint.
21401 Normal, explicitly set watchpoint.
21404 Internal breakpoint, used to handle correctly stepping through
21405 @code{longjmp} calls.
21407 @item longjmp resume
21408 Internal breakpoint at the target of a @code{longjmp}.
21411 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
21414 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
21417 Shared library events.
21421 @kindex maint check-symtabs
21422 @item maint check-symtabs
21423 Check the consistency of psymtabs and symtabs.
21425 @kindex maint cplus first_component
21426 @item maint cplus first_component @var{name}
21427 Print the first C@t{++} class/namespace component of @var{name}.
21429 @kindex maint cplus namespace
21430 @item maint cplus namespace
21431 Print the list of possible C@t{++} namespaces.
21433 @kindex maint demangle
21434 @item maint demangle @var{name}
21435 Demangle a C@t{++} or Objective-C manled @var{name}.
21437 @kindex maint deprecate
21438 @kindex maint undeprecate
21439 @cindex deprecated commands
21440 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
21441 @itemx maint undeprecate @var{command}
21442 Deprecate or undeprecate the named @var{command}. Deprecated commands
21443 cause @value{GDBN} to issue a warning when you use them. The optional
21444 argument @var{replacement} says which newer command should be used in
21445 favor of the deprecated one; if it is given, @value{GDBN} will mention
21446 the replacement as part of the warning.
21448 @kindex maint dump-me
21449 @item maint dump-me
21450 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
21451 Cause a fatal signal in the debugger and force it to dump its core.
21452 This is supported only on systems which support aborting a program
21453 with the @code{SIGQUIT} signal.
21455 @kindex maint internal-error
21456 @kindex maint internal-warning
21457 @item maint internal-error @r{[}@var{message-text}@r{]}
21458 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
21459 Cause @value{GDBN} to call the internal function @code{internal_error}
21460 or @code{internal_warning} and hence behave as though an internal error
21461 or internal warning has been detected. In addition to reporting the
21462 internal problem, these functions give the user the opportunity to
21463 either quit @value{GDBN} or create a core file of the current
21464 @value{GDBN} session.
21466 These commands take an optional parameter @var{message-text} that is
21467 used as the text of the error or warning message.
21469 Here's an example of using @code{indernal-error}:
21472 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
21473 @dots{}/maint.c:121: internal-error: testing, 1, 2
21474 A problem internal to GDB has been detected. Further
21475 debugging may prove unreliable.
21476 Quit this debugging session? (y or n) @kbd{n}
21477 Create a core file? (y or n) @kbd{n}
21481 @kindex maint packet
21482 @item maint packet @var{text}
21483 If @value{GDBN} is talking to an inferior via the serial protocol,
21484 then this command sends the string @var{text} to the inferior, and
21485 displays the response packet. @value{GDBN} supplies the initial
21486 @samp{$} character, the terminating @samp{#} character, and the
21489 @kindex maint print architecture
21490 @item maint print architecture @r{[}@var{file}@r{]}
21491 Print the entire architecture configuration. The optional argument
21492 @var{file} names the file where the output goes.
21494 @kindex maint print dummy-frames
21495 @item maint print dummy-frames
21496 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
21499 (@value{GDBP}) @kbd{b add}
21501 (@value{GDBP}) @kbd{print add(2,3)}
21502 Breakpoint 2, add (a=2, b=3) at @dots{}
21504 The program being debugged stopped while in a function called from GDB.
21506 (@value{GDBP}) @kbd{maint print dummy-frames}
21507 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
21508 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
21509 call_lo=0x01014000 call_hi=0x01014001
21513 Takes an optional file parameter.
21515 @kindex maint print registers
21516 @kindex maint print raw-registers
21517 @kindex maint print cooked-registers
21518 @kindex maint print register-groups
21519 @item maint print registers @r{[}@var{file}@r{]}
21520 @itemx maint print raw-registers @r{[}@var{file}@r{]}
21521 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
21522 @itemx maint print register-groups @r{[}@var{file}@r{]}
21523 Print @value{GDBN}'s internal register data structures.
21525 The command @code{maint print raw-registers} includes the contents of
21526 the raw register cache; the command @code{maint print cooked-registers}
21527 includes the (cooked) value of all registers; and the command
21528 @code{maint print register-groups} includes the groups that each
21529 register is a member of. @xref{Registers,, Registers, gdbint,
21530 @value{GDBN} Internals}.
21532 These commands take an optional parameter, a file name to which to
21533 write the information.
21535 @kindex maint print reggroups
21536 @item maint print reggroups @r{[}@var{file}@r{]}
21537 Print @value{GDBN}'s internal register group data structures. The
21538 optional argument @var{file} tells to what file to write the
21541 The register groups info looks like this:
21544 (@value{GDBP}) @kbd{maint print reggroups}
21557 This command forces @value{GDBN} to flush its internal register cache.
21559 @kindex maint print objfiles
21560 @cindex info for known object files
21561 @item maint print objfiles
21562 Print a dump of all known object files. For each object file, this
21563 command prints its name, address in memory, and all of its psymtabs
21566 @kindex maint print statistics
21567 @cindex bcache statistics
21568 @item maint print statistics
21569 This command prints, for each object file in the program, various data
21570 about that object file followed by the byte cache (@dfn{bcache})
21571 statistics for the object file. The objfile data includes the number
21572 of minimal, partical, full, and stabs symbols, the number of types
21573 defined by the objfile, the number of as yet unexpanded psym tables,
21574 the number of line tables and string tables, and the amount of memory
21575 used by the various tables. The bcache statistics include the counts,
21576 sizes, and counts of duplicates of all and unique objects, max,
21577 average, and median entry size, total memory used and its overhead and
21578 savings, and various measures of the hash table size and chain
21581 @kindex maint print type
21582 @cindex type chain of a data type
21583 @item maint print type @var{expr}
21584 Print the type chain for a type specified by @var{expr}. The argument
21585 can be either a type name or a symbol. If it is a symbol, the type of
21586 that symbol is described. The type chain produced by this command is
21587 a recursive definition of the data type as stored in @value{GDBN}'s
21588 data structures, including its flags and contained types.
21590 @kindex maint set dwarf2 max-cache-age
21591 @kindex maint show dwarf2 max-cache-age
21592 @item maint set dwarf2 max-cache-age
21593 @itemx maint show dwarf2 max-cache-age
21594 Control the DWARF 2 compilation unit cache.
21596 @cindex DWARF 2 compilation units cache
21597 In object files with inter-compilation-unit references, such as those
21598 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
21599 reader needs to frequently refer to previously read compilation units.
21600 This setting controls how long a compilation unit will remain in the
21601 cache if it is not referenced. A higher limit means that cached
21602 compilation units will be stored in memory longer, and more total
21603 memory will be used. Setting it to zero disables caching, which will
21604 slow down @value{GDBN} startup, but reduce memory consumption.
21606 @kindex maint set profile
21607 @kindex maint show profile
21608 @cindex profiling GDB
21609 @item maint set profile
21610 @itemx maint show profile
21611 Control profiling of @value{GDBN}.
21613 Profiling will be disabled until you use the @samp{maint set profile}
21614 command to enable it. When you enable profiling, the system will begin
21615 collecting timing and execution count data; when you disable profiling or
21616 exit @value{GDBN}, the results will be written to a log file. Remember that
21617 if you use profiling, @value{GDBN} will overwrite the profiling log file
21618 (often called @file{gmon.out}). If you have a record of important profiling
21619 data in a @file{gmon.out} file, be sure to move it to a safe location.
21621 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
21622 compiled with the @samp{-pg} compiler option.
21624 @kindex maint show-debug-regs
21625 @cindex x86 hardware debug registers
21626 @item maint show-debug-regs
21627 Control whether to show variables that mirror the x86 hardware debug
21628 registers. Use @code{ON} to enable, @code{OFF} to disable. If
21629 enabled, the debug registers values are shown when GDB inserts or
21630 removes a hardware breakpoint or watchpoint, and when the inferior
21631 triggers a hardware-assisted breakpoint or watchpoint.
21633 @kindex maint space
21634 @cindex memory used by commands
21636 Control whether to display memory usage for each command. If set to a
21637 nonzero value, @value{GDBN} will display how much memory each command
21638 took, following the command's own output. This can also be requested
21639 by invoking @value{GDBN} with the @option{--statistics} command-line
21640 switch (@pxref{Mode Options}).
21643 @cindex time of command execution
21645 Control whether to display the execution time for each command. If
21646 set to a nonzero value, @value{GDBN} will display how much time it
21647 took to execute each command, following the command's own output.
21648 This can also be requested by invoking @value{GDBN} with the
21649 @option{--statistics} command-line switch (@pxref{Mode Options}).
21651 @kindex maint translate-address
21652 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
21653 Find the symbol stored at the location specified by the address
21654 @var{addr} and an optional section name @var{section}. If found,
21655 @value{GDBN} prints the name of the closest symbol and an offset from
21656 the symbol's location to the specified address. This is similar to
21657 the @code{info address} command (@pxref{Symbols}), except that this
21658 command also allows to find symbols in other sections.
21662 The following command is useful for non-interactive invocations of
21663 @value{GDBN}, such as in the test suite.
21666 @item set watchdog @var{nsec}
21667 @kindex set watchdog
21668 @cindex watchdog timer
21669 @cindex timeout for commands
21670 Set the maximum number of seconds @value{GDBN} will wait for the
21671 target operation to finish. If this time expires, @value{GDBN}
21672 reports and error and the command is aborted.
21674 @item show watchdog
21675 Show the current setting of the target wait timeout.
21678 @node Remote Protocol
21679 @appendix @value{GDBN} Remote Serial Protocol
21684 * Stop Reply Packets::
21685 * General Query Packets::
21686 * Register Packet Format::
21688 * File-I/O remote protocol extension::
21694 There may be occasions when you need to know something about the
21695 protocol---for example, if there is only one serial port to your target
21696 machine, you might want your program to do something special if it
21697 recognizes a packet meant for @value{GDBN}.
21699 In the examples below, @samp{->} and @samp{<-} are used to indicate
21700 transmitted and received data respectfully.
21702 @cindex protocol, @value{GDBN} remote serial
21703 @cindex serial protocol, @value{GDBN} remote
21704 @cindex remote serial protocol
21705 All @value{GDBN} commands and responses (other than acknowledgments) are
21706 sent as a @var{packet}. A @var{packet} is introduced with the character
21707 @samp{$}, the actual @var{packet-data}, and the terminating character
21708 @samp{#} followed by a two-digit @var{checksum}:
21711 @code{$}@var{packet-data}@code{#}@var{checksum}
21715 @cindex checksum, for @value{GDBN} remote
21717 The two-digit @var{checksum} is computed as the modulo 256 sum of all
21718 characters between the leading @samp{$} and the trailing @samp{#} (an
21719 eight bit unsigned checksum).
21721 Implementors should note that prior to @value{GDBN} 5.0 the protocol
21722 specification also included an optional two-digit @var{sequence-id}:
21725 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
21728 @cindex sequence-id, for @value{GDBN} remote
21730 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
21731 has never output @var{sequence-id}s. Stubs that handle packets added
21732 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
21734 @cindex acknowledgment, for @value{GDBN} remote
21735 When either the host or the target machine receives a packet, the first
21736 response expected is an acknowledgment: either @samp{+} (to indicate
21737 the package was received correctly) or @samp{-} (to request
21741 -> @code{$}@var{packet-data}@code{#}@var{checksum}
21746 The host (@value{GDBN}) sends @var{command}s, and the target (the
21747 debugging stub incorporated in your program) sends a @var{response}. In
21748 the case of step and continue @var{command}s, the response is only sent
21749 when the operation has completed (the target has again stopped).
21751 @var{packet-data} consists of a sequence of characters with the
21752 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
21755 Fields within the packet should be separated using @samp{,} @samp{;} or
21756 @cindex remote protocol, field separator
21757 @samp{:}. Except where otherwise noted all numbers are represented in
21758 @sc{hex} with leading zeros suppressed.
21760 Implementors should note that prior to @value{GDBN} 5.0, the character
21761 @samp{:} could not appear as the third character in a packet (as it
21762 would potentially conflict with the @var{sequence-id}).
21764 Response @var{data} can be run-length encoded to save space. A @samp{*}
21765 means that the next character is an @sc{ascii} encoding giving a repeat count
21766 which stands for that many repetitions of the character preceding the
21767 @samp{*}. The encoding is @code{n+29}, yielding a printable character
21768 where @code{n >=3} (which is where rle starts to win). The printable
21769 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
21770 value greater than 126 should not be used.
21777 means the same as "0000".
21779 The error response returned for some packets includes a two character
21780 error number. That number is not well defined.
21782 For any @var{command} not supported by the stub, an empty response
21783 (@samp{$#00}) should be returned. That way it is possible to extend the
21784 protocol. A newer @value{GDBN} can tell if a packet is supported based
21787 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
21788 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
21794 The following table provides a complete list of all currently defined
21795 @var{command}s and their corresponding response @var{data}.
21796 @xref{File-I/O remote protocol extension}, for details about the File
21797 I/O extension of the remote protocol.
21801 @item @code{!} --- extended mode
21802 @cindex @code{!} packet
21804 Enable extended mode. In extended mode, the remote server is made
21805 persistent. The @samp{R} packet is used to restart the program being
21811 The remote target both supports and has enabled extended mode.
21814 @item @code{?} --- last signal
21815 @cindex @code{?} packet
21817 Indicate the reason the target halted. The reply is the same as for
21821 @xref{Stop Reply Packets}, for the reply specifications.
21823 @item @code{a} --- reserved
21825 Reserved for future use.
21827 @item @code{A}@var{arglen}@code{,}@var{argnum}@code{,}@var{arg}@code{,@dots{}} --- set program arguments @strong{(reserved)}
21828 @cindex @code{A} packet
21830 Initialized @samp{argv[]} array passed into program. @var{arglen}
21831 specifies the number of bytes in the hex encoded byte stream @var{arg}.
21832 See @code{gdbserver} for more details.
21840 @item @code{b}@var{baud} --- set baud @strong{(deprecated)}
21841 @cindex @code{b} packet
21843 Change the serial line speed to @var{baud}.
21845 JTC: @emph{When does the transport layer state change? When it's
21846 received, or after the ACK is transmitted. In either case, there are
21847 problems if the command or the acknowledgment packet is dropped.}
21849 Stan: @emph{If people really wanted to add something like this, and get
21850 it working for the first time, they ought to modify ser-unix.c to send
21851 some kind of out-of-band message to a specially-setup stub and have the
21852 switch happen "in between" packets, so that from remote protocol's point
21853 of view, nothing actually happened.}
21855 @item @code{B}@var{addr},@var{mode} --- set breakpoint @strong{(deprecated)}
21856 @cindex @code{B} packet
21858 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
21859 breakpoint at @var{addr}.
21861 This packet has been replaced by the @samp{Z} and @samp{z} packets
21862 (@pxref{insert breakpoint or watchpoint packet}).
21864 @item @code{c}@var{addr} --- continue
21865 @cindex @code{c} packet
21867 @var{addr} is address to resume. If @var{addr} is omitted, resume at
21871 @xref{Stop Reply Packets}, for the reply specifications.
21873 @item @code{C}@var{sig}@code{;}@var{addr} --- continue with signal
21874 @cindex @code{C} packet
21876 Continue with signal @var{sig} (hex signal number). If
21877 @code{;}@var{addr} is omitted, resume at same address.
21880 @xref{Stop Reply Packets}, for the reply specifications.
21882 @item @code{d} --- toggle debug @strong{(deprecated)}
21883 @cindex @code{d} packet
21887 @item @code{D} --- detach
21888 @cindex @code{D} packet
21890 Detach @value{GDBN} from the remote system. Sent to the remote target
21891 before @value{GDBN} disconnects via the @code{detach} command.
21895 @item @emph{no response}
21896 @value{GDBN} does not check for any response after sending this packet.
21899 @item @code{e} --- reserved
21901 Reserved for future use.
21903 @item @code{E} --- reserved
21905 Reserved for future use.
21907 @item @code{f} --- reserved
21909 Reserved for future use.
21911 @item @code{F}@var{RC}@code{,}@var{EE}@code{,}@var{CF}@code{;}@var{XX} --- Reply to target's F packet.
21912 @cindex @code{F} packet
21914 This packet is send by @value{GDBN} as reply to a @code{F} request packet
21915 sent by the target. This is part of the File-I/O protocol extension.
21916 @xref{File-I/O remote protocol extension}, for the specification.
21918 @item @code{g} --- read registers
21919 @anchor{read registers packet}
21920 @cindex @code{g} packet
21922 Read general registers.
21926 @item @var{XX@dots{}}
21927 Each byte of register data is described by two hex digits. The bytes
21928 with the register are transmitted in target byte order. The size of
21929 each register and their position within the @samp{g} @var{packet} are
21930 determined by the @value{GDBN} internal macros
21931 @var{DEPRECATED_REGISTER_RAW_SIZE} and @var{REGISTER_NAME} macros. The
21932 specification of several standard @code{g} packets is specified below.
21937 @item @code{G}@var{XX@dots{}} --- write regs
21938 @cindex @code{G} packet
21940 @xref{read registers packet}, for a description of the @var{XX@dots{}}
21951 @item @code{h} --- reserved
21953 Reserved for future use.
21955 @item @code{H}@var{c}@var{t@dots{}} --- set thread
21956 @cindex @code{H} packet
21958 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
21959 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
21960 should be @samp{c} for step and continue operations, @samp{g} for other
21961 operations. The thread designator @var{t@dots{}} may be -1, meaning all
21962 the threads, a thread number, or zero which means pick any thread.
21973 @c 'H': How restrictive (or permissive) is the thread model. If a
21974 @c thread is selected and stopped, are other threads allowed
21975 @c to continue to execute? As I mentioned above, I think the
21976 @c semantics of each command when a thread is selected must be
21977 @c described. For example:
21979 @c 'g': If the stub supports threads and a specific thread is
21980 @c selected, returns the register block from that thread;
21981 @c otherwise returns current registers.
21983 @c 'G' If the stub supports threads and a specific thread is
21984 @c selected, sets the registers of the register block of
21985 @c that thread; otherwise sets current registers.
21987 @item @code{i}@var{addr}@code{,}@var{nnn} --- cycle step @strong{(draft)}
21988 @anchor{cycle step packet}
21989 @cindex @code{i} packet
21991 Step the remote target by a single clock cycle. If @code{,}@var{nnn} is
21992 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
21993 step starting at that address.
21995 @item @code{I} --- signal then cycle step @strong{(reserved)}
21996 @cindex @code{I} packet
21998 @xref{step with signal packet}. @xref{cycle step packet}.
22000 @item @code{j} --- reserved
22002 Reserved for future use.
22004 @item @code{J} --- reserved
22006 Reserved for future use.
22008 @item @code{k} --- kill request
22009 @cindex @code{k} packet
22011 FIXME: @emph{There is no description of how to operate when a specific
22012 thread context has been selected (i.e.@: does 'k' kill only that
22015 @item @code{K} --- reserved
22017 Reserved for future use.
22019 @item @code{l} --- reserved
22021 Reserved for future use.
22023 @item @code{L} --- reserved
22025 Reserved for future use.
22027 @item @code{m}@var{addr}@code{,}@var{length} --- read memory
22028 @cindex @code{m} packet
22030 Read @var{length} bytes of memory starting at address @var{addr}.
22031 Neither @value{GDBN} nor the stub assume that sized memory transfers are
22032 assumed using word aligned accesses. FIXME: @emph{A word aligned memory
22033 transfer mechanism is needed.}
22037 @item @var{XX@dots{}}
22038 @var{XX@dots{}} is mem contents. Can be fewer bytes than requested if able
22039 to read only part of the data. Neither @value{GDBN} nor the stub assume
22040 that sized memory transfers are assumed using word aligned
22041 accesses. FIXME: @emph{A word aligned memory transfer mechanism is
22047 @item @code{M}@var{addr},@var{length}@code{:}@var{XX@dots{}} --- write mem
22048 @cindex @code{M} packet
22050 Write @var{length} bytes of memory starting at address @var{addr}.
22051 @var{XX@dots{}} is the data.
22058 for an error (this includes the case where only part of the data was
22062 @item @code{n} --- reserved
22064 Reserved for future use.
22066 @item @code{N} --- reserved
22068 Reserved for future use.
22070 @item @code{o} --- reserved
22072 Reserved for future use.
22074 @item @code{O} --- reserved
22076 @item @code{p}@var{hex number of register} --- read register packet
22077 @cindex @code{p} packet
22079 @xref{read registers packet}, for a description of how the returned
22080 register value is encoded.
22084 @item @var{XX@dots{}}
22085 the register's value
22089 Indicating an unrecognized @var{query}.
22092 @item @code{P}@var{n@dots{}}@code{=}@var{r@dots{}} --- write register
22093 @anchor{write register packet}
22094 @cindex @code{P} packet
22096 Write register @var{n@dots{}} with value @var{r@dots{}}, which contains two hex
22097 digits for each byte in the register (target byte order).
22107 @item @code{q}@var{query} --- general query
22108 @anchor{general query packet}
22109 @cindex @code{q} packet
22111 Request info about @var{query}. In general @value{GDBN} queries have a
22112 leading upper case letter. Custom vendor queries should use a company
22113 prefix (in lower case) ex: @samp{qfsf.var}. @var{query} may optionally
22114 be followed by a @samp{,} or @samp{;} separated list. Stubs must ensure
22115 that they match the full @var{query} name.
22119 @item @var{XX@dots{}}
22120 Hex encoded data from query. The reply can not be empty.
22124 Indicating an unrecognized @var{query}.
22127 @item @code{Q}@var{var}@code{=}@var{val} --- general set
22128 @cindex @code{Q} packet
22130 Set value of @var{var} to @var{val}.
22132 @xref{general query packet}, for a discussion of naming conventions.
22134 @item @code{r} --- reset @strong{(deprecated)}
22135 @cindex @code{r} packet
22137 Reset the entire system.
22139 @item @code{R}@var{XX} --- remote restart
22140 @cindex @code{R} packet
22142 Restart the program being debugged. @var{XX}, while needed, is ignored.
22143 This packet is only available in extended mode.
22147 @item @emph{no reply}
22148 The @samp{R} packet has no reply.
22151 @item @code{s}@var{addr} --- step
22152 @cindex @code{s} packet
22154 @var{addr} is address to resume. If @var{addr} is omitted, resume at
22158 @xref{Stop Reply Packets}, for the reply specifications.
22160 @item @code{S}@var{sig}@code{;}@var{addr} --- step with signal
22161 @anchor{step with signal packet}
22162 @cindex @code{S} packet
22164 Like @samp{C} but step not continue.
22167 @xref{Stop Reply Packets}, for the reply specifications.
22169 @item @code{t}@var{addr}@code{:}@var{PP}@code{,}@var{MM} --- search
22170 @cindex @code{t} packet
22172 Search backwards starting at address @var{addr} for a match with pattern
22173 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
22174 @var{addr} must be at least 3 digits.
22176 @item @code{T}@var{XX} --- thread alive
22177 @cindex @code{T} packet
22179 Find out if the thread XX is alive.
22184 thread is still alive
22189 @item @code{u} --- reserved
22191 Reserved for future use.
22193 @item @code{U} --- reserved
22195 Reserved for future use.
22197 @item @code{v} --- verbose packet prefix
22199 Packets starting with @code{v} are identified by a multi-letter name,
22200 up to the first @code{;} or @code{?} (or the end of the packet).
22202 @item @code{vCont}[;@var{action}[@code{:}@var{tid}]]... --- extended resume
22203 @cindex @code{vCont} packet
22205 Resume the inferior. Different actions may be specified for each thread.
22206 If an action is specified with no @var{tid}, then it is applied to any
22207 threads that don't have a specific action specified; if no default action is
22208 specified then other threads should remain stopped. Specifying multiple
22209 default actions is an error; specifying no actions is also an error.
22210 Thread IDs are specified in hexadecimal. Currently supported actions are:
22216 Continue with signal @var{sig}. @var{sig} should be two hex digits.
22220 Step with signal @var{sig}. @var{sig} should be two hex digits.
22223 The optional @var{addr} argument normally associated with these packets is
22224 not supported in @code{vCont}.
22227 @xref{Stop Reply Packets}, for the reply specifications.
22229 @item @code{vCont?} --- extended resume query
22230 @cindex @code{vCont?} packet
22232 Query support for the @code{vCont} packet.
22236 @item @code{vCont}[;@var{action}]...
22237 The @code{vCont} packet is supported. Each @var{action} is a supported
22238 command in the @code{vCont} packet.
22240 The @code{vCont} packet is not supported.
22243 @item @code{V} --- reserved
22245 Reserved for future use.
22247 @item @code{w} --- reserved
22249 Reserved for future use.
22251 @item @code{W} --- reserved
22253 Reserved for future use.
22255 @item @code{x} --- reserved
22257 Reserved for future use.
22259 @item @code{X}@var{addr}@code{,}@var{length}@var{:}@var{XX@dots{}} --- write mem (binary)
22260 @cindex @code{X} packet
22262 @var{addr} is address, @var{length} is number of bytes, @var{XX@dots{}}
22263 is binary data. The characters @code{$}, @code{#}, and @code{0x7d} are
22264 escaped using @code{0x7d}, and then XORed with @code{0x20}.
22265 For example, @code{0x7d} would be transmitted as @code{0x7d 0x5d}.
22275 @item @code{y} --- reserved
22277 Reserved for future use.
22279 @item @code{Y} reserved
22281 Reserved for future use.
22283 @item @code{z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- remove breakpoint or watchpoint @strong{(draft)}
22284 @itemx @code{Z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- insert breakpoint or watchpoint @strong{(draft)}
22285 @anchor{insert breakpoint or watchpoint packet}
22286 @cindex @code{z} packet
22287 @cindex @code{Z} packets
22289 Insert (@code{Z}) or remove (@code{z}) a @var{type} breakpoint or
22290 watchpoint starting at address @var{address} and covering the next
22291 @var{length} bytes.
22293 Each breakpoint and watchpoint packet @var{type} is documented
22296 @emph{Implementation notes: A remote target shall return an empty string
22297 for an unrecognized breakpoint or watchpoint packet @var{type}. A
22298 remote target shall support either both or neither of a given
22299 @code{Z}@var{type}@dots{} and @code{z}@var{type}@dots{} packet pair. To
22300 avoid potential problems with duplicate packets, the operations should
22301 be implemented in an idempotent way.}
22303 @item @code{z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- remove memory breakpoint @strong{(draft)}
22304 @item @code{Z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- insert memory breakpoint @strong{(draft)}
22305 @cindex @code{z0} packet
22306 @cindex @code{Z0} packet
22308 Insert (@code{Z0}) or remove (@code{z0}) a memory breakpoint at address
22309 @code{addr} of size @code{length}.
22311 A memory breakpoint is implemented by replacing the instruction at
22312 @var{addr} with a software breakpoint or trap instruction. The
22313 @code{length} is used by targets that indicates the size of the
22314 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
22315 @sc{mips} can insert either a 2 or 4 byte breakpoint).
22317 @emph{Implementation note: It is possible for a target to copy or move
22318 code that contains memory breakpoints (e.g., when implementing
22319 overlays). The behavior of this packet, in the presence of such a
22320 target, is not defined.}
22332 @item @code{z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- remove hardware breakpoint @strong{(draft)}
22333 @item @code{Z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- insert hardware breakpoint @strong{(draft)}
22334 @cindex @code{z1} packet
22335 @cindex @code{Z1} packet
22337 Insert (@code{Z1}) or remove (@code{z1}) a hardware breakpoint at
22338 address @code{addr} of size @code{length}.
22340 A hardware breakpoint is implemented using a mechanism that is not
22341 dependant on being able to modify the target's memory.
22343 @emph{Implementation note: A hardware breakpoint is not affected by code
22356 @item @code{z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- remove write watchpoint @strong{(draft)}
22357 @item @code{Z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- insert write watchpoint @strong{(draft)}
22358 @cindex @code{z2} packet
22359 @cindex @code{Z2} packet
22361 Insert (@code{Z2}) or remove (@code{z2}) a write watchpoint.
22373 @item @code{z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- remove read watchpoint @strong{(draft)}
22374 @item @code{Z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- insert read watchpoint @strong{(draft)}
22375 @cindex @code{z3} packet
22376 @cindex @code{Z3} packet
22378 Insert (@code{Z3}) or remove (@code{z3}) a read watchpoint.
22390 @item @code{z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- remove access watchpoint @strong{(draft)}
22391 @item @code{Z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- insert access watchpoint @strong{(draft)}
22392 @cindex @code{z4} packet
22393 @cindex @code{Z4} packet
22395 Insert (@code{Z4}) or remove (@code{z4}) an access watchpoint.
22409 @node Stop Reply Packets
22410 @section Stop Reply Packets
22411 @cindex stop reply packets
22413 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
22414 receive any of the below as a reply. In the case of the @samp{C},
22415 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
22416 when the target halts. In the below the exact meaning of @samp{signal
22417 number} is poorly defined. In general one of the UNIX signal numbering
22418 conventions is used.
22423 @var{AA} is the signal number
22425 @item @code{T}@var{AA}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}
22426 @cindex @code{T} packet reply
22428 @var{AA} = two hex digit signal number; @var{n...} = register number
22429 (hex), @var{r...} = target byte ordered register contents, size defined
22430 by @code{DEPRECATED_REGISTER_RAW_SIZE}; @var{n...} = @samp{thread},
22431 @var{r...} = thread process ID, this is a hex integer; @var{n...} =
22432 (@samp{watch} | @samp{rwatch} | @samp{awatch}, @var{r...} = data
22433 address, this is a hex integer; @var{n...} = other string not starting
22434 with valid hex digit. @value{GDBN} should ignore this @var{n...},
22435 @var{r...} pair and go on to the next. This way we can extend the
22440 The process exited, and @var{AA} is the exit status. This is only
22441 applicable to certain targets.
22445 The process terminated with signal @var{AA}.
22447 @item O@var{XX@dots{}}
22449 @var{XX@dots{}} is hex encoding of @sc{ascii} data. This can happen at
22450 any time while the program is running and the debugger should continue
22451 to wait for @samp{W}, @samp{T}, etc.
22453 @item F@var{call-id}@code{,}@var{parameter@dots{}}
22455 @var{call-id} is the identifier which says which host system call should
22456 be called. This is just the name of the function. Translation into the
22457 correct system call is only applicable as it's defined in @value{GDBN}.
22458 @xref{File-I/O remote protocol extension}, for a list of implemented
22461 @var{parameter@dots{}} is a list of parameters as defined for this very
22464 The target replies with this packet when it expects @value{GDBN} to call
22465 a host system call on behalf of the target. @value{GDBN} replies with
22466 an appropriate @code{F} packet and keeps up waiting for the next reply
22467 packet from the target. The latest @samp{C}, @samp{c}, @samp{S} or
22468 @samp{s} action is expected to be continued.
22469 @xref{File-I/O remote protocol extension}, for more details.
22473 @node General Query Packets
22474 @section General Query Packets
22475 @cindex remote query requests
22477 The following set and query packets have already been defined.
22481 @item @code{q}@code{C} --- current thread
22482 @cindex current thread, remote request
22483 @cindex @code{qC} packet
22484 Return the current thread id.
22488 @item @code{QC}@var{pid}
22489 Where @var{pid} is an unsigned hexidecimal process id.
22491 Any other reply implies the old pid.
22494 @item @code{q}@code{fThreadInfo} -- all thread ids
22495 @cindex list active threads, remote request
22496 @cindex @code{qfThreadInfo} packet
22497 @code{q}@code{sThreadInfo}
22499 Obtain a list of active thread ids from the target (OS). Since there
22500 may be too many active threads to fit into one reply packet, this query
22501 works iteratively: it may require more than one query/reply sequence to
22502 obtain the entire list of threads. The first query of the sequence will
22503 be the @code{qf}@code{ThreadInfo} query; subsequent queries in the
22504 sequence will be the @code{qs}@code{ThreadInfo} query.
22506 NOTE: replaces the @code{qL} query (see below).
22510 @item @code{m}@var{id}
22512 @item @code{m}@var{id},@var{id}@dots{}
22513 a comma-separated list of thread ids
22515 (lower case 'el') denotes end of list.
22518 In response to each query, the target will reply with a list of one or
22519 more thread ids, in big-endian unsigned hex, separated by commas.
22520 @value{GDBN} will respond to each reply with a request for more thread
22521 ids (using the @code{qs} form of the query), until the target responds
22522 with @code{l} (lower-case el, for @code{'last'}).
22524 @item @code{q}@code{ThreadExtraInfo}@code{,}@var{id} --- extra thread info
22525 @cindex thread attributes info, remote request
22526 @cindex @code{qThreadExtraInfo} packet
22527 Where @var{id} is a thread-id in big-endian hex. Obtain a printable
22528 string description of a thread's attributes from the target OS. This
22529 string may contain anything that the target OS thinks is interesting for
22530 @value{GDBN} to tell the user about the thread. The string is displayed
22531 in @value{GDBN}'s @samp{info threads} display. Some examples of
22532 possible thread extra info strings are ``Runnable'', or ``Blocked on
22537 @item @var{XX@dots{}}
22538 Where @var{XX@dots{}} is a hex encoding of @sc{ascii} data, comprising
22539 the printable string containing the extra information about the thread's
22543 @item @code{q}@code{L}@var{startflag}@var{threadcount}@var{nextthread} --- query @var{LIST} or @var{threadLIST} @strong{(deprecated)}
22545 Obtain thread information from RTOS. Where: @var{startflag} (one hex
22546 digit) is one to indicate the first query and zero to indicate a
22547 subsequent query; @var{threadcount} (two hex digits) is the maximum
22548 number of threads the response packet can contain; and @var{nextthread}
22549 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
22550 returned in the response as @var{argthread}.
22552 NOTE: this query is replaced by the @code{q}@code{fThreadInfo} query
22557 @item @code{q}@code{M}@var{count}@var{done}@var{argthread}@var{thread@dots{}}
22558 Where: @var{count} (two hex digits) is the number of threads being
22559 returned; @var{done} (one hex digit) is zero to indicate more threads
22560 and one indicates no further threads; @var{argthreadid} (eight hex
22561 digits) is @var{nextthread} from the request packet; @var{thread@dots{}}
22562 is a sequence of thread IDs from the target. @var{threadid} (eight hex
22563 digits). See @code{remote.c:parse_threadlist_response()}.
22566 @item @code{q}@code{CRC:}@var{addr}@code{,}@var{length} --- compute CRC of memory block
22567 @cindex CRC of memory block, remote request
22568 @cindex @code{qCRC} packet
22571 @item @code{E}@var{NN}
22572 An error (such as memory fault)
22573 @item @code{C}@var{CRC32}
22574 A 32 bit cyclic redundancy check of the specified memory region.
22577 @item @code{q}@code{Offsets} --- query sect offs
22578 @cindex section offsets, remote request
22579 @cindex @code{qOffsets} packet
22580 Get section offsets that the target used when re-locating the downloaded
22581 image. @emph{Note: while a @code{Bss} offset is included in the
22582 response, @value{GDBN} ignores this and instead applies the @code{Data}
22583 offset to the @code{Bss} section.}
22587 @item @code{Text=}@var{xxx}@code{;Data=}@var{yyy}@code{;Bss=}@var{zzz}
22590 @item @code{q}@code{P}@var{mode}@var{threadid} --- thread info request
22591 @cindex thread information, remote request
22592 @cindex @code{qP} packet
22593 Returns information on @var{threadid}. Where: @var{mode} is a hex
22594 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
22601 See @code{remote.c:remote_unpack_thread_info_response()}.
22603 @item @code{q}@code{Rcmd,}@var{command} --- remote command
22604 @cindex execute remote command, remote request
22605 @cindex @code{qRcmd} packet
22606 @var{command} (hex encoded) is passed to the local interpreter for
22607 execution. Invalid commands should be reported using the output string.
22608 Before the final result packet, the target may also respond with a
22609 number of intermediate @code{O}@var{output} console output packets.
22610 @emph{Implementors should note that providing access to a stubs's
22611 interpreter may have security implications}.
22616 A command response with no output.
22618 A command response with the hex encoded output string @var{OUTPUT}.
22619 @item @code{E}@var{NN}
22620 Indicate a badly formed request.
22622 When @samp{q}@samp{Rcmd} is not recognized.
22625 @item @code{qSymbol::} --- symbol lookup
22626 @cindex symbol lookup, remote request
22627 @cindex @code{qSymbol} packet
22628 Notify the target that @value{GDBN} is prepared to serve symbol lookup
22629 requests. Accept requests from the target for the values of symbols.
22634 The target does not need to look up any (more) symbols.
22635 @item @code{qSymbol:}@var{sym_name}
22636 The target requests the value of symbol @var{sym_name} (hex encoded).
22637 @value{GDBN} may provide the value by using the
22638 @code{qSymbol:}@var{sym_value}:@var{sym_name} message, described below.
22641 @item @code{qSymbol:}@var{sym_value}:@var{sym_name} --- symbol value
22643 Set the value of @var{sym_name} to @var{sym_value}.
22645 @var{sym_name} (hex encoded) is the name of a symbol whose value the
22646 target has previously requested.
22648 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
22649 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
22655 The target does not need to look up any (more) symbols.
22656 @item @code{qSymbol:}@var{sym_name}
22657 The target requests the value of a new symbol @var{sym_name} (hex
22658 encoded). @value{GDBN} will continue to supply the values of symbols
22659 (if available), until the target ceases to request them.
22662 @item @code{qPart}:@var{object}:@code{read}:@var{annex}:@var{offset},@var{length} --- read special data
22663 @cindex read special object, remote request
22664 @cindex @code{qPart} packet
22665 Read uninterpreted bytes from the target's special data area
22666 identified by the keyword @code{object}.
22667 Request @var{length} bytes starting at @var{offset} bytes into the data.
22668 The content and encoding of @var{annex} is specific to the object;
22669 it can supply additional details about what data to access.
22671 Here are the specific requests of this form defined so far.
22672 All @samp{@code{qPart}:@var{object}:@code{read}:@dots{}}
22673 requests use the same reply formats, listed below.
22676 @item @code{qPart}:@code{auxv}:@code{read}::@var{offset},@var{length}
22677 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
22678 auxiliary vector}, and see @ref{Remote configuration,
22679 read-aux-vector-packet}. Note @var{annex} must be empty.
22685 The @var{offset} in the request is at the end of the data.
22686 There is no more data to be read.
22688 @item @var{XX@dots{}}
22689 Hex encoded data bytes read.
22690 This may be fewer bytes than the @var{length} in the request.
22693 The request was malformed, or @var{annex} was invalid.
22695 @item @code{E}@var{nn}
22696 The offset was invalid, or there was an error encountered reading the data.
22697 @var{nn} is a hex-encoded @code{errno} value.
22699 @item @code{""} (empty)
22700 An empty reply indicates the @var{object} or @var{annex} string was not
22701 recognized by the stub.
22704 @item @code{qPart}:@var{object}:@code{write}:@var{annex}:@var{offset}:@var{data@dots{}}
22705 @cindex write data into object, remote request
22706 Write uninterpreted bytes into the target's special data area
22707 identified by the keyword @code{object},
22708 starting at @var{offset} bytes into the data.
22709 @var{data@dots{}} is the hex-encoded data to be written.
22710 The content and encoding of @var{annex} is specific to the object;
22711 it can supply additional details about what data to access.
22713 No requests of this form are presently in use. This specification
22714 serves as a placeholder to document the common format that new
22715 specific request specifications ought to use.
22720 @var{nn} (hex encoded) is the number of bytes written.
22721 This may be fewer bytes than supplied in the request.
22724 The request was malformed, or @var{annex} was invalid.
22726 @item @code{E}@var{nn}
22727 The offset was invalid, or there was an error encountered writing the data.
22728 @var{nn} is a hex-encoded @code{errno} value.
22730 @item @code{""} (empty)
22731 An empty reply indicates the @var{object} or @var{annex} string was not
22732 recognized by the stub, or that the object does not support writing.
22735 @item @code{qPart}:@var{object}:@var{operation}:@dots{}
22736 Requests of this form may be added in the future. When a stub does
22737 not recognize the @var{object} keyword, or its support for
22738 @var{object} does not recognize the @var{operation} keyword,
22739 the stub must respond with an empty packet.
22741 @item @code{qGetTLSAddr}:@var{thread-id},@var{offset},@var{lm} --- get thread local storage address
22742 @cindex get thread-local storage address, remote request
22743 @cindex @code{qGetTLSAddr} packet
22744 Fetch the address associated with thread local storage specified
22745 by @var{thread-id}, @var{offset}, and @var{lm}.
22747 @var{thread-id} is the (big endian, hex encoded) thread id associated with the
22748 thread for which to fetch the TLS address.
22750 @var{offset} is the (big endian, hex encoded) offset associated with the
22751 thread local variable. (This offset is obtained from the debug
22752 information associated with the variable.)
22754 @var{lm} is the (big endian, hex encoded) OS/ABI specific encoding of the
22755 the load module associated with the thread local storage. For example,
22756 a @sc{gnu}/Linux system will pass the link map address of the shared
22757 object associated with the thread local storage under consideration.
22758 Other operating environments may choose to represent the load module
22759 differently, so the precise meaning of this parameter will vary.
22763 @item @var{XX@dots{}}
22764 Hex encoded (big endian) bytes representing the address of the thread
22765 local storage requested.
22767 @item @code{E}@var{nn} (where @var{nn} are hex digits)
22770 @item @code{""} (empty)
22771 An empty reply indicates that @code{qGetTLSAddr} is not supported by the stub.
22776 @node Register Packet Format
22777 @section Register Packet Format
22779 The following @samp{g}/@samp{G} packets have previously been defined.
22780 In the below, some thirty-two bit registers are transferred as
22781 sixty-four bits. Those registers should be zero/sign extended (which?)
22782 to fill the space allocated. Register bytes are transfered in target
22783 byte order. The two nibbles within a register byte are transfered
22784 most-significant - least-significant.
22790 All registers are transfered as thirty-two bit quantities in the order:
22791 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
22792 registers; fsr; fir; fp.
22796 All registers are transfered as sixty-four bit quantities (including
22797 thirty-two bit registers such as @code{sr}). The ordering is the same
22805 Example sequence of a target being re-started. Notice how the restart
22806 does not get any direct output:
22811 @emph{target restarts}
22814 <- @code{T001:1234123412341234}
22818 Example sequence of a target being stepped by a single instruction:
22821 -> @code{G1445@dots{}}
22826 <- @code{T001:1234123412341234}
22830 <- @code{1455@dots{}}
22834 @node File-I/O remote protocol extension
22835 @section File-I/O remote protocol extension
22836 @cindex File-I/O remote protocol extension
22839 * File-I/O Overview::
22840 * Protocol basics::
22841 * The F request packet::
22842 * The F reply packet::
22843 * Memory transfer::
22844 * The Ctrl-C message::
22846 * The isatty call::
22847 * The system call::
22848 * List of supported calls::
22849 * Protocol specific representation of datatypes::
22851 * File-I/O Examples::
22854 @node File-I/O Overview
22855 @subsection File-I/O Overview
22856 @cindex file-i/o overview
22858 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
22859 target to use the host's file system and console I/O when calling various
22860 system calls. System calls on the target system are translated into a
22861 remote protocol packet to the host system which then performs the needed
22862 actions and returns with an adequate response packet to the target system.
22863 This simulates file system operations even on targets that lack file systems.
22865 The protocol is defined host- and target-system independent. It uses
22866 its own independent representation of datatypes and values. Both,
22867 @value{GDBN} and the target's @value{GDBN} stub are responsible for
22868 translating the system dependent values into the unified protocol values
22869 when data is transmitted.
22871 The communication is synchronous. A system call is possible only
22872 when GDB is waiting for the @samp{C}, @samp{c}, @samp{S} or @samp{s}
22873 packets. While @value{GDBN} handles the request for a system call,
22874 the target is stopped to allow deterministic access to the target's
22875 memory. Therefore File-I/O is not interuptible by target signals. It
22876 is possible to interrupt File-I/O by a user interrupt (Ctrl-C), though.
22878 The target's request to perform a host system call does not finish
22879 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
22880 after finishing the system call, the target returns to continuing the
22881 previous activity (continue, step). No additional continue or step
22882 request from @value{GDBN} is required.
22885 (@value{GDBP}) continue
22886 <- target requests 'system call X'
22887 target is stopped, @value{GDBN} executes system call
22888 -> GDB returns result
22889 ... target continues, GDB returns to wait for the target
22890 <- target hits breakpoint and sends a Txx packet
22893 The protocol is only used for files on the host file system and
22894 for I/O on the console. Character or block special devices, pipes,
22895 named pipes or sockets or any other communication method on the host
22896 system are not supported by this protocol.
22898 @node Protocol basics
22899 @subsection Protocol basics
22900 @cindex protocol basics, file-i/o
22902 The File-I/O protocol uses the @code{F} packet, as request as well
22903 as as reply packet. Since a File-I/O system call can only occur when
22904 @value{GDBN} is waiting for the continuing or stepping target, the
22905 File-I/O request is a reply that @value{GDBN} has to expect as a result
22906 of a former @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
22907 This @code{F} packet contains all information needed to allow @value{GDBN}
22908 to call the appropriate host system call:
22912 A unique identifier for the requested system call.
22915 All parameters to the system call. Pointers are given as addresses
22916 in the target memory address space. Pointers to strings are given as
22917 pointer/length pair. Numerical values are given as they are.
22918 Numerical control values are given in a protocol specific representation.
22922 At that point @value{GDBN} has to perform the following actions.
22926 If parameter pointer values are given, which point to data needed as input
22927 to a system call, @value{GDBN} requests this data from the target with a
22928 standard @code{m} packet request. This additional communication has to be
22929 expected by the target implementation and is handled as any other @code{m}
22933 @value{GDBN} translates all value from protocol representation to host
22934 representation as needed. Datatypes are coerced into the host types.
22937 @value{GDBN} calls the system call
22940 It then coerces datatypes back to protocol representation.
22943 If pointer parameters in the request packet point to buffer space in which
22944 a system call is expected to copy data to, the data is transmitted to the
22945 target using a @code{M} or @code{X} packet. This packet has to be expected
22946 by the target implementation and is handled as any other @code{M} or @code{X}
22951 Eventually @value{GDBN} replies with another @code{F} packet which contains all
22952 necessary information for the target to continue. This at least contains
22959 @code{errno}, if has been changed by the system call.
22966 After having done the needed type and value coercion, the target continues
22967 the latest continue or step action.
22969 @node The F request packet
22970 @subsection The @code{F} request packet
22971 @cindex file-i/o request packet
22972 @cindex @code{F} request packet
22974 The @code{F} request packet has the following format:
22979 @code{F}@var{call-id}@code{,}@var{parameter@dots{}}
22982 @var{call-id} is the identifier to indicate the host system call to be called.
22983 This is just the name of the function.
22985 @var{parameter@dots{}} are the parameters to the system call.
22989 Parameters are hexadecimal integer values, either the real values in case
22990 of scalar datatypes, as pointers to target buffer space in case of compound
22991 datatypes and unspecified memory areas or as pointer/length pairs in case
22992 of string parameters. These are appended to the call-id, each separated
22993 from its predecessor by a comma. All values are transmitted in ASCII
22994 string representation, pointer/length pairs separated by a slash.
22996 @node The F reply packet
22997 @subsection The @code{F} reply packet
22998 @cindex file-i/o reply packet
22999 @cindex @code{F} reply packet
23001 The @code{F} reply packet has the following format:
23006 @code{F}@var{retcode}@code{,}@var{errno}@code{,}@var{Ctrl-C flag}@code{;}@var{call specific attachment}
23009 @var{retcode} is the return code of the system call as hexadecimal value.
23011 @var{errno} is the errno set by the call, in protocol specific representation.
23012 This parameter can be omitted if the call was successful.
23014 @var{Ctrl-C flag} is only send if the user requested a break. In this
23015 case, @var{errno} must be send as well, even if the call was successful.
23016 The @var{Ctrl-C flag} itself consists of the character 'C':
23023 or, if the call was interupted before the host call has been performed:
23030 assuming 4 is the protocol specific representation of @code{EINTR}.
23034 @node Memory transfer
23035 @subsection Memory transfer
23036 @cindex memory transfer, in file-i/o protocol
23038 Structured data which is transferred using a memory read or write as e.g.@:
23039 a @code{struct stat} is expected to be in a protocol specific format with
23040 all scalar multibyte datatypes being big endian. This should be done by
23041 the target before the @code{F} packet is sent resp.@: by @value{GDBN} before
23042 it transfers memory to the target. Transferred pointers to structured
23043 data should point to the already coerced data at any time.
23045 @node The Ctrl-C message
23046 @subsection The Ctrl-C message
23047 @cindex ctrl-c message, in file-i/o protocol
23049 A special case is, if the @var{Ctrl-C flag} is set in the @value{GDBN}
23050 reply packet. In this case the target should behave, as if it had
23051 gotten a break message. The meaning for the target is ``system call
23052 interupted by @code{SIGINT}''. Consequentially, the target should actually stop
23053 (as with a break message) and return to @value{GDBN} with a @code{T02}
23054 packet. In this case, it's important for the target to know, in which
23055 state the system call was interrupted. Since this action is by design
23056 not an atomic operation, we have to differ between two cases:
23060 The system call hasn't been performed on the host yet.
23063 The system call on the host has been finished.
23067 These two states can be distinguished by the target by the value of the
23068 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
23069 call hasn't been performed. This is equivalent to the @code{EINTR} handling
23070 on POSIX systems. In any other case, the target may presume that the
23071 system call has been finished --- successful or not --- and should behave
23072 as if the break message arrived right after the system call.
23074 @value{GDBN} must behave reliable. If the system call has not been called
23075 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
23076 @code{errno} in the packet. If the system call on the host has been finished
23077 before the user requests a break, the full action must be finshed by
23078 @value{GDBN}. This requires sending @code{M} or @code{X} packets as they fit.
23079 The @code{F} packet may only be send when either nothing has happened
23080 or the full action has been completed.
23083 @subsection Console I/O
23084 @cindex console i/o as part of file-i/o
23086 By default and if not explicitely closed by the target system, the file
23087 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
23088 on the @value{GDBN} console is handled as any other file output operation
23089 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
23090 by @value{GDBN} so that after the target read request from file descriptor
23091 0 all following typing is buffered until either one of the following
23096 The user presses @kbd{Ctrl-C}. The behaviour is as explained above, the
23098 system call is treated as finished.
23101 The user presses @kbd{Enter}. This is treated as end of input with a trailing
23105 The user presses @kbd{Ctrl-D}. This is treated as end of input. No trailing
23106 character, especially no Ctrl-D is appended to the input.
23110 If the user has typed more characters as fit in the buffer given to
23111 the read call, the trailing characters are buffered in @value{GDBN} until
23112 either another @code{read(0, @dots{})} is requested by the target or debugging
23113 is stopped on users request.
23115 @node The isatty call
23116 @subsection The isatty(3) call
23117 @cindex isatty call, file-i/o protocol
23119 A special case in this protocol is the library call @code{isatty} which
23120 is implemented as its own call inside of this protocol. It returns
23121 1 to the target if the file descriptor given as parameter is attached
23122 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
23123 would require implementing @code{ioctl} and would be more complex than
23126 @node The system call
23127 @subsection The system(3) call
23128 @cindex system call, file-i/o protocol
23130 The other special case in this protocol is the @code{system} call which
23131 is implemented as its own call, too. @value{GDBN} is taking over the full
23132 task of calling the necessary host calls to perform the @code{system}
23133 call. The return value of @code{system} is simplified before it's returned
23134 to the target. Basically, the only signal transmitted back is @code{EINTR}
23135 in case the user pressed @kbd{Ctrl-C}. Otherwise the return value consists
23136 entirely of the exit status of the called command.
23138 Due to security concerns, the @code{system} call is by default refused
23139 by @value{GDBN}. The user has to allow this call explicitly with the
23140 @kbd{set remote system-call-allowed 1} command.
23143 @item set remote system-call-allowed
23144 @kindex set remote system-call-allowed
23145 Control whether to allow the @code{system} calls in the File I/O
23146 protocol for the remote target. The default is zero (disabled).
23148 @item show remote system-call-allowed
23149 @kindex show remote system-call-allowed
23150 Show the current setting of system calls for the remote File I/O
23154 @node List of supported calls
23155 @subsection List of supported calls
23156 @cindex list of supported file-i/o calls
23173 @unnumberedsubsubsec open
23174 @cindex open, file-i/o system call
23178 int open(const char *pathname, int flags);
23179 int open(const char *pathname, int flags, mode_t mode);
23182 Fopen,pathptr/len,flags,mode
23186 @code{flags} is the bitwise or of the following values:
23190 If the file does not exist it will be created. The host
23191 rules apply as far as file ownership and time stamps
23195 When used with O_CREAT, if the file already exists it is
23196 an error and open() fails.
23199 If the file already exists and the open mode allows
23200 writing (O_RDWR or O_WRONLY is given) it will be
23201 truncated to length 0.
23204 The file is opened in append mode.
23207 The file is opened for reading only.
23210 The file is opened for writing only.
23213 The file is opened for reading and writing.
23216 Each other bit is silently ignored.
23221 @code{mode} is the bitwise or of the following values:
23225 User has read permission.
23228 User has write permission.
23231 Group has read permission.
23234 Group has write permission.
23237 Others have read permission.
23240 Others have write permission.
23243 Each other bit is silently ignored.
23248 @exdent Return value:
23249 open returns the new file descriptor or -1 if an error
23257 pathname already exists and O_CREAT and O_EXCL were used.
23260 pathname refers to a directory.
23263 The requested access is not allowed.
23266 pathname was too long.
23269 A directory component in pathname does not exist.
23272 pathname refers to a device, pipe, named pipe or socket.
23275 pathname refers to a file on a read-only filesystem and
23276 write access was requested.
23279 pathname is an invalid pointer value.
23282 No space on device to create the file.
23285 The process already has the maximum number of files open.
23288 The limit on the total number of files open on the system
23292 The call was interrupted by the user.
23296 @unnumberedsubsubsec close
23297 @cindex close, file-i/o system call
23306 @exdent Return value:
23307 close returns zero on success, or -1 if an error occurred.
23314 fd isn't a valid open file descriptor.
23317 The call was interrupted by the user.
23321 @unnumberedsubsubsec read
23322 @cindex read, file-i/o system call
23326 int read(int fd, void *buf, unsigned int count);
23329 Fread,fd,bufptr,count
23331 @exdent Return value:
23332 On success, the number of bytes read is returned.
23333 Zero indicates end of file. If count is zero, read
23334 returns zero as well. On error, -1 is returned.
23341 fd is not a valid file descriptor or is not open for
23345 buf is an invalid pointer value.
23348 The call was interrupted by the user.
23352 @unnumberedsubsubsec write
23353 @cindex write, file-i/o system call
23357 int write(int fd, const void *buf, unsigned int count);
23360 Fwrite,fd,bufptr,count
23362 @exdent Return value:
23363 On success, the number of bytes written are returned.
23364 Zero indicates nothing was written. On error, -1
23372 fd is not a valid file descriptor or is not open for
23376 buf is an invalid pointer value.
23379 An attempt was made to write a file that exceeds the
23380 host specific maximum file size allowed.
23383 No space on device to write the data.
23386 The call was interrupted by the user.
23390 @unnumberedsubsubsec lseek
23391 @cindex lseek, file-i/o system call
23395 long lseek (int fd, long offset, int flag);
23398 Flseek,fd,offset,flag
23401 @code{flag} is one of:
23405 The offset is set to offset bytes.
23408 The offset is set to its current location plus offset
23412 The offset is set to the size of the file plus offset
23417 @exdent Return value:
23418 On success, the resulting unsigned offset in bytes from
23419 the beginning of the file is returned. Otherwise, a
23420 value of -1 is returned.
23427 fd is not a valid open file descriptor.
23430 fd is associated with the @value{GDBN} console.
23433 flag is not a proper value.
23436 The call was interrupted by the user.
23440 @unnumberedsubsubsec rename
23441 @cindex rename, file-i/o system call
23445 int rename(const char *oldpath, const char *newpath);
23448 Frename,oldpathptr/len,newpathptr/len
23450 @exdent Return value:
23451 On success, zero is returned. On error, -1 is returned.
23458 newpath is an existing directory, but oldpath is not a
23462 newpath is a non-empty directory.
23465 oldpath or newpath is a directory that is in use by some
23469 An attempt was made to make a directory a subdirectory
23473 A component used as a directory in oldpath or new
23474 path is not a directory. Or oldpath is a directory
23475 and newpath exists but is not a directory.
23478 oldpathptr or newpathptr are invalid pointer values.
23481 No access to the file or the path of the file.
23485 oldpath or newpath was too long.
23488 A directory component in oldpath or newpath does not exist.
23491 The file is on a read-only filesystem.
23494 The device containing the file has no room for the new
23498 The call was interrupted by the user.
23502 @unnumberedsubsubsec unlink
23503 @cindex unlink, file-i/o system call
23507 int unlink(const char *pathname);
23510 Funlink,pathnameptr/len
23512 @exdent Return value:
23513 On success, zero is returned. On error, -1 is returned.
23520 No access to the file or the path of the file.
23523 The system does not allow unlinking of directories.
23526 The file pathname cannot be unlinked because it's
23527 being used by another process.
23530 pathnameptr is an invalid pointer value.
23533 pathname was too long.
23536 A directory component in pathname does not exist.
23539 A component of the path is not a directory.
23542 The file is on a read-only filesystem.
23545 The call was interrupted by the user.
23549 @unnumberedsubsubsec stat/fstat
23550 @cindex fstat, file-i/o system call
23551 @cindex stat, file-i/o system call
23555 int stat(const char *pathname, struct stat *buf);
23556 int fstat(int fd, struct stat *buf);
23559 Fstat,pathnameptr/len,bufptr
23562 @exdent Return value:
23563 On success, zero is returned. On error, -1 is returned.
23570 fd is not a valid open file.
23573 A directory component in pathname does not exist or the
23574 path is an empty string.
23577 A component of the path is not a directory.
23580 pathnameptr is an invalid pointer value.
23583 No access to the file or the path of the file.
23586 pathname was too long.
23589 The call was interrupted by the user.
23593 @unnumberedsubsubsec gettimeofday
23594 @cindex gettimeofday, file-i/o system call
23598 int gettimeofday(struct timeval *tv, void *tz);
23601 Fgettimeofday,tvptr,tzptr
23603 @exdent Return value:
23604 On success, 0 is returned, -1 otherwise.
23611 tz is a non-NULL pointer.
23614 tvptr and/or tzptr is an invalid pointer value.
23618 @unnumberedsubsubsec isatty
23619 @cindex isatty, file-i/o system call
23623 int isatty(int fd);
23628 @exdent Return value:
23629 Returns 1 if fd refers to the @value{GDBN} console, 0 otherwise.
23636 The call was interrupted by the user.
23640 @unnumberedsubsubsec system
23641 @cindex system, file-i/o system call
23645 int system(const char *command);
23648 Fsystem,commandptr/len
23650 @exdent Return value:
23651 The value returned is -1 on error and the return status
23652 of the command otherwise. Only the exit status of the
23653 command is returned, which is extracted from the hosts
23654 system return value by calling WEXITSTATUS(retval).
23655 In case /bin/sh could not be executed, 127 is returned.
23662 The call was interrupted by the user.
23665 @node Protocol specific representation of datatypes
23666 @subsection Protocol specific representation of datatypes
23667 @cindex protocol specific representation of datatypes, in file-i/o protocol
23670 * Integral datatypes::
23676 @node Integral datatypes
23677 @unnumberedsubsubsec Integral datatypes
23678 @cindex integral datatypes, in file-i/o protocol
23680 The integral datatypes used in the system calls are
23683 int@r{,} unsigned int@r{,} long@r{,} unsigned long@r{,} mode_t @r{and} time_t
23686 @code{Int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
23687 implemented as 32 bit values in this protocol.
23689 @code{Long} and @code{unsigned long} are implemented as 64 bit types.
23691 @xref{Limits}, for corresponding MIN and MAX values (similar to those
23692 in @file{limits.h}) to allow range checking on host and target.
23694 @code{time_t} datatypes are defined as seconds since the Epoch.
23696 All integral datatypes transferred as part of a memory read or write of a
23697 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
23700 @node Pointer values
23701 @unnumberedsubsubsec Pointer values
23702 @cindex pointer values, in file-i/o protocol
23704 Pointers to target data are transmitted as they are. An exception
23705 is made for pointers to buffers for which the length isn't
23706 transmitted as part of the function call, namely strings. Strings
23707 are transmitted as a pointer/length pair, both as hex values, e.g.@:
23714 which is a pointer to data of length 18 bytes at position 0x1aaf.
23715 The length is defined as the full string length in bytes, including
23716 the trailing null byte. Example:
23719 ``hello, world'' at address 0x123456
23730 @unnumberedsubsubsec struct stat
23731 @cindex struct stat, in file-i/o protocol
23733 The buffer of type struct stat used by the target and @value{GDBN} is defined
23738 unsigned int st_dev; /* device */
23739 unsigned int st_ino; /* inode */
23740 mode_t st_mode; /* protection */
23741 unsigned int st_nlink; /* number of hard links */
23742 unsigned int st_uid; /* user ID of owner */
23743 unsigned int st_gid; /* group ID of owner */
23744 unsigned int st_rdev; /* device type (if inode device) */
23745 unsigned long st_size; /* total size, in bytes */
23746 unsigned long st_blksize; /* blocksize for filesystem I/O */
23747 unsigned long st_blocks; /* number of blocks allocated */
23748 time_t st_atime; /* time of last access */
23749 time_t st_mtime; /* time of last modification */
23750 time_t st_ctime; /* time of last change */
23754 The integral datatypes are conforming to the definitions given in the
23755 approriate section (see @ref{Integral datatypes}, for details) so this
23756 structure is of size 64 bytes.
23758 The values of several fields have a restricted meaning and/or
23765 st_ino: No valid meaning for the target. Transmitted unchanged.
23767 st_mode: Valid mode bits are described in Appendix C. Any other
23768 bits have currently no meaning for the target.
23770 st_uid: No valid meaning for the target. Transmitted unchanged.
23772 st_gid: No valid meaning for the target. Transmitted unchanged.
23774 st_rdev: No valid meaning for the target. Transmitted unchanged.
23776 st_atime, st_mtime, st_ctime:
23777 These values have a host and file system dependent
23778 accuracy. Especially on Windows hosts the file systems
23779 don't support exact timing values.
23782 The target gets a struct stat of the above representation and is
23783 responsible to coerce it to the target representation before
23786 Note that due to size differences between the host and target
23787 representation of stat members, these members could eventually
23788 get truncated on the target.
23790 @node struct timeval
23791 @unnumberedsubsubsec struct timeval
23792 @cindex struct timeval, in file-i/o protocol
23794 The buffer of type struct timeval used by the target and @value{GDBN}
23795 is defined as follows:
23799 time_t tv_sec; /* second */
23800 long tv_usec; /* microsecond */
23804 The integral datatypes are conforming to the definitions given in the
23805 approriate section (see @ref{Integral datatypes}, for details) so this
23806 structure is of size 8 bytes.
23809 @subsection Constants
23810 @cindex constants, in file-i/o protocol
23812 The following values are used for the constants inside of the
23813 protocol. @value{GDBN} and target are resposible to translate these
23814 values before and after the call as needed.
23825 @unnumberedsubsubsec Open flags
23826 @cindex open flags, in file-i/o protocol
23828 All values are given in hexadecimal representation.
23840 @node mode_t values
23841 @unnumberedsubsubsec mode_t values
23842 @cindex mode_t values, in file-i/o protocol
23844 All values are given in octal representation.
23861 @unnumberedsubsubsec Errno values
23862 @cindex errno values, in file-i/o protocol
23864 All values are given in decimal representation.
23889 EUNKNOWN is used as a fallback error value if a host system returns
23890 any error value not in the list of supported error numbers.
23893 @unnumberedsubsubsec Lseek flags
23894 @cindex lseek flags, in file-i/o protocol
23903 @unnumberedsubsubsec Limits
23904 @cindex limits, in file-i/o protocol
23906 All values are given in decimal representation.
23909 INT_MIN -2147483648
23911 UINT_MAX 4294967295
23912 LONG_MIN -9223372036854775808
23913 LONG_MAX 9223372036854775807
23914 ULONG_MAX 18446744073709551615
23917 @node File-I/O Examples
23918 @subsection File-I/O Examples
23919 @cindex file-i/o examples
23921 Example sequence of a write call, file descriptor 3, buffer is at target
23922 address 0x1234, 6 bytes should be written:
23925 <- @code{Fwrite,3,1234,6}
23926 @emph{request memory read from target}
23929 @emph{return "6 bytes written"}
23933 Example sequence of a read call, file descriptor 3, buffer is at target
23934 address 0x1234, 6 bytes should be read:
23937 <- @code{Fread,3,1234,6}
23938 @emph{request memory write to target}
23939 -> @code{X1234,6:XXXXXX}
23940 @emph{return "6 bytes read"}
23944 Example sequence of a read call, call fails on the host due to invalid
23945 file descriptor (EBADF):
23948 <- @code{Fread,3,1234,6}
23952 Example sequence of a read call, user presses Ctrl-C before syscall on
23956 <- @code{Fread,3,1234,6}
23961 Example sequence of a read call, user presses Ctrl-C after syscall on
23965 <- @code{Fread,3,1234,6}
23966 -> @code{X1234,6:XXXXXX}
23970 @include agentexpr.texi
23984 % I think something like @colophon should be in texinfo. In the
23986 \long\def\colophon{\hbox to0pt{}\vfill
23987 \centerline{The body of this manual is set in}
23988 \centerline{\fontname\tenrm,}
23989 \centerline{with headings in {\bf\fontname\tenbf}}
23990 \centerline{and examples in {\tt\fontname\tentt}.}
23991 \centerline{{\it\fontname\tenit\/},}
23992 \centerline{{\bf\fontname\tenbf}, and}
23993 \centerline{{\sl\fontname\tensl\/}}
23994 \centerline{are used for emphasis.}\vfill}
23996 % Blame: doc@cygnus.com, 1991.