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{--readnow}
945 Read each symbol file's entire symbol table immediately, rather than
946 the default, which is to read it incrementally as it is needed.
947 This makes startup slower, but makes future operations faster.
952 @subsection Choosing modes
954 You can run @value{GDBN} in various alternative modes---for example, in
955 batch mode or quiet mode.
962 Do not execute commands found in any initialization files. Normally,
963 @value{GDBN} executes the commands in these files after all the command
964 options and arguments have been processed. @xref{Command Files,,Command
970 @cindex @code{--quiet}
971 @cindex @code{--silent}
973 ``Quiet''. Do not print the introductory and copyright messages. These
974 messages are also suppressed in batch mode.
977 @cindex @code{--batch}
978 Run in batch mode. Exit with status @code{0} after processing all the
979 command files specified with @samp{-x} (and all commands from
980 initialization files, if not inhibited with @samp{-n}). Exit with
981 nonzero status if an error occurs in executing the @value{GDBN} commands
982 in the command files.
984 Batch mode may be useful for running @value{GDBN} as a filter, for
985 example to download and run a program on another computer; in order to
986 make this more useful, the message
989 Program exited normally.
993 (which is ordinarily issued whenever a program running under
994 @value{GDBN} control terminates) is not issued when running in batch
999 @cindex @code{--nowindows}
1001 ``No windows''. If @value{GDBN} comes with a graphical user interface
1002 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1003 interface. If no GUI is available, this option has no effect.
1007 @cindex @code{--windows}
1009 If @value{GDBN} includes a GUI, then this option requires it to be
1012 @item -cd @var{directory}
1014 Run @value{GDBN} using @var{directory} as its working directory,
1015 instead of the current directory.
1019 @cindex @code{--fullname}
1021 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1022 subprocess. It tells @value{GDBN} to output the full file name and line
1023 number in a standard, recognizable fashion each time a stack frame is
1024 displayed (which includes each time your program stops). This
1025 recognizable format looks like two @samp{\032} characters, followed by
1026 the file name, line number and character position separated by colons,
1027 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1028 @samp{\032} characters as a signal to display the source code for the
1032 @cindex @code{--epoch}
1033 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1034 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1035 routines so as to allow Epoch to display values of expressions in a
1038 @item -annotate @var{level}
1039 @cindex @code{--annotate}
1040 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1041 effect is identical to using @samp{set annotate @var{level}}
1042 (@pxref{Annotations}). The annotation @var{level} controls how much
1043 information @value{GDBN} prints together with its prompt, values of
1044 expressions, source lines, and other types of output. Level 0 is the
1045 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1046 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1047 that control @value{GDBN}, and level 2 has been deprecated.
1049 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1053 @cindex @code{--args}
1054 Change interpretation of command line so that arguments following the
1055 executable file are passed as command line arguments to the inferior.
1056 This option stops option processing.
1058 @item -baud @var{bps}
1060 @cindex @code{--baud}
1062 Set the line speed (baud rate or bits per second) of any serial
1063 interface used by @value{GDBN} for remote debugging.
1065 @item -l @var{timeout}
1067 Set the timeout (in seconds) of any communication used by @value{GDBN}
1068 for remote debugging.
1070 @item -tty @var{device}
1071 @itemx -t @var{device}
1072 @cindex @code{--tty}
1074 Run using @var{device} for your program's standard input and output.
1075 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1077 @c resolve the situation of these eventually
1079 @cindex @code{--tui}
1080 Activate the @dfn{Text User Interface} when starting. The Text User
1081 Interface manages several text windows on the terminal, showing
1082 source, assembly, registers and @value{GDBN} command outputs
1083 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1084 Text User Interface can be enabled by invoking the program
1085 @samp{gdbtui}. Do not use this option if you run @value{GDBN} from
1086 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1089 @c @cindex @code{--xdb}
1090 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1091 @c For information, see the file @file{xdb_trans.html}, which is usually
1092 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1095 @item -interpreter @var{interp}
1096 @cindex @code{--interpreter}
1097 Use the interpreter @var{interp} for interface with the controlling
1098 program or device. This option is meant to be set by programs which
1099 communicate with @value{GDBN} using it as a back end.
1100 @xref{Interpreters, , Command Interpreters}.
1102 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1103 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1104 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1105 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1106 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1107 @sc{gdb/mi} interfaces are no longer supported.
1110 @cindex @code{--write}
1111 Open the executable and core files for both reading and writing. This
1112 is equivalent to the @samp{set write on} command inside @value{GDBN}
1116 @cindex @code{--statistics}
1117 This option causes @value{GDBN} to print statistics about time and
1118 memory usage after it completes each command and returns to the prompt.
1121 @cindex @code{--version}
1122 This option causes @value{GDBN} to print its version number and
1123 no-warranty blurb, and exit.
1128 @subsection What @value{GDBN} does during startup
1129 @cindex @value{GDBN} startup
1131 Here's the description of what @value{GDBN} does during session startup:
1135 Sets up the command interpreter as specified by the command line
1136 (@pxref{Mode Options, interpreter}).
1140 Reads the @dfn{init file} (if any) in your home directory@footnote{On
1141 DOS/Windows systems, the home directory is the one pointed to by the
1142 @code{HOME} environment variable.} and executes all the commands in
1146 Processes command line options and operands.
1149 Reads and executes the commands from init file (if any) in the current
1150 working directory. This is only done if the current directory is
1151 different from your home directory. Thus, you can have more than one
1152 init file, one generic in your home directory, and another, specific
1153 to the program you are debugging, in the directory where you invoke
1157 Reads command files specified by the @samp{-x} option. @xref{Command
1158 Files}, for more details about @value{GDBN} command files.
1161 Reads the command history recorded in the @dfn{history file}.
1162 @xref{Command History}, for more details about the command history and the
1163 files where @value{GDBN} records it.
1166 Init files use the same syntax as @dfn{command files} (@pxref{Command
1167 Files}) and are processed by @value{GDBN} in the same way. The init
1168 file in your home directory can set options (such as @samp{set
1169 complaints}) that affect subsequent processing of command line options
1170 and operands. Init files are not executed if you use the @samp{-nx}
1171 option (@pxref{Mode Options, ,Choosing modes}).
1173 @cindex init file name
1174 @cindex @file{.gdbinit}
1175 The @value{GDBN} init files are normally called @file{.gdbinit}.
1176 On some configurations of @value{GDBN}, the init file is known by a
1177 different name (these are typically environments where a specialized
1178 form of @value{GDBN} may need to coexist with other forms, hence a
1179 different name for the specialized version's init file). These are the
1180 environments with special init file names:
1183 @cindex @file{gdb.ini}
1185 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1186 the limitations of file names imposed by DOS filesystems. The Windows
1187 ports of @value{GDBN} use the standard name, but if they find a
1188 @file{gdb.ini} file, they warn you about that and suggest to rename
1189 the file to the standard name.
1191 @cindex @file{.vxgdbinit}
1193 VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit}
1195 @cindex @file{.os68gdbinit}
1197 OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit}
1199 @cindex @file{.esgdbinit}
1201 ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit}
1204 CISCO 68k: @file{.cisco-gdbinit}
1209 @section Quitting @value{GDBN}
1210 @cindex exiting @value{GDBN}
1211 @cindex leaving @value{GDBN}
1214 @kindex quit @r{[}@var{expression}@r{]}
1215 @kindex q @r{(@code{quit})}
1216 @item quit @r{[}@var{expression}@r{]}
1218 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1219 @code{q}), or type an end-of-file character (usually @kbd{C-d}). If you
1220 do not supply @var{expression}, @value{GDBN} will terminate normally;
1221 otherwise it will terminate using the result of @var{expression} as the
1226 An interrupt (often @kbd{C-c}) does not exit from @value{GDBN}, but rather
1227 terminates the action of any @value{GDBN} command that is in progress and
1228 returns to @value{GDBN} command level. It is safe to type the interrupt
1229 character at any time because @value{GDBN} does not allow it to take effect
1230 until a time when it is safe.
1232 If you have been using @value{GDBN} to control an attached process or
1233 device, you can release it with the @code{detach} command
1234 (@pxref{Attach, ,Debugging an already-running process}).
1236 @node Shell Commands
1237 @section Shell commands
1239 If you need to execute occasional shell commands during your
1240 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1241 just use the @code{shell} command.
1245 @cindex shell escape
1246 @item shell @var{command string}
1247 Invoke a standard shell to execute @var{command string}.
1248 If it exists, the environment variable @code{SHELL} determines which
1249 shell to run. Otherwise @value{GDBN} uses the default shell
1250 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1253 The utility @code{make} is often needed in development environments.
1254 You do not have to use the @code{shell} command for this purpose in
1259 @cindex calling make
1260 @item make @var{make-args}
1261 Execute the @code{make} program with the specified
1262 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1265 @node Logging output
1266 @section Logging output
1267 @cindex logging @value{GDBN} output
1268 @cindex save @value{GDBN} output to a file
1270 You may want to save the output of @value{GDBN} commands to a file.
1271 There are several commands to control @value{GDBN}'s logging.
1275 @item set logging on
1277 @item set logging off
1279 @cindex logging file name
1280 @item set logging file @var{file}
1281 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1282 @item set logging overwrite [on|off]
1283 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1284 you want @code{set logging on} to overwrite the logfile instead.
1285 @item set logging redirect [on|off]
1286 By default, @value{GDBN} output will go to both the terminal and the logfile.
1287 Set @code{redirect} if you want output to go only to the log file.
1288 @kindex show logging
1290 Show the current values of the logging settings.
1294 @chapter @value{GDBN} Commands
1296 You can abbreviate a @value{GDBN} command to the first few letters of the command
1297 name, if that abbreviation is unambiguous; and you can repeat certain
1298 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1299 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1300 show you the alternatives available, if there is more than one possibility).
1303 * Command Syntax:: How to give commands to @value{GDBN}
1304 * Completion:: Command completion
1305 * Help:: How to ask @value{GDBN} for help
1308 @node Command Syntax
1309 @section Command syntax
1311 A @value{GDBN} command is a single line of input. There is no limit on
1312 how long it can be. It starts with a command name, which is followed by
1313 arguments whose meaning depends on the command name. For example, the
1314 command @code{step} accepts an argument which is the number of times to
1315 step, as in @samp{step 5}. You can also use the @code{step} command
1316 with no arguments. Some commands do not allow any arguments.
1318 @cindex abbreviation
1319 @value{GDBN} command names may always be truncated if that abbreviation is
1320 unambiguous. Other possible command abbreviations are listed in the
1321 documentation for individual commands. In some cases, even ambiguous
1322 abbreviations are allowed; for example, @code{s} is specially defined as
1323 equivalent to @code{step} even though there are other commands whose
1324 names start with @code{s}. You can test abbreviations by using them as
1325 arguments to the @code{help} command.
1327 @cindex repeating commands
1328 @kindex RET @r{(repeat last command)}
1329 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1330 repeat the previous command. Certain commands (for example, @code{run})
1331 will not repeat this way; these are commands whose unintentional
1332 repetition might cause trouble and which you are unlikely to want to
1333 repeat. User-defined commands can disable this feature; see
1334 @ref{Define, dont-repeat}.
1336 The @code{list} and @code{x} commands, when you repeat them with
1337 @key{RET}, construct new arguments rather than repeating
1338 exactly as typed. This permits easy scanning of source or memory.
1340 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1341 output, in a way similar to the common utility @code{more}
1342 (@pxref{Screen Size,,Screen size}). Since it is easy to press one
1343 @key{RET} too many in this situation, @value{GDBN} disables command
1344 repetition after any command that generates this sort of display.
1346 @kindex # @r{(a comment)}
1348 Any text from a @kbd{#} to the end of the line is a comment; it does
1349 nothing. This is useful mainly in command files (@pxref{Command
1350 Files,,Command files}).
1352 @cindex repeating command sequences
1353 @kindex C-o @r{(operate-and-get-next)}
1354 The @kbd{C-o} binding is useful for repeating a complex sequence of
1355 commands. This command accepts the current line, like @kbd{RET}, and
1356 then fetches the next line relative to the current line from the history
1360 @section Command completion
1363 @cindex word completion
1364 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1365 only one possibility; it can also show you what the valid possibilities
1366 are for the next word in a command, at any time. This works for @value{GDBN}
1367 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1369 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1370 of a word. If there is only one possibility, @value{GDBN} fills in the
1371 word, and waits for you to finish the command (or press @key{RET} to
1372 enter it). For example, if you type
1374 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1375 @c complete accuracy in these examples; space introduced for clarity.
1376 @c If texinfo enhancements make it unnecessary, it would be nice to
1377 @c replace " @key" by "@key" in the following...
1379 (@value{GDBP}) info bre @key{TAB}
1383 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1384 the only @code{info} subcommand beginning with @samp{bre}:
1387 (@value{GDBP}) info breakpoints
1391 You can either press @key{RET} at this point, to run the @code{info
1392 breakpoints} command, or backspace and enter something else, if
1393 @samp{breakpoints} does not look like the command you expected. (If you
1394 were sure you wanted @code{info breakpoints} in the first place, you
1395 might as well just type @key{RET} immediately after @samp{info bre},
1396 to exploit command abbreviations rather than command completion).
1398 If there is more than one possibility for the next word when you press
1399 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1400 characters and try again, or just press @key{TAB} a second time;
1401 @value{GDBN} displays all the possible completions for that word. For
1402 example, you might want to set a breakpoint on a subroutine whose name
1403 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1404 just sounds the bell. Typing @key{TAB} again displays all the
1405 function names in your program that begin with those characters, for
1409 (@value{GDBP}) b make_ @key{TAB}
1410 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1411 make_a_section_from_file make_environ
1412 make_abs_section make_function_type
1413 make_blockvector make_pointer_type
1414 make_cleanup make_reference_type
1415 make_command make_symbol_completion_list
1416 (@value{GDBP}) b make_
1420 After displaying the available possibilities, @value{GDBN} copies your
1421 partial input (@samp{b make_} in the example) so you can finish the
1424 If you just want to see the list of alternatives in the first place, you
1425 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1426 means @kbd{@key{META} ?}. You can type this either by holding down a
1427 key designated as the @key{META} shift on your keyboard (if there is
1428 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1430 @cindex quotes in commands
1431 @cindex completion of quoted strings
1432 Sometimes the string you need, while logically a ``word'', may contain
1433 parentheses or other characters that @value{GDBN} normally excludes from
1434 its notion of a word. To permit word completion to work in this
1435 situation, you may enclose words in @code{'} (single quote marks) in
1436 @value{GDBN} commands.
1438 The most likely situation where you might need this is in typing the
1439 name of a C@t{++} function. This is because C@t{++} allows function
1440 overloading (multiple definitions of the same function, distinguished
1441 by argument type). For example, when you want to set a breakpoint you
1442 may need to distinguish whether you mean the version of @code{name}
1443 that takes an @code{int} parameter, @code{name(int)}, or the version
1444 that takes a @code{float} parameter, @code{name(float)}. To use the
1445 word-completion facilities in this situation, type a single quote
1446 @code{'} at the beginning of the function name. This alerts
1447 @value{GDBN} that it may need to consider more information than usual
1448 when you press @key{TAB} or @kbd{M-?} to request word completion:
1451 (@value{GDBP}) b 'bubble( @kbd{M-?}
1452 bubble(double,double) bubble(int,int)
1453 (@value{GDBP}) b 'bubble(
1456 In some cases, @value{GDBN} can tell that completing a name requires using
1457 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1458 completing as much as it can) if you do not type the quote in the first
1462 (@value{GDBP}) b bub @key{TAB}
1463 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1464 (@value{GDBP}) b 'bubble(
1468 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1469 you have not yet started typing the argument list when you ask for
1470 completion on an overloaded symbol.
1472 For more information about overloaded functions, see @ref{C plus plus
1473 expressions, ,C@t{++} expressions}. You can use the command @code{set
1474 overload-resolution off} to disable overload resolution;
1475 see @ref{Debugging C plus plus, ,@value{GDBN} features for C@t{++}}.
1479 @section Getting help
1480 @cindex online documentation
1483 You can always ask @value{GDBN} itself for information on its commands,
1484 using the command @code{help}.
1487 @kindex h @r{(@code{help})}
1490 You can use @code{help} (abbreviated @code{h}) with no arguments to
1491 display a short list of named classes of commands:
1495 List of classes of commands:
1497 aliases -- Aliases of other commands
1498 breakpoints -- Making program stop at certain points
1499 data -- Examining data
1500 files -- Specifying and examining files
1501 internals -- Maintenance commands
1502 obscure -- Obscure features
1503 running -- Running the program
1504 stack -- Examining the stack
1505 status -- Status inquiries
1506 support -- Support facilities
1507 tracepoints -- Tracing of program execution without@*
1508 stopping the program
1509 user-defined -- User-defined commands
1511 Type "help" followed by a class name for a list of
1512 commands in that class.
1513 Type "help" followed by command name for full
1515 Command name abbreviations are allowed if unambiguous.
1518 @c the above line break eliminates huge line overfull...
1520 @item help @var{class}
1521 Using one of the general help classes as an argument, you can get a
1522 list of the individual commands in that class. For example, here is the
1523 help display for the class @code{status}:
1526 (@value{GDBP}) help status
1531 @c Line break in "show" line falsifies real output, but needed
1532 @c to fit in smallbook page size.
1533 info -- Generic command for showing things
1534 about the program being debugged
1535 show -- Generic command for showing things
1538 Type "help" followed by command name for full
1540 Command name abbreviations are allowed if unambiguous.
1544 @item help @var{command}
1545 With a command name as @code{help} argument, @value{GDBN} displays a
1546 short paragraph on how to use that command.
1549 @item apropos @var{args}
1550 The @code{apropos} command searches through all of the @value{GDBN}
1551 commands, and their documentation, for the regular expression specified in
1552 @var{args}. It prints out all matches found. For example:
1563 set symbol-reloading -- Set dynamic symbol table reloading
1564 multiple times in one run
1565 show symbol-reloading -- Show dynamic symbol table reloading
1566 multiple times in one run
1571 @item complete @var{args}
1572 The @code{complete @var{args}} command lists all the possible completions
1573 for the beginning of a command. Use @var{args} to specify the beginning of the
1574 command you want completed. For example:
1580 @noindent results in:
1591 @noindent This is intended for use by @sc{gnu} Emacs.
1594 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1595 and @code{show} to inquire about the state of your program, or the state
1596 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1597 manual introduces each of them in the appropriate context. The listings
1598 under @code{info} and under @code{show} in the Index point to
1599 all the sub-commands. @xref{Index}.
1604 @kindex i @r{(@code{info})}
1606 This command (abbreviated @code{i}) is for describing the state of your
1607 program. For example, you can list the arguments given to your program
1608 with @code{info args}, list the registers currently in use with @code{info
1609 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1610 You can get a complete list of the @code{info} sub-commands with
1611 @w{@code{help info}}.
1615 You can assign the result of an expression to an environment variable with
1616 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1617 @code{set prompt $}.
1621 In contrast to @code{info}, @code{show} is for describing the state of
1622 @value{GDBN} itself.
1623 You can change most of the things you can @code{show}, by using the
1624 related command @code{set}; for example, you can control what number
1625 system is used for displays with @code{set radix}, or simply inquire
1626 which is currently in use with @code{show radix}.
1629 To display all the settable parameters and their current
1630 values, you can use @code{show} with no arguments; you may also use
1631 @code{info set}. Both commands produce the same display.
1632 @c FIXME: "info set" violates the rule that "info" is for state of
1633 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1634 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1638 Here are three miscellaneous @code{show} subcommands, all of which are
1639 exceptional in lacking corresponding @code{set} commands:
1642 @kindex show version
1643 @cindex @value{GDBN} version number
1645 Show what version of @value{GDBN} is running. You should include this
1646 information in @value{GDBN} bug-reports. If multiple versions of
1647 @value{GDBN} are in use at your site, you may need to determine which
1648 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1649 commands are introduced, and old ones may wither away. Also, many
1650 system vendors ship variant versions of @value{GDBN}, and there are
1651 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1652 The version number is the same as the one announced when you start
1655 @kindex show copying
1656 @kindex info copying
1657 @cindex display @value{GDBN} copyright
1660 Display information about permission for copying @value{GDBN}.
1662 @kindex show warranty
1663 @kindex info warranty
1665 @itemx info warranty
1666 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1667 if your version of @value{GDBN} comes with one.
1672 @chapter Running Programs Under @value{GDBN}
1674 When you run a program under @value{GDBN}, you must first generate
1675 debugging information when you compile it.
1677 You may start @value{GDBN} with its arguments, if any, in an environment
1678 of your choice. If you are doing native debugging, you may redirect
1679 your program's input and output, debug an already running process, or
1680 kill a child process.
1683 * Compilation:: Compiling for debugging
1684 * Starting:: Starting your program
1685 * Arguments:: Your program's arguments
1686 * Environment:: Your program's environment
1688 * Working Directory:: Your program's working directory
1689 * Input/Output:: Your program's input and output
1690 * Attach:: Debugging an already-running process
1691 * Kill Process:: Killing the child process
1693 * Threads:: Debugging programs with multiple threads
1694 * Processes:: Debugging programs with multiple processes
1698 @section Compiling for debugging
1700 In order to debug a program effectively, you need to generate
1701 debugging information when you compile it. This debugging information
1702 is stored in the object file; it describes the data type of each
1703 variable or function and the correspondence between source line numbers
1704 and addresses in the executable code.
1706 To request debugging information, specify the @samp{-g} option when you run
1709 Programs that are to be shipped to your customers are compiled with
1710 optimizations, using the @samp{-O} compiler option. However, many
1711 compilers are unable to handle the @samp{-g} and @samp{-O} options
1712 together. Using those compilers, you cannot generate optimized
1713 executables containing debugging information.
1715 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1716 without @samp{-O}, making it possible to debug optimized code. We
1717 recommend that you @emph{always} use @samp{-g} whenever you compile a
1718 program. You may think your program is correct, but there is no sense
1719 in pushing your luck.
1721 @cindex optimized code, debugging
1722 @cindex debugging optimized code
1723 When you debug a program compiled with @samp{-g -O}, remember that the
1724 optimizer is rearranging your code; the debugger shows you what is
1725 really there. Do not be too surprised when the execution path does not
1726 exactly match your source file! An extreme example: if you define a
1727 variable, but never use it, @value{GDBN} never sees that
1728 variable---because the compiler optimizes it out of existence.
1730 Some things do not work as well with @samp{-g -O} as with just
1731 @samp{-g}, particularly on machines with instruction scheduling. If in
1732 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1733 please report it to us as a bug (including a test case!).
1734 @xref{Variables}, for more information about debugging optimized code.
1736 Older versions of the @sc{gnu} C compiler permitted a variant option
1737 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1738 format; if your @sc{gnu} C compiler has this option, do not use it.
1740 @value{GDBN} knows about preprocessor macros and can show you their
1741 expansion (@pxref{Macros}). Most compilers do not include information
1742 about preprocessor macros in the debugging information if you specify
1743 the @option{-g} flag alone, because this information is rather large.
1744 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1745 provides macro information if you specify the options
1746 @option{-gdwarf-2} and @option{-g3}; the former option requests
1747 debugging information in the Dwarf 2 format, and the latter requests
1748 ``extra information''. In the future, we hope to find more compact
1749 ways to represent macro information, so that it can be included with
1754 @section Starting your program
1760 @kindex r @r{(@code{run})}
1763 Use the @code{run} command to start your program under @value{GDBN}.
1764 You must first specify the program name (except on VxWorks) with an
1765 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1766 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1767 (@pxref{Files, ,Commands to specify files}).
1771 If you are running your program in an execution environment that
1772 supports processes, @code{run} creates an inferior process and makes
1773 that process run your program. (In environments without processes,
1774 @code{run} jumps to the start of your program.)
1776 The execution of a program is affected by certain information it
1777 receives from its superior. @value{GDBN} provides ways to specify this
1778 information, which you must do @emph{before} starting your program. (You
1779 can change it after starting your program, but such changes only affect
1780 your program the next time you start it.) This information may be
1781 divided into four categories:
1784 @item The @emph{arguments.}
1785 Specify the arguments to give your program as the arguments of the
1786 @code{run} command. If a shell is available on your target, the shell
1787 is used to pass the arguments, so that you may use normal conventions
1788 (such as wildcard expansion or variable substitution) in describing
1790 In Unix systems, you can control which shell is used with the
1791 @code{SHELL} environment variable.
1792 @xref{Arguments, ,Your program's arguments}.
1794 @item The @emph{environment.}
1795 Your program normally inherits its environment from @value{GDBN}, but you can
1796 use the @value{GDBN} commands @code{set environment} and @code{unset
1797 environment} to change parts of the environment that affect
1798 your program. @xref{Environment, ,Your program's environment}.
1800 @item The @emph{working directory.}
1801 Your program inherits its working directory from @value{GDBN}. You can set
1802 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1803 @xref{Working Directory, ,Your program's working directory}.
1805 @item The @emph{standard input and output.}
1806 Your program normally uses the same device for standard input and
1807 standard output as @value{GDBN} is using. You can redirect input and output
1808 in the @code{run} command line, or you can use the @code{tty} command to
1809 set a different device for your program.
1810 @xref{Input/Output, ,Your program's input and output}.
1813 @emph{Warning:} While input and output redirection work, you cannot use
1814 pipes to pass the output of the program you are debugging to another
1815 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1819 When you issue the @code{run} command, your program begins to execute
1820 immediately. @xref{Stopping, ,Stopping and continuing}, for discussion
1821 of how to arrange for your program to stop. Once your program has
1822 stopped, you may call functions in your program, using the @code{print}
1823 or @code{call} commands. @xref{Data, ,Examining Data}.
1825 If the modification time of your symbol file has changed since the last
1826 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1827 table, and reads it again. When it does this, @value{GDBN} tries to retain
1828 your current breakpoints.
1833 @cindex run to main procedure
1834 The name of the main procedure can vary from language to language.
1835 With C or C@t{++}, the main procedure name is always @code{main}, but
1836 other languages such as Ada do not require a specific name for their
1837 main procedure. The debugger provides a convenient way to start the
1838 execution of the program and to stop at the beginning of the main
1839 procedure, depending on the language used.
1841 The @samp{start} command does the equivalent of setting a temporary
1842 breakpoint at the beginning of the main procedure and then invoking
1843 the @samp{run} command.
1845 @cindex elaboration phase
1846 Some programs contain an @dfn{elaboration} phase where some startup code is
1847 executed before the main procedure is called. This depends on the
1848 languages used to write your program. In C@t{++}, for instance,
1849 constructors for static and global objects are executed before
1850 @code{main} is called. It is therefore possible that the debugger stops
1851 before reaching the main procedure. However, the temporary breakpoint
1852 will remain to halt execution.
1854 Specify the arguments to give to your program as arguments to the
1855 @samp{start} command. These arguments will be given verbatim to the
1856 underlying @samp{run} command. Note that the same arguments will be
1857 reused if no argument is provided during subsequent calls to
1858 @samp{start} or @samp{run}.
1860 It is sometimes necessary to debug the program during elaboration. In
1861 these cases, using the @code{start} command would stop the execution of
1862 your program too late, as the program would have already completed the
1863 elaboration phase. Under these circumstances, insert breakpoints in your
1864 elaboration code before running your program.
1868 @section Your program's arguments
1870 @cindex arguments (to your program)
1871 The arguments to your program can be specified by the arguments of the
1873 They are passed to a shell, which expands wildcard characters and
1874 performs redirection of I/O, and thence to your program. Your
1875 @code{SHELL} environment variable (if it exists) specifies what shell
1876 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1877 the default shell (@file{/bin/sh} on Unix).
1879 On non-Unix systems, the program is usually invoked directly by
1880 @value{GDBN}, which emulates I/O redirection via the appropriate system
1881 calls, and the wildcard characters are expanded by the startup code of
1882 the program, not by the shell.
1884 @code{run} with no arguments uses the same arguments used by the previous
1885 @code{run}, or those set by the @code{set args} command.
1890 Specify the arguments to be used the next time your program is run. If
1891 @code{set args} has no arguments, @code{run} executes your program
1892 with no arguments. Once you have run your program with arguments,
1893 using @code{set args} before the next @code{run} is the only way to run
1894 it again without arguments.
1898 Show the arguments to give your program when it is started.
1902 @section Your program's environment
1904 @cindex environment (of your program)
1905 The @dfn{environment} consists of a set of environment variables and
1906 their values. Environment variables conventionally record such things as
1907 your user name, your home directory, your terminal type, and your search
1908 path for programs to run. Usually you set up environment variables with
1909 the shell and they are inherited by all the other programs you run. When
1910 debugging, it can be useful to try running your program with a modified
1911 environment without having to start @value{GDBN} over again.
1915 @item path @var{directory}
1916 Add @var{directory} to the front of the @code{PATH} environment variable
1917 (the search path for executables) that will be passed to your program.
1918 The value of @code{PATH} used by @value{GDBN} does not change.
1919 You may specify several directory names, separated by whitespace or by a
1920 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1921 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1922 is moved to the front, so it is searched sooner.
1924 You can use the string @samp{$cwd} to refer to whatever is the current
1925 working directory at the time @value{GDBN} searches the path. If you
1926 use @samp{.} instead, it refers to the directory where you executed the
1927 @code{path} command. @value{GDBN} replaces @samp{.} in the
1928 @var{directory} argument (with the current path) before adding
1929 @var{directory} to the search path.
1930 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1931 @c document that, since repeating it would be a no-op.
1935 Display the list of search paths for executables (the @code{PATH}
1936 environment variable).
1938 @kindex show environment
1939 @item show environment @r{[}@var{varname}@r{]}
1940 Print the value of environment variable @var{varname} to be given to
1941 your program when it starts. If you do not supply @var{varname},
1942 print the names and values of all environment variables to be given to
1943 your program. You can abbreviate @code{environment} as @code{env}.
1945 @kindex set environment
1946 @item set environment @var{varname} @r{[}=@var{value}@r{]}
1947 Set environment variable @var{varname} to @var{value}. The value
1948 changes for your program only, not for @value{GDBN} itself. @var{value} may
1949 be any string; the values of environment variables are just strings, and
1950 any interpretation is supplied by your program itself. The @var{value}
1951 parameter is optional; if it is eliminated, the variable is set to a
1953 @c "any string" here does not include leading, trailing
1954 @c blanks. Gnu asks: does anyone care?
1956 For example, this command:
1963 tells the debugged program, when subsequently run, that its user is named
1964 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
1965 are not actually required.)
1967 @kindex unset environment
1968 @item unset environment @var{varname}
1969 Remove variable @var{varname} from the environment to be passed to your
1970 program. This is different from @samp{set env @var{varname} =};
1971 @code{unset environment} removes the variable from the environment,
1972 rather than assigning it an empty value.
1975 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
1977 by your @code{SHELL} environment variable if it exists (or
1978 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
1979 that runs an initialization file---such as @file{.cshrc} for C-shell, or
1980 @file{.bashrc} for BASH---any variables you set in that file affect
1981 your program. You may wish to move setting of environment variables to
1982 files that are only run when you sign on, such as @file{.login} or
1985 @node Working Directory
1986 @section Your program's working directory
1988 @cindex working directory (of your program)
1989 Each time you start your program with @code{run}, it inherits its
1990 working directory from the current working directory of @value{GDBN}.
1991 The @value{GDBN} working directory is initially whatever it inherited
1992 from its parent process (typically the shell), but you can specify a new
1993 working directory in @value{GDBN} with the @code{cd} command.
1995 The @value{GDBN} working directory also serves as a default for the commands
1996 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2001 @cindex change working directory
2002 @item cd @var{directory}
2003 Set the @value{GDBN} working directory to @var{directory}.
2007 Print the @value{GDBN} working directory.
2010 It is generally impossible to find the current working directory of
2011 the process being debugged (since a program can change its directory
2012 during its run). If you work on a system where @value{GDBN} is
2013 configured with the @file{/proc} support, you can use the @code{info
2014 proc} command (@pxref{SVR4 Process Information}) to find out the
2015 current working directory of the debuggee.
2018 @section Your program's input and output
2023 By default, the program you run under @value{GDBN} does input and output to
2024 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2025 to its own terminal modes to interact with you, but it records the terminal
2026 modes your program was using and switches back to them when you continue
2027 running your program.
2030 @kindex info terminal
2032 Displays information recorded by @value{GDBN} about the terminal modes your
2036 You can redirect your program's input and/or output using shell
2037 redirection with the @code{run} command. For example,
2044 starts your program, diverting its output to the file @file{outfile}.
2047 @cindex controlling terminal
2048 Another way to specify where your program should do input and output is
2049 with the @code{tty} command. This command accepts a file name as
2050 argument, and causes this file to be the default for future @code{run}
2051 commands. It also resets the controlling terminal for the child
2052 process, for future @code{run} commands. For example,
2059 directs that processes started with subsequent @code{run} commands
2060 default to do input and output on the terminal @file{/dev/ttyb} and have
2061 that as their controlling terminal.
2063 An explicit redirection in @code{run} overrides the @code{tty} command's
2064 effect on the input/output device, but not its effect on the controlling
2067 When you use the @code{tty} command or redirect input in the @code{run}
2068 command, only the input @emph{for your program} is affected. The input
2069 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2070 for @code{set inferior-tty}.
2072 @cindex inferior tty
2073 @cindex set inferior controlling terminal
2074 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2075 display the name of the terminal that will be used for future runs of your
2079 @item set inferior-tty /dev/ttyb
2080 @kindex set inferior-tty
2081 Set the tty for the program being debugged to /dev/ttyb.
2083 @item show inferior-tty
2084 @kindex show inferior-tty
2085 Show the current tty for the program being debugged.
2089 @section Debugging an already-running process
2094 @item attach @var{process-id}
2095 This command attaches to a running process---one that was started
2096 outside @value{GDBN}. (@code{info files} shows your active
2097 targets.) The command takes as argument a process ID. The usual way to
2098 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2099 or with the @samp{jobs -l} shell command.
2101 @code{attach} does not repeat if you press @key{RET} a second time after
2102 executing the command.
2105 To use @code{attach}, your program must be running in an environment
2106 which supports processes; for example, @code{attach} does not work for
2107 programs on bare-board targets that lack an operating system. You must
2108 also have permission to send the process a signal.
2110 When you use @code{attach}, the debugger finds the program running in
2111 the process first by looking in the current working directory, then (if
2112 the program is not found) by using the source file search path
2113 (@pxref{Source Path, ,Specifying source directories}). You can also use
2114 the @code{file} command to load the program. @xref{Files, ,Commands to
2117 The first thing @value{GDBN} does after arranging to debug the specified
2118 process is to stop it. You can examine and modify an attached process
2119 with all the @value{GDBN} commands that are ordinarily available when
2120 you start processes with @code{run}. You can insert breakpoints; you
2121 can step and continue; you can modify storage. If you would rather the
2122 process continue running, you may use the @code{continue} command after
2123 attaching @value{GDBN} to the process.
2128 When you have finished debugging the attached process, you can use the
2129 @code{detach} command to release it from @value{GDBN} control. Detaching
2130 the process continues its execution. After the @code{detach} command,
2131 that process and @value{GDBN} become completely independent once more, and you
2132 are ready to @code{attach} another process or start one with @code{run}.
2133 @code{detach} does not repeat if you press @key{RET} again after
2134 executing the command.
2137 If you exit @value{GDBN} or use the @code{run} command while you have an
2138 attached process, you kill that process. By default, @value{GDBN} asks
2139 for confirmation if you try to do either of these things; you can
2140 control whether or not you need to confirm by using the @code{set
2141 confirm} command (@pxref{Messages/Warnings, ,Optional warnings and
2145 @section Killing the child process
2150 Kill the child process in which your program is running under @value{GDBN}.
2153 This command is useful if you wish to debug a core dump instead of a
2154 running process. @value{GDBN} ignores any core dump file while your program
2157 On some operating systems, a program cannot be executed outside @value{GDBN}
2158 while you have breakpoints set on it inside @value{GDBN}. You can use the
2159 @code{kill} command in this situation to permit running your program
2160 outside the debugger.
2162 The @code{kill} command is also useful if you wish to recompile and
2163 relink your program, since on many systems it is impossible to modify an
2164 executable file while it is running in a process. In this case, when you
2165 next type @code{run}, @value{GDBN} notices that the file has changed, and
2166 reads the symbol table again (while trying to preserve your current
2167 breakpoint settings).
2170 @section Debugging programs with multiple threads
2172 @cindex threads of execution
2173 @cindex multiple threads
2174 @cindex switching threads
2175 In some operating systems, such as HP-UX and Solaris, a single program
2176 may have more than one @dfn{thread} of execution. The precise semantics
2177 of threads differ from one operating system to another, but in general
2178 the threads of a single program are akin to multiple processes---except
2179 that they share one address space (that is, they can all examine and
2180 modify the same variables). On the other hand, each thread has its own
2181 registers and execution stack, and perhaps private memory.
2183 @value{GDBN} provides these facilities for debugging multi-thread
2187 @item automatic notification of new threads
2188 @item @samp{thread @var{threadno}}, a command to switch among threads
2189 @item @samp{info threads}, a command to inquire about existing threads
2190 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2191 a command to apply a command to a list of threads
2192 @item thread-specific breakpoints
2196 @emph{Warning:} These facilities are not yet available on every
2197 @value{GDBN} configuration where the operating system supports threads.
2198 If your @value{GDBN} does not support threads, these commands have no
2199 effect. For example, a system without thread support shows no output
2200 from @samp{info threads}, and always rejects the @code{thread} command,
2204 (@value{GDBP}) info threads
2205 (@value{GDBP}) thread 1
2206 Thread ID 1 not known. Use the "info threads" command to
2207 see the IDs of currently known threads.
2209 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2210 @c doesn't support threads"?
2213 @cindex focus of debugging
2214 @cindex current thread
2215 The @value{GDBN} thread debugging facility allows you to observe all
2216 threads while your program runs---but whenever @value{GDBN} takes
2217 control, one thread in particular is always the focus of debugging.
2218 This thread is called the @dfn{current thread}. Debugging commands show
2219 program information from the perspective of the current thread.
2221 @cindex @code{New} @var{systag} message
2222 @cindex thread identifier (system)
2223 @c FIXME-implementors!! It would be more helpful if the [New...] message
2224 @c included GDB's numeric thread handle, so you could just go to that
2225 @c thread without first checking `info threads'.
2226 Whenever @value{GDBN} detects a new thread in your program, it displays
2227 the target system's identification for the thread with a message in the
2228 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2229 whose form varies depending on the particular system. For example, on
2230 LynxOS, you might see
2233 [New process 35 thread 27]
2237 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2238 the @var{systag} is simply something like @samp{process 368}, with no
2241 @c FIXME!! (1) Does the [New...] message appear even for the very first
2242 @c thread of a program, or does it only appear for the
2243 @c second---i.e.@: when it becomes obvious we have a multithread
2245 @c (2) *Is* there necessarily a first thread always? Or do some
2246 @c multithread systems permit starting a program with multiple
2247 @c threads ab initio?
2249 @cindex thread number
2250 @cindex thread identifier (GDB)
2251 For debugging purposes, @value{GDBN} associates its own thread
2252 number---always a single integer---with each thread in your program.
2255 @kindex info threads
2257 Display a summary of all threads currently in your
2258 program. @value{GDBN} displays for each thread (in this order):
2262 the thread number assigned by @value{GDBN}
2265 the target system's thread identifier (@var{systag})
2268 the current stack frame summary for that thread
2272 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2273 indicates the current thread.
2277 @c end table here to get a little more width for example
2280 (@value{GDBP}) info threads
2281 3 process 35 thread 27 0x34e5 in sigpause ()
2282 2 process 35 thread 23 0x34e5 in sigpause ()
2283 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2289 @cindex debugging multithreaded programs (on HP-UX)
2290 @cindex thread identifier (GDB), on HP-UX
2291 For debugging purposes, @value{GDBN} associates its own thread
2292 number---a small integer assigned in thread-creation order---with each
2293 thread in your program.
2295 @cindex @code{New} @var{systag} message, on HP-UX
2296 @cindex thread identifier (system), on HP-UX
2297 @c FIXME-implementors!! It would be more helpful if the [New...] message
2298 @c included GDB's numeric thread handle, so you could just go to that
2299 @c thread without first checking `info threads'.
2300 Whenever @value{GDBN} detects a new thread in your program, it displays
2301 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2302 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2303 whose form varies depending on the particular system. For example, on
2307 [New thread 2 (system thread 26594)]
2311 when @value{GDBN} notices a new thread.
2314 @kindex info threads (HP-UX)
2316 Display a summary of all threads currently in your
2317 program. @value{GDBN} displays for each thread (in this order):
2320 @item the thread number assigned by @value{GDBN}
2322 @item the target system's thread identifier (@var{systag})
2324 @item the current stack frame summary for that thread
2328 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2329 indicates the current thread.
2333 @c end table here to get a little more width for example
2336 (@value{GDBP}) info threads
2337 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2339 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2340 from /usr/lib/libc.2
2341 1 system thread 27905 0x7b003498 in _brk () \@*
2342 from /usr/lib/libc.2
2345 On Solaris, you can display more information about user threads with a
2346 Solaris-specific command:
2349 @item maint info sol-threads
2350 @kindex maint info sol-threads
2351 @cindex thread info (Solaris)
2352 Display info on Solaris user threads.
2356 @kindex thread @var{threadno}
2357 @item thread @var{threadno}
2358 Make thread number @var{threadno} the current thread. The command
2359 argument @var{threadno} is the internal @value{GDBN} thread number, as
2360 shown in the first field of the @samp{info threads} display.
2361 @value{GDBN} responds by displaying the system identifier of the thread
2362 you selected, and its current stack frame summary:
2365 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2366 (@value{GDBP}) thread 2
2367 [Switching to process 35 thread 23]
2368 0x34e5 in sigpause ()
2372 As with the @samp{[New @dots{}]} message, the form of the text after
2373 @samp{Switching to} depends on your system's conventions for identifying
2376 @kindex thread apply
2377 @cindex apply command to several threads
2378 @item thread apply [@var{threadno}] [@var{all}] @var{args}
2379 The @code{thread apply} command allows you to apply a command to one or
2380 more threads. Specify the numbers of the threads that you want affected
2381 with the command argument @var{threadno}. @var{threadno} is the internal
2382 @value{GDBN} thread number, as shown in the first field of the @samp{info
2383 threads} display. To apply a command to all threads, use
2384 @code{thread apply all} @var{args}.
2387 @cindex automatic thread selection
2388 @cindex switching threads automatically
2389 @cindex threads, automatic switching
2390 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2391 signal, it automatically selects the thread where that breakpoint or
2392 signal happened. @value{GDBN} alerts you to the context switch with a
2393 message of the form @samp{[Switching to @var{systag}]} to identify the
2396 @xref{Thread Stops,,Stopping and starting multi-thread programs}, for
2397 more information about how @value{GDBN} behaves when you stop and start
2398 programs with multiple threads.
2400 @xref{Set Watchpoints,,Setting watchpoints}, for information about
2401 watchpoints in programs with multiple threads.
2404 @section Debugging programs with multiple processes
2406 @cindex fork, debugging programs which call
2407 @cindex multiple processes
2408 @cindex processes, multiple
2409 On most systems, @value{GDBN} has no special support for debugging
2410 programs which create additional processes using the @code{fork}
2411 function. When a program forks, @value{GDBN} will continue to debug the
2412 parent process and the child process will run unimpeded. If you have
2413 set a breakpoint in any code which the child then executes, the child
2414 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2415 will cause it to terminate.
2417 However, if you want to debug the child process there is a workaround
2418 which isn't too painful. Put a call to @code{sleep} in the code which
2419 the child process executes after the fork. It may be useful to sleep
2420 only if a certain environment variable is set, or a certain file exists,
2421 so that the delay need not occur when you don't want to run @value{GDBN}
2422 on the child. While the child is sleeping, use the @code{ps} program to
2423 get its process ID. Then tell @value{GDBN} (a new invocation of
2424 @value{GDBN} if you are also debugging the parent process) to attach to
2425 the child process (@pxref{Attach}). From that point on you can debug
2426 the child process just like any other process which you attached to.
2428 On some systems, @value{GDBN} provides support for debugging programs that
2429 create additional processes using the @code{fork} or @code{vfork} functions.
2430 Currently, the only platforms with this feature are HP-UX (11.x and later
2431 only?) and GNU/Linux (kernel version 2.5.60 and later).
2433 By default, when a program forks, @value{GDBN} will continue to debug
2434 the parent process and the child process will run unimpeded.
2436 If you want to follow the child process instead of the parent process,
2437 use the command @w{@code{set follow-fork-mode}}.
2440 @kindex set follow-fork-mode
2441 @item set follow-fork-mode @var{mode}
2442 Set the debugger response to a program call of @code{fork} or
2443 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2444 process. The @var{mode} argument can be:
2448 The original process is debugged after a fork. The child process runs
2449 unimpeded. This is the default.
2452 The new process is debugged after a fork. The parent process runs
2457 @kindex show follow-fork-mode
2458 @item show follow-fork-mode
2459 Display the current debugger response to a @code{fork} or @code{vfork} call.
2462 If you ask to debug a child process and a @code{vfork} is followed by an
2463 @code{exec}, @value{GDBN} executes the new target up to the first
2464 breakpoint in the new target. If you have a breakpoint set on
2465 @code{main} in your original program, the breakpoint will also be set on
2466 the child process's @code{main}.
2468 When a child process is spawned by @code{vfork}, you cannot debug the
2469 child or parent until an @code{exec} call completes.
2471 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2472 call executes, the new target restarts. To restart the parent process,
2473 use the @code{file} command with the parent executable name as its
2476 You can use the @code{catch} command to make @value{GDBN} stop whenever
2477 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2478 Catchpoints, ,Setting catchpoints}.
2481 @chapter Stopping and Continuing
2483 The principal purposes of using a debugger are so that you can stop your
2484 program before it terminates; or so that, if your program runs into
2485 trouble, you can investigate and find out why.
2487 Inside @value{GDBN}, your program may stop for any of several reasons,
2488 such as a signal, a breakpoint, or reaching a new line after a
2489 @value{GDBN} command such as @code{step}. You may then examine and
2490 change variables, set new breakpoints or remove old ones, and then
2491 continue execution. Usually, the messages shown by @value{GDBN} provide
2492 ample explanation of the status of your program---but you can also
2493 explicitly request this information at any time.
2496 @kindex info program
2498 Display information about the status of your program: whether it is
2499 running or not, what process it is, and why it stopped.
2503 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2504 * Continuing and Stepping:: Resuming execution
2506 * Thread Stops:: Stopping and starting multi-thread programs
2510 @section Breakpoints, watchpoints, and catchpoints
2513 A @dfn{breakpoint} makes your program stop whenever a certain point in
2514 the program is reached. For each breakpoint, you can add conditions to
2515 control in finer detail whether your program stops. You can set
2516 breakpoints with the @code{break} command and its variants (@pxref{Set
2517 Breaks, ,Setting breakpoints}), to specify the place where your program
2518 should stop by line number, function name or exact address in the
2521 On some systems, you can set breakpoints in shared libraries before
2522 the executable is run. There is a minor limitation on HP-UX systems:
2523 you must wait until the executable is run in order to set breakpoints
2524 in shared library routines that are not called directly by the program
2525 (for example, routines that are arguments in a @code{pthread_create}
2529 @cindex memory tracing
2530 @cindex breakpoint on memory address
2531 @cindex breakpoint on variable modification
2532 A @dfn{watchpoint} is a special breakpoint that stops your program
2533 when the value of an expression changes. You must use a different
2534 command to set watchpoints (@pxref{Set Watchpoints, ,Setting
2535 watchpoints}), but aside from that, you can manage a watchpoint like
2536 any other breakpoint: you enable, disable, and delete both breakpoints
2537 and watchpoints using the same commands.
2539 You can arrange to have values from your program displayed automatically
2540 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2544 @cindex breakpoint on events
2545 A @dfn{catchpoint} is another special breakpoint that stops your program
2546 when a certain kind of event occurs, such as the throwing of a C@t{++}
2547 exception or the loading of a library. As with watchpoints, you use a
2548 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2549 catchpoints}), but aside from that, you can manage a catchpoint like any
2550 other breakpoint. (To stop when your program receives a signal, use the
2551 @code{handle} command; see @ref{Signals, ,Signals}.)
2553 @cindex breakpoint numbers
2554 @cindex numbers for breakpoints
2555 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2556 catchpoint when you create it; these numbers are successive integers
2557 starting with one. In many of the commands for controlling various
2558 features of breakpoints you use the breakpoint number to say which
2559 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2560 @dfn{disabled}; if disabled, it has no effect on your program until you
2563 @cindex breakpoint ranges
2564 @cindex ranges of breakpoints
2565 Some @value{GDBN} commands accept a range of breakpoints on which to
2566 operate. A breakpoint range is either a single breakpoint number, like
2567 @samp{5}, or two such numbers, in increasing order, separated by a
2568 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2569 all breakpoint in that range are operated on.
2572 * Set Breaks:: Setting breakpoints
2573 * Set Watchpoints:: Setting watchpoints
2574 * Set Catchpoints:: Setting catchpoints
2575 * Delete Breaks:: Deleting breakpoints
2576 * Disabling:: Disabling breakpoints
2577 * Conditions:: Break conditions
2578 * Break Commands:: Breakpoint command lists
2579 * Breakpoint Menus:: Breakpoint menus
2580 * Error in Breakpoints:: ``Cannot insert breakpoints''
2581 * Breakpoint related warnings:: ``Breakpoint address adjusted...''
2585 @subsection Setting breakpoints
2587 @c FIXME LMB what does GDB do if no code on line of breakpt?
2588 @c consider in particular declaration with/without initialization.
2590 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2593 @kindex b @r{(@code{break})}
2594 @vindex $bpnum@r{, convenience variable}
2595 @cindex latest breakpoint
2596 Breakpoints are set with the @code{break} command (abbreviated
2597 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2598 number of the breakpoint you've set most recently; see @ref{Convenience
2599 Vars,, Convenience variables}, for a discussion of what you can do with
2600 convenience variables.
2602 You have several ways to say where the breakpoint should go.
2605 @item break @var{function}
2606 Set a breakpoint at entry to function @var{function}.
2607 When using source languages that permit overloading of symbols, such as
2608 C@t{++}, @var{function} may refer to more than one possible place to break.
2609 @xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
2611 @item break +@var{offset}
2612 @itemx break -@var{offset}
2613 Set a breakpoint some number of lines forward or back from the position
2614 at which execution stopped in the currently selected @dfn{stack frame}.
2615 (@xref{Frames, ,Frames}, for a description of stack frames.)
2617 @item break @var{linenum}
2618 Set a breakpoint at line @var{linenum} in the current source file.
2619 The current source file is the last file whose source text was printed.
2620 The breakpoint will stop your program just before it executes any of the
2623 @item break @var{filename}:@var{linenum}
2624 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2626 @item break @var{filename}:@var{function}
2627 Set a breakpoint at entry to function @var{function} found in file
2628 @var{filename}. Specifying a file name as well as a function name is
2629 superfluous except when multiple files contain similarly named
2632 @item break *@var{address}
2633 Set a breakpoint at address @var{address}. You can use this to set
2634 breakpoints in parts of your program which do not have debugging
2635 information or source files.
2638 When called without any arguments, @code{break} sets a breakpoint at
2639 the next instruction to be executed in the selected stack frame
2640 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2641 innermost, this makes your program stop as soon as control
2642 returns to that frame. This is similar to the effect of a
2643 @code{finish} command in the frame inside the selected frame---except
2644 that @code{finish} does not leave an active breakpoint. If you use
2645 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2646 the next time it reaches the current location; this may be useful
2649 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2650 least one instruction has been executed. If it did not do this, you
2651 would be unable to proceed past a breakpoint without first disabling the
2652 breakpoint. This rule applies whether or not the breakpoint already
2653 existed when your program stopped.
2655 @item break @dots{} if @var{cond}
2656 Set a breakpoint with condition @var{cond}; evaluate the expression
2657 @var{cond} each time the breakpoint is reached, and stop only if the
2658 value is nonzero---that is, if @var{cond} evaluates as true.
2659 @samp{@dots{}} stands for one of the possible arguments described
2660 above (or no argument) specifying where to break. @xref{Conditions,
2661 ,Break conditions}, for more information on breakpoint conditions.
2664 @item tbreak @var{args}
2665 Set a breakpoint enabled only for one stop. @var{args} are the
2666 same as for the @code{break} command, and the breakpoint is set in the same
2667 way, but the breakpoint is automatically deleted after the first time your
2668 program stops there. @xref{Disabling, ,Disabling breakpoints}.
2671 @cindex hardware breakpoints
2672 @item hbreak @var{args}
2673 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2674 @code{break} command and the breakpoint is set in the same way, but the
2675 breakpoint requires hardware support and some target hardware may not
2676 have this support. The main purpose of this is EPROM/ROM code
2677 debugging, so you can set a breakpoint at an instruction without
2678 changing the instruction. This can be used with the new trap-generation
2679 provided by SPARClite DSU and most x86-based targets. These targets
2680 will generate traps when a program accesses some data or instruction
2681 address that is assigned to the debug registers. However the hardware
2682 breakpoint registers can take a limited number of breakpoints. For
2683 example, on the DSU, only two data breakpoints can be set at a time, and
2684 @value{GDBN} will reject this command if more than two are used. Delete
2685 or disable unused hardware breakpoints before setting new ones
2686 (@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}.
2687 For remote targets, you can restrict the number of hardware
2688 breakpoints @value{GDBN} will use, see @ref{set remote
2689 hardware-breakpoint-limit}.
2693 @item thbreak @var{args}
2694 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2695 are the same as for the @code{hbreak} command and the breakpoint is set in
2696 the same way. However, like the @code{tbreak} command,
2697 the breakpoint is automatically deleted after the
2698 first time your program stops there. Also, like the @code{hbreak}
2699 command, the breakpoint requires hardware support and some target hardware
2700 may not have this support. @xref{Disabling, ,Disabling breakpoints}.
2701 See also @ref{Conditions, ,Break conditions}.
2704 @cindex regular expression
2705 @cindex breakpoints in functions matching a regexp
2706 @cindex set breakpoints in many functions
2707 @item rbreak @var{regex}
2708 Set breakpoints on all functions matching the regular expression
2709 @var{regex}. This command sets an unconditional breakpoint on all
2710 matches, printing a list of all breakpoints it set. Once these
2711 breakpoints are set, they are treated just like the breakpoints set with
2712 the @code{break} command. You can delete them, disable them, or make
2713 them conditional the same way as any other breakpoint.
2715 The syntax of the regular expression is the standard one used with tools
2716 like @file{grep}. Note that this is different from the syntax used by
2717 shells, so for instance @code{foo*} matches all functions that include
2718 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2719 @code{.*} leading and trailing the regular expression you supply, so to
2720 match only functions that begin with @code{foo}, use @code{^foo}.
2722 @cindex non-member C@t{++} functions, set breakpoint in
2723 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2724 breakpoints on overloaded functions that are not members of any special
2727 @cindex set breakpoints on all functions
2728 The @code{rbreak} command can be used to set breakpoints in
2729 @strong{all} the functions in a program, like this:
2732 (@value{GDBP}) rbreak .
2735 @kindex info breakpoints
2736 @cindex @code{$_} and @code{info breakpoints}
2737 @item info breakpoints @r{[}@var{n}@r{]}
2738 @itemx info break @r{[}@var{n}@r{]}
2739 @itemx info watchpoints @r{[}@var{n}@r{]}
2740 Print a table of all breakpoints, watchpoints, and catchpoints set and
2741 not deleted, with the following columns for each breakpoint:
2744 @item Breakpoint Numbers
2746 Breakpoint, watchpoint, or catchpoint.
2748 Whether the breakpoint is marked to be disabled or deleted when hit.
2749 @item Enabled or Disabled
2750 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2751 that are not enabled.
2753 Where the breakpoint is in your program, as a memory address. If the
2754 breakpoint is pending (see below for details) on a future load of a shared library, the address
2755 will be listed as @samp{<PENDING>}.
2757 Where the breakpoint is in the source for your program, as a file and
2758 line number. For a pending breakpoint, the original string passed to
2759 the breakpoint command will be listed as it cannot be resolved until
2760 the appropriate shared library is loaded in the future.
2764 If a breakpoint is conditional, @code{info break} shows the condition on
2765 the line following the affected breakpoint; breakpoint commands, if any,
2766 are listed after that. A pending breakpoint is allowed to have a condition
2767 specified for it. The condition is not parsed for validity until a shared
2768 library is loaded that allows the pending breakpoint to resolve to a
2772 @code{info break} with a breakpoint
2773 number @var{n} as argument lists only that breakpoint. The
2774 convenience variable @code{$_} and the default examining-address for
2775 the @code{x} command are set to the address of the last breakpoint
2776 listed (@pxref{Memory, ,Examining memory}).
2779 @code{info break} displays a count of the number of times the breakpoint
2780 has been hit. This is especially useful in conjunction with the
2781 @code{ignore} command. You can ignore a large number of breakpoint
2782 hits, look at the breakpoint info to see how many times the breakpoint
2783 was hit, and then run again, ignoring one less than that number. This
2784 will get you quickly to the last hit of that breakpoint.
2787 @value{GDBN} allows you to set any number of breakpoints at the same place in
2788 your program. There is nothing silly or meaningless about this. When
2789 the breakpoints are conditional, this is even useful
2790 (@pxref{Conditions, ,Break conditions}).
2792 @cindex pending breakpoints
2793 If a specified breakpoint location cannot be found, it may be due to the fact
2794 that the location is in a shared library that is yet to be loaded. In such
2795 a case, you may want @value{GDBN} to create a special breakpoint (known as
2796 a @dfn{pending breakpoint}) that
2797 attempts to resolve itself in the future when an appropriate shared library
2800 Pending breakpoints are useful to set at the start of your
2801 @value{GDBN} session for locations that you know will be dynamically loaded
2802 later by the program being debugged. When shared libraries are loaded,
2803 a check is made to see if the load resolves any pending breakpoint locations.
2804 If a pending breakpoint location gets resolved,
2805 a regular breakpoint is created and the original pending breakpoint is removed.
2807 @value{GDBN} provides some additional commands for controlling pending
2810 @kindex set breakpoint pending
2811 @kindex show breakpoint pending
2813 @item set breakpoint pending auto
2814 This is the default behavior. When @value{GDBN} cannot find the breakpoint
2815 location, it queries you whether a pending breakpoint should be created.
2817 @item set breakpoint pending on
2818 This indicates that an unrecognized breakpoint location should automatically
2819 result in a pending breakpoint being created.
2821 @item set breakpoint pending off
2822 This indicates that pending breakpoints are not to be created. Any
2823 unrecognized breakpoint location results in an error. This setting does
2824 not affect any pending breakpoints previously created.
2826 @item show breakpoint pending
2827 Show the current behavior setting for creating pending breakpoints.
2830 @cindex operations allowed on pending breakpoints
2831 Normal breakpoint operations apply to pending breakpoints as well. You may
2832 specify a condition for a pending breakpoint and/or commands to run when the
2833 breakpoint is reached. You can also enable or disable
2834 the pending breakpoint. When you specify a condition for a pending breakpoint,
2835 the parsing of the condition will be deferred until the point where the
2836 pending breakpoint location is resolved. Disabling a pending breakpoint
2837 tells @value{GDBN} to not attempt to resolve the breakpoint on any subsequent
2838 shared library load. When a pending breakpoint is re-enabled,
2839 @value{GDBN} checks to see if the location is already resolved.
2840 This is done because any number of shared library loads could have
2841 occurred since the time the breakpoint was disabled and one or more
2842 of these loads could resolve the location.
2844 @cindex negative breakpoint numbers
2845 @cindex internal @value{GDBN} breakpoints
2846 @value{GDBN} itself sometimes sets breakpoints in your program for
2847 special purposes, such as proper handling of @code{longjmp} (in C
2848 programs). These internal breakpoints are assigned negative numbers,
2849 starting with @code{-1}; @samp{info breakpoints} does not display them.
2850 You can see these breakpoints with the @value{GDBN} maintenance command
2851 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
2854 @node Set Watchpoints
2855 @subsection Setting watchpoints
2857 @cindex setting watchpoints
2858 You can use a watchpoint to stop execution whenever the value of an
2859 expression changes, without having to predict a particular place where
2862 @cindex software watchpoints
2863 @cindex hardware watchpoints
2864 Depending on your system, watchpoints may be implemented in software or
2865 hardware. @value{GDBN} does software watchpointing by single-stepping your
2866 program and testing the variable's value each time, which is hundreds of
2867 times slower than normal execution. (But this may still be worth it, to
2868 catch errors where you have no clue what part of your program is the
2871 On some systems, such as HP-UX, @sc{gnu}/Linux and most other
2872 x86-based targets, @value{GDBN} includes support for hardware
2873 watchpoints, which do not slow down the running of your program.
2877 @item watch @var{expr}
2878 Set a watchpoint for an expression. @value{GDBN} will break when @var{expr}
2879 is written into by the program and its value changes.
2882 @item rwatch @var{expr}
2883 Set a watchpoint that will break when the value of @var{expr} is read
2887 @item awatch @var{expr}
2888 Set a watchpoint that will break when @var{expr} is either read from
2889 or written into by the program.
2891 @kindex info watchpoints
2892 @item info watchpoints
2893 This command prints a list of watchpoints, breakpoints, and catchpoints;
2894 it is the same as @code{info break} (@pxref{Set Breaks}).
2897 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
2898 watchpoints execute very quickly, and the debugger reports a change in
2899 value at the exact instruction where the change occurs. If @value{GDBN}
2900 cannot set a hardware watchpoint, it sets a software watchpoint, which
2901 executes more slowly and reports the change in value at the next
2902 @emph{statement}, not the instruction, after the change occurs.
2904 @cindex use only software watchpoints
2905 You can force @value{GDBN} to use only software watchpoints with the
2906 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
2907 zero, @value{GDBN} will never try to use hardware watchpoints, even if
2908 the underlying system supports them. (Note that hardware-assisted
2909 watchpoints that were set @emph{before} setting
2910 @code{can-use-hw-watchpoints} to zero will still use the hardware
2911 mechanism of watching expressiion values.)
2914 @item set can-use-hw-watchpoints
2915 @kindex set can-use-hw-watchpoints
2916 Set whether or not to use hardware watchpoints.
2918 @item show can-use-hw-watchpoints
2919 @kindex show can-use-hw-watchpoints
2920 Show the current mode of using hardware watchpoints.
2923 For remote targets, you can restrict the number of hardware
2924 watchpoints @value{GDBN} will use, see @ref{set remote
2925 hardware-breakpoint-limit}.
2927 When you issue the @code{watch} command, @value{GDBN} reports
2930 Hardware watchpoint @var{num}: @var{expr}
2934 if it was able to set a hardware watchpoint.
2936 Currently, the @code{awatch} and @code{rwatch} commands can only set
2937 hardware watchpoints, because accesses to data that don't change the
2938 value of the watched expression cannot be detected without examining
2939 every instruction as it is being executed, and @value{GDBN} does not do
2940 that currently. If @value{GDBN} finds that it is unable to set a
2941 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
2942 will print a message like this:
2945 Expression cannot be implemented with read/access watchpoint.
2948 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
2949 data type of the watched expression is wider than what a hardware
2950 watchpoint on the target machine can handle. For example, some systems
2951 can only watch regions that are up to 4 bytes wide; on such systems you
2952 cannot set hardware watchpoints for an expression that yields a
2953 double-precision floating-point number (which is typically 8 bytes
2954 wide). As a work-around, it might be possible to break the large region
2955 into a series of smaller ones and watch them with separate watchpoints.
2957 If you set too many hardware watchpoints, @value{GDBN} might be unable
2958 to insert all of them when you resume the execution of your program.
2959 Since the precise number of active watchpoints is unknown until such
2960 time as the program is about to be resumed, @value{GDBN} might not be
2961 able to warn you about this when you set the watchpoints, and the
2962 warning will be printed only when the program is resumed:
2965 Hardware watchpoint @var{num}: Could not insert watchpoint
2969 If this happens, delete or disable some of the watchpoints.
2971 The SPARClite DSU will generate traps when a program accesses some data
2972 or instruction address that is assigned to the debug registers. For the
2973 data addresses, DSU facilitates the @code{watch} command. However the
2974 hardware breakpoint registers can only take two data watchpoints, and
2975 both watchpoints must be the same kind. For example, you can set two
2976 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
2977 @strong{or} two with @code{awatch} commands, but you cannot set one
2978 watchpoint with one command and the other with a different command.
2979 @value{GDBN} will reject the command if you try to mix watchpoints.
2980 Delete or disable unused watchpoint commands before setting new ones.
2982 If you call a function interactively using @code{print} or @code{call},
2983 any watchpoints you have set will be inactive until @value{GDBN} reaches another
2984 kind of breakpoint or the call completes.
2986 @value{GDBN} automatically deletes watchpoints that watch local
2987 (automatic) variables, or expressions that involve such variables, when
2988 they go out of scope, that is, when the execution leaves the block in
2989 which these variables were defined. In particular, when the program
2990 being debugged terminates, @emph{all} local variables go out of scope,
2991 and so only watchpoints that watch global variables remain set. If you
2992 rerun the program, you will need to set all such watchpoints again. One
2993 way of doing that would be to set a code breakpoint at the entry to the
2994 @code{main} function and when it breaks, set all the watchpoints.
2997 @cindex watchpoints and threads
2998 @cindex threads and watchpoints
2999 @emph{Warning:} In multi-thread programs, watchpoints have only limited
3000 usefulness. With the current watchpoint implementation, @value{GDBN}
3001 can only watch the value of an expression @emph{in a single thread}. If
3002 you are confident that the expression can only change due to the current
3003 thread's activity (and if you are also confident that no other thread
3004 can become current), then you can use watchpoints as usual. However,
3005 @value{GDBN} may not notice when a non-current thread's activity changes
3008 @c FIXME: this is almost identical to the previous paragraph.
3009 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
3010 have only limited usefulness. If @value{GDBN} creates a software
3011 watchpoint, it can only watch the value of an expression @emph{in a
3012 single thread}. If you are confident that the expression can only
3013 change due to the current thread's activity (and if you are also
3014 confident that no other thread can become current), then you can use
3015 software watchpoints as usual. However, @value{GDBN} may not notice
3016 when a non-current thread's activity changes the expression. (Hardware
3017 watchpoints, in contrast, watch an expression in all threads.)
3020 @xref{set remote hardware-watchpoint-limit}.
3022 @node Set Catchpoints
3023 @subsection Setting catchpoints
3024 @cindex catchpoints, setting
3025 @cindex exception handlers
3026 @cindex event handling
3028 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3029 kinds of program events, such as C@t{++} exceptions or the loading of a
3030 shared library. Use the @code{catch} command to set a catchpoint.
3034 @item catch @var{event}
3035 Stop when @var{event} occurs. @var{event} can be any of the following:
3038 @cindex stop on C@t{++} exceptions
3039 The throwing of a C@t{++} exception.
3042 The catching of a C@t{++} exception.
3045 @cindex break on fork/exec
3046 A call to @code{exec}. This is currently only available for HP-UX.
3049 A call to @code{fork}. This is currently only available for HP-UX.
3052 A call to @code{vfork}. This is currently only available for HP-UX.
3055 @itemx load @var{libname}
3056 @cindex break on load/unload of shared library
3057 The dynamic loading of any shared library, or the loading of the library
3058 @var{libname}. This is currently only available for HP-UX.
3061 @itemx unload @var{libname}
3062 The unloading of any dynamically loaded shared library, or the unloading
3063 of the library @var{libname}. This is currently only available for HP-UX.
3066 @item tcatch @var{event}
3067 Set a catchpoint that is enabled only for one stop. The catchpoint is
3068 automatically deleted after the first time the event is caught.
3072 Use the @code{info break} command to list the current catchpoints.
3074 There are currently some limitations to C@t{++} exception handling
3075 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3079 If you call a function interactively, @value{GDBN} normally returns
3080 control to you when the function has finished executing. If the call
3081 raises an exception, however, the call may bypass the mechanism that
3082 returns control to you and cause your program either to abort or to
3083 simply continue running until it hits a breakpoint, catches a signal
3084 that @value{GDBN} is listening for, or exits. This is the case even if
3085 you set a catchpoint for the exception; catchpoints on exceptions are
3086 disabled within interactive calls.
3089 You cannot raise an exception interactively.
3092 You cannot install an exception handler interactively.
3095 @cindex raise exceptions
3096 Sometimes @code{catch} is not the best way to debug exception handling:
3097 if you need to know exactly where an exception is raised, it is better to
3098 stop @emph{before} the exception handler is called, since that way you
3099 can see the stack before any unwinding takes place. If you set a
3100 breakpoint in an exception handler instead, it may not be easy to find
3101 out where the exception was raised.
3103 To stop just before an exception handler is called, you need some
3104 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3105 raised by calling a library function named @code{__raise_exception}
3106 which has the following ANSI C interface:
3109 /* @var{addr} is where the exception identifier is stored.
3110 @var{id} is the exception identifier. */
3111 void __raise_exception (void **addr, void *id);
3115 To make the debugger catch all exceptions before any stack
3116 unwinding takes place, set a breakpoint on @code{__raise_exception}
3117 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
3119 With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
3120 that depends on the value of @var{id}, you can stop your program when
3121 a specific exception is raised. You can use multiple conditional
3122 breakpoints to stop your program when any of a number of exceptions are
3127 @subsection Deleting breakpoints
3129 @cindex clearing breakpoints, watchpoints, catchpoints
3130 @cindex deleting breakpoints, watchpoints, catchpoints
3131 It is often necessary to eliminate a breakpoint, watchpoint, or
3132 catchpoint once it has done its job and you no longer want your program
3133 to stop there. This is called @dfn{deleting} the breakpoint. A
3134 breakpoint that has been deleted no longer exists; it is forgotten.
3136 With the @code{clear} command you can delete breakpoints according to
3137 where they are in your program. With the @code{delete} command you can
3138 delete individual breakpoints, watchpoints, or catchpoints by specifying
3139 their breakpoint numbers.
3141 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3142 automatically ignores breakpoints on the first instruction to be executed
3143 when you continue execution without changing the execution address.
3148 Delete any breakpoints at the next instruction to be executed in the
3149 selected stack frame (@pxref{Selection, ,Selecting a frame}). When
3150 the innermost frame is selected, this is a good way to delete a
3151 breakpoint where your program just stopped.
3153 @item clear @var{function}
3154 @itemx clear @var{filename}:@var{function}
3155 Delete any breakpoints set at entry to the named @var{function}.
3157 @item clear @var{linenum}
3158 @itemx clear @var{filename}:@var{linenum}
3159 Delete any breakpoints set at or within the code of the specified
3160 @var{linenum} of the specified @var{filename}.
3162 @cindex delete breakpoints
3164 @kindex d @r{(@code{delete})}
3165 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3166 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3167 ranges specified as arguments. If no argument is specified, delete all
3168 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3169 confirm off}). You can abbreviate this command as @code{d}.
3173 @subsection Disabling breakpoints
3175 @cindex enable/disable a breakpoint
3176 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3177 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3178 it had been deleted, but remembers the information on the breakpoint so
3179 that you can @dfn{enable} it again later.
3181 You disable and enable breakpoints, watchpoints, and catchpoints with
3182 the @code{enable} and @code{disable} commands, optionally specifying one
3183 or more breakpoint numbers as arguments. Use @code{info break} or
3184 @code{info watch} to print a list of breakpoints, watchpoints, and
3185 catchpoints if you do not know which numbers to use.
3187 A breakpoint, watchpoint, or catchpoint can have any of four different
3188 states of enablement:
3192 Enabled. The breakpoint stops your program. A breakpoint set
3193 with the @code{break} command starts out in this state.
3195 Disabled. The breakpoint has no effect on your program.
3197 Enabled once. The breakpoint stops your program, but then becomes
3200 Enabled for deletion. The breakpoint stops your program, but
3201 immediately after it does so it is deleted permanently. A breakpoint
3202 set with the @code{tbreak} command starts out in this state.
3205 You can use the following commands to enable or disable breakpoints,
3206 watchpoints, and catchpoints:
3210 @kindex dis @r{(@code{disable})}
3211 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3212 Disable the specified breakpoints---or all breakpoints, if none are
3213 listed. A disabled breakpoint has no effect but is not forgotten. All
3214 options such as ignore-counts, conditions and commands are remembered in
3215 case the breakpoint is enabled again later. You may abbreviate
3216 @code{disable} as @code{dis}.
3219 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3220 Enable the specified breakpoints (or all defined breakpoints). They
3221 become effective once again in stopping your program.
3223 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3224 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3225 of these breakpoints immediately after stopping your program.
3227 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3228 Enable the specified breakpoints to work once, then die. @value{GDBN}
3229 deletes any of these breakpoints as soon as your program stops there.
3230 Breakpoints set by the @code{tbreak} command start out in this state.
3233 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3234 @c confusing: tbreak is also initially enabled.
3235 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3236 ,Setting breakpoints}), breakpoints that you set are initially enabled;
3237 subsequently, they become disabled or enabled only when you use one of
3238 the commands above. (The command @code{until} can set and delete a
3239 breakpoint of its own, but it does not change the state of your other
3240 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3244 @subsection Break conditions
3245 @cindex conditional breakpoints
3246 @cindex breakpoint conditions
3248 @c FIXME what is scope of break condition expr? Context where wanted?
3249 @c in particular for a watchpoint?
3250 The simplest sort of breakpoint breaks every time your program reaches a
3251 specified place. You can also specify a @dfn{condition} for a
3252 breakpoint. A condition is just a Boolean expression in your
3253 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3254 a condition evaluates the expression each time your program reaches it,
3255 and your program stops only if the condition is @emph{true}.
3257 This is the converse of using assertions for program validation; in that
3258 situation, you want to stop when the assertion is violated---that is,
3259 when the condition is false. In C, if you want to test an assertion expressed
3260 by the condition @var{assert}, you should set the condition
3261 @samp{! @var{assert}} on the appropriate breakpoint.
3263 Conditions are also accepted for watchpoints; you may not need them,
3264 since a watchpoint is inspecting the value of an expression anyhow---but
3265 it might be simpler, say, to just set a watchpoint on a variable name,
3266 and specify a condition that tests whether the new value is an interesting
3269 Break conditions can have side effects, and may even call functions in
3270 your program. This can be useful, for example, to activate functions
3271 that log program progress, or to use your own print functions to
3272 format special data structures. The effects are completely predictable
3273 unless there is another enabled breakpoint at the same address. (In
3274 that case, @value{GDBN} might see the other breakpoint first and stop your
3275 program without checking the condition of this one.) Note that
3276 breakpoint commands are usually more convenient and flexible than break
3278 purpose of performing side effects when a breakpoint is reached
3279 (@pxref{Break Commands, ,Breakpoint command lists}).
3281 Break conditions can be specified when a breakpoint is set, by using
3282 @samp{if} in the arguments to the @code{break} command. @xref{Set
3283 Breaks, ,Setting breakpoints}. They can also be changed at any time
3284 with the @code{condition} command.
3286 You can also use the @code{if} keyword with the @code{watch} command.
3287 The @code{catch} command does not recognize the @code{if} keyword;
3288 @code{condition} is the only way to impose a further condition on a
3293 @item condition @var{bnum} @var{expression}
3294 Specify @var{expression} as the break condition for breakpoint,
3295 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3296 breakpoint @var{bnum} stops your program only if the value of
3297 @var{expression} is true (nonzero, in C). When you use
3298 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3299 syntactic correctness, and to determine whether symbols in it have
3300 referents in the context of your breakpoint. If @var{expression} uses
3301 symbols not referenced in the context of the breakpoint, @value{GDBN}
3302 prints an error message:
3305 No symbol "foo" in current context.
3310 not actually evaluate @var{expression} at the time the @code{condition}
3311 command (or a command that sets a breakpoint with a condition, like
3312 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3314 @item condition @var{bnum}
3315 Remove the condition from breakpoint number @var{bnum}. It becomes
3316 an ordinary unconditional breakpoint.
3319 @cindex ignore count (of breakpoint)
3320 A special case of a breakpoint condition is to stop only when the
3321 breakpoint has been reached a certain number of times. This is so
3322 useful that there is a special way to do it, using the @dfn{ignore
3323 count} of the breakpoint. Every breakpoint has an ignore count, which
3324 is an integer. Most of the time, the ignore count is zero, and
3325 therefore has no effect. But if your program reaches a breakpoint whose
3326 ignore count is positive, then instead of stopping, it just decrements
3327 the ignore count by one and continues. As a result, if the ignore count
3328 value is @var{n}, the breakpoint does not stop the next @var{n} times
3329 your program reaches it.
3333 @item ignore @var{bnum} @var{count}
3334 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3335 The next @var{count} times the breakpoint is reached, your program's
3336 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3339 To make the breakpoint stop the next time it is reached, specify
3342 When you use @code{continue} to resume execution of your program from a
3343 breakpoint, you can specify an ignore count directly as an argument to
3344 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3345 Stepping,,Continuing and stepping}.
3347 If a breakpoint has a positive ignore count and a condition, the
3348 condition is not checked. Once the ignore count reaches zero,
3349 @value{GDBN} resumes checking the condition.
3351 You could achieve the effect of the ignore count with a condition such
3352 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3353 is decremented each time. @xref{Convenience Vars, ,Convenience
3357 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3360 @node Break Commands
3361 @subsection Breakpoint command lists
3363 @cindex breakpoint commands
3364 You can give any breakpoint (or watchpoint or catchpoint) a series of
3365 commands to execute when your program stops due to that breakpoint. For
3366 example, you might want to print the values of certain expressions, or
3367 enable other breakpoints.
3372 @item commands @r{[}@var{bnum}@r{]}
3373 @itemx @dots{} @var{command-list} @dots{}
3375 Specify a list of commands for breakpoint number @var{bnum}. The commands
3376 themselves appear on the following lines. Type a line containing just
3377 @code{end} to terminate the commands.
3379 To remove all commands from a breakpoint, type @code{commands} and
3380 follow it immediately with @code{end}; that is, give no commands.
3382 With no @var{bnum} argument, @code{commands} refers to the last
3383 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3384 recently encountered).
3387 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3388 disabled within a @var{command-list}.
3390 You can use breakpoint commands to start your program up again. Simply
3391 use the @code{continue} command, or @code{step}, or any other command
3392 that resumes execution.
3394 Any other commands in the command list, after a command that resumes
3395 execution, are ignored. This is because any time you resume execution
3396 (even with a simple @code{next} or @code{step}), you may encounter
3397 another breakpoint---which could have its own command list, leading to
3398 ambiguities about which list to execute.
3401 If the first command you specify in a command list is @code{silent}, the
3402 usual message about stopping at a breakpoint is not printed. This may
3403 be desirable for breakpoints that are to print a specific message and
3404 then continue. If none of the remaining commands print anything, you
3405 see no sign that the breakpoint was reached. @code{silent} is
3406 meaningful only at the beginning of a breakpoint command list.
3408 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3409 print precisely controlled output, and are often useful in silent
3410 breakpoints. @xref{Output, ,Commands for controlled output}.
3412 For example, here is how you could use breakpoint commands to print the
3413 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3419 printf "x is %d\n",x
3424 One application for breakpoint commands is to compensate for one bug so
3425 you can test for another. Put a breakpoint just after the erroneous line
3426 of code, give it a condition to detect the case in which something
3427 erroneous has been done, and give it commands to assign correct values
3428 to any variables that need them. End with the @code{continue} command
3429 so that your program does not stop, and start with the @code{silent}
3430 command so that no output is produced. Here is an example:
3441 @node Breakpoint Menus
3442 @subsection Breakpoint menus
3444 @cindex symbol overloading
3446 Some programming languages (notably C@t{++} and Objective-C) permit a
3447 single function name
3448 to be defined several times, for application in different contexts.
3449 This is called @dfn{overloading}. When a function name is overloaded,
3450 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3451 a breakpoint. If you realize this is a problem, you can use
3452 something like @samp{break @var{function}(@var{types})} to specify which
3453 particular version of the function you want. Otherwise, @value{GDBN} offers
3454 you a menu of numbered choices for different possible breakpoints, and
3455 waits for your selection with the prompt @samp{>}. The first two
3456 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3457 sets a breakpoint at each definition of @var{function}, and typing
3458 @kbd{0} aborts the @code{break} command without setting any new
3461 For example, the following session excerpt shows an attempt to set a
3462 breakpoint at the overloaded symbol @code{String::after}.
3463 We choose three particular definitions of that function name:
3465 @c FIXME! This is likely to change to show arg type lists, at least
3468 (@value{GDBP}) b String::after
3471 [2] file:String.cc; line number:867
3472 [3] file:String.cc; line number:860
3473 [4] file:String.cc; line number:875
3474 [5] file:String.cc; line number:853
3475 [6] file:String.cc; line number:846
3476 [7] file:String.cc; line number:735
3478 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3479 Breakpoint 2 at 0xb344: file String.cc, line 875.
3480 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3481 Multiple breakpoints were set.
3482 Use the "delete" command to delete unwanted
3488 @c @ifclear BARETARGET
3489 @node Error in Breakpoints
3490 @subsection ``Cannot insert breakpoints''
3492 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3494 Under some operating systems, breakpoints cannot be used in a program if
3495 any other process is running that program. In this situation,
3496 attempting to run or continue a program with a breakpoint causes
3497 @value{GDBN} to print an error message:
3500 Cannot insert breakpoints.
3501 The same program may be running in another process.
3504 When this happens, you have three ways to proceed:
3508 Remove or disable the breakpoints, then continue.
3511 Suspend @value{GDBN}, and copy the file containing your program to a new
3512 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3513 that @value{GDBN} should run your program under that name.
3514 Then start your program again.
3517 Relink your program so that the text segment is nonsharable, using the
3518 linker option @samp{-N}. The operating system limitation may not apply
3519 to nonsharable executables.
3523 A similar message can be printed if you request too many active
3524 hardware-assisted breakpoints and watchpoints:
3526 @c FIXME: the precise wording of this message may change; the relevant
3527 @c source change is not committed yet (Sep 3, 1999).
3529 Stopped; cannot insert breakpoints.
3530 You may have requested too many hardware breakpoints and watchpoints.
3534 This message is printed when you attempt to resume the program, since
3535 only then @value{GDBN} knows exactly how many hardware breakpoints and
3536 watchpoints it needs to insert.
3538 When this message is printed, you need to disable or remove some of the
3539 hardware-assisted breakpoints and watchpoints, and then continue.
3541 @node Breakpoint related warnings
3542 @subsection ``Breakpoint address adjusted...''
3543 @cindex breakpoint address adjusted
3545 Some processor architectures place constraints on the addresses at
3546 which breakpoints may be placed. For architectures thus constrained,
3547 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3548 with the constraints dictated by the architecture.
3550 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3551 a VLIW architecture in which a number of RISC-like instructions may be
3552 bundled together for parallel execution. The FR-V architecture
3553 constrains the location of a breakpoint instruction within such a
3554 bundle to the instruction with the lowest address. @value{GDBN}
3555 honors this constraint by adjusting a breakpoint's address to the
3556 first in the bundle.
3558 It is not uncommon for optimized code to have bundles which contain
3559 instructions from different source statements, thus it may happen that
3560 a breakpoint's address will be adjusted from one source statement to
3561 another. Since this adjustment may significantly alter @value{GDBN}'s
3562 breakpoint related behavior from what the user expects, a warning is
3563 printed when the breakpoint is first set and also when the breakpoint
3566 A warning like the one below is printed when setting a breakpoint
3567 that's been subject to address adjustment:
3570 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3573 Such warnings are printed both for user settable and @value{GDBN}'s
3574 internal breakpoints. If you see one of these warnings, you should
3575 verify that a breakpoint set at the adjusted address will have the
3576 desired affect. If not, the breakpoint in question may be removed and
3577 other breakpoints may be set which will have the desired behavior.
3578 E.g., it may be sufficient to place the breakpoint at a later
3579 instruction. A conditional breakpoint may also be useful in some
3580 cases to prevent the breakpoint from triggering too often.
3582 @value{GDBN} will also issue a warning when stopping at one of these
3583 adjusted breakpoints:
3586 warning: Breakpoint 1 address previously adjusted from 0x00010414
3590 When this warning is encountered, it may be too late to take remedial
3591 action except in cases where the breakpoint is hit earlier or more
3592 frequently than expected.
3594 @node Continuing and Stepping
3595 @section Continuing and stepping
3599 @cindex resuming execution
3600 @dfn{Continuing} means resuming program execution until your program
3601 completes normally. In contrast, @dfn{stepping} means executing just
3602 one more ``step'' of your program, where ``step'' may mean either one
3603 line of source code, or one machine instruction (depending on what
3604 particular command you use). Either when continuing or when stepping,
3605 your program may stop even sooner, due to a breakpoint or a signal. (If
3606 it stops due to a signal, you may want to use @code{handle}, or use
3607 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3611 @kindex c @r{(@code{continue})}
3612 @kindex fg @r{(resume foreground execution)}
3613 @item continue @r{[}@var{ignore-count}@r{]}
3614 @itemx c @r{[}@var{ignore-count}@r{]}
3615 @itemx fg @r{[}@var{ignore-count}@r{]}
3616 Resume program execution, at the address where your program last stopped;
3617 any breakpoints set at that address are bypassed. The optional argument
3618 @var{ignore-count} allows you to specify a further number of times to
3619 ignore a breakpoint at this location; its effect is like that of
3620 @code{ignore} (@pxref{Conditions, ,Break conditions}).
3622 The argument @var{ignore-count} is meaningful only when your program
3623 stopped due to a breakpoint. At other times, the argument to
3624 @code{continue} is ignored.
3626 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3627 debugged program is deemed to be the foreground program) are provided
3628 purely for convenience, and have exactly the same behavior as
3632 To resume execution at a different place, you can use @code{return}
3633 (@pxref{Returning, ,Returning from a function}) to go back to the
3634 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3635 different address}) to go to an arbitrary location in your program.
3637 A typical technique for using stepping is to set a breakpoint
3638 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the
3639 beginning of the function or the section of your program where a problem
3640 is believed to lie, run your program until it stops at that breakpoint,
3641 and then step through the suspect area, examining the variables that are
3642 interesting, until you see the problem happen.
3646 @kindex s @r{(@code{step})}
3648 Continue running your program until control reaches a different source
3649 line, then stop it and return control to @value{GDBN}. This command is
3650 abbreviated @code{s}.
3653 @c "without debugging information" is imprecise; actually "without line
3654 @c numbers in the debugging information". (gcc -g1 has debugging info but
3655 @c not line numbers). But it seems complex to try to make that
3656 @c distinction here.
3657 @emph{Warning:} If you use the @code{step} command while control is
3658 within a function that was compiled without debugging information,
3659 execution proceeds until control reaches a function that does have
3660 debugging information. Likewise, it will not step into a function which
3661 is compiled without debugging information. To step through functions
3662 without debugging information, use the @code{stepi} command, described
3666 The @code{step} command only stops at the first instruction of a source
3667 line. This prevents the multiple stops that could otherwise occur in
3668 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3669 to stop if a function that has debugging information is called within
3670 the line. In other words, @code{step} @emph{steps inside} any functions
3671 called within the line.
3673 Also, the @code{step} command only enters a function if there is line
3674 number information for the function. Otherwise it acts like the
3675 @code{next} command. This avoids problems when using @code{cc -gl}
3676 on MIPS machines. Previously, @code{step} entered subroutines if there
3677 was any debugging information about the routine.
3679 @item step @var{count}
3680 Continue running as in @code{step}, but do so @var{count} times. If a
3681 breakpoint is reached, or a signal not related to stepping occurs before
3682 @var{count} steps, stepping stops right away.
3685 @kindex n @r{(@code{next})}
3686 @item next @r{[}@var{count}@r{]}
3687 Continue to the next source line in the current (innermost) stack frame.
3688 This is similar to @code{step}, but function calls that appear within
3689 the line of code are executed without stopping. Execution stops when
3690 control reaches a different line of code at the original stack level
3691 that was executing when you gave the @code{next} command. This command
3692 is abbreviated @code{n}.
3694 An argument @var{count} is a repeat count, as for @code{step}.
3697 @c FIX ME!! Do we delete this, or is there a way it fits in with
3698 @c the following paragraph? --- Vctoria
3700 @c @code{next} within a function that lacks debugging information acts like
3701 @c @code{step}, but any function calls appearing within the code of the
3702 @c function are executed without stopping.
3704 The @code{next} command only stops at the first instruction of a
3705 source line. This prevents multiple stops that could otherwise occur in
3706 @code{switch} statements, @code{for} loops, etc.
3708 @kindex set step-mode
3710 @cindex functions without line info, and stepping
3711 @cindex stepping into functions with no line info
3712 @itemx set step-mode on
3713 The @code{set step-mode on} command causes the @code{step} command to
3714 stop at the first instruction of a function which contains no debug line
3715 information rather than stepping over it.
3717 This is useful in cases where you may be interested in inspecting the
3718 machine instructions of a function which has no symbolic info and do not
3719 want @value{GDBN} to automatically skip over this function.
3721 @item set step-mode off
3722 Causes the @code{step} command to step over any functions which contains no
3723 debug information. This is the default.
3725 @item show step-mode
3726 Show whether @value{GDBN} will stop in or step over functions without
3727 source line debug information.
3731 Continue running until just after function in the selected stack frame
3732 returns. Print the returned value (if any).
3734 Contrast this with the @code{return} command (@pxref{Returning,
3735 ,Returning from a function}).
3738 @kindex u @r{(@code{until})}
3739 @cindex run until specified location
3742 Continue running until a source line past the current line, in the
3743 current stack frame, is reached. This command is used to avoid single
3744 stepping through a loop more than once. It is like the @code{next}
3745 command, except that when @code{until} encounters a jump, it
3746 automatically continues execution until the program counter is greater
3747 than the address of the jump.
3749 This means that when you reach the end of a loop after single stepping
3750 though it, @code{until} makes your program continue execution until it
3751 exits the loop. In contrast, a @code{next} command at the end of a loop
3752 simply steps back to the beginning of the loop, which forces you to step
3753 through the next iteration.
3755 @code{until} always stops your program if it attempts to exit the current
3758 @code{until} may produce somewhat counterintuitive results if the order
3759 of machine code does not match the order of the source lines. For
3760 example, in the following excerpt from a debugging session, the @code{f}
3761 (@code{frame}) command shows that execution is stopped at line
3762 @code{206}; yet when we use @code{until}, we get to line @code{195}:
3766 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
3768 (@value{GDBP}) until
3769 195 for ( ; argc > 0; NEXTARG) @{
3772 This happened because, for execution efficiency, the compiler had
3773 generated code for the loop closure test at the end, rather than the
3774 start, of the loop---even though the test in a C @code{for}-loop is
3775 written before the body of the loop. The @code{until} command appeared
3776 to step back to the beginning of the loop when it advanced to this
3777 expression; however, it has not really gone to an earlier
3778 statement---not in terms of the actual machine code.
3780 @code{until} with no argument works by means of single
3781 instruction stepping, and hence is slower than @code{until} with an
3784 @item until @var{location}
3785 @itemx u @var{location}
3786 Continue running your program until either the specified location is
3787 reached, or the current stack frame returns. @var{location} is any of
3788 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
3789 ,Setting breakpoints}). This form of the command uses breakpoints, and
3790 hence is quicker than @code{until} without an argument. The specified
3791 location is actually reached only if it is in the current frame. This
3792 implies that @code{until} can be used to skip over recursive function
3793 invocations. For instance in the code below, if the current location is
3794 line @code{96}, issuing @code{until 99} will execute the program up to
3795 line @code{99} in the same invocation of factorial, i.e. after the inner
3796 invocations have returned.
3799 94 int factorial (int value)
3801 96 if (value > 1) @{
3802 97 value *= factorial (value - 1);
3809 @kindex advance @var{location}
3810 @itemx advance @var{location}
3811 Continue running the program up to the given @var{location}. An argument is
3812 required, which should be of the same form as arguments for the @code{break}
3813 command. Execution will also stop upon exit from the current stack
3814 frame. This command is similar to @code{until}, but @code{advance} will
3815 not skip over recursive function calls, and the target location doesn't
3816 have to be in the same frame as the current one.
3820 @kindex si @r{(@code{stepi})}
3822 @itemx stepi @var{arg}
3824 Execute one machine instruction, then stop and return to the debugger.
3826 It is often useful to do @samp{display/i $pc} when stepping by machine
3827 instructions. This makes @value{GDBN} automatically display the next
3828 instruction to be executed, each time your program stops. @xref{Auto
3829 Display,, Automatic display}.
3831 An argument is a repeat count, as in @code{step}.
3835 @kindex ni @r{(@code{nexti})}
3837 @itemx nexti @var{arg}
3839 Execute one machine instruction, but if it is a function call,
3840 proceed until the function returns.
3842 An argument is a repeat count, as in @code{next}.
3849 A signal is an asynchronous event that can happen in a program. The
3850 operating system defines the possible kinds of signals, and gives each
3851 kind a name and a number. For example, in Unix @code{SIGINT} is the
3852 signal a program gets when you type an interrupt character (often @kbd{C-c});
3853 @code{SIGSEGV} is the signal a program gets from referencing a place in
3854 memory far away from all the areas in use; @code{SIGALRM} occurs when
3855 the alarm clock timer goes off (which happens only if your program has
3856 requested an alarm).
3858 @cindex fatal signals
3859 Some signals, including @code{SIGALRM}, are a normal part of the
3860 functioning of your program. Others, such as @code{SIGSEGV}, indicate
3861 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
3862 program has not specified in advance some other way to handle the signal.
3863 @code{SIGINT} does not indicate an error in your program, but it is normally
3864 fatal so it can carry out the purpose of the interrupt: to kill the program.
3866 @value{GDBN} has the ability to detect any occurrence of a signal in your
3867 program. You can tell @value{GDBN} in advance what to do for each kind of
3870 @cindex handling signals
3871 Normally, @value{GDBN} is set up to let the non-erroneous signals like
3872 @code{SIGALRM} be silently passed to your program
3873 (so as not to interfere with their role in the program's functioning)
3874 but to stop your program immediately whenever an error signal happens.
3875 You can change these settings with the @code{handle} command.
3878 @kindex info signals
3882 Print a table of all the kinds of signals and how @value{GDBN} has been told to
3883 handle each one. You can use this to see the signal numbers of all
3884 the defined types of signals.
3886 @code{info handle} is an alias for @code{info signals}.
3889 @item handle @var{signal} @var{keywords}@dots{}
3890 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
3891 can be the number of a signal or its name (with or without the
3892 @samp{SIG} at the beginning); a list of signal numbers of the form
3893 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
3894 known signals. The @var{keywords} say what change to make.
3898 The keywords allowed by the @code{handle} command can be abbreviated.
3899 Their full names are:
3903 @value{GDBN} should not stop your program when this signal happens. It may
3904 still print a message telling you that the signal has come in.
3907 @value{GDBN} should stop your program when this signal happens. This implies
3908 the @code{print} keyword as well.
3911 @value{GDBN} should print a message when this signal happens.
3914 @value{GDBN} should not mention the occurrence of the signal at all. This
3915 implies the @code{nostop} keyword as well.
3919 @value{GDBN} should allow your program to see this signal; your program
3920 can handle the signal, or else it may terminate if the signal is fatal
3921 and not handled. @code{pass} and @code{noignore} are synonyms.
3925 @value{GDBN} should not allow your program to see this signal.
3926 @code{nopass} and @code{ignore} are synonyms.
3930 When a signal stops your program, the signal is not visible to the
3932 continue. Your program sees the signal then, if @code{pass} is in
3933 effect for the signal in question @emph{at that time}. In other words,
3934 after @value{GDBN} reports a signal, you can use the @code{handle}
3935 command with @code{pass} or @code{nopass} to control whether your
3936 program sees that signal when you continue.
3938 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
3939 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
3940 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
3943 You can also use the @code{signal} command to prevent your program from
3944 seeing a signal, or cause it to see a signal it normally would not see,
3945 or to give it any signal at any time. For example, if your program stopped
3946 due to some sort of memory reference error, you might store correct
3947 values into the erroneous variables and continue, hoping to see more
3948 execution; but your program would probably terminate immediately as
3949 a result of the fatal signal once it saw the signal. To prevent this,
3950 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
3954 @section Stopping and starting multi-thread programs
3956 When your program has multiple threads (@pxref{Threads,, Debugging
3957 programs with multiple threads}), you can choose whether to set
3958 breakpoints on all threads, or on a particular thread.
3961 @cindex breakpoints and threads
3962 @cindex thread breakpoints
3963 @kindex break @dots{} thread @var{threadno}
3964 @item break @var{linespec} thread @var{threadno}
3965 @itemx break @var{linespec} thread @var{threadno} if @dots{}
3966 @var{linespec} specifies source lines; there are several ways of
3967 writing them, but the effect is always to specify some source line.
3969 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
3970 to specify that you only want @value{GDBN} to stop the program when a
3971 particular thread reaches this breakpoint. @var{threadno} is one of the
3972 numeric thread identifiers assigned by @value{GDBN}, shown in the first
3973 column of the @samp{info threads} display.
3975 If you do not specify @samp{thread @var{threadno}} when you set a
3976 breakpoint, the breakpoint applies to @emph{all} threads of your
3979 You can use the @code{thread} qualifier on conditional breakpoints as
3980 well; in this case, place @samp{thread @var{threadno}} before the
3981 breakpoint condition, like this:
3984 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
3989 @cindex stopped threads
3990 @cindex threads, stopped
3991 Whenever your program stops under @value{GDBN} for any reason,
3992 @emph{all} threads of execution stop, not just the current thread. This
3993 allows you to examine the overall state of the program, including
3994 switching between threads, without worrying that things may change
3997 @cindex thread breakpoints and system calls
3998 @cindex system calls and thread breakpoints
3999 @cindex premature return from system calls
4000 There is an unfortunate side effect. If one thread stops for a
4001 breakpoint, or for some other reason, and another thread is blocked in a
4002 system call, then the system call may return prematurely. This is a
4003 consequence of the interaction between multiple threads and the signals
4004 that @value{GDBN} uses to implement breakpoints and other events that
4007 To handle this problem, your program should check the return value of
4008 each system call and react appropriately. This is good programming
4011 For example, do not write code like this:
4017 The call to @code{sleep} will return early if a different thread stops
4018 at a breakpoint or for some other reason.
4020 Instead, write this:
4025 unslept = sleep (unslept);
4028 A system call is allowed to return early, so the system is still
4029 conforming to its specification. But @value{GDBN} does cause your
4030 multi-threaded program to behave differently than it would without
4033 Also, @value{GDBN} uses internal breakpoints in the thread library to
4034 monitor certain events such as thread creation and thread destruction.
4035 When such an event happens, a system call in another thread may return
4036 prematurely, even though your program does not appear to stop.
4038 @cindex continuing threads
4039 @cindex threads, continuing
4040 Conversely, whenever you restart the program, @emph{all} threads start
4041 executing. @emph{This is true even when single-stepping} with commands
4042 like @code{step} or @code{next}.
4044 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4045 Since thread scheduling is up to your debugging target's operating
4046 system (not controlled by @value{GDBN}), other threads may
4047 execute more than one statement while the current thread completes a
4048 single step. Moreover, in general other threads stop in the middle of a
4049 statement, rather than at a clean statement boundary, when the program
4052 You might even find your program stopped in another thread after
4053 continuing or even single-stepping. This happens whenever some other
4054 thread runs into a breakpoint, a signal, or an exception before the
4055 first thread completes whatever you requested.
4057 On some OSes, you can lock the OS scheduler and thus allow only a single
4061 @item set scheduler-locking @var{mode}
4062 @cindex scheduler locking mode
4063 @cindex lock scheduler
4064 Set the scheduler locking mode. If it is @code{off}, then there is no
4065 locking and any thread may run at any time. If @code{on}, then only the
4066 current thread may run when the inferior is resumed. The @code{step}
4067 mode optimizes for single-stepping. It stops other threads from
4068 ``seizing the prompt'' by preempting the current thread while you are
4069 stepping. Other threads will only rarely (or never) get a chance to run
4070 when you step. They are more likely to run when you @samp{next} over a
4071 function call, and they are completely free to run when you use commands
4072 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4073 thread hits a breakpoint during its timeslice, they will never steal the
4074 @value{GDBN} prompt away from the thread that you are debugging.
4076 @item show scheduler-locking
4077 Display the current scheduler locking mode.
4082 @chapter Examining the Stack
4084 When your program has stopped, the first thing you need to know is where it
4085 stopped and how it got there.
4088 Each time your program performs a function call, information about the call
4090 That information includes the location of the call in your program,
4091 the arguments of the call,
4092 and the local variables of the function being called.
4093 The information is saved in a block of data called a @dfn{stack frame}.
4094 The stack frames are allocated in a region of memory called the @dfn{call
4097 When your program stops, the @value{GDBN} commands for examining the
4098 stack allow you to see all of this information.
4100 @cindex selected frame
4101 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4102 @value{GDBN} commands refer implicitly to the selected frame. In
4103 particular, whenever you ask @value{GDBN} for the value of a variable in
4104 your program, the value is found in the selected frame. There are
4105 special @value{GDBN} commands to select whichever frame you are
4106 interested in. @xref{Selection, ,Selecting a frame}.
4108 When your program stops, @value{GDBN} automatically selects the
4109 currently executing frame and describes it briefly, similar to the
4110 @code{frame} command (@pxref{Frame Info, ,Information about a frame}).
4113 * Frames:: Stack frames
4114 * Backtrace:: Backtraces
4115 * Selection:: Selecting a frame
4116 * Frame Info:: Information on a frame
4121 @section Stack frames
4123 @cindex frame, definition
4125 The call stack is divided up into contiguous pieces called @dfn{stack
4126 frames}, or @dfn{frames} for short; each frame is the data associated
4127 with one call to one function. The frame contains the arguments given
4128 to the function, the function's local variables, and the address at
4129 which the function is executing.
4131 @cindex initial frame
4132 @cindex outermost frame
4133 @cindex innermost frame
4134 When your program is started, the stack has only one frame, that of the
4135 function @code{main}. This is called the @dfn{initial} frame or the
4136 @dfn{outermost} frame. Each time a function is called, a new frame is
4137 made. Each time a function returns, the frame for that function invocation
4138 is eliminated. If a function is recursive, there can be many frames for
4139 the same function. The frame for the function in which execution is
4140 actually occurring is called the @dfn{innermost} frame. This is the most
4141 recently created of all the stack frames that still exist.
4143 @cindex frame pointer
4144 Inside your program, stack frames are identified by their addresses. A
4145 stack frame consists of many bytes, each of which has its own address; each
4146 kind of computer has a convention for choosing one byte whose
4147 address serves as the address of the frame. Usually this address is kept
4148 in a register called the @dfn{frame pointer register}
4149 (@pxref{Registers, $fp}) while execution is going on in that frame.
4151 @cindex frame number
4152 @value{GDBN} assigns numbers to all existing stack frames, starting with
4153 zero for the innermost frame, one for the frame that called it,
4154 and so on upward. These numbers do not really exist in your program;
4155 they are assigned by @value{GDBN} to give you a way of designating stack
4156 frames in @value{GDBN} commands.
4158 @c The -fomit-frame-pointer below perennially causes hbox overflow
4159 @c underflow problems.
4160 @cindex frameless execution
4161 Some compilers provide a way to compile functions so that they operate
4162 without stack frames. (For example, the @value{GCC} option
4164 @samp{-fomit-frame-pointer}
4166 generates functions without a frame.)
4167 This is occasionally done with heavily used library functions to save
4168 the frame setup time. @value{GDBN} has limited facilities for dealing
4169 with these function invocations. If the innermost function invocation
4170 has no stack frame, @value{GDBN} nevertheless regards it as though
4171 it had a separate frame, which is numbered zero as usual, allowing
4172 correct tracing of the function call chain. However, @value{GDBN} has
4173 no provision for frameless functions elsewhere in the stack.
4176 @kindex frame@r{, command}
4177 @cindex current stack frame
4178 @item frame @var{args}
4179 The @code{frame} command allows you to move from one stack frame to another,
4180 and to print the stack frame you select. @var{args} may be either the
4181 address of the frame or the stack frame number. Without an argument,
4182 @code{frame} prints the current stack frame.
4184 @kindex select-frame
4185 @cindex selecting frame silently
4187 The @code{select-frame} command allows you to move from one stack frame
4188 to another without printing the frame. This is the silent version of
4196 @cindex call stack traces
4197 A backtrace is a summary of how your program got where it is. It shows one
4198 line per frame, for many frames, starting with the currently executing
4199 frame (frame zero), followed by its caller (frame one), and on up the
4204 @kindex bt @r{(@code{backtrace})}
4207 Print a backtrace of the entire stack: one line per frame for all
4208 frames in the stack.
4210 You can stop the backtrace at any time by typing the system interrupt
4211 character, normally @kbd{C-c}.
4213 @item backtrace @var{n}
4215 Similar, but print only the innermost @var{n} frames.
4217 @item backtrace -@var{n}
4219 Similar, but print only the outermost @var{n} frames.
4221 @item backtrace full
4222 Print the values of the local variables also.
4228 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4229 are additional aliases for @code{backtrace}.
4231 Each line in the backtrace shows the frame number and the function name.
4232 The program counter value is also shown---unless you use @code{set
4233 print address off}. The backtrace also shows the source file name and
4234 line number, as well as the arguments to the function. The program
4235 counter value is omitted if it is at the beginning of the code for that
4238 Here is an example of a backtrace. It was made with the command
4239 @samp{bt 3}, so it shows the innermost three frames.
4243 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4245 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4246 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4248 (More stack frames follow...)
4253 The display for frame zero does not begin with a program counter
4254 value, indicating that your program has stopped at the beginning of the
4255 code for line @code{993} of @code{builtin.c}.
4257 @cindex value optimized out, in backtrace
4258 @cindex function call arguments, optimized out
4259 If your program was compiled with optimizations, some compilers will
4260 optimize away arguments passed to functions if those arguments are
4261 never used after the call. Such optimizations generate code that
4262 passes arguments through registers, but doesn't store those arguments
4263 in the stack frame. @value{GDBN} has no way of displaying such
4264 arguments in stack frames other than the innermost one. Here's what
4265 such a backtrace might look like:
4269 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4271 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
4272 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
4274 (More stack frames follow...)
4279 The values of arguments that were not saved in their stack frames are
4280 shown as @samp{<value optimized out>}.
4282 If you need to display the values of such optimized-out arguments,
4283 either deduce that from other variables whose values depend on the one
4284 you are interested in, or recompile without optimizations.
4286 @cindex backtrace beyond @code{main} function
4287 @cindex program entry point
4288 @cindex startup code, and backtrace
4289 Most programs have a standard user entry point---a place where system
4290 libraries and startup code transition into user code. For C this is
4291 @code{main}@footnote{
4292 Note that embedded programs (the so-called ``free-standing''
4293 environment) are not required to have a @code{main} function as the
4294 entry point. They could even have multiple entry points.}.
4295 When @value{GDBN} finds the entry function in a backtrace
4296 it will terminate the backtrace, to avoid tracing into highly
4297 system-specific (and generally uninteresting) code.
4299 If you need to examine the startup code, or limit the number of levels
4300 in a backtrace, you can change this behavior:
4303 @item set backtrace past-main
4304 @itemx set backtrace past-main on
4305 @kindex set backtrace
4306 Backtraces will continue past the user entry point.
4308 @item set backtrace past-main off
4309 Backtraces will stop when they encounter the user entry point. This is the
4312 @item show backtrace past-main
4313 @kindex show backtrace
4314 Display the current user entry point backtrace policy.
4316 @item set backtrace past-entry
4317 @itemx set backtrace past-entry on
4318 Backtraces will continue past the internal entry point of an application.
4319 This entry point is encoded by the linker when the application is built,
4320 and is likely before the user entry point @code{main} (or equivalent) is called.
4322 @item set backtrace past-entry off
4323 Backtraces will stop when they encouter the internal entry point of an
4324 application. This is the default.
4326 @item show backtrace past-entry
4327 Display the current internal entry point backtrace policy.
4329 @item set backtrace limit @var{n}
4330 @itemx set backtrace limit 0
4331 @cindex backtrace limit
4332 Limit the backtrace to @var{n} levels. A value of zero means
4335 @item show backtrace limit
4336 Display the current limit on backtrace levels.
4340 @section Selecting a frame
4342 Most commands for examining the stack and other data in your program work on
4343 whichever stack frame is selected at the moment. Here are the commands for
4344 selecting a stack frame; all of them finish by printing a brief description
4345 of the stack frame just selected.
4348 @kindex frame@r{, selecting}
4349 @kindex f @r{(@code{frame})}
4352 Select frame number @var{n}. Recall that frame zero is the innermost
4353 (currently executing) frame, frame one is the frame that called the
4354 innermost one, and so on. The highest-numbered frame is the one for
4357 @item frame @var{addr}
4359 Select the frame at address @var{addr}. This is useful mainly if the
4360 chaining of stack frames has been damaged by a bug, making it
4361 impossible for @value{GDBN} to assign numbers properly to all frames. In
4362 addition, this can be useful when your program has multiple stacks and
4363 switches between them.
4365 On the SPARC architecture, @code{frame} needs two addresses to
4366 select an arbitrary frame: a frame pointer and a stack pointer.
4368 On the MIPS and Alpha architecture, it needs two addresses: a stack
4369 pointer and a program counter.
4371 On the 29k architecture, it needs three addresses: a register stack
4372 pointer, a program counter, and a memory stack pointer.
4376 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4377 advances toward the outermost frame, to higher frame numbers, to frames
4378 that have existed longer. @var{n} defaults to one.
4381 @kindex do @r{(@code{down})}
4383 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4384 advances toward the innermost frame, to lower frame numbers, to frames
4385 that were created more recently. @var{n} defaults to one. You may
4386 abbreviate @code{down} as @code{do}.
4389 All of these commands end by printing two lines of output describing the
4390 frame. The first line shows the frame number, the function name, the
4391 arguments, and the source file and line number of execution in that
4392 frame. The second line shows the text of that source line.
4400 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4402 10 read_input_file (argv[i]);
4406 After such a printout, the @code{list} command with no arguments
4407 prints ten lines centered on the point of execution in the frame.
4408 You can also edit the program at the point of execution with your favorite
4409 editing program by typing @code{edit}.
4410 @xref{List, ,Printing source lines},
4414 @kindex down-silently
4416 @item up-silently @var{n}
4417 @itemx down-silently @var{n}
4418 These two commands are variants of @code{up} and @code{down},
4419 respectively; they differ in that they do their work silently, without
4420 causing display of the new frame. They are intended primarily for use
4421 in @value{GDBN} command scripts, where the output might be unnecessary and
4426 @section Information about a frame
4428 There are several other commands to print information about the selected
4434 When used without any argument, this command does not change which
4435 frame is selected, but prints a brief description of the currently
4436 selected stack frame. It can be abbreviated @code{f}. With an
4437 argument, this command is used to select a stack frame.
4438 @xref{Selection, ,Selecting a frame}.
4441 @kindex info f @r{(@code{info frame})}
4444 This command prints a verbose description of the selected stack frame,
4449 the address of the frame
4451 the address of the next frame down (called by this frame)
4453 the address of the next frame up (caller of this frame)
4455 the language in which the source code corresponding to this frame is written
4457 the address of the frame's arguments
4459 the address of the frame's local variables
4461 the program counter saved in it (the address of execution in the caller frame)
4463 which registers were saved in the frame
4466 @noindent The verbose description is useful when
4467 something has gone wrong that has made the stack format fail to fit
4468 the usual conventions.
4470 @item info frame @var{addr}
4471 @itemx info f @var{addr}
4472 Print a verbose description of the frame at address @var{addr}, without
4473 selecting that frame. The selected frame remains unchanged by this
4474 command. This requires the same kind of address (more than one for some
4475 architectures) that you specify in the @code{frame} command.
4476 @xref{Selection, ,Selecting a frame}.
4480 Print the arguments of the selected frame, each on a separate line.
4484 Print the local variables of the selected frame, each on a separate
4485 line. These are all variables (declared either static or automatic)
4486 accessible at the point of execution of the selected frame.
4489 @cindex catch exceptions, list active handlers
4490 @cindex exception handlers, how to list
4492 Print a list of all the exception handlers that are active in the
4493 current stack frame at the current point of execution. To see other
4494 exception handlers, visit the associated frame (using the @code{up},
4495 @code{down}, or @code{frame} commands); then type @code{info catch}.
4496 @xref{Set Catchpoints, , Setting catchpoints}.
4502 @chapter Examining Source Files
4504 @value{GDBN} can print parts of your program's source, since the debugging
4505 information recorded in the program tells @value{GDBN} what source files were
4506 used to build it. When your program stops, @value{GDBN} spontaneously prints
4507 the line where it stopped. Likewise, when you select a stack frame
4508 (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
4509 execution in that frame has stopped. You can print other portions of
4510 source files by explicit command.
4512 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4513 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4514 @value{GDBN} under @sc{gnu} Emacs}.
4517 * List:: Printing source lines
4518 * Edit:: Editing source files
4519 * Search:: Searching source files
4520 * Source Path:: Specifying source directories
4521 * Machine Code:: Source and machine code
4525 @section Printing source lines
4528 @kindex l @r{(@code{list})}
4529 To print lines from a source file, use the @code{list} command
4530 (abbreviated @code{l}). By default, ten lines are printed.
4531 There are several ways to specify what part of the file you want to print.
4533 Here are the forms of the @code{list} command most commonly used:
4536 @item list @var{linenum}
4537 Print lines centered around line number @var{linenum} in the
4538 current source file.
4540 @item list @var{function}
4541 Print lines centered around the beginning of function
4545 Print more lines. If the last lines printed were printed with a
4546 @code{list} command, this prints lines following the last lines
4547 printed; however, if the last line printed was a solitary line printed
4548 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4549 Stack}), this prints lines centered around that line.
4552 Print lines just before the lines last printed.
4555 @cindex @code{list}, how many lines to display
4556 By default, @value{GDBN} prints ten source lines with any of these forms of
4557 the @code{list} command. You can change this using @code{set listsize}:
4560 @kindex set listsize
4561 @item set listsize @var{count}
4562 Make the @code{list} command display @var{count} source lines (unless
4563 the @code{list} argument explicitly specifies some other number).
4565 @kindex show listsize
4567 Display the number of lines that @code{list} prints.
4570 Repeating a @code{list} command with @key{RET} discards the argument,
4571 so it is equivalent to typing just @code{list}. This is more useful
4572 than listing the same lines again. An exception is made for an
4573 argument of @samp{-}; that argument is preserved in repetition so that
4574 each repetition moves up in the source file.
4577 In general, the @code{list} command expects you to supply zero, one or two
4578 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4579 of writing them, but the effect is always to specify some source line.
4580 Here is a complete description of the possible arguments for @code{list}:
4583 @item list @var{linespec}
4584 Print lines centered around the line specified by @var{linespec}.
4586 @item list @var{first},@var{last}
4587 Print lines from @var{first} to @var{last}. Both arguments are
4590 @item list ,@var{last}
4591 Print lines ending with @var{last}.
4593 @item list @var{first},
4594 Print lines starting with @var{first}.
4597 Print lines just after the lines last printed.
4600 Print lines just before the lines last printed.
4603 As described in the preceding table.
4606 Here are the ways of specifying a single source line---all the
4611 Specifies line @var{number} of the current source file.
4612 When a @code{list} command has two linespecs, this refers to
4613 the same source file as the first linespec.
4616 Specifies the line @var{offset} lines after the last line printed.
4617 When used as the second linespec in a @code{list} command that has
4618 two, this specifies the line @var{offset} lines down from the
4622 Specifies the line @var{offset} lines before the last line printed.
4624 @item @var{filename}:@var{number}
4625 Specifies line @var{number} in the source file @var{filename}.
4627 @item @var{function}
4628 Specifies the line that begins the body of the function @var{function}.
4629 For example: in C, this is the line with the open brace.
4631 @item @var{filename}:@var{function}
4632 Specifies the line of the open-brace that begins the body of the
4633 function @var{function} in the file @var{filename}. You only need the
4634 file name with a function name to avoid ambiguity when there are
4635 identically named functions in different source files.
4637 @item *@var{address}
4638 Specifies the line containing the program address @var{address}.
4639 @var{address} may be any expression.
4643 @section Editing source files
4644 @cindex editing source files
4647 @kindex e @r{(@code{edit})}
4648 To edit the lines in a source file, use the @code{edit} command.
4649 The editing program of your choice
4650 is invoked with the current line set to
4651 the active line in the program.
4652 Alternatively, there are several ways to specify what part of the file you
4653 want to print if you want to see other parts of the program.
4655 Here are the forms of the @code{edit} command most commonly used:
4659 Edit the current source file at the active line number in the program.
4661 @item edit @var{number}
4662 Edit the current source file with @var{number} as the active line number.
4664 @item edit @var{function}
4665 Edit the file containing @var{function} at the beginning of its definition.
4667 @item edit @var{filename}:@var{number}
4668 Specifies line @var{number} in the source file @var{filename}.
4670 @item edit @var{filename}:@var{function}
4671 Specifies the line that begins the body of the
4672 function @var{function} in the file @var{filename}. You only need the
4673 file name with a function name to avoid ambiguity when there are
4674 identically named functions in different source files.
4676 @item edit *@var{address}
4677 Specifies the line containing the program address @var{address}.
4678 @var{address} may be any expression.
4681 @subsection Choosing your editor
4682 You can customize @value{GDBN} to use any editor you want
4684 The only restriction is that your editor (say @code{ex}), recognizes the
4685 following command-line syntax:
4687 ex +@var{number} file
4689 The optional numeric value +@var{number} specifies the number of the line in
4690 the file where to start editing.}.
4691 By default, it is @file{@value{EDITOR}}, but you can change this
4692 by setting the environment variable @code{EDITOR} before using
4693 @value{GDBN}. For example, to configure @value{GDBN} to use the
4694 @code{vi} editor, you could use these commands with the @code{sh} shell:
4700 or in the @code{csh} shell,
4702 setenv EDITOR /usr/bin/vi
4707 @section Searching source files
4708 @cindex searching source files
4710 There are two commands for searching through the current source file for a
4715 @kindex forward-search
4716 @item forward-search @var{regexp}
4717 @itemx search @var{regexp}
4718 The command @samp{forward-search @var{regexp}} checks each line,
4719 starting with the one following the last line listed, for a match for
4720 @var{regexp}. It lists the line that is found. You can use the
4721 synonym @samp{search @var{regexp}} or abbreviate the command name as
4724 @kindex reverse-search
4725 @item reverse-search @var{regexp}
4726 The command @samp{reverse-search @var{regexp}} checks each line, starting
4727 with the one before the last line listed and going backward, for a match
4728 for @var{regexp}. It lists the line that is found. You can abbreviate
4729 this command as @code{rev}.
4733 @section Specifying source directories
4736 @cindex directories for source files
4737 Executable programs sometimes do not record the directories of the source
4738 files from which they were compiled, just the names. Even when they do,
4739 the directories could be moved between the compilation and your debugging
4740 session. @value{GDBN} has a list of directories to search for source files;
4741 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
4742 it tries all the directories in the list, in the order they are present
4743 in the list, until it finds a file with the desired name.
4745 For example, suppose an executable references the file
4746 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
4747 @file{/mnt/cross}. The file is first looked up literally; if this
4748 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
4749 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
4750 message is printed. @value{GDBN} does not look up the parts of the
4751 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
4752 Likewise, the subdirectories of the source path are not searched: if
4753 the source path is @file{/mnt/cross}, and the binary refers to
4754 @file{foo.c}, @value{GDBN} would not find it under
4755 @file{/mnt/cross/usr/src/foo-1.0/lib}.
4757 Plain file names, relative file names with leading directories, file
4758 names containing dots, etc.@: are all treated as described above; for
4759 instance, if the source path is @file{/mnt/cross}, and the source file
4760 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
4761 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
4762 that---@file{/mnt/cross/foo.c}.
4764 Note that the executable search path is @emph{not} used to locate the
4765 source files. Neither is the current working directory, unless it
4766 happens to be in the source path.
4768 Whenever you reset or rearrange the source path, @value{GDBN} clears out
4769 any information it has cached about where source files are found and where
4770 each line is in the file.
4774 When you start @value{GDBN}, its source path includes only @samp{cdir}
4775 and @samp{cwd}, in that order.
4776 To add other directories, use the @code{directory} command.
4779 @item directory @var{dirname} @dots{}
4780 @item dir @var{dirname} @dots{}
4781 Add directory @var{dirname} to the front of the source path. Several
4782 directory names may be given to this command, separated by @samp{:}
4783 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
4784 part of absolute file names) or
4785 whitespace. You may specify a directory that is already in the source
4786 path; this moves it forward, so @value{GDBN} searches it sooner.
4790 @vindex $cdir@r{, convenience variable}
4791 @vindex $cwdr@r{, convenience variable}
4792 @cindex compilation directory
4793 @cindex current directory
4794 @cindex working directory
4795 @cindex directory, current
4796 @cindex directory, compilation
4797 You can use the string @samp{$cdir} to refer to the compilation
4798 directory (if one is recorded), and @samp{$cwd} to refer to the current
4799 working directory. @samp{$cwd} is not the same as @samp{.}---the former
4800 tracks the current working directory as it changes during your @value{GDBN}
4801 session, while the latter is immediately expanded to the current
4802 directory at the time you add an entry to the source path.
4805 Reset the source path to empty again. This requires confirmation.
4807 @c RET-repeat for @code{directory} is explicitly disabled, but since
4808 @c repeating it would be a no-op we do not say that. (thanks to RMS)
4810 @item show directories
4811 @kindex show directories
4812 Print the source path: show which directories it contains.
4815 If your source path is cluttered with directories that are no longer of
4816 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
4817 versions of source. You can correct the situation as follows:
4821 Use @code{directory} with no argument to reset the source path to empty.
4824 Use @code{directory} with suitable arguments to reinstall the
4825 directories you want in the source path. You can add all the
4826 directories in one command.
4830 @section Source and machine code
4831 @cindex source line and its code address
4833 You can use the command @code{info line} to map source lines to program
4834 addresses (and vice versa), and the command @code{disassemble} to display
4835 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
4836 mode, the @code{info line} command causes the arrow to point to the
4837 line specified. Also, @code{info line} prints addresses in symbolic form as
4842 @item info line @var{linespec}
4843 Print the starting and ending addresses of the compiled code for
4844 source line @var{linespec}. You can specify source lines in any of
4845 the ways understood by the @code{list} command (@pxref{List, ,Printing
4849 For example, we can use @code{info line} to discover the location of
4850 the object code for the first line of function
4851 @code{m4_changequote}:
4853 @c FIXME: I think this example should also show the addresses in
4854 @c symbolic form, as they usually would be displayed.
4856 (@value{GDBP}) info line m4_changequote
4857 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
4861 @cindex code address and its source line
4862 We can also inquire (using @code{*@var{addr}} as the form for
4863 @var{linespec}) what source line covers a particular address:
4865 (@value{GDBP}) info line *0x63ff
4866 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
4869 @cindex @code{$_} and @code{info line}
4870 @cindex @code{x} command, default address
4871 @kindex x@r{(examine), and} info line
4872 After @code{info line}, the default address for the @code{x} command
4873 is changed to the starting address of the line, so that @samp{x/i} is
4874 sufficient to begin examining the machine code (@pxref{Memory,
4875 ,Examining memory}). Also, this address is saved as the value of the
4876 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
4881 @cindex assembly instructions
4882 @cindex instructions, assembly
4883 @cindex machine instructions
4884 @cindex listing machine instructions
4886 This specialized command dumps a range of memory as machine
4887 instructions. The default memory range is the function surrounding the
4888 program counter of the selected frame. A single argument to this
4889 command is a program counter value; @value{GDBN} dumps the function
4890 surrounding this value. Two arguments specify a range of addresses
4891 (first inclusive, second exclusive) to dump.
4894 The following example shows the disassembly of a range of addresses of
4895 HP PA-RISC 2.0 code:
4898 (@value{GDBP}) disas 0x32c4 0x32e4
4899 Dump of assembler code from 0x32c4 to 0x32e4:
4900 0x32c4 <main+204>: addil 0,dp
4901 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
4902 0x32cc <main+212>: ldil 0x3000,r31
4903 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
4904 0x32d4 <main+220>: ldo 0(r31),rp
4905 0x32d8 <main+224>: addil -0x800,dp
4906 0x32dc <main+228>: ldo 0x588(r1),r26
4907 0x32e0 <main+232>: ldil 0x3000,r31
4908 End of assembler dump.
4911 Some architectures have more than one commonly-used set of instruction
4912 mnemonics or other syntax.
4914 For programs that were dynamically linked and use shared libraries,
4915 instructions that call functions or branch to locations in the shared
4916 libraries might show a seemingly bogus location---it's actually a
4917 location of the relocation table. On some architectures, @value{GDBN}
4918 might be able to resolve these to actual function names.
4921 @kindex set disassembly-flavor
4922 @cindex Intel disassembly flavor
4923 @cindex AT&T disassembly flavor
4924 @item set disassembly-flavor @var{instruction-set}
4925 Select the instruction set to use when disassembling the
4926 program via the @code{disassemble} or @code{x/i} commands.
4928 Currently this command is only defined for the Intel x86 family. You
4929 can set @var{instruction-set} to either @code{intel} or @code{att}.
4930 The default is @code{att}, the AT&T flavor used by default by Unix
4931 assemblers for x86-based targets.
4933 @kindex show disassembly-flavor
4934 @item show disassembly-flavor
4935 Show the current setting of the disassembly flavor.
4940 @chapter Examining Data
4942 @cindex printing data
4943 @cindex examining data
4946 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
4947 @c document because it is nonstandard... Under Epoch it displays in a
4948 @c different window or something like that.
4949 The usual way to examine data in your program is with the @code{print}
4950 command (abbreviated @code{p}), or its synonym @code{inspect}. It
4951 evaluates and prints the value of an expression of the language your
4952 program is written in (@pxref{Languages, ,Using @value{GDBN} with
4953 Different Languages}).
4956 @item print @var{expr}
4957 @itemx print /@var{f} @var{expr}
4958 @var{expr} is an expression (in the source language). By default the
4959 value of @var{expr} is printed in a format appropriate to its data type;
4960 you can choose a different format by specifying @samp{/@var{f}}, where
4961 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
4965 @itemx print /@var{f}
4966 @cindex reprint the last value
4967 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
4968 @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
4969 conveniently inspect the same value in an alternative format.
4972 A more low-level way of examining data is with the @code{x} command.
4973 It examines data in memory at a specified address and prints it in a
4974 specified format. @xref{Memory, ,Examining memory}.
4976 If you are interested in information about types, or about how the
4977 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
4978 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
4982 * Expressions:: Expressions
4983 * Variables:: Program variables
4984 * Arrays:: Artificial arrays
4985 * Output Formats:: Output formats
4986 * Memory:: Examining memory
4987 * Auto Display:: Automatic display
4988 * Print Settings:: Print settings
4989 * Value History:: Value history
4990 * Convenience Vars:: Convenience variables
4991 * Registers:: Registers
4992 * Floating Point Hardware:: Floating point hardware
4993 * Vector Unit:: Vector Unit
4994 * OS Information:: Auxiliary data provided by operating system
4995 * Memory Region Attributes:: Memory region attributes
4996 * Dump/Restore Files:: Copy between memory and a file
4997 * Core File Generation:: Cause a program dump its core
4998 * Character Sets:: Debugging programs that use a different
4999 character set than GDB does
5000 * Caching Remote Data:: Data caching for remote targets
5004 @section Expressions
5007 @code{print} and many other @value{GDBN} commands accept an expression and
5008 compute its value. Any kind of constant, variable or operator defined
5009 by the programming language you are using is valid in an expression in
5010 @value{GDBN}. This includes conditional expressions, function calls,
5011 casts, and string constants. It also includes preprocessor macros, if
5012 you compiled your program to include this information; see
5015 @cindex arrays in expressions
5016 @value{GDBN} supports array constants in expressions input by
5017 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
5018 you can use the command @code{print @{1, 2, 3@}} to build up an array in
5019 memory that is @code{malloc}ed in the target program.
5021 Because C is so widespread, most of the expressions shown in examples in
5022 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
5023 Languages}, for information on how to use expressions in other
5026 In this section, we discuss operators that you can use in @value{GDBN}
5027 expressions regardless of your programming language.
5029 @cindex casts, in expressions
5030 Casts are supported in all languages, not just in C, because it is so
5031 useful to cast a number into a pointer in order to examine a structure
5032 at that address in memory.
5033 @c FIXME: casts supported---Mod2 true?
5035 @value{GDBN} supports these operators, in addition to those common
5036 to programming languages:
5040 @samp{@@} is a binary operator for treating parts of memory as arrays.
5041 @xref{Arrays, ,Artificial arrays}, for more information.
5044 @samp{::} allows you to specify a variable in terms of the file or
5045 function where it is defined. @xref{Variables, ,Program variables}.
5047 @cindex @{@var{type}@}
5048 @cindex type casting memory
5049 @cindex memory, viewing as typed object
5050 @cindex casts, to view memory
5051 @item @{@var{type}@} @var{addr}
5052 Refers to an object of type @var{type} stored at address @var{addr} in
5053 memory. @var{addr} may be any expression whose value is an integer or
5054 pointer (but parentheses are required around binary operators, just as in
5055 a cast). This construct is allowed regardless of what kind of data is
5056 normally supposed to reside at @var{addr}.
5060 @section Program variables
5062 The most common kind of expression to use is the name of a variable
5065 Variables in expressions are understood in the selected stack frame
5066 (@pxref{Selection, ,Selecting a frame}); they must be either:
5070 global (or file-static)
5077 visible according to the scope rules of the
5078 programming language from the point of execution in that frame
5081 @noindent This means that in the function
5096 you can examine and use the variable @code{a} whenever your program is
5097 executing within the function @code{foo}, but you can only use or
5098 examine the variable @code{b} while your program is executing inside
5099 the block where @code{b} is declared.
5101 @cindex variable name conflict
5102 There is an exception: you can refer to a variable or function whose
5103 scope is a single source file even if the current execution point is not
5104 in this file. But it is possible to have more than one such variable or
5105 function with the same name (in different source files). If that
5106 happens, referring to that name has unpredictable effects. If you wish,
5107 you can specify a static variable in a particular function or file,
5108 using the colon-colon (@code{::}) notation:
5110 @cindex colon-colon, context for variables/functions
5112 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
5113 @cindex @code{::}, context for variables/functions
5116 @var{file}::@var{variable}
5117 @var{function}::@var{variable}
5121 Here @var{file} or @var{function} is the name of the context for the
5122 static @var{variable}. In the case of file names, you can use quotes to
5123 make sure @value{GDBN} parses the file name as a single word---for example,
5124 to print a global value of @code{x} defined in @file{f2.c}:
5127 (@value{GDBP}) p 'f2.c'::x
5130 @cindex C@t{++} scope resolution
5131 This use of @samp{::} is very rarely in conflict with the very similar
5132 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
5133 scope resolution operator in @value{GDBN} expressions.
5134 @c FIXME: Um, so what happens in one of those rare cases where it's in
5137 @cindex wrong values
5138 @cindex variable values, wrong
5139 @cindex function entry/exit, wrong values of variables
5140 @cindex optimized code, wrong values of variables
5142 @emph{Warning:} Occasionally, a local variable may appear to have the
5143 wrong value at certain points in a function---just after entry to a new
5144 scope, and just before exit.
5146 You may see this problem when you are stepping by machine instructions.
5147 This is because, on most machines, it takes more than one instruction to
5148 set up a stack frame (including local variable definitions); if you are
5149 stepping by machine instructions, variables may appear to have the wrong
5150 values until the stack frame is completely built. On exit, it usually
5151 also takes more than one machine instruction to destroy a stack frame;
5152 after you begin stepping through that group of instructions, local
5153 variable definitions may be gone.
5155 This may also happen when the compiler does significant optimizations.
5156 To be sure of always seeing accurate values, turn off all optimization
5159 @cindex ``No symbol "foo" in current context''
5160 Another possible effect of compiler optimizations is to optimize
5161 unused variables out of existence, or assign variables to registers (as
5162 opposed to memory addresses). Depending on the support for such cases
5163 offered by the debug info format used by the compiler, @value{GDBN}
5164 might not be able to display values for such local variables. If that
5165 happens, @value{GDBN} will print a message like this:
5168 No symbol "foo" in current context.
5171 To solve such problems, either recompile without optimizations, or use a
5172 different debug info format, if the compiler supports several such
5173 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
5174 usually supports the @option{-gstabs+} option. @option{-gstabs+}
5175 produces debug info in a format that is superior to formats such as
5176 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
5177 an effective form for debug info. @xref{Debugging Options,,Options
5178 for Debugging Your Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}.
5179 @xref{C, , Debugging C++}, for more info about debug info formats
5180 that are best suited to C@t{++} programs.
5183 @section Artificial arrays
5185 @cindex artificial array
5187 @kindex @@@r{, referencing memory as an array}
5188 It is often useful to print out several successive objects of the
5189 same type in memory; a section of an array, or an array of
5190 dynamically determined size for which only a pointer exists in the
5193 You can do this by referring to a contiguous span of memory as an
5194 @dfn{artificial array}, using the binary operator @samp{@@}. The left
5195 operand of @samp{@@} should be the first element of the desired array
5196 and be an individual object. The right operand should be the desired length
5197 of the array. The result is an array value whose elements are all of
5198 the type of the left argument. The first element is actually the left
5199 argument; the second element comes from bytes of memory immediately
5200 following those that hold the first element, and so on. Here is an
5201 example. If a program says
5204 int *array = (int *) malloc (len * sizeof (int));
5208 you can print the contents of @code{array} with
5214 The left operand of @samp{@@} must reside in memory. Array values made
5215 with @samp{@@} in this way behave just like other arrays in terms of
5216 subscripting, and are coerced to pointers when used in expressions.
5217 Artificial arrays most often appear in expressions via the value history
5218 (@pxref{Value History, ,Value history}), after printing one out.
5220 Another way to create an artificial array is to use a cast.
5221 This re-interprets a value as if it were an array.
5222 The value need not be in memory:
5224 (@value{GDBP}) p/x (short[2])0x12345678
5225 $1 = @{0x1234, 0x5678@}
5228 As a convenience, if you leave the array length out (as in
5229 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5230 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5232 (@value{GDBP}) p/x (short[])0x12345678
5233 $2 = @{0x1234, 0x5678@}
5236 Sometimes the artificial array mechanism is not quite enough; in
5237 moderately complex data structures, the elements of interest may not
5238 actually be adjacent---for example, if you are interested in the values
5239 of pointers in an array. One useful work-around in this situation is
5240 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5241 variables}) as a counter in an expression that prints the first
5242 interesting value, and then repeat that expression via @key{RET}. For
5243 instance, suppose you have an array @code{dtab} of pointers to
5244 structures, and you are interested in the values of a field @code{fv}
5245 in each structure. Here is an example of what you might type:
5255 @node Output Formats
5256 @section Output formats
5258 @cindex formatted output
5259 @cindex output formats
5260 By default, @value{GDBN} prints a value according to its data type. Sometimes
5261 this is not what you want. For example, you might want to print a number
5262 in hex, or a pointer in decimal. Or you might want to view data in memory
5263 at a certain address as a character string or as an instruction. To do
5264 these things, specify an @dfn{output format} when you print a value.
5266 The simplest use of output formats is to say how to print a value
5267 already computed. This is done by starting the arguments of the
5268 @code{print} command with a slash and a format letter. The format
5269 letters supported are:
5273 Regard the bits of the value as an integer, and print the integer in
5277 Print as integer in signed decimal.
5280 Print as integer in unsigned decimal.
5283 Print as integer in octal.
5286 Print as integer in binary. The letter @samp{t} stands for ``two''.
5287 @footnote{@samp{b} cannot be used because these format letters are also
5288 used with the @code{x} command, where @samp{b} stands for ``byte'';
5289 see @ref{Memory,,Examining memory}.}
5292 @cindex unknown address, locating
5293 @cindex locate address
5294 Print as an address, both absolute in hexadecimal and as an offset from
5295 the nearest preceding symbol. You can use this format used to discover
5296 where (in what function) an unknown address is located:
5299 (@value{GDBP}) p/a 0x54320
5300 $3 = 0x54320 <_initialize_vx+396>
5304 The command @code{info symbol 0x54320} yields similar results.
5305 @xref{Symbols, info symbol}.
5308 Regard as an integer and print it as a character constant. This
5309 prints both the numerical value and its character representation. The
5310 character representation is replaced with the octal escape @samp{\nnn}
5311 for characters outside the 7-bit @sc{ascii} range.
5314 Regard the bits of the value as a floating point number and print
5315 using typical floating point syntax.
5318 For example, to print the program counter in hex (@pxref{Registers}), type
5325 Note that no space is required before the slash; this is because command
5326 names in @value{GDBN} cannot contain a slash.
5328 To reprint the last value in the value history with a different format,
5329 you can use the @code{print} command with just a format and no
5330 expression. For example, @samp{p/x} reprints the last value in hex.
5333 @section Examining memory
5335 You can use the command @code{x} (for ``examine'') to examine memory in
5336 any of several formats, independently of your program's data types.
5338 @cindex examining memory
5340 @kindex x @r{(examine memory)}
5341 @item x/@var{nfu} @var{addr}
5344 Use the @code{x} command to examine memory.
5347 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5348 much memory to display and how to format it; @var{addr} is an
5349 expression giving the address where you want to start displaying memory.
5350 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5351 Several commands set convenient defaults for @var{addr}.
5354 @item @var{n}, the repeat count
5355 The repeat count is a decimal integer; the default is 1. It specifies
5356 how much memory (counting by units @var{u}) to display.
5357 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5360 @item @var{f}, the display format
5361 The display format is one of the formats used by @code{print}
5362 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
5363 @samp{f}), and in addition @samp{s} (for null-terminated strings) and
5364 @samp{i} (for machine instructions). The default is @samp{x}
5365 (hexadecimal) initially. The default changes each time you use either
5366 @code{x} or @code{print}.
5368 @item @var{u}, the unit size
5369 The unit size is any of
5375 Halfwords (two bytes).
5377 Words (four bytes). This is the initial default.
5379 Giant words (eight bytes).
5382 Each time you specify a unit size with @code{x}, that size becomes the
5383 default unit the next time you use @code{x}. (For the @samp{s} and
5384 @samp{i} formats, the unit size is ignored and is normally not written.)
5386 @item @var{addr}, starting display address
5387 @var{addr} is the address where you want @value{GDBN} to begin displaying
5388 memory. The expression need not have a pointer value (though it may);
5389 it is always interpreted as an integer address of a byte of memory.
5390 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5391 @var{addr} is usually just after the last address examined---but several
5392 other commands also set the default address: @code{info breakpoints} (to
5393 the address of the last breakpoint listed), @code{info line} (to the
5394 starting address of a line), and @code{print} (if you use it to display
5395 a value from memory).
5398 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5399 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5400 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5401 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5402 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5404 Since the letters indicating unit sizes are all distinct from the
5405 letters specifying output formats, you do not have to remember whether
5406 unit size or format comes first; either order works. The output
5407 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5408 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5410 Even though the unit size @var{u} is ignored for the formats @samp{s}
5411 and @samp{i}, you might still want to use a count @var{n}; for example,
5412 @samp{3i} specifies that you want to see three machine instructions,
5413 including any operands. The command @code{disassemble} gives an
5414 alternative way of inspecting machine instructions; see @ref{Machine
5415 Code,,Source and machine code}.
5417 All the defaults for the arguments to @code{x} are designed to make it
5418 easy to continue scanning memory with minimal specifications each time
5419 you use @code{x}. For example, after you have inspected three machine
5420 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5421 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5422 the repeat count @var{n} is used again; the other arguments default as
5423 for successive uses of @code{x}.
5425 @cindex @code{$_}, @code{$__}, and value history
5426 The addresses and contents printed by the @code{x} command are not saved
5427 in the value history because there is often too much of them and they
5428 would get in the way. Instead, @value{GDBN} makes these values available for
5429 subsequent use in expressions as values of the convenience variables
5430 @code{$_} and @code{$__}. After an @code{x} command, the last address
5431 examined is available for use in expressions in the convenience variable
5432 @code{$_}. The contents of that address, as examined, are available in
5433 the convenience variable @code{$__}.
5435 If the @code{x} command has a repeat count, the address and contents saved
5436 are from the last memory unit printed; this is not the same as the last
5437 address printed if several units were printed on the last line of output.
5439 @cindex remote memory comparison
5440 @cindex verify remote memory image
5441 When you are debugging a program running on a remote target machine
5442 (@pxref{Remote}), you may wish to verify the program's image in the
5443 remote machine's memory against the executable file you downloaded to
5444 the target. The @code{compare-sections} command is provided for such
5448 @kindex compare-sections
5449 @item compare-sections @r{[}@var{section-name}@r{]}
5450 Compare the data of a loadable section @var{section-name} in the
5451 executable file of the program being debugged with the same section in
5452 the remote machine's memory, and report any mismatches. With no
5453 arguments, compares all loadable sections. This command's
5454 availability depends on the target's support for the @code{"qCRC"}
5459 @section Automatic display
5460 @cindex automatic display
5461 @cindex display of expressions
5463 If you find that you want to print the value of an expression frequently
5464 (to see how it changes), you might want to add it to the @dfn{automatic
5465 display list} so that @value{GDBN} prints its value each time your program stops.
5466 Each expression added to the list is given a number to identify it;
5467 to remove an expression from the list, you specify that number.
5468 The automatic display looks like this:
5472 3: bar[5] = (struct hack *) 0x3804
5476 This display shows item numbers, expressions and their current values. As with
5477 displays you request manually using @code{x} or @code{print}, you can
5478 specify the output format you prefer; in fact, @code{display} decides
5479 whether to use @code{print} or @code{x} depending on how elaborate your
5480 format specification is---it uses @code{x} if you specify a unit size,
5481 or one of the two formats (@samp{i} and @samp{s}) that are only
5482 supported by @code{x}; otherwise it uses @code{print}.
5486 @item display @var{expr}
5487 Add the expression @var{expr} to the list of expressions to display
5488 each time your program stops. @xref{Expressions, ,Expressions}.
5490 @code{display} does not repeat if you press @key{RET} again after using it.
5492 @item display/@var{fmt} @var{expr}
5493 For @var{fmt} specifying only a display format and not a size or
5494 count, add the expression @var{expr} to the auto-display list but
5495 arrange to display it each time in the specified format @var{fmt}.
5496 @xref{Output Formats,,Output formats}.
5498 @item display/@var{fmt} @var{addr}
5499 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
5500 number of units, add the expression @var{addr} as a memory address to
5501 be examined each time your program stops. Examining means in effect
5502 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
5505 For example, @samp{display/i $pc} can be helpful, to see the machine
5506 instruction about to be executed each time execution stops (@samp{$pc}
5507 is a common name for the program counter; @pxref{Registers, ,Registers}).
5510 @kindex delete display
5512 @item undisplay @var{dnums}@dots{}
5513 @itemx delete display @var{dnums}@dots{}
5514 Remove item numbers @var{dnums} from the list of expressions to display.
5516 @code{undisplay} does not repeat if you press @key{RET} after using it.
5517 (Otherwise you would just get the error @samp{No display number @dots{}}.)
5519 @kindex disable display
5520 @item disable display @var{dnums}@dots{}
5521 Disable the display of item numbers @var{dnums}. A disabled display
5522 item is not printed automatically, but is not forgotten. It may be
5523 enabled again later.
5525 @kindex enable display
5526 @item enable display @var{dnums}@dots{}
5527 Enable display of item numbers @var{dnums}. It becomes effective once
5528 again in auto display of its expression, until you specify otherwise.
5531 Display the current values of the expressions on the list, just as is
5532 done when your program stops.
5534 @kindex info display
5536 Print the list of expressions previously set up to display
5537 automatically, each one with its item number, but without showing the
5538 values. This includes disabled expressions, which are marked as such.
5539 It also includes expressions which would not be displayed right now
5540 because they refer to automatic variables not currently available.
5543 @cindex display disabled out of scope
5544 If a display expression refers to local variables, then it does not make
5545 sense outside the lexical context for which it was set up. Such an
5546 expression is disabled when execution enters a context where one of its
5547 variables is not defined. For example, if you give the command
5548 @code{display last_char} while inside a function with an argument
5549 @code{last_char}, @value{GDBN} displays this argument while your program
5550 continues to stop inside that function. When it stops elsewhere---where
5551 there is no variable @code{last_char}---the display is disabled
5552 automatically. The next time your program stops where @code{last_char}
5553 is meaningful, you can enable the display expression once again.
5555 @node Print Settings
5556 @section Print settings
5558 @cindex format options
5559 @cindex print settings
5560 @value{GDBN} provides the following ways to control how arrays, structures,
5561 and symbols are printed.
5564 These settings are useful for debugging programs in any language:
5568 @item set print address
5569 @itemx set print address on
5570 @cindex print/don't print memory addresses
5571 @value{GDBN} prints memory addresses showing the location of stack
5572 traces, structure values, pointer values, breakpoints, and so forth,
5573 even when it also displays the contents of those addresses. The default
5574 is @code{on}. For example, this is what a stack frame display looks like with
5575 @code{set print address on}:
5580 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
5582 530 if (lquote != def_lquote)
5586 @item set print address off
5587 Do not print addresses when displaying their contents. For example,
5588 this is the same stack frame displayed with @code{set print address off}:
5592 (@value{GDBP}) set print addr off
5594 #0 set_quotes (lq="<<", rq=">>") at input.c:530
5595 530 if (lquote != def_lquote)
5599 You can use @samp{set print address off} to eliminate all machine
5600 dependent displays from the @value{GDBN} interface. For example, with
5601 @code{print address off}, you should get the same text for backtraces on
5602 all machines---whether or not they involve pointer arguments.
5605 @item show print address
5606 Show whether or not addresses are to be printed.
5609 When @value{GDBN} prints a symbolic address, it normally prints the
5610 closest earlier symbol plus an offset. If that symbol does not uniquely
5611 identify the address (for example, it is a name whose scope is a single
5612 source file), you may need to clarify. One way to do this is with
5613 @code{info line}, for example @samp{info line *0x4537}. Alternately,
5614 you can set @value{GDBN} to print the source file and line number when
5615 it prints a symbolic address:
5618 @item set print symbol-filename on
5619 @cindex source file and line of a symbol
5620 @cindex symbol, source file and line
5621 Tell @value{GDBN} to print the source file name and line number of a
5622 symbol in the symbolic form of an address.
5624 @item set print symbol-filename off
5625 Do not print source file name and line number of a symbol. This is the
5628 @item show print symbol-filename
5629 Show whether or not @value{GDBN} will print the source file name and
5630 line number of a symbol in the symbolic form of an address.
5633 Another situation where it is helpful to show symbol filenames and line
5634 numbers is when disassembling code; @value{GDBN} shows you the line
5635 number and source file that corresponds to each instruction.
5637 Also, you may wish to see the symbolic form only if the address being
5638 printed is reasonably close to the closest earlier symbol:
5641 @item set print max-symbolic-offset @var{max-offset}
5642 @cindex maximum value for offset of closest symbol
5643 Tell @value{GDBN} to only display the symbolic form of an address if the
5644 offset between the closest earlier symbol and the address is less than
5645 @var{max-offset}. The default is 0, which tells @value{GDBN}
5646 to always print the symbolic form of an address if any symbol precedes it.
5648 @item show print max-symbolic-offset
5649 Ask how large the maximum offset is that @value{GDBN} prints in a
5653 @cindex wild pointer, interpreting
5654 @cindex pointer, finding referent
5655 If you have a pointer and you are not sure where it points, try
5656 @samp{set print symbol-filename on}. Then you can determine the name
5657 and source file location of the variable where it points, using
5658 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
5659 For example, here @value{GDBN} shows that a variable @code{ptt} points
5660 at another variable @code{t}, defined in @file{hi2.c}:
5663 (@value{GDBP}) set print symbol-filename on
5664 (@value{GDBP}) p/a ptt
5665 $4 = 0xe008 <t in hi2.c>
5669 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
5670 does not show the symbol name and filename of the referent, even with
5671 the appropriate @code{set print} options turned on.
5674 Other settings control how different kinds of objects are printed:
5677 @item set print array
5678 @itemx set print array on
5679 @cindex pretty print arrays
5680 Pretty print arrays. This format is more convenient to read,
5681 but uses more space. The default is off.
5683 @item set print array off
5684 Return to compressed format for arrays.
5686 @item show print array
5687 Show whether compressed or pretty format is selected for displaying
5690 @item set print elements @var{number-of-elements}
5691 @cindex number of array elements to print
5692 @cindex limit on number of printed array elements
5693 Set a limit on how many elements of an array @value{GDBN} will print.
5694 If @value{GDBN} is printing a large array, it stops printing after it has
5695 printed the number of elements set by the @code{set print elements} command.
5696 This limit also applies to the display of strings.
5697 When @value{GDBN} starts, this limit is set to 200.
5698 Setting @var{number-of-elements} to zero means that the printing is unlimited.
5700 @item show print elements
5701 Display the number of elements of a large array that @value{GDBN} will print.
5702 If the number is 0, then the printing is unlimited.
5704 @item set print repeats
5705 @cindex repeated array elements
5706 Set the threshold for suppressing display of repeated array
5707 elelments. When the number of consecutive identical elements of an
5708 array exceeds the threshold, @value{GDBN} prints the string
5709 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
5710 identical repetitions, instead of displaying the identical elements
5711 themselves. Setting the threshold to zero will cause all elements to
5712 be individually printed. The default threshold is 10.
5714 @item show print repeats
5715 Display the current threshold for printing repeated identical
5718 @item set print null-stop
5719 @cindex @sc{null} elements in arrays
5720 Cause @value{GDBN} to stop printing the characters of an array when the first
5721 @sc{null} is encountered. This is useful when large arrays actually
5722 contain only short strings.
5725 @item show print null-stop
5726 Show whether @value{GDBN} stops printing an array on the first
5727 @sc{null} character.
5729 @item set print pretty on
5730 @cindex print structures in indented form
5731 @cindex indentation in structure display
5732 Cause @value{GDBN} to print structures in an indented format with one member
5733 per line, like this:
5748 @item set print pretty off
5749 Cause @value{GDBN} to print structures in a compact format, like this:
5753 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
5754 meat = 0x54 "Pork"@}
5759 This is the default format.
5761 @item show print pretty
5762 Show which format @value{GDBN} is using to print structures.
5764 @item set print sevenbit-strings on
5765 @cindex eight-bit characters in strings
5766 @cindex octal escapes in strings
5767 Print using only seven-bit characters; if this option is set,
5768 @value{GDBN} displays any eight-bit characters (in strings or
5769 character values) using the notation @code{\}@var{nnn}. This setting is
5770 best if you are working in English (@sc{ascii}) and you use the
5771 high-order bit of characters as a marker or ``meta'' bit.
5773 @item set print sevenbit-strings off
5774 Print full eight-bit characters. This allows the use of more
5775 international character sets, and is the default.
5777 @item show print sevenbit-strings
5778 Show whether or not @value{GDBN} is printing only seven-bit characters.
5780 @item set print union on
5781 @cindex unions in structures, printing
5782 Tell @value{GDBN} to print unions which are contained in structures
5783 and other unions. This is the default setting.
5785 @item set print union off
5786 Tell @value{GDBN} not to print unions which are contained in
5787 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
5790 @item show print union
5791 Ask @value{GDBN} whether or not it will print unions which are contained in
5792 structures and other unions.
5794 For example, given the declarations
5797 typedef enum @{Tree, Bug@} Species;
5798 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
5799 typedef enum @{Caterpillar, Cocoon, Butterfly@}
5810 struct thing foo = @{Tree, @{Acorn@}@};
5814 with @code{set print union on} in effect @samp{p foo} would print
5817 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
5821 and with @code{set print union off} in effect it would print
5824 $1 = @{it = Tree, form = @{...@}@}
5828 @code{set print union} affects programs written in C-like languages
5834 These settings are of interest when debugging C@t{++} programs:
5837 @cindex demangling C@t{++} names
5838 @item set print demangle
5839 @itemx set print demangle on
5840 Print C@t{++} names in their source form rather than in the encoded
5841 (``mangled'') form passed to the assembler and linker for type-safe
5842 linkage. The default is on.
5844 @item show print demangle
5845 Show whether C@t{++} names are printed in mangled or demangled form.
5847 @item set print asm-demangle
5848 @itemx set print asm-demangle on
5849 Print C@t{++} names in their source form rather than their mangled form, even
5850 in assembler code printouts such as instruction disassemblies.
5853 @item show print asm-demangle
5854 Show whether C@t{++} names in assembly listings are printed in mangled
5857 @cindex C@t{++} symbol decoding style
5858 @cindex symbol decoding style, C@t{++}
5859 @kindex set demangle-style
5860 @item set demangle-style @var{style}
5861 Choose among several encoding schemes used by different compilers to
5862 represent C@t{++} names. The choices for @var{style} are currently:
5866 Allow @value{GDBN} to choose a decoding style by inspecting your program.
5869 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
5870 This is the default.
5873 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
5876 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
5879 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
5880 @strong{Warning:} this setting alone is not sufficient to allow
5881 debugging @code{cfront}-generated executables. @value{GDBN} would
5882 require further enhancement to permit that.
5885 If you omit @var{style}, you will see a list of possible formats.
5887 @item show demangle-style
5888 Display the encoding style currently in use for decoding C@t{++} symbols.
5890 @item set print object
5891 @itemx set print object on
5892 @cindex derived type of an object, printing
5893 @cindex display derived types
5894 When displaying a pointer to an object, identify the @emph{actual}
5895 (derived) type of the object rather than the @emph{declared} type, using
5896 the virtual function table.
5898 @item set print object off
5899 Display only the declared type of objects, without reference to the
5900 virtual function table. This is the default setting.
5902 @item show print object
5903 Show whether actual, or declared, object types are displayed.
5905 @item set print static-members
5906 @itemx set print static-members on
5907 @cindex static members of C@t{++} objects
5908 Print static members when displaying a C@t{++} object. The default is on.
5910 @item set print static-members off
5911 Do not print static members when displaying a C@t{++} object.
5913 @item show print static-members
5914 Show whether C@t{++} static members are printed or not.
5916 @item set print pascal_static-members
5917 @itemx set print pascal_static-members on
5918 @cindex static members of Pacal objects
5919 @cindex Pacal objects, static members display
5920 Print static members when displaying a Pascal object. The default is on.
5922 @item set print pascal_static-members off
5923 Do not print static members when displaying a Pascal object.
5925 @item show print pascal_static-members
5926 Show whether Pascal static members are printed or not.
5928 @c These don't work with HP ANSI C++ yet.
5929 @item set print vtbl
5930 @itemx set print vtbl on
5931 @cindex pretty print C@t{++} virtual function tables
5932 @cindex virtual functions (C@t{++}) display
5933 @cindex VTBL display
5934 Pretty print C@t{++} virtual function tables. The default is off.
5935 (The @code{vtbl} commands do not work on programs compiled with the HP
5936 ANSI C@t{++} compiler (@code{aCC}).)
5938 @item set print vtbl off
5939 Do not pretty print C@t{++} virtual function tables.
5941 @item show print vtbl
5942 Show whether C@t{++} virtual function tables are pretty printed, or not.
5946 @section Value history
5948 @cindex value history
5949 @cindex history of values printed by @value{GDBN}
5950 Values printed by the @code{print} command are saved in the @value{GDBN}
5951 @dfn{value history}. This allows you to refer to them in other expressions.
5952 Values are kept until the symbol table is re-read or discarded
5953 (for example with the @code{file} or @code{symbol-file} commands).
5954 When the symbol table changes, the value history is discarded,
5955 since the values may contain pointers back to the types defined in the
5960 @cindex history number
5961 The values printed are given @dfn{history numbers} by which you can
5962 refer to them. These are successive integers starting with one.
5963 @code{print} shows you the history number assigned to a value by
5964 printing @samp{$@var{num} = } before the value; here @var{num} is the
5967 To refer to any previous value, use @samp{$} followed by the value's
5968 history number. The way @code{print} labels its output is designed to
5969 remind you of this. Just @code{$} refers to the most recent value in
5970 the history, and @code{$$} refers to the value before that.
5971 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
5972 is the value just prior to @code{$$}, @code{$$1} is equivalent to
5973 @code{$$}, and @code{$$0} is equivalent to @code{$}.
5975 For example, suppose you have just printed a pointer to a structure and
5976 want to see the contents of the structure. It suffices to type
5982 If you have a chain of structures where the component @code{next} points
5983 to the next one, you can print the contents of the next one with this:
5990 You can print successive links in the chain by repeating this
5991 command---which you can do by just typing @key{RET}.
5993 Note that the history records values, not expressions. If the value of
5994 @code{x} is 4 and you type these commands:
6002 then the value recorded in the value history by the @code{print} command
6003 remains 4 even though the value of @code{x} has changed.
6008 Print the last ten values in the value history, with their item numbers.
6009 This is like @samp{p@ $$9} repeated ten times, except that @code{show
6010 values} does not change the history.
6012 @item show values @var{n}
6013 Print ten history values centered on history item number @var{n}.
6016 Print ten history values just after the values last printed. If no more
6017 values are available, @code{show values +} produces no display.
6020 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
6021 same effect as @samp{show values +}.
6023 @node Convenience Vars
6024 @section Convenience variables
6026 @cindex convenience variables
6027 @cindex user-defined variables
6028 @value{GDBN} provides @dfn{convenience variables} that you can use within
6029 @value{GDBN} to hold on to a value and refer to it later. These variables
6030 exist entirely within @value{GDBN}; they are not part of your program, and
6031 setting a convenience variable has no direct effect on further execution
6032 of your program. That is why you can use them freely.
6034 Convenience variables are prefixed with @samp{$}. Any name preceded by
6035 @samp{$} can be used for a convenience variable, unless it is one of
6036 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
6037 (Value history references, in contrast, are @emph{numbers} preceded
6038 by @samp{$}. @xref{Value History, ,Value history}.)
6040 You can save a value in a convenience variable with an assignment
6041 expression, just as you would set a variable in your program.
6045 set $foo = *object_ptr
6049 would save in @code{$foo} the value contained in the object pointed to by
6052 Using a convenience variable for the first time creates it, but its
6053 value is @code{void} until you assign a new value. You can alter the
6054 value with another assignment at any time.
6056 Convenience variables have no fixed types. You can assign a convenience
6057 variable any type of value, including structures and arrays, even if
6058 that variable already has a value of a different type. The convenience
6059 variable, when used as an expression, has the type of its current value.
6062 @kindex show convenience
6063 @cindex show all user variables
6064 @item show convenience
6065 Print a list of convenience variables used so far, and their values.
6066 Abbreviated @code{show conv}.
6069 One of the ways to use a convenience variable is as a counter to be
6070 incremented or a pointer to be advanced. For example, to print
6071 a field from successive elements of an array of structures:
6075 print bar[$i++]->contents
6079 Repeat that command by typing @key{RET}.
6081 Some convenience variables are created automatically by @value{GDBN} and given
6082 values likely to be useful.
6085 @vindex $_@r{, convenience variable}
6087 The variable @code{$_} is automatically set by the @code{x} command to
6088 the last address examined (@pxref{Memory, ,Examining memory}). Other
6089 commands which provide a default address for @code{x} to examine also
6090 set @code{$_} to that address; these commands include @code{info line}
6091 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
6092 except when set by the @code{x} command, in which case it is a pointer
6093 to the type of @code{$__}.
6095 @vindex $__@r{, convenience variable}
6097 The variable @code{$__} is automatically set by the @code{x} command
6098 to the value found in the last address examined. Its type is chosen
6099 to match the format in which the data was printed.
6102 @vindex $_exitcode@r{, convenience variable}
6103 The variable @code{$_exitcode} is automatically set to the exit code when
6104 the program being debugged terminates.
6107 On HP-UX systems, if you refer to a function or variable name that
6108 begins with a dollar sign, @value{GDBN} searches for a user or system
6109 name first, before it searches for a convenience variable.
6115 You can refer to machine register contents, in expressions, as variables
6116 with names starting with @samp{$}. The names of registers are different
6117 for each machine; use @code{info registers} to see the names used on
6121 @kindex info registers
6122 @item info registers
6123 Print the names and values of all registers except floating-point
6124 and vector registers (in the selected stack frame).
6126 @kindex info all-registers
6127 @cindex floating point registers
6128 @item info all-registers
6129 Print the names and values of all registers, including floating-point
6130 and vector registers (in the selected stack frame).
6132 @item info registers @var{regname} @dots{}
6133 Print the @dfn{relativized} value of each specified register @var{regname}.
6134 As discussed in detail below, register values are normally relative to
6135 the selected stack frame. @var{regname} may be any register name valid on
6136 the machine you are using, with or without the initial @samp{$}.
6139 @cindex stack pointer register
6140 @cindex program counter register
6141 @cindex process status register
6142 @cindex frame pointer register
6143 @cindex standard registers
6144 @value{GDBN} has four ``standard'' register names that are available (in
6145 expressions) on most machines---whenever they do not conflict with an
6146 architecture's canonical mnemonics for registers. The register names
6147 @code{$pc} and @code{$sp} are used for the program counter register and
6148 the stack pointer. @code{$fp} is used for a register that contains a
6149 pointer to the current stack frame, and @code{$ps} is used for a
6150 register that contains the processor status. For example,
6151 you could print the program counter in hex with
6158 or print the instruction to be executed next with
6165 or add four to the stack pointer@footnote{This is a way of removing
6166 one word from the stack, on machines where stacks grow downward in
6167 memory (most machines, nowadays). This assumes that the innermost
6168 stack frame is selected; setting @code{$sp} is not allowed when other
6169 stack frames are selected. To pop entire frames off the stack,
6170 regardless of machine architecture, use @code{return};
6171 see @ref{Returning, ,Returning from a function}.} with
6177 Whenever possible, these four standard register names are available on
6178 your machine even though the machine has different canonical mnemonics,
6179 so long as there is no conflict. The @code{info registers} command
6180 shows the canonical names. For example, on the SPARC, @code{info
6181 registers} displays the processor status register as @code{$psr} but you
6182 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
6183 is an alias for the @sc{eflags} register.
6185 @value{GDBN} always considers the contents of an ordinary register as an
6186 integer when the register is examined in this way. Some machines have
6187 special registers which can hold nothing but floating point; these
6188 registers are considered to have floating point values. There is no way
6189 to refer to the contents of an ordinary register as floating point value
6190 (although you can @emph{print} it as a floating point value with
6191 @samp{print/f $@var{regname}}).
6193 Some registers have distinct ``raw'' and ``virtual'' data formats. This
6194 means that the data format in which the register contents are saved by
6195 the operating system is not the same one that your program normally
6196 sees. For example, the registers of the 68881 floating point
6197 coprocessor are always saved in ``extended'' (raw) format, but all C
6198 programs expect to work with ``double'' (virtual) format. In such
6199 cases, @value{GDBN} normally works with the virtual format only (the format
6200 that makes sense for your program), but the @code{info registers} command
6201 prints the data in both formats.
6203 Normally, register values are relative to the selected stack frame
6204 (@pxref{Selection, ,Selecting a frame}). This means that you get the
6205 value that the register would contain if all stack frames farther in
6206 were exited and their saved registers restored. In order to see the
6207 true contents of hardware registers, you must select the innermost
6208 frame (with @samp{frame 0}).
6210 However, @value{GDBN} must deduce where registers are saved, from the machine
6211 code generated by your compiler. If some registers are not saved, or if
6212 @value{GDBN} is unable to locate the saved registers, the selected stack
6213 frame makes no difference.
6215 @node Floating Point Hardware
6216 @section Floating point hardware
6217 @cindex floating point
6219 Depending on the configuration, @value{GDBN} may be able to give
6220 you more information about the status of the floating point hardware.
6225 Display hardware-dependent information about the floating
6226 point unit. The exact contents and layout vary depending on the
6227 floating point chip. Currently, @samp{info float} is supported on
6228 the ARM and x86 machines.
6232 @section Vector Unit
6235 Depending on the configuration, @value{GDBN} may be able to give you
6236 more information about the status of the vector unit.
6241 Display information about the vector unit. The exact contents and
6242 layout vary depending on the hardware.
6245 @node OS Information
6246 @section Operating system auxiliary information
6247 @cindex OS information
6249 @value{GDBN} provides interfaces to useful OS facilities that can help
6250 you debug your program.
6252 @cindex @code{ptrace} system call
6253 @cindex @code{struct user} contents
6254 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
6255 machines), it interfaces with the inferior via the @code{ptrace}
6256 system call. The operating system creates a special sata structure,
6257 called @code{struct user}, for this interface. You can use the
6258 command @code{info udot} to display the contents of this data
6264 Display the contents of the @code{struct user} maintained by the OS
6265 kernel for the program being debugged. @value{GDBN} displays the
6266 contents of @code{struct user} as a list of hex numbers, similar to
6267 the @code{examine} command.
6270 @cindex auxiliary vector
6271 @cindex vector, auxiliary
6272 Some operating systems supply an @dfn{auxiliary vector} to programs at
6273 startup. This is akin to the arguments and environment that you
6274 specify for a program, but contains a system-dependent variety of
6275 binary values that tell system libraries important details about the
6276 hardware, operating system, and process. Each value's purpose is
6277 identified by an integer tag; the meanings are well-known but system-specific.
6278 Depending on the configuration and operating system facilities,
6279 @value{GDBN} may be able to show you this information. For remote
6280 targets, this functionality may further depend on the remote stub's
6281 support of the @samp{qPart:auxv:read} packet, see @ref{Remote
6282 configuration, auxiliary vector}.
6287 Display the auxiliary vector of the inferior, which can be either a
6288 live process or a core dump file. @value{GDBN} prints each tag value
6289 numerically, and also shows names and text descriptions for recognized
6290 tags. Some values in the vector are numbers, some bit masks, and some
6291 pointers to strings or other data. @value{GDBN} displays each value in the
6292 most appropriate form for a recognized tag, and in hexadecimal for
6293 an unrecognized tag.
6297 @node Memory Region Attributes
6298 @section Memory region attributes
6299 @cindex memory region attributes
6301 @dfn{Memory region attributes} allow you to describe special handling
6302 required by regions of your target's memory. @value{GDBN} uses attributes
6303 to determine whether to allow certain types of memory accesses; whether to
6304 use specific width accesses; and whether to cache target memory.
6306 Defined memory regions can be individually enabled and disabled. When a
6307 memory region is disabled, @value{GDBN} uses the default attributes when
6308 accessing memory in that region. Similarly, if no memory regions have
6309 been defined, @value{GDBN} uses the default attributes when accessing
6312 When a memory region is defined, it is given a number to identify it;
6313 to enable, disable, or remove a memory region, you specify that number.
6317 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
6318 Define a memory region bounded by @var{lower} and @var{upper} with
6319 attributes @var{attributes}@dots{}, and add it to the list of regions
6320 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
6321 case: it is treated as the the target's maximum memory address.
6322 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
6325 @item delete mem @var{nums}@dots{}
6326 Remove memory regions @var{nums}@dots{} from the list of regions
6327 monitored by @value{GDBN}.
6330 @item disable mem @var{nums}@dots{}
6331 Disable monitoring of memory regions @var{nums}@dots{}.
6332 A disabled memory region is not forgotten.
6333 It may be enabled again later.
6336 @item enable mem @var{nums}@dots{}
6337 Enable monitoring of memory regions @var{nums}@dots{}.
6341 Print a table of all defined memory regions, with the following columns
6345 @item Memory Region Number
6346 @item Enabled or Disabled.
6347 Enabled memory regions are marked with @samp{y}.
6348 Disabled memory regions are marked with @samp{n}.
6351 The address defining the inclusive lower bound of the memory region.
6354 The address defining the exclusive upper bound of the memory region.
6357 The list of attributes set for this memory region.
6362 @subsection Attributes
6364 @subsubsection Memory Access Mode
6365 The access mode attributes set whether @value{GDBN} may make read or
6366 write accesses to a memory region.
6368 While these attributes prevent @value{GDBN} from performing invalid
6369 memory accesses, they do nothing to prevent the target system, I/O DMA,
6370 etc. from accessing memory.
6374 Memory is read only.
6376 Memory is write only.
6378 Memory is read/write. This is the default.
6381 @subsubsection Memory Access Size
6382 The acccess size attributes tells @value{GDBN} to use specific sized
6383 accesses in the memory region. Often memory mapped device registers
6384 require specific sized accesses. If no access size attribute is
6385 specified, @value{GDBN} may use accesses of any size.
6389 Use 8 bit memory accesses.
6391 Use 16 bit memory accesses.
6393 Use 32 bit memory accesses.
6395 Use 64 bit memory accesses.
6398 @c @subsubsection Hardware/Software Breakpoints
6399 @c The hardware/software breakpoint attributes set whether @value{GDBN}
6400 @c will use hardware or software breakpoints for the internal breakpoints
6401 @c used by the step, next, finish, until, etc. commands.
6405 @c Always use hardware breakpoints
6406 @c @item swbreak (default)
6409 @subsubsection Data Cache
6410 The data cache attributes set whether @value{GDBN} will cache target
6411 memory. While this generally improves performance by reducing debug
6412 protocol overhead, it can lead to incorrect results because @value{GDBN}
6413 does not know about volatile variables or memory mapped device
6418 Enable @value{GDBN} to cache target memory.
6420 Disable @value{GDBN} from caching target memory. This is the default.
6423 @c @subsubsection Memory Write Verification
6424 @c The memory write verification attributes set whether @value{GDBN}
6425 @c will re-reads data after each write to verify the write was successful.
6429 @c @item noverify (default)
6432 @node Dump/Restore Files
6433 @section Copy between memory and a file
6434 @cindex dump/restore files
6435 @cindex append data to a file
6436 @cindex dump data to a file
6437 @cindex restore data from a file
6439 You can use the commands @code{dump}, @code{append}, and
6440 @code{restore} to copy data between target memory and a file. The
6441 @code{dump} and @code{append} commands write data to a file, and the
6442 @code{restore} command reads data from a file back into the inferior's
6443 memory. Files may be in binary, Motorola S-record, Intel hex, or
6444 Tektronix Hex format; however, @value{GDBN} can only append to binary
6450 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6451 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
6452 Dump the contents of memory from @var{start_addr} to @var{end_addr},
6453 or the value of @var{expr}, to @var{filename} in the given format.
6455 The @var{format} parameter may be any one of:
6462 Motorola S-record format.
6464 Tektronix Hex format.
6467 @value{GDBN} uses the same definitions of these formats as the
6468 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
6469 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
6473 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6474 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
6475 Append the contents of memory from @var{start_addr} to @var{end_addr},
6476 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
6477 (@value{GDBN} can only append data to files in raw binary form.)
6480 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
6481 Restore the contents of file @var{filename} into memory. The
6482 @code{restore} command can automatically recognize any known @sc{bfd}
6483 file format, except for raw binary. To restore a raw binary file you
6484 must specify the optional keyword @code{binary} after the filename.
6486 If @var{bias} is non-zero, its value will be added to the addresses
6487 contained in the file. Binary files always start at address zero, so
6488 they will be restored at address @var{bias}. Other bfd files have
6489 a built-in location; they will be restored at offset @var{bias}
6492 If @var{start} and/or @var{end} are non-zero, then only data between
6493 file offset @var{start} and file offset @var{end} will be restored.
6494 These offsets are relative to the addresses in the file, before
6495 the @var{bias} argument is applied.
6499 @node Core File Generation
6500 @section How to Produce a Core File from Your Program
6501 @cindex dump core from inferior
6503 A @dfn{core file} or @dfn{core dump} is a file that records the memory
6504 image of a running process and its process status (register values
6505 etc.). Its primary use is post-mortem debugging of a program that
6506 crashed while it ran outside a debugger. A program that crashes
6507 automatically produces a core file, unless this feature is disabled by
6508 the user. @xref{Files}, for information on invoking @value{GDBN} in
6509 the post-mortem debugging mode.
6511 Occasionally, you may wish to produce a core file of the program you
6512 are debugging in order to preserve a snapshot of its state.
6513 @value{GDBN} has a special command for that.
6517 @kindex generate-core-file
6518 @item generate-core-file [@var{file}]
6519 @itemx gcore [@var{file}]
6520 Produce a core dump of the inferior process. The optional argument
6521 @var{file} specifies the file name where to put the core dump. If not
6522 specified, the file name defaults to @file{core.@var{pid}}, where
6523 @var{pid} is the inferior process ID.
6525 Note that this command is implemented only for some systems (as of
6526 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
6529 @node Character Sets
6530 @section Character Sets
6531 @cindex character sets
6533 @cindex translating between character sets
6534 @cindex host character set
6535 @cindex target character set
6537 If the program you are debugging uses a different character set to
6538 represent characters and strings than the one @value{GDBN} uses itself,
6539 @value{GDBN} can automatically translate between the character sets for
6540 you. The character set @value{GDBN} uses we call the @dfn{host
6541 character set}; the one the inferior program uses we call the
6542 @dfn{target character set}.
6544 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
6545 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
6546 remote protocol (@pxref{Remote,Remote Debugging}) to debug a program
6547 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
6548 then the host character set is Latin-1, and the target character set is
6549 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
6550 target-charset EBCDIC-US}, then @value{GDBN} translates between
6551 @sc{ebcdic} and Latin 1 as you print character or string values, or use
6552 character and string literals in expressions.
6554 @value{GDBN} has no way to automatically recognize which character set
6555 the inferior program uses; you must tell it, using the @code{set
6556 target-charset} command, described below.
6558 Here are the commands for controlling @value{GDBN}'s character set
6562 @item set target-charset @var{charset}
6563 @kindex set target-charset
6564 Set the current target character set to @var{charset}. We list the
6565 character set names @value{GDBN} recognizes below, but if you type
6566 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6567 list the target character sets it supports.
6571 @item set host-charset @var{charset}
6572 @kindex set host-charset
6573 Set the current host character set to @var{charset}.
6575 By default, @value{GDBN} uses a host character set appropriate to the
6576 system it is running on; you can override that default using the
6577 @code{set host-charset} command.
6579 @value{GDBN} can only use certain character sets as its host character
6580 set. We list the character set names @value{GDBN} recognizes below, and
6581 indicate which can be host character sets, but if you type
6582 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6583 list the host character sets it supports.
6585 @item set charset @var{charset}
6587 Set the current host and target character sets to @var{charset}. As
6588 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
6589 @value{GDBN} will list the name of the character sets that can be used
6590 for both host and target.
6594 @kindex show charset
6595 Show the names of the current host and target charsets.
6597 @itemx show host-charset
6598 @kindex show host-charset
6599 Show the name of the current host charset.
6601 @itemx show target-charset
6602 @kindex show target-charset
6603 Show the name of the current target charset.
6607 @value{GDBN} currently includes support for the following character
6613 @cindex ASCII character set
6614 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
6618 @cindex ISO 8859-1 character set
6619 @cindex ISO Latin 1 character set
6620 The ISO Latin 1 character set. This extends @sc{ascii} with accented
6621 characters needed for French, German, and Spanish. @value{GDBN} can use
6622 this as its host character set.
6626 @cindex EBCDIC character set
6627 @cindex IBM1047 character set
6628 Variants of the @sc{ebcdic} character set, used on some of IBM's
6629 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
6630 @value{GDBN} cannot use these as its host character set.
6634 Note that these are all single-byte character sets. More work inside
6635 GDB is needed to support multi-byte or variable-width character
6636 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
6638 Here is an example of @value{GDBN}'s character set support in action.
6639 Assume that the following source code has been placed in the file
6640 @file{charset-test.c}:
6646 = @{72, 101, 108, 108, 111, 44, 32, 119,
6647 111, 114, 108, 100, 33, 10, 0@};
6648 char ibm1047_hello[]
6649 = @{200, 133, 147, 147, 150, 107, 64, 166,
6650 150, 153, 147, 132, 90, 37, 0@};
6654 printf ("Hello, world!\n");
6658 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
6659 containing the string @samp{Hello, world!} followed by a newline,
6660 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
6662 We compile the program, and invoke the debugger on it:
6665 $ gcc -g charset-test.c -o charset-test
6666 $ gdb -nw charset-test
6667 GNU gdb 2001-12-19-cvs
6668 Copyright 2001 Free Software Foundation, Inc.
6673 We can use the @code{show charset} command to see what character sets
6674 @value{GDBN} is currently using to interpret and display characters and
6678 (@value{GDBP}) show charset
6679 The current host and target character set is `ISO-8859-1'.
6683 For the sake of printing this manual, let's use @sc{ascii} as our
6684 initial character set:
6686 (@value{GDBP}) set charset ASCII
6687 (@value{GDBP}) show charset
6688 The current host and target character set is `ASCII'.
6692 Let's assume that @sc{ascii} is indeed the correct character set for our
6693 host system --- in other words, let's assume that if @value{GDBN} prints
6694 characters using the @sc{ascii} character set, our terminal will display
6695 them properly. Since our current target character set is also
6696 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
6699 (@value{GDBP}) print ascii_hello
6700 $1 = 0x401698 "Hello, world!\n"
6701 (@value{GDBP}) print ascii_hello[0]
6706 @value{GDBN} uses the target character set for character and string
6707 literals you use in expressions:
6710 (@value{GDBP}) print '+'
6715 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
6718 @value{GDBN} relies on the user to tell it which character set the
6719 target program uses. If we print @code{ibm1047_hello} while our target
6720 character set is still @sc{ascii}, we get jibberish:
6723 (@value{GDBP}) print ibm1047_hello
6724 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
6725 (@value{GDBP}) print ibm1047_hello[0]
6730 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
6731 @value{GDBN} tells us the character sets it supports:
6734 (@value{GDBP}) set target-charset
6735 ASCII EBCDIC-US IBM1047 ISO-8859-1
6736 (@value{GDBP}) set target-charset
6739 We can select @sc{ibm1047} as our target character set, and examine the
6740 program's strings again. Now the @sc{ascii} string is wrong, but
6741 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
6742 target character set, @sc{ibm1047}, to the host character set,
6743 @sc{ascii}, and they display correctly:
6746 (@value{GDBP}) set target-charset IBM1047
6747 (@value{GDBP}) show charset
6748 The current host character set is `ASCII'.
6749 The current target character set is `IBM1047'.
6750 (@value{GDBP}) print ascii_hello
6751 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
6752 (@value{GDBP}) print ascii_hello[0]
6754 (@value{GDBP}) print ibm1047_hello
6755 $8 = 0x4016a8 "Hello, world!\n"
6756 (@value{GDBP}) print ibm1047_hello[0]
6761 As above, @value{GDBN} uses the target character set for character and
6762 string literals you use in expressions:
6765 (@value{GDBP}) print '+'
6770 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
6773 @node Caching Remote Data
6774 @section Caching Data of Remote Targets
6775 @cindex caching data of remote targets
6777 @value{GDBN} can cache data exchanged between the debugger and a
6778 remote target (@pxref{Remote}). Such caching generally improves
6779 performance, because it reduces the overhead of the remote protocol by
6780 bundling memory reads and writes into large chunks. Unfortunately,
6781 @value{GDBN} does not currently know anything about volatile
6782 registers, and thus data caching will produce incorrect results when
6783 volatile registers are in use.
6786 @kindex set remotecache
6787 @item set remotecache on
6788 @itemx set remotecache off
6789 Set caching state for remote targets. When @code{ON}, use data
6790 caching. By default, this option is @code{OFF}.
6792 @kindex show remotecache
6793 @item show remotecache
6794 Show the current state of data caching for remote targets.
6798 Print the information about the data cache performance. The
6799 information displayed includes: the dcache width and depth; and for
6800 each cache line, how many times it was referenced, and its data and
6801 state (dirty, bad, ok, etc.). This command is useful for debugging
6802 the data cache operation.
6807 @chapter C Preprocessor Macros
6809 Some languages, such as C and C@t{++}, provide a way to define and invoke
6810 ``preprocessor macros'' which expand into strings of tokens.
6811 @value{GDBN} can evaluate expressions containing macro invocations, show
6812 the result of macro expansion, and show a macro's definition, including
6813 where it was defined.
6815 You may need to compile your program specially to provide @value{GDBN}
6816 with information about preprocessor macros. Most compilers do not
6817 include macros in their debugging information, even when you compile
6818 with the @option{-g} flag. @xref{Compilation}.
6820 A program may define a macro at one point, remove that definition later,
6821 and then provide a different definition after that. Thus, at different
6822 points in the program, a macro may have different definitions, or have
6823 no definition at all. If there is a current stack frame, @value{GDBN}
6824 uses the macros in scope at that frame's source code line. Otherwise,
6825 @value{GDBN} uses the macros in scope at the current listing location;
6828 At the moment, @value{GDBN} does not support the @code{##}
6829 token-splicing operator, the @code{#} stringification operator, or
6830 variable-arity macros.
6832 Whenever @value{GDBN} evaluates an expression, it always expands any
6833 macro invocations present in the expression. @value{GDBN} also provides
6834 the following commands for working with macros explicitly.
6838 @kindex macro expand
6839 @cindex macro expansion, showing the results of preprocessor
6840 @cindex preprocessor macro expansion, showing the results of
6841 @cindex expanding preprocessor macros
6842 @item macro expand @var{expression}
6843 @itemx macro exp @var{expression}
6844 Show the results of expanding all preprocessor macro invocations in
6845 @var{expression}. Since @value{GDBN} simply expands macros, but does
6846 not parse the result, @var{expression} need not be a valid expression;
6847 it can be any string of tokens.
6850 @item macro expand-once @var{expression}
6851 @itemx macro exp1 @var{expression}
6852 @cindex expand macro once
6853 @i{(This command is not yet implemented.)} Show the results of
6854 expanding those preprocessor macro invocations that appear explicitly in
6855 @var{expression}. Macro invocations appearing in that expansion are
6856 left unchanged. This command allows you to see the effect of a
6857 particular macro more clearly, without being confused by further
6858 expansions. Since @value{GDBN} simply expands macros, but does not
6859 parse the result, @var{expression} need not be a valid expression; it
6860 can be any string of tokens.
6863 @cindex macro definition, showing
6864 @cindex definition, showing a macro's
6865 @item info macro @var{macro}
6866 Show the definition of the macro named @var{macro}, and describe the
6867 source location where that definition was established.
6869 @kindex macro define
6870 @cindex user-defined macros
6871 @cindex defining macros interactively
6872 @cindex macros, user-defined
6873 @item macro define @var{macro} @var{replacement-list}
6874 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
6875 @i{(This command is not yet implemented.)} Introduce a definition for a
6876 preprocessor macro named @var{macro}, invocations of which are replaced
6877 by the tokens given in @var{replacement-list}. The first form of this
6878 command defines an ``object-like'' macro, which takes no arguments; the
6879 second form defines a ``function-like'' macro, which takes the arguments
6880 given in @var{arglist}.
6882 A definition introduced by this command is in scope in every expression
6883 evaluated in @value{GDBN}, until it is removed with the @command{macro
6884 undef} command, described below. The definition overrides all
6885 definitions for @var{macro} present in the program being debugged, as
6886 well as any previous user-supplied definition.
6889 @item macro undef @var{macro}
6890 @i{(This command is not yet implemented.)} Remove any user-supplied
6891 definition for the macro named @var{macro}. This command only affects
6892 definitions provided with the @command{macro define} command, described
6893 above; it cannot remove definitions present in the program being
6898 @i{(This command is not yet implemented.)} List all the macros
6899 defined using the @code{macro define} command.
6902 @cindex macros, example of debugging with
6903 Here is a transcript showing the above commands in action. First, we
6904 show our source files:
6912 #define ADD(x) (M + x)
6917 printf ("Hello, world!\n");
6919 printf ("We're so creative.\n");
6921 printf ("Goodbye, world!\n");
6928 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
6929 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
6930 compiler includes information about preprocessor macros in the debugging
6934 $ gcc -gdwarf-2 -g3 sample.c -o sample
6938 Now, we start @value{GDBN} on our sample program:
6942 GNU gdb 2002-05-06-cvs
6943 Copyright 2002 Free Software Foundation, Inc.
6944 GDB is free software, @dots{}
6948 We can expand macros and examine their definitions, even when the
6949 program is not running. @value{GDBN} uses the current listing position
6950 to decide which macro definitions are in scope:
6953 (@value{GDBP}) list main
6956 5 #define ADD(x) (M + x)
6961 10 printf ("Hello, world!\n");
6963 12 printf ("We're so creative.\n");
6964 (@value{GDBP}) info macro ADD
6965 Defined at /home/jimb/gdb/macros/play/sample.c:5
6966 #define ADD(x) (M + x)
6967 (@value{GDBP}) info macro Q
6968 Defined at /home/jimb/gdb/macros/play/sample.h:1
6969 included at /home/jimb/gdb/macros/play/sample.c:2
6971 (@value{GDBP}) macro expand ADD(1)
6972 expands to: (42 + 1)
6973 (@value{GDBP}) macro expand-once ADD(1)
6974 expands to: once (M + 1)
6978 In the example above, note that @command{macro expand-once} expands only
6979 the macro invocation explicit in the original text --- the invocation of
6980 @code{ADD} --- but does not expand the invocation of the macro @code{M},
6981 which was introduced by @code{ADD}.
6983 Once the program is running, GDB uses the macro definitions in force at
6984 the source line of the current stack frame:
6987 (@value{GDBP}) break main
6988 Breakpoint 1 at 0x8048370: file sample.c, line 10.
6990 Starting program: /home/jimb/gdb/macros/play/sample
6992 Breakpoint 1, main () at sample.c:10
6993 10 printf ("Hello, world!\n");
6997 At line 10, the definition of the macro @code{N} at line 9 is in force:
7000 (@value{GDBP}) info macro N
7001 Defined at /home/jimb/gdb/macros/play/sample.c:9
7003 (@value{GDBP}) macro expand N Q M
7005 (@value{GDBP}) print N Q M
7010 As we step over directives that remove @code{N}'s definition, and then
7011 give it a new definition, @value{GDBN} finds the definition (or lack
7012 thereof) in force at each point:
7017 12 printf ("We're so creative.\n");
7018 (@value{GDBP}) info macro N
7019 The symbol `N' has no definition as a C/C++ preprocessor macro
7020 at /home/jimb/gdb/macros/play/sample.c:12
7023 14 printf ("Goodbye, world!\n");
7024 (@value{GDBP}) info macro N
7025 Defined at /home/jimb/gdb/macros/play/sample.c:13
7027 (@value{GDBP}) macro expand N Q M
7028 expands to: 1729 < 42
7029 (@value{GDBP}) print N Q M
7036 @chapter Tracepoints
7037 @c This chapter is based on the documentation written by Michael
7038 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
7041 In some applications, it is not feasible for the debugger to interrupt
7042 the program's execution long enough for the developer to learn
7043 anything helpful about its behavior. If the program's correctness
7044 depends on its real-time behavior, delays introduced by a debugger
7045 might cause the program to change its behavior drastically, or perhaps
7046 fail, even when the code itself is correct. It is useful to be able
7047 to observe the program's behavior without interrupting it.
7049 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
7050 specify locations in the program, called @dfn{tracepoints}, and
7051 arbitrary expressions to evaluate when those tracepoints are reached.
7052 Later, using the @code{tfind} command, you can examine the values
7053 those expressions had when the program hit the tracepoints. The
7054 expressions may also denote objects in memory---structures or arrays,
7055 for example---whose values @value{GDBN} should record; while visiting
7056 a particular tracepoint, you may inspect those objects as if they were
7057 in memory at that moment. However, because @value{GDBN} records these
7058 values without interacting with you, it can do so quickly and
7059 unobtrusively, hopefully not disturbing the program's behavior.
7061 The tracepoint facility is currently available only for remote
7062 targets. @xref{Targets}. In addition, your remote target must know how
7063 to collect trace data. This functionality is implemented in the remote
7064 stub; however, none of the stubs distributed with @value{GDBN} support
7065 tracepoints as of this writing.
7067 This chapter describes the tracepoint commands and features.
7071 * Analyze Collected Data::
7072 * Tracepoint Variables::
7075 @node Set Tracepoints
7076 @section Commands to Set Tracepoints
7078 Before running such a @dfn{trace experiment}, an arbitrary number of
7079 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
7080 tracepoint has a number assigned to it by @value{GDBN}. Like with
7081 breakpoints, tracepoint numbers are successive integers starting from
7082 one. Many of the commands associated with tracepoints take the
7083 tracepoint number as their argument, to identify which tracepoint to
7086 For each tracepoint, you can specify, in advance, some arbitrary set
7087 of data that you want the target to collect in the trace buffer when
7088 it hits that tracepoint. The collected data can include registers,
7089 local variables, or global data. Later, you can use @value{GDBN}
7090 commands to examine the values these data had at the time the
7093 This section describes commands to set tracepoints and associated
7094 conditions and actions.
7097 * Create and Delete Tracepoints::
7098 * Enable and Disable Tracepoints::
7099 * Tracepoint Passcounts::
7100 * Tracepoint Actions::
7101 * Listing Tracepoints::
7102 * Starting and Stopping Trace Experiment::
7105 @node Create and Delete Tracepoints
7106 @subsection Create and Delete Tracepoints
7109 @cindex set tracepoint
7112 The @code{trace} command is very similar to the @code{break} command.
7113 Its argument can be a source line, a function name, or an address in
7114 the target program. @xref{Set Breaks}. The @code{trace} command
7115 defines a tracepoint, which is a point in the target program where the
7116 debugger will briefly stop, collect some data, and then allow the
7117 program to continue. Setting a tracepoint or changing its commands
7118 doesn't take effect until the next @code{tstart} command; thus, you
7119 cannot change the tracepoint attributes once a trace experiment is
7122 Here are some examples of using the @code{trace} command:
7125 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
7127 (@value{GDBP}) @b{trace +2} // 2 lines forward
7129 (@value{GDBP}) @b{trace my_function} // first source line of function
7131 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
7133 (@value{GDBP}) @b{trace *0x2117c4} // an address
7137 You can abbreviate @code{trace} as @code{tr}.
7140 @cindex last tracepoint number
7141 @cindex recent tracepoint number
7142 @cindex tracepoint number
7143 The convenience variable @code{$tpnum} records the tracepoint number
7144 of the most recently set tracepoint.
7146 @kindex delete tracepoint
7147 @cindex tracepoint deletion
7148 @item delete tracepoint @r{[}@var{num}@r{]}
7149 Permanently delete one or more tracepoints. With no argument, the
7150 default is to delete all tracepoints.
7155 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
7157 (@value{GDBP}) @b{delete trace} // remove all tracepoints
7161 You can abbreviate this command as @code{del tr}.
7164 @node Enable and Disable Tracepoints
7165 @subsection Enable and Disable Tracepoints
7168 @kindex disable tracepoint
7169 @item disable tracepoint @r{[}@var{num}@r{]}
7170 Disable tracepoint @var{num}, or all tracepoints if no argument
7171 @var{num} is given. A disabled tracepoint will have no effect during
7172 the next trace experiment, but it is not forgotten. You can re-enable
7173 a disabled tracepoint using the @code{enable tracepoint} command.
7175 @kindex enable tracepoint
7176 @item enable tracepoint @r{[}@var{num}@r{]}
7177 Enable tracepoint @var{num}, or all tracepoints. The enabled
7178 tracepoints will become effective the next time a trace experiment is
7182 @node Tracepoint Passcounts
7183 @subsection Tracepoint Passcounts
7187 @cindex tracepoint pass count
7188 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
7189 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
7190 automatically stop a trace experiment. If a tracepoint's passcount is
7191 @var{n}, then the trace experiment will be automatically stopped on
7192 the @var{n}'th time that tracepoint is hit. If the tracepoint number
7193 @var{num} is not specified, the @code{passcount} command sets the
7194 passcount of the most recently defined tracepoint. If no passcount is
7195 given, the trace experiment will run until stopped explicitly by the
7201 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
7202 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
7204 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
7205 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
7206 (@value{GDBP}) @b{trace foo}
7207 (@value{GDBP}) @b{pass 3}
7208 (@value{GDBP}) @b{trace bar}
7209 (@value{GDBP}) @b{pass 2}
7210 (@value{GDBP}) @b{trace baz}
7211 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
7212 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
7213 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
7214 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
7218 @node Tracepoint Actions
7219 @subsection Tracepoint Action Lists
7223 @cindex tracepoint actions
7224 @item actions @r{[}@var{num}@r{]}
7225 This command will prompt for a list of actions to be taken when the
7226 tracepoint is hit. If the tracepoint number @var{num} is not
7227 specified, this command sets the actions for the one that was most
7228 recently defined (so that you can define a tracepoint and then say
7229 @code{actions} without bothering about its number). You specify the
7230 actions themselves on the following lines, one action at a time, and
7231 terminate the actions list with a line containing just @code{end}. So
7232 far, the only defined actions are @code{collect} and
7233 @code{while-stepping}.
7235 @cindex remove actions from a tracepoint
7236 To remove all actions from a tracepoint, type @samp{actions @var{num}}
7237 and follow it immediately with @samp{end}.
7240 (@value{GDBP}) @b{collect @var{data}} // collect some data
7242 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
7244 (@value{GDBP}) @b{end} // signals the end of actions.
7247 In the following example, the action list begins with @code{collect}
7248 commands indicating the things to be collected when the tracepoint is
7249 hit. Then, in order to single-step and collect additional data
7250 following the tracepoint, a @code{while-stepping} command is used,
7251 followed by the list of things to be collected while stepping. The
7252 @code{while-stepping} command is terminated by its own separate
7253 @code{end} command. Lastly, the action list is terminated by an
7257 (@value{GDBP}) @b{trace foo}
7258 (@value{GDBP}) @b{actions}
7259 Enter actions for tracepoint 1, one per line:
7268 @kindex collect @r{(tracepoints)}
7269 @item collect @var{expr1}, @var{expr2}, @dots{}
7270 Collect values of the given expressions when the tracepoint is hit.
7271 This command accepts a comma-separated list of any valid expressions.
7272 In addition to global, static, or local variables, the following
7273 special arguments are supported:
7277 collect all registers
7280 collect all function arguments
7283 collect all local variables.
7286 You can give several consecutive @code{collect} commands, each one
7287 with a single argument, or one @code{collect} command with several
7288 arguments separated by commas: the effect is the same.
7290 The command @code{info scope} (@pxref{Symbols, info scope}) is
7291 particularly useful for figuring out what data to collect.
7293 @kindex while-stepping @r{(tracepoints)}
7294 @item while-stepping @var{n}
7295 Perform @var{n} single-step traces after the tracepoint, collecting
7296 new data at each step. The @code{while-stepping} command is
7297 followed by the list of what to collect while stepping (followed by
7298 its own @code{end} command):
7302 > collect $regs, myglobal
7308 You may abbreviate @code{while-stepping} as @code{ws} or
7312 @node Listing Tracepoints
7313 @subsection Listing Tracepoints
7316 @kindex info tracepoints
7318 @cindex information about tracepoints
7319 @item info tracepoints @r{[}@var{num}@r{]}
7320 Display information about the tracepoint @var{num}. If you don't specify
7321 a tracepoint number, displays information about all the tracepoints
7322 defined so far. For each tracepoint, the following information is
7329 whether it is enabled or disabled
7333 its passcount as given by the @code{passcount @var{n}} command
7335 its step count as given by the @code{while-stepping @var{n}} command
7337 where in the source files is the tracepoint set
7339 its action list as given by the @code{actions} command
7343 (@value{GDBP}) @b{info trace}
7344 Num Enb Address PassC StepC What
7345 1 y 0x002117c4 0 0 <gdb_asm>
7346 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
7347 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
7352 This command can be abbreviated @code{info tp}.
7355 @node Starting and Stopping Trace Experiment
7356 @subsection Starting and Stopping Trace Experiment
7360 @cindex start a new trace experiment
7361 @cindex collected data discarded
7363 This command takes no arguments. It starts the trace experiment, and
7364 begins collecting data. This has the side effect of discarding all
7365 the data collected in the trace buffer during the previous trace
7369 @cindex stop a running trace experiment
7371 This command takes no arguments. It ends the trace experiment, and
7372 stops collecting data.
7374 @strong{Note}: a trace experiment and data collection may stop
7375 automatically if any tracepoint's passcount is reached
7376 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
7379 @cindex status of trace data collection
7380 @cindex trace experiment, status of
7382 This command displays the status of the current trace data
7386 Here is an example of the commands we described so far:
7389 (@value{GDBP}) @b{trace gdb_c_test}
7390 (@value{GDBP}) @b{actions}
7391 Enter actions for tracepoint #1, one per line.
7392 > collect $regs,$locals,$args
7397 (@value{GDBP}) @b{tstart}
7398 [time passes @dots{}]
7399 (@value{GDBP}) @b{tstop}
7403 @node Analyze Collected Data
7404 @section Using the collected data
7406 After the tracepoint experiment ends, you use @value{GDBN} commands
7407 for examining the trace data. The basic idea is that each tracepoint
7408 collects a trace @dfn{snapshot} every time it is hit and another
7409 snapshot every time it single-steps. All these snapshots are
7410 consecutively numbered from zero and go into a buffer, and you can
7411 examine them later. The way you examine them is to @dfn{focus} on a
7412 specific trace snapshot. When the remote stub is focused on a trace
7413 snapshot, it will respond to all @value{GDBN} requests for memory and
7414 registers by reading from the buffer which belongs to that snapshot,
7415 rather than from @emph{real} memory or registers of the program being
7416 debugged. This means that @strong{all} @value{GDBN} commands
7417 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
7418 behave as if we were currently debugging the program state as it was
7419 when the tracepoint occurred. Any requests for data that are not in
7420 the buffer will fail.
7423 * tfind:: How to select a trace snapshot
7424 * tdump:: How to display all data for a snapshot
7425 * save-tracepoints:: How to save tracepoints for a future run
7429 @subsection @code{tfind @var{n}}
7432 @cindex select trace snapshot
7433 @cindex find trace snapshot
7434 The basic command for selecting a trace snapshot from the buffer is
7435 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
7436 counting from zero. If no argument @var{n} is given, the next
7437 snapshot is selected.
7439 Here are the various forms of using the @code{tfind} command.
7443 Find the first snapshot in the buffer. This is a synonym for
7444 @code{tfind 0} (since 0 is the number of the first snapshot).
7447 Stop debugging trace snapshots, resume @emph{live} debugging.
7450 Same as @samp{tfind none}.
7453 No argument means find the next trace snapshot.
7456 Find the previous trace snapshot before the current one. This permits
7457 retracing earlier steps.
7459 @item tfind tracepoint @var{num}
7460 Find the next snapshot associated with tracepoint @var{num}. Search
7461 proceeds forward from the last examined trace snapshot. If no
7462 argument @var{num} is given, it means find the next snapshot collected
7463 for the same tracepoint as the current snapshot.
7465 @item tfind pc @var{addr}
7466 Find the next snapshot associated with the value @var{addr} of the
7467 program counter. Search proceeds forward from the last examined trace
7468 snapshot. If no argument @var{addr} is given, it means find the next
7469 snapshot with the same value of PC as the current snapshot.
7471 @item tfind outside @var{addr1}, @var{addr2}
7472 Find the next snapshot whose PC is outside the given range of
7475 @item tfind range @var{addr1}, @var{addr2}
7476 Find the next snapshot whose PC is between @var{addr1} and
7477 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
7479 @item tfind line @r{[}@var{file}:@r{]}@var{n}
7480 Find the next snapshot associated with the source line @var{n}. If
7481 the optional argument @var{file} is given, refer to line @var{n} in
7482 that source file. Search proceeds forward from the last examined
7483 trace snapshot. If no argument @var{n} is given, it means find the
7484 next line other than the one currently being examined; thus saying
7485 @code{tfind line} repeatedly can appear to have the same effect as
7486 stepping from line to line in a @emph{live} debugging session.
7489 The default arguments for the @code{tfind} commands are specifically
7490 designed to make it easy to scan through the trace buffer. For
7491 instance, @code{tfind} with no argument selects the next trace
7492 snapshot, and @code{tfind -} with no argument selects the previous
7493 trace snapshot. So, by giving one @code{tfind} command, and then
7494 simply hitting @key{RET} repeatedly you can examine all the trace
7495 snapshots in order. Or, by saying @code{tfind -} and then hitting
7496 @key{RET} repeatedly you can examine the snapshots in reverse order.
7497 The @code{tfind line} command with no argument selects the snapshot
7498 for the next source line executed. The @code{tfind pc} command with
7499 no argument selects the next snapshot with the same program counter
7500 (PC) as the current frame. The @code{tfind tracepoint} command with
7501 no argument selects the next trace snapshot collected by the same
7502 tracepoint as the current one.
7504 In addition to letting you scan through the trace buffer manually,
7505 these commands make it easy to construct @value{GDBN} scripts that
7506 scan through the trace buffer and print out whatever collected data
7507 you are interested in. Thus, if we want to examine the PC, FP, and SP
7508 registers from each trace frame in the buffer, we can say this:
7511 (@value{GDBP}) @b{tfind start}
7512 (@value{GDBP}) @b{while ($trace_frame != -1)}
7513 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
7514 $trace_frame, $pc, $sp, $fp
7518 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
7519 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
7520 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
7521 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
7522 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
7523 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
7524 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
7525 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
7526 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
7527 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
7528 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
7531 Or, if we want to examine the variable @code{X} at each source line in
7535 (@value{GDBP}) @b{tfind start}
7536 (@value{GDBP}) @b{while ($trace_frame != -1)}
7537 > printf "Frame %d, X == %d\n", $trace_frame, X
7547 @subsection @code{tdump}
7549 @cindex dump all data collected at tracepoint
7550 @cindex tracepoint data, display
7552 This command takes no arguments. It prints all the data collected at
7553 the current trace snapshot.
7556 (@value{GDBP}) @b{trace 444}
7557 (@value{GDBP}) @b{actions}
7558 Enter actions for tracepoint #2, one per line:
7559 > collect $regs, $locals, $args, gdb_long_test
7562 (@value{GDBP}) @b{tstart}
7564 (@value{GDBP}) @b{tfind line 444}
7565 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
7567 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
7569 (@value{GDBP}) @b{tdump}
7570 Data collected at tracepoint 2, trace frame 1:
7571 d0 0xc4aa0085 -995491707
7575 d4 0x71aea3d 119204413
7580 a1 0x3000668 50333288
7583 a4 0x3000698 50333336
7585 fp 0x30bf3c 0x30bf3c
7586 sp 0x30bf34 0x30bf34
7588 pc 0x20b2c8 0x20b2c8
7592 p = 0x20e5b4 "gdb-test"
7599 gdb_long_test = 17 '\021'
7604 @node save-tracepoints
7605 @subsection @code{save-tracepoints @var{filename}}
7606 @kindex save-tracepoints
7607 @cindex save tracepoints for future sessions
7609 This command saves all current tracepoint definitions together with
7610 their actions and passcounts, into a file @file{@var{filename}}
7611 suitable for use in a later debugging session. To read the saved
7612 tracepoint definitions, use the @code{source} command (@pxref{Command
7615 @node Tracepoint Variables
7616 @section Convenience Variables for Tracepoints
7617 @cindex tracepoint variables
7618 @cindex convenience variables for tracepoints
7621 @vindex $trace_frame
7622 @item (int) $trace_frame
7623 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
7624 snapshot is selected.
7627 @item (int) $tracepoint
7628 The tracepoint for the current trace snapshot.
7631 @item (int) $trace_line
7632 The line number for the current trace snapshot.
7635 @item (char []) $trace_file
7636 The source file for the current trace snapshot.
7639 @item (char []) $trace_func
7640 The name of the function containing @code{$tracepoint}.
7643 Note: @code{$trace_file} is not suitable for use in @code{printf},
7644 use @code{output} instead.
7646 Here's a simple example of using these convenience variables for
7647 stepping through all the trace snapshots and printing some of their
7651 (@value{GDBP}) @b{tfind start}
7653 (@value{GDBP}) @b{while $trace_frame != -1}
7654 > output $trace_file
7655 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
7661 @chapter Debugging Programs That Use Overlays
7664 If your program is too large to fit completely in your target system's
7665 memory, you can sometimes use @dfn{overlays} to work around this
7666 problem. @value{GDBN} provides some support for debugging programs that
7670 * How Overlays Work:: A general explanation of overlays.
7671 * Overlay Commands:: Managing overlays in @value{GDBN}.
7672 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
7673 mapped by asking the inferior.
7674 * Overlay Sample Program:: A sample program using overlays.
7677 @node How Overlays Work
7678 @section How Overlays Work
7679 @cindex mapped overlays
7680 @cindex unmapped overlays
7681 @cindex load address, overlay's
7682 @cindex mapped address
7683 @cindex overlay area
7685 Suppose you have a computer whose instruction address space is only 64
7686 kilobytes long, but which has much more memory which can be accessed by
7687 other means: special instructions, segment registers, or memory
7688 management hardware, for example. Suppose further that you want to
7689 adapt a program which is larger than 64 kilobytes to run on this system.
7691 One solution is to identify modules of your program which are relatively
7692 independent, and need not call each other directly; call these modules
7693 @dfn{overlays}. Separate the overlays from the main program, and place
7694 their machine code in the larger memory. Place your main program in
7695 instruction memory, but leave at least enough space there to hold the
7696 largest overlay as well.
7698 Now, to call a function located in an overlay, you must first copy that
7699 overlay's machine code from the large memory into the space set aside
7700 for it in the instruction memory, and then jump to its entry point
7703 @c NB: In the below the mapped area's size is greater or equal to the
7704 @c size of all overlays. This is intentional to remind the developer
7705 @c that overlays don't necessarily need to be the same size.
7709 Data Instruction Larger
7710 Address Space Address Space Address Space
7711 +-----------+ +-----------+ +-----------+
7713 +-----------+ +-----------+ +-----------+<-- overlay 1
7714 | program | | main | .----| overlay 1 | load address
7715 | variables | | program | | +-----------+
7716 | and heap | | | | | |
7717 +-----------+ | | | +-----------+<-- overlay 2
7718 | | +-----------+ | | | load address
7719 +-----------+ | | | .-| overlay 2 |
7721 mapped --->+-----------+ | | +-----------+
7723 | overlay | <-' | | |
7724 | area | <---' +-----------+<-- overlay 3
7725 | | <---. | | load address
7726 +-----------+ `--| overlay 3 |
7733 @anchor{A code overlay}A code overlay
7737 The diagram (@pxref{A code overlay}) shows a system with separate data
7738 and instruction address spaces. To map an overlay, the program copies
7739 its code from the larger address space to the instruction address space.
7740 Since the overlays shown here all use the same mapped address, only one
7741 may be mapped at a time. For a system with a single address space for
7742 data and instructions, the diagram would be similar, except that the
7743 program variables and heap would share an address space with the main
7744 program and the overlay area.
7746 An overlay loaded into instruction memory and ready for use is called a
7747 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
7748 instruction memory. An overlay not present (or only partially present)
7749 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
7750 is its address in the larger memory. The mapped address is also called
7751 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
7752 called the @dfn{load memory address}, or @dfn{LMA}.
7754 Unfortunately, overlays are not a completely transparent way to adapt a
7755 program to limited instruction memory. They introduce a new set of
7756 global constraints you must keep in mind as you design your program:
7761 Before calling or returning to a function in an overlay, your program
7762 must make sure that overlay is actually mapped. Otherwise, the call or
7763 return will transfer control to the right address, but in the wrong
7764 overlay, and your program will probably crash.
7767 If the process of mapping an overlay is expensive on your system, you
7768 will need to choose your overlays carefully to minimize their effect on
7769 your program's performance.
7772 The executable file you load onto your system must contain each
7773 overlay's instructions, appearing at the overlay's load address, not its
7774 mapped address. However, each overlay's instructions must be relocated
7775 and its symbols defined as if the overlay were at its mapped address.
7776 You can use GNU linker scripts to specify different load and relocation
7777 addresses for pieces of your program; see @ref{Overlay Description,,,
7778 ld.info, Using ld: the GNU linker}.
7781 The procedure for loading executable files onto your system must be able
7782 to load their contents into the larger address space as well as the
7783 instruction and data spaces.
7787 The overlay system described above is rather simple, and could be
7788 improved in many ways:
7793 If your system has suitable bank switch registers or memory management
7794 hardware, you could use those facilities to make an overlay's load area
7795 contents simply appear at their mapped address in instruction space.
7796 This would probably be faster than copying the overlay to its mapped
7797 area in the usual way.
7800 If your overlays are small enough, you could set aside more than one
7801 overlay area, and have more than one overlay mapped at a time.
7804 You can use overlays to manage data, as well as instructions. In
7805 general, data overlays are even less transparent to your design than
7806 code overlays: whereas code overlays only require care when you call or
7807 return to functions, data overlays require care every time you access
7808 the data. Also, if you change the contents of a data overlay, you
7809 must copy its contents back out to its load address before you can copy a
7810 different data overlay into the same mapped area.
7815 @node Overlay Commands
7816 @section Overlay Commands
7818 To use @value{GDBN}'s overlay support, each overlay in your program must
7819 correspond to a separate section of the executable file. The section's
7820 virtual memory address and load memory address must be the overlay's
7821 mapped and load addresses. Identifying overlays with sections allows
7822 @value{GDBN} to determine the appropriate address of a function or
7823 variable, depending on whether the overlay is mapped or not.
7825 @value{GDBN}'s overlay commands all start with the word @code{overlay};
7826 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
7831 Disable @value{GDBN}'s overlay support. When overlay support is
7832 disabled, @value{GDBN} assumes that all functions and variables are
7833 always present at their mapped addresses. By default, @value{GDBN}'s
7834 overlay support is disabled.
7836 @item overlay manual
7837 @cindex manual overlay debugging
7838 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
7839 relies on you to tell it which overlays are mapped, and which are not,
7840 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
7841 commands described below.
7843 @item overlay map-overlay @var{overlay}
7844 @itemx overlay map @var{overlay}
7845 @cindex map an overlay
7846 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
7847 be the name of the object file section containing the overlay. When an
7848 overlay is mapped, @value{GDBN} assumes it can find the overlay's
7849 functions and variables at their mapped addresses. @value{GDBN} assumes
7850 that any other overlays whose mapped ranges overlap that of
7851 @var{overlay} are now unmapped.
7853 @item overlay unmap-overlay @var{overlay}
7854 @itemx overlay unmap @var{overlay}
7855 @cindex unmap an overlay
7856 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
7857 must be the name of the object file section containing the overlay.
7858 When an overlay is unmapped, @value{GDBN} assumes it can find the
7859 overlay's functions and variables at their load addresses.
7862 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
7863 consults a data structure the overlay manager maintains in the inferior
7864 to see which overlays are mapped. For details, see @ref{Automatic
7867 @item overlay load-target
7869 @cindex reloading the overlay table
7870 Re-read the overlay table from the inferior. Normally, @value{GDBN}
7871 re-reads the table @value{GDBN} automatically each time the inferior
7872 stops, so this command should only be necessary if you have changed the
7873 overlay mapping yourself using @value{GDBN}. This command is only
7874 useful when using automatic overlay debugging.
7876 @item overlay list-overlays
7878 @cindex listing mapped overlays
7879 Display a list of the overlays currently mapped, along with their mapped
7880 addresses, load addresses, and sizes.
7884 Normally, when @value{GDBN} prints a code address, it includes the name
7885 of the function the address falls in:
7888 (@value{GDBP}) print main
7889 $3 = @{int ()@} 0x11a0 <main>
7892 When overlay debugging is enabled, @value{GDBN} recognizes code in
7893 unmapped overlays, and prints the names of unmapped functions with
7894 asterisks around them. For example, if @code{foo} is a function in an
7895 unmapped overlay, @value{GDBN} prints it this way:
7898 (@value{GDBP}) overlay list
7899 No sections are mapped.
7900 (@value{GDBP}) print foo
7901 $5 = @{int (int)@} 0x100000 <*foo*>
7904 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
7908 (@value{GDBP}) overlay list
7909 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
7910 mapped at 0x1016 - 0x104a
7911 (@value{GDBP}) print foo
7912 $6 = @{int (int)@} 0x1016 <foo>
7915 When overlay debugging is enabled, @value{GDBN} can find the correct
7916 address for functions and variables in an overlay, whether or not the
7917 overlay is mapped. This allows most @value{GDBN} commands, like
7918 @code{break} and @code{disassemble}, to work normally, even on unmapped
7919 code. However, @value{GDBN}'s breakpoint support has some limitations:
7923 @cindex breakpoints in overlays
7924 @cindex overlays, setting breakpoints in
7925 You can set breakpoints in functions in unmapped overlays, as long as
7926 @value{GDBN} can write to the overlay at its load address.
7928 @value{GDBN} can not set hardware or simulator-based breakpoints in
7929 unmapped overlays. However, if you set a breakpoint at the end of your
7930 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
7931 you are using manual overlay management), @value{GDBN} will re-set its
7932 breakpoints properly.
7936 @node Automatic Overlay Debugging
7937 @section Automatic Overlay Debugging
7938 @cindex automatic overlay debugging
7940 @value{GDBN} can automatically track which overlays are mapped and which
7941 are not, given some simple co-operation from the overlay manager in the
7942 inferior. If you enable automatic overlay debugging with the
7943 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
7944 looks in the inferior's memory for certain variables describing the
7945 current state of the overlays.
7947 Here are the variables your overlay manager must define to support
7948 @value{GDBN}'s automatic overlay debugging:
7952 @item @code{_ovly_table}:
7953 This variable must be an array of the following structures:
7958 /* The overlay's mapped address. */
7961 /* The size of the overlay, in bytes. */
7964 /* The overlay's load address. */
7967 /* Non-zero if the overlay is currently mapped;
7969 unsigned long mapped;
7973 @item @code{_novlys}:
7974 This variable must be a four-byte signed integer, holding the total
7975 number of elements in @code{_ovly_table}.
7979 To decide whether a particular overlay is mapped or not, @value{GDBN}
7980 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
7981 @code{lma} members equal the VMA and LMA of the overlay's section in the
7982 executable file. When @value{GDBN} finds a matching entry, it consults
7983 the entry's @code{mapped} member to determine whether the overlay is
7986 In addition, your overlay manager may define a function called
7987 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
7988 will silently set a breakpoint there. If the overlay manager then
7989 calls this function whenever it has changed the overlay table, this
7990 will enable @value{GDBN} to accurately keep track of which overlays
7991 are in program memory, and update any breakpoints that may be set
7992 in overlays. This will allow breakpoints to work even if the
7993 overlays are kept in ROM or other non-writable memory while they
7994 are not being executed.
7996 @node Overlay Sample Program
7997 @section Overlay Sample Program
7998 @cindex overlay example program
8000 When linking a program which uses overlays, you must place the overlays
8001 at their load addresses, while relocating them to run at their mapped
8002 addresses. To do this, you must write a linker script (@pxref{Overlay
8003 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
8004 since linker scripts are specific to a particular host system, target
8005 architecture, and target memory layout, this manual cannot provide
8006 portable sample code demonstrating @value{GDBN}'s overlay support.
8008 However, the @value{GDBN} source distribution does contain an overlaid
8009 program, with linker scripts for a few systems, as part of its test
8010 suite. The program consists of the following files from
8011 @file{gdb/testsuite/gdb.base}:
8015 The main program file.
8017 A simple overlay manager, used by @file{overlays.c}.
8022 Overlay modules, loaded and used by @file{overlays.c}.
8025 Linker scripts for linking the test program on the @code{d10v-elf}
8026 and @code{m32r-elf} targets.
8029 You can build the test program using the @code{d10v-elf} GCC
8030 cross-compiler like this:
8033 $ d10v-elf-gcc -g -c overlays.c
8034 $ d10v-elf-gcc -g -c ovlymgr.c
8035 $ d10v-elf-gcc -g -c foo.c
8036 $ d10v-elf-gcc -g -c bar.c
8037 $ d10v-elf-gcc -g -c baz.c
8038 $ d10v-elf-gcc -g -c grbx.c
8039 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
8040 baz.o grbx.o -Wl,-Td10v.ld -o overlays
8043 The build process is identical for any other architecture, except that
8044 you must substitute the appropriate compiler and linker script for the
8045 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
8049 @chapter Using @value{GDBN} with Different Languages
8052 Although programming languages generally have common aspects, they are
8053 rarely expressed in the same manner. For instance, in ANSI C,
8054 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
8055 Modula-2, it is accomplished by @code{p^}. Values can also be
8056 represented (and displayed) differently. Hex numbers in C appear as
8057 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
8059 @cindex working language
8060 Language-specific information is built into @value{GDBN} for some languages,
8061 allowing you to express operations like the above in your program's
8062 native language, and allowing @value{GDBN} to output values in a manner
8063 consistent with the syntax of your program's native language. The
8064 language you use to build expressions is called the @dfn{working
8068 * Setting:: Switching between source languages
8069 * Show:: Displaying the language
8070 * Checks:: Type and range checks
8071 * Supported languages:: Supported languages
8072 * Unsupported languages:: Unsupported languages
8076 @section Switching between source languages
8078 There are two ways to control the working language---either have @value{GDBN}
8079 set it automatically, or select it manually yourself. You can use the
8080 @code{set language} command for either purpose. On startup, @value{GDBN}
8081 defaults to setting the language automatically. The working language is
8082 used to determine how expressions you type are interpreted, how values
8085 In addition to the working language, every source file that
8086 @value{GDBN} knows about has its own working language. For some object
8087 file formats, the compiler might indicate which language a particular
8088 source file is in. However, most of the time @value{GDBN} infers the
8089 language from the name of the file. The language of a source file
8090 controls whether C@t{++} names are demangled---this way @code{backtrace} can
8091 show each frame appropriately for its own language. There is no way to
8092 set the language of a source file from within @value{GDBN}, but you can
8093 set the language associated with a filename extension. @xref{Show, ,
8094 Displaying the language}.
8096 This is most commonly a problem when you use a program, such
8097 as @code{cfront} or @code{f2c}, that generates C but is written in
8098 another language. In that case, make the
8099 program use @code{#line} directives in its C output; that way
8100 @value{GDBN} will know the correct language of the source code of the original
8101 program, and will display that source code, not the generated C code.
8104 * Filenames:: Filename extensions and languages.
8105 * Manually:: Setting the working language manually
8106 * Automatically:: Having @value{GDBN} infer the source language
8110 @subsection List of filename extensions and languages
8112 If a source file name ends in one of the following extensions, then
8113 @value{GDBN} infers that its language is the one indicated.
8134 Objective-C source file
8141 Modula-2 source file
8145 Assembler source file. This actually behaves almost like C, but
8146 @value{GDBN} does not skip over function prologues when stepping.
8149 In addition, you may set the language associated with a filename
8150 extension. @xref{Show, , Displaying the language}.
8153 @subsection Setting the working language
8155 If you allow @value{GDBN} to set the language automatically,
8156 expressions are interpreted the same way in your debugging session and
8159 @kindex set language
8160 If you wish, you may set the language manually. To do this, issue the
8161 command @samp{set language @var{lang}}, where @var{lang} is the name of
8163 @code{c} or @code{modula-2}.
8164 For a list of the supported languages, type @samp{set language}.
8166 Setting the language manually prevents @value{GDBN} from updating the working
8167 language automatically. This can lead to confusion if you try
8168 to debug a program when the working language is not the same as the
8169 source language, when an expression is acceptable to both
8170 languages---but means different things. For instance, if the current
8171 source file were written in C, and @value{GDBN} was parsing Modula-2, a
8179 might not have the effect you intended. In C, this means to add
8180 @code{b} and @code{c} and place the result in @code{a}. The result
8181 printed would be the value of @code{a}. In Modula-2, this means to compare
8182 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
8185 @subsection Having @value{GDBN} infer the source language
8187 To have @value{GDBN} set the working language automatically, use
8188 @samp{set language local} or @samp{set language auto}. @value{GDBN}
8189 then infers the working language. That is, when your program stops in a
8190 frame (usually by encountering a breakpoint), @value{GDBN} sets the
8191 working language to the language recorded for the function in that
8192 frame. If the language for a frame is unknown (that is, if the function
8193 or block corresponding to the frame was defined in a source file that
8194 does not have a recognized extension), the current working language is
8195 not changed, and @value{GDBN} issues a warning.
8197 This may not seem necessary for most programs, which are written
8198 entirely in one source language. However, program modules and libraries
8199 written in one source language can be used by a main program written in
8200 a different source language. Using @samp{set language auto} in this
8201 case frees you from having to set the working language manually.
8204 @section Displaying the language
8206 The following commands help you find out which language is the
8207 working language, and also what language source files were written in.
8211 @kindex show language
8212 Display the current working language. This is the
8213 language you can use with commands such as @code{print} to
8214 build and compute expressions that may involve variables in your program.
8217 @kindex info frame@r{, show the source language}
8218 Display the source language for this frame. This language becomes the
8219 working language if you use an identifier from this frame.
8220 @xref{Frame Info, ,Information about a frame}, to identify the other
8221 information listed here.
8224 @kindex info source@r{, show the source language}
8225 Display the source language of this source file.
8226 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
8227 information listed here.
8230 In unusual circumstances, you may have source files with extensions
8231 not in the standard list. You can then set the extension associated
8232 with a language explicitly:
8235 @item set extension-language @var{ext} @var{language}
8236 @kindex set extension-language
8237 Tell @value{GDBN} that source files with extension @var{ext} are to be
8238 assumed as written in the source language @var{language}.
8240 @item info extensions
8241 @kindex info extensions
8242 List all the filename extensions and the associated languages.
8246 @section Type and range checking
8249 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
8250 checking are included, but they do not yet have any effect. This
8251 section documents the intended facilities.
8253 @c FIXME remove warning when type/range code added
8255 Some languages are designed to guard you against making seemingly common
8256 errors through a series of compile- and run-time checks. These include
8257 checking the type of arguments to functions and operators, and making
8258 sure mathematical overflows are caught at run time. Checks such as
8259 these help to ensure a program's correctness once it has been compiled
8260 by eliminating type mismatches, and providing active checks for range
8261 errors when your program is running.
8263 @value{GDBN} can check for conditions like the above if you wish.
8264 Although @value{GDBN} does not check the statements in your program,
8265 it can check expressions entered directly into @value{GDBN} for
8266 evaluation via the @code{print} command, for example. As with the
8267 working language, @value{GDBN} can also decide whether or not to check
8268 automatically based on your program's source language.
8269 @xref{Supported languages, ,Supported languages}, for the default
8270 settings of supported languages.
8273 * Type Checking:: An overview of type checking
8274 * Range Checking:: An overview of range checking
8277 @cindex type checking
8278 @cindex checks, type
8280 @subsection An overview of type checking
8282 Some languages, such as Modula-2, are strongly typed, meaning that the
8283 arguments to operators and functions have to be of the correct type,
8284 otherwise an error occurs. These checks prevent type mismatch
8285 errors from ever causing any run-time problems. For example,
8293 The second example fails because the @code{CARDINAL} 1 is not
8294 type-compatible with the @code{REAL} 2.3.
8296 For the expressions you use in @value{GDBN} commands, you can tell the
8297 @value{GDBN} type checker to skip checking;
8298 to treat any mismatches as errors and abandon the expression;
8299 or to only issue warnings when type mismatches occur,
8300 but evaluate the expression anyway. When you choose the last of
8301 these, @value{GDBN} evaluates expressions like the second example above, but
8302 also issues a warning.
8304 Even if you turn type checking off, there may be other reasons
8305 related to type that prevent @value{GDBN} from evaluating an expression.
8306 For instance, @value{GDBN} does not know how to add an @code{int} and
8307 a @code{struct foo}. These particular type errors have nothing to do
8308 with the language in use, and usually arise from expressions, such as
8309 the one described above, which make little sense to evaluate anyway.
8311 Each language defines to what degree it is strict about type. For
8312 instance, both Modula-2 and C require the arguments to arithmetical
8313 operators to be numbers. In C, enumerated types and pointers can be
8314 represented as numbers, so that they are valid arguments to mathematical
8315 operators. @xref{Supported languages, ,Supported languages}, for further
8316 details on specific languages.
8318 @value{GDBN} provides some additional commands for controlling the type checker:
8320 @kindex set check type
8321 @kindex show check type
8323 @item set check type auto
8324 Set type checking on or off based on the current working language.
8325 @xref{Supported languages, ,Supported languages}, for the default settings for
8328 @item set check type on
8329 @itemx set check type off
8330 Set type checking on or off, overriding the default setting for the
8331 current working language. Issue a warning if the setting does not
8332 match the language default. If any type mismatches occur in
8333 evaluating an expression while type checking is on, @value{GDBN} prints a
8334 message and aborts evaluation of the expression.
8336 @item set check type warn
8337 Cause the type checker to issue warnings, but to always attempt to
8338 evaluate the expression. Evaluating the expression may still
8339 be impossible for other reasons. For example, @value{GDBN} cannot add
8340 numbers and structures.
8343 Show the current setting of the type checker, and whether or not @value{GDBN}
8344 is setting it automatically.
8347 @cindex range checking
8348 @cindex checks, range
8349 @node Range Checking
8350 @subsection An overview of range checking
8352 In some languages (such as Modula-2), it is an error to exceed the
8353 bounds of a type; this is enforced with run-time checks. Such range
8354 checking is meant to ensure program correctness by making sure
8355 computations do not overflow, or indices on an array element access do
8356 not exceed the bounds of the array.
8358 For expressions you use in @value{GDBN} commands, you can tell
8359 @value{GDBN} to treat range errors in one of three ways: ignore them,
8360 always treat them as errors and abandon the expression, or issue
8361 warnings but evaluate the expression anyway.
8363 A range error can result from numerical overflow, from exceeding an
8364 array index bound, or when you type a constant that is not a member
8365 of any type. Some languages, however, do not treat overflows as an
8366 error. In many implementations of C, mathematical overflow causes the
8367 result to ``wrap around'' to lower values---for example, if @var{m} is
8368 the largest integer value, and @var{s} is the smallest, then
8371 @var{m} + 1 @result{} @var{s}
8374 This, too, is specific to individual languages, and in some cases
8375 specific to individual compilers or machines. @xref{Supported languages, ,
8376 Supported languages}, for further details on specific languages.
8378 @value{GDBN} provides some additional commands for controlling the range checker:
8380 @kindex set check range
8381 @kindex show check range
8383 @item set check range auto
8384 Set range checking on or off based on the current working language.
8385 @xref{Supported languages, ,Supported languages}, for the default settings for
8388 @item set check range on
8389 @itemx set check range off
8390 Set range checking on or off, overriding the default setting for the
8391 current working language. A warning is issued if the setting does not
8392 match the language default. If a range error occurs and range checking is on,
8393 then a message is printed and evaluation of the expression is aborted.
8395 @item set check range warn
8396 Output messages when the @value{GDBN} range checker detects a range error,
8397 but attempt to evaluate the expression anyway. Evaluating the
8398 expression may still be impossible for other reasons, such as accessing
8399 memory that the process does not own (a typical example from many Unix
8403 Show the current setting of the range checker, and whether or not it is
8404 being set automatically by @value{GDBN}.
8407 @node Supported languages
8408 @section Supported languages
8410 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
8411 assembly, Modula-2, and Ada.
8412 @c This is false ...
8413 Some @value{GDBN} features may be used in expressions regardless of the
8414 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
8415 and the @samp{@{type@}addr} construct (@pxref{Expressions,
8416 ,Expressions}) can be used with the constructs of any supported
8419 The following sections detail to what degree each source language is
8420 supported by @value{GDBN}. These sections are not meant to be language
8421 tutorials or references, but serve only as a reference guide to what the
8422 @value{GDBN} expression parser accepts, and what input and output
8423 formats should look like for different languages. There are many good
8424 books written on each of these languages; please look to these for a
8425 language reference or tutorial.
8429 * Objective-C:: Objective-C
8432 * Modula-2:: Modula-2
8437 @subsection C and C@t{++}
8439 @cindex C and C@t{++}
8440 @cindex expressions in C or C@t{++}
8442 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
8443 to both languages. Whenever this is the case, we discuss those languages
8447 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
8448 @cindex @sc{gnu} C@t{++}
8449 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
8450 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
8451 effectively, you must compile your C@t{++} programs with a supported
8452 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
8453 compiler (@code{aCC}).
8455 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
8456 format; if it doesn't work on your system, try the stabs+ debugging
8457 format. You can select those formats explicitly with the @code{g++}
8458 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
8459 @xref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
8460 CC, gcc.info, Using @sc{gnu} CC}.
8463 * C Operators:: C and C@t{++} operators
8464 * C Constants:: C and C@t{++} constants
8465 * C plus plus expressions:: C@t{++} expressions
8466 * C Defaults:: Default settings for C and C@t{++}
8467 * C Checks:: C and C@t{++} type and range checks
8468 * Debugging C:: @value{GDBN} and C
8469 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
8473 @subsubsection C and C@t{++} operators
8475 @cindex C and C@t{++} operators
8477 Operators must be defined on values of specific types. For instance,
8478 @code{+} is defined on numbers, but not on structures. Operators are
8479 often defined on groups of types.
8481 For the purposes of C and C@t{++}, the following definitions hold:
8486 @emph{Integral types} include @code{int} with any of its storage-class
8487 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
8490 @emph{Floating-point types} include @code{float}, @code{double}, and
8491 @code{long double} (if supported by the target platform).
8494 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
8497 @emph{Scalar types} include all of the above.
8502 The following operators are supported. They are listed here
8503 in order of increasing precedence:
8507 The comma or sequencing operator. Expressions in a comma-separated list
8508 are evaluated from left to right, with the result of the entire
8509 expression being the last expression evaluated.
8512 Assignment. The value of an assignment expression is the value
8513 assigned. Defined on scalar types.
8516 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
8517 and translated to @w{@code{@var{a} = @var{a op b}}}.
8518 @w{@code{@var{op}=}} and @code{=} have the same precedence.
8519 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
8520 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
8523 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
8524 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
8528 Logical @sc{or}. Defined on integral types.
8531 Logical @sc{and}. Defined on integral types.
8534 Bitwise @sc{or}. Defined on integral types.
8537 Bitwise exclusive-@sc{or}. Defined on integral types.
8540 Bitwise @sc{and}. Defined on integral types.
8543 Equality and inequality. Defined on scalar types. The value of these
8544 expressions is 0 for false and non-zero for true.
8546 @item <@r{, }>@r{, }<=@r{, }>=
8547 Less than, greater than, less than or equal, greater than or equal.
8548 Defined on scalar types. The value of these expressions is 0 for false
8549 and non-zero for true.
8552 left shift, and right shift. Defined on integral types.
8555 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8558 Addition and subtraction. Defined on integral types, floating-point types and
8561 @item *@r{, }/@r{, }%
8562 Multiplication, division, and modulus. Multiplication and division are
8563 defined on integral and floating-point types. Modulus is defined on
8567 Increment and decrement. When appearing before a variable, the
8568 operation is performed before the variable is used in an expression;
8569 when appearing after it, the variable's value is used before the
8570 operation takes place.
8573 Pointer dereferencing. Defined on pointer types. Same precedence as
8577 Address operator. Defined on variables. Same precedence as @code{++}.
8579 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
8580 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
8581 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
8582 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
8586 Negative. Defined on integral and floating-point types. Same
8587 precedence as @code{++}.
8590 Logical negation. Defined on integral types. Same precedence as
8594 Bitwise complement operator. Defined on integral types. Same precedence as
8599 Structure member, and pointer-to-structure member. For convenience,
8600 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
8601 pointer based on the stored type information.
8602 Defined on @code{struct} and @code{union} data.
8605 Dereferences of pointers to members.
8608 Array indexing. @code{@var{a}[@var{i}]} is defined as
8609 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
8612 Function parameter list. Same precedence as @code{->}.
8615 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
8616 and @code{class} types.
8619 Doubled colons also represent the @value{GDBN} scope operator
8620 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
8624 If an operator is redefined in the user code, @value{GDBN} usually
8625 attempts to invoke the redefined version instead of using the operator's
8633 @subsubsection C and C@t{++} constants
8635 @cindex C and C@t{++} constants
8637 @value{GDBN} allows you to express the constants of C and C@t{++} in the
8642 Integer constants are a sequence of digits. Octal constants are
8643 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
8644 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
8645 @samp{l}, specifying that the constant should be treated as a
8649 Floating point constants are a sequence of digits, followed by a decimal
8650 point, followed by a sequence of digits, and optionally followed by an
8651 exponent. An exponent is of the form:
8652 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
8653 sequence of digits. The @samp{+} is optional for positive exponents.
8654 A floating-point constant may also end with a letter @samp{f} or
8655 @samp{F}, specifying that the constant should be treated as being of
8656 the @code{float} (as opposed to the default @code{double}) type; or with
8657 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
8661 Enumerated constants consist of enumerated identifiers, or their
8662 integral equivalents.
8665 Character constants are a single character surrounded by single quotes
8666 (@code{'}), or a number---the ordinal value of the corresponding character
8667 (usually its @sc{ascii} value). Within quotes, the single character may
8668 be represented by a letter or by @dfn{escape sequences}, which are of
8669 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
8670 of the character's ordinal value; or of the form @samp{\@var{x}}, where
8671 @samp{@var{x}} is a predefined special character---for example,
8672 @samp{\n} for newline.
8675 String constants are a sequence of character constants surrounded by
8676 double quotes (@code{"}). Any valid character constant (as described
8677 above) may appear. Double quotes within the string must be preceded by
8678 a backslash, so for instance @samp{"a\"b'c"} is a string of five
8682 Pointer constants are an integral value. You can also write pointers
8683 to constants using the C operator @samp{&}.
8686 Array constants are comma-separated lists surrounded by braces @samp{@{}
8687 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
8688 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
8689 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
8693 * C plus plus expressions::
8700 @node C plus plus expressions
8701 @subsubsection C@t{++} expressions
8703 @cindex expressions in C@t{++}
8704 @value{GDBN} expression handling can interpret most C@t{++} expressions.
8706 @cindex debugging C@t{++} programs
8707 @cindex C@t{++} compilers
8708 @cindex debug formats and C@t{++}
8709 @cindex @value{NGCC} and C@t{++}
8711 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
8712 proper compiler and the proper debug format. Currently, @value{GDBN}
8713 works best when debugging C@t{++} code that is compiled with
8714 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
8715 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
8716 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
8717 stabs+ as their default debug format, so you usually don't need to
8718 specify a debug format explicitly. Other compilers and/or debug formats
8719 are likely to work badly or not at all when using @value{GDBN} to debug
8725 @cindex member functions
8727 Member function calls are allowed; you can use expressions like
8730 count = aml->GetOriginal(x, y)
8733 @vindex this@r{, inside C@t{++} member functions}
8734 @cindex namespace in C@t{++}
8736 While a member function is active (in the selected stack frame), your
8737 expressions have the same namespace available as the member function;
8738 that is, @value{GDBN} allows implicit references to the class instance
8739 pointer @code{this} following the same rules as C@t{++}.
8741 @cindex call overloaded functions
8742 @cindex overloaded functions, calling
8743 @cindex type conversions in C@t{++}
8745 You can call overloaded functions; @value{GDBN} resolves the function
8746 call to the right definition, with some restrictions. @value{GDBN} does not
8747 perform overload resolution involving user-defined type conversions,
8748 calls to constructors, or instantiations of templates that do not exist
8749 in the program. It also cannot handle ellipsis argument lists or
8752 It does perform integral conversions and promotions, floating-point
8753 promotions, arithmetic conversions, pointer conversions, conversions of
8754 class objects to base classes, and standard conversions such as those of
8755 functions or arrays to pointers; it requires an exact match on the
8756 number of function arguments.
8758 Overload resolution is always performed, unless you have specified
8759 @code{set overload-resolution off}. @xref{Debugging C plus plus,
8760 ,@value{GDBN} features for C@t{++}}.
8762 You must specify @code{set overload-resolution off} in order to use an
8763 explicit function signature to call an overloaded function, as in
8765 p 'foo(char,int)'('x', 13)
8768 The @value{GDBN} command-completion facility can simplify this;
8769 see @ref{Completion, ,Command completion}.
8771 @cindex reference declarations
8773 @value{GDBN} understands variables declared as C@t{++} references; you can use
8774 them in expressions just as you do in C@t{++} source---they are automatically
8777 In the parameter list shown when @value{GDBN} displays a frame, the values of
8778 reference variables are not displayed (unlike other variables); this
8779 avoids clutter, since references are often used for large structures.
8780 The @emph{address} of a reference variable is always shown, unless
8781 you have specified @samp{set print address off}.
8784 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
8785 expressions can use it just as expressions in your program do. Since
8786 one scope may be defined in another, you can use @code{::} repeatedly if
8787 necessary, for example in an expression like
8788 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
8789 resolving name scope by reference to source files, in both C and C@t{++}
8790 debugging (@pxref{Variables, ,Program variables}).
8793 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
8794 calling virtual functions correctly, printing out virtual bases of
8795 objects, calling functions in a base subobject, casting objects, and
8796 invoking user-defined operators.
8799 @subsubsection C and C@t{++} defaults
8801 @cindex C and C@t{++} defaults
8803 If you allow @value{GDBN} to set type and range checking automatically, they
8804 both default to @code{off} whenever the working language changes to
8805 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
8806 selects the working language.
8808 If you allow @value{GDBN} to set the language automatically, it
8809 recognizes source files whose names end with @file{.c}, @file{.C}, or
8810 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
8811 these files, it sets the working language to C or C@t{++}.
8812 @xref{Automatically, ,Having @value{GDBN} infer the source language},
8813 for further details.
8815 @c Type checking is (a) primarily motivated by Modula-2, and (b)
8816 @c unimplemented. If (b) changes, it might make sense to let this node
8817 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
8820 @subsubsection C and C@t{++} type and range checks
8822 @cindex C and C@t{++} checks
8824 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
8825 is not used. However, if you turn type checking on, @value{GDBN}
8826 considers two variables type equivalent if:
8830 The two variables are structured and have the same structure, union, or
8834 The two variables have the same type name, or types that have been
8835 declared equivalent through @code{typedef}.
8838 @c leaving this out because neither J Gilmore nor R Pesch understand it.
8841 The two @code{struct}, @code{union}, or @code{enum} variables are
8842 declared in the same declaration. (Note: this may not be true for all C
8847 Range checking, if turned on, is done on mathematical operations. Array
8848 indices are not checked, since they are often used to index a pointer
8849 that is not itself an array.
8852 @subsubsection @value{GDBN} and C
8854 The @code{set print union} and @code{show print union} commands apply to
8855 the @code{union} type. When set to @samp{on}, any @code{union} that is
8856 inside a @code{struct} or @code{class} is also printed. Otherwise, it
8857 appears as @samp{@{...@}}.
8859 The @code{@@} operator aids in the debugging of dynamic arrays, formed
8860 with pointers and a memory allocation function. @xref{Expressions,
8864 * Debugging C plus plus::
8867 @node Debugging C plus plus
8868 @subsubsection @value{GDBN} features for C@t{++}
8870 @cindex commands for C@t{++}
8872 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
8873 designed specifically for use with C@t{++}. Here is a summary:
8876 @cindex break in overloaded functions
8877 @item @r{breakpoint menus}
8878 When you want a breakpoint in a function whose name is overloaded,
8879 @value{GDBN} breakpoint menus help you specify which function definition
8880 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
8882 @cindex overloading in C@t{++}
8883 @item rbreak @var{regex}
8884 Setting breakpoints using regular expressions is helpful for setting
8885 breakpoints on overloaded functions that are not members of any special
8887 @xref{Set Breaks, ,Setting breakpoints}.
8889 @cindex C@t{++} exception handling
8892 Debug C@t{++} exception handling using these commands. @xref{Set
8893 Catchpoints, , Setting catchpoints}.
8896 @item ptype @var{typename}
8897 Print inheritance relationships as well as other information for type
8899 @xref{Symbols, ,Examining the Symbol Table}.
8901 @cindex C@t{++} symbol display
8902 @item set print demangle
8903 @itemx show print demangle
8904 @itemx set print asm-demangle
8905 @itemx show print asm-demangle
8906 Control whether C@t{++} symbols display in their source form, both when
8907 displaying code as C@t{++} source and when displaying disassemblies.
8908 @xref{Print Settings, ,Print settings}.
8910 @item set print object
8911 @itemx show print object
8912 Choose whether to print derived (actual) or declared types of objects.
8913 @xref{Print Settings, ,Print settings}.
8915 @item set print vtbl
8916 @itemx show print vtbl
8917 Control the format for printing virtual function tables.
8918 @xref{Print Settings, ,Print settings}.
8919 (The @code{vtbl} commands do not work on programs compiled with the HP
8920 ANSI C@t{++} compiler (@code{aCC}).)
8922 @kindex set overload-resolution
8923 @cindex overloaded functions, overload resolution
8924 @item set overload-resolution on
8925 Enable overload resolution for C@t{++} expression evaluation. The default
8926 is on. For overloaded functions, @value{GDBN} evaluates the arguments
8927 and searches for a function whose signature matches the argument types,
8928 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
8929 expressions}, for details). If it cannot find a match, it emits a
8932 @item set overload-resolution off
8933 Disable overload resolution for C@t{++} expression evaluation. For
8934 overloaded functions that are not class member functions, @value{GDBN}
8935 chooses the first function of the specified name that it finds in the
8936 symbol table, whether or not its arguments are of the correct type. For
8937 overloaded functions that are class member functions, @value{GDBN}
8938 searches for a function whose signature @emph{exactly} matches the
8941 @kindex show overload-resolution
8942 @item show overload-resolution
8943 Show the current setting of overload resolution.
8945 @item @r{Overloaded symbol names}
8946 You can specify a particular definition of an overloaded symbol, using
8947 the same notation that is used to declare such symbols in C@t{++}: type
8948 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
8949 also use the @value{GDBN} command-line word completion facilities to list the
8950 available choices, or to finish the type list for you.
8951 @xref{Completion,, Command completion}, for details on how to do this.
8955 @subsection Objective-C
8958 This section provides information about some commands and command
8959 options that are useful for debugging Objective-C code. See also
8960 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
8961 few more commands specific to Objective-C support.
8964 * Method Names in Commands::
8965 * The Print Command with Objective-C::
8968 @node Method Names in Commands, The Print Command with Objective-C, Objective-C, Objective-C
8969 @subsubsection Method Names in Commands
8971 The following commands have been extended to accept Objective-C method
8972 names as line specifications:
8974 @kindex clear@r{, and Objective-C}
8975 @kindex break@r{, and Objective-C}
8976 @kindex info line@r{, and Objective-C}
8977 @kindex jump@r{, and Objective-C}
8978 @kindex list@r{, and Objective-C}
8982 @item @code{info line}
8987 A fully qualified Objective-C method name is specified as
8990 -[@var{Class} @var{methodName}]
8993 where the minus sign is used to indicate an instance method and a
8994 plus sign (not shown) is used to indicate a class method. The class
8995 name @var{Class} and method name @var{methodName} are enclosed in
8996 brackets, similar to the way messages are specified in Objective-C
8997 source code. For example, to set a breakpoint at the @code{create}
8998 instance method of class @code{Fruit} in the program currently being
9002 break -[Fruit create]
9005 To list ten program lines around the @code{initialize} class method,
9009 list +[NSText initialize]
9012 In the current version of @value{GDBN}, the plus or minus sign is
9013 required. In future versions of @value{GDBN}, the plus or minus
9014 sign will be optional, but you can use it to narrow the search. It
9015 is also possible to specify just a method name:
9021 You must specify the complete method name, including any colons. If
9022 your program's source files contain more than one @code{create} method,
9023 you'll be presented with a numbered list of classes that implement that
9024 method. Indicate your choice by number, or type @samp{0} to exit if
9027 As another example, to clear a breakpoint established at the
9028 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
9031 clear -[NSWindow makeKeyAndOrderFront:]
9034 @node The Print Command with Objective-C
9035 @subsubsection The Print Command With Objective-C
9036 @cindex Objective-C, print objects
9037 @kindex print-object
9038 @kindex po @r{(@code{print-object})}
9040 The print command has also been extended to accept methods. For example:
9043 print -[@var{object} hash]
9046 @cindex print an Objective-C object description
9047 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
9049 will tell @value{GDBN} to send the @code{hash} message to @var{object}
9050 and print the result. Also, an additional command has been added,
9051 @code{print-object} or @code{po} for short, which is meant to print
9052 the description of an object. However, this command may only work
9053 with certain Objective-C libraries that have a particular hook
9054 function, @code{_NSPrintForDebugger}, defined.
9058 @cindex Fortran-specific support in @value{GDBN}
9061 @cindex @code{COMMON} blocks, Fortran
9063 @item info common @r{[}@var{common-name}@r{]}
9064 This command prints the values contained in the Fortran @code{COMMON}
9065 block whose name is @var{common-name}. With no argument, the names of
9066 all @code{COMMON} blocks visible at current program location are
9070 Fortran symbols are usually case-insensitive, so @value{GDBN} by
9071 default uses case-insensitive matches for Fortran symbols. You can
9072 change that with the @samp{set case-insensitive} command, see
9073 @ref{Symbols}, for the details.
9078 @cindex Pascal support in @value{GDBN}, limitations
9079 Debugging Pascal programs which use sets, subranges, file variables, or
9080 nested functions does not currently work. @value{GDBN} does not support
9081 entering expressions, printing values, or similar features using Pascal
9084 The Pascal-specific command @code{set print pascal_static-members}
9085 controls whether static members of Pascal objects are displayed.
9086 @xref{Print Settings, pascal_static-members}.
9089 @subsection Modula-2
9091 @cindex Modula-2, @value{GDBN} support
9093 The extensions made to @value{GDBN} to support Modula-2 only support
9094 output from the @sc{gnu} Modula-2 compiler (which is currently being
9095 developed). Other Modula-2 compilers are not currently supported, and
9096 attempting to debug executables produced by them is most likely
9097 to give an error as @value{GDBN} reads in the executable's symbol
9100 @cindex expressions in Modula-2
9102 * M2 Operators:: Built-in operators
9103 * Built-In Func/Proc:: Built-in functions and procedures
9104 * M2 Constants:: Modula-2 constants
9105 * M2 Defaults:: Default settings for Modula-2
9106 * Deviations:: Deviations from standard Modula-2
9107 * M2 Checks:: Modula-2 type and range checks
9108 * M2 Scope:: The scope operators @code{::} and @code{.}
9109 * GDB/M2:: @value{GDBN} and Modula-2
9113 @subsubsection Operators
9114 @cindex Modula-2 operators
9116 Operators must be defined on values of specific types. For instance,
9117 @code{+} is defined on numbers, but not on structures. Operators are
9118 often defined on groups of types. For the purposes of Modula-2, the
9119 following definitions hold:
9124 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
9128 @emph{Character types} consist of @code{CHAR} and its subranges.
9131 @emph{Floating-point types} consist of @code{REAL}.
9134 @emph{Pointer types} consist of anything declared as @code{POINTER TO
9138 @emph{Scalar types} consist of all of the above.
9141 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
9144 @emph{Boolean types} consist of @code{BOOLEAN}.
9148 The following operators are supported, and appear in order of
9149 increasing precedence:
9153 Function argument or array index separator.
9156 Assignment. The value of @var{var} @code{:=} @var{value} is
9160 Less than, greater than on integral, floating-point, or enumerated
9164 Less than or equal to, greater than or equal to
9165 on integral, floating-point and enumerated types, or set inclusion on
9166 set types. Same precedence as @code{<}.
9168 @item =@r{, }<>@r{, }#
9169 Equality and two ways of expressing inequality, valid on scalar types.
9170 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
9171 available for inequality, since @code{#} conflicts with the script
9175 Set membership. Defined on set types and the types of their members.
9176 Same precedence as @code{<}.
9179 Boolean disjunction. Defined on boolean types.
9182 Boolean conjunction. Defined on boolean types.
9185 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9188 Addition and subtraction on integral and floating-point types, or union
9189 and difference on set types.
9192 Multiplication on integral and floating-point types, or set intersection
9196 Division on floating-point types, or symmetric set difference on set
9197 types. Same precedence as @code{*}.
9200 Integer division and remainder. Defined on integral types. Same
9201 precedence as @code{*}.
9204 Negative. Defined on @code{INTEGER} and @code{REAL} data.
9207 Pointer dereferencing. Defined on pointer types.
9210 Boolean negation. Defined on boolean types. Same precedence as
9214 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
9215 precedence as @code{^}.
9218 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
9221 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
9225 @value{GDBN} and Modula-2 scope operators.
9229 @emph{Warning:} Sets and their operations are not yet supported, so @value{GDBN}
9230 treats the use of the operator @code{IN}, or the use of operators
9231 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
9232 @code{<=}, and @code{>=} on sets as an error.
9236 @node Built-In Func/Proc
9237 @subsubsection Built-in functions and procedures
9238 @cindex Modula-2 built-ins
9240 Modula-2 also makes available several built-in procedures and functions.
9241 In describing these, the following metavariables are used:
9246 represents an @code{ARRAY} variable.
9249 represents a @code{CHAR} constant or variable.
9252 represents a variable or constant of integral type.
9255 represents an identifier that belongs to a set. Generally used in the
9256 same function with the metavariable @var{s}. The type of @var{s} should
9257 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
9260 represents a variable or constant of integral or floating-point type.
9263 represents a variable or constant of floating-point type.
9269 represents a variable.
9272 represents a variable or constant of one of many types. See the
9273 explanation of the function for details.
9276 All Modula-2 built-in procedures also return a result, described below.
9280 Returns the absolute value of @var{n}.
9283 If @var{c} is a lower case letter, it returns its upper case
9284 equivalent, otherwise it returns its argument.
9287 Returns the character whose ordinal value is @var{i}.
9290 Decrements the value in the variable @var{v} by one. Returns the new value.
9292 @item DEC(@var{v},@var{i})
9293 Decrements the value in the variable @var{v} by @var{i}. Returns the
9296 @item EXCL(@var{m},@var{s})
9297 Removes the element @var{m} from the set @var{s}. Returns the new
9300 @item FLOAT(@var{i})
9301 Returns the floating point equivalent of the integer @var{i}.
9304 Returns the index of the last member of @var{a}.
9307 Increments the value in the variable @var{v} by one. Returns the new value.
9309 @item INC(@var{v},@var{i})
9310 Increments the value in the variable @var{v} by @var{i}. Returns the
9313 @item INCL(@var{m},@var{s})
9314 Adds the element @var{m} to the set @var{s} if it is not already
9315 there. Returns the new set.
9318 Returns the maximum value of the type @var{t}.
9321 Returns the minimum value of the type @var{t}.
9324 Returns boolean TRUE if @var{i} is an odd number.
9327 Returns the ordinal value of its argument. For example, the ordinal
9328 value of a character is its @sc{ascii} value (on machines supporting the
9329 @sc{ascii} character set). @var{x} must be of an ordered type, which include
9330 integral, character and enumerated types.
9333 Returns the size of its argument. @var{x} can be a variable or a type.
9335 @item TRUNC(@var{r})
9336 Returns the integral part of @var{r}.
9338 @item VAL(@var{t},@var{i})
9339 Returns the member of the type @var{t} whose ordinal value is @var{i}.
9343 @emph{Warning:} Sets and their operations are not yet supported, so
9344 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
9348 @cindex Modula-2 constants
9350 @subsubsection Constants
9352 @value{GDBN} allows you to express the constants of Modula-2 in the following
9358 Integer constants are simply a sequence of digits. When used in an
9359 expression, a constant is interpreted to be type-compatible with the
9360 rest of the expression. Hexadecimal integers are specified by a
9361 trailing @samp{H}, and octal integers by a trailing @samp{B}.
9364 Floating point constants appear as a sequence of digits, followed by a
9365 decimal point and another sequence of digits. An optional exponent can
9366 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
9367 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
9368 digits of the floating point constant must be valid decimal (base 10)
9372 Character constants consist of a single character enclosed by a pair of
9373 like quotes, either single (@code{'}) or double (@code{"}). They may
9374 also be expressed by their ordinal value (their @sc{ascii} value, usually)
9375 followed by a @samp{C}.
9378 String constants consist of a sequence of characters enclosed by a
9379 pair of like quotes, either single (@code{'}) or double (@code{"}).
9380 Escape sequences in the style of C are also allowed. @xref{C
9381 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
9385 Enumerated constants consist of an enumerated identifier.
9388 Boolean constants consist of the identifiers @code{TRUE} and
9392 Pointer constants consist of integral values only.
9395 Set constants are not yet supported.
9399 @subsubsection Modula-2 defaults
9400 @cindex Modula-2 defaults
9402 If type and range checking are set automatically by @value{GDBN}, they
9403 both default to @code{on} whenever the working language changes to
9404 Modula-2. This happens regardless of whether you or @value{GDBN}
9405 selected the working language.
9407 If you allow @value{GDBN} to set the language automatically, then entering
9408 code compiled from a file whose name ends with @file{.mod} sets the
9409 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
9410 the language automatically}, for further details.
9413 @subsubsection Deviations from standard Modula-2
9414 @cindex Modula-2, deviations from
9416 A few changes have been made to make Modula-2 programs easier to debug.
9417 This is done primarily via loosening its type strictness:
9421 Unlike in standard Modula-2, pointer constants can be formed by
9422 integers. This allows you to modify pointer variables during
9423 debugging. (In standard Modula-2, the actual address contained in a
9424 pointer variable is hidden from you; it can only be modified
9425 through direct assignment to another pointer variable or expression that
9426 returned a pointer.)
9429 C escape sequences can be used in strings and characters to represent
9430 non-printable characters. @value{GDBN} prints out strings with these
9431 escape sequences embedded. Single non-printable characters are
9432 printed using the @samp{CHR(@var{nnn})} format.
9435 The assignment operator (@code{:=}) returns the value of its right-hand
9439 All built-in procedures both modify @emph{and} return their argument.
9443 @subsubsection Modula-2 type and range checks
9444 @cindex Modula-2 checks
9447 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
9450 @c FIXME remove warning when type/range checks added
9452 @value{GDBN} considers two Modula-2 variables type equivalent if:
9456 They are of types that have been declared equivalent via a @code{TYPE
9457 @var{t1} = @var{t2}} statement
9460 They have been declared on the same line. (Note: This is true of the
9461 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
9464 As long as type checking is enabled, any attempt to combine variables
9465 whose types are not equivalent is an error.
9467 Range checking is done on all mathematical operations, assignment, array
9468 index bounds, and all built-in functions and procedures.
9471 @subsubsection The scope operators @code{::} and @code{.}
9473 @cindex @code{.}, Modula-2 scope operator
9474 @cindex colon, doubled as scope operator
9476 @vindex colon-colon@r{, in Modula-2}
9477 @c Info cannot handle :: but TeX can.
9480 @vindex ::@r{, in Modula-2}
9483 There are a few subtle differences between the Modula-2 scope operator
9484 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
9489 @var{module} . @var{id}
9490 @var{scope} :: @var{id}
9494 where @var{scope} is the name of a module or a procedure,
9495 @var{module} the name of a module, and @var{id} is any declared
9496 identifier within your program, except another module.
9498 Using the @code{::} operator makes @value{GDBN} search the scope
9499 specified by @var{scope} for the identifier @var{id}. If it is not
9500 found in the specified scope, then @value{GDBN} searches all scopes
9501 enclosing the one specified by @var{scope}.
9503 Using the @code{.} operator makes @value{GDBN} search the current scope for
9504 the identifier specified by @var{id} that was imported from the
9505 definition module specified by @var{module}. With this operator, it is
9506 an error if the identifier @var{id} was not imported from definition
9507 module @var{module}, or if @var{id} is not an identifier in
9511 @subsubsection @value{GDBN} and Modula-2
9513 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
9514 Five subcommands of @code{set print} and @code{show print} apply
9515 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
9516 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
9517 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
9518 analogue in Modula-2.
9520 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
9521 with any language, is not useful with Modula-2. Its
9522 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
9523 created in Modula-2 as they can in C or C@t{++}. However, because an
9524 address can be specified by an integral constant, the construct
9525 @samp{@{@var{type}@}@var{adrexp}} is still useful.
9527 @cindex @code{#} in Modula-2
9528 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
9529 interpreted as the beginning of a comment. Use @code{<>} instead.
9535 The extensions made to @value{GDBN} for Ada only support
9536 output from the @sc{gnu} Ada (GNAT) compiler.
9537 Other Ada compilers are not currently supported, and
9538 attempting to debug executables produced by them is most likely
9542 @cindex expressions in Ada
9544 * Ada Mode Intro:: General remarks on the Ada syntax
9545 and semantics supported by Ada mode
9547 * Omissions from Ada:: Restrictions on the Ada expression syntax.
9548 * Additions to Ada:: Extensions of the Ada expression syntax.
9549 * Stopping Before Main Program:: Debugging the program during elaboration.
9550 * Ada Glitches:: Known peculiarities of Ada mode.
9553 @node Ada Mode Intro
9554 @subsubsection Introduction
9555 @cindex Ada mode, general
9557 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
9558 syntax, with some extensions.
9559 The philosophy behind the design of this subset is
9563 That @value{GDBN} should provide basic literals and access to operations for
9564 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
9565 leaving more sophisticated computations to subprograms written into the
9566 program (which therefore may be called from @value{GDBN}).
9569 That type safety and strict adherence to Ada language restrictions
9570 are not particularly important to the @value{GDBN} user.
9573 That brevity is important to the @value{GDBN} user.
9576 Thus, for brevity, the debugger acts as if there were
9577 implicit @code{with} and @code{use} clauses in effect for all user-written
9578 packages, making it unnecessary to fully qualify most names with
9579 their packages, regardless of context. Where this causes ambiguity,
9580 @value{GDBN} asks the user's intent.
9582 The debugger will start in Ada mode if it detects an Ada main program.
9583 As for other languages, it will enter Ada mode when stopped in a program that
9584 was translated from an Ada source file.
9586 While in Ada mode, you may use `@t{--}' for comments. This is useful
9587 mostly for documenting command files. The standard @value{GDBN} comment
9588 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
9589 middle (to allow based literals).
9591 The debugger supports limited overloading. Given a subprogram call in which
9592 the function symbol has multiple definitions, it will use the number of
9593 actual parameters and some information about their types to attempt to narrow
9594 the set of definitions. It also makes very limited use of context, preferring
9595 procedures to functions in the context of the @code{call} command, and
9596 functions to procedures elsewhere.
9598 @node Omissions from Ada
9599 @subsubsection Omissions from Ada
9600 @cindex Ada, omissions from
9602 Here are the notable omissions from the subset:
9606 Only a subset of the attributes are supported:
9610 @t{'First}, @t{'Last}, and @t{'Length}
9611 on array objects (not on types and subtypes).
9614 @t{'Min} and @t{'Max}.
9617 @t{'Pos} and @t{'Val}.
9623 @t{'Range} on array objects (not subtypes), but only as the right
9624 operand of the membership (@code{in}) operator.
9627 @t{'Access}, @t{'Unchecked_Access}, and
9628 @t{'Unrestricted_Access} (a GNAT extension).
9636 @code{Characters.Latin_1} are not available and
9637 concatenation is not implemented. Thus, escape characters in strings are
9638 not currently available.
9641 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
9642 equality of representations. They will generally work correctly
9643 for strings and arrays whose elements have integer or enumeration types.
9644 They may not work correctly for arrays whose element
9645 types have user-defined equality, for arrays of real values
9646 (in particular, IEEE-conformant floating point, because of negative
9647 zeroes and NaNs), and for arrays whose elements contain unused bits with
9648 indeterminate values.
9651 The other component-by-component array operations (@code{and}, @code{or},
9652 @code{xor}, @code{not}, and relational tests other than equality)
9653 are not implemented.
9656 There are no record or array aggregates.
9659 Calls to dispatching subprograms are not implemented.
9662 The overloading algorithm is much more limited (i.e., less selective)
9663 than that of real Ada. It makes only limited use of the context in which a subexpression
9664 appears to resolve its meaning, and it is much looser in its rules for allowing
9665 type matches. As a result, some function calls will be ambiguous, and the user
9666 will be asked to choose the proper resolution.
9669 The @code{new} operator is not implemented.
9672 Entry calls are not implemented.
9675 Aside from printing, arithmetic operations on the native VAX floating-point
9676 formats are not supported.
9679 It is not possible to slice a packed array.
9682 @node Additions to Ada
9683 @subsubsection Additions to Ada
9684 @cindex Ada, deviations from
9686 As it does for other languages, @value{GDBN} makes certain generic
9687 extensions to Ada (@pxref{Expressions}):
9691 If the expression @var{E} is a variable residing in memory
9692 (typically a local variable or array element) and @var{N} is
9693 a positive integer, then @code{@var{E}@@@var{N}} displays the values of
9694 @var{E} and the @var{N}-1 adjacent variables following it in memory as an array.
9695 In Ada, this operator is generally not necessary, since its prime use
9696 is in displaying parts of an array, and slicing will usually do this in Ada.
9697 However, there are occasional uses when debugging programs
9698 in which certain debugging information has been optimized away.
9701 @code{@var{B}::@var{var}} means ``the variable named @var{var} that appears
9702 in function or file @var{B}.'' When @var{B} is a file name, you must typically
9703 surround it in single quotes.
9706 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
9707 @var{type} that appears at address @var{addr}.''
9710 A name starting with @samp{$} is a convenience variable
9711 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
9714 In addition, @value{GDBN} provides a few other shortcuts and outright additions specific
9719 The assignment statement is allowed as an expression, returning
9720 its right-hand operand as its value. Thus, you may enter
9724 print A(tmp := y + 1)
9728 The semicolon is allowed as an ``operator,'' returning as its value
9729 the value of its right-hand operand.
9730 This allows, for example,
9731 complex conditional breaks:
9735 condition 1 (report(i); k += 1; A(k) > 100)
9739 Rather than use catenation and symbolic character names to introduce special
9740 characters into strings, one may instead use a special bracket notation,
9741 which is also used to print strings. A sequence of characters of the form
9742 @samp{["@var{XX}"]} within a string or character literal denotes the
9743 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
9744 sequence of characters @samp{["""]} also denotes a single quotation mark
9745 in strings. For example,
9747 "One line.["0a"]Next line.["0a"]"
9750 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF}) after each
9754 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
9755 @t{'Max} is optional (and is ignored in any case). For example, it is valid
9763 When printing arrays, @value{GDBN} uses positional notation when the
9764 array has a lower bound of 1, and uses a modified named notation otherwise.
9765 For example, a one-dimensional array of three integers with a lower bound of 3 might print as
9772 That is, in contrast to valid Ada, only the first component has a @code{=>}
9776 You may abbreviate attributes in expressions with any unique,
9777 multi-character subsequence of
9778 their names (an exact match gets preference).
9779 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
9780 in place of @t{a'length}.
9783 @cindex quoting Ada internal identifiers
9784 Since Ada is case-insensitive, the debugger normally maps identifiers you type
9785 to lower case. The GNAT compiler uses upper-case characters for
9786 some of its internal identifiers, which are normally of no interest to users.
9787 For the rare occasions when you actually have to look at them,
9788 enclose them in angle brackets to avoid the lower-case mapping.
9791 @value{GDBP} print <JMPBUF_SAVE>[0]
9795 Printing an object of class-wide type or dereferencing an
9796 access-to-class-wide value will display all the components of the object's
9797 specific type (as indicated by its run-time tag). Likewise, component
9798 selection on such a value will operate on the specific type of the
9803 @node Stopping Before Main Program
9804 @subsubsection Stopping at the Very Beginning
9806 @cindex breakpointing Ada elaboration code
9807 It is sometimes necessary to debug the program during elaboration, and
9808 before reaching the main procedure.
9809 As defined in the Ada Reference
9810 Manual, the elaboration code is invoked from a procedure called
9811 @code{adainit}. To run your program up to the beginning of
9812 elaboration, simply use the following two commands:
9813 @code{tbreak adainit} and @code{run}.
9816 @subsubsection Known Peculiarities of Ada Mode
9817 @cindex Ada, problems
9819 Besides the omissions listed previously (@pxref{Omissions from Ada}),
9820 we know of several problems with and limitations of Ada mode in
9822 some of which will be fixed with planned future releases of the debugger
9823 and the GNU Ada compiler.
9827 Currently, the debugger
9828 has insufficient information to determine whether certain pointers represent
9829 pointers to objects or the objects themselves.
9830 Thus, the user may have to tack an extra @code{.all} after an expression
9831 to get it printed properly.
9834 Static constants that the compiler chooses not to materialize as objects in
9835 storage are invisible to the debugger.
9838 Named parameter associations in function argument lists are ignored (the
9839 argument lists are treated as positional).
9842 Many useful library packages are currently invisible to the debugger.
9845 Fixed-point arithmetic, conversions, input, and output is carried out using
9846 floating-point arithmetic, and may give results that only approximate those on
9850 The type of the @t{'Address} attribute may not be @code{System.Address}.
9853 The GNAT compiler never generates the prefix @code{Standard} for any of
9854 the standard symbols defined by the Ada language. @value{GDBN} knows about
9855 this: it will strip the prefix from names when you use it, and will never
9856 look for a name you have so qualified among local symbols, nor match against
9857 symbols in other packages or subprograms. If you have
9858 defined entities anywhere in your program other than parameters and
9859 local variables whose simple names match names in @code{Standard},
9860 GNAT's lack of qualification here can cause confusion. When this happens,
9861 you can usually resolve the confusion
9862 by qualifying the problematic names with package
9863 @code{Standard} explicitly.
9866 @node Unsupported languages
9867 @section Unsupported languages
9869 @cindex unsupported languages
9870 @cindex minimal language
9871 In addition to the other fully-supported programming languages,
9872 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
9873 It does not represent a real programming language, but provides a set
9874 of capabilities close to what the C or assembly languages provide.
9875 This should allow most simple operations to be performed while debugging
9876 an application that uses a language currently not supported by @value{GDBN}.
9878 If the language is set to @code{auto}, @value{GDBN} will automatically
9879 select this language if the current frame corresponds to an unsupported
9883 @chapter Examining the Symbol Table
9885 The commands described in this chapter allow you to inquire about the
9886 symbols (names of variables, functions and types) defined in your
9887 program. This information is inherent in the text of your program and
9888 does not change as your program executes. @value{GDBN} finds it in your
9889 program's symbol table, in the file indicated when you started @value{GDBN}
9890 (@pxref{File Options, ,Choosing files}), or by one of the
9891 file-management commands (@pxref{Files, ,Commands to specify files}).
9893 @cindex symbol names
9894 @cindex names of symbols
9895 @cindex quoting names
9896 Occasionally, you may need to refer to symbols that contain unusual
9897 characters, which @value{GDBN} ordinarily treats as word delimiters. The
9898 most frequent case is in referring to static variables in other
9899 source files (@pxref{Variables,,Program variables}). File names
9900 are recorded in object files as debugging symbols, but @value{GDBN} would
9901 ordinarily parse a typical file name, like @file{foo.c}, as the three words
9902 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
9903 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
9910 looks up the value of @code{x} in the scope of the file @file{foo.c}.
9913 @cindex case-insensitive symbol names
9914 @cindex case sensitivity in symbol names
9915 @kindex set case-sensitive
9916 @item set case-sensitive on
9917 @itemx set case-sensitive off
9918 @itemx set case-sensitive auto
9919 Normally, when @value{GDBN} looks up symbols, it matches their names
9920 with case sensitivity determined by the current source language.
9921 Occasionally, you may wish to control that. The command @code{set
9922 case-sensitive} lets you do that by specifying @code{on} for
9923 case-sensitive matches or @code{off} for case-insensitive ones. If
9924 you specify @code{auto}, case sensitivity is reset to the default
9925 suitable for the source language. The default is case-sensitive
9926 matches for all languages except for Fortran, for which the default is
9927 case-insensitive matches.
9929 @kindex show case-sensitive
9930 @item show case-sensitive
9931 This command shows the current setting of case sensitivity for symbols
9934 @kindex info address
9935 @cindex address of a symbol
9936 @item info address @var{symbol}
9937 Describe where the data for @var{symbol} is stored. For a register
9938 variable, this says which register it is kept in. For a non-register
9939 local variable, this prints the stack-frame offset at which the variable
9942 Note the contrast with @samp{print &@var{symbol}}, which does not work
9943 at all for a register variable, and for a stack local variable prints
9944 the exact address of the current instantiation of the variable.
9947 @cindex symbol from address
9948 @cindex closest symbol and offset for an address
9949 @item info symbol @var{addr}
9950 Print the name of a symbol which is stored at the address @var{addr}.
9951 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
9952 nearest symbol and an offset from it:
9955 (@value{GDBP}) info symbol 0x54320
9956 _initialize_vx + 396 in section .text
9960 This is the opposite of the @code{info address} command. You can use
9961 it to find out the name of a variable or a function given its address.
9964 @item whatis @var{expr}
9965 Print the data type of expression @var{expr}. @var{expr} is not
9966 actually evaluated, and any side-effecting operations (such as
9967 assignments or function calls) inside it do not take place.
9968 @xref{Expressions, ,Expressions}.
9971 Print the data type of @code{$}, the last value in the value history.
9974 @item ptype @var{typename}
9975 Print a description of data type @var{typename}. @var{typename} may be
9976 the name of a type, or for C code it may have the form @samp{class
9977 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
9978 @var{union-tag}} or @samp{enum @var{enum-tag}}.
9980 @item ptype @var{expr}
9982 Print a description of the type of expression @var{expr}. @code{ptype}
9983 differs from @code{whatis} by printing a detailed description, instead
9984 of just the name of the type.
9986 For example, for this variable declaration:
9989 struct complex @{double real; double imag;@} v;
9993 the two commands give this output:
9997 (@value{GDBP}) whatis v
9998 type = struct complex
9999 (@value{GDBP}) ptype v
10000 type = struct complex @{
10008 As with @code{whatis}, using @code{ptype} without an argument refers to
10009 the type of @code{$}, the last value in the value history.
10012 @item info types @var{regexp}
10014 Print a brief description of all types whose names match the regular
10015 expression @var{regexp} (or all types in your program, if you supply
10016 no argument). Each complete typename is matched as though it were a
10017 complete line; thus, @samp{i type value} gives information on all
10018 types in your program whose names include the string @code{value}, but
10019 @samp{i type ^value$} gives information only on types whose complete
10020 name is @code{value}.
10022 This command differs from @code{ptype} in two ways: first, like
10023 @code{whatis}, it does not print a detailed description; second, it
10024 lists all source files where a type is defined.
10027 @cindex local variables
10028 @item info scope @var{location}
10029 List all the variables local to a particular scope. This command
10030 accepts a @var{location} argument---a function name, a source line, or
10031 an address preceded by a @samp{*}, and prints all the variables local
10032 to the scope defined by that location. For example:
10035 (@value{GDBP}) @b{info scope command_line_handler}
10036 Scope for command_line_handler:
10037 Symbol rl is an argument at stack/frame offset 8, length 4.
10038 Symbol linebuffer is in static storage at address 0x150a18, length 4.
10039 Symbol linelength is in static storage at address 0x150a1c, length 4.
10040 Symbol p is a local variable in register $esi, length 4.
10041 Symbol p1 is a local variable in register $ebx, length 4.
10042 Symbol nline is a local variable in register $edx, length 4.
10043 Symbol repeat is a local variable at frame offset -8, length 4.
10047 This command is especially useful for determining what data to collect
10048 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
10051 @kindex info source
10053 Show information about the current source file---that is, the source file for
10054 the function containing the current point of execution:
10057 the name of the source file, and the directory containing it,
10059 the directory it was compiled in,
10061 its length, in lines,
10063 which programming language it is written in,
10065 whether the executable includes debugging information for that file, and
10066 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
10068 whether the debugging information includes information about
10069 preprocessor macros.
10073 @kindex info sources
10075 Print the names of all source files in your program for which there is
10076 debugging information, organized into two lists: files whose symbols
10077 have already been read, and files whose symbols will be read when needed.
10079 @kindex info functions
10080 @item info functions
10081 Print the names and data types of all defined functions.
10083 @item info functions @var{regexp}
10084 Print the names and data types of all defined functions
10085 whose names contain a match for regular expression @var{regexp}.
10086 Thus, @samp{info fun step} finds all functions whose names
10087 include @code{step}; @samp{info fun ^step} finds those whose names
10088 start with @code{step}. If a function name contains characters
10089 that conflict with the regular expression language (eg.
10090 @samp{operator*()}), they may be quoted with a backslash.
10092 @kindex info variables
10093 @item info variables
10094 Print the names and data types of all variables that are declared
10095 outside of functions (i.e.@: excluding local variables).
10097 @item info variables @var{regexp}
10098 Print the names and data types of all variables (except for local
10099 variables) whose names contain a match for regular expression
10102 @kindex info classes
10103 @cindex Objective-C, classes and selectors
10105 @itemx info classes @var{regexp}
10106 Display all Objective-C classes in your program, or
10107 (with the @var{regexp} argument) all those matching a particular regular
10110 @kindex info selectors
10111 @item info selectors
10112 @itemx info selectors @var{regexp}
10113 Display all Objective-C selectors in your program, or
10114 (with the @var{regexp} argument) all those matching a particular regular
10118 This was never implemented.
10119 @kindex info methods
10121 @itemx info methods @var{regexp}
10122 The @code{info methods} command permits the user to examine all defined
10123 methods within C@t{++} program, or (with the @var{regexp} argument) a
10124 specific set of methods found in the various C@t{++} classes. Many
10125 C@t{++} classes provide a large number of methods. Thus, the output
10126 from the @code{ptype} command can be overwhelming and hard to use. The
10127 @code{info-methods} command filters the methods, printing only those
10128 which match the regular-expression @var{regexp}.
10131 @cindex reloading symbols
10132 Some systems allow individual object files that make up your program to
10133 be replaced without stopping and restarting your program. For example,
10134 in VxWorks you can simply recompile a defective object file and keep on
10135 running. If you are running on one of these systems, you can allow
10136 @value{GDBN} to reload the symbols for automatically relinked modules:
10139 @kindex set symbol-reloading
10140 @item set symbol-reloading on
10141 Replace symbol definitions for the corresponding source file when an
10142 object file with a particular name is seen again.
10144 @item set symbol-reloading off
10145 Do not replace symbol definitions when encountering object files of the
10146 same name more than once. This is the default state; if you are not
10147 running on a system that permits automatic relinking of modules, you
10148 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
10149 may discard symbols when linking large programs, that may contain
10150 several modules (from different directories or libraries) with the same
10153 @kindex show symbol-reloading
10154 @item show symbol-reloading
10155 Show the current @code{on} or @code{off} setting.
10158 @cindex opaque data types
10159 @kindex set opaque-type-resolution
10160 @item set opaque-type-resolution on
10161 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
10162 declared as a pointer to a @code{struct}, @code{class}, or
10163 @code{union}---for example, @code{struct MyType *}---that is used in one
10164 source file although the full declaration of @code{struct MyType} is in
10165 another source file. The default is on.
10167 A change in the setting of this subcommand will not take effect until
10168 the next time symbols for a file are loaded.
10170 @item set opaque-type-resolution off
10171 Tell @value{GDBN} not to resolve opaque types. In this case, the type
10172 is printed as follows:
10174 @{<no data fields>@}
10177 @kindex show opaque-type-resolution
10178 @item show opaque-type-resolution
10179 Show whether opaque types are resolved or not.
10181 @kindex maint print symbols
10182 @cindex symbol dump
10183 @kindex maint print psymbols
10184 @cindex partial symbol dump
10185 @item maint print symbols @var{filename}
10186 @itemx maint print psymbols @var{filename}
10187 @itemx maint print msymbols @var{filename}
10188 Write a dump of debugging symbol data into the file @var{filename}.
10189 These commands are used to debug the @value{GDBN} symbol-reading code. Only
10190 symbols with debugging data are included. If you use @samp{maint print
10191 symbols}, @value{GDBN} includes all the symbols for which it has already
10192 collected full details: that is, @var{filename} reflects symbols for
10193 only those files whose symbols @value{GDBN} has read. You can use the
10194 command @code{info sources} to find out which files these are. If you
10195 use @samp{maint print psymbols} instead, the dump shows information about
10196 symbols that @value{GDBN} only knows partially---that is, symbols defined in
10197 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
10198 @samp{maint print msymbols} dumps just the minimal symbol information
10199 required for each object file from which @value{GDBN} has read some symbols.
10200 @xref{Files, ,Commands to specify files}, for a discussion of how
10201 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
10203 @kindex maint info symtabs
10204 @kindex maint info psymtabs
10205 @cindex listing @value{GDBN}'s internal symbol tables
10206 @cindex symbol tables, listing @value{GDBN}'s internal
10207 @cindex full symbol tables, listing @value{GDBN}'s internal
10208 @cindex partial symbol tables, listing @value{GDBN}'s internal
10209 @item maint info symtabs @r{[} @var{regexp} @r{]}
10210 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
10212 List the @code{struct symtab} or @code{struct partial_symtab}
10213 structures whose names match @var{regexp}. If @var{regexp} is not
10214 given, list them all. The output includes expressions which you can
10215 copy into a @value{GDBN} debugging this one to examine a particular
10216 structure in more detail. For example:
10219 (@value{GDBP}) maint info psymtabs dwarf2read
10220 @{ objfile /home/gnu/build/gdb/gdb
10221 ((struct objfile *) 0x82e69d0)
10222 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
10223 ((struct partial_symtab *) 0x8474b10)
10226 text addresses 0x814d3c8 -- 0x8158074
10227 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
10228 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
10229 dependencies (none)
10232 (@value{GDBP}) maint info symtabs
10236 We see that there is one partial symbol table whose filename contains
10237 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
10238 and we see that @value{GDBN} has not read in any symtabs yet at all.
10239 If we set a breakpoint on a function, that will cause @value{GDBN} to
10240 read the symtab for the compilation unit containing that function:
10243 (@value{GDBP}) break dwarf2_psymtab_to_symtab
10244 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
10246 (@value{GDBP}) maint info symtabs
10247 @{ objfile /home/gnu/build/gdb/gdb
10248 ((struct objfile *) 0x82e69d0)
10249 @{ symtab /home/gnu/src/gdb/dwarf2read.c
10250 ((struct symtab *) 0x86c1f38)
10253 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
10254 debugformat DWARF 2
10263 @chapter Altering Execution
10265 Once you think you have found an error in your program, you might want to
10266 find out for certain whether correcting the apparent error would lead to
10267 correct results in the rest of the run. You can find the answer by
10268 experiment, using the @value{GDBN} features for altering execution of the
10271 For example, you can store new values into variables or memory
10272 locations, give your program a signal, restart it at a different
10273 address, or even return prematurely from a function.
10276 * Assignment:: Assignment to variables
10277 * Jumping:: Continuing at a different address
10278 * Signaling:: Giving your program a signal
10279 * Returning:: Returning from a function
10280 * Calling:: Calling your program's functions
10281 * Patching:: Patching your program
10285 @section Assignment to variables
10288 @cindex setting variables
10289 To alter the value of a variable, evaluate an assignment expression.
10290 @xref{Expressions, ,Expressions}. For example,
10297 stores the value 4 into the variable @code{x}, and then prints the
10298 value of the assignment expression (which is 4).
10299 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
10300 information on operators in supported languages.
10302 @kindex set variable
10303 @cindex variables, setting
10304 If you are not interested in seeing the value of the assignment, use the
10305 @code{set} command instead of the @code{print} command. @code{set} is
10306 really the same as @code{print} except that the expression's value is
10307 not printed and is not put in the value history (@pxref{Value History,
10308 ,Value history}). The expression is evaluated only for its effects.
10310 If the beginning of the argument string of the @code{set} command
10311 appears identical to a @code{set} subcommand, use the @code{set
10312 variable} command instead of just @code{set}. This command is identical
10313 to @code{set} except for its lack of subcommands. For example, if your
10314 program has a variable @code{width}, you get an error if you try to set
10315 a new value with just @samp{set width=13}, because @value{GDBN} has the
10316 command @code{set width}:
10319 (@value{GDBP}) whatis width
10321 (@value{GDBP}) p width
10323 (@value{GDBP}) set width=47
10324 Invalid syntax in expression.
10328 The invalid expression, of course, is @samp{=47}. In
10329 order to actually set the program's variable @code{width}, use
10332 (@value{GDBP}) set var width=47
10335 Because the @code{set} command has many subcommands that can conflict
10336 with the names of program variables, it is a good idea to use the
10337 @code{set variable} command instead of just @code{set}. For example, if
10338 your program has a variable @code{g}, you run into problems if you try
10339 to set a new value with just @samp{set g=4}, because @value{GDBN} has
10340 the command @code{set gnutarget}, abbreviated @code{set g}:
10344 (@value{GDBP}) whatis g
10348 (@value{GDBP}) set g=4
10352 The program being debugged has been started already.
10353 Start it from the beginning? (y or n) y
10354 Starting program: /home/smith/cc_progs/a.out
10355 "/home/smith/cc_progs/a.out": can't open to read symbols:
10356 Invalid bfd target.
10357 (@value{GDBP}) show g
10358 The current BFD target is "=4".
10363 The program variable @code{g} did not change, and you silently set the
10364 @code{gnutarget} to an invalid value. In order to set the variable
10368 (@value{GDBP}) set var g=4
10371 @value{GDBN} allows more implicit conversions in assignments than C; you can
10372 freely store an integer value into a pointer variable or vice versa,
10373 and you can convert any structure to any other structure that is the
10374 same length or shorter.
10375 @comment FIXME: how do structs align/pad in these conversions?
10376 @comment /doc@cygnus.com 18dec1990
10378 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
10379 construct to generate a value of specified type at a specified address
10380 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
10381 to memory location @code{0x83040} as an integer (which implies a certain size
10382 and representation in memory), and
10385 set @{int@}0x83040 = 4
10389 stores the value 4 into that memory location.
10392 @section Continuing at a different address
10394 Ordinarily, when you continue your program, you do so at the place where
10395 it stopped, with the @code{continue} command. You can instead continue at
10396 an address of your own choosing, with the following commands:
10400 @item jump @var{linespec}
10401 Resume execution at line @var{linespec}. Execution stops again
10402 immediately if there is a breakpoint there. @xref{List, ,Printing
10403 source lines}, for a description of the different forms of
10404 @var{linespec}. It is common practice to use the @code{tbreak} command
10405 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
10408 The @code{jump} command does not change the current stack frame, or
10409 the stack pointer, or the contents of any memory location or any
10410 register other than the program counter. If line @var{linespec} is in
10411 a different function from the one currently executing, the results may
10412 be bizarre if the two functions expect different patterns of arguments or
10413 of local variables. For this reason, the @code{jump} command requests
10414 confirmation if the specified line is not in the function currently
10415 executing. However, even bizarre results are predictable if you are
10416 well acquainted with the machine-language code of your program.
10418 @item jump *@var{address}
10419 Resume execution at the instruction at address @var{address}.
10422 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
10423 On many systems, you can get much the same effect as the @code{jump}
10424 command by storing a new value into the register @code{$pc}. The
10425 difference is that this does not start your program running; it only
10426 changes the address of where it @emph{will} run when you continue. For
10434 makes the next @code{continue} command or stepping command execute at
10435 address @code{0x485}, rather than at the address where your program stopped.
10436 @xref{Continuing and Stepping, ,Continuing and stepping}.
10438 The most common occasion to use the @code{jump} command is to back
10439 up---perhaps with more breakpoints set---over a portion of a program
10440 that has already executed, in order to examine its execution in more
10445 @section Giving your program a signal
10446 @cindex deliver a signal to a program
10450 @item signal @var{signal}
10451 Resume execution where your program stopped, but immediately give it the
10452 signal @var{signal}. @var{signal} can be the name or the number of a
10453 signal. For example, on many systems @code{signal 2} and @code{signal
10454 SIGINT} are both ways of sending an interrupt signal.
10456 Alternatively, if @var{signal} is zero, continue execution without
10457 giving a signal. This is useful when your program stopped on account of
10458 a signal and would ordinary see the signal when resumed with the
10459 @code{continue} command; @samp{signal 0} causes it to resume without a
10462 @code{signal} does not repeat when you press @key{RET} a second time
10463 after executing the command.
10467 Invoking the @code{signal} command is not the same as invoking the
10468 @code{kill} utility from the shell. Sending a signal with @code{kill}
10469 causes @value{GDBN} to decide what to do with the signal depending on
10470 the signal handling tables (@pxref{Signals}). The @code{signal} command
10471 passes the signal directly to your program.
10475 @section Returning from a function
10478 @cindex returning from a function
10481 @itemx return @var{expression}
10482 You can cancel execution of a function call with the @code{return}
10483 command. If you give an
10484 @var{expression} argument, its value is used as the function's return
10488 When you use @code{return}, @value{GDBN} discards the selected stack frame
10489 (and all frames within it). You can think of this as making the
10490 discarded frame return prematurely. If you wish to specify a value to
10491 be returned, give that value as the argument to @code{return}.
10493 This pops the selected stack frame (@pxref{Selection, ,Selecting a
10494 frame}), and any other frames inside of it, leaving its caller as the
10495 innermost remaining frame. That frame becomes selected. The
10496 specified value is stored in the registers used for returning values
10499 The @code{return} command does not resume execution; it leaves the
10500 program stopped in the state that would exist if the function had just
10501 returned. In contrast, the @code{finish} command (@pxref{Continuing
10502 and Stepping, ,Continuing and stepping}) resumes execution until the
10503 selected stack frame returns naturally.
10506 @section Calling program functions
10509 @cindex calling functions
10510 @cindex inferior functions, calling
10511 @item print @var{expr}
10512 Evaluate the expression @var{expr} and display the resuling value.
10513 @var{expr} may include calls to functions in the program being
10517 @item call @var{expr}
10518 Evaluate the expression @var{expr} without displaying @code{void}
10521 You can use this variant of the @code{print} command if you want to
10522 execute a function from your program that does not return anything
10523 (a.k.a.@: @dfn{a void function}), but without cluttering the output
10524 with @code{void} returned values that @value{GDBN} will otherwise
10525 print. If the result is not void, it is printed and saved in the
10529 It is possible for the function you call via the @code{print} or
10530 @code{call} command to generate a signal (e.g., if there's a bug in
10531 the function, or if you passed it incorrect arguments). What happens
10532 in that case is controlled by the @code{set unwindonsignal} command.
10535 @item set unwindonsignal
10536 @kindex set unwindonsignal
10537 @cindex unwind stack in called functions
10538 @cindex call dummy stack unwinding
10539 Set unwinding of the stack if a signal is received while in a function
10540 that @value{GDBN} called in the program being debugged. If set to on,
10541 @value{GDBN} unwinds the stack it created for the call and restores
10542 the context to what it was before the call. If set to off (the
10543 default), @value{GDBN} stops in the frame where the signal was
10546 @item show unwindonsignal
10547 @kindex show unwindonsignal
10548 Show the current setting of stack unwinding in the functions called by
10552 @cindex weak alias functions
10553 Sometimes, a function you wish to call is actually a @dfn{weak alias}
10554 for another function. In such case, @value{GDBN} might not pick up
10555 the type information, including the types of the function arguments,
10556 which causes @value{GDBN} to call the inferior function incorrectly.
10557 As a result, the called function will function erroneously and may
10558 even crash. A solution to that is to use the name of the aliased
10562 @section Patching programs
10564 @cindex patching binaries
10565 @cindex writing into executables
10566 @cindex writing into corefiles
10568 By default, @value{GDBN} opens the file containing your program's
10569 executable code (or the corefile) read-only. This prevents accidental
10570 alterations to machine code; but it also prevents you from intentionally
10571 patching your program's binary.
10573 If you'd like to be able to patch the binary, you can specify that
10574 explicitly with the @code{set write} command. For example, you might
10575 want to turn on internal debugging flags, or even to make emergency
10581 @itemx set write off
10582 If you specify @samp{set write on}, @value{GDBN} opens executable and
10583 core files for both reading and writing; if you specify @samp{set write
10584 off} (the default), @value{GDBN} opens them read-only.
10586 If you have already loaded a file, you must load it again (using the
10587 @code{exec-file} or @code{core-file} command) after changing @code{set
10588 write}, for your new setting to take effect.
10592 Display whether executable files and core files are opened for writing
10593 as well as reading.
10597 @chapter @value{GDBN} Files
10599 @value{GDBN} needs to know the file name of the program to be debugged,
10600 both in order to read its symbol table and in order to start your
10601 program. To debug a core dump of a previous run, you must also tell
10602 @value{GDBN} the name of the core dump file.
10605 * Files:: Commands to specify files
10606 * Separate Debug Files:: Debugging information in separate files
10607 * Symbol Errors:: Errors reading symbol files
10611 @section Commands to specify files
10613 @cindex symbol table
10614 @cindex core dump file
10616 You may want to specify executable and core dump file names. The usual
10617 way to do this is at start-up time, using the arguments to
10618 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
10619 Out of @value{GDBN}}).
10621 Occasionally it is necessary to change to a different file during a
10622 @value{GDBN} session. Or you may run @value{GDBN} and forget to
10623 specify a file you want to use. Or you are debugging a remote target
10624 via @code{gdbserver} (@pxref{Server, file}). In these situations the
10625 @value{GDBN} commands to specify new files are useful.
10628 @cindex executable file
10630 @item file @var{filename}
10631 Use @var{filename} as the program to be debugged. It is read for its
10632 symbols and for the contents of pure memory. It is also the program
10633 executed when you use the @code{run} command. If you do not specify a
10634 directory and the file is not found in the @value{GDBN} working directory,
10635 @value{GDBN} uses the environment variable @code{PATH} as a list of
10636 directories to search, just as the shell does when looking for a program
10637 to run. You can change the value of this variable, for both @value{GDBN}
10638 and your program, using the @code{path} command.
10640 @cindex unlinked object files
10641 @cindex patching object files
10642 You can load unlinked object @file{.o} files into @value{GDBN} using
10643 the @code{file} command. You will not be able to ``run'' an object
10644 file, but you can disassemble functions and inspect variables. Also,
10645 if the underlying BFD functionality supports it, you could use
10646 @kbd{gdb -write} to patch object files using this technique. Note
10647 that @value{GDBN} can neither interpret nor modify relocations in this
10648 case, so branches and some initialized variables will appear to go to
10649 the wrong place. But this feature is still handy from time to time.
10652 @code{file} with no argument makes @value{GDBN} discard any information it
10653 has on both executable file and the symbol table.
10656 @item exec-file @r{[} @var{filename} @r{]}
10657 Specify that the program to be run (but not the symbol table) is found
10658 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
10659 if necessary to locate your program. Omitting @var{filename} means to
10660 discard information on the executable file.
10662 @kindex symbol-file
10663 @item symbol-file @r{[} @var{filename} @r{]}
10664 Read symbol table information from file @var{filename}. @code{PATH} is
10665 searched when necessary. Use the @code{file} command to get both symbol
10666 table and program to run from the same file.
10668 @code{symbol-file} with no argument clears out @value{GDBN} information on your
10669 program's symbol table.
10671 The @code{symbol-file} command causes @value{GDBN} to forget the contents
10672 of its convenience variables, the value history, and all breakpoints and
10673 auto-display expressions. This is because they may contain pointers to
10674 the internal data recording symbols and data types, which are part of
10675 the old symbol table data being discarded inside @value{GDBN}.
10677 @code{symbol-file} does not repeat if you press @key{RET} again after
10680 When @value{GDBN} is configured for a particular environment, it
10681 understands debugging information in whatever format is the standard
10682 generated for that environment; you may use either a @sc{gnu} compiler, or
10683 other compilers that adhere to the local conventions.
10684 Best results are usually obtained from @sc{gnu} compilers; for example,
10685 using @code{@value{GCC}} you can generate debugging information for
10688 For most kinds of object files, with the exception of old SVR3 systems
10689 using COFF, the @code{symbol-file} command does not normally read the
10690 symbol table in full right away. Instead, it scans the symbol table
10691 quickly to find which source files and which symbols are present. The
10692 details are read later, one source file at a time, as they are needed.
10694 The purpose of this two-stage reading strategy is to make @value{GDBN}
10695 start up faster. For the most part, it is invisible except for
10696 occasional pauses while the symbol table details for a particular source
10697 file are being read. (The @code{set verbose} command can turn these
10698 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
10699 warnings and messages}.)
10701 We have not implemented the two-stage strategy for COFF yet. When the
10702 symbol table is stored in COFF format, @code{symbol-file} reads the
10703 symbol table data in full right away. Note that ``stabs-in-COFF''
10704 still does the two-stage strategy, since the debug info is actually
10708 @cindex reading symbols immediately
10709 @cindex symbols, reading immediately
10710 @item symbol-file @var{filename} @r{[} -readnow @r{]}
10711 @itemx file @var{filename} @r{[} -readnow @r{]}
10712 You can override the @value{GDBN} two-stage strategy for reading symbol
10713 tables by using the @samp{-readnow} option with any of the commands that
10714 load symbol table information, if you want to be sure @value{GDBN} has the
10715 entire symbol table available.
10717 @c FIXME: for now no mention of directories, since this seems to be in
10718 @c flux. 13mar1992 status is that in theory GDB would look either in
10719 @c current dir or in same dir as myprog; but issues like competing
10720 @c GDB's, or clutter in system dirs, mean that in practice right now
10721 @c only current dir is used. FFish says maybe a special GDB hierarchy
10722 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
10726 @item core-file @r{[}@var{filename}@r{]}
10728 Specify the whereabouts of a core dump file to be used as the ``contents
10729 of memory''. Traditionally, core files contain only some parts of the
10730 address space of the process that generated them; @value{GDBN} can access the
10731 executable file itself for other parts.
10733 @code{core-file} with no argument specifies that no core file is
10736 Note that the core file is ignored when your program is actually running
10737 under @value{GDBN}. So, if you have been running your program and you
10738 wish to debug a core file instead, you must kill the subprocess in which
10739 the program is running. To do this, use the @code{kill} command
10740 (@pxref{Kill Process, ,Killing the child process}).
10742 @kindex add-symbol-file
10743 @cindex dynamic linking
10744 @item add-symbol-file @var{filename} @var{address}
10745 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
10746 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
10747 The @code{add-symbol-file} command reads additional symbol table
10748 information from the file @var{filename}. You would use this command
10749 when @var{filename} has been dynamically loaded (by some other means)
10750 into the program that is running. @var{address} should be the memory
10751 address at which the file has been loaded; @value{GDBN} cannot figure
10752 this out for itself. You can additionally specify an arbitrary number
10753 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
10754 section name and base address for that section. You can specify any
10755 @var{address} as an expression.
10757 The symbol table of the file @var{filename} is added to the symbol table
10758 originally read with the @code{symbol-file} command. You can use the
10759 @code{add-symbol-file} command any number of times; the new symbol data
10760 thus read keeps adding to the old. To discard all old symbol data
10761 instead, use the @code{symbol-file} command without any arguments.
10763 @cindex relocatable object files, reading symbols from
10764 @cindex object files, relocatable, reading symbols from
10765 @cindex reading symbols from relocatable object files
10766 @cindex symbols, reading from relocatable object files
10767 @cindex @file{.o} files, reading symbols from
10768 Although @var{filename} is typically a shared library file, an
10769 executable file, or some other object file which has been fully
10770 relocated for loading into a process, you can also load symbolic
10771 information from relocatable @file{.o} files, as long as:
10775 the file's symbolic information refers only to linker symbols defined in
10776 that file, not to symbols defined by other object files,
10778 every section the file's symbolic information refers to has actually
10779 been loaded into the inferior, as it appears in the file, and
10781 you can determine the address at which every section was loaded, and
10782 provide these to the @code{add-symbol-file} command.
10786 Some embedded operating systems, like Sun Chorus and VxWorks, can load
10787 relocatable files into an already running program; such systems
10788 typically make the requirements above easy to meet. However, it's
10789 important to recognize that many native systems use complex link
10790 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
10791 assembly, for example) that make the requirements difficult to meet. In
10792 general, one cannot assume that using @code{add-symbol-file} to read a
10793 relocatable object file's symbolic information will have the same effect
10794 as linking the relocatable object file into the program in the normal
10797 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
10799 @kindex add-symbol-file-from-memory
10800 @cindex @code{syscall DSO}
10801 @cindex load symbols from memory
10802 @item add-symbol-file-from-memory @var{address}
10803 Load symbols from the given @var{address} in a dynamically loaded
10804 object file whose image is mapped directly into the inferior's memory.
10805 For example, the Linux kernel maps a @code{syscall DSO} into each
10806 process's address space; this DSO provides kernel-specific code for
10807 some system calls. The argument can be any expression whose
10808 evaluation yields the address of the file's shared object file header.
10809 For this command to work, you must have used @code{symbol-file} or
10810 @code{exec-file} commands in advance.
10812 @kindex add-shared-symbol-files
10814 @item add-shared-symbol-files @var{library-file}
10815 @itemx assf @var{library-file}
10816 The @code{add-shared-symbol-files} command can currently be used only
10817 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
10818 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
10819 @value{GDBN} automatically looks for shared libraries, however if
10820 @value{GDBN} does not find yours, you can invoke
10821 @code{add-shared-symbol-files}. It takes one argument: the shared
10822 library's file name. @code{assf} is a shorthand alias for
10823 @code{add-shared-symbol-files}.
10826 @item section @var{section} @var{addr}
10827 The @code{section} command changes the base address of the named
10828 @var{section} of the exec file to @var{addr}. This can be used if the
10829 exec file does not contain section addresses, (such as in the
10830 @code{a.out} format), or when the addresses specified in the file
10831 itself are wrong. Each section must be changed separately. The
10832 @code{info files} command, described below, lists all the sections and
10836 @kindex info target
10839 @code{info files} and @code{info target} are synonymous; both print the
10840 current target (@pxref{Targets, ,Specifying a Debugging Target}),
10841 including the names of the executable and core dump files currently in
10842 use by @value{GDBN}, and the files from which symbols were loaded. The
10843 command @code{help target} lists all possible targets rather than
10846 @kindex maint info sections
10847 @item maint info sections
10848 Another command that can give you extra information about program sections
10849 is @code{maint info sections}. In addition to the section information
10850 displayed by @code{info files}, this command displays the flags and file
10851 offset of each section in the executable and core dump files. In addition,
10852 @code{maint info sections} provides the following command options (which
10853 may be arbitrarily combined):
10857 Display sections for all loaded object files, including shared libraries.
10858 @item @var{sections}
10859 Display info only for named @var{sections}.
10860 @item @var{section-flags}
10861 Display info only for sections for which @var{section-flags} are true.
10862 The section flags that @value{GDBN} currently knows about are:
10865 Section will have space allocated in the process when loaded.
10866 Set for all sections except those containing debug information.
10868 Section will be loaded from the file into the child process memory.
10869 Set for pre-initialized code and data, clear for @code{.bss} sections.
10871 Section needs to be relocated before loading.
10873 Section cannot be modified by the child process.
10875 Section contains executable code only.
10877 Section contains data only (no executable code).
10879 Section will reside in ROM.
10881 Section contains data for constructor/destructor lists.
10883 Section is not empty.
10885 An instruction to the linker to not output the section.
10886 @item COFF_SHARED_LIBRARY
10887 A notification to the linker that the section contains
10888 COFF shared library information.
10890 Section contains common symbols.
10893 @kindex set trust-readonly-sections
10894 @cindex read-only sections
10895 @item set trust-readonly-sections on
10896 Tell @value{GDBN} that readonly sections in your object file
10897 really are read-only (i.e.@: that their contents will not change).
10898 In that case, @value{GDBN} can fetch values from these sections
10899 out of the object file, rather than from the target program.
10900 For some targets (notably embedded ones), this can be a significant
10901 enhancement to debugging performance.
10903 The default is off.
10905 @item set trust-readonly-sections off
10906 Tell @value{GDBN} not to trust readonly sections. This means that
10907 the contents of the section might change while the program is running,
10908 and must therefore be fetched from the target when needed.
10910 @item show trust-readonly-sections
10911 Show the current setting of trusting readonly sections.
10914 All file-specifying commands allow both absolute and relative file names
10915 as arguments. @value{GDBN} always converts the file name to an absolute file
10916 name and remembers it that way.
10918 @cindex shared libraries
10919 @value{GDBN} supports GNU/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
10920 and IBM RS/6000 AIX shared libraries.
10922 @value{GDBN} automatically loads symbol definitions from shared libraries
10923 when you use the @code{run} command, or when you examine a core file.
10924 (Before you issue the @code{run} command, @value{GDBN} does not understand
10925 references to a function in a shared library, however---unless you are
10926 debugging a core file).
10928 On HP-UX, if the program loads a library explicitly, @value{GDBN}
10929 automatically loads the symbols at the time of the @code{shl_load} call.
10931 @c FIXME: some @value{GDBN} release may permit some refs to undef
10932 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
10933 @c FIXME...lib; check this from time to time when updating manual
10935 There are times, however, when you may wish to not automatically load
10936 symbol definitions from shared libraries, such as when they are
10937 particularly large or there are many of them.
10939 To control the automatic loading of shared library symbols, use the
10943 @kindex set auto-solib-add
10944 @item set auto-solib-add @var{mode}
10945 If @var{mode} is @code{on}, symbols from all shared object libraries
10946 will be loaded automatically when the inferior begins execution, you
10947 attach to an independently started inferior, or when the dynamic linker
10948 informs @value{GDBN} that a new library has been loaded. If @var{mode}
10949 is @code{off}, symbols must be loaded manually, using the
10950 @code{sharedlibrary} command. The default value is @code{on}.
10952 @cindex memory used for symbol tables
10953 If your program uses lots of shared libraries with debug info that
10954 takes large amounts of memory, you can decrease the @value{GDBN}
10955 memory footprint by preventing it from automatically loading the
10956 symbols from shared libraries. To that end, type @kbd{set
10957 auto-solib-add off} before running the inferior, then load each
10958 library whose debug symbols you do need with @kbd{sharedlibrary
10959 @var{regexp}}, where @var{regexp} is a regular expresion that matches
10960 the libraries whose symbols you want to be loaded.
10962 @kindex show auto-solib-add
10963 @item show auto-solib-add
10964 Display the current autoloading mode.
10967 @cindex load shared library
10968 To explicitly load shared library symbols, use the @code{sharedlibrary}
10972 @kindex info sharedlibrary
10975 @itemx info sharedlibrary
10976 Print the names of the shared libraries which are currently loaded.
10978 @kindex sharedlibrary
10980 @item sharedlibrary @var{regex}
10981 @itemx share @var{regex}
10982 Load shared object library symbols for files matching a
10983 Unix regular expression.
10984 As with files loaded automatically, it only loads shared libraries
10985 required by your program for a core file or after typing @code{run}. If
10986 @var{regex} is omitted all shared libraries required by your program are
10989 @item nosharedlibrary
10990 @kindex nosharedlibrary
10991 @cindex unload symbols from shared libraries
10992 Unload all shared object library symbols. This discards all symbols
10993 that have been loaded from all shared libraries. Symbols from shared
10994 libraries that were loaded by explicit user requests are not
10998 Sometimes you may wish that @value{GDBN} stops and gives you control
10999 when any of shared library events happen. Use the @code{set
11000 stop-on-solib-events} command for this:
11003 @item set stop-on-solib-events
11004 @kindex set stop-on-solib-events
11005 This command controls whether @value{GDBN} should give you control
11006 when the dynamic linker notifies it about some shared library event.
11007 The most common event of interest is loading or unloading of a new
11010 @item show stop-on-solib-events
11011 @kindex show stop-on-solib-events
11012 Show whether @value{GDBN} stops and gives you control when shared
11013 library events happen.
11016 Shared libraries are also supported in many cross or remote debugging
11017 configurations. A copy of the target's libraries need to be present on the
11018 host system; they need to be the same as the target libraries, although the
11019 copies on the target can be stripped as long as the copies on the host are
11022 @cindex where to look for shared libraries
11023 For remote debugging, you need to tell @value{GDBN} where the target
11024 libraries are, so that it can load the correct copies---otherwise, it
11025 may try to load the host's libraries. @value{GDBN} has two variables
11026 to specify the search directories for target libraries.
11029 @cindex prefix for shared library file names
11030 @kindex set solib-absolute-prefix
11031 @item set solib-absolute-prefix @var{path}
11032 If this variable is set, @var{path} will be used as a prefix for any
11033 absolute shared library paths; many runtime loaders store the absolute
11034 paths to the shared library in the target program's memory. If you use
11035 @samp{solib-absolute-prefix} to find shared libraries, they need to be laid
11036 out in the same way that they are on the target, with e.g.@: a
11037 @file{/usr/lib} hierarchy under @var{path}.
11039 @cindex default value of @samp{solib-absolute-prefix}
11040 @cindex @samp{--with-sysroot}
11041 You can set the default value of @samp{solib-absolute-prefix} by using the
11042 configure-time @samp{--with-sysroot} option.
11044 @kindex show solib-absolute-prefix
11045 @item show solib-absolute-prefix
11046 Display the current shared library prefix.
11048 @kindex set solib-search-path
11049 @item set solib-search-path @var{path}
11050 If this variable is set, @var{path} is a colon-separated list of directories
11051 to search for shared libraries. @samp{solib-search-path} is used after
11052 @samp{solib-absolute-prefix} fails to locate the library, or if the path to
11053 the library is relative instead of absolute. If you want to use
11054 @samp{solib-search-path} instead of @samp{solib-absolute-prefix}, be sure to
11055 set @samp{solib-absolute-prefix} to a nonexistant directory to prevent
11056 @value{GDBN} from finding your host's libraries.
11058 @kindex show solib-search-path
11059 @item show solib-search-path
11060 Display the current shared library search path.
11064 @node Separate Debug Files
11065 @section Debugging Information in Separate Files
11066 @cindex separate debugging information files
11067 @cindex debugging information in separate files
11068 @cindex @file{.debug} subdirectories
11069 @cindex debugging information directory, global
11070 @cindex global debugging information directory
11072 @value{GDBN} allows you to put a program's debugging information in a
11073 file separate from the executable itself, in a way that allows
11074 @value{GDBN} to find and load the debugging information automatically.
11075 Since debugging information can be very large --- sometimes larger
11076 than the executable code itself --- some systems distribute debugging
11077 information for their executables in separate files, which users can
11078 install only when they need to debug a problem.
11080 If an executable's debugging information has been extracted to a
11081 separate file, the executable should contain a @dfn{debug link} giving
11082 the name of the debugging information file (with no directory
11083 components), and a checksum of its contents. (The exact form of a
11084 debug link is described below.) If the full name of the directory
11085 containing the executable is @var{execdir}, and the executable has a
11086 debug link that specifies the name @var{debugfile}, then @value{GDBN}
11087 will automatically search for the debugging information file in three
11092 the directory containing the executable file (that is, it will look
11093 for a file named @file{@var{execdir}/@var{debugfile}},
11095 a subdirectory of that directory named @file{.debug} (that is, the
11096 file @file{@var{execdir}/.debug/@var{debugfile}}, and
11098 a subdirectory of the global debug file directory that includes the
11099 executable's full path, and the name from the link (that is, the file
11100 @file{@var{globaldebugdir}/@var{execdir}/@var{debugfile}}, where
11101 @var{globaldebugdir} is the global debug file directory, and
11102 @var{execdir} has been turned into a relative path).
11105 @value{GDBN} checks under each of these names for a debugging
11106 information file whose checksum matches that given in the link, and
11107 reads the debugging information from the first one it finds.
11109 So, for example, if you ask @value{GDBN} to debug @file{/usr/bin/ls},
11110 which has a link containing the name @file{ls.debug}, and the global
11111 debug directory is @file{/usr/lib/debug}, then @value{GDBN} will look
11112 for debug information in @file{/usr/bin/ls.debug},
11113 @file{/usr/bin/.debug/ls.debug}, and
11114 @file{/usr/lib/debug/usr/bin/ls.debug}.
11116 You can set the global debugging info directory's name, and view the
11117 name @value{GDBN} is currently using.
11121 @kindex set debug-file-directory
11122 @item set debug-file-directory @var{directory}
11123 Set the directory which @value{GDBN} searches for separate debugging
11124 information files to @var{directory}.
11126 @kindex show debug-file-directory
11127 @item show debug-file-directory
11128 Show the directory @value{GDBN} searches for separate debugging
11133 @cindex @code{.gnu_debuglink} sections
11134 @cindex debug links
11135 A debug link is a special section of the executable file named
11136 @code{.gnu_debuglink}. The section must contain:
11140 A filename, with any leading directory components removed, followed by
11143 zero to three bytes of padding, as needed to reach the next four-byte
11144 boundary within the section, and
11146 a four-byte CRC checksum, stored in the same endianness used for the
11147 executable file itself. The checksum is computed on the debugging
11148 information file's full contents by the function given below, passing
11149 zero as the @var{crc} argument.
11152 Any executable file format can carry a debug link, as long as it can
11153 contain a section named @code{.gnu_debuglink} with the contents
11156 The debugging information file itself should be an ordinary
11157 executable, containing a full set of linker symbols, sections, and
11158 debugging information. The sections of the debugging information file
11159 should have the same names, addresses and sizes as the original file,
11160 but they need not contain any data --- much like a @code{.bss} section
11161 in an ordinary executable.
11163 As of December 2002, there is no standard GNU utility to produce
11164 separated executable / debugging information file pairs. Ulrich
11165 Drepper's @file{elfutils} package, starting with version 0.53,
11166 contains a version of the @code{strip} command such that the command
11167 @kbd{strip foo -f foo.debug} removes the debugging information from
11168 the executable file @file{foo}, places it in the file
11169 @file{foo.debug}, and leaves behind a debug link in @file{foo}.
11171 Since there are many different ways to compute CRC's (different
11172 polynomials, reversals, byte ordering, etc.), the simplest way to
11173 describe the CRC used in @code{.gnu_debuglink} sections is to give the
11174 complete code for a function that computes it:
11176 @kindex gnu_debuglink_crc32
11179 gnu_debuglink_crc32 (unsigned long crc,
11180 unsigned char *buf, size_t len)
11182 static const unsigned long crc32_table[256] =
11184 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
11185 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
11186 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
11187 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
11188 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
11189 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
11190 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
11191 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
11192 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
11193 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
11194 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
11195 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
11196 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
11197 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
11198 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
11199 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
11200 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
11201 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
11202 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
11203 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
11204 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
11205 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
11206 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
11207 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
11208 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
11209 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
11210 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
11211 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
11212 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
11213 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
11214 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
11215 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
11216 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
11217 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
11218 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
11219 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
11220 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
11221 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
11222 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
11223 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
11224 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
11225 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
11226 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
11227 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
11228 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
11229 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
11230 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
11231 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
11232 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
11233 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
11234 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
11237 unsigned char *end;
11239 crc = ~crc & 0xffffffff;
11240 for (end = buf + len; buf < end; ++buf)
11241 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
11242 return ~crc & 0xffffffff;
11247 @node Symbol Errors
11248 @section Errors reading symbol files
11250 While reading a symbol file, @value{GDBN} occasionally encounters problems,
11251 such as symbol types it does not recognize, or known bugs in compiler
11252 output. By default, @value{GDBN} does not notify you of such problems, since
11253 they are relatively common and primarily of interest to people
11254 debugging compilers. If you are interested in seeing information
11255 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
11256 only one message about each such type of problem, no matter how many
11257 times the problem occurs; or you can ask @value{GDBN} to print more messages,
11258 to see how many times the problems occur, with the @code{set
11259 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
11262 The messages currently printed, and their meanings, include:
11265 @item inner block not inside outer block in @var{symbol}
11267 The symbol information shows where symbol scopes begin and end
11268 (such as at the start of a function or a block of statements). This
11269 error indicates that an inner scope block is not fully contained
11270 in its outer scope blocks.
11272 @value{GDBN} circumvents the problem by treating the inner block as if it had
11273 the same scope as the outer block. In the error message, @var{symbol}
11274 may be shown as ``@code{(don't know)}'' if the outer block is not a
11277 @item block at @var{address} out of order
11279 The symbol information for symbol scope blocks should occur in
11280 order of increasing addresses. This error indicates that it does not
11283 @value{GDBN} does not circumvent this problem, and has trouble
11284 locating symbols in the source file whose symbols it is reading. (You
11285 can often determine what source file is affected by specifying
11286 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
11289 @item bad block start address patched
11291 The symbol information for a symbol scope block has a start address
11292 smaller than the address of the preceding source line. This is known
11293 to occur in the SunOS 4.1.1 (and earlier) C compiler.
11295 @value{GDBN} circumvents the problem by treating the symbol scope block as
11296 starting on the previous source line.
11298 @item bad string table offset in symbol @var{n}
11301 Symbol number @var{n} contains a pointer into the string table which is
11302 larger than the size of the string table.
11304 @value{GDBN} circumvents the problem by considering the symbol to have the
11305 name @code{foo}, which may cause other problems if many symbols end up
11308 @item unknown symbol type @code{0x@var{nn}}
11310 The symbol information contains new data types that @value{GDBN} does
11311 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
11312 uncomprehended information, in hexadecimal.
11314 @value{GDBN} circumvents the error by ignoring this symbol information.
11315 This usually allows you to debug your program, though certain symbols
11316 are not accessible. If you encounter such a problem and feel like
11317 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
11318 on @code{complain}, then go up to the function @code{read_dbx_symtab}
11319 and examine @code{*bufp} to see the symbol.
11321 @item stub type has NULL name
11323 @value{GDBN} could not find the full definition for a struct or class.
11325 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
11326 The symbol information for a C@t{++} member function is missing some
11327 information that recent versions of the compiler should have output for
11330 @item info mismatch between compiler and debugger
11332 @value{GDBN} could not parse a type specification output by the compiler.
11337 @chapter Specifying a Debugging Target
11339 @cindex debugging target
11340 A @dfn{target} is the execution environment occupied by your program.
11342 Often, @value{GDBN} runs in the same host environment as your program;
11343 in that case, the debugging target is specified as a side effect when
11344 you use the @code{file} or @code{core} commands. When you need more
11345 flexibility---for example, running @value{GDBN} on a physically separate
11346 host, or controlling a standalone system over a serial port or a
11347 realtime system over a TCP/IP connection---you can use the @code{target}
11348 command to specify one of the target types configured for @value{GDBN}
11349 (@pxref{Target Commands, ,Commands for managing targets}).
11351 @cindex target architecture
11352 It is possible to build @value{GDBN} for several different @dfn{target
11353 architectures}. When @value{GDBN} is built like that, you can choose
11354 one of the available architectures with the @kbd{set architecture}
11358 @kindex set architecture
11359 @kindex show architecture
11360 @item set architecture @var{arch}
11361 This command sets the current target architecture to @var{arch}. The
11362 value of @var{arch} can be @code{"auto"}, in addition to one of the
11363 supported architectures.
11365 @item show architecture
11366 Show the current target architecture.
11368 @item set processor
11370 @kindex set processor
11371 @kindex show processor
11372 These are alias commands for, respectively, @code{set architecture}
11373 and @code{show architecture}.
11377 * Active Targets:: Active targets
11378 * Target Commands:: Commands for managing targets
11379 * Byte Order:: Choosing target byte order
11380 * Remote:: Remote debugging
11381 * KOD:: Kernel Object Display
11385 @node Active Targets
11386 @section Active targets
11388 @cindex stacking targets
11389 @cindex active targets
11390 @cindex multiple targets
11392 There are three classes of targets: processes, core files, and
11393 executable files. @value{GDBN} can work concurrently on up to three
11394 active targets, one in each class. This allows you to (for example)
11395 start a process and inspect its activity without abandoning your work on
11398 For example, if you execute @samp{gdb a.out}, then the executable file
11399 @code{a.out} is the only active target. If you designate a core file as
11400 well---presumably from a prior run that crashed and coredumped---then
11401 @value{GDBN} has two active targets and uses them in tandem, looking
11402 first in the corefile target, then in the executable file, to satisfy
11403 requests for memory addresses. (Typically, these two classes of target
11404 are complementary, since core files contain only a program's
11405 read-write memory---variables and so on---plus machine status, while
11406 executable files contain only the program text and initialized data.)
11408 When you type @code{run}, your executable file becomes an active process
11409 target as well. When a process target is active, all @value{GDBN}
11410 commands requesting memory addresses refer to that target; addresses in
11411 an active core file or executable file target are obscured while the
11412 process target is active.
11414 Use the @code{core-file} and @code{exec-file} commands to select a new
11415 core file or executable target (@pxref{Files, ,Commands to specify
11416 files}). To specify as a target a process that is already running, use
11417 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
11420 @node Target Commands
11421 @section Commands for managing targets
11424 @item target @var{type} @var{parameters}
11425 Connects the @value{GDBN} host environment to a target machine or
11426 process. A target is typically a protocol for talking to debugging
11427 facilities. You use the argument @var{type} to specify the type or
11428 protocol of the target machine.
11430 Further @var{parameters} are interpreted by the target protocol, but
11431 typically include things like device names or host names to connect
11432 with, process numbers, and baud rates.
11434 The @code{target} command does not repeat if you press @key{RET} again
11435 after executing the command.
11437 @kindex help target
11439 Displays the names of all targets available. To display targets
11440 currently selected, use either @code{info target} or @code{info files}
11441 (@pxref{Files, ,Commands to specify files}).
11443 @item help target @var{name}
11444 Describe a particular target, including any parameters necessary to
11447 @kindex set gnutarget
11448 @item set gnutarget @var{args}
11449 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
11450 knows whether it is reading an @dfn{executable},
11451 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
11452 with the @code{set gnutarget} command. Unlike most @code{target} commands,
11453 with @code{gnutarget} the @code{target} refers to a program, not a machine.
11456 @emph{Warning:} To specify a file format with @code{set gnutarget},
11457 you must know the actual BFD name.
11461 @xref{Files, , Commands to specify files}.
11463 @kindex show gnutarget
11464 @item show gnutarget
11465 Use the @code{show gnutarget} command to display what file format
11466 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
11467 @value{GDBN} will determine the file format for each file automatically,
11468 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
11471 @cindex common targets
11472 Here are some common targets (available, or not, depending on the GDB
11477 @item target exec @var{program}
11478 @cindex executable file target
11479 An executable file. @samp{target exec @var{program}} is the same as
11480 @samp{exec-file @var{program}}.
11482 @item target core @var{filename}
11483 @cindex core dump file target
11484 A core dump file. @samp{target core @var{filename}} is the same as
11485 @samp{core-file @var{filename}}.
11487 @item target remote @var{dev}
11488 @cindex remote target
11489 Remote serial target in GDB-specific protocol. The argument @var{dev}
11490 specifies what serial device to use for the connection (e.g.
11491 @file{/dev/ttya}). @xref{Remote, ,Remote debugging}. @code{target remote}
11492 supports the @code{load} command. This is only useful if you have
11493 some other way of getting the stub to the target system, and you can put
11494 it somewhere in memory where it won't get clobbered by the download.
11497 @cindex built-in simulator target
11498 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
11506 works; however, you cannot assume that a specific memory map, device
11507 drivers, or even basic I/O is available, although some simulators do
11508 provide these. For info about any processor-specific simulator details,
11509 see the appropriate section in @ref{Embedded Processors, ,Embedded
11514 Some configurations may include these targets as well:
11518 @item target nrom @var{dev}
11519 @cindex NetROM ROM emulator target
11520 NetROM ROM emulator. This target only supports downloading.
11524 Different targets are available on different configurations of @value{GDBN};
11525 your configuration may have more or fewer targets.
11527 Many remote targets require you to download the executable's code once
11528 you've successfully established a connection. You may wish to control
11529 various aspects of this process, such as the size of the data chunks
11530 used by @value{GDBN} to download program parts to the remote target.
11533 @kindex set download-write-size
11534 @item set download-write-size @var{size}
11535 Set the write size used when downloading a program. Only used when
11536 downloading a program onto a remote target. Specify zero or a
11537 negative value to disable blocked writes. The actual size of each
11538 transfer is also limited by the size of the target packet and the
11541 @kindex show download-write-size
11542 @item show download-write-size
11543 @kindex show download-write-size
11544 Show the current value of the write size.
11547 @kindex set hash@r{, for remote monitors}
11548 @cindex hash mark while downloading
11549 This command controls whether a hash mark @samp{#} is displayed while
11550 downloading a file to the remote monitor. If on, a hash mark is
11551 displayed after each S-record is successfully downloaded to the
11555 @kindex show hash@r{, for remote monitors}
11556 Show the current status of displaying the hash mark.
11558 @item set debug monitor
11559 @kindex set debug monitor
11560 @cindex display remote monitor communications
11561 Enable or disable display of communications messages between
11562 @value{GDBN} and the remote monitor.
11564 @item show debug monitor
11565 @kindex show debug monitor
11566 Show the current status of displaying communications between
11567 @value{GDBN} and the remote monitor.
11572 @kindex load @var{filename}
11573 @item load @var{filename}
11574 Depending on what remote debugging facilities are configured into
11575 @value{GDBN}, the @code{load} command may be available. Where it exists, it
11576 is meant to make @var{filename} (an executable) available for debugging
11577 on the remote system---by downloading, or dynamic linking, for example.
11578 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
11579 the @code{add-symbol-file} command.
11581 If your @value{GDBN} does not have a @code{load} command, attempting to
11582 execute it gets the error message ``@code{You can't do that when your
11583 target is @dots{}}''
11585 The file is loaded at whatever address is specified in the executable.
11586 For some object file formats, you can specify the load address when you
11587 link the program; for other formats, like a.out, the object file format
11588 specifies a fixed address.
11589 @c FIXME! This would be a good place for an xref to the GNU linker doc.
11591 @code{load} does not repeat if you press @key{RET} again after using it.
11595 @section Choosing target byte order
11597 @cindex choosing target byte order
11598 @cindex target byte order
11600 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
11601 offer the ability to run either big-endian or little-endian byte
11602 orders. Usually the executable or symbol will include a bit to
11603 designate the endian-ness, and you will not need to worry about
11604 which to use. However, you may still find it useful to adjust
11605 @value{GDBN}'s idea of processor endian-ness manually.
11609 @item set endian big
11610 Instruct @value{GDBN} to assume the target is big-endian.
11612 @item set endian little
11613 Instruct @value{GDBN} to assume the target is little-endian.
11615 @item set endian auto
11616 Instruct @value{GDBN} to use the byte order associated with the
11620 Display @value{GDBN}'s current idea of the target byte order.
11624 Note that these commands merely adjust interpretation of symbolic
11625 data on the host, and that they have absolutely no effect on the
11629 @section Remote debugging
11630 @cindex remote debugging
11632 If you are trying to debug a program running on a machine that cannot run
11633 @value{GDBN} in the usual way, it is often useful to use remote debugging.
11634 For example, you might use remote debugging on an operating system kernel,
11635 or on a small system which does not have a general purpose operating system
11636 powerful enough to run a full-featured debugger.
11638 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
11639 to make this work with particular debugging targets. In addition,
11640 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
11641 but not specific to any particular target system) which you can use if you
11642 write the remote stubs---the code that runs on the remote system to
11643 communicate with @value{GDBN}.
11645 Other remote targets may be available in your
11646 configuration of @value{GDBN}; use @code{help target} to list them.
11648 Once you've connected to the remote target, @value{GDBN} allows you to
11649 send arbitrary commands to the remote monitor:
11652 @item remote @var{command}
11653 @kindex remote@r{, a command}
11654 @cindex send command to remote monitor
11655 Send an arbitrary @var{command} string to the remote monitor.
11660 @section Kernel Object Display
11661 @cindex kernel object display
11664 Some targets support kernel object display. Using this facility,
11665 @value{GDBN} communicates specially with the underlying operating system
11666 and can display information about operating system-level objects such as
11667 mutexes and other synchronization objects. Exactly which objects can be
11668 displayed is determined on a per-OS basis.
11671 Use the @code{set os} command to set the operating system. This tells
11672 @value{GDBN} which kernel object display module to initialize:
11675 (@value{GDBP}) set os cisco
11679 The associated command @code{show os} displays the operating system
11680 set with the @code{set os} command; if no operating system has been
11681 set, @code{show os} will display an empty string @samp{""}.
11683 If @code{set os} succeeds, @value{GDBN} will display some information
11684 about the operating system, and will create a new @code{info} command
11685 which can be used to query the target. The @code{info} command is named
11686 after the operating system:
11690 (@value{GDBP}) info cisco
11691 List of Cisco Kernel Objects
11693 any Any and all objects
11696 Further subcommands can be used to query about particular objects known
11699 There is currently no way to determine whether a given operating
11700 system is supported other than to try setting it with @kbd{set os
11701 @var{name}}, where @var{name} is the name of the operating system you
11705 @node Remote Debugging
11706 @chapter Debugging remote programs
11709 * Connecting:: Connecting to a remote target
11710 * Server:: Using the gdbserver program
11711 * NetWare:: Using the gdbserve.nlm program
11712 * Remote configuration:: Remote configuration
11713 * remote stub:: Implementing a remote stub
11717 @section Connecting to a remote target
11719 On the @value{GDBN} host machine, you will need an unstripped copy of
11720 your program, since @value{GDBN} needs symobl and debugging information.
11721 Start up @value{GDBN} as usual, using the name of the local copy of your
11722 program as the first argument.
11724 @cindex serial line, @code{target remote}
11725 If you're using a serial line, you may want to give @value{GDBN} the
11726 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
11727 (@pxref{Remote configuration, set remotebaud}) before the
11728 @code{target} command.
11730 After that, use @code{target remote} to establish communications with
11731 the target machine. Its argument specifies how to communicate---either
11732 via a devicename attached to a direct serial line, or a TCP or UDP port
11733 (possibly to a terminal server which in turn has a serial line to the
11734 target). For example, to use a serial line connected to the device
11735 named @file{/dev/ttyb}:
11738 target remote /dev/ttyb
11741 @cindex TCP port, @code{target remote}
11742 To use a TCP connection, use an argument of the form
11743 @code{@var{host}:@var{port}} or @code{tcp:@var{host}:@var{port}}.
11744 For example, to connect to port 2828 on a
11745 terminal server named @code{manyfarms}:
11748 target remote manyfarms:2828
11751 If your remote target is actually running on the same machine as
11752 your debugger session (e.g.@: a simulator of your target running on
11753 the same host), you can omit the hostname. For example, to connect
11754 to port 1234 on your local machine:
11757 target remote :1234
11761 Note that the colon is still required here.
11763 @cindex UDP port, @code{target remote}
11764 To use a UDP connection, use an argument of the form
11765 @code{udp:@var{host}:@var{port}}. For example, to connect to UDP port 2828
11766 on a terminal server named @code{manyfarms}:
11769 target remote udp:manyfarms:2828
11772 When using a UDP connection for remote debugging, you should keep in mind
11773 that the `U' stands for ``Unreliable''. UDP can silently drop packets on
11774 busy or unreliable networks, which will cause havoc with your debugging
11777 Now you can use all the usual commands to examine and change data and to
11778 step and continue the remote program.
11780 @cindex interrupting remote programs
11781 @cindex remote programs, interrupting
11782 Whenever @value{GDBN} is waiting for the remote program, if you type the
11783 interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the
11784 program. This may or may not succeed, depending in part on the hardware
11785 and the serial drivers the remote system uses. If you type the
11786 interrupt character once again, @value{GDBN} displays this prompt:
11789 Interrupted while waiting for the program.
11790 Give up (and stop debugging it)? (y or n)
11793 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
11794 (If you decide you want to try again later, you can use @samp{target
11795 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
11796 goes back to waiting.
11799 @kindex detach (remote)
11801 When you have finished debugging the remote program, you can use the
11802 @code{detach} command to release it from @value{GDBN} control.
11803 Detaching from the target normally resumes its execution, but the results
11804 will depend on your particular remote stub. After the @code{detach}
11805 command, @value{GDBN} is free to connect to another target.
11809 The @code{disconnect} command behaves like @code{detach}, except that
11810 the target is generally not resumed. It will wait for @value{GDBN}
11811 (this instance or another one) to connect and continue debugging. After
11812 the @code{disconnect} command, @value{GDBN} is again free to connect to
11815 @cindex send command to remote monitor
11817 @item monitor @var{cmd}
11818 This command allows you to send commands directly to the remote
11823 @section Using the @code{gdbserver} program
11826 @cindex remote connection without stubs
11827 @code{gdbserver} is a control program for Unix-like systems, which
11828 allows you to connect your program with a remote @value{GDBN} via
11829 @code{target remote}---but without linking in the usual debugging stub.
11831 @code{gdbserver} is not a complete replacement for the debugging stubs,
11832 because it requires essentially the same operating-system facilities
11833 that @value{GDBN} itself does. In fact, a system that can run
11834 @code{gdbserver} to connect to a remote @value{GDBN} could also run
11835 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
11836 because it is a much smaller program than @value{GDBN} itself. It is
11837 also easier to port than all of @value{GDBN}, so you may be able to get
11838 started more quickly on a new system by using @code{gdbserver}.
11839 Finally, if you develop code for real-time systems, you may find that
11840 the tradeoffs involved in real-time operation make it more convenient to
11841 do as much development work as possible on another system, for example
11842 by cross-compiling. You can use @code{gdbserver} to make a similar
11843 choice for debugging.
11845 @value{GDBN} and @code{gdbserver} communicate via either a serial line
11846 or a TCP connection, using the standard @value{GDBN} remote serial
11850 @item On the target machine,
11851 you need to have a copy of the program you want to debug.
11852 @code{gdbserver} does not need your program's symbol table, so you can
11853 strip the program if necessary to save space. @value{GDBN} on the host
11854 system does all the symbol handling.
11856 To use the server, you must tell it how to communicate with @value{GDBN};
11857 the name of your program; and the arguments for your program. The usual
11861 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
11864 @var{comm} is either a device name (to use a serial line) or a TCP
11865 hostname and portnumber. For example, to debug Emacs with the argument
11866 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
11870 target> gdbserver /dev/com1 emacs foo.txt
11873 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
11876 To use a TCP connection instead of a serial line:
11879 target> gdbserver host:2345 emacs foo.txt
11882 The only difference from the previous example is the first argument,
11883 specifying that you are communicating with the host @value{GDBN} via
11884 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
11885 expect a TCP connection from machine @samp{host} to local TCP port 2345.
11886 (Currently, the @samp{host} part is ignored.) You can choose any number
11887 you want for the port number as long as it does not conflict with any
11888 TCP ports already in use on the target system (for example, @code{23} is
11889 reserved for @code{telnet}).@footnote{If you choose a port number that
11890 conflicts with another service, @code{gdbserver} prints an error message
11891 and exits.} You must use the same port number with the host @value{GDBN}
11892 @code{target remote} command.
11894 On some targets, @code{gdbserver} can also attach to running programs.
11895 This is accomplished via the @code{--attach} argument. The syntax is:
11898 target> gdbserver @var{comm} --attach @var{pid}
11901 @var{pid} is the process ID of a currently running process. It isn't necessary
11902 to point @code{gdbserver} at a binary for the running process.
11905 @cindex attach to a program by name
11906 You can debug processes by name instead of process ID if your target has the
11907 @code{pidof} utility:
11910 target> gdbserver @var{comm} --attach `pidof @var{PROGRAM}`
11913 In case more than one copy of @var{PROGRAM} is running, or @var{PROGRAM}
11914 has multiple threads, most versions of @code{pidof} support the
11915 @code{-s} option to only return the first process ID.
11917 @item On the host machine,
11918 connect to your target (@pxref{Connecting,,Connecting to a remote target}).
11919 For TCP connections, you must start up @code{gdbserver} prior to using
11920 the @code{target remote} command. Otherwise you may get an error whose
11921 text depends on the host system, but which usually looks something like
11922 @samp{Connection refused}. You don't need to use the @code{load}
11923 command in @value{GDBN} when using @code{gdbserver}, since the program is
11924 already on the target. However, if you want to load the symbols (as
11925 you normally would), do that with the @code{file} command, and issue
11926 it @emph{before} connecting to the server; otherwise, you will get an
11927 error message saying @code{"Program is already running"}, since the
11928 program is considered running after the connection.
11933 @section Using the @code{gdbserve.nlm} program
11935 @kindex gdbserve.nlm
11936 @code{gdbserve.nlm} is a control program for NetWare systems, which
11937 allows you to connect your program with a remote @value{GDBN} via
11938 @code{target remote}.
11940 @value{GDBN} and @code{gdbserve.nlm} communicate via a serial line,
11941 using the standard @value{GDBN} remote serial protocol.
11944 @item On the target machine,
11945 you need to have a copy of the program you want to debug.
11946 @code{gdbserve.nlm} does not need your program's symbol table, so you
11947 can strip the program if necessary to save space. @value{GDBN} on the
11948 host system does all the symbol handling.
11950 To use the server, you must tell it how to communicate with
11951 @value{GDBN}; the name of your program; and the arguments for your
11952 program. The syntax is:
11955 load gdbserve [ BOARD=@var{board} ] [ PORT=@var{port} ]
11956 [ BAUD=@var{baud} ] @var{program} [ @var{args} @dots{} ]
11959 @var{board} and @var{port} specify the serial line; @var{baud} specifies
11960 the baud rate used by the connection. @var{port} and @var{node} default
11961 to 0, @var{baud} defaults to 9600@dmn{bps}.
11963 For example, to debug Emacs with the argument @samp{foo.txt}and
11964 communicate with @value{GDBN} over serial port number 2 or board 1
11965 using a 19200@dmn{bps} connection:
11968 load gdbserve BOARD=1 PORT=2 BAUD=19200 emacs foo.txt
11972 On the @value{GDBN} host machine, connect to your target (@pxref{Connecting,,
11973 Connecting to a remote target}).
11977 @node Remote configuration
11978 @section Remote configuration
11981 @kindex show remote
11982 This section documents the configuration options available when
11983 debugging remote programs. For the options related to the File I/O
11984 extensions of the remote protocol, see @ref{The system call,
11985 system-call-allowed}.
11988 @item set remoteaddresssize @var{bits}
11989 @cindex adress size for remote targets
11990 @cindex bits in remote address
11991 Set the maximum size of address in a memory packet to the specified
11992 number of bits. @value{GDBN} will mask off the address bits above
11993 that number, when it passes addresses to the remote target. The
11994 default value is the number of bits in the target's address.
11996 @item show remoteaddresssize
11997 Show the current value of remote address size in bits.
11999 @item set remotebaud @var{n}
12000 @cindex baud rate for remote targets
12001 Set the baud rate for the remote serial I/O to @var{n} baud. The
12002 value is used to set the speed of the serial port used for debugging
12005 @item show remotebaud
12006 Show the current speed of the remote connection.
12008 @item set remotebreak
12009 @cindex interrupt remote programs
12010 @cindex BREAK signal instead of Ctrl-C
12011 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
12012 when you press the @key{Ctrl-C} key to interrupt the program running
12013 on the remote. If set to off, @value{GDBN} sends the @samp{Strl-C}
12014 character instead. The default is off, since most remote systems
12015 expect to see @samp{Ctrl-C} as the interrupt signal.
12017 @item show remotebreak
12018 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
12019 interrupt the remote program.
12021 @item set remotedebug
12022 @cindex debug remote protocol
12023 @cindex remote protocol debugging
12024 @cindex display remote packets
12025 Control the debugging of the remote protocol. When enabled, each
12026 packet sent to or received from the remote target is displayed. The
12029 @item show remotedebug
12030 Show the current setting of the remote protocol debugging.
12032 @item set remotedevice @var{device}
12033 @cindex serial port name
12034 Set the name of the serial port through which to communicate to the
12035 remote target to @var{device}. This is the device used by
12036 @value{GDBN} to open the serial communications line to the remote
12037 target. There's no default, so you must set a valid port name for the
12038 remote serial communications to work. (Some varieties of the
12039 @code{target} command accept the port name as part of their
12042 @item show remotedevice
12043 Show the current name of the serial port.
12045 @item set remotelogbase @var{base}
12046 Set the base (a.k.a.@: radix) of logging serial protocol
12047 communications to @var{base}. Supported values of @var{base} are:
12048 @code{ascii}, @code{octal}, and @code{hex}. The default is
12051 @item show remotelogbase
12052 Show the current setting of the radix for logging remote serial
12055 @item set remotelogfile @var{file}
12056 @cindex record serial communications on file
12057 Record remote serial communications on the named @var{file}. The
12058 default is not to record at all.
12060 @item show remotelogfile.
12061 Show the current setting of the file name on which to record the
12062 serial communications.
12064 @item set remotetimeout @var{num}
12065 @cindex timeout for serial communications
12066 @cindex remote timeout
12067 Set the timeout limit to wait for the remote target to respond to
12068 @var{num} seconds. The default is 2 seconds.
12070 @item show remotetimeout
12071 Show the current number of seconds to wait for the remote target
12074 @cindex limit hardware breakpoints and watchpoints
12075 @cindex remote target, limit break- and watchpoints
12076 @anchor{set remote hardware-watchpoint-limit}
12077 @anchor{set remote hardware-breakpoint-limit}
12078 @item set remote hardware-watchpoint-limit @var{limit}
12079 @itemx set remote hardware-breakpoint-limit @var{limit}
12080 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
12081 watchpoints. A limit of -1, the default, is treated as unlimited.
12083 @item set remote fetch-register-packet
12084 @itemx set remote set-register-packet
12085 @itemx set remote P-packet
12086 @itemx set remote p-packet
12088 @cindex fetch registers from remote targets
12089 @cindex set registers in remote targets
12090 Determine whether @value{GDBN} can set and fetch registers from the
12091 remote target using the @samp{P} packets. The default depends on the
12092 remote stub's support of the @samp{P} packets (@value{GDBN} queries
12093 the stub when this packet is first required).
12095 @item show remote fetch-register-packet
12096 @itemx show remote set-register-packet
12097 @itemx show remote P-packet
12098 @itemx show remote p-packet
12099 Show the current setting of using the @samp{P} packets for setting and
12100 fetching registers from the remote target.
12102 @cindex binary downloads
12104 @item set remote binary-download-packet
12105 @itemx set remote X-packet
12106 Determine whether @value{GDBN} sends downloads in binary mode using
12107 the @samp{X} packets. The default is on.
12109 @item show remote binary-download-packet
12110 @itemx show remote X-packet
12111 Show the current setting of using the @samp{X} packets for binary
12114 @item set remote read-aux-vector-packet
12115 @cindex auxiliary vector of remote target
12116 @cindex @code{auxv}, and remote targets
12117 Set the use of the remote protocol's @samp{qPart:auxv:read} (target
12118 auxiliary vector read) request. This request is used to fetch the
12119 remote target's @dfn{auxiliary vector}, see @ref{OS Information,
12120 Auxiliary Vector}. The default setting depends on the remote stub's
12121 support of this request (@value{GDBN} queries the stub when this
12122 request is first required). @xref{General Query Packets, qPart}, for
12123 more information about this request.
12125 @item show remote read-aux-vector-packet
12126 Show the current setting of use of the @samp{qPart:auxv:read} request.
12128 @item set remote symbol-lookup-packet
12129 @cindex remote symbol lookup request
12130 Set the use of the remote protocol's @samp{qSymbol} (target symbol
12131 lookup) request. This request is used to communicate symbol
12132 information to the remote target, e.g., whenever a new shared library
12133 is loaded by the remote (@pxref{Files, shared libraries}). The
12134 default setting depends on the remote stub's support of this request
12135 (@value{GDBN} queries the stub when this request is first required).
12136 @xref{General Query Packets, qSymbol}, for more information about this
12139 @item show remote symbol-lookup-packet
12140 Show the current setting of use of the @samp{qSymbol} request.
12142 @item set remote verbose-resume-packet
12143 @cindex resume remote target
12144 @cindex signal thread, and remote targets
12145 @cindex single-step thread, and remote targets
12146 @cindex thread-specific operations on remote targets
12147 Set the use of the remote protocol's @samp{vCont} (descriptive resume)
12148 request. This request is used to resume specific threads in the
12149 remote target, and to single-step or signal them. The default setting
12150 depends on the remote stub's support of this request (@value{GDBN}
12151 queries the stub when this request is first required). This setting
12152 affects debugging of multithreaded programs: if @samp{vCont} cannot be
12153 used, @value{GDBN} might be unable to single-step a specific thread,
12154 especially under @code{set scheduler-locking off}; it is also
12155 impossible to pause a specific thread. @xref{Packets, vCont}, for
12158 @item show remote verbose-resume-packet
12159 Show the current setting of use of the @samp{vCont} request
12161 @item set remote software-breakpoint-packet
12162 @itemx set remote hardware-breakpoint-packet
12163 @itemx set remote write-watchpoint-packet
12164 @itemx set remote read-watchpoint-packet
12165 @itemx set remote access-watchpoint-packet
12166 @itemx set remote Z-packet
12168 @cindex remote hardware breakpoints and watchpoints
12169 These commands enable or disable the use of @samp{Z} packets for
12170 setting breakpoints and watchpoints in the remote target. The default
12171 depends on the remote stub's support of the @samp{Z} packets
12172 (@value{GDBN} queries the stub when each packet is first required).
12173 The command @code{set remote Z-packet}, kept for back-compatibility,
12174 turns on or off all the features that require the use of @samp{Z}
12177 @item show remote software-breakpoint-packet
12178 @itemx show remote hardware-breakpoint-packet
12179 @itemx show remote write-watchpoint-packet
12180 @itemx show remote read-watchpoint-packet
12181 @itemx show remote access-watchpoint-packet
12182 @itemx show remote Z-packet
12183 Show the current setting of @samp{Z} packets usage.
12185 @item set remote get-thread-local-storage-address
12186 @kindex set remote get-thread-local-storage-address
12187 @cindex thread local storage of remote targets
12188 This command enables or disables the use of the @samp{qGetTLSAddr}
12189 (Get Thread Local Storage Address) request packet. The default
12190 depends on whether the remote stub supports this request.
12191 @xref{General Query Packets, qGetTLSAddr}, for more details about this
12194 @item show remote get-thread-local-storage-address
12195 @kindex show remote get-thread-local-storage-address
12196 Show the current setting of @samp{qGetTLSAddr} packet usage.
12200 @section Implementing a remote stub
12202 @cindex debugging stub, example
12203 @cindex remote stub, example
12204 @cindex stub example, remote debugging
12205 The stub files provided with @value{GDBN} implement the target side of the
12206 communication protocol, and the @value{GDBN} side is implemented in the
12207 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
12208 these subroutines to communicate, and ignore the details. (If you're
12209 implementing your own stub file, you can still ignore the details: start
12210 with one of the existing stub files. @file{sparc-stub.c} is the best
12211 organized, and therefore the easiest to read.)
12213 @cindex remote serial debugging, overview
12214 To debug a program running on another machine (the debugging
12215 @dfn{target} machine), you must first arrange for all the usual
12216 prerequisites for the program to run by itself. For example, for a C
12221 A startup routine to set up the C runtime environment; these usually
12222 have a name like @file{crt0}. The startup routine may be supplied by
12223 your hardware supplier, or you may have to write your own.
12226 A C subroutine library to support your program's
12227 subroutine calls, notably managing input and output.
12230 A way of getting your program to the other machine---for example, a
12231 download program. These are often supplied by the hardware
12232 manufacturer, but you may have to write your own from hardware
12236 The next step is to arrange for your program to use a serial port to
12237 communicate with the machine where @value{GDBN} is running (the @dfn{host}
12238 machine). In general terms, the scheme looks like this:
12242 @value{GDBN} already understands how to use this protocol; when everything
12243 else is set up, you can simply use the @samp{target remote} command
12244 (@pxref{Targets,,Specifying a Debugging Target}).
12246 @item On the target,
12247 you must link with your program a few special-purpose subroutines that
12248 implement the @value{GDBN} remote serial protocol. The file containing these
12249 subroutines is called a @dfn{debugging stub}.
12251 On certain remote targets, you can use an auxiliary program
12252 @code{gdbserver} instead of linking a stub into your program.
12253 @xref{Server,,Using the @code{gdbserver} program}, for details.
12256 The debugging stub is specific to the architecture of the remote
12257 machine; for example, use @file{sparc-stub.c} to debug programs on
12260 @cindex remote serial stub list
12261 These working remote stubs are distributed with @value{GDBN}:
12266 @cindex @file{i386-stub.c}
12269 For Intel 386 and compatible architectures.
12272 @cindex @file{m68k-stub.c}
12273 @cindex Motorola 680x0
12275 For Motorola 680x0 architectures.
12278 @cindex @file{sh-stub.c}
12281 For Renesas SH architectures.
12284 @cindex @file{sparc-stub.c}
12286 For @sc{sparc} architectures.
12288 @item sparcl-stub.c
12289 @cindex @file{sparcl-stub.c}
12292 For Fujitsu @sc{sparclite} architectures.
12296 The @file{README} file in the @value{GDBN} distribution may list other
12297 recently added stubs.
12300 * Stub Contents:: What the stub can do for you
12301 * Bootstrapping:: What you must do for the stub
12302 * Debug Session:: Putting it all together
12305 @node Stub Contents
12306 @subsection What the stub can do for you
12308 @cindex remote serial stub
12309 The debugging stub for your architecture supplies these three
12313 @item set_debug_traps
12314 @findex set_debug_traps
12315 @cindex remote serial stub, initialization
12316 This routine arranges for @code{handle_exception} to run when your
12317 program stops. You must call this subroutine explicitly near the
12318 beginning of your program.
12320 @item handle_exception
12321 @findex handle_exception
12322 @cindex remote serial stub, main routine
12323 This is the central workhorse, but your program never calls it
12324 explicitly---the setup code arranges for @code{handle_exception} to
12325 run when a trap is triggered.
12327 @code{handle_exception} takes control when your program stops during
12328 execution (for example, on a breakpoint), and mediates communications
12329 with @value{GDBN} on the host machine. This is where the communications
12330 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
12331 representative on the target machine. It begins by sending summary
12332 information on the state of your program, then continues to execute,
12333 retrieving and transmitting any information @value{GDBN} needs, until you
12334 execute a @value{GDBN} command that makes your program resume; at that point,
12335 @code{handle_exception} returns control to your own code on the target
12339 @cindex @code{breakpoint} subroutine, remote
12340 Use this auxiliary subroutine to make your program contain a
12341 breakpoint. Depending on the particular situation, this may be the only
12342 way for @value{GDBN} to get control. For instance, if your target
12343 machine has some sort of interrupt button, you won't need to call this;
12344 pressing the interrupt button transfers control to
12345 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
12346 simply receiving characters on the serial port may also trigger a trap;
12347 again, in that situation, you don't need to call @code{breakpoint} from
12348 your own program---simply running @samp{target remote} from the host
12349 @value{GDBN} session gets control.
12351 Call @code{breakpoint} if none of these is true, or if you simply want
12352 to make certain your program stops at a predetermined point for the
12353 start of your debugging session.
12356 @node Bootstrapping
12357 @subsection What you must do for the stub
12359 @cindex remote stub, support routines
12360 The debugging stubs that come with @value{GDBN} are set up for a particular
12361 chip architecture, but they have no information about the rest of your
12362 debugging target machine.
12364 First of all you need to tell the stub how to communicate with the
12368 @item int getDebugChar()
12369 @findex getDebugChar
12370 Write this subroutine to read a single character from the serial port.
12371 It may be identical to @code{getchar} for your target system; a
12372 different name is used to allow you to distinguish the two if you wish.
12374 @item void putDebugChar(int)
12375 @findex putDebugChar
12376 Write this subroutine to write a single character to the serial port.
12377 It may be identical to @code{putchar} for your target system; a
12378 different name is used to allow you to distinguish the two if you wish.
12381 @cindex control C, and remote debugging
12382 @cindex interrupting remote targets
12383 If you want @value{GDBN} to be able to stop your program while it is
12384 running, you need to use an interrupt-driven serial driver, and arrange
12385 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
12386 character). That is the character which @value{GDBN} uses to tell the
12387 remote system to stop.
12389 Getting the debugging target to return the proper status to @value{GDBN}
12390 probably requires changes to the standard stub; one quick and dirty way
12391 is to just execute a breakpoint instruction (the ``dirty'' part is that
12392 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
12394 Other routines you need to supply are:
12397 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
12398 @findex exceptionHandler
12399 Write this function to install @var{exception_address} in the exception
12400 handling tables. You need to do this because the stub does not have any
12401 way of knowing what the exception handling tables on your target system
12402 are like (for example, the processor's table might be in @sc{rom},
12403 containing entries which point to a table in @sc{ram}).
12404 @var{exception_number} is the exception number which should be changed;
12405 its meaning is architecture-dependent (for example, different numbers
12406 might represent divide by zero, misaligned access, etc). When this
12407 exception occurs, control should be transferred directly to
12408 @var{exception_address}, and the processor state (stack, registers,
12409 and so on) should be just as it is when a processor exception occurs. So if
12410 you want to use a jump instruction to reach @var{exception_address}, it
12411 should be a simple jump, not a jump to subroutine.
12413 For the 386, @var{exception_address} should be installed as an interrupt
12414 gate so that interrupts are masked while the handler runs. The gate
12415 should be at privilege level 0 (the most privileged level). The
12416 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
12417 help from @code{exceptionHandler}.
12419 @item void flush_i_cache()
12420 @findex flush_i_cache
12421 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
12422 instruction cache, if any, on your target machine. If there is no
12423 instruction cache, this subroutine may be a no-op.
12425 On target machines that have instruction caches, @value{GDBN} requires this
12426 function to make certain that the state of your program is stable.
12430 You must also make sure this library routine is available:
12433 @item void *memset(void *, int, int)
12435 This is the standard library function @code{memset} that sets an area of
12436 memory to a known value. If you have one of the free versions of
12437 @code{libc.a}, @code{memset} can be found there; otherwise, you must
12438 either obtain it from your hardware manufacturer, or write your own.
12441 If you do not use the GNU C compiler, you may need other standard
12442 library subroutines as well; this varies from one stub to another,
12443 but in general the stubs are likely to use any of the common library
12444 subroutines which @code{@value{GCC}} generates as inline code.
12447 @node Debug Session
12448 @subsection Putting it all together
12450 @cindex remote serial debugging summary
12451 In summary, when your program is ready to debug, you must follow these
12456 Make sure you have defined the supporting low-level routines
12457 (@pxref{Bootstrapping,,What you must do for the stub}):
12459 @code{getDebugChar}, @code{putDebugChar},
12460 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
12464 Insert these lines near the top of your program:
12472 For the 680x0 stub only, you need to provide a variable called
12473 @code{exceptionHook}. Normally you just use:
12476 void (*exceptionHook)() = 0;
12480 but if before calling @code{set_debug_traps}, you set it to point to a
12481 function in your program, that function is called when
12482 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
12483 error). The function indicated by @code{exceptionHook} is called with
12484 one parameter: an @code{int} which is the exception number.
12487 Compile and link together: your program, the @value{GDBN} debugging stub for
12488 your target architecture, and the supporting subroutines.
12491 Make sure you have a serial connection between your target machine and
12492 the @value{GDBN} host, and identify the serial port on the host.
12495 @c The "remote" target now provides a `load' command, so we should
12496 @c document that. FIXME.
12497 Download your program to your target machine (or get it there by
12498 whatever means the manufacturer provides), and start it.
12501 Start @value{GDBN} on the host, and connect to the target
12502 (@pxref{Connecting,,Connecting to a remote target}).
12506 @node Configurations
12507 @chapter Configuration-Specific Information
12509 While nearly all @value{GDBN} commands are available for all native and
12510 cross versions of the debugger, there are some exceptions. This chapter
12511 describes things that are only available in certain configurations.
12513 There are three major categories of configurations: native
12514 configurations, where the host and target are the same, embedded
12515 operating system configurations, which are usually the same for several
12516 different processor architectures, and bare embedded processors, which
12517 are quite different from each other.
12522 * Embedded Processors::
12529 This section describes details specific to particular native
12534 * BSD libkvm Interface:: Debugging BSD kernel memory images
12535 * SVR4 Process Information:: SVR4 process information
12536 * DJGPP Native:: Features specific to the DJGPP port
12537 * Cygwin Native:: Features specific to the Cygwin port
12538 * Hurd Native:: Features specific to @sc{gnu} Hurd
12539 * Neutrino:: Features specific to QNX Neutrino
12545 On HP-UX systems, if you refer to a function or variable name that
12546 begins with a dollar sign, @value{GDBN} searches for a user or system
12547 name first, before it searches for a convenience variable.
12550 @node BSD libkvm Interface
12551 @subsection BSD libkvm Interface
12554 @cindex kernel memory image
12555 @cindex kernel crash dump
12557 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
12558 interface that provides a uniform interface for accessing kernel virtual
12559 memory images, including live systems and crash dumps. @value{GDBN}
12560 uses this interface to allow you to debug live kernels and kernel crash
12561 dumps on many native BSD configurations. This is implemented as a
12562 special @code{kvm} debugging target. For debugging a live system, load
12563 the currently running kernel into @value{GDBN} and connect to the
12567 (@value{GDBP}) @b{target kvm}
12570 For debugging crash dumps, provide the file name of the crash dump as an
12574 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
12577 Once connected to the @code{kvm} target, the following commands are
12583 Set current context from the @dfn{Process Control Block} (PCB) address.
12586 Set current context from proc address. This command isn't available on
12587 modern FreeBSD systems.
12590 @node SVR4 Process Information
12591 @subsection SVR4 process information
12593 @cindex examine process image
12594 @cindex process info via @file{/proc}
12596 Many versions of SVR4 and compatible systems provide a facility called
12597 @samp{/proc} that can be used to examine the image of a running
12598 process using file-system subroutines. If @value{GDBN} is configured
12599 for an operating system with this facility, the command @code{info
12600 proc} is available to report information about the process running
12601 your program, or about any process running on your system. @code{info
12602 proc} works only on SVR4 systems that include the @code{procfs} code.
12603 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
12604 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
12610 @itemx info proc @var{process-id}
12611 Summarize available information about any running process. If a
12612 process ID is specified by @var{process-id}, display information about
12613 that process; otherwise display information about the program being
12614 debugged. The summary includes the debugged process ID, the command
12615 line used to invoke it, its current working directory, and its
12616 executable file's absolute file name.
12618 On some systems, @var{process-id} can be of the form
12619 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
12620 within a process. If the optional @var{pid} part is missing, it means
12621 a thread from the process being debugged (the leading @samp{/} still
12622 needs to be present, or else @value{GDBN} will interpret the number as
12623 a process ID rather than a thread ID).
12625 @item info proc mappings
12626 @cindex memory address space mappings
12627 Report the memory address space ranges accessible in the program, with
12628 information on whether the process has read, write, or execute access
12629 rights to each range. On @sc{gnu}/Linux systems, each memory range
12630 includes the object file which is mapped to that range, instead of the
12631 memory access rights to that range.
12633 @item info proc stat
12634 @itemx info proc status
12635 @cindex process detailed status information
12636 These subcommands are specific to @sc{gnu}/Linux systems. They show
12637 the process-related information, including the user ID and group ID;
12638 how many threads are there in the process; its virtual memory usage;
12639 the signals that are pending, blocked, and ignored; its TTY; its
12640 consumption of system and user time; its stack size; its @samp{nice}
12641 value; etc. For more information, see the @samp{proc} man page
12642 (type @kbd{man 5 proc} from your shell prompt).
12644 @item info proc all
12645 Show all the information about the process described under all of the
12646 above @code{info proc} subcommands.
12649 @comment These sub-options of 'info proc' were not included when
12650 @comment procfs.c was re-written. Keep their descriptions around
12651 @comment against the day when someone finds the time to put them back in.
12652 @kindex info proc times
12653 @item info proc times
12654 Starting time, user CPU time, and system CPU time for your program and
12657 @kindex info proc id
12659 Report on the process IDs related to your program: its own process ID,
12660 the ID of its parent, the process group ID, and the session ID.
12663 @item set procfs-trace
12664 @kindex set procfs-trace
12665 @cindex @code{procfs} API calls
12666 This command enables and disables tracing of @code{procfs} API calls.
12668 @item show procfs-trace
12669 @kindex show procfs-trace
12670 Show the current state of @code{procfs} API call tracing.
12672 @item set procfs-file @var{file}
12673 @kindex set procfs-file
12674 Tell @value{GDBN} to write @code{procfs} API trace to the named
12675 @var{file}. @value{GDBN} appends the trace info to the previous
12676 contents of the file. The default is to display the trace on the
12679 @item show procfs-file
12680 @kindex show procfs-file
12681 Show the file to which @code{procfs} API trace is written.
12683 @item proc-trace-entry
12684 @itemx proc-trace-exit
12685 @itemx proc-untrace-entry
12686 @itemx proc-untrace-exit
12687 @kindex proc-trace-entry
12688 @kindex proc-trace-exit
12689 @kindex proc-untrace-entry
12690 @kindex proc-untrace-exit
12691 These commands enable and disable tracing of entries into and exits
12692 from the @code{syscall} interface.
12695 @kindex info pidlist
12696 @cindex process list, QNX Neutrino
12697 For QNX Neutrino only, this command displays the list of all the
12698 processes and all the threads within each process.
12701 @kindex info meminfo
12702 @cindex mapinfo list, QNX Neutrino
12703 For QNX Neutrino only, this command displays the list of all mapinfos.
12707 @subsection Features for Debugging @sc{djgpp} Programs
12708 @cindex @sc{djgpp} debugging
12709 @cindex native @sc{djgpp} debugging
12710 @cindex MS-DOS-specific commands
12713 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
12714 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
12715 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
12716 top of real-mode DOS systems and their emulations.
12718 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
12719 defines a few commands specific to the @sc{djgpp} port. This
12720 subsection describes those commands.
12725 This is a prefix of @sc{djgpp}-specific commands which print
12726 information about the target system and important OS structures.
12729 @cindex MS-DOS system info
12730 @cindex free memory information (MS-DOS)
12731 @item info dos sysinfo
12732 This command displays assorted information about the underlying
12733 platform: the CPU type and features, the OS version and flavor, the
12734 DPMI version, and the available conventional and DPMI memory.
12739 @cindex segment descriptor tables
12740 @cindex descriptor tables display
12742 @itemx info dos ldt
12743 @itemx info dos idt
12744 These 3 commands display entries from, respectively, Global, Local,
12745 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
12746 tables are data structures which store a descriptor for each segment
12747 that is currently in use. The segment's selector is an index into a
12748 descriptor table; the table entry for that index holds the
12749 descriptor's base address and limit, and its attributes and access
12752 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
12753 segment (used for both data and the stack), and a DOS segment (which
12754 allows access to DOS/BIOS data structures and absolute addresses in
12755 conventional memory). However, the DPMI host will usually define
12756 additional segments in order to support the DPMI environment.
12758 @cindex garbled pointers
12759 These commands allow to display entries from the descriptor tables.
12760 Without an argument, all entries from the specified table are
12761 displayed. An argument, which should be an integer expression, means
12762 display a single entry whose index is given by the argument. For
12763 example, here's a convenient way to display information about the
12764 debugged program's data segment:
12767 @exdent @code{(@value{GDBP}) info dos ldt $ds}
12768 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
12772 This comes in handy when you want to see whether a pointer is outside
12773 the data segment's limit (i.e.@: @dfn{garbled}).
12775 @cindex page tables display (MS-DOS)
12777 @itemx info dos pte
12778 These two commands display entries from, respectively, the Page
12779 Directory and the Page Tables. Page Directories and Page Tables are
12780 data structures which control how virtual memory addresses are mapped
12781 into physical addresses. A Page Table includes an entry for every
12782 page of memory that is mapped into the program's address space; there
12783 may be several Page Tables, each one holding up to 4096 entries. A
12784 Page Directory has up to 4096 entries, one each for every Page Table
12785 that is currently in use.
12787 Without an argument, @kbd{info dos pde} displays the entire Page
12788 Directory, and @kbd{info dos pte} displays all the entries in all of
12789 the Page Tables. An argument, an integer expression, given to the
12790 @kbd{info dos pde} command means display only that entry from the Page
12791 Directory table. An argument given to the @kbd{info dos pte} command
12792 means display entries from a single Page Table, the one pointed to by
12793 the specified entry in the Page Directory.
12795 @cindex direct memory access (DMA) on MS-DOS
12796 These commands are useful when your program uses @dfn{DMA} (Direct
12797 Memory Access), which needs physical addresses to program the DMA
12800 These commands are supported only with some DPMI servers.
12802 @cindex physical address from linear address
12803 @item info dos address-pte @var{addr}
12804 This command displays the Page Table entry for a specified linear
12805 address. The argument @var{addr} is a linear address which should
12806 already have the appropriate segment's base address added to it,
12807 because this command accepts addresses which may belong to @emph{any}
12808 segment. For example, here's how to display the Page Table entry for
12809 the page where a variable @code{i} is stored:
12812 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
12813 @exdent @code{Page Table entry for address 0x11a00d30:}
12814 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
12818 This says that @code{i} is stored at offset @code{0xd30} from the page
12819 whose physical base address is @code{0x02698000}, and shows all the
12820 attributes of that page.
12822 Note that you must cast the addresses of variables to a @code{char *},
12823 since otherwise the value of @code{__djgpp_base_address}, the base
12824 address of all variables and functions in a @sc{djgpp} program, will
12825 be added using the rules of C pointer arithmetics: if @code{i} is
12826 declared an @code{int}, @value{GDBN} will add 4 times the value of
12827 @code{__djgpp_base_address} to the address of @code{i}.
12829 Here's another example, it displays the Page Table entry for the
12833 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
12834 @exdent @code{Page Table entry for address 0x29110:}
12835 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
12839 (The @code{+ 3} offset is because the transfer buffer's address is the
12840 3rd member of the @code{_go32_info_block} structure.) The output
12841 clearly shows that this DPMI server maps the addresses in conventional
12842 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
12843 linear (@code{0x29110}) addresses are identical.
12845 This command is supported only with some DPMI servers.
12848 @cindex DOS serial data link, remote debugging
12849 In addition to native debugging, the DJGPP port supports remote
12850 debugging via a serial data link. The following commands are specific
12851 to remote serial debugging in the DJGPP port of @value{GDBN}.
12854 @kindex set com1base
12855 @kindex set com1irq
12856 @kindex set com2base
12857 @kindex set com2irq
12858 @kindex set com3base
12859 @kindex set com3irq
12860 @kindex set com4base
12861 @kindex set com4irq
12862 @item set com1base @var{addr}
12863 This command sets the base I/O port address of the @file{COM1} serial
12866 @item set com1irq @var{irq}
12867 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
12868 for the @file{COM1} serial port.
12870 There are similar commands @samp{set com2base}, @samp{set com3irq},
12871 etc.@: for setting the port address and the @code{IRQ} lines for the
12874 @kindex show com1base
12875 @kindex show com1irq
12876 @kindex show com2base
12877 @kindex show com2irq
12878 @kindex show com3base
12879 @kindex show com3irq
12880 @kindex show com4base
12881 @kindex show com4irq
12882 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
12883 display the current settings of the base address and the @code{IRQ}
12884 lines used by the COM ports.
12887 @kindex info serial
12888 @cindex DOS serial port status
12889 This command prints the status of the 4 DOS serial ports. For each
12890 port, it prints whether it's active or not, its I/O base address and
12891 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
12892 counts of various errors encountered so far.
12896 @node Cygwin Native
12897 @subsection Features for Debugging MS Windows PE executables
12898 @cindex MS Windows debugging
12899 @cindex native Cygwin debugging
12900 @cindex Cygwin-specific commands
12902 @value{GDBN} supports native debugging of MS Windows programs, including
12903 DLLs with and without symbolic debugging information. There are various
12904 additional Cygwin-specific commands, described in this subsection. The
12905 subsubsection @pxref{Non-debug DLL symbols} describes working with DLLs
12906 that have no debugging symbols.
12912 This is a prefix of MS Windows specific commands which print
12913 information about the target system and important OS structures.
12915 @item info w32 selector
12916 This command displays information returned by
12917 the Win32 API @code{GetThreadSelectorEntry} function.
12918 It takes an optional argument that is evaluated to
12919 a long value to give the information about this given selector.
12920 Without argument, this command displays information
12921 about the the six segment registers.
12925 This is a Cygwin specific alias of info shared.
12927 @kindex dll-symbols
12929 This command loads symbols from a dll similarly to
12930 add-sym command but without the need to specify a base address.
12932 @kindex set new-console
12933 @item set new-console @var{mode}
12934 If @var{mode} is @code{on} the debuggee will
12935 be started in a new console on next start.
12936 If @var{mode} is @code{off}i, the debuggee will
12937 be started in the same console as the debugger.
12939 @kindex show new-console
12940 @item show new-console
12941 Displays whether a new console is used
12942 when the debuggee is started.
12944 @kindex set new-group
12945 @item set new-group @var{mode}
12946 This boolean value controls whether the debuggee should
12947 start a new group or stay in the same group as the debugger.
12948 This affects the way the Windows OS handles
12951 @kindex show new-group
12952 @item show new-group
12953 Displays current value of new-group boolean.
12955 @kindex set debugevents
12956 @item set debugevents
12957 This boolean value adds debug output concerning events seen by the debugger.
12959 @kindex set debugexec
12960 @item set debugexec
12961 This boolean value adds debug output concerning execute events
12962 seen by the debugger.
12964 @kindex set debugexceptions
12965 @item set debugexceptions
12966 This boolean value adds debug ouptut concerning exception events
12967 seen by the debugger.
12969 @kindex set debugmemory
12970 @item set debugmemory
12971 This boolean value adds debug ouptut concerning memory events
12972 seen by the debugger.
12976 This boolean values specifies whether the debuggee is called
12977 via a shell or directly (default value is on).
12981 Displays if the debuggee will be started with a shell.
12986 * Non-debug DLL symbols:: Support for DLLs without debugging symbols
12989 @node Non-debug DLL symbols
12990 @subsubsection Support for DLLs without debugging symbols
12991 @cindex DLLs with no debugging symbols
12992 @cindex Minimal symbols and DLLs
12994 Very often on windows, some of the DLLs that your program relies on do
12995 not include symbolic debugging information (for example,
12996 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
12997 symbols in a DLL, it relies on the minimal amount of symbolic
12998 information contained in the DLL's export table. This subsubsection
12999 describes working with such symbols, known internally to @value{GDBN} as
13000 ``minimal symbols''.
13002 Note that before the debugged program has started execution, no DLLs
13003 will have been loaded. The easiest way around this problem is simply to
13004 start the program --- either by setting a breakpoint or letting the
13005 program run once to completion. It is also possible to force
13006 @value{GDBN} to load a particular DLL before starting the executable ---
13007 see the shared library information in @pxref{Files} or the
13008 @code{dll-symbols} command in @pxref{Cygwin Native}. Currently,
13009 explicitly loading symbols from a DLL with no debugging information will
13010 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
13011 which may adversely affect symbol lookup performance.
13013 @subsubsection DLL name prefixes
13015 In keeping with the naming conventions used by the Microsoft debugging
13016 tools, DLL export symbols are made available with a prefix based on the
13017 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
13018 also entered into the symbol table, so @code{CreateFileA} is often
13019 sufficient. In some cases there will be name clashes within a program
13020 (particularly if the executable itself includes full debugging symbols)
13021 necessitating the use of the fully qualified name when referring to the
13022 contents of the DLL. Use single-quotes around the name to avoid the
13023 exclamation mark (``!'') being interpreted as a language operator.
13025 Note that the internal name of the DLL may be all upper-case, even
13026 though the file name of the DLL is lower-case, or vice-versa. Since
13027 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
13028 some confusion. If in doubt, try the @code{info functions} and
13029 @code{info variables} commands or even @code{maint print msymbols} (see
13030 @pxref{Symbols}). Here's an example:
13033 (@value{GDBP}) info function CreateFileA
13034 All functions matching regular expression "CreateFileA":
13036 Non-debugging symbols:
13037 0x77e885f4 CreateFileA
13038 0x77e885f4 KERNEL32!CreateFileA
13042 (@value{GDBP}) info function !
13043 All functions matching regular expression "!":
13045 Non-debugging symbols:
13046 0x6100114c cygwin1!__assert
13047 0x61004034 cygwin1!_dll_crt0@@0
13048 0x61004240 cygwin1!dll_crt0(per_process *)
13052 @subsubsection Working with minimal symbols
13054 Symbols extracted from a DLL's export table do not contain very much
13055 type information. All that @value{GDBN} can do is guess whether a symbol
13056 refers to a function or variable depending on the linker section that
13057 contains the symbol. Also note that the actual contents of the memory
13058 contained in a DLL are not available unless the program is running. This
13059 means that you cannot examine the contents of a variable or disassemble
13060 a function within a DLL without a running program.
13062 Variables are generally treated as pointers and dereferenced
13063 automatically. For this reason, it is often necessary to prefix a
13064 variable name with the address-of operator (``&'') and provide explicit
13065 type information in the command. Here's an example of the type of
13069 (@value{GDBP}) print 'cygwin1!__argv'
13074 (@value{GDBP}) x 'cygwin1!__argv'
13075 0x10021610: "\230y\""
13078 And two possible solutions:
13081 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
13082 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
13086 (@value{GDBP}) x/2x &'cygwin1!__argv'
13087 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
13088 (@value{GDBP}) x/x 0x10021608
13089 0x10021608: 0x0022fd98
13090 (@value{GDBP}) x/s 0x0022fd98
13091 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
13094 Setting a break point within a DLL is possible even before the program
13095 starts execution. However, under these circumstances, @value{GDBN} can't
13096 examine the initial instructions of the function in order to skip the
13097 function's frame set-up code. You can work around this by using ``*&''
13098 to set the breakpoint at a raw memory address:
13101 (@value{GDBP}) break *&'python22!PyOS_Readline'
13102 Breakpoint 1 at 0x1e04eff0
13105 The author of these extensions is not entirely convinced that setting a
13106 break point within a shared DLL like @file{kernel32.dll} is completely
13110 @subsection Commands specific to @sc{gnu} Hurd systems
13111 @cindex @sc{gnu} Hurd debugging
13113 This subsection describes @value{GDBN} commands specific to the
13114 @sc{gnu} Hurd native debugging.
13119 @kindex set signals@r{, Hurd command}
13120 @kindex set sigs@r{, Hurd command}
13121 This command toggles the state of inferior signal interception by
13122 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
13123 affected by this command. @code{sigs} is a shorthand alias for
13128 @kindex show signals@r{, Hurd command}
13129 @kindex show sigs@r{, Hurd command}
13130 Show the current state of intercepting inferior's signals.
13132 @item set signal-thread
13133 @itemx set sigthread
13134 @kindex set signal-thread
13135 @kindex set sigthread
13136 This command tells @value{GDBN} which thread is the @code{libc} signal
13137 thread. That thread is run when a signal is delivered to a running
13138 process. @code{set sigthread} is the shorthand alias of @code{set
13141 @item show signal-thread
13142 @itemx show sigthread
13143 @kindex show signal-thread
13144 @kindex show sigthread
13145 These two commands show which thread will run when the inferior is
13146 delivered a signal.
13149 @kindex set stopped@r{, Hurd command}
13150 This commands tells @value{GDBN} that the inferior process is stopped,
13151 as with the @code{SIGSTOP} signal. The stopped process can be
13152 continued by delivering a signal to it.
13155 @kindex show stopped@r{, Hurd command}
13156 This command shows whether @value{GDBN} thinks the debuggee is
13159 @item set exceptions
13160 @kindex set exceptions@r{, Hurd command}
13161 Use this command to turn off trapping of exceptions in the inferior.
13162 When exception trapping is off, neither breakpoints nor
13163 single-stepping will work. To restore the default, set exception
13166 @item show exceptions
13167 @kindex show exceptions@r{, Hurd command}
13168 Show the current state of trapping exceptions in the inferior.
13170 @item set task pause
13171 @kindex set task@r{, Hurd commands}
13172 @cindex task attributes (@sc{gnu} Hurd)
13173 @cindex pause current task (@sc{gnu} Hurd)
13174 This command toggles task suspension when @value{GDBN} has control.
13175 Setting it to on takes effect immediately, and the task is suspended
13176 whenever @value{GDBN} gets control. Setting it to off will take
13177 effect the next time the inferior is continued. If this option is set
13178 to off, you can use @code{set thread default pause on} or @code{set
13179 thread pause on} (see below) to pause individual threads.
13181 @item show task pause
13182 @kindex show task@r{, Hurd commands}
13183 Show the current state of task suspension.
13185 @item set task detach-suspend-count
13186 @cindex task suspend count
13187 @cindex detach from task, @sc{gnu} Hurd
13188 This command sets the suspend count the task will be left with when
13189 @value{GDBN} detaches from it.
13191 @item show task detach-suspend-count
13192 Show the suspend count the task will be left with when detaching.
13194 @item set task exception-port
13195 @itemx set task excp
13196 @cindex task exception port, @sc{gnu} Hurd
13197 This command sets the task exception port to which @value{GDBN} will
13198 forward exceptions. The argument should be the value of the @dfn{send
13199 rights} of the task. @code{set task excp} is a shorthand alias.
13201 @item set noninvasive
13202 @cindex noninvasive task options
13203 This command switches @value{GDBN} to a mode that is the least
13204 invasive as far as interfering with the inferior is concerned. This
13205 is the same as using @code{set task pause}, @code{set exceptions}, and
13206 @code{set signals} to values opposite to the defaults.
13208 @item info send-rights
13209 @itemx info receive-rights
13210 @itemx info port-rights
13211 @itemx info port-sets
13212 @itemx info dead-names
13215 @cindex send rights, @sc{gnu} Hurd
13216 @cindex receive rights, @sc{gnu} Hurd
13217 @cindex port rights, @sc{gnu} Hurd
13218 @cindex port sets, @sc{gnu} Hurd
13219 @cindex dead names, @sc{gnu} Hurd
13220 These commands display information about, respectively, send rights,
13221 receive rights, port rights, port sets, and dead names of a task.
13222 There are also shorthand aliases: @code{info ports} for @code{info
13223 port-rights} and @code{info psets} for @code{info port-sets}.
13225 @item set thread pause
13226 @kindex set thread@r{, Hurd command}
13227 @cindex thread properties, @sc{gnu} Hurd
13228 @cindex pause current thread (@sc{gnu} Hurd)
13229 This command toggles current thread suspension when @value{GDBN} has
13230 control. Setting it to on takes effect immediately, and the current
13231 thread is suspended whenever @value{GDBN} gets control. Setting it to
13232 off will take effect the next time the inferior is continued.
13233 Normally, this command has no effect, since when @value{GDBN} has
13234 control, the whole task is suspended. However, if you used @code{set
13235 task pause off} (see above), this command comes in handy to suspend
13236 only the current thread.
13238 @item show thread pause
13239 @kindex show thread@r{, Hurd command}
13240 This command shows the state of current thread suspension.
13242 @item set thread run
13243 This comamnd sets whether the current thread is allowed to run.
13245 @item show thread run
13246 Show whether the current thread is allowed to run.
13248 @item set thread detach-suspend-count
13249 @cindex thread suspend count, @sc{gnu} Hurd
13250 @cindex detach from thread, @sc{gnu} Hurd
13251 This command sets the suspend count @value{GDBN} will leave on a
13252 thread when detaching. This number is relative to the suspend count
13253 found by @value{GDBN} when it notices the thread; use @code{set thread
13254 takeover-suspend-count} to force it to an absolute value.
13256 @item show thread detach-suspend-count
13257 Show the suspend count @value{GDBN} will leave on the thread when
13260 @item set thread exception-port
13261 @itemx set thread excp
13262 Set the thread exception port to which to forward exceptions. This
13263 overrides the port set by @code{set task exception-port} (see above).
13264 @code{set thread excp} is the shorthand alias.
13266 @item set thread takeover-suspend-count
13267 Normally, @value{GDBN}'s thread suspend counts are relative to the
13268 value @value{GDBN} finds when it notices each thread. This command
13269 changes the suspend counts to be absolute instead.
13271 @item set thread default
13272 @itemx show thread default
13273 @cindex thread default settings, @sc{gnu} Hurd
13274 Each of the above @code{set thread} commands has a @code{set thread
13275 default} counterpart (e.g., @code{set thread default pause}, @code{set
13276 thread default exception-port}, etc.). The @code{thread default}
13277 variety of commands sets the default thread properties for all
13278 threads; you can then change the properties of individual threads with
13279 the non-default commands.
13284 @subsection QNX Neutrino
13285 @cindex QNX Neutrino
13287 @value{GDBN} provides the following commands specific to the QNX
13291 @item set debug nto-debug
13292 @kindex set debug nto-debug
13293 When set to on, enables debugging messages specific to the QNX
13296 @item show debug nto-debug
13297 @kindex show debug nto-debug
13298 Show the current state of QNX Neutrino messages.
13303 @section Embedded Operating Systems
13305 This section describes configurations involving the debugging of
13306 embedded operating systems that are available for several different
13310 * VxWorks:: Using @value{GDBN} with VxWorks
13313 @value{GDBN} includes the ability to debug programs running on
13314 various real-time operating systems.
13317 @subsection Using @value{GDBN} with VxWorks
13323 @kindex target vxworks
13324 @item target vxworks @var{machinename}
13325 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
13326 is the target system's machine name or IP address.
13330 On VxWorks, @code{load} links @var{filename} dynamically on the
13331 current target system as well as adding its symbols in @value{GDBN}.
13333 @value{GDBN} enables developers to spawn and debug tasks running on networked
13334 VxWorks targets from a Unix host. Already-running tasks spawned from
13335 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
13336 both the Unix host and on the VxWorks target. The program
13337 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
13338 installed with the name @code{vxgdb}, to distinguish it from a
13339 @value{GDBN} for debugging programs on the host itself.)
13342 @item VxWorks-timeout @var{args}
13343 @kindex vxworks-timeout
13344 All VxWorks-based targets now support the option @code{vxworks-timeout}.
13345 This option is set by the user, and @var{args} represents the number of
13346 seconds @value{GDBN} waits for responses to rpc's. You might use this if
13347 your VxWorks target is a slow software simulator or is on the far side
13348 of a thin network line.
13351 The following information on connecting to VxWorks was current when
13352 this manual was produced; newer releases of VxWorks may use revised
13355 @findex INCLUDE_RDB
13356 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
13357 to include the remote debugging interface routines in the VxWorks
13358 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
13359 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
13360 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
13361 source debugging task @code{tRdbTask} when VxWorks is booted. For more
13362 information on configuring and remaking VxWorks, see the manufacturer's
13364 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
13366 Once you have included @file{rdb.a} in your VxWorks system image and set
13367 your Unix execution search path to find @value{GDBN}, you are ready to
13368 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
13369 @code{vxgdb}, depending on your installation).
13371 @value{GDBN} comes up showing the prompt:
13378 * VxWorks Connection:: Connecting to VxWorks
13379 * VxWorks Download:: VxWorks download
13380 * VxWorks Attach:: Running tasks
13383 @node VxWorks Connection
13384 @subsubsection Connecting to VxWorks
13386 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
13387 network. To connect to a target whose host name is ``@code{tt}'', type:
13390 (vxgdb) target vxworks tt
13394 @value{GDBN} displays messages like these:
13397 Attaching remote machine across net...
13402 @value{GDBN} then attempts to read the symbol tables of any object modules
13403 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
13404 these files by searching the directories listed in the command search
13405 path (@pxref{Environment, ,Your program's environment}); if it fails
13406 to find an object file, it displays a message such as:
13409 prog.o: No such file or directory.
13412 When this happens, add the appropriate directory to the search path with
13413 the @value{GDBN} command @code{path}, and execute the @code{target}
13416 @node VxWorks Download
13417 @subsubsection VxWorks download
13419 @cindex download to VxWorks
13420 If you have connected to the VxWorks target and you want to debug an
13421 object that has not yet been loaded, you can use the @value{GDBN}
13422 @code{load} command to download a file from Unix to VxWorks
13423 incrementally. The object file given as an argument to the @code{load}
13424 command is actually opened twice: first by the VxWorks target in order
13425 to download the code, then by @value{GDBN} in order to read the symbol
13426 table. This can lead to problems if the current working directories on
13427 the two systems differ. If both systems have NFS mounted the same
13428 filesystems, you can avoid these problems by using absolute paths.
13429 Otherwise, it is simplest to set the working directory on both systems
13430 to the directory in which the object file resides, and then to reference
13431 the file by its name, without any path. For instance, a program
13432 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
13433 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
13434 program, type this on VxWorks:
13437 -> cd "@var{vxpath}/vw/demo/rdb"
13441 Then, in @value{GDBN}, type:
13444 (vxgdb) cd @var{hostpath}/vw/demo/rdb
13445 (vxgdb) load prog.o
13448 @value{GDBN} displays a response similar to this:
13451 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
13454 You can also use the @code{load} command to reload an object module
13455 after editing and recompiling the corresponding source file. Note that
13456 this makes @value{GDBN} delete all currently-defined breakpoints,
13457 auto-displays, and convenience variables, and to clear the value
13458 history. (This is necessary in order to preserve the integrity of
13459 debugger's data structures that reference the target system's symbol
13462 @node VxWorks Attach
13463 @subsubsection Running tasks
13465 @cindex running VxWorks tasks
13466 You can also attach to an existing task using the @code{attach} command as
13470 (vxgdb) attach @var{task}
13474 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
13475 or suspended when you attach to it. Running tasks are suspended at
13476 the time of attachment.
13478 @node Embedded Processors
13479 @section Embedded Processors
13481 This section goes into details specific to particular embedded
13484 @cindex send command to simulator
13485 Whenever a specific embedded processor has a simulator, @value{GDBN}
13486 allows to send an arbitrary command to the simulator.
13489 @item sim @var{command}
13490 @kindex sim@r{, a command}
13491 Send an arbitrary @var{command} string to the simulator. Consult the
13492 documentation for the specific simulator in use for information about
13493 acceptable commands.
13499 * H8/300:: Renesas H8/300
13500 * H8/500:: Renesas H8/500
13501 * M32R/D:: Renesas M32R/D
13502 * M68K:: Motorola M68K
13503 * MIPS Embedded:: MIPS Embedded
13504 * OpenRISC 1000:: OpenRisc 1000
13505 * PA:: HP PA Embedded
13508 * Sparclet:: Tsqware Sparclet
13509 * Sparclite:: Fujitsu Sparclite
13510 * ST2000:: Tandem ST2000
13511 * Z8000:: Zilog Z8000
13514 * Super-H:: Renesas Super-H
13515 * WinCE:: Windows CE child processes
13524 @item target rdi @var{dev}
13525 ARM Angel monitor, via RDI library interface to ADP protocol. You may
13526 use this target to communicate with both boards running the Angel
13527 monitor, or with the EmbeddedICE JTAG debug device.
13530 @item target rdp @var{dev}
13535 @value{GDBN} provides the following ARM-specific commands:
13538 @item set arm disassembler
13540 This commands selects from a list of disassembly styles. The
13541 @code{"std"} style is the standard style.
13543 @item show arm disassembler
13545 Show the current disassembly style.
13547 @item set arm apcs32
13548 @cindex ARM 32-bit mode
13549 This command toggles ARM operation mode between 32-bit and 26-bit.
13551 @item show arm apcs32
13552 Display the current usage of the ARM 32-bit mode.
13554 @item set arm fpu @var{fputype}
13555 This command sets the ARM floating-point unit (FPU) type. The
13556 argument @var{fputype} can be one of these:
13560 Determine the FPU type by querying the OS ABI.
13562 Software FPU, with mixed-endian doubles on little-endian ARM
13565 GCC-compiled FPA co-processor.
13567 Software FPU with pure-endian doubles.
13573 Show the current type of the FPU.
13576 This command forces @value{GDBN} to use the specified ABI.
13579 Show the currently used ABI.
13581 @item set debug arm
13582 Toggle whether to display ARM-specific debugging messages from the ARM
13583 target support subsystem.
13585 @item show debug arm
13586 Show whether ARM-specific debugging messages are enabled.
13589 The following commands are available when an ARM target is debugged
13590 using the RDI interface:
13593 @item rdilogfile @r{[}@var{file}@r{]}
13595 @cindex ADP (Angel Debugger Protocol) logging
13596 Set the filename for the ADP (Angel Debugger Protocol) packet log.
13597 With an argument, sets the log file to the specified @var{file}. With
13598 no argument, show the current log file name. The default log file is
13601 @item rdilogenable @r{[}@var{arg}@r{]}
13602 @kindex rdilogenable
13603 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
13604 enables logging, with an argument 0 or @code{"no"} disables it. With
13605 no arguments displays the current setting. When logging is enabled,
13606 ADP packets exchanged between @value{GDBN} and the RDI target device
13607 are logged to a file.
13609 @item set rdiromatzero
13610 @kindex set rdiromatzero
13611 @cindex ROM at zero address, RDI
13612 Tell @value{GDBN} whether the target has ROM at address 0. If on,
13613 vector catching is disabled, so that zero address can be used. If off
13614 (the default), vector catching is enabled. For this command to take
13615 effect, it needs to be invoked prior to the @code{target rdi} command.
13617 @item show rdiromatzero
13618 @kindex show rdiromatzero
13619 Show the current setting of ROM at zero address.
13621 @item set rdiheartbeat
13622 @kindex set rdiheartbeat
13623 @cindex RDI heartbeat
13624 Enable or disable RDI heartbeat packets. It is not recommended to
13625 turn on this option, since it confuses ARM and EPI JTAG interface, as
13626 well as the Angel monitor.
13628 @item show rdiheartbeat
13629 @kindex show rdiheartbeat
13630 Show the setting of RDI heartbeat packets.
13635 @subsection Renesas H8/300
13639 @kindex target hms@r{, with H8/300}
13640 @item target hms @var{dev}
13641 A Renesas SH, H8/300, or H8/500 board, attached via serial line to your host.
13642 Use special commands @code{device} and @code{speed} to control the serial
13643 line and the communications speed used.
13645 @kindex target e7000@r{, with H8/300}
13646 @item target e7000 @var{dev}
13647 E7000 emulator for Renesas H8 and SH.
13649 @kindex target sh3@r{, with H8/300}
13650 @kindex target sh3e@r{, with H8/300}
13651 @item target sh3 @var{dev}
13652 @itemx target sh3e @var{dev}
13653 Renesas SH-3 and SH-3E target systems.
13657 @cindex download to H8/300 or H8/500
13658 @cindex H8/300 or H8/500 download
13659 @cindex download to Renesas SH
13660 @cindex Renesas SH download
13661 When you select remote debugging to a Renesas SH, H8/300, or H8/500
13662 board, the @code{load} command downloads your program to the Renesas
13663 board and also opens it as the current executable target for
13664 @value{GDBN} on your host (like the @code{file} command).
13666 @value{GDBN} needs to know these things to talk to your
13667 Renesas SH, H8/300, or H8/500:
13671 that you want to use @samp{target hms}, the remote debugging interface
13672 for Renesas microprocessors, or @samp{target e7000}, the in-circuit
13673 emulator for the Renesas SH and the Renesas 300H. (@samp{target hms} is
13674 the default when @value{GDBN} is configured specifically for the Renesas SH,
13675 H8/300, or H8/500.)
13678 what serial device connects your host to your Renesas board (the first
13679 serial device available on your host is the default).
13682 what speed to use over the serial device.
13686 * Renesas Boards:: Connecting to Renesas boards.
13687 * Renesas ICE:: Using the E7000 In-Circuit Emulator.
13688 * Renesas Special:: Special @value{GDBN} commands for Renesas micros.
13691 @node Renesas Boards
13692 @subsubsection Connecting to Renesas boards
13694 @c only for Unix hosts
13696 @cindex serial device, Renesas micros
13697 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
13698 need to explicitly set the serial device. The default @var{port} is the
13699 first available port on your host. This is only necessary on Unix
13700 hosts, where it is typically something like @file{/dev/ttya}.
13703 @cindex serial line speed, Renesas micros
13704 @code{@value{GDBN}} has another special command to set the communications
13705 speed: @samp{speed @var{bps}}. This command also is only used from Unix
13706 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
13707 the DOS @code{mode} command (for instance,
13708 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
13710 The @samp{device} and @samp{speed} commands are available only when you
13711 use a Unix host to debug your Renesas microprocessor programs. If you
13713 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
13714 called @code{asynctsr} to communicate with the development board
13715 through a PC serial port. You must also use the DOS @code{mode} command
13716 to set up the serial port on the DOS side.
13718 The following sample session illustrates the steps needed to start a
13719 program under @value{GDBN} control on an H8/300. The example uses a
13720 sample H8/300 program called @file{t.x}. The procedure is the same for
13721 the Renesas SH and the H8/500.
13723 First hook up your development board. In this example, we use a
13724 board attached to serial port @code{COM2}; if you use a different serial
13725 port, substitute its name in the argument of the @code{mode} command.
13726 When you call @code{asynctsr}, the auxiliary comms program used by the
13727 debugger, you give it just the numeric part of the serial port's name;
13728 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
13732 C:\H8300\TEST> asynctsr 2
13733 C:\H8300\TEST> mode com2:9600,n,8,1,p
13735 Resident portion of MODE loaded
13737 COM2: 9600, n, 8, 1, p
13742 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
13743 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
13744 disable it, or even boot without it, to use @code{asynctsr} to control
13745 your development board.
13748 @kindex target hms@r{, and serial protocol}
13749 Now that serial communications are set up, and the development board is
13750 connected, you can start up @value{GDBN}. Call @code{@value{GDBN}} with
13751 the name of your program as the argument. @code{@value{GDBN}} prompts
13752 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
13753 commands to begin your debugging session: @samp{target hms} to specify
13754 cross-debugging to the Renesas board, and the @code{load} command to
13755 download your program to the board. @code{load} displays the names of
13756 the program's sections, and a @samp{*} for each 2K of data downloaded.
13757 (If you want to refresh @value{GDBN} data on symbols or on the
13758 executable file without downloading, use the @value{GDBN} commands
13759 @code{file} or @code{symbol-file}. These commands, and @code{load}
13760 itself, are described in @ref{Files,,Commands to specify files}.)
13763 (eg-C:\H8300\TEST) @value{GDBP} t.x
13764 @value{GDBN} is free software and you are welcome to distribute copies
13765 of it under certain conditions; type "show copying" to see
13767 There is absolutely no warranty for @value{GDBN}; type "show warranty"
13769 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
13770 (@value{GDBP}) target hms
13771 Connected to remote H8/300 HMS system.
13772 (@value{GDBP}) load t.x
13773 .text : 0x8000 .. 0xabde ***********
13774 .data : 0xabde .. 0xad30 *
13775 .stack : 0xf000 .. 0xf014 *
13778 At this point, you're ready to run or debug your program. From here on,
13779 you can use all the usual @value{GDBN} commands. The @code{break} command
13780 sets breakpoints; the @code{run} command starts your program;
13781 @code{print} or @code{x} display data; the @code{continue} command
13782 resumes execution after stopping at a breakpoint. You can use the
13783 @code{help} command at any time to find out more about @value{GDBN} commands.
13785 Remember, however, that @emph{operating system} facilities aren't
13786 available on your development board; for example, if your program hangs,
13787 you can't send an interrupt---but you can press the @sc{reset} switch!
13789 Use the @sc{reset} button on the development board
13792 to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has
13793 no way to pass an interrupt signal to the development board); and
13796 to return to the @value{GDBN} command prompt after your program finishes
13797 normally. The communications protocol provides no other way for @value{GDBN}
13798 to detect program completion.
13801 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
13802 development board as a ``normal exit'' of your program.
13805 @subsubsection Using the E7000 in-circuit emulator
13807 @kindex target e7000@r{, with Renesas ICE}
13808 You can use the E7000 in-circuit emulator to develop code for either the
13809 Renesas SH or the H8/300H. Use one of these forms of the @samp{target
13810 e7000} command to connect @value{GDBN} to your E7000:
13813 @item target e7000 @var{port} @var{speed}
13814 Use this form if your E7000 is connected to a serial port. The
13815 @var{port} argument identifies what serial port to use (for example,
13816 @samp{com2}). The third argument is the line speed in bits per second
13817 (for example, @samp{9600}).
13819 @item target e7000 @var{hostname}
13820 If your E7000 is installed as a host on a TCP/IP network, you can just
13821 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
13824 The following special commands are available when debugging with the
13828 @item e7000 @var{command}
13830 @cindex send command to E7000 monitor
13831 This sends the specified @var{command} to the E7000 monitor.
13833 @item ftplogin @var{machine} @var{username} @var{password} @var{dir}
13834 @kindex ftplogin@r{, E7000}
13835 This command records information for subsequent interface with the
13836 E7000 monitor via the FTP protocol: @value{GDBN} will log into the
13837 named @var{machine} using specified @var{username} and @var{password},
13838 and then chdir to the named directory @var{dir}.
13840 @item ftpload @var{file}
13841 @kindex ftpload@r{, E7000}
13842 This command uses credentials recorded by @code{ftplogin} to fetch and
13843 load the named @var{file} from the E7000 monitor.
13846 @kindex drain@r{, E7000}
13847 This command drains any pending text buffers stored on the E7000.
13849 @item set usehardbreakpoints
13850 @itemx show usehardbreakpoints
13851 @kindex set usehardbreakpoints@r{, E7000}
13852 @kindex show usehardbreakpoints@r{, E7000}
13853 @cindex hardware breakpoints, and E7000
13854 These commands set and show the use of hardware breakpoints for all
13855 breakpoints. @xref{Set Breaks, hardware-assisted breakpoint}, for
13856 more information about using hardware breakpoints selectively.
13859 @node Renesas Special
13860 @subsubsection Special @value{GDBN} commands for Renesas micros
13862 Some @value{GDBN} commands are available only for the H8/300:
13866 @kindex set machine
13867 @kindex show machine
13868 @item set machine h8300
13869 @itemx set machine h8300h
13870 Condition @value{GDBN} for one of the two variants of the H8/300
13871 architecture with @samp{set machine}. You can use @samp{show machine}
13872 to check which variant is currently in effect.
13881 @kindex set memory @var{mod}
13882 @cindex memory models, H8/500
13883 @item set memory @var{mod}
13885 Specify which H8/500 memory model (@var{mod}) you are using with
13886 @samp{set memory}; check which memory model is in effect with @samp{show
13887 memory}. The accepted values for @var{mod} are @code{small},
13888 @code{big}, @code{medium}, and @code{compact}.
13893 @subsection Renesas M32R/D and M32R/SDI
13896 @kindex target m32r
13897 @item target m32r @var{dev}
13898 Renesas M32R/D ROM monitor.
13900 @kindex target m32rsdi
13901 @item target m32rsdi @var{dev}
13902 Renesas M32R SDI server, connected via parallel port to the board.
13905 The following @value{GDBN} commands are specific to the M32R monitor:
13908 @item set download-path @var{path}
13909 @kindex set download-path
13910 @cindex find downloadable @sc{srec} files (M32R)
13911 Set the default path for finding donwloadable @sc{srec} files.
13913 @item show download-path
13914 @kindex show download-path
13915 Show the default path for downloadable @sc{srec} files.
13917 @item set board-address @var{addr}
13918 @kindex set board-address
13919 @cindex M32-EVA target board address
13920 Set the IP address for the M32R-EVA target board.
13922 @item show board-address
13923 @kindex show board-address
13924 Show the current IP address of the target board.
13926 @item set server-address @var{addr}
13927 @kindex set server-address
13928 @cindex download server address (M32R)
13929 Set the IP address for the download server, which is the @value{GDBN}'s
13932 @item show server-address
13933 @kindex show server-address
13934 Display the IP address of the download server.
13936 @item upload @r{[}@var{file}@r{]}
13937 @kindex upload@r{, M32R}
13938 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
13939 upload capability. If no @var{file} argument is given, the current
13940 executable file is uploaded.
13942 @item tload @r{[}@var{file}@r{]}
13943 @kindex tload@r{, M32R}
13944 Test the @code{upload} command.
13947 The following commands are available for M32R/SDI:
13952 @cindex reset SDI connection, M32R
13953 This command resets the SDI connection.
13957 This command shows the SDI connection status.
13960 @kindex debug_chaos
13961 @cindex M32R/Chaos debugging
13962 Instructs the remote that M32R/Chaos debugging is to be used.
13964 @item use_debug_dma
13965 @kindex use_debug_dma
13966 Instructs the remote to use the DEBUG_DMA method of accessing memory.
13969 @kindex use_mon_code
13970 Instructs the remote to use the MON_CODE method of accessing memory.
13973 @kindex use_ib_break
13974 Instructs the remote to set breakpoints by IB break.
13976 @item use_dbt_break
13977 @kindex use_dbt_break
13978 Instructs the remote to set breakpoints by DBT.
13984 The Motorola m68k configuration includes ColdFire support, and
13985 target command for the following ROM monitors.
13989 @kindex target abug
13990 @item target abug @var{dev}
13991 ABug ROM monitor for M68K.
13993 @kindex target cpu32bug
13994 @item target cpu32bug @var{dev}
13995 CPU32BUG monitor, running on a CPU32 (M68K) board.
13997 @kindex target dbug
13998 @item target dbug @var{dev}
13999 dBUG ROM monitor for Motorola ColdFire.
14002 @item target est @var{dev}
14003 EST-300 ICE monitor, running on a CPU32 (M68K) board.
14005 @kindex target rom68k
14006 @item target rom68k @var{dev}
14007 ROM 68K monitor, running on an M68K IDP board.
14013 @kindex target rombug
14014 @item target rombug @var{dev}
14015 ROMBUG ROM monitor for OS/9000.
14019 @node MIPS Embedded
14020 @subsection MIPS Embedded
14022 @cindex MIPS boards
14023 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
14024 MIPS board attached to a serial line. This is available when
14025 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
14028 Use these @value{GDBN} commands to specify the connection to your target board:
14031 @item target mips @var{port}
14032 @kindex target mips @var{port}
14033 To run a program on the board, start up @code{@value{GDBP}} with the
14034 name of your program as the argument. To connect to the board, use the
14035 command @samp{target mips @var{port}}, where @var{port} is the name of
14036 the serial port connected to the board. If the program has not already
14037 been downloaded to the board, you may use the @code{load} command to
14038 download it. You can then use all the usual @value{GDBN} commands.
14040 For example, this sequence connects to the target board through a serial
14041 port, and loads and runs a program called @var{prog} through the
14045 host$ @value{GDBP} @var{prog}
14046 @value{GDBN} is free software and @dots{}
14047 (@value{GDBP}) target mips /dev/ttyb
14048 (@value{GDBP}) load @var{prog}
14052 @item target mips @var{hostname}:@var{portnumber}
14053 On some @value{GDBN} host configurations, you can specify a TCP
14054 connection (for instance, to a serial line managed by a terminal
14055 concentrator) instead of a serial port, using the syntax
14056 @samp{@var{hostname}:@var{portnumber}}.
14058 @item target pmon @var{port}
14059 @kindex target pmon @var{port}
14062 @item target ddb @var{port}
14063 @kindex target ddb @var{port}
14064 NEC's DDB variant of PMON for Vr4300.
14066 @item target lsi @var{port}
14067 @kindex target lsi @var{port}
14068 LSI variant of PMON.
14070 @kindex target r3900
14071 @item target r3900 @var{dev}
14072 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
14074 @kindex target array
14075 @item target array @var{dev}
14076 Array Tech LSI33K RAID controller board.
14082 @value{GDBN} also supports these special commands for MIPS targets:
14085 @item set mipsfpu double
14086 @itemx set mipsfpu single
14087 @itemx set mipsfpu none
14088 @itemx set mipsfpu auto
14089 @itemx show mipsfpu
14090 @kindex set mipsfpu
14091 @kindex show mipsfpu
14092 @cindex MIPS remote floating point
14093 @cindex floating point, MIPS remote
14094 If your target board does not support the MIPS floating point
14095 coprocessor, you should use the command @samp{set mipsfpu none} (if you
14096 need this, you may wish to put the command in your @value{GDBN} init
14097 file). This tells @value{GDBN} how to find the return value of
14098 functions which return floating point values. It also allows
14099 @value{GDBN} to avoid saving the floating point registers when calling
14100 functions on the board. If you are using a floating point coprocessor
14101 with only single precision floating point support, as on the @sc{r4650}
14102 processor, use the command @samp{set mipsfpu single}. The default
14103 double precision floating point coprocessor may be selected using
14104 @samp{set mipsfpu double}.
14106 In previous versions the only choices were double precision or no
14107 floating point, so @samp{set mipsfpu on} will select double precision
14108 and @samp{set mipsfpu off} will select no floating point.
14110 As usual, you can inquire about the @code{mipsfpu} variable with
14111 @samp{show mipsfpu}.
14113 @item set timeout @var{seconds}
14114 @itemx set retransmit-timeout @var{seconds}
14115 @itemx show timeout
14116 @itemx show retransmit-timeout
14117 @cindex @code{timeout}, MIPS protocol
14118 @cindex @code{retransmit-timeout}, MIPS protocol
14119 @kindex set timeout
14120 @kindex show timeout
14121 @kindex set retransmit-timeout
14122 @kindex show retransmit-timeout
14123 You can control the timeout used while waiting for a packet, in the MIPS
14124 remote protocol, with the @code{set timeout @var{seconds}} command. The
14125 default is 5 seconds. Similarly, you can control the timeout used while
14126 waiting for an acknowledgement of a packet with the @code{set
14127 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
14128 You can inspect both values with @code{show timeout} and @code{show
14129 retransmit-timeout}. (These commands are @emph{only} available when
14130 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
14132 The timeout set by @code{set timeout} does not apply when @value{GDBN}
14133 is waiting for your program to stop. In that case, @value{GDBN} waits
14134 forever because it has no way of knowing how long the program is going
14135 to run before stopping.
14137 @item set syn-garbage-limit @var{num}
14138 @kindex set syn-garbage-limit@r{, MIPS remote}
14139 @cindex synchronize with remote MIPS target
14140 Limit the maximum number of characters @value{GDBN} should ignore when
14141 it tries to synchronize with the remote target. The default is 10
14142 characters. Setting the limit to -1 means there's no limit.
14144 @item show syn-garbage-limit
14145 @kindex show syn-garbage-limit@r{, MIPS remote}
14146 Show the current limit on the number of characters to ignore when
14147 trying to synchronize with the remote system.
14149 @item set monitor-prompt @var{prompt}
14150 @kindex set monitor-prompt@r{, MIPS remote}
14151 @cindex remote monitor prompt
14152 Tell @value{GDBN} to expect the specified @var{prompt} string from the
14153 remote monitor. The default depends on the target:
14163 @item show monitor-prompt
14164 @kindex show monitor-prompt@r{, MIPS remote}
14165 Show the current strings @value{GDBN} expects as the prompt from the
14168 @item set monitor-warnings
14169 @kindex set monitor-warnings@r{, MIPS remote}
14170 Enable or disable monitor warnings about hardware breakpoints. This
14171 has effect only for the @code{lsi} target. When on, @value{GDBN} will
14172 display warning messages whose codes are returned by the @code{lsi}
14173 PMON monitor for breakpoint commands.
14175 @item show monitor-warnings
14176 @kindex show monitor-warnings@r{, MIPS remote}
14177 Show the current setting of printing monitor warnings.
14179 @item pmon @var{command}
14180 @kindex pmon@r{, MIPS remote}
14181 @cindex send PMON command
14182 This command allows sending an arbitrary @var{command} string to the
14183 monitor. The monitor must be in debug mode for this to work.
14186 @node OpenRISC 1000
14187 @subsection OpenRISC 1000
14188 @cindex OpenRISC 1000
14190 @cindex or1k boards
14191 See OR1k Architecture document (@uref{www.opencores.org}) for more information
14192 about platform and commands.
14196 @kindex target jtag
14197 @item target jtag jtag://@var{host}:@var{port}
14199 Connects to remote JTAG server.
14200 JTAG remote server can be either an or1ksim or JTAG server,
14201 connected via parallel port to the board.
14203 Example: @code{target jtag jtag://localhost:9999}
14206 @item or1ksim @var{command}
14207 If connected to @code{or1ksim} OpenRISC 1000 Architectural
14208 Simulator, proprietary commands can be executed.
14210 @kindex info or1k spr
14211 @item info or1k spr
14212 Displays spr groups.
14214 @item info or1k spr @var{group}
14215 @itemx info or1k spr @var{groupno}
14216 Displays register names in selected group.
14218 @item info or1k spr @var{group} @var{register}
14219 @itemx info or1k spr @var{register}
14220 @itemx info or1k spr @var{groupno} @var{registerno}
14221 @itemx info or1k spr @var{registerno}
14222 Shows information about specified spr register.
14225 @item spr @var{group} @var{register} @var{value}
14226 @itemx spr @var{register @var{value}}
14227 @itemx spr @var{groupno} @var{registerno @var{value}}
14228 @itemx spr @var{registerno @var{value}}
14229 Writes @var{value} to specified spr register.
14232 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
14233 It is very similar to @value{GDBN} trace, except it does not interfere with normal
14234 program execution and is thus much faster. Hardware breakpoints/watchpoint
14235 triggers can be set using:
14238 Load effective address/data
14240 Store effective address/data
14242 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
14247 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
14248 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
14250 @code{htrace} commands:
14251 @cindex OpenRISC 1000 htrace
14254 @item hwatch @var{conditional}
14255 Set hardware watchpoint on combination of Load/Store Effecive Address(es)
14256 or Data. For example:
14258 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14260 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14264 Display information about current HW trace configuration.
14266 @item htrace trigger @var{conditional}
14267 Set starting criteria for HW trace.
14269 @item htrace qualifier @var{conditional}
14270 Set acquisition qualifier for HW trace.
14272 @item htrace stop @var{conditional}
14273 Set HW trace stopping criteria.
14275 @item htrace record [@var{data}]*
14276 Selects the data to be recorded, when qualifier is met and HW trace was
14279 @item htrace enable
14280 @itemx htrace disable
14281 Enables/disables the HW trace.
14283 @item htrace rewind [@var{filename}]
14284 Clears currently recorded trace data.
14286 If filename is specified, new trace file is made and any newly collected data
14287 will be written there.
14289 @item htrace print [@var{start} [@var{len}]]
14290 Prints trace buffer, using current record configuration.
14292 @item htrace mode continuous
14293 Set continuous trace mode.
14295 @item htrace mode suspend
14296 Set suspend trace mode.
14301 @subsection PowerPC
14304 @kindex target dink32
14305 @item target dink32 @var{dev}
14306 DINK32 ROM monitor.
14308 @kindex target ppcbug
14309 @item target ppcbug @var{dev}
14310 @kindex target ppcbug1
14311 @item target ppcbug1 @var{dev}
14312 PPCBUG ROM monitor for PowerPC.
14315 @item target sds @var{dev}
14316 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
14319 @cindex SDS protocol
14320 The following commands specifi to the SDS protocol are supported
14324 @item set sdstimeout @var{nsec}
14325 @kindex set sdstimeout
14326 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
14327 default is 2 seconds.
14329 @item show sdstimeout
14330 @kindex show sdstimeout
14331 Show the current value of the SDS timeout.
14333 @item sds @var{command}
14334 @kindex sds@r{, a command}
14335 Send the specified @var{command} string to the SDS monitor.
14340 @subsection HP PA Embedded
14344 @kindex target op50n
14345 @item target op50n @var{dev}
14346 OP50N monitor, running on an OKI HPPA board.
14348 @kindex target w89k
14349 @item target w89k @var{dev}
14350 W89K monitor, running on a Winbond HPPA board.
14355 @subsection Renesas SH
14359 @kindex target hms@r{, with Renesas SH}
14360 @item target hms @var{dev}
14361 A Renesas SH board attached via serial line to your host. Use special
14362 commands @code{device} and @code{speed} to control the serial line and
14363 the communications speed used.
14365 @kindex target e7000@r{, with Renesas SH}
14366 @item target e7000 @var{dev}
14367 E7000 emulator for Renesas SH.
14369 @kindex target sh3@r{, with SH}
14370 @kindex target sh3e@r{, with SH}
14371 @item target sh3 @var{dev}
14372 @item target sh3e @var{dev}
14373 Renesas SH-3 and SH-3E target systems.
14378 @subsection Tsqware Sparclet
14382 @value{GDBN} enables developers to debug tasks running on
14383 Sparclet targets from a Unix host.
14384 @value{GDBN} uses code that runs on
14385 both the Unix host and on the Sparclet target. The program
14386 @code{@value{GDBP}} is installed and executed on the Unix host.
14389 @item remotetimeout @var{args}
14390 @kindex remotetimeout
14391 @value{GDBN} supports the option @code{remotetimeout}.
14392 This option is set by the user, and @var{args} represents the number of
14393 seconds @value{GDBN} waits for responses.
14396 @cindex compiling, on Sparclet
14397 When compiling for debugging, include the options @samp{-g} to get debug
14398 information and @samp{-Ttext} to relocate the program to where you wish to
14399 load it on the target. You may also want to add the options @samp{-n} or
14400 @samp{-N} in order to reduce the size of the sections. Example:
14403 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
14406 You can use @code{objdump} to verify that the addresses are what you intended:
14409 sparclet-aout-objdump --headers --syms prog
14412 @cindex running, on Sparclet
14414 your Unix execution search path to find @value{GDBN}, you are ready to
14415 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
14416 (or @code{sparclet-aout-gdb}, depending on your installation).
14418 @value{GDBN} comes up showing the prompt:
14425 * Sparclet File:: Setting the file to debug
14426 * Sparclet Connection:: Connecting to Sparclet
14427 * Sparclet Download:: Sparclet download
14428 * Sparclet Execution:: Running and debugging
14431 @node Sparclet File
14432 @subsubsection Setting file to debug
14434 The @value{GDBN} command @code{file} lets you choose with program to debug.
14437 (gdbslet) file prog
14441 @value{GDBN} then attempts to read the symbol table of @file{prog}.
14442 @value{GDBN} locates
14443 the file by searching the directories listed in the command search
14445 If the file was compiled with debug information (option "-g"), source
14446 files will be searched as well.
14447 @value{GDBN} locates
14448 the source files by searching the directories listed in the directory search
14449 path (@pxref{Environment, ,Your program's environment}).
14451 to find a file, it displays a message such as:
14454 prog: No such file or directory.
14457 When this happens, add the appropriate directories to the search paths with
14458 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
14459 @code{target} command again.
14461 @node Sparclet Connection
14462 @subsubsection Connecting to Sparclet
14464 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
14465 To connect to a target on serial port ``@code{ttya}'', type:
14468 (gdbslet) target sparclet /dev/ttya
14469 Remote target sparclet connected to /dev/ttya
14470 main () at ../prog.c:3
14474 @value{GDBN} displays messages like these:
14480 @node Sparclet Download
14481 @subsubsection Sparclet download
14483 @cindex download to Sparclet
14484 Once connected to the Sparclet target,
14485 you can use the @value{GDBN}
14486 @code{load} command to download the file from the host to the target.
14487 The file name and load offset should be given as arguments to the @code{load}
14489 Since the file format is aout, the program must be loaded to the starting
14490 address. You can use @code{objdump} to find out what this value is. The load
14491 offset is an offset which is added to the VMA (virtual memory address)
14492 of each of the file's sections.
14493 For instance, if the program
14494 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
14495 and bss at 0x12010170, in @value{GDBN}, type:
14498 (gdbslet) load prog 0x12010000
14499 Loading section .text, size 0xdb0 vma 0x12010000
14502 If the code is loaded at a different address then what the program was linked
14503 to, you may need to use the @code{section} and @code{add-symbol-file} commands
14504 to tell @value{GDBN} where to map the symbol table.
14506 @node Sparclet Execution
14507 @subsubsection Running and debugging
14509 @cindex running and debugging Sparclet programs
14510 You can now begin debugging the task using @value{GDBN}'s execution control
14511 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
14512 manual for the list of commands.
14516 Breakpoint 1 at 0x12010000: file prog.c, line 3.
14518 Starting program: prog
14519 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
14520 3 char *symarg = 0;
14522 4 char *execarg = "hello!";
14527 @subsection Fujitsu Sparclite
14531 @kindex target sparclite
14532 @item target sparclite @var{dev}
14533 Fujitsu sparclite boards, used only for the purpose of loading.
14534 You must use an additional command to debug the program.
14535 For example: target remote @var{dev} using @value{GDBN} standard
14541 @subsection Tandem ST2000
14543 @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
14546 To connect your ST2000 to the host system, see the manufacturer's
14547 manual. Once the ST2000 is physically attached, you can run:
14550 target st2000 @var{dev} @var{speed}
14554 to establish it as your debugging environment. @var{dev} is normally
14555 the name of a serial device, such as @file{/dev/ttya}, connected to the
14556 ST2000 via a serial line. You can instead specify @var{dev} as a TCP
14557 connection (for example, to a serial line attached via a terminal
14558 concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
14560 The @code{load} and @code{attach} commands are @emph{not} defined for
14561 this target; you must load your program into the ST2000 as you normally
14562 would for standalone operation. @value{GDBN} reads debugging information
14563 (such as symbols) from a separate, debugging version of the program
14564 available on your host computer.
14565 @c FIXME!! This is terribly vague; what little content is here is
14566 @c basically hearsay.
14568 @cindex ST2000 auxiliary commands
14569 These auxiliary @value{GDBN} commands are available to help you with the ST2000
14573 @item st2000 @var{command}
14574 @kindex st2000 @var{cmd}
14575 @cindex STDBUG commands (ST2000)
14576 @cindex commands to STDBUG (ST2000)
14577 Send a @var{command} to the STDBUG monitor. See the manufacturer's
14578 manual for available commands.
14581 @cindex connect (to STDBUG)
14582 Connect the controlling terminal to the STDBUG command monitor. When
14583 you are done interacting with STDBUG, typing either of two character
14584 sequences gets you back to the @value{GDBN} command prompt:
14585 @kbd{@key{RET}~.} (Return, followed by tilde and period) or
14586 @kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D).
14590 @subsection Zilog Z8000
14593 @cindex simulator, Z8000
14594 @cindex Zilog Z8000 simulator
14596 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
14599 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
14600 unsegmented variant of the Z8000 architecture) or the Z8001 (the
14601 segmented variant). The simulator recognizes which architecture is
14602 appropriate by inspecting the object code.
14605 @item target sim @var{args}
14607 @kindex target sim@r{, with Z8000}
14608 Debug programs on a simulated CPU. If the simulator supports setup
14609 options, specify them via @var{args}.
14613 After specifying this target, you can debug programs for the simulated
14614 CPU in the same style as programs for your host computer; use the
14615 @code{file} command to load a new program image, the @code{run} command
14616 to run your program, and so on.
14618 As well as making available all the usual machine registers
14619 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
14620 additional items of information as specially named registers:
14625 Counts clock-ticks in the simulator.
14628 Counts instructions run in the simulator.
14631 Execution time in 60ths of a second.
14635 You can refer to these values in @value{GDBN} expressions with the usual
14636 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
14637 conditional breakpoint that suspends only after at least 5000
14638 simulated clock ticks.
14641 @subsection Atmel AVR
14644 When configured for debugging the Atmel AVR, @value{GDBN} supports the
14645 following AVR-specific commands:
14648 @item info io_registers
14649 @kindex info io_registers@r{, AVR}
14650 @cindex I/O registers (Atmel AVR)
14651 This command displays information about the AVR I/O registers. For
14652 each register, @value{GDBN} prints its number and value.
14659 When configured for debugging CRIS, @value{GDBN} provides the
14660 following CRIS-specific commands:
14663 @item set cris-version @var{ver}
14664 @cindex CRIS version
14665 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
14666 The CRIS version affects register names and sizes. This command is useful in
14667 case autodetection of the CRIS version fails.
14669 @item show cris-version
14670 Show the current CRIS version.
14672 @item set cris-dwarf2-cfi
14673 @cindex DWARF-2 CFI and CRIS
14674 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
14675 Change to @samp{off} when using @code{gcc-cris} whose version is below
14678 @item show cris-dwarf2-cfi
14679 Show the current state of using DWARF-2 CFI.
14681 @item set cris-mode @var{mode}
14683 Set the current CRIS mode to @var{mode}. It should only be changed when
14684 debugging in guru mode, in which case it should be set to
14685 @samp{guru} (the default is @samp{normal}).
14687 @item show cris-mode
14688 Show the current CRIS mode.
14692 @subsection Renesas Super-H
14695 For the Renesas Super-H processor, @value{GDBN} provides these
14700 @kindex regs@r{, Super-H}
14701 Show the values of all Super-H registers.
14705 @subsection Windows CE
14708 The following commands are available for Windows CE:
14711 @item set remotedirectory @var{dir}
14712 @kindex set remotedirectory
14713 Tell @value{GDBN} to upload files from the named directory @var{dir}.
14714 The default is @file{/gdb}, i.e.@: the root directory on the current
14717 @item show remotedirectory
14718 @kindex show remotedirectory
14719 Show the current value of the upload directory.
14721 @item set remoteupload @var{method}
14722 @kindex set remoteupload
14723 Set the method used to upload files to remote device. Valid values
14724 for @var{method} are @samp{always}, @samp{newer}, and @samp{never}.
14725 The default is @samp{newer}.
14727 @item show remoteupload
14728 @kindex show remoteupload
14729 Show the current setting of the upload method.
14731 @item set remoteaddhost
14732 @kindex set remoteaddhost
14733 Tell @value{GDBN} whether to add this host to the remote stub's
14734 arguments when you debug over a network.
14736 @item show remoteaddhost
14737 @kindex show remoteaddhost
14738 Show whether to add this host to remote stub's arguments when
14739 debugging over a network.
14743 @node Architectures
14744 @section Architectures
14746 This section describes characteristics of architectures that affect
14747 all uses of @value{GDBN} with the architecture, both native and cross.
14754 * HPPA:: HP PA architecture
14758 @subsection x86 Architecture-specific issues.
14761 @item set struct-convention @var{mode}
14762 @kindex set struct-convention
14763 @cindex struct return convention
14764 @cindex struct/union returned in registers
14765 Set the convention used by the inferior to return @code{struct}s and
14766 @code{union}s from functions to @var{mode}. Possible values of
14767 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
14768 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
14769 are returned on the stack, while @code{"reg"} means that a
14770 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
14771 be returned in a register.
14773 @item show struct-convention
14774 @kindex show struct-convention
14775 Show the current setting of the convention to return @code{struct}s
14784 @kindex set rstack_high_address
14785 @cindex AMD 29K register stack
14786 @cindex register stack, AMD29K
14787 @item set rstack_high_address @var{address}
14788 On AMD 29000 family processors, registers are saved in a separate
14789 @dfn{register stack}. There is no way for @value{GDBN} to determine the
14790 extent of this stack. Normally, @value{GDBN} just assumes that the
14791 stack is ``large enough''. This may result in @value{GDBN} referencing
14792 memory locations that do not exist. If necessary, you can get around
14793 this problem by specifying the ending address of the register stack with
14794 the @code{set rstack_high_address} command. The argument should be an
14795 address, which you probably want to precede with @samp{0x} to specify in
14798 @kindex show rstack_high_address
14799 @item show rstack_high_address
14800 Display the current limit of the register stack, on AMD 29000 family
14808 See the following section.
14813 @cindex stack on Alpha
14814 @cindex stack on MIPS
14815 @cindex Alpha stack
14817 Alpha- and MIPS-based computers use an unusual stack frame, which
14818 sometimes requires @value{GDBN} to search backward in the object code to
14819 find the beginning of a function.
14821 @cindex response time, MIPS debugging
14822 To improve response time (especially for embedded applications, where
14823 @value{GDBN} may be restricted to a slow serial line for this search)
14824 you may want to limit the size of this search, using one of these
14828 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
14829 @item set heuristic-fence-post @var{limit}
14830 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
14831 search for the beginning of a function. A value of @var{0} (the
14832 default) means there is no limit. However, except for @var{0}, the
14833 larger the limit the more bytes @code{heuristic-fence-post} must search
14834 and therefore the longer it takes to run. You should only need to use
14835 this command when debugging a stripped executable.
14837 @item show heuristic-fence-post
14838 Display the current limit.
14842 These commands are available @emph{only} when @value{GDBN} is configured
14843 for debugging programs on Alpha or MIPS processors.
14845 Several MIPS-specific commands are available when debugging MIPS
14849 @item set mips saved-gpreg-size @var{size}
14850 @kindex set mips saved-gpreg-size
14851 @cindex MIPS GP register size on stack
14852 Set the size of MIPS general-purpose registers saved on the stack.
14853 The argument @var{size} can be one of the following:
14857 32-bit GP registers
14859 64-bit GP registers
14861 Use the target's default setting or autodetect the saved size from the
14862 information contained in the executable. This is the default
14865 @item show mips saved-gpreg-size
14866 @kindex show mips saved-gpreg-size
14867 Show the current size of MIPS GP registers on the stack.
14869 @item set mips stack-arg-size @var{size}
14870 @kindex set mips stack-arg-size
14871 @cindex MIPS stack space for arguments
14872 Set the amount of stack space reserved for arguments to functions.
14873 The argument can be one of @code{"32"}, @code{"64"} or @code{"auto"}
14876 @item set mips abi @var{arg}
14877 @kindex set mips abi
14878 @cindex set ABI for MIPS
14879 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
14880 values of @var{arg} are:
14884 The default ABI associated with the current binary (this is the
14895 @item show mips abi
14896 @kindex show mips abi
14897 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
14900 @itemx show mipsfpu
14901 @xref{MIPS Embedded, set mipsfpu}.
14903 @item set mips mask-address @var{arg}
14904 @kindex set mips mask-address
14905 @cindex MIPS addresses, masking
14906 This command determines whether the most-significant 32 bits of 64-bit
14907 MIPS addresses are masked off. The argument @var{arg} can be
14908 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
14909 setting, which lets @value{GDBN} determine the correct value.
14911 @item show mips mask-address
14912 @kindex show mips mask-address
14913 Show whether the upper 32 bits of MIPS addresses are masked off or
14916 @item set remote-mips64-transfers-32bit-regs
14917 @kindex set remote-mips64-transfers-32bit-regs
14918 This command controls compatibility with 64-bit MIPS targets that
14919 transfer data in 32-bit quantities. If you have an old MIPS 64 target
14920 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
14921 and 64 bits for other registers, set this option to @samp{on}.
14923 @item show remote-mips64-transfers-32bit-regs
14924 @kindex show remote-mips64-transfers-32bit-regs
14925 Show the current setting of compatibility with older MIPS 64 targets.
14927 @item set debug mips
14928 @kindex set debug mips
14929 This command turns on and off debugging messages for the MIPS-specific
14930 target code in @value{GDBN}.
14932 @item show debug mips
14933 @kindex show debug mips
14934 Show the current setting of MIPS debugging messages.
14940 @cindex HPPA support
14942 When @value{GDBN} is debugging te HP PA architecture, it provides the
14943 following special commands:
14946 @item set debug hppa
14947 @kindex set debug hppa
14948 THis command determines whether HPPA architecture specific debugging
14949 messages are to be displayed.
14951 @item show debug hppa
14952 Show whether HPPA debugging messages are displayed.
14954 @item maint print unwind @var{address}
14955 @kindex maint print unwind@r{, HPPA}
14956 This command displays the contents of the unwind table entry at the
14957 given @var{address}.
14962 @node Controlling GDB
14963 @chapter Controlling @value{GDBN}
14965 You can alter the way @value{GDBN} interacts with you by using the
14966 @code{set} command. For commands controlling how @value{GDBN} displays
14967 data, see @ref{Print Settings, ,Print settings}. Other settings are
14972 * Editing:: Command editing
14973 * Command History:: Command history
14974 * Screen Size:: Screen size
14975 * Numbers:: Numbers
14976 * ABI:: Configuring the current ABI
14977 * Messages/Warnings:: Optional warnings and messages
14978 * Debugging Output:: Optional messages about internal happenings
14986 @value{GDBN} indicates its readiness to read a command by printing a string
14987 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
14988 can change the prompt string with the @code{set prompt} command. For
14989 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
14990 the prompt in one of the @value{GDBN} sessions so that you can always tell
14991 which one you are talking to.
14993 @emph{Note:} @code{set prompt} does not add a space for you after the
14994 prompt you set. This allows you to set a prompt which ends in a space
14995 or a prompt that does not.
14999 @item set prompt @var{newprompt}
15000 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
15002 @kindex show prompt
15004 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
15008 @section Command editing
15010 @cindex command line editing
15012 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
15013 @sc{gnu} library provides consistent behavior for programs which provide a
15014 command line interface to the user. Advantages are @sc{gnu} Emacs-style
15015 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
15016 substitution, and a storage and recall of command history across
15017 debugging sessions.
15019 You may control the behavior of command line editing in @value{GDBN} with the
15020 command @code{set}.
15023 @kindex set editing
15026 @itemx set editing on
15027 Enable command line editing (enabled by default).
15029 @item set editing off
15030 Disable command line editing.
15032 @kindex show editing
15034 Show whether command line editing is enabled.
15037 @xref{Command Line Editing}, for more details about the Readline
15038 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
15039 encouraged to read that chapter.
15041 @node Command History
15042 @section Command history
15043 @cindex command history
15045 @value{GDBN} can keep track of the commands you type during your
15046 debugging sessions, so that you can be certain of precisely what
15047 happened. Use these commands to manage the @value{GDBN} command
15050 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
15051 package, to provide the history facility. @xref{Using History
15052 Interactively}, for the detailed description of the History library.
15054 To issue a command to @value{GDBN} without affecting certain aspects of
15055 the state which is seen by users, prefix it with @samp{server }. This
15056 means that this command will not affect the command history, nor will it
15057 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
15058 pressed on a line by itself.
15060 @cindex @code{server}, command prefix
15061 The server prefix does not affect the recording of values into the value
15062 history; to print a value without recording it into the value history,
15063 use the @code{output} command instead of the @code{print} command.
15065 Here is the description of @value{GDBN} commands related to command
15069 @cindex history substitution
15070 @cindex history file
15071 @kindex set history filename
15072 @cindex @env{GDBHISTFILE}, environment variable
15073 @item set history filename @var{fname}
15074 Set the name of the @value{GDBN} command history file to @var{fname}.
15075 This is the file where @value{GDBN} reads an initial command history
15076 list, and where it writes the command history from this session when it
15077 exits. You can access this list through history expansion or through
15078 the history command editing characters listed below. This file defaults
15079 to the value of the environment variable @code{GDBHISTFILE}, or to
15080 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
15083 @cindex save command history
15084 @kindex set history save
15085 @item set history save
15086 @itemx set history save on
15087 Record command history in a file, whose name may be specified with the
15088 @code{set history filename} command. By default, this option is disabled.
15090 @item set history save off
15091 Stop recording command history in a file.
15093 @cindex history size
15094 @kindex set history size
15095 @cindex @env{HISTSIZE}, environment variable
15096 @item set history size @var{size}
15097 Set the number of commands which @value{GDBN} keeps in its history list.
15098 This defaults to the value of the environment variable
15099 @code{HISTSIZE}, or to 256 if this variable is not set.
15102 History expansion assigns special meaning to the character @kbd{!}.
15103 @xref{Event Designators}, for more details.
15105 @cindex history expansion, turn on/off
15106 Since @kbd{!} is also the logical not operator in C, history expansion
15107 is off by default. If you decide to enable history expansion with the
15108 @code{set history expansion on} command, you may sometimes need to
15109 follow @kbd{!} (when it is used as logical not, in an expression) with
15110 a space or a tab to prevent it from being expanded. The readline
15111 history facilities do not attempt substitution on the strings
15112 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
15114 The commands to control history expansion are:
15117 @item set history expansion on
15118 @itemx set history expansion
15119 @kindex set history expansion
15120 Enable history expansion. History expansion is off by default.
15122 @item set history expansion off
15123 Disable history expansion.
15126 @kindex show history
15128 @itemx show history filename
15129 @itemx show history save
15130 @itemx show history size
15131 @itemx show history expansion
15132 These commands display the state of the @value{GDBN} history parameters.
15133 @code{show history} by itself displays all four states.
15138 @kindex show commands
15139 @cindex show last commands
15140 @cindex display command history
15141 @item show commands
15142 Display the last ten commands in the command history.
15144 @item show commands @var{n}
15145 Print ten commands centered on command number @var{n}.
15147 @item show commands +
15148 Print ten commands just after the commands last printed.
15152 @section Screen size
15153 @cindex size of screen
15154 @cindex pauses in output
15156 Certain commands to @value{GDBN} may produce large amounts of
15157 information output to the screen. To help you read all of it,
15158 @value{GDBN} pauses and asks you for input at the end of each page of
15159 output. Type @key{RET} when you want to continue the output, or @kbd{q}
15160 to discard the remaining output. Also, the screen width setting
15161 determines when to wrap lines of output. Depending on what is being
15162 printed, @value{GDBN} tries to break the line at a readable place,
15163 rather than simply letting it overflow onto the following line.
15165 Normally @value{GDBN} knows the size of the screen from the terminal
15166 driver software. For example, on Unix @value{GDBN} uses the termcap data base
15167 together with the value of the @code{TERM} environment variable and the
15168 @code{stty rows} and @code{stty cols} settings. If this is not correct,
15169 you can override it with the @code{set height} and @code{set
15176 @kindex show height
15177 @item set height @var{lpp}
15179 @itemx set width @var{cpl}
15181 These @code{set} commands specify a screen height of @var{lpp} lines and
15182 a screen width of @var{cpl} characters. The associated @code{show}
15183 commands display the current settings.
15185 If you specify a height of zero lines, @value{GDBN} does not pause during
15186 output no matter how long the output is. This is useful if output is to a
15187 file or to an editor buffer.
15189 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
15190 from wrapping its output.
15192 @item set pagination on
15193 @itemx set pagination off
15194 @kindex set pagination
15195 Turn the output pagination on or off; the default is on. Turning
15196 pagination off is the alternative to @code{set height 0}.
15198 @item show pagination
15199 @kindex show pagination
15200 Show the current pagination mode.
15205 @cindex number representation
15206 @cindex entering numbers
15208 You can always enter numbers in octal, decimal, or hexadecimal in
15209 @value{GDBN} by the usual conventions: octal numbers begin with
15210 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
15211 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
15212 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
15213 10; likewise, the default display for numbers---when no particular
15214 format is specified---is base 10. You can change the default base for
15215 both input and output with the commands described below.
15218 @kindex set input-radix
15219 @item set input-radix @var{base}
15220 Set the default base for numeric input. Supported choices
15221 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15222 specified either unambiguously or using the current input radix; for
15226 set input-radix 012
15227 set input-radix 10.
15228 set input-radix 0xa
15232 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
15233 leaves the input radix unchanged, no matter what it was, since
15234 @samp{10}, being without any leading or trailing signs of its base, is
15235 interpreted in the current radix. Thus, if the current radix is 16,
15236 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
15239 @kindex set output-radix
15240 @item set output-radix @var{base}
15241 Set the default base for numeric display. Supported choices
15242 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15243 specified either unambiguously or using the current input radix.
15245 @kindex show input-radix
15246 @item show input-radix
15247 Display the current default base for numeric input.
15249 @kindex show output-radix
15250 @item show output-radix
15251 Display the current default base for numeric display.
15253 @item set radix @r{[}@var{base}@r{]}
15257 These commands set and show the default base for both input and output
15258 of numbers. @code{set radix} sets the radix of input and output to
15259 the same base; without an argument, it resets the radix back to its
15260 default value of 10.
15265 @section Configuring the current ABI
15267 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
15268 application automatically. However, sometimes you need to override its
15269 conclusions. Use these commands to manage @value{GDBN}'s view of the
15276 One @value{GDBN} configuration can debug binaries for multiple operating
15277 system targets, either via remote debugging or native emulation.
15278 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
15279 but you can override its conclusion using the @code{set osabi} command.
15280 One example where this is useful is in debugging of binaries which use
15281 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
15282 not have the same identifying marks that the standard C library for your
15287 Show the OS ABI currently in use.
15290 With no argument, show the list of registered available OS ABI's.
15292 @item set osabi @var{abi}
15293 Set the current OS ABI to @var{abi}.
15296 @cindex float promotion
15298 Generally, the way that an argument of type @code{float} is passed to a
15299 function depends on whether the function is prototyped. For a prototyped
15300 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
15301 according to the architecture's convention for @code{float}. For unprototyped
15302 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
15303 @code{double} and then passed.
15305 Unfortunately, some forms of debug information do not reliably indicate whether
15306 a function is prototyped. If @value{GDBN} calls a function that is not marked
15307 as prototyped, it consults @kbd{set coerce-float-to-double}.
15310 @kindex set coerce-float-to-double
15311 @item set coerce-float-to-double
15312 @itemx set coerce-float-to-double on
15313 Arguments of type @code{float} will be promoted to @code{double} when passed
15314 to an unprototyped function. This is the default setting.
15316 @item set coerce-float-to-double off
15317 Arguments of type @code{float} will be passed directly to unprototyped
15320 @kindex show coerce-float-to-double
15321 @item show coerce-float-to-double
15322 Show the current setting of promoting @code{float} to @code{double}.
15326 @kindex show cp-abi
15327 @value{GDBN} needs to know the ABI used for your program's C@t{++}
15328 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
15329 used to build your application. @value{GDBN} only fully supports
15330 programs with a single C@t{++} ABI; if your program contains code using
15331 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
15332 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
15333 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
15334 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
15335 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
15336 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
15341 Show the C@t{++} ABI currently in use.
15344 With no argument, show the list of supported C@t{++} ABI's.
15346 @item set cp-abi @var{abi}
15347 @itemx set cp-abi auto
15348 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
15351 @node Messages/Warnings
15352 @section Optional warnings and messages
15354 @cindex verbose operation
15355 @cindex optional warnings
15356 By default, @value{GDBN} is silent about its inner workings. If you are
15357 running on a slow machine, you may want to use the @code{set verbose}
15358 command. This makes @value{GDBN} tell you when it does a lengthy
15359 internal operation, so you will not think it has crashed.
15361 Currently, the messages controlled by @code{set verbose} are those
15362 which announce that the symbol table for a source file is being read;
15363 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
15366 @kindex set verbose
15367 @item set verbose on
15368 Enables @value{GDBN} output of certain informational messages.
15370 @item set verbose off
15371 Disables @value{GDBN} output of certain informational messages.
15373 @kindex show verbose
15375 Displays whether @code{set verbose} is on or off.
15378 By default, if @value{GDBN} encounters bugs in the symbol table of an
15379 object file, it is silent; but if you are debugging a compiler, you may
15380 find this information useful (@pxref{Symbol Errors, ,Errors reading
15385 @kindex set complaints
15386 @item set complaints @var{limit}
15387 Permits @value{GDBN} to output @var{limit} complaints about each type of
15388 unusual symbols before becoming silent about the problem. Set
15389 @var{limit} to zero to suppress all complaints; set it to a large number
15390 to prevent complaints from being suppressed.
15392 @kindex show complaints
15393 @item show complaints
15394 Displays how many symbol complaints @value{GDBN} is permitted to produce.
15398 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
15399 lot of stupid questions to confirm certain commands. For example, if
15400 you try to run a program which is already running:
15404 The program being debugged has been started already.
15405 Start it from the beginning? (y or n)
15408 If you are willing to unflinchingly face the consequences of your own
15409 commands, you can disable this ``feature'':
15413 @kindex set confirm
15415 @cindex confirmation
15416 @cindex stupid questions
15417 @item set confirm off
15418 Disables confirmation requests.
15420 @item set confirm on
15421 Enables confirmation requests (the default).
15423 @kindex show confirm
15425 Displays state of confirmation requests.
15429 @node Debugging Output
15430 @section Optional messages about internal happenings
15431 @cindex optional debugging messages
15433 @value{GDBN} has commands that enable optional debugging messages from
15434 various @value{GDBN} subsystems; normally these commands are of
15435 interest to @value{GDBN} maintainers, or when reporting a bug. This
15436 section documents those commands.
15439 @kindex set exec-done-display
15440 @item set exec-done-display
15441 Turns on or off the notification of asynchronous commands'
15442 completion. When on, @value{GDBN} will print a message when an
15443 asynchronous command finishes its execution. The default is off.
15444 @kindex show exec-done-display
15445 @item show exec-done-display
15446 Displays the current setting of asynchronous command completion
15449 @cindex gdbarch debugging info
15450 @cindex architecture debugging info
15451 @item set debug arch
15452 Turns on or off display of gdbarch debugging info. The default is off
15454 @item show debug arch
15455 Displays the current state of displaying gdbarch debugging info.
15456 @item set debug aix-thread
15457 @cindex AIX threads
15458 Display debugging messages about inner workings of the AIX thread
15460 @item show debug aix-thread
15461 Show the current state of AIX thread debugging info display.
15462 @item set debug event
15463 @cindex event debugging info
15464 Turns on or off display of @value{GDBN} event debugging info. The
15466 @item show debug event
15467 Displays the current state of displaying @value{GDBN} event debugging
15469 @item set debug expression
15470 @cindex expression debugging info
15471 Turns on or off display of debugging info about @value{GDBN}
15472 expression parsing. The default is off.
15473 @item show debug expression
15474 Displays the current state of displaying debugging info about
15475 @value{GDBN} expression parsing.
15476 @item set debug frame
15477 @cindex frame debugging info
15478 Turns on or off display of @value{GDBN} frame debugging info. The
15480 @item show debug frame
15481 Displays the current state of displaying @value{GDBN} frame debugging
15483 @item set debug infrun
15484 @cindex inferior debugging info
15485 Turns on or off display of @value{GDBN} debugging info for running the inferior.
15486 The default is off. @file{infrun.c} contains GDB's runtime state machine used
15487 for implementing operations such as single-stepping the inferior.
15488 @item show debug infrun
15489 Displays the current state of @value{GDBN} inferior debugging.
15490 @item set debug lin-lwp
15491 @cindex @sc{gnu}/Linux LWP debug messages
15492 @cindex Linux lightweight processes
15493 Turns on or off debugging messages from the Linux LWP debug support.
15494 @item show debug lin-lwp
15495 Show the current state of Linux LWP debugging messages.
15496 @item set debug observer
15497 @cindex observer debugging info
15498 Turns on or off display of @value{GDBN} observer debugging. This
15499 includes info such as the notification of observable events.
15500 @item show debug observer
15501 Displays the current state of observer debugging.
15502 @item set debug overload
15503 @cindex C@t{++} overload debugging info
15504 Turns on or off display of @value{GDBN} C@t{++} overload debugging
15505 info. This includes info such as ranking of functions, etc. The default
15507 @item show debug overload
15508 Displays the current state of displaying @value{GDBN} C@t{++} overload
15510 @cindex packets, reporting on stdout
15511 @cindex serial connections, debugging
15512 @item set debug remote
15513 Turns on or off display of reports on all packets sent back and forth across
15514 the serial line to the remote machine. The info is printed on the
15515 @value{GDBN} standard output stream. The default is off.
15516 @item show debug remote
15517 Displays the state of display of remote packets.
15518 @item set debug serial
15519 Turns on or off display of @value{GDBN} serial debugging info. The
15521 @item show debug serial
15522 Displays the current state of displaying @value{GDBN} serial debugging
15524 @item set debug solib-frv
15525 @cindex FR-V shared-library debugging
15526 Turns on or off debugging messages for FR-V shared-library code.
15527 @item show debug solib-frv
15528 Display the current state of FR-V shared-library code debugging
15530 @item set debug target
15531 @cindex target debugging info
15532 Turns on or off display of @value{GDBN} target debugging info. This info
15533 includes what is going on at the target level of GDB, as it happens. The
15534 default is 0. Set it to 1 to track events, and to 2 to also track the
15535 value of large memory transfers. Changes to this flag do not take effect
15536 until the next time you connect to a target or use the @code{run} command.
15537 @item show debug target
15538 Displays the current state of displaying @value{GDBN} target debugging
15540 @item set debugvarobj
15541 @cindex variable object debugging info
15542 Turns on or off display of @value{GDBN} variable object debugging
15543 info. The default is off.
15544 @item show debugvarobj
15545 Displays the current state of displaying @value{GDBN} variable object
15550 @chapter Canned Sequences of Commands
15552 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
15553 command lists}), @value{GDBN} provides two ways to store sequences of
15554 commands for execution as a unit: user-defined commands and command
15558 * Define:: User-defined commands
15559 * Hooks:: User-defined command hooks
15560 * Command Files:: Command files
15561 * Output:: Commands for controlled output
15565 @section User-defined commands
15567 @cindex user-defined command
15568 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
15569 which you assign a new name as a command. This is done with the
15570 @code{define} command. User commands may accept up to 10 arguments
15571 separated by whitespace. Arguments are accessed within the user command
15572 via @var{$arg0@dots{}$arg9}. A trivial example:
15576 print $arg0 + $arg1 + $arg2
15580 To execute the command use:
15587 This defines the command @code{adder}, which prints the sum of
15588 its three arguments. Note the arguments are text substitutions, so they may
15589 reference variables, use complex expressions, or even perform inferior
15595 @item define @var{commandname}
15596 Define a command named @var{commandname}. If there is already a command
15597 by that name, you are asked to confirm that you want to redefine it.
15599 The definition of the command is made up of other @value{GDBN} command lines,
15600 which are given following the @code{define} command. The end of these
15601 commands is marked by a line containing @code{end}.
15607 Takes a single argument, which is an expression to evaluate.
15608 It is followed by a series of commands that are executed
15609 only if the expression is true (nonzero).
15610 There can then optionally be a line @code{else}, followed
15611 by a series of commands that are only executed if the expression
15612 was false. The end of the list is marked by a line containing @code{end}.
15616 The syntax is similar to @code{if}: the command takes a single argument,
15617 which is an expression to evaluate, and must be followed by the commands to
15618 execute, one per line, terminated by an @code{end}.
15619 The commands are executed repeatedly as long as the expression
15623 @item document @var{commandname}
15624 Document the user-defined command @var{commandname}, so that it can be
15625 accessed by @code{help}. The command @var{commandname} must already be
15626 defined. This command reads lines of documentation just as @code{define}
15627 reads the lines of the command definition, ending with @code{end}.
15628 After the @code{document} command is finished, @code{help} on command
15629 @var{commandname} displays the documentation you have written.
15631 You may use the @code{document} command again to change the
15632 documentation of a command. Redefining the command with @code{define}
15633 does not change the documentation.
15635 @kindex dont-repeat
15636 @cindex don't repeat command
15638 Used inside a user-defined command, this tells @value{GDBN} that this
15639 command should not be repeated when the user hits @key{RET}
15640 (@pxref{Command Syntax, repeat last command}).
15642 @kindex help user-defined
15643 @item help user-defined
15644 List all user-defined commands, with the first line of the documentation
15649 @itemx show user @var{commandname}
15650 Display the @value{GDBN} commands used to define @var{commandname} (but
15651 not its documentation). If no @var{commandname} is given, display the
15652 definitions for all user-defined commands.
15654 @cindex infinite recusrion in user-defined commands
15655 @kindex show max-user-call-depth
15656 @kindex set max-user-call-depth
15657 @item show max-user-call-depth
15658 @itemx set max-user-call-depth
15659 The value of @code{max-user-call-depth} controls how many recursion
15660 levels are allowed in user-defined commands before GDB suspects an
15661 infinite recursion and aborts the command.
15665 When user-defined commands are executed, the
15666 commands of the definition are not printed. An error in any command
15667 stops execution of the user-defined command.
15669 If used interactively, commands that would ask for confirmation proceed
15670 without asking when used inside a user-defined command. Many @value{GDBN}
15671 commands that normally print messages to say what they are doing omit the
15672 messages when used in a user-defined command.
15675 @section User-defined command hooks
15676 @cindex command hooks
15677 @cindex hooks, for commands
15678 @cindex hooks, pre-command
15681 You may define @dfn{hooks}, which are a special kind of user-defined
15682 command. Whenever you run the command @samp{foo}, if the user-defined
15683 command @samp{hook-foo} exists, it is executed (with no arguments)
15684 before that command.
15686 @cindex hooks, post-command
15688 A hook may also be defined which is run after the command you executed.
15689 Whenever you run the command @samp{foo}, if the user-defined command
15690 @samp{hookpost-foo} exists, it is executed (with no arguments) after
15691 that command. Post-execution hooks may exist simultaneously with
15692 pre-execution hooks, for the same command.
15694 It is valid for a hook to call the command which it hooks. If this
15695 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
15697 @c It would be nice if hookpost could be passed a parameter indicating
15698 @c if the command it hooks executed properly or not. FIXME!
15700 @kindex stop@r{, a pseudo-command}
15701 In addition, a pseudo-command, @samp{stop} exists. Defining
15702 (@samp{hook-stop}) makes the associated commands execute every time
15703 execution stops in your program: before breakpoint commands are run,
15704 displays are printed, or the stack frame is printed.
15706 For example, to ignore @code{SIGALRM} signals while
15707 single-stepping, but treat them normally during normal execution,
15712 handle SIGALRM nopass
15716 handle SIGALRM pass
15719 define hook-continue
15720 handle SIGLARM pass
15724 As a further example, to hook at the begining and end of the @code{echo}
15725 command, and to add extra text to the beginning and end of the message,
15733 define hookpost-echo
15737 (@value{GDBP}) echo Hello World
15738 <<<---Hello World--->>>
15743 You can define a hook for any single-word command in @value{GDBN}, but
15744 not for command aliases; you should define a hook for the basic command
15745 name, e.g. @code{backtrace} rather than @code{bt}.
15746 @c FIXME! So how does Joe User discover whether a command is an alias
15748 If an error occurs during the execution of your hook, execution of
15749 @value{GDBN} commands stops and @value{GDBN} issues a prompt
15750 (before the command that you actually typed had a chance to run).
15752 If you try to define a hook which does not match any known command, you
15753 get a warning from the @code{define} command.
15755 @node Command Files
15756 @section Command files
15758 @cindex command files
15759 A command file for @value{GDBN} is a text file made of lines that are
15760 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
15761 also be included. An empty line in a command file does nothing; it
15762 does not mean to repeat the last command, as it would from the
15765 You can request the execution of a command file with the @code{source}
15770 @item source @var{filename}
15771 Execute the command file @var{filename}.
15774 The lines in a command file are executed sequentially. They are not
15775 printed as they are executed. An error in any command terminates
15776 execution of the command file and control is returned to the console.
15778 Commands that would ask for confirmation if used interactively proceed
15779 without asking when used in a command file. Many @value{GDBN} commands that
15780 normally print messages to say what they are doing omit the messages
15781 when called from command files.
15783 @value{GDBN} also accepts command input from standard input. In this
15784 mode, normal output goes to standard output and error output goes to
15785 standard error. Errors in a command file supplied on standard input do
15786 not terminate execution of the command file---execution continues with
15790 gdb < cmds > log 2>&1
15793 (The syntax above will vary depending on the shell used.) This example
15794 will execute commands from the file @file{cmds}. All output and errors
15795 would be directed to @file{log}.
15798 @section Commands for controlled output
15800 During the execution of a command file or a user-defined command, normal
15801 @value{GDBN} output is suppressed; the only output that appears is what is
15802 explicitly printed by the commands in the definition. This section
15803 describes three commands useful for generating exactly the output you
15808 @item echo @var{text}
15809 @c I do not consider backslash-space a standard C escape sequence
15810 @c because it is not in ANSI.
15811 Print @var{text}. Nonprinting characters can be included in
15812 @var{text} using C escape sequences, such as @samp{\n} to print a
15813 newline. @strong{No newline is printed unless you specify one.}
15814 In addition to the standard C escape sequences, a backslash followed
15815 by a space stands for a space. This is useful for displaying a
15816 string with spaces at the beginning or the end, since leading and
15817 trailing spaces are otherwise trimmed from all arguments.
15818 To print @samp{@w{ }and foo =@w{ }}, use the command
15819 @samp{echo \@w{ }and foo = \@w{ }}.
15821 A backslash at the end of @var{text} can be used, as in C, to continue
15822 the command onto subsequent lines. For example,
15825 echo This is some text\n\
15826 which is continued\n\
15827 onto several lines.\n
15830 produces the same output as
15833 echo This is some text\n
15834 echo which is continued\n
15835 echo onto several lines.\n
15839 @item output @var{expression}
15840 Print the value of @var{expression} and nothing but that value: no
15841 newlines, no @samp{$@var{nn} = }. The value is not entered in the
15842 value history either. @xref{Expressions, ,Expressions}, for more information
15845 @item output/@var{fmt} @var{expression}
15846 Print the value of @var{expression} in format @var{fmt}. You can use
15847 the same formats as for @code{print}. @xref{Output Formats,,Output
15848 formats}, for more information.
15851 @item printf @var{string}, @var{expressions}@dots{}
15852 Print the values of the @var{expressions} under the control of
15853 @var{string}. The @var{expressions} are separated by commas and may be
15854 either numbers or pointers. Their values are printed as specified by
15855 @var{string}, exactly as if your program were to execute the C
15857 @c FIXME: the above implies that at least all ANSI C formats are
15858 @c supported, but it isn't true: %E and %G don't work (or so it seems).
15859 @c Either this is a bug, or the manual should document what formats are
15863 printf (@var{string}, @var{expressions}@dots{});
15866 For example, you can print two values in hex like this:
15869 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
15872 The only backslash-escape sequences that you can use in the format
15873 string are the simple ones that consist of backslash followed by a
15878 @chapter Command Interpreters
15879 @cindex command interpreters
15881 @value{GDBN} supports multiple command interpreters, and some command
15882 infrastructure to allow users or user interface writers to switch
15883 between interpreters or run commands in other interpreters.
15885 @value{GDBN} currently supports two command interpreters, the console
15886 interpreter (sometimes called the command-line interpreter or @sc{cli})
15887 and the machine interface interpreter (or @sc{gdb/mi}). This manual
15888 describes both of these interfaces in great detail.
15890 By default, @value{GDBN} will start with the console interpreter.
15891 However, the user may choose to start @value{GDBN} with another
15892 interpreter by specifying the @option{-i} or @option{--interpreter}
15893 startup options. Defined interpreters include:
15897 @cindex console interpreter
15898 The traditional console or command-line interpreter. This is the most often
15899 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
15900 @value{GDBN} will use this interpreter.
15903 @cindex mi interpreter
15904 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
15905 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
15906 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
15910 @cindex mi2 interpreter
15911 The current @sc{gdb/mi} interface.
15914 @cindex mi1 interpreter
15915 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
15919 @cindex invoke another interpreter
15920 The interpreter being used by @value{GDBN} may not be dynamically
15921 switched at runtime. Although possible, this could lead to a very
15922 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
15923 enters the command "interpreter-set console" in a console view,
15924 @value{GDBN} would switch to using the console interpreter, rendering
15925 the IDE inoperable!
15927 @kindex interpreter-exec
15928 Although you may only choose a single interpreter at startup, you may execute
15929 commands in any interpreter from the current interpreter using the appropriate
15930 command. If you are running the console interpreter, simply use the
15931 @code{interpreter-exec} command:
15934 interpreter-exec mi "-data-list-register-names"
15937 @sc{gdb/mi} has a similar command, although it is only available in versions of
15938 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
15941 @chapter @value{GDBN} Text User Interface
15943 @cindex Text User Interface
15946 * TUI Overview:: TUI overview
15947 * TUI Keys:: TUI key bindings
15948 * TUI Single Key Mode:: TUI single key mode
15949 * TUI Commands:: TUI specific commands
15950 * TUI Configuration:: TUI configuration variables
15953 The @value{GDBN} Text User Interface, TUI in short, is a terminal
15954 interface which uses the @code{curses} library to show the source
15955 file, the assembly output, the program registers and @value{GDBN}
15956 commands in separate text windows.
15958 The TUI is enabled by invoking @value{GDBN} using either
15960 @samp{gdbtui} or @samp{gdb -tui}.
15963 @section TUI overview
15965 The TUI has two display modes that can be switched while
15970 A curses (or TUI) mode in which it displays several text
15971 windows on the terminal.
15974 A standard mode which corresponds to the @value{GDBN} configured without
15978 In the TUI mode, @value{GDBN} can display several text window
15983 This window is the @value{GDBN} command window with the @value{GDBN}
15984 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
15985 managed using readline but through the TUI. The @emph{command}
15986 window is always visible.
15989 The source window shows the source file of the program. The current
15990 line as well as active breakpoints are displayed in this window.
15993 The assembly window shows the disassembly output of the program.
15996 This window shows the processor registers. It detects when
15997 a register is changed and when this is the case, registers that have
15998 changed are highlighted.
16002 The source and assembly windows show the current program position
16003 by highlighting the current line and marking them with the @samp{>} marker.
16004 Breakpoints are also indicated with two markers. A first one
16005 indicates the breakpoint type:
16009 Breakpoint which was hit at least once.
16012 Breakpoint which was never hit.
16015 Hardware breakpoint which was hit at least once.
16018 Hardware breakpoint which was never hit.
16022 The second marker indicates whether the breakpoint is enabled or not:
16026 Breakpoint is enabled.
16029 Breakpoint is disabled.
16033 The source, assembly and register windows are attached to the thread
16034 and the frame position. They are updated when the current thread
16035 changes, when the frame changes or when the program counter changes.
16036 These three windows are arranged by the TUI according to several
16037 layouts. The layout defines which of these three windows are visible.
16038 The following layouts are available:
16048 source and assembly
16051 source and registers
16054 assembly and registers
16058 On top of the command window a status line gives various information
16059 concerning the current process begin debugged. The status line is
16060 updated when the information it shows changes. The following fields
16065 Indicates the current gdb target
16066 (@pxref{Targets, ,Specifying a Debugging Target}).
16069 Gives information about the current process or thread number.
16070 When no process is being debugged, this field is set to @code{No process}.
16073 Gives the current function name for the selected frame.
16074 The name is demangled if demangling is turned on (@pxref{Print Settings}).
16075 When there is no symbol corresponding to the current program counter
16076 the string @code{??} is displayed.
16079 Indicates the current line number for the selected frame.
16080 When the current line number is not known the string @code{??} is displayed.
16083 Indicates the current program counter address.
16088 @section TUI Key Bindings
16089 @cindex TUI key bindings
16091 The TUI installs several key bindings in the readline keymaps
16092 (@pxref{Command Line Editing}).
16093 They allow to leave or enter in the TUI mode or they operate
16094 directly on the TUI layout and windows. The TUI also provides
16095 a @emph{SingleKey} keymap which binds several keys directly to
16096 @value{GDBN} commands. The following key bindings
16097 are installed for both TUI mode and the @value{GDBN} standard mode.
16106 Enter or leave the TUI mode. When the TUI mode is left,
16107 the curses window management is left and @value{GDBN} operates using
16108 its standard mode writing on the terminal directly. When the TUI
16109 mode is entered, the control is given back to the curses windows.
16110 The screen is then refreshed.
16114 Use a TUI layout with only one window. The layout will
16115 either be @samp{source} or @samp{assembly}. When the TUI mode
16116 is not active, it will switch to the TUI mode.
16118 Think of this key binding as the Emacs @kbd{C-x 1} binding.
16122 Use a TUI layout with at least two windows. When the current
16123 layout shows already two windows, a next layout with two windows is used.
16124 When a new layout is chosen, one window will always be common to the
16125 previous layout and the new one.
16127 Think of it as the Emacs @kbd{C-x 2} binding.
16131 Change the active window. The TUI associates several key bindings
16132 (like scrolling and arrow keys) to the active window. This command
16133 gives the focus to the next TUI window.
16135 Think of it as the Emacs @kbd{C-x o} binding.
16139 Use the TUI @emph{SingleKey} keymap that binds single key to gdb commands
16140 (@pxref{TUI Single Key Mode}).
16144 The following key bindings are handled only by the TUI mode:
16149 Scroll the active window one page up.
16153 Scroll the active window one page down.
16157 Scroll the active window one line up.
16161 Scroll the active window one line down.
16165 Scroll the active window one column left.
16169 Scroll the active window one column right.
16173 Refresh the screen.
16177 In the TUI mode, the arrow keys are used by the active window
16178 for scrolling. This means they are available for readline when the
16179 active window is the command window. When the command window
16180 does not have the focus, it is necessary to use other readline
16181 key bindings such as @key{C-p}, @key{C-n}, @key{C-b} and @key{C-f}.
16183 @node TUI Single Key Mode
16184 @section TUI Single Key Mode
16185 @cindex TUI single key mode
16187 The TUI provides a @emph{SingleKey} mode in which it installs a particular
16188 key binding in the readline keymaps to connect single keys to
16192 @kindex c @r{(SingleKey TUI key)}
16196 @kindex d @r{(SingleKey TUI key)}
16200 @kindex f @r{(SingleKey TUI key)}
16204 @kindex n @r{(SingleKey TUI key)}
16208 @kindex q @r{(SingleKey TUI key)}
16210 exit the @emph{SingleKey} mode.
16212 @kindex r @r{(SingleKey TUI key)}
16216 @kindex s @r{(SingleKey TUI key)}
16220 @kindex u @r{(SingleKey TUI key)}
16224 @kindex v @r{(SingleKey TUI key)}
16228 @kindex w @r{(SingleKey TUI key)}
16234 Other keys temporarily switch to the @value{GDBN} command prompt.
16235 The key that was pressed is inserted in the editing buffer so that
16236 it is possible to type most @value{GDBN} commands without interaction
16237 with the TUI @emph{SingleKey} mode. Once the command is entered the TUI
16238 @emph{SingleKey} mode is restored. The only way to permanently leave
16239 this mode is by hitting @key{q} or @samp{@key{C-x} @key{s}}.
16243 @section TUI specific commands
16244 @cindex TUI commands
16246 The TUI has specific commands to control the text windows.
16247 These commands are always available, that is they do not depend on
16248 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
16249 is in the standard mode, using these commands will automatically switch
16255 List and give the size of all displayed windows.
16259 Display the next layout.
16262 Display the previous layout.
16265 Display the source window only.
16268 Display the assembly window only.
16271 Display the source and assembly window.
16274 Display the register window together with the source or assembly window.
16276 @item focus next | prev | src | asm | regs | split
16278 Set the focus to the named window.
16279 This command allows to change the active window so that scrolling keys
16280 can be affected to another window.
16284 Refresh the screen. This is similar to using @key{C-L} key.
16286 @item tui reg float
16288 Show the floating point registers in the register window.
16290 @item tui reg general
16291 Show the general registers in the register window.
16294 Show the next register group. The list of register groups as well as
16295 their order is target specific. The predefined register groups are the
16296 following: @code{general}, @code{float}, @code{system}, @code{vector},
16297 @code{all}, @code{save}, @code{restore}.
16299 @item tui reg system
16300 Show the system registers in the register window.
16304 Update the source window and the current execution point.
16306 @item winheight @var{name} +@var{count}
16307 @itemx winheight @var{name} -@var{count}
16309 Change the height of the window @var{name} by @var{count}
16310 lines. Positive counts increase the height, while negative counts
16314 @kindex tabset @var{nchars}
16315 Set the width of tab stops to be @var{nchars} characters.
16319 @node TUI Configuration
16320 @section TUI configuration variables
16321 @cindex TUI configuration variables
16323 The TUI has several configuration variables that control the
16324 appearance of windows on the terminal.
16327 @item set tui border-kind @var{kind}
16328 @kindex set tui border-kind
16329 Select the border appearance for the source, assembly and register windows.
16330 The possible values are the following:
16333 Use a space character to draw the border.
16336 Use ascii characters + - and | to draw the border.
16339 Use the Alternate Character Set to draw the border. The border is
16340 drawn using character line graphics if the terminal supports them.
16344 @item set tui active-border-mode @var{mode}
16345 @kindex set tui active-border-mode
16346 Select the attributes to display the border of the active window.
16347 The possible values are @code{normal}, @code{standout}, @code{reverse},
16348 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
16350 @item set tui border-mode @var{mode}
16351 @kindex set tui border-mode
16352 Select the attributes to display the border of other windows.
16353 The @var{mode} can be one of the following:
16356 Use normal attributes to display the border.
16362 Use reverse video mode.
16365 Use half bright mode.
16367 @item half-standout
16368 Use half bright and standout mode.
16371 Use extra bright or bold mode.
16373 @item bold-standout
16374 Use extra bright or bold and standout mode.
16381 @chapter Using @value{GDBN} under @sc{gnu} Emacs
16384 @cindex @sc{gnu} Emacs
16385 A special interface allows you to use @sc{gnu} Emacs to view (and
16386 edit) the source files for the program you are debugging with
16389 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
16390 executable file you want to debug as an argument. This command starts
16391 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
16392 created Emacs buffer.
16393 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
16395 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
16400 All ``terminal'' input and output goes through the Emacs buffer.
16403 This applies both to @value{GDBN} commands and their output, and to the input
16404 and output done by the program you are debugging.
16406 This is useful because it means that you can copy the text of previous
16407 commands and input them again; you can even use parts of the output
16410 All the facilities of Emacs' Shell mode are available for interacting
16411 with your program. In particular, you can send signals the usual
16412 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
16417 @value{GDBN} displays source code through Emacs.
16420 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
16421 source file for that frame and puts an arrow (@samp{=>}) at the
16422 left margin of the current line. Emacs uses a separate buffer for
16423 source display, and splits the screen to show both your @value{GDBN} session
16426 Explicit @value{GDBN} @code{list} or search commands still produce output as
16427 usual, but you probably have no reason to use them from Emacs.
16429 If you specify an absolute file name when prompted for the @kbd{M-x
16430 gdb} argument, then Emacs sets your current working directory to where
16431 your program resides. If you only specify the file name, then Emacs
16432 sets your current working directory to to the directory associated
16433 with the previous buffer. In this case, @value{GDBN} may find your
16434 program by searching your environment's @code{PATH} variable, but on
16435 some operating systems it might not find the source. So, although the
16436 @value{GDBN} input and output session proceeds normally, the auxiliary
16437 buffer does not display the current source and line of execution.
16439 The initial working directory of @value{GDBN} is printed on the top
16440 line of the @value{GDBN} I/O buffer and this serves as a default for
16441 the commands that specify files for @value{GDBN} to operate
16442 on. @xref{Files, ,Commands to specify files}.
16444 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
16445 need to call @value{GDBN} by a different name (for example, if you
16446 keep several configurations around, with different names) you can
16447 customize the Emacs variable @code{gud-gdb-command-name} to run the
16450 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
16451 addition to the standard Shell mode commands:
16455 Describe the features of Emacs' @value{GDBN} Mode.
16458 Execute to another source line, like the @value{GDBN} @code{step} command; also
16459 update the display window to show the current file and location.
16462 Execute to next source line in this function, skipping all function
16463 calls, like the @value{GDBN} @code{next} command. Then update the display window
16464 to show the current file and location.
16467 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
16468 display window accordingly.
16471 Execute until exit from the selected stack frame, like the @value{GDBN}
16472 @code{finish} command.
16475 Continue execution of your program, like the @value{GDBN} @code{continue}
16479 Go up the number of frames indicated by the numeric argument
16480 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
16481 like the @value{GDBN} @code{up} command.
16484 Go down the number of frames indicated by the numeric argument, like the
16485 @value{GDBN} @code{down} command.
16488 In any source file, the Emacs command @kbd{C-x SPC} (@code{gud-break})
16489 tells @value{GDBN} to set a breakpoint on the source line point is on.
16491 If you type @kbd{M-x speedbar}, then Emacs displays a separate frame which
16492 shows a backtrace when the @value{GDBN} I/O buffer is current. Move
16493 point to any frame in the stack and type @key{RET} to make it become the
16494 current frame and display the associated source in the source buffer.
16495 Alternatively, click @kbd{Mouse-2} to make the selected frame become the
16498 If you accidentally delete the source-display buffer, an easy way to get
16499 it back is to type the command @code{f} in the @value{GDBN} buffer, to
16500 request a frame display; when you run under Emacs, this recreates
16501 the source buffer if necessary to show you the context of the current
16504 The source files displayed in Emacs are in ordinary Emacs buffers
16505 which are visiting the source files in the usual way. You can edit
16506 the files with these buffers if you wish; but keep in mind that @value{GDBN}
16507 communicates with Emacs in terms of line numbers. If you add or
16508 delete lines from the text, the line numbers that @value{GDBN} knows cease
16509 to correspond properly with the code.
16511 The description given here is for GNU Emacs version 21.3 and a more
16512 detailed description of its interaction with @value{GDBN} is given in
16513 the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu} Emacs Manual}).
16515 @c The following dropped because Epoch is nonstandard. Reactivate
16516 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
16518 @kindex Emacs Epoch environment
16522 Version 18 of @sc{gnu} Emacs has a built-in window system
16523 called the @code{epoch}
16524 environment. Users of this environment can use a new command,
16525 @code{inspect} which performs identically to @code{print} except that
16526 each value is printed in its own window.
16531 @chapter The @sc{gdb/mi} Interface
16533 @unnumberedsec Function and Purpose
16535 @cindex @sc{gdb/mi}, its purpose
16536 @sc{gdb/mi} is a line based machine oriented text interface to
16537 @value{GDBN} and is activated by specifying using the
16538 @option{--interpreter} command line option (@pxref{Mode Options}). It
16539 is specifically intended to support the development of systems which
16540 use the debugger as just one small component of a larger system.
16542 This chapter is a specification of the @sc{gdb/mi} interface. It is written
16543 in the form of a reference manual.
16545 Note that @sc{gdb/mi} is still under construction, so some of the
16546 features described below are incomplete and subject to change.
16548 @unnumberedsec Notation and Terminology
16550 @cindex notational conventions, for @sc{gdb/mi}
16551 This chapter uses the following notation:
16555 @code{|} separates two alternatives.
16558 @code{[ @var{something} ]} indicates that @var{something} is optional:
16559 it may or may not be given.
16562 @code{( @var{group} )*} means that @var{group} inside the parentheses
16563 may repeat zero or more times.
16566 @code{( @var{group} )+} means that @var{group} inside the parentheses
16567 may repeat one or more times.
16570 @code{"@var{string}"} means a literal @var{string}.
16574 @heading Dependencies
16577 @heading Acknowledgments
16579 In alphabetic order: Andrew Cagney, Fernando Nasser, Stan Shebs and
16583 * GDB/MI Command Syntax::
16584 * GDB/MI Compatibility with CLI::
16585 * GDB/MI Output Records::
16586 * GDB/MI Command Description Format::
16587 * GDB/MI Breakpoint Table Commands::
16588 * GDB/MI Data Manipulation::
16589 * GDB/MI Program Control::
16590 * GDB/MI Miscellaneous Commands::
16592 * GDB/MI Kod Commands::
16593 * GDB/MI Memory Overlay Commands::
16594 * GDB/MI Signal Handling Commands::
16596 * GDB/MI Stack Manipulation::
16597 * GDB/MI Symbol Query::
16598 * GDB/MI Target Manipulation::
16599 * GDB/MI Thread Commands::
16600 * GDB/MI Tracepoint Commands::
16601 * GDB/MI Variable Objects::
16604 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16605 @node GDB/MI Command Syntax
16606 @section @sc{gdb/mi} Command Syntax
16609 * GDB/MI Input Syntax::
16610 * GDB/MI Output Syntax::
16611 * GDB/MI Simple Examples::
16614 @node GDB/MI Input Syntax
16615 @subsection @sc{gdb/mi} Input Syntax
16617 @cindex input syntax for @sc{gdb/mi}
16618 @cindex @sc{gdb/mi}, input syntax
16620 @item @var{command} @expansion{}
16621 @code{@var{cli-command} | @var{mi-command}}
16623 @item @var{cli-command} @expansion{}
16624 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
16625 @var{cli-command} is any existing @value{GDBN} CLI command.
16627 @item @var{mi-command} @expansion{}
16628 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
16629 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
16631 @item @var{token} @expansion{}
16632 "any sequence of digits"
16634 @item @var{option} @expansion{}
16635 @code{"-" @var{parameter} [ " " @var{parameter} ]}
16637 @item @var{parameter} @expansion{}
16638 @code{@var{non-blank-sequence} | @var{c-string}}
16640 @item @var{operation} @expansion{}
16641 @emph{any of the operations described in this chapter}
16643 @item @var{non-blank-sequence} @expansion{}
16644 @emph{anything, provided it doesn't contain special characters such as
16645 "-", @var{nl}, """ and of course " "}
16647 @item @var{c-string} @expansion{}
16648 @code{""" @var{seven-bit-iso-c-string-content} """}
16650 @item @var{nl} @expansion{}
16659 The CLI commands are still handled by the @sc{mi} interpreter; their
16660 output is described below.
16663 The @code{@var{token}}, when present, is passed back when the command
16667 Some @sc{mi} commands accept optional arguments as part of the parameter
16668 list. Each option is identified by a leading @samp{-} (dash) and may be
16669 followed by an optional argument parameter. Options occur first in the
16670 parameter list and can be delimited from normal parameters using
16671 @samp{--} (this is useful when some parameters begin with a dash).
16678 We want easy access to the existing CLI syntax (for debugging).
16681 We want it to be easy to spot a @sc{mi} operation.
16684 @node GDB/MI Output Syntax
16685 @subsection @sc{gdb/mi} Output Syntax
16687 @cindex output syntax of @sc{gdb/mi}
16688 @cindex @sc{gdb/mi}, output syntax
16689 The output from @sc{gdb/mi} consists of zero or more out-of-band records
16690 followed, optionally, by a single result record. This result record
16691 is for the most recent command. The sequence of output records is
16692 terminated by @samp{(@value{GDBP})}.
16694 If an input command was prefixed with a @code{@var{token}} then the
16695 corresponding output for that command will also be prefixed by that same
16699 @item @var{output} @expansion{}
16700 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(@value{GDBP})" @var{nl}}
16702 @item @var{result-record} @expansion{}
16703 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
16705 @item @var{out-of-band-record} @expansion{}
16706 @code{@var{async-record} | @var{stream-record}}
16708 @item @var{async-record} @expansion{}
16709 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
16711 @item @var{exec-async-output} @expansion{}
16712 @code{[ @var{token} ] "*" @var{async-output}}
16714 @item @var{status-async-output} @expansion{}
16715 @code{[ @var{token} ] "+" @var{async-output}}
16717 @item @var{notify-async-output} @expansion{}
16718 @code{[ @var{token} ] "=" @var{async-output}}
16720 @item @var{async-output} @expansion{}
16721 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
16723 @item @var{result-class} @expansion{}
16724 @code{"done" | "running" | "connected" | "error" | "exit"}
16726 @item @var{async-class} @expansion{}
16727 @code{"stopped" | @var{others}} (where @var{others} will be added
16728 depending on the needs---this is still in development).
16730 @item @var{result} @expansion{}
16731 @code{ @var{variable} "=" @var{value}}
16733 @item @var{variable} @expansion{}
16734 @code{ @var{string} }
16736 @item @var{value} @expansion{}
16737 @code{ @var{const} | @var{tuple} | @var{list} }
16739 @item @var{const} @expansion{}
16740 @code{@var{c-string}}
16742 @item @var{tuple} @expansion{}
16743 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
16745 @item @var{list} @expansion{}
16746 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
16747 @var{result} ( "," @var{result} )* "]" }
16749 @item @var{stream-record} @expansion{}
16750 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
16752 @item @var{console-stream-output} @expansion{}
16753 @code{"~" @var{c-string}}
16755 @item @var{target-stream-output} @expansion{}
16756 @code{"@@" @var{c-string}}
16758 @item @var{log-stream-output} @expansion{}
16759 @code{"&" @var{c-string}}
16761 @item @var{nl} @expansion{}
16764 @item @var{token} @expansion{}
16765 @emph{any sequence of digits}.
16773 All output sequences end in a single line containing a period.
16776 The @code{@var{token}} is from the corresponding request. If an execution
16777 command is interrupted by the @samp{-exec-interrupt} command, the
16778 @var{token} associated with the @samp{*stopped} message is the one of the
16779 original execution command, not the one of the interrupt command.
16782 @cindex status output in @sc{gdb/mi}
16783 @var{status-async-output} contains on-going status information about the
16784 progress of a slow operation. It can be discarded. All status output is
16785 prefixed by @samp{+}.
16788 @cindex async output in @sc{gdb/mi}
16789 @var{exec-async-output} contains asynchronous state change on the target
16790 (stopped, started, disappeared). All async output is prefixed by
16794 @cindex notify output in @sc{gdb/mi}
16795 @var{notify-async-output} contains supplementary information that the
16796 client should handle (e.g., a new breakpoint information). All notify
16797 output is prefixed by @samp{=}.
16800 @cindex console output in @sc{gdb/mi}
16801 @var{console-stream-output} is output that should be displayed as is in the
16802 console. It is the textual response to a CLI command. All the console
16803 output is prefixed by @samp{~}.
16806 @cindex target output in @sc{gdb/mi}
16807 @var{target-stream-output} is the output produced by the target program.
16808 All the target output is prefixed by @samp{@@}.
16811 @cindex log output in @sc{gdb/mi}
16812 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
16813 instance messages that should be displayed as part of an error log. All
16814 the log output is prefixed by @samp{&}.
16817 @cindex list output in @sc{gdb/mi}
16818 New @sc{gdb/mi} commands should only output @var{lists} containing
16824 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
16825 details about the various output records.
16827 @node GDB/MI Simple Examples
16828 @subsection Simple Examples of @sc{gdb/mi} Interaction
16829 @cindex @sc{gdb/mi}, simple examples
16831 This subsection presents several simple examples of interaction using
16832 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
16833 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
16834 the output received from @sc{gdb/mi}.
16836 @subsubheading Target Stop
16837 @c Ummm... There is no "-stop" command. This assumes async, no?
16838 Here's an example of stopping the inferior process:
16849 <- *stop,reason="stop",address="0x123",source="a.c:123"
16853 @subsubheading Simple CLI Command
16855 Here's an example of a simple CLI command being passed through
16856 @sc{gdb/mi} and on to the CLI.
16866 @subsubheading Command With Side Effects
16869 -> -symbol-file xyz.exe
16870 <- *breakpoint,nr="3",address="0x123",source="a.c:123"
16874 @subsubheading A Bad Command
16876 Here's what happens if you pass a non-existent command:
16880 <- ^error,msg="Undefined MI command: rubbish"
16884 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16885 @node GDB/MI Compatibility with CLI
16886 @section @sc{gdb/mi} Compatibility with CLI
16888 @cindex compatibility, @sc{gdb/mi} and CLI
16889 @cindex @sc{gdb/mi}, compatibility with CLI
16890 To help users familiar with @value{GDBN}'s existing CLI interface, @sc{gdb/mi}
16891 accepts existing CLI commands. As specified by the syntax, such
16892 commands can be directly entered into the @sc{gdb/mi} interface and @value{GDBN} will
16895 This mechanism is provided as an aid to developers of @sc{gdb/mi}
16896 clients and not as a reliable interface into the CLI. Since the command
16897 is being interpreteted in an environment that assumes @sc{gdb/mi}
16898 behaviour, the exact output of such commands is likely to end up being
16899 an un-supported hybrid of @sc{gdb/mi} and CLI output.
16901 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16902 @node GDB/MI Output Records
16903 @section @sc{gdb/mi} Output Records
16906 * GDB/MI Result Records::
16907 * GDB/MI Stream Records::
16908 * GDB/MI Out-of-band Records::
16911 @node GDB/MI Result Records
16912 @subsection @sc{gdb/mi} Result Records
16914 @cindex result records in @sc{gdb/mi}
16915 @cindex @sc{gdb/mi}, result records
16916 In addition to a number of out-of-band notifications, the response to a
16917 @sc{gdb/mi} command includes one of the following result indications:
16921 @item "^done" [ "," @var{results} ]
16922 The synchronous operation was successful, @code{@var{results}} are the return
16927 @c Is this one correct? Should it be an out-of-band notification?
16928 The asynchronous operation was successfully started. The target is
16931 @item "^error" "," @var{c-string}
16933 The operation failed. The @code{@var{c-string}} contains the corresponding
16937 @node GDB/MI Stream Records
16938 @subsection @sc{gdb/mi} Stream Records
16940 @cindex @sc{gdb/mi}, stream records
16941 @cindex stream records in @sc{gdb/mi}
16942 @value{GDBN} internally maintains a number of output streams: the console, the
16943 target, and the log. The output intended for each of these streams is
16944 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
16946 Each stream record begins with a unique @dfn{prefix character} which
16947 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
16948 Syntax}). In addition to the prefix, each stream record contains a
16949 @code{@var{string-output}}. This is either raw text (with an implicit new
16950 line) or a quoted C string (which does not contain an implicit newline).
16953 @item "~" @var{string-output}
16954 The console output stream contains text that should be displayed in the
16955 CLI console window. It contains the textual responses to CLI commands.
16957 @item "@@" @var{string-output}
16958 The target output stream contains any textual output from the running
16961 @item "&" @var{string-output}
16962 The log stream contains debugging messages being produced by @value{GDBN}'s
16966 @node GDB/MI Out-of-band Records
16967 @subsection @sc{gdb/mi} Out-of-band Records
16969 @cindex out-of-band records in @sc{gdb/mi}
16970 @cindex @sc{gdb/mi}, out-of-band records
16971 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
16972 additional changes that have occurred. Those changes can either be a
16973 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
16974 target activity (e.g., target stopped).
16976 The following is a preliminary list of possible out-of-band records.
16977 In particular, the @var{exec-async-output} records.
16980 @item *stopped,reason="@var{reason}"
16983 @var{reason} can be one of the following:
16986 @item breakpoint-hit
16987 A breakpoint was reached.
16988 @item watchpoint-trigger
16989 A watchpoint was triggered.
16990 @item read-watchpoint-trigger
16991 A read watchpoint was triggered.
16992 @item access-watchpoint-trigger
16993 An access watchpoint was triggered.
16994 @item function-finished
16995 An -exec-finish or similar CLI command was accomplished.
16996 @item location-reached
16997 An -exec-until or similar CLI command was accomplished.
16998 @item watchpoint-scope
16999 A watchpoint has gone out of scope.
17000 @item end-stepping-range
17001 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
17002 similar CLI command was accomplished.
17003 @item exited-signalled
17004 The inferior exited because of a signal.
17006 The inferior exited.
17007 @item exited-normally
17008 The inferior exited normally.
17009 @item signal-received
17010 A signal was received by the inferior.
17014 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17015 @node GDB/MI Command Description Format
17016 @section @sc{gdb/mi} Command Description Format
17018 The remaining sections describe blocks of commands. Each block of
17019 commands is laid out in a fashion similar to this section.
17021 Note the the line breaks shown in the examples are here only for
17022 readability. They don't appear in the real output.
17023 Also note that the commands with a non-available example (N.A.@:) are
17024 not yet implemented.
17026 @subheading Motivation
17028 The motivation for this collection of commands.
17030 @subheading Introduction
17032 A brief introduction to this collection of commands as a whole.
17034 @subheading Commands
17036 For each command in the block, the following is described:
17038 @subsubheading Synopsis
17041 -command @var{args}@dots{}
17044 @subsubheading Result
17046 @subsubheading @value{GDBN} Command
17048 The corresponding @value{GDBN} CLI command(s), if any.
17050 @subsubheading Example
17052 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17053 @node GDB/MI Breakpoint Table Commands
17054 @section @sc{gdb/mi} Breakpoint table commands
17056 @cindex breakpoint commands for @sc{gdb/mi}
17057 @cindex @sc{gdb/mi}, breakpoint commands
17058 This section documents @sc{gdb/mi} commands for manipulating
17061 @subheading The @code{-break-after} Command
17062 @findex -break-after
17064 @subsubheading Synopsis
17067 -break-after @var{number} @var{count}
17070 The breakpoint number @var{number} is not in effect until it has been
17071 hit @var{count} times. To see how this is reflected in the output of
17072 the @samp{-break-list} command, see the description of the
17073 @samp{-break-list} command below.
17075 @subsubheading @value{GDBN} Command
17077 The corresponding @value{GDBN} command is @samp{ignore}.
17079 @subsubheading Example
17084 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",line="5"@}
17091 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17092 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17093 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17094 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17095 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17096 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17097 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17098 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17099 addr="0x000100d0",func="main",file="hello.c",line="5",times="0",
17105 @subheading The @code{-break-catch} Command
17106 @findex -break-catch
17108 @subheading The @code{-break-commands} Command
17109 @findex -break-commands
17113 @subheading The @code{-break-condition} Command
17114 @findex -break-condition
17116 @subsubheading Synopsis
17119 -break-condition @var{number} @var{expr}
17122 Breakpoint @var{number} will stop the program only if the condition in
17123 @var{expr} is true. The condition becomes part of the
17124 @samp{-break-list} output (see the description of the @samp{-break-list}
17127 @subsubheading @value{GDBN} Command
17129 The corresponding @value{GDBN} command is @samp{condition}.
17131 @subsubheading Example
17135 -break-condition 1 1
17139 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17140 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17141 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17142 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17143 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17144 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17145 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17146 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17147 addr="0x000100d0",func="main",file="hello.c",line="5",cond="1",
17148 times="0",ignore="3"@}]@}
17152 @subheading The @code{-break-delete} Command
17153 @findex -break-delete
17155 @subsubheading Synopsis
17158 -break-delete ( @var{breakpoint} )+
17161 Delete the breakpoint(s) whose number(s) are specified in the argument
17162 list. This is obviously reflected in the breakpoint list.
17164 @subsubheading @value{GDBN} command
17166 The corresponding @value{GDBN} command is @samp{delete}.
17168 @subsubheading Example
17176 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
17177 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17178 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17179 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17180 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17181 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17182 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17187 @subheading The @code{-break-disable} Command
17188 @findex -break-disable
17190 @subsubheading Synopsis
17193 -break-disable ( @var{breakpoint} )+
17196 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
17197 break list is now set to @samp{n} for the named @var{breakpoint}(s).
17199 @subsubheading @value{GDBN} Command
17201 The corresponding @value{GDBN} command is @samp{disable}.
17203 @subsubheading Example
17211 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17212 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17213 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17214 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17215 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17216 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17217 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17218 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
17219 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
17223 @subheading The @code{-break-enable} Command
17224 @findex -break-enable
17226 @subsubheading Synopsis
17229 -break-enable ( @var{breakpoint} )+
17232 Enable (previously disabled) @var{breakpoint}(s).
17234 @subsubheading @value{GDBN} Command
17236 The corresponding @value{GDBN} command is @samp{enable}.
17238 @subsubheading Example
17246 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17247 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17248 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17249 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17250 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17251 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17252 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17253 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
17254 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
17258 @subheading The @code{-break-info} Command
17259 @findex -break-info
17261 @subsubheading Synopsis
17264 -break-info @var{breakpoint}
17268 Get information about a single breakpoint.
17270 @subsubheading @value{GDBN} command
17272 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
17274 @subsubheading Example
17277 @subheading The @code{-break-insert} Command
17278 @findex -break-insert
17280 @subsubheading Synopsis
17283 -break-insert [ -t ] [ -h ] [ -r ]
17284 [ -c @var{condition} ] [ -i @var{ignore-count} ]
17285 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
17289 If specified, @var{line}, can be one of:
17296 @item filename:linenum
17297 @item filename:function
17301 The possible optional parameters of this command are:
17305 Insert a tempoary breakpoint.
17307 Insert a hardware breakpoint.
17308 @item -c @var{condition}
17309 Make the breakpoint conditional on @var{condition}.
17310 @item -i @var{ignore-count}
17311 Initialize the @var{ignore-count}.
17313 Insert a regular breakpoint in all the functions whose names match the
17314 given regular expression. Other flags are not applicable to regular
17318 @subsubheading Result
17320 The result is in the form:
17323 ^done,bkptno="@var{number}",func="@var{funcname}",
17324 file="@var{filename}",line="@var{lineno}"
17328 where @var{number} is the @value{GDBN} number for this breakpoint, @var{funcname}
17329 is the name of the function where the breakpoint was inserted,
17330 @var{filename} is the name of the source file which contains this
17331 function, and @var{lineno} is the source line number within that file.
17333 Note: this format is open to change.
17334 @c An out-of-band breakpoint instead of part of the result?
17336 @subsubheading @value{GDBN} Command
17338 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
17339 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
17341 @subsubheading Example
17346 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
17348 -break-insert -t foo
17349 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",line="11"@}
17352 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17353 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17354 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17355 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17356 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17357 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17358 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17359 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17360 addr="0x0001072c", func="main",file="recursive2.c",line="4",times="0"@},
17361 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
17362 addr="0x00010774",func="foo",file="recursive2.c",line="11",times="0"@}]@}
17364 -break-insert -r foo.*
17365 ~int foo(int, int);
17366 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c",line="11"@}
17370 @subheading The @code{-break-list} Command
17371 @findex -break-list
17373 @subsubheading Synopsis
17379 Displays the list of inserted breakpoints, showing the following fields:
17383 number of the breakpoint
17385 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
17387 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
17390 is the breakpoint enabled or no: @samp{y} or @samp{n}
17392 memory location at which the breakpoint is set
17394 logical location of the breakpoint, expressed by function name, file
17397 number of times the breakpoint has been hit
17400 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
17401 @code{body} field is an empty list.
17403 @subsubheading @value{GDBN} Command
17405 The corresponding @value{GDBN} command is @samp{info break}.
17407 @subsubheading Example
17412 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17413 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17414 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17415 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17416 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17417 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17418 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17419 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17420 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
17421 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
17422 addr="0x00010114",func="foo",file="hello.c",line="13",times="0"@}]@}
17426 Here's an example of the result when there are no breakpoints:
17431 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
17432 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17433 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17434 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17435 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17436 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17437 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17442 @subheading The @code{-break-watch} Command
17443 @findex -break-watch
17445 @subsubheading Synopsis
17448 -break-watch [ -a | -r ]
17451 Create a watchpoint. With the @samp{-a} option it will create an
17452 @dfn{access} watchpoint, i.e. a watchpoint that triggers either on a
17453 read from or on a write to the memory location. With the @samp{-r}
17454 option, the watchpoint created is a @dfn{read} watchpoint, i.e. it will
17455 trigger only when the memory location is accessed for reading. Without
17456 either of the options, the watchpoint created is a regular watchpoint,
17457 i.e. it will trigger when the memory location is accessed for writing.
17458 @xref{Set Watchpoints, , Setting watchpoints}.
17460 Note that @samp{-break-list} will report a single list of watchpoints and
17461 breakpoints inserted.
17463 @subsubheading @value{GDBN} Command
17465 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
17468 @subsubheading Example
17470 Setting a watchpoint on a variable in the @code{main} function:
17475 ^done,wpt=@{number="2",exp="x"@}
17479 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
17480 value=@{old="-268439212",new="55"@},
17481 frame=@{func="main",args=[],file="recursive2.c",
17482 fullname="/home/foo/bar/devo/myproject/recursive2.c",line="5"@}
17486 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
17487 the program execution twice: first for the variable changing value, then
17488 for the watchpoint going out of scope.
17493 ^done,wpt=@{number="5",exp="C"@}
17497 ^done,reason="watchpoint-trigger",
17498 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
17499 frame=@{func="callee4",args=[],
17500 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
17501 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
17505 ^done,reason="watchpoint-scope",wpnum="5",
17506 frame=@{func="callee3",args=[@{name="strarg",
17507 value="0x11940 \"A string argument.\""@}],
17508 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
17509 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
17513 Listing breakpoints and watchpoints, at different points in the program
17514 execution. Note that once the watchpoint goes out of scope, it is
17520 ^done,wpt=@{number="2",exp="C"@}
17523 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17524 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17525 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17526 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17527 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17528 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17529 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17530 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17531 addr="0x00010734",func="callee4",
17532 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
17533 bkpt=@{number="2",type="watchpoint",disp="keep",
17534 enabled="y",addr="",what="C",times="0"@}]@}
17538 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
17539 value=@{old="-276895068",new="3"@},
17540 frame=@{func="callee4",args=[],
17541 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
17542 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
17545 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17546 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17547 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17548 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17549 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17550 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17551 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17552 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17553 addr="0x00010734",func="callee4",
17554 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
17555 bkpt=@{number="2",type="watchpoint",disp="keep",
17556 enabled="y",addr="",what="C",times="-5"@}]@}
17560 ^done,reason="watchpoint-scope",wpnum="2",
17561 frame=@{func="callee3",args=[@{name="strarg",
17562 value="0x11940 \"A string argument.\""@}],
17563 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
17564 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
17567 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17568 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17569 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17570 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17571 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17572 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17573 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17574 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17575 addr="0x00010734",func="callee4",
17576 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@}]@}
17580 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17581 @node GDB/MI Data Manipulation
17582 @section @sc{gdb/mi} Data Manipulation
17584 @cindex data manipulation, in @sc{gdb/mi}
17585 @cindex @sc{gdb/mi}, data manipulation
17586 This section describes the @sc{gdb/mi} commands that manipulate data:
17587 examine memory and registers, evaluate expressions, etc.
17589 @c REMOVED FROM THE INTERFACE.
17590 @c @subheading -data-assign
17591 @c Change the value of a program variable. Plenty of side effects.
17592 @c @subsubheading GDB command
17594 @c @subsubheading Example
17597 @subheading The @code{-data-disassemble} Command
17598 @findex -data-disassemble
17600 @subsubheading Synopsis
17604 [ -s @var{start-addr} -e @var{end-addr} ]
17605 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
17613 @item @var{start-addr}
17614 is the beginning address (or @code{$pc})
17615 @item @var{end-addr}
17617 @item @var{filename}
17618 is the name of the file to disassemble
17619 @item @var{linenum}
17620 is the line number to disassemble around
17622 is the the number of disassembly lines to be produced. If it is -1,
17623 the whole function will be disassembled, in case no @var{end-addr} is
17624 specified. If @var{end-addr} is specified as a non-zero value, and
17625 @var{lines} is lower than the number of disassembly lines between
17626 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
17627 displayed; if @var{lines} is higher than the number of lines between
17628 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
17631 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
17635 @subsubheading Result
17637 The output for each instruction is composed of four fields:
17646 Note that whatever included in the instruction field, is not manipulated
17647 directely by @sc{gdb/mi}, i.e. it is not possible to adjust its format.
17649 @subsubheading @value{GDBN} Command
17651 There's no direct mapping from this command to the CLI.
17653 @subsubheading Example
17655 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
17659 -data-disassemble -s $pc -e "$pc + 20" -- 0
17662 @{address="0x000107c0",func-name="main",offset="4",
17663 inst="mov 2, %o0"@},
17664 @{address="0x000107c4",func-name="main",offset="8",
17665 inst="sethi %hi(0x11800), %o2"@},
17666 @{address="0x000107c8",func-name="main",offset="12",
17667 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
17668 @{address="0x000107cc",func-name="main",offset="16",
17669 inst="sethi %hi(0x11800), %o2"@},
17670 @{address="0x000107d0",func-name="main",offset="20",
17671 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
17675 Disassemble the whole @code{main} function. Line 32 is part of
17679 -data-disassemble -f basics.c -l 32 -- 0
17681 @{address="0x000107bc",func-name="main",offset="0",
17682 inst="save %sp, -112, %sp"@},
17683 @{address="0x000107c0",func-name="main",offset="4",
17684 inst="mov 2, %o0"@},
17685 @{address="0x000107c4",func-name="main",offset="8",
17686 inst="sethi %hi(0x11800), %o2"@},
17688 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
17689 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
17693 Disassemble 3 instructions from the start of @code{main}:
17697 -data-disassemble -f basics.c -l 32 -n 3 -- 0
17699 @{address="0x000107bc",func-name="main",offset="0",
17700 inst="save %sp, -112, %sp"@},
17701 @{address="0x000107c0",func-name="main",offset="4",
17702 inst="mov 2, %o0"@},
17703 @{address="0x000107c4",func-name="main",offset="8",
17704 inst="sethi %hi(0x11800), %o2"@}]
17708 Disassemble 3 instructions from the start of @code{main} in mixed mode:
17712 -data-disassemble -f basics.c -l 32 -n 3 -- 1
17714 src_and_asm_line=@{line="31",
17715 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
17716 testsuite/gdb.mi/basics.c",line_asm_insn=[
17717 @{address="0x000107bc",func-name="main",offset="0",
17718 inst="save %sp, -112, %sp"@}]@},
17719 src_and_asm_line=@{line="32",
17720 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
17721 testsuite/gdb.mi/basics.c",line_asm_insn=[
17722 @{address="0x000107c0",func-name="main",offset="4",
17723 inst="mov 2, %o0"@},
17724 @{address="0x000107c4",func-name="main",offset="8",
17725 inst="sethi %hi(0x11800), %o2"@}]@}]
17730 @subheading The @code{-data-evaluate-expression} Command
17731 @findex -data-evaluate-expression
17733 @subsubheading Synopsis
17736 -data-evaluate-expression @var{expr}
17739 Evaluate @var{expr} as an expression. The expression could contain an
17740 inferior function call. The function call will execute synchronously.
17741 If the expression contains spaces, it must be enclosed in double quotes.
17743 @subsubheading @value{GDBN} Command
17745 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
17746 @samp{call}. In @code{gdbtk} only, there's a corresponding
17747 @samp{gdb_eval} command.
17749 @subsubheading Example
17751 In the following example, the numbers that precede the commands are the
17752 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
17753 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
17757 211-data-evaluate-expression A
17760 311-data-evaluate-expression &A
17761 311^done,value="0xefffeb7c"
17763 411-data-evaluate-expression A+3
17766 511-data-evaluate-expression "A + 3"
17772 @subheading The @code{-data-list-changed-registers} Command
17773 @findex -data-list-changed-registers
17775 @subsubheading Synopsis
17778 -data-list-changed-registers
17781 Display a list of the registers that have changed.
17783 @subsubheading @value{GDBN} Command
17785 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
17786 has the corresponding command @samp{gdb_changed_register_list}.
17788 @subsubheading Example
17790 On a PPC MBX board:
17798 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
17799 args=[],file="try.c",fullname="/home/foo/bar/devo/myproject/try.c",line="5"@}
17801 -data-list-changed-registers
17802 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
17803 "10","11","13","14","15","16","17","18","19","20","21","22","23",
17804 "24","25","26","27","28","30","31","64","65","66","67","69"]
17809 @subheading The @code{-data-list-register-names} Command
17810 @findex -data-list-register-names
17812 @subsubheading Synopsis
17815 -data-list-register-names [ ( @var{regno} )+ ]
17818 Show a list of register names for the current target. If no arguments
17819 are given, it shows a list of the names of all the registers. If
17820 integer numbers are given as arguments, it will print a list of the
17821 names of the registers corresponding to the arguments. To ensure
17822 consistency between a register name and its number, the output list may
17823 include empty register names.
17825 @subsubheading @value{GDBN} Command
17827 @value{GDBN} does not have a command which corresponds to
17828 @samp{-data-list-register-names}. In @code{gdbtk} there is a
17829 corresponding command @samp{gdb_regnames}.
17831 @subsubheading Example
17833 For the PPC MBX board:
17836 -data-list-register-names
17837 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
17838 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
17839 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
17840 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
17841 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
17842 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
17843 "", "pc","ps","cr","lr","ctr","xer"]
17845 -data-list-register-names 1 2 3
17846 ^done,register-names=["r1","r2","r3"]
17850 @subheading The @code{-data-list-register-values} Command
17851 @findex -data-list-register-values
17853 @subsubheading Synopsis
17856 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
17859 Display the registers' contents. @var{fmt} is the format according to
17860 which the registers' contents are to be returned, followed by an optional
17861 list of numbers specifying the registers to display. A missing list of
17862 numbers indicates that the contents of all the registers must be returned.
17864 Allowed formats for @var{fmt} are:
17881 @subsubheading @value{GDBN} Command
17883 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
17884 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
17886 @subsubheading Example
17888 For a PPC MBX board (note: line breaks are for readability only, they
17889 don't appear in the actual output):
17893 -data-list-register-values r 64 65
17894 ^done,register-values=[@{number="64",value="0xfe00a300"@},
17895 @{number="65",value="0x00029002"@}]
17897 -data-list-register-values x
17898 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
17899 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
17900 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
17901 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
17902 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
17903 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
17904 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
17905 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
17906 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
17907 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
17908 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
17909 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
17910 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
17911 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
17912 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
17913 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
17914 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
17915 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
17916 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
17917 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
17918 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
17919 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
17920 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
17921 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
17922 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
17923 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
17924 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
17925 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
17926 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
17927 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
17928 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
17929 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
17930 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
17931 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
17932 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
17933 @{number="69",value="0x20002b03"@}]
17938 @subheading The @code{-data-read-memory} Command
17939 @findex -data-read-memory
17941 @subsubheading Synopsis
17944 -data-read-memory [ -o @var{byte-offset} ]
17945 @var{address} @var{word-format} @var{word-size}
17946 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
17953 @item @var{address}
17954 An expression specifying the address of the first memory word to be
17955 read. Complex expressions containing embedded white space should be
17956 quoted using the C convention.
17958 @item @var{word-format}
17959 The format to be used to print the memory words. The notation is the
17960 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
17963 @item @var{word-size}
17964 The size of each memory word in bytes.
17966 @item @var{nr-rows}
17967 The number of rows in the output table.
17969 @item @var{nr-cols}
17970 The number of columns in the output table.
17973 If present, indicates that each row should include an @sc{ascii} dump. The
17974 value of @var{aschar} is used as a padding character when a byte is not a
17975 member of the printable @sc{ascii} character set (printable @sc{ascii}
17976 characters are those whose code is between 32 and 126, inclusively).
17978 @item @var{byte-offset}
17979 An offset to add to the @var{address} before fetching memory.
17982 This command displays memory contents as a table of @var{nr-rows} by
17983 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
17984 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
17985 (returned as @samp{total-bytes}). Should less than the requested number
17986 of bytes be returned by the target, the missing words are identified
17987 using @samp{N/A}. The number of bytes read from the target is returned
17988 in @samp{nr-bytes} and the starting address used to read memory in
17991 The address of the next/previous row or page is available in
17992 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
17995 @subsubheading @value{GDBN} Command
17997 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
17998 @samp{gdb_get_mem} memory read command.
18000 @subsubheading Example
18002 Read six bytes of memory starting at @code{bytes+6} but then offset by
18003 @code{-6} bytes. Format as three rows of two columns. One byte per
18004 word. Display each word in hex.
18008 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
18009 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
18010 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
18011 prev-page="0x0000138a",memory=[
18012 @{addr="0x00001390",data=["0x00","0x01"]@},
18013 @{addr="0x00001392",data=["0x02","0x03"]@},
18014 @{addr="0x00001394",data=["0x04","0x05"]@}]
18018 Read two bytes of memory starting at address @code{shorts + 64} and
18019 display as a single word formatted in decimal.
18023 5-data-read-memory shorts+64 d 2 1 1
18024 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
18025 next-row="0x00001512",prev-row="0x0000150e",
18026 next-page="0x00001512",prev-page="0x0000150e",memory=[
18027 @{addr="0x00001510",data=["128"]@}]
18031 Read thirty two bytes of memory starting at @code{bytes+16} and format
18032 as eight rows of four columns. Include a string encoding with @samp{x}
18033 used as the non-printable character.
18037 4-data-read-memory bytes+16 x 1 8 4 x
18038 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
18039 next-row="0x000013c0",prev-row="0x0000139c",
18040 next-page="0x000013c0",prev-page="0x00001380",memory=[
18041 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
18042 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
18043 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
18044 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
18045 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
18046 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
18047 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
18048 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
18052 @subheading The @code{-display-delete} Command
18053 @findex -display-delete
18055 @subsubheading Synopsis
18058 -display-delete @var{number}
18061 Delete the display @var{number}.
18063 @subsubheading @value{GDBN} Command
18065 The corresponding @value{GDBN} command is @samp{delete display}.
18067 @subsubheading Example
18071 @subheading The @code{-display-disable} Command
18072 @findex -display-disable
18074 @subsubheading Synopsis
18077 -display-disable @var{number}
18080 Disable display @var{number}.
18082 @subsubheading @value{GDBN} Command
18084 The corresponding @value{GDBN} command is @samp{disable display}.
18086 @subsubheading Example
18090 @subheading The @code{-display-enable} Command
18091 @findex -display-enable
18093 @subsubheading Synopsis
18096 -display-enable @var{number}
18099 Enable display @var{number}.
18101 @subsubheading @value{GDBN} Command
18103 The corresponding @value{GDBN} command is @samp{enable display}.
18105 @subsubheading Example
18109 @subheading The @code{-display-insert} Command
18110 @findex -display-insert
18112 @subsubheading Synopsis
18115 -display-insert @var{expression}
18118 Display @var{expression} every time the program stops.
18120 @subsubheading @value{GDBN} Command
18122 The corresponding @value{GDBN} command is @samp{display}.
18124 @subsubheading Example
18128 @subheading The @code{-display-list} Command
18129 @findex -display-list
18131 @subsubheading Synopsis
18137 List the displays. Do not show the current values.
18139 @subsubheading @value{GDBN} Command
18141 The corresponding @value{GDBN} command is @samp{info display}.
18143 @subsubheading Example
18147 @subheading The @code{-environment-cd} Command
18148 @findex -environment-cd
18150 @subsubheading Synopsis
18153 -environment-cd @var{pathdir}
18156 Set @value{GDBN}'s working directory.
18158 @subsubheading @value{GDBN} Command
18160 The corresponding @value{GDBN} command is @samp{cd}.
18162 @subsubheading Example
18166 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18172 @subheading The @code{-environment-directory} Command
18173 @findex -environment-directory
18175 @subsubheading Synopsis
18178 -environment-directory [ -r ] [ @var{pathdir} ]+
18181 Add directories @var{pathdir} to beginning of search path for source files.
18182 If the @samp{-r} option is used, the search path is reset to the default
18183 search path. If directories @var{pathdir} are supplied in addition to the
18184 @samp{-r} option, the search path is first reset and then addition
18186 Multiple directories may be specified, separated by blanks. Specifying
18187 multiple directories in a single command
18188 results in the directories added to the beginning of the
18189 search path in the same order they were presented in the command.
18190 If blanks are needed as
18191 part of a directory name, double-quotes should be used around
18192 the name. In the command output, the path will show up separated
18193 by the system directory-separator character. The directory-seperator
18194 character must not be used
18195 in any directory name.
18196 If no directories are specified, the current search path is displayed.
18198 @subsubheading @value{GDBN} Command
18200 The corresponding @value{GDBN} command is @samp{dir}.
18202 @subsubheading Example
18206 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18207 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18209 -environment-directory ""
18210 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18212 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
18213 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
18215 -environment-directory -r
18216 ^done,source-path="$cdir:$cwd"
18221 @subheading The @code{-environment-path} Command
18222 @findex -environment-path
18224 @subsubheading Synopsis
18227 -environment-path [ -r ] [ @var{pathdir} ]+
18230 Add directories @var{pathdir} to beginning of search path for object files.
18231 If the @samp{-r} option is used, the search path is reset to the original
18232 search path that existed at gdb start-up. If directories @var{pathdir} are
18233 supplied in addition to the
18234 @samp{-r} option, the search path is first reset and then addition
18236 Multiple directories may be specified, separated by blanks. Specifying
18237 multiple directories in a single command
18238 results in the directories added to the beginning of the
18239 search path in the same order they were presented in the command.
18240 If blanks are needed as
18241 part of a directory name, double-quotes should be used around
18242 the name. In the command output, the path will show up separated
18243 by the system directory-separator character. The directory-seperator
18244 character must not be used
18245 in any directory name.
18246 If no directories are specified, the current path is displayed.
18249 @subsubheading @value{GDBN} Command
18251 The corresponding @value{GDBN} command is @samp{path}.
18253 @subsubheading Example
18258 ^done,path="/usr/bin"
18260 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
18261 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
18263 -environment-path -r /usr/local/bin
18264 ^done,path="/usr/local/bin:/usr/bin"
18269 @subheading The @code{-environment-pwd} Command
18270 @findex -environment-pwd
18272 @subsubheading Synopsis
18278 Show the current working directory.
18280 @subsubheading @value{GDBN} command
18282 The corresponding @value{GDBN} command is @samp{pwd}.
18284 @subsubheading Example
18289 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
18293 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18294 @node GDB/MI Program Control
18295 @section @sc{gdb/mi} Program control
18297 @subsubheading Program termination
18299 As a result of execution, the inferior program can run to completion, if
18300 it doesn't encounter any breakpoints. In this case the output will
18301 include an exit code, if the program has exited exceptionally.
18303 @subsubheading Examples
18306 Program exited normally:
18314 *stopped,reason="exited-normally"
18319 Program exited exceptionally:
18327 *stopped,reason="exited",exit-code="01"
18331 Another way the program can terminate is if it receives a signal such as
18332 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
18336 *stopped,reason="exited-signalled",signal-name="SIGINT",
18337 signal-meaning="Interrupt"
18341 @subheading The @code{-exec-abort} Command
18342 @findex -exec-abort
18344 @subsubheading Synopsis
18350 Kill the inferior running program.
18352 @subsubheading @value{GDBN} Command
18354 The corresponding @value{GDBN} command is @samp{kill}.
18356 @subsubheading Example
18360 @subheading The @code{-exec-arguments} Command
18361 @findex -exec-arguments
18363 @subsubheading Synopsis
18366 -exec-arguments @var{args}
18369 Set the inferior program arguments, to be used in the next
18372 @subsubheading @value{GDBN} Command
18374 The corresponding @value{GDBN} command is @samp{set args}.
18376 @subsubheading Example
18379 Don't have one around.
18382 @subheading The @code{-exec-continue} Command
18383 @findex -exec-continue
18385 @subsubheading Synopsis
18391 Asynchronous command. Resumes the execution of the inferior program
18392 until a breakpoint is encountered, or until the inferior exits.
18394 @subsubheading @value{GDBN} Command
18396 The corresponding @value{GDBN} corresponding is @samp{continue}.
18398 @subsubheading Example
18405 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
18406 file="hello.c",fullname="/home/foo/bar/devo/myproject/hello.c",line="13"@}
18411 @subheading The @code{-exec-finish} Command
18412 @findex -exec-finish
18414 @subsubheading Synopsis
18420 Asynchronous command. Resumes the execution of the inferior program
18421 until the current function is exited. Displays the results returned by
18424 @subsubheading @value{GDBN} Command
18426 The corresponding @value{GDBN} command is @samp{finish}.
18428 @subsubheading Example
18430 Function returning @code{void}.
18437 *stopped,reason="function-finished",frame=@{func="main",args=[],
18438 file="hello.c",fullname="/home/foo/bar/devo/myproject/hello.c",line="7"@}
18442 Function returning other than @code{void}. The name of the internal
18443 @value{GDBN} variable storing the result is printed, together with the
18450 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
18451 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
18452 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
18453 gdb-result-var="$1",return-value="0"
18458 @subheading The @code{-exec-interrupt} Command
18459 @findex -exec-interrupt
18461 @subsubheading Synopsis
18467 Asynchronous command. Interrupts the background execution of the target.
18468 Note how the token associated with the stop message is the one for the
18469 execution command that has been interrupted. The token for the interrupt
18470 itself only appears in the @samp{^done} output. If the user is trying to
18471 interrupt a non-running program, an error message will be printed.
18473 @subsubheading @value{GDBN} Command
18475 The corresponding @value{GDBN} command is @samp{interrupt}.
18477 @subsubheading Example
18488 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
18489 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
18490 fullname="/home/foo/bar/devo/myproject/try.c",line="13"@}
18495 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
18500 @subheading The @code{-exec-next} Command
18503 @subsubheading Synopsis
18509 Asynchronous command. Resumes execution of the inferior program, stopping
18510 when the beginning of the next source line is reached.
18512 @subsubheading @value{GDBN} Command
18514 The corresponding @value{GDBN} command is @samp{next}.
18516 @subsubheading Example
18522 *stopped,reason="end-stepping-range",line="8",file="hello.c"
18527 @subheading The @code{-exec-next-instruction} Command
18528 @findex -exec-next-instruction
18530 @subsubheading Synopsis
18533 -exec-next-instruction
18536 Asynchronous command. Executes one machine instruction. If the
18537 instruction is a function call continues until the function returns. If
18538 the program stops at an instruction in the middle of a source line, the
18539 address will be printed as well.
18541 @subsubheading @value{GDBN} Command
18543 The corresponding @value{GDBN} command is @samp{nexti}.
18545 @subsubheading Example
18549 -exec-next-instruction
18553 *stopped,reason="end-stepping-range",
18554 addr="0x000100d4",line="5",file="hello.c"
18559 @subheading The @code{-exec-return} Command
18560 @findex -exec-return
18562 @subsubheading Synopsis
18568 Makes current function return immediately. Doesn't execute the inferior.
18569 Displays the new current frame.
18571 @subsubheading @value{GDBN} Command
18573 The corresponding @value{GDBN} command is @samp{return}.
18575 @subsubheading Example
18579 200-break-insert callee4
18580 200^done,bkpt=@{number="1",addr="0x00010734",
18581 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
18586 000*stopped,reason="breakpoint-hit",bkptno="1",
18587 frame=@{func="callee4",args=[],
18588 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18589 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
18595 111^done,frame=@{level="0",func="callee3",
18596 args=[@{name="strarg",
18597 value="0x11940 \"A string argument.\""@}],
18598 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18599 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18604 @subheading The @code{-exec-run} Command
18607 @subsubheading Synopsis
18613 Asynchronous command. Starts execution of the inferior from the
18614 beginning. The inferior executes until either a breakpoint is
18615 encountered or the program exits.
18617 @subsubheading @value{GDBN} Command
18619 The corresponding @value{GDBN} command is @samp{run}.
18621 @subsubheading Example
18626 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
18631 *stopped,reason="breakpoint-hit",bkptno="1",
18632 frame=@{func="main",args=[],file="recursive2.c",
18633 fullname="/home/foo/bar/devo/myproject/recursive2.c",line="4"@}
18638 @subheading The @code{-exec-show-arguments} Command
18639 @findex -exec-show-arguments
18641 @subsubheading Synopsis
18644 -exec-show-arguments
18647 Print the arguments of the program.
18649 @subsubheading @value{GDBN} Command
18651 The corresponding @value{GDBN} command is @samp{show args}.
18653 @subsubheading Example
18656 @c @subheading -exec-signal
18658 @subheading The @code{-exec-step} Command
18661 @subsubheading Synopsis
18667 Asynchronous command. Resumes execution of the inferior program, stopping
18668 when the beginning of the next source line is reached, if the next
18669 source line is not a function call. If it is, stop at the first
18670 instruction of the called function.
18672 @subsubheading @value{GDBN} Command
18674 The corresponding @value{GDBN} command is @samp{step}.
18676 @subsubheading Example
18678 Stepping into a function:
18684 *stopped,reason="end-stepping-range",
18685 frame=@{func="foo",args=[@{name="a",value="10"@},
18686 @{name="b",value="0"@}],file="recursive2.c",
18687 fullname="/home/foo/bar/devo/myproject/recursive2.c",line="11"@}
18697 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
18702 @subheading The @code{-exec-step-instruction} Command
18703 @findex -exec-step-instruction
18705 @subsubheading Synopsis
18708 -exec-step-instruction
18711 Asynchronous command. Resumes the inferior which executes one machine
18712 instruction. The output, once @value{GDBN} has stopped, will vary depending on
18713 whether we have stopped in the middle of a source line or not. In the
18714 former case, the address at which the program stopped will be printed as
18717 @subsubheading @value{GDBN} Command
18719 The corresponding @value{GDBN} command is @samp{stepi}.
18721 @subsubheading Example
18725 -exec-step-instruction
18729 *stopped,reason="end-stepping-range",
18730 frame=@{func="foo",args=[],file="try.c",
18731 fullname="/home/foo/bar/devo/myproject/try.c",line="10"@}
18733 -exec-step-instruction
18737 *stopped,reason="end-stepping-range",
18738 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
18739 fullname="/home/foo/bar/devo/myproject/try.c",line="10"@}
18744 @subheading The @code{-exec-until} Command
18745 @findex -exec-until
18747 @subsubheading Synopsis
18750 -exec-until [ @var{location} ]
18753 Asynchronous command. Executes the inferior until the @var{location}
18754 specified in the argument is reached. If there is no argument, the inferior
18755 executes until a source line greater than the current one is reached.
18756 The reason for stopping in this case will be @samp{location-reached}.
18758 @subsubheading @value{GDBN} Command
18760 The corresponding @value{GDBN} command is @samp{until}.
18762 @subsubheading Example
18766 -exec-until recursive2.c:6
18770 *stopped,reason="location-reached",frame=@{func="main",args=[],
18771 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="6"@}
18776 @subheading -file-clear
18777 Is this going away????
18781 @subheading The @code{-file-exec-and-symbols} Command
18782 @findex -file-exec-and-symbols
18784 @subsubheading Synopsis
18787 -file-exec-and-symbols @var{file}
18790 Specify the executable file to be debugged. This file is the one from
18791 which the symbol table is also read. If no file is specified, the
18792 command clears the executable and symbol information. If breakpoints
18793 are set when using this command with no arguments, @value{GDBN} will produce
18794 error messages. Otherwise, no output is produced, except a completion
18797 @subsubheading @value{GDBN} Command
18799 The corresponding @value{GDBN} command is @samp{file}.
18801 @subsubheading Example
18805 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
18811 @subheading The @code{-file-exec-file} Command
18812 @findex -file-exec-file
18814 @subsubheading Synopsis
18817 -file-exec-file @var{file}
18820 Specify the executable file to be debugged. Unlike
18821 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
18822 from this file. If used without argument, @value{GDBN} clears the information
18823 about the executable file. No output is produced, except a completion
18826 @subsubheading @value{GDBN} Command
18828 The corresponding @value{GDBN} command is @samp{exec-file}.
18830 @subsubheading Example
18834 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
18840 @subheading The @code{-file-list-exec-sections} Command
18841 @findex -file-list-exec-sections
18843 @subsubheading Synopsis
18846 -file-list-exec-sections
18849 List the sections of the current executable file.
18851 @subsubheading @value{GDBN} Command
18853 The @value{GDBN} command @samp{info file} shows, among the rest, the same
18854 information as this command. @code{gdbtk} has a corresponding command
18855 @samp{gdb_load_info}.
18857 @subsubheading Example
18861 @subheading The @code{-file-list-exec-source-file} Command
18862 @findex -file-list-exec-source-file
18864 @subsubheading Synopsis
18867 -file-list-exec-source-file
18870 List the line number, the current source file, and the absolute path
18871 to the current source file for the current executable.
18873 @subsubheading @value{GDBN} Command
18875 There's no @value{GDBN} command which directly corresponds to this one.
18877 @subsubheading Example
18881 123-file-list-exec-source-file
18882 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
18887 @subheading The @code{-file-list-exec-source-files} Command
18888 @findex -file-list-exec-source-files
18890 @subsubheading Synopsis
18893 -file-list-exec-source-files
18896 List the source files for the current executable.
18898 It will always output the filename, but only when GDB can find the absolute
18899 file name of a source file, will it output the fullname.
18901 @subsubheading @value{GDBN} Command
18903 There's no @value{GDBN} command which directly corresponds to this one.
18904 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
18906 @subsubheading Example
18909 -file-list-exec-source-files
18911 @{file=foo.c,fullname=/home/foo.c@},
18912 @{file=/home/bar.c,fullname=/home/bar.c@},
18913 @{file=gdb_could_not_find_fullpath.c@}]
18917 @subheading The @code{-file-list-shared-libraries} Command
18918 @findex -file-list-shared-libraries
18920 @subsubheading Synopsis
18923 -file-list-shared-libraries
18926 List the shared libraries in the program.
18928 @subsubheading @value{GDBN} Command
18930 The corresponding @value{GDBN} command is @samp{info shared}.
18932 @subsubheading Example
18936 @subheading The @code{-file-list-symbol-files} Command
18937 @findex -file-list-symbol-files
18939 @subsubheading Synopsis
18942 -file-list-symbol-files
18947 @subsubheading @value{GDBN} Command
18949 The corresponding @value{GDBN} command is @samp{info file} (part of it).
18951 @subsubheading Example
18955 @subheading The @code{-file-symbol-file} Command
18956 @findex -file-symbol-file
18958 @subsubheading Synopsis
18961 -file-symbol-file @var{file}
18964 Read symbol table info from the specified @var{file} argument. When
18965 used without arguments, clears @value{GDBN}'s symbol table info. No output is
18966 produced, except for a completion notification.
18968 @subsubheading @value{GDBN} Command
18970 The corresponding @value{GDBN} command is @samp{symbol-file}.
18972 @subsubheading Example
18976 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
18981 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18982 @node GDB/MI Miscellaneous Commands
18983 @section Miscellaneous @value{GDBN} commands in @sc{gdb/mi}
18985 @c @subheading -gdb-complete
18987 @subheading The @code{-gdb-exit} Command
18990 @subsubheading Synopsis
18996 Exit @value{GDBN} immediately.
18998 @subsubheading @value{GDBN} Command
19000 Approximately corresponds to @samp{quit}.
19002 @subsubheading Example
19009 @subheading The @code{-gdb-set} Command
19012 @subsubheading Synopsis
19018 Set an internal @value{GDBN} variable.
19019 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
19021 @subsubheading @value{GDBN} Command
19023 The corresponding @value{GDBN} command is @samp{set}.
19025 @subsubheading Example
19035 @subheading The @code{-gdb-show} Command
19038 @subsubheading Synopsis
19044 Show the current value of a @value{GDBN} variable.
19046 @subsubheading @value{GDBN} command
19048 The corresponding @value{GDBN} command is @samp{show}.
19050 @subsubheading Example
19059 @c @subheading -gdb-source
19062 @subheading The @code{-gdb-version} Command
19063 @findex -gdb-version
19065 @subsubheading Synopsis
19071 Show version information for @value{GDBN}. Used mostly in testing.
19073 @subsubheading @value{GDBN} Command
19075 There's no equivalent @value{GDBN} command. @value{GDBN} by default shows this
19076 information when you start an interactive session.
19078 @subsubheading Example
19080 @c This example modifies the actual output from GDB to avoid overfull
19086 ~Copyright 2000 Free Software Foundation, Inc.
19087 ~GDB is free software, covered by the GNU General Public License, and
19088 ~you are welcome to change it and/or distribute copies of it under
19089 ~ certain conditions.
19090 ~Type "show copying" to see the conditions.
19091 ~There is absolutely no warranty for GDB. Type "show warranty" for
19093 ~This GDB was configured as
19094 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
19099 @subheading The @code{-interpreter-exec} Command
19100 @findex -interpreter-exec
19102 @subheading Synopsis
19105 -interpreter-exec @var{interpreter} @var{command}
19108 Execute the specified @var{command} in the given @var{interpreter}.
19110 @subheading @value{GDBN} Command
19112 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
19114 @subheading Example
19118 -interpreter-exec console "break main"
19119 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
19120 &"During symbol reading, bad structure-type format.\n"
19121 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
19126 @subheading The @code{-inferior-tty-set} Command
19127 @findex -inferior-tty-set
19129 @subheading Synopsis
19132 -inferior-tty-set /dev/pts/1
19135 Set terminal for future runs of the program being debugged.
19137 @subheading @value{GDBN} Command
19139 The corresponding @value{GDBN} command is @samp{set inferior-tty /dev/pts/1}.
19141 @subheading Example
19145 -inferior-tty-set /dev/pts/1
19150 @subheading The @code{-inferior-tty-show} Command
19151 @findex -inferior-tty-show
19153 @subheading Synopsis
19159 Show terminal for future runs of program being debugged.
19161 @subheading @value{GDBN} Command
19163 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
19165 @subheading Example
19169 -inferior-tty-set /dev/pts/1
19173 ^done,inferior_tty_terminal="/dev/pts/1"
19178 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19179 @node GDB/MI Kod Commands
19180 @section @sc{gdb/mi} Kod Commands
19182 The Kod commands are not implemented.
19184 @c @subheading -kod-info
19186 @c @subheading -kod-list
19188 @c @subheading -kod-list-object-types
19190 @c @subheading -kod-show
19192 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19193 @node GDB/MI Memory Overlay Commands
19194 @section @sc{gdb/mi} Memory Overlay Commands
19196 The memory overlay commands are not implemented.
19198 @c @subheading -overlay-auto
19200 @c @subheading -overlay-list-mapping-state
19202 @c @subheading -overlay-list-overlays
19204 @c @subheading -overlay-map
19206 @c @subheading -overlay-off
19208 @c @subheading -overlay-on
19210 @c @subheading -overlay-unmap
19212 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19213 @node GDB/MI Signal Handling Commands
19214 @section @sc{gdb/mi} Signal Handling Commands
19216 Signal handling commands are not implemented.
19218 @c @subheading -signal-handle
19220 @c @subheading -signal-list-handle-actions
19222 @c @subheading -signal-list-signal-types
19226 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19227 @node GDB/MI Stack Manipulation
19228 @section @sc{gdb/mi} Stack Manipulation Commands
19231 @subheading The @code{-stack-info-frame} Command
19232 @findex -stack-info-frame
19234 @subsubheading Synopsis
19240 Get info on the selected frame.
19242 @subsubheading @value{GDBN} Command
19244 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
19245 (without arguments).
19247 @subsubheading Example
19252 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
19253 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19254 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
19258 @subheading The @code{-stack-info-depth} Command
19259 @findex -stack-info-depth
19261 @subsubheading Synopsis
19264 -stack-info-depth [ @var{max-depth} ]
19267 Return the depth of the stack. If the integer argument @var{max-depth}
19268 is specified, do not count beyond @var{max-depth} frames.
19270 @subsubheading @value{GDBN} Command
19272 There's no equivalent @value{GDBN} command.
19274 @subsubheading Example
19276 For a stack with frame levels 0 through 11:
19283 -stack-info-depth 4
19286 -stack-info-depth 12
19289 -stack-info-depth 11
19292 -stack-info-depth 13
19297 @subheading The @code{-stack-list-arguments} Command
19298 @findex -stack-list-arguments
19300 @subsubheading Synopsis
19303 -stack-list-arguments @var{show-values}
19304 [ @var{low-frame} @var{high-frame} ]
19307 Display a list of the arguments for the frames between @var{low-frame}
19308 and @var{high-frame} (inclusive). If @var{low-frame} and
19309 @var{high-frame} are not provided, list the arguments for the whole call
19312 The @var{show-values} argument must have a value of 0 or 1. A value of
19313 0 means that only the names of the arguments are listed, a value of 1
19314 means that both names and values of the arguments are printed.
19316 @subsubheading @value{GDBN} Command
19318 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
19319 @samp{gdb_get_args} command which partially overlaps with the
19320 functionality of @samp{-stack-list-arguments}.
19322 @subsubheading Example
19329 frame=@{level="0",addr="0x00010734",func="callee4",
19330 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19331 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
19332 frame=@{level="1",addr="0x0001076c",func="callee3",
19333 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19334 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
19335 frame=@{level="2",addr="0x0001078c",func="callee2",
19336 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19337 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
19338 frame=@{level="3",addr="0x000107b4",func="callee1",
19339 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19340 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
19341 frame=@{level="4",addr="0x000107e0",func="main",
19342 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19343 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
19345 -stack-list-arguments 0
19348 frame=@{level="0",args=[]@},
19349 frame=@{level="1",args=[name="strarg"]@},
19350 frame=@{level="2",args=[name="intarg",name="strarg"]@},
19351 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
19352 frame=@{level="4",args=[]@}]
19354 -stack-list-arguments 1
19357 frame=@{level="0",args=[]@},
19359 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19360 frame=@{level="2",args=[
19361 @{name="intarg",value="2"@},
19362 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19363 @{frame=@{level="3",args=[
19364 @{name="intarg",value="2"@},
19365 @{name="strarg",value="0x11940 \"A string argument.\""@},
19366 @{name="fltarg",value="3.5"@}]@},
19367 frame=@{level="4",args=[]@}]
19369 -stack-list-arguments 0 2 2
19370 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
19372 -stack-list-arguments 1 2 2
19373 ^done,stack-args=[frame=@{level="2",
19374 args=[@{name="intarg",value="2"@},
19375 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
19379 @c @subheading -stack-list-exception-handlers
19382 @subheading The @code{-stack-list-frames} Command
19383 @findex -stack-list-frames
19385 @subsubheading Synopsis
19388 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
19391 List the frames currently on the stack. For each frame it displays the
19396 The frame number, 0 being the topmost frame, i.e. the innermost function.
19398 The @code{$pc} value for that frame.
19402 File name of the source file where the function lives.
19404 Line number corresponding to the @code{$pc}.
19407 If invoked without arguments, this command prints a backtrace for the
19408 whole stack. If given two integer arguments, it shows the frames whose
19409 levels are between the two arguments (inclusive). If the two arguments
19410 are equal, it shows the single frame at the corresponding level.
19412 @subsubheading @value{GDBN} Command
19414 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
19416 @subsubheading Example
19418 Full stack backtrace:
19424 [frame=@{level="0",addr="0x0001076c",func="foo",
19425 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="11"@},
19426 frame=@{level="1",addr="0x000107a4",func="foo",
19427 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19428 frame=@{level="2",addr="0x000107a4",func="foo",
19429 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19430 frame=@{level="3",addr="0x000107a4",func="foo",
19431 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19432 frame=@{level="4",addr="0x000107a4",func="foo",
19433 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19434 frame=@{level="5",addr="0x000107a4",func="foo",
19435 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19436 frame=@{level="6",addr="0x000107a4",func="foo",
19437 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19438 frame=@{level="7",addr="0x000107a4",func="foo",
19439 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19440 frame=@{level="8",addr="0x000107a4",func="foo",
19441 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19442 frame=@{level="9",addr="0x000107a4",func="foo",
19443 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19444 frame=@{level="10",addr="0x000107a4",func="foo",
19445 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19446 frame=@{level="11",addr="0x00010738",func="main",
19447 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="4"@}]
19451 Show frames between @var{low_frame} and @var{high_frame}:
19455 -stack-list-frames 3 5
19457 [frame=@{level="3",addr="0x000107a4",func="foo",
19458 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19459 frame=@{level="4",addr="0x000107a4",func="foo",
19460 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19461 frame=@{level="5",addr="0x000107a4",func="foo",
19462 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@}]
19466 Show a single frame:
19470 -stack-list-frames 3 3
19472 [frame=@{level="3",addr="0x000107a4",func="foo",
19473 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@}]
19478 @subheading The @code{-stack-list-locals} Command
19479 @findex -stack-list-locals
19481 @subsubheading Synopsis
19484 -stack-list-locals @var{print-values}
19487 Display the local variable names for the selected frame. If
19488 @var{print-values} is 0 or @code{--no-values}, print only the names of
19489 the variables; if it is 1 or @code{--all-values}, print also their
19490 values; and if it is 2 or @code{--simple-values}, print the name,
19491 type and value for simple data types and the name and type for arrays,
19492 structures and unions. In this last case, a frontend can immediately
19493 display the value of simple data types and create variable objects for
19494 other data types when the the user wishes to explore their values in
19497 @subsubheading @value{GDBN} Command
19499 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
19501 @subsubheading Example
19505 -stack-list-locals 0
19506 ^done,locals=[name="A",name="B",name="C"]
19508 -stack-list-locals --all-values
19509 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
19510 @{name="C",value="@{1, 2, 3@}"@}]
19511 -stack-list-locals --simple-values
19512 ^done,locals=[@{name="A",type="int",value="1"@},
19513 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
19518 @subheading The @code{-stack-select-frame} Command
19519 @findex -stack-select-frame
19521 @subsubheading Synopsis
19524 -stack-select-frame @var{framenum}
19527 Change the selected frame. Select a different frame @var{framenum} on
19530 @subsubheading @value{GDBN} Command
19532 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
19533 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
19535 @subsubheading Example
19539 -stack-select-frame 2
19544 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19545 @node GDB/MI Symbol Query
19546 @section @sc{gdb/mi} Symbol Query Commands
19549 @subheading The @code{-symbol-info-address} Command
19550 @findex -symbol-info-address
19552 @subsubheading Synopsis
19555 -symbol-info-address @var{symbol}
19558 Describe where @var{symbol} is stored.
19560 @subsubheading @value{GDBN} Command
19562 The corresponding @value{GDBN} command is @samp{info address}.
19564 @subsubheading Example
19568 @subheading The @code{-symbol-info-file} Command
19569 @findex -symbol-info-file
19571 @subsubheading Synopsis
19577 Show the file for the symbol.
19579 @subsubheading @value{GDBN} Command
19581 There's no equivalent @value{GDBN} command. @code{gdbtk} has
19582 @samp{gdb_find_file}.
19584 @subsubheading Example
19588 @subheading The @code{-symbol-info-function} Command
19589 @findex -symbol-info-function
19591 @subsubheading Synopsis
19594 -symbol-info-function
19597 Show which function the symbol lives in.
19599 @subsubheading @value{GDBN} Command
19601 @samp{gdb_get_function} in @code{gdbtk}.
19603 @subsubheading Example
19607 @subheading The @code{-symbol-info-line} Command
19608 @findex -symbol-info-line
19610 @subsubheading Synopsis
19616 Show the core addresses of the code for a source line.
19618 @subsubheading @value{GDBN} Command
19620 The corresponding @value{GDBN} command is @samp{info line}.
19621 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
19623 @subsubheading Example
19627 @subheading The @code{-symbol-info-symbol} Command
19628 @findex -symbol-info-symbol
19630 @subsubheading Synopsis
19633 -symbol-info-symbol @var{addr}
19636 Describe what symbol is at location @var{addr}.
19638 @subsubheading @value{GDBN} Command
19640 The corresponding @value{GDBN} command is @samp{info symbol}.
19642 @subsubheading Example
19646 @subheading The @code{-symbol-list-functions} Command
19647 @findex -symbol-list-functions
19649 @subsubheading Synopsis
19652 -symbol-list-functions
19655 List the functions in the executable.
19657 @subsubheading @value{GDBN} Command
19659 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
19660 @samp{gdb_search} in @code{gdbtk}.
19662 @subsubheading Example
19666 @subheading The @code{-symbol-list-lines} Command
19667 @findex -symbol-list-lines
19669 @subsubheading Synopsis
19672 -symbol-list-lines @var{filename}
19675 Print the list of lines that contain code and their associated program
19676 addresses for the given source filename. The entries are sorted in
19677 ascending PC order.
19679 @subsubheading @value{GDBN} Command
19681 There is no corresponding @value{GDBN} command.
19683 @subsubheading Example
19686 -symbol-list-lines basics.c
19687 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
19692 @subheading The @code{-symbol-list-types} Command
19693 @findex -symbol-list-types
19695 @subsubheading Synopsis
19701 List all the type names.
19703 @subsubheading @value{GDBN} Command
19705 The corresponding commands are @samp{info types} in @value{GDBN},
19706 @samp{gdb_search} in @code{gdbtk}.
19708 @subsubheading Example
19712 @subheading The @code{-symbol-list-variables} Command
19713 @findex -symbol-list-variables
19715 @subsubheading Synopsis
19718 -symbol-list-variables
19721 List all the global and static variable names.
19723 @subsubheading @value{GDBN} Command
19725 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
19727 @subsubheading Example
19731 @subheading The @code{-symbol-locate} Command
19732 @findex -symbol-locate
19734 @subsubheading Synopsis
19740 @subsubheading @value{GDBN} Command
19742 @samp{gdb_loc} in @code{gdbtk}.
19744 @subsubheading Example
19748 @subheading The @code{-symbol-type} Command
19749 @findex -symbol-type
19751 @subsubheading Synopsis
19754 -symbol-type @var{variable}
19757 Show type of @var{variable}.
19759 @subsubheading @value{GDBN} Command
19761 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
19762 @samp{gdb_obj_variable}.
19764 @subsubheading Example
19768 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19769 @node GDB/MI Target Manipulation
19770 @section @sc{gdb/mi} Target Manipulation Commands
19773 @subheading The @code{-target-attach} Command
19774 @findex -target-attach
19776 @subsubheading Synopsis
19779 -target-attach @var{pid} | @var{file}
19782 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
19784 @subsubheading @value{GDBN} command
19786 The corresponding @value{GDBN} command is @samp{attach}.
19788 @subsubheading Example
19792 @subheading The @code{-target-compare-sections} Command
19793 @findex -target-compare-sections
19795 @subsubheading Synopsis
19798 -target-compare-sections [ @var{section} ]
19801 Compare data of section @var{section} on target to the exec file.
19802 Without the argument, all sections are compared.
19804 @subsubheading @value{GDBN} Command
19806 The @value{GDBN} equivalent is @samp{compare-sections}.
19808 @subsubheading Example
19812 @subheading The @code{-target-detach} Command
19813 @findex -target-detach
19815 @subsubheading Synopsis
19821 Disconnect from the remote target. There's no output.
19823 @subsubheading @value{GDBN} command
19825 The corresponding @value{GDBN} command is @samp{detach}.
19827 @subsubheading Example
19837 @subheading The @code{-target-disconnect} Command
19838 @findex -target-disconnect
19840 @subsubheading Synopsis
19846 Disconnect from the remote target. There's no output.
19848 @subsubheading @value{GDBN} command
19850 The corresponding @value{GDBN} command is @samp{disconnect}.
19852 @subsubheading Example
19862 @subheading The @code{-target-download} Command
19863 @findex -target-download
19865 @subsubheading Synopsis
19871 Loads the executable onto the remote target.
19872 It prints out an update message every half second, which includes the fields:
19876 The name of the section.
19878 The size of what has been sent so far for that section.
19880 The size of the section.
19882 The total size of what was sent so far (the current and the previous sections).
19884 The size of the overall executable to download.
19888 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
19889 @sc{gdb/mi} Output Syntax}).
19891 In addition, it prints the name and size of the sections, as they are
19892 downloaded. These messages include the following fields:
19896 The name of the section.
19898 The size of the section.
19900 The size of the overall executable to download.
19904 At the end, a summary is printed.
19906 @subsubheading @value{GDBN} Command
19908 The corresponding @value{GDBN} command is @samp{load}.
19910 @subsubheading Example
19912 Note: each status message appears on a single line. Here the messages
19913 have been broken down so that they can fit onto a page.
19918 +download,@{section=".text",section-size="6668",total-size="9880"@}
19919 +download,@{section=".text",section-sent="512",section-size="6668",
19920 total-sent="512",total-size="9880"@}
19921 +download,@{section=".text",section-sent="1024",section-size="6668",
19922 total-sent="1024",total-size="9880"@}
19923 +download,@{section=".text",section-sent="1536",section-size="6668",
19924 total-sent="1536",total-size="9880"@}
19925 +download,@{section=".text",section-sent="2048",section-size="6668",
19926 total-sent="2048",total-size="9880"@}
19927 +download,@{section=".text",section-sent="2560",section-size="6668",
19928 total-sent="2560",total-size="9880"@}
19929 +download,@{section=".text",section-sent="3072",section-size="6668",
19930 total-sent="3072",total-size="9880"@}
19931 +download,@{section=".text",section-sent="3584",section-size="6668",
19932 total-sent="3584",total-size="9880"@}
19933 +download,@{section=".text",section-sent="4096",section-size="6668",
19934 total-sent="4096",total-size="9880"@}
19935 +download,@{section=".text",section-sent="4608",section-size="6668",
19936 total-sent="4608",total-size="9880"@}
19937 +download,@{section=".text",section-sent="5120",section-size="6668",
19938 total-sent="5120",total-size="9880"@}
19939 +download,@{section=".text",section-sent="5632",section-size="6668",
19940 total-sent="5632",total-size="9880"@}
19941 +download,@{section=".text",section-sent="6144",section-size="6668",
19942 total-sent="6144",total-size="9880"@}
19943 +download,@{section=".text",section-sent="6656",section-size="6668",
19944 total-sent="6656",total-size="9880"@}
19945 +download,@{section=".init",section-size="28",total-size="9880"@}
19946 +download,@{section=".fini",section-size="28",total-size="9880"@}
19947 +download,@{section=".data",section-size="3156",total-size="9880"@}
19948 +download,@{section=".data",section-sent="512",section-size="3156",
19949 total-sent="7236",total-size="9880"@}
19950 +download,@{section=".data",section-sent="1024",section-size="3156",
19951 total-sent="7748",total-size="9880"@}
19952 +download,@{section=".data",section-sent="1536",section-size="3156",
19953 total-sent="8260",total-size="9880"@}
19954 +download,@{section=".data",section-sent="2048",section-size="3156",
19955 total-sent="8772",total-size="9880"@}
19956 +download,@{section=".data",section-sent="2560",section-size="3156",
19957 total-sent="9284",total-size="9880"@}
19958 +download,@{section=".data",section-sent="3072",section-size="3156",
19959 total-sent="9796",total-size="9880"@}
19960 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
19966 @subheading The @code{-target-exec-status} Command
19967 @findex -target-exec-status
19969 @subsubheading Synopsis
19972 -target-exec-status
19975 Provide information on the state of the target (whether it is running or
19976 not, for instance).
19978 @subsubheading @value{GDBN} Command
19980 There's no equivalent @value{GDBN} command.
19982 @subsubheading Example
19986 @subheading The @code{-target-list-available-targets} Command
19987 @findex -target-list-available-targets
19989 @subsubheading Synopsis
19992 -target-list-available-targets
19995 List the possible targets to connect to.
19997 @subsubheading @value{GDBN} Command
19999 The corresponding @value{GDBN} command is @samp{help target}.
20001 @subsubheading Example
20005 @subheading The @code{-target-list-current-targets} Command
20006 @findex -target-list-current-targets
20008 @subsubheading Synopsis
20011 -target-list-current-targets
20014 Describe the current target.
20016 @subsubheading @value{GDBN} Command
20018 The corresponding information is printed by @samp{info file} (among
20021 @subsubheading Example
20025 @subheading The @code{-target-list-parameters} Command
20026 @findex -target-list-parameters
20028 @subsubheading Synopsis
20031 -target-list-parameters
20036 @subsubheading @value{GDBN} Command
20040 @subsubheading Example
20044 @subheading The @code{-target-select} Command
20045 @findex -target-select
20047 @subsubheading Synopsis
20050 -target-select @var{type} @var{parameters @dots{}}
20053 Connect @value{GDBN} to the remote target. This command takes two args:
20057 The type of target, for instance @samp{async}, @samp{remote}, etc.
20058 @item @var{parameters}
20059 Device names, host names and the like. @xref{Target Commands, ,
20060 Commands for managing targets}, for more details.
20063 The output is a connection notification, followed by the address at
20064 which the target program is, in the following form:
20067 ^connected,addr="@var{address}",func="@var{function name}",
20068 args=[@var{arg list}]
20071 @subsubheading @value{GDBN} Command
20073 The corresponding @value{GDBN} command is @samp{target}.
20075 @subsubheading Example
20079 -target-select async /dev/ttya
20080 ^connected,addr="0xfe00a300",func="??",args=[]
20084 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20085 @node GDB/MI Thread Commands
20086 @section @sc{gdb/mi} Thread Commands
20089 @subheading The @code{-thread-info} Command
20090 @findex -thread-info
20092 @subsubheading Synopsis
20098 @subsubheading @value{GDBN} command
20102 @subsubheading Example
20106 @subheading The @code{-thread-list-all-threads} Command
20107 @findex -thread-list-all-threads
20109 @subsubheading Synopsis
20112 -thread-list-all-threads
20115 @subsubheading @value{GDBN} Command
20117 The equivalent @value{GDBN} command is @samp{info threads}.
20119 @subsubheading Example
20123 @subheading The @code{-thread-list-ids} Command
20124 @findex -thread-list-ids
20126 @subsubheading Synopsis
20132 Produces a list of the currently known @value{GDBN} thread ids. At the
20133 end of the list it also prints the total number of such threads.
20135 @subsubheading @value{GDBN} Command
20137 Part of @samp{info threads} supplies the same information.
20139 @subsubheading Example
20141 No threads present, besides the main process:
20146 ^done,thread-ids=@{@},number-of-threads="0"
20156 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
20157 number-of-threads="3"
20162 @subheading The @code{-thread-select} Command
20163 @findex -thread-select
20165 @subsubheading Synopsis
20168 -thread-select @var{threadnum}
20171 Make @var{threadnum} the current thread. It prints the number of the new
20172 current thread, and the topmost frame for that thread.
20174 @subsubheading @value{GDBN} Command
20176 The corresponding @value{GDBN} command is @samp{thread}.
20178 @subsubheading Example
20185 *stopped,reason="end-stepping-range",thread-id="2",line="187",
20186 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
20190 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
20191 number-of-threads="3"
20194 ^done,new-thread-id="3",
20195 frame=@{level="0",func="vprintf",
20196 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
20197 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
20201 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20202 @node GDB/MI Tracepoint Commands
20203 @section @sc{gdb/mi} Tracepoint Commands
20205 The tracepoint commands are not yet implemented.
20207 @c @subheading -trace-actions
20209 @c @subheading -trace-delete
20211 @c @subheading -trace-disable
20213 @c @subheading -trace-dump
20215 @c @subheading -trace-enable
20217 @c @subheading -trace-exists
20219 @c @subheading -trace-find
20221 @c @subheading -trace-frame-number
20223 @c @subheading -trace-info
20225 @c @subheading -trace-insert
20227 @c @subheading -trace-list
20229 @c @subheading -trace-pass-count
20231 @c @subheading -trace-save
20233 @c @subheading -trace-start
20235 @c @subheading -trace-stop
20238 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20239 @node GDB/MI Variable Objects
20240 @section @sc{gdb/mi} Variable Objects
20243 @subheading Motivation for Variable Objects in @sc{gdb/mi}
20245 For the implementation of a variable debugger window (locals, watched
20246 expressions, etc.), we are proposing the adaptation of the existing code
20247 used by @code{Insight}.
20249 The two main reasons for that are:
20253 It has been proven in practice (it is already on its second generation).
20256 It will shorten development time (needless to say how important it is
20260 The original interface was designed to be used by Tcl code, so it was
20261 slightly changed so it could be used through @sc{gdb/mi}. This section
20262 describes the @sc{gdb/mi} operations that will be available and gives some
20263 hints about their use.
20265 @emph{Note}: In addition to the set of operations described here, we
20266 expect the @sc{gui} implementation of a variable window to require, at
20267 least, the following operations:
20270 @item @code{-gdb-show} @code{output-radix}
20271 @item @code{-stack-list-arguments}
20272 @item @code{-stack-list-locals}
20273 @item @code{-stack-select-frame}
20276 @subheading Introduction to Variable Objects in @sc{gdb/mi}
20278 @cindex variable objects in @sc{gdb/mi}
20279 The basic idea behind variable objects is the creation of a named object
20280 to represent a variable, an expression, a memory location or even a CPU
20281 register. For each object created, a set of operations is available for
20282 examining or changing its properties.
20284 Furthermore, complex data types, such as C structures, are represented
20285 in a tree format. For instance, the @code{struct} type variable is the
20286 root and the children will represent the struct members. If a child
20287 is itself of a complex type, it will also have children of its own.
20288 Appropriate language differences are handled for C, C@t{++} and Java.
20290 When returning the actual values of the objects, this facility allows
20291 for the individual selection of the display format used in the result
20292 creation. It can be chosen among: binary, decimal, hexadecimal, octal
20293 and natural. Natural refers to a default format automatically
20294 chosen based on the variable type (like decimal for an @code{int}, hex
20295 for pointers, etc.).
20297 The following is the complete set of @sc{gdb/mi} operations defined to
20298 access this functionality:
20300 @multitable @columnfractions .4 .6
20301 @item @strong{Operation}
20302 @tab @strong{Description}
20304 @item @code{-var-create}
20305 @tab create a variable object
20306 @item @code{-var-delete}
20307 @tab delete the variable object and its children
20308 @item @code{-var-set-format}
20309 @tab set the display format of this variable
20310 @item @code{-var-show-format}
20311 @tab show the display format of this variable
20312 @item @code{-var-info-num-children}
20313 @tab tells how many children this object has
20314 @item @code{-var-list-children}
20315 @tab return a list of the object's children
20316 @item @code{-var-info-type}
20317 @tab show the type of this variable object
20318 @item @code{-var-info-expression}
20319 @tab print what this variable object represents
20320 @item @code{-var-show-attributes}
20321 @tab is this variable editable? does it exist here?
20322 @item @code{-var-evaluate-expression}
20323 @tab get the value of this variable
20324 @item @code{-var-assign}
20325 @tab set the value of this variable
20326 @item @code{-var-update}
20327 @tab update the variable and its children
20330 In the next subsection we describe each operation in detail and suggest
20331 how it can be used.
20333 @subheading Description And Use of Operations on Variable Objects
20335 @subheading The @code{-var-create} Command
20336 @findex -var-create
20338 @subsubheading Synopsis
20341 -var-create @{@var{name} | "-"@}
20342 @{@var{frame-addr} | "*"@} @var{expression}
20345 This operation creates a variable object, which allows the monitoring of
20346 a variable, the result of an expression, a memory cell or a CPU
20349 The @var{name} parameter is the string by which the object can be
20350 referenced. It must be unique. If @samp{-} is specified, the varobj
20351 system will generate a string ``varNNNNNN'' automatically. It will be
20352 unique provided that one does not specify @var{name} on that format.
20353 The command fails if a duplicate name is found.
20355 The frame under which the expression should be evaluated can be
20356 specified by @var{frame-addr}. A @samp{*} indicates that the current
20357 frame should be used.
20359 @var{expression} is any expression valid on the current language set (must not
20360 begin with a @samp{*}), or one of the following:
20364 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
20367 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
20370 @samp{$@var{regname}} --- a CPU register name
20373 @subsubheading Result
20375 This operation returns the name, number of children and the type of the
20376 object created. Type is returned as a string as the ones generated by
20377 the @value{GDBN} CLI:
20380 name="@var{name}",numchild="N",type="@var{type}"
20384 @subheading The @code{-var-delete} Command
20385 @findex -var-delete
20387 @subsubheading Synopsis
20390 -var-delete @var{name}
20393 Deletes a previously created variable object and all of its children.
20395 Returns an error if the object @var{name} is not found.
20398 @subheading The @code{-var-set-format} Command
20399 @findex -var-set-format
20401 @subsubheading Synopsis
20404 -var-set-format @var{name} @var{format-spec}
20407 Sets the output format for the value of the object @var{name} to be
20410 The syntax for the @var{format-spec} is as follows:
20413 @var{format-spec} @expansion{}
20414 @{binary | decimal | hexadecimal | octal | natural@}
20418 @subheading The @code{-var-show-format} Command
20419 @findex -var-show-format
20421 @subsubheading Synopsis
20424 -var-show-format @var{name}
20427 Returns the format used to display the value of the object @var{name}.
20430 @var{format} @expansion{}
20435 @subheading The @code{-var-info-num-children} Command
20436 @findex -var-info-num-children
20438 @subsubheading Synopsis
20441 -var-info-num-children @var{name}
20444 Returns the number of children of a variable object @var{name}:
20451 @subheading The @code{-var-list-children} Command
20452 @findex -var-list-children
20454 @subsubheading Synopsis
20457 -var-list-children [@var{print-values}] @var{name}
20459 @anchor{-var-list-children}
20461 Return a list of the children of the specified variable object and
20462 create variable objects for them, if they do not already exist. With
20463 a single argument or if @var{print-values} has a value for of 0 or
20464 @code{--no-values}, print only the names of the variables; if
20465 @var{print-values} is 1 or @code{--all-values}, also print their
20466 values; and if it is 2 or @code{--simple-values} print the name and
20467 value for simple data types and just the name for arrays, structures
20470 @subsubheading Example
20474 -var-list-children n
20475 ^done,numchild=@var{n},children=[@{name=@var{name},
20476 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
20478 -var-list-children --all-values n
20479 ^done,numchild=@var{n},children=[@{name=@var{name},
20480 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
20484 @subheading The @code{-var-info-type} Command
20485 @findex -var-info-type
20487 @subsubheading Synopsis
20490 -var-info-type @var{name}
20493 Returns the type of the specified variable @var{name}. The type is
20494 returned as a string in the same format as it is output by the
20498 type=@var{typename}
20502 @subheading The @code{-var-info-expression} Command
20503 @findex -var-info-expression
20505 @subsubheading Synopsis
20508 -var-info-expression @var{name}
20511 Returns what is represented by the variable object @var{name}:
20514 lang=@var{lang-spec},exp=@var{expression}
20518 where @var{lang-spec} is @code{@{"C" | "C++" | "Java"@}}.
20520 @subheading The @code{-var-show-attributes} Command
20521 @findex -var-show-attributes
20523 @subsubheading Synopsis
20526 -var-show-attributes @var{name}
20529 List attributes of the specified variable object @var{name}:
20532 status=@var{attr} [ ( ,@var{attr} )* ]
20536 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
20538 @subheading The @code{-var-evaluate-expression} Command
20539 @findex -var-evaluate-expression
20541 @subsubheading Synopsis
20544 -var-evaluate-expression @var{name}
20547 Evaluates the expression that is represented by the specified variable
20548 object and returns its value as a string in the current format specified
20555 Note that one must invoke @code{-var-list-children} for a variable
20556 before the value of a child variable can be evaluated.
20558 @subheading The @code{-var-assign} Command
20559 @findex -var-assign
20561 @subsubheading Synopsis
20564 -var-assign @var{name} @var{expression}
20567 Assigns the value of @var{expression} to the variable object specified
20568 by @var{name}. The object must be @samp{editable}. If the variable's
20569 value is altered by the assign, the variable will show up in any
20570 subsequent @code{-var-update} list.
20572 @subsubheading Example
20580 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
20584 @subheading The @code{-var-update} Command
20585 @findex -var-update
20587 @subsubheading Synopsis
20590 -var-update [@var{print-values}] @{@var{name} | "*"@}
20593 Update the value of the variable object @var{name} by evaluating its
20594 expression after fetching all the new values from memory or registers.
20595 A @samp{*} causes all existing variable objects to be updated. The
20596 option @var{print-values} determines whether names and values, or just
20597 names are printed in the manner described for
20598 @code{@pxref{-var-list-children}}.
20600 @subsubheading Example
20607 -var-update --all-values var1
20608 ^done,changelist=[@{name="var1",value="3",in_scope="true",
20609 type_changed="false"@}]
20614 @chapter @value{GDBN} Annotations
20616 This chapter describes annotations in @value{GDBN}. Annotations were
20617 designed to interface @value{GDBN} to graphical user interfaces or other
20618 similar programs which want to interact with @value{GDBN} at a
20619 relatively high level.
20621 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
20625 This is Edition @value{EDITION}, @value{DATE}.
20629 * Annotations Overview:: What annotations are; the general syntax.
20630 * Prompting:: Annotations marking @value{GDBN}'s need for input.
20631 * Errors:: Annotations for error messages.
20632 * Invalidation:: Some annotations describe things now invalid.
20633 * Annotations for Running::
20634 Whether the program is running, how it stopped, etc.
20635 * Source Annotations:: Annotations describing source code.
20638 @node Annotations Overview
20639 @section What is an Annotation?
20640 @cindex annotations
20642 Annotations start with a newline character, two @samp{control-z}
20643 characters, and the name of the annotation. If there is no additional
20644 information associated with this annotation, the name of the annotation
20645 is followed immediately by a newline. If there is additional
20646 information, the name of the annotation is followed by a space, the
20647 additional information, and a newline. The additional information
20648 cannot contain newline characters.
20650 Any output not beginning with a newline and two @samp{control-z}
20651 characters denotes literal output from @value{GDBN}. Currently there is
20652 no need for @value{GDBN} to output a newline followed by two
20653 @samp{control-z} characters, but if there was such a need, the
20654 annotations could be extended with an @samp{escape} annotation which
20655 means those three characters as output.
20657 The annotation @var{level}, which is specified using the
20658 @option{--annotate} command line option (@pxref{Mode Options}), controls
20659 how much information @value{GDBN} prints together with its prompt,
20660 values of expressions, source lines, and other types of output. Level 0
20661 is for no anntations, level 1 is for use when @value{GDBN} is run as a
20662 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
20663 for programs that control @value{GDBN}, and level 2 annotations have
20664 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
20665 Interface, annotate, GDB's Obsolete Annotations}).
20668 @kindex set annotate
20669 @item set annotate @var{level}
20670 The @value{GDBN} command @code{set annotate} sets the level of
20671 annotations to the specified @var{level}.
20673 @item show annotate
20674 @kindex show annotate
20675 Show the current annotation level.
20678 This chapter describes level 3 annotations.
20680 A simple example of starting up @value{GDBN} with annotations is:
20683 $ @kbd{gdb --annotate=3}
20685 Copyright 2003 Free Software Foundation, Inc.
20686 GDB is free software, covered by the GNU General Public License,
20687 and you are welcome to change it and/or distribute copies of it
20688 under certain conditions.
20689 Type "show copying" to see the conditions.
20690 There is absolutely no warranty for GDB. Type "show warranty"
20692 This GDB was configured as "i386-pc-linux-gnu"
20703 Here @samp{quit} is input to @value{GDBN}; the rest is output from
20704 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
20705 denotes a @samp{control-z} character) are annotations; the rest is
20706 output from @value{GDBN}.
20709 @section Annotation for @value{GDBN} Input
20711 @cindex annotations for prompts
20712 When @value{GDBN} prompts for input, it annotates this fact so it is possible
20713 to know when to send output, when the output from a given command is
20716 Different kinds of input each have a different @dfn{input type}. Each
20717 input type has three annotations: a @code{pre-} annotation, which
20718 denotes the beginning of any prompt which is being output, a plain
20719 annotation, which denotes the end of the prompt, and then a @code{post-}
20720 annotation which denotes the end of any echo which may (or may not) be
20721 associated with the input. For example, the @code{prompt} input type
20722 features the following annotations:
20730 The input types are
20735 @findex post-prompt
20737 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
20739 @findex pre-commands
20741 @findex post-commands
20743 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
20744 command. The annotations are repeated for each command which is input.
20746 @findex pre-overload-choice
20747 @findex overload-choice
20748 @findex post-overload-choice
20749 @item overload-choice
20750 When @value{GDBN} wants the user to select between various overloaded functions.
20756 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
20758 @findex pre-prompt-for-continue
20759 @findex prompt-for-continue
20760 @findex post-prompt-for-continue
20761 @item prompt-for-continue
20762 When @value{GDBN} is asking the user to press return to continue. Note: Don't
20763 expect this to work well; instead use @code{set height 0} to disable
20764 prompting. This is because the counting of lines is buggy in the
20765 presence of annotations.
20770 @cindex annotations for errors, warnings and interrupts
20777 This annotation occurs right before @value{GDBN} responds to an interrupt.
20784 This annotation occurs right before @value{GDBN} responds to an error.
20786 Quit and error annotations indicate that any annotations which @value{GDBN} was
20787 in the middle of may end abruptly. For example, if a
20788 @code{value-history-begin} annotation is followed by a @code{error}, one
20789 cannot expect to receive the matching @code{value-history-end}. One
20790 cannot expect not to receive it either, however; an error annotation
20791 does not necessarily mean that @value{GDBN} is immediately returning all the way
20794 @findex error-begin
20795 A quit or error annotation may be preceded by
20801 Any output between that and the quit or error annotation is the error
20804 Warning messages are not yet annotated.
20805 @c If we want to change that, need to fix warning(), type_error(),
20806 @c range_error(), and possibly other places.
20809 @section Invalidation Notices
20811 @cindex annotations for invalidation messages
20812 The following annotations say that certain pieces of state may have
20816 @findex frames-invalid
20817 @item ^Z^Zframes-invalid
20819 The frames (for example, output from the @code{backtrace} command) may
20822 @findex breakpoints-invalid
20823 @item ^Z^Zbreakpoints-invalid
20825 The breakpoints may have changed. For example, the user just added or
20826 deleted a breakpoint.
20829 @node Annotations for Running
20830 @section Running the Program
20831 @cindex annotations for running programs
20835 When the program starts executing due to a @value{GDBN} command such as
20836 @code{step} or @code{continue},
20842 is output. When the program stops,
20848 is output. Before the @code{stopped} annotation, a variety of
20849 annotations describe how the program stopped.
20853 @item ^Z^Zexited @var{exit-status}
20854 The program exited, and @var{exit-status} is the exit status (zero for
20855 successful exit, otherwise nonzero).
20858 @findex signal-name
20859 @findex signal-name-end
20860 @findex signal-string
20861 @findex signal-string-end
20862 @item ^Z^Zsignalled
20863 The program exited with a signal. After the @code{^Z^Zsignalled}, the
20864 annotation continues:
20870 ^Z^Zsignal-name-end
20874 ^Z^Zsignal-string-end
20879 where @var{name} is the name of the signal, such as @code{SIGILL} or
20880 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
20881 as @code{Illegal Instruction} or @code{Segmentation fault}.
20882 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
20883 user's benefit and have no particular format.
20887 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
20888 just saying that the program received the signal, not that it was
20889 terminated with it.
20892 @item ^Z^Zbreakpoint @var{number}
20893 The program hit breakpoint number @var{number}.
20896 @item ^Z^Zwatchpoint @var{number}
20897 The program hit watchpoint number @var{number}.
20900 @node Source Annotations
20901 @section Displaying Source
20902 @cindex annotations for source display
20905 The following annotation is used instead of displaying source code:
20908 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
20911 where @var{filename} is an absolute file name indicating which source
20912 file, @var{line} is the line number within that file (where 1 is the
20913 first line in the file), @var{character} is the character position
20914 within the file (where 0 is the first character in the file) (for most
20915 debug formats this will necessarily point to the beginning of a line),
20916 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
20917 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
20918 @var{addr} is the address in the target program associated with the
20919 source which is being displayed. @var{addr} is in the form @samp{0x}
20920 followed by one or more lowercase hex digits (note that this does not
20921 depend on the language).
20924 @chapter Reporting Bugs in @value{GDBN}
20925 @cindex bugs in @value{GDBN}
20926 @cindex reporting bugs in @value{GDBN}
20928 Your bug reports play an essential role in making @value{GDBN} reliable.
20930 Reporting a bug may help you by bringing a solution to your problem, or it
20931 may not. But in any case the principal function of a bug report is to help
20932 the entire community by making the next version of @value{GDBN} work better. Bug
20933 reports are your contribution to the maintenance of @value{GDBN}.
20935 In order for a bug report to serve its purpose, you must include the
20936 information that enables us to fix the bug.
20939 * Bug Criteria:: Have you found a bug?
20940 * Bug Reporting:: How to report bugs
20944 @section Have you found a bug?
20945 @cindex bug criteria
20947 If you are not sure whether you have found a bug, here are some guidelines:
20950 @cindex fatal signal
20951 @cindex debugger crash
20952 @cindex crash of debugger
20954 If the debugger gets a fatal signal, for any input whatever, that is a
20955 @value{GDBN} bug. Reliable debuggers never crash.
20957 @cindex error on valid input
20959 If @value{GDBN} produces an error message for valid input, that is a
20960 bug. (Note that if you're cross debugging, the problem may also be
20961 somewhere in the connection to the target.)
20963 @cindex invalid input
20965 If @value{GDBN} does not produce an error message for invalid input,
20966 that is a bug. However, you should note that your idea of
20967 ``invalid input'' might be our idea of ``an extension'' or ``support
20968 for traditional practice''.
20971 If you are an experienced user of debugging tools, your suggestions
20972 for improvement of @value{GDBN} are welcome in any case.
20975 @node Bug Reporting
20976 @section How to report bugs
20977 @cindex bug reports
20978 @cindex @value{GDBN} bugs, reporting
20980 A number of companies and individuals offer support for @sc{gnu} products.
20981 If you obtained @value{GDBN} from a support organization, we recommend you
20982 contact that organization first.
20984 You can find contact information for many support companies and
20985 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
20987 @c should add a web page ref...
20989 In any event, we also recommend that you submit bug reports for
20990 @value{GDBN}. The prefered method is to submit them directly using
20991 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
20992 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
20995 @strong{Do not send bug reports to @samp{info-gdb}, or to
20996 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
20997 not want to receive bug reports. Those that do have arranged to receive
21000 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
21001 serves as a repeater. The mailing list and the newsgroup carry exactly
21002 the same messages. Often people think of posting bug reports to the
21003 newsgroup instead of mailing them. This appears to work, but it has one
21004 problem which can be crucial: a newsgroup posting often lacks a mail
21005 path back to the sender. Thus, if we need to ask for more information,
21006 we may be unable to reach you. For this reason, it is better to send
21007 bug reports to the mailing list.
21009 The fundamental principle of reporting bugs usefully is this:
21010 @strong{report all the facts}. If you are not sure whether to state a
21011 fact or leave it out, state it!
21013 Often people omit facts because they think they know what causes the
21014 problem and assume that some details do not matter. Thus, you might
21015 assume that the name of the variable you use in an example does not matter.
21016 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
21017 stray memory reference which happens to fetch from the location where that
21018 name is stored in memory; perhaps, if the name were different, the contents
21019 of that location would fool the debugger into doing the right thing despite
21020 the bug. Play it safe and give a specific, complete example. That is the
21021 easiest thing for you to do, and the most helpful.
21023 Keep in mind that the purpose of a bug report is to enable us to fix the
21024 bug. It may be that the bug has been reported previously, but neither
21025 you nor we can know that unless your bug report is complete and
21028 Sometimes people give a few sketchy facts and ask, ``Does this ring a
21029 bell?'' Those bug reports are useless, and we urge everyone to
21030 @emph{refuse to respond to them} except to chide the sender to report
21033 To enable us to fix the bug, you should include all these things:
21037 The version of @value{GDBN}. @value{GDBN} announces it if you start
21038 with no arguments; you can also print it at any time using @code{show
21041 Without this, we will not know whether there is any point in looking for
21042 the bug in the current version of @value{GDBN}.
21045 The type of machine you are using, and the operating system name and
21049 What compiler (and its version) was used to compile @value{GDBN}---e.g.
21050 ``@value{GCC}--2.8.1''.
21053 What compiler (and its version) was used to compile the program you are
21054 debugging---e.g. ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
21055 C Compiler''. For GCC, you can say @code{gcc --version} to get this
21056 information; for other compilers, see the documentation for those
21060 The command arguments you gave the compiler to compile your example and
21061 observe the bug. For example, did you use @samp{-O}? To guarantee
21062 you will not omit something important, list them all. A copy of the
21063 Makefile (or the output from make) is sufficient.
21065 If we were to try to guess the arguments, we would probably guess wrong
21066 and then we might not encounter the bug.
21069 A complete input script, and all necessary source files, that will
21073 A description of what behavior you observe that you believe is
21074 incorrect. For example, ``It gets a fatal signal.''
21076 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
21077 will certainly notice it. But if the bug is incorrect output, we might
21078 not notice unless it is glaringly wrong. You might as well not give us
21079 a chance to make a mistake.
21081 Even if the problem you experience is a fatal signal, you should still
21082 say so explicitly. Suppose something strange is going on, such as, your
21083 copy of @value{GDBN} is out of synch, or you have encountered a bug in
21084 the C library on your system. (This has happened!) Your copy might
21085 crash and ours would not. If you told us to expect a crash, then when
21086 ours fails to crash, we would know that the bug was not happening for
21087 us. If you had not told us to expect a crash, then we would not be able
21088 to draw any conclusion from our observations.
21091 @cindex recording a session script
21092 To collect all this information, you can use a session recording program
21093 such as @command{script}, which is available on many Unix systems.
21094 Just run your @value{GDBN} session inside @command{script} and then
21095 include the @file{typescript} file with your bug report.
21097 Another way to record a @value{GDBN} session is to run @value{GDBN}
21098 inside Emacs and then save the entire buffer to a file.
21101 If you wish to suggest changes to the @value{GDBN} source, send us context
21102 diffs. If you even discuss something in the @value{GDBN} source, refer to
21103 it by context, not by line number.
21105 The line numbers in our development sources will not match those in your
21106 sources. Your line numbers would convey no useful information to us.
21110 Here are some things that are not necessary:
21114 A description of the envelope of the bug.
21116 Often people who encounter a bug spend a lot of time investigating
21117 which changes to the input file will make the bug go away and which
21118 changes will not affect it.
21120 This is often time consuming and not very useful, because the way we
21121 will find the bug is by running a single example under the debugger
21122 with breakpoints, not by pure deduction from a series of examples.
21123 We recommend that you save your time for something else.
21125 Of course, if you can find a simpler example to report @emph{instead}
21126 of the original one, that is a convenience for us. Errors in the
21127 output will be easier to spot, running under the debugger will take
21128 less time, and so on.
21130 However, simplification is not vital; if you do not want to do this,
21131 report the bug anyway and send us the entire test case you used.
21134 A patch for the bug.
21136 A patch for the bug does help us if it is a good one. But do not omit
21137 the necessary information, such as the test case, on the assumption that
21138 a patch is all we need. We might see problems with your patch and decide
21139 to fix the problem another way, or we might not understand it at all.
21141 Sometimes with a program as complicated as @value{GDBN} it is very hard to
21142 construct an example that will make the program follow a certain path
21143 through the code. If you do not send us the example, we will not be able
21144 to construct one, so we will not be able to verify that the bug is fixed.
21146 And if we cannot understand what bug you are trying to fix, or why your
21147 patch should be an improvement, we will not install it. A test case will
21148 help us to understand.
21151 A guess about what the bug is or what it depends on.
21153 Such guesses are usually wrong. Even we cannot guess right about such
21154 things without first using the debugger to find the facts.
21157 @c The readline documentation is distributed with the readline code
21158 @c and consists of the two following files:
21160 @c inc-hist.texinfo
21161 @c Use -I with makeinfo to point to the appropriate directory,
21162 @c environment var TEXINPUTS with TeX.
21163 @include rluser.texinfo
21164 @include inc-hist.texinfo
21167 @node Formatting Documentation
21168 @appendix Formatting Documentation
21170 @cindex @value{GDBN} reference card
21171 @cindex reference card
21172 The @value{GDBN} 4 release includes an already-formatted reference card, ready
21173 for printing with PostScript or Ghostscript, in the @file{gdb}
21174 subdirectory of the main source directory@footnote{In
21175 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
21176 release.}. If you can use PostScript or Ghostscript with your printer,
21177 you can print the reference card immediately with @file{refcard.ps}.
21179 The release also includes the source for the reference card. You
21180 can format it, using @TeX{}, by typing:
21186 The @value{GDBN} reference card is designed to print in @dfn{landscape}
21187 mode on US ``letter'' size paper;
21188 that is, on a sheet 11 inches wide by 8.5 inches
21189 high. You will need to specify this form of printing as an option to
21190 your @sc{dvi} output program.
21192 @cindex documentation
21194 All the documentation for @value{GDBN} comes as part of the machine-readable
21195 distribution. The documentation is written in Texinfo format, which is
21196 a documentation system that uses a single source file to produce both
21197 on-line information and a printed manual. You can use one of the Info
21198 formatting commands to create the on-line version of the documentation
21199 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
21201 @value{GDBN} includes an already formatted copy of the on-line Info
21202 version of this manual in the @file{gdb} subdirectory. The main Info
21203 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
21204 subordinate files matching @samp{gdb.info*} in the same directory. If
21205 necessary, you can print out these files, or read them with any editor;
21206 but they are easier to read using the @code{info} subsystem in @sc{gnu}
21207 Emacs or the standalone @code{info} program, available as part of the
21208 @sc{gnu} Texinfo distribution.
21210 If you want to format these Info files yourself, you need one of the
21211 Info formatting programs, such as @code{texinfo-format-buffer} or
21214 If you have @code{makeinfo} installed, and are in the top level
21215 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
21216 version @value{GDBVN}), you can make the Info file by typing:
21223 If you want to typeset and print copies of this manual, you need @TeX{},
21224 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
21225 Texinfo definitions file.
21227 @TeX{} is a typesetting program; it does not print files directly, but
21228 produces output files called @sc{dvi} files. To print a typeset
21229 document, you need a program to print @sc{dvi} files. If your system
21230 has @TeX{} installed, chances are it has such a program. The precise
21231 command to use depends on your system; @kbd{lpr -d} is common; another
21232 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
21233 require a file name without any extension or a @samp{.dvi} extension.
21235 @TeX{} also requires a macro definitions file called
21236 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
21237 written in Texinfo format. On its own, @TeX{} cannot either read or
21238 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
21239 and is located in the @file{gdb-@var{version-number}/texinfo}
21242 If you have @TeX{} and a @sc{dvi} printer program installed, you can
21243 typeset and print this manual. First switch to the the @file{gdb}
21244 subdirectory of the main source directory (for example, to
21245 @file{gdb-@value{GDBVN}/gdb}) and type:
21251 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
21253 @node Installing GDB
21254 @appendix Installing @value{GDBN}
21255 @cindex configuring @value{GDBN}
21256 @cindex installation
21257 @cindex configuring @value{GDBN}, and source tree subdirectories
21259 @value{GDBN} comes with a @code{configure} script that automates the process
21260 of preparing @value{GDBN} for installation; you can then use @code{make} to
21261 build the @code{gdb} program.
21263 @c irrelevant in info file; it's as current as the code it lives with.
21264 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
21265 look at the @file{README} file in the sources; we may have improved the
21266 installation procedures since publishing this manual.}
21269 The @value{GDBN} distribution includes all the source code you need for
21270 @value{GDBN} in a single directory, whose name is usually composed by
21271 appending the version number to @samp{gdb}.
21273 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
21274 @file{gdb-@value{GDBVN}} directory. That directory contains:
21277 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
21278 script for configuring @value{GDBN} and all its supporting libraries
21280 @item gdb-@value{GDBVN}/gdb
21281 the source specific to @value{GDBN} itself
21283 @item gdb-@value{GDBVN}/bfd
21284 source for the Binary File Descriptor library
21286 @item gdb-@value{GDBVN}/include
21287 @sc{gnu} include files
21289 @item gdb-@value{GDBVN}/libiberty
21290 source for the @samp{-liberty} free software library
21292 @item gdb-@value{GDBVN}/opcodes
21293 source for the library of opcode tables and disassemblers
21295 @item gdb-@value{GDBVN}/readline
21296 source for the @sc{gnu} command-line interface
21298 @item gdb-@value{GDBVN}/glob
21299 source for the @sc{gnu} filename pattern-matching subroutine
21301 @item gdb-@value{GDBVN}/mmalloc
21302 source for the @sc{gnu} memory-mapped malloc package
21305 The simplest way to configure and build @value{GDBN} is to run @code{configure}
21306 from the @file{gdb-@var{version-number}} source directory, which in
21307 this example is the @file{gdb-@value{GDBVN}} directory.
21309 First switch to the @file{gdb-@var{version-number}} source directory
21310 if you are not already in it; then run @code{configure}. Pass the
21311 identifier for the platform on which @value{GDBN} will run as an
21317 cd gdb-@value{GDBVN}
21318 ./configure @var{host}
21323 where @var{host} is an identifier such as @samp{sun4} or
21324 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
21325 (You can often leave off @var{host}; @code{configure} tries to guess the
21326 correct value by examining your system.)
21328 Running @samp{configure @var{host}} and then running @code{make} builds the
21329 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
21330 libraries, then @code{gdb} itself. The configured source files, and the
21331 binaries, are left in the corresponding source directories.
21334 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
21335 system does not recognize this automatically when you run a different
21336 shell, you may need to run @code{sh} on it explicitly:
21339 sh configure @var{host}
21342 If you run @code{configure} from a directory that contains source
21343 directories for multiple libraries or programs, such as the
21344 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
21345 creates configuration files for every directory level underneath (unless
21346 you tell it not to, with the @samp{--norecursion} option).
21348 You should run the @code{configure} script from the top directory in the
21349 source tree, the @file{gdb-@var{version-number}} directory. If you run
21350 @code{configure} from one of the subdirectories, you will configure only
21351 that subdirectory. That is usually not what you want. In particular,
21352 if you run the first @code{configure} from the @file{gdb} subdirectory
21353 of the @file{gdb-@var{version-number}} directory, you will omit the
21354 configuration of @file{bfd}, @file{readline}, and other sibling
21355 directories of the @file{gdb} subdirectory. This leads to build errors
21356 about missing include files such as @file{bfd/bfd.h}.
21358 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
21359 However, you should make sure that the shell on your path (named by
21360 the @samp{SHELL} environment variable) is publicly readable. Remember
21361 that @value{GDBN} uses the shell to start your program---some systems refuse to
21362 let @value{GDBN} debug child processes whose programs are not readable.
21365 * Separate Objdir:: Compiling @value{GDBN} in another directory
21366 * Config Names:: Specifying names for hosts and targets
21367 * Configure Options:: Summary of options for configure
21370 @node Separate Objdir
21371 @section Compiling @value{GDBN} in another directory
21373 If you want to run @value{GDBN} versions for several host or target machines,
21374 you need a different @code{gdb} compiled for each combination of
21375 host and target. @code{configure} is designed to make this easy by
21376 allowing you to generate each configuration in a separate subdirectory,
21377 rather than in the source directory. If your @code{make} program
21378 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
21379 @code{make} in each of these directories builds the @code{gdb}
21380 program specified there.
21382 To build @code{gdb} in a separate directory, run @code{configure}
21383 with the @samp{--srcdir} option to specify where to find the source.
21384 (You also need to specify a path to find @code{configure}
21385 itself from your working directory. If the path to @code{configure}
21386 would be the same as the argument to @samp{--srcdir}, you can leave out
21387 the @samp{--srcdir} option; it is assumed.)
21389 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
21390 separate directory for a Sun 4 like this:
21394 cd gdb-@value{GDBVN}
21397 ../gdb-@value{GDBVN}/configure sun4
21402 When @code{configure} builds a configuration using a remote source
21403 directory, it creates a tree for the binaries with the same structure
21404 (and using the same names) as the tree under the source directory. In
21405 the example, you'd find the Sun 4 library @file{libiberty.a} in the
21406 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
21407 @file{gdb-sun4/gdb}.
21409 Make sure that your path to the @file{configure} script has just one
21410 instance of @file{gdb} in it. If your path to @file{configure} looks
21411 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
21412 one subdirectory of @value{GDBN}, not the whole package. This leads to
21413 build errors about missing include files such as @file{bfd/bfd.h}.
21415 One popular reason to build several @value{GDBN} configurations in separate
21416 directories is to configure @value{GDBN} for cross-compiling (where
21417 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
21418 programs that run on another machine---the @dfn{target}).
21419 You specify a cross-debugging target by
21420 giving the @samp{--target=@var{target}} option to @code{configure}.
21422 When you run @code{make} to build a program or library, you must run
21423 it in a configured directory---whatever directory you were in when you
21424 called @code{configure} (or one of its subdirectories).
21426 The @code{Makefile} that @code{configure} generates in each source
21427 directory also runs recursively. If you type @code{make} in a source
21428 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
21429 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
21430 will build all the required libraries, and then build GDB.
21432 When you have multiple hosts or targets configured in separate
21433 directories, you can run @code{make} on them in parallel (for example,
21434 if they are NFS-mounted on each of the hosts); they will not interfere
21438 @section Specifying names for hosts and targets
21440 The specifications used for hosts and targets in the @code{configure}
21441 script are based on a three-part naming scheme, but some short predefined
21442 aliases are also supported. The full naming scheme encodes three pieces
21443 of information in the following pattern:
21446 @var{architecture}-@var{vendor}-@var{os}
21449 For example, you can use the alias @code{sun4} as a @var{host} argument,
21450 or as the value for @var{target} in a @code{--target=@var{target}}
21451 option. The equivalent full name is @samp{sparc-sun-sunos4}.
21453 The @code{configure} script accompanying @value{GDBN} does not provide
21454 any query facility to list all supported host and target names or
21455 aliases. @code{configure} calls the Bourne shell script
21456 @code{config.sub} to map abbreviations to full names; you can read the
21457 script, if you wish, or you can use it to test your guesses on
21458 abbreviations---for example:
21461 % sh config.sub i386-linux
21463 % sh config.sub alpha-linux
21464 alpha-unknown-linux-gnu
21465 % sh config.sub hp9k700
21467 % sh config.sub sun4
21468 sparc-sun-sunos4.1.1
21469 % sh config.sub sun3
21470 m68k-sun-sunos4.1.1
21471 % sh config.sub i986v
21472 Invalid configuration `i986v': machine `i986v' not recognized
21476 @code{config.sub} is also distributed in the @value{GDBN} source
21477 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
21479 @node Configure Options
21480 @section @code{configure} options
21482 Here is a summary of the @code{configure} options and arguments that
21483 are most often useful for building @value{GDBN}. @code{configure} also has
21484 several other options not listed here. @inforef{What Configure
21485 Does,,configure.info}, for a full explanation of @code{configure}.
21488 configure @r{[}--help@r{]}
21489 @r{[}--prefix=@var{dir}@r{]}
21490 @r{[}--exec-prefix=@var{dir}@r{]}
21491 @r{[}--srcdir=@var{dirname}@r{]}
21492 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
21493 @r{[}--target=@var{target}@r{]}
21498 You may introduce options with a single @samp{-} rather than
21499 @samp{--} if you prefer; but you may abbreviate option names if you use
21504 Display a quick summary of how to invoke @code{configure}.
21506 @item --prefix=@var{dir}
21507 Configure the source to install programs and files under directory
21510 @item --exec-prefix=@var{dir}
21511 Configure the source to install programs under directory
21514 @c avoid splitting the warning from the explanation:
21516 @item --srcdir=@var{dirname}
21517 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
21518 @code{make} that implements the @code{VPATH} feature.}@*
21519 Use this option to make configurations in directories separate from the
21520 @value{GDBN} source directories. Among other things, you can use this to
21521 build (or maintain) several configurations simultaneously, in separate
21522 directories. @code{configure} writes configuration specific files in
21523 the current directory, but arranges for them to use the source in the
21524 directory @var{dirname}. @code{configure} creates directories under
21525 the working directory in parallel to the source directories below
21528 @item --norecursion
21529 Configure only the directory level where @code{configure} is executed; do not
21530 propagate configuration to subdirectories.
21532 @item --target=@var{target}
21533 Configure @value{GDBN} for cross-debugging programs running on the specified
21534 @var{target}. Without this option, @value{GDBN} is configured to debug
21535 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
21537 There is no convenient way to generate a list of all available targets.
21539 @item @var{host} @dots{}
21540 Configure @value{GDBN} to run on the specified @var{host}.
21542 There is no convenient way to generate a list of all available hosts.
21545 There are many other options available as well, but they are generally
21546 needed for special purposes only.
21548 @node Maintenance Commands
21549 @appendix Maintenance Commands
21550 @cindex maintenance commands
21551 @cindex internal commands
21553 In addition to commands intended for @value{GDBN} users, @value{GDBN}
21554 includes a number of commands intended for @value{GDBN} developers,
21555 that are not documented elsewhere in this manual. These commands are
21556 provided here for reference. (For commands that turn on debugging
21557 messages, see @ref{Debugging Output}.)
21560 @kindex maint agent
21561 @item maint agent @var{expression}
21562 Translate the given @var{expression} into remote agent bytecodes.
21563 This command is useful for debugging the Agent Expression mechanism
21564 (@pxref{Agent Expressions}).
21566 @kindex maint info breakpoints
21567 @item @anchor{maint info breakpoints}maint info breakpoints
21568 Using the same format as @samp{info breakpoints}, display both the
21569 breakpoints you've set explicitly, and those @value{GDBN} is using for
21570 internal purposes. Internal breakpoints are shown with negative
21571 breakpoint numbers. The type column identifies what kind of breakpoint
21576 Normal, explicitly set breakpoint.
21579 Normal, explicitly set watchpoint.
21582 Internal breakpoint, used to handle correctly stepping through
21583 @code{longjmp} calls.
21585 @item longjmp resume
21586 Internal breakpoint at the target of a @code{longjmp}.
21589 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
21592 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
21595 Shared library events.
21599 @kindex maint check-symtabs
21600 @item maint check-symtabs
21601 Check the consistency of psymtabs and symtabs.
21603 @kindex maint cplus first_component
21604 @item maint cplus first_component @var{name}
21605 Print the first C@t{++} class/namespace component of @var{name}.
21607 @kindex maint cplus namespace
21608 @item maint cplus namespace
21609 Print the list of possible C@t{++} namespaces.
21611 @kindex maint demangle
21612 @item maint demangle @var{name}
21613 Demangle a C@t{++} or Objective-C manled @var{name}.
21615 @kindex maint deprecate
21616 @kindex maint undeprecate
21617 @cindex deprecated commands
21618 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
21619 @itemx maint undeprecate @var{command}
21620 Deprecate or undeprecate the named @var{command}. Deprecated commands
21621 cause @value{GDBN} to issue a warning when you use them. The optional
21622 argument @var{replacement} says which newer command should be used in
21623 favor of the deprecated one; if it is given, @value{GDBN} will mention
21624 the replacement as part of the warning.
21626 @kindex maint dump-me
21627 @item maint dump-me
21628 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
21629 Cause a fatal signal in the debugger and force it to dump its core.
21630 This is supported only on systems which support aborting a program
21631 with the @code{SIGQUIT} signal.
21633 @kindex maint internal-error
21634 @kindex maint internal-warning
21635 @item maint internal-error @r{[}@var{message-text}@r{]}
21636 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
21637 Cause @value{GDBN} to call the internal function @code{internal_error}
21638 or @code{internal_warning} and hence behave as though an internal error
21639 or internal warning has been detected. In addition to reporting the
21640 internal problem, these functions give the user the opportunity to
21641 either quit @value{GDBN} or create a core file of the current
21642 @value{GDBN} session.
21644 These commands take an optional parameter @var{message-text} that is
21645 used as the text of the error or warning message.
21647 Here's an example of using @code{indernal-error}:
21650 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
21651 @dots{}/maint.c:121: internal-error: testing, 1, 2
21652 A problem internal to GDB has been detected. Further
21653 debugging may prove unreliable.
21654 Quit this debugging session? (y or n) @kbd{n}
21655 Create a core file? (y or n) @kbd{n}
21659 @kindex maint packet
21660 @item maint packet @var{text}
21661 If @value{GDBN} is talking to an inferior via the serial protocol,
21662 then this command sends the string @var{text} to the inferior, and
21663 displays the response packet. @value{GDBN} supplies the initial
21664 @samp{$} character, the terminating @samp{#} character, and the
21667 @kindex maint print architecture
21668 @item maint print architecture @r{[}@var{file}@r{]}
21669 Print the entire architecture configuration. The optional argument
21670 @var{file} names the file where the output goes.
21672 @kindex maint print dummy-frames
21673 @item maint print dummy-frames
21674 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
21677 (@value{GDBP}) @kbd{b add}
21679 (@value{GDBP}) @kbd{print add(2,3)}
21680 Breakpoint 2, add (a=2, b=3) at @dots{}
21682 The program being debugged stopped while in a function called from GDB.
21684 (@value{GDBP}) @kbd{maint print dummy-frames}
21685 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
21686 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
21687 call_lo=0x01014000 call_hi=0x01014001
21691 Takes an optional file parameter.
21693 @kindex maint print registers
21694 @kindex maint print raw-registers
21695 @kindex maint print cooked-registers
21696 @kindex maint print register-groups
21697 @item maint print registers @r{[}@var{file}@r{]}
21698 @itemx maint print raw-registers @r{[}@var{file}@r{]}
21699 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
21700 @itemx maint print register-groups @r{[}@var{file}@r{]}
21701 Print @value{GDBN}'s internal register data structures.
21703 The command @code{maint print raw-registers} includes the contents of
21704 the raw register cache; the command @code{maint print cooked-registers}
21705 includes the (cooked) value of all registers; and the command
21706 @code{maint print register-groups} includes the groups that each
21707 register is a member of. @xref{Registers,, Registers, gdbint,
21708 @value{GDBN} Internals}.
21710 These commands take an optional parameter, a file name to which to
21711 write the information.
21713 @kindex maint print reggroups
21714 @item maint print reggroups @r{[}@var{file}@r{]}
21715 Print @value{GDBN}'s internal register group data structures. The
21716 optional argument @var{file} tells to what file to write the
21719 The register groups info looks like this:
21722 (@value{GDBP}) @kbd{maint print reggroups}
21735 This command forces @value{GDBN} to flush its internal register cache.
21737 @kindex maint print objfiles
21738 @cindex info for known object files
21739 @item maint print objfiles
21740 Print a dump of all known object files. For each object file, this
21741 command prints its name, address in memory, and all of its psymtabs
21744 @kindex maint print statistics
21745 @cindex bcache statistics
21746 @item maint print statistics
21747 This command prints, for each object file in the program, various data
21748 about that object file followed by the byte cache (@dfn{bcache})
21749 statistics for the object file. The objfile data includes the number
21750 of minimal, partical, full, and stabs symbols, the number of types
21751 defined by the objfile, the number of as yet unexpanded psym tables,
21752 the number of line tables and string tables, and the amount of memory
21753 used by the various tables. The bcache statistics include the counts,
21754 sizes, and counts of duplicates of all and unique objects, max,
21755 average, and median entry size, total memory used and its overhead and
21756 savings, and various measures of the hash table size and chain
21759 @kindex maint print type
21760 @cindex type chain of a data type
21761 @item maint print type @var{expr}
21762 Print the type chain for a type specified by @var{expr}. The argument
21763 can be either a type name or a symbol. If it is a symbol, the type of
21764 that symbol is described. The type chain produced by this command is
21765 a recursive definition of the data type as stored in @value{GDBN}'s
21766 data structures, including its flags and contained types.
21768 @kindex maint set dwarf2 max-cache-age
21769 @kindex maint show dwarf2 max-cache-age
21770 @item maint set dwarf2 max-cache-age
21771 @itemx maint show dwarf2 max-cache-age
21772 Control the DWARF 2 compilation unit cache.
21774 @cindex DWARF 2 compilation units cache
21775 In object files with inter-compilation-unit references, such as those
21776 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
21777 reader needs to frequently refer to previously read compilation units.
21778 This setting controls how long a compilation unit will remain in the
21779 cache if it is not referenced. A higher limit means that cached
21780 compilation units will be stored in memory longer, and more total
21781 memory will be used. Setting it to zero disables caching, which will
21782 slow down @value{GDBN} startup, but reduce memory consumption.
21784 @kindex maint set profile
21785 @kindex maint show profile
21786 @cindex profiling GDB
21787 @item maint set profile
21788 @itemx maint show profile
21789 Control profiling of @value{GDBN}.
21791 Profiling will be disabled until you use the @samp{maint set profile}
21792 command to enable it. When you enable profiling, the system will begin
21793 collecting timing and execution count data; when you disable profiling or
21794 exit @value{GDBN}, the results will be written to a log file. Remember that
21795 if you use profiling, @value{GDBN} will overwrite the profiling log file
21796 (often called @file{gmon.out}). If you have a record of important profiling
21797 data in a @file{gmon.out} file, be sure to move it to a safe location.
21799 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
21800 compiled with the @samp{-pg} compiler option.
21802 @kindex maint show-debug-regs
21803 @cindex x86 hardware debug registers
21804 @item maint show-debug-regs
21805 Control whether to show variables that mirror the x86 hardware debug
21806 registers. Use @code{ON} to enable, @code{OFF} to disable. If
21807 enabled, the debug registers values are shown when GDB inserts or
21808 removes a hardware breakpoint or watchpoint, and when the inferior
21809 triggers a hardware-assisted breakpoint or watchpoint.
21811 @kindex maint space
21812 @cindex memory used by commands
21814 Control whether to display memory usage for each command. If set to a
21815 nonzero value, @value{GDBN} will display how much memory each command
21816 took, following the command's own output. This can also be requested
21817 by invoking @value{GDBN} with the @option{--statistics} command-line
21818 switch (@pxref{Mode Options}).
21821 @cindex time of command execution
21823 Control whether to display the execution time for each command. If
21824 set to a nonzero value, @value{GDBN} will display how much time it
21825 took to execute each command, following the command's own output.
21826 This can also be requested by invoking @value{GDBN} with the
21827 @option{--statistics} command-line switch (@pxref{Mode Options}).
21829 @kindex maint translate-address
21830 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
21831 Find the symbol stored at the location specified by the address
21832 @var{addr} and an optional section name @var{section}. If found,
21833 @value{GDBN} prints the name of the closest symbol and an offset from
21834 the symbol's location to the specified address. This is similar to
21835 the @code{info address} command (@pxref{Symbols}), except that this
21836 command also allows to find symbols in other sections.
21840 The following command is useful for non-interactive invocations of
21841 @value{GDBN}, such as in the test suite.
21844 @item set watchdog @var{nsec}
21845 @kindex set watchdog
21846 @cindex watchdog timer
21847 @cindex timeout for commands
21848 Set the maximum number of seconds @value{GDBN} will wait for the
21849 target operation to finish. If this time expires, @value{GDBN}
21850 reports and error and the command is aborted.
21852 @item show watchdog
21853 Show the current setting of the target wait timeout.
21856 @node Remote Protocol
21857 @appendix @value{GDBN} Remote Serial Protocol
21862 * Stop Reply Packets::
21863 * General Query Packets::
21864 * Register Packet Format::
21866 * File-I/O remote protocol extension::
21872 There may be occasions when you need to know something about the
21873 protocol---for example, if there is only one serial port to your target
21874 machine, you might want your program to do something special if it
21875 recognizes a packet meant for @value{GDBN}.
21877 In the examples below, @samp{->} and @samp{<-} are used to indicate
21878 transmitted and received data respectfully.
21880 @cindex protocol, @value{GDBN} remote serial
21881 @cindex serial protocol, @value{GDBN} remote
21882 @cindex remote serial protocol
21883 All @value{GDBN} commands and responses (other than acknowledgments) are
21884 sent as a @var{packet}. A @var{packet} is introduced with the character
21885 @samp{$}, the actual @var{packet-data}, and the terminating character
21886 @samp{#} followed by a two-digit @var{checksum}:
21889 @code{$}@var{packet-data}@code{#}@var{checksum}
21893 @cindex checksum, for @value{GDBN} remote
21895 The two-digit @var{checksum} is computed as the modulo 256 sum of all
21896 characters between the leading @samp{$} and the trailing @samp{#} (an
21897 eight bit unsigned checksum).
21899 Implementors should note that prior to @value{GDBN} 5.0 the protocol
21900 specification also included an optional two-digit @var{sequence-id}:
21903 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
21906 @cindex sequence-id, for @value{GDBN} remote
21908 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
21909 has never output @var{sequence-id}s. Stubs that handle packets added
21910 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
21912 @cindex acknowledgment, for @value{GDBN} remote
21913 When either the host or the target machine receives a packet, the first
21914 response expected is an acknowledgment: either @samp{+} (to indicate
21915 the package was received correctly) or @samp{-} (to request
21919 -> @code{$}@var{packet-data}@code{#}@var{checksum}
21924 The host (@value{GDBN}) sends @var{command}s, and the target (the
21925 debugging stub incorporated in your program) sends a @var{response}. In
21926 the case of step and continue @var{command}s, the response is only sent
21927 when the operation has completed (the target has again stopped).
21929 @var{packet-data} consists of a sequence of characters with the
21930 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
21933 Fields within the packet should be separated using @samp{,} @samp{;} or
21934 @cindex remote protocol, field separator
21935 @samp{:}. Except where otherwise noted all numbers are represented in
21936 @sc{hex} with leading zeros suppressed.
21938 Implementors should note that prior to @value{GDBN} 5.0, the character
21939 @samp{:} could not appear as the third character in a packet (as it
21940 would potentially conflict with the @var{sequence-id}).
21942 Response @var{data} can be run-length encoded to save space. A @samp{*}
21943 means that the next character is an @sc{ascii} encoding giving a repeat count
21944 which stands for that many repetitions of the character preceding the
21945 @samp{*}. The encoding is @code{n+29}, yielding a printable character
21946 where @code{n >=3} (which is where rle starts to win). The printable
21947 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
21948 value greater than 126 should not be used.
21955 means the same as "0000".
21957 The error response returned for some packets includes a two character
21958 error number. That number is not well defined.
21960 For any @var{command} not supported by the stub, an empty response
21961 (@samp{$#00}) should be returned. That way it is possible to extend the
21962 protocol. A newer @value{GDBN} can tell if a packet is supported based
21965 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
21966 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
21972 The following table provides a complete list of all currently defined
21973 @var{command}s and their corresponding response @var{data}.
21974 @xref{File-I/O remote protocol extension}, for details about the File
21975 I/O extension of the remote protocol.
21979 @item @code{!} --- extended mode
21980 @cindex @code{!} packet
21982 Enable extended mode. In extended mode, the remote server is made
21983 persistent. The @samp{R} packet is used to restart the program being
21989 The remote target both supports and has enabled extended mode.
21992 @item @code{?} --- last signal
21993 @cindex @code{?} packet
21995 Indicate the reason the target halted. The reply is the same as for
21999 @xref{Stop Reply Packets}, for the reply specifications.
22001 @item @code{a} --- reserved
22003 Reserved for future use.
22005 @item @code{A}@var{arglen}@code{,}@var{argnum}@code{,}@var{arg}@code{,@dots{}} --- set program arguments @strong{(reserved)}
22006 @cindex @code{A} packet
22008 Initialized @samp{argv[]} array passed into program. @var{arglen}
22009 specifies the number of bytes in the hex encoded byte stream @var{arg}.
22010 See @code{gdbserver} for more details.
22018 @item @code{b}@var{baud} --- set baud @strong{(deprecated)}
22019 @cindex @code{b} packet
22021 Change the serial line speed to @var{baud}.
22023 JTC: @emph{When does the transport layer state change? When it's
22024 received, or after the ACK is transmitted. In either case, there are
22025 problems if the command or the acknowledgment packet is dropped.}
22027 Stan: @emph{If people really wanted to add something like this, and get
22028 it working for the first time, they ought to modify ser-unix.c to send
22029 some kind of out-of-band message to a specially-setup stub and have the
22030 switch happen "in between" packets, so that from remote protocol's point
22031 of view, nothing actually happened.}
22033 @item @code{B}@var{addr},@var{mode} --- set breakpoint @strong{(deprecated)}
22034 @cindex @code{B} packet
22036 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
22037 breakpoint at @var{addr}.
22039 This packet has been replaced by the @samp{Z} and @samp{z} packets
22040 (@pxref{insert breakpoint or watchpoint packet}).
22042 @item @code{c}@var{addr} --- continue
22043 @cindex @code{c} packet
22045 @var{addr} is address to resume. If @var{addr} is omitted, resume at
22049 @xref{Stop Reply Packets}, for the reply specifications.
22051 @item @code{C}@var{sig}@code{;}@var{addr} --- continue with signal
22052 @cindex @code{C} packet
22054 Continue with signal @var{sig} (hex signal number). If
22055 @code{;}@var{addr} is omitted, resume at same address.
22058 @xref{Stop Reply Packets}, for the reply specifications.
22060 @item @code{d} --- toggle debug @strong{(deprecated)}
22061 @cindex @code{d} packet
22065 @item @code{D} --- detach
22066 @cindex @code{D} packet
22068 Detach @value{GDBN} from the remote system. Sent to the remote target
22069 before @value{GDBN} disconnects via the @code{detach} command.
22079 @item @code{e} --- reserved
22081 Reserved for future use.
22083 @item @code{E} --- reserved
22085 Reserved for future use.
22087 @item @code{f} --- reserved
22089 Reserved for future use.
22091 @item @code{F}@var{RC}@code{,}@var{EE}@code{,}@var{CF}@code{;}@var{XX} --- Reply to target's F packet.
22092 @cindex @code{F} packet
22094 This packet is send by @value{GDBN} as reply to a @code{F} request packet
22095 sent by the target. This is part of the File-I/O protocol extension.
22096 @xref{File-I/O remote protocol extension}, for the specification.
22098 @item @code{g} --- read registers
22099 @anchor{read registers packet}
22100 @cindex @code{g} packet
22102 Read general registers.
22106 @item @var{XX@dots{}}
22107 Each byte of register data is described by two hex digits. The bytes
22108 with the register are transmitted in target byte order. The size of
22109 each register and their position within the @samp{g} @var{packet} are
22110 determined by the @value{GDBN} internal macros
22111 @var{DEPRECATED_REGISTER_RAW_SIZE} and @var{REGISTER_NAME} macros. The
22112 specification of several standard @code{g} packets is specified below.
22117 @item @code{G}@var{XX@dots{}} --- write regs
22118 @cindex @code{G} packet
22120 @xref{read registers packet}, for a description of the @var{XX@dots{}}
22131 @item @code{h} --- reserved
22133 Reserved for future use.
22135 @item @code{H}@var{c}@var{t@dots{}} --- set thread
22136 @cindex @code{H} packet
22138 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
22139 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
22140 should be @samp{c} for step and continue operations, @samp{g} for other
22141 operations. The thread designator @var{t@dots{}} may be -1, meaning all
22142 the threads, a thread number, or zero which means pick any thread.
22153 @c 'H': How restrictive (or permissive) is the thread model. If a
22154 @c thread is selected and stopped, are other threads allowed
22155 @c to continue to execute? As I mentioned above, I think the
22156 @c semantics of each command when a thread is selected must be
22157 @c described. For example:
22159 @c 'g': If the stub supports threads and a specific thread is
22160 @c selected, returns the register block from that thread;
22161 @c otherwise returns current registers.
22163 @c 'G' If the stub supports threads and a specific thread is
22164 @c selected, sets the registers of the register block of
22165 @c that thread; otherwise sets current registers.
22167 @item @code{i}@var{addr}@code{,}@var{nnn} --- cycle step @strong{(draft)}
22168 @anchor{cycle step packet}
22169 @cindex @code{i} packet
22171 Step the remote target by a single clock cycle. If @code{,}@var{nnn} is
22172 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
22173 step starting at that address.
22175 @item @code{I} --- signal then cycle step @strong{(reserved)}
22176 @cindex @code{I} packet
22178 @xref{step with signal packet}. @xref{cycle step packet}.
22180 @item @code{j} --- reserved
22182 Reserved for future use.
22184 @item @code{J} --- reserved
22186 Reserved for future use.
22188 @item @code{k} --- kill request
22189 @cindex @code{k} packet
22191 FIXME: @emph{There is no description of how to operate when a specific
22192 thread context has been selected (i.e.@: does 'k' kill only that
22195 @item @code{K} --- reserved
22197 Reserved for future use.
22199 @item @code{l} --- reserved
22201 Reserved for future use.
22203 @item @code{L} --- reserved
22205 Reserved for future use.
22207 @item @code{m}@var{addr}@code{,}@var{length} --- read memory
22208 @cindex @code{m} packet
22210 Read @var{length} bytes of memory starting at address @var{addr}.
22211 Neither @value{GDBN} nor the stub assume that sized memory transfers are
22212 assumed using word aligned accesses. FIXME: @emph{A word aligned memory
22213 transfer mechanism is needed.}
22217 @item @var{XX@dots{}}
22218 @var{XX@dots{}} is mem contents. Can be fewer bytes than requested if able
22219 to read only part of the data. Neither @value{GDBN} nor the stub assume
22220 that sized memory transfers are assumed using word aligned
22221 accesses. FIXME: @emph{A word aligned memory transfer mechanism is
22227 @item @code{M}@var{addr},@var{length}@code{:}@var{XX@dots{}} --- write mem
22228 @cindex @code{M} packet
22230 Write @var{length} bytes of memory starting at address @var{addr}.
22231 @var{XX@dots{}} is the data.
22238 for an error (this includes the case where only part of the data was
22242 @item @code{n} --- reserved
22244 Reserved for future use.
22246 @item @code{N} --- reserved
22248 Reserved for future use.
22250 @item @code{o} --- reserved
22252 Reserved for future use.
22254 @item @code{O} --- reserved
22256 @item @code{p}@var{hex number of register} --- read register packet
22257 @cindex @code{p} packet
22259 @xref{read registers packet}, for a description of how the returned
22260 register value is encoded.
22264 @item @var{XX@dots{}}
22265 the register's value
22269 Indicating an unrecognized @var{query}.
22272 @item @code{P}@var{n@dots{}}@code{=}@var{r@dots{}} --- write register
22273 @anchor{write register packet}
22274 @cindex @code{P} packet
22276 Write register @var{n@dots{}} with value @var{r@dots{}}, which contains two hex
22277 digits for each byte in the register (target byte order).
22287 @item @code{q}@var{query} --- general query
22288 @anchor{general query packet}
22289 @cindex @code{q} packet
22291 Request info about @var{query}. In general @value{GDBN} queries have a
22292 leading upper case letter. Custom vendor queries should use a company
22293 prefix (in lower case) ex: @samp{qfsf.var}. @var{query} may optionally
22294 be followed by a @samp{,} or @samp{;} separated list. Stubs must ensure
22295 that they match the full @var{query} name.
22299 @item @var{XX@dots{}}
22300 Hex encoded data from query. The reply can not be empty.
22304 Indicating an unrecognized @var{query}.
22307 @item @code{Q}@var{var}@code{=}@var{val} --- general set
22308 @cindex @code{Q} packet
22310 Set value of @var{var} to @var{val}.
22312 @xref{general query packet}, for a discussion of naming conventions.
22314 @item @code{r} --- reset @strong{(deprecated)}
22315 @cindex @code{r} packet
22317 Reset the entire system.
22319 @item @code{R}@var{XX} --- remote restart
22320 @cindex @code{R} packet
22322 Restart the program being debugged. @var{XX}, while needed, is ignored.
22323 This packet is only available in extended mode.
22327 @item @emph{no reply}
22328 The @samp{R} packet has no reply.
22331 @item @code{s}@var{addr} --- step
22332 @cindex @code{s} packet
22334 @var{addr} is address to resume. If @var{addr} is omitted, resume at
22338 @xref{Stop Reply Packets}, for the reply specifications.
22340 @item @code{S}@var{sig}@code{;}@var{addr} --- step with signal
22341 @anchor{step with signal packet}
22342 @cindex @code{S} packet
22344 Like @samp{C} but step not continue.
22347 @xref{Stop Reply Packets}, for the reply specifications.
22349 @item @code{t}@var{addr}@code{:}@var{PP}@code{,}@var{MM} --- search
22350 @cindex @code{t} packet
22352 Search backwards starting at address @var{addr} for a match with pattern
22353 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
22354 @var{addr} must be at least 3 digits.
22356 @item @code{T}@var{XX} --- thread alive
22357 @cindex @code{T} packet
22359 Find out if the thread XX is alive.
22364 thread is still alive
22369 @item @code{u} --- reserved
22371 Reserved for future use.
22373 @item @code{U} --- reserved
22375 Reserved for future use.
22377 @item @code{v} --- verbose packet prefix
22379 Packets starting with @code{v} are identified by a multi-letter name,
22380 up to the first @code{;} or @code{?} (or the end of the packet).
22382 @item @code{vCont}[;@var{action}[@code{:}@var{tid}]]... --- extended resume
22383 @cindex @code{vCont} packet
22385 Resume the inferior. Different actions may be specified for each thread.
22386 If an action is specified with no @var{tid}, then it is applied to any
22387 threads that don't have a specific action specified; if no default action is
22388 specified then other threads should remain stopped. Specifying multiple
22389 default actions is an error; specifying no actions is also an error.
22390 Thread IDs are specified in hexadecimal. Currently supported actions are:
22396 Continue with signal @var{sig}. @var{sig} should be two hex digits.
22400 Step with signal @var{sig}. @var{sig} should be two hex digits.
22403 The optional @var{addr} argument normally associated with these packets is
22404 not supported in @code{vCont}.
22407 @xref{Stop Reply Packets}, for the reply specifications.
22409 @item @code{vCont?} --- extended resume query
22410 @cindex @code{vCont?} packet
22412 Query support for the @code{vCont} packet.
22416 @item @code{vCont}[;@var{action}]...
22417 The @code{vCont} packet is supported. Each @var{action} is a supported
22418 command in the @code{vCont} packet.
22420 The @code{vCont} packet is not supported.
22423 @item @code{V} --- reserved
22425 Reserved for future use.
22427 @item @code{w} --- reserved
22429 Reserved for future use.
22431 @item @code{W} --- reserved
22433 Reserved for future use.
22435 @item @code{x} --- reserved
22437 Reserved for future use.
22439 @item @code{X}@var{addr}@code{,}@var{length}@var{:}@var{XX@dots{}} --- write mem (binary)
22440 @cindex @code{X} packet
22442 @var{addr} is address, @var{length} is number of bytes, @var{XX@dots{}}
22443 is binary data. The characters @code{$}, @code{#}, and @code{0x7d} are
22444 escaped using @code{0x7d}, and then XORed with @code{0x20}.
22445 For example, @code{0x7d} would be transmitted as @code{0x7d 0x5d}.
22455 @item @code{y} --- reserved
22457 Reserved for future use.
22459 @item @code{Y} reserved
22461 Reserved for future use.
22463 @item @code{z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- remove breakpoint or watchpoint @strong{(draft)}
22464 @itemx @code{Z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- insert breakpoint or watchpoint @strong{(draft)}
22465 @anchor{insert breakpoint or watchpoint packet}
22466 @cindex @code{z} packet
22467 @cindex @code{Z} packets
22469 Insert (@code{Z}) or remove (@code{z}) a @var{type} breakpoint or
22470 watchpoint starting at address @var{address} and covering the next
22471 @var{length} bytes.
22473 Each breakpoint and watchpoint packet @var{type} is documented
22476 @emph{Implementation notes: A remote target shall return an empty string
22477 for an unrecognized breakpoint or watchpoint packet @var{type}. A
22478 remote target shall support either both or neither of a given
22479 @code{Z}@var{type}@dots{} and @code{z}@var{type}@dots{} packet pair. To
22480 avoid potential problems with duplicate packets, the operations should
22481 be implemented in an idempotent way.}
22483 @item @code{z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- remove memory breakpoint @strong{(draft)}
22484 @item @code{Z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- insert memory breakpoint @strong{(draft)}
22485 @cindex @code{z0} packet
22486 @cindex @code{Z0} packet
22488 Insert (@code{Z0}) or remove (@code{z0}) a memory breakpoint at address
22489 @code{addr} of size @code{length}.
22491 A memory breakpoint is implemented by replacing the instruction at
22492 @var{addr} with a software breakpoint or trap instruction. The
22493 @code{length} is used by targets that indicates the size of the
22494 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
22495 @sc{mips} can insert either a 2 or 4 byte breakpoint).
22497 @emph{Implementation note: It is possible for a target to copy or move
22498 code that contains memory breakpoints (e.g., when implementing
22499 overlays). The behavior of this packet, in the presence of such a
22500 target, is not defined.}
22512 @item @code{z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- remove hardware breakpoint @strong{(draft)}
22513 @item @code{Z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- insert hardware breakpoint @strong{(draft)}
22514 @cindex @code{z1} packet
22515 @cindex @code{Z1} packet
22517 Insert (@code{Z1}) or remove (@code{z1}) a hardware breakpoint at
22518 address @code{addr} of size @code{length}.
22520 A hardware breakpoint is implemented using a mechanism that is not
22521 dependant on being able to modify the target's memory.
22523 @emph{Implementation note: A hardware breakpoint is not affected by code
22536 @item @code{z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- remove write watchpoint @strong{(draft)}
22537 @item @code{Z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- insert write watchpoint @strong{(draft)}
22538 @cindex @code{z2} packet
22539 @cindex @code{Z2} packet
22541 Insert (@code{Z2}) or remove (@code{z2}) a write watchpoint.
22553 @item @code{z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- remove read watchpoint @strong{(draft)}
22554 @item @code{Z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- insert read watchpoint @strong{(draft)}
22555 @cindex @code{z3} packet
22556 @cindex @code{Z3} packet
22558 Insert (@code{Z3}) or remove (@code{z3}) a read watchpoint.
22570 @item @code{z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- remove access watchpoint @strong{(draft)}
22571 @item @code{Z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- insert access watchpoint @strong{(draft)}
22572 @cindex @code{z4} packet
22573 @cindex @code{Z4} packet
22575 Insert (@code{Z4}) or remove (@code{z4}) an access watchpoint.
22589 @node Stop Reply Packets
22590 @section Stop Reply Packets
22591 @cindex stop reply packets
22593 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
22594 receive any of the below as a reply. In the case of the @samp{C},
22595 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
22596 when the target halts. In the below the exact meaning of @samp{signal
22597 number} is poorly defined. In general one of the UNIX signal numbering
22598 conventions is used.
22603 @var{AA} is the signal number
22605 @item @code{T}@var{AA}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}
22606 @cindex @code{T} packet reply
22608 @var{AA} = two hex digit signal number; @var{n...} = register number
22609 (hex), @var{r...} = target byte ordered register contents, size defined
22610 by @code{DEPRECATED_REGISTER_RAW_SIZE}; @var{n...} = @samp{thread},
22611 @var{r...} = thread process ID, this is a hex integer; @var{n...} =
22612 (@samp{watch} | @samp{rwatch} | @samp{awatch}, @var{r...} = data
22613 address, this is a hex integer; @var{n...} = other string not starting
22614 with valid hex digit. @value{GDBN} should ignore this @var{n...},
22615 @var{r...} pair and go on to the next. This way we can extend the
22620 The process exited, and @var{AA} is the exit status. This is only
22621 applicable to certain targets.
22625 The process terminated with signal @var{AA}.
22627 @item O@var{XX@dots{}}
22629 @var{XX@dots{}} is hex encoding of @sc{ascii} data. This can happen at
22630 any time while the program is running and the debugger should continue
22631 to wait for @samp{W}, @samp{T}, etc.
22633 @item F@var{call-id}@code{,}@var{parameter@dots{}}
22635 @var{call-id} is the identifier which says which host system call should
22636 be called. This is just the name of the function. Translation into the
22637 correct system call is only applicable as it's defined in @value{GDBN}.
22638 @xref{File-I/O remote protocol extension}, for a list of implemented
22641 @var{parameter@dots{}} is a list of parameters as defined for this very
22644 The target replies with this packet when it expects @value{GDBN} to call
22645 a host system call on behalf of the target. @value{GDBN} replies with
22646 an appropriate @code{F} packet and keeps up waiting for the next reply
22647 packet from the target. The latest @samp{C}, @samp{c}, @samp{S} or
22648 @samp{s} action is expected to be continued.
22649 @xref{File-I/O remote protocol extension}, for more details.
22653 @node General Query Packets
22654 @section General Query Packets
22655 @cindex remote query requests
22657 The following set and query packets have already been defined.
22661 @item @code{q}@code{C} --- current thread
22662 @cindex current thread, remote request
22663 @cindex @code{qC} packet
22664 Return the current thread id.
22668 @item @code{QC}@var{pid}
22669 Where @var{pid} is an unsigned hexidecimal process id.
22671 Any other reply implies the old pid.
22674 @item @code{q}@code{fThreadInfo} -- all thread ids
22675 @cindex list active threads, remote request
22676 @cindex @code{qfThreadInfo} packet
22677 @code{q}@code{sThreadInfo}
22679 Obtain a list of active thread ids from the target (OS). Since there
22680 may be too many active threads to fit into one reply packet, this query
22681 works iteratively: it may require more than one query/reply sequence to
22682 obtain the entire list of threads. The first query of the sequence will
22683 be the @code{qf}@code{ThreadInfo} query; subsequent queries in the
22684 sequence will be the @code{qs}@code{ThreadInfo} query.
22686 NOTE: replaces the @code{qL} query (see below).
22690 @item @code{m}@var{id}
22692 @item @code{m}@var{id},@var{id}@dots{}
22693 a comma-separated list of thread ids
22695 (lower case 'el') denotes end of list.
22698 In response to each query, the target will reply with a list of one or
22699 more thread ids, in big-endian unsigned hex, separated by commas.
22700 @value{GDBN} will respond to each reply with a request for more thread
22701 ids (using the @code{qs} form of the query), until the target responds
22702 with @code{l} (lower-case el, for @code{'last'}).
22704 @item @code{q}@code{ThreadExtraInfo}@code{,}@var{id} --- extra thread info
22705 @cindex thread attributes info, remote request
22706 @cindex @code{qThreadExtraInfo} packet
22707 Where @var{id} is a thread-id in big-endian hex. Obtain a printable
22708 string description of a thread's attributes from the target OS. This
22709 string may contain anything that the target OS thinks is interesting for
22710 @value{GDBN} to tell the user about the thread. The string is displayed
22711 in @value{GDBN}'s @samp{info threads} display. Some examples of
22712 possible thread extra info strings are ``Runnable'', or ``Blocked on
22717 @item @var{XX@dots{}}
22718 Where @var{XX@dots{}} is a hex encoding of @sc{ascii} data, comprising
22719 the printable string containing the extra information about the thread's
22723 @item @code{q}@code{L}@var{startflag}@var{threadcount}@var{nextthread} --- query @var{LIST} or @var{threadLIST} @strong{(deprecated)}
22725 Obtain thread information from RTOS. Where: @var{startflag} (one hex
22726 digit) is one to indicate the first query and zero to indicate a
22727 subsequent query; @var{threadcount} (two hex digits) is the maximum
22728 number of threads the response packet can contain; and @var{nextthread}
22729 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
22730 returned in the response as @var{argthread}.
22732 NOTE: this query is replaced by the @code{q}@code{fThreadInfo} query
22737 @item @code{q}@code{M}@var{count}@var{done}@var{argthread}@var{thread@dots{}}
22738 Where: @var{count} (two hex digits) is the number of threads being
22739 returned; @var{done} (one hex digit) is zero to indicate more threads
22740 and one indicates no further threads; @var{argthreadid} (eight hex
22741 digits) is @var{nextthread} from the request packet; @var{thread@dots{}}
22742 is a sequence of thread IDs from the target. @var{threadid} (eight hex
22743 digits). See @code{remote.c:parse_threadlist_response()}.
22746 @item @code{q}@code{CRC:}@var{addr}@code{,}@var{length} --- compute CRC of memory block
22747 @cindex CRC of memory block, remote request
22748 @cindex @code{qCRC} packet
22751 @item @code{E}@var{NN}
22752 An error (such as memory fault)
22753 @item @code{C}@var{CRC32}
22754 A 32 bit cyclic redundancy check of the specified memory region.
22757 @item @code{q}@code{Offsets} --- query sect offs
22758 @cindex section offsets, remote request
22759 @cindex @code{qOffsets} packet
22760 Get section offsets that the target used when re-locating the downloaded
22761 image. @emph{Note: while a @code{Bss} offset is included in the
22762 response, @value{GDBN} ignores this and instead applies the @code{Data}
22763 offset to the @code{Bss} section.}
22767 @item @code{Text=}@var{xxx}@code{;Data=}@var{yyy}@code{;Bss=}@var{zzz}
22770 @item @code{q}@code{P}@var{mode}@var{threadid} --- thread info request
22771 @cindex thread information, remote request
22772 @cindex @code{qP} packet
22773 Returns information on @var{threadid}. Where: @var{mode} is a hex
22774 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
22781 See @code{remote.c:remote_unpack_thread_info_response()}.
22783 @item @code{q}@code{Rcmd,}@var{command} --- remote command
22784 @cindex execute remote command, remote request
22785 @cindex @code{qRcmd} packet
22786 @var{command} (hex encoded) is passed to the local interpreter for
22787 execution. Invalid commands should be reported using the output string.
22788 Before the final result packet, the target may also respond with a
22789 number of intermediate @code{O}@var{output} console output packets.
22790 @emph{Implementors should note that providing access to a stubs's
22791 interpreter may have security implications}.
22796 A command response with no output.
22798 A command response with the hex encoded output string @var{OUTPUT}.
22799 @item @code{E}@var{NN}
22800 Indicate a badly formed request.
22802 When @samp{q}@samp{Rcmd} is not recognized.
22805 @item @code{qSymbol::} --- symbol lookup
22806 @cindex symbol lookup, remote request
22807 @cindex @code{qSymbol} packet
22808 Notify the target that @value{GDBN} is prepared to serve symbol lookup
22809 requests. Accept requests from the target for the values of symbols.
22814 The target does not need to look up any (more) symbols.
22815 @item @code{qSymbol:}@var{sym_name}
22816 The target requests the value of symbol @var{sym_name} (hex encoded).
22817 @value{GDBN} may provide the value by using the
22818 @code{qSymbol:}@var{sym_value}:@var{sym_name} message, described below.
22821 @item @code{qSymbol:}@var{sym_value}:@var{sym_name} --- symbol value
22823 Set the value of @var{sym_name} to @var{sym_value}.
22825 @var{sym_name} (hex encoded) is the name of a symbol whose value the
22826 target has previously requested.
22828 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
22829 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
22835 The target does not need to look up any (more) symbols.
22836 @item @code{qSymbol:}@var{sym_name}
22837 The target requests the value of a new symbol @var{sym_name} (hex
22838 encoded). @value{GDBN} will continue to supply the values of symbols
22839 (if available), until the target ceases to request them.
22842 @item @code{qPart}:@var{object}:@code{read}:@var{annex}:@var{offset},@var{length} --- read special data
22843 @cindex read special object, remote request
22844 @cindex @code{qPart} packet
22845 Read uninterpreted bytes from the target's special data area
22846 identified by the keyword @code{object}.
22847 Request @var{length} bytes starting at @var{offset} bytes into the data.
22848 The content and encoding of @var{annex} is specific to the object;
22849 it can supply additional details about what data to access.
22851 Here are the specific requests of this form defined so far.
22852 All @samp{@code{qPart}:@var{object}:@code{read}:@dots{}}
22853 requests use the same reply formats, listed below.
22856 @item @code{qPart}:@code{auxv}:@code{read}::@var{offset},@var{length}
22857 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
22858 auxiliary vector}, and see @ref{Remote configuration,
22859 read-aux-vector-packet}. Note @var{annex} must be empty.
22865 The @var{offset} in the request is at the end of the data.
22866 There is no more data to be read.
22868 @item @var{XX@dots{}}
22869 Hex encoded data bytes read.
22870 This may be fewer bytes than the @var{length} in the request.
22873 The request was malformed, or @var{annex} was invalid.
22875 @item @code{E}@var{nn}
22876 The offset was invalid, or there was an error encountered reading the data.
22877 @var{nn} is a hex-encoded @code{errno} value.
22879 @item @code{""} (empty)
22880 An empty reply indicates the @var{object} or @var{annex} string was not
22881 recognized by the stub.
22884 @item @code{qPart}:@var{object}:@code{write}:@var{annex}:@var{offset}:@var{data@dots{}}
22885 @cindex write data into object, remote request
22886 Write uninterpreted bytes into the target's special data area
22887 identified by the keyword @code{object},
22888 starting at @var{offset} bytes into the data.
22889 @var{data@dots{}} is the hex-encoded data to be written.
22890 The content and encoding of @var{annex} is specific to the object;
22891 it can supply additional details about what data to access.
22893 No requests of this form are presently in use. This specification
22894 serves as a placeholder to document the common format that new
22895 specific request specifications ought to use.
22900 @var{nn} (hex encoded) is the number of bytes written.
22901 This may be fewer bytes than supplied in the request.
22904 The request was malformed, or @var{annex} was invalid.
22906 @item @code{E}@var{nn}
22907 The offset was invalid, or there was an error encountered writing the data.
22908 @var{nn} is a hex-encoded @code{errno} value.
22910 @item @code{""} (empty)
22911 An empty reply indicates the @var{object} or @var{annex} string was not
22912 recognized by the stub, or that the object does not support writing.
22915 @item @code{qPart}:@var{object}:@var{operation}:@dots{}
22916 Requests of this form may be added in the future. When a stub does
22917 not recognize the @var{object} keyword, or its support for
22918 @var{object} does not recognize the @var{operation} keyword,
22919 the stub must respond with an empty packet.
22921 @item @code{qGetTLSAddr}:@var{thread-id},@var{offset},@var{lm} --- get thread local storage address
22922 @cindex get thread-local storage address, remote request
22923 @cindex @code{qGetTLSAddr} packet
22924 Fetch the address associated with thread local storage specified
22925 by @var{thread-id}, @var{offset}, and @var{lm}.
22927 @var{thread-id} is the (big endian, hex encoded) thread id associated with the
22928 thread for which to fetch the TLS address.
22930 @var{offset} is the (big endian, hex encoded) offset associated with the
22931 thread local variable. (This offset is obtained from the debug
22932 information associated with the variable.)
22934 @var{lm} is the (big endian, hex encoded) OS/ABI specific encoding of the
22935 the load module associated with the thread local storage. For example,
22936 a @sc{gnu}/Linux system will pass the link map address of the shared
22937 object associated with the thread local storage under consideration.
22938 Other operating environments may choose to represent the load module
22939 differently, so the precise meaning of this parameter will vary.
22943 @item @var{XX@dots{}}
22944 Hex encoded (big endian) bytes representing the address of the thread
22945 local storage requested.
22947 @item @code{E}@var{nn} (where @var{nn} are hex digits)
22950 @item @code{""} (empty)
22951 An empty reply indicates that @code{qGetTLSAddr} is not supported by the stub.
22954 Use of this request packet is controlled by the @code{set remote
22955 get-thread-local-storage-address} command (@pxref{Remote
22956 configuration, set remote get-thread-local-storage-address}).
22960 @node Register Packet Format
22961 @section Register Packet Format
22963 The following @samp{g}/@samp{G} packets have previously been defined.
22964 In the below, some thirty-two bit registers are transferred as
22965 sixty-four bits. Those registers should be zero/sign extended (which?)
22966 to fill the space allocated. Register bytes are transfered in target
22967 byte order. The two nibbles within a register byte are transfered
22968 most-significant - least-significant.
22974 All registers are transfered as thirty-two bit quantities in the order:
22975 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
22976 registers; fsr; fir; fp.
22980 All registers are transfered as sixty-four bit quantities (including
22981 thirty-two bit registers such as @code{sr}). The ordering is the same
22989 Example sequence of a target being re-started. Notice how the restart
22990 does not get any direct output:
22995 @emph{target restarts}
22998 <- @code{T001:1234123412341234}
23002 Example sequence of a target being stepped by a single instruction:
23005 -> @code{G1445@dots{}}
23010 <- @code{T001:1234123412341234}
23014 <- @code{1455@dots{}}
23018 @node File-I/O remote protocol extension
23019 @section File-I/O remote protocol extension
23020 @cindex File-I/O remote protocol extension
23023 * File-I/O Overview::
23024 * Protocol basics::
23025 * The F request packet::
23026 * The F reply packet::
23027 * Memory transfer::
23028 * The Ctrl-C message::
23030 * The isatty call::
23031 * The system call::
23032 * List of supported calls::
23033 * Protocol specific representation of datatypes::
23035 * File-I/O Examples::
23038 @node File-I/O Overview
23039 @subsection File-I/O Overview
23040 @cindex file-i/o overview
23042 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
23043 target to use the host's file system and console I/O when calling various
23044 system calls. System calls on the target system are translated into a
23045 remote protocol packet to the host system which then performs the needed
23046 actions and returns with an adequate response packet to the target system.
23047 This simulates file system operations even on targets that lack file systems.
23049 The protocol is defined host- and target-system independent. It uses
23050 its own independent representation of datatypes and values. Both,
23051 @value{GDBN} and the target's @value{GDBN} stub are responsible for
23052 translating the system dependent values into the unified protocol values
23053 when data is transmitted.
23055 The communication is synchronous. A system call is possible only
23056 when GDB is waiting for the @samp{C}, @samp{c}, @samp{S} or @samp{s}
23057 packets. While @value{GDBN} handles the request for a system call,
23058 the target is stopped to allow deterministic access to the target's
23059 memory. Therefore File-I/O is not interuptible by target signals. It
23060 is possible to interrupt File-I/O by a user interrupt (Ctrl-C), though.
23062 The target's request to perform a host system call does not finish
23063 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
23064 after finishing the system call, the target returns to continuing the
23065 previous activity (continue, step). No additional continue or step
23066 request from @value{GDBN} is required.
23069 (@value{GDBP}) continue
23070 <- target requests 'system call X'
23071 target is stopped, @value{GDBN} executes system call
23072 -> GDB returns result
23073 ... target continues, GDB returns to wait for the target
23074 <- target hits breakpoint and sends a Txx packet
23077 The protocol is only used for files on the host file system and
23078 for I/O on the console. Character or block special devices, pipes,
23079 named pipes or sockets or any other communication method on the host
23080 system are not supported by this protocol.
23082 @node Protocol basics
23083 @subsection Protocol basics
23084 @cindex protocol basics, file-i/o
23086 The File-I/O protocol uses the @code{F} packet, as request as well
23087 as as reply packet. Since a File-I/O system call can only occur when
23088 @value{GDBN} is waiting for the continuing or stepping target, the
23089 File-I/O request is a reply that @value{GDBN} has to expect as a result
23090 of a former @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
23091 This @code{F} packet contains all information needed to allow @value{GDBN}
23092 to call the appropriate host system call:
23096 A unique identifier for the requested system call.
23099 All parameters to the system call. Pointers are given as addresses
23100 in the target memory address space. Pointers to strings are given as
23101 pointer/length pair. Numerical values are given as they are.
23102 Numerical control values are given in a protocol specific representation.
23106 At that point @value{GDBN} has to perform the following actions.
23110 If parameter pointer values are given, which point to data needed as input
23111 to a system call, @value{GDBN} requests this data from the target with a
23112 standard @code{m} packet request. This additional communication has to be
23113 expected by the target implementation and is handled as any other @code{m}
23117 @value{GDBN} translates all value from protocol representation to host
23118 representation as needed. Datatypes are coerced into the host types.
23121 @value{GDBN} calls the system call
23124 It then coerces datatypes back to protocol representation.
23127 If pointer parameters in the request packet point to buffer space in which
23128 a system call is expected to copy data to, the data is transmitted to the
23129 target using a @code{M} or @code{X} packet. This packet has to be expected
23130 by the target implementation and is handled as any other @code{M} or @code{X}
23135 Eventually @value{GDBN} replies with another @code{F} packet which contains all
23136 necessary information for the target to continue. This at least contains
23143 @code{errno}, if has been changed by the system call.
23150 After having done the needed type and value coercion, the target continues
23151 the latest continue or step action.
23153 @node The F request packet
23154 @subsection The @code{F} request packet
23155 @cindex file-i/o request packet
23156 @cindex @code{F} request packet
23158 The @code{F} request packet has the following format:
23163 @code{F}@var{call-id}@code{,}@var{parameter@dots{}}
23166 @var{call-id} is the identifier to indicate the host system call to be called.
23167 This is just the name of the function.
23169 @var{parameter@dots{}} are the parameters to the system call.
23173 Parameters are hexadecimal integer values, either the real values in case
23174 of scalar datatypes, as pointers to target buffer space in case of compound
23175 datatypes and unspecified memory areas or as pointer/length pairs in case
23176 of string parameters. These are appended to the call-id, each separated
23177 from its predecessor by a comma. All values are transmitted in ASCII
23178 string representation, pointer/length pairs separated by a slash.
23180 @node The F reply packet
23181 @subsection The @code{F} reply packet
23182 @cindex file-i/o reply packet
23183 @cindex @code{F} reply packet
23185 The @code{F} reply packet has the following format:
23190 @code{F}@var{retcode}@code{,}@var{errno}@code{,}@var{Ctrl-C flag}@code{;}@var{call specific attachment}
23193 @var{retcode} is the return code of the system call as hexadecimal value.
23195 @var{errno} is the errno set by the call, in protocol specific representation.
23196 This parameter can be omitted if the call was successful.
23198 @var{Ctrl-C flag} is only send if the user requested a break. In this
23199 case, @var{errno} must be send as well, even if the call was successful.
23200 The @var{Ctrl-C flag} itself consists of the character 'C':
23207 or, if the call was interupted before the host call has been performed:
23214 assuming 4 is the protocol specific representation of @code{EINTR}.
23218 @node Memory transfer
23219 @subsection Memory transfer
23220 @cindex memory transfer, in file-i/o protocol
23222 Structured data which is transferred using a memory read or write as e.g.@:
23223 a @code{struct stat} is expected to be in a protocol specific format with
23224 all scalar multibyte datatypes being big endian. This should be done by
23225 the target before the @code{F} packet is sent resp.@: by @value{GDBN} before
23226 it transfers memory to the target. Transferred pointers to structured
23227 data should point to the already coerced data at any time.
23229 @node The Ctrl-C message
23230 @subsection The Ctrl-C message
23231 @cindex ctrl-c message, in file-i/o protocol
23233 A special case is, if the @var{Ctrl-C flag} is set in the @value{GDBN}
23234 reply packet. In this case the target should behave, as if it had
23235 gotten a break message. The meaning for the target is ``system call
23236 interupted by @code{SIGINT}''. Consequentially, the target should actually stop
23237 (as with a break message) and return to @value{GDBN} with a @code{T02}
23238 packet. In this case, it's important for the target to know, in which
23239 state the system call was interrupted. Since this action is by design
23240 not an atomic operation, we have to differ between two cases:
23244 The system call hasn't been performed on the host yet.
23247 The system call on the host has been finished.
23251 These two states can be distinguished by the target by the value of the
23252 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
23253 call hasn't been performed. This is equivalent to the @code{EINTR} handling
23254 on POSIX systems. In any other case, the target may presume that the
23255 system call has been finished --- successful or not --- and should behave
23256 as if the break message arrived right after the system call.
23258 @value{GDBN} must behave reliable. If the system call has not been called
23259 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
23260 @code{errno} in the packet. If the system call on the host has been finished
23261 before the user requests a break, the full action must be finshed by
23262 @value{GDBN}. This requires sending @code{M} or @code{X} packets as they fit.
23263 The @code{F} packet may only be send when either nothing has happened
23264 or the full action has been completed.
23267 @subsection Console I/O
23268 @cindex console i/o as part of file-i/o
23270 By default and if not explicitely closed by the target system, the file
23271 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
23272 on the @value{GDBN} console is handled as any other file output operation
23273 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
23274 by @value{GDBN} so that after the target read request from file descriptor
23275 0 all following typing is buffered until either one of the following
23280 The user presses @kbd{Ctrl-C}. The behaviour is as explained above, the
23282 system call is treated as finished.
23285 The user presses @kbd{Enter}. This is treated as end of input with a trailing
23289 The user presses @kbd{Ctrl-D}. This is treated as end of input. No trailing
23290 character, especially no Ctrl-D is appended to the input.
23294 If the user has typed more characters as fit in the buffer given to
23295 the read call, the trailing characters are buffered in @value{GDBN} until
23296 either another @code{read(0, @dots{})} is requested by the target or debugging
23297 is stopped on users request.
23299 @node The isatty call
23300 @subsection The @samp{isatty} function call
23301 @cindex isatty call, file-i/o protocol
23303 A special case in this protocol is the library call @code{isatty} which
23304 is implemented as its own call inside of this protocol. It returns
23305 1 to the target if the file descriptor given as parameter is attached
23306 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
23307 would require implementing @code{ioctl} and would be more complex than
23310 @node The system call
23311 @subsection The @samp{system} function call
23312 @cindex system call, file-i/o protocol
23314 The other special case in this protocol is the @code{system} call which
23315 is implemented as its own call, too. @value{GDBN} is taking over the full
23316 task of calling the necessary host calls to perform the @code{system}
23317 call. The return value of @code{system} is simplified before it's returned
23318 to the target. Basically, the only signal transmitted back is @code{EINTR}
23319 in case the user pressed @kbd{Ctrl-C}. Otherwise the return value consists
23320 entirely of the exit status of the called command.
23322 Due to security concerns, the @code{system} call is by default refused
23323 by @value{GDBN}. The user has to allow this call explicitly with the
23324 @kbd{set remote system-call-allowed 1} command.
23327 @item set remote system-call-allowed
23328 @kindex set remote system-call-allowed
23329 Control whether to allow the @code{system} calls in the File I/O
23330 protocol for the remote target. The default is zero (disabled).
23332 @item show remote system-call-allowed
23333 @kindex show remote system-call-allowed
23334 Show the current setting of system calls for the remote File I/O
23338 @node List of supported calls
23339 @subsection List of supported calls
23340 @cindex list of supported file-i/o calls
23357 @unnumberedsubsubsec open
23358 @cindex open, file-i/o system call
23362 int open(const char *pathname, int flags);
23363 int open(const char *pathname, int flags, mode_t mode);
23366 Fopen,pathptr/len,flags,mode
23370 @code{flags} is the bitwise or of the following values:
23374 If the file does not exist it will be created. The host
23375 rules apply as far as file ownership and time stamps
23379 When used with O_CREAT, if the file already exists it is
23380 an error and open() fails.
23383 If the file already exists and the open mode allows
23384 writing (O_RDWR or O_WRONLY is given) it will be
23385 truncated to length 0.
23388 The file is opened in append mode.
23391 The file is opened for reading only.
23394 The file is opened for writing only.
23397 The file is opened for reading and writing.
23400 Each other bit is silently ignored.
23405 @code{mode} is the bitwise or of the following values:
23409 User has read permission.
23412 User has write permission.
23415 Group has read permission.
23418 Group has write permission.
23421 Others have read permission.
23424 Others have write permission.
23427 Each other bit is silently ignored.
23432 @exdent Return value:
23433 open returns the new file descriptor or -1 if an error
23441 pathname already exists and O_CREAT and O_EXCL were used.
23444 pathname refers to a directory.
23447 The requested access is not allowed.
23450 pathname was too long.
23453 A directory component in pathname does not exist.
23456 pathname refers to a device, pipe, named pipe or socket.
23459 pathname refers to a file on a read-only filesystem and
23460 write access was requested.
23463 pathname is an invalid pointer value.
23466 No space on device to create the file.
23469 The process already has the maximum number of files open.
23472 The limit on the total number of files open on the system
23476 The call was interrupted by the user.
23480 @unnumberedsubsubsec close
23481 @cindex close, file-i/o system call
23490 @exdent Return value:
23491 close returns zero on success, or -1 if an error occurred.
23498 fd isn't a valid open file descriptor.
23501 The call was interrupted by the user.
23505 @unnumberedsubsubsec read
23506 @cindex read, file-i/o system call
23510 int read(int fd, void *buf, unsigned int count);
23513 Fread,fd,bufptr,count
23515 @exdent Return value:
23516 On success, the number of bytes read is returned.
23517 Zero indicates end of file. If count is zero, read
23518 returns zero as well. On error, -1 is returned.
23525 fd is not a valid file descriptor or is not open for
23529 buf is an invalid pointer value.
23532 The call was interrupted by the user.
23536 @unnumberedsubsubsec write
23537 @cindex write, file-i/o system call
23541 int write(int fd, const void *buf, unsigned int count);
23544 Fwrite,fd,bufptr,count
23546 @exdent Return value:
23547 On success, the number of bytes written are returned.
23548 Zero indicates nothing was written. On error, -1
23556 fd is not a valid file descriptor or is not open for
23560 buf is an invalid pointer value.
23563 An attempt was made to write a file that exceeds the
23564 host specific maximum file size allowed.
23567 No space on device to write the data.
23570 The call was interrupted by the user.
23574 @unnumberedsubsubsec lseek
23575 @cindex lseek, file-i/o system call
23579 long lseek (int fd, long offset, int flag);
23582 Flseek,fd,offset,flag
23585 @code{flag} is one of:
23589 The offset is set to offset bytes.
23592 The offset is set to its current location plus offset
23596 The offset is set to the size of the file plus offset
23601 @exdent Return value:
23602 On success, the resulting unsigned offset in bytes from
23603 the beginning of the file is returned. Otherwise, a
23604 value of -1 is returned.
23611 fd is not a valid open file descriptor.
23614 fd is associated with the @value{GDBN} console.
23617 flag is not a proper value.
23620 The call was interrupted by the user.
23624 @unnumberedsubsubsec rename
23625 @cindex rename, file-i/o system call
23629 int rename(const char *oldpath, const char *newpath);
23632 Frename,oldpathptr/len,newpathptr/len
23634 @exdent Return value:
23635 On success, zero is returned. On error, -1 is returned.
23642 newpath is an existing directory, but oldpath is not a
23646 newpath is a non-empty directory.
23649 oldpath or newpath is a directory that is in use by some
23653 An attempt was made to make a directory a subdirectory
23657 A component used as a directory in oldpath or new
23658 path is not a directory. Or oldpath is a directory
23659 and newpath exists but is not a directory.
23662 oldpathptr or newpathptr are invalid pointer values.
23665 No access to the file or the path of the file.
23669 oldpath or newpath was too long.
23672 A directory component in oldpath or newpath does not exist.
23675 The file is on a read-only filesystem.
23678 The device containing the file has no room for the new
23682 The call was interrupted by the user.
23686 @unnumberedsubsubsec unlink
23687 @cindex unlink, file-i/o system call
23691 int unlink(const char *pathname);
23694 Funlink,pathnameptr/len
23696 @exdent Return value:
23697 On success, zero is returned. On error, -1 is returned.
23704 No access to the file or the path of the file.
23707 The system does not allow unlinking of directories.
23710 The file pathname cannot be unlinked because it's
23711 being used by another process.
23714 pathnameptr is an invalid pointer value.
23717 pathname was too long.
23720 A directory component in pathname does not exist.
23723 A component of the path is not a directory.
23726 The file is on a read-only filesystem.
23729 The call was interrupted by the user.
23733 @unnumberedsubsubsec stat/fstat
23734 @cindex fstat, file-i/o system call
23735 @cindex stat, file-i/o system call
23739 int stat(const char *pathname, struct stat *buf);
23740 int fstat(int fd, struct stat *buf);
23743 Fstat,pathnameptr/len,bufptr
23746 @exdent Return value:
23747 On success, zero is returned. On error, -1 is returned.
23754 fd is not a valid open file.
23757 A directory component in pathname does not exist or the
23758 path is an empty string.
23761 A component of the path is not a directory.
23764 pathnameptr is an invalid pointer value.
23767 No access to the file or the path of the file.
23770 pathname was too long.
23773 The call was interrupted by the user.
23777 @unnumberedsubsubsec gettimeofday
23778 @cindex gettimeofday, file-i/o system call
23782 int gettimeofday(struct timeval *tv, void *tz);
23785 Fgettimeofday,tvptr,tzptr
23787 @exdent Return value:
23788 On success, 0 is returned, -1 otherwise.
23795 tz is a non-NULL pointer.
23798 tvptr and/or tzptr is an invalid pointer value.
23802 @unnumberedsubsubsec isatty
23803 @cindex isatty, file-i/o system call
23807 int isatty(int fd);
23812 @exdent Return value:
23813 Returns 1 if fd refers to the @value{GDBN} console, 0 otherwise.
23820 The call was interrupted by the user.
23824 @unnumberedsubsubsec system
23825 @cindex system, file-i/o system call
23829 int system(const char *command);
23832 Fsystem,commandptr/len
23834 @exdent Return value:
23835 The value returned is -1 on error and the return status
23836 of the command otherwise. Only the exit status of the
23837 command is returned, which is extracted from the hosts
23838 system return value by calling WEXITSTATUS(retval).
23839 In case /bin/sh could not be executed, 127 is returned.
23846 The call was interrupted by the user.
23849 @node Protocol specific representation of datatypes
23850 @subsection Protocol specific representation of datatypes
23851 @cindex protocol specific representation of datatypes, in file-i/o protocol
23854 * Integral datatypes::
23860 @node Integral datatypes
23861 @unnumberedsubsubsec Integral datatypes
23862 @cindex integral datatypes, in file-i/o protocol
23864 The integral datatypes used in the system calls are
23867 int@r{,} unsigned int@r{,} long@r{,} unsigned long@r{,} mode_t @r{and} time_t
23870 @code{Int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
23871 implemented as 32 bit values in this protocol.
23873 @code{Long} and @code{unsigned long} are implemented as 64 bit types.
23875 @xref{Limits}, for corresponding MIN and MAX values (similar to those
23876 in @file{limits.h}) to allow range checking on host and target.
23878 @code{time_t} datatypes are defined as seconds since the Epoch.
23880 All integral datatypes transferred as part of a memory read or write of a
23881 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
23884 @node Pointer values
23885 @unnumberedsubsubsec Pointer values
23886 @cindex pointer values, in file-i/o protocol
23888 Pointers to target data are transmitted as they are. An exception
23889 is made for pointers to buffers for which the length isn't
23890 transmitted as part of the function call, namely strings. Strings
23891 are transmitted as a pointer/length pair, both as hex values, e.g.@:
23898 which is a pointer to data of length 18 bytes at position 0x1aaf.
23899 The length is defined as the full string length in bytes, including
23900 the trailing null byte. Example:
23903 ``hello, world'' at address 0x123456
23914 @unnumberedsubsubsec struct stat
23915 @cindex struct stat, in file-i/o protocol
23917 The buffer of type struct stat used by the target and @value{GDBN} is defined
23922 unsigned int st_dev; /* device */
23923 unsigned int st_ino; /* inode */
23924 mode_t st_mode; /* protection */
23925 unsigned int st_nlink; /* number of hard links */
23926 unsigned int st_uid; /* user ID of owner */
23927 unsigned int st_gid; /* group ID of owner */
23928 unsigned int st_rdev; /* device type (if inode device) */
23929 unsigned long st_size; /* total size, in bytes */
23930 unsigned long st_blksize; /* blocksize for filesystem I/O */
23931 unsigned long st_blocks; /* number of blocks allocated */
23932 time_t st_atime; /* time of last access */
23933 time_t st_mtime; /* time of last modification */
23934 time_t st_ctime; /* time of last change */
23938 The integral datatypes are conforming to the definitions given in the
23939 approriate section (see @ref{Integral datatypes}, for details) so this
23940 structure is of size 64 bytes.
23942 The values of several fields have a restricted meaning and/or
23949 st_ino: No valid meaning for the target. Transmitted unchanged.
23951 st_mode: Valid mode bits are described in Appendix C. Any other
23952 bits have currently no meaning for the target.
23954 st_uid: No valid meaning for the target. Transmitted unchanged.
23956 st_gid: No valid meaning for the target. Transmitted unchanged.
23958 st_rdev: No valid meaning for the target. Transmitted unchanged.
23960 st_atime, st_mtime, st_ctime:
23961 These values have a host and file system dependent
23962 accuracy. Especially on Windows hosts the file systems
23963 don't support exact timing values.
23966 The target gets a struct stat of the above representation and is
23967 responsible to coerce it to the target representation before
23970 Note that due to size differences between the host and target
23971 representation of stat members, these members could eventually
23972 get truncated on the target.
23974 @node struct timeval
23975 @unnumberedsubsubsec struct timeval
23976 @cindex struct timeval, in file-i/o protocol
23978 The buffer of type struct timeval used by the target and @value{GDBN}
23979 is defined as follows:
23983 time_t tv_sec; /* second */
23984 long tv_usec; /* microsecond */
23988 The integral datatypes are conforming to the definitions given in the
23989 approriate section (see @ref{Integral datatypes}, for details) so this
23990 structure is of size 8 bytes.
23993 @subsection Constants
23994 @cindex constants, in file-i/o protocol
23996 The following values are used for the constants inside of the
23997 protocol. @value{GDBN} and target are resposible to translate these
23998 values before and after the call as needed.
24009 @unnumberedsubsubsec Open flags
24010 @cindex open flags, in file-i/o protocol
24012 All values are given in hexadecimal representation.
24024 @node mode_t values
24025 @unnumberedsubsubsec mode_t values
24026 @cindex mode_t values, in file-i/o protocol
24028 All values are given in octal representation.
24045 @unnumberedsubsubsec Errno values
24046 @cindex errno values, in file-i/o protocol
24048 All values are given in decimal representation.
24073 EUNKNOWN is used as a fallback error value if a host system returns
24074 any error value not in the list of supported error numbers.
24077 @unnumberedsubsubsec Lseek flags
24078 @cindex lseek flags, in file-i/o protocol
24087 @unnumberedsubsubsec Limits
24088 @cindex limits, in file-i/o protocol
24090 All values are given in decimal representation.
24093 INT_MIN -2147483648
24095 UINT_MAX 4294967295
24096 LONG_MIN -9223372036854775808
24097 LONG_MAX 9223372036854775807
24098 ULONG_MAX 18446744073709551615
24101 @node File-I/O Examples
24102 @subsection File-I/O Examples
24103 @cindex file-i/o examples
24105 Example sequence of a write call, file descriptor 3, buffer is at target
24106 address 0x1234, 6 bytes should be written:
24109 <- @code{Fwrite,3,1234,6}
24110 @emph{request memory read from target}
24113 @emph{return "6 bytes written"}
24117 Example sequence of a read call, file descriptor 3, buffer is at target
24118 address 0x1234, 6 bytes should be read:
24121 <- @code{Fread,3,1234,6}
24122 @emph{request memory write to target}
24123 -> @code{X1234,6:XXXXXX}
24124 @emph{return "6 bytes read"}
24128 Example sequence of a read call, call fails on the host due to invalid
24129 file descriptor (EBADF):
24132 <- @code{Fread,3,1234,6}
24136 Example sequence of a read call, user presses Ctrl-C before syscall on
24140 <- @code{Fread,3,1234,6}
24145 Example sequence of a read call, user presses Ctrl-C after syscall on
24149 <- @code{Fread,3,1234,6}
24150 -> @code{X1234,6:XXXXXX}
24154 @include agentexpr.texi
24168 % I think something like @colophon should be in texinfo. In the
24170 \long\def\colophon{\hbox to0pt{}\vfill
24171 \centerline{The body of this manual is set in}
24172 \centerline{\fontname\tenrm,}
24173 \centerline{with headings in {\bf\fontname\tenbf}}
24174 \centerline{and examples in {\tt\fontname\tentt}.}
24175 \centerline{{\it\fontname\tenit\/},}
24176 \centerline{{\bf\fontname\tenbf}, and}
24177 \centerline{{\sl\fontname\tensl\/}}
24178 \centerline{are used for emphasis.}\vfill}
24180 % Blame: doc@cygnus.com, 1991.