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
850 * Startup:: What @value{GDBN} does during startup
854 @subsection Choosing files
856 When @value{GDBN} starts, it reads any arguments other than options as
857 specifying an executable file and core file (or process ID). This is
858 the same as if the arguments were specified by the @samp{-se} and
859 @samp{-c} (or @samp{-p} options respectively. (@value{GDBN} reads the
860 first argument that does not have an associated option flag as
861 equivalent to the @samp{-se} option followed by that argument; and the
862 second argument that does not have an associated option flag, if any, as
863 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
864 If the second argument begins with a decimal digit, @value{GDBN} will
865 first attempt to attach to it as a process, and if that fails, attempt
866 to open it as a corefile. If you have a corefile whose name begins with
867 a digit, you can prevent @value{GDBN} from treating it as a pid by
868 prefixing it with @file{./}, eg. @file{./12345}.
870 If @value{GDBN} has not been configured to included core file support,
871 such as for most embedded targets, then it will complain about a second
872 argument and ignore it.
874 Many options have both long and short forms; both are shown in the
875 following list. @value{GDBN} also recognizes the long forms if you truncate
876 them, so long as enough of the option is present to be unambiguous.
877 (If you prefer, you can flag option arguments with @samp{--} rather
878 than @samp{-}, though we illustrate the more usual convention.)
880 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
881 @c way, both those who look for -foo and --foo in the index, will find
885 @item -symbols @var{file}
887 @cindex @code{--symbols}
889 Read symbol table from file @var{file}.
891 @item -exec @var{file}
893 @cindex @code{--exec}
895 Use file @var{file} as the executable file to execute when appropriate,
896 and for examining pure data in conjunction with a core dump.
900 Read symbol table from file @var{file} and use it as the executable
903 @item -core @var{file}
905 @cindex @code{--core}
907 Use file @var{file} as a core dump to examine.
909 @item -c @var{number}
910 @item -pid @var{number}
911 @itemx -p @var{number}
914 Connect to process ID @var{number}, as with the @code{attach} command.
915 If there is no such process, @value{GDBN} will attempt to open a core
916 file named @var{number}.
918 @item -command @var{file}
920 @cindex @code{--command}
922 Execute @value{GDBN} commands from file @var{file}. @xref{Command
923 Files,, Command files}.
925 @item -directory @var{directory}
926 @itemx -d @var{directory}
927 @cindex @code{--directory}
929 Add @var{directory} to the path to search for source files.
933 @cindex @code{--mapped}
935 @emph{Warning: this option depends on operating system facilities that are not
936 supported on all systems.}@*
937 If memory-mapped files are available on your system through the @code{mmap}
938 system call, you can use this option
939 to have @value{GDBN} write the symbols from your
940 program into a reusable file in the current directory. If the program you are debugging is
941 called @file{/tmp/fred}, the mapped symbol file is @file{/tmp/fred.syms}.
942 Future @value{GDBN} debugging sessions notice the presence of this file,
943 and can quickly map in symbol information from it, rather than reading
944 the symbol table from the executable program.
946 The @file{.syms} file is specific to the host machine where @value{GDBN}
947 is run. It holds an exact image of the internal @value{GDBN} symbol
948 table. It cannot be shared across multiple host platforms.
952 @cindex @code{--readnow}
954 Read each symbol file's entire symbol table immediately, rather than
955 the default, which is to read it incrementally as it is needed.
956 This makes startup slower, but makes future operations faster.
960 You typically combine the @code{-mapped} and @code{-readnow} options in
961 order to build a @file{.syms} file that contains complete symbol
962 information. (@xref{Files,,Commands to specify files}, for information
963 on @file{.syms} files.) A simple @value{GDBN} invocation to do nothing
964 but build a @file{.syms} file for future use is:
967 gdb -batch -nx -mapped -readnow programname
971 @subsection Choosing modes
973 You can run @value{GDBN} in various alternative modes---for example, in
974 batch mode or quiet mode.
981 Do not execute commands found in any initialization files. Normally,
982 @value{GDBN} executes the commands in these files after all the command
983 options and arguments have been processed. @xref{Command Files,,Command
989 @cindex @code{--quiet}
990 @cindex @code{--silent}
992 ``Quiet''. Do not print the introductory and copyright messages. These
993 messages are also suppressed in batch mode.
996 @cindex @code{--batch}
997 Run in batch mode. Exit with status @code{0} after processing all the
998 command files specified with @samp{-x} (and all commands from
999 initialization files, if not inhibited with @samp{-n}). Exit with
1000 nonzero status if an error occurs in executing the @value{GDBN} commands
1001 in the command files.
1003 Batch mode may be useful for running @value{GDBN} as a filter, for
1004 example to download and run a program on another computer; in order to
1005 make this more useful, the message
1008 Program exited normally.
1012 (which is ordinarily issued whenever a program running under
1013 @value{GDBN} control terminates) is not issued when running in batch
1018 @cindex @code{--nowindows}
1020 ``No windows''. If @value{GDBN} comes with a graphical user interface
1021 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1022 interface. If no GUI is available, this option has no effect.
1026 @cindex @code{--windows}
1028 If @value{GDBN} includes a GUI, then this option requires it to be
1031 @item -cd @var{directory}
1033 Run @value{GDBN} using @var{directory} as its working directory,
1034 instead of the current directory.
1038 @cindex @code{--fullname}
1040 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1041 subprocess. It tells @value{GDBN} to output the full file name and line
1042 number in a standard, recognizable fashion each time a stack frame is
1043 displayed (which includes each time your program stops). This
1044 recognizable format looks like two @samp{\032} characters, followed by
1045 the file name, line number and character position separated by colons,
1046 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1047 @samp{\032} characters as a signal to display the source code for the
1051 @cindex @code{--epoch}
1052 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1053 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1054 routines so as to allow Epoch to display values of expressions in a
1057 @item -annotate @var{level}
1058 @cindex @code{--annotate}
1059 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1060 effect is identical to using @samp{set annotate @var{level}}
1061 (@pxref{Annotations}). The annotation @var{level} controls how much
1062 information @value{GDBN} prints together with its prompt, values of
1063 expressions, source lines, and other types of output. Level 0 is the
1064 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1065 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1066 that control @value{GDBN}, and level 2 has been deprecated.
1068 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
1072 @cindex @code{--args}
1073 Change interpretation of command line so that arguments following the
1074 executable file are passed as command line arguments to the inferior.
1075 This option stops option processing.
1077 @item -baud @var{bps}
1079 @cindex @code{--baud}
1081 Set the line speed (baud rate or bits per second) of any serial
1082 interface used by @value{GDBN} for remote debugging.
1084 @item -l @var{timeout}
1086 Set the timeout (in seconds) of any communication used by @value{GDBN}
1087 for remote debugging.
1089 @item -tty @var{device}
1090 @itemx -t @var{device}
1091 @cindex @code{--tty}
1093 Run using @var{device} for your program's standard input and output.
1094 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1096 @c resolve the situation of these eventually
1098 @cindex @code{--tui}
1099 Activate the @dfn{Text User Interface} when starting. The Text User
1100 Interface manages several text windows on the terminal, showing
1101 source, assembly, registers and @value{GDBN} command outputs
1102 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1103 Text User Interface can be enabled by invoking the program
1104 @samp{gdbtui}. Do not use this option if you run @value{GDBN} from
1105 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1108 @c @cindex @code{--xdb}
1109 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1110 @c For information, see the file @file{xdb_trans.html}, which is usually
1111 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1114 @item -interpreter @var{interp}
1115 @cindex @code{--interpreter}
1116 Use the interpreter @var{interp} for interface with the controlling
1117 program or device. This option is meant to be set by programs which
1118 communicate with @value{GDBN} using it as a back end.
1119 @xref{Interpreters, , Command Interpreters}.
1121 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1122 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1123 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1124 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1125 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1126 @sc{gdb/mi} interfaces are no longer supported.
1129 @cindex @code{--write}
1130 Open the executable and core files for both reading and writing. This
1131 is equivalent to the @samp{set write on} command inside @value{GDBN}
1135 @cindex @code{--statistics}
1136 This option causes @value{GDBN} to print statistics about time and
1137 memory usage after it completes each command and returns to the prompt.
1140 @cindex @code{--version}
1141 This option causes @value{GDBN} to print its version number and
1142 no-warranty blurb, and exit.
1147 @subsection What @value{GDBN} does during startup
1148 @cindex @value{GDBN} startup
1150 Here's the description of what @value{GDBN} does during session startup:
1154 Sets up the command interpreter as specified by the command line
1155 (@pxref{Mode Options, interpreter}).
1159 Reads the @dfn{init file} (if any) in your home directory@footnote{On
1160 DOS/Windows systems, the home directory is the one pointed to by the
1161 @code{HOME} environment variable.} and executes all the commands in
1165 Processes command line options and operands.
1168 Reads and executes the commands from init file (if any) in the current
1169 working directory. This is only done if the current directory is
1170 different from your home directory. Thus, you can have more than one
1171 init file, one generic in your home directory, and another, specific
1172 to the program you are debugging, in the directory where you invoke
1176 Reads command files specified by the @samp{-x} option. @xref{Command
1177 Files}, for more details about @value{GDBN} command files.
1180 Reads the command history recorded in the @dfn{history file}.
1181 @xref{History}, for more details about the command history and the
1182 files where @value{GDBN} records it.
1185 Init files use the same syntax as @dfn{command files} (@pxref{Command
1186 Files}) and are processed by @value{GDBN} in the same way. The init
1187 file in your home directory can set options (such as @samp{set
1188 complaints}) that affect subsequent processing of command line options
1189 and operands. Init files are not executed if you use the @samp{-nx}
1190 option (@pxref{Mode Options, ,Choosing modes}).
1192 @cindex init file name
1193 @cindex @file{.gdbinit}
1194 The @value{GDBN} init files are normally called @file{.gdbinit}.
1195 On some configurations of @value{GDBN}, the init file is known by a
1196 different name (these are typically environments where a specialized
1197 form of @value{GDBN} may need to coexist with other forms, hence a
1198 different name for the specialized version's init file). These are the
1199 environments with special init file names:
1202 @cindex @file{gdb.ini}
1204 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1205 the limitations of file names imposed by DOS filesystems. The Windows
1206 ports of @value{GDBN} use the standard name, but if they find a
1207 @file{gdb.ini} file, they warn you about that and suggest to rename
1208 the file to the standard name.
1210 @cindex @file{.vxgdbinit}
1212 VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit}
1214 @cindex @file{.os68gdbinit}
1216 OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit}
1218 @cindex @file{.esgdbinit}
1220 ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit}
1223 CISCO 68k: @file{.cisco-gdbinit}
1228 @section Quitting @value{GDBN}
1229 @cindex exiting @value{GDBN}
1230 @cindex leaving @value{GDBN}
1233 @kindex quit @r{[}@var{expression}@r{]}
1234 @kindex q @r{(@code{quit})}
1235 @item quit @r{[}@var{expression}@r{]}
1237 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1238 @code{q}), or type an end-of-file character (usually @kbd{C-d}). If you
1239 do not supply @var{expression}, @value{GDBN} will terminate normally;
1240 otherwise it will terminate using the result of @var{expression} as the
1245 An interrupt (often @kbd{C-c}) does not exit from @value{GDBN}, but rather
1246 terminates the action of any @value{GDBN} command that is in progress and
1247 returns to @value{GDBN} command level. It is safe to type the interrupt
1248 character at any time because @value{GDBN} does not allow it to take effect
1249 until a time when it is safe.
1251 If you have been using @value{GDBN} to control an attached process or
1252 device, you can release it with the @code{detach} command
1253 (@pxref{Attach, ,Debugging an already-running process}).
1255 @node Shell Commands
1256 @section Shell commands
1258 If you need to execute occasional shell commands during your
1259 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1260 just use the @code{shell} command.
1264 @cindex shell escape
1265 @item shell @var{command string}
1266 Invoke a standard shell to execute @var{command string}.
1267 If it exists, the environment variable @code{SHELL} determines which
1268 shell to run. Otherwise @value{GDBN} uses the default shell
1269 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1272 The utility @code{make} is often needed in development environments.
1273 You do not have to use the @code{shell} command for this purpose in
1278 @cindex calling make
1279 @item make @var{make-args}
1280 Execute the @code{make} program with the specified
1281 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1284 @node Logging output
1285 @section Logging output
1286 @cindex logging @value{GDBN} output
1287 @cindex save @value{GDBN} output to a file
1289 You may want to save the output of @value{GDBN} commands to a file.
1290 There are several commands to control @value{GDBN}'s logging.
1294 @item set logging on
1296 @item set logging off
1298 @cindex logging file name
1299 @item set logging file @var{file}
1300 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1301 @item set logging overwrite [on|off]
1302 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1303 you want @code{set logging on} to overwrite the logfile instead.
1304 @item set logging redirect [on|off]
1305 By default, @value{GDBN} output will go to both the terminal and the logfile.
1306 Set @code{redirect} if you want output to go only to the log file.
1307 @kindex show logging
1309 Show the current values of the logging settings.
1313 @chapter @value{GDBN} Commands
1315 You can abbreviate a @value{GDBN} command to the first few letters of the command
1316 name, if that abbreviation is unambiguous; and you can repeat certain
1317 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1318 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1319 show you the alternatives available, if there is more than one possibility).
1322 * Command Syntax:: How to give commands to @value{GDBN}
1323 * Completion:: Command completion
1324 * Help:: How to ask @value{GDBN} for help
1327 @node Command Syntax
1328 @section Command syntax
1330 A @value{GDBN} command is a single line of input. There is no limit on
1331 how long it can be. It starts with a command name, which is followed by
1332 arguments whose meaning depends on the command name. For example, the
1333 command @code{step} accepts an argument which is the number of times to
1334 step, as in @samp{step 5}. You can also use the @code{step} command
1335 with no arguments. Some commands do not allow any arguments.
1337 @cindex abbreviation
1338 @value{GDBN} command names may always be truncated if that abbreviation is
1339 unambiguous. Other possible command abbreviations are listed in the
1340 documentation for individual commands. In some cases, even ambiguous
1341 abbreviations are allowed; for example, @code{s} is specially defined as
1342 equivalent to @code{step} even though there are other commands whose
1343 names start with @code{s}. You can test abbreviations by using them as
1344 arguments to the @code{help} command.
1346 @cindex repeating commands
1347 @kindex RET @r{(repeat last command)}
1348 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1349 repeat the previous command. Certain commands (for example, @code{run})
1350 will not repeat this way; these are commands whose unintentional
1351 repetition might cause trouble and which you are unlikely to want to
1352 repeat. User-defined commands can disable this feature; see
1353 @ref{Define, dont-repeat}.
1355 The @code{list} and @code{x} commands, when you repeat them with
1356 @key{RET}, construct new arguments rather than repeating
1357 exactly as typed. This permits easy scanning of source or memory.
1359 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1360 output, in a way similar to the common utility @code{more}
1361 (@pxref{Screen Size,,Screen size}). Since it is easy to press one
1362 @key{RET} too many in this situation, @value{GDBN} disables command
1363 repetition after any command that generates this sort of display.
1365 @kindex # @r{(a comment)}
1367 Any text from a @kbd{#} to the end of the line is a comment; it does
1368 nothing. This is useful mainly in command files (@pxref{Command
1369 Files,,Command files}).
1371 @cindex repeating command sequences
1372 @kindex C-o @r{(operate-and-get-next)}
1373 The @kbd{C-o} binding is useful for repeating a complex sequence of
1374 commands. This command accepts the current line, like @kbd{RET}, and
1375 then fetches the next line relative to the current line from the history
1379 @section Command completion
1382 @cindex word completion
1383 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1384 only one possibility; it can also show you what the valid possibilities
1385 are for the next word in a command, at any time. This works for @value{GDBN}
1386 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1388 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1389 of a word. If there is only one possibility, @value{GDBN} fills in the
1390 word, and waits for you to finish the command (or press @key{RET} to
1391 enter it). For example, if you type
1393 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1394 @c complete accuracy in these examples; space introduced for clarity.
1395 @c If texinfo enhancements make it unnecessary, it would be nice to
1396 @c replace " @key" by "@key" in the following...
1398 (@value{GDBP}) info bre @key{TAB}
1402 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1403 the only @code{info} subcommand beginning with @samp{bre}:
1406 (@value{GDBP}) info breakpoints
1410 You can either press @key{RET} at this point, to run the @code{info
1411 breakpoints} command, or backspace and enter something else, if
1412 @samp{breakpoints} does not look like the command you expected. (If you
1413 were sure you wanted @code{info breakpoints} in the first place, you
1414 might as well just type @key{RET} immediately after @samp{info bre},
1415 to exploit command abbreviations rather than command completion).
1417 If there is more than one possibility for the next word when you press
1418 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1419 characters and try again, or just press @key{TAB} a second time;
1420 @value{GDBN} displays all the possible completions for that word. For
1421 example, you might want to set a breakpoint on a subroutine whose name
1422 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1423 just sounds the bell. Typing @key{TAB} again displays all the
1424 function names in your program that begin with those characters, for
1428 (@value{GDBP}) b make_ @key{TAB}
1429 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1430 make_a_section_from_file make_environ
1431 make_abs_section make_function_type
1432 make_blockvector make_pointer_type
1433 make_cleanup make_reference_type
1434 make_command make_symbol_completion_list
1435 (@value{GDBP}) b make_
1439 After displaying the available possibilities, @value{GDBN} copies your
1440 partial input (@samp{b make_} in the example) so you can finish the
1443 If you just want to see the list of alternatives in the first place, you
1444 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1445 means @kbd{@key{META} ?}. You can type this either by holding down a
1446 key designated as the @key{META} shift on your keyboard (if there is
1447 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1449 @cindex quotes in commands
1450 @cindex completion of quoted strings
1451 Sometimes the string you need, while logically a ``word'', may contain
1452 parentheses or other characters that @value{GDBN} normally excludes from
1453 its notion of a word. To permit word completion to work in this
1454 situation, you may enclose words in @code{'} (single quote marks) in
1455 @value{GDBN} commands.
1457 The most likely situation where you might need this is in typing the
1458 name of a C@t{++} function. This is because C@t{++} allows function
1459 overloading (multiple definitions of the same function, distinguished
1460 by argument type). For example, when you want to set a breakpoint you
1461 may need to distinguish whether you mean the version of @code{name}
1462 that takes an @code{int} parameter, @code{name(int)}, or the version
1463 that takes a @code{float} parameter, @code{name(float)}. To use the
1464 word-completion facilities in this situation, type a single quote
1465 @code{'} at the beginning of the function name. This alerts
1466 @value{GDBN} that it may need to consider more information than usual
1467 when you press @key{TAB} or @kbd{M-?} to request word completion:
1470 (@value{GDBP}) b 'bubble( @kbd{M-?}
1471 bubble(double,double) bubble(int,int)
1472 (@value{GDBP}) b 'bubble(
1475 In some cases, @value{GDBN} can tell that completing a name requires using
1476 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1477 completing as much as it can) if you do not type the quote in the first
1481 (@value{GDBP}) b bub @key{TAB}
1482 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1483 (@value{GDBP}) b 'bubble(
1487 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1488 you have not yet started typing the argument list when you ask for
1489 completion on an overloaded symbol.
1491 For more information about overloaded functions, see @ref{C plus plus
1492 expressions, ,C@t{++} expressions}. You can use the command @code{set
1493 overload-resolution off} to disable overload resolution;
1494 see @ref{Debugging C plus plus, ,@value{GDBN} features for C@t{++}}.
1498 @section Getting help
1499 @cindex online documentation
1502 You can always ask @value{GDBN} itself for information on its commands,
1503 using the command @code{help}.
1506 @kindex h @r{(@code{help})}
1509 You can use @code{help} (abbreviated @code{h}) with no arguments to
1510 display a short list of named classes of commands:
1514 List of classes of commands:
1516 aliases -- Aliases of other commands
1517 breakpoints -- Making program stop at certain points
1518 data -- Examining data
1519 files -- Specifying and examining files
1520 internals -- Maintenance commands
1521 obscure -- Obscure features
1522 running -- Running the program
1523 stack -- Examining the stack
1524 status -- Status inquiries
1525 support -- Support facilities
1526 tracepoints -- Tracing of program execution without@*
1527 stopping the program
1528 user-defined -- User-defined commands
1530 Type "help" followed by a class name for a list of
1531 commands in that class.
1532 Type "help" followed by command name for full
1534 Command name abbreviations are allowed if unambiguous.
1537 @c the above line break eliminates huge line overfull...
1539 @item help @var{class}
1540 Using one of the general help classes as an argument, you can get a
1541 list of the individual commands in that class. For example, here is the
1542 help display for the class @code{status}:
1545 (@value{GDBP}) help status
1550 @c Line break in "show" line falsifies real output, but needed
1551 @c to fit in smallbook page size.
1552 info -- Generic command for showing things
1553 about the program being debugged
1554 show -- Generic command for showing things
1557 Type "help" followed by command name for full
1559 Command name abbreviations are allowed if unambiguous.
1563 @item help @var{command}
1564 With a command name as @code{help} argument, @value{GDBN} displays a
1565 short paragraph on how to use that command.
1568 @item apropos @var{args}
1569 The @code{apropos} command searches through all of the @value{GDBN}
1570 commands, and their documentation, for the regular expression specified in
1571 @var{args}. It prints out all matches found. For example:
1582 set symbol-reloading -- Set dynamic symbol table reloading
1583 multiple times in one run
1584 show symbol-reloading -- Show dynamic symbol table reloading
1585 multiple times in one run
1590 @item complete @var{args}
1591 The @code{complete @var{args}} command lists all the possible completions
1592 for the beginning of a command. Use @var{args} to specify the beginning of the
1593 command you want completed. For example:
1599 @noindent results in:
1610 @noindent This is intended for use by @sc{gnu} Emacs.
1613 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1614 and @code{show} to inquire about the state of your program, or the state
1615 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1616 manual introduces each of them in the appropriate context. The listings
1617 under @code{info} and under @code{show} in the Index point to
1618 all the sub-commands. @xref{Index}.
1623 @kindex i @r{(@code{info})}
1625 This command (abbreviated @code{i}) is for describing the state of your
1626 program. For example, you can list the arguments given to your program
1627 with @code{info args}, list the registers currently in use with @code{info
1628 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1629 You can get a complete list of the @code{info} sub-commands with
1630 @w{@code{help info}}.
1634 You can assign the result of an expression to an environment variable with
1635 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1636 @code{set prompt $}.
1640 In contrast to @code{info}, @code{show} is for describing the state of
1641 @value{GDBN} itself.
1642 You can change most of the things you can @code{show}, by using the
1643 related command @code{set}; for example, you can control what number
1644 system is used for displays with @code{set radix}, or simply inquire
1645 which is currently in use with @code{show radix}.
1648 To display all the settable parameters and their current
1649 values, you can use @code{show} with no arguments; you may also use
1650 @code{info set}. Both commands produce the same display.
1651 @c FIXME: "info set" violates the rule that "info" is for state of
1652 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1653 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1657 Here are three miscellaneous @code{show} subcommands, all of which are
1658 exceptional in lacking corresponding @code{set} commands:
1661 @kindex show version
1662 @cindex @value{GDBN} version number
1664 Show what version of @value{GDBN} is running. You should include this
1665 information in @value{GDBN} bug-reports. If multiple versions of
1666 @value{GDBN} are in use at your site, you may need to determine which
1667 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1668 commands are introduced, and old ones may wither away. Also, many
1669 system vendors ship variant versions of @value{GDBN}, and there are
1670 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1671 The version number is the same as the one announced when you start
1674 @kindex show copying
1675 @kindex info copying
1676 @cindex display @value{GDBN} copyright
1679 Display information about permission for copying @value{GDBN}.
1681 @kindex show warranty
1682 @kindex info warranty
1684 @itemx info warranty
1685 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1686 if your version of @value{GDBN} comes with one.
1691 @chapter Running Programs Under @value{GDBN}
1693 When you run a program under @value{GDBN}, you must first generate
1694 debugging information when you compile it.
1696 You may start @value{GDBN} with its arguments, if any, in an environment
1697 of your choice. If you are doing native debugging, you may redirect
1698 your program's input and output, debug an already running process, or
1699 kill a child process.
1702 * Compilation:: Compiling for debugging
1703 * Starting:: Starting your program
1704 * Arguments:: Your program's arguments
1705 * Environment:: Your program's environment
1707 * Working Directory:: Your program's working directory
1708 * Input/Output:: Your program's input and output
1709 * Attach:: Debugging an already-running process
1710 * Kill Process:: Killing the child process
1712 * Threads:: Debugging programs with multiple threads
1713 * Processes:: Debugging programs with multiple processes
1717 @section Compiling for debugging
1719 In order to debug a program effectively, you need to generate
1720 debugging information when you compile it. This debugging information
1721 is stored in the object file; it describes the data type of each
1722 variable or function and the correspondence between source line numbers
1723 and addresses in the executable code.
1725 To request debugging information, specify the @samp{-g} option when you run
1728 Programs that are to be shipped to your customers are compiled with
1729 optimizations, using the @samp{-O} compiler option. However, many
1730 compilers are unable to handle the @samp{-g} and @samp{-O} options
1731 together. Using those compilers, you cannot generate optimized
1732 executables containing debugging information.
1734 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1735 without @samp{-O}, making it possible to debug optimized code. We
1736 recommend that you @emph{always} use @samp{-g} whenever you compile a
1737 program. You may think your program is correct, but there is no sense
1738 in pushing your luck.
1740 @cindex optimized code, debugging
1741 @cindex debugging optimized code
1742 When you debug a program compiled with @samp{-g -O}, remember that the
1743 optimizer is rearranging your code; the debugger shows you what is
1744 really there. Do not be too surprised when the execution path does not
1745 exactly match your source file! An extreme example: if you define a
1746 variable, but never use it, @value{GDBN} never sees that
1747 variable---because the compiler optimizes it out of existence.
1749 Some things do not work as well with @samp{-g -O} as with just
1750 @samp{-g}, particularly on machines with instruction scheduling. If in
1751 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1752 please report it to us as a bug (including a test case!).
1753 @xref{Variables}, for more information about debugging optimized code.
1755 Older versions of the @sc{gnu} C compiler permitted a variant option
1756 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1757 format; if your @sc{gnu} C compiler has this option, do not use it.
1759 @value{GDBN} knows about preprocessor macros and can show you their
1760 expansion (@pxref{Macros}). Most compilers do not include information
1761 about preprocessor macros in the debugging information if you specify
1762 the @option{-g} flag alone, because this information is rather large.
1763 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1764 provides macro information if you specify the options
1765 @option{-gdwarf-2} and @option{-g3}; the former option requests
1766 debugging information in the Dwarf 2 format, and the latter requests
1767 ``extra information''. In the future, we hope to find more compact
1768 ways to represent macro information, so that it can be included with
1773 @section Starting your program
1779 @kindex r @r{(@code{run})}
1782 Use the @code{run} command to start your program under @value{GDBN}.
1783 You must first specify the program name (except on VxWorks) with an
1784 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1785 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1786 (@pxref{Files, ,Commands to specify files}).
1790 If you are running your program in an execution environment that
1791 supports processes, @code{run} creates an inferior process and makes
1792 that process run your program. (In environments without processes,
1793 @code{run} jumps to the start of your program.)
1795 The execution of a program is affected by certain information it
1796 receives from its superior. @value{GDBN} provides ways to specify this
1797 information, which you must do @emph{before} starting your program. (You
1798 can change it after starting your program, but such changes only affect
1799 your program the next time you start it.) This information may be
1800 divided into four categories:
1803 @item The @emph{arguments.}
1804 Specify the arguments to give your program as the arguments of the
1805 @code{run} command. If a shell is available on your target, the shell
1806 is used to pass the arguments, so that you may use normal conventions
1807 (such as wildcard expansion or variable substitution) in describing
1809 In Unix systems, you can control which shell is used with the
1810 @code{SHELL} environment variable.
1811 @xref{Arguments, ,Your program's arguments}.
1813 @item The @emph{environment.}
1814 Your program normally inherits its environment from @value{GDBN}, but you can
1815 use the @value{GDBN} commands @code{set environment} and @code{unset
1816 environment} to change parts of the environment that affect
1817 your program. @xref{Environment, ,Your program's environment}.
1819 @item The @emph{working directory.}
1820 Your program inherits its working directory from @value{GDBN}. You can set
1821 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1822 @xref{Working Directory, ,Your program's working directory}.
1824 @item The @emph{standard input and output.}
1825 Your program normally uses the same device for standard input and
1826 standard output as @value{GDBN} is using. You can redirect input and output
1827 in the @code{run} command line, or you can use the @code{tty} command to
1828 set a different device for your program.
1829 @xref{Input/Output, ,Your program's input and output}.
1832 @emph{Warning:} While input and output redirection work, you cannot use
1833 pipes to pass the output of the program you are debugging to another
1834 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1838 When you issue the @code{run} command, your program begins to execute
1839 immediately. @xref{Stopping, ,Stopping and continuing}, for discussion
1840 of how to arrange for your program to stop. Once your program has
1841 stopped, you may call functions in your program, using the @code{print}
1842 or @code{call} commands. @xref{Data, ,Examining Data}.
1844 If the modification time of your symbol file has changed since the last
1845 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1846 table, and reads it again. When it does this, @value{GDBN} tries to retain
1847 your current breakpoints.
1852 @cindex run to main procedure
1853 The name of the main procedure can vary from language to language.
1854 With C or C@t{++}, the main procedure name is always @code{main}, but
1855 other languages such as Ada do not require a specific name for their
1856 main procedure. The debugger provides a convenient way to start the
1857 execution of the program and to stop at the beginning of the main
1858 procedure, depending on the language used.
1860 The @samp{start} command does the equivalent of setting a temporary
1861 breakpoint at the beginning of the main procedure and then invoking
1862 the @samp{run} command.
1864 @cindex elaboration phase
1865 Some programs contain an @dfn{elaboration} phase where some startup code is
1866 executed before the main procedure is called. This depends on the
1867 languages used to write your program. In C@t{++}, for instance,
1868 constructors for static and global objects are executed before
1869 @code{main} is called. It is therefore possible that the debugger stops
1870 before reaching the main procedure. However, the temporary breakpoint
1871 will remain to halt execution.
1873 Specify the arguments to give to your program as arguments to the
1874 @samp{start} command. These arguments will be given verbatim to the
1875 underlying @samp{run} command. Note that the same arguments will be
1876 reused if no argument is provided during subsequent calls to
1877 @samp{start} or @samp{run}.
1879 It is sometimes necessary to debug the program during elaboration. In
1880 these cases, using the @code{start} command would stop the execution of
1881 your program too late, as the program would have already completed the
1882 elaboration phase. Under these circumstances, insert breakpoints in your
1883 elaboration code before running your program.
1887 @section Your program's arguments
1889 @cindex arguments (to your program)
1890 The arguments to your program can be specified by the arguments of the
1892 They are passed to a shell, which expands wildcard characters and
1893 performs redirection of I/O, and thence to your program. Your
1894 @code{SHELL} environment variable (if it exists) specifies what shell
1895 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1896 the default shell (@file{/bin/sh} on Unix).
1898 On non-Unix systems, the program is usually invoked directly by
1899 @value{GDBN}, which emulates I/O redirection via the appropriate system
1900 calls, and the wildcard characters are expanded by the startup code of
1901 the program, not by the shell.
1903 @code{run} with no arguments uses the same arguments used by the previous
1904 @code{run}, or those set by the @code{set args} command.
1909 Specify the arguments to be used the next time your program is run. If
1910 @code{set args} has no arguments, @code{run} executes your program
1911 with no arguments. Once you have run your program with arguments,
1912 using @code{set args} before the next @code{run} is the only way to run
1913 it again without arguments.
1917 Show the arguments to give your program when it is started.
1921 @section Your program's environment
1923 @cindex environment (of your program)
1924 The @dfn{environment} consists of a set of environment variables and
1925 their values. Environment variables conventionally record such things as
1926 your user name, your home directory, your terminal type, and your search
1927 path for programs to run. Usually you set up environment variables with
1928 the shell and they are inherited by all the other programs you run. When
1929 debugging, it can be useful to try running your program with a modified
1930 environment without having to start @value{GDBN} over again.
1934 @item path @var{directory}
1935 Add @var{directory} to the front of the @code{PATH} environment variable
1936 (the search path for executables) that will be passed to your program.
1937 The value of @code{PATH} used by @value{GDBN} does not change.
1938 You may specify several directory names, separated by whitespace or by a
1939 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1940 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1941 is moved to the front, so it is searched sooner.
1943 You can use the string @samp{$cwd} to refer to whatever is the current
1944 working directory at the time @value{GDBN} searches the path. If you
1945 use @samp{.} instead, it refers to the directory where you executed the
1946 @code{path} command. @value{GDBN} replaces @samp{.} in the
1947 @var{directory} argument (with the current path) before adding
1948 @var{directory} to the search path.
1949 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1950 @c document that, since repeating it would be a no-op.
1954 Display the list of search paths for executables (the @code{PATH}
1955 environment variable).
1957 @kindex show environment
1958 @item show environment @r{[}@var{varname}@r{]}
1959 Print the value of environment variable @var{varname} to be given to
1960 your program when it starts. If you do not supply @var{varname},
1961 print the names and values of all environment variables to be given to
1962 your program. You can abbreviate @code{environment} as @code{env}.
1964 @kindex set environment
1965 @item set environment @var{varname} @r{[}=@var{value}@r{]}
1966 Set environment variable @var{varname} to @var{value}. The value
1967 changes for your program only, not for @value{GDBN} itself. @var{value} may
1968 be any string; the values of environment variables are just strings, and
1969 any interpretation is supplied by your program itself. The @var{value}
1970 parameter is optional; if it is eliminated, the variable is set to a
1972 @c "any string" here does not include leading, trailing
1973 @c blanks. Gnu asks: does anyone care?
1975 For example, this command:
1982 tells the debugged program, when subsequently run, that its user is named
1983 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
1984 are not actually required.)
1986 @kindex unset environment
1987 @item unset environment @var{varname}
1988 Remove variable @var{varname} from the environment to be passed to your
1989 program. This is different from @samp{set env @var{varname} =};
1990 @code{unset environment} removes the variable from the environment,
1991 rather than assigning it an empty value.
1994 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
1996 by your @code{SHELL} environment variable if it exists (or
1997 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
1998 that runs an initialization file---such as @file{.cshrc} for C-shell, or
1999 @file{.bashrc} for BASH---any variables you set in that file affect
2000 your program. You may wish to move setting of environment variables to
2001 files that are only run when you sign on, such as @file{.login} or
2004 @node Working Directory
2005 @section Your program's working directory
2007 @cindex working directory (of your program)
2008 Each time you start your program with @code{run}, it inherits its
2009 working directory from the current working directory of @value{GDBN}.
2010 The @value{GDBN} working directory is initially whatever it inherited
2011 from its parent process (typically the shell), but you can specify a new
2012 working directory in @value{GDBN} with the @code{cd} command.
2014 The @value{GDBN} working directory also serves as a default for the commands
2015 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2020 @cindex change working directory
2021 @item cd @var{directory}
2022 Set the @value{GDBN} working directory to @var{directory}.
2026 Print the @value{GDBN} working directory.
2029 It is generally impossible to find the current working directory of
2030 the process being debugged (since a program can change its directory
2031 during its run). If you work on a system where @value{GDBN} is
2032 configured with the @file{/proc} support, you can use the @code{info
2033 proc} command (@pxref{SVR4 Process Information}) to find out the
2034 current working directory of the debuggee.
2037 @section Your program's input and output
2042 By default, the program you run under @value{GDBN} does input and output to
2043 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2044 to its own terminal modes to interact with you, but it records the terminal
2045 modes your program was using and switches back to them when you continue
2046 running your program.
2049 @kindex info terminal
2051 Displays information recorded by @value{GDBN} about the terminal modes your
2055 You can redirect your program's input and/or output using shell
2056 redirection with the @code{run} command. For example,
2063 starts your program, diverting its output to the file @file{outfile}.
2066 @cindex controlling terminal
2067 Another way to specify where your program should do input and output is
2068 with the @code{tty} command. This command accepts a file name as
2069 argument, and causes this file to be the default for future @code{run}
2070 commands. It also resets the controlling terminal for the child
2071 process, for future @code{run} commands. For example,
2078 directs that processes started with subsequent @code{run} commands
2079 default to do input and output on the terminal @file{/dev/ttyb} and have
2080 that as their controlling terminal.
2082 An explicit redirection in @code{run} overrides the @code{tty} command's
2083 effect on the input/output device, but not its effect on the controlling
2086 When you use the @code{tty} command or redirect input in the @code{run}
2087 command, only the input @emph{for your program} is affected. The input
2088 for @value{GDBN} still comes from your terminal.
2091 @section Debugging an already-running process
2096 @item attach @var{process-id}
2097 This command attaches to a running process---one that was started
2098 outside @value{GDBN}. (@code{info files} shows your active
2099 targets.) The command takes as argument a process ID. The usual way to
2100 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2101 or with the @samp{jobs -l} shell command.
2103 @code{attach} does not repeat if you press @key{RET} a second time after
2104 executing the command.
2107 To use @code{attach}, your program must be running in an environment
2108 which supports processes; for example, @code{attach} does not work for
2109 programs on bare-board targets that lack an operating system. You must
2110 also have permission to send the process a signal.
2112 When you use @code{attach}, the debugger finds the program running in
2113 the process first by looking in the current working directory, then (if
2114 the program is not found) by using the source file search path
2115 (@pxref{Source Path, ,Specifying source directories}). You can also use
2116 the @code{file} command to load the program. @xref{Files, ,Commands to
2119 The first thing @value{GDBN} does after arranging to debug the specified
2120 process is to stop it. You can examine and modify an attached process
2121 with all the @value{GDBN} commands that are ordinarily available when
2122 you start processes with @code{run}. You can insert breakpoints; you
2123 can step and continue; you can modify storage. If you would rather the
2124 process continue running, you may use the @code{continue} command after
2125 attaching @value{GDBN} to the process.
2130 When you have finished debugging the attached process, you can use the
2131 @code{detach} command to release it from @value{GDBN} control. Detaching
2132 the process continues its execution. After the @code{detach} command,
2133 that process and @value{GDBN} become completely independent once more, and you
2134 are ready to @code{attach} another process or start one with @code{run}.
2135 @code{detach} does not repeat if you press @key{RET} again after
2136 executing the command.
2139 If you exit @value{GDBN} or use the @code{run} command while you have an
2140 attached process, you kill that process. By default, @value{GDBN} asks
2141 for confirmation if you try to do either of these things; you can
2142 control whether or not you need to confirm by using the @code{set
2143 confirm} command (@pxref{Messages/Warnings, ,Optional warnings and
2147 @section Killing the child process
2152 Kill the child process in which your program is running under @value{GDBN}.
2155 This command is useful if you wish to debug a core dump instead of a
2156 running process. @value{GDBN} ignores any core dump file while your program
2159 On some operating systems, a program cannot be executed outside @value{GDBN}
2160 while you have breakpoints set on it inside @value{GDBN}. You can use the
2161 @code{kill} command in this situation to permit running your program
2162 outside the debugger.
2164 The @code{kill} command is also useful if you wish to recompile and
2165 relink your program, since on many systems it is impossible to modify an
2166 executable file while it is running in a process. In this case, when you
2167 next type @code{run}, @value{GDBN} notices that the file has changed, and
2168 reads the symbol table again (while trying to preserve your current
2169 breakpoint settings).
2172 @section Debugging programs with multiple threads
2174 @cindex threads of execution
2175 @cindex multiple threads
2176 @cindex switching threads
2177 In some operating systems, such as HP-UX and Solaris, a single program
2178 may have more than one @dfn{thread} of execution. The precise semantics
2179 of threads differ from one operating system to another, but in general
2180 the threads of a single program are akin to multiple processes---except
2181 that they share one address space (that is, they can all examine and
2182 modify the same variables). On the other hand, each thread has its own
2183 registers and execution stack, and perhaps private memory.
2185 @value{GDBN} provides these facilities for debugging multi-thread
2189 @item automatic notification of new threads
2190 @item @samp{thread @var{threadno}}, a command to switch among threads
2191 @item @samp{info threads}, a command to inquire about existing threads
2192 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2193 a command to apply a command to a list of threads
2194 @item thread-specific breakpoints
2198 @emph{Warning:} These facilities are not yet available on every
2199 @value{GDBN} configuration where the operating system supports threads.
2200 If your @value{GDBN} does not support threads, these commands have no
2201 effect. For example, a system without thread support shows no output
2202 from @samp{info threads}, and always rejects the @code{thread} command,
2206 (@value{GDBP}) info threads
2207 (@value{GDBP}) thread 1
2208 Thread ID 1 not known. Use the "info threads" command to
2209 see the IDs of currently known threads.
2211 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2212 @c doesn't support threads"?
2215 @cindex focus of debugging
2216 @cindex current thread
2217 The @value{GDBN} thread debugging facility allows you to observe all
2218 threads while your program runs---but whenever @value{GDBN} takes
2219 control, one thread in particular is always the focus of debugging.
2220 This thread is called the @dfn{current thread}. Debugging commands show
2221 program information from the perspective of the current thread.
2223 @cindex @code{New} @var{systag} message
2224 @cindex thread identifier (system)
2225 @c FIXME-implementors!! It would be more helpful if the [New...] message
2226 @c included GDB's numeric thread handle, so you could just go to that
2227 @c thread without first checking `info threads'.
2228 Whenever @value{GDBN} detects a new thread in your program, it displays
2229 the target system's identification for the thread with a message in the
2230 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2231 whose form varies depending on the particular system. For example, on
2232 LynxOS, you might see
2235 [New process 35 thread 27]
2239 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2240 the @var{systag} is simply something like @samp{process 368}, with no
2243 @c FIXME!! (1) Does the [New...] message appear even for the very first
2244 @c thread of a program, or does it only appear for the
2245 @c second---i.e.@: when it becomes obvious we have a multithread
2247 @c (2) *Is* there necessarily a first thread always? Or do some
2248 @c multithread systems permit starting a program with multiple
2249 @c threads ab initio?
2251 @cindex thread number
2252 @cindex thread identifier (GDB)
2253 For debugging purposes, @value{GDBN} associates its own thread
2254 number---always a single integer---with each thread in your program.
2257 @kindex info threads
2259 Display a summary of all threads currently in your
2260 program. @value{GDBN} displays for each thread (in this order):
2264 the thread number assigned by @value{GDBN}
2267 the target system's thread identifier (@var{systag})
2270 the current stack frame summary for that thread
2274 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2275 indicates the current thread.
2279 @c end table here to get a little more width for example
2282 (@value{GDBP}) info threads
2283 3 process 35 thread 27 0x34e5 in sigpause ()
2284 2 process 35 thread 23 0x34e5 in sigpause ()
2285 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2291 @cindex debugging multithreaded programs (on HP-UX)
2292 @cindex thread identifier (GDB), on HP-UX
2293 For debugging purposes, @value{GDBN} associates its own thread
2294 number---a small integer assigned in thread-creation order---with each
2295 thread in your program.
2297 @cindex @code{New} @var{systag} message, on HP-UX
2298 @cindex thread identifier (system), on HP-UX
2299 @c FIXME-implementors!! It would be more helpful if the [New...] message
2300 @c included GDB's numeric thread handle, so you could just go to that
2301 @c thread without first checking `info threads'.
2302 Whenever @value{GDBN} detects a new thread in your program, it displays
2303 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2304 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2305 whose form varies depending on the particular system. For example, on
2309 [New thread 2 (system thread 26594)]
2313 when @value{GDBN} notices a new thread.
2316 @kindex info threads (HP-UX)
2318 Display a summary of all threads currently in your
2319 program. @value{GDBN} displays for each thread (in this order):
2322 @item the thread number assigned by @value{GDBN}
2324 @item the target system's thread identifier (@var{systag})
2326 @item the current stack frame summary for that thread
2330 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2331 indicates the current thread.
2335 @c end table here to get a little more width for example
2338 (@value{GDBP}) info threads
2339 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2341 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2342 from /usr/lib/libc.2
2343 1 system thread 27905 0x7b003498 in _brk () \@*
2344 from /usr/lib/libc.2
2347 On Solaris, you can display more information about user threads with a
2348 Solaris-specific command:
2351 @item maint info sol-threads
2352 @kindex maint info sol-threads
2353 @cindex thread info (Solaris)
2354 Display info on Solaris user threads.
2358 @kindex thread @var{threadno}
2359 @item thread @var{threadno}
2360 Make thread number @var{threadno} the current thread. The command
2361 argument @var{threadno} is the internal @value{GDBN} thread number, as
2362 shown in the first field of the @samp{info threads} display.
2363 @value{GDBN} responds by displaying the system identifier of the thread
2364 you selected, and its current stack frame summary:
2367 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2368 (@value{GDBP}) thread 2
2369 [Switching to process 35 thread 23]
2370 0x34e5 in sigpause ()
2374 As with the @samp{[New @dots{}]} message, the form of the text after
2375 @samp{Switching to} depends on your system's conventions for identifying
2378 @kindex thread apply
2379 @item thread apply [@var{threadno}] [@var{all}] @var{args}
2380 The @code{thread apply} command allows you to apply a command to one or
2381 more threads. Specify the numbers of the threads that you want affected
2382 with the command argument @var{threadno}. @var{threadno} is the internal
2383 @value{GDBN} thread number, as shown in the first field of the @samp{info
2384 threads} display. To apply a command to all threads, use
2385 @code{thread apply all} @var{args}.
2388 @cindex automatic thread selection
2389 @cindex switching threads automatically
2390 @cindex threads, automatic switching
2391 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2392 signal, it automatically selects the thread where that breakpoint or
2393 signal happened. @value{GDBN} alerts you to the context switch with a
2394 message of the form @samp{[Switching to @var{systag}]} to identify the
2397 @xref{Thread Stops,,Stopping and starting multi-thread programs}, for
2398 more information about how @value{GDBN} behaves when you stop and start
2399 programs with multiple threads.
2401 @xref{Set Watchpoints,,Setting watchpoints}, for information about
2402 watchpoints in programs with multiple threads.
2405 @section Debugging programs with multiple processes
2407 @cindex fork, debugging programs which call
2408 @cindex multiple processes
2409 @cindex processes, multiple
2410 On most systems, @value{GDBN} has no special support for debugging
2411 programs which create additional processes using the @code{fork}
2412 function. When a program forks, @value{GDBN} will continue to debug the
2413 parent process and the child process will run unimpeded. If you have
2414 set a breakpoint in any code which the child then executes, the child
2415 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2416 will cause it to terminate.
2418 However, if you want to debug the child process there is a workaround
2419 which isn't too painful. Put a call to @code{sleep} in the code which
2420 the child process executes after the fork. It may be useful to sleep
2421 only if a certain environment variable is set, or a certain file exists,
2422 so that the delay need not occur when you don't want to run @value{GDBN}
2423 on the child. While the child is sleeping, use the @code{ps} program to
2424 get its process ID. Then tell @value{GDBN} (a new invocation of
2425 @value{GDBN} if you are also debugging the parent process) to attach to
2426 the child process (@pxref{Attach}). From that point on you can debug
2427 the child process just like any other process which you attached to.
2429 On some systems, @value{GDBN} provides support for debugging programs that
2430 create additional processes using the @code{fork} or @code{vfork} functions.
2431 Currently, the only platforms with this feature are HP-UX (11.x and later
2432 only?) and GNU/Linux (kernel version 2.5.60 and later).
2434 By default, when a program forks, @value{GDBN} will continue to debug
2435 the parent process and the child process will run unimpeded.
2437 If you want to follow the child process instead of the parent process,
2438 use the command @w{@code{set follow-fork-mode}}.
2441 @kindex set follow-fork-mode
2442 @item set follow-fork-mode @var{mode}
2443 Set the debugger response to a program call of @code{fork} or
2444 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2445 process. The @var{mode} argument can be:
2449 The original process is debugged after a fork. The child process runs
2450 unimpeded. This is the default.
2453 The new process is debugged after a fork. The parent process runs
2458 @kindex show follow-fork-mode
2459 @item show follow-fork-mode
2460 Display the current debugger response to a @code{fork} or @code{vfork} call.
2463 If you ask to debug a child process and a @code{vfork} is followed by an
2464 @code{exec}, @value{GDBN} executes the new target up to the first
2465 breakpoint in the new target. If you have a breakpoint set on
2466 @code{main} in your original program, the breakpoint will also be set on
2467 the child process's @code{main}.
2469 When a child process is spawned by @code{vfork}, you cannot debug the
2470 child or parent until an @code{exec} call completes.
2472 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2473 call executes, the new target restarts. To restart the parent process,
2474 use the @code{file} command with the parent executable name as its
2477 You can use the @code{catch} command to make @value{GDBN} stop whenever
2478 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2479 Catchpoints, ,Setting catchpoints}.
2482 @chapter Stopping and Continuing
2484 The principal purposes of using a debugger are so that you can stop your
2485 program before it terminates; or so that, if your program runs into
2486 trouble, you can investigate and find out why.
2488 Inside @value{GDBN}, your program may stop for any of several reasons,
2489 such as a signal, a breakpoint, or reaching a new line after a
2490 @value{GDBN} command such as @code{step}. You may then examine and
2491 change variables, set new breakpoints or remove old ones, and then
2492 continue execution. Usually, the messages shown by @value{GDBN} provide
2493 ample explanation of the status of your program---but you can also
2494 explicitly request this information at any time.
2497 @kindex info program
2499 Display information about the status of your program: whether it is
2500 running or not, what process it is, and why it stopped.
2504 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2505 * Continuing and Stepping:: Resuming execution
2507 * Thread Stops:: Stopping and starting multi-thread programs
2511 @section Breakpoints, watchpoints, and catchpoints
2514 A @dfn{breakpoint} makes your program stop whenever a certain point in
2515 the program is reached. For each breakpoint, you can add conditions to
2516 control in finer detail whether your program stops. You can set
2517 breakpoints with the @code{break} command and its variants (@pxref{Set
2518 Breaks, ,Setting breakpoints}), to specify the place where your program
2519 should stop by line number, function name or exact address in the
2522 On some systems, you can set breakpoints in shared libraries before
2523 the executable is run. There is a minor limitation on HP-UX systems:
2524 you must wait until the executable is run in order to set breakpoints
2525 in shared library routines that are not called directly by the program
2526 (for example, routines that are arguments in a @code{pthread_create}
2530 @cindex memory tracing
2531 @cindex breakpoint on memory address
2532 @cindex breakpoint on variable modification
2533 A @dfn{watchpoint} is a special breakpoint that stops your program
2534 when the value of an expression changes. You must use a different
2535 command to set watchpoints (@pxref{Set Watchpoints, ,Setting
2536 watchpoints}), but aside from that, you can manage a watchpoint like
2537 any other breakpoint: you enable, disable, and delete both breakpoints
2538 and watchpoints using the same commands.
2540 You can arrange to have values from your program displayed automatically
2541 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2545 @cindex breakpoint on events
2546 A @dfn{catchpoint} is another special breakpoint that stops your program
2547 when a certain kind of event occurs, such as the throwing of a C@t{++}
2548 exception or the loading of a library. As with watchpoints, you use a
2549 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2550 catchpoints}), but aside from that, you can manage a catchpoint like any
2551 other breakpoint. (To stop when your program receives a signal, use the
2552 @code{handle} command; see @ref{Signals, ,Signals}.)
2554 @cindex breakpoint numbers
2555 @cindex numbers for breakpoints
2556 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2557 catchpoint when you create it; these numbers are successive integers
2558 starting with one. In many of the commands for controlling various
2559 features of breakpoints you use the breakpoint number to say which
2560 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2561 @dfn{disabled}; if disabled, it has no effect on your program until you
2564 @cindex breakpoint ranges
2565 @cindex ranges of breakpoints
2566 Some @value{GDBN} commands accept a range of breakpoints on which to
2567 operate. A breakpoint range is either a single breakpoint number, like
2568 @samp{5}, or two such numbers, in increasing order, separated by a
2569 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2570 all breakpoint in that range are operated on.
2573 * Set Breaks:: Setting breakpoints
2574 * Set Watchpoints:: Setting watchpoints
2575 * Set Catchpoints:: Setting catchpoints
2576 * Delete Breaks:: Deleting breakpoints
2577 * Disabling:: Disabling breakpoints
2578 * Conditions:: Break conditions
2579 * Break Commands:: Breakpoint command lists
2580 * Breakpoint Menus:: Breakpoint menus
2581 * Error in Breakpoints:: ``Cannot insert breakpoints''
2582 * Breakpoint related warnings:: ``Breakpoint address adjusted...''
2586 @subsection Setting breakpoints
2588 @c FIXME LMB what does GDB do if no code on line of breakpt?
2589 @c consider in particular declaration with/without initialization.
2591 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2594 @kindex b @r{(@code{break})}
2595 @vindex $bpnum@r{, convenience variable}
2596 @cindex latest breakpoint
2597 Breakpoints are set with the @code{break} command (abbreviated
2598 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2599 number of the breakpoint you've set most recently; see @ref{Convenience
2600 Vars,, Convenience variables}, for a discussion of what you can do with
2601 convenience variables.
2603 You have several ways to say where the breakpoint should go.
2606 @item break @var{function}
2607 Set a breakpoint at entry to function @var{function}.
2608 When using source languages that permit overloading of symbols, such as
2609 C@t{++}, @var{function} may refer to more than one possible place to break.
2610 @xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
2612 @item break +@var{offset}
2613 @itemx break -@var{offset}
2614 Set a breakpoint some number of lines forward or back from the position
2615 at which execution stopped in the currently selected @dfn{stack frame}.
2616 (@xref{Frames, ,Frames}, for a description of stack frames.)
2618 @item break @var{linenum}
2619 Set a breakpoint at line @var{linenum} in the current source file.
2620 The current source file is the last file whose source text was printed.
2621 The breakpoint will stop your program just before it executes any of the
2624 @item break @var{filename}:@var{linenum}
2625 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2627 @item break @var{filename}:@var{function}
2628 Set a breakpoint at entry to function @var{function} found in file
2629 @var{filename}. Specifying a file name as well as a function name is
2630 superfluous except when multiple files contain similarly named
2633 @item break *@var{address}
2634 Set a breakpoint at address @var{address}. You can use this to set
2635 breakpoints in parts of your program which do not have debugging
2636 information or source files.
2639 When called without any arguments, @code{break} sets a breakpoint at
2640 the next instruction to be executed in the selected stack frame
2641 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2642 innermost, this makes your program stop as soon as control
2643 returns to that frame. This is similar to the effect of a
2644 @code{finish} command in the frame inside the selected frame---except
2645 that @code{finish} does not leave an active breakpoint. If you use
2646 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2647 the next time it reaches the current location; this may be useful
2650 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2651 least one instruction has been executed. If it did not do this, you
2652 would be unable to proceed past a breakpoint without first disabling the
2653 breakpoint. This rule applies whether or not the breakpoint already
2654 existed when your program stopped.
2656 @item break @dots{} if @var{cond}
2657 Set a breakpoint with condition @var{cond}; evaluate the expression
2658 @var{cond} each time the breakpoint is reached, and stop only if the
2659 value is nonzero---that is, if @var{cond} evaluates as true.
2660 @samp{@dots{}} stands for one of the possible arguments described
2661 above (or no argument) specifying where to break. @xref{Conditions,
2662 ,Break conditions}, for more information on breakpoint conditions.
2665 @item tbreak @var{args}
2666 Set a breakpoint enabled only for one stop. @var{args} are the
2667 same as for the @code{break} command, and the breakpoint is set in the same
2668 way, but the breakpoint is automatically deleted after the first time your
2669 program stops there. @xref{Disabling, ,Disabling breakpoints}.
2672 @cindex hardware breakpoints
2673 @item hbreak @var{args}
2674 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2675 @code{break} command and the breakpoint is set in the same way, but the
2676 breakpoint requires hardware support and some target hardware may not
2677 have this support. The main purpose of this is EPROM/ROM code
2678 debugging, so you can set a breakpoint at an instruction without
2679 changing the instruction. This can be used with the new trap-generation
2680 provided by SPARClite DSU and most x86-based targets. These targets
2681 will generate traps when a program accesses some data or instruction
2682 address that is assigned to the debug registers. However the hardware
2683 breakpoint registers can take a limited number of breakpoints. For
2684 example, on the DSU, only two data breakpoints can be set at a time, and
2685 @value{GDBN} will reject this command if more than two are used. Delete
2686 or disable unused hardware breakpoints before setting new ones
2687 (@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}.
2688 For remote targets, you can restrict the number of hardware
2689 breakpoints @value{GDBN} will use, see @ref{set remote
2690 hardware-breakpoint-limit}.
2694 @item thbreak @var{args}
2695 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2696 are the same as for the @code{hbreak} command and the breakpoint is set in
2697 the same way. However, like the @code{tbreak} command,
2698 the breakpoint is automatically deleted after the
2699 first time your program stops there. Also, like the @code{hbreak}
2700 command, the breakpoint requires hardware support and some target hardware
2701 may not have this support. @xref{Disabling, ,Disabling breakpoints}.
2702 See also @ref{Conditions, ,Break conditions}.
2705 @cindex regular expression
2706 @cindex breakpoints in functions matching a regexp
2707 @cindex set breakpoints in many functions
2708 @item rbreak @var{regex}
2709 Set breakpoints on all functions matching the regular expression
2710 @var{regex}. This command sets an unconditional breakpoint on all
2711 matches, printing a list of all breakpoints it set. Once these
2712 breakpoints are set, they are treated just like the breakpoints set with
2713 the @code{break} command. You can delete them, disable them, or make
2714 them conditional the same way as any other breakpoint.
2716 The syntax of the regular expression is the standard one used with tools
2717 like @file{grep}. Note that this is different from the syntax used by
2718 shells, so for instance @code{foo*} matches all functions that include
2719 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2720 @code{.*} leading and trailing the regular expression you supply, so to
2721 match only functions that begin with @code{foo}, use @code{^foo}.
2723 @cindex non-member C@t{++} functions, set breakpoint in
2724 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2725 breakpoints on overloaded functions that are not members of any special
2728 @cindex set breakpoints on all functions
2729 The @code{rbreak} command can be used to set breakpoints in
2730 @strong{all} the functions in a program, like this:
2733 (@value{GDBP}) rbreak .
2736 @kindex info breakpoints
2737 @cindex @code{$_} and @code{info breakpoints}
2738 @item info breakpoints @r{[}@var{n}@r{]}
2739 @itemx info break @r{[}@var{n}@r{]}
2740 @itemx info watchpoints @r{[}@var{n}@r{]}
2741 Print a table of all breakpoints, watchpoints, and catchpoints set and
2742 not deleted, with the following columns for each breakpoint:
2745 @item Breakpoint Numbers
2747 Breakpoint, watchpoint, or catchpoint.
2749 Whether the breakpoint is marked to be disabled or deleted when hit.
2750 @item Enabled or Disabled
2751 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2752 that are not enabled.
2754 Where the breakpoint is in your program, as a memory address. If the
2755 breakpoint is pending (see below for details) on a future load of a shared library, the address
2756 will be listed as @samp{<PENDING>}.
2758 Where the breakpoint is in the source for your program, as a file and
2759 line number. For a pending breakpoint, the original string passed to
2760 the breakpoint command will be listed as it cannot be resolved until
2761 the appropriate shared library is loaded in the future.
2765 If a breakpoint is conditional, @code{info break} shows the condition on
2766 the line following the affected breakpoint; breakpoint commands, if any,
2767 are listed after that. A pending breakpoint is allowed to have a condition
2768 specified for it. The condition is not parsed for validity until a shared
2769 library is loaded that allows the pending breakpoint to resolve to a
2773 @code{info break} with a breakpoint
2774 number @var{n} as argument lists only that breakpoint. The
2775 convenience variable @code{$_} and the default examining-address for
2776 the @code{x} command are set to the address of the last breakpoint
2777 listed (@pxref{Memory, ,Examining memory}).
2780 @code{info break} displays a count of the number of times the breakpoint
2781 has been hit. This is especially useful in conjunction with the
2782 @code{ignore} command. You can ignore a large number of breakpoint
2783 hits, look at the breakpoint info to see how many times the breakpoint
2784 was hit, and then run again, ignoring one less than that number. This
2785 will get you quickly to the last hit of that breakpoint.
2788 @value{GDBN} allows you to set any number of breakpoints at the same place in
2789 your program. There is nothing silly or meaningless about this. When
2790 the breakpoints are conditional, this is even useful
2791 (@pxref{Conditions, ,Break conditions}).
2793 @cindex pending breakpoints
2794 If a specified breakpoint location cannot be found, it may be due to the fact
2795 that the location is in a shared library that is yet to be loaded. In such
2796 a case, you may want @value{GDBN} to create a special breakpoint (known as
2797 a @dfn{pending breakpoint}) that
2798 attempts to resolve itself in the future when an appropriate shared library
2801 Pending breakpoints are useful to set at the start of your
2802 @value{GDBN} session for locations that you know will be dynamically loaded
2803 later by the program being debugged. When shared libraries are loaded,
2804 a check is made to see if the load resolves any pending breakpoint locations.
2805 If a pending breakpoint location gets resolved,
2806 a regular breakpoint is created and the original pending breakpoint is removed.
2808 @value{GDBN} provides some additional commands for controlling pending
2811 @kindex set breakpoint pending
2812 @kindex show breakpoint pending
2814 @item set breakpoint pending auto
2815 This is the default behavior. When @value{GDBN} cannot find the breakpoint
2816 location, it queries you whether a pending breakpoint should be created.
2818 @item set breakpoint pending on
2819 This indicates that an unrecognized breakpoint location should automatically
2820 result in a pending breakpoint being created.
2822 @item set breakpoint pending off
2823 This indicates that pending breakpoints are not to be created. Any
2824 unrecognized breakpoint location results in an error. This setting does
2825 not affect any pending breakpoints previously created.
2827 @item show breakpoint pending
2828 Show the current behavior setting for creating pending breakpoints.
2831 @cindex operations allowed on pending breakpoints
2832 Normal breakpoint operations apply to pending breakpoints as well. You may
2833 specify a condition for a pending breakpoint and/or commands to run when the
2834 breakpoint is reached. You can also enable or disable
2835 the pending breakpoint. When you specify a condition for a pending breakpoint,
2836 the parsing of the condition will be deferred until the point where the
2837 pending breakpoint location is resolved. Disabling a pending breakpoint
2838 tells @value{GDBN} to not attempt to resolve the breakpoint on any subsequent
2839 shared library load. When a pending breakpoint is re-enabled,
2840 @value{GDBN} checks to see if the location is already resolved.
2841 This is done because any number of shared library loads could have
2842 occurred since the time the breakpoint was disabled and one or more
2843 of these loads could resolve the location.
2845 @cindex negative breakpoint numbers
2846 @cindex internal @value{GDBN} breakpoints
2847 @value{GDBN} itself sometimes sets breakpoints in your program for
2848 special purposes, such as proper handling of @code{longjmp} (in C
2849 programs). These internal breakpoints are assigned negative numbers,
2850 starting with @code{-1}; @samp{info breakpoints} does not display them.
2851 You can see these breakpoints with the @value{GDBN} maintenance command
2852 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
2855 @node Set Watchpoints
2856 @subsection Setting watchpoints
2858 @cindex setting watchpoints
2859 You can use a watchpoint to stop execution whenever the value of an
2860 expression changes, without having to predict a particular place where
2863 @cindex software watchpoints
2864 @cindex hardware watchpoints
2865 Depending on your system, watchpoints may be implemented in software or
2866 hardware. @value{GDBN} does software watchpointing by single-stepping your
2867 program and testing the variable's value each time, which is hundreds of
2868 times slower than normal execution. (But this may still be worth it, to
2869 catch errors where you have no clue what part of your program is the
2872 On some systems, such as HP-UX, @sc{gnu}/Linux and most other
2873 x86-based targets, @value{GDBN} includes support for hardware
2874 watchpoints, which do not slow down the running of your program.
2878 @item watch @var{expr}
2879 Set a watchpoint for an expression. @value{GDBN} will break when @var{expr}
2880 is written into by the program and its value changes.
2883 @item rwatch @var{expr}
2884 Set a watchpoint that will break when the value of @var{expr} is read
2888 @item awatch @var{expr}
2889 Set a watchpoint that will break when @var{expr} is either read from
2890 or written into by the program.
2892 @kindex info watchpoints
2893 @item info watchpoints
2894 This command prints a list of watchpoints, breakpoints, and catchpoints;
2895 it is the same as @code{info break} (@pxref{Set Breaks}).
2898 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
2899 watchpoints execute very quickly, and the debugger reports a change in
2900 value at the exact instruction where the change occurs. If @value{GDBN}
2901 cannot set a hardware watchpoint, it sets a software watchpoint, which
2902 executes more slowly and reports the change in value at the next
2903 @emph{statement}, not the instruction, after the change occurs.
2905 @vindex can-use-hw-watchpoints
2906 @cindex use only software watchpoints
2907 You can force @value{GDBN} to use only software watchpoints with the
2908 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
2909 zero, @value{GDBN} will never try to use hardware watchpoints, even if
2910 the underlying system supports them. (Note that hardware-assisted
2911 watchpoints that were set @emph{before} setting
2912 @code{can-use-hw-watchpoints} to zero will still use the hardware
2913 mechanism of watching expressiion values.)
2916 @item set can-use-hw-watchpoints
2917 @kindex set can-use-hw-watchpoints
2918 Set whether or not to use hardware watchpoints.
2920 @item show can-use-hw-watchpoints
2921 @kindex show can-use-hw-watchpoints
2922 Show the current mode of using hardware watchpoints.
2925 For remote targets, you can restrict the number of hardware
2926 watchpoints @value{GDBN} will use, see @ref{set remote
2927 hardware-breakpoint-limit}.
2929 When you issue the @code{watch} command, @value{GDBN} reports
2932 Hardware watchpoint @var{num}: @var{expr}
2936 if it was able to set a hardware watchpoint.
2938 Currently, the @code{awatch} and @code{rwatch} commands can only set
2939 hardware watchpoints, because accesses to data that don't change the
2940 value of the watched expression cannot be detected without examining
2941 every instruction as it is being executed, and @value{GDBN} does not do
2942 that currently. If @value{GDBN} finds that it is unable to set a
2943 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
2944 will print a message like this:
2947 Expression cannot be implemented with read/access watchpoint.
2950 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
2951 data type of the watched expression is wider than what a hardware
2952 watchpoint on the target machine can handle. For example, some systems
2953 can only watch regions that are up to 4 bytes wide; on such systems you
2954 cannot set hardware watchpoints for an expression that yields a
2955 double-precision floating-point number (which is typically 8 bytes
2956 wide). As a work-around, it might be possible to break the large region
2957 into a series of smaller ones and watch them with separate watchpoints.
2959 If you set too many hardware watchpoints, @value{GDBN} might be unable
2960 to insert all of them when you resume the execution of your program.
2961 Since the precise number of active watchpoints is unknown until such
2962 time as the program is about to be resumed, @value{GDBN} might not be
2963 able to warn you about this when you set the watchpoints, and the
2964 warning will be printed only when the program is resumed:
2967 Hardware watchpoint @var{num}: Could not insert watchpoint
2971 If this happens, delete or disable some of the watchpoints.
2973 The SPARClite DSU will generate traps when a program accesses some data
2974 or instruction address that is assigned to the debug registers. For the
2975 data addresses, DSU facilitates the @code{watch} command. However the
2976 hardware breakpoint registers can only take two data watchpoints, and
2977 both watchpoints must be the same kind. For example, you can set two
2978 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
2979 @strong{or} two with @code{awatch} commands, but you cannot set one
2980 watchpoint with one command and the other with a different command.
2981 @value{GDBN} will reject the command if you try to mix watchpoints.
2982 Delete or disable unused watchpoint commands before setting new ones.
2984 If you call a function interactively using @code{print} or @code{call},
2985 any watchpoints you have set will be inactive until @value{GDBN} reaches another
2986 kind of breakpoint or the call completes.
2988 @value{GDBN} automatically deletes watchpoints that watch local
2989 (automatic) variables, or expressions that involve such variables, when
2990 they go out of scope, that is, when the execution leaves the block in
2991 which these variables were defined. In particular, when the program
2992 being debugged terminates, @emph{all} local variables go out of scope,
2993 and so only watchpoints that watch global variables remain set. If you
2994 rerun the program, you will need to set all such watchpoints again. One
2995 way of doing that would be to set a code breakpoint at the entry to the
2996 @code{main} function and when it breaks, set all the watchpoints.
2999 @cindex watchpoints and threads
3000 @cindex threads and watchpoints
3001 @emph{Warning:} In multi-thread programs, watchpoints have only limited
3002 usefulness. With the current watchpoint implementation, @value{GDBN}
3003 can only watch the value of an expression @emph{in a single thread}. If
3004 you are confident that the expression can only change due to the current
3005 thread's activity (and if you are also confident that no other thread
3006 can become current), then you can use watchpoints as usual. However,
3007 @value{GDBN} may not notice when a non-current thread's activity changes
3010 @c FIXME: this is almost identical to the previous paragraph.
3011 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
3012 have only limited usefulness. If @value{GDBN} creates a software
3013 watchpoint, it can only watch the value of an expression @emph{in a
3014 single thread}. If you are confident that the expression can only
3015 change due to the current thread's activity (and if you are also
3016 confident that no other thread can become current), then you can use
3017 software watchpoints as usual. However, @value{GDBN} may not notice
3018 when a non-current thread's activity changes the expression. (Hardware
3019 watchpoints, in contrast, watch an expression in all threads.)
3022 @xref{set remote hardware-watchpoint-limit}.
3024 @node Set Catchpoints
3025 @subsection Setting catchpoints
3026 @cindex catchpoints, setting
3027 @cindex exception handlers
3028 @cindex event handling
3030 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3031 kinds of program events, such as C@t{++} exceptions or the loading of a
3032 shared library. Use the @code{catch} command to set a catchpoint.
3036 @item catch @var{event}
3037 Stop when @var{event} occurs. @var{event} can be any of the following:
3040 @cindex stop on C@t{++} exceptions
3041 The throwing of a C@t{++} exception.
3044 The catching of a C@t{++} exception.
3047 @cindex break on fork/exec
3048 A call to @code{exec}. This is currently only available for HP-UX.
3051 A call to @code{fork}. This is currently only available for HP-UX.
3054 A call to @code{vfork}. This is currently only available for HP-UX.
3057 @itemx load @var{libname}
3058 @cindex break on load/unload of shared library
3059 The dynamic loading of any shared library, or the loading of the library
3060 @var{libname}. This is currently only available for HP-UX.
3063 @itemx unload @var{libname}
3064 The unloading of any dynamically loaded shared library, or the unloading
3065 of the library @var{libname}. This is currently only available for HP-UX.
3068 @item tcatch @var{event}
3069 Set a catchpoint that is enabled only for one stop. The catchpoint is
3070 automatically deleted after the first time the event is caught.
3074 Use the @code{info break} command to list the current catchpoints.
3076 There are currently some limitations to C@t{++} exception handling
3077 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3081 If you call a function interactively, @value{GDBN} normally returns
3082 control to you when the function has finished executing. If the call
3083 raises an exception, however, the call may bypass the mechanism that
3084 returns control to you and cause your program either to abort or to
3085 simply continue running until it hits a breakpoint, catches a signal
3086 that @value{GDBN} is listening for, or exits. This is the case even if
3087 you set a catchpoint for the exception; catchpoints on exceptions are
3088 disabled within interactive calls.
3091 You cannot raise an exception interactively.
3094 You cannot install an exception handler interactively.
3097 @cindex raise exceptions
3098 Sometimes @code{catch} is not the best way to debug exception handling:
3099 if you need to know exactly where an exception is raised, it is better to
3100 stop @emph{before} the exception handler is called, since that way you
3101 can see the stack before any unwinding takes place. If you set a
3102 breakpoint in an exception handler instead, it may not be easy to find
3103 out where the exception was raised.
3105 To stop just before an exception handler is called, you need some
3106 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3107 raised by calling a library function named @code{__raise_exception}
3108 which has the following ANSI C interface:
3111 /* @var{addr} is where the exception identifier is stored.
3112 @var{id} is the exception identifier. */
3113 void __raise_exception (void **addr, void *id);
3117 To make the debugger catch all exceptions before any stack
3118 unwinding takes place, set a breakpoint on @code{__raise_exception}
3119 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
3121 With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
3122 that depends on the value of @var{id}, you can stop your program when
3123 a specific exception is raised. You can use multiple conditional
3124 breakpoints to stop your program when any of a number of exceptions are
3129 @subsection Deleting breakpoints
3131 @cindex clearing breakpoints, watchpoints, catchpoints
3132 @cindex deleting breakpoints, watchpoints, catchpoints
3133 It is often necessary to eliminate a breakpoint, watchpoint, or
3134 catchpoint once it has done its job and you no longer want your program
3135 to stop there. This is called @dfn{deleting} the breakpoint. A
3136 breakpoint that has been deleted no longer exists; it is forgotten.
3138 With the @code{clear} command you can delete breakpoints according to
3139 where they are in your program. With the @code{delete} command you can
3140 delete individual breakpoints, watchpoints, or catchpoints by specifying
3141 their breakpoint numbers.
3143 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3144 automatically ignores breakpoints on the first instruction to be executed
3145 when you continue execution without changing the execution address.
3150 Delete any breakpoints at the next instruction to be executed in the
3151 selected stack frame (@pxref{Selection, ,Selecting a frame}). When
3152 the innermost frame is selected, this is a good way to delete a
3153 breakpoint where your program just stopped.
3155 @item clear @var{function}
3156 @itemx clear @var{filename}:@var{function}
3157 Delete any breakpoints set at entry to the named @var{function}.
3159 @item clear @var{linenum}
3160 @itemx clear @var{filename}:@var{linenum}
3161 Delete any breakpoints set at or within the code of the specified
3162 @var{linenum} of the specified @var{filename}.
3164 @cindex delete breakpoints
3166 @kindex d @r{(@code{delete})}
3167 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3168 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3169 ranges specified as arguments. If no argument is specified, delete all
3170 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3171 confirm off}). You can abbreviate this command as @code{d}.
3175 @subsection Disabling breakpoints
3177 @cindex enable/disable a breakpoint
3178 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3179 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3180 it had been deleted, but remembers the information on the breakpoint so
3181 that you can @dfn{enable} it again later.
3183 You disable and enable breakpoints, watchpoints, and catchpoints with
3184 the @code{enable} and @code{disable} commands, optionally specifying one
3185 or more breakpoint numbers as arguments. Use @code{info break} or
3186 @code{info watch} to print a list of breakpoints, watchpoints, and
3187 catchpoints if you do not know which numbers to use.
3189 A breakpoint, watchpoint, or catchpoint can have any of four different
3190 states of enablement:
3194 Enabled. The breakpoint stops your program. A breakpoint set
3195 with the @code{break} command starts out in this state.
3197 Disabled. The breakpoint has no effect on your program.
3199 Enabled once. The breakpoint stops your program, but then becomes
3202 Enabled for deletion. The breakpoint stops your program, but
3203 immediately after it does so it is deleted permanently. A breakpoint
3204 set with the @code{tbreak} command starts out in this state.
3207 You can use the following commands to enable or disable breakpoints,
3208 watchpoints, and catchpoints:
3212 @kindex dis @r{(@code{disable})}
3213 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3214 Disable the specified breakpoints---or all breakpoints, if none are
3215 listed. A disabled breakpoint has no effect but is not forgotten. All
3216 options such as ignore-counts, conditions and commands are remembered in
3217 case the breakpoint is enabled again later. You may abbreviate
3218 @code{disable} as @code{dis}.
3221 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3222 Enable the specified breakpoints (or all defined breakpoints). They
3223 become effective once again in stopping your program.
3225 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3226 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3227 of these breakpoints immediately after stopping your program.
3229 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3230 Enable the specified breakpoints to work once, then die. @value{GDBN}
3231 deletes any of these breakpoints as soon as your program stops there.
3232 Breakpoints set by the @code{tbreak} command start out in this state.
3235 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3236 @c confusing: tbreak is also initially enabled.
3237 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3238 ,Setting breakpoints}), breakpoints that you set are initially enabled;
3239 subsequently, they become disabled or enabled only when you use one of
3240 the commands above. (The command @code{until} can set and delete a
3241 breakpoint of its own, but it does not change the state of your other
3242 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3246 @subsection Break conditions
3247 @cindex conditional breakpoints
3248 @cindex breakpoint conditions
3250 @c FIXME what is scope of break condition expr? Context where wanted?
3251 @c in particular for a watchpoint?
3252 The simplest sort of breakpoint breaks every time your program reaches a
3253 specified place. You can also specify a @dfn{condition} for a
3254 breakpoint. A condition is just a Boolean expression in your
3255 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3256 a condition evaluates the expression each time your program reaches it,
3257 and your program stops only if the condition is @emph{true}.
3259 This is the converse of using assertions for program validation; in that
3260 situation, you want to stop when the assertion is violated---that is,
3261 when the condition is false. In C, if you want to test an assertion expressed
3262 by the condition @var{assert}, you should set the condition
3263 @samp{! @var{assert}} on the appropriate breakpoint.
3265 Conditions are also accepted for watchpoints; you may not need them,
3266 since a watchpoint is inspecting the value of an expression anyhow---but
3267 it might be simpler, say, to just set a watchpoint on a variable name,
3268 and specify a condition that tests whether the new value is an interesting
3271 Break conditions can have side effects, and may even call functions in
3272 your program. This can be useful, for example, to activate functions
3273 that log program progress, or to use your own print functions to
3274 format special data structures. The effects are completely predictable
3275 unless there is another enabled breakpoint at the same address. (In
3276 that case, @value{GDBN} might see the other breakpoint first and stop your
3277 program without checking the condition of this one.) Note that
3278 breakpoint commands are usually more convenient and flexible than break
3280 purpose of performing side effects when a breakpoint is reached
3281 (@pxref{Break Commands, ,Breakpoint command lists}).
3283 Break conditions can be specified when a breakpoint is set, by using
3284 @samp{if} in the arguments to the @code{break} command. @xref{Set
3285 Breaks, ,Setting breakpoints}. They can also be changed at any time
3286 with the @code{condition} command.
3288 You can also use the @code{if} keyword with the @code{watch} command.
3289 The @code{catch} command does not recognize the @code{if} keyword;
3290 @code{condition} is the only way to impose a further condition on a
3295 @item condition @var{bnum} @var{expression}
3296 Specify @var{expression} as the break condition for breakpoint,
3297 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3298 breakpoint @var{bnum} stops your program only if the value of
3299 @var{expression} is true (nonzero, in C). When you use
3300 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3301 syntactic correctness, and to determine whether symbols in it have
3302 referents in the context of your breakpoint. If @var{expression} uses
3303 symbols not referenced in the context of the breakpoint, @value{GDBN}
3304 prints an error message:
3307 No symbol "foo" in current context.
3312 not actually evaluate @var{expression} at the time the @code{condition}
3313 command (or a command that sets a breakpoint with a condition, like
3314 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3316 @item condition @var{bnum}
3317 Remove the condition from breakpoint number @var{bnum}. It becomes
3318 an ordinary unconditional breakpoint.
3321 @cindex ignore count (of breakpoint)
3322 A special case of a breakpoint condition is to stop only when the
3323 breakpoint has been reached a certain number of times. This is so
3324 useful that there is a special way to do it, using the @dfn{ignore
3325 count} of the breakpoint. Every breakpoint has an ignore count, which
3326 is an integer. Most of the time, the ignore count is zero, and
3327 therefore has no effect. But if your program reaches a breakpoint whose
3328 ignore count is positive, then instead of stopping, it just decrements
3329 the ignore count by one and continues. As a result, if the ignore count
3330 value is @var{n}, the breakpoint does not stop the next @var{n} times
3331 your program reaches it.
3335 @item ignore @var{bnum} @var{count}
3336 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3337 The next @var{count} times the breakpoint is reached, your program's
3338 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3341 To make the breakpoint stop the next time it is reached, specify
3344 When you use @code{continue} to resume execution of your program from a
3345 breakpoint, you can specify an ignore count directly as an argument to
3346 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3347 Stepping,,Continuing and stepping}.
3349 If a breakpoint has a positive ignore count and a condition, the
3350 condition is not checked. Once the ignore count reaches zero,
3351 @value{GDBN} resumes checking the condition.
3353 You could achieve the effect of the ignore count with a condition such
3354 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3355 is decremented each time. @xref{Convenience Vars, ,Convenience
3359 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3362 @node Break Commands
3363 @subsection Breakpoint command lists
3365 @cindex breakpoint commands
3366 You can give any breakpoint (or watchpoint or catchpoint) a series of
3367 commands to execute when your program stops due to that breakpoint. For
3368 example, you might want to print the values of certain expressions, or
3369 enable other breakpoints.
3374 @item commands @r{[}@var{bnum}@r{]}
3375 @itemx @dots{} @var{command-list} @dots{}
3377 Specify a list of commands for breakpoint number @var{bnum}. The commands
3378 themselves appear on the following lines. Type a line containing just
3379 @code{end} to terminate the commands.
3381 To remove all commands from a breakpoint, type @code{commands} and
3382 follow it immediately with @code{end}; that is, give no commands.
3384 With no @var{bnum} argument, @code{commands} refers to the last
3385 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3386 recently encountered).
3389 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3390 disabled within a @var{command-list}.
3392 You can use breakpoint commands to start your program up again. Simply
3393 use the @code{continue} command, or @code{step}, or any other command
3394 that resumes execution.
3396 Any other commands in the command list, after a command that resumes
3397 execution, are ignored. This is because any time you resume execution
3398 (even with a simple @code{next} or @code{step}), you may encounter
3399 another breakpoint---which could have its own command list, leading to
3400 ambiguities about which list to execute.
3403 If the first command you specify in a command list is @code{silent}, the
3404 usual message about stopping at a breakpoint is not printed. This may
3405 be desirable for breakpoints that are to print a specific message and
3406 then continue. If none of the remaining commands print anything, you
3407 see no sign that the breakpoint was reached. @code{silent} is
3408 meaningful only at the beginning of a breakpoint command list.
3410 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3411 print precisely controlled output, and are often useful in silent
3412 breakpoints. @xref{Output, ,Commands for controlled output}.
3414 For example, here is how you could use breakpoint commands to print the
3415 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3421 printf "x is %d\n",x
3426 One application for breakpoint commands is to compensate for one bug so
3427 you can test for another. Put a breakpoint just after the erroneous line
3428 of code, give it a condition to detect the case in which something
3429 erroneous has been done, and give it commands to assign correct values
3430 to any variables that need them. End with the @code{continue} command
3431 so that your program does not stop, and start with the @code{silent}
3432 command so that no output is produced. Here is an example:
3443 @node Breakpoint Menus
3444 @subsection Breakpoint menus
3446 @cindex symbol overloading
3448 Some programming languages (notably C@t{++} and Objective-C) permit a
3449 single function name
3450 to be defined several times, for application in different contexts.
3451 This is called @dfn{overloading}. When a function name is overloaded,
3452 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3453 a breakpoint. If you realize this is a problem, you can use
3454 something like @samp{break @var{function}(@var{types})} to specify which
3455 particular version of the function you want. Otherwise, @value{GDBN} offers
3456 you a menu of numbered choices for different possible breakpoints, and
3457 waits for your selection with the prompt @samp{>}. The first two
3458 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3459 sets a breakpoint at each definition of @var{function}, and typing
3460 @kbd{0} aborts the @code{break} command without setting any new
3463 For example, the following session excerpt shows an attempt to set a
3464 breakpoint at the overloaded symbol @code{String::after}.
3465 We choose three particular definitions of that function name:
3467 @c FIXME! This is likely to change to show arg type lists, at least
3470 (@value{GDBP}) b String::after
3473 [2] file:String.cc; line number:867
3474 [3] file:String.cc; line number:860
3475 [4] file:String.cc; line number:875
3476 [5] file:String.cc; line number:853
3477 [6] file:String.cc; line number:846
3478 [7] file:String.cc; line number:735
3480 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3481 Breakpoint 2 at 0xb344: file String.cc, line 875.
3482 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3483 Multiple breakpoints were set.
3484 Use the "delete" command to delete unwanted
3490 @c @ifclear BARETARGET
3491 @node Error in Breakpoints
3492 @subsection ``Cannot insert breakpoints''
3494 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3496 Under some operating systems, breakpoints cannot be used in a program if
3497 any other process is running that program. In this situation,
3498 attempting to run or continue a program with a breakpoint causes
3499 @value{GDBN} to print an error message:
3502 Cannot insert breakpoints.
3503 The same program may be running in another process.
3506 When this happens, you have three ways to proceed:
3510 Remove or disable the breakpoints, then continue.
3513 Suspend @value{GDBN}, and copy the file containing your program to a new
3514 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3515 that @value{GDBN} should run your program under that name.
3516 Then start your program again.
3519 Relink your program so that the text segment is nonsharable, using the
3520 linker option @samp{-N}. The operating system limitation may not apply
3521 to nonsharable executables.
3525 A similar message can be printed if you request too many active
3526 hardware-assisted breakpoints and watchpoints:
3528 @c FIXME: the precise wording of this message may change; the relevant
3529 @c source change is not committed yet (Sep 3, 1999).
3531 Stopped; cannot insert breakpoints.
3532 You may have requested too many hardware breakpoints and watchpoints.
3536 This message is printed when you attempt to resume the program, since
3537 only then @value{GDBN} knows exactly how many hardware breakpoints and
3538 watchpoints it needs to insert.
3540 When this message is printed, you need to disable or remove some of the
3541 hardware-assisted breakpoints and watchpoints, and then continue.
3543 @node Breakpoint related warnings
3544 @subsection ``Breakpoint address adjusted...''
3545 @cindex breakpoint address adjusted
3547 Some processor architectures place constraints on the addresses at
3548 which breakpoints may be placed. For architectures thus constrained,
3549 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3550 with the constraints dictated by the architecture.
3552 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3553 a VLIW architecture in which a number of RISC-like instructions may be
3554 bundled together for parallel execution. The FR-V architecture
3555 constrains the location of a breakpoint instruction within such a
3556 bundle to the instruction with the lowest address. @value{GDBN}
3557 honors this constraint by adjusting a breakpoint's address to the
3558 first in the bundle.
3560 It is not uncommon for optimized code to have bundles which contain
3561 instructions from different source statements, thus it may happen that
3562 a breakpoint's address will be adjusted from one source statement to
3563 another. Since this adjustment may significantly alter @value{GDBN}'s
3564 breakpoint related behavior from what the user expects, a warning is
3565 printed when the breakpoint is first set and also when the breakpoint
3568 A warning like the one below is printed when setting a breakpoint
3569 that's been subject to address adjustment:
3572 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3575 Such warnings are printed both for user settable and @value{GDBN}'s
3576 internal breakpoints. If you see one of these warnings, you should
3577 verify that a breakpoint set at the adjusted address will have the
3578 desired affect. If not, the breakpoint in question may be removed and
3579 other breakpoints may be set which will have the desired behavior.
3580 E.g., it may be sufficient to place the breakpoint at a later
3581 instruction. A conditional breakpoint may also be useful in some
3582 cases to prevent the breakpoint from triggering too often.
3584 @value{GDBN} will also issue a warning when stopping at one of these
3585 adjusted breakpoints:
3588 warning: Breakpoint 1 address previously adjusted from 0x00010414
3592 When this warning is encountered, it may be too late to take remedial
3593 action except in cases where the breakpoint is hit earlier or more
3594 frequently than expected.
3596 @node Continuing and Stepping
3597 @section Continuing and stepping
3601 @cindex resuming execution
3602 @dfn{Continuing} means resuming program execution until your program
3603 completes normally. In contrast, @dfn{stepping} means executing just
3604 one more ``step'' of your program, where ``step'' may mean either one
3605 line of source code, or one machine instruction (depending on what
3606 particular command you use). Either when continuing or when stepping,
3607 your program may stop even sooner, due to a breakpoint or a signal. (If
3608 it stops due to a signal, you may want to use @code{handle}, or use
3609 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3613 @kindex c @r{(@code{continue})}
3614 @kindex fg @r{(resume foreground execution)}
3615 @item continue @r{[}@var{ignore-count}@r{]}
3616 @itemx c @r{[}@var{ignore-count}@r{]}
3617 @itemx fg @r{[}@var{ignore-count}@r{]}
3618 Resume program execution, at the address where your program last stopped;
3619 any breakpoints set at that address are bypassed. The optional argument
3620 @var{ignore-count} allows you to specify a further number of times to
3621 ignore a breakpoint at this location; its effect is like that of
3622 @code{ignore} (@pxref{Conditions, ,Break conditions}).
3624 The argument @var{ignore-count} is meaningful only when your program
3625 stopped due to a breakpoint. At other times, the argument to
3626 @code{continue} is ignored.
3628 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3629 debugged program is deemed to be the foreground program) are provided
3630 purely for convenience, and have exactly the same behavior as
3634 To resume execution at a different place, you can use @code{return}
3635 (@pxref{Returning, ,Returning from a function}) to go back to the
3636 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3637 different address}) to go to an arbitrary location in your program.
3639 A typical technique for using stepping is to set a breakpoint
3640 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the
3641 beginning of the function or the section of your program where a problem
3642 is believed to lie, run your program until it stops at that breakpoint,
3643 and then step through the suspect area, examining the variables that are
3644 interesting, until you see the problem happen.
3648 @kindex s @r{(@code{step})}
3650 Continue running your program until control reaches a different source
3651 line, then stop it and return control to @value{GDBN}. This command is
3652 abbreviated @code{s}.
3655 @c "without debugging information" is imprecise; actually "without line
3656 @c numbers in the debugging information". (gcc -g1 has debugging info but
3657 @c not line numbers). But it seems complex to try to make that
3658 @c distinction here.
3659 @emph{Warning:} If you use the @code{step} command while control is
3660 within a function that was compiled without debugging information,
3661 execution proceeds until control reaches a function that does have
3662 debugging information. Likewise, it will not step into a function which
3663 is compiled without debugging information. To step through functions
3664 without debugging information, use the @code{stepi} command, described
3668 The @code{step} command only stops at the first instruction of a source
3669 line. This prevents the multiple stops that could otherwise occur in
3670 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3671 to stop if a function that has debugging information is called within
3672 the line. In other words, @code{step} @emph{steps inside} any functions
3673 called within the line.
3675 Also, the @code{step} command only enters a function if there is line
3676 number information for the function. Otherwise it acts like the
3677 @code{next} command. This avoids problems when using @code{cc -gl}
3678 on MIPS machines. Previously, @code{step} entered subroutines if there
3679 was any debugging information about the routine.
3681 @item step @var{count}
3682 Continue running as in @code{step}, but do so @var{count} times. If a
3683 breakpoint is reached, or a signal not related to stepping occurs before
3684 @var{count} steps, stepping stops right away.
3687 @kindex n @r{(@code{next})}
3688 @item next @r{[}@var{count}@r{]}
3689 Continue to the next source line in the current (innermost) stack frame.
3690 This is similar to @code{step}, but function calls that appear within
3691 the line of code are executed without stopping. Execution stops when
3692 control reaches a different line of code at the original stack level
3693 that was executing when you gave the @code{next} command. This command
3694 is abbreviated @code{n}.
3696 An argument @var{count} is a repeat count, as for @code{step}.
3699 @c FIX ME!! Do we delete this, or is there a way it fits in with
3700 @c the following paragraph? --- Vctoria
3702 @c @code{next} within a function that lacks debugging information acts like
3703 @c @code{step}, but any function calls appearing within the code of the
3704 @c function are executed without stopping.
3706 The @code{next} command only stops at the first instruction of a
3707 source line. This prevents multiple stops that could otherwise occur in
3708 @code{switch} statements, @code{for} loops, etc.
3710 @kindex set step-mode
3712 @cindex functions without line info, and stepping
3713 @cindex stepping into functions with no line info
3714 @itemx set step-mode on
3715 The @code{set step-mode on} command causes the @code{step} command to
3716 stop at the first instruction of a function which contains no debug line
3717 information rather than stepping over it.
3719 This is useful in cases where you may be interested in inspecting the
3720 machine instructions of a function which has no symbolic info and do not
3721 want @value{GDBN} to automatically skip over this function.
3723 @item set step-mode off
3724 Causes the @code{step} command to step over any functions which contains no
3725 debug information. This is the default.
3727 @item show step-mode
3728 Show whether @value{GDBN} will stop in or step over functions without
3729 source line debug information.
3733 Continue running until just after function in the selected stack frame
3734 returns. Print the returned value (if any).
3736 Contrast this with the @code{return} command (@pxref{Returning,
3737 ,Returning from a function}).
3740 @kindex u @r{(@code{until})}
3741 @cindex run until specified location
3744 Continue running until a source line past the current line, in the
3745 current stack frame, is reached. This command is used to avoid single
3746 stepping through a loop more than once. It is like the @code{next}
3747 command, except that when @code{until} encounters a jump, it
3748 automatically continues execution until the program counter is greater
3749 than the address of the jump.
3751 This means that when you reach the end of a loop after single stepping
3752 though it, @code{until} makes your program continue execution until it
3753 exits the loop. In contrast, a @code{next} command at the end of a loop
3754 simply steps back to the beginning of the loop, which forces you to step
3755 through the next iteration.
3757 @code{until} always stops your program if it attempts to exit the current
3760 @code{until} may produce somewhat counterintuitive results if the order
3761 of machine code does not match the order of the source lines. For
3762 example, in the following excerpt from a debugging session, the @code{f}
3763 (@code{frame}) command shows that execution is stopped at line
3764 @code{206}; yet when we use @code{until}, we get to line @code{195}:
3768 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
3770 (@value{GDBP}) until
3771 195 for ( ; argc > 0; NEXTARG) @{
3774 This happened because, for execution efficiency, the compiler had
3775 generated code for the loop closure test at the end, rather than the
3776 start, of the loop---even though the test in a C @code{for}-loop is
3777 written before the body of the loop. The @code{until} command appeared
3778 to step back to the beginning of the loop when it advanced to this
3779 expression; however, it has not really gone to an earlier
3780 statement---not in terms of the actual machine code.
3782 @code{until} with no argument works by means of single
3783 instruction stepping, and hence is slower than @code{until} with an
3786 @item until @var{location}
3787 @itemx u @var{location}
3788 Continue running your program until either the specified location is
3789 reached, or the current stack frame returns. @var{location} is any of
3790 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
3791 ,Setting breakpoints}). This form of the command uses breakpoints, and
3792 hence is quicker than @code{until} without an argument. The specified
3793 location is actually reached only if it is in the current frame. This
3794 implies that @code{until} can be used to skip over recursive function
3795 invocations. For instance in the code below, if the current location is
3796 line @code{96}, issuing @code{until 99} will execute the program up to
3797 line @code{99} in the same invocation of factorial, i.e. after the inner
3798 invocations have returned.
3801 94 int factorial (int value)
3803 96 if (value > 1) @{
3804 97 value *= factorial (value - 1);
3811 @kindex advance @var{location}
3812 @itemx advance @var{location}
3813 Continue running the program up to the given @var{location}. An argument is
3814 required, which should be of the same form as arguments for the @code{break}
3815 command. Execution will also stop upon exit from the current stack
3816 frame. This command is similar to @code{until}, but @code{advance} will
3817 not skip over recursive function calls, and the target location doesn't
3818 have to be in the same frame as the current one.
3822 @kindex si @r{(@code{stepi})}
3824 @itemx stepi @var{arg}
3826 Execute one machine instruction, then stop and return to the debugger.
3828 It is often useful to do @samp{display/i $pc} when stepping by machine
3829 instructions. This makes @value{GDBN} automatically display the next
3830 instruction to be executed, each time your program stops. @xref{Auto
3831 Display,, Automatic display}.
3833 An argument is a repeat count, as in @code{step}.
3837 @kindex ni @r{(@code{nexti})}
3839 @itemx nexti @var{arg}
3841 Execute one machine instruction, but if it is a function call,
3842 proceed until the function returns.
3844 An argument is a repeat count, as in @code{next}.
3851 A signal is an asynchronous event that can happen in a program. The
3852 operating system defines the possible kinds of signals, and gives each
3853 kind a name and a number. For example, in Unix @code{SIGINT} is the
3854 signal a program gets when you type an interrupt character (often @kbd{C-c});
3855 @code{SIGSEGV} is the signal a program gets from referencing a place in
3856 memory far away from all the areas in use; @code{SIGALRM} occurs when
3857 the alarm clock timer goes off (which happens only if your program has
3858 requested an alarm).
3860 @cindex fatal signals
3861 Some signals, including @code{SIGALRM}, are a normal part of the
3862 functioning of your program. Others, such as @code{SIGSEGV}, indicate
3863 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
3864 program has not specified in advance some other way to handle the signal.
3865 @code{SIGINT} does not indicate an error in your program, but it is normally
3866 fatal so it can carry out the purpose of the interrupt: to kill the program.
3868 @value{GDBN} has the ability to detect any occurrence of a signal in your
3869 program. You can tell @value{GDBN} in advance what to do for each kind of
3872 @cindex handling signals
3873 Normally, @value{GDBN} is set up to let the non-erroneous signals like
3874 @code{SIGALRM} be silently passed to your program
3875 (so as not to interfere with their role in the program's functioning)
3876 but to stop your program immediately whenever an error signal happens.
3877 You can change these settings with the @code{handle} command.
3880 @kindex info signals
3884 Print a table of all the kinds of signals and how @value{GDBN} has been told to
3885 handle each one. You can use this to see the signal numbers of all
3886 the defined types of signals.
3888 @code{info handle} is an alias for @code{info signals}.
3891 @item handle @var{signal} @var{keywords}@dots{}
3892 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
3893 can be the number of a signal or its name (with or without the
3894 @samp{SIG} at the beginning); a list of signal numbers of the form
3895 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
3896 known signals. The @var{keywords} say what change to make.
3900 The keywords allowed by the @code{handle} command can be abbreviated.
3901 Their full names are:
3905 @value{GDBN} should not stop your program when this signal happens. It may
3906 still print a message telling you that the signal has come in.
3909 @value{GDBN} should stop your program when this signal happens. This implies
3910 the @code{print} keyword as well.
3913 @value{GDBN} should print a message when this signal happens.
3916 @value{GDBN} should not mention the occurrence of the signal at all. This
3917 implies the @code{nostop} keyword as well.
3921 @value{GDBN} should allow your program to see this signal; your program
3922 can handle the signal, or else it may terminate if the signal is fatal
3923 and not handled. @code{pass} and @code{noignore} are synonyms.
3927 @value{GDBN} should not allow your program to see this signal.
3928 @code{nopass} and @code{ignore} are synonyms.
3932 When a signal stops your program, the signal is not visible to the
3934 continue. Your program sees the signal then, if @code{pass} is in
3935 effect for the signal in question @emph{at that time}. In other words,
3936 after @value{GDBN} reports a signal, you can use the @code{handle}
3937 command with @code{pass} or @code{nopass} to control whether your
3938 program sees that signal when you continue.
3940 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
3941 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
3942 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
3945 You can also use the @code{signal} command to prevent your program from
3946 seeing a signal, or cause it to see a signal it normally would not see,
3947 or to give it any signal at any time. For example, if your program stopped
3948 due to some sort of memory reference error, you might store correct
3949 values into the erroneous variables and continue, hoping to see more
3950 execution; but your program would probably terminate immediately as
3951 a result of the fatal signal once it saw the signal. To prevent this,
3952 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
3956 @section Stopping and starting multi-thread programs
3958 When your program has multiple threads (@pxref{Threads,, Debugging
3959 programs with multiple threads}), you can choose whether to set
3960 breakpoints on all threads, or on a particular thread.
3963 @cindex breakpoints and threads
3964 @cindex thread breakpoints
3965 @kindex break @dots{} thread @var{threadno}
3966 @item break @var{linespec} thread @var{threadno}
3967 @itemx break @var{linespec} thread @var{threadno} if @dots{}
3968 @var{linespec} specifies source lines; there are several ways of
3969 writing them, but the effect is always to specify some source line.
3971 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
3972 to specify that you only want @value{GDBN} to stop the program when a
3973 particular thread reaches this breakpoint. @var{threadno} is one of the
3974 numeric thread identifiers assigned by @value{GDBN}, shown in the first
3975 column of the @samp{info threads} display.
3977 If you do not specify @samp{thread @var{threadno}} when you set a
3978 breakpoint, the breakpoint applies to @emph{all} threads of your
3981 You can use the @code{thread} qualifier on conditional breakpoints as
3982 well; in this case, place @samp{thread @var{threadno}} before the
3983 breakpoint condition, like this:
3986 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
3991 @cindex stopped threads
3992 @cindex threads, stopped
3993 Whenever your program stops under @value{GDBN} for any reason,
3994 @emph{all} threads of execution stop, not just the current thread. This
3995 allows you to examine the overall state of the program, including
3996 switching between threads, without worrying that things may change
3999 @cindex thread breakpoints and system calls
4000 @cindex system calls and thread breakpoints
4001 @cindex premature return from system calls
4002 There is an unfortunate side effect. If one thread stops for a
4003 breakpoint, or for some other reason, and another thread is blocked in a
4004 system call, then the system call may return prematurely. This is a
4005 consequence of the interaction between multiple threads and the signals
4006 that @value{GDBN} uses to implement breakpoints and other events that
4009 To handle this problem, your program should check the return value of
4010 each system call and react appropriately. This is good programming
4013 For example, do not write code like this:
4019 The call to @code{sleep} will return early if a different thread stops
4020 at a breakpoint or for some other reason.
4022 Instead, write this:
4027 unslept = sleep (unslept);
4030 A system call is allowed to return early, so the system is still
4031 conforming to its specification. But @value{GDBN} does cause your
4032 multi-threaded program to behave differently than it would without
4035 Also, @value{GDBN} uses internal breakpoints in the thread library to
4036 monitor certain events such as thread creation and thread destruction.
4037 When such an event happens, a system call in another thread may return
4038 prematurely, even though your program does not appear to stop.
4040 @cindex continuing threads
4041 @cindex threads, continuing
4042 Conversely, whenever you restart the program, @emph{all} threads start
4043 executing. @emph{This is true even when single-stepping} with commands
4044 like @code{step} or @code{next}.
4046 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4047 Since thread scheduling is up to your debugging target's operating
4048 system (not controlled by @value{GDBN}), other threads may
4049 execute more than one statement while the current thread completes a
4050 single step. Moreover, in general other threads stop in the middle of a
4051 statement, rather than at a clean statement boundary, when the program
4054 You might even find your program stopped in another thread after
4055 continuing or even single-stepping. This happens whenever some other
4056 thread runs into a breakpoint, a signal, or an exception before the
4057 first thread completes whatever you requested.
4059 On some OSes, you can lock the OS scheduler and thus allow only a single
4063 @item set scheduler-locking @var{mode}
4064 @cindex scheduler locking mode
4065 @cindex lock scheduler
4066 Set the scheduler locking mode. If it is @code{off}, then there is no
4067 locking and any thread may run at any time. If @code{on}, then only the
4068 current thread may run when the inferior is resumed. The @code{step}
4069 mode optimizes for single-stepping. It stops other threads from
4070 ``seizing the prompt'' by preempting the current thread while you are
4071 stepping. Other threads will only rarely (or never) get a chance to run
4072 when you step. They are more likely to run when you @samp{next} over a
4073 function call, and they are completely free to run when you use commands
4074 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4075 thread hits a breakpoint during its timeslice, they will never steal the
4076 @value{GDBN} prompt away from the thread that you are debugging.
4078 @item show scheduler-locking
4079 Display the current scheduler locking mode.
4084 @chapter Examining the Stack
4086 When your program has stopped, the first thing you need to know is where it
4087 stopped and how it got there.
4090 Each time your program performs a function call, information about the call
4092 That information includes the location of the call in your program,
4093 the arguments of the call,
4094 and the local variables of the function being called.
4095 The information is saved in a block of data called a @dfn{stack frame}.
4096 The stack frames are allocated in a region of memory called the @dfn{call
4099 When your program stops, the @value{GDBN} commands for examining the
4100 stack allow you to see all of this information.
4102 @cindex selected frame
4103 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4104 @value{GDBN} commands refer implicitly to the selected frame. In
4105 particular, whenever you ask @value{GDBN} for the value of a variable in
4106 your program, the value is found in the selected frame. There are
4107 special @value{GDBN} commands to select whichever frame you are
4108 interested in. @xref{Selection, ,Selecting a frame}.
4110 When your program stops, @value{GDBN} automatically selects the
4111 currently executing frame and describes it briefly, similar to the
4112 @code{frame} command (@pxref{Frame Info, ,Information about a frame}).
4115 * Frames:: Stack frames
4116 * Backtrace:: Backtraces
4117 * Selection:: Selecting a frame
4118 * Frame Info:: Information on a frame
4123 @section Stack frames
4125 @cindex frame, definition
4127 The call stack is divided up into contiguous pieces called @dfn{stack
4128 frames}, or @dfn{frames} for short; each frame is the data associated
4129 with one call to one function. The frame contains the arguments given
4130 to the function, the function's local variables, and the address at
4131 which the function is executing.
4133 @cindex initial frame
4134 @cindex outermost frame
4135 @cindex innermost frame
4136 When your program is started, the stack has only one frame, that of the
4137 function @code{main}. This is called the @dfn{initial} frame or the
4138 @dfn{outermost} frame. Each time a function is called, a new frame is
4139 made. Each time a function returns, the frame for that function invocation
4140 is eliminated. If a function is recursive, there can be many frames for
4141 the same function. The frame for the function in which execution is
4142 actually occurring is called the @dfn{innermost} frame. This is the most
4143 recently created of all the stack frames that still exist.
4145 @cindex frame pointer
4146 Inside your program, stack frames are identified by their addresses. A
4147 stack frame consists of many bytes, each of which has its own address; each
4148 kind of computer has a convention for choosing one byte whose
4149 address serves as the address of the frame. Usually this address is kept
4150 in a register called the @dfn{frame pointer register} while execution is
4151 going on in that frame.
4153 @cindex frame number
4154 @value{GDBN} assigns numbers to all existing stack frames, starting with
4155 zero for the innermost frame, one for the frame that called it,
4156 and so on upward. These numbers do not really exist in your program;
4157 they are assigned by @value{GDBN} to give you a way of designating stack
4158 frames in @value{GDBN} commands.
4160 @c The -fomit-frame-pointer below perennially causes hbox overflow
4161 @c underflow problems.
4162 @cindex frameless execution
4163 Some compilers provide a way to compile functions so that they operate
4164 without stack frames. (For example, the @value{GCC} option
4166 @samp{-fomit-frame-pointer}
4168 generates functions without a frame.)
4169 This is occasionally done with heavily used library functions to save
4170 the frame setup time. @value{GDBN} has limited facilities for dealing
4171 with these function invocations. If the innermost function invocation
4172 has no stack frame, @value{GDBN} nevertheless regards it as though
4173 it had a separate frame, which is numbered zero as usual, allowing
4174 correct tracing of the function call chain. However, @value{GDBN} has
4175 no provision for frameless functions elsewhere in the stack.
4178 @kindex frame@r{, command}
4179 @cindex current stack frame
4180 @item frame @var{args}
4181 The @code{frame} command allows you to move from one stack frame to another,
4182 and to print the stack frame you select. @var{args} may be either the
4183 address of the frame or the stack frame number. Without an argument,
4184 @code{frame} prints the current stack frame.
4186 @kindex select-frame
4187 @cindex selecting frame silently
4189 The @code{select-frame} command allows you to move from one stack frame
4190 to another without printing the frame. This is the silent version of
4198 @cindex call stack traces
4199 A backtrace is a summary of how your program got where it is. It shows one
4200 line per frame, for many frames, starting with the currently executing
4201 frame (frame zero), followed by its caller (frame one), and on up the
4206 @kindex bt @r{(@code{backtrace})}
4209 Print a backtrace of the entire stack: one line per frame for all
4210 frames in the stack.
4212 You can stop the backtrace at any time by typing the system interrupt
4213 character, normally @kbd{C-c}.
4215 @item backtrace @var{n}
4217 Similar, but print only the innermost @var{n} frames.
4219 @item backtrace -@var{n}
4221 Similar, but print only the outermost @var{n} frames.
4223 @item backtrace full
4224 Print the values of the local variables also.
4230 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4231 are additional aliases for @code{backtrace}.
4233 Each line in the backtrace shows the frame number and the function name.
4234 The program counter value is also shown---unless you use @code{set
4235 print address off}. The backtrace also shows the source file name and
4236 line number, as well as the arguments to the function. The program
4237 counter value is omitted if it is at the beginning of the code for that
4240 Here is an example of a backtrace. It was made with the command
4241 @samp{bt 3}, so it shows the innermost three frames.
4245 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4247 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4248 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4250 (More stack frames follow...)
4255 The display for frame zero does not begin with a program counter
4256 value, indicating that your program has stopped at the beginning of the
4257 code for line @code{993} of @code{builtin.c}.
4259 @cindex value optimized out, in backtrace
4260 @cindex function call arguments, optimized out
4261 If your program was compiled with optimizations, some compilers will
4262 optimize away arguments passed to functions if those arguments are
4263 never used after the call. Such optimizations generate code that
4264 passes arguments through registers, but doesn't store those arguments
4265 in the stack frame. @value{GDBN} has no way of displaying such
4266 arguments in stack frames other than the innermost one. Here's what
4267 such a backtrace might look like:
4271 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4273 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
4274 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
4276 (More stack frames follow...)
4281 The values of arguments that were not saved in their stack frames are
4282 shown as @samp{<value optimized out>}.
4284 If you need to display the values of such optimized-out arguments,
4285 either deduce that from other variables whose values depend on the one
4286 you are interested in, or recompile without optimizations.
4288 @cindex backtrace beyond @code{main} function
4289 @cindex program entry point
4290 @cindex startup code, and backtrace
4291 Most programs have a standard user entry point---a place where system
4292 libraries and startup code transition into user code. For C this is
4293 @code{main}. When @value{GDBN} finds the entry function in a backtrace
4294 it will terminate the backtrace, to avoid tracing into highly
4295 system-specific (and generally uninteresting) code.
4297 If you need to examine the startup code, or limit the number of levels
4298 in a backtrace, you can change this behavior:
4301 @item set backtrace past-main
4302 @itemx set backtrace past-main on
4303 @kindex set backtrace
4304 Backtraces will continue past the user entry point.
4306 @item set backtrace past-main off
4307 Backtraces will stop when they encounter the user entry point. This is the
4310 @item show backtrace past-main
4311 @kindex show backtrace
4312 Display the current user entry point backtrace policy.
4314 @item set backtrace past-entry
4315 @itemx set backtrace past-entry on
4316 Backtraces will continue past the internal entry point of an application.
4317 This entry point is encoded by the linker when the application is built,
4318 and is likely before the user entry point @code{main} (or equivalent) is called.
4320 @item set backtrace past-entry off
4321 Backtraces will stop when they encouter the internal entry point of an
4322 application. This is the default.
4324 @item show backtrace past-entry
4325 Display the current internal entry point backtrace policy.
4327 @item set backtrace limit @var{n}
4328 @itemx set backtrace limit 0
4329 @cindex backtrace limit
4330 Limit the backtrace to @var{n} levels. A value of zero means
4333 @item show backtrace limit
4334 Display the current limit on backtrace levels.
4338 @section Selecting a frame
4340 Most commands for examining the stack and other data in your program work on
4341 whichever stack frame is selected at the moment. Here are the commands for
4342 selecting a stack frame; all of them finish by printing a brief description
4343 of the stack frame just selected.
4346 @kindex frame@r{, selecting}
4347 @kindex f @r{(@code{frame})}
4350 Select frame number @var{n}. Recall that frame zero is the innermost
4351 (currently executing) frame, frame one is the frame that called the
4352 innermost one, and so on. The highest-numbered frame is the one for
4355 @item frame @var{addr}
4357 Select the frame at address @var{addr}. This is useful mainly if the
4358 chaining of stack frames has been damaged by a bug, making it
4359 impossible for @value{GDBN} to assign numbers properly to all frames. In
4360 addition, this can be useful when your program has multiple stacks and
4361 switches between them.
4363 On the SPARC architecture, @code{frame} needs two addresses to
4364 select an arbitrary frame: a frame pointer and a stack pointer.
4366 On the MIPS and Alpha architecture, it needs two addresses: a stack
4367 pointer and a program counter.
4369 On the 29k architecture, it needs three addresses: a register stack
4370 pointer, a program counter, and a memory stack pointer.
4371 @c note to future updaters: this is conditioned on a flag
4372 @c SETUP_ARBITRARY_FRAME in the tm-*.h files. The above is up to date
4373 @c as of 27 Jan 1994.
4377 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4378 advances toward the outermost frame, to higher frame numbers, to frames
4379 that have existed longer. @var{n} defaults to one.
4382 @kindex do @r{(@code{down})}
4384 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4385 advances toward the innermost frame, to lower frame numbers, to frames
4386 that were created more recently. @var{n} defaults to one. You may
4387 abbreviate @code{down} as @code{do}.
4390 All of these commands end by printing two lines of output describing the
4391 frame. The first line shows the frame number, the function name, the
4392 arguments, and the source file and line number of execution in that
4393 frame. The second line shows the text of that source line.
4401 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4403 10 read_input_file (argv[i]);
4407 After such a printout, the @code{list} command with no arguments
4408 prints ten lines centered on the point of execution in the frame.
4409 You can also edit the program at the point of execution with your favorite
4410 editing program by typing @code{edit}.
4411 @xref{List, ,Printing source lines},
4415 @kindex down-silently
4417 @item up-silently @var{n}
4418 @itemx down-silently @var{n}
4419 These two commands are variants of @code{up} and @code{down},
4420 respectively; they differ in that they do their work silently, without
4421 causing display of the new frame. They are intended primarily for use
4422 in @value{GDBN} command scripts, where the output might be unnecessary and
4427 @section Information about a frame
4429 There are several other commands to print information about the selected
4435 When used without any argument, this command does not change which
4436 frame is selected, but prints a brief description of the currently
4437 selected stack frame. It can be abbreviated @code{f}. With an
4438 argument, this command is used to select a stack frame.
4439 @xref{Selection, ,Selecting a frame}.
4442 @kindex info f @r{(@code{info frame})}
4445 This command prints a verbose description of the selected stack frame,
4450 the address of the frame
4452 the address of the next frame down (called by this frame)
4454 the address of the next frame up (caller of this frame)
4456 the language in which the source code corresponding to this frame is written
4458 the address of the frame's arguments
4460 the address of the frame's local variables
4462 the program counter saved in it (the address of execution in the caller frame)
4464 which registers were saved in the frame
4467 @noindent The verbose description is useful when
4468 something has gone wrong that has made the stack format fail to fit
4469 the usual conventions.
4471 @item info frame @var{addr}
4472 @itemx info f @var{addr}
4473 Print a verbose description of the frame at address @var{addr}, without
4474 selecting that frame. The selected frame remains unchanged by this
4475 command. This requires the same kind of address (more than one for some
4476 architectures) that you specify in the @code{frame} command.
4477 @xref{Selection, ,Selecting a frame}.
4481 Print the arguments of the selected frame, each on a separate line.
4485 Print the local variables of the selected frame, each on a separate
4486 line. These are all variables (declared either static or automatic)
4487 accessible at the point of execution of the selected frame.
4490 @cindex catch exceptions, list active handlers
4491 @cindex exception handlers, how to list
4493 Print a list of all the exception handlers that are active in the
4494 current stack frame at the current point of execution. To see other
4495 exception handlers, visit the associated frame (using the @code{up},
4496 @code{down}, or @code{frame} commands); then type @code{info catch}.
4497 @xref{Set Catchpoints, , Setting catchpoints}.
4503 @chapter Examining Source Files
4505 @value{GDBN} can print parts of your program's source, since the debugging
4506 information recorded in the program tells @value{GDBN} what source files were
4507 used to build it. When your program stops, @value{GDBN} spontaneously prints
4508 the line where it stopped. Likewise, when you select a stack frame
4509 (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
4510 execution in that frame has stopped. You can print other portions of
4511 source files by explicit command.
4513 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4514 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4515 @value{GDBN} under @sc{gnu} Emacs}.
4518 * List:: Printing source lines
4519 * Edit:: Editing source files
4520 * Search:: Searching source files
4521 * Source Path:: Specifying source directories
4522 * Machine Code:: Source and machine code
4526 @section Printing source lines
4529 @kindex l @r{(@code{list})}
4530 To print lines from a source file, use the @code{list} command
4531 (abbreviated @code{l}). By default, ten lines are printed.
4532 There are several ways to specify what part of the file you want to print.
4534 Here are the forms of the @code{list} command most commonly used:
4537 @item list @var{linenum}
4538 Print lines centered around line number @var{linenum} in the
4539 current source file.
4541 @item list @var{function}
4542 Print lines centered around the beginning of function
4546 Print more lines. If the last lines printed were printed with a
4547 @code{list} command, this prints lines following the last lines
4548 printed; however, if the last line printed was a solitary line printed
4549 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4550 Stack}), this prints lines centered around that line.
4553 Print lines just before the lines last printed.
4556 @cindex @code{list}, how many lines to display
4557 By default, @value{GDBN} prints ten source lines with any of these forms of
4558 the @code{list} command. You can change this using @code{set listsize}:
4561 @kindex set listsize
4562 @item set listsize @var{count}
4563 Make the @code{list} command display @var{count} source lines (unless
4564 the @code{list} argument explicitly specifies some other number).
4566 @kindex show listsize
4568 Display the number of lines that @code{list} prints.
4571 Repeating a @code{list} command with @key{RET} discards the argument,
4572 so it is equivalent to typing just @code{list}. This is more useful
4573 than listing the same lines again. An exception is made for an
4574 argument of @samp{-}; that argument is preserved in repetition so that
4575 each repetition moves up in the source file.
4578 In general, the @code{list} command expects you to supply zero, one or two
4579 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4580 of writing them, but the effect is always to specify some source line.
4581 Here is a complete description of the possible arguments for @code{list}:
4584 @item list @var{linespec}
4585 Print lines centered around the line specified by @var{linespec}.
4587 @item list @var{first},@var{last}
4588 Print lines from @var{first} to @var{last}. Both arguments are
4591 @item list ,@var{last}
4592 Print lines ending with @var{last}.
4594 @item list @var{first},
4595 Print lines starting with @var{first}.
4598 Print lines just after the lines last printed.
4601 Print lines just before the lines last printed.
4604 As described in the preceding table.
4607 Here are the ways of specifying a single source line---all the
4612 Specifies line @var{number} of the current source file.
4613 When a @code{list} command has two linespecs, this refers to
4614 the same source file as the first linespec.
4617 Specifies the line @var{offset} lines after the last line printed.
4618 When used as the second linespec in a @code{list} command that has
4619 two, this specifies the line @var{offset} lines down from the
4623 Specifies the line @var{offset} lines before the last line printed.
4625 @item @var{filename}:@var{number}
4626 Specifies line @var{number} in the source file @var{filename}.
4628 @item @var{function}
4629 Specifies the line that begins the body of the function @var{function}.
4630 For example: in C, this is the line with the open brace.
4632 @item @var{filename}:@var{function}
4633 Specifies the line of the open-brace that begins the body of the
4634 function @var{function} in the file @var{filename}. You only need the
4635 file name with a function name to avoid ambiguity when there are
4636 identically named functions in different source files.
4638 @item *@var{address}
4639 Specifies the line containing the program address @var{address}.
4640 @var{address} may be any expression.
4644 @section Editing source files
4645 @cindex editing source files
4648 @kindex e @r{(@code{edit})}
4649 To edit the lines in a source file, use the @code{edit} command.
4650 The editing program of your choice
4651 is invoked with the current line set to
4652 the active line in the program.
4653 Alternatively, there are several ways to specify what part of the file you
4654 want to print if you want to see other parts of the program.
4656 Here are the forms of the @code{edit} command most commonly used:
4660 Edit the current source file at the active line number in the program.
4662 @item edit @var{number}
4663 Edit the current source file with @var{number} as the active line number.
4665 @item edit @var{function}
4666 Edit the file containing @var{function} at the beginning of its definition.
4668 @item edit @var{filename}:@var{number}
4669 Specifies line @var{number} in the source file @var{filename}.
4671 @item edit @var{filename}:@var{function}
4672 Specifies the line that begins the body of the
4673 function @var{function} in the file @var{filename}. You only need the
4674 file name with a function name to avoid ambiguity when there are
4675 identically named functions in different source files.
4677 @item edit *@var{address}
4678 Specifies the line containing the program address @var{address}.
4679 @var{address} may be any expression.
4682 @subsection Choosing your editor
4683 You can customize @value{GDBN} to use any editor you want
4685 The only restriction is that your editor (say @code{ex}), recognizes the
4686 following command-line syntax:
4688 ex +@var{number} file
4690 The optional numeric value +@var{number} specifies the number of the line in
4691 the file where to start editing.}.
4692 By default, it is @file{@value{EDITOR}}, but you can change this
4693 by setting the environment variable @code{EDITOR} before using
4694 @value{GDBN}. For example, to configure @value{GDBN} to use the
4695 @code{vi} editor, you could use these commands with the @code{sh} shell:
4701 or in the @code{csh} shell,
4703 setenv EDITOR /usr/bin/vi
4708 @section Searching source files
4709 @cindex searching source files
4711 There are two commands for searching through the current source file for a
4716 @kindex forward-search
4717 @item forward-search @var{regexp}
4718 @itemx search @var{regexp}
4719 The command @samp{forward-search @var{regexp}} checks each line,
4720 starting with the one following the last line listed, for a match for
4721 @var{regexp}. It lists the line that is found. You can use the
4722 synonym @samp{search @var{regexp}} or abbreviate the command name as
4725 @kindex reverse-search
4726 @item reverse-search @var{regexp}
4727 The command @samp{reverse-search @var{regexp}} checks each line, starting
4728 with the one before the last line listed and going backward, for a match
4729 for @var{regexp}. It lists the line that is found. You can abbreviate
4730 this command as @code{rev}.
4734 @section Specifying source directories
4737 @cindex directories for source files
4738 Executable programs sometimes do not record the directories of the source
4739 files from which they were compiled, just the names. Even when they do,
4740 the directories could be moved between the compilation and your debugging
4741 session. @value{GDBN} has a list of directories to search for source files;
4742 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
4743 it tries all the directories in the list, in the order they are present
4744 in the list, until it finds a file with the desired name.
4746 For example, suppose an executable references the file
4747 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
4748 @file{/mnt/cross}. The file is first looked up literally; if this
4749 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
4750 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
4751 message is printed. @value{GDBN} does not look up the parts of the
4752 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
4753 Likewise, the subdirectories of the source path are not searched: if
4754 the source path is @file{/mnt/cross}, and the binary refers to
4755 @file{foo.c}, @value{GDBN} would not find it under
4756 @file{/mnt/cross/usr/src/foo-1.0/lib}.
4758 Plain file names, relative file names with leading directories, file
4759 names containing dots, etc.@: are all treated as described above; for
4760 instance, if the source path is @file{/mnt/cross}, and the source file
4761 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
4762 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
4763 that---@file{/mnt/cross/foo.c}.
4765 Note that the executable search path is @emph{not} used to locate the
4766 source files. Neither is the current working directory, unless it
4767 happens to be in the source path.
4769 Whenever you reset or rearrange the source path, @value{GDBN} clears out
4770 any information it has cached about where source files are found and where
4771 each line is in the file.
4775 When you start @value{GDBN}, its source path includes only @samp{cdir}
4776 and @samp{cwd}, in that order.
4777 To add other directories, use the @code{directory} command.
4780 @item directory @var{dirname} @dots{}
4781 @item dir @var{dirname} @dots{}
4782 Add directory @var{dirname} to the front of the source path. Several
4783 directory names may be given to this command, separated by @samp{:}
4784 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
4785 part of absolute file names) or
4786 whitespace. You may specify a directory that is already in the source
4787 path; this moves it forward, so @value{GDBN} searches it sooner.
4791 @vindex $cdir@r{, convenience variable}
4792 @vindex $cwdr@r{, convenience variable}
4793 @cindex compilation directory
4794 @cindex current directory
4795 @cindex working directory
4796 @cindex directory, current
4797 @cindex directory, compilation
4798 You can use the string @samp{$cdir} to refer to the compilation
4799 directory (if one is recorded), and @samp{$cwd} to refer to the current
4800 working directory. @samp{$cwd} is not the same as @samp{.}---the former
4801 tracks the current working directory as it changes during your @value{GDBN}
4802 session, while the latter is immediately expanded to the current
4803 directory at the time you add an entry to the source path.
4806 Reset the source path to empty again. This requires confirmation.
4808 @c RET-repeat for @code{directory} is explicitly disabled, but since
4809 @c repeating it would be a no-op we do not say that. (thanks to RMS)
4811 @item show directories
4812 @kindex show directories
4813 Print the source path: show which directories it contains.
4816 If your source path is cluttered with directories that are no longer of
4817 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
4818 versions of source. You can correct the situation as follows:
4822 Use @code{directory} with no argument to reset the source path to empty.
4825 Use @code{directory} with suitable arguments to reinstall the
4826 directories you want in the source path. You can add all the
4827 directories in one command.
4831 @section Source and machine code
4832 @cindex source line and its code address
4834 You can use the command @code{info line} to map source lines to program
4835 addresses (and vice versa), and the command @code{disassemble} to display
4836 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
4837 mode, the @code{info line} command causes the arrow to point to the
4838 line specified. Also, @code{info line} prints addresses in symbolic form as
4843 @item info line @var{linespec}
4844 Print the starting and ending addresses of the compiled code for
4845 source line @var{linespec}. You can specify source lines in any of
4846 the ways understood by the @code{list} command (@pxref{List, ,Printing
4850 For example, we can use @code{info line} to discover the location of
4851 the object code for the first line of function
4852 @code{m4_changequote}:
4854 @c FIXME: I think this example should also show the addresses in
4855 @c symbolic form, as they usually would be displayed.
4857 (@value{GDBP}) info line m4_changequote
4858 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
4862 @cindex code address and its source line
4863 We can also inquire (using @code{*@var{addr}} as the form for
4864 @var{linespec}) what source line covers a particular address:
4866 (@value{GDBP}) info line *0x63ff
4867 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
4870 @cindex @code{$_} and @code{info line}
4871 @cindex @code{x} command, default address
4872 @kindex x@r{(examine), and} info line
4873 After @code{info line}, the default address for the @code{x} command
4874 is changed to the starting address of the line, so that @samp{x/i} is
4875 sufficient to begin examining the machine code (@pxref{Memory,
4876 ,Examining memory}). Also, this address is saved as the value of the
4877 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
4882 @cindex assembly instructions
4883 @cindex instructions, assembly
4884 @cindex machine instructions
4885 @cindex listing machine instructions
4887 This specialized command dumps a range of memory as machine
4888 instructions. The default memory range is the function surrounding the
4889 program counter of the selected frame. A single argument to this
4890 command is a program counter value; @value{GDBN} dumps the function
4891 surrounding this value. Two arguments specify a range of addresses
4892 (first inclusive, second exclusive) to dump.
4895 The following example shows the disassembly of a range of addresses of
4896 HP PA-RISC 2.0 code:
4899 (@value{GDBP}) disas 0x32c4 0x32e4
4900 Dump of assembler code from 0x32c4 to 0x32e4:
4901 0x32c4 <main+204>: addil 0,dp
4902 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
4903 0x32cc <main+212>: ldil 0x3000,r31
4904 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
4905 0x32d4 <main+220>: ldo 0(r31),rp
4906 0x32d8 <main+224>: addil -0x800,dp
4907 0x32dc <main+228>: ldo 0x588(r1),r26
4908 0x32e0 <main+232>: ldil 0x3000,r31
4909 End of assembler dump.
4912 Some architectures have more than one commonly-used set of instruction
4913 mnemonics or other syntax.
4916 @kindex set disassembly-flavor
4917 @cindex Intel disassembly flavor
4918 @cindex AT&T disassembly flavor
4919 @item set disassembly-flavor @var{instruction-set}
4920 Select the instruction set to use when disassembling the
4921 program via the @code{disassemble} or @code{x/i} commands.
4923 Currently this command is only defined for the Intel x86 family. You
4924 can set @var{instruction-set} to either @code{intel} or @code{att}.
4925 The default is @code{att}, the AT&T flavor used by default by Unix
4926 assemblers for x86-based targets.
4928 @kindex show disassembly-flavor
4929 @item show disassembly-flavor
4930 Show the current setting of the disassembly flavor.
4935 @chapter Examining Data
4937 @cindex printing data
4938 @cindex examining data
4941 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
4942 @c document because it is nonstandard... Under Epoch it displays in a
4943 @c different window or something like that.
4944 The usual way to examine data in your program is with the @code{print}
4945 command (abbreviated @code{p}), or its synonym @code{inspect}. It
4946 evaluates and prints the value of an expression of the language your
4947 program is written in (@pxref{Languages, ,Using @value{GDBN} with
4948 Different Languages}).
4951 @item print @var{expr}
4952 @itemx print /@var{f} @var{expr}
4953 @var{expr} is an expression (in the source language). By default the
4954 value of @var{expr} is printed in a format appropriate to its data type;
4955 you can choose a different format by specifying @samp{/@var{f}}, where
4956 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
4960 @itemx print /@var{f}
4961 @cindex reprint the last value
4962 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
4963 @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
4964 conveniently inspect the same value in an alternative format.
4967 A more low-level way of examining data is with the @code{x} command.
4968 It examines data in memory at a specified address and prints it in a
4969 specified format. @xref{Memory, ,Examining memory}.
4971 If you are interested in information about types, or about how the
4972 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
4973 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
4977 * Expressions:: Expressions
4978 * Variables:: Program variables
4979 * Arrays:: Artificial arrays
4980 * Output Formats:: Output formats
4981 * Memory:: Examining memory
4982 * Auto Display:: Automatic display
4983 * Print Settings:: Print settings
4984 * Value History:: Value history
4985 * Convenience Vars:: Convenience variables
4986 * Registers:: Registers
4987 * Floating Point Hardware:: Floating point hardware
4988 * Vector Unit:: Vector Unit
4989 * OS Information:: Auxiliary data provided by operating system
4990 * Memory Region Attributes:: Memory region attributes
4991 * Dump/Restore Files:: Copy between memory and a file
4992 * Core File Generation:: Cause a program dump its core
4993 * Character Sets:: Debugging programs that use a different
4994 character set than GDB does
4995 * Caching Remote Data:: Data caching for remote targets
4999 @section Expressions
5002 @code{print} and many other @value{GDBN} commands accept an expression and
5003 compute its value. Any kind of constant, variable or operator defined
5004 by the programming language you are using is valid in an expression in
5005 @value{GDBN}. This includes conditional expressions, function calls,
5006 casts, and string constants. It also includes preprocessor macros, if
5007 you compiled your program to include this information; see
5010 @cindex arrays in expressions
5011 @value{GDBN} supports array constants in expressions input by
5012 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
5013 you can use the command @code{print @{1, 2, 3@}} to build up an array in
5014 memory that is @code{malloc}ed in the target program.
5016 Because C is so widespread, most of the expressions shown in examples in
5017 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
5018 Languages}, for information on how to use expressions in other
5021 In this section, we discuss operators that you can use in @value{GDBN}
5022 expressions regardless of your programming language.
5024 @cindex casts, in expressions
5025 Casts are supported in all languages, not just in C, because it is so
5026 useful to cast a number into a pointer in order to examine a structure
5027 at that address in memory.
5028 @c FIXME: casts supported---Mod2 true?
5030 @value{GDBN} supports these operators, in addition to those common
5031 to programming languages:
5035 @samp{@@} is a binary operator for treating parts of memory as arrays.
5036 @xref{Arrays, ,Artificial arrays}, for more information.
5039 @samp{::} allows you to specify a variable in terms of the file or
5040 function where it is defined. @xref{Variables, ,Program variables}.
5042 @cindex @{@var{type}@}
5043 @cindex type casting memory
5044 @cindex memory, viewing as typed object
5045 @cindex casts, to view memory
5046 @item @{@var{type}@} @var{addr}
5047 Refers to an object of type @var{type} stored at address @var{addr} in
5048 memory. @var{addr} may be any expression whose value is an integer or
5049 pointer (but parentheses are required around binary operators, just as in
5050 a cast). This construct is allowed regardless of what kind of data is
5051 normally supposed to reside at @var{addr}.
5055 @section Program variables
5057 The most common kind of expression to use is the name of a variable
5060 Variables in expressions are understood in the selected stack frame
5061 (@pxref{Selection, ,Selecting a frame}); they must be either:
5065 global (or file-static)
5072 visible according to the scope rules of the
5073 programming language from the point of execution in that frame
5076 @noindent This means that in the function
5091 you can examine and use the variable @code{a} whenever your program is
5092 executing within the function @code{foo}, but you can only use or
5093 examine the variable @code{b} while your program is executing inside
5094 the block where @code{b} is declared.
5096 @cindex variable name conflict
5097 There is an exception: you can refer to a variable or function whose
5098 scope is a single source file even if the current execution point is not
5099 in this file. But it is possible to have more than one such variable or
5100 function with the same name (in different source files). If that
5101 happens, referring to that name has unpredictable effects. If you wish,
5102 you can specify a static variable in a particular function or file,
5103 using the colon-colon (@code{::}) notation:
5105 @cindex colon-colon, context for variables/functions
5107 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
5108 @cindex @code{::}, context for variables/functions
5111 @var{file}::@var{variable}
5112 @var{function}::@var{variable}
5116 Here @var{file} or @var{function} is the name of the context for the
5117 static @var{variable}. In the case of file names, you can use quotes to
5118 make sure @value{GDBN} parses the file name as a single word---for example,
5119 to print a global value of @code{x} defined in @file{f2.c}:
5122 (@value{GDBP}) p 'f2.c'::x
5125 @cindex C@t{++} scope resolution
5126 This use of @samp{::} is very rarely in conflict with the very similar
5127 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
5128 scope resolution operator in @value{GDBN} expressions.
5129 @c FIXME: Um, so what happens in one of those rare cases where it's in
5132 @cindex wrong values
5133 @cindex variable values, wrong
5134 @cindex function entry/exit, wrong values of variables
5135 @cindex optimized code, wrong values of variables
5137 @emph{Warning:} Occasionally, a local variable may appear to have the
5138 wrong value at certain points in a function---just after entry to a new
5139 scope, and just before exit.
5141 You may see this problem when you are stepping by machine instructions.
5142 This is because, on most machines, it takes more than one instruction to
5143 set up a stack frame (including local variable definitions); if you are
5144 stepping by machine instructions, variables may appear to have the wrong
5145 values until the stack frame is completely built. On exit, it usually
5146 also takes more than one machine instruction to destroy a stack frame;
5147 after you begin stepping through that group of instructions, local
5148 variable definitions may be gone.
5150 This may also happen when the compiler does significant optimizations.
5151 To be sure of always seeing accurate values, turn off all optimization
5154 @cindex ``No symbol "foo" in current context''
5155 Another possible effect of compiler optimizations is to optimize
5156 unused variables out of existence, or assign variables to registers (as
5157 opposed to memory addresses). Depending on the support for such cases
5158 offered by the debug info format used by the compiler, @value{GDBN}
5159 might not be able to display values for such local variables. If that
5160 happens, @value{GDBN} will print a message like this:
5163 No symbol "foo" in current context.
5166 To solve such problems, either recompile without optimizations, or use a
5167 different debug info format, if the compiler supports several such
5168 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
5169 usually supports the @option{-gstabs+} option. @option{-gstabs+}
5170 produces debug info in a format that is superior to formats such as
5171 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
5172 an effective form for debug info. @xref{Debugging Options,,Options
5173 for Debugging Your Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}.
5174 @xref{C, , Debugging C++}, for more info about debug info formats
5175 that are best suited to C@t{++} programs.
5178 @section Artificial arrays
5180 @cindex artificial array
5182 @kindex @@@r{, referencing memory as an array}
5183 It is often useful to print out several successive objects of the
5184 same type in memory; a section of an array, or an array of
5185 dynamically determined size for which only a pointer exists in the
5188 You can do this by referring to a contiguous span of memory as an
5189 @dfn{artificial array}, using the binary operator @samp{@@}. The left
5190 operand of @samp{@@} should be the first element of the desired array
5191 and be an individual object. The right operand should be the desired length
5192 of the array. The result is an array value whose elements are all of
5193 the type of the left argument. The first element is actually the left
5194 argument; the second element comes from bytes of memory immediately
5195 following those that hold the first element, and so on. Here is an
5196 example. If a program says
5199 int *array = (int *) malloc (len * sizeof (int));
5203 you can print the contents of @code{array} with
5209 The left operand of @samp{@@} must reside in memory. Array values made
5210 with @samp{@@} in this way behave just like other arrays in terms of
5211 subscripting, and are coerced to pointers when used in expressions.
5212 Artificial arrays most often appear in expressions via the value history
5213 (@pxref{Value History, ,Value history}), after printing one out.
5215 Another way to create an artificial array is to use a cast.
5216 This re-interprets a value as if it were an array.
5217 The value need not be in memory:
5219 (@value{GDBP}) p/x (short[2])0x12345678
5220 $1 = @{0x1234, 0x5678@}
5223 As a convenience, if you leave the array length out (as in
5224 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5225 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5227 (@value{GDBP}) p/x (short[])0x12345678
5228 $2 = @{0x1234, 0x5678@}
5231 Sometimes the artificial array mechanism is not quite enough; in
5232 moderately complex data structures, the elements of interest may not
5233 actually be adjacent---for example, if you are interested in the values
5234 of pointers in an array. One useful work-around in this situation is
5235 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5236 variables}) as a counter in an expression that prints the first
5237 interesting value, and then repeat that expression via @key{RET}. For
5238 instance, suppose you have an array @code{dtab} of pointers to
5239 structures, and you are interested in the values of a field @code{fv}
5240 in each structure. Here is an example of what you might type:
5250 @node Output Formats
5251 @section Output formats
5253 @cindex formatted output
5254 @cindex output formats
5255 By default, @value{GDBN} prints a value according to its data type. Sometimes
5256 this is not what you want. For example, you might want to print a number
5257 in hex, or a pointer in decimal. Or you might want to view data in memory
5258 at a certain address as a character string or as an instruction. To do
5259 these things, specify an @dfn{output format} when you print a value.
5261 The simplest use of output formats is to say how to print a value
5262 already computed. This is done by starting the arguments of the
5263 @code{print} command with a slash and a format letter. The format
5264 letters supported are:
5268 Regard the bits of the value as an integer, and print the integer in
5272 Print as integer in signed decimal.
5275 Print as integer in unsigned decimal.
5278 Print as integer in octal.
5281 Print as integer in binary. The letter @samp{t} stands for ``two''.
5282 @footnote{@samp{b} cannot be used because these format letters are also
5283 used with the @code{x} command, where @samp{b} stands for ``byte'';
5284 see @ref{Memory,,Examining memory}.}
5287 @cindex unknown address, locating
5288 @cindex locate address
5289 Print as an address, both absolute in hexadecimal and as an offset from
5290 the nearest preceding symbol. You can use this format used to discover
5291 where (in what function) an unknown address is located:
5294 (@value{GDBP}) p/a 0x54320
5295 $3 = 0x54320 <_initialize_vx+396>
5299 The command @code{info symbol 0x54320} yields similar results.
5300 @xref{Symbols, info symbol}.
5303 Regard as an integer and print it as a character constant.
5306 Regard the bits of the value as a floating point number and print
5307 using typical floating point syntax.
5310 For example, to print the program counter in hex (@pxref{Registers}), type
5317 Note that no space is required before the slash; this is because command
5318 names in @value{GDBN} cannot contain a slash.
5320 To reprint the last value in the value history with a different format,
5321 you can use the @code{print} command with just a format and no
5322 expression. For example, @samp{p/x} reprints the last value in hex.
5325 @section Examining memory
5327 You can use the command @code{x} (for ``examine'') to examine memory in
5328 any of several formats, independently of your program's data types.
5330 @cindex examining memory
5332 @kindex x @r{(examine memory)}
5333 @item x/@var{nfu} @var{addr}
5336 Use the @code{x} command to examine memory.
5339 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5340 much memory to display and how to format it; @var{addr} is an
5341 expression giving the address where you want to start displaying memory.
5342 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5343 Several commands set convenient defaults for @var{addr}.
5346 @item @var{n}, the repeat count
5347 The repeat count is a decimal integer; the default is 1. It specifies
5348 how much memory (counting by units @var{u}) to display.
5349 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5352 @item @var{f}, the display format
5353 The display format is one of the formats used by @code{print},
5354 @samp{s} (null-terminated string), or @samp{i} (machine instruction).
5355 The default is @samp{x} (hexadecimal) initially.
5356 The default changes each time you use either @code{x} or @code{print}.
5358 @item @var{u}, the unit size
5359 The unit size is any of
5365 Halfwords (two bytes).
5367 Words (four bytes). This is the initial default.
5369 Giant words (eight bytes).
5372 Each time you specify a unit size with @code{x}, that size becomes the
5373 default unit the next time you use @code{x}. (For the @samp{s} and
5374 @samp{i} formats, the unit size is ignored and is normally not written.)
5376 @item @var{addr}, starting display address
5377 @var{addr} is the address where you want @value{GDBN} to begin displaying
5378 memory. The expression need not have a pointer value (though it may);
5379 it is always interpreted as an integer address of a byte of memory.
5380 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5381 @var{addr} is usually just after the last address examined---but several
5382 other commands also set the default address: @code{info breakpoints} (to
5383 the address of the last breakpoint listed), @code{info line} (to the
5384 starting address of a line), and @code{print} (if you use it to display
5385 a value from memory).
5388 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5389 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5390 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5391 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5392 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5394 Since the letters indicating unit sizes are all distinct from the
5395 letters specifying output formats, you do not have to remember whether
5396 unit size or format comes first; either order works. The output
5397 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5398 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5400 Even though the unit size @var{u} is ignored for the formats @samp{s}
5401 and @samp{i}, you might still want to use a count @var{n}; for example,
5402 @samp{3i} specifies that you want to see three machine instructions,
5403 including any operands. The command @code{disassemble} gives an
5404 alternative way of inspecting machine instructions; see @ref{Machine
5405 Code,,Source and machine code}.
5407 All the defaults for the arguments to @code{x} are designed to make it
5408 easy to continue scanning memory with minimal specifications each time
5409 you use @code{x}. For example, after you have inspected three machine
5410 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5411 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5412 the repeat count @var{n} is used again; the other arguments default as
5413 for successive uses of @code{x}.
5415 @cindex @code{$_}, @code{$__}, and value history
5416 The addresses and contents printed by the @code{x} command are not saved
5417 in the value history because there is often too much of them and they
5418 would get in the way. Instead, @value{GDBN} makes these values available for
5419 subsequent use in expressions as values of the convenience variables
5420 @code{$_} and @code{$__}. After an @code{x} command, the last address
5421 examined is available for use in expressions in the convenience variable
5422 @code{$_}. The contents of that address, as examined, are available in
5423 the convenience variable @code{$__}.
5425 If the @code{x} command has a repeat count, the address and contents saved
5426 are from the last memory unit printed; this is not the same as the last
5427 address printed if several units were printed on the last line of output.
5429 @cindex remote memory comparison
5430 @cindex verify remote memory image
5431 When you are debugging a program running on a remote target machine
5432 (@pxref{Remote}), you may wish to verify the program's image in the
5433 remote machine's memory against the executable file you downloaded to
5434 the target. The @code{compare-sections} command is provided for such
5438 @kindex compare-sections
5439 @item compare-sections @r{[}@var{section-name}@r{]}
5440 Compare the data of a loadable section @var{section-name} in the
5441 executable file of the program being debugged with the same section in
5442 the remote machine's memory, and report any mismatches. With no
5443 arguments, compares all loadable sections. This command's
5444 availability depends on the target's support for the @code{"qCRC"}
5449 @section Automatic display
5450 @cindex automatic display
5451 @cindex display of expressions
5453 If you find that you want to print the value of an expression frequently
5454 (to see how it changes), you might want to add it to the @dfn{automatic
5455 display list} so that @value{GDBN} prints its value each time your program stops.
5456 Each expression added to the list is given a number to identify it;
5457 to remove an expression from the list, you specify that number.
5458 The automatic display looks like this:
5462 3: bar[5] = (struct hack *) 0x3804
5466 This display shows item numbers, expressions and their current values. As with
5467 displays you request manually using @code{x} or @code{print}, you can
5468 specify the output format you prefer; in fact, @code{display} decides
5469 whether to use @code{print} or @code{x} depending on how elaborate your
5470 format specification is---it uses @code{x} if you specify a unit size,
5471 or one of the two formats (@samp{i} and @samp{s}) that are only
5472 supported by @code{x}; otherwise it uses @code{print}.
5476 @item display @var{expr}
5477 Add the expression @var{expr} to the list of expressions to display
5478 each time your program stops. @xref{Expressions, ,Expressions}.
5480 @code{display} does not repeat if you press @key{RET} again after using it.
5482 @item display/@var{fmt} @var{expr}
5483 For @var{fmt} specifying only a display format and not a size or
5484 count, add the expression @var{expr} to the auto-display list but
5485 arrange to display it each time in the specified format @var{fmt}.
5486 @xref{Output Formats,,Output formats}.
5488 @item display/@var{fmt} @var{addr}
5489 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
5490 number of units, add the expression @var{addr} as a memory address to
5491 be examined each time your program stops. Examining means in effect
5492 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
5495 For example, @samp{display/i $pc} can be helpful, to see the machine
5496 instruction about to be executed each time execution stops (@samp{$pc}
5497 is a common name for the program counter; @pxref{Registers, ,Registers}).
5500 @kindex delete display
5502 @item undisplay @var{dnums}@dots{}
5503 @itemx delete display @var{dnums}@dots{}
5504 Remove item numbers @var{dnums} from the list of expressions to display.
5506 @code{undisplay} does not repeat if you press @key{RET} after using it.
5507 (Otherwise you would just get the error @samp{No display number @dots{}}.)
5509 @kindex disable display
5510 @item disable display @var{dnums}@dots{}
5511 Disable the display of item numbers @var{dnums}. A disabled display
5512 item is not printed automatically, but is not forgotten. It may be
5513 enabled again later.
5515 @kindex enable display
5516 @item enable display @var{dnums}@dots{}
5517 Enable display of item numbers @var{dnums}. It becomes effective once
5518 again in auto display of its expression, until you specify otherwise.
5521 Display the current values of the expressions on the list, just as is
5522 done when your program stops.
5524 @kindex info display
5526 Print the list of expressions previously set up to display
5527 automatically, each one with its item number, but without showing the
5528 values. This includes disabled expressions, which are marked as such.
5529 It also includes expressions which would not be displayed right now
5530 because they refer to automatic variables not currently available.
5533 @cindex display disabled out of scope
5534 If a display expression refers to local variables, then it does not make
5535 sense outside the lexical context for which it was set up. Such an
5536 expression is disabled when execution enters a context where one of its
5537 variables is not defined. For example, if you give the command
5538 @code{display last_char} while inside a function with an argument
5539 @code{last_char}, @value{GDBN} displays this argument while your program
5540 continues to stop inside that function. When it stops elsewhere---where
5541 there is no variable @code{last_char}---the display is disabled
5542 automatically. The next time your program stops where @code{last_char}
5543 is meaningful, you can enable the display expression once again.
5545 @node Print Settings
5546 @section Print settings
5548 @cindex format options
5549 @cindex print settings
5550 @value{GDBN} provides the following ways to control how arrays, structures,
5551 and symbols are printed.
5554 These settings are useful for debugging programs in any language:
5558 @item set print address
5559 @itemx set print address on
5560 @cindex print/don't print memory addresses
5561 @value{GDBN} prints memory addresses showing the location of stack
5562 traces, structure values, pointer values, breakpoints, and so forth,
5563 even when it also displays the contents of those addresses. The default
5564 is @code{on}. For example, this is what a stack frame display looks like with
5565 @code{set print address on}:
5570 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
5572 530 if (lquote != def_lquote)
5576 @item set print address off
5577 Do not print addresses when displaying their contents. For example,
5578 this is the same stack frame displayed with @code{set print address off}:
5582 (@value{GDBP}) set print addr off
5584 #0 set_quotes (lq="<<", rq=">>") at input.c:530
5585 530 if (lquote != def_lquote)
5589 You can use @samp{set print address off} to eliminate all machine
5590 dependent displays from the @value{GDBN} interface. For example, with
5591 @code{print address off}, you should get the same text for backtraces on
5592 all machines---whether or not they involve pointer arguments.
5595 @item show print address
5596 Show whether or not addresses are to be printed.
5599 When @value{GDBN} prints a symbolic address, it normally prints the
5600 closest earlier symbol plus an offset. If that symbol does not uniquely
5601 identify the address (for example, it is a name whose scope is a single
5602 source file), you may need to clarify. One way to do this is with
5603 @code{info line}, for example @samp{info line *0x4537}. Alternately,
5604 you can set @value{GDBN} to print the source file and line number when
5605 it prints a symbolic address:
5608 @item set print symbol-filename on
5609 @cindex source file and line of a symbol
5610 @cindex symbol, source file and line
5611 Tell @value{GDBN} to print the source file name and line number of a
5612 symbol in the symbolic form of an address.
5614 @item set print symbol-filename off
5615 Do not print source file name and line number of a symbol. This is the
5618 @item show print symbol-filename
5619 Show whether or not @value{GDBN} will print the source file name and
5620 line number of a symbol in the symbolic form of an address.
5623 Another situation where it is helpful to show symbol filenames and line
5624 numbers is when disassembling code; @value{GDBN} shows you the line
5625 number and source file that corresponds to each instruction.
5627 Also, you may wish to see the symbolic form only if the address being
5628 printed is reasonably close to the closest earlier symbol:
5631 @item set print max-symbolic-offset @var{max-offset}
5632 @cindex maximum value for offset of closest symbol
5633 Tell @value{GDBN} to only display the symbolic form of an address if the
5634 offset between the closest earlier symbol and the address is less than
5635 @var{max-offset}. The default is 0, which tells @value{GDBN}
5636 to always print the symbolic form of an address if any symbol precedes it.
5638 @item show print max-symbolic-offset
5639 Ask how large the maximum offset is that @value{GDBN} prints in a
5643 @cindex wild pointer, interpreting
5644 @cindex pointer, finding referent
5645 If you have a pointer and you are not sure where it points, try
5646 @samp{set print symbol-filename on}. Then you can determine the name
5647 and source file location of the variable where it points, using
5648 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
5649 For example, here @value{GDBN} shows that a variable @code{ptt} points
5650 at another variable @code{t}, defined in @file{hi2.c}:
5653 (@value{GDBP}) set print symbol-filename on
5654 (@value{GDBP}) p/a ptt
5655 $4 = 0xe008 <t in hi2.c>
5659 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
5660 does not show the symbol name and filename of the referent, even with
5661 the appropriate @code{set print} options turned on.
5664 Other settings control how different kinds of objects are printed:
5667 @item set print array
5668 @itemx set print array on
5669 @cindex pretty print arrays
5670 Pretty print arrays. This format is more convenient to read,
5671 but uses more space. The default is off.
5673 @item set print array off
5674 Return to compressed format for arrays.
5676 @item show print array
5677 Show whether compressed or pretty format is selected for displaying
5680 @item set print elements @var{number-of-elements}
5681 @cindex number of array elements to print
5682 @cindex limit on number of printed array elements
5683 Set a limit on how many elements of an array @value{GDBN} will print.
5684 If @value{GDBN} is printing a large array, it stops printing after it has
5685 printed the number of elements set by the @code{set print elements} command.
5686 This limit also applies to the display of strings.
5687 When @value{GDBN} starts, this limit is set to 200.
5688 Setting @var{number-of-elements} to zero means that the printing is unlimited.
5690 @item show print elements
5691 Display the number of elements of a large array that @value{GDBN} will print.
5692 If the number is 0, then the printing is unlimited.
5694 @item set print repeats
5695 @cindex repeated array elements
5696 Set the threshold for suppressing display of repeated array
5697 elelments. When the number of consecutive identical elements of an
5698 array exceeds the threshold, @value{GDBN} prints the string
5699 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
5700 identical repetitions, instead of displaying the identical elements
5701 themselves. Setting the threshold to zero will cause all elements to
5702 be individually printed. The default threshold is 10.
5704 @item show print repeats
5705 Display the current threshold for printing repeated identical
5708 @item set print null-stop
5709 @cindex @sc{null} elements in arrays
5710 Cause @value{GDBN} to stop printing the characters of an array when the first
5711 @sc{null} is encountered. This is useful when large arrays actually
5712 contain only short strings.
5715 @item show print null-stop
5716 Show whether @value{GDBN} stops printing an array on the first
5717 @sc{null} character.
5719 @item set print pretty on
5720 @cindex print structures in indented form
5721 @cindex indentation in structure display
5722 Cause @value{GDBN} to print structures in an indented format with one member
5723 per line, like this:
5738 @item set print pretty off
5739 Cause @value{GDBN} to print structures in a compact format, like this:
5743 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
5744 meat = 0x54 "Pork"@}
5749 This is the default format.
5751 @item show print pretty
5752 Show which format @value{GDBN} is using to print structures.
5754 @item set print sevenbit-strings on
5755 @cindex eight-bit characters in strings
5756 @cindex octal escapes in strings
5757 Print using only seven-bit characters; if this option is set,
5758 @value{GDBN} displays any eight-bit characters (in strings or
5759 character values) using the notation @code{\}@var{nnn}. This setting is
5760 best if you are working in English (@sc{ascii}) and you use the
5761 high-order bit of characters as a marker or ``meta'' bit.
5763 @item set print sevenbit-strings off
5764 Print full eight-bit characters. This allows the use of more
5765 international character sets, and is the default.
5767 @item show print sevenbit-strings
5768 Show whether or not @value{GDBN} is printing only seven-bit characters.
5770 @item set print union on
5771 @cindex unions in structures, printing
5772 Tell @value{GDBN} to print unions which are contained in structures
5773 and other unions. This is the default setting.
5775 @item set print union off
5776 Tell @value{GDBN} not to print unions which are contained in
5777 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
5780 @item show print union
5781 Ask @value{GDBN} whether or not it will print unions which are contained in
5782 structures and other unions.
5784 For example, given the declarations
5787 typedef enum @{Tree, Bug@} Species;
5788 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
5789 typedef enum @{Caterpillar, Cocoon, Butterfly@}
5800 struct thing foo = @{Tree, @{Acorn@}@};
5804 with @code{set print union on} in effect @samp{p foo} would print
5807 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
5811 and with @code{set print union off} in effect it would print
5814 $1 = @{it = Tree, form = @{...@}@}
5818 @code{set print union} affects programs written in C-like languages
5824 These settings are of interest when debugging C@t{++} programs:
5827 @cindex demangling C@t{++} names
5828 @item set print demangle
5829 @itemx set print demangle on
5830 Print C@t{++} names in their source form rather than in the encoded
5831 (``mangled'') form passed to the assembler and linker for type-safe
5832 linkage. The default is on.
5834 @item show print demangle
5835 Show whether C@t{++} names are printed in mangled or demangled form.
5837 @item set print asm-demangle
5838 @itemx set print asm-demangle on
5839 Print C@t{++} names in their source form rather than their mangled form, even
5840 in assembler code printouts such as instruction disassemblies.
5843 @item show print asm-demangle
5844 Show whether C@t{++} names in assembly listings are printed in mangled
5847 @cindex C@t{++} symbol decoding style
5848 @cindex symbol decoding style, C@t{++}
5849 @kindex set demangle-style
5850 @item set demangle-style @var{style}
5851 Choose among several encoding schemes used by different compilers to
5852 represent C@t{++} names. The choices for @var{style} are currently:
5856 Allow @value{GDBN} to choose a decoding style by inspecting your program.
5859 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
5860 This is the default.
5863 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
5866 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
5869 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
5870 @strong{Warning:} this setting alone is not sufficient to allow
5871 debugging @code{cfront}-generated executables. @value{GDBN} would
5872 require further enhancement to permit that.
5875 If you omit @var{style}, you will see a list of possible formats.
5877 @item show demangle-style
5878 Display the encoding style currently in use for decoding C@t{++} symbols.
5880 @item set print object
5881 @itemx set print object on
5882 @cindex derived type of an object, printing
5883 @cindex display derived types
5884 When displaying a pointer to an object, identify the @emph{actual}
5885 (derived) type of the object rather than the @emph{declared} type, using
5886 the virtual function table.
5888 @item set print object off
5889 Display only the declared type of objects, without reference to the
5890 virtual function table. This is the default setting.
5892 @item show print object
5893 Show whether actual, or declared, object types are displayed.
5895 @item set print static-members
5896 @itemx set print static-members on
5897 @cindex static members of C@t{++} objects
5898 Print static members when displaying a C@t{++} object. The default is on.
5900 @item set print static-members off
5901 Do not print static members when displaying a C@t{++} object.
5903 @item show print static-members
5904 Show whether C@t{++} static members are printed or not.
5906 @item set print pascal_static-members
5907 @itemx set print pascal_static-members on
5908 @cindex static members of Pacal objects
5909 @cindex Pacal objects, static members display
5910 Print static members when displaying a Pascal object. The default is on.
5912 @item set print pascal_static-members off
5913 Do not print static members when displaying a Pascal object.
5915 @item show print pascal_static-members
5916 Show whether Pascal static members are printed or not.
5918 @c These don't work with HP ANSI C++ yet.
5919 @item set print vtbl
5920 @itemx set print vtbl on
5921 @cindex pretty print C@t{++} virtual function tables
5922 @cindex virtual functions (C@t{++}) display
5923 @cindex VTBL display
5924 Pretty print C@t{++} virtual function tables. The default is off.
5925 (The @code{vtbl} commands do not work on programs compiled with the HP
5926 ANSI C@t{++} compiler (@code{aCC}).)
5928 @item set print vtbl off
5929 Do not pretty print C@t{++} virtual function tables.
5931 @item show print vtbl
5932 Show whether C@t{++} virtual function tables are pretty printed, or not.
5936 @section Value history
5938 @cindex value history
5939 @cindex history of values printed by @value{GDBN}
5940 Values printed by the @code{print} command are saved in the @value{GDBN}
5941 @dfn{value history}. This allows you to refer to them in other expressions.
5942 Values are kept until the symbol table is re-read or discarded
5943 (for example with the @code{file} or @code{symbol-file} commands).
5944 When the symbol table changes, the value history is discarded,
5945 since the values may contain pointers back to the types defined in the
5950 @cindex history number
5951 The values printed are given @dfn{history numbers} by which you can
5952 refer to them. These are successive integers starting with one.
5953 @code{print} shows you the history number assigned to a value by
5954 printing @samp{$@var{num} = } before the value; here @var{num} is the
5957 To refer to any previous value, use @samp{$} followed by the value's
5958 history number. The way @code{print} labels its output is designed to
5959 remind you of this. Just @code{$} refers to the most recent value in
5960 the history, and @code{$$} refers to the value before that.
5961 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
5962 is the value just prior to @code{$$}, @code{$$1} is equivalent to
5963 @code{$$}, and @code{$$0} is equivalent to @code{$}.
5965 For example, suppose you have just printed a pointer to a structure and
5966 want to see the contents of the structure. It suffices to type
5972 If you have a chain of structures where the component @code{next} points
5973 to the next one, you can print the contents of the next one with this:
5980 You can print successive links in the chain by repeating this
5981 command---which you can do by just typing @key{RET}.
5983 Note that the history records values, not expressions. If the value of
5984 @code{x} is 4 and you type these commands:
5992 then the value recorded in the value history by the @code{print} command
5993 remains 4 even though the value of @code{x} has changed.
5998 Print the last ten values in the value history, with their item numbers.
5999 This is like @samp{p@ $$9} repeated ten times, except that @code{show
6000 values} does not change the history.
6002 @item show values @var{n}
6003 Print ten history values centered on history item number @var{n}.
6006 Print ten history values just after the values last printed. If no more
6007 values are available, @code{show values +} produces no display.
6010 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
6011 same effect as @samp{show values +}.
6013 @node Convenience Vars
6014 @section Convenience variables
6016 @cindex convenience variables
6017 @cindex user-defined variables
6018 @value{GDBN} provides @dfn{convenience variables} that you can use within
6019 @value{GDBN} to hold on to a value and refer to it later. These variables
6020 exist entirely within @value{GDBN}; they are not part of your program, and
6021 setting a convenience variable has no direct effect on further execution
6022 of your program. That is why you can use them freely.
6024 Convenience variables are prefixed with @samp{$}. Any name preceded by
6025 @samp{$} can be used for a convenience variable, unless it is one of
6026 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
6027 (Value history references, in contrast, are @emph{numbers} preceded
6028 by @samp{$}. @xref{Value History, ,Value history}.)
6030 You can save a value in a convenience variable with an assignment
6031 expression, just as you would set a variable in your program.
6035 set $foo = *object_ptr
6039 would save in @code{$foo} the value contained in the object pointed to by
6042 Using a convenience variable for the first time creates it, but its
6043 value is @code{void} until you assign a new value. You can alter the
6044 value with another assignment at any time.
6046 Convenience variables have no fixed types. You can assign a convenience
6047 variable any type of value, including structures and arrays, even if
6048 that variable already has a value of a different type. The convenience
6049 variable, when used as an expression, has the type of its current value.
6052 @kindex show convenience
6053 @cindex show all user variables
6054 @item show convenience
6055 Print a list of convenience variables used so far, and their values.
6056 Abbreviated @code{show conv}.
6059 One of the ways to use a convenience variable is as a counter to be
6060 incremented or a pointer to be advanced. For example, to print
6061 a field from successive elements of an array of structures:
6065 print bar[$i++]->contents
6069 Repeat that command by typing @key{RET}.
6071 Some convenience variables are created automatically by @value{GDBN} and given
6072 values likely to be useful.
6075 @vindex $_@r{, convenience variable}
6077 The variable @code{$_} is automatically set by the @code{x} command to
6078 the last address examined (@pxref{Memory, ,Examining memory}). Other
6079 commands which provide a default address for @code{x} to examine also
6080 set @code{$_} to that address; these commands include @code{info line}
6081 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
6082 except when set by the @code{x} command, in which case it is a pointer
6083 to the type of @code{$__}.
6085 @vindex $__@r{, convenience variable}
6087 The variable @code{$__} is automatically set by the @code{x} command
6088 to the value found in the last address examined. Its type is chosen
6089 to match the format in which the data was printed.
6092 @vindex $_exitcode@r{, convenience variable}
6093 The variable @code{$_exitcode} is automatically set to the exit code when
6094 the program being debugged terminates.
6097 On HP-UX systems, if you refer to a function or variable name that
6098 begins with a dollar sign, @value{GDBN} searches for a user or system
6099 name first, before it searches for a convenience variable.
6105 You can refer to machine register contents, in expressions, as variables
6106 with names starting with @samp{$}. The names of registers are different
6107 for each machine; use @code{info registers} to see the names used on
6111 @kindex info registers
6112 @item info registers
6113 Print the names and values of all registers except floating-point
6114 and vector registers (in the selected stack frame).
6116 @kindex info all-registers
6117 @cindex floating point registers
6118 @item info all-registers
6119 Print the names and values of all registers, including floating-point
6120 and vector registers (in the selected stack frame).
6122 @item info registers @var{regname} @dots{}
6123 Print the @dfn{relativized} value of each specified register @var{regname}.
6124 As discussed in detail below, register values are normally relative to
6125 the selected stack frame. @var{regname} may be any register name valid on
6126 the machine you are using, with or without the initial @samp{$}.
6129 @value{GDBN} has four ``standard'' register names that are available (in
6130 expressions) on most machines---whenever they do not conflict with an
6131 architecture's canonical mnemonics for registers. The register names
6132 @code{$pc} and @code{$sp} are used for the program counter register and
6133 the stack pointer. @code{$fp} is used for a register that contains a
6134 pointer to the current stack frame, and @code{$ps} is used for a
6135 register that contains the processor status. For example,
6136 you could print the program counter in hex with
6143 or print the instruction to be executed next with
6150 or add four to the stack pointer@footnote{This is a way of removing
6151 one word from the stack, on machines where stacks grow downward in
6152 memory (most machines, nowadays). This assumes that the innermost
6153 stack frame is selected; setting @code{$sp} is not allowed when other
6154 stack frames are selected. To pop entire frames off the stack,
6155 regardless of machine architecture, use @code{return};
6156 see @ref{Returning, ,Returning from a function}.} with
6162 Whenever possible, these four standard register names are available on
6163 your machine even though the machine has different canonical mnemonics,
6164 so long as there is no conflict. The @code{info registers} command
6165 shows the canonical names. For example, on the SPARC, @code{info
6166 registers} displays the processor status register as @code{$psr} but you
6167 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
6168 is an alias for the @sc{eflags} register.
6170 @value{GDBN} always considers the contents of an ordinary register as an
6171 integer when the register is examined in this way. Some machines have
6172 special registers which can hold nothing but floating point; these
6173 registers are considered to have floating point values. There is no way
6174 to refer to the contents of an ordinary register as floating point value
6175 (although you can @emph{print} it as a floating point value with
6176 @samp{print/f $@var{regname}}).
6178 Some registers have distinct ``raw'' and ``virtual'' data formats. This
6179 means that the data format in which the register contents are saved by
6180 the operating system is not the same one that your program normally
6181 sees. For example, the registers of the 68881 floating point
6182 coprocessor are always saved in ``extended'' (raw) format, but all C
6183 programs expect to work with ``double'' (virtual) format. In such
6184 cases, @value{GDBN} normally works with the virtual format only (the format
6185 that makes sense for your program), but the @code{info registers} command
6186 prints the data in both formats.
6188 Normally, register values are relative to the selected stack frame
6189 (@pxref{Selection, ,Selecting a frame}). This means that you get the
6190 value that the register would contain if all stack frames farther in
6191 were exited and their saved registers restored. In order to see the
6192 true contents of hardware registers, you must select the innermost
6193 frame (with @samp{frame 0}).
6195 However, @value{GDBN} must deduce where registers are saved, from the machine
6196 code generated by your compiler. If some registers are not saved, or if
6197 @value{GDBN} is unable to locate the saved registers, the selected stack
6198 frame makes no difference.
6200 @node Floating Point Hardware
6201 @section Floating point hardware
6202 @cindex floating point
6204 Depending on the configuration, @value{GDBN} may be able to give
6205 you more information about the status of the floating point hardware.
6210 Display hardware-dependent information about the floating
6211 point unit. The exact contents and layout vary depending on the
6212 floating point chip. Currently, @samp{info float} is supported on
6213 the ARM and x86 machines.
6217 @section Vector Unit
6220 Depending on the configuration, @value{GDBN} may be able to give you
6221 more information about the status of the vector unit.
6226 Display information about the vector unit. The exact contents and
6227 layout vary depending on the hardware.
6230 @node OS Information
6231 @section Operating system auxiliary information
6232 @cindex OS information
6234 @value{GDBN} provides interfaces to useful OS facilities that can help
6235 you debug your program.
6237 @cindex @code{ptrace} system call
6238 @cindex @code{struct user} contents
6239 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
6240 machines), it interfaces with the inferior via the @code{ptrace}
6241 system call. The operating system creates a special sata structure,
6242 called @code{struct user}, for this interface. You can use the
6243 command @code{info udot} to display the contents of this data
6249 Display the contents of the @code{struct user} maintained by the OS
6250 kernel for the program being debugged. @value{GDBN} displays the
6251 contents of @code{struct user} as a list of hex numbers, similar to
6252 the @code{examine} command.
6255 @cindex auxiliary vector
6256 @cindex vector, auxiliary
6257 Some operating systems supply an @dfn{auxiliary vector} to programs at
6258 startup. This is akin to the arguments and environment that you
6259 specify for a program, but contains a system-dependent variety of
6260 binary values that tell system libraries important details about the
6261 hardware, operating system, and process. Each value's purpose is
6262 identified by an integer tag; the meanings are well-known but system-specific.
6263 Depending on the configuration and operating system facilities,
6264 @value{GDBN} may be able to show you this information. For remote
6265 targets, this functionality may further depend on the remote stub's
6266 support of the @samp{qPart:auxv:read} packet, see @ref{Remote
6267 configuration, auxiliary vector}.
6272 Display the auxiliary vector of the inferior, which can be either a
6273 live process or a core dump file. @value{GDBN} prints each tag value
6274 numerically, and also shows names and text descriptions for recognized
6275 tags. Some values in the vector are numbers, some bit masks, and some
6276 pointers to strings or other data. @value{GDBN} displays each value in the
6277 most appropriate form for a recognized tag, and in hexadecimal for
6278 an unrecognized tag.
6282 @node Memory Region Attributes
6283 @section Memory region attributes
6284 @cindex memory region attributes
6286 @dfn{Memory region attributes} allow you to describe special handling
6287 required by regions of your target's memory. @value{GDBN} uses attributes
6288 to determine whether to allow certain types of memory accesses; whether to
6289 use specific width accesses; and whether to cache target memory.
6291 Defined memory regions can be individually enabled and disabled. When a
6292 memory region is disabled, @value{GDBN} uses the default attributes when
6293 accessing memory in that region. Similarly, if no memory regions have
6294 been defined, @value{GDBN} uses the default attributes when accessing
6297 When a memory region is defined, it is given a number to identify it;
6298 to enable, disable, or remove a memory region, you specify that number.
6302 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
6303 Define a memory region bounded by @var{lower} and @var{upper} with
6304 attributes @var{attributes}@dots{}, and add it to the list of regions
6305 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
6306 case: it is treated as the the target's maximum memory address.
6307 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
6310 @item delete mem @var{nums}@dots{}
6311 Remove memory regions @var{nums}@dots{} from the list of regions
6312 monitored by @value{GDBN}.
6315 @item disable mem @var{nums}@dots{}
6316 Disable monitoring of memory regions @var{nums}@dots{}.
6317 A disabled memory region is not forgotten.
6318 It may be enabled again later.
6321 @item enable mem @var{nums}@dots{}
6322 Enable monitoring of memory regions @var{nums}@dots{}.
6326 Print a table of all defined memory regions, with the following columns
6330 @item Memory Region Number
6331 @item Enabled or Disabled.
6332 Enabled memory regions are marked with @samp{y}.
6333 Disabled memory regions are marked with @samp{n}.
6336 The address defining the inclusive lower bound of the memory region.
6339 The address defining the exclusive upper bound of the memory region.
6342 The list of attributes set for this memory region.
6347 @subsection Attributes
6349 @subsubsection Memory Access Mode
6350 The access mode attributes set whether @value{GDBN} may make read or
6351 write accesses to a memory region.
6353 While these attributes prevent @value{GDBN} from performing invalid
6354 memory accesses, they do nothing to prevent the target system, I/O DMA,
6355 etc. from accessing memory.
6359 Memory is read only.
6361 Memory is write only.
6363 Memory is read/write. This is the default.
6366 @subsubsection Memory Access Size
6367 The acccess size attributes tells @value{GDBN} to use specific sized
6368 accesses in the memory region. Often memory mapped device registers
6369 require specific sized accesses. If no access size attribute is
6370 specified, @value{GDBN} may use accesses of any size.
6374 Use 8 bit memory accesses.
6376 Use 16 bit memory accesses.
6378 Use 32 bit memory accesses.
6380 Use 64 bit memory accesses.
6383 @c @subsubsection Hardware/Software Breakpoints
6384 @c The hardware/software breakpoint attributes set whether @value{GDBN}
6385 @c will use hardware or software breakpoints for the internal breakpoints
6386 @c used by the step, next, finish, until, etc. commands.
6390 @c Always use hardware breakpoints
6391 @c @item swbreak (default)
6394 @subsubsection Data Cache
6395 The data cache attributes set whether @value{GDBN} will cache target
6396 memory. While this generally improves performance by reducing debug
6397 protocol overhead, it can lead to incorrect results because @value{GDBN}
6398 does not know about volatile variables or memory mapped device
6403 Enable @value{GDBN} to cache target memory.
6405 Disable @value{GDBN} from caching target memory. This is the default.
6408 @c @subsubsection Memory Write Verification
6409 @c The memory write verification attributes set whether @value{GDBN}
6410 @c will re-reads data after each write to verify the write was successful.
6414 @c @item noverify (default)
6417 @node Dump/Restore Files
6418 @section Copy between memory and a file
6419 @cindex dump/restore files
6420 @cindex append data to a file
6421 @cindex dump data to a file
6422 @cindex restore data from a file
6424 You can use the commands @code{dump}, @code{append}, and
6425 @code{restore} to copy data between target memory and a file. The
6426 @code{dump} and @code{append} commands write data to a file, and the
6427 @code{restore} command reads data from a file back into the inferior's
6428 memory. Files may be in binary, Motorola S-record, Intel hex, or
6429 Tektronix Hex format; however, @value{GDBN} can only append to binary
6435 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6436 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
6437 Dump the contents of memory from @var{start_addr} to @var{end_addr},
6438 or the value of @var{expr}, to @var{filename} in the given format.
6440 The @var{format} parameter may be any one of:
6447 Motorola S-record format.
6449 Tektronix Hex format.
6452 @value{GDBN} uses the same definitions of these formats as the
6453 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
6454 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
6458 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6459 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
6460 Append the contents of memory from @var{start_addr} to @var{end_addr},
6461 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
6462 (@value{GDBN} can only append data to files in raw binary form.)
6465 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
6466 Restore the contents of file @var{filename} into memory. The
6467 @code{restore} command can automatically recognize any known @sc{bfd}
6468 file format, except for raw binary. To restore a raw binary file you
6469 must specify the optional keyword @code{binary} after the filename.
6471 If @var{bias} is non-zero, its value will be added to the addresses
6472 contained in the file. Binary files always start at address zero, so
6473 they will be restored at address @var{bias}. Other bfd files have
6474 a built-in location; they will be restored at offset @var{bias}
6477 If @var{start} and/or @var{end} are non-zero, then only data between
6478 file offset @var{start} and file offset @var{end} will be restored.
6479 These offsets are relative to the addresses in the file, before
6480 the @var{bias} argument is applied.
6484 @node Core File Generation
6485 @section How to Produce a Core File from Your Program
6486 @cindex dump core from inferior
6488 A @dfn{core file} or @dfn{core dump} is a file that records the memory
6489 image of a running process and its process status (register values
6490 etc.). Its primary use is post-mortem debugging of a program that
6491 crashed while it ran outside a debugger. A program that crashes
6492 automatically produces a core file, unless this feature is disabled by
6493 the user. @xref{Files}, for information on invoking @value{GDBN} in
6494 the post-mortem debugging mode.
6496 Occasionally, you may wish to produce a core file of the program you
6497 are debugging in order to preserve a snapshot of its state.
6498 @value{GDBN} has a special command for that.
6502 @kindex generate-core-file
6503 @item generate-core-file [@var{file}]
6504 @itemx gcore [@var{file}]
6505 Produce a core dump of the inferior process. The optional argument
6506 @var{file} specifies the file name where to put the core dump. If not
6507 specified, the file name defaults to @file{core.@var{pid}}, where
6508 @var{pid} is the inferior process ID.
6510 Note that this command is implemented only for some systems (as of
6511 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
6514 @node Character Sets
6515 @section Character Sets
6516 @cindex character sets
6518 @cindex translating between character sets
6519 @cindex host character set
6520 @cindex target character set
6522 If the program you are debugging uses a different character set to
6523 represent characters and strings than the one @value{GDBN} uses itself,
6524 @value{GDBN} can automatically translate between the character sets for
6525 you. The character set @value{GDBN} uses we call the @dfn{host
6526 character set}; the one the inferior program uses we call the
6527 @dfn{target character set}.
6529 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
6530 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
6531 remote protocol (@pxref{Remote,Remote Debugging}) to debug a program
6532 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
6533 then the host character set is Latin-1, and the target character set is
6534 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
6535 target-charset EBCDIC-US}, then @value{GDBN} translates between
6536 @sc{ebcdic} and Latin 1 as you print character or string values, or use
6537 character and string literals in expressions.
6539 @value{GDBN} has no way to automatically recognize which character set
6540 the inferior program uses; you must tell it, using the @code{set
6541 target-charset} command, described below.
6543 Here are the commands for controlling @value{GDBN}'s character set
6547 @item set target-charset @var{charset}
6548 @kindex set target-charset
6549 Set the current target character set to @var{charset}. We list the
6550 character set names @value{GDBN} recognizes below, but if you type
6551 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6552 list the target character sets it supports.
6556 @item set host-charset @var{charset}
6557 @kindex set host-charset
6558 Set the current host character set to @var{charset}.
6560 By default, @value{GDBN} uses a host character set appropriate to the
6561 system it is running on; you can override that default using the
6562 @code{set host-charset} command.
6564 @value{GDBN} can only use certain character sets as its host character
6565 set. We list the character set names @value{GDBN} recognizes below, and
6566 indicate which can be host character sets, but if you type
6567 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6568 list the host character sets it supports.
6570 @item set charset @var{charset}
6572 Set the current host and target character sets to @var{charset}. As
6573 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
6574 @value{GDBN} will list the name of the character sets that can be used
6575 for both host and target.
6579 @kindex show charset
6580 Show the names of the current host and target charsets.
6582 @itemx show host-charset
6583 @kindex show host-charset
6584 Show the name of the current host charset.
6586 @itemx show target-charset
6587 @kindex show target-charset
6588 Show the name of the current target charset.
6592 @value{GDBN} currently includes support for the following character
6598 @cindex ASCII character set
6599 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
6603 @cindex ISO 8859-1 character set
6604 @cindex ISO Latin 1 character set
6605 The ISO Latin 1 character set. This extends @sc{ascii} with accented
6606 characters needed for French, German, and Spanish. @value{GDBN} can use
6607 this as its host character set.
6611 @cindex EBCDIC character set
6612 @cindex IBM1047 character set
6613 Variants of the @sc{ebcdic} character set, used on some of IBM's
6614 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
6615 @value{GDBN} cannot use these as its host character set.
6619 Note that these are all single-byte character sets. More work inside
6620 GDB is needed to support multi-byte or variable-width character
6621 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
6623 Here is an example of @value{GDBN}'s character set support in action.
6624 Assume that the following source code has been placed in the file
6625 @file{charset-test.c}:
6631 = @{72, 101, 108, 108, 111, 44, 32, 119,
6632 111, 114, 108, 100, 33, 10, 0@};
6633 char ibm1047_hello[]
6634 = @{200, 133, 147, 147, 150, 107, 64, 166,
6635 150, 153, 147, 132, 90, 37, 0@};
6639 printf ("Hello, world!\n");
6643 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
6644 containing the string @samp{Hello, world!} followed by a newline,
6645 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
6647 We compile the program, and invoke the debugger on it:
6650 $ gcc -g charset-test.c -o charset-test
6651 $ gdb -nw charset-test
6652 GNU gdb 2001-12-19-cvs
6653 Copyright 2001 Free Software Foundation, Inc.
6658 We can use the @code{show charset} command to see what character sets
6659 @value{GDBN} is currently using to interpret and display characters and
6663 (@value{GDBP}) show charset
6664 The current host and target character set is `ISO-8859-1'.
6668 For the sake of printing this manual, let's use @sc{ascii} as our
6669 initial character set:
6671 (@value{GDBP}) set charset ASCII
6672 (@value{GDBP}) show charset
6673 The current host and target character set is `ASCII'.
6677 Let's assume that @sc{ascii} is indeed the correct character set for our
6678 host system --- in other words, let's assume that if @value{GDBN} prints
6679 characters using the @sc{ascii} character set, our terminal will display
6680 them properly. Since our current target character set is also
6681 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
6684 (@value{GDBP}) print ascii_hello
6685 $1 = 0x401698 "Hello, world!\n"
6686 (@value{GDBP}) print ascii_hello[0]
6691 @value{GDBN} uses the target character set for character and string
6692 literals you use in expressions:
6695 (@value{GDBP}) print '+'
6700 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
6703 @value{GDBN} relies on the user to tell it which character set the
6704 target program uses. If we print @code{ibm1047_hello} while our target
6705 character set is still @sc{ascii}, we get jibberish:
6708 (@value{GDBP}) print ibm1047_hello
6709 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
6710 (@value{GDBP}) print ibm1047_hello[0]
6715 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
6716 @value{GDBN} tells us the character sets it supports:
6719 (@value{GDBP}) set target-charset
6720 ASCII EBCDIC-US IBM1047 ISO-8859-1
6721 (@value{GDBP}) set target-charset
6724 We can select @sc{ibm1047} as our target character set, and examine the
6725 program's strings again. Now the @sc{ascii} string is wrong, but
6726 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
6727 target character set, @sc{ibm1047}, to the host character set,
6728 @sc{ascii}, and they display correctly:
6731 (@value{GDBP}) set target-charset IBM1047
6732 (@value{GDBP}) show charset
6733 The current host character set is `ASCII'.
6734 The current target character set is `IBM1047'.
6735 (@value{GDBP}) print ascii_hello
6736 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
6737 (@value{GDBP}) print ascii_hello[0]
6739 (@value{GDBP}) print ibm1047_hello
6740 $8 = 0x4016a8 "Hello, world!\n"
6741 (@value{GDBP}) print ibm1047_hello[0]
6746 As above, @value{GDBN} uses the target character set for character and
6747 string literals you use in expressions:
6750 (@value{GDBP}) print '+'
6755 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
6758 @node Caching Remote Data
6759 @section Caching Data of Remote Targets
6760 @cindex caching data of remote targets
6762 @value{GDBN} can cache data exchanged between the debugger and a
6763 remote target (@pxref{Remote}). Such caching generally improves
6764 performance, because it reduces the overhead of the remote protocol by
6765 bundling memory reads and writes into large chunks. Unfortunately,
6766 @value{GDBN} does not currently know anything about volatile
6767 registers, and thus data caching will produce incorrect results when
6768 volatile registers are in use.
6771 @kindex set remotecache
6772 @item set remotecache on
6773 @itemx set remotecache off
6774 Set caching state for remote targets. When @code{ON}, use data
6775 caching. By default, this option is @code{OFF}.
6777 @kindex show remotecache
6778 @item show remotecache
6779 Show the current state of data caching for remote targets.
6783 Print the information about the data cache performance. The
6784 information displayed includes: the dcache width and depth; and for
6785 each cache line, how many times it was referenced, and its data and
6786 state (dirty, bad, ok, etc.). This command is useful for debugging
6787 the data cache operation.
6792 @chapter C Preprocessor Macros
6794 Some languages, such as C and C@t{++}, provide a way to define and invoke
6795 ``preprocessor macros'' which expand into strings of tokens.
6796 @value{GDBN} can evaluate expressions containing macro invocations, show
6797 the result of macro expansion, and show a macro's definition, including
6798 where it was defined.
6800 You may need to compile your program specially to provide @value{GDBN}
6801 with information about preprocessor macros. Most compilers do not
6802 include macros in their debugging information, even when you compile
6803 with the @option{-g} flag. @xref{Compilation}.
6805 A program may define a macro at one point, remove that definition later,
6806 and then provide a different definition after that. Thus, at different
6807 points in the program, a macro may have different definitions, or have
6808 no definition at all. If there is a current stack frame, @value{GDBN}
6809 uses the macros in scope at that frame's source code line. Otherwise,
6810 @value{GDBN} uses the macros in scope at the current listing location;
6813 At the moment, @value{GDBN} does not support the @code{##}
6814 token-splicing operator, the @code{#} stringification operator, or
6815 variable-arity macros.
6817 Whenever @value{GDBN} evaluates an expression, it always expands any
6818 macro invocations present in the expression. @value{GDBN} also provides
6819 the following commands for working with macros explicitly.
6823 @kindex macro expand
6824 @cindex macro expansion, showing the results of preprocessor
6825 @cindex preprocessor macro expansion, showing the results of
6826 @cindex expanding preprocessor macros
6827 @item macro expand @var{expression}
6828 @itemx macro exp @var{expression}
6829 Show the results of expanding all preprocessor macro invocations in
6830 @var{expression}. Since @value{GDBN} simply expands macros, but does
6831 not parse the result, @var{expression} need not be a valid expression;
6832 it can be any string of tokens.
6835 @item macro expand-once @var{expression}
6836 @itemx macro exp1 @var{expression}
6837 @cindex expand macro once
6838 @i{(This command is not yet implemented.)} Show the results of
6839 expanding those preprocessor macro invocations that appear explicitly in
6840 @var{expression}. Macro invocations appearing in that expansion are
6841 left unchanged. This command allows you to see the effect of a
6842 particular macro more clearly, without being confused by further
6843 expansions. Since @value{GDBN} simply expands macros, but does not
6844 parse the result, @var{expression} need not be a valid expression; it
6845 can be any string of tokens.
6848 @cindex macro definition, showing
6849 @cindex definition, showing a macro's
6850 @item info macro @var{macro}
6851 Show the definition of the macro named @var{macro}, and describe the
6852 source location where that definition was established.
6854 @kindex macro define
6855 @cindex user-defined macros
6856 @cindex defining macros interactively
6857 @cindex macros, user-defined
6858 @item macro define @var{macro} @var{replacement-list}
6859 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
6860 @i{(This command is not yet implemented.)} Introduce a definition for a
6861 preprocessor macro named @var{macro}, invocations of which are replaced
6862 by the tokens given in @var{replacement-list}. The first form of this
6863 command defines an ``object-like'' macro, which takes no arguments; the
6864 second form defines a ``function-like'' macro, which takes the arguments
6865 given in @var{arglist}.
6867 A definition introduced by this command is in scope in every expression
6868 evaluated in @value{GDBN}, until it is removed with the @command{macro
6869 undef} command, described below. The definition overrides all
6870 definitions for @var{macro} present in the program being debugged, as
6871 well as any previous user-supplied definition.
6874 @item macro undef @var{macro}
6875 @i{(This command is not yet implemented.)} Remove any user-supplied
6876 definition for the macro named @var{macro}. This command only affects
6877 definitions provided with the @command{macro define} command, described
6878 above; it cannot remove definitions present in the program being
6883 @i{(This command is not yet implemented.)} List all the macros
6884 defined using the @code{macro define} command.
6887 @cindex macros, example of debugging with
6888 Here is a transcript showing the above commands in action. First, we
6889 show our source files:
6897 #define ADD(x) (M + x)
6902 printf ("Hello, world!\n");
6904 printf ("We're so creative.\n");
6906 printf ("Goodbye, world!\n");
6913 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
6914 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
6915 compiler includes information about preprocessor macros in the debugging
6919 $ gcc -gdwarf-2 -g3 sample.c -o sample
6923 Now, we start @value{GDBN} on our sample program:
6927 GNU gdb 2002-05-06-cvs
6928 Copyright 2002 Free Software Foundation, Inc.
6929 GDB is free software, @dots{}
6933 We can expand macros and examine their definitions, even when the
6934 program is not running. @value{GDBN} uses the current listing position
6935 to decide which macro definitions are in scope:
6938 (@value{GDBP}) list main
6941 5 #define ADD(x) (M + x)
6946 10 printf ("Hello, world!\n");
6948 12 printf ("We're so creative.\n");
6949 (@value{GDBP}) info macro ADD
6950 Defined at /home/jimb/gdb/macros/play/sample.c:5
6951 #define ADD(x) (M + x)
6952 (@value{GDBP}) info macro Q
6953 Defined at /home/jimb/gdb/macros/play/sample.h:1
6954 included at /home/jimb/gdb/macros/play/sample.c:2
6956 (@value{GDBP}) macro expand ADD(1)
6957 expands to: (42 + 1)
6958 (@value{GDBP}) macro expand-once ADD(1)
6959 expands to: once (M + 1)
6963 In the example above, note that @command{macro expand-once} expands only
6964 the macro invocation explicit in the original text --- the invocation of
6965 @code{ADD} --- but does not expand the invocation of the macro @code{M},
6966 which was introduced by @code{ADD}.
6968 Once the program is running, GDB uses the macro definitions in force at
6969 the source line of the current stack frame:
6972 (@value{GDBP}) break main
6973 Breakpoint 1 at 0x8048370: file sample.c, line 10.
6975 Starting program: /home/jimb/gdb/macros/play/sample
6977 Breakpoint 1, main () at sample.c:10
6978 10 printf ("Hello, world!\n");
6982 At line 10, the definition of the macro @code{N} at line 9 is in force:
6985 (@value{GDBP}) info macro N
6986 Defined at /home/jimb/gdb/macros/play/sample.c:9
6988 (@value{GDBP}) macro expand N Q M
6990 (@value{GDBP}) print N Q M
6995 As we step over directives that remove @code{N}'s definition, and then
6996 give it a new definition, @value{GDBN} finds the definition (or lack
6997 thereof) in force at each point:
7002 12 printf ("We're so creative.\n");
7003 (@value{GDBP}) info macro N
7004 The symbol `N' has no definition as a C/C++ preprocessor macro
7005 at /home/jimb/gdb/macros/play/sample.c:12
7008 14 printf ("Goodbye, world!\n");
7009 (@value{GDBP}) info macro N
7010 Defined at /home/jimb/gdb/macros/play/sample.c:13
7012 (@value{GDBP}) macro expand N Q M
7013 expands to: 1729 < 42
7014 (@value{GDBP}) print N Q M
7021 @chapter Tracepoints
7022 @c This chapter is based on the documentation written by Michael
7023 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
7026 In some applications, it is not feasible for the debugger to interrupt
7027 the program's execution long enough for the developer to learn
7028 anything helpful about its behavior. If the program's correctness
7029 depends on its real-time behavior, delays introduced by a debugger
7030 might cause the program to change its behavior drastically, or perhaps
7031 fail, even when the code itself is correct. It is useful to be able
7032 to observe the program's behavior without interrupting it.
7034 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
7035 specify locations in the program, called @dfn{tracepoints}, and
7036 arbitrary expressions to evaluate when those tracepoints are reached.
7037 Later, using the @code{tfind} command, you can examine the values
7038 those expressions had when the program hit the tracepoints. The
7039 expressions may also denote objects in memory---structures or arrays,
7040 for example---whose values @value{GDBN} should record; while visiting
7041 a particular tracepoint, you may inspect those objects as if they were
7042 in memory at that moment. However, because @value{GDBN} records these
7043 values without interacting with you, it can do so quickly and
7044 unobtrusively, hopefully not disturbing the program's behavior.
7046 The tracepoint facility is currently available only for remote
7047 targets. @xref{Targets}. In addition, your remote target must know how
7048 to collect trace data. This functionality is implemented in the remote
7049 stub; however, none of the stubs distributed with @value{GDBN} support
7050 tracepoints as of this writing.
7052 This chapter describes the tracepoint commands and features.
7056 * Analyze Collected Data::
7057 * Tracepoint Variables::
7060 @node Set Tracepoints
7061 @section Commands to Set Tracepoints
7063 Before running such a @dfn{trace experiment}, an arbitrary number of
7064 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
7065 tracepoint has a number assigned to it by @value{GDBN}. Like with
7066 breakpoints, tracepoint numbers are successive integers starting from
7067 one. Many of the commands associated with tracepoints take the
7068 tracepoint number as their argument, to identify which tracepoint to
7071 For each tracepoint, you can specify, in advance, some arbitrary set
7072 of data that you want the target to collect in the trace buffer when
7073 it hits that tracepoint. The collected data can include registers,
7074 local variables, or global data. Later, you can use @value{GDBN}
7075 commands to examine the values these data had at the time the
7078 This section describes commands to set tracepoints and associated
7079 conditions and actions.
7082 * Create and Delete Tracepoints::
7083 * Enable and Disable Tracepoints::
7084 * Tracepoint Passcounts::
7085 * Tracepoint Actions::
7086 * Listing Tracepoints::
7087 * Starting and Stopping Trace Experiment::
7090 @node Create and Delete Tracepoints
7091 @subsection Create and Delete Tracepoints
7094 @cindex set tracepoint
7097 The @code{trace} command is very similar to the @code{break} command.
7098 Its argument can be a source line, a function name, or an address in
7099 the target program. @xref{Set Breaks}. The @code{trace} command
7100 defines a tracepoint, which is a point in the target program where the
7101 debugger will briefly stop, collect some data, and then allow the
7102 program to continue. Setting a tracepoint or changing its commands
7103 doesn't take effect until the next @code{tstart} command; thus, you
7104 cannot change the tracepoint attributes once a trace experiment is
7107 Here are some examples of using the @code{trace} command:
7110 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
7112 (@value{GDBP}) @b{trace +2} // 2 lines forward
7114 (@value{GDBP}) @b{trace my_function} // first source line of function
7116 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
7118 (@value{GDBP}) @b{trace *0x2117c4} // an address
7122 You can abbreviate @code{trace} as @code{tr}.
7125 @cindex last tracepoint number
7126 @cindex recent tracepoint number
7127 @cindex tracepoint number
7128 The convenience variable @code{$tpnum} records the tracepoint number
7129 of the most recently set tracepoint.
7131 @kindex delete tracepoint
7132 @cindex tracepoint deletion
7133 @item delete tracepoint @r{[}@var{num}@r{]}
7134 Permanently delete one or more tracepoints. With no argument, the
7135 default is to delete all tracepoints.
7140 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
7142 (@value{GDBP}) @b{delete trace} // remove all tracepoints
7146 You can abbreviate this command as @code{del tr}.
7149 @node Enable and Disable Tracepoints
7150 @subsection Enable and Disable Tracepoints
7153 @kindex disable tracepoint
7154 @item disable tracepoint @r{[}@var{num}@r{]}
7155 Disable tracepoint @var{num}, or all tracepoints if no argument
7156 @var{num} is given. A disabled tracepoint will have no effect during
7157 the next trace experiment, but it is not forgotten. You can re-enable
7158 a disabled tracepoint using the @code{enable tracepoint} command.
7160 @kindex enable tracepoint
7161 @item enable tracepoint @r{[}@var{num}@r{]}
7162 Enable tracepoint @var{num}, or all tracepoints. The enabled
7163 tracepoints will become effective the next time a trace experiment is
7167 @node Tracepoint Passcounts
7168 @subsection Tracepoint Passcounts
7172 @cindex tracepoint pass count
7173 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
7174 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
7175 automatically stop a trace experiment. If a tracepoint's passcount is
7176 @var{n}, then the trace experiment will be automatically stopped on
7177 the @var{n}'th time that tracepoint is hit. If the tracepoint number
7178 @var{num} is not specified, the @code{passcount} command sets the
7179 passcount of the most recently defined tracepoint. If no passcount is
7180 given, the trace experiment will run until stopped explicitly by the
7186 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
7187 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
7189 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
7190 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
7191 (@value{GDBP}) @b{trace foo}
7192 (@value{GDBP}) @b{pass 3}
7193 (@value{GDBP}) @b{trace bar}
7194 (@value{GDBP}) @b{pass 2}
7195 (@value{GDBP}) @b{trace baz}
7196 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
7197 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
7198 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
7199 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
7203 @node Tracepoint Actions
7204 @subsection Tracepoint Action Lists
7208 @cindex tracepoint actions
7209 @item actions @r{[}@var{num}@r{]}
7210 This command will prompt for a list of actions to be taken when the
7211 tracepoint is hit. If the tracepoint number @var{num} is not
7212 specified, this command sets the actions for the one that was most
7213 recently defined (so that you can define a tracepoint and then say
7214 @code{actions} without bothering about its number). You specify the
7215 actions themselves on the following lines, one action at a time, and
7216 terminate the actions list with a line containing just @code{end}. So
7217 far, the only defined actions are @code{collect} and
7218 @code{while-stepping}.
7220 @cindex remove actions from a tracepoint
7221 To remove all actions from a tracepoint, type @samp{actions @var{num}}
7222 and follow it immediately with @samp{end}.
7225 (@value{GDBP}) @b{collect @var{data}} // collect some data
7227 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
7229 (@value{GDBP}) @b{end} // signals the end of actions.
7232 In the following example, the action list begins with @code{collect}
7233 commands indicating the things to be collected when the tracepoint is
7234 hit. Then, in order to single-step and collect additional data
7235 following the tracepoint, a @code{while-stepping} command is used,
7236 followed by the list of things to be collected while stepping. The
7237 @code{while-stepping} command is terminated by its own separate
7238 @code{end} command. Lastly, the action list is terminated by an
7242 (@value{GDBP}) @b{trace foo}
7243 (@value{GDBP}) @b{actions}
7244 Enter actions for tracepoint 1, one per line:
7253 @kindex collect @r{(tracepoints)}
7254 @item collect @var{expr1}, @var{expr2}, @dots{}
7255 Collect values of the given expressions when the tracepoint is hit.
7256 This command accepts a comma-separated list of any valid expressions.
7257 In addition to global, static, or local variables, the following
7258 special arguments are supported:
7262 collect all registers
7265 collect all function arguments
7268 collect all local variables.
7271 You can give several consecutive @code{collect} commands, each one
7272 with a single argument, or one @code{collect} command with several
7273 arguments separated by commas: the effect is the same.
7275 The command @code{info scope} (@pxref{Symbols, info scope}) is
7276 particularly useful for figuring out what data to collect.
7278 @kindex while-stepping @r{(tracepoints)}
7279 @item while-stepping @var{n}
7280 Perform @var{n} single-step traces after the tracepoint, collecting
7281 new data at each step. The @code{while-stepping} command is
7282 followed by the list of what to collect while stepping (followed by
7283 its own @code{end} command):
7287 > collect $regs, myglobal
7293 You may abbreviate @code{while-stepping} as @code{ws} or
7297 @node Listing Tracepoints
7298 @subsection Listing Tracepoints
7301 @kindex info tracepoints
7303 @cindex information about tracepoints
7304 @item info tracepoints @r{[}@var{num}@r{]}
7305 Display information about the tracepoint @var{num}. If you don't specify
7306 a tracepoint number, displays information about all the tracepoints
7307 defined so far. For each tracepoint, the following information is
7314 whether it is enabled or disabled
7318 its passcount as given by the @code{passcount @var{n}} command
7320 its step count as given by the @code{while-stepping @var{n}} command
7322 where in the source files is the tracepoint set
7324 its action list as given by the @code{actions} command
7328 (@value{GDBP}) @b{info trace}
7329 Num Enb Address PassC StepC What
7330 1 y 0x002117c4 0 0 <gdb_asm>
7331 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
7332 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
7337 This command can be abbreviated @code{info tp}.
7340 @node Starting and Stopping Trace Experiment
7341 @subsection Starting and Stopping Trace Experiment
7345 @cindex start a new trace experiment
7346 @cindex collected data discarded
7348 This command takes no arguments. It starts the trace experiment, and
7349 begins collecting data. This has the side effect of discarding all
7350 the data collected in the trace buffer during the previous trace
7354 @cindex stop a running trace experiment
7356 This command takes no arguments. It ends the trace experiment, and
7357 stops collecting data.
7359 @strong{Note}: a trace experiment and data collection may stop
7360 automatically if any tracepoint's passcount is reached
7361 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
7364 @cindex status of trace data collection
7365 @cindex trace experiment, status of
7367 This command displays the status of the current trace data
7371 Here is an example of the commands we described so far:
7374 (@value{GDBP}) @b{trace gdb_c_test}
7375 (@value{GDBP}) @b{actions}
7376 Enter actions for tracepoint #1, one per line.
7377 > collect $regs,$locals,$args
7382 (@value{GDBP}) @b{tstart}
7383 [time passes @dots{}]
7384 (@value{GDBP}) @b{tstop}
7388 @node Analyze Collected Data
7389 @section Using the collected data
7391 After the tracepoint experiment ends, you use @value{GDBN} commands
7392 for examining the trace data. The basic idea is that each tracepoint
7393 collects a trace @dfn{snapshot} every time it is hit and another
7394 snapshot every time it single-steps. All these snapshots are
7395 consecutively numbered from zero and go into a buffer, and you can
7396 examine them later. The way you examine them is to @dfn{focus} on a
7397 specific trace snapshot. When the remote stub is focused on a trace
7398 snapshot, it will respond to all @value{GDBN} requests for memory and
7399 registers by reading from the buffer which belongs to that snapshot,
7400 rather than from @emph{real} memory or registers of the program being
7401 debugged. This means that @strong{all} @value{GDBN} commands
7402 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
7403 behave as if we were currently debugging the program state as it was
7404 when the tracepoint occurred. Any requests for data that are not in
7405 the buffer will fail.
7408 * tfind:: How to select a trace snapshot
7409 * tdump:: How to display all data for a snapshot
7410 * save-tracepoints:: How to save tracepoints for a future run
7414 @subsection @code{tfind @var{n}}
7417 @cindex select trace snapshot
7418 @cindex find trace snapshot
7419 The basic command for selecting a trace snapshot from the buffer is
7420 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
7421 counting from zero. If no argument @var{n} is given, the next
7422 snapshot is selected.
7424 Here are the various forms of using the @code{tfind} command.
7428 Find the first snapshot in the buffer. This is a synonym for
7429 @code{tfind 0} (since 0 is the number of the first snapshot).
7432 Stop debugging trace snapshots, resume @emph{live} debugging.
7435 Same as @samp{tfind none}.
7438 No argument means find the next trace snapshot.
7441 Find the previous trace snapshot before the current one. This permits
7442 retracing earlier steps.
7444 @item tfind tracepoint @var{num}
7445 Find the next snapshot associated with tracepoint @var{num}. Search
7446 proceeds forward from the last examined trace snapshot. If no
7447 argument @var{num} is given, it means find the next snapshot collected
7448 for the same tracepoint as the current snapshot.
7450 @item tfind pc @var{addr}
7451 Find the next snapshot associated with the value @var{addr} of the
7452 program counter. Search proceeds forward from the last examined trace
7453 snapshot. If no argument @var{addr} is given, it means find the next
7454 snapshot with the same value of PC as the current snapshot.
7456 @item tfind outside @var{addr1}, @var{addr2}
7457 Find the next snapshot whose PC is outside the given range of
7460 @item tfind range @var{addr1}, @var{addr2}
7461 Find the next snapshot whose PC is between @var{addr1} and
7462 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
7464 @item tfind line @r{[}@var{file}:@r{]}@var{n}
7465 Find the next snapshot associated with the source line @var{n}. If
7466 the optional argument @var{file} is given, refer to line @var{n} in
7467 that source file. Search proceeds forward from the last examined
7468 trace snapshot. If no argument @var{n} is given, it means find the
7469 next line other than the one currently being examined; thus saying
7470 @code{tfind line} repeatedly can appear to have the same effect as
7471 stepping from line to line in a @emph{live} debugging session.
7474 The default arguments for the @code{tfind} commands are specifically
7475 designed to make it easy to scan through the trace buffer. For
7476 instance, @code{tfind} with no argument selects the next trace
7477 snapshot, and @code{tfind -} with no argument selects the previous
7478 trace snapshot. So, by giving one @code{tfind} command, and then
7479 simply hitting @key{RET} repeatedly you can examine all the trace
7480 snapshots in order. Or, by saying @code{tfind -} and then hitting
7481 @key{RET} repeatedly you can examine the snapshots in reverse order.
7482 The @code{tfind line} command with no argument selects the snapshot
7483 for the next source line executed. The @code{tfind pc} command with
7484 no argument selects the next snapshot with the same program counter
7485 (PC) as the current frame. The @code{tfind tracepoint} command with
7486 no argument selects the next trace snapshot collected by the same
7487 tracepoint as the current one.
7489 In addition to letting you scan through the trace buffer manually,
7490 these commands make it easy to construct @value{GDBN} scripts that
7491 scan through the trace buffer and print out whatever collected data
7492 you are interested in. Thus, if we want to examine the PC, FP, and SP
7493 registers from each trace frame in the buffer, we can say this:
7496 (@value{GDBP}) @b{tfind start}
7497 (@value{GDBP}) @b{while ($trace_frame != -1)}
7498 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
7499 $trace_frame, $pc, $sp, $fp
7503 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
7504 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
7505 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
7506 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
7507 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
7508 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
7509 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
7510 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
7511 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
7512 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
7513 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
7516 Or, if we want to examine the variable @code{X} at each source line in
7520 (@value{GDBP}) @b{tfind start}
7521 (@value{GDBP}) @b{while ($trace_frame != -1)}
7522 > printf "Frame %d, X == %d\n", $trace_frame, X
7532 @subsection @code{tdump}
7534 @cindex dump all data collected at tracepoint
7535 @cindex tracepoint data, display
7537 This command takes no arguments. It prints all the data collected at
7538 the current trace snapshot.
7541 (@value{GDBP}) @b{trace 444}
7542 (@value{GDBP}) @b{actions}
7543 Enter actions for tracepoint #2, one per line:
7544 > collect $regs, $locals, $args, gdb_long_test
7547 (@value{GDBP}) @b{tstart}
7549 (@value{GDBP}) @b{tfind line 444}
7550 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
7552 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
7554 (@value{GDBP}) @b{tdump}
7555 Data collected at tracepoint 2, trace frame 1:
7556 d0 0xc4aa0085 -995491707
7560 d4 0x71aea3d 119204413
7565 a1 0x3000668 50333288
7568 a4 0x3000698 50333336
7570 fp 0x30bf3c 0x30bf3c
7571 sp 0x30bf34 0x30bf34
7573 pc 0x20b2c8 0x20b2c8
7577 p = 0x20e5b4 "gdb-test"
7584 gdb_long_test = 17 '\021'
7589 @node save-tracepoints
7590 @subsection @code{save-tracepoints @var{filename}}
7591 @kindex save-tracepoints
7592 @cindex save tracepoints for future sessions
7594 This command saves all current tracepoint definitions together with
7595 their actions and passcounts, into a file @file{@var{filename}}
7596 suitable for use in a later debugging session. To read the saved
7597 tracepoint definitions, use the @code{source} command (@pxref{Command
7600 @node Tracepoint Variables
7601 @section Convenience Variables for Tracepoints
7602 @cindex tracepoint variables
7603 @cindex convenience variables for tracepoints
7606 @vindex $trace_frame
7607 @item (int) $trace_frame
7608 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
7609 snapshot is selected.
7612 @item (int) $tracepoint
7613 The tracepoint for the current trace snapshot.
7616 @item (int) $trace_line
7617 The line number for the current trace snapshot.
7620 @item (char []) $trace_file
7621 The source file for the current trace snapshot.
7624 @item (char []) $trace_func
7625 The name of the function containing @code{$tracepoint}.
7628 Note: @code{$trace_file} is not suitable for use in @code{printf},
7629 use @code{output} instead.
7631 Here's a simple example of using these convenience variables for
7632 stepping through all the trace snapshots and printing some of their
7636 (@value{GDBP}) @b{tfind start}
7638 (@value{GDBP}) @b{while $trace_frame != -1}
7639 > output $trace_file
7640 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
7646 @chapter Debugging Programs That Use Overlays
7649 If your program is too large to fit completely in your target system's
7650 memory, you can sometimes use @dfn{overlays} to work around this
7651 problem. @value{GDBN} provides some support for debugging programs that
7655 * How Overlays Work:: A general explanation of overlays.
7656 * Overlay Commands:: Managing overlays in @value{GDBN}.
7657 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
7658 mapped by asking the inferior.
7659 * Overlay Sample Program:: A sample program using overlays.
7662 @node How Overlays Work
7663 @section How Overlays Work
7664 @cindex mapped overlays
7665 @cindex unmapped overlays
7666 @cindex load address, overlay's
7667 @cindex mapped address
7668 @cindex overlay area
7670 Suppose you have a computer whose instruction address space is only 64
7671 kilobytes long, but which has much more memory which can be accessed by
7672 other means: special instructions, segment registers, or memory
7673 management hardware, for example. Suppose further that you want to
7674 adapt a program which is larger than 64 kilobytes to run on this system.
7676 One solution is to identify modules of your program which are relatively
7677 independent, and need not call each other directly; call these modules
7678 @dfn{overlays}. Separate the overlays from the main program, and place
7679 their machine code in the larger memory. Place your main program in
7680 instruction memory, but leave at least enough space there to hold the
7681 largest overlay as well.
7683 Now, to call a function located in an overlay, you must first copy that
7684 overlay's machine code from the large memory into the space set aside
7685 for it in the instruction memory, and then jump to its entry point
7688 @c NB: In the below the mapped area's size is greater or equal to the
7689 @c size of all overlays. This is intentional to remind the developer
7690 @c that overlays don't necessarily need to be the same size.
7694 Data Instruction Larger
7695 Address Space Address Space Address Space
7696 +-----------+ +-----------+ +-----------+
7698 +-----------+ +-----------+ +-----------+<-- overlay 1
7699 | program | | main | .----| overlay 1 | load address
7700 | variables | | program | | +-----------+
7701 | and heap | | | | | |
7702 +-----------+ | | | +-----------+<-- overlay 2
7703 | | +-----------+ | | | load address
7704 +-----------+ | | | .-| overlay 2 |
7706 mapped --->+-----------+ | | +-----------+
7708 | overlay | <-' | | |
7709 | area | <---' +-----------+<-- overlay 3
7710 | | <---. | | load address
7711 +-----------+ `--| overlay 3 |
7718 @anchor{A code overlay}A code overlay
7722 The diagram (@pxref{A code overlay}) shows a system with separate data
7723 and instruction address spaces. To map an overlay, the program copies
7724 its code from the larger address space to the instruction address space.
7725 Since the overlays shown here all use the same mapped address, only one
7726 may be mapped at a time. For a system with a single address space for
7727 data and instructions, the diagram would be similar, except that the
7728 program variables and heap would share an address space with the main
7729 program and the overlay area.
7731 An overlay loaded into instruction memory and ready for use is called a
7732 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
7733 instruction memory. An overlay not present (or only partially present)
7734 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
7735 is its address in the larger memory. The mapped address is also called
7736 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
7737 called the @dfn{load memory address}, or @dfn{LMA}.
7739 Unfortunately, overlays are not a completely transparent way to adapt a
7740 program to limited instruction memory. They introduce a new set of
7741 global constraints you must keep in mind as you design your program:
7746 Before calling or returning to a function in an overlay, your program
7747 must make sure that overlay is actually mapped. Otherwise, the call or
7748 return will transfer control to the right address, but in the wrong
7749 overlay, and your program will probably crash.
7752 If the process of mapping an overlay is expensive on your system, you
7753 will need to choose your overlays carefully to minimize their effect on
7754 your program's performance.
7757 The executable file you load onto your system must contain each
7758 overlay's instructions, appearing at the overlay's load address, not its
7759 mapped address. However, each overlay's instructions must be relocated
7760 and its symbols defined as if the overlay were at its mapped address.
7761 You can use GNU linker scripts to specify different load and relocation
7762 addresses for pieces of your program; see @ref{Overlay Description,,,
7763 ld.info, Using ld: the GNU linker}.
7766 The procedure for loading executable files onto your system must be able
7767 to load their contents into the larger address space as well as the
7768 instruction and data spaces.
7772 The overlay system described above is rather simple, and could be
7773 improved in many ways:
7778 If your system has suitable bank switch registers or memory management
7779 hardware, you could use those facilities to make an overlay's load area
7780 contents simply appear at their mapped address in instruction space.
7781 This would probably be faster than copying the overlay to its mapped
7782 area in the usual way.
7785 If your overlays are small enough, you could set aside more than one
7786 overlay area, and have more than one overlay mapped at a time.
7789 You can use overlays to manage data, as well as instructions. In
7790 general, data overlays are even less transparent to your design than
7791 code overlays: whereas code overlays only require care when you call or
7792 return to functions, data overlays require care every time you access
7793 the data. Also, if you change the contents of a data overlay, you
7794 must copy its contents back out to its load address before you can copy a
7795 different data overlay into the same mapped area.
7800 @node Overlay Commands
7801 @section Overlay Commands
7803 To use @value{GDBN}'s overlay support, each overlay in your program must
7804 correspond to a separate section of the executable file. The section's
7805 virtual memory address and load memory address must be the overlay's
7806 mapped and load addresses. Identifying overlays with sections allows
7807 @value{GDBN} to determine the appropriate address of a function or
7808 variable, depending on whether the overlay is mapped or not.
7810 @value{GDBN}'s overlay commands all start with the word @code{overlay};
7811 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
7816 Disable @value{GDBN}'s overlay support. When overlay support is
7817 disabled, @value{GDBN} assumes that all functions and variables are
7818 always present at their mapped addresses. By default, @value{GDBN}'s
7819 overlay support is disabled.
7821 @item overlay manual
7822 @cindex manual overlay debugging
7823 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
7824 relies on you to tell it which overlays are mapped, and which are not,
7825 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
7826 commands described below.
7828 @item overlay map-overlay @var{overlay}
7829 @itemx overlay map @var{overlay}
7830 @cindex map an overlay
7831 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
7832 be the name of the object file section containing the overlay. When an
7833 overlay is mapped, @value{GDBN} assumes it can find the overlay's
7834 functions and variables at their mapped addresses. @value{GDBN} assumes
7835 that any other overlays whose mapped ranges overlap that of
7836 @var{overlay} are now unmapped.
7838 @item overlay unmap-overlay @var{overlay}
7839 @itemx overlay unmap @var{overlay}
7840 @cindex unmap an overlay
7841 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
7842 must be the name of the object file section containing the overlay.
7843 When an overlay is unmapped, @value{GDBN} assumes it can find the
7844 overlay's functions and variables at their load addresses.
7847 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
7848 consults a data structure the overlay manager maintains in the inferior
7849 to see which overlays are mapped. For details, see @ref{Automatic
7852 @item overlay load-target
7854 @cindex reloading the overlay table
7855 Re-read the overlay table from the inferior. Normally, @value{GDBN}
7856 re-reads the table @value{GDBN} automatically each time the inferior
7857 stops, so this command should only be necessary if you have changed the
7858 overlay mapping yourself using @value{GDBN}. This command is only
7859 useful when using automatic overlay debugging.
7861 @item overlay list-overlays
7863 @cindex listing mapped overlays
7864 Display a list of the overlays currently mapped, along with their mapped
7865 addresses, load addresses, and sizes.
7869 Normally, when @value{GDBN} prints a code address, it includes the name
7870 of the function the address falls in:
7873 (@value{GDBP}) print main
7874 $3 = @{int ()@} 0x11a0 <main>
7877 When overlay debugging is enabled, @value{GDBN} recognizes code in
7878 unmapped overlays, and prints the names of unmapped functions with
7879 asterisks around them. For example, if @code{foo} is a function in an
7880 unmapped overlay, @value{GDBN} prints it this way:
7883 (@value{GDBP}) overlay list
7884 No sections are mapped.
7885 (@value{GDBP}) print foo
7886 $5 = @{int (int)@} 0x100000 <*foo*>
7889 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
7893 (@value{GDBP}) overlay list
7894 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
7895 mapped at 0x1016 - 0x104a
7896 (@value{GDBP}) print foo
7897 $6 = @{int (int)@} 0x1016 <foo>
7900 When overlay debugging is enabled, @value{GDBN} can find the correct
7901 address for functions and variables in an overlay, whether or not the
7902 overlay is mapped. This allows most @value{GDBN} commands, like
7903 @code{break} and @code{disassemble}, to work normally, even on unmapped
7904 code. However, @value{GDBN}'s breakpoint support has some limitations:
7908 @cindex breakpoints in overlays
7909 @cindex overlays, setting breakpoints in
7910 You can set breakpoints in functions in unmapped overlays, as long as
7911 @value{GDBN} can write to the overlay at its load address.
7913 @value{GDBN} can not set hardware or simulator-based breakpoints in
7914 unmapped overlays. However, if you set a breakpoint at the end of your
7915 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
7916 you are using manual overlay management), @value{GDBN} will re-set its
7917 breakpoints properly.
7921 @node Automatic Overlay Debugging
7922 @section Automatic Overlay Debugging
7923 @cindex automatic overlay debugging
7925 @value{GDBN} can automatically track which overlays are mapped and which
7926 are not, given some simple co-operation from the overlay manager in the
7927 inferior. If you enable automatic overlay debugging with the
7928 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
7929 looks in the inferior's memory for certain variables describing the
7930 current state of the overlays.
7932 Here are the variables your overlay manager must define to support
7933 @value{GDBN}'s automatic overlay debugging:
7937 @item @code{_ovly_table}:
7938 This variable must be an array of the following structures:
7943 /* The overlay's mapped address. */
7946 /* The size of the overlay, in bytes. */
7949 /* The overlay's load address. */
7952 /* Non-zero if the overlay is currently mapped;
7954 unsigned long mapped;
7958 @item @code{_novlys}:
7959 This variable must be a four-byte signed integer, holding the total
7960 number of elements in @code{_ovly_table}.
7964 To decide whether a particular overlay is mapped or not, @value{GDBN}
7965 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
7966 @code{lma} members equal the VMA and LMA of the overlay's section in the
7967 executable file. When @value{GDBN} finds a matching entry, it consults
7968 the entry's @code{mapped} member to determine whether the overlay is
7971 In addition, your overlay manager may define a function called
7972 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
7973 will silently set a breakpoint there. If the overlay manager then
7974 calls this function whenever it has changed the overlay table, this
7975 will enable @value{GDBN} to accurately keep track of which overlays
7976 are in program memory, and update any breakpoints that may be set
7977 in overlays. This will allow breakpoints to work even if the
7978 overlays are kept in ROM or other non-writable memory while they
7979 are not being executed.
7981 @node Overlay Sample Program
7982 @section Overlay Sample Program
7983 @cindex overlay example program
7985 When linking a program which uses overlays, you must place the overlays
7986 at their load addresses, while relocating them to run at their mapped
7987 addresses. To do this, you must write a linker script (@pxref{Overlay
7988 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
7989 since linker scripts are specific to a particular host system, target
7990 architecture, and target memory layout, this manual cannot provide
7991 portable sample code demonstrating @value{GDBN}'s overlay support.
7993 However, the @value{GDBN} source distribution does contain an overlaid
7994 program, with linker scripts for a few systems, as part of its test
7995 suite. The program consists of the following files from
7996 @file{gdb/testsuite/gdb.base}:
8000 The main program file.
8002 A simple overlay manager, used by @file{overlays.c}.
8007 Overlay modules, loaded and used by @file{overlays.c}.
8010 Linker scripts for linking the test program on the @code{d10v-elf}
8011 and @code{m32r-elf} targets.
8014 You can build the test program using the @code{d10v-elf} GCC
8015 cross-compiler like this:
8018 $ d10v-elf-gcc -g -c overlays.c
8019 $ d10v-elf-gcc -g -c ovlymgr.c
8020 $ d10v-elf-gcc -g -c foo.c
8021 $ d10v-elf-gcc -g -c bar.c
8022 $ d10v-elf-gcc -g -c baz.c
8023 $ d10v-elf-gcc -g -c grbx.c
8024 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
8025 baz.o grbx.o -Wl,-Td10v.ld -o overlays
8028 The build process is identical for any other architecture, except that
8029 you must substitute the appropriate compiler and linker script for the
8030 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
8034 @chapter Using @value{GDBN} with Different Languages
8037 Although programming languages generally have common aspects, they are
8038 rarely expressed in the same manner. For instance, in ANSI C,
8039 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
8040 Modula-2, it is accomplished by @code{p^}. Values can also be
8041 represented (and displayed) differently. Hex numbers in C appear as
8042 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
8044 @cindex working language
8045 Language-specific information is built into @value{GDBN} for some languages,
8046 allowing you to express operations like the above in your program's
8047 native language, and allowing @value{GDBN} to output values in a manner
8048 consistent with the syntax of your program's native language. The
8049 language you use to build expressions is called the @dfn{working
8053 * Setting:: Switching between source languages
8054 * Show:: Displaying the language
8055 * Checks:: Type and range checks
8056 * Supported languages:: Supported languages
8057 * Unsupported languages:: Unsupported languages
8061 @section Switching between source languages
8063 There are two ways to control the working language---either have @value{GDBN}
8064 set it automatically, or select it manually yourself. You can use the
8065 @code{set language} command for either purpose. On startup, @value{GDBN}
8066 defaults to setting the language automatically. The working language is
8067 used to determine how expressions you type are interpreted, how values
8070 In addition to the working language, every source file that
8071 @value{GDBN} knows about has its own working language. For some object
8072 file formats, the compiler might indicate which language a particular
8073 source file is in. However, most of the time @value{GDBN} infers the
8074 language from the name of the file. The language of a source file
8075 controls whether C@t{++} names are demangled---this way @code{backtrace} can
8076 show each frame appropriately for its own language. There is no way to
8077 set the language of a source file from within @value{GDBN}, but you can
8078 set the language associated with a filename extension. @xref{Show, ,
8079 Displaying the language}.
8081 This is most commonly a problem when you use a program, such
8082 as @code{cfront} or @code{f2c}, that generates C but is written in
8083 another language. In that case, make the
8084 program use @code{#line} directives in its C output; that way
8085 @value{GDBN} will know the correct language of the source code of the original
8086 program, and will display that source code, not the generated C code.
8089 * Filenames:: Filename extensions and languages.
8090 * Manually:: Setting the working language manually
8091 * Automatically:: Having @value{GDBN} infer the source language
8095 @subsection List of filename extensions and languages
8097 If a source file name ends in one of the following extensions, then
8098 @value{GDBN} infers that its language is the one indicated.
8119 Objective-C source file
8126 Modula-2 source file
8130 Assembler source file. This actually behaves almost like C, but
8131 @value{GDBN} does not skip over function prologues when stepping.
8134 In addition, you may set the language associated with a filename
8135 extension. @xref{Show, , Displaying the language}.
8138 @subsection Setting the working language
8140 If you allow @value{GDBN} to set the language automatically,
8141 expressions are interpreted the same way in your debugging session and
8144 @kindex set language
8145 If you wish, you may set the language manually. To do this, issue the
8146 command @samp{set language @var{lang}}, where @var{lang} is the name of
8148 @code{c} or @code{modula-2}.
8149 For a list of the supported languages, type @samp{set language}.
8151 Setting the language manually prevents @value{GDBN} from updating the working
8152 language automatically. This can lead to confusion if you try
8153 to debug a program when the working language is not the same as the
8154 source language, when an expression is acceptable to both
8155 languages---but means different things. For instance, if the current
8156 source file were written in C, and @value{GDBN} was parsing Modula-2, a
8164 might not have the effect you intended. In C, this means to add
8165 @code{b} and @code{c} and place the result in @code{a}. The result
8166 printed would be the value of @code{a}. In Modula-2, this means to compare
8167 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
8170 @subsection Having @value{GDBN} infer the source language
8172 To have @value{GDBN} set the working language automatically, use
8173 @samp{set language local} or @samp{set language auto}. @value{GDBN}
8174 then infers the working language. That is, when your program stops in a
8175 frame (usually by encountering a breakpoint), @value{GDBN} sets the
8176 working language to the language recorded for the function in that
8177 frame. If the language for a frame is unknown (that is, if the function
8178 or block corresponding to the frame was defined in a source file that
8179 does not have a recognized extension), the current working language is
8180 not changed, and @value{GDBN} issues a warning.
8182 This may not seem necessary for most programs, which are written
8183 entirely in one source language. However, program modules and libraries
8184 written in one source language can be used by a main program written in
8185 a different source language. Using @samp{set language auto} in this
8186 case frees you from having to set the working language manually.
8189 @section Displaying the language
8191 The following commands help you find out which language is the
8192 working language, and also what language source files were written in.
8196 @kindex show language
8197 Display the current working language. This is the
8198 language you can use with commands such as @code{print} to
8199 build and compute expressions that may involve variables in your program.
8202 @kindex info frame@r{, show the source language}
8203 Display the source language for this frame. This language becomes the
8204 working language if you use an identifier from this frame.
8205 @xref{Frame Info, ,Information about a frame}, to identify the other
8206 information listed here.
8209 @kindex info source@r{, show the source language}
8210 Display the source language of this source file.
8211 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
8212 information listed here.
8215 In unusual circumstances, you may have source files with extensions
8216 not in the standard list. You can then set the extension associated
8217 with a language explicitly:
8220 @item set extension-language @var{ext} @var{language}
8221 @kindex set extension-language
8222 Tell @value{GDBN} that source files with extension @var{ext} are to be
8223 assumed as written in the source language @var{language}.
8225 @item info extensions
8226 @kindex info extensions
8227 List all the filename extensions and the associated languages.
8231 @section Type and range checking
8234 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
8235 checking are included, but they do not yet have any effect. This
8236 section documents the intended facilities.
8238 @c FIXME remove warning when type/range code added
8240 Some languages are designed to guard you against making seemingly common
8241 errors through a series of compile- and run-time checks. These include
8242 checking the type of arguments to functions and operators, and making
8243 sure mathematical overflows are caught at run time. Checks such as
8244 these help to ensure a program's correctness once it has been compiled
8245 by eliminating type mismatches, and providing active checks for range
8246 errors when your program is running.
8248 @value{GDBN} can check for conditions like the above if you wish.
8249 Although @value{GDBN} does not check the statements in your program,
8250 it can check expressions entered directly into @value{GDBN} for
8251 evaluation via the @code{print} command, for example. As with the
8252 working language, @value{GDBN} can also decide whether or not to check
8253 automatically based on your program's source language.
8254 @xref{Supported languages, ,Supported languages}, for the default
8255 settings of supported languages.
8258 * Type Checking:: An overview of type checking
8259 * Range Checking:: An overview of range checking
8262 @cindex type checking
8263 @cindex checks, type
8265 @subsection An overview of type checking
8267 Some languages, such as Modula-2, are strongly typed, meaning that the
8268 arguments to operators and functions have to be of the correct type,
8269 otherwise an error occurs. These checks prevent type mismatch
8270 errors from ever causing any run-time problems. For example,
8278 The second example fails because the @code{CARDINAL} 1 is not
8279 type-compatible with the @code{REAL} 2.3.
8281 For the expressions you use in @value{GDBN} commands, you can tell the
8282 @value{GDBN} type checker to skip checking;
8283 to treat any mismatches as errors and abandon the expression;
8284 or to only issue warnings when type mismatches occur,
8285 but evaluate the expression anyway. When you choose the last of
8286 these, @value{GDBN} evaluates expressions like the second example above, but
8287 also issues a warning.
8289 Even if you turn type checking off, there may be other reasons
8290 related to type that prevent @value{GDBN} from evaluating an expression.
8291 For instance, @value{GDBN} does not know how to add an @code{int} and
8292 a @code{struct foo}. These particular type errors have nothing to do
8293 with the language in use, and usually arise from expressions, such as
8294 the one described above, which make little sense to evaluate anyway.
8296 Each language defines to what degree it is strict about type. For
8297 instance, both Modula-2 and C require the arguments to arithmetical
8298 operators to be numbers. In C, enumerated types and pointers can be
8299 represented as numbers, so that they are valid arguments to mathematical
8300 operators. @xref{Supported languages, ,Supported languages}, for further
8301 details on specific languages.
8303 @value{GDBN} provides some additional commands for controlling the type checker:
8305 @kindex set check type
8306 @kindex show check type
8308 @item set check type auto
8309 Set type checking on or off based on the current working language.
8310 @xref{Supported languages, ,Supported languages}, for the default settings for
8313 @item set check type on
8314 @itemx set check type off
8315 Set type checking on or off, overriding the default setting for the
8316 current working language. Issue a warning if the setting does not
8317 match the language default. If any type mismatches occur in
8318 evaluating an expression while type checking is on, @value{GDBN} prints a
8319 message and aborts evaluation of the expression.
8321 @item set check type warn
8322 Cause the type checker to issue warnings, but to always attempt to
8323 evaluate the expression. Evaluating the expression may still
8324 be impossible for other reasons. For example, @value{GDBN} cannot add
8325 numbers and structures.
8328 Show the current setting of the type checker, and whether or not @value{GDBN}
8329 is setting it automatically.
8332 @cindex range checking
8333 @cindex checks, range
8334 @node Range Checking
8335 @subsection An overview of range checking
8337 In some languages (such as Modula-2), it is an error to exceed the
8338 bounds of a type; this is enforced with run-time checks. Such range
8339 checking is meant to ensure program correctness by making sure
8340 computations do not overflow, or indices on an array element access do
8341 not exceed the bounds of the array.
8343 For expressions you use in @value{GDBN} commands, you can tell
8344 @value{GDBN} to treat range errors in one of three ways: ignore them,
8345 always treat them as errors and abandon the expression, or issue
8346 warnings but evaluate the expression anyway.
8348 A range error can result from numerical overflow, from exceeding an
8349 array index bound, or when you type a constant that is not a member
8350 of any type. Some languages, however, do not treat overflows as an
8351 error. In many implementations of C, mathematical overflow causes the
8352 result to ``wrap around'' to lower values---for example, if @var{m} is
8353 the largest integer value, and @var{s} is the smallest, then
8356 @var{m} + 1 @result{} @var{s}
8359 This, too, is specific to individual languages, and in some cases
8360 specific to individual compilers or machines. @xref{Supported languages, ,
8361 Supported languages}, for further details on specific languages.
8363 @value{GDBN} provides some additional commands for controlling the range checker:
8365 @kindex set check range
8366 @kindex show check range
8368 @item set check range auto
8369 Set range checking on or off based on the current working language.
8370 @xref{Supported languages, ,Supported languages}, for the default settings for
8373 @item set check range on
8374 @itemx set check range off
8375 Set range checking on or off, overriding the default setting for the
8376 current working language. A warning is issued if the setting does not
8377 match the language default. If a range error occurs and range checking is on,
8378 then a message is printed and evaluation of the expression is aborted.
8380 @item set check range warn
8381 Output messages when the @value{GDBN} range checker detects a range error,
8382 but attempt to evaluate the expression anyway. Evaluating the
8383 expression may still be impossible for other reasons, such as accessing
8384 memory that the process does not own (a typical example from many Unix
8388 Show the current setting of the range checker, and whether or not it is
8389 being set automatically by @value{GDBN}.
8392 @node Supported languages
8393 @section Supported languages
8395 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
8396 assembly, Modula-2, and Ada.
8397 @c This is false ...
8398 Some @value{GDBN} features may be used in expressions regardless of the
8399 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
8400 and the @samp{@{type@}addr} construct (@pxref{Expressions,
8401 ,Expressions}) can be used with the constructs of any supported
8404 The following sections detail to what degree each source language is
8405 supported by @value{GDBN}. These sections are not meant to be language
8406 tutorials or references, but serve only as a reference guide to what the
8407 @value{GDBN} expression parser accepts, and what input and output
8408 formats should look like for different languages. There are many good
8409 books written on each of these languages; please look to these for a
8410 language reference or tutorial.
8414 * Objective-C:: Objective-C
8417 * Modula-2:: Modula-2
8422 @subsection C and C@t{++}
8424 @cindex C and C@t{++}
8425 @cindex expressions in C or C@t{++}
8427 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
8428 to both languages. Whenever this is the case, we discuss those languages
8432 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
8433 @cindex @sc{gnu} C@t{++}
8434 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
8435 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
8436 effectively, you must compile your C@t{++} programs with a supported
8437 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
8438 compiler (@code{aCC}).
8440 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
8441 format; if it doesn't work on your system, try the stabs+ debugging
8442 format. You can select those formats explicitly with the @code{g++}
8443 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
8444 @xref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
8445 CC, gcc.info, Using @sc{gnu} CC}.
8448 * C Operators:: C and C@t{++} operators
8449 * C Constants:: C and C@t{++} constants
8450 * C plus plus expressions:: C@t{++} expressions
8451 * C Defaults:: Default settings for C and C@t{++}
8452 * C Checks:: C and C@t{++} type and range checks
8453 * Debugging C:: @value{GDBN} and C
8454 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
8458 @subsubsection C and C@t{++} operators
8460 @cindex C and C@t{++} operators
8462 Operators must be defined on values of specific types. For instance,
8463 @code{+} is defined on numbers, but not on structures. Operators are
8464 often defined on groups of types.
8466 For the purposes of C and C@t{++}, the following definitions hold:
8471 @emph{Integral types} include @code{int} with any of its storage-class
8472 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
8475 @emph{Floating-point types} include @code{float}, @code{double}, and
8476 @code{long double} (if supported by the target platform).
8479 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
8482 @emph{Scalar types} include all of the above.
8487 The following operators are supported. They are listed here
8488 in order of increasing precedence:
8492 The comma or sequencing operator. Expressions in a comma-separated list
8493 are evaluated from left to right, with the result of the entire
8494 expression being the last expression evaluated.
8497 Assignment. The value of an assignment expression is the value
8498 assigned. Defined on scalar types.
8501 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
8502 and translated to @w{@code{@var{a} = @var{a op b}}}.
8503 @w{@code{@var{op}=}} and @code{=} have the same precedence.
8504 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
8505 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
8508 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
8509 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
8513 Logical @sc{or}. Defined on integral types.
8516 Logical @sc{and}. Defined on integral types.
8519 Bitwise @sc{or}. Defined on integral types.
8522 Bitwise exclusive-@sc{or}. Defined on integral types.
8525 Bitwise @sc{and}. Defined on integral types.
8528 Equality and inequality. Defined on scalar types. The value of these
8529 expressions is 0 for false and non-zero for true.
8531 @item <@r{, }>@r{, }<=@r{, }>=
8532 Less than, greater than, less than or equal, greater than or equal.
8533 Defined on scalar types. The value of these expressions is 0 for false
8534 and non-zero for true.
8537 left shift, and right shift. Defined on integral types.
8540 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8543 Addition and subtraction. Defined on integral types, floating-point types and
8546 @item *@r{, }/@r{, }%
8547 Multiplication, division, and modulus. Multiplication and division are
8548 defined on integral and floating-point types. Modulus is defined on
8552 Increment and decrement. When appearing before a variable, the
8553 operation is performed before the variable is used in an expression;
8554 when appearing after it, the variable's value is used before the
8555 operation takes place.
8558 Pointer dereferencing. Defined on pointer types. Same precedence as
8562 Address operator. Defined on variables. Same precedence as @code{++}.
8564 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
8565 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
8566 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
8567 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
8571 Negative. Defined on integral and floating-point types. Same
8572 precedence as @code{++}.
8575 Logical negation. Defined on integral types. Same precedence as
8579 Bitwise complement operator. Defined on integral types. Same precedence as
8584 Structure member, and pointer-to-structure member. For convenience,
8585 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
8586 pointer based on the stored type information.
8587 Defined on @code{struct} and @code{union} data.
8590 Dereferences of pointers to members.
8593 Array indexing. @code{@var{a}[@var{i}]} is defined as
8594 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
8597 Function parameter list. Same precedence as @code{->}.
8600 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
8601 and @code{class} types.
8604 Doubled colons also represent the @value{GDBN} scope operator
8605 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
8609 If an operator is redefined in the user code, @value{GDBN} usually
8610 attempts to invoke the redefined version instead of using the operator's
8618 @subsubsection C and C@t{++} constants
8620 @cindex C and C@t{++} constants
8622 @value{GDBN} allows you to express the constants of C and C@t{++} in the
8627 Integer constants are a sequence of digits. Octal constants are
8628 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
8629 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
8630 @samp{l}, specifying that the constant should be treated as a
8634 Floating point constants are a sequence of digits, followed by a decimal
8635 point, followed by a sequence of digits, and optionally followed by an
8636 exponent. An exponent is of the form:
8637 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
8638 sequence of digits. The @samp{+} is optional for positive exponents.
8639 A floating-point constant may also end with a letter @samp{f} or
8640 @samp{F}, specifying that the constant should be treated as being of
8641 the @code{float} (as opposed to the default @code{double}) type; or with
8642 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
8646 Enumerated constants consist of enumerated identifiers, or their
8647 integral equivalents.
8650 Character constants are a single character surrounded by single quotes
8651 (@code{'}), or a number---the ordinal value of the corresponding character
8652 (usually its @sc{ascii} value). Within quotes, the single character may
8653 be represented by a letter or by @dfn{escape sequences}, which are of
8654 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
8655 of the character's ordinal value; or of the form @samp{\@var{x}}, where
8656 @samp{@var{x}} is a predefined special character---for example,
8657 @samp{\n} for newline.
8660 String constants are a sequence of character constants surrounded by
8661 double quotes (@code{"}). Any valid character constant (as described
8662 above) may appear. Double quotes within the string must be preceded by
8663 a backslash, so for instance @samp{"a\"b'c"} is a string of five
8667 Pointer constants are an integral value. You can also write pointers
8668 to constants using the C operator @samp{&}.
8671 Array constants are comma-separated lists surrounded by braces @samp{@{}
8672 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
8673 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
8674 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
8678 * C plus plus expressions::
8685 @node C plus plus expressions
8686 @subsubsection C@t{++} expressions
8688 @cindex expressions in C@t{++}
8689 @value{GDBN} expression handling can interpret most C@t{++} expressions.
8691 @cindex debugging C@t{++} programs
8692 @cindex C@t{++} compilers
8693 @cindex debug formats and C@t{++}
8694 @cindex @value{NGCC} and C@t{++}
8696 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
8697 proper compiler and the proper debug format. Currently, @value{GDBN}
8698 works best when debugging C@t{++} code that is compiled with
8699 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
8700 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
8701 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
8702 stabs+ as their default debug format, so you usually don't need to
8703 specify a debug format explicitly. Other compilers and/or debug formats
8704 are likely to work badly or not at all when using @value{GDBN} to debug
8710 @cindex member functions
8712 Member function calls are allowed; you can use expressions like
8715 count = aml->GetOriginal(x, y)
8718 @vindex this@r{, inside C@t{++} member functions}
8719 @cindex namespace in C@t{++}
8721 While a member function is active (in the selected stack frame), your
8722 expressions have the same namespace available as the member function;
8723 that is, @value{GDBN} allows implicit references to the class instance
8724 pointer @code{this} following the same rules as C@t{++}.
8726 @cindex call overloaded functions
8727 @cindex overloaded functions, calling
8728 @cindex type conversions in C@t{++}
8730 You can call overloaded functions; @value{GDBN} resolves the function
8731 call to the right definition, with some restrictions. @value{GDBN} does not
8732 perform overload resolution involving user-defined type conversions,
8733 calls to constructors, or instantiations of templates that do not exist
8734 in the program. It also cannot handle ellipsis argument lists or
8737 It does perform integral conversions and promotions, floating-point
8738 promotions, arithmetic conversions, pointer conversions, conversions of
8739 class objects to base classes, and standard conversions such as those of
8740 functions or arrays to pointers; it requires an exact match on the
8741 number of function arguments.
8743 Overload resolution is always performed, unless you have specified
8744 @code{set overload-resolution off}. @xref{Debugging C plus plus,
8745 ,@value{GDBN} features for C@t{++}}.
8747 You must specify @code{set overload-resolution off} in order to use an
8748 explicit function signature to call an overloaded function, as in
8750 p 'foo(char,int)'('x', 13)
8753 The @value{GDBN} command-completion facility can simplify this;
8754 see @ref{Completion, ,Command completion}.
8756 @cindex reference declarations
8758 @value{GDBN} understands variables declared as C@t{++} references; you can use
8759 them in expressions just as you do in C@t{++} source---they are automatically
8762 In the parameter list shown when @value{GDBN} displays a frame, the values of
8763 reference variables are not displayed (unlike other variables); this
8764 avoids clutter, since references are often used for large structures.
8765 The @emph{address} of a reference variable is always shown, unless
8766 you have specified @samp{set print address off}.
8769 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
8770 expressions can use it just as expressions in your program do. Since
8771 one scope may be defined in another, you can use @code{::} repeatedly if
8772 necessary, for example in an expression like
8773 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
8774 resolving name scope by reference to source files, in both C and C@t{++}
8775 debugging (@pxref{Variables, ,Program variables}).
8778 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
8779 calling virtual functions correctly, printing out virtual bases of
8780 objects, calling functions in a base subobject, casting objects, and
8781 invoking user-defined operators.
8784 @subsubsection C and C@t{++} defaults
8786 @cindex C and C@t{++} defaults
8788 If you allow @value{GDBN} to set type and range checking automatically, they
8789 both default to @code{off} whenever the working language changes to
8790 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
8791 selects the working language.
8793 If you allow @value{GDBN} to set the language automatically, it
8794 recognizes source files whose names end with @file{.c}, @file{.C}, or
8795 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
8796 these files, it sets the working language to C or C@t{++}.
8797 @xref{Automatically, ,Having @value{GDBN} infer the source language},
8798 for further details.
8800 @c Type checking is (a) primarily motivated by Modula-2, and (b)
8801 @c unimplemented. If (b) changes, it might make sense to let this node
8802 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
8805 @subsubsection C and C@t{++} type and range checks
8807 @cindex C and C@t{++} checks
8809 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
8810 is not used. However, if you turn type checking on, @value{GDBN}
8811 considers two variables type equivalent if:
8815 The two variables are structured and have the same structure, union, or
8819 The two variables have the same type name, or types that have been
8820 declared equivalent through @code{typedef}.
8823 @c leaving this out because neither J Gilmore nor R Pesch understand it.
8826 The two @code{struct}, @code{union}, or @code{enum} variables are
8827 declared in the same declaration. (Note: this may not be true for all C
8832 Range checking, if turned on, is done on mathematical operations. Array
8833 indices are not checked, since they are often used to index a pointer
8834 that is not itself an array.
8837 @subsubsection @value{GDBN} and C
8839 The @code{set print union} and @code{show print union} commands apply to
8840 the @code{union} type. When set to @samp{on}, any @code{union} that is
8841 inside a @code{struct} or @code{class} is also printed. Otherwise, it
8842 appears as @samp{@{...@}}.
8844 The @code{@@} operator aids in the debugging of dynamic arrays, formed
8845 with pointers and a memory allocation function. @xref{Expressions,
8849 * Debugging C plus plus::
8852 @node Debugging C plus plus
8853 @subsubsection @value{GDBN} features for C@t{++}
8855 @cindex commands for C@t{++}
8857 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
8858 designed specifically for use with C@t{++}. Here is a summary:
8861 @cindex break in overloaded functions
8862 @item @r{breakpoint menus}
8863 When you want a breakpoint in a function whose name is overloaded,
8864 @value{GDBN} breakpoint menus help you specify which function definition
8865 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
8867 @cindex overloading in C@t{++}
8868 @item rbreak @var{regex}
8869 Setting breakpoints using regular expressions is helpful for setting
8870 breakpoints on overloaded functions that are not members of any special
8872 @xref{Set Breaks, ,Setting breakpoints}.
8874 @cindex C@t{++} exception handling
8877 Debug C@t{++} exception handling using these commands. @xref{Set
8878 Catchpoints, , Setting catchpoints}.
8881 @item ptype @var{typename}
8882 Print inheritance relationships as well as other information for type
8884 @xref{Symbols, ,Examining the Symbol Table}.
8886 @cindex C@t{++} symbol display
8887 @item set print demangle
8888 @itemx show print demangle
8889 @itemx set print asm-demangle
8890 @itemx show print asm-demangle
8891 Control whether C@t{++} symbols display in their source form, both when
8892 displaying code as C@t{++} source and when displaying disassemblies.
8893 @xref{Print Settings, ,Print settings}.
8895 @item set print object
8896 @itemx show print object
8897 Choose whether to print derived (actual) or declared types of objects.
8898 @xref{Print Settings, ,Print settings}.
8900 @item set print vtbl
8901 @itemx show print vtbl
8902 Control the format for printing virtual function tables.
8903 @xref{Print Settings, ,Print settings}.
8904 (The @code{vtbl} commands do not work on programs compiled with the HP
8905 ANSI C@t{++} compiler (@code{aCC}).)
8907 @kindex set overload-resolution
8908 @cindex overloaded functions, overload resolution
8909 @item set overload-resolution on
8910 Enable overload resolution for C@t{++} expression evaluation. The default
8911 is on. For overloaded functions, @value{GDBN} evaluates the arguments
8912 and searches for a function whose signature matches the argument types,
8913 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
8914 expressions}, for details). If it cannot find a match, it emits a
8917 @item set overload-resolution off
8918 Disable overload resolution for C@t{++} expression evaluation. For
8919 overloaded functions that are not class member functions, @value{GDBN}
8920 chooses the first function of the specified name that it finds in the
8921 symbol table, whether or not its arguments are of the correct type. For
8922 overloaded functions that are class member functions, @value{GDBN}
8923 searches for a function whose signature @emph{exactly} matches the
8926 @kindex show overload-resolution
8927 @item show overload-resolution
8928 Show the current setting of overload resolution.
8930 @item @r{Overloaded symbol names}
8931 You can specify a particular definition of an overloaded symbol, using
8932 the same notation that is used to declare such symbols in C@t{++}: type
8933 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
8934 also use the @value{GDBN} command-line word completion facilities to list the
8935 available choices, or to finish the type list for you.
8936 @xref{Completion,, Command completion}, for details on how to do this.
8940 @subsection Objective-C
8943 This section provides information about some commands and command
8944 options that are useful for debugging Objective-C code. See also
8945 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
8946 few more commands specific to Objective-C support.
8949 * Method Names in Commands::
8950 * The Print Command with Objective-C::
8953 @node Method Names in Commands, The Print Command with Objective-C, Objective-C, Objective-C
8954 @subsubsection Method Names in Commands
8956 The following commands have been extended to accept Objective-C method
8957 names as line specifications:
8959 @kindex clear@r{, and Objective-C}
8960 @kindex break@r{, and Objective-C}
8961 @kindex info line@r{, and Objective-C}
8962 @kindex jump@r{, and Objective-C}
8963 @kindex list@r{, and Objective-C}
8967 @item @code{info line}
8972 A fully qualified Objective-C method name is specified as
8975 -[@var{Class} @var{methodName}]
8978 where the minus sign is used to indicate an instance method and a
8979 plus sign (not shown) is used to indicate a class method. The class
8980 name @var{Class} and method name @var{methodName} are enclosed in
8981 brackets, similar to the way messages are specified in Objective-C
8982 source code. For example, to set a breakpoint at the @code{create}
8983 instance method of class @code{Fruit} in the program currently being
8987 break -[Fruit create]
8990 To list ten program lines around the @code{initialize} class method,
8994 list +[NSText initialize]
8997 In the current version of @value{GDBN}, the plus or minus sign is
8998 required. In future versions of @value{GDBN}, the plus or minus
8999 sign will be optional, but you can use it to narrow the search. It
9000 is also possible to specify just a method name:
9006 You must specify the complete method name, including any colons. If
9007 your program's source files contain more than one @code{create} method,
9008 you'll be presented with a numbered list of classes that implement that
9009 method. Indicate your choice by number, or type @samp{0} to exit if
9012 As another example, to clear a breakpoint established at the
9013 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
9016 clear -[NSWindow makeKeyAndOrderFront:]
9019 @node The Print Command with Objective-C
9020 @subsubsection The Print Command With Objective-C
9021 @cindex Objective-C, print objects
9022 @kindex print-object
9023 @kindex po @r{(@code{print-object})}
9025 The print command has also been extended to accept methods. For example:
9028 print -[@var{object} hash]
9031 @cindex print an Objective-C object description
9032 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
9034 will tell @value{GDBN} to send the @code{hash} message to @var{object}
9035 and print the result. Also, an additional command has been added,
9036 @code{print-object} or @code{po} for short, which is meant to print
9037 the description of an object. However, this command may only work
9038 with certain Objective-C libraries that have a particular hook
9039 function, @code{_NSPrintForDebugger}, defined.
9043 @cindex Fortran-specific support in @value{GDBN}
9046 @cindex @code{COMMON} blocks, Fortran
9048 @item info common @r{[}@var{common-name}@r{]}
9049 This command prints the values contained in the Fortran @code{COMMON}
9050 block whose name is @var{common-name}. With no argument, the names of
9051 all @code{COMMON} blocks visible at current program location are
9055 Fortran symbols are usually case-insensitive, so @value{GDBN} by
9056 default uses case-insensitive matches for Fortran symbols. You can
9057 change that with the @samp{set case-insensitive} command, see
9058 @ref{Symbols}, for the details.
9063 @cindex Pascal support in @value{GDBN}, limitations
9064 Debugging Pascal programs which use sets, subranges, file variables, or
9065 nested functions does not currently work. @value{GDBN} does not support
9066 entering expressions, printing values, or similar features using Pascal
9069 The Pascal-specific command @code{set print pascal_static-members}
9070 controls whether static members of Pascal objects are displayed.
9071 @xref{Print Settings, pascal_static-members}.
9074 @subsection Modula-2
9076 @cindex Modula-2, @value{GDBN} support
9078 The extensions made to @value{GDBN} to support Modula-2 only support
9079 output from the @sc{gnu} Modula-2 compiler (which is currently being
9080 developed). Other Modula-2 compilers are not currently supported, and
9081 attempting to debug executables produced by them is most likely
9082 to give an error as @value{GDBN} reads in the executable's symbol
9085 @cindex expressions in Modula-2
9087 * M2 Operators:: Built-in operators
9088 * Built-In Func/Proc:: Built-in functions and procedures
9089 * M2 Constants:: Modula-2 constants
9090 * M2 Defaults:: Default settings for Modula-2
9091 * Deviations:: Deviations from standard Modula-2
9092 * M2 Checks:: Modula-2 type and range checks
9093 * M2 Scope:: The scope operators @code{::} and @code{.}
9094 * GDB/M2:: @value{GDBN} and Modula-2
9098 @subsubsection Operators
9099 @cindex Modula-2 operators
9101 Operators must be defined on values of specific types. For instance,
9102 @code{+} is defined on numbers, but not on structures. Operators are
9103 often defined on groups of types. For the purposes of Modula-2, the
9104 following definitions hold:
9109 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
9113 @emph{Character types} consist of @code{CHAR} and its subranges.
9116 @emph{Floating-point types} consist of @code{REAL}.
9119 @emph{Pointer types} consist of anything declared as @code{POINTER TO
9123 @emph{Scalar types} consist of all of the above.
9126 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
9129 @emph{Boolean types} consist of @code{BOOLEAN}.
9133 The following operators are supported, and appear in order of
9134 increasing precedence:
9138 Function argument or array index separator.
9141 Assignment. The value of @var{var} @code{:=} @var{value} is
9145 Less than, greater than on integral, floating-point, or enumerated
9149 Less than or equal to, greater than or equal to
9150 on integral, floating-point and enumerated types, or set inclusion on
9151 set types. Same precedence as @code{<}.
9153 @item =@r{, }<>@r{, }#
9154 Equality and two ways of expressing inequality, valid on scalar types.
9155 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
9156 available for inequality, since @code{#} conflicts with the script
9160 Set membership. Defined on set types and the types of their members.
9161 Same precedence as @code{<}.
9164 Boolean disjunction. Defined on boolean types.
9167 Boolean conjunction. Defined on boolean types.
9170 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9173 Addition and subtraction on integral and floating-point types, or union
9174 and difference on set types.
9177 Multiplication on integral and floating-point types, or set intersection
9181 Division on floating-point types, or symmetric set difference on set
9182 types. Same precedence as @code{*}.
9185 Integer division and remainder. Defined on integral types. Same
9186 precedence as @code{*}.
9189 Negative. Defined on @code{INTEGER} and @code{REAL} data.
9192 Pointer dereferencing. Defined on pointer types.
9195 Boolean negation. Defined on boolean types. Same precedence as
9199 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
9200 precedence as @code{^}.
9203 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
9206 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
9210 @value{GDBN} and Modula-2 scope operators.
9214 @emph{Warning:} Sets and their operations are not yet supported, so @value{GDBN}
9215 treats the use of the operator @code{IN}, or the use of operators
9216 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
9217 @code{<=}, and @code{>=} on sets as an error.
9221 @node Built-In Func/Proc
9222 @subsubsection Built-in functions and procedures
9223 @cindex Modula-2 built-ins
9225 Modula-2 also makes available several built-in procedures and functions.
9226 In describing these, the following metavariables are used:
9231 represents an @code{ARRAY} variable.
9234 represents a @code{CHAR} constant or variable.
9237 represents a variable or constant of integral type.
9240 represents an identifier that belongs to a set. Generally used in the
9241 same function with the metavariable @var{s}. The type of @var{s} should
9242 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
9245 represents a variable or constant of integral or floating-point type.
9248 represents a variable or constant of floating-point type.
9254 represents a variable.
9257 represents a variable or constant of one of many types. See the
9258 explanation of the function for details.
9261 All Modula-2 built-in procedures also return a result, described below.
9265 Returns the absolute value of @var{n}.
9268 If @var{c} is a lower case letter, it returns its upper case
9269 equivalent, otherwise it returns its argument.
9272 Returns the character whose ordinal value is @var{i}.
9275 Decrements the value in the variable @var{v} by one. Returns the new value.
9277 @item DEC(@var{v},@var{i})
9278 Decrements the value in the variable @var{v} by @var{i}. Returns the
9281 @item EXCL(@var{m},@var{s})
9282 Removes the element @var{m} from the set @var{s}. Returns the new
9285 @item FLOAT(@var{i})
9286 Returns the floating point equivalent of the integer @var{i}.
9289 Returns the index of the last member of @var{a}.
9292 Increments the value in the variable @var{v} by one. Returns the new value.
9294 @item INC(@var{v},@var{i})
9295 Increments the value in the variable @var{v} by @var{i}. Returns the
9298 @item INCL(@var{m},@var{s})
9299 Adds the element @var{m} to the set @var{s} if it is not already
9300 there. Returns the new set.
9303 Returns the maximum value of the type @var{t}.
9306 Returns the minimum value of the type @var{t}.
9309 Returns boolean TRUE if @var{i} is an odd number.
9312 Returns the ordinal value of its argument. For example, the ordinal
9313 value of a character is its @sc{ascii} value (on machines supporting the
9314 @sc{ascii} character set). @var{x} must be of an ordered type, which include
9315 integral, character and enumerated types.
9318 Returns the size of its argument. @var{x} can be a variable or a type.
9320 @item TRUNC(@var{r})
9321 Returns the integral part of @var{r}.
9323 @item VAL(@var{t},@var{i})
9324 Returns the member of the type @var{t} whose ordinal value is @var{i}.
9328 @emph{Warning:} Sets and their operations are not yet supported, so
9329 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
9333 @cindex Modula-2 constants
9335 @subsubsection Constants
9337 @value{GDBN} allows you to express the constants of Modula-2 in the following
9343 Integer constants are simply a sequence of digits. When used in an
9344 expression, a constant is interpreted to be type-compatible with the
9345 rest of the expression. Hexadecimal integers are specified by a
9346 trailing @samp{H}, and octal integers by a trailing @samp{B}.
9349 Floating point constants appear as a sequence of digits, followed by a
9350 decimal point and another sequence of digits. An optional exponent can
9351 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
9352 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
9353 digits of the floating point constant must be valid decimal (base 10)
9357 Character constants consist of a single character enclosed by a pair of
9358 like quotes, either single (@code{'}) or double (@code{"}). They may
9359 also be expressed by their ordinal value (their @sc{ascii} value, usually)
9360 followed by a @samp{C}.
9363 String constants consist of a sequence of characters enclosed by a
9364 pair of like quotes, either single (@code{'}) or double (@code{"}).
9365 Escape sequences in the style of C are also allowed. @xref{C
9366 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
9370 Enumerated constants consist of an enumerated identifier.
9373 Boolean constants consist of the identifiers @code{TRUE} and
9377 Pointer constants consist of integral values only.
9380 Set constants are not yet supported.
9384 @subsubsection Modula-2 defaults
9385 @cindex Modula-2 defaults
9387 If type and range checking are set automatically by @value{GDBN}, they
9388 both default to @code{on} whenever the working language changes to
9389 Modula-2. This happens regardless of whether you or @value{GDBN}
9390 selected the working language.
9392 If you allow @value{GDBN} to set the language automatically, then entering
9393 code compiled from a file whose name ends with @file{.mod} sets the
9394 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
9395 the language automatically}, for further details.
9398 @subsubsection Deviations from standard Modula-2
9399 @cindex Modula-2, deviations from
9401 A few changes have been made to make Modula-2 programs easier to debug.
9402 This is done primarily via loosening its type strictness:
9406 Unlike in standard Modula-2, pointer constants can be formed by
9407 integers. This allows you to modify pointer variables during
9408 debugging. (In standard Modula-2, the actual address contained in a
9409 pointer variable is hidden from you; it can only be modified
9410 through direct assignment to another pointer variable or expression that
9411 returned a pointer.)
9414 C escape sequences can be used in strings and characters to represent
9415 non-printable characters. @value{GDBN} prints out strings with these
9416 escape sequences embedded. Single non-printable characters are
9417 printed using the @samp{CHR(@var{nnn})} format.
9420 The assignment operator (@code{:=}) returns the value of its right-hand
9424 All built-in procedures both modify @emph{and} return their argument.
9428 @subsubsection Modula-2 type and range checks
9429 @cindex Modula-2 checks
9432 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
9435 @c FIXME remove warning when type/range checks added
9437 @value{GDBN} considers two Modula-2 variables type equivalent if:
9441 They are of types that have been declared equivalent via a @code{TYPE
9442 @var{t1} = @var{t2}} statement
9445 They have been declared on the same line. (Note: This is true of the
9446 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
9449 As long as type checking is enabled, any attempt to combine variables
9450 whose types are not equivalent is an error.
9452 Range checking is done on all mathematical operations, assignment, array
9453 index bounds, and all built-in functions and procedures.
9456 @subsubsection The scope operators @code{::} and @code{.}
9458 @cindex @code{.}, Modula-2 scope operator
9459 @cindex colon, doubled as scope operator
9461 @vindex colon-colon@r{, in Modula-2}
9462 @c Info cannot handle :: but TeX can.
9465 @vindex ::@r{, in Modula-2}
9468 There are a few subtle differences between the Modula-2 scope operator
9469 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
9474 @var{module} . @var{id}
9475 @var{scope} :: @var{id}
9479 where @var{scope} is the name of a module or a procedure,
9480 @var{module} the name of a module, and @var{id} is any declared
9481 identifier within your program, except another module.
9483 Using the @code{::} operator makes @value{GDBN} search the scope
9484 specified by @var{scope} for the identifier @var{id}. If it is not
9485 found in the specified scope, then @value{GDBN} searches all scopes
9486 enclosing the one specified by @var{scope}.
9488 Using the @code{.} operator makes @value{GDBN} search the current scope for
9489 the identifier specified by @var{id} that was imported from the
9490 definition module specified by @var{module}. With this operator, it is
9491 an error if the identifier @var{id} was not imported from definition
9492 module @var{module}, or if @var{id} is not an identifier in
9496 @subsubsection @value{GDBN} and Modula-2
9498 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
9499 Five subcommands of @code{set print} and @code{show print} apply
9500 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
9501 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
9502 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
9503 analogue in Modula-2.
9505 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
9506 with any language, is not useful with Modula-2. Its
9507 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
9508 created in Modula-2 as they can in C or C@t{++}. However, because an
9509 address can be specified by an integral constant, the construct
9510 @samp{@{@var{type}@}@var{adrexp}} is still useful.
9512 @cindex @code{#} in Modula-2
9513 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
9514 interpreted as the beginning of a comment. Use @code{<>} instead.
9520 The extensions made to @value{GDBN} for Ada only support
9521 output from the @sc{gnu} Ada (GNAT) compiler.
9522 Other Ada compilers are not currently supported, and
9523 attempting to debug executables produced by them is most likely
9527 @cindex expressions in Ada
9529 * Ada Mode Intro:: General remarks on the Ada syntax
9530 and semantics supported by Ada mode
9532 * Omissions from Ada:: Restrictions on the Ada expression syntax.
9533 * Additions to Ada:: Extensions of the Ada expression syntax.
9534 * Stopping Before Main Program:: Debugging the program during elaboration.
9535 * Ada Glitches:: Known peculiarities of Ada mode.
9538 @node Ada Mode Intro
9539 @subsubsection Introduction
9540 @cindex Ada mode, general
9542 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
9543 syntax, with some extensions.
9544 The philosophy behind the design of this subset is
9548 That @value{GDBN} should provide basic literals and access to operations for
9549 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
9550 leaving more sophisticated computations to subprograms written into the
9551 program (which therefore may be called from @value{GDBN}).
9554 That type safety and strict adherence to Ada language restrictions
9555 are not particularly important to the @value{GDBN} user.
9558 That brevity is important to the @value{GDBN} user.
9561 Thus, for brevity, the debugger acts as if there were
9562 implicit @code{with} and @code{use} clauses in effect for all user-written
9563 packages, making it unnecessary to fully qualify most names with
9564 their packages, regardless of context. Where this causes ambiguity,
9565 @value{GDBN} asks the user's intent.
9567 The debugger will start in Ada mode if it detects an Ada main program.
9568 As for other languages, it will enter Ada mode when stopped in a program that
9569 was translated from an Ada source file.
9571 While in Ada mode, you may use `@t{--}' for comments. This is useful
9572 mostly for documenting command files. The standard @value{GDBN} comment
9573 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
9574 middle (to allow based literals).
9576 The debugger supports limited overloading. Given a subprogram call in which
9577 the function symbol has multiple definitions, it will use the number of
9578 actual parameters and some information about their types to attempt to narrow
9579 the set of definitions. It also makes very limited use of context, preferring
9580 procedures to functions in the context of the @code{call} command, and
9581 functions to procedures elsewhere.
9583 @node Omissions from Ada
9584 @subsubsection Omissions from Ada
9585 @cindex Ada, omissions from
9587 Here are the notable omissions from the subset:
9591 Only a subset of the attributes are supported:
9595 @t{'First}, @t{'Last}, and @t{'Length}
9596 on array objects (not on types and subtypes).
9599 @t{'Min} and @t{'Max}.
9602 @t{'Pos} and @t{'Val}.
9608 @t{'Range} on array objects (not subtypes), but only as the right
9609 operand of the membership (@code{in}) operator.
9612 @t{'Access}, @t{'Unchecked_Access}, and
9613 @t{'Unrestricted_Access} (a GNAT extension).
9621 @code{Characters.Latin_1} are not available and
9622 concatenation is not implemented. Thus, escape characters in strings are
9623 not currently available.
9626 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
9627 equality of representations. They will generally work correctly
9628 for strings and arrays whose elements have integer or enumeration types.
9629 They may not work correctly for arrays whose element
9630 types have user-defined equality, for arrays of real values
9631 (in particular, IEEE-conformant floating point, because of negative
9632 zeroes and NaNs), and for arrays whose elements contain unused bits with
9633 indeterminate values.
9636 The other component-by-component array operations (@code{and}, @code{or},
9637 @code{xor}, @code{not}, and relational tests other than equality)
9638 are not implemented.
9641 There are no record or array aggregates.
9644 Calls to dispatching subprograms are not implemented.
9647 The overloading algorithm is much more limited (i.e., less selective)
9648 than that of real Ada. It makes only limited use of the context in which a subexpression
9649 appears to resolve its meaning, and it is much looser in its rules for allowing
9650 type matches. As a result, some function calls will be ambiguous, and the user
9651 will be asked to choose the proper resolution.
9654 The @code{new} operator is not implemented.
9657 Entry calls are not implemented.
9660 Aside from printing, arithmetic operations on the native VAX floating-point
9661 formats are not supported.
9664 It is not possible to slice a packed array.
9667 @node Additions to Ada
9668 @subsubsection Additions to Ada
9669 @cindex Ada, deviations from
9671 As it does for other languages, @value{GDBN} makes certain generic
9672 extensions to Ada (@pxref{Expressions}):
9676 If the expression @var{E} is a variable residing in memory
9677 (typically a local variable or array element) and @var{N} is
9678 a positive integer, then @code{@var{E}@@@var{N}} displays the values of
9679 @var{E} and the @var{N}-1 adjacent variables following it in memory as an array.
9680 In Ada, this operator is generally not necessary, since its prime use
9681 is in displaying parts of an array, and slicing will usually do this in Ada.
9682 However, there are occasional uses when debugging programs
9683 in which certain debugging information has been optimized away.
9686 @code{@var{B}::@var{var}} means ``the variable named @var{var} that appears
9687 in function or file @var{B}.'' When @var{B} is a file name, you must typically
9688 surround it in single quotes.
9691 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
9692 @var{type} that appears at address @var{addr}.''
9695 A name starting with @samp{$} is a convenience variable
9696 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
9699 In addition, @value{GDBN} provides a few other shortcuts and outright additions specific
9704 The assignment statement is allowed as an expression, returning
9705 its right-hand operand as its value. Thus, you may enter
9709 print A(tmp := y + 1)
9713 The semicolon is allowed as an ``operator,'' returning as its value
9714 the value of its right-hand operand.
9715 This allows, for example,
9716 complex conditional breaks:
9720 condition 1 (report(i); k += 1; A(k) > 100)
9724 Rather than use catenation and symbolic character names to introduce special
9725 characters into strings, one may instead use a special bracket notation,
9726 which is also used to print strings. A sequence of characters of the form
9727 @samp{["@var{XX}"]} within a string or character literal denotes the
9728 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
9729 sequence of characters @samp{["""]} also denotes a single quotation mark
9730 in strings. For example,
9732 "One line.["0a"]Next line.["0a"]"
9735 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF}) after each
9739 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
9740 @t{'Max} is optional (and is ignored in any case). For example, it is valid
9748 When printing arrays, @value{GDBN} uses positional notation when the
9749 array has a lower bound of 1, and uses a modified named notation otherwise.
9750 For example, a one-dimensional array of three integers with a lower bound of 3 might print as
9757 That is, in contrast to valid Ada, only the first component has a @code{=>}
9761 You may abbreviate attributes in expressions with any unique,
9762 multi-character subsequence of
9763 their names (an exact match gets preference).
9764 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
9765 in place of @t{a'length}.
9768 @cindex quoting Ada internal identifiers
9769 Since Ada is case-insensitive, the debugger normally maps identifiers you type
9770 to lower case. The GNAT compiler uses upper-case characters for
9771 some of its internal identifiers, which are normally of no interest to users.
9772 For the rare occasions when you actually have to look at them,
9773 enclose them in angle brackets to avoid the lower-case mapping.
9776 @value{GDBP} print <JMPBUF_SAVE>[0]
9780 Printing an object of class-wide type or dereferencing an
9781 access-to-class-wide value will display all the components of the object's
9782 specific type (as indicated by its run-time tag). Likewise, component
9783 selection on such a value will operate on the specific type of the
9788 @node Stopping Before Main Program
9789 @subsubsection Stopping at the Very Beginning
9791 @cindex breakpointing Ada elaboration code
9792 It is sometimes necessary to debug the program during elaboration, and
9793 before reaching the main procedure.
9794 As defined in the Ada Reference
9795 Manual, the elaboration code is invoked from a procedure called
9796 @code{adainit}. To run your program up to the beginning of
9797 elaboration, simply use the following two commands:
9798 @code{tbreak adainit} and @code{run}.
9801 @subsubsection Known Peculiarities of Ada Mode
9802 @cindex Ada, problems
9804 Besides the omissions listed previously (@pxref{Omissions from Ada}),
9805 we know of several problems with and limitations of Ada mode in
9807 some of which will be fixed with planned future releases of the debugger
9808 and the GNU Ada compiler.
9812 Currently, the debugger
9813 has insufficient information to determine whether certain pointers represent
9814 pointers to objects or the objects themselves.
9815 Thus, the user may have to tack an extra @code{.all} after an expression
9816 to get it printed properly.
9819 Static constants that the compiler chooses not to materialize as objects in
9820 storage are invisible to the debugger.
9823 Named parameter associations in function argument lists are ignored (the
9824 argument lists are treated as positional).
9827 Many useful library packages are currently invisible to the debugger.
9830 Fixed-point arithmetic, conversions, input, and output is carried out using
9831 floating-point arithmetic, and may give results that only approximate those on
9835 The type of the @t{'Address} attribute may not be @code{System.Address}.
9838 The GNAT compiler never generates the prefix @code{Standard} for any of
9839 the standard symbols defined by the Ada language. @value{GDBN} knows about
9840 this: it will strip the prefix from names when you use it, and will never
9841 look for a name you have so qualified among local symbols, nor match against
9842 symbols in other packages or subprograms. If you have
9843 defined entities anywhere in your program other than parameters and
9844 local variables whose simple names match names in @code{Standard},
9845 GNAT's lack of qualification here can cause confusion. When this happens,
9846 you can usually resolve the confusion
9847 by qualifying the problematic names with package
9848 @code{Standard} explicitly.
9851 @node Unsupported languages
9852 @section Unsupported languages
9854 @cindex unsupported languages
9855 @cindex minimal language
9856 In addition to the other fully-supported programming languages,
9857 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
9858 It does not represent a real programming language, but provides a set
9859 of capabilities close to what the C or assembly languages provide.
9860 This should allow most simple operations to be performed while debugging
9861 an application that uses a language currently not supported by @value{GDBN}.
9863 If the language is set to @code{auto}, @value{GDBN} will automatically
9864 select this language if the current frame corresponds to an unsupported
9868 @chapter Examining the Symbol Table
9870 The commands described in this chapter allow you to inquire about the
9871 symbols (names of variables, functions and types) defined in your
9872 program. This information is inherent in the text of your program and
9873 does not change as your program executes. @value{GDBN} finds it in your
9874 program's symbol table, in the file indicated when you started @value{GDBN}
9875 (@pxref{File Options, ,Choosing files}), or by one of the
9876 file-management commands (@pxref{Files, ,Commands to specify files}).
9878 @cindex symbol names
9879 @cindex names of symbols
9880 @cindex quoting names
9881 Occasionally, you may need to refer to symbols that contain unusual
9882 characters, which @value{GDBN} ordinarily treats as word delimiters. The
9883 most frequent case is in referring to static variables in other
9884 source files (@pxref{Variables,,Program variables}). File names
9885 are recorded in object files as debugging symbols, but @value{GDBN} would
9886 ordinarily parse a typical file name, like @file{foo.c}, as the three words
9887 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
9888 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
9895 looks up the value of @code{x} in the scope of the file @file{foo.c}.
9898 @cindex case-insensitive symbol names
9899 @cindex case sensitivity in symbol names
9900 @kindex set case-sensitive
9901 @item set case-sensitive on
9902 @itemx set case-sensitive off
9903 @itemx set case-sensitive auto
9904 Normally, when @value{GDBN} looks up symbols, it matches their names
9905 with case sensitivity determined by the current source language.
9906 Occasionally, you may wish to control that. The command @code{set
9907 case-sensitive} lets you do that by specifying @code{on} for
9908 case-sensitive matches or @code{off} for case-insensitive ones. If
9909 you specify @code{auto}, case sensitivity is reset to the default
9910 suitable for the source language. The default is case-sensitive
9911 matches for all languages except for Fortran, for which the default is
9912 case-insensitive matches.
9914 @kindex show case-sensitive
9915 @item show case-sensitive
9916 This command shows the current setting of case sensitivity for symbols
9919 @kindex info address
9920 @cindex address of a symbol
9921 @item info address @var{symbol}
9922 Describe where the data for @var{symbol} is stored. For a register
9923 variable, this says which register it is kept in. For a non-register
9924 local variable, this prints the stack-frame offset at which the variable
9927 Note the contrast with @samp{print &@var{symbol}}, which does not work
9928 at all for a register variable, and for a stack local variable prints
9929 the exact address of the current instantiation of the variable.
9932 @cindex symbol from address
9933 @cindex closest symbol and offset for an address
9934 @item info symbol @var{addr}
9935 Print the name of a symbol which is stored at the address @var{addr}.
9936 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
9937 nearest symbol and an offset from it:
9940 (@value{GDBP}) info symbol 0x54320
9941 _initialize_vx + 396 in section .text
9945 This is the opposite of the @code{info address} command. You can use
9946 it to find out the name of a variable or a function given its address.
9949 @item whatis @var{expr}
9950 Print the data type of expression @var{expr}. @var{expr} is not
9951 actually evaluated, and any side-effecting operations (such as
9952 assignments or function calls) inside it do not take place.
9953 @xref{Expressions, ,Expressions}.
9956 Print the data type of @code{$}, the last value in the value history.
9959 @item ptype @var{typename}
9960 Print a description of data type @var{typename}. @var{typename} may be
9961 the name of a type, or for C code it may have the form @samp{class
9962 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
9963 @var{union-tag}} or @samp{enum @var{enum-tag}}.
9965 @item ptype @var{expr}
9967 Print a description of the type of expression @var{expr}. @code{ptype}
9968 differs from @code{whatis} by printing a detailed description, instead
9969 of just the name of the type.
9971 For example, for this variable declaration:
9974 struct complex @{double real; double imag;@} v;
9978 the two commands give this output:
9982 (@value{GDBP}) whatis v
9983 type = struct complex
9984 (@value{GDBP}) ptype v
9985 type = struct complex @{
9993 As with @code{whatis}, using @code{ptype} without an argument refers to
9994 the type of @code{$}, the last value in the value history.
9997 @item info types @var{regexp}
9999 Print a brief description of all types whose names match the regular
10000 expression @var{regexp} (or all types in your program, if you supply
10001 no argument). Each complete typename is matched as though it were a
10002 complete line; thus, @samp{i type value} gives information on all
10003 types in your program whose names include the string @code{value}, but
10004 @samp{i type ^value$} gives information only on types whose complete
10005 name is @code{value}.
10007 This command differs from @code{ptype} in two ways: first, like
10008 @code{whatis}, it does not print a detailed description; second, it
10009 lists all source files where a type is defined.
10012 @cindex local variables
10013 @item info scope @var{location}
10014 List all the variables local to a particular scope. This command
10015 accepts a @var{location} argument---a function name, a source line, or
10016 an address preceded by a @samp{*}, and prints all the variables local
10017 to the scope defined by that location. For example:
10020 (@value{GDBP}) @b{info scope command_line_handler}
10021 Scope for command_line_handler:
10022 Symbol rl is an argument at stack/frame offset 8, length 4.
10023 Symbol linebuffer is in static storage at address 0x150a18, length 4.
10024 Symbol linelength is in static storage at address 0x150a1c, length 4.
10025 Symbol p is a local variable in register $esi, length 4.
10026 Symbol p1 is a local variable in register $ebx, length 4.
10027 Symbol nline is a local variable in register $edx, length 4.
10028 Symbol repeat is a local variable at frame offset -8, length 4.
10032 This command is especially useful for determining what data to collect
10033 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
10036 @kindex info source
10038 Show information about the current source file---that is, the source file for
10039 the function containing the current point of execution:
10042 the name of the source file, and the directory containing it,
10044 the directory it was compiled in,
10046 its length, in lines,
10048 which programming language it is written in,
10050 whether the executable includes debugging information for that file, and
10051 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
10053 whether the debugging information includes information about
10054 preprocessor macros.
10058 @kindex info sources
10060 Print the names of all source files in your program for which there is
10061 debugging information, organized into two lists: files whose symbols
10062 have already been read, and files whose symbols will be read when needed.
10064 @kindex info functions
10065 @item info functions
10066 Print the names and data types of all defined functions.
10068 @item info functions @var{regexp}
10069 Print the names and data types of all defined functions
10070 whose names contain a match for regular expression @var{regexp}.
10071 Thus, @samp{info fun step} finds all functions whose names
10072 include @code{step}; @samp{info fun ^step} finds those whose names
10073 start with @code{step}. If a function name contains characters
10074 that conflict with the regular expression language (eg.
10075 @samp{operator*()}), they may be quoted with a backslash.
10077 @kindex info variables
10078 @item info variables
10079 Print the names and data types of all variables that are declared
10080 outside of functions (i.e.@: excluding local variables).
10082 @item info variables @var{regexp}
10083 Print the names and data types of all variables (except for local
10084 variables) whose names contain a match for regular expression
10087 @kindex info classes
10088 @cindex Objective-C, classes and selectors
10090 @itemx info classes @var{regexp}
10091 Display all Objective-C classes in your program, or
10092 (with the @var{regexp} argument) all those matching a particular regular
10095 @kindex info selectors
10096 @item info selectors
10097 @itemx info selectors @var{regexp}
10098 Display all Objective-C selectors in your program, or
10099 (with the @var{regexp} argument) all those matching a particular regular
10103 This was never implemented.
10104 @kindex info methods
10106 @itemx info methods @var{regexp}
10107 The @code{info methods} command permits the user to examine all defined
10108 methods within C@t{++} program, or (with the @var{regexp} argument) a
10109 specific set of methods found in the various C@t{++} classes. Many
10110 C@t{++} classes provide a large number of methods. Thus, the output
10111 from the @code{ptype} command can be overwhelming and hard to use. The
10112 @code{info-methods} command filters the methods, printing only those
10113 which match the regular-expression @var{regexp}.
10116 @cindex reloading symbols
10117 Some systems allow individual object files that make up your program to
10118 be replaced without stopping and restarting your program. For example,
10119 in VxWorks you can simply recompile a defective object file and keep on
10120 running. If you are running on one of these systems, you can allow
10121 @value{GDBN} to reload the symbols for automatically relinked modules:
10124 @kindex set symbol-reloading
10125 @item set symbol-reloading on
10126 Replace symbol definitions for the corresponding source file when an
10127 object file with a particular name is seen again.
10129 @item set symbol-reloading off
10130 Do not replace symbol definitions when encountering object files of the
10131 same name more than once. This is the default state; if you are not
10132 running on a system that permits automatic relinking of modules, you
10133 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
10134 may discard symbols when linking large programs, that may contain
10135 several modules (from different directories or libraries) with the same
10138 @kindex show symbol-reloading
10139 @item show symbol-reloading
10140 Show the current @code{on} or @code{off} setting.
10143 @cindex opaque data types
10144 @kindex set opaque-type-resolution
10145 @item set opaque-type-resolution on
10146 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
10147 declared as a pointer to a @code{struct}, @code{class}, or
10148 @code{union}---for example, @code{struct MyType *}---that is used in one
10149 source file although the full declaration of @code{struct MyType} is in
10150 another source file. The default is on.
10152 A change in the setting of this subcommand will not take effect until
10153 the next time symbols for a file are loaded.
10155 @item set opaque-type-resolution off
10156 Tell @value{GDBN} not to resolve opaque types. In this case, the type
10157 is printed as follows:
10159 @{<no data fields>@}
10162 @kindex show opaque-type-resolution
10163 @item show opaque-type-resolution
10164 Show whether opaque types are resolved or not.
10166 @kindex maint print symbols
10167 @cindex symbol dump
10168 @kindex maint print psymbols
10169 @cindex partial symbol dump
10170 @item maint print symbols @var{filename}
10171 @itemx maint print psymbols @var{filename}
10172 @itemx maint print msymbols @var{filename}
10173 Write a dump of debugging symbol data into the file @var{filename}.
10174 These commands are used to debug the @value{GDBN} symbol-reading code. Only
10175 symbols with debugging data are included. If you use @samp{maint print
10176 symbols}, @value{GDBN} includes all the symbols for which it has already
10177 collected full details: that is, @var{filename} reflects symbols for
10178 only those files whose symbols @value{GDBN} has read. You can use the
10179 command @code{info sources} to find out which files these are. If you
10180 use @samp{maint print psymbols} instead, the dump shows information about
10181 symbols that @value{GDBN} only knows partially---that is, symbols defined in
10182 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
10183 @samp{maint print msymbols} dumps just the minimal symbol information
10184 required for each object file from which @value{GDBN} has read some symbols.
10185 @xref{Files, ,Commands to specify files}, for a discussion of how
10186 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
10188 @kindex maint info symtabs
10189 @kindex maint info psymtabs
10190 @cindex listing @value{GDBN}'s internal symbol tables
10191 @cindex symbol tables, listing @value{GDBN}'s internal
10192 @cindex full symbol tables, listing @value{GDBN}'s internal
10193 @cindex partial symbol tables, listing @value{GDBN}'s internal
10194 @item maint info symtabs @r{[} @var{regexp} @r{]}
10195 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
10197 List the @code{struct symtab} or @code{struct partial_symtab}
10198 structures whose names match @var{regexp}. If @var{regexp} is not
10199 given, list them all. The output includes expressions which you can
10200 copy into a @value{GDBN} debugging this one to examine a particular
10201 structure in more detail. For example:
10204 (@value{GDBP}) maint info psymtabs dwarf2read
10205 @{ objfile /home/gnu/build/gdb/gdb
10206 ((struct objfile *) 0x82e69d0)
10207 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
10208 ((struct partial_symtab *) 0x8474b10)
10211 text addresses 0x814d3c8 -- 0x8158074
10212 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
10213 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
10214 dependencies (none)
10217 (@value{GDBP}) maint info symtabs
10221 We see that there is one partial symbol table whose filename contains
10222 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
10223 and we see that @value{GDBN} has not read in any symtabs yet at all.
10224 If we set a breakpoint on a function, that will cause @value{GDBN} to
10225 read the symtab for the compilation unit containing that function:
10228 (@value{GDBP}) break dwarf2_psymtab_to_symtab
10229 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
10231 (@value{GDBP}) maint info symtabs
10232 @{ objfile /home/gnu/build/gdb/gdb
10233 ((struct objfile *) 0x82e69d0)
10234 @{ symtab /home/gnu/src/gdb/dwarf2read.c
10235 ((struct symtab *) 0x86c1f38)
10238 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
10239 debugformat DWARF 2
10248 @chapter Altering Execution
10250 Once you think you have found an error in your program, you might want to
10251 find out for certain whether correcting the apparent error would lead to
10252 correct results in the rest of the run. You can find the answer by
10253 experiment, using the @value{GDBN} features for altering execution of the
10256 For example, you can store new values into variables or memory
10257 locations, give your program a signal, restart it at a different
10258 address, or even return prematurely from a function.
10261 * Assignment:: Assignment to variables
10262 * Jumping:: Continuing at a different address
10263 * Signaling:: Giving your program a signal
10264 * Returning:: Returning from a function
10265 * Calling:: Calling your program's functions
10266 * Patching:: Patching your program
10270 @section Assignment to variables
10273 @cindex setting variables
10274 To alter the value of a variable, evaluate an assignment expression.
10275 @xref{Expressions, ,Expressions}. For example,
10282 stores the value 4 into the variable @code{x}, and then prints the
10283 value of the assignment expression (which is 4).
10284 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
10285 information on operators in supported languages.
10287 @kindex set variable
10288 @cindex variables, setting
10289 If you are not interested in seeing the value of the assignment, use the
10290 @code{set} command instead of the @code{print} command. @code{set} is
10291 really the same as @code{print} except that the expression's value is
10292 not printed and is not put in the value history (@pxref{Value History,
10293 ,Value history}). The expression is evaluated only for its effects.
10295 If the beginning of the argument string of the @code{set} command
10296 appears identical to a @code{set} subcommand, use the @code{set
10297 variable} command instead of just @code{set}. This command is identical
10298 to @code{set} except for its lack of subcommands. For example, if your
10299 program has a variable @code{width}, you get an error if you try to set
10300 a new value with just @samp{set width=13}, because @value{GDBN} has the
10301 command @code{set width}:
10304 (@value{GDBP}) whatis width
10306 (@value{GDBP}) p width
10308 (@value{GDBP}) set width=47
10309 Invalid syntax in expression.
10313 The invalid expression, of course, is @samp{=47}. In
10314 order to actually set the program's variable @code{width}, use
10317 (@value{GDBP}) set var width=47
10320 Because the @code{set} command has many subcommands that can conflict
10321 with the names of program variables, it is a good idea to use the
10322 @code{set variable} command instead of just @code{set}. For example, if
10323 your program has a variable @code{g}, you run into problems if you try
10324 to set a new value with just @samp{set g=4}, because @value{GDBN} has
10325 the command @code{set gnutarget}, abbreviated @code{set g}:
10329 (@value{GDBP}) whatis g
10333 (@value{GDBP}) set g=4
10337 The program being debugged has been started already.
10338 Start it from the beginning? (y or n) y
10339 Starting program: /home/smith/cc_progs/a.out
10340 "/home/smith/cc_progs/a.out": can't open to read symbols:
10341 Invalid bfd target.
10342 (@value{GDBP}) show g
10343 The current BFD target is "=4".
10348 The program variable @code{g} did not change, and you silently set the
10349 @code{gnutarget} to an invalid value. In order to set the variable
10353 (@value{GDBP}) set var g=4
10356 @value{GDBN} allows more implicit conversions in assignments than C; you can
10357 freely store an integer value into a pointer variable or vice versa,
10358 and you can convert any structure to any other structure that is the
10359 same length or shorter.
10360 @comment FIXME: how do structs align/pad in these conversions?
10361 @comment /doc@cygnus.com 18dec1990
10363 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
10364 construct to generate a value of specified type at a specified address
10365 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
10366 to memory location @code{0x83040} as an integer (which implies a certain size
10367 and representation in memory), and
10370 set @{int@}0x83040 = 4
10374 stores the value 4 into that memory location.
10377 @section Continuing at a different address
10379 Ordinarily, when you continue your program, you do so at the place where
10380 it stopped, with the @code{continue} command. You can instead continue at
10381 an address of your own choosing, with the following commands:
10385 @item jump @var{linespec}
10386 Resume execution at line @var{linespec}. Execution stops again
10387 immediately if there is a breakpoint there. @xref{List, ,Printing
10388 source lines}, for a description of the different forms of
10389 @var{linespec}. It is common practice to use the @code{tbreak} command
10390 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
10393 The @code{jump} command does not change the current stack frame, or
10394 the stack pointer, or the contents of any memory location or any
10395 register other than the program counter. If line @var{linespec} is in
10396 a different function from the one currently executing, the results may
10397 be bizarre if the two functions expect different patterns of arguments or
10398 of local variables. For this reason, the @code{jump} command requests
10399 confirmation if the specified line is not in the function currently
10400 executing. However, even bizarre results are predictable if you are
10401 well acquainted with the machine-language code of your program.
10403 @item jump *@var{address}
10404 Resume execution at the instruction at address @var{address}.
10407 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
10408 On many systems, you can get much the same effect as the @code{jump}
10409 command by storing a new value into the register @code{$pc}. The
10410 difference is that this does not start your program running; it only
10411 changes the address of where it @emph{will} run when you continue. For
10419 makes the next @code{continue} command or stepping command execute at
10420 address @code{0x485}, rather than at the address where your program stopped.
10421 @xref{Continuing and Stepping, ,Continuing and stepping}.
10423 The most common occasion to use the @code{jump} command is to back
10424 up---perhaps with more breakpoints set---over a portion of a program
10425 that has already executed, in order to examine its execution in more
10430 @section Giving your program a signal
10431 @cindex deliver a signal to a program
10435 @item signal @var{signal}
10436 Resume execution where your program stopped, but immediately give it the
10437 signal @var{signal}. @var{signal} can be the name or the number of a
10438 signal. For example, on many systems @code{signal 2} and @code{signal
10439 SIGINT} are both ways of sending an interrupt signal.
10441 Alternatively, if @var{signal} is zero, continue execution without
10442 giving a signal. This is useful when your program stopped on account of
10443 a signal and would ordinary see the signal when resumed with the
10444 @code{continue} command; @samp{signal 0} causes it to resume without a
10447 @code{signal} does not repeat when you press @key{RET} a second time
10448 after executing the command.
10452 Invoking the @code{signal} command is not the same as invoking the
10453 @code{kill} utility from the shell. Sending a signal with @code{kill}
10454 causes @value{GDBN} to decide what to do with the signal depending on
10455 the signal handling tables (@pxref{Signals}). The @code{signal} command
10456 passes the signal directly to your program.
10460 @section Returning from a function
10463 @cindex returning from a function
10466 @itemx return @var{expression}
10467 You can cancel execution of a function call with the @code{return}
10468 command. If you give an
10469 @var{expression} argument, its value is used as the function's return
10473 When you use @code{return}, @value{GDBN} discards the selected stack frame
10474 (and all frames within it). You can think of this as making the
10475 discarded frame return prematurely. If you wish to specify a value to
10476 be returned, give that value as the argument to @code{return}.
10478 This pops the selected stack frame (@pxref{Selection, ,Selecting a
10479 frame}), and any other frames inside of it, leaving its caller as the
10480 innermost remaining frame. That frame becomes selected. The
10481 specified value is stored in the registers used for returning values
10484 The @code{return} command does not resume execution; it leaves the
10485 program stopped in the state that would exist if the function had just
10486 returned. In contrast, the @code{finish} command (@pxref{Continuing
10487 and Stepping, ,Continuing and stepping}) resumes execution until the
10488 selected stack frame returns naturally.
10491 @section Calling program functions
10494 @cindex calling functions
10495 @cindex inferior functions, calling
10496 @item print @var{expr}
10497 Evaluate the expression @var{expr} and display the resuling value.
10498 @var{expr} may include calls to functions in the program being
10502 @item call @var{expr}
10503 Evaluate the expression @var{expr} without displaying @code{void}
10506 You can use this variant of the @code{print} command if you want to
10507 execute a function from your program that does not return anything
10508 (a.k.a.@: @dfn{a void function}), but without cluttering the output
10509 with @code{void} returned values that @value{GDBN} will otherwise
10510 print. If the result is not void, it is printed and saved in the
10514 It is possible for the function you call via the @code{print} or
10515 @code{call} command to generate a signal (e.g., if there's a bug in
10516 the function, or if you passed it incorrect arguments). What happens
10517 in that case is controlled by the @code{set unwindonsignal} command.
10520 @item set unwindonsignal
10521 @kindex set unwindonsignal
10522 @cindex unwind stack in called functions
10523 @cindex call dummy stack unwinding
10524 Set unwinding of the stack if a signal is received while in a function
10525 that @value{GDBN} called in the program being debugged. If set to on,
10526 @value{GDBN} unwinds the stack it created for the call and restores
10527 the context to what it was before the call. If set to off (the
10528 default), @value{GDBN} stops in the frame where the signal was
10531 @item show unwindonsignal
10532 @kindex show unwindonsignal
10533 Show the current setting of stack unwinding in the functions called by
10537 @cindex weak alias functions
10538 Sometimes, a function you wish to call is actually a @dfn{weak alias}
10539 for another function. In such case, @value{GDBN} might not pick up
10540 the type information, including the types of the function arguments,
10541 which causes @value{GDBN} to call the inferior function incorrectly.
10542 As a result, the called function will function erroneously and may
10543 even crash. A solution to that is to use the name of the aliased
10547 @section Patching programs
10549 @cindex patching binaries
10550 @cindex writing into executables
10551 @cindex writing into corefiles
10553 By default, @value{GDBN} opens the file containing your program's
10554 executable code (or the corefile) read-only. This prevents accidental
10555 alterations to machine code; but it also prevents you from intentionally
10556 patching your program's binary.
10558 If you'd like to be able to patch the binary, you can specify that
10559 explicitly with the @code{set write} command. For example, you might
10560 want to turn on internal debugging flags, or even to make emergency
10566 @itemx set write off
10567 If you specify @samp{set write on}, @value{GDBN} opens executable and
10568 core files for both reading and writing; if you specify @samp{set write
10569 off} (the default), @value{GDBN} opens them read-only.
10571 If you have already loaded a file, you must load it again (using the
10572 @code{exec-file} or @code{core-file} command) after changing @code{set
10573 write}, for your new setting to take effect.
10577 Display whether executable files and core files are opened for writing
10578 as well as reading.
10582 @chapter @value{GDBN} Files
10584 @value{GDBN} needs to know the file name of the program to be debugged,
10585 both in order to read its symbol table and in order to start your
10586 program. To debug a core dump of a previous run, you must also tell
10587 @value{GDBN} the name of the core dump file.
10590 * Files:: Commands to specify files
10591 * Separate Debug Files:: Debugging information in separate files
10592 * Symbol Errors:: Errors reading symbol files
10596 @section Commands to specify files
10598 @cindex symbol table
10599 @cindex core dump file
10601 You may want to specify executable and core dump file names. The usual
10602 way to do this is at start-up time, using the arguments to
10603 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
10604 Out of @value{GDBN}}).
10606 Occasionally it is necessary to change to a different file during a
10607 @value{GDBN} session. Or you may run @value{GDBN} and forget to specify
10608 a file you want to use. In these situations the @value{GDBN} commands
10609 to specify new files are useful.
10612 @cindex executable file
10614 @item file @var{filename}
10615 Use @var{filename} as the program to be debugged. It is read for its
10616 symbols and for the contents of pure memory. It is also the program
10617 executed when you use the @code{run} command. If you do not specify a
10618 directory and the file is not found in the @value{GDBN} working directory,
10619 @value{GDBN} uses the environment variable @code{PATH} as a list of
10620 directories to search, just as the shell does when looking for a program
10621 to run. You can change the value of this variable, for both @value{GDBN}
10622 and your program, using the @code{path} command.
10624 On systems with memory-mapped files, an auxiliary file named
10625 @file{@var{filename}.syms} may hold symbol table information for
10626 @var{filename}. If so, @value{GDBN} maps in the symbol table from
10627 @file{@var{filename}.syms}, starting up more quickly. See the
10628 descriptions of the file options @samp{-mapped} and @samp{-readnow}
10629 (available on the command line, see @ref{File Options, , -readnow},
10630 and with the commands @code{file}, @code{symbol-file}, or
10631 @code{add-symbol-file}, described below), for more information.
10634 @code{file} with no argument makes @value{GDBN} discard any information it
10635 has on both executable file and the symbol table.
10638 @item exec-file @r{[} @var{filename} @r{]}
10639 Specify that the program to be run (but not the symbol table) is found
10640 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
10641 if necessary to locate your program. Omitting @var{filename} means to
10642 discard information on the executable file.
10644 @kindex symbol-file
10645 @item symbol-file @r{[} @var{filename} @r{]}
10646 Read symbol table information from file @var{filename}. @code{PATH} is
10647 searched when necessary. Use the @code{file} command to get both symbol
10648 table and program to run from the same file.
10650 @code{symbol-file} with no argument clears out @value{GDBN} information on your
10651 program's symbol table.
10653 The @code{symbol-file} command causes @value{GDBN} to forget the contents
10654 of its convenience variables, the value history, and all breakpoints and
10655 auto-display expressions. This is because they may contain pointers to
10656 the internal data recording symbols and data types, which are part of
10657 the old symbol table data being discarded inside @value{GDBN}.
10659 @code{symbol-file} does not repeat if you press @key{RET} again after
10662 When @value{GDBN} is configured for a particular environment, it
10663 understands debugging information in whatever format is the standard
10664 generated for that environment; you may use either a @sc{gnu} compiler, or
10665 other compilers that adhere to the local conventions.
10666 Best results are usually obtained from @sc{gnu} compilers; for example,
10667 using @code{@value{GCC}} you can generate debugging information for
10670 For most kinds of object files, with the exception of old SVR3 systems
10671 using COFF, the @code{symbol-file} command does not normally read the
10672 symbol table in full right away. Instead, it scans the symbol table
10673 quickly to find which source files and which symbols are present. The
10674 details are read later, one source file at a time, as they are needed.
10676 The purpose of this two-stage reading strategy is to make @value{GDBN}
10677 start up faster. For the most part, it is invisible except for
10678 occasional pauses while the symbol table details for a particular source
10679 file are being read. (The @code{set verbose} command can turn these
10680 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
10681 warnings and messages}.)
10683 We have not implemented the two-stage strategy for COFF yet. When the
10684 symbol table is stored in COFF format, @code{symbol-file} reads the
10685 symbol table data in full right away. Note that ``stabs-in-COFF''
10686 still does the two-stage strategy, since the debug info is actually
10690 @cindex reading symbols immediately
10691 @cindex symbols, reading immediately
10693 @cindex memory-mapped symbol file
10694 @cindex saving symbol table
10695 @item symbol-file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10696 @itemx file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10697 You can override the @value{GDBN} two-stage strategy for reading symbol
10698 tables by using the @samp{-readnow} option with any of the commands that
10699 load symbol table information, if you want to be sure @value{GDBN} has the
10700 entire symbol table available.
10702 If memory-mapped files are available on your system through the
10703 @code{mmap} system call, you can use another option, @samp{-mapped}, to
10704 cause @value{GDBN} to write the symbols for your program into a reusable
10705 file. Future @value{GDBN} debugging sessions map in symbol information
10706 from this auxiliary symbol file (if the program has not changed), rather
10707 than spending time reading the symbol table from the executable
10708 program. Using the @samp{-mapped} option has the same effect as
10709 starting @value{GDBN} with the @samp{-mapped} command-line option.
10711 You can use both options together, to make sure the auxiliary symbol
10712 file has all the symbol information for your program.
10714 The auxiliary symbol file for a program called @var{myprog} is called
10715 @samp{@var{myprog}.syms}. Once this file exists (so long as it is newer
10716 than the corresponding executable), @value{GDBN} always attempts to use
10717 it when you debug @var{myprog}; no special options or commands are
10720 The @file{.syms} file is specific to the host machine where you run
10721 @value{GDBN}. It holds an exact image of the internal @value{GDBN}
10722 symbol table. It cannot be shared across multiple host platforms.
10724 @c FIXME: for now no mention of directories, since this seems to be in
10725 @c flux. 13mar1992 status is that in theory GDB would look either in
10726 @c current dir or in same dir as myprog; but issues like competing
10727 @c GDB's, or clutter in system dirs, mean that in practice right now
10728 @c only current dir is used. FFish says maybe a special GDB hierarchy
10729 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
10733 @item core-file @r{[}@var{filename}@r{]}
10735 Specify the whereabouts of a core dump file to be used as the ``contents
10736 of memory''. Traditionally, core files contain only some parts of the
10737 address space of the process that generated them; @value{GDBN} can access the
10738 executable file itself for other parts.
10740 @code{core-file} with no argument specifies that no core file is
10743 Note that the core file is ignored when your program is actually running
10744 under @value{GDBN}. So, if you have been running your program and you
10745 wish to debug a core file instead, you must kill the subprocess in which
10746 the program is running. To do this, use the @code{kill} command
10747 (@pxref{Kill Process, ,Killing the child process}).
10749 @kindex add-symbol-file
10750 @cindex dynamic linking
10751 @item add-symbol-file @var{filename} @var{address}
10752 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10753 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
10754 The @code{add-symbol-file} command reads additional symbol table
10755 information from the file @var{filename}. You would use this command
10756 when @var{filename} has been dynamically loaded (by some other means)
10757 into the program that is running. @var{address} should be the memory
10758 address at which the file has been loaded; @value{GDBN} cannot figure
10759 this out for itself. You can additionally specify an arbitrary number
10760 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
10761 section name and base address for that section. You can specify any
10762 @var{address} as an expression.
10764 The symbol table of the file @var{filename} is added to the symbol table
10765 originally read with the @code{symbol-file} command. You can use the
10766 @code{add-symbol-file} command any number of times; the new symbol data
10767 thus read keeps adding to the old. To discard all old symbol data
10768 instead, use the @code{symbol-file} command without any arguments.
10770 @cindex relocatable object files, reading symbols from
10771 @cindex object files, relocatable, reading symbols from
10772 @cindex reading symbols from relocatable object files
10773 @cindex symbols, reading from relocatable object files
10774 @cindex @file{.o} files, reading symbols from
10775 Although @var{filename} is typically a shared library file, an
10776 executable file, or some other object file which has been fully
10777 relocated for loading into a process, you can also load symbolic
10778 information from relocatable @file{.o} files, as long as:
10782 the file's symbolic information refers only to linker symbols defined in
10783 that file, not to symbols defined by other object files,
10785 every section the file's symbolic information refers to has actually
10786 been loaded into the inferior, as it appears in the file, and
10788 you can determine the address at which every section was loaded, and
10789 provide these to the @code{add-symbol-file} command.
10793 Some embedded operating systems, like Sun Chorus and VxWorks, can load
10794 relocatable files into an already running program; such systems
10795 typically make the requirements above easy to meet. However, it's
10796 important to recognize that many native systems use complex link
10797 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
10798 assembly, for example) that make the requirements difficult to meet. In
10799 general, one cannot assume that using @code{add-symbol-file} to read a
10800 relocatable object file's symbolic information will have the same effect
10801 as linking the relocatable object file into the program in the normal
10804 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
10806 You can use the @samp{-mapped} and @samp{-readnow} options just as with
10807 the @code{symbol-file} command, to change how @value{GDBN} manages the symbol
10808 table information for @var{filename}.
10810 @kindex add-symbol-file-from-memory
10811 @cindex @code{syscall DSO}
10812 @cindex load symbols from memory
10813 @item add-symbol-file-from-memory @var{address}
10814 Load symbols from the given @var{address} in a dynamically loaded
10815 object file whose image is mapped directly into the inferior's memory.
10816 For example, the Linux kernel maps a @code{syscall DSO} into each
10817 process's address space; this DSO provides kernel-specific code for
10818 some system calls. The argument can be any expression whose
10819 evaluation yields the address of the file's shared object file header.
10820 For this command to work, you must have used @code{symbol-file} or
10821 @code{exec-file} commands in advance.
10823 @kindex add-shared-symbol-files
10825 @item add-shared-symbol-files @var{library-file}
10826 @itemx assf @var{library-file}
10827 The @code{add-shared-symbol-files} command can currently be used only
10828 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
10829 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
10830 @value{GDBN} automatically looks for shared libraries, however if
10831 @value{GDBN} does not find yours, you can invoke
10832 @code{add-shared-symbol-files}. It takes one argument: the shared
10833 library's file name. @code{assf} is a shorthand alias for
10834 @code{add-shared-symbol-files}.
10837 @item section @var{section} @var{addr}
10838 The @code{section} command changes the base address of the named
10839 @var{section} of the exec file to @var{addr}. This can be used if the
10840 exec file does not contain section addresses, (such as in the
10841 @code{a.out} format), or when the addresses specified in the file
10842 itself are wrong. Each section must be changed separately. The
10843 @code{info files} command, described below, lists all the sections and
10847 @kindex info target
10850 @code{info files} and @code{info target} are synonymous; both print the
10851 current target (@pxref{Targets, ,Specifying a Debugging Target}),
10852 including the names of the executable and core dump files currently in
10853 use by @value{GDBN}, and the files from which symbols were loaded. The
10854 command @code{help target} lists all possible targets rather than
10857 @kindex maint info sections
10858 @item maint info sections
10859 Another command that can give you extra information about program sections
10860 is @code{maint info sections}. In addition to the section information
10861 displayed by @code{info files}, this command displays the flags and file
10862 offset of each section in the executable and core dump files. In addition,
10863 @code{maint info sections} provides the following command options (which
10864 may be arbitrarily combined):
10868 Display sections for all loaded object files, including shared libraries.
10869 @item @var{sections}
10870 Display info only for named @var{sections}.
10871 @item @var{section-flags}
10872 Display info only for sections for which @var{section-flags} are true.
10873 The section flags that @value{GDBN} currently knows about are:
10876 Section will have space allocated in the process when loaded.
10877 Set for all sections except those containing debug information.
10879 Section will be loaded from the file into the child process memory.
10880 Set for pre-initialized code and data, clear for @code{.bss} sections.
10882 Section needs to be relocated before loading.
10884 Section cannot be modified by the child process.
10886 Section contains executable code only.
10888 Section contains data only (no executable code).
10890 Section will reside in ROM.
10892 Section contains data for constructor/destructor lists.
10894 Section is not empty.
10896 An instruction to the linker to not output the section.
10897 @item COFF_SHARED_LIBRARY
10898 A notification to the linker that the section contains
10899 COFF shared library information.
10901 Section contains common symbols.
10904 @kindex set trust-readonly-sections
10905 @cindex read-only sections
10906 @item set trust-readonly-sections on
10907 Tell @value{GDBN} that readonly sections in your object file
10908 really are read-only (i.e.@: that their contents will not change).
10909 In that case, @value{GDBN} can fetch values from these sections
10910 out of the object file, rather than from the target program.
10911 For some targets (notably embedded ones), this can be a significant
10912 enhancement to debugging performance.
10914 The default is off.
10916 @item set trust-readonly-sections off
10917 Tell @value{GDBN} not to trust readonly sections. This means that
10918 the contents of the section might change while the program is running,
10919 and must therefore be fetched from the target when needed.
10921 @item show trust-readonly-sections
10922 Show the current setting of trusting readonly sections.
10925 All file-specifying commands allow both absolute and relative file names
10926 as arguments. @value{GDBN} always converts the file name to an absolute file
10927 name and remembers it that way.
10929 @cindex shared libraries
10930 @value{GDBN} supports GNU/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
10931 and IBM RS/6000 AIX shared libraries.
10933 @value{GDBN} automatically loads symbol definitions from shared libraries
10934 when you use the @code{run} command, or when you examine a core file.
10935 (Before you issue the @code{run} command, @value{GDBN} does not understand
10936 references to a function in a shared library, however---unless you are
10937 debugging a core file).
10939 On HP-UX, if the program loads a library explicitly, @value{GDBN}
10940 automatically loads the symbols at the time of the @code{shl_load} call.
10942 @c FIXME: some @value{GDBN} release may permit some refs to undef
10943 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
10944 @c FIXME...lib; check this from time to time when updating manual
10946 There are times, however, when you may wish to not automatically load
10947 symbol definitions from shared libraries, such as when they are
10948 particularly large or there are many of them.
10950 To control the automatic loading of shared library symbols, use the
10954 @kindex set auto-solib-add
10955 @item set auto-solib-add @var{mode}
10956 If @var{mode} is @code{on}, symbols from all shared object libraries
10957 will be loaded automatically when the inferior begins execution, you
10958 attach to an independently started inferior, or when the dynamic linker
10959 informs @value{GDBN} that a new library has been loaded. If @var{mode}
10960 is @code{off}, symbols must be loaded manually, using the
10961 @code{sharedlibrary} command. The default value is @code{on}.
10963 @cindex memory used for symbol tables
10964 If your program uses lots of shared libraries with debug info that
10965 takes large amounts of memory, you can decrease the @value{GDBN}
10966 memory footprint by preventing it from automatically loading the
10967 symbols from shared libraries. To that end, type @kbd{set
10968 auto-solib-add off} before running the inferior, then load each
10969 library whose debug symbols you do need with @kbd{sharedlibrary
10970 @var{regexp}}, where @var{regexp} is a regular expresion that matches
10971 the libraries whose symbols you want to be loaded.
10973 @kindex show auto-solib-add
10974 @item show auto-solib-add
10975 Display the current autoloading mode.
10978 @cindex load shared library
10979 To explicitly load shared library symbols, use the @code{sharedlibrary}
10983 @kindex info sharedlibrary
10986 @itemx info sharedlibrary
10987 Print the names of the shared libraries which are currently loaded.
10989 @kindex sharedlibrary
10991 @item sharedlibrary @var{regex}
10992 @itemx share @var{regex}
10993 Load shared object library symbols for files matching a
10994 Unix regular expression.
10995 As with files loaded automatically, it only loads shared libraries
10996 required by your program for a core file or after typing @code{run}. If
10997 @var{regex} is omitted all shared libraries required by your program are
11000 @item nosharedlibrary
11001 @kindex nosharedlibrary
11002 @cindex unload symbols from shared libraries
11003 Unload all shared object library symbols. This discards all symbols
11004 that have been loaded from all shared libraries. Symbols from shared
11005 libraries that were loaded by explicit user requests are not
11009 Sometimes you may wish that @value{GDBN} stops and gives you control
11010 when any of shared library events happen. Use the @code{set
11011 stop-on-solib-events} command for this:
11014 @item set stop-on-solib-events
11015 @kindex set stop-on-solib-events
11016 This command controls whether @value{GDBN} should give you control
11017 when the dynamic linker notifies it about some shared library event.
11018 The most common event of interest is loading or unloading of a new
11021 @item show stop-on-solib-events
11022 @kindex show stop-on-solib-events
11023 Show whether @value{GDBN} stops and gives you control when shared
11024 library events happen.
11027 Shared libraries are also supported in many cross or remote debugging
11028 configurations. A copy of the target's libraries need to be present on the
11029 host system; they need to be the same as the target libraries, although the
11030 copies on the target can be stripped as long as the copies on the host are
11033 You need to tell @value{GDBN} where the target libraries are, so that it can
11034 load the correct copies---otherwise, it may try to load the host's libraries.
11035 @value{GDBN} has two variables to specify the search directories for target
11039 @kindex set solib-absolute-prefix
11040 @item set solib-absolute-prefix @var{path}
11041 If this variable is set, @var{path} will be used as a prefix for any
11042 absolute shared library paths; many runtime loaders store the absolute
11043 paths to the shared library in the target program's memory. If you use
11044 @samp{solib-absolute-prefix} to find shared libraries, they need to be laid
11045 out in the same way that they are on the target, with e.g.@: a
11046 @file{/usr/lib} hierarchy under @var{path}.
11048 You can set the default value of @samp{solib-absolute-prefix} by using the
11049 configure-time @samp{--with-sysroot} option.
11051 @kindex show solib-absolute-prefix
11052 @item show solib-absolute-prefix
11053 Display the current shared library prefix.
11055 @kindex set solib-search-path
11056 @item set solib-search-path @var{path}
11057 If this variable is set, @var{path} is a colon-separated list of directories
11058 to search for shared libraries. @samp{solib-search-path} is used after
11059 @samp{solib-absolute-prefix} fails to locate the library, or if the path to
11060 the library is relative instead of absolute. If you want to use
11061 @samp{solib-search-path} instead of @samp{solib-absolute-prefix}, be sure to
11062 set @samp{solib-absolute-prefix} to a nonexistant directory to prevent
11063 @value{GDBN} from finding your host's libraries.
11065 @kindex show solib-search-path
11066 @item show solib-search-path
11067 Display the current shared library search path.
11071 @node Separate Debug Files
11072 @section Debugging Information in Separate Files
11073 @cindex separate debugging information files
11074 @cindex debugging information in separate files
11075 @cindex @file{.debug} subdirectories
11076 @cindex debugging information directory, global
11077 @cindex global debugging information directory
11079 @value{GDBN} allows you to put a program's debugging information in a
11080 file separate from the executable itself, in a way that allows
11081 @value{GDBN} to find and load the debugging information automatically.
11082 Since debugging information can be very large --- sometimes larger
11083 than the executable code itself --- some systems distribute debugging
11084 information for their executables in separate files, which users can
11085 install only when they need to debug a problem.
11087 If an executable's debugging information has been extracted to a
11088 separate file, the executable should contain a @dfn{debug link} giving
11089 the name of the debugging information file (with no directory
11090 components), and a checksum of its contents. (The exact form of a
11091 debug link is described below.) If the full name of the directory
11092 containing the executable is @var{execdir}, and the executable has a
11093 debug link that specifies the name @var{debugfile}, then @value{GDBN}
11094 will automatically search for the debugging information file in three
11099 the directory containing the executable file (that is, it will look
11100 for a file named @file{@var{execdir}/@var{debugfile}},
11102 a subdirectory of that directory named @file{.debug} (that is, the
11103 file @file{@var{execdir}/.debug/@var{debugfile}}, and
11105 a subdirectory of the global debug file directory that includes the
11106 executable's full path, and the name from the link (that is, the file
11107 @file{@var{globaldebugdir}/@var{execdir}/@var{debugfile}}, where
11108 @var{globaldebugdir} is the global debug file directory, and
11109 @var{execdir} has been turned into a relative path).
11112 @value{GDBN} checks under each of these names for a debugging
11113 information file whose checksum matches that given in the link, and
11114 reads the debugging information from the first one it finds.
11116 So, for example, if you ask @value{GDBN} to debug @file{/usr/bin/ls},
11117 which has a link containing the name @file{ls.debug}, and the global
11118 debug directory is @file{/usr/lib/debug}, then @value{GDBN} will look
11119 for debug information in @file{/usr/bin/ls.debug},
11120 @file{/usr/bin/.debug/ls.debug}, and
11121 @file{/usr/lib/debug/usr/bin/ls.debug}.
11123 You can set the global debugging info directory's name, and view the
11124 name @value{GDBN} is currently using.
11128 @kindex set debug-file-directory
11129 @item set debug-file-directory @var{directory}
11130 Set the directory which @value{GDBN} searches for separate debugging
11131 information files to @var{directory}.
11133 @kindex show debug-file-directory
11134 @item show debug-file-directory
11135 Show the directory @value{GDBN} searches for separate debugging
11140 @cindex @code{.gnu_debuglink} sections
11141 @cindex debug links
11142 A debug link is a special section of the executable file named
11143 @code{.gnu_debuglink}. The section must contain:
11147 A filename, with any leading directory components removed, followed by
11150 zero to three bytes of padding, as needed to reach the next four-byte
11151 boundary within the section, and
11153 a four-byte CRC checksum, stored in the same endianness used for the
11154 executable file itself. The checksum is computed on the debugging
11155 information file's full contents by the function given below, passing
11156 zero as the @var{crc} argument.
11159 Any executable file format can carry a debug link, as long as it can
11160 contain a section named @code{.gnu_debuglink} with the contents
11163 The debugging information file itself should be an ordinary
11164 executable, containing a full set of linker symbols, sections, and
11165 debugging information. The sections of the debugging information file
11166 should have the same names, addresses and sizes as the original file,
11167 but they need not contain any data --- much like a @code{.bss} section
11168 in an ordinary executable.
11170 As of December 2002, there is no standard GNU utility to produce
11171 separated executable / debugging information file pairs. Ulrich
11172 Drepper's @file{elfutils} package, starting with version 0.53,
11173 contains a version of the @code{strip} command such that the command
11174 @kbd{strip foo -f foo.debug} removes the debugging information from
11175 the executable file @file{foo}, places it in the file
11176 @file{foo.debug}, and leaves behind a debug link in @file{foo}.
11178 Since there are many different ways to compute CRC's (different
11179 polynomials, reversals, byte ordering, etc.), the simplest way to
11180 describe the CRC used in @code{.gnu_debuglink} sections is to give the
11181 complete code for a function that computes it:
11183 @kindex gnu_debuglink_crc32
11186 gnu_debuglink_crc32 (unsigned long crc,
11187 unsigned char *buf, size_t len)
11189 static const unsigned long crc32_table[256] =
11191 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
11192 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
11193 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
11194 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
11195 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
11196 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
11197 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
11198 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
11199 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
11200 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
11201 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
11202 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
11203 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
11204 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
11205 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
11206 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
11207 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
11208 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
11209 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
11210 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
11211 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
11212 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
11213 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
11214 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
11215 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
11216 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
11217 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
11218 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
11219 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
11220 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
11221 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
11222 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
11223 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
11224 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
11225 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
11226 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
11227 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
11228 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
11229 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
11230 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
11231 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
11232 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
11233 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
11234 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
11235 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
11236 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
11237 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
11238 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
11239 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
11240 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
11241 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
11244 unsigned char *end;
11246 crc = ~crc & 0xffffffff;
11247 for (end = buf + len; buf < end; ++buf)
11248 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
11249 return ~crc & 0xffffffff;
11254 @node Symbol Errors
11255 @section Errors reading symbol files
11257 While reading a symbol file, @value{GDBN} occasionally encounters problems,
11258 such as symbol types it does not recognize, or known bugs in compiler
11259 output. By default, @value{GDBN} does not notify you of such problems, since
11260 they are relatively common and primarily of interest to people
11261 debugging compilers. If you are interested in seeing information
11262 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
11263 only one message about each such type of problem, no matter how many
11264 times the problem occurs; or you can ask @value{GDBN} to print more messages,
11265 to see how many times the problems occur, with the @code{set
11266 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
11269 The messages currently printed, and their meanings, include:
11272 @item inner block not inside outer block in @var{symbol}
11274 The symbol information shows where symbol scopes begin and end
11275 (such as at the start of a function or a block of statements). This
11276 error indicates that an inner scope block is not fully contained
11277 in its outer scope blocks.
11279 @value{GDBN} circumvents the problem by treating the inner block as if it had
11280 the same scope as the outer block. In the error message, @var{symbol}
11281 may be shown as ``@code{(don't know)}'' if the outer block is not a
11284 @item block at @var{address} out of order
11286 The symbol information for symbol scope blocks should occur in
11287 order of increasing addresses. This error indicates that it does not
11290 @value{GDBN} does not circumvent this problem, and has trouble
11291 locating symbols in the source file whose symbols it is reading. (You
11292 can often determine what source file is affected by specifying
11293 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
11296 @item bad block start address patched
11298 The symbol information for a symbol scope block has a start address
11299 smaller than the address of the preceding source line. This is known
11300 to occur in the SunOS 4.1.1 (and earlier) C compiler.
11302 @value{GDBN} circumvents the problem by treating the symbol scope block as
11303 starting on the previous source line.
11305 @item bad string table offset in symbol @var{n}
11308 Symbol number @var{n} contains a pointer into the string table which is
11309 larger than the size of the string table.
11311 @value{GDBN} circumvents the problem by considering the symbol to have the
11312 name @code{foo}, which may cause other problems if many symbols end up
11315 @item unknown symbol type @code{0x@var{nn}}
11317 The symbol information contains new data types that @value{GDBN} does
11318 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
11319 uncomprehended information, in hexadecimal.
11321 @value{GDBN} circumvents the error by ignoring this symbol information.
11322 This usually allows you to debug your program, though certain symbols
11323 are not accessible. If you encounter such a problem and feel like
11324 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
11325 on @code{complain}, then go up to the function @code{read_dbx_symtab}
11326 and examine @code{*bufp} to see the symbol.
11328 @item stub type has NULL name
11330 @value{GDBN} could not find the full definition for a struct or class.
11332 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
11333 The symbol information for a C@t{++} member function is missing some
11334 information that recent versions of the compiler should have output for
11337 @item info mismatch between compiler and debugger
11339 @value{GDBN} could not parse a type specification output by the compiler.
11344 @chapter Specifying a Debugging Target
11346 @cindex debugging target
11347 A @dfn{target} is the execution environment occupied by your program.
11349 Often, @value{GDBN} runs in the same host environment as your program;
11350 in that case, the debugging target is specified as a side effect when
11351 you use the @code{file} or @code{core} commands. When you need more
11352 flexibility---for example, running @value{GDBN} on a physically separate
11353 host, or controlling a standalone system over a serial port or a
11354 realtime system over a TCP/IP connection---you can use the @code{target}
11355 command to specify one of the target types configured for @value{GDBN}
11356 (@pxref{Target Commands, ,Commands for managing targets}).
11358 @cindex target architecture
11359 It is possible to build @value{GDBN} for several different @dfn{target
11360 architectures}. When @value{GDBN} is built like that, you can choose
11361 one of the available architectures with the @kbd{set architecture}
11365 @kindex set architecture
11366 @kindex show architecture
11367 @item set architecture @var{arch}
11368 This command sets the current target architecture to @var{arch}. The
11369 value of @var{arch} can be @code{"auto"}, in addition to one of the
11370 supported architectures.
11372 @item show architecture
11373 Show the current target architecture.
11375 @item set processor
11377 @kindex set processor
11378 @kindex show processor
11379 These are alias commands for, respectively, @code{set architecture}
11380 and @code{show architecture}.
11384 * Active Targets:: Active targets
11385 * Target Commands:: Commands for managing targets
11386 * Byte Order:: Choosing target byte order
11387 * Remote:: Remote debugging
11388 * KOD:: Kernel Object Display
11392 @node Active Targets
11393 @section Active targets
11395 @cindex stacking targets
11396 @cindex active targets
11397 @cindex multiple targets
11399 There are three classes of targets: processes, core files, and
11400 executable files. @value{GDBN} can work concurrently on up to three
11401 active targets, one in each class. This allows you to (for example)
11402 start a process and inspect its activity without abandoning your work on
11405 For example, if you execute @samp{gdb a.out}, then the executable file
11406 @code{a.out} is the only active target. If you designate a core file as
11407 well---presumably from a prior run that crashed and coredumped---then
11408 @value{GDBN} has two active targets and uses them in tandem, looking
11409 first in the corefile target, then in the executable file, to satisfy
11410 requests for memory addresses. (Typically, these two classes of target
11411 are complementary, since core files contain only a program's
11412 read-write memory---variables and so on---plus machine status, while
11413 executable files contain only the program text and initialized data.)
11415 When you type @code{run}, your executable file becomes an active process
11416 target as well. When a process target is active, all @value{GDBN}
11417 commands requesting memory addresses refer to that target; addresses in
11418 an active core file or executable file target are obscured while the
11419 process target is active.
11421 Use the @code{core-file} and @code{exec-file} commands to select a new
11422 core file or executable target (@pxref{Files, ,Commands to specify
11423 files}). To specify as a target a process that is already running, use
11424 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
11427 @node Target Commands
11428 @section Commands for managing targets
11431 @item target @var{type} @var{parameters}
11432 Connects the @value{GDBN} host environment to a target machine or
11433 process. A target is typically a protocol for talking to debugging
11434 facilities. You use the argument @var{type} to specify the type or
11435 protocol of the target machine.
11437 Further @var{parameters} are interpreted by the target protocol, but
11438 typically include things like device names or host names to connect
11439 with, process numbers, and baud rates.
11441 The @code{target} command does not repeat if you press @key{RET} again
11442 after executing the command.
11444 @kindex help target
11446 Displays the names of all targets available. To display targets
11447 currently selected, use either @code{info target} or @code{info files}
11448 (@pxref{Files, ,Commands to specify files}).
11450 @item help target @var{name}
11451 Describe a particular target, including any parameters necessary to
11454 @kindex set gnutarget
11455 @item set gnutarget @var{args}
11456 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
11457 knows whether it is reading an @dfn{executable},
11458 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
11459 with the @code{set gnutarget} command. Unlike most @code{target} commands,
11460 with @code{gnutarget} the @code{target} refers to a program, not a machine.
11463 @emph{Warning:} To specify a file format with @code{set gnutarget},
11464 you must know the actual BFD name.
11468 @xref{Files, , Commands to specify files}.
11470 @kindex show gnutarget
11471 @item show gnutarget
11472 Use the @code{show gnutarget} command to display what file format
11473 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
11474 @value{GDBN} will determine the file format for each file automatically,
11475 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
11478 @cindex common targets
11479 Here are some common targets (available, or not, depending on the GDB
11484 @item target exec @var{program}
11485 @cindex executable file target
11486 An executable file. @samp{target exec @var{program}} is the same as
11487 @samp{exec-file @var{program}}.
11489 @item target core @var{filename}
11490 @cindex core dump file target
11491 A core dump file. @samp{target core @var{filename}} is the same as
11492 @samp{core-file @var{filename}}.
11494 @item target remote @var{dev}
11495 @cindex remote target
11496 Remote serial target in GDB-specific protocol. The argument @var{dev}
11497 specifies what serial device to use for the connection (e.g.
11498 @file{/dev/ttya}). @xref{Remote, ,Remote debugging}. @code{target remote}
11499 supports the @code{load} command. This is only useful if you have
11500 some other way of getting the stub to the target system, and you can put
11501 it somewhere in memory where it won't get clobbered by the download.
11504 @cindex built-in simulator target
11505 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
11513 works; however, you cannot assume that a specific memory map, device
11514 drivers, or even basic I/O is available, although some simulators do
11515 provide these. For info about any processor-specific simulator details,
11516 see the appropriate section in @ref{Embedded Processors, ,Embedded
11521 Some configurations may include these targets as well:
11525 @item target nrom @var{dev}
11526 @cindex NetROM ROM emulator target
11527 NetROM ROM emulator. This target only supports downloading.
11531 Different targets are available on different configurations of @value{GDBN};
11532 your configuration may have more or fewer targets.
11534 Many remote targets require you to download the executable's code once
11535 you've successfully established a connection. You may wish to control
11536 various aspects of this process, such as the size of the data chunks
11537 used by @value{GDBN} to download program parts to the remote target.
11540 @kindex set download-write-size
11541 @item set download-write-size @var{size}
11542 Set the write size used when downloading a program. Only used when
11543 downloading a program onto a remote target. Specify zero or a
11544 negative value to disable blocked writes. The actual size of each
11545 transfer is also limited by the size of the target packet and the
11548 @kindex show download-write-size
11549 @item show download-write-size
11550 @kindex show download-write-size
11551 Show the current value of the write size.
11554 @kindex set hash@r{, for remote monitors}
11555 @cindex hash mark while downloading
11556 This command controls whether a hash mark @samp{#} is displayed while
11557 downloading a file to the remote monitor. If on, a hash mark is
11558 displayed after each S-record is successfully downloaded to the
11562 @kindex show hash@r{, for remote monitors}
11563 Show the current status of displaying the hash mark.
11565 @item set debug monitor
11566 @kindex set debug monitor
11567 @cindex display remote monitor communications
11568 Enable or disable display of communications messages between
11569 @value{GDBN} and the remote monitor.
11571 @item show debug monitor
11572 @kindex show debug monitor
11573 Show the current status of displaying communications between
11574 @value{GDBN} and the remote monitor.
11579 @kindex load @var{filename}
11580 @item load @var{filename}
11581 Depending on what remote debugging facilities are configured into
11582 @value{GDBN}, the @code{load} command may be available. Where it exists, it
11583 is meant to make @var{filename} (an executable) available for debugging
11584 on the remote system---by downloading, or dynamic linking, for example.
11585 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
11586 the @code{add-symbol-file} command.
11588 If your @value{GDBN} does not have a @code{load} command, attempting to
11589 execute it gets the error message ``@code{You can't do that when your
11590 target is @dots{}}''
11592 The file is loaded at whatever address is specified in the executable.
11593 For some object file formats, you can specify the load address when you
11594 link the program; for other formats, like a.out, the object file format
11595 specifies a fixed address.
11596 @c FIXME! This would be a good place for an xref to the GNU linker doc.
11598 @code{load} does not repeat if you press @key{RET} again after using it.
11602 @section Choosing target byte order
11604 @cindex choosing target byte order
11605 @cindex target byte order
11607 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
11608 offer the ability to run either big-endian or little-endian byte
11609 orders. Usually the executable or symbol will include a bit to
11610 designate the endian-ness, and you will not need to worry about
11611 which to use. However, you may still find it useful to adjust
11612 @value{GDBN}'s idea of processor endian-ness manually.
11616 @item set endian big
11617 Instruct @value{GDBN} to assume the target is big-endian.
11619 @item set endian little
11620 Instruct @value{GDBN} to assume the target is little-endian.
11622 @item set endian auto
11623 Instruct @value{GDBN} to use the byte order associated with the
11627 Display @value{GDBN}'s current idea of the target byte order.
11631 Note that these commands merely adjust interpretation of symbolic
11632 data on the host, and that they have absolutely no effect on the
11636 @section Remote debugging
11637 @cindex remote debugging
11639 If you are trying to debug a program running on a machine that cannot run
11640 @value{GDBN} in the usual way, it is often useful to use remote debugging.
11641 For example, you might use remote debugging on an operating system kernel,
11642 or on a small system which does not have a general purpose operating system
11643 powerful enough to run a full-featured debugger.
11645 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
11646 to make this work with particular debugging targets. In addition,
11647 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
11648 but not specific to any particular target system) which you can use if you
11649 write the remote stubs---the code that runs on the remote system to
11650 communicate with @value{GDBN}.
11652 Other remote targets may be available in your
11653 configuration of @value{GDBN}; use @code{help target} to list them.
11655 Once you've connected to the remote target, @value{GDBN} allows you to
11656 send arbitrary commands to the remote monitor:
11659 @item remote @var{command}
11660 @kindex remote@r{, a command}
11661 @cindex send command to remote monitor
11662 Send an arbitrary @var{command} string to the remote monitor.
11667 @section Kernel Object Display
11668 @cindex kernel object display
11671 Some targets support kernel object display. Using this facility,
11672 @value{GDBN} communicates specially with the underlying operating system
11673 and can display information about operating system-level objects such as
11674 mutexes and other synchronization objects. Exactly which objects can be
11675 displayed is determined on a per-OS basis.
11678 Use the @code{set os} command to set the operating system. This tells
11679 @value{GDBN} which kernel object display module to initialize:
11682 (@value{GDBP}) set os cisco
11686 The associated command @code{show os} displays the operating system
11687 set with the @code{set os} command; if no operating system has been
11688 set, @code{show os} will display an empty string @samp{""}.
11690 If @code{set os} succeeds, @value{GDBN} will display some information
11691 about the operating system, and will create a new @code{info} command
11692 which can be used to query the target. The @code{info} command is named
11693 after the operating system:
11697 (@value{GDBP}) info cisco
11698 List of Cisco Kernel Objects
11700 any Any and all objects
11703 Further subcommands can be used to query about particular objects known
11706 There is currently no way to determine whether a given operating
11707 system is supported other than to try setting it with @kbd{set os
11708 @var{name}}, where @var{name} is the name of the operating system you
11712 @node Remote Debugging
11713 @chapter Debugging remote programs
11716 * Connecting:: Connecting to a remote target
11717 * Server:: Using the gdbserver program
11718 * NetWare:: Using the gdbserve.nlm program
11719 * Remote configuration:: Remote configuration
11720 * remote stub:: Implementing a remote stub
11724 @section Connecting to a remote target
11726 On the @value{GDBN} host machine, you will need an unstripped copy of
11727 your program, since @value{GDBN} needs symobl and debugging information.
11728 Start up @value{GDBN} as usual, using the name of the local copy of your
11729 program as the first argument.
11731 @cindex serial line, @code{target remote}
11732 If you're using a serial line, you may want to give @value{GDBN} the
11733 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
11734 (@pxref{Remote configuration, set remotebaud}) before the
11735 @code{target} command.
11737 After that, use @code{target remote} to establish communications with
11738 the target machine. Its argument specifies how to communicate---either
11739 via a devicename attached to a direct serial line, or a TCP or UDP port
11740 (possibly to a terminal server which in turn has a serial line to the
11741 target). For example, to use a serial line connected to the device
11742 named @file{/dev/ttyb}:
11745 target remote /dev/ttyb
11748 @cindex TCP port, @code{target remote}
11749 To use a TCP connection, use an argument of the form
11750 @code{@var{host}:@var{port}} or @code{tcp:@var{host}:@var{port}}.
11751 For example, to connect to port 2828 on a
11752 terminal server named @code{manyfarms}:
11755 target remote manyfarms:2828
11758 If your remote target is actually running on the same machine as
11759 your debugger session (e.g.@: a simulator of your target running on
11760 the same host), you can omit the hostname. For example, to connect
11761 to port 1234 on your local machine:
11764 target remote :1234
11768 Note that the colon is still required here.
11770 @cindex UDP port, @code{target remote}
11771 To use a UDP connection, use an argument of the form
11772 @code{udp:@var{host}:@var{port}}. For example, to connect to UDP port 2828
11773 on a terminal server named @code{manyfarms}:
11776 target remote udp:manyfarms:2828
11779 When using a UDP connection for remote debugging, you should keep in mind
11780 that the `U' stands for ``Unreliable''. UDP can silently drop packets on
11781 busy or unreliable networks, which will cause havoc with your debugging
11784 Now you can use all the usual commands to examine and change data and to
11785 step and continue the remote program.
11787 @cindex interrupting remote programs
11788 @cindex remote programs, interrupting
11789 Whenever @value{GDBN} is waiting for the remote program, if you type the
11790 interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the
11791 program. This may or may not succeed, depending in part on the hardware
11792 and the serial drivers the remote system uses. If you type the
11793 interrupt character once again, @value{GDBN} displays this prompt:
11796 Interrupted while waiting for the program.
11797 Give up (and stop debugging it)? (y or n)
11800 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
11801 (If you decide you want to try again later, you can use @samp{target
11802 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
11803 goes back to waiting.
11806 @kindex detach (remote)
11808 When you have finished debugging the remote program, you can use the
11809 @code{detach} command to release it from @value{GDBN} control.
11810 Detaching from the target normally resumes its execution, but the results
11811 will depend on your particular remote stub. After the @code{detach}
11812 command, @value{GDBN} is free to connect to another target.
11816 The @code{disconnect} command behaves like @code{detach}, except that
11817 the target is generally not resumed. It will wait for @value{GDBN}
11818 (this instance or another one) to connect and continue debugging. After
11819 the @code{disconnect} command, @value{GDBN} is again free to connect to
11822 @cindex send command to remote monitor
11824 @item monitor @var{cmd}
11825 This command allows you to send commands directly to the remote
11830 @section Using the @code{gdbserver} program
11833 @cindex remote connection without stubs
11834 @code{gdbserver} is a control program for Unix-like systems, which
11835 allows you to connect your program with a remote @value{GDBN} via
11836 @code{target remote}---but without linking in the usual debugging stub.
11838 @code{gdbserver} is not a complete replacement for the debugging stubs,
11839 because it requires essentially the same operating-system facilities
11840 that @value{GDBN} itself does. In fact, a system that can run
11841 @code{gdbserver} to connect to a remote @value{GDBN} could also run
11842 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
11843 because it is a much smaller program than @value{GDBN} itself. It is
11844 also easier to port than all of @value{GDBN}, so you may be able to get
11845 started more quickly on a new system by using @code{gdbserver}.
11846 Finally, if you develop code for real-time systems, you may find that
11847 the tradeoffs involved in real-time operation make it more convenient to
11848 do as much development work as possible on another system, for example
11849 by cross-compiling. You can use @code{gdbserver} to make a similar
11850 choice for debugging.
11852 @value{GDBN} and @code{gdbserver} communicate via either a serial line
11853 or a TCP connection, using the standard @value{GDBN} remote serial
11857 @item On the target machine,
11858 you need to have a copy of the program you want to debug.
11859 @code{gdbserver} does not need your program's symbol table, so you can
11860 strip the program if necessary to save space. @value{GDBN} on the host
11861 system does all the symbol handling.
11863 To use the server, you must tell it how to communicate with @value{GDBN};
11864 the name of your program; and the arguments for your program. The usual
11868 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
11871 @var{comm} is either a device name (to use a serial line) or a TCP
11872 hostname and portnumber. For example, to debug Emacs with the argument
11873 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
11877 target> gdbserver /dev/com1 emacs foo.txt
11880 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
11883 To use a TCP connection instead of a serial line:
11886 target> gdbserver host:2345 emacs foo.txt
11889 The only difference from the previous example is the first argument,
11890 specifying that you are communicating with the host @value{GDBN} via
11891 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
11892 expect a TCP connection from machine @samp{host} to local TCP port 2345.
11893 (Currently, the @samp{host} part is ignored.) You can choose any number
11894 you want for the port number as long as it does not conflict with any
11895 TCP ports already in use on the target system (for example, @code{23} is
11896 reserved for @code{telnet}).@footnote{If you choose a port number that
11897 conflicts with another service, @code{gdbserver} prints an error message
11898 and exits.} You must use the same port number with the host @value{GDBN}
11899 @code{target remote} command.
11901 On some targets, @code{gdbserver} can also attach to running programs.
11902 This is accomplished via the @code{--attach} argument. The syntax is:
11905 target> gdbserver @var{comm} --attach @var{pid}
11908 @var{pid} is the process ID of a currently running process. It isn't necessary
11909 to point @code{gdbserver} at a binary for the running process.
11912 @cindex attach to a program by name
11913 You can debug processes by name instead of process ID if your target has the
11914 @code{pidof} utility:
11917 target> gdbserver @var{comm} --attach `pidof @var{PROGRAM}`
11920 In case more than one copy of @var{PROGRAM} is running, or @var{PROGRAM}
11921 has multiple threads, most versions of @code{pidof} support the
11922 @code{-s} option to only return the first process ID.
11924 @item On the host machine,
11925 connect to your target (@pxref{Connecting,,Connecting to a remote target}).
11926 For TCP connections, you must start up @code{gdbserver} prior to using
11927 the @code{target remote} command. Otherwise you may get an error whose
11928 text depends on the host system, but which usually looks something like
11929 @samp{Connection refused}. You don't need to use the @code{load}
11930 command in @value{GDBN} when using gdbserver, since the program is
11931 already on the target.
11936 @section Using the @code{gdbserve.nlm} program
11938 @kindex gdbserve.nlm
11939 @code{gdbserve.nlm} is a control program for NetWare systems, which
11940 allows you to connect your program with a remote @value{GDBN} via
11941 @code{target remote}.
11943 @value{GDBN} and @code{gdbserve.nlm} communicate via a serial line,
11944 using the standard @value{GDBN} remote serial protocol.
11947 @item On the target machine,
11948 you need to have a copy of the program you want to debug.
11949 @code{gdbserve.nlm} does not need your program's symbol table, so you
11950 can strip the program if necessary to save space. @value{GDBN} on the
11951 host system does all the symbol handling.
11953 To use the server, you must tell it how to communicate with
11954 @value{GDBN}; the name of your program; and the arguments for your
11955 program. The syntax is:
11958 load gdbserve [ BOARD=@var{board} ] [ PORT=@var{port} ]
11959 [ BAUD=@var{baud} ] @var{program} [ @var{args} @dots{} ]
11962 @var{board} and @var{port} specify the serial line; @var{baud} specifies
11963 the baud rate used by the connection. @var{port} and @var{node} default
11964 to 0, @var{baud} defaults to 9600@dmn{bps}.
11966 For example, to debug Emacs with the argument @samp{foo.txt}and
11967 communicate with @value{GDBN} over serial port number 2 or board 1
11968 using a 19200@dmn{bps} connection:
11971 load gdbserve BOARD=1 PORT=2 BAUD=19200 emacs foo.txt
11975 On the @value{GDBN} host machine, connect to your target (@pxref{Connecting,,
11976 Connecting to a remote target}).
11980 @node Remote configuration
11981 @section Remote configuration
11984 @kindex show remote
11985 This section documents the configuration options available when
11986 debugging remote programs. For the options related to the File I/O
11987 extensions of the remote protocol, see @ref{The system call,
11988 system-call-allowed}.
11991 @item set remoteaddresssize @var{bits}
11992 @cindex adress size for remote targets
11993 @cindex bits in remote address
11994 Set the maximum size of address in a memory packet to the specified
11995 number of bits. @value{GDBN} will mask off the address bits above
11996 that number, when it passes addresses to the remote target. The
11997 default value is the number of bits in the target's address.
11999 @item show remoteaddresssize
12000 Show the current value of remote address size in bits.
12002 @item set remotebaud @var{n}
12003 @cindex baud rate for remote targets
12004 Set the baud rate for the remote serial I/O to @var{n} baud. The
12005 value is used to set the speed of the serial port used for debugging
12008 @item show remotebaud
12009 Show the current speed of the remote connection.
12011 @item set remotebreak
12012 @cindex interrupt remote programs
12013 @cindex BREAK signal instead of Ctrl-C
12014 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
12015 when you press the @key{Ctrl-C} key to interrupt the program running
12016 on the remote. If set to off, @value{GDBN} sends the @samp{Strl-C}
12017 character instead. The default is off, since most remote systems
12018 expect to see @samp{Ctrl-C} as the interrupt signal.
12020 @item show remotebreak
12021 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
12022 interrupt the remote program.
12024 @item set remotedebug
12025 @cindex debug remote protocol
12026 @cindex remote protocol debugging
12027 @cindex display remote packets
12028 Control the debugging of the remote protocol. When enabled, each
12029 packet sent to or received from the remote target is displayed. The
12032 @item show remotedebug
12033 Show the current setting of the remote protocol debugging.
12035 @item set remotedevice @var{device}
12036 @cindex serial port name
12037 Set the name of the serial port through which to communicate to the
12038 remote target to @var{device}. This is the device used by
12039 @value{GDBN} to open the serial communications line to the remote
12040 target. There's no default, so you must set a valid port name for the
12041 remote serial communications to work. (Some varieties of the
12042 @code{target} command accept the port name as part of their
12045 @item show remotedevice
12046 Show the current name of the serial port.
12048 @item set remotelogbase @var{base}
12049 Set the base (a.k.a.@: radix) of logging serial protocol
12050 communications to @var{base}. Supported values of @var{base} are:
12051 @code{ascii}, @code{octal}, and @code{hex}. The default is
12054 @item show remotelogbase
12055 Show the current setting of the radix for logging remote serial
12058 @item set remotelogfile @var{file}
12059 @cindex record serial communications on file
12060 Record remote serial communications on the named @var{file}. The
12061 default is not to record at all.
12063 @item show remotelogfile.
12064 Show the current setting of the file name on which to record the
12065 serial communications.
12067 @item set remotetimeout @var{num}
12068 @cindex timeout for serial communications
12069 @cindex remote timeout
12070 Set the timeout limit to wait for the remote target to respond to
12071 @var{num} seconds. The default is 2 seconds.
12073 @item show remotetimeout
12074 Show the current number of seconds to wait for the remote target
12077 @cindex limit hardware breakpoints and watchpoints
12078 @cindex remote target, limit break- and watchpoints
12079 @anchor{set remote hardware-watchpoint-limit}
12080 @anchor{set remote hardware-breakpoint-limit}
12081 @item set remote hardware-watchpoint-limit @var{limit}
12082 @itemx set remote hardware-breakpoint-limit @var{limit}
12083 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
12084 watchpoints. A limit of -1, the default, is treated as unlimited.
12086 @item set remote fetch-register-packet
12087 @itemx set remote set-register-packet
12088 @itemx set remote P-packet
12089 @itemx set remote p-packet
12091 @cindex fetch registers from remote targets
12092 @cindex set registers in remote targets
12093 Determine whether @value{GDBN} can set and fetch registers from the
12094 remote target using the @samp{P} packets. The default depends on the
12095 remote stub's support of the @samp{P} packets (@value{GDBN} queries
12096 the stub when this packet is first required).
12098 @item show remote fetch-register-packet
12099 @itemx show remote set-register-packet
12100 @itemx show remote P-packet
12101 @itemx show remote p-packet
12102 Show the current setting of using the @samp{P} packets for setting and
12103 fetching registers from the remote target.
12105 @cindex binary downloads
12107 @item set remote binary-download-packet
12108 @itemx set remote X-packet
12109 Determine whether @value{GDBN} sends downloads in binary mode using
12110 the @samp{X} packets. The default is on.
12112 @item show remote binary-download-packet
12113 @itemx show remote X-packet
12114 Show the current setting of using the @samp{X} packets for binary
12117 @item set remote read-aux-vector-packet
12118 @cindex auxiliary vector of remote target
12119 @cindex @code{auxv}, and remote targets
12120 Set the use of the remote protocol's @samp{qPart:auxv:read} (target
12121 auxiliary vector read) request. This request is used to fetch the
12122 remote target's @dfn{auxiliary vector}, see @ref{OS Information,
12123 Auxiliary Vector}. The default setting depends on the remote stub's
12124 support of this request (@value{GDBN} queries the stub when this
12125 request is first required). @xref{General Query Packets, qPart}, for
12126 more information about this request.
12128 @item show remote read-aux-vector-packet
12129 Show the current setting of use of the @samp{qPart:auxv:read} request.
12131 @item set remote symbol-lookup-packet
12132 @cindex remote symbol lookup request
12133 Set the use of the remote protocol's @samp{qSymbol} (target symbol
12134 lookup) request. This request is used to communicate symbol
12135 information to the remote target, e.g., whenever a new shared library
12136 is loaded by the remote (@pxref{Files, shared libraries}). The
12137 default setting depends on the remote stub's support of this request
12138 (@value{GDBN} queries the stub when this request is first required).
12139 @xref{General Query Packets, qSymbol}, for more information about this
12142 @item show remote symbol-lookup-packet
12143 Show the current setting of use of the @samp{qSymbol} request.
12145 @item set remote verbose-resume-packet
12146 @cindex resume remote target
12147 @cindex signal thread, and remote targets
12148 @cindex single-step thread, and remote targets
12149 @cindex thread-specific operations on remote targets
12150 Set the use of the remote protocol's @samp{vCont} (descriptive resume)
12151 request. This request is used to resume specific threads in the
12152 remote target, and to single-step or signal them. The default setting
12153 depends on the remote stub's support of this request (@value{GDBN}
12154 queries the stub when this request is first required). This setting
12155 affects debugging of multithreaded programs: if @samp{vCont} cannot be
12156 used, @value{GDBN} might be unable to single-step a specific thread,
12157 especially under @code{set scheduler-locking off}; it is also
12158 impossible to pause a specific thread. @xref{Packets, vCont}, for
12161 @item show remote verbose-resume-packet
12162 Show the current setting of use of the @samp{vCont} request
12164 @item set remote software-breakpoint-packet
12165 @itemx set remote hardware-breakpoint-packet
12166 @itemx set remote write-watchpoint-packet
12167 @itemx set remote read-watchpoint-packet
12168 @itemx set remote access-watchpoint-packet
12169 @itemx set remote Z-packet
12171 @cindex remote hardware breakpoints and watchpoints
12172 These commands enable or disable the use of @samp{Z} packets for
12173 setting breakpoints and watchpoints in the remote target. The default
12174 depends on the remote stub's support of the @samp{Z} packets
12175 (@value{GDBN} queries the stub when each packet is first required).
12176 The command @code{set remote Z-packet}, kept for back-compatibility,
12177 turns on or off all the features that require the use of @samp{Z}
12180 @item show remote software-breakpoint-packet
12181 @itemx show remote hardware-breakpoint-packet
12182 @itemx show remote write-watchpoint-packet
12183 @itemx show remote read-watchpoint-packet
12184 @itemx show remote access-watchpoint-packet
12185 @itemx show remote Z-packet
12186 Show the current setting of @samp{Z} packets usage.
12188 @item set remote get-thread-local-storage-address
12189 @kindex set remote get-thread-local-storage-address
12190 @cindex thread local storage of remote targets
12191 This command enables or disables the use of the @samp{qGetTLSAddr}
12192 (Get Thread Local Storage Address) request packet. The default
12193 depends on whether the remote stub supports this request.
12194 @xref{General Query Packets, qGetTLSAddr}, for more details about this
12197 @item show remote get-thread-local-storage-address
12198 @kindex show remote get-thread-local-storage-address
12199 Show the current setting of @samp{qGetTLSAddr} packet usage.
12203 @section Implementing a remote stub
12205 @cindex debugging stub, example
12206 @cindex remote stub, example
12207 @cindex stub example, remote debugging
12208 The stub files provided with @value{GDBN} implement the target side of the
12209 communication protocol, and the @value{GDBN} side is implemented in the
12210 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
12211 these subroutines to communicate, and ignore the details. (If you're
12212 implementing your own stub file, you can still ignore the details: start
12213 with one of the existing stub files. @file{sparc-stub.c} is the best
12214 organized, and therefore the easiest to read.)
12216 @cindex remote serial debugging, overview
12217 To debug a program running on another machine (the debugging
12218 @dfn{target} machine), you must first arrange for all the usual
12219 prerequisites for the program to run by itself. For example, for a C
12224 A startup routine to set up the C runtime environment; these usually
12225 have a name like @file{crt0}. The startup routine may be supplied by
12226 your hardware supplier, or you may have to write your own.
12229 A C subroutine library to support your program's
12230 subroutine calls, notably managing input and output.
12233 A way of getting your program to the other machine---for example, a
12234 download program. These are often supplied by the hardware
12235 manufacturer, but you may have to write your own from hardware
12239 The next step is to arrange for your program to use a serial port to
12240 communicate with the machine where @value{GDBN} is running (the @dfn{host}
12241 machine). In general terms, the scheme looks like this:
12245 @value{GDBN} already understands how to use this protocol; when everything
12246 else is set up, you can simply use the @samp{target remote} command
12247 (@pxref{Targets,,Specifying a Debugging Target}).
12249 @item On the target,
12250 you must link with your program a few special-purpose subroutines that
12251 implement the @value{GDBN} remote serial protocol. The file containing these
12252 subroutines is called a @dfn{debugging stub}.
12254 On certain remote targets, you can use an auxiliary program
12255 @code{gdbserver} instead of linking a stub into your program.
12256 @xref{Server,,Using the @code{gdbserver} program}, for details.
12259 The debugging stub is specific to the architecture of the remote
12260 machine; for example, use @file{sparc-stub.c} to debug programs on
12263 @cindex remote serial stub list
12264 These working remote stubs are distributed with @value{GDBN}:
12269 @cindex @file{i386-stub.c}
12272 For Intel 386 and compatible architectures.
12275 @cindex @file{m68k-stub.c}
12276 @cindex Motorola 680x0
12278 For Motorola 680x0 architectures.
12281 @cindex @file{sh-stub.c}
12284 For Renesas SH architectures.
12287 @cindex @file{sparc-stub.c}
12289 For @sc{sparc} architectures.
12291 @item sparcl-stub.c
12292 @cindex @file{sparcl-stub.c}
12295 For Fujitsu @sc{sparclite} architectures.
12299 The @file{README} file in the @value{GDBN} distribution may list other
12300 recently added stubs.
12303 * Stub Contents:: What the stub can do for you
12304 * Bootstrapping:: What you must do for the stub
12305 * Debug Session:: Putting it all together
12308 @node Stub Contents
12309 @subsection What the stub can do for you
12311 @cindex remote serial stub
12312 The debugging stub for your architecture supplies these three
12316 @item set_debug_traps
12317 @findex set_debug_traps
12318 @cindex remote serial stub, initialization
12319 This routine arranges for @code{handle_exception} to run when your
12320 program stops. You must call this subroutine explicitly near the
12321 beginning of your program.
12323 @item handle_exception
12324 @findex handle_exception
12325 @cindex remote serial stub, main routine
12326 This is the central workhorse, but your program never calls it
12327 explicitly---the setup code arranges for @code{handle_exception} to
12328 run when a trap is triggered.
12330 @code{handle_exception} takes control when your program stops during
12331 execution (for example, on a breakpoint), and mediates communications
12332 with @value{GDBN} on the host machine. This is where the communications
12333 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
12334 representative on the target machine. It begins by sending summary
12335 information on the state of your program, then continues to execute,
12336 retrieving and transmitting any information @value{GDBN} needs, until you
12337 execute a @value{GDBN} command that makes your program resume; at that point,
12338 @code{handle_exception} returns control to your own code on the target
12342 @cindex @code{breakpoint} subroutine, remote
12343 Use this auxiliary subroutine to make your program contain a
12344 breakpoint. Depending on the particular situation, this may be the only
12345 way for @value{GDBN} to get control. For instance, if your target
12346 machine has some sort of interrupt button, you won't need to call this;
12347 pressing the interrupt button transfers control to
12348 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
12349 simply receiving characters on the serial port may also trigger a trap;
12350 again, in that situation, you don't need to call @code{breakpoint} from
12351 your own program---simply running @samp{target remote} from the host
12352 @value{GDBN} session gets control.
12354 Call @code{breakpoint} if none of these is true, or if you simply want
12355 to make certain your program stops at a predetermined point for the
12356 start of your debugging session.
12359 @node Bootstrapping
12360 @subsection What you must do for the stub
12362 @cindex remote stub, support routines
12363 The debugging stubs that come with @value{GDBN} are set up for a particular
12364 chip architecture, but they have no information about the rest of your
12365 debugging target machine.
12367 First of all you need to tell the stub how to communicate with the
12371 @item int getDebugChar()
12372 @findex getDebugChar
12373 Write this subroutine to read a single character from the serial port.
12374 It may be identical to @code{getchar} for your target system; a
12375 different name is used to allow you to distinguish the two if you wish.
12377 @item void putDebugChar(int)
12378 @findex putDebugChar
12379 Write this subroutine to write a single character to the serial port.
12380 It may be identical to @code{putchar} for your target system; a
12381 different name is used to allow you to distinguish the two if you wish.
12384 @cindex control C, and remote debugging
12385 @cindex interrupting remote targets
12386 If you want @value{GDBN} to be able to stop your program while it is
12387 running, you need to use an interrupt-driven serial driver, and arrange
12388 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
12389 character). That is the character which @value{GDBN} uses to tell the
12390 remote system to stop.
12392 Getting the debugging target to return the proper status to @value{GDBN}
12393 probably requires changes to the standard stub; one quick and dirty way
12394 is to just execute a breakpoint instruction (the ``dirty'' part is that
12395 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
12397 Other routines you need to supply are:
12400 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
12401 @findex exceptionHandler
12402 Write this function to install @var{exception_address} in the exception
12403 handling tables. You need to do this because the stub does not have any
12404 way of knowing what the exception handling tables on your target system
12405 are like (for example, the processor's table might be in @sc{rom},
12406 containing entries which point to a table in @sc{ram}).
12407 @var{exception_number} is the exception number which should be changed;
12408 its meaning is architecture-dependent (for example, different numbers
12409 might represent divide by zero, misaligned access, etc). When this
12410 exception occurs, control should be transferred directly to
12411 @var{exception_address}, and the processor state (stack, registers,
12412 and so on) should be just as it is when a processor exception occurs. So if
12413 you want to use a jump instruction to reach @var{exception_address}, it
12414 should be a simple jump, not a jump to subroutine.
12416 For the 386, @var{exception_address} should be installed as an interrupt
12417 gate so that interrupts are masked while the handler runs. The gate
12418 should be at privilege level 0 (the most privileged level). The
12419 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
12420 help from @code{exceptionHandler}.
12422 @item void flush_i_cache()
12423 @findex flush_i_cache
12424 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
12425 instruction cache, if any, on your target machine. If there is no
12426 instruction cache, this subroutine may be a no-op.
12428 On target machines that have instruction caches, @value{GDBN} requires this
12429 function to make certain that the state of your program is stable.
12433 You must also make sure this library routine is available:
12436 @item void *memset(void *, int, int)
12438 This is the standard library function @code{memset} that sets an area of
12439 memory to a known value. If you have one of the free versions of
12440 @code{libc.a}, @code{memset} can be found there; otherwise, you must
12441 either obtain it from your hardware manufacturer, or write your own.
12444 If you do not use the GNU C compiler, you may need other standard
12445 library subroutines as well; this varies from one stub to another,
12446 but in general the stubs are likely to use any of the common library
12447 subroutines which @code{@value{GCC}} generates as inline code.
12450 @node Debug Session
12451 @subsection Putting it all together
12453 @cindex remote serial debugging summary
12454 In summary, when your program is ready to debug, you must follow these
12459 Make sure you have defined the supporting low-level routines
12460 (@pxref{Bootstrapping,,What you must do for the stub}):
12462 @code{getDebugChar}, @code{putDebugChar},
12463 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
12467 Insert these lines near the top of your program:
12475 For the 680x0 stub only, you need to provide a variable called
12476 @code{exceptionHook}. Normally you just use:
12479 void (*exceptionHook)() = 0;
12483 but if before calling @code{set_debug_traps}, you set it to point to a
12484 function in your program, that function is called when
12485 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
12486 error). The function indicated by @code{exceptionHook} is called with
12487 one parameter: an @code{int} which is the exception number.
12490 Compile and link together: your program, the @value{GDBN} debugging stub for
12491 your target architecture, and the supporting subroutines.
12494 Make sure you have a serial connection between your target machine and
12495 the @value{GDBN} host, and identify the serial port on the host.
12498 @c The "remote" target now provides a `load' command, so we should
12499 @c document that. FIXME.
12500 Download your program to your target machine (or get it there by
12501 whatever means the manufacturer provides), and start it.
12504 Start @value{GDBN} on the host, and connect to the target
12505 (@pxref{Connecting,,Connecting to a remote target}).
12509 @node Configurations
12510 @chapter Configuration-Specific Information
12512 While nearly all @value{GDBN} commands are available for all native and
12513 cross versions of the debugger, there are some exceptions. This chapter
12514 describes things that are only available in certain configurations.
12516 There are three major categories of configurations: native
12517 configurations, where the host and target are the same, embedded
12518 operating system configurations, which are usually the same for several
12519 different processor architectures, and bare embedded processors, which
12520 are quite different from each other.
12525 * Embedded Processors::
12532 This section describes details specific to particular native
12537 * BSD libkvm Interface:: Debugging BSD kernel memory images
12538 * SVR4 Process Information:: SVR4 process information
12539 * DJGPP Native:: Features specific to the DJGPP port
12540 * Cygwin Native:: Features specific to the Cygwin port
12541 * Hurd Native:: Features specific to @sc{gnu} Hurd
12542 * Neutrino:: Features specific to QNX Neutrino
12548 On HP-UX systems, if you refer to a function or variable name that
12549 begins with a dollar sign, @value{GDBN} searches for a user or system
12550 name first, before it searches for a convenience variable.
12553 @node BSD libkvm Interface
12554 @subsection BSD libkvm Interface
12557 @cindex kernel memory image
12558 @cindex kernel crash dump
12560 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
12561 interface that provides a uniform interface for accessing kernel virtual
12562 memory images, including live systems and crash dumps. @value{GDBN}
12563 uses this interface to allow you to debug live kernels and kernel crash
12564 dumps on many native BSD configurations. This is implemented as a
12565 special @code{kvm} debugging target. For debugging a live system, load
12566 the currently running kernel into @value{GDBN} and connect to the
12570 (@value{GDBP}) @b{target kvm}
12573 For debugging crash dumps, provide the file name of the crash dump as an
12577 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
12580 Once connected to the @code{kvm} target, the following commands are
12586 Set current context from the @dfn{Process Control Block} (PCB) address.
12589 Set current context from proc address. This command isn't available on
12590 modern FreeBSD systems.
12593 @node SVR4 Process Information
12594 @subsection SVR4 process information
12596 @cindex examine process image
12597 @cindex process info via @file{/proc}
12599 Many versions of SVR4 and compatible systems provide a facility called
12600 @samp{/proc} that can be used to examine the image of a running
12601 process using file-system subroutines. If @value{GDBN} is configured
12602 for an operating system with this facility, the command @code{info
12603 proc} is available to report information about the process running
12604 your program, or about any process running on your system. @code{info
12605 proc} works only on SVR4 systems that include the @code{procfs} code.
12606 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
12607 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
12613 @itemx info proc @var{process-id}
12614 Summarize available information about any running process. If a
12615 process ID is specified by @var{process-id}, display information about
12616 that process; otherwise display information about the program being
12617 debugged. The summary includes the debugged process ID, the command
12618 line used to invoke it, its current working directory, and its
12619 executable file's absolute file name.
12621 On some systems, @var{process-id} can be of the form
12622 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
12623 within a process. If the optional @var{pid} part is missing, it means
12624 a thread from the process being debugged (the leading @samp{/} still
12625 needs to be present, or else @value{GDBN} will interpret the number as
12626 a process ID rather than a thread ID).
12628 @item info proc mappings
12629 @cindex memory address space mappings
12630 Report the memory address space ranges accessible in the program, with
12631 information on whether the process has read, write, or execute access
12632 rights to each range. On @sc{gnu}/Linux systems, each memory range
12633 includes the object file which is mapped to that range, instead of the
12634 memory access rights to that range.
12636 @item info proc stat
12637 @itemx info proc status
12638 @cindex process detailed status information
12639 These subcommands are specific to @sc{gnu}/Linux systems. They show
12640 the process-related information, including the user ID and group ID;
12641 how many threads are there in the process; its virtual memory usage;
12642 the signals that are pending, blocked, and ignored; its TTY; its
12643 consumption of system and user time; its stack size; its @samp{nice}
12644 value; etc. For more information, see the @samp{proc} man page
12645 (type @kbd{man 5 proc} from your shell prompt).
12647 @item info proc all
12648 Show all the information about the process described under all of the
12649 above @code{info proc} subcommands.
12652 @comment These sub-options of 'info proc' were not included when
12653 @comment procfs.c was re-written. Keep their descriptions around
12654 @comment against the day when someone finds the time to put them back in.
12655 @kindex info proc times
12656 @item info proc times
12657 Starting time, user CPU time, and system CPU time for your program and
12660 @kindex info proc id
12662 Report on the process IDs related to your program: its own process ID,
12663 the ID of its parent, the process group ID, and the session ID.
12666 @item set procfs-trace
12667 @kindex set procfs-trace
12668 @cindex @code{procfs} API calls
12669 This command enables and disables tracing of @code{procfs} API calls.
12671 @item show procfs-trace
12672 @kindex show procfs-trace
12673 Show the current state of @code{procfs} API call tracing.
12675 @item set procfs-file @var{file}
12676 @kindex set procfs-file
12677 Tell @value{GDBN} to write @code{procfs} API trace to the named
12678 @var{file}. @value{GDBN} appends the trace info to the previous
12679 contents of the file. The default is to display the trace on the
12682 @item show procfs-file
12683 @kindex show procfs-file
12684 Show the file to which @code{procfs} API trace is written.
12686 @item proc-trace-entry
12687 @itemx proc-trace-exit
12688 @itemx proc-untrace-entry
12689 @itemx proc-untrace-exit
12690 @kindex proc-trace-entry
12691 @kindex proc-trace-exit
12692 @kindex proc-untrace-entry
12693 @kindex proc-untrace-exit
12694 These commands enable and disable tracing of entries into and exits
12695 from the @code{syscall} interface.
12698 @kindex info pidlist
12699 @cindex process list, QNX Neutrino
12700 For QNX Neutrino only, this command displays the list of all the
12701 processes and all the threads within each process.
12704 @kindex info meminfo
12705 @cindex mapinfo list, QNX Neutrino
12706 For QNX Neutrino only, this command displays the list of all mapinfos.
12710 @subsection Features for Debugging @sc{djgpp} Programs
12711 @cindex @sc{djgpp} debugging
12712 @cindex native @sc{djgpp} debugging
12713 @cindex MS-DOS-specific commands
12716 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
12717 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
12718 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
12719 top of real-mode DOS systems and their emulations.
12721 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
12722 defines a few commands specific to the @sc{djgpp} port. This
12723 subsection describes those commands.
12728 This is a prefix of @sc{djgpp}-specific commands which print
12729 information about the target system and important OS structures.
12732 @cindex MS-DOS system info
12733 @cindex free memory information (MS-DOS)
12734 @item info dos sysinfo
12735 This command displays assorted information about the underlying
12736 platform: the CPU type and features, the OS version and flavor, the
12737 DPMI version, and the available conventional and DPMI memory.
12742 @cindex segment descriptor tables
12743 @cindex descriptor tables display
12745 @itemx info dos ldt
12746 @itemx info dos idt
12747 These 3 commands display entries from, respectively, Global, Local,
12748 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
12749 tables are data structures which store a descriptor for each segment
12750 that is currently in use. The segment's selector is an index into a
12751 descriptor table; the table entry for that index holds the
12752 descriptor's base address and limit, and its attributes and access
12755 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
12756 segment (used for both data and the stack), and a DOS segment (which
12757 allows access to DOS/BIOS data structures and absolute addresses in
12758 conventional memory). However, the DPMI host will usually define
12759 additional segments in order to support the DPMI environment.
12761 @cindex garbled pointers
12762 These commands allow to display entries from the descriptor tables.
12763 Without an argument, all entries from the specified table are
12764 displayed. An argument, which should be an integer expression, means
12765 display a single entry whose index is given by the argument. For
12766 example, here's a convenient way to display information about the
12767 debugged program's data segment:
12770 @exdent @code{(@value{GDBP}) info dos ldt $ds}
12771 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
12775 This comes in handy when you want to see whether a pointer is outside
12776 the data segment's limit (i.e.@: @dfn{garbled}).
12778 @cindex page tables display (MS-DOS)
12780 @itemx info dos pte
12781 These two commands display entries from, respectively, the Page
12782 Directory and the Page Tables. Page Directories and Page Tables are
12783 data structures which control how virtual memory addresses are mapped
12784 into physical addresses. A Page Table includes an entry for every
12785 page of memory that is mapped into the program's address space; there
12786 may be several Page Tables, each one holding up to 4096 entries. A
12787 Page Directory has up to 4096 entries, one each for every Page Table
12788 that is currently in use.
12790 Without an argument, @kbd{info dos pde} displays the entire Page
12791 Directory, and @kbd{info dos pte} displays all the entries in all of
12792 the Page Tables. An argument, an integer expression, given to the
12793 @kbd{info dos pde} command means display only that entry from the Page
12794 Directory table. An argument given to the @kbd{info dos pte} command
12795 means display entries from a single Page Table, the one pointed to by
12796 the specified entry in the Page Directory.
12798 @cindex direct memory access (DMA) on MS-DOS
12799 These commands are useful when your program uses @dfn{DMA} (Direct
12800 Memory Access), which needs physical addresses to program the DMA
12803 These commands are supported only with some DPMI servers.
12805 @cindex physical address from linear address
12806 @item info dos address-pte @var{addr}
12807 This command displays the Page Table entry for a specified linear
12808 address. The argument @var{addr} is a linear address which should
12809 already have the appropriate segment's base address added to it,
12810 because this command accepts addresses which may belong to @emph{any}
12811 segment. For example, here's how to display the Page Table entry for
12812 the page where a variable @code{i} is stored:
12815 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
12816 @exdent @code{Page Table entry for address 0x11a00d30:}
12817 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
12821 This says that @code{i} is stored at offset @code{0xd30} from the page
12822 whose physical base address is @code{0x02698000}, and shows all the
12823 attributes of that page.
12825 Note that you must cast the addresses of variables to a @code{char *},
12826 since otherwise the value of @code{__djgpp_base_address}, the base
12827 address of all variables and functions in a @sc{djgpp} program, will
12828 be added using the rules of C pointer arithmetics: if @code{i} is
12829 declared an @code{int}, @value{GDBN} will add 4 times the value of
12830 @code{__djgpp_base_address} to the address of @code{i}.
12832 Here's another example, it displays the Page Table entry for the
12836 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
12837 @exdent @code{Page Table entry for address 0x29110:}
12838 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
12842 (The @code{+ 3} offset is because the transfer buffer's address is the
12843 3rd member of the @code{_go32_info_block} structure.) The output
12844 clearly shows that this DPMI server maps the addresses in conventional
12845 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
12846 linear (@code{0x29110}) addresses are identical.
12848 This command is supported only with some DPMI servers.
12851 @cindex DOS serial data link, remote debugging
12852 In addition to native debugging, the DJGPP port supports remote
12853 debugging via a serial data link. The following commands are specific
12854 to remote serial debugging in the DJGPP port of @value{GDBN}.
12857 @kindex set com1base
12858 @kindex set com1irq
12859 @kindex set com2base
12860 @kindex set com2irq
12861 @kindex set com3base
12862 @kindex set com3irq
12863 @kindex set com4base
12864 @kindex set com4irq
12865 @item set com1base @var{addr}
12866 This command sets the base I/O port address of the @file{COM1} serial
12869 @item set com1irq @var{irq}
12870 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
12871 for the @file{COM1} serial port.
12873 There are similar commands @samp{set com2base}, @samp{set com3irq},
12874 etc.@: for setting the port address and the @code{IRQ} lines for the
12877 @kindex show com1base
12878 @kindex show com1irq
12879 @kindex show com2base
12880 @kindex show com2irq
12881 @kindex show com3base
12882 @kindex show com3irq
12883 @kindex show com4base
12884 @kindex show com4irq
12885 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
12886 display the current settings of the base address and the @code{IRQ}
12887 lines used by the COM ports.
12890 @kindex info serial
12891 @cindex DOS serial port status
12892 This command prints the status of the 4 DOS serial ports. For each
12893 port, it prints whether it's active or not, its I/O base address and
12894 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
12895 counts of various errors encountered so far.
12899 @node Cygwin Native
12900 @subsection Features for Debugging MS Windows PE executables
12901 @cindex MS Windows debugging
12902 @cindex native Cygwin debugging
12903 @cindex Cygwin-specific commands
12905 @value{GDBN} supports native debugging of MS Windows programs, including
12906 DLLs with and without symbolic debugging information. There are various
12907 additional Cygwin-specific commands, described in this subsection. The
12908 subsubsection @pxref{Non-debug DLL symbols} describes working with DLLs
12909 that have no debugging symbols.
12915 This is a prefix of MS Windows specific commands which print
12916 information about the target system and important OS structures.
12918 @item info w32 selector
12919 This command displays information returned by
12920 the Win32 API @code{GetThreadSelectorEntry} function.
12921 It takes an optional argument that is evaluated to
12922 a long value to give the information about this given selector.
12923 Without argument, this command displays information
12924 about the the six segment registers.
12928 This is a Cygwin specific alias of info shared.
12930 @kindex dll-symbols
12932 This command loads symbols from a dll similarly to
12933 add-sym command but without the need to specify a base address.
12935 @kindex set new-console
12936 @item set new-console @var{mode}
12937 If @var{mode} is @code{on} the debuggee will
12938 be started in a new console on next start.
12939 If @var{mode} is @code{off}i, the debuggee will
12940 be started in the same console as the debugger.
12942 @kindex show new-console
12943 @item show new-console
12944 Displays whether a new console is used
12945 when the debuggee is started.
12947 @kindex set new-group
12948 @item set new-group @var{mode}
12949 This boolean value controls whether the debuggee should
12950 start a new group or stay in the same group as the debugger.
12951 This affects the way the Windows OS handles
12954 @kindex show new-group
12955 @item show new-group
12956 Displays current value of new-group boolean.
12958 @kindex set debugevents
12959 @item set debugevents
12960 This boolean value adds debug output concerning events seen by the debugger.
12962 @kindex set debugexec
12963 @item set debugexec
12964 This boolean value adds debug output concerning execute events
12965 seen by the debugger.
12967 @kindex set debugexceptions
12968 @item set debugexceptions
12969 This boolean value adds debug ouptut concerning exception events
12970 seen by the debugger.
12972 @kindex set debugmemory
12973 @item set debugmemory
12974 This boolean value adds debug ouptut concerning memory events
12975 seen by the debugger.
12979 This boolean values specifies whether the debuggee is called
12980 via a shell or directly (default value is on).
12984 Displays if the debuggee will be started with a shell.
12989 * Non-debug DLL symbols:: Support for DLLs without debugging symbols
12992 @node Non-debug DLL symbols
12993 @subsubsection Support for DLLs without debugging symbols
12994 @cindex DLLs with no debugging symbols
12995 @cindex Minimal symbols and DLLs
12997 Very often on windows, some of the DLLs that your program relies on do
12998 not include symbolic debugging information (for example,
12999 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
13000 symbols in a DLL, it relies on the minimal amount of symbolic
13001 information contained in the DLL's export table. This subsubsection
13002 describes working with such symbols, known internally to @value{GDBN} as
13003 ``minimal symbols''.
13005 Note that before the debugged program has started execution, no DLLs
13006 will have been loaded. The easiest way around this problem is simply to
13007 start the program --- either by setting a breakpoint or letting the
13008 program run once to completion. It is also possible to force
13009 @value{GDBN} to load a particular DLL before starting the executable ---
13010 see the shared library information in @pxref{Files} or the
13011 @code{dll-symbols} command in @pxref{Cygwin Native}. Currently,
13012 explicitly loading symbols from a DLL with no debugging information will
13013 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
13014 which may adversely affect symbol lookup performance.
13016 @subsubsection DLL name prefixes
13018 In keeping with the naming conventions used by the Microsoft debugging
13019 tools, DLL export symbols are made available with a prefix based on the
13020 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
13021 also entered into the symbol table, so @code{CreateFileA} is often
13022 sufficient. In some cases there will be name clashes within a program
13023 (particularly if the executable itself includes full debugging symbols)
13024 necessitating the use of the fully qualified name when referring to the
13025 contents of the DLL. Use single-quotes around the name to avoid the
13026 exclamation mark (``!'') being interpreted as a language operator.
13028 Note that the internal name of the DLL may be all upper-case, even
13029 though the file name of the DLL is lower-case, or vice-versa. Since
13030 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
13031 some confusion. If in doubt, try the @code{info functions} and
13032 @code{info variables} commands or even @code{maint print msymbols} (see
13033 @pxref{Symbols}). Here's an example:
13036 (@value{GDBP}) info function CreateFileA
13037 All functions matching regular expression "CreateFileA":
13039 Non-debugging symbols:
13040 0x77e885f4 CreateFileA
13041 0x77e885f4 KERNEL32!CreateFileA
13045 (@value{GDBP}) info function !
13046 All functions matching regular expression "!":
13048 Non-debugging symbols:
13049 0x6100114c cygwin1!__assert
13050 0x61004034 cygwin1!_dll_crt0@@0
13051 0x61004240 cygwin1!dll_crt0(per_process *)
13055 @subsubsection Working with minimal symbols
13057 Symbols extracted from a DLL's export table do not contain very much
13058 type information. All that @value{GDBN} can do is guess whether a symbol
13059 refers to a function or variable depending on the linker section that
13060 contains the symbol. Also note that the actual contents of the memory
13061 contained in a DLL are not available unless the program is running. This
13062 means that you cannot examine the contents of a variable or disassemble
13063 a function within a DLL without a running program.
13065 Variables are generally treated as pointers and dereferenced
13066 automatically. For this reason, it is often necessary to prefix a
13067 variable name with the address-of operator (``&'') and provide explicit
13068 type information in the command. Here's an example of the type of
13072 (@value{GDBP}) print 'cygwin1!__argv'
13077 (@value{GDBP}) x 'cygwin1!__argv'
13078 0x10021610: "\230y\""
13081 And two possible solutions:
13084 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
13085 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
13089 (@value{GDBP}) x/2x &'cygwin1!__argv'
13090 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
13091 (@value{GDBP}) x/x 0x10021608
13092 0x10021608: 0x0022fd98
13093 (@value{GDBP}) x/s 0x0022fd98
13094 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
13097 Setting a break point within a DLL is possible even before the program
13098 starts execution. However, under these circumstances, @value{GDBN} can't
13099 examine the initial instructions of the function in order to skip the
13100 function's frame set-up code. You can work around this by using ``*&''
13101 to set the breakpoint at a raw memory address:
13104 (@value{GDBP}) break *&'python22!PyOS_Readline'
13105 Breakpoint 1 at 0x1e04eff0
13108 The author of these extensions is not entirely convinced that setting a
13109 break point within a shared DLL like @file{kernel32.dll} is completely
13113 @subsection Commands specific to @sc{gnu} Hurd systems
13114 @cindex @sc{gnu} Hurd debugging
13116 This subsection describes @value{GDBN} commands specific to the
13117 @sc{gnu} Hurd native debugging.
13122 @kindex set signals@r{, Hurd command}
13123 @kindex set sigs@r{, Hurd command}
13124 This command toggles the state of inferior signal interception by
13125 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
13126 affected by this command. @code{sigs} is a shorthand alias for
13131 @kindex show signals@r{, Hurd command}
13132 @kindex show sigs@r{, Hurd command}
13133 Show the current state of intercepting inferior's signals.
13135 @item set signal-thread
13136 @itemx set sigthread
13137 @kindex set signal-thread
13138 @kindex set sigthread
13139 This command tells @value{GDBN} which thread is the @code{libc} signal
13140 thread. That thread is run when a signal is delivered to a running
13141 process. @code{set sigthread} is the shorthand alias of @code{set
13144 @item show signal-thread
13145 @itemx show sigthread
13146 @kindex show signal-thread
13147 @kindex show sigthread
13148 These two commands show which thread will run when the inferior is
13149 delivered a signal.
13152 @kindex set stopped@r{, Hurd command}
13153 This commands tells @value{GDBN} that the inferior process is stopped,
13154 as with the @code{SIGSTOP} signal. The stopped process can be
13155 continued by delivering a signal to it.
13158 @kindex show stopped@r{, Hurd command}
13159 This command shows whether @value{GDBN} thinks the debuggee is
13162 @item set exceptions
13163 @kindex set exceptions@r{, Hurd command}
13164 Use this command to turn off trapping of exceptions in the inferior.
13165 When exception trapping is off, neither breakpoints nor
13166 single-stepping will work. To restore the default, set exception
13169 @item show exceptions
13170 @kindex show exceptions@r{, Hurd command}
13171 Show the current state of trapping exceptions in the inferior.
13173 @item set task pause
13174 @kindex set task@r{, Hurd commands}
13175 @cindex task attributes (@sc{gnu} Hurd)
13176 @cindex pause current task (@sc{gnu} Hurd)
13177 This command toggles task suspension when @value{GDBN} has control.
13178 Setting it to on takes effect immediately, and the task is suspended
13179 whenever @value{GDBN} gets control. Setting it to off will take
13180 effect the next time the inferior is continued. If this option is set
13181 to off, you can use @code{set thread default pause on} or @code{set
13182 thread pause on} (see below) to pause individual threads.
13184 @item show task pause
13185 @kindex show task@r{, Hurd commands}
13186 Show the current state of task suspension.
13188 @item set task detach-suspend-count
13189 @cindex task suspend count
13190 @cindex detach from task, @sc{gnu} Hurd
13191 This command sets the suspend count the task will be left with when
13192 @value{GDBN} detaches from it.
13194 @item show task detach-suspend-count
13195 Show the suspend count the task will be left with when detaching.
13197 @item set task exception-port
13198 @itemx set task excp
13199 @cindex task exception port, @sc{gnu} Hurd
13200 This command sets the task exception port to which @value{GDBN} will
13201 forward exceptions. The argument should be the value of the @dfn{send
13202 rights} of the task. @code{set task excp} is a shorthand alias.
13204 @item set noninvasive
13205 @cindex noninvasive task options
13206 This command switches @value{GDBN} to a mode that is the least
13207 invasive as far as interfering with the inferior is concerned. This
13208 is the same as using @code{set task pause}, @code{set exceptions}, and
13209 @code{set signals} to values opposite to the defaults.
13211 @item info send-rights
13212 @itemx info receive-rights
13213 @itemx info port-rights
13214 @itemx info port-sets
13215 @itemx info dead-names
13218 @cindex send rights, @sc{gnu} Hurd
13219 @cindex receive rights, @sc{gnu} Hurd
13220 @cindex port rights, @sc{gnu} Hurd
13221 @cindex port sets, @sc{gnu} Hurd
13222 @cindex dead names, @sc{gnu} Hurd
13223 These commands display information about, respectively, send rights,
13224 receive rights, port rights, port sets, and dead names of a task.
13225 There are also shorthand aliases: @code{info ports} for @code{info
13226 port-rights} and @code{info psets} for @code{info port-sets}.
13228 @item set thread pause
13229 @kindex set thread@r{, Hurd command}
13230 @cindex thread properties, @sc{gnu} Hurd
13231 @cindex pause current thread (@sc{gnu} Hurd)
13232 This command toggles current thread suspension when @value{GDBN} has
13233 control. Setting it to on takes effect immediately, and the current
13234 thread is suspended whenever @value{GDBN} gets control. Setting it to
13235 off will take effect the next time the inferior is continued.
13236 Normally, this command has no effect, since when @value{GDBN} has
13237 control, the whole task is suspended. However, if you used @code{set
13238 task pause off} (see above), this command comes in handy to suspend
13239 only the current thread.
13241 @item show thread pause
13242 @kindex show thread@r{, Hurd command}
13243 This command shows the state of current thread suspension.
13245 @item set thread run
13246 This comamnd sets whether the current thread is allowed to run.
13248 @item show thread run
13249 Show whether the current thread is allowed to run.
13251 @item set thread detach-suspend-count
13252 @cindex thread suspend count, @sc{gnu} Hurd
13253 @cindex detach from thread, @sc{gnu} Hurd
13254 This command sets the suspend count @value{GDBN} will leave on a
13255 thread when detaching. This number is relative to the suspend count
13256 found by @value{GDBN} when it notices the thread; use @code{set thread
13257 takeover-suspend-count} to force it to an absolute value.
13259 @item show thread detach-suspend-count
13260 Show the suspend count @value{GDBN} will leave on the thread when
13263 @item set thread exception-port
13264 @itemx set thread excp
13265 Set the thread exception port to which to forward exceptions. This
13266 overrides the port set by @code{set task exception-port} (see above).
13267 @code{set thread excp} is the shorthand alias.
13269 @item set thread takeover-suspend-count
13270 Normally, @value{GDBN}'s thread suspend counts are relative to the
13271 value @value{GDBN} finds when it notices each thread. This command
13272 changes the suspend counts to be absolute instead.
13274 @item set thread default
13275 @itemx show thread default
13276 @cindex thread default settings, @sc{gnu} Hurd
13277 Each of the above @code{set thread} commands has a @code{set thread
13278 default} counterpart (e.g., @code{set thread default pause}, @code{set
13279 thread default exception-port}, etc.). The @code{thread default}
13280 variety of commands sets the default thread properties for all
13281 threads; you can then change the properties of individual threads with
13282 the non-default commands.
13287 @subsection QNX Neutrino
13288 @cindex QNX Neutrino
13290 @value{GDBN} provides the following commands specific to the QNX
13294 @item set debug nto-debug
13295 @kindex set debug nto-debug
13296 When set to on, enables debugging messages specific to the QNX
13299 @item show debug nto-debug
13300 @kindex show debug nto-debug
13301 Show the current state of QNX Neutrino messages.
13306 @section Embedded Operating Systems
13308 This section describes configurations involving the debugging of
13309 embedded operating systems that are available for several different
13313 * VxWorks:: Using @value{GDBN} with VxWorks
13316 @value{GDBN} includes the ability to debug programs running on
13317 various real-time operating systems.
13320 @subsection Using @value{GDBN} with VxWorks
13326 @kindex target vxworks
13327 @item target vxworks @var{machinename}
13328 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
13329 is the target system's machine name or IP address.
13333 On VxWorks, @code{load} links @var{filename} dynamically on the
13334 current target system as well as adding its symbols in @value{GDBN}.
13336 @value{GDBN} enables developers to spawn and debug tasks running on networked
13337 VxWorks targets from a Unix host. Already-running tasks spawned from
13338 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
13339 both the Unix host and on the VxWorks target. The program
13340 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
13341 installed with the name @code{vxgdb}, to distinguish it from a
13342 @value{GDBN} for debugging programs on the host itself.)
13345 @item VxWorks-timeout @var{args}
13346 @kindex vxworks-timeout
13347 All VxWorks-based targets now support the option @code{vxworks-timeout}.
13348 This option is set by the user, and @var{args} represents the number of
13349 seconds @value{GDBN} waits for responses to rpc's. You might use this if
13350 your VxWorks target is a slow software simulator or is on the far side
13351 of a thin network line.
13354 The following information on connecting to VxWorks was current when
13355 this manual was produced; newer releases of VxWorks may use revised
13358 @findex INCLUDE_RDB
13359 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
13360 to include the remote debugging interface routines in the VxWorks
13361 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
13362 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
13363 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
13364 source debugging task @code{tRdbTask} when VxWorks is booted. For more
13365 information on configuring and remaking VxWorks, see the manufacturer's
13367 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
13369 Once you have included @file{rdb.a} in your VxWorks system image and set
13370 your Unix execution search path to find @value{GDBN}, you are ready to
13371 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
13372 @code{vxgdb}, depending on your installation).
13374 @value{GDBN} comes up showing the prompt:
13381 * VxWorks Connection:: Connecting to VxWorks
13382 * VxWorks Download:: VxWorks download
13383 * VxWorks Attach:: Running tasks
13386 @node VxWorks Connection
13387 @subsubsection Connecting to VxWorks
13389 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
13390 network. To connect to a target whose host name is ``@code{tt}'', type:
13393 (vxgdb) target vxworks tt
13397 @value{GDBN} displays messages like these:
13400 Attaching remote machine across net...
13405 @value{GDBN} then attempts to read the symbol tables of any object modules
13406 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
13407 these files by searching the directories listed in the command search
13408 path (@pxref{Environment, ,Your program's environment}); if it fails
13409 to find an object file, it displays a message such as:
13412 prog.o: No such file or directory.
13415 When this happens, add the appropriate directory to the search path with
13416 the @value{GDBN} command @code{path}, and execute the @code{target}
13419 @node VxWorks Download
13420 @subsubsection VxWorks download
13422 @cindex download to VxWorks
13423 If you have connected to the VxWorks target and you want to debug an
13424 object that has not yet been loaded, you can use the @value{GDBN}
13425 @code{load} command to download a file from Unix to VxWorks
13426 incrementally. The object file given as an argument to the @code{load}
13427 command is actually opened twice: first by the VxWorks target in order
13428 to download the code, then by @value{GDBN} in order to read the symbol
13429 table. This can lead to problems if the current working directories on
13430 the two systems differ. If both systems have NFS mounted the same
13431 filesystems, you can avoid these problems by using absolute paths.
13432 Otherwise, it is simplest to set the working directory on both systems
13433 to the directory in which the object file resides, and then to reference
13434 the file by its name, without any path. For instance, a program
13435 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
13436 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
13437 program, type this on VxWorks:
13440 -> cd "@var{vxpath}/vw/demo/rdb"
13444 Then, in @value{GDBN}, type:
13447 (vxgdb) cd @var{hostpath}/vw/demo/rdb
13448 (vxgdb) load prog.o
13451 @value{GDBN} displays a response similar to this:
13454 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
13457 You can also use the @code{load} command to reload an object module
13458 after editing and recompiling the corresponding source file. Note that
13459 this makes @value{GDBN} delete all currently-defined breakpoints,
13460 auto-displays, and convenience variables, and to clear the value
13461 history. (This is necessary in order to preserve the integrity of
13462 debugger's data structures that reference the target system's symbol
13465 @node VxWorks Attach
13466 @subsubsection Running tasks
13468 @cindex running VxWorks tasks
13469 You can also attach to an existing task using the @code{attach} command as
13473 (vxgdb) attach @var{task}
13477 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
13478 or suspended when you attach to it. Running tasks are suspended at
13479 the time of attachment.
13481 @node Embedded Processors
13482 @section Embedded Processors
13484 This section goes into details specific to particular embedded
13487 @cindex send command to simulator
13488 Whenever a specific embedded processor has a simulator, @value{GDBN}
13489 allows to send an arbitrary command to the simulator.
13492 @item sim @var{command}
13493 @kindex sim@r{, a command}
13494 Send an arbitrary @var{command} string to the simulator. Consult the
13495 documentation for the specific simulator in use for information about
13496 acceptable commands.
13502 * H8/300:: Renesas H8/300
13503 * H8/500:: Renesas H8/500
13504 * M32R/D:: Renesas M32R/D
13505 * M68K:: Motorola M68K
13506 * MIPS Embedded:: MIPS Embedded
13507 * OpenRISC 1000:: OpenRisc 1000
13508 * PA:: HP PA Embedded
13511 * Sparclet:: Tsqware Sparclet
13512 * Sparclite:: Fujitsu Sparclite
13513 * ST2000:: Tandem ST2000
13514 * Z8000:: Zilog Z8000
13517 * Super-H:: Renesas Super-H
13518 * WinCE:: Windows CE child processes
13527 @item target rdi @var{dev}
13528 ARM Angel monitor, via RDI library interface to ADP protocol. You may
13529 use this target to communicate with both boards running the Angel
13530 monitor, or with the EmbeddedICE JTAG debug device.
13533 @item target rdp @var{dev}
13538 @value{GDBN} provides the following ARM-specific commands:
13541 @item set arm disassembler
13543 This commands selects from a list of disassembly styles. The
13544 @code{"std"} style is the standard style.
13546 @item show arm disassembler
13548 Show the current disassembly style.
13550 @item set arm apcs32
13551 @cindex ARM 32-bit mode
13552 This command toggles ARM operation mode between 32-bit and 26-bit.
13554 @item show arm apcs32
13555 Display the current usage of the ARM 32-bit mode.
13557 @item set arm fpu @var{fputype}
13558 This command sets the ARM floating-point unit (FPU) type. The
13559 argument @var{fputype} can be one of these:
13563 Determine the FPU type by querying the OS ABI.
13565 Software FPU, with mixed-endian doubles on little-endian ARM
13568 GCC-compiled FPA co-processor.
13570 Software FPU with pure-endian doubles.
13576 Show the current type of the FPU.
13579 This command forces @value{GDBN} to use the specified ABI.
13582 Show the currently used ABI.
13584 @item set debug arm
13585 Toggle whether to display ARM-specific debugging messages from the ARM
13586 target support subsystem.
13588 @item show debug arm
13589 Show whether ARM-specific debugging messages are enabled.
13592 The following commands are available when an ARM target is debugged
13593 using the RDI interface:
13596 @item rdilogfile @r{[}@var{file}@r{]}
13598 @cindex ADP (Angel Debugger Protocol) logging
13599 Set the filename for the ADP (Angel Debugger Protocol) packet log.
13600 With an argument, sets the log file to the specified @var{file}. With
13601 no argument, show the current log file name. The default log file is
13604 @item rdilogenable @r{[}@var{arg}@r{]}
13605 @kindex rdilogenable
13606 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
13607 enables logging, with an argument 0 or @code{"no"} disables it. With
13608 no arguments displays the current setting. When logging is enabled,
13609 ADP packets exchanged between @value{GDBN} and the RDI target device
13610 are logged to a file.
13612 @item set rdiromatzero
13613 @kindex set rdiromatzero
13614 @cindex ROM at zero address, RDI
13615 Tell @value{GDBN} whether the target has ROM at address 0. If on,
13616 vector catching is disabled, so that zero address can be used. If off
13617 (the default), vector catching is enabled. For this command to take
13618 effect, it needs to be invoked prior to the @code{target rdi} command.
13620 @item show rdiromatzero
13621 @kindex show rdiromatzero
13622 Show the current setting of ROM at zero address.
13624 @item set rdiheartbeat
13625 @kindex set rdiheartbeat
13626 @cindex RDI heartbeat
13627 Enable or disable RDI heartbeat packets. It is not recommended to
13628 turn on this option, since it confuses ARM and EPI JTAG interface, as
13629 well as the Angel monitor.
13631 @item show rdiheartbeat
13632 @kindex show rdiheartbeat
13633 Show the setting of RDI heartbeat packets.
13638 @subsection Renesas H8/300
13642 @kindex target hms@r{, with H8/300}
13643 @item target hms @var{dev}
13644 A Renesas SH, H8/300, or H8/500 board, attached via serial line to your host.
13645 Use special commands @code{device} and @code{speed} to control the serial
13646 line and the communications speed used.
13648 @kindex target e7000@r{, with H8/300}
13649 @item target e7000 @var{dev}
13650 E7000 emulator for Renesas H8 and SH.
13652 @kindex target sh3@r{, with H8/300}
13653 @kindex target sh3e@r{, with H8/300}
13654 @item target sh3 @var{dev}
13655 @itemx target sh3e @var{dev}
13656 Renesas SH-3 and SH-3E target systems.
13660 @cindex download to H8/300 or H8/500
13661 @cindex H8/300 or H8/500 download
13662 @cindex download to Renesas SH
13663 @cindex Renesas SH download
13664 When you select remote debugging to a Renesas SH, H8/300, or H8/500
13665 board, the @code{load} command downloads your program to the Renesas
13666 board and also opens it as the current executable target for
13667 @value{GDBN} on your host (like the @code{file} command).
13669 @value{GDBN} needs to know these things to talk to your
13670 Renesas SH, H8/300, or H8/500:
13674 that you want to use @samp{target hms}, the remote debugging interface
13675 for Renesas microprocessors, or @samp{target e7000}, the in-circuit
13676 emulator for the Renesas SH and the Renesas 300H. (@samp{target hms} is
13677 the default when @value{GDBN} is configured specifically for the Renesas SH,
13678 H8/300, or H8/500.)
13681 what serial device connects your host to your Renesas board (the first
13682 serial device available on your host is the default).
13685 what speed to use over the serial device.
13689 * Renesas Boards:: Connecting to Renesas boards.
13690 * Renesas ICE:: Using the E7000 In-Circuit Emulator.
13691 * Renesas Special:: Special @value{GDBN} commands for Renesas micros.
13694 @node Renesas Boards
13695 @subsubsection Connecting to Renesas boards
13697 @c only for Unix hosts
13699 @cindex serial device, Renesas micros
13700 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
13701 need to explicitly set the serial device. The default @var{port} is the
13702 first available port on your host. This is only necessary on Unix
13703 hosts, where it is typically something like @file{/dev/ttya}.
13706 @cindex serial line speed, Renesas micros
13707 @code{@value{GDBN}} has another special command to set the communications
13708 speed: @samp{speed @var{bps}}. This command also is only used from Unix
13709 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
13710 the DOS @code{mode} command (for instance,
13711 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
13713 The @samp{device} and @samp{speed} commands are available only when you
13714 use a Unix host to debug your Renesas microprocessor programs. If you
13716 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
13717 called @code{asynctsr} to communicate with the development board
13718 through a PC serial port. You must also use the DOS @code{mode} command
13719 to set up the serial port on the DOS side.
13721 The following sample session illustrates the steps needed to start a
13722 program under @value{GDBN} control on an H8/300. The example uses a
13723 sample H8/300 program called @file{t.x}. The procedure is the same for
13724 the Renesas SH and the H8/500.
13726 First hook up your development board. In this example, we use a
13727 board attached to serial port @code{COM2}; if you use a different serial
13728 port, substitute its name in the argument of the @code{mode} command.
13729 When you call @code{asynctsr}, the auxiliary comms program used by the
13730 debugger, you give it just the numeric part of the serial port's name;
13731 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
13735 C:\H8300\TEST> asynctsr 2
13736 C:\H8300\TEST> mode com2:9600,n,8,1,p
13738 Resident portion of MODE loaded
13740 COM2: 9600, n, 8, 1, p
13745 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
13746 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
13747 disable it, or even boot without it, to use @code{asynctsr} to control
13748 your development board.
13751 @kindex target hms@r{, and serial protocol}
13752 Now that serial communications are set up, and the development board is
13753 connected, you can start up @value{GDBN}. Call @code{@value{GDBN}} with
13754 the name of your program as the argument. @code{@value{GDBN}} prompts
13755 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
13756 commands to begin your debugging session: @samp{target hms} to specify
13757 cross-debugging to the Renesas board, and the @code{load} command to
13758 download your program to the board. @code{load} displays the names of
13759 the program's sections, and a @samp{*} for each 2K of data downloaded.
13760 (If you want to refresh @value{GDBN} data on symbols or on the
13761 executable file without downloading, use the @value{GDBN} commands
13762 @code{file} or @code{symbol-file}. These commands, and @code{load}
13763 itself, are described in @ref{Files,,Commands to specify files}.)
13766 (eg-C:\H8300\TEST) @value{GDBP} t.x
13767 @value{GDBN} is free software and you are welcome to distribute copies
13768 of it under certain conditions; type "show copying" to see
13770 There is absolutely no warranty for @value{GDBN}; type "show warranty"
13772 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
13773 (@value{GDBP}) target hms
13774 Connected to remote H8/300 HMS system.
13775 (@value{GDBP}) load t.x
13776 .text : 0x8000 .. 0xabde ***********
13777 .data : 0xabde .. 0xad30 *
13778 .stack : 0xf000 .. 0xf014 *
13781 At this point, you're ready to run or debug your program. From here on,
13782 you can use all the usual @value{GDBN} commands. The @code{break} command
13783 sets breakpoints; the @code{run} command starts your program;
13784 @code{print} or @code{x} display data; the @code{continue} command
13785 resumes execution after stopping at a breakpoint. You can use the
13786 @code{help} command at any time to find out more about @value{GDBN} commands.
13788 Remember, however, that @emph{operating system} facilities aren't
13789 available on your development board; for example, if your program hangs,
13790 you can't send an interrupt---but you can press the @sc{reset} switch!
13792 Use the @sc{reset} button on the development board
13795 to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has
13796 no way to pass an interrupt signal to the development board); and
13799 to return to the @value{GDBN} command prompt after your program finishes
13800 normally. The communications protocol provides no other way for @value{GDBN}
13801 to detect program completion.
13804 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
13805 development board as a ``normal exit'' of your program.
13808 @subsubsection Using the E7000 in-circuit emulator
13810 @kindex target e7000@r{, with Renesas ICE}
13811 You can use the E7000 in-circuit emulator to develop code for either the
13812 Renesas SH or the H8/300H. Use one of these forms of the @samp{target
13813 e7000} command to connect @value{GDBN} to your E7000:
13816 @item target e7000 @var{port} @var{speed}
13817 Use this form if your E7000 is connected to a serial port. The
13818 @var{port} argument identifies what serial port to use (for example,
13819 @samp{com2}). The third argument is the line speed in bits per second
13820 (for example, @samp{9600}).
13822 @item target e7000 @var{hostname}
13823 If your E7000 is installed as a host on a TCP/IP network, you can just
13824 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
13827 The following special commands are available when debugging with the
13831 @item e7000 @var{command}
13833 @cindex send command to E7000 monitor
13834 This sends the specified @var{command} to the E7000 monitor.
13836 @item ftplogin @var{machine} @var{username} @var{password} @var{dir}
13837 @kindex ftplogin@r{, E7000}
13838 This command records information for subsequent interface with the
13839 E7000 monitor via the FTP protocol: @value{GDBN} will log into the
13840 named @var{machine} using specified @var{username} and @var{password},
13841 and then chdir to the named directory @var{dir}.
13843 @item ftpload @var{file}
13844 @kindex ftpload@r{, E7000}
13845 This command uses credentials recorded by @code{ftplogin} to fetch and
13846 load the named @var{file} from the E7000 monitor.
13849 @kindex drain@r{, E7000}
13850 This command drains any pending text buffers stored on the E7000.
13852 @item set usehardbreakpoints
13853 @itemx show usehardbreakpoints
13854 @kindex set usehardbreakpoints@r{, E7000}
13855 @kindex show usehardbreakpoints@r{, E7000}
13856 @cindex hardware breakpoints, and E7000
13857 These commands set and show the use of hardware breakpoints for all
13858 breakpoints. @xref{Set Breaks, hardware-assisted breakpoint}, for
13859 more information about using hardware breakpoints selectively.
13862 @node Renesas Special
13863 @subsubsection Special @value{GDBN} commands for Renesas micros
13865 Some @value{GDBN} commands are available only for the H8/300:
13869 @kindex set machine
13870 @kindex show machine
13871 @item set machine h8300
13872 @itemx set machine h8300h
13873 Condition @value{GDBN} for one of the two variants of the H8/300
13874 architecture with @samp{set machine}. You can use @samp{show machine}
13875 to check which variant is currently in effect.
13884 @kindex set memory @var{mod}
13885 @cindex memory models, H8/500
13886 @item set memory @var{mod}
13888 Specify which H8/500 memory model (@var{mod}) you are using with
13889 @samp{set memory}; check which memory model is in effect with @samp{show
13890 memory}. The accepted values for @var{mod} are @code{small},
13891 @code{big}, @code{medium}, and @code{compact}.
13896 @subsection Renesas M32R/D and M32R/SDI
13899 @kindex target m32r
13900 @item target m32r @var{dev}
13901 Renesas M32R/D ROM monitor.
13903 @kindex target m32rsdi
13904 @item target m32rsdi @var{dev}
13905 Renesas M32R SDI server, connected via parallel port to the board.
13908 The following @value{GDBN} commands are specific to the M32R monitor:
13911 @item set download-path @var{path}
13912 @kindex set download-path
13913 @cindex find downloadable @sc{srec} files (M32R)
13914 Set the default path for finding donwloadable @sc{srec} files.
13916 @item show download-path
13917 @kindex show download-path
13918 Show the default path for downloadable @sc{srec} files.
13920 @item set board-address @var{addr}
13921 @kindex set board-address
13922 @cindex M32-EVA target board address
13923 Set the IP address for the M32R-EVA target board.
13925 @item show board-address
13926 @kindex show board-address
13927 Show the current IP address of the target board.
13929 @item set server-address @var{addr}
13930 @kindex set server-address
13931 @cindex download server address (M32R)
13932 Set the IP address for the download server, which is the @value{GDBN}'s
13935 @item show server-address
13936 @kindex show server-address
13937 Display the IP address of the download server.
13939 @item upload @r{[}@var{file}@r{]}
13940 @kindex upload@r{, M32R}
13941 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
13942 upload capability. If no @var{file} argument is given, the current
13943 executable file is uploaded.
13945 @item tload @r{[}@var{file}@r{]}
13946 @kindex tload@r{, M32R}
13947 Test the @code{upload} command.
13950 The following commands are available for M32R/SDI:
13955 @cindex reset SDI connection, M32R
13956 This command resets the SDI connection.
13960 This command shows the SDI connection status.
13963 @kindex debug_chaos
13964 @cindex M32R/Chaos debugging
13965 Instructs the remote that M32R/Chaos debugging is to be used.
13967 @item use_debug_dma
13968 @kindex use_debug_dma
13969 Instructs the remote to use the DEBUG_DMA method of accessing memory.
13972 @kindex use_mon_code
13973 Instructs the remote to use the MON_CODE method of accessing memory.
13976 @kindex use_ib_break
13977 Instructs the remote to set breakpoints by IB break.
13979 @item use_dbt_break
13980 @kindex use_dbt_break
13981 Instructs the remote to set breakpoints by DBT.
13987 The Motorola m68k configuration includes ColdFire support, and
13988 target command for the following ROM monitors.
13992 @kindex target abug
13993 @item target abug @var{dev}
13994 ABug ROM monitor for M68K.
13996 @kindex target cpu32bug
13997 @item target cpu32bug @var{dev}
13998 CPU32BUG monitor, running on a CPU32 (M68K) board.
14000 @kindex target dbug
14001 @item target dbug @var{dev}
14002 dBUG ROM monitor for Motorola ColdFire.
14005 @item target est @var{dev}
14006 EST-300 ICE monitor, running on a CPU32 (M68K) board.
14008 @kindex target rom68k
14009 @item target rom68k @var{dev}
14010 ROM 68K monitor, running on an M68K IDP board.
14016 @kindex target rombug
14017 @item target rombug @var{dev}
14018 ROMBUG ROM monitor for OS/9000.
14022 @node MIPS Embedded
14023 @subsection MIPS Embedded
14025 @cindex MIPS boards
14026 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
14027 MIPS board attached to a serial line. This is available when
14028 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
14031 Use these @value{GDBN} commands to specify the connection to your target board:
14034 @item target mips @var{port}
14035 @kindex target mips @var{port}
14036 To run a program on the board, start up @code{@value{GDBP}} with the
14037 name of your program as the argument. To connect to the board, use the
14038 command @samp{target mips @var{port}}, where @var{port} is the name of
14039 the serial port connected to the board. If the program has not already
14040 been downloaded to the board, you may use the @code{load} command to
14041 download it. You can then use all the usual @value{GDBN} commands.
14043 For example, this sequence connects to the target board through a serial
14044 port, and loads and runs a program called @var{prog} through the
14048 host$ @value{GDBP} @var{prog}
14049 @value{GDBN} is free software and @dots{}
14050 (@value{GDBP}) target mips /dev/ttyb
14051 (@value{GDBP}) load @var{prog}
14055 @item target mips @var{hostname}:@var{portnumber}
14056 On some @value{GDBN} host configurations, you can specify a TCP
14057 connection (for instance, to a serial line managed by a terminal
14058 concentrator) instead of a serial port, using the syntax
14059 @samp{@var{hostname}:@var{portnumber}}.
14061 @item target pmon @var{port}
14062 @kindex target pmon @var{port}
14065 @item target ddb @var{port}
14066 @kindex target ddb @var{port}
14067 NEC's DDB variant of PMON for Vr4300.
14069 @item target lsi @var{port}
14070 @kindex target lsi @var{port}
14071 LSI variant of PMON.
14073 @kindex target r3900
14074 @item target r3900 @var{dev}
14075 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
14077 @kindex target array
14078 @item target array @var{dev}
14079 Array Tech LSI33K RAID controller board.
14085 @value{GDBN} also supports these special commands for MIPS targets:
14088 @item set mipsfpu double
14089 @itemx set mipsfpu single
14090 @itemx set mipsfpu none
14091 @itemx set mipsfpu auto
14092 @itemx show mipsfpu
14093 @kindex set mipsfpu
14094 @kindex show mipsfpu
14095 @cindex MIPS remote floating point
14096 @cindex floating point, MIPS remote
14097 If your target board does not support the MIPS floating point
14098 coprocessor, you should use the command @samp{set mipsfpu none} (if you
14099 need this, you may wish to put the command in your @value{GDBN} init
14100 file). This tells @value{GDBN} how to find the return value of
14101 functions which return floating point values. It also allows
14102 @value{GDBN} to avoid saving the floating point registers when calling
14103 functions on the board. If you are using a floating point coprocessor
14104 with only single precision floating point support, as on the @sc{r4650}
14105 processor, use the command @samp{set mipsfpu single}. The default
14106 double precision floating point coprocessor may be selected using
14107 @samp{set mipsfpu double}.
14109 In previous versions the only choices were double precision or no
14110 floating point, so @samp{set mipsfpu on} will select double precision
14111 and @samp{set mipsfpu off} will select no floating point.
14113 As usual, you can inquire about the @code{mipsfpu} variable with
14114 @samp{show mipsfpu}.
14116 @item set timeout @var{seconds}
14117 @itemx set retransmit-timeout @var{seconds}
14118 @itemx show timeout
14119 @itemx show retransmit-timeout
14120 @cindex @code{timeout}, MIPS protocol
14121 @cindex @code{retransmit-timeout}, MIPS protocol
14122 @kindex set timeout
14123 @kindex show timeout
14124 @kindex set retransmit-timeout
14125 @kindex show retransmit-timeout
14126 You can control the timeout used while waiting for a packet, in the MIPS
14127 remote protocol, with the @code{set timeout @var{seconds}} command. The
14128 default is 5 seconds. Similarly, you can control the timeout used while
14129 waiting for an acknowledgement of a packet with the @code{set
14130 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
14131 You can inspect both values with @code{show timeout} and @code{show
14132 retransmit-timeout}. (These commands are @emph{only} available when
14133 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
14135 The timeout set by @code{set timeout} does not apply when @value{GDBN}
14136 is waiting for your program to stop. In that case, @value{GDBN} waits
14137 forever because it has no way of knowing how long the program is going
14138 to run before stopping.
14140 @item set syn-garbage-limit @var{num}
14141 @kindex set syn-garbage-limit@r{, MIPS remote}
14142 @cindex synchronize with remote MIPS target
14143 Limit the maximum number of characters @value{GDBN} should ignore when
14144 it tries to synchronize with the remote target. The default is 10
14145 characters. Setting the limit to -1 means there's no limit.
14147 @item show syn-garbage-limit
14148 @kindex show syn-garbage-limit@r{, MIPS remote}
14149 Show the current limit on the number of characters to ignore when
14150 trying to synchronize with the remote system.
14152 @item set monitor-prompt @var{prompt}
14153 @kindex set monitor-prompt@r{, MIPS remote}
14154 @cindex remote monitor prompt
14155 Tell @value{GDBN} to expect the specified @var{prompt} string from the
14156 remote monitor. The default depends on the target:
14166 @item show monitor-prompt
14167 @kindex show monitor-prompt@r{, MIPS remote}
14168 Show the current strings @value{GDBN} expects as the prompt from the
14171 @item set monitor-warnings
14172 @kindex set monitor-warnings@r{, MIPS remote}
14173 Enable or disable monitor warnings about hardware breakpoints. This
14174 has effect only for the @code{lsi} target. When on, @value{GDBN} will
14175 display warning messages whose codes are returned by the @code{lsi}
14176 PMON monitor for breakpoint commands.
14178 @item show monitor-warnings
14179 @kindex show monitor-warnings@r{, MIPS remote}
14180 Show the current setting of printing monitor warnings.
14182 @item pmon @var{command}
14183 @kindex pmon@r{, MIPS remote}
14184 @cindex send PMON command
14185 This command allows sending an arbitrary @var{command} string to the
14186 monitor. The monitor must be in debug mode for this to work.
14189 @node OpenRISC 1000
14190 @subsection OpenRISC 1000
14191 @cindex OpenRISC 1000
14193 @cindex or1k boards
14194 See OR1k Architecture document (@uref{www.opencores.org}) for more information
14195 about platform and commands.
14199 @kindex target jtag
14200 @item target jtag jtag://@var{host}:@var{port}
14202 Connects to remote JTAG server.
14203 JTAG remote server can be either an or1ksim or JTAG server,
14204 connected via parallel port to the board.
14206 Example: @code{target jtag jtag://localhost:9999}
14209 @item or1ksim @var{command}
14210 If connected to @code{or1ksim} OpenRISC 1000 Architectural
14211 Simulator, proprietary commands can be executed.
14213 @kindex info or1k spr
14214 @item info or1k spr
14215 Displays spr groups.
14217 @item info or1k spr @var{group}
14218 @itemx info or1k spr @var{groupno}
14219 Displays register names in selected group.
14221 @item info or1k spr @var{group} @var{register}
14222 @itemx info or1k spr @var{register}
14223 @itemx info or1k spr @var{groupno} @var{registerno}
14224 @itemx info or1k spr @var{registerno}
14225 Shows information about specified spr register.
14228 @item spr @var{group} @var{register} @var{value}
14229 @itemx spr @var{register @var{value}}
14230 @itemx spr @var{groupno} @var{registerno @var{value}}
14231 @itemx spr @var{registerno @var{value}}
14232 Writes @var{value} to specified spr register.
14235 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
14236 It is very similar to @value{GDBN} trace, except it does not interfere with normal
14237 program execution and is thus much faster. Hardware breakpoints/watchpoint
14238 triggers can be set using:
14241 Load effective address/data
14243 Store effective address/data
14245 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
14250 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
14251 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
14253 @code{htrace} commands:
14254 @cindex OpenRISC 1000 htrace
14257 @item hwatch @var{conditional}
14258 Set hardware watchpoint on combination of Load/Store Effecive Address(es)
14259 or Data. For example:
14261 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14263 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14267 Display information about current HW trace configuration.
14269 @item htrace trigger @var{conditional}
14270 Set starting criteria for HW trace.
14272 @item htrace qualifier @var{conditional}
14273 Set acquisition qualifier for HW trace.
14275 @item htrace stop @var{conditional}
14276 Set HW trace stopping criteria.
14278 @item htrace record [@var{data}]*
14279 Selects the data to be recorded, when qualifier is met and HW trace was
14282 @item htrace enable
14283 @itemx htrace disable
14284 Enables/disables the HW trace.
14286 @item htrace rewind [@var{filename}]
14287 Clears currently recorded trace data.
14289 If filename is specified, new trace file is made and any newly collected data
14290 will be written there.
14292 @item htrace print [@var{start} [@var{len}]]
14293 Prints trace buffer, using current record configuration.
14295 @item htrace mode continuous
14296 Set continuous trace mode.
14298 @item htrace mode suspend
14299 Set suspend trace mode.
14304 @subsection PowerPC
14307 @kindex target dink32
14308 @item target dink32 @var{dev}
14309 DINK32 ROM monitor.
14311 @kindex target ppcbug
14312 @item target ppcbug @var{dev}
14313 @kindex target ppcbug1
14314 @item target ppcbug1 @var{dev}
14315 PPCBUG ROM monitor for PowerPC.
14318 @item target sds @var{dev}
14319 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
14322 @cindex SDS protocol
14323 The following commands specifi to the SDS protocol are supported
14327 @item set sdstimeout @var{nsec}
14328 @kindex set sdstimeout
14329 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
14330 default is 2 seconds.
14332 @item show sdstimeout
14333 @kindex show sdstimeout
14334 Show the current value of the SDS timeout.
14336 @item sds @var{command}
14337 @kindex sds@r{, a command}
14338 Send the specified @var{command} string to the SDS monitor.
14343 @subsection HP PA Embedded
14347 @kindex target op50n
14348 @item target op50n @var{dev}
14349 OP50N monitor, running on an OKI HPPA board.
14351 @kindex target w89k
14352 @item target w89k @var{dev}
14353 W89K monitor, running on a Winbond HPPA board.
14358 @subsection Renesas SH
14362 @kindex target hms@r{, with Renesas SH}
14363 @item target hms @var{dev}
14364 A Renesas SH board attached via serial line to your host. Use special
14365 commands @code{device} and @code{speed} to control the serial line and
14366 the communications speed used.
14368 @kindex target e7000@r{, with Renesas SH}
14369 @item target e7000 @var{dev}
14370 E7000 emulator for Renesas SH.
14372 @kindex target sh3@r{, with SH}
14373 @kindex target sh3e@r{, with SH}
14374 @item target sh3 @var{dev}
14375 @item target sh3e @var{dev}
14376 Renesas SH-3 and SH-3E target systems.
14381 @subsection Tsqware Sparclet
14385 @value{GDBN} enables developers to debug tasks running on
14386 Sparclet targets from a Unix host.
14387 @value{GDBN} uses code that runs on
14388 both the Unix host and on the Sparclet target. The program
14389 @code{@value{GDBP}} is installed and executed on the Unix host.
14392 @item remotetimeout @var{args}
14393 @kindex remotetimeout
14394 @value{GDBN} supports the option @code{remotetimeout}.
14395 This option is set by the user, and @var{args} represents the number of
14396 seconds @value{GDBN} waits for responses.
14399 @cindex compiling, on Sparclet
14400 When compiling for debugging, include the options @samp{-g} to get debug
14401 information and @samp{-Ttext} to relocate the program to where you wish to
14402 load it on the target. You may also want to add the options @samp{-n} or
14403 @samp{-N} in order to reduce the size of the sections. Example:
14406 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
14409 You can use @code{objdump} to verify that the addresses are what you intended:
14412 sparclet-aout-objdump --headers --syms prog
14415 @cindex running, on Sparclet
14417 your Unix execution search path to find @value{GDBN}, you are ready to
14418 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
14419 (or @code{sparclet-aout-gdb}, depending on your installation).
14421 @value{GDBN} comes up showing the prompt:
14428 * Sparclet File:: Setting the file to debug
14429 * Sparclet Connection:: Connecting to Sparclet
14430 * Sparclet Download:: Sparclet download
14431 * Sparclet Execution:: Running and debugging
14434 @node Sparclet File
14435 @subsubsection Setting file to debug
14437 The @value{GDBN} command @code{file} lets you choose with program to debug.
14440 (gdbslet) file prog
14444 @value{GDBN} then attempts to read the symbol table of @file{prog}.
14445 @value{GDBN} locates
14446 the file by searching the directories listed in the command search
14448 If the file was compiled with debug information (option "-g"), source
14449 files will be searched as well.
14450 @value{GDBN} locates
14451 the source files by searching the directories listed in the directory search
14452 path (@pxref{Environment, ,Your program's environment}).
14454 to find a file, it displays a message such as:
14457 prog: No such file or directory.
14460 When this happens, add the appropriate directories to the search paths with
14461 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
14462 @code{target} command again.
14464 @node Sparclet Connection
14465 @subsubsection Connecting to Sparclet
14467 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
14468 To connect to a target on serial port ``@code{ttya}'', type:
14471 (gdbslet) target sparclet /dev/ttya
14472 Remote target sparclet connected to /dev/ttya
14473 main () at ../prog.c:3
14477 @value{GDBN} displays messages like these:
14483 @node Sparclet Download
14484 @subsubsection Sparclet download
14486 @cindex download to Sparclet
14487 Once connected to the Sparclet target,
14488 you can use the @value{GDBN}
14489 @code{load} command to download the file from the host to the target.
14490 The file name and load offset should be given as arguments to the @code{load}
14492 Since the file format is aout, the program must be loaded to the starting
14493 address. You can use @code{objdump} to find out what this value is. The load
14494 offset is an offset which is added to the VMA (virtual memory address)
14495 of each of the file's sections.
14496 For instance, if the program
14497 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
14498 and bss at 0x12010170, in @value{GDBN}, type:
14501 (gdbslet) load prog 0x12010000
14502 Loading section .text, size 0xdb0 vma 0x12010000
14505 If the code is loaded at a different address then what the program was linked
14506 to, you may need to use the @code{section} and @code{add-symbol-file} commands
14507 to tell @value{GDBN} where to map the symbol table.
14509 @node Sparclet Execution
14510 @subsubsection Running and debugging
14512 @cindex running and debugging Sparclet programs
14513 You can now begin debugging the task using @value{GDBN}'s execution control
14514 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
14515 manual for the list of commands.
14519 Breakpoint 1 at 0x12010000: file prog.c, line 3.
14521 Starting program: prog
14522 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
14523 3 char *symarg = 0;
14525 4 char *execarg = "hello!";
14530 @subsection Fujitsu Sparclite
14534 @kindex target sparclite
14535 @item target sparclite @var{dev}
14536 Fujitsu sparclite boards, used only for the purpose of loading.
14537 You must use an additional command to debug the program.
14538 For example: target remote @var{dev} using @value{GDBN} standard
14544 @subsection Tandem ST2000
14546 @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
14549 To connect your ST2000 to the host system, see the manufacturer's
14550 manual. Once the ST2000 is physically attached, you can run:
14553 target st2000 @var{dev} @var{speed}
14557 to establish it as your debugging environment. @var{dev} is normally
14558 the name of a serial device, such as @file{/dev/ttya}, connected to the
14559 ST2000 via a serial line. You can instead specify @var{dev} as a TCP
14560 connection (for example, to a serial line attached via a terminal
14561 concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
14563 The @code{load} and @code{attach} commands are @emph{not} defined for
14564 this target; you must load your program into the ST2000 as you normally
14565 would for standalone operation. @value{GDBN} reads debugging information
14566 (such as symbols) from a separate, debugging version of the program
14567 available on your host computer.
14568 @c FIXME!! This is terribly vague; what little content is here is
14569 @c basically hearsay.
14571 @cindex ST2000 auxiliary commands
14572 These auxiliary @value{GDBN} commands are available to help you with the ST2000
14576 @item st2000 @var{command}
14577 @kindex st2000 @var{cmd}
14578 @cindex STDBUG commands (ST2000)
14579 @cindex commands to STDBUG (ST2000)
14580 Send a @var{command} to the STDBUG monitor. See the manufacturer's
14581 manual for available commands.
14584 @cindex connect (to STDBUG)
14585 Connect the controlling terminal to the STDBUG command monitor. When
14586 you are done interacting with STDBUG, typing either of two character
14587 sequences gets you back to the @value{GDBN} command prompt:
14588 @kbd{@key{RET}~.} (Return, followed by tilde and period) or
14589 @kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D).
14593 @subsection Zilog Z8000
14596 @cindex simulator, Z8000
14597 @cindex Zilog Z8000 simulator
14599 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
14602 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
14603 unsegmented variant of the Z8000 architecture) or the Z8001 (the
14604 segmented variant). The simulator recognizes which architecture is
14605 appropriate by inspecting the object code.
14608 @item target sim @var{args}
14610 @kindex target sim@r{, with Z8000}
14611 Debug programs on a simulated CPU. If the simulator supports setup
14612 options, specify them via @var{args}.
14616 After specifying this target, you can debug programs for the simulated
14617 CPU in the same style as programs for your host computer; use the
14618 @code{file} command to load a new program image, the @code{run} command
14619 to run your program, and so on.
14621 As well as making available all the usual machine registers
14622 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
14623 additional items of information as specially named registers:
14628 Counts clock-ticks in the simulator.
14631 Counts instructions run in the simulator.
14634 Execution time in 60ths of a second.
14638 You can refer to these values in @value{GDBN} expressions with the usual
14639 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
14640 conditional breakpoint that suspends only after at least 5000
14641 simulated clock ticks.
14644 @subsection Atmel AVR
14647 When configured for debugging the Atmel AVR, @value{GDBN} supports the
14648 following AVR-specific commands:
14651 @item info io_registers
14652 @kindex info io_registers@r{, AVR}
14653 @cindex I/O registers (Atmel AVR)
14654 This command displays information about the AVR I/O registers. For
14655 each register, @value{GDBN} prints its number and value.
14662 When configured for debugging CRIS, @value{GDBN} provides the
14663 following CRIS-specific commands:
14666 @item set cris-version @var{ver}
14667 @cindex CRIS version
14668 Set the current CRIS version to @var{ver}. The CRIS version affects
14669 register names and sizes. This command is useful in case
14670 autodetection of the CRIS version fails.
14672 @item show cris-version
14673 Show the current CRIS version.
14675 @item set cris-dwarf2-cfi
14676 @cindex DWARF-2 CFI and CRIS
14677 Set the usage of DWARF-2 CFI for CRIS debugging. The default is off
14678 if using @code{gcc-cris} whose version is below @code{R59}, otherwise
14681 @item show cris-dwarf2-cfi
14682 Show the current state of using DWARF-2 CFI.
14686 @subsection Renesas Super-H
14689 For the Renesas Super-H processor, @value{GDBN} provides these
14694 @kindex regs@r{, Super-H}
14695 Show the values of all Super-H registers.
14699 @subsection Windows CE
14702 The following commands are available for Windows CE:
14705 @item set remotedirectory @var{dir}
14706 @kindex set remotedirectory
14707 Tell @value{GDBN} to upload files from the named directory @var{dir}.
14708 The default is @file{/gdb}, i.e.@: the root directory on the current
14711 @item show remotedirectory
14712 @kindex show remotedirectory
14713 Show the current value of the upload directory.
14715 @item set remoteupload @var{method}
14716 @kindex set remoteupload
14717 Set the method used to upload files to remote device. Valid values
14718 for @var{method} are @samp{always}, @samp{newer}, and @samp{never}.
14719 The default is @samp{newer}.
14721 @item show remoteupload
14722 @kindex show remoteupload
14723 Show the current setting of the upload method.
14725 @item set remoteaddhost
14726 @kindex set remoteaddhost
14727 Tell @value{GDBN} whether to add this host to the remote stub's
14728 arguments when you debug over a network.
14730 @item show remoteaddhost
14731 @kindex show remoteaddhost
14732 Show whether to add this host to remote stub's arguments when
14733 debugging over a network.
14737 @node Architectures
14738 @section Architectures
14740 This section describes characteristics of architectures that affect
14741 all uses of @value{GDBN} with the architecture, both native and cross.
14748 * HPPA:: HP PA architecture
14752 @subsection x86 Architecture-specific issues.
14755 @item set struct-convention @var{mode}
14756 @kindex set struct-convention
14757 @cindex struct return convention
14758 @cindex struct/union returned in registers
14759 Set the convention used by the inferior to return @code{struct}s and
14760 @code{union}s from functions to @var{mode}. Possible values of
14761 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
14762 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
14763 are returned on the stack, while @code{"reg"} means that a
14764 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
14765 be returned in a register.
14767 @item show struct-convention
14768 @kindex show struct-convention
14769 Show the current setting of the convention to return @code{struct}s
14778 @kindex set rstack_high_address
14779 @cindex AMD 29K register stack
14780 @cindex register stack, AMD29K
14781 @item set rstack_high_address @var{address}
14782 On AMD 29000 family processors, registers are saved in a separate
14783 @dfn{register stack}. There is no way for @value{GDBN} to determine the
14784 extent of this stack. Normally, @value{GDBN} just assumes that the
14785 stack is ``large enough''. This may result in @value{GDBN} referencing
14786 memory locations that do not exist. If necessary, you can get around
14787 this problem by specifying the ending address of the register stack with
14788 the @code{set rstack_high_address} command. The argument should be an
14789 address, which you probably want to precede with @samp{0x} to specify in
14792 @kindex show rstack_high_address
14793 @item show rstack_high_address
14794 Display the current limit of the register stack, on AMD 29000 family
14802 See the following section.
14807 @cindex stack on Alpha
14808 @cindex stack on MIPS
14809 @cindex Alpha stack
14811 Alpha- and MIPS-based computers use an unusual stack frame, which
14812 sometimes requires @value{GDBN} to search backward in the object code to
14813 find the beginning of a function.
14815 @cindex response time, MIPS debugging
14816 To improve response time (especially for embedded applications, where
14817 @value{GDBN} may be restricted to a slow serial line for this search)
14818 you may want to limit the size of this search, using one of these
14822 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
14823 @item set heuristic-fence-post @var{limit}
14824 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
14825 search for the beginning of a function. A value of @var{0} (the
14826 default) means there is no limit. However, except for @var{0}, the
14827 larger the limit the more bytes @code{heuristic-fence-post} must search
14828 and therefore the longer it takes to run. You should only need to use
14829 this command when debugging a stripped executable.
14831 @item show heuristic-fence-post
14832 Display the current limit.
14836 These commands are available @emph{only} when @value{GDBN} is configured
14837 for debugging programs on Alpha or MIPS processors.
14839 Several MIPS-specific commands are available when debugging MIPS
14843 @item set mips saved-gpreg-size @var{size}
14844 @kindex set mips saved-gpreg-size
14845 @cindex MIPS GP register size on stack
14846 Set the size of MIPS general-purpose registers saved on the stack.
14847 The argument @var{size} can be one of the following:
14851 32-bit GP registers
14853 64-bit GP registers
14855 Use the target's default setting or autodetect the saved size from the
14856 information contained in the executable. This is the default
14859 @item show mips saved-gpreg-size
14860 @kindex show mips saved-gpreg-size
14861 Show the current size of MIPS GP registers on the stack.
14863 @item set mips stack-arg-size @var{size}
14864 @kindex set mips stack-arg-size
14865 @cindex MIPS stack space for arguments
14866 Set the amount of stack space reserved for arguments to functions.
14867 The argument can be one of @code{"32"}, @code{"64"} or @code{"auto"}
14870 @item set mips abi @var{arg}
14871 @kindex set mips abi
14872 @cindex set ABI for MIPS
14873 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
14874 values of @var{arg} are:
14878 The default ABI associated with the current binary (this is the
14889 @item show mips abi
14890 @kindex show mips abi
14891 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
14894 @itemx show mipsfpu
14895 @xref{MIPS Embedded, set mipsfpu}.
14897 @item set mips mask-address @var{arg}
14898 @kindex set mips mask-address
14899 @cindex MIPS addresses, masking
14900 This command determines whether the most-significant 32 bits of 64-bit
14901 MIPS addresses are masked off. The argument @var{arg} can be
14902 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
14903 setting, which lets @value{GDBN} determine the correct value.
14905 @item show mips mask-address
14906 @kindex show mips mask-address
14907 Show whether the upper 32 bits of MIPS addresses are masked off or
14910 @item set remote-mips64-transfers-32bit-regs
14911 @kindex set remote-mips64-transfers-32bit-regs
14912 This command controls compatibility with 64-bit MIPS targets that
14913 transfer data in 32-bit quantities. If you have an old MIPS 64 target
14914 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
14915 and 64 bits for other registers, set this option to @samp{on}.
14917 @item show remote-mips64-transfers-32bit-regs
14918 @kindex show remote-mips64-transfers-32bit-regs
14919 Show the current setting of compatibility with older MIPS 64 targets.
14921 @item set debug mips
14922 @kindex set debug mips
14923 This command turns on and off debugging messages for the MIPS-specific
14924 target code in @value{GDBN}.
14926 @item show debug mips
14927 @kindex show debug mips
14928 Show the current setting of MIPS debugging messages.
14934 @cindex HPPA support
14936 When @value{GDBN} is debugging te HP PA architecture, it provides the
14937 following special commands:
14940 @item set debug hppa
14941 @kindex set debug hppa
14942 THis command determines whether HPPA architecture specific debugging
14943 messages are to be displayed.
14945 @item show debug hppa
14946 Show whether HPPA debugging messages are displayed.
14948 @item maint print unwind @var{address}
14949 @kindex maint print unwind@r{, HPPA}
14950 This command displays the contents of the unwind table entry at the
14951 given @var{address}.
14956 @node Controlling GDB
14957 @chapter Controlling @value{GDBN}
14959 You can alter the way @value{GDBN} interacts with you by using the
14960 @code{set} command. For commands controlling how @value{GDBN} displays
14961 data, see @ref{Print Settings, ,Print settings}. Other settings are
14966 * Editing:: Command editing
14967 * History:: Command history
14968 * Screen Size:: Screen size
14969 * Numbers:: Numbers
14970 * ABI:: Configuring the current ABI
14971 * Messages/Warnings:: Optional warnings and messages
14972 * Debugging Output:: Optional messages about internal happenings
14980 @value{GDBN} indicates its readiness to read a command by printing a string
14981 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
14982 can change the prompt string with the @code{set prompt} command. For
14983 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
14984 the prompt in one of the @value{GDBN} sessions so that you can always tell
14985 which one you are talking to.
14987 @emph{Note:} @code{set prompt} does not add a space for you after the
14988 prompt you set. This allows you to set a prompt which ends in a space
14989 or a prompt that does not.
14993 @item set prompt @var{newprompt}
14994 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
14996 @kindex show prompt
14998 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
15002 @section Command editing
15004 @cindex command line editing
15006 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
15007 @sc{gnu} library provides consistent behavior for programs which provide a
15008 command line interface to the user. Advantages are @sc{gnu} Emacs-style
15009 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
15010 substitution, and a storage and recall of command history across
15011 debugging sessions.
15013 You may control the behavior of command line editing in @value{GDBN} with the
15014 command @code{set}.
15017 @kindex set editing
15020 @itemx set editing on
15021 Enable command line editing (enabled by default).
15023 @item set editing off
15024 Disable command line editing.
15026 @kindex show editing
15028 Show whether command line editing is enabled.
15031 @xref{Command Line Editing}, for more details about the Readline
15032 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
15033 encouraged to read that chapter.
15036 @section Command history
15037 @cindex command history
15039 @value{GDBN} can keep track of the commands you type during your
15040 debugging sessions, so that you can be certain of precisely what
15041 happened. Use these commands to manage the @value{GDBN} command
15044 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
15045 package, to provide the history facility. @xref{Using History
15046 Interactively}, for the detailed description of the History library.
15048 Here is the description of @value{GDBN} commands related to command
15052 @cindex history substitution
15053 @cindex history file
15054 @kindex set history filename
15055 @cindex @env{GDBHISTFILE}, environment variable
15056 @item set history filename @var{fname}
15057 Set the name of the @value{GDBN} command history file to @var{fname}.
15058 This is the file where @value{GDBN} reads an initial command history
15059 list, and where it writes the command history from this session when it
15060 exits. You can access this list through history expansion or through
15061 the history command editing characters listed below. This file defaults
15062 to the value of the environment variable @code{GDBHISTFILE}, or to
15063 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
15066 @cindex save command history
15067 @kindex set history save
15068 @item set history save
15069 @itemx set history save on
15070 Record command history in a file, whose name may be specified with the
15071 @code{set history filename} command. By default, this option is disabled.
15073 @item set history save off
15074 Stop recording command history in a file.
15076 @cindex history size
15077 @kindex set history size
15078 @cindex @env{HISTSIZE}, environment variable
15079 @item set history size @var{size}
15080 Set the number of commands which @value{GDBN} keeps in its history list.
15081 This defaults to the value of the environment variable
15082 @code{HISTSIZE}, or to 256 if this variable is not set.
15085 History expansion assigns special meaning to the character @kbd{!}.
15086 @xref{Event Designators}, for more details.
15088 @cindex history expansion, turn on/off
15089 Since @kbd{!} is also the logical not operator in C, history expansion
15090 is off by default. If you decide to enable history expansion with the
15091 @code{set history expansion on} command, you may sometimes need to
15092 follow @kbd{!} (when it is used as logical not, in an expression) with
15093 a space or a tab to prevent it from being expanded. The readline
15094 history facilities do not attempt substitution on the strings
15095 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
15097 The commands to control history expansion are:
15100 @item set history expansion on
15101 @itemx set history expansion
15102 @kindex set history expansion
15103 Enable history expansion. History expansion is off by default.
15105 @item set history expansion off
15106 Disable history expansion.
15109 @kindex show history
15111 @itemx show history filename
15112 @itemx show history save
15113 @itemx show history size
15114 @itemx show history expansion
15115 These commands display the state of the @value{GDBN} history parameters.
15116 @code{show history} by itself displays all four states.
15121 @kindex show commands
15122 @cindex show last commands
15123 @cindex display command history
15124 @item show commands
15125 Display the last ten commands in the command history.
15127 @item show commands @var{n}
15128 Print ten commands centered on command number @var{n}.
15130 @item show commands +
15131 Print ten commands just after the commands last printed.
15135 @section Screen size
15136 @cindex size of screen
15137 @cindex pauses in output
15139 Certain commands to @value{GDBN} may produce large amounts of
15140 information output to the screen. To help you read all of it,
15141 @value{GDBN} pauses and asks you for input at the end of each page of
15142 output. Type @key{RET} when you want to continue the output, or @kbd{q}
15143 to discard the remaining output. Also, the screen width setting
15144 determines when to wrap lines of output. Depending on what is being
15145 printed, @value{GDBN} tries to break the line at a readable place,
15146 rather than simply letting it overflow onto the following line.
15148 Normally @value{GDBN} knows the size of the screen from the terminal
15149 driver software. For example, on Unix @value{GDBN} uses the termcap data base
15150 together with the value of the @code{TERM} environment variable and the
15151 @code{stty rows} and @code{stty cols} settings. If this is not correct,
15152 you can override it with the @code{set height} and @code{set
15159 @kindex show height
15160 @item set height @var{lpp}
15162 @itemx set width @var{cpl}
15164 These @code{set} commands specify a screen height of @var{lpp} lines and
15165 a screen width of @var{cpl} characters. The associated @code{show}
15166 commands display the current settings.
15168 If you specify a height of zero lines, @value{GDBN} does not pause during
15169 output no matter how long the output is. This is useful if output is to a
15170 file or to an editor buffer.
15172 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
15173 from wrapping its output.
15175 @item set pagination on
15176 @itemx set pagination off
15177 @kindex set pagination
15178 Turn the output pagination on or off; the default is on. Turning
15179 pagination off is the alternative to @code{set height 0}.
15181 @item show pagination
15182 @kindex show pagination
15183 Show the current pagination mode.
15188 @cindex number representation
15189 @cindex entering numbers
15191 You can always enter numbers in octal, decimal, or hexadecimal in
15192 @value{GDBN} by the usual conventions: octal numbers begin with
15193 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
15194 begin with @samp{0x}. Numbers that begin with none of these are, by
15195 default, entered in base 10; likewise, the default display for
15196 numbers---when no particular format is specified---is base 10. You can
15197 change the default base for both input and output with the @code{set
15201 @kindex set input-radix
15202 @item set input-radix @var{base}
15203 Set the default base for numeric input. Supported choices
15204 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15205 specified either unambiguously or using the current default radix; for
15209 set input-radix 012
15210 set input-radix 10.
15211 set input-radix 0xa
15215 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
15216 leaves the input radix unchanged, no matter what it was.
15218 @kindex set output-radix
15219 @item set output-radix @var{base}
15220 Set the default base for numeric display. Supported choices
15221 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15222 specified either unambiguously or using the current default radix.
15224 @kindex show input-radix
15225 @item show input-radix
15226 Display the current default base for numeric input.
15228 @kindex show output-radix
15229 @item show output-radix
15230 Display the current default base for numeric display.
15232 @item set radix @r{[}@var{base}@r{]}
15236 These commands set and show the default base for both input and output
15237 of numbers. @code{set radix} sets the radix of input and output to
15238 the same base; without an argument, it resets the radix back to its
15239 default value of 10.
15244 @section Configuring the current ABI
15246 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
15247 application automatically. However, sometimes you need to override its
15248 conclusions. Use these commands to manage @value{GDBN}'s view of the
15255 One @value{GDBN} configuration can debug binaries for multiple operating
15256 system targets, either via remote debugging or native emulation.
15257 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
15258 but you can override its conclusion using the @code{set osabi} command.
15259 One example where this is useful is in debugging of binaries which use
15260 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
15261 not have the same identifying marks that the standard C library for your
15266 Show the OS ABI currently in use.
15269 With no argument, show the list of registered available OS ABI's.
15271 @item set osabi @var{abi}
15272 Set the current OS ABI to @var{abi}.
15275 @cindex float promotion
15277 Generally, the way that an argument of type @code{float} is passed to a
15278 function depends on whether the function is prototyped. For a prototyped
15279 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
15280 according to the architecture's convention for @code{float}. For unprototyped
15281 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
15282 @code{double} and then passed.
15284 Unfortunately, some forms of debug information do not reliably indicate whether
15285 a function is prototyped. If @value{GDBN} calls a function that is not marked
15286 as prototyped, it consults @kbd{set coerce-float-to-double}.
15289 @kindex set coerce-float-to-double
15290 @item set coerce-float-to-double
15291 @itemx set coerce-float-to-double on
15292 Arguments of type @code{float} will be promoted to @code{double} when passed
15293 to an unprototyped function. This is the default setting.
15295 @item set coerce-float-to-double off
15296 Arguments of type @code{float} will be passed directly to unprototyped
15299 @kindex show coerce-float-to-double
15300 @item show coerce-float-to-double
15301 Show the current setting of promoting @code{float} to @code{double}.
15305 @kindex show cp-abi
15306 @value{GDBN} needs to know the ABI used for your program's C@t{++}
15307 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
15308 used to build your application. @value{GDBN} only fully supports
15309 programs with a single C@t{++} ABI; if your program contains code using
15310 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
15311 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
15312 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
15313 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
15314 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
15315 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
15320 Show the C@t{++} ABI currently in use.
15323 With no argument, show the list of supported C@t{++} ABI's.
15325 @item set cp-abi @var{abi}
15326 @itemx set cp-abi auto
15327 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
15330 @node Messages/Warnings
15331 @section Optional warnings and messages
15333 @cindex verbose operation
15334 @cindex optional warnings
15335 By default, @value{GDBN} is silent about its inner workings. If you are
15336 running on a slow machine, you may want to use the @code{set verbose}
15337 command. This makes @value{GDBN} tell you when it does a lengthy
15338 internal operation, so you will not think it has crashed.
15340 Currently, the messages controlled by @code{set verbose} are those
15341 which announce that the symbol table for a source file is being read;
15342 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
15345 @kindex set verbose
15346 @item set verbose on
15347 Enables @value{GDBN} output of certain informational messages.
15349 @item set verbose off
15350 Disables @value{GDBN} output of certain informational messages.
15352 @kindex show verbose
15354 Displays whether @code{set verbose} is on or off.
15357 By default, if @value{GDBN} encounters bugs in the symbol table of an
15358 object file, it is silent; but if you are debugging a compiler, you may
15359 find this information useful (@pxref{Symbol Errors, ,Errors reading
15364 @kindex set complaints
15365 @item set complaints @var{limit}
15366 Permits @value{GDBN} to output @var{limit} complaints about each type of
15367 unusual symbols before becoming silent about the problem. Set
15368 @var{limit} to zero to suppress all complaints; set it to a large number
15369 to prevent complaints from being suppressed.
15371 @kindex show complaints
15372 @item show complaints
15373 Displays how many symbol complaints @value{GDBN} is permitted to produce.
15377 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
15378 lot of stupid questions to confirm certain commands. For example, if
15379 you try to run a program which is already running:
15383 The program being debugged has been started already.
15384 Start it from the beginning? (y or n)
15387 If you are willing to unflinchingly face the consequences of your own
15388 commands, you can disable this ``feature'':
15392 @kindex set confirm
15394 @cindex confirmation
15395 @cindex stupid questions
15396 @item set confirm off
15397 Disables confirmation requests.
15399 @item set confirm on
15400 Enables confirmation requests (the default).
15402 @kindex show confirm
15404 Displays state of confirmation requests.
15408 @node Debugging Output
15409 @section Optional messages about internal happenings
15410 @cindex optional debugging messages
15412 @value{GDBN} has commands that enable optional debugging messages from
15413 various @value{GDBN} subsystems; normally these commands are of
15414 interest to @value{GDBN} maintainers, or when reporting a bug. This
15415 section documents those commands.
15418 @kindex set exec-done-display
15419 @item set exec-done-display
15420 Turns on or off the notification of asynchronous commands'
15421 completion. When on, @value{GDBN} will print a message when an
15422 asynchronous command finishes its execution. The default is off.
15423 @kindex show exec-done-display
15424 @item show exec-done-display
15425 Displays the current setting of asynchronous command completion
15428 @cindex gdbarch debugging info
15429 @cindex architecture debugging info
15430 @item set debug arch
15431 Turns on or off display of gdbarch debugging info. The default is off
15433 @item show debug arch
15434 Displays the current state of displaying gdbarch debugging info.
15435 @item set debug aix-thread
15436 @cindex AIX threads
15437 Display debugging messages about inner workings of the AIX thread
15439 @item show debug aix-thread
15440 Show the current state of AIX thread debugging info display.
15441 @item set debug event
15442 @cindex event debugging info
15443 Turns on or off display of @value{GDBN} event debugging info. The
15445 @item show debug event
15446 Displays the current state of displaying @value{GDBN} event debugging
15448 @item set debug expression
15449 @cindex expression debugging info
15450 Turns on or off display of debugging info about @value{GDBN}
15451 expression parsing. The default is off.
15452 @item show debug expression
15453 Displays the current state of displaying debugging info about
15454 @value{GDBN} expression parsing.
15455 @item set debug frame
15456 @cindex frame debugging info
15457 Turns on or off display of @value{GDBN} frame debugging info. The
15459 @item show debug frame
15460 Displays the current state of displaying @value{GDBN} frame debugging
15462 @item set debug infrun
15463 @cindex inferior debugging info
15464 Turns on or off display of @value{GDBN} debugging info for running the inferior.
15465 The default is off. @file{infrun.c} contains GDB's runtime state machine used
15466 for implementing operations such as single-stepping the inferior.
15467 @item show debug infrun
15468 Displays the current state of @value{GDBN} inferior debugging.
15469 @item set debug lin-lwp
15470 @cindex @sc{gnu}/Linux LWP debug messages
15471 @cindex Linux lightweight processes
15472 Turns on or off debugging messages from the Linux LWP debug support.
15473 @item show debug lin-lwp
15474 Show the current state of Linux LWP debugging messages.
15475 @item set debug observer
15476 @cindex observer debugging info
15477 Turns on or off display of @value{GDBN} observer debugging. This
15478 includes info such as the notification of observable events.
15479 @item show debug observer
15480 Displays the current state of observer debugging.
15481 @item set debug overload
15482 @cindex C@t{++} overload debugging info
15483 Turns on or off display of @value{GDBN} C@t{++} overload debugging
15484 info. This includes info such as ranking of functions, etc. The default
15486 @item show debug overload
15487 Displays the current state of displaying @value{GDBN} C@t{++} overload
15489 @cindex packets, reporting on stdout
15490 @cindex serial connections, debugging
15491 @item set debug remote
15492 Turns on or off display of reports on all packets sent back and forth across
15493 the serial line to the remote machine. The info is printed on the
15494 @value{GDBN} standard output stream. The default is off.
15495 @item show debug remote
15496 Displays the state of display of remote packets.
15497 @item set debug serial
15498 Turns on or off display of @value{GDBN} serial debugging info. The
15500 @item show debug serial
15501 Displays the current state of displaying @value{GDBN} serial debugging
15503 @item set debug solib-frv
15504 @cindex FR-V shared-library debugging
15505 Turns on or off debugging messages for FR-V shared-library code.
15506 @item show debug solib-frv
15507 Display the current state of FR-V shared-library code debugging
15509 @item set debug target
15510 @cindex target debugging info
15511 Turns on or off display of @value{GDBN} target debugging info. This info
15512 includes what is going on at the target level of GDB, as it happens. The
15513 default is 0. Set it to 1 to track events, and to 2 to also track the
15514 value of large memory transfers. Changes to this flag do not take effect
15515 until the next time you connect to a target or use the @code{run} command.
15516 @item show debug target
15517 Displays the current state of displaying @value{GDBN} target debugging
15519 @item set debugvarobj
15520 @cindex variable object debugging info
15521 Turns on or off display of @value{GDBN} variable object debugging
15522 info. The default is off.
15523 @item show debugvarobj
15524 Displays the current state of displaying @value{GDBN} variable object
15529 @chapter Canned Sequences of Commands
15531 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
15532 command lists}), @value{GDBN} provides two ways to store sequences of
15533 commands for execution as a unit: user-defined commands and command
15537 * Define:: User-defined commands
15538 * Hooks:: User-defined command hooks
15539 * Command Files:: Command files
15540 * Output:: Commands for controlled output
15544 @section User-defined commands
15546 @cindex user-defined command
15547 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
15548 which you assign a new name as a command. This is done with the
15549 @code{define} command. User commands may accept up to 10 arguments
15550 separated by whitespace. Arguments are accessed within the user command
15551 via @var{$arg0@dots{}$arg9}. A trivial example:
15555 print $arg0 + $arg1 + $arg2
15559 To execute the command use:
15566 This defines the command @code{adder}, which prints the sum of
15567 its three arguments. Note the arguments are text substitutions, so they may
15568 reference variables, use complex expressions, or even perform inferior
15574 @item define @var{commandname}
15575 Define a command named @var{commandname}. If there is already a command
15576 by that name, you are asked to confirm that you want to redefine it.
15578 The definition of the command is made up of other @value{GDBN} command lines,
15579 which are given following the @code{define} command. The end of these
15580 commands is marked by a line containing @code{end}.
15586 Takes a single argument, which is an expression to evaluate.
15587 It is followed by a series of commands that are executed
15588 only if the expression is true (nonzero).
15589 There can then optionally be a line @code{else}, followed
15590 by a series of commands that are only executed if the expression
15591 was false. The end of the list is marked by a line containing @code{end}.
15595 The syntax is similar to @code{if}: the command takes a single argument,
15596 which is an expression to evaluate, and must be followed by the commands to
15597 execute, one per line, terminated by an @code{end}.
15598 The commands are executed repeatedly as long as the expression
15602 @item document @var{commandname}
15603 Document the user-defined command @var{commandname}, so that it can be
15604 accessed by @code{help}. The command @var{commandname} must already be
15605 defined. This command reads lines of documentation just as @code{define}
15606 reads the lines of the command definition, ending with @code{end}.
15607 After the @code{document} command is finished, @code{help} on command
15608 @var{commandname} displays the documentation you have written.
15610 You may use the @code{document} command again to change the
15611 documentation of a command. Redefining the command with @code{define}
15612 does not change the documentation.
15614 @kindex dont-repeat
15615 @cindex don't repeat command
15617 Used inside a user-defined command, this tells @value{GDBN} that this
15618 command should not be repeated when the user hits @key{RET}
15619 (@pxref{Command Syntax, repeat last command}).
15621 @kindex help user-defined
15622 @item help user-defined
15623 List all user-defined commands, with the first line of the documentation
15628 @itemx show user @var{commandname}
15629 Display the @value{GDBN} commands used to define @var{commandname} (but
15630 not its documentation). If no @var{commandname} is given, display the
15631 definitions for all user-defined commands.
15633 @cindex infinite recusrion in user-defined commands
15634 @kindex show max-user-call-depth
15635 @kindex set max-user-call-depth
15636 @item show max-user-call-depth
15637 @itemx set max-user-call-depth
15638 The value of @code{max-user-call-depth} controls how many recursion
15639 levels are allowed in user-defined commands before GDB suspects an
15640 infinite recursion and aborts the command.
15644 When user-defined commands are executed, the
15645 commands of the definition are not printed. An error in any command
15646 stops execution of the user-defined command.
15648 If used interactively, commands that would ask for confirmation proceed
15649 without asking when used inside a user-defined command. Many @value{GDBN}
15650 commands that normally print messages to say what they are doing omit the
15651 messages when used in a user-defined command.
15654 @section User-defined command hooks
15655 @cindex command hooks
15656 @cindex hooks, for commands
15657 @cindex hooks, pre-command
15660 You may define @dfn{hooks}, which are a special kind of user-defined
15661 command. Whenever you run the command @samp{foo}, if the user-defined
15662 command @samp{hook-foo} exists, it is executed (with no arguments)
15663 before that command.
15665 @cindex hooks, post-command
15667 A hook may also be defined which is run after the command you executed.
15668 Whenever you run the command @samp{foo}, if the user-defined command
15669 @samp{hookpost-foo} exists, it is executed (with no arguments) after
15670 that command. Post-execution hooks may exist simultaneously with
15671 pre-execution hooks, for the same command.
15673 It is valid for a hook to call the command which it hooks. If this
15674 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
15676 @c It would be nice if hookpost could be passed a parameter indicating
15677 @c if the command it hooks executed properly or not. FIXME!
15679 @kindex stop@r{, a pseudo-command}
15680 In addition, a pseudo-command, @samp{stop} exists. Defining
15681 (@samp{hook-stop}) makes the associated commands execute every time
15682 execution stops in your program: before breakpoint commands are run,
15683 displays are printed, or the stack frame is printed.
15685 For example, to ignore @code{SIGALRM} signals while
15686 single-stepping, but treat them normally during normal execution,
15691 handle SIGALRM nopass
15695 handle SIGALRM pass
15698 define hook-continue
15699 handle SIGLARM pass
15703 As a further example, to hook at the begining and end of the @code{echo}
15704 command, and to add extra text to the beginning and end of the message,
15712 define hookpost-echo
15716 (@value{GDBP}) echo Hello World
15717 <<<---Hello World--->>>
15722 You can define a hook for any single-word command in @value{GDBN}, but
15723 not for command aliases; you should define a hook for the basic command
15724 name, e.g. @code{backtrace} rather than @code{bt}.
15725 @c FIXME! So how does Joe User discover whether a command is an alias
15727 If an error occurs during the execution of your hook, execution of
15728 @value{GDBN} commands stops and @value{GDBN} issues a prompt
15729 (before the command that you actually typed had a chance to run).
15731 If you try to define a hook which does not match any known command, you
15732 get a warning from the @code{define} command.
15734 @node Command Files
15735 @section Command files
15737 @cindex command files
15738 A command file for @value{GDBN} is a text file made of lines that are
15739 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
15740 also be included. An empty line in a command file does nothing; it
15741 does not mean to repeat the last command, as it would from the
15744 You can request the execution of a command file with the @code{source}
15749 @item source @var{filename}
15750 Execute the command file @var{filename}.
15753 The lines in a command file are executed sequentially. They are not
15754 printed as they are executed. An error in any command terminates
15755 execution of the command file and control is returned to the console.
15757 Commands that would ask for confirmation if used interactively proceed
15758 without asking when used in a command file. Many @value{GDBN} commands that
15759 normally print messages to say what they are doing omit the messages
15760 when called from command files.
15762 @value{GDBN} also accepts command input from standard input. In this
15763 mode, normal output goes to standard output and error output goes to
15764 standard error. Errors in a command file supplied on standard input do
15765 not terminate execution of the command file---execution continues with
15769 gdb < cmds > log 2>&1
15772 (The syntax above will vary depending on the shell used.) This example
15773 will execute commands from the file @file{cmds}. All output and errors
15774 would be directed to @file{log}.
15777 @section Commands for controlled output
15779 During the execution of a command file or a user-defined command, normal
15780 @value{GDBN} output is suppressed; the only output that appears is what is
15781 explicitly printed by the commands in the definition. This section
15782 describes three commands useful for generating exactly the output you
15787 @item echo @var{text}
15788 @c I do not consider backslash-space a standard C escape sequence
15789 @c because it is not in ANSI.
15790 Print @var{text}. Nonprinting characters can be included in
15791 @var{text} using C escape sequences, such as @samp{\n} to print a
15792 newline. @strong{No newline is printed unless you specify one.}
15793 In addition to the standard C escape sequences, a backslash followed
15794 by a space stands for a space. This is useful for displaying a
15795 string with spaces at the beginning or the end, since leading and
15796 trailing spaces are otherwise trimmed from all arguments.
15797 To print @samp{@w{ }and foo =@w{ }}, use the command
15798 @samp{echo \@w{ }and foo = \@w{ }}.
15800 A backslash at the end of @var{text} can be used, as in C, to continue
15801 the command onto subsequent lines. For example,
15804 echo This is some text\n\
15805 which is continued\n\
15806 onto several lines.\n
15809 produces the same output as
15812 echo This is some text\n
15813 echo which is continued\n
15814 echo onto several lines.\n
15818 @item output @var{expression}
15819 Print the value of @var{expression} and nothing but that value: no
15820 newlines, no @samp{$@var{nn} = }. The value is not entered in the
15821 value history either. @xref{Expressions, ,Expressions}, for more information
15824 @item output/@var{fmt} @var{expression}
15825 Print the value of @var{expression} in format @var{fmt}. You can use
15826 the same formats as for @code{print}. @xref{Output Formats,,Output
15827 formats}, for more information.
15830 @item printf @var{string}, @var{expressions}@dots{}
15831 Print the values of the @var{expressions} under the control of
15832 @var{string}. The @var{expressions} are separated by commas and may be
15833 either numbers or pointers. Their values are printed as specified by
15834 @var{string}, exactly as if your program were to execute the C
15836 @c FIXME: the above implies that at least all ANSI C formats are
15837 @c supported, but it isn't true: %E and %G don't work (or so it seems).
15838 @c Either this is a bug, or the manual should document what formats are
15842 printf (@var{string}, @var{expressions}@dots{});
15845 For example, you can print two values in hex like this:
15848 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
15851 The only backslash-escape sequences that you can use in the format
15852 string are the simple ones that consist of backslash followed by a
15857 @chapter Command Interpreters
15858 @cindex command interpreters
15860 @value{GDBN} supports multiple command interpreters, and some command
15861 infrastructure to allow users or user interface writers to switch
15862 between interpreters or run commands in other interpreters.
15864 @value{GDBN} currently supports two command interpreters, the console
15865 interpreter (sometimes called the command-line interpreter or @sc{cli})
15866 and the machine interface interpreter (or @sc{gdb/mi}). This manual
15867 describes both of these interfaces in great detail.
15869 By default, @value{GDBN} will start with the console interpreter.
15870 However, the user may choose to start @value{GDBN} with another
15871 interpreter by specifying the @option{-i} or @option{--interpreter}
15872 startup options. Defined interpreters include:
15876 @cindex console interpreter
15877 The traditional console or command-line interpreter. This is the most often
15878 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
15879 @value{GDBN} will use this interpreter.
15882 @cindex mi interpreter
15883 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
15884 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
15885 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
15889 @cindex mi2 interpreter
15890 The current @sc{gdb/mi} interface.
15893 @cindex mi1 interpreter
15894 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
15898 @cindex invoke another interpreter
15899 The interpreter being used by @value{GDBN} may not be dynamically
15900 switched at runtime. Although possible, this could lead to a very
15901 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
15902 enters the command "interpreter-set console" in a console view,
15903 @value{GDBN} would switch to using the console interpreter, rendering
15904 the IDE inoperable!
15906 @kindex interpreter-exec
15907 Although you may only choose a single interpreter at startup, you may execute
15908 commands in any interpreter from the current interpreter using the appropriate
15909 command. If you are running the console interpreter, simply use the
15910 @code{interpreter-exec} command:
15913 interpreter-exec mi "-data-list-register-names"
15916 @sc{gdb/mi} has a similar command, although it is only available in versions of
15917 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
15920 @chapter @value{GDBN} Text User Interface
15922 @cindex Text User Interface
15925 * TUI Overview:: TUI overview
15926 * TUI Keys:: TUI key bindings
15927 * TUI Single Key Mode:: TUI single key mode
15928 * TUI Commands:: TUI specific commands
15929 * TUI Configuration:: TUI configuration variables
15932 The @value{GDBN} Text User Interface, TUI in short, is a terminal
15933 interface which uses the @code{curses} library to show the source
15934 file, the assembly output, the program registers and @value{GDBN}
15935 commands in separate text windows.
15937 The TUI is enabled by invoking @value{GDBN} using either
15939 @samp{gdbtui} or @samp{gdb -tui}.
15942 @section TUI overview
15944 The TUI has two display modes that can be switched while
15949 A curses (or TUI) mode in which it displays several text
15950 windows on the terminal.
15953 A standard mode which corresponds to the @value{GDBN} configured without
15957 In the TUI mode, @value{GDBN} can display several text window
15962 This window is the @value{GDBN} command window with the @value{GDBN}
15963 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
15964 managed using readline but through the TUI. The @emph{command}
15965 window is always visible.
15968 The source window shows the source file of the program. The current
15969 line as well as active breakpoints are displayed in this window.
15972 The assembly window shows the disassembly output of the program.
15975 This window shows the processor registers. It detects when
15976 a register is changed and when this is the case, registers that have
15977 changed are highlighted.
15981 The source and assembly windows show the current program position
15982 by highlighting the current line and marking them with the @samp{>} marker.
15983 Breakpoints are also indicated with two markers. A first one
15984 indicates the breakpoint type:
15988 Breakpoint which was hit at least once.
15991 Breakpoint which was never hit.
15994 Hardware breakpoint which was hit at least once.
15997 Hardware breakpoint which was never hit.
16001 The second marker indicates whether the breakpoint is enabled or not:
16005 Breakpoint is enabled.
16008 Breakpoint is disabled.
16012 The source, assembly and register windows are attached to the thread
16013 and the frame position. They are updated when the current thread
16014 changes, when the frame changes or when the program counter changes.
16015 These three windows are arranged by the TUI according to several
16016 layouts. The layout defines which of these three windows are visible.
16017 The following layouts are available:
16027 source and assembly
16030 source and registers
16033 assembly and registers
16037 On top of the command window a status line gives various information
16038 concerning the current process begin debugged. The status line is
16039 updated when the information it shows changes. The following fields
16044 Indicates the current gdb target
16045 (@pxref{Targets, ,Specifying a Debugging Target}).
16048 Gives information about the current process or thread number.
16049 When no process is being debugged, this field is set to @code{No process}.
16052 Gives the current function name for the selected frame.
16053 The name is demangled if demangling is turned on (@pxref{Print Settings}).
16054 When there is no symbol corresponding to the current program counter
16055 the string @code{??} is displayed.
16058 Indicates the current line number for the selected frame.
16059 When the current line number is not known the string @code{??} is displayed.
16062 Indicates the current program counter address.
16067 @section TUI Key Bindings
16068 @cindex TUI key bindings
16070 The TUI installs several key bindings in the readline keymaps
16071 (@pxref{Command Line Editing}).
16072 They allow to leave or enter in the TUI mode or they operate
16073 directly on the TUI layout and windows. The TUI also provides
16074 a @emph{SingleKey} keymap which binds several keys directly to
16075 @value{GDBN} commands. The following key bindings
16076 are installed for both TUI mode and the @value{GDBN} standard mode.
16085 Enter or leave the TUI mode. When the TUI mode is left,
16086 the curses window management is left and @value{GDBN} operates using
16087 its standard mode writing on the terminal directly. When the TUI
16088 mode is entered, the control is given back to the curses windows.
16089 The screen is then refreshed.
16093 Use a TUI layout with only one window. The layout will
16094 either be @samp{source} or @samp{assembly}. When the TUI mode
16095 is not active, it will switch to the TUI mode.
16097 Think of this key binding as the Emacs @kbd{C-x 1} binding.
16101 Use a TUI layout with at least two windows. When the current
16102 layout shows already two windows, a next layout with two windows is used.
16103 When a new layout is chosen, one window will always be common to the
16104 previous layout and the new one.
16106 Think of it as the Emacs @kbd{C-x 2} binding.
16110 Change the active window. The TUI associates several key bindings
16111 (like scrolling and arrow keys) to the active window. This command
16112 gives the focus to the next TUI window.
16114 Think of it as the Emacs @kbd{C-x o} binding.
16118 Use the TUI @emph{SingleKey} keymap that binds single key to gdb commands
16119 (@pxref{TUI Single Key Mode}).
16123 The following key bindings are handled only by the TUI mode:
16128 Scroll the active window one page up.
16132 Scroll the active window one page down.
16136 Scroll the active window one line up.
16140 Scroll the active window one line down.
16144 Scroll the active window one column left.
16148 Scroll the active window one column right.
16152 Refresh the screen.
16156 In the TUI mode, the arrow keys are used by the active window
16157 for scrolling. This means they are available for readline when the
16158 active window is the command window. When the command window
16159 does not have the focus, it is necessary to use other readline
16160 key bindings such as @key{C-p}, @key{C-n}, @key{C-b} and @key{C-f}.
16162 @node TUI Single Key Mode
16163 @section TUI Single Key Mode
16164 @cindex TUI single key mode
16166 The TUI provides a @emph{SingleKey} mode in which it installs a particular
16167 key binding in the readline keymaps to connect single keys to
16171 @kindex c @r{(SingleKey TUI key)}
16175 @kindex d @r{(SingleKey TUI key)}
16179 @kindex f @r{(SingleKey TUI key)}
16183 @kindex n @r{(SingleKey TUI key)}
16187 @kindex q @r{(SingleKey TUI key)}
16189 exit the @emph{SingleKey} mode.
16191 @kindex r @r{(SingleKey TUI key)}
16195 @kindex s @r{(SingleKey TUI key)}
16199 @kindex u @r{(SingleKey TUI key)}
16203 @kindex v @r{(SingleKey TUI key)}
16207 @kindex w @r{(SingleKey TUI key)}
16213 Other keys temporarily switch to the @value{GDBN} command prompt.
16214 The key that was pressed is inserted in the editing buffer so that
16215 it is possible to type most @value{GDBN} commands without interaction
16216 with the TUI @emph{SingleKey} mode. Once the command is entered the TUI
16217 @emph{SingleKey} mode is restored. The only way to permanently leave
16218 this mode is by hitting @key{q} or @samp{@key{C-x} @key{s}}.
16222 @section TUI specific commands
16223 @cindex TUI commands
16225 The TUI has specific commands to control the text windows.
16226 These commands are always available, that is they do not depend on
16227 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
16228 is in the standard mode, using these commands will automatically switch
16234 List and give the size of all displayed windows.
16238 Display the next layout.
16241 Display the previous layout.
16244 Display the source window only.
16247 Display the assembly window only.
16250 Display the source and assembly window.
16253 Display the register window together with the source or assembly window.
16255 @item focus next | prev | src | asm | regs | split
16257 Set the focus to the named window.
16258 This command allows to change the active window so that scrolling keys
16259 can be affected to another window.
16263 Refresh the screen. This is similar to using @key{C-L} key.
16265 @item tui reg float
16267 Show the floating point registers in the register window.
16269 @item tui reg general
16270 Show the general registers in the register window.
16273 Show the next register group. The list of register groups as well as
16274 their order is target specific. The predefined register groups are the
16275 following: @code{general}, @code{float}, @code{system}, @code{vector},
16276 @code{all}, @code{save}, @code{restore}.
16278 @item tui reg system
16279 Show the system registers in the register window.
16283 Update the source window and the current execution point.
16285 @item winheight @var{name} +@var{count}
16286 @itemx winheight @var{name} -@var{count}
16288 Change the height of the window @var{name} by @var{count}
16289 lines. Positive counts increase the height, while negative counts
16293 @kindex tabset @var{nchars}
16294 Set the width of tab stops to be @var{nchars} characters.
16298 @node TUI Configuration
16299 @section TUI configuration variables
16300 @cindex TUI configuration variables
16302 The TUI has several configuration variables that control the
16303 appearance of windows on the terminal.
16306 @item set tui border-kind @var{kind}
16307 @kindex set tui border-kind
16308 Select the border appearance for the source, assembly and register windows.
16309 The possible values are the following:
16312 Use a space character to draw the border.
16315 Use ascii characters + - and | to draw the border.
16318 Use the Alternate Character Set to draw the border. The border is
16319 drawn using character line graphics if the terminal supports them.
16323 @item set tui active-border-mode @var{mode}
16324 @kindex set tui active-border-mode
16325 Select the attributes to display the border of the active window.
16326 The possible values are @code{normal}, @code{standout}, @code{reverse},
16327 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
16329 @item set tui border-mode @var{mode}
16330 @kindex set tui border-mode
16331 Select the attributes to display the border of other windows.
16332 The @var{mode} can be one of the following:
16335 Use normal attributes to display the border.
16341 Use reverse video mode.
16344 Use half bright mode.
16346 @item half-standout
16347 Use half bright and standout mode.
16350 Use extra bright or bold mode.
16352 @item bold-standout
16353 Use extra bright or bold and standout mode.
16360 @chapter Using @value{GDBN} under @sc{gnu} Emacs
16363 @cindex @sc{gnu} Emacs
16364 A special interface allows you to use @sc{gnu} Emacs to view (and
16365 edit) the source files for the program you are debugging with
16368 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
16369 executable file you want to debug as an argument. This command starts
16370 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
16371 created Emacs buffer.
16372 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
16374 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
16379 All ``terminal'' input and output goes through the Emacs buffer.
16382 This applies both to @value{GDBN} commands and their output, and to the input
16383 and output done by the program you are debugging.
16385 This is useful because it means that you can copy the text of previous
16386 commands and input them again; you can even use parts of the output
16389 All the facilities of Emacs' Shell mode are available for interacting
16390 with your program. In particular, you can send signals the usual
16391 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
16396 @value{GDBN} displays source code through Emacs.
16399 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
16400 source file for that frame and puts an arrow (@samp{=>}) at the
16401 left margin of the current line. Emacs uses a separate buffer for
16402 source display, and splits the screen to show both your @value{GDBN} session
16405 Explicit @value{GDBN} @code{list} or search commands still produce output as
16406 usual, but you probably have no reason to use them from Emacs.
16408 If you specify an absolute file name when prompted for the @kbd{M-x
16409 gdb} argument, then Emacs sets your current working directory to where
16410 your program resides. If you only specify the file name, then Emacs
16411 sets your current working directory to to the directory associated
16412 with the previous buffer. In this case, @value{GDBN} may find your
16413 program by searching your environment's @code{PATH} variable, but on
16414 some operating systems it might not find the source. So, although the
16415 @value{GDBN} input and output session proceeds normally, the auxiliary
16416 buffer does not display the current source and line of execution.
16418 The initial working directory of @value{GDBN} is printed on the top
16419 line of the @value{GDBN} I/O buffer and this serves as a default for
16420 the commands that specify files for @value{GDBN} to operate
16421 on. @xref{Files, ,Commands to specify files}.
16423 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
16424 need to call @value{GDBN} by a different name (for example, if you
16425 keep several configurations around, with different names) you can
16426 customize the Emacs variable @code{gud-gdb-command-name} to run the
16429 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
16430 addition to the standard Shell mode commands:
16434 Describe the features of Emacs' @value{GDBN} Mode.
16437 Execute to another source line, like the @value{GDBN} @code{step} command; also
16438 update the display window to show the current file and location.
16441 Execute to next source line in this function, skipping all function
16442 calls, like the @value{GDBN} @code{next} command. Then update the display window
16443 to show the current file and location.
16446 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
16447 display window accordingly.
16450 Execute until exit from the selected stack frame, like the @value{GDBN}
16451 @code{finish} command.
16454 Continue execution of your program, like the @value{GDBN} @code{continue}
16458 Go up the number of frames indicated by the numeric argument
16459 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
16460 like the @value{GDBN} @code{up} command.
16463 Go down the number of frames indicated by the numeric argument, like the
16464 @value{GDBN} @code{down} command.
16467 In any source file, the Emacs command @kbd{C-x SPC} (@code{gud-break})
16468 tells @value{GDBN} to set a breakpoint on the source line point is on.
16470 If you type @kbd{M-x speedbar}, then Emacs displays a separate frame which
16471 shows a backtrace when the @value{GDBN} I/O buffer is current. Move
16472 point to any frame in the stack and type @key{RET} to make it become the
16473 current frame and display the associated source in the source buffer.
16474 Alternatively, click @kbd{Mouse-2} to make the selected frame become the
16477 If you accidentally delete the source-display buffer, an easy way to get
16478 it back is to type the command @code{f} in the @value{GDBN} buffer, to
16479 request a frame display; when you run under Emacs, this recreates
16480 the source buffer if necessary to show you the context of the current
16483 The source files displayed in Emacs are in ordinary Emacs buffers
16484 which are visiting the source files in the usual way. You can edit
16485 the files with these buffers if you wish; but keep in mind that @value{GDBN}
16486 communicates with Emacs in terms of line numbers. If you add or
16487 delete lines from the text, the line numbers that @value{GDBN} knows cease
16488 to correspond properly with the code.
16490 The description given here is for GNU Emacs version 21.3 and a more
16491 detailed description of its interaction with @value{GDBN} is given in
16492 the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu} Emacs Manual}).
16494 @c The following dropped because Epoch is nonstandard. Reactivate
16495 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
16497 @kindex Emacs Epoch environment
16501 Version 18 of @sc{gnu} Emacs has a built-in window system
16502 called the @code{epoch}
16503 environment. Users of this environment can use a new command,
16504 @code{inspect} which performs identically to @code{print} except that
16505 each value is printed in its own window.
16510 @chapter The @sc{gdb/mi} Interface
16512 @unnumberedsec Function and Purpose
16514 @cindex @sc{gdb/mi}, its purpose
16515 @sc{gdb/mi} is a line based machine oriented text interface to
16516 @value{GDBN} and is activated by specifying using the
16517 @option{--interpreter} command line option (@pxref{Mode Options}). It
16518 is specifically intended to support the development of systems which
16519 use the debugger as just one small component of a larger system.
16521 This chapter is a specification of the @sc{gdb/mi} interface. It is written
16522 in the form of a reference manual.
16524 Note that @sc{gdb/mi} is still under construction, so some of the
16525 features described below are incomplete and subject to change.
16527 @unnumberedsec Notation and Terminology
16529 @cindex notational conventions, for @sc{gdb/mi}
16530 This chapter uses the following notation:
16534 @code{|} separates two alternatives.
16537 @code{[ @var{something} ]} indicates that @var{something} is optional:
16538 it may or may not be given.
16541 @code{( @var{group} )*} means that @var{group} inside the parentheses
16542 may repeat zero or more times.
16545 @code{( @var{group} )+} means that @var{group} inside the parentheses
16546 may repeat one or more times.
16549 @code{"@var{string}"} means a literal @var{string}.
16553 @heading Dependencies
16556 @heading Acknowledgments
16558 In alphabetic order: Andrew Cagney, Fernando Nasser, Stan Shebs and
16562 * GDB/MI Command Syntax::
16563 * GDB/MI Compatibility with CLI::
16564 * GDB/MI Output Records::
16565 * GDB/MI Command Description Format::
16566 * GDB/MI Breakpoint Table Commands::
16567 * GDB/MI Data Manipulation::
16568 * GDB/MI Program Control::
16569 * GDB/MI Miscellaneous Commands::
16571 * GDB/MI Kod Commands::
16572 * GDB/MI Memory Overlay Commands::
16573 * GDB/MI Signal Handling Commands::
16575 * GDB/MI Stack Manipulation::
16576 * GDB/MI Symbol Query::
16577 * GDB/MI Target Manipulation::
16578 * GDB/MI Thread Commands::
16579 * GDB/MI Tracepoint Commands::
16580 * GDB/MI Variable Objects::
16583 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16584 @node GDB/MI Command Syntax
16585 @section @sc{gdb/mi} Command Syntax
16588 * GDB/MI Input Syntax::
16589 * GDB/MI Output Syntax::
16590 * GDB/MI Simple Examples::
16593 @node GDB/MI Input Syntax
16594 @subsection @sc{gdb/mi} Input Syntax
16596 @cindex input syntax for @sc{gdb/mi}
16597 @cindex @sc{gdb/mi}, input syntax
16599 @item @var{command} @expansion{}
16600 @code{@var{cli-command} | @var{mi-command}}
16602 @item @var{cli-command} @expansion{}
16603 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
16604 @var{cli-command} is any existing @value{GDBN} CLI command.
16606 @item @var{mi-command} @expansion{}
16607 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
16608 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
16610 @item @var{token} @expansion{}
16611 "any sequence of digits"
16613 @item @var{option} @expansion{}
16614 @code{"-" @var{parameter} [ " " @var{parameter} ]}
16616 @item @var{parameter} @expansion{}
16617 @code{@var{non-blank-sequence} | @var{c-string}}
16619 @item @var{operation} @expansion{}
16620 @emph{any of the operations described in this chapter}
16622 @item @var{non-blank-sequence} @expansion{}
16623 @emph{anything, provided it doesn't contain special characters such as
16624 "-", @var{nl}, """ and of course " "}
16626 @item @var{c-string} @expansion{}
16627 @code{""" @var{seven-bit-iso-c-string-content} """}
16629 @item @var{nl} @expansion{}
16638 The CLI commands are still handled by the @sc{mi} interpreter; their
16639 output is described below.
16642 The @code{@var{token}}, when present, is passed back when the command
16646 Some @sc{mi} commands accept optional arguments as part of the parameter
16647 list. Each option is identified by a leading @samp{-} (dash) and may be
16648 followed by an optional argument parameter. Options occur first in the
16649 parameter list and can be delimited from normal parameters using
16650 @samp{--} (this is useful when some parameters begin with a dash).
16657 We want easy access to the existing CLI syntax (for debugging).
16660 We want it to be easy to spot a @sc{mi} operation.
16663 @node GDB/MI Output Syntax
16664 @subsection @sc{gdb/mi} Output Syntax
16666 @cindex output syntax of @sc{gdb/mi}
16667 @cindex @sc{gdb/mi}, output syntax
16668 The output from @sc{gdb/mi} consists of zero or more out-of-band records
16669 followed, optionally, by a single result record. This result record
16670 is for the most recent command. The sequence of output records is
16671 terminated by @samp{(@value{GDBP})}.
16673 If an input command was prefixed with a @code{@var{token}} then the
16674 corresponding output for that command will also be prefixed by that same
16678 @item @var{output} @expansion{}
16679 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(@value{GDBP})" @var{nl}}
16681 @item @var{result-record} @expansion{}
16682 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
16684 @item @var{out-of-band-record} @expansion{}
16685 @code{@var{async-record} | @var{stream-record}}
16687 @item @var{async-record} @expansion{}
16688 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
16690 @item @var{exec-async-output} @expansion{}
16691 @code{[ @var{token} ] "*" @var{async-output}}
16693 @item @var{status-async-output} @expansion{}
16694 @code{[ @var{token} ] "+" @var{async-output}}
16696 @item @var{notify-async-output} @expansion{}
16697 @code{[ @var{token} ] "=" @var{async-output}}
16699 @item @var{async-output} @expansion{}
16700 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
16702 @item @var{result-class} @expansion{}
16703 @code{"done" | "running" | "connected" | "error" | "exit"}
16705 @item @var{async-class} @expansion{}
16706 @code{"stopped" | @var{others}} (where @var{others} will be added
16707 depending on the needs---this is still in development).
16709 @item @var{result} @expansion{}
16710 @code{ @var{variable} "=" @var{value}}
16712 @item @var{variable} @expansion{}
16713 @code{ @var{string} }
16715 @item @var{value} @expansion{}
16716 @code{ @var{const} | @var{tuple} | @var{list} }
16718 @item @var{const} @expansion{}
16719 @code{@var{c-string}}
16721 @item @var{tuple} @expansion{}
16722 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
16724 @item @var{list} @expansion{}
16725 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
16726 @var{result} ( "," @var{result} )* "]" }
16728 @item @var{stream-record} @expansion{}
16729 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
16731 @item @var{console-stream-output} @expansion{}
16732 @code{"~" @var{c-string}}
16734 @item @var{target-stream-output} @expansion{}
16735 @code{"@@" @var{c-string}}
16737 @item @var{log-stream-output} @expansion{}
16738 @code{"&" @var{c-string}}
16740 @item @var{nl} @expansion{}
16743 @item @var{token} @expansion{}
16744 @emph{any sequence of digits}.
16752 All output sequences end in a single line containing a period.
16755 The @code{@var{token}} is from the corresponding request. If an execution
16756 command is interrupted by the @samp{-exec-interrupt} command, the
16757 @var{token} associated with the @samp{*stopped} message is the one of the
16758 original execution command, not the one of the interrupt command.
16761 @cindex status output in @sc{gdb/mi}
16762 @var{status-async-output} contains on-going status information about the
16763 progress of a slow operation. It can be discarded. All status output is
16764 prefixed by @samp{+}.
16767 @cindex async output in @sc{gdb/mi}
16768 @var{exec-async-output} contains asynchronous state change on the target
16769 (stopped, started, disappeared). All async output is prefixed by
16773 @cindex notify output in @sc{gdb/mi}
16774 @var{notify-async-output} contains supplementary information that the
16775 client should handle (e.g., a new breakpoint information). All notify
16776 output is prefixed by @samp{=}.
16779 @cindex console output in @sc{gdb/mi}
16780 @var{console-stream-output} is output that should be displayed as is in the
16781 console. It is the textual response to a CLI command. All the console
16782 output is prefixed by @samp{~}.
16785 @cindex target output in @sc{gdb/mi}
16786 @var{target-stream-output} is the output produced by the target program.
16787 All the target output is prefixed by @samp{@@}.
16790 @cindex log output in @sc{gdb/mi}
16791 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
16792 instance messages that should be displayed as part of an error log. All
16793 the log output is prefixed by @samp{&}.
16796 @cindex list output in @sc{gdb/mi}
16797 New @sc{gdb/mi} commands should only output @var{lists} containing
16803 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
16804 details about the various output records.
16806 @node GDB/MI Simple Examples
16807 @subsection Simple Examples of @sc{gdb/mi} Interaction
16808 @cindex @sc{gdb/mi}, simple examples
16810 This subsection presents several simple examples of interaction using
16811 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
16812 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
16813 the output received from @sc{gdb/mi}.
16815 @subsubheading Target Stop
16816 @c Ummm... There is no "-stop" command. This assumes async, no?
16817 Here's an example of stopping the inferior process:
16828 <- *stop,reason="stop",address="0x123",source="a.c:123"
16832 @subsubheading Simple CLI Command
16834 Here's an example of a simple CLI command being passed through
16835 @sc{gdb/mi} and on to the CLI.
16845 @subsubheading Command With Side Effects
16848 -> -symbol-file xyz.exe
16849 <- *breakpoint,nr="3",address="0x123",source="a.c:123"
16853 @subsubheading A Bad Command
16855 Here's what happens if you pass a non-existent command:
16859 <- ^error,msg="Undefined MI command: rubbish"
16863 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16864 @node GDB/MI Compatibility with CLI
16865 @section @sc{gdb/mi} Compatibility with CLI
16867 @cindex compatibility, @sc{gdb/mi} and CLI
16868 @cindex @sc{gdb/mi}, compatibility with CLI
16869 To help users familiar with @value{GDBN}'s existing CLI interface, @sc{gdb/mi}
16870 accepts existing CLI commands. As specified by the syntax, such
16871 commands can be directly entered into the @sc{gdb/mi} interface and @value{GDBN} will
16874 This mechanism is provided as an aid to developers of @sc{gdb/mi}
16875 clients and not as a reliable interface into the CLI. Since the command
16876 is being interpreteted in an environment that assumes @sc{gdb/mi}
16877 behaviour, the exact output of such commands is likely to end up being
16878 an un-supported hybrid of @sc{gdb/mi} and CLI output.
16880 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16881 @node GDB/MI Output Records
16882 @section @sc{gdb/mi} Output Records
16885 * GDB/MI Result Records::
16886 * GDB/MI Stream Records::
16887 * GDB/MI Out-of-band Records::
16890 @node GDB/MI Result Records
16891 @subsection @sc{gdb/mi} Result Records
16893 @cindex result records in @sc{gdb/mi}
16894 @cindex @sc{gdb/mi}, result records
16895 In addition to a number of out-of-band notifications, the response to a
16896 @sc{gdb/mi} command includes one of the following result indications:
16900 @item "^done" [ "," @var{results} ]
16901 The synchronous operation was successful, @code{@var{results}} are the return
16906 @c Is this one correct? Should it be an out-of-band notification?
16907 The asynchronous operation was successfully started. The target is
16910 @item "^error" "," @var{c-string}
16912 The operation failed. The @code{@var{c-string}} contains the corresponding
16916 @node GDB/MI Stream Records
16917 @subsection @sc{gdb/mi} Stream Records
16919 @cindex @sc{gdb/mi}, stream records
16920 @cindex stream records in @sc{gdb/mi}
16921 @value{GDBN} internally maintains a number of output streams: the console, the
16922 target, and the log. The output intended for each of these streams is
16923 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
16925 Each stream record begins with a unique @dfn{prefix character} which
16926 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
16927 Syntax}). In addition to the prefix, each stream record contains a
16928 @code{@var{string-output}}. This is either raw text (with an implicit new
16929 line) or a quoted C string (which does not contain an implicit newline).
16932 @item "~" @var{string-output}
16933 The console output stream contains text that should be displayed in the
16934 CLI console window. It contains the textual responses to CLI commands.
16936 @item "@@" @var{string-output}
16937 The target output stream contains any textual output from the running
16940 @item "&" @var{string-output}
16941 The log stream contains debugging messages being produced by @value{GDBN}'s
16945 @node GDB/MI Out-of-band Records
16946 @subsection @sc{gdb/mi} Out-of-band Records
16948 @cindex out-of-band records in @sc{gdb/mi}
16949 @cindex @sc{gdb/mi}, out-of-band records
16950 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
16951 additional changes that have occurred. Those changes can either be a
16952 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
16953 target activity (e.g., target stopped).
16955 The following is a preliminary list of possible out-of-band records.
16962 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16963 @node GDB/MI Command Description Format
16964 @section @sc{gdb/mi} Command Description Format
16966 The remaining sections describe blocks of commands. Each block of
16967 commands is laid out in a fashion similar to this section.
16969 Note the the line breaks shown in the examples are here only for
16970 readability. They don't appear in the real output.
16971 Also note that the commands with a non-available example (N.A.@:) are
16972 not yet implemented.
16974 @subheading Motivation
16976 The motivation for this collection of commands.
16978 @subheading Introduction
16980 A brief introduction to this collection of commands as a whole.
16982 @subheading Commands
16984 For each command in the block, the following is described:
16986 @subsubheading Synopsis
16989 -command @var{args}@dots{}
16992 @subsubheading @value{GDBN} Command
16994 The corresponding @value{GDBN} CLI command.
16996 @subsubheading Result
16998 @subsubheading Out-of-band
17000 @subsubheading Notes
17002 @subsubheading Example
17005 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17006 @node GDB/MI Breakpoint Table Commands
17007 @section @sc{gdb/mi} Breakpoint table commands
17009 @cindex breakpoint commands for @sc{gdb/mi}
17010 @cindex @sc{gdb/mi}, breakpoint commands
17011 This section documents @sc{gdb/mi} commands for manipulating
17014 @subheading The @code{-break-after} Command
17015 @findex -break-after
17017 @subsubheading Synopsis
17020 -break-after @var{number} @var{count}
17023 The breakpoint number @var{number} is not in effect until it has been
17024 hit @var{count} times. To see how this is reflected in the output of
17025 the @samp{-break-list} command, see the description of the
17026 @samp{-break-list} command below.
17028 @subsubheading @value{GDBN} Command
17030 The corresponding @value{GDBN} command is @samp{ignore}.
17032 @subsubheading Example
17037 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",line="5"@}
17044 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17045 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17046 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17047 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17048 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17049 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17050 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17051 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17052 addr="0x000100d0",func="main",file="hello.c",line="5",times="0",
17058 @subheading The @code{-break-catch} Command
17059 @findex -break-catch
17061 @subheading The @code{-break-commands} Command
17062 @findex -break-commands
17066 @subheading The @code{-break-condition} Command
17067 @findex -break-condition
17069 @subsubheading Synopsis
17072 -break-condition @var{number} @var{expr}
17075 Breakpoint @var{number} will stop the program only if the condition in
17076 @var{expr} is true. The condition becomes part of the
17077 @samp{-break-list} output (see the description of the @samp{-break-list}
17080 @subsubheading @value{GDBN} Command
17082 The corresponding @value{GDBN} command is @samp{condition}.
17084 @subsubheading Example
17088 -break-condition 1 1
17092 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17093 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17094 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17095 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17096 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17097 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17098 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17099 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17100 addr="0x000100d0",func="main",file="hello.c",line="5",cond="1",
17101 times="0",ignore="3"@}]@}
17105 @subheading The @code{-break-delete} Command
17106 @findex -break-delete
17108 @subsubheading Synopsis
17111 -break-delete ( @var{breakpoint} )+
17114 Delete the breakpoint(s) whose number(s) are specified in the argument
17115 list. This is obviously reflected in the breakpoint list.
17117 @subsubheading @value{GDBN} command
17119 The corresponding @value{GDBN} command is @samp{delete}.
17121 @subsubheading Example
17129 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
17130 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17131 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17132 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17133 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17134 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17135 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17140 @subheading The @code{-break-disable} Command
17141 @findex -break-disable
17143 @subsubheading Synopsis
17146 -break-disable ( @var{breakpoint} )+
17149 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
17150 break list is now set to @samp{n} for the named @var{breakpoint}(s).
17152 @subsubheading @value{GDBN} Command
17154 The corresponding @value{GDBN} command is @samp{disable}.
17156 @subsubheading Example
17164 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17165 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17166 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17167 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17168 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17169 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17170 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17171 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
17172 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
17176 @subheading The @code{-break-enable} Command
17177 @findex -break-enable
17179 @subsubheading Synopsis
17182 -break-enable ( @var{breakpoint} )+
17185 Enable (previously disabled) @var{breakpoint}(s).
17187 @subsubheading @value{GDBN} Command
17189 The corresponding @value{GDBN} command is @samp{enable}.
17191 @subsubheading Example
17199 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17200 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17201 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17202 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17203 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17204 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17205 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17206 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
17207 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
17211 @subheading The @code{-break-info} Command
17212 @findex -break-info
17214 @subsubheading Synopsis
17217 -break-info @var{breakpoint}
17221 Get information about a single breakpoint.
17223 @subsubheading @value{GDBN} command
17225 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
17227 @subsubheading Example
17230 @subheading The @code{-break-insert} Command
17231 @findex -break-insert
17233 @subsubheading Synopsis
17236 -break-insert [ -t ] [ -h ] [ -r ]
17237 [ -c @var{condition} ] [ -i @var{ignore-count} ]
17238 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
17242 If specified, @var{line}, can be one of:
17249 @item filename:linenum
17250 @item filename:function
17254 The possible optional parameters of this command are:
17258 Insert a tempoary breakpoint.
17260 Insert a hardware breakpoint.
17261 @item -c @var{condition}
17262 Make the breakpoint conditional on @var{condition}.
17263 @item -i @var{ignore-count}
17264 Initialize the @var{ignore-count}.
17266 Insert a regular breakpoint in all the functions whose names match the
17267 given regular expression. Other flags are not applicable to regular
17271 @subsubheading Result
17273 The result is in the form:
17276 ^done,bkptno="@var{number}",func="@var{funcname}",
17277 file="@var{filename}",line="@var{lineno}"
17281 where @var{number} is the @value{GDBN} number for this breakpoint, @var{funcname}
17282 is the name of the function where the breakpoint was inserted,
17283 @var{filename} is the name of the source file which contains this
17284 function, and @var{lineno} is the source line number within that file.
17286 Note: this format is open to change.
17287 @c An out-of-band breakpoint instead of part of the result?
17289 @subsubheading @value{GDBN} Command
17291 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
17292 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
17294 @subsubheading Example
17299 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
17301 -break-insert -t foo
17302 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",line="11"@}
17305 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17306 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17307 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17308 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17309 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17310 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17311 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17312 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17313 addr="0x0001072c", func="main",file="recursive2.c",line="4",times="0"@},
17314 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
17315 addr="0x00010774",func="foo",file="recursive2.c",line="11",times="0"@}]@}
17317 -break-insert -r foo.*
17318 ~int foo(int, int);
17319 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c",line="11"@}
17323 @subheading The @code{-break-list} Command
17324 @findex -break-list
17326 @subsubheading Synopsis
17332 Displays the list of inserted breakpoints, showing the following fields:
17336 number of the breakpoint
17338 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
17340 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
17343 is the breakpoint enabled or no: @samp{y} or @samp{n}
17345 memory location at which the breakpoint is set
17347 logical location of the breakpoint, expressed by function name, file
17350 number of times the breakpoint has been hit
17353 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
17354 @code{body} field is an empty list.
17356 @subsubheading @value{GDBN} Command
17358 The corresponding @value{GDBN} command is @samp{info break}.
17360 @subsubheading Example
17365 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17366 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17367 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17368 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17369 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17370 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17371 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17372 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17373 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
17374 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
17375 addr="0x00010114",func="foo",file="hello.c",line="13",times="0"@}]@}
17379 Here's an example of the result when there are no breakpoints:
17384 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
17385 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17386 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17387 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17388 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17389 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17390 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17395 @subheading The @code{-break-watch} Command
17396 @findex -break-watch
17398 @subsubheading Synopsis
17401 -break-watch [ -a | -r ]
17404 Create a watchpoint. With the @samp{-a} option it will create an
17405 @dfn{access} watchpoint, i.e. a watchpoint that triggers either on a
17406 read from or on a write to the memory location. With the @samp{-r}
17407 option, the watchpoint created is a @dfn{read} watchpoint, i.e. it will
17408 trigger only when the memory location is accessed for reading. Without
17409 either of the options, the watchpoint created is a regular watchpoint,
17410 i.e. it will trigger when the memory location is accessed for writing.
17411 @xref{Set Watchpoints, , Setting watchpoints}.
17413 Note that @samp{-break-list} will report a single list of watchpoints and
17414 breakpoints inserted.
17416 @subsubheading @value{GDBN} Command
17418 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
17421 @subsubheading Example
17423 Setting a watchpoint on a variable in the @code{main} function:
17428 ^done,wpt=@{number="2",exp="x"@}
17432 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
17433 value=@{old="-268439212",new="55"@},
17434 frame=@{func="main",args=[],file="recursive2.c",
17435 fullname="/home/foo/bar/devo/myproject/recursive2.c",line="5"@}
17439 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
17440 the program execution twice: first for the variable changing value, then
17441 for the watchpoint going out of scope.
17446 ^done,wpt=@{number="5",exp="C"@}
17450 ^done,reason="watchpoint-trigger",
17451 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
17452 frame=@{func="callee4",args=[],
17453 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
17454 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
17458 ^done,reason="watchpoint-scope",wpnum="5",
17459 frame=@{func="callee3",args=[@{name="strarg",
17460 value="0x11940 \"A string argument.\""@}],
17461 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
17462 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
17466 Listing breakpoints and watchpoints, at different points in the program
17467 execution. Note that once the watchpoint goes out of scope, it is
17473 ^done,wpt=@{number="2",exp="C"@}
17476 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17477 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17478 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17479 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17480 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17481 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17482 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17483 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17484 addr="0x00010734",func="callee4",
17485 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
17486 bkpt=@{number="2",type="watchpoint",disp="keep",
17487 enabled="y",addr="",what="C",times="0"@}]@}
17491 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
17492 value=@{old="-276895068",new="3"@},
17493 frame=@{func="callee4",args=[],
17494 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
17495 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
17498 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17499 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17500 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17501 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17502 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17503 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17504 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17505 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17506 addr="0x00010734",func="callee4",
17507 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
17508 bkpt=@{number="2",type="watchpoint",disp="keep",
17509 enabled="y",addr="",what="C",times="-5"@}]@}
17513 ^done,reason="watchpoint-scope",wpnum="2",
17514 frame=@{func="callee3",args=[@{name="strarg",
17515 value="0x11940 \"A string argument.\""@}],
17516 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
17517 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
17520 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17521 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17522 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17523 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17524 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17525 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17526 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17527 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17528 addr="0x00010734",func="callee4",
17529 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@}]@}
17533 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17534 @node GDB/MI Data Manipulation
17535 @section @sc{gdb/mi} Data Manipulation
17537 @cindex data manipulation, in @sc{gdb/mi}
17538 @cindex @sc{gdb/mi}, data manipulation
17539 This section describes the @sc{gdb/mi} commands that manipulate data:
17540 examine memory and registers, evaluate expressions, etc.
17542 @c REMOVED FROM THE INTERFACE.
17543 @c @subheading -data-assign
17544 @c Change the value of a program variable. Plenty of side effects.
17545 @c @subsubheading GDB command
17547 @c @subsubheading Example
17550 @subheading The @code{-data-disassemble} Command
17551 @findex -data-disassemble
17553 @subsubheading Synopsis
17557 [ -s @var{start-addr} -e @var{end-addr} ]
17558 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
17566 @item @var{start-addr}
17567 is the beginning address (or @code{$pc})
17568 @item @var{end-addr}
17570 @item @var{filename}
17571 is the name of the file to disassemble
17572 @item @var{linenum}
17573 is the line number to disassemble around
17575 is the the number of disassembly lines to be produced. If it is -1,
17576 the whole function will be disassembled, in case no @var{end-addr} is
17577 specified. If @var{end-addr} is specified as a non-zero value, and
17578 @var{lines} is lower than the number of disassembly lines between
17579 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
17580 displayed; if @var{lines} is higher than the number of lines between
17581 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
17584 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
17588 @subsubheading Result
17590 The output for each instruction is composed of four fields:
17599 Note that whatever included in the instruction field, is not manipulated
17600 directely by @sc{gdb/mi}, i.e. it is not possible to adjust its format.
17602 @subsubheading @value{GDBN} Command
17604 There's no direct mapping from this command to the CLI.
17606 @subsubheading Example
17608 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
17612 -data-disassemble -s $pc -e "$pc + 20" -- 0
17615 @{address="0x000107c0",func-name="main",offset="4",
17616 inst="mov 2, %o0"@},
17617 @{address="0x000107c4",func-name="main",offset="8",
17618 inst="sethi %hi(0x11800), %o2"@},
17619 @{address="0x000107c8",func-name="main",offset="12",
17620 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
17621 @{address="0x000107cc",func-name="main",offset="16",
17622 inst="sethi %hi(0x11800), %o2"@},
17623 @{address="0x000107d0",func-name="main",offset="20",
17624 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
17628 Disassemble the whole @code{main} function. Line 32 is part of
17632 -data-disassemble -f basics.c -l 32 -- 0
17634 @{address="0x000107bc",func-name="main",offset="0",
17635 inst="save %sp, -112, %sp"@},
17636 @{address="0x000107c0",func-name="main",offset="4",
17637 inst="mov 2, %o0"@},
17638 @{address="0x000107c4",func-name="main",offset="8",
17639 inst="sethi %hi(0x11800), %o2"@},
17641 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
17642 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
17646 Disassemble 3 instructions from the start of @code{main}:
17650 -data-disassemble -f basics.c -l 32 -n 3 -- 0
17652 @{address="0x000107bc",func-name="main",offset="0",
17653 inst="save %sp, -112, %sp"@},
17654 @{address="0x000107c0",func-name="main",offset="4",
17655 inst="mov 2, %o0"@},
17656 @{address="0x000107c4",func-name="main",offset="8",
17657 inst="sethi %hi(0x11800), %o2"@}]
17661 Disassemble 3 instructions from the start of @code{main} in mixed mode:
17665 -data-disassemble -f basics.c -l 32 -n 3 -- 1
17667 src_and_asm_line=@{line="31",
17668 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
17669 testsuite/gdb.mi/basics.c",line_asm_insn=[
17670 @{address="0x000107bc",func-name="main",offset="0",
17671 inst="save %sp, -112, %sp"@}]@},
17672 src_and_asm_line=@{line="32",
17673 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
17674 testsuite/gdb.mi/basics.c",line_asm_insn=[
17675 @{address="0x000107c0",func-name="main",offset="4",
17676 inst="mov 2, %o0"@},
17677 @{address="0x000107c4",func-name="main",offset="8",
17678 inst="sethi %hi(0x11800), %o2"@}]@}]
17683 @subheading The @code{-data-evaluate-expression} Command
17684 @findex -data-evaluate-expression
17686 @subsubheading Synopsis
17689 -data-evaluate-expression @var{expr}
17692 Evaluate @var{expr} as an expression. The expression could contain an
17693 inferior function call. The function call will execute synchronously.
17694 If the expression contains spaces, it must be enclosed in double quotes.
17696 @subsubheading @value{GDBN} Command
17698 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
17699 @samp{call}. In @code{gdbtk} only, there's a corresponding
17700 @samp{gdb_eval} command.
17702 @subsubheading Example
17704 In the following example, the numbers that precede the commands are the
17705 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
17706 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
17710 211-data-evaluate-expression A
17713 311-data-evaluate-expression &A
17714 311^done,value="0xefffeb7c"
17716 411-data-evaluate-expression A+3
17719 511-data-evaluate-expression "A + 3"
17725 @subheading The @code{-data-list-changed-registers} Command
17726 @findex -data-list-changed-registers
17728 @subsubheading Synopsis
17731 -data-list-changed-registers
17734 Display a list of the registers that have changed.
17736 @subsubheading @value{GDBN} Command
17738 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
17739 has the corresponding command @samp{gdb_changed_register_list}.
17741 @subsubheading Example
17743 On a PPC MBX board:
17751 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
17752 args=[],file="try.c",fullname="/home/foo/bar/devo/myproject/try.c",line="5"@}
17754 -data-list-changed-registers
17755 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
17756 "10","11","13","14","15","16","17","18","19","20","21","22","23",
17757 "24","25","26","27","28","30","31","64","65","66","67","69"]
17762 @subheading The @code{-data-list-register-names} Command
17763 @findex -data-list-register-names
17765 @subsubheading Synopsis
17768 -data-list-register-names [ ( @var{regno} )+ ]
17771 Show a list of register names for the current target. If no arguments
17772 are given, it shows a list of the names of all the registers. If
17773 integer numbers are given as arguments, it will print a list of the
17774 names of the registers corresponding to the arguments. To ensure
17775 consistency between a register name and its number, the output list may
17776 include empty register names.
17778 @subsubheading @value{GDBN} Command
17780 @value{GDBN} does not have a command which corresponds to
17781 @samp{-data-list-register-names}. In @code{gdbtk} there is a
17782 corresponding command @samp{gdb_regnames}.
17784 @subsubheading Example
17786 For the PPC MBX board:
17789 -data-list-register-names
17790 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
17791 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
17792 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
17793 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
17794 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
17795 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
17796 "", "pc","ps","cr","lr","ctr","xer"]
17798 -data-list-register-names 1 2 3
17799 ^done,register-names=["r1","r2","r3"]
17803 @subheading The @code{-data-list-register-values} Command
17804 @findex -data-list-register-values
17806 @subsubheading Synopsis
17809 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
17812 Display the registers' contents. @var{fmt} is the format according to
17813 which the registers' contents are to be returned, followed by an optional
17814 list of numbers specifying the registers to display. A missing list of
17815 numbers indicates that the contents of all the registers must be returned.
17817 Allowed formats for @var{fmt} are:
17834 @subsubheading @value{GDBN} Command
17836 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
17837 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
17839 @subsubheading Example
17841 For a PPC MBX board (note: line breaks are for readability only, they
17842 don't appear in the actual output):
17846 -data-list-register-values r 64 65
17847 ^done,register-values=[@{number="64",value="0xfe00a300"@},
17848 @{number="65",value="0x00029002"@}]
17850 -data-list-register-values x
17851 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
17852 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
17853 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
17854 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
17855 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
17856 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
17857 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
17858 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
17859 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
17860 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
17861 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
17862 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
17863 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
17864 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
17865 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
17866 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
17867 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
17868 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
17869 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
17870 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
17871 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
17872 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
17873 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
17874 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
17875 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
17876 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
17877 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
17878 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
17879 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
17880 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
17881 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
17882 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
17883 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
17884 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
17885 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
17886 @{number="69",value="0x20002b03"@}]
17891 @subheading The @code{-data-read-memory} Command
17892 @findex -data-read-memory
17894 @subsubheading Synopsis
17897 -data-read-memory [ -o @var{byte-offset} ]
17898 @var{address} @var{word-format} @var{word-size}
17899 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
17906 @item @var{address}
17907 An expression specifying the address of the first memory word to be
17908 read. Complex expressions containing embedded white space should be
17909 quoted using the C convention.
17911 @item @var{word-format}
17912 The format to be used to print the memory words. The notation is the
17913 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
17916 @item @var{word-size}
17917 The size of each memory word in bytes.
17919 @item @var{nr-rows}
17920 The number of rows in the output table.
17922 @item @var{nr-cols}
17923 The number of columns in the output table.
17926 If present, indicates that each row should include an @sc{ascii} dump. The
17927 value of @var{aschar} is used as a padding character when a byte is not a
17928 member of the printable @sc{ascii} character set (printable @sc{ascii}
17929 characters are those whose code is between 32 and 126, inclusively).
17931 @item @var{byte-offset}
17932 An offset to add to the @var{address} before fetching memory.
17935 This command displays memory contents as a table of @var{nr-rows} by
17936 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
17937 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
17938 (returned as @samp{total-bytes}). Should less than the requested number
17939 of bytes be returned by the target, the missing words are identified
17940 using @samp{N/A}. The number of bytes read from the target is returned
17941 in @samp{nr-bytes} and the starting address used to read memory in
17944 The address of the next/previous row or page is available in
17945 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
17948 @subsubheading @value{GDBN} Command
17950 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
17951 @samp{gdb_get_mem} memory read command.
17953 @subsubheading Example
17955 Read six bytes of memory starting at @code{bytes+6} but then offset by
17956 @code{-6} bytes. Format as three rows of two columns. One byte per
17957 word. Display each word in hex.
17961 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
17962 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
17963 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
17964 prev-page="0x0000138a",memory=[
17965 @{addr="0x00001390",data=["0x00","0x01"]@},
17966 @{addr="0x00001392",data=["0x02","0x03"]@},
17967 @{addr="0x00001394",data=["0x04","0x05"]@}]
17971 Read two bytes of memory starting at address @code{shorts + 64} and
17972 display as a single word formatted in decimal.
17976 5-data-read-memory shorts+64 d 2 1 1
17977 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
17978 next-row="0x00001512",prev-row="0x0000150e",
17979 next-page="0x00001512",prev-page="0x0000150e",memory=[
17980 @{addr="0x00001510",data=["128"]@}]
17984 Read thirty two bytes of memory starting at @code{bytes+16} and format
17985 as eight rows of four columns. Include a string encoding with @samp{x}
17986 used as the non-printable character.
17990 4-data-read-memory bytes+16 x 1 8 4 x
17991 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
17992 next-row="0x000013c0",prev-row="0x0000139c",
17993 next-page="0x000013c0",prev-page="0x00001380",memory=[
17994 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
17995 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
17996 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
17997 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
17998 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
17999 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
18000 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
18001 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
18005 @subheading The @code{-display-delete} Command
18006 @findex -display-delete
18008 @subsubheading Synopsis
18011 -display-delete @var{number}
18014 Delete the display @var{number}.
18016 @subsubheading @value{GDBN} Command
18018 The corresponding @value{GDBN} command is @samp{delete display}.
18020 @subsubheading Example
18024 @subheading The @code{-display-disable} Command
18025 @findex -display-disable
18027 @subsubheading Synopsis
18030 -display-disable @var{number}
18033 Disable display @var{number}.
18035 @subsubheading @value{GDBN} Command
18037 The corresponding @value{GDBN} command is @samp{disable display}.
18039 @subsubheading Example
18043 @subheading The @code{-display-enable} Command
18044 @findex -display-enable
18046 @subsubheading Synopsis
18049 -display-enable @var{number}
18052 Enable display @var{number}.
18054 @subsubheading @value{GDBN} Command
18056 The corresponding @value{GDBN} command is @samp{enable display}.
18058 @subsubheading Example
18062 @subheading The @code{-display-insert} Command
18063 @findex -display-insert
18065 @subsubheading Synopsis
18068 -display-insert @var{expression}
18071 Display @var{expression} every time the program stops.
18073 @subsubheading @value{GDBN} Command
18075 The corresponding @value{GDBN} command is @samp{display}.
18077 @subsubheading Example
18081 @subheading The @code{-display-list} Command
18082 @findex -display-list
18084 @subsubheading Synopsis
18090 List the displays. Do not show the current values.
18092 @subsubheading @value{GDBN} Command
18094 The corresponding @value{GDBN} command is @samp{info display}.
18096 @subsubheading Example
18100 @subheading The @code{-environment-cd} Command
18101 @findex -environment-cd
18103 @subsubheading Synopsis
18106 -environment-cd @var{pathdir}
18109 Set @value{GDBN}'s working directory.
18111 @subsubheading @value{GDBN} Command
18113 The corresponding @value{GDBN} command is @samp{cd}.
18115 @subsubheading Example
18119 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18125 @subheading The @code{-environment-directory} Command
18126 @findex -environment-directory
18128 @subsubheading Synopsis
18131 -environment-directory [ -r ] [ @var{pathdir} ]+
18134 Add directories @var{pathdir} to beginning of search path for source files.
18135 If the @samp{-r} option is used, the search path is reset to the default
18136 search path. If directories @var{pathdir} are supplied in addition to the
18137 @samp{-r} option, the search path is first reset and then addition
18139 Multiple directories may be specified, separated by blanks. Specifying
18140 multiple directories in a single command
18141 results in the directories added to the beginning of the
18142 search path in the same order they were presented in the command.
18143 If blanks are needed as
18144 part of a directory name, double-quotes should be used around
18145 the name. In the command output, the path will show up separated
18146 by the system directory-separator character. The directory-seperator
18147 character must not be used
18148 in any directory name.
18149 If no directories are specified, the current search path is displayed.
18151 @subsubheading @value{GDBN} Command
18153 The corresponding @value{GDBN} command is @samp{dir}.
18155 @subsubheading Example
18159 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18160 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18162 -environment-directory ""
18163 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18165 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
18166 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
18168 -environment-directory -r
18169 ^done,source-path="$cdir:$cwd"
18174 @subheading The @code{-environment-path} Command
18175 @findex -environment-path
18177 @subsubheading Synopsis
18180 -environment-path [ -r ] [ @var{pathdir} ]+
18183 Add directories @var{pathdir} to beginning of search path for object files.
18184 If the @samp{-r} option is used, the search path is reset to the original
18185 search path that existed at gdb start-up. If directories @var{pathdir} are
18186 supplied in addition to the
18187 @samp{-r} option, the search path is first reset and then addition
18189 Multiple directories may be specified, separated by blanks. Specifying
18190 multiple directories in a single command
18191 results in the directories added to the beginning of the
18192 search path in the same order they were presented in the command.
18193 If blanks are needed as
18194 part of a directory name, double-quotes should be used around
18195 the name. In the command output, the path will show up separated
18196 by the system directory-separator character. The directory-seperator
18197 character must not be used
18198 in any directory name.
18199 If no directories are specified, the current path is displayed.
18202 @subsubheading @value{GDBN} Command
18204 The corresponding @value{GDBN} command is @samp{path}.
18206 @subsubheading Example
18211 ^done,path="/usr/bin"
18213 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
18214 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
18216 -environment-path -r /usr/local/bin
18217 ^done,path="/usr/local/bin:/usr/bin"
18222 @subheading The @code{-environment-pwd} Command
18223 @findex -environment-pwd
18225 @subsubheading Synopsis
18231 Show the current working directory.
18233 @subsubheading @value{GDBN} command
18235 The corresponding @value{GDBN} command is @samp{pwd}.
18237 @subsubheading Example
18242 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
18246 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18247 @node GDB/MI Program Control
18248 @section @sc{gdb/mi} Program control
18250 @subsubheading Program termination
18252 As a result of execution, the inferior program can run to completion, if
18253 it doesn't encounter any breakpoints. In this case the output will
18254 include an exit code, if the program has exited exceptionally.
18256 @subsubheading Examples
18259 Program exited normally:
18267 *stopped,reason="exited-normally"
18272 Program exited exceptionally:
18280 *stopped,reason="exited",exit-code="01"
18284 Another way the program can terminate is if it receives a signal such as
18285 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
18289 *stopped,reason="exited-signalled",signal-name="SIGINT",
18290 signal-meaning="Interrupt"
18294 @subheading The @code{-exec-abort} Command
18295 @findex -exec-abort
18297 @subsubheading Synopsis
18303 Kill the inferior running program.
18305 @subsubheading @value{GDBN} Command
18307 The corresponding @value{GDBN} command is @samp{kill}.
18309 @subsubheading Example
18313 @subheading The @code{-exec-arguments} Command
18314 @findex -exec-arguments
18316 @subsubheading Synopsis
18319 -exec-arguments @var{args}
18322 Set the inferior program arguments, to be used in the next
18325 @subsubheading @value{GDBN} Command
18327 The corresponding @value{GDBN} command is @samp{set args}.
18329 @subsubheading Example
18332 Don't have one around.
18335 @subheading The @code{-exec-continue} Command
18336 @findex -exec-continue
18338 @subsubheading Synopsis
18344 Asynchronous command. Resumes the execution of the inferior program
18345 until a breakpoint is encountered, or until the inferior exits.
18347 @subsubheading @value{GDBN} Command
18349 The corresponding @value{GDBN} corresponding is @samp{continue}.
18351 @subsubheading Example
18358 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
18359 file="hello.c",fullname="/home/foo/bar/devo/myproject/hello.c",line="13"@}
18364 @subheading The @code{-exec-finish} Command
18365 @findex -exec-finish
18367 @subsubheading Synopsis
18373 Asynchronous command. Resumes the execution of the inferior program
18374 until the current function is exited. Displays the results returned by
18377 @subsubheading @value{GDBN} Command
18379 The corresponding @value{GDBN} command is @samp{finish}.
18381 @subsubheading Example
18383 Function returning @code{void}.
18390 *stopped,reason="function-finished",frame=@{func="main",args=[],
18391 file="hello.c",fullname="/home/foo/bar/devo/myproject/hello.c",line="7"@}
18395 Function returning other than @code{void}. The name of the internal
18396 @value{GDBN} variable storing the result is printed, together with the
18403 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
18404 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
18405 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
18406 gdb-result-var="$1",return-value="0"
18411 @subheading The @code{-exec-interrupt} Command
18412 @findex -exec-interrupt
18414 @subsubheading Synopsis
18420 Asynchronous command. Interrupts the background execution of the target.
18421 Note how the token associated with the stop message is the one for the
18422 execution command that has been interrupted. The token for the interrupt
18423 itself only appears in the @samp{^done} output. If the user is trying to
18424 interrupt a non-running program, an error message will be printed.
18426 @subsubheading @value{GDBN} Command
18428 The corresponding @value{GDBN} command is @samp{interrupt}.
18430 @subsubheading Example
18441 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
18442 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
18443 fullname="/home/foo/bar/devo/myproject/try.c",line="13"@}
18448 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
18453 @subheading The @code{-exec-next} Command
18456 @subsubheading Synopsis
18462 Asynchronous command. Resumes execution of the inferior program, stopping
18463 when the beginning of the next source line is reached.
18465 @subsubheading @value{GDBN} Command
18467 The corresponding @value{GDBN} command is @samp{next}.
18469 @subsubheading Example
18475 *stopped,reason="end-stepping-range",line="8",file="hello.c"
18480 @subheading The @code{-exec-next-instruction} Command
18481 @findex -exec-next-instruction
18483 @subsubheading Synopsis
18486 -exec-next-instruction
18489 Asynchronous command. Executes one machine instruction. If the
18490 instruction is a function call continues until the function returns. If
18491 the program stops at an instruction in the middle of a source line, the
18492 address will be printed as well.
18494 @subsubheading @value{GDBN} Command
18496 The corresponding @value{GDBN} command is @samp{nexti}.
18498 @subsubheading Example
18502 -exec-next-instruction
18506 *stopped,reason="end-stepping-range",
18507 addr="0x000100d4",line="5",file="hello.c"
18512 @subheading The @code{-exec-return} Command
18513 @findex -exec-return
18515 @subsubheading Synopsis
18521 Makes current function return immediately. Doesn't execute the inferior.
18522 Displays the new current frame.
18524 @subsubheading @value{GDBN} Command
18526 The corresponding @value{GDBN} command is @samp{return}.
18528 @subsubheading Example
18532 200-break-insert callee4
18533 200^done,bkpt=@{number="1",addr="0x00010734",
18534 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
18539 000*stopped,reason="breakpoint-hit",bkptno="1",
18540 frame=@{func="callee4",args=[],
18541 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18542 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
18548 111^done,frame=@{level="0",func="callee3",
18549 args=[@{name="strarg",
18550 value="0x11940 \"A string argument.\""@}],
18551 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18552 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18557 @subheading The @code{-exec-run} Command
18560 @subsubheading Synopsis
18566 Asynchronous command. Starts execution of the inferior from the
18567 beginning. The inferior executes until either a breakpoint is
18568 encountered or the program exits.
18570 @subsubheading @value{GDBN} Command
18572 The corresponding @value{GDBN} command is @samp{run}.
18574 @subsubheading Example
18579 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
18584 *stopped,reason="breakpoint-hit",bkptno="1",
18585 frame=@{func="main",args=[],file="recursive2.c",
18586 fullname="/home/foo/bar/devo/myproject/recursive2.c",line="4"@}
18591 @subheading The @code{-exec-show-arguments} Command
18592 @findex -exec-show-arguments
18594 @subsubheading Synopsis
18597 -exec-show-arguments
18600 Print the arguments of the program.
18602 @subsubheading @value{GDBN} Command
18604 The corresponding @value{GDBN} command is @samp{show args}.
18606 @subsubheading Example
18609 @c @subheading -exec-signal
18611 @subheading The @code{-exec-step} Command
18614 @subsubheading Synopsis
18620 Asynchronous command. Resumes execution of the inferior program, stopping
18621 when the beginning of the next source line is reached, if the next
18622 source line is not a function call. If it is, stop at the first
18623 instruction of the called function.
18625 @subsubheading @value{GDBN} Command
18627 The corresponding @value{GDBN} command is @samp{step}.
18629 @subsubheading Example
18631 Stepping into a function:
18637 *stopped,reason="end-stepping-range",
18638 frame=@{func="foo",args=[@{name="a",value="10"@},
18639 @{name="b",value="0"@}],file="recursive2.c",
18640 fullname="/home/foo/bar/devo/myproject/recursive2.c",line="11"@}
18650 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
18655 @subheading The @code{-exec-step-instruction} Command
18656 @findex -exec-step-instruction
18658 @subsubheading Synopsis
18661 -exec-step-instruction
18664 Asynchronous command. Resumes the inferior which executes one machine
18665 instruction. The output, once @value{GDBN} has stopped, will vary depending on
18666 whether we have stopped in the middle of a source line or not. In the
18667 former case, the address at which the program stopped will be printed as
18670 @subsubheading @value{GDBN} Command
18672 The corresponding @value{GDBN} command is @samp{stepi}.
18674 @subsubheading Example
18678 -exec-step-instruction
18682 *stopped,reason="end-stepping-range",
18683 frame=@{func="foo",args=[],file="try.c",
18684 fullname="/home/foo/bar/devo/myproject/try.c",line="10"@}
18686 -exec-step-instruction
18690 *stopped,reason="end-stepping-range",
18691 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
18692 fullname="/home/foo/bar/devo/myproject/try.c",line="10"@}
18697 @subheading The @code{-exec-until} Command
18698 @findex -exec-until
18700 @subsubheading Synopsis
18703 -exec-until [ @var{location} ]
18706 Asynchronous command. Executes the inferior until the @var{location}
18707 specified in the argument is reached. If there is no argument, the inferior
18708 executes until a source line greater than the current one is reached.
18709 The reason for stopping in this case will be @samp{location-reached}.
18711 @subsubheading @value{GDBN} Command
18713 The corresponding @value{GDBN} command is @samp{until}.
18715 @subsubheading Example
18719 -exec-until recursive2.c:6
18723 *stopped,reason="location-reached",frame=@{func="main",args=[],
18724 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="6"@}
18729 @subheading -file-clear
18730 Is this going away????
18734 @subheading The @code{-file-exec-and-symbols} Command
18735 @findex -file-exec-and-symbols
18737 @subsubheading Synopsis
18740 -file-exec-and-symbols @var{file}
18743 Specify the executable file to be debugged. This file is the one from
18744 which the symbol table is also read. If no file is specified, the
18745 command clears the executable and symbol information. If breakpoints
18746 are set when using this command with no arguments, @value{GDBN} will produce
18747 error messages. Otherwise, no output is produced, except a completion
18750 @subsubheading @value{GDBN} Command
18752 The corresponding @value{GDBN} command is @samp{file}.
18754 @subsubheading Example
18758 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
18764 @subheading The @code{-file-exec-file} Command
18765 @findex -file-exec-file
18767 @subsubheading Synopsis
18770 -file-exec-file @var{file}
18773 Specify the executable file to be debugged. Unlike
18774 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
18775 from this file. If used without argument, @value{GDBN} clears the information
18776 about the executable file. No output is produced, except a completion
18779 @subsubheading @value{GDBN} Command
18781 The corresponding @value{GDBN} command is @samp{exec-file}.
18783 @subsubheading Example
18787 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
18793 @subheading The @code{-file-list-exec-sections} Command
18794 @findex -file-list-exec-sections
18796 @subsubheading Synopsis
18799 -file-list-exec-sections
18802 List the sections of the current executable file.
18804 @subsubheading @value{GDBN} Command
18806 The @value{GDBN} command @samp{info file} shows, among the rest, the same
18807 information as this command. @code{gdbtk} has a corresponding command
18808 @samp{gdb_load_info}.
18810 @subsubheading Example
18814 @subheading The @code{-file-list-exec-source-file} Command
18815 @findex -file-list-exec-source-file
18817 @subsubheading Synopsis
18820 -file-list-exec-source-file
18823 List the line number, the current source file, and the absolute path
18824 to the current source file for the current executable.
18826 @subsubheading @value{GDBN} Command
18828 There's no @value{GDBN} command which directly corresponds to this one.
18830 @subsubheading Example
18834 123-file-list-exec-source-file
18835 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
18840 @subheading The @code{-file-list-exec-source-files} Command
18841 @findex -file-list-exec-source-files
18843 @subsubheading Synopsis
18846 -file-list-exec-source-files
18849 List the source files for the current executable.
18851 It will always output the filename, but only when GDB can find the absolute
18852 file name of a source file, will it output the fullname.
18854 @subsubheading @value{GDBN} Command
18856 There's no @value{GDBN} command which directly corresponds to this one.
18857 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
18859 @subsubheading Example
18862 -file-list-exec-source-files
18864 @{file=foo.c,fullname=/home/foo.c@},
18865 @{file=/home/bar.c,fullname=/home/bar.c@},
18866 @{file=gdb_could_not_find_fullpath.c@}]
18870 @subheading The @code{-file-list-shared-libraries} Command
18871 @findex -file-list-shared-libraries
18873 @subsubheading Synopsis
18876 -file-list-shared-libraries
18879 List the shared libraries in the program.
18881 @subsubheading @value{GDBN} Command
18883 The corresponding @value{GDBN} command is @samp{info shared}.
18885 @subsubheading Example
18889 @subheading The @code{-file-list-symbol-files} Command
18890 @findex -file-list-symbol-files
18892 @subsubheading Synopsis
18895 -file-list-symbol-files
18900 @subsubheading @value{GDBN} Command
18902 The corresponding @value{GDBN} command is @samp{info file} (part of it).
18904 @subsubheading Example
18908 @subheading The @code{-file-symbol-file} Command
18909 @findex -file-symbol-file
18911 @subsubheading Synopsis
18914 -file-symbol-file @var{file}
18917 Read symbol table info from the specified @var{file} argument. When
18918 used without arguments, clears @value{GDBN}'s symbol table info. No output is
18919 produced, except for a completion notification.
18921 @subsubheading @value{GDBN} Command
18923 The corresponding @value{GDBN} command is @samp{symbol-file}.
18925 @subsubheading Example
18929 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
18934 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18935 @node GDB/MI Miscellaneous Commands
18936 @section Miscellaneous @value{GDBN} commands in @sc{gdb/mi}
18938 @c @subheading -gdb-complete
18940 @subheading The @code{-gdb-exit} Command
18943 @subsubheading Synopsis
18949 Exit @value{GDBN} immediately.
18951 @subsubheading @value{GDBN} Command
18953 Approximately corresponds to @samp{quit}.
18955 @subsubheading Example
18962 @subheading The @code{-gdb-set} Command
18965 @subsubheading Synopsis
18971 Set an internal @value{GDBN} variable.
18972 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
18974 @subsubheading @value{GDBN} Command
18976 The corresponding @value{GDBN} command is @samp{set}.
18978 @subsubheading Example
18988 @subheading The @code{-gdb-show} Command
18991 @subsubheading Synopsis
18997 Show the current value of a @value{GDBN} variable.
18999 @subsubheading @value{GDBN} command
19001 The corresponding @value{GDBN} command is @samp{show}.
19003 @subsubheading Example
19012 @c @subheading -gdb-source
19015 @subheading The @code{-gdb-version} Command
19016 @findex -gdb-version
19018 @subsubheading Synopsis
19024 Show version information for @value{GDBN}. Used mostly in testing.
19026 @subsubheading @value{GDBN} Command
19028 There's no equivalent @value{GDBN} command. @value{GDBN} by default shows this
19029 information when you start an interactive session.
19031 @subsubheading Example
19033 @c This example modifies the actual output from GDB to avoid overfull
19039 ~Copyright 2000 Free Software Foundation, Inc.
19040 ~GDB is free software, covered by the GNU General Public License, and
19041 ~you are welcome to change it and/or distribute copies of it under
19042 ~ certain conditions.
19043 ~Type "show copying" to see the conditions.
19044 ~There is absolutely no warranty for GDB. Type "show warranty" for
19046 ~This GDB was configured as
19047 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
19052 @subheading The @code{-interpreter-exec} Command
19053 @findex -interpreter-exec
19055 @subheading Synopsis
19058 -interpreter-exec @var{interpreter} @var{command}
19061 Execute the specified @var{command} in the given @var{interpreter}.
19063 @subheading @value{GDBN} Command
19065 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
19067 @subheading Example
19071 -interpreter-exec console "break main"
19072 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
19073 &"During symbol reading, bad structure-type format.\n"
19074 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
19080 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19081 @node GDB/MI Kod Commands
19082 @section @sc{gdb/mi} Kod Commands
19084 The Kod commands are not implemented.
19086 @c @subheading -kod-info
19088 @c @subheading -kod-list
19090 @c @subheading -kod-list-object-types
19092 @c @subheading -kod-show
19094 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19095 @node GDB/MI Memory Overlay Commands
19096 @section @sc{gdb/mi} Memory Overlay Commands
19098 The memory overlay commands are not implemented.
19100 @c @subheading -overlay-auto
19102 @c @subheading -overlay-list-mapping-state
19104 @c @subheading -overlay-list-overlays
19106 @c @subheading -overlay-map
19108 @c @subheading -overlay-off
19110 @c @subheading -overlay-on
19112 @c @subheading -overlay-unmap
19114 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19115 @node GDB/MI Signal Handling Commands
19116 @section @sc{gdb/mi} Signal Handling Commands
19118 Signal handling commands are not implemented.
19120 @c @subheading -signal-handle
19122 @c @subheading -signal-list-handle-actions
19124 @c @subheading -signal-list-signal-types
19128 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19129 @node GDB/MI Stack Manipulation
19130 @section @sc{gdb/mi} Stack Manipulation Commands
19133 @subheading The @code{-stack-info-frame} Command
19134 @findex -stack-info-frame
19136 @subsubheading Synopsis
19142 Get info on the current frame.
19144 @subsubheading @value{GDBN} Command
19146 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
19147 (without arguments).
19149 @subsubheading Example
19152 @subheading The @code{-stack-info-depth} Command
19153 @findex -stack-info-depth
19155 @subsubheading Synopsis
19158 -stack-info-depth [ @var{max-depth} ]
19161 Return the depth of the stack. If the integer argument @var{max-depth}
19162 is specified, do not count beyond @var{max-depth} frames.
19164 @subsubheading @value{GDBN} Command
19166 There's no equivalent @value{GDBN} command.
19168 @subsubheading Example
19170 For a stack with frame levels 0 through 11:
19177 -stack-info-depth 4
19180 -stack-info-depth 12
19183 -stack-info-depth 11
19186 -stack-info-depth 13
19191 @subheading The @code{-stack-list-arguments} Command
19192 @findex -stack-list-arguments
19194 @subsubheading Synopsis
19197 -stack-list-arguments @var{show-values}
19198 [ @var{low-frame} @var{high-frame} ]
19201 Display a list of the arguments for the frames between @var{low-frame}
19202 and @var{high-frame} (inclusive). If @var{low-frame} and
19203 @var{high-frame} are not provided, list the arguments for the whole call
19206 The @var{show-values} argument must have a value of 0 or 1. A value of
19207 0 means that only the names of the arguments are listed, a value of 1
19208 means that both names and values of the arguments are printed.
19210 @subsubheading @value{GDBN} Command
19212 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
19213 @samp{gdb_get_args} command which partially overlaps with the
19214 functionality of @samp{-stack-list-arguments}.
19216 @subsubheading Example
19223 frame=@{level="0",addr="0x00010734",func="callee4",
19224 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19225 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
19226 frame=@{level="1",addr="0x0001076c",func="callee3",
19227 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19228 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
19229 frame=@{level="2",addr="0x0001078c",func="callee2",
19230 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19231 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
19232 frame=@{level="3",addr="0x000107b4",func="callee1",
19233 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19234 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
19235 frame=@{level="4",addr="0x000107e0",func="main",
19236 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19237 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
19239 -stack-list-arguments 0
19242 frame=@{level="0",args=[]@},
19243 frame=@{level="1",args=[name="strarg"]@},
19244 frame=@{level="2",args=[name="intarg",name="strarg"]@},
19245 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
19246 frame=@{level="4",args=[]@}]
19248 -stack-list-arguments 1
19251 frame=@{level="0",args=[]@},
19253 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19254 frame=@{level="2",args=[
19255 @{name="intarg",value="2"@},
19256 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19257 @{frame=@{level="3",args=[
19258 @{name="intarg",value="2"@},
19259 @{name="strarg",value="0x11940 \"A string argument.\""@},
19260 @{name="fltarg",value="3.5"@}]@},
19261 frame=@{level="4",args=[]@}]
19263 -stack-list-arguments 0 2 2
19264 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
19266 -stack-list-arguments 1 2 2
19267 ^done,stack-args=[frame=@{level="2",
19268 args=[@{name="intarg",value="2"@},
19269 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
19273 @c @subheading -stack-list-exception-handlers
19276 @subheading The @code{-stack-list-frames} Command
19277 @findex -stack-list-frames
19279 @subsubheading Synopsis
19282 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
19285 List the frames currently on the stack. For each frame it displays the
19290 The frame number, 0 being the topmost frame, i.e. the innermost function.
19292 The @code{$pc} value for that frame.
19296 File name of the source file where the function lives.
19298 Line number corresponding to the @code{$pc}.
19301 If invoked without arguments, this command prints a backtrace for the
19302 whole stack. If given two integer arguments, it shows the frames whose
19303 levels are between the two arguments (inclusive). If the two arguments
19304 are equal, it shows the single frame at the corresponding level.
19306 @subsubheading @value{GDBN} Command
19308 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
19310 @subsubheading Example
19312 Full stack backtrace:
19318 [frame=@{level="0",addr="0x0001076c",func="foo",
19319 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="11"@},
19320 frame=@{level="1",addr="0x000107a4",func="foo",
19321 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19322 frame=@{level="2",addr="0x000107a4",func="foo",
19323 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19324 frame=@{level="3",addr="0x000107a4",func="foo",
19325 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19326 frame=@{level="4",addr="0x000107a4",func="foo",
19327 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19328 frame=@{level="5",addr="0x000107a4",func="foo",
19329 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19330 frame=@{level="6",addr="0x000107a4",func="foo",
19331 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19332 frame=@{level="7",addr="0x000107a4",func="foo",
19333 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19334 frame=@{level="8",addr="0x000107a4",func="foo",
19335 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19336 frame=@{level="9",addr="0x000107a4",func="foo",
19337 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19338 frame=@{level="10",addr="0x000107a4",func="foo",
19339 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19340 frame=@{level="11",addr="0x00010738",func="main",
19341 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="4"@}]
19345 Show frames between @var{low_frame} and @var{high_frame}:
19349 -stack-list-frames 3 5
19351 [frame=@{level="3",addr="0x000107a4",func="foo",
19352 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19353 frame=@{level="4",addr="0x000107a4",func="foo",
19354 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19355 frame=@{level="5",addr="0x000107a4",func="foo",
19356 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@}]
19360 Show a single frame:
19364 -stack-list-frames 3 3
19366 [frame=@{level="3",addr="0x000107a4",func="foo",
19367 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@}]
19372 @subheading The @code{-stack-list-locals} Command
19373 @findex -stack-list-locals
19375 @subsubheading Synopsis
19378 -stack-list-locals @var{print-values}
19381 Display the local variable names for the current frame. With an
19382 argument of 0 or @code{--no-values}, prints only the names of the variables.
19383 With argument of 1 or @code{--all-values}, prints also their values. With
19384 argument of 2 or @code{--simple-values}, prints the name, type and value for
19385 simple data types and the name and type for arrays, structures and
19386 unions. In this last case, the idea is that the user can see the
19387 value of simple data types immediately and he can create variable
19388 objects for other data types if he wishes to explore their values in
19391 @subsubheading @value{GDBN} Command
19393 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
19395 @subsubheading Example
19399 -stack-list-locals 0
19400 ^done,locals=[name="A",name="B",name="C"]
19402 -stack-list-locals --all-values
19403 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
19404 @{name="C",value="@{1, 2, 3@}"@}]
19405 -stack-list-locals --simple-values
19406 ^done,locals=[@{name="A",type="int",value="1"@},
19407 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
19412 @subheading The @code{-stack-select-frame} Command
19413 @findex -stack-select-frame
19415 @subsubheading Synopsis
19418 -stack-select-frame @var{framenum}
19421 Change the current frame. Select a different frame @var{framenum} on
19424 @subsubheading @value{GDBN} Command
19426 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
19427 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
19429 @subsubheading Example
19433 -stack-select-frame 2
19438 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19439 @node GDB/MI Symbol Query
19440 @section @sc{gdb/mi} Symbol Query Commands
19443 @subheading The @code{-symbol-info-address} Command
19444 @findex -symbol-info-address
19446 @subsubheading Synopsis
19449 -symbol-info-address @var{symbol}
19452 Describe where @var{symbol} is stored.
19454 @subsubheading @value{GDBN} Command
19456 The corresponding @value{GDBN} command is @samp{info address}.
19458 @subsubheading Example
19462 @subheading The @code{-symbol-info-file} Command
19463 @findex -symbol-info-file
19465 @subsubheading Synopsis
19471 Show the file for the symbol.
19473 @subsubheading @value{GDBN} Command
19475 There's no equivalent @value{GDBN} command. @code{gdbtk} has
19476 @samp{gdb_find_file}.
19478 @subsubheading Example
19482 @subheading The @code{-symbol-info-function} Command
19483 @findex -symbol-info-function
19485 @subsubheading Synopsis
19488 -symbol-info-function
19491 Show which function the symbol lives in.
19493 @subsubheading @value{GDBN} Command
19495 @samp{gdb_get_function} in @code{gdbtk}.
19497 @subsubheading Example
19501 @subheading The @code{-symbol-info-line} Command
19502 @findex -symbol-info-line
19504 @subsubheading Synopsis
19510 Show the core addresses of the code for a source line.
19512 @subsubheading @value{GDBN} Command
19514 The corresponding @value{GDBN} command is @samp{info line}.
19515 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
19517 @subsubheading Example
19521 @subheading The @code{-symbol-info-symbol} Command
19522 @findex -symbol-info-symbol
19524 @subsubheading Synopsis
19527 -symbol-info-symbol @var{addr}
19530 Describe what symbol is at location @var{addr}.
19532 @subsubheading @value{GDBN} Command
19534 The corresponding @value{GDBN} command is @samp{info symbol}.
19536 @subsubheading Example
19540 @subheading The @code{-symbol-list-functions} Command
19541 @findex -symbol-list-functions
19543 @subsubheading Synopsis
19546 -symbol-list-functions
19549 List the functions in the executable.
19551 @subsubheading @value{GDBN} Command
19553 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
19554 @samp{gdb_search} in @code{gdbtk}.
19556 @subsubheading Example
19560 @subheading The @code{-symbol-list-lines} Command
19561 @findex -symbol-list-lines
19563 @subsubheading Synopsis
19566 -symbol-list-lines @var{filename}
19569 Print the list of lines that contain code and their associated program
19570 addresses for the given source filename. The entries are sorted in
19571 ascending PC order.
19573 @subsubheading @value{GDBN} Command
19575 There is no corresponding @value{GDBN} command.
19577 @subsubheading Example
19580 -symbol-list-lines basics.c
19581 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
19586 @subheading The @code{-symbol-list-types} Command
19587 @findex -symbol-list-types
19589 @subsubheading Synopsis
19595 List all the type names.
19597 @subsubheading @value{GDBN} Command
19599 The corresponding commands are @samp{info types} in @value{GDBN},
19600 @samp{gdb_search} in @code{gdbtk}.
19602 @subsubheading Example
19606 @subheading The @code{-symbol-list-variables} Command
19607 @findex -symbol-list-variables
19609 @subsubheading Synopsis
19612 -symbol-list-variables
19615 List all the global and static variable names.
19617 @subsubheading @value{GDBN} Command
19619 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
19621 @subsubheading Example
19625 @subheading The @code{-symbol-locate} Command
19626 @findex -symbol-locate
19628 @subsubheading Synopsis
19634 @subsubheading @value{GDBN} Command
19636 @samp{gdb_loc} in @code{gdbtk}.
19638 @subsubheading Example
19642 @subheading The @code{-symbol-type} Command
19643 @findex -symbol-type
19645 @subsubheading Synopsis
19648 -symbol-type @var{variable}
19651 Show type of @var{variable}.
19653 @subsubheading @value{GDBN} Command
19655 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
19656 @samp{gdb_obj_variable}.
19658 @subsubheading Example
19662 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19663 @node GDB/MI Target Manipulation
19664 @section @sc{gdb/mi} Target Manipulation Commands
19667 @subheading The @code{-target-attach} Command
19668 @findex -target-attach
19670 @subsubheading Synopsis
19673 -target-attach @var{pid} | @var{file}
19676 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
19678 @subsubheading @value{GDBN} command
19680 The corresponding @value{GDBN} command is @samp{attach}.
19682 @subsubheading Example
19686 @subheading The @code{-target-compare-sections} Command
19687 @findex -target-compare-sections
19689 @subsubheading Synopsis
19692 -target-compare-sections [ @var{section} ]
19695 Compare data of section @var{section} on target to the exec file.
19696 Without the argument, all sections are compared.
19698 @subsubheading @value{GDBN} Command
19700 The @value{GDBN} equivalent is @samp{compare-sections}.
19702 @subsubheading Example
19706 @subheading The @code{-target-detach} Command
19707 @findex -target-detach
19709 @subsubheading Synopsis
19715 Disconnect from the remote target. There's no output.
19717 @subsubheading @value{GDBN} command
19719 The corresponding @value{GDBN} command is @samp{detach}.
19721 @subsubheading Example
19731 @subheading The @code{-target-disconnect} Command
19732 @findex -target-disconnect
19734 @subsubheading Synopsis
19740 Disconnect from the remote target. There's no output.
19742 @subsubheading @value{GDBN} command
19744 The corresponding @value{GDBN} command is @samp{disconnect}.
19746 @subsubheading Example
19756 @subheading The @code{-target-download} Command
19757 @findex -target-download
19759 @subsubheading Synopsis
19765 Loads the executable onto the remote target.
19766 It prints out an update message every half second, which includes the fields:
19770 The name of the section.
19772 The size of what has been sent so far for that section.
19774 The size of the section.
19776 The total size of what was sent so far (the current and the previous sections).
19778 The size of the overall executable to download.
19782 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
19783 @sc{gdb/mi} Output Syntax}).
19785 In addition, it prints the name and size of the sections, as they are
19786 downloaded. These messages include the following fields:
19790 The name of the section.
19792 The size of the section.
19794 The size of the overall executable to download.
19798 At the end, a summary is printed.
19800 @subsubheading @value{GDBN} Command
19802 The corresponding @value{GDBN} command is @samp{load}.
19804 @subsubheading Example
19806 Note: each status message appears on a single line. Here the messages
19807 have been broken down so that they can fit onto a page.
19812 +download,@{section=".text",section-size="6668",total-size="9880"@}
19813 +download,@{section=".text",section-sent="512",section-size="6668",
19814 total-sent="512",total-size="9880"@}
19815 +download,@{section=".text",section-sent="1024",section-size="6668",
19816 total-sent="1024",total-size="9880"@}
19817 +download,@{section=".text",section-sent="1536",section-size="6668",
19818 total-sent="1536",total-size="9880"@}
19819 +download,@{section=".text",section-sent="2048",section-size="6668",
19820 total-sent="2048",total-size="9880"@}
19821 +download,@{section=".text",section-sent="2560",section-size="6668",
19822 total-sent="2560",total-size="9880"@}
19823 +download,@{section=".text",section-sent="3072",section-size="6668",
19824 total-sent="3072",total-size="9880"@}
19825 +download,@{section=".text",section-sent="3584",section-size="6668",
19826 total-sent="3584",total-size="9880"@}
19827 +download,@{section=".text",section-sent="4096",section-size="6668",
19828 total-sent="4096",total-size="9880"@}
19829 +download,@{section=".text",section-sent="4608",section-size="6668",
19830 total-sent="4608",total-size="9880"@}
19831 +download,@{section=".text",section-sent="5120",section-size="6668",
19832 total-sent="5120",total-size="9880"@}
19833 +download,@{section=".text",section-sent="5632",section-size="6668",
19834 total-sent="5632",total-size="9880"@}
19835 +download,@{section=".text",section-sent="6144",section-size="6668",
19836 total-sent="6144",total-size="9880"@}
19837 +download,@{section=".text",section-sent="6656",section-size="6668",
19838 total-sent="6656",total-size="9880"@}
19839 +download,@{section=".init",section-size="28",total-size="9880"@}
19840 +download,@{section=".fini",section-size="28",total-size="9880"@}
19841 +download,@{section=".data",section-size="3156",total-size="9880"@}
19842 +download,@{section=".data",section-sent="512",section-size="3156",
19843 total-sent="7236",total-size="9880"@}
19844 +download,@{section=".data",section-sent="1024",section-size="3156",
19845 total-sent="7748",total-size="9880"@}
19846 +download,@{section=".data",section-sent="1536",section-size="3156",
19847 total-sent="8260",total-size="9880"@}
19848 +download,@{section=".data",section-sent="2048",section-size="3156",
19849 total-sent="8772",total-size="9880"@}
19850 +download,@{section=".data",section-sent="2560",section-size="3156",
19851 total-sent="9284",total-size="9880"@}
19852 +download,@{section=".data",section-sent="3072",section-size="3156",
19853 total-sent="9796",total-size="9880"@}
19854 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
19860 @subheading The @code{-target-exec-status} Command
19861 @findex -target-exec-status
19863 @subsubheading Synopsis
19866 -target-exec-status
19869 Provide information on the state of the target (whether it is running or
19870 not, for instance).
19872 @subsubheading @value{GDBN} Command
19874 There's no equivalent @value{GDBN} command.
19876 @subsubheading Example
19880 @subheading The @code{-target-list-available-targets} Command
19881 @findex -target-list-available-targets
19883 @subsubheading Synopsis
19886 -target-list-available-targets
19889 List the possible targets to connect to.
19891 @subsubheading @value{GDBN} Command
19893 The corresponding @value{GDBN} command is @samp{help target}.
19895 @subsubheading Example
19899 @subheading The @code{-target-list-current-targets} Command
19900 @findex -target-list-current-targets
19902 @subsubheading Synopsis
19905 -target-list-current-targets
19908 Describe the current target.
19910 @subsubheading @value{GDBN} Command
19912 The corresponding information is printed by @samp{info file} (among
19915 @subsubheading Example
19919 @subheading The @code{-target-list-parameters} Command
19920 @findex -target-list-parameters
19922 @subsubheading Synopsis
19925 -target-list-parameters
19930 @subsubheading @value{GDBN} Command
19934 @subsubheading Example
19938 @subheading The @code{-target-select} Command
19939 @findex -target-select
19941 @subsubheading Synopsis
19944 -target-select @var{type} @var{parameters @dots{}}
19947 Connect @value{GDBN} to the remote target. This command takes two args:
19951 The type of target, for instance @samp{async}, @samp{remote}, etc.
19952 @item @var{parameters}
19953 Device names, host names and the like. @xref{Target Commands, ,
19954 Commands for managing targets}, for more details.
19957 The output is a connection notification, followed by the address at
19958 which the target program is, in the following form:
19961 ^connected,addr="@var{address}",func="@var{function name}",
19962 args=[@var{arg list}]
19965 @subsubheading @value{GDBN} Command
19967 The corresponding @value{GDBN} command is @samp{target}.
19969 @subsubheading Example
19973 -target-select async /dev/ttya
19974 ^connected,addr="0xfe00a300",func="??",args=[]
19978 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19979 @node GDB/MI Thread Commands
19980 @section @sc{gdb/mi} Thread Commands
19983 @subheading The @code{-thread-info} Command
19984 @findex -thread-info
19986 @subsubheading Synopsis
19992 @subsubheading @value{GDBN} command
19996 @subsubheading Example
20000 @subheading The @code{-thread-list-all-threads} Command
20001 @findex -thread-list-all-threads
20003 @subsubheading Synopsis
20006 -thread-list-all-threads
20009 @subsubheading @value{GDBN} Command
20011 The equivalent @value{GDBN} command is @samp{info threads}.
20013 @subsubheading Example
20017 @subheading The @code{-thread-list-ids} Command
20018 @findex -thread-list-ids
20020 @subsubheading Synopsis
20026 Produces a list of the currently known @value{GDBN} thread ids. At the
20027 end of the list it also prints the total number of such threads.
20029 @subsubheading @value{GDBN} Command
20031 Part of @samp{info threads} supplies the same information.
20033 @subsubheading Example
20035 No threads present, besides the main process:
20040 ^done,thread-ids=@{@},number-of-threads="0"
20050 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
20051 number-of-threads="3"
20056 @subheading The @code{-thread-select} Command
20057 @findex -thread-select
20059 @subsubheading Synopsis
20062 -thread-select @var{threadnum}
20065 Make @var{threadnum} the current thread. It prints the number of the new
20066 current thread, and the topmost frame for that thread.
20068 @subsubheading @value{GDBN} Command
20070 The corresponding @value{GDBN} command is @samp{thread}.
20072 @subsubheading Example
20079 *stopped,reason="end-stepping-range",thread-id="2",line="187",
20080 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
20084 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
20085 number-of-threads="3"
20088 ^done,new-thread-id="3",
20089 frame=@{level="0",func="vprintf",
20090 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
20091 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
20095 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20096 @node GDB/MI Tracepoint Commands
20097 @section @sc{gdb/mi} Tracepoint Commands
20099 The tracepoint commands are not yet implemented.
20101 @c @subheading -trace-actions
20103 @c @subheading -trace-delete
20105 @c @subheading -trace-disable
20107 @c @subheading -trace-dump
20109 @c @subheading -trace-enable
20111 @c @subheading -trace-exists
20113 @c @subheading -trace-find
20115 @c @subheading -trace-frame-number
20117 @c @subheading -trace-info
20119 @c @subheading -trace-insert
20121 @c @subheading -trace-list
20123 @c @subheading -trace-pass-count
20125 @c @subheading -trace-save
20127 @c @subheading -trace-start
20129 @c @subheading -trace-stop
20132 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20133 @node GDB/MI Variable Objects
20134 @section @sc{gdb/mi} Variable Objects
20137 @subheading Motivation for Variable Objects in @sc{gdb/mi}
20139 For the implementation of a variable debugger window (locals, watched
20140 expressions, etc.), we are proposing the adaptation of the existing code
20141 used by @code{Insight}.
20143 The two main reasons for that are:
20147 It has been proven in practice (it is already on its second generation).
20150 It will shorten development time (needless to say how important it is
20154 The original interface was designed to be used by Tcl code, so it was
20155 slightly changed so it could be used through @sc{gdb/mi}. This section
20156 describes the @sc{gdb/mi} operations that will be available and gives some
20157 hints about their use.
20159 @emph{Note}: In addition to the set of operations described here, we
20160 expect the @sc{gui} implementation of a variable window to require, at
20161 least, the following operations:
20164 @item @code{-gdb-show} @code{output-radix}
20165 @item @code{-stack-list-arguments}
20166 @item @code{-stack-list-locals}
20167 @item @code{-stack-select-frame}
20170 @subheading Introduction to Variable Objects in @sc{gdb/mi}
20172 @cindex variable objects in @sc{gdb/mi}
20173 The basic idea behind variable objects is the creation of a named object
20174 to represent a variable, an expression, a memory location or even a CPU
20175 register. For each object created, a set of operations is available for
20176 examining or changing its properties.
20178 Furthermore, complex data types, such as C structures, are represented
20179 in a tree format. For instance, the @code{struct} type variable is the
20180 root and the children will represent the struct members. If a child
20181 is itself of a complex type, it will also have children of its own.
20182 Appropriate language differences are handled for C, C@t{++} and Java.
20184 When returning the actual values of the objects, this facility allows
20185 for the individual selection of the display format used in the result
20186 creation. It can be chosen among: binary, decimal, hexadecimal, octal
20187 and natural. Natural refers to a default format automatically
20188 chosen based on the variable type (like decimal for an @code{int}, hex
20189 for pointers, etc.).
20191 The following is the complete set of @sc{gdb/mi} operations defined to
20192 access this functionality:
20194 @multitable @columnfractions .4 .6
20195 @item @strong{Operation}
20196 @tab @strong{Description}
20198 @item @code{-var-create}
20199 @tab create a variable object
20200 @item @code{-var-delete}
20201 @tab delete the variable object and its children
20202 @item @code{-var-set-format}
20203 @tab set the display format of this variable
20204 @item @code{-var-show-format}
20205 @tab show the display format of this variable
20206 @item @code{-var-info-num-children}
20207 @tab tells how many children this object has
20208 @item @code{-var-list-children}
20209 @tab return a list of the object's children
20210 @item @code{-var-info-type}
20211 @tab show the type of this variable object
20212 @item @code{-var-info-expression}
20213 @tab print what this variable object represents
20214 @item @code{-var-show-attributes}
20215 @tab is this variable editable? does it exist here?
20216 @item @code{-var-evaluate-expression}
20217 @tab get the value of this variable
20218 @item @code{-var-assign}
20219 @tab set the value of this variable
20220 @item @code{-var-update}
20221 @tab update the variable and its children
20224 In the next subsection we describe each operation in detail and suggest
20225 how it can be used.
20227 @subheading Description And Use of Operations on Variable Objects
20229 @subheading The @code{-var-create} Command
20230 @findex -var-create
20232 @subsubheading Synopsis
20235 -var-create @{@var{name} | "-"@}
20236 @{@var{frame-addr} | "*"@} @var{expression}
20239 This operation creates a variable object, which allows the monitoring of
20240 a variable, the result of an expression, a memory cell or a CPU
20243 The @var{name} parameter is the string by which the object can be
20244 referenced. It must be unique. If @samp{-} is specified, the varobj
20245 system will generate a string ``varNNNNNN'' automatically. It will be
20246 unique provided that one does not specify @var{name} on that format.
20247 The command fails if a duplicate name is found.
20249 The frame under which the expression should be evaluated can be
20250 specified by @var{frame-addr}. A @samp{*} indicates that the current
20251 frame should be used.
20253 @var{expression} is any expression valid on the current language set (must not
20254 begin with a @samp{*}), or one of the following:
20258 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
20261 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
20264 @samp{$@var{regname}} --- a CPU register name
20267 @subsubheading Result
20269 This operation returns the name, number of children and the type of the
20270 object created. Type is returned as a string as the ones generated by
20271 the @value{GDBN} CLI:
20274 name="@var{name}",numchild="N",type="@var{type}"
20278 @subheading The @code{-var-delete} Command
20279 @findex -var-delete
20281 @subsubheading Synopsis
20284 -var-delete @var{name}
20287 Deletes a previously created variable object and all of its children.
20289 Returns an error if the object @var{name} is not found.
20292 @subheading The @code{-var-set-format} Command
20293 @findex -var-set-format
20295 @subsubheading Synopsis
20298 -var-set-format @var{name} @var{format-spec}
20301 Sets the output format for the value of the object @var{name} to be
20304 The syntax for the @var{format-spec} is as follows:
20307 @var{format-spec} @expansion{}
20308 @{binary | decimal | hexadecimal | octal | natural@}
20312 @subheading The @code{-var-show-format} Command
20313 @findex -var-show-format
20315 @subsubheading Synopsis
20318 -var-show-format @var{name}
20321 Returns the format used to display the value of the object @var{name}.
20324 @var{format} @expansion{}
20329 @subheading The @code{-var-info-num-children} Command
20330 @findex -var-info-num-children
20332 @subsubheading Synopsis
20335 -var-info-num-children @var{name}
20338 Returns the number of children of a variable object @var{name}:
20345 @subheading The @code{-var-list-children} Command
20346 @findex -var-list-children
20348 @subsubheading Synopsis
20351 -var-list-children [@var{print-values}] @var{name}
20354 Returns a list of the children of the specified variable object. With
20355 just the variable object name as an argument or with an optional
20356 preceding argument of 0 or @code{--no-values}, prints only the names of the
20357 variables. With an optional preceding argument of 1 or @code{--all-values},
20358 also prints their values.
20360 @subsubheading Example
20364 -var-list-children n
20365 numchild=@var{n},children=[@{name=@var{name},
20366 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
20368 -var-list-children --all-values n
20369 numchild=@var{n},children=[@{name=@var{name},
20370 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
20374 @subheading The @code{-var-info-type} Command
20375 @findex -var-info-type
20377 @subsubheading Synopsis
20380 -var-info-type @var{name}
20383 Returns the type of the specified variable @var{name}. The type is
20384 returned as a string in the same format as it is output by the
20388 type=@var{typename}
20392 @subheading The @code{-var-info-expression} Command
20393 @findex -var-info-expression
20395 @subsubheading Synopsis
20398 -var-info-expression @var{name}
20401 Returns what is represented by the variable object @var{name}:
20404 lang=@var{lang-spec},exp=@var{expression}
20408 where @var{lang-spec} is @code{@{"C" | "C++" | "Java"@}}.
20410 @subheading The @code{-var-show-attributes} Command
20411 @findex -var-show-attributes
20413 @subsubheading Synopsis
20416 -var-show-attributes @var{name}
20419 List attributes of the specified variable object @var{name}:
20422 status=@var{attr} [ ( ,@var{attr} )* ]
20426 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
20428 @subheading The @code{-var-evaluate-expression} Command
20429 @findex -var-evaluate-expression
20431 @subsubheading Synopsis
20434 -var-evaluate-expression @var{name}
20437 Evaluates the expression that is represented by the specified variable
20438 object and returns its value as a string in the current format specified
20445 Note that one must invoke @code{-var-list-children} for a variable
20446 before the value of a child variable can be evaluated.
20448 @subheading The @code{-var-assign} Command
20449 @findex -var-assign
20451 @subsubheading Synopsis
20454 -var-assign @var{name} @var{expression}
20457 Assigns the value of @var{expression} to the variable object specified
20458 by @var{name}. The object must be @samp{editable}. If the variable's
20459 value is altered by the assign, the variable will show up in any
20460 subsequent @code{-var-update} list.
20462 @subsubheading Example
20470 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
20474 @subheading The @code{-var-update} Command
20475 @findex -var-update
20477 @subsubheading Synopsis
20480 -var-update @{@var{name} | "*"@}
20483 Update the value of the variable object @var{name} by evaluating its
20484 expression after fetching all the new values from memory or registers.
20485 A @samp{*} causes all existing variable objects to be updated.
20489 @chapter @value{GDBN} Annotations
20491 This chapter describes annotations in @value{GDBN}. Annotations were
20492 designed to interface @value{GDBN} to graphical user interfaces or other
20493 similar programs which want to interact with @value{GDBN} at a
20494 relatively high level.
20496 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
20500 This is Edition @value{EDITION}, @value{DATE}.
20504 * Annotations Overview:: What annotations are; the general syntax.
20505 * Server Prefix:: Issuing a command without affecting user state.
20506 * Prompting:: Annotations marking @value{GDBN}'s need for input.
20507 * Errors:: Annotations for error messages.
20508 * Invalidation:: Some annotations describe things now invalid.
20509 * Annotations for Running::
20510 Whether the program is running, how it stopped, etc.
20511 * Source Annotations:: Annotations describing source code.
20514 @node Annotations Overview
20515 @section What is an Annotation?
20516 @cindex annotations
20518 Annotations start with a newline character, two @samp{control-z}
20519 characters, and the name of the annotation. If there is no additional
20520 information associated with this annotation, the name of the annotation
20521 is followed immediately by a newline. If there is additional
20522 information, the name of the annotation is followed by a space, the
20523 additional information, and a newline. The additional information
20524 cannot contain newline characters.
20526 Any output not beginning with a newline and two @samp{control-z}
20527 characters denotes literal output from @value{GDBN}. Currently there is
20528 no need for @value{GDBN} to output a newline followed by two
20529 @samp{control-z} characters, but if there was such a need, the
20530 annotations could be extended with an @samp{escape} annotation which
20531 means those three characters as output.
20533 The annotation @var{level}, which is specified using the
20534 @option{--annotate} command line option (@pxref{Mode Options}), controls
20535 how much information @value{GDBN} prints together with its prompt,
20536 values of expressions, source lines, and other types of output. Level 0
20537 is for no anntations, level 1 is for use when @value{GDBN} is run as a
20538 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
20539 for programs that control @value{GDBN}, and level 2 annotations have
20540 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
20541 Interface, annotate, GDB's Obsolete Annotations}).
20544 @kindex set annotate
20545 @item set annotate @var{level}
20546 The @value{GDB} command @code{set annotate} sets the level of
20547 annotations to the specified @var{level}.
20549 @item show annotate
20550 @kindex show annotate
20551 Show the current annotation level.
20554 This chapter describes level 3 annotations.
20556 A simple example of starting up @value{GDBN} with annotations is:
20559 $ @kbd{gdb --annotate=3}
20561 Copyright 2003 Free Software Foundation, Inc.
20562 GDB is free software, covered by the GNU General Public License,
20563 and you are welcome to change it and/or distribute copies of it
20564 under certain conditions.
20565 Type "show copying" to see the conditions.
20566 There is absolutely no warranty for GDB. Type "show warranty"
20568 This GDB was configured as "i386-pc-linux-gnu"
20579 Here @samp{quit} is input to @value{GDBN}; the rest is output from
20580 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
20581 denotes a @samp{control-z} character) are annotations; the rest is
20582 output from @value{GDBN}.
20584 @node Server Prefix
20585 @section The Server Prefix
20586 @cindex server prefix for annotations
20588 To issue a command to @value{GDBN} without affecting certain aspects of
20589 the state which is seen by users, prefix it with @samp{server }. This
20590 means that this command will not affect the command history, nor will it
20591 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
20592 pressed on a line by itself.
20594 The server prefix does not affect the recording of values into the value
20595 history; to print a value without recording it into the value history,
20596 use the @code{output} command instead of the @code{print} command.
20599 @section Annotation for @value{GDBN} Input
20601 @cindex annotations for prompts
20602 When @value{GDBN} prompts for input, it annotates this fact so it is possible
20603 to know when to send output, when the output from a given command is
20606 Different kinds of input each have a different @dfn{input type}. Each
20607 input type has three annotations: a @code{pre-} annotation, which
20608 denotes the beginning of any prompt which is being output, a plain
20609 annotation, which denotes the end of the prompt, and then a @code{post-}
20610 annotation which denotes the end of any echo which may (or may not) be
20611 associated with the input. For example, the @code{prompt} input type
20612 features the following annotations:
20620 The input types are
20625 @findex post-prompt
20627 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
20629 @findex pre-commands
20631 @findex post-commands
20633 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
20634 command. The annotations are repeated for each command which is input.
20636 @findex pre-overload-choice
20637 @findex overload-choice
20638 @findex post-overload-choice
20639 @item overload-choice
20640 When @value{GDBN} wants the user to select between various overloaded functions.
20646 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
20648 @findex pre-prompt-for-continue
20649 @findex prompt-for-continue
20650 @findex post-prompt-for-continue
20651 @item prompt-for-continue
20652 When @value{GDBN} is asking the user to press return to continue. Note: Don't
20653 expect this to work well; instead use @code{set height 0} to disable
20654 prompting. This is because the counting of lines is buggy in the
20655 presence of annotations.
20660 @cindex annotations for errors, warnings and interrupts
20667 This annotation occurs right before @value{GDBN} responds to an interrupt.
20674 This annotation occurs right before @value{GDBN} responds to an error.
20676 Quit and error annotations indicate that any annotations which @value{GDBN} was
20677 in the middle of may end abruptly. For example, if a
20678 @code{value-history-begin} annotation is followed by a @code{error}, one
20679 cannot expect to receive the matching @code{value-history-end}. One
20680 cannot expect not to receive it either, however; an error annotation
20681 does not necessarily mean that @value{GDBN} is immediately returning all the way
20684 @findex error-begin
20685 A quit or error annotation may be preceded by
20691 Any output between that and the quit or error annotation is the error
20694 Warning messages are not yet annotated.
20695 @c If we want to change that, need to fix warning(), type_error(),
20696 @c range_error(), and possibly other places.
20699 @section Invalidation Notices
20701 @cindex annotations for invalidation messages
20702 The following annotations say that certain pieces of state may have
20706 @findex frames-invalid
20707 @item ^Z^Zframes-invalid
20709 The frames (for example, output from the @code{backtrace} command) may
20712 @findex breakpoints-invalid
20713 @item ^Z^Zbreakpoints-invalid
20715 The breakpoints may have changed. For example, the user just added or
20716 deleted a breakpoint.
20719 @node Annotations for Running
20720 @section Running the Program
20721 @cindex annotations for running programs
20725 When the program starts executing due to a @value{GDBN} command such as
20726 @code{step} or @code{continue},
20732 is output. When the program stops,
20738 is output. Before the @code{stopped} annotation, a variety of
20739 annotations describe how the program stopped.
20743 @item ^Z^Zexited @var{exit-status}
20744 The program exited, and @var{exit-status} is the exit status (zero for
20745 successful exit, otherwise nonzero).
20748 @findex signal-name
20749 @findex signal-name-end
20750 @findex signal-string
20751 @findex signal-string-end
20752 @item ^Z^Zsignalled
20753 The program exited with a signal. After the @code{^Z^Zsignalled}, the
20754 annotation continues:
20760 ^Z^Zsignal-name-end
20764 ^Z^Zsignal-string-end
20769 where @var{name} is the name of the signal, such as @code{SIGILL} or
20770 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
20771 as @code{Illegal Instruction} or @code{Segmentation fault}.
20772 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
20773 user's benefit and have no particular format.
20777 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
20778 just saying that the program received the signal, not that it was
20779 terminated with it.
20782 @item ^Z^Zbreakpoint @var{number}
20783 The program hit breakpoint number @var{number}.
20786 @item ^Z^Zwatchpoint @var{number}
20787 The program hit watchpoint number @var{number}.
20790 @node Source Annotations
20791 @section Displaying Source
20792 @cindex annotations for source display
20795 The following annotation is used instead of displaying source code:
20798 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
20801 where @var{filename} is an absolute file name indicating which source
20802 file, @var{line} is the line number within that file (where 1 is the
20803 first line in the file), @var{character} is the character position
20804 within the file (where 0 is the first character in the file) (for most
20805 debug formats this will necessarily point to the beginning of a line),
20806 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
20807 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
20808 @var{addr} is the address in the target program associated with the
20809 source which is being displayed. @var{addr} is in the form @samp{0x}
20810 followed by one or more lowercase hex digits (note that this does not
20811 depend on the language).
20814 @chapter Reporting Bugs in @value{GDBN}
20815 @cindex bugs in @value{GDBN}
20816 @cindex reporting bugs in @value{GDBN}
20818 Your bug reports play an essential role in making @value{GDBN} reliable.
20820 Reporting a bug may help you by bringing a solution to your problem, or it
20821 may not. But in any case the principal function of a bug report is to help
20822 the entire community by making the next version of @value{GDBN} work better. Bug
20823 reports are your contribution to the maintenance of @value{GDBN}.
20825 In order for a bug report to serve its purpose, you must include the
20826 information that enables us to fix the bug.
20829 * Bug Criteria:: Have you found a bug?
20830 * Bug Reporting:: How to report bugs
20834 @section Have you found a bug?
20835 @cindex bug criteria
20837 If you are not sure whether you have found a bug, here are some guidelines:
20840 @cindex fatal signal
20841 @cindex debugger crash
20842 @cindex crash of debugger
20844 If the debugger gets a fatal signal, for any input whatever, that is a
20845 @value{GDBN} bug. Reliable debuggers never crash.
20847 @cindex error on valid input
20849 If @value{GDBN} produces an error message for valid input, that is a
20850 bug. (Note that if you're cross debugging, the problem may also be
20851 somewhere in the connection to the target.)
20853 @cindex invalid input
20855 If @value{GDBN} does not produce an error message for invalid input,
20856 that is a bug. However, you should note that your idea of
20857 ``invalid input'' might be our idea of ``an extension'' or ``support
20858 for traditional practice''.
20861 If you are an experienced user of debugging tools, your suggestions
20862 for improvement of @value{GDBN} are welcome in any case.
20865 @node Bug Reporting
20866 @section How to report bugs
20867 @cindex bug reports
20868 @cindex @value{GDBN} bugs, reporting
20870 A number of companies and individuals offer support for @sc{gnu} products.
20871 If you obtained @value{GDBN} from a support organization, we recommend you
20872 contact that organization first.
20874 You can find contact information for many support companies and
20875 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
20877 @c should add a web page ref...
20879 In any event, we also recommend that you submit bug reports for
20880 @value{GDBN}. The prefered method is to submit them directly using
20881 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
20882 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
20885 @strong{Do not send bug reports to @samp{info-gdb}, or to
20886 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
20887 not want to receive bug reports. Those that do have arranged to receive
20890 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
20891 serves as a repeater. The mailing list and the newsgroup carry exactly
20892 the same messages. Often people think of posting bug reports to the
20893 newsgroup instead of mailing them. This appears to work, but it has one
20894 problem which can be crucial: a newsgroup posting often lacks a mail
20895 path back to the sender. Thus, if we need to ask for more information,
20896 we may be unable to reach you. For this reason, it is better to send
20897 bug reports to the mailing list.
20899 The fundamental principle of reporting bugs usefully is this:
20900 @strong{report all the facts}. If you are not sure whether to state a
20901 fact or leave it out, state it!
20903 Often people omit facts because they think they know what causes the
20904 problem and assume that some details do not matter. Thus, you might
20905 assume that the name of the variable you use in an example does not matter.
20906 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
20907 stray memory reference which happens to fetch from the location where that
20908 name is stored in memory; perhaps, if the name were different, the contents
20909 of that location would fool the debugger into doing the right thing despite
20910 the bug. Play it safe and give a specific, complete example. That is the
20911 easiest thing for you to do, and the most helpful.
20913 Keep in mind that the purpose of a bug report is to enable us to fix the
20914 bug. It may be that the bug has been reported previously, but neither
20915 you nor we can know that unless your bug report is complete and
20918 Sometimes people give a few sketchy facts and ask, ``Does this ring a
20919 bell?'' Those bug reports are useless, and we urge everyone to
20920 @emph{refuse to respond to them} except to chide the sender to report
20923 To enable us to fix the bug, you should include all these things:
20927 The version of @value{GDBN}. @value{GDBN} announces it if you start
20928 with no arguments; you can also print it at any time using @code{show
20931 Without this, we will not know whether there is any point in looking for
20932 the bug in the current version of @value{GDBN}.
20935 The type of machine you are using, and the operating system name and
20939 What compiler (and its version) was used to compile @value{GDBN}---e.g.
20940 ``@value{GCC}--2.8.1''.
20943 What compiler (and its version) was used to compile the program you are
20944 debugging---e.g. ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
20945 C Compiler''. For GCC, you can say @code{gcc --version} to get this
20946 information; for other compilers, see the documentation for those
20950 The command arguments you gave the compiler to compile your example and
20951 observe the bug. For example, did you use @samp{-O}? To guarantee
20952 you will not omit something important, list them all. A copy of the
20953 Makefile (or the output from make) is sufficient.
20955 If we were to try to guess the arguments, we would probably guess wrong
20956 and then we might not encounter the bug.
20959 A complete input script, and all necessary source files, that will
20963 A description of what behavior you observe that you believe is
20964 incorrect. For example, ``It gets a fatal signal.''
20966 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
20967 will certainly notice it. But if the bug is incorrect output, we might
20968 not notice unless it is glaringly wrong. You might as well not give us
20969 a chance to make a mistake.
20971 Even if the problem you experience is a fatal signal, you should still
20972 say so explicitly. Suppose something strange is going on, such as, your
20973 copy of @value{GDBN} is out of synch, or you have encountered a bug in
20974 the C library on your system. (This has happened!) Your copy might
20975 crash and ours would not. If you told us to expect a crash, then when
20976 ours fails to crash, we would know that the bug was not happening for
20977 us. If you had not told us to expect a crash, then we would not be able
20978 to draw any conclusion from our observations.
20981 @cindex recording a session script
20982 To collect all this information, you can use a session recording program
20983 such as @command{script}, which is available on many Unix systems.
20984 Just run your @value{GDBN} session inside @command{script} and then
20985 include the @file{typescript} file with your bug report.
20987 Another way to record a @value{GDBN} session is to run @value{GDBN}
20988 inside Emacs and then save the entire buffer to a file.
20991 If you wish to suggest changes to the @value{GDBN} source, send us context
20992 diffs. If you even discuss something in the @value{GDBN} source, refer to
20993 it by context, not by line number.
20995 The line numbers in our development sources will not match those in your
20996 sources. Your line numbers would convey no useful information to us.
21000 Here are some things that are not necessary:
21004 A description of the envelope of the bug.
21006 Often people who encounter a bug spend a lot of time investigating
21007 which changes to the input file will make the bug go away and which
21008 changes will not affect it.
21010 This is often time consuming and not very useful, because the way we
21011 will find the bug is by running a single example under the debugger
21012 with breakpoints, not by pure deduction from a series of examples.
21013 We recommend that you save your time for something else.
21015 Of course, if you can find a simpler example to report @emph{instead}
21016 of the original one, that is a convenience for us. Errors in the
21017 output will be easier to spot, running under the debugger will take
21018 less time, and so on.
21020 However, simplification is not vital; if you do not want to do this,
21021 report the bug anyway and send us the entire test case you used.
21024 A patch for the bug.
21026 A patch for the bug does help us if it is a good one. But do not omit
21027 the necessary information, such as the test case, on the assumption that
21028 a patch is all we need. We might see problems with your patch and decide
21029 to fix the problem another way, or we might not understand it at all.
21031 Sometimes with a program as complicated as @value{GDBN} it is very hard to
21032 construct an example that will make the program follow a certain path
21033 through the code. If you do not send us the example, we will not be able
21034 to construct one, so we will not be able to verify that the bug is fixed.
21036 And if we cannot understand what bug you are trying to fix, or why your
21037 patch should be an improvement, we will not install it. A test case will
21038 help us to understand.
21041 A guess about what the bug is or what it depends on.
21043 Such guesses are usually wrong. Even we cannot guess right about such
21044 things without first using the debugger to find the facts.
21047 @c The readline documentation is distributed with the readline code
21048 @c and consists of the two following files:
21050 @c inc-hist.texinfo
21051 @c Use -I with makeinfo to point to the appropriate directory,
21052 @c environment var TEXINPUTS with TeX.
21053 @include rluser.texinfo
21054 @include inc-hist.texinfo
21057 @node Formatting Documentation
21058 @appendix Formatting Documentation
21060 @cindex @value{GDBN} reference card
21061 @cindex reference card
21062 The @value{GDBN} 4 release includes an already-formatted reference card, ready
21063 for printing with PostScript or Ghostscript, in the @file{gdb}
21064 subdirectory of the main source directory@footnote{In
21065 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
21066 release.}. If you can use PostScript or Ghostscript with your printer,
21067 you can print the reference card immediately with @file{refcard.ps}.
21069 The release also includes the source for the reference card. You
21070 can format it, using @TeX{}, by typing:
21076 The @value{GDBN} reference card is designed to print in @dfn{landscape}
21077 mode on US ``letter'' size paper;
21078 that is, on a sheet 11 inches wide by 8.5 inches
21079 high. You will need to specify this form of printing as an option to
21080 your @sc{dvi} output program.
21082 @cindex documentation
21084 All the documentation for @value{GDBN} comes as part of the machine-readable
21085 distribution. The documentation is written in Texinfo format, which is
21086 a documentation system that uses a single source file to produce both
21087 on-line information and a printed manual. You can use one of the Info
21088 formatting commands to create the on-line version of the documentation
21089 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
21091 @value{GDBN} includes an already formatted copy of the on-line Info
21092 version of this manual in the @file{gdb} subdirectory. The main Info
21093 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
21094 subordinate files matching @samp{gdb.info*} in the same directory. If
21095 necessary, you can print out these files, or read them with any editor;
21096 but they are easier to read using the @code{info} subsystem in @sc{gnu}
21097 Emacs or the standalone @code{info} program, available as part of the
21098 @sc{gnu} Texinfo distribution.
21100 If you want to format these Info files yourself, you need one of the
21101 Info formatting programs, such as @code{texinfo-format-buffer} or
21104 If you have @code{makeinfo} installed, and are in the top level
21105 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
21106 version @value{GDBVN}), you can make the Info file by typing:
21113 If you want to typeset and print copies of this manual, you need @TeX{},
21114 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
21115 Texinfo definitions file.
21117 @TeX{} is a typesetting program; it does not print files directly, but
21118 produces output files called @sc{dvi} files. To print a typeset
21119 document, you need a program to print @sc{dvi} files. If your system
21120 has @TeX{} installed, chances are it has such a program. The precise
21121 command to use depends on your system; @kbd{lpr -d} is common; another
21122 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
21123 require a file name without any extension or a @samp{.dvi} extension.
21125 @TeX{} also requires a macro definitions file called
21126 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
21127 written in Texinfo format. On its own, @TeX{} cannot either read or
21128 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
21129 and is located in the @file{gdb-@var{version-number}/texinfo}
21132 If you have @TeX{} and a @sc{dvi} printer program installed, you can
21133 typeset and print this manual. First switch to the the @file{gdb}
21134 subdirectory of the main source directory (for example, to
21135 @file{gdb-@value{GDBVN}/gdb}) and type:
21141 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
21143 @node Installing GDB
21144 @appendix Installing @value{GDBN}
21145 @cindex configuring @value{GDBN}
21146 @cindex installation
21147 @cindex configuring @value{GDBN}, and source tree subdirectories
21149 @value{GDBN} comes with a @code{configure} script that automates the process
21150 of preparing @value{GDBN} for installation; you can then use @code{make} to
21151 build the @code{gdb} program.
21153 @c irrelevant in info file; it's as current as the code it lives with.
21154 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
21155 look at the @file{README} file in the sources; we may have improved the
21156 installation procedures since publishing this manual.}
21159 The @value{GDBN} distribution includes all the source code you need for
21160 @value{GDBN} in a single directory, whose name is usually composed by
21161 appending the version number to @samp{gdb}.
21163 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
21164 @file{gdb-@value{GDBVN}} directory. That directory contains:
21167 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
21168 script for configuring @value{GDBN} and all its supporting libraries
21170 @item gdb-@value{GDBVN}/gdb
21171 the source specific to @value{GDBN} itself
21173 @item gdb-@value{GDBVN}/bfd
21174 source for the Binary File Descriptor library
21176 @item gdb-@value{GDBVN}/include
21177 @sc{gnu} include files
21179 @item gdb-@value{GDBVN}/libiberty
21180 source for the @samp{-liberty} free software library
21182 @item gdb-@value{GDBVN}/opcodes
21183 source for the library of opcode tables and disassemblers
21185 @item gdb-@value{GDBVN}/readline
21186 source for the @sc{gnu} command-line interface
21188 @item gdb-@value{GDBVN}/glob
21189 source for the @sc{gnu} filename pattern-matching subroutine
21191 @item gdb-@value{GDBVN}/mmalloc
21192 source for the @sc{gnu} memory-mapped malloc package
21195 The simplest way to configure and build @value{GDBN} is to run @code{configure}
21196 from the @file{gdb-@var{version-number}} source directory, which in
21197 this example is the @file{gdb-@value{GDBVN}} directory.
21199 First switch to the @file{gdb-@var{version-number}} source directory
21200 if you are not already in it; then run @code{configure}. Pass the
21201 identifier for the platform on which @value{GDBN} will run as an
21207 cd gdb-@value{GDBVN}
21208 ./configure @var{host}
21213 where @var{host} is an identifier such as @samp{sun4} or
21214 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
21215 (You can often leave off @var{host}; @code{configure} tries to guess the
21216 correct value by examining your system.)
21218 Running @samp{configure @var{host}} and then running @code{make} builds the
21219 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
21220 libraries, then @code{gdb} itself. The configured source files, and the
21221 binaries, are left in the corresponding source directories.
21224 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
21225 system does not recognize this automatically when you run a different
21226 shell, you may need to run @code{sh} on it explicitly:
21229 sh configure @var{host}
21232 If you run @code{configure} from a directory that contains source
21233 directories for multiple libraries or programs, such as the
21234 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
21235 creates configuration files for every directory level underneath (unless
21236 you tell it not to, with the @samp{--norecursion} option).
21238 You should run the @code{configure} script from the top directory in the
21239 source tree, the @file{gdb-@var{version-number}} directory. If you run
21240 @code{configure} from one of the subdirectories, you will configure only
21241 that subdirectory. That is usually not what you want. In particular,
21242 if you run the first @code{configure} from the @file{gdb} subdirectory
21243 of the @file{gdb-@var{version-number}} directory, you will omit the
21244 configuration of @file{bfd}, @file{readline}, and other sibling
21245 directories of the @file{gdb} subdirectory. This leads to build errors
21246 about missing include files such as @file{bfd/bfd.h}.
21248 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
21249 However, you should make sure that the shell on your path (named by
21250 the @samp{SHELL} environment variable) is publicly readable. Remember
21251 that @value{GDBN} uses the shell to start your program---some systems refuse to
21252 let @value{GDBN} debug child processes whose programs are not readable.
21255 * Separate Objdir:: Compiling @value{GDBN} in another directory
21256 * Config Names:: Specifying names for hosts and targets
21257 * Configure Options:: Summary of options for configure
21260 @node Separate Objdir
21261 @section Compiling @value{GDBN} in another directory
21263 If you want to run @value{GDBN} versions for several host or target machines,
21264 you need a different @code{gdb} compiled for each combination of
21265 host and target. @code{configure} is designed to make this easy by
21266 allowing you to generate each configuration in a separate subdirectory,
21267 rather than in the source directory. If your @code{make} program
21268 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
21269 @code{make} in each of these directories builds the @code{gdb}
21270 program specified there.
21272 To build @code{gdb} in a separate directory, run @code{configure}
21273 with the @samp{--srcdir} option to specify where to find the source.
21274 (You also need to specify a path to find @code{configure}
21275 itself from your working directory. If the path to @code{configure}
21276 would be the same as the argument to @samp{--srcdir}, you can leave out
21277 the @samp{--srcdir} option; it is assumed.)
21279 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
21280 separate directory for a Sun 4 like this:
21284 cd gdb-@value{GDBVN}
21287 ../gdb-@value{GDBVN}/configure sun4
21292 When @code{configure} builds a configuration using a remote source
21293 directory, it creates a tree for the binaries with the same structure
21294 (and using the same names) as the tree under the source directory. In
21295 the example, you'd find the Sun 4 library @file{libiberty.a} in the
21296 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
21297 @file{gdb-sun4/gdb}.
21299 Make sure that your path to the @file{configure} script has just one
21300 instance of @file{gdb} in it. If your path to @file{configure} looks
21301 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
21302 one subdirectory of @value{GDBN}, not the whole package. This leads to
21303 build errors about missing include files such as @file{bfd/bfd.h}.
21305 One popular reason to build several @value{GDBN} configurations in separate
21306 directories is to configure @value{GDBN} for cross-compiling (where
21307 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
21308 programs that run on another machine---the @dfn{target}).
21309 You specify a cross-debugging target by
21310 giving the @samp{--target=@var{target}} option to @code{configure}.
21312 When you run @code{make} to build a program or library, you must run
21313 it in a configured directory---whatever directory you were in when you
21314 called @code{configure} (or one of its subdirectories).
21316 The @code{Makefile} that @code{configure} generates in each source
21317 directory also runs recursively. If you type @code{make} in a source
21318 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
21319 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
21320 will build all the required libraries, and then build GDB.
21322 When you have multiple hosts or targets configured in separate
21323 directories, you can run @code{make} on them in parallel (for example,
21324 if they are NFS-mounted on each of the hosts); they will not interfere
21328 @section Specifying names for hosts and targets
21330 The specifications used for hosts and targets in the @code{configure}
21331 script are based on a three-part naming scheme, but some short predefined
21332 aliases are also supported. The full naming scheme encodes three pieces
21333 of information in the following pattern:
21336 @var{architecture}-@var{vendor}-@var{os}
21339 For example, you can use the alias @code{sun4} as a @var{host} argument,
21340 or as the value for @var{target} in a @code{--target=@var{target}}
21341 option. The equivalent full name is @samp{sparc-sun-sunos4}.
21343 The @code{configure} script accompanying @value{GDBN} does not provide
21344 any query facility to list all supported host and target names or
21345 aliases. @code{configure} calls the Bourne shell script
21346 @code{config.sub} to map abbreviations to full names; you can read the
21347 script, if you wish, or you can use it to test your guesses on
21348 abbreviations---for example:
21351 % sh config.sub i386-linux
21353 % sh config.sub alpha-linux
21354 alpha-unknown-linux-gnu
21355 % sh config.sub hp9k700
21357 % sh config.sub sun4
21358 sparc-sun-sunos4.1.1
21359 % sh config.sub sun3
21360 m68k-sun-sunos4.1.1
21361 % sh config.sub i986v
21362 Invalid configuration `i986v': machine `i986v' not recognized
21366 @code{config.sub} is also distributed in the @value{GDBN} source
21367 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
21369 @node Configure Options
21370 @section @code{configure} options
21372 Here is a summary of the @code{configure} options and arguments that
21373 are most often useful for building @value{GDBN}. @code{configure} also has
21374 several other options not listed here. @inforef{What Configure
21375 Does,,configure.info}, for a full explanation of @code{configure}.
21378 configure @r{[}--help@r{]}
21379 @r{[}--prefix=@var{dir}@r{]}
21380 @r{[}--exec-prefix=@var{dir}@r{]}
21381 @r{[}--srcdir=@var{dirname}@r{]}
21382 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
21383 @r{[}--target=@var{target}@r{]}
21388 You may introduce options with a single @samp{-} rather than
21389 @samp{--} if you prefer; but you may abbreviate option names if you use
21394 Display a quick summary of how to invoke @code{configure}.
21396 @item --prefix=@var{dir}
21397 Configure the source to install programs and files under directory
21400 @item --exec-prefix=@var{dir}
21401 Configure the source to install programs under directory
21404 @c avoid splitting the warning from the explanation:
21406 @item --srcdir=@var{dirname}
21407 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
21408 @code{make} that implements the @code{VPATH} feature.}@*
21409 Use this option to make configurations in directories separate from the
21410 @value{GDBN} source directories. Among other things, you can use this to
21411 build (or maintain) several configurations simultaneously, in separate
21412 directories. @code{configure} writes configuration specific files in
21413 the current directory, but arranges for them to use the source in the
21414 directory @var{dirname}. @code{configure} creates directories under
21415 the working directory in parallel to the source directories below
21418 @item --norecursion
21419 Configure only the directory level where @code{configure} is executed; do not
21420 propagate configuration to subdirectories.
21422 @item --target=@var{target}
21423 Configure @value{GDBN} for cross-debugging programs running on the specified
21424 @var{target}. Without this option, @value{GDBN} is configured to debug
21425 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
21427 There is no convenient way to generate a list of all available targets.
21429 @item @var{host} @dots{}
21430 Configure @value{GDBN} to run on the specified @var{host}.
21432 There is no convenient way to generate a list of all available hosts.
21435 There are many other options available as well, but they are generally
21436 needed for special purposes only.
21438 @node Maintenance Commands
21439 @appendix Maintenance Commands
21440 @cindex maintenance commands
21441 @cindex internal commands
21443 In addition to commands intended for @value{GDBN} users, @value{GDBN}
21444 includes a number of commands intended for @value{GDBN} developers,
21445 that are not documented elsewhere in this manual. These commands are
21446 provided here for reference. (For commands that turn on debugging
21447 messages, see @ref{Debugging Output}.)
21450 @kindex maint agent
21451 @item maint agent @var{expression}
21452 Translate the given @var{expression} into remote agent bytecodes.
21453 This command is useful for debugging the Agent Expression mechanism
21454 (@pxref{Agent Expressions}).
21456 @kindex maint info breakpoints
21457 @item @anchor{maint info breakpoints}maint info breakpoints
21458 Using the same format as @samp{info breakpoints}, display both the
21459 breakpoints you've set explicitly, and those @value{GDBN} is using for
21460 internal purposes. Internal breakpoints are shown with negative
21461 breakpoint numbers. The type column identifies what kind of breakpoint
21466 Normal, explicitly set breakpoint.
21469 Normal, explicitly set watchpoint.
21472 Internal breakpoint, used to handle correctly stepping through
21473 @code{longjmp} calls.
21475 @item longjmp resume
21476 Internal breakpoint at the target of a @code{longjmp}.
21479 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
21482 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
21485 Shared library events.
21489 @kindex maint check-symtabs
21490 @item maint check-symtabs
21491 Check the consistency of psymtabs and symtabs.
21493 @kindex maint cplus first_component
21494 @item maint cplus first_component @var{name}
21495 Print the first C@t{++} class/namespace component of @var{name}.
21497 @kindex maint cplus namespace
21498 @item maint cplus namespace
21499 Print the list of possible C@t{++} namespaces.
21501 @kindex maint demangle
21502 @item maint demangle @var{name}
21503 Demangle a C@t{++} or Objective-C manled @var{name}.
21505 @kindex maint deprecate
21506 @kindex maint undeprecate
21507 @cindex deprecated commands
21508 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
21509 @itemx maint undeprecate @var{command}
21510 Deprecate or undeprecate the named @var{command}. Deprecated commands
21511 cause @value{GDBN} to issue a warning when you use them. The optional
21512 argument @var{replacement} says which newer command should be used in
21513 favor of the deprecated one; if it is given, @value{GDBN} will mention
21514 the replacement as part of the warning.
21516 @kindex maint dump-me
21517 @item maint dump-me
21518 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
21519 Cause a fatal signal in the debugger and force it to dump its core.
21520 This is supported only on systems which support aborting a program
21521 with the @code{SIGQUIT} signal.
21523 @kindex maint internal-error
21524 @kindex maint internal-warning
21525 @item maint internal-error @r{[}@var{message-text}@r{]}
21526 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
21527 Cause @value{GDBN} to call the internal function @code{internal_error}
21528 or @code{internal_warning} and hence behave as though an internal error
21529 or internal warning has been detected. In addition to reporting the
21530 internal problem, these functions give the user the opportunity to
21531 either quit @value{GDBN} or create a core file of the current
21532 @value{GDBN} session.
21534 These commands take an optional parameter @var{message-text} that is
21535 used as the text of the error or warning message.
21537 Here's an example of using @code{indernal-error}:
21540 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
21541 @dots{}/maint.c:121: internal-error: testing, 1, 2
21542 A problem internal to GDB has been detected. Further
21543 debugging may prove unreliable.
21544 Quit this debugging session? (y or n) @kbd{n}
21545 Create a core file? (y or n) @kbd{n}
21549 @kindex maint packet
21550 @item maint packet @var{text}
21551 If @value{GDBN} is talking to an inferior via the serial protocol,
21552 then this command sends the string @var{text} to the inferior, and
21553 displays the response packet. @value{GDBN} supplies the initial
21554 @samp{$} character, the terminating @samp{#} character, and the
21557 @kindex maint print architecture
21558 @item maint print architecture @r{[}@var{file}@r{]}
21559 Print the entire architecture configuration. The optional argument
21560 @var{file} names the file where the output goes.
21562 @kindex maint print dummy-frames
21563 @item maint print dummy-frames
21564 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
21567 (@value{GDBP}) @kbd{b add}
21569 (@value{GDBP}) @kbd{print add(2,3)}
21570 Breakpoint 2, add (a=2, b=3) at @dots{}
21572 The program being debugged stopped while in a function called from GDB.
21574 (@value{GDBP}) @kbd{maint print dummy-frames}
21575 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
21576 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
21577 call_lo=0x01014000 call_hi=0x01014001
21581 Takes an optional file parameter.
21583 @kindex maint print registers
21584 @kindex maint print raw-registers
21585 @kindex maint print cooked-registers
21586 @kindex maint print register-groups
21587 @item maint print registers @r{[}@var{file}@r{]}
21588 @itemx maint print raw-registers @r{[}@var{file}@r{]}
21589 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
21590 @itemx maint print register-groups @r{[}@var{file}@r{]}
21591 Print @value{GDBN}'s internal register data structures.
21593 The command @code{maint print raw-registers} includes the contents of
21594 the raw register cache; the command @code{maint print cooked-registers}
21595 includes the (cooked) value of all registers; and the command
21596 @code{maint print register-groups} includes the groups that each
21597 register is a member of. @xref{Registers,, Registers, gdbint,
21598 @value{GDBN} Internals}.
21600 These commands take an optional parameter, a file name to which to
21601 write the information.
21603 @kindex maint print reggroups
21604 @item maint print reggroups @r{[}@var{file}@r{]}
21605 Print @value{GDBN}'s internal register group data structures. The
21606 optional argument @var{file} tells to what file to write the
21609 The register groups info looks like this:
21612 (@value{GDBP}) @kbd{maint print reggroups}
21625 This command forces @value{GDBN} to flush its internal register cache.
21627 @kindex maint print objfiles
21628 @cindex info for known object files
21629 @item maint print objfiles
21630 Print a dump of all known object files. For each object file, this
21631 command prints its name, address in memory, and all of its psymtabs
21634 @kindex maint print statistics
21635 @cindex bcache statistics
21636 @item maint print statistics
21637 This command prints, for each object file in the program, various data
21638 about that object file followed by the byte cache (@dfn{bcache})
21639 statistics for the object file. The objfile data includes the number
21640 of minimal, partical, full, and stabs symbols, the number of types
21641 defined by the objfile, the number of as yet unexpanded psym tables,
21642 the number of line tables and string tables, and the amount of memory
21643 used by the various tables. The bcache statistics include the counts,
21644 sizes, and counts of duplicates of all and unique objects, max,
21645 average, and median entry size, total memory used and its overhead and
21646 savings, and various measures of the hash table size and chain
21649 @kindex maint print type
21650 @cindex type chain of a data type
21651 @item maint print type @var{expr}
21652 Print the type chain for a type specified by @var{expr}. The argument
21653 can be either a type name or a symbol. If it is a symbol, the type of
21654 that symbol is described. The type chain produced by this command is
21655 a recursive definition of the data type as stored in @value{GDBN}'s
21656 data structures, including its flags and contained types.
21658 @kindex maint set dwarf2 max-cache-age
21659 @kindex maint show dwarf2 max-cache-age
21660 @item maint set dwarf2 max-cache-age
21661 @itemx maint show dwarf2 max-cache-age
21662 Control the DWARF 2 compilation unit cache.
21664 @cindex DWARF 2 compilation units cache
21665 In object files with inter-compilation-unit references, such as those
21666 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
21667 reader needs to frequently refer to previously read compilation units.
21668 This setting controls how long a compilation unit will remain in the
21669 cache if it is not referenced. A higher limit means that cached
21670 compilation units will be stored in memory longer, and more total
21671 memory will be used. Setting it to zero disables caching, which will
21672 slow down @value{GDBN} startup, but reduce memory consumption.
21674 @kindex maint set profile
21675 @kindex maint show profile
21676 @cindex profiling GDB
21677 @item maint set profile
21678 @itemx maint show profile
21679 Control profiling of @value{GDBN}.
21681 Profiling will be disabled until you use the @samp{maint set profile}
21682 command to enable it. When you enable profiling, the system will begin
21683 collecting timing and execution count data; when you disable profiling or
21684 exit @value{GDBN}, the results will be written to a log file. Remember that
21685 if you use profiling, @value{GDBN} will overwrite the profiling log file
21686 (often called @file{gmon.out}). If you have a record of important profiling
21687 data in a @file{gmon.out} file, be sure to move it to a safe location.
21689 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
21690 compiled with the @samp{-pg} compiler option.
21692 @kindex maint show-debug-regs
21693 @cindex x86 hardware debug registers
21694 @item maint show-debug-regs
21695 Control whether to show variables that mirror the x86 hardware debug
21696 registers. Use @code{ON} to enable, @code{OFF} to disable. If
21697 enabled, the debug registers values are shown when GDB inserts or
21698 removes a hardware breakpoint or watchpoint, and when the inferior
21699 triggers a hardware-assisted breakpoint or watchpoint.
21701 @kindex maint space
21702 @cindex memory used by commands
21704 Control whether to display memory usage for each command. If set to a
21705 nonzero value, @value{GDBN} will display how much memory each command
21706 took, following the command's own output. This can also be requested
21707 by invoking @value{GDBN} with the @option{--statistics} command-line
21708 switch (@pxref{Mode Options}).
21711 @cindex time of command execution
21713 Control whether to display the execution time for each command. If
21714 set to a nonzero value, @value{GDBN} will display how much time it
21715 took to execute each command, following the command's own output.
21716 This can also be requested by invoking @value{GDBN} with the
21717 @option{--statistics} command-line switch (@pxref{Mode Options}).
21719 @kindex maint translate-address
21720 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
21721 Find the symbol stored at the location specified by the address
21722 @var{addr} and an optional section name @var{section}. If found,
21723 @value{GDBN} prints the name of the closest symbol and an offset from
21724 the symbol's location to the specified address. This is similar to
21725 the @code{info address} command (@pxref{Symbols}), except that this
21726 command also allows to find symbols in other sections.
21730 The following command is useful for non-interactive invocations of
21731 @value{GDBN}, such as in the test suite.
21734 @item set watchdog @var{nsec}
21735 @kindex set watchdog
21736 @cindex watchdog timer
21737 @cindex timeout for commands
21738 Set the maximum number of seconds @value{GDBN} will wait for the
21739 target operation to finish. If this time expires, @value{GDBN}
21740 reports and error and the command is aborted.
21742 @item show watchdog
21743 Show the current setting of the target wait timeout.
21746 @node Remote Protocol
21747 @appendix @value{GDBN} Remote Serial Protocol
21752 * Stop Reply Packets::
21753 * General Query Packets::
21754 * Register Packet Format::
21756 * File-I/O remote protocol extension::
21762 There may be occasions when you need to know something about the
21763 protocol---for example, if there is only one serial port to your target
21764 machine, you might want your program to do something special if it
21765 recognizes a packet meant for @value{GDBN}.
21767 In the examples below, @samp{->} and @samp{<-} are used to indicate
21768 transmitted and received data respectfully.
21770 @cindex protocol, @value{GDBN} remote serial
21771 @cindex serial protocol, @value{GDBN} remote
21772 @cindex remote serial protocol
21773 All @value{GDBN} commands and responses (other than acknowledgments) are
21774 sent as a @var{packet}. A @var{packet} is introduced with the character
21775 @samp{$}, the actual @var{packet-data}, and the terminating character
21776 @samp{#} followed by a two-digit @var{checksum}:
21779 @code{$}@var{packet-data}@code{#}@var{checksum}
21783 @cindex checksum, for @value{GDBN} remote
21785 The two-digit @var{checksum} is computed as the modulo 256 sum of all
21786 characters between the leading @samp{$} and the trailing @samp{#} (an
21787 eight bit unsigned checksum).
21789 Implementors should note that prior to @value{GDBN} 5.0 the protocol
21790 specification also included an optional two-digit @var{sequence-id}:
21793 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
21796 @cindex sequence-id, for @value{GDBN} remote
21798 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
21799 has never output @var{sequence-id}s. Stubs that handle packets added
21800 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
21802 @cindex acknowledgment, for @value{GDBN} remote
21803 When either the host or the target machine receives a packet, the first
21804 response expected is an acknowledgment: either @samp{+} (to indicate
21805 the package was received correctly) or @samp{-} (to request
21809 -> @code{$}@var{packet-data}@code{#}@var{checksum}
21814 The host (@value{GDBN}) sends @var{command}s, and the target (the
21815 debugging stub incorporated in your program) sends a @var{response}. In
21816 the case of step and continue @var{command}s, the response is only sent
21817 when the operation has completed (the target has again stopped).
21819 @var{packet-data} consists of a sequence of characters with the
21820 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
21823 Fields within the packet should be separated using @samp{,} @samp{;} or
21824 @cindex remote protocol, field separator
21825 @samp{:}. Except where otherwise noted all numbers are represented in
21826 @sc{hex} with leading zeros suppressed.
21828 Implementors should note that prior to @value{GDBN} 5.0, the character
21829 @samp{:} could not appear as the third character in a packet (as it
21830 would potentially conflict with the @var{sequence-id}).
21832 Response @var{data} can be run-length encoded to save space. A @samp{*}
21833 means that the next character is an @sc{ascii} encoding giving a repeat count
21834 which stands for that many repetitions of the character preceding the
21835 @samp{*}. The encoding is @code{n+29}, yielding a printable character
21836 where @code{n >=3} (which is where rle starts to win). The printable
21837 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
21838 value greater than 126 should not be used.
21845 means the same as "0000".
21847 The error response returned for some packets includes a two character
21848 error number. That number is not well defined.
21850 For any @var{command} not supported by the stub, an empty response
21851 (@samp{$#00}) should be returned. That way it is possible to extend the
21852 protocol. A newer @value{GDBN} can tell if a packet is supported based
21855 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
21856 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
21862 The following table provides a complete list of all currently defined
21863 @var{command}s and their corresponding response @var{data}.
21864 @xref{File-I/O remote protocol extension}, for details about the File
21865 I/O extension of the remote protocol.
21869 @item @code{!} --- extended mode
21870 @cindex @code{!} packet
21872 Enable extended mode. In extended mode, the remote server is made
21873 persistent. The @samp{R} packet is used to restart the program being
21879 The remote target both supports and has enabled extended mode.
21882 @item @code{?} --- last signal
21883 @cindex @code{?} packet
21885 Indicate the reason the target halted. The reply is the same as for
21889 @xref{Stop Reply Packets}, for the reply specifications.
21891 @item @code{a} --- reserved
21893 Reserved for future use.
21895 @item @code{A}@var{arglen}@code{,}@var{argnum}@code{,}@var{arg}@code{,@dots{}} --- set program arguments @strong{(reserved)}
21896 @cindex @code{A} packet
21898 Initialized @samp{argv[]} array passed into program. @var{arglen}
21899 specifies the number of bytes in the hex encoded byte stream @var{arg}.
21900 See @code{gdbserver} for more details.
21908 @item @code{b}@var{baud} --- set baud @strong{(deprecated)}
21909 @cindex @code{b} packet
21911 Change the serial line speed to @var{baud}.
21913 JTC: @emph{When does the transport layer state change? When it's
21914 received, or after the ACK is transmitted. In either case, there are
21915 problems if the command or the acknowledgment packet is dropped.}
21917 Stan: @emph{If people really wanted to add something like this, and get
21918 it working for the first time, they ought to modify ser-unix.c to send
21919 some kind of out-of-band message to a specially-setup stub and have the
21920 switch happen "in between" packets, so that from remote protocol's point
21921 of view, nothing actually happened.}
21923 @item @code{B}@var{addr},@var{mode} --- set breakpoint @strong{(deprecated)}
21924 @cindex @code{B} packet
21926 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
21927 breakpoint at @var{addr}.
21929 This packet has been replaced by the @samp{Z} and @samp{z} packets
21930 (@pxref{insert breakpoint or watchpoint packet}).
21932 @item @code{c}@var{addr} --- continue
21933 @cindex @code{c} packet
21935 @var{addr} is address to resume. If @var{addr} is omitted, resume at
21939 @xref{Stop Reply Packets}, for the reply specifications.
21941 @item @code{C}@var{sig}@code{;}@var{addr} --- continue with signal
21942 @cindex @code{C} packet
21944 Continue with signal @var{sig} (hex signal number). If
21945 @code{;}@var{addr} is omitted, resume at same address.
21948 @xref{Stop Reply Packets}, for the reply specifications.
21950 @item @code{d} --- toggle debug @strong{(deprecated)}
21951 @cindex @code{d} packet
21955 @item @code{D} --- detach
21956 @cindex @code{D} packet
21958 Detach @value{GDBN} from the remote system. Sent to the remote target
21959 before @value{GDBN} disconnects via the @code{detach} command.
21963 @item @emph{no response}
21964 @value{GDBN} does not check for any response after sending this packet.
21967 @item @code{e} --- reserved
21969 Reserved for future use.
21971 @item @code{E} --- reserved
21973 Reserved for future use.
21975 @item @code{f} --- reserved
21977 Reserved for future use.
21979 @item @code{F}@var{RC}@code{,}@var{EE}@code{,}@var{CF}@code{;}@var{XX} --- Reply to target's F packet.
21980 @cindex @code{F} packet
21982 This packet is send by @value{GDBN} as reply to a @code{F} request packet
21983 sent by the target. This is part of the File-I/O protocol extension.
21984 @xref{File-I/O remote protocol extension}, for the specification.
21986 @item @code{g} --- read registers
21987 @anchor{read registers packet}
21988 @cindex @code{g} packet
21990 Read general registers.
21994 @item @var{XX@dots{}}
21995 Each byte of register data is described by two hex digits. The bytes
21996 with the register are transmitted in target byte order. The size of
21997 each register and their position within the @samp{g} @var{packet} are
21998 determined by the @value{GDBN} internal macros
21999 @var{DEPRECATED_REGISTER_RAW_SIZE} and @var{REGISTER_NAME} macros. The
22000 specification of several standard @code{g} packets is specified below.
22005 @item @code{G}@var{XX@dots{}} --- write regs
22006 @cindex @code{G} packet
22008 @xref{read registers packet}, for a description of the @var{XX@dots{}}
22019 @item @code{h} --- reserved
22021 Reserved for future use.
22023 @item @code{H}@var{c}@var{t@dots{}} --- set thread
22024 @cindex @code{H} packet
22026 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
22027 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
22028 should be @samp{c} for step and continue operations, @samp{g} for other
22029 operations. The thread designator @var{t@dots{}} may be -1, meaning all
22030 the threads, a thread number, or zero which means pick any thread.
22041 @c 'H': How restrictive (or permissive) is the thread model. If a
22042 @c thread is selected and stopped, are other threads allowed
22043 @c to continue to execute? As I mentioned above, I think the
22044 @c semantics of each command when a thread is selected must be
22045 @c described. For example:
22047 @c 'g': If the stub supports threads and a specific thread is
22048 @c selected, returns the register block from that thread;
22049 @c otherwise returns current registers.
22051 @c 'G' If the stub supports threads and a specific thread is
22052 @c selected, sets the registers of the register block of
22053 @c that thread; otherwise sets current registers.
22055 @item @code{i}@var{addr}@code{,}@var{nnn} --- cycle step @strong{(draft)}
22056 @anchor{cycle step packet}
22057 @cindex @code{i} packet
22059 Step the remote target by a single clock cycle. If @code{,}@var{nnn} is
22060 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
22061 step starting at that address.
22063 @item @code{I} --- signal then cycle step @strong{(reserved)}
22064 @cindex @code{I} packet
22066 @xref{step with signal packet}. @xref{cycle step packet}.
22068 @item @code{j} --- reserved
22070 Reserved for future use.
22072 @item @code{J} --- reserved
22074 Reserved for future use.
22076 @item @code{k} --- kill request
22077 @cindex @code{k} packet
22079 FIXME: @emph{There is no description of how to operate when a specific
22080 thread context has been selected (i.e.@: does 'k' kill only that
22083 @item @code{K} --- reserved
22085 Reserved for future use.
22087 @item @code{l} --- reserved
22089 Reserved for future use.
22091 @item @code{L} --- reserved
22093 Reserved for future use.
22095 @item @code{m}@var{addr}@code{,}@var{length} --- read memory
22096 @cindex @code{m} packet
22098 Read @var{length} bytes of memory starting at address @var{addr}.
22099 Neither @value{GDBN} nor the stub assume that sized memory transfers are
22100 assumed using word aligned accesses. FIXME: @emph{A word aligned memory
22101 transfer mechanism is needed.}
22105 @item @var{XX@dots{}}
22106 @var{XX@dots{}} is mem contents. Can be fewer bytes than requested if able
22107 to read only part of the data. Neither @value{GDBN} nor the stub assume
22108 that sized memory transfers are assumed using word aligned
22109 accesses. FIXME: @emph{A word aligned memory transfer mechanism is
22115 @item @code{M}@var{addr},@var{length}@code{:}@var{XX@dots{}} --- write mem
22116 @cindex @code{M} packet
22118 Write @var{length} bytes of memory starting at address @var{addr}.
22119 @var{XX@dots{}} is the data.
22126 for an error (this includes the case where only part of the data was
22130 @item @code{n} --- reserved
22132 Reserved for future use.
22134 @item @code{N} --- reserved
22136 Reserved for future use.
22138 @item @code{o} --- reserved
22140 Reserved for future use.
22142 @item @code{O} --- reserved
22144 @item @code{p}@var{hex number of register} --- read register packet
22145 @cindex @code{p} packet
22147 @xref{read registers packet}, for a description of how the returned
22148 register value is encoded.
22152 @item @var{XX@dots{}}
22153 the register's value
22157 Indicating an unrecognized @var{query}.
22160 @item @code{P}@var{n@dots{}}@code{=}@var{r@dots{}} --- write register
22161 @anchor{write register packet}
22162 @cindex @code{P} packet
22164 Write register @var{n@dots{}} with value @var{r@dots{}}, which contains two hex
22165 digits for each byte in the register (target byte order).
22175 @item @code{q}@var{query} --- general query
22176 @anchor{general query packet}
22177 @cindex @code{q} packet
22179 Request info about @var{query}. In general @value{GDBN} queries have a
22180 leading upper case letter. Custom vendor queries should use a company
22181 prefix (in lower case) ex: @samp{qfsf.var}. @var{query} may optionally
22182 be followed by a @samp{,} or @samp{;} separated list. Stubs must ensure
22183 that they match the full @var{query} name.
22187 @item @var{XX@dots{}}
22188 Hex encoded data from query. The reply can not be empty.
22192 Indicating an unrecognized @var{query}.
22195 @item @code{Q}@var{var}@code{=}@var{val} --- general set
22196 @cindex @code{Q} packet
22198 Set value of @var{var} to @var{val}.
22200 @xref{general query packet}, for a discussion of naming conventions.
22202 @item @code{r} --- reset @strong{(deprecated)}
22203 @cindex @code{r} packet
22205 Reset the entire system.
22207 @item @code{R}@var{XX} --- remote restart
22208 @cindex @code{R} packet
22210 Restart the program being debugged. @var{XX}, while needed, is ignored.
22211 This packet is only available in extended mode.
22215 @item @emph{no reply}
22216 The @samp{R} packet has no reply.
22219 @item @code{s}@var{addr} --- step
22220 @cindex @code{s} packet
22222 @var{addr} is address to resume. If @var{addr} is omitted, resume at
22226 @xref{Stop Reply Packets}, for the reply specifications.
22228 @item @code{S}@var{sig}@code{;}@var{addr} --- step with signal
22229 @anchor{step with signal packet}
22230 @cindex @code{S} packet
22232 Like @samp{C} but step not continue.
22235 @xref{Stop Reply Packets}, for the reply specifications.
22237 @item @code{t}@var{addr}@code{:}@var{PP}@code{,}@var{MM} --- search
22238 @cindex @code{t} packet
22240 Search backwards starting at address @var{addr} for a match with pattern
22241 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
22242 @var{addr} must be at least 3 digits.
22244 @item @code{T}@var{XX} --- thread alive
22245 @cindex @code{T} packet
22247 Find out if the thread XX is alive.
22252 thread is still alive
22257 @item @code{u} --- reserved
22259 Reserved for future use.
22261 @item @code{U} --- reserved
22263 Reserved for future use.
22265 @item @code{v} --- verbose packet prefix
22267 Packets starting with @code{v} are identified by a multi-letter name,
22268 up to the first @code{;} or @code{?} (or the end of the packet).
22270 @item @code{vCont}[;@var{action}[@code{:}@var{tid}]]... --- extended resume
22271 @cindex @code{vCont} packet
22273 Resume the inferior. Different actions may be specified for each thread.
22274 If an action is specified with no @var{tid}, then it is applied to any
22275 threads that don't have a specific action specified; if no default action is
22276 specified then other threads should remain stopped. Specifying multiple
22277 default actions is an error; specifying no actions is also an error.
22278 Thread IDs are specified in hexadecimal. Currently supported actions are:
22284 Continue with signal @var{sig}. @var{sig} should be two hex digits.
22288 Step with signal @var{sig}. @var{sig} should be two hex digits.
22291 The optional @var{addr} argument normally associated with these packets is
22292 not supported in @code{vCont}.
22295 @xref{Stop Reply Packets}, for the reply specifications.
22297 @item @code{vCont?} --- extended resume query
22298 @cindex @code{vCont?} packet
22300 Query support for the @code{vCont} packet.
22304 @item @code{vCont}[;@var{action}]...
22305 The @code{vCont} packet is supported. Each @var{action} is a supported
22306 command in the @code{vCont} packet.
22308 The @code{vCont} packet is not supported.
22311 @item @code{V} --- reserved
22313 Reserved for future use.
22315 @item @code{w} --- reserved
22317 Reserved for future use.
22319 @item @code{W} --- reserved
22321 Reserved for future use.
22323 @item @code{x} --- reserved
22325 Reserved for future use.
22327 @item @code{X}@var{addr}@code{,}@var{length}@var{:}@var{XX@dots{}} --- write mem (binary)
22328 @cindex @code{X} packet
22330 @var{addr} is address, @var{length} is number of bytes, @var{XX@dots{}}
22331 is binary data. The characters @code{$}, @code{#}, and @code{0x7d} are
22332 escaped using @code{0x7d}, and then XORed with @code{0x20}.
22333 For example, @code{0x7d} would be transmitted as @code{0x7d 0x5d}.
22343 @item @code{y} --- reserved
22345 Reserved for future use.
22347 @item @code{Y} reserved
22349 Reserved for future use.
22351 @item @code{z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- remove breakpoint or watchpoint @strong{(draft)}
22352 @itemx @code{Z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- insert breakpoint or watchpoint @strong{(draft)}
22353 @anchor{insert breakpoint or watchpoint packet}
22354 @cindex @code{z} packet
22355 @cindex @code{Z} packets
22357 Insert (@code{Z}) or remove (@code{z}) a @var{type} breakpoint or
22358 watchpoint starting at address @var{address} and covering the next
22359 @var{length} bytes.
22361 Each breakpoint and watchpoint packet @var{type} is documented
22364 @emph{Implementation notes: A remote target shall return an empty string
22365 for an unrecognized breakpoint or watchpoint packet @var{type}. A
22366 remote target shall support either both or neither of a given
22367 @code{Z}@var{type}@dots{} and @code{z}@var{type}@dots{} packet pair. To
22368 avoid potential problems with duplicate packets, the operations should
22369 be implemented in an idempotent way.}
22371 @item @code{z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- remove memory breakpoint @strong{(draft)}
22372 @item @code{Z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- insert memory breakpoint @strong{(draft)}
22373 @cindex @code{z0} packet
22374 @cindex @code{Z0} packet
22376 Insert (@code{Z0}) or remove (@code{z0}) a memory breakpoint at address
22377 @code{addr} of size @code{length}.
22379 A memory breakpoint is implemented by replacing the instruction at
22380 @var{addr} with a software breakpoint or trap instruction. The
22381 @code{length} is used by targets that indicates the size of the
22382 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
22383 @sc{mips} can insert either a 2 or 4 byte breakpoint).
22385 @emph{Implementation note: It is possible for a target to copy or move
22386 code that contains memory breakpoints (e.g., when implementing
22387 overlays). The behavior of this packet, in the presence of such a
22388 target, is not defined.}
22400 @item @code{z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- remove hardware breakpoint @strong{(draft)}
22401 @item @code{Z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- insert hardware breakpoint @strong{(draft)}
22402 @cindex @code{z1} packet
22403 @cindex @code{Z1} packet
22405 Insert (@code{Z1}) or remove (@code{z1}) a hardware breakpoint at
22406 address @code{addr} of size @code{length}.
22408 A hardware breakpoint is implemented using a mechanism that is not
22409 dependant on being able to modify the target's memory.
22411 @emph{Implementation note: A hardware breakpoint is not affected by code
22424 @item @code{z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- remove write watchpoint @strong{(draft)}
22425 @item @code{Z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- insert write watchpoint @strong{(draft)}
22426 @cindex @code{z2} packet
22427 @cindex @code{Z2} packet
22429 Insert (@code{Z2}) or remove (@code{z2}) a write watchpoint.
22441 @item @code{z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- remove read watchpoint @strong{(draft)}
22442 @item @code{Z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- insert read watchpoint @strong{(draft)}
22443 @cindex @code{z3} packet
22444 @cindex @code{Z3} packet
22446 Insert (@code{Z3}) or remove (@code{z3}) a read watchpoint.
22458 @item @code{z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- remove access watchpoint @strong{(draft)}
22459 @item @code{Z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- insert access watchpoint @strong{(draft)}
22460 @cindex @code{z4} packet
22461 @cindex @code{Z4} packet
22463 Insert (@code{Z4}) or remove (@code{z4}) an access watchpoint.
22477 @node Stop Reply Packets
22478 @section Stop Reply Packets
22479 @cindex stop reply packets
22481 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
22482 receive any of the below as a reply. In the case of the @samp{C},
22483 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
22484 when the target halts. In the below the exact meaning of @samp{signal
22485 number} is poorly defined. In general one of the UNIX signal numbering
22486 conventions is used.
22491 @var{AA} is the signal number
22493 @item @code{T}@var{AA}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}
22494 @cindex @code{T} packet reply
22496 @var{AA} = two hex digit signal number; @var{n...} = register number
22497 (hex), @var{r...} = target byte ordered register contents, size defined
22498 by @code{DEPRECATED_REGISTER_RAW_SIZE}; @var{n...} = @samp{thread},
22499 @var{r...} = thread process ID, this is a hex integer; @var{n...} =
22500 (@samp{watch} | @samp{rwatch} | @samp{awatch}, @var{r...} = data
22501 address, this is a hex integer; @var{n...} = other string not starting
22502 with valid hex digit. @value{GDBN} should ignore this @var{n...},
22503 @var{r...} pair and go on to the next. This way we can extend the
22508 The process exited, and @var{AA} is the exit status. This is only
22509 applicable to certain targets.
22513 The process terminated with signal @var{AA}.
22515 @item O@var{XX@dots{}}
22517 @var{XX@dots{}} is hex encoding of @sc{ascii} data. This can happen at
22518 any time while the program is running and the debugger should continue
22519 to wait for @samp{W}, @samp{T}, etc.
22521 @item F@var{call-id}@code{,}@var{parameter@dots{}}
22523 @var{call-id} is the identifier which says which host system call should
22524 be called. This is just the name of the function. Translation into the
22525 correct system call is only applicable as it's defined in @value{GDBN}.
22526 @xref{File-I/O remote protocol extension}, for a list of implemented
22529 @var{parameter@dots{}} is a list of parameters as defined for this very
22532 The target replies with this packet when it expects @value{GDBN} to call
22533 a host system call on behalf of the target. @value{GDBN} replies with
22534 an appropriate @code{F} packet and keeps up waiting for the next reply
22535 packet from the target. The latest @samp{C}, @samp{c}, @samp{S} or
22536 @samp{s} action is expected to be continued.
22537 @xref{File-I/O remote protocol extension}, for more details.
22541 @node General Query Packets
22542 @section General Query Packets
22543 @cindex remote query requests
22545 The following set and query packets have already been defined.
22549 @item @code{q}@code{C} --- current thread
22550 @cindex current thread, remote request
22551 @cindex @code{qC} packet
22552 Return the current thread id.
22556 @item @code{QC}@var{pid}
22557 Where @var{pid} is an unsigned hexidecimal process id.
22559 Any other reply implies the old pid.
22562 @item @code{q}@code{fThreadInfo} -- all thread ids
22563 @cindex list active threads, remote request
22564 @cindex @code{qfThreadInfo} packet
22565 @code{q}@code{sThreadInfo}
22567 Obtain a list of active thread ids from the target (OS). Since there
22568 may be too many active threads to fit into one reply packet, this query
22569 works iteratively: it may require more than one query/reply sequence to
22570 obtain the entire list of threads. The first query of the sequence will
22571 be the @code{qf}@code{ThreadInfo} query; subsequent queries in the
22572 sequence will be the @code{qs}@code{ThreadInfo} query.
22574 NOTE: replaces the @code{qL} query (see below).
22578 @item @code{m}@var{id}
22580 @item @code{m}@var{id},@var{id}@dots{}
22581 a comma-separated list of thread ids
22583 (lower case 'el') denotes end of list.
22586 In response to each query, the target will reply with a list of one or
22587 more thread ids, in big-endian unsigned hex, separated by commas.
22588 @value{GDBN} will respond to each reply with a request for more thread
22589 ids (using the @code{qs} form of the query), until the target responds
22590 with @code{l} (lower-case el, for @code{'last'}).
22592 @item @code{q}@code{ThreadExtraInfo}@code{,}@var{id} --- extra thread info
22593 @cindex thread attributes info, remote request
22594 @cindex @code{qThreadExtraInfo} packet
22595 Where @var{id} is a thread-id in big-endian hex. Obtain a printable
22596 string description of a thread's attributes from the target OS. This
22597 string may contain anything that the target OS thinks is interesting for
22598 @value{GDBN} to tell the user about the thread. The string is displayed
22599 in @value{GDBN}'s @samp{info threads} display. Some examples of
22600 possible thread extra info strings are ``Runnable'', or ``Blocked on
22605 @item @var{XX@dots{}}
22606 Where @var{XX@dots{}} is a hex encoding of @sc{ascii} data, comprising
22607 the printable string containing the extra information about the thread's
22611 @item @code{q}@code{L}@var{startflag}@var{threadcount}@var{nextthread} --- query @var{LIST} or @var{threadLIST} @strong{(deprecated)}
22613 Obtain thread information from RTOS. Where: @var{startflag} (one hex
22614 digit) is one to indicate the first query and zero to indicate a
22615 subsequent query; @var{threadcount} (two hex digits) is the maximum
22616 number of threads the response packet can contain; and @var{nextthread}
22617 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
22618 returned in the response as @var{argthread}.
22620 NOTE: this query is replaced by the @code{q}@code{fThreadInfo} query
22625 @item @code{q}@code{M}@var{count}@var{done}@var{argthread}@var{thread@dots{}}
22626 Where: @var{count} (two hex digits) is the number of threads being
22627 returned; @var{done} (one hex digit) is zero to indicate more threads
22628 and one indicates no further threads; @var{argthreadid} (eight hex
22629 digits) is @var{nextthread} from the request packet; @var{thread@dots{}}
22630 is a sequence of thread IDs from the target. @var{threadid} (eight hex
22631 digits). See @code{remote.c:parse_threadlist_response()}.
22634 @item @code{q}@code{CRC:}@var{addr}@code{,}@var{length} --- compute CRC of memory block
22635 @cindex CRC of memory block, remote request
22636 @cindex @code{qCRC} packet
22639 @item @code{E}@var{NN}
22640 An error (such as memory fault)
22641 @item @code{C}@var{CRC32}
22642 A 32 bit cyclic redundancy check of the specified memory region.
22645 @item @code{q}@code{Offsets} --- query sect offs
22646 @cindex section offsets, remote request
22647 @cindex @code{qOffsets} packet
22648 Get section offsets that the target used when re-locating the downloaded
22649 image. @emph{Note: while a @code{Bss} offset is included in the
22650 response, @value{GDBN} ignores this and instead applies the @code{Data}
22651 offset to the @code{Bss} section.}
22655 @item @code{Text=}@var{xxx}@code{;Data=}@var{yyy}@code{;Bss=}@var{zzz}
22658 @item @code{q}@code{P}@var{mode}@var{threadid} --- thread info request
22659 @cindex thread information, remote request
22660 @cindex @code{qP} packet
22661 Returns information on @var{threadid}. Where: @var{mode} is a hex
22662 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
22669 See @code{remote.c:remote_unpack_thread_info_response()}.
22671 @item @code{q}@code{Rcmd,}@var{command} --- remote command
22672 @cindex execute remote command, remote request
22673 @cindex @code{qRcmd} packet
22674 @var{command} (hex encoded) is passed to the local interpreter for
22675 execution. Invalid commands should be reported using the output string.
22676 Before the final result packet, the target may also respond with a
22677 number of intermediate @code{O}@var{output} console output packets.
22678 @emph{Implementors should note that providing access to a stubs's
22679 interpreter may have security implications}.
22684 A command response with no output.
22686 A command response with the hex encoded output string @var{OUTPUT}.
22687 @item @code{E}@var{NN}
22688 Indicate a badly formed request.
22690 When @samp{q}@samp{Rcmd} is not recognized.
22693 @item @code{qSymbol::} --- symbol lookup
22694 @cindex symbol lookup, remote request
22695 @cindex @code{qSymbol} packet
22696 Notify the target that @value{GDBN} is prepared to serve symbol lookup
22697 requests. Accept requests from the target for the values of symbols.
22702 The target does not need to look up any (more) symbols.
22703 @item @code{qSymbol:}@var{sym_name}
22704 The target requests the value of symbol @var{sym_name} (hex encoded).
22705 @value{GDBN} may provide the value by using the
22706 @code{qSymbol:}@var{sym_value}:@var{sym_name} message, described below.
22709 @item @code{qSymbol:}@var{sym_value}:@var{sym_name} --- symbol value
22711 Set the value of @var{sym_name} to @var{sym_value}.
22713 @var{sym_name} (hex encoded) is the name of a symbol whose value the
22714 target has previously requested.
22716 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
22717 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
22723 The target does not need to look up any (more) symbols.
22724 @item @code{qSymbol:}@var{sym_name}
22725 The target requests the value of a new symbol @var{sym_name} (hex
22726 encoded). @value{GDBN} will continue to supply the values of symbols
22727 (if available), until the target ceases to request them.
22730 @item @code{qPart}:@var{object}:@code{read}:@var{annex}:@var{offset},@var{length} --- read special data
22731 @cindex read special object, remote request
22732 @cindex @code{qPart} packet
22733 Read uninterpreted bytes from the target's special data area
22734 identified by the keyword @code{object}.
22735 Request @var{length} bytes starting at @var{offset} bytes into the data.
22736 The content and encoding of @var{annex} is specific to the object;
22737 it can supply additional details about what data to access.
22739 Here are the specific requests of this form defined so far.
22740 All @samp{@code{qPart}:@var{object}:@code{read}:@dots{}}
22741 requests use the same reply formats, listed below.
22744 @item @code{qPart}:@code{auxv}:@code{read}::@var{offset},@var{length}
22745 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
22746 auxiliary vector}, and see @ref{Remote configuration,
22747 read-aux-vector-packet}. Note @var{annex} must be empty.
22753 The @var{offset} in the request is at the end of the data.
22754 There is no more data to be read.
22756 @item @var{XX@dots{}}
22757 Hex encoded data bytes read.
22758 This may be fewer bytes than the @var{length} in the request.
22761 The request was malformed, or @var{annex} was invalid.
22763 @item @code{E}@var{nn}
22764 The offset was invalid, or there was an error encountered reading the data.
22765 @var{nn} is a hex-encoded @code{errno} value.
22767 @item @code{""} (empty)
22768 An empty reply indicates the @var{object} or @var{annex} string was not
22769 recognized by the stub.
22772 @item @code{qPart}:@var{object}:@code{write}:@var{annex}:@var{offset}:@var{data@dots{}}
22773 @cindex write data into object, remote request
22774 Write uninterpreted bytes into the target's special data area
22775 identified by the keyword @code{object},
22776 starting at @var{offset} bytes into the data.
22777 @var{data@dots{}} is the hex-encoded data to be written.
22778 The content and encoding of @var{annex} is specific to the object;
22779 it can supply additional details about what data to access.
22781 No requests of this form are presently in use. This specification
22782 serves as a placeholder to document the common format that new
22783 specific request specifications ought to use.
22788 @var{nn} (hex encoded) is the number of bytes written.
22789 This may be fewer bytes than supplied in the request.
22792 The request was malformed, or @var{annex} was invalid.
22794 @item @code{E}@var{nn}
22795 The offset was invalid, or there was an error encountered writing the data.
22796 @var{nn} is a hex-encoded @code{errno} value.
22798 @item @code{""} (empty)
22799 An empty reply indicates the @var{object} or @var{annex} string was not
22800 recognized by the stub, or that the object does not support writing.
22803 @item @code{qPart}:@var{object}:@var{operation}:@dots{}
22804 Requests of this form may be added in the future. When a stub does
22805 not recognize the @var{object} keyword, or its support for
22806 @var{object} does not recognize the @var{operation} keyword,
22807 the stub must respond with an empty packet.
22809 @item @code{qGetTLSAddr}:@var{thread-id},@var{offset},@var{lm} --- get thread local storage address
22810 @cindex get thread-local storage address, remote request
22811 @cindex @code{qGetTLSAddr} packet
22812 Fetch the address associated with thread local storage specified
22813 by @var{thread-id}, @var{offset}, and @var{lm}.
22815 @var{thread-id} is the (big endian, hex encoded) thread id associated with the
22816 thread for which to fetch the TLS address.
22818 @var{offset} is the (big endian, hex encoded) offset associated with the
22819 thread local variable. (This offset is obtained from the debug
22820 information associated with the variable.)
22822 @var{lm} is the (big endian, hex encoded) OS/ABI specific encoding of the
22823 the load module associated with the thread local storage. For example,
22824 a @sc{gnu}/Linux system will pass the link map address of the shared
22825 object associated with the thread local storage under consideration.
22826 Other operating environments may choose to represent the load module
22827 differently, so the precise meaning of this parameter will vary.
22831 @item @var{XX@dots{}}
22832 Hex encoded (big endian) bytes representing the address of the thread
22833 local storage requested.
22835 @item @code{E}@var{nn} (where @var{nn} are hex digits)
22838 @item @code{""} (empty)
22839 An empty reply indicates that @code{qGetTLSAddr} is not supported by the stub.
22842 Use of this request packet is controlled by the @code{set remote
22843 get-thread-local-storage-address} command (@pxref{Remote
22844 configuration, set remote get-thread-local-storage-address}).
22848 @node Register Packet Format
22849 @section Register Packet Format
22851 The following @samp{g}/@samp{G} packets have previously been defined.
22852 In the below, some thirty-two bit registers are transferred as
22853 sixty-four bits. Those registers should be zero/sign extended (which?)
22854 to fill the space allocated. Register bytes are transfered in target
22855 byte order. The two nibbles within a register byte are transfered
22856 most-significant - least-significant.
22862 All registers are transfered as thirty-two bit quantities in the order:
22863 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
22864 registers; fsr; fir; fp.
22868 All registers are transfered as sixty-four bit quantities (including
22869 thirty-two bit registers such as @code{sr}). The ordering is the same
22877 Example sequence of a target being re-started. Notice how the restart
22878 does not get any direct output:
22883 @emph{target restarts}
22886 <- @code{T001:1234123412341234}
22890 Example sequence of a target being stepped by a single instruction:
22893 -> @code{G1445@dots{}}
22898 <- @code{T001:1234123412341234}
22902 <- @code{1455@dots{}}
22906 @node File-I/O remote protocol extension
22907 @section File-I/O remote protocol extension
22908 @cindex File-I/O remote protocol extension
22911 * File-I/O Overview::
22912 * Protocol basics::
22913 * The F request packet::
22914 * The F reply packet::
22915 * Memory transfer::
22916 * The Ctrl-C message::
22918 * The isatty call::
22919 * The system call::
22920 * List of supported calls::
22921 * Protocol specific representation of datatypes::
22923 * File-I/O Examples::
22926 @node File-I/O Overview
22927 @subsection File-I/O Overview
22928 @cindex file-i/o overview
22930 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
22931 target to use the host's file system and console I/O when calling various
22932 system calls. System calls on the target system are translated into a
22933 remote protocol packet to the host system which then performs the needed
22934 actions and returns with an adequate response packet to the target system.
22935 This simulates file system operations even on targets that lack file systems.
22937 The protocol is defined host- and target-system independent. It uses
22938 its own independent representation of datatypes and values. Both,
22939 @value{GDBN} and the target's @value{GDBN} stub are responsible for
22940 translating the system dependent values into the unified protocol values
22941 when data is transmitted.
22943 The communication is synchronous. A system call is possible only
22944 when GDB is waiting for the @samp{C}, @samp{c}, @samp{S} or @samp{s}
22945 packets. While @value{GDBN} handles the request for a system call,
22946 the target is stopped to allow deterministic access to the target's
22947 memory. Therefore File-I/O is not interuptible by target signals. It
22948 is possible to interrupt File-I/O by a user interrupt (Ctrl-C), though.
22950 The target's request to perform a host system call does not finish
22951 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
22952 after finishing the system call, the target returns to continuing the
22953 previous activity (continue, step). No additional continue or step
22954 request from @value{GDBN} is required.
22957 (@value{GDBP}) continue
22958 <- target requests 'system call X'
22959 target is stopped, @value{GDBN} executes system call
22960 -> GDB returns result
22961 ... target continues, GDB returns to wait for the target
22962 <- target hits breakpoint and sends a Txx packet
22965 The protocol is only used for files on the host file system and
22966 for I/O on the console. Character or block special devices, pipes,
22967 named pipes or sockets or any other communication method on the host
22968 system are not supported by this protocol.
22970 @node Protocol basics
22971 @subsection Protocol basics
22972 @cindex protocol basics, file-i/o
22974 The File-I/O protocol uses the @code{F} packet, as request as well
22975 as as reply packet. Since a File-I/O system call can only occur when
22976 @value{GDBN} is waiting for the continuing or stepping target, the
22977 File-I/O request is a reply that @value{GDBN} has to expect as a result
22978 of a former @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
22979 This @code{F} packet contains all information needed to allow @value{GDBN}
22980 to call the appropriate host system call:
22984 A unique identifier for the requested system call.
22987 All parameters to the system call. Pointers are given as addresses
22988 in the target memory address space. Pointers to strings are given as
22989 pointer/length pair. Numerical values are given as they are.
22990 Numerical control values are given in a protocol specific representation.
22994 At that point @value{GDBN} has to perform the following actions.
22998 If parameter pointer values are given, which point to data needed as input
22999 to a system call, @value{GDBN} requests this data from the target with a
23000 standard @code{m} packet request. This additional communication has to be
23001 expected by the target implementation and is handled as any other @code{m}
23005 @value{GDBN} translates all value from protocol representation to host
23006 representation as needed. Datatypes are coerced into the host types.
23009 @value{GDBN} calls the system call
23012 It then coerces datatypes back to protocol representation.
23015 If pointer parameters in the request packet point to buffer space in which
23016 a system call is expected to copy data to, the data is transmitted to the
23017 target using a @code{M} or @code{X} packet. This packet has to be expected
23018 by the target implementation and is handled as any other @code{M} or @code{X}
23023 Eventually @value{GDBN} replies with another @code{F} packet which contains all
23024 necessary information for the target to continue. This at least contains
23031 @code{errno}, if has been changed by the system call.
23038 After having done the needed type and value coercion, the target continues
23039 the latest continue or step action.
23041 @node The F request packet
23042 @subsection The @code{F} request packet
23043 @cindex file-i/o request packet
23044 @cindex @code{F} request packet
23046 The @code{F} request packet has the following format:
23051 @code{F}@var{call-id}@code{,}@var{parameter@dots{}}
23054 @var{call-id} is the identifier to indicate the host system call to be called.
23055 This is just the name of the function.
23057 @var{parameter@dots{}} are the parameters to the system call.
23061 Parameters are hexadecimal integer values, either the real values in case
23062 of scalar datatypes, as pointers to target buffer space in case of compound
23063 datatypes and unspecified memory areas or as pointer/length pairs in case
23064 of string parameters. These are appended to the call-id, each separated
23065 from its predecessor by a comma. All values are transmitted in ASCII
23066 string representation, pointer/length pairs separated by a slash.
23068 @node The F reply packet
23069 @subsection The @code{F} reply packet
23070 @cindex file-i/o reply packet
23071 @cindex @code{F} reply packet
23073 The @code{F} reply packet has the following format:
23078 @code{F}@var{retcode}@code{,}@var{errno}@code{,}@var{Ctrl-C flag}@code{;}@var{call specific attachment}
23081 @var{retcode} is the return code of the system call as hexadecimal value.
23083 @var{errno} is the errno set by the call, in protocol specific representation.
23084 This parameter can be omitted if the call was successful.
23086 @var{Ctrl-C flag} is only send if the user requested a break. In this
23087 case, @var{errno} must be send as well, even if the call was successful.
23088 The @var{Ctrl-C flag} itself consists of the character 'C':
23095 or, if the call was interupted before the host call has been performed:
23102 assuming 4 is the protocol specific representation of @code{EINTR}.
23106 @node Memory transfer
23107 @subsection Memory transfer
23108 @cindex memory transfer, in file-i/o protocol
23110 Structured data which is transferred using a memory read or write as e.g.@:
23111 a @code{struct stat} is expected to be in a protocol specific format with
23112 all scalar multibyte datatypes being big endian. This should be done by
23113 the target before the @code{F} packet is sent resp.@: by @value{GDBN} before
23114 it transfers memory to the target. Transferred pointers to structured
23115 data should point to the already coerced data at any time.
23117 @node The Ctrl-C message
23118 @subsection The Ctrl-C message
23119 @cindex ctrl-c message, in file-i/o protocol
23121 A special case is, if the @var{Ctrl-C flag} is set in the @value{GDBN}
23122 reply packet. In this case the target should behave, as if it had
23123 gotten a break message. The meaning for the target is ``system call
23124 interupted by @code{SIGINT}''. Consequentially, the target should actually stop
23125 (as with a break message) and return to @value{GDBN} with a @code{T02}
23126 packet. In this case, it's important for the target to know, in which
23127 state the system call was interrupted. Since this action is by design
23128 not an atomic operation, we have to differ between two cases:
23132 The system call hasn't been performed on the host yet.
23135 The system call on the host has been finished.
23139 These two states can be distinguished by the target by the value of the
23140 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
23141 call hasn't been performed. This is equivalent to the @code{EINTR} handling
23142 on POSIX systems. In any other case, the target may presume that the
23143 system call has been finished --- successful or not --- and should behave
23144 as if the break message arrived right after the system call.
23146 @value{GDBN} must behave reliable. If the system call has not been called
23147 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
23148 @code{errno} in the packet. If the system call on the host has been finished
23149 before the user requests a break, the full action must be finshed by
23150 @value{GDBN}. This requires sending @code{M} or @code{X} packets as they fit.
23151 The @code{F} packet may only be send when either nothing has happened
23152 or the full action has been completed.
23155 @subsection Console I/O
23156 @cindex console i/o as part of file-i/o
23158 By default and if not explicitely closed by the target system, the file
23159 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
23160 on the @value{GDBN} console is handled as any other file output operation
23161 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
23162 by @value{GDBN} so that after the target read request from file descriptor
23163 0 all following typing is buffered until either one of the following
23168 The user presses @kbd{Ctrl-C}. The behaviour is as explained above, the
23170 system call is treated as finished.
23173 The user presses @kbd{Enter}. This is treated as end of input with a trailing
23177 The user presses @kbd{Ctrl-D}. This is treated as end of input. No trailing
23178 character, especially no Ctrl-D is appended to the input.
23182 If the user has typed more characters as fit in the buffer given to
23183 the read call, the trailing characters are buffered in @value{GDBN} until
23184 either another @code{read(0, @dots{})} is requested by the target or debugging
23185 is stopped on users request.
23187 @node The isatty call
23188 @subsection The @samp{isatty} function call
23189 @cindex isatty call, file-i/o protocol
23191 A special case in this protocol is the library call @code{isatty} which
23192 is implemented as its own call inside of this protocol. It returns
23193 1 to the target if the file descriptor given as parameter is attached
23194 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
23195 would require implementing @code{ioctl} and would be more complex than
23198 @node The system call
23199 @subsection The @samp{system} function call
23200 @cindex system call, file-i/o protocol
23202 The other special case in this protocol is the @code{system} call which
23203 is implemented as its own call, too. @value{GDBN} is taking over the full
23204 task of calling the necessary host calls to perform the @code{system}
23205 call. The return value of @code{system} is simplified before it's returned
23206 to the target. Basically, the only signal transmitted back is @code{EINTR}
23207 in case the user pressed @kbd{Ctrl-C}. Otherwise the return value consists
23208 entirely of the exit status of the called command.
23210 Due to security concerns, the @code{system} call is by default refused
23211 by @value{GDBN}. The user has to allow this call explicitly with the
23212 @kbd{set remote system-call-allowed 1} command.
23215 @item set remote system-call-allowed
23216 @kindex set remote system-call-allowed
23217 Control whether to allow the @code{system} calls in the File I/O
23218 protocol for the remote target. The default is zero (disabled).
23220 @item show remote system-call-allowed
23221 @kindex show remote system-call-allowed
23222 Show the current setting of system calls for the remote File I/O
23226 @node List of supported calls
23227 @subsection List of supported calls
23228 @cindex list of supported file-i/o calls
23245 @unnumberedsubsubsec open
23246 @cindex open, file-i/o system call
23250 int open(const char *pathname, int flags);
23251 int open(const char *pathname, int flags, mode_t mode);
23254 Fopen,pathptr/len,flags,mode
23258 @code{flags} is the bitwise or of the following values:
23262 If the file does not exist it will be created. The host
23263 rules apply as far as file ownership and time stamps
23267 When used with O_CREAT, if the file already exists it is
23268 an error and open() fails.
23271 If the file already exists and the open mode allows
23272 writing (O_RDWR or O_WRONLY is given) it will be
23273 truncated to length 0.
23276 The file is opened in append mode.
23279 The file is opened for reading only.
23282 The file is opened for writing only.
23285 The file is opened for reading and writing.
23288 Each other bit is silently ignored.
23293 @code{mode} is the bitwise or of the following values:
23297 User has read permission.
23300 User has write permission.
23303 Group has read permission.
23306 Group has write permission.
23309 Others have read permission.
23312 Others have write permission.
23315 Each other bit is silently ignored.
23320 @exdent Return value:
23321 open returns the new file descriptor or -1 if an error
23329 pathname already exists and O_CREAT and O_EXCL were used.
23332 pathname refers to a directory.
23335 The requested access is not allowed.
23338 pathname was too long.
23341 A directory component in pathname does not exist.
23344 pathname refers to a device, pipe, named pipe or socket.
23347 pathname refers to a file on a read-only filesystem and
23348 write access was requested.
23351 pathname is an invalid pointer value.
23354 No space on device to create the file.
23357 The process already has the maximum number of files open.
23360 The limit on the total number of files open on the system
23364 The call was interrupted by the user.
23368 @unnumberedsubsubsec close
23369 @cindex close, file-i/o system call
23378 @exdent Return value:
23379 close returns zero on success, or -1 if an error occurred.
23386 fd isn't a valid open file descriptor.
23389 The call was interrupted by the user.
23393 @unnumberedsubsubsec read
23394 @cindex read, file-i/o system call
23398 int read(int fd, void *buf, unsigned int count);
23401 Fread,fd,bufptr,count
23403 @exdent Return value:
23404 On success, the number of bytes read is returned.
23405 Zero indicates end of file. If count is zero, read
23406 returns zero as well. On error, -1 is returned.
23413 fd is not a valid file descriptor or is not open for
23417 buf is an invalid pointer value.
23420 The call was interrupted by the user.
23424 @unnumberedsubsubsec write
23425 @cindex write, file-i/o system call
23429 int write(int fd, const void *buf, unsigned int count);
23432 Fwrite,fd,bufptr,count
23434 @exdent Return value:
23435 On success, the number of bytes written are returned.
23436 Zero indicates nothing was written. On error, -1
23444 fd is not a valid file descriptor or is not open for
23448 buf is an invalid pointer value.
23451 An attempt was made to write a file that exceeds the
23452 host specific maximum file size allowed.
23455 No space on device to write the data.
23458 The call was interrupted by the user.
23462 @unnumberedsubsubsec lseek
23463 @cindex lseek, file-i/o system call
23467 long lseek (int fd, long offset, int flag);
23470 Flseek,fd,offset,flag
23473 @code{flag} is one of:
23477 The offset is set to offset bytes.
23480 The offset is set to its current location plus offset
23484 The offset is set to the size of the file plus offset
23489 @exdent Return value:
23490 On success, the resulting unsigned offset in bytes from
23491 the beginning of the file is returned. Otherwise, a
23492 value of -1 is returned.
23499 fd is not a valid open file descriptor.
23502 fd is associated with the @value{GDBN} console.
23505 flag is not a proper value.
23508 The call was interrupted by the user.
23512 @unnumberedsubsubsec rename
23513 @cindex rename, file-i/o system call
23517 int rename(const char *oldpath, const char *newpath);
23520 Frename,oldpathptr/len,newpathptr/len
23522 @exdent Return value:
23523 On success, zero is returned. On error, -1 is returned.
23530 newpath is an existing directory, but oldpath is not a
23534 newpath is a non-empty directory.
23537 oldpath or newpath is a directory that is in use by some
23541 An attempt was made to make a directory a subdirectory
23545 A component used as a directory in oldpath or new
23546 path is not a directory. Or oldpath is a directory
23547 and newpath exists but is not a directory.
23550 oldpathptr or newpathptr are invalid pointer values.
23553 No access to the file or the path of the file.
23557 oldpath or newpath was too long.
23560 A directory component in oldpath or newpath does not exist.
23563 The file is on a read-only filesystem.
23566 The device containing the file has no room for the new
23570 The call was interrupted by the user.
23574 @unnumberedsubsubsec unlink
23575 @cindex unlink, file-i/o system call
23579 int unlink(const char *pathname);
23582 Funlink,pathnameptr/len
23584 @exdent Return value:
23585 On success, zero is returned. On error, -1 is returned.
23592 No access to the file or the path of the file.
23595 The system does not allow unlinking of directories.
23598 The file pathname cannot be unlinked because it's
23599 being used by another process.
23602 pathnameptr is an invalid pointer value.
23605 pathname was too long.
23608 A directory component in pathname does not exist.
23611 A component of the path is not a directory.
23614 The file is on a read-only filesystem.
23617 The call was interrupted by the user.
23621 @unnumberedsubsubsec stat/fstat
23622 @cindex fstat, file-i/o system call
23623 @cindex stat, file-i/o system call
23627 int stat(const char *pathname, struct stat *buf);
23628 int fstat(int fd, struct stat *buf);
23631 Fstat,pathnameptr/len,bufptr
23634 @exdent Return value:
23635 On success, zero is returned. On error, -1 is returned.
23642 fd is not a valid open file.
23645 A directory component in pathname does not exist or the
23646 path is an empty string.
23649 A component of the path is not a directory.
23652 pathnameptr is an invalid pointer value.
23655 No access to the file or the path of the file.
23658 pathname was too long.
23661 The call was interrupted by the user.
23665 @unnumberedsubsubsec gettimeofday
23666 @cindex gettimeofday, file-i/o system call
23670 int gettimeofday(struct timeval *tv, void *tz);
23673 Fgettimeofday,tvptr,tzptr
23675 @exdent Return value:
23676 On success, 0 is returned, -1 otherwise.
23683 tz is a non-NULL pointer.
23686 tvptr and/or tzptr is an invalid pointer value.
23690 @unnumberedsubsubsec isatty
23691 @cindex isatty, file-i/o system call
23695 int isatty(int fd);
23700 @exdent Return value:
23701 Returns 1 if fd refers to the @value{GDBN} console, 0 otherwise.
23708 The call was interrupted by the user.
23712 @unnumberedsubsubsec system
23713 @cindex system, file-i/o system call
23717 int system(const char *command);
23720 Fsystem,commandptr/len
23722 @exdent Return value:
23723 The value returned is -1 on error and the return status
23724 of the command otherwise. Only the exit status of the
23725 command is returned, which is extracted from the hosts
23726 system return value by calling WEXITSTATUS(retval).
23727 In case /bin/sh could not be executed, 127 is returned.
23734 The call was interrupted by the user.
23737 @node Protocol specific representation of datatypes
23738 @subsection Protocol specific representation of datatypes
23739 @cindex protocol specific representation of datatypes, in file-i/o protocol
23742 * Integral datatypes::
23748 @node Integral datatypes
23749 @unnumberedsubsubsec Integral datatypes
23750 @cindex integral datatypes, in file-i/o protocol
23752 The integral datatypes used in the system calls are
23755 int@r{,} unsigned int@r{,} long@r{,} unsigned long@r{,} mode_t @r{and} time_t
23758 @code{Int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
23759 implemented as 32 bit values in this protocol.
23761 @code{Long} and @code{unsigned long} are implemented as 64 bit types.
23763 @xref{Limits}, for corresponding MIN and MAX values (similar to those
23764 in @file{limits.h}) to allow range checking on host and target.
23766 @code{time_t} datatypes are defined as seconds since the Epoch.
23768 All integral datatypes transferred as part of a memory read or write of a
23769 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
23772 @node Pointer values
23773 @unnumberedsubsubsec Pointer values
23774 @cindex pointer values, in file-i/o protocol
23776 Pointers to target data are transmitted as they are. An exception
23777 is made for pointers to buffers for which the length isn't
23778 transmitted as part of the function call, namely strings. Strings
23779 are transmitted as a pointer/length pair, both as hex values, e.g.@:
23786 which is a pointer to data of length 18 bytes at position 0x1aaf.
23787 The length is defined as the full string length in bytes, including
23788 the trailing null byte. Example:
23791 ``hello, world'' at address 0x123456
23802 @unnumberedsubsubsec struct stat
23803 @cindex struct stat, in file-i/o protocol
23805 The buffer of type struct stat used by the target and @value{GDBN} is defined
23810 unsigned int st_dev; /* device */
23811 unsigned int st_ino; /* inode */
23812 mode_t st_mode; /* protection */
23813 unsigned int st_nlink; /* number of hard links */
23814 unsigned int st_uid; /* user ID of owner */
23815 unsigned int st_gid; /* group ID of owner */
23816 unsigned int st_rdev; /* device type (if inode device) */
23817 unsigned long st_size; /* total size, in bytes */
23818 unsigned long st_blksize; /* blocksize for filesystem I/O */
23819 unsigned long st_blocks; /* number of blocks allocated */
23820 time_t st_atime; /* time of last access */
23821 time_t st_mtime; /* time of last modification */
23822 time_t st_ctime; /* time of last change */
23826 The integral datatypes are conforming to the definitions given in the
23827 approriate section (see @ref{Integral datatypes}, for details) so this
23828 structure is of size 64 bytes.
23830 The values of several fields have a restricted meaning and/or
23837 st_ino: No valid meaning for the target. Transmitted unchanged.
23839 st_mode: Valid mode bits are described in Appendix C. Any other
23840 bits have currently no meaning for the target.
23842 st_uid: No valid meaning for the target. Transmitted unchanged.
23844 st_gid: No valid meaning for the target. Transmitted unchanged.
23846 st_rdev: No valid meaning for the target. Transmitted unchanged.
23848 st_atime, st_mtime, st_ctime:
23849 These values have a host and file system dependent
23850 accuracy. Especially on Windows hosts the file systems
23851 don't support exact timing values.
23854 The target gets a struct stat of the above representation and is
23855 responsible to coerce it to the target representation before
23858 Note that due to size differences between the host and target
23859 representation of stat members, these members could eventually
23860 get truncated on the target.
23862 @node struct timeval
23863 @unnumberedsubsubsec struct timeval
23864 @cindex struct timeval, in file-i/o protocol
23866 The buffer of type struct timeval used by the target and @value{GDBN}
23867 is defined as follows:
23871 time_t tv_sec; /* second */
23872 long tv_usec; /* microsecond */
23876 The integral datatypes are conforming to the definitions given in the
23877 approriate section (see @ref{Integral datatypes}, for details) so this
23878 structure is of size 8 bytes.
23881 @subsection Constants
23882 @cindex constants, in file-i/o protocol
23884 The following values are used for the constants inside of the
23885 protocol. @value{GDBN} and target are resposible to translate these
23886 values before and after the call as needed.
23897 @unnumberedsubsubsec Open flags
23898 @cindex open flags, in file-i/o protocol
23900 All values are given in hexadecimal representation.
23912 @node mode_t values
23913 @unnumberedsubsubsec mode_t values
23914 @cindex mode_t values, in file-i/o protocol
23916 All values are given in octal representation.
23933 @unnumberedsubsubsec Errno values
23934 @cindex errno values, in file-i/o protocol
23936 All values are given in decimal representation.
23961 EUNKNOWN is used as a fallback error value if a host system returns
23962 any error value not in the list of supported error numbers.
23965 @unnumberedsubsubsec Lseek flags
23966 @cindex lseek flags, in file-i/o protocol
23975 @unnumberedsubsubsec Limits
23976 @cindex limits, in file-i/o protocol
23978 All values are given in decimal representation.
23981 INT_MIN -2147483648
23983 UINT_MAX 4294967295
23984 LONG_MIN -9223372036854775808
23985 LONG_MAX 9223372036854775807
23986 ULONG_MAX 18446744073709551615
23989 @node File-I/O Examples
23990 @subsection File-I/O Examples
23991 @cindex file-i/o examples
23993 Example sequence of a write call, file descriptor 3, buffer is at target
23994 address 0x1234, 6 bytes should be written:
23997 <- @code{Fwrite,3,1234,6}
23998 @emph{request memory read from target}
24001 @emph{return "6 bytes written"}
24005 Example sequence of a read call, file descriptor 3, buffer is at target
24006 address 0x1234, 6 bytes should be read:
24009 <- @code{Fread,3,1234,6}
24010 @emph{request memory write to target}
24011 -> @code{X1234,6:XXXXXX}
24012 @emph{return "6 bytes read"}
24016 Example sequence of a read call, call fails on the host due to invalid
24017 file descriptor (EBADF):
24020 <- @code{Fread,3,1234,6}
24024 Example sequence of a read call, user presses Ctrl-C before syscall on
24028 <- @code{Fread,3,1234,6}
24033 Example sequence of a read call, user presses Ctrl-C after syscall on
24037 <- @code{Fread,3,1234,6}
24038 -> @code{X1234,6:XXXXXX}
24042 @include agentexpr.texi
24056 % I think something like @colophon should be in texinfo. In the
24058 \long\def\colophon{\hbox to0pt{}\vfill
24059 \centerline{The body of this manual is set in}
24060 \centerline{\fontname\tenrm,}
24061 \centerline{with headings in {\bf\fontname\tenbf}}
24062 \centerline{and examples in {\tt\fontname\tentt}.}
24063 \centerline{{\it\fontname\tenit\/},}
24064 \centerline{{\bf\fontname\tenbf}, and}
24065 \centerline{{\sl\fontname\tensl\/}}
24066 \centerline{are used for emphasis.}\vfill}
24068 % Blame: doc@cygnus.com, 1991.