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 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
475 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
477 Jim Blandy added support for preprocessor macros, while working for Red
480 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
481 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
482 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
483 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
484 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
485 with the migration of old architectures to this new framework.
488 @chapter A Sample @value{GDBN} Session
490 You can use this manual at your leisure to read all about @value{GDBN}.
491 However, a handful of commands are enough to get started using the
492 debugger. This chapter illustrates those commands.
495 In this sample session, we emphasize user input like this: @b{input},
496 to make it easier to pick out from the surrounding output.
499 @c FIXME: this example may not be appropriate for some configs, where
500 @c FIXME...primary interest is in remote use.
502 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
503 processor) exhibits the following bug: sometimes, when we change its
504 quote strings from the default, the commands used to capture one macro
505 definition within another stop working. In the following short @code{m4}
506 session, we define a macro @code{foo} which expands to @code{0000}; we
507 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
508 same thing. However, when we change the open quote string to
509 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
510 procedure fails to define a new synonym @code{baz}:
519 @b{define(bar,defn(`foo'))}
523 @b{changequote(<QUOTE>,<UNQUOTE>)}
525 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
528 m4: End of input: 0: fatal error: EOF in string
532 Let us use @value{GDBN} to try to see what is going on.
535 $ @b{@value{GDBP} m4}
536 @c FIXME: this falsifies the exact text played out, to permit smallbook
537 @c FIXME... format to come out better.
538 @value{GDBN} is free software and you are welcome to distribute copies
539 of it under certain conditions; type "show copying" to see
541 There is absolutely no warranty for @value{GDBN}; type "show warranty"
544 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
549 @value{GDBN} reads only enough symbol data to know where to find the
550 rest when needed; as a result, the first prompt comes up very quickly.
551 We now tell @value{GDBN} to use a narrower display width than usual, so
552 that examples fit in this manual.
555 (@value{GDBP}) @b{set width 70}
559 We need to see how the @code{m4} built-in @code{changequote} works.
560 Having looked at the source, we know the relevant subroutine is
561 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
562 @code{break} command.
565 (@value{GDBP}) @b{break m4_changequote}
566 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
570 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
571 control; as long as control does not reach the @code{m4_changequote}
572 subroutine, the program runs as usual:
575 (@value{GDBP}) @b{run}
576 Starting program: /work/Editorial/gdb/gnu/m4/m4
584 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
585 suspends execution of @code{m4}, displaying information about the
586 context where it stops.
589 @b{changequote(<QUOTE>,<UNQUOTE>)}
591 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
593 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
597 Now we use the command @code{n} (@code{next}) to advance execution to
598 the next line of the current function.
602 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
607 @code{set_quotes} looks like a promising subroutine. We can go into it
608 by using the command @code{s} (@code{step}) instead of @code{next}.
609 @code{step} goes to the next line to be executed in @emph{any}
610 subroutine, so it steps into @code{set_quotes}.
614 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
616 530 if (lquote != def_lquote)
620 The display that shows the subroutine where @code{m4} is now
621 suspended (and its arguments) is called a stack frame display. It
622 shows a summary of the stack. We can use the @code{backtrace}
623 command (which can also be spelled @code{bt}), to see where we are
624 in the stack as a whole: the @code{backtrace} command displays a
625 stack frame for each active subroutine.
628 (@value{GDBP}) @b{bt}
629 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
631 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
633 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
634 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
636 #4 0x79dc in expand_input () at macro.c:40
637 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
641 We step through a few more lines to see what happens. The first two
642 times, we can use @samp{s}; the next two times we use @code{n} to avoid
643 falling into the @code{xstrdup} subroutine.
647 0x3b5c 532 if (rquote != def_rquote)
649 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
650 def_lquote : xstrdup(lq);
652 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
655 538 len_lquote = strlen(rquote);
659 The last line displayed looks a little odd; we can examine the variables
660 @code{lquote} and @code{rquote} to see if they are in fact the new left
661 and right quotes we specified. We use the command @code{p}
662 (@code{print}) to see their values.
665 (@value{GDBP}) @b{p lquote}
666 $1 = 0x35d40 "<QUOTE>"
667 (@value{GDBP}) @b{p rquote}
668 $2 = 0x35d50 "<UNQUOTE>"
672 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
673 To look at some context, we can display ten lines of source
674 surrounding the current line with the @code{l} (@code{list}) command.
680 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
682 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
685 538 len_lquote = strlen(rquote);
686 539 len_rquote = strlen(lquote);
693 Let us step past the two lines that set @code{len_lquote} and
694 @code{len_rquote}, and then examine the values of those variables.
698 539 len_rquote = strlen(lquote);
701 (@value{GDBP}) @b{p len_lquote}
703 (@value{GDBP}) @b{p len_rquote}
708 That certainly looks wrong, assuming @code{len_lquote} and
709 @code{len_rquote} are meant to be the lengths of @code{lquote} and
710 @code{rquote} respectively. We can set them to better values using
711 the @code{p} command, since it can print the value of
712 any expression---and that expression can include subroutine calls and
716 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
718 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
723 Is that enough to fix the problem of using the new quotes with the
724 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
725 executing with the @code{c} (@code{continue}) command, and then try the
726 example that caused trouble initially:
732 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
739 Success! The new quotes now work just as well as the default ones. The
740 problem seems to have been just the two typos defining the wrong
741 lengths. We allow @code{m4} exit by giving it an EOF as input:
745 Program exited normally.
749 The message @samp{Program exited normally.} is from @value{GDBN}; it
750 indicates @code{m4} has finished executing. We can end our @value{GDBN}
751 session with the @value{GDBN} @code{quit} command.
754 (@value{GDBP}) @b{quit}
758 @chapter Getting In and Out of @value{GDBN}
760 This chapter discusses how to start @value{GDBN}, and how to get out of it.
764 type @samp{@value{GDBP}} to start @value{GDBN}.
766 type @kbd{quit} or @kbd{C-d} to exit.
770 * Invoking GDB:: How to start @value{GDBN}
771 * Quitting GDB:: How to quit @value{GDBN}
772 * Shell Commands:: How to use shell commands inside @value{GDBN}
773 * Logging output:: How to log @value{GDBN}'s output to a file
777 @section Invoking @value{GDBN}
779 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
780 @value{GDBN} reads commands from the terminal until you tell it to exit.
782 You can also run @code{@value{GDBP}} with a variety of arguments and options,
783 to specify more of your debugging environment at the outset.
785 The command-line options described here are designed
786 to cover a variety of situations; in some environments, some of these
787 options may effectively be unavailable.
789 The most usual way to start @value{GDBN} is with one argument,
790 specifying an executable program:
793 @value{GDBP} @var{program}
797 You can also start with both an executable program and a core file
801 @value{GDBP} @var{program} @var{core}
804 You can, instead, specify a process ID as a second argument, if you want
805 to debug a running process:
808 @value{GDBP} @var{program} 1234
812 would attach @value{GDBN} to process @code{1234} (unless you also have a file
813 named @file{1234}; @value{GDBN} does check for a core file first).
815 Taking advantage of the second command-line argument requires a fairly
816 complete operating system; when you use @value{GDBN} as a remote
817 debugger attached to a bare board, there may not be any notion of
818 ``process'', and there is often no way to get a core dump. @value{GDBN}
819 will warn you if it is unable to attach or to read core dumps.
821 You can optionally have @code{@value{GDBP}} pass any arguments after the
822 executable file to the inferior using @code{--args}. This option stops
825 gdb --args gcc -O2 -c foo.c
827 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
828 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
830 You can run @code{@value{GDBP}} without printing the front material, which describes
831 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
838 You can further control how @value{GDBN} starts up by using command-line
839 options. @value{GDBN} itself can remind you of the options available.
849 to display all available options and briefly describe their use
850 (@samp{@value{GDBP} -h} is a shorter equivalent).
852 All options and command line arguments you give are processed
853 in sequential order. The order makes a difference when the
854 @samp{-x} option is used.
858 * File Options:: Choosing files
859 * Mode Options:: Choosing modes
860 * Startup:: What @value{GDBN} does during startup
864 @subsection Choosing files
866 When @value{GDBN} starts, it reads any arguments other than options as
867 specifying an executable file and core file (or process ID). This is
868 the same as if the arguments were specified by the @samp{-se} and
869 @samp{-c} (or @samp{-p} options respectively. (@value{GDBN} reads the
870 first argument that does not have an associated option flag as
871 equivalent to the @samp{-se} option followed by that argument; and the
872 second argument that does not have an associated option flag, if any, as
873 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
874 If the second argument begins with a decimal digit, @value{GDBN} will
875 first attempt to attach to it as a process, and if that fails, attempt
876 to open it as a corefile. If you have a corefile whose name begins with
877 a digit, you can prevent @value{GDBN} from treating it as a pid by
878 prefixing it with @file{./}, eg. @file{./12345}.
880 If @value{GDBN} has not been configured to included core file support,
881 such as for most embedded targets, then it will complain about a second
882 argument and ignore it.
884 Many options have both long and short forms; both are shown in the
885 following list. @value{GDBN} also recognizes the long forms if you truncate
886 them, so long as enough of the option is present to be unambiguous.
887 (If you prefer, you can flag option arguments with @samp{--} rather
888 than @samp{-}, though we illustrate the more usual convention.)
890 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
891 @c way, both those who look for -foo and --foo in the index, will find
895 @item -symbols @var{file}
897 @cindex @code{--symbols}
899 Read symbol table from file @var{file}.
901 @item -exec @var{file}
903 @cindex @code{--exec}
905 Use file @var{file} as the executable file to execute when appropriate,
906 and for examining pure data in conjunction with a core dump.
910 Read symbol table from file @var{file} and use it as the executable
913 @item -core @var{file}
915 @cindex @code{--core}
917 Use file @var{file} as a core dump to examine.
919 @item -c @var{number}
920 @item -pid @var{number}
921 @itemx -p @var{number}
924 Connect to process ID @var{number}, as with the @code{attach} command.
925 If there is no such process, @value{GDBN} will attempt to open a core
926 file named @var{number}.
928 @item -command @var{file}
930 @cindex @code{--command}
932 Execute @value{GDBN} commands from file @var{file}. @xref{Command
933 Files,, Command files}.
935 @item -directory @var{directory}
936 @itemx -d @var{directory}
937 @cindex @code{--directory}
939 Add @var{directory} to the path to search for source files.
943 @cindex @code{--mapped}
945 @emph{Warning: this option depends on operating system facilities that are not
946 supported on all systems.}@*
947 If memory-mapped files are available on your system through the @code{mmap}
948 system call, you can use this option
949 to have @value{GDBN} write the symbols from your
950 program into a reusable file in the current directory. If the program you are debugging is
951 called @file{/tmp/fred}, the mapped symbol file is @file{/tmp/fred.syms}.
952 Future @value{GDBN} debugging sessions notice the presence of this file,
953 and can quickly map in symbol information from it, rather than reading
954 the symbol table from the executable program.
956 The @file{.syms} file is specific to the host machine where @value{GDBN}
957 is run. It holds an exact image of the internal @value{GDBN} symbol
958 table. It cannot be shared across multiple host platforms.
962 @cindex @code{--readnow}
964 Read each symbol file's entire symbol table immediately, rather than
965 the default, which is to read it incrementally as it is needed.
966 This makes startup slower, but makes future operations faster.
970 You typically combine the @code{-mapped} and @code{-readnow} options in
971 order to build a @file{.syms} file that contains complete symbol
972 information. (@xref{Files,,Commands to specify files}, for information
973 on @file{.syms} files.) A simple @value{GDBN} invocation to do nothing
974 but build a @file{.syms} file for future use is:
977 gdb -batch -nx -mapped -readnow programname
981 @subsection Choosing modes
983 You can run @value{GDBN} in various alternative modes---for example, in
984 batch mode or quiet mode.
991 Do not execute commands found in any initialization files. Normally,
992 @value{GDBN} executes the commands in these files after all the command
993 options and arguments have been processed. @xref{Command Files,,Command
999 @cindex @code{--quiet}
1000 @cindex @code{--silent}
1002 ``Quiet''. Do not print the introductory and copyright messages. These
1003 messages are also suppressed in batch mode.
1006 @cindex @code{--batch}
1007 Run in batch mode. Exit with status @code{0} after processing all the
1008 command files specified with @samp{-x} (and all commands from
1009 initialization files, if not inhibited with @samp{-n}). Exit with
1010 nonzero status if an error occurs in executing the @value{GDBN} commands
1011 in the command files.
1013 Batch mode may be useful for running @value{GDBN} as a filter, for
1014 example to download and run a program on another computer; in order to
1015 make this more useful, the message
1018 Program exited normally.
1022 (which is ordinarily issued whenever a program running under
1023 @value{GDBN} control terminates) is not issued when running in batch
1028 @cindex @code{--nowindows}
1030 ``No windows''. If @value{GDBN} comes with a graphical user interface
1031 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1032 interface. If no GUI is available, this option has no effect.
1036 @cindex @code{--windows}
1038 If @value{GDBN} includes a GUI, then this option requires it to be
1041 @item -cd @var{directory}
1043 Run @value{GDBN} using @var{directory} as its working directory,
1044 instead of the current directory.
1048 @cindex @code{--fullname}
1050 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1051 subprocess. It tells @value{GDBN} to output the full file name and line
1052 number in a standard, recognizable fashion each time a stack frame is
1053 displayed (which includes each time your program stops). This
1054 recognizable format looks like two @samp{\032} characters, followed by
1055 the file name, line number and character position separated by colons,
1056 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1057 @samp{\032} characters as a signal to display the source code for the
1061 @cindex @code{--epoch}
1062 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1063 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1064 routines so as to allow Epoch to display values of expressions in a
1067 @item -annotate @var{level}
1068 @cindex @code{--annotate}
1069 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1070 effect is identical to using @samp{set annotate @var{level}}
1071 (@pxref{Annotations}). The annotation @var{level} controls how much
1072 information @value{GDBN} prints together with its prompt, values of
1073 expressions, source lines, and other types of output. Level 0 is the
1074 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1075 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1076 that control @value{GDBN}, and level 2 has been deprecated.
1078 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
1082 @cindex @code{--args}
1083 Change interpretation of command line so that arguments following the
1084 executable file are passed as command line arguments to the inferior.
1085 This option stops option processing.
1087 @item -baud @var{bps}
1089 @cindex @code{--baud}
1091 Set the line speed (baud rate or bits per second) of any serial
1092 interface used by @value{GDBN} for remote debugging.
1094 @item -l @var{timeout}
1096 Set the timeout (in seconds) of any communication used by @value{GDBN}
1097 for remote debugging.
1099 @item -tty @var{device}
1100 @itemx -t @var{device}
1101 @cindex @code{--tty}
1103 Run using @var{device} for your program's standard input and output.
1104 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1106 @c resolve the situation of these eventually
1108 @cindex @code{--tui}
1109 Activate the @dfn{Text User Interface} when starting. The Text User
1110 Interface manages several text windows on the terminal, showing
1111 source, assembly, registers and @value{GDBN} command outputs
1112 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1113 Text User Interface can be enabled by invoking the program
1114 @samp{gdbtui}. Do not use this option if you run @value{GDBN} from
1115 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1118 @c @cindex @code{--xdb}
1119 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1120 @c For information, see the file @file{xdb_trans.html}, which is usually
1121 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1124 @item -interpreter @var{interp}
1125 @cindex @code{--interpreter}
1126 Use the interpreter @var{interp} for interface with the controlling
1127 program or device. This option is meant to be set by programs which
1128 communicate with @value{GDBN} using it as a back end.
1129 @xref{Interpreters, , Command Interpreters}.
1131 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1132 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1133 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1134 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1135 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1136 @sc{gdb/mi} interfaces are no longer supported.
1139 @cindex @code{--write}
1140 Open the executable and core files for both reading and writing. This
1141 is equivalent to the @samp{set write on} command inside @value{GDBN}
1145 @cindex @code{--statistics}
1146 This option causes @value{GDBN} to print statistics about time and
1147 memory usage after it completes each command and returns to the prompt.
1150 @cindex @code{--version}
1151 This option causes @value{GDBN} to print its version number and
1152 no-warranty blurb, and exit.
1157 @subsection What @value{GDBN} does during startup
1158 @cindex @value{GDBN} startup
1160 Here's the description of what @value{GDBN} does during session startup:
1164 Sets up the command interpreter as specified by the command line
1165 (@pxref{Mode Options, interpreter}).
1169 Reads the @dfn{init file} (if any) in your home directory@footnote{On
1170 DOS/Windows systems, the home directory is the one pointed to by the
1171 @code{HOME} environment variable.} and executes all the commands in
1175 Processes command line options and operands.
1178 Reads and executes the commands from init file (if any) in the current
1179 working directory. This is only done if the current directory is
1180 different from your home directory. Thus, you can have more than one
1181 init file, one generic in your home directory, and another, specific
1182 to the program you are debugging, in the directory where you invoke
1186 Reads command files specified by the @samp{-x} option. @xref{Command
1187 Files}, for more details about @value{GDBN} command files.
1190 Reads the command history recorded in the @dfn{history file}.
1191 @xref{Command History}, for more details about the command history and the
1192 files where @value{GDBN} records it.
1195 Init files use the same syntax as @dfn{command files} (@pxref{Command
1196 Files}) and are processed by @value{GDBN} in the same way. The init
1197 file in your home directory can set options (such as @samp{set
1198 complaints}) that affect subsequent processing of command line options
1199 and operands. Init files are not executed if you use the @samp{-nx}
1200 option (@pxref{Mode Options, ,Choosing modes}).
1202 @cindex init file name
1203 @cindex @file{.gdbinit}
1204 The @value{GDBN} init files are normally called @file{.gdbinit}.
1205 On some configurations of @value{GDBN}, the init file is known by a
1206 different name (these are typically environments where a specialized
1207 form of @value{GDBN} may need to coexist with other forms, hence a
1208 different name for the specialized version's init file). These are the
1209 environments with special init file names:
1212 @cindex @file{gdb.ini}
1214 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1215 the limitations of file names imposed by DOS filesystems. The Windows
1216 ports of @value{GDBN} use the standard name, but if they find a
1217 @file{gdb.ini} file, they warn you about that and suggest to rename
1218 the file to the standard name.
1220 @cindex @file{.vxgdbinit}
1222 VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit}
1224 @cindex @file{.os68gdbinit}
1226 OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit}
1228 @cindex @file{.esgdbinit}
1230 ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit}
1233 CISCO 68k: @file{.cisco-gdbinit}
1238 @section Quitting @value{GDBN}
1239 @cindex exiting @value{GDBN}
1240 @cindex leaving @value{GDBN}
1243 @kindex quit @r{[}@var{expression}@r{]}
1244 @kindex q @r{(@code{quit})}
1245 @item quit @r{[}@var{expression}@r{]}
1247 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1248 @code{q}), or type an end-of-file character (usually @kbd{C-d}). If you
1249 do not supply @var{expression}, @value{GDBN} will terminate normally;
1250 otherwise it will terminate using the result of @var{expression} as the
1255 An interrupt (often @kbd{C-c}) does not exit from @value{GDBN}, but rather
1256 terminates the action of any @value{GDBN} command that is in progress and
1257 returns to @value{GDBN} command level. It is safe to type the interrupt
1258 character at any time because @value{GDBN} does not allow it to take effect
1259 until a time when it is safe.
1261 If you have been using @value{GDBN} to control an attached process or
1262 device, you can release it with the @code{detach} command
1263 (@pxref{Attach, ,Debugging an already-running process}).
1265 @node Shell Commands
1266 @section Shell commands
1268 If you need to execute occasional shell commands during your
1269 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1270 just use the @code{shell} command.
1274 @cindex shell escape
1275 @item shell @var{command string}
1276 Invoke a standard shell to execute @var{command string}.
1277 If it exists, the environment variable @code{SHELL} determines which
1278 shell to run. Otherwise @value{GDBN} uses the default shell
1279 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1282 The utility @code{make} is often needed in development environments.
1283 You do not have to use the @code{shell} command for this purpose in
1288 @cindex calling make
1289 @item make @var{make-args}
1290 Execute the @code{make} program with the specified
1291 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1294 @node Logging output
1295 @section Logging output
1296 @cindex logging @value{GDBN} output
1297 @cindex save @value{GDBN} output to a file
1299 You may want to save the output of @value{GDBN} commands to a file.
1300 There are several commands to control @value{GDBN}'s logging.
1304 @item set logging on
1306 @item set logging off
1308 @cindex logging file name
1309 @item set logging file @var{file}
1310 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1311 @item set logging overwrite [on|off]
1312 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1313 you want @code{set logging on} to overwrite the logfile instead.
1314 @item set logging redirect [on|off]
1315 By default, @value{GDBN} output will go to both the terminal and the logfile.
1316 Set @code{redirect} if you want output to go only to the log file.
1317 @kindex show logging
1319 Show the current values of the logging settings.
1323 @chapter @value{GDBN} Commands
1325 You can abbreviate a @value{GDBN} command to the first few letters of the command
1326 name, if that abbreviation is unambiguous; and you can repeat certain
1327 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1328 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1329 show you the alternatives available, if there is more than one possibility).
1332 * Command Syntax:: How to give commands to @value{GDBN}
1333 * Completion:: Command completion
1334 * Help:: How to ask @value{GDBN} for help
1337 @node Command Syntax
1338 @section Command syntax
1340 A @value{GDBN} command is a single line of input. There is no limit on
1341 how long it can be. It starts with a command name, which is followed by
1342 arguments whose meaning depends on the command name. For example, the
1343 command @code{step} accepts an argument which is the number of times to
1344 step, as in @samp{step 5}. You can also use the @code{step} command
1345 with no arguments. Some commands do not allow any arguments.
1347 @cindex abbreviation
1348 @value{GDBN} command names may always be truncated if that abbreviation is
1349 unambiguous. Other possible command abbreviations are listed in the
1350 documentation for individual commands. In some cases, even ambiguous
1351 abbreviations are allowed; for example, @code{s} is specially defined as
1352 equivalent to @code{step} even though there are other commands whose
1353 names start with @code{s}. You can test abbreviations by using them as
1354 arguments to the @code{help} command.
1356 @cindex repeating commands
1357 @kindex RET @r{(repeat last command)}
1358 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1359 repeat the previous command. Certain commands (for example, @code{run})
1360 will not repeat this way; these are commands whose unintentional
1361 repetition might cause trouble and which you are unlikely to want to
1362 repeat. User-defined commands can disable this feature; see
1363 @ref{Define, dont-repeat}.
1365 The @code{list} and @code{x} commands, when you repeat them with
1366 @key{RET}, construct new arguments rather than repeating
1367 exactly as typed. This permits easy scanning of source or memory.
1369 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1370 output, in a way similar to the common utility @code{more}
1371 (@pxref{Screen Size,,Screen size}). Since it is easy to press one
1372 @key{RET} too many in this situation, @value{GDBN} disables command
1373 repetition after any command that generates this sort of display.
1375 @kindex # @r{(a comment)}
1377 Any text from a @kbd{#} to the end of the line is a comment; it does
1378 nothing. This is useful mainly in command files (@pxref{Command
1379 Files,,Command files}).
1381 @cindex repeating command sequences
1382 @kindex C-o @r{(operate-and-get-next)}
1383 The @kbd{C-o} binding is useful for repeating a complex sequence of
1384 commands. This command accepts the current line, like @kbd{RET}, and
1385 then fetches the next line relative to the current line from the history
1389 @section Command completion
1392 @cindex word completion
1393 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1394 only one possibility; it can also show you what the valid possibilities
1395 are for the next word in a command, at any time. This works for @value{GDBN}
1396 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1398 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1399 of a word. If there is only one possibility, @value{GDBN} fills in the
1400 word, and waits for you to finish the command (or press @key{RET} to
1401 enter it). For example, if you type
1403 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1404 @c complete accuracy in these examples; space introduced for clarity.
1405 @c If texinfo enhancements make it unnecessary, it would be nice to
1406 @c replace " @key" by "@key" in the following...
1408 (@value{GDBP}) info bre @key{TAB}
1412 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1413 the only @code{info} subcommand beginning with @samp{bre}:
1416 (@value{GDBP}) info breakpoints
1420 You can either press @key{RET} at this point, to run the @code{info
1421 breakpoints} command, or backspace and enter something else, if
1422 @samp{breakpoints} does not look like the command you expected. (If you
1423 were sure you wanted @code{info breakpoints} in the first place, you
1424 might as well just type @key{RET} immediately after @samp{info bre},
1425 to exploit command abbreviations rather than command completion).
1427 If there is more than one possibility for the next word when you press
1428 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1429 characters and try again, or just press @key{TAB} a second time;
1430 @value{GDBN} displays all the possible completions for that word. For
1431 example, you might want to set a breakpoint on a subroutine whose name
1432 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1433 just sounds the bell. Typing @key{TAB} again displays all the
1434 function names in your program that begin with those characters, for
1438 (@value{GDBP}) b make_ @key{TAB}
1439 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1440 make_a_section_from_file make_environ
1441 make_abs_section make_function_type
1442 make_blockvector make_pointer_type
1443 make_cleanup make_reference_type
1444 make_command make_symbol_completion_list
1445 (@value{GDBP}) b make_
1449 After displaying the available possibilities, @value{GDBN} copies your
1450 partial input (@samp{b make_} in the example) so you can finish the
1453 If you just want to see the list of alternatives in the first place, you
1454 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1455 means @kbd{@key{META} ?}. You can type this either by holding down a
1456 key designated as the @key{META} shift on your keyboard (if there is
1457 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1459 @cindex quotes in commands
1460 @cindex completion of quoted strings
1461 Sometimes the string you need, while logically a ``word'', may contain
1462 parentheses or other characters that @value{GDBN} normally excludes from
1463 its notion of a word. To permit word completion to work in this
1464 situation, you may enclose words in @code{'} (single quote marks) in
1465 @value{GDBN} commands.
1467 The most likely situation where you might need this is in typing the
1468 name of a C@t{++} function. This is because C@t{++} allows function
1469 overloading (multiple definitions of the same function, distinguished
1470 by argument type). For example, when you want to set a breakpoint you
1471 may need to distinguish whether you mean the version of @code{name}
1472 that takes an @code{int} parameter, @code{name(int)}, or the version
1473 that takes a @code{float} parameter, @code{name(float)}. To use the
1474 word-completion facilities in this situation, type a single quote
1475 @code{'} at the beginning of the function name. This alerts
1476 @value{GDBN} that it may need to consider more information than usual
1477 when you press @key{TAB} or @kbd{M-?} to request word completion:
1480 (@value{GDBP}) b 'bubble( @kbd{M-?}
1481 bubble(double,double) bubble(int,int)
1482 (@value{GDBP}) b 'bubble(
1485 In some cases, @value{GDBN} can tell that completing a name requires using
1486 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1487 completing as much as it can) if you do not type the quote in the first
1491 (@value{GDBP}) b bub @key{TAB}
1492 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1493 (@value{GDBP}) b 'bubble(
1497 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1498 you have not yet started typing the argument list when you ask for
1499 completion on an overloaded symbol.
1501 For more information about overloaded functions, see @ref{C plus plus
1502 expressions, ,C@t{++} expressions}. You can use the command @code{set
1503 overload-resolution off} to disable overload resolution;
1504 see @ref{Debugging C plus plus, ,@value{GDBN} features for C@t{++}}.
1508 @section Getting help
1509 @cindex online documentation
1512 You can always ask @value{GDBN} itself for information on its commands,
1513 using the command @code{help}.
1516 @kindex h @r{(@code{help})}
1519 You can use @code{help} (abbreviated @code{h}) with no arguments to
1520 display a short list of named classes of commands:
1524 List of classes of commands:
1526 aliases -- Aliases of other commands
1527 breakpoints -- Making program stop at certain points
1528 data -- Examining data
1529 files -- Specifying and examining files
1530 internals -- Maintenance commands
1531 obscure -- Obscure features
1532 running -- Running the program
1533 stack -- Examining the stack
1534 status -- Status inquiries
1535 support -- Support facilities
1536 tracepoints -- Tracing of program execution without@*
1537 stopping the program
1538 user-defined -- User-defined commands
1540 Type "help" followed by a class name for a list of
1541 commands in that class.
1542 Type "help" followed by command name for full
1544 Command name abbreviations are allowed if unambiguous.
1547 @c the above line break eliminates huge line overfull...
1549 @item help @var{class}
1550 Using one of the general help classes as an argument, you can get a
1551 list of the individual commands in that class. For example, here is the
1552 help display for the class @code{status}:
1555 (@value{GDBP}) help status
1560 @c Line break in "show" line falsifies real output, but needed
1561 @c to fit in smallbook page size.
1562 info -- Generic command for showing things
1563 about the program being debugged
1564 show -- Generic command for showing things
1567 Type "help" followed by command name for full
1569 Command name abbreviations are allowed if unambiguous.
1573 @item help @var{command}
1574 With a command name as @code{help} argument, @value{GDBN} displays a
1575 short paragraph on how to use that command.
1578 @item apropos @var{args}
1579 The @code{apropos} command searches through all of the @value{GDBN}
1580 commands, and their documentation, for the regular expression specified in
1581 @var{args}. It prints out all matches found. For example:
1592 set symbol-reloading -- Set dynamic symbol table reloading
1593 multiple times in one run
1594 show symbol-reloading -- Show dynamic symbol table reloading
1595 multiple times in one run
1600 @item complete @var{args}
1601 The @code{complete @var{args}} command lists all the possible completions
1602 for the beginning of a command. Use @var{args} to specify the beginning of the
1603 command you want completed. For example:
1609 @noindent results in:
1620 @noindent This is intended for use by @sc{gnu} Emacs.
1623 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1624 and @code{show} to inquire about the state of your program, or the state
1625 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1626 manual introduces each of them in the appropriate context. The listings
1627 under @code{info} and under @code{show} in the Index point to
1628 all the sub-commands. @xref{Index}.
1633 @kindex i @r{(@code{info})}
1635 This command (abbreviated @code{i}) is for describing the state of your
1636 program. For example, you can list the arguments given to your program
1637 with @code{info args}, list the registers currently in use with @code{info
1638 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1639 You can get a complete list of the @code{info} sub-commands with
1640 @w{@code{help info}}.
1644 You can assign the result of an expression to an environment variable with
1645 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1646 @code{set prompt $}.
1650 In contrast to @code{info}, @code{show} is for describing the state of
1651 @value{GDBN} itself.
1652 You can change most of the things you can @code{show}, by using the
1653 related command @code{set}; for example, you can control what number
1654 system is used for displays with @code{set radix}, or simply inquire
1655 which is currently in use with @code{show radix}.
1658 To display all the settable parameters and their current
1659 values, you can use @code{show} with no arguments; you may also use
1660 @code{info set}. Both commands produce the same display.
1661 @c FIXME: "info set" violates the rule that "info" is for state of
1662 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1663 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1667 Here are three miscellaneous @code{show} subcommands, all of which are
1668 exceptional in lacking corresponding @code{set} commands:
1671 @kindex show version
1672 @cindex @value{GDBN} version number
1674 Show what version of @value{GDBN} is running. You should include this
1675 information in @value{GDBN} bug-reports. If multiple versions of
1676 @value{GDBN} are in use at your site, you may need to determine which
1677 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1678 commands are introduced, and old ones may wither away. Also, many
1679 system vendors ship variant versions of @value{GDBN}, and there are
1680 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1681 The version number is the same as the one announced when you start
1684 @kindex show copying
1685 @kindex info copying
1686 @cindex display @value{GDBN} copyright
1689 Display information about permission for copying @value{GDBN}.
1691 @kindex show warranty
1692 @kindex info warranty
1694 @itemx info warranty
1695 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1696 if your version of @value{GDBN} comes with one.
1701 @chapter Running Programs Under @value{GDBN}
1703 When you run a program under @value{GDBN}, you must first generate
1704 debugging information when you compile it.
1706 You may start @value{GDBN} with its arguments, if any, in an environment
1707 of your choice. If you are doing native debugging, you may redirect
1708 your program's input and output, debug an already running process, or
1709 kill a child process.
1712 * Compilation:: Compiling for debugging
1713 * Starting:: Starting your program
1714 * Arguments:: Your program's arguments
1715 * Environment:: Your program's environment
1717 * Working Directory:: Your program's working directory
1718 * Input/Output:: Your program's input and output
1719 * Attach:: Debugging an already-running process
1720 * Kill Process:: Killing the child process
1722 * Threads:: Debugging programs with multiple threads
1723 * Processes:: Debugging programs with multiple processes
1727 @section Compiling for debugging
1729 In order to debug a program effectively, you need to generate
1730 debugging information when you compile it. This debugging information
1731 is stored in the object file; it describes the data type of each
1732 variable or function and the correspondence between source line numbers
1733 and addresses in the executable code.
1735 To request debugging information, specify the @samp{-g} option when you run
1738 Programs that are to be shipped to your customers are compiled with
1739 optimizations, using the @samp{-O} compiler option. However, many
1740 compilers are unable to handle the @samp{-g} and @samp{-O} options
1741 together. Using those compilers, you cannot generate optimized
1742 executables containing debugging information.
1744 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1745 without @samp{-O}, making it possible to debug optimized code. We
1746 recommend that you @emph{always} use @samp{-g} whenever you compile a
1747 program. You may think your program is correct, but there is no sense
1748 in pushing your luck.
1750 @cindex optimized code, debugging
1751 @cindex debugging optimized code
1752 When you debug a program compiled with @samp{-g -O}, remember that the
1753 optimizer is rearranging your code; the debugger shows you what is
1754 really there. Do not be too surprised when the execution path does not
1755 exactly match your source file! An extreme example: if you define a
1756 variable, but never use it, @value{GDBN} never sees that
1757 variable---because the compiler optimizes it out of existence.
1759 Some things do not work as well with @samp{-g -O} as with just
1760 @samp{-g}, particularly on machines with instruction scheduling. If in
1761 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1762 please report it to us as a bug (including a test case!).
1763 @xref{Variables}, for more information about debugging optimized code.
1765 Older versions of the @sc{gnu} C compiler permitted a variant option
1766 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1767 format; if your @sc{gnu} C compiler has this option, do not use it.
1769 @value{GDBN} knows about preprocessor macros and can show you their
1770 expansion (@pxref{Macros}). Most compilers do not include information
1771 about preprocessor macros in the debugging information if you specify
1772 the @option{-g} flag alone, because this information is rather large.
1773 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1774 provides macro information if you specify the options
1775 @option{-gdwarf-2} and @option{-g3}; the former option requests
1776 debugging information in the Dwarf 2 format, and the latter requests
1777 ``extra information''. In the future, we hope to find more compact
1778 ways to represent macro information, so that it can be included with
1783 @section Starting your program
1789 @kindex r @r{(@code{run})}
1792 Use the @code{run} command to start your program under @value{GDBN}.
1793 You must first specify the program name (except on VxWorks) with an
1794 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1795 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1796 (@pxref{Files, ,Commands to specify files}).
1800 If you are running your program in an execution environment that
1801 supports processes, @code{run} creates an inferior process and makes
1802 that process run your program. (In environments without processes,
1803 @code{run} jumps to the start of your program.)
1805 The execution of a program is affected by certain information it
1806 receives from its superior. @value{GDBN} provides ways to specify this
1807 information, which you must do @emph{before} starting your program. (You
1808 can change it after starting your program, but such changes only affect
1809 your program the next time you start it.) This information may be
1810 divided into four categories:
1813 @item The @emph{arguments.}
1814 Specify the arguments to give your program as the arguments of the
1815 @code{run} command. If a shell is available on your target, the shell
1816 is used to pass the arguments, so that you may use normal conventions
1817 (such as wildcard expansion or variable substitution) in describing
1819 In Unix systems, you can control which shell is used with the
1820 @code{SHELL} environment variable.
1821 @xref{Arguments, ,Your program's arguments}.
1823 @item The @emph{environment.}
1824 Your program normally inherits its environment from @value{GDBN}, but you can
1825 use the @value{GDBN} commands @code{set environment} and @code{unset
1826 environment} to change parts of the environment that affect
1827 your program. @xref{Environment, ,Your program's environment}.
1829 @item The @emph{working directory.}
1830 Your program inherits its working directory from @value{GDBN}. You can set
1831 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1832 @xref{Working Directory, ,Your program's working directory}.
1834 @item The @emph{standard input and output.}
1835 Your program normally uses the same device for standard input and
1836 standard output as @value{GDBN} is using. You can redirect input and output
1837 in the @code{run} command line, or you can use the @code{tty} command to
1838 set a different device for your program.
1839 @xref{Input/Output, ,Your program's input and output}.
1842 @emph{Warning:} While input and output redirection work, you cannot use
1843 pipes to pass the output of the program you are debugging to another
1844 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1848 When you issue the @code{run} command, your program begins to execute
1849 immediately. @xref{Stopping, ,Stopping and continuing}, for discussion
1850 of how to arrange for your program to stop. Once your program has
1851 stopped, you may call functions in your program, using the @code{print}
1852 or @code{call} commands. @xref{Data, ,Examining Data}.
1854 If the modification time of your symbol file has changed since the last
1855 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1856 table, and reads it again. When it does this, @value{GDBN} tries to retain
1857 your current breakpoints.
1862 @cindex run to main procedure
1863 The name of the main procedure can vary from language to language.
1864 With C or C@t{++}, the main procedure name is always @code{main}, but
1865 other languages such as Ada do not require a specific name for their
1866 main procedure. The debugger provides a convenient way to start the
1867 execution of the program and to stop at the beginning of the main
1868 procedure, depending on the language used.
1870 The @samp{start} command does the equivalent of setting a temporary
1871 breakpoint at the beginning of the main procedure and then invoking
1872 the @samp{run} command.
1874 @cindex elaboration phase
1875 Some programs contain an @dfn{elaboration} phase where some startup code is
1876 executed before the main procedure is called. This depends on the
1877 languages used to write your program. In C@t{++}, for instance,
1878 constructors for static and global objects are executed before
1879 @code{main} is called. It is therefore possible that the debugger stops
1880 before reaching the main procedure. However, the temporary breakpoint
1881 will remain to halt execution.
1883 Specify the arguments to give to your program as arguments to the
1884 @samp{start} command. These arguments will be given verbatim to the
1885 underlying @samp{run} command. Note that the same arguments will be
1886 reused if no argument is provided during subsequent calls to
1887 @samp{start} or @samp{run}.
1889 It is sometimes necessary to debug the program during elaboration. In
1890 these cases, using the @code{start} command would stop the execution of
1891 your program too late, as the program would have already completed the
1892 elaboration phase. Under these circumstances, insert breakpoints in your
1893 elaboration code before running your program.
1897 @section Your program's arguments
1899 @cindex arguments (to your program)
1900 The arguments to your program can be specified by the arguments of the
1902 They are passed to a shell, which expands wildcard characters and
1903 performs redirection of I/O, and thence to your program. Your
1904 @code{SHELL} environment variable (if it exists) specifies what shell
1905 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1906 the default shell (@file{/bin/sh} on Unix).
1908 On non-Unix systems, the program is usually invoked directly by
1909 @value{GDBN}, which emulates I/O redirection via the appropriate system
1910 calls, and the wildcard characters are expanded by the startup code of
1911 the program, not by the shell.
1913 @code{run} with no arguments uses the same arguments used by the previous
1914 @code{run}, or those set by the @code{set args} command.
1919 Specify the arguments to be used the next time your program is run. If
1920 @code{set args} has no arguments, @code{run} executes your program
1921 with no arguments. Once you have run your program with arguments,
1922 using @code{set args} before the next @code{run} is the only way to run
1923 it again without arguments.
1927 Show the arguments to give your program when it is started.
1931 @section Your program's environment
1933 @cindex environment (of your program)
1934 The @dfn{environment} consists of a set of environment variables and
1935 their values. Environment variables conventionally record such things as
1936 your user name, your home directory, your terminal type, and your search
1937 path for programs to run. Usually you set up environment variables with
1938 the shell and they are inherited by all the other programs you run. When
1939 debugging, it can be useful to try running your program with a modified
1940 environment without having to start @value{GDBN} over again.
1944 @item path @var{directory}
1945 Add @var{directory} to the front of the @code{PATH} environment variable
1946 (the search path for executables) that will be passed to your program.
1947 The value of @code{PATH} used by @value{GDBN} does not change.
1948 You may specify several directory names, separated by whitespace or by a
1949 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1950 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1951 is moved to the front, so it is searched sooner.
1953 You can use the string @samp{$cwd} to refer to whatever is the current
1954 working directory at the time @value{GDBN} searches the path. If you
1955 use @samp{.} instead, it refers to the directory where you executed the
1956 @code{path} command. @value{GDBN} replaces @samp{.} in the
1957 @var{directory} argument (with the current path) before adding
1958 @var{directory} to the search path.
1959 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1960 @c document that, since repeating it would be a no-op.
1964 Display the list of search paths for executables (the @code{PATH}
1965 environment variable).
1967 @kindex show environment
1968 @item show environment @r{[}@var{varname}@r{]}
1969 Print the value of environment variable @var{varname} to be given to
1970 your program when it starts. If you do not supply @var{varname},
1971 print the names and values of all environment variables to be given to
1972 your program. You can abbreviate @code{environment} as @code{env}.
1974 @kindex set environment
1975 @item set environment @var{varname} @r{[}=@var{value}@r{]}
1976 Set environment variable @var{varname} to @var{value}. The value
1977 changes for your program only, not for @value{GDBN} itself. @var{value} may
1978 be any string; the values of environment variables are just strings, and
1979 any interpretation is supplied by your program itself. The @var{value}
1980 parameter is optional; if it is eliminated, the variable is set to a
1982 @c "any string" here does not include leading, trailing
1983 @c blanks. Gnu asks: does anyone care?
1985 For example, this command:
1992 tells the debugged program, when subsequently run, that its user is named
1993 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
1994 are not actually required.)
1996 @kindex unset environment
1997 @item unset environment @var{varname}
1998 Remove variable @var{varname} from the environment to be passed to your
1999 program. This is different from @samp{set env @var{varname} =};
2000 @code{unset environment} removes the variable from the environment,
2001 rather than assigning it an empty value.
2004 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2006 by your @code{SHELL} environment variable if it exists (or
2007 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2008 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2009 @file{.bashrc} for BASH---any variables you set in that file affect
2010 your program. You may wish to move setting of environment variables to
2011 files that are only run when you sign on, such as @file{.login} or
2014 @node Working Directory
2015 @section Your program's working directory
2017 @cindex working directory (of your program)
2018 Each time you start your program with @code{run}, it inherits its
2019 working directory from the current working directory of @value{GDBN}.
2020 The @value{GDBN} working directory is initially whatever it inherited
2021 from its parent process (typically the shell), but you can specify a new
2022 working directory in @value{GDBN} with the @code{cd} command.
2024 The @value{GDBN} working directory also serves as a default for the commands
2025 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2030 @cindex change working directory
2031 @item cd @var{directory}
2032 Set the @value{GDBN} working directory to @var{directory}.
2036 Print the @value{GDBN} working directory.
2039 It is generally impossible to find the current working directory of
2040 the process being debugged (since a program can change its directory
2041 during its run). If you work on a system where @value{GDBN} is
2042 configured with the @file{/proc} support, you can use the @code{info
2043 proc} command (@pxref{SVR4 Process Information}) to find out the
2044 current working directory of the debuggee.
2047 @section Your program's input and output
2052 By default, the program you run under @value{GDBN} does input and output to
2053 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2054 to its own terminal modes to interact with you, but it records the terminal
2055 modes your program was using and switches back to them when you continue
2056 running your program.
2059 @kindex info terminal
2061 Displays information recorded by @value{GDBN} about the terminal modes your
2065 You can redirect your program's input and/or output using shell
2066 redirection with the @code{run} command. For example,
2073 starts your program, diverting its output to the file @file{outfile}.
2076 @cindex controlling terminal
2077 Another way to specify where your program should do input and output is
2078 with the @code{tty} command. This command accepts a file name as
2079 argument, and causes this file to be the default for future @code{run}
2080 commands. It also resets the controlling terminal for the child
2081 process, for future @code{run} commands. For example,
2088 directs that processes started with subsequent @code{run} commands
2089 default to do input and output on the terminal @file{/dev/ttyb} and have
2090 that as their controlling terminal.
2092 An explicit redirection in @code{run} overrides the @code{tty} command's
2093 effect on the input/output device, but not its effect on the controlling
2096 When you use the @code{tty} command or redirect input in the @code{run}
2097 command, only the input @emph{for your program} is affected. The input
2098 for @value{GDBN} still comes from your terminal.
2101 @section Debugging an already-running process
2106 @item attach @var{process-id}
2107 This command attaches to a running process---one that was started
2108 outside @value{GDBN}. (@code{info files} shows your active
2109 targets.) The command takes as argument a process ID. The usual way to
2110 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2111 or with the @samp{jobs -l} shell command.
2113 @code{attach} does not repeat if you press @key{RET} a second time after
2114 executing the command.
2117 To use @code{attach}, your program must be running in an environment
2118 which supports processes; for example, @code{attach} does not work for
2119 programs on bare-board targets that lack an operating system. You must
2120 also have permission to send the process a signal.
2122 When you use @code{attach}, the debugger finds the program running in
2123 the process first by looking in the current working directory, then (if
2124 the program is not found) by using the source file search path
2125 (@pxref{Source Path, ,Specifying source directories}). You can also use
2126 the @code{file} command to load the program. @xref{Files, ,Commands to
2129 The first thing @value{GDBN} does after arranging to debug the specified
2130 process is to stop it. You can examine and modify an attached process
2131 with all the @value{GDBN} commands that are ordinarily available when
2132 you start processes with @code{run}. You can insert breakpoints; you
2133 can step and continue; you can modify storage. If you would rather the
2134 process continue running, you may use the @code{continue} command after
2135 attaching @value{GDBN} to the process.
2140 When you have finished debugging the attached process, you can use the
2141 @code{detach} command to release it from @value{GDBN} control. Detaching
2142 the process continues its execution. After the @code{detach} command,
2143 that process and @value{GDBN} become completely independent once more, and you
2144 are ready to @code{attach} another process or start one with @code{run}.
2145 @code{detach} does not repeat if you press @key{RET} again after
2146 executing the command.
2149 If you exit @value{GDBN} or use the @code{run} command while you have an
2150 attached process, you kill that process. By default, @value{GDBN} asks
2151 for confirmation if you try to do either of these things; you can
2152 control whether or not you need to confirm by using the @code{set
2153 confirm} command (@pxref{Messages/Warnings, ,Optional warnings and
2157 @section Killing the child process
2162 Kill the child process in which your program is running under @value{GDBN}.
2165 This command is useful if you wish to debug a core dump instead of a
2166 running process. @value{GDBN} ignores any core dump file while your program
2169 On some operating systems, a program cannot be executed outside @value{GDBN}
2170 while you have breakpoints set on it inside @value{GDBN}. You can use the
2171 @code{kill} command in this situation to permit running your program
2172 outside the debugger.
2174 The @code{kill} command is also useful if you wish to recompile and
2175 relink your program, since on many systems it is impossible to modify an
2176 executable file while it is running in a process. In this case, when you
2177 next type @code{run}, @value{GDBN} notices that the file has changed, and
2178 reads the symbol table again (while trying to preserve your current
2179 breakpoint settings).
2182 @section Debugging programs with multiple threads
2184 @cindex threads of execution
2185 @cindex multiple threads
2186 @cindex switching threads
2187 In some operating systems, such as HP-UX and Solaris, a single program
2188 may have more than one @dfn{thread} of execution. The precise semantics
2189 of threads differ from one operating system to another, but in general
2190 the threads of a single program are akin to multiple processes---except
2191 that they share one address space (that is, they can all examine and
2192 modify the same variables). On the other hand, each thread has its own
2193 registers and execution stack, and perhaps private memory.
2195 @value{GDBN} provides these facilities for debugging multi-thread
2199 @item automatic notification of new threads
2200 @item @samp{thread @var{threadno}}, a command to switch among threads
2201 @item @samp{info threads}, a command to inquire about existing threads
2202 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2203 a command to apply a command to a list of threads
2204 @item thread-specific breakpoints
2208 @emph{Warning:} These facilities are not yet available on every
2209 @value{GDBN} configuration where the operating system supports threads.
2210 If your @value{GDBN} does not support threads, these commands have no
2211 effect. For example, a system without thread support shows no output
2212 from @samp{info threads}, and always rejects the @code{thread} command,
2216 (@value{GDBP}) info threads
2217 (@value{GDBP}) thread 1
2218 Thread ID 1 not known. Use the "info threads" command to
2219 see the IDs of currently known threads.
2221 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2222 @c doesn't support threads"?
2225 @cindex focus of debugging
2226 @cindex current thread
2227 The @value{GDBN} thread debugging facility allows you to observe all
2228 threads while your program runs---but whenever @value{GDBN} takes
2229 control, one thread in particular is always the focus of debugging.
2230 This thread is called the @dfn{current thread}. Debugging commands show
2231 program information from the perspective of the current thread.
2233 @cindex @code{New} @var{systag} message
2234 @cindex thread identifier (system)
2235 @c FIXME-implementors!! It would be more helpful if the [New...] message
2236 @c included GDB's numeric thread handle, so you could just go to that
2237 @c thread without first checking `info threads'.
2238 Whenever @value{GDBN} detects a new thread in your program, it displays
2239 the target system's identification for the thread with a message in the
2240 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2241 whose form varies depending on the particular system. For example, on
2242 LynxOS, you might see
2245 [New process 35 thread 27]
2249 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2250 the @var{systag} is simply something like @samp{process 368}, with no
2253 @c FIXME!! (1) Does the [New...] message appear even for the very first
2254 @c thread of a program, or does it only appear for the
2255 @c second---i.e.@: when it becomes obvious we have a multithread
2257 @c (2) *Is* there necessarily a first thread always? Or do some
2258 @c multithread systems permit starting a program with multiple
2259 @c threads ab initio?
2261 @cindex thread number
2262 @cindex thread identifier (GDB)
2263 For debugging purposes, @value{GDBN} associates its own thread
2264 number---always a single integer---with each thread in your program.
2267 @kindex info threads
2269 Display a summary of all threads currently in your
2270 program. @value{GDBN} displays for each thread (in this order):
2274 the thread number assigned by @value{GDBN}
2277 the target system's thread identifier (@var{systag})
2280 the current stack frame summary for that thread
2284 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2285 indicates the current thread.
2289 @c end table here to get a little more width for example
2292 (@value{GDBP}) info threads
2293 3 process 35 thread 27 0x34e5 in sigpause ()
2294 2 process 35 thread 23 0x34e5 in sigpause ()
2295 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2301 @cindex debugging multithreaded programs (on HP-UX)
2302 @cindex thread identifier (GDB), on HP-UX
2303 For debugging purposes, @value{GDBN} associates its own thread
2304 number---a small integer assigned in thread-creation order---with each
2305 thread in your program.
2307 @cindex @code{New} @var{systag} message, on HP-UX
2308 @cindex thread identifier (system), on HP-UX
2309 @c FIXME-implementors!! It would be more helpful if the [New...] message
2310 @c included GDB's numeric thread handle, so you could just go to that
2311 @c thread without first checking `info threads'.
2312 Whenever @value{GDBN} detects a new thread in your program, it displays
2313 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2314 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2315 whose form varies depending on the particular system. For example, on
2319 [New thread 2 (system thread 26594)]
2323 when @value{GDBN} notices a new thread.
2326 @kindex info threads (HP-UX)
2328 Display a summary of all threads currently in your
2329 program. @value{GDBN} displays for each thread (in this order):
2332 @item the thread number assigned by @value{GDBN}
2334 @item the target system's thread identifier (@var{systag})
2336 @item the current stack frame summary for that thread
2340 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2341 indicates the current thread.
2345 @c end table here to get a little more width for example
2348 (@value{GDBP}) info threads
2349 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2351 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2352 from /usr/lib/libc.2
2353 1 system thread 27905 0x7b003498 in _brk () \@*
2354 from /usr/lib/libc.2
2357 On Solaris, you can display more information about user threads with a
2358 Solaris-specific command:
2361 @item maint info sol-threads
2362 @kindex maint info sol-threads
2363 @cindex thread info (Solaris)
2364 Display info on Solaris user threads.
2368 @kindex thread @var{threadno}
2369 @item thread @var{threadno}
2370 Make thread number @var{threadno} the current thread. The command
2371 argument @var{threadno} is the internal @value{GDBN} thread number, as
2372 shown in the first field of the @samp{info threads} display.
2373 @value{GDBN} responds by displaying the system identifier of the thread
2374 you selected, and its current stack frame summary:
2377 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2378 (@value{GDBP}) thread 2
2379 [Switching to process 35 thread 23]
2380 0x34e5 in sigpause ()
2384 As with the @samp{[New @dots{}]} message, the form of the text after
2385 @samp{Switching to} depends on your system's conventions for identifying
2388 @kindex thread apply
2389 @cindex apply command to several threads
2390 @item thread apply [@var{threadno}] [@var{all}] @var{args}
2391 The @code{thread apply} command allows you to apply a command to one or
2392 more threads. Specify the numbers of the threads that you want affected
2393 with the command argument @var{threadno}. @var{threadno} is the internal
2394 @value{GDBN} thread number, as shown in the first field of the @samp{info
2395 threads} display. To apply a command to all threads, use
2396 @code{thread apply all} @var{args}.
2399 @cindex automatic thread selection
2400 @cindex switching threads automatically
2401 @cindex threads, automatic switching
2402 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2403 signal, it automatically selects the thread where that breakpoint or
2404 signal happened. @value{GDBN} alerts you to the context switch with a
2405 message of the form @samp{[Switching to @var{systag}]} to identify the
2408 @xref{Thread Stops,,Stopping and starting multi-thread programs}, for
2409 more information about how @value{GDBN} behaves when you stop and start
2410 programs with multiple threads.
2412 @xref{Set Watchpoints,,Setting watchpoints}, for information about
2413 watchpoints in programs with multiple threads.
2416 @section Debugging programs with multiple processes
2418 @cindex fork, debugging programs which call
2419 @cindex multiple processes
2420 @cindex processes, multiple
2421 On most systems, @value{GDBN} has no special support for debugging
2422 programs which create additional processes using the @code{fork}
2423 function. When a program forks, @value{GDBN} will continue to debug the
2424 parent process and the child process will run unimpeded. If you have
2425 set a breakpoint in any code which the child then executes, the child
2426 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2427 will cause it to terminate.
2429 However, if you want to debug the child process there is a workaround
2430 which isn't too painful. Put a call to @code{sleep} in the code which
2431 the child process executes after the fork. It may be useful to sleep
2432 only if a certain environment variable is set, or a certain file exists,
2433 so that the delay need not occur when you don't want to run @value{GDBN}
2434 on the child. While the child is sleeping, use the @code{ps} program to
2435 get its process ID. Then tell @value{GDBN} (a new invocation of
2436 @value{GDBN} if you are also debugging the parent process) to attach to
2437 the child process (@pxref{Attach}). From that point on you can debug
2438 the child process just like any other process which you attached to.
2440 On some systems, @value{GDBN} provides support for debugging programs that
2441 create additional processes using the @code{fork} or @code{vfork} functions.
2442 Currently, the only platforms with this feature are HP-UX (11.x and later
2443 only?) and GNU/Linux (kernel version 2.5.60 and later).
2445 By default, when a program forks, @value{GDBN} will continue to debug
2446 the parent process and the child process will run unimpeded.
2448 If you want to follow the child process instead of the parent process,
2449 use the command @w{@code{set follow-fork-mode}}.
2452 @kindex set follow-fork-mode
2453 @item set follow-fork-mode @var{mode}
2454 Set the debugger response to a program call of @code{fork} or
2455 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2456 process. The @var{mode} argument can be:
2460 The original process is debugged after a fork. The child process runs
2461 unimpeded. This is the default.
2464 The new process is debugged after a fork. The parent process runs
2469 @kindex show follow-fork-mode
2470 @item show follow-fork-mode
2471 Display the current debugger response to a @code{fork} or @code{vfork} call.
2474 If you ask to debug a child process and a @code{vfork} is followed by an
2475 @code{exec}, @value{GDBN} executes the new target up to the first
2476 breakpoint in the new target. If you have a breakpoint set on
2477 @code{main} in your original program, the breakpoint will also be set on
2478 the child process's @code{main}.
2480 When a child process is spawned by @code{vfork}, you cannot debug the
2481 child or parent until an @code{exec} call completes.
2483 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2484 call executes, the new target restarts. To restart the parent process,
2485 use the @code{file} command with the parent executable name as its
2488 You can use the @code{catch} command to make @value{GDBN} stop whenever
2489 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2490 Catchpoints, ,Setting catchpoints}.
2493 @chapter Stopping and Continuing
2495 The principal purposes of using a debugger are so that you can stop your
2496 program before it terminates; or so that, if your program runs into
2497 trouble, you can investigate and find out why.
2499 Inside @value{GDBN}, your program may stop for any of several reasons,
2500 such as a signal, a breakpoint, or reaching a new line after a
2501 @value{GDBN} command such as @code{step}. You may then examine and
2502 change variables, set new breakpoints or remove old ones, and then
2503 continue execution. Usually, the messages shown by @value{GDBN} provide
2504 ample explanation of the status of your program---but you can also
2505 explicitly request this information at any time.
2508 @kindex info program
2510 Display information about the status of your program: whether it is
2511 running or not, what process it is, and why it stopped.
2515 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2516 * Continuing and Stepping:: Resuming execution
2518 * Thread Stops:: Stopping and starting multi-thread programs
2522 @section Breakpoints, watchpoints, and catchpoints
2525 A @dfn{breakpoint} makes your program stop whenever a certain point in
2526 the program is reached. For each breakpoint, you can add conditions to
2527 control in finer detail whether your program stops. You can set
2528 breakpoints with the @code{break} command and its variants (@pxref{Set
2529 Breaks, ,Setting breakpoints}), to specify the place where your program
2530 should stop by line number, function name or exact address in the
2533 On some systems, you can set breakpoints in shared libraries before
2534 the executable is run. There is a minor limitation on HP-UX systems:
2535 you must wait until the executable is run in order to set breakpoints
2536 in shared library routines that are not called directly by the program
2537 (for example, routines that are arguments in a @code{pthread_create}
2541 @cindex memory tracing
2542 @cindex breakpoint on memory address
2543 @cindex breakpoint on variable modification
2544 A @dfn{watchpoint} is a special breakpoint that stops your program
2545 when the value of an expression changes. You must use a different
2546 command to set watchpoints (@pxref{Set Watchpoints, ,Setting
2547 watchpoints}), but aside from that, you can manage a watchpoint like
2548 any other breakpoint: you enable, disable, and delete both breakpoints
2549 and watchpoints using the same commands.
2551 You can arrange to have values from your program displayed automatically
2552 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2556 @cindex breakpoint on events
2557 A @dfn{catchpoint} is another special breakpoint that stops your program
2558 when a certain kind of event occurs, such as the throwing of a C@t{++}
2559 exception or the loading of a library. As with watchpoints, you use a
2560 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2561 catchpoints}), but aside from that, you can manage a catchpoint like any
2562 other breakpoint. (To stop when your program receives a signal, use the
2563 @code{handle} command; see @ref{Signals, ,Signals}.)
2565 @cindex breakpoint numbers
2566 @cindex numbers for breakpoints
2567 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2568 catchpoint when you create it; these numbers are successive integers
2569 starting with one. In many of the commands for controlling various
2570 features of breakpoints you use the breakpoint number to say which
2571 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2572 @dfn{disabled}; if disabled, it has no effect on your program until you
2575 @cindex breakpoint ranges
2576 @cindex ranges of breakpoints
2577 Some @value{GDBN} commands accept a range of breakpoints on which to
2578 operate. A breakpoint range is either a single breakpoint number, like
2579 @samp{5}, or two such numbers, in increasing order, separated by a
2580 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2581 all breakpoint in that range are operated on.
2584 * Set Breaks:: Setting breakpoints
2585 * Set Watchpoints:: Setting watchpoints
2586 * Set Catchpoints:: Setting catchpoints
2587 * Delete Breaks:: Deleting breakpoints
2588 * Disabling:: Disabling breakpoints
2589 * Conditions:: Break conditions
2590 * Break Commands:: Breakpoint command lists
2591 * Breakpoint Menus:: Breakpoint menus
2592 * Error in Breakpoints:: ``Cannot insert breakpoints''
2593 * Breakpoint related warnings:: ``Breakpoint address adjusted...''
2597 @subsection Setting breakpoints
2599 @c FIXME LMB what does GDB do if no code on line of breakpt?
2600 @c consider in particular declaration with/without initialization.
2602 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2605 @kindex b @r{(@code{break})}
2606 @vindex $bpnum@r{, convenience variable}
2607 @cindex latest breakpoint
2608 Breakpoints are set with the @code{break} command (abbreviated
2609 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2610 number of the breakpoint you've set most recently; see @ref{Convenience
2611 Vars,, Convenience variables}, for a discussion of what you can do with
2612 convenience variables.
2614 You have several ways to say where the breakpoint should go.
2617 @item break @var{function}
2618 Set a breakpoint at entry to function @var{function}.
2619 When using source languages that permit overloading of symbols, such as
2620 C@t{++}, @var{function} may refer to more than one possible place to break.
2621 @xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
2623 @item break +@var{offset}
2624 @itemx break -@var{offset}
2625 Set a breakpoint some number of lines forward or back from the position
2626 at which execution stopped in the currently selected @dfn{stack frame}.
2627 (@xref{Frames, ,Frames}, for a description of stack frames.)
2629 @item break @var{linenum}
2630 Set a breakpoint at line @var{linenum} in the current source file.
2631 The current source file is the last file whose source text was printed.
2632 The breakpoint will stop your program just before it executes any of the
2635 @item break @var{filename}:@var{linenum}
2636 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2638 @item break @var{filename}:@var{function}
2639 Set a breakpoint at entry to function @var{function} found in file
2640 @var{filename}. Specifying a file name as well as a function name is
2641 superfluous except when multiple files contain similarly named
2644 @item break *@var{address}
2645 Set a breakpoint at address @var{address}. You can use this to set
2646 breakpoints in parts of your program which do not have debugging
2647 information or source files.
2650 When called without any arguments, @code{break} sets a breakpoint at
2651 the next instruction to be executed in the selected stack frame
2652 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2653 innermost, this makes your program stop as soon as control
2654 returns to that frame. This is similar to the effect of a
2655 @code{finish} command in the frame inside the selected frame---except
2656 that @code{finish} does not leave an active breakpoint. If you use
2657 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2658 the next time it reaches the current location; this may be useful
2661 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2662 least one instruction has been executed. If it did not do this, you
2663 would be unable to proceed past a breakpoint without first disabling the
2664 breakpoint. This rule applies whether or not the breakpoint already
2665 existed when your program stopped.
2667 @item break @dots{} if @var{cond}
2668 Set a breakpoint with condition @var{cond}; evaluate the expression
2669 @var{cond} each time the breakpoint is reached, and stop only if the
2670 value is nonzero---that is, if @var{cond} evaluates as true.
2671 @samp{@dots{}} stands for one of the possible arguments described
2672 above (or no argument) specifying where to break. @xref{Conditions,
2673 ,Break conditions}, for more information on breakpoint conditions.
2676 @item tbreak @var{args}
2677 Set a breakpoint enabled only for one stop. @var{args} are the
2678 same as for the @code{break} command, and the breakpoint is set in the same
2679 way, but the breakpoint is automatically deleted after the first time your
2680 program stops there. @xref{Disabling, ,Disabling breakpoints}.
2683 @cindex hardware breakpoints
2684 @item hbreak @var{args}
2685 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2686 @code{break} command and the breakpoint is set in the same way, but the
2687 breakpoint requires hardware support and some target hardware may not
2688 have this support. The main purpose of this is EPROM/ROM code
2689 debugging, so you can set a breakpoint at an instruction without
2690 changing the instruction. This can be used with the new trap-generation
2691 provided by SPARClite DSU and most x86-based targets. These targets
2692 will generate traps when a program accesses some data or instruction
2693 address that is assigned to the debug registers. However the hardware
2694 breakpoint registers can take a limited number of breakpoints. For
2695 example, on the DSU, only two data breakpoints can be set at a time, and
2696 @value{GDBN} will reject this command if more than two are used. Delete
2697 or disable unused hardware breakpoints before setting new ones
2698 (@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}.
2699 For remote targets, you can restrict the number of hardware
2700 breakpoints @value{GDBN} will use, see @ref{set remote
2701 hardware-breakpoint-limit}.
2705 @item thbreak @var{args}
2706 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2707 are the same as for the @code{hbreak} command and the breakpoint is set in
2708 the same way. However, like the @code{tbreak} command,
2709 the breakpoint is automatically deleted after the
2710 first time your program stops there. Also, like the @code{hbreak}
2711 command, the breakpoint requires hardware support and some target hardware
2712 may not have this support. @xref{Disabling, ,Disabling breakpoints}.
2713 See also @ref{Conditions, ,Break conditions}.
2716 @cindex regular expression
2717 @cindex breakpoints in functions matching a regexp
2718 @cindex set breakpoints in many functions
2719 @item rbreak @var{regex}
2720 Set breakpoints on all functions matching the regular expression
2721 @var{regex}. This command sets an unconditional breakpoint on all
2722 matches, printing a list of all breakpoints it set. Once these
2723 breakpoints are set, they are treated just like the breakpoints set with
2724 the @code{break} command. You can delete them, disable them, or make
2725 them conditional the same way as any other breakpoint.
2727 The syntax of the regular expression is the standard one used with tools
2728 like @file{grep}. Note that this is different from the syntax used by
2729 shells, so for instance @code{foo*} matches all functions that include
2730 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2731 @code{.*} leading and trailing the regular expression you supply, so to
2732 match only functions that begin with @code{foo}, use @code{^foo}.
2734 @cindex non-member C@t{++} functions, set breakpoint in
2735 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2736 breakpoints on overloaded functions that are not members of any special
2739 @cindex set breakpoints on all functions
2740 The @code{rbreak} command can be used to set breakpoints in
2741 @strong{all} the functions in a program, like this:
2744 (@value{GDBP}) rbreak .
2747 @kindex info breakpoints
2748 @cindex @code{$_} and @code{info breakpoints}
2749 @item info breakpoints @r{[}@var{n}@r{]}
2750 @itemx info break @r{[}@var{n}@r{]}
2751 @itemx info watchpoints @r{[}@var{n}@r{]}
2752 Print a table of all breakpoints, watchpoints, and catchpoints set and
2753 not deleted, with the following columns for each breakpoint:
2756 @item Breakpoint Numbers
2758 Breakpoint, watchpoint, or catchpoint.
2760 Whether the breakpoint is marked to be disabled or deleted when hit.
2761 @item Enabled or Disabled
2762 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2763 that are not enabled.
2765 Where the breakpoint is in your program, as a memory address. If the
2766 breakpoint is pending (see below for details) on a future load of a shared library, the address
2767 will be listed as @samp{<PENDING>}.
2769 Where the breakpoint is in the source for your program, as a file and
2770 line number. For a pending breakpoint, the original string passed to
2771 the breakpoint command will be listed as it cannot be resolved until
2772 the appropriate shared library is loaded in the future.
2776 If a breakpoint is conditional, @code{info break} shows the condition on
2777 the line following the affected breakpoint; breakpoint commands, if any,
2778 are listed after that. A pending breakpoint is allowed to have a condition
2779 specified for it. The condition is not parsed for validity until a shared
2780 library is loaded that allows the pending breakpoint to resolve to a
2784 @code{info break} with a breakpoint
2785 number @var{n} as argument lists only that breakpoint. The
2786 convenience variable @code{$_} and the default examining-address for
2787 the @code{x} command are set to the address of the last breakpoint
2788 listed (@pxref{Memory, ,Examining memory}).
2791 @code{info break} displays a count of the number of times the breakpoint
2792 has been hit. This is especially useful in conjunction with the
2793 @code{ignore} command. You can ignore a large number of breakpoint
2794 hits, look at the breakpoint info to see how many times the breakpoint
2795 was hit, and then run again, ignoring one less than that number. This
2796 will get you quickly to the last hit of that breakpoint.
2799 @value{GDBN} allows you to set any number of breakpoints at the same place in
2800 your program. There is nothing silly or meaningless about this. When
2801 the breakpoints are conditional, this is even useful
2802 (@pxref{Conditions, ,Break conditions}).
2804 @cindex pending breakpoints
2805 If a specified breakpoint location cannot be found, it may be due to the fact
2806 that the location is in a shared library that is yet to be loaded. In such
2807 a case, you may want @value{GDBN} to create a special breakpoint (known as
2808 a @dfn{pending breakpoint}) that
2809 attempts to resolve itself in the future when an appropriate shared library
2812 Pending breakpoints are useful to set at the start of your
2813 @value{GDBN} session for locations that you know will be dynamically loaded
2814 later by the program being debugged. When shared libraries are loaded,
2815 a check is made to see if the load resolves any pending breakpoint locations.
2816 If a pending breakpoint location gets resolved,
2817 a regular breakpoint is created and the original pending breakpoint is removed.
2819 @value{GDBN} provides some additional commands for controlling pending
2822 @kindex set breakpoint pending
2823 @kindex show breakpoint pending
2825 @item set breakpoint pending auto
2826 This is the default behavior. When @value{GDBN} cannot find the breakpoint
2827 location, it queries you whether a pending breakpoint should be created.
2829 @item set breakpoint pending on
2830 This indicates that an unrecognized breakpoint location should automatically
2831 result in a pending breakpoint being created.
2833 @item set breakpoint pending off
2834 This indicates that pending breakpoints are not to be created. Any
2835 unrecognized breakpoint location results in an error. This setting does
2836 not affect any pending breakpoints previously created.
2838 @item show breakpoint pending
2839 Show the current behavior setting for creating pending breakpoints.
2842 @cindex operations allowed on pending breakpoints
2843 Normal breakpoint operations apply to pending breakpoints as well. You may
2844 specify a condition for a pending breakpoint and/or commands to run when the
2845 breakpoint is reached. You can also enable or disable
2846 the pending breakpoint. When you specify a condition for a pending breakpoint,
2847 the parsing of the condition will be deferred until the point where the
2848 pending breakpoint location is resolved. Disabling a pending breakpoint
2849 tells @value{GDBN} to not attempt to resolve the breakpoint on any subsequent
2850 shared library load. When a pending breakpoint is re-enabled,
2851 @value{GDBN} checks to see if the location is already resolved.
2852 This is done because any number of shared library loads could have
2853 occurred since the time the breakpoint was disabled and one or more
2854 of these loads could resolve the location.
2856 @cindex negative breakpoint numbers
2857 @cindex internal @value{GDBN} breakpoints
2858 @value{GDBN} itself sometimes sets breakpoints in your program for
2859 special purposes, such as proper handling of @code{longjmp} (in C
2860 programs). These internal breakpoints are assigned negative numbers,
2861 starting with @code{-1}; @samp{info breakpoints} does not display them.
2862 You can see these breakpoints with the @value{GDBN} maintenance command
2863 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
2866 @node Set Watchpoints
2867 @subsection Setting watchpoints
2869 @cindex setting watchpoints
2870 You can use a watchpoint to stop execution whenever the value of an
2871 expression changes, without having to predict a particular place where
2874 @cindex software watchpoints
2875 @cindex hardware watchpoints
2876 Depending on your system, watchpoints may be implemented in software or
2877 hardware. @value{GDBN} does software watchpointing by single-stepping your
2878 program and testing the variable's value each time, which is hundreds of
2879 times slower than normal execution. (But this may still be worth it, to
2880 catch errors where you have no clue what part of your program is the
2883 On some systems, such as HP-UX, @sc{gnu}/Linux and most other
2884 x86-based targets, @value{GDBN} includes support for hardware
2885 watchpoints, which do not slow down the running of your program.
2889 @item watch @var{expr}
2890 Set a watchpoint for an expression. @value{GDBN} will break when @var{expr}
2891 is written into by the program and its value changes.
2894 @item rwatch @var{expr}
2895 Set a watchpoint that will break when the value of @var{expr} is read
2899 @item awatch @var{expr}
2900 Set a watchpoint that will break when @var{expr} is either read from
2901 or written into by the program.
2903 @kindex info watchpoints
2904 @item info watchpoints
2905 This command prints a list of watchpoints, breakpoints, and catchpoints;
2906 it is the same as @code{info break} (@pxref{Set Breaks}).
2909 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
2910 watchpoints execute very quickly, and the debugger reports a change in
2911 value at the exact instruction where the change occurs. If @value{GDBN}
2912 cannot set a hardware watchpoint, it sets a software watchpoint, which
2913 executes more slowly and reports the change in value at the next
2914 @emph{statement}, not the instruction, after the change occurs.
2916 @cindex use only software watchpoints
2917 You can force @value{GDBN} to use only software watchpoints with the
2918 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
2919 zero, @value{GDBN} will never try to use hardware watchpoints, even if
2920 the underlying system supports them. (Note that hardware-assisted
2921 watchpoints that were set @emph{before} setting
2922 @code{can-use-hw-watchpoints} to zero will still use the hardware
2923 mechanism of watching expressiion values.)
2926 @item set can-use-hw-watchpoints
2927 @kindex set can-use-hw-watchpoints
2928 Set whether or not to use hardware watchpoints.
2930 @item show can-use-hw-watchpoints
2931 @kindex show can-use-hw-watchpoints
2932 Show the current mode of using hardware watchpoints.
2935 For remote targets, you can restrict the number of hardware
2936 watchpoints @value{GDBN} will use, see @ref{set remote
2937 hardware-breakpoint-limit}.
2939 When you issue the @code{watch} command, @value{GDBN} reports
2942 Hardware watchpoint @var{num}: @var{expr}
2946 if it was able to set a hardware watchpoint.
2948 Currently, the @code{awatch} and @code{rwatch} commands can only set
2949 hardware watchpoints, because accesses to data that don't change the
2950 value of the watched expression cannot be detected without examining
2951 every instruction as it is being executed, and @value{GDBN} does not do
2952 that currently. If @value{GDBN} finds that it is unable to set a
2953 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
2954 will print a message like this:
2957 Expression cannot be implemented with read/access watchpoint.
2960 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
2961 data type of the watched expression is wider than what a hardware
2962 watchpoint on the target machine can handle. For example, some systems
2963 can only watch regions that are up to 4 bytes wide; on such systems you
2964 cannot set hardware watchpoints for an expression that yields a
2965 double-precision floating-point number (which is typically 8 bytes
2966 wide). As a work-around, it might be possible to break the large region
2967 into a series of smaller ones and watch them with separate watchpoints.
2969 If you set too many hardware watchpoints, @value{GDBN} might be unable
2970 to insert all of them when you resume the execution of your program.
2971 Since the precise number of active watchpoints is unknown until such
2972 time as the program is about to be resumed, @value{GDBN} might not be
2973 able to warn you about this when you set the watchpoints, and the
2974 warning will be printed only when the program is resumed:
2977 Hardware watchpoint @var{num}: Could not insert watchpoint
2981 If this happens, delete or disable some of the watchpoints.
2983 The SPARClite DSU will generate traps when a program accesses some data
2984 or instruction address that is assigned to the debug registers. For the
2985 data addresses, DSU facilitates the @code{watch} command. However the
2986 hardware breakpoint registers can only take two data watchpoints, and
2987 both watchpoints must be the same kind. For example, you can set two
2988 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
2989 @strong{or} two with @code{awatch} commands, but you cannot set one
2990 watchpoint with one command and the other with a different command.
2991 @value{GDBN} will reject the command if you try to mix watchpoints.
2992 Delete or disable unused watchpoint commands before setting new ones.
2994 If you call a function interactively using @code{print} or @code{call},
2995 any watchpoints you have set will be inactive until @value{GDBN} reaches another
2996 kind of breakpoint or the call completes.
2998 @value{GDBN} automatically deletes watchpoints that watch local
2999 (automatic) variables, or expressions that involve such variables, when
3000 they go out of scope, that is, when the execution leaves the block in
3001 which these variables were defined. In particular, when the program
3002 being debugged terminates, @emph{all} local variables go out of scope,
3003 and so only watchpoints that watch global variables remain set. If you
3004 rerun the program, you will need to set all such watchpoints again. One
3005 way of doing that would be to set a code breakpoint at the entry to the
3006 @code{main} function and when it breaks, set all the watchpoints.
3009 @cindex watchpoints and threads
3010 @cindex threads and watchpoints
3011 @emph{Warning:} In multi-thread programs, watchpoints have only limited
3012 usefulness. With the current watchpoint implementation, @value{GDBN}
3013 can only watch the value of an expression @emph{in a single thread}. If
3014 you are confident that the expression can only change due to the current
3015 thread's activity (and if you are also confident that no other thread
3016 can become current), then you can use watchpoints as usual. However,
3017 @value{GDBN} may not notice when a non-current thread's activity changes
3020 @c FIXME: this is almost identical to the previous paragraph.
3021 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
3022 have only limited usefulness. If @value{GDBN} creates a software
3023 watchpoint, it can only watch the value of an expression @emph{in a
3024 single thread}. If you are confident that the expression can only
3025 change due to the current thread's activity (and if you are also
3026 confident that no other thread can become current), then you can use
3027 software watchpoints as usual. However, @value{GDBN} may not notice
3028 when a non-current thread's activity changes the expression. (Hardware
3029 watchpoints, in contrast, watch an expression in all threads.)
3032 @xref{set remote hardware-watchpoint-limit}.
3034 @node Set Catchpoints
3035 @subsection Setting catchpoints
3036 @cindex catchpoints, setting
3037 @cindex exception handlers
3038 @cindex event handling
3040 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3041 kinds of program events, such as C@t{++} exceptions or the loading of a
3042 shared library. Use the @code{catch} command to set a catchpoint.
3046 @item catch @var{event}
3047 Stop when @var{event} occurs. @var{event} can be any of the following:
3050 @cindex stop on C@t{++} exceptions
3051 The throwing of a C@t{++} exception.
3054 The catching of a C@t{++} exception.
3057 @cindex break on fork/exec
3058 A call to @code{exec}. This is currently only available for HP-UX.
3061 A call to @code{fork}. This is currently only available for HP-UX.
3064 A call to @code{vfork}. This is currently only available for HP-UX.
3067 @itemx load @var{libname}
3068 @cindex break on load/unload of shared library
3069 The dynamic loading of any shared library, or the loading of the library
3070 @var{libname}. This is currently only available for HP-UX.
3073 @itemx unload @var{libname}
3074 The unloading of any dynamically loaded shared library, or the unloading
3075 of the library @var{libname}. This is currently only available for HP-UX.
3078 @item tcatch @var{event}
3079 Set a catchpoint that is enabled only for one stop. The catchpoint is
3080 automatically deleted after the first time the event is caught.
3084 Use the @code{info break} command to list the current catchpoints.
3086 There are currently some limitations to C@t{++} exception handling
3087 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3091 If you call a function interactively, @value{GDBN} normally returns
3092 control to you when the function has finished executing. If the call
3093 raises an exception, however, the call may bypass the mechanism that
3094 returns control to you and cause your program either to abort or to
3095 simply continue running until it hits a breakpoint, catches a signal
3096 that @value{GDBN} is listening for, or exits. This is the case even if
3097 you set a catchpoint for the exception; catchpoints on exceptions are
3098 disabled within interactive calls.
3101 You cannot raise an exception interactively.
3104 You cannot install an exception handler interactively.
3107 @cindex raise exceptions
3108 Sometimes @code{catch} is not the best way to debug exception handling:
3109 if you need to know exactly where an exception is raised, it is better to
3110 stop @emph{before} the exception handler is called, since that way you
3111 can see the stack before any unwinding takes place. If you set a
3112 breakpoint in an exception handler instead, it may not be easy to find
3113 out where the exception was raised.
3115 To stop just before an exception handler is called, you need some
3116 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3117 raised by calling a library function named @code{__raise_exception}
3118 which has the following ANSI C interface:
3121 /* @var{addr} is where the exception identifier is stored.
3122 @var{id} is the exception identifier. */
3123 void __raise_exception (void **addr, void *id);
3127 To make the debugger catch all exceptions before any stack
3128 unwinding takes place, set a breakpoint on @code{__raise_exception}
3129 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
3131 With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
3132 that depends on the value of @var{id}, you can stop your program when
3133 a specific exception is raised. You can use multiple conditional
3134 breakpoints to stop your program when any of a number of exceptions are
3139 @subsection Deleting breakpoints
3141 @cindex clearing breakpoints, watchpoints, catchpoints
3142 @cindex deleting breakpoints, watchpoints, catchpoints
3143 It is often necessary to eliminate a breakpoint, watchpoint, or
3144 catchpoint once it has done its job and you no longer want your program
3145 to stop there. This is called @dfn{deleting} the breakpoint. A
3146 breakpoint that has been deleted no longer exists; it is forgotten.
3148 With the @code{clear} command you can delete breakpoints according to
3149 where they are in your program. With the @code{delete} command you can
3150 delete individual breakpoints, watchpoints, or catchpoints by specifying
3151 their breakpoint numbers.
3153 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3154 automatically ignores breakpoints on the first instruction to be executed
3155 when you continue execution without changing the execution address.
3160 Delete any breakpoints at the next instruction to be executed in the
3161 selected stack frame (@pxref{Selection, ,Selecting a frame}). When
3162 the innermost frame is selected, this is a good way to delete a
3163 breakpoint where your program just stopped.
3165 @item clear @var{function}
3166 @itemx clear @var{filename}:@var{function}
3167 Delete any breakpoints set at entry to the named @var{function}.
3169 @item clear @var{linenum}
3170 @itemx clear @var{filename}:@var{linenum}
3171 Delete any breakpoints set at or within the code of the specified
3172 @var{linenum} of the specified @var{filename}.
3174 @cindex delete breakpoints
3176 @kindex d @r{(@code{delete})}
3177 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3178 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3179 ranges specified as arguments. If no argument is specified, delete all
3180 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3181 confirm off}). You can abbreviate this command as @code{d}.
3185 @subsection Disabling breakpoints
3187 @cindex enable/disable a breakpoint
3188 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3189 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3190 it had been deleted, but remembers the information on the breakpoint so
3191 that you can @dfn{enable} it again later.
3193 You disable and enable breakpoints, watchpoints, and catchpoints with
3194 the @code{enable} and @code{disable} commands, optionally specifying one
3195 or more breakpoint numbers as arguments. Use @code{info break} or
3196 @code{info watch} to print a list of breakpoints, watchpoints, and
3197 catchpoints if you do not know which numbers to use.
3199 A breakpoint, watchpoint, or catchpoint can have any of four different
3200 states of enablement:
3204 Enabled. The breakpoint stops your program. A breakpoint set
3205 with the @code{break} command starts out in this state.
3207 Disabled. The breakpoint has no effect on your program.
3209 Enabled once. The breakpoint stops your program, but then becomes
3212 Enabled for deletion. The breakpoint stops your program, but
3213 immediately after it does so it is deleted permanently. A breakpoint
3214 set with the @code{tbreak} command starts out in this state.
3217 You can use the following commands to enable or disable breakpoints,
3218 watchpoints, and catchpoints:
3222 @kindex dis @r{(@code{disable})}
3223 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3224 Disable the specified breakpoints---or all breakpoints, if none are
3225 listed. A disabled breakpoint has no effect but is not forgotten. All
3226 options such as ignore-counts, conditions and commands are remembered in
3227 case the breakpoint is enabled again later. You may abbreviate
3228 @code{disable} as @code{dis}.
3231 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3232 Enable the specified breakpoints (or all defined breakpoints). They
3233 become effective once again in stopping your program.
3235 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3236 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3237 of these breakpoints immediately after stopping your program.
3239 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3240 Enable the specified breakpoints to work once, then die. @value{GDBN}
3241 deletes any of these breakpoints as soon as your program stops there.
3242 Breakpoints set by the @code{tbreak} command start out in this state.
3245 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3246 @c confusing: tbreak is also initially enabled.
3247 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3248 ,Setting breakpoints}), breakpoints that you set are initially enabled;
3249 subsequently, they become disabled or enabled only when you use one of
3250 the commands above. (The command @code{until} can set and delete a
3251 breakpoint of its own, but it does not change the state of your other
3252 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3256 @subsection Break conditions
3257 @cindex conditional breakpoints
3258 @cindex breakpoint conditions
3260 @c FIXME what is scope of break condition expr? Context where wanted?
3261 @c in particular for a watchpoint?
3262 The simplest sort of breakpoint breaks every time your program reaches a
3263 specified place. You can also specify a @dfn{condition} for a
3264 breakpoint. A condition is just a Boolean expression in your
3265 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3266 a condition evaluates the expression each time your program reaches it,
3267 and your program stops only if the condition is @emph{true}.
3269 This is the converse of using assertions for program validation; in that
3270 situation, you want to stop when the assertion is violated---that is,
3271 when the condition is false. In C, if you want to test an assertion expressed
3272 by the condition @var{assert}, you should set the condition
3273 @samp{! @var{assert}} on the appropriate breakpoint.
3275 Conditions are also accepted for watchpoints; you may not need them,
3276 since a watchpoint is inspecting the value of an expression anyhow---but
3277 it might be simpler, say, to just set a watchpoint on a variable name,
3278 and specify a condition that tests whether the new value is an interesting
3281 Break conditions can have side effects, and may even call functions in
3282 your program. This can be useful, for example, to activate functions
3283 that log program progress, or to use your own print functions to
3284 format special data structures. The effects are completely predictable
3285 unless there is another enabled breakpoint at the same address. (In
3286 that case, @value{GDBN} might see the other breakpoint first and stop your
3287 program without checking the condition of this one.) Note that
3288 breakpoint commands are usually more convenient and flexible than break
3290 purpose of performing side effects when a breakpoint is reached
3291 (@pxref{Break Commands, ,Breakpoint command lists}).
3293 Break conditions can be specified when a breakpoint is set, by using
3294 @samp{if} in the arguments to the @code{break} command. @xref{Set
3295 Breaks, ,Setting breakpoints}. They can also be changed at any time
3296 with the @code{condition} command.
3298 You can also use the @code{if} keyword with the @code{watch} command.
3299 The @code{catch} command does not recognize the @code{if} keyword;
3300 @code{condition} is the only way to impose a further condition on a
3305 @item condition @var{bnum} @var{expression}
3306 Specify @var{expression} as the break condition for breakpoint,
3307 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3308 breakpoint @var{bnum} stops your program only if the value of
3309 @var{expression} is true (nonzero, in C). When you use
3310 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3311 syntactic correctness, and to determine whether symbols in it have
3312 referents in the context of your breakpoint. If @var{expression} uses
3313 symbols not referenced in the context of the breakpoint, @value{GDBN}
3314 prints an error message:
3317 No symbol "foo" in current context.
3322 not actually evaluate @var{expression} at the time the @code{condition}
3323 command (or a command that sets a breakpoint with a condition, like
3324 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3326 @item condition @var{bnum}
3327 Remove the condition from breakpoint number @var{bnum}. It becomes
3328 an ordinary unconditional breakpoint.
3331 @cindex ignore count (of breakpoint)
3332 A special case of a breakpoint condition is to stop only when the
3333 breakpoint has been reached a certain number of times. This is so
3334 useful that there is a special way to do it, using the @dfn{ignore
3335 count} of the breakpoint. Every breakpoint has an ignore count, which
3336 is an integer. Most of the time, the ignore count is zero, and
3337 therefore has no effect. But if your program reaches a breakpoint whose
3338 ignore count is positive, then instead of stopping, it just decrements
3339 the ignore count by one and continues. As a result, if the ignore count
3340 value is @var{n}, the breakpoint does not stop the next @var{n} times
3341 your program reaches it.
3345 @item ignore @var{bnum} @var{count}
3346 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3347 The next @var{count} times the breakpoint is reached, your program's
3348 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3351 To make the breakpoint stop the next time it is reached, specify
3354 When you use @code{continue} to resume execution of your program from a
3355 breakpoint, you can specify an ignore count directly as an argument to
3356 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3357 Stepping,,Continuing and stepping}.
3359 If a breakpoint has a positive ignore count and a condition, the
3360 condition is not checked. Once the ignore count reaches zero,
3361 @value{GDBN} resumes checking the condition.
3363 You could achieve the effect of the ignore count with a condition such
3364 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3365 is decremented each time. @xref{Convenience Vars, ,Convenience
3369 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3372 @node Break Commands
3373 @subsection Breakpoint command lists
3375 @cindex breakpoint commands
3376 You can give any breakpoint (or watchpoint or catchpoint) a series of
3377 commands to execute when your program stops due to that breakpoint. For
3378 example, you might want to print the values of certain expressions, or
3379 enable other breakpoints.
3384 @item commands @r{[}@var{bnum}@r{]}
3385 @itemx @dots{} @var{command-list} @dots{}
3387 Specify a list of commands for breakpoint number @var{bnum}. The commands
3388 themselves appear on the following lines. Type a line containing just
3389 @code{end} to terminate the commands.
3391 To remove all commands from a breakpoint, type @code{commands} and
3392 follow it immediately with @code{end}; that is, give no commands.
3394 With no @var{bnum} argument, @code{commands} refers to the last
3395 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3396 recently encountered).
3399 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3400 disabled within a @var{command-list}.
3402 You can use breakpoint commands to start your program up again. Simply
3403 use the @code{continue} command, or @code{step}, or any other command
3404 that resumes execution.
3406 Any other commands in the command list, after a command that resumes
3407 execution, are ignored. This is because any time you resume execution
3408 (even with a simple @code{next} or @code{step}), you may encounter
3409 another breakpoint---which could have its own command list, leading to
3410 ambiguities about which list to execute.
3413 If the first command you specify in a command list is @code{silent}, the
3414 usual message about stopping at a breakpoint is not printed. This may
3415 be desirable for breakpoints that are to print a specific message and
3416 then continue. If none of the remaining commands print anything, you
3417 see no sign that the breakpoint was reached. @code{silent} is
3418 meaningful only at the beginning of a breakpoint command list.
3420 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3421 print precisely controlled output, and are often useful in silent
3422 breakpoints. @xref{Output, ,Commands for controlled output}.
3424 For example, here is how you could use breakpoint commands to print the
3425 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3431 printf "x is %d\n",x
3436 One application for breakpoint commands is to compensate for one bug so
3437 you can test for another. Put a breakpoint just after the erroneous line
3438 of code, give it a condition to detect the case in which something
3439 erroneous has been done, and give it commands to assign correct values
3440 to any variables that need them. End with the @code{continue} command
3441 so that your program does not stop, and start with the @code{silent}
3442 command so that no output is produced. Here is an example:
3453 @node Breakpoint Menus
3454 @subsection Breakpoint menus
3456 @cindex symbol overloading
3458 Some programming languages (notably C@t{++} and Objective-C) permit a
3459 single function name
3460 to be defined several times, for application in different contexts.
3461 This is called @dfn{overloading}. When a function name is overloaded,
3462 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3463 a breakpoint. If you realize this is a problem, you can use
3464 something like @samp{break @var{function}(@var{types})} to specify which
3465 particular version of the function you want. Otherwise, @value{GDBN} offers
3466 you a menu of numbered choices for different possible breakpoints, and
3467 waits for your selection with the prompt @samp{>}. The first two
3468 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3469 sets a breakpoint at each definition of @var{function}, and typing
3470 @kbd{0} aborts the @code{break} command without setting any new
3473 For example, the following session excerpt shows an attempt to set a
3474 breakpoint at the overloaded symbol @code{String::after}.
3475 We choose three particular definitions of that function name:
3477 @c FIXME! This is likely to change to show arg type lists, at least
3480 (@value{GDBP}) b String::after
3483 [2] file:String.cc; line number:867
3484 [3] file:String.cc; line number:860
3485 [4] file:String.cc; line number:875
3486 [5] file:String.cc; line number:853
3487 [6] file:String.cc; line number:846
3488 [7] file:String.cc; line number:735
3490 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3491 Breakpoint 2 at 0xb344: file String.cc, line 875.
3492 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3493 Multiple breakpoints were set.
3494 Use the "delete" command to delete unwanted
3500 @c @ifclear BARETARGET
3501 @node Error in Breakpoints
3502 @subsection ``Cannot insert breakpoints''
3504 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3506 Under some operating systems, breakpoints cannot be used in a program if
3507 any other process is running that program. In this situation,
3508 attempting to run or continue a program with a breakpoint causes
3509 @value{GDBN} to print an error message:
3512 Cannot insert breakpoints.
3513 The same program may be running in another process.
3516 When this happens, you have three ways to proceed:
3520 Remove or disable the breakpoints, then continue.
3523 Suspend @value{GDBN}, and copy the file containing your program to a new
3524 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3525 that @value{GDBN} should run your program under that name.
3526 Then start your program again.
3529 Relink your program so that the text segment is nonsharable, using the
3530 linker option @samp{-N}. The operating system limitation may not apply
3531 to nonsharable executables.
3535 A similar message can be printed if you request too many active
3536 hardware-assisted breakpoints and watchpoints:
3538 @c FIXME: the precise wording of this message may change; the relevant
3539 @c source change is not committed yet (Sep 3, 1999).
3541 Stopped; cannot insert breakpoints.
3542 You may have requested too many hardware breakpoints and watchpoints.
3546 This message is printed when you attempt to resume the program, since
3547 only then @value{GDBN} knows exactly how many hardware breakpoints and
3548 watchpoints it needs to insert.
3550 When this message is printed, you need to disable or remove some of the
3551 hardware-assisted breakpoints and watchpoints, and then continue.
3553 @node Breakpoint related warnings
3554 @subsection ``Breakpoint address adjusted...''
3555 @cindex breakpoint address adjusted
3557 Some processor architectures place constraints on the addresses at
3558 which breakpoints may be placed. For architectures thus constrained,
3559 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3560 with the constraints dictated by the architecture.
3562 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3563 a VLIW architecture in which a number of RISC-like instructions may be
3564 bundled together for parallel execution. The FR-V architecture
3565 constrains the location of a breakpoint instruction within such a
3566 bundle to the instruction with the lowest address. @value{GDBN}
3567 honors this constraint by adjusting a breakpoint's address to the
3568 first in the bundle.
3570 It is not uncommon for optimized code to have bundles which contain
3571 instructions from different source statements, thus it may happen that
3572 a breakpoint's address will be adjusted from one source statement to
3573 another. Since this adjustment may significantly alter @value{GDBN}'s
3574 breakpoint related behavior from what the user expects, a warning is
3575 printed when the breakpoint is first set and also when the breakpoint
3578 A warning like the one below is printed when setting a breakpoint
3579 that's been subject to address adjustment:
3582 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3585 Such warnings are printed both for user settable and @value{GDBN}'s
3586 internal breakpoints. If you see one of these warnings, you should
3587 verify that a breakpoint set at the adjusted address will have the
3588 desired affect. If not, the breakpoint in question may be removed and
3589 other breakpoints may be set which will have the desired behavior.
3590 E.g., it may be sufficient to place the breakpoint at a later
3591 instruction. A conditional breakpoint may also be useful in some
3592 cases to prevent the breakpoint from triggering too often.
3594 @value{GDBN} will also issue a warning when stopping at one of these
3595 adjusted breakpoints:
3598 warning: Breakpoint 1 address previously adjusted from 0x00010414
3602 When this warning is encountered, it may be too late to take remedial
3603 action except in cases where the breakpoint is hit earlier or more
3604 frequently than expected.
3606 @node Continuing and Stepping
3607 @section Continuing and stepping
3611 @cindex resuming execution
3612 @dfn{Continuing} means resuming program execution until your program
3613 completes normally. In contrast, @dfn{stepping} means executing just
3614 one more ``step'' of your program, where ``step'' may mean either one
3615 line of source code, or one machine instruction (depending on what
3616 particular command you use). Either when continuing or when stepping,
3617 your program may stop even sooner, due to a breakpoint or a signal. (If
3618 it stops due to a signal, you may want to use @code{handle}, or use
3619 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3623 @kindex c @r{(@code{continue})}
3624 @kindex fg @r{(resume foreground execution)}
3625 @item continue @r{[}@var{ignore-count}@r{]}
3626 @itemx c @r{[}@var{ignore-count}@r{]}
3627 @itemx fg @r{[}@var{ignore-count}@r{]}
3628 Resume program execution, at the address where your program last stopped;
3629 any breakpoints set at that address are bypassed. The optional argument
3630 @var{ignore-count} allows you to specify a further number of times to
3631 ignore a breakpoint at this location; its effect is like that of
3632 @code{ignore} (@pxref{Conditions, ,Break conditions}).
3634 The argument @var{ignore-count} is meaningful only when your program
3635 stopped due to a breakpoint. At other times, the argument to
3636 @code{continue} is ignored.
3638 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3639 debugged program is deemed to be the foreground program) are provided
3640 purely for convenience, and have exactly the same behavior as
3644 To resume execution at a different place, you can use @code{return}
3645 (@pxref{Returning, ,Returning from a function}) to go back to the
3646 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3647 different address}) to go to an arbitrary location in your program.
3649 A typical technique for using stepping is to set a breakpoint
3650 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the
3651 beginning of the function or the section of your program where a problem
3652 is believed to lie, run your program until it stops at that breakpoint,
3653 and then step through the suspect area, examining the variables that are
3654 interesting, until you see the problem happen.
3658 @kindex s @r{(@code{step})}
3660 Continue running your program until control reaches a different source
3661 line, then stop it and return control to @value{GDBN}. This command is
3662 abbreviated @code{s}.
3665 @c "without debugging information" is imprecise; actually "without line
3666 @c numbers in the debugging information". (gcc -g1 has debugging info but
3667 @c not line numbers). But it seems complex to try to make that
3668 @c distinction here.
3669 @emph{Warning:} If you use the @code{step} command while control is
3670 within a function that was compiled without debugging information,
3671 execution proceeds until control reaches a function that does have
3672 debugging information. Likewise, it will not step into a function which
3673 is compiled without debugging information. To step through functions
3674 without debugging information, use the @code{stepi} command, described
3678 The @code{step} command only stops at the first instruction of a source
3679 line. This prevents the multiple stops that could otherwise occur in
3680 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3681 to stop if a function that has debugging information is called within
3682 the line. In other words, @code{step} @emph{steps inside} any functions
3683 called within the line.
3685 Also, the @code{step} command only enters a function if there is line
3686 number information for the function. Otherwise it acts like the
3687 @code{next} command. This avoids problems when using @code{cc -gl}
3688 on MIPS machines. Previously, @code{step} entered subroutines if there
3689 was any debugging information about the routine.
3691 @item step @var{count}
3692 Continue running as in @code{step}, but do so @var{count} times. If a
3693 breakpoint is reached, or a signal not related to stepping occurs before
3694 @var{count} steps, stepping stops right away.
3697 @kindex n @r{(@code{next})}
3698 @item next @r{[}@var{count}@r{]}
3699 Continue to the next source line in the current (innermost) stack frame.
3700 This is similar to @code{step}, but function calls that appear within
3701 the line of code are executed without stopping. Execution stops when
3702 control reaches a different line of code at the original stack level
3703 that was executing when you gave the @code{next} command. This command
3704 is abbreviated @code{n}.
3706 An argument @var{count} is a repeat count, as for @code{step}.
3709 @c FIX ME!! Do we delete this, or is there a way it fits in with
3710 @c the following paragraph? --- Vctoria
3712 @c @code{next} within a function that lacks debugging information acts like
3713 @c @code{step}, but any function calls appearing within the code of the
3714 @c function are executed without stopping.
3716 The @code{next} command only stops at the first instruction of a
3717 source line. This prevents multiple stops that could otherwise occur in
3718 @code{switch} statements, @code{for} loops, etc.
3720 @kindex set step-mode
3722 @cindex functions without line info, and stepping
3723 @cindex stepping into functions with no line info
3724 @itemx set step-mode on
3725 The @code{set step-mode on} command causes the @code{step} command to
3726 stop at the first instruction of a function which contains no debug line
3727 information rather than stepping over it.
3729 This is useful in cases where you may be interested in inspecting the
3730 machine instructions of a function which has no symbolic info and do not
3731 want @value{GDBN} to automatically skip over this function.
3733 @item set step-mode off
3734 Causes the @code{step} command to step over any functions which contains no
3735 debug information. This is the default.
3737 @item show step-mode
3738 Show whether @value{GDBN} will stop in or step over functions without
3739 source line debug information.
3743 Continue running until just after function in the selected stack frame
3744 returns. Print the returned value (if any).
3746 Contrast this with the @code{return} command (@pxref{Returning,
3747 ,Returning from a function}).
3750 @kindex u @r{(@code{until})}
3751 @cindex run until specified location
3754 Continue running until a source line past the current line, in the
3755 current stack frame, is reached. This command is used to avoid single
3756 stepping through a loop more than once. It is like the @code{next}
3757 command, except that when @code{until} encounters a jump, it
3758 automatically continues execution until the program counter is greater
3759 than the address of the jump.
3761 This means that when you reach the end of a loop after single stepping
3762 though it, @code{until} makes your program continue execution until it
3763 exits the loop. In contrast, a @code{next} command at the end of a loop
3764 simply steps back to the beginning of the loop, which forces you to step
3765 through the next iteration.
3767 @code{until} always stops your program if it attempts to exit the current
3770 @code{until} may produce somewhat counterintuitive results if the order
3771 of machine code does not match the order of the source lines. For
3772 example, in the following excerpt from a debugging session, the @code{f}
3773 (@code{frame}) command shows that execution is stopped at line
3774 @code{206}; yet when we use @code{until}, we get to line @code{195}:
3778 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
3780 (@value{GDBP}) until
3781 195 for ( ; argc > 0; NEXTARG) @{
3784 This happened because, for execution efficiency, the compiler had
3785 generated code for the loop closure test at the end, rather than the
3786 start, of the loop---even though the test in a C @code{for}-loop is
3787 written before the body of the loop. The @code{until} command appeared
3788 to step back to the beginning of the loop when it advanced to this
3789 expression; however, it has not really gone to an earlier
3790 statement---not in terms of the actual machine code.
3792 @code{until} with no argument works by means of single
3793 instruction stepping, and hence is slower than @code{until} with an
3796 @item until @var{location}
3797 @itemx u @var{location}
3798 Continue running your program until either the specified location is
3799 reached, or the current stack frame returns. @var{location} is any of
3800 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
3801 ,Setting breakpoints}). This form of the command uses breakpoints, and
3802 hence is quicker than @code{until} without an argument. The specified
3803 location is actually reached only if it is in the current frame. This
3804 implies that @code{until} can be used to skip over recursive function
3805 invocations. For instance in the code below, if the current location is
3806 line @code{96}, issuing @code{until 99} will execute the program up to
3807 line @code{99} in the same invocation of factorial, i.e. after the inner
3808 invocations have returned.
3811 94 int factorial (int value)
3813 96 if (value > 1) @{
3814 97 value *= factorial (value - 1);
3821 @kindex advance @var{location}
3822 @itemx advance @var{location}
3823 Continue running the program up to the given @var{location}. An argument is
3824 required, which should be of the same form as arguments for the @code{break}
3825 command. Execution will also stop upon exit from the current stack
3826 frame. This command is similar to @code{until}, but @code{advance} will
3827 not skip over recursive function calls, and the target location doesn't
3828 have to be in the same frame as the current one.
3832 @kindex si @r{(@code{stepi})}
3834 @itemx stepi @var{arg}
3836 Execute one machine instruction, then stop and return to the debugger.
3838 It is often useful to do @samp{display/i $pc} when stepping by machine
3839 instructions. This makes @value{GDBN} automatically display the next
3840 instruction to be executed, each time your program stops. @xref{Auto
3841 Display,, Automatic display}.
3843 An argument is a repeat count, as in @code{step}.
3847 @kindex ni @r{(@code{nexti})}
3849 @itemx nexti @var{arg}
3851 Execute one machine instruction, but if it is a function call,
3852 proceed until the function returns.
3854 An argument is a repeat count, as in @code{next}.
3861 A signal is an asynchronous event that can happen in a program. The
3862 operating system defines the possible kinds of signals, and gives each
3863 kind a name and a number. For example, in Unix @code{SIGINT} is the
3864 signal a program gets when you type an interrupt character (often @kbd{C-c});
3865 @code{SIGSEGV} is the signal a program gets from referencing a place in
3866 memory far away from all the areas in use; @code{SIGALRM} occurs when
3867 the alarm clock timer goes off (which happens only if your program has
3868 requested an alarm).
3870 @cindex fatal signals
3871 Some signals, including @code{SIGALRM}, are a normal part of the
3872 functioning of your program. Others, such as @code{SIGSEGV}, indicate
3873 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
3874 program has not specified in advance some other way to handle the signal.
3875 @code{SIGINT} does not indicate an error in your program, but it is normally
3876 fatal so it can carry out the purpose of the interrupt: to kill the program.
3878 @value{GDBN} has the ability to detect any occurrence of a signal in your
3879 program. You can tell @value{GDBN} in advance what to do for each kind of
3882 @cindex handling signals
3883 Normally, @value{GDBN} is set up to let the non-erroneous signals like
3884 @code{SIGALRM} be silently passed to your program
3885 (so as not to interfere with their role in the program's functioning)
3886 but to stop your program immediately whenever an error signal happens.
3887 You can change these settings with the @code{handle} command.
3890 @kindex info signals
3894 Print a table of all the kinds of signals and how @value{GDBN} has been told to
3895 handle each one. You can use this to see the signal numbers of all
3896 the defined types of signals.
3898 @code{info handle} is an alias for @code{info signals}.
3901 @item handle @var{signal} @var{keywords}@dots{}
3902 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
3903 can be the number of a signal or its name (with or without the
3904 @samp{SIG} at the beginning); a list of signal numbers of the form
3905 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
3906 known signals. The @var{keywords} say what change to make.
3910 The keywords allowed by the @code{handle} command can be abbreviated.
3911 Their full names are:
3915 @value{GDBN} should not stop your program when this signal happens. It may
3916 still print a message telling you that the signal has come in.
3919 @value{GDBN} should stop your program when this signal happens. This implies
3920 the @code{print} keyword as well.
3923 @value{GDBN} should print a message when this signal happens.
3926 @value{GDBN} should not mention the occurrence of the signal at all. This
3927 implies the @code{nostop} keyword as well.
3931 @value{GDBN} should allow your program to see this signal; your program
3932 can handle the signal, or else it may terminate if the signal is fatal
3933 and not handled. @code{pass} and @code{noignore} are synonyms.
3937 @value{GDBN} should not allow your program to see this signal.
3938 @code{nopass} and @code{ignore} are synonyms.
3942 When a signal stops your program, the signal is not visible to the
3944 continue. Your program sees the signal then, if @code{pass} is in
3945 effect for the signal in question @emph{at that time}. In other words,
3946 after @value{GDBN} reports a signal, you can use the @code{handle}
3947 command with @code{pass} or @code{nopass} to control whether your
3948 program sees that signal when you continue.
3950 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
3951 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
3952 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
3955 You can also use the @code{signal} command to prevent your program from
3956 seeing a signal, or cause it to see a signal it normally would not see,
3957 or to give it any signal at any time. For example, if your program stopped
3958 due to some sort of memory reference error, you might store correct
3959 values into the erroneous variables and continue, hoping to see more
3960 execution; but your program would probably terminate immediately as
3961 a result of the fatal signal once it saw the signal. To prevent this,
3962 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
3966 @section Stopping and starting multi-thread programs
3968 When your program has multiple threads (@pxref{Threads,, Debugging
3969 programs with multiple threads}), you can choose whether to set
3970 breakpoints on all threads, or on a particular thread.
3973 @cindex breakpoints and threads
3974 @cindex thread breakpoints
3975 @kindex break @dots{} thread @var{threadno}
3976 @item break @var{linespec} thread @var{threadno}
3977 @itemx break @var{linespec} thread @var{threadno} if @dots{}
3978 @var{linespec} specifies source lines; there are several ways of
3979 writing them, but the effect is always to specify some source line.
3981 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
3982 to specify that you only want @value{GDBN} to stop the program when a
3983 particular thread reaches this breakpoint. @var{threadno} is one of the
3984 numeric thread identifiers assigned by @value{GDBN}, shown in the first
3985 column of the @samp{info threads} display.
3987 If you do not specify @samp{thread @var{threadno}} when you set a
3988 breakpoint, the breakpoint applies to @emph{all} threads of your
3991 You can use the @code{thread} qualifier on conditional breakpoints as
3992 well; in this case, place @samp{thread @var{threadno}} before the
3993 breakpoint condition, like this:
3996 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4001 @cindex stopped threads
4002 @cindex threads, stopped
4003 Whenever your program stops under @value{GDBN} for any reason,
4004 @emph{all} threads of execution stop, not just the current thread. This
4005 allows you to examine the overall state of the program, including
4006 switching between threads, without worrying that things may change
4009 @cindex thread breakpoints and system calls
4010 @cindex system calls and thread breakpoints
4011 @cindex premature return from system calls
4012 There is an unfortunate side effect. If one thread stops for a
4013 breakpoint, or for some other reason, and another thread is blocked in a
4014 system call, then the system call may return prematurely. This is a
4015 consequence of the interaction between multiple threads and the signals
4016 that @value{GDBN} uses to implement breakpoints and other events that
4019 To handle this problem, your program should check the return value of
4020 each system call and react appropriately. This is good programming
4023 For example, do not write code like this:
4029 The call to @code{sleep} will return early if a different thread stops
4030 at a breakpoint or for some other reason.
4032 Instead, write this:
4037 unslept = sleep (unslept);
4040 A system call is allowed to return early, so the system is still
4041 conforming to its specification. But @value{GDBN} does cause your
4042 multi-threaded program to behave differently than it would without
4045 Also, @value{GDBN} uses internal breakpoints in the thread library to
4046 monitor certain events such as thread creation and thread destruction.
4047 When such an event happens, a system call in another thread may return
4048 prematurely, even though your program does not appear to stop.
4050 @cindex continuing threads
4051 @cindex threads, continuing
4052 Conversely, whenever you restart the program, @emph{all} threads start
4053 executing. @emph{This is true even when single-stepping} with commands
4054 like @code{step} or @code{next}.
4056 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4057 Since thread scheduling is up to your debugging target's operating
4058 system (not controlled by @value{GDBN}), other threads may
4059 execute more than one statement while the current thread completes a
4060 single step. Moreover, in general other threads stop in the middle of a
4061 statement, rather than at a clean statement boundary, when the program
4064 You might even find your program stopped in another thread after
4065 continuing or even single-stepping. This happens whenever some other
4066 thread runs into a breakpoint, a signal, or an exception before the
4067 first thread completes whatever you requested.
4069 On some OSes, you can lock the OS scheduler and thus allow only a single
4073 @item set scheduler-locking @var{mode}
4074 @cindex scheduler locking mode
4075 @cindex lock scheduler
4076 Set the scheduler locking mode. If it is @code{off}, then there is no
4077 locking and any thread may run at any time. If @code{on}, then only the
4078 current thread may run when the inferior is resumed. The @code{step}
4079 mode optimizes for single-stepping. It stops other threads from
4080 ``seizing the prompt'' by preempting the current thread while you are
4081 stepping. Other threads will only rarely (or never) get a chance to run
4082 when you step. They are more likely to run when you @samp{next} over a
4083 function call, and they are completely free to run when you use commands
4084 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4085 thread hits a breakpoint during its timeslice, they will never steal the
4086 @value{GDBN} prompt away from the thread that you are debugging.
4088 @item show scheduler-locking
4089 Display the current scheduler locking mode.
4094 @chapter Examining the Stack
4096 When your program has stopped, the first thing you need to know is where it
4097 stopped and how it got there.
4100 Each time your program performs a function call, information about the call
4102 That information includes the location of the call in your program,
4103 the arguments of the call,
4104 and the local variables of the function being called.
4105 The information is saved in a block of data called a @dfn{stack frame}.
4106 The stack frames are allocated in a region of memory called the @dfn{call
4109 When your program stops, the @value{GDBN} commands for examining the
4110 stack allow you to see all of this information.
4112 @cindex selected frame
4113 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4114 @value{GDBN} commands refer implicitly to the selected frame. In
4115 particular, whenever you ask @value{GDBN} for the value of a variable in
4116 your program, the value is found in the selected frame. There are
4117 special @value{GDBN} commands to select whichever frame you are
4118 interested in. @xref{Selection, ,Selecting a frame}.
4120 When your program stops, @value{GDBN} automatically selects the
4121 currently executing frame and describes it briefly, similar to the
4122 @code{frame} command (@pxref{Frame Info, ,Information about a frame}).
4125 * Frames:: Stack frames
4126 * Backtrace:: Backtraces
4127 * Selection:: Selecting a frame
4128 * Frame Info:: Information on a frame
4133 @section Stack frames
4135 @cindex frame, definition
4137 The call stack is divided up into contiguous pieces called @dfn{stack
4138 frames}, or @dfn{frames} for short; each frame is the data associated
4139 with one call to one function. The frame contains the arguments given
4140 to the function, the function's local variables, and the address at
4141 which the function is executing.
4143 @cindex initial frame
4144 @cindex outermost frame
4145 @cindex innermost frame
4146 When your program is started, the stack has only one frame, that of the
4147 function @code{main}. This is called the @dfn{initial} frame or the
4148 @dfn{outermost} frame. Each time a function is called, a new frame is
4149 made. Each time a function returns, the frame for that function invocation
4150 is eliminated. If a function is recursive, there can be many frames for
4151 the same function. The frame for the function in which execution is
4152 actually occurring is called the @dfn{innermost} frame. This is the most
4153 recently created of all the stack frames that still exist.
4155 @cindex frame pointer
4156 Inside your program, stack frames are identified by their addresses. A
4157 stack frame consists of many bytes, each of which has its own address; each
4158 kind of computer has a convention for choosing one byte whose
4159 address serves as the address of the frame. Usually this address is kept
4160 in a register called the @dfn{frame pointer register}
4161 (@pxref{Registers, $fp}) while execution is going on in that frame.
4163 @cindex frame number
4164 @value{GDBN} assigns numbers to all existing stack frames, starting with
4165 zero for the innermost frame, one for the frame that called it,
4166 and so on upward. These numbers do not really exist in your program;
4167 they are assigned by @value{GDBN} to give you a way of designating stack
4168 frames in @value{GDBN} commands.
4170 @c The -fomit-frame-pointer below perennially causes hbox overflow
4171 @c underflow problems.
4172 @cindex frameless execution
4173 Some compilers provide a way to compile functions so that they operate
4174 without stack frames. (For example, the @value{GCC} option
4176 @samp{-fomit-frame-pointer}
4178 generates functions without a frame.)
4179 This is occasionally done with heavily used library functions to save
4180 the frame setup time. @value{GDBN} has limited facilities for dealing
4181 with these function invocations. If the innermost function invocation
4182 has no stack frame, @value{GDBN} nevertheless regards it as though
4183 it had a separate frame, which is numbered zero as usual, allowing
4184 correct tracing of the function call chain. However, @value{GDBN} has
4185 no provision for frameless functions elsewhere in the stack.
4188 @kindex frame@r{, command}
4189 @cindex current stack frame
4190 @item frame @var{args}
4191 The @code{frame} command allows you to move from one stack frame to another,
4192 and to print the stack frame you select. @var{args} may be either the
4193 address of the frame or the stack frame number. Without an argument,
4194 @code{frame} prints the current stack frame.
4196 @kindex select-frame
4197 @cindex selecting frame silently
4199 The @code{select-frame} command allows you to move from one stack frame
4200 to another without printing the frame. This is the silent version of
4208 @cindex call stack traces
4209 A backtrace is a summary of how your program got where it is. It shows one
4210 line per frame, for many frames, starting with the currently executing
4211 frame (frame zero), followed by its caller (frame one), and on up the
4216 @kindex bt @r{(@code{backtrace})}
4219 Print a backtrace of the entire stack: one line per frame for all
4220 frames in the stack.
4222 You can stop the backtrace at any time by typing the system interrupt
4223 character, normally @kbd{C-c}.
4225 @item backtrace @var{n}
4227 Similar, but print only the innermost @var{n} frames.
4229 @item backtrace -@var{n}
4231 Similar, but print only the outermost @var{n} frames.
4233 @item backtrace full
4234 Print the values of the local variables also.
4240 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4241 are additional aliases for @code{backtrace}.
4243 Each line in the backtrace shows the frame number and the function name.
4244 The program counter value is also shown---unless you use @code{set
4245 print address off}. The backtrace also shows the source file name and
4246 line number, as well as the arguments to the function. The program
4247 counter value is omitted if it is at the beginning of the code for that
4250 Here is an example of a backtrace. It was made with the command
4251 @samp{bt 3}, so it shows the innermost three frames.
4255 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4257 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4258 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4260 (More stack frames follow...)
4265 The display for frame zero does not begin with a program counter
4266 value, indicating that your program has stopped at the beginning of the
4267 code for line @code{993} of @code{builtin.c}.
4269 @cindex value optimized out, in backtrace
4270 @cindex function call arguments, optimized out
4271 If your program was compiled with optimizations, some compilers will
4272 optimize away arguments passed to functions if those arguments are
4273 never used after the call. Such optimizations generate code that
4274 passes arguments through registers, but doesn't store those arguments
4275 in the stack frame. @value{GDBN} has no way of displaying such
4276 arguments in stack frames other than the innermost one. Here's what
4277 such a backtrace might look like:
4281 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4283 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
4284 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
4286 (More stack frames follow...)
4291 The values of arguments that were not saved in their stack frames are
4292 shown as @samp{<value optimized out>}.
4294 If you need to display the values of such optimized-out arguments,
4295 either deduce that from other variables whose values depend on the one
4296 you are interested in, or recompile without optimizations.
4298 @cindex backtrace beyond @code{main} function
4299 @cindex program entry point
4300 @cindex startup code, and backtrace
4301 Most programs have a standard user entry point---a place where system
4302 libraries and startup code transition into user code. For C this is
4303 @code{main}@footnote{
4304 Note that embedded programs (the so-called ``free-standing''
4305 environment) are not required to have a @code{main} function as the
4306 entry point. They could even have multiple entry points.}.
4307 When @value{GDBN} finds the entry function in a backtrace
4308 it will terminate the backtrace, to avoid tracing into highly
4309 system-specific (and generally uninteresting) code.
4311 If you need to examine the startup code, or limit the number of levels
4312 in a backtrace, you can change this behavior:
4315 @item set backtrace past-main
4316 @itemx set backtrace past-main on
4317 @kindex set backtrace
4318 Backtraces will continue past the user entry point.
4320 @item set backtrace past-main off
4321 Backtraces will stop when they encounter the user entry point. This is the
4324 @item show backtrace past-main
4325 @kindex show backtrace
4326 Display the current user entry point backtrace policy.
4328 @item set backtrace past-entry
4329 @itemx set backtrace past-entry on
4330 Backtraces will continue past the internal entry point of an application.
4331 This entry point is encoded by the linker when the application is built,
4332 and is likely before the user entry point @code{main} (or equivalent) is called.
4334 @item set backtrace past-entry off
4335 Backtraces will stop when they encouter the internal entry point of an
4336 application. This is the default.
4338 @item show backtrace past-entry
4339 Display the current internal entry point backtrace policy.
4341 @item set backtrace limit @var{n}
4342 @itemx set backtrace limit 0
4343 @cindex backtrace limit
4344 Limit the backtrace to @var{n} levels. A value of zero means
4347 @item show backtrace limit
4348 Display the current limit on backtrace levels.
4352 @section Selecting a frame
4354 Most commands for examining the stack and other data in your program work on
4355 whichever stack frame is selected at the moment. Here are the commands for
4356 selecting a stack frame; all of them finish by printing a brief description
4357 of the stack frame just selected.
4360 @kindex frame@r{, selecting}
4361 @kindex f @r{(@code{frame})}
4364 Select frame number @var{n}. Recall that frame zero is the innermost
4365 (currently executing) frame, frame one is the frame that called the
4366 innermost one, and so on. The highest-numbered frame is the one for
4369 @item frame @var{addr}
4371 Select the frame at address @var{addr}. This is useful mainly if the
4372 chaining of stack frames has been damaged by a bug, making it
4373 impossible for @value{GDBN} to assign numbers properly to all frames. In
4374 addition, this can be useful when your program has multiple stacks and
4375 switches between them.
4377 On the SPARC architecture, @code{frame} needs two addresses to
4378 select an arbitrary frame: a frame pointer and a stack pointer.
4380 On the MIPS and Alpha architecture, it needs two addresses: a stack
4381 pointer and a program counter.
4383 On the 29k architecture, it needs three addresses: a register stack
4384 pointer, a program counter, and a memory stack pointer.
4385 @c note to future updaters: this is conditioned on a flag
4386 @c SETUP_ARBITRARY_FRAME in the tm-*.h files. The above is up to date
4387 @c as of 27 Jan 1994.
4391 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4392 advances toward the outermost frame, to higher frame numbers, to frames
4393 that have existed longer. @var{n} defaults to one.
4396 @kindex do @r{(@code{down})}
4398 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4399 advances toward the innermost frame, to lower frame numbers, to frames
4400 that were created more recently. @var{n} defaults to one. You may
4401 abbreviate @code{down} as @code{do}.
4404 All of these commands end by printing two lines of output describing the
4405 frame. The first line shows the frame number, the function name, the
4406 arguments, and the source file and line number of execution in that
4407 frame. The second line shows the text of that source line.
4415 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4417 10 read_input_file (argv[i]);
4421 After such a printout, the @code{list} command with no arguments
4422 prints ten lines centered on the point of execution in the frame.
4423 You can also edit the program at the point of execution with your favorite
4424 editing program by typing @code{edit}.
4425 @xref{List, ,Printing source lines},
4429 @kindex down-silently
4431 @item up-silently @var{n}
4432 @itemx down-silently @var{n}
4433 These two commands are variants of @code{up} and @code{down},
4434 respectively; they differ in that they do their work silently, without
4435 causing display of the new frame. They are intended primarily for use
4436 in @value{GDBN} command scripts, where the output might be unnecessary and
4441 @section Information about a frame
4443 There are several other commands to print information about the selected
4449 When used without any argument, this command does not change which
4450 frame is selected, but prints a brief description of the currently
4451 selected stack frame. It can be abbreviated @code{f}. With an
4452 argument, this command is used to select a stack frame.
4453 @xref{Selection, ,Selecting a frame}.
4456 @kindex info f @r{(@code{info frame})}
4459 This command prints a verbose description of the selected stack frame,
4464 the address of the frame
4466 the address of the next frame down (called by this frame)
4468 the address of the next frame up (caller of this frame)
4470 the language in which the source code corresponding to this frame is written
4472 the address of the frame's arguments
4474 the address of the frame's local variables
4476 the program counter saved in it (the address of execution in the caller frame)
4478 which registers were saved in the frame
4481 @noindent The verbose description is useful when
4482 something has gone wrong that has made the stack format fail to fit
4483 the usual conventions.
4485 @item info frame @var{addr}
4486 @itemx info f @var{addr}
4487 Print a verbose description of the frame at address @var{addr}, without
4488 selecting that frame. The selected frame remains unchanged by this
4489 command. This requires the same kind of address (more than one for some
4490 architectures) that you specify in the @code{frame} command.
4491 @xref{Selection, ,Selecting a frame}.
4495 Print the arguments of the selected frame, each on a separate line.
4499 Print the local variables of the selected frame, each on a separate
4500 line. These are all variables (declared either static or automatic)
4501 accessible at the point of execution of the selected frame.
4504 @cindex catch exceptions, list active handlers
4505 @cindex exception handlers, how to list
4507 Print a list of all the exception handlers that are active in the
4508 current stack frame at the current point of execution. To see other
4509 exception handlers, visit the associated frame (using the @code{up},
4510 @code{down}, or @code{frame} commands); then type @code{info catch}.
4511 @xref{Set Catchpoints, , Setting catchpoints}.
4517 @chapter Examining Source Files
4519 @value{GDBN} can print parts of your program's source, since the debugging
4520 information recorded in the program tells @value{GDBN} what source files were
4521 used to build it. When your program stops, @value{GDBN} spontaneously prints
4522 the line where it stopped. Likewise, when you select a stack frame
4523 (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
4524 execution in that frame has stopped. You can print other portions of
4525 source files by explicit command.
4527 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4528 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4529 @value{GDBN} under @sc{gnu} Emacs}.
4532 * List:: Printing source lines
4533 * Edit:: Editing source files
4534 * Search:: Searching source files
4535 * Source Path:: Specifying source directories
4536 * Machine Code:: Source and machine code
4540 @section Printing source lines
4543 @kindex l @r{(@code{list})}
4544 To print lines from a source file, use the @code{list} command
4545 (abbreviated @code{l}). By default, ten lines are printed.
4546 There are several ways to specify what part of the file you want to print.
4548 Here are the forms of the @code{list} command most commonly used:
4551 @item list @var{linenum}
4552 Print lines centered around line number @var{linenum} in the
4553 current source file.
4555 @item list @var{function}
4556 Print lines centered around the beginning of function
4560 Print more lines. If the last lines printed were printed with a
4561 @code{list} command, this prints lines following the last lines
4562 printed; however, if the last line printed was a solitary line printed
4563 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4564 Stack}), this prints lines centered around that line.
4567 Print lines just before the lines last printed.
4570 @cindex @code{list}, how many lines to display
4571 By default, @value{GDBN} prints ten source lines with any of these forms of
4572 the @code{list} command. You can change this using @code{set listsize}:
4575 @kindex set listsize
4576 @item set listsize @var{count}
4577 Make the @code{list} command display @var{count} source lines (unless
4578 the @code{list} argument explicitly specifies some other number).
4580 @kindex show listsize
4582 Display the number of lines that @code{list} prints.
4585 Repeating a @code{list} command with @key{RET} discards the argument,
4586 so it is equivalent to typing just @code{list}. This is more useful
4587 than listing the same lines again. An exception is made for an
4588 argument of @samp{-}; that argument is preserved in repetition so that
4589 each repetition moves up in the source file.
4592 In general, the @code{list} command expects you to supply zero, one or two
4593 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4594 of writing them, but the effect is always to specify some source line.
4595 Here is a complete description of the possible arguments for @code{list}:
4598 @item list @var{linespec}
4599 Print lines centered around the line specified by @var{linespec}.
4601 @item list @var{first},@var{last}
4602 Print lines from @var{first} to @var{last}. Both arguments are
4605 @item list ,@var{last}
4606 Print lines ending with @var{last}.
4608 @item list @var{first},
4609 Print lines starting with @var{first}.
4612 Print lines just after the lines last printed.
4615 Print lines just before the lines last printed.
4618 As described in the preceding table.
4621 Here are the ways of specifying a single source line---all the
4626 Specifies line @var{number} of the current source file.
4627 When a @code{list} command has two linespecs, this refers to
4628 the same source file as the first linespec.
4631 Specifies the line @var{offset} lines after the last line printed.
4632 When used as the second linespec in a @code{list} command that has
4633 two, this specifies the line @var{offset} lines down from the
4637 Specifies the line @var{offset} lines before the last line printed.
4639 @item @var{filename}:@var{number}
4640 Specifies line @var{number} in the source file @var{filename}.
4642 @item @var{function}
4643 Specifies the line that begins the body of the function @var{function}.
4644 For example: in C, this is the line with the open brace.
4646 @item @var{filename}:@var{function}
4647 Specifies the line of the open-brace that begins the body of the
4648 function @var{function} in the file @var{filename}. You only need the
4649 file name with a function name to avoid ambiguity when there are
4650 identically named functions in different source files.
4652 @item *@var{address}
4653 Specifies the line containing the program address @var{address}.
4654 @var{address} may be any expression.
4658 @section Editing source files
4659 @cindex editing source files
4662 @kindex e @r{(@code{edit})}
4663 To edit the lines in a source file, use the @code{edit} command.
4664 The editing program of your choice
4665 is invoked with the current line set to
4666 the active line in the program.
4667 Alternatively, there are several ways to specify what part of the file you
4668 want to print if you want to see other parts of the program.
4670 Here are the forms of the @code{edit} command most commonly used:
4674 Edit the current source file at the active line number in the program.
4676 @item edit @var{number}
4677 Edit the current source file with @var{number} as the active line number.
4679 @item edit @var{function}
4680 Edit the file containing @var{function} at the beginning of its definition.
4682 @item edit @var{filename}:@var{number}
4683 Specifies line @var{number} in the source file @var{filename}.
4685 @item edit @var{filename}:@var{function}
4686 Specifies the line that begins the body of the
4687 function @var{function} in the file @var{filename}. You only need the
4688 file name with a function name to avoid ambiguity when there are
4689 identically named functions in different source files.
4691 @item edit *@var{address}
4692 Specifies the line containing the program address @var{address}.
4693 @var{address} may be any expression.
4696 @subsection Choosing your editor
4697 You can customize @value{GDBN} to use any editor you want
4699 The only restriction is that your editor (say @code{ex}), recognizes the
4700 following command-line syntax:
4702 ex +@var{number} file
4704 The optional numeric value +@var{number} specifies the number of the line in
4705 the file where to start editing.}.
4706 By default, it is @file{@value{EDITOR}}, but you can change this
4707 by setting the environment variable @code{EDITOR} before using
4708 @value{GDBN}. For example, to configure @value{GDBN} to use the
4709 @code{vi} editor, you could use these commands with the @code{sh} shell:
4715 or in the @code{csh} shell,
4717 setenv EDITOR /usr/bin/vi
4722 @section Searching source files
4723 @cindex searching source files
4725 There are two commands for searching through the current source file for a
4730 @kindex forward-search
4731 @item forward-search @var{regexp}
4732 @itemx search @var{regexp}
4733 The command @samp{forward-search @var{regexp}} checks each line,
4734 starting with the one following the last line listed, for a match for
4735 @var{regexp}. It lists the line that is found. You can use the
4736 synonym @samp{search @var{regexp}} or abbreviate the command name as
4739 @kindex reverse-search
4740 @item reverse-search @var{regexp}
4741 The command @samp{reverse-search @var{regexp}} checks each line, starting
4742 with the one before the last line listed and going backward, for a match
4743 for @var{regexp}. It lists the line that is found. You can abbreviate
4744 this command as @code{rev}.
4748 @section Specifying source directories
4751 @cindex directories for source files
4752 Executable programs sometimes do not record the directories of the source
4753 files from which they were compiled, just the names. Even when they do,
4754 the directories could be moved between the compilation and your debugging
4755 session. @value{GDBN} has a list of directories to search for source files;
4756 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
4757 it tries all the directories in the list, in the order they are present
4758 in the list, until it finds a file with the desired name.
4760 For example, suppose an executable references the file
4761 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
4762 @file{/mnt/cross}. The file is first looked up literally; if this
4763 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
4764 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
4765 message is printed. @value{GDBN} does not look up the parts of the
4766 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
4767 Likewise, the subdirectories of the source path are not searched: if
4768 the source path is @file{/mnt/cross}, and the binary refers to
4769 @file{foo.c}, @value{GDBN} would not find it under
4770 @file{/mnt/cross/usr/src/foo-1.0/lib}.
4772 Plain file names, relative file names with leading directories, file
4773 names containing dots, etc.@: are all treated as described above; for
4774 instance, if the source path is @file{/mnt/cross}, and the source file
4775 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
4776 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
4777 that---@file{/mnt/cross/foo.c}.
4779 Note that the executable search path is @emph{not} used to locate the
4780 source files. Neither is the current working directory, unless it
4781 happens to be in the source path.
4783 Whenever you reset or rearrange the source path, @value{GDBN} clears out
4784 any information it has cached about where source files are found and where
4785 each line is in the file.
4789 When you start @value{GDBN}, its source path includes only @samp{cdir}
4790 and @samp{cwd}, in that order.
4791 To add other directories, use the @code{directory} command.
4794 @item directory @var{dirname} @dots{}
4795 @item dir @var{dirname} @dots{}
4796 Add directory @var{dirname} to the front of the source path. Several
4797 directory names may be given to this command, separated by @samp{:}
4798 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
4799 part of absolute file names) or
4800 whitespace. You may specify a directory that is already in the source
4801 path; this moves it forward, so @value{GDBN} searches it sooner.
4805 @vindex $cdir@r{, convenience variable}
4806 @vindex $cwdr@r{, convenience variable}
4807 @cindex compilation directory
4808 @cindex current directory
4809 @cindex working directory
4810 @cindex directory, current
4811 @cindex directory, compilation
4812 You can use the string @samp{$cdir} to refer to the compilation
4813 directory (if one is recorded), and @samp{$cwd} to refer to the current
4814 working directory. @samp{$cwd} is not the same as @samp{.}---the former
4815 tracks the current working directory as it changes during your @value{GDBN}
4816 session, while the latter is immediately expanded to the current
4817 directory at the time you add an entry to the source path.
4820 Reset the source path to empty again. This requires confirmation.
4822 @c RET-repeat for @code{directory} is explicitly disabled, but since
4823 @c repeating it would be a no-op we do not say that. (thanks to RMS)
4825 @item show directories
4826 @kindex show directories
4827 Print the source path: show which directories it contains.
4830 If your source path is cluttered with directories that are no longer of
4831 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
4832 versions of source. You can correct the situation as follows:
4836 Use @code{directory} with no argument to reset the source path to empty.
4839 Use @code{directory} with suitable arguments to reinstall the
4840 directories you want in the source path. You can add all the
4841 directories in one command.
4845 @section Source and machine code
4846 @cindex source line and its code address
4848 You can use the command @code{info line} to map source lines to program
4849 addresses (and vice versa), and the command @code{disassemble} to display
4850 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
4851 mode, the @code{info line} command causes the arrow to point to the
4852 line specified. Also, @code{info line} prints addresses in symbolic form as
4857 @item info line @var{linespec}
4858 Print the starting and ending addresses of the compiled code for
4859 source line @var{linespec}. You can specify source lines in any of
4860 the ways understood by the @code{list} command (@pxref{List, ,Printing
4864 For example, we can use @code{info line} to discover the location of
4865 the object code for the first line of function
4866 @code{m4_changequote}:
4868 @c FIXME: I think this example should also show the addresses in
4869 @c symbolic form, as they usually would be displayed.
4871 (@value{GDBP}) info line m4_changequote
4872 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
4876 @cindex code address and its source line
4877 We can also inquire (using @code{*@var{addr}} as the form for
4878 @var{linespec}) what source line covers a particular address:
4880 (@value{GDBP}) info line *0x63ff
4881 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
4884 @cindex @code{$_} and @code{info line}
4885 @cindex @code{x} command, default address
4886 @kindex x@r{(examine), and} info line
4887 After @code{info line}, the default address for the @code{x} command
4888 is changed to the starting address of the line, so that @samp{x/i} is
4889 sufficient to begin examining the machine code (@pxref{Memory,
4890 ,Examining memory}). Also, this address is saved as the value of the
4891 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
4896 @cindex assembly instructions
4897 @cindex instructions, assembly
4898 @cindex machine instructions
4899 @cindex listing machine instructions
4901 This specialized command dumps a range of memory as machine
4902 instructions. The default memory range is the function surrounding the
4903 program counter of the selected frame. A single argument to this
4904 command is a program counter value; @value{GDBN} dumps the function
4905 surrounding this value. Two arguments specify a range of addresses
4906 (first inclusive, second exclusive) to dump.
4909 The following example shows the disassembly of a range of addresses of
4910 HP PA-RISC 2.0 code:
4913 (@value{GDBP}) disas 0x32c4 0x32e4
4914 Dump of assembler code from 0x32c4 to 0x32e4:
4915 0x32c4 <main+204>: addil 0,dp
4916 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
4917 0x32cc <main+212>: ldil 0x3000,r31
4918 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
4919 0x32d4 <main+220>: ldo 0(r31),rp
4920 0x32d8 <main+224>: addil -0x800,dp
4921 0x32dc <main+228>: ldo 0x588(r1),r26
4922 0x32e0 <main+232>: ldil 0x3000,r31
4923 End of assembler dump.
4926 Some architectures have more than one commonly-used set of instruction
4927 mnemonics or other syntax.
4929 For programs that were dynamically linked and use shared libraries,
4930 instructions that call functions or branch to locations in the shared
4931 libraries might show a seemingly bogus location---it's actually a
4932 location of the relocation table. On some architectures, @value{GDBN}
4933 might be able to resolve these to actual function names.
4936 @kindex set disassembly-flavor
4937 @cindex Intel disassembly flavor
4938 @cindex AT&T disassembly flavor
4939 @item set disassembly-flavor @var{instruction-set}
4940 Select the instruction set to use when disassembling the
4941 program via the @code{disassemble} or @code{x/i} commands.
4943 Currently this command is only defined for the Intel x86 family. You
4944 can set @var{instruction-set} to either @code{intel} or @code{att}.
4945 The default is @code{att}, the AT&T flavor used by default by Unix
4946 assemblers for x86-based targets.
4948 @kindex show disassembly-flavor
4949 @item show disassembly-flavor
4950 Show the current setting of the disassembly flavor.
4955 @chapter Examining Data
4957 @cindex printing data
4958 @cindex examining data
4961 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
4962 @c document because it is nonstandard... Under Epoch it displays in a
4963 @c different window or something like that.
4964 The usual way to examine data in your program is with the @code{print}
4965 command (abbreviated @code{p}), or its synonym @code{inspect}. It
4966 evaluates and prints the value of an expression of the language your
4967 program is written in (@pxref{Languages, ,Using @value{GDBN} with
4968 Different Languages}).
4971 @item print @var{expr}
4972 @itemx print /@var{f} @var{expr}
4973 @var{expr} is an expression (in the source language). By default the
4974 value of @var{expr} is printed in a format appropriate to its data type;
4975 you can choose a different format by specifying @samp{/@var{f}}, where
4976 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
4980 @itemx print /@var{f}
4981 @cindex reprint the last value
4982 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
4983 @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
4984 conveniently inspect the same value in an alternative format.
4987 A more low-level way of examining data is with the @code{x} command.
4988 It examines data in memory at a specified address and prints it in a
4989 specified format. @xref{Memory, ,Examining memory}.
4991 If you are interested in information about types, or about how the
4992 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
4993 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
4997 * Expressions:: Expressions
4998 * Variables:: Program variables
4999 * Arrays:: Artificial arrays
5000 * Output Formats:: Output formats
5001 * Memory:: Examining memory
5002 * Auto Display:: Automatic display
5003 * Print Settings:: Print settings
5004 * Value History:: Value history
5005 * Convenience Vars:: Convenience variables
5006 * Registers:: Registers
5007 * Floating Point Hardware:: Floating point hardware
5008 * Vector Unit:: Vector Unit
5009 * OS Information:: Auxiliary data provided by operating system
5010 * Memory Region Attributes:: Memory region attributes
5011 * Dump/Restore Files:: Copy between memory and a file
5012 * Core File Generation:: Cause a program dump its core
5013 * Character Sets:: Debugging programs that use a different
5014 character set than GDB does
5015 * Caching Remote Data:: Data caching for remote targets
5019 @section Expressions
5022 @code{print} and many other @value{GDBN} commands accept an expression and
5023 compute its value. Any kind of constant, variable or operator defined
5024 by the programming language you are using is valid in an expression in
5025 @value{GDBN}. This includes conditional expressions, function calls,
5026 casts, and string constants. It also includes preprocessor macros, if
5027 you compiled your program to include this information; see
5030 @cindex arrays in expressions
5031 @value{GDBN} supports array constants in expressions input by
5032 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
5033 you can use the command @code{print @{1, 2, 3@}} to build up an array in
5034 memory that is @code{malloc}ed in the target program.
5036 Because C is so widespread, most of the expressions shown in examples in
5037 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
5038 Languages}, for information on how to use expressions in other
5041 In this section, we discuss operators that you can use in @value{GDBN}
5042 expressions regardless of your programming language.
5044 @cindex casts, in expressions
5045 Casts are supported in all languages, not just in C, because it is so
5046 useful to cast a number into a pointer in order to examine a structure
5047 at that address in memory.
5048 @c FIXME: casts supported---Mod2 true?
5050 @value{GDBN} supports these operators, in addition to those common
5051 to programming languages:
5055 @samp{@@} is a binary operator for treating parts of memory as arrays.
5056 @xref{Arrays, ,Artificial arrays}, for more information.
5059 @samp{::} allows you to specify a variable in terms of the file or
5060 function where it is defined. @xref{Variables, ,Program variables}.
5062 @cindex @{@var{type}@}
5063 @cindex type casting memory
5064 @cindex memory, viewing as typed object
5065 @cindex casts, to view memory
5066 @item @{@var{type}@} @var{addr}
5067 Refers to an object of type @var{type} stored at address @var{addr} in
5068 memory. @var{addr} may be any expression whose value is an integer or
5069 pointer (but parentheses are required around binary operators, just as in
5070 a cast). This construct is allowed regardless of what kind of data is
5071 normally supposed to reside at @var{addr}.
5075 @section Program variables
5077 The most common kind of expression to use is the name of a variable
5080 Variables in expressions are understood in the selected stack frame
5081 (@pxref{Selection, ,Selecting a frame}); they must be either:
5085 global (or file-static)
5092 visible according to the scope rules of the
5093 programming language from the point of execution in that frame
5096 @noindent This means that in the function
5111 you can examine and use the variable @code{a} whenever your program is
5112 executing within the function @code{foo}, but you can only use or
5113 examine the variable @code{b} while your program is executing inside
5114 the block where @code{b} is declared.
5116 @cindex variable name conflict
5117 There is an exception: you can refer to a variable or function whose
5118 scope is a single source file even if the current execution point is not
5119 in this file. But it is possible to have more than one such variable or
5120 function with the same name (in different source files). If that
5121 happens, referring to that name has unpredictable effects. If you wish,
5122 you can specify a static variable in a particular function or file,
5123 using the colon-colon (@code{::}) notation:
5125 @cindex colon-colon, context for variables/functions
5127 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
5128 @cindex @code{::}, context for variables/functions
5131 @var{file}::@var{variable}
5132 @var{function}::@var{variable}
5136 Here @var{file} or @var{function} is the name of the context for the
5137 static @var{variable}. In the case of file names, you can use quotes to
5138 make sure @value{GDBN} parses the file name as a single word---for example,
5139 to print a global value of @code{x} defined in @file{f2.c}:
5142 (@value{GDBP}) p 'f2.c'::x
5145 @cindex C@t{++} scope resolution
5146 This use of @samp{::} is very rarely in conflict with the very similar
5147 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
5148 scope resolution operator in @value{GDBN} expressions.
5149 @c FIXME: Um, so what happens in one of those rare cases where it's in
5152 @cindex wrong values
5153 @cindex variable values, wrong
5154 @cindex function entry/exit, wrong values of variables
5155 @cindex optimized code, wrong values of variables
5157 @emph{Warning:} Occasionally, a local variable may appear to have the
5158 wrong value at certain points in a function---just after entry to a new
5159 scope, and just before exit.
5161 You may see this problem when you are stepping by machine instructions.
5162 This is because, on most machines, it takes more than one instruction to
5163 set up a stack frame (including local variable definitions); if you are
5164 stepping by machine instructions, variables may appear to have the wrong
5165 values until the stack frame is completely built. On exit, it usually
5166 also takes more than one machine instruction to destroy a stack frame;
5167 after you begin stepping through that group of instructions, local
5168 variable definitions may be gone.
5170 This may also happen when the compiler does significant optimizations.
5171 To be sure of always seeing accurate values, turn off all optimization
5174 @cindex ``No symbol "foo" in current context''
5175 Another possible effect of compiler optimizations is to optimize
5176 unused variables out of existence, or assign variables to registers (as
5177 opposed to memory addresses). Depending on the support for such cases
5178 offered by the debug info format used by the compiler, @value{GDBN}
5179 might not be able to display values for such local variables. If that
5180 happens, @value{GDBN} will print a message like this:
5183 No symbol "foo" in current context.
5186 To solve such problems, either recompile without optimizations, or use a
5187 different debug info format, if the compiler supports several such
5188 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
5189 usually supports the @option{-gstabs+} option. @option{-gstabs+}
5190 produces debug info in a format that is superior to formats such as
5191 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
5192 an effective form for debug info. @xref{Debugging Options,,Options
5193 for Debugging Your Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}.
5194 @xref{C, , Debugging C++}, for more info about debug info formats
5195 that are best suited to C@t{++} programs.
5198 @section Artificial arrays
5200 @cindex artificial array
5202 @kindex @@@r{, referencing memory as an array}
5203 It is often useful to print out several successive objects of the
5204 same type in memory; a section of an array, or an array of
5205 dynamically determined size for which only a pointer exists in the
5208 You can do this by referring to a contiguous span of memory as an
5209 @dfn{artificial array}, using the binary operator @samp{@@}. The left
5210 operand of @samp{@@} should be the first element of the desired array
5211 and be an individual object. The right operand should be the desired length
5212 of the array. The result is an array value whose elements are all of
5213 the type of the left argument. The first element is actually the left
5214 argument; the second element comes from bytes of memory immediately
5215 following those that hold the first element, and so on. Here is an
5216 example. If a program says
5219 int *array = (int *) malloc (len * sizeof (int));
5223 you can print the contents of @code{array} with
5229 The left operand of @samp{@@} must reside in memory. Array values made
5230 with @samp{@@} in this way behave just like other arrays in terms of
5231 subscripting, and are coerced to pointers when used in expressions.
5232 Artificial arrays most often appear in expressions via the value history
5233 (@pxref{Value History, ,Value history}), after printing one out.
5235 Another way to create an artificial array is to use a cast.
5236 This re-interprets a value as if it were an array.
5237 The value need not be in memory:
5239 (@value{GDBP}) p/x (short[2])0x12345678
5240 $1 = @{0x1234, 0x5678@}
5243 As a convenience, if you leave the array length out (as in
5244 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5245 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5247 (@value{GDBP}) p/x (short[])0x12345678
5248 $2 = @{0x1234, 0x5678@}
5251 Sometimes the artificial array mechanism is not quite enough; in
5252 moderately complex data structures, the elements of interest may not
5253 actually be adjacent---for example, if you are interested in the values
5254 of pointers in an array. One useful work-around in this situation is
5255 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5256 variables}) as a counter in an expression that prints the first
5257 interesting value, and then repeat that expression via @key{RET}. For
5258 instance, suppose you have an array @code{dtab} of pointers to
5259 structures, and you are interested in the values of a field @code{fv}
5260 in each structure. Here is an example of what you might type:
5270 @node Output Formats
5271 @section Output formats
5273 @cindex formatted output
5274 @cindex output formats
5275 By default, @value{GDBN} prints a value according to its data type. Sometimes
5276 this is not what you want. For example, you might want to print a number
5277 in hex, or a pointer in decimal. Or you might want to view data in memory
5278 at a certain address as a character string or as an instruction. To do
5279 these things, specify an @dfn{output format} when you print a value.
5281 The simplest use of output formats is to say how to print a value
5282 already computed. This is done by starting the arguments of the
5283 @code{print} command with a slash and a format letter. The format
5284 letters supported are:
5288 Regard the bits of the value as an integer, and print the integer in
5292 Print as integer in signed decimal.
5295 Print as integer in unsigned decimal.
5298 Print as integer in octal.
5301 Print as integer in binary. The letter @samp{t} stands for ``two''.
5302 @footnote{@samp{b} cannot be used because these format letters are also
5303 used with the @code{x} command, where @samp{b} stands for ``byte'';
5304 see @ref{Memory,,Examining memory}.}
5307 @cindex unknown address, locating
5308 @cindex locate address
5309 Print as an address, both absolute in hexadecimal and as an offset from
5310 the nearest preceding symbol. You can use this format used to discover
5311 where (in what function) an unknown address is located:
5314 (@value{GDBP}) p/a 0x54320
5315 $3 = 0x54320 <_initialize_vx+396>
5319 The command @code{info symbol 0x54320} yields similar results.
5320 @xref{Symbols, info symbol}.
5323 Regard as an integer and print it as a character constant. This
5324 prints both the numerical value and its character representation. The
5325 character representation is replaced with the octal escape @samp{\nnn}
5326 for characters outside the 7-bit @sc{ascii} range.
5329 Regard the bits of the value as a floating point number and print
5330 using typical floating point syntax.
5333 For example, to print the program counter in hex (@pxref{Registers}), type
5340 Note that no space is required before the slash; this is because command
5341 names in @value{GDBN} cannot contain a slash.
5343 To reprint the last value in the value history with a different format,
5344 you can use the @code{print} command with just a format and no
5345 expression. For example, @samp{p/x} reprints the last value in hex.
5348 @section Examining memory
5350 You can use the command @code{x} (for ``examine'') to examine memory in
5351 any of several formats, independently of your program's data types.
5353 @cindex examining memory
5355 @kindex x @r{(examine memory)}
5356 @item x/@var{nfu} @var{addr}
5359 Use the @code{x} command to examine memory.
5362 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5363 much memory to display and how to format it; @var{addr} is an
5364 expression giving the address where you want to start displaying memory.
5365 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5366 Several commands set convenient defaults for @var{addr}.
5369 @item @var{n}, the repeat count
5370 The repeat count is a decimal integer; the default is 1. It specifies
5371 how much memory (counting by units @var{u}) to display.
5372 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5375 @item @var{f}, the display format
5376 The display format is one of the formats used by @code{print}
5377 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
5378 @samp{f}), and in addition @samp{s} (for null-terminated strings) and
5379 @samp{i} (for machine instructions). The default is @samp{x}
5380 (hexadecimal) initially. The default changes each time you use either
5381 @code{x} or @code{print}.
5383 @item @var{u}, the unit size
5384 The unit size is any of
5390 Halfwords (two bytes).
5392 Words (four bytes). This is the initial default.
5394 Giant words (eight bytes).
5397 Each time you specify a unit size with @code{x}, that size becomes the
5398 default unit the next time you use @code{x}. (For the @samp{s} and
5399 @samp{i} formats, the unit size is ignored and is normally not written.)
5401 @item @var{addr}, starting display address
5402 @var{addr} is the address where you want @value{GDBN} to begin displaying
5403 memory. The expression need not have a pointer value (though it may);
5404 it is always interpreted as an integer address of a byte of memory.
5405 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5406 @var{addr} is usually just after the last address examined---but several
5407 other commands also set the default address: @code{info breakpoints} (to
5408 the address of the last breakpoint listed), @code{info line} (to the
5409 starting address of a line), and @code{print} (if you use it to display
5410 a value from memory).
5413 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5414 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5415 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5416 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5417 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5419 Since the letters indicating unit sizes are all distinct from the
5420 letters specifying output formats, you do not have to remember whether
5421 unit size or format comes first; either order works. The output
5422 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5423 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5425 Even though the unit size @var{u} is ignored for the formats @samp{s}
5426 and @samp{i}, you might still want to use a count @var{n}; for example,
5427 @samp{3i} specifies that you want to see three machine instructions,
5428 including any operands. The command @code{disassemble} gives an
5429 alternative way of inspecting machine instructions; see @ref{Machine
5430 Code,,Source and machine code}.
5432 All the defaults for the arguments to @code{x} are designed to make it
5433 easy to continue scanning memory with minimal specifications each time
5434 you use @code{x}. For example, after you have inspected three machine
5435 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5436 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5437 the repeat count @var{n} is used again; the other arguments default as
5438 for successive uses of @code{x}.
5440 @cindex @code{$_}, @code{$__}, and value history
5441 The addresses and contents printed by the @code{x} command are not saved
5442 in the value history because there is often too much of them and they
5443 would get in the way. Instead, @value{GDBN} makes these values available for
5444 subsequent use in expressions as values of the convenience variables
5445 @code{$_} and @code{$__}. After an @code{x} command, the last address
5446 examined is available for use in expressions in the convenience variable
5447 @code{$_}. The contents of that address, as examined, are available in
5448 the convenience variable @code{$__}.
5450 If the @code{x} command has a repeat count, the address and contents saved
5451 are from the last memory unit printed; this is not the same as the last
5452 address printed if several units were printed on the last line of output.
5454 @cindex remote memory comparison
5455 @cindex verify remote memory image
5456 When you are debugging a program running on a remote target machine
5457 (@pxref{Remote}), you may wish to verify the program's image in the
5458 remote machine's memory against the executable file you downloaded to
5459 the target. The @code{compare-sections} command is provided for such
5463 @kindex compare-sections
5464 @item compare-sections @r{[}@var{section-name}@r{]}
5465 Compare the data of a loadable section @var{section-name} in the
5466 executable file of the program being debugged with the same section in
5467 the remote machine's memory, and report any mismatches. With no
5468 arguments, compares all loadable sections. This command's
5469 availability depends on the target's support for the @code{"qCRC"}
5474 @section Automatic display
5475 @cindex automatic display
5476 @cindex display of expressions
5478 If you find that you want to print the value of an expression frequently
5479 (to see how it changes), you might want to add it to the @dfn{automatic
5480 display list} so that @value{GDBN} prints its value each time your program stops.
5481 Each expression added to the list is given a number to identify it;
5482 to remove an expression from the list, you specify that number.
5483 The automatic display looks like this:
5487 3: bar[5] = (struct hack *) 0x3804
5491 This display shows item numbers, expressions and their current values. As with
5492 displays you request manually using @code{x} or @code{print}, you can
5493 specify the output format you prefer; in fact, @code{display} decides
5494 whether to use @code{print} or @code{x} depending on how elaborate your
5495 format specification is---it uses @code{x} if you specify a unit size,
5496 or one of the two formats (@samp{i} and @samp{s}) that are only
5497 supported by @code{x}; otherwise it uses @code{print}.
5501 @item display @var{expr}
5502 Add the expression @var{expr} to the list of expressions to display
5503 each time your program stops. @xref{Expressions, ,Expressions}.
5505 @code{display} does not repeat if you press @key{RET} again after using it.
5507 @item display/@var{fmt} @var{expr}
5508 For @var{fmt} specifying only a display format and not a size or
5509 count, add the expression @var{expr} to the auto-display list but
5510 arrange to display it each time in the specified format @var{fmt}.
5511 @xref{Output Formats,,Output formats}.
5513 @item display/@var{fmt} @var{addr}
5514 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
5515 number of units, add the expression @var{addr} as a memory address to
5516 be examined each time your program stops. Examining means in effect
5517 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
5520 For example, @samp{display/i $pc} can be helpful, to see the machine
5521 instruction about to be executed each time execution stops (@samp{$pc}
5522 is a common name for the program counter; @pxref{Registers, ,Registers}).
5525 @kindex delete display
5527 @item undisplay @var{dnums}@dots{}
5528 @itemx delete display @var{dnums}@dots{}
5529 Remove item numbers @var{dnums} from the list of expressions to display.
5531 @code{undisplay} does not repeat if you press @key{RET} after using it.
5532 (Otherwise you would just get the error @samp{No display number @dots{}}.)
5534 @kindex disable display
5535 @item disable display @var{dnums}@dots{}
5536 Disable the display of item numbers @var{dnums}. A disabled display
5537 item is not printed automatically, but is not forgotten. It may be
5538 enabled again later.
5540 @kindex enable display
5541 @item enable display @var{dnums}@dots{}
5542 Enable display of item numbers @var{dnums}. It becomes effective once
5543 again in auto display of its expression, until you specify otherwise.
5546 Display the current values of the expressions on the list, just as is
5547 done when your program stops.
5549 @kindex info display
5551 Print the list of expressions previously set up to display
5552 automatically, each one with its item number, but without showing the
5553 values. This includes disabled expressions, which are marked as such.
5554 It also includes expressions which would not be displayed right now
5555 because they refer to automatic variables not currently available.
5558 @cindex display disabled out of scope
5559 If a display expression refers to local variables, then it does not make
5560 sense outside the lexical context for which it was set up. Such an
5561 expression is disabled when execution enters a context where one of its
5562 variables is not defined. For example, if you give the command
5563 @code{display last_char} while inside a function with an argument
5564 @code{last_char}, @value{GDBN} displays this argument while your program
5565 continues to stop inside that function. When it stops elsewhere---where
5566 there is no variable @code{last_char}---the display is disabled
5567 automatically. The next time your program stops where @code{last_char}
5568 is meaningful, you can enable the display expression once again.
5570 @node Print Settings
5571 @section Print settings
5573 @cindex format options
5574 @cindex print settings
5575 @value{GDBN} provides the following ways to control how arrays, structures,
5576 and symbols are printed.
5579 These settings are useful for debugging programs in any language:
5583 @item set print address
5584 @itemx set print address on
5585 @cindex print/don't print memory addresses
5586 @value{GDBN} prints memory addresses showing the location of stack
5587 traces, structure values, pointer values, breakpoints, and so forth,
5588 even when it also displays the contents of those addresses. The default
5589 is @code{on}. For example, this is what a stack frame display looks like with
5590 @code{set print address on}:
5595 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
5597 530 if (lquote != def_lquote)
5601 @item set print address off
5602 Do not print addresses when displaying their contents. For example,
5603 this is the same stack frame displayed with @code{set print address off}:
5607 (@value{GDBP}) set print addr off
5609 #0 set_quotes (lq="<<", rq=">>") at input.c:530
5610 530 if (lquote != def_lquote)
5614 You can use @samp{set print address off} to eliminate all machine
5615 dependent displays from the @value{GDBN} interface. For example, with
5616 @code{print address off}, you should get the same text for backtraces on
5617 all machines---whether or not they involve pointer arguments.
5620 @item show print address
5621 Show whether or not addresses are to be printed.
5624 When @value{GDBN} prints a symbolic address, it normally prints the
5625 closest earlier symbol plus an offset. If that symbol does not uniquely
5626 identify the address (for example, it is a name whose scope is a single
5627 source file), you may need to clarify. One way to do this is with
5628 @code{info line}, for example @samp{info line *0x4537}. Alternately,
5629 you can set @value{GDBN} to print the source file and line number when
5630 it prints a symbolic address:
5633 @item set print symbol-filename on
5634 @cindex source file and line of a symbol
5635 @cindex symbol, source file and line
5636 Tell @value{GDBN} to print the source file name and line number of a
5637 symbol in the symbolic form of an address.
5639 @item set print symbol-filename off
5640 Do not print source file name and line number of a symbol. This is the
5643 @item show print symbol-filename
5644 Show whether or not @value{GDBN} will print the source file name and
5645 line number of a symbol in the symbolic form of an address.
5648 Another situation where it is helpful to show symbol filenames and line
5649 numbers is when disassembling code; @value{GDBN} shows you the line
5650 number and source file that corresponds to each instruction.
5652 Also, you may wish to see the symbolic form only if the address being
5653 printed is reasonably close to the closest earlier symbol:
5656 @item set print max-symbolic-offset @var{max-offset}
5657 @cindex maximum value for offset of closest symbol
5658 Tell @value{GDBN} to only display the symbolic form of an address if the
5659 offset between the closest earlier symbol and the address is less than
5660 @var{max-offset}. The default is 0, which tells @value{GDBN}
5661 to always print the symbolic form of an address if any symbol precedes it.
5663 @item show print max-symbolic-offset
5664 Ask how large the maximum offset is that @value{GDBN} prints in a
5668 @cindex wild pointer, interpreting
5669 @cindex pointer, finding referent
5670 If you have a pointer and you are not sure where it points, try
5671 @samp{set print symbol-filename on}. Then you can determine the name
5672 and source file location of the variable where it points, using
5673 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
5674 For example, here @value{GDBN} shows that a variable @code{ptt} points
5675 at another variable @code{t}, defined in @file{hi2.c}:
5678 (@value{GDBP}) set print symbol-filename on
5679 (@value{GDBP}) p/a ptt
5680 $4 = 0xe008 <t in hi2.c>
5684 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
5685 does not show the symbol name and filename of the referent, even with
5686 the appropriate @code{set print} options turned on.
5689 Other settings control how different kinds of objects are printed:
5692 @item set print array
5693 @itemx set print array on
5694 @cindex pretty print arrays
5695 Pretty print arrays. This format is more convenient to read,
5696 but uses more space. The default is off.
5698 @item set print array off
5699 Return to compressed format for arrays.
5701 @item show print array
5702 Show whether compressed or pretty format is selected for displaying
5705 @item set print elements @var{number-of-elements}
5706 @cindex number of array elements to print
5707 @cindex limit on number of printed array elements
5708 Set a limit on how many elements of an array @value{GDBN} will print.
5709 If @value{GDBN} is printing a large array, it stops printing after it has
5710 printed the number of elements set by the @code{set print elements} command.
5711 This limit also applies to the display of strings.
5712 When @value{GDBN} starts, this limit is set to 200.
5713 Setting @var{number-of-elements} to zero means that the printing is unlimited.
5715 @item show print elements
5716 Display the number of elements of a large array that @value{GDBN} will print.
5717 If the number is 0, then the printing is unlimited.
5719 @item set print repeats
5720 @cindex repeated array elements
5721 Set the threshold for suppressing display of repeated array
5722 elelments. When the number of consecutive identical elements of an
5723 array exceeds the threshold, @value{GDBN} prints the string
5724 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
5725 identical repetitions, instead of displaying the identical elements
5726 themselves. Setting the threshold to zero will cause all elements to
5727 be individually printed. The default threshold is 10.
5729 @item show print repeats
5730 Display the current threshold for printing repeated identical
5733 @item set print null-stop
5734 @cindex @sc{null} elements in arrays
5735 Cause @value{GDBN} to stop printing the characters of an array when the first
5736 @sc{null} is encountered. This is useful when large arrays actually
5737 contain only short strings.
5740 @item show print null-stop
5741 Show whether @value{GDBN} stops printing an array on the first
5742 @sc{null} character.
5744 @item set print pretty on
5745 @cindex print structures in indented form
5746 @cindex indentation in structure display
5747 Cause @value{GDBN} to print structures in an indented format with one member
5748 per line, like this:
5763 @item set print pretty off
5764 Cause @value{GDBN} to print structures in a compact format, like this:
5768 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
5769 meat = 0x54 "Pork"@}
5774 This is the default format.
5776 @item show print pretty
5777 Show which format @value{GDBN} is using to print structures.
5779 @item set print sevenbit-strings on
5780 @cindex eight-bit characters in strings
5781 @cindex octal escapes in strings
5782 Print using only seven-bit characters; if this option is set,
5783 @value{GDBN} displays any eight-bit characters (in strings or
5784 character values) using the notation @code{\}@var{nnn}. This setting is
5785 best if you are working in English (@sc{ascii}) and you use the
5786 high-order bit of characters as a marker or ``meta'' bit.
5788 @item set print sevenbit-strings off
5789 Print full eight-bit characters. This allows the use of more
5790 international character sets, and is the default.
5792 @item show print sevenbit-strings
5793 Show whether or not @value{GDBN} is printing only seven-bit characters.
5795 @item set print union on
5796 @cindex unions in structures, printing
5797 Tell @value{GDBN} to print unions which are contained in structures
5798 and other unions. This is the default setting.
5800 @item set print union off
5801 Tell @value{GDBN} not to print unions which are contained in
5802 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
5805 @item show print union
5806 Ask @value{GDBN} whether or not it will print unions which are contained in
5807 structures and other unions.
5809 For example, given the declarations
5812 typedef enum @{Tree, Bug@} Species;
5813 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
5814 typedef enum @{Caterpillar, Cocoon, Butterfly@}
5825 struct thing foo = @{Tree, @{Acorn@}@};
5829 with @code{set print union on} in effect @samp{p foo} would print
5832 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
5836 and with @code{set print union off} in effect it would print
5839 $1 = @{it = Tree, form = @{...@}@}
5843 @code{set print union} affects programs written in C-like languages
5849 These settings are of interest when debugging C@t{++} programs:
5852 @cindex demangling C@t{++} names
5853 @item set print demangle
5854 @itemx set print demangle on
5855 Print C@t{++} names in their source form rather than in the encoded
5856 (``mangled'') form passed to the assembler and linker for type-safe
5857 linkage. The default is on.
5859 @item show print demangle
5860 Show whether C@t{++} names are printed in mangled or demangled form.
5862 @item set print asm-demangle
5863 @itemx set print asm-demangle on
5864 Print C@t{++} names in their source form rather than their mangled form, even
5865 in assembler code printouts such as instruction disassemblies.
5868 @item show print asm-demangle
5869 Show whether C@t{++} names in assembly listings are printed in mangled
5872 @cindex C@t{++} symbol decoding style
5873 @cindex symbol decoding style, C@t{++}
5874 @kindex set demangle-style
5875 @item set demangle-style @var{style}
5876 Choose among several encoding schemes used by different compilers to
5877 represent C@t{++} names. The choices for @var{style} are currently:
5881 Allow @value{GDBN} to choose a decoding style by inspecting your program.
5884 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
5885 This is the default.
5888 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
5891 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
5894 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
5895 @strong{Warning:} this setting alone is not sufficient to allow
5896 debugging @code{cfront}-generated executables. @value{GDBN} would
5897 require further enhancement to permit that.
5900 If you omit @var{style}, you will see a list of possible formats.
5902 @item show demangle-style
5903 Display the encoding style currently in use for decoding C@t{++} symbols.
5905 @item set print object
5906 @itemx set print object on
5907 @cindex derived type of an object, printing
5908 @cindex display derived types
5909 When displaying a pointer to an object, identify the @emph{actual}
5910 (derived) type of the object rather than the @emph{declared} type, using
5911 the virtual function table.
5913 @item set print object off
5914 Display only the declared type of objects, without reference to the
5915 virtual function table. This is the default setting.
5917 @item show print object
5918 Show whether actual, or declared, object types are displayed.
5920 @item set print static-members
5921 @itemx set print static-members on
5922 @cindex static members of C@t{++} objects
5923 Print static members when displaying a C@t{++} object. The default is on.
5925 @item set print static-members off
5926 Do not print static members when displaying a C@t{++} object.
5928 @item show print static-members
5929 Show whether C@t{++} static members are printed or not.
5931 @item set print pascal_static-members
5932 @itemx set print pascal_static-members on
5933 @cindex static members of Pacal objects
5934 @cindex Pacal objects, static members display
5935 Print static members when displaying a Pascal object. The default is on.
5937 @item set print pascal_static-members off
5938 Do not print static members when displaying a Pascal object.
5940 @item show print pascal_static-members
5941 Show whether Pascal static members are printed or not.
5943 @c These don't work with HP ANSI C++ yet.
5944 @item set print vtbl
5945 @itemx set print vtbl on
5946 @cindex pretty print C@t{++} virtual function tables
5947 @cindex virtual functions (C@t{++}) display
5948 @cindex VTBL display
5949 Pretty print C@t{++} virtual function tables. The default is off.
5950 (The @code{vtbl} commands do not work on programs compiled with the HP
5951 ANSI C@t{++} compiler (@code{aCC}).)
5953 @item set print vtbl off
5954 Do not pretty print C@t{++} virtual function tables.
5956 @item show print vtbl
5957 Show whether C@t{++} virtual function tables are pretty printed, or not.
5961 @section Value history
5963 @cindex value history
5964 @cindex history of values printed by @value{GDBN}
5965 Values printed by the @code{print} command are saved in the @value{GDBN}
5966 @dfn{value history}. This allows you to refer to them in other expressions.
5967 Values are kept until the symbol table is re-read or discarded
5968 (for example with the @code{file} or @code{symbol-file} commands).
5969 When the symbol table changes, the value history is discarded,
5970 since the values may contain pointers back to the types defined in the
5975 @cindex history number
5976 The values printed are given @dfn{history numbers} by which you can
5977 refer to them. These are successive integers starting with one.
5978 @code{print} shows you the history number assigned to a value by
5979 printing @samp{$@var{num} = } before the value; here @var{num} is the
5982 To refer to any previous value, use @samp{$} followed by the value's
5983 history number. The way @code{print} labels its output is designed to
5984 remind you of this. Just @code{$} refers to the most recent value in
5985 the history, and @code{$$} refers to the value before that.
5986 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
5987 is the value just prior to @code{$$}, @code{$$1} is equivalent to
5988 @code{$$}, and @code{$$0} is equivalent to @code{$}.
5990 For example, suppose you have just printed a pointer to a structure and
5991 want to see the contents of the structure. It suffices to type
5997 If you have a chain of structures where the component @code{next} points
5998 to the next one, you can print the contents of the next one with this:
6005 You can print successive links in the chain by repeating this
6006 command---which you can do by just typing @key{RET}.
6008 Note that the history records values, not expressions. If the value of
6009 @code{x} is 4 and you type these commands:
6017 then the value recorded in the value history by the @code{print} command
6018 remains 4 even though the value of @code{x} has changed.
6023 Print the last ten values in the value history, with their item numbers.
6024 This is like @samp{p@ $$9} repeated ten times, except that @code{show
6025 values} does not change the history.
6027 @item show values @var{n}
6028 Print ten history values centered on history item number @var{n}.
6031 Print ten history values just after the values last printed. If no more
6032 values are available, @code{show values +} produces no display.
6035 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
6036 same effect as @samp{show values +}.
6038 @node Convenience Vars
6039 @section Convenience variables
6041 @cindex convenience variables
6042 @cindex user-defined variables
6043 @value{GDBN} provides @dfn{convenience variables} that you can use within
6044 @value{GDBN} to hold on to a value and refer to it later. These variables
6045 exist entirely within @value{GDBN}; they are not part of your program, and
6046 setting a convenience variable has no direct effect on further execution
6047 of your program. That is why you can use them freely.
6049 Convenience variables are prefixed with @samp{$}. Any name preceded by
6050 @samp{$} can be used for a convenience variable, unless it is one of
6051 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
6052 (Value history references, in contrast, are @emph{numbers} preceded
6053 by @samp{$}. @xref{Value History, ,Value history}.)
6055 You can save a value in a convenience variable with an assignment
6056 expression, just as you would set a variable in your program.
6060 set $foo = *object_ptr
6064 would save in @code{$foo} the value contained in the object pointed to by
6067 Using a convenience variable for the first time creates it, but its
6068 value is @code{void} until you assign a new value. You can alter the
6069 value with another assignment at any time.
6071 Convenience variables have no fixed types. You can assign a convenience
6072 variable any type of value, including structures and arrays, even if
6073 that variable already has a value of a different type. The convenience
6074 variable, when used as an expression, has the type of its current value.
6077 @kindex show convenience
6078 @cindex show all user variables
6079 @item show convenience
6080 Print a list of convenience variables used so far, and their values.
6081 Abbreviated @code{show conv}.
6084 One of the ways to use a convenience variable is as a counter to be
6085 incremented or a pointer to be advanced. For example, to print
6086 a field from successive elements of an array of structures:
6090 print bar[$i++]->contents
6094 Repeat that command by typing @key{RET}.
6096 Some convenience variables are created automatically by @value{GDBN} and given
6097 values likely to be useful.
6100 @vindex $_@r{, convenience variable}
6102 The variable @code{$_} is automatically set by the @code{x} command to
6103 the last address examined (@pxref{Memory, ,Examining memory}). Other
6104 commands which provide a default address for @code{x} to examine also
6105 set @code{$_} to that address; these commands include @code{info line}
6106 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
6107 except when set by the @code{x} command, in which case it is a pointer
6108 to the type of @code{$__}.
6110 @vindex $__@r{, convenience variable}
6112 The variable @code{$__} is automatically set by the @code{x} command
6113 to the value found in the last address examined. Its type is chosen
6114 to match the format in which the data was printed.
6117 @vindex $_exitcode@r{, convenience variable}
6118 The variable @code{$_exitcode} is automatically set to the exit code when
6119 the program being debugged terminates.
6122 On HP-UX systems, if you refer to a function or variable name that
6123 begins with a dollar sign, @value{GDBN} searches for a user or system
6124 name first, before it searches for a convenience variable.
6130 You can refer to machine register contents, in expressions, as variables
6131 with names starting with @samp{$}. The names of registers are different
6132 for each machine; use @code{info registers} to see the names used on
6136 @kindex info registers
6137 @item info registers
6138 Print the names and values of all registers except floating-point
6139 and vector registers (in the selected stack frame).
6141 @kindex info all-registers
6142 @cindex floating point registers
6143 @item info all-registers
6144 Print the names and values of all registers, including floating-point
6145 and vector registers (in the selected stack frame).
6147 @item info registers @var{regname} @dots{}
6148 Print the @dfn{relativized} value of each specified register @var{regname}.
6149 As discussed in detail below, register values are normally relative to
6150 the selected stack frame. @var{regname} may be any register name valid on
6151 the machine you are using, with or without the initial @samp{$}.
6154 @cindex stack pointer register
6155 @cindex program counter register
6156 @cindex process status register
6157 @cindex frame pointer register
6158 @cindex standard registers
6159 @value{GDBN} has four ``standard'' register names that are available (in
6160 expressions) on most machines---whenever they do not conflict with an
6161 architecture's canonical mnemonics for registers. The register names
6162 @code{$pc} and @code{$sp} are used for the program counter register and
6163 the stack pointer. @code{$fp} is used for a register that contains a
6164 pointer to the current stack frame, and @code{$ps} is used for a
6165 register that contains the processor status. For example,
6166 you could print the program counter in hex with
6173 or print the instruction to be executed next with
6180 or add four to the stack pointer@footnote{This is a way of removing
6181 one word from the stack, on machines where stacks grow downward in
6182 memory (most machines, nowadays). This assumes that the innermost
6183 stack frame is selected; setting @code{$sp} is not allowed when other
6184 stack frames are selected. To pop entire frames off the stack,
6185 regardless of machine architecture, use @code{return};
6186 see @ref{Returning, ,Returning from a function}.} with
6192 Whenever possible, these four standard register names are available on
6193 your machine even though the machine has different canonical mnemonics,
6194 so long as there is no conflict. The @code{info registers} command
6195 shows the canonical names. For example, on the SPARC, @code{info
6196 registers} displays the processor status register as @code{$psr} but you
6197 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
6198 is an alias for the @sc{eflags} register.
6200 @value{GDBN} always considers the contents of an ordinary register as an
6201 integer when the register is examined in this way. Some machines have
6202 special registers which can hold nothing but floating point; these
6203 registers are considered to have floating point values. There is no way
6204 to refer to the contents of an ordinary register as floating point value
6205 (although you can @emph{print} it as a floating point value with
6206 @samp{print/f $@var{regname}}).
6208 Some registers have distinct ``raw'' and ``virtual'' data formats. This
6209 means that the data format in which the register contents are saved by
6210 the operating system is not the same one that your program normally
6211 sees. For example, the registers of the 68881 floating point
6212 coprocessor are always saved in ``extended'' (raw) format, but all C
6213 programs expect to work with ``double'' (virtual) format. In such
6214 cases, @value{GDBN} normally works with the virtual format only (the format
6215 that makes sense for your program), but the @code{info registers} command
6216 prints the data in both formats.
6218 Normally, register values are relative to the selected stack frame
6219 (@pxref{Selection, ,Selecting a frame}). This means that you get the
6220 value that the register would contain if all stack frames farther in
6221 were exited and their saved registers restored. In order to see the
6222 true contents of hardware registers, you must select the innermost
6223 frame (with @samp{frame 0}).
6225 However, @value{GDBN} must deduce where registers are saved, from the machine
6226 code generated by your compiler. If some registers are not saved, or if
6227 @value{GDBN} is unable to locate the saved registers, the selected stack
6228 frame makes no difference.
6230 @node Floating Point Hardware
6231 @section Floating point hardware
6232 @cindex floating point
6234 Depending on the configuration, @value{GDBN} may be able to give
6235 you more information about the status of the floating point hardware.
6240 Display hardware-dependent information about the floating
6241 point unit. The exact contents and layout vary depending on the
6242 floating point chip. Currently, @samp{info float} is supported on
6243 the ARM and x86 machines.
6247 @section Vector Unit
6250 Depending on the configuration, @value{GDBN} may be able to give you
6251 more information about the status of the vector unit.
6256 Display information about the vector unit. The exact contents and
6257 layout vary depending on the hardware.
6260 @node OS Information
6261 @section Operating system auxiliary information
6262 @cindex OS information
6264 @value{GDBN} provides interfaces to useful OS facilities that can help
6265 you debug your program.
6267 @cindex @code{ptrace} system call
6268 @cindex @code{struct user} contents
6269 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
6270 machines), it interfaces with the inferior via the @code{ptrace}
6271 system call. The operating system creates a special sata structure,
6272 called @code{struct user}, for this interface. You can use the
6273 command @code{info udot} to display the contents of this data
6279 Display the contents of the @code{struct user} maintained by the OS
6280 kernel for the program being debugged. @value{GDBN} displays the
6281 contents of @code{struct user} as a list of hex numbers, similar to
6282 the @code{examine} command.
6285 @cindex auxiliary vector
6286 @cindex vector, auxiliary
6287 Some operating systems supply an @dfn{auxiliary vector} to programs at
6288 startup. This is akin to the arguments and environment that you
6289 specify for a program, but contains a system-dependent variety of
6290 binary values that tell system libraries important details about the
6291 hardware, operating system, and process. Each value's purpose is
6292 identified by an integer tag; the meanings are well-known but system-specific.
6293 Depending on the configuration and operating system facilities,
6294 @value{GDBN} may be able to show you this information. For remote
6295 targets, this functionality may further depend on the remote stub's
6296 support of the @samp{qPart:auxv:read} packet, see @ref{Remote
6297 configuration, auxiliary vector}.
6302 Display the auxiliary vector of the inferior, which can be either a
6303 live process or a core dump file. @value{GDBN} prints each tag value
6304 numerically, and also shows names and text descriptions for recognized
6305 tags. Some values in the vector are numbers, some bit masks, and some
6306 pointers to strings or other data. @value{GDBN} displays each value in the
6307 most appropriate form for a recognized tag, and in hexadecimal for
6308 an unrecognized tag.
6312 @node Memory Region Attributes
6313 @section Memory region attributes
6314 @cindex memory region attributes
6316 @dfn{Memory region attributes} allow you to describe special handling
6317 required by regions of your target's memory. @value{GDBN} uses attributes
6318 to determine whether to allow certain types of memory accesses; whether to
6319 use specific width accesses; and whether to cache target memory.
6321 Defined memory regions can be individually enabled and disabled. When a
6322 memory region is disabled, @value{GDBN} uses the default attributes when
6323 accessing memory in that region. Similarly, if no memory regions have
6324 been defined, @value{GDBN} uses the default attributes when accessing
6327 When a memory region is defined, it is given a number to identify it;
6328 to enable, disable, or remove a memory region, you specify that number.
6332 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
6333 Define a memory region bounded by @var{lower} and @var{upper} with
6334 attributes @var{attributes}@dots{}, and add it to the list of regions
6335 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
6336 case: it is treated as the the target's maximum memory address.
6337 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
6340 @item delete mem @var{nums}@dots{}
6341 Remove memory regions @var{nums}@dots{} from the list of regions
6342 monitored by @value{GDBN}.
6345 @item disable mem @var{nums}@dots{}
6346 Disable monitoring of memory regions @var{nums}@dots{}.
6347 A disabled memory region is not forgotten.
6348 It may be enabled again later.
6351 @item enable mem @var{nums}@dots{}
6352 Enable monitoring of memory regions @var{nums}@dots{}.
6356 Print a table of all defined memory regions, with the following columns
6360 @item Memory Region Number
6361 @item Enabled or Disabled.
6362 Enabled memory regions are marked with @samp{y}.
6363 Disabled memory regions are marked with @samp{n}.
6366 The address defining the inclusive lower bound of the memory region.
6369 The address defining the exclusive upper bound of the memory region.
6372 The list of attributes set for this memory region.
6377 @subsection Attributes
6379 @subsubsection Memory Access Mode
6380 The access mode attributes set whether @value{GDBN} may make read or
6381 write accesses to a memory region.
6383 While these attributes prevent @value{GDBN} from performing invalid
6384 memory accesses, they do nothing to prevent the target system, I/O DMA,
6385 etc. from accessing memory.
6389 Memory is read only.
6391 Memory is write only.
6393 Memory is read/write. This is the default.
6396 @subsubsection Memory Access Size
6397 The acccess size attributes tells @value{GDBN} to use specific sized
6398 accesses in the memory region. Often memory mapped device registers
6399 require specific sized accesses. If no access size attribute is
6400 specified, @value{GDBN} may use accesses of any size.
6404 Use 8 bit memory accesses.
6406 Use 16 bit memory accesses.
6408 Use 32 bit memory accesses.
6410 Use 64 bit memory accesses.
6413 @c @subsubsection Hardware/Software Breakpoints
6414 @c The hardware/software breakpoint attributes set whether @value{GDBN}
6415 @c will use hardware or software breakpoints for the internal breakpoints
6416 @c used by the step, next, finish, until, etc. commands.
6420 @c Always use hardware breakpoints
6421 @c @item swbreak (default)
6424 @subsubsection Data Cache
6425 The data cache attributes set whether @value{GDBN} will cache target
6426 memory. While this generally improves performance by reducing debug
6427 protocol overhead, it can lead to incorrect results because @value{GDBN}
6428 does not know about volatile variables or memory mapped device
6433 Enable @value{GDBN} to cache target memory.
6435 Disable @value{GDBN} from caching target memory. This is the default.
6438 @c @subsubsection Memory Write Verification
6439 @c The memory write verification attributes set whether @value{GDBN}
6440 @c will re-reads data after each write to verify the write was successful.
6444 @c @item noverify (default)
6447 @node Dump/Restore Files
6448 @section Copy between memory and a file
6449 @cindex dump/restore files
6450 @cindex append data to a file
6451 @cindex dump data to a file
6452 @cindex restore data from a file
6454 You can use the commands @code{dump}, @code{append}, and
6455 @code{restore} to copy data between target memory and a file. The
6456 @code{dump} and @code{append} commands write data to a file, and the
6457 @code{restore} command reads data from a file back into the inferior's
6458 memory. Files may be in binary, Motorola S-record, Intel hex, or
6459 Tektronix Hex format; however, @value{GDBN} can only append to binary
6465 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6466 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
6467 Dump the contents of memory from @var{start_addr} to @var{end_addr},
6468 or the value of @var{expr}, to @var{filename} in the given format.
6470 The @var{format} parameter may be any one of:
6477 Motorola S-record format.
6479 Tektronix Hex format.
6482 @value{GDBN} uses the same definitions of these formats as the
6483 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
6484 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
6488 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6489 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
6490 Append the contents of memory from @var{start_addr} to @var{end_addr},
6491 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
6492 (@value{GDBN} can only append data to files in raw binary form.)
6495 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
6496 Restore the contents of file @var{filename} into memory. The
6497 @code{restore} command can automatically recognize any known @sc{bfd}
6498 file format, except for raw binary. To restore a raw binary file you
6499 must specify the optional keyword @code{binary} after the filename.
6501 If @var{bias} is non-zero, its value will be added to the addresses
6502 contained in the file. Binary files always start at address zero, so
6503 they will be restored at address @var{bias}. Other bfd files have
6504 a built-in location; they will be restored at offset @var{bias}
6507 If @var{start} and/or @var{end} are non-zero, then only data between
6508 file offset @var{start} and file offset @var{end} will be restored.
6509 These offsets are relative to the addresses in the file, before
6510 the @var{bias} argument is applied.
6514 @node Core File Generation
6515 @section How to Produce a Core File from Your Program
6516 @cindex dump core from inferior
6518 A @dfn{core file} or @dfn{core dump} is a file that records the memory
6519 image of a running process and its process status (register values
6520 etc.). Its primary use is post-mortem debugging of a program that
6521 crashed while it ran outside a debugger. A program that crashes
6522 automatically produces a core file, unless this feature is disabled by
6523 the user. @xref{Files}, for information on invoking @value{GDBN} in
6524 the post-mortem debugging mode.
6526 Occasionally, you may wish to produce a core file of the program you
6527 are debugging in order to preserve a snapshot of its state.
6528 @value{GDBN} has a special command for that.
6532 @kindex generate-core-file
6533 @item generate-core-file [@var{file}]
6534 @itemx gcore [@var{file}]
6535 Produce a core dump of the inferior process. The optional argument
6536 @var{file} specifies the file name where to put the core dump. If not
6537 specified, the file name defaults to @file{core.@var{pid}}, where
6538 @var{pid} is the inferior process ID.
6540 Note that this command is implemented only for some systems (as of
6541 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
6544 @node Character Sets
6545 @section Character Sets
6546 @cindex character sets
6548 @cindex translating between character sets
6549 @cindex host character set
6550 @cindex target character set
6552 If the program you are debugging uses a different character set to
6553 represent characters and strings than the one @value{GDBN} uses itself,
6554 @value{GDBN} can automatically translate between the character sets for
6555 you. The character set @value{GDBN} uses we call the @dfn{host
6556 character set}; the one the inferior program uses we call the
6557 @dfn{target character set}.
6559 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
6560 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
6561 remote protocol (@pxref{Remote,Remote Debugging}) to debug a program
6562 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
6563 then the host character set is Latin-1, and the target character set is
6564 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
6565 target-charset EBCDIC-US}, then @value{GDBN} translates between
6566 @sc{ebcdic} and Latin 1 as you print character or string values, or use
6567 character and string literals in expressions.
6569 @value{GDBN} has no way to automatically recognize which character set
6570 the inferior program uses; you must tell it, using the @code{set
6571 target-charset} command, described below.
6573 Here are the commands for controlling @value{GDBN}'s character set
6577 @item set target-charset @var{charset}
6578 @kindex set target-charset
6579 Set the current target character set to @var{charset}. We list the
6580 character set names @value{GDBN} recognizes below, but if you type
6581 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6582 list the target character sets it supports.
6586 @item set host-charset @var{charset}
6587 @kindex set host-charset
6588 Set the current host character set to @var{charset}.
6590 By default, @value{GDBN} uses a host character set appropriate to the
6591 system it is running on; you can override that default using the
6592 @code{set host-charset} command.
6594 @value{GDBN} can only use certain character sets as its host character
6595 set. We list the character set names @value{GDBN} recognizes below, and
6596 indicate which can be host character sets, but if you type
6597 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6598 list the host character sets it supports.
6600 @item set charset @var{charset}
6602 Set the current host and target character sets to @var{charset}. As
6603 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
6604 @value{GDBN} will list the name of the character sets that can be used
6605 for both host and target.
6609 @kindex show charset
6610 Show the names of the current host and target charsets.
6612 @itemx show host-charset
6613 @kindex show host-charset
6614 Show the name of the current host charset.
6616 @itemx show target-charset
6617 @kindex show target-charset
6618 Show the name of the current target charset.
6622 @value{GDBN} currently includes support for the following character
6628 @cindex ASCII character set
6629 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
6633 @cindex ISO 8859-1 character set
6634 @cindex ISO Latin 1 character set
6635 The ISO Latin 1 character set. This extends @sc{ascii} with accented
6636 characters needed for French, German, and Spanish. @value{GDBN} can use
6637 this as its host character set.
6641 @cindex EBCDIC character set
6642 @cindex IBM1047 character set
6643 Variants of the @sc{ebcdic} character set, used on some of IBM's
6644 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
6645 @value{GDBN} cannot use these as its host character set.
6649 Note that these are all single-byte character sets. More work inside
6650 GDB is needed to support multi-byte or variable-width character
6651 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
6653 Here is an example of @value{GDBN}'s character set support in action.
6654 Assume that the following source code has been placed in the file
6655 @file{charset-test.c}:
6661 = @{72, 101, 108, 108, 111, 44, 32, 119,
6662 111, 114, 108, 100, 33, 10, 0@};
6663 char ibm1047_hello[]
6664 = @{200, 133, 147, 147, 150, 107, 64, 166,
6665 150, 153, 147, 132, 90, 37, 0@};
6669 printf ("Hello, world!\n");
6673 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
6674 containing the string @samp{Hello, world!} followed by a newline,
6675 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
6677 We compile the program, and invoke the debugger on it:
6680 $ gcc -g charset-test.c -o charset-test
6681 $ gdb -nw charset-test
6682 GNU gdb 2001-12-19-cvs
6683 Copyright 2001 Free Software Foundation, Inc.
6688 We can use the @code{show charset} command to see what character sets
6689 @value{GDBN} is currently using to interpret and display characters and
6693 (@value{GDBP}) show charset
6694 The current host and target character set is `ISO-8859-1'.
6698 For the sake of printing this manual, let's use @sc{ascii} as our
6699 initial character set:
6701 (@value{GDBP}) set charset ASCII
6702 (@value{GDBP}) show charset
6703 The current host and target character set is `ASCII'.
6707 Let's assume that @sc{ascii} is indeed the correct character set for our
6708 host system --- in other words, let's assume that if @value{GDBN} prints
6709 characters using the @sc{ascii} character set, our terminal will display
6710 them properly. Since our current target character set is also
6711 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
6714 (@value{GDBP}) print ascii_hello
6715 $1 = 0x401698 "Hello, world!\n"
6716 (@value{GDBP}) print ascii_hello[0]
6721 @value{GDBN} uses the target character set for character and string
6722 literals you use in expressions:
6725 (@value{GDBP}) print '+'
6730 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
6733 @value{GDBN} relies on the user to tell it which character set the
6734 target program uses. If we print @code{ibm1047_hello} while our target
6735 character set is still @sc{ascii}, we get jibberish:
6738 (@value{GDBP}) print ibm1047_hello
6739 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
6740 (@value{GDBP}) print ibm1047_hello[0]
6745 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
6746 @value{GDBN} tells us the character sets it supports:
6749 (@value{GDBP}) set target-charset
6750 ASCII EBCDIC-US IBM1047 ISO-8859-1
6751 (@value{GDBP}) set target-charset
6754 We can select @sc{ibm1047} as our target character set, and examine the
6755 program's strings again. Now the @sc{ascii} string is wrong, but
6756 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
6757 target character set, @sc{ibm1047}, to the host character set,
6758 @sc{ascii}, and they display correctly:
6761 (@value{GDBP}) set target-charset IBM1047
6762 (@value{GDBP}) show charset
6763 The current host character set is `ASCII'.
6764 The current target character set is `IBM1047'.
6765 (@value{GDBP}) print ascii_hello
6766 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
6767 (@value{GDBP}) print ascii_hello[0]
6769 (@value{GDBP}) print ibm1047_hello
6770 $8 = 0x4016a8 "Hello, world!\n"
6771 (@value{GDBP}) print ibm1047_hello[0]
6776 As above, @value{GDBN} uses the target character set for character and
6777 string literals you use in expressions:
6780 (@value{GDBP}) print '+'
6785 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
6788 @node Caching Remote Data
6789 @section Caching Data of Remote Targets
6790 @cindex caching data of remote targets
6792 @value{GDBN} can cache data exchanged between the debugger and a
6793 remote target (@pxref{Remote}). Such caching generally improves
6794 performance, because it reduces the overhead of the remote protocol by
6795 bundling memory reads and writes into large chunks. Unfortunately,
6796 @value{GDBN} does not currently know anything about volatile
6797 registers, and thus data caching will produce incorrect results when
6798 volatile registers are in use.
6801 @kindex set remotecache
6802 @item set remotecache on
6803 @itemx set remotecache off
6804 Set caching state for remote targets. When @code{ON}, use data
6805 caching. By default, this option is @code{OFF}.
6807 @kindex show remotecache
6808 @item show remotecache
6809 Show the current state of data caching for remote targets.
6813 Print the information about the data cache performance. The
6814 information displayed includes: the dcache width and depth; and for
6815 each cache line, how many times it was referenced, and its data and
6816 state (dirty, bad, ok, etc.). This command is useful for debugging
6817 the data cache operation.
6822 @chapter C Preprocessor Macros
6824 Some languages, such as C and C@t{++}, provide a way to define and invoke
6825 ``preprocessor macros'' which expand into strings of tokens.
6826 @value{GDBN} can evaluate expressions containing macro invocations, show
6827 the result of macro expansion, and show a macro's definition, including
6828 where it was defined.
6830 You may need to compile your program specially to provide @value{GDBN}
6831 with information about preprocessor macros. Most compilers do not
6832 include macros in their debugging information, even when you compile
6833 with the @option{-g} flag. @xref{Compilation}.
6835 A program may define a macro at one point, remove that definition later,
6836 and then provide a different definition after that. Thus, at different
6837 points in the program, a macro may have different definitions, or have
6838 no definition at all. If there is a current stack frame, @value{GDBN}
6839 uses the macros in scope at that frame's source code line. Otherwise,
6840 @value{GDBN} uses the macros in scope at the current listing location;
6843 At the moment, @value{GDBN} does not support the @code{##}
6844 token-splicing operator, the @code{#} stringification operator, or
6845 variable-arity macros.
6847 Whenever @value{GDBN} evaluates an expression, it always expands any
6848 macro invocations present in the expression. @value{GDBN} also provides
6849 the following commands for working with macros explicitly.
6853 @kindex macro expand
6854 @cindex macro expansion, showing the results of preprocessor
6855 @cindex preprocessor macro expansion, showing the results of
6856 @cindex expanding preprocessor macros
6857 @item macro expand @var{expression}
6858 @itemx macro exp @var{expression}
6859 Show the results of expanding all preprocessor macro invocations in
6860 @var{expression}. Since @value{GDBN} simply expands macros, but does
6861 not parse the result, @var{expression} need not be a valid expression;
6862 it can be any string of tokens.
6865 @item macro expand-once @var{expression}
6866 @itemx macro exp1 @var{expression}
6867 @cindex expand macro once
6868 @i{(This command is not yet implemented.)} Show the results of
6869 expanding those preprocessor macro invocations that appear explicitly in
6870 @var{expression}. Macro invocations appearing in that expansion are
6871 left unchanged. This command allows you to see the effect of a
6872 particular macro more clearly, without being confused by further
6873 expansions. Since @value{GDBN} simply expands macros, but does not
6874 parse the result, @var{expression} need not be a valid expression; it
6875 can be any string of tokens.
6878 @cindex macro definition, showing
6879 @cindex definition, showing a macro's
6880 @item info macro @var{macro}
6881 Show the definition of the macro named @var{macro}, and describe the
6882 source location where that definition was established.
6884 @kindex macro define
6885 @cindex user-defined macros
6886 @cindex defining macros interactively
6887 @cindex macros, user-defined
6888 @item macro define @var{macro} @var{replacement-list}
6889 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
6890 @i{(This command is not yet implemented.)} Introduce a definition for a
6891 preprocessor macro named @var{macro}, invocations of which are replaced
6892 by the tokens given in @var{replacement-list}. The first form of this
6893 command defines an ``object-like'' macro, which takes no arguments; the
6894 second form defines a ``function-like'' macro, which takes the arguments
6895 given in @var{arglist}.
6897 A definition introduced by this command is in scope in every expression
6898 evaluated in @value{GDBN}, until it is removed with the @command{macro
6899 undef} command, described below. The definition overrides all
6900 definitions for @var{macro} present in the program being debugged, as
6901 well as any previous user-supplied definition.
6904 @item macro undef @var{macro}
6905 @i{(This command is not yet implemented.)} Remove any user-supplied
6906 definition for the macro named @var{macro}. This command only affects
6907 definitions provided with the @command{macro define} command, described
6908 above; it cannot remove definitions present in the program being
6913 @i{(This command is not yet implemented.)} List all the macros
6914 defined using the @code{macro define} command.
6917 @cindex macros, example of debugging with
6918 Here is a transcript showing the above commands in action. First, we
6919 show our source files:
6927 #define ADD(x) (M + x)
6932 printf ("Hello, world!\n");
6934 printf ("We're so creative.\n");
6936 printf ("Goodbye, world!\n");
6943 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
6944 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
6945 compiler includes information about preprocessor macros in the debugging
6949 $ gcc -gdwarf-2 -g3 sample.c -o sample
6953 Now, we start @value{GDBN} on our sample program:
6957 GNU gdb 2002-05-06-cvs
6958 Copyright 2002 Free Software Foundation, Inc.
6959 GDB is free software, @dots{}
6963 We can expand macros and examine their definitions, even when the
6964 program is not running. @value{GDBN} uses the current listing position
6965 to decide which macro definitions are in scope:
6968 (@value{GDBP}) list main
6971 5 #define ADD(x) (M + x)
6976 10 printf ("Hello, world!\n");
6978 12 printf ("We're so creative.\n");
6979 (@value{GDBP}) info macro ADD
6980 Defined at /home/jimb/gdb/macros/play/sample.c:5
6981 #define ADD(x) (M + x)
6982 (@value{GDBP}) info macro Q
6983 Defined at /home/jimb/gdb/macros/play/sample.h:1
6984 included at /home/jimb/gdb/macros/play/sample.c:2
6986 (@value{GDBP}) macro expand ADD(1)
6987 expands to: (42 + 1)
6988 (@value{GDBP}) macro expand-once ADD(1)
6989 expands to: once (M + 1)
6993 In the example above, note that @command{macro expand-once} expands only
6994 the macro invocation explicit in the original text --- the invocation of
6995 @code{ADD} --- but does not expand the invocation of the macro @code{M},
6996 which was introduced by @code{ADD}.
6998 Once the program is running, GDB uses the macro definitions in force at
6999 the source line of the current stack frame:
7002 (@value{GDBP}) break main
7003 Breakpoint 1 at 0x8048370: file sample.c, line 10.
7005 Starting program: /home/jimb/gdb/macros/play/sample
7007 Breakpoint 1, main () at sample.c:10
7008 10 printf ("Hello, world!\n");
7012 At line 10, the definition of the macro @code{N} at line 9 is in force:
7015 (@value{GDBP}) info macro N
7016 Defined at /home/jimb/gdb/macros/play/sample.c:9
7018 (@value{GDBP}) macro expand N Q M
7020 (@value{GDBP}) print N Q M
7025 As we step over directives that remove @code{N}'s definition, and then
7026 give it a new definition, @value{GDBN} finds the definition (or lack
7027 thereof) in force at each point:
7032 12 printf ("We're so creative.\n");
7033 (@value{GDBP}) info macro N
7034 The symbol `N' has no definition as a C/C++ preprocessor macro
7035 at /home/jimb/gdb/macros/play/sample.c:12
7038 14 printf ("Goodbye, world!\n");
7039 (@value{GDBP}) info macro N
7040 Defined at /home/jimb/gdb/macros/play/sample.c:13
7042 (@value{GDBP}) macro expand N Q M
7043 expands to: 1729 < 42
7044 (@value{GDBP}) print N Q M
7051 @chapter Tracepoints
7052 @c This chapter is based on the documentation written by Michael
7053 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
7056 In some applications, it is not feasible for the debugger to interrupt
7057 the program's execution long enough for the developer to learn
7058 anything helpful about its behavior. If the program's correctness
7059 depends on its real-time behavior, delays introduced by a debugger
7060 might cause the program to change its behavior drastically, or perhaps
7061 fail, even when the code itself is correct. It is useful to be able
7062 to observe the program's behavior without interrupting it.
7064 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
7065 specify locations in the program, called @dfn{tracepoints}, and
7066 arbitrary expressions to evaluate when those tracepoints are reached.
7067 Later, using the @code{tfind} command, you can examine the values
7068 those expressions had when the program hit the tracepoints. The
7069 expressions may also denote objects in memory---structures or arrays,
7070 for example---whose values @value{GDBN} should record; while visiting
7071 a particular tracepoint, you may inspect those objects as if they were
7072 in memory at that moment. However, because @value{GDBN} records these
7073 values without interacting with you, it can do so quickly and
7074 unobtrusively, hopefully not disturbing the program's behavior.
7076 The tracepoint facility is currently available only for remote
7077 targets. @xref{Targets}. In addition, your remote target must know how
7078 to collect trace data. This functionality is implemented in the remote
7079 stub; however, none of the stubs distributed with @value{GDBN} support
7080 tracepoints as of this writing.
7082 This chapter describes the tracepoint commands and features.
7086 * Analyze Collected Data::
7087 * Tracepoint Variables::
7090 @node Set Tracepoints
7091 @section Commands to Set Tracepoints
7093 Before running such a @dfn{trace experiment}, an arbitrary number of
7094 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
7095 tracepoint has a number assigned to it by @value{GDBN}. Like with
7096 breakpoints, tracepoint numbers are successive integers starting from
7097 one. Many of the commands associated with tracepoints take the
7098 tracepoint number as their argument, to identify which tracepoint to
7101 For each tracepoint, you can specify, in advance, some arbitrary set
7102 of data that you want the target to collect in the trace buffer when
7103 it hits that tracepoint. The collected data can include registers,
7104 local variables, or global data. Later, you can use @value{GDBN}
7105 commands to examine the values these data had at the time the
7108 This section describes commands to set tracepoints and associated
7109 conditions and actions.
7112 * Create and Delete Tracepoints::
7113 * Enable and Disable Tracepoints::
7114 * Tracepoint Passcounts::
7115 * Tracepoint Actions::
7116 * Listing Tracepoints::
7117 * Starting and Stopping Trace Experiment::
7120 @node Create and Delete Tracepoints
7121 @subsection Create and Delete Tracepoints
7124 @cindex set tracepoint
7127 The @code{trace} command is very similar to the @code{break} command.
7128 Its argument can be a source line, a function name, or an address in
7129 the target program. @xref{Set Breaks}. The @code{trace} command
7130 defines a tracepoint, which is a point in the target program where the
7131 debugger will briefly stop, collect some data, and then allow the
7132 program to continue. Setting a tracepoint or changing its commands
7133 doesn't take effect until the next @code{tstart} command; thus, you
7134 cannot change the tracepoint attributes once a trace experiment is
7137 Here are some examples of using the @code{trace} command:
7140 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
7142 (@value{GDBP}) @b{trace +2} // 2 lines forward
7144 (@value{GDBP}) @b{trace my_function} // first source line of function
7146 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
7148 (@value{GDBP}) @b{trace *0x2117c4} // an address
7152 You can abbreviate @code{trace} as @code{tr}.
7155 @cindex last tracepoint number
7156 @cindex recent tracepoint number
7157 @cindex tracepoint number
7158 The convenience variable @code{$tpnum} records the tracepoint number
7159 of the most recently set tracepoint.
7161 @kindex delete tracepoint
7162 @cindex tracepoint deletion
7163 @item delete tracepoint @r{[}@var{num}@r{]}
7164 Permanently delete one or more tracepoints. With no argument, the
7165 default is to delete all tracepoints.
7170 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
7172 (@value{GDBP}) @b{delete trace} // remove all tracepoints
7176 You can abbreviate this command as @code{del tr}.
7179 @node Enable and Disable Tracepoints
7180 @subsection Enable and Disable Tracepoints
7183 @kindex disable tracepoint
7184 @item disable tracepoint @r{[}@var{num}@r{]}
7185 Disable tracepoint @var{num}, or all tracepoints if no argument
7186 @var{num} is given. A disabled tracepoint will have no effect during
7187 the next trace experiment, but it is not forgotten. You can re-enable
7188 a disabled tracepoint using the @code{enable tracepoint} command.
7190 @kindex enable tracepoint
7191 @item enable tracepoint @r{[}@var{num}@r{]}
7192 Enable tracepoint @var{num}, or all tracepoints. The enabled
7193 tracepoints will become effective the next time a trace experiment is
7197 @node Tracepoint Passcounts
7198 @subsection Tracepoint Passcounts
7202 @cindex tracepoint pass count
7203 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
7204 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
7205 automatically stop a trace experiment. If a tracepoint's passcount is
7206 @var{n}, then the trace experiment will be automatically stopped on
7207 the @var{n}'th time that tracepoint is hit. If the tracepoint number
7208 @var{num} is not specified, the @code{passcount} command sets the
7209 passcount of the most recently defined tracepoint. If no passcount is
7210 given, the trace experiment will run until stopped explicitly by the
7216 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
7217 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
7219 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
7220 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
7221 (@value{GDBP}) @b{trace foo}
7222 (@value{GDBP}) @b{pass 3}
7223 (@value{GDBP}) @b{trace bar}
7224 (@value{GDBP}) @b{pass 2}
7225 (@value{GDBP}) @b{trace baz}
7226 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
7227 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
7228 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
7229 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
7233 @node Tracepoint Actions
7234 @subsection Tracepoint Action Lists
7238 @cindex tracepoint actions
7239 @item actions @r{[}@var{num}@r{]}
7240 This command will prompt for a list of actions to be taken when the
7241 tracepoint is hit. If the tracepoint number @var{num} is not
7242 specified, this command sets the actions for the one that was most
7243 recently defined (so that you can define a tracepoint and then say
7244 @code{actions} without bothering about its number). You specify the
7245 actions themselves on the following lines, one action at a time, and
7246 terminate the actions list with a line containing just @code{end}. So
7247 far, the only defined actions are @code{collect} and
7248 @code{while-stepping}.
7250 @cindex remove actions from a tracepoint
7251 To remove all actions from a tracepoint, type @samp{actions @var{num}}
7252 and follow it immediately with @samp{end}.
7255 (@value{GDBP}) @b{collect @var{data}} // collect some data
7257 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
7259 (@value{GDBP}) @b{end} // signals the end of actions.
7262 In the following example, the action list begins with @code{collect}
7263 commands indicating the things to be collected when the tracepoint is
7264 hit. Then, in order to single-step and collect additional data
7265 following the tracepoint, a @code{while-stepping} command is used,
7266 followed by the list of things to be collected while stepping. The
7267 @code{while-stepping} command is terminated by its own separate
7268 @code{end} command. Lastly, the action list is terminated by an
7272 (@value{GDBP}) @b{trace foo}
7273 (@value{GDBP}) @b{actions}
7274 Enter actions for tracepoint 1, one per line:
7283 @kindex collect @r{(tracepoints)}
7284 @item collect @var{expr1}, @var{expr2}, @dots{}
7285 Collect values of the given expressions when the tracepoint is hit.
7286 This command accepts a comma-separated list of any valid expressions.
7287 In addition to global, static, or local variables, the following
7288 special arguments are supported:
7292 collect all registers
7295 collect all function arguments
7298 collect all local variables.
7301 You can give several consecutive @code{collect} commands, each one
7302 with a single argument, or one @code{collect} command with several
7303 arguments separated by commas: the effect is the same.
7305 The command @code{info scope} (@pxref{Symbols, info scope}) is
7306 particularly useful for figuring out what data to collect.
7308 @kindex while-stepping @r{(tracepoints)}
7309 @item while-stepping @var{n}
7310 Perform @var{n} single-step traces after the tracepoint, collecting
7311 new data at each step. The @code{while-stepping} command is
7312 followed by the list of what to collect while stepping (followed by
7313 its own @code{end} command):
7317 > collect $regs, myglobal
7323 You may abbreviate @code{while-stepping} as @code{ws} or
7327 @node Listing Tracepoints
7328 @subsection Listing Tracepoints
7331 @kindex info tracepoints
7333 @cindex information about tracepoints
7334 @item info tracepoints @r{[}@var{num}@r{]}
7335 Display information about the tracepoint @var{num}. If you don't specify
7336 a tracepoint number, displays information about all the tracepoints
7337 defined so far. For each tracepoint, the following information is
7344 whether it is enabled or disabled
7348 its passcount as given by the @code{passcount @var{n}} command
7350 its step count as given by the @code{while-stepping @var{n}} command
7352 where in the source files is the tracepoint set
7354 its action list as given by the @code{actions} command
7358 (@value{GDBP}) @b{info trace}
7359 Num Enb Address PassC StepC What
7360 1 y 0x002117c4 0 0 <gdb_asm>
7361 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
7362 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
7367 This command can be abbreviated @code{info tp}.
7370 @node Starting and Stopping Trace Experiment
7371 @subsection Starting and Stopping Trace Experiment
7375 @cindex start a new trace experiment
7376 @cindex collected data discarded
7378 This command takes no arguments. It starts the trace experiment, and
7379 begins collecting data. This has the side effect of discarding all
7380 the data collected in the trace buffer during the previous trace
7384 @cindex stop a running trace experiment
7386 This command takes no arguments. It ends the trace experiment, and
7387 stops collecting data.
7389 @strong{Note}: a trace experiment and data collection may stop
7390 automatically if any tracepoint's passcount is reached
7391 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
7394 @cindex status of trace data collection
7395 @cindex trace experiment, status of
7397 This command displays the status of the current trace data
7401 Here is an example of the commands we described so far:
7404 (@value{GDBP}) @b{trace gdb_c_test}
7405 (@value{GDBP}) @b{actions}
7406 Enter actions for tracepoint #1, one per line.
7407 > collect $regs,$locals,$args
7412 (@value{GDBP}) @b{tstart}
7413 [time passes @dots{}]
7414 (@value{GDBP}) @b{tstop}
7418 @node Analyze Collected Data
7419 @section Using the collected data
7421 After the tracepoint experiment ends, you use @value{GDBN} commands
7422 for examining the trace data. The basic idea is that each tracepoint
7423 collects a trace @dfn{snapshot} every time it is hit and another
7424 snapshot every time it single-steps. All these snapshots are
7425 consecutively numbered from zero and go into a buffer, and you can
7426 examine them later. The way you examine them is to @dfn{focus} on a
7427 specific trace snapshot. When the remote stub is focused on a trace
7428 snapshot, it will respond to all @value{GDBN} requests for memory and
7429 registers by reading from the buffer which belongs to that snapshot,
7430 rather than from @emph{real} memory or registers of the program being
7431 debugged. This means that @strong{all} @value{GDBN} commands
7432 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
7433 behave as if we were currently debugging the program state as it was
7434 when the tracepoint occurred. Any requests for data that are not in
7435 the buffer will fail.
7438 * tfind:: How to select a trace snapshot
7439 * tdump:: How to display all data for a snapshot
7440 * save-tracepoints:: How to save tracepoints for a future run
7444 @subsection @code{tfind @var{n}}
7447 @cindex select trace snapshot
7448 @cindex find trace snapshot
7449 The basic command for selecting a trace snapshot from the buffer is
7450 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
7451 counting from zero. If no argument @var{n} is given, the next
7452 snapshot is selected.
7454 Here are the various forms of using the @code{tfind} command.
7458 Find the first snapshot in the buffer. This is a synonym for
7459 @code{tfind 0} (since 0 is the number of the first snapshot).
7462 Stop debugging trace snapshots, resume @emph{live} debugging.
7465 Same as @samp{tfind none}.
7468 No argument means find the next trace snapshot.
7471 Find the previous trace snapshot before the current one. This permits
7472 retracing earlier steps.
7474 @item tfind tracepoint @var{num}
7475 Find the next snapshot associated with tracepoint @var{num}. Search
7476 proceeds forward from the last examined trace snapshot. If no
7477 argument @var{num} is given, it means find the next snapshot collected
7478 for the same tracepoint as the current snapshot.
7480 @item tfind pc @var{addr}
7481 Find the next snapshot associated with the value @var{addr} of the
7482 program counter. Search proceeds forward from the last examined trace
7483 snapshot. If no argument @var{addr} is given, it means find the next
7484 snapshot with the same value of PC as the current snapshot.
7486 @item tfind outside @var{addr1}, @var{addr2}
7487 Find the next snapshot whose PC is outside the given range of
7490 @item tfind range @var{addr1}, @var{addr2}
7491 Find the next snapshot whose PC is between @var{addr1} and
7492 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
7494 @item tfind line @r{[}@var{file}:@r{]}@var{n}
7495 Find the next snapshot associated with the source line @var{n}. If
7496 the optional argument @var{file} is given, refer to line @var{n} in
7497 that source file. Search proceeds forward from the last examined
7498 trace snapshot. If no argument @var{n} is given, it means find the
7499 next line other than the one currently being examined; thus saying
7500 @code{tfind line} repeatedly can appear to have the same effect as
7501 stepping from line to line in a @emph{live} debugging session.
7504 The default arguments for the @code{tfind} commands are specifically
7505 designed to make it easy to scan through the trace buffer. For
7506 instance, @code{tfind} with no argument selects the next trace
7507 snapshot, and @code{tfind -} with no argument selects the previous
7508 trace snapshot. So, by giving one @code{tfind} command, and then
7509 simply hitting @key{RET} repeatedly you can examine all the trace
7510 snapshots in order. Or, by saying @code{tfind -} and then hitting
7511 @key{RET} repeatedly you can examine the snapshots in reverse order.
7512 The @code{tfind line} command with no argument selects the snapshot
7513 for the next source line executed. The @code{tfind pc} command with
7514 no argument selects the next snapshot with the same program counter
7515 (PC) as the current frame. The @code{tfind tracepoint} command with
7516 no argument selects the next trace snapshot collected by the same
7517 tracepoint as the current one.
7519 In addition to letting you scan through the trace buffer manually,
7520 these commands make it easy to construct @value{GDBN} scripts that
7521 scan through the trace buffer and print out whatever collected data
7522 you are interested in. Thus, if we want to examine the PC, FP, and SP
7523 registers from each trace frame in the buffer, we can say this:
7526 (@value{GDBP}) @b{tfind start}
7527 (@value{GDBP}) @b{while ($trace_frame != -1)}
7528 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
7529 $trace_frame, $pc, $sp, $fp
7533 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
7534 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
7535 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
7536 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
7537 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
7538 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
7539 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
7540 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
7541 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
7542 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
7543 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
7546 Or, if we want to examine the variable @code{X} at each source line in
7550 (@value{GDBP}) @b{tfind start}
7551 (@value{GDBP}) @b{while ($trace_frame != -1)}
7552 > printf "Frame %d, X == %d\n", $trace_frame, X
7562 @subsection @code{tdump}
7564 @cindex dump all data collected at tracepoint
7565 @cindex tracepoint data, display
7567 This command takes no arguments. It prints all the data collected at
7568 the current trace snapshot.
7571 (@value{GDBP}) @b{trace 444}
7572 (@value{GDBP}) @b{actions}
7573 Enter actions for tracepoint #2, one per line:
7574 > collect $regs, $locals, $args, gdb_long_test
7577 (@value{GDBP}) @b{tstart}
7579 (@value{GDBP}) @b{tfind line 444}
7580 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
7582 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
7584 (@value{GDBP}) @b{tdump}
7585 Data collected at tracepoint 2, trace frame 1:
7586 d0 0xc4aa0085 -995491707
7590 d4 0x71aea3d 119204413
7595 a1 0x3000668 50333288
7598 a4 0x3000698 50333336
7600 fp 0x30bf3c 0x30bf3c
7601 sp 0x30bf34 0x30bf34
7603 pc 0x20b2c8 0x20b2c8
7607 p = 0x20e5b4 "gdb-test"
7614 gdb_long_test = 17 '\021'
7619 @node save-tracepoints
7620 @subsection @code{save-tracepoints @var{filename}}
7621 @kindex save-tracepoints
7622 @cindex save tracepoints for future sessions
7624 This command saves all current tracepoint definitions together with
7625 their actions and passcounts, into a file @file{@var{filename}}
7626 suitable for use in a later debugging session. To read the saved
7627 tracepoint definitions, use the @code{source} command (@pxref{Command
7630 @node Tracepoint Variables
7631 @section Convenience Variables for Tracepoints
7632 @cindex tracepoint variables
7633 @cindex convenience variables for tracepoints
7636 @vindex $trace_frame
7637 @item (int) $trace_frame
7638 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
7639 snapshot is selected.
7642 @item (int) $tracepoint
7643 The tracepoint for the current trace snapshot.
7646 @item (int) $trace_line
7647 The line number for the current trace snapshot.
7650 @item (char []) $trace_file
7651 The source file for the current trace snapshot.
7654 @item (char []) $trace_func
7655 The name of the function containing @code{$tracepoint}.
7658 Note: @code{$trace_file} is not suitable for use in @code{printf},
7659 use @code{output} instead.
7661 Here's a simple example of using these convenience variables for
7662 stepping through all the trace snapshots and printing some of their
7666 (@value{GDBP}) @b{tfind start}
7668 (@value{GDBP}) @b{while $trace_frame != -1}
7669 > output $trace_file
7670 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
7676 @chapter Debugging Programs That Use Overlays
7679 If your program is too large to fit completely in your target system's
7680 memory, you can sometimes use @dfn{overlays} to work around this
7681 problem. @value{GDBN} provides some support for debugging programs that
7685 * How Overlays Work:: A general explanation of overlays.
7686 * Overlay Commands:: Managing overlays in @value{GDBN}.
7687 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
7688 mapped by asking the inferior.
7689 * Overlay Sample Program:: A sample program using overlays.
7692 @node How Overlays Work
7693 @section How Overlays Work
7694 @cindex mapped overlays
7695 @cindex unmapped overlays
7696 @cindex load address, overlay's
7697 @cindex mapped address
7698 @cindex overlay area
7700 Suppose you have a computer whose instruction address space is only 64
7701 kilobytes long, but which has much more memory which can be accessed by
7702 other means: special instructions, segment registers, or memory
7703 management hardware, for example. Suppose further that you want to
7704 adapt a program which is larger than 64 kilobytes to run on this system.
7706 One solution is to identify modules of your program which are relatively
7707 independent, and need not call each other directly; call these modules
7708 @dfn{overlays}. Separate the overlays from the main program, and place
7709 their machine code in the larger memory. Place your main program in
7710 instruction memory, but leave at least enough space there to hold the
7711 largest overlay as well.
7713 Now, to call a function located in an overlay, you must first copy that
7714 overlay's machine code from the large memory into the space set aside
7715 for it in the instruction memory, and then jump to its entry point
7718 @c NB: In the below the mapped area's size is greater or equal to the
7719 @c size of all overlays. This is intentional to remind the developer
7720 @c that overlays don't necessarily need to be the same size.
7724 Data Instruction Larger
7725 Address Space Address Space Address Space
7726 +-----------+ +-----------+ +-----------+
7728 +-----------+ +-----------+ +-----------+<-- overlay 1
7729 | program | | main | .----| overlay 1 | load address
7730 | variables | | program | | +-----------+
7731 | and heap | | | | | |
7732 +-----------+ | | | +-----------+<-- overlay 2
7733 | | +-----------+ | | | load address
7734 +-----------+ | | | .-| overlay 2 |
7736 mapped --->+-----------+ | | +-----------+
7738 | overlay | <-' | | |
7739 | area | <---' +-----------+<-- overlay 3
7740 | | <---. | | load address
7741 +-----------+ `--| overlay 3 |
7748 @anchor{A code overlay}A code overlay
7752 The diagram (@pxref{A code overlay}) shows a system with separate data
7753 and instruction address spaces. To map an overlay, the program copies
7754 its code from the larger address space to the instruction address space.
7755 Since the overlays shown here all use the same mapped address, only one
7756 may be mapped at a time. For a system with a single address space for
7757 data and instructions, the diagram would be similar, except that the
7758 program variables and heap would share an address space with the main
7759 program and the overlay area.
7761 An overlay loaded into instruction memory and ready for use is called a
7762 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
7763 instruction memory. An overlay not present (or only partially present)
7764 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
7765 is its address in the larger memory. The mapped address is also called
7766 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
7767 called the @dfn{load memory address}, or @dfn{LMA}.
7769 Unfortunately, overlays are not a completely transparent way to adapt a
7770 program to limited instruction memory. They introduce a new set of
7771 global constraints you must keep in mind as you design your program:
7776 Before calling or returning to a function in an overlay, your program
7777 must make sure that overlay is actually mapped. Otherwise, the call or
7778 return will transfer control to the right address, but in the wrong
7779 overlay, and your program will probably crash.
7782 If the process of mapping an overlay is expensive on your system, you
7783 will need to choose your overlays carefully to minimize their effect on
7784 your program's performance.
7787 The executable file you load onto your system must contain each
7788 overlay's instructions, appearing at the overlay's load address, not its
7789 mapped address. However, each overlay's instructions must be relocated
7790 and its symbols defined as if the overlay were at its mapped address.
7791 You can use GNU linker scripts to specify different load and relocation
7792 addresses for pieces of your program; see @ref{Overlay Description,,,
7793 ld.info, Using ld: the GNU linker}.
7796 The procedure for loading executable files onto your system must be able
7797 to load their contents into the larger address space as well as the
7798 instruction and data spaces.
7802 The overlay system described above is rather simple, and could be
7803 improved in many ways:
7808 If your system has suitable bank switch registers or memory management
7809 hardware, you could use those facilities to make an overlay's load area
7810 contents simply appear at their mapped address in instruction space.
7811 This would probably be faster than copying the overlay to its mapped
7812 area in the usual way.
7815 If your overlays are small enough, you could set aside more than one
7816 overlay area, and have more than one overlay mapped at a time.
7819 You can use overlays to manage data, as well as instructions. In
7820 general, data overlays are even less transparent to your design than
7821 code overlays: whereas code overlays only require care when you call or
7822 return to functions, data overlays require care every time you access
7823 the data. Also, if you change the contents of a data overlay, you
7824 must copy its contents back out to its load address before you can copy a
7825 different data overlay into the same mapped area.
7830 @node Overlay Commands
7831 @section Overlay Commands
7833 To use @value{GDBN}'s overlay support, each overlay in your program must
7834 correspond to a separate section of the executable file. The section's
7835 virtual memory address and load memory address must be the overlay's
7836 mapped and load addresses. Identifying overlays with sections allows
7837 @value{GDBN} to determine the appropriate address of a function or
7838 variable, depending on whether the overlay is mapped or not.
7840 @value{GDBN}'s overlay commands all start with the word @code{overlay};
7841 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
7846 Disable @value{GDBN}'s overlay support. When overlay support is
7847 disabled, @value{GDBN} assumes that all functions and variables are
7848 always present at their mapped addresses. By default, @value{GDBN}'s
7849 overlay support is disabled.
7851 @item overlay manual
7852 @cindex manual overlay debugging
7853 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
7854 relies on you to tell it which overlays are mapped, and which are not,
7855 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
7856 commands described below.
7858 @item overlay map-overlay @var{overlay}
7859 @itemx overlay map @var{overlay}
7860 @cindex map an overlay
7861 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
7862 be the name of the object file section containing the overlay. When an
7863 overlay is mapped, @value{GDBN} assumes it can find the overlay's
7864 functions and variables at their mapped addresses. @value{GDBN} assumes
7865 that any other overlays whose mapped ranges overlap that of
7866 @var{overlay} are now unmapped.
7868 @item overlay unmap-overlay @var{overlay}
7869 @itemx overlay unmap @var{overlay}
7870 @cindex unmap an overlay
7871 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
7872 must be the name of the object file section containing the overlay.
7873 When an overlay is unmapped, @value{GDBN} assumes it can find the
7874 overlay's functions and variables at their load addresses.
7877 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
7878 consults a data structure the overlay manager maintains in the inferior
7879 to see which overlays are mapped. For details, see @ref{Automatic
7882 @item overlay load-target
7884 @cindex reloading the overlay table
7885 Re-read the overlay table from the inferior. Normally, @value{GDBN}
7886 re-reads the table @value{GDBN} automatically each time the inferior
7887 stops, so this command should only be necessary if you have changed the
7888 overlay mapping yourself using @value{GDBN}. This command is only
7889 useful when using automatic overlay debugging.
7891 @item overlay list-overlays
7893 @cindex listing mapped overlays
7894 Display a list of the overlays currently mapped, along with their mapped
7895 addresses, load addresses, and sizes.
7899 Normally, when @value{GDBN} prints a code address, it includes the name
7900 of the function the address falls in:
7903 (@value{GDBP}) print main
7904 $3 = @{int ()@} 0x11a0 <main>
7907 When overlay debugging is enabled, @value{GDBN} recognizes code in
7908 unmapped overlays, and prints the names of unmapped functions with
7909 asterisks around them. For example, if @code{foo} is a function in an
7910 unmapped overlay, @value{GDBN} prints it this way:
7913 (@value{GDBP}) overlay list
7914 No sections are mapped.
7915 (@value{GDBP}) print foo
7916 $5 = @{int (int)@} 0x100000 <*foo*>
7919 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
7923 (@value{GDBP}) overlay list
7924 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
7925 mapped at 0x1016 - 0x104a
7926 (@value{GDBP}) print foo
7927 $6 = @{int (int)@} 0x1016 <foo>
7930 When overlay debugging is enabled, @value{GDBN} can find the correct
7931 address for functions and variables in an overlay, whether or not the
7932 overlay is mapped. This allows most @value{GDBN} commands, like
7933 @code{break} and @code{disassemble}, to work normally, even on unmapped
7934 code. However, @value{GDBN}'s breakpoint support has some limitations:
7938 @cindex breakpoints in overlays
7939 @cindex overlays, setting breakpoints in
7940 You can set breakpoints in functions in unmapped overlays, as long as
7941 @value{GDBN} can write to the overlay at its load address.
7943 @value{GDBN} can not set hardware or simulator-based breakpoints in
7944 unmapped overlays. However, if you set a breakpoint at the end of your
7945 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
7946 you are using manual overlay management), @value{GDBN} will re-set its
7947 breakpoints properly.
7951 @node Automatic Overlay Debugging
7952 @section Automatic Overlay Debugging
7953 @cindex automatic overlay debugging
7955 @value{GDBN} can automatically track which overlays are mapped and which
7956 are not, given some simple co-operation from the overlay manager in the
7957 inferior. If you enable automatic overlay debugging with the
7958 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
7959 looks in the inferior's memory for certain variables describing the
7960 current state of the overlays.
7962 Here are the variables your overlay manager must define to support
7963 @value{GDBN}'s automatic overlay debugging:
7967 @item @code{_ovly_table}:
7968 This variable must be an array of the following structures:
7973 /* The overlay's mapped address. */
7976 /* The size of the overlay, in bytes. */
7979 /* The overlay's load address. */
7982 /* Non-zero if the overlay is currently mapped;
7984 unsigned long mapped;
7988 @item @code{_novlys}:
7989 This variable must be a four-byte signed integer, holding the total
7990 number of elements in @code{_ovly_table}.
7994 To decide whether a particular overlay is mapped or not, @value{GDBN}
7995 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
7996 @code{lma} members equal the VMA and LMA of the overlay's section in the
7997 executable file. When @value{GDBN} finds a matching entry, it consults
7998 the entry's @code{mapped} member to determine whether the overlay is
8001 In addition, your overlay manager may define a function called
8002 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
8003 will silently set a breakpoint there. If the overlay manager then
8004 calls this function whenever it has changed the overlay table, this
8005 will enable @value{GDBN} to accurately keep track of which overlays
8006 are in program memory, and update any breakpoints that may be set
8007 in overlays. This will allow breakpoints to work even if the
8008 overlays are kept in ROM or other non-writable memory while they
8009 are not being executed.
8011 @node Overlay Sample Program
8012 @section Overlay Sample Program
8013 @cindex overlay example program
8015 When linking a program which uses overlays, you must place the overlays
8016 at their load addresses, while relocating them to run at their mapped
8017 addresses. To do this, you must write a linker script (@pxref{Overlay
8018 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
8019 since linker scripts are specific to a particular host system, target
8020 architecture, and target memory layout, this manual cannot provide
8021 portable sample code demonstrating @value{GDBN}'s overlay support.
8023 However, the @value{GDBN} source distribution does contain an overlaid
8024 program, with linker scripts for a few systems, as part of its test
8025 suite. The program consists of the following files from
8026 @file{gdb/testsuite/gdb.base}:
8030 The main program file.
8032 A simple overlay manager, used by @file{overlays.c}.
8037 Overlay modules, loaded and used by @file{overlays.c}.
8040 Linker scripts for linking the test program on the @code{d10v-elf}
8041 and @code{m32r-elf} targets.
8044 You can build the test program using the @code{d10v-elf} GCC
8045 cross-compiler like this:
8048 $ d10v-elf-gcc -g -c overlays.c
8049 $ d10v-elf-gcc -g -c ovlymgr.c
8050 $ d10v-elf-gcc -g -c foo.c
8051 $ d10v-elf-gcc -g -c bar.c
8052 $ d10v-elf-gcc -g -c baz.c
8053 $ d10v-elf-gcc -g -c grbx.c
8054 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
8055 baz.o grbx.o -Wl,-Td10v.ld -o overlays
8058 The build process is identical for any other architecture, except that
8059 you must substitute the appropriate compiler and linker script for the
8060 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
8064 @chapter Using @value{GDBN} with Different Languages
8067 Although programming languages generally have common aspects, they are
8068 rarely expressed in the same manner. For instance, in ANSI C,
8069 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
8070 Modula-2, it is accomplished by @code{p^}. Values can also be
8071 represented (and displayed) differently. Hex numbers in C appear as
8072 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
8074 @cindex working language
8075 Language-specific information is built into @value{GDBN} for some languages,
8076 allowing you to express operations like the above in your program's
8077 native language, and allowing @value{GDBN} to output values in a manner
8078 consistent with the syntax of your program's native language. The
8079 language you use to build expressions is called the @dfn{working
8083 * Setting:: Switching between source languages
8084 * Show:: Displaying the language
8085 * Checks:: Type and range checks
8086 * Supported languages:: Supported languages
8087 * Unsupported languages:: Unsupported languages
8091 @section Switching between source languages
8093 There are two ways to control the working language---either have @value{GDBN}
8094 set it automatically, or select it manually yourself. You can use the
8095 @code{set language} command for either purpose. On startup, @value{GDBN}
8096 defaults to setting the language automatically. The working language is
8097 used to determine how expressions you type are interpreted, how values
8100 In addition to the working language, every source file that
8101 @value{GDBN} knows about has its own working language. For some object
8102 file formats, the compiler might indicate which language a particular
8103 source file is in. However, most of the time @value{GDBN} infers the
8104 language from the name of the file. The language of a source file
8105 controls whether C@t{++} names are demangled---this way @code{backtrace} can
8106 show each frame appropriately for its own language. There is no way to
8107 set the language of a source file from within @value{GDBN}, but you can
8108 set the language associated with a filename extension. @xref{Show, ,
8109 Displaying the language}.
8111 This is most commonly a problem when you use a program, such
8112 as @code{cfront} or @code{f2c}, that generates C but is written in
8113 another language. In that case, make the
8114 program use @code{#line} directives in its C output; that way
8115 @value{GDBN} will know the correct language of the source code of the original
8116 program, and will display that source code, not the generated C code.
8119 * Filenames:: Filename extensions and languages.
8120 * Manually:: Setting the working language manually
8121 * Automatically:: Having @value{GDBN} infer the source language
8125 @subsection List of filename extensions and languages
8127 If a source file name ends in one of the following extensions, then
8128 @value{GDBN} infers that its language is the one indicated.
8149 Objective-C source file
8156 Modula-2 source file
8160 Assembler source file. This actually behaves almost like C, but
8161 @value{GDBN} does not skip over function prologues when stepping.
8164 In addition, you may set the language associated with a filename
8165 extension. @xref{Show, , Displaying the language}.
8168 @subsection Setting the working language
8170 If you allow @value{GDBN} to set the language automatically,
8171 expressions are interpreted the same way in your debugging session and
8174 @kindex set language
8175 If you wish, you may set the language manually. To do this, issue the
8176 command @samp{set language @var{lang}}, where @var{lang} is the name of
8178 @code{c} or @code{modula-2}.
8179 For a list of the supported languages, type @samp{set language}.
8181 Setting the language manually prevents @value{GDBN} from updating the working
8182 language automatically. This can lead to confusion if you try
8183 to debug a program when the working language is not the same as the
8184 source language, when an expression is acceptable to both
8185 languages---but means different things. For instance, if the current
8186 source file were written in C, and @value{GDBN} was parsing Modula-2, a
8194 might not have the effect you intended. In C, this means to add
8195 @code{b} and @code{c} and place the result in @code{a}. The result
8196 printed would be the value of @code{a}. In Modula-2, this means to compare
8197 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
8200 @subsection Having @value{GDBN} infer the source language
8202 To have @value{GDBN} set the working language automatically, use
8203 @samp{set language local} or @samp{set language auto}. @value{GDBN}
8204 then infers the working language. That is, when your program stops in a
8205 frame (usually by encountering a breakpoint), @value{GDBN} sets the
8206 working language to the language recorded for the function in that
8207 frame. If the language for a frame is unknown (that is, if the function
8208 or block corresponding to the frame was defined in a source file that
8209 does not have a recognized extension), the current working language is
8210 not changed, and @value{GDBN} issues a warning.
8212 This may not seem necessary for most programs, which are written
8213 entirely in one source language. However, program modules and libraries
8214 written in one source language can be used by a main program written in
8215 a different source language. Using @samp{set language auto} in this
8216 case frees you from having to set the working language manually.
8219 @section Displaying the language
8221 The following commands help you find out which language is the
8222 working language, and also what language source files were written in.
8226 @kindex show language
8227 Display the current working language. This is the
8228 language you can use with commands such as @code{print} to
8229 build and compute expressions that may involve variables in your program.
8232 @kindex info frame@r{, show the source language}
8233 Display the source language for this frame. This language becomes the
8234 working language if you use an identifier from this frame.
8235 @xref{Frame Info, ,Information about a frame}, to identify the other
8236 information listed here.
8239 @kindex info source@r{, show the source language}
8240 Display the source language of this source file.
8241 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
8242 information listed here.
8245 In unusual circumstances, you may have source files with extensions
8246 not in the standard list. You can then set the extension associated
8247 with a language explicitly:
8250 @item set extension-language @var{ext} @var{language}
8251 @kindex set extension-language
8252 Tell @value{GDBN} that source files with extension @var{ext} are to be
8253 assumed as written in the source language @var{language}.
8255 @item info extensions
8256 @kindex info extensions
8257 List all the filename extensions and the associated languages.
8261 @section Type and range checking
8264 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
8265 checking are included, but they do not yet have any effect. This
8266 section documents the intended facilities.
8268 @c FIXME remove warning when type/range code added
8270 Some languages are designed to guard you against making seemingly common
8271 errors through a series of compile- and run-time checks. These include
8272 checking the type of arguments to functions and operators, and making
8273 sure mathematical overflows are caught at run time. Checks such as
8274 these help to ensure a program's correctness once it has been compiled
8275 by eliminating type mismatches, and providing active checks for range
8276 errors when your program is running.
8278 @value{GDBN} can check for conditions like the above if you wish.
8279 Although @value{GDBN} does not check the statements in your program,
8280 it can check expressions entered directly into @value{GDBN} for
8281 evaluation via the @code{print} command, for example. As with the
8282 working language, @value{GDBN} can also decide whether or not to check
8283 automatically based on your program's source language.
8284 @xref{Supported languages, ,Supported languages}, for the default
8285 settings of supported languages.
8288 * Type Checking:: An overview of type checking
8289 * Range Checking:: An overview of range checking
8292 @cindex type checking
8293 @cindex checks, type
8295 @subsection An overview of type checking
8297 Some languages, such as Modula-2, are strongly typed, meaning that the
8298 arguments to operators and functions have to be of the correct type,
8299 otherwise an error occurs. These checks prevent type mismatch
8300 errors from ever causing any run-time problems. For example,
8308 The second example fails because the @code{CARDINAL} 1 is not
8309 type-compatible with the @code{REAL} 2.3.
8311 For the expressions you use in @value{GDBN} commands, you can tell the
8312 @value{GDBN} type checker to skip checking;
8313 to treat any mismatches as errors and abandon the expression;
8314 or to only issue warnings when type mismatches occur,
8315 but evaluate the expression anyway. When you choose the last of
8316 these, @value{GDBN} evaluates expressions like the second example above, but
8317 also issues a warning.
8319 Even if you turn type checking off, there may be other reasons
8320 related to type that prevent @value{GDBN} from evaluating an expression.
8321 For instance, @value{GDBN} does not know how to add an @code{int} and
8322 a @code{struct foo}. These particular type errors have nothing to do
8323 with the language in use, and usually arise from expressions, such as
8324 the one described above, which make little sense to evaluate anyway.
8326 Each language defines to what degree it is strict about type. For
8327 instance, both Modula-2 and C require the arguments to arithmetical
8328 operators to be numbers. In C, enumerated types and pointers can be
8329 represented as numbers, so that they are valid arguments to mathematical
8330 operators. @xref{Supported languages, ,Supported languages}, for further
8331 details on specific languages.
8333 @value{GDBN} provides some additional commands for controlling the type checker:
8335 @kindex set check type
8336 @kindex show check type
8338 @item set check type auto
8339 Set type checking on or off based on the current working language.
8340 @xref{Supported languages, ,Supported languages}, for the default settings for
8343 @item set check type on
8344 @itemx set check type off
8345 Set type checking on or off, overriding the default setting for the
8346 current working language. Issue a warning if the setting does not
8347 match the language default. If any type mismatches occur in
8348 evaluating an expression while type checking is on, @value{GDBN} prints a
8349 message and aborts evaluation of the expression.
8351 @item set check type warn
8352 Cause the type checker to issue warnings, but to always attempt to
8353 evaluate the expression. Evaluating the expression may still
8354 be impossible for other reasons. For example, @value{GDBN} cannot add
8355 numbers and structures.
8358 Show the current setting of the type checker, and whether or not @value{GDBN}
8359 is setting it automatically.
8362 @cindex range checking
8363 @cindex checks, range
8364 @node Range Checking
8365 @subsection An overview of range checking
8367 In some languages (such as Modula-2), it is an error to exceed the
8368 bounds of a type; this is enforced with run-time checks. Such range
8369 checking is meant to ensure program correctness by making sure
8370 computations do not overflow, or indices on an array element access do
8371 not exceed the bounds of the array.
8373 For expressions you use in @value{GDBN} commands, you can tell
8374 @value{GDBN} to treat range errors in one of three ways: ignore them,
8375 always treat them as errors and abandon the expression, or issue
8376 warnings but evaluate the expression anyway.
8378 A range error can result from numerical overflow, from exceeding an
8379 array index bound, or when you type a constant that is not a member
8380 of any type. Some languages, however, do not treat overflows as an
8381 error. In many implementations of C, mathematical overflow causes the
8382 result to ``wrap around'' to lower values---for example, if @var{m} is
8383 the largest integer value, and @var{s} is the smallest, then
8386 @var{m} + 1 @result{} @var{s}
8389 This, too, is specific to individual languages, and in some cases
8390 specific to individual compilers or machines. @xref{Supported languages, ,
8391 Supported languages}, for further details on specific languages.
8393 @value{GDBN} provides some additional commands for controlling the range checker:
8395 @kindex set check range
8396 @kindex show check range
8398 @item set check range auto
8399 Set range checking on or off based on the current working language.
8400 @xref{Supported languages, ,Supported languages}, for the default settings for
8403 @item set check range on
8404 @itemx set check range off
8405 Set range checking on or off, overriding the default setting for the
8406 current working language. A warning is issued if the setting does not
8407 match the language default. If a range error occurs and range checking is on,
8408 then a message is printed and evaluation of the expression is aborted.
8410 @item set check range warn
8411 Output messages when the @value{GDBN} range checker detects a range error,
8412 but attempt to evaluate the expression anyway. Evaluating the
8413 expression may still be impossible for other reasons, such as accessing
8414 memory that the process does not own (a typical example from many Unix
8418 Show the current setting of the range checker, and whether or not it is
8419 being set automatically by @value{GDBN}.
8422 @node Supported languages
8423 @section Supported languages
8425 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
8426 assembly, Modula-2, and Ada.
8427 @c This is false ...
8428 Some @value{GDBN} features may be used in expressions regardless of the
8429 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
8430 and the @samp{@{type@}addr} construct (@pxref{Expressions,
8431 ,Expressions}) can be used with the constructs of any supported
8434 The following sections detail to what degree each source language is
8435 supported by @value{GDBN}. These sections are not meant to be language
8436 tutorials or references, but serve only as a reference guide to what the
8437 @value{GDBN} expression parser accepts, and what input and output
8438 formats should look like for different languages. There are many good
8439 books written on each of these languages; please look to these for a
8440 language reference or tutorial.
8444 * Objective-C:: Objective-C
8447 * Modula-2:: Modula-2
8452 @subsection C and C@t{++}
8454 @cindex C and C@t{++}
8455 @cindex expressions in C or C@t{++}
8457 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
8458 to both languages. Whenever this is the case, we discuss those languages
8462 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
8463 @cindex @sc{gnu} C@t{++}
8464 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
8465 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
8466 effectively, you must compile your C@t{++} programs with a supported
8467 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
8468 compiler (@code{aCC}).
8470 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
8471 format; if it doesn't work on your system, try the stabs+ debugging
8472 format. You can select those formats explicitly with the @code{g++}
8473 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
8474 @xref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
8475 CC, gcc.info, Using @sc{gnu} CC}.
8478 * C Operators:: C and C@t{++} operators
8479 * C Constants:: C and C@t{++} constants
8480 * C plus plus expressions:: C@t{++} expressions
8481 * C Defaults:: Default settings for C and C@t{++}
8482 * C Checks:: C and C@t{++} type and range checks
8483 * Debugging C:: @value{GDBN} and C
8484 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
8488 @subsubsection C and C@t{++} operators
8490 @cindex C and C@t{++} operators
8492 Operators must be defined on values of specific types. For instance,
8493 @code{+} is defined on numbers, but not on structures. Operators are
8494 often defined on groups of types.
8496 For the purposes of C and C@t{++}, the following definitions hold:
8501 @emph{Integral types} include @code{int} with any of its storage-class
8502 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
8505 @emph{Floating-point types} include @code{float}, @code{double}, and
8506 @code{long double} (if supported by the target platform).
8509 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
8512 @emph{Scalar types} include all of the above.
8517 The following operators are supported. They are listed here
8518 in order of increasing precedence:
8522 The comma or sequencing operator. Expressions in a comma-separated list
8523 are evaluated from left to right, with the result of the entire
8524 expression being the last expression evaluated.
8527 Assignment. The value of an assignment expression is the value
8528 assigned. Defined on scalar types.
8531 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
8532 and translated to @w{@code{@var{a} = @var{a op b}}}.
8533 @w{@code{@var{op}=}} and @code{=} have the same precedence.
8534 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
8535 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
8538 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
8539 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
8543 Logical @sc{or}. Defined on integral types.
8546 Logical @sc{and}. Defined on integral types.
8549 Bitwise @sc{or}. Defined on integral types.
8552 Bitwise exclusive-@sc{or}. Defined on integral types.
8555 Bitwise @sc{and}. Defined on integral types.
8558 Equality and inequality. Defined on scalar types. The value of these
8559 expressions is 0 for false and non-zero for true.
8561 @item <@r{, }>@r{, }<=@r{, }>=
8562 Less than, greater than, less than or equal, greater than or equal.
8563 Defined on scalar types. The value of these expressions is 0 for false
8564 and non-zero for true.
8567 left shift, and right shift. Defined on integral types.
8570 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8573 Addition and subtraction. Defined on integral types, floating-point types and
8576 @item *@r{, }/@r{, }%
8577 Multiplication, division, and modulus. Multiplication and division are
8578 defined on integral and floating-point types. Modulus is defined on
8582 Increment and decrement. When appearing before a variable, the
8583 operation is performed before the variable is used in an expression;
8584 when appearing after it, the variable's value is used before the
8585 operation takes place.
8588 Pointer dereferencing. Defined on pointer types. Same precedence as
8592 Address operator. Defined on variables. Same precedence as @code{++}.
8594 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
8595 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
8596 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
8597 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
8601 Negative. Defined on integral and floating-point types. Same
8602 precedence as @code{++}.
8605 Logical negation. Defined on integral types. Same precedence as
8609 Bitwise complement operator. Defined on integral types. Same precedence as
8614 Structure member, and pointer-to-structure member. For convenience,
8615 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
8616 pointer based on the stored type information.
8617 Defined on @code{struct} and @code{union} data.
8620 Dereferences of pointers to members.
8623 Array indexing. @code{@var{a}[@var{i}]} is defined as
8624 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
8627 Function parameter list. Same precedence as @code{->}.
8630 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
8631 and @code{class} types.
8634 Doubled colons also represent the @value{GDBN} scope operator
8635 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
8639 If an operator is redefined in the user code, @value{GDBN} usually
8640 attempts to invoke the redefined version instead of using the operator's
8648 @subsubsection C and C@t{++} constants
8650 @cindex C and C@t{++} constants
8652 @value{GDBN} allows you to express the constants of C and C@t{++} in the
8657 Integer constants are a sequence of digits. Octal constants are
8658 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
8659 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
8660 @samp{l}, specifying that the constant should be treated as a
8664 Floating point constants are a sequence of digits, followed by a decimal
8665 point, followed by a sequence of digits, and optionally followed by an
8666 exponent. An exponent is of the form:
8667 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
8668 sequence of digits. The @samp{+} is optional for positive exponents.
8669 A floating-point constant may also end with a letter @samp{f} or
8670 @samp{F}, specifying that the constant should be treated as being of
8671 the @code{float} (as opposed to the default @code{double}) type; or with
8672 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
8676 Enumerated constants consist of enumerated identifiers, or their
8677 integral equivalents.
8680 Character constants are a single character surrounded by single quotes
8681 (@code{'}), or a number---the ordinal value of the corresponding character
8682 (usually its @sc{ascii} value). Within quotes, the single character may
8683 be represented by a letter or by @dfn{escape sequences}, which are of
8684 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
8685 of the character's ordinal value; or of the form @samp{\@var{x}}, where
8686 @samp{@var{x}} is a predefined special character---for example,
8687 @samp{\n} for newline.
8690 String constants are a sequence of character constants surrounded by
8691 double quotes (@code{"}). Any valid character constant (as described
8692 above) may appear. Double quotes within the string must be preceded by
8693 a backslash, so for instance @samp{"a\"b'c"} is a string of five
8697 Pointer constants are an integral value. You can also write pointers
8698 to constants using the C operator @samp{&}.
8701 Array constants are comma-separated lists surrounded by braces @samp{@{}
8702 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
8703 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
8704 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
8708 * C plus plus expressions::
8715 @node C plus plus expressions
8716 @subsubsection C@t{++} expressions
8718 @cindex expressions in C@t{++}
8719 @value{GDBN} expression handling can interpret most C@t{++} expressions.
8721 @cindex debugging C@t{++} programs
8722 @cindex C@t{++} compilers
8723 @cindex debug formats and C@t{++}
8724 @cindex @value{NGCC} and C@t{++}
8726 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
8727 proper compiler and the proper debug format. Currently, @value{GDBN}
8728 works best when debugging C@t{++} code that is compiled with
8729 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
8730 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
8731 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
8732 stabs+ as their default debug format, so you usually don't need to
8733 specify a debug format explicitly. Other compilers and/or debug formats
8734 are likely to work badly or not at all when using @value{GDBN} to debug
8740 @cindex member functions
8742 Member function calls are allowed; you can use expressions like
8745 count = aml->GetOriginal(x, y)
8748 @vindex this@r{, inside C@t{++} member functions}
8749 @cindex namespace in C@t{++}
8751 While a member function is active (in the selected stack frame), your
8752 expressions have the same namespace available as the member function;
8753 that is, @value{GDBN} allows implicit references to the class instance
8754 pointer @code{this} following the same rules as C@t{++}.
8756 @cindex call overloaded functions
8757 @cindex overloaded functions, calling
8758 @cindex type conversions in C@t{++}
8760 You can call overloaded functions; @value{GDBN} resolves the function
8761 call to the right definition, with some restrictions. @value{GDBN} does not
8762 perform overload resolution involving user-defined type conversions,
8763 calls to constructors, or instantiations of templates that do not exist
8764 in the program. It also cannot handle ellipsis argument lists or
8767 It does perform integral conversions and promotions, floating-point
8768 promotions, arithmetic conversions, pointer conversions, conversions of
8769 class objects to base classes, and standard conversions such as those of
8770 functions or arrays to pointers; it requires an exact match on the
8771 number of function arguments.
8773 Overload resolution is always performed, unless you have specified
8774 @code{set overload-resolution off}. @xref{Debugging C plus plus,
8775 ,@value{GDBN} features for C@t{++}}.
8777 You must specify @code{set overload-resolution off} in order to use an
8778 explicit function signature to call an overloaded function, as in
8780 p 'foo(char,int)'('x', 13)
8783 The @value{GDBN} command-completion facility can simplify this;
8784 see @ref{Completion, ,Command completion}.
8786 @cindex reference declarations
8788 @value{GDBN} understands variables declared as C@t{++} references; you can use
8789 them in expressions just as you do in C@t{++} source---they are automatically
8792 In the parameter list shown when @value{GDBN} displays a frame, the values of
8793 reference variables are not displayed (unlike other variables); this
8794 avoids clutter, since references are often used for large structures.
8795 The @emph{address} of a reference variable is always shown, unless
8796 you have specified @samp{set print address off}.
8799 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
8800 expressions can use it just as expressions in your program do. Since
8801 one scope may be defined in another, you can use @code{::} repeatedly if
8802 necessary, for example in an expression like
8803 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
8804 resolving name scope by reference to source files, in both C and C@t{++}
8805 debugging (@pxref{Variables, ,Program variables}).
8808 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
8809 calling virtual functions correctly, printing out virtual bases of
8810 objects, calling functions in a base subobject, casting objects, and
8811 invoking user-defined operators.
8814 @subsubsection C and C@t{++} defaults
8816 @cindex C and C@t{++} defaults
8818 If you allow @value{GDBN} to set type and range checking automatically, they
8819 both default to @code{off} whenever the working language changes to
8820 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
8821 selects the working language.
8823 If you allow @value{GDBN} to set the language automatically, it
8824 recognizes source files whose names end with @file{.c}, @file{.C}, or
8825 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
8826 these files, it sets the working language to C or C@t{++}.
8827 @xref{Automatically, ,Having @value{GDBN} infer the source language},
8828 for further details.
8830 @c Type checking is (a) primarily motivated by Modula-2, and (b)
8831 @c unimplemented. If (b) changes, it might make sense to let this node
8832 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
8835 @subsubsection C and C@t{++} type and range checks
8837 @cindex C and C@t{++} checks
8839 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
8840 is not used. However, if you turn type checking on, @value{GDBN}
8841 considers two variables type equivalent if:
8845 The two variables are structured and have the same structure, union, or
8849 The two variables have the same type name, or types that have been
8850 declared equivalent through @code{typedef}.
8853 @c leaving this out because neither J Gilmore nor R Pesch understand it.
8856 The two @code{struct}, @code{union}, or @code{enum} variables are
8857 declared in the same declaration. (Note: this may not be true for all C
8862 Range checking, if turned on, is done on mathematical operations. Array
8863 indices are not checked, since they are often used to index a pointer
8864 that is not itself an array.
8867 @subsubsection @value{GDBN} and C
8869 The @code{set print union} and @code{show print union} commands apply to
8870 the @code{union} type. When set to @samp{on}, any @code{union} that is
8871 inside a @code{struct} or @code{class} is also printed. Otherwise, it
8872 appears as @samp{@{...@}}.
8874 The @code{@@} operator aids in the debugging of dynamic arrays, formed
8875 with pointers and a memory allocation function. @xref{Expressions,
8879 * Debugging C plus plus::
8882 @node Debugging C plus plus
8883 @subsubsection @value{GDBN} features for C@t{++}
8885 @cindex commands for C@t{++}
8887 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
8888 designed specifically for use with C@t{++}. Here is a summary:
8891 @cindex break in overloaded functions
8892 @item @r{breakpoint menus}
8893 When you want a breakpoint in a function whose name is overloaded,
8894 @value{GDBN} breakpoint menus help you specify which function definition
8895 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
8897 @cindex overloading in C@t{++}
8898 @item rbreak @var{regex}
8899 Setting breakpoints using regular expressions is helpful for setting
8900 breakpoints on overloaded functions that are not members of any special
8902 @xref{Set Breaks, ,Setting breakpoints}.
8904 @cindex C@t{++} exception handling
8907 Debug C@t{++} exception handling using these commands. @xref{Set
8908 Catchpoints, , Setting catchpoints}.
8911 @item ptype @var{typename}
8912 Print inheritance relationships as well as other information for type
8914 @xref{Symbols, ,Examining the Symbol Table}.
8916 @cindex C@t{++} symbol display
8917 @item set print demangle
8918 @itemx show print demangle
8919 @itemx set print asm-demangle
8920 @itemx show print asm-demangle
8921 Control whether C@t{++} symbols display in their source form, both when
8922 displaying code as C@t{++} source and when displaying disassemblies.
8923 @xref{Print Settings, ,Print settings}.
8925 @item set print object
8926 @itemx show print object
8927 Choose whether to print derived (actual) or declared types of objects.
8928 @xref{Print Settings, ,Print settings}.
8930 @item set print vtbl
8931 @itemx show print vtbl
8932 Control the format for printing virtual function tables.
8933 @xref{Print Settings, ,Print settings}.
8934 (The @code{vtbl} commands do not work on programs compiled with the HP
8935 ANSI C@t{++} compiler (@code{aCC}).)
8937 @kindex set overload-resolution
8938 @cindex overloaded functions, overload resolution
8939 @item set overload-resolution on
8940 Enable overload resolution for C@t{++} expression evaluation. The default
8941 is on. For overloaded functions, @value{GDBN} evaluates the arguments
8942 and searches for a function whose signature matches the argument types,
8943 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
8944 expressions}, for details). If it cannot find a match, it emits a
8947 @item set overload-resolution off
8948 Disable overload resolution for C@t{++} expression evaluation. For
8949 overloaded functions that are not class member functions, @value{GDBN}
8950 chooses the first function of the specified name that it finds in the
8951 symbol table, whether or not its arguments are of the correct type. For
8952 overloaded functions that are class member functions, @value{GDBN}
8953 searches for a function whose signature @emph{exactly} matches the
8956 @kindex show overload-resolution
8957 @item show overload-resolution
8958 Show the current setting of overload resolution.
8960 @item @r{Overloaded symbol names}
8961 You can specify a particular definition of an overloaded symbol, using
8962 the same notation that is used to declare such symbols in C@t{++}: type
8963 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
8964 also use the @value{GDBN} command-line word completion facilities to list the
8965 available choices, or to finish the type list for you.
8966 @xref{Completion,, Command completion}, for details on how to do this.
8970 @subsection Objective-C
8973 This section provides information about some commands and command
8974 options that are useful for debugging Objective-C code. See also
8975 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
8976 few more commands specific to Objective-C support.
8979 * Method Names in Commands::
8980 * The Print Command with Objective-C::
8983 @node Method Names in Commands, The Print Command with Objective-C, Objective-C, Objective-C
8984 @subsubsection Method Names in Commands
8986 The following commands have been extended to accept Objective-C method
8987 names as line specifications:
8989 @kindex clear@r{, and Objective-C}
8990 @kindex break@r{, and Objective-C}
8991 @kindex info line@r{, and Objective-C}
8992 @kindex jump@r{, and Objective-C}
8993 @kindex list@r{, and Objective-C}
8997 @item @code{info line}
9002 A fully qualified Objective-C method name is specified as
9005 -[@var{Class} @var{methodName}]
9008 where the minus sign is used to indicate an instance method and a
9009 plus sign (not shown) is used to indicate a class method. The class
9010 name @var{Class} and method name @var{methodName} are enclosed in
9011 brackets, similar to the way messages are specified in Objective-C
9012 source code. For example, to set a breakpoint at the @code{create}
9013 instance method of class @code{Fruit} in the program currently being
9017 break -[Fruit create]
9020 To list ten program lines around the @code{initialize} class method,
9024 list +[NSText initialize]
9027 In the current version of @value{GDBN}, the plus or minus sign is
9028 required. In future versions of @value{GDBN}, the plus or minus
9029 sign will be optional, but you can use it to narrow the search. It
9030 is also possible to specify just a method name:
9036 You must specify the complete method name, including any colons. If
9037 your program's source files contain more than one @code{create} method,
9038 you'll be presented with a numbered list of classes that implement that
9039 method. Indicate your choice by number, or type @samp{0} to exit if
9042 As another example, to clear a breakpoint established at the
9043 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
9046 clear -[NSWindow makeKeyAndOrderFront:]
9049 @node The Print Command with Objective-C
9050 @subsubsection The Print Command With Objective-C
9051 @cindex Objective-C, print objects
9052 @kindex print-object
9053 @kindex po @r{(@code{print-object})}
9055 The print command has also been extended to accept methods. For example:
9058 print -[@var{object} hash]
9061 @cindex print an Objective-C object description
9062 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
9064 will tell @value{GDBN} to send the @code{hash} message to @var{object}
9065 and print the result. Also, an additional command has been added,
9066 @code{print-object} or @code{po} for short, which is meant to print
9067 the description of an object. However, this command may only work
9068 with certain Objective-C libraries that have a particular hook
9069 function, @code{_NSPrintForDebugger}, defined.
9073 @cindex Fortran-specific support in @value{GDBN}
9076 @cindex @code{COMMON} blocks, Fortran
9078 @item info common @r{[}@var{common-name}@r{]}
9079 This command prints the values contained in the Fortran @code{COMMON}
9080 block whose name is @var{common-name}. With no argument, the names of
9081 all @code{COMMON} blocks visible at current program location are
9085 Fortran symbols are usually case-insensitive, so @value{GDBN} by
9086 default uses case-insensitive matches for Fortran symbols. You can
9087 change that with the @samp{set case-insensitive} command, see
9088 @ref{Symbols}, for the details.
9093 @cindex Pascal support in @value{GDBN}, limitations
9094 Debugging Pascal programs which use sets, subranges, file variables, or
9095 nested functions does not currently work. @value{GDBN} does not support
9096 entering expressions, printing values, or similar features using Pascal
9099 The Pascal-specific command @code{set print pascal_static-members}
9100 controls whether static members of Pascal objects are displayed.
9101 @xref{Print Settings, pascal_static-members}.
9104 @subsection Modula-2
9106 @cindex Modula-2, @value{GDBN} support
9108 The extensions made to @value{GDBN} to support Modula-2 only support
9109 output from the @sc{gnu} Modula-2 compiler (which is currently being
9110 developed). Other Modula-2 compilers are not currently supported, and
9111 attempting to debug executables produced by them is most likely
9112 to give an error as @value{GDBN} reads in the executable's symbol
9115 @cindex expressions in Modula-2
9117 * M2 Operators:: Built-in operators
9118 * Built-In Func/Proc:: Built-in functions and procedures
9119 * M2 Constants:: Modula-2 constants
9120 * M2 Defaults:: Default settings for Modula-2
9121 * Deviations:: Deviations from standard Modula-2
9122 * M2 Checks:: Modula-2 type and range checks
9123 * M2 Scope:: The scope operators @code{::} and @code{.}
9124 * GDB/M2:: @value{GDBN} and Modula-2
9128 @subsubsection Operators
9129 @cindex Modula-2 operators
9131 Operators must be defined on values of specific types. For instance,
9132 @code{+} is defined on numbers, but not on structures. Operators are
9133 often defined on groups of types. For the purposes of Modula-2, the
9134 following definitions hold:
9139 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
9143 @emph{Character types} consist of @code{CHAR} and its subranges.
9146 @emph{Floating-point types} consist of @code{REAL}.
9149 @emph{Pointer types} consist of anything declared as @code{POINTER TO
9153 @emph{Scalar types} consist of all of the above.
9156 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
9159 @emph{Boolean types} consist of @code{BOOLEAN}.
9163 The following operators are supported, and appear in order of
9164 increasing precedence:
9168 Function argument or array index separator.
9171 Assignment. The value of @var{var} @code{:=} @var{value} is
9175 Less than, greater than on integral, floating-point, or enumerated
9179 Less than or equal to, greater than or equal to
9180 on integral, floating-point and enumerated types, or set inclusion on
9181 set types. Same precedence as @code{<}.
9183 @item =@r{, }<>@r{, }#
9184 Equality and two ways of expressing inequality, valid on scalar types.
9185 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
9186 available for inequality, since @code{#} conflicts with the script
9190 Set membership. Defined on set types and the types of their members.
9191 Same precedence as @code{<}.
9194 Boolean disjunction. Defined on boolean types.
9197 Boolean conjunction. Defined on boolean types.
9200 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9203 Addition and subtraction on integral and floating-point types, or union
9204 and difference on set types.
9207 Multiplication on integral and floating-point types, or set intersection
9211 Division on floating-point types, or symmetric set difference on set
9212 types. Same precedence as @code{*}.
9215 Integer division and remainder. Defined on integral types. Same
9216 precedence as @code{*}.
9219 Negative. Defined on @code{INTEGER} and @code{REAL} data.
9222 Pointer dereferencing. Defined on pointer types.
9225 Boolean negation. Defined on boolean types. Same precedence as
9229 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
9230 precedence as @code{^}.
9233 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
9236 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
9240 @value{GDBN} and Modula-2 scope operators.
9244 @emph{Warning:} Sets and their operations are not yet supported, so @value{GDBN}
9245 treats the use of the operator @code{IN}, or the use of operators
9246 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
9247 @code{<=}, and @code{>=} on sets as an error.
9251 @node Built-In Func/Proc
9252 @subsubsection Built-in functions and procedures
9253 @cindex Modula-2 built-ins
9255 Modula-2 also makes available several built-in procedures and functions.
9256 In describing these, the following metavariables are used:
9261 represents an @code{ARRAY} variable.
9264 represents a @code{CHAR} constant or variable.
9267 represents a variable or constant of integral type.
9270 represents an identifier that belongs to a set. Generally used in the
9271 same function with the metavariable @var{s}. The type of @var{s} should
9272 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
9275 represents a variable or constant of integral or floating-point type.
9278 represents a variable or constant of floating-point type.
9284 represents a variable.
9287 represents a variable or constant of one of many types. See the
9288 explanation of the function for details.
9291 All Modula-2 built-in procedures also return a result, described below.
9295 Returns the absolute value of @var{n}.
9298 If @var{c} is a lower case letter, it returns its upper case
9299 equivalent, otherwise it returns its argument.
9302 Returns the character whose ordinal value is @var{i}.
9305 Decrements the value in the variable @var{v} by one. Returns the new value.
9307 @item DEC(@var{v},@var{i})
9308 Decrements the value in the variable @var{v} by @var{i}. Returns the
9311 @item EXCL(@var{m},@var{s})
9312 Removes the element @var{m} from the set @var{s}. Returns the new
9315 @item FLOAT(@var{i})
9316 Returns the floating point equivalent of the integer @var{i}.
9319 Returns the index of the last member of @var{a}.
9322 Increments the value in the variable @var{v} by one. Returns the new value.
9324 @item INC(@var{v},@var{i})
9325 Increments the value in the variable @var{v} by @var{i}. Returns the
9328 @item INCL(@var{m},@var{s})
9329 Adds the element @var{m} to the set @var{s} if it is not already
9330 there. Returns the new set.
9333 Returns the maximum value of the type @var{t}.
9336 Returns the minimum value of the type @var{t}.
9339 Returns boolean TRUE if @var{i} is an odd number.
9342 Returns the ordinal value of its argument. For example, the ordinal
9343 value of a character is its @sc{ascii} value (on machines supporting the
9344 @sc{ascii} character set). @var{x} must be of an ordered type, which include
9345 integral, character and enumerated types.
9348 Returns the size of its argument. @var{x} can be a variable or a type.
9350 @item TRUNC(@var{r})
9351 Returns the integral part of @var{r}.
9353 @item VAL(@var{t},@var{i})
9354 Returns the member of the type @var{t} whose ordinal value is @var{i}.
9358 @emph{Warning:} Sets and their operations are not yet supported, so
9359 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
9363 @cindex Modula-2 constants
9365 @subsubsection Constants
9367 @value{GDBN} allows you to express the constants of Modula-2 in the following
9373 Integer constants are simply a sequence of digits. When used in an
9374 expression, a constant is interpreted to be type-compatible with the
9375 rest of the expression. Hexadecimal integers are specified by a
9376 trailing @samp{H}, and octal integers by a trailing @samp{B}.
9379 Floating point constants appear as a sequence of digits, followed by a
9380 decimal point and another sequence of digits. An optional exponent can
9381 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
9382 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
9383 digits of the floating point constant must be valid decimal (base 10)
9387 Character constants consist of a single character enclosed by a pair of
9388 like quotes, either single (@code{'}) or double (@code{"}). They may
9389 also be expressed by their ordinal value (their @sc{ascii} value, usually)
9390 followed by a @samp{C}.
9393 String constants consist of a sequence of characters enclosed by a
9394 pair of like quotes, either single (@code{'}) or double (@code{"}).
9395 Escape sequences in the style of C are also allowed. @xref{C
9396 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
9400 Enumerated constants consist of an enumerated identifier.
9403 Boolean constants consist of the identifiers @code{TRUE} and
9407 Pointer constants consist of integral values only.
9410 Set constants are not yet supported.
9414 @subsubsection Modula-2 defaults
9415 @cindex Modula-2 defaults
9417 If type and range checking are set automatically by @value{GDBN}, they
9418 both default to @code{on} whenever the working language changes to
9419 Modula-2. This happens regardless of whether you or @value{GDBN}
9420 selected the working language.
9422 If you allow @value{GDBN} to set the language automatically, then entering
9423 code compiled from a file whose name ends with @file{.mod} sets the
9424 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
9425 the language automatically}, for further details.
9428 @subsubsection Deviations from standard Modula-2
9429 @cindex Modula-2, deviations from
9431 A few changes have been made to make Modula-2 programs easier to debug.
9432 This is done primarily via loosening its type strictness:
9436 Unlike in standard Modula-2, pointer constants can be formed by
9437 integers. This allows you to modify pointer variables during
9438 debugging. (In standard Modula-2, the actual address contained in a
9439 pointer variable is hidden from you; it can only be modified
9440 through direct assignment to another pointer variable or expression that
9441 returned a pointer.)
9444 C escape sequences can be used in strings and characters to represent
9445 non-printable characters. @value{GDBN} prints out strings with these
9446 escape sequences embedded. Single non-printable characters are
9447 printed using the @samp{CHR(@var{nnn})} format.
9450 The assignment operator (@code{:=}) returns the value of its right-hand
9454 All built-in procedures both modify @emph{and} return their argument.
9458 @subsubsection Modula-2 type and range checks
9459 @cindex Modula-2 checks
9462 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
9465 @c FIXME remove warning when type/range checks added
9467 @value{GDBN} considers two Modula-2 variables type equivalent if:
9471 They are of types that have been declared equivalent via a @code{TYPE
9472 @var{t1} = @var{t2}} statement
9475 They have been declared on the same line. (Note: This is true of the
9476 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
9479 As long as type checking is enabled, any attempt to combine variables
9480 whose types are not equivalent is an error.
9482 Range checking is done on all mathematical operations, assignment, array
9483 index bounds, and all built-in functions and procedures.
9486 @subsubsection The scope operators @code{::} and @code{.}
9488 @cindex @code{.}, Modula-2 scope operator
9489 @cindex colon, doubled as scope operator
9491 @vindex colon-colon@r{, in Modula-2}
9492 @c Info cannot handle :: but TeX can.
9495 @vindex ::@r{, in Modula-2}
9498 There are a few subtle differences between the Modula-2 scope operator
9499 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
9504 @var{module} . @var{id}
9505 @var{scope} :: @var{id}
9509 where @var{scope} is the name of a module or a procedure,
9510 @var{module} the name of a module, and @var{id} is any declared
9511 identifier within your program, except another module.
9513 Using the @code{::} operator makes @value{GDBN} search the scope
9514 specified by @var{scope} for the identifier @var{id}. If it is not
9515 found in the specified scope, then @value{GDBN} searches all scopes
9516 enclosing the one specified by @var{scope}.
9518 Using the @code{.} operator makes @value{GDBN} search the current scope for
9519 the identifier specified by @var{id} that was imported from the
9520 definition module specified by @var{module}. With this operator, it is
9521 an error if the identifier @var{id} was not imported from definition
9522 module @var{module}, or if @var{id} is not an identifier in
9526 @subsubsection @value{GDBN} and Modula-2
9528 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
9529 Five subcommands of @code{set print} and @code{show print} apply
9530 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
9531 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
9532 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
9533 analogue in Modula-2.
9535 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
9536 with any language, is not useful with Modula-2. Its
9537 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
9538 created in Modula-2 as they can in C or C@t{++}. However, because an
9539 address can be specified by an integral constant, the construct
9540 @samp{@{@var{type}@}@var{adrexp}} is still useful.
9542 @cindex @code{#} in Modula-2
9543 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
9544 interpreted as the beginning of a comment. Use @code{<>} instead.
9550 The extensions made to @value{GDBN} for Ada only support
9551 output from the @sc{gnu} Ada (GNAT) compiler.
9552 Other Ada compilers are not currently supported, and
9553 attempting to debug executables produced by them is most likely
9557 @cindex expressions in Ada
9559 * Ada Mode Intro:: General remarks on the Ada syntax
9560 and semantics supported by Ada mode
9562 * Omissions from Ada:: Restrictions on the Ada expression syntax.
9563 * Additions to Ada:: Extensions of the Ada expression syntax.
9564 * Stopping Before Main Program:: Debugging the program during elaboration.
9565 * Ada Glitches:: Known peculiarities of Ada mode.
9568 @node Ada Mode Intro
9569 @subsubsection Introduction
9570 @cindex Ada mode, general
9572 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
9573 syntax, with some extensions.
9574 The philosophy behind the design of this subset is
9578 That @value{GDBN} should provide basic literals and access to operations for
9579 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
9580 leaving more sophisticated computations to subprograms written into the
9581 program (which therefore may be called from @value{GDBN}).
9584 That type safety and strict adherence to Ada language restrictions
9585 are not particularly important to the @value{GDBN} user.
9588 That brevity is important to the @value{GDBN} user.
9591 Thus, for brevity, the debugger acts as if there were
9592 implicit @code{with} and @code{use} clauses in effect for all user-written
9593 packages, making it unnecessary to fully qualify most names with
9594 their packages, regardless of context. Where this causes ambiguity,
9595 @value{GDBN} asks the user's intent.
9597 The debugger will start in Ada mode if it detects an Ada main program.
9598 As for other languages, it will enter Ada mode when stopped in a program that
9599 was translated from an Ada source file.
9601 While in Ada mode, you may use `@t{--}' for comments. This is useful
9602 mostly for documenting command files. The standard @value{GDBN} comment
9603 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
9604 middle (to allow based literals).
9606 The debugger supports limited overloading. Given a subprogram call in which
9607 the function symbol has multiple definitions, it will use the number of
9608 actual parameters and some information about their types to attempt to narrow
9609 the set of definitions. It also makes very limited use of context, preferring
9610 procedures to functions in the context of the @code{call} command, and
9611 functions to procedures elsewhere.
9613 @node Omissions from Ada
9614 @subsubsection Omissions from Ada
9615 @cindex Ada, omissions from
9617 Here are the notable omissions from the subset:
9621 Only a subset of the attributes are supported:
9625 @t{'First}, @t{'Last}, and @t{'Length}
9626 on array objects (not on types and subtypes).
9629 @t{'Min} and @t{'Max}.
9632 @t{'Pos} and @t{'Val}.
9638 @t{'Range} on array objects (not subtypes), but only as the right
9639 operand of the membership (@code{in}) operator.
9642 @t{'Access}, @t{'Unchecked_Access}, and
9643 @t{'Unrestricted_Access} (a GNAT extension).
9651 @code{Characters.Latin_1} are not available and
9652 concatenation is not implemented. Thus, escape characters in strings are
9653 not currently available.
9656 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
9657 equality of representations. They will generally work correctly
9658 for strings and arrays whose elements have integer or enumeration types.
9659 They may not work correctly for arrays whose element
9660 types have user-defined equality, for arrays of real values
9661 (in particular, IEEE-conformant floating point, because of negative
9662 zeroes and NaNs), and for arrays whose elements contain unused bits with
9663 indeterminate values.
9666 The other component-by-component array operations (@code{and}, @code{or},
9667 @code{xor}, @code{not}, and relational tests other than equality)
9668 are not implemented.
9671 There are no record or array aggregates.
9674 Calls to dispatching subprograms are not implemented.
9677 The overloading algorithm is much more limited (i.e., less selective)
9678 than that of real Ada. It makes only limited use of the context in which a subexpression
9679 appears to resolve its meaning, and it is much looser in its rules for allowing
9680 type matches. As a result, some function calls will be ambiguous, and the user
9681 will be asked to choose the proper resolution.
9684 The @code{new} operator is not implemented.
9687 Entry calls are not implemented.
9690 Aside from printing, arithmetic operations on the native VAX floating-point
9691 formats are not supported.
9694 It is not possible to slice a packed array.
9697 @node Additions to Ada
9698 @subsubsection Additions to Ada
9699 @cindex Ada, deviations from
9701 As it does for other languages, @value{GDBN} makes certain generic
9702 extensions to Ada (@pxref{Expressions}):
9706 If the expression @var{E} is a variable residing in memory
9707 (typically a local variable or array element) and @var{N} is
9708 a positive integer, then @code{@var{E}@@@var{N}} displays the values of
9709 @var{E} and the @var{N}-1 adjacent variables following it in memory as an array.
9710 In Ada, this operator is generally not necessary, since its prime use
9711 is in displaying parts of an array, and slicing will usually do this in Ada.
9712 However, there are occasional uses when debugging programs
9713 in which certain debugging information has been optimized away.
9716 @code{@var{B}::@var{var}} means ``the variable named @var{var} that appears
9717 in function or file @var{B}.'' When @var{B} is a file name, you must typically
9718 surround it in single quotes.
9721 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
9722 @var{type} that appears at address @var{addr}.''
9725 A name starting with @samp{$} is a convenience variable
9726 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
9729 In addition, @value{GDBN} provides a few other shortcuts and outright additions specific
9734 The assignment statement is allowed as an expression, returning
9735 its right-hand operand as its value. Thus, you may enter
9739 print A(tmp := y + 1)
9743 The semicolon is allowed as an ``operator,'' returning as its value
9744 the value of its right-hand operand.
9745 This allows, for example,
9746 complex conditional breaks:
9750 condition 1 (report(i); k += 1; A(k) > 100)
9754 Rather than use catenation and symbolic character names to introduce special
9755 characters into strings, one may instead use a special bracket notation,
9756 which is also used to print strings. A sequence of characters of the form
9757 @samp{["@var{XX}"]} within a string or character literal denotes the
9758 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
9759 sequence of characters @samp{["""]} also denotes a single quotation mark
9760 in strings. For example,
9762 "One line.["0a"]Next line.["0a"]"
9765 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF}) after each
9769 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
9770 @t{'Max} is optional (and is ignored in any case). For example, it is valid
9778 When printing arrays, @value{GDBN} uses positional notation when the
9779 array has a lower bound of 1, and uses a modified named notation otherwise.
9780 For example, a one-dimensional array of three integers with a lower bound of 3 might print as
9787 That is, in contrast to valid Ada, only the first component has a @code{=>}
9791 You may abbreviate attributes in expressions with any unique,
9792 multi-character subsequence of
9793 their names (an exact match gets preference).
9794 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
9795 in place of @t{a'length}.
9798 @cindex quoting Ada internal identifiers
9799 Since Ada is case-insensitive, the debugger normally maps identifiers you type
9800 to lower case. The GNAT compiler uses upper-case characters for
9801 some of its internal identifiers, which are normally of no interest to users.
9802 For the rare occasions when you actually have to look at them,
9803 enclose them in angle brackets to avoid the lower-case mapping.
9806 @value{GDBP} print <JMPBUF_SAVE>[0]
9810 Printing an object of class-wide type or dereferencing an
9811 access-to-class-wide value will display all the components of the object's
9812 specific type (as indicated by its run-time tag). Likewise, component
9813 selection on such a value will operate on the specific type of the
9818 @node Stopping Before Main Program
9819 @subsubsection Stopping at the Very Beginning
9821 @cindex breakpointing Ada elaboration code
9822 It is sometimes necessary to debug the program during elaboration, and
9823 before reaching the main procedure.
9824 As defined in the Ada Reference
9825 Manual, the elaboration code is invoked from a procedure called
9826 @code{adainit}. To run your program up to the beginning of
9827 elaboration, simply use the following two commands:
9828 @code{tbreak adainit} and @code{run}.
9831 @subsubsection Known Peculiarities of Ada Mode
9832 @cindex Ada, problems
9834 Besides the omissions listed previously (@pxref{Omissions from Ada}),
9835 we know of several problems with and limitations of Ada mode in
9837 some of which will be fixed with planned future releases of the debugger
9838 and the GNU Ada compiler.
9842 Currently, the debugger
9843 has insufficient information to determine whether certain pointers represent
9844 pointers to objects or the objects themselves.
9845 Thus, the user may have to tack an extra @code{.all} after an expression
9846 to get it printed properly.
9849 Static constants that the compiler chooses not to materialize as objects in
9850 storage are invisible to the debugger.
9853 Named parameter associations in function argument lists are ignored (the
9854 argument lists are treated as positional).
9857 Many useful library packages are currently invisible to the debugger.
9860 Fixed-point arithmetic, conversions, input, and output is carried out using
9861 floating-point arithmetic, and may give results that only approximate those on
9865 The type of the @t{'Address} attribute may not be @code{System.Address}.
9868 The GNAT compiler never generates the prefix @code{Standard} for any of
9869 the standard symbols defined by the Ada language. @value{GDBN} knows about
9870 this: it will strip the prefix from names when you use it, and will never
9871 look for a name you have so qualified among local symbols, nor match against
9872 symbols in other packages or subprograms. If you have
9873 defined entities anywhere in your program other than parameters and
9874 local variables whose simple names match names in @code{Standard},
9875 GNAT's lack of qualification here can cause confusion. When this happens,
9876 you can usually resolve the confusion
9877 by qualifying the problematic names with package
9878 @code{Standard} explicitly.
9881 @node Unsupported languages
9882 @section Unsupported languages
9884 @cindex unsupported languages
9885 @cindex minimal language
9886 In addition to the other fully-supported programming languages,
9887 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
9888 It does not represent a real programming language, but provides a set
9889 of capabilities close to what the C or assembly languages provide.
9890 This should allow most simple operations to be performed while debugging
9891 an application that uses a language currently not supported by @value{GDBN}.
9893 If the language is set to @code{auto}, @value{GDBN} will automatically
9894 select this language if the current frame corresponds to an unsupported
9898 @chapter Examining the Symbol Table
9900 The commands described in this chapter allow you to inquire about the
9901 symbols (names of variables, functions and types) defined in your
9902 program. This information is inherent in the text of your program and
9903 does not change as your program executes. @value{GDBN} finds it in your
9904 program's symbol table, in the file indicated when you started @value{GDBN}
9905 (@pxref{File Options, ,Choosing files}), or by one of the
9906 file-management commands (@pxref{Files, ,Commands to specify files}).
9908 @cindex symbol names
9909 @cindex names of symbols
9910 @cindex quoting names
9911 Occasionally, you may need to refer to symbols that contain unusual
9912 characters, which @value{GDBN} ordinarily treats as word delimiters. The
9913 most frequent case is in referring to static variables in other
9914 source files (@pxref{Variables,,Program variables}). File names
9915 are recorded in object files as debugging symbols, but @value{GDBN} would
9916 ordinarily parse a typical file name, like @file{foo.c}, as the three words
9917 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
9918 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
9925 looks up the value of @code{x} in the scope of the file @file{foo.c}.
9928 @cindex case-insensitive symbol names
9929 @cindex case sensitivity in symbol names
9930 @kindex set case-sensitive
9931 @item set case-sensitive on
9932 @itemx set case-sensitive off
9933 @itemx set case-sensitive auto
9934 Normally, when @value{GDBN} looks up symbols, it matches their names
9935 with case sensitivity determined by the current source language.
9936 Occasionally, you may wish to control that. The command @code{set
9937 case-sensitive} lets you do that by specifying @code{on} for
9938 case-sensitive matches or @code{off} for case-insensitive ones. If
9939 you specify @code{auto}, case sensitivity is reset to the default
9940 suitable for the source language. The default is case-sensitive
9941 matches for all languages except for Fortran, for which the default is
9942 case-insensitive matches.
9944 @kindex show case-sensitive
9945 @item show case-sensitive
9946 This command shows the current setting of case sensitivity for symbols
9949 @kindex info address
9950 @cindex address of a symbol
9951 @item info address @var{symbol}
9952 Describe where the data for @var{symbol} is stored. For a register
9953 variable, this says which register it is kept in. For a non-register
9954 local variable, this prints the stack-frame offset at which the variable
9957 Note the contrast with @samp{print &@var{symbol}}, which does not work
9958 at all for a register variable, and for a stack local variable prints
9959 the exact address of the current instantiation of the variable.
9962 @cindex symbol from address
9963 @cindex closest symbol and offset for an address
9964 @item info symbol @var{addr}
9965 Print the name of a symbol which is stored at the address @var{addr}.
9966 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
9967 nearest symbol and an offset from it:
9970 (@value{GDBP}) info symbol 0x54320
9971 _initialize_vx + 396 in section .text
9975 This is the opposite of the @code{info address} command. You can use
9976 it to find out the name of a variable or a function given its address.
9979 @item whatis @var{expr}
9980 Print the data type of expression @var{expr}. @var{expr} is not
9981 actually evaluated, and any side-effecting operations (such as
9982 assignments or function calls) inside it do not take place.
9983 @xref{Expressions, ,Expressions}.
9986 Print the data type of @code{$}, the last value in the value history.
9989 @item ptype @var{typename}
9990 Print a description of data type @var{typename}. @var{typename} may be
9991 the name of a type, or for C code it may have the form @samp{class
9992 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
9993 @var{union-tag}} or @samp{enum @var{enum-tag}}.
9995 @item ptype @var{expr}
9997 Print a description of the type of expression @var{expr}. @code{ptype}
9998 differs from @code{whatis} by printing a detailed description, instead
9999 of just the name of the type.
10001 For example, for this variable declaration:
10004 struct complex @{double real; double imag;@} v;
10008 the two commands give this output:
10012 (@value{GDBP}) whatis v
10013 type = struct complex
10014 (@value{GDBP}) ptype v
10015 type = struct complex @{
10023 As with @code{whatis}, using @code{ptype} without an argument refers to
10024 the type of @code{$}, the last value in the value history.
10027 @item info types @var{regexp}
10029 Print a brief description of all types whose names match the regular
10030 expression @var{regexp} (or all types in your program, if you supply
10031 no argument). Each complete typename is matched as though it were a
10032 complete line; thus, @samp{i type value} gives information on all
10033 types in your program whose names include the string @code{value}, but
10034 @samp{i type ^value$} gives information only on types whose complete
10035 name is @code{value}.
10037 This command differs from @code{ptype} in two ways: first, like
10038 @code{whatis}, it does not print a detailed description; second, it
10039 lists all source files where a type is defined.
10042 @cindex local variables
10043 @item info scope @var{location}
10044 List all the variables local to a particular scope. This command
10045 accepts a @var{location} argument---a function name, a source line, or
10046 an address preceded by a @samp{*}, and prints all the variables local
10047 to the scope defined by that location. For example:
10050 (@value{GDBP}) @b{info scope command_line_handler}
10051 Scope for command_line_handler:
10052 Symbol rl is an argument at stack/frame offset 8, length 4.
10053 Symbol linebuffer is in static storage at address 0x150a18, length 4.
10054 Symbol linelength is in static storage at address 0x150a1c, length 4.
10055 Symbol p is a local variable in register $esi, length 4.
10056 Symbol p1 is a local variable in register $ebx, length 4.
10057 Symbol nline is a local variable in register $edx, length 4.
10058 Symbol repeat is a local variable at frame offset -8, length 4.
10062 This command is especially useful for determining what data to collect
10063 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
10066 @kindex info source
10068 Show information about the current source file---that is, the source file for
10069 the function containing the current point of execution:
10072 the name of the source file, and the directory containing it,
10074 the directory it was compiled in,
10076 its length, in lines,
10078 which programming language it is written in,
10080 whether the executable includes debugging information for that file, and
10081 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
10083 whether the debugging information includes information about
10084 preprocessor macros.
10088 @kindex info sources
10090 Print the names of all source files in your program for which there is
10091 debugging information, organized into two lists: files whose symbols
10092 have already been read, and files whose symbols will be read when needed.
10094 @kindex info functions
10095 @item info functions
10096 Print the names and data types of all defined functions.
10098 @item info functions @var{regexp}
10099 Print the names and data types of all defined functions
10100 whose names contain a match for regular expression @var{regexp}.
10101 Thus, @samp{info fun step} finds all functions whose names
10102 include @code{step}; @samp{info fun ^step} finds those whose names
10103 start with @code{step}. If a function name contains characters
10104 that conflict with the regular expression language (eg.
10105 @samp{operator*()}), they may be quoted with a backslash.
10107 @kindex info variables
10108 @item info variables
10109 Print the names and data types of all variables that are declared
10110 outside of functions (i.e.@: excluding local variables).
10112 @item info variables @var{regexp}
10113 Print the names and data types of all variables (except for local
10114 variables) whose names contain a match for regular expression
10117 @kindex info classes
10118 @cindex Objective-C, classes and selectors
10120 @itemx info classes @var{regexp}
10121 Display all Objective-C classes in your program, or
10122 (with the @var{regexp} argument) all those matching a particular regular
10125 @kindex info selectors
10126 @item info selectors
10127 @itemx info selectors @var{regexp}
10128 Display all Objective-C selectors in your program, or
10129 (with the @var{regexp} argument) all those matching a particular regular
10133 This was never implemented.
10134 @kindex info methods
10136 @itemx info methods @var{regexp}
10137 The @code{info methods} command permits the user to examine all defined
10138 methods within C@t{++} program, or (with the @var{regexp} argument) a
10139 specific set of methods found in the various C@t{++} classes. Many
10140 C@t{++} classes provide a large number of methods. Thus, the output
10141 from the @code{ptype} command can be overwhelming and hard to use. The
10142 @code{info-methods} command filters the methods, printing only those
10143 which match the regular-expression @var{regexp}.
10146 @cindex reloading symbols
10147 Some systems allow individual object files that make up your program to
10148 be replaced without stopping and restarting your program. For example,
10149 in VxWorks you can simply recompile a defective object file and keep on
10150 running. If you are running on one of these systems, you can allow
10151 @value{GDBN} to reload the symbols for automatically relinked modules:
10154 @kindex set symbol-reloading
10155 @item set symbol-reloading on
10156 Replace symbol definitions for the corresponding source file when an
10157 object file with a particular name is seen again.
10159 @item set symbol-reloading off
10160 Do not replace symbol definitions when encountering object files of the
10161 same name more than once. This is the default state; if you are not
10162 running on a system that permits automatic relinking of modules, you
10163 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
10164 may discard symbols when linking large programs, that may contain
10165 several modules (from different directories or libraries) with the same
10168 @kindex show symbol-reloading
10169 @item show symbol-reloading
10170 Show the current @code{on} or @code{off} setting.
10173 @cindex opaque data types
10174 @kindex set opaque-type-resolution
10175 @item set opaque-type-resolution on
10176 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
10177 declared as a pointer to a @code{struct}, @code{class}, or
10178 @code{union}---for example, @code{struct MyType *}---that is used in one
10179 source file although the full declaration of @code{struct MyType} is in
10180 another source file. The default is on.
10182 A change in the setting of this subcommand will not take effect until
10183 the next time symbols for a file are loaded.
10185 @item set opaque-type-resolution off
10186 Tell @value{GDBN} not to resolve opaque types. In this case, the type
10187 is printed as follows:
10189 @{<no data fields>@}
10192 @kindex show opaque-type-resolution
10193 @item show opaque-type-resolution
10194 Show whether opaque types are resolved or not.
10196 @kindex maint print symbols
10197 @cindex symbol dump
10198 @kindex maint print psymbols
10199 @cindex partial symbol dump
10200 @item maint print symbols @var{filename}
10201 @itemx maint print psymbols @var{filename}
10202 @itemx maint print msymbols @var{filename}
10203 Write a dump of debugging symbol data into the file @var{filename}.
10204 These commands are used to debug the @value{GDBN} symbol-reading code. Only
10205 symbols with debugging data are included. If you use @samp{maint print
10206 symbols}, @value{GDBN} includes all the symbols for which it has already
10207 collected full details: that is, @var{filename} reflects symbols for
10208 only those files whose symbols @value{GDBN} has read. You can use the
10209 command @code{info sources} to find out which files these are. If you
10210 use @samp{maint print psymbols} instead, the dump shows information about
10211 symbols that @value{GDBN} only knows partially---that is, symbols defined in
10212 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
10213 @samp{maint print msymbols} dumps just the minimal symbol information
10214 required for each object file from which @value{GDBN} has read some symbols.
10215 @xref{Files, ,Commands to specify files}, for a discussion of how
10216 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
10218 @kindex maint info symtabs
10219 @kindex maint info psymtabs
10220 @cindex listing @value{GDBN}'s internal symbol tables
10221 @cindex symbol tables, listing @value{GDBN}'s internal
10222 @cindex full symbol tables, listing @value{GDBN}'s internal
10223 @cindex partial symbol tables, listing @value{GDBN}'s internal
10224 @item maint info symtabs @r{[} @var{regexp} @r{]}
10225 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
10227 List the @code{struct symtab} or @code{struct partial_symtab}
10228 structures whose names match @var{regexp}. If @var{regexp} is not
10229 given, list them all. The output includes expressions which you can
10230 copy into a @value{GDBN} debugging this one to examine a particular
10231 structure in more detail. For example:
10234 (@value{GDBP}) maint info psymtabs dwarf2read
10235 @{ objfile /home/gnu/build/gdb/gdb
10236 ((struct objfile *) 0x82e69d0)
10237 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
10238 ((struct partial_symtab *) 0x8474b10)
10241 text addresses 0x814d3c8 -- 0x8158074
10242 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
10243 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
10244 dependencies (none)
10247 (@value{GDBP}) maint info symtabs
10251 We see that there is one partial symbol table whose filename contains
10252 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
10253 and we see that @value{GDBN} has not read in any symtabs yet at all.
10254 If we set a breakpoint on a function, that will cause @value{GDBN} to
10255 read the symtab for the compilation unit containing that function:
10258 (@value{GDBP}) break dwarf2_psymtab_to_symtab
10259 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
10261 (@value{GDBP}) maint info symtabs
10262 @{ objfile /home/gnu/build/gdb/gdb
10263 ((struct objfile *) 0x82e69d0)
10264 @{ symtab /home/gnu/src/gdb/dwarf2read.c
10265 ((struct symtab *) 0x86c1f38)
10268 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
10269 debugformat DWARF 2
10278 @chapter Altering Execution
10280 Once you think you have found an error in your program, you might want to
10281 find out for certain whether correcting the apparent error would lead to
10282 correct results in the rest of the run. You can find the answer by
10283 experiment, using the @value{GDBN} features for altering execution of the
10286 For example, you can store new values into variables or memory
10287 locations, give your program a signal, restart it at a different
10288 address, or even return prematurely from a function.
10291 * Assignment:: Assignment to variables
10292 * Jumping:: Continuing at a different address
10293 * Signaling:: Giving your program a signal
10294 * Returning:: Returning from a function
10295 * Calling:: Calling your program's functions
10296 * Patching:: Patching your program
10300 @section Assignment to variables
10303 @cindex setting variables
10304 To alter the value of a variable, evaluate an assignment expression.
10305 @xref{Expressions, ,Expressions}. For example,
10312 stores the value 4 into the variable @code{x}, and then prints the
10313 value of the assignment expression (which is 4).
10314 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
10315 information on operators in supported languages.
10317 @kindex set variable
10318 @cindex variables, setting
10319 If you are not interested in seeing the value of the assignment, use the
10320 @code{set} command instead of the @code{print} command. @code{set} is
10321 really the same as @code{print} except that the expression's value is
10322 not printed and is not put in the value history (@pxref{Value History,
10323 ,Value history}). The expression is evaluated only for its effects.
10325 If the beginning of the argument string of the @code{set} command
10326 appears identical to a @code{set} subcommand, use the @code{set
10327 variable} command instead of just @code{set}. This command is identical
10328 to @code{set} except for its lack of subcommands. For example, if your
10329 program has a variable @code{width}, you get an error if you try to set
10330 a new value with just @samp{set width=13}, because @value{GDBN} has the
10331 command @code{set width}:
10334 (@value{GDBP}) whatis width
10336 (@value{GDBP}) p width
10338 (@value{GDBP}) set width=47
10339 Invalid syntax in expression.
10343 The invalid expression, of course, is @samp{=47}. In
10344 order to actually set the program's variable @code{width}, use
10347 (@value{GDBP}) set var width=47
10350 Because the @code{set} command has many subcommands that can conflict
10351 with the names of program variables, it is a good idea to use the
10352 @code{set variable} command instead of just @code{set}. For example, if
10353 your program has a variable @code{g}, you run into problems if you try
10354 to set a new value with just @samp{set g=4}, because @value{GDBN} has
10355 the command @code{set gnutarget}, abbreviated @code{set g}:
10359 (@value{GDBP}) whatis g
10363 (@value{GDBP}) set g=4
10367 The program being debugged has been started already.
10368 Start it from the beginning? (y or n) y
10369 Starting program: /home/smith/cc_progs/a.out
10370 "/home/smith/cc_progs/a.out": can't open to read symbols:
10371 Invalid bfd target.
10372 (@value{GDBP}) show g
10373 The current BFD target is "=4".
10378 The program variable @code{g} did not change, and you silently set the
10379 @code{gnutarget} to an invalid value. In order to set the variable
10383 (@value{GDBP}) set var g=4
10386 @value{GDBN} allows more implicit conversions in assignments than C; you can
10387 freely store an integer value into a pointer variable or vice versa,
10388 and you can convert any structure to any other structure that is the
10389 same length or shorter.
10390 @comment FIXME: how do structs align/pad in these conversions?
10391 @comment /doc@cygnus.com 18dec1990
10393 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
10394 construct to generate a value of specified type at a specified address
10395 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
10396 to memory location @code{0x83040} as an integer (which implies a certain size
10397 and representation in memory), and
10400 set @{int@}0x83040 = 4
10404 stores the value 4 into that memory location.
10407 @section Continuing at a different address
10409 Ordinarily, when you continue your program, you do so at the place where
10410 it stopped, with the @code{continue} command. You can instead continue at
10411 an address of your own choosing, with the following commands:
10415 @item jump @var{linespec}
10416 Resume execution at line @var{linespec}. Execution stops again
10417 immediately if there is a breakpoint there. @xref{List, ,Printing
10418 source lines}, for a description of the different forms of
10419 @var{linespec}. It is common practice to use the @code{tbreak} command
10420 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
10423 The @code{jump} command does not change the current stack frame, or
10424 the stack pointer, or the contents of any memory location or any
10425 register other than the program counter. If line @var{linespec} is in
10426 a different function from the one currently executing, the results may
10427 be bizarre if the two functions expect different patterns of arguments or
10428 of local variables. For this reason, the @code{jump} command requests
10429 confirmation if the specified line is not in the function currently
10430 executing. However, even bizarre results are predictable if you are
10431 well acquainted with the machine-language code of your program.
10433 @item jump *@var{address}
10434 Resume execution at the instruction at address @var{address}.
10437 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
10438 On many systems, you can get much the same effect as the @code{jump}
10439 command by storing a new value into the register @code{$pc}. The
10440 difference is that this does not start your program running; it only
10441 changes the address of where it @emph{will} run when you continue. For
10449 makes the next @code{continue} command or stepping command execute at
10450 address @code{0x485}, rather than at the address where your program stopped.
10451 @xref{Continuing and Stepping, ,Continuing and stepping}.
10453 The most common occasion to use the @code{jump} command is to back
10454 up---perhaps with more breakpoints set---over a portion of a program
10455 that has already executed, in order to examine its execution in more
10460 @section Giving your program a signal
10461 @cindex deliver a signal to a program
10465 @item signal @var{signal}
10466 Resume execution where your program stopped, but immediately give it the
10467 signal @var{signal}. @var{signal} can be the name or the number of a
10468 signal. For example, on many systems @code{signal 2} and @code{signal
10469 SIGINT} are both ways of sending an interrupt signal.
10471 Alternatively, if @var{signal} is zero, continue execution without
10472 giving a signal. This is useful when your program stopped on account of
10473 a signal and would ordinary see the signal when resumed with the
10474 @code{continue} command; @samp{signal 0} causes it to resume without a
10477 @code{signal} does not repeat when you press @key{RET} a second time
10478 after executing the command.
10482 Invoking the @code{signal} command is not the same as invoking the
10483 @code{kill} utility from the shell. Sending a signal with @code{kill}
10484 causes @value{GDBN} to decide what to do with the signal depending on
10485 the signal handling tables (@pxref{Signals}). The @code{signal} command
10486 passes the signal directly to your program.
10490 @section Returning from a function
10493 @cindex returning from a function
10496 @itemx return @var{expression}
10497 You can cancel execution of a function call with the @code{return}
10498 command. If you give an
10499 @var{expression} argument, its value is used as the function's return
10503 When you use @code{return}, @value{GDBN} discards the selected stack frame
10504 (and all frames within it). You can think of this as making the
10505 discarded frame return prematurely. If you wish to specify a value to
10506 be returned, give that value as the argument to @code{return}.
10508 This pops the selected stack frame (@pxref{Selection, ,Selecting a
10509 frame}), and any other frames inside of it, leaving its caller as the
10510 innermost remaining frame. That frame becomes selected. The
10511 specified value is stored in the registers used for returning values
10514 The @code{return} command does not resume execution; it leaves the
10515 program stopped in the state that would exist if the function had just
10516 returned. In contrast, the @code{finish} command (@pxref{Continuing
10517 and Stepping, ,Continuing and stepping}) resumes execution until the
10518 selected stack frame returns naturally.
10521 @section Calling program functions
10524 @cindex calling functions
10525 @cindex inferior functions, calling
10526 @item print @var{expr}
10527 Evaluate the expression @var{expr} and display the resuling value.
10528 @var{expr} may include calls to functions in the program being
10532 @item call @var{expr}
10533 Evaluate the expression @var{expr} without displaying @code{void}
10536 You can use this variant of the @code{print} command if you want to
10537 execute a function from your program that does not return anything
10538 (a.k.a.@: @dfn{a void function}), but without cluttering the output
10539 with @code{void} returned values that @value{GDBN} will otherwise
10540 print. If the result is not void, it is printed and saved in the
10544 It is possible for the function you call via the @code{print} or
10545 @code{call} command to generate a signal (e.g., if there's a bug in
10546 the function, or if you passed it incorrect arguments). What happens
10547 in that case is controlled by the @code{set unwindonsignal} command.
10550 @item set unwindonsignal
10551 @kindex set unwindonsignal
10552 @cindex unwind stack in called functions
10553 @cindex call dummy stack unwinding
10554 Set unwinding of the stack if a signal is received while in a function
10555 that @value{GDBN} called in the program being debugged. If set to on,
10556 @value{GDBN} unwinds the stack it created for the call and restores
10557 the context to what it was before the call. If set to off (the
10558 default), @value{GDBN} stops in the frame where the signal was
10561 @item show unwindonsignal
10562 @kindex show unwindonsignal
10563 Show the current setting of stack unwinding in the functions called by
10567 @cindex weak alias functions
10568 Sometimes, a function you wish to call is actually a @dfn{weak alias}
10569 for another function. In such case, @value{GDBN} might not pick up
10570 the type information, including the types of the function arguments,
10571 which causes @value{GDBN} to call the inferior function incorrectly.
10572 As a result, the called function will function erroneously and may
10573 even crash. A solution to that is to use the name of the aliased
10577 @section Patching programs
10579 @cindex patching binaries
10580 @cindex writing into executables
10581 @cindex writing into corefiles
10583 By default, @value{GDBN} opens the file containing your program's
10584 executable code (or the corefile) read-only. This prevents accidental
10585 alterations to machine code; but it also prevents you from intentionally
10586 patching your program's binary.
10588 If you'd like to be able to patch the binary, you can specify that
10589 explicitly with the @code{set write} command. For example, you might
10590 want to turn on internal debugging flags, or even to make emergency
10596 @itemx set write off
10597 If you specify @samp{set write on}, @value{GDBN} opens executable and
10598 core files for both reading and writing; if you specify @samp{set write
10599 off} (the default), @value{GDBN} opens them read-only.
10601 If you have already loaded a file, you must load it again (using the
10602 @code{exec-file} or @code{core-file} command) after changing @code{set
10603 write}, for your new setting to take effect.
10607 Display whether executable files and core files are opened for writing
10608 as well as reading.
10612 @chapter @value{GDBN} Files
10614 @value{GDBN} needs to know the file name of the program to be debugged,
10615 both in order to read its symbol table and in order to start your
10616 program. To debug a core dump of a previous run, you must also tell
10617 @value{GDBN} the name of the core dump file.
10620 * Files:: Commands to specify files
10621 * Separate Debug Files:: Debugging information in separate files
10622 * Symbol Errors:: Errors reading symbol files
10626 @section Commands to specify files
10628 @cindex symbol table
10629 @cindex core dump file
10631 You may want to specify executable and core dump file names. The usual
10632 way to do this is at start-up time, using the arguments to
10633 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
10634 Out of @value{GDBN}}).
10636 Occasionally it is necessary to change to a different file during a
10637 @value{GDBN} session. Or you may run @value{GDBN} and forget to
10638 specify a file you want to use. Or you are debugging a remote target
10639 via @code{gdbserver} (@pxref{Server, file}). In these situations the
10640 @value{GDBN} commands to specify new files are useful.
10643 @cindex executable file
10645 @item file @var{filename}
10646 Use @var{filename} as the program to be debugged. It is read for its
10647 symbols and for the contents of pure memory. It is also the program
10648 executed when you use the @code{run} command. If you do not specify a
10649 directory and the file is not found in the @value{GDBN} working directory,
10650 @value{GDBN} uses the environment variable @code{PATH} as a list of
10651 directories to search, just as the shell does when looking for a program
10652 to run. You can change the value of this variable, for both @value{GDBN}
10653 and your program, using the @code{path} command.
10655 On systems with memory-mapped files, an auxiliary file named
10656 @file{@var{filename}.syms} may hold symbol table information for
10657 @var{filename}. If so, @value{GDBN} maps in the symbol table from
10658 @file{@var{filename}.syms}, starting up more quickly. See the
10659 descriptions of the file options @samp{-mapped} and @samp{-readnow}
10660 (available on the command line, see @ref{File Options, , -readnow},
10661 and with the commands @code{file}, @code{symbol-file}, or
10662 @code{add-symbol-file}, described below), for more information.
10664 @cindex unlinked object files
10665 @cindex patching object files
10666 You can load unlinked object @file{.o} files into @value{GDBN} using
10667 the @code{file} command. You will not be able to ``run'' an object
10668 file, but you can disassemble functions and inspect variables. Also,
10669 if the underlying BFD functionality supports it, you could use
10670 @kbd{gdb -write} to patch object files using this technique. Note
10671 that @value{GDBN} can neither interpret nor modify relocations in this
10672 case, so branches and some initialized variables will appear to go to
10673 the wrong place. But this feature is still handy from time to time.
10676 @code{file} with no argument makes @value{GDBN} discard any information it
10677 has on both executable file and the symbol table.
10680 @item exec-file @r{[} @var{filename} @r{]}
10681 Specify that the program to be run (but not the symbol table) is found
10682 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
10683 if necessary to locate your program. Omitting @var{filename} means to
10684 discard information on the executable file.
10686 @kindex symbol-file
10687 @item symbol-file @r{[} @var{filename} @r{]}
10688 Read symbol table information from file @var{filename}. @code{PATH} is
10689 searched when necessary. Use the @code{file} command to get both symbol
10690 table and program to run from the same file.
10692 @code{symbol-file} with no argument clears out @value{GDBN} information on your
10693 program's symbol table.
10695 The @code{symbol-file} command causes @value{GDBN} to forget the contents
10696 of its convenience variables, the value history, and all breakpoints and
10697 auto-display expressions. This is because they may contain pointers to
10698 the internal data recording symbols and data types, which are part of
10699 the old symbol table data being discarded inside @value{GDBN}.
10701 @code{symbol-file} does not repeat if you press @key{RET} again after
10704 When @value{GDBN} is configured for a particular environment, it
10705 understands debugging information in whatever format is the standard
10706 generated for that environment; you may use either a @sc{gnu} compiler, or
10707 other compilers that adhere to the local conventions.
10708 Best results are usually obtained from @sc{gnu} compilers; for example,
10709 using @code{@value{GCC}} you can generate debugging information for
10712 For most kinds of object files, with the exception of old SVR3 systems
10713 using COFF, the @code{symbol-file} command does not normally read the
10714 symbol table in full right away. Instead, it scans the symbol table
10715 quickly to find which source files and which symbols are present. The
10716 details are read later, one source file at a time, as they are needed.
10718 The purpose of this two-stage reading strategy is to make @value{GDBN}
10719 start up faster. For the most part, it is invisible except for
10720 occasional pauses while the symbol table details for a particular source
10721 file are being read. (The @code{set verbose} command can turn these
10722 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
10723 warnings and messages}.)
10725 We have not implemented the two-stage strategy for COFF yet. When the
10726 symbol table is stored in COFF format, @code{symbol-file} reads the
10727 symbol table data in full right away. Note that ``stabs-in-COFF''
10728 still does the two-stage strategy, since the debug info is actually
10732 @cindex reading symbols immediately
10733 @cindex symbols, reading immediately
10735 @cindex memory-mapped symbol file
10736 @cindex saving symbol table
10737 @item symbol-file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10738 @itemx file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10739 You can override the @value{GDBN} two-stage strategy for reading symbol
10740 tables by using the @samp{-readnow} option with any of the commands that
10741 load symbol table information, if you want to be sure @value{GDBN} has the
10742 entire symbol table available.
10744 If memory-mapped files are available on your system through the
10745 @code{mmap} system call, you can use another option, @samp{-mapped}, to
10746 cause @value{GDBN} to write the symbols for your program into a reusable
10747 file. Future @value{GDBN} debugging sessions map in symbol information
10748 from this auxiliary symbol file (if the program has not changed), rather
10749 than spending time reading the symbol table from the executable
10750 program. Using the @samp{-mapped} option has the same effect as
10751 starting @value{GDBN} with the @samp{-mapped} command-line option.
10753 You can use both options together, to make sure the auxiliary symbol
10754 file has all the symbol information for your program.
10756 The auxiliary symbol file for a program called @var{myprog} is called
10757 @samp{@var{myprog}.syms}. Once this file exists (so long as it is newer
10758 than the corresponding executable), @value{GDBN} always attempts to use
10759 it when you debug @var{myprog}; no special options or commands are
10762 The @file{.syms} file is specific to the host machine where you run
10763 @value{GDBN}. It holds an exact image of the internal @value{GDBN}
10764 symbol table. It cannot be shared across multiple host platforms.
10766 @c FIXME: for now no mention of directories, since this seems to be in
10767 @c flux. 13mar1992 status is that in theory GDB would look either in
10768 @c current dir or in same dir as myprog; but issues like competing
10769 @c GDB's, or clutter in system dirs, mean that in practice right now
10770 @c only current dir is used. FFish says maybe a special GDB hierarchy
10771 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
10775 @item core-file @r{[}@var{filename}@r{]}
10777 Specify the whereabouts of a core dump file to be used as the ``contents
10778 of memory''. Traditionally, core files contain only some parts of the
10779 address space of the process that generated them; @value{GDBN} can access the
10780 executable file itself for other parts.
10782 @code{core-file} with no argument specifies that no core file is
10785 Note that the core file is ignored when your program is actually running
10786 under @value{GDBN}. So, if you have been running your program and you
10787 wish to debug a core file instead, you must kill the subprocess in which
10788 the program is running. To do this, use the @code{kill} command
10789 (@pxref{Kill Process, ,Killing the child process}).
10791 @kindex add-symbol-file
10792 @cindex dynamic linking
10793 @item add-symbol-file @var{filename} @var{address}
10794 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10795 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
10796 The @code{add-symbol-file} command reads additional symbol table
10797 information from the file @var{filename}. You would use this command
10798 when @var{filename} has been dynamically loaded (by some other means)
10799 into the program that is running. @var{address} should be the memory
10800 address at which the file has been loaded; @value{GDBN} cannot figure
10801 this out for itself. You can additionally specify an arbitrary number
10802 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
10803 section name and base address for that section. You can specify any
10804 @var{address} as an expression.
10806 The symbol table of the file @var{filename} is added to the symbol table
10807 originally read with the @code{symbol-file} command. You can use the
10808 @code{add-symbol-file} command any number of times; the new symbol data
10809 thus read keeps adding to the old. To discard all old symbol data
10810 instead, use the @code{symbol-file} command without any arguments.
10812 @cindex relocatable object files, reading symbols from
10813 @cindex object files, relocatable, reading symbols from
10814 @cindex reading symbols from relocatable object files
10815 @cindex symbols, reading from relocatable object files
10816 @cindex @file{.o} files, reading symbols from
10817 Although @var{filename} is typically a shared library file, an
10818 executable file, or some other object file which has been fully
10819 relocated for loading into a process, you can also load symbolic
10820 information from relocatable @file{.o} files, as long as:
10824 the file's symbolic information refers only to linker symbols defined in
10825 that file, not to symbols defined by other object files,
10827 every section the file's symbolic information refers to has actually
10828 been loaded into the inferior, as it appears in the file, and
10830 you can determine the address at which every section was loaded, and
10831 provide these to the @code{add-symbol-file} command.
10835 Some embedded operating systems, like Sun Chorus and VxWorks, can load
10836 relocatable files into an already running program; such systems
10837 typically make the requirements above easy to meet. However, it's
10838 important to recognize that many native systems use complex link
10839 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
10840 assembly, for example) that make the requirements difficult to meet. In
10841 general, one cannot assume that using @code{add-symbol-file} to read a
10842 relocatable object file's symbolic information will have the same effect
10843 as linking the relocatable object file into the program in the normal
10846 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
10848 You can use the @samp{-mapped} and @samp{-readnow} options just as with
10849 the @code{symbol-file} command, to change how @value{GDBN} manages the symbol
10850 table information for @var{filename}.
10852 @kindex add-symbol-file-from-memory
10853 @cindex @code{syscall DSO}
10854 @cindex load symbols from memory
10855 @item add-symbol-file-from-memory @var{address}
10856 Load symbols from the given @var{address} in a dynamically loaded
10857 object file whose image is mapped directly into the inferior's memory.
10858 For example, the Linux kernel maps a @code{syscall DSO} into each
10859 process's address space; this DSO provides kernel-specific code for
10860 some system calls. The argument can be any expression whose
10861 evaluation yields the address of the file's shared object file header.
10862 For this command to work, you must have used @code{symbol-file} or
10863 @code{exec-file} commands in advance.
10865 @kindex add-shared-symbol-files
10867 @item add-shared-symbol-files @var{library-file}
10868 @itemx assf @var{library-file}
10869 The @code{add-shared-symbol-files} command can currently be used only
10870 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
10871 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
10872 @value{GDBN} automatically looks for shared libraries, however if
10873 @value{GDBN} does not find yours, you can invoke
10874 @code{add-shared-symbol-files}. It takes one argument: the shared
10875 library's file name. @code{assf} is a shorthand alias for
10876 @code{add-shared-symbol-files}.
10879 @item section @var{section} @var{addr}
10880 The @code{section} command changes the base address of the named
10881 @var{section} of the exec file to @var{addr}. This can be used if the
10882 exec file does not contain section addresses, (such as in the
10883 @code{a.out} format), or when the addresses specified in the file
10884 itself are wrong. Each section must be changed separately. The
10885 @code{info files} command, described below, lists all the sections and
10889 @kindex info target
10892 @code{info files} and @code{info target} are synonymous; both print the
10893 current target (@pxref{Targets, ,Specifying a Debugging Target}),
10894 including the names of the executable and core dump files currently in
10895 use by @value{GDBN}, and the files from which symbols were loaded. The
10896 command @code{help target} lists all possible targets rather than
10899 @kindex maint info sections
10900 @item maint info sections
10901 Another command that can give you extra information about program sections
10902 is @code{maint info sections}. In addition to the section information
10903 displayed by @code{info files}, this command displays the flags and file
10904 offset of each section in the executable and core dump files. In addition,
10905 @code{maint info sections} provides the following command options (which
10906 may be arbitrarily combined):
10910 Display sections for all loaded object files, including shared libraries.
10911 @item @var{sections}
10912 Display info only for named @var{sections}.
10913 @item @var{section-flags}
10914 Display info only for sections for which @var{section-flags} are true.
10915 The section flags that @value{GDBN} currently knows about are:
10918 Section will have space allocated in the process when loaded.
10919 Set for all sections except those containing debug information.
10921 Section will be loaded from the file into the child process memory.
10922 Set for pre-initialized code and data, clear for @code{.bss} sections.
10924 Section needs to be relocated before loading.
10926 Section cannot be modified by the child process.
10928 Section contains executable code only.
10930 Section contains data only (no executable code).
10932 Section will reside in ROM.
10934 Section contains data for constructor/destructor lists.
10936 Section is not empty.
10938 An instruction to the linker to not output the section.
10939 @item COFF_SHARED_LIBRARY
10940 A notification to the linker that the section contains
10941 COFF shared library information.
10943 Section contains common symbols.
10946 @kindex set trust-readonly-sections
10947 @cindex read-only sections
10948 @item set trust-readonly-sections on
10949 Tell @value{GDBN} that readonly sections in your object file
10950 really are read-only (i.e.@: that their contents will not change).
10951 In that case, @value{GDBN} can fetch values from these sections
10952 out of the object file, rather than from the target program.
10953 For some targets (notably embedded ones), this can be a significant
10954 enhancement to debugging performance.
10956 The default is off.
10958 @item set trust-readonly-sections off
10959 Tell @value{GDBN} not to trust readonly sections. This means that
10960 the contents of the section might change while the program is running,
10961 and must therefore be fetched from the target when needed.
10963 @item show trust-readonly-sections
10964 Show the current setting of trusting readonly sections.
10967 All file-specifying commands allow both absolute and relative file names
10968 as arguments. @value{GDBN} always converts the file name to an absolute file
10969 name and remembers it that way.
10971 @cindex shared libraries
10972 @value{GDBN} supports GNU/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
10973 and IBM RS/6000 AIX shared libraries.
10975 @value{GDBN} automatically loads symbol definitions from shared libraries
10976 when you use the @code{run} command, or when you examine a core file.
10977 (Before you issue the @code{run} command, @value{GDBN} does not understand
10978 references to a function in a shared library, however---unless you are
10979 debugging a core file).
10981 On HP-UX, if the program loads a library explicitly, @value{GDBN}
10982 automatically loads the symbols at the time of the @code{shl_load} call.
10984 @c FIXME: some @value{GDBN} release may permit some refs to undef
10985 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
10986 @c FIXME...lib; check this from time to time when updating manual
10988 There are times, however, when you may wish to not automatically load
10989 symbol definitions from shared libraries, such as when they are
10990 particularly large or there are many of them.
10992 To control the automatic loading of shared library symbols, use the
10996 @kindex set auto-solib-add
10997 @item set auto-solib-add @var{mode}
10998 If @var{mode} is @code{on}, symbols from all shared object libraries
10999 will be loaded automatically when the inferior begins execution, you
11000 attach to an independently started inferior, or when the dynamic linker
11001 informs @value{GDBN} that a new library has been loaded. If @var{mode}
11002 is @code{off}, symbols must be loaded manually, using the
11003 @code{sharedlibrary} command. The default value is @code{on}.
11005 @cindex memory used for symbol tables
11006 If your program uses lots of shared libraries with debug info that
11007 takes large amounts of memory, you can decrease the @value{GDBN}
11008 memory footprint by preventing it from automatically loading the
11009 symbols from shared libraries. To that end, type @kbd{set
11010 auto-solib-add off} before running the inferior, then load each
11011 library whose debug symbols you do need with @kbd{sharedlibrary
11012 @var{regexp}}, where @var{regexp} is a regular expresion that matches
11013 the libraries whose symbols you want to be loaded.
11015 @kindex show auto-solib-add
11016 @item show auto-solib-add
11017 Display the current autoloading mode.
11020 @cindex load shared library
11021 To explicitly load shared library symbols, use the @code{sharedlibrary}
11025 @kindex info sharedlibrary
11028 @itemx info sharedlibrary
11029 Print the names of the shared libraries which are currently loaded.
11031 @kindex sharedlibrary
11033 @item sharedlibrary @var{regex}
11034 @itemx share @var{regex}
11035 Load shared object library symbols for files matching a
11036 Unix regular expression.
11037 As with files loaded automatically, it only loads shared libraries
11038 required by your program for a core file or after typing @code{run}. If
11039 @var{regex} is omitted all shared libraries required by your program are
11042 @item nosharedlibrary
11043 @kindex nosharedlibrary
11044 @cindex unload symbols from shared libraries
11045 Unload all shared object library symbols. This discards all symbols
11046 that have been loaded from all shared libraries. Symbols from shared
11047 libraries that were loaded by explicit user requests are not
11051 Sometimes you may wish that @value{GDBN} stops and gives you control
11052 when any of shared library events happen. Use the @code{set
11053 stop-on-solib-events} command for this:
11056 @item set stop-on-solib-events
11057 @kindex set stop-on-solib-events
11058 This command controls whether @value{GDBN} should give you control
11059 when the dynamic linker notifies it about some shared library event.
11060 The most common event of interest is loading or unloading of a new
11063 @item show stop-on-solib-events
11064 @kindex show stop-on-solib-events
11065 Show whether @value{GDBN} stops and gives you control when shared
11066 library events happen.
11069 Shared libraries are also supported in many cross or remote debugging
11070 configurations. A copy of the target's libraries need to be present on the
11071 host system; they need to be the same as the target libraries, although the
11072 copies on the target can be stripped as long as the copies on the host are
11075 @cindex where to look for shared libraries
11076 For remote debugging, you need to tell @value{GDBN} where the target
11077 libraries are, so that it can load the correct copies---otherwise, it
11078 may try to load the host's libraries. @value{GDBN} has two variables
11079 to specify the search directories for target libraries.
11082 @cindex prefix for shared library file names
11083 @kindex set solib-absolute-prefix
11084 @item set solib-absolute-prefix @var{path}
11085 If this variable is set, @var{path} will be used as a prefix for any
11086 absolute shared library paths; many runtime loaders store the absolute
11087 paths to the shared library in the target program's memory. If you use
11088 @samp{solib-absolute-prefix} to find shared libraries, they need to be laid
11089 out in the same way that they are on the target, with e.g.@: a
11090 @file{/usr/lib} hierarchy under @var{path}.
11092 @cindex default value of @samp{solib-absolute-prefix}
11093 @cindex @samp{--with-sysroot}
11094 You can set the default value of @samp{solib-absolute-prefix} by using the
11095 configure-time @samp{--with-sysroot} option.
11097 @kindex show solib-absolute-prefix
11098 @item show solib-absolute-prefix
11099 Display the current shared library prefix.
11101 @kindex set solib-search-path
11102 @item set solib-search-path @var{path}
11103 If this variable is set, @var{path} is a colon-separated list of directories
11104 to search for shared libraries. @samp{solib-search-path} is used after
11105 @samp{solib-absolute-prefix} fails to locate the library, or if the path to
11106 the library is relative instead of absolute. If you want to use
11107 @samp{solib-search-path} instead of @samp{solib-absolute-prefix}, be sure to
11108 set @samp{solib-absolute-prefix} to a nonexistant directory to prevent
11109 @value{GDBN} from finding your host's libraries.
11111 @kindex show solib-search-path
11112 @item show solib-search-path
11113 Display the current shared library search path.
11117 @node Separate Debug Files
11118 @section Debugging Information in Separate Files
11119 @cindex separate debugging information files
11120 @cindex debugging information in separate files
11121 @cindex @file{.debug} subdirectories
11122 @cindex debugging information directory, global
11123 @cindex global debugging information directory
11125 @value{GDBN} allows you to put a program's debugging information in a
11126 file separate from the executable itself, in a way that allows
11127 @value{GDBN} to find and load the debugging information automatically.
11128 Since debugging information can be very large --- sometimes larger
11129 than the executable code itself --- some systems distribute debugging
11130 information for their executables in separate files, which users can
11131 install only when they need to debug a problem.
11133 If an executable's debugging information has been extracted to a
11134 separate file, the executable should contain a @dfn{debug link} giving
11135 the name of the debugging information file (with no directory
11136 components), and a checksum of its contents. (The exact form of a
11137 debug link is described below.) If the full name of the directory
11138 containing the executable is @var{execdir}, and the executable has a
11139 debug link that specifies the name @var{debugfile}, then @value{GDBN}
11140 will automatically search for the debugging information file in three
11145 the directory containing the executable file (that is, it will look
11146 for a file named @file{@var{execdir}/@var{debugfile}},
11148 a subdirectory of that directory named @file{.debug} (that is, the
11149 file @file{@var{execdir}/.debug/@var{debugfile}}, and
11151 a subdirectory of the global debug file directory that includes the
11152 executable's full path, and the name from the link (that is, the file
11153 @file{@var{globaldebugdir}/@var{execdir}/@var{debugfile}}, where
11154 @var{globaldebugdir} is the global debug file directory, and
11155 @var{execdir} has been turned into a relative path).
11158 @value{GDBN} checks under each of these names for a debugging
11159 information file whose checksum matches that given in the link, and
11160 reads the debugging information from the first one it finds.
11162 So, for example, if you ask @value{GDBN} to debug @file{/usr/bin/ls},
11163 which has a link containing the name @file{ls.debug}, and the global
11164 debug directory is @file{/usr/lib/debug}, then @value{GDBN} will look
11165 for debug information in @file{/usr/bin/ls.debug},
11166 @file{/usr/bin/.debug/ls.debug}, and
11167 @file{/usr/lib/debug/usr/bin/ls.debug}.
11169 You can set the global debugging info directory's name, and view the
11170 name @value{GDBN} is currently using.
11174 @kindex set debug-file-directory
11175 @item set debug-file-directory @var{directory}
11176 Set the directory which @value{GDBN} searches for separate debugging
11177 information files to @var{directory}.
11179 @kindex show debug-file-directory
11180 @item show debug-file-directory
11181 Show the directory @value{GDBN} searches for separate debugging
11186 @cindex @code{.gnu_debuglink} sections
11187 @cindex debug links
11188 A debug link is a special section of the executable file named
11189 @code{.gnu_debuglink}. The section must contain:
11193 A filename, with any leading directory components removed, followed by
11196 zero to three bytes of padding, as needed to reach the next four-byte
11197 boundary within the section, and
11199 a four-byte CRC checksum, stored in the same endianness used for the
11200 executable file itself. The checksum is computed on the debugging
11201 information file's full contents by the function given below, passing
11202 zero as the @var{crc} argument.
11205 Any executable file format can carry a debug link, as long as it can
11206 contain a section named @code{.gnu_debuglink} with the contents
11209 The debugging information file itself should be an ordinary
11210 executable, containing a full set of linker symbols, sections, and
11211 debugging information. The sections of the debugging information file
11212 should have the same names, addresses and sizes as the original file,
11213 but they need not contain any data --- much like a @code{.bss} section
11214 in an ordinary executable.
11216 As of December 2002, there is no standard GNU utility to produce
11217 separated executable / debugging information file pairs. Ulrich
11218 Drepper's @file{elfutils} package, starting with version 0.53,
11219 contains a version of the @code{strip} command such that the command
11220 @kbd{strip foo -f foo.debug} removes the debugging information from
11221 the executable file @file{foo}, places it in the file
11222 @file{foo.debug}, and leaves behind a debug link in @file{foo}.
11224 Since there are many different ways to compute CRC's (different
11225 polynomials, reversals, byte ordering, etc.), the simplest way to
11226 describe the CRC used in @code{.gnu_debuglink} sections is to give the
11227 complete code for a function that computes it:
11229 @kindex gnu_debuglink_crc32
11232 gnu_debuglink_crc32 (unsigned long crc,
11233 unsigned char *buf, size_t len)
11235 static const unsigned long crc32_table[256] =
11237 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
11238 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
11239 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
11240 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
11241 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
11242 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
11243 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
11244 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
11245 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
11246 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
11247 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
11248 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
11249 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
11250 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
11251 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
11252 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
11253 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
11254 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
11255 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
11256 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
11257 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
11258 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
11259 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
11260 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
11261 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
11262 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
11263 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
11264 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
11265 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
11266 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
11267 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
11268 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
11269 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
11270 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
11271 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
11272 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
11273 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
11274 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
11275 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
11276 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
11277 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
11278 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
11279 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
11280 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
11281 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
11282 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
11283 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
11284 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
11285 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
11286 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
11287 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
11290 unsigned char *end;
11292 crc = ~crc & 0xffffffff;
11293 for (end = buf + len; buf < end; ++buf)
11294 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
11295 return ~crc & 0xffffffff;
11300 @node Symbol Errors
11301 @section Errors reading symbol files
11303 While reading a symbol file, @value{GDBN} occasionally encounters problems,
11304 such as symbol types it does not recognize, or known bugs in compiler
11305 output. By default, @value{GDBN} does not notify you of such problems, since
11306 they are relatively common and primarily of interest to people
11307 debugging compilers. If you are interested in seeing information
11308 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
11309 only one message about each such type of problem, no matter how many
11310 times the problem occurs; or you can ask @value{GDBN} to print more messages,
11311 to see how many times the problems occur, with the @code{set
11312 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
11315 The messages currently printed, and their meanings, include:
11318 @item inner block not inside outer block in @var{symbol}
11320 The symbol information shows where symbol scopes begin and end
11321 (such as at the start of a function or a block of statements). This
11322 error indicates that an inner scope block is not fully contained
11323 in its outer scope blocks.
11325 @value{GDBN} circumvents the problem by treating the inner block as if it had
11326 the same scope as the outer block. In the error message, @var{symbol}
11327 may be shown as ``@code{(don't know)}'' if the outer block is not a
11330 @item block at @var{address} out of order
11332 The symbol information for symbol scope blocks should occur in
11333 order of increasing addresses. This error indicates that it does not
11336 @value{GDBN} does not circumvent this problem, and has trouble
11337 locating symbols in the source file whose symbols it is reading. (You
11338 can often determine what source file is affected by specifying
11339 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
11342 @item bad block start address patched
11344 The symbol information for a symbol scope block has a start address
11345 smaller than the address of the preceding source line. This is known
11346 to occur in the SunOS 4.1.1 (and earlier) C compiler.
11348 @value{GDBN} circumvents the problem by treating the symbol scope block as
11349 starting on the previous source line.
11351 @item bad string table offset in symbol @var{n}
11354 Symbol number @var{n} contains a pointer into the string table which is
11355 larger than the size of the string table.
11357 @value{GDBN} circumvents the problem by considering the symbol to have the
11358 name @code{foo}, which may cause other problems if many symbols end up
11361 @item unknown symbol type @code{0x@var{nn}}
11363 The symbol information contains new data types that @value{GDBN} does
11364 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
11365 uncomprehended information, in hexadecimal.
11367 @value{GDBN} circumvents the error by ignoring this symbol information.
11368 This usually allows you to debug your program, though certain symbols
11369 are not accessible. If you encounter such a problem and feel like
11370 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
11371 on @code{complain}, then go up to the function @code{read_dbx_symtab}
11372 and examine @code{*bufp} to see the symbol.
11374 @item stub type has NULL name
11376 @value{GDBN} could not find the full definition for a struct or class.
11378 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
11379 The symbol information for a C@t{++} member function is missing some
11380 information that recent versions of the compiler should have output for
11383 @item info mismatch between compiler and debugger
11385 @value{GDBN} could not parse a type specification output by the compiler.
11390 @chapter Specifying a Debugging Target
11392 @cindex debugging target
11393 A @dfn{target} is the execution environment occupied by your program.
11395 Often, @value{GDBN} runs in the same host environment as your program;
11396 in that case, the debugging target is specified as a side effect when
11397 you use the @code{file} or @code{core} commands. When you need more
11398 flexibility---for example, running @value{GDBN} on a physically separate
11399 host, or controlling a standalone system over a serial port or a
11400 realtime system over a TCP/IP connection---you can use the @code{target}
11401 command to specify one of the target types configured for @value{GDBN}
11402 (@pxref{Target Commands, ,Commands for managing targets}).
11404 @cindex target architecture
11405 It is possible to build @value{GDBN} for several different @dfn{target
11406 architectures}. When @value{GDBN} is built like that, you can choose
11407 one of the available architectures with the @kbd{set architecture}
11411 @kindex set architecture
11412 @kindex show architecture
11413 @item set architecture @var{arch}
11414 This command sets the current target architecture to @var{arch}. The
11415 value of @var{arch} can be @code{"auto"}, in addition to one of the
11416 supported architectures.
11418 @item show architecture
11419 Show the current target architecture.
11421 @item set processor
11423 @kindex set processor
11424 @kindex show processor
11425 These are alias commands for, respectively, @code{set architecture}
11426 and @code{show architecture}.
11430 * Active Targets:: Active targets
11431 * Target Commands:: Commands for managing targets
11432 * Byte Order:: Choosing target byte order
11433 * Remote:: Remote debugging
11434 * KOD:: Kernel Object Display
11438 @node Active Targets
11439 @section Active targets
11441 @cindex stacking targets
11442 @cindex active targets
11443 @cindex multiple targets
11445 There are three classes of targets: processes, core files, and
11446 executable files. @value{GDBN} can work concurrently on up to three
11447 active targets, one in each class. This allows you to (for example)
11448 start a process and inspect its activity without abandoning your work on
11451 For example, if you execute @samp{gdb a.out}, then the executable file
11452 @code{a.out} is the only active target. If you designate a core file as
11453 well---presumably from a prior run that crashed and coredumped---then
11454 @value{GDBN} has two active targets and uses them in tandem, looking
11455 first in the corefile target, then in the executable file, to satisfy
11456 requests for memory addresses. (Typically, these two classes of target
11457 are complementary, since core files contain only a program's
11458 read-write memory---variables and so on---plus machine status, while
11459 executable files contain only the program text and initialized data.)
11461 When you type @code{run}, your executable file becomes an active process
11462 target as well. When a process target is active, all @value{GDBN}
11463 commands requesting memory addresses refer to that target; addresses in
11464 an active core file or executable file target are obscured while the
11465 process target is active.
11467 Use the @code{core-file} and @code{exec-file} commands to select a new
11468 core file or executable target (@pxref{Files, ,Commands to specify
11469 files}). To specify as a target a process that is already running, use
11470 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
11473 @node Target Commands
11474 @section Commands for managing targets
11477 @item target @var{type} @var{parameters}
11478 Connects the @value{GDBN} host environment to a target machine or
11479 process. A target is typically a protocol for talking to debugging
11480 facilities. You use the argument @var{type} to specify the type or
11481 protocol of the target machine.
11483 Further @var{parameters} are interpreted by the target protocol, but
11484 typically include things like device names or host names to connect
11485 with, process numbers, and baud rates.
11487 The @code{target} command does not repeat if you press @key{RET} again
11488 after executing the command.
11490 @kindex help target
11492 Displays the names of all targets available. To display targets
11493 currently selected, use either @code{info target} or @code{info files}
11494 (@pxref{Files, ,Commands to specify files}).
11496 @item help target @var{name}
11497 Describe a particular target, including any parameters necessary to
11500 @kindex set gnutarget
11501 @item set gnutarget @var{args}
11502 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
11503 knows whether it is reading an @dfn{executable},
11504 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
11505 with the @code{set gnutarget} command. Unlike most @code{target} commands,
11506 with @code{gnutarget} the @code{target} refers to a program, not a machine.
11509 @emph{Warning:} To specify a file format with @code{set gnutarget},
11510 you must know the actual BFD name.
11514 @xref{Files, , Commands to specify files}.
11516 @kindex show gnutarget
11517 @item show gnutarget
11518 Use the @code{show gnutarget} command to display what file format
11519 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
11520 @value{GDBN} will determine the file format for each file automatically,
11521 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
11524 @cindex common targets
11525 Here are some common targets (available, or not, depending on the GDB
11530 @item target exec @var{program}
11531 @cindex executable file target
11532 An executable file. @samp{target exec @var{program}} is the same as
11533 @samp{exec-file @var{program}}.
11535 @item target core @var{filename}
11536 @cindex core dump file target
11537 A core dump file. @samp{target core @var{filename}} is the same as
11538 @samp{core-file @var{filename}}.
11540 @item target remote @var{dev}
11541 @cindex remote target
11542 Remote serial target in GDB-specific protocol. The argument @var{dev}
11543 specifies what serial device to use for the connection (e.g.
11544 @file{/dev/ttya}). @xref{Remote, ,Remote debugging}. @code{target remote}
11545 supports the @code{load} command. This is only useful if you have
11546 some other way of getting the stub to the target system, and you can put
11547 it somewhere in memory where it won't get clobbered by the download.
11550 @cindex built-in simulator target
11551 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
11559 works; however, you cannot assume that a specific memory map, device
11560 drivers, or even basic I/O is available, although some simulators do
11561 provide these. For info about any processor-specific simulator details,
11562 see the appropriate section in @ref{Embedded Processors, ,Embedded
11567 Some configurations may include these targets as well:
11571 @item target nrom @var{dev}
11572 @cindex NetROM ROM emulator target
11573 NetROM ROM emulator. This target only supports downloading.
11577 Different targets are available on different configurations of @value{GDBN};
11578 your configuration may have more or fewer targets.
11580 Many remote targets require you to download the executable's code once
11581 you've successfully established a connection. You may wish to control
11582 various aspects of this process, such as the size of the data chunks
11583 used by @value{GDBN} to download program parts to the remote target.
11586 @kindex set download-write-size
11587 @item set download-write-size @var{size}
11588 Set the write size used when downloading a program. Only used when
11589 downloading a program onto a remote target. Specify zero or a
11590 negative value to disable blocked writes. The actual size of each
11591 transfer is also limited by the size of the target packet and the
11594 @kindex show download-write-size
11595 @item show download-write-size
11596 @kindex show download-write-size
11597 Show the current value of the write size.
11600 @kindex set hash@r{, for remote monitors}
11601 @cindex hash mark while downloading
11602 This command controls whether a hash mark @samp{#} is displayed while
11603 downloading a file to the remote monitor. If on, a hash mark is
11604 displayed after each S-record is successfully downloaded to the
11608 @kindex show hash@r{, for remote monitors}
11609 Show the current status of displaying the hash mark.
11611 @item set debug monitor
11612 @kindex set debug monitor
11613 @cindex display remote monitor communications
11614 Enable or disable display of communications messages between
11615 @value{GDBN} and the remote monitor.
11617 @item show debug monitor
11618 @kindex show debug monitor
11619 Show the current status of displaying communications between
11620 @value{GDBN} and the remote monitor.
11625 @kindex load @var{filename}
11626 @item load @var{filename}
11627 Depending on what remote debugging facilities are configured into
11628 @value{GDBN}, the @code{load} command may be available. Where it exists, it
11629 is meant to make @var{filename} (an executable) available for debugging
11630 on the remote system---by downloading, or dynamic linking, for example.
11631 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
11632 the @code{add-symbol-file} command.
11634 If your @value{GDBN} does not have a @code{load} command, attempting to
11635 execute it gets the error message ``@code{You can't do that when your
11636 target is @dots{}}''
11638 The file is loaded at whatever address is specified in the executable.
11639 For some object file formats, you can specify the load address when you
11640 link the program; for other formats, like a.out, the object file format
11641 specifies a fixed address.
11642 @c FIXME! This would be a good place for an xref to the GNU linker doc.
11644 @code{load} does not repeat if you press @key{RET} again after using it.
11648 @section Choosing target byte order
11650 @cindex choosing target byte order
11651 @cindex target byte order
11653 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
11654 offer the ability to run either big-endian or little-endian byte
11655 orders. Usually the executable or symbol will include a bit to
11656 designate the endian-ness, and you will not need to worry about
11657 which to use. However, you may still find it useful to adjust
11658 @value{GDBN}'s idea of processor endian-ness manually.
11662 @item set endian big
11663 Instruct @value{GDBN} to assume the target is big-endian.
11665 @item set endian little
11666 Instruct @value{GDBN} to assume the target is little-endian.
11668 @item set endian auto
11669 Instruct @value{GDBN} to use the byte order associated with the
11673 Display @value{GDBN}'s current idea of the target byte order.
11677 Note that these commands merely adjust interpretation of symbolic
11678 data on the host, and that they have absolutely no effect on the
11682 @section Remote debugging
11683 @cindex remote debugging
11685 If you are trying to debug a program running on a machine that cannot run
11686 @value{GDBN} in the usual way, it is often useful to use remote debugging.
11687 For example, you might use remote debugging on an operating system kernel,
11688 or on a small system which does not have a general purpose operating system
11689 powerful enough to run a full-featured debugger.
11691 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
11692 to make this work with particular debugging targets. In addition,
11693 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
11694 but not specific to any particular target system) which you can use if you
11695 write the remote stubs---the code that runs on the remote system to
11696 communicate with @value{GDBN}.
11698 Other remote targets may be available in your
11699 configuration of @value{GDBN}; use @code{help target} to list them.
11701 Once you've connected to the remote target, @value{GDBN} allows you to
11702 send arbitrary commands to the remote monitor:
11705 @item remote @var{command}
11706 @kindex remote@r{, a command}
11707 @cindex send command to remote monitor
11708 Send an arbitrary @var{command} string to the remote monitor.
11713 @section Kernel Object Display
11714 @cindex kernel object display
11717 Some targets support kernel object display. Using this facility,
11718 @value{GDBN} communicates specially with the underlying operating system
11719 and can display information about operating system-level objects such as
11720 mutexes and other synchronization objects. Exactly which objects can be
11721 displayed is determined on a per-OS basis.
11724 Use the @code{set os} command to set the operating system. This tells
11725 @value{GDBN} which kernel object display module to initialize:
11728 (@value{GDBP}) set os cisco
11732 The associated command @code{show os} displays the operating system
11733 set with the @code{set os} command; if no operating system has been
11734 set, @code{show os} will display an empty string @samp{""}.
11736 If @code{set os} succeeds, @value{GDBN} will display some information
11737 about the operating system, and will create a new @code{info} command
11738 which can be used to query the target. The @code{info} command is named
11739 after the operating system:
11743 (@value{GDBP}) info cisco
11744 List of Cisco Kernel Objects
11746 any Any and all objects
11749 Further subcommands can be used to query about particular objects known
11752 There is currently no way to determine whether a given operating
11753 system is supported other than to try setting it with @kbd{set os
11754 @var{name}}, where @var{name} is the name of the operating system you
11758 @node Remote Debugging
11759 @chapter Debugging remote programs
11762 * Connecting:: Connecting to a remote target
11763 * Server:: Using the gdbserver program
11764 * NetWare:: Using the gdbserve.nlm program
11765 * Remote configuration:: Remote configuration
11766 * remote stub:: Implementing a remote stub
11770 @section Connecting to a remote target
11772 On the @value{GDBN} host machine, you will need an unstripped copy of
11773 your program, since @value{GDBN} needs symobl and debugging information.
11774 Start up @value{GDBN} as usual, using the name of the local copy of your
11775 program as the first argument.
11777 @cindex serial line, @code{target remote}
11778 If you're using a serial line, you may want to give @value{GDBN} the
11779 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
11780 (@pxref{Remote configuration, set remotebaud}) before the
11781 @code{target} command.
11783 After that, use @code{target remote} to establish communications with
11784 the target machine. Its argument specifies how to communicate---either
11785 via a devicename attached to a direct serial line, or a TCP or UDP port
11786 (possibly to a terminal server which in turn has a serial line to the
11787 target). For example, to use a serial line connected to the device
11788 named @file{/dev/ttyb}:
11791 target remote /dev/ttyb
11794 @cindex TCP port, @code{target remote}
11795 To use a TCP connection, use an argument of the form
11796 @code{@var{host}:@var{port}} or @code{tcp:@var{host}:@var{port}}.
11797 For example, to connect to port 2828 on a
11798 terminal server named @code{manyfarms}:
11801 target remote manyfarms:2828
11804 If your remote target is actually running on the same machine as
11805 your debugger session (e.g.@: a simulator of your target running on
11806 the same host), you can omit the hostname. For example, to connect
11807 to port 1234 on your local machine:
11810 target remote :1234
11814 Note that the colon is still required here.
11816 @cindex UDP port, @code{target remote}
11817 To use a UDP connection, use an argument of the form
11818 @code{udp:@var{host}:@var{port}}. For example, to connect to UDP port 2828
11819 on a terminal server named @code{manyfarms}:
11822 target remote udp:manyfarms:2828
11825 When using a UDP connection for remote debugging, you should keep in mind
11826 that the `U' stands for ``Unreliable''. UDP can silently drop packets on
11827 busy or unreliable networks, which will cause havoc with your debugging
11830 Now you can use all the usual commands to examine and change data and to
11831 step and continue the remote program.
11833 @cindex interrupting remote programs
11834 @cindex remote programs, interrupting
11835 Whenever @value{GDBN} is waiting for the remote program, if you type the
11836 interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the
11837 program. This may or may not succeed, depending in part on the hardware
11838 and the serial drivers the remote system uses. If you type the
11839 interrupt character once again, @value{GDBN} displays this prompt:
11842 Interrupted while waiting for the program.
11843 Give up (and stop debugging it)? (y or n)
11846 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
11847 (If you decide you want to try again later, you can use @samp{target
11848 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
11849 goes back to waiting.
11852 @kindex detach (remote)
11854 When you have finished debugging the remote program, you can use the
11855 @code{detach} command to release it from @value{GDBN} control.
11856 Detaching from the target normally resumes its execution, but the results
11857 will depend on your particular remote stub. After the @code{detach}
11858 command, @value{GDBN} is free to connect to another target.
11862 The @code{disconnect} command behaves like @code{detach}, except that
11863 the target is generally not resumed. It will wait for @value{GDBN}
11864 (this instance or another one) to connect and continue debugging. After
11865 the @code{disconnect} command, @value{GDBN} is again free to connect to
11868 @cindex send command to remote monitor
11870 @item monitor @var{cmd}
11871 This command allows you to send commands directly to the remote
11876 @section Using the @code{gdbserver} program
11879 @cindex remote connection without stubs
11880 @code{gdbserver} is a control program for Unix-like systems, which
11881 allows you to connect your program with a remote @value{GDBN} via
11882 @code{target remote}---but without linking in the usual debugging stub.
11884 @code{gdbserver} is not a complete replacement for the debugging stubs,
11885 because it requires essentially the same operating-system facilities
11886 that @value{GDBN} itself does. In fact, a system that can run
11887 @code{gdbserver} to connect to a remote @value{GDBN} could also run
11888 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
11889 because it is a much smaller program than @value{GDBN} itself. It is
11890 also easier to port than all of @value{GDBN}, so you may be able to get
11891 started more quickly on a new system by using @code{gdbserver}.
11892 Finally, if you develop code for real-time systems, you may find that
11893 the tradeoffs involved in real-time operation make it more convenient to
11894 do as much development work as possible on another system, for example
11895 by cross-compiling. You can use @code{gdbserver} to make a similar
11896 choice for debugging.
11898 @value{GDBN} and @code{gdbserver} communicate via either a serial line
11899 or a TCP connection, using the standard @value{GDBN} remote serial
11903 @item On the target machine,
11904 you need to have a copy of the program you want to debug.
11905 @code{gdbserver} does not need your program's symbol table, so you can
11906 strip the program if necessary to save space. @value{GDBN} on the host
11907 system does all the symbol handling.
11909 To use the server, you must tell it how to communicate with @value{GDBN};
11910 the name of your program; and the arguments for your program. The usual
11914 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
11917 @var{comm} is either a device name (to use a serial line) or a TCP
11918 hostname and portnumber. For example, to debug Emacs with the argument
11919 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
11923 target> gdbserver /dev/com1 emacs foo.txt
11926 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
11929 To use a TCP connection instead of a serial line:
11932 target> gdbserver host:2345 emacs foo.txt
11935 The only difference from the previous example is the first argument,
11936 specifying that you are communicating with the host @value{GDBN} via
11937 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
11938 expect a TCP connection from machine @samp{host} to local TCP port 2345.
11939 (Currently, the @samp{host} part is ignored.) You can choose any number
11940 you want for the port number as long as it does not conflict with any
11941 TCP ports already in use on the target system (for example, @code{23} is
11942 reserved for @code{telnet}).@footnote{If you choose a port number that
11943 conflicts with another service, @code{gdbserver} prints an error message
11944 and exits.} You must use the same port number with the host @value{GDBN}
11945 @code{target remote} command.
11947 On some targets, @code{gdbserver} can also attach to running programs.
11948 This is accomplished via the @code{--attach} argument. The syntax is:
11951 target> gdbserver @var{comm} --attach @var{pid}
11954 @var{pid} is the process ID of a currently running process. It isn't necessary
11955 to point @code{gdbserver} at a binary for the running process.
11958 @cindex attach to a program by name
11959 You can debug processes by name instead of process ID if your target has the
11960 @code{pidof} utility:
11963 target> gdbserver @var{comm} --attach `pidof @var{PROGRAM}`
11966 In case more than one copy of @var{PROGRAM} is running, or @var{PROGRAM}
11967 has multiple threads, most versions of @code{pidof} support the
11968 @code{-s} option to only return the first process ID.
11970 @item On the host machine,
11971 connect to your target (@pxref{Connecting,,Connecting to a remote target}).
11972 For TCP connections, you must start up @code{gdbserver} prior to using
11973 the @code{target remote} command. Otherwise you may get an error whose
11974 text depends on the host system, but which usually looks something like
11975 @samp{Connection refused}. You don't need to use the @code{load}
11976 command in @value{GDBN} when using @code{gdbserver}, since the program is
11977 already on the target. However, if you want to load the symbols (as
11978 you normally would), do that with the @code{file} command, and issue
11979 it @emph{before} connecting to the server; otherwise, you will get an
11980 error message saying @code{"Program is already running"}, since the
11981 program is considered running after the connection.
11986 @section Using the @code{gdbserve.nlm} program
11988 @kindex gdbserve.nlm
11989 @code{gdbserve.nlm} is a control program for NetWare systems, which
11990 allows you to connect your program with a remote @value{GDBN} via
11991 @code{target remote}.
11993 @value{GDBN} and @code{gdbserve.nlm} communicate via a serial line,
11994 using the standard @value{GDBN} remote serial protocol.
11997 @item On the target machine,
11998 you need to have a copy of the program you want to debug.
11999 @code{gdbserve.nlm} does not need your program's symbol table, so you
12000 can strip the program if necessary to save space. @value{GDBN} on the
12001 host system does all the symbol handling.
12003 To use the server, you must tell it how to communicate with
12004 @value{GDBN}; the name of your program; and the arguments for your
12005 program. The syntax is:
12008 load gdbserve [ BOARD=@var{board} ] [ PORT=@var{port} ]
12009 [ BAUD=@var{baud} ] @var{program} [ @var{args} @dots{} ]
12012 @var{board} and @var{port} specify the serial line; @var{baud} specifies
12013 the baud rate used by the connection. @var{port} and @var{node} default
12014 to 0, @var{baud} defaults to 9600@dmn{bps}.
12016 For example, to debug Emacs with the argument @samp{foo.txt}and
12017 communicate with @value{GDBN} over serial port number 2 or board 1
12018 using a 19200@dmn{bps} connection:
12021 load gdbserve BOARD=1 PORT=2 BAUD=19200 emacs foo.txt
12025 On the @value{GDBN} host machine, connect to your target (@pxref{Connecting,,
12026 Connecting to a remote target}).
12030 @node Remote configuration
12031 @section Remote configuration
12034 @kindex show remote
12035 This section documents the configuration options available when
12036 debugging remote programs. For the options related to the File I/O
12037 extensions of the remote protocol, see @ref{The system call,
12038 system-call-allowed}.
12041 @item set remoteaddresssize @var{bits}
12042 @cindex adress size for remote targets
12043 @cindex bits in remote address
12044 Set the maximum size of address in a memory packet to the specified
12045 number of bits. @value{GDBN} will mask off the address bits above
12046 that number, when it passes addresses to the remote target. The
12047 default value is the number of bits in the target's address.
12049 @item show remoteaddresssize
12050 Show the current value of remote address size in bits.
12052 @item set remotebaud @var{n}
12053 @cindex baud rate for remote targets
12054 Set the baud rate for the remote serial I/O to @var{n} baud. The
12055 value is used to set the speed of the serial port used for debugging
12058 @item show remotebaud
12059 Show the current speed of the remote connection.
12061 @item set remotebreak
12062 @cindex interrupt remote programs
12063 @cindex BREAK signal instead of Ctrl-C
12064 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
12065 when you press the @key{Ctrl-C} key to interrupt the program running
12066 on the remote. If set to off, @value{GDBN} sends the @samp{Strl-C}
12067 character instead. The default is off, since most remote systems
12068 expect to see @samp{Ctrl-C} as the interrupt signal.
12070 @item show remotebreak
12071 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
12072 interrupt the remote program.
12074 @item set remotedebug
12075 @cindex debug remote protocol
12076 @cindex remote protocol debugging
12077 @cindex display remote packets
12078 Control the debugging of the remote protocol. When enabled, each
12079 packet sent to or received from the remote target is displayed. The
12082 @item show remotedebug
12083 Show the current setting of the remote protocol debugging.
12085 @item set remotedevice @var{device}
12086 @cindex serial port name
12087 Set the name of the serial port through which to communicate to the
12088 remote target to @var{device}. This is the device used by
12089 @value{GDBN} to open the serial communications line to the remote
12090 target. There's no default, so you must set a valid port name for the
12091 remote serial communications to work. (Some varieties of the
12092 @code{target} command accept the port name as part of their
12095 @item show remotedevice
12096 Show the current name of the serial port.
12098 @item set remotelogbase @var{base}
12099 Set the base (a.k.a.@: radix) of logging serial protocol
12100 communications to @var{base}. Supported values of @var{base} are:
12101 @code{ascii}, @code{octal}, and @code{hex}. The default is
12104 @item show remotelogbase
12105 Show the current setting of the radix for logging remote serial
12108 @item set remotelogfile @var{file}
12109 @cindex record serial communications on file
12110 Record remote serial communications on the named @var{file}. The
12111 default is not to record at all.
12113 @item show remotelogfile.
12114 Show the current setting of the file name on which to record the
12115 serial communications.
12117 @item set remotetimeout @var{num}
12118 @cindex timeout for serial communications
12119 @cindex remote timeout
12120 Set the timeout limit to wait for the remote target to respond to
12121 @var{num} seconds. The default is 2 seconds.
12123 @item show remotetimeout
12124 Show the current number of seconds to wait for the remote target
12127 @cindex limit hardware breakpoints and watchpoints
12128 @cindex remote target, limit break- and watchpoints
12129 @anchor{set remote hardware-watchpoint-limit}
12130 @anchor{set remote hardware-breakpoint-limit}
12131 @item set remote hardware-watchpoint-limit @var{limit}
12132 @itemx set remote hardware-breakpoint-limit @var{limit}
12133 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
12134 watchpoints. A limit of -1, the default, is treated as unlimited.
12136 @item set remote fetch-register-packet
12137 @itemx set remote set-register-packet
12138 @itemx set remote P-packet
12139 @itemx set remote p-packet
12141 @cindex fetch registers from remote targets
12142 @cindex set registers in remote targets
12143 Determine whether @value{GDBN} can set and fetch registers from the
12144 remote target using the @samp{P} packets. The default depends on the
12145 remote stub's support of the @samp{P} packets (@value{GDBN} queries
12146 the stub when this packet is first required).
12148 @item show remote fetch-register-packet
12149 @itemx show remote set-register-packet
12150 @itemx show remote P-packet
12151 @itemx show remote p-packet
12152 Show the current setting of using the @samp{P} packets for setting and
12153 fetching registers from the remote target.
12155 @cindex binary downloads
12157 @item set remote binary-download-packet
12158 @itemx set remote X-packet
12159 Determine whether @value{GDBN} sends downloads in binary mode using
12160 the @samp{X} packets. The default is on.
12162 @item show remote binary-download-packet
12163 @itemx show remote X-packet
12164 Show the current setting of using the @samp{X} packets for binary
12167 @item set remote read-aux-vector-packet
12168 @cindex auxiliary vector of remote target
12169 @cindex @code{auxv}, and remote targets
12170 Set the use of the remote protocol's @samp{qPart:auxv:read} (target
12171 auxiliary vector read) request. This request is used to fetch the
12172 remote target's @dfn{auxiliary vector}, see @ref{OS Information,
12173 Auxiliary Vector}. The default setting depends on the remote stub's
12174 support of this request (@value{GDBN} queries the stub when this
12175 request is first required). @xref{General Query Packets, qPart}, for
12176 more information about this request.
12178 @item show remote read-aux-vector-packet
12179 Show the current setting of use of the @samp{qPart:auxv:read} request.
12181 @item set remote symbol-lookup-packet
12182 @cindex remote symbol lookup request
12183 Set the use of the remote protocol's @samp{qSymbol} (target symbol
12184 lookup) request. This request is used to communicate symbol
12185 information to the remote target, e.g., whenever a new shared library
12186 is loaded by the remote (@pxref{Files, shared libraries}). The
12187 default setting depends on the remote stub's support of this request
12188 (@value{GDBN} queries the stub when this request is first required).
12189 @xref{General Query Packets, qSymbol}, for more information about this
12192 @item show remote symbol-lookup-packet
12193 Show the current setting of use of the @samp{qSymbol} request.
12195 @item set remote verbose-resume-packet
12196 @cindex resume remote target
12197 @cindex signal thread, and remote targets
12198 @cindex single-step thread, and remote targets
12199 @cindex thread-specific operations on remote targets
12200 Set the use of the remote protocol's @samp{vCont} (descriptive resume)
12201 request. This request is used to resume specific threads in the
12202 remote target, and to single-step or signal them. The default setting
12203 depends on the remote stub's support of this request (@value{GDBN}
12204 queries the stub when this request is first required). This setting
12205 affects debugging of multithreaded programs: if @samp{vCont} cannot be
12206 used, @value{GDBN} might be unable to single-step a specific thread,
12207 especially under @code{set scheduler-locking off}; it is also
12208 impossible to pause a specific thread. @xref{Packets, vCont}, for
12211 @item show remote verbose-resume-packet
12212 Show the current setting of use of the @samp{vCont} request
12214 @item set remote software-breakpoint-packet
12215 @itemx set remote hardware-breakpoint-packet
12216 @itemx set remote write-watchpoint-packet
12217 @itemx set remote read-watchpoint-packet
12218 @itemx set remote access-watchpoint-packet
12219 @itemx set remote Z-packet
12221 @cindex remote hardware breakpoints and watchpoints
12222 These commands enable or disable the use of @samp{Z} packets for
12223 setting breakpoints and watchpoints in the remote target. The default
12224 depends on the remote stub's support of the @samp{Z} packets
12225 (@value{GDBN} queries the stub when each packet is first required).
12226 The command @code{set remote Z-packet}, kept for back-compatibility,
12227 turns on or off all the features that require the use of @samp{Z}
12230 @item show remote software-breakpoint-packet
12231 @itemx show remote hardware-breakpoint-packet
12232 @itemx show remote write-watchpoint-packet
12233 @itemx show remote read-watchpoint-packet
12234 @itemx show remote access-watchpoint-packet
12235 @itemx show remote Z-packet
12236 Show the current setting of @samp{Z} packets usage.
12238 @item set remote get-thread-local-storage-address
12239 @kindex set remote get-thread-local-storage-address
12240 @cindex thread local storage of remote targets
12241 This command enables or disables the use of the @samp{qGetTLSAddr}
12242 (Get Thread Local Storage Address) request packet. The default
12243 depends on whether the remote stub supports this request.
12244 @xref{General Query Packets, qGetTLSAddr}, for more details about this
12247 @item show remote get-thread-local-storage-address
12248 @kindex show remote get-thread-local-storage-address
12249 Show the current setting of @samp{qGetTLSAddr} packet usage.
12253 @section Implementing a remote stub
12255 @cindex debugging stub, example
12256 @cindex remote stub, example
12257 @cindex stub example, remote debugging
12258 The stub files provided with @value{GDBN} implement the target side of the
12259 communication protocol, and the @value{GDBN} side is implemented in the
12260 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
12261 these subroutines to communicate, and ignore the details. (If you're
12262 implementing your own stub file, you can still ignore the details: start
12263 with one of the existing stub files. @file{sparc-stub.c} is the best
12264 organized, and therefore the easiest to read.)
12266 @cindex remote serial debugging, overview
12267 To debug a program running on another machine (the debugging
12268 @dfn{target} machine), you must first arrange for all the usual
12269 prerequisites for the program to run by itself. For example, for a C
12274 A startup routine to set up the C runtime environment; these usually
12275 have a name like @file{crt0}. The startup routine may be supplied by
12276 your hardware supplier, or you may have to write your own.
12279 A C subroutine library to support your program's
12280 subroutine calls, notably managing input and output.
12283 A way of getting your program to the other machine---for example, a
12284 download program. These are often supplied by the hardware
12285 manufacturer, but you may have to write your own from hardware
12289 The next step is to arrange for your program to use a serial port to
12290 communicate with the machine where @value{GDBN} is running (the @dfn{host}
12291 machine). In general terms, the scheme looks like this:
12295 @value{GDBN} already understands how to use this protocol; when everything
12296 else is set up, you can simply use the @samp{target remote} command
12297 (@pxref{Targets,,Specifying a Debugging Target}).
12299 @item On the target,
12300 you must link with your program a few special-purpose subroutines that
12301 implement the @value{GDBN} remote serial protocol. The file containing these
12302 subroutines is called a @dfn{debugging stub}.
12304 On certain remote targets, you can use an auxiliary program
12305 @code{gdbserver} instead of linking a stub into your program.
12306 @xref{Server,,Using the @code{gdbserver} program}, for details.
12309 The debugging stub is specific to the architecture of the remote
12310 machine; for example, use @file{sparc-stub.c} to debug programs on
12313 @cindex remote serial stub list
12314 These working remote stubs are distributed with @value{GDBN}:
12319 @cindex @file{i386-stub.c}
12322 For Intel 386 and compatible architectures.
12325 @cindex @file{m68k-stub.c}
12326 @cindex Motorola 680x0
12328 For Motorola 680x0 architectures.
12331 @cindex @file{sh-stub.c}
12334 For Renesas SH architectures.
12337 @cindex @file{sparc-stub.c}
12339 For @sc{sparc} architectures.
12341 @item sparcl-stub.c
12342 @cindex @file{sparcl-stub.c}
12345 For Fujitsu @sc{sparclite} architectures.
12349 The @file{README} file in the @value{GDBN} distribution may list other
12350 recently added stubs.
12353 * Stub Contents:: What the stub can do for you
12354 * Bootstrapping:: What you must do for the stub
12355 * Debug Session:: Putting it all together
12358 @node Stub Contents
12359 @subsection What the stub can do for you
12361 @cindex remote serial stub
12362 The debugging stub for your architecture supplies these three
12366 @item set_debug_traps
12367 @findex set_debug_traps
12368 @cindex remote serial stub, initialization
12369 This routine arranges for @code{handle_exception} to run when your
12370 program stops. You must call this subroutine explicitly near the
12371 beginning of your program.
12373 @item handle_exception
12374 @findex handle_exception
12375 @cindex remote serial stub, main routine
12376 This is the central workhorse, but your program never calls it
12377 explicitly---the setup code arranges for @code{handle_exception} to
12378 run when a trap is triggered.
12380 @code{handle_exception} takes control when your program stops during
12381 execution (for example, on a breakpoint), and mediates communications
12382 with @value{GDBN} on the host machine. This is where the communications
12383 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
12384 representative on the target machine. It begins by sending summary
12385 information on the state of your program, then continues to execute,
12386 retrieving and transmitting any information @value{GDBN} needs, until you
12387 execute a @value{GDBN} command that makes your program resume; at that point,
12388 @code{handle_exception} returns control to your own code on the target
12392 @cindex @code{breakpoint} subroutine, remote
12393 Use this auxiliary subroutine to make your program contain a
12394 breakpoint. Depending on the particular situation, this may be the only
12395 way for @value{GDBN} to get control. For instance, if your target
12396 machine has some sort of interrupt button, you won't need to call this;
12397 pressing the interrupt button transfers control to
12398 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
12399 simply receiving characters on the serial port may also trigger a trap;
12400 again, in that situation, you don't need to call @code{breakpoint} from
12401 your own program---simply running @samp{target remote} from the host
12402 @value{GDBN} session gets control.
12404 Call @code{breakpoint} if none of these is true, or if you simply want
12405 to make certain your program stops at a predetermined point for the
12406 start of your debugging session.
12409 @node Bootstrapping
12410 @subsection What you must do for the stub
12412 @cindex remote stub, support routines
12413 The debugging stubs that come with @value{GDBN} are set up for a particular
12414 chip architecture, but they have no information about the rest of your
12415 debugging target machine.
12417 First of all you need to tell the stub how to communicate with the
12421 @item int getDebugChar()
12422 @findex getDebugChar
12423 Write this subroutine to read a single character from the serial port.
12424 It may be identical to @code{getchar} for your target system; a
12425 different name is used to allow you to distinguish the two if you wish.
12427 @item void putDebugChar(int)
12428 @findex putDebugChar
12429 Write this subroutine to write a single character to the serial port.
12430 It may be identical to @code{putchar} for your target system; a
12431 different name is used to allow you to distinguish the two if you wish.
12434 @cindex control C, and remote debugging
12435 @cindex interrupting remote targets
12436 If you want @value{GDBN} to be able to stop your program while it is
12437 running, you need to use an interrupt-driven serial driver, and arrange
12438 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
12439 character). That is the character which @value{GDBN} uses to tell the
12440 remote system to stop.
12442 Getting the debugging target to return the proper status to @value{GDBN}
12443 probably requires changes to the standard stub; one quick and dirty way
12444 is to just execute a breakpoint instruction (the ``dirty'' part is that
12445 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
12447 Other routines you need to supply are:
12450 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
12451 @findex exceptionHandler
12452 Write this function to install @var{exception_address} in the exception
12453 handling tables. You need to do this because the stub does not have any
12454 way of knowing what the exception handling tables on your target system
12455 are like (for example, the processor's table might be in @sc{rom},
12456 containing entries which point to a table in @sc{ram}).
12457 @var{exception_number} is the exception number which should be changed;
12458 its meaning is architecture-dependent (for example, different numbers
12459 might represent divide by zero, misaligned access, etc). When this
12460 exception occurs, control should be transferred directly to
12461 @var{exception_address}, and the processor state (stack, registers,
12462 and so on) should be just as it is when a processor exception occurs. So if
12463 you want to use a jump instruction to reach @var{exception_address}, it
12464 should be a simple jump, not a jump to subroutine.
12466 For the 386, @var{exception_address} should be installed as an interrupt
12467 gate so that interrupts are masked while the handler runs. The gate
12468 should be at privilege level 0 (the most privileged level). The
12469 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
12470 help from @code{exceptionHandler}.
12472 @item void flush_i_cache()
12473 @findex flush_i_cache
12474 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
12475 instruction cache, if any, on your target machine. If there is no
12476 instruction cache, this subroutine may be a no-op.
12478 On target machines that have instruction caches, @value{GDBN} requires this
12479 function to make certain that the state of your program is stable.
12483 You must also make sure this library routine is available:
12486 @item void *memset(void *, int, int)
12488 This is the standard library function @code{memset} that sets an area of
12489 memory to a known value. If you have one of the free versions of
12490 @code{libc.a}, @code{memset} can be found there; otherwise, you must
12491 either obtain it from your hardware manufacturer, or write your own.
12494 If you do not use the GNU C compiler, you may need other standard
12495 library subroutines as well; this varies from one stub to another,
12496 but in general the stubs are likely to use any of the common library
12497 subroutines which @code{@value{GCC}} generates as inline code.
12500 @node Debug Session
12501 @subsection Putting it all together
12503 @cindex remote serial debugging summary
12504 In summary, when your program is ready to debug, you must follow these
12509 Make sure you have defined the supporting low-level routines
12510 (@pxref{Bootstrapping,,What you must do for the stub}):
12512 @code{getDebugChar}, @code{putDebugChar},
12513 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
12517 Insert these lines near the top of your program:
12525 For the 680x0 stub only, you need to provide a variable called
12526 @code{exceptionHook}. Normally you just use:
12529 void (*exceptionHook)() = 0;
12533 but if before calling @code{set_debug_traps}, you set it to point to a
12534 function in your program, that function is called when
12535 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
12536 error). The function indicated by @code{exceptionHook} is called with
12537 one parameter: an @code{int} which is the exception number.
12540 Compile and link together: your program, the @value{GDBN} debugging stub for
12541 your target architecture, and the supporting subroutines.
12544 Make sure you have a serial connection between your target machine and
12545 the @value{GDBN} host, and identify the serial port on the host.
12548 @c The "remote" target now provides a `load' command, so we should
12549 @c document that. FIXME.
12550 Download your program to your target machine (or get it there by
12551 whatever means the manufacturer provides), and start it.
12554 Start @value{GDBN} on the host, and connect to the target
12555 (@pxref{Connecting,,Connecting to a remote target}).
12559 @node Configurations
12560 @chapter Configuration-Specific Information
12562 While nearly all @value{GDBN} commands are available for all native and
12563 cross versions of the debugger, there are some exceptions. This chapter
12564 describes things that are only available in certain configurations.
12566 There are three major categories of configurations: native
12567 configurations, where the host and target are the same, embedded
12568 operating system configurations, which are usually the same for several
12569 different processor architectures, and bare embedded processors, which
12570 are quite different from each other.
12575 * Embedded Processors::
12582 This section describes details specific to particular native
12587 * BSD libkvm Interface:: Debugging BSD kernel memory images
12588 * SVR4 Process Information:: SVR4 process information
12589 * DJGPP Native:: Features specific to the DJGPP port
12590 * Cygwin Native:: Features specific to the Cygwin port
12591 * Hurd Native:: Features specific to @sc{gnu} Hurd
12592 * Neutrino:: Features specific to QNX Neutrino
12598 On HP-UX systems, if you refer to a function or variable name that
12599 begins with a dollar sign, @value{GDBN} searches for a user or system
12600 name first, before it searches for a convenience variable.
12603 @node BSD libkvm Interface
12604 @subsection BSD libkvm Interface
12607 @cindex kernel memory image
12608 @cindex kernel crash dump
12610 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
12611 interface that provides a uniform interface for accessing kernel virtual
12612 memory images, including live systems and crash dumps. @value{GDBN}
12613 uses this interface to allow you to debug live kernels and kernel crash
12614 dumps on many native BSD configurations. This is implemented as a
12615 special @code{kvm} debugging target. For debugging a live system, load
12616 the currently running kernel into @value{GDBN} and connect to the
12620 (@value{GDBP}) @b{target kvm}
12623 For debugging crash dumps, provide the file name of the crash dump as an
12627 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
12630 Once connected to the @code{kvm} target, the following commands are
12636 Set current context from the @dfn{Process Control Block} (PCB) address.
12639 Set current context from proc address. This command isn't available on
12640 modern FreeBSD systems.
12643 @node SVR4 Process Information
12644 @subsection SVR4 process information
12646 @cindex examine process image
12647 @cindex process info via @file{/proc}
12649 Many versions of SVR4 and compatible systems provide a facility called
12650 @samp{/proc} that can be used to examine the image of a running
12651 process using file-system subroutines. If @value{GDBN} is configured
12652 for an operating system with this facility, the command @code{info
12653 proc} is available to report information about the process running
12654 your program, or about any process running on your system. @code{info
12655 proc} works only on SVR4 systems that include the @code{procfs} code.
12656 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
12657 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
12663 @itemx info proc @var{process-id}
12664 Summarize available information about any running process. If a
12665 process ID is specified by @var{process-id}, display information about
12666 that process; otherwise display information about the program being
12667 debugged. The summary includes the debugged process ID, the command
12668 line used to invoke it, its current working directory, and its
12669 executable file's absolute file name.
12671 On some systems, @var{process-id} can be of the form
12672 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
12673 within a process. If the optional @var{pid} part is missing, it means
12674 a thread from the process being debugged (the leading @samp{/} still
12675 needs to be present, or else @value{GDBN} will interpret the number as
12676 a process ID rather than a thread ID).
12678 @item info proc mappings
12679 @cindex memory address space mappings
12680 Report the memory address space ranges accessible in the program, with
12681 information on whether the process has read, write, or execute access
12682 rights to each range. On @sc{gnu}/Linux systems, each memory range
12683 includes the object file which is mapped to that range, instead of the
12684 memory access rights to that range.
12686 @item info proc stat
12687 @itemx info proc status
12688 @cindex process detailed status information
12689 These subcommands are specific to @sc{gnu}/Linux systems. They show
12690 the process-related information, including the user ID and group ID;
12691 how many threads are there in the process; its virtual memory usage;
12692 the signals that are pending, blocked, and ignored; its TTY; its
12693 consumption of system and user time; its stack size; its @samp{nice}
12694 value; etc. For more information, see the @samp{proc} man page
12695 (type @kbd{man 5 proc} from your shell prompt).
12697 @item info proc all
12698 Show all the information about the process described under all of the
12699 above @code{info proc} subcommands.
12702 @comment These sub-options of 'info proc' were not included when
12703 @comment procfs.c was re-written. Keep their descriptions around
12704 @comment against the day when someone finds the time to put them back in.
12705 @kindex info proc times
12706 @item info proc times
12707 Starting time, user CPU time, and system CPU time for your program and
12710 @kindex info proc id
12712 Report on the process IDs related to your program: its own process ID,
12713 the ID of its parent, the process group ID, and the session ID.
12716 @item set procfs-trace
12717 @kindex set procfs-trace
12718 @cindex @code{procfs} API calls
12719 This command enables and disables tracing of @code{procfs} API calls.
12721 @item show procfs-trace
12722 @kindex show procfs-trace
12723 Show the current state of @code{procfs} API call tracing.
12725 @item set procfs-file @var{file}
12726 @kindex set procfs-file
12727 Tell @value{GDBN} to write @code{procfs} API trace to the named
12728 @var{file}. @value{GDBN} appends the trace info to the previous
12729 contents of the file. The default is to display the trace on the
12732 @item show procfs-file
12733 @kindex show procfs-file
12734 Show the file to which @code{procfs} API trace is written.
12736 @item proc-trace-entry
12737 @itemx proc-trace-exit
12738 @itemx proc-untrace-entry
12739 @itemx proc-untrace-exit
12740 @kindex proc-trace-entry
12741 @kindex proc-trace-exit
12742 @kindex proc-untrace-entry
12743 @kindex proc-untrace-exit
12744 These commands enable and disable tracing of entries into and exits
12745 from the @code{syscall} interface.
12748 @kindex info pidlist
12749 @cindex process list, QNX Neutrino
12750 For QNX Neutrino only, this command displays the list of all the
12751 processes and all the threads within each process.
12754 @kindex info meminfo
12755 @cindex mapinfo list, QNX Neutrino
12756 For QNX Neutrino only, this command displays the list of all mapinfos.
12760 @subsection Features for Debugging @sc{djgpp} Programs
12761 @cindex @sc{djgpp} debugging
12762 @cindex native @sc{djgpp} debugging
12763 @cindex MS-DOS-specific commands
12766 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
12767 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
12768 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
12769 top of real-mode DOS systems and their emulations.
12771 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
12772 defines a few commands specific to the @sc{djgpp} port. This
12773 subsection describes those commands.
12778 This is a prefix of @sc{djgpp}-specific commands which print
12779 information about the target system and important OS structures.
12782 @cindex MS-DOS system info
12783 @cindex free memory information (MS-DOS)
12784 @item info dos sysinfo
12785 This command displays assorted information about the underlying
12786 platform: the CPU type and features, the OS version and flavor, the
12787 DPMI version, and the available conventional and DPMI memory.
12792 @cindex segment descriptor tables
12793 @cindex descriptor tables display
12795 @itemx info dos ldt
12796 @itemx info dos idt
12797 These 3 commands display entries from, respectively, Global, Local,
12798 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
12799 tables are data structures which store a descriptor for each segment
12800 that is currently in use. The segment's selector is an index into a
12801 descriptor table; the table entry for that index holds the
12802 descriptor's base address and limit, and its attributes and access
12805 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
12806 segment (used for both data and the stack), and a DOS segment (which
12807 allows access to DOS/BIOS data structures and absolute addresses in
12808 conventional memory). However, the DPMI host will usually define
12809 additional segments in order to support the DPMI environment.
12811 @cindex garbled pointers
12812 These commands allow to display entries from the descriptor tables.
12813 Without an argument, all entries from the specified table are
12814 displayed. An argument, which should be an integer expression, means
12815 display a single entry whose index is given by the argument. For
12816 example, here's a convenient way to display information about the
12817 debugged program's data segment:
12820 @exdent @code{(@value{GDBP}) info dos ldt $ds}
12821 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
12825 This comes in handy when you want to see whether a pointer is outside
12826 the data segment's limit (i.e.@: @dfn{garbled}).
12828 @cindex page tables display (MS-DOS)
12830 @itemx info dos pte
12831 These two commands display entries from, respectively, the Page
12832 Directory and the Page Tables. Page Directories and Page Tables are
12833 data structures which control how virtual memory addresses are mapped
12834 into physical addresses. A Page Table includes an entry for every
12835 page of memory that is mapped into the program's address space; there
12836 may be several Page Tables, each one holding up to 4096 entries. A
12837 Page Directory has up to 4096 entries, one each for every Page Table
12838 that is currently in use.
12840 Without an argument, @kbd{info dos pde} displays the entire Page
12841 Directory, and @kbd{info dos pte} displays all the entries in all of
12842 the Page Tables. An argument, an integer expression, given to the
12843 @kbd{info dos pde} command means display only that entry from the Page
12844 Directory table. An argument given to the @kbd{info dos pte} command
12845 means display entries from a single Page Table, the one pointed to by
12846 the specified entry in the Page Directory.
12848 @cindex direct memory access (DMA) on MS-DOS
12849 These commands are useful when your program uses @dfn{DMA} (Direct
12850 Memory Access), which needs physical addresses to program the DMA
12853 These commands are supported only with some DPMI servers.
12855 @cindex physical address from linear address
12856 @item info dos address-pte @var{addr}
12857 This command displays the Page Table entry for a specified linear
12858 address. The argument @var{addr} is a linear address which should
12859 already have the appropriate segment's base address added to it,
12860 because this command accepts addresses which may belong to @emph{any}
12861 segment. For example, here's how to display the Page Table entry for
12862 the page where a variable @code{i} is stored:
12865 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
12866 @exdent @code{Page Table entry for address 0x11a00d30:}
12867 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
12871 This says that @code{i} is stored at offset @code{0xd30} from the page
12872 whose physical base address is @code{0x02698000}, and shows all the
12873 attributes of that page.
12875 Note that you must cast the addresses of variables to a @code{char *},
12876 since otherwise the value of @code{__djgpp_base_address}, the base
12877 address of all variables and functions in a @sc{djgpp} program, will
12878 be added using the rules of C pointer arithmetics: if @code{i} is
12879 declared an @code{int}, @value{GDBN} will add 4 times the value of
12880 @code{__djgpp_base_address} to the address of @code{i}.
12882 Here's another example, it displays the Page Table entry for the
12886 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
12887 @exdent @code{Page Table entry for address 0x29110:}
12888 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
12892 (The @code{+ 3} offset is because the transfer buffer's address is the
12893 3rd member of the @code{_go32_info_block} structure.) The output
12894 clearly shows that this DPMI server maps the addresses in conventional
12895 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
12896 linear (@code{0x29110}) addresses are identical.
12898 This command is supported only with some DPMI servers.
12901 @cindex DOS serial data link, remote debugging
12902 In addition to native debugging, the DJGPP port supports remote
12903 debugging via a serial data link. The following commands are specific
12904 to remote serial debugging in the DJGPP port of @value{GDBN}.
12907 @kindex set com1base
12908 @kindex set com1irq
12909 @kindex set com2base
12910 @kindex set com2irq
12911 @kindex set com3base
12912 @kindex set com3irq
12913 @kindex set com4base
12914 @kindex set com4irq
12915 @item set com1base @var{addr}
12916 This command sets the base I/O port address of the @file{COM1} serial
12919 @item set com1irq @var{irq}
12920 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
12921 for the @file{COM1} serial port.
12923 There are similar commands @samp{set com2base}, @samp{set com3irq},
12924 etc.@: for setting the port address and the @code{IRQ} lines for the
12927 @kindex show com1base
12928 @kindex show com1irq
12929 @kindex show com2base
12930 @kindex show com2irq
12931 @kindex show com3base
12932 @kindex show com3irq
12933 @kindex show com4base
12934 @kindex show com4irq
12935 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
12936 display the current settings of the base address and the @code{IRQ}
12937 lines used by the COM ports.
12940 @kindex info serial
12941 @cindex DOS serial port status
12942 This command prints the status of the 4 DOS serial ports. For each
12943 port, it prints whether it's active or not, its I/O base address and
12944 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
12945 counts of various errors encountered so far.
12949 @node Cygwin Native
12950 @subsection Features for Debugging MS Windows PE executables
12951 @cindex MS Windows debugging
12952 @cindex native Cygwin debugging
12953 @cindex Cygwin-specific commands
12955 @value{GDBN} supports native debugging of MS Windows programs, including
12956 DLLs with and without symbolic debugging information. There are various
12957 additional Cygwin-specific commands, described in this subsection. The
12958 subsubsection @pxref{Non-debug DLL symbols} describes working with DLLs
12959 that have no debugging symbols.
12965 This is a prefix of MS Windows specific commands which print
12966 information about the target system and important OS structures.
12968 @item info w32 selector
12969 This command displays information returned by
12970 the Win32 API @code{GetThreadSelectorEntry} function.
12971 It takes an optional argument that is evaluated to
12972 a long value to give the information about this given selector.
12973 Without argument, this command displays information
12974 about the the six segment registers.
12978 This is a Cygwin specific alias of info shared.
12980 @kindex dll-symbols
12982 This command loads symbols from a dll similarly to
12983 add-sym command but without the need to specify a base address.
12985 @kindex set new-console
12986 @item set new-console @var{mode}
12987 If @var{mode} is @code{on} the debuggee will
12988 be started in a new console on next start.
12989 If @var{mode} is @code{off}i, the debuggee will
12990 be started in the same console as the debugger.
12992 @kindex show new-console
12993 @item show new-console
12994 Displays whether a new console is used
12995 when the debuggee is started.
12997 @kindex set new-group
12998 @item set new-group @var{mode}
12999 This boolean value controls whether the debuggee should
13000 start a new group or stay in the same group as the debugger.
13001 This affects the way the Windows OS handles
13004 @kindex show new-group
13005 @item show new-group
13006 Displays current value of new-group boolean.
13008 @kindex set debugevents
13009 @item set debugevents
13010 This boolean value adds debug output concerning events seen by the debugger.
13012 @kindex set debugexec
13013 @item set debugexec
13014 This boolean value adds debug output concerning execute events
13015 seen by the debugger.
13017 @kindex set debugexceptions
13018 @item set debugexceptions
13019 This boolean value adds debug ouptut concerning exception events
13020 seen by the debugger.
13022 @kindex set debugmemory
13023 @item set debugmemory
13024 This boolean value adds debug ouptut concerning memory events
13025 seen by the debugger.
13029 This boolean values specifies whether the debuggee is called
13030 via a shell or directly (default value is on).
13034 Displays if the debuggee will be started with a shell.
13039 * Non-debug DLL symbols:: Support for DLLs without debugging symbols
13042 @node Non-debug DLL symbols
13043 @subsubsection Support for DLLs without debugging symbols
13044 @cindex DLLs with no debugging symbols
13045 @cindex Minimal symbols and DLLs
13047 Very often on windows, some of the DLLs that your program relies on do
13048 not include symbolic debugging information (for example,
13049 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
13050 symbols in a DLL, it relies on the minimal amount of symbolic
13051 information contained in the DLL's export table. This subsubsection
13052 describes working with such symbols, known internally to @value{GDBN} as
13053 ``minimal symbols''.
13055 Note that before the debugged program has started execution, no DLLs
13056 will have been loaded. The easiest way around this problem is simply to
13057 start the program --- either by setting a breakpoint or letting the
13058 program run once to completion. It is also possible to force
13059 @value{GDBN} to load a particular DLL before starting the executable ---
13060 see the shared library information in @pxref{Files} or the
13061 @code{dll-symbols} command in @pxref{Cygwin Native}. Currently,
13062 explicitly loading symbols from a DLL with no debugging information will
13063 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
13064 which may adversely affect symbol lookup performance.
13066 @subsubsection DLL name prefixes
13068 In keeping with the naming conventions used by the Microsoft debugging
13069 tools, DLL export symbols are made available with a prefix based on the
13070 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
13071 also entered into the symbol table, so @code{CreateFileA} is often
13072 sufficient. In some cases there will be name clashes within a program
13073 (particularly if the executable itself includes full debugging symbols)
13074 necessitating the use of the fully qualified name when referring to the
13075 contents of the DLL. Use single-quotes around the name to avoid the
13076 exclamation mark (``!'') being interpreted as a language operator.
13078 Note that the internal name of the DLL may be all upper-case, even
13079 though the file name of the DLL is lower-case, or vice-versa. Since
13080 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
13081 some confusion. If in doubt, try the @code{info functions} and
13082 @code{info variables} commands or even @code{maint print msymbols} (see
13083 @pxref{Symbols}). Here's an example:
13086 (@value{GDBP}) info function CreateFileA
13087 All functions matching regular expression "CreateFileA":
13089 Non-debugging symbols:
13090 0x77e885f4 CreateFileA
13091 0x77e885f4 KERNEL32!CreateFileA
13095 (@value{GDBP}) info function !
13096 All functions matching regular expression "!":
13098 Non-debugging symbols:
13099 0x6100114c cygwin1!__assert
13100 0x61004034 cygwin1!_dll_crt0@@0
13101 0x61004240 cygwin1!dll_crt0(per_process *)
13105 @subsubsection Working with minimal symbols
13107 Symbols extracted from a DLL's export table do not contain very much
13108 type information. All that @value{GDBN} can do is guess whether a symbol
13109 refers to a function or variable depending on the linker section that
13110 contains the symbol. Also note that the actual contents of the memory
13111 contained in a DLL are not available unless the program is running. This
13112 means that you cannot examine the contents of a variable or disassemble
13113 a function within a DLL without a running program.
13115 Variables are generally treated as pointers and dereferenced
13116 automatically. For this reason, it is often necessary to prefix a
13117 variable name with the address-of operator (``&'') and provide explicit
13118 type information in the command. Here's an example of the type of
13122 (@value{GDBP}) print 'cygwin1!__argv'
13127 (@value{GDBP}) x 'cygwin1!__argv'
13128 0x10021610: "\230y\""
13131 And two possible solutions:
13134 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
13135 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
13139 (@value{GDBP}) x/2x &'cygwin1!__argv'
13140 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
13141 (@value{GDBP}) x/x 0x10021608
13142 0x10021608: 0x0022fd98
13143 (@value{GDBP}) x/s 0x0022fd98
13144 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
13147 Setting a break point within a DLL is possible even before the program
13148 starts execution. However, under these circumstances, @value{GDBN} can't
13149 examine the initial instructions of the function in order to skip the
13150 function's frame set-up code. You can work around this by using ``*&''
13151 to set the breakpoint at a raw memory address:
13154 (@value{GDBP}) break *&'python22!PyOS_Readline'
13155 Breakpoint 1 at 0x1e04eff0
13158 The author of these extensions is not entirely convinced that setting a
13159 break point within a shared DLL like @file{kernel32.dll} is completely
13163 @subsection Commands specific to @sc{gnu} Hurd systems
13164 @cindex @sc{gnu} Hurd debugging
13166 This subsection describes @value{GDBN} commands specific to the
13167 @sc{gnu} Hurd native debugging.
13172 @kindex set signals@r{, Hurd command}
13173 @kindex set sigs@r{, Hurd command}
13174 This command toggles the state of inferior signal interception by
13175 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
13176 affected by this command. @code{sigs} is a shorthand alias for
13181 @kindex show signals@r{, Hurd command}
13182 @kindex show sigs@r{, Hurd command}
13183 Show the current state of intercepting inferior's signals.
13185 @item set signal-thread
13186 @itemx set sigthread
13187 @kindex set signal-thread
13188 @kindex set sigthread
13189 This command tells @value{GDBN} which thread is the @code{libc} signal
13190 thread. That thread is run when a signal is delivered to a running
13191 process. @code{set sigthread} is the shorthand alias of @code{set
13194 @item show signal-thread
13195 @itemx show sigthread
13196 @kindex show signal-thread
13197 @kindex show sigthread
13198 These two commands show which thread will run when the inferior is
13199 delivered a signal.
13202 @kindex set stopped@r{, Hurd command}
13203 This commands tells @value{GDBN} that the inferior process is stopped,
13204 as with the @code{SIGSTOP} signal. The stopped process can be
13205 continued by delivering a signal to it.
13208 @kindex show stopped@r{, Hurd command}
13209 This command shows whether @value{GDBN} thinks the debuggee is
13212 @item set exceptions
13213 @kindex set exceptions@r{, Hurd command}
13214 Use this command to turn off trapping of exceptions in the inferior.
13215 When exception trapping is off, neither breakpoints nor
13216 single-stepping will work. To restore the default, set exception
13219 @item show exceptions
13220 @kindex show exceptions@r{, Hurd command}
13221 Show the current state of trapping exceptions in the inferior.
13223 @item set task pause
13224 @kindex set task@r{, Hurd commands}
13225 @cindex task attributes (@sc{gnu} Hurd)
13226 @cindex pause current task (@sc{gnu} Hurd)
13227 This command toggles task suspension when @value{GDBN} has control.
13228 Setting it to on takes effect immediately, and the task is suspended
13229 whenever @value{GDBN} gets control. Setting it to off will take
13230 effect the next time the inferior is continued. If this option is set
13231 to off, you can use @code{set thread default pause on} or @code{set
13232 thread pause on} (see below) to pause individual threads.
13234 @item show task pause
13235 @kindex show task@r{, Hurd commands}
13236 Show the current state of task suspension.
13238 @item set task detach-suspend-count
13239 @cindex task suspend count
13240 @cindex detach from task, @sc{gnu} Hurd
13241 This command sets the suspend count the task will be left with when
13242 @value{GDBN} detaches from it.
13244 @item show task detach-suspend-count
13245 Show the suspend count the task will be left with when detaching.
13247 @item set task exception-port
13248 @itemx set task excp
13249 @cindex task exception port, @sc{gnu} Hurd
13250 This command sets the task exception port to which @value{GDBN} will
13251 forward exceptions. The argument should be the value of the @dfn{send
13252 rights} of the task. @code{set task excp} is a shorthand alias.
13254 @item set noninvasive
13255 @cindex noninvasive task options
13256 This command switches @value{GDBN} to a mode that is the least
13257 invasive as far as interfering with the inferior is concerned. This
13258 is the same as using @code{set task pause}, @code{set exceptions}, and
13259 @code{set signals} to values opposite to the defaults.
13261 @item info send-rights
13262 @itemx info receive-rights
13263 @itemx info port-rights
13264 @itemx info port-sets
13265 @itemx info dead-names
13268 @cindex send rights, @sc{gnu} Hurd
13269 @cindex receive rights, @sc{gnu} Hurd
13270 @cindex port rights, @sc{gnu} Hurd
13271 @cindex port sets, @sc{gnu} Hurd
13272 @cindex dead names, @sc{gnu} Hurd
13273 These commands display information about, respectively, send rights,
13274 receive rights, port rights, port sets, and dead names of a task.
13275 There are also shorthand aliases: @code{info ports} for @code{info
13276 port-rights} and @code{info psets} for @code{info port-sets}.
13278 @item set thread pause
13279 @kindex set thread@r{, Hurd command}
13280 @cindex thread properties, @sc{gnu} Hurd
13281 @cindex pause current thread (@sc{gnu} Hurd)
13282 This command toggles current thread suspension when @value{GDBN} has
13283 control. Setting it to on takes effect immediately, and the current
13284 thread is suspended whenever @value{GDBN} gets control. Setting it to
13285 off will take effect the next time the inferior is continued.
13286 Normally, this command has no effect, since when @value{GDBN} has
13287 control, the whole task is suspended. However, if you used @code{set
13288 task pause off} (see above), this command comes in handy to suspend
13289 only the current thread.
13291 @item show thread pause
13292 @kindex show thread@r{, Hurd command}
13293 This command shows the state of current thread suspension.
13295 @item set thread run
13296 This comamnd sets whether the current thread is allowed to run.
13298 @item show thread run
13299 Show whether the current thread is allowed to run.
13301 @item set thread detach-suspend-count
13302 @cindex thread suspend count, @sc{gnu} Hurd
13303 @cindex detach from thread, @sc{gnu} Hurd
13304 This command sets the suspend count @value{GDBN} will leave on a
13305 thread when detaching. This number is relative to the suspend count
13306 found by @value{GDBN} when it notices the thread; use @code{set thread
13307 takeover-suspend-count} to force it to an absolute value.
13309 @item show thread detach-suspend-count
13310 Show the suspend count @value{GDBN} will leave on the thread when
13313 @item set thread exception-port
13314 @itemx set thread excp
13315 Set the thread exception port to which to forward exceptions. This
13316 overrides the port set by @code{set task exception-port} (see above).
13317 @code{set thread excp} is the shorthand alias.
13319 @item set thread takeover-suspend-count
13320 Normally, @value{GDBN}'s thread suspend counts are relative to the
13321 value @value{GDBN} finds when it notices each thread. This command
13322 changes the suspend counts to be absolute instead.
13324 @item set thread default
13325 @itemx show thread default
13326 @cindex thread default settings, @sc{gnu} Hurd
13327 Each of the above @code{set thread} commands has a @code{set thread
13328 default} counterpart (e.g., @code{set thread default pause}, @code{set
13329 thread default exception-port}, etc.). The @code{thread default}
13330 variety of commands sets the default thread properties for all
13331 threads; you can then change the properties of individual threads with
13332 the non-default commands.
13337 @subsection QNX Neutrino
13338 @cindex QNX Neutrino
13340 @value{GDBN} provides the following commands specific to the QNX
13344 @item set debug nto-debug
13345 @kindex set debug nto-debug
13346 When set to on, enables debugging messages specific to the QNX
13349 @item show debug nto-debug
13350 @kindex show debug nto-debug
13351 Show the current state of QNX Neutrino messages.
13356 @section Embedded Operating Systems
13358 This section describes configurations involving the debugging of
13359 embedded operating systems that are available for several different
13363 * VxWorks:: Using @value{GDBN} with VxWorks
13366 @value{GDBN} includes the ability to debug programs running on
13367 various real-time operating systems.
13370 @subsection Using @value{GDBN} with VxWorks
13376 @kindex target vxworks
13377 @item target vxworks @var{machinename}
13378 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
13379 is the target system's machine name or IP address.
13383 On VxWorks, @code{load} links @var{filename} dynamically on the
13384 current target system as well as adding its symbols in @value{GDBN}.
13386 @value{GDBN} enables developers to spawn and debug tasks running on networked
13387 VxWorks targets from a Unix host. Already-running tasks spawned from
13388 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
13389 both the Unix host and on the VxWorks target. The program
13390 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
13391 installed with the name @code{vxgdb}, to distinguish it from a
13392 @value{GDBN} for debugging programs on the host itself.)
13395 @item VxWorks-timeout @var{args}
13396 @kindex vxworks-timeout
13397 All VxWorks-based targets now support the option @code{vxworks-timeout}.
13398 This option is set by the user, and @var{args} represents the number of
13399 seconds @value{GDBN} waits for responses to rpc's. You might use this if
13400 your VxWorks target is a slow software simulator or is on the far side
13401 of a thin network line.
13404 The following information on connecting to VxWorks was current when
13405 this manual was produced; newer releases of VxWorks may use revised
13408 @findex INCLUDE_RDB
13409 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
13410 to include the remote debugging interface routines in the VxWorks
13411 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
13412 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
13413 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
13414 source debugging task @code{tRdbTask} when VxWorks is booted. For more
13415 information on configuring and remaking VxWorks, see the manufacturer's
13417 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
13419 Once you have included @file{rdb.a} in your VxWorks system image and set
13420 your Unix execution search path to find @value{GDBN}, you are ready to
13421 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
13422 @code{vxgdb}, depending on your installation).
13424 @value{GDBN} comes up showing the prompt:
13431 * VxWorks Connection:: Connecting to VxWorks
13432 * VxWorks Download:: VxWorks download
13433 * VxWorks Attach:: Running tasks
13436 @node VxWorks Connection
13437 @subsubsection Connecting to VxWorks
13439 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
13440 network. To connect to a target whose host name is ``@code{tt}'', type:
13443 (vxgdb) target vxworks tt
13447 @value{GDBN} displays messages like these:
13450 Attaching remote machine across net...
13455 @value{GDBN} then attempts to read the symbol tables of any object modules
13456 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
13457 these files by searching the directories listed in the command search
13458 path (@pxref{Environment, ,Your program's environment}); if it fails
13459 to find an object file, it displays a message such as:
13462 prog.o: No such file or directory.
13465 When this happens, add the appropriate directory to the search path with
13466 the @value{GDBN} command @code{path}, and execute the @code{target}
13469 @node VxWorks Download
13470 @subsubsection VxWorks download
13472 @cindex download to VxWorks
13473 If you have connected to the VxWorks target and you want to debug an
13474 object that has not yet been loaded, you can use the @value{GDBN}
13475 @code{load} command to download a file from Unix to VxWorks
13476 incrementally. The object file given as an argument to the @code{load}
13477 command is actually opened twice: first by the VxWorks target in order
13478 to download the code, then by @value{GDBN} in order to read the symbol
13479 table. This can lead to problems if the current working directories on
13480 the two systems differ. If both systems have NFS mounted the same
13481 filesystems, you can avoid these problems by using absolute paths.
13482 Otherwise, it is simplest to set the working directory on both systems
13483 to the directory in which the object file resides, and then to reference
13484 the file by its name, without any path. For instance, a program
13485 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
13486 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
13487 program, type this on VxWorks:
13490 -> cd "@var{vxpath}/vw/demo/rdb"
13494 Then, in @value{GDBN}, type:
13497 (vxgdb) cd @var{hostpath}/vw/demo/rdb
13498 (vxgdb) load prog.o
13501 @value{GDBN} displays a response similar to this:
13504 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
13507 You can also use the @code{load} command to reload an object module
13508 after editing and recompiling the corresponding source file. Note that
13509 this makes @value{GDBN} delete all currently-defined breakpoints,
13510 auto-displays, and convenience variables, and to clear the value
13511 history. (This is necessary in order to preserve the integrity of
13512 debugger's data structures that reference the target system's symbol
13515 @node VxWorks Attach
13516 @subsubsection Running tasks
13518 @cindex running VxWorks tasks
13519 You can also attach to an existing task using the @code{attach} command as
13523 (vxgdb) attach @var{task}
13527 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
13528 or suspended when you attach to it. Running tasks are suspended at
13529 the time of attachment.
13531 @node Embedded Processors
13532 @section Embedded Processors
13534 This section goes into details specific to particular embedded
13537 @cindex send command to simulator
13538 Whenever a specific embedded processor has a simulator, @value{GDBN}
13539 allows to send an arbitrary command to the simulator.
13542 @item sim @var{command}
13543 @kindex sim@r{, a command}
13544 Send an arbitrary @var{command} string to the simulator. Consult the
13545 documentation for the specific simulator in use for information about
13546 acceptable commands.
13552 * H8/300:: Renesas H8/300
13553 * H8/500:: Renesas H8/500
13554 * M32R/D:: Renesas M32R/D
13555 * M68K:: Motorola M68K
13556 * MIPS Embedded:: MIPS Embedded
13557 * OpenRISC 1000:: OpenRisc 1000
13558 * PA:: HP PA Embedded
13561 * Sparclet:: Tsqware Sparclet
13562 * Sparclite:: Fujitsu Sparclite
13563 * ST2000:: Tandem ST2000
13564 * Z8000:: Zilog Z8000
13567 * Super-H:: Renesas Super-H
13568 * WinCE:: Windows CE child processes
13577 @item target rdi @var{dev}
13578 ARM Angel monitor, via RDI library interface to ADP protocol. You may
13579 use this target to communicate with both boards running the Angel
13580 monitor, or with the EmbeddedICE JTAG debug device.
13583 @item target rdp @var{dev}
13588 @value{GDBN} provides the following ARM-specific commands:
13591 @item set arm disassembler
13593 This commands selects from a list of disassembly styles. The
13594 @code{"std"} style is the standard style.
13596 @item show arm disassembler
13598 Show the current disassembly style.
13600 @item set arm apcs32
13601 @cindex ARM 32-bit mode
13602 This command toggles ARM operation mode between 32-bit and 26-bit.
13604 @item show arm apcs32
13605 Display the current usage of the ARM 32-bit mode.
13607 @item set arm fpu @var{fputype}
13608 This command sets the ARM floating-point unit (FPU) type. The
13609 argument @var{fputype} can be one of these:
13613 Determine the FPU type by querying the OS ABI.
13615 Software FPU, with mixed-endian doubles on little-endian ARM
13618 GCC-compiled FPA co-processor.
13620 Software FPU with pure-endian doubles.
13626 Show the current type of the FPU.
13629 This command forces @value{GDBN} to use the specified ABI.
13632 Show the currently used ABI.
13634 @item set debug arm
13635 Toggle whether to display ARM-specific debugging messages from the ARM
13636 target support subsystem.
13638 @item show debug arm
13639 Show whether ARM-specific debugging messages are enabled.
13642 The following commands are available when an ARM target is debugged
13643 using the RDI interface:
13646 @item rdilogfile @r{[}@var{file}@r{]}
13648 @cindex ADP (Angel Debugger Protocol) logging
13649 Set the filename for the ADP (Angel Debugger Protocol) packet log.
13650 With an argument, sets the log file to the specified @var{file}. With
13651 no argument, show the current log file name. The default log file is
13654 @item rdilogenable @r{[}@var{arg}@r{]}
13655 @kindex rdilogenable
13656 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
13657 enables logging, with an argument 0 or @code{"no"} disables it. With
13658 no arguments displays the current setting. When logging is enabled,
13659 ADP packets exchanged between @value{GDBN} and the RDI target device
13660 are logged to a file.
13662 @item set rdiromatzero
13663 @kindex set rdiromatzero
13664 @cindex ROM at zero address, RDI
13665 Tell @value{GDBN} whether the target has ROM at address 0. If on,
13666 vector catching is disabled, so that zero address can be used. If off
13667 (the default), vector catching is enabled. For this command to take
13668 effect, it needs to be invoked prior to the @code{target rdi} command.
13670 @item show rdiromatzero
13671 @kindex show rdiromatzero
13672 Show the current setting of ROM at zero address.
13674 @item set rdiheartbeat
13675 @kindex set rdiheartbeat
13676 @cindex RDI heartbeat
13677 Enable or disable RDI heartbeat packets. It is not recommended to
13678 turn on this option, since it confuses ARM and EPI JTAG interface, as
13679 well as the Angel monitor.
13681 @item show rdiheartbeat
13682 @kindex show rdiheartbeat
13683 Show the setting of RDI heartbeat packets.
13688 @subsection Renesas H8/300
13692 @kindex target hms@r{, with H8/300}
13693 @item target hms @var{dev}
13694 A Renesas SH, H8/300, or H8/500 board, attached via serial line to your host.
13695 Use special commands @code{device} and @code{speed} to control the serial
13696 line and the communications speed used.
13698 @kindex target e7000@r{, with H8/300}
13699 @item target e7000 @var{dev}
13700 E7000 emulator for Renesas H8 and SH.
13702 @kindex target sh3@r{, with H8/300}
13703 @kindex target sh3e@r{, with H8/300}
13704 @item target sh3 @var{dev}
13705 @itemx target sh3e @var{dev}
13706 Renesas SH-3 and SH-3E target systems.
13710 @cindex download to H8/300 or H8/500
13711 @cindex H8/300 or H8/500 download
13712 @cindex download to Renesas SH
13713 @cindex Renesas SH download
13714 When you select remote debugging to a Renesas SH, H8/300, or H8/500
13715 board, the @code{load} command downloads your program to the Renesas
13716 board and also opens it as the current executable target for
13717 @value{GDBN} on your host (like the @code{file} command).
13719 @value{GDBN} needs to know these things to talk to your
13720 Renesas SH, H8/300, or H8/500:
13724 that you want to use @samp{target hms}, the remote debugging interface
13725 for Renesas microprocessors, or @samp{target e7000}, the in-circuit
13726 emulator for the Renesas SH and the Renesas 300H. (@samp{target hms} is
13727 the default when @value{GDBN} is configured specifically for the Renesas SH,
13728 H8/300, or H8/500.)
13731 what serial device connects your host to your Renesas board (the first
13732 serial device available on your host is the default).
13735 what speed to use over the serial device.
13739 * Renesas Boards:: Connecting to Renesas boards.
13740 * Renesas ICE:: Using the E7000 In-Circuit Emulator.
13741 * Renesas Special:: Special @value{GDBN} commands for Renesas micros.
13744 @node Renesas Boards
13745 @subsubsection Connecting to Renesas boards
13747 @c only for Unix hosts
13749 @cindex serial device, Renesas micros
13750 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
13751 need to explicitly set the serial device. The default @var{port} is the
13752 first available port on your host. This is only necessary on Unix
13753 hosts, where it is typically something like @file{/dev/ttya}.
13756 @cindex serial line speed, Renesas micros
13757 @code{@value{GDBN}} has another special command to set the communications
13758 speed: @samp{speed @var{bps}}. This command also is only used from Unix
13759 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
13760 the DOS @code{mode} command (for instance,
13761 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
13763 The @samp{device} and @samp{speed} commands are available only when you
13764 use a Unix host to debug your Renesas microprocessor programs. If you
13766 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
13767 called @code{asynctsr} to communicate with the development board
13768 through a PC serial port. You must also use the DOS @code{mode} command
13769 to set up the serial port on the DOS side.
13771 The following sample session illustrates the steps needed to start a
13772 program under @value{GDBN} control on an H8/300. The example uses a
13773 sample H8/300 program called @file{t.x}. The procedure is the same for
13774 the Renesas SH and the H8/500.
13776 First hook up your development board. In this example, we use a
13777 board attached to serial port @code{COM2}; if you use a different serial
13778 port, substitute its name in the argument of the @code{mode} command.
13779 When you call @code{asynctsr}, the auxiliary comms program used by the
13780 debugger, you give it just the numeric part of the serial port's name;
13781 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
13785 C:\H8300\TEST> asynctsr 2
13786 C:\H8300\TEST> mode com2:9600,n,8,1,p
13788 Resident portion of MODE loaded
13790 COM2: 9600, n, 8, 1, p
13795 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
13796 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
13797 disable it, or even boot without it, to use @code{asynctsr} to control
13798 your development board.
13801 @kindex target hms@r{, and serial protocol}
13802 Now that serial communications are set up, and the development board is
13803 connected, you can start up @value{GDBN}. Call @code{@value{GDBN}} with
13804 the name of your program as the argument. @code{@value{GDBN}} prompts
13805 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
13806 commands to begin your debugging session: @samp{target hms} to specify
13807 cross-debugging to the Renesas board, and the @code{load} command to
13808 download your program to the board. @code{load} displays the names of
13809 the program's sections, and a @samp{*} for each 2K of data downloaded.
13810 (If you want to refresh @value{GDBN} data on symbols or on the
13811 executable file without downloading, use the @value{GDBN} commands
13812 @code{file} or @code{symbol-file}. These commands, and @code{load}
13813 itself, are described in @ref{Files,,Commands to specify files}.)
13816 (eg-C:\H8300\TEST) @value{GDBP} t.x
13817 @value{GDBN} is free software and you are welcome to distribute copies
13818 of it under certain conditions; type "show copying" to see
13820 There is absolutely no warranty for @value{GDBN}; type "show warranty"
13822 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
13823 (@value{GDBP}) target hms
13824 Connected to remote H8/300 HMS system.
13825 (@value{GDBP}) load t.x
13826 .text : 0x8000 .. 0xabde ***********
13827 .data : 0xabde .. 0xad30 *
13828 .stack : 0xf000 .. 0xf014 *
13831 At this point, you're ready to run or debug your program. From here on,
13832 you can use all the usual @value{GDBN} commands. The @code{break} command
13833 sets breakpoints; the @code{run} command starts your program;
13834 @code{print} or @code{x} display data; the @code{continue} command
13835 resumes execution after stopping at a breakpoint. You can use the
13836 @code{help} command at any time to find out more about @value{GDBN} commands.
13838 Remember, however, that @emph{operating system} facilities aren't
13839 available on your development board; for example, if your program hangs,
13840 you can't send an interrupt---but you can press the @sc{reset} switch!
13842 Use the @sc{reset} button on the development board
13845 to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has
13846 no way to pass an interrupt signal to the development board); and
13849 to return to the @value{GDBN} command prompt after your program finishes
13850 normally. The communications protocol provides no other way for @value{GDBN}
13851 to detect program completion.
13854 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
13855 development board as a ``normal exit'' of your program.
13858 @subsubsection Using the E7000 in-circuit emulator
13860 @kindex target e7000@r{, with Renesas ICE}
13861 You can use the E7000 in-circuit emulator to develop code for either the
13862 Renesas SH or the H8/300H. Use one of these forms of the @samp{target
13863 e7000} command to connect @value{GDBN} to your E7000:
13866 @item target e7000 @var{port} @var{speed}
13867 Use this form if your E7000 is connected to a serial port. The
13868 @var{port} argument identifies what serial port to use (for example,
13869 @samp{com2}). The third argument is the line speed in bits per second
13870 (for example, @samp{9600}).
13872 @item target e7000 @var{hostname}
13873 If your E7000 is installed as a host on a TCP/IP network, you can just
13874 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
13877 The following special commands are available when debugging with the
13881 @item e7000 @var{command}
13883 @cindex send command to E7000 monitor
13884 This sends the specified @var{command} to the E7000 monitor.
13886 @item ftplogin @var{machine} @var{username} @var{password} @var{dir}
13887 @kindex ftplogin@r{, E7000}
13888 This command records information for subsequent interface with the
13889 E7000 monitor via the FTP protocol: @value{GDBN} will log into the
13890 named @var{machine} using specified @var{username} and @var{password},
13891 and then chdir to the named directory @var{dir}.
13893 @item ftpload @var{file}
13894 @kindex ftpload@r{, E7000}
13895 This command uses credentials recorded by @code{ftplogin} to fetch and
13896 load the named @var{file} from the E7000 monitor.
13899 @kindex drain@r{, E7000}
13900 This command drains any pending text buffers stored on the E7000.
13902 @item set usehardbreakpoints
13903 @itemx show usehardbreakpoints
13904 @kindex set usehardbreakpoints@r{, E7000}
13905 @kindex show usehardbreakpoints@r{, E7000}
13906 @cindex hardware breakpoints, and E7000
13907 These commands set and show the use of hardware breakpoints for all
13908 breakpoints. @xref{Set Breaks, hardware-assisted breakpoint}, for
13909 more information about using hardware breakpoints selectively.
13912 @node Renesas Special
13913 @subsubsection Special @value{GDBN} commands for Renesas micros
13915 Some @value{GDBN} commands are available only for the H8/300:
13919 @kindex set machine
13920 @kindex show machine
13921 @item set machine h8300
13922 @itemx set machine h8300h
13923 Condition @value{GDBN} for one of the two variants of the H8/300
13924 architecture with @samp{set machine}. You can use @samp{show machine}
13925 to check which variant is currently in effect.
13934 @kindex set memory @var{mod}
13935 @cindex memory models, H8/500
13936 @item set memory @var{mod}
13938 Specify which H8/500 memory model (@var{mod}) you are using with
13939 @samp{set memory}; check which memory model is in effect with @samp{show
13940 memory}. The accepted values for @var{mod} are @code{small},
13941 @code{big}, @code{medium}, and @code{compact}.
13946 @subsection Renesas M32R/D and M32R/SDI
13949 @kindex target m32r
13950 @item target m32r @var{dev}
13951 Renesas M32R/D ROM monitor.
13953 @kindex target m32rsdi
13954 @item target m32rsdi @var{dev}
13955 Renesas M32R SDI server, connected via parallel port to the board.
13958 The following @value{GDBN} commands are specific to the M32R monitor:
13961 @item set download-path @var{path}
13962 @kindex set download-path
13963 @cindex find downloadable @sc{srec} files (M32R)
13964 Set the default path for finding donwloadable @sc{srec} files.
13966 @item show download-path
13967 @kindex show download-path
13968 Show the default path for downloadable @sc{srec} files.
13970 @item set board-address @var{addr}
13971 @kindex set board-address
13972 @cindex M32-EVA target board address
13973 Set the IP address for the M32R-EVA target board.
13975 @item show board-address
13976 @kindex show board-address
13977 Show the current IP address of the target board.
13979 @item set server-address @var{addr}
13980 @kindex set server-address
13981 @cindex download server address (M32R)
13982 Set the IP address for the download server, which is the @value{GDBN}'s
13985 @item show server-address
13986 @kindex show server-address
13987 Display the IP address of the download server.
13989 @item upload @r{[}@var{file}@r{]}
13990 @kindex upload@r{, M32R}
13991 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
13992 upload capability. If no @var{file} argument is given, the current
13993 executable file is uploaded.
13995 @item tload @r{[}@var{file}@r{]}
13996 @kindex tload@r{, M32R}
13997 Test the @code{upload} command.
14000 The following commands are available for M32R/SDI:
14005 @cindex reset SDI connection, M32R
14006 This command resets the SDI connection.
14010 This command shows the SDI connection status.
14013 @kindex debug_chaos
14014 @cindex M32R/Chaos debugging
14015 Instructs the remote that M32R/Chaos debugging is to be used.
14017 @item use_debug_dma
14018 @kindex use_debug_dma
14019 Instructs the remote to use the DEBUG_DMA method of accessing memory.
14022 @kindex use_mon_code
14023 Instructs the remote to use the MON_CODE method of accessing memory.
14026 @kindex use_ib_break
14027 Instructs the remote to set breakpoints by IB break.
14029 @item use_dbt_break
14030 @kindex use_dbt_break
14031 Instructs the remote to set breakpoints by DBT.
14037 The Motorola m68k configuration includes ColdFire support, and
14038 target command for the following ROM monitors.
14042 @kindex target abug
14043 @item target abug @var{dev}
14044 ABug ROM monitor for M68K.
14046 @kindex target cpu32bug
14047 @item target cpu32bug @var{dev}
14048 CPU32BUG monitor, running on a CPU32 (M68K) board.
14050 @kindex target dbug
14051 @item target dbug @var{dev}
14052 dBUG ROM monitor for Motorola ColdFire.
14055 @item target est @var{dev}
14056 EST-300 ICE monitor, running on a CPU32 (M68K) board.
14058 @kindex target rom68k
14059 @item target rom68k @var{dev}
14060 ROM 68K monitor, running on an M68K IDP board.
14066 @kindex target rombug
14067 @item target rombug @var{dev}
14068 ROMBUG ROM monitor for OS/9000.
14072 @node MIPS Embedded
14073 @subsection MIPS Embedded
14075 @cindex MIPS boards
14076 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
14077 MIPS board attached to a serial line. This is available when
14078 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
14081 Use these @value{GDBN} commands to specify the connection to your target board:
14084 @item target mips @var{port}
14085 @kindex target mips @var{port}
14086 To run a program on the board, start up @code{@value{GDBP}} with the
14087 name of your program as the argument. To connect to the board, use the
14088 command @samp{target mips @var{port}}, where @var{port} is the name of
14089 the serial port connected to the board. If the program has not already
14090 been downloaded to the board, you may use the @code{load} command to
14091 download it. You can then use all the usual @value{GDBN} commands.
14093 For example, this sequence connects to the target board through a serial
14094 port, and loads and runs a program called @var{prog} through the
14098 host$ @value{GDBP} @var{prog}
14099 @value{GDBN} is free software and @dots{}
14100 (@value{GDBP}) target mips /dev/ttyb
14101 (@value{GDBP}) load @var{prog}
14105 @item target mips @var{hostname}:@var{portnumber}
14106 On some @value{GDBN} host configurations, you can specify a TCP
14107 connection (for instance, to a serial line managed by a terminal
14108 concentrator) instead of a serial port, using the syntax
14109 @samp{@var{hostname}:@var{portnumber}}.
14111 @item target pmon @var{port}
14112 @kindex target pmon @var{port}
14115 @item target ddb @var{port}
14116 @kindex target ddb @var{port}
14117 NEC's DDB variant of PMON for Vr4300.
14119 @item target lsi @var{port}
14120 @kindex target lsi @var{port}
14121 LSI variant of PMON.
14123 @kindex target r3900
14124 @item target r3900 @var{dev}
14125 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
14127 @kindex target array
14128 @item target array @var{dev}
14129 Array Tech LSI33K RAID controller board.
14135 @value{GDBN} also supports these special commands for MIPS targets:
14138 @item set mipsfpu double
14139 @itemx set mipsfpu single
14140 @itemx set mipsfpu none
14141 @itemx set mipsfpu auto
14142 @itemx show mipsfpu
14143 @kindex set mipsfpu
14144 @kindex show mipsfpu
14145 @cindex MIPS remote floating point
14146 @cindex floating point, MIPS remote
14147 If your target board does not support the MIPS floating point
14148 coprocessor, you should use the command @samp{set mipsfpu none} (if you
14149 need this, you may wish to put the command in your @value{GDBN} init
14150 file). This tells @value{GDBN} how to find the return value of
14151 functions which return floating point values. It also allows
14152 @value{GDBN} to avoid saving the floating point registers when calling
14153 functions on the board. If you are using a floating point coprocessor
14154 with only single precision floating point support, as on the @sc{r4650}
14155 processor, use the command @samp{set mipsfpu single}. The default
14156 double precision floating point coprocessor may be selected using
14157 @samp{set mipsfpu double}.
14159 In previous versions the only choices were double precision or no
14160 floating point, so @samp{set mipsfpu on} will select double precision
14161 and @samp{set mipsfpu off} will select no floating point.
14163 As usual, you can inquire about the @code{mipsfpu} variable with
14164 @samp{show mipsfpu}.
14166 @item set timeout @var{seconds}
14167 @itemx set retransmit-timeout @var{seconds}
14168 @itemx show timeout
14169 @itemx show retransmit-timeout
14170 @cindex @code{timeout}, MIPS protocol
14171 @cindex @code{retransmit-timeout}, MIPS protocol
14172 @kindex set timeout
14173 @kindex show timeout
14174 @kindex set retransmit-timeout
14175 @kindex show retransmit-timeout
14176 You can control the timeout used while waiting for a packet, in the MIPS
14177 remote protocol, with the @code{set timeout @var{seconds}} command. The
14178 default is 5 seconds. Similarly, you can control the timeout used while
14179 waiting for an acknowledgement of a packet with the @code{set
14180 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
14181 You can inspect both values with @code{show timeout} and @code{show
14182 retransmit-timeout}. (These commands are @emph{only} available when
14183 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
14185 The timeout set by @code{set timeout} does not apply when @value{GDBN}
14186 is waiting for your program to stop. In that case, @value{GDBN} waits
14187 forever because it has no way of knowing how long the program is going
14188 to run before stopping.
14190 @item set syn-garbage-limit @var{num}
14191 @kindex set syn-garbage-limit@r{, MIPS remote}
14192 @cindex synchronize with remote MIPS target
14193 Limit the maximum number of characters @value{GDBN} should ignore when
14194 it tries to synchronize with the remote target. The default is 10
14195 characters. Setting the limit to -1 means there's no limit.
14197 @item show syn-garbage-limit
14198 @kindex show syn-garbage-limit@r{, MIPS remote}
14199 Show the current limit on the number of characters to ignore when
14200 trying to synchronize with the remote system.
14202 @item set monitor-prompt @var{prompt}
14203 @kindex set monitor-prompt@r{, MIPS remote}
14204 @cindex remote monitor prompt
14205 Tell @value{GDBN} to expect the specified @var{prompt} string from the
14206 remote monitor. The default depends on the target:
14216 @item show monitor-prompt
14217 @kindex show monitor-prompt@r{, MIPS remote}
14218 Show the current strings @value{GDBN} expects as the prompt from the
14221 @item set monitor-warnings
14222 @kindex set monitor-warnings@r{, MIPS remote}
14223 Enable or disable monitor warnings about hardware breakpoints. This
14224 has effect only for the @code{lsi} target. When on, @value{GDBN} will
14225 display warning messages whose codes are returned by the @code{lsi}
14226 PMON monitor for breakpoint commands.
14228 @item show monitor-warnings
14229 @kindex show monitor-warnings@r{, MIPS remote}
14230 Show the current setting of printing monitor warnings.
14232 @item pmon @var{command}
14233 @kindex pmon@r{, MIPS remote}
14234 @cindex send PMON command
14235 This command allows sending an arbitrary @var{command} string to the
14236 monitor. The monitor must be in debug mode for this to work.
14239 @node OpenRISC 1000
14240 @subsection OpenRISC 1000
14241 @cindex OpenRISC 1000
14243 @cindex or1k boards
14244 See OR1k Architecture document (@uref{www.opencores.org}) for more information
14245 about platform and commands.
14249 @kindex target jtag
14250 @item target jtag jtag://@var{host}:@var{port}
14252 Connects to remote JTAG server.
14253 JTAG remote server can be either an or1ksim or JTAG server,
14254 connected via parallel port to the board.
14256 Example: @code{target jtag jtag://localhost:9999}
14259 @item or1ksim @var{command}
14260 If connected to @code{or1ksim} OpenRISC 1000 Architectural
14261 Simulator, proprietary commands can be executed.
14263 @kindex info or1k spr
14264 @item info or1k spr
14265 Displays spr groups.
14267 @item info or1k spr @var{group}
14268 @itemx info or1k spr @var{groupno}
14269 Displays register names in selected group.
14271 @item info or1k spr @var{group} @var{register}
14272 @itemx info or1k spr @var{register}
14273 @itemx info or1k spr @var{groupno} @var{registerno}
14274 @itemx info or1k spr @var{registerno}
14275 Shows information about specified spr register.
14278 @item spr @var{group} @var{register} @var{value}
14279 @itemx spr @var{register @var{value}}
14280 @itemx spr @var{groupno} @var{registerno @var{value}}
14281 @itemx spr @var{registerno @var{value}}
14282 Writes @var{value} to specified spr register.
14285 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
14286 It is very similar to @value{GDBN} trace, except it does not interfere with normal
14287 program execution and is thus much faster. Hardware breakpoints/watchpoint
14288 triggers can be set using:
14291 Load effective address/data
14293 Store effective address/data
14295 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
14300 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
14301 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
14303 @code{htrace} commands:
14304 @cindex OpenRISC 1000 htrace
14307 @item hwatch @var{conditional}
14308 Set hardware watchpoint on combination of Load/Store Effecive Address(es)
14309 or Data. For example:
14311 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14313 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14317 Display information about current HW trace configuration.
14319 @item htrace trigger @var{conditional}
14320 Set starting criteria for HW trace.
14322 @item htrace qualifier @var{conditional}
14323 Set acquisition qualifier for HW trace.
14325 @item htrace stop @var{conditional}
14326 Set HW trace stopping criteria.
14328 @item htrace record [@var{data}]*
14329 Selects the data to be recorded, when qualifier is met and HW trace was
14332 @item htrace enable
14333 @itemx htrace disable
14334 Enables/disables the HW trace.
14336 @item htrace rewind [@var{filename}]
14337 Clears currently recorded trace data.
14339 If filename is specified, new trace file is made and any newly collected data
14340 will be written there.
14342 @item htrace print [@var{start} [@var{len}]]
14343 Prints trace buffer, using current record configuration.
14345 @item htrace mode continuous
14346 Set continuous trace mode.
14348 @item htrace mode suspend
14349 Set suspend trace mode.
14354 @subsection PowerPC
14357 @kindex target dink32
14358 @item target dink32 @var{dev}
14359 DINK32 ROM monitor.
14361 @kindex target ppcbug
14362 @item target ppcbug @var{dev}
14363 @kindex target ppcbug1
14364 @item target ppcbug1 @var{dev}
14365 PPCBUG ROM monitor for PowerPC.
14368 @item target sds @var{dev}
14369 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
14372 @cindex SDS protocol
14373 The following commands specifi to the SDS protocol are supported
14377 @item set sdstimeout @var{nsec}
14378 @kindex set sdstimeout
14379 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
14380 default is 2 seconds.
14382 @item show sdstimeout
14383 @kindex show sdstimeout
14384 Show the current value of the SDS timeout.
14386 @item sds @var{command}
14387 @kindex sds@r{, a command}
14388 Send the specified @var{command} string to the SDS monitor.
14393 @subsection HP PA Embedded
14397 @kindex target op50n
14398 @item target op50n @var{dev}
14399 OP50N monitor, running on an OKI HPPA board.
14401 @kindex target w89k
14402 @item target w89k @var{dev}
14403 W89K monitor, running on a Winbond HPPA board.
14408 @subsection Renesas SH
14412 @kindex target hms@r{, with Renesas SH}
14413 @item target hms @var{dev}
14414 A Renesas SH board attached via serial line to your host. Use special
14415 commands @code{device} and @code{speed} to control the serial line and
14416 the communications speed used.
14418 @kindex target e7000@r{, with Renesas SH}
14419 @item target e7000 @var{dev}
14420 E7000 emulator for Renesas SH.
14422 @kindex target sh3@r{, with SH}
14423 @kindex target sh3e@r{, with SH}
14424 @item target sh3 @var{dev}
14425 @item target sh3e @var{dev}
14426 Renesas SH-3 and SH-3E target systems.
14431 @subsection Tsqware Sparclet
14435 @value{GDBN} enables developers to debug tasks running on
14436 Sparclet targets from a Unix host.
14437 @value{GDBN} uses code that runs on
14438 both the Unix host and on the Sparclet target. The program
14439 @code{@value{GDBP}} is installed and executed on the Unix host.
14442 @item remotetimeout @var{args}
14443 @kindex remotetimeout
14444 @value{GDBN} supports the option @code{remotetimeout}.
14445 This option is set by the user, and @var{args} represents the number of
14446 seconds @value{GDBN} waits for responses.
14449 @cindex compiling, on Sparclet
14450 When compiling for debugging, include the options @samp{-g} to get debug
14451 information and @samp{-Ttext} to relocate the program to where you wish to
14452 load it on the target. You may also want to add the options @samp{-n} or
14453 @samp{-N} in order to reduce the size of the sections. Example:
14456 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
14459 You can use @code{objdump} to verify that the addresses are what you intended:
14462 sparclet-aout-objdump --headers --syms prog
14465 @cindex running, on Sparclet
14467 your Unix execution search path to find @value{GDBN}, you are ready to
14468 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
14469 (or @code{sparclet-aout-gdb}, depending on your installation).
14471 @value{GDBN} comes up showing the prompt:
14478 * Sparclet File:: Setting the file to debug
14479 * Sparclet Connection:: Connecting to Sparclet
14480 * Sparclet Download:: Sparclet download
14481 * Sparclet Execution:: Running and debugging
14484 @node Sparclet File
14485 @subsubsection Setting file to debug
14487 The @value{GDBN} command @code{file} lets you choose with program to debug.
14490 (gdbslet) file prog
14494 @value{GDBN} then attempts to read the symbol table of @file{prog}.
14495 @value{GDBN} locates
14496 the file by searching the directories listed in the command search
14498 If the file was compiled with debug information (option "-g"), source
14499 files will be searched as well.
14500 @value{GDBN} locates
14501 the source files by searching the directories listed in the directory search
14502 path (@pxref{Environment, ,Your program's environment}).
14504 to find a file, it displays a message such as:
14507 prog: No such file or directory.
14510 When this happens, add the appropriate directories to the search paths with
14511 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
14512 @code{target} command again.
14514 @node Sparclet Connection
14515 @subsubsection Connecting to Sparclet
14517 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
14518 To connect to a target on serial port ``@code{ttya}'', type:
14521 (gdbslet) target sparclet /dev/ttya
14522 Remote target sparclet connected to /dev/ttya
14523 main () at ../prog.c:3
14527 @value{GDBN} displays messages like these:
14533 @node Sparclet Download
14534 @subsubsection Sparclet download
14536 @cindex download to Sparclet
14537 Once connected to the Sparclet target,
14538 you can use the @value{GDBN}
14539 @code{load} command to download the file from the host to the target.
14540 The file name and load offset should be given as arguments to the @code{load}
14542 Since the file format is aout, the program must be loaded to the starting
14543 address. You can use @code{objdump} to find out what this value is. The load
14544 offset is an offset which is added to the VMA (virtual memory address)
14545 of each of the file's sections.
14546 For instance, if the program
14547 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
14548 and bss at 0x12010170, in @value{GDBN}, type:
14551 (gdbslet) load prog 0x12010000
14552 Loading section .text, size 0xdb0 vma 0x12010000
14555 If the code is loaded at a different address then what the program was linked
14556 to, you may need to use the @code{section} and @code{add-symbol-file} commands
14557 to tell @value{GDBN} where to map the symbol table.
14559 @node Sparclet Execution
14560 @subsubsection Running and debugging
14562 @cindex running and debugging Sparclet programs
14563 You can now begin debugging the task using @value{GDBN}'s execution control
14564 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
14565 manual for the list of commands.
14569 Breakpoint 1 at 0x12010000: file prog.c, line 3.
14571 Starting program: prog
14572 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
14573 3 char *symarg = 0;
14575 4 char *execarg = "hello!";
14580 @subsection Fujitsu Sparclite
14584 @kindex target sparclite
14585 @item target sparclite @var{dev}
14586 Fujitsu sparclite boards, used only for the purpose of loading.
14587 You must use an additional command to debug the program.
14588 For example: target remote @var{dev} using @value{GDBN} standard
14594 @subsection Tandem ST2000
14596 @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
14599 To connect your ST2000 to the host system, see the manufacturer's
14600 manual. Once the ST2000 is physically attached, you can run:
14603 target st2000 @var{dev} @var{speed}
14607 to establish it as your debugging environment. @var{dev} is normally
14608 the name of a serial device, such as @file{/dev/ttya}, connected to the
14609 ST2000 via a serial line. You can instead specify @var{dev} as a TCP
14610 connection (for example, to a serial line attached via a terminal
14611 concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
14613 The @code{load} and @code{attach} commands are @emph{not} defined for
14614 this target; you must load your program into the ST2000 as you normally
14615 would for standalone operation. @value{GDBN} reads debugging information
14616 (such as symbols) from a separate, debugging version of the program
14617 available on your host computer.
14618 @c FIXME!! This is terribly vague; what little content is here is
14619 @c basically hearsay.
14621 @cindex ST2000 auxiliary commands
14622 These auxiliary @value{GDBN} commands are available to help you with the ST2000
14626 @item st2000 @var{command}
14627 @kindex st2000 @var{cmd}
14628 @cindex STDBUG commands (ST2000)
14629 @cindex commands to STDBUG (ST2000)
14630 Send a @var{command} to the STDBUG monitor. See the manufacturer's
14631 manual for available commands.
14634 @cindex connect (to STDBUG)
14635 Connect the controlling terminal to the STDBUG command monitor. When
14636 you are done interacting with STDBUG, typing either of two character
14637 sequences gets you back to the @value{GDBN} command prompt:
14638 @kbd{@key{RET}~.} (Return, followed by tilde and period) or
14639 @kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D).
14643 @subsection Zilog Z8000
14646 @cindex simulator, Z8000
14647 @cindex Zilog Z8000 simulator
14649 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
14652 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
14653 unsegmented variant of the Z8000 architecture) or the Z8001 (the
14654 segmented variant). The simulator recognizes which architecture is
14655 appropriate by inspecting the object code.
14658 @item target sim @var{args}
14660 @kindex target sim@r{, with Z8000}
14661 Debug programs on a simulated CPU. If the simulator supports setup
14662 options, specify them via @var{args}.
14666 After specifying this target, you can debug programs for the simulated
14667 CPU in the same style as programs for your host computer; use the
14668 @code{file} command to load a new program image, the @code{run} command
14669 to run your program, and so on.
14671 As well as making available all the usual machine registers
14672 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
14673 additional items of information as specially named registers:
14678 Counts clock-ticks in the simulator.
14681 Counts instructions run in the simulator.
14684 Execution time in 60ths of a second.
14688 You can refer to these values in @value{GDBN} expressions with the usual
14689 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
14690 conditional breakpoint that suspends only after at least 5000
14691 simulated clock ticks.
14694 @subsection Atmel AVR
14697 When configured for debugging the Atmel AVR, @value{GDBN} supports the
14698 following AVR-specific commands:
14701 @item info io_registers
14702 @kindex info io_registers@r{, AVR}
14703 @cindex I/O registers (Atmel AVR)
14704 This command displays information about the AVR I/O registers. For
14705 each register, @value{GDBN} prints its number and value.
14712 When configured for debugging CRIS, @value{GDBN} provides the
14713 following CRIS-specific commands:
14716 @item set cris-version @var{ver}
14717 @cindex CRIS version
14718 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
14719 The CRIS version affects register names and sizes. This command is useful in
14720 case autodetection of the CRIS version fails.
14722 @item show cris-version
14723 Show the current CRIS version.
14725 @item set cris-dwarf2-cfi
14726 @cindex DWARF-2 CFI and CRIS
14727 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
14728 Change to @samp{off} when using @code{gcc-cris} whose version is below
14731 @item show cris-dwarf2-cfi
14732 Show the current state of using DWARF-2 CFI.
14734 @item set cris-mode @var{mode}
14736 Set the current CRIS mode to @var{mode}. It should only be changed when
14737 debugging in guru mode, in which case it should be set to
14738 @samp{guru} (the default is @samp{normal}).
14740 @item show cris-mode
14741 Show the current CRIS mode.
14745 @subsection Renesas Super-H
14748 For the Renesas Super-H processor, @value{GDBN} provides these
14753 @kindex regs@r{, Super-H}
14754 Show the values of all Super-H registers.
14758 @subsection Windows CE
14761 The following commands are available for Windows CE:
14764 @item set remotedirectory @var{dir}
14765 @kindex set remotedirectory
14766 Tell @value{GDBN} to upload files from the named directory @var{dir}.
14767 The default is @file{/gdb}, i.e.@: the root directory on the current
14770 @item show remotedirectory
14771 @kindex show remotedirectory
14772 Show the current value of the upload directory.
14774 @item set remoteupload @var{method}
14775 @kindex set remoteupload
14776 Set the method used to upload files to remote device. Valid values
14777 for @var{method} are @samp{always}, @samp{newer}, and @samp{never}.
14778 The default is @samp{newer}.
14780 @item show remoteupload
14781 @kindex show remoteupload
14782 Show the current setting of the upload method.
14784 @item set remoteaddhost
14785 @kindex set remoteaddhost
14786 Tell @value{GDBN} whether to add this host to the remote stub's
14787 arguments when you debug over a network.
14789 @item show remoteaddhost
14790 @kindex show remoteaddhost
14791 Show whether to add this host to remote stub's arguments when
14792 debugging over a network.
14796 @node Architectures
14797 @section Architectures
14799 This section describes characteristics of architectures that affect
14800 all uses of @value{GDBN} with the architecture, both native and cross.
14807 * HPPA:: HP PA architecture
14811 @subsection x86 Architecture-specific issues.
14814 @item set struct-convention @var{mode}
14815 @kindex set struct-convention
14816 @cindex struct return convention
14817 @cindex struct/union returned in registers
14818 Set the convention used by the inferior to return @code{struct}s and
14819 @code{union}s from functions to @var{mode}. Possible values of
14820 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
14821 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
14822 are returned on the stack, while @code{"reg"} means that a
14823 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
14824 be returned in a register.
14826 @item show struct-convention
14827 @kindex show struct-convention
14828 Show the current setting of the convention to return @code{struct}s
14837 @kindex set rstack_high_address
14838 @cindex AMD 29K register stack
14839 @cindex register stack, AMD29K
14840 @item set rstack_high_address @var{address}
14841 On AMD 29000 family processors, registers are saved in a separate
14842 @dfn{register stack}. There is no way for @value{GDBN} to determine the
14843 extent of this stack. Normally, @value{GDBN} just assumes that the
14844 stack is ``large enough''. This may result in @value{GDBN} referencing
14845 memory locations that do not exist. If necessary, you can get around
14846 this problem by specifying the ending address of the register stack with
14847 the @code{set rstack_high_address} command. The argument should be an
14848 address, which you probably want to precede with @samp{0x} to specify in
14851 @kindex show rstack_high_address
14852 @item show rstack_high_address
14853 Display the current limit of the register stack, on AMD 29000 family
14861 See the following section.
14866 @cindex stack on Alpha
14867 @cindex stack on MIPS
14868 @cindex Alpha stack
14870 Alpha- and MIPS-based computers use an unusual stack frame, which
14871 sometimes requires @value{GDBN} to search backward in the object code to
14872 find the beginning of a function.
14874 @cindex response time, MIPS debugging
14875 To improve response time (especially for embedded applications, where
14876 @value{GDBN} may be restricted to a slow serial line for this search)
14877 you may want to limit the size of this search, using one of these
14881 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
14882 @item set heuristic-fence-post @var{limit}
14883 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
14884 search for the beginning of a function. A value of @var{0} (the
14885 default) means there is no limit. However, except for @var{0}, the
14886 larger the limit the more bytes @code{heuristic-fence-post} must search
14887 and therefore the longer it takes to run. You should only need to use
14888 this command when debugging a stripped executable.
14890 @item show heuristic-fence-post
14891 Display the current limit.
14895 These commands are available @emph{only} when @value{GDBN} is configured
14896 for debugging programs on Alpha or MIPS processors.
14898 Several MIPS-specific commands are available when debugging MIPS
14902 @item set mips saved-gpreg-size @var{size}
14903 @kindex set mips saved-gpreg-size
14904 @cindex MIPS GP register size on stack
14905 Set the size of MIPS general-purpose registers saved on the stack.
14906 The argument @var{size} can be one of the following:
14910 32-bit GP registers
14912 64-bit GP registers
14914 Use the target's default setting or autodetect the saved size from the
14915 information contained in the executable. This is the default
14918 @item show mips saved-gpreg-size
14919 @kindex show mips saved-gpreg-size
14920 Show the current size of MIPS GP registers on the stack.
14922 @item set mips stack-arg-size @var{size}
14923 @kindex set mips stack-arg-size
14924 @cindex MIPS stack space for arguments
14925 Set the amount of stack space reserved for arguments to functions.
14926 The argument can be one of @code{"32"}, @code{"64"} or @code{"auto"}
14929 @item set mips abi @var{arg}
14930 @kindex set mips abi
14931 @cindex set ABI for MIPS
14932 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
14933 values of @var{arg} are:
14937 The default ABI associated with the current binary (this is the
14948 @item show mips abi
14949 @kindex show mips abi
14950 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
14953 @itemx show mipsfpu
14954 @xref{MIPS Embedded, set mipsfpu}.
14956 @item set mips mask-address @var{arg}
14957 @kindex set mips mask-address
14958 @cindex MIPS addresses, masking
14959 This command determines whether the most-significant 32 bits of 64-bit
14960 MIPS addresses are masked off. The argument @var{arg} can be
14961 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
14962 setting, which lets @value{GDBN} determine the correct value.
14964 @item show mips mask-address
14965 @kindex show mips mask-address
14966 Show whether the upper 32 bits of MIPS addresses are masked off or
14969 @item set remote-mips64-transfers-32bit-regs
14970 @kindex set remote-mips64-transfers-32bit-regs
14971 This command controls compatibility with 64-bit MIPS targets that
14972 transfer data in 32-bit quantities. If you have an old MIPS 64 target
14973 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
14974 and 64 bits for other registers, set this option to @samp{on}.
14976 @item show remote-mips64-transfers-32bit-regs
14977 @kindex show remote-mips64-transfers-32bit-regs
14978 Show the current setting of compatibility with older MIPS 64 targets.
14980 @item set debug mips
14981 @kindex set debug mips
14982 This command turns on and off debugging messages for the MIPS-specific
14983 target code in @value{GDBN}.
14985 @item show debug mips
14986 @kindex show debug mips
14987 Show the current setting of MIPS debugging messages.
14993 @cindex HPPA support
14995 When @value{GDBN} is debugging te HP PA architecture, it provides the
14996 following special commands:
14999 @item set debug hppa
15000 @kindex set debug hppa
15001 THis command determines whether HPPA architecture specific debugging
15002 messages are to be displayed.
15004 @item show debug hppa
15005 Show whether HPPA debugging messages are displayed.
15007 @item maint print unwind @var{address}
15008 @kindex maint print unwind@r{, HPPA}
15009 This command displays the contents of the unwind table entry at the
15010 given @var{address}.
15015 @node Controlling GDB
15016 @chapter Controlling @value{GDBN}
15018 You can alter the way @value{GDBN} interacts with you by using the
15019 @code{set} command. For commands controlling how @value{GDBN} displays
15020 data, see @ref{Print Settings, ,Print settings}. Other settings are
15025 * Editing:: Command editing
15026 * Command History:: Command history
15027 * Screen Size:: Screen size
15028 * Numbers:: Numbers
15029 * ABI:: Configuring the current ABI
15030 * Messages/Warnings:: Optional warnings and messages
15031 * Debugging Output:: Optional messages about internal happenings
15039 @value{GDBN} indicates its readiness to read a command by printing a string
15040 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
15041 can change the prompt string with the @code{set prompt} command. For
15042 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
15043 the prompt in one of the @value{GDBN} sessions so that you can always tell
15044 which one you are talking to.
15046 @emph{Note:} @code{set prompt} does not add a space for you after the
15047 prompt you set. This allows you to set a prompt which ends in a space
15048 or a prompt that does not.
15052 @item set prompt @var{newprompt}
15053 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
15055 @kindex show prompt
15057 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
15061 @section Command editing
15063 @cindex command line editing
15065 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
15066 @sc{gnu} library provides consistent behavior for programs which provide a
15067 command line interface to the user. Advantages are @sc{gnu} Emacs-style
15068 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
15069 substitution, and a storage and recall of command history across
15070 debugging sessions.
15072 You may control the behavior of command line editing in @value{GDBN} with the
15073 command @code{set}.
15076 @kindex set editing
15079 @itemx set editing on
15080 Enable command line editing (enabled by default).
15082 @item set editing off
15083 Disable command line editing.
15085 @kindex show editing
15087 Show whether command line editing is enabled.
15090 @xref{Command Line Editing}, for more details about the Readline
15091 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
15092 encouraged to read that chapter.
15094 @node Command History
15095 @section Command history
15096 @cindex command history
15098 @value{GDBN} can keep track of the commands you type during your
15099 debugging sessions, so that you can be certain of precisely what
15100 happened. Use these commands to manage the @value{GDBN} command
15103 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
15104 package, to provide the history facility. @xref{Using History
15105 Interactively}, for the detailed description of the History library.
15107 To issue a command to @value{GDBN} without affecting certain aspects of
15108 the state which is seen by users, prefix it with @samp{server }. This
15109 means that this command will not affect the command history, nor will it
15110 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
15111 pressed on a line by itself.
15113 @cindex @code{server}, command prefix
15114 The server prefix does not affect the recording of values into the value
15115 history; to print a value without recording it into the value history,
15116 use the @code{output} command instead of the @code{print} command.
15118 Here is the description of @value{GDBN} commands related to command
15122 @cindex history substitution
15123 @cindex history file
15124 @kindex set history filename
15125 @cindex @env{GDBHISTFILE}, environment variable
15126 @item set history filename @var{fname}
15127 Set the name of the @value{GDBN} command history file to @var{fname}.
15128 This is the file where @value{GDBN} reads an initial command history
15129 list, and where it writes the command history from this session when it
15130 exits. You can access this list through history expansion or through
15131 the history command editing characters listed below. This file defaults
15132 to the value of the environment variable @code{GDBHISTFILE}, or to
15133 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
15136 @cindex save command history
15137 @kindex set history save
15138 @item set history save
15139 @itemx set history save on
15140 Record command history in a file, whose name may be specified with the
15141 @code{set history filename} command. By default, this option is disabled.
15143 @item set history save off
15144 Stop recording command history in a file.
15146 @cindex history size
15147 @kindex set history size
15148 @cindex @env{HISTSIZE}, environment variable
15149 @item set history size @var{size}
15150 Set the number of commands which @value{GDBN} keeps in its history list.
15151 This defaults to the value of the environment variable
15152 @code{HISTSIZE}, or to 256 if this variable is not set.
15155 History expansion assigns special meaning to the character @kbd{!}.
15156 @xref{Event Designators}, for more details.
15158 @cindex history expansion, turn on/off
15159 Since @kbd{!} is also the logical not operator in C, history expansion
15160 is off by default. If you decide to enable history expansion with the
15161 @code{set history expansion on} command, you may sometimes need to
15162 follow @kbd{!} (when it is used as logical not, in an expression) with
15163 a space or a tab to prevent it from being expanded. The readline
15164 history facilities do not attempt substitution on the strings
15165 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
15167 The commands to control history expansion are:
15170 @item set history expansion on
15171 @itemx set history expansion
15172 @kindex set history expansion
15173 Enable history expansion. History expansion is off by default.
15175 @item set history expansion off
15176 Disable history expansion.
15179 @kindex show history
15181 @itemx show history filename
15182 @itemx show history save
15183 @itemx show history size
15184 @itemx show history expansion
15185 These commands display the state of the @value{GDBN} history parameters.
15186 @code{show history} by itself displays all four states.
15191 @kindex show commands
15192 @cindex show last commands
15193 @cindex display command history
15194 @item show commands
15195 Display the last ten commands in the command history.
15197 @item show commands @var{n}
15198 Print ten commands centered on command number @var{n}.
15200 @item show commands +
15201 Print ten commands just after the commands last printed.
15205 @section Screen size
15206 @cindex size of screen
15207 @cindex pauses in output
15209 Certain commands to @value{GDBN} may produce large amounts of
15210 information output to the screen. To help you read all of it,
15211 @value{GDBN} pauses and asks you for input at the end of each page of
15212 output. Type @key{RET} when you want to continue the output, or @kbd{q}
15213 to discard the remaining output. Also, the screen width setting
15214 determines when to wrap lines of output. Depending on what is being
15215 printed, @value{GDBN} tries to break the line at a readable place,
15216 rather than simply letting it overflow onto the following line.
15218 Normally @value{GDBN} knows the size of the screen from the terminal
15219 driver software. For example, on Unix @value{GDBN} uses the termcap data base
15220 together with the value of the @code{TERM} environment variable and the
15221 @code{stty rows} and @code{stty cols} settings. If this is not correct,
15222 you can override it with the @code{set height} and @code{set
15229 @kindex show height
15230 @item set height @var{lpp}
15232 @itemx set width @var{cpl}
15234 These @code{set} commands specify a screen height of @var{lpp} lines and
15235 a screen width of @var{cpl} characters. The associated @code{show}
15236 commands display the current settings.
15238 If you specify a height of zero lines, @value{GDBN} does not pause during
15239 output no matter how long the output is. This is useful if output is to a
15240 file or to an editor buffer.
15242 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
15243 from wrapping its output.
15245 @item set pagination on
15246 @itemx set pagination off
15247 @kindex set pagination
15248 Turn the output pagination on or off; the default is on. Turning
15249 pagination off is the alternative to @code{set height 0}.
15251 @item show pagination
15252 @kindex show pagination
15253 Show the current pagination mode.
15258 @cindex number representation
15259 @cindex entering numbers
15261 You can always enter numbers in octal, decimal, or hexadecimal in
15262 @value{GDBN} by the usual conventions: octal numbers begin with
15263 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
15264 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
15265 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
15266 10; likewise, the default display for numbers---when no particular
15267 format is specified---is base 10. You can change the default base for
15268 both input and output with the commands described below.
15271 @kindex set input-radix
15272 @item set input-radix @var{base}
15273 Set the default base for numeric input. Supported choices
15274 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15275 specified either unambiguously or using the current input radix; for
15279 set input-radix 012
15280 set input-radix 10.
15281 set input-radix 0xa
15285 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
15286 leaves the input radix unchanged, no matter what it was, since
15287 @samp{10}, being without any leading or trailing signs of its base, is
15288 interpreted in the current radix. Thus, if the current radix is 16,
15289 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
15292 @kindex set output-radix
15293 @item set output-radix @var{base}
15294 Set the default base for numeric display. Supported choices
15295 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15296 specified either unambiguously or using the current input radix.
15298 @kindex show input-radix
15299 @item show input-radix
15300 Display the current default base for numeric input.
15302 @kindex show output-radix
15303 @item show output-radix
15304 Display the current default base for numeric display.
15306 @item set radix @r{[}@var{base}@r{]}
15310 These commands set and show the default base for both input and output
15311 of numbers. @code{set radix} sets the radix of input and output to
15312 the same base; without an argument, it resets the radix back to its
15313 default value of 10.
15318 @section Configuring the current ABI
15320 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
15321 application automatically. However, sometimes you need to override its
15322 conclusions. Use these commands to manage @value{GDBN}'s view of the
15329 One @value{GDBN} configuration can debug binaries for multiple operating
15330 system targets, either via remote debugging or native emulation.
15331 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
15332 but you can override its conclusion using the @code{set osabi} command.
15333 One example where this is useful is in debugging of binaries which use
15334 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
15335 not have the same identifying marks that the standard C library for your
15340 Show the OS ABI currently in use.
15343 With no argument, show the list of registered available OS ABI's.
15345 @item set osabi @var{abi}
15346 Set the current OS ABI to @var{abi}.
15349 @cindex float promotion
15351 Generally, the way that an argument of type @code{float} is passed to a
15352 function depends on whether the function is prototyped. For a prototyped
15353 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
15354 according to the architecture's convention for @code{float}. For unprototyped
15355 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
15356 @code{double} and then passed.
15358 Unfortunately, some forms of debug information do not reliably indicate whether
15359 a function is prototyped. If @value{GDBN} calls a function that is not marked
15360 as prototyped, it consults @kbd{set coerce-float-to-double}.
15363 @kindex set coerce-float-to-double
15364 @item set coerce-float-to-double
15365 @itemx set coerce-float-to-double on
15366 Arguments of type @code{float} will be promoted to @code{double} when passed
15367 to an unprototyped function. This is the default setting.
15369 @item set coerce-float-to-double off
15370 Arguments of type @code{float} will be passed directly to unprototyped
15373 @kindex show coerce-float-to-double
15374 @item show coerce-float-to-double
15375 Show the current setting of promoting @code{float} to @code{double}.
15379 @kindex show cp-abi
15380 @value{GDBN} needs to know the ABI used for your program's C@t{++}
15381 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
15382 used to build your application. @value{GDBN} only fully supports
15383 programs with a single C@t{++} ABI; if your program contains code using
15384 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
15385 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
15386 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
15387 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
15388 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
15389 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
15394 Show the C@t{++} ABI currently in use.
15397 With no argument, show the list of supported C@t{++} ABI's.
15399 @item set cp-abi @var{abi}
15400 @itemx set cp-abi auto
15401 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
15404 @node Messages/Warnings
15405 @section Optional warnings and messages
15407 @cindex verbose operation
15408 @cindex optional warnings
15409 By default, @value{GDBN} is silent about its inner workings. If you are
15410 running on a slow machine, you may want to use the @code{set verbose}
15411 command. This makes @value{GDBN} tell you when it does a lengthy
15412 internal operation, so you will not think it has crashed.
15414 Currently, the messages controlled by @code{set verbose} are those
15415 which announce that the symbol table for a source file is being read;
15416 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
15419 @kindex set verbose
15420 @item set verbose on
15421 Enables @value{GDBN} output of certain informational messages.
15423 @item set verbose off
15424 Disables @value{GDBN} output of certain informational messages.
15426 @kindex show verbose
15428 Displays whether @code{set verbose} is on or off.
15431 By default, if @value{GDBN} encounters bugs in the symbol table of an
15432 object file, it is silent; but if you are debugging a compiler, you may
15433 find this information useful (@pxref{Symbol Errors, ,Errors reading
15438 @kindex set complaints
15439 @item set complaints @var{limit}
15440 Permits @value{GDBN} to output @var{limit} complaints about each type of
15441 unusual symbols before becoming silent about the problem. Set
15442 @var{limit} to zero to suppress all complaints; set it to a large number
15443 to prevent complaints from being suppressed.
15445 @kindex show complaints
15446 @item show complaints
15447 Displays how many symbol complaints @value{GDBN} is permitted to produce.
15451 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
15452 lot of stupid questions to confirm certain commands. For example, if
15453 you try to run a program which is already running:
15457 The program being debugged has been started already.
15458 Start it from the beginning? (y or n)
15461 If you are willing to unflinchingly face the consequences of your own
15462 commands, you can disable this ``feature'':
15466 @kindex set confirm
15468 @cindex confirmation
15469 @cindex stupid questions
15470 @item set confirm off
15471 Disables confirmation requests.
15473 @item set confirm on
15474 Enables confirmation requests (the default).
15476 @kindex show confirm
15478 Displays state of confirmation requests.
15482 @node Debugging Output
15483 @section Optional messages about internal happenings
15484 @cindex optional debugging messages
15486 @value{GDBN} has commands that enable optional debugging messages from
15487 various @value{GDBN} subsystems; normally these commands are of
15488 interest to @value{GDBN} maintainers, or when reporting a bug. This
15489 section documents those commands.
15492 @kindex set exec-done-display
15493 @item set exec-done-display
15494 Turns on or off the notification of asynchronous commands'
15495 completion. When on, @value{GDBN} will print a message when an
15496 asynchronous command finishes its execution. The default is off.
15497 @kindex show exec-done-display
15498 @item show exec-done-display
15499 Displays the current setting of asynchronous command completion
15502 @cindex gdbarch debugging info
15503 @cindex architecture debugging info
15504 @item set debug arch
15505 Turns on or off display of gdbarch debugging info. The default is off
15507 @item show debug arch
15508 Displays the current state of displaying gdbarch debugging info.
15509 @item set debug aix-thread
15510 @cindex AIX threads
15511 Display debugging messages about inner workings of the AIX thread
15513 @item show debug aix-thread
15514 Show the current state of AIX thread debugging info display.
15515 @item set debug event
15516 @cindex event debugging info
15517 Turns on or off display of @value{GDBN} event debugging info. The
15519 @item show debug event
15520 Displays the current state of displaying @value{GDBN} event debugging
15522 @item set debug expression
15523 @cindex expression debugging info
15524 Turns on or off display of debugging info about @value{GDBN}
15525 expression parsing. The default is off.
15526 @item show debug expression
15527 Displays the current state of displaying debugging info about
15528 @value{GDBN} expression parsing.
15529 @item set debug frame
15530 @cindex frame debugging info
15531 Turns on or off display of @value{GDBN} frame debugging info. The
15533 @item show debug frame
15534 Displays the current state of displaying @value{GDBN} frame debugging
15536 @item set debug infrun
15537 @cindex inferior debugging info
15538 Turns on or off display of @value{GDBN} debugging info for running the inferior.
15539 The default is off. @file{infrun.c} contains GDB's runtime state machine used
15540 for implementing operations such as single-stepping the inferior.
15541 @item show debug infrun
15542 Displays the current state of @value{GDBN} inferior debugging.
15543 @item set debug lin-lwp
15544 @cindex @sc{gnu}/Linux LWP debug messages
15545 @cindex Linux lightweight processes
15546 Turns on or off debugging messages from the Linux LWP debug support.
15547 @item show debug lin-lwp
15548 Show the current state of Linux LWP debugging messages.
15549 @item set debug observer
15550 @cindex observer debugging info
15551 Turns on or off display of @value{GDBN} observer debugging. This
15552 includes info such as the notification of observable events.
15553 @item show debug observer
15554 Displays the current state of observer debugging.
15555 @item set debug overload
15556 @cindex C@t{++} overload debugging info
15557 Turns on or off display of @value{GDBN} C@t{++} overload debugging
15558 info. This includes info such as ranking of functions, etc. The default
15560 @item show debug overload
15561 Displays the current state of displaying @value{GDBN} C@t{++} overload
15563 @cindex packets, reporting on stdout
15564 @cindex serial connections, debugging
15565 @item set debug remote
15566 Turns on or off display of reports on all packets sent back and forth across
15567 the serial line to the remote machine. The info is printed on the
15568 @value{GDBN} standard output stream. The default is off.
15569 @item show debug remote
15570 Displays the state of display of remote packets.
15571 @item set debug serial
15572 Turns on or off display of @value{GDBN} serial debugging info. The
15574 @item show debug serial
15575 Displays the current state of displaying @value{GDBN} serial debugging
15577 @item set debug solib-frv
15578 @cindex FR-V shared-library debugging
15579 Turns on or off debugging messages for FR-V shared-library code.
15580 @item show debug solib-frv
15581 Display the current state of FR-V shared-library code debugging
15583 @item set debug target
15584 @cindex target debugging info
15585 Turns on or off display of @value{GDBN} target debugging info. This info
15586 includes what is going on at the target level of GDB, as it happens. The
15587 default is 0. Set it to 1 to track events, and to 2 to also track the
15588 value of large memory transfers. Changes to this flag do not take effect
15589 until the next time you connect to a target or use the @code{run} command.
15590 @item show debug target
15591 Displays the current state of displaying @value{GDBN} target debugging
15593 @item set debugvarobj
15594 @cindex variable object debugging info
15595 Turns on or off display of @value{GDBN} variable object debugging
15596 info. The default is off.
15597 @item show debugvarobj
15598 Displays the current state of displaying @value{GDBN} variable object
15603 @chapter Canned Sequences of Commands
15605 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
15606 command lists}), @value{GDBN} provides two ways to store sequences of
15607 commands for execution as a unit: user-defined commands and command
15611 * Define:: User-defined commands
15612 * Hooks:: User-defined command hooks
15613 * Command Files:: Command files
15614 * Output:: Commands for controlled output
15618 @section User-defined commands
15620 @cindex user-defined command
15621 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
15622 which you assign a new name as a command. This is done with the
15623 @code{define} command. User commands may accept up to 10 arguments
15624 separated by whitespace. Arguments are accessed within the user command
15625 via @var{$arg0@dots{}$arg9}. A trivial example:
15629 print $arg0 + $arg1 + $arg2
15633 To execute the command use:
15640 This defines the command @code{adder}, which prints the sum of
15641 its three arguments. Note the arguments are text substitutions, so they may
15642 reference variables, use complex expressions, or even perform inferior
15648 @item define @var{commandname}
15649 Define a command named @var{commandname}. If there is already a command
15650 by that name, you are asked to confirm that you want to redefine it.
15652 The definition of the command is made up of other @value{GDBN} command lines,
15653 which are given following the @code{define} command. The end of these
15654 commands is marked by a line containing @code{end}.
15660 Takes a single argument, which is an expression to evaluate.
15661 It is followed by a series of commands that are executed
15662 only if the expression is true (nonzero).
15663 There can then optionally be a line @code{else}, followed
15664 by a series of commands that are only executed if the expression
15665 was false. The end of the list is marked by a line containing @code{end}.
15669 The syntax is similar to @code{if}: the command takes a single argument,
15670 which is an expression to evaluate, and must be followed by the commands to
15671 execute, one per line, terminated by an @code{end}.
15672 The commands are executed repeatedly as long as the expression
15676 @item document @var{commandname}
15677 Document the user-defined command @var{commandname}, so that it can be
15678 accessed by @code{help}. The command @var{commandname} must already be
15679 defined. This command reads lines of documentation just as @code{define}
15680 reads the lines of the command definition, ending with @code{end}.
15681 After the @code{document} command is finished, @code{help} on command
15682 @var{commandname} displays the documentation you have written.
15684 You may use the @code{document} command again to change the
15685 documentation of a command. Redefining the command with @code{define}
15686 does not change the documentation.
15688 @kindex dont-repeat
15689 @cindex don't repeat command
15691 Used inside a user-defined command, this tells @value{GDBN} that this
15692 command should not be repeated when the user hits @key{RET}
15693 (@pxref{Command Syntax, repeat last command}).
15695 @kindex help user-defined
15696 @item help user-defined
15697 List all user-defined commands, with the first line of the documentation
15702 @itemx show user @var{commandname}
15703 Display the @value{GDBN} commands used to define @var{commandname} (but
15704 not its documentation). If no @var{commandname} is given, display the
15705 definitions for all user-defined commands.
15707 @cindex infinite recusrion in user-defined commands
15708 @kindex show max-user-call-depth
15709 @kindex set max-user-call-depth
15710 @item show max-user-call-depth
15711 @itemx set max-user-call-depth
15712 The value of @code{max-user-call-depth} controls how many recursion
15713 levels are allowed in user-defined commands before GDB suspects an
15714 infinite recursion and aborts the command.
15718 When user-defined commands are executed, the
15719 commands of the definition are not printed. An error in any command
15720 stops execution of the user-defined command.
15722 If used interactively, commands that would ask for confirmation proceed
15723 without asking when used inside a user-defined command. Many @value{GDBN}
15724 commands that normally print messages to say what they are doing omit the
15725 messages when used in a user-defined command.
15728 @section User-defined command hooks
15729 @cindex command hooks
15730 @cindex hooks, for commands
15731 @cindex hooks, pre-command
15734 You may define @dfn{hooks}, which are a special kind of user-defined
15735 command. Whenever you run the command @samp{foo}, if the user-defined
15736 command @samp{hook-foo} exists, it is executed (with no arguments)
15737 before that command.
15739 @cindex hooks, post-command
15741 A hook may also be defined which is run after the command you executed.
15742 Whenever you run the command @samp{foo}, if the user-defined command
15743 @samp{hookpost-foo} exists, it is executed (with no arguments) after
15744 that command. Post-execution hooks may exist simultaneously with
15745 pre-execution hooks, for the same command.
15747 It is valid for a hook to call the command which it hooks. If this
15748 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
15750 @c It would be nice if hookpost could be passed a parameter indicating
15751 @c if the command it hooks executed properly or not. FIXME!
15753 @kindex stop@r{, a pseudo-command}
15754 In addition, a pseudo-command, @samp{stop} exists. Defining
15755 (@samp{hook-stop}) makes the associated commands execute every time
15756 execution stops in your program: before breakpoint commands are run,
15757 displays are printed, or the stack frame is printed.
15759 For example, to ignore @code{SIGALRM} signals while
15760 single-stepping, but treat them normally during normal execution,
15765 handle SIGALRM nopass
15769 handle SIGALRM pass
15772 define hook-continue
15773 handle SIGLARM pass
15777 As a further example, to hook at the begining and end of the @code{echo}
15778 command, and to add extra text to the beginning and end of the message,
15786 define hookpost-echo
15790 (@value{GDBP}) echo Hello World
15791 <<<---Hello World--->>>
15796 You can define a hook for any single-word command in @value{GDBN}, but
15797 not for command aliases; you should define a hook for the basic command
15798 name, e.g. @code{backtrace} rather than @code{bt}.
15799 @c FIXME! So how does Joe User discover whether a command is an alias
15801 If an error occurs during the execution of your hook, execution of
15802 @value{GDBN} commands stops and @value{GDBN} issues a prompt
15803 (before the command that you actually typed had a chance to run).
15805 If you try to define a hook which does not match any known command, you
15806 get a warning from the @code{define} command.
15808 @node Command Files
15809 @section Command files
15811 @cindex command files
15812 A command file for @value{GDBN} is a text file made of lines that are
15813 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
15814 also be included. An empty line in a command file does nothing; it
15815 does not mean to repeat the last command, as it would from the
15818 You can request the execution of a command file with the @code{source}
15823 @item source @var{filename}
15824 Execute the command file @var{filename}.
15827 The lines in a command file are executed sequentially. They are not
15828 printed as they are executed. An error in any command terminates
15829 execution of the command file and control is returned to the console.
15831 Commands that would ask for confirmation if used interactively proceed
15832 without asking when used in a command file. Many @value{GDBN} commands that
15833 normally print messages to say what they are doing omit the messages
15834 when called from command files.
15836 @value{GDBN} also accepts command input from standard input. In this
15837 mode, normal output goes to standard output and error output goes to
15838 standard error. Errors in a command file supplied on standard input do
15839 not terminate execution of the command file---execution continues with
15843 gdb < cmds > log 2>&1
15846 (The syntax above will vary depending on the shell used.) This example
15847 will execute commands from the file @file{cmds}. All output and errors
15848 would be directed to @file{log}.
15851 @section Commands for controlled output
15853 During the execution of a command file or a user-defined command, normal
15854 @value{GDBN} output is suppressed; the only output that appears is what is
15855 explicitly printed by the commands in the definition. This section
15856 describes three commands useful for generating exactly the output you
15861 @item echo @var{text}
15862 @c I do not consider backslash-space a standard C escape sequence
15863 @c because it is not in ANSI.
15864 Print @var{text}. Nonprinting characters can be included in
15865 @var{text} using C escape sequences, such as @samp{\n} to print a
15866 newline. @strong{No newline is printed unless you specify one.}
15867 In addition to the standard C escape sequences, a backslash followed
15868 by a space stands for a space. This is useful for displaying a
15869 string with spaces at the beginning or the end, since leading and
15870 trailing spaces are otherwise trimmed from all arguments.
15871 To print @samp{@w{ }and foo =@w{ }}, use the command
15872 @samp{echo \@w{ }and foo = \@w{ }}.
15874 A backslash at the end of @var{text} can be used, as in C, to continue
15875 the command onto subsequent lines. For example,
15878 echo This is some text\n\
15879 which is continued\n\
15880 onto several lines.\n
15883 produces the same output as
15886 echo This is some text\n
15887 echo which is continued\n
15888 echo onto several lines.\n
15892 @item output @var{expression}
15893 Print the value of @var{expression} and nothing but that value: no
15894 newlines, no @samp{$@var{nn} = }. The value is not entered in the
15895 value history either. @xref{Expressions, ,Expressions}, for more information
15898 @item output/@var{fmt} @var{expression}
15899 Print the value of @var{expression} in format @var{fmt}. You can use
15900 the same formats as for @code{print}. @xref{Output Formats,,Output
15901 formats}, for more information.
15904 @item printf @var{string}, @var{expressions}@dots{}
15905 Print the values of the @var{expressions} under the control of
15906 @var{string}. The @var{expressions} are separated by commas and may be
15907 either numbers or pointers. Their values are printed as specified by
15908 @var{string}, exactly as if your program were to execute the C
15910 @c FIXME: the above implies that at least all ANSI C formats are
15911 @c supported, but it isn't true: %E and %G don't work (or so it seems).
15912 @c Either this is a bug, or the manual should document what formats are
15916 printf (@var{string}, @var{expressions}@dots{});
15919 For example, you can print two values in hex like this:
15922 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
15925 The only backslash-escape sequences that you can use in the format
15926 string are the simple ones that consist of backslash followed by a
15931 @chapter Command Interpreters
15932 @cindex command interpreters
15934 @value{GDBN} supports multiple command interpreters, and some command
15935 infrastructure to allow users or user interface writers to switch
15936 between interpreters or run commands in other interpreters.
15938 @value{GDBN} currently supports two command interpreters, the console
15939 interpreter (sometimes called the command-line interpreter or @sc{cli})
15940 and the machine interface interpreter (or @sc{gdb/mi}). This manual
15941 describes both of these interfaces in great detail.
15943 By default, @value{GDBN} will start with the console interpreter.
15944 However, the user may choose to start @value{GDBN} with another
15945 interpreter by specifying the @option{-i} or @option{--interpreter}
15946 startup options. Defined interpreters include:
15950 @cindex console interpreter
15951 The traditional console or command-line interpreter. This is the most often
15952 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
15953 @value{GDBN} will use this interpreter.
15956 @cindex mi interpreter
15957 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
15958 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
15959 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
15963 @cindex mi2 interpreter
15964 The current @sc{gdb/mi} interface.
15967 @cindex mi1 interpreter
15968 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
15972 @cindex invoke another interpreter
15973 The interpreter being used by @value{GDBN} may not be dynamically
15974 switched at runtime. Although possible, this could lead to a very
15975 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
15976 enters the command "interpreter-set console" in a console view,
15977 @value{GDBN} would switch to using the console interpreter, rendering
15978 the IDE inoperable!
15980 @kindex interpreter-exec
15981 Although you may only choose a single interpreter at startup, you may execute
15982 commands in any interpreter from the current interpreter using the appropriate
15983 command. If you are running the console interpreter, simply use the
15984 @code{interpreter-exec} command:
15987 interpreter-exec mi "-data-list-register-names"
15990 @sc{gdb/mi} has a similar command, although it is only available in versions of
15991 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
15994 @chapter @value{GDBN} Text User Interface
15996 @cindex Text User Interface
15999 * TUI Overview:: TUI overview
16000 * TUI Keys:: TUI key bindings
16001 * TUI Single Key Mode:: TUI single key mode
16002 * TUI Commands:: TUI specific commands
16003 * TUI Configuration:: TUI configuration variables
16006 The @value{GDBN} Text User Interface, TUI in short, is a terminal
16007 interface which uses the @code{curses} library to show the source
16008 file, the assembly output, the program registers and @value{GDBN}
16009 commands in separate text windows.
16011 The TUI is enabled by invoking @value{GDBN} using either
16013 @samp{gdbtui} or @samp{gdb -tui}.
16016 @section TUI overview
16018 The TUI has two display modes that can be switched while
16023 A curses (or TUI) mode in which it displays several text
16024 windows on the terminal.
16027 A standard mode which corresponds to the @value{GDBN} configured without
16031 In the TUI mode, @value{GDBN} can display several text window
16036 This window is the @value{GDBN} command window with the @value{GDBN}
16037 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
16038 managed using readline but through the TUI. The @emph{command}
16039 window is always visible.
16042 The source window shows the source file of the program. The current
16043 line as well as active breakpoints are displayed in this window.
16046 The assembly window shows the disassembly output of the program.
16049 This window shows the processor registers. It detects when
16050 a register is changed and when this is the case, registers that have
16051 changed are highlighted.
16055 The source and assembly windows show the current program position
16056 by highlighting the current line and marking them with the @samp{>} marker.
16057 Breakpoints are also indicated with two markers. A first one
16058 indicates the breakpoint type:
16062 Breakpoint which was hit at least once.
16065 Breakpoint which was never hit.
16068 Hardware breakpoint which was hit at least once.
16071 Hardware breakpoint which was never hit.
16075 The second marker indicates whether the breakpoint is enabled or not:
16079 Breakpoint is enabled.
16082 Breakpoint is disabled.
16086 The source, assembly and register windows are attached to the thread
16087 and the frame position. They are updated when the current thread
16088 changes, when the frame changes or when the program counter changes.
16089 These three windows are arranged by the TUI according to several
16090 layouts. The layout defines which of these three windows are visible.
16091 The following layouts are available:
16101 source and assembly
16104 source and registers
16107 assembly and registers
16111 On top of the command window a status line gives various information
16112 concerning the current process begin debugged. The status line is
16113 updated when the information it shows changes. The following fields
16118 Indicates the current gdb target
16119 (@pxref{Targets, ,Specifying a Debugging Target}).
16122 Gives information about the current process or thread number.
16123 When no process is being debugged, this field is set to @code{No process}.
16126 Gives the current function name for the selected frame.
16127 The name is demangled if demangling is turned on (@pxref{Print Settings}).
16128 When there is no symbol corresponding to the current program counter
16129 the string @code{??} is displayed.
16132 Indicates the current line number for the selected frame.
16133 When the current line number is not known the string @code{??} is displayed.
16136 Indicates the current program counter address.
16141 @section TUI Key Bindings
16142 @cindex TUI key bindings
16144 The TUI installs several key bindings in the readline keymaps
16145 (@pxref{Command Line Editing}).
16146 They allow to leave or enter in the TUI mode or they operate
16147 directly on the TUI layout and windows. The TUI also provides
16148 a @emph{SingleKey} keymap which binds several keys directly to
16149 @value{GDBN} commands. The following key bindings
16150 are installed for both TUI mode and the @value{GDBN} standard mode.
16159 Enter or leave the TUI mode. When the TUI mode is left,
16160 the curses window management is left and @value{GDBN} operates using
16161 its standard mode writing on the terminal directly. When the TUI
16162 mode is entered, the control is given back to the curses windows.
16163 The screen is then refreshed.
16167 Use a TUI layout with only one window. The layout will
16168 either be @samp{source} or @samp{assembly}. When the TUI mode
16169 is not active, it will switch to the TUI mode.
16171 Think of this key binding as the Emacs @kbd{C-x 1} binding.
16175 Use a TUI layout with at least two windows. When the current
16176 layout shows already two windows, a next layout with two windows is used.
16177 When a new layout is chosen, one window will always be common to the
16178 previous layout and the new one.
16180 Think of it as the Emacs @kbd{C-x 2} binding.
16184 Change the active window. The TUI associates several key bindings
16185 (like scrolling and arrow keys) to the active window. This command
16186 gives the focus to the next TUI window.
16188 Think of it as the Emacs @kbd{C-x o} binding.
16192 Use the TUI @emph{SingleKey} keymap that binds single key to gdb commands
16193 (@pxref{TUI Single Key Mode}).
16197 The following key bindings are handled only by the TUI mode:
16202 Scroll the active window one page up.
16206 Scroll the active window one page down.
16210 Scroll the active window one line up.
16214 Scroll the active window one line down.
16218 Scroll the active window one column left.
16222 Scroll the active window one column right.
16226 Refresh the screen.
16230 In the TUI mode, the arrow keys are used by the active window
16231 for scrolling. This means they are available for readline when the
16232 active window is the command window. When the command window
16233 does not have the focus, it is necessary to use other readline
16234 key bindings such as @key{C-p}, @key{C-n}, @key{C-b} and @key{C-f}.
16236 @node TUI Single Key Mode
16237 @section TUI Single Key Mode
16238 @cindex TUI single key mode
16240 The TUI provides a @emph{SingleKey} mode in which it installs a particular
16241 key binding in the readline keymaps to connect single keys to
16245 @kindex c @r{(SingleKey TUI key)}
16249 @kindex d @r{(SingleKey TUI key)}
16253 @kindex f @r{(SingleKey TUI key)}
16257 @kindex n @r{(SingleKey TUI key)}
16261 @kindex q @r{(SingleKey TUI key)}
16263 exit the @emph{SingleKey} mode.
16265 @kindex r @r{(SingleKey TUI key)}
16269 @kindex s @r{(SingleKey TUI key)}
16273 @kindex u @r{(SingleKey TUI key)}
16277 @kindex v @r{(SingleKey TUI key)}
16281 @kindex w @r{(SingleKey TUI key)}
16287 Other keys temporarily switch to the @value{GDBN} command prompt.
16288 The key that was pressed is inserted in the editing buffer so that
16289 it is possible to type most @value{GDBN} commands without interaction
16290 with the TUI @emph{SingleKey} mode. Once the command is entered the TUI
16291 @emph{SingleKey} mode is restored. The only way to permanently leave
16292 this mode is by hitting @key{q} or @samp{@key{C-x} @key{s}}.
16296 @section TUI specific commands
16297 @cindex TUI commands
16299 The TUI has specific commands to control the text windows.
16300 These commands are always available, that is they do not depend on
16301 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
16302 is in the standard mode, using these commands will automatically switch
16308 List and give the size of all displayed windows.
16312 Display the next layout.
16315 Display the previous layout.
16318 Display the source window only.
16321 Display the assembly window only.
16324 Display the source and assembly window.
16327 Display the register window together with the source or assembly window.
16329 @item focus next | prev | src | asm | regs | split
16331 Set the focus to the named window.
16332 This command allows to change the active window so that scrolling keys
16333 can be affected to another window.
16337 Refresh the screen. This is similar to using @key{C-L} key.
16339 @item tui reg float
16341 Show the floating point registers in the register window.
16343 @item tui reg general
16344 Show the general registers in the register window.
16347 Show the next register group. The list of register groups as well as
16348 their order is target specific. The predefined register groups are the
16349 following: @code{general}, @code{float}, @code{system}, @code{vector},
16350 @code{all}, @code{save}, @code{restore}.
16352 @item tui reg system
16353 Show the system registers in the register window.
16357 Update the source window and the current execution point.
16359 @item winheight @var{name} +@var{count}
16360 @itemx winheight @var{name} -@var{count}
16362 Change the height of the window @var{name} by @var{count}
16363 lines. Positive counts increase the height, while negative counts
16367 @kindex tabset @var{nchars}
16368 Set the width of tab stops to be @var{nchars} characters.
16372 @node TUI Configuration
16373 @section TUI configuration variables
16374 @cindex TUI configuration variables
16376 The TUI has several configuration variables that control the
16377 appearance of windows on the terminal.
16380 @item set tui border-kind @var{kind}
16381 @kindex set tui border-kind
16382 Select the border appearance for the source, assembly and register windows.
16383 The possible values are the following:
16386 Use a space character to draw the border.
16389 Use ascii characters + - and | to draw the border.
16392 Use the Alternate Character Set to draw the border. The border is
16393 drawn using character line graphics if the terminal supports them.
16397 @item set tui active-border-mode @var{mode}
16398 @kindex set tui active-border-mode
16399 Select the attributes to display the border of the active window.
16400 The possible values are @code{normal}, @code{standout}, @code{reverse},
16401 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
16403 @item set tui border-mode @var{mode}
16404 @kindex set tui border-mode
16405 Select the attributes to display the border of other windows.
16406 The @var{mode} can be one of the following:
16409 Use normal attributes to display the border.
16415 Use reverse video mode.
16418 Use half bright mode.
16420 @item half-standout
16421 Use half bright and standout mode.
16424 Use extra bright or bold mode.
16426 @item bold-standout
16427 Use extra bright or bold and standout mode.
16434 @chapter Using @value{GDBN} under @sc{gnu} Emacs
16437 @cindex @sc{gnu} Emacs
16438 A special interface allows you to use @sc{gnu} Emacs to view (and
16439 edit) the source files for the program you are debugging with
16442 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
16443 executable file you want to debug as an argument. This command starts
16444 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
16445 created Emacs buffer.
16446 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
16448 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
16453 All ``terminal'' input and output goes through the Emacs buffer.
16456 This applies both to @value{GDBN} commands and their output, and to the input
16457 and output done by the program you are debugging.
16459 This is useful because it means that you can copy the text of previous
16460 commands and input them again; you can even use parts of the output
16463 All the facilities of Emacs' Shell mode are available for interacting
16464 with your program. In particular, you can send signals the usual
16465 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
16470 @value{GDBN} displays source code through Emacs.
16473 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
16474 source file for that frame and puts an arrow (@samp{=>}) at the
16475 left margin of the current line. Emacs uses a separate buffer for
16476 source display, and splits the screen to show both your @value{GDBN} session
16479 Explicit @value{GDBN} @code{list} or search commands still produce output as
16480 usual, but you probably have no reason to use them from Emacs.
16482 If you specify an absolute file name when prompted for the @kbd{M-x
16483 gdb} argument, then Emacs sets your current working directory to where
16484 your program resides. If you only specify the file name, then Emacs
16485 sets your current working directory to to the directory associated
16486 with the previous buffer. In this case, @value{GDBN} may find your
16487 program by searching your environment's @code{PATH} variable, but on
16488 some operating systems it might not find the source. So, although the
16489 @value{GDBN} input and output session proceeds normally, the auxiliary
16490 buffer does not display the current source and line of execution.
16492 The initial working directory of @value{GDBN} is printed on the top
16493 line of the @value{GDBN} I/O buffer and this serves as a default for
16494 the commands that specify files for @value{GDBN} to operate
16495 on. @xref{Files, ,Commands to specify files}.
16497 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
16498 need to call @value{GDBN} by a different name (for example, if you
16499 keep several configurations around, with different names) you can
16500 customize the Emacs variable @code{gud-gdb-command-name} to run the
16503 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
16504 addition to the standard Shell mode commands:
16508 Describe the features of Emacs' @value{GDBN} Mode.
16511 Execute to another source line, like the @value{GDBN} @code{step} command; also
16512 update the display window to show the current file and location.
16515 Execute to next source line in this function, skipping all function
16516 calls, like the @value{GDBN} @code{next} command. Then update the display window
16517 to show the current file and location.
16520 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
16521 display window accordingly.
16524 Execute until exit from the selected stack frame, like the @value{GDBN}
16525 @code{finish} command.
16528 Continue execution of your program, like the @value{GDBN} @code{continue}
16532 Go up the number of frames indicated by the numeric argument
16533 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
16534 like the @value{GDBN} @code{up} command.
16537 Go down the number of frames indicated by the numeric argument, like the
16538 @value{GDBN} @code{down} command.
16541 In any source file, the Emacs command @kbd{C-x SPC} (@code{gud-break})
16542 tells @value{GDBN} to set a breakpoint on the source line point is on.
16544 If you type @kbd{M-x speedbar}, then Emacs displays a separate frame which
16545 shows a backtrace when the @value{GDBN} I/O buffer is current. Move
16546 point to any frame in the stack and type @key{RET} to make it become the
16547 current frame and display the associated source in the source buffer.
16548 Alternatively, click @kbd{Mouse-2} to make the selected frame become the
16551 If you accidentally delete the source-display buffer, an easy way to get
16552 it back is to type the command @code{f} in the @value{GDBN} buffer, to
16553 request a frame display; when you run under Emacs, this recreates
16554 the source buffer if necessary to show you the context of the current
16557 The source files displayed in Emacs are in ordinary Emacs buffers
16558 which are visiting the source files in the usual way. You can edit
16559 the files with these buffers if you wish; but keep in mind that @value{GDBN}
16560 communicates with Emacs in terms of line numbers. If you add or
16561 delete lines from the text, the line numbers that @value{GDBN} knows cease
16562 to correspond properly with the code.
16564 The description given here is for GNU Emacs version 21.3 and a more
16565 detailed description of its interaction with @value{GDBN} is given in
16566 the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu} Emacs Manual}).
16568 @c The following dropped because Epoch is nonstandard. Reactivate
16569 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
16571 @kindex Emacs Epoch environment
16575 Version 18 of @sc{gnu} Emacs has a built-in window system
16576 called the @code{epoch}
16577 environment. Users of this environment can use a new command,
16578 @code{inspect} which performs identically to @code{print} except that
16579 each value is printed in its own window.
16584 @chapter The @sc{gdb/mi} Interface
16586 @unnumberedsec Function and Purpose
16588 @cindex @sc{gdb/mi}, its purpose
16589 @sc{gdb/mi} is a line based machine oriented text interface to
16590 @value{GDBN} and is activated by specifying using the
16591 @option{--interpreter} command line option (@pxref{Mode Options}). It
16592 is specifically intended to support the development of systems which
16593 use the debugger as just one small component of a larger system.
16595 This chapter is a specification of the @sc{gdb/mi} interface. It is written
16596 in the form of a reference manual.
16598 Note that @sc{gdb/mi} is still under construction, so some of the
16599 features described below are incomplete and subject to change.
16601 @unnumberedsec Notation and Terminology
16603 @cindex notational conventions, for @sc{gdb/mi}
16604 This chapter uses the following notation:
16608 @code{|} separates two alternatives.
16611 @code{[ @var{something} ]} indicates that @var{something} is optional:
16612 it may or may not be given.
16615 @code{( @var{group} )*} means that @var{group} inside the parentheses
16616 may repeat zero or more times.
16619 @code{( @var{group} )+} means that @var{group} inside the parentheses
16620 may repeat one or more times.
16623 @code{"@var{string}"} means a literal @var{string}.
16627 @heading Dependencies
16630 @heading Acknowledgments
16632 In alphabetic order: Andrew Cagney, Fernando Nasser, Stan Shebs and
16636 * GDB/MI Command Syntax::
16637 * GDB/MI Compatibility with CLI::
16638 * GDB/MI Output Records::
16639 * GDB/MI Command Description Format::
16640 * GDB/MI Breakpoint Table Commands::
16641 * GDB/MI Data Manipulation::
16642 * GDB/MI Program Control::
16643 * GDB/MI Miscellaneous Commands::
16645 * GDB/MI Kod Commands::
16646 * GDB/MI Memory Overlay Commands::
16647 * GDB/MI Signal Handling Commands::
16649 * GDB/MI Stack Manipulation::
16650 * GDB/MI Symbol Query::
16651 * GDB/MI Target Manipulation::
16652 * GDB/MI Thread Commands::
16653 * GDB/MI Tracepoint Commands::
16654 * GDB/MI Variable Objects::
16657 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16658 @node GDB/MI Command Syntax
16659 @section @sc{gdb/mi} Command Syntax
16662 * GDB/MI Input Syntax::
16663 * GDB/MI Output Syntax::
16664 * GDB/MI Simple Examples::
16667 @node GDB/MI Input Syntax
16668 @subsection @sc{gdb/mi} Input Syntax
16670 @cindex input syntax for @sc{gdb/mi}
16671 @cindex @sc{gdb/mi}, input syntax
16673 @item @var{command} @expansion{}
16674 @code{@var{cli-command} | @var{mi-command}}
16676 @item @var{cli-command} @expansion{}
16677 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
16678 @var{cli-command} is any existing @value{GDBN} CLI command.
16680 @item @var{mi-command} @expansion{}
16681 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
16682 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
16684 @item @var{token} @expansion{}
16685 "any sequence of digits"
16687 @item @var{option} @expansion{}
16688 @code{"-" @var{parameter} [ " " @var{parameter} ]}
16690 @item @var{parameter} @expansion{}
16691 @code{@var{non-blank-sequence} | @var{c-string}}
16693 @item @var{operation} @expansion{}
16694 @emph{any of the operations described in this chapter}
16696 @item @var{non-blank-sequence} @expansion{}
16697 @emph{anything, provided it doesn't contain special characters such as
16698 "-", @var{nl}, """ and of course " "}
16700 @item @var{c-string} @expansion{}
16701 @code{""" @var{seven-bit-iso-c-string-content} """}
16703 @item @var{nl} @expansion{}
16712 The CLI commands are still handled by the @sc{mi} interpreter; their
16713 output is described below.
16716 The @code{@var{token}}, when present, is passed back when the command
16720 Some @sc{mi} commands accept optional arguments as part of the parameter
16721 list. Each option is identified by a leading @samp{-} (dash) and may be
16722 followed by an optional argument parameter. Options occur first in the
16723 parameter list and can be delimited from normal parameters using
16724 @samp{--} (this is useful when some parameters begin with a dash).
16731 We want easy access to the existing CLI syntax (for debugging).
16734 We want it to be easy to spot a @sc{mi} operation.
16737 @node GDB/MI Output Syntax
16738 @subsection @sc{gdb/mi} Output Syntax
16740 @cindex output syntax of @sc{gdb/mi}
16741 @cindex @sc{gdb/mi}, output syntax
16742 The output from @sc{gdb/mi} consists of zero or more out-of-band records
16743 followed, optionally, by a single result record. This result record
16744 is for the most recent command. The sequence of output records is
16745 terminated by @samp{(@value{GDBP})}.
16747 If an input command was prefixed with a @code{@var{token}} then the
16748 corresponding output for that command will also be prefixed by that same
16752 @item @var{output} @expansion{}
16753 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(@value{GDBP})" @var{nl}}
16755 @item @var{result-record} @expansion{}
16756 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
16758 @item @var{out-of-band-record} @expansion{}
16759 @code{@var{async-record} | @var{stream-record}}
16761 @item @var{async-record} @expansion{}
16762 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
16764 @item @var{exec-async-output} @expansion{}
16765 @code{[ @var{token} ] "*" @var{async-output}}
16767 @item @var{status-async-output} @expansion{}
16768 @code{[ @var{token} ] "+" @var{async-output}}
16770 @item @var{notify-async-output} @expansion{}
16771 @code{[ @var{token} ] "=" @var{async-output}}
16773 @item @var{async-output} @expansion{}
16774 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
16776 @item @var{result-class} @expansion{}
16777 @code{"done" | "running" | "connected" | "error" | "exit"}
16779 @item @var{async-class} @expansion{}
16780 @code{"stopped" | @var{others}} (where @var{others} will be added
16781 depending on the needs---this is still in development).
16783 @item @var{result} @expansion{}
16784 @code{ @var{variable} "=" @var{value}}
16786 @item @var{variable} @expansion{}
16787 @code{ @var{string} }
16789 @item @var{value} @expansion{}
16790 @code{ @var{const} | @var{tuple} | @var{list} }
16792 @item @var{const} @expansion{}
16793 @code{@var{c-string}}
16795 @item @var{tuple} @expansion{}
16796 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
16798 @item @var{list} @expansion{}
16799 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
16800 @var{result} ( "," @var{result} )* "]" }
16802 @item @var{stream-record} @expansion{}
16803 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
16805 @item @var{console-stream-output} @expansion{}
16806 @code{"~" @var{c-string}}
16808 @item @var{target-stream-output} @expansion{}
16809 @code{"@@" @var{c-string}}
16811 @item @var{log-stream-output} @expansion{}
16812 @code{"&" @var{c-string}}
16814 @item @var{nl} @expansion{}
16817 @item @var{token} @expansion{}
16818 @emph{any sequence of digits}.
16826 All output sequences end in a single line containing a period.
16829 The @code{@var{token}} is from the corresponding request. If an execution
16830 command is interrupted by the @samp{-exec-interrupt} command, the
16831 @var{token} associated with the @samp{*stopped} message is the one of the
16832 original execution command, not the one of the interrupt command.
16835 @cindex status output in @sc{gdb/mi}
16836 @var{status-async-output} contains on-going status information about the
16837 progress of a slow operation. It can be discarded. All status output is
16838 prefixed by @samp{+}.
16841 @cindex async output in @sc{gdb/mi}
16842 @var{exec-async-output} contains asynchronous state change on the target
16843 (stopped, started, disappeared). All async output is prefixed by
16847 @cindex notify output in @sc{gdb/mi}
16848 @var{notify-async-output} contains supplementary information that the
16849 client should handle (e.g., a new breakpoint information). All notify
16850 output is prefixed by @samp{=}.
16853 @cindex console output in @sc{gdb/mi}
16854 @var{console-stream-output} is output that should be displayed as is in the
16855 console. It is the textual response to a CLI command. All the console
16856 output is prefixed by @samp{~}.
16859 @cindex target output in @sc{gdb/mi}
16860 @var{target-stream-output} is the output produced by the target program.
16861 All the target output is prefixed by @samp{@@}.
16864 @cindex log output in @sc{gdb/mi}
16865 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
16866 instance messages that should be displayed as part of an error log. All
16867 the log output is prefixed by @samp{&}.
16870 @cindex list output in @sc{gdb/mi}
16871 New @sc{gdb/mi} commands should only output @var{lists} containing
16877 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
16878 details about the various output records.
16880 @node GDB/MI Simple Examples
16881 @subsection Simple Examples of @sc{gdb/mi} Interaction
16882 @cindex @sc{gdb/mi}, simple examples
16884 This subsection presents several simple examples of interaction using
16885 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
16886 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
16887 the output received from @sc{gdb/mi}.
16889 @subsubheading Target Stop
16890 @c Ummm... There is no "-stop" command. This assumes async, no?
16891 Here's an example of stopping the inferior process:
16902 <- *stop,reason="stop",address="0x123",source="a.c:123"
16906 @subsubheading Simple CLI Command
16908 Here's an example of a simple CLI command being passed through
16909 @sc{gdb/mi} and on to the CLI.
16919 @subsubheading Command With Side Effects
16922 -> -symbol-file xyz.exe
16923 <- *breakpoint,nr="3",address="0x123",source="a.c:123"
16927 @subsubheading A Bad Command
16929 Here's what happens if you pass a non-existent command:
16933 <- ^error,msg="Undefined MI command: rubbish"
16937 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16938 @node GDB/MI Compatibility with CLI
16939 @section @sc{gdb/mi} Compatibility with CLI
16941 @cindex compatibility, @sc{gdb/mi} and CLI
16942 @cindex @sc{gdb/mi}, compatibility with CLI
16943 To help users familiar with @value{GDBN}'s existing CLI interface, @sc{gdb/mi}
16944 accepts existing CLI commands. As specified by the syntax, such
16945 commands can be directly entered into the @sc{gdb/mi} interface and @value{GDBN} will
16948 This mechanism is provided as an aid to developers of @sc{gdb/mi}
16949 clients and not as a reliable interface into the CLI. Since the command
16950 is being interpreteted in an environment that assumes @sc{gdb/mi}
16951 behaviour, the exact output of such commands is likely to end up being
16952 an un-supported hybrid of @sc{gdb/mi} and CLI output.
16954 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16955 @node GDB/MI Output Records
16956 @section @sc{gdb/mi} Output Records
16959 * GDB/MI Result Records::
16960 * GDB/MI Stream Records::
16961 * GDB/MI Out-of-band Records::
16964 @node GDB/MI Result Records
16965 @subsection @sc{gdb/mi} Result Records
16967 @cindex result records in @sc{gdb/mi}
16968 @cindex @sc{gdb/mi}, result records
16969 In addition to a number of out-of-band notifications, the response to a
16970 @sc{gdb/mi} command includes one of the following result indications:
16974 @item "^done" [ "," @var{results} ]
16975 The synchronous operation was successful, @code{@var{results}} are the return
16980 @c Is this one correct? Should it be an out-of-band notification?
16981 The asynchronous operation was successfully started. The target is
16984 @item "^error" "," @var{c-string}
16986 The operation failed. The @code{@var{c-string}} contains the corresponding
16990 @node GDB/MI Stream Records
16991 @subsection @sc{gdb/mi} Stream Records
16993 @cindex @sc{gdb/mi}, stream records
16994 @cindex stream records in @sc{gdb/mi}
16995 @value{GDBN} internally maintains a number of output streams: the console, the
16996 target, and the log. The output intended for each of these streams is
16997 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
16999 Each stream record begins with a unique @dfn{prefix character} which
17000 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
17001 Syntax}). In addition to the prefix, each stream record contains a
17002 @code{@var{string-output}}. This is either raw text (with an implicit new
17003 line) or a quoted C string (which does not contain an implicit newline).
17006 @item "~" @var{string-output}
17007 The console output stream contains text that should be displayed in the
17008 CLI console window. It contains the textual responses to CLI commands.
17010 @item "@@" @var{string-output}
17011 The target output stream contains any textual output from the running
17014 @item "&" @var{string-output}
17015 The log stream contains debugging messages being produced by @value{GDBN}'s
17019 @node GDB/MI Out-of-band Records
17020 @subsection @sc{gdb/mi} Out-of-band Records
17022 @cindex out-of-band records in @sc{gdb/mi}
17023 @cindex @sc{gdb/mi}, out-of-band records
17024 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
17025 additional changes that have occurred. Those changes can either be a
17026 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
17027 target activity (e.g., target stopped).
17029 The following is a preliminary list of possible out-of-band records.
17030 In particular, the @var{exec-async-output} records.
17033 @item *stopped,reason="@var{reason}"
17036 @var{reason} can be one of the following:
17039 @item breakpoint-hit
17040 A breakpoint was reached.
17041 @item watchpoint-trigger
17042 A watchpoint was triggered.
17043 @item read-watchpoint-trigger
17044 A read watchpoint was triggered.
17045 @item access-watchpoint-trigger
17046 An access watchpoint was triggered.
17047 @item function-finished
17048 An -exec-finish or similar CLI command was accomplished.
17049 @item location-reached
17050 An -exec-until or similar CLI command was accomplished.
17051 @item watchpoint-scope
17052 A watchpoint has gone out of scope.
17053 @item end-stepping-range
17054 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
17055 similar CLI command was accomplished.
17056 @item exited-signalled
17057 The inferior exited because of a signal.
17059 The inferior exited.
17060 @item exited-normally
17061 The inferior exited normally.
17062 @item signal-received
17063 A signal was received by the inferior.
17067 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17068 @node GDB/MI Command Description Format
17069 @section @sc{gdb/mi} Command Description Format
17071 The remaining sections describe blocks of commands. Each block of
17072 commands is laid out in a fashion similar to this section.
17074 Note the the line breaks shown in the examples are here only for
17075 readability. They don't appear in the real output.
17076 Also note that the commands with a non-available example (N.A.@:) are
17077 not yet implemented.
17079 @subheading Motivation
17081 The motivation for this collection of commands.
17083 @subheading Introduction
17085 A brief introduction to this collection of commands as a whole.
17087 @subheading Commands
17089 For each command in the block, the following is described:
17091 @subsubheading Synopsis
17094 -command @var{args}@dots{}
17097 @subsubheading @value{GDBN} Command
17099 The corresponding @value{GDBN} CLI command.
17101 @subsubheading Result
17103 @subsubheading Out-of-band
17105 @subsubheading Notes
17107 @subsubheading Example
17110 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17111 @node GDB/MI Breakpoint Table Commands
17112 @section @sc{gdb/mi} Breakpoint table commands
17114 @cindex breakpoint commands for @sc{gdb/mi}
17115 @cindex @sc{gdb/mi}, breakpoint commands
17116 This section documents @sc{gdb/mi} commands for manipulating
17119 @subheading The @code{-break-after} Command
17120 @findex -break-after
17122 @subsubheading Synopsis
17125 -break-after @var{number} @var{count}
17128 The breakpoint number @var{number} is not in effect until it has been
17129 hit @var{count} times. To see how this is reflected in the output of
17130 the @samp{-break-list} command, see the description of the
17131 @samp{-break-list} command below.
17133 @subsubheading @value{GDBN} Command
17135 The corresponding @value{GDBN} command is @samp{ignore}.
17137 @subsubheading Example
17142 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",line="5"@}
17149 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17150 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17151 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17152 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17153 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17154 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17155 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17156 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17157 addr="0x000100d0",func="main",file="hello.c",line="5",times="0",
17163 @subheading The @code{-break-catch} Command
17164 @findex -break-catch
17166 @subheading The @code{-break-commands} Command
17167 @findex -break-commands
17171 @subheading The @code{-break-condition} Command
17172 @findex -break-condition
17174 @subsubheading Synopsis
17177 -break-condition @var{number} @var{expr}
17180 Breakpoint @var{number} will stop the program only if the condition in
17181 @var{expr} is true. The condition becomes part of the
17182 @samp{-break-list} output (see the description of the @samp{-break-list}
17185 @subsubheading @value{GDBN} Command
17187 The corresponding @value{GDBN} command is @samp{condition}.
17189 @subsubheading Example
17193 -break-condition 1 1
17197 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17198 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17199 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17200 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17201 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17202 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17203 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17204 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17205 addr="0x000100d0",func="main",file="hello.c",line="5",cond="1",
17206 times="0",ignore="3"@}]@}
17210 @subheading The @code{-break-delete} Command
17211 @findex -break-delete
17213 @subsubheading Synopsis
17216 -break-delete ( @var{breakpoint} )+
17219 Delete the breakpoint(s) whose number(s) are specified in the argument
17220 list. This is obviously reflected in the breakpoint list.
17222 @subsubheading @value{GDBN} command
17224 The corresponding @value{GDBN} command is @samp{delete}.
17226 @subsubheading Example
17234 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
17235 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17236 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17237 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17238 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17239 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17240 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17245 @subheading The @code{-break-disable} Command
17246 @findex -break-disable
17248 @subsubheading Synopsis
17251 -break-disable ( @var{breakpoint} )+
17254 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
17255 break list is now set to @samp{n} for the named @var{breakpoint}(s).
17257 @subsubheading @value{GDBN} Command
17259 The corresponding @value{GDBN} command is @samp{disable}.
17261 @subsubheading Example
17269 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17270 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17271 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17272 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17273 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17274 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17275 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17276 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
17277 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
17281 @subheading The @code{-break-enable} Command
17282 @findex -break-enable
17284 @subsubheading Synopsis
17287 -break-enable ( @var{breakpoint} )+
17290 Enable (previously disabled) @var{breakpoint}(s).
17292 @subsubheading @value{GDBN} Command
17294 The corresponding @value{GDBN} command is @samp{enable}.
17296 @subsubheading Example
17304 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17305 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17306 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17307 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17308 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17309 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17310 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17311 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
17312 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
17316 @subheading The @code{-break-info} Command
17317 @findex -break-info
17319 @subsubheading Synopsis
17322 -break-info @var{breakpoint}
17326 Get information about a single breakpoint.
17328 @subsubheading @value{GDBN} command
17330 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
17332 @subsubheading Example
17335 @subheading The @code{-break-insert} Command
17336 @findex -break-insert
17338 @subsubheading Synopsis
17341 -break-insert [ -t ] [ -h ] [ -r ]
17342 [ -c @var{condition} ] [ -i @var{ignore-count} ]
17343 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
17347 If specified, @var{line}, can be one of:
17354 @item filename:linenum
17355 @item filename:function
17359 The possible optional parameters of this command are:
17363 Insert a tempoary breakpoint.
17365 Insert a hardware breakpoint.
17366 @item -c @var{condition}
17367 Make the breakpoint conditional on @var{condition}.
17368 @item -i @var{ignore-count}
17369 Initialize the @var{ignore-count}.
17371 Insert a regular breakpoint in all the functions whose names match the
17372 given regular expression. Other flags are not applicable to regular
17376 @subsubheading Result
17378 The result is in the form:
17381 ^done,bkptno="@var{number}",func="@var{funcname}",
17382 file="@var{filename}",line="@var{lineno}"
17386 where @var{number} is the @value{GDBN} number for this breakpoint, @var{funcname}
17387 is the name of the function where the breakpoint was inserted,
17388 @var{filename} is the name of the source file which contains this
17389 function, and @var{lineno} is the source line number within that file.
17391 Note: this format is open to change.
17392 @c An out-of-band breakpoint instead of part of the result?
17394 @subsubheading @value{GDBN} Command
17396 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
17397 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
17399 @subsubheading Example
17404 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
17406 -break-insert -t foo
17407 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",line="11"@}
17410 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17411 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17412 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17413 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17414 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17415 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17416 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17417 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17418 addr="0x0001072c", func="main",file="recursive2.c",line="4",times="0"@},
17419 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
17420 addr="0x00010774",func="foo",file="recursive2.c",line="11",times="0"@}]@}
17422 -break-insert -r foo.*
17423 ~int foo(int, int);
17424 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c",line="11"@}
17428 @subheading The @code{-break-list} Command
17429 @findex -break-list
17431 @subsubheading Synopsis
17437 Displays the list of inserted breakpoints, showing the following fields:
17441 number of the breakpoint
17443 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
17445 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
17448 is the breakpoint enabled or no: @samp{y} or @samp{n}
17450 memory location at which the breakpoint is set
17452 logical location of the breakpoint, expressed by function name, file
17455 number of times the breakpoint has been hit
17458 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
17459 @code{body} field is an empty list.
17461 @subsubheading @value{GDBN} Command
17463 The corresponding @value{GDBN} command is @samp{info break}.
17465 @subsubheading Example
17470 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17471 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17472 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17473 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17474 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17475 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17476 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17477 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17478 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
17479 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
17480 addr="0x00010114",func="foo",file="hello.c",line="13",times="0"@}]@}
17484 Here's an example of the result when there are no breakpoints:
17489 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
17490 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17491 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17492 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17493 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17494 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17495 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17500 @subheading The @code{-break-watch} Command
17501 @findex -break-watch
17503 @subsubheading Synopsis
17506 -break-watch [ -a | -r ]
17509 Create a watchpoint. With the @samp{-a} option it will create an
17510 @dfn{access} watchpoint, i.e. a watchpoint that triggers either on a
17511 read from or on a write to the memory location. With the @samp{-r}
17512 option, the watchpoint created is a @dfn{read} watchpoint, i.e. it will
17513 trigger only when the memory location is accessed for reading. Without
17514 either of the options, the watchpoint created is a regular watchpoint,
17515 i.e. it will trigger when the memory location is accessed for writing.
17516 @xref{Set Watchpoints, , Setting watchpoints}.
17518 Note that @samp{-break-list} will report a single list of watchpoints and
17519 breakpoints inserted.
17521 @subsubheading @value{GDBN} Command
17523 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
17526 @subsubheading Example
17528 Setting a watchpoint on a variable in the @code{main} function:
17533 ^done,wpt=@{number="2",exp="x"@}
17537 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
17538 value=@{old="-268439212",new="55"@},
17539 frame=@{func="main",args=[],file="recursive2.c",
17540 fullname="/home/foo/bar/devo/myproject/recursive2.c",line="5"@}
17544 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
17545 the program execution twice: first for the variable changing value, then
17546 for the watchpoint going out of scope.
17551 ^done,wpt=@{number="5",exp="C"@}
17555 ^done,reason="watchpoint-trigger",
17556 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
17557 frame=@{func="callee4",args=[],
17558 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
17559 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
17563 ^done,reason="watchpoint-scope",wpnum="5",
17564 frame=@{func="callee3",args=[@{name="strarg",
17565 value="0x11940 \"A string argument.\""@}],
17566 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
17567 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
17571 Listing breakpoints and watchpoints, at different points in the program
17572 execution. Note that once the watchpoint goes out of scope, it is
17578 ^done,wpt=@{number="2",exp="C"@}
17581 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17582 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17583 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17584 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17585 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17586 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17587 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17588 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17589 addr="0x00010734",func="callee4",
17590 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
17591 bkpt=@{number="2",type="watchpoint",disp="keep",
17592 enabled="y",addr="",what="C",times="0"@}]@}
17596 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
17597 value=@{old="-276895068",new="3"@},
17598 frame=@{func="callee4",args=[],
17599 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
17600 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
17603 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17604 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17605 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17606 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17607 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17608 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17609 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17610 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17611 addr="0x00010734",func="callee4",
17612 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
17613 bkpt=@{number="2",type="watchpoint",disp="keep",
17614 enabled="y",addr="",what="C",times="-5"@}]@}
17618 ^done,reason="watchpoint-scope",wpnum="2",
17619 frame=@{func="callee3",args=[@{name="strarg",
17620 value="0x11940 \"A string argument.\""@}],
17621 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
17622 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
17625 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17626 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17627 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17628 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17629 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17630 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17631 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17632 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17633 addr="0x00010734",func="callee4",
17634 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@}]@}
17638 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17639 @node GDB/MI Data Manipulation
17640 @section @sc{gdb/mi} Data Manipulation
17642 @cindex data manipulation, in @sc{gdb/mi}
17643 @cindex @sc{gdb/mi}, data manipulation
17644 This section describes the @sc{gdb/mi} commands that manipulate data:
17645 examine memory and registers, evaluate expressions, etc.
17647 @c REMOVED FROM THE INTERFACE.
17648 @c @subheading -data-assign
17649 @c Change the value of a program variable. Plenty of side effects.
17650 @c @subsubheading GDB command
17652 @c @subsubheading Example
17655 @subheading The @code{-data-disassemble} Command
17656 @findex -data-disassemble
17658 @subsubheading Synopsis
17662 [ -s @var{start-addr} -e @var{end-addr} ]
17663 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
17671 @item @var{start-addr}
17672 is the beginning address (or @code{$pc})
17673 @item @var{end-addr}
17675 @item @var{filename}
17676 is the name of the file to disassemble
17677 @item @var{linenum}
17678 is the line number to disassemble around
17680 is the the number of disassembly lines to be produced. If it is -1,
17681 the whole function will be disassembled, in case no @var{end-addr} is
17682 specified. If @var{end-addr} is specified as a non-zero value, and
17683 @var{lines} is lower than the number of disassembly lines between
17684 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
17685 displayed; if @var{lines} is higher than the number of lines between
17686 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
17689 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
17693 @subsubheading Result
17695 The output for each instruction is composed of four fields:
17704 Note that whatever included in the instruction field, is not manipulated
17705 directely by @sc{gdb/mi}, i.e. it is not possible to adjust its format.
17707 @subsubheading @value{GDBN} Command
17709 There's no direct mapping from this command to the CLI.
17711 @subsubheading Example
17713 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
17717 -data-disassemble -s $pc -e "$pc + 20" -- 0
17720 @{address="0x000107c0",func-name="main",offset="4",
17721 inst="mov 2, %o0"@},
17722 @{address="0x000107c4",func-name="main",offset="8",
17723 inst="sethi %hi(0x11800), %o2"@},
17724 @{address="0x000107c8",func-name="main",offset="12",
17725 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
17726 @{address="0x000107cc",func-name="main",offset="16",
17727 inst="sethi %hi(0x11800), %o2"@},
17728 @{address="0x000107d0",func-name="main",offset="20",
17729 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
17733 Disassemble the whole @code{main} function. Line 32 is part of
17737 -data-disassemble -f basics.c -l 32 -- 0
17739 @{address="0x000107bc",func-name="main",offset="0",
17740 inst="save %sp, -112, %sp"@},
17741 @{address="0x000107c0",func-name="main",offset="4",
17742 inst="mov 2, %o0"@},
17743 @{address="0x000107c4",func-name="main",offset="8",
17744 inst="sethi %hi(0x11800), %o2"@},
17746 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
17747 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
17751 Disassemble 3 instructions from the start of @code{main}:
17755 -data-disassemble -f basics.c -l 32 -n 3 -- 0
17757 @{address="0x000107bc",func-name="main",offset="0",
17758 inst="save %sp, -112, %sp"@},
17759 @{address="0x000107c0",func-name="main",offset="4",
17760 inst="mov 2, %o0"@},
17761 @{address="0x000107c4",func-name="main",offset="8",
17762 inst="sethi %hi(0x11800), %o2"@}]
17766 Disassemble 3 instructions from the start of @code{main} in mixed mode:
17770 -data-disassemble -f basics.c -l 32 -n 3 -- 1
17772 src_and_asm_line=@{line="31",
17773 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
17774 testsuite/gdb.mi/basics.c",line_asm_insn=[
17775 @{address="0x000107bc",func-name="main",offset="0",
17776 inst="save %sp, -112, %sp"@}]@},
17777 src_and_asm_line=@{line="32",
17778 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
17779 testsuite/gdb.mi/basics.c",line_asm_insn=[
17780 @{address="0x000107c0",func-name="main",offset="4",
17781 inst="mov 2, %o0"@},
17782 @{address="0x000107c4",func-name="main",offset="8",
17783 inst="sethi %hi(0x11800), %o2"@}]@}]
17788 @subheading The @code{-data-evaluate-expression} Command
17789 @findex -data-evaluate-expression
17791 @subsubheading Synopsis
17794 -data-evaluate-expression @var{expr}
17797 Evaluate @var{expr} as an expression. The expression could contain an
17798 inferior function call. The function call will execute synchronously.
17799 If the expression contains spaces, it must be enclosed in double quotes.
17801 @subsubheading @value{GDBN} Command
17803 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
17804 @samp{call}. In @code{gdbtk} only, there's a corresponding
17805 @samp{gdb_eval} command.
17807 @subsubheading Example
17809 In the following example, the numbers that precede the commands are the
17810 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
17811 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
17815 211-data-evaluate-expression A
17818 311-data-evaluate-expression &A
17819 311^done,value="0xefffeb7c"
17821 411-data-evaluate-expression A+3
17824 511-data-evaluate-expression "A + 3"
17830 @subheading The @code{-data-list-changed-registers} Command
17831 @findex -data-list-changed-registers
17833 @subsubheading Synopsis
17836 -data-list-changed-registers
17839 Display a list of the registers that have changed.
17841 @subsubheading @value{GDBN} Command
17843 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
17844 has the corresponding command @samp{gdb_changed_register_list}.
17846 @subsubheading Example
17848 On a PPC MBX board:
17856 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
17857 args=[],file="try.c",fullname="/home/foo/bar/devo/myproject/try.c",line="5"@}
17859 -data-list-changed-registers
17860 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
17861 "10","11","13","14","15","16","17","18","19","20","21","22","23",
17862 "24","25","26","27","28","30","31","64","65","66","67","69"]
17867 @subheading The @code{-data-list-register-names} Command
17868 @findex -data-list-register-names
17870 @subsubheading Synopsis
17873 -data-list-register-names [ ( @var{regno} )+ ]
17876 Show a list of register names for the current target. If no arguments
17877 are given, it shows a list of the names of all the registers. If
17878 integer numbers are given as arguments, it will print a list of the
17879 names of the registers corresponding to the arguments. To ensure
17880 consistency between a register name and its number, the output list may
17881 include empty register names.
17883 @subsubheading @value{GDBN} Command
17885 @value{GDBN} does not have a command which corresponds to
17886 @samp{-data-list-register-names}. In @code{gdbtk} there is a
17887 corresponding command @samp{gdb_regnames}.
17889 @subsubheading Example
17891 For the PPC MBX board:
17894 -data-list-register-names
17895 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
17896 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
17897 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
17898 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
17899 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
17900 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
17901 "", "pc","ps","cr","lr","ctr","xer"]
17903 -data-list-register-names 1 2 3
17904 ^done,register-names=["r1","r2","r3"]
17908 @subheading The @code{-data-list-register-values} Command
17909 @findex -data-list-register-values
17911 @subsubheading Synopsis
17914 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
17917 Display the registers' contents. @var{fmt} is the format according to
17918 which the registers' contents are to be returned, followed by an optional
17919 list of numbers specifying the registers to display. A missing list of
17920 numbers indicates that the contents of all the registers must be returned.
17922 Allowed formats for @var{fmt} are:
17939 @subsubheading @value{GDBN} Command
17941 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
17942 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
17944 @subsubheading Example
17946 For a PPC MBX board (note: line breaks are for readability only, they
17947 don't appear in the actual output):
17951 -data-list-register-values r 64 65
17952 ^done,register-values=[@{number="64",value="0xfe00a300"@},
17953 @{number="65",value="0x00029002"@}]
17955 -data-list-register-values x
17956 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
17957 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
17958 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
17959 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
17960 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
17961 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
17962 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
17963 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
17964 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
17965 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
17966 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
17967 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
17968 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
17969 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
17970 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
17971 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
17972 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
17973 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
17974 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
17975 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
17976 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
17977 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
17978 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
17979 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
17980 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
17981 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
17982 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
17983 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
17984 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
17985 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
17986 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
17987 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
17988 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
17989 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
17990 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
17991 @{number="69",value="0x20002b03"@}]
17996 @subheading The @code{-data-read-memory} Command
17997 @findex -data-read-memory
17999 @subsubheading Synopsis
18002 -data-read-memory [ -o @var{byte-offset} ]
18003 @var{address} @var{word-format} @var{word-size}
18004 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
18011 @item @var{address}
18012 An expression specifying the address of the first memory word to be
18013 read. Complex expressions containing embedded white space should be
18014 quoted using the C convention.
18016 @item @var{word-format}
18017 The format to be used to print the memory words. The notation is the
18018 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
18021 @item @var{word-size}
18022 The size of each memory word in bytes.
18024 @item @var{nr-rows}
18025 The number of rows in the output table.
18027 @item @var{nr-cols}
18028 The number of columns in the output table.
18031 If present, indicates that each row should include an @sc{ascii} dump. The
18032 value of @var{aschar} is used as a padding character when a byte is not a
18033 member of the printable @sc{ascii} character set (printable @sc{ascii}
18034 characters are those whose code is between 32 and 126, inclusively).
18036 @item @var{byte-offset}
18037 An offset to add to the @var{address} before fetching memory.
18040 This command displays memory contents as a table of @var{nr-rows} by
18041 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
18042 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
18043 (returned as @samp{total-bytes}). Should less than the requested number
18044 of bytes be returned by the target, the missing words are identified
18045 using @samp{N/A}. The number of bytes read from the target is returned
18046 in @samp{nr-bytes} and the starting address used to read memory in
18049 The address of the next/previous row or page is available in
18050 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
18053 @subsubheading @value{GDBN} Command
18055 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
18056 @samp{gdb_get_mem} memory read command.
18058 @subsubheading Example
18060 Read six bytes of memory starting at @code{bytes+6} but then offset by
18061 @code{-6} bytes. Format as three rows of two columns. One byte per
18062 word. Display each word in hex.
18066 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
18067 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
18068 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
18069 prev-page="0x0000138a",memory=[
18070 @{addr="0x00001390",data=["0x00","0x01"]@},
18071 @{addr="0x00001392",data=["0x02","0x03"]@},
18072 @{addr="0x00001394",data=["0x04","0x05"]@}]
18076 Read two bytes of memory starting at address @code{shorts + 64} and
18077 display as a single word formatted in decimal.
18081 5-data-read-memory shorts+64 d 2 1 1
18082 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
18083 next-row="0x00001512",prev-row="0x0000150e",
18084 next-page="0x00001512",prev-page="0x0000150e",memory=[
18085 @{addr="0x00001510",data=["128"]@}]
18089 Read thirty two bytes of memory starting at @code{bytes+16} and format
18090 as eight rows of four columns. Include a string encoding with @samp{x}
18091 used as the non-printable character.
18095 4-data-read-memory bytes+16 x 1 8 4 x
18096 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
18097 next-row="0x000013c0",prev-row="0x0000139c",
18098 next-page="0x000013c0",prev-page="0x00001380",memory=[
18099 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
18100 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
18101 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
18102 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
18103 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
18104 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
18105 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
18106 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
18110 @subheading The @code{-display-delete} Command
18111 @findex -display-delete
18113 @subsubheading Synopsis
18116 -display-delete @var{number}
18119 Delete the display @var{number}.
18121 @subsubheading @value{GDBN} Command
18123 The corresponding @value{GDBN} command is @samp{delete display}.
18125 @subsubheading Example
18129 @subheading The @code{-display-disable} Command
18130 @findex -display-disable
18132 @subsubheading Synopsis
18135 -display-disable @var{number}
18138 Disable display @var{number}.
18140 @subsubheading @value{GDBN} Command
18142 The corresponding @value{GDBN} command is @samp{disable display}.
18144 @subsubheading Example
18148 @subheading The @code{-display-enable} Command
18149 @findex -display-enable
18151 @subsubheading Synopsis
18154 -display-enable @var{number}
18157 Enable display @var{number}.
18159 @subsubheading @value{GDBN} Command
18161 The corresponding @value{GDBN} command is @samp{enable display}.
18163 @subsubheading Example
18167 @subheading The @code{-display-insert} Command
18168 @findex -display-insert
18170 @subsubheading Synopsis
18173 -display-insert @var{expression}
18176 Display @var{expression} every time the program stops.
18178 @subsubheading @value{GDBN} Command
18180 The corresponding @value{GDBN} command is @samp{display}.
18182 @subsubheading Example
18186 @subheading The @code{-display-list} Command
18187 @findex -display-list
18189 @subsubheading Synopsis
18195 List the displays. Do not show the current values.
18197 @subsubheading @value{GDBN} Command
18199 The corresponding @value{GDBN} command is @samp{info display}.
18201 @subsubheading Example
18205 @subheading The @code{-environment-cd} Command
18206 @findex -environment-cd
18208 @subsubheading Synopsis
18211 -environment-cd @var{pathdir}
18214 Set @value{GDBN}'s working directory.
18216 @subsubheading @value{GDBN} Command
18218 The corresponding @value{GDBN} command is @samp{cd}.
18220 @subsubheading Example
18224 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18230 @subheading The @code{-environment-directory} Command
18231 @findex -environment-directory
18233 @subsubheading Synopsis
18236 -environment-directory [ -r ] [ @var{pathdir} ]+
18239 Add directories @var{pathdir} to beginning of search path for source files.
18240 If the @samp{-r} option is used, the search path is reset to the default
18241 search path. If directories @var{pathdir} are supplied in addition to the
18242 @samp{-r} option, the search path is first reset and then addition
18244 Multiple directories may be specified, separated by blanks. Specifying
18245 multiple directories in a single command
18246 results in the directories added to the beginning of the
18247 search path in the same order they were presented in the command.
18248 If blanks are needed as
18249 part of a directory name, double-quotes should be used around
18250 the name. In the command output, the path will show up separated
18251 by the system directory-separator character. The directory-seperator
18252 character must not be used
18253 in any directory name.
18254 If no directories are specified, the current search path is displayed.
18256 @subsubheading @value{GDBN} Command
18258 The corresponding @value{GDBN} command is @samp{dir}.
18260 @subsubheading Example
18264 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18265 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18267 -environment-directory ""
18268 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18270 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
18271 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
18273 -environment-directory -r
18274 ^done,source-path="$cdir:$cwd"
18279 @subheading The @code{-environment-path} Command
18280 @findex -environment-path
18282 @subsubheading Synopsis
18285 -environment-path [ -r ] [ @var{pathdir} ]+
18288 Add directories @var{pathdir} to beginning of search path for object files.
18289 If the @samp{-r} option is used, the search path is reset to the original
18290 search path that existed at gdb start-up. If directories @var{pathdir} are
18291 supplied in addition to the
18292 @samp{-r} option, the search path is first reset and then addition
18294 Multiple directories may be specified, separated by blanks. Specifying
18295 multiple directories in a single command
18296 results in the directories added to the beginning of the
18297 search path in the same order they were presented in the command.
18298 If blanks are needed as
18299 part of a directory name, double-quotes should be used around
18300 the name. In the command output, the path will show up separated
18301 by the system directory-separator character. The directory-seperator
18302 character must not be used
18303 in any directory name.
18304 If no directories are specified, the current path is displayed.
18307 @subsubheading @value{GDBN} Command
18309 The corresponding @value{GDBN} command is @samp{path}.
18311 @subsubheading Example
18316 ^done,path="/usr/bin"
18318 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
18319 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
18321 -environment-path -r /usr/local/bin
18322 ^done,path="/usr/local/bin:/usr/bin"
18327 @subheading The @code{-environment-pwd} Command
18328 @findex -environment-pwd
18330 @subsubheading Synopsis
18336 Show the current working directory.
18338 @subsubheading @value{GDBN} command
18340 The corresponding @value{GDBN} command is @samp{pwd}.
18342 @subsubheading Example
18347 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
18351 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18352 @node GDB/MI Program Control
18353 @section @sc{gdb/mi} Program control
18355 @subsubheading Program termination
18357 As a result of execution, the inferior program can run to completion, if
18358 it doesn't encounter any breakpoints. In this case the output will
18359 include an exit code, if the program has exited exceptionally.
18361 @subsubheading Examples
18364 Program exited normally:
18372 *stopped,reason="exited-normally"
18377 Program exited exceptionally:
18385 *stopped,reason="exited",exit-code="01"
18389 Another way the program can terminate is if it receives a signal such as
18390 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
18394 *stopped,reason="exited-signalled",signal-name="SIGINT",
18395 signal-meaning="Interrupt"
18399 @subheading The @code{-exec-abort} Command
18400 @findex -exec-abort
18402 @subsubheading Synopsis
18408 Kill the inferior running program.
18410 @subsubheading @value{GDBN} Command
18412 The corresponding @value{GDBN} command is @samp{kill}.
18414 @subsubheading Example
18418 @subheading The @code{-exec-arguments} Command
18419 @findex -exec-arguments
18421 @subsubheading Synopsis
18424 -exec-arguments @var{args}
18427 Set the inferior program arguments, to be used in the next
18430 @subsubheading @value{GDBN} Command
18432 The corresponding @value{GDBN} command is @samp{set args}.
18434 @subsubheading Example
18437 Don't have one around.
18440 @subheading The @code{-exec-continue} Command
18441 @findex -exec-continue
18443 @subsubheading Synopsis
18449 Asynchronous command. Resumes the execution of the inferior program
18450 until a breakpoint is encountered, or until the inferior exits.
18452 @subsubheading @value{GDBN} Command
18454 The corresponding @value{GDBN} corresponding is @samp{continue}.
18456 @subsubheading Example
18463 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
18464 file="hello.c",fullname="/home/foo/bar/devo/myproject/hello.c",line="13"@}
18469 @subheading The @code{-exec-finish} Command
18470 @findex -exec-finish
18472 @subsubheading Synopsis
18478 Asynchronous command. Resumes the execution of the inferior program
18479 until the current function is exited. Displays the results returned by
18482 @subsubheading @value{GDBN} Command
18484 The corresponding @value{GDBN} command is @samp{finish}.
18486 @subsubheading Example
18488 Function returning @code{void}.
18495 *stopped,reason="function-finished",frame=@{func="main",args=[],
18496 file="hello.c",fullname="/home/foo/bar/devo/myproject/hello.c",line="7"@}
18500 Function returning other than @code{void}. The name of the internal
18501 @value{GDBN} variable storing the result is printed, together with the
18508 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
18509 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
18510 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
18511 gdb-result-var="$1",return-value="0"
18516 @subheading The @code{-exec-interrupt} Command
18517 @findex -exec-interrupt
18519 @subsubheading Synopsis
18525 Asynchronous command. Interrupts the background execution of the target.
18526 Note how the token associated with the stop message is the one for the
18527 execution command that has been interrupted. The token for the interrupt
18528 itself only appears in the @samp{^done} output. If the user is trying to
18529 interrupt a non-running program, an error message will be printed.
18531 @subsubheading @value{GDBN} Command
18533 The corresponding @value{GDBN} command is @samp{interrupt}.
18535 @subsubheading Example
18546 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
18547 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
18548 fullname="/home/foo/bar/devo/myproject/try.c",line="13"@}
18553 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
18558 @subheading The @code{-exec-next} Command
18561 @subsubheading Synopsis
18567 Asynchronous command. Resumes execution of the inferior program, stopping
18568 when the beginning of the next source line is reached.
18570 @subsubheading @value{GDBN} Command
18572 The corresponding @value{GDBN} command is @samp{next}.
18574 @subsubheading Example
18580 *stopped,reason="end-stepping-range",line="8",file="hello.c"
18585 @subheading The @code{-exec-next-instruction} Command
18586 @findex -exec-next-instruction
18588 @subsubheading Synopsis
18591 -exec-next-instruction
18594 Asynchronous command. Executes one machine instruction. If the
18595 instruction is a function call continues until the function returns. If
18596 the program stops at an instruction in the middle of a source line, the
18597 address will be printed as well.
18599 @subsubheading @value{GDBN} Command
18601 The corresponding @value{GDBN} command is @samp{nexti}.
18603 @subsubheading Example
18607 -exec-next-instruction
18611 *stopped,reason="end-stepping-range",
18612 addr="0x000100d4",line="5",file="hello.c"
18617 @subheading The @code{-exec-return} Command
18618 @findex -exec-return
18620 @subsubheading Synopsis
18626 Makes current function return immediately. Doesn't execute the inferior.
18627 Displays the new current frame.
18629 @subsubheading @value{GDBN} Command
18631 The corresponding @value{GDBN} command is @samp{return}.
18633 @subsubheading Example
18637 200-break-insert callee4
18638 200^done,bkpt=@{number="1",addr="0x00010734",
18639 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
18644 000*stopped,reason="breakpoint-hit",bkptno="1",
18645 frame=@{func="callee4",args=[],
18646 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18647 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
18653 111^done,frame=@{level="0",func="callee3",
18654 args=[@{name="strarg",
18655 value="0x11940 \"A string argument.\""@}],
18656 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18657 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18662 @subheading The @code{-exec-run} Command
18665 @subsubheading Synopsis
18671 Asynchronous command. Starts execution of the inferior from the
18672 beginning. The inferior executes until either a breakpoint is
18673 encountered or the program exits.
18675 @subsubheading @value{GDBN} Command
18677 The corresponding @value{GDBN} command is @samp{run}.
18679 @subsubheading Example
18684 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
18689 *stopped,reason="breakpoint-hit",bkptno="1",
18690 frame=@{func="main",args=[],file="recursive2.c",
18691 fullname="/home/foo/bar/devo/myproject/recursive2.c",line="4"@}
18696 @subheading The @code{-exec-show-arguments} Command
18697 @findex -exec-show-arguments
18699 @subsubheading Synopsis
18702 -exec-show-arguments
18705 Print the arguments of the program.
18707 @subsubheading @value{GDBN} Command
18709 The corresponding @value{GDBN} command is @samp{show args}.
18711 @subsubheading Example
18714 @c @subheading -exec-signal
18716 @subheading The @code{-exec-step} Command
18719 @subsubheading Synopsis
18725 Asynchronous command. Resumes execution of the inferior program, stopping
18726 when the beginning of the next source line is reached, if the next
18727 source line is not a function call. If it is, stop at the first
18728 instruction of the called function.
18730 @subsubheading @value{GDBN} Command
18732 The corresponding @value{GDBN} command is @samp{step}.
18734 @subsubheading Example
18736 Stepping into a function:
18742 *stopped,reason="end-stepping-range",
18743 frame=@{func="foo",args=[@{name="a",value="10"@},
18744 @{name="b",value="0"@}],file="recursive2.c",
18745 fullname="/home/foo/bar/devo/myproject/recursive2.c",line="11"@}
18755 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
18760 @subheading The @code{-exec-step-instruction} Command
18761 @findex -exec-step-instruction
18763 @subsubheading Synopsis
18766 -exec-step-instruction
18769 Asynchronous command. Resumes the inferior which executes one machine
18770 instruction. The output, once @value{GDBN} has stopped, will vary depending on
18771 whether we have stopped in the middle of a source line or not. In the
18772 former case, the address at which the program stopped will be printed as
18775 @subsubheading @value{GDBN} Command
18777 The corresponding @value{GDBN} command is @samp{stepi}.
18779 @subsubheading Example
18783 -exec-step-instruction
18787 *stopped,reason="end-stepping-range",
18788 frame=@{func="foo",args=[],file="try.c",
18789 fullname="/home/foo/bar/devo/myproject/try.c",line="10"@}
18791 -exec-step-instruction
18795 *stopped,reason="end-stepping-range",
18796 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
18797 fullname="/home/foo/bar/devo/myproject/try.c",line="10"@}
18802 @subheading The @code{-exec-until} Command
18803 @findex -exec-until
18805 @subsubheading Synopsis
18808 -exec-until [ @var{location} ]
18811 Asynchronous command. Executes the inferior until the @var{location}
18812 specified in the argument is reached. If there is no argument, the inferior
18813 executes until a source line greater than the current one is reached.
18814 The reason for stopping in this case will be @samp{location-reached}.
18816 @subsubheading @value{GDBN} Command
18818 The corresponding @value{GDBN} command is @samp{until}.
18820 @subsubheading Example
18824 -exec-until recursive2.c:6
18828 *stopped,reason="location-reached",frame=@{func="main",args=[],
18829 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="6"@}
18834 @subheading -file-clear
18835 Is this going away????
18839 @subheading The @code{-file-exec-and-symbols} Command
18840 @findex -file-exec-and-symbols
18842 @subsubheading Synopsis
18845 -file-exec-and-symbols @var{file}
18848 Specify the executable file to be debugged. This file is the one from
18849 which the symbol table is also read. If no file is specified, the
18850 command clears the executable and symbol information. If breakpoints
18851 are set when using this command with no arguments, @value{GDBN} will produce
18852 error messages. Otherwise, no output is produced, except a completion
18855 @subsubheading @value{GDBN} Command
18857 The corresponding @value{GDBN} command is @samp{file}.
18859 @subsubheading Example
18863 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
18869 @subheading The @code{-file-exec-file} Command
18870 @findex -file-exec-file
18872 @subsubheading Synopsis
18875 -file-exec-file @var{file}
18878 Specify the executable file to be debugged. Unlike
18879 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
18880 from this file. If used without argument, @value{GDBN} clears the information
18881 about the executable file. No output is produced, except a completion
18884 @subsubheading @value{GDBN} Command
18886 The corresponding @value{GDBN} command is @samp{exec-file}.
18888 @subsubheading Example
18892 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
18898 @subheading The @code{-file-list-exec-sections} Command
18899 @findex -file-list-exec-sections
18901 @subsubheading Synopsis
18904 -file-list-exec-sections
18907 List the sections of the current executable file.
18909 @subsubheading @value{GDBN} Command
18911 The @value{GDBN} command @samp{info file} shows, among the rest, the same
18912 information as this command. @code{gdbtk} has a corresponding command
18913 @samp{gdb_load_info}.
18915 @subsubheading Example
18919 @subheading The @code{-file-list-exec-source-file} Command
18920 @findex -file-list-exec-source-file
18922 @subsubheading Synopsis
18925 -file-list-exec-source-file
18928 List the line number, the current source file, and the absolute path
18929 to the current source file for the current executable.
18931 @subsubheading @value{GDBN} Command
18933 There's no @value{GDBN} command which directly corresponds to this one.
18935 @subsubheading Example
18939 123-file-list-exec-source-file
18940 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
18945 @subheading The @code{-file-list-exec-source-files} Command
18946 @findex -file-list-exec-source-files
18948 @subsubheading Synopsis
18951 -file-list-exec-source-files
18954 List the source files for the current executable.
18956 It will always output the filename, but only when GDB can find the absolute
18957 file name of a source file, will it output the fullname.
18959 @subsubheading @value{GDBN} Command
18961 There's no @value{GDBN} command which directly corresponds to this one.
18962 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
18964 @subsubheading Example
18967 -file-list-exec-source-files
18969 @{file=foo.c,fullname=/home/foo.c@},
18970 @{file=/home/bar.c,fullname=/home/bar.c@},
18971 @{file=gdb_could_not_find_fullpath.c@}]
18975 @subheading The @code{-file-list-shared-libraries} Command
18976 @findex -file-list-shared-libraries
18978 @subsubheading Synopsis
18981 -file-list-shared-libraries
18984 List the shared libraries in the program.
18986 @subsubheading @value{GDBN} Command
18988 The corresponding @value{GDBN} command is @samp{info shared}.
18990 @subsubheading Example
18994 @subheading The @code{-file-list-symbol-files} Command
18995 @findex -file-list-symbol-files
18997 @subsubheading Synopsis
19000 -file-list-symbol-files
19005 @subsubheading @value{GDBN} Command
19007 The corresponding @value{GDBN} command is @samp{info file} (part of it).
19009 @subsubheading Example
19013 @subheading The @code{-file-symbol-file} Command
19014 @findex -file-symbol-file
19016 @subsubheading Synopsis
19019 -file-symbol-file @var{file}
19022 Read symbol table info from the specified @var{file} argument. When
19023 used without arguments, clears @value{GDBN}'s symbol table info. No output is
19024 produced, except for a completion notification.
19026 @subsubheading @value{GDBN} Command
19028 The corresponding @value{GDBN} command is @samp{symbol-file}.
19030 @subsubheading Example
19034 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
19039 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19040 @node GDB/MI Miscellaneous Commands
19041 @section Miscellaneous @value{GDBN} commands in @sc{gdb/mi}
19043 @c @subheading -gdb-complete
19045 @subheading The @code{-gdb-exit} Command
19048 @subsubheading Synopsis
19054 Exit @value{GDBN} immediately.
19056 @subsubheading @value{GDBN} Command
19058 Approximately corresponds to @samp{quit}.
19060 @subsubheading Example
19067 @subheading The @code{-gdb-set} Command
19070 @subsubheading Synopsis
19076 Set an internal @value{GDBN} variable.
19077 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
19079 @subsubheading @value{GDBN} Command
19081 The corresponding @value{GDBN} command is @samp{set}.
19083 @subsubheading Example
19093 @subheading The @code{-gdb-show} Command
19096 @subsubheading Synopsis
19102 Show the current value of a @value{GDBN} variable.
19104 @subsubheading @value{GDBN} command
19106 The corresponding @value{GDBN} command is @samp{show}.
19108 @subsubheading Example
19117 @c @subheading -gdb-source
19120 @subheading The @code{-gdb-version} Command
19121 @findex -gdb-version
19123 @subsubheading Synopsis
19129 Show version information for @value{GDBN}. Used mostly in testing.
19131 @subsubheading @value{GDBN} Command
19133 There's no equivalent @value{GDBN} command. @value{GDBN} by default shows this
19134 information when you start an interactive session.
19136 @subsubheading Example
19138 @c This example modifies the actual output from GDB to avoid overfull
19144 ~Copyright 2000 Free Software Foundation, Inc.
19145 ~GDB is free software, covered by the GNU General Public License, and
19146 ~you are welcome to change it and/or distribute copies of it under
19147 ~ certain conditions.
19148 ~Type "show copying" to see the conditions.
19149 ~There is absolutely no warranty for GDB. Type "show warranty" for
19151 ~This GDB was configured as
19152 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
19157 @subheading The @code{-interpreter-exec} Command
19158 @findex -interpreter-exec
19160 @subheading Synopsis
19163 -interpreter-exec @var{interpreter} @var{command}
19166 Execute the specified @var{command} in the given @var{interpreter}.
19168 @subheading @value{GDBN} Command
19170 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
19172 @subheading Example
19176 -interpreter-exec console "break main"
19177 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
19178 &"During symbol reading, bad structure-type format.\n"
19179 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
19185 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19186 @node GDB/MI Kod Commands
19187 @section @sc{gdb/mi} Kod Commands
19189 The Kod commands are not implemented.
19191 @c @subheading -kod-info
19193 @c @subheading -kod-list
19195 @c @subheading -kod-list-object-types
19197 @c @subheading -kod-show
19199 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19200 @node GDB/MI Memory Overlay Commands
19201 @section @sc{gdb/mi} Memory Overlay Commands
19203 The memory overlay commands are not implemented.
19205 @c @subheading -overlay-auto
19207 @c @subheading -overlay-list-mapping-state
19209 @c @subheading -overlay-list-overlays
19211 @c @subheading -overlay-map
19213 @c @subheading -overlay-off
19215 @c @subheading -overlay-on
19217 @c @subheading -overlay-unmap
19219 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19220 @node GDB/MI Signal Handling Commands
19221 @section @sc{gdb/mi} Signal Handling Commands
19223 Signal handling commands are not implemented.
19225 @c @subheading -signal-handle
19227 @c @subheading -signal-list-handle-actions
19229 @c @subheading -signal-list-signal-types
19233 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19234 @node GDB/MI Stack Manipulation
19235 @section @sc{gdb/mi} Stack Manipulation Commands
19238 @subheading The @code{-stack-info-frame} Command
19239 @findex -stack-info-frame
19241 @subsubheading Synopsis
19247 Get info on the selected frame.
19249 @subsubheading @value{GDBN} Command
19251 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
19252 (without arguments).
19254 @subsubheading Example
19259 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
19260 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19261 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
19265 @subheading The @code{-stack-info-depth} Command
19266 @findex -stack-info-depth
19268 @subsubheading Synopsis
19271 -stack-info-depth [ @var{max-depth} ]
19274 Return the depth of the stack. If the integer argument @var{max-depth}
19275 is specified, do not count beyond @var{max-depth} frames.
19277 @subsubheading @value{GDBN} Command
19279 There's no equivalent @value{GDBN} command.
19281 @subsubheading Example
19283 For a stack with frame levels 0 through 11:
19290 -stack-info-depth 4
19293 -stack-info-depth 12
19296 -stack-info-depth 11
19299 -stack-info-depth 13
19304 @subheading The @code{-stack-list-arguments} Command
19305 @findex -stack-list-arguments
19307 @subsubheading Synopsis
19310 -stack-list-arguments @var{show-values}
19311 [ @var{low-frame} @var{high-frame} ]
19314 Display a list of the arguments for the frames between @var{low-frame}
19315 and @var{high-frame} (inclusive). If @var{low-frame} and
19316 @var{high-frame} are not provided, list the arguments for the whole call
19319 The @var{show-values} argument must have a value of 0 or 1. A value of
19320 0 means that only the names of the arguments are listed, a value of 1
19321 means that both names and values of the arguments are printed.
19323 @subsubheading @value{GDBN} Command
19325 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
19326 @samp{gdb_get_args} command which partially overlaps with the
19327 functionality of @samp{-stack-list-arguments}.
19329 @subsubheading Example
19336 frame=@{level="0",addr="0x00010734",func="callee4",
19337 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19338 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
19339 frame=@{level="1",addr="0x0001076c",func="callee3",
19340 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19341 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
19342 frame=@{level="2",addr="0x0001078c",func="callee2",
19343 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19344 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
19345 frame=@{level="3",addr="0x000107b4",func="callee1",
19346 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19347 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
19348 frame=@{level="4",addr="0x000107e0",func="main",
19349 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19350 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
19352 -stack-list-arguments 0
19355 frame=@{level="0",args=[]@},
19356 frame=@{level="1",args=[name="strarg"]@},
19357 frame=@{level="2",args=[name="intarg",name="strarg"]@},
19358 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
19359 frame=@{level="4",args=[]@}]
19361 -stack-list-arguments 1
19364 frame=@{level="0",args=[]@},
19366 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19367 frame=@{level="2",args=[
19368 @{name="intarg",value="2"@},
19369 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19370 @{frame=@{level="3",args=[
19371 @{name="intarg",value="2"@},
19372 @{name="strarg",value="0x11940 \"A string argument.\""@},
19373 @{name="fltarg",value="3.5"@}]@},
19374 frame=@{level="4",args=[]@}]
19376 -stack-list-arguments 0 2 2
19377 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
19379 -stack-list-arguments 1 2 2
19380 ^done,stack-args=[frame=@{level="2",
19381 args=[@{name="intarg",value="2"@},
19382 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
19386 @c @subheading -stack-list-exception-handlers
19389 @subheading The @code{-stack-list-frames} Command
19390 @findex -stack-list-frames
19392 @subsubheading Synopsis
19395 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
19398 List the frames currently on the stack. For each frame it displays the
19403 The frame number, 0 being the topmost frame, i.e. the innermost function.
19405 The @code{$pc} value for that frame.
19409 File name of the source file where the function lives.
19411 Line number corresponding to the @code{$pc}.
19414 If invoked without arguments, this command prints a backtrace for the
19415 whole stack. If given two integer arguments, it shows the frames whose
19416 levels are between the two arguments (inclusive). If the two arguments
19417 are equal, it shows the single frame at the corresponding level.
19419 @subsubheading @value{GDBN} Command
19421 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
19423 @subsubheading Example
19425 Full stack backtrace:
19431 [frame=@{level="0",addr="0x0001076c",func="foo",
19432 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="11"@},
19433 frame=@{level="1",addr="0x000107a4",func="foo",
19434 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19435 frame=@{level="2",addr="0x000107a4",func="foo",
19436 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19437 frame=@{level="3",addr="0x000107a4",func="foo",
19438 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19439 frame=@{level="4",addr="0x000107a4",func="foo",
19440 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19441 frame=@{level="5",addr="0x000107a4",func="foo",
19442 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19443 frame=@{level="6",addr="0x000107a4",func="foo",
19444 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19445 frame=@{level="7",addr="0x000107a4",func="foo",
19446 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19447 frame=@{level="8",addr="0x000107a4",func="foo",
19448 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19449 frame=@{level="9",addr="0x000107a4",func="foo",
19450 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19451 frame=@{level="10",addr="0x000107a4",func="foo",
19452 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19453 frame=@{level="11",addr="0x00010738",func="main",
19454 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="4"@}]
19458 Show frames between @var{low_frame} and @var{high_frame}:
19462 -stack-list-frames 3 5
19464 [frame=@{level="3",addr="0x000107a4",func="foo",
19465 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19466 frame=@{level="4",addr="0x000107a4",func="foo",
19467 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19468 frame=@{level="5",addr="0x000107a4",func="foo",
19469 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@}]
19473 Show a single frame:
19477 -stack-list-frames 3 3
19479 [frame=@{level="3",addr="0x000107a4",func="foo",
19480 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@}]
19485 @subheading The @code{-stack-list-locals} Command
19486 @findex -stack-list-locals
19488 @subsubheading Synopsis
19491 -stack-list-locals @var{print-values}
19494 Display the local variable names for the current frame. With an
19495 argument of 0 or @code{--no-values}, prints only the names of the variables.
19496 With argument of 1 or @code{--all-values}, prints also their values. With
19497 argument of 2 or @code{--simple-values}, prints the name, type and value for
19498 simple data types and the name and type for arrays, structures and
19499 unions. In this last case, the idea is that the user can see the
19500 value of simple data types immediately and he can create variable
19501 objects for other data types if he wishes to explore their values in
19504 @subsubheading @value{GDBN} Command
19506 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
19508 @subsubheading Example
19512 -stack-list-locals 0
19513 ^done,locals=[name="A",name="B",name="C"]
19515 -stack-list-locals --all-values
19516 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
19517 @{name="C",value="@{1, 2, 3@}"@}]
19518 -stack-list-locals --simple-values
19519 ^done,locals=[@{name="A",type="int",value="1"@},
19520 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
19525 @subheading The @code{-stack-select-frame} Command
19526 @findex -stack-select-frame
19528 @subsubheading Synopsis
19531 -stack-select-frame @var{framenum}
19534 Change the current frame. Select a different frame @var{framenum} on
19537 @subsubheading @value{GDBN} Command
19539 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
19540 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
19542 @subsubheading Example
19546 -stack-select-frame 2
19551 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19552 @node GDB/MI Symbol Query
19553 @section @sc{gdb/mi} Symbol Query Commands
19556 @subheading The @code{-symbol-info-address} Command
19557 @findex -symbol-info-address
19559 @subsubheading Synopsis
19562 -symbol-info-address @var{symbol}
19565 Describe where @var{symbol} is stored.
19567 @subsubheading @value{GDBN} Command
19569 The corresponding @value{GDBN} command is @samp{info address}.
19571 @subsubheading Example
19575 @subheading The @code{-symbol-info-file} Command
19576 @findex -symbol-info-file
19578 @subsubheading Synopsis
19584 Show the file for the symbol.
19586 @subsubheading @value{GDBN} Command
19588 There's no equivalent @value{GDBN} command. @code{gdbtk} has
19589 @samp{gdb_find_file}.
19591 @subsubheading Example
19595 @subheading The @code{-symbol-info-function} Command
19596 @findex -symbol-info-function
19598 @subsubheading Synopsis
19601 -symbol-info-function
19604 Show which function the symbol lives in.
19606 @subsubheading @value{GDBN} Command
19608 @samp{gdb_get_function} in @code{gdbtk}.
19610 @subsubheading Example
19614 @subheading The @code{-symbol-info-line} Command
19615 @findex -symbol-info-line
19617 @subsubheading Synopsis
19623 Show the core addresses of the code for a source line.
19625 @subsubheading @value{GDBN} Command
19627 The corresponding @value{GDBN} command is @samp{info line}.
19628 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
19630 @subsubheading Example
19634 @subheading The @code{-symbol-info-symbol} Command
19635 @findex -symbol-info-symbol
19637 @subsubheading Synopsis
19640 -symbol-info-symbol @var{addr}
19643 Describe what symbol is at location @var{addr}.
19645 @subsubheading @value{GDBN} Command
19647 The corresponding @value{GDBN} command is @samp{info symbol}.
19649 @subsubheading Example
19653 @subheading The @code{-symbol-list-functions} Command
19654 @findex -symbol-list-functions
19656 @subsubheading Synopsis
19659 -symbol-list-functions
19662 List the functions in the executable.
19664 @subsubheading @value{GDBN} Command
19666 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
19667 @samp{gdb_search} in @code{gdbtk}.
19669 @subsubheading Example
19673 @subheading The @code{-symbol-list-lines} Command
19674 @findex -symbol-list-lines
19676 @subsubheading Synopsis
19679 -symbol-list-lines @var{filename}
19682 Print the list of lines that contain code and their associated program
19683 addresses for the given source filename. The entries are sorted in
19684 ascending PC order.
19686 @subsubheading @value{GDBN} Command
19688 There is no corresponding @value{GDBN} command.
19690 @subsubheading Example
19693 -symbol-list-lines basics.c
19694 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
19699 @subheading The @code{-symbol-list-types} Command
19700 @findex -symbol-list-types
19702 @subsubheading Synopsis
19708 List all the type names.
19710 @subsubheading @value{GDBN} Command
19712 The corresponding commands are @samp{info types} in @value{GDBN},
19713 @samp{gdb_search} in @code{gdbtk}.
19715 @subsubheading Example
19719 @subheading The @code{-symbol-list-variables} Command
19720 @findex -symbol-list-variables
19722 @subsubheading Synopsis
19725 -symbol-list-variables
19728 List all the global and static variable names.
19730 @subsubheading @value{GDBN} Command
19732 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
19734 @subsubheading Example
19738 @subheading The @code{-symbol-locate} Command
19739 @findex -symbol-locate
19741 @subsubheading Synopsis
19747 @subsubheading @value{GDBN} Command
19749 @samp{gdb_loc} in @code{gdbtk}.
19751 @subsubheading Example
19755 @subheading The @code{-symbol-type} Command
19756 @findex -symbol-type
19758 @subsubheading Synopsis
19761 -symbol-type @var{variable}
19764 Show type of @var{variable}.
19766 @subsubheading @value{GDBN} Command
19768 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
19769 @samp{gdb_obj_variable}.
19771 @subsubheading Example
19775 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19776 @node GDB/MI Target Manipulation
19777 @section @sc{gdb/mi} Target Manipulation Commands
19780 @subheading The @code{-target-attach} Command
19781 @findex -target-attach
19783 @subsubheading Synopsis
19786 -target-attach @var{pid} | @var{file}
19789 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
19791 @subsubheading @value{GDBN} command
19793 The corresponding @value{GDBN} command is @samp{attach}.
19795 @subsubheading Example
19799 @subheading The @code{-target-compare-sections} Command
19800 @findex -target-compare-sections
19802 @subsubheading Synopsis
19805 -target-compare-sections [ @var{section} ]
19808 Compare data of section @var{section} on target to the exec file.
19809 Without the argument, all sections are compared.
19811 @subsubheading @value{GDBN} Command
19813 The @value{GDBN} equivalent is @samp{compare-sections}.
19815 @subsubheading Example
19819 @subheading The @code{-target-detach} Command
19820 @findex -target-detach
19822 @subsubheading Synopsis
19828 Disconnect from the remote target. There's no output.
19830 @subsubheading @value{GDBN} command
19832 The corresponding @value{GDBN} command is @samp{detach}.
19834 @subsubheading Example
19844 @subheading The @code{-target-disconnect} Command
19845 @findex -target-disconnect
19847 @subsubheading Synopsis
19853 Disconnect from the remote target. There's no output.
19855 @subsubheading @value{GDBN} command
19857 The corresponding @value{GDBN} command is @samp{disconnect}.
19859 @subsubheading Example
19869 @subheading The @code{-target-download} Command
19870 @findex -target-download
19872 @subsubheading Synopsis
19878 Loads the executable onto the remote target.
19879 It prints out an update message every half second, which includes the fields:
19883 The name of the section.
19885 The size of what has been sent so far for that section.
19887 The size of the section.
19889 The total size of what was sent so far (the current and the previous sections).
19891 The size of the overall executable to download.
19895 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
19896 @sc{gdb/mi} Output Syntax}).
19898 In addition, it prints the name and size of the sections, as they are
19899 downloaded. These messages include the following fields:
19903 The name of the section.
19905 The size of the section.
19907 The size of the overall executable to download.
19911 At the end, a summary is printed.
19913 @subsubheading @value{GDBN} Command
19915 The corresponding @value{GDBN} command is @samp{load}.
19917 @subsubheading Example
19919 Note: each status message appears on a single line. Here the messages
19920 have been broken down so that they can fit onto a page.
19925 +download,@{section=".text",section-size="6668",total-size="9880"@}
19926 +download,@{section=".text",section-sent="512",section-size="6668",
19927 total-sent="512",total-size="9880"@}
19928 +download,@{section=".text",section-sent="1024",section-size="6668",
19929 total-sent="1024",total-size="9880"@}
19930 +download,@{section=".text",section-sent="1536",section-size="6668",
19931 total-sent="1536",total-size="9880"@}
19932 +download,@{section=".text",section-sent="2048",section-size="6668",
19933 total-sent="2048",total-size="9880"@}
19934 +download,@{section=".text",section-sent="2560",section-size="6668",
19935 total-sent="2560",total-size="9880"@}
19936 +download,@{section=".text",section-sent="3072",section-size="6668",
19937 total-sent="3072",total-size="9880"@}
19938 +download,@{section=".text",section-sent="3584",section-size="6668",
19939 total-sent="3584",total-size="9880"@}
19940 +download,@{section=".text",section-sent="4096",section-size="6668",
19941 total-sent="4096",total-size="9880"@}
19942 +download,@{section=".text",section-sent="4608",section-size="6668",
19943 total-sent="4608",total-size="9880"@}
19944 +download,@{section=".text",section-sent="5120",section-size="6668",
19945 total-sent="5120",total-size="9880"@}
19946 +download,@{section=".text",section-sent="5632",section-size="6668",
19947 total-sent="5632",total-size="9880"@}
19948 +download,@{section=".text",section-sent="6144",section-size="6668",
19949 total-sent="6144",total-size="9880"@}
19950 +download,@{section=".text",section-sent="6656",section-size="6668",
19951 total-sent="6656",total-size="9880"@}
19952 +download,@{section=".init",section-size="28",total-size="9880"@}
19953 +download,@{section=".fini",section-size="28",total-size="9880"@}
19954 +download,@{section=".data",section-size="3156",total-size="9880"@}
19955 +download,@{section=".data",section-sent="512",section-size="3156",
19956 total-sent="7236",total-size="9880"@}
19957 +download,@{section=".data",section-sent="1024",section-size="3156",
19958 total-sent="7748",total-size="9880"@}
19959 +download,@{section=".data",section-sent="1536",section-size="3156",
19960 total-sent="8260",total-size="9880"@}
19961 +download,@{section=".data",section-sent="2048",section-size="3156",
19962 total-sent="8772",total-size="9880"@}
19963 +download,@{section=".data",section-sent="2560",section-size="3156",
19964 total-sent="9284",total-size="9880"@}
19965 +download,@{section=".data",section-sent="3072",section-size="3156",
19966 total-sent="9796",total-size="9880"@}
19967 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
19973 @subheading The @code{-target-exec-status} Command
19974 @findex -target-exec-status
19976 @subsubheading Synopsis
19979 -target-exec-status
19982 Provide information on the state of the target (whether it is running or
19983 not, for instance).
19985 @subsubheading @value{GDBN} Command
19987 There's no equivalent @value{GDBN} command.
19989 @subsubheading Example
19993 @subheading The @code{-target-list-available-targets} Command
19994 @findex -target-list-available-targets
19996 @subsubheading Synopsis
19999 -target-list-available-targets
20002 List the possible targets to connect to.
20004 @subsubheading @value{GDBN} Command
20006 The corresponding @value{GDBN} command is @samp{help target}.
20008 @subsubheading Example
20012 @subheading The @code{-target-list-current-targets} Command
20013 @findex -target-list-current-targets
20015 @subsubheading Synopsis
20018 -target-list-current-targets
20021 Describe the current target.
20023 @subsubheading @value{GDBN} Command
20025 The corresponding information is printed by @samp{info file} (among
20028 @subsubheading Example
20032 @subheading The @code{-target-list-parameters} Command
20033 @findex -target-list-parameters
20035 @subsubheading Synopsis
20038 -target-list-parameters
20043 @subsubheading @value{GDBN} Command
20047 @subsubheading Example
20051 @subheading The @code{-target-select} Command
20052 @findex -target-select
20054 @subsubheading Synopsis
20057 -target-select @var{type} @var{parameters @dots{}}
20060 Connect @value{GDBN} to the remote target. This command takes two args:
20064 The type of target, for instance @samp{async}, @samp{remote}, etc.
20065 @item @var{parameters}
20066 Device names, host names and the like. @xref{Target Commands, ,
20067 Commands for managing targets}, for more details.
20070 The output is a connection notification, followed by the address at
20071 which the target program is, in the following form:
20074 ^connected,addr="@var{address}",func="@var{function name}",
20075 args=[@var{arg list}]
20078 @subsubheading @value{GDBN} Command
20080 The corresponding @value{GDBN} command is @samp{target}.
20082 @subsubheading Example
20086 -target-select async /dev/ttya
20087 ^connected,addr="0xfe00a300",func="??",args=[]
20091 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20092 @node GDB/MI Thread Commands
20093 @section @sc{gdb/mi} Thread Commands
20096 @subheading The @code{-thread-info} Command
20097 @findex -thread-info
20099 @subsubheading Synopsis
20105 @subsubheading @value{GDBN} command
20109 @subsubheading Example
20113 @subheading The @code{-thread-list-all-threads} Command
20114 @findex -thread-list-all-threads
20116 @subsubheading Synopsis
20119 -thread-list-all-threads
20122 @subsubheading @value{GDBN} Command
20124 The equivalent @value{GDBN} command is @samp{info threads}.
20126 @subsubheading Example
20130 @subheading The @code{-thread-list-ids} Command
20131 @findex -thread-list-ids
20133 @subsubheading Synopsis
20139 Produces a list of the currently known @value{GDBN} thread ids. At the
20140 end of the list it also prints the total number of such threads.
20142 @subsubheading @value{GDBN} Command
20144 Part of @samp{info threads} supplies the same information.
20146 @subsubheading Example
20148 No threads present, besides the main process:
20153 ^done,thread-ids=@{@},number-of-threads="0"
20163 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
20164 number-of-threads="3"
20169 @subheading The @code{-thread-select} Command
20170 @findex -thread-select
20172 @subsubheading Synopsis
20175 -thread-select @var{threadnum}
20178 Make @var{threadnum} the current thread. It prints the number of the new
20179 current thread, and the topmost frame for that thread.
20181 @subsubheading @value{GDBN} Command
20183 The corresponding @value{GDBN} command is @samp{thread}.
20185 @subsubheading Example
20192 *stopped,reason="end-stepping-range",thread-id="2",line="187",
20193 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
20197 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
20198 number-of-threads="3"
20201 ^done,new-thread-id="3",
20202 frame=@{level="0",func="vprintf",
20203 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
20204 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
20208 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20209 @node GDB/MI Tracepoint Commands
20210 @section @sc{gdb/mi} Tracepoint Commands
20212 The tracepoint commands are not yet implemented.
20214 @c @subheading -trace-actions
20216 @c @subheading -trace-delete
20218 @c @subheading -trace-disable
20220 @c @subheading -trace-dump
20222 @c @subheading -trace-enable
20224 @c @subheading -trace-exists
20226 @c @subheading -trace-find
20228 @c @subheading -trace-frame-number
20230 @c @subheading -trace-info
20232 @c @subheading -trace-insert
20234 @c @subheading -trace-list
20236 @c @subheading -trace-pass-count
20238 @c @subheading -trace-save
20240 @c @subheading -trace-start
20242 @c @subheading -trace-stop
20245 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20246 @node GDB/MI Variable Objects
20247 @section @sc{gdb/mi} Variable Objects
20250 @subheading Motivation for Variable Objects in @sc{gdb/mi}
20252 For the implementation of a variable debugger window (locals, watched
20253 expressions, etc.), we are proposing the adaptation of the existing code
20254 used by @code{Insight}.
20256 The two main reasons for that are:
20260 It has been proven in practice (it is already on its second generation).
20263 It will shorten development time (needless to say how important it is
20267 The original interface was designed to be used by Tcl code, so it was
20268 slightly changed so it could be used through @sc{gdb/mi}. This section
20269 describes the @sc{gdb/mi} operations that will be available and gives some
20270 hints about their use.
20272 @emph{Note}: In addition to the set of operations described here, we
20273 expect the @sc{gui} implementation of a variable window to require, at
20274 least, the following operations:
20277 @item @code{-gdb-show} @code{output-radix}
20278 @item @code{-stack-list-arguments}
20279 @item @code{-stack-list-locals}
20280 @item @code{-stack-select-frame}
20283 @subheading Introduction to Variable Objects in @sc{gdb/mi}
20285 @cindex variable objects in @sc{gdb/mi}
20286 The basic idea behind variable objects is the creation of a named object
20287 to represent a variable, an expression, a memory location or even a CPU
20288 register. For each object created, a set of operations is available for
20289 examining or changing its properties.
20291 Furthermore, complex data types, such as C structures, are represented
20292 in a tree format. For instance, the @code{struct} type variable is the
20293 root and the children will represent the struct members. If a child
20294 is itself of a complex type, it will also have children of its own.
20295 Appropriate language differences are handled for C, C@t{++} and Java.
20297 When returning the actual values of the objects, this facility allows
20298 for the individual selection of the display format used in the result
20299 creation. It can be chosen among: binary, decimal, hexadecimal, octal
20300 and natural. Natural refers to a default format automatically
20301 chosen based on the variable type (like decimal for an @code{int}, hex
20302 for pointers, etc.).
20304 The following is the complete set of @sc{gdb/mi} operations defined to
20305 access this functionality:
20307 @multitable @columnfractions .4 .6
20308 @item @strong{Operation}
20309 @tab @strong{Description}
20311 @item @code{-var-create}
20312 @tab create a variable object
20313 @item @code{-var-delete}
20314 @tab delete the variable object and its children
20315 @item @code{-var-set-format}
20316 @tab set the display format of this variable
20317 @item @code{-var-show-format}
20318 @tab show the display format of this variable
20319 @item @code{-var-info-num-children}
20320 @tab tells how many children this object has
20321 @item @code{-var-list-children}
20322 @tab return a list of the object's children
20323 @item @code{-var-info-type}
20324 @tab show the type of this variable object
20325 @item @code{-var-info-expression}
20326 @tab print what this variable object represents
20327 @item @code{-var-show-attributes}
20328 @tab is this variable editable? does it exist here?
20329 @item @code{-var-evaluate-expression}
20330 @tab get the value of this variable
20331 @item @code{-var-assign}
20332 @tab set the value of this variable
20333 @item @code{-var-update}
20334 @tab update the variable and its children
20337 In the next subsection we describe each operation in detail and suggest
20338 how it can be used.
20340 @subheading Description And Use of Operations on Variable Objects
20342 @subheading The @code{-var-create} Command
20343 @findex -var-create
20345 @subsubheading Synopsis
20348 -var-create @{@var{name} | "-"@}
20349 @{@var{frame-addr} | "*"@} @var{expression}
20352 This operation creates a variable object, which allows the monitoring of
20353 a variable, the result of an expression, a memory cell or a CPU
20356 The @var{name} parameter is the string by which the object can be
20357 referenced. It must be unique. If @samp{-} is specified, the varobj
20358 system will generate a string ``varNNNNNN'' automatically. It will be
20359 unique provided that one does not specify @var{name} on that format.
20360 The command fails if a duplicate name is found.
20362 The frame under which the expression should be evaluated can be
20363 specified by @var{frame-addr}. A @samp{*} indicates that the current
20364 frame should be used.
20366 @var{expression} is any expression valid on the current language set (must not
20367 begin with a @samp{*}), or one of the following:
20371 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
20374 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
20377 @samp{$@var{regname}} --- a CPU register name
20380 @subsubheading Result
20382 This operation returns the name, number of children and the type of the
20383 object created. Type is returned as a string as the ones generated by
20384 the @value{GDBN} CLI:
20387 name="@var{name}",numchild="N",type="@var{type}"
20391 @subheading The @code{-var-delete} Command
20392 @findex -var-delete
20394 @subsubheading Synopsis
20397 -var-delete @var{name}
20400 Deletes a previously created variable object and all of its children.
20402 Returns an error if the object @var{name} is not found.
20405 @subheading The @code{-var-set-format} Command
20406 @findex -var-set-format
20408 @subsubheading Synopsis
20411 -var-set-format @var{name} @var{format-spec}
20414 Sets the output format for the value of the object @var{name} to be
20417 The syntax for the @var{format-spec} is as follows:
20420 @var{format-spec} @expansion{}
20421 @{binary | decimal | hexadecimal | octal | natural@}
20425 @subheading The @code{-var-show-format} Command
20426 @findex -var-show-format
20428 @subsubheading Synopsis
20431 -var-show-format @var{name}
20434 Returns the format used to display the value of the object @var{name}.
20437 @var{format} @expansion{}
20442 @subheading The @code{-var-info-num-children} Command
20443 @findex -var-info-num-children
20445 @subsubheading Synopsis
20448 -var-info-num-children @var{name}
20451 Returns the number of children of a variable object @var{name}:
20458 @subheading The @code{-var-list-children} Command
20459 @findex -var-list-children
20461 @subsubheading Synopsis
20464 -var-list-children [@var{print-values}] @var{name}
20467 Returns a list of the children of the specified variable object. With
20468 just the variable object name as an argument or with an optional
20469 preceding argument of 0 or @code{--no-values}, prints only the names of the
20470 variables. With an optional preceding argument of 1 or @code{--all-values},
20471 also prints their values.
20473 @subsubheading Example
20477 -var-list-children n
20478 numchild=@var{n},children=[@{name=@var{name},
20479 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
20481 -var-list-children --all-values n
20482 numchild=@var{n},children=[@{name=@var{name},
20483 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
20487 @subheading The @code{-var-info-type} Command
20488 @findex -var-info-type
20490 @subsubheading Synopsis
20493 -var-info-type @var{name}
20496 Returns the type of the specified variable @var{name}. The type is
20497 returned as a string in the same format as it is output by the
20501 type=@var{typename}
20505 @subheading The @code{-var-info-expression} Command
20506 @findex -var-info-expression
20508 @subsubheading Synopsis
20511 -var-info-expression @var{name}
20514 Returns what is represented by the variable object @var{name}:
20517 lang=@var{lang-spec},exp=@var{expression}
20521 where @var{lang-spec} is @code{@{"C" | "C++" | "Java"@}}.
20523 @subheading The @code{-var-show-attributes} Command
20524 @findex -var-show-attributes
20526 @subsubheading Synopsis
20529 -var-show-attributes @var{name}
20532 List attributes of the specified variable object @var{name}:
20535 status=@var{attr} [ ( ,@var{attr} )* ]
20539 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
20541 @subheading The @code{-var-evaluate-expression} Command
20542 @findex -var-evaluate-expression
20544 @subsubheading Synopsis
20547 -var-evaluate-expression @var{name}
20550 Evaluates the expression that is represented by the specified variable
20551 object and returns its value as a string in the current format specified
20558 Note that one must invoke @code{-var-list-children} for a variable
20559 before the value of a child variable can be evaluated.
20561 @subheading The @code{-var-assign} Command
20562 @findex -var-assign
20564 @subsubheading Synopsis
20567 -var-assign @var{name} @var{expression}
20570 Assigns the value of @var{expression} to the variable object specified
20571 by @var{name}. The object must be @samp{editable}. If the variable's
20572 value is altered by the assign, the variable will show up in any
20573 subsequent @code{-var-update} list.
20575 @subsubheading Example
20583 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
20587 @subheading The @code{-var-update} Command
20588 @findex -var-update
20590 @subsubheading Synopsis
20593 -var-update @{@var{name} | "*"@}
20596 Update the value of the variable object @var{name} by evaluating its
20597 expression after fetching all the new values from memory or registers.
20598 A @samp{*} causes all existing variable objects to be updated.
20602 @chapter @value{GDBN} Annotations
20604 This chapter describes annotations in @value{GDBN}. Annotations were
20605 designed to interface @value{GDBN} to graphical user interfaces or other
20606 similar programs which want to interact with @value{GDBN} at a
20607 relatively high level.
20609 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
20613 This is Edition @value{EDITION}, @value{DATE}.
20617 * Annotations Overview:: What annotations are; the general syntax.
20618 * Prompting:: Annotations marking @value{GDBN}'s need for input.
20619 * Errors:: Annotations for error messages.
20620 * Invalidation:: Some annotations describe things now invalid.
20621 * Annotations for Running::
20622 Whether the program is running, how it stopped, etc.
20623 * Source Annotations:: Annotations describing source code.
20626 @node Annotations Overview
20627 @section What is an Annotation?
20628 @cindex annotations
20630 Annotations start with a newline character, two @samp{control-z}
20631 characters, and the name of the annotation. If there is no additional
20632 information associated with this annotation, the name of the annotation
20633 is followed immediately by a newline. If there is additional
20634 information, the name of the annotation is followed by a space, the
20635 additional information, and a newline. The additional information
20636 cannot contain newline characters.
20638 Any output not beginning with a newline and two @samp{control-z}
20639 characters denotes literal output from @value{GDBN}. Currently there is
20640 no need for @value{GDBN} to output a newline followed by two
20641 @samp{control-z} characters, but if there was such a need, the
20642 annotations could be extended with an @samp{escape} annotation which
20643 means those three characters as output.
20645 The annotation @var{level}, which is specified using the
20646 @option{--annotate} command line option (@pxref{Mode Options}), controls
20647 how much information @value{GDBN} prints together with its prompt,
20648 values of expressions, source lines, and other types of output. Level 0
20649 is for no anntations, level 1 is for use when @value{GDBN} is run as a
20650 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
20651 for programs that control @value{GDBN}, and level 2 annotations have
20652 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
20653 Interface, annotate, GDB's Obsolete Annotations}).
20656 @kindex set annotate
20657 @item set annotate @var{level}
20658 The @value{GDBN} command @code{set annotate} sets the level of
20659 annotations to the specified @var{level}.
20661 @item show annotate
20662 @kindex show annotate
20663 Show the current annotation level.
20666 This chapter describes level 3 annotations.
20668 A simple example of starting up @value{GDBN} with annotations is:
20671 $ @kbd{gdb --annotate=3}
20673 Copyright 2003 Free Software Foundation, Inc.
20674 GDB is free software, covered by the GNU General Public License,
20675 and you are welcome to change it and/or distribute copies of it
20676 under certain conditions.
20677 Type "show copying" to see the conditions.
20678 There is absolutely no warranty for GDB. Type "show warranty"
20680 This GDB was configured as "i386-pc-linux-gnu"
20691 Here @samp{quit} is input to @value{GDBN}; the rest is output from
20692 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
20693 denotes a @samp{control-z} character) are annotations; the rest is
20694 output from @value{GDBN}.
20697 @section Annotation for @value{GDBN} Input
20699 @cindex annotations for prompts
20700 When @value{GDBN} prompts for input, it annotates this fact so it is possible
20701 to know when to send output, when the output from a given command is
20704 Different kinds of input each have a different @dfn{input type}. Each
20705 input type has three annotations: a @code{pre-} annotation, which
20706 denotes the beginning of any prompt which is being output, a plain
20707 annotation, which denotes the end of the prompt, and then a @code{post-}
20708 annotation which denotes the end of any echo which may (or may not) be
20709 associated with the input. For example, the @code{prompt} input type
20710 features the following annotations:
20718 The input types are
20723 @findex post-prompt
20725 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
20727 @findex pre-commands
20729 @findex post-commands
20731 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
20732 command. The annotations are repeated for each command which is input.
20734 @findex pre-overload-choice
20735 @findex overload-choice
20736 @findex post-overload-choice
20737 @item overload-choice
20738 When @value{GDBN} wants the user to select between various overloaded functions.
20744 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
20746 @findex pre-prompt-for-continue
20747 @findex prompt-for-continue
20748 @findex post-prompt-for-continue
20749 @item prompt-for-continue
20750 When @value{GDBN} is asking the user to press return to continue. Note: Don't
20751 expect this to work well; instead use @code{set height 0} to disable
20752 prompting. This is because the counting of lines is buggy in the
20753 presence of annotations.
20758 @cindex annotations for errors, warnings and interrupts
20765 This annotation occurs right before @value{GDBN} responds to an interrupt.
20772 This annotation occurs right before @value{GDBN} responds to an error.
20774 Quit and error annotations indicate that any annotations which @value{GDBN} was
20775 in the middle of may end abruptly. For example, if a
20776 @code{value-history-begin} annotation is followed by a @code{error}, one
20777 cannot expect to receive the matching @code{value-history-end}. One
20778 cannot expect not to receive it either, however; an error annotation
20779 does not necessarily mean that @value{GDBN} is immediately returning all the way
20782 @findex error-begin
20783 A quit or error annotation may be preceded by
20789 Any output between that and the quit or error annotation is the error
20792 Warning messages are not yet annotated.
20793 @c If we want to change that, need to fix warning(), type_error(),
20794 @c range_error(), and possibly other places.
20797 @section Invalidation Notices
20799 @cindex annotations for invalidation messages
20800 The following annotations say that certain pieces of state may have
20804 @findex frames-invalid
20805 @item ^Z^Zframes-invalid
20807 The frames (for example, output from the @code{backtrace} command) may
20810 @findex breakpoints-invalid
20811 @item ^Z^Zbreakpoints-invalid
20813 The breakpoints may have changed. For example, the user just added or
20814 deleted a breakpoint.
20817 @node Annotations for Running
20818 @section Running the Program
20819 @cindex annotations for running programs
20823 When the program starts executing due to a @value{GDBN} command such as
20824 @code{step} or @code{continue},
20830 is output. When the program stops,
20836 is output. Before the @code{stopped} annotation, a variety of
20837 annotations describe how the program stopped.
20841 @item ^Z^Zexited @var{exit-status}
20842 The program exited, and @var{exit-status} is the exit status (zero for
20843 successful exit, otherwise nonzero).
20846 @findex signal-name
20847 @findex signal-name-end
20848 @findex signal-string
20849 @findex signal-string-end
20850 @item ^Z^Zsignalled
20851 The program exited with a signal. After the @code{^Z^Zsignalled}, the
20852 annotation continues:
20858 ^Z^Zsignal-name-end
20862 ^Z^Zsignal-string-end
20867 where @var{name} is the name of the signal, such as @code{SIGILL} or
20868 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
20869 as @code{Illegal Instruction} or @code{Segmentation fault}.
20870 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
20871 user's benefit and have no particular format.
20875 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
20876 just saying that the program received the signal, not that it was
20877 terminated with it.
20880 @item ^Z^Zbreakpoint @var{number}
20881 The program hit breakpoint number @var{number}.
20884 @item ^Z^Zwatchpoint @var{number}
20885 The program hit watchpoint number @var{number}.
20888 @node Source Annotations
20889 @section Displaying Source
20890 @cindex annotations for source display
20893 The following annotation is used instead of displaying source code:
20896 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
20899 where @var{filename} is an absolute file name indicating which source
20900 file, @var{line} is the line number within that file (where 1 is the
20901 first line in the file), @var{character} is the character position
20902 within the file (where 0 is the first character in the file) (for most
20903 debug formats this will necessarily point to the beginning of a line),
20904 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
20905 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
20906 @var{addr} is the address in the target program associated with the
20907 source which is being displayed. @var{addr} is in the form @samp{0x}
20908 followed by one or more lowercase hex digits (note that this does not
20909 depend on the language).
20912 @chapter Reporting Bugs in @value{GDBN}
20913 @cindex bugs in @value{GDBN}
20914 @cindex reporting bugs in @value{GDBN}
20916 Your bug reports play an essential role in making @value{GDBN} reliable.
20918 Reporting a bug may help you by bringing a solution to your problem, or it
20919 may not. But in any case the principal function of a bug report is to help
20920 the entire community by making the next version of @value{GDBN} work better. Bug
20921 reports are your contribution to the maintenance of @value{GDBN}.
20923 In order for a bug report to serve its purpose, you must include the
20924 information that enables us to fix the bug.
20927 * Bug Criteria:: Have you found a bug?
20928 * Bug Reporting:: How to report bugs
20932 @section Have you found a bug?
20933 @cindex bug criteria
20935 If you are not sure whether you have found a bug, here are some guidelines:
20938 @cindex fatal signal
20939 @cindex debugger crash
20940 @cindex crash of debugger
20942 If the debugger gets a fatal signal, for any input whatever, that is a
20943 @value{GDBN} bug. Reliable debuggers never crash.
20945 @cindex error on valid input
20947 If @value{GDBN} produces an error message for valid input, that is a
20948 bug. (Note that if you're cross debugging, the problem may also be
20949 somewhere in the connection to the target.)
20951 @cindex invalid input
20953 If @value{GDBN} does not produce an error message for invalid input,
20954 that is a bug. However, you should note that your idea of
20955 ``invalid input'' might be our idea of ``an extension'' or ``support
20956 for traditional practice''.
20959 If you are an experienced user of debugging tools, your suggestions
20960 for improvement of @value{GDBN} are welcome in any case.
20963 @node Bug Reporting
20964 @section How to report bugs
20965 @cindex bug reports
20966 @cindex @value{GDBN} bugs, reporting
20968 A number of companies and individuals offer support for @sc{gnu} products.
20969 If you obtained @value{GDBN} from a support organization, we recommend you
20970 contact that organization first.
20972 You can find contact information for many support companies and
20973 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
20975 @c should add a web page ref...
20977 In any event, we also recommend that you submit bug reports for
20978 @value{GDBN}. The prefered method is to submit them directly using
20979 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
20980 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
20983 @strong{Do not send bug reports to @samp{info-gdb}, or to
20984 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
20985 not want to receive bug reports. Those that do have arranged to receive
20988 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
20989 serves as a repeater. The mailing list and the newsgroup carry exactly
20990 the same messages. Often people think of posting bug reports to the
20991 newsgroup instead of mailing them. This appears to work, but it has one
20992 problem which can be crucial: a newsgroup posting often lacks a mail
20993 path back to the sender. Thus, if we need to ask for more information,
20994 we may be unable to reach you. For this reason, it is better to send
20995 bug reports to the mailing list.
20997 The fundamental principle of reporting bugs usefully is this:
20998 @strong{report all the facts}. If you are not sure whether to state a
20999 fact or leave it out, state it!
21001 Often people omit facts because they think they know what causes the
21002 problem and assume that some details do not matter. Thus, you might
21003 assume that the name of the variable you use in an example does not matter.
21004 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
21005 stray memory reference which happens to fetch from the location where that
21006 name is stored in memory; perhaps, if the name were different, the contents
21007 of that location would fool the debugger into doing the right thing despite
21008 the bug. Play it safe and give a specific, complete example. That is the
21009 easiest thing for you to do, and the most helpful.
21011 Keep in mind that the purpose of a bug report is to enable us to fix the
21012 bug. It may be that the bug has been reported previously, but neither
21013 you nor we can know that unless your bug report is complete and
21016 Sometimes people give a few sketchy facts and ask, ``Does this ring a
21017 bell?'' Those bug reports are useless, and we urge everyone to
21018 @emph{refuse to respond to them} except to chide the sender to report
21021 To enable us to fix the bug, you should include all these things:
21025 The version of @value{GDBN}. @value{GDBN} announces it if you start
21026 with no arguments; you can also print it at any time using @code{show
21029 Without this, we will not know whether there is any point in looking for
21030 the bug in the current version of @value{GDBN}.
21033 The type of machine you are using, and the operating system name and
21037 What compiler (and its version) was used to compile @value{GDBN}---e.g.
21038 ``@value{GCC}--2.8.1''.
21041 What compiler (and its version) was used to compile the program you are
21042 debugging---e.g. ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
21043 C Compiler''. For GCC, you can say @code{gcc --version} to get this
21044 information; for other compilers, see the documentation for those
21048 The command arguments you gave the compiler to compile your example and
21049 observe the bug. For example, did you use @samp{-O}? To guarantee
21050 you will not omit something important, list them all. A copy of the
21051 Makefile (or the output from make) is sufficient.
21053 If we were to try to guess the arguments, we would probably guess wrong
21054 and then we might not encounter the bug.
21057 A complete input script, and all necessary source files, that will
21061 A description of what behavior you observe that you believe is
21062 incorrect. For example, ``It gets a fatal signal.''
21064 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
21065 will certainly notice it. But if the bug is incorrect output, we might
21066 not notice unless it is glaringly wrong. You might as well not give us
21067 a chance to make a mistake.
21069 Even if the problem you experience is a fatal signal, you should still
21070 say so explicitly. Suppose something strange is going on, such as, your
21071 copy of @value{GDBN} is out of synch, or you have encountered a bug in
21072 the C library on your system. (This has happened!) Your copy might
21073 crash and ours would not. If you told us to expect a crash, then when
21074 ours fails to crash, we would know that the bug was not happening for
21075 us. If you had not told us to expect a crash, then we would not be able
21076 to draw any conclusion from our observations.
21079 @cindex recording a session script
21080 To collect all this information, you can use a session recording program
21081 such as @command{script}, which is available on many Unix systems.
21082 Just run your @value{GDBN} session inside @command{script} and then
21083 include the @file{typescript} file with your bug report.
21085 Another way to record a @value{GDBN} session is to run @value{GDBN}
21086 inside Emacs and then save the entire buffer to a file.
21089 If you wish to suggest changes to the @value{GDBN} source, send us context
21090 diffs. If you even discuss something in the @value{GDBN} source, refer to
21091 it by context, not by line number.
21093 The line numbers in our development sources will not match those in your
21094 sources. Your line numbers would convey no useful information to us.
21098 Here are some things that are not necessary:
21102 A description of the envelope of the bug.
21104 Often people who encounter a bug spend a lot of time investigating
21105 which changes to the input file will make the bug go away and which
21106 changes will not affect it.
21108 This is often time consuming and not very useful, because the way we
21109 will find the bug is by running a single example under the debugger
21110 with breakpoints, not by pure deduction from a series of examples.
21111 We recommend that you save your time for something else.
21113 Of course, if you can find a simpler example to report @emph{instead}
21114 of the original one, that is a convenience for us. Errors in the
21115 output will be easier to spot, running under the debugger will take
21116 less time, and so on.
21118 However, simplification is not vital; if you do not want to do this,
21119 report the bug anyway and send us the entire test case you used.
21122 A patch for the bug.
21124 A patch for the bug does help us if it is a good one. But do not omit
21125 the necessary information, such as the test case, on the assumption that
21126 a patch is all we need. We might see problems with your patch and decide
21127 to fix the problem another way, or we might not understand it at all.
21129 Sometimes with a program as complicated as @value{GDBN} it is very hard to
21130 construct an example that will make the program follow a certain path
21131 through the code. If you do not send us the example, we will not be able
21132 to construct one, so we will not be able to verify that the bug is fixed.
21134 And if we cannot understand what bug you are trying to fix, or why your
21135 patch should be an improvement, we will not install it. A test case will
21136 help us to understand.
21139 A guess about what the bug is or what it depends on.
21141 Such guesses are usually wrong. Even we cannot guess right about such
21142 things without first using the debugger to find the facts.
21145 @c The readline documentation is distributed with the readline code
21146 @c and consists of the two following files:
21148 @c inc-hist.texinfo
21149 @c Use -I with makeinfo to point to the appropriate directory,
21150 @c environment var TEXINPUTS with TeX.
21151 @include rluser.texinfo
21152 @include inc-hist.texinfo
21155 @node Formatting Documentation
21156 @appendix Formatting Documentation
21158 @cindex @value{GDBN} reference card
21159 @cindex reference card
21160 The @value{GDBN} 4 release includes an already-formatted reference card, ready
21161 for printing with PostScript or Ghostscript, in the @file{gdb}
21162 subdirectory of the main source directory@footnote{In
21163 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
21164 release.}. If you can use PostScript or Ghostscript with your printer,
21165 you can print the reference card immediately with @file{refcard.ps}.
21167 The release also includes the source for the reference card. You
21168 can format it, using @TeX{}, by typing:
21174 The @value{GDBN} reference card is designed to print in @dfn{landscape}
21175 mode on US ``letter'' size paper;
21176 that is, on a sheet 11 inches wide by 8.5 inches
21177 high. You will need to specify this form of printing as an option to
21178 your @sc{dvi} output program.
21180 @cindex documentation
21182 All the documentation for @value{GDBN} comes as part of the machine-readable
21183 distribution. The documentation is written in Texinfo format, which is
21184 a documentation system that uses a single source file to produce both
21185 on-line information and a printed manual. You can use one of the Info
21186 formatting commands to create the on-line version of the documentation
21187 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
21189 @value{GDBN} includes an already formatted copy of the on-line Info
21190 version of this manual in the @file{gdb} subdirectory. The main Info
21191 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
21192 subordinate files matching @samp{gdb.info*} in the same directory. If
21193 necessary, you can print out these files, or read them with any editor;
21194 but they are easier to read using the @code{info} subsystem in @sc{gnu}
21195 Emacs or the standalone @code{info} program, available as part of the
21196 @sc{gnu} Texinfo distribution.
21198 If you want to format these Info files yourself, you need one of the
21199 Info formatting programs, such as @code{texinfo-format-buffer} or
21202 If you have @code{makeinfo} installed, and are in the top level
21203 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
21204 version @value{GDBVN}), you can make the Info file by typing:
21211 If you want to typeset and print copies of this manual, you need @TeX{},
21212 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
21213 Texinfo definitions file.
21215 @TeX{} is a typesetting program; it does not print files directly, but
21216 produces output files called @sc{dvi} files. To print a typeset
21217 document, you need a program to print @sc{dvi} files. If your system
21218 has @TeX{} installed, chances are it has such a program. The precise
21219 command to use depends on your system; @kbd{lpr -d} is common; another
21220 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
21221 require a file name without any extension or a @samp{.dvi} extension.
21223 @TeX{} also requires a macro definitions file called
21224 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
21225 written in Texinfo format. On its own, @TeX{} cannot either read or
21226 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
21227 and is located in the @file{gdb-@var{version-number}/texinfo}
21230 If you have @TeX{} and a @sc{dvi} printer program installed, you can
21231 typeset and print this manual. First switch to the the @file{gdb}
21232 subdirectory of the main source directory (for example, to
21233 @file{gdb-@value{GDBVN}/gdb}) and type:
21239 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
21241 @node Installing GDB
21242 @appendix Installing @value{GDBN}
21243 @cindex configuring @value{GDBN}
21244 @cindex installation
21245 @cindex configuring @value{GDBN}, and source tree subdirectories
21247 @value{GDBN} comes with a @code{configure} script that automates the process
21248 of preparing @value{GDBN} for installation; you can then use @code{make} to
21249 build the @code{gdb} program.
21251 @c irrelevant in info file; it's as current as the code it lives with.
21252 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
21253 look at the @file{README} file in the sources; we may have improved the
21254 installation procedures since publishing this manual.}
21257 The @value{GDBN} distribution includes all the source code you need for
21258 @value{GDBN} in a single directory, whose name is usually composed by
21259 appending the version number to @samp{gdb}.
21261 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
21262 @file{gdb-@value{GDBVN}} directory. That directory contains:
21265 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
21266 script for configuring @value{GDBN} and all its supporting libraries
21268 @item gdb-@value{GDBVN}/gdb
21269 the source specific to @value{GDBN} itself
21271 @item gdb-@value{GDBVN}/bfd
21272 source for the Binary File Descriptor library
21274 @item gdb-@value{GDBVN}/include
21275 @sc{gnu} include files
21277 @item gdb-@value{GDBVN}/libiberty
21278 source for the @samp{-liberty} free software library
21280 @item gdb-@value{GDBVN}/opcodes
21281 source for the library of opcode tables and disassemblers
21283 @item gdb-@value{GDBVN}/readline
21284 source for the @sc{gnu} command-line interface
21286 @item gdb-@value{GDBVN}/glob
21287 source for the @sc{gnu} filename pattern-matching subroutine
21289 @item gdb-@value{GDBVN}/mmalloc
21290 source for the @sc{gnu} memory-mapped malloc package
21293 The simplest way to configure and build @value{GDBN} is to run @code{configure}
21294 from the @file{gdb-@var{version-number}} source directory, which in
21295 this example is the @file{gdb-@value{GDBVN}} directory.
21297 First switch to the @file{gdb-@var{version-number}} source directory
21298 if you are not already in it; then run @code{configure}. Pass the
21299 identifier for the platform on which @value{GDBN} will run as an
21305 cd gdb-@value{GDBVN}
21306 ./configure @var{host}
21311 where @var{host} is an identifier such as @samp{sun4} or
21312 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
21313 (You can often leave off @var{host}; @code{configure} tries to guess the
21314 correct value by examining your system.)
21316 Running @samp{configure @var{host}} and then running @code{make} builds the
21317 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
21318 libraries, then @code{gdb} itself. The configured source files, and the
21319 binaries, are left in the corresponding source directories.
21322 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
21323 system does not recognize this automatically when you run a different
21324 shell, you may need to run @code{sh} on it explicitly:
21327 sh configure @var{host}
21330 If you run @code{configure} from a directory that contains source
21331 directories for multiple libraries or programs, such as the
21332 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
21333 creates configuration files for every directory level underneath (unless
21334 you tell it not to, with the @samp{--norecursion} option).
21336 You should run the @code{configure} script from the top directory in the
21337 source tree, the @file{gdb-@var{version-number}} directory. If you run
21338 @code{configure} from one of the subdirectories, you will configure only
21339 that subdirectory. That is usually not what you want. In particular,
21340 if you run the first @code{configure} from the @file{gdb} subdirectory
21341 of the @file{gdb-@var{version-number}} directory, you will omit the
21342 configuration of @file{bfd}, @file{readline}, and other sibling
21343 directories of the @file{gdb} subdirectory. This leads to build errors
21344 about missing include files such as @file{bfd/bfd.h}.
21346 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
21347 However, you should make sure that the shell on your path (named by
21348 the @samp{SHELL} environment variable) is publicly readable. Remember
21349 that @value{GDBN} uses the shell to start your program---some systems refuse to
21350 let @value{GDBN} debug child processes whose programs are not readable.
21353 * Separate Objdir:: Compiling @value{GDBN} in another directory
21354 * Config Names:: Specifying names for hosts and targets
21355 * Configure Options:: Summary of options for configure
21358 @node Separate Objdir
21359 @section Compiling @value{GDBN} in another directory
21361 If you want to run @value{GDBN} versions for several host or target machines,
21362 you need a different @code{gdb} compiled for each combination of
21363 host and target. @code{configure} is designed to make this easy by
21364 allowing you to generate each configuration in a separate subdirectory,
21365 rather than in the source directory. If your @code{make} program
21366 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
21367 @code{make} in each of these directories builds the @code{gdb}
21368 program specified there.
21370 To build @code{gdb} in a separate directory, run @code{configure}
21371 with the @samp{--srcdir} option to specify where to find the source.
21372 (You also need to specify a path to find @code{configure}
21373 itself from your working directory. If the path to @code{configure}
21374 would be the same as the argument to @samp{--srcdir}, you can leave out
21375 the @samp{--srcdir} option; it is assumed.)
21377 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
21378 separate directory for a Sun 4 like this:
21382 cd gdb-@value{GDBVN}
21385 ../gdb-@value{GDBVN}/configure sun4
21390 When @code{configure} builds a configuration using a remote source
21391 directory, it creates a tree for the binaries with the same structure
21392 (and using the same names) as the tree under the source directory. In
21393 the example, you'd find the Sun 4 library @file{libiberty.a} in the
21394 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
21395 @file{gdb-sun4/gdb}.
21397 Make sure that your path to the @file{configure} script has just one
21398 instance of @file{gdb} in it. If your path to @file{configure} looks
21399 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
21400 one subdirectory of @value{GDBN}, not the whole package. This leads to
21401 build errors about missing include files such as @file{bfd/bfd.h}.
21403 One popular reason to build several @value{GDBN} configurations in separate
21404 directories is to configure @value{GDBN} for cross-compiling (where
21405 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
21406 programs that run on another machine---the @dfn{target}).
21407 You specify a cross-debugging target by
21408 giving the @samp{--target=@var{target}} option to @code{configure}.
21410 When you run @code{make} to build a program or library, you must run
21411 it in a configured directory---whatever directory you were in when you
21412 called @code{configure} (or one of its subdirectories).
21414 The @code{Makefile} that @code{configure} generates in each source
21415 directory also runs recursively. If you type @code{make} in a source
21416 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
21417 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
21418 will build all the required libraries, and then build GDB.
21420 When you have multiple hosts or targets configured in separate
21421 directories, you can run @code{make} on them in parallel (for example,
21422 if they are NFS-mounted on each of the hosts); they will not interfere
21426 @section Specifying names for hosts and targets
21428 The specifications used for hosts and targets in the @code{configure}
21429 script are based on a three-part naming scheme, but some short predefined
21430 aliases are also supported. The full naming scheme encodes three pieces
21431 of information in the following pattern:
21434 @var{architecture}-@var{vendor}-@var{os}
21437 For example, you can use the alias @code{sun4} as a @var{host} argument,
21438 or as the value for @var{target} in a @code{--target=@var{target}}
21439 option. The equivalent full name is @samp{sparc-sun-sunos4}.
21441 The @code{configure} script accompanying @value{GDBN} does not provide
21442 any query facility to list all supported host and target names or
21443 aliases. @code{configure} calls the Bourne shell script
21444 @code{config.sub} to map abbreviations to full names; you can read the
21445 script, if you wish, or you can use it to test your guesses on
21446 abbreviations---for example:
21449 % sh config.sub i386-linux
21451 % sh config.sub alpha-linux
21452 alpha-unknown-linux-gnu
21453 % sh config.sub hp9k700
21455 % sh config.sub sun4
21456 sparc-sun-sunos4.1.1
21457 % sh config.sub sun3
21458 m68k-sun-sunos4.1.1
21459 % sh config.sub i986v
21460 Invalid configuration `i986v': machine `i986v' not recognized
21464 @code{config.sub} is also distributed in the @value{GDBN} source
21465 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
21467 @node Configure Options
21468 @section @code{configure} options
21470 Here is a summary of the @code{configure} options and arguments that
21471 are most often useful for building @value{GDBN}. @code{configure} also has
21472 several other options not listed here. @inforef{What Configure
21473 Does,,configure.info}, for a full explanation of @code{configure}.
21476 configure @r{[}--help@r{]}
21477 @r{[}--prefix=@var{dir}@r{]}
21478 @r{[}--exec-prefix=@var{dir}@r{]}
21479 @r{[}--srcdir=@var{dirname}@r{]}
21480 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
21481 @r{[}--target=@var{target}@r{]}
21486 You may introduce options with a single @samp{-} rather than
21487 @samp{--} if you prefer; but you may abbreviate option names if you use
21492 Display a quick summary of how to invoke @code{configure}.
21494 @item --prefix=@var{dir}
21495 Configure the source to install programs and files under directory
21498 @item --exec-prefix=@var{dir}
21499 Configure the source to install programs under directory
21502 @c avoid splitting the warning from the explanation:
21504 @item --srcdir=@var{dirname}
21505 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
21506 @code{make} that implements the @code{VPATH} feature.}@*
21507 Use this option to make configurations in directories separate from the
21508 @value{GDBN} source directories. Among other things, you can use this to
21509 build (or maintain) several configurations simultaneously, in separate
21510 directories. @code{configure} writes configuration specific files in
21511 the current directory, but arranges for them to use the source in the
21512 directory @var{dirname}. @code{configure} creates directories under
21513 the working directory in parallel to the source directories below
21516 @item --norecursion
21517 Configure only the directory level where @code{configure} is executed; do not
21518 propagate configuration to subdirectories.
21520 @item --target=@var{target}
21521 Configure @value{GDBN} for cross-debugging programs running on the specified
21522 @var{target}. Without this option, @value{GDBN} is configured to debug
21523 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
21525 There is no convenient way to generate a list of all available targets.
21527 @item @var{host} @dots{}
21528 Configure @value{GDBN} to run on the specified @var{host}.
21530 There is no convenient way to generate a list of all available hosts.
21533 There are many other options available as well, but they are generally
21534 needed for special purposes only.
21536 @node Maintenance Commands
21537 @appendix Maintenance Commands
21538 @cindex maintenance commands
21539 @cindex internal commands
21541 In addition to commands intended for @value{GDBN} users, @value{GDBN}
21542 includes a number of commands intended for @value{GDBN} developers,
21543 that are not documented elsewhere in this manual. These commands are
21544 provided here for reference. (For commands that turn on debugging
21545 messages, see @ref{Debugging Output}.)
21548 @kindex maint agent
21549 @item maint agent @var{expression}
21550 Translate the given @var{expression} into remote agent bytecodes.
21551 This command is useful for debugging the Agent Expression mechanism
21552 (@pxref{Agent Expressions}).
21554 @kindex maint info breakpoints
21555 @item @anchor{maint info breakpoints}maint info breakpoints
21556 Using the same format as @samp{info breakpoints}, display both the
21557 breakpoints you've set explicitly, and those @value{GDBN} is using for
21558 internal purposes. Internal breakpoints are shown with negative
21559 breakpoint numbers. The type column identifies what kind of breakpoint
21564 Normal, explicitly set breakpoint.
21567 Normal, explicitly set watchpoint.
21570 Internal breakpoint, used to handle correctly stepping through
21571 @code{longjmp} calls.
21573 @item longjmp resume
21574 Internal breakpoint at the target of a @code{longjmp}.
21577 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
21580 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
21583 Shared library events.
21587 @kindex maint check-symtabs
21588 @item maint check-symtabs
21589 Check the consistency of psymtabs and symtabs.
21591 @kindex maint cplus first_component
21592 @item maint cplus first_component @var{name}
21593 Print the first C@t{++} class/namespace component of @var{name}.
21595 @kindex maint cplus namespace
21596 @item maint cplus namespace
21597 Print the list of possible C@t{++} namespaces.
21599 @kindex maint demangle
21600 @item maint demangle @var{name}
21601 Demangle a C@t{++} or Objective-C manled @var{name}.
21603 @kindex maint deprecate
21604 @kindex maint undeprecate
21605 @cindex deprecated commands
21606 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
21607 @itemx maint undeprecate @var{command}
21608 Deprecate or undeprecate the named @var{command}. Deprecated commands
21609 cause @value{GDBN} to issue a warning when you use them. The optional
21610 argument @var{replacement} says which newer command should be used in
21611 favor of the deprecated one; if it is given, @value{GDBN} will mention
21612 the replacement as part of the warning.
21614 @kindex maint dump-me
21615 @item maint dump-me
21616 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
21617 Cause a fatal signal in the debugger and force it to dump its core.
21618 This is supported only on systems which support aborting a program
21619 with the @code{SIGQUIT} signal.
21621 @kindex maint internal-error
21622 @kindex maint internal-warning
21623 @item maint internal-error @r{[}@var{message-text}@r{]}
21624 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
21625 Cause @value{GDBN} to call the internal function @code{internal_error}
21626 or @code{internal_warning} and hence behave as though an internal error
21627 or internal warning has been detected. In addition to reporting the
21628 internal problem, these functions give the user the opportunity to
21629 either quit @value{GDBN} or create a core file of the current
21630 @value{GDBN} session.
21632 These commands take an optional parameter @var{message-text} that is
21633 used as the text of the error or warning message.
21635 Here's an example of using @code{indernal-error}:
21638 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
21639 @dots{}/maint.c:121: internal-error: testing, 1, 2
21640 A problem internal to GDB has been detected. Further
21641 debugging may prove unreliable.
21642 Quit this debugging session? (y or n) @kbd{n}
21643 Create a core file? (y or n) @kbd{n}
21647 @kindex maint packet
21648 @item maint packet @var{text}
21649 If @value{GDBN} is talking to an inferior via the serial protocol,
21650 then this command sends the string @var{text} to the inferior, and
21651 displays the response packet. @value{GDBN} supplies the initial
21652 @samp{$} character, the terminating @samp{#} character, and the
21655 @kindex maint print architecture
21656 @item maint print architecture @r{[}@var{file}@r{]}
21657 Print the entire architecture configuration. The optional argument
21658 @var{file} names the file where the output goes.
21660 @kindex maint print dummy-frames
21661 @item maint print dummy-frames
21662 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
21665 (@value{GDBP}) @kbd{b add}
21667 (@value{GDBP}) @kbd{print add(2,3)}
21668 Breakpoint 2, add (a=2, b=3) at @dots{}
21670 The program being debugged stopped while in a function called from GDB.
21672 (@value{GDBP}) @kbd{maint print dummy-frames}
21673 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
21674 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
21675 call_lo=0x01014000 call_hi=0x01014001
21679 Takes an optional file parameter.
21681 @kindex maint print registers
21682 @kindex maint print raw-registers
21683 @kindex maint print cooked-registers
21684 @kindex maint print register-groups
21685 @item maint print registers @r{[}@var{file}@r{]}
21686 @itemx maint print raw-registers @r{[}@var{file}@r{]}
21687 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
21688 @itemx maint print register-groups @r{[}@var{file}@r{]}
21689 Print @value{GDBN}'s internal register data structures.
21691 The command @code{maint print raw-registers} includes the contents of
21692 the raw register cache; the command @code{maint print cooked-registers}
21693 includes the (cooked) value of all registers; and the command
21694 @code{maint print register-groups} includes the groups that each
21695 register is a member of. @xref{Registers,, Registers, gdbint,
21696 @value{GDBN} Internals}.
21698 These commands take an optional parameter, a file name to which to
21699 write the information.
21701 @kindex maint print reggroups
21702 @item maint print reggroups @r{[}@var{file}@r{]}
21703 Print @value{GDBN}'s internal register group data structures. The
21704 optional argument @var{file} tells to what file to write the
21707 The register groups info looks like this:
21710 (@value{GDBP}) @kbd{maint print reggroups}
21723 This command forces @value{GDBN} to flush its internal register cache.
21725 @kindex maint print objfiles
21726 @cindex info for known object files
21727 @item maint print objfiles
21728 Print a dump of all known object files. For each object file, this
21729 command prints its name, address in memory, and all of its psymtabs
21732 @kindex maint print statistics
21733 @cindex bcache statistics
21734 @item maint print statistics
21735 This command prints, for each object file in the program, various data
21736 about that object file followed by the byte cache (@dfn{bcache})
21737 statistics for the object file. The objfile data includes the number
21738 of minimal, partical, full, and stabs symbols, the number of types
21739 defined by the objfile, the number of as yet unexpanded psym tables,
21740 the number of line tables and string tables, and the amount of memory
21741 used by the various tables. The bcache statistics include the counts,
21742 sizes, and counts of duplicates of all and unique objects, max,
21743 average, and median entry size, total memory used and its overhead and
21744 savings, and various measures of the hash table size and chain
21747 @kindex maint print type
21748 @cindex type chain of a data type
21749 @item maint print type @var{expr}
21750 Print the type chain for a type specified by @var{expr}. The argument
21751 can be either a type name or a symbol. If it is a symbol, the type of
21752 that symbol is described. The type chain produced by this command is
21753 a recursive definition of the data type as stored in @value{GDBN}'s
21754 data structures, including its flags and contained types.
21756 @kindex maint set dwarf2 max-cache-age
21757 @kindex maint show dwarf2 max-cache-age
21758 @item maint set dwarf2 max-cache-age
21759 @itemx maint show dwarf2 max-cache-age
21760 Control the DWARF 2 compilation unit cache.
21762 @cindex DWARF 2 compilation units cache
21763 In object files with inter-compilation-unit references, such as those
21764 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
21765 reader needs to frequently refer to previously read compilation units.
21766 This setting controls how long a compilation unit will remain in the
21767 cache if it is not referenced. A higher limit means that cached
21768 compilation units will be stored in memory longer, and more total
21769 memory will be used. Setting it to zero disables caching, which will
21770 slow down @value{GDBN} startup, but reduce memory consumption.
21772 @kindex maint set profile
21773 @kindex maint show profile
21774 @cindex profiling GDB
21775 @item maint set profile
21776 @itemx maint show profile
21777 Control profiling of @value{GDBN}.
21779 Profiling will be disabled until you use the @samp{maint set profile}
21780 command to enable it. When you enable profiling, the system will begin
21781 collecting timing and execution count data; when you disable profiling or
21782 exit @value{GDBN}, the results will be written to a log file. Remember that
21783 if you use profiling, @value{GDBN} will overwrite the profiling log file
21784 (often called @file{gmon.out}). If you have a record of important profiling
21785 data in a @file{gmon.out} file, be sure to move it to a safe location.
21787 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
21788 compiled with the @samp{-pg} compiler option.
21790 @kindex maint show-debug-regs
21791 @cindex x86 hardware debug registers
21792 @item maint show-debug-regs
21793 Control whether to show variables that mirror the x86 hardware debug
21794 registers. Use @code{ON} to enable, @code{OFF} to disable. If
21795 enabled, the debug registers values are shown when GDB inserts or
21796 removes a hardware breakpoint or watchpoint, and when the inferior
21797 triggers a hardware-assisted breakpoint or watchpoint.
21799 @kindex maint space
21800 @cindex memory used by commands
21802 Control whether to display memory usage for each command. If set to a
21803 nonzero value, @value{GDBN} will display how much memory each command
21804 took, following the command's own output. This can also be requested
21805 by invoking @value{GDBN} with the @option{--statistics} command-line
21806 switch (@pxref{Mode Options}).
21809 @cindex time of command execution
21811 Control whether to display the execution time for each command. If
21812 set to a nonzero value, @value{GDBN} will display how much time it
21813 took to execute each command, following the command's own output.
21814 This can also be requested by invoking @value{GDBN} with the
21815 @option{--statistics} command-line switch (@pxref{Mode Options}).
21817 @kindex maint translate-address
21818 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
21819 Find the symbol stored at the location specified by the address
21820 @var{addr} and an optional section name @var{section}. If found,
21821 @value{GDBN} prints the name of the closest symbol and an offset from
21822 the symbol's location to the specified address. This is similar to
21823 the @code{info address} command (@pxref{Symbols}), except that this
21824 command also allows to find symbols in other sections.
21828 The following command is useful for non-interactive invocations of
21829 @value{GDBN}, such as in the test suite.
21832 @item set watchdog @var{nsec}
21833 @kindex set watchdog
21834 @cindex watchdog timer
21835 @cindex timeout for commands
21836 Set the maximum number of seconds @value{GDBN} will wait for the
21837 target operation to finish. If this time expires, @value{GDBN}
21838 reports and error and the command is aborted.
21840 @item show watchdog
21841 Show the current setting of the target wait timeout.
21844 @node Remote Protocol
21845 @appendix @value{GDBN} Remote Serial Protocol
21850 * Stop Reply Packets::
21851 * General Query Packets::
21852 * Register Packet Format::
21854 * File-I/O remote protocol extension::
21860 There may be occasions when you need to know something about the
21861 protocol---for example, if there is only one serial port to your target
21862 machine, you might want your program to do something special if it
21863 recognizes a packet meant for @value{GDBN}.
21865 In the examples below, @samp{->} and @samp{<-} are used to indicate
21866 transmitted and received data respectfully.
21868 @cindex protocol, @value{GDBN} remote serial
21869 @cindex serial protocol, @value{GDBN} remote
21870 @cindex remote serial protocol
21871 All @value{GDBN} commands and responses (other than acknowledgments) are
21872 sent as a @var{packet}. A @var{packet} is introduced with the character
21873 @samp{$}, the actual @var{packet-data}, and the terminating character
21874 @samp{#} followed by a two-digit @var{checksum}:
21877 @code{$}@var{packet-data}@code{#}@var{checksum}
21881 @cindex checksum, for @value{GDBN} remote
21883 The two-digit @var{checksum} is computed as the modulo 256 sum of all
21884 characters between the leading @samp{$} and the trailing @samp{#} (an
21885 eight bit unsigned checksum).
21887 Implementors should note that prior to @value{GDBN} 5.0 the protocol
21888 specification also included an optional two-digit @var{sequence-id}:
21891 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
21894 @cindex sequence-id, for @value{GDBN} remote
21896 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
21897 has never output @var{sequence-id}s. Stubs that handle packets added
21898 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
21900 @cindex acknowledgment, for @value{GDBN} remote
21901 When either the host or the target machine receives a packet, the first
21902 response expected is an acknowledgment: either @samp{+} (to indicate
21903 the package was received correctly) or @samp{-} (to request
21907 -> @code{$}@var{packet-data}@code{#}@var{checksum}
21912 The host (@value{GDBN}) sends @var{command}s, and the target (the
21913 debugging stub incorporated in your program) sends a @var{response}. In
21914 the case of step and continue @var{command}s, the response is only sent
21915 when the operation has completed (the target has again stopped).
21917 @var{packet-data} consists of a sequence of characters with the
21918 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
21921 Fields within the packet should be separated using @samp{,} @samp{;} or
21922 @cindex remote protocol, field separator
21923 @samp{:}. Except where otherwise noted all numbers are represented in
21924 @sc{hex} with leading zeros suppressed.
21926 Implementors should note that prior to @value{GDBN} 5.0, the character
21927 @samp{:} could not appear as the third character in a packet (as it
21928 would potentially conflict with the @var{sequence-id}).
21930 Response @var{data} can be run-length encoded to save space. A @samp{*}
21931 means that the next character is an @sc{ascii} encoding giving a repeat count
21932 which stands for that many repetitions of the character preceding the
21933 @samp{*}. The encoding is @code{n+29}, yielding a printable character
21934 where @code{n >=3} (which is where rle starts to win). The printable
21935 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
21936 value greater than 126 should not be used.
21943 means the same as "0000".
21945 The error response returned for some packets includes a two character
21946 error number. That number is not well defined.
21948 For any @var{command} not supported by the stub, an empty response
21949 (@samp{$#00}) should be returned. That way it is possible to extend the
21950 protocol. A newer @value{GDBN} can tell if a packet is supported based
21953 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
21954 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
21960 The following table provides a complete list of all currently defined
21961 @var{command}s and their corresponding response @var{data}.
21962 @xref{File-I/O remote protocol extension}, for details about the File
21963 I/O extension of the remote protocol.
21967 @item @code{!} --- extended mode
21968 @cindex @code{!} packet
21970 Enable extended mode. In extended mode, the remote server is made
21971 persistent. The @samp{R} packet is used to restart the program being
21977 The remote target both supports and has enabled extended mode.
21980 @item @code{?} --- last signal
21981 @cindex @code{?} packet
21983 Indicate the reason the target halted. The reply is the same as for
21987 @xref{Stop Reply Packets}, for the reply specifications.
21989 @item @code{a} --- reserved
21991 Reserved for future use.
21993 @item @code{A}@var{arglen}@code{,}@var{argnum}@code{,}@var{arg}@code{,@dots{}} --- set program arguments @strong{(reserved)}
21994 @cindex @code{A} packet
21996 Initialized @samp{argv[]} array passed into program. @var{arglen}
21997 specifies the number of bytes in the hex encoded byte stream @var{arg}.
21998 See @code{gdbserver} for more details.
22006 @item @code{b}@var{baud} --- set baud @strong{(deprecated)}
22007 @cindex @code{b} packet
22009 Change the serial line speed to @var{baud}.
22011 JTC: @emph{When does the transport layer state change? When it's
22012 received, or after the ACK is transmitted. In either case, there are
22013 problems if the command or the acknowledgment packet is dropped.}
22015 Stan: @emph{If people really wanted to add something like this, and get
22016 it working for the first time, they ought to modify ser-unix.c to send
22017 some kind of out-of-band message to a specially-setup stub and have the
22018 switch happen "in between" packets, so that from remote protocol's point
22019 of view, nothing actually happened.}
22021 @item @code{B}@var{addr},@var{mode} --- set breakpoint @strong{(deprecated)}
22022 @cindex @code{B} packet
22024 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
22025 breakpoint at @var{addr}.
22027 This packet has been replaced by the @samp{Z} and @samp{z} packets
22028 (@pxref{insert breakpoint or watchpoint packet}).
22030 @item @code{c}@var{addr} --- continue
22031 @cindex @code{c} packet
22033 @var{addr} is address to resume. If @var{addr} is omitted, resume at
22037 @xref{Stop Reply Packets}, for the reply specifications.
22039 @item @code{C}@var{sig}@code{;}@var{addr} --- continue with signal
22040 @cindex @code{C} packet
22042 Continue with signal @var{sig} (hex signal number). If
22043 @code{;}@var{addr} is omitted, resume at same address.
22046 @xref{Stop Reply Packets}, for the reply specifications.
22048 @item @code{d} --- toggle debug @strong{(deprecated)}
22049 @cindex @code{d} packet
22053 @item @code{D} --- detach
22054 @cindex @code{D} packet
22056 Detach @value{GDBN} from the remote system. Sent to the remote target
22057 before @value{GDBN} disconnects via the @code{detach} command.
22067 @item @code{e} --- reserved
22069 Reserved for future use.
22071 @item @code{E} --- reserved
22073 Reserved for future use.
22075 @item @code{f} --- reserved
22077 Reserved for future use.
22079 @item @code{F}@var{RC}@code{,}@var{EE}@code{,}@var{CF}@code{;}@var{XX} --- Reply to target's F packet.
22080 @cindex @code{F} packet
22082 This packet is send by @value{GDBN} as reply to a @code{F} request packet
22083 sent by the target. This is part of the File-I/O protocol extension.
22084 @xref{File-I/O remote protocol extension}, for the specification.
22086 @item @code{g} --- read registers
22087 @anchor{read registers packet}
22088 @cindex @code{g} packet
22090 Read general registers.
22094 @item @var{XX@dots{}}
22095 Each byte of register data is described by two hex digits. The bytes
22096 with the register are transmitted in target byte order. The size of
22097 each register and their position within the @samp{g} @var{packet} are
22098 determined by the @value{GDBN} internal macros
22099 @var{DEPRECATED_REGISTER_RAW_SIZE} and @var{REGISTER_NAME} macros. The
22100 specification of several standard @code{g} packets is specified below.
22105 @item @code{G}@var{XX@dots{}} --- write regs
22106 @cindex @code{G} packet
22108 @xref{read registers packet}, for a description of the @var{XX@dots{}}
22119 @item @code{h} --- reserved
22121 Reserved for future use.
22123 @item @code{H}@var{c}@var{t@dots{}} --- set thread
22124 @cindex @code{H} packet
22126 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
22127 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
22128 should be @samp{c} for step and continue operations, @samp{g} for other
22129 operations. The thread designator @var{t@dots{}} may be -1, meaning all
22130 the threads, a thread number, or zero which means pick any thread.
22141 @c 'H': How restrictive (or permissive) is the thread model. If a
22142 @c thread is selected and stopped, are other threads allowed
22143 @c to continue to execute? As I mentioned above, I think the
22144 @c semantics of each command when a thread is selected must be
22145 @c described. For example:
22147 @c 'g': If the stub supports threads and a specific thread is
22148 @c selected, returns the register block from that thread;
22149 @c otherwise returns current registers.
22151 @c 'G' If the stub supports threads and a specific thread is
22152 @c selected, sets the registers of the register block of
22153 @c that thread; otherwise sets current registers.
22155 @item @code{i}@var{addr}@code{,}@var{nnn} --- cycle step @strong{(draft)}
22156 @anchor{cycle step packet}
22157 @cindex @code{i} packet
22159 Step the remote target by a single clock cycle. If @code{,}@var{nnn} is
22160 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
22161 step starting at that address.
22163 @item @code{I} --- signal then cycle step @strong{(reserved)}
22164 @cindex @code{I} packet
22166 @xref{step with signal packet}. @xref{cycle step packet}.
22168 @item @code{j} --- reserved
22170 Reserved for future use.
22172 @item @code{J} --- reserved
22174 Reserved for future use.
22176 @item @code{k} --- kill request
22177 @cindex @code{k} packet
22179 FIXME: @emph{There is no description of how to operate when a specific
22180 thread context has been selected (i.e.@: does 'k' kill only that
22183 @item @code{K} --- reserved
22185 Reserved for future use.
22187 @item @code{l} --- reserved
22189 Reserved for future use.
22191 @item @code{L} --- reserved
22193 Reserved for future use.
22195 @item @code{m}@var{addr}@code{,}@var{length} --- read memory
22196 @cindex @code{m} packet
22198 Read @var{length} bytes of memory starting at address @var{addr}.
22199 Neither @value{GDBN} nor the stub assume that sized memory transfers are
22200 assumed using word aligned accesses. FIXME: @emph{A word aligned memory
22201 transfer mechanism is needed.}
22205 @item @var{XX@dots{}}
22206 @var{XX@dots{}} is mem contents. Can be fewer bytes than requested if able
22207 to read only part of the data. Neither @value{GDBN} nor the stub assume
22208 that sized memory transfers are assumed using word aligned
22209 accesses. FIXME: @emph{A word aligned memory transfer mechanism is
22215 @item @code{M}@var{addr},@var{length}@code{:}@var{XX@dots{}} --- write mem
22216 @cindex @code{M} packet
22218 Write @var{length} bytes of memory starting at address @var{addr}.
22219 @var{XX@dots{}} is the data.
22226 for an error (this includes the case where only part of the data was
22230 @item @code{n} --- reserved
22232 Reserved for future use.
22234 @item @code{N} --- reserved
22236 Reserved for future use.
22238 @item @code{o} --- reserved
22240 Reserved for future use.
22242 @item @code{O} --- reserved
22244 @item @code{p}@var{hex number of register} --- read register packet
22245 @cindex @code{p} packet
22247 @xref{read registers packet}, for a description of how the returned
22248 register value is encoded.
22252 @item @var{XX@dots{}}
22253 the register's value
22257 Indicating an unrecognized @var{query}.
22260 @item @code{P}@var{n@dots{}}@code{=}@var{r@dots{}} --- write register
22261 @anchor{write register packet}
22262 @cindex @code{P} packet
22264 Write register @var{n@dots{}} with value @var{r@dots{}}, which contains two hex
22265 digits for each byte in the register (target byte order).
22275 @item @code{q}@var{query} --- general query
22276 @anchor{general query packet}
22277 @cindex @code{q} packet
22279 Request info about @var{query}. In general @value{GDBN} queries have a
22280 leading upper case letter. Custom vendor queries should use a company
22281 prefix (in lower case) ex: @samp{qfsf.var}. @var{query} may optionally
22282 be followed by a @samp{,} or @samp{;} separated list. Stubs must ensure
22283 that they match the full @var{query} name.
22287 @item @var{XX@dots{}}
22288 Hex encoded data from query. The reply can not be empty.
22292 Indicating an unrecognized @var{query}.
22295 @item @code{Q}@var{var}@code{=}@var{val} --- general set
22296 @cindex @code{Q} packet
22298 Set value of @var{var} to @var{val}.
22300 @xref{general query packet}, for a discussion of naming conventions.
22302 @item @code{r} --- reset @strong{(deprecated)}
22303 @cindex @code{r} packet
22305 Reset the entire system.
22307 @item @code{R}@var{XX} --- remote restart
22308 @cindex @code{R} packet
22310 Restart the program being debugged. @var{XX}, while needed, is ignored.
22311 This packet is only available in extended mode.
22315 @item @emph{no reply}
22316 The @samp{R} packet has no reply.
22319 @item @code{s}@var{addr} --- step
22320 @cindex @code{s} packet
22322 @var{addr} is address to resume. If @var{addr} is omitted, resume at
22326 @xref{Stop Reply Packets}, for the reply specifications.
22328 @item @code{S}@var{sig}@code{;}@var{addr} --- step with signal
22329 @anchor{step with signal packet}
22330 @cindex @code{S} packet
22332 Like @samp{C} but step not continue.
22335 @xref{Stop Reply Packets}, for the reply specifications.
22337 @item @code{t}@var{addr}@code{:}@var{PP}@code{,}@var{MM} --- search
22338 @cindex @code{t} packet
22340 Search backwards starting at address @var{addr} for a match with pattern
22341 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
22342 @var{addr} must be at least 3 digits.
22344 @item @code{T}@var{XX} --- thread alive
22345 @cindex @code{T} packet
22347 Find out if the thread XX is alive.
22352 thread is still alive
22357 @item @code{u} --- reserved
22359 Reserved for future use.
22361 @item @code{U} --- reserved
22363 Reserved for future use.
22365 @item @code{v} --- verbose packet prefix
22367 Packets starting with @code{v} are identified by a multi-letter name,
22368 up to the first @code{;} or @code{?} (or the end of the packet).
22370 @item @code{vCont}[;@var{action}[@code{:}@var{tid}]]... --- extended resume
22371 @cindex @code{vCont} packet
22373 Resume the inferior. Different actions may be specified for each thread.
22374 If an action is specified with no @var{tid}, then it is applied to any
22375 threads that don't have a specific action specified; if no default action is
22376 specified then other threads should remain stopped. Specifying multiple
22377 default actions is an error; specifying no actions is also an error.
22378 Thread IDs are specified in hexadecimal. Currently supported actions are:
22384 Continue with signal @var{sig}. @var{sig} should be two hex digits.
22388 Step with signal @var{sig}. @var{sig} should be two hex digits.
22391 The optional @var{addr} argument normally associated with these packets is
22392 not supported in @code{vCont}.
22395 @xref{Stop Reply Packets}, for the reply specifications.
22397 @item @code{vCont?} --- extended resume query
22398 @cindex @code{vCont?} packet
22400 Query support for the @code{vCont} packet.
22404 @item @code{vCont}[;@var{action}]...
22405 The @code{vCont} packet is supported. Each @var{action} is a supported
22406 command in the @code{vCont} packet.
22408 The @code{vCont} packet is not supported.
22411 @item @code{V} --- reserved
22413 Reserved for future use.
22415 @item @code{w} --- reserved
22417 Reserved for future use.
22419 @item @code{W} --- reserved
22421 Reserved for future use.
22423 @item @code{x} --- reserved
22425 Reserved for future use.
22427 @item @code{X}@var{addr}@code{,}@var{length}@var{:}@var{XX@dots{}} --- write mem (binary)
22428 @cindex @code{X} packet
22430 @var{addr} is address, @var{length} is number of bytes, @var{XX@dots{}}
22431 is binary data. The characters @code{$}, @code{#}, and @code{0x7d} are
22432 escaped using @code{0x7d}, and then XORed with @code{0x20}.
22433 For example, @code{0x7d} would be transmitted as @code{0x7d 0x5d}.
22443 @item @code{y} --- reserved
22445 Reserved for future use.
22447 @item @code{Y} reserved
22449 Reserved for future use.
22451 @item @code{z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- remove breakpoint or watchpoint @strong{(draft)}
22452 @itemx @code{Z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- insert breakpoint or watchpoint @strong{(draft)}
22453 @anchor{insert breakpoint or watchpoint packet}
22454 @cindex @code{z} packet
22455 @cindex @code{Z} packets
22457 Insert (@code{Z}) or remove (@code{z}) a @var{type} breakpoint or
22458 watchpoint starting at address @var{address} and covering the next
22459 @var{length} bytes.
22461 Each breakpoint and watchpoint packet @var{type} is documented
22464 @emph{Implementation notes: A remote target shall return an empty string
22465 for an unrecognized breakpoint or watchpoint packet @var{type}. A
22466 remote target shall support either both or neither of a given
22467 @code{Z}@var{type}@dots{} and @code{z}@var{type}@dots{} packet pair. To
22468 avoid potential problems with duplicate packets, the operations should
22469 be implemented in an idempotent way.}
22471 @item @code{z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- remove memory breakpoint @strong{(draft)}
22472 @item @code{Z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- insert memory breakpoint @strong{(draft)}
22473 @cindex @code{z0} packet
22474 @cindex @code{Z0} packet
22476 Insert (@code{Z0}) or remove (@code{z0}) a memory breakpoint at address
22477 @code{addr} of size @code{length}.
22479 A memory breakpoint is implemented by replacing the instruction at
22480 @var{addr} with a software breakpoint or trap instruction. The
22481 @code{length} is used by targets that indicates the size of the
22482 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
22483 @sc{mips} can insert either a 2 or 4 byte breakpoint).
22485 @emph{Implementation note: It is possible for a target to copy or move
22486 code that contains memory breakpoints (e.g., when implementing
22487 overlays). The behavior of this packet, in the presence of such a
22488 target, is not defined.}
22500 @item @code{z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- remove hardware breakpoint @strong{(draft)}
22501 @item @code{Z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- insert hardware breakpoint @strong{(draft)}
22502 @cindex @code{z1} packet
22503 @cindex @code{Z1} packet
22505 Insert (@code{Z1}) or remove (@code{z1}) a hardware breakpoint at
22506 address @code{addr} of size @code{length}.
22508 A hardware breakpoint is implemented using a mechanism that is not
22509 dependant on being able to modify the target's memory.
22511 @emph{Implementation note: A hardware breakpoint is not affected by code
22524 @item @code{z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- remove write watchpoint @strong{(draft)}
22525 @item @code{Z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- insert write watchpoint @strong{(draft)}
22526 @cindex @code{z2} packet
22527 @cindex @code{Z2} packet
22529 Insert (@code{Z2}) or remove (@code{z2}) a write watchpoint.
22541 @item @code{z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- remove read watchpoint @strong{(draft)}
22542 @item @code{Z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- insert read watchpoint @strong{(draft)}
22543 @cindex @code{z3} packet
22544 @cindex @code{Z3} packet
22546 Insert (@code{Z3}) or remove (@code{z3}) a read watchpoint.
22558 @item @code{z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- remove access watchpoint @strong{(draft)}
22559 @item @code{Z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- insert access watchpoint @strong{(draft)}
22560 @cindex @code{z4} packet
22561 @cindex @code{Z4} packet
22563 Insert (@code{Z4}) or remove (@code{z4}) an access watchpoint.
22577 @node Stop Reply Packets
22578 @section Stop Reply Packets
22579 @cindex stop reply packets
22581 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
22582 receive any of the below as a reply. In the case of the @samp{C},
22583 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
22584 when the target halts. In the below the exact meaning of @samp{signal
22585 number} is poorly defined. In general one of the UNIX signal numbering
22586 conventions is used.
22591 @var{AA} is the signal number
22593 @item @code{T}@var{AA}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}
22594 @cindex @code{T} packet reply
22596 @var{AA} = two hex digit signal number; @var{n...} = register number
22597 (hex), @var{r...} = target byte ordered register contents, size defined
22598 by @code{DEPRECATED_REGISTER_RAW_SIZE}; @var{n...} = @samp{thread},
22599 @var{r...} = thread process ID, this is a hex integer; @var{n...} =
22600 (@samp{watch} | @samp{rwatch} | @samp{awatch}, @var{r...} = data
22601 address, this is a hex integer; @var{n...} = other string not starting
22602 with valid hex digit. @value{GDBN} should ignore this @var{n...},
22603 @var{r...} pair and go on to the next. This way we can extend the
22608 The process exited, and @var{AA} is the exit status. This is only
22609 applicable to certain targets.
22613 The process terminated with signal @var{AA}.
22615 @item O@var{XX@dots{}}
22617 @var{XX@dots{}} is hex encoding of @sc{ascii} data. This can happen at
22618 any time while the program is running and the debugger should continue
22619 to wait for @samp{W}, @samp{T}, etc.
22621 @item F@var{call-id}@code{,}@var{parameter@dots{}}
22623 @var{call-id} is the identifier which says which host system call should
22624 be called. This is just the name of the function. Translation into the
22625 correct system call is only applicable as it's defined in @value{GDBN}.
22626 @xref{File-I/O remote protocol extension}, for a list of implemented
22629 @var{parameter@dots{}} is a list of parameters as defined for this very
22632 The target replies with this packet when it expects @value{GDBN} to call
22633 a host system call on behalf of the target. @value{GDBN} replies with
22634 an appropriate @code{F} packet and keeps up waiting for the next reply
22635 packet from the target. The latest @samp{C}, @samp{c}, @samp{S} or
22636 @samp{s} action is expected to be continued.
22637 @xref{File-I/O remote protocol extension}, for more details.
22641 @node General Query Packets
22642 @section General Query Packets
22643 @cindex remote query requests
22645 The following set and query packets have already been defined.
22649 @item @code{q}@code{C} --- current thread
22650 @cindex current thread, remote request
22651 @cindex @code{qC} packet
22652 Return the current thread id.
22656 @item @code{QC}@var{pid}
22657 Where @var{pid} is an unsigned hexidecimal process id.
22659 Any other reply implies the old pid.
22662 @item @code{q}@code{fThreadInfo} -- all thread ids
22663 @cindex list active threads, remote request
22664 @cindex @code{qfThreadInfo} packet
22665 @code{q}@code{sThreadInfo}
22667 Obtain a list of active thread ids from the target (OS). Since there
22668 may be too many active threads to fit into one reply packet, this query
22669 works iteratively: it may require more than one query/reply sequence to
22670 obtain the entire list of threads. The first query of the sequence will
22671 be the @code{qf}@code{ThreadInfo} query; subsequent queries in the
22672 sequence will be the @code{qs}@code{ThreadInfo} query.
22674 NOTE: replaces the @code{qL} query (see below).
22678 @item @code{m}@var{id}
22680 @item @code{m}@var{id},@var{id}@dots{}
22681 a comma-separated list of thread ids
22683 (lower case 'el') denotes end of list.
22686 In response to each query, the target will reply with a list of one or
22687 more thread ids, in big-endian unsigned hex, separated by commas.
22688 @value{GDBN} will respond to each reply with a request for more thread
22689 ids (using the @code{qs} form of the query), until the target responds
22690 with @code{l} (lower-case el, for @code{'last'}).
22692 @item @code{q}@code{ThreadExtraInfo}@code{,}@var{id} --- extra thread info
22693 @cindex thread attributes info, remote request
22694 @cindex @code{qThreadExtraInfo} packet
22695 Where @var{id} is a thread-id in big-endian hex. Obtain a printable
22696 string description of a thread's attributes from the target OS. This
22697 string may contain anything that the target OS thinks is interesting for
22698 @value{GDBN} to tell the user about the thread. The string is displayed
22699 in @value{GDBN}'s @samp{info threads} display. Some examples of
22700 possible thread extra info strings are ``Runnable'', or ``Blocked on
22705 @item @var{XX@dots{}}
22706 Where @var{XX@dots{}} is a hex encoding of @sc{ascii} data, comprising
22707 the printable string containing the extra information about the thread's
22711 @item @code{q}@code{L}@var{startflag}@var{threadcount}@var{nextthread} --- query @var{LIST} or @var{threadLIST} @strong{(deprecated)}
22713 Obtain thread information from RTOS. Where: @var{startflag} (one hex
22714 digit) is one to indicate the first query and zero to indicate a
22715 subsequent query; @var{threadcount} (two hex digits) is the maximum
22716 number of threads the response packet can contain; and @var{nextthread}
22717 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
22718 returned in the response as @var{argthread}.
22720 NOTE: this query is replaced by the @code{q}@code{fThreadInfo} query
22725 @item @code{q}@code{M}@var{count}@var{done}@var{argthread}@var{thread@dots{}}
22726 Where: @var{count} (two hex digits) is the number of threads being
22727 returned; @var{done} (one hex digit) is zero to indicate more threads
22728 and one indicates no further threads; @var{argthreadid} (eight hex
22729 digits) is @var{nextthread} from the request packet; @var{thread@dots{}}
22730 is a sequence of thread IDs from the target. @var{threadid} (eight hex
22731 digits). See @code{remote.c:parse_threadlist_response()}.
22734 @item @code{q}@code{CRC:}@var{addr}@code{,}@var{length} --- compute CRC of memory block
22735 @cindex CRC of memory block, remote request
22736 @cindex @code{qCRC} packet
22739 @item @code{E}@var{NN}
22740 An error (such as memory fault)
22741 @item @code{C}@var{CRC32}
22742 A 32 bit cyclic redundancy check of the specified memory region.
22745 @item @code{q}@code{Offsets} --- query sect offs
22746 @cindex section offsets, remote request
22747 @cindex @code{qOffsets} packet
22748 Get section offsets that the target used when re-locating the downloaded
22749 image. @emph{Note: while a @code{Bss} offset is included in the
22750 response, @value{GDBN} ignores this and instead applies the @code{Data}
22751 offset to the @code{Bss} section.}
22755 @item @code{Text=}@var{xxx}@code{;Data=}@var{yyy}@code{;Bss=}@var{zzz}
22758 @item @code{q}@code{P}@var{mode}@var{threadid} --- thread info request
22759 @cindex thread information, remote request
22760 @cindex @code{qP} packet
22761 Returns information on @var{threadid}. Where: @var{mode} is a hex
22762 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
22769 See @code{remote.c:remote_unpack_thread_info_response()}.
22771 @item @code{q}@code{Rcmd,}@var{command} --- remote command
22772 @cindex execute remote command, remote request
22773 @cindex @code{qRcmd} packet
22774 @var{command} (hex encoded) is passed to the local interpreter for
22775 execution. Invalid commands should be reported using the output string.
22776 Before the final result packet, the target may also respond with a
22777 number of intermediate @code{O}@var{output} console output packets.
22778 @emph{Implementors should note that providing access to a stubs's
22779 interpreter may have security implications}.
22784 A command response with no output.
22786 A command response with the hex encoded output string @var{OUTPUT}.
22787 @item @code{E}@var{NN}
22788 Indicate a badly formed request.
22790 When @samp{q}@samp{Rcmd} is not recognized.
22793 @item @code{qSymbol::} --- symbol lookup
22794 @cindex symbol lookup, remote request
22795 @cindex @code{qSymbol} packet
22796 Notify the target that @value{GDBN} is prepared to serve symbol lookup
22797 requests. Accept requests from the target for the values of symbols.
22802 The target does not need to look up any (more) symbols.
22803 @item @code{qSymbol:}@var{sym_name}
22804 The target requests the value of symbol @var{sym_name} (hex encoded).
22805 @value{GDBN} may provide the value by using the
22806 @code{qSymbol:}@var{sym_value}:@var{sym_name} message, described below.
22809 @item @code{qSymbol:}@var{sym_value}:@var{sym_name} --- symbol value
22811 Set the value of @var{sym_name} to @var{sym_value}.
22813 @var{sym_name} (hex encoded) is the name of a symbol whose value the
22814 target has previously requested.
22816 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
22817 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
22823 The target does not need to look up any (more) symbols.
22824 @item @code{qSymbol:}@var{sym_name}
22825 The target requests the value of a new symbol @var{sym_name} (hex
22826 encoded). @value{GDBN} will continue to supply the values of symbols
22827 (if available), until the target ceases to request them.
22830 @item @code{qPart}:@var{object}:@code{read}:@var{annex}:@var{offset},@var{length} --- read special data
22831 @cindex read special object, remote request
22832 @cindex @code{qPart} packet
22833 Read uninterpreted bytes from the target's special data area
22834 identified by the keyword @code{object}.
22835 Request @var{length} bytes starting at @var{offset} bytes into the data.
22836 The content and encoding of @var{annex} is specific to the object;
22837 it can supply additional details about what data to access.
22839 Here are the specific requests of this form defined so far.
22840 All @samp{@code{qPart}:@var{object}:@code{read}:@dots{}}
22841 requests use the same reply formats, listed below.
22844 @item @code{qPart}:@code{auxv}:@code{read}::@var{offset},@var{length}
22845 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
22846 auxiliary vector}, and see @ref{Remote configuration,
22847 read-aux-vector-packet}. Note @var{annex} must be empty.
22853 The @var{offset} in the request is at the end of the data.
22854 There is no more data to be read.
22856 @item @var{XX@dots{}}
22857 Hex encoded data bytes read.
22858 This may be fewer bytes than the @var{length} in the request.
22861 The request was malformed, or @var{annex} was invalid.
22863 @item @code{E}@var{nn}
22864 The offset was invalid, or there was an error encountered reading the data.
22865 @var{nn} is a hex-encoded @code{errno} value.
22867 @item @code{""} (empty)
22868 An empty reply indicates the @var{object} or @var{annex} string was not
22869 recognized by the stub.
22872 @item @code{qPart}:@var{object}:@code{write}:@var{annex}:@var{offset}:@var{data@dots{}}
22873 @cindex write data into object, remote request
22874 Write uninterpreted bytes into the target's special data area
22875 identified by the keyword @code{object},
22876 starting at @var{offset} bytes into the data.
22877 @var{data@dots{}} is the hex-encoded data to be written.
22878 The content and encoding of @var{annex} is specific to the object;
22879 it can supply additional details about what data to access.
22881 No requests of this form are presently in use. This specification
22882 serves as a placeholder to document the common format that new
22883 specific request specifications ought to use.
22888 @var{nn} (hex encoded) is the number of bytes written.
22889 This may be fewer bytes than supplied in the request.
22892 The request was malformed, or @var{annex} was invalid.
22894 @item @code{E}@var{nn}
22895 The offset was invalid, or there was an error encountered writing the data.
22896 @var{nn} is a hex-encoded @code{errno} value.
22898 @item @code{""} (empty)
22899 An empty reply indicates the @var{object} or @var{annex} string was not
22900 recognized by the stub, or that the object does not support writing.
22903 @item @code{qPart}:@var{object}:@var{operation}:@dots{}
22904 Requests of this form may be added in the future. When a stub does
22905 not recognize the @var{object} keyword, or its support for
22906 @var{object} does not recognize the @var{operation} keyword,
22907 the stub must respond with an empty packet.
22909 @item @code{qGetTLSAddr}:@var{thread-id},@var{offset},@var{lm} --- get thread local storage address
22910 @cindex get thread-local storage address, remote request
22911 @cindex @code{qGetTLSAddr} packet
22912 Fetch the address associated with thread local storage specified
22913 by @var{thread-id}, @var{offset}, and @var{lm}.
22915 @var{thread-id} is the (big endian, hex encoded) thread id associated with the
22916 thread for which to fetch the TLS address.
22918 @var{offset} is the (big endian, hex encoded) offset associated with the
22919 thread local variable. (This offset is obtained from the debug
22920 information associated with the variable.)
22922 @var{lm} is the (big endian, hex encoded) OS/ABI specific encoding of the
22923 the load module associated with the thread local storage. For example,
22924 a @sc{gnu}/Linux system will pass the link map address of the shared
22925 object associated with the thread local storage under consideration.
22926 Other operating environments may choose to represent the load module
22927 differently, so the precise meaning of this parameter will vary.
22931 @item @var{XX@dots{}}
22932 Hex encoded (big endian) bytes representing the address of the thread
22933 local storage requested.
22935 @item @code{E}@var{nn} (where @var{nn} are hex digits)
22938 @item @code{""} (empty)
22939 An empty reply indicates that @code{qGetTLSAddr} is not supported by the stub.
22942 Use of this request packet is controlled by the @code{set remote
22943 get-thread-local-storage-address} command (@pxref{Remote
22944 configuration, set remote get-thread-local-storage-address}).
22948 @node Register Packet Format
22949 @section Register Packet Format
22951 The following @samp{g}/@samp{G} packets have previously been defined.
22952 In the below, some thirty-two bit registers are transferred as
22953 sixty-four bits. Those registers should be zero/sign extended (which?)
22954 to fill the space allocated. Register bytes are transfered in target
22955 byte order. The two nibbles within a register byte are transfered
22956 most-significant - least-significant.
22962 All registers are transfered as thirty-two bit quantities in the order:
22963 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
22964 registers; fsr; fir; fp.
22968 All registers are transfered as sixty-four bit quantities (including
22969 thirty-two bit registers such as @code{sr}). The ordering is the same
22977 Example sequence of a target being re-started. Notice how the restart
22978 does not get any direct output:
22983 @emph{target restarts}
22986 <- @code{T001:1234123412341234}
22990 Example sequence of a target being stepped by a single instruction:
22993 -> @code{G1445@dots{}}
22998 <- @code{T001:1234123412341234}
23002 <- @code{1455@dots{}}
23006 @node File-I/O remote protocol extension
23007 @section File-I/O remote protocol extension
23008 @cindex File-I/O remote protocol extension
23011 * File-I/O Overview::
23012 * Protocol basics::
23013 * The F request packet::
23014 * The F reply packet::
23015 * Memory transfer::
23016 * The Ctrl-C message::
23018 * The isatty call::
23019 * The system call::
23020 * List of supported calls::
23021 * Protocol specific representation of datatypes::
23023 * File-I/O Examples::
23026 @node File-I/O Overview
23027 @subsection File-I/O Overview
23028 @cindex file-i/o overview
23030 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
23031 target to use the host's file system and console I/O when calling various
23032 system calls. System calls on the target system are translated into a
23033 remote protocol packet to the host system which then performs the needed
23034 actions and returns with an adequate response packet to the target system.
23035 This simulates file system operations even on targets that lack file systems.
23037 The protocol is defined host- and target-system independent. It uses
23038 its own independent representation of datatypes and values. Both,
23039 @value{GDBN} and the target's @value{GDBN} stub are responsible for
23040 translating the system dependent values into the unified protocol values
23041 when data is transmitted.
23043 The communication is synchronous. A system call is possible only
23044 when GDB is waiting for the @samp{C}, @samp{c}, @samp{S} or @samp{s}
23045 packets. While @value{GDBN} handles the request for a system call,
23046 the target is stopped to allow deterministic access to the target's
23047 memory. Therefore File-I/O is not interuptible by target signals. It
23048 is possible to interrupt File-I/O by a user interrupt (Ctrl-C), though.
23050 The target's request to perform a host system call does not finish
23051 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
23052 after finishing the system call, the target returns to continuing the
23053 previous activity (continue, step). No additional continue or step
23054 request from @value{GDBN} is required.
23057 (@value{GDBP}) continue
23058 <- target requests 'system call X'
23059 target is stopped, @value{GDBN} executes system call
23060 -> GDB returns result
23061 ... target continues, GDB returns to wait for the target
23062 <- target hits breakpoint and sends a Txx packet
23065 The protocol is only used for files on the host file system and
23066 for I/O on the console. Character or block special devices, pipes,
23067 named pipes or sockets or any other communication method on the host
23068 system are not supported by this protocol.
23070 @node Protocol basics
23071 @subsection Protocol basics
23072 @cindex protocol basics, file-i/o
23074 The File-I/O protocol uses the @code{F} packet, as request as well
23075 as as reply packet. Since a File-I/O system call can only occur when
23076 @value{GDBN} is waiting for the continuing or stepping target, the
23077 File-I/O request is a reply that @value{GDBN} has to expect as a result
23078 of a former @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
23079 This @code{F} packet contains all information needed to allow @value{GDBN}
23080 to call the appropriate host system call:
23084 A unique identifier for the requested system call.
23087 All parameters to the system call. Pointers are given as addresses
23088 in the target memory address space. Pointers to strings are given as
23089 pointer/length pair. Numerical values are given as they are.
23090 Numerical control values are given in a protocol specific representation.
23094 At that point @value{GDBN} has to perform the following actions.
23098 If parameter pointer values are given, which point to data needed as input
23099 to a system call, @value{GDBN} requests this data from the target with a
23100 standard @code{m} packet request. This additional communication has to be
23101 expected by the target implementation and is handled as any other @code{m}
23105 @value{GDBN} translates all value from protocol representation to host
23106 representation as needed. Datatypes are coerced into the host types.
23109 @value{GDBN} calls the system call
23112 It then coerces datatypes back to protocol representation.
23115 If pointer parameters in the request packet point to buffer space in which
23116 a system call is expected to copy data to, the data is transmitted to the
23117 target using a @code{M} or @code{X} packet. This packet has to be expected
23118 by the target implementation and is handled as any other @code{M} or @code{X}
23123 Eventually @value{GDBN} replies with another @code{F} packet which contains all
23124 necessary information for the target to continue. This at least contains
23131 @code{errno}, if has been changed by the system call.
23138 After having done the needed type and value coercion, the target continues
23139 the latest continue or step action.
23141 @node The F request packet
23142 @subsection The @code{F} request packet
23143 @cindex file-i/o request packet
23144 @cindex @code{F} request packet
23146 The @code{F} request packet has the following format:
23151 @code{F}@var{call-id}@code{,}@var{parameter@dots{}}
23154 @var{call-id} is the identifier to indicate the host system call to be called.
23155 This is just the name of the function.
23157 @var{parameter@dots{}} are the parameters to the system call.
23161 Parameters are hexadecimal integer values, either the real values in case
23162 of scalar datatypes, as pointers to target buffer space in case of compound
23163 datatypes and unspecified memory areas or as pointer/length pairs in case
23164 of string parameters. These are appended to the call-id, each separated
23165 from its predecessor by a comma. All values are transmitted in ASCII
23166 string representation, pointer/length pairs separated by a slash.
23168 @node The F reply packet
23169 @subsection The @code{F} reply packet
23170 @cindex file-i/o reply packet
23171 @cindex @code{F} reply packet
23173 The @code{F} reply packet has the following format:
23178 @code{F}@var{retcode}@code{,}@var{errno}@code{,}@var{Ctrl-C flag}@code{;}@var{call specific attachment}
23181 @var{retcode} is the return code of the system call as hexadecimal value.
23183 @var{errno} is the errno set by the call, in protocol specific representation.
23184 This parameter can be omitted if the call was successful.
23186 @var{Ctrl-C flag} is only send if the user requested a break. In this
23187 case, @var{errno} must be send as well, even if the call was successful.
23188 The @var{Ctrl-C flag} itself consists of the character 'C':
23195 or, if the call was interupted before the host call has been performed:
23202 assuming 4 is the protocol specific representation of @code{EINTR}.
23206 @node Memory transfer
23207 @subsection Memory transfer
23208 @cindex memory transfer, in file-i/o protocol
23210 Structured data which is transferred using a memory read or write as e.g.@:
23211 a @code{struct stat} is expected to be in a protocol specific format with
23212 all scalar multibyte datatypes being big endian. This should be done by
23213 the target before the @code{F} packet is sent resp.@: by @value{GDBN} before
23214 it transfers memory to the target. Transferred pointers to structured
23215 data should point to the already coerced data at any time.
23217 @node The Ctrl-C message
23218 @subsection The Ctrl-C message
23219 @cindex ctrl-c message, in file-i/o protocol
23221 A special case is, if the @var{Ctrl-C flag} is set in the @value{GDBN}
23222 reply packet. In this case the target should behave, as if it had
23223 gotten a break message. The meaning for the target is ``system call
23224 interupted by @code{SIGINT}''. Consequentially, the target should actually stop
23225 (as with a break message) and return to @value{GDBN} with a @code{T02}
23226 packet. In this case, it's important for the target to know, in which
23227 state the system call was interrupted. Since this action is by design
23228 not an atomic operation, we have to differ between two cases:
23232 The system call hasn't been performed on the host yet.
23235 The system call on the host has been finished.
23239 These two states can be distinguished by the target by the value of the
23240 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
23241 call hasn't been performed. This is equivalent to the @code{EINTR} handling
23242 on POSIX systems. In any other case, the target may presume that the
23243 system call has been finished --- successful or not --- and should behave
23244 as if the break message arrived right after the system call.
23246 @value{GDBN} must behave reliable. If the system call has not been called
23247 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
23248 @code{errno} in the packet. If the system call on the host has been finished
23249 before the user requests a break, the full action must be finshed by
23250 @value{GDBN}. This requires sending @code{M} or @code{X} packets as they fit.
23251 The @code{F} packet may only be send when either nothing has happened
23252 or the full action has been completed.
23255 @subsection Console I/O
23256 @cindex console i/o as part of file-i/o
23258 By default and if not explicitely closed by the target system, the file
23259 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
23260 on the @value{GDBN} console is handled as any other file output operation
23261 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
23262 by @value{GDBN} so that after the target read request from file descriptor
23263 0 all following typing is buffered until either one of the following
23268 The user presses @kbd{Ctrl-C}. The behaviour is as explained above, the
23270 system call is treated as finished.
23273 The user presses @kbd{Enter}. This is treated as end of input with a trailing
23277 The user presses @kbd{Ctrl-D}. This is treated as end of input. No trailing
23278 character, especially no Ctrl-D is appended to the input.
23282 If the user has typed more characters as fit in the buffer given to
23283 the read call, the trailing characters are buffered in @value{GDBN} until
23284 either another @code{read(0, @dots{})} is requested by the target or debugging
23285 is stopped on users request.
23287 @node The isatty call
23288 @subsection The @samp{isatty} function call
23289 @cindex isatty call, file-i/o protocol
23291 A special case in this protocol is the library call @code{isatty} which
23292 is implemented as its own call inside of this protocol. It returns
23293 1 to the target if the file descriptor given as parameter is attached
23294 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
23295 would require implementing @code{ioctl} and would be more complex than
23298 @node The system call
23299 @subsection The @samp{system} function call
23300 @cindex system call, file-i/o protocol
23302 The other special case in this protocol is the @code{system} call which
23303 is implemented as its own call, too. @value{GDBN} is taking over the full
23304 task of calling the necessary host calls to perform the @code{system}
23305 call. The return value of @code{system} is simplified before it's returned
23306 to the target. Basically, the only signal transmitted back is @code{EINTR}
23307 in case the user pressed @kbd{Ctrl-C}. Otherwise the return value consists
23308 entirely of the exit status of the called command.
23310 Due to security concerns, the @code{system} call is by default refused
23311 by @value{GDBN}. The user has to allow this call explicitly with the
23312 @kbd{set remote system-call-allowed 1} command.
23315 @item set remote system-call-allowed
23316 @kindex set remote system-call-allowed
23317 Control whether to allow the @code{system} calls in the File I/O
23318 protocol for the remote target. The default is zero (disabled).
23320 @item show remote system-call-allowed
23321 @kindex show remote system-call-allowed
23322 Show the current setting of system calls for the remote File I/O
23326 @node List of supported calls
23327 @subsection List of supported calls
23328 @cindex list of supported file-i/o calls
23345 @unnumberedsubsubsec open
23346 @cindex open, file-i/o system call
23350 int open(const char *pathname, int flags);
23351 int open(const char *pathname, int flags, mode_t mode);
23354 Fopen,pathptr/len,flags,mode
23358 @code{flags} is the bitwise or of the following values:
23362 If the file does not exist it will be created. The host
23363 rules apply as far as file ownership and time stamps
23367 When used with O_CREAT, if the file already exists it is
23368 an error and open() fails.
23371 If the file already exists and the open mode allows
23372 writing (O_RDWR or O_WRONLY is given) it will be
23373 truncated to length 0.
23376 The file is opened in append mode.
23379 The file is opened for reading only.
23382 The file is opened for writing only.
23385 The file is opened for reading and writing.
23388 Each other bit is silently ignored.
23393 @code{mode} is the bitwise or of the following values:
23397 User has read permission.
23400 User has write permission.
23403 Group has read permission.
23406 Group has write permission.
23409 Others have read permission.
23412 Others have write permission.
23415 Each other bit is silently ignored.
23420 @exdent Return value:
23421 open returns the new file descriptor or -1 if an error
23429 pathname already exists and O_CREAT and O_EXCL were used.
23432 pathname refers to a directory.
23435 The requested access is not allowed.
23438 pathname was too long.
23441 A directory component in pathname does not exist.
23444 pathname refers to a device, pipe, named pipe or socket.
23447 pathname refers to a file on a read-only filesystem and
23448 write access was requested.
23451 pathname is an invalid pointer value.
23454 No space on device to create the file.
23457 The process already has the maximum number of files open.
23460 The limit on the total number of files open on the system
23464 The call was interrupted by the user.
23468 @unnumberedsubsubsec close
23469 @cindex close, file-i/o system call
23478 @exdent Return value:
23479 close returns zero on success, or -1 if an error occurred.
23486 fd isn't a valid open file descriptor.
23489 The call was interrupted by the user.
23493 @unnumberedsubsubsec read
23494 @cindex read, file-i/o system call
23498 int read(int fd, void *buf, unsigned int count);
23501 Fread,fd,bufptr,count
23503 @exdent Return value:
23504 On success, the number of bytes read is returned.
23505 Zero indicates end of file. If count is zero, read
23506 returns zero as well. On error, -1 is returned.
23513 fd is not a valid file descriptor or is not open for
23517 buf is an invalid pointer value.
23520 The call was interrupted by the user.
23524 @unnumberedsubsubsec write
23525 @cindex write, file-i/o system call
23529 int write(int fd, const void *buf, unsigned int count);
23532 Fwrite,fd,bufptr,count
23534 @exdent Return value:
23535 On success, the number of bytes written are returned.
23536 Zero indicates nothing was written. On error, -1
23544 fd is not a valid file descriptor or is not open for
23548 buf is an invalid pointer value.
23551 An attempt was made to write a file that exceeds the
23552 host specific maximum file size allowed.
23555 No space on device to write the data.
23558 The call was interrupted by the user.
23562 @unnumberedsubsubsec lseek
23563 @cindex lseek, file-i/o system call
23567 long lseek (int fd, long offset, int flag);
23570 Flseek,fd,offset,flag
23573 @code{flag} is one of:
23577 The offset is set to offset bytes.
23580 The offset is set to its current location plus offset
23584 The offset is set to the size of the file plus offset
23589 @exdent Return value:
23590 On success, the resulting unsigned offset in bytes from
23591 the beginning of the file is returned. Otherwise, a
23592 value of -1 is returned.
23599 fd is not a valid open file descriptor.
23602 fd is associated with the @value{GDBN} console.
23605 flag is not a proper value.
23608 The call was interrupted by the user.
23612 @unnumberedsubsubsec rename
23613 @cindex rename, file-i/o system call
23617 int rename(const char *oldpath, const char *newpath);
23620 Frename,oldpathptr/len,newpathptr/len
23622 @exdent Return value:
23623 On success, zero is returned. On error, -1 is returned.
23630 newpath is an existing directory, but oldpath is not a
23634 newpath is a non-empty directory.
23637 oldpath or newpath is a directory that is in use by some
23641 An attempt was made to make a directory a subdirectory
23645 A component used as a directory in oldpath or new
23646 path is not a directory. Or oldpath is a directory
23647 and newpath exists but is not a directory.
23650 oldpathptr or newpathptr are invalid pointer values.
23653 No access to the file or the path of the file.
23657 oldpath or newpath was too long.
23660 A directory component in oldpath or newpath does not exist.
23663 The file is on a read-only filesystem.
23666 The device containing the file has no room for the new
23670 The call was interrupted by the user.
23674 @unnumberedsubsubsec unlink
23675 @cindex unlink, file-i/o system call
23679 int unlink(const char *pathname);
23682 Funlink,pathnameptr/len
23684 @exdent Return value:
23685 On success, zero is returned. On error, -1 is returned.
23692 No access to the file or the path of the file.
23695 The system does not allow unlinking of directories.
23698 The file pathname cannot be unlinked because it's
23699 being used by another process.
23702 pathnameptr is an invalid pointer value.
23705 pathname was too long.
23708 A directory component in pathname does not exist.
23711 A component of the path is not a directory.
23714 The file is on a read-only filesystem.
23717 The call was interrupted by the user.
23721 @unnumberedsubsubsec stat/fstat
23722 @cindex fstat, file-i/o system call
23723 @cindex stat, file-i/o system call
23727 int stat(const char *pathname, struct stat *buf);
23728 int fstat(int fd, struct stat *buf);
23731 Fstat,pathnameptr/len,bufptr
23734 @exdent Return value:
23735 On success, zero is returned. On error, -1 is returned.
23742 fd is not a valid open file.
23745 A directory component in pathname does not exist or the
23746 path is an empty string.
23749 A component of the path is not a directory.
23752 pathnameptr is an invalid pointer value.
23755 No access to the file or the path of the file.
23758 pathname was too long.
23761 The call was interrupted by the user.
23765 @unnumberedsubsubsec gettimeofday
23766 @cindex gettimeofday, file-i/o system call
23770 int gettimeofday(struct timeval *tv, void *tz);
23773 Fgettimeofday,tvptr,tzptr
23775 @exdent Return value:
23776 On success, 0 is returned, -1 otherwise.
23783 tz is a non-NULL pointer.
23786 tvptr and/or tzptr is an invalid pointer value.
23790 @unnumberedsubsubsec isatty
23791 @cindex isatty, file-i/o system call
23795 int isatty(int fd);
23800 @exdent Return value:
23801 Returns 1 if fd refers to the @value{GDBN} console, 0 otherwise.
23808 The call was interrupted by the user.
23812 @unnumberedsubsubsec system
23813 @cindex system, file-i/o system call
23817 int system(const char *command);
23820 Fsystem,commandptr/len
23822 @exdent Return value:
23823 The value returned is -1 on error and the return status
23824 of the command otherwise. Only the exit status of the
23825 command is returned, which is extracted from the hosts
23826 system return value by calling WEXITSTATUS(retval).
23827 In case /bin/sh could not be executed, 127 is returned.
23834 The call was interrupted by the user.
23837 @node Protocol specific representation of datatypes
23838 @subsection Protocol specific representation of datatypes
23839 @cindex protocol specific representation of datatypes, in file-i/o protocol
23842 * Integral datatypes::
23848 @node Integral datatypes
23849 @unnumberedsubsubsec Integral datatypes
23850 @cindex integral datatypes, in file-i/o protocol
23852 The integral datatypes used in the system calls are
23855 int@r{,} unsigned int@r{,} long@r{,} unsigned long@r{,} mode_t @r{and} time_t
23858 @code{Int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
23859 implemented as 32 bit values in this protocol.
23861 @code{Long} and @code{unsigned long} are implemented as 64 bit types.
23863 @xref{Limits}, for corresponding MIN and MAX values (similar to those
23864 in @file{limits.h}) to allow range checking on host and target.
23866 @code{time_t} datatypes are defined as seconds since the Epoch.
23868 All integral datatypes transferred as part of a memory read or write of a
23869 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
23872 @node Pointer values
23873 @unnumberedsubsubsec Pointer values
23874 @cindex pointer values, in file-i/o protocol
23876 Pointers to target data are transmitted as they are. An exception
23877 is made for pointers to buffers for which the length isn't
23878 transmitted as part of the function call, namely strings. Strings
23879 are transmitted as a pointer/length pair, both as hex values, e.g.@:
23886 which is a pointer to data of length 18 bytes at position 0x1aaf.
23887 The length is defined as the full string length in bytes, including
23888 the trailing null byte. Example:
23891 ``hello, world'' at address 0x123456
23902 @unnumberedsubsubsec struct stat
23903 @cindex struct stat, in file-i/o protocol
23905 The buffer of type struct stat used by the target and @value{GDBN} is defined
23910 unsigned int st_dev; /* device */
23911 unsigned int st_ino; /* inode */
23912 mode_t st_mode; /* protection */
23913 unsigned int st_nlink; /* number of hard links */
23914 unsigned int st_uid; /* user ID of owner */
23915 unsigned int st_gid; /* group ID of owner */
23916 unsigned int st_rdev; /* device type (if inode device) */
23917 unsigned long st_size; /* total size, in bytes */
23918 unsigned long st_blksize; /* blocksize for filesystem I/O */
23919 unsigned long st_blocks; /* number of blocks allocated */
23920 time_t st_atime; /* time of last access */
23921 time_t st_mtime; /* time of last modification */
23922 time_t st_ctime; /* time of last change */
23926 The integral datatypes are conforming to the definitions given in the
23927 approriate section (see @ref{Integral datatypes}, for details) so this
23928 structure is of size 64 bytes.
23930 The values of several fields have a restricted meaning and/or
23937 st_ino: No valid meaning for the target. Transmitted unchanged.
23939 st_mode: Valid mode bits are described in Appendix C. Any other
23940 bits have currently no meaning for the target.
23942 st_uid: No valid meaning for the target. Transmitted unchanged.
23944 st_gid: No valid meaning for the target. Transmitted unchanged.
23946 st_rdev: No valid meaning for the target. Transmitted unchanged.
23948 st_atime, st_mtime, st_ctime:
23949 These values have a host and file system dependent
23950 accuracy. Especially on Windows hosts the file systems
23951 don't support exact timing values.
23954 The target gets a struct stat of the above representation and is
23955 responsible to coerce it to the target representation before
23958 Note that due to size differences between the host and target
23959 representation of stat members, these members could eventually
23960 get truncated on the target.
23962 @node struct timeval
23963 @unnumberedsubsubsec struct timeval
23964 @cindex struct timeval, in file-i/o protocol
23966 The buffer of type struct timeval used by the target and @value{GDBN}
23967 is defined as follows:
23971 time_t tv_sec; /* second */
23972 long tv_usec; /* microsecond */
23976 The integral datatypes are conforming to the definitions given in the
23977 approriate section (see @ref{Integral datatypes}, for details) so this
23978 structure is of size 8 bytes.
23981 @subsection Constants
23982 @cindex constants, in file-i/o protocol
23984 The following values are used for the constants inside of the
23985 protocol. @value{GDBN} and target are resposible to translate these
23986 values before and after the call as needed.
23997 @unnumberedsubsubsec Open flags
23998 @cindex open flags, in file-i/o protocol
24000 All values are given in hexadecimal representation.
24012 @node mode_t values
24013 @unnumberedsubsubsec mode_t values
24014 @cindex mode_t values, in file-i/o protocol
24016 All values are given in octal representation.
24033 @unnumberedsubsubsec Errno values
24034 @cindex errno values, in file-i/o protocol
24036 All values are given in decimal representation.
24061 EUNKNOWN is used as a fallback error value if a host system returns
24062 any error value not in the list of supported error numbers.
24065 @unnumberedsubsubsec Lseek flags
24066 @cindex lseek flags, in file-i/o protocol
24075 @unnumberedsubsubsec Limits
24076 @cindex limits, in file-i/o protocol
24078 All values are given in decimal representation.
24081 INT_MIN -2147483648
24083 UINT_MAX 4294967295
24084 LONG_MIN -9223372036854775808
24085 LONG_MAX 9223372036854775807
24086 ULONG_MAX 18446744073709551615
24089 @node File-I/O Examples
24090 @subsection File-I/O Examples
24091 @cindex file-i/o examples
24093 Example sequence of a write call, file descriptor 3, buffer is at target
24094 address 0x1234, 6 bytes should be written:
24097 <- @code{Fwrite,3,1234,6}
24098 @emph{request memory read from target}
24101 @emph{return "6 bytes written"}
24105 Example sequence of a read call, file descriptor 3, buffer is at target
24106 address 0x1234, 6 bytes should be read:
24109 <- @code{Fread,3,1234,6}
24110 @emph{request memory write to target}
24111 -> @code{X1234,6:XXXXXX}
24112 @emph{return "6 bytes read"}
24116 Example sequence of a read call, call fails on the host due to invalid
24117 file descriptor (EBADF):
24120 <- @code{Fread,3,1234,6}
24124 Example sequence of a read call, user presses Ctrl-C before syscall on
24128 <- @code{Fread,3,1234,6}
24133 Example sequence of a read call, user presses Ctrl-C after syscall on
24137 <- @code{Fread,3,1234,6}
24138 -> @code{X1234,6:XXXXXX}
24142 @include agentexpr.texi
24156 % I think something like @colophon should be in texinfo. In the
24158 \long\def\colophon{\hbox to0pt{}\vfill
24159 \centerline{The body of this manual is set in}
24160 \centerline{\fontname\tenrm,}
24161 \centerline{with headings in {\bf\fontname\tenbf}}
24162 \centerline{and examples in {\tt\fontname\tentt}.}
24163 \centerline{{\it\fontname\tenit\/},}
24164 \centerline{{\bf\fontname\tenbf}, and}
24165 \centerline{{\sl\fontname\tensl\/}}
24166 \centerline{are used for emphasis.}\vfill}
24168 % Blame: doc@cygnus.com, 1991.